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linux/kernel/module/Kconfig
Christophe Leroy 73b4fc92f9 module: Move module's Kconfig items in kernel/module/ 
In init/Kconfig, the part dedicated to modules is quite large.

Move it into a dedicated Kconfig in kernel/module/

MODULES_TREE_LOOKUP was outside of the 'if MODULES', but as it is
only used when MODULES are set, move it in with everything else to
avoid confusion.

MODULE_SIG_FORMAT is left in init/Kconfig because this configuration
item is not used in kernel/modules/ but in kernel/ and can be
selected independently from CONFIG_MODULES. It is for instance
selected from security/integrity/ima/Kconfig.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
2022-07-12 12:07:25 -07:00

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# SPDX-License-Identifier: GPL-2.0-only
menuconfig MODULES
bool "Enable loadable module support"
modules
help
Kernel modules are small pieces of compiled code which can
be inserted in the running kernel, rather than being
permanently built into the kernel. You use the "modprobe"
tool to add (and sometimes remove) them. If you say Y here,
many parts of the kernel can be built as modules (by
answering M instead of Y where indicated): this is most
useful for infrequently used options which are not required
for booting. For more information, see the man pages for
modprobe, lsmod, modinfo, insmod and rmmod.
If you say Y here, you will need to run "make
modules_install" to put the modules under /lib/modules/
where modprobe can find them (you may need to be root to do
this).
If unsure, say Y.
if MODULES
config MODULE_FORCE_LOAD
bool "Forced module loading"
default n
help
Allow loading of modules without version information (ie. modprobe
--force). Forced module loading sets the 'F' (forced) taint flag and
is usually a really bad idea.
config MODULE_UNLOAD
bool "Module unloading"
help
Without this option you will not be able to unload any
modules (note that some modules may not be unloadable
anyway), which makes your kernel smaller, faster
and simpler. If unsure, say Y.
config MODULE_FORCE_UNLOAD
bool "Forced module unloading"
depends on MODULE_UNLOAD
help
This option allows you to force a module to unload, even if the
kernel believes it is unsafe: the kernel will remove the module
without waiting for anyone to stop using it (using the -f option to
rmmod). This is mainly for kernel developers and desperate users.
If unsure, say N.
config MODULE_UNLOAD_TAINT_TRACKING
bool "Tainted module unload tracking"
depends on MODULE_UNLOAD
default n
help
This option allows you to maintain a record of each unloaded
module that tainted the kernel. In addition to displaying a
list of linked (or loaded) modules e.g. on detection of a bad
page (see bad_page()), the aforementioned details are also
shown. If unsure, say N.
config MODVERSIONS
bool "Module versioning support"
help
Usually, you have to use modules compiled with your kernel.
Saying Y here makes it sometimes possible to use modules
compiled for different kernels, by adding enough information
to the modules to (hopefully) spot any changes which would
make them incompatible with the kernel you are running. If
unsure, say N.
config ASM_MODVERSIONS
bool
default HAVE_ASM_MODVERSIONS && MODVERSIONS
help
This enables module versioning for exported symbols also from
assembly. This can be enabled only when the target architecture
supports it.
config MODULE_SRCVERSION_ALL
bool "Source checksum for all modules"
help
Modules which contain a MODULE_VERSION get an extra "srcversion"
field inserted into their modinfo section, which contains a
sum of the source files which made it. This helps maintainers
see exactly which source was used to build a module (since
others sometimes change the module source without updating
the version). With this option, such a "srcversion" field
will be created for all modules. If unsure, say N.
config MODULE_SIG
bool "Module signature verification"
select MODULE_SIG_FORMAT
help
Check modules for valid signatures upon load: the signature
is simply appended to the module. For more information see
<file:Documentation/admin-guide/module-signing.rst>.
Note that this option adds the OpenSSL development packages as a
kernel build dependency so that the signing tool can use its crypto
library.
You should enable this option if you wish to use either
CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
another LSM - otherwise unsigned modules will be loadable regardless
of the lockdown policy.
!!!WARNING!!! If you enable this option, you MUST make sure that the
module DOES NOT get stripped after being signed. This includes the
debuginfo strip done by some packagers (such as rpmbuild) and
inclusion into an initramfs that wants the module size reduced.
config MODULE_SIG_FORCE
bool "Require modules to be validly signed"
depends on MODULE_SIG
help
Reject unsigned modules or signed modules for which we don't have a
key. Without this, such modules will simply taint the kernel.
config MODULE_SIG_ALL
bool "Automatically sign all modules"
default y
depends on MODULE_SIG || IMA_APPRAISE_MODSIG
help
Sign all modules during make modules_install. Without this option,
modules must be signed manually, using the scripts/sign-file tool.
comment "Do not forget to sign required modules with scripts/sign-file"
depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
choice
prompt "Which hash algorithm should modules be signed with?"
depends on MODULE_SIG || IMA_APPRAISE_MODSIG
help
This determines which sort of hashing algorithm will be used during
signature generation. This algorithm _must_ be built into the kernel
directly so that signature verification can take place. It is not
possible to load a signed module containing the algorithm to check
the signature on that module.
config MODULE_SIG_SHA1
bool "Sign modules with SHA-1"
select CRYPTO_SHA1
config MODULE_SIG_SHA224
bool "Sign modules with SHA-224"
select CRYPTO_SHA256
config MODULE_SIG_SHA256
bool "Sign modules with SHA-256"
select CRYPTO_SHA256
config MODULE_SIG_SHA384
bool "Sign modules with SHA-384"
select CRYPTO_SHA512
config MODULE_SIG_SHA512
bool "Sign modules with SHA-512"
select CRYPTO_SHA512
endchoice
config MODULE_SIG_HASH
string
depends on MODULE_SIG || IMA_APPRAISE_MODSIG
default "sha1" if MODULE_SIG_SHA1
default "sha224" if MODULE_SIG_SHA224
default "sha256" if MODULE_SIG_SHA256
default "sha384" if MODULE_SIG_SHA384
default "sha512" if MODULE_SIG_SHA512
choice
prompt "Module compression mode"
help
This option allows you to choose the algorithm which will be used to
compress modules when 'make modules_install' is run. (or, you can
choose to not compress modules at all.)
External modules will also be compressed in the same way during the
installation.
For modules inside an initrd or initramfs, it's more efficient to
compress the whole initrd or initramfs instead.
This is fully compatible with signed modules.
Please note that the tool used to load modules needs to support the
corresponding algorithm. module-init-tools MAY support gzip, and kmod
MAY support gzip, xz and zstd.
Your build system needs to provide the appropriate compression tool
to compress the modules.
If in doubt, select 'None'.
config MODULE_COMPRESS_NONE
bool "None"
help
Do not compress modules. The installed modules are suffixed
with .ko.
config MODULE_COMPRESS_GZIP
bool "GZIP"
help
Compress modules with GZIP. The installed modules are suffixed
with .ko.gz.
config MODULE_COMPRESS_XZ
bool "XZ"
help
Compress modules with XZ. The installed modules are suffixed
with .ko.xz.
config MODULE_COMPRESS_ZSTD
bool "ZSTD"
help
Compress modules with ZSTD. The installed modules are suffixed
with .ko.zst.
endchoice
config MODULE_DECOMPRESS
bool "Support in-kernel module decompression"
depends on MODULE_COMPRESS_GZIP || MODULE_COMPRESS_XZ
select ZLIB_INFLATE if MODULE_COMPRESS_GZIP
select XZ_DEC if MODULE_COMPRESS_XZ
help
Support for decompressing kernel modules by the kernel itself
instead of relying on userspace to perform this task. Useful when
load pinning security policy is enabled.
If unsure, say N.
config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
bool "Allow loading of modules with missing namespace imports"
help
Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
a namespace. A module that makes use of a symbol exported with such a
namespace is required to import the namespace via MODULE_IMPORT_NS().
There is no technical reason to enforce correct namespace imports,
but it creates consistency between symbols defining namespaces and
users importing namespaces they make use of. This option relaxes this
requirement and lifts the enforcement when loading a module.
If unsure, say N.
config MODPROBE_PATH
string "Path to modprobe binary"
default "/sbin/modprobe"
help
When kernel code requests a module, it does so by calling
the "modprobe" userspace utility. This option allows you to
set the path where that binary is found. This can be changed
at runtime via the sysctl file
/proc/sys/kernel/modprobe. Setting this to the empty string
removes the kernel's ability to request modules (but
userspace can still load modules explicitly).
config TRIM_UNUSED_KSYMS
bool "Trim unused exported kernel symbols" if EXPERT
depends on !COMPILE_TEST
help
The kernel and some modules make many symbols available for
other modules to use via EXPORT_SYMBOL() and variants. Depending
on the set of modules being selected in your kernel configuration,
many of those exported symbols might never be used.
This option allows for unused exported symbols to be dropped from
the build. In turn, this provides the compiler more opportunities
(especially when using LTO) for optimizing the code and reducing
binary size. This might have some security advantages as well.
If unsure, or if you need to build out-of-tree modules, say N.
config UNUSED_KSYMS_WHITELIST
string "Whitelist of symbols to keep in ksymtab"
depends on TRIM_UNUSED_KSYMS
help
By default, all unused exported symbols will be un-exported from the
build when TRIM_UNUSED_KSYMS is selected.
UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
exported at all times, even in absence of in-tree users. The value to
set here is the path to a text file containing the list of symbols,
one per line. The path can be absolute, or relative to the kernel
source tree.
config MODULES_TREE_LOOKUP
def_bool y
depends on PERF_EVENTS || TRACING || CFI_CLANG
endif # MODULES
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