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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_DEBUGFS
+ bool
+
+config MODULE_DEBUG
+ bool "Module debugging"
+ depends on DEBUG_FS
+ help
+ Allows you to enable / disable features which can help you debug
+ modules. You don't need these options on production systems.
+
+if MODULE_DEBUG
+
+config MODULE_STATS
+ bool "Module statistics"
+ depends on DEBUG_FS
+ select MODULE_DEBUGFS
+ help
+ This option allows you to maintain a record of module statistics.
+ For example, size of all modules, average size, text size, a list
+ of failed modules and the size for each of those. For failed
+ modules we keep track of modules which failed due to either the
+ existing module taking too long to load or that module was already
+ loaded.
+
+ You should enable this if you are debugging production loads
+ and want to see if userspace or the kernel is doing stupid things
+ with loading modules when it shouldn't or if you want to help
+ optimize userspace / kernel space module autoloading schemes.
+ You might want to do this because failed modules tend to use
+ up significant amount of memory, and so you'd be doing everyone a
+ favor in avoiding these failures proactively.
+
+ This functionality is also useful for those experimenting with
+ module .text ELF section optimization.
+
+ If unsure, say N.
+
+config MODULE_DEBUG_AUTOLOAD_DUPS
+ bool "Debug duplicate modules with auto-loading"
+ help
+ Module autoloading allows in-kernel code to request modules through
+ the *request_module*() API calls. This in turn just calls userspace
+ modprobe. Although modprobe checks to see if a module is already
+ loaded before trying to load a module there is a small time window in
+ which multiple duplicate requests can end up in userspace and multiple
+ modprobe calls race calling finit_module() around the same time for
+ duplicate modules. The finit_module() system call can consume in the
+ worst case more than twice the respective module size in virtual
+ memory for each duplicate module requests. Although duplicate module
+ requests are non-fatal virtual memory is a limited resource and each
+ duplicate module request ends up just unnecessarily straining virtual
+ memory.
+
+ This debugging facility will create pr_warn() splats for duplicate
+ module requests to help identify if module auto-loading may be the
+ culprit to your early boot virtual memory pressure. Since virtual
+ memory abuse caused by duplicate module requests could render a
+ system unusable this functionality will also converge races in
+ requests for the same module to a single request. You can boot with
+ the module.enable_dups_trace=1 kernel parameter to use WARN_ON()
+ instead of the pr_warn().
+
+ If the first module request used request_module_nowait() we cannot
+ use that as the anchor to wait for duplicate module requests, since
+ users of request_module() do want a proper return value. If a call
+ for the same module happened earlier with request_module() though,
+ then a duplicate request_module_nowait() would be detected. The
+ non-wait request_module() call is synchronous and waits until modprobe
+ completes. Subsequent auto-loading requests for the same module do
+ not trigger a new finit_module() calls and do not strain virtual
+ memory, and so as soon as modprobe successfully completes we remove
+ tracking for duplicates for that module.
+
+ Enable this functionality to try to debug virtual memory abuse during
+ boot on systems which are failing to boot or if you suspect you may be
+ straining virtual memory during boot, and you want to identify if the
+ abuse was due to module auto-loading. These issues are currently only
+ known to occur on systems with many CPUs (over 400) and is likely the
+ result of udev issuing duplicate module requests for each CPU, and so
+ module auto-loading is not the culprit. There may very well still be
+ many duplicate module auto-loading requests which could be optimized
+ for and this debugging facility can be used to help identify them.
+
+ Only enable this for debugging system functionality, never have it
+ enabled on real systems.
+
+config MODULE_DEBUG_AUTOLOAD_DUPS_TRACE
+ bool "Force full stack trace when duplicates are found"
+ depends on MODULE_DEBUG_AUTOLOAD_DUPS
+ help
+ Enabling this will force a full stack trace for duplicate module
+ auto-loading requests using WARN_ON() instead of pr_warn(). You
+ should keep this disabled at all times unless you are a developer
+ and are doing a manual inspection and want to debug exactly why
+ these duplicates occur.
+
+endif # MODULE_DEBUG
+
+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
+ select MODULE_DEBUGFS
+ 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 || MODULE_COMPRESS_ZSTD
+ select ZLIB_INFLATE if MODULE_COMPRESS_GZIP
+ select XZ_DEC if MODULE_COMPRESS_XZ
+ select ZSTD_DECOMPRESS if MODULE_COMPRESS_ZSTD
+ 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