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 # To avoid conflicts with the discarded __gendwarfksyms_ptr symbols on 196 # X86, requires pahole before commit 47dcb534e253 ("btf_encoder: Stop 197 # indexing symbols for VARs") or after commit 9810758003ce ("btf_encoder: 198 # Verify 0 address DWARF variables are in ELF section"). 199 depends on !X86 || !DEBUG_INFO_BTF || PAHOLE_VERSION < 128 || PAHOLE_VERSION > 129 200 help 201 Calculate symbol versions from DWARF debugging information using 202 gendwarfksyms. Requires DEBUG_INFO to be enabled. 203 204 If unsure, say N. 205endchoice 206 207config ASM_MODVERSIONS 208 bool 209 default HAVE_ASM_MODVERSIONS && MODVERSIONS 210 help 211 This enables module versioning for exported symbols also from 212 assembly. This can be enabled only when the target architecture 213 supports it. 214 215config EXTENDED_MODVERSIONS 216 bool "Extended Module Versioning Support" 217 depends on MODVERSIONS 218 help 219 This enables extended MODVERSIONs support, allowing long symbol 220 names to be versioned. 221 222 The most likely reason you would enable this is to enable Rust 223 support. If unsure, say N. 224 225config BASIC_MODVERSIONS 226 bool "Basic Module Versioning Support" 227 depends on MODVERSIONS 228 default y 229 help 230 This enables basic MODVERSIONS support, allowing older tools or 231 kernels to potentially load modules. 232 233 Disabling this may cause older `modprobe` or `kmod` to be unable 234 to read MODVERSIONS information from built modules. With this 235 disabled, older kernels may treat this module as unversioned. 236 237 This is enabled by default when MODVERSIONS are enabled. 238 If unsure, say Y. 239 240config MODULE_SRCVERSION_ALL 241 bool "Source checksum for all modules" 242 help 243 Modules which contain a MODULE_VERSION get an extra "srcversion" 244 field inserted into their modinfo section, which contains a 245 sum of the source files which made it. This helps maintainers 246 see exactly which source was used to build a module (since 247 others sometimes change the module source without updating 248 the version). With this option, such a "srcversion" field 249 will be created for all modules. If unsure, say N. 250 251config MODULE_SIG 252 bool "Module signature verification" 253 select MODULE_SIG_FORMAT 254 help 255 Check modules for valid signatures upon load: the signature 256 is simply appended to the module. For more information see 257 <file:Documentation/admin-guide/module-signing.rst>. 258 259 Note that this option adds the OpenSSL development packages as a 260 kernel build dependency so that the signing tool can use its crypto 261 library. 262 263 You should enable this option if you wish to use either 264 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 265 another LSM - otherwise unsigned modules will be loadable regardless 266 of the lockdown policy. 267 268 !!!WARNING!!! If you enable this option, you MUST make sure that the 269 module DOES NOT get stripped after being signed. This includes the 270 debuginfo strip done by some packagers (such as rpmbuild) and 271 inclusion into an initramfs that wants the module size reduced. 272 273config MODULE_SIG_FORCE 274 bool "Require modules to be validly signed" 275 depends on MODULE_SIG 276 help 277 Reject unsigned modules or signed modules for which we don't have a 278 key. Without this, such modules will simply taint the kernel. 279 280config MODULE_SIG_ALL 281 bool "Automatically sign all modules" 282 default y 283 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 284 help 285 Sign all modules during make modules_install. Without this option, 286 modules must be signed manually, using the scripts/sign-file tool. 287 288comment "Do not forget to sign required modules with scripts/sign-file" 289 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 290 291choice 292 prompt "Hash algorithm to sign modules" 293 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 294 default MODULE_SIG_SHA512 295 help 296 This determines which sort of hashing algorithm will be used during 297 signature generation. This algorithm _must_ be built into the kernel 298 directly so that signature verification can take place. It is not 299 possible to load a signed module containing the algorithm to check 300 the signature on that module. 301 302config MODULE_SIG_SHA1 303 bool "SHA-1" 304 select CRYPTO_SHA1 305 306config MODULE_SIG_SHA256 307 bool "SHA-256" 308 select CRYPTO_SHA256 309 310config MODULE_SIG_SHA384 311 bool "SHA-384" 312 select CRYPTO_SHA512 313 314config MODULE_SIG_SHA512 315 bool "SHA-512" 316 select CRYPTO_SHA512 317 318config MODULE_SIG_SHA3_256 319 bool "SHA3-256" 320 select CRYPTO_SHA3 321 322config MODULE_SIG_SHA3_384 323 bool "SHA3-384" 324 select CRYPTO_SHA3 325 326config MODULE_SIG_SHA3_512 327 bool "SHA3-512" 328 select CRYPTO_SHA3 329 330endchoice 331 332config MODULE_SIG_HASH 333 string 334 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 335 default "sha1" if MODULE_SIG_SHA1 336 default "sha256" if MODULE_SIG_SHA256 337 default "sha384" if MODULE_SIG_SHA384 338 default "sha512" if MODULE_SIG_SHA512 339 default "sha3-256" if MODULE_SIG_SHA3_256 340 default "sha3-384" if MODULE_SIG_SHA3_384 341 default "sha3-512" if MODULE_SIG_SHA3_512 342 343config MODULE_COMPRESS 344 bool "Module compression" 345 help 346 Enable module compression to reduce on-disk size of module binaries. 347 This is fully compatible with signed modules. 348 349 The tool used to work with modules needs to support the selected 350 compression type. kmod MAY support gzip, xz and zstd. Other tools 351 might have a limited selection of the supported types. 352 353 Note that for modules inside an initrd or initramfs, it's more 354 efficient to compress the whole ramdisk instead. 355 356 If unsure, say N. 357 358choice 359 prompt "Module compression type" 360 depends on MODULE_COMPRESS 361 help 362 Choose the supported algorithm for module compression. 363 364config MODULE_COMPRESS_GZIP 365 bool "GZIP" 366 help 367 Support modules compressed with GZIP. The installed modules are 368 suffixed with .ko.gz. 369 370config MODULE_COMPRESS_XZ 371 bool "XZ" 372 help 373 Support modules compressed with XZ. The installed modules are 374 suffixed with .ko.xz. 375 376config MODULE_COMPRESS_ZSTD 377 bool "ZSTD" 378 help 379 Support modules compressed with ZSTD. The installed modules are 380 suffixed with .ko.zst. 381 382endchoice 383 384config MODULE_COMPRESS_ALL 385 bool "Automatically compress all modules" 386 default y 387 depends on MODULE_COMPRESS 388 help 389 Compress all modules during 'make modules_install'. 390 391 Your build system needs to provide the appropriate compression tool 392 for the selected compression type. External modules will also be 393 compressed in the same way during the installation. 394 395config MODULE_DECOMPRESS 396 bool "Support in-kernel module decompression" 397 depends on MODULE_COMPRESS 398 select ZLIB_INFLATE if MODULE_COMPRESS_GZIP 399 select XZ_DEC if MODULE_COMPRESS_XZ 400 select ZSTD_DECOMPRESS if MODULE_COMPRESS_ZSTD 401 help 402 Support for decompressing kernel modules by the kernel itself 403 instead of relying on userspace to perform this task. Useful when 404 load pinning security policy is enabled. 405 406 If unsure, say N. 407 408config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 409 bool "Allow loading of modules with missing namespace imports" 410 help 411 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 412 a namespace. A module that makes use of a symbol exported with such a 413 namespace is required to import the namespace via MODULE_IMPORT_NS(""). 414 There is no technical reason to enforce correct namespace imports, 415 but it creates consistency between symbols defining namespaces and 416 users importing namespaces they make use of. This option relaxes this 417 requirement and lifts the enforcement when loading a module. 418 419 If unsure, say N. 420 421config MODPROBE_PATH 422 string "Path to modprobe binary" 423 default "/sbin/modprobe" 424 help 425 When kernel code requests a module, it does so by calling 426 the "modprobe" userspace utility. This option allows you to 427 set the path where that binary is found. This can be changed 428 at runtime via the sysctl file 429 /proc/sys/kernel/modprobe. Setting this to the empty string 430 removes the kernel's ability to request modules (but 431 userspace can still load modules explicitly). 432 433config TRIM_UNUSED_KSYMS 434 bool "Trim unused exported kernel symbols" 435 help 436 The kernel and some modules make many symbols available for 437 other modules to use via EXPORT_SYMBOL() and variants. Depending 438 on the set of modules being selected in your kernel configuration, 439 many of those exported symbols might never be used. 440 441 This option allows for unused exported symbols to be dropped from 442 the build. In turn, this provides the compiler more opportunities 443 (especially when using LTO) for optimizing the code and reducing 444 binary size. This might have some security advantages as well. 445 446 If unsure, or if you need to build out-of-tree modules, say N. 447 448config UNUSED_KSYMS_WHITELIST 449 string "Whitelist of symbols to keep in ksymtab" 450 depends on TRIM_UNUSED_KSYMS 451 help 452 By default, all unused exported symbols will be un-exported from the 453 build when TRIM_UNUSED_KSYMS is selected. 454 455 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 456 exported at all times, even in absence of in-tree users. The value to 457 set here is the path to a text file containing the list of symbols, 458 one per line. The path can be absolute, or relative to the kernel 459 source or obj tree. 460 461config MODULES_TREE_LOOKUP 462 def_bool y 463 depends on PERF_EVENTS || TRACING || CFI_CLANG 464 465endif # MODULES 466