License cleanup: add SPDX GPL-2.0 license identifier to files with no license
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.
By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.
How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,
Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.
The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.
The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.
Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).
All documentation files were explicitly excluded.
The following heuristics were used to determine which SPDX license
identifiers to apply.
- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.
For non */uapi/* files that summary was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139
and resulted in the first patch in this series.
If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930
and resulted in the second patch in this series.
- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:
SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1
and that resulted in the third patch in this series.
- when the two scanners agreed on the detected license(s), that became
the concluded license(s).
- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.
- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).
- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.
- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.
In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.
Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.
Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.
In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.
Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct
This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.
These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-11-01 17:07:57 +03:00
# SPDX-License-Identifier: GPL-2.0
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VERSION = 5
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PATCHLEVEL = 15
2011-05-30 04:43:36 +04:00
SUBLEVEL = 0
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EXTRAVERSION = -rc1
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NAME = Opossums on Parade
2005-04-17 02:20:36 +04:00
# *DOCUMENTATION*
# To see a list of typical targets execute "make help"
# More info can be located in ./README
# Comments in this file are targeted only to the developer, do not
# expect to learn how to build the kernel reading this file.
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$( if $ ( filter __ %, $ ( MAKECMDGOALS ) ) , \
$( error targets prefixed with '__' are only for internal use) )
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# That's our default target when none is given on the command line
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PHONY := __all
__all :
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# We are using a recursive build, so we need to do a little thinking
# to get the ordering right.
#
# Most importantly: sub-Makefiles should only ever modify files in
# their own directory. If in some directory we have a dependency on
# a file in another dir (which doesn't happen often, but it's often
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# unavoidable when linking the built-in.a targets which finally
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# turn into vmlinux), we will call a sub make in that other dir, and
# after that we are sure that everything which is in that other dir
# is now up to date.
#
# The only cases where we need to modify files which have global
# effects are thus separated out and done before the recursive
# descending is started. They are now explicitly listed as the
# prepare rule.
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i f n e q ( $( sub_make_done ) , 1 )
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# Do not use make's built-in rules and variables
# (this increases performance and avoids hard-to-debug behaviour)
MAKEFLAGS += -rR
# Avoid funny character set dependencies
u n export LC_ALL
LC_COLLATE = C
LC_NUMERIC = C
export LC_COLLATE LC_NUMERIC
# Avoid interference with shell env settings
u n export GREP_OPTIONS
2014-07-04 16:29:30 +04:00
# Beautify output
# ---------------------------------------------------------------------------
#
# Normally, we echo the whole command before executing it. By making
# that echo $($(quiet)$(cmd)), we now have the possibility to set
# $(quiet) to choose other forms of output instead, e.g.
#
# quiet_cmd_cc_o_c = Compiling $(RELDIR)/$@
# cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
#
# If $(quiet) is empty, the whole command will be printed.
# If it is set to "quiet_", only the short version will be printed.
# If it is set to "silent_", nothing will be printed at all, since
# the variable $(silent_cmd_cc_o_c) doesn't exist.
#
# A simple variant is to prefix commands with $(Q) - that's useful
# for commands that shall be hidden in non-verbose mode.
#
# $(Q)ln $@ :<
#
# If KBUILD_VERBOSE equals 0 then the above command will be hidden.
# If KBUILD_VERBOSE equals 1 then the above command is displayed.
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# If KBUILD_VERBOSE equals 2 then give the reason why each target is rebuilt.
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#
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# To put more focus on warnings, be less verbose as default
# Use 'make V=1' to see the full commands
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i f e q ( "$(origin V)" , "command line" )
KBUILD_VERBOSE = $( V)
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e n d i f
i f n d e f K B U I L D _ V E R B O S E
KBUILD_VERBOSE = 0
e n d i f
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i f e q ( $( KBUILD_VERBOSE ) , 1 )
quiet =
Q =
e l s e
quiet = quiet_
Q = @
e n d i f
# If the user is running make -s (silent mode), suppress echoing of
# commands
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i f n e q ( $( findstring s ,$ ( filter -out --%,$ ( MAKEFLAGS ) ) ) , )
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quiet = silent_
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KBUILD_VERBOSE = 0
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e n d i f
export quiet Q KBUILD_VERBOSE
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# Call a source code checker (by default, "sparse") as part of the
# C compilation.
#
# Use 'make C=1' to enable checking of only re-compiled files.
# Use 'make C=2' to enable checking of *all* source files, regardless
# of whether they are re-compiled or not.
#
# See the file "Documentation/dev-tools/sparse.rst" for more details,
# including where to get the "sparse" utility.
i f e q ( "$(origin C)" , "command line" )
KBUILD_CHECKSRC = $( C)
e n d i f
i f n d e f K B U I L D _ C H E C K S R C
KBUILD_CHECKSRC = 0
e n d i f
export KBUILD_CHECKSRC
# Use make M=dir or set the environment variable KBUILD_EXTMOD to specify the
# directory of external module to build. Setting M= takes precedence.
i f e q ( "$(origin M)" , "command line" )
KBUILD_EXTMOD := $( M)
e n d i f
$( if $ ( word 2, $ ( KBUILD_EXTMOD ) ) , \
$( error building multiple external modules is not supported) )
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# Remove trailing slashes
i f n e q ( $( filter %/, $ ( KBUILD_EXTMOD ) ) , )
KBUILD_EXTMOD := $( shell dirname $( KBUILD_EXTMOD) .)
e n d i f
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export KBUILD_EXTMOD
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# Kbuild will save output files in the current working directory.
# This does not need to match to the root of the kernel source tree.
#
# For example, you can do this:
#
# cd /dir/to/store/output/files; make -f /dir/to/kernel/source/Makefile
#
# If you want to save output files in a different location, there are
# two syntaxes to specify it.
#
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# 1) O=
# Use "make O=dir/to/store/output/files/"
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#
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# 2) Set KBUILD_OUTPUT
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# Set the environment variable KBUILD_OUTPUT to point to the output directory.
# export KBUILD_OUTPUT=dir/to/store/output/files/; make
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#
# The O= assignment takes precedence over the KBUILD_OUTPUT environment
# variable.
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# Do we want to change the working directory?
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i f e q ( "$(origin O)" , "command line" )
KBUILD_OUTPUT := $( O)
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e n d i f
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i f n e q ( $( KBUILD_OUTPUT ) , )
# Make's built-in functions such as $(abspath ...), $(realpath ...) cannot
# expand a shell special character '~'. We use a somewhat tedious way here.
abs_objtree := $( shell mkdir -p $( KBUILD_OUTPUT) && cd $( KBUILD_OUTPUT) && pwd )
$( if $ ( abs_objtree ) ,, \
$( error failed to create output directory " $( KBUILD_OUTPUT) " ) )
# $(realpath ...) resolves symlinks
abs_objtree := $( realpath $( abs_objtree) )
e l s e
abs_objtree := $( CURDIR)
e n d i f # ifneq ($(KBUILD_OUTPUT),)
i f e q ( $( abs_objtree ) , $( CURDIR ) )
# Suppress "Entering directory ..." unless we are changing the work directory.
MAKEFLAGS += --no-print-directory
e l s e
need-sub-make := 1
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e n d i f
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this-makefile := $( lastword $( MAKEFILE_LIST) )
abs_srctree := $( realpath $( dir $( this-makefile) ) )
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ifneq ($(words $(subst : , , $( abs_srctree ) )), 1)
$( error source directory cannot contain spaces or colons )
e n d i f
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i f n e q ( $( abs_srctree ) , $( abs_objtree ) )
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# Look for make include files relative to root of kernel src
#
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# --included-dir is added for backward compatibility, but you should not rely on
# it. Please add $(srctree)/ prefix to include Makefiles in the source tree.
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MAKEFLAGS += --include-dir= $( abs_srctree)
e n d i f
2019-02-22 10:40:07 +03:00
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i f n e q ( $( filter 3.%,$ ( MAKE_VERSION ) ) , )
# 'MAKEFLAGS += -rR' does not immediately become effective for GNU Make 3.x
# We need to invoke sub-make to avoid implicit rules in the top Makefile.
need-sub-make := 1
# Cancel implicit rules for this Makefile.
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$(this-makefile) : ;
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e n d i f
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export abs_srctree abs_objtree
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export sub_make_done := 1
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i f e q ( $( need -sub -make ) , 1 )
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PHONY += $( MAKECMDGOALS) __sub-make
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$(filter-out $(this-makefile), $(MAKECMDGOALS)) __all : __sub -make
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@:
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# Invoke a second make in the output directory, passing relevant variables
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__sub-make :
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$( Q) $( MAKE) -C $( abs_objtree) -f $( abs_srctree) /Makefile $( MAKECMDGOALS)
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e n d i f # need-sub-make
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e n d i f # sub_make_done
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# We process the rest of the Makefile if this is the final invocation of make
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i f e q ( $( need -sub -make ) , )
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# Do not print "Entering directory ...",
# but we want to display it when entering to the output directory
# so that IDEs/editors are able to understand relative filenames.
MAKEFLAGS += --no-print-directory
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i f e q ( $( abs_srctree ) , $( abs_objtree ) )
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# building in the source tree
srctree := .
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building_out_of_srctree :=
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e l s e
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ifeq ( $( abs_srctree) /,$( dir $( abs_objtree) ) )
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# building in a subdirectory of the source tree
srctree := ..
else
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srctree := $( abs_srctree)
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endif
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building_out_of_srctree := 1
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e n d i f
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i f n e q ( $( KBUILD_ABS_SRCTREE ) , )
srctree := $( abs_srctree)
e n d i f
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objtree := .
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VPATH := $( srctree)
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export building_out_of_srctree srctree objtree VPATH
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# To make sure we do not include .config for any of the *config targets
# catch them early, and hand them over to scripts/kconfig/Makefile
# It is allowed to specify more targets when calling make, including
# mixing *config targets and build targets.
# For example 'make oldconfig all'.
# Detect when mixed targets is specified, and make a second invocation
# of make so .config is not included in this case either (for *config).
version_h := include/generated/uapi/linux/version.h
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clean-targets := %clean mrproper cleandocs
no-dot-config-targets := $( clean-targets) \
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cscope gtags TAGS tags help% %docs check% coccicheck \
kbuild: add 'headers' target to build up uapi headers in usr/include
In Linux build system, build targets and installation targets are
separated.
Examples are:
- 'make vmlinux' -> 'make install'
- 'make modules' -> 'make modules_install'
- 'make dtbs' -> 'make dtbs_install'
- 'make vdso' -> 'make vdso_install'
The intention is to run the build targets under the normal privilege,
then the installation targets under the root privilege since we need
the write permission to the system directories.
We have 'make headers_install' but the corresponding 'make headers'
stage does not exist. The purpose of headers_install is to provide
the kernel interface to C library. So, nobody would try to install
headers to /usr/include directly.
If 'sudo make INSTALL_HDR_PATH=/usr/include headers_install' were run,
some build artifacts in the kernel tree would be owned by root because
some of uapi headers are generated by 'uapi-asm-generic', 'archheaders'
targets.
Anyway, I believe it makes sense to split the header installation into
two stages.
[1] 'make headers'
Process headers in uapi directories by scripts/headers_install.sh
and copy them to usr/include
[2] 'make headers_install'
Copy '*.h' verbatim from usr/include to $(INSTALL_HDR_PATH)/include
For the backward compatibility, 'headers_install' depends on 'headers'.
Some samples expect uapi headers in usr/include. So, the 'headers'
target is useful to build up them in the fixed location usr/include
irrespective of INSTALL_HDR_PATH.
Another benefit is to stop polluting the final destination with the
time-stamp files '.install' and '.check'. Maybe you can see them in
your toolchains.
Lastly, my main motivation is to prepare for compile-testing uapi
headers. To build something, we have to save an object and .*.cmd
somewhere. The usr/include/ will be the work directory for that.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2019-06-04 13:14:02 +03:00
$( version_h) headers headers_% archheaders archscripts \
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%asm-generic kernelversion %src-pkg dt_binding_check \
outputmakefile
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# Installation targets should not require compiler. Unfortunately, vdso_install
# is an exception where build artifacts may be updated. This must be fixed.
no-compiler-targets := $( no-dot-config-targets) install dtbs_install \
headers_install modules_install kernelrelease image_name
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no-sync-config-targets := $( no-dot-config-targets) %install kernelrelease \
image_name
kbuild: make single targets work more correctly
Currently, the single target build directly descends into the directory
of the target. For example,
$ make foo/bar/baz.o
... directly descends into foo/bar/.
On the other hand, the normal build usually descends one directory at
a time, i.e. descends into foo/, and then foo/bar/.
This difference causes some problems.
[1] miss subdir-asflags-y, subdir-ccflags-y in upper Makefiles
The options in subdir-{as,cc}flags-y take effect in the current
and its sub-directories. In other words, they are inherited
downward. In the example above, the single target will miss
subdir-{as,cc}flags-y if they are defined in foo/Makefile.
[2] could be built in a different directory
As Documentation/kbuild/modules.rst section 4.3 says, Kbuild can
handle files that are spread over several sub-directories.
The build rule of foo/bar/baz.o may not necessarily be specified in
foo/bar/Makefile. It might be specifies in foo/Makefile as follows:
[foo/Makefile]
obj-y := bar/baz.o
This often happens when a module is so big that its source files
are divided into sub-directories.
In this case, there is no Makefile in the foo/bar/ directory, yet
the single target descends into foo/bar/, then fails due to the
missing Makefile. You can still do 'make foo/bar/' for partial
building, but cannot do 'make foo/bar/baz.s'. I believe the single
target '%.s' is a useful feature for inspecting the compiler output.
Some modules work around this issue by putting an empty Makefile
in every sub-directory.
This commit fixes those problems by making the single target build
descend in the same way as the normal build does.
Another change is the single target build will observe the CONFIG
options. Previously, it allowed users to build the foo.o even when
the corresponding CONFIG_FOO is disabled:
obj-$(CONFIG_FOO) += foo.o
In the new behavior, the single target build will just fail and show
"No rule to make target ..." (or "Nothing to be done for ..." if the
stale object already exists, but cannot be updated).
The disadvantage of this commit is the build speed. Now that the
single target build visits every directory and parses lots of
Makefiles, it is slower than before. (But, I hope it will not be
too slow.)
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2019-08-14 18:19:18 +03:00
single-targets := %.a %.i %.ko %.lds %.ll %.lst %.mod %.o %.s %.symtypes %/
2017-10-04 06:56:06 +03:00
2019-08-10 18:53:03 +03:00
config-build :=
mixed-build :=
need-config := 1
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need-compiler := 1
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may-sync-config := 1
kbuild: make single targets work more correctly
Currently, the single target build directly descends into the directory
of the target. For example,
$ make foo/bar/baz.o
... directly descends into foo/bar/.
On the other hand, the normal build usually descends one directory at
a time, i.e. descends into foo/, and then foo/bar/.
This difference causes some problems.
[1] miss subdir-asflags-y, subdir-ccflags-y in upper Makefiles
The options in subdir-{as,cc}flags-y take effect in the current
and its sub-directories. In other words, they are inherited
downward. In the example above, the single target will miss
subdir-{as,cc}flags-y if they are defined in foo/Makefile.
[2] could be built in a different directory
As Documentation/kbuild/modules.rst section 4.3 says, Kbuild can
handle files that are spread over several sub-directories.
The build rule of foo/bar/baz.o may not necessarily be specified in
foo/bar/Makefile. It might be specifies in foo/Makefile as follows:
[foo/Makefile]
obj-y := bar/baz.o
This often happens when a module is so big that its source files
are divided into sub-directories.
In this case, there is no Makefile in the foo/bar/ directory, yet
the single target descends into foo/bar/, then fails due to the
missing Makefile. You can still do 'make foo/bar/' for partial
building, but cannot do 'make foo/bar/baz.s'. I believe the single
target '%.s' is a useful feature for inspecting the compiler output.
Some modules work around this issue by putting an empty Makefile
in every sub-directory.
This commit fixes those problems by making the single target build
descend in the same way as the normal build does.
Another change is the single target build will observe the CONFIG
options. Previously, it allowed users to build the foo.o even when
the corresponding CONFIG_FOO is disabled:
obj-$(CONFIG_FOO) += foo.o
In the new behavior, the single target build will just fail and show
"No rule to make target ..." (or "Nothing to be done for ..." if the
stale object already exists, but cannot be updated).
The disadvantage of this commit is the build speed. Now that the
single target build visits every directory and parses lots of
Makefiles, it is slower than before. (But, I hope it will not be
too slow.)
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2019-08-14 18:19:18 +03:00
single-build :=
2017-10-04 06:56:06 +03:00
i f n e q ( $( filter $ ( no -dot -config -targets ) , $ ( MAKECMDGOALS ) ) , )
ifeq ( $( filter-out $( no-dot-config-targets) , $( MAKECMDGOALS) ) ,)
2019-08-10 18:53:03 +03:00
need-config :=
2017-10-04 06:56:06 +03:00
endif
e n d i f
2021-02-28 09:10:28 +03:00
i f n e q ( $( filter $ ( no -compiler -targets ) , $ ( MAKECMDGOALS ) ) , )
ifeq ( $( filter-out $( no-compiler-targets) , $( MAKECMDGOALS) ) ,)
need-compiler :=
endif
e n d i f
kbuild: do not update config when running install targets
"make syncconfig" is automatically invoked when any of the following
happens:
- .config is updated
- any of Kconfig files is updated
- any of environment variables referenced in Kconfig is changed
Then, it updates configuration files such as include/config/auto.conf
include/generated/autoconf.h, etc.
Even install targets (install, modules_install, etc.) are no exception.
However, they should never ever modify the source tree. Install
targets are often run with root privileges. Once those configuration
files are owned by root, "make mrproper" would end up with permission
error.
Install targets should just copy things blindly. They should not care
whether the configuration is up-to-date or not. This makes more sense
because we are interested in the configuration that was used in the
previous kernel building.
This issue has existed since before, but rarely happened. I expect
more chance where people are hit by this; with the new Kconfig syntax
extension, the .config now contains the compiler information. If you
cross-compile the kernel with CROSS_COMPILE, but forget to pass it
for "make install", you meet "any of environment variables referenced
in Kconfig is changed" because $(CC) is referenced in Kconfig.
Another scenario is the compiler upgrade before the installation.
Install targets need the configuration. "make modules_install" refer
to CONFIG_MODULES etc. "make dtbs_install" also needs CONFIG_ARCH_*
to decide which dtb files to install. However, the auto-update of
the configuration files should be avoided. We already do this for
external modules.
Now, Make targets are categorized into 3 groups:
[1] Do not need the kernel configuration at all
help, coccicheck, headers_install etc.
[2] Need the latest kernel configuration
If new config options are added, Kconfig will show prompt to
ask user's selection.
Build targets such as vmlinux, in-kernel modules are the cases.
[3] Need the kernel configuration, but do not want to update it
Install targets except headers_install, and external modules
are the cases.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2018-07-20 10:46:34 +03:00
i f n e q ( $( filter $ ( no -sync -config -targets ) , $ ( MAKECMDGOALS ) ) , )
ifeq ( $( filter-out $( no-sync-config-targets) , $( MAKECMDGOALS) ) ,)
2019-08-10 18:53:03 +03:00
may-sync-config :=
kbuild: do not update config when running install targets
"make syncconfig" is automatically invoked when any of the following
happens:
- .config is updated
- any of Kconfig files is updated
- any of environment variables referenced in Kconfig is changed
Then, it updates configuration files such as include/config/auto.conf
include/generated/autoconf.h, etc.
Even install targets (install, modules_install, etc.) are no exception.
However, they should never ever modify the source tree. Install
targets are often run with root privileges. Once those configuration
files are owned by root, "make mrproper" would end up with permission
error.
Install targets should just copy things blindly. They should not care
whether the configuration is up-to-date or not. This makes more sense
because we are interested in the configuration that was used in the
previous kernel building.
This issue has existed since before, but rarely happened. I expect
more chance where people are hit by this; with the new Kconfig syntax
extension, the .config now contains the compiler information. If you
cross-compile the kernel with CROSS_COMPILE, but forget to pass it
for "make install", you meet "any of environment variables referenced
in Kconfig is changed" because $(CC) is referenced in Kconfig.
Another scenario is the compiler upgrade before the installation.
Install targets need the configuration. "make modules_install" refer
to CONFIG_MODULES etc. "make dtbs_install" also needs CONFIG_ARCH_*
to decide which dtb files to install. However, the auto-update of
the configuration files should be avoided. We already do this for
external modules.
Now, Make targets are categorized into 3 groups:
[1] Do not need the kernel configuration at all
help, coccicheck, headers_install etc.
[2] Need the latest kernel configuration
If new config options are added, Kconfig will show prompt to
ask user's selection.
Build targets such as vmlinux, in-kernel modules are the cases.
[3] Need the kernel configuration, but do not want to update it
Install targets except headers_install, and external modules
are the cases.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2018-07-20 10:46:34 +03:00
endif
e n d i f
i f n e q ( $( KBUILD_EXTMOD ) , )
2019-08-10 18:53:03 +03:00
may-sync-config :=
kbuild: do not update config when running install targets
"make syncconfig" is automatically invoked when any of the following
happens:
- .config is updated
- any of Kconfig files is updated
- any of environment variables referenced in Kconfig is changed
Then, it updates configuration files such as include/config/auto.conf
include/generated/autoconf.h, etc.
Even install targets (install, modules_install, etc.) are no exception.
However, they should never ever modify the source tree. Install
targets are often run with root privileges. Once those configuration
files are owned by root, "make mrproper" would end up with permission
error.
Install targets should just copy things blindly. They should not care
whether the configuration is up-to-date or not. This makes more sense
because we are interested in the configuration that was used in the
previous kernel building.
This issue has existed since before, but rarely happened. I expect
more chance where people are hit by this; with the new Kconfig syntax
extension, the .config now contains the compiler information. If you
cross-compile the kernel with CROSS_COMPILE, but forget to pass it
for "make install", you meet "any of environment variables referenced
in Kconfig is changed" because $(CC) is referenced in Kconfig.
Another scenario is the compiler upgrade before the installation.
Install targets need the configuration. "make modules_install" refer
to CONFIG_MODULES etc. "make dtbs_install" also needs CONFIG_ARCH_*
to decide which dtb files to install. However, the auto-update of
the configuration files should be avoided. We already do this for
external modules.
Now, Make targets are categorized into 3 groups:
[1] Do not need the kernel configuration at all
help, coccicheck, headers_install etc.
[2] Need the latest kernel configuration
If new config options are added, Kconfig will show prompt to
ask user's selection.
Build targets such as vmlinux, in-kernel modules are the cases.
[3] Need the kernel configuration, but do not want to update it
Install targets except headers_install, and external modules
are the cases.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2018-07-20 10:46:34 +03:00
e n d i f
2017-10-04 06:56:06 +03:00
i f e q ( $( KBUILD_EXTMOD ) , )
2020-08-12 17:49:23 +03:00
ifneq ( $( filter %config,$( MAKECMDGOALS) ) ,)
2019-08-10 18:53:03 +03:00
config-build := 1
2017-10-04 06:56:06 +03:00
ifneq ( $( words $( MAKECMDGOALS) ) ,1)
2019-08-10 18:53:03 +03:00
mixed-build := 1
2017-10-04 06:56:06 +03:00
endif
endif
e n d i f
2018-02-11 11:40:29 +03:00
kbuild: make single targets work more correctly
Currently, the single target build directly descends into the directory
of the target. For example,
$ make foo/bar/baz.o
... directly descends into foo/bar/.
On the other hand, the normal build usually descends one directory at
a time, i.e. descends into foo/, and then foo/bar/.
This difference causes some problems.
[1] miss subdir-asflags-y, subdir-ccflags-y in upper Makefiles
The options in subdir-{as,cc}flags-y take effect in the current
and its sub-directories. In other words, they are inherited
downward. In the example above, the single target will miss
subdir-{as,cc}flags-y if they are defined in foo/Makefile.
[2] could be built in a different directory
As Documentation/kbuild/modules.rst section 4.3 says, Kbuild can
handle files that are spread over several sub-directories.
The build rule of foo/bar/baz.o may not necessarily be specified in
foo/bar/Makefile. It might be specifies in foo/Makefile as follows:
[foo/Makefile]
obj-y := bar/baz.o
This often happens when a module is so big that its source files
are divided into sub-directories.
In this case, there is no Makefile in the foo/bar/ directory, yet
the single target descends into foo/bar/, then fails due to the
missing Makefile. You can still do 'make foo/bar/' for partial
building, but cannot do 'make foo/bar/baz.s'. I believe the single
target '%.s' is a useful feature for inspecting the compiler output.
Some modules work around this issue by putting an empty Makefile
in every sub-directory.
This commit fixes those problems by making the single target build
descend in the same way as the normal build does.
Another change is the single target build will observe the CONFIG
options. Previously, it allowed users to build the foo.o even when
the corresponding CONFIG_FOO is disabled:
obj-$(CONFIG_FOO) += foo.o
In the new behavior, the single target build will just fail and show
"No rule to make target ..." (or "Nothing to be done for ..." if the
stale object already exists, but cannot be updated).
The disadvantage of this commit is the build speed. Now that the
single target build visits every directory and parses lots of
Makefiles, it is slower than before. (But, I hope it will not be
too slow.)
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2019-08-14 18:19:18 +03:00
# We cannot build single targets and the others at the same time
i f n e q ( $( filter $ ( single -targets ) , $ ( MAKECMDGOALS ) ) , )
single-build := 1
ifneq ( $( filter-out $( single-targets) , $( MAKECMDGOALS) ) ,)
mixed-build := 1
endif
e n d i f
2018-02-11 11:40:29 +03:00
# For "make -j clean all", "make -j mrproper defconfig all", etc.
i f n e q ( $( filter $ ( clean -targets ) ,$ ( MAKECMDGOALS ) ) , )
ifneq ( $( filter-out $( clean-targets) ,$( MAKECMDGOALS) ) ,)
2019-08-10 18:53:03 +03:00
mixed-build := 1
2018-02-11 11:40:29 +03:00
endif
e n d i f
2017-10-04 06:56:06 +03:00
# install and modules_install need also be processed one by one
i f n e q ( $( filter install ,$ ( MAKECMDGOALS ) ) , )
ifneq ( $( filter modules_install,$( MAKECMDGOALS) ) ,)
2019-08-10 18:53:03 +03:00
mixed-build := 1
2017-10-04 06:56:06 +03:00
endif
e n d i f
2019-08-10 18:53:03 +03:00
i f d e f m i x e d - b u i l d
2017-10-04 06:56:06 +03:00
# ===========================================================================
# We're called with mixed targets (*config and build targets).
# Handle them one by one.
PHONY += $( MAKECMDGOALS) __build_one_by_one
2020-05-11 06:50:13 +03:00
$(MAKECMDGOALS) : __build_one_by_one
2017-10-04 06:56:06 +03:00
@:
__build_one_by_one :
$( Q) set -e; \
for i in $( MAKECMDGOALS) ; do \
$( MAKE) -f $( srctree) /Makefile $$ i; \
done
2019-08-10 18:53:03 +03:00
e l s e # !mixed-build
2017-10-04 06:56:06 +03:00
2021-02-28 09:10:26 +03:00
i n c l u d e $( srctree ) / s c r i p t s / K b u i l d . i n c l u d e
2017-10-04 06:56:06 +03:00
# Read KERNELRELEASE from include/config/kernel.release (if it exists)
KERNELRELEASE = $( shell cat include/config/kernel.release 2> /dev/null)
KERNELVERSION = $( VERSION) $( if $( PATCHLEVEL) ,.$( PATCHLEVEL) $( if $( SUBLEVEL) ,.$( SUBLEVEL) ) ) $( EXTRAVERSION)
export VERSION PATCHLEVEL SUBLEVEL KERNELRELEASE KERNELVERSION
2021-02-28 09:10:26 +03:00
i n c l u d e $( srctree ) / s c r i p t s / s u b a r c h . i n c l u d e
2005-04-17 02:20:36 +04:00
# Cross compiling and selecting different set of gcc/bin-utils
# ---------------------------------------------------------------------------
#
# When performing cross compilation for other architectures ARCH shall be set
# to the target architecture. (See arch/* for the possibilities).
# ARCH can be set during invocation of make:
# make ARCH=ia64
# Another way is to have ARCH set in the environment.
# The default ARCH is the host where make is executed.
# CROSS_COMPILE specify the prefix used for all executables used
# during compilation. Only gcc and related bin-utils executables
# are prefixed with $(CROSS_COMPILE).
# CROSS_COMPILE can be set on the command line
# make CROSS_COMPILE=ia64-linux-
# Alternatively CROSS_COMPILE can be set in the environment.
# Default value for CROSS_COMPILE is not to prefix executables
# Note: Some architectures assign CROSS_COMPILE in their arch/*/Makefile
2009-10-12 01:22:58 +04:00
ARCH ?= $( SUBARCH)
2005-04-17 02:20:36 +04:00
# Architecture as present in compile.h
2007-10-11 13:11:36 +04:00
UTS_MACHINE := $( ARCH)
SRCARCH := $( ARCH)
2005-04-17 02:20:36 +04:00
2007-11-12 22:14:19 +03:00
# Additional ARCH settings for x86
i f e q ( $( ARCH ) , i 3 8 6 )
SRCARCH := x86
e n d i f
i f e q ( $( ARCH ) , x 8 6 _ 6 4 )
SRCARCH := x86
e n d i f
2007-10-25 21:42:04 +04:00
2008-12-03 10:17:12 +03:00
# Additional ARCH settings for sparc
2010-10-25 09:48:23 +04:00
i f e q ( $( ARCH ) , s p a r c 3 2 )
SRCARCH := sparc
e n d i f
2008-07-28 01:00:59 +04:00
i f e q ( $( ARCH ) , s p a r c 6 4 )
2008-12-03 10:17:12 +03:00
SRCARCH := sparc
2008-07-28 01:00:59 +04:00
e n d i f
2008-06-21 02:24:17 +04:00
2021-06-10 05:03:31 +03:00
# Additional ARCH settings for parisc
i f e q ( $( ARCH ) , p a r i s c 6 4 )
SRCARCH := parisc
e n d i f
kconfig: use /boot/config-* etc. as DEFCONFIG_LIST only for native build
When the .config file is missing, 'make config', 'make menuconfig', etc.
uses a file listed in DEFCONFIG_LIST, if found, as base configuration.
Ususally, /boot/config-$(uname -r) exists, and is used as default.
However, when you are cross-compiling the kernel, it does not make
sense to use /boot/config-* on the build host. It should default to
arch/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG).
UML previously did not use DEFCONFIG_LIST at all, but it should be
able to use arch/um/configs/$(KBUILD_DEFCONFIG) as a base config file.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-04-10 17:31:58 +03:00
export cross_compiling :=
i f n e q ( $( SRCARCH ) , $( SUBARCH ) )
cross_compiling := 1
e n d i f
2006-06-09 09:12:51 +04:00
KCONFIG_CONFIG ?= .config
2010-12-14 19:39:44 +03:00
export KCONFIG_CONFIG
2006-06-09 09:12:51 +04:00
2005-04-17 02:20:36 +04:00
# SHELL used by kbuild
2019-08-25 16:28:37 +03:00
CONFIG_SHELL := sh
2005-04-17 02:20:36 +04:00
2018-07-12 13:38:36 +03:00
HOST_LFS_CFLAGS := $( shell getconf LFS_CFLAGS 2>/dev/null)
HOST_LFS_LDFLAGS := $( shell getconf LFS_LDFLAGS 2>/dev/null)
HOST_LFS_LIBS := $( shell getconf LFS_LIBS 2>/dev/null)
2017-07-09 21:02:36 +03:00
2020-04-08 04:36:23 +03:00
i f n e q ( $( LLVM ) , )
HOSTCC = clang
HOSTCXX = clang++
e l s e
HOSTCC = gcc
HOSTCXX = g++
e n d i f
kbuild: add infrastructure to build userspace programs
Kbuild supports the infrastructure to build host programs, but there
was no support to build userspace programs for the target architecture
(i.e. the same architecture as the kernel).
Sam Ravnborg worked on this in 2014 (https://lkml.org/lkml/2014/7/13/154),
but it was not merged. One problem at that time was, there was no good way
to know whether $(CC) can link standalone programs. In fact, pre-built
kernel.org toolchains [1] are often used for building the kernel, but they
do not provide libc.
Now, we can handle this cleanly because the compiler capability is
evaluated at the Kconfig time. If $(CC) cannot link standalone programs,
the relevant options are hidden by 'depends on CC_CAN_LINK'.
The implementation just mimics scripts/Makefile.host
The userspace programs are compiled with the same flags as the host
programs. In addition, it uses -m32 or -m64 if it is found in
$(KBUILD_CFLAGS).
This new syntax has two usecases.
- Sample programs
Several userspace programs under samples/ include UAPI headers
installed in usr/include. Most of them were previously built for
the host architecture just to use the 'hostprogs' syntax.
However, 'make headers' always works for the target architecture.
This caused the arch mismatch in cross-compiling. To fix this
distortion, sample code should be built for the target architecture.
- Bpfilter
net/bpfilter/Makefile compiles bpfilter_umh as the user mode helper,
and embeds it into the kernel. Currently, it overrides HOSTCC with
CC to use the 'hostprogs' syntax. This hack should go away.
[1]: https://mirrors.edge.kernel.org/pub/tools/crosstool/
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
2020-04-29 06:45:14 +03:00
export KBUILD_USERCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \
-O2 -fomit-frame-pointer -std= gnu89
export KBUILD_USERLDFLAGS :=
KBUILD_HOSTCFLAGS := $( KBUILD_USERCFLAGS) $( HOST_LFS_CFLAGS) $( HOSTCFLAGS)
kbuild: add -Wall to KBUILD_HOSTCXXFLAGS
Add -Wall to catch more warnings for C++ host programs.
When I submitted the previous version, the 0-day bot reported
-Wc++11-compat warnings for old GCC:
HOSTCXX -fPIC scripts/gcc-plugins/latent_entropy_plugin.o
In file included from /usr/lib/gcc/x86_64-linux-gnu/4.8/plugin/include/tm.h:28:0,
from scripts/gcc-plugins/gcc-common.h:15,
from scripts/gcc-plugins/latent_entropy_plugin.c:78:
/usr/lib/gcc/x86_64-linux-gnu/4.8/plugin/include/config/elfos.h:102:21: warning: C++11 requires a space between string literal and macro [-Wc++11-compat]
fprintf ((FILE), "%s"HOST_WIDE_INT_PRINT_UNSIGNED"\n",\
^
/usr/lib/gcc/x86_64-linux-gnu/4.8/plugin/include/config/elfos.h:170:24: warning: C++11 requires a space between string literal and macro [-Wc++11-compat]
fprintf ((FILE), ","HOST_WIDE_INT_PRINT_UNSIGNED",%u\n", \
^
In file included from /usr/lib/gcc/x86_64-linux-gnu/4.8/plugin/include/tm.h:42:0,
from scripts/gcc-plugins/gcc-common.h:15,
from scripts/gcc-plugins/latent_entropy_plugin.c:78:
/usr/lib/gcc/x86_64-linux-gnu/4.8/plugin/include/defaults.h:126:24: warning: C++11 requires a space between string literal and macro [-Wc++11-compat]
fprintf ((FILE), ","HOST_WIDE_INT_PRINT_UNSIGNED",%u\n", \
^
The source of the warnings is in the plugin headers, so we have no
control of it. I just suppressed them by adding -Wno-c++11-compat to
scripts/gcc-plugins/Makefile.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
2020-03-25 06:14:32 +03:00
KBUILD_HOSTCXXFLAGS := -Wall -O2 $( HOST_LFS_CFLAGS) $( HOSTCXXFLAGS)
2018-07-10 03:46:02 +03:00
KBUILD_HOSTLDFLAGS := $( HOST_LFS_LDFLAGS) $( HOSTLDFLAGS)
KBUILD_HOSTLDLIBS := $( HOST_LFS_LIBS) $( HOSTLDLIBS)
2005-04-17 02:20:36 +04:00
# Make variables (CC, etc...)
CPP = $( CC) -E
2020-04-08 04:36:23 +03:00
i f n e q ( $( LLVM ) , )
CC = clang
LD = ld.lld
AR = llvm-ar
NM = llvm-nm
OBJCOPY = llvm-objcopy
OBJDUMP = llvm-objdump
READELF = llvm-readelf
STRIP = llvm-strip
e l s e
CC = $( CROSS_COMPILE) gcc
LD = $( CROSS_COMPILE) ld
2005-04-17 02:20:36 +04:00
AR = $( CROSS_COMPILE) ar
NM = $( CROSS_COMPILE) nm
OBJCOPY = $( CROSS_COMPILE) objcopy
OBJDUMP = $( CROSS_COMPILE) objdump
2019-12-05 01:54:41 +03:00
READELF = $( CROSS_COMPILE) readelf
2020-04-08 04:36:23 +03:00
STRIP = $( CROSS_COMPILE) strip
e n d i f
kbuild: add ability to generate BTF type info for vmlinux
This patch adds new config option to trigger generation of BTF type
information from DWARF debuginfo for vmlinux and kernel modules through
pahole, which in turn relies on libbpf for btf_dedup() algorithm.
The intent is to record compact type information of all types used
inside kernel, including all the structs/unions/typedefs/etc. This
enables BPF's compile-once-run-everywhere ([0]) approach, in which
tracing programs that are inspecting kernel's internal data (e.g.,
struct task_struct) can be compiled on a system running some kernel
version, but would be possible to run on other kernel versions (and
configurations) without recompilation, even if the layout of structs
changed and/or some of the fields were added, removed, or renamed.
This is only possible if BPF loader can get kernel type info to adjust
all the offsets correctly. This patch is a first time in this direction,
making sure that BTF type info is part of Linux kernel image in
non-loadable ELF section.
BTF deduplication ([1]) algorithm typically provides 100x savings
compared to DWARF data, so resulting .BTF section is not big as is
typically about 2MB in size.
[0] http://vger.kernel.org/lpc-bpf2018.html#session-2
[1] https://facebookmicrosites.github.io/bpf/blog/2018/11/14/btf-enhancement.html
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Yonghong Song <yhs@fb.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2019-04-02 19:49:50 +03:00
PAHOLE = pahole
2020-07-12 00:53:24 +03:00
RESOLVE_BTFIDS = $( objtree) /tools/bpf/resolve_btfids/resolve_btfids
2017-12-09 19:02:28 +03:00
LEX = flex
YACC = bison
2005-04-17 02:20:36 +04:00
AWK = awk
2009-07-20 23:37:11 +04:00
INSTALLKERNEL := installkernel
2020-12-01 16:17:30 +03:00
DEPMOD = depmod
2005-04-17 02:20:36 +04:00
PERL = perl
kbuild: add PYTHON2 and PYTHON3 variables
The variable 'PYTHON' allows users to specify a proper executable
name in case the default 'python' does not work. However, this does
not address the case where both Python 2.x and 3.x scripts are used
in one source tree.
PEP 394 (https://www.python.org/dev/peps/pep-0394/) provides a
convention for Python scripts portability. Here is a quotation:
In order to tolerate differences across platforms, all new code
that needs to invoke the Python interpreter should not specify
'python', but rather should specify either 'python2' or 'python3'.
This distinction should be made in shebangs, when invoking from a
shell script, when invoking via the system() call, or when invoking
in any other context.
One exception to this is scripts that are deliberately written to
be source compatible with both Python 2.x and 3.x. Such scripts may
continue to use python on their shebang line without affecting their
portability.
To meet this requirement, this commit adds new variables 'PYTHON2'
and 'PYTHON3'.
arch/ia64/scripts/unwcheck.py is the only script that has ever used
$(PYTHON). Recent commit bd5edbe67794 ("ia64: convert unwcheck.py to
python3") converted it to be compatible with both Python 2.x and 3.x,
so this is the exceptional case where the use of 'python' is allowed.
So, I did not touch arch/ia64/Makefile.
tools/perf/Makefile.config sets PYTHON and PYTHON2 by itself, so it
is not affected by this commit.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2018-03-13 12:12:02 +03:00
PYTHON3 = python3
2005-04-17 02:20:36 +04:00
CHECK = sparse
2019-08-25 16:28:37 +03:00
BASH = bash
kbuild: fix broken builds because of GZIP,BZIP2,LZOP variables
Redefine GZIP, BZIP2, LZOP variables as KGZIP, KBZIP2, KLZOP resp.
GZIP, BZIP2, LZOP env variables are reserved by the tools. The original
attempt to redefine them internally doesn't work in makefiles/scripts
intercall scenarios, e.g., "make GZIP=gzip bindeb-pkg" and results in
broken builds. There can be other broken build commands because of this,
so the universal solution is to use non-reserved env variables for the
compression tools.
Fixes: 8dfb61dcbace ("kbuild: add variables for compression tools")
Signed-off-by: Denis Efremov <efremov@linux.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2020-06-08 12:59:44 +03:00
KGZIP = gzip
KBZIP2 = bzip2
KLZOP = lzop
kbuild: add variables for compression tools
Allow user to use alternative implementations of compression tools,
such as pigz, pbzip2, pxz. For example, multi-threaded tools to
speed up the build:
$ make GZIP=pigz BZIP2=pbzip2
Variables _GZIP, _BZIP2, _LZOP are used internally because original env
vars are reserved by the tools. The use of GZIP in gzip tool is obsolete
since 2015. However, alternative implementations (e.g., pigz) still rely
on it. BZIP2, BZIP, LZOP vars are not obsolescent.
The credit goes to @grsecurity.
As a sidenote, for multi-threaded lzma, xz compression one can use:
$ export XZ_OPT="--threads=0"
Signed-off-by: Denis Efremov <efremov@linux.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2020-06-05 10:39:55 +03:00
LZMA = lzma
LZ4 = lz4c
XZ = xz
2020-07-30 22:08:36 +03:00
ZSTD = zstd
kbuild: add variables for compression tools
Allow user to use alternative implementations of compression tools,
such as pigz, pbzip2, pxz. For example, multi-threaded tools to
speed up the build:
$ make GZIP=pigz BZIP2=pbzip2
Variables _GZIP, _BZIP2, _LZOP are used internally because original env
vars are reserved by the tools. The use of GZIP in gzip tool is obsolete
since 2015. However, alternative implementations (e.g., pigz) still rely
on it. BZIP2, BZIP, LZOP vars are not obsolescent.
The credit goes to @grsecurity.
As a sidenote, for multi-threaded lzma, xz compression one can use:
$ export XZ_OPT="--threads=0"
Signed-off-by: Denis Efremov <efremov@linux.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2020-06-05 10:39:55 +03:00
2008-12-28 00:38:44 +03:00
CHECKFLAGS := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ \
2018-02-16 00:07:50 +03:00
-Wbitwise -Wno-return-void -Wno-unknown-attribute $( CF)
2019-03-15 02:41:59 +03:00
NOSTDINC_FLAGS :=
kbuild: allow assignment to {A,C,LD}FLAGS_MODULE on the command line
It is now possible to assign options to AS, CC and LD
on the command line - which is only used when building modules.
{A,C,LD}FLAGS_MODULE was all used both in the top-level Makefile
in the arch makefiles, thus users had no way to specify
additional options to AS, CC, LD when building modules
without overriding the original value.
Introduce a new set of variables KBUILD_{A,C,LD}FLAGS_MODULE
that is used by arch specific files and free up
{A,C,LD}FLAGS_MODULE so they can be assigned on
the command line.
All arch Makefiles that used the old variables has been updated.
Note: Previously we had a MODFLAGS variable for both
AS and CC. But in favour of consistency this was dropped.
So in some cases arch Makefile has one assignmnet replaced by
two assignmnets.
Note2: MODFLAGS was not documented and is dropped
without any notice. I do not expect much/any breakage
from this.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Chen Liqin <liqin.chen@sunplusct.com>
Acked-by: Mike Frysinger <vapier@gentoo.org> [blackfin]
Acked-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com> [avr32]
Signed-off-by: Michal Marek <mmarek@suse.cz>
2010-07-28 19:33:09 +04:00
CFLAGS_MODULE =
AFLAGS_MODULE =
LDFLAGS_MODULE =
2005-04-17 02:20:36 +04:00
CFLAGS_KERNEL =
AFLAGS_KERNEL =
2016-06-07 12:57:02 +03:00
LDFLAGS_vmlinux =
2005-04-17 02:20:36 +04:00
2012-10-02 21:01:26 +04:00
# Use USERINCLUDE when you must reference the UAPI directories only.
USERINCLUDE := \
2017-10-04 06:56:04 +03:00
-I$( srctree) /arch/$( SRCARCH) /include/uapi \
-I$( objtree) /arch/$( SRCARCH) /include/generated/uapi \
2012-10-02 21:01:26 +04:00
-I$( srctree) /include/uapi \
2016-06-15 18:45:45 +03:00
-I$( objtree) /include/generated/uapi \
2021-03-04 14:37:08 +03:00
-include $( srctree) /include/linux/compiler-version.h \
2012-10-02 21:01:26 +04:00
-include $( srctree) /include/linux/kconfig.h
2005-04-17 02:20:36 +04:00
# Use LINUXINCLUDE when you must reference the include/ directory.
# Needed to be compatible with the O= option
2012-10-02 21:01:26 +04:00
LINUXINCLUDE := \
2017-10-04 06:56:04 +03:00
-I$( srctree) /arch/$( SRCARCH) /include \
-I$( objtree) /arch/$( SRCARCH) /include/generated \
2019-07-06 06:07:12 +03:00
$( if $( building_out_of_srctree) ,-I$( srctree) /include) \
2017-06-06 10:15:28 +03:00
-I$( objtree) /include \
$( USERINCLUDE)
2005-04-17 02:20:36 +04:00
2018-12-14 11:05:37 +03:00
KBUILD_AFLAGS := -D__ASSEMBLY__ -fno-PIE
2018-12-14 11:05:38 +03:00
KBUILD_CFLAGS := -Wall -Wundef -Werror= strict-prototypes -Wno-trigraphs \
2018-12-14 11:05:37 +03:00
-fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE \
2019-03-04 15:55:20 +03:00
-Werror= implicit-function-declaration -Werror= implicit-int \
2020-10-11 21:54:31 +03:00
-Werror= return -type -Wno-format-security \
kbuild: do not call cc-option before KBUILD_CFLAGS initialization
Some $(call cc-option,...) are invoked very early, even before
KBUILD_CFLAGS, etc. are initialized.
The returned string from $(call cc-option,...) depends on
KBUILD_CPPFLAGS, KBUILD_CFLAGS, and GCC_PLUGINS_CFLAGS.
Since they are exported, they are not empty when the top Makefile
is recursively invoked.
The recursion occurs in several places. For example, the top
Makefile invokes itself for silentoldconfig. "make tinyconfig",
"make rpm-pkg" are the cases, too.
In those cases, the second call of cc-option from the same line
runs a different shell command due to non-pristine KBUILD_CFLAGS.
To get the same result all the time, KBUILD_* and GCC_PLUGINS_CFLAGS
must be initialized before any call of cc-option. This avoids
garbage data in the .cache.mk file.
Move all calls of cc-option below the config targets because target
compiler flags are unnecessary for Kconfig.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
2017-10-12 12:22:25 +03:00
-std= gnu89
KBUILD_CPPFLAGS := -D__KERNEL__
2010-07-28 21:11:27 +04:00
KBUILD_AFLAGS_KERNEL :=
KBUILD_CFLAGS_KERNEL :=
kbuild: allow assignment to {A,C,LD}FLAGS_MODULE on the command line
It is now possible to assign options to AS, CC and LD
on the command line - which is only used when building modules.
{A,C,LD}FLAGS_MODULE was all used both in the top-level Makefile
in the arch makefiles, thus users had no way to specify
additional options to AS, CC, LD when building modules
without overriding the original value.
Introduce a new set of variables KBUILD_{A,C,LD}FLAGS_MODULE
that is used by arch specific files and free up
{A,C,LD}FLAGS_MODULE so they can be assigned on
the command line.
All arch Makefiles that used the old variables has been updated.
Note: Previously we had a MODFLAGS variable for both
AS and CC. But in favour of consistency this was dropped.
So in some cases arch Makefile has one assignmnet replaced by
two assignmnets.
Note2: MODFLAGS was not documented and is dropped
without any notice. I do not expect much/any breakage
from this.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Chen Liqin <liqin.chen@sunplusct.com>
Acked-by: Mike Frysinger <vapier@gentoo.org> [blackfin]
Acked-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com> [avr32]
Signed-off-by: Michal Marek <mmarek@suse.cz>
2010-07-28 19:33:09 +04:00
KBUILD_AFLAGS_MODULE := -DMODULE
KBUILD_CFLAGS_MODULE := -DMODULE
2019-08-14 19:06:22 +03:00
KBUILD_LDFLAGS_MODULE :=
2018-08-24 02:20:39 +03:00
KBUILD_LDFLAGS :=
2019-07-29 12:15:17 +03:00
CLANG_FLAGS :=
2005-04-17 02:20:36 +04:00
2020-03-26 08:57:18 +03:00
export ARCH SRCARCH CONFIG_SHELL BASH HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE LD CC
2020-10-23 14:57:32 +03:00
export CPP AR NM STRIP OBJCOPY OBJDUMP READELF PAHOLE RESOLVE_BTFIDS LEX YACC AWK INSTALLKERNEL
2021-02-01 04:00:24 +03:00
export PERL PYTHON3 CHECK CHECKFLAGS MAKE UTS_MACHINE HOSTCXX
2020-07-30 22:08:36 +03:00
export KGZIP KBZIP2 KLZOP LZMA LZ4 XZ ZSTD
2019-01-21 15:54:39 +03:00
export KBUILD_HOSTCXXFLAGS KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS LDFLAGS_MODULE
2005-04-17 02:20:36 +04:00
2018-08-24 02:20:39 +03:00
export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS KBUILD_LDFLAGS
2018-02-07 02:36:00 +03:00
export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE
2007-10-15 23:59:31 +04:00
export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE
kbuild: allow assignment to {A,C,LD}FLAGS_MODULE on the command line
It is now possible to assign options to AS, CC and LD
on the command line - which is only used when building modules.
{A,C,LD}FLAGS_MODULE was all used both in the top-level Makefile
in the arch makefiles, thus users had no way to specify
additional options to AS, CC, LD when building modules
without overriding the original value.
Introduce a new set of variables KBUILD_{A,C,LD}FLAGS_MODULE
that is used by arch specific files and free up
{A,C,LD}FLAGS_MODULE so they can be assigned on
the command line.
All arch Makefiles that used the old variables has been updated.
Note: Previously we had a MODFLAGS variable for both
AS and CC. But in favour of consistency this was dropped.
So in some cases arch Makefile has one assignmnet replaced by
two assignmnets.
Note2: MODFLAGS was not documented and is dropped
without any notice. I do not expect much/any breakage
from this.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Chen Liqin <liqin.chen@sunplusct.com>
Acked-by: Mike Frysinger <vapier@gentoo.org> [blackfin]
Acked-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com> [avr32]
Signed-off-by: Michal Marek <mmarek@suse.cz>
2010-07-28 19:33:09 +04:00
export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_LDFLAGS_MODULE
2010-07-28 21:11:27 +04:00
export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL
2005-04-17 02:20:36 +04:00
# Files to ignore in find ... statements
2014-02-06 16:51:42 +04:00
export RCS_FIND_IGNORE := \( -name SCCS -o -name BitKeeper -o -name .svn -o \
-name CVS -o -name .pc -o -name .hg -o -name .git \) \
-prune -o
2012-02-17 01:49:15 +04:00
export RCS_TAR_IGNORE := --exclude SCCS --exclude BitKeeper --exclude .svn \
--exclude CVS --exclude .pc --exclude .hg --exclude .git
2005-04-17 02:20:36 +04:00
# ===========================================================================
# Rules shared between *config targets and build targets
2017-08-02 05:31:06 +03:00
# Basic helpers built in scripts/basic/
2006-03-06 01:14:10 +03:00
PHONY += scripts_basic
2005-04-17 02:20:36 +04:00
scripts_basic :
$( Q) $( MAKE) $( build) = scripts/basic
2006-03-06 01:14:10 +03:00
PHONY += outputmakefile
2021-05-17 10:03:11 +03:00
i f d e f b u i l d i n g _ o u t _ o f _ s r c t r e e
2019-08-22 07:46:11 +03:00
# Before starting out-of-tree build, make sure the source tree is clean.
2006-05-02 14:33:20 +04:00
# outputmakefile generates a Makefile in the output directory, if using a
# separate output directory. This allows convenient use of make in the
# output directory.
2019-02-03 11:48:40 +03:00
# At the same time when output Makefile generated, generate .gitignore to
# ignore whole output directory
2021-05-17 10:03:11 +03:00
quiet_cmd_makefile = GEN Makefile
cmd_makefile = { \
echo " \# Automatically generated by $( srctree) /Makefile: don't edit " ; \
echo " include $( srctree) /Makefile " ; \
} > Makefile
2005-04-17 02:20:36 +04:00
outputmakefile :
2019-08-22 07:46:11 +03:00
$( Q) if [ -f $( srctree) /.config -o \
-d $( srctree) /include/config -o \
-d $( srctree) /arch/$( SRCARCH) /include/generated ] ; then \
echo >& 2 "***" ; \
echo >& 2 " *** The source tree is not clean, please run 'make $( if $( findstring command line, $( origin ARCH) ) , ARCH = $( ARCH) ) mrproper' " ; \
echo >& 2 " *** in $( abs_srctree) " ; \
echo >& 2 "***" ; \
false; \
fi
2009-01-10 06:56:13 +03:00
$( Q) ln -fsn $( srctree) source
2021-05-17 10:03:11 +03:00
$( call cmd,makefile)
2019-03-26 07:26:58 +03:00
$( Q) test -e .gitignore || \
{ echo "# this is build directory, ignore it" ; echo "*" ; } > .gitignore
2006-05-02 14:33:20 +04:00
e n d i f
2005-04-17 02:20:36 +04:00
2021-02-06 01:01:25 +03:00
# The expansion should be delayed until arch/$(SRCARCH)/Makefile is included.
# Some architectures define CROSS_COMPILE in arch/$(SRCARCH)/Makefile.
# CC_VERSION_TEXT is referenced from Kconfig (so it needs export),
# and from include/config/auto.conf.cmd to detect the compiler upgrade.
2021-08-01 05:53:46 +03:00
CC_VERSION_TEXT = $( subst $( pound) ,,$( shell LC_ALL = C $( CC) --version 2>/dev/null | head -n 1) )
2021-02-06 01:01:25 +03:00
i f n e q ( $( findstring clang ,$ ( CC_VERSION_TEXT ) ) , )
2021-08-02 21:39:08 +03:00
i n c l u d e $( srctree ) / s c r i p t s / M a k e f i l e . c l a n g
2017-11-07 22:46:13 +03:00
e n d i f
2021-02-28 09:10:27 +03:00
# Include this also for config targets because some architectures need
# cc-cross-prefix to determine CROSS_COMPILE.
2021-02-28 09:10:28 +03:00
i f d e f n e e d - c o m p i l e r
2021-02-28 09:10:27 +03:00
i n c l u d e $( srctree ) / s c r i p t s / M a k e f i l e . c o m p i l e r
2021-02-28 09:10:28 +03:00
e n d i f
2021-02-28 09:10:27 +03:00
2019-08-10 18:53:03 +03:00
i f d e f c o n f i g - b u i l d
2005-04-17 02:20:36 +04:00
# ===========================================================================
# *config targets only - make sure prerequisites are updated, and descend
# in scripts/kconfig to make the *config target
# Read arch specific Makefile to set KBUILD_DEFCONFIG as needed.
# KBUILD_DEFCONFIG may point out an alternative default configuration
# used for 'make defconfig'
2021-02-28 09:10:26 +03:00
i n c l u d e $( srctree ) / a r c h / $( SRCARCH ) / M a k e f i l e
kbuild: fix endless syncconfig in case arch Makefile sets CROSS_COMPILE
Commit 21c54b774744 ("kconfig: show compiler version text in the top
comment") was intended to detect the compiler upgrade, but Geert
reported a breakage on the m68k build.
The compiler upgrade is detected by the change of the environment
variable, CC_VERSION_TEXT, which contains the first line of the output
from $(CC) --version. Currently, this works well when CROSS_COMPILE
is given via the environment variable or the Make command line.
However, some architectures such as m68k can specify CROSS_COMPILE
from arch/$(SRCARCH)/Makefile as well. In this case, "make ARCH=m68k"
ends up with endless syncconfig loop.
$ make ARCH=m68k defconfig
*** Default configuration is based on 'multi_defconfig'
#
# configuration written to .config
#
$ make ARCH=m68k
scripts/kconfig/conf --syncconfig Kconfig
scripts/kconfig/conf --syncconfig Kconfig
scripts/kconfig/conf --syncconfig Kconfig
scripts/kconfig/conf --syncconfig Kconfig
Things are happening like this:
Because arch/$(SRCARCH)/Makefile is included after CC_VERSION_TEXT
is set, it contains the host compiler version in the defconfig phase.
To create or update auto.conf, the following line is triggered:
include/config/%.conf: $(KCONFIG_CONFIG) include/config/auto.conf.cmd
$(Q)$(MAKE) -f $(srctree)/Makefile syncconfig
This recurses the top Makefile after arch/$(SRCARCH)/Makefile is
included. CROSS_COMPILE is set to a m68k toolchain prefix and
exported to the recursed Make. Then, syncconfig is invoked with
the target compiler version in CC_VERSION_TEXT.
The Make will restart because auto.conf and auto.conf.cmd have been
updated. At this point, CROSS_COMPILE is reset, so CC_VERSION_TEXT
is set to the host compiler version again. Then, syncconfig is
triggered due to the change of CC_VERSION_TEXT. This loop continues
eternally.
To fix this problem, $(CC_VERSION_TEXT) must be evaluated only after
arch/$(SRCARCH)/Makefile. Setting it earlier is OK as long as it is
defined by using the '=' operator instead of ':='.
For the defconfig phase, $(CC_VERSION_TEXT) is evaluated when Kbuild
descends into scripts/kconfig/, so it contains the target compiler
version correctly.
include/config/auto.conf.cmd references $(CC_VERSION_TEXT) as well,
so it must be included after arch/$(SRCARCH)/Makefile.
Fixes: 21c54b774744 ("kconfig: show compiler version text in the top comment")
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
2018-06-08 03:21:43 +03:00
export KBUILD_DEFCONFIG KBUILD_KCONFIG CC_VERSION_TEXT
2005-04-17 02:20:36 +04:00
2019-08-22 07:46:13 +03:00
config : outputmakefile scripts_basic FORCE
2008-12-14 01:00:45 +03:00
$( Q) $( MAKE) $( build) = scripts/kconfig $@
2019-08-22 07:46:13 +03:00
%config : outputmakefile scripts_basic FORCE
2005-04-17 02:20:36 +04:00
$( Q) $( MAKE) $( build) = scripts/kconfig $@
2019-08-10 18:53:03 +03:00
e l s e #!config-build
2005-04-17 02:20:36 +04:00
# ===========================================================================
# Build targets only - this includes vmlinux, arch specific targets, clean
# targets and others. In general all targets except *config targets.
2017-10-04 06:56:06 +03:00
# If building an external module we do not care about the all: rule
2020-05-11 06:50:13 +03:00
# but instead __all depend on modules
2017-10-04 06:56:06 +03:00
PHONY += all
i f e q ( $( KBUILD_EXTMOD ) , )
2020-05-11 06:50:13 +03:00
__all : all
2017-10-04 06:56:06 +03:00
e l s e
2020-05-11 06:50:13 +03:00
__all : modules
2017-10-04 06:56:06 +03:00
e n d i f
# Decide whether to build built-in, modular, or both.
# Normally, just do built-in.
KBUILD_MODULES :=
KBUILD_BUILTIN := 1
# If we have only "make modules", don't compile built-in objects.
i f e q ( $( MAKECMDGOALS ) , m o d u l e s )
2020-05-31 11:47:06 +03:00
KBUILD_BUILTIN :=
2017-10-04 06:56:06 +03:00
e n d i f
# If we have "make <whatever> modules", compile modules
# in addition to whatever we do anyway.
# Just "make" or "make all" shall build modules as well
2020-08-22 17:56:18 +03:00
i f n e q ( $( filter all modules nsdeps %compile_commands .json clang -%,$ ( MAKECMDGOALS ) ) , )
2017-10-04 06:56:06 +03:00
KBUILD_MODULES := 1
e n d i f
i f e q ( $( MAKECMDGOALS ) , )
KBUILD_MODULES := 1
e n d i f
export KBUILD_MODULES KBUILD_BUILTIN
2019-08-10 18:53:03 +03:00
i f d e f n e e d - c o n f i g
2019-04-27 06:33:36 +03:00
i n c l u d e i n c l u d e / c o n f i g / a u t o . c o n f
e n d i f
2005-04-17 02:20:36 +04:00
i f e q ( $( KBUILD_EXTMOD ) , )
# Objects we will link into vmlinux / subdirs we need to visit
2021-05-12 10:57:25 +03:00
core-y := init/ usr/ arch/$( SRCARCH) /
2019-01-11 12:52:00 +03:00
drivers-y := drivers/ sound/
2019-04-27 06:33:36 +03:00
drivers-$(CONFIG_SAMPLES) += samples/
2021-01-26 02:16:55 +03:00
drivers-$(CONFIG_NET) += net/
drivers-y += virt/
2005-04-17 02:20:36 +04:00
libs-y := lib/
e n d i f # KBUILD_EXTMOD
kbuild: fix endless syncconfig in case arch Makefile sets CROSS_COMPILE
Commit 21c54b774744 ("kconfig: show compiler version text in the top
comment") was intended to detect the compiler upgrade, but Geert
reported a breakage on the m68k build.
The compiler upgrade is detected by the change of the environment
variable, CC_VERSION_TEXT, which contains the first line of the output
from $(CC) --version. Currently, this works well when CROSS_COMPILE
is given via the environment variable or the Make command line.
However, some architectures such as m68k can specify CROSS_COMPILE
from arch/$(SRCARCH)/Makefile as well. In this case, "make ARCH=m68k"
ends up with endless syncconfig loop.
$ make ARCH=m68k defconfig
*** Default configuration is based on 'multi_defconfig'
#
# configuration written to .config
#
$ make ARCH=m68k
scripts/kconfig/conf --syncconfig Kconfig
scripts/kconfig/conf --syncconfig Kconfig
scripts/kconfig/conf --syncconfig Kconfig
scripts/kconfig/conf --syncconfig Kconfig
Things are happening like this:
Because arch/$(SRCARCH)/Makefile is included after CC_VERSION_TEXT
is set, it contains the host compiler version in the defconfig phase.
To create or update auto.conf, the following line is triggered:
include/config/%.conf: $(KCONFIG_CONFIG) include/config/auto.conf.cmd
$(Q)$(MAKE) -f $(srctree)/Makefile syncconfig
This recurses the top Makefile after arch/$(SRCARCH)/Makefile is
included. CROSS_COMPILE is set to a m68k toolchain prefix and
exported to the recursed Make. Then, syncconfig is invoked with
the target compiler version in CC_VERSION_TEXT.
The Make will restart because auto.conf and auto.conf.cmd have been
updated. At this point, CROSS_COMPILE is reset, so CC_VERSION_TEXT
is set to the host compiler version again. Then, syncconfig is
triggered due to the change of CC_VERSION_TEXT. This loop continues
eternally.
To fix this problem, $(CC_VERSION_TEXT) must be evaluated only after
arch/$(SRCARCH)/Makefile. Setting it earlier is OK as long as it is
defined by using the '=' operator instead of ':='.
For the defconfig phase, $(CC_VERSION_TEXT) is evaluated when Kbuild
descends into scripts/kconfig/, so it contains the target compiler
version correctly.
include/config/auto.conf.cmd references $(CC_VERSION_TEXT) as well,
so it must be included after arch/$(SRCARCH)/Makefile.
Fixes: 21c54b774744 ("kconfig: show compiler version text in the top comment")
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
2018-06-08 03:21:43 +03:00
# The all: target is the default when no target is given on the
# command line.
# This allow a user to issue only 'make' to build a kernel including modules
# Defaults to vmlinux, but the arch makefile usually adds further targets
all : vmlinux
Makefile: remove stale cc-option checks
cc-option, cc-option-yn, and cc-disable-warning all invoke the compiler
during build time, and can slow down the build when these checks become
stale for our supported compilers, whose minimally supported versions
increases over time. See Documentation/process/changes.rst for the
current supported minimal versions (GCC 4.9+, clang 10.0.1+). Compiler
version support for these flags may be verified on godbolt.org.
The following flags are GCC only and supported since at least GCC 4.9.
Remove cc-option and cc-disable-warning tests.
* -fno-tree-loop-im
* -Wno-maybe-uninitialized
* -fno-reorder-blocks
* -fno-ipa-cp-clone
* -fno-partial-inlining
* -femit-struct-debug-baseonly
* -fno-inline-functions-called-once
* -fconserve-stack
The following flags are supported by all supported versions of GCC and
Clang. Remove their cc-option, cc-option-yn, and cc-disable-warning tests.
* -fno-delete-null-pointer-checks
* -fno-var-tracking
* -Wno-array-bounds
The following configs are made dependent on GCC, since they use GCC
specific flags.
* READABLE_ASM
* DEBUG_SECTION_MISMATCH
-mfentry was not supported by s390-linux-gnu-gcc until gcc-9+, add a
comment.
--param=allow-store-data-races=0 was renamed to -fno-allow-store-data-races
in the GCC 10 release; add a comment.
-Wmaybe-uninitialized (GCC specific) was being added for CONFIG_GCOV,
then again unconditionally; add it only once.
Also, base RETPOLINE_CFLAGS and RETPOLINE_VDSO_CFLAGS on CONFIC_CC_IS_*
then remove cc-option tests for Clang.
Link: https://github.com/ClangBuiltLinux/linux/issues/1436
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-08-16 23:25:01 +03:00
CFLAGS_GCOV := -fprofile-arcs -ftest-coverage
i f d e f C O N F I G _ C C _ I S _ G C C
CFLAGS_GCOV += -fno-tree-loop-im
e n d i f
2018-05-28 12:22:04 +03:00
export CFLAGS_GCOV
kbuild: fix endless syncconfig in case arch Makefile sets CROSS_COMPILE
Commit 21c54b774744 ("kconfig: show compiler version text in the top
comment") was intended to detect the compiler upgrade, but Geert
reported a breakage on the m68k build.
The compiler upgrade is detected by the change of the environment
variable, CC_VERSION_TEXT, which contains the first line of the output
from $(CC) --version. Currently, this works well when CROSS_COMPILE
is given via the environment variable or the Make command line.
However, some architectures such as m68k can specify CROSS_COMPILE
from arch/$(SRCARCH)/Makefile as well. In this case, "make ARCH=m68k"
ends up with endless syncconfig loop.
$ make ARCH=m68k defconfig
*** Default configuration is based on 'multi_defconfig'
#
# configuration written to .config
#
$ make ARCH=m68k
scripts/kconfig/conf --syncconfig Kconfig
scripts/kconfig/conf --syncconfig Kconfig
scripts/kconfig/conf --syncconfig Kconfig
scripts/kconfig/conf --syncconfig Kconfig
Things are happening like this:
Because arch/$(SRCARCH)/Makefile is included after CC_VERSION_TEXT
is set, it contains the host compiler version in the defconfig phase.
To create or update auto.conf, the following line is triggered:
include/config/%.conf: $(KCONFIG_CONFIG) include/config/auto.conf.cmd
$(Q)$(MAKE) -f $(srctree)/Makefile syncconfig
This recurses the top Makefile after arch/$(SRCARCH)/Makefile is
included. CROSS_COMPILE is set to a m68k toolchain prefix and
exported to the recursed Make. Then, syncconfig is invoked with
the target compiler version in CC_VERSION_TEXT.
The Make will restart because auto.conf and auto.conf.cmd have been
updated. At this point, CROSS_COMPILE is reset, so CC_VERSION_TEXT
is set to the host compiler version again. Then, syncconfig is
triggered due to the change of CC_VERSION_TEXT. This loop continues
eternally.
To fix this problem, $(CC_VERSION_TEXT) must be evaluated only after
arch/$(SRCARCH)/Makefile. Setting it earlier is OK as long as it is
defined by using the '=' operator instead of ':='.
For the defconfig phase, $(CC_VERSION_TEXT) is evaluated when Kbuild
descends into scripts/kconfig/, so it contains the target compiler
version correctly.
include/config/auto.conf.cmd references $(CC_VERSION_TEXT) as well,
so it must be included after arch/$(SRCARCH)/Makefile.
Fixes: 21c54b774744 ("kconfig: show compiler version text in the top comment")
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
2018-06-08 03:21:43 +03:00
tracing/Makefile: Fix handling redefinition of CC_FLAGS_FTRACE
As a Kernel developer, I make heavy use of "make targz-pkg" in order
to locally compile and remotely install my development Kernels. The
nice feature I rely on is that after a normal "make", "make targz-pkg"
only generates the tarball without having to recompile everything.
That was true until commit f28bc3c32c05 ("tracing: Handle
CC_FLAGS_FTRACE more accurately"). After it, running "make targz-pkg"
after "make" will recompile the whole Kernel tree, making my
development workflow much slower.
The Kernel is choosing to recompile everything because it claims the
command line has changed. A diff of the .cmd files show a repeated
-mfentry in one of the files. That is because "make targz-pkg" calls
"make modules_install" and the environment is already populated with
the exported variables, CC_FLAGS_FTRACE being one of them. Then,
-mfentry gets duplicated because it is not protected behind an ifndef
block, like -pg.
To complicate the problem a little bit more, architectures can define
their own version CC_FLAGS_FTRACE, so our code not only has to
consider recursive Makefiles, but also architecture overrides.
So in this patch we move CC_FLAGS_FTRACE up and unconditionally
define it to -pg. Then we let the architecture Makefiles possibly
override it, and finally append the extra options later. This ensures
the variable is always fully redefined at each invocation so recursive
Makefiles don't keep appending, and hopefully it maintains the
intended behavior on how architectures can override the defaults..
Thanks Steven Rostedt and Vasily Gorbik for the help on this
regression.
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: linux-kbuild@vger.kernel.org
Fixes: commit f28bc3c32c05 ("tracing: Handle CC_FLAGS_FTRACE more accurately")
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2018-09-10 20:59:56 +03:00
# The arch Makefiles can override CC_FLAGS_FTRACE. We may also append it later.
i f d e f C O N F I G _ F U N C T I O N _ T R A C E R
CC_FLAGS_FTRACE := -pg
e n d i f
Makefile: remove stale cc-option checks
cc-option, cc-option-yn, and cc-disable-warning all invoke the compiler
during build time, and can slow down the build when these checks become
stale for our supported compilers, whose minimally supported versions
increases over time. See Documentation/process/changes.rst for the
current supported minimal versions (GCC 4.9+, clang 10.0.1+). Compiler
version support for these flags may be verified on godbolt.org.
The following flags are GCC only and supported since at least GCC 4.9.
Remove cc-option and cc-disable-warning tests.
* -fno-tree-loop-im
* -Wno-maybe-uninitialized
* -fno-reorder-blocks
* -fno-ipa-cp-clone
* -fno-partial-inlining
* -femit-struct-debug-baseonly
* -fno-inline-functions-called-once
* -fconserve-stack
The following flags are supported by all supported versions of GCC and
Clang. Remove their cc-option, cc-option-yn, and cc-disable-warning tests.
* -fno-delete-null-pointer-checks
* -fno-var-tracking
* -Wno-array-bounds
The following configs are made dependent on GCC, since they use GCC
specific flags.
* READABLE_ASM
* DEBUG_SECTION_MISMATCH
-mfentry was not supported by s390-linux-gnu-gcc until gcc-9+, add a
comment.
--param=allow-store-data-races=0 was renamed to -fno-allow-store-data-races
in the GCC 10 release; add a comment.
-Wmaybe-uninitialized (GCC specific) was being added for CONFIG_GCOV,
then again unconditionally; add it only once.
Also, base RETPOLINE_CFLAGS and RETPOLINE_VDSO_CFLAGS on CONFIC_CC_IS_*
then remove cc-option tests for Clang.
Link: https://github.com/ClangBuiltLinux/linux/issues/1436
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-08-16 23:25:01 +03:00
i f d e f C O N F I G _ C C _ I S _ G C C
RETPOLINE_CFLAGS := $( call cc-option,-mindirect-branch= thunk-extern -mindirect-branch-register)
RETPOLINE_VDSO_CFLAGS := $( call cc-option,-mindirect-branch= thunk-inline -mindirect-branch-register)
e n d i f
i f d e f C O N F I G _ C C _ I S _ C L A N G
RETPOLINE_CFLAGS := -mretpoline-external-thunk
RETPOLINE_VDSO_CFLAGS := -mretpoline
e n d i f
2019-03-26 09:11:12 +03:00
export RETPOLINE_CFLAGS
export RETPOLINE_VDSO_CFLAGS
2021-02-28 09:10:26 +03:00
i n c l u d e $( srctree ) / a r c h / $( SRCARCH ) / M a k e f i l e
2005-04-17 02:20:36 +04:00
2019-08-10 18:53:03 +03:00
i f d e f n e e d - c o n f i g
i f d e f m a y - s y n c - c o n f i g
kbuild: fix endless syncconfig in case arch Makefile sets CROSS_COMPILE
Commit 21c54b774744 ("kconfig: show compiler version text in the top
comment") was intended to detect the compiler upgrade, but Geert
reported a breakage on the m68k build.
The compiler upgrade is detected by the change of the environment
variable, CC_VERSION_TEXT, which contains the first line of the output
from $(CC) --version. Currently, this works well when CROSS_COMPILE
is given via the environment variable or the Make command line.
However, some architectures such as m68k can specify CROSS_COMPILE
from arch/$(SRCARCH)/Makefile as well. In this case, "make ARCH=m68k"
ends up with endless syncconfig loop.
$ make ARCH=m68k defconfig
*** Default configuration is based on 'multi_defconfig'
#
# configuration written to .config
#
$ make ARCH=m68k
scripts/kconfig/conf --syncconfig Kconfig
scripts/kconfig/conf --syncconfig Kconfig
scripts/kconfig/conf --syncconfig Kconfig
scripts/kconfig/conf --syncconfig Kconfig
Things are happening like this:
Because arch/$(SRCARCH)/Makefile is included after CC_VERSION_TEXT
is set, it contains the host compiler version in the defconfig phase.
To create or update auto.conf, the following line is triggered:
include/config/%.conf: $(KCONFIG_CONFIG) include/config/auto.conf.cmd
$(Q)$(MAKE) -f $(srctree)/Makefile syncconfig
This recurses the top Makefile after arch/$(SRCARCH)/Makefile is
included. CROSS_COMPILE is set to a m68k toolchain prefix and
exported to the recursed Make. Then, syncconfig is invoked with
the target compiler version in CC_VERSION_TEXT.
The Make will restart because auto.conf and auto.conf.cmd have been
updated. At this point, CROSS_COMPILE is reset, so CC_VERSION_TEXT
is set to the host compiler version again. Then, syncconfig is
triggered due to the change of CC_VERSION_TEXT. This loop continues
eternally.
To fix this problem, $(CC_VERSION_TEXT) must be evaluated only after
arch/$(SRCARCH)/Makefile. Setting it earlier is OK as long as it is
defined by using the '=' operator instead of ':='.
For the defconfig phase, $(CC_VERSION_TEXT) is evaluated when Kbuild
descends into scripts/kconfig/, so it contains the target compiler
version correctly.
include/config/auto.conf.cmd references $(CC_VERSION_TEXT) as well,
so it must be included after arch/$(SRCARCH)/Makefile.
Fixes: 21c54b774744 ("kconfig: show compiler version text in the top comment")
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
2018-06-08 03:21:43 +03:00
# Read in dependencies to all Kconfig* files, make sure to run syncconfig if
# changes are detected. This should be included after arch/$(SRCARCH)/Makefile
# because some architectures define CROSS_COMPILE there.
kbuild: turn auto.conf.cmd into a mandatory include file
syncconfig is responsible for keeping auto.conf up-to-date, so if it
fails for any reason, the build must be terminated immediately.
However, since commit 9390dff66a52 ("kbuild: invoke syncconfig if
include/config/auto.conf.cmd is missing"), Kbuild continues running
even after syncconfig fails.
You can confirm this by intentionally making syncconfig error out:
diff --git a/scripts/kconfig/confdata.c b/scripts/kconfig/confdata.c
index 08ba146..307b9de 100644
--- a/scripts/kconfig/confdata.c
+++ b/scripts/kconfig/confdata.c
@@ -1023,6 +1023,9 @@ int conf_write_autoconf(int overwrite)
FILE *out, *tristate, *out_h;
int i;
+ if (overwrite)
+ return 1;
+
if (!overwrite && is_present(autoconf_name))
return 0;
Then, syncconfig fails, but Make would not stop:
$ make -s mrproper allyesconfig defconfig
$ make
scripts/kconfig/conf --syncconfig Kconfig
*** Error during sync of the configuration.
make[2]: *** [scripts/kconfig/Makefile;69: syncconfig] Error 1
make[1]: *** [Makefile;557: syncconfig] Error 2
make: *** [include/config/auto.conf.cmd] Deleting file 'include/config/tristate.conf'
make: Failed to remake makefile 'include/config/auto.conf'.
SYSTBL arch/x86/include/generated/asm/syscalls_32.h
SYSHDR arch/x86/include/generated/asm/unistd_32_ia32.h
SYSHDR arch/x86/include/generated/asm/unistd_64_x32.h
SYSTBL arch/x86/include/generated/asm/syscalls_64.h
[ continue running ... ]
The reason is in the behavior of a pattern rule with multi-targets.
%/auto.conf %/auto.conf.cmd %/tristate.conf: $(KCONFIG_CONFIG)
$(Q)$(MAKE) -f $(srctree)/Makefile syncconfig
GNU Make knows this rule is responsible for making all the three files
simultaneously. As far as examined, auto.conf.cmd is the target in
question when this rule is invoked. It is probably because auto.conf.cmd
is included below the inclusion of auto.conf.
The inclusion of auto.conf is mandatory, while that of auto.conf.cmd
is optional. GNU Make does not care about the failure in the process
of updating optional include files.
I filed this issue (https://savannah.gnu.org/bugs/?56301) in case this
behavior could be improved somehow in future releases of GNU Make.
Anyway, it is quite easy to fix our Makefile.
Given that auto.conf is already a mandatory include file, there is no
reason to stick auto.conf.cmd optional. Make it mandatory as well.
Cc: linux-stable <stable@vger.kernel.org> # 5.0+
Fixes: 9390dff66a52 ("kbuild: invoke syncconfig if include/config/auto.conf.cmd is missing")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2019-05-12 05:13:48 +03:00
i n c l u d e i n c l u d e / c o n f i g / a u t o . c o n f . c m d
2005-04-17 02:20:36 +04:00
2019-02-22 10:40:11 +03:00
$(KCONFIG_CONFIG) :
@echo >& 2 '***'
@echo >& 2 '*** Configuration file "$@" not found!'
@echo >& 2 '***'
@echo >& 2 '*** Please run some configurator (e.g. "make oldconfig" or'
@echo >& 2 '*** "make menuconfig" or "make xconfig").'
@echo >& 2 '***'
@/bin/false
2005-04-17 02:20:36 +04:00
2018-02-13 10:58:20 +03:00
# The actual configuration files used during the build are stored in
# include/generated/ and include/config/. Update them if .config is newer than
# include/config/auto.conf (which mirrors .config).
2019-02-22 10:40:10 +03:00
#
# This exploits the 'multi-target pattern rule' trick.
# The syncconfig should be executed only once to make all the targets.
2020-03-25 06:16:30 +03:00
# (Note: use the grouped target '&:' when we bump to GNU Make 4.3)
2021-07-14 07:23:49 +03:00
#
# Do not use $(call cmd,...) here. That would suppress prompts from syncconfig,
# so you cannot notice that Kconfig is waiting for the user input.
2020-05-01 09:01:41 +03:00
%/config/auto.conf %/config/auto.conf.cmd %/generated/autoconf.h : $( KCONFIG_CONFIG )
2021-07-14 07:23:49 +03:00
$( Q) $( kecho) " SYNC $@ "
$( Q) $( MAKE) -f $( srctree) /Makefile syncconfig
2019-08-10 18:53:03 +03:00
e l s e # !may-sync-config
kbuild: do not update config when running install targets
"make syncconfig" is automatically invoked when any of the following
happens:
- .config is updated
- any of Kconfig files is updated
- any of environment variables referenced in Kconfig is changed
Then, it updates configuration files such as include/config/auto.conf
include/generated/autoconf.h, etc.
Even install targets (install, modules_install, etc.) are no exception.
However, they should never ever modify the source tree. Install
targets are often run with root privileges. Once those configuration
files are owned by root, "make mrproper" would end up with permission
error.
Install targets should just copy things blindly. They should not care
whether the configuration is up-to-date or not. This makes more sense
because we are interested in the configuration that was used in the
previous kernel building.
This issue has existed since before, but rarely happened. I expect
more chance where people are hit by this; with the new Kconfig syntax
extension, the .config now contains the compiler information. If you
cross-compile the kernel with CROSS_COMPILE, but forget to pass it
for "make install", you meet "any of environment variables referenced
in Kconfig is changed" because $(CC) is referenced in Kconfig.
Another scenario is the compiler upgrade before the installation.
Install targets need the configuration. "make modules_install" refer
to CONFIG_MODULES etc. "make dtbs_install" also needs CONFIG_ARCH_*
to decide which dtb files to install. However, the auto-update of
the configuration files should be avoided. We already do this for
external modules.
Now, Make targets are categorized into 3 groups:
[1] Do not need the kernel configuration at all
help, coccicheck, headers_install etc.
[2] Need the latest kernel configuration
If new config options are added, Kconfig will show prompt to
ask user's selection.
Build targets such as vmlinux, in-kernel modules are the cases.
[3] Need the kernel configuration, but do not want to update it
Install targets except headers_install, and external modules
are the cases.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2018-07-20 10:46:34 +03:00
# External modules and some install targets need include/generated/autoconf.h
# and include/config/auto.conf but do not care if they are up-to-date.
# Use auto.conf to trigger the test
2006-08-07 23:01:36 +04:00
PHONY += include/config/auto.conf
include/config/auto.conf :
2009-10-18 02:49:24 +04:00
$( Q) test -e include/generated/autoconf.h -a -e $@ || ( \
2012-07-08 01:04:40 +04:00
echo >& 2; \
echo >& 2 " ERROR: Kernel configuration is invalid." ; \
echo >& 2 " include/generated/autoconf.h or $@ are missing. " ; \
echo >& 2 " Run 'make oldconfig && make prepare' on kernel src to fix it." ; \
echo >& 2 ; \
2006-08-07 23:01:36 +04:00
/bin/false)
kbuild: do not update config when running install targets
"make syncconfig" is automatically invoked when any of the following
happens:
- .config is updated
- any of Kconfig files is updated
- any of environment variables referenced in Kconfig is changed
Then, it updates configuration files such as include/config/auto.conf
include/generated/autoconf.h, etc.
Even install targets (install, modules_install, etc.) are no exception.
However, they should never ever modify the source tree. Install
targets are often run with root privileges. Once those configuration
files are owned by root, "make mrproper" would end up with permission
error.
Install targets should just copy things blindly. They should not care
whether the configuration is up-to-date or not. This makes more sense
because we are interested in the configuration that was used in the
previous kernel building.
This issue has existed since before, but rarely happened. I expect
more chance where people are hit by this; with the new Kconfig syntax
extension, the .config now contains the compiler information. If you
cross-compile the kernel with CROSS_COMPILE, but forget to pass it
for "make install", you meet "any of environment variables referenced
in Kconfig is changed" because $(CC) is referenced in Kconfig.
Another scenario is the compiler upgrade before the installation.
Install targets need the configuration. "make modules_install" refer
to CONFIG_MODULES etc. "make dtbs_install" also needs CONFIG_ARCH_*
to decide which dtb files to install. However, the auto-update of
the configuration files should be avoided. We already do this for
external modules.
Now, Make targets are categorized into 3 groups:
[1] Do not need the kernel configuration at all
help, coccicheck, headers_install etc.
[2] Need the latest kernel configuration
If new config options are added, Kconfig will show prompt to
ask user's selection.
Build targets such as vmlinux, in-kernel modules are the cases.
[3] Need the kernel configuration, but do not want to update it
Install targets except headers_install, and external modules
are the cases.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2018-07-20 10:46:34 +03:00
e n d i f # may-sync-config
2019-08-10 18:53:03 +03:00
e n d i f # need-config
2005-04-17 02:20:36 +04:00
Makefile: remove stale cc-option checks
cc-option, cc-option-yn, and cc-disable-warning all invoke the compiler
during build time, and can slow down the build when these checks become
stale for our supported compilers, whose minimally supported versions
increases over time. See Documentation/process/changes.rst for the
current supported minimal versions (GCC 4.9+, clang 10.0.1+). Compiler
version support for these flags may be verified on godbolt.org.
The following flags are GCC only and supported since at least GCC 4.9.
Remove cc-option and cc-disable-warning tests.
* -fno-tree-loop-im
* -Wno-maybe-uninitialized
* -fno-reorder-blocks
* -fno-ipa-cp-clone
* -fno-partial-inlining
* -femit-struct-debug-baseonly
* -fno-inline-functions-called-once
* -fconserve-stack
The following flags are supported by all supported versions of GCC and
Clang. Remove their cc-option, cc-option-yn, and cc-disable-warning tests.
* -fno-delete-null-pointer-checks
* -fno-var-tracking
* -Wno-array-bounds
The following configs are made dependent on GCC, since they use GCC
specific flags.
* READABLE_ASM
* DEBUG_SECTION_MISMATCH
-mfentry was not supported by s390-linux-gnu-gcc until gcc-9+, add a
comment.
--param=allow-store-data-races=0 was renamed to -fno-allow-store-data-races
in the GCC 10 release; add a comment.
-Wmaybe-uninitialized (GCC specific) was being added for CONFIG_GCOV,
then again unconditionally; add it only once.
Also, base RETPOLINE_CFLAGS and RETPOLINE_VDSO_CFLAGS on CONFIC_CC_IS_*
then remove cc-option tests for Clang.
Link: https://github.com/ClangBuiltLinux/linux/issues/1436
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-08-16 23:25:01 +03:00
KBUILD_CFLAGS += -fno-delete-null-pointer-checks
2016-10-12 20:23:41 +03:00
KBUILD_CFLAGS += $( call cc-disable-warning,frame-address,)
2017-07-13 05:25:47 +03:00
KBUILD_CFLAGS += $( call cc-disable-warning, format-truncation)
KBUILD_CFLAGS += $( call cc-disable-warning, format-overflow)
2019-05-01 21:05:41 +03:00
KBUILD_CFLAGS += $( call cc-disable-warning, address-of-packed-member)
Makefile: Fix unrecognized cross-compiler command line options
On architectures that setup CROSS_COMPILE in their arch/*/Makefile
(arc, blackfin, m68k, mips, parisc, score, sh, tile, unicore32, xtensa),
cc-option and cc-disable-warning may check against the wrong compiler,
causing errors like
cc1: error: unrecognized command line option "-Wno-maybe-uninitialized"
if the host gcc supports a compiler option, while the cross compiler
doesn't support that option.
Move all logic using cc-option or cc-disable-warning below the inclusion
of the arch's Makefile to fix this.
Introduced by
- commit e74fc973b6e531fef1fce8b101ffff05ecfb774c ("Turn off
-Wmaybe-uninitialized when building with -Os"),
- commit 61163efae02040f66a95c8ed17f4407951ba58fa ("kbuild: LLVMLinux:
Add Kbuild support for building kernel with Clang").
As -Wno-maybe-uninitialized requires a quite recent gcc (gcc 4.6.3 on
Ubuntu 12.04 LTS doesn't support it), this only showed up recently (gcc
4.8.2 on Ubuntu 14.04 LTS does support it).
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>
2014-05-27 11:54:12 +04:00
2019-08-20 20:09:40 +03:00
i f d e f C O N F I G _ C C _ O P T I M I Z E _ F O R _ P E R F O R M A N C E
KBUILD_CFLAGS += -O2
e l s e i f d e f C O N F I G _ C C _ O P T I M I Z E _ F O R _ P E R F O R M A N C E _ O 3
KBUILD_CFLAGS += -O3
e l s e i f d e f C O N F I G _ C C _ O P T I M I Z E _ F O R _ S I Z E
KBUILD_CFLAGS += -Os
2016-04-25 18:35:28 +03:00
e n d i f
2005-04-17 02:20:36 +04:00
./Makefile: tell gcc optimizer to never introduce new data races
We have been chasing a memory corruption bug, which turned out to be
caused by very old gcc (4.3.4), which happily turned conditional load
into a non-conditional one, and that broke correctness (the condition
was met only if lock was held) and corrupted memory.
This particular problem with that particular code did not happen when
never gccs were used. I've brought this up with our gcc folks, as I
wanted to make sure that this can't really happen again, and it turns
out it actually can.
Quoting Martin Jambor <mjambor@suse.cz>:
"More current GCCs are more careful when it comes to replacing a
conditional load with a non-conditional one, most notably they check
that a store happens in each iteration of _a_ loop but they assume
loops are executed. They also perform a simple check whether the
store cannot trap which currently passes only for non-const
variables. A simple testcase demonstrating it on an x86_64 is for
example the following:
$ cat cond_store.c
int g_1 = 1;
int g_2[1024] __attribute__((section ("safe_section"), aligned (4096)));
int c = 4;
int __attribute__ ((noinline))
foo (void)
{
int l;
for (l = 0; (l != 4); l++) {
if (g_1)
return l;
for (g_2[0] = 0; (g_2[0] >= 26); ++g_2[0])
;
}
return 2;
}
int main (int argc, char* argv[])
{
if (mprotect (g_2, sizeof(g_2), PROT_READ) == -1)
{
int e = errno;
error (e, e, "mprotect error %i", e);
}
foo ();
__builtin_printf("OK\n");
return 0;
}
/* EOF */
$ ~/gcc/trunk/inst/bin/gcc cond_store.c -O2 --param allow-store-data-races=0
$ ./a.out
OK
$ ~/gcc/trunk/inst/bin/gcc cond_store.c -O2 --param allow-store-data-races=1
$ ./a.out
Segmentation fault
The testcase fails the same at least with 4.9, 4.8 and 4.7. Therefore
I would suggest building kernels with this parameter set to zero. I
also agree with Jikos that the default should be changed for -O2. I
have run most of the SPEC 2k6 CPU benchmarks (gamess and dealII
failed, at -O2, not sure why) compiled with and without this option
and did not see any real difference between respective run-times"
Hopefully the default will be changed in newer gccs, but let's force it
for kernel builds so that we are on a safe side even when older gcc are
used.
The code in question was out-of-tree printk-in-NMI (yeah, surprise
suprise, once again) patch written by Petr Mladek, let me quote his
comment from our internal bugzilla:
"I have spent few days investigating inconsistent state of kernel ring buffer.
It went out that it was caused by speculative store generated by
gcc-4.3.4.
The problem is in assembly generated for make_free_space(). The functions is
called the following way:
+ vprintk_emit();
+ log = MAIN_LOG; // with logbuf_lock
or
log = NMI_LOG; // with nmi_logbuf_lock
cont_add(log, ...);
+ cont_flush(log, ...);
+ log_store(log, ...);
+ log_make_free_space(log, ...);
If called with log = NMI_LOG then only nmi_log_* global variables are safe to
modify but the generated code does store also into (main_)log_* global
variables:
<log_make_free_space>:
55 push %rbp
89 f6 mov %esi,%esi
48 8b 05 03 99 51 01 mov 0x1519903(%rip),%rax # ffffffff82620868 <nmi_log_next_id>
44 8b 1d ec 98 51 01 mov 0x15198ec(%rip),%r11d # ffffffff82620858 <log_next_idx>
8b 35 36 60 14 01 mov 0x1146036(%rip),%esi # ffffffff8224cfa8 <log_buf_len>
44 8b 35 33 60 14 01 mov 0x1146033(%rip),%r14d # ffffffff8224cfac <nmi_log_buf_len>
4c 8b 2d d0 98 51 01 mov 0x15198d0(%rip),%r13 # ffffffff82620850 <log_next_seq>
4c 8b 25 11 61 14 01 mov 0x1146111(%rip),%r12 # ffffffff8224d098 <log_buf>
49 89 c2 mov %rax,%r10
48 21 c2 and %rax,%rdx
48 8b 1d 0c 99 55 01 mov 0x155990c(%rip),%rbx # ffffffff826608a0 <nmi_log_buf>
49 c1 ea 20 shr $0x20,%r10
48 89 55 d0 mov %rdx,-0x30(%rbp)
44 29 de sub %r11d,%esi
45 29 d6 sub %r10d,%r14d
4c 8b 0d 97 98 51 01 mov 0x1519897(%rip),%r9 # ffffffff82620840 <log_first_seq>
eb 7e jmp ffffffff81107029 <log_make_free_space+0xe9>
[...]
85 ff test %edi,%edi # edi = 1 for NMI_LOG
4c 89 e8 mov %r13,%rax
4c 89 ca mov %r9,%rdx
74 0a je ffffffff8110703d <log_make_free_space+0xfd>
8b 15 27 98 51 01 mov 0x1519827(%rip),%edx # ffffffff82620860 <nmi_log_first_id>
48 8b 45 d0 mov -0x30(%rbp),%rax
48 39 c2 cmp %rax,%rdx # end of loop
0f 84 da 00 00 00 je ffffffff81107120 <log_make_free_space+0x1e0>
[...]
85 ff test %edi,%edi # edi = 1 for NMI_LOG
4c 89 0d 17 97 51 01 mov %r9,0x1519717(%rip) # ffffffff82620840 <log_first_seq>
^^^^^^^^^^^^^^^^^^^^^^^^^^
KABOOOM
74 35 je ffffffff81107160 <log_make_free_space+0x220>
It stores log_first_seq when edi == NMI_LOG. This instructions are used also
when edi == MAIN_LOG but the store is done speculatively before the condition
is decided. It is unsafe because we do not have "logbuf_lock" in NMI context
and some other process migh modify "log_first_seq" in parallel"
I believe that the best course of action is both
- building kernel (and anything multi-threaded, I guess) with that
optimization turned off
- persuade gcc folks to change the default for future releases
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Cc: Martin Jambor <mjambor@suse.cz>
Cc: Petr Mladek <pmladek@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Marek Polacek <polacek@redhat.com>
Cc: Jakub Jelinek <jakub@redhat.com>
Cc: Steven Noonan <steven@uplinklabs.net>
Cc: Richard Biener <richard.guenther@gmail.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-08-07 03:08:43 +04:00
# Tell gcc to never replace conditional load with a non-conditional one
Makefile: remove stale cc-option checks
cc-option, cc-option-yn, and cc-disable-warning all invoke the compiler
during build time, and can slow down the build when these checks become
stale for our supported compilers, whose minimally supported versions
increases over time. See Documentation/process/changes.rst for the
current supported minimal versions (GCC 4.9+, clang 10.0.1+). Compiler
version support for these flags may be verified on godbolt.org.
The following flags are GCC only and supported since at least GCC 4.9.
Remove cc-option and cc-disable-warning tests.
* -fno-tree-loop-im
* -Wno-maybe-uninitialized
* -fno-reorder-blocks
* -fno-ipa-cp-clone
* -fno-partial-inlining
* -femit-struct-debug-baseonly
* -fno-inline-functions-called-once
* -fconserve-stack
The following flags are supported by all supported versions of GCC and
Clang. Remove their cc-option, cc-option-yn, and cc-disable-warning tests.
* -fno-delete-null-pointer-checks
* -fno-var-tracking
* -Wno-array-bounds
The following configs are made dependent on GCC, since they use GCC
specific flags.
* READABLE_ASM
* DEBUG_SECTION_MISMATCH
-mfentry was not supported by s390-linux-gnu-gcc until gcc-9+, add a
comment.
--param=allow-store-data-races=0 was renamed to -fno-allow-store-data-races
in the GCC 10 release; add a comment.
-Wmaybe-uninitialized (GCC specific) was being added for CONFIG_GCOV,
then again unconditionally; add it only once.
Also, base RETPOLINE_CFLAGS and RETPOLINE_VDSO_CFLAGS on CONFIC_CC_IS_*
then remove cc-option tests for Clang.
Link: https://github.com/ClangBuiltLinux/linux/issues/1436
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-08-16 23:25:01 +03:00
i f d e f C O N F I G _ C C _ I S _ G C C
# gcc-10 renamed --param=allow-store-data-races=0 to
# -fno-allow-store-data-races.
./Makefile: tell gcc optimizer to never introduce new data races
We have been chasing a memory corruption bug, which turned out to be
caused by very old gcc (4.3.4), which happily turned conditional load
into a non-conditional one, and that broke correctness (the condition
was met only if lock was held) and corrupted memory.
This particular problem with that particular code did not happen when
never gccs were used. I've brought this up with our gcc folks, as I
wanted to make sure that this can't really happen again, and it turns
out it actually can.
Quoting Martin Jambor <mjambor@suse.cz>:
"More current GCCs are more careful when it comes to replacing a
conditional load with a non-conditional one, most notably they check
that a store happens in each iteration of _a_ loop but they assume
loops are executed. They also perform a simple check whether the
store cannot trap which currently passes only for non-const
variables. A simple testcase demonstrating it on an x86_64 is for
example the following:
$ cat cond_store.c
int g_1 = 1;
int g_2[1024] __attribute__((section ("safe_section"), aligned (4096)));
int c = 4;
int __attribute__ ((noinline))
foo (void)
{
int l;
for (l = 0; (l != 4); l++) {
if (g_1)
return l;
for (g_2[0] = 0; (g_2[0] >= 26); ++g_2[0])
;
}
return 2;
}
int main (int argc, char* argv[])
{
if (mprotect (g_2, sizeof(g_2), PROT_READ) == -1)
{
int e = errno;
error (e, e, "mprotect error %i", e);
}
foo ();
__builtin_printf("OK\n");
return 0;
}
/* EOF */
$ ~/gcc/trunk/inst/bin/gcc cond_store.c -O2 --param allow-store-data-races=0
$ ./a.out
OK
$ ~/gcc/trunk/inst/bin/gcc cond_store.c -O2 --param allow-store-data-races=1
$ ./a.out
Segmentation fault
The testcase fails the same at least with 4.9, 4.8 and 4.7. Therefore
I would suggest building kernels with this parameter set to zero. I
also agree with Jikos that the default should be changed for -O2. I
have run most of the SPEC 2k6 CPU benchmarks (gamess and dealII
failed, at -O2, not sure why) compiled with and without this option
and did not see any real difference between respective run-times"
Hopefully the default will be changed in newer gccs, but let's force it
for kernel builds so that we are on a safe side even when older gcc are
used.
The code in question was out-of-tree printk-in-NMI (yeah, surprise
suprise, once again) patch written by Petr Mladek, let me quote his
comment from our internal bugzilla:
"I have spent few days investigating inconsistent state of kernel ring buffer.
It went out that it was caused by speculative store generated by
gcc-4.3.4.
The problem is in assembly generated for make_free_space(). The functions is
called the following way:
+ vprintk_emit();
+ log = MAIN_LOG; // with logbuf_lock
or
log = NMI_LOG; // with nmi_logbuf_lock
cont_add(log, ...);
+ cont_flush(log, ...);
+ log_store(log, ...);
+ log_make_free_space(log, ...);
If called with log = NMI_LOG then only nmi_log_* global variables are safe to
modify but the generated code does store also into (main_)log_* global
variables:
<log_make_free_space>:
55 push %rbp
89 f6 mov %esi,%esi
48 8b 05 03 99 51 01 mov 0x1519903(%rip),%rax # ffffffff82620868 <nmi_log_next_id>
44 8b 1d ec 98 51 01 mov 0x15198ec(%rip),%r11d # ffffffff82620858 <log_next_idx>
8b 35 36 60 14 01 mov 0x1146036(%rip),%esi # ffffffff8224cfa8 <log_buf_len>
44 8b 35 33 60 14 01 mov 0x1146033(%rip),%r14d # ffffffff8224cfac <nmi_log_buf_len>
4c 8b 2d d0 98 51 01 mov 0x15198d0(%rip),%r13 # ffffffff82620850 <log_next_seq>
4c 8b 25 11 61 14 01 mov 0x1146111(%rip),%r12 # ffffffff8224d098 <log_buf>
49 89 c2 mov %rax,%r10
48 21 c2 and %rax,%rdx
48 8b 1d 0c 99 55 01 mov 0x155990c(%rip),%rbx # ffffffff826608a0 <nmi_log_buf>
49 c1 ea 20 shr $0x20,%r10
48 89 55 d0 mov %rdx,-0x30(%rbp)
44 29 de sub %r11d,%esi
45 29 d6 sub %r10d,%r14d
4c 8b 0d 97 98 51 01 mov 0x1519897(%rip),%r9 # ffffffff82620840 <log_first_seq>
eb 7e jmp ffffffff81107029 <log_make_free_space+0xe9>
[...]
85 ff test %edi,%edi # edi = 1 for NMI_LOG
4c 89 e8 mov %r13,%rax
4c 89 ca mov %r9,%rdx
74 0a je ffffffff8110703d <log_make_free_space+0xfd>
8b 15 27 98 51 01 mov 0x1519827(%rip),%edx # ffffffff82620860 <nmi_log_first_id>
48 8b 45 d0 mov -0x30(%rbp),%rax
48 39 c2 cmp %rax,%rdx # end of loop
0f 84 da 00 00 00 je ffffffff81107120 <log_make_free_space+0x1e0>
[...]
85 ff test %edi,%edi # edi = 1 for NMI_LOG
4c 89 0d 17 97 51 01 mov %r9,0x1519717(%rip) # ffffffff82620840 <log_first_seq>
^^^^^^^^^^^^^^^^^^^^^^^^^^
KABOOOM
74 35 je ffffffff81107160 <log_make_free_space+0x220>
It stores log_first_seq when edi == NMI_LOG. This instructions are used also
when edi == MAIN_LOG but the store is done speculatively before the condition
is decided. It is unsafe because we do not have "logbuf_lock" in NMI context
and some other process migh modify "log_first_seq" in parallel"
I believe that the best course of action is both
- building kernel (and anything multi-threaded, I guess) with that
optimization turned off
- persuade gcc folks to change the default for future releases
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Cc: Martin Jambor <mjambor@suse.cz>
Cc: Petr Mladek <pmladek@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Marek Polacek <polacek@redhat.com>
Cc: Jakub Jelinek <jakub@redhat.com>
Cc: Steven Noonan <steven@uplinklabs.net>
Cc: Richard Biener <richard.guenther@gmail.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-08-07 03:08:43 +04:00
KBUILD_CFLAGS += $( call cc-option,--param= allow-store-data-races= 0)
2020-03-17 03:07:18 +03:00
KBUILD_CFLAGS += $( call cc-option,-fno-allow-store-data-races)
Makefile: remove stale cc-option checks
cc-option, cc-option-yn, and cc-disable-warning all invoke the compiler
during build time, and can slow down the build when these checks become
stale for our supported compilers, whose minimally supported versions
increases over time. See Documentation/process/changes.rst for the
current supported minimal versions (GCC 4.9+, clang 10.0.1+). Compiler
version support for these flags may be verified on godbolt.org.
The following flags are GCC only and supported since at least GCC 4.9.
Remove cc-option and cc-disable-warning tests.
* -fno-tree-loop-im
* -Wno-maybe-uninitialized
* -fno-reorder-blocks
* -fno-ipa-cp-clone
* -fno-partial-inlining
* -femit-struct-debug-baseonly
* -fno-inline-functions-called-once
* -fconserve-stack
The following flags are supported by all supported versions of GCC and
Clang. Remove their cc-option, cc-option-yn, and cc-disable-warning tests.
* -fno-delete-null-pointer-checks
* -fno-var-tracking
* -Wno-array-bounds
The following configs are made dependent on GCC, since they use GCC
specific flags.
* READABLE_ASM
* DEBUG_SECTION_MISMATCH
-mfentry was not supported by s390-linux-gnu-gcc until gcc-9+, add a
comment.
--param=allow-store-data-races=0 was renamed to -fno-allow-store-data-races
in the GCC 10 release; add a comment.
-Wmaybe-uninitialized (GCC specific) was being added for CONFIG_GCOV,
then again unconditionally; add it only once.
Also, base RETPOLINE_CFLAGS and RETPOLINE_VDSO_CFLAGS on CONFIC_CC_IS_*
then remove cc-option tests for Clang.
Link: https://github.com/ClangBuiltLinux/linux/issues/1436
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-08-16 23:25:01 +03:00
e n d i f
./Makefile: tell gcc optimizer to never introduce new data races
We have been chasing a memory corruption bug, which turned out to be
caused by very old gcc (4.3.4), which happily turned conditional load
into a non-conditional one, and that broke correctness (the condition
was met only if lock was held) and corrupted memory.
This particular problem with that particular code did not happen when
never gccs were used. I've brought this up with our gcc folks, as I
wanted to make sure that this can't really happen again, and it turns
out it actually can.
Quoting Martin Jambor <mjambor@suse.cz>:
"More current GCCs are more careful when it comes to replacing a
conditional load with a non-conditional one, most notably they check
that a store happens in each iteration of _a_ loop but they assume
loops are executed. They also perform a simple check whether the
store cannot trap which currently passes only for non-const
variables. A simple testcase demonstrating it on an x86_64 is for
example the following:
$ cat cond_store.c
int g_1 = 1;
int g_2[1024] __attribute__((section ("safe_section"), aligned (4096)));
int c = 4;
int __attribute__ ((noinline))
foo (void)
{
int l;
for (l = 0; (l != 4); l++) {
if (g_1)
return l;
for (g_2[0] = 0; (g_2[0] >= 26); ++g_2[0])
;
}
return 2;
}
int main (int argc, char* argv[])
{
if (mprotect (g_2, sizeof(g_2), PROT_READ) == -1)
{
int e = errno;
error (e, e, "mprotect error %i", e);
}
foo ();
__builtin_printf("OK\n");
return 0;
}
/* EOF */
$ ~/gcc/trunk/inst/bin/gcc cond_store.c -O2 --param allow-store-data-races=0
$ ./a.out
OK
$ ~/gcc/trunk/inst/bin/gcc cond_store.c -O2 --param allow-store-data-races=1
$ ./a.out
Segmentation fault
The testcase fails the same at least with 4.9, 4.8 and 4.7. Therefore
I would suggest building kernels with this parameter set to zero. I
also agree with Jikos that the default should be changed for -O2. I
have run most of the SPEC 2k6 CPU benchmarks (gamess and dealII
failed, at -O2, not sure why) compiled with and without this option
and did not see any real difference between respective run-times"
Hopefully the default will be changed in newer gccs, but let's force it
for kernel builds so that we are on a safe side even when older gcc are
used.
The code in question was out-of-tree printk-in-NMI (yeah, surprise
suprise, once again) patch written by Petr Mladek, let me quote his
comment from our internal bugzilla:
"I have spent few days investigating inconsistent state of kernel ring buffer.
It went out that it was caused by speculative store generated by
gcc-4.3.4.
The problem is in assembly generated for make_free_space(). The functions is
called the following way:
+ vprintk_emit();
+ log = MAIN_LOG; // with logbuf_lock
or
log = NMI_LOG; // with nmi_logbuf_lock
cont_add(log, ...);
+ cont_flush(log, ...);
+ log_store(log, ...);
+ log_make_free_space(log, ...);
If called with log = NMI_LOG then only nmi_log_* global variables are safe to
modify but the generated code does store also into (main_)log_* global
variables:
<log_make_free_space>:
55 push %rbp
89 f6 mov %esi,%esi
48 8b 05 03 99 51 01 mov 0x1519903(%rip),%rax # ffffffff82620868 <nmi_log_next_id>
44 8b 1d ec 98 51 01 mov 0x15198ec(%rip),%r11d # ffffffff82620858 <log_next_idx>
8b 35 36 60 14 01 mov 0x1146036(%rip),%esi # ffffffff8224cfa8 <log_buf_len>
44 8b 35 33 60 14 01 mov 0x1146033(%rip),%r14d # ffffffff8224cfac <nmi_log_buf_len>
4c 8b 2d d0 98 51 01 mov 0x15198d0(%rip),%r13 # ffffffff82620850 <log_next_seq>
4c 8b 25 11 61 14 01 mov 0x1146111(%rip),%r12 # ffffffff8224d098 <log_buf>
49 89 c2 mov %rax,%r10
48 21 c2 and %rax,%rdx
48 8b 1d 0c 99 55 01 mov 0x155990c(%rip),%rbx # ffffffff826608a0 <nmi_log_buf>
49 c1 ea 20 shr $0x20,%r10
48 89 55 d0 mov %rdx,-0x30(%rbp)
44 29 de sub %r11d,%esi
45 29 d6 sub %r10d,%r14d
4c 8b 0d 97 98 51 01 mov 0x1519897(%rip),%r9 # ffffffff82620840 <log_first_seq>
eb 7e jmp ffffffff81107029 <log_make_free_space+0xe9>
[...]
85 ff test %edi,%edi # edi = 1 for NMI_LOG
4c 89 e8 mov %r13,%rax
4c 89 ca mov %r9,%rdx
74 0a je ffffffff8110703d <log_make_free_space+0xfd>
8b 15 27 98 51 01 mov 0x1519827(%rip),%edx # ffffffff82620860 <nmi_log_first_id>
48 8b 45 d0 mov -0x30(%rbp),%rax
48 39 c2 cmp %rax,%rdx # end of loop
0f 84 da 00 00 00 je ffffffff81107120 <log_make_free_space+0x1e0>
[...]
85 ff test %edi,%edi # edi = 1 for NMI_LOG
4c 89 0d 17 97 51 01 mov %r9,0x1519717(%rip) # ffffffff82620840 <log_first_seq>
^^^^^^^^^^^^^^^^^^^^^^^^^^
KABOOOM
74 35 je ffffffff81107160 <log_make_free_space+0x220>
It stores log_first_seq when edi == NMI_LOG. This instructions are used also
when edi == MAIN_LOG but the store is done speculatively before the condition
is decided. It is unsafe because we do not have "logbuf_lock" in NMI context
and some other process migh modify "log_first_seq" in parallel"
I believe that the best course of action is both
- building kernel (and anything multi-threaded, I guess) with that
optimization turned off
- persuade gcc folks to change the default for future releases
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Cc: Martin Jambor <mjambor@suse.cz>
Cc: Petr Mladek <pmladek@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Marek Polacek <polacek@redhat.com>
Cc: Jakub Jelinek <jakub@redhat.com>
Cc: Steven Noonan <steven@uplinklabs.net>
Cc: Richard Biener <richard.guenther@gmail.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-08-07 03:08:43 +04:00
2012-03-28 22:51:18 +04:00
i f d e f C O N F I G _ R E A D A B L E _ A S M
# Disable optimizations that make assembler listings hard to read.
# reorder blocks reorders the control in the function
# ipa clone creates specialized cloned functions
# partial inlining inlines only parts of functions
Makefile: remove stale cc-option checks
cc-option, cc-option-yn, and cc-disable-warning all invoke the compiler
during build time, and can slow down the build when these checks become
stale for our supported compilers, whose minimally supported versions
increases over time. See Documentation/process/changes.rst for the
current supported minimal versions (GCC 4.9+, clang 10.0.1+). Compiler
version support for these flags may be verified on godbolt.org.
The following flags are GCC only and supported since at least GCC 4.9.
Remove cc-option and cc-disable-warning tests.
* -fno-tree-loop-im
* -Wno-maybe-uninitialized
* -fno-reorder-blocks
* -fno-ipa-cp-clone
* -fno-partial-inlining
* -femit-struct-debug-baseonly
* -fno-inline-functions-called-once
* -fconserve-stack
The following flags are supported by all supported versions of GCC and
Clang. Remove their cc-option, cc-option-yn, and cc-disable-warning tests.
* -fno-delete-null-pointer-checks
* -fno-var-tracking
* -Wno-array-bounds
The following configs are made dependent on GCC, since they use GCC
specific flags.
* READABLE_ASM
* DEBUG_SECTION_MISMATCH
-mfentry was not supported by s390-linux-gnu-gcc until gcc-9+, add a
comment.
--param=allow-store-data-races=0 was renamed to -fno-allow-store-data-races
in the GCC 10 release; add a comment.
-Wmaybe-uninitialized (GCC specific) was being added for CONFIG_GCOV,
then again unconditionally; add it only once.
Also, base RETPOLINE_CFLAGS and RETPOLINE_VDSO_CFLAGS on CONFIC_CC_IS_*
then remove cc-option tests for Clang.
Link: https://github.com/ClangBuiltLinux/linux/issues/1436
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-08-16 23:25:01 +03:00
KBUILD_CFLAGS += -fno-reorder-blocks -fno-ipa-cp-clone -fno-partial-inlining
2012-03-28 22:51:18 +04:00
e n d i f
2009-06-05 03:29:08 +04:00
i f n e q ( $( CONFIG_FRAME_WARN ) , 0 )
2020-02-16 18:19:36 +03:00
KBUILD_CFLAGS += -Wframe-larger-than= $( CONFIG_FRAME_WARN)
2008-02-22 17:15:03 +03:00
e n d i f
2020-06-26 21:59:12 +03:00
stackp-flags-y := -fno-stack-protector
Kbuild: rename CC_STACKPROTECTOR[_STRONG] config variables
The changes to automatically test for working stack protector compiler
support in the Kconfig files removed the special STACKPROTECTOR_AUTO
option that picked the strongest stack protector that the compiler
supported.
That was all a nice cleanup - it makes no sense to have the AUTO case
now that the Kconfig phase can just determine the compiler support
directly.
HOWEVER.
It also meant that doing "make oldconfig" would now _disable_ the strong
stackprotector if you had AUTO enabled, because in a legacy config file,
the sane stack protector configuration would look like
CONFIG_HAVE_CC_STACKPROTECTOR=y
# CONFIG_CC_STACKPROTECTOR_NONE is not set
# CONFIG_CC_STACKPROTECTOR_REGULAR is not set
# CONFIG_CC_STACKPROTECTOR_STRONG is not set
CONFIG_CC_STACKPROTECTOR_AUTO=y
and when you ran this through "make oldconfig" with the Kbuild changes,
it would ask you about the regular CONFIG_CC_STACKPROTECTOR (that had
been renamed from CONFIG_CC_STACKPROTECTOR_REGULAR to just
CONFIG_CC_STACKPROTECTOR), but it would think that the STRONG version
used to be disabled (because it was really enabled by AUTO), and would
disable it in the new config, resulting in:
CONFIG_HAVE_CC_STACKPROTECTOR=y
CONFIG_CC_HAS_STACKPROTECTOR_NONE=y
CONFIG_CC_STACKPROTECTOR=y
# CONFIG_CC_STACKPROTECTOR_STRONG is not set
CONFIG_CC_HAS_SANE_STACKPROTECTOR=y
That's dangerously subtle - people could suddenly find themselves with
the weaker stack protector setup without even realizing.
The solution here is to just rename not just the old RECULAR stack
protector option, but also the strong one. This does that by just
removing the CC_ prefix entirely for the user choices, because it really
is not about the compiler support (the compiler support now instead
automatially impacts _visibility_ of the options to users).
This results in "make oldconfig" actually asking the user for their
choice, so that we don't have any silent subtle security model changes.
The end result would generally look like this:
CONFIG_HAVE_CC_STACKPROTECTOR=y
CONFIG_CC_HAS_STACKPROTECTOR_NONE=y
CONFIG_STACKPROTECTOR=y
CONFIG_STACKPROTECTOR_STRONG=y
CONFIG_CC_HAS_SANE_STACKPROTECTOR=y
where the "CC_" versions really are about internal compiler
infrastructure, not the user selections.
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-06-14 06:21:18 +03:00
stackp-flags-$(CONFIG_STACKPROTECTOR) := -fstack-protector
stackp-flags-$(CONFIG_STACKPROTECTOR_STRONG) := -fstack-protector-strong
stack-protector: test compiler capability in Kconfig and drop AUTO mode
Move the test for -fstack-protector(-strong) option to Kconfig.
If the compiler does not support the option, the corresponding menu
is automatically hidden. If STRONG is not supported, it will fall
back to REGULAR. If REGULAR is not supported, it will be disabled.
This means, AUTO is implicitly handled by the dependency solver of
Kconfig, hence removed.
I also turned the 'choice' into only two boolean symbols. The use of
'choice' is not a good idea here, because all of all{yes,mod,no}config
would choose the first visible value, while we want allnoconfig to
disable as many features as possible.
X86 has additional shell scripts in case the compiler supports those
options, but generates broken code. I added CC_HAS_SANE_STACKPROTECTOR
to test this. I had to add -m32 to gcc-x86_32-has-stack-protector.sh
to make it work correctly.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Kees Cook <keescook@chromium.org>
2018-05-28 12:22:00 +03:00
KBUILD_CFLAGS += $( stackp-flags-y)
2008-02-14 00:43:28 +03:00
2021-09-05 21:24:05 +03:00
KBUILD_CFLAGS-$(CONFIG_WERROR) += -Werror
KBUILD_CFLAGS += $( KBUILD_CFLAGS-y)
2018-10-30 16:26:33 +03:00
i f d e f C O N F I G _ C C _ I S _ C L A N G
2019-05-10 17:10:09 +03:00
KBUILD_CPPFLAGS += -Qunused-arguments
2021-08-16 23:20:55 +03:00
# The kernel builds with '-std=gnu89' so use of GNU extensions is acceptable.
2019-05-10 17:10:09 +03:00
KBUILD_CFLAGS += -Wno-gnu
2017-11-27 15:15:13 +03:00
# CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the
# source of a reference will be _MergedGlobals and not on of the whitelisted names.
# See modpost pattern 2
2019-05-10 17:10:09 +03:00
KBUILD_CFLAGS += -mno-global-merge
Revert "Makefile: Enable -Wimplicit-fallthrough for Clang"
This reverts commit b7eb335e26a9c7f258c96b3962c283c379d3ede0.
It turns out that the problem with the clang -Wimplicit-fallthrough
warning is not about the kernel source code, but about clang itself, and
that the warning is unusable until clang fixes its broken ways.
In particular, when you enable this warning for clang, you not only get
warnings about implicit fallthroughs. You also get this:
warning: fallthrough annotation in unreachable code [-Wimplicit-fallthrough]
which is completely broken becasue it
(a) doesn't even tell you where the problem is (seriously: no line
numbers, no filename, no nothing).
(b) is fundamentally broken anyway, because there are perfectly valid
reasons to have a fallthrough statement even if it turns out that
it can perhaps not be reached.
In the kernel, an example of that second case is code in the scheduler:
switch (state) {
case cpuset:
if (IS_ENABLED(CONFIG_CPUSETS)) {
cpuset_cpus_allowed_fallback(p);
state = possible;
break;
}
fallthrough;
case possible:
where if CONFIG_CPUSETS is enabled you actually never hit the
fallthrough case at all. But that in no way makes the fallthrough
wrong.
So the warning is completely broken, and enabling it for clang is a very
bad idea.
In the meantime, we can keep the gcc option enabled, and make the gcc
build use
-Wimplicit-fallthrough=5
which means that we will at least continue to require a proper
fallthrough statement, and that gcc won't silently accept the magic
comment versions. Because gcc does this all correctly, and while the odd
"=5" part is kind of obscure, it's documented in [1]:
"-Wimplicit-fallthrough=5 doesn’t recognize any comments as
fallthrough comments, only attributes disable the warning"
so if clang ever fixes its bad behavior we can try enabling it there again.
Link: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html [1]
Cc: Kees Cook <keescook@chromium.org>
Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-07-16 04:05:31 +03:00
e l s e
# Warn about unmarked fall-throughs in switch statement.
# Disabled for clang while comment to attribute conversion happens and
# https://github.com/ClangBuiltLinux/linux/issues/636 is discussed.
KBUILD_CFLAGS += $( call cc-option,-Wimplicit-fallthrough= 5,)
2021-09-08 01:42:02 +03:00
# gcc inanely warns about local variables called 'main'
KBUILD_CFLAGS += -Wno-main
2017-11-27 15:15:13 +03:00
e n d i f
2021-04-29 04:23:50 +03:00
# These warnings generated too much noise in a regular build.
# Use make W=1 to enable them (see scripts/Makefile.extrawarn)
KBUILD_CFLAGS += $( call cc-disable-warning, unused-but-set-variable)
2018-02-07 02:46:51 +03:00
KBUILD_CFLAGS += $( call cc-disable-warning, unused-const-variable)
2021-08-16 23:20:56 +03:00
2005-04-17 02:20:36 +04:00
i f d e f C O N F I G _ F R A M E _ P O I N T E R
2007-10-15 00:21:35 +04:00
KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls
2005-04-17 02:20:36 +04:00
e l s e
2010-08-10 22:20:53 +04:00
# Some targets (ARM with Thumb2, for example), can't be built with frame
# pointers. For those, we don't have FUNCTION_TRACER automatically
# select FRAME_POINTER. However, FUNCTION_TRACER adds -pg, and this is
# incompatible with -fomit-frame-pointer with current GCC, so we don't use
# -fomit-frame-pointer with FUNCTION_TRACER.
i f n d e f C O N F I G _ F U N C T I O N _ T R A C E R
2007-10-15 00:21:35 +04:00
KBUILD_CFLAGS += -fomit-frame-pointer
2005-04-17 02:20:36 +04:00
e n d i f
2010-08-10 22:20:53 +04:00
e n d i f
2005-04-17 02:20:36 +04:00
security: allow using Clang's zero initialization for stack variables
In addition to -ftrivial-auto-var-init=pattern (used by
CONFIG_INIT_STACK_ALL now) Clang also supports zero initialization for
locals enabled by -ftrivial-auto-var-init=zero. The future of this flag
is still being debated (see https://bugs.llvm.org/show_bug.cgi?id=45497).
Right now it is guarded by another flag,
-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang,
which means it may not be supported by future Clang releases. Another
possible resolution is that -ftrivial-auto-var-init=zero will persist
(as certain users have already started depending on it), but the name
of the guard flag will change.
In the meantime, zero initialization has proven itself as a good
production mitigation measure against uninitialized locals. Unlike pattern
initialization, which has a higher chance of triggering existing bugs,
zero initialization provides safe defaults for strings, pointers, indexes,
and sizes. On the other hand, pattern initialization remains safer for
return values. Chrome OS and Android are moving to using zero
initialization for production builds.
Performance-wise, the difference between pattern and zero initialization
is usually negligible, although the generated code for zero
initialization is more compact.
This patch renames CONFIG_INIT_STACK_ALL to CONFIG_INIT_STACK_ALL_PATTERN
and introduces another config option, CONFIG_INIT_STACK_ALL_ZERO, that
enables zero initialization for locals if the corresponding flags are
supported by Clang.
Cc: Kees Cook <keescook@chromium.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Alexander Potapenko <glider@google.com>
Link: https://lore.kernel.org/r/20200616083435.223038-1-glider@google.com
Reviewed-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
2020-06-16 11:34:35 +03:00
# Initialize all stack variables with a 0xAA pattern.
i f d e f C O N F I G _ I N I T _ S T A C K _ A L L _ P A T T E R N
2019-04-10 18:48:31 +03:00
KBUILD_CFLAGS += -ftrivial-auto-var-init= pattern
e n d i f
security: allow using Clang's zero initialization for stack variables
In addition to -ftrivial-auto-var-init=pattern (used by
CONFIG_INIT_STACK_ALL now) Clang also supports zero initialization for
locals enabled by -ftrivial-auto-var-init=zero. The future of this flag
is still being debated (see https://bugs.llvm.org/show_bug.cgi?id=45497).
Right now it is guarded by another flag,
-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang,
which means it may not be supported by future Clang releases. Another
possible resolution is that -ftrivial-auto-var-init=zero will persist
(as certain users have already started depending on it), but the name
of the guard flag will change.
In the meantime, zero initialization has proven itself as a good
production mitigation measure against uninitialized locals. Unlike pattern
initialization, which has a higher chance of triggering existing bugs,
zero initialization provides safe defaults for strings, pointers, indexes,
and sizes. On the other hand, pattern initialization remains safer for
return values. Chrome OS and Android are moving to using zero
initialization for production builds.
Performance-wise, the difference between pattern and zero initialization
is usually negligible, although the generated code for zero
initialization is more compact.
This patch renames CONFIG_INIT_STACK_ALL to CONFIG_INIT_STACK_ALL_PATTERN
and introduces another config option, CONFIG_INIT_STACK_ALL_ZERO, that
enables zero initialization for locals if the corresponding flags are
supported by Clang.
Cc: Kees Cook <keescook@chromium.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Alexander Potapenko <glider@google.com>
Link: https://lore.kernel.org/r/20200616083435.223038-1-glider@google.com
Reviewed-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
2020-06-16 11:34:35 +03:00
# Initialize all stack variables with a zero value.
i f d e f C O N F I G _ I N I T _ S T A C K _ A L L _ Z E R O
# Future support for zero initialization is still being debated, see
# https://bugs.llvm.org/show_bug.cgi?id=45497. These flags are subject to being
# renamed or dropped.
KBUILD_CFLAGS += -ftrivial-auto-var-init= zero
KBUILD_CFLAGS += -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
e n d i f
stack: Optionally randomize kernel stack offset each syscall
This provides the ability for architectures to enable kernel stack base
address offset randomization. This feature is controlled by the boot
param "randomize_kstack_offset=on/off", with its default value set by
CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.
This feature is based on the original idea from the last public release
of PaX's RANDKSTACK feature: https://pax.grsecurity.net/docs/randkstack.txt
All the credit for the original idea goes to the PaX team. Note that
the design and implementation of this upstream randomize_kstack_offset
feature differs greatly from the RANDKSTACK feature (see below).
Reasoning for the feature:
This feature aims to make harder the various stack-based attacks that
rely on deterministic stack structure. We have had many such attacks in
past (just to name few):
https://jon.oberheide.org/files/infiltrate12-thestackisback.pdf
https://jon.oberheide.org/files/stackjacking-infiltrate11.pdf
https://googleprojectzero.blogspot.com/2016/06/exploiting-recursion-in-linux-kernel_20.html
As Linux kernel stack protections have been constantly improving
(vmap-based stack allocation with guard pages, removal of thread_info,
STACKLEAK), attackers have had to find new ways for their exploits
to work. They have done so, continuing to rely on the kernel's stack
determinism, in situations where VMAP_STACK and THREAD_INFO_IN_TASK_STRUCT
were not relevant. For example, the following recent attacks would have
been hampered if the stack offset was non-deterministic between syscalls:
https://repositorio-aberto.up.pt/bitstream/10216/125357/2/374717.pdf
(page 70: targeting the pt_regs copy with linear stack overflow)
https://a13xp0p0v.github.io/2020/02/15/CVE-2019-18683.html
(leaked stack address from one syscall as a target during next syscall)
The main idea is that since the stack offset is randomized on each system
call, it is harder for an attack to reliably land in any particular place
on the thread stack, even with address exposures, as the stack base will
change on the next syscall. Also, since randomization is performed after
placing pt_regs, the ptrace-based approach[1] to discover the randomized
offset during a long-running syscall should not be possible.
Design description:
During most of the kernel's execution, it runs on the "thread stack",
which is pretty deterministic in its structure: it is fixed in size,
and on every entry from userspace to kernel on a syscall the thread
stack starts construction from an address fetched from the per-cpu
cpu_current_top_of_stack variable. The first element to be pushed to the
thread stack is the pt_regs struct that stores all required CPU registers
and syscall parameters. Finally the specific syscall function is called,
with the stack being used as the kernel executes the resulting request.
The goal of randomize_kstack_offset feature is to add a random offset
after the pt_regs has been pushed to the stack and before the rest of the
thread stack is used during the syscall processing, and to change it every
time a process issues a syscall. The source of randomness is currently
architecture-defined (but x86 is using the low byte of rdtsc()). Future
improvements for different entropy sources is possible, but out of scope
for this patch. Further more, to add more unpredictability, new offsets
are chosen at the end of syscalls (the timing of which should be less
easy to measure from userspace than at syscall entry time), and stored
in a per-CPU variable, so that the life of the value does not stay
explicitly tied to a single task.
As suggested by Andy Lutomirski, the offset is added using alloca()
and an empty asm() statement with an output constraint, since it avoids
changes to assembly syscall entry code, to the unwinder, and provides
correct stack alignment as defined by the compiler.
In order to make this available by default with zero performance impact
for those that don't want it, it is boot-time selectable with static
branches. This way, if the overhead is not wanted, it can just be
left turned off with no performance impact.
The generated assembly for x86_64 with GCC looks like this:
...
ffffffff81003977: 65 8b 05 02 ea 00 7f mov %gs:0x7f00ea02(%rip),%eax
# 12380 <kstack_offset>
ffffffff8100397e: 25 ff 03 00 00 and $0x3ff,%eax
ffffffff81003983: 48 83 c0 0f add $0xf,%rax
ffffffff81003987: 25 f8 07 00 00 and $0x7f8,%eax
ffffffff8100398c: 48 29 c4 sub %rax,%rsp
ffffffff8100398f: 48 8d 44 24 0f lea 0xf(%rsp),%rax
ffffffff81003994: 48 83 e0 f0 and $0xfffffffffffffff0,%rax
...
As a result of the above stack alignment, this patch introduces about
5 bits of randomness after pt_regs is spilled to the thread stack on
x86_64, and 6 bits on x86_32 (since its has 1 fewer bit required for
stack alignment). The amount of entropy could be adjusted based on how
much of the stack space we wish to trade for security.
My measure of syscall performance overhead (on x86_64):
lmbench: /usr/lib/lmbench/bin/x86_64-linux-gnu/lat_syscall -N 10000 null
randomize_kstack_offset=y Simple syscall: 0.7082 microseconds
randomize_kstack_offset=n Simple syscall: 0.7016 microseconds
So, roughly 0.9% overhead growth for a no-op syscall, which is very
manageable. And for people that don't want this, it's off by default.
There are two gotchas with using the alloca() trick. First,
compilers that have Stack Clash protection (-fstack-clash-protection)
enabled by default (e.g. Ubuntu[3]) add pagesize stack probes to
any dynamic stack allocations. While the randomization offset is
always less than a page, the resulting assembly would still contain
(unreachable!) probing routines, bloating the resulting assembly. To
avoid this, -fno-stack-clash-protection is unconditionally added to
the kernel Makefile since this is the only dynamic stack allocation in
the kernel (now that VLAs have been removed) and it is provably safe
from Stack Clash style attacks.
The second gotcha with alloca() is a negative interaction with
-fstack-protector*, in that it sees the alloca() as an array allocation,
which triggers the unconditional addition of the stack canary function
pre/post-amble which slows down syscalls regardless of the static
branch. In order to avoid adding this unneeded check and its associated
performance impact, architectures need to carefully remove uses of
-fstack-protector-strong (or -fstack-protector) in the compilation units
that use the add_random_kstack() macro and to audit the resulting stack
mitigation coverage (to make sure no desired coverage disappears). No
change is visible for this on x86 because the stack protector is already
unconditionally disabled for the compilation unit, but the change is
required on arm64. There is, unfortunately, no attribute that can be
used to disable stack protector for specific functions.
Comparison to PaX RANDKSTACK feature:
The RANDKSTACK feature randomizes the location of the stack start
(cpu_current_top_of_stack), i.e. including the location of pt_regs
structure itself on the stack. Initially this patch followed the same
approach, but during the recent discussions[2], it has been determined
to be of a little value since, if ptrace functionality is available for
an attacker, they can use PTRACE_PEEKUSR/PTRACE_POKEUSR to read/write
different offsets in the pt_regs struct, observe the cache behavior of
the pt_regs accesses, and figure out the random stack offset. Another
difference is that the random offset is stored in a per-cpu variable,
rather than having it be per-thread. As a result, these implementations
differ a fair bit in their implementation details and results, though
obviously the intent is similar.
[1] https://lore.kernel.org/kernel-hardening/2236FBA76BA1254E88B949DDB74E612BA4BC57C1@IRSMSX102.ger.corp.intel.com/
[2] https://lore.kernel.org/kernel-hardening/20190329081358.30497-1-elena.reshetova@intel.com/
[3] https://lists.ubuntu.com/archives/ubuntu-devel/2019-June/040741.html
Co-developed-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210401232347.2791257-4-keescook@chromium.org
2021-04-02 02:23:44 +03:00
# While VLAs have been removed, GCC produces unreachable stack probes
# for the randomize_kstack_offset feature. Disable it for all compilers.
KBUILD_CFLAGS += $( call cc-option, -fno-stack-clash-protection)
hardening: Introduce CONFIG_ZERO_CALL_USED_REGS
When CONFIG_ZERO_CALL_USED_REGS is enabled, build the kernel with
"-fzero-call-used-regs=used-gpr" (in GCC 11). This option will zero any
caller-used register contents just before returning from a function,
ensuring that temporary values are not leaked beyond the function
boundary. This means that register contents are less likely to be
available for side channel attacks and information exposures.
Additionally this helps reduce the number of useful ROP gadgets in the
kernel image by about 20%:
$ ROPgadget.py --nosys --nojop --binary vmlinux.stock | tail -n1
Unique gadgets found: 337245
$ ROPgadget.py --nosys --nojop --binary vmlinux.zero-call-regs | tail -n1
Unique gadgets found: 267175
and more notably removes simple "write-what-where" gadgets:
$ ROPgadget.py --ropchain --binary vmlinux.stock | sed -n '/Step 1/,/Step 2/p'
- Step 1 -- Write-what-where gadgets
[+] Gadget found: 0xffffffff8102d76c mov qword ptr [rsi], rdx ; ret
[+] Gadget found: 0xffffffff81000cf5 pop rsi ; ret
[+] Gadget found: 0xffffffff8104d7c8 pop rdx ; ret
[-] Can't find the 'xor rdx, rdx' gadget. Try with another 'mov [reg], reg'
[+] Gadget found: 0xffffffff814c2b4c mov qword ptr [rsi], rdi ; ret
[+] Gadget found: 0xffffffff81000cf5 pop rsi ; ret
[+] Gadget found: 0xffffffff81001e51 pop rdi ; ret
[-] Can't find the 'xor rdi, rdi' gadget. Try with another 'mov [reg], reg'
[+] Gadget found: 0xffffffff81540d61 mov qword ptr [rsi], rdi ; pop rbx ; pop rbp ; ret
[+] Gadget found: 0xffffffff81000cf5 pop rsi ; ret
[+] Gadget found: 0xffffffff81001e51 pop rdi ; ret
[-] Can't find the 'xor rdi, rdi' gadget. Try with another 'mov [reg], reg'
[+] Gadget found: 0xffffffff8105341e mov qword ptr [rsi], rax ; ret
[+] Gadget found: 0xffffffff81000cf5 pop rsi ; ret
[+] Gadget found: 0xffffffff81029a11 pop rax ; ret
[+] Gadget found: 0xffffffff811f1c3b xor rax, rax ; ret
- Step 2 -- Init syscall number gadgets
$ ROPgadget.py --ropchain --binary vmlinux.zero* | sed -n '/Step 1/,/Step 2/p'
- Step 1 -- Write-what-where gadgets
[-] Can't find the 'mov qword ptr [r64], r64' gadget
For an x86_64 parallel build tests, this has a less than 1% performance
impact, and grows the image size less than 1%:
$ size vmlinux.stock vmlinux.zero-call-regs
text data bss dec hex filename
22437676 8559152 14127340 45124168 2b08a48 vmlinux.stock
22453184 8563248 14110956 45127388 2b096dc vmlinux.zero-call-regs
Impact for other architectures may vary. For example, arm64 sees a 5.5%
image size growth, mainly due to needing to always clear x16 and x17:
https://lore.kernel.org/lkml/20210510134503.GA88495@C02TD0UTHF1T.local/
Signed-off-by: Kees Cook <keescook@chromium.org>
2021-04-13 05:56:54 +03:00
# Clear used registers at func exit (to reduce data lifetime and ROP gadgets).
i f d e f C O N F I G _ Z E R O _ C A L L _ U S E D _ R E G S
KBUILD_CFLAGS += -fzero-call-used-regs= used-gpr
e n d i f
2021-02-03 10:52:39 +03:00
DEBUG_CFLAGS :=
2020-10-17 15:01:35 +03:00
# Workaround for GCC versions < 5.0
# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61801
i f d e f C O N F I G _ C C _ I S _ G C C
2021-02-03 10:52:39 +03:00
DEBUG_CFLAGS += $( call cc-ifversion, -lt, 0500, $( call cc-option, -fno-var-tracking-assignments) )
2020-10-17 15:01:35 +03:00
e n d i f
Fix gcc-4.9.0 miscompilation of load_balance() in scheduler
Michel Dänzer and a couple of other people reported inexplicable random
oopses in the scheduler, and the cause turns out to be gcc mis-compiling
the load_balance() function when debugging is enabled. The gcc bug
apparently goes back to gcc-4.5, but slight optimization changes means
that it now showed up as a problem in 4.9.0 and 4.9.1.
The instruction scheduling problem causes gcc to schedule a spill
operation to before the stack frame has been created, which in turn can
corrupt the spilled value if an interrupt comes in. There may be other
effects of this bug too, but that's the code generation problem seen in
Michel's case.
This is fixed in current gcc HEAD, but the workaround as suggested by
Markus Trippelsdorf is pretty simple: use -fno-var-tracking-assignments
when compiling the kernel, which disables the gcc code that causes the
problem. This can result in slightly worse debug information for
variable accesses, but that is infinitely preferable to actual code
generation problems.
Doing this unconditionally (not just for CONFIG_DEBUG_INFO) also allows
non-debug builds to verify that the debug build would be identical: we
can do
export GCC_COMPARE_DEBUG=1
to make gcc internally verify that the result of the build is
independent of the "-g" flag (it will make the compiler build everything
twice, toggling the debug flag, and compare the results).
Without the "-fno-var-tracking-assignments" option, the build would fail
(even with 4.8.3 that didn't show the actual stack frame bug) with a gcc
compare failure.
See also gcc bugzilla:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61801
Reported-by: Michel Dänzer <michel@daenzer.net>
Suggested-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Cc: Jakub Jelinek <jakub@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-07-27 01:52:01 +04:00
2005-04-17 02:20:36 +04:00
i f d e f C O N F I G _ D E B U G _ I N F O
2020-08-16 15:32:44 +03:00
2014-07-30 22:50:18 +04:00
i f d e f C O N F I G _ D E B U G _ I N F O _ S P L I T
2019-02-22 10:56:09 +03:00
DEBUG_CFLAGS += -gsplit-dwarf
2014-07-30 22:50:18 +04:00
e l s e
kbuild: Disable extra debugging info in .s output
Modern gcc adds view assignments, reset assertion checking in .loc
directives and a couple more additional debug markers, which clutters
the asm output unnecessarily:
For example:
bsp_resume:
.LFB3466:
.loc 1 1868 1 is_stmt 1 view -0
.cfi_startproc
.loc 1 1869 2 view .LVU73
# arch/x86/kernel/cpu/common.c:1869: if (this_cpu->c_bsp_resume)
.loc 1 1869 14 is_stmt 0 view .LVU74
movq this_cpu(%rip), %rax # this_cpu, this_cpu
movq 64(%rax), %rax # this_cpu.94_1->c_bsp_resume, _2
# arch/x86/kernel/cpu/common.c:1869: if (this_cpu->c_bsp_resume)
.loc 1 1869 5 view .LVU75
testq %rax, %rax # _2
je .L8 #,
.loc 1 1870 3 is_stmt 1 view .LVU76
movq $boot_cpu_data, %rdi #,
jmp __x86_indirect_thunk_rax
or
.loc 2 57 9 view .LVU478
.loc 2 57 9 view .LVU479
.loc 2 57 9 view .LVU480
.loc 2 57 9 view .LVU481
.LBB1385:
.LBB1383:
.LBB1379:
.LBB1377:
.LBB1375:
.loc 2 57 9 view .LVU482
.loc 2 57 9 view .LVU483
movl %edi, %edx # cpu, cpu
.LVL87:
.loc 2 57 9 is_stmt 0 view .LVU484
That MOV in there is drowned in debugging information and latter makes
it hard to follow the asm. And that DWARF info is not really needed for
asm output staring.
Disable the debug information generation which clutters the asm output
unnecessarily:
bsp_resume:
# arch/x86/kernel/cpu/common.c:1869: if (this_cpu->c_bsp_resume)
movq this_cpu(%rip), %rax # this_cpu, this_cpu
movq 64(%rax), %rax # this_cpu.94_1->c_bsp_resume, _2
# arch/x86/kernel/cpu/common.c:1869: if (this_cpu->c_bsp_resume)
testq %rax, %rax # _2
je .L8 #,
# arch/x86/kernel/cpu/common.c:1870: this_cpu->c_bsp_resume(&boot_cpu_data);
movq $boot_cpu_data, %rdi #,
jmp __x86_indirect_thunk_rax
.L8:
# arch/x86/kernel/cpu/common.c:1871: }
rep ret
.size bsp_resume, .-bsp_resume
[ bp: write commit message. ]
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
2019-02-10 09:51:00 +03:00
DEBUG_CFLAGS += -g
2014-07-30 22:50:18 +04:00
e n d i f
2020-08-16 15:32:44 +03:00
2021-08-05 18:01:02 +03:00
i f n d e f C O N F I G _ A S _ I S _ L L V M
2014-02-15 03:19:17 +04:00
KBUILD_AFLAGS += -Wa,-gdwarf-2
2020-11-09 21:35:28 +03:00
e n d i f
2020-08-16 15:32:44 +03:00
2021-02-05 23:22:19 +03:00
i f n d e f C O N F I G _ D E B U G _ I N F O _ D W A R F _ T O O L C H A I N _ D E F A U L T
dwarf-version-$(CONFIG_DEBUG_INFO_DWARF4) := 4
Kconfig: allow explicit opt in to DWARF v5
DWARF v5 is the latest standard of the DWARF debug info format. GCC 11
will change the implicit default DWARF version, if left unspecified, to
DWARF v5.
Allow users of Clang and older versions of GCC that have not changed the
implicit default DWARF version to DWARF v5 to opt in. This can help
testing consumers of DWARF debug info in preparation of v5 becoming more
widespread, as well as result in significant binary size savings of the
pre-stripped vmlinux image.
DWARF5 wins significantly in terms of size when mixed with compression
(CONFIG_DEBUG_INFO_COMPRESSED).
363M vmlinux.clang12.dwarf5.compressed
434M vmlinux.clang12.dwarf4.compressed
439M vmlinux.clang12.dwarf2.compressed
457M vmlinux.clang12.dwarf5
536M vmlinux.clang12.dwarf4
548M vmlinux.clang12.dwarf2
515M vmlinux.gcc10.2.dwarf5.compressed
599M vmlinux.gcc10.2.dwarf4.compressed
624M vmlinux.gcc10.2.dwarf2.compressed
630M vmlinux.gcc10.2.dwarf5
765M vmlinux.gcc10.2.dwarf4
809M vmlinux.gcc10.2.dwarf2
Though the quality of debug info is harder to quantify; size is not a
proxy for quality.
Jakub notes:
One thing is GCC DWARF-5 support, that is whether the compiler will
support -gdwarf-5 flag, and that support should be there from GCC 7
onwards.
All [GCC] 5.1 - 6.x did was start accepting -gdwarf-5 as experimental
option that enabled some small DWARF subset (initially only a few
DW_LANG_* codes newly added to DWARF5 drafts). Only GCC 7 (released
after DWARF 5 has been finalized) started emitting DWARF5 section
headers and got most of the DWARF5 changes in...
Another separate thing is whether the assembler does support
the -gdwarf-5 option (i.e. if you can compile assembler files
with -Wa,-gdwarf-5) ... That option is about whether the assembler
will emit DWARF5 or DWARF2 .debug_line. It is fine to compile C sources
with -gdwarf-5 and use DWARF2 .debug_line for assembler files if as
doesn't support it.
Version check GCC so that we don't need to worry about the difference in
command line args between GNU readelf and llvm-readelf/llvm-dwarfdump to
validate the DWARF Version in the assembler feature detection script.
Most issues with clang produced assembler were fixed in binutils 2.35.1,
but 2.35.2 fixed issues related to requiring the flag -Wa,-gdwarf-5
explicitly. The added shell script test checks for the latter, and is
only required when using clang without its integrated assembler, though
we use for clang regardless as we do not yet have a way to query the
assembler from Kconfig.
Disabled for now if CONFIG_DEBUG_INFO_BTF is set; pahole doesn't yet
recognize the new additions to the DWARF debug info.
This only modifies the DWARF version emitted by the compiler, not the
assembler.
The DWARF version of a binary can be validated with:
$ llvm-dwarfdump <object file> | head -n 4 | grep version
or
$ readelf --debug-dump=info <object file> 2>/dev/null | grep Version
Parts of the tree don't reuse DEBUG_CFLAGS as they should; such cleanup
is left as a follow up.
Link: http://www.dwarfstd.org/doc/DWARF5.pdf
Link: https://bugzilla.redhat.com/show_bug.cgi?id=1922707
Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
Suggested-by: Arvind Sankar <nivedita@alum.mit.edu>
Suggested-by: Caroline Tice <cmtice@google.com>
Suggested-by: Fangrui Song <maskray@google.com>
Suggested-by: Jakub Jelinek <jakub@redhat.com>
Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
Suggested-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM/Clang v12.0.0-rc1 x86-64
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-02-05 23:22:20 +03:00
dwarf-version-$(CONFIG_DEBUG_INFO_DWARF5) := 5
2021-02-05 23:22:19 +03:00
DEBUG_CFLAGS += -gdwarf-$( dwarf-version-y)
2014-07-30 22:50:19 +04:00
e n d i f
2005-04-17 02:20:36 +04:00
2010-07-14 17:43:52 +04:00
i f d e f C O N F I G _ D E B U G _ I N F O _ R E D U C E D
Makefile: remove stale cc-option checks
cc-option, cc-option-yn, and cc-disable-warning all invoke the compiler
during build time, and can slow down the build when these checks become
stale for our supported compilers, whose minimally supported versions
increases over time. See Documentation/process/changes.rst for the
current supported minimal versions (GCC 4.9+, clang 10.0.1+). Compiler
version support for these flags may be verified on godbolt.org.
The following flags are GCC only and supported since at least GCC 4.9.
Remove cc-option and cc-disable-warning tests.
* -fno-tree-loop-im
* -Wno-maybe-uninitialized
* -fno-reorder-blocks
* -fno-ipa-cp-clone
* -fno-partial-inlining
* -femit-struct-debug-baseonly
* -fno-inline-functions-called-once
* -fconserve-stack
The following flags are supported by all supported versions of GCC and
Clang. Remove their cc-option, cc-option-yn, and cc-disable-warning tests.
* -fno-delete-null-pointer-checks
* -fno-var-tracking
* -Wno-array-bounds
The following configs are made dependent on GCC, since they use GCC
specific flags.
* READABLE_ASM
* DEBUG_SECTION_MISMATCH
-mfentry was not supported by s390-linux-gnu-gcc until gcc-9+, add a
comment.
--param=allow-store-data-races=0 was renamed to -fno-allow-store-data-races
in the GCC 10 release; add a comment.
-Wmaybe-uninitialized (GCC specific) was being added for CONFIG_GCOV,
then again unconditionally; add it only once.
Also, base RETPOLINE_CFLAGS and RETPOLINE_VDSO_CFLAGS on CONFIC_CC_IS_*
then remove cc-option tests for Clang.
Link: https://github.com/ClangBuiltLinux/linux/issues/1436
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-08-16 23:25:01 +03:00
DEBUG_CFLAGS += -fno-var-tracking
i f d e f C O N F I G _ C C _ I S _ G C C
DEBUG_CFLAGS += -femit-struct-debug-baseonly
e n d i f
2010-07-14 17:43:52 +04:00
e n d i f
2020-05-26 20:18:29 +03:00
i f d e f C O N F I G _ D E B U G _ I N F O _ C O M P R E S S E D
DEBUG_CFLAGS += -gz= zlib
Makefile: Improve compressed debug info support detection
Commit
10e68b02c861 ("Makefile: support compressed debug info")
added support for compressed debug sections.
Support is detected by checking
- does the compiler support -gz=zlib
- does the assembler support --compressed-debug-sections=zlib
- does the linker support --compressed-debug-sections=zlib
However, the gcc driver's support for this option is somewhat
convoluted. The driver's builtin specs are set based on the version of
binutils that it was configured with. It reports an error if the
configure-time linker/assembler (i.e., not necessarily the actual
assembler that will be run) do not support the option, but only if the
assembler (or linker) is actually invoked when -gz=zlib is passed.
The cc-option check in scripts/Kconfig.include does not invoke the
assembler, so the gcc driver reports success even if it does not support
the option being passed to the assembler.
Because the as-option check passes the option directly to the assembler
via -Wa,--compressed-debug-sections=zlib, the gcc driver does not see
this option and will never report an error.
Combined with an installed version of binutils that is more recent than
the one the compiler was built with, it is possible for all three tests
to succeed, yet an actual compilation with -gz=zlib to fail.
Moreover, it is unnecessary to explicitly pass
--compressed-debug-sections=zlib to the assembler via -Wa, since the
driver will do that automatically when it supports -gz=zlib.
Convert the as-option to just -gz=zlib, simplifying it as well as
performing a better test of the gcc driver's capabilities.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2020-06-12 01:03:39 +03:00
KBUILD_AFLAGS += -gz= zlib
2020-05-26 20:18:29 +03:00
KBUILD_LDFLAGS += --compress-debug-sections= zlib
e n d i f
2020-08-16 15:32:44 +03:00
e n d i f # CONFIG_DEBUG_INFO
kbuild: Disable extra debugging info in .s output
Modern gcc adds view assignments, reset assertion checking in .loc
directives and a couple more additional debug markers, which clutters
the asm output unnecessarily:
For example:
bsp_resume:
.LFB3466:
.loc 1 1868 1 is_stmt 1 view -0
.cfi_startproc
.loc 1 1869 2 view .LVU73
# arch/x86/kernel/cpu/common.c:1869: if (this_cpu->c_bsp_resume)
.loc 1 1869 14 is_stmt 0 view .LVU74
movq this_cpu(%rip), %rax # this_cpu, this_cpu
movq 64(%rax), %rax # this_cpu.94_1->c_bsp_resume, _2
# arch/x86/kernel/cpu/common.c:1869: if (this_cpu->c_bsp_resume)
.loc 1 1869 5 view .LVU75
testq %rax, %rax # _2
je .L8 #,
.loc 1 1870 3 is_stmt 1 view .LVU76
movq $boot_cpu_data, %rdi #,
jmp __x86_indirect_thunk_rax
or
.loc 2 57 9 view .LVU478
.loc 2 57 9 view .LVU479
.loc 2 57 9 view .LVU480
.loc 2 57 9 view .LVU481
.LBB1385:
.LBB1383:
.LBB1379:
.LBB1377:
.LBB1375:
.loc 2 57 9 view .LVU482
.loc 2 57 9 view .LVU483
movl %edi, %edx # cpu, cpu
.LVL87:
.loc 2 57 9 is_stmt 0 view .LVU484
That MOV in there is drowned in debugging information and latter makes
it hard to follow the asm. And that DWARF info is not really needed for
asm output staring.
Disable the debug information generation which clutters the asm output
unnecessarily:
bsp_resume:
# arch/x86/kernel/cpu/common.c:1869: if (this_cpu->c_bsp_resume)
movq this_cpu(%rip), %rax # this_cpu, this_cpu
movq 64(%rax), %rax # this_cpu.94_1->c_bsp_resume, _2
# arch/x86/kernel/cpu/common.c:1869: if (this_cpu->c_bsp_resume)
testq %rax, %rax # _2
je .L8 #,
# arch/x86/kernel/cpu/common.c:1870: this_cpu->c_bsp_resume(&boot_cpu_data);
movq $boot_cpu_data, %rdi #,
jmp __x86_indirect_thunk_rax
.L8:
# arch/x86/kernel/cpu/common.c:1871: }
rep ret
.size bsp_resume, .-bsp_resume
[ bp: write commit message. ]
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
2019-02-10 09:51:00 +03:00
KBUILD_CFLAGS += $( DEBUG_CFLAGS)
export DEBUG_CFLAGS
2008-10-07 03:06:12 +04:00
i f d e f C O N F I G _ F U N C T I O N _ T R A C E R
2020-12-11 21:46:18 +03:00
i f d e f C O N F I G _ F T R A C E _ M C O U N T _ U S E _ C C
CC_FLAGS_FTRACE += -mrecord-mcount
2018-08-06 16:17:46 +03:00
ifdef CONFIG_HAVE_NOP_MCOUNT
ifeq ( $( call cc-option-yn, -mnop-mcount) ,y)
CC_FLAGS_FTRACE += -mnop-mcount
CC_FLAGS_USING += -DCC_USING_NOP_MCOUNT
endif
endif
2018-08-06 16:17:44 +03:00
e n d i f
2020-09-26 02:43:53 +03:00
i f d e f C O N F I G _ F T R A C E _ M C O U N T _ U S E _ O B J T O O L
CC_FLAGS_USING += -DCC_USING_NOP_MCOUNT
e n d i f
2020-12-11 21:46:18 +03:00
i f d e f C O N F I G _ F T R A C E _ M C O U N T _ U S E _ R E C O R D M C O U N T
ifdef CONFIG_HAVE_C_RECORDMCOUNT
BUILD_C_RECORDMCOUNT := y
export BUILD_C_RECORDMCOUNT
endif
e n d i f
2011-02-09 21:15:59 +03:00
i f d e f C O N F I G _ H A V E _ F E N T R Y
Makefile: remove stale cc-option checks
cc-option, cc-option-yn, and cc-disable-warning all invoke the compiler
during build time, and can slow down the build when these checks become
stale for our supported compilers, whose minimally supported versions
increases over time. See Documentation/process/changes.rst for the
current supported minimal versions (GCC 4.9+, clang 10.0.1+). Compiler
version support for these flags may be verified on godbolt.org.
The following flags are GCC only and supported since at least GCC 4.9.
Remove cc-option and cc-disable-warning tests.
* -fno-tree-loop-im
* -Wno-maybe-uninitialized
* -fno-reorder-blocks
* -fno-ipa-cp-clone
* -fno-partial-inlining
* -femit-struct-debug-baseonly
* -fno-inline-functions-called-once
* -fconserve-stack
The following flags are supported by all supported versions of GCC and
Clang. Remove their cc-option, cc-option-yn, and cc-disable-warning tests.
* -fno-delete-null-pointer-checks
* -fno-var-tracking
* -Wno-array-bounds
The following configs are made dependent on GCC, since they use GCC
specific flags.
* READABLE_ASM
* DEBUG_SECTION_MISMATCH
-mfentry was not supported by s390-linux-gnu-gcc until gcc-9+, add a
comment.
--param=allow-store-data-races=0 was renamed to -fno-allow-store-data-races
in the GCC 10 release; add a comment.
-Wmaybe-uninitialized (GCC specific) was being added for CONFIG_GCOV,
then again unconditionally; add it only once.
Also, base RETPOLINE_CFLAGS and RETPOLINE_VDSO_CFLAGS on CONFIC_CC_IS_*
then remove cc-option tests for Clang.
Link: https://github.com/ClangBuiltLinux/linux/issues/1436
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-08-16 23:25:01 +03:00
# s390-linux-gnu-gcc did not support -mfentry until gcc-9.
2018-08-06 16:17:42 +03:00
ifeq ( $( call cc-option-yn, -mfentry) ,y)
CC_FLAGS_FTRACE += -mfentry
CC_FLAGS_USING += -DCC_USING_FENTRY
endif
2011-02-09 21:15:59 +03:00
e n d i f
2018-08-06 16:17:42 +03:00
export CC_FLAGS_FTRACE
KBUILD_CFLAGS += $( CC_FLAGS_FTRACE) $( CC_FLAGS_USING)
KBUILD_AFLAGS += $( CC_FLAGS_USING)
2008-05-12 23:20:42 +04:00
e n d i f
2008-01-21 23:31:44 +03:00
# We trigger additional mismatches with less inlining
i f d e f C O N F I G _ D E B U G _ S E C T I O N _ M I S M A T C H
Makefile: remove stale cc-option checks
cc-option, cc-option-yn, and cc-disable-warning all invoke the compiler
during build time, and can slow down the build when these checks become
stale for our supported compilers, whose minimally supported versions
increases over time. See Documentation/process/changes.rst for the
current supported minimal versions (GCC 4.9+, clang 10.0.1+). Compiler
version support for these flags may be verified on godbolt.org.
The following flags are GCC only and supported since at least GCC 4.9.
Remove cc-option and cc-disable-warning tests.
* -fno-tree-loop-im
* -Wno-maybe-uninitialized
* -fno-reorder-blocks
* -fno-ipa-cp-clone
* -fno-partial-inlining
* -femit-struct-debug-baseonly
* -fno-inline-functions-called-once
* -fconserve-stack
The following flags are supported by all supported versions of GCC and
Clang. Remove their cc-option, cc-option-yn, and cc-disable-warning tests.
* -fno-delete-null-pointer-checks
* -fno-var-tracking
* -Wno-array-bounds
The following configs are made dependent on GCC, since they use GCC
specific flags.
* READABLE_ASM
* DEBUG_SECTION_MISMATCH
-mfentry was not supported by s390-linux-gnu-gcc until gcc-9+, add a
comment.
--param=allow-store-data-races=0 was renamed to -fno-allow-store-data-races
in the GCC 10 release; add a comment.
-Wmaybe-uninitialized (GCC specific) was being added for CONFIG_GCOV,
then again unconditionally; add it only once.
Also, base RETPOLINE_CFLAGS and RETPOLINE_VDSO_CFLAGS on CONFIC_CC_IS_*
then remove cc-option tests for Clang.
Link: https://github.com/ClangBuiltLinux/linux/issues/1436
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-08-16 23:25:01 +03:00
KBUILD_CFLAGS += -fno-inline-functions-called-once
2008-01-21 23:31:44 +03:00
e n d i f
2017-04-14 09:17:26 +03:00
i f d e f C O N F I G _ L D _ D E A D _ C O D E _ D A T A _ E L I M I N A T I O N
2018-08-22 16:51:09 +03:00
KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections
LDFLAGS_vmlinux += --gc-sections
2017-04-14 09:17:26 +03:00
e n d i f
2020-04-27 19:00:07 +03:00
i f d e f C O N F I G _ S H A D O W _ C A L L _ S T A C K
CC_FLAGS_SCS := -fsanitize= shadow-call-stack
KBUILD_CFLAGS += $( CC_FLAGS_SCS)
export CC_FLAGS_SCS
e n d i f
kbuild: add support for Clang LTO
This change adds build system support for Clang's Link Time
Optimization (LTO). With -flto, instead of ELF object files, Clang
produces LLVM bitcode, which is compiled into native code at link
time, allowing the final binary to be optimized globally. For more
details, see:
https://llvm.org/docs/LinkTimeOptimization.html
The Kconfig option CONFIG_LTO_CLANG is implemented as a choice,
which defaults to LTO being disabled. To use LTO, the architecture
must select ARCH_SUPPORTS_LTO_CLANG and support:
- compiling with Clang,
- compiling all assembly code with Clang's integrated assembler,
- and linking with LLD.
While using CONFIG_LTO_CLANG_FULL results in the best runtime
performance, the compilation is not scalable in time or
memory. CONFIG_LTO_CLANG_THIN enables ThinLTO, which allows
parallel optimization and faster incremental builds. ThinLTO is
used by default if the architecture also selects
ARCH_SUPPORTS_LTO_CLANG_THIN:
https://clang.llvm.org/docs/ThinLTO.html
To enable LTO, LLVM tools must be used to handle bitcode files, by
passing LLVM=1 and LLVM_IAS=1 options to make:
$ make LLVM=1 LLVM_IAS=1 defconfig
$ scripts/config -e LTO_CLANG_THIN
$ make LLVM=1 LLVM_IAS=1
To prepare for LTO support with other compilers, common parts are
gated behind the CONFIG_LTO option, and LTO can be disabled for
specific files by filtering out CC_FLAGS_LTO.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201211184633.3213045-3-samitolvanen@google.com
2020-12-11 21:46:19 +03:00
i f d e f C O N F I G _ L T O _ C L A N G
i f d e f C O N F I G _ L T O _ C L A N G _ T H I N
2021-01-21 21:45:55 +03:00
CC_FLAGS_LTO := -flto= thin -fsplit-lto-unit
2021-03-31 16:38:06 +03:00
KBUILD_LDFLAGS += --thinlto-cache-dir= $( extmod_prefix) .thinlto-cache
kbuild: add support for Clang LTO
This change adds build system support for Clang's Link Time
Optimization (LTO). With -flto, instead of ELF object files, Clang
produces LLVM bitcode, which is compiled into native code at link
time, allowing the final binary to be optimized globally. For more
details, see:
https://llvm.org/docs/LinkTimeOptimization.html
The Kconfig option CONFIG_LTO_CLANG is implemented as a choice,
which defaults to LTO being disabled. To use LTO, the architecture
must select ARCH_SUPPORTS_LTO_CLANG and support:
- compiling with Clang,
- compiling all assembly code with Clang's integrated assembler,
- and linking with LLD.
While using CONFIG_LTO_CLANG_FULL results in the best runtime
performance, the compilation is not scalable in time or
memory. CONFIG_LTO_CLANG_THIN enables ThinLTO, which allows
parallel optimization and faster incremental builds. ThinLTO is
used by default if the architecture also selects
ARCH_SUPPORTS_LTO_CLANG_THIN:
https://clang.llvm.org/docs/ThinLTO.html
To enable LTO, LLVM tools must be used to handle bitcode files, by
passing LLVM=1 and LLVM_IAS=1 options to make:
$ make LLVM=1 LLVM_IAS=1 defconfig
$ scripts/config -e LTO_CLANG_THIN
$ make LLVM=1 LLVM_IAS=1
To prepare for LTO support with other compilers, common parts are
gated behind the CONFIG_LTO option, and LTO can be disabled for
specific files by filtering out CC_FLAGS_LTO.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201211184633.3213045-3-samitolvanen@google.com
2020-12-11 21:46:19 +03:00
e l s e
2021-01-21 21:45:55 +03:00
CC_FLAGS_LTO := -flto
kbuild: add support for Clang LTO
This change adds build system support for Clang's Link Time
Optimization (LTO). With -flto, instead of ELF object files, Clang
produces LLVM bitcode, which is compiled into native code at link
time, allowing the final binary to be optimized globally. For more
details, see:
https://llvm.org/docs/LinkTimeOptimization.html
The Kconfig option CONFIG_LTO_CLANG is implemented as a choice,
which defaults to LTO being disabled. To use LTO, the architecture
must select ARCH_SUPPORTS_LTO_CLANG and support:
- compiling with Clang,
- compiling all assembly code with Clang's integrated assembler,
- and linking with LLD.
While using CONFIG_LTO_CLANG_FULL results in the best runtime
performance, the compilation is not scalable in time or
memory. CONFIG_LTO_CLANG_THIN enables ThinLTO, which allows
parallel optimization and faster incremental builds. ThinLTO is
used by default if the architecture also selects
ARCH_SUPPORTS_LTO_CLANG_THIN:
https://clang.llvm.org/docs/ThinLTO.html
To enable LTO, LLVM tools must be used to handle bitcode files, by
passing LLVM=1 and LLVM_IAS=1 options to make:
$ make LLVM=1 LLVM_IAS=1 defconfig
$ scripts/config -e LTO_CLANG_THIN
$ make LLVM=1 LLVM_IAS=1
To prepare for LTO support with other compilers, common parts are
gated behind the CONFIG_LTO option, and LTO can be disabled for
specific files by filtering out CC_FLAGS_LTO.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201211184633.3213045-3-samitolvanen@google.com
2020-12-11 21:46:19 +03:00
e n d i f
CC_FLAGS_LTO += -fvisibility= hidden
2020-12-11 21:46:21 +03:00
# Limit inlining across translation units to reduce binary size
KBUILD_LDFLAGS += -mllvm -import-instr-limit= 5
2021-03-12 04:09:41 +03:00
2021-06-13 16:07:49 +03:00
# Check for frame size exceeding threshold during prolog/epilog insertion
# when using lld < 13.0.0.
2021-03-12 04:09:41 +03:00
i f n e q ( $( CONFIG_FRAME_WARN ) , 0 )
2021-06-13 16:07:49 +03:00
i f e q ( $( shell test $ ( CONFIG_LLD_VERSION ) -lt 130000; echo $ $ ?) , 0 )
2021-03-12 04:09:41 +03:00
KBUILD_LDFLAGS += -plugin-opt= -warn-stack-size= $( CONFIG_FRAME_WARN)
e n d i f
kbuild: add support for Clang LTO
This change adds build system support for Clang's Link Time
Optimization (LTO). With -flto, instead of ELF object files, Clang
produces LLVM bitcode, which is compiled into native code at link
time, allowing the final binary to be optimized globally. For more
details, see:
https://llvm.org/docs/LinkTimeOptimization.html
The Kconfig option CONFIG_LTO_CLANG is implemented as a choice,
which defaults to LTO being disabled. To use LTO, the architecture
must select ARCH_SUPPORTS_LTO_CLANG and support:
- compiling with Clang,
- compiling all assembly code with Clang's integrated assembler,
- and linking with LLD.
While using CONFIG_LTO_CLANG_FULL results in the best runtime
performance, the compilation is not scalable in time or
memory. CONFIG_LTO_CLANG_THIN enables ThinLTO, which allows
parallel optimization and faster incremental builds. ThinLTO is
used by default if the architecture also selects
ARCH_SUPPORTS_LTO_CLANG_THIN:
https://clang.llvm.org/docs/ThinLTO.html
To enable LTO, LLVM tools must be used to handle bitcode files, by
passing LLVM=1 and LLVM_IAS=1 options to make:
$ make LLVM=1 LLVM_IAS=1 defconfig
$ scripts/config -e LTO_CLANG_THIN
$ make LLVM=1 LLVM_IAS=1
To prepare for LTO support with other compilers, common parts are
gated behind the CONFIG_LTO option, and LTO can be disabled for
specific files by filtering out CC_FLAGS_LTO.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201211184633.3213045-3-samitolvanen@google.com
2020-12-11 21:46:19 +03:00
e n d i f
2021-06-13 16:07:49 +03:00
e n d i f
kbuild: add support for Clang LTO
This change adds build system support for Clang's Link Time
Optimization (LTO). With -flto, instead of ELF object files, Clang
produces LLVM bitcode, which is compiled into native code at link
time, allowing the final binary to be optimized globally. For more
details, see:
https://llvm.org/docs/LinkTimeOptimization.html
The Kconfig option CONFIG_LTO_CLANG is implemented as a choice,
which defaults to LTO being disabled. To use LTO, the architecture
must select ARCH_SUPPORTS_LTO_CLANG and support:
- compiling with Clang,
- compiling all assembly code with Clang's integrated assembler,
- and linking with LLD.
While using CONFIG_LTO_CLANG_FULL results in the best runtime
performance, the compilation is not scalable in time or
memory. CONFIG_LTO_CLANG_THIN enables ThinLTO, which allows
parallel optimization and faster incremental builds. ThinLTO is
used by default if the architecture also selects
ARCH_SUPPORTS_LTO_CLANG_THIN:
https://clang.llvm.org/docs/ThinLTO.html
To enable LTO, LLVM tools must be used to handle bitcode files, by
passing LLVM=1 and LLVM_IAS=1 options to make:
$ make LLVM=1 LLVM_IAS=1 defconfig
$ scripts/config -e LTO_CLANG_THIN
$ make LLVM=1 LLVM_IAS=1
To prepare for LTO support with other compilers, common parts are
gated behind the CONFIG_LTO option, and LTO can be disabled for
specific files by filtering out CC_FLAGS_LTO.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201211184633.3213045-3-samitolvanen@google.com
2020-12-11 21:46:19 +03:00
i f d e f C O N F I G _ L T O
2021-02-24 00:59:52 +03:00
KBUILD_CFLAGS += -fno-lto $( CC_FLAGS_LTO)
KBUILD_AFLAGS += -fno-lto
kbuild: add support for Clang LTO
This change adds build system support for Clang's Link Time
Optimization (LTO). With -flto, instead of ELF object files, Clang
produces LLVM bitcode, which is compiled into native code at link
time, allowing the final binary to be optimized globally. For more
details, see:
https://llvm.org/docs/LinkTimeOptimization.html
The Kconfig option CONFIG_LTO_CLANG is implemented as a choice,
which defaults to LTO being disabled. To use LTO, the architecture
must select ARCH_SUPPORTS_LTO_CLANG and support:
- compiling with Clang,
- compiling all assembly code with Clang's integrated assembler,
- and linking with LLD.
While using CONFIG_LTO_CLANG_FULL results in the best runtime
performance, the compilation is not scalable in time or
memory. CONFIG_LTO_CLANG_THIN enables ThinLTO, which allows
parallel optimization and faster incremental builds. ThinLTO is
used by default if the architecture also selects
ARCH_SUPPORTS_LTO_CLANG_THIN:
https://clang.llvm.org/docs/ThinLTO.html
To enable LTO, LLVM tools must be used to handle bitcode files, by
passing LLVM=1 and LLVM_IAS=1 options to make:
$ make LLVM=1 LLVM_IAS=1 defconfig
$ scripts/config -e LTO_CLANG_THIN
$ make LLVM=1 LLVM_IAS=1
To prepare for LTO support with other compilers, common parts are
gated behind the CONFIG_LTO option, and LTO can be disabled for
specific files by filtering out CC_FLAGS_LTO.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201211184633.3213045-3-samitolvanen@google.com
2020-12-11 21:46:19 +03:00
export CC_FLAGS_LTO
e n d i f
add support for Clang CFI
This change adds support for Clang’s forward-edge Control Flow
Integrity (CFI) checking. With CONFIG_CFI_CLANG, the compiler
injects a runtime check before each indirect function call to ensure
the target is a valid function with the correct static type. This
restricts possible call targets and makes it more difficult for
an attacker to exploit bugs that allow the modification of stored
function pointers. For more details, see:
https://clang.llvm.org/docs/ControlFlowIntegrity.html
Clang requires CONFIG_LTO_CLANG to be enabled with CFI to gain
visibility to possible call targets. Kernel modules are supported
with Clang’s cross-DSO CFI mode, which allows checking between
independently compiled components.
With CFI enabled, the compiler injects a __cfi_check() function into
the kernel and each module for validating local call targets. For
cross-module calls that cannot be validated locally, the compiler
calls the global __cfi_slowpath_diag() function, which determines
the target module and calls the correct __cfi_check() function. This
patch includes a slowpath implementation that uses __module_address()
to resolve call targets, and with CONFIG_CFI_CLANG_SHADOW enabled, a
shadow map that speeds up module look-ups by ~3x.
Clang implements indirect call checking using jump tables and
offers two methods of generating them. With canonical jump tables,
the compiler renames each address-taken function to <function>.cfi
and points the original symbol to a jump table entry, which passes
__cfi_check() validation. This isn’t compatible with stand-alone
assembly code, which the compiler doesn’t instrument, and would
result in indirect calls to assembly code to fail. Therefore, we
default to using non-canonical jump tables instead, where the compiler
generates a local jump table entry <function>.cfi_jt for each
address-taken function, and replaces all references to the function
with the address of the jump table entry.
Note that because non-canonical jump table addresses are local
to each component, they break cross-module function address
equality. Specifically, the address of a global function will be
different in each module, as it's replaced with the address of a local
jump table entry. If this address is passed to a different module,
it won’t match the address of the same function taken there. This
may break code that relies on comparing addresses passed from other
components.
CFI checking can be disabled in a function with the __nocfi attribute.
Additionally, CFI can be disabled for an entire compilation unit by
filtering out CC_FLAGS_CFI.
By default, CFI failures result in a kernel panic to stop a potential
exploit. CONFIG_CFI_PERMISSIVE enables a permissive mode, where the
kernel prints out a rate-limited warning instead, and allows execution
to continue. This option is helpful for locating type mismatches, but
should only be enabled during development.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210408182843.1754385-2-samitolvanen@google.com
2021-04-08 21:28:26 +03:00
i f d e f C O N F I G _ C F I _ C L A N G
CC_FLAGS_CFI := -fsanitize= cfi \
-fsanitize-cfi-cross-dso \
-fno-sanitize-cfi-canonical-jump-tables \
-fno-sanitize-trap= cfi \
-fno-sanitize-blacklist
i f d e f C O N F I G _ C F I _ P E R M I S S I V E
CC_FLAGS_CFI += -fsanitize-recover= cfi
e n d i f
# If LTO flags are filtered out, we must also filter out CFI.
CC_FLAGS_LTO += $( CC_FLAGS_CFI)
KBUILD_CFLAGS += $( CC_FLAGS_CFI)
export CC_FLAGS_CFI
e n d i f
2021-05-06 10:34:59 +03:00
i f d e f C O N F I G _ D E B U G _ F O R C E _ F U N C T I O N _ A L I G N _ 6 4 B
KBUILD_CFLAGS += -falign-functions= 64
./Makefile: add debug option to enable function aligned on 32 bytes
Recently 0day reported many strange performance changes (regression or
improvement), in which there was no obvious relation between the culprit
commit and the benchmark at the first look, and it causes people to doubt
the test itself is wrong.
Upon further check, many of these cases are caused by the change to the
alignment of kernel text or data, as whole text/data of kernel are linked
together, change in one domain may affect alignments of other domains.
gcc has an option '-falign-functions=n' to force text aligned, and with
that option enabled, some of those performance changes will be gone, like
[1][2][3].
Add this option so that developers and 0day can easily find performance
bump caused by text alignment change, as tracking these strange bump is
quite time consuming. Though it can't help in other cases like data
alignment changes like [4].
Following is some size data for v5.7 kernel built with a RHEL config used
in 0day:
text data bss dec filename
19738771 13292906 5554236 38585913 vmlinux.noalign
19758591 13297002 5529660 38585253 vmlinux.align32
Raw vmlinux size in bytes:
v5.7 v5.7+align32
253950832 254018000 +0.02%
Some benchmark data, most of them have no big change:
* hackbench: [ -1.8%, +0.5%]
* fsmark: [ -3.2%, +3.4%] # ext4/xfs/btrfs
* kbuild: [ -2.0%, +0.9%]
* will-it-scale: [ -0.5%, +1.8%] # mmap1/pagefault3
* netperf:
- TCP_CRR [+16.6%, +97.4%]
- TCP_RR [-18.5%, -1.8%]
- TCP_STREAM [ -1.1%, +1.9%]
[1] https://lore.kernel.org/lkml/20200114085637.GA29297@shao2-debian/
[2] https://lore.kernel.org/lkml/20200330011254.GA14393@feng-iot/
[3] https://lore.kernel.org/lkml/1d98d1f0-fe84-6df7-f5bd-f4cb2cdb7f45@intel.com/
[4] https://lore.kernel.org/lkml/20200205123216.GO12867@shao2-debian/
Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Andi Kleen <andi.kleen@intel.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Andy Shevchenko <andriy.shevchenko@intel.com>
Link: http://lkml.kernel.org/r/1595475001-90945-1-git-send-email-feng.tang@intel.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-08-12 04:34:13 +03:00
e n d i f
2005-05-01 03:51:42 +04:00
# arch Makefile may override CC so keep this after arch Makefile is included
kbuild: remove kbuild cache
The kbuild cache was introduced to remember the result of shell
commands, some of which are expensive to compute, such as
$(call cc-option,...).
However, this turned out not so clever as I had first expected.
Actually, it is problematic. For example, "$(CC) -print-file-name"
is cached. If the compiler is updated, the stale search path causes
build error, which is difficult to figure out. Another problem
scenario is cache files could be touched while install targets are
running under the root permission. We can patch them if desired,
but the build infrastructure is getting uglier and uglier.
Now, we are going to move compiler flag tests to the configuration
phase. If this is completed, the result of compiler tests will be
naturally cached in the .config file. We will not have performance
issues of incremental building since this testing only happens at
Kconfig time.
To start this work with a cleaner code base, remove the kbuild
cache first.
Revert the following commits:
Commit 9a234a2e3843 ("kbuild: create directory for make cache only when necessary")
Commit e17c400ae194 ("kbuild: shrink .cache.mk when it exceeds 1000 lines")
Commit 4e56207130ed ("kbuild: Cache a few more calls to the compiler")
Commit 3298b690b21c ("kbuild: Add a cache for generated variables")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
2018-05-28 12:21:38 +03:00
NOSTDINC_FLAGS += -nostdinc -isystem $( shell $( CC) -print-file-name= include)
2005-05-01 03:51:42 +04:00
2005-04-17 02:20:36 +04:00
# warn about C99 declaration after statement
2018-10-01 12:44:37 +03:00
KBUILD_CFLAGS += -Wdeclaration-after-statement
2005-04-17 02:20:36 +04:00
2018-06-26 01:59:34 +03:00
# Variable Length Arrays (VLAs) should not be used anywhere in the kernel
2019-05-09 09:45:49 +03:00
KBUILD_CFLAGS += -Wvla
2018-06-26 01:59:34 +03:00
2006-06-25 02:07:55 +04:00
# disable pointer signed / unsigned warnings in gcc 4.0
2018-10-01 12:44:36 +03:00
KBUILD_CFLAGS += -Wno-pointer-sign
2005-04-17 02:20:36 +04:00
2018-08-31 00:47:28 +03:00
# disable stringop warnings in gcc 8+
KBUILD_CFLAGS += $( call cc-disable-warning, stringop-truncation)
2020-05-10 00:30:29 +03:00
# We'll want to enable this eventually, but it's not going away for 5.7 at least
KBUILD_CFLAGS += $( call cc-disable-warning, zero-length-bounds)
Makefile: remove stale cc-option checks
cc-option, cc-option-yn, and cc-disable-warning all invoke the compiler
during build time, and can slow down the build when these checks become
stale for our supported compilers, whose minimally supported versions
increases over time. See Documentation/process/changes.rst for the
current supported minimal versions (GCC 4.9+, clang 10.0.1+). Compiler
version support for these flags may be verified on godbolt.org.
The following flags are GCC only and supported since at least GCC 4.9.
Remove cc-option and cc-disable-warning tests.
* -fno-tree-loop-im
* -Wno-maybe-uninitialized
* -fno-reorder-blocks
* -fno-ipa-cp-clone
* -fno-partial-inlining
* -femit-struct-debug-baseonly
* -fno-inline-functions-called-once
* -fconserve-stack
The following flags are supported by all supported versions of GCC and
Clang. Remove their cc-option, cc-option-yn, and cc-disable-warning tests.
* -fno-delete-null-pointer-checks
* -fno-var-tracking
* -Wno-array-bounds
The following configs are made dependent on GCC, since they use GCC
specific flags.
* READABLE_ASM
* DEBUG_SECTION_MISMATCH
-mfentry was not supported by s390-linux-gnu-gcc until gcc-9+, add a
comment.
--param=allow-store-data-races=0 was renamed to -fno-allow-store-data-races
in the GCC 10 release; add a comment.
-Wmaybe-uninitialized (GCC specific) was being added for CONFIG_GCOV,
then again unconditionally; add it only once.
Also, base RETPOLINE_CFLAGS and RETPOLINE_VDSO_CFLAGS on CONFIC_CC_IS_*
then remove cc-option tests for Clang.
Link: https://github.com/ClangBuiltLinux/linux/issues/1436
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-08-16 23:25:01 +03:00
KBUILD_CFLAGS += -Wno-array-bounds
2020-05-10 01:40:52 +03:00
KBUILD_CFLAGS += $( call cc-disable-warning, stringop-overflow)
2020-05-10 00:30:29 +03:00
gcc-10: disable 'restrict' warning for now
gcc-10 now warns about passing aliasing pointers to functions that take
restricted pointers.
That's actually a great warning, and if we ever start using 'restrict'
in the kernel, it might be quite useful. But right now we don't, and it
turns out that the only thing this warns about is an idiom where we have
declared a few functions to be "printf-like" (which seems to make gcc
pick up the restricted pointer thing), and then we print to the same
buffer that we also use as an input.
And people do that as an odd concatenation pattern, with code like this:
#define sysfs_show_gen_prop(buffer, fmt, ...) \
snprintf(buffer, PAGE_SIZE, "%s"fmt, buffer, __VA_ARGS__)
where we have 'buffer' as both the destination of the final result, and
as the initial argument.
Yes, it's a bit questionable. And outside of the kernel, people do have
standard declarations like
int snprintf( char *restrict buffer, size_t bufsz,
const char *restrict format, ... );
where that output buffer is marked as a restrict pointer that cannot
alias with any other arguments.
But in the context of the kernel, that 'use snprintf() to concatenate to
the end result' does work, and the pattern shows up in multiple places.
And we have not marked our own version of snprintf() as taking restrict
pointers, so the warning is incorrect for now, and gcc picks it up on
its own.
If we do start using 'restrict' in the kernel (and it might be a good
idea if people find places where it matters), we'll need to figure out
how to avoid this issue for snprintf and friends. But in the meantime,
this warning is not useful.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-05-10 01:45:21 +03:00
# Another good warning that we'll want to enable eventually
KBUILD_CFLAGS += $( call cc-disable-warning, restrict)
Stop the ad-hoc games with -Wno-maybe-initialized
We have some rather random rules about when we accept the
"maybe-initialized" warnings, and when we don't.
For example, we consider it unreliable for gcc versions < 4.9, but also
if -O3 is enabled, or if optimizing for size. And then various kernel
config options disabled it, because they know that they trigger that
warning by confusing gcc sufficiently (ie PROFILE_ALL_BRANCHES).
And now gcc-10 seems to be introducing a lot of those warnings too, so
it falls under the same heading as 4.9 did.
At the same time, we have a very straightforward way to _enable_ that
warning when wanted: use "W=2" to enable more warnings.
So stop playing these ad-hoc games, and just disable that warning by
default, with the known and straight-forward "if you want to work on the
extra compiler warnings, use W=123".
Would it be great to have code that is always so obvious that it never
confuses the compiler whether a variable is used initialized or not?
Yes, it would. In a perfect world, the compilers would be smarter, and
our source code would be simpler.
That's currently not the world we live in, though.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-05-09 23:57:10 +03:00
# Enabled with W=2, disabled by default as noisy
Makefile: remove stale cc-option checks
cc-option, cc-option-yn, and cc-disable-warning all invoke the compiler
during build time, and can slow down the build when these checks become
stale for our supported compilers, whose minimally supported versions
increases over time. See Documentation/process/changes.rst for the
current supported minimal versions (GCC 4.9+, clang 10.0.1+). Compiler
version support for these flags may be verified on godbolt.org.
The following flags are GCC only and supported since at least GCC 4.9.
Remove cc-option and cc-disable-warning tests.
* -fno-tree-loop-im
* -Wno-maybe-uninitialized
* -fno-reorder-blocks
* -fno-ipa-cp-clone
* -fno-partial-inlining
* -femit-struct-debug-baseonly
* -fno-inline-functions-called-once
* -fconserve-stack
The following flags are supported by all supported versions of GCC and
Clang. Remove their cc-option, cc-option-yn, and cc-disable-warning tests.
* -fno-delete-null-pointer-checks
* -fno-var-tracking
* -Wno-array-bounds
The following configs are made dependent on GCC, since they use GCC
specific flags.
* READABLE_ASM
* DEBUG_SECTION_MISMATCH
-mfentry was not supported by s390-linux-gnu-gcc until gcc-9+, add a
comment.
--param=allow-store-data-races=0 was renamed to -fno-allow-store-data-races
in the GCC 10 release; add a comment.
-Wmaybe-uninitialized (GCC specific) was being added for CONFIG_GCOV,
then again unconditionally; add it only once.
Also, base RETPOLINE_CFLAGS and RETPOLINE_VDSO_CFLAGS on CONFIC_CC_IS_*
then remove cc-option tests for Clang.
Link: https://github.com/ClangBuiltLinux/linux/issues/1436
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-08-16 23:25:01 +03:00
i f d e f C O N F I G _ C C _ I S _ G C C
KBUILD_CFLAGS += -Wno-maybe-uninitialized
e n d i f
Stop the ad-hoc games with -Wno-maybe-initialized
We have some rather random rules about when we accept the
"maybe-initialized" warnings, and when we don't.
For example, we consider it unreliable for gcc versions < 4.9, but also
if -O3 is enabled, or if optimizing for size. And then various kernel
config options disabled it, because they know that they trigger that
warning by confusing gcc sufficiently (ie PROFILE_ALL_BRANCHES).
And now gcc-10 seems to be introducing a lot of those warnings too, so
it falls under the same heading as 4.9 did.
At the same time, we have a very straightforward way to _enable_ that
warning when wanted: use "W=2" to enable more warnings.
So stop playing these ad-hoc games, and just disable that warning by
default, with the known and straight-forward "if you want to work on the
extra compiler warnings, use W=123".
Would it be great to have code that is always so obvious that it never
confuses the compiler whether a variable is used initialized or not?
Yes, it would. In a perfect world, the compilers would be smarter, and
our source code would be simpler.
That's currently not the world we live in, though.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-05-09 23:57:10 +03:00
2009-04-09 15:34:34 +04:00
# disable invalid "can't wrap" optimizations for signed / pointers
2020-09-10 16:51:17 +03:00
KBUILD_CFLAGS += -fno-strict-overflow
2009-03-20 01:53:19 +03:00
2017-12-30 04:34:43 +03:00
# Make sure -fstack-check isn't enabled (like gentoo apparently did)
2020-09-10 16:51:19 +03:00
KBUILD_CFLAGS += -fno-stack-check
2017-12-30 04:34:43 +03:00
2009-09-18 23:49:37 +04:00
# conserve stack if available
Makefile: remove stale cc-option checks
cc-option, cc-option-yn, and cc-disable-warning all invoke the compiler
during build time, and can slow down the build when these checks become
stale for our supported compilers, whose minimally supported versions
increases over time. See Documentation/process/changes.rst for the
current supported minimal versions (GCC 4.9+, clang 10.0.1+). Compiler
version support for these flags may be verified on godbolt.org.
The following flags are GCC only and supported since at least GCC 4.9.
Remove cc-option and cc-disable-warning tests.
* -fno-tree-loop-im
* -Wno-maybe-uninitialized
* -fno-reorder-blocks
* -fno-ipa-cp-clone
* -fno-partial-inlining
* -femit-struct-debug-baseonly
* -fno-inline-functions-called-once
* -fconserve-stack
The following flags are supported by all supported versions of GCC and
Clang. Remove their cc-option, cc-option-yn, and cc-disable-warning tests.
* -fno-delete-null-pointer-checks
* -fno-var-tracking
* -Wno-array-bounds
The following configs are made dependent on GCC, since they use GCC
specific flags.
* READABLE_ASM
* DEBUG_SECTION_MISMATCH
-mfentry was not supported by s390-linux-gnu-gcc until gcc-9+, add a
comment.
--param=allow-store-data-races=0 was renamed to -fno-allow-store-data-races
in the GCC 10 release; add a comment.
-Wmaybe-uninitialized (GCC specific) was being added for CONFIG_GCOV,
then again unconditionally; add it only once.
Also, base RETPOLINE_CFLAGS and RETPOLINE_VDSO_CFLAGS on CONFIC_CC_IS_*
then remove cc-option tests for Clang.
Link: https://github.com/ClangBuiltLinux/linux/issues/1436
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-08-16 23:25:01 +03:00
i f d e f C O N F I G _ C C _ I S _ G C C
KBUILD_CFLAGS += -fconserve-stack
e n d i f
2009-09-18 23:49:37 +04:00
2013-12-24 01:56:06 +04:00
# Prohibit date/time macros, which would make the build non-deterministic
2020-09-10 16:51:20 +03:00
KBUILD_CFLAGS += -Werror= date-time
2013-12-24 01:56:06 +04:00
2016-03-08 11:29:09 +03:00
# enforce correct pointer usage
KBUILD_CFLAGS += $( call cc-option,-Werror= incompatible-pointer-types)
2017-03-21 03:14:11 +03:00
# Require designated initializers for all marked structures
KBUILD_CFLAGS += $( call cc-option,-Werror= designated-init)
2018-03-30 07:15:26 +03:00
# change __FILE__ to the relative path from the srctree
2020-11-02 15:08:53 +03:00
KBUILD_CPPFLAGS += $( call cc-option,-fmacro-prefix-map= $( srctree) /= )
2018-03-30 07:15:26 +03:00
2020-08-01 18:00:49 +03:00
# include additional Makefiles when needed
include-y := scripts/Makefile.extrawarn
include-$(CONFIG_KASAN) += scripts/Makefile.kasan
include-$(CONFIG_KCSAN) += scripts/Makefile.kcsan
include-$(CONFIG_UBSAN) += scripts/Makefile.ubsan
include-$(CONFIG_KCOV) += scripts/Makefile.kcov
include-$(CONFIG_GCC_PLUGINS) += scripts/Makefile.gcc-plugins
i n c l u d e $( addprefix $ ( srctree ) /, $ ( include -y ) )
2014-04-14 13:27:10 +04:00
2020-08-01 18:00:50 +03:00
# scripts/Makefile.gcc-plugins is intentionally included last.
# Do not add $(call cc-option,...) below this line. When you build the kernel
# from the clean source tree, the GCC plugins do not exist at this point.
2014-04-14 13:27:10 +04:00
2019-08-20 20:09:41 +03:00
# Add user supplied CPPFLAGS, AFLAGS and CFLAGS as the last assignments
KBUILD_CPPFLAGS += $( KCPPFLAGS)
KBUILD_AFLAGS += $( KAFLAGS)
KBUILD_CFLAGS += $( KCFLAGS)
2007-10-16 00:03:58 +04:00
2020-09-23 02:21:40 +03:00
KBUILD_LDFLAGS_MODULE += --build-id= sha1
LDFLAGS_vmlinux += --build-id= sha1
2007-07-19 12:48:40 +04:00
2009-03-04 22:59:07 +03:00
i f e q ( $( CONFIG_STRIP_ASM_SYMS ) , y )
2009-09-17 00:36:55 +04:00
LDFLAGS_vmlinux += $( call ld-option, -X,)
2009-03-04 22:59:07 +03:00
e n d i f
2019-08-01 04:18:42 +03:00
i f e q ( $( CONFIG_RELR ) , y )
2021-05-22 04:26:24 +03:00
LDFLAGS_vmlinux += --pack-dyn-relocs= relr --use-android-relr-tags
2019-08-01 04:18:42 +03:00
e n d i f
2020-11-19 23:46:56 +03:00
# We never want expected sections to be placed heuristically by the
# linker. All sections should be explicitly named in the linker script.
i f d e f C O N F I G _ L D _ O R P H A N _ W A R N
LDFLAGS_vmlinux += --orphan-handling= warn
e n d i f
kbuild: add infrastructure to build userspace programs
Kbuild supports the infrastructure to build host programs, but there
was no support to build userspace programs for the target architecture
(i.e. the same architecture as the kernel).
Sam Ravnborg worked on this in 2014 (https://lkml.org/lkml/2014/7/13/154),
but it was not merged. One problem at that time was, there was no good way
to know whether $(CC) can link standalone programs. In fact, pre-built
kernel.org toolchains [1] are often used for building the kernel, but they
do not provide libc.
Now, we can handle this cleanly because the compiler capability is
evaluated at the Kconfig time. If $(CC) cannot link standalone programs,
the relevant options are hidden by 'depends on CC_CAN_LINK'.
The implementation just mimics scripts/Makefile.host
The userspace programs are compiled with the same flags as the host
programs. In addition, it uses -m32 or -m64 if it is found in
$(KBUILD_CFLAGS).
This new syntax has two usecases.
- Sample programs
Several userspace programs under samples/ include UAPI headers
installed in usr/include. Most of them were previously built for
the host architecture just to use the 'hostprogs' syntax.
However, 'make headers' always works for the target architecture.
This caused the arch mismatch in cross-compiling. To fix this
distortion, sample code should be built for the target architecture.
- Bpfilter
net/bpfilter/Makefile compiles bpfilter_umh as the user mode helper,
and embeds it into the kernel. Currently, it overrides HOSTCC with
CC to use the 'hostprogs' syntax. This hack should go away.
[1]: https://mirrors.edge.kernel.org/pub/tools/crosstool/
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
2020-04-29 06:45:14 +03:00
# Align the bit size of userspace programs with the kernel
2020-06-30 18:06:25 +03:00
KBUILD_USERCFLAGS += $( filter -m32 -m64 --target= %, $( KBUILD_CFLAGS) )
KBUILD_USERLDFLAGS += $( filter -m32 -m64 --target= %, $( KBUILD_CFLAGS) )
kbuild: add infrastructure to build userspace programs
Kbuild supports the infrastructure to build host programs, but there
was no support to build userspace programs for the target architecture
(i.e. the same architecture as the kernel).
Sam Ravnborg worked on this in 2014 (https://lkml.org/lkml/2014/7/13/154),
but it was not merged. One problem at that time was, there was no good way
to know whether $(CC) can link standalone programs. In fact, pre-built
kernel.org toolchains [1] are often used for building the kernel, but they
do not provide libc.
Now, we can handle this cleanly because the compiler capability is
evaluated at the Kconfig time. If $(CC) cannot link standalone programs,
the relevant options are hidden by 'depends on CC_CAN_LINK'.
The implementation just mimics scripts/Makefile.host
The userspace programs are compiled with the same flags as the host
programs. In addition, it uses -m32 or -m64 if it is found in
$(KBUILD_CFLAGS).
This new syntax has two usecases.
- Sample programs
Several userspace programs under samples/ include UAPI headers
installed in usr/include. Most of them were previously built for
the host architecture just to use the 'hostprogs' syntax.
However, 'make headers' always works for the target architecture.
This caused the arch mismatch in cross-compiling. To fix this
distortion, sample code should be built for the target architecture.
- Bpfilter
net/bpfilter/Makefile compiles bpfilter_umh as the user mode helper,
and embeds it into the kernel. Currently, it overrides HOSTCC with
CC to use the 'hostprogs' syntax. This hack should go away.
[1]: https://mirrors.edge.kernel.org/pub/tools/crosstool/
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
2020-04-29 06:45:14 +03:00
2019-11-09 15:12:16 +03:00
# make the checker run with the right architecture
CHECKFLAGS += --arch= $( ARCH)
2018-05-28 21:27:35 +03:00
# insure the checker run with the right endianness
CHECKFLAGS += $( if $( CONFIG_CPU_BIG_ENDIAN) ,-mbig-endian,-mlittle-endian)
2018-05-30 23:48:38 +03:00
# the checker needs the correct machine size
CHECKFLAGS += $( if $( CONFIG_64BIT) ,-m64,-m32)
2005-04-17 02:20:36 +04:00
# Default kernel image to build when no specific target is given.
2006-06-25 02:07:55 +04:00
# KBUILD_IMAGE may be overruled on the command line or
2005-04-17 02:20:36 +04:00
# set in the environment
# Also any assignments in arch/$(ARCH)/Makefile take precedence over
# this default value
export KBUILD_IMAGE ?= vmlinux
#
# INSTALL_PATH specifies where to place the updated kernel and system map
# images. Default is /boot, but you can set it to other values
export INSTALL_PATH ?= /boot
2013-12-02 03:56:28 +04:00
#
# INSTALL_DTBS_PATH specifies a prefix for relocations required by build roots.
# Like INSTALL_MOD_PATH, it isn't defined in the Makefile, but can be passed as
# an argument if needed. Otherwise it defaults to the kernel install path
#
export INSTALL_DTBS_PATH ?= $( INSTALL_PATH) /dtbs/$( KERNELRELEASE)
2005-04-17 02:20:36 +04:00
#
# INSTALL_MOD_PATH specifies a prefix to MODLIB for module directory
# relocations required by build roots. This is not defined in the
2006-06-25 02:07:55 +04:00
# makefile but the argument can be passed to make if needed.
2005-04-17 02:20:36 +04:00
#
2006-01-16 14:46:07 +03:00
MODLIB = $( INSTALL_MOD_PATH) /lib/modules/$( KERNELRELEASE)
2005-04-17 02:20:36 +04:00
export MODLIB
2019-01-15 10:19:00 +03:00
PHONY += prepare0
2012-10-19 05:23:15 +04:00
2021-03-31 16:38:07 +03:00
export extmod_prefix = $( if $( KBUILD_EXTMOD) ,$( KBUILD_EXTMOD) /)
2021-03-31 16:38:06 +03:00
export MODORDER := $( extmod_prefix) modules.order
export MODULES_NSDEPS := $( extmod_prefix) modules.nsdeps
2019-08-02 13:23:58 +03:00
2005-04-17 02:20:36 +04:00
i f e q ( $( KBUILD_EXTMOD ) , )
2015-08-14 17:20:41 +03:00
core-y += kernel/ certs/ mm/ fs/ ipc/ security/ crypto/ block/
2005-04-17 02:20:36 +04:00
2020-06-01 08:56:57 +03:00
vmlinux-dirs := $( patsubst %/,%,$( filter %/, \
2005-04-17 02:20:36 +04:00
$( core-y) $( core-m) $( drivers-y) $( drivers-m) \
2020-06-01 08:56:58 +03:00
$( libs-y) $( libs-m) ) )
2005-04-17 02:20:36 +04:00
2019-04-27 06:33:37 +03:00
vmlinux-alldirs := $( sort $( vmlinux-dirs) Documentation \
2020-06-01 08:56:57 +03:00
$( patsubst %/,%,$( filter %/, $( core-) \
2020-06-01 08:56:58 +03:00
$( drivers-) $( libs-) ) ) )
2005-04-17 02:20:36 +04:00
2020-06-01 08:57:00 +03:00
subdir-modorder := $( addsuffix modules.order,$( filter %/, \
$( core-y) $( core-m) $( libs-y) $( libs-m) \
$( drivers-y) $( drivers-m) ) )
2005-04-17 02:20:36 +04:00
2019-08-10 18:53:04 +03:00
build-dirs := $( vmlinux-dirs)
2019-08-10 18:53:05 +03:00
clean-dirs := $( vmlinux-alldirs)
2019-08-10 18:53:04 +03:00
2020-06-01 08:56:59 +03:00
# Externally visible symbols (used by link-vmlinux.sh)
KBUILD_VMLINUX_OBJS := $( head-y) $( patsubst %/,%/built-in.a, $( core-y) )
KBUILD_VMLINUX_OBJS += $( addsuffix built-in.a, $( filter %/, $( libs-y) ) )
kbuild: link lib-y objects to vmlinux forcibly when CONFIG_MODULES=y
Kbuild supports not only obj-y but also lib-y to list objects linked to
vmlinux.
The difference between them is that all the objects from obj-y are
forcibly linked to vmlinux, whereas the objects from lib-y are linked
as needed; if there is no user of a lib-y object, it is not linked.
lib-y is intended to list utility functions that may be called from all
over the place (and may be unused at all), but it is a problem for
EXPORT_SYMBOL(). Even if there is no call-site in the vmlinux, we need
to keep exported symbols for the use from loadable modules.
Commit 7f2084fa55e6 ("[kbuild] handle exports in lib-y objects reliably")
worked around it by linking a dummy object, lib-ksyms.o, which contains
references to all the symbols exported from lib.a in that directory.
It uses the linker script command, EXTERN. Unfortunately, the meaning of
EXTERN of ld.lld is different from that of ld.bfd. Therefore, this does
not work with LD=ld.lld (CBL issue #515).
Anyway, the build rule of lib-ksyms.o is somewhat tricky. So, I want to
get rid of it.
At first, I was thinking of accumulating lib-y objects into obj-y
(or even replacing lib-y with obj-y entirely), but the lib-y syntax
is used beyond the ordinary use in lib/ and arch/*/lib/.
Examples:
- drivers/firmware/efi/libstub/Makefile builds lib.a, which is linked
into vmlinux in the own way (arm64), or linked to the decompressor
(arm, x86).
- arch/alpha/lib/Makefile builds lib.a which is linked not only to
vmlinux, but also to bootloaders in arch/alpha/boot/Makefile.
- arch/xtensa/boot/lib/Makefile builds lib.a for use from
arch/xtensa/boot/boot-redboot/Makefile.
One more thing, adding everything to obj-y would increase the vmlinux
size of allnoconfig (or tinyconfig).
For less impact, I tweaked the destination of lib.a at the top Makefile;
when CONFIG_MODULES=y, lib.a goes to KBUILD_VMLINUX_OBJS, which is
forcibly linked to vmlinux, otherwise lib.a goes to KBUILD_VMLINUX_LIBS
as before.
The size impact for normal usecases is quite small since at lease one
symbol in every lib-y object is eventually called by someone. In case
you are intrested, here are the figures.
x86_64_defconfig:
text data bss dec hex filename
19566602 5422072 1589328 26578002 1958c52 vmlinux.before
19566932 5422104 1589328 26578364 1958dbc vmlinux.after
The case with the biggest impact is allnoconfig + CONFIG_MODULES=y.
ARCH=x86 allnoconfig + CONFIG_MODULES=y:
text data bss dec hex filename
1175162 254740 1220608 2650510 28718e vmlinux.before
1177974 254836 1220608 2653418 287cea vmlinux.after
Hopefully this is still not a big deal. The per-file trimming with the
static library is not so effective after all.
If fine-grained optimization is desired, some architectures support
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION, which trims dead code per-symbol
basis. When LTO is supported in mainline, even better optimization will
be possible.
Link: https://github.com/ClangBuiltLinux/linux/issues/515
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reported-by: kbuild test robot <lkp@intel.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
2020-03-12 01:37:25 +03:00
i f d e f C O N F I G _ M O D U L E S
2020-06-01 08:56:59 +03:00
KBUILD_VMLINUX_OBJS += $( patsubst %/, %/lib.a, $( filter %/, $( libs-y) ) )
KBUILD_VMLINUX_LIBS := $( filter-out %/, $( libs-y) )
kbuild: link lib-y objects to vmlinux forcibly when CONFIG_MODULES=y
Kbuild supports not only obj-y but also lib-y to list objects linked to
vmlinux.
The difference between them is that all the objects from obj-y are
forcibly linked to vmlinux, whereas the objects from lib-y are linked
as needed; if there is no user of a lib-y object, it is not linked.
lib-y is intended to list utility functions that may be called from all
over the place (and may be unused at all), but it is a problem for
EXPORT_SYMBOL(). Even if there is no call-site in the vmlinux, we need
to keep exported symbols for the use from loadable modules.
Commit 7f2084fa55e6 ("[kbuild] handle exports in lib-y objects reliably")
worked around it by linking a dummy object, lib-ksyms.o, which contains
references to all the symbols exported from lib.a in that directory.
It uses the linker script command, EXTERN. Unfortunately, the meaning of
EXTERN of ld.lld is different from that of ld.bfd. Therefore, this does
not work with LD=ld.lld (CBL issue #515).
Anyway, the build rule of lib-ksyms.o is somewhat tricky. So, I want to
get rid of it.
At first, I was thinking of accumulating lib-y objects into obj-y
(or even replacing lib-y with obj-y entirely), but the lib-y syntax
is used beyond the ordinary use in lib/ and arch/*/lib/.
Examples:
- drivers/firmware/efi/libstub/Makefile builds lib.a, which is linked
into vmlinux in the own way (arm64), or linked to the decompressor
(arm, x86).
- arch/alpha/lib/Makefile builds lib.a which is linked not only to
vmlinux, but also to bootloaders in arch/alpha/boot/Makefile.
- arch/xtensa/boot/lib/Makefile builds lib.a for use from
arch/xtensa/boot/boot-redboot/Makefile.
One more thing, adding everything to obj-y would increase the vmlinux
size of allnoconfig (or tinyconfig).
For less impact, I tweaked the destination of lib.a at the top Makefile;
when CONFIG_MODULES=y, lib.a goes to KBUILD_VMLINUX_OBJS, which is
forcibly linked to vmlinux, otherwise lib.a goes to KBUILD_VMLINUX_LIBS
as before.
The size impact for normal usecases is quite small since at lease one
symbol in every lib-y object is eventually called by someone. In case
you are intrested, here are the figures.
x86_64_defconfig:
text data bss dec hex filename
19566602 5422072 1589328 26578002 1958c52 vmlinux.before
19566932 5422104 1589328 26578364 1958dbc vmlinux.after
The case with the biggest impact is allnoconfig + CONFIG_MODULES=y.
ARCH=x86 allnoconfig + CONFIG_MODULES=y:
text data bss dec hex filename
1175162 254740 1220608 2650510 28718e vmlinux.before
1177974 254836 1220608 2653418 287cea vmlinux.after
Hopefully this is still not a big deal. The per-file trimming with the
static library is not so effective after all.
If fine-grained optimization is desired, some architectures support
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION, which trims dead code per-symbol
basis. When LTO is supported in mainline, even better optimization will
be possible.
Link: https://github.com/ClangBuiltLinux/linux/issues/515
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reported-by: kbuild test robot <lkp@intel.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
2020-03-12 01:37:25 +03:00
e l s e
2020-06-01 08:56:59 +03:00
KBUILD_VMLINUX_LIBS := $( patsubst %/,%/lib.a, $( libs-y) )
kbuild: link lib-y objects to vmlinux forcibly when CONFIG_MODULES=y
Kbuild supports not only obj-y but also lib-y to list objects linked to
vmlinux.
The difference between them is that all the objects from obj-y are
forcibly linked to vmlinux, whereas the objects from lib-y are linked
as needed; if there is no user of a lib-y object, it is not linked.
lib-y is intended to list utility functions that may be called from all
over the place (and may be unused at all), but it is a problem for
EXPORT_SYMBOL(). Even if there is no call-site in the vmlinux, we need
to keep exported symbols for the use from loadable modules.
Commit 7f2084fa55e6 ("[kbuild] handle exports in lib-y objects reliably")
worked around it by linking a dummy object, lib-ksyms.o, which contains
references to all the symbols exported from lib.a in that directory.
It uses the linker script command, EXTERN. Unfortunately, the meaning of
EXTERN of ld.lld is different from that of ld.bfd. Therefore, this does
not work with LD=ld.lld (CBL issue #515).
Anyway, the build rule of lib-ksyms.o is somewhat tricky. So, I want to
get rid of it.
At first, I was thinking of accumulating lib-y objects into obj-y
(or even replacing lib-y with obj-y entirely), but the lib-y syntax
is used beyond the ordinary use in lib/ and arch/*/lib/.
Examples:
- drivers/firmware/efi/libstub/Makefile builds lib.a, which is linked
into vmlinux in the own way (arm64), or linked to the decompressor
(arm, x86).
- arch/alpha/lib/Makefile builds lib.a which is linked not only to
vmlinux, but also to bootloaders in arch/alpha/boot/Makefile.
- arch/xtensa/boot/lib/Makefile builds lib.a for use from
arch/xtensa/boot/boot-redboot/Makefile.
One more thing, adding everything to obj-y would increase the vmlinux
size of allnoconfig (or tinyconfig).
For less impact, I tweaked the destination of lib.a at the top Makefile;
when CONFIG_MODULES=y, lib.a goes to KBUILD_VMLINUX_OBJS, which is
forcibly linked to vmlinux, otherwise lib.a goes to KBUILD_VMLINUX_LIBS
as before.
The size impact for normal usecases is quite small since at lease one
symbol in every lib-y object is eventually called by someone. In case
you are intrested, here are the figures.
x86_64_defconfig:
text data bss dec hex filename
19566602 5422072 1589328 26578002 1958c52 vmlinux.before
19566932 5422104 1589328 26578364 1958dbc vmlinux.after
The case with the biggest impact is allnoconfig + CONFIG_MODULES=y.
ARCH=x86 allnoconfig + CONFIG_MODULES=y:
text data bss dec hex filename
1175162 254740 1220608 2650510 28718e vmlinux.before
1177974 254836 1220608 2653418 287cea vmlinux.after
Hopefully this is still not a big deal. The per-file trimming with the
static library is not so effective after all.
If fine-grained optimization is desired, some architectures support
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION, which trims dead code per-symbol
basis. When LTO is supported in mainline, even better optimization will
be possible.
Link: https://github.com/ClangBuiltLinux/linux/issues/515
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reported-by: kbuild test robot <lkp@intel.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
2020-03-12 01:37:25 +03:00
e n d i f
2020-06-01 08:56:59 +03:00
KBUILD_VMLINUX_OBJS += $( patsubst %/,%/built-in.a, $( drivers-y) )
2005-04-17 02:20:36 +04:00
2020-06-01 08:56:59 +03:00
export KBUILD_VMLINUX_OBJS KBUILD_VMLINUX_LIBS
2012-05-05 12:18:40 +04:00
export KBUILD_LDS := arch/$( SRCARCH) /kernel/vmlinux.lds
2019-09-21 16:18:46 +03:00
# used by scripts/Makefile.package
2019-05-15 19:18:54 +03:00
export KBUILD_ALLDIRS := $( sort $( filter-out arch/%,$( vmlinux-alldirs) ) LICENSES arch include scripts tools)
2008-12-16 14:30:08 +03:00
2019-01-17 03:10:04 +03:00
vmlinux-deps := $( KBUILD_LDS) $( KBUILD_VMLINUX_OBJS) $( KBUILD_VMLINUX_LIBS)
2005-04-17 02:20:36 +04:00
2018-03-16 10:37:15 +03:00
# Recurse until adjust_autoksyms.sh is satisfied
PHONY += autoksyms_recursive
2016-04-22 22:25:00 +03:00
i f d e f C O N F I G _ T R I M _ U N U S E D _ K S Y M S
2018-03-16 10:37:13 +03:00
# For the kernel to actually contain only the needed exported symbols,
# we have to build modules as well to determine what those symbols are.
# (this can be evaluated only once include/config/auto.conf has been included)
2020-05-31 13:11:39 +03:00
KBUILD_MODULES := 1
autoksyms_recursive : descend modules .order
$( Q) $( CONFIG_SHELL) $( srctree) /scripts/adjust_autoksyms.sh \
" $( MAKE) -f $( srctree) /Makefile vmlinux "
2018-03-16 10:37:13 +03:00
e n d i f
kbuild: restore autoksyms.h touch to the top Makefile
Commit d3fc425e819b ("kbuild: make sure autoksyms.h exists early")
moved the code that touches autoksyms.h to scripts/kconfig/Makefile
with obscure reason.
From Nicolas' comment [1], he did not seem to be sure about the root
cause.
I guess I figured it out, so here is a fix-up I think is more correct.
According to the error log in the original post [2], the build failed
in scripts/mod/devicetable-offsets.c
scripts/mod/Makefile is descended from scripts/Makefile, which is
invoked from the top-level Makefile by the 'scripts' target.
To build vmlinux and/or modules, Kbuild descend into $(vmlinux-dirs).
This depends on 'prepare' and 'scripts' as follows:
$(vmlinux-dirs): prepare scripts
Because there is no dependency between 'prepare' and 'scripts', the
parallel building can execute them simultaneously.
'prepare' depends on 'prepare1', which touched autoksyms.h, while
'scripts' descends into script/, then scripts/mod/, which needs
<generated/autoksyms.h> if CONFIG_TRIM_UNUSED_KSYMS. It was the
reason of the race.
I am not happy to have unrelated code in the Kconfig Makefile, so
getting it back to the top Makefile.
I removed the standalone test target because I want to use it to
create an empty autoksyms.h file. Here is a little improvement;
unnecessary autoksyms.h is not created when CONFIG_TRIM_UNUSED_KSYMS
is disabled.
[1] https://lkml.org/lkml/2016/11/30/734
[2] https://lkml.org/lkml/2016/11/30/531
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
2018-03-16 10:37:12 +03:00
autoksyms_h := $( if $( CONFIG_TRIM_UNUSED_KSYMS) , include/generated/autoksyms.h)
2020-02-28 20:20:15 +03:00
quiet_cmd_autoksyms_h = GEN $@
cmd_autoksyms_h = mkdir -p $( dir $@ ) ; \
$( CONFIG_SHELL) $( srctree) /scripts/gen_autoksyms.sh $@
kbuild: restore autoksyms.h touch to the top Makefile
Commit d3fc425e819b ("kbuild: make sure autoksyms.h exists early")
moved the code that touches autoksyms.h to scripts/kconfig/Makefile
with obscure reason.
From Nicolas' comment [1], he did not seem to be sure about the root
cause.
I guess I figured it out, so here is a fix-up I think is more correct.
According to the error log in the original post [2], the build failed
in scripts/mod/devicetable-offsets.c
scripts/mod/Makefile is descended from scripts/Makefile, which is
invoked from the top-level Makefile by the 'scripts' target.
To build vmlinux and/or modules, Kbuild descend into $(vmlinux-dirs).
This depends on 'prepare' and 'scripts' as follows:
$(vmlinux-dirs): prepare scripts
Because there is no dependency between 'prepare' and 'scripts', the
parallel building can execute them simultaneously.
'prepare' depends on 'prepare1', which touched autoksyms.h, while
'scripts' descends into script/, then scripts/mod/, which needs
<generated/autoksyms.h> if CONFIG_TRIM_UNUSED_KSYMS. It was the
reason of the race.
I am not happy to have unrelated code in the Kconfig Makefile, so
getting it back to the top Makefile.
I removed the standalone test target because I want to use it to
create an empty autoksyms.h file. Here is a little improvement;
unnecessary autoksyms.h is not created when CONFIG_TRIM_UNUSED_KSYMS
is disabled.
[1] https://lkml.org/lkml/2016/11/30/734
[2] https://lkml.org/lkml/2016/11/30/531
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
2018-03-16 10:37:12 +03:00
$(autoksyms_h) :
2020-02-28 20:20:15 +03:00
$( call cmd,autoksyms_h)
2016-01-27 05:50:18 +03:00
2016-08-24 15:29:21 +03:00
ARCH_POSTLINK := $( wildcard $( srctree) /arch/$( SRCARCH) /Makefile.postlink)
# Final link of vmlinux with optional arch pass after final link
2017-08-02 05:31:06 +03:00
cmd_link-vmlinux = \
kbuild: do not export LDFLAGS_vmlinux
When you clean the build tree for ARCH=arm, you may see the following
error message from 'nm' command:
$ make -j24 ARCH=arm clean
CLEAN arch/arm/crypto
CLEAN arch/arm/kernel
CLEAN arch/arm/mach-at91
CLEAN arch/arm/mach-omap2
CLEAN arch/arm/vdso
CLEAN certs
CLEAN lib
CLEAN usr
CLEAN net/wireless
CLEAN drivers/firmware/efi/libstub
nm: 'arch/arm/boot/compressed/../../../../vmlinux': No such file
/bin/sh: 1: arithmetic expression: expecting primary: " "
CLEAN arch/arm/boot/compressed
CLEAN drivers/scsi
CLEAN drivers/tty/vt
CLEAN arch/arm/boot
CLEAN vmlinux.symvers modules.builtin modules.builtin.modinfo
Even if you rerun the same command, the error message will not be
shown despite vmlinux is already gone.
To reproduce it, the parallel option -j is needed. Single thread
cleaning always executes 'archclean', 'vmlinuxclean' in this order,
so vmlinux still exists when arch/arm/boot/compressed/ is cleaned.
Looking at arch/arm/boot/compressed/Makefile does not help understand
the reason of the error message. Both KBSS_SZ and LDFLAGS_vmlinux are
assigned with '=' operator, hence, they are not expanded unless used.
Obviously, 'make clean' does not use them.
In fact, the root cause exists in the top Makefile:
export LDFLAGS_vmlinux
Since LDFLAGS_vmlinux is an exported variable, LDFLAGS_vmlinux in
arch/arm/boot/compressed/Makefile is expanded when scripts/Makefile.clean
has a command to execute. This is why the error message shows up only
when there exist build artifacts in arch/arm/boot/compressed/.
Adding 'unexport LDFLAGS_vmlinux' to arch/arm/boot/compressed/Makefile
will fix it as far as ARCH=arm is concerned, but I think the proper fix
is to get rid of 'export LDFLAGS_vmlinux' from the top Makefile.
LDFLAGS_vmlinux in the top Makefile contains linker flags for the top
vmlinux. LDFLAGS_vmlinux in arch/arm/boot/compressed/Makefile is for
arch/arm/boot/compressed/vmlinux. They just happen to have the same
variable name, but are used for different purposes. Stop shadowing
LDFLAGS_vmlinux.
This commit passes LDFLAGS_vmlinux to scripts/link-vmlinux.sh via a
command line parameter instead of via an environment variable. LD and
KBUILD_LDFLAGS are exported, but I did the same for consistency. Anyway,
they must be included in cmd_link-vmlinux to allow if_changed to detect
the changes in LD or KBUILD_LDFLAGS.
The following Makefiles are not affected:
arch/arm/boot/compressed/Makefile
arch/h8300/boot/compressed/Makefile
arch/nios2/boot/compressed/Makefile
arch/parisc/boot/compressed/Makefile
arch/s390/boot/compressed/Makefile
arch/sh/boot/compressed/Makefile
arch/sh/boot/romimage/Makefile
arch/x86/boot/compressed/Makefile
They use ':=' or '=' to clear the LDFLAGS_vmlinux inherited from the
top Makefile.
We need to take a closer look at the impact to unicore32 and xtensa.
arch/unicore32/boot/compressed/Makefile only uses '+=' operator for
LDFLAGS_vmlinux. So, the decompressor previously inherited the linker
flags from the top Makefile.
However, commit 70fac51feaf2 ("unicore32 additional architecture files:
boot process") was merged before commit 1f2bfbd00e46 ("kbuild: link of
vmlinux moved to a script"). So, I rather consider this is a bug fix of
1f2bfbd00e46.
arch/xtensa/boot/boot-elf/Makefile is also affected, but this is also
considered a fix for the same reason. It did not inherit LDFLAGS_vmlinux
when commit 4bedea945451 ("[PATCH] xtensa: Architecture support for
Tensilica Xtensa Part 2") was merged. I deleted $(LDFLAGS_vmlinux),
which is now empty.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
2020-07-01 22:29:36 +03:00
$( CONFIG_SHELL) $< " $( LD) " " $( KBUILD_LDFLAGS) " " $( LDFLAGS_vmlinux) " ; \
2016-08-24 15:29:21 +03:00
$( if $( ARCH_POSTLINK) , $( MAKE) -f $( ARCH_POSTLINK) $@ , true )
2016-04-22 22:25:00 +03:00
2018-03-16 10:37:15 +03:00
vmlinux : scripts /link -vmlinux .sh autoksyms_recursive $( vmlinux -deps ) FORCE
2021-03-05 13:02:12 +03:00
+$( call if_changed_dep,link-vmlinux)
2007-07-17 12:54:06 +04:00
kbuild: let fixdep directly write to .*.cmd files
Currently, fixdep writes dependencies to .*.tmp, which is renamed to
.*.cmd after everything succeeds. This is a very safe way to avoid
corrupted .*.cmd files. The if_changed_dep has carried this safety
mechanism since it was added in 2002.
If fixdep fails for some reasons or a user terminates the build while
fixdep is running, the incomplete output from the fixdep could be
troublesome.
This is my insight about some bad scenarios:
[1] If the compiler succeeds to generate *.o file, but fixdep fails
to write necessary dependencies to .*.cmd file, Make will miss
to rebuild the object when headers or CONFIG options are changed.
In this case, fixdep should not generate .*.cmd file at all so
that 'arg-check' will surely trigger the rebuild of the object.
[2] A partially constructed .*.cmd file may not be a syntactically
correct makefile. The next time Make runs, it would include it,
then fail to parse it. Once this happens, 'make clean' is be the
only way to fix it.
In fact, [1] is no longer a problem since commit 9c2af1c7377a ("kbuild:
add .DELETE_ON_ERROR special target"). Make deletes a target file on
any failure in its recipe. Because fixdep is a part of the recipe of
*.o target, if it fails, the *.o is deleted anyway. However, I am a
bit worried about the slight possibility of [2].
So, here is a solution. Let fixdep directly write to a .*.cmd file,
but allow makefiles to include it only when its corresponding target
exists.
This effectively reverts commit 2982c953570b ("kbuild: remove redundant
$(wildcard ...) for cmd_files calculation"), and commit 00d78ab2ba75
("kbuild: remove dead code in cmd_files calculation in top Makefile")
because now we must check the presence of targets.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2018-11-30 04:05:22 +03:00
targets := vmlinux
2014-04-28 11:26:18 +04:00
# The actual objects are generated when descending,
2005-04-17 02:20:36 +04:00
# make sure no implicit rule kicks in
2020-06-01 08:57:00 +03:00
$(sort $(vmlinux-deps) $(subdir-modorder)) : descend ;
2005-04-17 02:20:36 +04:00
2019-01-03 04:16:54 +03:00
filechk_kernel.release = \
2013-07-11 17:34:51 +04:00
echo " $( KERNELVERSION) $$ ( $( CONFIG_SHELL) $( srctree) /scripts/setlocalversion $( srctree) ) "
2013-06-28 13:27:31 +04:00
# Store (new) KERNELRELEASE string in include/config/kernel.release
2019-04-07 13:03:18 +03:00
include/config/kernel.release : FORCE
2013-07-11 17:34:51 +04:00
$( call filechk,kernel.release)
2006-01-09 23:20:34 +03:00
2018-03-16 10:37:11 +03:00
# Additional helpers built in scripts/
# Carefully list dependencies so we do not try to build scripts twice
# in parallel
PHONY += scripts
2018-11-29 06:13:24 +03:00
scripts : scripts_basic scripts_dtc
2018-03-16 10:37:11 +03:00
$( Q) $( MAKE) $( build) = $( @)
2006-01-09 23:20:34 +03:00
2005-04-17 02:20:36 +04:00
# Things we need to do before we recursively start building the kernel
2005-09-12 00:30:22 +04:00
# or the modules are listed in "prepare".
# A multi level approach is used. prepareN is processed before prepareN-1.
# archprepare is used in arch Makefiles and when processed asm symlink,
# version.h and scripts_basic is processed / created.
2005-04-17 02:20:36 +04:00
2019-08-22 07:46:12 +03:00
PHONY += prepare archprepare
2005-09-12 00:30:22 +04:00
2019-08-22 07:46:13 +03:00
archprepare : outputmakefile archheaders archscripts scripts include /config /kernel .release \
2020-05-01 09:01:41 +03:00
asm-generic $( version_h) $( autoksyms_h) include/generated/utsrelease.h \
2021-04-25 10:07:12 +03:00
include/generated/autoconf.h remove-stale-files
2005-09-12 00:30:22 +04:00
2018-11-29 05:58:50 +03:00
prepare0 : archprepare
2018-11-29 06:13:24 +03:00
$( Q) $( MAKE) $( build) = scripts/mod
2005-09-10 23:05:36 +04:00
$( Q) $( MAKE) $( build) = .
2005-09-09 21:28:28 +04:00
2005-04-17 02:20:36 +04:00
# All the preparing..
kbuild: remove libelf checks from top Makefile
I do not see a good reason why only the libelf development package must
be so carefully checked.
Kbuild generally does not check host tools or libraries.
For example, x86_64 defconfig fails to build with no libssl development
package installed.
scripts/extract-cert.c:21:10: fatal error: openssl/bio.h: No such file or directory
21 | #include <openssl/bio.h>
| ^~~~~~~~~~~~~~~
To solve the build error, you need to install libssl-dev or openssl-devel
package, depending on your distribution.
'apt-file search', 'dnf provides', etc. is your frined to find a proper
package to install.
This commit removes all the libelf checks from the top Makefile.
If libelf is missing, objtool will fail to build in a similar pattern:
.../linux/tools/objtool/include/objtool/elf.h:10:10: fatal error: gelf.h: No such file or directory
10 | #include <gelf.h>
You need to install libelf-dev, libelf-devel, or elfutils-libelf-devel
to proceed.
Another remarkable change is, CONFIG_STACK_VALIDATION (without
CONFIG_UNWINDER_ORC) previously continued to build with a warning,
but now it will treat missing libelf as an error.
This is just a one-time installation, so it should not hurt to break
a build and make a user install the package.
BTW, the traditional way to handle such checks is autotool, but according
to [1], I do not expect the kernel build would have similar scripting
like './configure' does.
[1]: https://lore.kernel.org/lkml/CA+55aFzr2HTZVOuzpHYDwmtRJLsVzE-yqg2DHpHi_9ePsYp5ug@mail.gmail.com/
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
2021-05-12 09:52:01 +03:00
prepare : prepare 0
2016-02-29 07:22:42 +03:00
2021-04-25 10:07:12 +03:00
PHONY += remove-stale-files
remove-stale-files :
$( Q) $( srctree) /scripts/remove-stale-files
2017-10-04 06:56:06 +03:00
# Support for using generic headers in asm-generic
2018-12-05 14:28:04 +03:00
asm-generic := -f $( srctree) /scripts/Makefile.asm-generic obj
2017-10-04 06:56:06 +03:00
PHONY += asm-generic uapi-asm-generic
asm-generic : uapi -asm -generic
2019-03-17 05:01:09 +03:00
$( Q) $( MAKE) $( asm-generic) = arch/$( SRCARCH) /include/generated/asm \
generic = include/asm-generic
2017-10-04 06:56:06 +03:00
uapi-asm-generic :
2019-03-17 05:01:09 +03:00
$( Q) $( MAKE) $( asm-generic) = arch/$( SRCARCH) /include/generated/uapi/asm \
generic = include/uapi/asm-generic
2017-10-04 06:56:06 +03:00
2005-04-17 02:20:36 +04:00
# Generate some files
# ---------------------------------------------------------------------------
# KERNELRELEASE can change from a few different places, meaning version.h
# needs to be updated, so this check is forced on all builds
uts_len := 64
2006-07-04 01:30:54 +04:00
d e f i n e f i l e c h k _ u t s r e l e a s e . h
if [ ` echo -n " $( KERNELRELEASE) " | wc -c ` -gt $( uts_len) ] ; then \
echo '"$(KERNELRELEASE)" exceeds $(uts_len) characters' >& 2; \
exit 1; \
fi ; \
2018-12-31 11:24:09 +03:00
echo \# define UTS_RELEASE \" $( KERNELRELEASE) \"
2006-07-04 01:30:54 +04:00
e n d e f
2005-04-17 02:20:36 +04:00
d e f i n e f i l e c h k _ v e r s i o n . h
2021-02-06 06:50:32 +03:00
if [ $( SUBLEVEL) -gt 255 ] ; then \
echo \# define LINUX_VERSION_CODE $( shell \
2021-02-27 17:20:23 +03:00
expr $( VERSION) \* 65536 + $( PATCHLEVEL) \* 256 + 255) ; \
2021-02-06 06:50:32 +03:00
else \
echo \# define LINUX_VERSION_CODE $( shell \
2021-02-27 17:20:23 +03:00
expr $( VERSION) \* 65536 + $( PATCHLEVEL) \* 256 + $( SUBLEVEL) ) ; \
2021-02-06 06:50:32 +03:00
fi ; \
echo ' #define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + \
2021-02-12 19:29:24 +03:00
( ( c) > 255 ? 255 : ( c) ) ) ' ; \
echo \# define LINUX_VERSION_MAJOR $( VERSION) ; \
echo \# define LINUX_VERSION_PATCHLEVEL $( PATCHLEVEL) ; \
echo \# define LINUX_VERSION_SUBLEVEL $( SUBLEVEL)
2005-04-17 02:20:36 +04:00
e n d e f
2021-02-27 17:20:23 +03:00
$(version_h) : PATCHLEVEL := $( if $ ( PATCHLEVEL ) , $ ( PATCHLEVEL ) , 0)
$(version_h) : SUBLEVEL := $( if $ ( SUBLEVEL ) , $ ( SUBLEVEL ) , 0)
2018-07-25 08:16:11 +03:00
$(version_h) : FORCE
2005-04-17 02:20:36 +04:00
$( call filechk,version.h)
2009-10-18 02:52:28 +04:00
include/generated/utsrelease.h : include /config /kernel .release FORCE
2006-07-04 01:30:54 +04:00
$( call filechk,utsrelease.h)
2008-12-16 14:33:43 +03:00
PHONY += headerdep
headerdep :
2011-04-27 01:17:11 +04:00
$( Q) find $( srctree) /include/ -name '*.h' | xargs --max-args 1 \
$( srctree) /scripts/headerdep.pl -I$( srctree) /include
2008-12-16 14:33:43 +03:00
2006-06-18 14:58:39 +04:00
# ---------------------------------------------------------------------------
# Kernel headers
2008-06-05 18:43:46 +04:00
#Default location for installed headers
export INSTALL_HDR_PATH = $( objtree) /usr
2006-09-25 01:16:03 +04:00
kbuild: add 'headers' target to build up uapi headers in usr/include
In Linux build system, build targets and installation targets are
separated.
Examples are:
- 'make vmlinux' -> 'make install'
- 'make modules' -> 'make modules_install'
- 'make dtbs' -> 'make dtbs_install'
- 'make vdso' -> 'make vdso_install'
The intention is to run the build targets under the normal privilege,
then the installation targets under the root privilege since we need
the write permission to the system directories.
We have 'make headers_install' but the corresponding 'make headers'
stage does not exist. The purpose of headers_install is to provide
the kernel interface to C library. So, nobody would try to install
headers to /usr/include directly.
If 'sudo make INSTALL_HDR_PATH=/usr/include headers_install' were run,
some build artifacts in the kernel tree would be owned by root because
some of uapi headers are generated by 'uapi-asm-generic', 'archheaders'
targets.
Anyway, I believe it makes sense to split the header installation into
two stages.
[1] 'make headers'
Process headers in uapi directories by scripts/headers_install.sh
and copy them to usr/include
[2] 'make headers_install'
Copy '*.h' verbatim from usr/include to $(INSTALL_HDR_PATH)/include
For the backward compatibility, 'headers_install' depends on 'headers'.
Some samples expect uapi headers in usr/include. So, the 'headers'
target is useful to build up them in the fixed location usr/include
irrespective of INSTALL_HDR_PATH.
Another benefit is to stop polluting the final destination with the
time-stamp files '.install' and '.check'. Maybe you can see them in
your toolchains.
Lastly, my main motivation is to prepare for compile-testing uapi
headers. To build something, we have to save an object and .*.cmd
somewhere. The usr/include/ will be the work directory for that.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2019-06-04 13:14:02 +03:00
quiet_cmd_headers_install = INSTALL $( INSTALL_HDR_PATH) /include
cmd_headers_install = \
mkdir -p $( INSTALL_HDR_PATH) ; \
rsync -mrl --include= '*/' --include= '*\.h' --exclude= '*' \
usr/include $( INSTALL_HDR_PATH)
2008-06-05 18:43:46 +04:00
2006-06-18 14:58:39 +04:00
PHONY += headers_install
kbuild: add 'headers' target to build up uapi headers in usr/include
In Linux build system, build targets and installation targets are
separated.
Examples are:
- 'make vmlinux' -> 'make install'
- 'make modules' -> 'make modules_install'
- 'make dtbs' -> 'make dtbs_install'
- 'make vdso' -> 'make vdso_install'
The intention is to run the build targets under the normal privilege,
then the installation targets under the root privilege since we need
the write permission to the system directories.
We have 'make headers_install' but the corresponding 'make headers'
stage does not exist. The purpose of headers_install is to provide
the kernel interface to C library. So, nobody would try to install
headers to /usr/include directly.
If 'sudo make INSTALL_HDR_PATH=/usr/include headers_install' were run,
some build artifacts in the kernel tree would be owned by root because
some of uapi headers are generated by 'uapi-asm-generic', 'archheaders'
targets.
Anyway, I believe it makes sense to split the header installation into
two stages.
[1] 'make headers'
Process headers in uapi directories by scripts/headers_install.sh
and copy them to usr/include
[2] 'make headers_install'
Copy '*.h' verbatim from usr/include to $(INSTALL_HDR_PATH)/include
For the backward compatibility, 'headers_install' depends on 'headers'.
Some samples expect uapi headers in usr/include. So, the 'headers'
target is useful to build up them in the fixed location usr/include
irrespective of INSTALL_HDR_PATH.
Another benefit is to stop polluting the final destination with the
time-stamp files '.install' and '.check'. Maybe you can see them in
your toolchains.
Lastly, my main motivation is to prepare for compile-testing uapi
headers. To build something, we have to save an object and .*.cmd
somewhere. The usr/include/ will be the work directory for that.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2019-06-04 13:14:02 +03:00
headers_install : headers
$( call cmd,headers_install)
2012-05-08 22:22:24 +04:00
kbuild: add 'headers' target to build up uapi headers in usr/include
In Linux build system, build targets and installation targets are
separated.
Examples are:
- 'make vmlinux' -> 'make install'
- 'make modules' -> 'make modules_install'
- 'make dtbs' -> 'make dtbs_install'
- 'make vdso' -> 'make vdso_install'
The intention is to run the build targets under the normal privilege,
then the installation targets under the root privilege since we need
the write permission to the system directories.
We have 'make headers_install' but the corresponding 'make headers'
stage does not exist. The purpose of headers_install is to provide
the kernel interface to C library. So, nobody would try to install
headers to /usr/include directly.
If 'sudo make INSTALL_HDR_PATH=/usr/include headers_install' were run,
some build artifacts in the kernel tree would be owned by root because
some of uapi headers are generated by 'uapi-asm-generic', 'archheaders'
targets.
Anyway, I believe it makes sense to split the header installation into
two stages.
[1] 'make headers'
Process headers in uapi directories by scripts/headers_install.sh
and copy them to usr/include
[2] 'make headers_install'
Copy '*.h' verbatim from usr/include to $(INSTALL_HDR_PATH)/include
For the backward compatibility, 'headers_install' depends on 'headers'.
Some samples expect uapi headers in usr/include. So, the 'headers'
target is useful to build up them in the fixed location usr/include
irrespective of INSTALL_HDR_PATH.
Another benefit is to stop polluting the final destination with the
time-stamp files '.install' and '.check'. Maybe you can see them in
your toolchains.
Lastly, my main motivation is to prepare for compile-testing uapi
headers. To build something, we have to save an object and .*.cmd
somewhere. The usr/include/ will be the work directory for that.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2019-06-04 13:14:02 +03:00
PHONY += archheaders archscripts
2008-06-05 18:43:46 +04:00
2019-06-04 13:14:04 +03:00
hdr-inst := -f $( srctree) /scripts/Makefile.headersinst obj
2006-09-25 01:16:03 +04:00
kbuild: add 'headers' target to build up uapi headers in usr/include
In Linux build system, build targets and installation targets are
separated.
Examples are:
- 'make vmlinux' -> 'make install'
- 'make modules' -> 'make modules_install'
- 'make dtbs' -> 'make dtbs_install'
- 'make vdso' -> 'make vdso_install'
The intention is to run the build targets under the normal privilege,
then the installation targets under the root privilege since we need
the write permission to the system directories.
We have 'make headers_install' but the corresponding 'make headers'
stage does not exist. The purpose of headers_install is to provide
the kernel interface to C library. So, nobody would try to install
headers to /usr/include directly.
If 'sudo make INSTALL_HDR_PATH=/usr/include headers_install' were run,
some build artifacts in the kernel tree would be owned by root because
some of uapi headers are generated by 'uapi-asm-generic', 'archheaders'
targets.
Anyway, I believe it makes sense to split the header installation into
two stages.
[1] 'make headers'
Process headers in uapi directories by scripts/headers_install.sh
and copy them to usr/include
[2] 'make headers_install'
Copy '*.h' verbatim from usr/include to $(INSTALL_HDR_PATH)/include
For the backward compatibility, 'headers_install' depends on 'headers'.
Some samples expect uapi headers in usr/include. So, the 'headers'
target is useful to build up them in the fixed location usr/include
irrespective of INSTALL_HDR_PATH.
Another benefit is to stop polluting the final destination with the
time-stamp files '.install' and '.check'. Maybe you can see them in
your toolchains.
Lastly, my main motivation is to prepare for compile-testing uapi
headers. To build something, we have to save an object and .*.cmd
somewhere. The usr/include/ will be the work directory for that.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2019-06-04 13:14:02 +03:00
PHONY += headers
headers : $( version_h ) scripts_unifdef uapi -asm -generic archheaders archscripts
2017-10-04 06:56:04 +03:00
$( if $( wildcard $( srctree) /arch/$( SRCARCH) /include/uapi/asm/Kbuild) ,, \
2012-10-02 21:01:57 +04:00
$( error Headers not exportable for the $( SRCARCH) architecture) )
2019-06-04 13:14:03 +03:00
$( Q) $( MAKE) $( hdr-inst) = include/uapi
$( Q) $( MAKE) $( hdr-inst) = arch/$( SRCARCH) /include/uapi
2007-02-14 11:33:02 +03:00
2019-11-07 10:14:41 +03:00
# Deprecated. It is no-op now.
2006-06-18 15:02:10 +04:00
PHONY += headers_check
2019-11-07 10:14:41 +03:00
headers_check :
2021-03-02 17:26:14 +03:00
@echo >& 2 "=================== WARNING ==================="
@echo >& 2 "Since Linux 5.5, 'make headers_check' is no-op,"
@echo >& 2 "and will be removed after Linux 5.15 release."
@echo >& 2 "Please remove headers_check from your scripts."
@echo >& 2 "==============================================="
2006-06-18 15:02:10 +04:00
2019-06-04 13:13:59 +03:00
i f d e f C O N F I G _ H E A D E R S _ I N S T A L L
kbuild: add 'headers' target to build up uapi headers in usr/include
In Linux build system, build targets and installation targets are
separated.
Examples are:
- 'make vmlinux' -> 'make install'
- 'make modules' -> 'make modules_install'
- 'make dtbs' -> 'make dtbs_install'
- 'make vdso' -> 'make vdso_install'
The intention is to run the build targets under the normal privilege,
then the installation targets under the root privilege since we need
the write permission to the system directories.
We have 'make headers_install' but the corresponding 'make headers'
stage does not exist. The purpose of headers_install is to provide
the kernel interface to C library. So, nobody would try to install
headers to /usr/include directly.
If 'sudo make INSTALL_HDR_PATH=/usr/include headers_install' were run,
some build artifacts in the kernel tree would be owned by root because
some of uapi headers are generated by 'uapi-asm-generic', 'archheaders'
targets.
Anyway, I believe it makes sense to split the header installation into
two stages.
[1] 'make headers'
Process headers in uapi directories by scripts/headers_install.sh
and copy them to usr/include
[2] 'make headers_install'
Copy '*.h' verbatim from usr/include to $(INSTALL_HDR_PATH)/include
For the backward compatibility, 'headers_install' depends on 'headers'.
Some samples expect uapi headers in usr/include. So, the 'headers'
target is useful to build up them in the fixed location usr/include
irrespective of INSTALL_HDR_PATH.
Another benefit is to stop polluting the final destination with the
time-stamp files '.install' and '.check'. Maybe you can see them in
your toolchains.
Lastly, my main motivation is to prepare for compile-testing uapi
headers. To build something, we have to save an object and .*.cmd
somewhere. The usr/include/ will be the work directory for that.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2019-06-04 13:14:02 +03:00
prepare : headers
2019-06-04 13:13:59 +03:00
e n d i f
2006-06-18 15:02:10 +04:00
2019-06-04 13:14:01 +03:00
PHONY += scripts_unifdef
scripts_unifdef : scripts_basic
$( Q) $( MAKE) $( build) = scripts scripts/unifdef
2021-07-29 03:12:54 +03:00
# ---------------------------------------------------------------------------
# Install
# Many distributions have the custom install script, /sbin/installkernel.
# If DKMS is installed, 'make install' will eventually recuses back
# to the this Makefile to build and install external modules.
# Cancel sub_make_done so that options such as M=, V=, etc. are parsed.
install : sub_make_done :=
2021-05-12 09:52:00 +03:00
# ---------------------------------------------------------------------------
# Tools
kbuild: remove libelf checks from top Makefile
I do not see a good reason why only the libelf development package must
be so carefully checked.
Kbuild generally does not check host tools or libraries.
For example, x86_64 defconfig fails to build with no libssl development
package installed.
scripts/extract-cert.c:21:10: fatal error: openssl/bio.h: No such file or directory
21 | #include <openssl/bio.h>
| ^~~~~~~~~~~~~~~
To solve the build error, you need to install libssl-dev or openssl-devel
package, depending on your distribution.
'apt-file search', 'dnf provides', etc. is your frined to find a proper
package to install.
This commit removes all the libelf checks from the top Makefile.
If libelf is missing, objtool will fail to build in a similar pattern:
.../linux/tools/objtool/include/objtool/elf.h:10:10: fatal error: gelf.h: No such file or directory
10 | #include <gelf.h>
You need to install libelf-dev, libelf-devel, or elfutils-libelf-devel
to proceed.
Another remarkable change is, CONFIG_STACK_VALIDATION (without
CONFIG_UNWINDER_ORC) previously continued to build with a warning,
but now it will treat missing libelf as an error.
This is just a one-time installation, so it should not hurt to break
a build and make a user install the package.
BTW, the traditional way to handle such checks is autotool, but according
to [1], I do not expect the kernel build would have similar scripting
like './configure' does.
[1]: https://lore.kernel.org/lkml/CA+55aFzr2HTZVOuzpHYDwmtRJLsVzE-yqg2DHpHi_9ePsYp5ug@mail.gmail.com/
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
2021-05-12 09:52:01 +03:00
i f d e f C O N F I G _ S T A C K _ V A L I D A T I O N
prepare : tools /objtool
e n d i f
i f d e f C O N F I G _ B P F
i f d e f C O N F I G _ D E B U G _ I N F O _ B T F
prepare : tools /bpf /resolve_btfids
e n d i f
e n d i f
PHONY += resolve_btfids_clean
resolve_btfids_O = $( abspath $( objtree) ) /tools/bpf/resolve_btfids
# tools/bpf/resolve_btfids directory might not exist
# in output directory, skip its clean in that case
resolve_btfids_clean :
i f n e q ( $( wildcard $ ( resolve_btfids_O ) ) , )
$( Q) $( MAKE) -sC $( srctree) /tools/bpf/resolve_btfids O = $( resolve_btfids_O) clean
e n d i f
2021-05-12 09:52:00 +03:00
# Clear a bunch of variables before executing the submake
i f e q ( $( quiet ) , s i l e n t _ )
tools_silent = s
e n d i f
tools/ : FORCE
$( Q) mkdir -p $( objtree) /tools
$( Q) $( MAKE) LDFLAGS = MAKEFLAGS = " $( tools_silent) $( filter --j% -j,$( MAKEFLAGS) ) " O = $( abspath $( objtree) ) subdir = tools -C $( srctree) /tools/
tools/% : FORCE
$( Q) mkdir -p $( objtree) /tools
$( Q) $( MAKE) LDFLAGS = MAKEFLAGS = " $( tools_silent) $( filter --j% -j,$( MAKEFLAGS) ) " O = $( abspath $( objtree) ) subdir = tools -C $( srctree) /tools/ $*
2014-08-07 23:07:46 +04:00
# ---------------------------------------------------------------------------
# Kernel selftest
PHONY += kselftest
kselftest :
2017-09-07 01:44:35 +03:00
$( Q) $( MAKE) -C $( srctree) /tools/testing/selftests run_tests
2014-08-07 23:07:46 +04:00
2019-09-27 01:40:14 +03:00
kselftest-% : FORCE
$( Q) $( MAKE) -C $( srctree) /tools/testing/selftests $*
2015-10-08 05:41:18 +03:00
2016-01-08 10:27:34 +03:00
PHONY += kselftest-merge
kselftest-merge :
$( if $( wildcard $( objtree) /.config) ,, $( error No .config exists, config your kernel first!) )
2019-05-20 18:16:14 +03:00
$( Q) find $( srctree) /tools/testing/selftests -name config | \
xargs $( srctree) /scripts/kconfig/merge_config.sh -m $( objtree) /.config
2019-08-21 10:03:48 +03:00
$( Q) $( MAKE) -f $( srctree) /Makefile olddefconfig
2016-01-08 10:27:34 +03:00
2018-01-11 00:19:37 +03:00
# ---------------------------------------------------------------------------
# Devicetree files
i f n e q ( $( wildcard $ ( srctree ) /arch /$ ( SRCARCH ) /boot /dts /) , )
dtstree := arch/$( SRCARCH) /boot/dts
e n d i f
i f n e q ( $( dtstree ) , )
2019-08-22 07:46:12 +03:00
%.dtb : include /config /kernel .release scripts_dtc
2018-01-11 00:19:37 +03:00
$( Q) $( MAKE) $( build) = $( dtstree) $( dtstree) /$@
2021-01-29 10:24:08 +03:00
%.dtbo : include /config /kernel .release scripts_dtc
$( Q) $( MAKE) $( build) = $( dtstree) $( dtstree) /$@
2020-02-22 22:04:34 +03:00
PHONY += dtbs dtbs_install dtbs_check
2020-03-04 06:20:36 +03:00
dtbs : include /config /kernel .release scripts_dtc
2018-01-11 00:19:37 +03:00
$( Q) $( MAKE) $( build) = $( dtstree)
2020-03-04 06:20:36 +03:00
i f n e q ( $( filter dtbs_check , $ ( MAKECMDGOALS ) ) , )
2020-03-04 06:20:37 +03:00
export CHECK_DTBS = y
2020-03-04 06:20:36 +03:00
dtbs : dt_binding_check
e n d i f
dtbs_check : dtbs
2018-09-06 21:26:07 +03:00
2018-01-11 00:19:37 +03:00
dtbs_install :
2020-03-06 20:08:51 +03:00
$( Q) $( MAKE) $( dtbinst) = $( dtstree) dst = $( INSTALL_DTBS_PATH)
2018-01-11 00:19:37 +03:00
i f d e f C O N F I G _ O F _ E A R L Y _ F L A T T R E E
all : dtbs
e n d i f
e n d i f
PHONY += scripts_dtc
scripts_dtc : scripts_basic
$( Q) $( MAKE) $( build) = scripts/dtc
2020-03-04 06:20:37 +03:00
i f n e q ( $( filter dt_binding_check , $ ( MAKECMDGOALS ) ) , )
export CHECK_DT_BINDING = y
e n d i f
2020-02-22 22:04:34 +03:00
PHONY += dt_binding_check
2018-09-06 21:26:07 +03:00
dt_binding_check : scripts_dtc
$( Q) $( MAKE) $( build) = Documentation/devicetree/bindings
2005-04-17 02:20:36 +04:00
# ---------------------------------------------------------------------------
# Modules
i f d e f C O N F I G _ M O D U L E S
2006-06-25 02:07:55 +04:00
# By default, build modules as well
2005-04-17 02:20:36 +04:00
2010-03-10 14:28:58 +03:00
all : modules
2005-04-17 02:20:36 +04:00
2020-05-31 11:47:06 +03:00
# When we're building modules with modversions, we need to consider
# the built-in objects during the descend as well, in order to
# make sure the checksums are up to date before we record them.
i f d e f C O N F I G _ M O D V E R S I O N S
KBUILD_BUILTIN := 1
e n d i f
2014-04-28 11:32:43 +04:00
# Build modules
2007-12-07 15:04:30 +03:00
#
2014-04-28 11:32:43 +04:00
# A module can be listed more than once in obj-m resulting in
# duplicate lines in modules.order files. Those are removed
# using awk while concatenating to the final file.
2005-04-17 02:20:36 +04:00
2006-03-06 01:14:10 +03:00
PHONY += modules
2020-09-08 07:27:08 +03:00
modules : $( if $ ( KBUILD_BUILTIN ) ,vmlinux ) modules_check modules_prepare
2005-04-17 02:20:36 +04:00
2020-06-01 08:57:00 +03:00
cmd_modules_order = $( AWK) '!x[$$0]++' $( real-prereqs) > $@
modules.order : $( subdir -modorder ) FORCE
$( call if_changed,modules_order)
targets += modules.order
2019-06-23 19:13:28 +03:00
2005-04-17 02:20:36 +04:00
# Target to prepare building external modules
2006-03-06 01:14:10 +03:00
PHONY += modules_prepare
2018-11-29 06:56:30 +03:00
modules_prepare : prepare
2020-09-08 07:27:08 +03:00
$( Q) $( MAKE) $( build) = scripts scripts/module.lds
2005-04-17 02:20:36 +04:00
2021-03-31 16:38:09 +03:00
export modules_sign_only :=
i f e q ( $( CONFIG_MODULE_SIG ) , y )
PHONY += modules_sign
modules_sign : modules_install
@:
2005-04-17 02:20:36 +04:00
2021-03-31 16:38:09 +03:00
# modules_sign is a subset of modules_install.
# 'make modules_install modules_sign' is equivalent to 'make modules_install'.
i f e q ( $( filter modules_install ,$ ( MAKECMDGOALS ) ) , )
modules_sign_only := y
e n d i f
e n d i f
modinst_pre :=
i f n e q ( $( filter modules_install ,$ ( MAKECMDGOALS ) ) , )
modinst_pre := __modinst_pre
e n d i f
modules_install : $( modinst_pre )
2021-03-31 16:38:03 +03:00
PHONY += __modinst_pre
__modinst_pre :
2005-04-17 02:20:36 +04:00
@rm -rf $( MODLIB) /kernel
@rm -f $( MODLIB) /source
@mkdir -p $( MODLIB) /kernel
2017-08-20 09:04:11 +03:00
@ln -s $( abspath $( srctree) ) $( MODLIB) /source
2005-04-17 02:20:36 +04:00
@if [ ! $( objtree) -ef $( MODLIB) /build ] ; then \
rm -f $( MODLIB) /build ; \
2014-04-25 19:29:45 +04:00
ln -s $( CURDIR) $( MODLIB) /build ; \
2005-04-17 02:20:36 +04:00
fi
2019-07-17 09:17:50 +03:00
@sed 's:^:kernel/:' modules.order > $( MODLIB) /modules.order
2020-06-19 18:09:55 +03:00
@cp -f modules.builtin $( MODLIB) /
@cp -f $( objtree) /modules.builtin.modinfo $( MODLIB) /
2005-04-17 02:20:36 +04:00
e n d i f # CONFIG_MODULES
###
# Cleaning is done on three levels.
# make clean Delete most generated files
# Leave enough to build external modules
# make mrproper Delete the current configuration, and all generated files
# make distclean Remove editor backup files, patch leftover files and the like
# Directories & files removed with 'make clean'
2021-03-25 21:54:09 +03:00
CLEAN_FILES += include/ksym vmlinux.symvers modules-only.symvers \
kbuild: wire up the build rule of compile_commands.json to Makefile
Currently, you need to manually run scripts/gen_compile_commands.py
to create compile_commands.json. It parses all the .*.cmd files found
under the specified directory.
If you rebuild the kernel over again without 'make clean',
.*.cmd files from older builds will create stale entries in
compile_commands.json.
This commit wires up the compile_commands.json rule to Makefile, and
makes it parse only the .*.cmd files involved in the current build.
Pass $(KBUILD_VMLINUX_OBJS), $(KBUILD_VMLINUX_LIBS), and modules.order
to the script. The objects or archives linked to vmlinux are listed in
$(KBUILD_VMLINUX_OBJS) or $(KBUILD_VMLINUX_LIBS). All the modules are
listed in modules.order.
You can create compile_commands.json from Make:
$ make -j$(nproc) CC=clang compile_commands.json
You can also build vmlinux, modules, and compile_commands.json all
together in a single command:
$ make -j$(nproc) CC=clang all compile_commands.json
It works for M= builds as well. In this case, compile_commands.json
is created in the top directory of the external module.
This is convenient, but it has a drawback; the coverage of the
compile_commands.json is reduced because only the objects linked to
vmlinux or modules are handled. For example, the following C files are
not included in the compile_commands.json:
- Decompressor source files (arch/*/boot/)
- VDSO source files
- C files used to generate intermediates (e.g. kernel/bounds.c)
- Standalone host programs
I think it is fine for most developers because our main interest is
the kernel-space code.
If you want to cover all the compiled C files, please build the kernel,
then run the script manually as you did before:
$ make clean # if you want to remove stale .cmd files [optional]
$ make -j$(nproc) CC=clang
$ scripts/gen_compile_commands.py
Here is a note for out-of-tree builds. 'make compile_commands.json'
works with O= option, but please notice compile_commands.json is
created in the object tree instead of the source tree.
Some people may want to have compile_commands.json in the source tree
because Clang Tools searches for it through all parent paths of the
first input source file.
However, you cannot do this for O= builds. Kbuild should never generate
any build artifact in the source tree when O= is given because the
source tree might be read-only. Any write attempt to the source tree
is monitored and the violation may be reported. See the commit log of
8ef14c2c41d9.
So, the only possible way is to create compile_commands.json in the
object tree, then specify '-p <build-path>' when you use clang-check,
clang-tidy, etc.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
2020-08-22 17:56:16 +03:00
modules.builtin modules.builtin.modinfo modules.nsdeps \
2021-02-25 22:39:12 +03:00
compile_commands.json .thinlto-cache
2005-04-17 02:20:36 +04:00
# Directories & files removed with 'make mrproper'
2020-05-04 11:08:07 +03:00
MRPROPER_FILES += include/config include/generated \
2019-08-21 10:02:02 +03:00
arch/$( SRCARCH) /include/generated .tmp_objdiff \
2020-05-04 11:08:07 +03:00
debian snap tar-install \
.config .config.old .version \
2019-07-15 17:01:49 +03:00
Module.symvers \
2021-04-09 17:35:05 +03:00
certs/signing_key.pem certs/signing_key.x509 \
certs/x509.genkey \
vmlinux-gdb.py \
2019-08-21 10:02:02 +03:00
*.spec
2005-04-17 02:20:36 +04:00
# clean - Delete most, but leave enough to build external modules
#
clean : rm -files := $( CLEAN_FILES )
2019-08-10 18:53:05 +03:00
PHONY += archclean vmlinuxclean
2005-04-17 02:20:36 +04:00
2012-10-29 15:23:02 +04:00
vmlinuxclean :
$( Q) $( CONFIG_SHELL) $( srctree) /scripts/link-vmlinux.sh clean
2016-08-24 15:29:21 +03:00
$( Q) $( if $( ARCH_POSTLINK) , $( MAKE) -f $( ARCH_POSTLINK) clean)
2012-10-29 15:23:02 +04:00
2021-02-05 15:40:20 +03:00
clean : archclean vmlinuxclean resolve_btfids_clean
2005-04-17 02:20:36 +04:00
# mrproper - Delete all generated files, including .config
#
mrproper : rm -files := $( wildcard $ ( MRPROPER_FILES ) )
2017-05-14 17:50:01 +03:00
mrproper-dirs := $( addprefix _mrproper_,scripts)
2005-04-17 02:20:36 +04:00
2019-01-14 11:29:29 +03:00
PHONY += $( mrproper-dirs) mrproper
2005-04-17 02:20:36 +04:00
$(mrproper-dirs) :
$( Q) $( MAKE) $( clean) = $( patsubst _mrproper_%,%,$@ )
2019-01-14 11:29:29 +03:00
mrproper : clean $( mrproper -dirs )
2005-04-17 02:20:36 +04:00
$( call cmd,rmfiles)
# distclean
#
2006-03-06 01:14:10 +03:00
PHONY += distclean
2005-04-17 02:20:36 +04:00
distclean : mrproper
2021-05-04 13:10:56 +03:00
@find . $( RCS_FIND_IGNORE) \
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\( -name '*.orig' -o -name '*.rej' -o -name '*~' \
2017-01-22 17:02:32 +03:00
-o -name '*.bak' -o -name '#*#' -o -name '*%' \
2021-05-04 13:10:57 +03:00
-o -name 'core' -o -name tags -o -name TAGS -o -name 'cscope*' \
-o -name GPATH -o -name GRTAGS -o -name GSYMS -o -name GTAGS \) \
2005-04-17 02:20:36 +04:00
-type f -print | xargs rm -f
# Packaging of the kernel to various formats
# ---------------------------------------------------------------------------
2010-06-07 14:44:25 +04:00
%src-pkg : FORCE
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$( Q) $( MAKE) -f $( srctree) /scripts/Makefile.package $@
2006-06-09 09:12:37 +04:00
%pkg : include /config /kernel .release FORCE
2019-08-21 10:02:04 +03:00
$( Q) $( MAKE) -f $( srctree) /scripts/Makefile.package $@
2005-04-17 02:20:36 +04:00
# Brief documentation of the typical targets used
# ---------------------------------------------------------------------------
2008-04-07 00:16:07 +04:00
boards := $( wildcard $( srctree) /arch/$( SRCARCH) /configs/*_defconfig)
2014-10-28 16:18:20 +03:00
boards := $( sort $( notdir $( boards) ) )
2008-04-07 00:16:07 +04:00
board-dirs := $( dir $( wildcard $( srctree) /arch/$( SRCARCH) /configs/*/*_defconfig) )
board-dirs := $( sort $( notdir $( board-dirs:/= ) ) )
2005-04-17 02:20:36 +04:00
2016-03-13 03:39:55 +03:00
PHONY += help
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help :
@echo 'Cleaning targets:'
2006-12-12 21:09:40 +03:00
@echo ' clean - Remove most generated files but keep the config and'
2006-09-24 16:01:08 +04:00
@echo ' enough build support to build external modules'
2006-12-12 21:09:40 +03:00
@echo ' mrproper - Remove all generated files + config + various backup files'
2006-09-24 16:01:08 +04:00
@echo ' distclean - mrproper + remove editor backup and patch files'
2005-04-17 02:20:36 +04:00
@echo ''
@echo 'Configuration targets:'
@$( MAKE) -f $( srctree) /scripts/kconfig/Makefile help
@echo ''
@echo 'Other generic targets:'
@echo ' all - Build all targets marked with [*]'
@echo '* vmlinux - Build the bare kernel'
@echo '* modules - Build all modules'
2005-11-23 22:11:34 +03:00
@echo ' modules_install - Install all modules to INSTALL_MOD_PATH (default: /)'
2005-04-17 02:20:36 +04:00
@echo ' dir/ - Build all files in dir and below'
2015-12-10 19:35:19 +03:00
@echo ' dir/file.[ois] - Build specified target only'
2017-04-24 23:04:58 +03:00
@echo ' dir/file.ll - Build the LLVM assembly file'
@echo ' (requires compiler support for LLVM assembly generation)'
2010-01-13 20:31:44 +03:00
@echo ' dir/file.lst - Build specified mixed source/assembly target only'
@echo ' (requires a recent binutils and recent build (System.map))'
2005-07-08 04:56:08 +04:00
@echo ' dir/file.ko - Build module including final link'
2009-04-24 20:35:23 +04:00
@echo ' modules_prepare - Set up for building external modules'
2005-04-17 02:20:36 +04:00
@echo ' tags/TAGS - Generate tags file for editors'
@echo ' cscope - Generate cscope index'
2011-01-14 15:07:05 +03:00
@echo ' gtags - Generate GNU GLOBAL index'
2014-07-11 17:57:24 +04:00
@echo ' kernelrelease - Output the release version string (use with make -s)'
@echo ' kernelversion - Output the version stored in Makefile (use with make -s)'
@echo ' image_name - Output the image name (use with make -s)'
2008-06-21 02:24:17 +04:00
@echo ' headers_install - Install sanitised kernel headers to INSTALL_HDR_PATH' ; \
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echo ' (default: $(INSTALL_HDR_PATH))' ; \
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echo ''
2017-05-09 01:55:08 +03:00
@echo 'Static analysers:'
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@echo ' checkstack - Generate a list of stack hogs'
2007-11-14 23:34:55 +03:00
@echo ' versioncheck - Sanity check on version.h usage'
2007-11-04 23:01:55 +03:00
@echo ' includecheck - Check for duplicate included header files'
2007-08-25 01:04:56 +04:00
@echo ' export_report - List the usages of all exported symbols'
2010-06-06 19:15:01 +04:00
@echo ' headerdep - Detect inclusion cycles in headers'
2017-11-14 12:47:20 +03:00
@echo ' coccicheck - Check with Coccinelle'
2020-08-22 17:56:18 +03:00
@echo ' clang-analyzer - Check with clang static analyzer'
@echo ' clang-tidy - Check with clang-tidy'
2010-06-06 19:15:01 +04:00
@echo ''
2019-09-06 13:32:32 +03:00
@echo 'Tools:'
@echo ' nsdeps - Generate missing symbol namespace dependencies'
@echo ''
2017-05-09 01:55:08 +03:00
@echo 'Kernel selftest:'
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@echo ' kselftest - Build and run kernel selftest'
@echo ' Build, install, and boot kernel before'
@echo ' running kselftest on it'
@echo ' Run as root for full coverage'
@echo ' kselftest-all - Build kernel selftest'
@echo ' kselftest-install - Build and install kernel selftest'
@echo ' kselftest-clean - Remove all generated kselftest files'
@echo ' kselftest-merge - Merge all the config dependencies of'
@echo ' kselftest to existing .config.'
2014-08-07 23:07:46 +04:00
@echo ''
2018-01-11 00:19:37 +03:00
@$( if $( dtstree) , \
echo 'Devicetree:' ; \
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echo '* dtbs - Build device tree blobs for enabled boards' ; \
echo ' dtbs_install - Install dtbs to $(INSTALL_DTBS_PATH)' ; \
echo ' dt_binding_check - Validate device tree binding documents' ; \
echo ' dtbs_check - Validate device tree source files' ; \
2018-01-11 00:19:37 +03:00
echo '' )
2017-05-09 01:55:08 +03:00
@echo 'Userspace tools targets:'
@echo ' use "make tools/help"'
@echo ' or "cd tools; make help"'
@echo ''
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@echo 'Kernel packaging:'
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@$( MAKE) -f $( srctree) /scripts/Makefile.package help
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@echo ''
@echo 'Documentation targets:'
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@$( MAKE) -f $( srctree) /Documentation/Makefile dochelp
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@echo ''
2008-04-26 06:34:58 +04:00
@echo 'Architecture specific targets ($(SRCARCH)):'
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@$( if $( archhelp) ,$( archhelp) ,\
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echo ' No architecture specific help defined for $(SRCARCH)' )
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@echo ''
@$( if $( boards) , \
$( foreach b, $( boards) , \
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printf " %-27s - Build for %s\\n" $( b) $( subst _defconfig,,$( b) ) ; ) \
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echo '' )
2008-04-07 00:16:07 +04:00
@$( if $( board-dirs) , \
$( foreach b, $( board-dirs) , \
printf " %-16s - Show %s-specific targets\\n" help-$( b) $( b) ; ) \
printf " %-16s - Show all of the above\\n" help-boards; \
echo '' )
2005-04-17 02:20:36 +04:00
@echo ' make V=0|1 [targets] 0 => quiet build (default), 1 => verbose build'
2006-08-08 23:35:14 +04:00
@echo ' make V=2 [targets] 2 => give reason for rebuild of target'
2005-04-17 02:20:36 +04:00
@echo ' make O=dir [targets] Locate all output files in "dir", including .config'
2019-10-25 14:52:32 +03:00
@echo ' make C=1 [targets] Check re-compiled c source with $$CHECK'
@echo ' (sparse by default)'
2006-05-24 00:57:23 +04:00
@echo ' make C=2 [targets] Force check of all c source with $$CHECK'
2011-06-16 15:26:23 +04:00
@echo ' make RECORDMCOUNT_WARN=1 [targets] Warn about ignored mcount sections'
2019-08-31 19:25:55 +03:00
@echo ' make W=n [targets] Enable extra build checks, n=1,2,3 where'
2011-04-28 00:15:27 +04:00
@echo ' 1: warnings which may be relevant and do not occur too often'
@echo ' 2: warnings which occur quite often but may still be relevant'
@echo ' 3: more obscure warnings, can most likely be ignored'
2011-04-29 16:45:31 +04:00
@echo ' Multiple levels can be combined with W=12 or W=123'
2005-04-17 02:20:36 +04:00
@echo ''
@echo 'Execute "make" or "make all" to build all targets marked with [*] '
@echo 'For further info see the ./README file'
2008-04-07 00:16:07 +04:00
help-board-dirs := $( addprefix help-,$( board-dirs) )
help-boards : $( help -board -dirs )
2014-11-28 15:31:43 +03:00
boards-per-dir = $( sort $( notdir $( wildcard $( srctree) /arch/$( SRCARCH) /configs/$* /*_defconfig) ) )
2008-04-07 00:16:07 +04:00
$(help-board-dirs) : help -%:
@echo 'Architecture specific targets ($(SRCARCH) $*):'
@$( if $( boards-per-dir) , \
$( foreach b, $( boards-per-dir) , \
printf " %-24s - Build for %s\\n" $* /$( b) $( subst _defconfig,,$( b) ) ; ) \
echo '' )
2005-04-17 02:20:36 +04:00
# Documentation targets
# ---------------------------------------------------------------------------
2017-10-09 18:26:15 +03:00
DOC_TARGETS := xmldocs latexdocs pdfdocs htmldocs epubdocs cleandocs \
linkcheckdocs dochelp refcheckdocs
Documentation/sphinx: add basic working Sphinx configuration and build
Add basic configuration and makefile to build documentation from any
.rst files under Documentation using Sphinx. For starters, there's just
the placeholder index.rst.
At the top level Makefile, hook Sphinx documentation targets alongside
(but independent of) the DocBook toolchain, having both be run on the
various 'make *docs' targets.
All Sphinx processing is placed into Documentation/Makefile.sphinx. Both
that and the Documentation/DocBook/Makefile are now expected to handle
all the documentation targets, explicitly ignoring them if they're not
relevant for that particular toolchain. The changes to the existing
DocBook Makefile are kept minimal.
There is graceful handling of missing Sphinx and rst2pdf (which is
needed for pdf output) by checking for the tool and python module,
respectively, with informative messages to the user.
If the Read the Docs theme (sphinx_rtd_theme) is available, use it, but
otherwise gracefully fall back to the Sphinx default theme, with an
informative message to the user, and slightly less pretty HTML output.
Sphinx can now handle htmldocs, pdfdocs (if rst2pdf is available),
epubdocs and xmldocs targets. The output documents are written into per
output type subdirectories under Documentation/output.
Finally, you can pass options to sphinx-build using the SPHINXBUILD make
variable. For example, 'make SPHINXOPTS=-v htmldocs' for more verbose
output from Sphinx.
This is based on the original work by Jonathan Corbet, but he probably
wouldn't recognize this as his own anymore.
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
2016-05-19 15:14:05 +03:00
PHONY += $( DOC_TARGETS)
2019-08-21 20:33:21 +03:00
$(DOC_TARGETS) :
2017-05-14 17:50:01 +03:00
$( Q) $( MAKE) $( build) = Documentation $@
2005-04-17 02:20:36 +04:00
2019-02-19 12:33:02 +03:00
# Misc
# ---------------------------------------------------------------------------
PHONY += scripts_gdb
2019-06-04 13:13:57 +03:00
scripts_gdb : prepare 0
2019-02-19 12:33:04 +03:00
$( Q) $( MAKE) $( build) = scripts/gdb
2019-02-19 12:33:05 +03:00
$( Q) ln -fsn $( abspath $( srctree) /scripts/gdb/vmlinux-gdb.py)
2019-02-19 12:33:02 +03:00
i f d e f C O N F I G _ G D B _ S C R I P T S
all : scripts_gdb
e n d i f
2005-04-17 02:20:36 +04:00
e l s e # KBUILD_EXTMOD
###
# External module support.
# When building external modules the kernel used as basis is considered
# read-only, and no consistency checks are made and the make
# system is not used on the basis kernel. If updates are required
2021-05-04 13:10:58 +03:00
# in the basis kernel ordinary make commands (without M=...) must be used.
2005-04-17 02:20:36 +04:00
2020-09-08 23:55:57 +03:00
# We are always building only modules.
KBUILD_BUILTIN :=
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KBUILD_MODULES := 1
2019-08-10 18:53:04 +03:00
build-dirs := $( KBUILD_EXTMOD)
kbuild: wire up the build rule of compile_commands.json to Makefile
Currently, you need to manually run scripts/gen_compile_commands.py
to create compile_commands.json. It parses all the .*.cmd files found
under the specified directory.
If you rebuild the kernel over again without 'make clean',
.*.cmd files from older builds will create stale entries in
compile_commands.json.
This commit wires up the compile_commands.json rule to Makefile, and
makes it parse only the .*.cmd files involved in the current build.
Pass $(KBUILD_VMLINUX_OBJS), $(KBUILD_VMLINUX_LIBS), and modules.order
to the script. The objects or archives linked to vmlinux are listed in
$(KBUILD_VMLINUX_OBJS) or $(KBUILD_VMLINUX_LIBS). All the modules are
listed in modules.order.
You can create compile_commands.json from Make:
$ make -j$(nproc) CC=clang compile_commands.json
You can also build vmlinux, modules, and compile_commands.json all
together in a single command:
$ make -j$(nproc) CC=clang all compile_commands.json
It works for M= builds as well. In this case, compile_commands.json
is created in the top directory of the external module.
This is convenient, but it has a drawback; the coverage of the
compile_commands.json is reduced because only the objects linked to
vmlinux or modules are handled. For example, the following C files are
not included in the compile_commands.json:
- Decompressor source files (arch/*/boot/)
- VDSO source files
- C files used to generate intermediates (e.g. kernel/bounds.c)
- Standalone host programs
I think it is fine for most developers because our main interest is
the kernel-space code.
If you want to cover all the compiled C files, please build the kernel,
then run the script manually as you did before:
$ make clean # if you want to remove stale .cmd files [optional]
$ make -j$(nproc) CC=clang
$ scripts/gen_compile_commands.py
Here is a note for out-of-tree builds. 'make compile_commands.json'
works with O= option, but please notice compile_commands.json is
created in the object tree instead of the source tree.
Some people may want to have compile_commands.json in the source tree
because Clang Tools searches for it through all parent paths of the
first input source file.
However, you cannot do this for O= builds. Kbuild should never generate
any build artifact in the source tree when O= is given because the
source tree might be read-only. Any write attempt to the source tree
is monitored and the violation may be reported. See the commit log of
8ef14c2c41d9.
So, the only possible way is to create compile_commands.json in the
object tree, then specify '-p <build-path>' when you use clang-check,
clang-tidy, etc.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
2020-08-22 17:56:16 +03:00
$(MODORDER) : descend
@:
2021-03-31 16:38:06 +03:00
compile_commands.json : $( extmod_prefix ) compile_commands .json
kbuild: wire up the build rule of compile_commands.json to Makefile
Currently, you need to manually run scripts/gen_compile_commands.py
to create compile_commands.json. It parses all the .*.cmd files found
under the specified directory.
If you rebuild the kernel over again without 'make clean',
.*.cmd files from older builds will create stale entries in
compile_commands.json.
This commit wires up the compile_commands.json rule to Makefile, and
makes it parse only the .*.cmd files involved in the current build.
Pass $(KBUILD_VMLINUX_OBJS), $(KBUILD_VMLINUX_LIBS), and modules.order
to the script. The objects or archives linked to vmlinux are listed in
$(KBUILD_VMLINUX_OBJS) or $(KBUILD_VMLINUX_LIBS). All the modules are
listed in modules.order.
You can create compile_commands.json from Make:
$ make -j$(nproc) CC=clang compile_commands.json
You can also build vmlinux, modules, and compile_commands.json all
together in a single command:
$ make -j$(nproc) CC=clang all compile_commands.json
It works for M= builds as well. In this case, compile_commands.json
is created in the top directory of the external module.
This is convenient, but it has a drawback; the coverage of the
compile_commands.json is reduced because only the objects linked to
vmlinux or modules are handled. For example, the following C files are
not included in the compile_commands.json:
- Decompressor source files (arch/*/boot/)
- VDSO source files
- C files used to generate intermediates (e.g. kernel/bounds.c)
- Standalone host programs
I think it is fine for most developers because our main interest is
the kernel-space code.
If you want to cover all the compiled C files, please build the kernel,
then run the script manually as you did before:
$ make clean # if you want to remove stale .cmd files [optional]
$ make -j$(nproc) CC=clang
$ scripts/gen_compile_commands.py
Here is a note for out-of-tree builds. 'make compile_commands.json'
works with O= option, but please notice compile_commands.json is
created in the object tree instead of the source tree.
Some people may want to have compile_commands.json in the source tree
because Clang Tools searches for it through all parent paths of the
first input source file.
However, you cannot do this for O= builds. Kbuild should never generate
any build artifact in the source tree when O= is given because the
source tree might be read-only. Any write attempt to the source tree
is monitored and the violation may be reported. See the commit log of
8ef14c2c41d9.
So, the only possible way is to create compile_commands.json in the
object tree, then specify '-p <build-path>' when you use clang-check,
clang-tidy, etc.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
2020-08-22 17:56:16 +03:00
PHONY += compile_commands.json
2019-08-10 18:53:05 +03:00
clean-dirs := $( KBUILD_EXTMOD)
kbuild: wire up the build rule of compile_commands.json to Makefile
Currently, you need to manually run scripts/gen_compile_commands.py
to create compile_commands.json. It parses all the .*.cmd files found
under the specified directory.
If you rebuild the kernel over again without 'make clean',
.*.cmd files from older builds will create stale entries in
compile_commands.json.
This commit wires up the compile_commands.json rule to Makefile, and
makes it parse only the .*.cmd files involved in the current build.
Pass $(KBUILD_VMLINUX_OBJS), $(KBUILD_VMLINUX_LIBS), and modules.order
to the script. The objects or archives linked to vmlinux are listed in
$(KBUILD_VMLINUX_OBJS) or $(KBUILD_VMLINUX_LIBS). All the modules are
listed in modules.order.
You can create compile_commands.json from Make:
$ make -j$(nproc) CC=clang compile_commands.json
You can also build vmlinux, modules, and compile_commands.json all
together in a single command:
$ make -j$(nproc) CC=clang all compile_commands.json
It works for M= builds as well. In this case, compile_commands.json
is created in the top directory of the external module.
This is convenient, but it has a drawback; the coverage of the
compile_commands.json is reduced because only the objects linked to
vmlinux or modules are handled. For example, the following C files are
not included in the compile_commands.json:
- Decompressor source files (arch/*/boot/)
- VDSO source files
- C files used to generate intermediates (e.g. kernel/bounds.c)
- Standalone host programs
I think it is fine for most developers because our main interest is
the kernel-space code.
If you want to cover all the compiled C files, please build the kernel,
then run the script manually as you did before:
$ make clean # if you want to remove stale .cmd files [optional]
$ make -j$(nproc) CC=clang
$ scripts/gen_compile_commands.py
Here is a note for out-of-tree builds. 'make compile_commands.json'
works with O= option, but please notice compile_commands.json is
created in the object tree instead of the source tree.
Some people may want to have compile_commands.json in the source tree
because Clang Tools searches for it through all parent paths of the
first input source file.
However, you cannot do this for O= builds. Kbuild should never generate
any build artifact in the source tree when O= is given because the
source tree might be read-only. Any write attempt to the source tree
is monitored and the violation may be reported. See the commit log of
8ef14c2c41d9.
So, the only possible way is to create compile_commands.json in the
object tree, then specify '-p <build-path>' when you use clang-check,
clang-tidy, etc.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
2020-08-22 17:56:16 +03:00
clean : rm -files := $( KBUILD_EXTMOD ) /Module .symvers $( KBUILD_EXTMOD ) /modules .nsdeps \
kbuild: add support for Clang LTO
This change adds build system support for Clang's Link Time
Optimization (LTO). With -flto, instead of ELF object files, Clang
produces LLVM bitcode, which is compiled into native code at link
time, allowing the final binary to be optimized globally. For more
details, see:
https://llvm.org/docs/LinkTimeOptimization.html
The Kconfig option CONFIG_LTO_CLANG is implemented as a choice,
which defaults to LTO being disabled. To use LTO, the architecture
must select ARCH_SUPPORTS_LTO_CLANG and support:
- compiling with Clang,
- compiling all assembly code with Clang's integrated assembler,
- and linking with LLD.
While using CONFIG_LTO_CLANG_FULL results in the best runtime
performance, the compilation is not scalable in time or
memory. CONFIG_LTO_CLANG_THIN enables ThinLTO, which allows
parallel optimization and faster incremental builds. ThinLTO is
used by default if the architecture also selects
ARCH_SUPPORTS_LTO_CLANG_THIN:
https://clang.llvm.org/docs/ThinLTO.html
To enable LTO, LLVM tools must be used to handle bitcode files, by
passing LLVM=1 and LLVM_IAS=1 options to make:
$ make LLVM=1 LLVM_IAS=1 defconfig
$ scripts/config -e LTO_CLANG_THIN
$ make LLVM=1 LLVM_IAS=1
To prepare for LTO support with other compilers, common parts are
gated behind the CONFIG_LTO option, and LTO can be disabled for
specific files by filtering out CC_FLAGS_LTO.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201211184633.3213045-3-samitolvanen@google.com
2020-12-11 21:46:19 +03:00
$( KBUILD_EXTMOD) /compile_commands.json $( KBUILD_EXTMOD) /.thinlto-cache
2005-04-17 02:20:36 +04:00
2021-08-01 05:53:46 +03:00
PHONY += prepare
# now expand this into a simple variable to reduce the cost of shell evaluations
prepare : CC_VERSION_TEXT := $( CC_VERSION_TEXT )
prepare :
@if [ " $( CC_VERSION_TEXT) " != $( CONFIG_CC_VERSION_TEXT) ] ; then \
echo >& 2 "warning: the compiler differs from the one used to build the kernel" ; \
echo >& 2 " The kernel was built by: " $( CONFIG_CC_VERSION_TEXT) ; \
echo >& 2 " You are using: $( CC_VERSION_TEXT) " ; \
fi
2016-03-13 03:39:55 +03:00
PHONY += help
2005-04-17 02:20:36 +04:00
help :
@echo ' Building external modules.'
@echo ' Syntax: make -C path/to/kernel/src M=$$PWD target'
@echo ''
@echo ' modules - default target, build the module(s)'
@echo ' modules_install - install the module'
@echo ' clean - remove generated files in module directory only'
@echo ''
2006-01-25 09:13:18 +03:00
2020-09-08 07:27:08 +03:00
# no-op for external module builds
2021-08-01 05:53:46 +03:00
PHONY += modules_prepare
2020-09-08 07:27:08 +03:00
2005-04-17 02:20:36 +04:00
e n d i f # KBUILD_EXTMOD
2021-03-31 16:38:03 +03:00
# ---------------------------------------------------------------------------
# Modules
PHONY += modules modules_install
i f d e f C O N F I G _ M O D U L E S
2021-03-31 16:38:05 +03:00
modules : modules_check
2021-03-31 16:38:03 +03:00
$( Q) $( MAKE) -f $( srctree) /scripts/Makefile.modpost
2021-03-31 16:38:05 +03:00
PHONY += modules_check
modules_check : $( MODORDER )
$( Q) $( CONFIG_SHELL) $( srctree) /scripts/modules-check.sh $<
2021-03-31 16:38:04 +03:00
quiet_cmd_depmod = DEPMOD $( MODLIB)
2021-03-31 16:38:03 +03:00
cmd_depmod = $( CONFIG_SHELL) $( srctree) /scripts/depmod.sh $( DEPMOD) \
$( KERNELRELEASE)
modules_install :
$( Q) $( MAKE) -f $( srctree) /scripts/Makefile.modinst
$( call cmd,depmod)
e l s e # CONFIG_MODULES
# Modules not configured
# ---------------------------------------------------------------------------
modules modules_install :
@echo >& 2 '***'
@echo >& 2 '*** The present kernel configuration has modules disabled.'
@echo >& 2 '*** To use the module feature, please run "make menuconfig" etc.'
@echo >& 2 '*** to enable CONFIG_MODULES.'
@echo >& 2 '***'
@exit 1
e n d i f # CONFIG_MODULES
2019-11-18 07:52:47 +03:00
# Single targets
# ---------------------------------------------------------------------------
# To build individual files in subdirectories, you can do like this:
#
# make foo/bar/baz.s
#
# The supported suffixes for single-target are listed in 'single-targets'
#
# To build only under specific subdirectories, you can do like this:
#
# make foo/bar/baz/
i f d e f s i n g l e - b u i l d
# .ko is special because modpost is needed
single-ko := $( sort $( filter %.ko, $( MAKECMDGOALS) ) )
single-no-ko := $( sort $( patsubst %.ko,%.mod, $( MAKECMDGOALS) ) )
$(single-ko) : single_modpost
@:
$(single-no-ko) : descend
@:
i f e q ( $( KBUILD_EXTMOD ) , )
# For the single build of in-tree modules, use a temporary file to avoid
# the situation of modules_install installing an invalid modules.order.
MODORDER := .modules.tmp
e n d i f
PHONY += single_modpost
2020-09-08 07:27:08 +03:00
single_modpost : $( single -no -ko ) modules_prepare
2021-03-31 16:38:06 +03:00
$( Q) { $( foreach m, $( single-ko) , echo $( extmod_prefix) $m ; ) } > $( MODORDER)
2019-11-18 07:52:47 +03:00
$( Q) $( MAKE) -f $( srctree) /scripts/Makefile.modpost
KBUILD_MODULES := 1
2021-03-31 16:38:06 +03:00
export KBUILD_SINGLE_TARGETS := $( addprefix $( extmod_prefix) , $( single-no-ko) )
2019-11-18 07:52:47 +03:00
# trim unrelated directories
build-dirs := $( foreach d, $( build-dirs) , \
$( if $( filter $( d) /%, $( KBUILD_SINGLE_TARGETS) ) , $( d) ) )
e n d i f
2020-05-22 04:59:59 +03:00
i f n d e f C O N F I G _ M O D U L E S
KBUILD_MODULES :=
e n d i f
2019-08-10 18:53:04 +03:00
# Handle descending into subdirectories listed in $(build-dirs)
# Preset locale variables to speed up the build process. Limit locale
# tweaks to this spot to avoid wrong language settings when running
# make menuconfig etc.
# Error messages still appears in the original language
PHONY += descend $( build-dirs)
descend : $( build -dirs )
$(build-dirs) : prepare
2019-11-18 07:52:47 +03:00
$( Q) $( MAKE) $( build) = $@ \
2020-07-07 19:35:08 +03:00
single-build= $( if $( filter-out $@ /, $( filter $@ /%, $( KBUILD_SINGLE_TARGETS) ) ) ,1) \
2019-11-18 07:52:47 +03:00
need-builtin= 1 need-modorder= 1
2019-08-10 18:53:04 +03:00
2019-08-10 18:53:05 +03:00
clean-dirs := $( addprefix _clean_, $( clean-dirs) )
PHONY += $( clean-dirs) clean
$(clean-dirs) :
$( Q) $( MAKE) $( clean) = $( patsubst _clean_%,%,$@ )
2010-09-06 14:00:08 +04:00
clean : $( clean -dirs )
$( call cmd,rmfiles)
2011-05-11 02:47:16 +04:00
@find $( if $( KBUILD_EXTMOD) , $( KBUILD_EXTMOD) , .) $( RCS_FIND_IGNORE) \
2017-11-16 19:49:13 +03:00
\( -name '*.[aios]' -o -name '*.ko' -o -name '.*.cmd' \
2018-09-06 21:26:07 +03:00
-o -name '*.ko.*' \
2021-01-29 10:24:08 +03:00
-o -name '*.dtb' -o -name '*.dtbo' -o -name '*.dtb.S' -o -name '*.dt.yaml' \
2017-11-16 19:49:13 +03:00
-o -name '*.dwo' -o -name '*.lst' \
2019-10-29 15:38:07 +03:00
-o -name '*.su' -o -name '*.mod' \
2010-09-06 14:00:08 +04:00
-o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \
2018-03-23 16:04:31 +03:00
-o -name '*.lex.c' -o -name '*.tab.[ch]' \
2018-03-23 16:04:37 +03:00
-o -name '*.asn1.[ch]' \
2010-09-06 14:00:08 +04:00
-o -name '*.symtypes' -o -name 'modules.order' \
kbuild: create modules.builtin without Makefile.modbuiltin or tristate.conf
Commit bc081dd6e9f6 ("kbuild: generate modules.builtin") added
infrastructure to generate modules.builtin, the list of all
builtin modules.
Basically, it works like this:
- Kconfig generates include/config/tristate.conf, the list of
tristate CONFIG options with a value in a capital letter.
- scripts/Makefile.modbuiltin makes Kbuild descend into
directories to collect the information of builtin modules.
I am not a big fan of it because Kbuild ends up with traversing
the source tree twice.
I am not sure how perfectly it should work, but this approach cannot
avoid false positives; even if the relevant CONFIG option is tristate,
some Makefiles forces obj-m to obj-y.
Some examples are:
arch/powerpc/platforms/powermac/Makefile:
obj-$(CONFIG_NVRAM:m=y) += nvram.o
net/ipv6/Makefile:
obj-$(subst m,y,$(CONFIG_IPV6)) += inet6_hashtables.o
net/netlabel/Makefile:
obj-$(subst m,y,$(CONFIG_IPV6)) += netlabel_calipso.o
Nobody has complained about (or noticed) it, so it is probably fine to
have false positives in modules.builtin.
This commit simplifies the implementation. Let's exploit the fact
that every module has MODULE_LICENSE(). (modpost shows a warning if
MODULE_LICENSE is missing. If so, 0-day bot would already have blocked
such a module.)
I added MODULE_FILE to <linux/module.h>. When the code is being compiled
as builtin, it will be filled with the file path of the module, and
collected into modules.builtin.info. Then, scripts/link-vmlinux.sh
extracts the list of builtin modules out of it.
This new approach fixes the false-positives above, but adds another
type of false-positives; non-modular code may have MODULE_LICENSE()
by mistake. This is not a big deal, it is just the code is always
orphan. We can clean it up if we like. You can see cleanup examples by:
$ git log --grep='make.* explicitly non-modular'
To sum up, this commits deletes lots of code, but still produces almost
equivalent results. Please note it does not increase the vmlinux size at
all. As you can see in include/asm-generic/vmlinux.lds.h, the .modinfo
section is discarded in the link stage.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2019-12-19 11:33:29 +03:00
-o -name '.tmp_*.o.*' \
2016-05-24 01:09:38 +03:00
-o -name '*.c.[012]*.*' \
2017-04-24 23:04:58 +03:00
-o -name '*.ll' \
2020-12-11 21:46:20 +03:00
-o -name '*.gcno' \
-o -name '*.*.symversions' \) -type f -print | xargs rm -f
2010-09-06 14:00:08 +04:00
2005-04-17 02:20:36 +04:00
# Generate tags for editors
# ---------------------------------------------------------------------------
2008-12-04 00:24:13 +03:00
quiet_cmd_tags = GEN $@
2019-08-25 16:28:37 +03:00
cmd_tags = $( BASH) $( srctree) /scripts/tags.sh $@
2005-04-17 02:20:36 +04:00
2011-01-14 15:07:05 +03:00
tags TAGS cscope gtags : FORCE
2005-04-17 02:20:36 +04:00
$( call cmd,tags)
2019-09-06 13:32:32 +03:00
# Script to generate missing namespace dependencies
# ---------------------------------------------------------------------------
PHONY += nsdeps
2019-10-29 15:38:06 +03:00
nsdeps : export KBUILD_NSDEPS =1
2019-09-06 13:32:32 +03:00
nsdeps : modules
2019-10-29 15:38:06 +03:00
$( Q) $( CONFIG_SHELL) $( srctree) /scripts/nsdeps
2019-09-06 13:32:32 +03:00
kbuild: wire up the build rule of compile_commands.json to Makefile
Currently, you need to manually run scripts/gen_compile_commands.py
to create compile_commands.json. It parses all the .*.cmd files found
under the specified directory.
If you rebuild the kernel over again without 'make clean',
.*.cmd files from older builds will create stale entries in
compile_commands.json.
This commit wires up the compile_commands.json rule to Makefile, and
makes it parse only the .*.cmd files involved in the current build.
Pass $(KBUILD_VMLINUX_OBJS), $(KBUILD_VMLINUX_LIBS), and modules.order
to the script. The objects or archives linked to vmlinux are listed in
$(KBUILD_VMLINUX_OBJS) or $(KBUILD_VMLINUX_LIBS). All the modules are
listed in modules.order.
You can create compile_commands.json from Make:
$ make -j$(nproc) CC=clang compile_commands.json
You can also build vmlinux, modules, and compile_commands.json all
together in a single command:
$ make -j$(nproc) CC=clang all compile_commands.json
It works for M= builds as well. In this case, compile_commands.json
is created in the top directory of the external module.
This is convenient, but it has a drawback; the coverage of the
compile_commands.json is reduced because only the objects linked to
vmlinux or modules are handled. For example, the following C files are
not included in the compile_commands.json:
- Decompressor source files (arch/*/boot/)
- VDSO source files
- C files used to generate intermediates (e.g. kernel/bounds.c)
- Standalone host programs
I think it is fine for most developers because our main interest is
the kernel-space code.
If you want to cover all the compiled C files, please build the kernel,
then run the script manually as you did before:
$ make clean # if you want to remove stale .cmd files [optional]
$ make -j$(nproc) CC=clang
$ scripts/gen_compile_commands.py
Here is a note for out-of-tree builds. 'make compile_commands.json'
works with O= option, but please notice compile_commands.json is
created in the object tree instead of the source tree.
Some people may want to have compile_commands.json in the source tree
because Clang Tools searches for it through all parent paths of the
first input source file.
However, you cannot do this for O= builds. Kbuild should never generate
any build artifact in the source tree when O= is given because the
source tree might be read-only. Any write attempt to the source tree
is monitored and the violation may be reported. See the commit log of
8ef14c2c41d9.
So, the only possible way is to create compile_commands.json in the
object tree, then specify '-p <build-path>' when you use clang-check,
clang-tidy, etc.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
2020-08-22 17:56:16 +03:00
# Clang Tooling
# ---------------------------------------------------------------------------
quiet_cmd_gen_compile_commands = GEN $@
cmd_gen_compile_commands = $( PYTHON3) $< -a $( AR) -o $@ $( filter-out $<, $( real-prereqs) )
2021-03-31 16:38:06 +03:00
$(extmod_prefix)compile_commands.json : scripts /clang -tools /gen_compile_commands .py \
kbuild: wire up the build rule of compile_commands.json to Makefile
Currently, you need to manually run scripts/gen_compile_commands.py
to create compile_commands.json. It parses all the .*.cmd files found
under the specified directory.
If you rebuild the kernel over again without 'make clean',
.*.cmd files from older builds will create stale entries in
compile_commands.json.
This commit wires up the compile_commands.json rule to Makefile, and
makes it parse only the .*.cmd files involved in the current build.
Pass $(KBUILD_VMLINUX_OBJS), $(KBUILD_VMLINUX_LIBS), and modules.order
to the script. The objects or archives linked to vmlinux are listed in
$(KBUILD_VMLINUX_OBJS) or $(KBUILD_VMLINUX_LIBS). All the modules are
listed in modules.order.
You can create compile_commands.json from Make:
$ make -j$(nproc) CC=clang compile_commands.json
You can also build vmlinux, modules, and compile_commands.json all
together in a single command:
$ make -j$(nproc) CC=clang all compile_commands.json
It works for M= builds as well. In this case, compile_commands.json
is created in the top directory of the external module.
This is convenient, but it has a drawback; the coverage of the
compile_commands.json is reduced because only the objects linked to
vmlinux or modules are handled. For example, the following C files are
not included in the compile_commands.json:
- Decompressor source files (arch/*/boot/)
- VDSO source files
- C files used to generate intermediates (e.g. kernel/bounds.c)
- Standalone host programs
I think it is fine for most developers because our main interest is
the kernel-space code.
If you want to cover all the compiled C files, please build the kernel,
then run the script manually as you did before:
$ make clean # if you want to remove stale .cmd files [optional]
$ make -j$(nproc) CC=clang
$ scripts/gen_compile_commands.py
Here is a note for out-of-tree builds. 'make compile_commands.json'
works with O= option, but please notice compile_commands.json is
created in the object tree instead of the source tree.
Some people may want to have compile_commands.json in the source tree
because Clang Tools searches for it through all parent paths of the
first input source file.
However, you cannot do this for O= builds. Kbuild should never generate
any build artifact in the source tree when O= is given because the
source tree might be read-only. Any write attempt to the source tree
is monitored and the violation may be reported. See the commit log of
8ef14c2c41d9.
So, the only possible way is to create compile_commands.json in the
object tree, then specify '-p <build-path>' when you use clang-check,
clang-tidy, etc.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
2020-08-22 17:56:16 +03:00
$( if $( KBUILD_EXTMOD) ,,$( KBUILD_VMLINUX_OBJS) $( KBUILD_VMLINUX_LIBS) ) \
$( if $( CONFIG_MODULES) , $( MODORDER) ) FORCE
$( call if_changed,gen_compile_commands)
2021-03-31 16:38:06 +03:00
targets += $( extmod_prefix) compile_commands.json
kbuild: wire up the build rule of compile_commands.json to Makefile
Currently, you need to manually run scripts/gen_compile_commands.py
to create compile_commands.json. It parses all the .*.cmd files found
under the specified directory.
If you rebuild the kernel over again without 'make clean',
.*.cmd files from older builds will create stale entries in
compile_commands.json.
This commit wires up the compile_commands.json rule to Makefile, and
makes it parse only the .*.cmd files involved in the current build.
Pass $(KBUILD_VMLINUX_OBJS), $(KBUILD_VMLINUX_LIBS), and modules.order
to the script. The objects or archives linked to vmlinux are listed in
$(KBUILD_VMLINUX_OBJS) or $(KBUILD_VMLINUX_LIBS). All the modules are
listed in modules.order.
You can create compile_commands.json from Make:
$ make -j$(nproc) CC=clang compile_commands.json
You can also build vmlinux, modules, and compile_commands.json all
together in a single command:
$ make -j$(nproc) CC=clang all compile_commands.json
It works for M= builds as well. In this case, compile_commands.json
is created in the top directory of the external module.
This is convenient, but it has a drawback; the coverage of the
compile_commands.json is reduced because only the objects linked to
vmlinux or modules are handled. For example, the following C files are
not included in the compile_commands.json:
- Decompressor source files (arch/*/boot/)
- VDSO source files
- C files used to generate intermediates (e.g. kernel/bounds.c)
- Standalone host programs
I think it is fine for most developers because our main interest is
the kernel-space code.
If you want to cover all the compiled C files, please build the kernel,
then run the script manually as you did before:
$ make clean # if you want to remove stale .cmd files [optional]
$ make -j$(nproc) CC=clang
$ scripts/gen_compile_commands.py
Here is a note for out-of-tree builds. 'make compile_commands.json'
works with O= option, but please notice compile_commands.json is
created in the object tree instead of the source tree.
Some people may want to have compile_commands.json in the source tree
because Clang Tools searches for it through all parent paths of the
first input source file.
However, you cannot do this for O= builds. Kbuild should never generate
any build artifact in the source tree when O= is given because the
source tree might be read-only. Any write attempt to the source tree
is monitored and the violation may be reported. See the commit log of
8ef14c2c41d9.
So, the only possible way is to create compile_commands.json in the
object tree, then specify '-p <build-path>' when you use clang-check,
clang-tidy, etc.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
2020-08-22 17:56:16 +03:00
2020-08-22 17:56:18 +03:00
PHONY += clang-tidy clang-analyzer
i f d e f C O N F I G _ C C _ I S _ C L A N G
quiet_cmd_clang_tools = CHECK $<
cmd_clang_tools = $( PYTHON3) $( srctree) /scripts/clang-tools/run-clang-tools.py $@ $<
2021-03-31 16:38:06 +03:00
clang-tidy clang-analyzer : $( extmod_prefix ) compile_commands .json
2020-08-22 17:56:18 +03:00
$( call cmd,clang_tools)
e l s e
clang-tidy clang-analyzer :
@echo " $@ requires CC=clang " >& 2
@false
e n d i f
2005-04-17 02:20:36 +04:00
# Scripts to check various things for consistency
# ---------------------------------------------------------------------------
scripts: remove namespace.pl
namespace.pl is intended to help locate symbols which are defined but
are not used externally. The goal is to avoid bloat of the namespace in
the resulting kernel image.
The script relies on object data, and only finds unused symbols for the
configuration used to generate that object data. This results in a lot
of false positive warnings such as symbols only used by a single
architecture, or symbols which are used externally only under certain
configurations.
Running namespace.pl using allyesconfig, allmodconfig, and
x86_64_defconfig yields the following results:
* allmodconfig
* 11122 unique symbol names with no external reference
* 1194 symbols listed as multiply defined
* 214 symbols it can't resolve
* allyesconfig
* 10997 unique symbol names with no external reference
* 1194 symbols listed as multiply defined
* 214 symbols it can't resolve
* x86_64_defconfig
* 5757 unique symbol names with no external reference
* 528 symbols listed as multiply defined
* 154 symbols it can't resolve
The script also has no way to easily limit the scope of the checks to
a given subset of the kernel, such as only checking for symbols defined
within a module or subsystem.
Discussion on public mailing lists seems to indicate that many view the
tool output as suspect or not very useful (see discussions at [1] and
[2] for further context).
As described by Masahiro Yamada at [2], namespace.pl provides 3 types of
checks: listing multiply defined symbols, resolving external symbols,
and warnings about symbols with no reference.
The first category of issues is easily caught by the linker as any set
of multiply defined symbols should fail to link. The second category of
issues is also caught by linking, as undefined symbols would cause
issues. Even with modules, these types of issues where a module relies
on an external symbol are caught by modpost.
The remaining category of issues reported is the list of symbols with no
external reference, and is the primary motivation of this script.
However, it ought to be clear from the above examples that the output is
difficult to sort through. Even allyesconfig has ~10000 entries.
The current submit-checklist indicates that patches ought to go through
namespacecheck and fix any new issues arising. But that itself presents
problems. As described at [1], many cases of reports are due to
configuration where a function is used externally by some configuration
settings. Prominent maintainers appear to dislike changes modify code
such that symbols become static based on CONFIG_* flags ([3], and [4])
One possible solution is to adjust the advice and indicate that we only
care about the output of namespacecheck on allyesconfig or allmodconfig
builds...
However, given the discussion at [2], I suspect that few people are
actively using this tool. It doesn't have a maintainer in the
MAINTAINERS flie, and it produces so many warnings for unused symbols
that it is difficult to use effectively. Thus, I propose we simply
remove it.
[1] https://lore.kernel.org/netdev/20200708164812.384ae8ea@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com/
[2] https://lore.kernel.org/lkml/20190129204319.15238-1-jacob.e.keller@intel.com/
[3] https://lore.kernel.org/netdev/20190828.154744.2058157956381129672.davem@davemloft.net/
[4] https://lore.kernel.org/netdev/20190827210928.576c5fef@cakuba.netronome.com/
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2020-10-10 03:18:44 +03:00
PHONY += includecheck versioncheck coccicheck export_report
2011-04-27 01:15:01 +04:00
2005-04-17 02:20:36 +04:00
includecheck :
2011-04-27 01:18:29 +04:00
find $( srctree) /* $( RCS_FIND_IGNORE) \
2005-04-17 02:20:36 +04:00
-name '*.[hcS]' -type f -print | sort \
2007-11-05 13:51:44 +03:00
| xargs $( PERL) -w $( srctree) /scripts/checkincludes.pl
2005-04-17 02:20:36 +04:00
versioncheck :
2011-04-27 01:19:28 +04:00
find $( srctree) /* $( RCS_FIND_IGNORE) \
2005-04-17 02:20:36 +04:00
-name '*.[hcS]' -type f -print | sort \
2007-11-05 13:51:44 +03:00
| xargs $( PERL) -w $( srctree) /scripts/checkversion.pl
2005-04-17 02:20:36 +04:00
2010-06-06 19:15:01 +04:00
coccicheck :
2019-08-25 16:28:37 +03:00
$( Q) $( BASH) $( srctree) /scripts/$@
2010-06-06 19:15:01 +04:00
2007-08-25 01:04:56 +04:00
export_report :
$( PERL) $( srctree) /scripts/export_report.pl
2013-06-24 16:48:37 +04:00
PHONY += checkstack kernelrelease kernelversion image_name
2006-09-27 12:50:37 +04:00
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# UML needs a little special treatment here. It wants to use the host
# toolchain, so needs $(SUBARCH) passed to checkstack.pl. Everyone
# else wants $(ARCH), including people doing cross-builds, which means
# that $(SUBARCH) doesn't work here.
i f e q ( $( ARCH ) , u m )
CHECKSTACK_ARCH := $( SUBARCH)
e l s e
CHECKSTACK_ARCH := $( ARCH)
e n d i f
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checkstack :
$( OBJDUMP) -d vmlinux $$ ( find . -name '*.ko' ) | \
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$( PERL) $( srctree) /scripts/checkstack.pl $( CHECKSTACK_ARCH)
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kernelrelease :
@echo " $( KERNELVERSION) $$ ( $( CONFIG_SHELL) $( srctree) /scripts/setlocalversion $( srctree) ) "
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kernelversion :
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@echo $( KERNELVERSION)
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image_name :
@echo $( KBUILD_IMAGE)
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quiet_cmd_rmfiles = $( if $( wildcard $( rm-files) ) ,CLEAN $( wildcard $( rm-files) ) )
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cmd_rmfiles = rm -rf $( rm-files)
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kbuild: let fixdep directly write to .*.cmd files
Currently, fixdep writes dependencies to .*.tmp, which is renamed to
.*.cmd after everything succeeds. This is a very safe way to avoid
corrupted .*.cmd files. The if_changed_dep has carried this safety
mechanism since it was added in 2002.
If fixdep fails for some reasons or a user terminates the build while
fixdep is running, the incomplete output from the fixdep could be
troublesome.
This is my insight about some bad scenarios:
[1] If the compiler succeeds to generate *.o file, but fixdep fails
to write necessary dependencies to .*.cmd file, Make will miss
to rebuild the object when headers or CONFIG options are changed.
In this case, fixdep should not generate .*.cmd file at all so
that 'arg-check' will surely trigger the rebuild of the object.
[2] A partially constructed .*.cmd file may not be a syntactically
correct makefile. The next time Make runs, it would include it,
then fail to parse it. Once this happens, 'make clean' is be the
only way to fix it.
In fact, [1] is no longer a problem since commit 9c2af1c7377a ("kbuild:
add .DELETE_ON_ERROR special target"). Make deletes a target file on
any failure in its recipe. Because fixdep is a part of the recipe of
*.o target, if it fails, the *.o is deleted anyway. However, I am a
bit worried about the slight possibility of [2].
So, here is a solution. Let fixdep directly write to a .*.cmd file,
but allow makefiles to include it only when its corresponding target
exists.
This effectively reverts commit 2982c953570b ("kbuild: remove redundant
$(wildcard ...) for cmd_files calculation"), and commit 00d78ab2ba75
("kbuild: remove dead code in cmd_files calculation in top Makefile")
because now we must check the presence of targets.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
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# read saved command lines for existing targets
existing-targets := $( wildcard $( sort $( targets) ) )
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- i n c l u d e $( foreach f ,$ ( existing -targets ) ,$ ( dir $ ( f ) ) .$ ( notdir $ ( f ) ) .cmd )
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e n d i f # config-build
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e n d i f # mixed-build
e n d i f # need-sub-make
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PHONY += FORCE
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FORCE :
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# Declare the contents of the PHONY variable as phony. We keep that
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# information in a variable so we can use it in if_changed and friends.
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.PHONY : $( PHONY )
