1# SPDX-License-Identifier: GPL-2.0-only 2menuconfig MODULES 3 bool "Enable loadable module support" 4 modules 5 select EXECMEM 6 help 7 Kernel modules are small pieces of compiled code which can 8 be inserted in the running kernel, rather than being 9 permanently built into the kernel. You use the "modprobe" 10 tool to add (and sometimes remove) them. If you say Y here, 11 many parts of the kernel can be built as modules (by 12 answering M instead of Y where indicated): this is most 13 useful for infrequently used options which are not required 14 for booting. For more information, see the man pages for 15 modprobe, lsmod, modinfo, insmod and rmmod. 16 17 If you say Y here, you will need to run "make 18 modules_install" to put the modules under /lib/modules/ 19 where modprobe can find them (you may need to be root to do 20 this). 21 22 If unsure, say Y. 23 24if MODULES 25 26config MODULE_DEBUGFS 27 bool 28 29config MODULE_DEBUG 30 bool "Module debugging" 31 depends on DEBUG_FS 32 help 33 Allows you to enable / disable features which can help you debug 34 modules. You don't need these options on production systems. 35 36if MODULE_DEBUG 37 38config MODULE_STATS 39 bool "Module statistics" 40 depends on DEBUG_FS 41 select MODULE_DEBUGFS 42 help 43 This option allows you to maintain a record of module statistics. 44 For example, size of all modules, average size, text size, a list 45 of failed modules and the size for each of those. For failed 46 modules we keep track of modules which failed due to either the 47 existing module taking too long to load or that module was already 48 loaded. 49 50 You should enable this if you are debugging production loads 51 and want to see if userspace or the kernel is doing stupid things 52 with loading modules when it shouldn't or if you want to help 53 optimize userspace / kernel space module autoloading schemes. 54 You might want to do this because failed modules tend to use 55 up significant amount of memory, and so you'd be doing everyone a 56 favor in avoiding these failures proactively. 57 58 This functionality is also useful for those experimenting with 59 module .text ELF section optimization. 60 61 If unsure, say N. 62 63config MODULE_DEBUG_AUTOLOAD_DUPS 64 bool "Debug duplicate modules with auto-loading" 65 help 66 Module autoloading allows in-kernel code to request modules through 67 the *request_module*() API calls. This in turn just calls userspace 68 modprobe. Although modprobe checks to see if a module is already 69 loaded before trying to load a module there is a small time window in 70 which multiple duplicate requests can end up in userspace and multiple 71 modprobe calls race calling finit_module() around the same time for 72 duplicate modules. The finit_module() system call can consume in the 73 worst case more than twice the respective module size in virtual 74 memory for each duplicate module requests. Although duplicate module 75 requests are non-fatal virtual memory is a limited resource and each 76 duplicate module request ends up just unnecessarily straining virtual 77 memory. 78 79 This debugging facility will create pr_warn() splats for duplicate 80 module requests to help identify if module auto-loading may be the 81 culprit to your early boot virtual memory pressure. Since virtual 82 memory abuse caused by duplicate module requests could render a 83 system unusable this functionality will also converge races in 84 requests for the same module to a single request. You can boot with 85 the module.enable_dups_trace=1 kernel parameter to use WARN_ON() 86 instead of the pr_warn(). 87 88 If the first module request used request_module_nowait() we cannot 89 use that as the anchor to wait for duplicate module requests, since 90 users of request_module() do want a proper return value. If a call 91 for the same module happened earlier with request_module() though, 92 then a duplicate request_module_nowait() would be detected. The 93 non-wait request_module() call is synchronous and waits until modprobe 94 completes. Subsequent auto-loading requests for the same module do 95 not trigger a new finit_module() calls and do not strain virtual 96 memory, and so as soon as modprobe successfully completes we remove 97 tracking for duplicates for that module. 98 99 Enable this functionality to try to debug virtual memory abuse during 100 boot on systems which are failing to boot or if you suspect you may be 101 straining virtual memory during boot, and you want to identify if the 102 abuse was due to module auto-loading. These issues are currently only 103 known to occur on systems with many CPUs (over 400) and is likely the 104 result of udev issuing duplicate module requests for each CPU, and so 105 module auto-loading is not the culprit. There may very well still be 106 many duplicate module auto-loading requests which could be optimized 107 for and this debugging facility can be used to help identify them. 108 109 Only enable this for debugging system functionality, never have it 110 enabled on real systems. 111 112config MODULE_DEBUG_AUTOLOAD_DUPS_TRACE 113 bool "Force full stack trace when duplicates are found" 114 depends on MODULE_DEBUG_AUTOLOAD_DUPS 115 help 116 Enabling this will force a full stack trace for duplicate module 117 auto-loading requests using WARN_ON() instead of pr_warn(). You 118 should keep this disabled at all times unless you are a developer 119 and are doing a manual inspection and want to debug exactly why 120 these duplicates occur. 121 122endif # MODULE_DEBUG 123 124config MODULE_FORCE_LOAD 125 bool "Forced module loading" 126 default n 127 help 128 Allow loading of modules without version information (ie. modprobe 129 --force). Forced module loading sets the 'F' (forced) taint flag and 130 is usually a really bad idea. 131 132config MODULE_UNLOAD 133 bool "Module unloading" 134 help 135 Without this option you will not be able to unload any 136 modules (note that some modules may not be unloadable 137 anyway), which makes your kernel smaller, faster 138 and simpler. If unsure, say Y. 139 140config MODULE_FORCE_UNLOAD 141 bool "Forced module unloading" 142 depends on MODULE_UNLOAD 143 help 144 This option allows you to force a module to unload, even if the 145 kernel believes it is unsafe: the kernel will remove the module 146 without waiting for anyone to stop using it (using the -f option to 147 rmmod). This is mainly for kernel developers and desperate users. 148 If unsure, say N. 149 150config MODULE_UNLOAD_TAINT_TRACKING 151 bool "Tainted module unload tracking" 152 depends on MODULE_UNLOAD 153 select MODULE_DEBUGFS 154 help 155 This option allows you to maintain a record of each unloaded 156 module that tainted the kernel. In addition to displaying a 157 list of linked (or loaded) modules e.g. on detection of a bad 158 page (see bad_page()), the aforementioned details are also 159 shown. If unsure, say N. 160 161config MODVERSIONS 162 bool "Module versioning support" 163 depends on !COMPILE_TEST 164 help 165 Usually, you have to use modules compiled with your kernel. 166 Saying Y here makes it sometimes possible to use modules 167 compiled for different kernels, by adding enough information 168 to the modules to (hopefully) spot any changes which would 169 make them incompatible with the kernel you are running. If 170 unsure, say N. 171 172config ASM_MODVERSIONS 173 bool 174 default HAVE_ASM_MODVERSIONS && MODVERSIONS 175 help 176 This enables module versioning for exported symbols also from 177 assembly. This can be enabled only when the target architecture 178 supports it. 179 180config MODULE_SRCVERSION_ALL 181 bool "Source checksum for all modules" 182 help 183 Modules which contain a MODULE_VERSION get an extra "srcversion" 184 field inserted into their modinfo section, which contains a 185 sum of the source files which made it. This helps maintainers 186 see exactly which source was used to build a module (since 187 others sometimes change the module source without updating 188 the version). With this option, such a "srcversion" field 189 will be created for all modules. If unsure, say N. 190 191config MODULE_SIG 192 bool "Module signature verification" 193 select MODULE_SIG_FORMAT 194 help 195 Check modules for valid signatures upon load: the signature 196 is simply appended to the module. For more information see 197 <file:Documentation/admin-guide/module-signing.rst>. 198 199 Note that this option adds the OpenSSL development packages as a 200 kernel build dependency so that the signing tool can use its crypto 201 library. 202 203 You should enable this option if you wish to use either 204 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 205 another LSM - otherwise unsigned modules will be loadable regardless 206 of the lockdown policy. 207 208 !!!WARNING!!! If you enable this option, you MUST make sure that the 209 module DOES NOT get stripped after being signed. This includes the 210 debuginfo strip done by some packagers (such as rpmbuild) and 211 inclusion into an initramfs that wants the module size reduced. 212 213config MODULE_SIG_FORCE 214 bool "Require modules to be validly signed" 215 depends on MODULE_SIG 216 help 217 Reject unsigned modules or signed modules for which we don't have a 218 key. Without this, such modules will simply taint the kernel. 219 220config MODULE_SIG_ALL 221 bool "Automatically sign all modules" 222 default y 223 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 224 help 225 Sign all modules during make modules_install. Without this option, 226 modules must be signed manually, using the scripts/sign-file tool. 227 228comment "Do not forget to sign required modules with scripts/sign-file" 229 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 230 231choice 232 prompt "Which hash algorithm should modules be signed with?" 233 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 234 help 235 This determines which sort of hashing algorithm will be used during 236 signature generation. This algorithm _must_ be built into the kernel 237 directly so that signature verification can take place. It is not 238 possible to load a signed module containing the algorithm to check 239 the signature on that module. 240 241config MODULE_SIG_SHA1 242 bool "Sign modules with SHA-1" 243 select CRYPTO_SHA1 244 245config MODULE_SIG_SHA256 246 bool "Sign modules with SHA-256" 247 select CRYPTO_SHA256 248 249config MODULE_SIG_SHA384 250 bool "Sign modules with SHA-384" 251 select CRYPTO_SHA512 252 253config MODULE_SIG_SHA512 254 bool "Sign modules with SHA-512" 255 select CRYPTO_SHA512 256 257config MODULE_SIG_SHA3_256 258 bool "Sign modules with SHA3-256" 259 select CRYPTO_SHA3 260 261config MODULE_SIG_SHA3_384 262 bool "Sign modules with SHA3-384" 263 select CRYPTO_SHA3 264 265config MODULE_SIG_SHA3_512 266 bool "Sign modules with SHA3-512" 267 select CRYPTO_SHA3 268 269endchoice 270 271config MODULE_SIG_HASH 272 string 273 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 274 default "sha1" if MODULE_SIG_SHA1 275 default "sha256" if MODULE_SIG_SHA256 276 default "sha384" if MODULE_SIG_SHA384 277 default "sha512" if MODULE_SIG_SHA512 278 default "sha3-256" if MODULE_SIG_SHA3_256 279 default "sha3-384" if MODULE_SIG_SHA3_384 280 default "sha3-512" if MODULE_SIG_SHA3_512 281 282choice 283 prompt "Module compression mode" 284 help 285 This option allows you to choose the algorithm which will be used to 286 compress modules when 'make modules_install' is run. (or, you can 287 choose to not compress modules at all.) 288 289 External modules will also be compressed in the same way during the 290 installation. 291 292 For modules inside an initrd or initramfs, it's more efficient to 293 compress the whole initrd or initramfs instead. 294 295 This is fully compatible with signed modules. 296 297 Please note that the tool used to load modules needs to support the 298 corresponding algorithm. module-init-tools MAY support gzip, and kmod 299 MAY support gzip, xz and zstd. 300 301 Your build system needs to provide the appropriate compression tool 302 to compress the modules. 303 304 If in doubt, select 'None'. 305 306config MODULE_COMPRESS_NONE 307 bool "None" 308 help 309 Do not compress modules. The installed modules are suffixed 310 with .ko. 311 312config MODULE_COMPRESS_GZIP 313 bool "GZIP" 314 help 315 Compress modules with GZIP. The installed modules are suffixed 316 with .ko.gz. 317 318config MODULE_COMPRESS_XZ 319 bool "XZ" 320 help 321 Compress modules with XZ. The installed modules are suffixed 322 with .ko.xz. 323 324config MODULE_COMPRESS_ZSTD 325 bool "ZSTD" 326 help 327 Compress modules with ZSTD. The installed modules are suffixed 328 with .ko.zst. 329 330endchoice 331 332config MODULE_DECOMPRESS 333 bool "Support in-kernel module decompression" 334 depends on MODULE_COMPRESS_GZIP || MODULE_COMPRESS_XZ || MODULE_COMPRESS_ZSTD 335 select ZLIB_INFLATE if MODULE_COMPRESS_GZIP 336 select XZ_DEC if MODULE_COMPRESS_XZ 337 select ZSTD_DECOMPRESS if MODULE_COMPRESS_ZSTD 338 help 339 340 Support for decompressing kernel modules by the kernel itself 341 instead of relying on userspace to perform this task. Useful when 342 load pinning security policy is enabled. 343 344 If unsure, say N. 345 346config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 347 bool "Allow loading of modules with missing namespace imports" 348 help 349 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 350 a namespace. A module that makes use of a symbol exported with such a 351 namespace is required to import the namespace via MODULE_IMPORT_NS(). 352 There is no technical reason to enforce correct namespace imports, 353 but it creates consistency between symbols defining namespaces and 354 users importing namespaces they make use of. This option relaxes this 355 requirement and lifts the enforcement when loading a module. 356 357 If unsure, say N. 358 359config MODPROBE_PATH 360 string "Path to modprobe binary" 361 default "/sbin/modprobe" 362 help 363 When kernel code requests a module, it does so by calling 364 the "modprobe" userspace utility. This option allows you to 365 set the path where that binary is found. This can be changed 366 at runtime via the sysctl file 367 /proc/sys/kernel/modprobe. Setting this to the empty string 368 removes the kernel's ability to request modules (but 369 userspace can still load modules explicitly). 370 371config TRIM_UNUSED_KSYMS 372 bool "Trim unused exported kernel symbols" 373 help 374 The kernel and some modules make many symbols available for 375 other modules to use via EXPORT_SYMBOL() and variants. Depending 376 on the set of modules being selected in your kernel configuration, 377 many of those exported symbols might never be used. 378 379 This option allows for unused exported symbols to be dropped from 380 the build. In turn, this provides the compiler more opportunities 381 (especially when using LTO) for optimizing the code and reducing 382 binary size. This might have some security advantages as well. 383 384 If unsure, or if you need to build out-of-tree modules, say N. 385 386config UNUSED_KSYMS_WHITELIST 387 string "Whitelist of symbols to keep in ksymtab" 388 depends on TRIM_UNUSED_KSYMS 389 help 390 By default, all unused exported symbols will be un-exported from the 391 build when TRIM_UNUSED_KSYMS is selected. 392 393 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 394 exported at all times, even in absence of in-tree users. The value to 395 set here is the path to a text file containing the list of symbols, 396 one per line. The path can be absolute, or relative to the kernel 397 source or obj tree. 398 399config MODULES_TREE_LOOKUP 400 def_bool y 401 depends on PERF_EVENTS || TRACING || CFI_CLANG 402 403endif # MODULES 404