riscv/purgatory: Omit use of bin2c
[linux-block.git] / init / Kconfig
CommitLineData
ec8f24b7 1# SPDX-License-Identifier: GPL-2.0-only
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2config CC_VERSION_TEXT
3 string
4 default "$(CC_VERSION_TEXT)"
5 help
6 This is used in unclear ways:
7
8 - Re-run Kconfig when the compiler is updated
9 The 'default' property references the environment variable,
10 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd.
11 When the compiler is updated, Kconfig will be invoked.
12
f9c8bc46 13 - Ensure full rebuild when the compiler is updated
ce6ed1c4 14 include/linux/compiler-version.h contains this option in the comment
0e0345b7 15 line so fixdep adds include/config/CC_VERSION_TEXT into the
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16 auto-generated dependency. When the compiler is updated, syncconfig
17 will touch it and then every file will be rebuilt.
8b59cd81 18
a4353898 19config CC_IS_GCC
aec6c60a 20 def_bool $(success,test "$(cc-name)" = GCC)
a4353898
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21
22config GCC_VERSION
23 int
aec6c60a 24 default $(cc-version) if CC_IS_GCC
a4353898
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25 default 0
26
469cb737 27config CC_IS_CLANG
aec6c60a 28 def_bool $(success,test "$(cc-name)" = Clang)
b744b43f 29
469cb737
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30config CLANG_VERSION
31 int
aec6c60a
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32 default $(cc-version) if CC_IS_CLANG
33 default 0
469cb737 34
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35config AS_IS_GNU
36 def_bool $(success,test "$(as-name)" = GNU)
37
38config AS_IS_LLVM
39 def_bool $(success,test "$(as-name)" = LLVM)
40
41config AS_VERSION
42 int
43 # Use clang version if this is the integrated assembler
44 default CLANG_VERSION if AS_IS_LLVM
45 default $(as-version)
46
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47config LD_IS_BFD
48 def_bool $(success,test "$(ld-name)" = BFD)
49
50config LD_VERSION
51 int
52 default $(ld-version) if LD_IS_BFD
53 default 0
54
55config LD_IS_LLD
56 def_bool $(success,test "$(ld-name)" = LLD)
469cb737 57
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58config LLD_VERSION
59 int
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60 default $(ld-version) if LD_IS_LLD
61 default 0
d5750cd3 62
1a927fd3 63config CC_CAN_LINK
9371f86e 64 bool
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65 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT
66 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag))
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67
68config CC_CAN_LINK_STATIC
69 bool
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70 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT
71 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static)
1a927fd3 72
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73config CC_HAS_ASM_GOTO
74 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
75
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76config CC_HAS_ASM_GOTO_OUTPUT
77 depends on CC_HAS_ASM_GOTO
78 def_bool $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null)
79
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80config CC_HAS_ASM_GOTO_TIED_OUTPUT
81 depends on CC_HAS_ASM_GOTO_OUTPUT
82 # Detect buggy gcc and clang, fixed in gcc-11 clang-14.
83 def_bool $(success,echo 'int foo(int *x) { asm goto (".long (%l[bar]) - .\n": "+m"(*x) ::: bar); return *x; bar: return 0; }' | $CC -x c - -c -o /dev/null)
84
5cf896fb 85config TOOLS_SUPPORT_RELR
2d122942 86 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
5cf896fb 87
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88config CC_HAS_ASM_INLINE
89 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
90
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91config CC_HAS_NO_PROFILE_FN_ATTR
92 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
93
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94config PAHOLE_VERSION
95 int
96 default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))
97
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98config CONSTRUCTORS
99 bool
b99b87f7 100
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101config IRQ_WORK
102 bool
e360adbe 103
10916706 104config BUILDTIME_TABLE_SORT
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105 bool
106
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107config THREAD_INFO_IN_TASK
108 bool
109 help
110 Select this to move thread_info off the stack into task_struct. To
111 make this work, an arch will need to remove all thread_info fields
112 except flags and fix any runtime bugs.
113
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114 One subtle change that will be needed is to use try_get_task_stack()
115 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
116
ff0cfc66 117menu "General setup"
1da177e4 118
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119config BROKEN
120 bool
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121
122config BROKEN_ON_SMP
123 bool
124 depends on BROKEN || !SMP
125 default y
126
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127config INIT_ENV_ARG_LIMIT
128 int
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129 default 32 if !UML
130 default 128 if UML
1da177e4 131 help
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132 Maximum of each of the number of arguments and environment
133 variables passed to init from the kernel command line.
1da177e4 134
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135config COMPILE_TEST
136 bool "Compile also drivers which will not load"
ea29b20a 137 depends on HAS_IOMEM
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138 help
139 Some drivers can be compiled on a different platform than they are
140 intended to be run on. Despite they cannot be loaded there (or even
141 when they load they cannot be used due to missing HW support),
142 developers still, opposing to distributors, might want to build such
143 drivers to compile-test them.
144
145 If you are a developer and want to build everything available, say Y
146 here. If you are a user/distributor, say N here to exclude useless
147 drivers to be distributed.
148
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149config WERROR
150 bool "Compile the kernel with warnings as errors"
b339ec9c 151 default COMPILE_TEST
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152 help
153 A kernel build should not cause any compiler warnings, and this
154 enables the '-Werror' flag to enforce that rule by default.
155
156 However, if you have a new (or very old) compiler with odd and
157 unusual warnings, or you have some architecture with problems,
158 you may need to disable this config option in order to
159 successfully build the kernel.
160
161 If in doubt, say Y.
162
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163config UAPI_HEADER_TEST
164 bool "Compile test UAPI headers"
fcbb8461 165 depends on HEADERS_INSTALL && CC_CAN_LINK
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166 help
167 Compile test headers exported to user-space to ensure they are
168 self-contained, i.e. compilable as standalone units.
169
170 If you are a developer or tester and want to ensure the exported
171 headers are self-contained, say Y here. Otherwise, choose N.
172
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173config LOCALVERSION
174 string "Local version - append to kernel release"
175 help
176 Append an extra string to the end of your kernel version.
177 This will show up when you type uname, for example.
178 The string you set here will be appended after the contents of
179 any files with a filename matching localversion* in your
180 object and source tree, in that order. Your total string can
181 be a maximum of 64 characters.
182
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183config LOCALVERSION_AUTO
184 bool "Automatically append version information to the version string"
185 default y
ac3339ba 186 depends on !COMPILE_TEST
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187 help
188 This will try to automatically determine if the current tree is a
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189 release tree by looking for git tags that belong to the current
190 top of tree revision.
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191
192 A string of the format -gxxxxxxxx will be added to the localversion
6e5a5420 193 if a git-based tree is found. The string generated by this will be
aaebf433 194 appended after any matching localversion* files, and after the value
6e5a5420 195 set in CONFIG_LOCALVERSION.
aaebf433 196
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197 (The actual string used here is the first eight characters produced
198 by running the command:
199
200 $ git rev-parse --verify HEAD
201
202 which is done within the script "scripts/setlocalversion".)
aaebf433 203
9afb719e 204config BUILD_SALT
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205 string "Build ID Salt"
206 default ""
207 help
208 The build ID is used to link binaries and their debug info. Setting
209 this option will use the value in the calculation of the build id.
210 This is mostly useful for distributions which want to ensure the
211 build is unique between builds. It's safe to leave the default.
9afb719e 212
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213config HAVE_KERNEL_GZIP
214 bool
215
216config HAVE_KERNEL_BZIP2
217 bool
218
219config HAVE_KERNEL_LZMA
220 bool
221
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222config HAVE_KERNEL_XZ
223 bool
224
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225config HAVE_KERNEL_LZO
226 bool
227
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228config HAVE_KERNEL_LZ4
229 bool
230
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231config HAVE_KERNEL_ZSTD
232 bool
233
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234config HAVE_KERNEL_UNCOMPRESSED
235 bool
236
30d65dbf 237choice
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238 prompt "Kernel compression mode"
239 default KERNEL_GZIP
48f7ddf7 240 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_ZSTD || HAVE_KERNEL_UNCOMPRESSED
2e9f3bdd 241 help
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242 The linux kernel is a kind of self-extracting executable.
243 Several compression algorithms are available, which differ
244 in efficiency, compression and decompression speed.
245 Compression speed is only relevant when building a kernel.
246 Decompression speed is relevant at each boot.
247
248 If you have any problems with bzip2 or lzma compressed
249 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
250 version of this functionality (bzip2 only), for 2.4, was
251 supplied by Christian Ludwig)
252
253 High compression options are mostly useful for users, who
254 are low on disk space (embedded systems), but for whom ram
255 size matters less.
256
257 If in doubt, select 'gzip'
258
259config KERNEL_GZIP
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260 bool "Gzip"
261 depends on HAVE_KERNEL_GZIP
262 help
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263 The old and tried gzip compression. It provides a good balance
264 between compression ratio and decompression speed.
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265
266config KERNEL_BZIP2
267 bool "Bzip2"
2e9f3bdd 268 depends on HAVE_KERNEL_BZIP2
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269 help
270 Its compression ratio and speed is intermediate.
0a4dd35c 271 Decompression speed is slowest among the choices. The kernel
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272 size is about 10% smaller with bzip2, in comparison to gzip.
273 Bzip2 uses a large amount of memory. For modern kernels you
274 will need at least 8MB RAM or more for booting.
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275
276config KERNEL_LZMA
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277 bool "LZMA"
278 depends on HAVE_KERNEL_LZMA
279 help
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280 This compression algorithm's ratio is best. Decompression speed
281 is between gzip and bzip2. Compression is slowest.
282 The kernel size is about 33% smaller with LZMA in comparison to gzip.
30d65dbf 283
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284config KERNEL_XZ
285 bool "XZ"
286 depends on HAVE_KERNEL_XZ
287 help
288 XZ uses the LZMA2 algorithm and instruction set specific
289 BCJ filters which can improve compression ratio of executable
290 code. The size of the kernel is about 30% smaller with XZ in
291 comparison to gzip. On architectures for which there is a BCJ
292 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
293 will create a few percent smaller kernel than plain LZMA.
294
295 The speed is about the same as with LZMA: The decompression
296 speed of XZ is better than that of bzip2 but worse than gzip
297 and LZO. Compression is slow.
298
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299config KERNEL_LZO
300 bool "LZO"
301 depends on HAVE_KERNEL_LZO
302 help
0a4dd35c 303 Its compression ratio is the poorest among the choices. The kernel
681b3049 304 size is about 10% bigger than gzip; however its speed
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305 (both compression and decompression) is the fastest.
306
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307config KERNEL_LZ4
308 bool "LZ4"
309 depends on HAVE_KERNEL_LZ4
310 help
311 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
312 A preliminary version of LZ4 de/compression tool is available at
313 <https://code.google.com/p/lz4/>.
314
315 Its compression ratio is worse than LZO. The size of the kernel
316 is about 8% bigger than LZO. But the decompression speed is
317 faster than LZO.
318
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319config KERNEL_ZSTD
320 bool "ZSTD"
321 depends on HAVE_KERNEL_ZSTD
322 help
323 ZSTD is a compression algorithm targeting intermediate compression
324 with fast decompression speed. It will compress better than GZIP and
325 decompress around the same speed as LZO, but slower than LZ4. You
326 will need at least 192 KB RAM or more for booting. The zstd command
327 line tool is required for compression.
328
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329config KERNEL_UNCOMPRESSED
330 bool "None"
331 depends on HAVE_KERNEL_UNCOMPRESSED
332 help
333 Produce uncompressed kernel image. This option is usually not what
334 you want. It is useful for debugging the kernel in slow simulation
335 environments, where decompressing and moving the kernel is awfully
336 slow. This option allows early boot code to skip the decompressor
337 and jump right at uncompressed kernel image.
338
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339endchoice
340
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341config DEFAULT_INIT
342 string "Default init path"
343 default ""
344 help
345 This option determines the default init for the system if no init=
346 option is passed on the kernel command line. If the requested path is
347 not present, we will still then move on to attempting further
348 locations (e.g. /sbin/init, etc). If this is empty, we will just use
349 the fallback list when init= is not passed.
350
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351config DEFAULT_HOSTNAME
352 string "Default hostname"
353 default "(none)"
354 help
355 This option determines the default system hostname before userspace
356 calls sethostname(2). The kernel traditionally uses "(none)" here,
357 but you may wish to use a different default here to make a minimal
358 system more usable with less configuration.
359
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360config SYSVIPC
361 bool "System V IPC"
a7f7f624 362 help
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363 Inter Process Communication is a suite of library functions and
364 system calls which let processes (running programs) synchronize and
365 exchange information. It is generally considered to be a good thing,
366 and some programs won't run unless you say Y here. In particular, if
367 you want to run the DOS emulator dosemu under Linux (read the
368 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
369 you'll need to say Y here.
370
371 You can find documentation about IPC with "info ipc" and also in
372 section 6.4 of the Linux Programmer's Guide, available from
373 <http://www.tldp.org/guides.html>.
374
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375config SYSVIPC_SYSCTL
376 bool
377 depends on SYSVIPC
378 depends on SYSCTL
379 default y
380
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381config SYSVIPC_COMPAT
382 def_bool y
383 depends on COMPAT && SYSVIPC
384
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385config POSIX_MQUEUE
386 bool "POSIX Message Queues"
19c92399 387 depends on NET
a7f7f624 388 help
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389 POSIX variant of message queues is a part of IPC. In POSIX message
390 queues every message has a priority which decides about succession
391 of receiving it by a process. If you want to compile and run
392 programs written e.g. for Solaris with use of its POSIX message
b0e37650 393 queues (functions mq_*) say Y here.
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394
395 POSIX message queues are visible as a filesystem called 'mqueue'
396 and can be mounted somewhere if you want to do filesystem
397 operations on message queues.
398
399 If unsure, say Y.
400
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401config POSIX_MQUEUE_SYSCTL
402 bool
403 depends on POSIX_MQUEUE
404 depends on SYSCTL
405 default y
406
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407config WATCH_QUEUE
408 bool "General notification queue"
409 default n
410 help
411
412 This is a general notification queue for the kernel to pass events to
413 userspace by splicing them into pipes. It can be used in conjunction
414 with watches for key/keyring change notifications and device
415 notifications.
416
c02b872a 417 See Documentation/core-api/watch_queue.rst
c73be61c 418
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419config CROSS_MEMORY_ATTACH
420 bool "Enable process_vm_readv/writev syscalls"
421 depends on MMU
422 default y
423 help
424 Enabling this option adds the system calls process_vm_readv and
425 process_vm_writev which allow a process with the correct privileges
a2a368d9 426 to directly read from or write to another process' address space.
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427 See the man page for more details.
428
69369a70 429config USELIB
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430 bool "uselib syscall (for libc5 and earlier)"
431 default ALPHA || M68K || SPARC
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432 help
433 This option enables the uselib syscall, a system call used in the
434 dynamic linker from libc5 and earlier. glibc does not use this
435 system call. If you intend to run programs built on libc5 or
436 earlier, you may need to enable this syscall. Current systems
437 running glibc can safely disable this.
438
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439config AUDIT
440 bool "Auditing support"
441 depends on NET
442 help
443 Enable auditing infrastructure that can be used with another
444 kernel subsystem, such as SELinux (which requires this for
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445 logging of avc messages output). System call auditing is included
446 on architectures which support it.
391dc69c 447
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448config HAVE_ARCH_AUDITSYSCALL
449 bool
450
391dc69c 451config AUDITSYSCALL
cb74ed27 452 def_bool y
7a017721 453 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
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454 select FSNOTIFY
455
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456source "kernel/irq/Kconfig"
457source "kernel/time/Kconfig"
b24abcff 458source "kernel/bpf/Kconfig"
87a4c375 459source "kernel/Kconfig.preempt"
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460
461menu "CPU/Task time and stats accounting"
462
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463config VIRT_CPU_ACCOUNTING
464 bool
465
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466choice
467 prompt "Cputime accounting"
468 default TICK_CPU_ACCOUNTING if !PPC64
02fc8d37 469 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
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470
471# Kind of a stub config for the pure tick based cputime accounting
472config TICK_CPU_ACCOUNTING
473 bool "Simple tick based cputime accounting"
c58b0df1 474 depends on !S390 && !NO_HZ_FULL
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475 help
476 This is the basic tick based cputime accounting that maintains
477 statistics about user, system and idle time spent on per jiffies
478 granularity.
479
480 If unsure, say Y.
481
abf917cd 482config VIRT_CPU_ACCOUNTING_NATIVE
b952741c 483 bool "Deterministic task and CPU time accounting"
c58b0df1 484 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
abf917cd 485 select VIRT_CPU_ACCOUNTING
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486 help
487 Select this option to enable more accurate task and CPU time
488 accounting. This is done by reading a CPU counter on each
489 kernel entry and exit and on transitions within the kernel
490 between system, softirq and hardirq state, so there is a
491 small performance impact. In the case of s390 or IBM POWER > 5,
492 this also enables accounting of stolen time on logically-partitioned
493 systems.
494
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495config VIRT_CPU_ACCOUNTING_GEN
496 bool "Full dynticks CPU time accounting"
24a9c541 497 depends on HAVE_CONTEXT_TRACKING_USER
554b0004 498 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
041a1574 499 depends on GENERIC_CLOCKEVENTS
abf917cd 500 select VIRT_CPU_ACCOUNTING
24a9c541 501 select CONTEXT_TRACKING_USER
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502 help
503 Select this option to enable task and CPU time accounting on full
504 dynticks systems. This accounting is implemented by watching every
505 kernel-user boundaries using the context tracking subsystem.
506 The accounting is thus performed at the expense of some significant
507 overhead.
508
509 For now this is only useful if you are working on the full
510 dynticks subsystem development.
511
512 If unsure, say N.
513
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514endchoice
515
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516config IRQ_TIME_ACCOUNTING
517 bool "Fine granularity task level IRQ time accounting"
b58c3584 518 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
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519 help
520 Select this option to enable fine granularity task irq time
521 accounting. This is done by reading a timestamp on each
522 transitions between softirq and hardirq state, so there can be a
523 small performance impact.
524
525 If in doubt, say N here.
526
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527config HAVE_SCHED_AVG_IRQ
528 def_bool y
529 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
530 depends on SMP
531
76504793 532config SCHED_THERMAL_PRESSURE
98eb401d 533 bool
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534 default y if ARM && ARM_CPU_TOPOLOGY
535 default y if ARM64
76504793 536 depends on SMP
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537 depends on CPU_FREQ_THERMAL
538 help
539 Select this option to enable thermal pressure accounting in the
540 scheduler. Thermal pressure is the value conveyed to the scheduler
541 that reflects the reduction in CPU compute capacity resulted from
542 thermal throttling. Thermal throttling occurs when the performance of
543 a CPU is capped due to high operating temperatures.
544
545 If selected, the scheduler will be able to balance tasks accordingly,
546 i.e. put less load on throttled CPUs than on non/less throttled ones.
547
548 This requires the architecture to implement
7e97b3dc 549 arch_update_thermal_pressure() and arch_scale_thermal_pressure().
76504793 550
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551config BSD_PROCESS_ACCT
552 bool "BSD Process Accounting"
2813893f 553 depends on MULTIUSER
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554 help
555 If you say Y here, a user level program will be able to instruct the
556 kernel (via a special system call) to write process accounting
557 information to a file: whenever a process exits, information about
558 that process will be appended to the file by the kernel. The
559 information includes things such as creation time, owning user,
560 command name, memory usage, controlling terminal etc. (the complete
561 list is in the struct acct in <file:include/linux/acct.h>). It is
562 up to the user level program to do useful things with this
563 information. This is generally a good idea, so say Y.
564
565config BSD_PROCESS_ACCT_V3
566 bool "BSD Process Accounting version 3 file format"
567 depends on BSD_PROCESS_ACCT
568 default n
569 help
570 If you say Y here, the process accounting information is written
571 in a new file format that also logs the process IDs of each
3903bf94 572 process and its parent. Note that this file format is incompatible
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573 with previous v0/v1/v2 file formats, so you will need updated tools
574 for processing it. A preliminary version of these tools is available
37a4c940 575 at <http://www.gnu.org/software/acct/>.
1da177e4 576
c757249a 577config TASKSTATS
19c92399 578 bool "Export task/process statistics through netlink"
c757249a 579 depends on NET
2813893f 580 depends on MULTIUSER
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581 default n
582 help
583 Export selected statistics for tasks/processes through the
584 generic netlink interface. Unlike BSD process accounting, the
585 statistics are available during the lifetime of tasks/processes as
586 responses to commands. Like BSD accounting, they are sent to user
587 space on task exit.
588
589 Say N if unsure.
590
ca74e92b 591config TASK_DELAY_ACCT
19c92399 592 bool "Enable per-task delay accounting"
6f44993f 593 depends on TASKSTATS
f6db8347 594 select SCHED_INFO
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595 help
596 Collect information on time spent by a task waiting for system
597 resources like cpu, synchronous block I/O completion and swapping
598 in pages. Such statistics can help in setting a task's priorities
599 relative to other tasks for cpu, io, rss limits etc.
600
601 Say N if unsure.
602
18f705f4 603config TASK_XACCT
19c92399 604 bool "Enable extended accounting over taskstats"
18f705f4
AD
605 depends on TASKSTATS
606 help
607 Collect extended task accounting data and send the data
608 to userland for processing over the taskstats interface.
609
610 Say N if unsure.
611
612config TASK_IO_ACCOUNTING
19c92399 613 bool "Enable per-task storage I/O accounting"
18f705f4
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614 depends on TASK_XACCT
615 help
616 Collect information on the number of bytes of storage I/O which this
617 task has caused.
618
619 Say N if unsure.
620
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621config PSI
622 bool "Pressure stall information tracking"
623 help
624 Collect metrics that indicate how overcommitted the CPU, memory,
625 and IO capacity are in the system.
626
627 If you say Y here, the kernel will create /proc/pressure/ with the
628 pressure statistics files cpu, memory, and io. These will indicate
629 the share of walltime in which some or all tasks in the system are
630 delayed due to contention of the respective resource.
631
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632 In kernels with cgroup support, cgroups (cgroup2 only) will
633 have cpu.pressure, memory.pressure, and io.pressure files,
634 which aggregate pressure stalls for the grouped tasks only.
635
c3123552 636 For more details see Documentation/accounting/psi.rst.
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637
638 Say N if unsure.
639
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640config PSI_DEFAULT_DISABLED
641 bool "Require boot parameter to enable pressure stall information tracking"
642 default n
643 depends on PSI
644 help
645 If set, pressure stall information tracking will be disabled
428a1cb4
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646 per default but can be enabled through passing psi=1 on the
647 kernel commandline during boot.
e0c27447 648
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649 This feature adds some code to the task wakeup and sleep
650 paths of the scheduler. The overhead is too low to affect
651 common scheduling-intense workloads in practice (such as
652 webservers, memcache), but it does show up in artificial
653 scheduler stress tests, such as hackbench.
654
655 If you are paranoid and not sure what the kernel will be
656 used for, say Y.
657
658 Say N if unsure.
659
391dc69c 660endmenu # "CPU/Task time and stats accounting"
d9817ebe 661
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FW
662config CPU_ISOLATION
663 bool "CPU isolation"
414a2dc1 664 depends on SMP || COMPILE_TEST
2c43838c 665 default y
5c4991e2
FW
666 help
667 Make sure that CPUs running critical tasks are not disturbed by
668 any source of "noise" such as unbound workqueues, timers, kthreads...
2c43838c
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669 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
670 the "isolcpus=" boot parameter.
671
672 Say Y if unsure.
5c4991e2 673
0af92d46 674source "kernel/rcu/Kconfig"
c903ff83 675
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676config BUILD_BIN2C
677 bool
678 default n
679
1da177e4 680config IKCONFIG
f2443ab6 681 tristate "Kernel .config support"
a7f7f624 682 help
1da177e4
LT
683 This option enables the complete Linux kernel ".config" file
684 contents to be saved in the kernel. It provides documentation
685 of which kernel options are used in a running kernel or in an
686 on-disk kernel. This information can be extracted from the kernel
687 image file with the script scripts/extract-ikconfig and used as
688 input to rebuild the current kernel or to build another kernel.
689 It can also be extracted from a running kernel by reading
690 /proc/config.gz if enabled (below).
691
692config IKCONFIG_PROC
693 bool "Enable access to .config through /proc/config.gz"
694 depends on IKCONFIG && PROC_FS
a7f7f624 695 help
1da177e4
LT
696 This option enables access to the kernel configuration file
697 through /proc/config.gz.
698
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699config IKHEADERS
700 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
701 depends on SYSFS
702 help
703 This option enables access to the in-kernel headers that are generated during
704 the build process. These can be used to build eBPF tracing programs,
705 or similar programs. If you build the headers as a module, a module called
706 kheaders.ko is built which can be loaded on-demand to get access to headers.
43d8ce9d 707
794543a2
AJS
708config LOG_BUF_SHIFT
709 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
1c4b5ecb 710 range 12 25
f17a32e9 711 default 17
361e9dfb 712 depends on PRINTK
794543a2 713 help
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714 Select the minimal kernel log buffer size as a power of 2.
715 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
716 parameter, see below. Any higher size also might be forced
717 by "log_buf_len" boot parameter.
718
f17a32e9 719 Examples:
23b2899f 720 17 => 128 KB
f17a32e9 721 16 => 64 KB
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722 15 => 32 KB
723 14 => 16 KB
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724 13 => 8 KB
725 12 => 4 KB
726
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727config LOG_CPU_MAX_BUF_SHIFT
728 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
2240a31d 729 depends on SMP
23b2899f
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730 range 0 21
731 default 12 if !BASE_SMALL
732 default 0 if BASE_SMALL
361e9dfb 733 depends on PRINTK
23b2899f
LR
734 help
735 This option allows to increase the default ring buffer size
736 according to the number of CPUs. The value defines the contribution
737 of each CPU as a power of 2. The used space is typically only few
738 lines however it might be much more when problems are reported,
739 e.g. backtraces.
740
741 The increased size means that a new buffer has to be allocated and
742 the original static one is unused. It makes sense only on systems
743 with more CPUs. Therefore this value is used only when the sum of
744 contributions is greater than the half of the default kernel ring
745 buffer as defined by LOG_BUF_SHIFT. The default values are set
0f7636e1 746 so that more than 16 CPUs are needed to trigger the allocation.
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747
748 Also this option is ignored when "log_buf_len" kernel parameter is
749 used as it forces an exact (power of two) size of the ring buffer.
750
751 The number of possible CPUs is used for this computation ignoring
5e0d8d59
GU
752 hotplugging making the computation optimal for the worst case
753 scenario while allowing a simple algorithm to be used from bootup.
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754
755 Examples shift values and their meaning:
756 17 => 128 KB for each CPU
757 16 => 64 KB for each CPU
758 15 => 32 KB for each CPU
759 14 => 16 KB for each CPU
760 13 => 8 KB for each CPU
761 12 => 4 KB for each CPU
762
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SS
763config PRINTK_SAFE_LOG_BUF_SHIFT
764 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
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765 range 10 21
766 default 13
f92bac3b 767 depends on PRINTK
427934b8 768 help
f92bac3b
SS
769 Select the size of an alternate printk per-CPU buffer where messages
770 printed from usafe contexts are temporary stored. One example would
771 be NMI messages, another one - printk recursion. The messages are
772 copied to the main log buffer in a safe context to avoid a deadlock.
773 The value defines the size as a power of 2.
427934b8 774
f92bac3b 775 Those messages are rare and limited. The largest one is when
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PM
776 a backtrace is printed. It usually fits into 4KB. Select
777 8KB if you want to be on the safe side.
778
779 Examples:
780 17 => 128 KB for each CPU
781 16 => 64 KB for each CPU
782 15 => 32 KB for each CPU
783 14 => 16 KB for each CPU
784 13 => 8 KB for each CPU
785 12 => 4 KB for each CPU
786
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787config PRINTK_INDEX
788 bool "Printk indexing debugfs interface"
789 depends on PRINTK && DEBUG_FS
790 help
791 Add support for indexing of all printk formats known at compile time
792 at <debugfs>/printk/index/<module>.
793
794 This can be used as part of maintaining daemons which monitor
795 /dev/kmsg, as it permits auditing the printk formats present in a
796 kernel, allowing detection of cases where monitored printks are
797 changed or no longer present.
798
799 There is no additional runtime cost to printk with this enabled.
800
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801#
802# Architectures with an unreliable sched_clock() should select this:
803#
804config HAVE_UNSTABLE_SCHED_CLOCK
805 bool
806
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807config GENERIC_SCHED_CLOCK
808 bool
809
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810menu "Scheduler features"
811
812config UCLAMP_TASK
813 bool "Enable utilization clamping for RT/FAIR tasks"
814 depends on CPU_FREQ_GOV_SCHEDUTIL
815 help
816 This feature enables the scheduler to track the clamped utilization
817 of each CPU based on RUNNABLE tasks scheduled on that CPU.
818
819 With this option, the user can specify the min and max CPU
820 utilization allowed for RUNNABLE tasks. The max utilization defines
821 the maximum frequency a task should use while the min utilization
822 defines the minimum frequency it should use.
823
824 Both min and max utilization clamp values are hints to the scheduler,
825 aiming at improving its frequency selection policy, but they do not
826 enforce or grant any specific bandwidth for tasks.
827
828 If in doubt, say N.
829
830config UCLAMP_BUCKETS_COUNT
831 int "Number of supported utilization clamp buckets"
832 range 5 20
833 default 5
834 depends on UCLAMP_TASK
835 help
836 Defines the number of clamp buckets to use. The range of each bucket
837 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
838 number of clamp buckets the finer their granularity and the higher
839 the precision of clamping aggregation and tracking at run-time.
840
841 For example, with the minimum configuration value we will have 5
842 clamp buckets tracking 20% utilization each. A 25% boosted tasks will
843 be refcounted in the [20..39]% bucket and will set the bucket clamp
844 effective value to 25%.
845 If a second 30% boosted task should be co-scheduled on the same CPU,
846 that task will be refcounted in the same bucket of the first task and
847 it will boost the bucket clamp effective value to 30%.
848 The clamp effective value of a bucket is reset to its nominal value
849 (20% in the example above) when there are no more tasks refcounted in
850 that bucket.
851
852 An additional boost/capping margin can be added to some tasks. In the
853 example above the 25% task will be boosted to 30% until it exits the
854 CPU. If that should be considered not acceptable on certain systems,
855 it's always possible to reduce the margin by increasing the number of
856 clamp buckets to trade off used memory for run-time tracking
857 precision.
858
859 If in doubt, use the default value.
860
861endmenu
862
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AA
863#
864# For architectures that want to enable the support for NUMA-affine scheduler
865# balancing logic:
866#
867config ARCH_SUPPORTS_NUMA_BALANCING
868 bool
869
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MG
870#
871# For architectures that prefer to flush all TLBs after a number of pages
872# are unmapped instead of sending one IPI per page to flush. The architecture
873# must provide guarantees on what happens if a clean TLB cache entry is
874# written after the unmap. Details are in mm/rmap.c near the check for
875# should_defer_flush. The architecture should also consider if the full flush
876# and the refill costs are offset by the savings of sending fewer IPIs.
877config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
878 bool
879
c12d3362 880config CC_HAS_INT128
3a7c7331 881 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
c12d3362 882
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GS
883config CC_IMPLICIT_FALLTHROUGH
884 string
158ea2d2 885 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
dee2b702
GS
886 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough)
887
f0be87c4
LT
888# Currently, disable gcc-12 array-bounds globally.
889# We may want to target only particular configurations some day.
890config GCC12_NO_ARRAY_BOUNDS
891 def_bool y
892
893config CC_NO_ARRAY_BOUNDS
894 bool
895 default y if CC_IS_GCC && GCC_VERSION >= 120000 && GCC_VERSION < 130000 && GCC12_NO_ARRAY_BOUNDS
896
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PZ
897#
898# For architectures that know their GCC __int128 support is sound
899#
900config ARCH_SUPPORTS_INT128
901 bool
902
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AA
903# For architectures that (ab)use NUMA to represent different memory regions
904# all cpu-local but of different latencies, such as SuperH.
905#
906config ARCH_WANT_NUMA_VARIABLE_LOCALITY
907 bool
908
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AA
909config NUMA_BALANCING
910 bool "Memory placement aware NUMA scheduler"
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AA
911 depends on ARCH_SUPPORTS_NUMA_BALANCING
912 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
554b0f3c 913 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT
be3a7284
AA
914 help
915 This option adds support for automatic NUMA aware memory/task placement.
916 The mechanism is quite primitive and is based on migrating memory when
6d56a410 917 it has references to the node the task is running on.
be3a7284
AA
918
919 This system will be inactive on UMA systems.
920
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AK
921config NUMA_BALANCING_DEFAULT_ENABLED
922 bool "Automatically enable NUMA aware memory/task placement"
923 default y
924 depends on NUMA_BALANCING
925 help
926 If set, automatic NUMA balancing will be enabled if running on a NUMA
927 machine.
928
23964d2d 929menuconfig CGROUPS
6341e62b 930 bool "Control Group support"
2bd59d48 931 select KERNFS
5cdc38f9 932 help
23964d2d 933 This option adds support for grouping sets of processes together, for
5cdc38f9
KH
934 use with process control subsystems such as Cpusets, CFS, memory
935 controls or device isolation.
936 See
d6a3b247 937 - Documentation/scheduler/sched-design-CFS.rst (CFS)
da82c92f 938 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
45ce80fb 939 and resource control)
5cdc38f9
KH
940
941 Say N if unsure.
942
23964d2d
LZ
943if CGROUPS
944
3e32cb2e 945config PAGE_COUNTER
e8cf4e9c 946 bool
3e32cb2e 947
6a010a49
TH
948config CGROUP_FAVOR_DYNMODS
949 bool "Favor dynamic modification latency reduction by default"
950 help
951 This option enables the "favordynmods" mount option by default
952 which reduces the latencies of dynamic cgroup modifications such
953 as task migrations and controller on/offs at the cost of making
954 hot path operations such as forks and exits more expensive.
955
956 Say N if unsure.
957
c255a458 958config MEMCG
a0166ec4 959 bool "Memory controller"
3e32cb2e 960 select PAGE_COUNTER
79bd9814 961 select EVENTFD
00f0b825 962 help
a0166ec4 963 Provides control over the memory footprint of tasks in a cgroup.
00f0b825 964
c255a458 965config MEMCG_SWAP
2d1c4980 966 bool
c255a458 967 depends on MEMCG && SWAP
a42c390c 968 default y
c077719b 969
84c07d11
KT
970config MEMCG_KMEM
971 bool
972 depends on MEMCG && !SLOB
973 default y
974
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JW
975config BLK_CGROUP
976 bool "IO controller"
977 depends on BLOCK
2bc64a20 978 default n
a7f7f624 979 help
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JW
980 Generic block IO controller cgroup interface. This is the common
981 cgroup interface which should be used by various IO controlling
982 policies.
2bc64a20 983
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JW
984 Currently, CFQ IO scheduler uses it to recognize task groups and
985 control disk bandwidth allocation (proportional time slice allocation)
986 to such task groups. It is also used by bio throttling logic in
987 block layer to implement upper limit in IO rates on a device.
e5d1367f 988
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989 This option only enables generic Block IO controller infrastructure.
990 One needs to also enable actual IO controlling logic/policy. For
991 enabling proportional weight division of disk bandwidth in CFQ, set
7baf2199 992 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
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993 CONFIG_BLK_DEV_THROTTLING=y.
994
da82c92f 995 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
6bf024e6 996
6bf024e6
JW
997config CGROUP_WRITEBACK
998 bool
999 depends on MEMCG && BLK_CGROUP
1000 default y
e5d1367f 1001
7c941438 1002menuconfig CGROUP_SCHED
a0166ec4 1003 bool "CPU controller"
7c941438
DG
1004 default n
1005 help
1006 This feature lets CPU scheduler recognize task groups and control CPU
1007 bandwidth allocation to such task groups. It uses cgroups to group
1008 tasks.
1009
1010if CGROUP_SCHED
1011config FAIR_GROUP_SCHED
1012 bool "Group scheduling for SCHED_OTHER"
1013 depends on CGROUP_SCHED
1014 default CGROUP_SCHED
1015
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PT
1016config CFS_BANDWIDTH
1017 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
ab84d31e
PT
1018 depends on FAIR_GROUP_SCHED
1019 default n
1020 help
1021 This option allows users to define CPU bandwidth rates (limits) for
1022 tasks running within the fair group scheduler. Groups with no limit
1023 set are considered to be unconstrained and will run with no
1024 restriction.
d6a3b247 1025 See Documentation/scheduler/sched-bwc.rst for more information.
ab84d31e 1026
7c941438
DG
1027config RT_GROUP_SCHED
1028 bool "Group scheduling for SCHED_RR/FIFO"
7c941438
DG
1029 depends on CGROUP_SCHED
1030 default n
1031 help
1032 This feature lets you explicitly allocate real CPU bandwidth
32bd7eb5 1033 to task groups. If enabled, it will also make it impossible to
7c941438
DG
1034 schedule realtime tasks for non-root users until you allocate
1035 realtime bandwidth for them.
d6a3b247 1036 See Documentation/scheduler/sched-rt-group.rst for more information.
7c941438
DG
1037
1038endif #CGROUP_SCHED
1039
2480c093
PB
1040config UCLAMP_TASK_GROUP
1041 bool "Utilization clamping per group of tasks"
1042 depends on CGROUP_SCHED
1043 depends on UCLAMP_TASK
1044 default n
1045 help
1046 This feature enables the scheduler to track the clamped utilization
1047 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
1048
1049 When this option is enabled, the user can specify a min and max
1050 CPU bandwidth which is allowed for each single task in a group.
1051 The max bandwidth allows to clamp the maximum frequency a task
1052 can use, while the min bandwidth allows to define a minimum
1053 frequency a task will always use.
1054
1055 When task group based utilization clamping is enabled, an eventually
1056 specified task-specific clamp value is constrained by the cgroup
1057 specified clamp value. Both minimum and maximum task clamping cannot
1058 be bigger than the corresponding clamping defined at task group level.
1059
1060 If in doubt, say N.
1061
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1062config CGROUP_PIDS
1063 bool "PIDs controller"
1064 help
1065 Provides enforcement of process number limits in the scope of a
1066 cgroup. Any attempt to fork more processes than is allowed in the
1067 cgroup will fail. PIDs are fundamentally a global resource because it
1068 is fairly trivial to reach PID exhaustion before you reach even a
1069 conservative kmemcg limit. As a result, it is possible to grind a
1070 system to halt without being limited by other cgroup policies. The
6cc578df 1071 PIDs controller is designed to stop this from happening.
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JW
1072
1073 It should be noted that organisational operations (such as attaching
98076833 1074 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
6bf024e6
JW
1075 since the PIDs limit only affects a process's ability to fork, not to
1076 attach to a cgroup.
1077
39d3e758
PP
1078config CGROUP_RDMA
1079 bool "RDMA controller"
1080 help
1081 Provides enforcement of RDMA resources defined by IB stack.
1082 It is fairly easy for consumers to exhaust RDMA resources, which
1083 can result into resource unavailability to other consumers.
1084 RDMA controller is designed to stop this from happening.
1085 Attaching processes with active RDMA resources to the cgroup
1086 hierarchy is allowed even if can cross the hierarchy's limit.
1087
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1088config CGROUP_FREEZER
1089 bool "Freezer controller"
1090 help
1091 Provides a way to freeze and unfreeze all tasks in a
1092 cgroup.
1093
489c2a20
JW
1094 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1095 controller includes important in-kernel memory consumers per default.
1096
1097 If you're using cgroup2, say N.
1098
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1099config CGROUP_HUGETLB
1100 bool "HugeTLB controller"
1101 depends on HUGETLB_PAGE
1102 select PAGE_COUNTER
afc24d49 1103 default n
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1104 help
1105 Provides a cgroup controller for HugeTLB pages.
1106 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1107 The limit is enforced during page fault. Since HugeTLB doesn't
1108 support page reclaim, enforcing the limit at page fault time implies
1109 that, the application will get SIGBUS signal if it tries to access
1110 HugeTLB pages beyond its limit. This requires the application to know
1111 beforehand how much HugeTLB pages it would require for its use. The
1112 control group is tracked in the third page lru pointer. This means
1113 that we cannot use the controller with huge page less than 3 pages.
afc24d49 1114
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1115config CPUSETS
1116 bool "Cpuset controller"
e1d4eeec 1117 depends on SMP
6bf024e6
JW
1118 help
1119 This option will let you create and manage CPUSETs which
1120 allow dynamically partitioning a system into sets of CPUs and
1121 Memory Nodes and assigning tasks to run only within those sets.
1122 This is primarily useful on large SMP or NUMA systems.
afc24d49 1123
6bf024e6 1124 Say N if unsure.
afc24d49 1125
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1126config PROC_PID_CPUSET
1127 bool "Include legacy /proc/<pid>/cpuset file"
1128 depends on CPUSETS
1129 default y
afc24d49 1130
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1131config CGROUP_DEVICE
1132 bool "Device controller"
1133 help
1134 Provides a cgroup controller implementing whitelists for
1135 devices which a process in the cgroup can mknod or open.
1136
1137config CGROUP_CPUACCT
1138 bool "Simple CPU accounting controller"
1139 help
1140 Provides a simple controller for monitoring the
1141 total CPU consumed by the tasks in a cgroup.
1142
1143config CGROUP_PERF
1144 bool "Perf controller"
1145 depends on PERF_EVENTS
1146 help
1147 This option extends the perf per-cpu mode to restrict monitoring
1148 to threads which belong to the cgroup specified and run on the
6546b19f
NK
1149 designated cpu. Or this can be used to have cgroup ID in samples
1150 so that it can monitor performance events among cgroups.
6bf024e6
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1151
1152 Say N if unsure.
1153
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1154config CGROUP_BPF
1155 bool "Support for eBPF programs attached to cgroups"
483c4933
AL
1156 depends on BPF_SYSCALL
1157 select SOCK_CGROUP_DATA
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DM
1158 help
1159 Allow attaching eBPF programs to a cgroup using the bpf(2)
1160 syscall command BPF_PROG_ATTACH.
1161
1162 In which context these programs are accessed depends on the type
1163 of attachment. For instance, programs that are attached using
1164 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1165 inet sockets.
1166
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VS
1167config CGROUP_MISC
1168 bool "Misc resource controller"
1169 default n
1170 help
1171 Provides a controller for miscellaneous resources on a host.
1172
1173 Miscellaneous scalar resources are the resources on the host system
1174 which cannot be abstracted like the other cgroups. This controller
1175 tracks and limits the miscellaneous resources used by a process
1176 attached to a cgroup hierarchy.
1177
1178 For more information, please check misc cgroup section in
1179 /Documentation/admin-guide/cgroup-v2.rst.
1180
6bf024e6 1181config CGROUP_DEBUG
23b0be48 1182 bool "Debug controller"
afc24d49 1183 default n
23b0be48 1184 depends on DEBUG_KERNEL
6bf024e6
JW
1185 help
1186 This option enables a simple controller that exports
23b0be48
WL
1187 debugging information about the cgroups framework. This
1188 controller is for control cgroup debugging only. Its
1189 interfaces are not stable.
afc24d49 1190
6bf024e6 1191 Say N.
89e9b9e0 1192
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1193config SOCK_CGROUP_DATA
1194 bool
1195 default n
1196
23964d2d 1197endif # CGROUPS
c077719b 1198
8dd2a82c 1199menuconfig NAMESPACES
6a108a14 1200 bool "Namespaces support" if EXPERT
2813893f 1201 depends on MULTIUSER
6a108a14 1202 default !EXPERT
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1203 help
1204 Provides the way to make tasks work with different objects using
1205 the same id. For example same IPC id may refer to different objects
1206 or same user id or pid may refer to different tasks when used in
1207 different namespaces.
1208
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DL
1209if NAMESPACES
1210
58bfdd6d
PE
1211config UTS_NS
1212 bool "UTS namespace"
17a6d441 1213 default y
58bfdd6d
PE
1214 help
1215 In this namespace tasks see different info provided with the
1216 uname() system call
1217
769071ac
AV
1218config TIME_NS
1219 bool "TIME namespace"
660fd04f 1220 depends on GENERIC_VDSO_TIME_NS
769071ac
AV
1221 default y
1222 help
1223 In this namespace boottime and monotonic clocks can be set.
1224 The time will keep going with the same pace.
1225
ae5e1b22
PE
1226config IPC_NS
1227 bool "IPC namespace"
8dd2a82c 1228 depends on (SYSVIPC || POSIX_MQUEUE)
17a6d441 1229 default y
ae5e1b22
PE
1230 help
1231 In this namespace tasks work with IPC ids which correspond to
614b84cf 1232 different IPC objects in different namespaces.
ae5e1b22 1233
aee16ce7 1234config USER_NS
19c92399 1235 bool "User namespace"
5673a94c 1236 default n
aee16ce7
PE
1237 help
1238 This allows containers, i.e. vservers, to use user namespaces
1239 to provide different user info for different servers.
e11f0ae3
EB
1240
1241 When user namespaces are enabled in the kernel it is
d886f4e4
JW
1242 recommended that the MEMCG option also be enabled and that
1243 user-space use the memory control groups to limit the amount
1244 of memory a memory unprivileged users can use.
e11f0ae3 1245
aee16ce7
PE
1246 If unsure, say N.
1247
74bd59bb 1248config PID_NS
9bd38c2c 1249 bool "PID Namespaces"
17a6d441 1250 default y
74bd59bb 1251 help
12d2b8f9 1252 Support process id namespaces. This allows having multiple
692105b8 1253 processes with the same pid as long as they are in different
74bd59bb
PE
1254 pid namespaces. This is a building block of containers.
1255
d6eb633f
MH
1256config NET_NS
1257 bool "Network namespace"
8dd2a82c 1258 depends on NET
17a6d441 1259 default y
d6eb633f
MH
1260 help
1261 Allow user space to create what appear to be multiple instances
1262 of the network stack.
1263
8dd2a82c
DL
1264endif # NAMESPACES
1265
5cb366bb
AR
1266config CHECKPOINT_RESTORE
1267 bool "Checkpoint/restore support"
1268 select PROC_CHILDREN
bfe3911a 1269 select KCMP
5cb366bb
AR
1270 default n
1271 help
1272 Enables additional kernel features in a sake of checkpoint/restore.
1273 In particular it adds auxiliary prctl codes to setup process text,
1274 data and heap segment sizes, and a few additional /proc filesystem
1275 entries.
1276
1277 If unsure, say N here.
1278
5091faa4
MG
1279config SCHED_AUTOGROUP
1280 bool "Automatic process group scheduling"
5091faa4
MG
1281 select CGROUPS
1282 select CGROUP_SCHED
1283 select FAIR_GROUP_SCHED
1284 help
1285 This option optimizes the scheduler for common desktop workloads by
1286 automatically creating and populating task groups. This separation
1287 of workloads isolates aggressive CPU burners (like build jobs) from
1288 desktop applications. Task group autogeneration is currently based
1289 upon task session.
1290
7af37bec 1291config SYSFS_DEPRECATED
5d6a4ea5 1292 bool "Enable deprecated sysfs features to support old userspace tools"
7af37bec
DL
1293 depends on SYSFS
1294 default n
1295 help
1296 This option adds code that switches the layout of the "block" class
1297 devices, to not show up in /sys/class/block/, but only in
1298 /sys/block/.
1299
1300 This switch is only active when the sysfs.deprecated=1 boot option is
1301 passed or the SYSFS_DEPRECATED_V2 option is set.
1302
1303 This option allows new kernels to run on old distributions and tools,
1304 which might get confused by /sys/class/block/. Since 2007/2008 all
1305 major distributions and tools handle this just fine.
1306
1307 Recent distributions and userspace tools after 2009/2010 depend on
1308 the existence of /sys/class/block/, and will not work with this
1309 option enabled.
1310
1311 Only if you are using a new kernel on an old distribution, you might
1312 need to say Y here.
1313
1314config SYSFS_DEPRECATED_V2
5d6a4ea5 1315 bool "Enable deprecated sysfs features by default"
7af37bec
DL
1316 default n
1317 depends on SYSFS
1318 depends on SYSFS_DEPRECATED
1319 help
1320 Enable deprecated sysfs by default.
1321
1322 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1323 option.
1324
1325 Only if you are using a new kernel on an old distribution, you might
1326 need to say Y here. Even then, odds are you would not need it
1327 enabled, you can always pass the boot option if absolutely necessary.
1328
1329config RELAY
1330 bool "Kernel->user space relay support (formerly relayfs)"
26b5679e 1331 select IRQ_WORK
7af37bec
DL
1332 help
1333 This option enables support for relay interface support in
1334 certain file systems (such as debugfs).
1335 It is designed to provide an efficient mechanism for tools and
1336 facilities to relay large amounts of data from kernel space to
1337 user space.
1338
1339 If unsure, say N.
1340
f991633d
DG
1341config BLK_DEV_INITRD
1342 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
f991633d
DG
1343 help
1344 The initial RAM filesystem is a ramfs which is loaded by the
1345 boot loader (loadlin or lilo) and that is mounted as root
1346 before the normal boot procedure. It is typically used to
1347 load modules needed to mount the "real" root file system,
8c27ceff 1348 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
f991633d
DG
1349
1350 If RAM disk support (BLK_DEV_RAM) is also included, this
1351 also enables initial RAM disk (initrd) support and adds
1352 15 Kbytes (more on some other architectures) to the kernel size.
1353
1354 If unsure say Y.
1355
c33df4ea
JPS
1356if BLK_DEV_INITRD
1357
dbec4866
SR
1358source "usr/Kconfig"
1359
c33df4ea
JPS
1360endif
1361
76db5a27
MH
1362config BOOT_CONFIG
1363 bool "Boot config support"
a2a9d67a 1364 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED
76db5a27
MH
1365 help
1366 Extra boot config allows system admin to pass a config file as
1367 complemental extension of kernel cmdline when booting.
0947db01 1368 The boot config file must be attached at the end of initramfs
85c46b78 1369 with checksum, size and magic word.
0947db01 1370 See <file:Documentation/admin-guide/bootconfig.rst> for details.
76db5a27
MH
1371
1372 If unsure, say Y.
1373
a2a9d67a
MH
1374config BOOT_CONFIG_EMBED
1375 bool "Embed bootconfig file in the kernel"
1376 depends on BOOT_CONFIG
1377 help
1378 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the
1379 kernel. Usually, the bootconfig file is loaded with the initrd
1380 image. But if the system doesn't support initrd, this option will
1381 help you by embedding a bootconfig file while building the kernel.
1382
1383 If unsure, say N.
1384
1385config BOOT_CONFIG_EMBED_FILE
1386 string "Embedded bootconfig file path"
1387 depends on BOOT_CONFIG_EMBED
1388 help
1389 Specify a bootconfig file which will be embedded to the kernel.
1390 This bootconfig will be used if there is no initrd or no other
1391 bootconfig in the initrd.
1392
1274aea1
DD
1393config INITRAMFS_PRESERVE_MTIME
1394 bool "Preserve cpio archive mtimes in initramfs"
1395 default y
1396 help
1397 Each entry in an initramfs cpio archive carries an mtime value. When
1398 enabled, extracted cpio items take this mtime, with directory mtime
1399 setting deferred until after creation of any child entries.
1400
1401 If unsure, say Y.
76db5a27 1402
877417e6
AB
1403choice
1404 prompt "Compiler optimization level"
2cc3ce24 1405 default CC_OPTIMIZE_FOR_PERFORMANCE
877417e6
AB
1406
1407config CC_OPTIMIZE_FOR_PERFORMANCE
15f5db60 1408 bool "Optimize for performance (-O2)"
877417e6
AB
1409 help
1410 This is the default optimization level for the kernel, building
1411 with the "-O2" compiler flag for best performance and most
1412 helpful compile-time warnings.
1413
15f5db60
MY
1414config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1415 bool "Optimize more for performance (-O3)"
1416 depends on ARC
c45b4f1f 1417 help
15f5db60
MY
1418 Choosing this option will pass "-O3" to your compiler to optimize
1419 the kernel yet more for performance.
c45b4f1f 1420
c45b4f1f 1421config CC_OPTIMIZE_FOR_SIZE
15f5db60 1422 bool "Optimize for size (-Os)"
c45b4f1f 1423 help
ce3b487f
MY
1424 Choosing this option will pass "-Os" to your compiler resulting
1425 in a smaller kernel.
c45b4f1f 1426
877417e6
AB
1427endchoice
1428
5d20ee31
NP
1429config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1430 bool
1431 help
1432 This requires that the arch annotates or otherwise protects
1433 its external entry points from being discarded. Linker scripts
1434 must also merge .text.*, .data.*, and .bss.* correctly into
1435 output sections. Care must be taken not to pull in unrelated
1436 sections (e.g., '.text.init'). Typically '.' in section names
1437 is used to distinguish them from label names / C identifiers.
1438
1439config LD_DEAD_CODE_DATA_ELIMINATION
1440 bool "Dead code and data elimination (EXPERIMENTAL)"
1441 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1442 depends on EXPERT
e85d1d65
MY
1443 depends on $(cc-option,-ffunction-sections -fdata-sections)
1444 depends on $(ld-option,--gc-sections)
5d20ee31 1445 help
8b9d2712
MY
1446 Enable this if you want to do dead code and data elimination with
1447 the linker by compiling with -ffunction-sections -fdata-sections,
1448 and linking with --gc-sections.
5d20ee31
NP
1449
1450 This can reduce on disk and in-memory size of the kernel
1451 code and static data, particularly for small configs and
1452 on small systems. This has the possibility of introducing
1453 silently broken kernel if the required annotations are not
1454 present. This option is not well tested yet, so use at your
1455 own risk.
1456
59612b24
NC
1457config LD_ORPHAN_WARN
1458 def_bool y
1459 depends on ARCH_WANT_LD_ORPHAN_WARN
1460 depends on $(ld-option,--orphan-handling=warn)
1461
0847062a
RD
1462config SYSCTL
1463 bool
1464
657a5209
MF
1465config HAVE_UID16
1466 bool
1467
1468config SYSCTL_EXCEPTION_TRACE
1469 bool
1470 help
1471 Enable support for /proc/sys/debug/exception-trace.
1472
1473config SYSCTL_ARCH_UNALIGN_NO_WARN
1474 bool
1475 help
1476 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1477 Allows arch to define/use @no_unaligned_warning to possibly warn
1478 about unaligned access emulation going on under the hood.
1479
1480config SYSCTL_ARCH_UNALIGN_ALLOW
1481 bool
1482 help
1483 Enable support for /proc/sys/kernel/unaligned-trap
1484 Allows arches to define/use @unaligned_enabled to runtime toggle
1485 the unaligned access emulation.
1486 see arch/parisc/kernel/unaligned.c for reference
1487
657a5209
MF
1488config HAVE_PCSPKR_PLATFORM
1489 bool
1490
f89b7755
AS
1491# interpreter that classic socket filters depend on
1492config BPF
1493 bool
ec8f7f48 1494 select CRYPTO_LIB_SHA1
f89b7755 1495
6a108a14
DR
1496menuconfig EXPERT
1497 bool "Configure standard kernel features (expert users)"
f505c553
JT
1498 # Unhide debug options, to make the on-by-default options visible
1499 select DEBUG_KERNEL
1da177e4
LT
1500 help
1501 This option allows certain base kernel options and settings
e8cf4e9c
KK
1502 to be disabled or tweaked. This is for specialized
1503 environments which can tolerate a "non-standard" kernel.
1504 Only use this if you really know what you are doing.
1da177e4 1505
ae81f9e3 1506config UID16
6a108a14 1507 bool "Enable 16-bit UID system calls" if EXPERT
2813893f 1508 depends on HAVE_UID16 && MULTIUSER
ae81f9e3
CE
1509 default y
1510 help
1511 This enables the legacy 16-bit UID syscall wrappers.
1512
2813893f
IM
1513config MULTIUSER
1514 bool "Multiple users, groups and capabilities support" if EXPERT
1515 default y
1516 help
1517 This option enables support for non-root users, groups and
1518 capabilities.
1519
1520 If you say N here, all processes will run with UID 0, GID 0, and all
1521 possible capabilities. Saying N here also compiles out support for
1522 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1523 setgid, and capset.
1524
1525 If unsure, say Y here.
1526
f6187769
FF
1527config SGETMASK_SYSCALL
1528 bool "sgetmask/ssetmask syscalls support" if EXPERT
a687a533 1529 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
a7f7f624 1530 help
f6187769
FF
1531 sys_sgetmask and sys_ssetmask are obsolete system calls
1532 no longer supported in libc but still enabled by default in some
1533 architectures.
1534
1535 If unsure, leave the default option here.
1536
6af9f7bf
FF
1537config SYSFS_SYSCALL
1538 bool "Sysfs syscall support" if EXPERT
1539 default y
a7f7f624 1540 help
6af9f7bf
FF
1541 sys_sysfs is an obsolete system call no longer supported in libc.
1542 Note that disabling this option is more secure but might break
1543 compatibility with some systems.
1544
1545 If unsure say Y here.
1546
d1b069f5
RD
1547config FHANDLE
1548 bool "open by fhandle syscalls" if EXPERT
1549 select EXPORTFS
1550 default y
1551 help
1552 If you say Y here, a user level program will be able to map
1553 file names to handle and then later use the handle for
1554 different file system operations. This is useful in implementing
1555 userspace file servers, which now track files using handles instead
1556 of names. The handle would remain the same even if file names
1557 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1558 syscalls.
1559
baa73d9e
NP
1560config POSIX_TIMERS
1561 bool "Posix Clocks & timers" if EXPERT
1562 default y
1563 help
1564 This includes native support for POSIX timers to the kernel.
1565 Some embedded systems have no use for them and therefore they
1566 can be configured out to reduce the size of the kernel image.
1567
1568 When this option is disabled, the following syscalls won't be
1569 available: timer_create, timer_gettime: timer_getoverrun,
1570 timer_settime, timer_delete, clock_adjtime, getitimer,
1571 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1572 clock_getres and clock_nanosleep syscalls will be limited to
1573 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1574
1575 If unsure say y.
1576
d59745ce
MM
1577config PRINTK
1578 default y
6a108a14 1579 bool "Enable support for printk" if EXPERT
74876a98 1580 select IRQ_WORK
d59745ce
MM
1581 help
1582 This option enables normal printk support. Removing it
1583 eliminates most of the message strings from the kernel image
1584 and makes the kernel more or less silent. As this makes it
1585 very difficult to diagnose system problems, saying N here is
1586 strongly discouraged.
1587
c8538a7a 1588config BUG
6a108a14 1589 bool "BUG() support" if EXPERT
c8538a7a
MM
1590 default y
1591 help
e8cf4e9c
KK
1592 Disabling this option eliminates support for BUG and WARN, reducing
1593 the size of your kernel image and potentially quietly ignoring
1594 numerous fatal conditions. You should only consider disabling this
1595 option for embedded systems with no facilities for reporting errors.
1596 Just say Y.
c8538a7a 1597
708e9a79 1598config ELF_CORE
046d662f 1599 depends on COREDUMP
708e9a79 1600 default y
6a108a14 1601 bool "Enable ELF core dumps" if EXPERT
708e9a79
MM
1602 help
1603 Enable support for generating core dumps. Disabling saves about 4k.
1604
8761f1ab 1605
e5e1d3cb 1606config PCSPKR_PLATFORM
6a108a14 1607 bool "Enable PC-Speaker support" if EXPERT
8761f1ab 1608 depends on HAVE_PCSPKR_PLATFORM
15f304b6 1609 select I8253_LOCK
e5e1d3cb
SS
1610 default y
1611 help
e8cf4e9c
KK
1612 This option allows to disable the internal PC-Speaker
1613 support, saving some memory.
e5e1d3cb 1614
1da177e4
LT
1615config BASE_FULL
1616 default y
6a108a14 1617 bool "Enable full-sized data structures for core" if EXPERT
1da177e4
LT
1618 help
1619 Disabling this option reduces the size of miscellaneous core
1620 kernel data structures. This saves memory on small machines,
1621 but may reduce performance.
1622
1623config FUTEX
6a108a14 1624 bool "Enable futex support" if EXPERT
3f2bedab 1625 depends on !(SPARC32 && SMP)
1da177e4 1626 default y
bc2eecd7 1627 imply RT_MUTEXES
1da177e4
LT
1628 help
1629 Disabling this option will cause the kernel to be built without
1630 support for "fast userspace mutexes". The resulting kernel may not
1631 run glibc-based applications correctly.
1632
bc2eecd7
NP
1633config FUTEX_PI
1634 bool
1635 depends on FUTEX && RT_MUTEXES
1636 default y
1637
1da177e4 1638config EPOLL
6a108a14 1639 bool "Enable eventpoll support" if EXPERT
1da177e4
LT
1640 default y
1641 help
1642 Disabling this option will cause the kernel to be built without
1643 support for epoll family of system calls.
1644
fba2afaa 1645config SIGNALFD
6a108a14 1646 bool "Enable signalfd() system call" if EXPERT
fba2afaa
DL
1647 default y
1648 help
1649 Enable the signalfd() system call that allows to receive signals
1650 on a file descriptor.
1651
1652 If unsure, say Y.
1653
b215e283 1654config TIMERFD
6a108a14 1655 bool "Enable timerfd() system call" if EXPERT
b215e283
DL
1656 default y
1657 help
1658 Enable the timerfd() system call that allows to receive timer
1659 events on a file descriptor.
1660
1661 If unsure, say Y.
1662
e1ad7468 1663config EVENTFD
6a108a14 1664 bool "Enable eventfd() system call" if EXPERT
e1ad7468
DL
1665 default y
1666 help
1667 Enable the eventfd() system call that allows to receive both
1668 kernel notification (ie. KAIO) or userspace notifications.
1669
1670 If unsure, say Y.
1671
1da177e4 1672config SHMEM
6a108a14 1673 bool "Use full shmem filesystem" if EXPERT
1da177e4
LT
1674 default y
1675 depends on MMU
1676 help
1677 The shmem is an internal filesystem used to manage shared memory.
1678 It is backed by swap and manages resource limits. It is also exported
1679 to userspace as tmpfs if TMPFS is enabled. Disabling this
1680 option replaces shmem and tmpfs with the much simpler ramfs code,
1681 which may be appropriate on small systems without swap.
1682
ebf3f09c 1683config AIO
6a108a14 1684 bool "Enable AIO support" if EXPERT
ebf3f09c
TP
1685 default y
1686 help
1687 This option enables POSIX asynchronous I/O which may by used
657a5209
MF
1688 by some high performance threaded applications. Disabling
1689 this option saves about 7k.
1690
2b188cc1
JA
1691config IO_URING
1692 bool "Enable IO uring support" if EXPERT
561fb04a 1693 select IO_WQ
2b188cc1
JA
1694 default y
1695 help
1696 This option enables support for the io_uring interface, enabling
1697 applications to submit and complete IO through submission and
1698 completion rings that are shared between the kernel and application.
1699
d3ac21ca
JT
1700config ADVISE_SYSCALLS
1701 bool "Enable madvise/fadvise syscalls" if EXPERT
1702 default y
1703 help
1704 This option enables the madvise and fadvise syscalls, used by
1705 applications to advise the kernel about their future memory or file
1706 usage, improving performance. If building an embedded system where no
1707 applications use these syscalls, you can disable this option to save
1708 space.
1709
5b25b13a
MD
1710config MEMBARRIER
1711 bool "Enable membarrier() system call" if EXPERT
1712 default y
1713 help
1714 Enable the membarrier() system call that allows issuing memory
1715 barriers across all running threads, which can be used to distribute
1716 the cost of user-space memory barriers asymmetrically by transforming
1717 pairs of memory barriers into pairs consisting of membarrier() and a
1718 compiler barrier.
1719
1720 If unsure, say Y.
1721
d1b069f5 1722config KALLSYMS
e8cf4e9c
KK
1723 bool "Load all symbols for debugging/ksymoops" if EXPERT
1724 default y
1725 help
1726 Say Y here to let the kernel print out symbolic crash information and
1727 symbolic stack backtraces. This increases the size of the kernel
1728 somewhat, as all symbols have to be loaded into the kernel image.
d1b069f5
RD
1729
1730config KALLSYMS_ALL
1731 bool "Include all symbols in kallsyms"
1732 depends on DEBUG_KERNEL && KALLSYMS
1733 help
e8cf4e9c
KK
1734 Normally kallsyms only contains the symbols of functions for nicer
1735 OOPS messages and backtraces (i.e., symbols from the text and inittext
1736 sections). This is sufficient for most cases. And only in very rare
1737 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1738 names of variables from the data sections, etc).
d1b069f5 1739
e8cf4e9c
KK
1740 This option makes sure that all symbols are loaded into the kernel
1741 image (i.e., symbols from all sections) in cost of increased kernel
1742 size (depending on the kernel configuration, it may be 300KiB or
1743 something like this).
d1b069f5 1744
e8cf4e9c 1745 Say N unless you really need all symbols.
d1b069f5
RD
1746
1747config KALLSYMS_ABSOLUTE_PERCPU
1748 bool
1749 depends on KALLSYMS
1750 default X86_64 && SMP
1751
1752config KALLSYMS_BASE_RELATIVE
1753 bool
1754 depends on KALLSYMS
a687a533 1755 default !IA64
d1b069f5
RD
1756 help
1757 Instead of emitting them as absolute values in the native word size,
1758 emit the symbol references in the kallsyms table as 32-bit entries,
1759 each containing a relative value in the range [base, base + U32_MAX]
1760 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1761 an absolute value in the range [0, S32_MAX] or a relative value in the
1762 range [base, base + S32_MAX], where base is the lowest relative symbol
1763 address encountered in the image.
1764
1765 On 64-bit builds, this reduces the size of the address table by 50%,
1766 but more importantly, it results in entries whose values are build
1767 time constants, and no relocation pass is required at runtime to fix
1768 up the entries based on the runtime load address of the kernel.
1769
1770# end of the "standard kernel features (expert users)" menu
1771
1772# syscall, maps, verifier
fc611f47 1773
3ccfebed
MD
1774config ARCH_HAS_MEMBARRIER_CALLBACKS
1775 bool
1776
70216e18
MD
1777config ARCH_HAS_MEMBARRIER_SYNC_CORE
1778 bool
1779
bfe3911a
CW
1780config KCMP
1781 bool "Enable kcmp() system call" if EXPERT
1782 help
1783 Enable the kernel resource comparison system call. It provides
1784 user-space with the ability to compare two processes to see if they
1785 share a common resource, such as a file descriptor or even virtual
1786 memory space.
1787
1788 If unsure, say N.
1789
d7822b1e
MD
1790config RSEQ
1791 bool "Enable rseq() system call" if EXPERT
1792 default y
1793 depends on HAVE_RSEQ
1794 select MEMBARRIER
1795 help
1796 Enable the restartable sequences system call. It provides a
1797 user-space cache for the current CPU number value, which
1798 speeds up getting the current CPU number from user-space,
1799 as well as an ABI to speed up user-space operations on
1800 per-CPU data.
1801
1802 If unsure, say Y.
1803
1804config DEBUG_RSEQ
1805 default n
1806 bool "Enabled debugging of rseq() system call" if EXPERT
1807 depends on RSEQ && DEBUG_KERNEL
1808 help
1809 Enable extra debugging checks for the rseq system call.
1810
1811 If unsure, say N.
1812
6befe5f6
RD
1813config EMBEDDED
1814 bool "Embedded system"
1815 select EXPERT
1816 help
1817 This option should be enabled if compiling the kernel for
1818 an embedded system so certain expert options are available
1819 for configuration.
1820
cdd6c482 1821config HAVE_PERF_EVENTS
0793a61d 1822 bool
018df72d
MF
1823 help
1824 See tools/perf/design.txt for details.
0793a61d 1825
2aef6f30
SC
1826config GUEST_PERF_EVENTS
1827 bool
1828 depends on HAVE_PERF_EVENTS
1829
906010b2
PZ
1830config PERF_USE_VMALLOC
1831 bool
1832 help
1833 See tools/perf/design.txt for details
1834
ad90a3de 1835config PC104
424529fb 1836 bool "PC/104 support" if EXPERT
ad90a3de
WBG
1837 help
1838 Expose PC/104 form factor device drivers and options available for
1839 selection and configuration. Enable this option if your target
1840 machine has a PC/104 bus.
1841
57c0c15b 1842menu "Kernel Performance Events And Counters"
0793a61d 1843
cdd6c482 1844config PERF_EVENTS
57c0c15b 1845 bool "Kernel performance events and counters"
392d65a9 1846 default y if PROFILING
cdd6c482 1847 depends on HAVE_PERF_EVENTS
e360adbe 1848 select IRQ_WORK
83fe27ea 1849 select SRCU
0793a61d 1850 help
57c0c15b
IM
1851 Enable kernel support for various performance events provided
1852 by software and hardware.
0793a61d 1853
dd77038d 1854 Software events are supported either built-in or via the
57c0c15b 1855 use of generic tracepoints.
0793a61d 1856
57c0c15b
IM
1857 Most modern CPUs support performance events via performance
1858 counter registers. These registers count the number of certain
0793a61d
TG
1859 types of hw events: such as instructions executed, cachemisses
1860 suffered, or branches mis-predicted - without slowing down the
1861 kernel or applications. These registers can also trigger interrupts
1862 when a threshold number of events have passed - and can thus be
1863 used to profile the code that runs on that CPU.
1864
57c0c15b 1865 The Linux Performance Event subsystem provides an abstraction of
dd77038d 1866 these software and hardware event capabilities, available via a
57c0c15b 1867 system call and used by the "perf" utility in tools/perf/. It
0793a61d
TG
1868 provides per task and per CPU counters, and it provides event
1869 capabilities on top of those.
1870
1871 Say Y if unsure.
1872
906010b2
PZ
1873config DEBUG_PERF_USE_VMALLOC
1874 default n
1875 bool "Debug: use vmalloc to back perf mmap() buffers"
cb307113 1876 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
906010b2
PZ
1877 select PERF_USE_VMALLOC
1878 help
e8cf4e9c 1879 Use vmalloc memory to back perf mmap() buffers.
906010b2 1880
e8cf4e9c
KK
1881 Mostly useful for debugging the vmalloc code on platforms
1882 that don't require it.
906010b2 1883
e8cf4e9c 1884 Say N if unsure.
906010b2 1885
0793a61d
TG
1886endmenu
1887
091f6e26
DH
1888config SYSTEM_DATA_VERIFICATION
1889 def_bool n
1890 select SYSTEM_TRUSTED_KEYRING
1891 select KEYS
1892 select CRYPTO
d43de6c7 1893 select CRYPTO_RSA
091f6e26
DH
1894 select ASYMMETRIC_KEY_TYPE
1895 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
091f6e26
DH
1896 select ASN1
1897 select OID_REGISTRY
1898 select X509_CERTIFICATE_PARSER
1899 select PKCS7_MESSAGE_PARSER
82c04ff8 1900 help
091f6e26
DH
1901 Provide PKCS#7 message verification using the contents of the system
1902 trusted keyring to provide public keys. This then can be used for
1903 module verification, kexec image verification and firmware blob
1904 verification.
82c04ff8 1905
125e5645 1906config PROFILING
b309a294 1907 bool "Profiling support"
125e5645
MD
1908 help
1909 Say Y here to enable the extended profiling support mechanisms used
f8408264 1910 by profilers.
125e5645 1911
5f87f112
IM
1912#
1913# Place an empty function call at each tracepoint site. Can be
1914# dynamically changed for a probe function.
1915#
97e1c18e 1916config TRACEPOINTS
5f87f112 1917 bool
97e1c18e 1918
1da177e4
LT
1919endmenu # General setup
1920
1572497c
CH
1921source "arch/Kconfig"
1922
ae81f9e3 1923config RT_MUTEXES
6341e62b 1924 bool
1c6f9ec0 1925 default y if PREEMPT_RT
ae81f9e3 1926
1da177e4
LT
1927config BASE_SMALL
1928 int
1929 default 0 if BASE_FULL
1930 default 1 if !BASE_FULL
1931
c8424e77
TJB
1932config MODULE_SIG_FORMAT
1933 def_bool n
1934 select SYSTEM_DATA_VERIFICATION
1935
66da5733 1936menuconfig MODULES
1da177e4 1937 bool "Enable loadable module support"
6dd85ff1 1938 modules
1da177e4
LT
1939 help
1940 Kernel modules are small pieces of compiled code which can
1941 be inserted in the running kernel, rather than being
1942 permanently built into the kernel. You use the "modprobe"
1943 tool to add (and sometimes remove) them. If you say Y here,
1944 many parts of the kernel can be built as modules (by
1945 answering M instead of Y where indicated): this is most
1946 useful for infrequently used options which are not required
1947 for booting. For more information, see the man pages for
1948 modprobe, lsmod, modinfo, insmod and rmmod.
1949
1950 If you say Y here, you will need to run "make
1951 modules_install" to put the modules under /lib/modules/
1952 where modprobe can find them (you may need to be root to do
1953 this).
1954
1955 If unsure, say Y.
1956
0b0de144
RD
1957if MODULES
1958
826e4506
LT
1959config MODULE_FORCE_LOAD
1960 bool "Forced module loading"
826e4506
LT
1961 default n
1962 help
91e37a79
RR
1963 Allow loading of modules without version information (ie. modprobe
1964 --force). Forced module loading sets the 'F' (forced) taint flag and
1965 is usually a really bad idea.
826e4506 1966
1da177e4
LT
1967config MODULE_UNLOAD
1968 bool "Module unloading"
1da177e4
LT
1969 help
1970 Without this option you will not be able to unload any
1971 modules (note that some modules may not be unloadable
f7f5b675
DV
1972 anyway), which makes your kernel smaller, faster
1973 and simpler. If unsure, say Y.
1da177e4
LT
1974
1975config MODULE_FORCE_UNLOAD
1976 bool "Forced module unloading"
19c92399 1977 depends on MODULE_UNLOAD
1da177e4
LT
1978 help
1979 This option allows you to force a module to unload, even if the
1980 kernel believes it is unsafe: the kernel will remove the module
1981 without waiting for anyone to stop using it (using the -f option to
1982 rmmod). This is mainly for kernel developers and desperate users.
1983 If unsure, say N.
1984
99bd9956
AT
1985config MODULE_UNLOAD_TAINT_TRACKING
1986 bool "Tainted module unload tracking"
1987 depends on MODULE_UNLOAD
1988 default n
1989 help
1990 This option allows you to maintain a record of each unloaded
1991 module that tainted the kernel. In addition to displaying a
1992 list of linked (or loaded) modules e.g. on detection of a bad
1993 page (see bad_page()), the aforementioned details are also
1994 shown. If unsure, say N.
1995
1da177e4 1996config MODVERSIONS
0d541643 1997 bool "Module versioning support"
1da177e4
LT
1998 help
1999 Usually, you have to use modules compiled with your kernel.
2000 Saying Y here makes it sometimes possible to use modules
2001 compiled for different kernels, by adding enough information
2002 to the modules to (hopefully) spot any changes which would
2003 make them incompatible with the kernel you are running. If
2004 unsure, say N.
2005
2ff2b7ec
MY
2006config ASM_MODVERSIONS
2007 bool
2008 default HAVE_ASM_MODVERSIONS && MODVERSIONS
2009 help
2010 This enables module versioning for exported symbols also from
2011 assembly. This can be enabled only when the target architecture
2012 supports it.
2013
1da177e4
LT
2014config MODULE_SRCVERSION_ALL
2015 bool "Source checksum for all modules"
1da177e4
LT
2016 help
2017 Modules which contain a MODULE_VERSION get an extra "srcversion"
2018 field inserted into their modinfo section, which contains a
2019 sum of the source files which made it. This helps maintainers
2020 see exactly which source was used to build a module (since
2021 others sometimes change the module source without updating
2022 the version). With this option, such a "srcversion" field
2023 will be created for all modules. If unsure, say N.
2024
106a4ee2
RR
2025config MODULE_SIG
2026 bool "Module signature verification"
c8424e77 2027 select MODULE_SIG_FORMAT
106a4ee2
RR
2028 help
2029 Check modules for valid signatures upon load: the signature
2030 is simply appended to the module. For more information see
cbdc8217 2031 <file:Documentation/admin-guide/module-signing.rst>.
106a4ee2 2032
228c37ff
DH
2033 Note that this option adds the OpenSSL development packages as a
2034 kernel build dependency so that the signing tool can use its crypto
2035 library.
2036
49fcf732
DH
2037 You should enable this option if you wish to use either
2038 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2039 another LSM - otherwise unsigned modules will be loadable regardless
2040 of the lockdown policy.
2041
ea0b6dcf
DH
2042 !!!WARNING!!! If you enable this option, you MUST make sure that the
2043 module DOES NOT get stripped after being signed. This includes the
2044 debuginfo strip done by some packagers (such as rpmbuild) and
2045 inclusion into an initramfs that wants the module size reduced.
2046
106a4ee2
RR
2047config MODULE_SIG_FORCE
2048 bool "Require modules to be validly signed"
2049 depends on MODULE_SIG
2050 help
2051 Reject unsigned modules or signed modules for which we don't have a
2052 key. Without this, such modules will simply taint the kernel.
ea0b6dcf 2053
d9d8d7ed
MM
2054config MODULE_SIG_ALL
2055 bool "Automatically sign all modules"
2056 default y
0165f4ca 2057 depends on MODULE_SIG || IMA_APPRAISE_MODSIG
d9d8d7ed
MM
2058 help
2059 Sign all modules during make modules_install. Without this option,
2060 modules must be signed manually, using the scripts/sign-file tool.
2061
2062comment "Do not forget to sign required modules with scripts/sign-file"
2063 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2064
ea0b6dcf
DH
2065choice
2066 prompt "Which hash algorithm should modules be signed with?"
0165f4ca 2067 depends on MODULE_SIG || IMA_APPRAISE_MODSIG
ea0b6dcf
DH
2068 help
2069 This determines which sort of hashing algorithm will be used during
2070 signature generation. This algorithm _must_ be built into the kernel
2071 directly so that signature verification can take place. It is not
2072 possible to load a signed module containing the algorithm to check
2073 the signature on that module.
2074
2075config MODULE_SIG_SHA1
2076 bool "Sign modules with SHA-1"
2077 select CRYPTO_SHA1
2078
2079config MODULE_SIG_SHA224
2080 bool "Sign modules with SHA-224"
2081 select CRYPTO_SHA256
2082
2083config MODULE_SIG_SHA256
2084 bool "Sign modules with SHA-256"
2085 select CRYPTO_SHA256
2086
2087config MODULE_SIG_SHA384
2088 bool "Sign modules with SHA-384"
2089 select CRYPTO_SHA512
2090
2091config MODULE_SIG_SHA512
2092 bool "Sign modules with SHA-512"
2093 select CRYPTO_SHA512
2094
2095endchoice
2096
22753674
MM
2097config MODULE_SIG_HASH
2098 string
0165f4ca 2099 depends on MODULE_SIG || IMA_APPRAISE_MODSIG
22753674
MM
2100 default "sha1" if MODULE_SIG_SHA1
2101 default "sha224" if MODULE_SIG_SHA224
2102 default "sha256" if MODULE_SIG_SHA256
2103 default "sha384" if MODULE_SIG_SHA384
2104 default "sha512" if MODULE_SIG_SHA512
2105
d4bbe942
MY
2106choice
2107 prompt "Module compression mode"
beb50df3 2108 help
d4bbe942
MY
2109 This option allows you to choose the algorithm which will be used to
2110 compress modules when 'make modules_install' is run. (or, you can
2111 choose to not compress modules at all.)
beb50df3 2112
d4bbe942
MY
2113 External modules will also be compressed in the same way during the
2114 installation.
beb50df3 2115
d4bbe942
MY
2116 For modules inside an initrd or initramfs, it's more efficient to
2117 compress the whole initrd or initramfs instead.
beb50df3 2118
d4bbe942 2119 This is fully compatible with signed modules.
beb50df3 2120
d4bbe942
MY
2121 Please note that the tool used to load modules needs to support the
2122 corresponding algorithm. module-init-tools MAY support gzip, and kmod
c3d7ef37 2123 MAY support gzip, xz and zstd.
beb50df3 2124
d4bbe942
MY
2125 Your build system needs to provide the appropriate compression tool
2126 to compress the modules.
b6c09b51 2127
d4bbe942 2128 If in doubt, select 'None'.
beb50df3 2129
d4bbe942
MY
2130config MODULE_COMPRESS_NONE
2131 bool "None"
beb50df3 2132 help
d4bbe942
MY
2133 Do not compress modules. The installed modules are suffixed
2134 with .ko.
beb50df3
BJ
2135
2136config MODULE_COMPRESS_GZIP
2137 bool "GZIP"
d4bbe942
MY
2138 help
2139 Compress modules with GZIP. The installed modules are suffixed
2140 with .ko.gz.
beb50df3
BJ
2141
2142config MODULE_COMPRESS_XZ
2143 bool "XZ"
d4bbe942
MY
2144 help
2145 Compress modules with XZ. The installed modules are suffixed
2146 with .ko.xz.
beb50df3 2147
c3d7ef37
PG
2148config MODULE_COMPRESS_ZSTD
2149 bool "ZSTD"
2150 help
2151 Compress modules with ZSTD. The installed modules are suffixed
2152 with .ko.zst.
beb50df3
BJ
2153
2154endchoice
2155
b1ae6dc4
DT
2156config MODULE_DECOMPRESS
2157 bool "Support in-kernel module decompression"
2158 depends on MODULE_COMPRESS_GZIP || MODULE_COMPRESS_XZ
2159 select ZLIB_INFLATE if MODULE_COMPRESS_GZIP
2160 select XZ_DEC if MODULE_COMPRESS_XZ
2161 help
2162
2163 Support for decompressing kernel modules by the kernel itself
2164 instead of relying on userspace to perform this task. Useful when
2165 load pinning security policy is enabled.
2166
2167 If unsure, say N.
2168
3d52ec5e
MM
2169config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2170 bool "Allow loading of modules with missing namespace imports"
2171 help
2172 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2173 a namespace. A module that makes use of a symbol exported with such a
2174 namespace is required to import the namespace via MODULE_IMPORT_NS().
2175 There is no technical reason to enforce correct namespace imports,
2176 but it creates consistency between symbols defining namespaces and
2177 users importing namespaces they make use of. This option relaxes this
2178 requirement and lifts the enforcement when loading a module.
2179
2180 If unsure, say N.
2181
17652f42
RV
2182config MODPROBE_PATH
2183 string "Path to modprobe binary"
2184 default "/sbin/modprobe"
2185 help
2186 When kernel code requests a module, it does so by calling
2187 the "modprobe" userspace utility. This option allows you to
2188 set the path where that binary is found. This can be changed
2189 at runtime via the sysctl file
2190 /proc/sys/kernel/modprobe. Setting this to the empty string
2191 removes the kernel's ability to request modules (but
2192 userspace can still load modules explicitly).
2193
dbacb0ef 2194config TRIM_UNUSED_KSYMS
a555bdd0
LT
2195 bool "Trim unused exported kernel symbols" if EXPERT
2196 depends on !COMPILE_TEST
dbacb0ef
NP
2197 help
2198 The kernel and some modules make many symbols available for
2199 other modules to use via EXPORT_SYMBOL() and variants. Depending
2200 on the set of modules being selected in your kernel configuration,
2201 many of those exported symbols might never be used.
2202
2203 This option allows for unused exported symbols to be dropped from
2204 the build. In turn, this provides the compiler more opportunities
2205 (especially when using LTO) for optimizing the code and reducing
2206 binary size. This might have some security advantages as well.
2207
f1cb637e 2208 If unsure, or if you need to build out-of-tree modules, say N.
dbacb0ef 2209
1518c633
QP
2210config UNUSED_KSYMS_WHITELIST
2211 string "Whitelist of symbols to keep in ksymtab"
2212 depends on TRIM_UNUSED_KSYMS
2213 help
2214 By default, all unused exported symbols will be un-exported from the
2215 build when TRIM_UNUSED_KSYMS is selected.
2216
2217 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
2218 exported at all times, even in absence of in-tree users. The value to
2219 set here is the path to a text file containing the list of symbols,
2220 one per line. The path can be absolute, or relative to the kernel
2221 source tree.
2222
0b0de144
RD
2223endif # MODULES
2224
6c9692e2
PZ
2225config MODULES_TREE_LOOKUP
2226 def_bool y
cf68fffb 2227 depends on PERF_EVENTS || TRACING || CFI_CLANG
6c9692e2 2228
98a79d6a
RR
2229config INIT_ALL_POSSIBLE
2230 bool
2231 help
5f054e31
RR
2232 Back when each arch used to define their own cpu_online_mask and
2233 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
98a79d6a
RR
2234 with all 1s, and others with all 0s. When they were centralised,
2235 it was better to provide this option than to break all the archs
692105b8 2236 and have several arch maintainers pursuing me down dark alleys.
98a79d6a 2237
3a65dfe8 2238source "block/Kconfig"
e98c3202
AK
2239
2240config PREEMPT_NOTIFIERS
2241 bool
e260be67 2242
16295bec
SK
2243config PADATA
2244 depends on SMP
2245 bool
2246
4520c6a4
DH
2247config ASN1
2248 tristate
2249 help
2250 Build a simple ASN.1 grammar compiler that produces a bytecode output
2251 that can be interpreted by the ASN.1 stream decoder and used to
2252 inform it as to what tags are to be expected in a stream and what
2253 functions to call on what tags.
2254
6beb0009 2255source "kernel/Kconfig.locks"
e61938a9 2256
0ebeea8c
DB
2257config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2258 bool
2259
e61938a9
MD
2260config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2261 bool
1bd21c6c
DB
2262
2263# It may be useful for an architecture to override the definitions of the
7303e30e
DB
2264# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2265# and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2266# different calling convention for syscalls. They can also override the
2267# macros for not-implemented syscalls in kernel/sys_ni.c and
2268# kernel/time/posix-stubs.c. All these overrides need to be available in
2269# <asm/syscall_wrapper.h>.
1bd21c6c
DB
2270config ARCH_HAS_SYSCALL_WRAPPER
2271 def_bool n