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 RUST_IS_AVAILABLE
64	def_bool $(success,$(srctree)/scripts/rust_is_available.sh)
65	help
66	  This shows whether a suitable Rust toolchain is available (found).
67
68	  Please see Documentation/rust/quick-start.rst for instructions on how
69	  to satisfy the build requirements of Rust support.
70
71	  In particular, the Makefile target 'rustavailable' is useful to check
72	  why the Rust toolchain is not being detected.
73
74config CC_CAN_LINK
75	bool
76	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT
77	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag))
78
79config CC_CAN_LINK_STATIC
80	bool
81	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT
82	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static)
83
84config CC_HAS_ASM_GOTO_OUTPUT
85	def_bool $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null)
86
87config CC_HAS_ASM_GOTO_TIED_OUTPUT
88	depends on CC_HAS_ASM_GOTO_OUTPUT
89	# Detect buggy gcc and clang, fixed in gcc-11 clang-14.
90	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)
91
92config GCC_ASM_GOTO_OUTPUT_WORKAROUND
93	bool
94	depends on CC_IS_GCC && CC_HAS_ASM_GOTO_OUTPUT
95	# Fixed in GCC 14, 13.3, 12.4 and 11.5
96	# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113921
97	default y if GCC_VERSION < 110500
98	default y if GCC_VERSION >= 120000 && GCC_VERSION < 120400
99	default y if GCC_VERSION >= 130000 && GCC_VERSION < 130300
100
101config TOOLS_SUPPORT_RELR
102	def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
103
104config CC_HAS_ASM_INLINE
105	def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
106
107config CC_HAS_NO_PROFILE_FN_ATTR
108	def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
109
110config PAHOLE_VERSION
111	int
112	default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))
113
114config CONSTRUCTORS
115	bool
116
117config IRQ_WORK
118	bool
119
120config BUILDTIME_TABLE_SORT
121	bool
122
123config THREAD_INFO_IN_TASK
124	bool
125	help
126	  Select this to move thread_info off the stack into task_struct.  To
127	  make this work, an arch will need to remove all thread_info fields
128	  except flags and fix any runtime bugs.
129
130	  One subtle change that will be needed is to use try_get_task_stack()
131	  and put_task_stack() in save_thread_stack_tsk() and get_wchan().
132
133menu "General setup"
134
135config BROKEN
136	bool
137
138config BROKEN_ON_SMP
139	bool
140	depends on BROKEN || !SMP
141	default y
142
143config INIT_ENV_ARG_LIMIT
144	int
145	default 32 if !UML
146	default 128 if UML
147	help
148	  Maximum of each of the number of arguments and environment
149	  variables passed to init from the kernel command line.
150
151config COMPILE_TEST
152	bool "Compile also drivers which will not load"
153	depends on HAS_IOMEM
154	help
155	  Some drivers can be compiled on a different platform than they are
156	  intended to be run on. Despite they cannot be loaded there (or even
157	  when they load they cannot be used due to missing HW support),
158	  developers still, opposing to distributors, might want to build such
159	  drivers to compile-test them.
160
161	  If you are a developer and want to build everything available, say Y
162	  here. If you are a user/distributor, say N here to exclude useless
163	  drivers to be distributed.
164
165config WERROR
166	bool "Compile the kernel with warnings as errors"
167	default COMPILE_TEST
168	help
169	  A kernel build should not cause any compiler warnings, and this
170	  enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags
171	  to enforce that rule by default. Certain warnings from other tools
172	  such as the linker may be upgraded to errors with this option as
173	  well.
174
175	  However, if you have a new (or very old) compiler or linker with odd
176	  and unusual warnings, or you have some architecture with problems,
177	  you may need to disable this config option in order to
178	  successfully build the kernel.
179
180	  If in doubt, say Y.
181
182config UAPI_HEADER_TEST
183	bool "Compile test UAPI headers"
184	depends on HEADERS_INSTALL && CC_CAN_LINK
185	help
186	  Compile test headers exported to user-space to ensure they are
187	  self-contained, i.e. compilable as standalone units.
188
189	  If you are a developer or tester and want to ensure the exported
190	  headers are self-contained, say Y here. Otherwise, choose N.
191
192config LOCALVERSION
193	string "Local version - append to kernel release"
194	help
195	  Append an extra string to the end of your kernel version.
196	  This will show up when you type uname, for example.
197	  The string you set here will be appended after the contents of
198	  any files with a filename matching localversion* in your
199	  object and source tree, in that order.  Your total string can
200	  be a maximum of 64 characters.
201
202config LOCALVERSION_AUTO
203	bool "Automatically append version information to the version string"
204	default y
205	depends on !COMPILE_TEST
206	help
207	  This will try to automatically determine if the current tree is a
208	  release tree by looking for git tags that belong to the current
209	  top of tree revision.
210
211	  A string of the format -gxxxxxxxx will be added to the localversion
212	  if a git-based tree is found.  The string generated by this will be
213	  appended after any matching localversion* files, and after the value
214	  set in CONFIG_LOCALVERSION.
215
216	  (The actual string used here is the first 12 characters produced
217	  by running the command:
218
219	    $ git rev-parse --verify HEAD
220
221	  which is done within the script "scripts/setlocalversion".)
222
223config BUILD_SALT
224	string "Build ID Salt"
225	default ""
226	help
227	  The build ID is used to link binaries and their debug info. Setting
228	  this option will use the value in the calculation of the build id.
229	  This is mostly useful for distributions which want to ensure the
230	  build is unique between builds. It's safe to leave the default.
231
232config HAVE_KERNEL_GZIP
233	bool
234
235config HAVE_KERNEL_BZIP2
236	bool
237
238config HAVE_KERNEL_LZMA
239	bool
240
241config HAVE_KERNEL_XZ
242	bool
243
244config HAVE_KERNEL_LZO
245	bool
246
247config HAVE_KERNEL_LZ4
248	bool
249
250config HAVE_KERNEL_ZSTD
251	bool
252
253config HAVE_KERNEL_UNCOMPRESSED
254	bool
255
256choice
257	prompt "Kernel compression mode"
258	default KERNEL_GZIP
259	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
260	help
261	  The linux kernel is a kind of self-extracting executable.
262	  Several compression algorithms are available, which differ
263	  in efficiency, compression and decompression speed.
264	  Compression speed is only relevant when building a kernel.
265	  Decompression speed is relevant at each boot.
266
267	  If you have any problems with bzip2 or lzma compressed
268	  kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
269	  version of this functionality (bzip2 only), for 2.4, was
270	  supplied by Christian Ludwig)
271
272	  High compression options are mostly useful for users, who
273	  are low on disk space (embedded systems), but for whom ram
274	  size matters less.
275
276	  If in doubt, select 'gzip'
277
278config KERNEL_GZIP
279	bool "Gzip"
280	depends on HAVE_KERNEL_GZIP
281	help
282	  The old and tried gzip compression. It provides a good balance
283	  between compression ratio and decompression speed.
284
285config KERNEL_BZIP2
286	bool "Bzip2"
287	depends on HAVE_KERNEL_BZIP2
288	help
289	  Its compression ratio and speed is intermediate.
290	  Decompression speed is slowest among the choices.  The kernel
291	  size is about 10% smaller with bzip2, in comparison to gzip.
292	  Bzip2 uses a large amount of memory. For modern kernels you
293	  will need at least 8MB RAM or more for booting.
294
295config KERNEL_LZMA
296	bool "LZMA"
297	depends on HAVE_KERNEL_LZMA
298	help
299	  This compression algorithm's ratio is best.  Decompression speed
300	  is between gzip and bzip2.  Compression is slowest.
301	  The kernel size is about 33% smaller with LZMA in comparison to gzip.
302
303config KERNEL_XZ
304	bool "XZ"
305	depends on HAVE_KERNEL_XZ
306	help
307	  XZ uses the LZMA2 algorithm and instruction set specific
308	  BCJ filters which can improve compression ratio of executable
309	  code. The size of the kernel is about 30% smaller with XZ in
310	  comparison to gzip. On architectures for which there is a BCJ
311	  filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
312	  will create a few percent smaller kernel than plain LZMA.
313
314	  The speed is about the same as with LZMA: The decompression
315	  speed of XZ is better than that of bzip2 but worse than gzip
316	  and LZO. Compression is slow.
317
318config KERNEL_LZO
319	bool "LZO"
320	depends on HAVE_KERNEL_LZO
321	help
322	  Its compression ratio is the poorest among the choices. The kernel
323	  size is about 10% bigger than gzip; however its speed
324	  (both compression and decompression) is the fastest.
325
326config KERNEL_LZ4
327	bool "LZ4"
328	depends on HAVE_KERNEL_LZ4
329	help
330	  LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
331	  A preliminary version of LZ4 de/compression tool is available at
332	  <https://code.google.com/p/lz4/>.
333
334	  Its compression ratio is worse than LZO. The size of the kernel
335	  is about 8% bigger than LZO. But the decompression speed is
336	  faster than LZO.
337
338config KERNEL_ZSTD
339	bool "ZSTD"
340	depends on HAVE_KERNEL_ZSTD
341	help
342	  ZSTD is a compression algorithm targeting intermediate compression
343	  with fast decompression speed. It will compress better than GZIP and
344	  decompress around the same speed as LZO, but slower than LZ4. You
345	  will need at least 192 KB RAM or more for booting. The zstd command
346	  line tool is required for compression.
347
348config KERNEL_UNCOMPRESSED
349	bool "None"
350	depends on HAVE_KERNEL_UNCOMPRESSED
351	help
352	  Produce uncompressed kernel image. This option is usually not what
353	  you want. It is useful for debugging the kernel in slow simulation
354	  environments, where decompressing and moving the kernel is awfully
355	  slow. This option allows early boot code to skip the decompressor
356	  and jump right at uncompressed kernel image.
357
358endchoice
359
360config DEFAULT_INIT
361	string "Default init path"
362	default ""
363	help
364	  This option determines the default init for the system if no init=
365	  option is passed on the kernel command line. If the requested path is
366	  not present, we will still then move on to attempting further
367	  locations (e.g. /sbin/init, etc). If this is empty, we will just use
368	  the fallback list when init= is not passed.
369
370config DEFAULT_HOSTNAME
371	string "Default hostname"
372	default "(none)"
373	help
374	  This option determines the default system hostname before userspace
375	  calls sethostname(2). The kernel traditionally uses "(none)" here,
376	  but you may wish to use a different default here to make a minimal
377	  system more usable with less configuration.
378
379config SYSVIPC
380	bool "System V IPC"
381	help
382	  Inter Process Communication is a suite of library functions and
383	  system calls which let processes (running programs) synchronize and
384	  exchange information. It is generally considered to be a good thing,
385	  and some programs won't run unless you say Y here. In particular, if
386	  you want to run the DOS emulator dosemu under Linux (read the
387	  DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
388	  you'll need to say Y here.
389
390	  You can find documentation about IPC with "info ipc" and also in
391	  section 6.4 of the Linux Programmer's Guide, available from
392	  <http://www.tldp.org/guides.html>.
393
394config SYSVIPC_SYSCTL
395	bool
396	depends on SYSVIPC
397	depends on SYSCTL
398	default y
399
400config SYSVIPC_COMPAT
401	def_bool y
402	depends on COMPAT && SYSVIPC
403
404config POSIX_MQUEUE
405	bool "POSIX Message Queues"
406	depends on NET
407	help
408	  POSIX variant of message queues is a part of IPC. In POSIX message
409	  queues every message has a priority which decides about succession
410	  of receiving it by a process. If you want to compile and run
411	  programs written e.g. for Solaris with use of its POSIX message
412	  queues (functions mq_*) say Y here.
413
414	  POSIX message queues are visible as a filesystem called 'mqueue'
415	  and can be mounted somewhere if you want to do filesystem
416	  operations on message queues.
417
418	  If unsure, say Y.
419
420config POSIX_MQUEUE_SYSCTL
421	bool
422	depends on POSIX_MQUEUE
423	depends on SYSCTL
424	default y
425
426config WATCH_QUEUE
427	bool "General notification queue"
428	default n
429	help
430
431	  This is a general notification queue for the kernel to pass events to
432	  userspace by splicing them into pipes.  It can be used in conjunction
433	  with watches for key/keyring change notifications and device
434	  notifications.
435
436	  See Documentation/core-api/watch_queue.rst
437
438config CROSS_MEMORY_ATTACH
439	bool "Enable process_vm_readv/writev syscalls"
440	depends on MMU
441	default y
442	help
443	  Enabling this option adds the system calls process_vm_readv and
444	  process_vm_writev which allow a process with the correct privileges
445	  to directly read from or write to another process' address space.
446	  See the man page for more details.
447
448config USELIB
449	bool "uselib syscall (for libc5 and earlier)"
450	default ALPHA || M68K || SPARC
451	help
452	  This option enables the uselib syscall, a system call used in the
453	  dynamic linker from libc5 and earlier.  glibc does not use this
454	  system call.  If you intend to run programs built on libc5 or
455	  earlier, you may need to enable this syscall.  Current systems
456	  running glibc can safely disable this.
457
458config AUDIT
459	bool "Auditing support"
460	depends on NET
461	help
462	  Enable auditing infrastructure that can be used with another
463	  kernel subsystem, such as SELinux (which requires this for
464	  logging of avc messages output).  System call auditing is included
465	  on architectures which support it.
466
467config HAVE_ARCH_AUDITSYSCALL
468	bool
469
470config AUDITSYSCALL
471	def_bool y
472	depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
473	select FSNOTIFY
474
475source "kernel/irq/Kconfig"
476source "kernel/time/Kconfig"
477source "kernel/bpf/Kconfig"
478source "kernel/Kconfig.preempt"
479
480menu "CPU/Task time and stats accounting"
481
482config VIRT_CPU_ACCOUNTING
483	bool
484
485choice
486	prompt "Cputime accounting"
487	default TICK_CPU_ACCOUNTING
488
489# Kind of a stub config for the pure tick based cputime accounting
490config TICK_CPU_ACCOUNTING
491	bool "Simple tick based cputime accounting"
492	depends on !S390 && !NO_HZ_FULL
493	help
494	  This is the basic tick based cputime accounting that maintains
495	  statistics about user, system and idle time spent on per jiffies
496	  granularity.
497
498	  If unsure, say Y.
499
500config VIRT_CPU_ACCOUNTING_NATIVE
501	bool "Deterministic task and CPU time accounting"
502	depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
503	select VIRT_CPU_ACCOUNTING
504	help
505	  Select this option to enable more accurate task and CPU time
506	  accounting.  This is done by reading a CPU counter on each
507	  kernel entry and exit and on transitions within the kernel
508	  between system, softirq and hardirq state, so there is a
509	  small performance impact.  In the case of s390 or IBM POWER > 5,
510	  this also enables accounting of stolen time on logically-partitioned
511	  systems.
512
513config VIRT_CPU_ACCOUNTING_GEN
514	bool "Full dynticks CPU time accounting"
515	depends on HAVE_CONTEXT_TRACKING_USER
516	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
517	depends on GENERIC_CLOCKEVENTS
518	select VIRT_CPU_ACCOUNTING
519	select CONTEXT_TRACKING_USER
520	help
521	  Select this option to enable task and CPU time accounting on full
522	  dynticks systems. This accounting is implemented by watching every
523	  kernel-user boundaries using the context tracking subsystem.
524	  The accounting is thus performed at the expense of some significant
525	  overhead.
526
527	  For now this is only useful if you are working on the full
528	  dynticks subsystem development.
529
530	  If unsure, say N.
531
532endchoice
533
534config IRQ_TIME_ACCOUNTING
535	bool "Fine granularity task level IRQ time accounting"
536	depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
537	help
538	  Select this option to enable fine granularity task irq time
539	  accounting. This is done by reading a timestamp on each
540	  transitions between softirq and hardirq state, so there can be a
541	  small performance impact.
542
543	  If in doubt, say N here.
544
545config HAVE_SCHED_AVG_IRQ
546	def_bool y
547	depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
548	depends on SMP
549
550config SCHED_THERMAL_PRESSURE
551	bool
552	default y if ARM && ARM_CPU_TOPOLOGY
553	default y if ARM64
554	depends on SMP
555	depends on CPU_FREQ_THERMAL
556	help
557	  Select this option to enable thermal pressure accounting in the
558	  scheduler. Thermal pressure is the value conveyed to the scheduler
559	  that reflects the reduction in CPU compute capacity resulted from
560	  thermal throttling. Thermal throttling occurs when the performance of
561	  a CPU is capped due to high operating temperatures.
562
563	  If selected, the scheduler will be able to balance tasks accordingly,
564	  i.e. put less load on throttled CPUs than on non/less throttled ones.
565
566	  This requires the architecture to implement
567	  arch_update_thermal_pressure() and arch_scale_thermal_pressure().
568
569config BSD_PROCESS_ACCT
570	bool "BSD Process Accounting"
571	depends on MULTIUSER
572	help
573	  If you say Y here, a user level program will be able to instruct the
574	  kernel (via a special system call) to write process accounting
575	  information to a file: whenever a process exits, information about
576	  that process will be appended to the file by the kernel.  The
577	  information includes things such as creation time, owning user,
578	  command name, memory usage, controlling terminal etc. (the complete
579	  list is in the struct acct in <file:include/linux/acct.h>).  It is
580	  up to the user level program to do useful things with this
581	  information.  This is generally a good idea, so say Y.
582
583config BSD_PROCESS_ACCT_V3
584	bool "BSD Process Accounting version 3 file format"
585	depends on BSD_PROCESS_ACCT
586	default n
587	help
588	  If you say Y here, the process accounting information is written
589	  in a new file format that also logs the process IDs of each
590	  process and its parent. Note that this file format is incompatible
591	  with previous v0/v1/v2 file formats, so you will need updated tools
592	  for processing it. A preliminary version of these tools is available
593	  at <http://www.gnu.org/software/acct/>.
594
595config TASKSTATS
596	bool "Export task/process statistics through netlink"
597	depends on NET
598	depends on MULTIUSER
599	default n
600	help
601	  Export selected statistics for tasks/processes through the
602	  generic netlink interface. Unlike BSD process accounting, the
603	  statistics are available during the lifetime of tasks/processes as
604	  responses to commands. Like BSD accounting, they are sent to user
605	  space on task exit.
606
607	  Say N if unsure.
608
609config TASK_DELAY_ACCT
610	bool "Enable per-task delay accounting"
611	depends on TASKSTATS
612	select SCHED_INFO
613	help
614	  Collect information on time spent by a task waiting for system
615	  resources like cpu, synchronous block I/O completion and swapping
616	  in pages. Such statistics can help in setting a task's priorities
617	  relative to other tasks for cpu, io, rss limits etc.
618
619	  Say N if unsure.
620
621config TASK_XACCT
622	bool "Enable extended accounting over taskstats"
623	depends on TASKSTATS
624	help
625	  Collect extended task accounting data and send the data
626	  to userland for processing over the taskstats interface.
627
628	  Say N if unsure.
629
630config TASK_IO_ACCOUNTING
631	bool "Enable per-task storage I/O accounting"
632	depends on TASK_XACCT
633	help
634	  Collect information on the number of bytes of storage I/O which this
635	  task has caused.
636
637	  Say N if unsure.
638
639config PSI
640	bool "Pressure stall information tracking"
641	select KERNFS
642	help
643	  Collect metrics that indicate how overcommitted the CPU, memory,
644	  and IO capacity are in the system.
645
646	  If you say Y here, the kernel will create /proc/pressure/ with the
647	  pressure statistics files cpu, memory, and io. These will indicate
648	  the share of walltime in which some or all tasks in the system are
649	  delayed due to contention of the respective resource.
650
651	  In kernels with cgroup support, cgroups (cgroup2 only) will
652	  have cpu.pressure, memory.pressure, and io.pressure files,
653	  which aggregate pressure stalls for the grouped tasks only.
654
655	  For more details see Documentation/accounting/psi.rst.
656
657	  Say N if unsure.
658
659config PSI_DEFAULT_DISABLED
660	bool "Require boot parameter to enable pressure stall information tracking"
661	default n
662	depends on PSI
663	help
664	  If set, pressure stall information tracking will be disabled
665	  per default but can be enabled through passing psi=1 on the
666	  kernel commandline during boot.
667
668	  This feature adds some code to the task wakeup and sleep
669	  paths of the scheduler. The overhead is too low to affect
670	  common scheduling-intense workloads in practice (such as
671	  webservers, memcache), but it does show up in artificial
672	  scheduler stress tests, such as hackbench.
673
674	  If you are paranoid and not sure what the kernel will be
675	  used for, say Y.
676
677	  Say N if unsure.
678
679endmenu # "CPU/Task time and stats accounting"
680
681config CPU_ISOLATION
682	bool "CPU isolation"
683	depends on SMP || COMPILE_TEST
684	default y
685	help
686	  Make sure that CPUs running critical tasks are not disturbed by
687	  any source of "noise" such as unbound workqueues, timers, kthreads...
688	  Unbound jobs get offloaded to housekeeping CPUs. This is driven by
689	  the "isolcpus=" boot parameter.
690
691	  Say Y if unsure.
692
693source "kernel/rcu/Kconfig"
694
695config IKCONFIG
696	tristate "Kernel .config support"
697	help
698	  This option enables the complete Linux kernel ".config" file
699	  contents to be saved in the kernel. It provides documentation
700	  of which kernel options are used in a running kernel or in an
701	  on-disk kernel.  This information can be extracted from the kernel
702	  image file with the script scripts/extract-ikconfig and used as
703	  input to rebuild the current kernel or to build another kernel.
704	  It can also be extracted from a running kernel by reading
705	  /proc/config.gz if enabled (below).
706
707config IKCONFIG_PROC
708	bool "Enable access to .config through /proc/config.gz"
709	depends on IKCONFIG && PROC_FS
710	help
711	  This option enables access to the kernel configuration file
712	  through /proc/config.gz.
713
714config IKHEADERS
715	tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
716	depends on SYSFS
717	help
718	  This option enables access to the in-kernel headers that are generated during
719	  the build process. These can be used to build eBPF tracing programs,
720	  or similar programs.  If you build the headers as a module, a module called
721	  kheaders.ko is built which can be loaded on-demand to get access to headers.
722
723config LOG_BUF_SHIFT
724	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
725	range 12 25
726	default 17
727	depends on PRINTK
728	help
729	  Select the minimal kernel log buffer size as a power of 2.
730	  The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
731	  parameter, see below. Any higher size also might be forced
732	  by "log_buf_len" boot parameter.
733
734	  Examples:
735		     17 => 128 KB
736		     16 => 64 KB
737		     15 => 32 KB
738		     14 => 16 KB
739		     13 =>  8 KB
740		     12 =>  4 KB
741
742config LOG_CPU_MAX_BUF_SHIFT
743	int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
744	depends on SMP
745	range 0 21
746	default 12 if !BASE_SMALL
747	default 0 if BASE_SMALL
748	depends on PRINTK
749	help
750	  This option allows to increase the default ring buffer size
751	  according to the number of CPUs. The value defines the contribution
752	  of each CPU as a power of 2. The used space is typically only few
753	  lines however it might be much more when problems are reported,
754	  e.g. backtraces.
755
756	  The increased size means that a new buffer has to be allocated and
757	  the original static one is unused. It makes sense only on systems
758	  with more CPUs. Therefore this value is used only when the sum of
759	  contributions is greater than the half of the default kernel ring
760	  buffer as defined by LOG_BUF_SHIFT. The default values are set
761	  so that more than 16 CPUs are needed to trigger the allocation.
762
763	  Also this option is ignored when "log_buf_len" kernel parameter is
764	  used as it forces an exact (power of two) size of the ring buffer.
765
766	  The number of possible CPUs is used for this computation ignoring
767	  hotplugging making the computation optimal for the worst case
768	  scenario while allowing a simple algorithm to be used from bootup.
769
770	  Examples shift values and their meaning:
771		     17 => 128 KB for each CPU
772		     16 =>  64 KB for each CPU
773		     15 =>  32 KB for each CPU
774		     14 =>  16 KB for each CPU
775		     13 =>   8 KB for each CPU
776		     12 =>   4 KB for each CPU
777
778config PRINTK_INDEX
779	bool "Printk indexing debugfs interface"
780	depends on PRINTK && DEBUG_FS
781	help
782	  Add support for indexing of all printk formats known at compile time
783	  at <debugfs>/printk/index/<module>.
784
785	  This can be used as part of maintaining daemons which monitor
786	  /dev/kmsg, as it permits auditing the printk formats present in a
787	  kernel, allowing detection of cases where monitored printks are
788	  changed or no longer present.
789
790	  There is no additional runtime cost to printk with this enabled.
791
792#
793# Architectures with an unreliable sched_clock() should select this:
794#
795config HAVE_UNSTABLE_SCHED_CLOCK
796	bool
797
798config GENERIC_SCHED_CLOCK
799	bool
800
801menu "Scheduler features"
802
803config UCLAMP_TASK
804	bool "Enable utilization clamping for RT/FAIR tasks"
805	depends on CPU_FREQ_GOV_SCHEDUTIL
806	help
807	  This feature enables the scheduler to track the clamped utilization
808	  of each CPU based on RUNNABLE tasks scheduled on that CPU.
809
810	  With this option, the user can specify the min and max CPU
811	  utilization allowed for RUNNABLE tasks. The max utilization defines
812	  the maximum frequency a task should use while the min utilization
813	  defines the minimum frequency it should use.
814
815	  Both min and max utilization clamp values are hints to the scheduler,
816	  aiming at improving its frequency selection policy, but they do not
817	  enforce or grant any specific bandwidth for tasks.
818
819	  If in doubt, say N.
820
821config UCLAMP_BUCKETS_COUNT
822	int "Number of supported utilization clamp buckets"
823	range 5 20
824	default 5
825	depends on UCLAMP_TASK
826	help
827	  Defines the number of clamp buckets to use. The range of each bucket
828	  will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
829	  number of clamp buckets the finer their granularity and the higher
830	  the precision of clamping aggregation and tracking at run-time.
831
832	  For example, with the minimum configuration value we will have 5
833	  clamp buckets tracking 20% utilization each. A 25% boosted tasks will
834	  be refcounted in the [20..39]% bucket and will set the bucket clamp
835	  effective value to 25%.
836	  If a second 30% boosted task should be co-scheduled on the same CPU,
837	  that task will be refcounted in the same bucket of the first task and
838	  it will boost the bucket clamp effective value to 30%.
839	  The clamp effective value of a bucket is reset to its nominal value
840	  (20% in the example above) when there are no more tasks refcounted in
841	  that bucket.
842
843	  An additional boost/capping margin can be added to some tasks. In the
844	  example above the 25% task will be boosted to 30% until it exits the
845	  CPU. If that should be considered not acceptable on certain systems,
846	  it's always possible to reduce the margin by increasing the number of
847	  clamp buckets to trade off used memory for run-time tracking
848	  precision.
849
850	  If in doubt, use the default value.
851
852endmenu
853
854#
855# For architectures that want to enable the support for NUMA-affine scheduler
856# balancing logic:
857#
858config ARCH_SUPPORTS_NUMA_BALANCING
859	bool
860
861#
862# For architectures that prefer to flush all TLBs after a number of pages
863# are unmapped instead of sending one IPI per page to flush. The architecture
864# must provide guarantees on what happens if a clean TLB cache entry is
865# written after the unmap. Details are in mm/rmap.c near the check for
866# should_defer_flush. The architecture should also consider if the full flush
867# and the refill costs are offset by the savings of sending fewer IPIs.
868config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
869	bool
870
871config CC_HAS_INT128
872	def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
873
874config CC_IMPLICIT_FALLTHROUGH
875	string
876	default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
877	default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough)
878
879# Currently, disable gcc-11+ array-bounds globally.
880# It's still broken in gcc-13, so no upper bound yet.
881config GCC11_NO_ARRAY_BOUNDS
882	def_bool y
883
884config CC_NO_ARRAY_BOUNDS
885	bool
886	default y if CC_IS_GCC && GCC_VERSION >= 110000 && GCC11_NO_ARRAY_BOUNDS
887
888#
889# For architectures that know their GCC __int128 support is sound
890#
891config ARCH_SUPPORTS_INT128
892	bool
893
894# For architectures that (ab)use NUMA to represent different memory regions
895# all cpu-local but of different latencies, such as SuperH.
896#
897config ARCH_WANT_NUMA_VARIABLE_LOCALITY
898	bool
899
900config NUMA_BALANCING
901	bool "Memory placement aware NUMA scheduler"
902	depends on ARCH_SUPPORTS_NUMA_BALANCING
903	depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
904	depends on SMP && NUMA && MIGRATION && !PREEMPT_RT
905	help
906	  This option adds support for automatic NUMA aware memory/task placement.
907	  The mechanism is quite primitive and is based on migrating memory when
908	  it has references to the node the task is running on.
909
910	  This system will be inactive on UMA systems.
911
912config NUMA_BALANCING_DEFAULT_ENABLED
913	bool "Automatically enable NUMA aware memory/task placement"
914	default y
915	depends on NUMA_BALANCING
916	help
917	  If set, automatic NUMA balancing will be enabled if running on a NUMA
918	  machine.
919
920menuconfig CGROUPS
921	bool "Control Group support"
922	select KERNFS
923	help
924	  This option adds support for grouping sets of processes together, for
925	  use with process control subsystems such as Cpusets, CFS, memory
926	  controls or device isolation.
927	  See
928		- Documentation/scheduler/sched-design-CFS.rst	(CFS)
929		- Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
930					  and resource control)
931
932	  Say N if unsure.
933
934if CGROUPS
935
936config PAGE_COUNTER
937	bool
938
939config CGROUP_FAVOR_DYNMODS
940        bool "Favor dynamic modification latency reduction by default"
941        help
942          This option enables the "favordynmods" mount option by default
943          which reduces the latencies of dynamic cgroup modifications such
944          as task migrations and controller on/offs at the cost of making
945          hot path operations such as forks and exits more expensive.
946
947          Say N if unsure.
948
949config MEMCG
950	bool "Memory controller"
951	select PAGE_COUNTER
952	select EVENTFD
953	help
954	  Provides control over the memory footprint of tasks in a cgroup.
955
956config MEMCG_KMEM
957	bool
958	depends on MEMCG
959	default y
960
961config BLK_CGROUP
962	bool "IO controller"
963	depends on BLOCK
964	default n
965	help
966	Generic block IO controller cgroup interface. This is the common
967	cgroup interface which should be used by various IO controlling
968	policies.
969
970	Currently, CFQ IO scheduler uses it to recognize task groups and
971	control disk bandwidth allocation (proportional time slice allocation)
972	to such task groups. It is also used by bio throttling logic in
973	block layer to implement upper limit in IO rates on a device.
974
975	This option only enables generic Block IO controller infrastructure.
976	One needs to also enable actual IO controlling logic/policy. For
977	enabling proportional weight division of disk bandwidth in CFQ, set
978	CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
979	CONFIG_BLK_DEV_THROTTLING=y.
980
981	See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
982
983config CGROUP_WRITEBACK
984	bool
985	depends on MEMCG && BLK_CGROUP
986	default y
987
988menuconfig CGROUP_SCHED
989	bool "CPU controller"
990	default n
991	help
992	  This feature lets CPU scheduler recognize task groups and control CPU
993	  bandwidth allocation to such task groups. It uses cgroups to group
994	  tasks.
995
996if CGROUP_SCHED
997config FAIR_GROUP_SCHED
998	bool "Group scheduling for SCHED_OTHER"
999	depends on CGROUP_SCHED
1000	default CGROUP_SCHED
1001
1002config CFS_BANDWIDTH
1003	bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1004	depends on FAIR_GROUP_SCHED
1005	default n
1006	help
1007	  This option allows users to define CPU bandwidth rates (limits) for
1008	  tasks running within the fair group scheduler.  Groups with no limit
1009	  set are considered to be unconstrained and will run with no
1010	  restriction.
1011	  See Documentation/scheduler/sched-bwc.rst for more information.
1012
1013config RT_GROUP_SCHED
1014	bool "Group scheduling for SCHED_RR/FIFO"
1015	depends on CGROUP_SCHED
1016	default n
1017	help
1018	  This feature lets you explicitly allocate real CPU bandwidth
1019	  to task groups. If enabled, it will also make it impossible to
1020	  schedule realtime tasks for non-root users until you allocate
1021	  realtime bandwidth for them.
1022	  See Documentation/scheduler/sched-rt-group.rst for more information.
1023
1024endif #CGROUP_SCHED
1025
1026config SCHED_MM_CID
1027	def_bool y
1028	depends on SMP && RSEQ
1029
1030config UCLAMP_TASK_GROUP
1031	bool "Utilization clamping per group of tasks"
1032	depends on CGROUP_SCHED
1033	depends on UCLAMP_TASK
1034	default n
1035	help
1036	  This feature enables the scheduler to track the clamped utilization
1037	  of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
1038
1039	  When this option is enabled, the user can specify a min and max
1040	  CPU bandwidth which is allowed for each single task in a group.
1041	  The max bandwidth allows to clamp the maximum frequency a task
1042	  can use, while the min bandwidth allows to define a minimum
1043	  frequency a task will always use.
1044
1045	  When task group based utilization clamping is enabled, an eventually
1046	  specified task-specific clamp value is constrained by the cgroup
1047	  specified clamp value. Both minimum and maximum task clamping cannot
1048	  be bigger than the corresponding clamping defined at task group level.
1049
1050	  If in doubt, say N.
1051
1052config CGROUP_PIDS
1053	bool "PIDs controller"
1054	help
1055	  Provides enforcement of process number limits in the scope of a
1056	  cgroup. Any attempt to fork more processes than is allowed in the
1057	  cgroup will fail. PIDs are fundamentally a global resource because it
1058	  is fairly trivial to reach PID exhaustion before you reach even a
1059	  conservative kmemcg limit. As a result, it is possible to grind a
1060	  system to halt without being limited by other cgroup policies. The
1061	  PIDs controller is designed to stop this from happening.
1062
1063	  It should be noted that organisational operations (such as attaching
1064	  to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1065	  since the PIDs limit only affects a process's ability to fork, not to
1066	  attach to a cgroup.
1067
1068config CGROUP_RDMA
1069	bool "RDMA controller"
1070	help
1071	  Provides enforcement of RDMA resources defined by IB stack.
1072	  It is fairly easy for consumers to exhaust RDMA resources, which
1073	  can result into resource unavailability to other consumers.
1074	  RDMA controller is designed to stop this from happening.
1075	  Attaching processes with active RDMA resources to the cgroup
1076	  hierarchy is allowed even if can cross the hierarchy's limit.
1077
1078config CGROUP_FREEZER
1079	bool "Freezer controller"
1080	help
1081	  Provides a way to freeze and unfreeze all tasks in a
1082	  cgroup.
1083
1084	  This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1085	  controller includes important in-kernel memory consumers per default.
1086
1087	  If you're using cgroup2, say N.
1088
1089config CGROUP_HUGETLB
1090	bool "HugeTLB controller"
1091	depends on HUGETLB_PAGE
1092	select PAGE_COUNTER
1093	default n
1094	help
1095	  Provides a cgroup controller for HugeTLB pages.
1096	  When you enable this, you can put a per cgroup limit on HugeTLB usage.
1097	  The limit is enforced during page fault. Since HugeTLB doesn't
1098	  support page reclaim, enforcing the limit at page fault time implies
1099	  that, the application will get SIGBUS signal if it tries to access
1100	  HugeTLB pages beyond its limit. This requires the application to know
1101	  beforehand how much HugeTLB pages it would require for its use. The
1102	  control group is tracked in the third page lru pointer. This means
1103	  that we cannot use the controller with huge page less than 3 pages.
1104
1105config CPUSETS
1106	bool "Cpuset controller"
1107	depends on SMP
1108	help
1109	  This option will let you create and manage CPUSETs which
1110	  allow dynamically partitioning a system into sets of CPUs and
1111	  Memory Nodes and assigning tasks to run only within those sets.
1112	  This is primarily useful on large SMP or NUMA systems.
1113
1114	  Say N if unsure.
1115
1116config PROC_PID_CPUSET
1117	bool "Include legacy /proc/<pid>/cpuset file"
1118	depends on CPUSETS
1119	default y
1120
1121config CGROUP_DEVICE
1122	bool "Device controller"
1123	help
1124	  Provides a cgroup controller implementing whitelists for
1125	  devices which a process in the cgroup can mknod or open.
1126
1127config CGROUP_CPUACCT
1128	bool "Simple CPU accounting controller"
1129	help
1130	  Provides a simple controller for monitoring the
1131	  total CPU consumed by the tasks in a cgroup.
1132
1133config CGROUP_PERF
1134	bool "Perf controller"
1135	depends on PERF_EVENTS
1136	help
1137	  This option extends the perf per-cpu mode to restrict monitoring
1138	  to threads which belong to the cgroup specified and run on the
1139	  designated cpu.  Or this can be used to have cgroup ID in samples
1140	  so that it can monitor performance events among cgroups.
1141
1142	  Say N if unsure.
1143
1144config CGROUP_BPF
1145	bool "Support for eBPF programs attached to cgroups"
1146	depends on BPF_SYSCALL
1147	select SOCK_CGROUP_DATA
1148	help
1149	  Allow attaching eBPF programs to a cgroup using the bpf(2)
1150	  syscall command BPF_PROG_ATTACH.
1151
1152	  In which context these programs are accessed depends on the type
1153	  of attachment. For instance, programs that are attached using
1154	  BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1155	  inet sockets.
1156
1157config CGROUP_MISC
1158	bool "Misc resource controller"
1159	default n
1160	help
1161	  Provides a controller for miscellaneous resources on a host.
1162
1163	  Miscellaneous scalar resources are the resources on the host system
1164	  which cannot be abstracted like the other cgroups. This controller
1165	  tracks and limits the miscellaneous resources used by a process
1166	  attached to a cgroup hierarchy.
1167
1168	  For more information, please check misc cgroup section in
1169	  /Documentation/admin-guide/cgroup-v2.rst.
1170
1171config CGROUP_DEBUG
1172	bool "Debug controller"
1173	default n
1174	depends on DEBUG_KERNEL
1175	help
1176	  This option enables a simple controller that exports
1177	  debugging information about the cgroups framework. This
1178	  controller is for control cgroup debugging only. Its
1179	  interfaces are not stable.
1180
1181	  Say N.
1182
1183config SOCK_CGROUP_DATA
1184	bool
1185	default n
1186
1187endif # CGROUPS
1188
1189menuconfig NAMESPACES
1190	bool "Namespaces support" if EXPERT
1191	depends on MULTIUSER
1192	default !EXPERT
1193	help
1194	  Provides the way to make tasks work with different objects using
1195	  the same id. For example same IPC id may refer to different objects
1196	  or same user id or pid may refer to different tasks when used in
1197	  different namespaces.
1198
1199if NAMESPACES
1200
1201config UTS_NS
1202	bool "UTS namespace"
1203	default y
1204	help
1205	  In this namespace tasks see different info provided with the
1206	  uname() system call
1207
1208config TIME_NS
1209	bool "TIME namespace"
1210	depends on GENERIC_VDSO_TIME_NS
1211	default y
1212	help
1213	  In this namespace boottime and monotonic clocks can be set.
1214	  The time will keep going with the same pace.
1215
1216config IPC_NS
1217	bool "IPC namespace"
1218	depends on (SYSVIPC || POSIX_MQUEUE)
1219	default y
1220	help
1221	  In this namespace tasks work with IPC ids which correspond to
1222	  different IPC objects in different namespaces.
1223
1224config USER_NS
1225	bool "User namespace"
1226	default n
1227	help
1228	  This allows containers, i.e. vservers, to use user namespaces
1229	  to provide different user info for different servers.
1230
1231	  When user namespaces are enabled in the kernel it is
1232	  recommended that the MEMCG option also be enabled and that
1233	  user-space use the memory control groups to limit the amount
1234	  of memory a memory unprivileged users can use.
1235
1236	  If unsure, say N.
1237
1238config PID_NS
1239	bool "PID Namespaces"
1240	default y
1241	help
1242	  Support process id namespaces.  This allows having multiple
1243	  processes with the same pid as long as they are in different
1244	  pid namespaces.  This is a building block of containers.
1245
1246config NET_NS
1247	bool "Network namespace"
1248	depends on NET
1249	default y
1250	help
1251	  Allow user space to create what appear to be multiple instances
1252	  of the network stack.
1253
1254endif # NAMESPACES
1255
1256config CHECKPOINT_RESTORE
1257	bool "Checkpoint/restore support"
1258	depends on PROC_FS
1259	select PROC_CHILDREN
1260	select KCMP
1261	default n
1262	help
1263	  Enables additional kernel features in a sake of checkpoint/restore.
1264	  In particular it adds auxiliary prctl codes to setup process text,
1265	  data and heap segment sizes, and a few additional /proc filesystem
1266	  entries.
1267
1268	  If unsure, say N here.
1269
1270config SCHED_AUTOGROUP
1271	bool "Automatic process group scheduling"
1272	select CGROUPS
1273	select CGROUP_SCHED
1274	select FAIR_GROUP_SCHED
1275	help
1276	  This option optimizes the scheduler for common desktop workloads by
1277	  automatically creating and populating task groups.  This separation
1278	  of workloads isolates aggressive CPU burners (like build jobs) from
1279	  desktop applications.  Task group autogeneration is currently based
1280	  upon task session.
1281
1282config RELAY
1283	bool "Kernel->user space relay support (formerly relayfs)"
1284	select IRQ_WORK
1285	help
1286	  This option enables support for relay interface support in
1287	  certain file systems (such as debugfs).
1288	  It is designed to provide an efficient mechanism for tools and
1289	  facilities to relay large amounts of data from kernel space to
1290	  user space.
1291
1292	  If unsure, say N.
1293
1294config BLK_DEV_INITRD
1295	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1296	help
1297	  The initial RAM filesystem is a ramfs which is loaded by the
1298	  boot loader (loadlin or lilo) and that is mounted as root
1299	  before the normal boot procedure. It is typically used to
1300	  load modules needed to mount the "real" root file system,
1301	  etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1302
1303	  If RAM disk support (BLK_DEV_RAM) is also included, this
1304	  also enables initial RAM disk (initrd) support and adds
1305	  15 Kbytes (more on some other architectures) to the kernel size.
1306
1307	  If unsure say Y.
1308
1309if BLK_DEV_INITRD
1310
1311source "usr/Kconfig"
1312
1313endif
1314
1315config BOOT_CONFIG
1316	bool "Boot config support"
1317	select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED
1318	help
1319	  Extra boot config allows system admin to pass a config file as
1320	  complemental extension of kernel cmdline when booting.
1321	  The boot config file must be attached at the end of initramfs
1322	  with checksum, size and magic word.
1323	  See <file:Documentation/admin-guide/bootconfig.rst> for details.
1324
1325	  If unsure, say Y.
1326
1327config BOOT_CONFIG_FORCE
1328	bool "Force unconditional bootconfig processing"
1329	depends on BOOT_CONFIG
1330	default y if BOOT_CONFIG_EMBED
1331	help
1332	  With this Kconfig option set, BOOT_CONFIG processing is carried
1333	  out even when the "bootconfig" kernel-boot parameter is omitted.
1334	  In fact, with this Kconfig option set, there is no way to
1335	  make the kernel ignore the BOOT_CONFIG-supplied kernel-boot
1336	  parameters.
1337
1338	  If unsure, say N.
1339
1340config BOOT_CONFIG_EMBED
1341	bool "Embed bootconfig file in the kernel"
1342	depends on BOOT_CONFIG
1343	help
1344	  Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the
1345	  kernel. Usually, the bootconfig file is loaded with the initrd
1346	  image. But if the system doesn't support initrd, this option will
1347	  help you by embedding a bootconfig file while building the kernel.
1348
1349	  If unsure, say N.
1350
1351config BOOT_CONFIG_EMBED_FILE
1352	string "Embedded bootconfig file path"
1353	depends on BOOT_CONFIG_EMBED
1354	help
1355	  Specify a bootconfig file which will be embedded to the kernel.
1356	  This bootconfig will be used if there is no initrd or no other
1357	  bootconfig in the initrd.
1358
1359config INITRAMFS_PRESERVE_MTIME
1360	bool "Preserve cpio archive mtimes in initramfs"
1361	default y
1362	help
1363	  Each entry in an initramfs cpio archive carries an mtime value. When
1364	  enabled, extracted cpio items take this mtime, with directory mtime
1365	  setting deferred until after creation of any child entries.
1366
1367	  If unsure, say Y.
1368
1369choice
1370	prompt "Compiler optimization level"
1371	default CC_OPTIMIZE_FOR_PERFORMANCE
1372
1373config CC_OPTIMIZE_FOR_PERFORMANCE
1374	bool "Optimize for performance (-O2)"
1375	help
1376	  This is the default optimization level for the kernel, building
1377	  with the "-O2" compiler flag for best performance and most
1378	  helpful compile-time warnings.
1379
1380config CC_OPTIMIZE_FOR_SIZE
1381	bool "Optimize for size (-Os)"
1382	help
1383	  Choosing this option will pass "-Os" to your compiler resulting
1384	  in a smaller kernel.
1385
1386endchoice
1387
1388config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1389	bool
1390	help
1391	  This requires that the arch annotates or otherwise protects
1392	  its external entry points from being discarded. Linker scripts
1393	  must also merge .text.*, .data.*, and .bss.* correctly into
1394	  output sections. Care must be taken not to pull in unrelated
1395	  sections (e.g., '.text.init'). Typically '.' in section names
1396	  is used to distinguish them from label names / C identifiers.
1397
1398config LD_DEAD_CODE_DATA_ELIMINATION
1399	bool "Dead code and data elimination (EXPERIMENTAL)"
1400	depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1401	depends on EXPERT
1402	depends on $(cc-option,-ffunction-sections -fdata-sections)
1403	depends on $(ld-option,--gc-sections)
1404	help
1405	  Enable this if you want to do dead code and data elimination with
1406	  the linker by compiling with -ffunction-sections -fdata-sections,
1407	  and linking with --gc-sections.
1408
1409	  This can reduce on disk and in-memory size of the kernel
1410	  code and static data, particularly for small configs and
1411	  on small systems. This has the possibility of introducing
1412	  silently broken kernel if the required annotations are not
1413	  present. This option is not well tested yet, so use at your
1414	  own risk.
1415
1416config LD_ORPHAN_WARN
1417	def_bool y
1418	depends on ARCH_WANT_LD_ORPHAN_WARN
1419	depends on $(ld-option,--orphan-handling=warn)
1420	depends on $(ld-option,--orphan-handling=error)
1421
1422config LD_ORPHAN_WARN_LEVEL
1423        string
1424        depends on LD_ORPHAN_WARN
1425        default "error" if WERROR
1426        default "warn"
1427
1428config SYSCTL
1429	bool
1430
1431config HAVE_UID16
1432	bool
1433
1434config SYSCTL_EXCEPTION_TRACE
1435	bool
1436	help
1437	  Enable support for /proc/sys/debug/exception-trace.
1438
1439config SYSCTL_ARCH_UNALIGN_NO_WARN
1440	bool
1441	help
1442	  Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1443	  Allows arch to define/use @no_unaligned_warning to possibly warn
1444	  about unaligned access emulation going on under the hood.
1445
1446config SYSCTL_ARCH_UNALIGN_ALLOW
1447	bool
1448	help
1449	  Enable support for /proc/sys/kernel/unaligned-trap
1450	  Allows arches to define/use @unaligned_enabled to runtime toggle
1451	  the unaligned access emulation.
1452	  see arch/parisc/kernel/unaligned.c for reference
1453
1454config HAVE_PCSPKR_PLATFORM
1455	bool
1456
1457# interpreter that classic socket filters depend on
1458config BPF
1459	bool
1460	select CRYPTO_LIB_SHA1
1461
1462menuconfig EXPERT
1463	bool "Configure standard kernel features (expert users)"
1464	# Unhide debug options, to make the on-by-default options visible
1465	select DEBUG_KERNEL
1466	help
1467	  This option allows certain base kernel options and settings
1468	  to be disabled or tweaked. This is for specialized
1469	  environments which can tolerate a "non-standard" kernel.
1470	  Only use this if you really know what you are doing.
1471
1472config UID16
1473	bool "Enable 16-bit UID system calls" if EXPERT
1474	depends on HAVE_UID16 && MULTIUSER
1475	default y
1476	help
1477	  This enables the legacy 16-bit UID syscall wrappers.
1478
1479config MULTIUSER
1480	bool "Multiple users, groups and capabilities support" if EXPERT
1481	default y
1482	help
1483	  This option enables support for non-root users, groups and
1484	  capabilities.
1485
1486	  If you say N here, all processes will run with UID 0, GID 0, and all
1487	  possible capabilities.  Saying N here also compiles out support for
1488	  system calls related to UIDs, GIDs, and capabilities, such as setuid,
1489	  setgid, and capset.
1490
1491	  If unsure, say Y here.
1492
1493config SGETMASK_SYSCALL
1494	bool "sgetmask/ssetmask syscalls support" if EXPERT
1495	def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1496	help
1497	  sys_sgetmask and sys_ssetmask are obsolete system calls
1498	  no longer supported in libc but still enabled by default in some
1499	  architectures.
1500
1501	  If unsure, leave the default option here.
1502
1503config SYSFS_SYSCALL
1504	bool "Sysfs syscall support" if EXPERT
1505	default y
1506	help
1507	  sys_sysfs is an obsolete system call no longer supported in libc.
1508	  Note that disabling this option is more secure but might break
1509	  compatibility with some systems.
1510
1511	  If unsure say Y here.
1512
1513config FHANDLE
1514	bool "open by fhandle syscalls" if EXPERT
1515	select EXPORTFS
1516	default y
1517	help
1518	  If you say Y here, a user level program will be able to map
1519	  file names to handle and then later use the handle for
1520	  different file system operations. This is useful in implementing
1521	  userspace file servers, which now track files using handles instead
1522	  of names. The handle would remain the same even if file names
1523	  get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1524	  syscalls.
1525
1526config POSIX_TIMERS
1527	bool "Posix Clocks & timers" if EXPERT
1528	default y
1529	help
1530	  This includes native support for POSIX timers to the kernel.
1531	  Some embedded systems have no use for them and therefore they
1532	  can be configured out to reduce the size of the kernel image.
1533
1534	  When this option is disabled, the following syscalls won't be
1535	  available: timer_create, timer_gettime: timer_getoverrun,
1536	  timer_settime, timer_delete, clock_adjtime, getitimer,
1537	  setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1538	  clock_getres and clock_nanosleep syscalls will be limited to
1539	  CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1540
1541	  If unsure say y.
1542
1543config PRINTK
1544	default y
1545	bool "Enable support for printk" if EXPERT
1546	select IRQ_WORK
1547	help
1548	  This option enables normal printk support. Removing it
1549	  eliminates most of the message strings from the kernel image
1550	  and makes the kernel more or less silent. As this makes it
1551	  very difficult to diagnose system problems, saying N here is
1552	  strongly discouraged.
1553
1554config BUG
1555	bool "BUG() support" if EXPERT
1556	default y
1557	help
1558	  Disabling this option eliminates support for BUG and WARN, reducing
1559	  the size of your kernel image and potentially quietly ignoring
1560	  numerous fatal conditions. You should only consider disabling this
1561	  option for embedded systems with no facilities for reporting errors.
1562	  Just say Y.
1563
1564config ELF_CORE
1565	depends on COREDUMP
1566	default y
1567	bool "Enable ELF core dumps" if EXPERT
1568	help
1569	  Enable support for generating core dumps. Disabling saves about 4k.
1570
1571
1572config PCSPKR_PLATFORM
1573	bool "Enable PC-Speaker support" if EXPERT
1574	depends on HAVE_PCSPKR_PLATFORM
1575	select I8253_LOCK
1576	default y
1577	help
1578	  This option allows to disable the internal PC-Speaker
1579	  support, saving some memory.
1580
1581config BASE_FULL
1582	default y
1583	bool "Enable full-sized data structures for core" if EXPERT
1584	help
1585	  Disabling this option reduces the size of miscellaneous core
1586	  kernel data structures. This saves memory on small machines,
1587	  but may reduce performance.
1588
1589config FUTEX
1590	bool "Enable futex support" if EXPERT
1591	depends on !(SPARC32 && SMP)
1592	default y
1593	imply RT_MUTEXES
1594	help
1595	  Disabling this option will cause the kernel to be built without
1596	  support for "fast userspace mutexes".  The resulting kernel may not
1597	  run glibc-based applications correctly.
1598
1599config FUTEX_PI
1600	bool
1601	depends on FUTEX && RT_MUTEXES
1602	default y
1603
1604config EPOLL
1605	bool "Enable eventpoll support" if EXPERT
1606	default y
1607	help
1608	  Disabling this option will cause the kernel to be built without
1609	  support for epoll family of system calls.
1610
1611config SIGNALFD
1612	bool "Enable signalfd() system call" if EXPERT
1613	default y
1614	help
1615	  Enable the signalfd() system call that allows to receive signals
1616	  on a file descriptor.
1617
1618	  If unsure, say Y.
1619
1620config TIMERFD
1621	bool "Enable timerfd() system call" if EXPERT
1622	default y
1623	help
1624	  Enable the timerfd() system call that allows to receive timer
1625	  events on a file descriptor.
1626
1627	  If unsure, say Y.
1628
1629config EVENTFD
1630	bool "Enable eventfd() system call" if EXPERT
1631	default y
1632	help
1633	  Enable the eventfd() system call that allows to receive both
1634	  kernel notification (ie. KAIO) or userspace notifications.
1635
1636	  If unsure, say Y.
1637
1638config SHMEM
1639	bool "Use full shmem filesystem" if EXPERT
1640	default y
1641	depends on MMU
1642	help
1643	  The shmem is an internal filesystem used to manage shared memory.
1644	  It is backed by swap and manages resource limits. It is also exported
1645	  to userspace as tmpfs if TMPFS is enabled. Disabling this
1646	  option replaces shmem and tmpfs with the much simpler ramfs code,
1647	  which may be appropriate on small systems without swap.
1648
1649config AIO
1650	bool "Enable AIO support" if EXPERT
1651	default y
1652	help
1653	  This option enables POSIX asynchronous I/O which may by used
1654	  by some high performance threaded applications. Disabling
1655	  this option saves about 7k.
1656
1657config IO_URING
1658	bool "Enable IO uring support" if EXPERT
1659	select IO_WQ
1660	default y
1661	help
1662	  This option enables support for the io_uring interface, enabling
1663	  applications to submit and complete IO through submission and
1664	  completion rings that are shared between the kernel and application.
1665
1666config ADVISE_SYSCALLS
1667	bool "Enable madvise/fadvise syscalls" if EXPERT
1668	default y
1669	help
1670	  This option enables the madvise and fadvise syscalls, used by
1671	  applications to advise the kernel about their future memory or file
1672	  usage, improving performance. If building an embedded system where no
1673	  applications use these syscalls, you can disable this option to save
1674	  space.
1675
1676config MEMBARRIER
1677	bool "Enable membarrier() system call" if EXPERT
1678	default y
1679	help
1680	  Enable the membarrier() system call that allows issuing memory
1681	  barriers across all running threads, which can be used to distribute
1682	  the cost of user-space memory barriers asymmetrically by transforming
1683	  pairs of memory barriers into pairs consisting of membarrier() and a
1684	  compiler barrier.
1685
1686	  If unsure, say Y.
1687
1688config KALLSYMS
1689	bool "Load all symbols for debugging/ksymoops" if EXPERT
1690	default y
1691	help
1692	  Say Y here to let the kernel print out symbolic crash information and
1693	  symbolic stack backtraces. This increases the size of the kernel
1694	  somewhat, as all symbols have to be loaded into the kernel image.
1695
1696config KALLSYMS_SELFTEST
1697	bool "Test the basic functions and performance of kallsyms"
1698	depends on KALLSYMS
1699	default n
1700	help
1701	  Test the basic functions and performance of some interfaces, such as
1702	  kallsyms_lookup_name. It also calculates the compression rate of the
1703	  kallsyms compression algorithm for the current symbol set.
1704
1705	  Start self-test automatically after system startup. Suggest executing
1706	  "dmesg | grep kallsyms_selftest" to collect test results. "finish" is
1707	  displayed in the last line, indicating that the test is complete.
1708
1709config KALLSYMS_ALL
1710	bool "Include all symbols in kallsyms"
1711	depends on DEBUG_KERNEL && KALLSYMS
1712	help
1713	  Normally kallsyms only contains the symbols of functions for nicer
1714	  OOPS messages and backtraces (i.e., symbols from the text and inittext
1715	  sections). This is sufficient for most cases. And only if you want to
1716	  enable kernel live patching, or other less common use cases (e.g.,
1717	  when a debugger is used) all symbols are required (i.e., names of
1718	  variables from the data sections, etc).
1719
1720	  This option makes sure that all symbols are loaded into the kernel
1721	  image (i.e., symbols from all sections) in cost of increased kernel
1722	  size (depending on the kernel configuration, it may be 300KiB or
1723	  something like this).
1724
1725	  Say N unless you really need all symbols, or kernel live patching.
1726
1727config KALLSYMS_ABSOLUTE_PERCPU
1728	bool
1729	depends on KALLSYMS
1730	default X86_64 && SMP
1731
1732config KALLSYMS_BASE_RELATIVE
1733	bool
1734	depends on KALLSYMS
1735	default !IA64
1736	help
1737	  Instead of emitting them as absolute values in the native word size,
1738	  emit the symbol references in the kallsyms table as 32-bit entries,
1739	  each containing a relative value in the range [base, base + U32_MAX]
1740	  or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1741	  an absolute value in the range [0, S32_MAX] or a relative value in the
1742	  range [base, base + S32_MAX], where base is the lowest relative symbol
1743	  address encountered in the image.
1744
1745	  On 64-bit builds, this reduces the size of the address table by 50%,
1746	  but more importantly, it results in entries whose values are build
1747	  time constants, and no relocation pass is required at runtime to fix
1748	  up the entries based on the runtime load address of the kernel.
1749
1750# end of the "standard kernel features (expert users)" menu
1751
1752# syscall, maps, verifier
1753
1754config ARCH_HAS_MEMBARRIER_CALLBACKS
1755	bool
1756
1757config ARCH_HAS_MEMBARRIER_SYNC_CORE
1758	bool
1759
1760config 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
1770config 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
1784config CACHESTAT_SYSCALL
1785	bool "Enable cachestat() system call" if EXPERT
1786	default y
1787	help
1788	  Enable the cachestat system call, which queries the page cache
1789	  statistics of a file (number of cached pages, dirty pages,
1790	  pages marked for writeback, (recently) evicted pages).
1791
1792	  If unsure say Y here.
1793
1794config DEBUG_RSEQ
1795	default n
1796	bool "Enabled debugging of rseq() system call" if EXPERT
1797	depends on RSEQ && DEBUG_KERNEL
1798	help
1799	  Enable extra debugging checks for the rseq system call.
1800
1801	  If unsure, say N.
1802
1803config HAVE_PERF_EVENTS
1804	bool
1805	help
1806	  See tools/perf/design.txt for details.
1807
1808config GUEST_PERF_EVENTS
1809	bool
1810	depends on HAVE_PERF_EVENTS
1811
1812config PERF_USE_VMALLOC
1813	bool
1814	help
1815	  See tools/perf/design.txt for details
1816
1817config PC104
1818	bool "PC/104 support" if EXPERT
1819	help
1820	  Expose PC/104 form factor device drivers and options available for
1821	  selection and configuration. Enable this option if your target
1822	  machine has a PC/104 bus.
1823
1824menu "Kernel Performance Events And Counters"
1825
1826config PERF_EVENTS
1827	bool "Kernel performance events and counters"
1828	default y if PROFILING
1829	depends on HAVE_PERF_EVENTS
1830	select IRQ_WORK
1831	help
1832	  Enable kernel support for various performance events provided
1833	  by software and hardware.
1834
1835	  Software events are supported either built-in or via the
1836	  use of generic tracepoints.
1837
1838	  Most modern CPUs support performance events via performance
1839	  counter registers. These registers count the number of certain
1840	  types of hw events: such as instructions executed, cachemisses
1841	  suffered, or branches mis-predicted - without slowing down the
1842	  kernel or applications. These registers can also trigger interrupts
1843	  when a threshold number of events have passed - and can thus be
1844	  used to profile the code that runs on that CPU.
1845
1846	  The Linux Performance Event subsystem provides an abstraction of
1847	  these software and hardware event capabilities, available via a
1848	  system call and used by the "perf" utility in tools/perf/. It
1849	  provides per task and per CPU counters, and it provides event
1850	  capabilities on top of those.
1851
1852	  Say Y if unsure.
1853
1854config DEBUG_PERF_USE_VMALLOC
1855	default n
1856	bool "Debug: use vmalloc to back perf mmap() buffers"
1857	depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1858	select PERF_USE_VMALLOC
1859	help
1860	  Use vmalloc memory to back perf mmap() buffers.
1861
1862	  Mostly useful for debugging the vmalloc code on platforms
1863	  that don't require it.
1864
1865	  Say N if unsure.
1866
1867endmenu
1868
1869config SYSTEM_DATA_VERIFICATION
1870	def_bool n
1871	select SYSTEM_TRUSTED_KEYRING
1872	select KEYS
1873	select CRYPTO
1874	select CRYPTO_RSA
1875	select ASYMMETRIC_KEY_TYPE
1876	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1877	select ASN1
1878	select OID_REGISTRY
1879	select X509_CERTIFICATE_PARSER
1880	select PKCS7_MESSAGE_PARSER
1881	help
1882	  Provide PKCS#7 message verification using the contents of the system
1883	  trusted keyring to provide public keys.  This then can be used for
1884	  module verification, kexec image verification and firmware blob
1885	  verification.
1886
1887config PROFILING
1888	bool "Profiling support"
1889	help
1890	  Say Y here to enable the extended profiling support mechanisms used
1891	  by profilers.
1892
1893config RUST
1894	bool "Rust support"
1895	depends on HAVE_RUST
1896	depends on RUST_IS_AVAILABLE
1897	depends on !MODVERSIONS
1898	depends on !GCC_PLUGINS
1899	depends on !RANDSTRUCT
1900	depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE
1901	select CONSTRUCTORS
1902	help
1903	  Enables Rust support in the kernel.
1904
1905	  This allows other Rust-related options, like drivers written in Rust,
1906	  to be selected.
1907
1908	  It is also required to be able to load external kernel modules
1909	  written in Rust.
1910
1911	  See Documentation/rust/ for more information.
1912
1913	  If unsure, say N.
1914
1915config RUSTC_VERSION_TEXT
1916	string
1917	depends on RUST
1918	default $(shell,command -v $(RUSTC) >/dev/null 2>&1 && $(RUSTC) --version || echo n)
1919
1920config BINDGEN_VERSION_TEXT
1921	string
1922	depends on RUST
1923	default $(shell,command -v $(BINDGEN) >/dev/null 2>&1 && $(BINDGEN) --version || echo n)
1924
1925#
1926# Place an empty function call at each tracepoint site. Can be
1927# dynamically changed for a probe function.
1928#
1929config TRACEPOINTS
1930	bool
1931
1932source "kernel/Kconfig.kexec"
1933
1934endmenu		# General setup
1935
1936source "arch/Kconfig"
1937
1938config RT_MUTEXES
1939	bool
1940	default y if PREEMPT_RT
1941
1942config BASE_SMALL
1943	int
1944	default 0 if BASE_FULL
1945	default 1 if !BASE_FULL
1946
1947config MODULE_SIG_FORMAT
1948	def_bool n
1949	select SYSTEM_DATA_VERIFICATION
1950
1951source "kernel/module/Kconfig"
1952
1953config INIT_ALL_POSSIBLE
1954	bool
1955	help
1956	  Back when each arch used to define their own cpu_online_mask and
1957	  cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1958	  with all 1s, and others with all 0s.  When they were centralised,
1959	  it was better to provide this option than to break all the archs
1960	  and have several arch maintainers pursuing me down dark alleys.
1961
1962source "block/Kconfig"
1963
1964config PREEMPT_NOTIFIERS
1965	bool
1966
1967config PADATA
1968	depends on SMP
1969	bool
1970
1971config ASN1
1972	tristate
1973	help
1974	  Build a simple ASN.1 grammar compiler that produces a bytecode output
1975	  that can be interpreted by the ASN.1 stream decoder and used to
1976	  inform it as to what tags are to be expected in a stream and what
1977	  functions to call on what tags.
1978
1979source "kernel/Kconfig.locks"
1980
1981config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
1982	bool
1983
1984config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
1985	bool
1986
1987# It may be useful for an architecture to override the definitions of the
1988# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
1989# and the COMPAT_ variants in <linux/compat.h>, in particular to use a
1990# different calling convention for syscalls. They can also override the
1991# macros for not-implemented syscalls in kernel/sys_ni.c and
1992# kernel/time/posix-stubs.c. All these overrides need to be available in
1993# <asm/syscall_wrapper.h>.
1994config ARCH_HAS_SYSCALL_WRAPPER
1995	def_bool n
1996