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 172choice 173 prompt "Module versioning implementation" 174 depends on MODVERSIONS 175 help 176 Select the tool used to calculate symbol versions for modules. 177 178 If unsure, select GENKSYMS. 179 180config GENKSYMS 181 bool "genksyms (from source code)" 182 help 183 Calculate symbol versions from pre-processed source code using 184 genksyms. 185 186 If unsure, say Y. 187 188config GENDWARFKSYMS 189 bool "gendwarfksyms (from debugging information)" 190 depends on DEBUG_INFO 191 # Requires full debugging information, split DWARF not supported. 192 depends on !DEBUG_INFO_REDUCED && !DEBUG_INFO_SPLIT 193 # Requires ELF object files. 194 depends on !LTO 195 help 196 Calculate symbol versions from DWARF debugging information using 197 gendwarfksyms. Requires DEBUG_INFO to be enabled. 198 199 If unsure, say N. 200endchoice 201 202config ASM_MODVERSIONS 203 bool 204 default HAVE_ASM_MODVERSIONS && MODVERSIONS 205 help 206 This enables module versioning for exported symbols also from 207 assembly. This can be enabled only when the target architecture 208 supports it. 209 210config EXTENDED_MODVERSIONS 211 bool "Extended Module Versioning Support" 212 depends on MODVERSIONS 213 help 214 This enables extended MODVERSIONs support, allowing long symbol 215 names to be versioned. 216 217 The most likely reason you would enable this is to enable Rust 218 support. If unsure, say N. 219 220config BASIC_MODVERSIONS 221 bool "Basic Module Versioning Support" 222 depends on MODVERSIONS 223 default y 224 help 225 This enables basic MODVERSIONS support, allowing older tools or 226 kernels to potentially load modules. 227 228 Disabling this may cause older `modprobe` or `kmod` to be unable 229 to read MODVERSIONS information from built modules. With this 230 disabled, older kernels may treat this module as unversioned. 231 232 This is enabled by default when MODVERSIONS are enabled. 233 If unsure, say Y. 234 235config MODULE_SRCVERSION_ALL 236 bool "Source checksum for all modules" 237 help 238 Modules which contain a MODULE_VERSION get an extra "srcversion" 239 field inserted into their modinfo section, which contains a 240 sum of the source files which made it. This helps maintainers 241 see exactly which source was used to build a module (since 242 others sometimes change the module source without updating 243 the version). With this option, such a "srcversion" field 244 will be created for all modules. If unsure, say N. 245 246config MODULE_SCMVERSION 247 bool "SCM version for modules" 248 depends on LOCALVERSION_AUTO 249 help 250 This enables the module attribute "scmversion" which can be used 251 by developers to identify the SCM version of a given module, e.g. 252 git sha1 or hg sha1. The SCM version can be queried by modinfo or 253 via the sysfs node: /sys/modules/MODULENAME/scmversion. This is 254 useful when the kernel or kernel modules are updated separately 255 since that causes the vermagic of the kernel and the module to 256 differ. 257 258 If unsure, say N. 259 260config MODULE_SIG 261 bool "Module signature verification" 262 select MODULE_SIG_FORMAT 263 help 264 Check modules for valid signatures upon load: the signature 265 is simply appended to the module. For more information see 266 <file:Documentation/admin-guide/module-signing.rst>. 267 268 Note that this option adds the OpenSSL development packages as a 269 kernel build dependency so that the signing tool can use its crypto 270 library. 271 272 You should enable this option if you wish to use either 273 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 274 another LSM - otherwise unsigned modules will be loadable regardless 275 of the lockdown policy. 276 277 !!!WARNING!!! If you enable this option, you MUST make sure that the 278 module DOES NOT get stripped after being signed. This includes the 279 debuginfo strip done by some packagers (such as rpmbuild) and 280 inclusion into an initramfs that wants the module size reduced. 281 282config MODULE_SIG_FORCE 283 bool "Require modules to be validly signed" 284 depends on MODULE_SIG 285 help 286 Reject unsigned modules or signed modules for which we don't have a 287 key. Without this, such modules will simply taint the kernel. 288 289config MODULE_SIG_ALL 290 bool "Automatically sign all modules" 291 default y 292 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 293 help 294 Sign all modules during make modules_install. Without this option, 295 modules must be signed manually, using the scripts/sign-file tool. 296 297comment "Do not forget to sign required modules with scripts/sign-file" 298 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 299 300config MODULE_SIG_PROTECT_LIST 301 string "File with signed module names whose exports are to be protected" 302 default "" 303 depends on MODULE_SIG && !MODULE_SIG_FORCE 304 help 305 Enables symbol export protection support for the listed signed 306 modules. This option prevents unsigned modules from exporting symbols 307 which are exported by the listed modules. Any unsigned module which 308 tries to export such a symbol will fail to load. 309 310 The value to set here is the path to a text file in the source 311 directory containing the list of module names, one per line. The path 312 can be absolute, or relative to the kernel source or obj tree. 313 314config MODULE_SIG_PROTECT 315 def_bool y 316 depends on MODULE_SIG_PROTECT_LIST != "" 317 318choice 319 prompt "Hash algorithm to sign modules" 320 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 321 help 322 This determines which sort of hashing algorithm will be used during 323 signature generation. This algorithm _must_ be built into the kernel 324 directly so that signature verification can take place. It is not 325 possible to load a signed module containing the algorithm to check 326 the signature on that module. 327 328config MODULE_SIG_SHA1 329 bool "SHA-1" 330 select CRYPTO_SHA1 331 332config MODULE_SIG_SHA256 333 bool "SHA-256" 334 select CRYPTO_SHA256 335 336config MODULE_SIG_SHA384 337 bool "SHA-384" 338 select CRYPTO_SHA512 339 340config MODULE_SIG_SHA512 341 bool "SHA-512" 342 select CRYPTO_SHA512 343 344config MODULE_SIG_SHA3_256 345 bool "SHA3-256" 346 select CRYPTO_SHA3 347 348config MODULE_SIG_SHA3_384 349 bool "SHA3-384" 350 select CRYPTO_SHA3 351 352config MODULE_SIG_SHA3_512 353 bool "SHA3-512" 354 select CRYPTO_SHA3 355 356endchoice 357 358config MODULE_SIG_HASH 359 string 360 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 361 default "sha1" if MODULE_SIG_SHA1 362 default "sha256" if MODULE_SIG_SHA256 363 default "sha384" if MODULE_SIG_SHA384 364 default "sha512" if MODULE_SIG_SHA512 365 default "sha3-256" if MODULE_SIG_SHA3_256 366 default "sha3-384" if MODULE_SIG_SHA3_384 367 default "sha3-512" if MODULE_SIG_SHA3_512 368 369config MODULE_COMPRESS 370 bool "Module compression" 371 help 372 Enable module compression to reduce on-disk size of module binaries. 373 This is fully compatible with signed modules. 374 375 The tool used to work with modules needs to support the selected 376 compression type. kmod MAY support gzip, xz and zstd. Other tools 377 might have a limited selection of the supported types. 378 379 Note that for modules inside an initrd or initramfs, it's more 380 efficient to compress the whole ramdisk instead. 381 382 If unsure, say N. 383 384choice 385 prompt "Module compression type" 386 depends on MODULE_COMPRESS 387 help 388 Choose the supported algorithm for module compression. 389 390config MODULE_COMPRESS_GZIP 391 bool "GZIP" 392 help 393 Support modules compressed with GZIP. The installed modules are 394 suffixed with .ko.gz. 395 396config MODULE_COMPRESS_XZ 397 bool "XZ" 398 help 399 Support modules compressed with XZ. The installed modules are 400 suffixed with .ko.xz. 401 402config MODULE_COMPRESS_ZSTD 403 bool "ZSTD" 404 help 405 Support modules compressed with ZSTD. The installed modules are 406 suffixed with .ko.zst. 407 408endchoice 409 410config MODULE_COMPRESS_ALL 411 bool "Automatically compress all modules" 412 default y 413 depends on MODULE_COMPRESS 414 help 415 Compress all modules during 'make modules_install'. 416 417 Your build system needs to provide the appropriate compression tool 418 for the selected compression type. External modules will also be 419 compressed in the same way during the installation. 420 421config MODULE_DECOMPRESS 422 bool "Support in-kernel module decompression" 423 depends on MODULE_COMPRESS 424 select ZLIB_INFLATE if MODULE_COMPRESS_GZIP 425 select XZ_DEC if MODULE_COMPRESS_XZ 426 select ZSTD_DECOMPRESS if MODULE_COMPRESS_ZSTD 427 help 428 Support for decompressing kernel modules by the kernel itself 429 instead of relying on userspace to perform this task. Useful when 430 load pinning security policy is enabled. 431 432 If unsure, say N. 433 434config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 435 bool "Allow loading of modules with missing namespace imports" 436 help 437 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 438 a namespace. A module that makes use of a symbol exported with such a 439 namespace is required to import the namespace via MODULE_IMPORT_NS(). 440 There is no technical reason to enforce correct namespace imports, 441 but it creates consistency between symbols defining namespaces and 442 users importing namespaces they make use of. This option relaxes this 443 requirement and lifts the enforcement when loading a module. 444 445 If unsure, say N. 446 447config MODPROBE_PATH 448 string "Path to modprobe binary" 449 default "/sbin/modprobe" 450 help 451 When kernel code requests a module, it does so by calling 452 the "modprobe" userspace utility. This option allows you to 453 set the path where that binary is found. This can be changed 454 at runtime via the sysctl file 455 /proc/sys/kernel/modprobe. Setting this to the empty string 456 removes the kernel's ability to request modules (but 457 userspace can still load modules explicitly). 458 459config TRIM_UNUSED_KSYMS 460 bool "Trim unused exported kernel symbols" 461 help 462 The kernel and some modules make many symbols available for 463 other modules to use via EXPORT_SYMBOL() and variants. Depending 464 on the set of modules being selected in your kernel configuration, 465 many of those exported symbols might never be used. 466 467 This option allows for unused exported symbols to be dropped from 468 the build. In turn, this provides the compiler more opportunities 469 (especially when using LTO) for optimizing the code and reducing 470 binary size. This might have some security advantages as well. 471 472 If unsure, or if you need to build out-of-tree modules, say N. 473 474config UNUSED_KSYMS_WHITELIST 475 string "Whitelist of symbols to keep in ksymtab" 476 depends on TRIM_UNUSED_KSYMS 477 help 478 By default, all unused exported symbols will be un-exported from the 479 build when TRIM_UNUSED_KSYMS is selected. 480 481 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 482 exported at all times, even in absence of in-tree users. The value to 483 set here is the path to a text file containing the list of symbols, 484 one per line. The path can be absolute, or relative to the kernel 485 source or obj tree. 486 487config MODULES_TREE_LOOKUP 488 def_bool y 489 depends on PERF_EVENTS || TRACING || CFI_CLANG 490 491endif # MODULES 492