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 172if MODVERSIONS 173 174choice 175 prompt "Module versioning implementation" 176 help 177 Select the tool used to calculate symbol versions for modules. 178 179 If unsure, select GENKSYMS. 180 181config GENKSYMS 182 bool "genksyms (from source code)" 183 help 184 Calculate symbol versions from pre-processed source code using 185 genksyms. 186 187 If unsure, say Y. 188 189config GENDWARFKSYMS 190 bool "gendwarfksyms (from debugging information)" 191 depends on DEBUG_INFO 192 # Requires full debugging information, split DWARF not supported. 193 depends on !DEBUG_INFO_REDUCED && !DEBUG_INFO_SPLIT 194 # Requires ELF object files. 195 depends on !LTO 196 # To avoid conflicts with the discarded __gendwarfksyms_ptr symbols on 197 # X86, requires pahole before commit 47dcb534e253 ("btf_encoder: Stop 198 # indexing symbols for VARs") or after commit 9810758003ce ("btf_encoder: 199 # Verify 0 address DWARF variables are in ELF section"). 200 depends on !X86 || !DEBUG_INFO_BTF || PAHOLE_VERSION < 128 || PAHOLE_VERSION > 129 201 help 202 Calculate symbol versions from DWARF debugging information using 203 gendwarfksyms. Requires DEBUG_INFO to be enabled. 204 205 If unsure, say N. 206endchoice 207 208config ASM_MODVERSIONS 209 bool 210 default HAVE_ASM_MODVERSIONS 211 help 212 This enables module versioning for exported symbols also from 213 assembly. This can be enabled only when the target architecture 214 supports it. 215 216config EXTENDED_MODVERSIONS 217 bool "Extended Module Versioning Support" 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 default y 228 help 229 This enables basic MODVERSIONS support, allowing older tools or 230 kernels to potentially load modules. 231 232 Disabling this may cause older `modprobe` or `kmod` to be unable 233 to read MODVERSIONS information from built modules. With this 234 disabled, older kernels may treat this module as unversioned. 235 236 This is enabled by default when MODVERSIONS are enabled. 237 If unsure, say Y. 238 239endif # MODVERSIONS 240 241config MODULE_SRCVERSION_ALL 242 bool "Source checksum for all modules" 243 help 244 Modules which contain a MODULE_VERSION get an extra "srcversion" 245 field inserted into their modinfo section, which contains a 246 sum of the source files which made it. This helps maintainers 247 see exactly which source was used to build a module (since 248 others sometimes change the module source without updating 249 the version). With this option, such a "srcversion" field 250 will be created for all modules. If unsure, say N. 251 252config MODULE_SIG 253 bool "Module signature verification" 254 select MODULE_SIG_FORMAT 255 help 256 Check modules for valid signatures upon load: the signature 257 is simply appended to the module. For more information see 258 <file:Documentation/admin-guide/module-signing.rst>. 259 260 Note that this option adds the OpenSSL development packages as a 261 kernel build dependency so that the signing tool can use its crypto 262 library. 263 264 You should enable this option if you wish to use either 265 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 266 another LSM - otherwise unsigned modules will be loadable regardless 267 of the lockdown policy. 268 269 !!!WARNING!!! If you enable this option, you MUST make sure that the 270 module DOES NOT get stripped after being signed. This includes the 271 debuginfo strip done by some packagers (such as rpmbuild) and 272 inclusion into an initramfs that wants the module size reduced. 273 274config MODULE_SIG_FORCE 275 bool "Require modules to be validly signed" 276 depends on MODULE_SIG 277 help 278 Reject unsigned modules or signed modules for which we don't have a 279 key. Without this, such modules will simply taint the kernel. 280 281if MODULE_SIG || IMA_APPRAISE_MODSIG 282 283config MODULE_SIG_ALL 284 bool "Automatically sign all modules" 285 default y 286 help 287 Sign all modules during make modules_install. Without this option, 288 modules must be signed manually, using the scripts/sign-file tool. 289 290comment "Do not forget to sign required modules with scripts/sign-file" 291 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 292 293choice 294 prompt "Hash algorithm to sign modules" 295 default MODULE_SIG_SHA512 296 help 297 This determines which sort of hashing algorithm will be used during 298 signature generation. This algorithm _must_ be built into the kernel 299 directly so that signature verification can take place. It is not 300 possible to load a signed module containing the algorithm to check 301 the signature on that module. 302 303config MODULE_SIG_SHA256 304 bool "SHA-256" 305 select CRYPTO_SHA256 306 307config MODULE_SIG_SHA384 308 bool "SHA-384" 309 select CRYPTO_SHA512 310 311config MODULE_SIG_SHA512 312 bool "SHA-512" 313 select CRYPTO_SHA512 314 315config MODULE_SIG_SHA3_256 316 bool "SHA3-256" 317 select CRYPTO_SHA3 318 319config MODULE_SIG_SHA3_384 320 bool "SHA3-384" 321 select CRYPTO_SHA3 322 323config MODULE_SIG_SHA3_512 324 bool "SHA3-512" 325 select CRYPTO_SHA3 326 327endchoice 328 329config MODULE_SIG_HASH 330 string 331 default "sha256" if MODULE_SIG_SHA256 332 default "sha384" if MODULE_SIG_SHA384 333 default "sha512" if MODULE_SIG_SHA512 334 default "sha3-256" if MODULE_SIG_SHA3_256 335 default "sha3-384" if MODULE_SIG_SHA3_384 336 default "sha3-512" if MODULE_SIG_SHA3_512 337 338endif # MODULE_SIG || IMA_APPRAISE_MODSIG 339 340config MODULE_COMPRESS 341 bool "Module compression" 342 help 343 Enable module compression to reduce on-disk size of module binaries. 344 This is fully compatible with signed modules. 345 346 The tool used to work with modules needs to support the selected 347 compression type. kmod MAY support gzip, xz and zstd. Other tools 348 might have a limited selection of the supported types. 349 350 Note that for modules inside an initrd or initramfs, it's more 351 efficient to compress the whole ramdisk instead. 352 353 If unsure, say N. 354 355if MODULE_COMPRESS 356 357choice 358 prompt "Module compression type" 359 help 360 Choose the supported algorithm for module compression. 361 362config MODULE_COMPRESS_GZIP 363 bool "GZIP" 364 help 365 Support modules compressed with GZIP. The installed modules are 366 suffixed with .ko.gz. 367 368config MODULE_COMPRESS_XZ 369 bool "XZ" 370 help 371 Support modules compressed with XZ. The installed modules are 372 suffixed with .ko.xz. 373 374config MODULE_COMPRESS_ZSTD 375 bool "ZSTD" 376 help 377 Support modules compressed with ZSTD. The installed modules are 378 suffixed with .ko.zst. 379 380endchoice 381 382config MODULE_COMPRESS_ALL 383 bool "Automatically compress all modules" 384 default y 385 help 386 Compress all modules during 'make modules_install'. 387 388 Your build system needs to provide the appropriate compression tool 389 for the selected compression type. External modules will also be 390 compressed in the same way during the installation. 391 392config MODULE_DECOMPRESS 393 bool "Support in-kernel module decompression" 394 select ZLIB_INFLATE if MODULE_COMPRESS_GZIP 395 select XZ_DEC if MODULE_COMPRESS_XZ 396 select ZSTD_DECOMPRESS if MODULE_COMPRESS_ZSTD 397 help 398 Support for decompressing kernel modules by the kernel itself 399 instead of relying on userspace to perform this task. Useful when 400 load pinning security policy is enabled. 401 402 If unsure, say N. 403 404endif # MODULE_COMPRESS 405 406config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 407 bool "Allow loading of modules with missing namespace imports" 408 help 409 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 410 a namespace. A module that makes use of a symbol exported with such a 411 namespace is required to import the namespace via MODULE_IMPORT_NS(""). 412 There is no technical reason to enforce correct namespace imports, 413 but it creates consistency between symbols defining namespaces and 414 users importing namespaces they make use of. This option relaxes this 415 requirement and lifts the enforcement when loading a module. 416 417 If unsure, say N. 418 419config MODPROBE_PATH 420 string "Path to modprobe binary" 421 default "/sbin/modprobe" 422 help 423 When kernel code requests a module, it does so by calling 424 the "modprobe" userspace utility. This option allows you to 425 set the path where that binary is found. This can be changed 426 at runtime via the sysctl file 427 /proc/sys/kernel/modprobe. Setting this to the empty string 428 removes the kernel's ability to request modules (but 429 userspace can still load modules explicitly). 430 431config TRIM_UNUSED_KSYMS 432 bool "Trim unused exported kernel symbols" 433 help 434 The kernel and some modules make many symbols available for 435 other modules to use via EXPORT_SYMBOL() and variants. Depending 436 on the set of modules being selected in your kernel configuration, 437 many of those exported symbols might never be used. 438 439 This option allows for unused exported symbols to be dropped from 440 the build. In turn, this provides the compiler more opportunities 441 (especially when using LTO) for optimizing the code and reducing 442 binary size. This might have some security advantages as well. 443 444 If unsure, or if you need to build out-of-tree modules, say N. 445 446config UNUSED_KSYMS_WHITELIST 447 string "Whitelist of symbols to keep in ksymtab" 448 depends on TRIM_UNUSED_KSYMS 449 help 450 By default, all unused exported symbols will be un-exported from the 451 build when TRIM_UNUSED_KSYMS is selected. 452 453 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 454 exported at all times, even in absence of in-tree users. The value to 455 set here is the path to a text file containing the list of symbols, 456 one per line. The path can be absolute, or relative to the kernel 457 source or obj tree. 458 459config MODULES_TREE_LOOKUP 460 def_bool y 461 depends on PERF_EVENTS || TRACING || CFI 462 463endif # MODULES 464