MIPS: unexport __flush_icache_user_range
[linux-block.git] / init / Kconfig
CommitLineData
ec8f24b7 1# SPDX-License-Identifier: GPL-2.0-only
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2config DEFCONFIG_LIST
3 string
b2670eac 4 depends on !UML
face4374 5 option defconfig_list
47f38ae0 6 default "/lib/modules/$(shell,uname -r)/.config"
face4374 7 default "/etc/kernel-config"
47f38ae0 8 default "/boot/config-$(shell,uname -r)"
2a86f661 9 default "arch/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG)"
face4374 10
a4353898
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11config CC_IS_GCC
12 def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc)
13
14config GCC_VERSION
15 int
fa7295ab 16 default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC
a4353898
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17 default 0
18
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19config LD_VERSION
20 int
21 default $(shell,$(LD) --version | $(srctree)/scripts/ld-version.sh)
22
469cb737
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23config CC_IS_CLANG
24 def_bool $(success,$(CC) --version | head -n 1 | grep -q clang)
25
26config CLANG_VERSION
27 int
28 default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
29
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30config CC_CAN_LINK
31 def_bool $(success,$(srctree)/scripts/cc-can-link.sh $(CC))
32
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33config CC_HAS_ASM_GOTO
34 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
35
5cf896fb 36config TOOLS_SUPPORT_RELR
2d122942 37 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
5cf896fb 38
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39config CC_HAS_ASM_INLINE
40 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
41
b303c6df
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42config CC_HAS_WARN_MAYBE_UNINITIALIZED
43 def_bool $(cc-option,-Wmaybe-uninitialized)
44 help
45 GCC >= 4.7 supports this option.
46
47config CC_DISABLE_WARN_MAYBE_UNINITIALIZED
48 bool
49 depends on CC_HAS_WARN_MAYBE_UNINITIALIZED
50 default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9
51 help
52 GCC's -Wmaybe-uninitialized is not reliable by definition.
53 Lots of false positive warnings are produced in some cases.
54
55 If this option is enabled, -Wno-maybe-uninitialzed is passed
56 to the compiler to suppress maybe-uninitialized warnings.
57
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58config CONSTRUCTORS
59 bool
87c9366e 60 depends on !UML
b99b87f7 61
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62config IRQ_WORK
63 bool
e360adbe 64
10916706 65config BUILDTIME_TABLE_SORT
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66 bool
67
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68config THREAD_INFO_IN_TASK
69 bool
70 help
71 Select this to move thread_info off the stack into task_struct. To
72 make this work, an arch will need to remove all thread_info fields
73 except flags and fix any runtime bugs.
74
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75 One subtle change that will be needed is to use try_get_task_stack()
76 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
77
ff0cfc66 78menu "General setup"
1da177e4 79
1da177e4
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80config BROKEN
81 bool
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82
83config BROKEN_ON_SMP
84 bool
85 depends on BROKEN || !SMP
86 default y
87
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88config INIT_ENV_ARG_LIMIT
89 int
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90 default 32 if !UML
91 default 128 if UML
1da177e4 92 help
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93 Maximum of each of the number of arguments and environment
94 variables passed to init from the kernel command line.
1da177e4 95
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96config COMPILE_TEST
97 bool "Compile also drivers which will not load"
bc083a64 98 depends on !UML
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99 default n
100 help
101 Some drivers can be compiled on a different platform than they are
102 intended to be run on. Despite they cannot be loaded there (or even
103 when they load they cannot be used due to missing HW support),
104 developers still, opposing to distributors, might want to build such
105 drivers to compile-test them.
106
107 If you are a developer and want to build everything available, say Y
108 here. If you are a user/distributor, say N here to exclude useless
109 drivers to be distributed.
110
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111config UAPI_HEADER_TEST
112 bool "Compile test UAPI headers"
fcbb8461 113 depends on HEADERS_INSTALL && CC_CAN_LINK
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114 help
115 Compile test headers exported to user-space to ensure they are
116 self-contained, i.e. compilable as standalone units.
117
118 If you are a developer or tester and want to ensure the exported
119 headers are self-contained, say Y here. Otherwise, choose N.
120
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121config LOCALVERSION
122 string "Local version - append to kernel release"
123 help
124 Append an extra string to the end of your kernel version.
125 This will show up when you type uname, for example.
126 The string you set here will be appended after the contents of
127 any files with a filename matching localversion* in your
128 object and source tree, in that order. Your total string can
129 be a maximum of 64 characters.
130
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131config LOCALVERSION_AUTO
132 bool "Automatically append version information to the version string"
133 default y
ac3339ba 134 depends on !COMPILE_TEST
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135 help
136 This will try to automatically determine if the current tree is a
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137 release tree by looking for git tags that belong to the current
138 top of tree revision.
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139
140 A string of the format -gxxxxxxxx will be added to the localversion
6e5a5420 141 if a git-based tree is found. The string generated by this will be
aaebf433 142 appended after any matching localversion* files, and after the value
6e5a5420 143 set in CONFIG_LOCALVERSION.
aaebf433 144
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145 (The actual string used here is the first eight characters produced
146 by running the command:
147
148 $ git rev-parse --verify HEAD
149
150 which is done within the script "scripts/setlocalversion".)
aaebf433 151
9afb719e 152config BUILD_SALT
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153 string "Build ID Salt"
154 default ""
155 help
156 The build ID is used to link binaries and their debug info. Setting
157 this option will use the value in the calculation of the build id.
158 This is mostly useful for distributions which want to ensure the
159 build is unique between builds. It's safe to leave the default.
9afb719e 160
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161config HAVE_KERNEL_GZIP
162 bool
163
164config HAVE_KERNEL_BZIP2
165 bool
166
167config HAVE_KERNEL_LZMA
168 bool
169
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170config HAVE_KERNEL_XZ
171 bool
172
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173config HAVE_KERNEL_LZO
174 bool
175
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176config HAVE_KERNEL_LZ4
177 bool
178
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179config HAVE_KERNEL_UNCOMPRESSED
180 bool
181
30d65dbf 182choice
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183 prompt "Kernel compression mode"
184 default KERNEL_GZIP
f16466af 185 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED
2e9f3bdd 186 help
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187 The linux kernel is a kind of self-extracting executable.
188 Several compression algorithms are available, which differ
189 in efficiency, compression and decompression speed.
190 Compression speed is only relevant when building a kernel.
191 Decompression speed is relevant at each boot.
192
193 If you have any problems with bzip2 or lzma compressed
194 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
195 version of this functionality (bzip2 only), for 2.4, was
196 supplied by Christian Ludwig)
197
198 High compression options are mostly useful for users, who
199 are low on disk space (embedded systems), but for whom ram
200 size matters less.
201
202 If in doubt, select 'gzip'
203
204config KERNEL_GZIP
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205 bool "Gzip"
206 depends on HAVE_KERNEL_GZIP
207 help
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208 The old and tried gzip compression. It provides a good balance
209 between compression ratio and decompression speed.
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210
211config KERNEL_BZIP2
212 bool "Bzip2"
2e9f3bdd 213 depends on HAVE_KERNEL_BZIP2
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214 help
215 Its compression ratio and speed is intermediate.
0a4dd35c 216 Decompression speed is slowest among the choices. The kernel
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217 size is about 10% smaller with bzip2, in comparison to gzip.
218 Bzip2 uses a large amount of memory. For modern kernels you
219 will need at least 8MB RAM or more for booting.
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220
221config KERNEL_LZMA
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222 bool "LZMA"
223 depends on HAVE_KERNEL_LZMA
224 help
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225 This compression algorithm's ratio is best. Decompression speed
226 is between gzip and bzip2. Compression is slowest.
227 The kernel size is about 33% smaller with LZMA in comparison to gzip.
30d65dbf 228
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229config KERNEL_XZ
230 bool "XZ"
231 depends on HAVE_KERNEL_XZ
232 help
233 XZ uses the LZMA2 algorithm and instruction set specific
234 BCJ filters which can improve compression ratio of executable
235 code. The size of the kernel is about 30% smaller with XZ in
236 comparison to gzip. On architectures for which there is a BCJ
237 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
238 will create a few percent smaller kernel than plain LZMA.
239
240 The speed is about the same as with LZMA: The decompression
241 speed of XZ is better than that of bzip2 but worse than gzip
242 and LZO. Compression is slow.
243
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244config KERNEL_LZO
245 bool "LZO"
246 depends on HAVE_KERNEL_LZO
247 help
0a4dd35c 248 Its compression ratio is the poorest among the choices. The kernel
681b3049 249 size is about 10% bigger than gzip; however its speed
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250 (both compression and decompression) is the fastest.
251
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252config KERNEL_LZ4
253 bool "LZ4"
254 depends on HAVE_KERNEL_LZ4
255 help
256 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
257 A preliminary version of LZ4 de/compression tool is available at
258 <https://code.google.com/p/lz4/>.
259
260 Its compression ratio is worse than LZO. The size of the kernel
261 is about 8% bigger than LZO. But the decompression speed is
262 faster than LZO.
263
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264config KERNEL_UNCOMPRESSED
265 bool "None"
266 depends on HAVE_KERNEL_UNCOMPRESSED
267 help
268 Produce uncompressed kernel image. This option is usually not what
269 you want. It is useful for debugging the kernel in slow simulation
270 environments, where decompressing and moving the kernel is awfully
271 slow. This option allows early boot code to skip the decompressor
272 and jump right at uncompressed kernel image.
273
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274endchoice
275
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276config DEFAULT_HOSTNAME
277 string "Default hostname"
278 default "(none)"
279 help
280 This option determines the default system hostname before userspace
281 calls sethostname(2). The kernel traditionally uses "(none)" here,
282 but you may wish to use a different default here to make a minimal
283 system more usable with less configuration.
284
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285#
286# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
287# add proper SWAP support to them, in which case this can be remove.
288#
289config ARCH_NO_SWAP
290 bool
291
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292config SWAP
293 bool "Support for paging of anonymous memory (swap)"
17c46a6a 294 depends on MMU && BLOCK && !ARCH_NO_SWAP
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295 default y
296 help
297 This option allows you to choose whether you want to have support
92c3504e 298 for so called swap devices or swap files in your kernel that are
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299 used to provide more virtual memory than the actual RAM present
300 in your computer. If unsure say Y.
301
302config SYSVIPC
303 bool "System V IPC"
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304 ---help---
305 Inter Process Communication is a suite of library functions and
306 system calls which let processes (running programs) synchronize and
307 exchange information. It is generally considered to be a good thing,
308 and some programs won't run unless you say Y here. In particular, if
309 you want to run the DOS emulator dosemu under Linux (read the
310 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
311 you'll need to say Y here.
312
313 You can find documentation about IPC with "info ipc" and also in
314 section 6.4 of the Linux Programmer's Guide, available from
315 <http://www.tldp.org/guides.html>.
316
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317config SYSVIPC_SYSCTL
318 bool
319 depends on SYSVIPC
320 depends on SYSCTL
321 default y
322
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323config POSIX_MQUEUE
324 bool "POSIX Message Queues"
19c92399 325 depends on NET
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326 ---help---
327 POSIX variant of message queues is a part of IPC. In POSIX message
328 queues every message has a priority which decides about succession
329 of receiving it by a process. If you want to compile and run
330 programs written e.g. for Solaris with use of its POSIX message
b0e37650 331 queues (functions mq_*) say Y here.
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332
333 POSIX message queues are visible as a filesystem called 'mqueue'
334 and can be mounted somewhere if you want to do filesystem
335 operations on message queues.
336
337 If unsure, say Y.
338
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339config POSIX_MQUEUE_SYSCTL
340 bool
341 depends on POSIX_MQUEUE
342 depends on SYSCTL
343 default y
344
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345config CROSS_MEMORY_ATTACH
346 bool "Enable process_vm_readv/writev syscalls"
347 depends on MMU
348 default y
349 help
350 Enabling this option adds the system calls process_vm_readv and
351 process_vm_writev which allow a process with the correct privileges
a2a368d9 352 to directly read from or write to another process' address space.
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353 See the man page for more details.
354
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355config USELIB
356 bool "uselib syscall"
b2113a41 357 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
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358 help
359 This option enables the uselib syscall, a system call used in the
360 dynamic linker from libc5 and earlier. glibc does not use this
361 system call. If you intend to run programs built on libc5 or
362 earlier, you may need to enable this syscall. Current systems
363 running glibc can safely disable this.
364
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365config AUDIT
366 bool "Auditing support"
367 depends on NET
368 help
369 Enable auditing infrastructure that can be used with another
370 kernel subsystem, such as SELinux (which requires this for
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371 logging of avc messages output). System call auditing is included
372 on architectures which support it.
391dc69c 373
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374config HAVE_ARCH_AUDITSYSCALL
375 bool
376
391dc69c 377config AUDITSYSCALL
cb74ed27 378 def_bool y
7a017721 379 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
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380 select FSNOTIFY
381
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382source "kernel/irq/Kconfig"
383source "kernel/time/Kconfig"
87a4c375 384source "kernel/Kconfig.preempt"
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385
386menu "CPU/Task time and stats accounting"
387
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388config VIRT_CPU_ACCOUNTING
389 bool
390
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391choice
392 prompt "Cputime accounting"
393 default TICK_CPU_ACCOUNTING if !PPC64
02fc8d37 394 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
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395
396# Kind of a stub config for the pure tick based cputime accounting
397config TICK_CPU_ACCOUNTING
398 bool "Simple tick based cputime accounting"
c58b0df1 399 depends on !S390 && !NO_HZ_FULL
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400 help
401 This is the basic tick based cputime accounting that maintains
402 statistics about user, system and idle time spent on per jiffies
403 granularity.
404
405 If unsure, say Y.
406
abf917cd 407config VIRT_CPU_ACCOUNTING_NATIVE
b952741c 408 bool "Deterministic task and CPU time accounting"
c58b0df1 409 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
abf917cd 410 select VIRT_CPU_ACCOUNTING
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411 help
412 Select this option to enable more accurate task and CPU time
413 accounting. This is done by reading a CPU counter on each
414 kernel entry and exit and on transitions within the kernel
415 between system, softirq and hardirq state, so there is a
416 small performance impact. In the case of s390 or IBM POWER > 5,
417 this also enables accounting of stolen time on logically-partitioned
418 systems.
419
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420config VIRT_CPU_ACCOUNTING_GEN
421 bool "Full dynticks CPU time accounting"
ff3fb254 422 depends on HAVE_CONTEXT_TRACKING
554b0004 423 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
041a1574 424 depends on GENERIC_CLOCKEVENTS
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425 select VIRT_CPU_ACCOUNTING
426 select CONTEXT_TRACKING
427 help
428 Select this option to enable task and CPU time accounting on full
429 dynticks systems. This accounting is implemented by watching every
430 kernel-user boundaries using the context tracking subsystem.
431 The accounting is thus performed at the expense of some significant
432 overhead.
433
434 For now this is only useful if you are working on the full
435 dynticks subsystem development.
436
437 If unsure, say N.
438
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439endchoice
440
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441config IRQ_TIME_ACCOUNTING
442 bool "Fine granularity task level IRQ time accounting"
b58c3584 443 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
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444 help
445 Select this option to enable fine granularity task irq time
446 accounting. This is done by reading a timestamp on each
447 transitions between softirq and hardirq state, so there can be a
448 small performance impact.
449
450 If in doubt, say N here.
451
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452config HAVE_SCHED_AVG_IRQ
453 def_bool y
454 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
455 depends on SMP
456
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457config SCHED_THERMAL_PRESSURE
458 bool "Enable periodic averaging of thermal pressure"
459 depends on SMP
460
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461config BSD_PROCESS_ACCT
462 bool "BSD Process Accounting"
2813893f 463 depends on MULTIUSER
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464 help
465 If you say Y here, a user level program will be able to instruct the
466 kernel (via a special system call) to write process accounting
467 information to a file: whenever a process exits, information about
468 that process will be appended to the file by the kernel. The
469 information includes things such as creation time, owning user,
470 command name, memory usage, controlling terminal etc. (the complete
471 list is in the struct acct in <file:include/linux/acct.h>). It is
472 up to the user level program to do useful things with this
473 information. This is generally a good idea, so say Y.
474
475config BSD_PROCESS_ACCT_V3
476 bool "BSD Process Accounting version 3 file format"
477 depends on BSD_PROCESS_ACCT
478 default n
479 help
480 If you say Y here, the process accounting information is written
481 in a new file format that also logs the process IDs of each
3903bf94 482 process and its parent. Note that this file format is incompatible
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483 with previous v0/v1/v2 file formats, so you will need updated tools
484 for processing it. A preliminary version of these tools is available
37a4c940 485 at <http://www.gnu.org/software/acct/>.
1da177e4 486
c757249a 487config TASKSTATS
19c92399 488 bool "Export task/process statistics through netlink"
c757249a 489 depends on NET
2813893f 490 depends on MULTIUSER
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491 default n
492 help
493 Export selected statistics for tasks/processes through the
494 generic netlink interface. Unlike BSD process accounting, the
495 statistics are available during the lifetime of tasks/processes as
496 responses to commands. Like BSD accounting, they are sent to user
497 space on task exit.
498
499 Say N if unsure.
500
ca74e92b 501config TASK_DELAY_ACCT
19c92399 502 bool "Enable per-task delay accounting"
6f44993f 503 depends on TASKSTATS
f6db8347 504 select SCHED_INFO
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505 help
506 Collect information on time spent by a task waiting for system
507 resources like cpu, synchronous block I/O completion and swapping
508 in pages. Such statistics can help in setting a task's priorities
509 relative to other tasks for cpu, io, rss limits etc.
510
511 Say N if unsure.
512
18f705f4 513config TASK_XACCT
19c92399 514 bool "Enable extended accounting over taskstats"
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515 depends on TASKSTATS
516 help
517 Collect extended task accounting data and send the data
518 to userland for processing over the taskstats interface.
519
520 Say N if unsure.
521
522config TASK_IO_ACCOUNTING
19c92399 523 bool "Enable per-task storage I/O accounting"
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524 depends on TASK_XACCT
525 help
526 Collect information on the number of bytes of storage I/O which this
527 task has caused.
528
529 Say N if unsure.
530
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531config PSI
532 bool "Pressure stall information tracking"
533 help
534 Collect metrics that indicate how overcommitted the CPU, memory,
535 and IO capacity are in the system.
536
537 If you say Y here, the kernel will create /proc/pressure/ with the
538 pressure statistics files cpu, memory, and io. These will indicate
539 the share of walltime in which some or all tasks in the system are
540 delayed due to contention of the respective resource.
541
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542 In kernels with cgroup support, cgroups (cgroup2 only) will
543 have cpu.pressure, memory.pressure, and io.pressure files,
544 which aggregate pressure stalls for the grouped tasks only.
545
c3123552 546 For more details see Documentation/accounting/psi.rst.
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547
548 Say N if unsure.
549
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550config PSI_DEFAULT_DISABLED
551 bool "Require boot parameter to enable pressure stall information tracking"
552 default n
553 depends on PSI
554 help
555 If set, pressure stall information tracking will be disabled
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556 per default but can be enabled through passing psi=1 on the
557 kernel commandline during boot.
e0c27447 558
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559 This feature adds some code to the task wakeup and sleep
560 paths of the scheduler. The overhead is too low to affect
561 common scheduling-intense workloads in practice (such as
562 webservers, memcache), but it does show up in artificial
563 scheduler stress tests, such as hackbench.
564
565 If you are paranoid and not sure what the kernel will be
566 used for, say Y.
567
568 Say N if unsure.
569
391dc69c 570endmenu # "CPU/Task time and stats accounting"
d9817ebe 571
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572config CPU_ISOLATION
573 bool "CPU isolation"
414a2dc1 574 depends on SMP || COMPILE_TEST
2c43838c 575 default y
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576 help
577 Make sure that CPUs running critical tasks are not disturbed by
578 any source of "noise" such as unbound workqueues, timers, kthreads...
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579 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
580 the "isolcpus=" boot parameter.
581
582 Say Y if unsure.
5c4991e2 583
0af92d46 584source "kernel/rcu/Kconfig"
c903ff83 585
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586config BUILD_BIN2C
587 bool
588 default n
589
1da177e4 590config IKCONFIG
f2443ab6 591 tristate "Kernel .config support"
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592 ---help---
593 This option enables the complete Linux kernel ".config" file
594 contents to be saved in the kernel. It provides documentation
595 of which kernel options are used in a running kernel or in an
596 on-disk kernel. This information can be extracted from the kernel
597 image file with the script scripts/extract-ikconfig and used as
598 input to rebuild the current kernel or to build another kernel.
599 It can also be extracted from a running kernel by reading
600 /proc/config.gz if enabled (below).
601
602config IKCONFIG_PROC
603 bool "Enable access to .config through /proc/config.gz"
604 depends on IKCONFIG && PROC_FS
605 ---help---
606 This option enables access to the kernel configuration file
607 through /proc/config.gz.
608
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609config IKHEADERS
610 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
611 depends on SYSFS
612 help
613 This option enables access to the in-kernel headers that are generated during
614 the build process. These can be used to build eBPF tracing programs,
615 or similar programs. If you build the headers as a module, a module called
616 kheaders.ko is built which can be loaded on-demand to get access to headers.
43d8ce9d 617
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618config LOG_BUF_SHIFT
619 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
fb39f98d 620 range 12 25
f17a32e9 621 default 17
361e9dfb 622 depends on PRINTK
794543a2 623 help
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624 Select the minimal kernel log buffer size as a power of 2.
625 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
626 parameter, see below. Any higher size also might be forced
627 by "log_buf_len" boot parameter.
628
f17a32e9 629 Examples:
23b2899f 630 17 => 128 KB
f17a32e9 631 16 => 64 KB
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632 15 => 32 KB
633 14 => 16 KB
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634 13 => 8 KB
635 12 => 4 KB
636
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637config LOG_CPU_MAX_BUF_SHIFT
638 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
2240a31d 639 depends on SMP
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640 range 0 21
641 default 12 if !BASE_SMALL
642 default 0 if BASE_SMALL
361e9dfb 643 depends on PRINTK
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644 help
645 This option allows to increase the default ring buffer size
646 according to the number of CPUs. The value defines the contribution
647 of each CPU as a power of 2. The used space is typically only few
648 lines however it might be much more when problems are reported,
649 e.g. backtraces.
650
651 The increased size means that a new buffer has to be allocated and
652 the original static one is unused. It makes sense only on systems
653 with more CPUs. Therefore this value is used only when the sum of
654 contributions is greater than the half of the default kernel ring
655 buffer as defined by LOG_BUF_SHIFT. The default values are set
656 so that more than 64 CPUs are needed to trigger the allocation.
657
658 Also this option is ignored when "log_buf_len" kernel parameter is
659 used as it forces an exact (power of two) size of the ring buffer.
660
661 The number of possible CPUs is used for this computation ignoring
5e0d8d59
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662 hotplugging making the computation optimal for the worst case
663 scenario while allowing a simple algorithm to be used from bootup.
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664
665 Examples shift values and their meaning:
666 17 => 128 KB for each CPU
667 16 => 64 KB for each CPU
668 15 => 32 KB for each CPU
669 14 => 16 KB for each CPU
670 13 => 8 KB for each CPU
671 12 => 4 KB for each CPU
672
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673config PRINTK_SAFE_LOG_BUF_SHIFT
674 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
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675 range 10 21
676 default 13
f92bac3b 677 depends on PRINTK
427934b8 678 help
f92bac3b
SS
679 Select the size of an alternate printk per-CPU buffer where messages
680 printed from usafe contexts are temporary stored. One example would
681 be NMI messages, another one - printk recursion. The messages are
682 copied to the main log buffer in a safe context to avoid a deadlock.
683 The value defines the size as a power of 2.
427934b8 684
f92bac3b 685 Those messages are rare and limited. The largest one is when
427934b8
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686 a backtrace is printed. It usually fits into 4KB. Select
687 8KB if you want to be on the safe side.
688
689 Examples:
690 17 => 128 KB for each CPU
691 16 => 64 KB for each CPU
692 15 => 32 KB for each CPU
693 14 => 16 KB for each CPU
694 13 => 8 KB for each CPU
695 12 => 4 KB for each CPU
696
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697#
698# Architectures with an unreliable sched_clock() should select this:
699#
700config HAVE_UNSTABLE_SCHED_CLOCK
701 bool
702
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703config GENERIC_SCHED_CLOCK
704 bool
705
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706menu "Scheduler features"
707
708config UCLAMP_TASK
709 bool "Enable utilization clamping for RT/FAIR tasks"
710 depends on CPU_FREQ_GOV_SCHEDUTIL
711 help
712 This feature enables the scheduler to track the clamped utilization
713 of each CPU based on RUNNABLE tasks scheduled on that CPU.
714
715 With this option, the user can specify the min and max CPU
716 utilization allowed for RUNNABLE tasks. The max utilization defines
717 the maximum frequency a task should use while the min utilization
718 defines the minimum frequency it should use.
719
720 Both min and max utilization clamp values are hints to the scheduler,
721 aiming at improving its frequency selection policy, but they do not
722 enforce or grant any specific bandwidth for tasks.
723
724 If in doubt, say N.
725
726config UCLAMP_BUCKETS_COUNT
727 int "Number of supported utilization clamp buckets"
728 range 5 20
729 default 5
730 depends on UCLAMP_TASK
731 help
732 Defines the number of clamp buckets to use. The range of each bucket
733 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
734 number of clamp buckets the finer their granularity and the higher
735 the precision of clamping aggregation and tracking at run-time.
736
737 For example, with the minimum configuration value we will have 5
738 clamp buckets tracking 20% utilization each. A 25% boosted tasks will
739 be refcounted in the [20..39]% bucket and will set the bucket clamp
740 effective value to 25%.
741 If a second 30% boosted task should be co-scheduled on the same CPU,
742 that task will be refcounted in the same bucket of the first task and
743 it will boost the bucket clamp effective value to 30%.
744 The clamp effective value of a bucket is reset to its nominal value
745 (20% in the example above) when there are no more tasks refcounted in
746 that bucket.
747
748 An additional boost/capping margin can be added to some tasks. In the
749 example above the 25% task will be boosted to 30% until it exits the
750 CPU. If that should be considered not acceptable on certain systems,
751 it's always possible to reduce the margin by increasing the number of
752 clamp buckets to trade off used memory for run-time tracking
753 precision.
754
755 If in doubt, use the default value.
756
757endmenu
758
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759#
760# For architectures that want to enable the support for NUMA-affine scheduler
761# balancing logic:
762#
763config ARCH_SUPPORTS_NUMA_BALANCING
764 bool
765
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766#
767# For architectures that prefer to flush all TLBs after a number of pages
768# are unmapped instead of sending one IPI per page to flush. The architecture
769# must provide guarantees on what happens if a clean TLB cache entry is
770# written after the unmap. Details are in mm/rmap.c near the check for
771# should_defer_flush. The architecture should also consider if the full flush
772# and the refill costs are offset by the savings of sending fewer IPIs.
773config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
774 bool
775
c12d3362 776config CC_HAS_INT128
3a7c7331 777 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
c12d3362 778
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779#
780# For architectures that know their GCC __int128 support is sound
781#
782config ARCH_SUPPORTS_INT128
783 bool
784
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785# For architectures that (ab)use NUMA to represent different memory regions
786# all cpu-local but of different latencies, such as SuperH.
787#
788config ARCH_WANT_NUMA_VARIABLE_LOCALITY
789 bool
790
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791config NUMA_BALANCING
792 bool "Memory placement aware NUMA scheduler"
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793 depends on ARCH_SUPPORTS_NUMA_BALANCING
794 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
795 depends on SMP && NUMA && MIGRATION
796 help
797 This option adds support for automatic NUMA aware memory/task placement.
798 The mechanism is quite primitive and is based on migrating memory when
6d56a410 799 it has references to the node the task is running on.
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800
801 This system will be inactive on UMA systems.
802
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803config NUMA_BALANCING_DEFAULT_ENABLED
804 bool "Automatically enable NUMA aware memory/task placement"
805 default y
806 depends on NUMA_BALANCING
807 help
808 If set, automatic NUMA balancing will be enabled if running on a NUMA
809 machine.
810
23964d2d 811menuconfig CGROUPS
6341e62b 812 bool "Control Group support"
2bd59d48 813 select KERNFS
5cdc38f9 814 help
23964d2d 815 This option adds support for grouping sets of processes together, for
5cdc38f9
KH
816 use with process control subsystems such as Cpusets, CFS, memory
817 controls or device isolation.
818 See
d6a3b247 819 - Documentation/scheduler/sched-design-CFS.rst (CFS)
da82c92f 820 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
45ce80fb 821 and resource control)
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KH
822
823 Say N if unsure.
824
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825if CGROUPS
826
3e32cb2e 827config PAGE_COUNTER
e8cf4e9c 828 bool
3e32cb2e 829
c255a458 830config MEMCG
a0166ec4 831 bool "Memory controller"
3e32cb2e 832 select PAGE_COUNTER
79bd9814 833 select EVENTFD
00f0b825 834 help
a0166ec4 835 Provides control over the memory footprint of tasks in a cgroup.
00f0b825 836
c255a458 837config MEMCG_SWAP
a0166ec4 838 bool "Swap controller"
c255a458 839 depends on MEMCG && SWAP
c077719b 840 help
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JW
841 Provides control over the swap space consumed by tasks in a cgroup.
842
c255a458 843config MEMCG_SWAP_ENABLED
a0166ec4 844 bool "Swap controller enabled by default"
c255a458 845 depends on MEMCG_SWAP
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MH
846 default y
847 help
848 Memory Resource Controller Swap Extension comes with its price in
849 a bigger memory consumption. General purpose distribution kernels
43d547f9 850 which want to enable the feature but keep it disabled by default
07555ac1 851 and let the user enable it by swapaccount=1 boot command line
a42c390c
MH
852 parameter should have this option unselected.
853 For those who want to have the feature enabled by default should
854 select this option (if, for some reason, they need to disable it
00a66d29 855 then swapaccount=0 does the trick).
c077719b 856
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KT
857config MEMCG_KMEM
858 bool
859 depends on MEMCG && !SLOB
860 default y
861
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862config BLK_CGROUP
863 bool "IO controller"
864 depends on BLOCK
2bc64a20 865 default n
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866 ---help---
867 Generic block IO controller cgroup interface. This is the common
868 cgroup interface which should be used by various IO controlling
869 policies.
2bc64a20 870
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871 Currently, CFQ IO scheduler uses it to recognize task groups and
872 control disk bandwidth allocation (proportional time slice allocation)
873 to such task groups. It is also used by bio throttling logic in
874 block layer to implement upper limit in IO rates on a device.
e5d1367f 875
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876 This option only enables generic Block IO controller infrastructure.
877 One needs to also enable actual IO controlling logic/policy. For
878 enabling proportional weight division of disk bandwidth in CFQ, set
7baf2199 879 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
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880 CONFIG_BLK_DEV_THROTTLING=y.
881
da82c92f 882 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
6bf024e6 883
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884config CGROUP_WRITEBACK
885 bool
886 depends on MEMCG && BLK_CGROUP
887 default y
e5d1367f 888
7c941438 889menuconfig CGROUP_SCHED
a0166ec4 890 bool "CPU controller"
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DG
891 default n
892 help
893 This feature lets CPU scheduler recognize task groups and control CPU
894 bandwidth allocation to such task groups. It uses cgroups to group
895 tasks.
896
897if CGROUP_SCHED
898config FAIR_GROUP_SCHED
899 bool "Group scheduling for SCHED_OTHER"
900 depends on CGROUP_SCHED
901 default CGROUP_SCHED
902
ab84d31e
PT
903config CFS_BANDWIDTH
904 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
ab84d31e
PT
905 depends on FAIR_GROUP_SCHED
906 default n
907 help
908 This option allows users to define CPU bandwidth rates (limits) for
909 tasks running within the fair group scheduler. Groups with no limit
910 set are considered to be unconstrained and will run with no
911 restriction.
d6a3b247 912 See Documentation/scheduler/sched-bwc.rst for more information.
ab84d31e 913
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DG
914config RT_GROUP_SCHED
915 bool "Group scheduling for SCHED_RR/FIFO"
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DG
916 depends on CGROUP_SCHED
917 default n
918 help
919 This feature lets you explicitly allocate real CPU bandwidth
32bd7eb5 920 to task groups. If enabled, it will also make it impossible to
7c941438
DG
921 schedule realtime tasks for non-root users until you allocate
922 realtime bandwidth for them.
d6a3b247 923 See Documentation/scheduler/sched-rt-group.rst for more information.
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DG
924
925endif #CGROUP_SCHED
926
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PB
927config UCLAMP_TASK_GROUP
928 bool "Utilization clamping per group of tasks"
929 depends on CGROUP_SCHED
930 depends on UCLAMP_TASK
931 default n
932 help
933 This feature enables the scheduler to track the clamped utilization
934 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
935
936 When this option is enabled, the user can specify a min and max
937 CPU bandwidth which is allowed for each single task in a group.
938 The max bandwidth allows to clamp the maximum frequency a task
939 can use, while the min bandwidth allows to define a minimum
940 frequency a task will always use.
941
942 When task group based utilization clamping is enabled, an eventually
943 specified task-specific clamp value is constrained by the cgroup
944 specified clamp value. Both minimum and maximum task clamping cannot
945 be bigger than the corresponding clamping defined at task group level.
946
947 If in doubt, say N.
948
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949config CGROUP_PIDS
950 bool "PIDs controller"
951 help
952 Provides enforcement of process number limits in the scope of a
953 cgroup. Any attempt to fork more processes than is allowed in the
954 cgroup will fail. PIDs are fundamentally a global resource because it
955 is fairly trivial to reach PID exhaustion before you reach even a
956 conservative kmemcg limit. As a result, it is possible to grind a
957 system to halt without being limited by other cgroup policies. The
6cc578df 958 PIDs controller is designed to stop this from happening.
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959
960 It should be noted that organisational operations (such as attaching
98076833 961 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
6bf024e6
JW
962 since the PIDs limit only affects a process's ability to fork, not to
963 attach to a cgroup.
964
39d3e758
PP
965config CGROUP_RDMA
966 bool "RDMA controller"
967 help
968 Provides enforcement of RDMA resources defined by IB stack.
969 It is fairly easy for consumers to exhaust RDMA resources, which
970 can result into resource unavailability to other consumers.
971 RDMA controller is designed to stop this from happening.
972 Attaching processes with active RDMA resources to the cgroup
973 hierarchy is allowed even if can cross the hierarchy's limit.
974
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975config CGROUP_FREEZER
976 bool "Freezer controller"
977 help
978 Provides a way to freeze and unfreeze all tasks in a
979 cgroup.
980
489c2a20
JW
981 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
982 controller includes important in-kernel memory consumers per default.
983
984 If you're using cgroup2, say N.
985
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JW
986config CGROUP_HUGETLB
987 bool "HugeTLB controller"
988 depends on HUGETLB_PAGE
989 select PAGE_COUNTER
afc24d49 990 default n
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JW
991 help
992 Provides a cgroup controller for HugeTLB pages.
993 When you enable this, you can put a per cgroup limit on HugeTLB usage.
994 The limit is enforced during page fault. Since HugeTLB doesn't
995 support page reclaim, enforcing the limit at page fault time implies
996 that, the application will get SIGBUS signal if it tries to access
997 HugeTLB pages beyond its limit. This requires the application to know
998 beforehand how much HugeTLB pages it would require for its use. The
999 control group is tracked in the third page lru pointer. This means
1000 that we cannot use the controller with huge page less than 3 pages.
afc24d49 1001
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JW
1002config CPUSETS
1003 bool "Cpuset controller"
e1d4eeec 1004 depends on SMP
6bf024e6
JW
1005 help
1006 This option will let you create and manage CPUSETs which
1007 allow dynamically partitioning a system into sets of CPUs and
1008 Memory Nodes and assigning tasks to run only within those sets.
1009 This is primarily useful on large SMP or NUMA systems.
afc24d49 1010
6bf024e6 1011 Say N if unsure.
afc24d49 1012
6bf024e6
JW
1013config PROC_PID_CPUSET
1014 bool "Include legacy /proc/<pid>/cpuset file"
1015 depends on CPUSETS
1016 default y
afc24d49 1017
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JW
1018config CGROUP_DEVICE
1019 bool "Device controller"
1020 help
1021 Provides a cgroup controller implementing whitelists for
1022 devices which a process in the cgroup can mknod or open.
1023
1024config CGROUP_CPUACCT
1025 bool "Simple CPU accounting controller"
1026 help
1027 Provides a simple controller for monitoring the
1028 total CPU consumed by the tasks in a cgroup.
1029
1030config CGROUP_PERF
1031 bool "Perf controller"
1032 depends on PERF_EVENTS
1033 help
1034 This option extends the perf per-cpu mode to restrict monitoring
1035 to threads which belong to the cgroup specified and run on the
6546b19f
NK
1036 designated cpu. Or this can be used to have cgroup ID in samples
1037 so that it can monitor performance events among cgroups.
6bf024e6
JW
1038
1039 Say N if unsure.
1040
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DM
1041config CGROUP_BPF
1042 bool "Support for eBPF programs attached to cgroups"
483c4933
AL
1043 depends on BPF_SYSCALL
1044 select SOCK_CGROUP_DATA
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DM
1045 help
1046 Allow attaching eBPF programs to a cgroup using the bpf(2)
1047 syscall command BPF_PROG_ATTACH.
1048
1049 In which context these programs are accessed depends on the type
1050 of attachment. For instance, programs that are attached using
1051 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1052 inet sockets.
1053
6bf024e6 1054config CGROUP_DEBUG
23b0be48 1055 bool "Debug controller"
afc24d49 1056 default n
23b0be48 1057 depends on DEBUG_KERNEL
6bf024e6
JW
1058 help
1059 This option enables a simple controller that exports
23b0be48
WL
1060 debugging information about the cgroups framework. This
1061 controller is for control cgroup debugging only. Its
1062 interfaces are not stable.
afc24d49 1063
6bf024e6 1064 Say N.
89e9b9e0 1065
73b35147
AB
1066config SOCK_CGROUP_DATA
1067 bool
1068 default n
1069
23964d2d 1070endif # CGROUPS
c077719b 1071
8dd2a82c 1072menuconfig NAMESPACES
6a108a14 1073 bool "Namespaces support" if EXPERT
2813893f 1074 depends on MULTIUSER
6a108a14 1075 default !EXPERT
c5289a69
PE
1076 help
1077 Provides the way to make tasks work with different objects using
1078 the same id. For example same IPC id may refer to different objects
1079 or same user id or pid may refer to different tasks when used in
1080 different namespaces.
1081
8dd2a82c
DL
1082if NAMESPACES
1083
58bfdd6d
PE
1084config UTS_NS
1085 bool "UTS namespace"
17a6d441 1086 default y
58bfdd6d
PE
1087 help
1088 In this namespace tasks see different info provided with the
1089 uname() system call
1090
769071ac
AV
1091config TIME_NS
1092 bool "TIME namespace"
660fd04f 1093 depends on GENERIC_VDSO_TIME_NS
769071ac
AV
1094 default y
1095 help
1096 In this namespace boottime and monotonic clocks can be set.
1097 The time will keep going with the same pace.
1098
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PE
1099config IPC_NS
1100 bool "IPC namespace"
8dd2a82c 1101 depends on (SYSVIPC || POSIX_MQUEUE)
17a6d441 1102 default y
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PE
1103 help
1104 In this namespace tasks work with IPC ids which correspond to
614b84cf 1105 different IPC objects in different namespaces.
ae5e1b22 1106
aee16ce7 1107config USER_NS
19c92399 1108 bool "User namespace"
5673a94c 1109 default n
aee16ce7
PE
1110 help
1111 This allows containers, i.e. vservers, to use user namespaces
1112 to provide different user info for different servers.
e11f0ae3
EB
1113
1114 When user namespaces are enabled in the kernel it is
d886f4e4
JW
1115 recommended that the MEMCG option also be enabled and that
1116 user-space use the memory control groups to limit the amount
1117 of memory a memory unprivileged users can use.
e11f0ae3 1118
aee16ce7
PE
1119 If unsure, say N.
1120
74bd59bb 1121config PID_NS
9bd38c2c 1122 bool "PID Namespaces"
17a6d441 1123 default y
74bd59bb 1124 help
12d2b8f9 1125 Support process id namespaces. This allows having multiple
692105b8 1126 processes with the same pid as long as they are in different
74bd59bb
PE
1127 pid namespaces. This is a building block of containers.
1128
d6eb633f
MH
1129config NET_NS
1130 bool "Network namespace"
8dd2a82c 1131 depends on NET
17a6d441 1132 default y
d6eb633f
MH
1133 help
1134 Allow user space to create what appear to be multiple instances
1135 of the network stack.
1136
8dd2a82c
DL
1137endif # NAMESPACES
1138
5cb366bb
AR
1139config CHECKPOINT_RESTORE
1140 bool "Checkpoint/restore support"
1141 select PROC_CHILDREN
1142 default n
1143 help
1144 Enables additional kernel features in a sake of checkpoint/restore.
1145 In particular it adds auxiliary prctl codes to setup process text,
1146 data and heap segment sizes, and a few additional /proc filesystem
1147 entries.
1148
1149 If unsure, say N here.
1150
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MG
1151config SCHED_AUTOGROUP
1152 bool "Automatic process group scheduling"
5091faa4
MG
1153 select CGROUPS
1154 select CGROUP_SCHED
1155 select FAIR_GROUP_SCHED
1156 help
1157 This option optimizes the scheduler for common desktop workloads by
1158 automatically creating and populating task groups. This separation
1159 of workloads isolates aggressive CPU burners (like build jobs) from
1160 desktop applications. Task group autogeneration is currently based
1161 upon task session.
1162
7af37bec 1163config SYSFS_DEPRECATED
5d6a4ea5 1164 bool "Enable deprecated sysfs features to support old userspace tools"
7af37bec
DL
1165 depends on SYSFS
1166 default n
1167 help
1168 This option adds code that switches the layout of the "block" class
1169 devices, to not show up in /sys/class/block/, but only in
1170 /sys/block/.
1171
1172 This switch is only active when the sysfs.deprecated=1 boot option is
1173 passed or the SYSFS_DEPRECATED_V2 option is set.
1174
1175 This option allows new kernels to run on old distributions and tools,
1176 which might get confused by /sys/class/block/. Since 2007/2008 all
1177 major distributions and tools handle this just fine.
1178
1179 Recent distributions and userspace tools after 2009/2010 depend on
1180 the existence of /sys/class/block/, and will not work with this
1181 option enabled.
1182
1183 Only if you are using a new kernel on an old distribution, you might
1184 need to say Y here.
1185
1186config SYSFS_DEPRECATED_V2
5d6a4ea5 1187 bool "Enable deprecated sysfs features by default"
7af37bec
DL
1188 default n
1189 depends on SYSFS
1190 depends on SYSFS_DEPRECATED
1191 help
1192 Enable deprecated sysfs by default.
1193
1194 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1195 option.
1196
1197 Only if you are using a new kernel on an old distribution, you might
1198 need to say Y here. Even then, odds are you would not need it
1199 enabled, you can always pass the boot option if absolutely necessary.
1200
1201config RELAY
1202 bool "Kernel->user space relay support (formerly relayfs)"
26b5679e 1203 select IRQ_WORK
7af37bec
DL
1204 help
1205 This option enables support for relay interface support in
1206 certain file systems (such as debugfs).
1207 It is designed to provide an efficient mechanism for tools and
1208 facilities to relay large amounts of data from kernel space to
1209 user space.
1210
1211 If unsure, say N.
1212
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DG
1213config BLK_DEV_INITRD
1214 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
f991633d
DG
1215 help
1216 The initial RAM filesystem is a ramfs which is loaded by the
1217 boot loader (loadlin or lilo) and that is mounted as root
1218 before the normal boot procedure. It is typically used to
1219 load modules needed to mount the "real" root file system,
8c27ceff 1220 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
f991633d
DG
1221
1222 If RAM disk support (BLK_DEV_RAM) is also included, this
1223 also enables initial RAM disk (initrd) support and adds
1224 15 Kbytes (more on some other architectures) to the kernel size.
1225
1226 If unsure say Y.
1227
c33df4ea
JPS
1228if BLK_DEV_INITRD
1229
dbec4866
SR
1230source "usr/Kconfig"
1231
c33df4ea
JPS
1232endif
1233
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MH
1234config BOOT_CONFIG
1235 bool "Boot config support"
2910b5aa 1236 select BLK_DEV_INITRD
76db5a27
MH
1237 help
1238 Extra boot config allows system admin to pass a config file as
1239 complemental extension of kernel cmdline when booting.
0947db01 1240 The boot config file must be attached at the end of initramfs
85c46b78 1241 with checksum, size and magic word.
0947db01 1242 See <file:Documentation/admin-guide/bootconfig.rst> for details.
76db5a27
MH
1243
1244 If unsure, say Y.
1245
877417e6
AB
1246choice
1247 prompt "Compiler optimization level"
2cc3ce24 1248 default CC_OPTIMIZE_FOR_PERFORMANCE
877417e6
AB
1249
1250config CC_OPTIMIZE_FOR_PERFORMANCE
15f5db60 1251 bool "Optimize for performance (-O2)"
877417e6
AB
1252 help
1253 This is the default optimization level for the kernel, building
1254 with the "-O2" compiler flag for best performance and most
1255 helpful compile-time warnings.
1256
15f5db60
MY
1257config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1258 bool "Optimize more for performance (-O3)"
1259 depends on ARC
b303c6df 1260 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives
c45b4f1f 1261 help
15f5db60
MY
1262 Choosing this option will pass "-O3" to your compiler to optimize
1263 the kernel yet more for performance.
c45b4f1f 1264
c45b4f1f 1265config CC_OPTIMIZE_FOR_SIZE
15f5db60 1266 bool "Optimize for size (-Os)"
b303c6df 1267 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives
c45b4f1f 1268 help
ce3b487f
MY
1269 Choosing this option will pass "-Os" to your compiler resulting
1270 in a smaller kernel.
c45b4f1f 1271
877417e6
AB
1272endchoice
1273
5d20ee31
NP
1274config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1275 bool
1276 help
1277 This requires that the arch annotates or otherwise protects
1278 its external entry points from being discarded. Linker scripts
1279 must also merge .text.*, .data.*, and .bss.* correctly into
1280 output sections. Care must be taken not to pull in unrelated
1281 sections (e.g., '.text.init'). Typically '.' in section names
1282 is used to distinguish them from label names / C identifiers.
1283
1284config LD_DEAD_CODE_DATA_ELIMINATION
1285 bool "Dead code and data elimination (EXPERIMENTAL)"
1286 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1287 depends on EXPERT
16fd20aa 1288 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800)
e85d1d65
MY
1289 depends on $(cc-option,-ffunction-sections -fdata-sections)
1290 depends on $(ld-option,--gc-sections)
5d20ee31 1291 help
8b9d2712
MY
1292 Enable this if you want to do dead code and data elimination with
1293 the linker by compiling with -ffunction-sections -fdata-sections,
1294 and linking with --gc-sections.
5d20ee31
NP
1295
1296 This can reduce on disk and in-memory size of the kernel
1297 code and static data, particularly for small configs and
1298 on small systems. This has the possibility of introducing
1299 silently broken kernel if the required annotations are not
1300 present. This option is not well tested yet, so use at your
1301 own risk.
1302
0847062a
RD
1303config SYSCTL
1304 bool
1305
657a5209
MF
1306config HAVE_UID16
1307 bool
1308
1309config SYSCTL_EXCEPTION_TRACE
1310 bool
1311 help
1312 Enable support for /proc/sys/debug/exception-trace.
1313
1314config SYSCTL_ARCH_UNALIGN_NO_WARN
1315 bool
1316 help
1317 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1318 Allows arch to define/use @no_unaligned_warning to possibly warn
1319 about unaligned access emulation going on under the hood.
1320
1321config SYSCTL_ARCH_UNALIGN_ALLOW
1322 bool
1323 help
1324 Enable support for /proc/sys/kernel/unaligned-trap
1325 Allows arches to define/use @unaligned_enabled to runtime toggle
1326 the unaligned access emulation.
1327 see arch/parisc/kernel/unaligned.c for reference
1328
657a5209
MF
1329config HAVE_PCSPKR_PLATFORM
1330 bool
1331
f89b7755
AS
1332# interpreter that classic socket filters depend on
1333config BPF
1334 bool
1335
6a108a14
DR
1336menuconfig EXPERT
1337 bool "Configure standard kernel features (expert users)"
f505c553
JT
1338 # Unhide debug options, to make the on-by-default options visible
1339 select DEBUG_KERNEL
1da177e4
LT
1340 help
1341 This option allows certain base kernel options and settings
e8cf4e9c
KK
1342 to be disabled or tweaked. This is for specialized
1343 environments which can tolerate a "non-standard" kernel.
1344 Only use this if you really know what you are doing.
1da177e4 1345
ae81f9e3 1346config UID16
6a108a14 1347 bool "Enable 16-bit UID system calls" if EXPERT
2813893f 1348 depends on HAVE_UID16 && MULTIUSER
ae81f9e3
CE
1349 default y
1350 help
1351 This enables the legacy 16-bit UID syscall wrappers.
1352
2813893f
IM
1353config MULTIUSER
1354 bool "Multiple users, groups and capabilities support" if EXPERT
1355 default y
1356 help
1357 This option enables support for non-root users, groups and
1358 capabilities.
1359
1360 If you say N here, all processes will run with UID 0, GID 0, and all
1361 possible capabilities. Saying N here also compiles out support for
1362 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1363 setgid, and capset.
1364
1365 If unsure, say Y here.
1366
f6187769
FF
1367config SGETMASK_SYSCALL
1368 bool "sgetmask/ssetmask syscalls support" if EXPERT
a687a533 1369 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
f6187769
FF
1370 ---help---
1371 sys_sgetmask and sys_ssetmask are obsolete system calls
1372 no longer supported in libc but still enabled by default in some
1373 architectures.
1374
1375 If unsure, leave the default option here.
1376
6af9f7bf
FF
1377config SYSFS_SYSCALL
1378 bool "Sysfs syscall support" if EXPERT
1379 default y
1380 ---help---
1381 sys_sysfs is an obsolete system call no longer supported in libc.
1382 Note that disabling this option is more secure but might break
1383 compatibility with some systems.
1384
1385 If unsure say Y here.
1386
d1b069f5
RD
1387config FHANDLE
1388 bool "open by fhandle syscalls" if EXPERT
1389 select EXPORTFS
1390 default y
1391 help
1392 If you say Y here, a user level program will be able to map
1393 file names to handle and then later use the handle for
1394 different file system operations. This is useful in implementing
1395 userspace file servers, which now track files using handles instead
1396 of names. The handle would remain the same even if file names
1397 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1398 syscalls.
1399
baa73d9e
NP
1400config POSIX_TIMERS
1401 bool "Posix Clocks & timers" if EXPERT
1402 default y
1403 help
1404 This includes native support for POSIX timers to the kernel.
1405 Some embedded systems have no use for them and therefore they
1406 can be configured out to reduce the size of the kernel image.
1407
1408 When this option is disabled, the following syscalls won't be
1409 available: timer_create, timer_gettime: timer_getoverrun,
1410 timer_settime, timer_delete, clock_adjtime, getitimer,
1411 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1412 clock_getres and clock_nanosleep syscalls will be limited to
1413 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1414
1415 If unsure say y.
1416
d59745ce
MM
1417config PRINTK
1418 default y
6a108a14 1419 bool "Enable support for printk" if EXPERT
74876a98 1420 select IRQ_WORK
d59745ce
MM
1421 help
1422 This option enables normal printk support. Removing it
1423 eliminates most of the message strings from the kernel image
1424 and makes the kernel more or less silent. As this makes it
1425 very difficult to diagnose system problems, saying N here is
1426 strongly discouraged.
1427
42a0bb3f
PM
1428config PRINTK_NMI
1429 def_bool y
1430 depends on PRINTK
1431 depends on HAVE_NMI
1432
c8538a7a 1433config BUG
6a108a14 1434 bool "BUG() support" if EXPERT
c8538a7a
MM
1435 default y
1436 help
e8cf4e9c
KK
1437 Disabling this option eliminates support for BUG and WARN, reducing
1438 the size of your kernel image and potentially quietly ignoring
1439 numerous fatal conditions. You should only consider disabling this
1440 option for embedded systems with no facilities for reporting errors.
1441 Just say Y.
c8538a7a 1442
708e9a79 1443config ELF_CORE
046d662f 1444 depends on COREDUMP
708e9a79 1445 default y
6a108a14 1446 bool "Enable ELF core dumps" if EXPERT
708e9a79
MM
1447 help
1448 Enable support for generating core dumps. Disabling saves about 4k.
1449
8761f1ab 1450
e5e1d3cb 1451config PCSPKR_PLATFORM
6a108a14 1452 bool "Enable PC-Speaker support" if EXPERT
8761f1ab 1453 depends on HAVE_PCSPKR_PLATFORM
15f304b6 1454 select I8253_LOCK
e5e1d3cb
SS
1455 default y
1456 help
e8cf4e9c
KK
1457 This option allows to disable the internal PC-Speaker
1458 support, saving some memory.
e5e1d3cb 1459
1da177e4
LT
1460config BASE_FULL
1461 default y
6a108a14 1462 bool "Enable full-sized data structures for core" if EXPERT
1da177e4
LT
1463 help
1464 Disabling this option reduces the size of miscellaneous core
1465 kernel data structures. This saves memory on small machines,
1466 but may reduce performance.
1467
1468config FUTEX
6a108a14 1469 bool "Enable futex support" if EXPERT
1da177e4 1470 default y
bc2eecd7 1471 imply RT_MUTEXES
1da177e4
LT
1472 help
1473 Disabling this option will cause the kernel to be built without
1474 support for "fast userspace mutexes". The resulting kernel may not
1475 run glibc-based applications correctly.
1476
bc2eecd7
NP
1477config FUTEX_PI
1478 bool
1479 depends on FUTEX && RT_MUTEXES
1480 default y
1481
03b8c7b6
HC
1482config HAVE_FUTEX_CMPXCHG
1483 bool
62b4d204 1484 depends on FUTEX
03b8c7b6
HC
1485 help
1486 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1487 is implemented and always working. This removes a couple of runtime
1488 checks.
1489
1da177e4 1490config EPOLL
6a108a14 1491 bool "Enable eventpoll support" if EXPERT
1da177e4
LT
1492 default y
1493 help
1494 Disabling this option will cause the kernel to be built without
1495 support for epoll family of system calls.
1496
fba2afaa 1497config SIGNALFD
6a108a14 1498 bool "Enable signalfd() system call" if EXPERT
fba2afaa
DL
1499 default y
1500 help
1501 Enable the signalfd() system call that allows to receive signals
1502 on a file descriptor.
1503
1504 If unsure, say Y.
1505
b215e283 1506config TIMERFD
6a108a14 1507 bool "Enable timerfd() system call" if EXPERT
b215e283
DL
1508 default y
1509 help
1510 Enable the timerfd() system call that allows to receive timer
1511 events on a file descriptor.
1512
1513 If unsure, say Y.
1514
e1ad7468 1515config EVENTFD
6a108a14 1516 bool "Enable eventfd() system call" if EXPERT
e1ad7468
DL
1517 default y
1518 help
1519 Enable the eventfd() system call that allows to receive both
1520 kernel notification (ie. KAIO) or userspace notifications.
1521
1522 If unsure, say Y.
1523
1da177e4 1524config SHMEM
6a108a14 1525 bool "Use full shmem filesystem" if EXPERT
1da177e4
LT
1526 default y
1527 depends on MMU
1528 help
1529 The shmem is an internal filesystem used to manage shared memory.
1530 It is backed by swap and manages resource limits. It is also exported
1531 to userspace as tmpfs if TMPFS is enabled. Disabling this
1532 option replaces shmem and tmpfs with the much simpler ramfs code,
1533 which may be appropriate on small systems without swap.
1534
ebf3f09c 1535config AIO
6a108a14 1536 bool "Enable AIO support" if EXPERT
ebf3f09c
TP
1537 default y
1538 help
1539 This option enables POSIX asynchronous I/O which may by used
657a5209
MF
1540 by some high performance threaded applications. Disabling
1541 this option saves about 7k.
1542
2b188cc1
JA
1543config IO_URING
1544 bool "Enable IO uring support" if EXPERT
561fb04a 1545 select IO_WQ
2b188cc1
JA
1546 default y
1547 help
1548 This option enables support for the io_uring interface, enabling
1549 applications to submit and complete IO through submission and
1550 completion rings that are shared between the kernel and application.
1551
d3ac21ca
JT
1552config ADVISE_SYSCALLS
1553 bool "Enable madvise/fadvise syscalls" if EXPERT
1554 default y
1555 help
1556 This option enables the madvise and fadvise syscalls, used by
1557 applications to advise the kernel about their future memory or file
1558 usage, improving performance. If building an embedded system where no
1559 applications use these syscalls, you can disable this option to save
1560 space.
1561
5a281062
AA
1562config HAVE_ARCH_USERFAULTFD_WP
1563 bool
1564 help
1565 Arch has userfaultfd write protection support
1566
5b25b13a
MD
1567config MEMBARRIER
1568 bool "Enable membarrier() system call" if EXPERT
1569 default y
1570 help
1571 Enable the membarrier() system call that allows issuing memory
1572 barriers across all running threads, which can be used to distribute
1573 the cost of user-space memory barriers asymmetrically by transforming
1574 pairs of memory barriers into pairs consisting of membarrier() and a
1575 compiler barrier.
1576
1577 If unsure, say Y.
1578
d1b069f5 1579config KALLSYMS
e8cf4e9c
KK
1580 bool "Load all symbols for debugging/ksymoops" if EXPERT
1581 default y
1582 help
1583 Say Y here to let the kernel print out symbolic crash information and
1584 symbolic stack backtraces. This increases the size of the kernel
1585 somewhat, as all symbols have to be loaded into the kernel image.
d1b069f5
RD
1586
1587config KALLSYMS_ALL
1588 bool "Include all symbols in kallsyms"
1589 depends on DEBUG_KERNEL && KALLSYMS
1590 help
e8cf4e9c
KK
1591 Normally kallsyms only contains the symbols of functions for nicer
1592 OOPS messages and backtraces (i.e., symbols from the text and inittext
1593 sections). This is sufficient for most cases. And only in very rare
1594 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1595 names of variables from the data sections, etc).
d1b069f5 1596
e8cf4e9c
KK
1597 This option makes sure that all symbols are loaded into the kernel
1598 image (i.e., symbols from all sections) in cost of increased kernel
1599 size (depending on the kernel configuration, it may be 300KiB or
1600 something like this).
d1b069f5 1601
e8cf4e9c 1602 Say N unless you really need all symbols.
d1b069f5
RD
1603
1604config KALLSYMS_ABSOLUTE_PERCPU
1605 bool
1606 depends on KALLSYMS
1607 default X86_64 && SMP
1608
1609config KALLSYMS_BASE_RELATIVE
1610 bool
1611 depends on KALLSYMS
a687a533 1612 default !IA64
d1b069f5
RD
1613 help
1614 Instead of emitting them as absolute values in the native word size,
1615 emit the symbol references in the kallsyms table as 32-bit entries,
1616 each containing a relative value in the range [base, base + U32_MAX]
1617 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1618 an absolute value in the range [0, S32_MAX] or a relative value in the
1619 range [base, base + S32_MAX], where base is the lowest relative symbol
1620 address encountered in the image.
1621
1622 On 64-bit builds, this reduces the size of the address table by 50%,
1623 but more importantly, it results in entries whose values are build
1624 time constants, and no relocation pass is required at runtime to fix
1625 up the entries based on the runtime load address of the kernel.
1626
1627# end of the "standard kernel features (expert users)" menu
1628
1629# syscall, maps, verifier
fc611f47
KS
1630
1631config BPF_LSM
1632 bool "LSM Instrumentation with BPF"
4edf16b7 1633 depends on BPF_EVENTS
fc611f47
KS
1634 depends on BPF_SYSCALL
1635 depends on SECURITY
1636 depends on BPF_JIT
1637 help
1638 Enables instrumentation of the security hooks with eBPF programs for
1639 implementing dynamic MAC and Audit Policies.
1640
1641 If you are unsure how to answer this question, answer N.
1642
d1b069f5
RD
1643config BPF_SYSCALL
1644 bool "Enable bpf() system call"
d1b069f5 1645 select BPF
bae77c5e 1646 select IRQ_WORK
d1b069f5
RD
1647 default n
1648 help
1649 Enable the bpf() system call that allows to manipulate eBPF
1650 programs and maps via file descriptors.
1651
81c22041
DB
1652config ARCH_WANT_DEFAULT_BPF_JIT
1653 bool
1654
290af866
AS
1655config BPF_JIT_ALWAYS_ON
1656 bool "Permanently enable BPF JIT and remove BPF interpreter"
1657 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1658 help
1659 Enables BPF JIT and removes BPF interpreter to avoid
1660 speculative execution of BPF instructions by the interpreter
1661
81c22041
DB
1662config BPF_JIT_DEFAULT_ON
1663 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
1664 depends on HAVE_EBPF_JIT && BPF_JIT
1665
d1b069f5
RD
1666config USERFAULTFD
1667 bool "Enable userfaultfd() system call"
d1b069f5
RD
1668 depends on MMU
1669 help
1670 Enable the userfaultfd() system call that allows to intercept and
1671 handle page faults in userland.
1672
3ccfebed
MD
1673config ARCH_HAS_MEMBARRIER_CALLBACKS
1674 bool
1675
70216e18
MD
1676config ARCH_HAS_MEMBARRIER_SYNC_CORE
1677 bool
1678
d7822b1e
MD
1679config RSEQ
1680 bool "Enable rseq() system call" if EXPERT
1681 default y
1682 depends on HAVE_RSEQ
1683 select MEMBARRIER
1684 help
1685 Enable the restartable sequences system call. It provides a
1686 user-space cache for the current CPU number value, which
1687 speeds up getting the current CPU number from user-space,
1688 as well as an ABI to speed up user-space operations on
1689 per-CPU data.
1690
1691 If unsure, say Y.
1692
1693config DEBUG_RSEQ
1694 default n
1695 bool "Enabled debugging of rseq() system call" if EXPERT
1696 depends on RSEQ && DEBUG_KERNEL
1697 help
1698 Enable extra debugging checks for the rseq system call.
1699
1700 If unsure, say N.
1701
6befe5f6
RD
1702config EMBEDDED
1703 bool "Embedded system"
5d2acfc7 1704 option allnoconfig_y
6befe5f6
RD
1705 select EXPERT
1706 help
1707 This option should be enabled if compiling the kernel for
1708 an embedded system so certain expert options are available
1709 for configuration.
1710
cdd6c482 1711config HAVE_PERF_EVENTS
0793a61d 1712 bool
018df72d
MF
1713 help
1714 See tools/perf/design.txt for details.
0793a61d 1715
906010b2
PZ
1716config PERF_USE_VMALLOC
1717 bool
1718 help
1719 See tools/perf/design.txt for details
1720
ad90a3de 1721config PC104
424529fb 1722 bool "PC/104 support" if EXPERT
ad90a3de
WBG
1723 help
1724 Expose PC/104 form factor device drivers and options available for
1725 selection and configuration. Enable this option if your target
1726 machine has a PC/104 bus.
1727
57c0c15b 1728menu "Kernel Performance Events And Counters"
0793a61d 1729
cdd6c482 1730config PERF_EVENTS
57c0c15b 1731 bool "Kernel performance events and counters"
392d65a9 1732 default y if PROFILING
cdd6c482 1733 depends on HAVE_PERF_EVENTS
e360adbe 1734 select IRQ_WORK
83fe27ea 1735 select SRCU
0793a61d 1736 help
57c0c15b
IM
1737 Enable kernel support for various performance events provided
1738 by software and hardware.
0793a61d 1739
dd77038d 1740 Software events are supported either built-in or via the
57c0c15b 1741 use of generic tracepoints.
0793a61d 1742
57c0c15b
IM
1743 Most modern CPUs support performance events via performance
1744 counter registers. These registers count the number of certain
0793a61d
TG
1745 types of hw events: such as instructions executed, cachemisses
1746 suffered, or branches mis-predicted - without slowing down the
1747 kernel or applications. These registers can also trigger interrupts
1748 when a threshold number of events have passed - and can thus be
1749 used to profile the code that runs on that CPU.
1750
57c0c15b 1751 The Linux Performance Event subsystem provides an abstraction of
dd77038d 1752 these software and hardware event capabilities, available via a
57c0c15b 1753 system call and used by the "perf" utility in tools/perf/. It
0793a61d
TG
1754 provides per task and per CPU counters, and it provides event
1755 capabilities on top of those.
1756
1757 Say Y if unsure.
1758
906010b2
PZ
1759config DEBUG_PERF_USE_VMALLOC
1760 default n
1761 bool "Debug: use vmalloc to back perf mmap() buffers"
cb307113 1762 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
906010b2
PZ
1763 select PERF_USE_VMALLOC
1764 help
e8cf4e9c 1765 Use vmalloc memory to back perf mmap() buffers.
906010b2 1766
e8cf4e9c
KK
1767 Mostly useful for debugging the vmalloc code on platforms
1768 that don't require it.
906010b2 1769
e8cf4e9c 1770 Say N if unsure.
906010b2 1771
0793a61d
TG
1772endmenu
1773
f8891e5e
CL
1774config VM_EVENT_COUNTERS
1775 default y
6a108a14 1776 bool "Enable VM event counters for /proc/vmstat" if EXPERT
f8891e5e 1777 help
2aea4fb6
PJ
1778 VM event counters are needed for event counts to be shown.
1779 This option allows the disabling of the VM event counters
6a108a14 1780 on EXPERT systems. /proc/vmstat will only show page counts
2aea4fb6 1781 if VM event counters are disabled.
f8891e5e 1782
41ecc55b
CL
1783config SLUB_DEBUG
1784 default y
6a108a14 1785 bool "Enable SLUB debugging support" if EXPERT
f6acb635 1786 depends on SLUB && SYSFS
41ecc55b
CL
1787 help
1788 SLUB has extensive debug support features. Disabling these can
1789 result in significant savings in code size. This also disables
1790 SLUB sysfs support. /sys/slab will not exist and there will be
1791 no support for cache validation etc.
1792
1663f26d
TH
1793config SLUB_MEMCG_SYSFS_ON
1794 default n
1795 bool "Enable memcg SLUB sysfs support by default" if EXPERT
1796 depends on SLUB && SYSFS && MEMCG
1797 help
1798 SLUB creates a directory under /sys/kernel/slab for each
1799 allocation cache to host info and debug files. If memory
1800 cgroup is enabled, each cache can have per memory cgroup
1801 caches. SLUB can create the same sysfs directories for these
1802 caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1803 to a very high number of debug files being created. This is
1804 controlled by slub_memcg_sysfs boot parameter and this
1805 config option determines the parameter's default value.
1806
b943c460
RD
1807config COMPAT_BRK
1808 bool "Disable heap randomization"
1809 default y
1810 help
1811 Randomizing heap placement makes heap exploits harder, but it
1812 also breaks ancient binaries (including anything libc5 based).
1813 This option changes the bootup default to heap randomization
692105b8 1814 disabled, and can be overridden at runtime by setting
b943c460
RD
1815 /proc/sys/kernel/randomize_va_space to 2.
1816
1817 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1818
81819f0f
CL
1819choice
1820 prompt "Choose SLAB allocator"
a0acd820 1821 default SLUB
81819f0f
CL
1822 help
1823 This option allows to select a slab allocator.
1824
1825config SLAB
1826 bool "SLAB"
04385fc5 1827 select HAVE_HARDENED_USERCOPY_ALLOCATOR
81819f0f
CL
1828 help
1829 The regular slab allocator that is established and known to work
34013886 1830 well in all environments. It organizes cache hot objects in
02f56210 1831 per cpu and per node queues.
81819f0f
CL
1832
1833config SLUB
81819f0f 1834 bool "SLUB (Unqueued Allocator)"
ed18adc1 1835 select HAVE_HARDENED_USERCOPY_ALLOCATOR
81819f0f
CL
1836 help
1837 SLUB is a slab allocator that minimizes cache line usage
1838 instead of managing queues of cached objects (SLAB approach).
1839 Per cpu caching is realized using slabs of objects instead
1840 of queues of objects. SLUB can use memory efficiently
02f56210
SA
1841 and has enhanced diagnostics. SLUB is the default choice for
1842 a slab allocator.
81819f0f
CL
1843
1844config SLOB
6a108a14 1845 depends on EXPERT
81819f0f
CL
1846 bool "SLOB (Simple Allocator)"
1847 help
37291458
MM
1848 SLOB replaces the stock allocator with a drastically simpler
1849 allocator. SLOB is generally more space efficient but
1850 does not perform as well on large systems.
81819f0f
CL
1851
1852endchoice
1853
7660a6fd
KC
1854config SLAB_MERGE_DEFAULT
1855 bool "Allow slab caches to be merged"
1856 default y
1857 help
1858 For reduced kernel memory fragmentation, slab caches can be
1859 merged when they share the same size and other characteristics.
1860 This carries a risk of kernel heap overflows being able to
1861 overwrite objects from merged caches (and more easily control
1862 cache layout), which makes such heap attacks easier to exploit
1863 by attackers. By keeping caches unmerged, these kinds of exploits
1864 can usually only damage objects in the same cache. To disable
1865 merging at runtime, "slab_nomerge" can be passed on the kernel
1866 command line.
1867
c7ce4f60
TG
1868config SLAB_FREELIST_RANDOM
1869 default n
210e7a43 1870 depends on SLAB || SLUB
c7ce4f60
TG
1871 bool "SLAB freelist randomization"
1872 help
210e7a43 1873 Randomizes the freelist order used on creating new pages. This
c7ce4f60
TG
1874 security feature reduces the predictability of the kernel slab
1875 allocator against heap overflows.
1876
2482ddec
KC
1877config SLAB_FREELIST_HARDENED
1878 bool "Harden slab freelist metadata"
1879 depends on SLUB
1880 help
1881 Many kernel heap attacks try to target slab cache metadata and
1882 other infrastructure. This options makes minor performance
92bae787 1883 sacrifices to harden the kernel slab allocator against common
2482ddec
KC
1884 freelist exploit methods.
1885
e900a918
DW
1886config SHUFFLE_PAGE_ALLOCATOR
1887 bool "Page allocator randomization"
1888 default SLAB_FREELIST_RANDOM && ACPI_NUMA
1889 help
1890 Randomization of the page allocator improves the average
1891 utilization of a direct-mapped memory-side-cache. See section
1892 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1893 6.2a specification for an example of how a platform advertises
1894 the presence of a memory-side-cache. There are also incidental
1895 security benefits as it reduces the predictability of page
1896 allocations to compliment SLAB_FREELIST_RANDOM, but the
1897 default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1898 10th order of pages is selected based on cache utilization
1899 benefits on x86.
1900
1901 While the randomization improves cache utilization it may
1902 negatively impact workloads on platforms without a cache. For
1903 this reason, by default, the randomization is enabled only
1904 after runtime detection of a direct-mapped memory-side-cache.
1905 Otherwise, the randomization may be force enabled with the
1906 'page_alloc.shuffle' kernel command line parameter.
1907
1908 Say Y if unsure.
1909
345c905d
JK
1910config SLUB_CPU_PARTIAL
1911 default y
b39ffbf8 1912 depends on SLUB && SMP
345c905d
JK
1913 bool "SLUB per cpu partial cache"
1914 help
92bae787 1915 Per cpu partial caches accelerate objects allocation and freeing
345c905d
JK
1916 that is local to a processor at the price of more indeterminism
1917 in the latency of the free. On overflow these caches will be cleared
1918 which requires the taking of locks that may cause latency spikes.
1919 Typically one would choose no for a realtime system.
1920
ea637639
JZ
1921config MMAP_ALLOW_UNINITIALIZED
1922 bool "Allow mmapped anonymous memory to be uninitialized"
6a108a14 1923 depends on EXPERT && !MMU
ea637639
JZ
1924 default n
1925 help
1926 Normally, and according to the Linux spec, anonymous memory obtained
3903bf94 1927 from mmap() has its contents cleared before it is passed to
ea637639
JZ
1928 userspace. Enabling this config option allows you to request that
1929 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1930 providing a huge performance boost. If this option is not enabled,
1931 then the flag will be ignored.
1932
1933 This is taken advantage of by uClibc's malloc(), and also by
1934 ELF-FDPIC binfmt's brk and stack allocator.
1935
1936 Because of the obvious security issues, this option should only be
1937 enabled on embedded devices where you control what is run in
1938 userspace. Since that isn't generally a problem on no-MMU systems,
1939 it is normally safe to say Y here.
1940
1941 See Documentation/nommu-mmap.txt for more information.
1942
091f6e26
DH
1943config SYSTEM_DATA_VERIFICATION
1944 def_bool n
1945 select SYSTEM_TRUSTED_KEYRING
1946 select KEYS
1947 select CRYPTO
d43de6c7 1948 select CRYPTO_RSA
091f6e26
DH
1949 select ASYMMETRIC_KEY_TYPE
1950 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
091f6e26
DH
1951 select ASN1
1952 select OID_REGISTRY
1953 select X509_CERTIFICATE_PARSER
1954 select PKCS7_MESSAGE_PARSER
82c04ff8 1955 help
091f6e26
DH
1956 Provide PKCS#7 message verification using the contents of the system
1957 trusted keyring to provide public keys. This then can be used for
1958 module verification, kexec image verification and firmware blob
1959 verification.
82c04ff8 1960
125e5645 1961config PROFILING
b309a294 1962 bool "Profiling support"
125e5645
MD
1963 help
1964 Say Y here to enable the extended profiling support mechanisms used
1965 by profilers such as OProfile.
1966
5f87f112
IM
1967#
1968# Place an empty function call at each tracepoint site. Can be
1969# dynamically changed for a probe function.
1970#
97e1c18e 1971config TRACEPOINTS
5f87f112 1972 bool
97e1c18e 1973
1da177e4
LT
1974endmenu # General setup
1975
1572497c
CH
1976source "arch/Kconfig"
1977
ae81f9e3 1978config RT_MUTEXES
6341e62b 1979 bool
ae81f9e3 1980
1da177e4
LT
1981config BASE_SMALL
1982 int
1983 default 0 if BASE_FULL
1984 default 1 if !BASE_FULL
1985
c8424e77
TJB
1986config MODULE_SIG_FORMAT
1987 def_bool n
1988 select SYSTEM_DATA_VERIFICATION
1989
66da5733 1990menuconfig MODULES
1da177e4 1991 bool "Enable loadable module support"
11097a03 1992 option modules
1da177e4
LT
1993 help
1994 Kernel modules are small pieces of compiled code which can
1995 be inserted in the running kernel, rather than being
1996 permanently built into the kernel. You use the "modprobe"
1997 tool to add (and sometimes remove) them. If you say Y here,
1998 many parts of the kernel can be built as modules (by
1999 answering M instead of Y where indicated): this is most
2000 useful for infrequently used options which are not required
2001 for booting. For more information, see the man pages for
2002 modprobe, lsmod, modinfo, insmod and rmmod.
2003
2004 If you say Y here, you will need to run "make
2005 modules_install" to put the modules under /lib/modules/
2006 where modprobe can find them (you may need to be root to do
2007 this).
2008
2009 If unsure, say Y.
2010
0b0de144
RD
2011if MODULES
2012
826e4506
LT
2013config MODULE_FORCE_LOAD
2014 bool "Forced module loading"
826e4506
LT
2015 default n
2016 help
91e37a79
RR
2017 Allow loading of modules without version information (ie. modprobe
2018 --force). Forced module loading sets the 'F' (forced) taint flag and
2019 is usually a really bad idea.
826e4506 2020
1da177e4
LT
2021config MODULE_UNLOAD
2022 bool "Module unloading"
1da177e4
LT
2023 help
2024 Without this option you will not be able to unload any
2025 modules (note that some modules may not be unloadable
f7f5b675
DV
2026 anyway), which makes your kernel smaller, faster
2027 and simpler. If unsure, say Y.
1da177e4
LT
2028
2029config MODULE_FORCE_UNLOAD
2030 bool "Forced module unloading"
19c92399 2031 depends on MODULE_UNLOAD
1da177e4
LT
2032 help
2033 This option allows you to force a module to unload, even if the
2034 kernel believes it is unsafe: the kernel will remove the module
2035 without waiting for anyone to stop using it (using the -f option to
2036 rmmod). This is mainly for kernel developers and desperate users.
2037 If unsure, say N.
2038
1da177e4 2039config MODVERSIONS
0d541643 2040 bool "Module versioning support"
1da177e4
LT
2041 help
2042 Usually, you have to use modules compiled with your kernel.
2043 Saying Y here makes it sometimes possible to use modules
2044 compiled for different kernels, by adding enough information
2045 to the modules to (hopefully) spot any changes which would
2046 make them incompatible with the kernel you are running. If
2047 unsure, say N.
2048
2ff2b7ec
MY
2049config ASM_MODVERSIONS
2050 bool
2051 default HAVE_ASM_MODVERSIONS && MODVERSIONS
2052 help
2053 This enables module versioning for exported symbols also from
2054 assembly. This can be enabled only when the target architecture
2055 supports it.
2056
56067812
AB
2057config MODULE_REL_CRCS
2058 bool
2059 depends on MODVERSIONS
2060
1da177e4
LT
2061config MODULE_SRCVERSION_ALL
2062 bool "Source checksum for all modules"
1da177e4
LT
2063 help
2064 Modules which contain a MODULE_VERSION get an extra "srcversion"
2065 field inserted into their modinfo section, which contains a
2066 sum of the source files which made it. This helps maintainers
2067 see exactly which source was used to build a module (since
2068 others sometimes change the module source without updating
2069 the version). With this option, such a "srcversion" field
2070 will be created for all modules. If unsure, say N.
2071
106a4ee2
RR
2072config MODULE_SIG
2073 bool "Module signature verification"
c8424e77 2074 select MODULE_SIG_FORMAT
106a4ee2
RR
2075 help
2076 Check modules for valid signatures upon load: the signature
2077 is simply appended to the module. For more information see
cbdc8217 2078 <file:Documentation/admin-guide/module-signing.rst>.
106a4ee2 2079
228c37ff
DH
2080 Note that this option adds the OpenSSL development packages as a
2081 kernel build dependency so that the signing tool can use its crypto
2082 library.
2083
49fcf732
DH
2084 You should enable this option if you wish to use either
2085 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2086 another LSM - otherwise unsigned modules will be loadable regardless
2087 of the lockdown policy.
2088
ea0b6dcf
DH
2089 !!!WARNING!!! If you enable this option, you MUST make sure that the
2090 module DOES NOT get stripped after being signed. This includes the
2091 debuginfo strip done by some packagers (such as rpmbuild) and
2092 inclusion into an initramfs that wants the module size reduced.
2093
106a4ee2
RR
2094config MODULE_SIG_FORCE
2095 bool "Require modules to be validly signed"
2096 depends on MODULE_SIG
2097 help
2098 Reject unsigned modules or signed modules for which we don't have a
2099 key. Without this, such modules will simply taint the kernel.
ea0b6dcf 2100
d9d8d7ed
MM
2101config MODULE_SIG_ALL
2102 bool "Automatically sign all modules"
2103 default y
2104 depends on MODULE_SIG
2105 help
2106 Sign all modules during make modules_install. Without this option,
2107 modules must be signed manually, using the scripts/sign-file tool.
2108
2109comment "Do not forget to sign required modules with scripts/sign-file"
2110 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2111
ea0b6dcf
DH
2112choice
2113 prompt "Which hash algorithm should modules be signed with?"
2114 depends on MODULE_SIG
2115 help
2116 This determines which sort of hashing algorithm will be used during
2117 signature generation. This algorithm _must_ be built into the kernel
2118 directly so that signature verification can take place. It is not
2119 possible to load a signed module containing the algorithm to check
2120 the signature on that module.
2121
2122config MODULE_SIG_SHA1
2123 bool "Sign modules with SHA-1"
2124 select CRYPTO_SHA1
2125
2126config MODULE_SIG_SHA224
2127 bool "Sign modules with SHA-224"
2128 select CRYPTO_SHA256
2129
2130config MODULE_SIG_SHA256
2131 bool "Sign modules with SHA-256"
2132 select CRYPTO_SHA256
2133
2134config MODULE_SIG_SHA384
2135 bool "Sign modules with SHA-384"
2136 select CRYPTO_SHA512
2137
2138config MODULE_SIG_SHA512
2139 bool "Sign modules with SHA-512"
2140 select CRYPTO_SHA512
2141
2142endchoice
2143
22753674
MM
2144config MODULE_SIG_HASH
2145 string
2146 depends on MODULE_SIG
2147 default "sha1" if MODULE_SIG_SHA1
2148 default "sha224" if MODULE_SIG_SHA224
2149 default "sha256" if MODULE_SIG_SHA256
2150 default "sha384" if MODULE_SIG_SHA384
2151 default "sha512" if MODULE_SIG_SHA512
2152
beb50df3
BJ
2153config MODULE_COMPRESS
2154 bool "Compress modules on installation"
beb50df3 2155 help
beb50df3 2156
b6c09b51
RR
2157 Compresses kernel modules when 'make modules_install' is run; gzip or
2158 xz depending on "Compression algorithm" below.
beb50df3 2159
b6c09b51 2160 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
beb50df3 2161
b6c09b51
RR
2162 Out-of-tree kernel modules installed using Kbuild will also be
2163 compressed upon installation.
beb50df3 2164
b6c09b51
RR
2165 Note: for modules inside an initrd or initramfs, it's more efficient
2166 to compress the whole initrd or initramfs instead.
beb50df3 2167
b6c09b51
RR
2168 Note: This is fully compatible with signed modules.
2169
2170 If in doubt, say N.
beb50df3
BJ
2171
2172choice
2173 prompt "Compression algorithm"
2174 depends on MODULE_COMPRESS
2175 default MODULE_COMPRESS_GZIP
2176 help
2177 This determines which sort of compression will be used during
2178 'make modules_install'.
2179
2180 GZIP (default) and XZ are supported.
2181
2182config MODULE_COMPRESS_GZIP
2183 bool "GZIP"
2184
2185config MODULE_COMPRESS_XZ
2186 bool "XZ"
2187
2188endchoice
2189
3d52ec5e
MM
2190config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2191 bool "Allow loading of modules with missing namespace imports"
2192 help
2193 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2194 a namespace. A module that makes use of a symbol exported with such a
2195 namespace is required to import the namespace via MODULE_IMPORT_NS().
2196 There is no technical reason to enforce correct namespace imports,
2197 but it creates consistency between symbols defining namespaces and
2198 users importing namespaces they make use of. This option relaxes this
2199 requirement and lifts the enforcement when loading a module.
2200
2201 If unsure, say N.
2202
efd9763d
MY
2203config UNUSED_SYMBOLS
2204 bool "Enable unused/obsolete exported symbols"
2205 default y if X86
2206 help
2207 Unused but exported symbols make the kernel needlessly bigger. For
2208 that reason most of these unused exports will soon be removed. This
2209 option is provided temporarily to provide a transition period in case
2210 some external kernel module needs one of these symbols anyway. If you
2211 encounter such a case in your module, consider if you are actually
2212 using the right API. (rationale: since nobody in the kernel is using
2213 this in a module, there is a pretty good chance it's actually the
2214 wrong interface to use). If you really need the symbol, please send a
2215 mail to the linux kernel mailing list mentioning the symbol and why
2216 you really need it, and what the merge plan to the mainline kernel for
2217 your module is.
2218
dbacb0ef
NP
2219config TRIM_UNUSED_KSYMS
2220 bool "Trim unused exported kernel symbols"
d189c2a4 2221 depends on !UNUSED_SYMBOLS
dbacb0ef
NP
2222 help
2223 The kernel and some modules make many symbols available for
2224 other modules to use via EXPORT_SYMBOL() and variants. Depending
2225 on the set of modules being selected in your kernel configuration,
2226 many of those exported symbols might never be used.
2227
2228 This option allows for unused exported symbols to be dropped from
2229 the build. In turn, this provides the compiler more opportunities
2230 (especially when using LTO) for optimizing the code and reducing
2231 binary size. This might have some security advantages as well.
2232
f1cb637e 2233 If unsure, or if you need to build out-of-tree modules, say N.
dbacb0ef 2234
1518c633
QP
2235config UNUSED_KSYMS_WHITELIST
2236 string "Whitelist of symbols to keep in ksymtab"
2237 depends on TRIM_UNUSED_KSYMS
2238 help
2239 By default, all unused exported symbols will be un-exported from the
2240 build when TRIM_UNUSED_KSYMS is selected.
2241
2242 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
2243 exported at all times, even in absence of in-tree users. The value to
2244 set here is the path to a text file containing the list of symbols,
2245 one per line. The path can be absolute, or relative to the kernel
2246 source tree.
2247
0b0de144
RD
2248endif # MODULES
2249
6c9692e2
PZ
2250config MODULES_TREE_LOOKUP
2251 def_bool y
2252 depends on PERF_EVENTS || TRACING
2253
98a79d6a
RR
2254config INIT_ALL_POSSIBLE
2255 bool
2256 help
5f054e31
RR
2257 Back when each arch used to define their own cpu_online_mask and
2258 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
98a79d6a
RR
2259 with all 1s, and others with all 0s. When they were centralised,
2260 it was better to provide this option than to break all the archs
692105b8 2261 and have several arch maintainers pursuing me down dark alleys.
98a79d6a 2262
3a65dfe8 2263source "block/Kconfig"
e98c3202
AK
2264
2265config PREEMPT_NOTIFIERS
2266 bool
e260be67 2267
16295bec
SK
2268config PADATA
2269 depends on SMP
2270 bool
2271
4520c6a4
DH
2272config ASN1
2273 tristate
2274 help
2275 Build a simple ASN.1 grammar compiler that produces a bytecode output
2276 that can be interpreted by the ASN.1 stream decoder and used to
2277 inform it as to what tags are to be expected in a stream and what
2278 functions to call on what tags.
2279
6beb0009 2280source "kernel/Kconfig.locks"
e61938a9
MD
2281
2282config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2283 bool
1bd21c6c
DB
2284
2285# It may be useful for an architecture to override the definitions of the
7303e30e
DB
2286# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2287# and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2288# different calling convention for syscalls. They can also override the
2289# macros for not-implemented syscalls in kernel/sys_ni.c and
2290# kernel/time/posix-stubs.c. All these overrides need to be available in
2291# <asm/syscall_wrapper.h>.
1bd21c6c
DB
2292config ARCH_HAS_SYSCALL_WRAPPER
2293 def_bool n