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Borislav Petkov (AMD) 54babdc034 kbuild: Disable KCSAN for autogenerated *.mod.c intermediaries
When KCSAN and CONSTRUCTORS are enabled, one can trigger the

  "Unpatched return thunk in use. This should not happen!"

catch-all warning.

Usually, when objtool runs on the .o objects, it does generate a section
.return_sites which contains all offsets in the objects to the return
thunks of the functions present there. Those return thunks then get
patched at runtime by the alternatives.

KCSAN and CONSTRUCTORS add this to the object file's .text.startup
section:

  -------------------
  Disassembly of section .text.startup:

  ...

  0000000000000010 <_sub_I_00099_0>:
    10:   f3 0f 1e fa             endbr64
    14:   e8 00 00 00 00          call   19 <_sub_I_00099_0+0x9>
                          15: R_X86_64_PLT32      __tsan_init-0x4
    19:   e9 00 00 00 00          jmp    1e <__UNIQUE_ID___addressable_cryptd_alloc_aead349+0x6>
                          1a: R_X86_64_PLT32      __x86_return_thunk-0x4
  -------------------

which, if it is built as a module goes through the intermediary stage of
creating a <module>.mod.c file which, when translated, receives a second
constructor:

  -------------------
  Disassembly of section .text.startup:

  0000000000000010 <_sub_I_00099_0>:
    10:   f3 0f 1e fa             endbr64
    14:   e8 00 00 00 00          call   19 <_sub_I_00099_0+0x9>
                          15: R_X86_64_PLT32      __tsan_init-0x4
    19:   e9 00 00 00 00          jmp    1e <_sub_I_00099_0+0xe>
                          1a: R_X86_64_PLT32      __x86_return_thunk-0x4

  ...

  0000000000000030 <_sub_I_00099_0>:
    30:   f3 0f 1e fa             endbr64
    34:   e8 00 00 00 00          call   39 <_sub_I_00099_0+0x9>
                          35: R_X86_64_PLT32      __tsan_init-0x4
    39:   e9 00 00 00 00          jmp    3e <__ksymtab_cryptd_alloc_ahash+0x2>
                          3a: R_X86_64_PLT32      __x86_return_thunk-0x4
  -------------------

in the .ko file.

Objtool has run already so that second constructor's return thunk cannot
be added to the .return_sites section and thus the return thunk remains
unpatched and the warning rightfully fires.

Drop KCSAN flags from the mod.c generation stage as those constructors
do not contain data races one would be interested about.

Debugged together with David Kaplan <David.Kaplan@amd.com> and Nikolay
Borisov <nik.borisov@suse.com>.

Reported-by: Paul Menzel <pmenzel@molgen.mpg.de>
Closes: https://lore.kernel.org/r/0851a207-7143-417e-be31-8bf2b3afb57d@molgen.mpg.de
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Paul Menzel <pmenzel@molgen.mpg.de> # Dell XPS 13
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Reviewed-by: Marco Elver <elver@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2024-03-31 21:09:41 +09:00
arch MIPS: move unselectable FIT_IMAGE_FDT_EPM5 out of the "System type" choice 2024-03-27 01:58:34 +09:00
block vfs-6.9-rc1.fixes 2024-03-18 09:15:50 -07:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto RISC-V Patches for the 6.9 Merge Window 2024-03-22 10:41:13 -07:00
Documentation A set of x86 fixes: 2024-03-24 11:13:56 -07:00
drivers kbuild: make -Woverride-init warnings more consistent 2024-03-31 11:32:26 +09:00
fs kbuild: make -Woverride-init warnings more consistent 2024-03-31 11:32:26 +09:00
include export.h: remove include/asm-generic/export.h 2024-03-28 11:04:20 +09:00
init RISC-V Patches for the 6.9 Merge Window 2024-03-22 10:41:13 -07:00
io_uring io_uring/sqpoll: early exit thread if task_context wasn't allocated 2024-03-18 20:22:42 -06:00
ipc sysctl changes for v6.9-rc1 2024-03-18 14:59:13 -07:00
kernel kbuild: make -Woverride-init warnings more consistent 2024-03-31 11:32:26 +09:00
lib hardening fixes for v6.9-rc1 2024-03-23 08:43:21 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm kbuild: make -Woverride-init warnings more consistent 2024-03-31 11:32:26 +09:00
net Including fixes from CAN, netfilter, wireguard and IPsec. 2024-03-21 14:50:39 -07:00
rust Kbuild updates for v6.9 2024-03-21 14:41:00 -07:00
samples Tracing updates for 6.9: 2024-03-18 15:11:44 -07:00
scripts kbuild: Disable KCSAN for autogenerated *.mod.c intermediaries 2024-03-31 21:09:41 +09:00
security - Kuan-Wei Chiu has developed the well-named series "lib min_heap: Min 2024-03-14 18:03:09 -07:00
sound sound fixes #2 for 6.9-rc2 2024-03-22 09:44:19 -07:00
tools RISC-V Patches for the 6.9 Merge Window 2024-03-22 10:41:13 -07:00
usr Kbuild updates for v6.8 2024-01-18 17:57:07 -08:00
virt KVM Xen and pfncache changes for 6.9: 2024-03-11 10:42:55 -04:00
.clang-format clang-format: Update with v6.7-rc4's for_each macro list 2023-12-08 23:54:38 +01:00
.cocciconfig
.editorconfig Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: create a list of all built DTB files 2024-02-19 18:20:39 +09:00
.mailmap Char/Misc and other driver subsystem updates for 6.9-rc1 2024-03-21 13:21:31 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS Not a ton of stuff happening in the clk framework in this pull request. We got 2024-03-15 11:48:01 -07:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS RISC-V Patches for the 6.9 Merge Window 2024-03-22 10:41:13 -07:00
Makefile Linux 6.9-rc1 2024-03-24 14:10:05 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.