1 # SPDX-License-Identifier: GPL-2.0-only
2 config 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
19 config CC_IS_GCC
20 def_bool $(success,test "$(cc-name)" = GCC)
21
22 config GCC_VERSION
23 int
24 default $(cc-version) if CC_IS_GCC
25 default 0
26
27 config CC_IS_CLANG
28 def_bool $(success,test "$(cc-name)" = Clang)
29
30 config CLANG_VERSION
31 int
32 default $(cc-version) if CC_IS_CLANG
33 default 0
34
35 config AS_IS_GNU
36 def_bool $(success,test "$(as-name)" = GNU)
37
38 config AS_IS_LLVM
39 def_bool $(success,test "$(as-name)" = LLVM)
40
41 config 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
47 config LD_IS_BFD
48 def_bool $(success,test "$(ld-name)" = BFD)
49
50 config LD_VERSION
51 int
52 default $(ld-version) if LD_IS_BFD
53 default 0
54
55 config LD_IS_LLD
56 def_bool $(success,test "$(ld-name)" = LLD)
57
58 config LLD_VERSION
59 int
60 default $(ld-version) if LD_IS_LLD
61 default 0
62
63 config 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
70 config 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
81 config RUSTC_LLVM_VERSION
82 int
83 default $(rustc-llvm-version)
84
85 config CC_CAN_LINK
86 bool
87 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT
88 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag))
89
90 config CC_CAN_LINK_STATIC
91 bool
92 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT
93 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static)
94
95 # Fixed in GCC 14, 13.3, 12.4 and 11.5
96 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113921
97 config GCC_ASM_GOTO_OUTPUT_BROKEN
98 bool
99 depends on CC_IS_GCC
100 default y if GCC_VERSION < 110500
101 default y if GCC_VERSION >= 120000 && GCC_VERSION < 120400
102 default y if GCC_VERSION >= 130000 && GCC_VERSION < 130300
103
104 config CC_HAS_ASM_GOTO_OUTPUT
105 def_bool y
106 depends on !GCC_ASM_GOTO_OUTPUT_BROKEN
107 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)
108
109 config CC_HAS_ASM_GOTO_TIED_OUTPUT
110 depends on CC_HAS_ASM_GOTO_OUTPUT
111 # Detect buggy gcc and clang, fixed in gcc-11 clang-14.
112 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)
113
114 config TOOLS_SUPPORT_RELR
115 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
116
117 config CC_HAS_ASM_INLINE
118 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
119
120 config CC_HAS_NO_PROFILE_FN_ATTR
121 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
122
123 config PAHOLE_VERSION
124 int
125 default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))
126
127 config CONSTRUCTORS
128 bool
129
130 config IRQ_WORK
131 def_bool y if SMP
132
133 config BUILDTIME_TABLE_SORT
134 bool
135
136 config THREAD_INFO_IN_TASK
137 bool
138 help
139 Select this to move thread_info off the stack into task_struct. To
140 make this work, an arch will need to remove all thread_info fields
141 except flags and fix any runtime bugs.
142
143 One subtle change that will be needed is to use try_get_task_stack()
144 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
145
146 menu "General setup"
147
148 config BROKEN
149 bool
150
151 config BROKEN_ON_SMP
152 bool
153 depends on BROKEN || !SMP
154 default y
155
156 config INIT_ENV_ARG_LIMIT
157 int
158 default 32 if !UML
159 default 128 if UML
160 help
161 Maximum of each of the number of arguments and environment
162 variables passed to init from the kernel command line.
163
164 config COMPILE_TEST
165 bool "Compile also drivers which will not load"
166 depends on HAS_IOMEM
167 help
168 Some drivers can be compiled on a different platform than they are
169 intended to be run on. Despite they cannot be loaded there (or even
170 when they load they cannot be used due to missing HW support),
171 developers still, opposing to distributors, might want to build such
172 drivers to compile-test them.
173
174 If you are a developer and want to build everything available, say Y
175 here. If you are a user/distributor, say N here to exclude useless
176 drivers to be distributed.
177
178 config WERROR
179 bool "Compile the kernel with warnings as errors"
180 default COMPILE_TEST
181 help
182 A kernel build should not cause any compiler warnings, and this
183 enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags
184 to enforce that rule by default. Certain warnings from other tools
185 such as the linker may be upgraded to errors with this option as
186 well.
187
188 However, if you have a new (or very old) compiler or linker with odd
189 and unusual warnings, or you have some architecture with problems,
190 you may need to disable this config option in order to
191 successfully build the kernel.
192
193 If in doubt, say Y.
194
195 config UAPI_HEADER_TEST
196 bool "Compile test UAPI headers"
197 depends on HEADERS_INSTALL && CC_CAN_LINK
198 help
199 Compile test headers exported to user-space to ensure they are
200 self-contained, i.e. compilable as standalone units.
201
202 If you are a developer or tester and want to ensure the exported
203 headers are self-contained, say Y here. Otherwise, choose N.
204
205 config LOCALVERSION
206 string "Local version - append to kernel release"
207 help
208 Append an extra string to the end of your kernel version.
209 This will show up when you type uname, for example.
210 The string you set here will be appended after the contents of
211 any files with a filename matching localversion* in your
212 object and source tree, in that order. Your total string can
213 be a maximum of 64 characters.
214
215 config LOCALVERSION_AUTO
216 bool "Automatically append version information to the version string"
217 default y
218 depends on !COMPILE_TEST
219 help
220 This will try to automatically determine if the current tree is a
221 release tree by looking for git tags that belong to the current
222 top of tree revision.
223
224 A string of the format -gxxxxxxxx will be added to the localversion
225 if a git-based tree is found. The string generated by this will be
226 appended after any matching localversion* files, and after the value
227 set in CONFIG_LOCALVERSION.
228
229 (The actual string used here is the first 12 characters produced
230 by running the command:
231
232 $ git rev-parse --verify HEAD
233
234 which is done within the script "scripts/setlocalversion".)
235
236 config BUILD_SALT
237 string "Build ID Salt"
238 default ""
239 help
240 The build ID is used to link binaries and their debug info. Setting
241 this option will use the value in the calculation of the build id.
242 This is mostly useful for distributions which want to ensure the
243 build is unique between builds. It's safe to leave the default.
244
245 config HAVE_KERNEL_GZIP
246 bool
247
248 config HAVE_KERNEL_BZIP2
249 bool
250
251 config HAVE_KERNEL_LZMA
252 bool
253
254 config HAVE_KERNEL_XZ
255 bool
256
257 config HAVE_KERNEL_LZO
258 bool
259
260 config HAVE_KERNEL_LZ4
261 bool
262
263 config HAVE_KERNEL_ZSTD
264 bool
265
266 config HAVE_KERNEL_UNCOMPRESSED
267 bool
268
269 choice
270 prompt "Kernel compression mode"
271 default KERNEL_GZIP
272 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
273 help
274 The linux kernel is a kind of self-extracting executable.
275 Several compression algorithms are available, which differ
276 in efficiency, compression and decompression speed.
277 Compression speed is only relevant when building a kernel.
278 Decompression speed is relevant at each boot.
279
280 If you have any problems with bzip2 or lzma compressed
281 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
282 version of this functionality (bzip2 only), for 2.4, was
283 supplied by Christian Ludwig)
284
285 High compression options are mostly useful for users, who
286 are low on disk space (embedded systems), but for whom ram
287 size matters less.
288
289 If in doubt, select 'gzip'
290
291 config KERNEL_GZIP
292 bool "Gzip"
293 depends on HAVE_KERNEL_GZIP
294 help
295 The old and tried gzip compression. It provides a good balance
296 between compression ratio and decompression speed.
297
298 config KERNEL_BZIP2
299 bool "Bzip2"
300 depends on HAVE_KERNEL_BZIP2
301 help
302 Its compression ratio and speed is intermediate.
303 Decompression speed is slowest among the choices. The kernel
304 size is about 10% smaller with bzip2, in comparison to gzip.
305 Bzip2 uses a large amount of memory. For modern kernels you
306 will need at least 8MB RAM or more for booting.
307
308 config KERNEL_LZMA
309 bool "LZMA"
310 depends on HAVE_KERNEL_LZMA
311 help
312 This compression algorithm's ratio is best. Decompression speed
313 is between gzip and bzip2. Compression is slowest.
314 The kernel size is about 33% smaller with LZMA in comparison to gzip.
315
316 config KERNEL_XZ
317 bool "XZ"
318 depends on HAVE_KERNEL_XZ
319 help
320 XZ uses the LZMA2 algorithm and instruction set specific
321 BCJ filters which can improve compression ratio of executable
322 code. The size of the kernel is about 30% smaller with XZ in
323 comparison to gzip. On architectures for which there is a BCJ
324 filter (i386, x86_64, ARM, ARM64, RISC-V, big endian PowerPC,
325 and SPARC), XZ will create a few percent smaller kernel than
326 plain LZMA.
327
328 The speed is about the same as with LZMA: The decompression
329 speed of XZ is better than that of bzip2 but worse than gzip
330 and LZO. Compression is slow.
331
332 config KERNEL_LZO
333 bool "LZO"
334 depends on HAVE_KERNEL_LZO
335 help
336 Its compression ratio is the poorest among the choices. The kernel
337 size is about 10% bigger than gzip; however its speed
338 (both compression and decompression) is the fastest.
339
340 config KERNEL_LZ4
341 bool "LZ4"
342 depends on HAVE_KERNEL_LZ4
343 help
344 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
345 A preliminary version of LZ4 de/compression tool is available at
346 <https://code.google.com/p/lz4/>.
347
348 Its compression ratio is worse than LZO. The size of the kernel
349 is about 8% bigger than LZO. But the decompression speed is
350 faster than LZO.
351
352 config KERNEL_ZSTD
353 bool "ZSTD"
354 depends on HAVE_KERNEL_ZSTD
355 help
356 ZSTD is a compression algorithm targeting intermediate compression
357 with fast decompression speed. It will compress better than GZIP and
358 decompress around the same speed as LZO, but slower than LZ4. You
359 will need at least 192 KB RAM or more for booting. The zstd command
360 line tool is required for compression.
361
362 config KERNEL_UNCOMPRESSED
363 bool "None"
364 depends on HAVE_KERNEL_UNCOMPRESSED
365 help
366 Produce uncompressed kernel image. This option is usually not what
367 you want. It is useful for debugging the kernel in slow simulation
368 environments, where decompressing and moving the kernel is awfully
369 slow. This option allows early boot code to skip the decompressor
370 and jump right at uncompressed kernel image.
371
372 endchoice
373
374 config DEFAULT_INIT
375 string "Default init path"
376 default ""
377 help
378 This option determines the default init for the system if no init=
379 option is passed on the kernel command line. If the requested path is
380 not present, we will still then move on to attempting further
381 locations (e.g. /sbin/init, etc). If this is empty, we will just use
382 the fallback list when init= is not passed.
383
384 config DEFAULT_HOSTNAME
385 string "Default hostname"
386 default "(none)"
387 help
388 This option determines the default system hostname before userspace
389 calls sethostname(2). The kernel traditionally uses "(none)" here,
390 but you may wish to use a different default here to make a minimal
391 system more usable with less configuration.
392
393 config SYSVIPC
394 bool "System V IPC"
395 help
396 Inter Process Communication is a suite of library functions and
397 system calls which let processes (running programs) synchronize and
398 exchange information. It is generally considered to be a good thing,
399 and some programs won't run unless you say Y here. In particular, if
400 you want to run the DOS emulator dosemu under Linux (read the
401 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
402 you'll need to say Y here.
403
404 You can find documentation about IPC with "info ipc" and also in
405 section 6.4 of the Linux Programmer's Guide, available from
406 <http://www.tldp.org/guides.html>.
407
408 config SYSVIPC_SYSCTL
409 bool
410 depends on SYSVIPC
411 depends on SYSCTL
412 default y
413
414 config SYSVIPC_COMPAT
415 def_bool y
416 depends on COMPAT && SYSVIPC
417
418 config POSIX_MQUEUE
419 bool "POSIX Message Queues"
420 depends on NET
421 help
422 POSIX variant of message queues is a part of IPC. In POSIX message
423 queues every message has a priority which decides about succession
424 of receiving it by a process. If you want to compile and run
425 programs written e.g. for Solaris with use of its POSIX message
426 queues (functions mq_*) say Y here.
427
428 POSIX message queues are visible as a filesystem called 'mqueue'
429 and can be mounted somewhere if you want to do filesystem
430 operations on message queues.
431
432 If unsure, say Y.
433
434 config POSIX_MQUEUE_SYSCTL
435 bool
436 depends on POSIX_MQUEUE
437 depends on SYSCTL
438 default y
439
440 config WATCH_QUEUE
441 bool "General notification queue"
442 default n
443 help
444
445 This is a general notification queue for the kernel to pass events to
446 userspace by splicing them into pipes. It can be used in conjunction
447 with watches for key/keyring change notifications and device
448 notifications.
449
450 See Documentation/core-api/watch_queue.rst
451
452 config CROSS_MEMORY_ATTACH
453 bool "Enable process_vm_readv/writev syscalls"
454 depends on MMU
455 default y
456 help
457 Enabling this option adds the system calls process_vm_readv and
458 process_vm_writev which allow a process with the correct privileges
459 to directly read from or write to another process' address space.
460 See the man page for more details.
461
462 config USELIB
463 bool "uselib syscall (for libc5 and earlier)"
464 default ALPHA || M68K || SPARC
465 help
466 This option enables the uselib syscall, a system call used in the
467 dynamic linker from libc5 and earlier. glibc does not use this
468 system call. If you intend to run programs built on libc5 or
469 earlier, you may need to enable this syscall. Current systems
470 running glibc can safely disable this.
471
472 config AUDIT
473 bool "Auditing support"
474 depends on NET
475 help
476 Enable auditing infrastructure that can be used with another
477 kernel subsystem, such as SELinux (which requires this for
478 logging of avc messages output). System call auditing is included
479 on architectures which support it.
480
481 config HAVE_ARCH_AUDITSYSCALL
482 bool
483
484 config AUDITSYSCALL
485 def_bool y
486 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
487 select FSNOTIFY
488
489 source "kernel/irq/Kconfig"
490 source "kernel/time/Kconfig"
491 source "kernel/bpf/Kconfig"
492 source "kernel/Kconfig.preempt"
493
494 menu "CPU/Task time and stats accounting"
495
496 config VIRT_CPU_ACCOUNTING
497 bool
498
499 choice
500 prompt "Cputime accounting"
501 default TICK_CPU_ACCOUNTING
502
503 # Kind of a stub config for the pure tick based cputime accounting
504 config TICK_CPU_ACCOUNTING
505 bool "Simple tick based cputime accounting"
506 depends on !S390 && !NO_HZ_FULL
507 help
508 This is the basic tick based cputime accounting that maintains
509 statistics about user, system and idle time spent on per jiffies
510 granularity.
511
512 If unsure, say Y.
513
514 config VIRT_CPU_ACCOUNTING_NATIVE
515 bool "Deterministic task and CPU time accounting"
516 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
517 select VIRT_CPU_ACCOUNTING
518 help
519 Select this option to enable more accurate task and CPU time
520 accounting. This is done by reading a CPU counter on each
521 kernel entry and exit and on transitions within the kernel
522 between system, softirq and hardirq state, so there is a
523 small performance impact. In the case of s390 or IBM POWER > 5,
524 this also enables accounting of stolen time on logically-partitioned
525 systems.
526
527 config VIRT_CPU_ACCOUNTING_GEN
528 bool "Full dynticks CPU time accounting"
529 depends on HAVE_CONTEXT_TRACKING_USER
530 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
531 depends on GENERIC_CLOCKEVENTS
532 select VIRT_CPU_ACCOUNTING
533 select CONTEXT_TRACKING_USER
534 help
535 Select this option to enable task and CPU time accounting on full
536 dynticks systems. This accounting is implemented by watching every
537 kernel-user boundaries using the context tracking subsystem.
538 The accounting is thus performed at the expense of some significant
539 overhead.
540
541 For now this is only useful if you are working on the full
542 dynticks subsystem development.
543
544 If unsure, say N.
545
546 endchoice
547
548 config IRQ_TIME_ACCOUNTING
549 bool "Fine granularity task level IRQ time accounting"
550 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
551 help
552 Select this option to enable fine granularity task irq time
553 accounting. This is done by reading a timestamp on each
554 transitions between softirq and hardirq state, so there can be a
555 small performance impact.
556
557 If in doubt, say N here.
558
559 config HAVE_SCHED_AVG_IRQ
560 def_bool y
561 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
562 depends on SMP
563
564 config SCHED_HW_PRESSURE
565 bool
566 default y if ARM && ARM_CPU_TOPOLOGY
567 default y if ARM64
568 depends on SMP
569 depends on CPU_FREQ_THERMAL
570 help
571 Select this option to enable HW pressure accounting in the
572 scheduler. HW pressure is the value conveyed to the scheduler
573 that reflects the reduction in CPU compute capacity resulted from
574 HW throttling. HW throttling occurs when the performance of
575 a CPU is capped due to high operating temperatures as an example.
576
577 If selected, the scheduler will be able to balance tasks accordingly,
578 i.e. put less load on throttled CPUs than on non/less throttled ones.
579
580 This requires the architecture to implement
581 arch_update_hw_pressure() and arch_scale_thermal_pressure().
582
583 config BSD_PROCESS_ACCT
584 bool "BSD Process Accounting"
585 depends on MULTIUSER
586 help
587 If you say Y here, a user level program will be able to instruct the
588 kernel (via a special system call) to write process accounting
589 information to a file: whenever a process exits, information about
590 that process will be appended to the file by the kernel. The
591 information includes things such as creation time, owning user,
592 command name, memory usage, controlling terminal etc. (the complete
593 list is in the struct acct in <file:include/linux/acct.h>). It is
594 up to the user level program to do useful things with this
595 information. This is generally a good idea, so say Y.
596
597 config BSD_PROCESS_ACCT_V3
598 bool "BSD Process Accounting version 3 file format"
599 depends on BSD_PROCESS_ACCT
600 default n
601 help
602 If you say Y here, the process accounting information is written
603 in a new file format that also logs the process IDs of each
604 process and its parent. Note that this file format is incompatible
605 with previous v0/v1/v2 file formats, so you will need updated tools
606 for processing it. A preliminary version of these tools is available
607 at <http://www.gnu.org/software/acct/>.
608
609 config TASKSTATS
610 bool "Export task/process statistics through netlink"
611 depends on NET
612 depends on MULTIUSER
613 default n
614 help
615 Export selected statistics for tasks/processes through the
616 generic netlink interface. Unlike BSD process accounting, the
617 statistics are available during the lifetime of tasks/processes as
618 responses to commands. Like BSD accounting, they are sent to user
619 space on task exit.
620
621 Say N if unsure.
622
623 config TASK_DELAY_ACCT
624 bool "Enable per-task delay accounting"
625 depends on TASKSTATS
626 select SCHED_INFO
627 help
628 Collect information on time spent by a task waiting for system
629 resources like cpu, synchronous block I/O completion and swapping
630 in pages. Such statistics can help in setting a task's priorities
631 relative to other tasks for cpu, io, rss limits etc.
632
633 Say N if unsure.
634
635 config TASK_XACCT
636 bool "Enable extended accounting over taskstats"
637 depends on TASKSTATS
638 help
639 Collect extended task accounting data and send the data
640 to userland for processing over the taskstats interface.
641
642 Say N if unsure.
643
644 config TASK_IO_ACCOUNTING
645 bool "Enable per-task storage I/O accounting"
646 depends on TASK_XACCT
647 help
648 Collect information on the number of bytes of storage I/O which this
649 task has caused.
650
651 Say N if unsure.
652
653 config PSI
654 bool "Pressure stall information tracking"
655 select KERNFS
656 help
657 Collect metrics that indicate how overcommitted the CPU, memory,
658 and IO capacity are in the system.
659
660 If you say Y here, the kernel will create /proc/pressure/ with the
661 pressure statistics files cpu, memory, and io. These will indicate
662 the share of walltime in which some or all tasks in the system are
663 delayed due to contention of the respective resource.
664
665 In kernels with cgroup support, cgroups (cgroup2 only) will
666 have cpu.pressure, memory.pressure, and io.pressure files,
667 which aggregate pressure stalls for the grouped tasks only.
668
669 For more details see Documentation/accounting/psi.rst.
670
671 Say N if unsure.
672
673 config PSI_DEFAULT_DISABLED
674 bool "Require boot parameter to enable pressure stall information tracking"
675 default n
676 depends on PSI
677 help
678 If set, pressure stall information tracking will be disabled
679 per default but can be enabled through passing psi=1 on the
680 kernel commandline during boot.
681
682 This feature adds some code to the task wakeup and sleep
683 paths of the scheduler. The overhead is too low to affect
684 common scheduling-intense workloads in practice (such as
685 webservers, memcache), but it does show up in artificial
686 scheduler stress tests, such as hackbench.
687
688 If you are paranoid and not sure what the kernel will be
689 used for, say Y.
690
691 Say N if unsure.
692
693 endmenu # "CPU/Task time and stats accounting"
694
695 config CPU_ISOLATION
696 bool "CPU isolation"
697 depends on SMP || COMPILE_TEST
698 default y
699 help
700 Make sure that CPUs running critical tasks are not disturbed by
701 any source of "noise" such as unbound workqueues, timers, kthreads...
702 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
703 the "isolcpus=" boot parameter.
704
705 Say Y if unsure.
706
707 source "kernel/rcu/Kconfig"
708
709 config IKCONFIG
710 tristate "Kernel .config support"
711 help
712 This option enables the complete Linux kernel ".config" file
713 contents to be saved in the kernel. It provides documentation
714 of which kernel options are used in a running kernel or in an
715 on-disk kernel. This information can be extracted from the kernel
716 image file with the script scripts/extract-ikconfig and used as
717 input to rebuild the current kernel or to build another kernel.
718 It can also be extracted from a running kernel by reading
719 /proc/config.gz if enabled (below).
720
721 config IKCONFIG_PROC
722 bool "Enable access to .config through /proc/config.gz"
723 depends on IKCONFIG && PROC_FS
724 help
725 This option enables access to the kernel configuration file
726 through /proc/config.gz.
727
728 config IKHEADERS
729 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
730 depends on SYSFS
731 help
732 This option enables access to the in-kernel headers that are generated during
733 the build process. These can be used to build eBPF tracing programs,
734 or similar programs. If you build the headers as a module, a module called
735 kheaders.ko is built which can be loaded on-demand to get access to headers.
736
737 config LOG_BUF_SHIFT
738 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
739 range 12 25
740 default 17
741 depends on PRINTK
742 help
743 Select the minimal kernel log buffer size as a power of 2.
744 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
745 parameter, see below. Any higher size also might be forced
746 by "log_buf_len" boot parameter.
747
748 Examples:
749 17 => 128 KB
750 16 => 64 KB
751 15 => 32 KB
752 14 => 16 KB
753 13 => 8 KB
754 12 => 4 KB
755
756 config LOG_CPU_MAX_BUF_SHIFT
757 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
758 depends on SMP
759 range 0 21
760 default 0 if BASE_SMALL
761 default 12
762 depends on PRINTK
763 help
764 This option allows to increase the default ring buffer size
765 according to the number of CPUs. The value defines the contribution
766 of each CPU as a power of 2. The used space is typically only few
767 lines however it might be much more when problems are reported,
768 e.g. backtraces.
769
770 The increased size means that a new buffer has to be allocated and
771 the original static one is unused. It makes sense only on systems
772 with more CPUs. Therefore this value is used only when the sum of
773 contributions is greater than the half of the default kernel ring
774 buffer as defined by LOG_BUF_SHIFT. The default values are set
775 so that more than 16 CPUs are needed to trigger the allocation.
776
777 Also this option is ignored when "log_buf_len" kernel parameter is
778 used as it forces an exact (power of two) size of the ring buffer.
779
780 The number of possible CPUs is used for this computation ignoring
781 hotplugging making the computation optimal for the worst case
782 scenario while allowing a simple algorithm to be used from bootup.
783
784 Examples shift values and their meaning:
785 17 => 128 KB for each CPU
786 16 => 64 KB for each CPU
787 15 => 32 KB for each CPU
788 14 => 16 KB for each CPU
789 13 => 8 KB for each CPU
790 12 => 4 KB for each CPU
791
792 config PRINTK_INDEX
793 bool "Printk indexing debugfs interface"
794 depends on PRINTK && DEBUG_FS
795 help
796 Add support for indexing of all printk formats known at compile time
797 at <debugfs>/printk/index/<module>.
798
799 This can be used as part of maintaining daemons which monitor
800 /dev/kmsg, as it permits auditing the printk formats present in a
801 kernel, allowing detection of cases where monitored printks are
802 changed or no longer present.
803
804 There is no additional runtime cost to printk with this enabled.
805
806 #
807 # Architectures with an unreliable sched_clock() should select this:
808 #
809 config HAVE_UNSTABLE_SCHED_CLOCK
810 bool
811
812 config GENERIC_SCHED_CLOCK
813 bool
814
815 menu "Scheduler features"
816
817 config UCLAMP_TASK
818 bool "Enable utilization clamping for RT/FAIR tasks"
819 depends on CPU_FREQ_GOV_SCHEDUTIL
820 help
821 This feature enables the scheduler to track the clamped utilization
822 of each CPU based on RUNNABLE tasks scheduled on that CPU.
823
824 With this option, the user can specify the min and max CPU
825 utilization allowed for RUNNABLE tasks. The max utilization defines
826 the maximum frequency a task should use while the min utilization
827 defines the minimum frequency it should use.
828
829 Both min and max utilization clamp values are hints to the scheduler,
830 aiming at improving its frequency selection policy, but they do not
831 enforce or grant any specific bandwidth for tasks.
832
833 If in doubt, say N.
834
835 config UCLAMP_BUCKETS_COUNT
836 int "Number of supported utilization clamp buckets"
837 range 5 20
838 default 5
839 depends on UCLAMP_TASK
840 help
841 Defines the number of clamp buckets to use. The range of each bucket
842 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
843 number of clamp buckets the finer their granularity and the higher
844 the precision of clamping aggregation and tracking at run-time.
845
846 For example, with the minimum configuration value we will have 5
847 clamp buckets tracking 20% utilization each. A 25% boosted tasks will
848 be refcounted in the [20..39]% bucket and will set the bucket clamp
849 effective value to 25%.
850 If a second 30% boosted task should be co-scheduled on the same CPU,
851 that task will be refcounted in the same bucket of the first task and
852 it will boost the bucket clamp effective value to 30%.
853 The clamp effective value of a bucket is reset to its nominal value
854 (20% in the example above) when there are no more tasks refcounted in
855 that bucket.
856
857 An additional boost/capping margin can be added to some tasks. In the
858 example above the 25% task will be boosted to 30% until it exits the
859 CPU. If that should be considered not acceptable on certain systems,
860 it's always possible to reduce the margin by increasing the number of
861 clamp buckets to trade off used memory for run-time tracking
862 precision.
863
864 If in doubt, use the default value.
865
866 endmenu
867
868 #
869 # For architectures that want to enable the support for NUMA-affine scheduler
870 # balancing logic:
871 #
872 config ARCH_SUPPORTS_NUMA_BALANCING
873 bool
874
875 #
876 # For architectures that prefer to flush all TLBs after a number of pages
877 # are unmapped instead of sending one IPI per page to flush. The architecture
878 # must provide guarantees on what happens if a clean TLB cache entry is
879 # written after the unmap. Details are in mm/rmap.c near the check for
880 # should_defer_flush. The architecture should also consider if the full flush
881 # and the refill costs are offset by the savings of sending fewer IPIs.
882 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
883 bool
884
885 config CC_HAS_INT128
886 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
887
888 config CC_IMPLICIT_FALLTHROUGH
889 string
890 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
891 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough)
892
893 # Currently, disable gcc-10+ array-bounds globally.
894 # It's still broken in gcc-13, so no upper bound yet.
895 config GCC10_NO_ARRAY_BOUNDS
896 def_bool y
897
898 config CC_NO_ARRAY_BOUNDS
899 bool
900 default y if CC_IS_GCC && GCC_VERSION >= 90000 && GCC10_NO_ARRAY_BOUNDS
901
902 # Currently, disable -Wstringop-overflow for GCC globally.
903 config GCC_NO_STRINGOP_OVERFLOW
904 def_bool y
905
906 config CC_NO_STRINGOP_OVERFLOW
907 bool
908 default y if CC_IS_GCC && GCC_NO_STRINGOP_OVERFLOW
909
910 config CC_STRINGOP_OVERFLOW
911 bool
912 default y if CC_IS_GCC && !CC_NO_STRINGOP_OVERFLOW
913
914 #
915 # For architectures that know their GCC __int128 support is sound
916 #
917 config ARCH_SUPPORTS_INT128
918 bool
919
920 # For architectures that (ab)use NUMA to represent different memory regions
921 # all cpu-local but of different latencies, such as SuperH.
922 #
923 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
924 bool
925
926 config NUMA_BALANCING
927 bool "Memory placement aware NUMA scheduler"
928 depends on ARCH_SUPPORTS_NUMA_BALANCING
929 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
930 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT
931 help
932 This option adds support for automatic NUMA aware memory/task placement.
933 The mechanism is quite primitive and is based on migrating memory when
934 it has references to the node the task is running on.
935
936 This system will be inactive on UMA systems.
937
938 config NUMA_BALANCING_DEFAULT_ENABLED
939 bool "Automatically enable NUMA aware memory/task placement"
940 default y
941 depends on NUMA_BALANCING
942 help
943 If set, automatic NUMA balancing will be enabled if running on a NUMA
944 machine.
945
946 config SLAB_OBJ_EXT
947 bool
948
949 menuconfig CGROUPS
950 bool "Control Group support"
951 select KERNFS
952 help
953 This option adds support for grouping sets of processes together, for
954 use with process control subsystems such as Cpusets, CFS, memory
955 controls or device isolation.
956 See
957 - Documentation/scheduler/sched-design-CFS.rst (CFS)
958 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
959 and resource control)
960
961 Say N if unsure.
962
963 if CGROUPS
964
965 config PAGE_COUNTER
966 bool
967
968 config CGROUP_FAVOR_DYNMODS
969 bool "Favor dynamic modification latency reduction by default"
970 help
971 This option enables the "favordynmods" mount option by default
972 which reduces the latencies of dynamic cgroup modifications such
973 as task migrations and controller on/offs at the cost of making
974 hot path operations such as forks and exits more expensive.
975
976 Say N if unsure.
977
978 config MEMCG
979 bool "Memory controller"
980 select PAGE_COUNTER
981 select EVENTFD
982 select SLAB_OBJ_EXT
983 help
984 Provides control over the memory footprint of tasks in a cgroup.
985
986 config MEMCG_V1
987 bool "Legacy cgroup v1 memory controller"
988 depends on MEMCG
989 default n
990 help
991 Legacy cgroup v1 memory controller which has been deprecated by
992 cgroup v2 implementation. The v1 is there for legacy applications
993 which haven't migrated to the new cgroup v2 interface yet. If you
994 do not have any such application then you are completely fine leaving
995 this option disabled.
996
997 Please note that feature set of the legacy memory controller is likely
998 going to shrink due to deprecation process. New deployments with v1
999 controller are highly discouraged.
1000
1001 Say N if unsure.
1002
1003 config BLK_CGROUP
1004 bool "IO controller"
1005 depends on BLOCK
1006 default n
1007 help
1008 Generic block IO controller cgroup interface. This is the common
1009 cgroup interface which should be used by various IO controlling
1010 policies.
1011
1012 Currently, CFQ IO scheduler uses it to recognize task groups and
1013 control disk bandwidth allocation (proportional time slice allocation)
1014 to such task groups. It is also used by bio throttling logic in
1015 block layer to implement upper limit in IO rates on a device.
1016
1017 This option only enables generic Block IO controller infrastructure.
1018 One needs to also enable actual IO controlling logic/policy. For
1019 enabling proportional weight division of disk bandwidth in CFQ, set
1020 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1021 CONFIG_BLK_DEV_THROTTLING=y.
1022
1023 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
1024
1025 config CGROUP_WRITEBACK
1026 bool
1027 depends on MEMCG && BLK_CGROUP
1028 default y
1029
1030 menuconfig CGROUP_SCHED
1031 bool "CPU controller"
1032 default n
1033 help
1034 This feature lets CPU scheduler recognize task groups and control CPU
1035 bandwidth allocation to such task groups. It uses cgroups to group
1036 tasks.
1037
1038 if CGROUP_SCHED
1039 config GROUP_SCHED_WEIGHT
1040 def_bool n
1041
1042 config FAIR_GROUP_SCHED
1043 bool "Group scheduling for SCHED_OTHER"
1044 depends on CGROUP_SCHED
1045 select GROUP_SCHED_WEIGHT
1046 default CGROUP_SCHED
1047
1048 config CFS_BANDWIDTH
1049 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1050 depends on FAIR_GROUP_SCHED
1051 default n
1052 help
1053 This option allows users to define CPU bandwidth rates (limits) for
1054 tasks running within the fair group scheduler. Groups with no limit
1055 set are considered to be unconstrained and will run with no
1056 restriction.
1057 See Documentation/scheduler/sched-bwc.rst for more information.
1058
1059 config RT_GROUP_SCHED
1060 bool "Group scheduling for SCHED_RR/FIFO"
1061 depends on CGROUP_SCHED
1062 default n
1063 help
1064 This feature lets you explicitly allocate real CPU bandwidth
1065 to task groups. If enabled, it will also make it impossible to
1066 schedule realtime tasks for non-root users until you allocate
1067 realtime bandwidth for them.
1068 See Documentation/scheduler/sched-rt-group.rst for more information.
1069
1070 config EXT_GROUP_SCHED
1071 bool
1072 depends on SCHED_CLASS_EXT && CGROUP_SCHED
1073 select GROUP_SCHED_WEIGHT
1074 default y
1075
1076 endif #CGROUP_SCHED
1077
1078 config SCHED_MM_CID
1079 def_bool y
1080 depends on SMP && RSEQ
1081
1082 config UCLAMP_TASK_GROUP
1083 bool "Utilization clamping per group of tasks"
1084 depends on CGROUP_SCHED
1085 depends on UCLAMP_TASK
1086 default n
1087 help
1088 This feature enables the scheduler to track the clamped utilization
1089 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
1090
1091 When this option is enabled, the user can specify a min and max
1092 CPU bandwidth which is allowed for each single task in a group.
1093 The max bandwidth allows to clamp the maximum frequency a task
1094 can use, while the min bandwidth allows to define a minimum
1095 frequency a task will always use.
1096
1097 When task group based utilization clamping is enabled, an eventually
1098 specified task-specific clamp value is constrained by the cgroup
1099 specified clamp value. Both minimum and maximum task clamping cannot
1100 be bigger than the corresponding clamping defined at task group level.
1101
1102 If in doubt, say N.
1103
1104 config CGROUP_PIDS
1105 bool "PIDs controller"
1106 help
1107 Provides enforcement of process number limits in the scope of a
1108 cgroup. Any attempt to fork more processes than is allowed in the
1109 cgroup will fail. PIDs are fundamentally a global resource because it
1110 is fairly trivial to reach PID exhaustion before you reach even a
1111 conservative kmemcg limit. As a result, it is possible to grind a
1112 system to halt without being limited by other cgroup policies. The
1113 PIDs controller is designed to stop this from happening.
1114
1115 It should be noted that organisational operations (such as attaching
1116 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1117 since the PIDs limit only affects a process's ability to fork, not to
1118 attach to a cgroup.
1119
1120 config CGROUP_RDMA
1121 bool "RDMA controller"
1122 help
1123 Provides enforcement of RDMA resources defined by IB stack.
1124 It is fairly easy for consumers to exhaust RDMA resources, which
1125 can result into resource unavailability to other consumers.
1126 RDMA controller is designed to stop this from happening.
1127 Attaching processes with active RDMA resources to the cgroup
1128 hierarchy is allowed even if can cross the hierarchy's limit.
1129
1130 config CGROUP_FREEZER
1131 bool "Freezer controller"
1132 help
1133 Provides a way to freeze and unfreeze all tasks in a
1134 cgroup.
1135
1136 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1137 controller includes important in-kernel memory consumers per default.
1138
1139 If you're using cgroup2, say N.
1140
1141 config CGROUP_HUGETLB
1142 bool "HugeTLB controller"
1143 depends on HUGETLB_PAGE
1144 select PAGE_COUNTER
1145 default n
1146 help
1147 Provides a cgroup controller for HugeTLB pages.
1148 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1149 The limit is enforced during page fault. Since HugeTLB doesn't
1150 support page reclaim, enforcing the limit at page fault time implies
1151 that, the application will get SIGBUS signal if it tries to access
1152 HugeTLB pages beyond its limit. This requires the application to know
1153 beforehand how much HugeTLB pages it would require for its use. The
1154 control group is tracked in the third page lru pointer. This means
1155 that we cannot use the controller with huge page less than 3 pages.
1156
1157 config CPUSETS
1158 bool "Cpuset controller"
1159 depends on SMP
1160 help
1161 This option will let you create and manage CPUSETs which
1162 allow dynamically partitioning a system into sets of CPUs and
1163 Memory Nodes and assigning tasks to run only within those sets.
1164 This is primarily useful on large SMP or NUMA systems.
1165
1166 Say N if unsure.
1167
1168 config CPUSETS_V1
1169 bool "Legacy cgroup v1 cpusets controller"
1170 depends on CPUSETS
1171 default n
1172 help
1173 Legacy cgroup v1 cpusets controller which has been deprecated by
1174 cgroup v2 implementation. The v1 is there for legacy applications
1175 which haven't migrated to the new cgroup v2 interface yet. If you
1176 do not have any such application then you are completely fine leaving
1177 this option disabled.
1178
1179 Say N if unsure.
1180
1181 config PROC_PID_CPUSET
1182 bool "Include legacy /proc/<pid>/cpuset file"
1183 depends on CPUSETS
1184 default y
1185
1186 config CGROUP_DEVICE
1187 bool "Device controller"
1188 help
1189 Provides a cgroup controller implementing whitelists for
1190 devices which a process in the cgroup can mknod or open.
1191
1192 config CGROUP_CPUACCT
1193 bool "Simple CPU accounting controller"
1194 help
1195 Provides a simple controller for monitoring the
1196 total CPU consumed by the tasks in a cgroup.
1197
1198 config CGROUP_PERF
1199 bool "Perf controller"
1200 depends on PERF_EVENTS
1201 help
1202 This option extends the perf per-cpu mode to restrict monitoring
1203 to threads which belong to the cgroup specified and run on the
1204 designated cpu. Or this can be used to have cgroup ID in samples
1205 so that it can monitor performance events among cgroups.
1206
1207 Say N if unsure.
1208
1209 config CGROUP_BPF
1210 bool "Support for eBPF programs attached to cgroups"
1211 depends on BPF_SYSCALL
1212 select SOCK_CGROUP_DATA
1213 help
1214 Allow attaching eBPF programs to a cgroup using the bpf(2)
1215 syscall command BPF_PROG_ATTACH.
1216
1217 In which context these programs are accessed depends on the type
1218 of attachment. For instance, programs that are attached using
1219 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1220 inet sockets.
1221
1222 config CGROUP_MISC
1223 bool "Misc resource controller"
1224 default n
1225 help
1226 Provides a controller for miscellaneous resources on a host.
1227
1228 Miscellaneous scalar resources are the resources on the host system
1229 which cannot be abstracted like the other cgroups. This controller
1230 tracks and limits the miscellaneous resources used by a process
1231 attached to a cgroup hierarchy.
1232
1233 For more information, please check misc cgroup section in
1234 /Documentation/admin-guide/cgroup-v2.rst.
1235
1236 config CGROUP_DEBUG
1237 bool "Debug controller"
1238 default n
1239 depends on DEBUG_KERNEL
1240 help
1241 This option enables a simple controller that exports
1242 debugging information about the cgroups framework. This
1243 controller is for control cgroup debugging only. Its
1244 interfaces are not stable.
1245
1246 Say N.
1247
1248 config SOCK_CGROUP_DATA
1249 bool
1250 default n
1251
1252 endif # CGROUPS
1253
1254 menuconfig NAMESPACES
1255 bool "Namespaces support" if EXPERT
1256 depends on MULTIUSER
1257 default !EXPERT
1258 help
1259 Provides the way to make tasks work with different objects using
1260 the same id. For example same IPC id may refer to different objects
1261 or same user id or pid may refer to different tasks when used in
1262 different namespaces.
1263
1264 if NAMESPACES
1265
1266 config UTS_NS
1267 bool "UTS namespace"
1268 default y
1269 help
1270 In this namespace tasks see different info provided with the
1271 uname() system call
1272
1273 config TIME_NS
1274 bool "TIME namespace"
1275 depends on GENERIC_VDSO_TIME_NS
1276 default y
1277 help
1278 In this namespace boottime and monotonic clocks can be set.
1279 The time will keep going with the same pace.
1280
1281 config IPC_NS
1282 bool "IPC namespace"
1283 depends on (SYSVIPC || POSIX_MQUEUE)
1284 default y
1285 help
1286 In this namespace tasks work with IPC ids which correspond to
1287 different IPC objects in different namespaces.
1288
1289 config USER_NS
1290 bool "User namespace"
1291 default n
1292 help
1293 This allows containers, i.e. vservers, to use user namespaces
1294 to provide different user info for different servers.
1295
1296 When user namespaces are enabled in the kernel it is
1297 recommended that the MEMCG option also be enabled and that
1298 user-space use the memory control groups to limit the amount
1299 of memory a memory unprivileged users can use.
1300
1301 If unsure, say N.
1302
1303 config PID_NS
1304 bool "PID Namespaces"
1305 default y
1306 help
1307 Support process id namespaces. This allows having multiple
1308 processes with the same pid as long as they are in different
1309 pid namespaces. This is a building block of containers.
1310
1311 config NET_NS
1312 bool "Network namespace"
1313 depends on NET
1314 default y
1315 help
1316 Allow user space to create what appear to be multiple instances
1317 of the network stack.
1318
1319 endif # NAMESPACES
1320
1321 config CHECKPOINT_RESTORE
1322 bool "Checkpoint/restore support"
1323 depends on PROC_FS
1324 select PROC_CHILDREN
1325 select KCMP
1326 default n
1327 help
1328 Enables additional kernel features in a sake of checkpoint/restore.
1329 In particular it adds auxiliary prctl codes to setup process text,
1330 data and heap segment sizes, and a few additional /proc filesystem
1331 entries.
1332
1333 If unsure, say N here.
1334
1335 config SCHED_AUTOGROUP
1336 bool "Automatic process group scheduling"
1337 select CGROUPS
1338 select CGROUP_SCHED
1339 select FAIR_GROUP_SCHED
1340 help
1341 This option optimizes the scheduler for common desktop workloads by
1342 automatically creating and populating task groups. This separation
1343 of workloads isolates aggressive CPU burners (like build jobs) from
1344 desktop applications. Task group autogeneration is currently based
1345 upon task session.
1346
1347 config RELAY
1348 bool "Kernel->user space relay support (formerly relayfs)"
1349 select IRQ_WORK
1350 help
1351 This option enables support for relay interface support in
1352 certain file systems (such as debugfs).
1353 It is designed to provide an efficient mechanism for tools and
1354 facilities to relay large amounts of data from kernel space to
1355 user space.
1356
1357 If unsure, say N.
1358
1359 config BLK_DEV_INITRD
1360 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1361 help
1362 The initial RAM filesystem is a ramfs which is loaded by the
1363 boot loader (loadlin or lilo) and that is mounted as root
1364 before the normal boot procedure. It is typically used to
1365 load modules needed to mount the "real" root file system,
1366 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1367
1368 If RAM disk support (BLK_DEV_RAM) is also included, this
1369 also enables initial RAM disk (initrd) support and adds
1370 15 Kbytes (more on some other architectures) to the kernel size.
1371
1372 If unsure say Y.
1373
1374 if BLK_DEV_INITRD
1375
1376 source "usr/Kconfig"
1377
1378 endif
1379
1380 config BOOT_CONFIG
1381 bool "Boot config support"
1382 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED
1383 help
1384 Extra boot config allows system admin to pass a config file as
1385 complemental extension of kernel cmdline when booting.
1386 The boot config file must be attached at the end of initramfs
1387 with checksum, size and magic word.
1388 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1389
1390 If unsure, say Y.
1391
1392 config BOOT_CONFIG_FORCE
1393 bool "Force unconditional bootconfig processing"
1394 depends on BOOT_CONFIG
1395 default y if BOOT_CONFIG_EMBED
1396 help
1397 With this Kconfig option set, BOOT_CONFIG processing is carried
1398 out even when the "bootconfig" kernel-boot parameter is omitted.
1399 In fact, with this Kconfig option set, there is no way to
1400 make the kernel ignore the BOOT_CONFIG-supplied kernel-boot
1401 parameters.
1402
1403 If unsure, say N.
1404
1405 config BOOT_CONFIG_EMBED
1406 bool "Embed bootconfig file in the kernel"
1407 depends on BOOT_CONFIG
1408 help
1409 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the
1410 kernel. Usually, the bootconfig file is loaded with the initrd
1411 image. But if the system doesn't support initrd, this option will
1412 help you by embedding a bootconfig file while building the kernel.
1413
1414 If unsure, say N.
1415
1416 config BOOT_CONFIG_EMBED_FILE
1417 string "Embedded bootconfig file path"
1418 depends on BOOT_CONFIG_EMBED
1419 help
1420 Specify a bootconfig file which will be embedded to the kernel.
1421 This bootconfig will be used if there is no initrd or no other
1422 bootconfig in the initrd.
1423
1424 config INITRAMFS_PRESERVE_MTIME
1425 bool "Preserve cpio archive mtimes in initramfs"
1426 default y
1427 help
1428 Each entry in an initramfs cpio archive carries an mtime value. When
1429 enabled, extracted cpio items take this mtime, with directory mtime
1430 setting deferred until after creation of any child entries.
1431
1432 If unsure, say Y.
1433
1434 choice
1435 prompt "Compiler optimization level"
1436 default CC_OPTIMIZE_FOR_PERFORMANCE
1437
1438 config CC_OPTIMIZE_FOR_PERFORMANCE
1439 bool "Optimize for performance (-O2)"
1440 help
1441 This is the default optimization level for the kernel, building
1442 with the "-O2" compiler flag for best performance and most
1443 helpful compile-time warnings.
1444
1445 config CC_OPTIMIZE_FOR_SIZE
1446 bool "Optimize for size (-Os)"
1447 help
1448 Choosing this option will pass "-Os" to your compiler resulting
1449 in a smaller kernel.
1450
1451 endchoice
1452
1453 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1454 bool
1455 help
1456 This requires that the arch annotates or otherwise protects
1457 its external entry points from being discarded. Linker scripts
1458 must also merge .text.*, .data.*, and .bss.* correctly into
1459 output sections. Care must be taken not to pull in unrelated
1460 sections (e.g., '.text.init'). Typically '.' in section names
1461 is used to distinguish them from label names / C identifiers.
1462
1463 config LD_DEAD_CODE_DATA_ELIMINATION
1464 bool "Dead code and data elimination (EXPERIMENTAL)"
1465 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1466 depends on EXPERT
1467 depends on $(cc-option,-ffunction-sections -fdata-sections)
1468 depends on $(ld-option,--gc-sections)
1469 help
1470 Enable this if you want to do dead code and data elimination with
1471 the linker by compiling with -ffunction-sections -fdata-sections,
1472 and linking with --gc-sections.
1473
1474 This can reduce on disk and in-memory size of the kernel
1475 code and static data, particularly for small configs and
1476 on small systems. This has the possibility of introducing
1477 silently broken kernel if the required annotations are not
1478 present. This option is not well tested yet, so use at your
1479 own risk.
1480
1481 config LD_ORPHAN_WARN
1482 def_bool y
1483 depends on ARCH_WANT_LD_ORPHAN_WARN
1484 depends on $(ld-option,--orphan-handling=warn)
1485 depends on $(ld-option,--orphan-handling=error)
1486
1487 config LD_ORPHAN_WARN_LEVEL
1488 string
1489 depends on LD_ORPHAN_WARN
1490 default "error" if WERROR
1491 default "warn"
1492
1493 config SYSCTL
1494 bool
1495
1496 config HAVE_UID16
1497 bool
1498
1499 config SYSCTL_EXCEPTION_TRACE
1500 bool
1501 help
1502 Enable support for /proc/sys/debug/exception-trace.
1503
1504 config SYSCTL_ARCH_UNALIGN_NO_WARN
1505 bool
1506 help
1507 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1508 Allows arch to define/use @no_unaligned_warning to possibly warn
1509 about unaligned access emulation going on under the hood.
1510
1511 config SYSCTL_ARCH_UNALIGN_ALLOW
1512 bool
1513 help
1514 Enable support for /proc/sys/kernel/unaligned-trap
1515 Allows arches to define/use @unaligned_enabled to runtime toggle
1516 the unaligned access emulation.
1517 see arch/parisc/kernel/unaligned.c for reference
1518
1519 config HAVE_PCSPKR_PLATFORM
1520 bool
1521
1522 menuconfig EXPERT
1523 bool "Configure standard kernel features (expert users)"
1524 # Unhide debug options, to make the on-by-default options visible
1525 select DEBUG_KERNEL
1526 help
1527 This option allows certain base kernel options and settings
1528 to be disabled or tweaked. This is for specialized
1529 environments which can tolerate a "non-standard" kernel.
1530 Only use this if you really know what you are doing.
1531
1532 config UID16
1533 bool "Enable 16-bit UID system calls" if EXPERT
1534 depends on HAVE_UID16 && MULTIUSER
1535 default y
1536 help
1537 This enables the legacy 16-bit UID syscall wrappers.
1538
1539 config MULTIUSER
1540 bool "Multiple users, groups and capabilities support" if EXPERT
1541 default y
1542 help
1543 This option enables support for non-root users, groups and
1544 capabilities.
1545
1546 If you say N here, all processes will run with UID 0, GID 0, and all
1547 possible capabilities. Saying N here also compiles out support for
1548 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1549 setgid, and capset.
1550
1551 If unsure, say Y here.
1552
1553 config SGETMASK_SYSCALL
1554 bool "sgetmask/ssetmask syscalls support" if EXPERT
1555 default PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1556 help
1557 sys_sgetmask and sys_ssetmask are obsolete system calls
1558 no longer supported in libc but still enabled by default in some
1559 architectures.
1560
1561 If unsure, leave the default option here.
1562
1563 config SYSFS_SYSCALL
1564 bool "Sysfs syscall support" if EXPERT
1565 default y
1566 help
1567 sys_sysfs is an obsolete system call no longer supported in libc.
1568 Note that disabling this option is more secure but might break
1569 compatibility with some systems.
1570
1571 If unsure say Y here.
1572
1573 config FHANDLE
1574 bool "open by fhandle syscalls" if EXPERT
1575 select EXPORTFS
1576 default y
1577 help
1578 If you say Y here, a user level program will be able to map
1579 file names to handle and then later use the handle for
1580 different file system operations. This is useful in implementing
1581 userspace file servers, which now track files using handles instead
1582 of names. The handle would remain the same even if file names
1583 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1584 syscalls.
1585
1586 config POSIX_TIMERS
1587 bool "Posix Clocks & timers" if EXPERT
1588 default y
1589 help
1590 This includes native support for POSIX timers to the kernel.
1591 Some embedded systems have no use for them and therefore they
1592 can be configured out to reduce the size of the kernel image.
1593
1594 When this option is disabled, the following syscalls won't be
1595 available: timer_create, timer_gettime: timer_getoverrun,
1596 timer_settime, timer_delete, clock_adjtime, getitimer,
1597 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1598 clock_getres and clock_nanosleep syscalls will be limited to
1599 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1600
1601 If unsure say y.
1602
1603 config PRINTK
1604 default y
1605 bool "Enable support for printk" if EXPERT
1606 select IRQ_WORK
1607 help
1608 This option enables normal printk support. Removing it
1609 eliminates most of the message strings from the kernel image
1610 and makes the kernel more or less silent. As this makes it
1611 very difficult to diagnose system problems, saying N here is
1612 strongly discouraged.
1613
1614 config BUG
1615 bool "BUG() support" if EXPERT
1616 default y
1617 help
1618 Disabling this option eliminates support for BUG and WARN, reducing
1619 the size of your kernel image and potentially quietly ignoring
1620 numerous fatal conditions. You should only consider disabling this
1621 option for embedded systems with no facilities for reporting errors.
1622 Just say Y.
1623
1624 config ELF_CORE
1625 depends on COREDUMP
1626 default y
1627 bool "Enable ELF core dumps" if EXPERT
1628 help
1629 Enable support for generating core dumps. Disabling saves about 4k.
1630
1631
1632 config PCSPKR_PLATFORM
1633 bool "Enable PC-Speaker support" if EXPERT
1634 depends on HAVE_PCSPKR_PLATFORM
1635 select I8253_LOCK
1636 default y
1637 help
1638 This option allows to disable the internal PC-Speaker
1639 support, saving some memory.
1640
1641 config BASE_SMALL
1642 bool "Enable smaller-sized data structures for core" if EXPERT
1643 help
1644 Enabling this option reduces the size of miscellaneous core
1645 kernel data structures. This saves memory on small machines,
1646 but may reduce performance.
1647
1648 config FUTEX
1649 bool "Enable futex support" if EXPERT
1650 depends on !(SPARC32 && SMP)
1651 default y
1652 imply RT_MUTEXES
1653 help
1654 Disabling this option will cause the kernel to be built without
1655 support for "fast userspace mutexes". The resulting kernel may not
1656 run glibc-based applications correctly.
1657
1658 config FUTEX_PI
1659 bool
1660 depends on FUTEX && RT_MUTEXES
1661 default y
1662
1663 config EPOLL
1664 bool "Enable eventpoll support" if EXPERT
1665 default y
1666 help
1667 Disabling this option will cause the kernel to be built without
1668 support for epoll family of system calls.
1669
1670 config SIGNALFD
1671 bool "Enable signalfd() system call" if EXPERT
1672 default y
1673 help
1674 Enable the signalfd() system call that allows to receive signals
1675 on a file descriptor.
1676
1677 If unsure, say Y.
1678
1679 config TIMERFD
1680 bool "Enable timerfd() system call" if EXPERT
1681 default y
1682 help
1683 Enable the timerfd() system call that allows to receive timer
1684 events on a file descriptor.
1685
1686 If unsure, say Y.
1687
1688 config EVENTFD
1689 bool "Enable eventfd() system call" if EXPERT
1690 default y
1691 help
1692 Enable the eventfd() system call that allows to receive both
1693 kernel notification (ie. KAIO) or userspace notifications.
1694
1695 If unsure, say Y.
1696
1697 config SHMEM
1698 bool "Use full shmem filesystem" if EXPERT
1699 default y
1700 depends on MMU
1701 help
1702 The shmem is an internal filesystem used to manage shared memory.
1703 It is backed by swap and manages resource limits. It is also exported
1704 to userspace as tmpfs if TMPFS is enabled. Disabling this
1705 option replaces shmem and tmpfs with the much simpler ramfs code,
1706 which may be appropriate on small systems without swap.
1707
1708 config AIO
1709 bool "Enable AIO support" if EXPERT
1710 default y
1711 help
1712 This option enables POSIX asynchronous I/O which may by used
1713 by some high performance threaded applications. Disabling
1714 this option saves about 7k.
1715
1716 config IO_URING
1717 bool "Enable IO uring support" if EXPERT
1718 select IO_WQ
1719 default y
1720 help
1721 This option enables support for the io_uring interface, enabling
1722 applications to submit and complete IO through submission and
1723 completion rings that are shared between the kernel and application.
1724
1725 config GCOV_PROFILE_URING
1726 bool "Enable GCOV profiling on the io_uring subsystem"
1727 depends on GCOV_KERNEL
1728 help
1729 Enable GCOV profiling on the io_uring subsystem, to facilitate
1730 code coverage testing.
1731
1732 If unsure, say N.
1733
1734 Note that this will have a negative impact on the performance of
1735 the io_uring subsystem, hence this should only be enabled for
1736 specific test purposes.
1737
1738 config ADVISE_SYSCALLS
1739 bool "Enable madvise/fadvise syscalls" if EXPERT
1740 default y
1741 help
1742 This option enables the madvise and fadvise syscalls, used by
1743 applications to advise the kernel about their future memory or file
1744 usage, improving performance. If building an embedded system where no
1745 applications use these syscalls, you can disable this option to save
1746 space.
1747
1748 config MEMBARRIER
1749 bool "Enable membarrier() system call" if EXPERT
1750 default y
1751 help
1752 Enable the membarrier() system call that allows issuing memory
1753 barriers across all running threads, which can be used to distribute
1754 the cost of user-space memory barriers asymmetrically by transforming
1755 pairs of memory barriers into pairs consisting of membarrier() and a
1756 compiler barrier.
1757
1758 If unsure, say Y.
1759
1760 config KCMP
1761 bool "Enable kcmp() system call" if EXPERT
1762 help
1763 Enable the kernel resource comparison system call. It provides
1764 user-space with the ability to compare two processes to see if they
1765 share a common resource, such as a file descriptor or even virtual
1766 memory space.
1767
1768 If unsure, say N.
1769
1770 config RSEQ
1771 bool "Enable rseq() system call" if EXPERT
1772 default y
1773 depends on HAVE_RSEQ
1774 select MEMBARRIER
1775 help
1776 Enable the restartable sequences system call. It provides a
1777 user-space cache for the current CPU number value, which
1778 speeds up getting the current CPU number from user-space,
1779 as well as an ABI to speed up user-space operations on
1780 per-CPU data.
1781
1782 If unsure, say Y.
1783
1784 config DEBUG_RSEQ
1785 default n
1786 bool "Enable debugging of rseq() system call" if EXPERT
1787 depends on RSEQ && DEBUG_KERNEL
1788 help
1789 Enable extra debugging checks for the rseq system call.
1790
1791 If unsure, say N.
1792
1793 config CACHESTAT_SYSCALL
1794 bool "Enable cachestat() system call" if EXPERT
1795 default y
1796 help
1797 Enable the cachestat system call, which queries the page cache
1798 statistics of a file (number of cached pages, dirty pages,
1799 pages marked for writeback, (recently) evicted pages).
1800
1801 If unsure say Y here.
1802
1803 config PC104
1804 bool "PC/104 support" if EXPERT
1805 help
1806 Expose PC/104 form factor device drivers and options available for
1807 selection and configuration. Enable this option if your target
1808 machine has a PC/104 bus.
1809
1810 config KALLSYMS
1811 bool "Load all symbols for debugging/ksymoops" if EXPERT
1812 default y
1813 help
1814 Say Y here to let the kernel print out symbolic crash information and
1815 symbolic stack backtraces. This increases the size of the kernel
1816 somewhat, as all symbols have to be loaded into the kernel image.
1817
1818 config KALLSYMS_SELFTEST
1819 bool "Test the basic functions and performance of kallsyms"
1820 depends on KALLSYMS
1821 default n
1822 help
1823 Test the basic functions and performance of some interfaces, such as
1824 kallsyms_lookup_name. It also calculates the compression rate of the
1825 kallsyms compression algorithm for the current symbol set.
1826
1827 Start self-test automatically after system startup. Suggest executing
1828 "dmesg | grep kallsyms_selftest" to collect test results. "finish" is
1829 displayed in the last line, indicating that the test is complete.
1830
1831 config KALLSYMS_ALL
1832 bool "Include all symbols in kallsyms"
1833 depends on DEBUG_KERNEL && KALLSYMS
1834 help
1835 Normally kallsyms only contains the symbols of functions for nicer
1836 OOPS messages and backtraces (i.e., symbols from the text and inittext
1837 sections). This is sufficient for most cases. And only if you want to
1838 enable kernel live patching, or other less common use cases (e.g.,
1839 when a debugger is used) all symbols are required (i.e., names of
1840 variables from the data sections, etc).
1841
1842 This option makes sure that all symbols are loaded into the kernel
1843 image (i.e., symbols from all sections) in cost of increased kernel
1844 size (depending on the kernel configuration, it may be 300KiB or
1845 something like this).
1846
1847 Say N unless you really need all symbols, or kernel live patching.
1848
1849 config KALLSYMS_ABSOLUTE_PERCPU
1850 bool
1851 depends on KALLSYMS
1852 default X86_64 && SMP
1853
1854 # end of the "standard kernel features (expert users)" menu
1855
1856 config ARCH_HAS_MEMBARRIER_CALLBACKS
1857 bool
1858
1859 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1860 bool
1861
1862 config HAVE_PERF_EVENTS
1863 bool
1864 help
1865 See tools/perf/design.txt for details.
1866
1867 config GUEST_PERF_EVENTS
1868 bool
1869 depends on HAVE_PERF_EVENTS
1870
1871 config PERF_USE_VMALLOC
1872 bool
1873 help
1874 See tools/perf/design.txt for details
1875
1876 menu "Kernel Performance Events And Counters"
1877
1878 config PERF_EVENTS
1879 bool "Kernel performance events and counters"
1880 default y if PROFILING
1881 depends on HAVE_PERF_EVENTS
1882 select IRQ_WORK
1883 help
1884 Enable kernel support for various performance events provided
1885 by software and hardware.
1886
1887 Software events are supported either built-in or via the
1888 use of generic tracepoints.
1889
1890 Most modern CPUs support performance events via performance
1891 counter registers. These registers count the number of certain
1892 types of hw events: such as instructions executed, cachemisses
1893 suffered, or branches mis-predicted - without slowing down the
1894 kernel or applications. These registers can also trigger interrupts
1895 when a threshold number of events have passed - and can thus be
1896 used to profile the code that runs on that CPU.
1897
1898 The Linux Performance Event subsystem provides an abstraction of
1899 these software and hardware event capabilities, available via a
1900 system call and used by the "perf" utility in tools/perf/. It
1901 provides per task and per CPU counters, and it provides event
1902 capabilities on top of those.
1903
1904 Say Y if unsure.
1905
1906 config DEBUG_PERF_USE_VMALLOC
1907 default n
1908 bool "Debug: use vmalloc to back perf mmap() buffers"
1909 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1910 select PERF_USE_VMALLOC
1911 help
1912 Use vmalloc memory to back perf mmap() buffers.
1913
1914 Mostly useful for debugging the vmalloc code on platforms
1915 that don't require it.
1916
1917 Say N if unsure.
1918
1919 endmenu
1920
1921 config SYSTEM_DATA_VERIFICATION
1922 def_bool n
1923 select SYSTEM_TRUSTED_KEYRING
1924 select KEYS
1925 select CRYPTO
1926 select CRYPTO_RSA
1927 select ASYMMETRIC_KEY_TYPE
1928 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1929 select ASN1
1930 select OID_REGISTRY
1931 select X509_CERTIFICATE_PARSER
1932 select PKCS7_MESSAGE_PARSER
1933 help
1934 Provide PKCS#7 message verification using the contents of the system
1935 trusted keyring to provide public keys. This then can be used for
1936 module verification, kexec image verification and firmware blob
1937 verification.
1938
1939 config PROFILING
1940 bool "Profiling support"
1941 help
1942 Say Y here to enable the extended profiling support mechanisms used
1943 by profilers.
1944
1945 config RUST
1946 bool "Rust support"
1947 depends on HAVE_RUST
1948 depends on RUST_IS_AVAILABLE
1949 depends on !MODVERSIONS
1950 depends on !GCC_PLUGIN_RANDSTRUCT
1951 depends on !RANDSTRUCT
1952 depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE
1953 depends on !CFI_CLANG || HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC
1954 select CFI_ICALL_NORMALIZE_INTEGERS if CFI_CLANG
1955 depends on !CALL_PADDING || RUSTC_VERSION >= 108100
1956 depends on !KASAN_SW_TAGS
1957 depends on !(MITIGATION_RETHUNK && KASAN) || RUSTC_VERSION >= 108300
1958 help
1959 Enables Rust support in the kernel.
1960
1961 This allows other Rust-related options, like drivers written in Rust,
1962 to be selected.
1963
1964 It is also required to be able to load external kernel modules
1965 written in Rust.
1966
1967 See Documentation/rust/ for more information.
1968
1969 If unsure, say N.
1970
1971 config RUSTC_VERSION_TEXT
1972 string
1973 depends on RUST
1974 default "$(RUSTC_VERSION_TEXT)"
1975 help
1976 See `CC_VERSION_TEXT`.
1977
1978 config BINDGEN_VERSION_TEXT
1979 string
1980 depends on RUST
1981 # The dummy parameter `workaround-for-0.69.0` is required to support 0.69.0
1982 # (https://github.com/rust-lang/rust-bindgen/pull/2678). It can be removed when
1983 # the minimum version is upgraded past that (0.69.1 already fixed the issue).
1984 default "$(shell,$(BINDGEN) --version workaround-for-0.69.0 2>/dev/null)"
1985
1986 #
1987 # Place an empty function call at each tracepoint site. Can be
1988 # dynamically changed for a probe function.
1989 #
1990 config TRACEPOINTS
1991 bool
1992
1993 source "kernel/Kconfig.kexec"
1994
1995 endmenu # General setup
1996
1997 source "arch/Kconfig"
1998
1999 config RT_MUTEXES
2000 bool
2001 default y if PREEMPT_RT
2002
2003 config MODULE_SIG_FORMAT
2004 def_bool n
2005 select SYSTEM_DATA_VERIFICATION
2006
2007 source "kernel/module/Kconfig"
2008
2009 config INIT_ALL_POSSIBLE
2010 bool
2011 help
2012 Back when each arch used to define their own cpu_online_mask and
2013 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2014 with all 1s, and others with all 0s. When they were centralised,
2015 it was better to provide this option than to break all the archs
2016 and have several arch maintainers pursuing me down dark alleys.
2017
2018 source "block/Kconfig"
2019
2020 config PREEMPT_NOTIFIERS
2021 bool
2022
2023 config PADATA
2024 depends on SMP
2025 bool
2026
2027 config ASN1
2028 tristate
2029 help
2030 Build a simple ASN.1 grammar compiler that produces a bytecode output
2031 that can be interpreted by the ASN.1 stream decoder and used to
2032 inform it as to what tags are to be expected in a stream and what
2033 functions to call on what tags.
2034
2035 source "kernel/Kconfig.locks"
2036
2037 config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2038 bool
2039
2040 config ARCH_HAS_PREPARE_SYNC_CORE_CMD
2041 bool
2042
2043 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2044 bool
2045
2046 # It may be useful for an architecture to override the definitions of the
2047 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2048 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2049 # different calling convention for syscalls. They can also override the
2050 # macros for not-implemented syscalls in kernel/sys_ni.c and
2051 # kernel/time/posix-stubs.c. All these overrides need to be available in
2052 # <asm/syscall_wrapper.h>.
2053 config ARCH_HAS_SYSCALL_WRAPPER
2054 def_bool n
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