Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1# SPDX-License-Identifier: GPL-2.0-only
2config CC_VERSION_TEXT
3 string
4 default "$(CC_VERSION_TEXT)"
5 help
6 This is used in unclear ways:
7
8 - Re-run Kconfig when the compiler is updated
9 The 'default' property references the environment variable,
10 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd.
11 When the compiler is updated, Kconfig will be invoked.
12
13 - Ensure full rebuild when the compiler is updated
14 include/linux/compiler-version.h contains this option in the comment
15 line so fixdep adds include/config/CC_VERSION_TEXT into the
16 auto-generated dependency. When the compiler is updated, syncconfig
17 will touch it and then every file will be rebuilt.
18
19config CC_IS_GCC
20 def_bool $(success,test "$(cc-name)" = GCC)
21
22config GCC_VERSION
23 int
24 default $(cc-version) if CC_IS_GCC
25 default 0
26
27config CC_IS_CLANG
28 def_bool $(success,test "$(cc-name)" = Clang)
29
30config CLANG_VERSION
31 int
32 default $(cc-version) if CC_IS_CLANG
33 default 0
34
35config AS_IS_GNU
36 def_bool $(success,test "$(as-name)" = GNU)
37
38config AS_IS_LLVM
39 def_bool $(success,test "$(as-name)" = LLVM)
40
41config AS_VERSION
42 int
43 # Use clang version if this is the integrated assembler
44 default CLANG_VERSION if AS_IS_LLVM
45 default $(as-version)
46
47config LD_IS_BFD
48 def_bool $(success,test "$(ld-name)" = BFD)
49
50config LD_VERSION
51 int
52 default $(ld-version) if LD_IS_BFD
53 default 0
54
55config LD_IS_LLD
56 def_bool $(success,test "$(ld-name)" = LLD)
57
58config LLD_VERSION
59 int
60 default $(ld-version) if LD_IS_LLD
61 default 0
62
63config RUSTC_VERSION
64 int
65 default $(rustc-version)
66 help
67 It does not depend on `RUST` since that one may need to use the version
68 in a `depends on`.
69
70config RUST_IS_AVAILABLE
71 def_bool $(success,$(srctree)/scripts/rust_is_available.sh)
72 help
73 This shows whether a suitable Rust toolchain is available (found).
74
75 Please see Documentation/rust/quick-start.rst for instructions on how
76 to satisfy the build requirements of Rust support.
77
78 In particular, the Makefile target 'rustavailable' is useful to check
79 why the Rust toolchain is not being detected.
80
81config RUSTC_LLVM_VERSION
82 int
83 default $(rustc-llvm-version)
84
85config RUSTC_LLVM_MAJOR_VERSION
86 int
87 default $(shell,expr $(rustc-llvm-version) / 10000)
88
89config RUSTC_CLANG_LLVM_COMPATIBLE
90 bool
91 default y if CC_IS_CLANG && RUSTC_LLVM_MAJOR_VERSION = $(shell,expr $(cc-version) / 10000)
92 help
93 This indicates whether Rust and Clang use LLVM of the same major
94 version.
95
96 Operations involving handling LLVM IR or bitcode (e.g. cross-language
97 LTO) require the same LLVM major version to work properly. For best
98 compatibility it is recommended that the exact same LLVM is used.
99
100config ARCH_HAS_CC_CAN_LINK
101 bool
102
103config CC_CAN_LINK
104 bool
105 default ARCH_CC_CAN_LINK if ARCH_HAS_CC_CAN_LINK
106 default $(cc_can_link_user,$(m64-flag)) if 64BIT
107 default $(cc_can_link_user,$(m32-flag))
108
109# Fixed in GCC 14, 13.3, 12.4 and 11.5
110# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113921
111config GCC_ASM_GOTO_OUTPUT_BROKEN
112 bool
113 depends on CC_IS_GCC
114 default y if GCC_VERSION < 110500
115 default y if GCC_VERSION >= 120000 && GCC_VERSION < 120400
116 default y if GCC_VERSION >= 130000 && GCC_VERSION < 130300
117
118config CC_HAS_ASM_GOTO_OUTPUT
119 def_bool y
120 depends on !GCC_ASM_GOTO_OUTPUT_BROKEN
121 # Detect basic support
122 depends on $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null)
123 # Detect clang (< v17) scoped label issues
124 depends on $(success,echo 'void b(void **);void* c(void);int f(void){{asm goto(""::::l0);return 0;l0:return 1;}void *x __attribute__((cleanup(b)))=c();{asm goto(""::::l1);return 2;l1:return 3;}}' | $(CC) -x c - -c -o /dev/null)
125
126config CC_HAS_ASM_GOTO_TIED_OUTPUT
127 depends on CC_HAS_ASM_GOTO_OUTPUT
128 # Detect buggy gcc and clang, fixed in gcc-11 clang-14.
129 def_bool $(success,echo 'int foo(int *x) { asm goto (".long (%l[bar]) - .": "+m"(*x) ::: bar); return *x; bar: return 0; }' | $CC -x c - -c -o /dev/null)
130
131config TOOLS_SUPPORT_RELR
132 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
133
134config CC_HAS_ASM_INLINE
135 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
136
137config CC_HAS_ASSUME
138 bool
139 # clang needs to be at least 19.1.0 since the meaning of the assume
140 # attribute changed:
141 # https://github.com/llvm/llvm-project/commit/c44fa3e8a9a44c2e9a575768a3c185354b9f6c17
142 default y if CC_IS_CLANG && CLANG_VERSION >= 190100
143 # supported since gcc 13.1.0
144 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106654
145 default y if CC_IS_GCC && GCC_VERSION >= 130100
146
147config CC_HAS_NO_PROFILE_FN_ATTR
148 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
149
150config CC_HAS_COUNTED_BY
151 bool
152 # clang needs to be at least 20.1.0 to avoid potential crashes
153 # when building structures that contain __counted_by
154 # https://github.com/ClangBuiltLinux/linux/issues/2114
155 # https://github.com/llvm/llvm-project/commit/160fb1121cdf703c3ef5e61fb26c5659eb581489
156 default y if CC_IS_CLANG && CLANG_VERSION >= 200100
157 # supported since gcc 15.1.0
158 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108896
159 default y if CC_IS_GCC && GCC_VERSION >= 150100
160
161config CC_HAS_COUNTED_BY_PTR
162 bool
163 # supported since clang 22
164 default y if CC_IS_CLANG && CLANG_VERSION >= 220100
165 # supported since gcc 16.0.0
166 default y if CC_IS_GCC && GCC_VERSION >= 160000
167
168config CC_HAS_BROKEN_COUNTED_BY_REF
169 bool
170 # https://github.com/llvm/llvm-project/issues/182575
171 default y if CC_IS_CLANG && CLANG_VERSION < 220100
172
173config CC_HAS_MULTIDIMENSIONAL_NONSTRING
174 def_bool $(success,echo 'char tag[][4] __attribute__((__nonstring__)) = { };' | $(CC) $(CLANG_FLAGS) -x c - -c -o /dev/null -Werror)
175
176config LD_CAN_USE_KEEP_IN_OVERLAY
177 # ld.lld prior to 21.0.0 did not support KEEP within an overlay description
178 # https://github.com/llvm/llvm-project/pull/130661
179 def_bool LD_IS_BFD || LLD_VERSION >= 210000
180
181config RUSTC_HAS_SPAN_FILE
182 def_bool RUSTC_VERSION >= 108800
183
184config RUSTC_HAS_UNNECESSARY_TRANSMUTES
185 def_bool RUSTC_VERSION >= 108800
186
187config RUSTC_HAS_FILE_WITH_NUL
188 def_bool RUSTC_VERSION >= 108900
189
190config RUSTC_HAS_FILE_AS_C_STR
191 def_bool RUSTC_VERSION >= 109100
192
193config PAHOLE_VERSION
194 int
195 default "$(PAHOLE_VERSION)"
196
197config CONSTRUCTORS
198 bool
199
200config IRQ_WORK
201 def_bool y if SMP
202
203config BUILDTIME_TABLE_SORT
204 bool
205
206config THREAD_INFO_IN_TASK
207 bool
208 help
209 Select this to move thread_info off the stack into task_struct. To
210 make this work, an arch will need to remove all thread_info fields
211 except flags and fix any runtime bugs.
212
213 One subtle change that will be needed is to use try_get_task_stack()
214 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
215
216menu "General setup"
217
218config BROKEN
219 bool
220 help
221 This option allows you to choose whether you want to try to
222 compile (and fix) old drivers that haven't been updated to
223 new infrastructure.
224
225config BROKEN_ON_SMP
226 bool
227 depends on BROKEN || !SMP
228 default y
229
230config INIT_ENV_ARG_LIMIT
231 int
232 default 32 if !UML
233 default 128 if UML
234 help
235 Maximum of each of the number of arguments and environment
236 variables passed to init from the kernel command line.
237
238config COMPILE_TEST
239 bool "Compile also drivers which will not load"
240 depends on HAS_IOMEM
241 help
242 Some drivers can be compiled on a different platform than they are
243 intended to be run on. Despite they cannot be loaded there (or even
244 when they load they cannot be used due to missing HW support),
245 developers still, opposing to distributors, might want to build such
246 drivers to compile-test them.
247
248 If you are a developer and want to build everything available, say Y
249 here. If you are a user/distributor, say N here to exclude useless
250 drivers to be distributed.
251
252config WERROR
253 bool "Compile the kernel with warnings as errors"
254 default COMPILE_TEST
255 help
256 A kernel build should not cause any compiler warnings, and this
257 enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags
258 to enforce that rule by default. Certain warnings from other tools
259 such as the linker may be upgraded to errors with this option as
260 well.
261
262 However, if you have a new (or very old) compiler or linker with odd
263 and unusual warnings, or you have some architecture with problems,
264 you may need to disable this config option in order to
265 successfully build the kernel.
266
267 If in doubt, say Y.
268
269config UAPI_HEADER_TEST
270 bool "Compile test UAPI headers"
271 depends on HEADERS_INSTALL
272 help
273 Compile test headers exported to user-space to ensure they are
274 self-contained, i.e. compilable as standalone units.
275
276 If you are a developer or tester and want to ensure the exported
277 headers are self-contained, say Y here. Otherwise, choose N.
278
279config LOCALVERSION
280 string "Local version - append to kernel release"
281 help
282 Append an extra string to the end of your kernel version.
283 This will show up when you type uname, for example.
284 The string you set here will be appended after the contents of
285 any files with a filename matching localversion* in your
286 object and source tree, in that order. Your total string can
287 be a maximum of 64 characters.
288
289config LOCALVERSION_AUTO
290 bool "Automatically append version information to the version string"
291 default y
292 depends on !COMPILE_TEST
293 help
294 This will try to automatically determine if the current tree is a
295 release tree by looking for git tags that belong to the current
296 top of tree revision.
297
298 A string of the format -gxxxxxxxx will be added to the localversion
299 if a git-based tree is found. The string generated by this will be
300 appended after any matching localversion* files, and after the value
301 set in CONFIG_LOCALVERSION.
302
303 (The actual string used here is the first 12 characters produced
304 by running the command:
305
306 $ git rev-parse --verify HEAD
307
308 which is done within the script "scripts/setlocalversion".)
309
310config BUILD_SALT
311 string "Build ID Salt"
312 default ""
313 help
314 The build ID is used to link binaries and their debug info. Setting
315 this option will use the value in the calculation of the build id.
316 This is mostly useful for distributions which want to ensure the
317 build is unique between builds. It's safe to leave the default.
318
319config HAVE_KERNEL_GZIP
320 bool
321
322config HAVE_KERNEL_BZIP2
323 bool
324
325config HAVE_KERNEL_LZMA
326 bool
327
328config HAVE_KERNEL_XZ
329 bool
330
331config HAVE_KERNEL_LZO
332 bool
333
334config HAVE_KERNEL_LZ4
335 bool
336
337config HAVE_KERNEL_ZSTD
338 bool
339
340config HAVE_KERNEL_UNCOMPRESSED
341 bool
342
343choice
344 prompt "Kernel compression mode"
345 default KERNEL_GZIP
346 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_ZSTD || HAVE_KERNEL_UNCOMPRESSED
347 help
348 The linux kernel is a kind of self-extracting executable.
349 Several compression algorithms are available, which differ
350 in efficiency, compression and decompression speed.
351 Compression speed is only relevant when building a kernel.
352 Decompression speed is relevant at each boot.
353
354 If you have any problems with bzip2 or lzma compressed
355 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
356 version of this functionality (bzip2 only), for 2.4, was
357 supplied by Christian Ludwig)
358
359 High compression options are mostly useful for users, who
360 are low on disk space (embedded systems), but for whom ram
361 size matters less.
362
363 If in doubt, select 'gzip'
364
365config KERNEL_GZIP
366 bool "Gzip"
367 depends on HAVE_KERNEL_GZIP
368 help
369 The old and tried gzip compression. It provides a good balance
370 between compression ratio and decompression speed.
371
372config KERNEL_BZIP2
373 bool "Bzip2"
374 depends on HAVE_KERNEL_BZIP2
375 help
376 Its compression ratio and speed is intermediate.
377 Decompression speed is slowest among the choices. The kernel
378 size is about 10% smaller with bzip2, in comparison to gzip.
379 Bzip2 uses a large amount of memory. For modern kernels you
380 will need at least 8MB RAM or more for booting.
381
382config KERNEL_LZMA
383 bool "LZMA"
384 depends on HAVE_KERNEL_LZMA
385 help
386 This compression algorithm's ratio is best. Decompression speed
387 is between gzip and bzip2. Compression is slowest.
388 The kernel size is about 33% smaller with LZMA in comparison to gzip.
389
390config KERNEL_XZ
391 bool "XZ"
392 depends on HAVE_KERNEL_XZ
393 help
394 XZ uses the LZMA2 algorithm and instruction set specific
395 BCJ filters which can improve compression ratio of executable
396 code. The size of the kernel is about 30% smaller with XZ in
397 comparison to gzip. On architectures for which there is a BCJ
398 filter (i386, x86_64, ARM, ARM64, RISC-V, big endian PowerPC,
399 and SPARC), XZ will create a few percent smaller kernel than
400 plain LZMA.
401
402 The speed is about the same as with LZMA: The decompression
403 speed of XZ is better than that of bzip2 but worse than gzip
404 and LZO. Compression is slow.
405
406config KERNEL_LZO
407 bool "LZO"
408 depends on HAVE_KERNEL_LZO
409 help
410 Its compression ratio is the poorest among the choices. The kernel
411 size is about 10% bigger than gzip; however its speed
412 (both compression and decompression) is the fastest.
413
414config KERNEL_LZ4
415 bool "LZ4"
416 depends on HAVE_KERNEL_LZ4
417 help
418 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
419 A preliminary version of LZ4 de/compression tool is available at
420 <https://code.google.com/p/lz4/>.
421
422 Its compression ratio is worse than LZO. The size of the kernel
423 is about 8% bigger than LZO. But the decompression speed is
424 faster than LZO.
425
426config KERNEL_ZSTD
427 bool "ZSTD"
428 depends on HAVE_KERNEL_ZSTD
429 help
430 ZSTD is a compression algorithm targeting intermediate compression
431 with fast decompression speed. It will compress better than GZIP and
432 decompress around the same speed as LZO, but slower than LZ4. You
433 will need at least 192 KB RAM or more for booting. The zstd command
434 line tool is required for compression.
435
436config KERNEL_UNCOMPRESSED
437 bool "None"
438 depends on HAVE_KERNEL_UNCOMPRESSED
439 help
440 Produce uncompressed kernel image. This option is usually not what
441 you want. It is useful for debugging the kernel in slow simulation
442 environments, where decompressing and moving the kernel is awfully
443 slow. This option allows early boot code to skip the decompressor
444 and jump right at uncompressed kernel image.
445
446endchoice
447
448config DEFAULT_INIT
449 string "Default init path"
450 default ""
451 help
452 This option determines the default init for the system if no init=
453 option is passed on the kernel command line. If the requested path is
454 not present, we will still then move on to attempting further
455 locations (e.g. /sbin/init, etc). If this is empty, we will just use
456 the fallback list when init= is not passed.
457
458config DEFAULT_HOSTNAME
459 string "Default hostname"
460 default "(none)"
461 help
462 This option determines the default system hostname before userspace
463 calls sethostname(2). The kernel traditionally uses "(none)" here,
464 but you may wish to use a different default here to make a minimal
465 system more usable with less configuration.
466
467config SYSVIPC
468 bool "System V IPC"
469 help
470 Inter Process Communication is a suite of library functions and
471 system calls which let processes (running programs) synchronize and
472 exchange information. It is generally considered to be a good thing,
473 and some programs won't run unless you say Y here. In particular, if
474 you want to run the DOS emulator dosemu under Linux (read the
475 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
476 you'll need to say Y here.
477
478 You can find documentation about IPC with "info ipc" and also in
479 section 6.4 of the Linux Programmer's Guide, available from
480 <http://www.tldp.org/guides.html>.
481
482config SYSVIPC_SYSCTL
483 bool
484 depends on SYSVIPC
485 depends on SYSCTL
486 default y
487
488config SYSVIPC_COMPAT
489 def_bool y
490 depends on COMPAT && SYSVIPC
491
492config POSIX_MQUEUE
493 bool "POSIX Message Queues"
494 depends on NET
495 help
496 POSIX variant of message queues is a part of IPC. In POSIX message
497 queues every message has a priority which decides about succession
498 of receiving it by a process. If you want to compile and run
499 programs written e.g. for Solaris with use of its POSIX message
500 queues (functions mq_*) say Y here.
501
502 POSIX message queues are visible as a filesystem called 'mqueue'
503 and can be mounted somewhere if you want to do filesystem
504 operations on message queues.
505
506 If unsure, say Y.
507
508config POSIX_MQUEUE_SYSCTL
509 bool
510 depends on POSIX_MQUEUE
511 depends on SYSCTL
512 default y
513
514config WATCH_QUEUE
515 bool "General notification queue"
516 default n
517 help
518
519 This is a general notification queue for the kernel to pass events to
520 userspace by splicing them into pipes. It can be used in conjunction
521 with watches for key/keyring change notifications and device
522 notifications.
523
524 See Documentation/core-api/watch_queue.rst
525
526config CROSS_MEMORY_ATTACH
527 bool "Enable process_vm_readv/writev syscalls"
528 depends on MMU
529 default y
530 help
531 Enabling this option adds the system calls process_vm_readv and
532 process_vm_writev which allow a process with the correct privileges
533 to directly read from or write to another process' address space.
534 See the man page for more details.
535
536config AUDIT
537 bool "Auditing support"
538 depends on NET
539 help
540 Enable auditing infrastructure that can be used with another
541 kernel subsystem, such as SELinux (which requires this for
542 logging of avc messages output). System call auditing is included
543 on architectures which support it.
544
545config HAVE_ARCH_AUDITSYSCALL
546 bool
547
548config AUDITSYSCALL
549 def_bool y
550 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
551 select FSNOTIFY
552
553source "kernel/irq/Kconfig"
554source "kernel/time/Kconfig"
555source "kernel/bpf/Kconfig"
556source "kernel/Kconfig.preempt"
557
558menu "CPU/Task time and stats accounting"
559
560config VIRT_CPU_ACCOUNTING
561 bool
562
563choice
564 prompt "Cputime accounting"
565 default TICK_CPU_ACCOUNTING
566
567# Kind of a stub config for the pure tick based cputime accounting
568config TICK_CPU_ACCOUNTING
569 bool "Simple tick based cputime accounting"
570 depends on !S390 && !NO_HZ_FULL
571 help
572 This is the basic tick based cputime accounting that maintains
573 statistics about user, system and idle time spent on per jiffies
574 granularity.
575
576 If unsure, say Y.
577
578config VIRT_CPU_ACCOUNTING_NATIVE
579 bool "Deterministic task and CPU time accounting"
580 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
581 select VIRT_CPU_ACCOUNTING
582 help
583 Select this option to enable more accurate task and CPU time
584 accounting. This is done by reading a CPU counter on each
585 kernel entry and exit and on transitions within the kernel
586 between system, softirq and hardirq state, so there is a
587 small performance impact. In the case of s390 or IBM POWER > 5,
588 this also enables accounting of stolen time on logically-partitioned
589 systems.
590
591config VIRT_CPU_ACCOUNTING_GEN
592 bool "Full dynticks CPU time accounting"
593 depends on HAVE_CONTEXT_TRACKING_USER
594 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
595 depends on GENERIC_CLOCKEVENTS
596 select VIRT_CPU_ACCOUNTING
597 select CONTEXT_TRACKING_USER
598 help
599 Select this option to enable task and CPU time accounting on full
600 dynticks systems. This accounting is implemented by watching every
601 kernel-user boundaries using the context tracking subsystem.
602 The accounting is thus performed at the expense of some significant
603 overhead.
604
605 For now this is only useful if you are working on the full
606 dynticks subsystem development.
607
608 If unsure, say N.
609
610endchoice
611
612config IRQ_TIME_ACCOUNTING
613 bool "Fine granularity task level IRQ time accounting"
614 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
615 help
616 Select this option to enable fine granularity task irq time
617 accounting. This is done by reading a timestamp on each
618 transitions between softirq and hardirq state, so there can be a
619 small performance impact.
620
621 If in doubt, say N here.
622
623config HAVE_SCHED_AVG_IRQ
624 def_bool y
625 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
626 depends on SMP
627
628config SCHED_HW_PRESSURE
629 bool
630 default y if ARM && ARM_CPU_TOPOLOGY
631 default y if ARM64
632 depends on SMP
633 depends on CPU_FREQ_THERMAL
634 help
635 Select this option to enable HW pressure accounting in the
636 scheduler. HW pressure is the value conveyed to the scheduler
637 that reflects the reduction in CPU compute capacity resulted from
638 HW throttling. HW throttling occurs when the performance of
639 a CPU is capped due to high operating temperatures as an example.
640
641 If selected, the scheduler will be able to balance tasks accordingly,
642 i.e. put less load on throttled CPUs than on non/less throttled ones.
643
644 This requires the architecture to implement
645 arch_update_hw_pressure() and arch_scale_thermal_pressure().
646
647config BSD_PROCESS_ACCT
648 bool "BSD Process Accounting (DEPRECATED)"
649 depends on MULTIUSER
650 default n
651 help
652 If you say Y here, a user level program will be able to instruct the
653 kernel (via a special system call) to write process accounting
654 information to a file: whenever a process exits, information about
655 that process will be appended to the file by the kernel. The
656 information includes things such as creation time, owning user,
657 command name, memory usage, controlling terminal etc. (the complete
658 list is in the struct acct in <file:include/linux/acct.h>). It is
659 up to the user level program to do useful things with this
660 information. This mechanism is antiquated and has significant
661 scalability issues. You probably want to use eBPF instead. Say
662 N unless you really need this.
663
664config BSD_PROCESS_ACCT_V3
665 bool "BSD Process Accounting version 3 file format"
666 depends on BSD_PROCESS_ACCT
667 default n
668 help
669 If you say Y here, the process accounting information is written
670 in a new file format that also logs the process IDs of each
671 process and its parent. Note that this file format is incompatible
672 with previous v0/v1/v2 file formats, so you will need updated tools
673 for processing it. A preliminary version of these tools is available
674 at <http://www.gnu.org/software/acct/>.
675
676config TASKSTATS
677 bool "Export task/process statistics through netlink"
678 depends on NET
679 depends on MULTIUSER
680 default n
681 help
682 Export selected statistics for tasks/processes through the
683 generic netlink interface. Unlike BSD process accounting, the
684 statistics are available during the lifetime of tasks/processes as
685 responses to commands. Like BSD accounting, they are sent to user
686 space on task exit.
687
688 Say N if unsure.
689
690config TASK_DELAY_ACCT
691 bool "Enable per-task delay accounting"
692 depends on TASKSTATS
693 select SCHED_INFO
694 help
695 Collect information on time spent by a task waiting for system
696 resources like cpu, synchronous block I/O completion and swapping
697 in pages. Such statistics can help in setting a task's priorities
698 relative to other tasks for cpu, io, rss limits etc.
699
700 Say N if unsure.
701
702config TASK_XACCT
703 bool "Enable extended accounting over taskstats"
704 depends on TASKSTATS
705 help
706 Collect extended task accounting data and send the data
707 to userland for processing over the taskstats interface.
708
709 Say N if unsure.
710
711config TASK_IO_ACCOUNTING
712 bool "Enable per-task storage I/O accounting"
713 depends on TASK_XACCT
714 help
715 Collect information on the number of bytes of storage I/O which this
716 task has caused.
717
718 Say N if unsure.
719
720config PSI
721 bool "Pressure stall information tracking"
722 select KERNFS
723 help
724 Collect metrics that indicate how overcommitted the CPU, memory,
725 and IO capacity are in the system.
726
727 If you say Y here, the kernel will create /proc/pressure/ with the
728 pressure statistics files cpu, memory, and io. These will indicate
729 the share of walltime in which some or all tasks in the system are
730 delayed due to contention of the respective resource.
731
732 In kernels with cgroup support, cgroups (cgroup2 only) will
733 have cpu.pressure, memory.pressure, and io.pressure files,
734 which aggregate pressure stalls for the grouped tasks only.
735
736 For more details see Documentation/accounting/psi.rst.
737
738 Say N if unsure.
739
740config PSI_DEFAULT_DISABLED
741 bool "Require boot parameter to enable pressure stall information tracking"
742 default n
743 depends on PSI
744 help
745 If set, pressure stall information tracking will be disabled
746 per default but can be enabled through passing psi=1 on the
747 kernel commandline during boot.
748
749 This feature adds some code to the task wakeup and sleep
750 paths of the scheduler. The overhead is too low to affect
751 common scheduling-intense workloads in practice (such as
752 webservers, memcache), but it does show up in artificial
753 scheduler stress tests, such as hackbench.
754
755 If you are paranoid and not sure what the kernel will be
756 used for, say Y.
757
758 Say N if unsure.
759
760endmenu # "CPU/Task time and stats accounting"
761
762config CPU_ISOLATION
763 bool "CPU isolation"
764 depends on SMP
765 default y
766 help
767 Make sure that CPUs running critical tasks are not disturbed by
768 any source of "noise" such as unbound workqueues, timers, kthreads...
769 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
770 the "isolcpus=" boot parameter.
771
772 Say Y if unsure.
773
774source "kernel/rcu/Kconfig"
775
776config IKCONFIG
777 tristate "Kernel .config support"
778 help
779 This option enables the complete Linux kernel ".config" file
780 contents to be saved in the kernel. It provides documentation
781 of which kernel options are used in a running kernel or in an
782 on-disk kernel. This information can be extracted from the kernel
783 image file with the script scripts/extract-ikconfig and used as
784 input to rebuild the current kernel or to build another kernel.
785 It can also be extracted from a running kernel by reading
786 /proc/config.gz if enabled (below).
787
788config IKCONFIG_PROC
789 bool "Enable access to .config through /proc/config.gz"
790 depends on IKCONFIG && PROC_FS
791 help
792 This option enables access to the kernel configuration file
793 through /proc/config.gz.
794
795config IKHEADERS
796 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
797 depends on SYSFS
798 help
799 This option enables access to the in-kernel headers that are generated during
800 the build process. These can be used to build eBPF tracing programs,
801 or similar programs. If you build the headers as a module, a module called
802 kheaders.ko is built which can be loaded on-demand to get access to headers.
803
804config LOG_BUF_SHIFT
805 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
806 range 12 25
807 default 17
808 depends on PRINTK
809 help
810 Select the minimal kernel log buffer size as a power of 2.
811 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
812 parameter, see below. Any higher size also might be forced
813 by "log_buf_len" boot parameter.
814
815 Examples:
816 17 => 128 KB
817 16 => 64 KB
818 15 => 32 KB
819 14 => 16 KB
820 13 => 8 KB
821 12 => 4 KB
822
823config LOG_CPU_MAX_BUF_SHIFT
824 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
825 depends on SMP
826 range 0 21
827 default 0 if BASE_SMALL
828 default 12
829 depends on PRINTK
830 help
831 This option allows to increase the default ring buffer size
832 according to the number of CPUs. The value defines the contribution
833 of each CPU as a power of 2. The used space is typically only few
834 lines however it might be much more when problems are reported,
835 e.g. backtraces.
836
837 The increased size means that a new buffer has to be allocated and
838 the original static one is unused. It makes sense only on systems
839 with more CPUs. Therefore this value is used only when the sum of
840 contributions is greater than the half of the default kernel ring
841 buffer as defined by LOG_BUF_SHIFT. The default values are set
842 so that more than 16 CPUs are needed to trigger the allocation.
843
844 Also this option is ignored when "log_buf_len" kernel parameter is
845 used as it forces an exact (power of two) size of the ring buffer.
846
847 The number of possible CPUs is used for this computation ignoring
848 hotplugging making the computation optimal for the worst case
849 scenario while allowing a simple algorithm to be used from bootup.
850
851 Examples shift values and their meaning:
852 17 => 128 KB for each CPU
853 16 => 64 KB for each CPU
854 15 => 32 KB for each CPU
855 14 => 16 KB for each CPU
856 13 => 8 KB for each CPU
857 12 => 4 KB for each CPU
858
859config PRINTK_INDEX
860 bool "Printk indexing debugfs interface"
861 depends on PRINTK && DEBUG_FS
862 help
863 Add support for indexing of all printk formats known at compile time
864 at <debugfs>/printk/index/<module>.
865
866 This can be used as part of maintaining daemons which monitor
867 /dev/kmsg, as it permits auditing the printk formats present in a
868 kernel, allowing detection of cases where monitored printks are
869 changed or no longer present.
870
871 There is no additional runtime cost to printk with this enabled.
872
873#
874# Architectures with an unreliable sched_clock() should select this:
875#
876config HAVE_UNSTABLE_SCHED_CLOCK
877 bool
878
879config GENERIC_SCHED_CLOCK
880 bool
881
882menu "Scheduler features"
883
884config UCLAMP_TASK
885 bool "Enable utilization clamping for RT/FAIR tasks"
886 depends on CPU_FREQ_GOV_SCHEDUTIL
887 help
888 This feature enables the scheduler to track the clamped utilization
889 of each CPU based on RUNNABLE tasks scheduled on that CPU.
890
891 With this option, the user can specify the min and max CPU
892 utilization allowed for RUNNABLE tasks. The max utilization defines
893 the maximum frequency a task should use while the min utilization
894 defines the minimum frequency it should use.
895
896 Both min and max utilization clamp values are hints to the scheduler,
897 aiming at improving its frequency selection policy, but they do not
898 enforce or grant any specific bandwidth for tasks.
899
900 If in doubt, say N.
901
902config UCLAMP_BUCKETS_COUNT
903 int "Number of supported utilization clamp buckets"
904 range 5 20
905 default 5
906 depends on UCLAMP_TASK
907 help
908 Defines the number of clamp buckets to use. The range of each bucket
909 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
910 number of clamp buckets the finer their granularity and the higher
911 the precision of clamping aggregation and tracking at run-time.
912
913 For example, with the minimum configuration value we will have 5
914 clamp buckets tracking 20% utilization each. A 25% boosted tasks will
915 be refcounted in the [20..39]% bucket and will set the bucket clamp
916 effective value to 25%.
917 If a second 30% boosted task should be co-scheduled on the same CPU,
918 that task will be refcounted in the same bucket of the first task and
919 it will boost the bucket clamp effective value to 30%.
920 The clamp effective value of a bucket is reset to its nominal value
921 (20% in the example above) when there are no more tasks refcounted in
922 that bucket.
923
924 An additional boost/capping margin can be added to some tasks. In the
925 example above the 25% task will be boosted to 30% until it exits the
926 CPU. If that should be considered not acceptable on certain systems,
927 it's always possible to reduce the margin by increasing the number of
928 clamp buckets to trade off used memory for run-time tracking
929 precision.
930
931 If in doubt, use the default value.
932
933config SCHED_PROXY_EXEC
934 bool "Proxy Execution"
935 # Avoid some build failures w/ PREEMPT_RT until it can be fixed
936 depends on !PREEMPT_RT
937 # Need to investigate how to inform sched_ext of split contexts
938 depends on !SCHED_CLASS_EXT
939 # Not particularly useful until we get to multi-rq proxying
940 depends on EXPERT
941 help
942 This option enables proxy execution, a mechanism for mutex-owning
943 tasks to inherit the scheduling context of higher priority waiters.
944
945endmenu
946
947#
948# For architectures that want to enable the support for NUMA-affine scheduler
949# balancing logic:
950#
951config ARCH_SUPPORTS_NUMA_BALANCING
952 bool
953
954#
955# For architectures that prefer to flush all TLBs after a number of pages
956# are unmapped instead of sending one IPI per page to flush. The architecture
957# must provide guarantees on what happens if a clean TLB cache entry is
958# written after the unmap. Details are in mm/rmap.c near the check for
959# should_defer_flush. The architecture should also consider if the full flush
960# and the refill costs are offset by the savings of sending fewer IPIs.
961config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
962 bool
963
964config CC_HAS_INT128
965 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
966
967config CC_IMPLICIT_FALLTHROUGH
968 string
969 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
970 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough)
971
972config CC_MS_EXTENSIONS
973 string
974 default "-fms-anonymous-structs" if $(cc-option,-fms-anonymous-structs)
975 default "-fms-extensions"
976
977# Currently, disable gcc-10+ array-bounds globally.
978# It's still broken in gcc-13, so no upper bound yet.
979config GCC10_NO_ARRAY_BOUNDS
980 def_bool y
981
982config CC_NO_ARRAY_BOUNDS
983 bool
984 default y if CC_IS_GCC && GCC_VERSION >= 90000 && GCC10_NO_ARRAY_BOUNDS
985
986# Currently, disable -Wstringop-overflow for GCC globally.
987config GCC_NO_STRINGOP_OVERFLOW
988 def_bool y
989
990config CC_NO_STRINGOP_OVERFLOW
991 bool
992 default y if CC_IS_GCC && GCC_NO_STRINGOP_OVERFLOW
993
994config CC_STRINGOP_OVERFLOW
995 bool
996 default y if CC_IS_GCC && !CC_NO_STRINGOP_OVERFLOW
997
998#
999# For architectures that know their GCC __int128 support is sound
1000#
1001config ARCH_SUPPORTS_INT128
1002 bool
1003
1004# For architectures that (ab)use NUMA to represent different memory regions
1005# all cpu-local but of different latencies, such as SuperH.
1006#
1007config ARCH_WANT_NUMA_VARIABLE_LOCALITY
1008 bool
1009
1010config NUMA_BALANCING
1011 bool "Memory placement aware NUMA scheduler"
1012 depends on ARCH_SUPPORTS_NUMA_BALANCING
1013 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
1014 depends on SMP && NUMA_MIGRATION && !PREEMPT_RT
1015 help
1016 This option adds support for automatic NUMA aware memory/task placement.
1017 The mechanism is quite primitive and is based on migrating memory when
1018 it has references to the node the task is running on.
1019
1020 This system will be inactive on UMA systems.
1021
1022config NUMA_BALANCING_DEFAULT_ENABLED
1023 bool "Automatically enable NUMA aware memory/task placement"
1024 default y
1025 depends on NUMA_BALANCING
1026 help
1027 If set, automatic NUMA balancing will be enabled if running on a NUMA
1028 machine.
1029
1030config SLAB_OBJ_EXT
1031 bool
1032
1033menuconfig CGROUPS
1034 bool "Control Group support"
1035 select KERNFS
1036 help
1037 This option adds support for grouping sets of processes together, for
1038 use with process control subsystems such as Cpusets, CFS, memory
1039 controls or device isolation.
1040 See
1041 - Documentation/scheduler/sched-design-CFS.rst (CFS)
1042 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
1043 and resource control)
1044
1045 Say N if unsure.
1046
1047if CGROUPS
1048
1049config PAGE_COUNTER
1050 bool
1051
1052config CGROUP_FAVOR_DYNMODS
1053 bool "Favor dynamic modification latency reduction by default"
1054 help
1055 This option enables the "favordynmods" mount option by default
1056 which reduces the latencies of dynamic cgroup modifications such
1057 as task migrations and controller on/offs at the cost of making
1058 hot path operations such as forks and exits more expensive.
1059
1060 Say N if unsure.
1061
1062config MEMCG
1063 bool "Memory controller"
1064 select PAGE_COUNTER
1065 select EVENTFD
1066 select SLAB_OBJ_EXT
1067 select VM_EVENT_COUNTERS
1068 help
1069 Provides control over the memory footprint of tasks in a cgroup.
1070
1071config MEMCG_NMI_UNSAFE
1072 bool
1073 depends on MEMCG
1074 depends on HAVE_NMI
1075 depends on !ARCH_HAS_NMI_SAFE_THIS_CPU_OPS && !ARCH_HAVE_NMI_SAFE_CMPXCHG
1076 default y
1077
1078config MEMCG_NMI_SAFETY_REQUIRES_ATOMIC
1079 bool
1080 depends on MEMCG
1081 depends on HAVE_NMI
1082 depends on !ARCH_HAS_NMI_SAFE_THIS_CPU_OPS && ARCH_HAVE_NMI_SAFE_CMPXCHG
1083 default y
1084
1085config MEMCG_V1
1086 bool "Legacy cgroup v1 memory controller"
1087 depends on MEMCG
1088 default n
1089 help
1090 Legacy cgroup v1 memory controller which has been deprecated by
1091 cgroup v2 implementation. The v1 is there for legacy applications
1092 which haven't migrated to the new cgroup v2 interface yet. If you
1093 do not have any such application then you are completely fine leaving
1094 this option disabled.
1095
1096 Please note that feature set of the legacy memory controller is likely
1097 going to shrink due to deprecation process. New deployments with v1
1098 controller are highly discouraged.
1099
1100 Say N if unsure.
1101
1102config BLK_CGROUP
1103 bool "IO controller"
1104 depends on BLOCK
1105 default n
1106 help
1107 Generic block IO controller cgroup interface. This is the common
1108 cgroup interface which should be used by various IO controlling
1109 policies.
1110
1111 Currently, CFQ IO scheduler uses it to recognize task groups and
1112 control disk bandwidth allocation (proportional time slice allocation)
1113 to such task groups. It is also used by bio throttling logic in
1114 block layer to implement upper limit in IO rates on a device.
1115
1116 This option only enables generic Block IO controller infrastructure.
1117 One needs to also enable actual IO controlling logic/policy. For
1118 enabling proportional weight division of disk bandwidth in CFQ, set
1119 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1120 CONFIG_BLK_DEV_THROTTLING=y.
1121
1122 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
1123
1124config CGROUP_WRITEBACK
1125 bool
1126 depends on MEMCG && BLK_CGROUP
1127 default y
1128
1129menuconfig CGROUP_SCHED
1130 bool "CPU controller"
1131 default n
1132 help
1133 This feature lets CPU scheduler recognize task groups and control CPU
1134 bandwidth allocation to such task groups. It uses cgroups to group
1135 tasks.
1136
1137if CGROUP_SCHED
1138config GROUP_SCHED_WEIGHT
1139 def_bool n
1140
1141config GROUP_SCHED_BANDWIDTH
1142 def_bool n
1143
1144config FAIR_GROUP_SCHED
1145 bool "Group scheduling for SCHED_OTHER"
1146 depends on CGROUP_SCHED
1147 select GROUP_SCHED_WEIGHT
1148 default CGROUP_SCHED
1149
1150config CFS_BANDWIDTH
1151 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1152 depends on FAIR_GROUP_SCHED
1153 select GROUP_SCHED_BANDWIDTH
1154 default n
1155 help
1156 This option allows users to define CPU bandwidth rates (limits) for
1157 tasks running within the fair group scheduler. Groups with no limit
1158 set are considered to be unconstrained and will run with no
1159 restriction.
1160 See Documentation/scheduler/sched-bwc.rst for more information.
1161
1162config RT_GROUP_SCHED
1163 bool "Group scheduling for SCHED_RR/FIFO"
1164 depends on CGROUP_SCHED
1165 default n
1166 help
1167 This feature lets you explicitly allocate real CPU bandwidth
1168 to task groups. If enabled, it will also make it impossible to
1169 schedule realtime tasks for non-root users until you allocate
1170 realtime bandwidth for them.
1171 See Documentation/scheduler/sched-rt-group.rst for more information.
1172
1173config RT_GROUP_SCHED_DEFAULT_DISABLED
1174 bool "Require boot parameter to enable group scheduling for SCHED_RR/FIFO"
1175 depends on RT_GROUP_SCHED
1176 default n
1177 help
1178 When set, the RT group scheduling is disabled by default. The option
1179 is in inverted form so that mere RT_GROUP_SCHED enables the group
1180 scheduling.
1181
1182 Say N if unsure.
1183
1184config EXT_GROUP_SCHED
1185 bool
1186 depends on SCHED_CLASS_EXT && CGROUP_SCHED
1187 select GROUP_SCHED_WEIGHT
1188 select GROUP_SCHED_BANDWIDTH
1189 default y
1190
1191endif #CGROUP_SCHED
1192
1193config EXT_SUB_SCHED
1194 def_bool y
1195 depends on SCHED_CLASS_EXT && CGROUPS
1196
1197config SCHED_MM_CID
1198 def_bool y
1199 depends on SMP && RSEQ
1200
1201config UCLAMP_TASK_GROUP
1202 bool "Utilization clamping per group of tasks"
1203 depends on CGROUP_SCHED
1204 depends on UCLAMP_TASK
1205 default n
1206 help
1207 This feature enables the scheduler to track the clamped utilization
1208 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
1209
1210 When this option is enabled, the user can specify a min and max
1211 CPU bandwidth which is allowed for each single task in a group.
1212 The max bandwidth allows to clamp the maximum frequency a task
1213 can use, while the min bandwidth allows to define a minimum
1214 frequency a task will always use.
1215
1216 When task group based utilization clamping is enabled, an eventually
1217 specified task-specific clamp value is constrained by the cgroup
1218 specified clamp value. Both minimum and maximum task clamping cannot
1219 be bigger than the corresponding clamping defined at task group level.
1220
1221 If in doubt, say N.
1222
1223config CGROUP_PIDS
1224 bool "PIDs controller"
1225 help
1226 Provides enforcement of process number limits in the scope of a
1227 cgroup. Any attempt to fork more processes than is allowed in the
1228 cgroup will fail. PIDs are fundamentally a global resource because it
1229 is fairly trivial to reach PID exhaustion before you reach even a
1230 conservative kmemcg limit. As a result, it is possible to grind a
1231 system to halt without being limited by other cgroup policies. The
1232 PIDs controller is designed to stop this from happening.
1233
1234 It should be noted that organisational operations (such as attaching
1235 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1236 since the PIDs limit only affects a process's ability to fork, not to
1237 attach to a cgroup.
1238
1239config CGROUP_RDMA
1240 bool "RDMA controller"
1241 help
1242 Provides enforcement of RDMA resources defined by IB stack.
1243 It is fairly easy for consumers to exhaust RDMA resources, which
1244 can result into resource unavailability to other consumers.
1245 RDMA controller is designed to stop this from happening.
1246 Attaching processes with active RDMA resources to the cgroup
1247 hierarchy is allowed even if can cross the hierarchy's limit.
1248
1249config CGROUP_DMEM
1250 bool "Device memory controller (DMEM)"
1251 select PAGE_COUNTER
1252 help
1253 The DMEM controller allows compatible devices to restrict device
1254 memory usage based on the cgroup hierarchy.
1255
1256 As an example, it allows you to restrict VRAM usage for applications
1257 in the DRM subsystem.
1258
1259config CGROUP_FREEZER
1260 bool "Freezer controller"
1261 help
1262 Provides a way to freeze and unfreeze all tasks in a
1263 cgroup.
1264
1265 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1266 controller includes important in-kernel memory consumers per default.
1267
1268 If you're using cgroup2, say N.
1269
1270config CGROUP_HUGETLB
1271 bool "HugeTLB controller"
1272 depends on HUGETLB_PAGE
1273 select PAGE_COUNTER
1274 default n
1275 help
1276 Provides a cgroup controller for HugeTLB pages.
1277 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1278 The limit is enforced during page fault. Since HugeTLB doesn't
1279 support page reclaim, enforcing the limit at page fault time implies
1280 that, the application will get SIGBUS signal if it tries to access
1281 HugeTLB pages beyond its limit. This requires the application to know
1282 beforehand how much HugeTLB pages it would require for its use. The
1283 control group is tracked in the third page lru pointer. This means
1284 that we cannot use the controller with huge page less than 3 pages.
1285
1286config CPUSETS
1287 bool "Cpuset controller"
1288 depends on SMP
1289 select UNION_FIND
1290 select CPU_ISOLATION
1291 help
1292 This option will let you create and manage CPUSETs which
1293 allow dynamically partitioning a system into sets of CPUs and
1294 Memory Nodes and assigning tasks to run only within those sets.
1295 This is primarily useful on large SMP or NUMA systems.
1296
1297 Say N if unsure.
1298
1299config CPUSETS_V1
1300 bool "Legacy cgroup v1 cpusets controller"
1301 depends on CPUSETS
1302 default n
1303 help
1304 Legacy cgroup v1 cpusets controller which has been deprecated by
1305 cgroup v2 implementation. The v1 is there for legacy applications
1306 which haven't migrated to the new cgroup v2 interface yet. Legacy
1307 interface includes cpuset filesystem and /proc/<pid>/cpuset. If you
1308 do not have any such application then you are completely fine leaving
1309 this option disabled.
1310
1311 Say N if unsure.
1312
1313config PROC_PID_CPUSET
1314 bool "Include legacy /proc/<pid>/cpuset file"
1315 depends on CPUSETS_V1
1316 default y
1317
1318config CGROUP_DEVICE
1319 bool "Device controller"
1320 help
1321 Provides a cgroup controller implementing whitelists for
1322 devices which a process in the cgroup can mknod or open.
1323
1324config CGROUP_CPUACCT
1325 bool "Simple CPU accounting controller"
1326 help
1327 Provides a simple controller for monitoring the
1328 total CPU consumed by the tasks in a cgroup.
1329
1330config CGROUP_PERF
1331 bool "Perf controller"
1332 depends on PERF_EVENTS
1333 help
1334 This option extends the perf per-cpu mode to restrict monitoring
1335 to threads which belong to the cgroup specified and run on the
1336 designated cpu. Or this can be used to have cgroup ID in samples
1337 so that it can monitor performance events among cgroups.
1338
1339 Say N if unsure.
1340
1341config CGROUP_BPF
1342 bool "Support for eBPF programs attached to cgroups"
1343 depends on BPF_SYSCALL
1344 select SOCK_CGROUP_DATA
1345 help
1346 Allow attaching eBPF programs to a cgroup using the bpf(2)
1347 syscall command BPF_PROG_ATTACH.
1348
1349 In which context these programs are accessed depends on the type
1350 of attachment. For instance, programs that are attached using
1351 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1352 inet sockets.
1353
1354config CGROUP_MISC
1355 bool "Misc resource controller"
1356 default n
1357 help
1358 Provides a controller for miscellaneous resources on a host.
1359
1360 Miscellaneous scalar resources are the resources on the host system
1361 which cannot be abstracted like the other cgroups. This controller
1362 tracks and limits the miscellaneous resources used by a process
1363 attached to a cgroup hierarchy.
1364
1365 For more information, please check misc cgroup section in
1366 /Documentation/admin-guide/cgroup-v2.rst.
1367
1368config CGROUP_DEBUG
1369 bool "Debug controller"
1370 default n
1371 depends on DEBUG_KERNEL
1372 help
1373 This option enables a simple controller that exports
1374 debugging information about the cgroups framework. This
1375 controller is for control cgroup debugging only. Its
1376 interfaces are not stable.
1377
1378 Say N.
1379
1380config SOCK_CGROUP_DATA
1381 bool
1382 default n
1383
1384endif # CGROUPS
1385
1386menuconfig NAMESPACES
1387 bool "Namespaces support" if EXPERT
1388 depends on MULTIUSER
1389 default !EXPERT
1390 help
1391 Provides the way to make tasks work with different objects using
1392 the same id. For example same IPC id may refer to different objects
1393 or same user id or pid may refer to different tasks when used in
1394 different namespaces.
1395
1396if NAMESPACES
1397
1398config UTS_NS
1399 bool "UTS namespace"
1400 default y
1401 help
1402 In this namespace tasks see different info provided with the
1403 uname() system call
1404
1405config TIME_NS
1406 bool "TIME namespace"
1407 default y
1408 help
1409 In this namespace boottime and monotonic clocks can be set.
1410 The time will keep going with the same pace.
1411
1412config TIME_NS_VDSO
1413 def_bool TIME_NS && GENERIC_GETTIMEOFDAY
1414
1415config IPC_NS
1416 bool "IPC namespace"
1417 depends on (SYSVIPC || POSIX_MQUEUE)
1418 default y
1419 help
1420 In this namespace tasks work with IPC ids which correspond to
1421 different IPC objects in different namespaces.
1422
1423config USER_NS
1424 bool "User namespace"
1425 default n
1426 help
1427 This allows containers, i.e. vservers, to use user namespaces
1428 to provide different user info for different servers.
1429
1430 When user namespaces are enabled in the kernel it is
1431 recommended that the MEMCG option also be enabled and that
1432 user-space use the memory control groups to limit the amount
1433 of memory a memory unprivileged users can use.
1434
1435 If unsure, say N.
1436
1437config PID_NS
1438 bool "PID Namespaces"
1439 default y
1440 help
1441 Support process id namespaces. This allows having multiple
1442 processes with the same pid as long as they are in different
1443 pid namespaces. This is a building block of containers.
1444
1445config NET_NS
1446 bool "Network namespace"
1447 depends on NET
1448 default y
1449 help
1450 Allow user space to create what appear to be multiple instances
1451 of the network stack.
1452
1453endif # NAMESPACES
1454
1455config CHECKPOINT_RESTORE
1456 bool "Checkpoint/restore support"
1457 depends on PROC_FS
1458 select PROC_CHILDREN
1459 select KCMP
1460 default n
1461 help
1462 Enables additional kernel features in a sake of checkpoint/restore.
1463 In particular it adds auxiliary prctl codes to setup process text,
1464 data and heap segment sizes, and a few additional /proc filesystem
1465 entries.
1466
1467 If unsure, say N here.
1468
1469config SCHED_AUTOGROUP
1470 bool "Automatic process group scheduling"
1471 select CGROUPS
1472 select CGROUP_SCHED
1473 select FAIR_GROUP_SCHED
1474 help
1475 This option optimizes the scheduler for common desktop workloads by
1476 automatically creating and populating task groups. This separation
1477 of workloads isolates aggressive CPU burners (like build jobs) from
1478 desktop applications. Task group autogeneration is currently based
1479 upon task session.
1480
1481config RELAY
1482 bool "Kernel->user space relay support (formerly relayfs)"
1483 select IRQ_WORK
1484 help
1485 This option enables support for relay interface support in
1486 certain file systems (such as debugfs).
1487 It is designed to provide an efficient mechanism for tools and
1488 facilities to relay large amounts of data from kernel space to
1489 user space.
1490
1491 If unsure, say N.
1492
1493config BLK_DEV_INITRD
1494 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1495 help
1496 The initial RAM filesystem is a ramfs which is loaded by the
1497 boot loader (loadlin or lilo) and that is mounted as root
1498 before the normal boot procedure. It is typically used to
1499 load modules needed to mount the "real" root file system,
1500 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1501
1502 If RAM disk support (BLK_DEV_RAM) is also included, this
1503 also enables initial RAM disk (initrd) support and adds
1504 15 Kbytes (more on some other architectures) to the kernel size.
1505
1506 If unsure say Y.
1507
1508if BLK_DEV_INITRD
1509
1510source "usr/Kconfig"
1511
1512endif
1513
1514config BOOT_CONFIG
1515 bool "Boot config support"
1516 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED
1517 help
1518 Extra boot config allows system admin to pass a config file as
1519 complemental extension of kernel cmdline when booting.
1520 The boot config file must be attached at the end of initramfs
1521 with checksum, size and magic word.
1522 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1523
1524 If unsure, say Y.
1525
1526config BOOT_CONFIG_FORCE
1527 bool "Force unconditional bootconfig processing"
1528 depends on BOOT_CONFIG
1529 default y if BOOT_CONFIG_EMBED
1530 help
1531 With this Kconfig option set, BOOT_CONFIG processing is carried
1532 out even when the "bootconfig" kernel-boot parameter is omitted.
1533 In fact, with this Kconfig option set, there is no way to
1534 make the kernel ignore the BOOT_CONFIG-supplied kernel-boot
1535 parameters.
1536
1537 If unsure, say N.
1538
1539config BOOT_CONFIG_EMBED
1540 bool "Embed bootconfig file in the kernel"
1541 depends on BOOT_CONFIG
1542 help
1543 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the
1544 kernel. Usually, the bootconfig file is loaded with the initrd
1545 image. But if the system doesn't support initrd, this option will
1546 help you by embedding a bootconfig file while building the kernel.
1547
1548 If unsure, say N.
1549
1550config BOOT_CONFIG_EMBED_FILE
1551 string "Embedded bootconfig file path"
1552 depends on BOOT_CONFIG_EMBED
1553 help
1554 Specify a bootconfig file which will be embedded to the kernel.
1555 This bootconfig will be used if there is no initrd or no other
1556 bootconfig in the initrd.
1557
1558config CMDLINE_LOG_WRAP_IDEAL_LEN
1559 int "Length to try to wrap the cmdline when logged at boot"
1560 default 1021
1561 range 0 1021
1562 help
1563 At boot time, the kernel command line is logged to the console.
1564 The log message will start with the prefix "Kernel command line: ".
1565 The log message will attempt to be wrapped (split into multiple log
1566 messages) at spaces based on CMDLINE_LOG_WRAP_IDEAL_LEN characters.
1567 If wrapping happens, each log message will start with the prefix and
1568 all but the last message will end with " \". Messages may exceed the
1569 ideal length if a place to wrap isn't found before the specified
1570 number of characters.
1571
1572 A value of 0 disables wrapping, though be warned that the maximum
1573 length of a log message (1021 characters) may cause the cmdline to
1574 be truncated.
1575
1576config INITRAMFS_PRESERVE_MTIME
1577 bool "Preserve cpio archive mtimes in initramfs"
1578 depends on BLK_DEV_INITRD
1579 default y
1580 help
1581 Each entry in an initramfs cpio archive carries an mtime value. When
1582 enabled, extracted cpio items take this mtime, with directory mtime
1583 setting deferred until after creation of any child entries.
1584
1585 If unsure, say Y.
1586
1587config INITRAMFS_TEST
1588 bool "Test initramfs cpio archive extraction" if !KUNIT_ALL_TESTS
1589 depends on BLK_DEV_INITRD && KUNIT=y
1590 default KUNIT_ALL_TESTS
1591 help
1592 Build KUnit tests for initramfs. See Documentation/dev-tools/kunit
1593
1594choice
1595 prompt "Compiler optimization level"
1596 default CC_OPTIMIZE_FOR_PERFORMANCE
1597
1598config CC_OPTIMIZE_FOR_PERFORMANCE
1599 bool "Optimize for performance (-O2)"
1600 help
1601 This is the default optimization level for the kernel, building
1602 with the "-O2" compiler flag for best performance and most
1603 helpful compile-time warnings.
1604
1605config CC_OPTIMIZE_FOR_SIZE
1606 bool "Optimize for size (-Os)"
1607 help
1608 Choosing this option will pass "-Os" to your compiler resulting
1609 in a smaller kernel.
1610
1611endchoice
1612
1613config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1614 bool
1615 help
1616 This requires that the arch annotates or otherwise protects
1617 its external entry points from being discarded. Linker scripts
1618 must also merge .text.*, .data.*, and .bss.* correctly into
1619 output sections. Care must be taken not to pull in unrelated
1620 sections (e.g., '.text.init'). Typically '.' in section names
1621 is used to distinguish them from label names / C identifiers.
1622
1623config LD_DEAD_CODE_DATA_ELIMINATION
1624 bool "Dead code and data elimination (EXPERIMENTAL)"
1625 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1626 depends on EXPERT
1627 depends on $(cc-option,-ffunction-sections -fdata-sections)
1628 depends on $(ld-option,--gc-sections)
1629 help
1630 Enable this if you want to do dead code and data elimination with
1631 the linker by compiling with -ffunction-sections -fdata-sections,
1632 and linking with --gc-sections.
1633
1634 This can reduce on disk and in-memory size of the kernel
1635 code and static data, particularly for small configs and
1636 on small systems. This has the possibility of introducing
1637 silently broken kernel if the required annotations are not
1638 present. This option is not well tested yet, so use at your
1639 own risk.
1640
1641config LD_ORPHAN_WARN
1642 def_bool y
1643 depends on ARCH_WANT_LD_ORPHAN_WARN
1644 depends on $(ld-option,--orphan-handling=warn)
1645 depends on $(ld-option,--orphan-handling=error)
1646
1647config LD_ORPHAN_WARN_LEVEL
1648 string
1649 depends on LD_ORPHAN_WARN
1650 default "error" if WERROR
1651 default "warn"
1652
1653config SYSCTL
1654 bool
1655
1656config HAVE_UID16
1657 bool
1658
1659config SYSCTL_EXCEPTION_TRACE
1660 bool
1661 help
1662 Enable support for /proc/sys/debug/exception-trace.
1663
1664config SYSCTL_ARCH_UNALIGN_NO_WARN
1665 bool
1666 help
1667 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1668 Allows arch to define/use @no_unaligned_warning to possibly warn
1669 about unaligned access emulation going on under the hood.
1670
1671config SYSCTL_ARCH_UNALIGN_ALLOW
1672 bool
1673 help
1674 Enable support for /proc/sys/kernel/unaligned-trap
1675 Allows arches to define/use @unaligned_enabled to runtime toggle
1676 the unaligned access emulation.
1677 see arch/parisc/kernel/unaligned.c for reference
1678
1679config SYSFS_SYSCALL
1680 bool "Sysfs syscall support"
1681 default n
1682 help
1683 sys_sysfs is an obsolete system call no longer supported in libc.
1684 Note that disabling this option is more secure but might break
1685 compatibility with some systems.
1686
1687 If unsure say N here.
1688
1689config HAVE_PCSPKR_PLATFORM
1690 bool
1691
1692menuconfig EXPERT
1693 bool "Configure standard kernel features (expert users)"
1694 # Unhide debug options, to make the on-by-default options visible
1695 select DEBUG_KERNEL
1696 help
1697 This option allows certain base kernel options and settings
1698 to be disabled or tweaked. This is for specialized
1699 environments which can tolerate a "non-standard" kernel.
1700 Only use this if you really know what you are doing.
1701
1702config UID16
1703 bool "Enable 16-bit UID system calls" if EXPERT
1704 depends on HAVE_UID16 && MULTIUSER
1705 default y
1706 help
1707 This enables the legacy 16-bit UID syscall wrappers.
1708
1709config MULTIUSER
1710 bool "Multiple users, groups and capabilities support" if EXPERT
1711 default y
1712 help
1713 This option enables support for non-root users, groups and
1714 capabilities.
1715
1716 If you say N here, all processes will run with UID 0, GID 0, and all
1717 possible capabilities. Saying N here also compiles out support for
1718 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1719 setgid, and capset.
1720
1721 If unsure, say Y here.
1722
1723config SGETMASK_SYSCALL
1724 bool "sgetmask/ssetmask syscalls support" if EXPERT
1725 default PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1726 help
1727 sys_sgetmask and sys_ssetmask are obsolete system calls
1728 no longer supported in libc but still enabled by default in some
1729 architectures.
1730
1731 If unsure, leave the default option here.
1732
1733config FHANDLE
1734 bool "open by fhandle syscalls" if EXPERT
1735 select EXPORTFS
1736 default y
1737 help
1738 If you say Y here, a user level program will be able to map
1739 file names to handle and then later use the handle for
1740 different file system operations. This is useful in implementing
1741 userspace file servers, which now track files using handles instead
1742 of names. The handle would remain the same even if file names
1743 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1744 syscalls.
1745
1746config POSIX_TIMERS
1747 bool "Posix Clocks & timers" if EXPERT
1748 default y
1749 help
1750 This includes native support for POSIX timers to the kernel.
1751 Some embedded systems have no use for them and therefore they
1752 can be configured out to reduce the size of the kernel image.
1753
1754 When this option is disabled, the following syscalls won't be
1755 available: timer_create, timer_gettime: timer_getoverrun,
1756 timer_settime, timer_delete, clock_adjtime, getitimer,
1757 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1758 clock_getres and clock_nanosleep syscalls will be limited to
1759 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1760
1761 If unsure say y.
1762
1763config PRINTK
1764 default y
1765 bool "Enable support for printk" if EXPERT
1766 select IRQ_WORK
1767 help
1768 This option enables normal printk support. Removing it
1769 eliminates most of the message strings from the kernel image
1770 and makes the kernel more or less silent. As this makes it
1771 very difficult to diagnose system problems, saying N here is
1772 strongly discouraged.
1773
1774config PRINTK_RINGBUFFER_KUNIT_TEST
1775 tristate "KUnit Test for the printk ringbuffer" if !KUNIT_ALL_TESTS
1776 depends on PRINTK && KUNIT
1777 default KUNIT_ALL_TESTS
1778 help
1779 This builds the printk ringbuffer KUnit test suite.
1780
1781 For more information on KUnit and unit tests in general, please refer
1782 to the KUnit documentation.
1783
1784 If unsure, say N.
1785
1786config BUG
1787 bool "BUG() support" if EXPERT
1788 default y
1789 help
1790 Disabling this option eliminates support for BUG and WARN, reducing
1791 the size of your kernel image and potentially quietly ignoring
1792 numerous fatal conditions. You should only consider disabling this
1793 option for embedded systems with no facilities for reporting errors.
1794 Just say Y.
1795
1796config ELF_CORE
1797 depends on COREDUMP
1798 default y
1799 bool "Enable ELF core dumps" if EXPERT
1800 help
1801 Enable support for generating core dumps. Disabling saves about 4k.
1802
1803
1804config PCSPKR_PLATFORM
1805 bool "Enable PC-Speaker support" if EXPERT
1806 depends on HAVE_PCSPKR_PLATFORM
1807 select I8253_LOCK
1808 default y
1809 help
1810 This option allows to disable the internal PC-Speaker
1811 support, saving some memory.
1812
1813config BASE_SMALL
1814 bool "Enable smaller-sized data structures for core" if EXPERT
1815 help
1816 Enabling this option reduces the size of miscellaneous core
1817 kernel data structures. This saves memory on small machines,
1818 but may reduce performance.
1819
1820config FUTEX
1821 bool "Enable futex support" if EXPERT
1822 depends on !(SPARC32 && SMP)
1823 default y
1824 imply RT_MUTEXES
1825 help
1826 Disabling this option will cause the kernel to be built without
1827 support for "fast userspace mutexes". The resulting kernel may not
1828 run glibc-based applications correctly.
1829
1830config FUTEX_PI
1831 bool
1832 depends on FUTEX && RT_MUTEXES
1833 default y
1834
1835config FUTEX_PRIVATE_HASH
1836 bool
1837 depends on FUTEX && !BASE_SMALL && MMU
1838 default y
1839
1840config FUTEX_MPOL
1841 bool
1842 depends on FUTEX && NUMA
1843 default y
1844
1845config EPOLL
1846 bool "Enable eventpoll support" if EXPERT
1847 default y
1848 help
1849 Disabling this option will cause the kernel to be built without
1850 support for epoll family of system calls.
1851
1852config SIGNALFD
1853 bool "Enable signalfd() system call" if EXPERT
1854 default y
1855 help
1856 Enable the signalfd() system call that allows to receive signals
1857 on a file descriptor.
1858
1859 If unsure, say Y.
1860
1861config TIMERFD
1862 bool "Enable timerfd() system call" if EXPERT
1863 default y
1864 help
1865 Enable the timerfd() system call that allows to receive timer
1866 events on a file descriptor.
1867
1868 If unsure, say Y.
1869
1870config EVENTFD
1871 bool "Enable eventfd() system call" if EXPERT
1872 default y
1873 help
1874 Enable the eventfd() system call that allows to receive both
1875 kernel notification (ie. KAIO) or userspace notifications.
1876
1877 If unsure, say Y.
1878
1879config SHMEM
1880 bool "Use full shmem filesystem" if EXPERT
1881 default y
1882 depends on MMU
1883 help
1884 The shmem is an internal filesystem used to manage shared memory.
1885 It is backed by swap and manages resource limits. It is also exported
1886 to userspace as tmpfs if TMPFS is enabled. Disabling this
1887 option replaces shmem and tmpfs with the much simpler ramfs code,
1888 which may be appropriate on small systems without swap.
1889
1890config AIO
1891 bool "Enable AIO support" if EXPERT
1892 default y
1893 help
1894 This option enables POSIX asynchronous I/O which may by used
1895 by some high performance threaded applications. Disabling
1896 this option saves about 7k.
1897
1898config IO_URING
1899 bool "Enable IO uring support" if EXPERT
1900 select IO_WQ
1901 default y
1902 help
1903 This option enables support for the io_uring interface, enabling
1904 applications to submit and complete IO through submission and
1905 completion rings that are shared between the kernel and application.
1906
1907config GCOV_PROFILE_URING
1908 bool "Enable GCOV profiling on the io_uring subsystem"
1909 depends on IO_URING && GCOV_KERNEL
1910 help
1911 Enable GCOV profiling on the io_uring subsystem, to facilitate
1912 code coverage testing.
1913
1914 If unsure, say N.
1915
1916 Note that this will have a negative impact on the performance of
1917 the io_uring subsystem, hence this should only be enabled for
1918 specific test purposes.
1919
1920config IO_URING_MOCK_FILE
1921 tristate "Enable io_uring mock files (Experimental)" if EXPERT
1922 default n
1923 depends on IO_URING
1924 help
1925 Enable mock files for io_uring subsystem testing. The ABI might
1926 still change, so it's still experimental and should only be enabled
1927 for specific test purposes.
1928
1929 If unsure, say N.
1930
1931config ADVISE_SYSCALLS
1932 bool "Enable madvise/fadvise syscalls" if EXPERT
1933 default y
1934 help
1935 This option enables the madvise and fadvise syscalls, used by
1936 applications to advise the kernel about their future memory or file
1937 usage, improving performance. If building an embedded system where no
1938 applications use these syscalls, you can disable this option to save
1939 space.
1940
1941config MEMBARRIER
1942 bool "Enable membarrier() system call" if EXPERT
1943 default y
1944 help
1945 Enable the membarrier() system call that allows issuing memory
1946 barriers across all running threads, which can be used to distribute
1947 the cost of user-space memory barriers asymmetrically by transforming
1948 pairs of memory barriers into pairs consisting of membarrier() and a
1949 compiler barrier.
1950
1951 If unsure, say Y.
1952
1953config KCMP
1954 bool "Enable kcmp() system call" if EXPERT
1955 help
1956 Enable the kernel resource comparison system call. It provides
1957 user-space with the ability to compare two processes to see if they
1958 share a common resource, such as a file descriptor or even virtual
1959 memory space.
1960
1961 If unsure, say N.
1962
1963config RSEQ
1964 bool "Enable rseq() system call" if EXPERT
1965 default y
1966 depends on HAVE_RSEQ
1967 select MEMBARRIER
1968 help
1969 Enable the restartable sequences system call. It provides a
1970 user-space cache for the current CPU number value, which
1971 speeds up getting the current CPU number from user-space,
1972 as well as an ABI to speed up user-space operations on
1973 per-CPU data.
1974
1975 If unsure, say Y.
1976
1977config RSEQ_SLICE_EXTENSION
1978 bool "Enable rseq-based time slice extension mechanism"
1979 depends on RSEQ && HIGH_RES_TIMERS && GENERIC_ENTRY && HAVE_GENERIC_TIF_BITS
1980 help
1981 Allows userspace to request a limited time slice extension when
1982 returning from an interrupt to user space via the RSEQ shared
1983 data ABI. If granted, that allows to complete a critical section,
1984 so that other threads are not stuck on a conflicted resource,
1985 while the task is scheduled out.
1986
1987 If unsure, say N.
1988
1989config RSEQ_STATS
1990 default n
1991 bool "Enable lightweight statistics of restartable sequences" if EXPERT
1992 depends on RSEQ && DEBUG_FS
1993 help
1994 Enable lightweight counters which expose information about the
1995 frequency of RSEQ operations via debugfs. Mostly interesting for
1996 kernel debugging or performance analysis. While lightweight it's
1997 still adding code into the user/kernel mode transitions.
1998
1999 If unsure, say N.
2000
2001config RSEQ_DEBUG_DEFAULT_ENABLE
2002 default n
2003 bool "Enable restartable sequences debug mode by default" if EXPERT
2004 depends on RSEQ
2005 help
2006 This enables the static branch for debug mode of restartable
2007 sequences.
2008
2009 This also can be controlled on the kernel command line via the
2010 command line parameter "rseq_debug=0/1" and through debugfs.
2011
2012 If unsure, say N.
2013
2014config DEBUG_RSEQ
2015 default n
2016 bool "Enable debugging of rseq() system call" if EXPERT
2017 depends on RSEQ && DEBUG_KERNEL && !GENERIC_ENTRY
2018 select RSEQ_DEBUG_DEFAULT_ENABLE
2019 help
2020 Enable extra debugging checks for the rseq system call.
2021
2022 If unsure, say N.
2023
2024config CACHESTAT_SYSCALL
2025 bool "Enable cachestat() system call" if EXPERT
2026 default y
2027 help
2028 Enable the cachestat system call, which queries the page cache
2029 statistics of a file (number of cached pages, dirty pages,
2030 pages marked for writeback, (recently) evicted pages).
2031
2032 If unsure say Y here.
2033
2034config KALLSYMS
2035 bool "Load all symbols for debugging/ksymoops" if EXPERT
2036 default y
2037 help
2038 Say Y here to let the kernel print out symbolic crash information and
2039 symbolic stack backtraces. This increases the size of the kernel
2040 somewhat, as all symbols have to be loaded into the kernel image.
2041
2042config KALLSYMS_SELFTEST
2043 bool "Test the basic functions and performance of kallsyms"
2044 depends on KALLSYMS
2045 default n
2046 help
2047 Test the basic functions and performance of some interfaces, such as
2048 kallsyms_lookup_name. It also calculates the compression rate of the
2049 kallsyms compression algorithm for the current symbol set.
2050
2051 Start self-test automatically after system startup. Suggest executing
2052 "dmesg | grep kallsyms_selftest" to collect test results. "finish" is
2053 displayed in the last line, indicating that the test is complete.
2054
2055config KALLSYMS_ALL
2056 bool "Include all symbols in kallsyms"
2057 depends on DEBUG_KERNEL && KALLSYMS
2058 help
2059 Normally kallsyms only contains the symbols of functions for nicer
2060 OOPS messages and backtraces (i.e., symbols from the text and inittext
2061 sections). This is sufficient for most cases. And only if you want to
2062 enable kernel live patching, or other less common use cases (e.g.,
2063 when a debugger is used) all symbols are required (i.e., names of
2064 variables from the data sections, etc).
2065
2066 This option makes sure that all symbols are loaded into the kernel
2067 image (i.e., symbols from all sections) in cost of increased kernel
2068 size (depending on the kernel configuration, it may be 300KiB or
2069 something like this).
2070
2071 Say N unless you really need all symbols, or kernel live patching.
2072
2073# end of the "standard kernel features (expert users)" menu
2074
2075config ARCH_HAS_MEMBARRIER_CALLBACKS
2076 bool
2077
2078config ARCH_HAS_MEMBARRIER_SYNC_CORE
2079 bool
2080
2081config ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS
2082 bool
2083 help
2084 Control MSEAL_SYSTEM_MAPPINGS access based on architecture.
2085
2086 A 64-bit kernel is required for the memory sealing feature.
2087 No specific hardware features from the CPU are needed.
2088
2089 To enable this feature, the architecture needs to update their
2090 special mappings calls to include the sealing flag and confirm
2091 that it doesn't unmap/remap system mappings during the life
2092 time of the process. The existence of this flag for an architecture
2093 implies that it does not require the remapping of the system
2094 mappings during process lifetime, so sealing these mappings is safe
2095 from a kernel perspective.
2096
2097 After the architecture enables this, a distribution can set
2098 CONFIG_MSEAL_SYSTEM_MAPPING to manage access to the feature.
2099
2100 For complete descriptions of memory sealing, please see
2101 Documentation/userspace-api/mseal.rst
2102
2103config HAVE_PERF_EVENTS
2104 bool
2105 help
2106 See tools/perf/design.txt for details.
2107
2108config GUEST_PERF_EVENTS
2109 bool
2110 depends on HAVE_PERF_EVENTS
2111
2112config PERF_GUEST_MEDIATED_PMU
2113 bool
2114 depends on GUEST_PERF_EVENTS
2115
2116config PERF_USE_VMALLOC
2117 bool
2118 help
2119 See tools/perf/design.txt for details
2120
2121menu "Kernel Performance Events And Counters"
2122
2123config PERF_EVENTS
2124 bool "Kernel performance events and counters"
2125 default y if PROFILING
2126 depends on HAVE_PERF_EVENTS
2127 select IRQ_WORK
2128 help
2129 Enable kernel support for various performance events provided
2130 by software and hardware.
2131
2132 Software events are supported either built-in or via the
2133 use of generic tracepoints.
2134
2135 Most modern CPUs support performance events via performance
2136 counter registers. These registers count the number of certain
2137 types of hw events: such as instructions executed, cachemisses
2138 suffered, or branches mis-predicted - without slowing down the
2139 kernel or applications. These registers can also trigger interrupts
2140 when a threshold number of events have passed - and can thus be
2141 used to profile the code that runs on that CPU.
2142
2143 The Linux Performance Event subsystem provides an abstraction of
2144 these software and hardware event capabilities, available via a
2145 system call and used by the "perf" utility in tools/perf/. It
2146 provides per task and per CPU counters, and it provides event
2147 capabilities on top of those.
2148
2149 Say Y if unsure.
2150
2151config DEBUG_PERF_USE_VMALLOC
2152 default n
2153 bool "Debug: use vmalloc to back perf mmap() buffers"
2154 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
2155 select PERF_USE_VMALLOC
2156 help
2157 Use vmalloc memory to back perf mmap() buffers.
2158
2159 Mostly useful for debugging the vmalloc code on platforms
2160 that don't require it.
2161
2162 Say N if unsure.
2163
2164endmenu
2165
2166config SYSTEM_DATA_VERIFICATION
2167 def_bool n
2168 select SYSTEM_TRUSTED_KEYRING
2169 select KEYS
2170 select CRYPTO
2171 select CRYPTO_RSA
2172 select ASYMMETRIC_KEY_TYPE
2173 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
2174 select ASN1
2175 select OID_REGISTRY
2176 select X509_CERTIFICATE_PARSER
2177 select PKCS7_MESSAGE_PARSER
2178 help
2179 Provide PKCS#7 message verification using the contents of the system
2180 trusted keyring to provide public keys. This then can be used for
2181 module verification, kexec image verification and firmware blob
2182 verification.
2183
2184config PROFILING
2185 bool "Profiling support"
2186 help
2187 Say Y here to enable the extended profiling support mechanisms used
2188 by profilers.
2189
2190config RUST
2191 bool "Rust support"
2192 depends on HAVE_RUST
2193 depends on RUST_IS_AVAILABLE
2194 select EXTENDED_MODVERSIONS if MODVERSIONS
2195 depends on !MODVERSIONS || GENDWARFKSYMS
2196 depends on !GCC_PLUGIN_RANDSTRUCT
2197 depends on !RANDSTRUCT
2198 depends on !DEBUG_INFO_BTF || (PAHOLE_HAS_LANG_EXCLUDE && !LTO)
2199 depends on !CFI || HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC
2200 select CFI_ICALL_NORMALIZE_INTEGERS if CFI
2201 depends on !KASAN_SW_TAGS
2202 help
2203 Enables Rust support in the kernel.
2204
2205 This allows other Rust-related options, like drivers written in Rust,
2206 to be selected.
2207
2208 It is also required to be able to load external kernel modules
2209 written in Rust.
2210
2211 See Documentation/rust/ for more information.
2212
2213 If unsure, say N.
2214
2215config RUSTC_VERSION_TEXT
2216 string
2217 depends on RUST
2218 default "$(RUSTC_VERSION_TEXT)"
2219 help
2220 See `CC_VERSION_TEXT`.
2221
2222config BINDGEN_VERSION_TEXT
2223 string
2224 depends on RUST
2225 default "$(shell,$(BINDGEN) --version 2>/dev/null)"
2226
2227#
2228# Place an empty function call at each tracepoint site. Can be
2229# dynamically changed for a probe function.
2230#
2231config TRACEPOINTS
2232 bool
2233 select TASKS_TRACE_RCU
2234
2235source "kernel/Kconfig.kexec"
2236
2237source "kernel/liveupdate/Kconfig"
2238
2239endmenu # General setup
2240
2241source "arch/Kconfig"
2242
2243config RT_MUTEXES
2244 bool
2245 default y if PREEMPT_RT
2246
2247config MODULE_SIG_FORMAT
2248 def_bool n
2249 select SYSTEM_DATA_VERIFICATION
2250
2251source "kernel/module/Kconfig"
2252
2253config INIT_ALL_POSSIBLE
2254 bool
2255 help
2256 Back when each arch used to define their own cpu_online_mask and
2257 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2258 with all 1s, and others with all 0s. When they were centralised,
2259 it was better to provide this option than to break all the archs
2260 and have several arch maintainers pursuing me down dark alleys.
2261
2262source "block/Kconfig"
2263
2264config PREEMPT_NOTIFIERS
2265 bool
2266
2267config PADATA
2268 depends on SMP
2269 bool
2270
2271config ASN1
2272 tristate
2273 help
2274 Build a simple ASN.1 grammar compiler that produces a bytecode output
2275 that can be interpreted by the ASN.1 stream decoder and used to
2276 inform it as to what tags are to be expected in a stream and what
2277 functions to call on what tags.
2278
2279source "kernel/Kconfig.locks"
2280
2281config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2282 bool
2283
2284config ARCH_HAS_PREPARE_SYNC_CORE_CMD
2285 bool
2286
2287config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2288 bool
2289
2290# It may be useful for an architecture to override the definitions of the
2291# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2292# and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2293# different calling convention for syscalls. They can also override the
2294# macros for not-implemented syscalls in kernel/sys_ni.c and
2295# kernel/time/posix-stubs.c. All these overrides need to be available in
2296# <asm/syscall_wrapper.h>.
2297config ARCH_HAS_SYSCALL_WRAPPER
2298 def_bool n