1 # SPDX-License-Identifier: GPL-2.0-only 2 menuconfig 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 24 if MODULES 25 26 config MODULE_DEBUGFS 27 bool 28 29 config 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 36 if MODULE_DEBUG 37 38 config 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 63 config 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. 111 112 config 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. 121 122 endif # MODULE_DEBUG 123 124 config 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. 131 132 config 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. 139 140 config 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. 149 150 config 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. 160 161 config MODVERSIONS 162 bool "Module versioning support" 163 help 164 Usually, you have to use modules compiled with your kernel. 165 Saying Y here makes it sometimes possible to use modules 166 compiled for different kernels, by adding enough information 167 to the modules to (hopefully) spot any changes which would 168 make them incompatible with the kernel you are running. If 169 unsure, say N. 170 171 config ASM_MODVERSIONS 172 bool 173 default HAVE_ASM_MODVERSIONS && MODVERSIONS 174 help 175 This enables module versioning for exported symbols also from 176 assembly. This can be enabled only when the target architecture 177 supports it. 178 179 config MODULE_SRCVERSION_ALL 180 bool "Source checksum for all modules" 181 help 182 Modules which contain a MODULE_VERSION get an extra "srcversion" 183 field inserted into their modinfo section, which contains a 184 sum of the source files which made it. This helps maintainers 185 see exactly which source was used to build a module (since 186 others sometimes change the module source without updating 187 the version). With this option, such a "srcversion" field 188 will be created for all modules. If unsure, say N. 189 190 config MODULE_SIG 191 bool "Module signature verification" 192 select MODULE_SIG_FORMAT 193 help 194 Check modules for valid signatures upon load: the signature 195 is simply appended to the module. For more information see 196 <file:Documentation/admin-guide/module-signing.rst>. 197 198 Note that this option adds the OpenSSL development packages as a 199 kernel build dependency so that the signing tool can use its crypto 200 library. 201 202 You should enable this option if you wish to use either 203 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 204 another LSM - otherwise unsigned modules will be loadable regardless 205 of the lockdown policy. 206 207 !!!WARNING!!! If you enable this option, you MUST make sure that the 208 module DOES NOT get stripped after being signed. This includes the 209 debuginfo strip done by some packagers (such as rpmbuild) and 210 inclusion into an initramfs that wants the module size reduced. 211 212 config MODULE_SIG_FORCE 213 bool "Require modules to be validly signed" 214 depends on MODULE_SIG 215 help 216 Reject unsigned modules or signed modules for which we don't have a 217 key. Without this, such modules will simply taint the kernel. 218 219 config MODULE_SIG_ALL 220 bool "Automatically sign all modules" 221 default y 222 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 223 help 224 Sign all modules during make modules_install. Without this option, 225 modules must be signed manually, using the scripts/sign-file tool. 226 227 comment "Do not forget to sign required modules with scripts/sign-file" 228 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 229 230 choice 231 prompt "Which hash algorithm should modules be signed with?" 232 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 233 help 234 This determines which sort of hashing algorithm will be used during 235 signature generation. This algorithm _must_ be built into the kernel 236 directly so that signature verification can take place. It is not 237 possible to load a signed module containing the algorithm to check 238 the signature on that module. 239 240 config MODULE_SIG_SHA1 241 bool "Sign modules with SHA-1" 242 select CRYPTO_SHA1 243 244 config MODULE_SIG_SHA256 245 bool "Sign modules with SHA-256" 246 select CRYPTO_SHA256 247 248 config MODULE_SIG_SHA384 249 bool "Sign modules with SHA-384" 250 select CRYPTO_SHA512 251 252 config MODULE_SIG_SHA512 253 bool "Sign modules with SHA-512" 254 select CRYPTO_SHA512 255 256 config MODULE_SIG_SHA3_256 257 bool "Sign modules with SHA3-256" 258 select CRYPTO_SHA3 259 260 config MODULE_SIG_SHA3_384 261 bool "Sign modules with SHA3-384" 262 select CRYPTO_SHA3 263 264 config MODULE_SIG_SHA3_512 265 bool "Sign modules with SHA3-512" 266 select CRYPTO_SHA3 267 268 endchoice 269 270 config MODULE_SIG_HASH 271 string 272 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 273 default "sha1" if MODULE_SIG_SHA1 274 default "sha256" if MODULE_SIG_SHA256 275 default "sha384" if MODULE_SIG_SHA384 276 default "sha512" if MODULE_SIG_SHA512 277 default "sha3-256" if MODULE_SIG_SHA3_256 278 default "sha3-384" if MODULE_SIG_SHA3_384 279 default "sha3-512" if MODULE_SIG_SHA3_512 280 281 choice 282 prompt "Module compression mode" 283 help 284 This option allows you to choose the algorithm which will be used to 285 compress modules when 'make modules_install' is run. (or, you can 286 choose to not compress modules at all.) 287 288 External modules will also be compressed in the same way during the 289 installation. 290 291 For modules inside an initrd or initramfs, it's more efficient to 292 compress the whole initrd or initramfs instead. 293 294 This is fully compatible with signed modules. 295 296 Please note that the tool used to load modules needs to support the 297 corresponding algorithm. module-init-tools MAY support gzip, and kmod 298 MAY support gzip, xz and zstd. 299 300 Your build system needs to provide the appropriate compression tool 301 to compress the modules. 302 303 If in doubt, select 'None'. 304 305 config MODULE_COMPRESS_NONE 306 bool "None" 307 help 308 Do not compress modules. The installed modules are suffixed 309 with .ko. 310 311 config MODULE_COMPRESS_GZIP 312 bool "GZIP" 313 help 314 Compress modules with GZIP. The installed modules are suffixed 315 with .ko.gz. 316 317 config MODULE_COMPRESS_XZ 318 bool "XZ" 319 help 320 Compress modules with XZ. The installed modules are suffixed 321 with .ko.xz. 322 323 config MODULE_COMPRESS_ZSTD 324 bool "ZSTD" 325 help 326 Compress modules with ZSTD. The installed modules are suffixed 327 with .ko.zst. 328 329 endchoice 330 331 config MODULE_DECOMPRESS 332 bool "Support in-kernel module decompression" 333 depends on MODULE_COMPRESS_GZIP || MODULE_COMPRESS_XZ || MODULE_COMPRESS_ZSTD 334 select ZLIB_INFLATE if MODULE_COMPRESS_GZIP 335 select XZ_DEC if MODULE_COMPRESS_XZ 336 select ZSTD_DECOMPRESS if MODULE_COMPRESS_ZSTD 337 help 338 339 Support for decompressing kernel modules by the kernel itself 340 instead of relying on userspace to perform this task. Useful when 341 load pinning security policy is enabled. 342 343 If unsure, say N. 344 345 config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 346 bool "Allow loading of modules with missing namespace imports" 347 help 348 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 349 a namespace. A module that makes use of a symbol exported with such a 350 namespace is required to import the namespace via MODULE_IMPORT_NS(). 351 There is no technical reason to enforce correct namespace imports, 352 but it creates consistency between symbols defining namespaces and 353 users importing namespaces they make use of. This option relaxes this 354 requirement and lifts the enforcement when loading a module. 355 356 If unsure, say N. 357 358 config MODPROBE_PATH 359 string "Path to modprobe binary" 360 default "/sbin/modprobe" 361 help 362 When kernel code requests a module, it does so by calling 363 the "modprobe" userspace utility. This option allows you to 364 set the path where that binary is found. This can be changed 365 at runtime via the sysctl file 366 /proc/sys/kernel/modprobe. Setting this to the empty string 367 removes the kernel's ability to request modules (but 368 userspace can still load modules explicitly). 369 370 config TRIM_UNUSED_KSYMS 371 bool "Trim unused exported kernel symbols" 372 help 373 The kernel and some modules make many symbols available for 374 other modules to use via EXPORT_SYMBOL() and variants. Depending 375 on the set of modules being selected in your kernel configuration, 376 many of those exported symbols might never be used. 377 378 This option allows for unused exported symbols to be dropped from 379 the build. In turn, this provides the compiler more opportunities 380 (especially when using LTO) for optimizing the code and reducing 381 binary size. This might have some security advantages as well. 382 383 If unsure, or if you need to build out-of-tree modules, say N. 384 385 config UNUSED_KSYMS_WHITELIST 386 string "Whitelist of symbols to keep in ksymtab" 387 depends on TRIM_UNUSED_KSYMS 388 help 389 By default, all unused exported symbols will be un-exported from the 390 build when TRIM_UNUSED_KSYMS is selected. 391 392 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 393 exported at all times, even in absence of in-tree users. The value to 394 set here is the path to a text file containing the list of symbols, 395 one per line. The path can be absolute, or relative to the kernel 396 source or obj tree. 397 398 config MODULES_TREE_LOOKUP 399 def_bool y 400 depends on PERF_EVENTS || TRACING || CFI_CLANG 401 402 endif # MODULES
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