linux - init/Kconfig

2368 lines · 74.3 KiB

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 RUSTC_LLVM_MAJOR_VERSION
86	int
87	default $(shell,expr $(rustc-llvm-version) / 10000)
88
89	config RUSTC_CLANG_LLVM_COMPATIBLE
90	bool
91	default y if CC_IS_CLANG && RUSTC_LLVM_MAJOR_VERSION = $(shell,expr $(cc-version) / 10000)
92	help
93	This indicates whether Rust and Clang use LLVM of the same major
94	version.
95
96	Operations involving handling LLVM IR or bitcode (e.g. cross-language
97	LTO) require the same LLVM major version to work properly. For best
98	compatibility it is recommended that the exact same LLVM is used.
99
100	config ARCH_HAS_CC_CAN_LINK
101	bool
102
103	config CC_CAN_LINK
104	bool
105	default ARCH_CC_CAN_LINK if ARCH_HAS_CC_CAN_LINK
106	default $(cc_can_link_user,$(m64-flag)) if 64BIT
107	default $(cc_can_link_user,$(m32-flag))
108
109	# Fixed in GCC 14, 13.3, 12.4 and 11.5
110	# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113921
111	config GCC_ASM_GOTO_OUTPUT_BROKEN
112	bool
113	depends on CC_IS_GCC
114	default y if GCC_VERSION < 110500
115	default y if GCC_VERSION >= 120000 && GCC_VERSION < 120400
116	default y if GCC_VERSION >= 130000 && GCC_VERSION < 130300
117
118	config CC_HAS_ASM_GOTO_OUTPUT
119	def_bool y
120	depends on !GCC_ASM_GOTO_OUTPUT_BROKEN
121	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)
122
123	config CC_HAS_ASM_GOTO_TIED_OUTPUT
124	depends on CC_HAS_ASM_GOTO_OUTPUT
125	# Detect buggy gcc and clang, fixed in gcc-11 clang-14.
126	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)
127
128	config TOOLS_SUPPORT_RELR
129	def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
130
131	config CC_HAS_ASM_INLINE
132	def_bool $(success,echo 'void foo(void) { asm inline (""); }' \| $(CC) -x c - -c -o /dev/null)
133
134	config CC_HAS_ASSUME
135	bool
136	# clang needs to be at least 19.1.0 since the meaning of the assume
137	# attribute changed:
138	# https://github.com/llvm/llvm-project/commit/c44fa3e8a9a44c2e9a575768a3c185354b9f6c17
139	default y if CC_IS_CLANG && CLANG_VERSION >= 190100
140	# supported since gcc 13.1.0
141	# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106654
142	default y if CC_IS_GCC && GCC_VERSION >= 130100
143
144	config CC_HAS_NO_PROFILE_FN_ATTR
145	def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' \| $(CC) -x c - -c -o /dev/null -Werror)
146
147	config CC_HAS_COUNTED_BY
148	bool
149	# clang needs to be at least 20.1.0 to avoid potential crashes
150	# when building structures that contain __counted_by
151	# https://github.com/ClangBuiltLinux/linux/issues/2114
152	# https://github.com/llvm/llvm-project/commit/160fb1121cdf703c3ef5e61fb26c5659eb581489
153	default y if CC_IS_CLANG && CLANG_VERSION >= 200100
154	# supported since gcc 15.1.0
155	# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108896
156	default y if CC_IS_GCC && GCC_VERSION >= 150100
157
158	config CC_HAS_COUNTED_BY_PTR
159	bool
160	# supported since clang 22
161	default y if CC_IS_CLANG && CLANG_VERSION >= 220100
162	# supported since gcc 16.0.0
163	default y if CC_IS_GCC && GCC_VERSION >= 160000
164
165	config CC_HAS_BROKEN_COUNTED_BY_REF
166	bool
167	# https://github.com/llvm/llvm-project/issues/182575
168	default y if CC_IS_CLANG && CLANG_VERSION < 220100
169
170	config CC_HAS_ALLOC_TOKEN
171	def_bool $(cc-option,-falloc-token-max=123)
172
173	config CC_HAS_MULTIDIMENSIONAL_NONSTRING
174	def_bool $(success,echo 'char tag[][4] __attribute__((__nonstring__)) = { };' \| $(CC) $(CLANG_FLAGS) -x c - -c -o /dev/null -Werror)
175
176	config CC_OPT_INLINE_MEMSET
177	string
178	default "-finline-stringops=memset" if $(cc-option,-finline-stringops=memset)
179	default "-mllvm -max-store-memset=4294967294" if $(cc-option,-mllvm -max-store-memset=4294967294)
180
181	config LD_CAN_USE_KEEP_IN_OVERLAY
182	# ld.lld prior to 21.0.0 did not support KEEP within an overlay description
183	# https://github.com/llvm/llvm-project/pull/130661
184	def_bool LD_IS_BFD \|\| LLD_VERSION >= 210000
185
186	config RUSTC_HAS_SPAN_FILE
187	def_bool RUSTC_VERSION >= 108800
188
189	config RUSTC_HAS_UNNECESSARY_TRANSMUTES
190	def_bool RUSTC_VERSION >= 108800
191
192	config RUSTC_HAS_FILE_WITH_NUL
193	def_bool RUSTC_VERSION >= 108900
194
195	config RUSTC_HAS_FILE_AS_C_STR
196	def_bool RUSTC_VERSION >= 109100
197
198	config RUSTC_HAS_SUSPICIOUS_RUNTIME_SYMBOL_DEFINITIONS
199	def_bool RUSTC_VERSION >= 109800
200
201	config PAHOLE_VERSION
202	int
203	default "$(PAHOLE_VERSION)"
204
205	config CONSTRUCTORS
206	bool
207
208	config IRQ_WORK
209	def_bool y if SMP
210
211	config BUILDTIME_TABLE_SORT
212	bool
213
214	config THREAD_INFO_IN_TASK
215	bool
216	help
217	Select this to move thread_info off the stack into task_struct. To
218	make this work, an arch will need to remove all thread_info fields
219	except flags and fix any runtime bugs.
220
221	One subtle change that will be needed is to use try_get_task_stack()
222	and put_task_stack() in save_thread_stack_tsk() and get_wchan().
223
224	menu "General setup"
225
226	config BROKEN
227	bool
228	help
229	This option allows you to choose whether you want to try to
230	compile (and fix) old drivers that haven't been updated to
231	new infrastructure.
232
233	config BROKEN_ON_SMP
234	bool
235	depends on BROKEN \|\| !SMP
236	default y
237
238	config INIT_ENV_ARG_LIMIT
239	int
240	default 32 if !UML
241	default 128 if UML
242	help
243	Maximum of each of the number of arguments and environment
244	variables passed to init from the kernel command line.
245
246	config COMPILE_TEST
247	bool "Compile also drivers which will not load"
248	depends on HAS_IOMEM
249	help
250	Some drivers can be compiled on a different platform than they are
251	intended to be run on. Despite they cannot be loaded there (or even
252	when they load they cannot be used due to missing HW support),
253	developers still, opposing to distributors, might want to build such
254	drivers to compile-test them.
255
256	If you are a developer and want to build everything available, say Y
257	here. If you are a user/distributor, say N here to exclude useless
258	drivers to be distributed.
259
260	config WERROR
261	bool "Compile the kernel with warnings as errors"
262	default COMPILE_TEST
263	help
264	A kernel build should not cause any compiler warnings, and this
265	enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags
266	to enforce that rule by default. Certain warnings from other tools
267	such as the linker may be upgraded to errors with this option as
268	well.
269
270	However, if you have a new (or very old) compiler or linker with odd
271	and unusual warnings, or you have some architecture with problems,
272	you may need to disable this config option in order to
273	successfully build the kernel.
274
275	If in doubt, say Y.
276
277	config UAPI_HEADER_TEST
278	bool "Compile test UAPI headers"
279	depends on HEADERS_INSTALL
280	help
281	Compile test headers exported to user-space to ensure they are
282	self-contained, i.e. compilable as standalone units.
283
284	If you are a developer or tester and want to ensure the exported
285	headers are self-contained, say Y here. Otherwise, choose N.
286
287	config LOCALVERSION
288	string "Local version - append to kernel release"
289	help
290	Append an extra string to the end of your kernel version.
291	This will show up when you type uname, for example.
292	The string you set here will be appended after the contents of
293	any files with a filename matching localversion* in your
294	object and source tree, in that order. Your total string can
295	be a maximum of 64 characters.
296
297	config LOCALVERSION_AUTO
298	bool "Automatically append version information to the version string"
299	default y
300	depends on !COMPILE_TEST
301	help
302	This will try to automatically determine if the current tree is a
303	release tree by looking for git tags that belong to the current
304	top of tree revision.
305
306	A string of the format -gxxxxxxxx will be added to the localversion
307	if a git-based tree is found. The string generated by this will be
308	appended after any matching localversion* files, and after the value
309	set in CONFIG_LOCALVERSION.
310
311	(The actual string used here is the first 12 characters produced
312	by running the command:
313
314	$ git rev-parse --verify HEAD
315
316	which is done within the script "scripts/setlocalversion".)
317
318	config BUILD_SALT
319	string "Build ID Salt"
320	default ""
321	help
322	The build ID is used to link binaries and their debug info. Setting
323	this option will use the value in the calculation of the build id.
324	This is mostly useful for distributions which want to ensure the
325	build is unique between builds. It's safe to leave the default.
326
327	config HAVE_KERNEL_GZIP
328	bool
329
330	config HAVE_KERNEL_BZIP2
331	bool
332
333	config HAVE_KERNEL_LZMA
334	bool
335
336	config HAVE_KERNEL_XZ
337	bool
338
339	config HAVE_KERNEL_LZO
340	bool
341
342	config HAVE_KERNEL_LZ4
343	bool
344
345	config HAVE_KERNEL_ZSTD
346	bool
347
348	config HAVE_KERNEL_UNCOMPRESSED
349	bool
350
351	choice
352	prompt "Kernel compression mode"
353	default KERNEL_GZIP
354	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
355	help
356	The linux kernel is a kind of self-extracting executable.
357	Several compression algorithms are available, which differ
358	in efficiency, compression and decompression speed.
359	Compression speed is only relevant when building a kernel.
360	Decompression speed is relevant at each boot.
361
362	If you have any problems with bzip2 or lzma compressed
363	kernels, mail me (Alain Knaff) <[email protected]>. (An older
364	version of this functionality (bzip2 only), for 2.4, was
365	supplied by Christian Ludwig)
366
367	High compression options are mostly useful for users, who
368	are low on disk space (embedded systems), but for whom ram
369	size matters less.
370
371	If in doubt, select 'gzip'
372
373	config KERNEL_GZIP
374	bool "Gzip"
375	depends on HAVE_KERNEL_GZIP
376	help
377	The old and tried gzip compression. It provides a good balance
378	between compression ratio and decompression speed.
379
380	config KERNEL_BZIP2
381	bool "Bzip2"
382	depends on HAVE_KERNEL_BZIP2
383	help
384	Its compression ratio and speed is intermediate.
385	Decompression speed is slowest among the choices. The kernel
386	size is about 10% smaller with bzip2, in comparison to gzip.
387	Bzip2 uses a large amount of memory. For modern kernels you
388	will need at least 8MB RAM or more for booting.
389
390	config KERNEL_LZMA
391	bool "LZMA"
392	depends on HAVE_KERNEL_LZMA
393	help
394	This compression algorithm's ratio is best. Decompression speed
395	is between gzip and bzip2. Compression is slowest.
396	The kernel size is about 33% smaller with LZMA in comparison to gzip.
397
398	config KERNEL_XZ
399	bool "XZ"
400	depends on HAVE_KERNEL_XZ
401	help
402	XZ uses the LZMA2 algorithm and instruction set specific
403	BCJ filters which can improve compression ratio of executable
404	code. The size of the kernel is about 30% smaller with XZ in
405	comparison to gzip. On architectures for which there is a BCJ
406	filter (i386, x86_64, ARM, ARM64, RISC-V, big endian PowerPC,
407	and SPARC), XZ will create a few percent smaller kernel than
408	plain LZMA.
409
410	The speed is about the same as with LZMA: The decompression
411	speed of XZ is better than that of bzip2 but worse than gzip
412	and LZO. Compression is slow.
413
414	config KERNEL_LZO
415	bool "LZO"
416	depends on HAVE_KERNEL_LZO
417	help
418	Its compression ratio is the poorest among the choices. The kernel
419	size is about 10% bigger than gzip; however its speed
420	(both compression and decompression) is the fastest.
421
422	config KERNEL_LZ4
423	bool "LZ4"
424	depends on HAVE_KERNEL_LZ4
425	help
426	LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
427	A preliminary version of LZ4 de/compression tool is available at
428	<https://code.google.com/p/lz4/>.
429
430	Its compression ratio is worse than LZO. The size of the kernel
431	is about 8% bigger than LZO. But the decompression speed is
432	faster than LZO.
433
434	config KERNEL_ZSTD
435	bool "ZSTD"
436	depends on HAVE_KERNEL_ZSTD
437	help
438	ZSTD is a compression algorithm targeting intermediate compression
439	with fast decompression speed. It will compress better than GZIP and
440	decompress around the same speed as LZO, but slower than LZ4. You
441	will need at least 192 KB RAM or more for booting. The zstd command
442	line tool is required for compression.
443
444	config KERNEL_UNCOMPRESSED
445	bool "None"
446	depends on HAVE_KERNEL_UNCOMPRESSED
447	help
448	Produce uncompressed kernel image. This option is usually not what
449	you want. It is useful for debugging the kernel in slow simulation
450	environments, where decompressing and moving the kernel is awfully
451	slow. This option allows early boot code to skip the decompressor
452	and jump right at uncompressed kernel image.
453
454	endchoice
455
456	config DEFAULT_INIT
457	string "Default init path"
458	default ""
459	help
460	This option determines the default init for the system if no init=
461	option is passed on the kernel command line. If the requested path is
462	not present, we will still then move on to attempting further
463	locations (e.g. /sbin/init, etc). If this is empty, we will just use
464	the fallback list when init= is not passed.
465
466	config DEFAULT_HOSTNAME
467	string "Default hostname"
468	default "(none)"
469	help
470	This option determines the default system hostname before userspace
471	calls sethostname(2). The kernel traditionally uses "(none)" here,
472	but you may wish to use a different default here to make a minimal
473	system more usable with less configuration.
474
475	config SYSVIPC
476	bool "System V IPC"
477	help
478	Inter Process Communication is a suite of library functions and
479	system calls which let processes (running programs) synchronize and
480	exchange information. It is generally considered to be a good thing,
481	and some programs won't run unless you say Y here. In particular, if
482	you want to run the DOS emulator dosemu under Linux (read the
483	DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
484	you'll need to say Y here.
485
486	You can find documentation about IPC with "info ipc" and also in
487	section 6.4 of the Linux Programmer's Guide, available from
488	<http://www.tldp.org/guides.html>.
489
490	config SYSVIPC_SYSCTL
491	bool
492	depends on SYSVIPC
493	depends on SYSCTL
494	default y
495
496	config SYSVIPC_COMPAT
497	def_bool y
498	depends on COMPAT && SYSVIPC
499
500	config POSIX_MQUEUE
501	bool "POSIX Message Queues"
502	depends on NET
503	help
504	POSIX variant of message queues is a part of IPC. In POSIX message
505	queues every message has a priority which decides about succession
506	of receiving it by a process. If you want to compile and run
507	programs written e.g. for Solaris with use of its POSIX message
508	queues (functions mq_*) say Y here.
509
510	POSIX message queues are visible as a filesystem called 'mqueue'
511	and can be mounted somewhere if you want to do filesystem
512	operations on message queues.
513
514	If unsure, say Y.
515
516	config POSIX_MQUEUE_SYSCTL
517	bool
518	depends on POSIX_MQUEUE
519	depends on SYSCTL
520	default y
521
522	config WATCH_QUEUE
523	bool "General notification queue"
524	default n
525	help
526
527	This is a general notification queue for the kernel to pass events to
528	userspace by splicing them into pipes. It can be used in conjunction
529	with watches for key/keyring change notifications and device
530	notifications.
531
532	See Documentation/core-api/watch_queue.rst
533
534	config CROSS_MEMORY_ATTACH
535	bool "Enable process_vm_readv/writev syscalls"
536	depends on MMU
537	default y
538	help
539	Enabling this option adds the system calls process_vm_readv and
540	process_vm_writev which allow a process with the correct privileges
541	to directly read from or write to another process' address space.
542	See the man page for more details.
543
544	config AUDIT
545	bool "Auditing support"
546	depends on NET
547	help
548	Enable auditing infrastructure that can be used with another
549	kernel subsystem, such as SELinux (which requires this for
550	logging of avc messages output). System call auditing is included
551	on architectures which support it.
552
553	config HAVE_ARCH_AUDITSYSCALL
554	bool
555
556	config AUDITSYSCALL
557	def_bool y
558	depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
559	select FSNOTIFY
560
561	source "kernel/irq/Kconfig"
562	source "kernel/time/Kconfig"
563	source "kernel/bpf/Kconfig"
564	source "kernel/Kconfig.preempt"
565
566	menu "CPU/Task time and stats accounting"
567
568	config VIRT_CPU_ACCOUNTING
569	bool
570
571	choice
572	prompt "Cputime accounting"
573	default VIRT_CPU_ACCOUNTING_GEN if NO_HZ_FULL
574	default TICK_CPU_ACCOUNTING
575
576	# Kind of a stub config for the pure tick based cputime accounting
577	config TICK_CPU_ACCOUNTING
578	bool "Simple tick based cputime accounting"
579	depends on !S390 && !NO_HZ_FULL
580	help
581	This is the basic tick based cputime accounting that maintains
582	statistics about user, system and idle time spent on per jiffies
583	granularity.
584
585	If unsure, say Y.
586
587	config VIRT_CPU_ACCOUNTING_NATIVE
588	bool "Deterministic task and CPU time accounting"
589	depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
590	select VIRT_CPU_ACCOUNTING
591	help
592	Select this option to enable more accurate task and CPU time
593	accounting. This is done by reading a CPU counter on each
594	kernel entry and exit and on transitions within the kernel
595	between system, softirq and hardirq state, so there is a
596	small performance impact. In the case of s390 or IBM POWER > 5,
597	this also enables accounting of stolen time on logically-partitioned
598	systems.
599
600	config VIRT_CPU_ACCOUNTING_GEN
601	bool "Full dynticks CPU time accounting"
602	depends on HAVE_CONTEXT_TRACKING_USER
603	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
604	depends on GENERIC_CLOCKEVENTS
605	select VIRT_CPU_ACCOUNTING
606	select CONTEXT_TRACKING_USER
607	help
608	Select this option to enable task and CPU time accounting on full
609	dynticks systems. This accounting is implemented by watching every
610	kernel-user boundaries using the context tracking subsystem.
611	The accounting is thus performed at the expense of some significant
612	overhead.
613
614	For now this is only useful if you are working on the full
615	dynticks subsystem development.
616
617	If unsure, say N.
618
619	endchoice
620
621	config IRQ_TIME_ACCOUNTING
622	bool "Fine granularity task level IRQ time accounting"
623	depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
624	help
625	Select this option to enable fine granularity task irq time
626	accounting. This is done by reading a timestamp on each
627	transitions between softirq and hardirq state, so there can be a
628	small performance impact.
629
630	If in doubt, say N here.
631
632	config HAVE_SCHED_AVG_IRQ
633	def_bool y
634	depends on IRQ_TIME_ACCOUNTING \|\| PARAVIRT_TIME_ACCOUNTING
635	depends on SMP
636
637	config SCHED_HW_PRESSURE
638	bool
639	default y if ARM && ARM_CPU_TOPOLOGY
640	default y if ARM64
641	depends on SMP
642	depends on CPU_FREQ_THERMAL
643	help
644	Select this option to enable HW pressure accounting in the
645	scheduler. HW pressure is the value conveyed to the scheduler
646	that reflects the reduction in CPU compute capacity resulted from
647	HW throttling. HW throttling occurs when the performance of
648	a CPU is capped due to high operating temperatures as an example.
649
650	If selected, the scheduler will be able to balance tasks accordingly,
651	i.e. put less load on throttled CPUs than on non/less throttled ones.
652
653	This requires the architecture to implement
654	arch_update_hw_pressure() and arch_scale_thermal_pressure().
655
656	config BSD_PROCESS_ACCT
657	bool "BSD Process Accounting (DEPRECATED)"
658	depends on MULTIUSER
659	default n
660	help
661	If you say Y here, a user level program will be able to instruct the
662	kernel (via a special system call) to write process accounting
663	information to a file: whenever a process exits, information about
664	that process will be appended to the file by the kernel. The
665	information includes things such as creation time, owning user,
666	command name, memory usage, controlling terminal etc. (the complete
667	list is in the struct acct in <file:include/linux/acct.h>). It is
668	up to the user level program to do useful things with this
669	information. This mechanism is antiquated and has significant
670	scalability issues. You probably want to use eBPF instead. Say
671	N unless you really need this.
672
673	config BSD_PROCESS_ACCT_V3
674	bool "BSD Process Accounting version 3 file format"
675	depends on BSD_PROCESS_ACCT
676	default n
677	help
678	If you say Y here, the process accounting information is written
679	in a new file format that also logs the process IDs of each
680	process and its parent. Note that this file format is incompatible
681	with previous v0/v1/v2 file formats, so you will need updated tools
682	for processing it. A preliminary version of these tools is available
683	at <http://www.gnu.org/software/acct/>.
684
685	config TASKSTATS
686	bool "Export task/process statistics through netlink"
687	depends on NET
688	depends on MULTIUSER
689	default n
690	help
691	Export selected statistics for tasks/processes through the
692	generic netlink interface. Unlike BSD process accounting, the
693	statistics are available during the lifetime of tasks/processes as
694	responses to commands. Like BSD accounting, they are sent to user
695	space on task exit.
696
697	Say N if unsure.
698
699	config TASK_DELAY_ACCT
700	bool "Enable per-task delay accounting"
701	depends on TASKSTATS
702	select SCHED_INFO
703	help
704	Collect information on time spent by a task waiting for system
705	resources like cpu, synchronous block I/O completion and swapping
706	in pages. Such statistics can help in setting a task's priorities
707	relative to other tasks for cpu, io, rss limits etc.
708
709	Say N if unsure.
710
711	config TASK_XACCT
712	bool "Enable extended accounting over taskstats"
713	depends on TASKSTATS
714	help
715	Collect extended task accounting data and send the data
716	to userland for processing over the taskstats interface.
717
718	Say N if unsure.
719
720	config TASK_IO_ACCOUNTING
721	bool "Enable per-task storage I/O accounting"
722	depends on TASK_XACCT
723	help
724	Collect information on the number of bytes of storage I/O which this
725	task has caused.
726
727	Say N if unsure.
728
729	config PSI
730	bool "Pressure stall information tracking"
731	select KERNFS
732	help
733	Collect metrics that indicate how overcommitted the CPU, memory,
734	and IO capacity are in the system.
735
736	If you say Y here, the kernel will create /proc/pressure/ with the
737	pressure statistics files cpu, memory, and io. These will indicate
738	the share of walltime in which some or all tasks in the system are
739	delayed due to contention of the respective resource.
740
741	In kernels with cgroup support, cgroups (cgroup2 only) will
742	have cpu.pressure, memory.pressure, and io.pressure files,
743	which aggregate pressure stalls for the grouped tasks only.
744
745	For more details see Documentation/accounting/psi.rst.
746
747	Say N if unsure.
748
749	config PSI_DEFAULT_DISABLED
750	bool "Require boot parameter to enable pressure stall information tracking"
751	default n
752	depends on PSI
753	help
754	If set, pressure stall information tracking will be disabled
755	per default but can be enabled through passing psi=1 on the
756	kernel commandline during boot.
757
758	This feature adds some code to the task wakeup and sleep
759	paths of the scheduler. The overhead is too low to affect
760	common scheduling-intense workloads in practice (such as
761	webservers, memcache), but it does show up in artificial
762	scheduler stress tests, such as hackbench.
763
764	If you are paranoid and not sure what the kernel will be
765	used for, say Y.
766
767	Say N if unsure.
768
769	endmenu # "CPU/Task time and stats accounting"
770
771	config CPU_ISOLATION
772	bool "CPU isolation"
773	depends on SMP
774	default y
775	help
776	Make sure that CPUs running critical tasks are not disturbed by
777	any source of "noise" such as unbound workqueues, timers, kthreads...
778	Unbound jobs get offloaded to housekeeping CPUs. This is driven by
779	the "isolcpus=" boot parameter.
780
781	Say Y if unsure.
782
783	source "kernel/rcu/Kconfig"
784
785	config IKCONFIG
786	tristate "Kernel .config support"
787	help
788	This option enables the complete Linux kernel ".config" file
789	contents to be saved in the kernel. It provides documentation
790	of which kernel options are used in a running kernel or in an
791	on-disk kernel. This information can be extracted from the kernel
792	image file with the script scripts/extract-ikconfig and used as
793	input to rebuild the current kernel or to build another kernel.
794	It can also be extracted from a running kernel by reading
795	/proc/config.gz if enabled (below).
796
797	config IKCONFIG_PROC
798	bool "Enable access to .config through /proc/config.gz"
799	depends on IKCONFIG && PROC_FS
800	help
801	This option enables access to the kernel configuration file
802	through /proc/config.gz.
803
804	config IKHEADERS
805	tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
806	depends on SYSFS
807	help
808	This option enables access to the in-kernel headers that are generated during
809	the build process. These can be used to build eBPF tracing programs,
810	or similar programs. If you build the headers as a module, a module called
811	kheaders.ko is built which can be loaded on-demand to get access to headers.
812
813	config LOG_BUF_SHIFT
814	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
815	range 12 25
816	default 17
817	depends on PRINTK
818	help
819	Select the minimal kernel log buffer size as a power of 2.
820	The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
821	parameter, see below. Any higher size also might be forced
822	by "log_buf_len" boot parameter.
823
824	Examples:
825	17 => 128 KB
826	16 => 64 KB
827	15 => 32 KB
828	14 => 16 KB
829	13 => 8 KB
830	12 => 4 KB
831
832	config LOG_CPU_MAX_BUF_SHIFT
833	int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
834	depends on SMP
835	range 0 21
836	default 0 if BASE_SMALL
837	default 12
838	depends on PRINTK
839	help
840	This option allows to increase the default ring buffer size
841	according to the number of CPUs. The value defines the contribution
842	of each CPU as a power of 2. The used space is typically only few
843	lines however it might be much more when problems are reported,
844	e.g. backtraces.
845
846	The increased size means that a new buffer has to be allocated and
847	the original static one is unused. It makes sense only on systems
848	with more CPUs. Therefore this value is used only when the sum of
849	contributions is greater than the half of the default kernel ring
850	buffer as defined by LOG_BUF_SHIFT. The default values are set
851	so that more than 16 CPUs are needed to trigger the allocation.
852
853	Also this option is ignored when "log_buf_len" kernel parameter is
854	used as it forces an exact (power of two) size of the ring buffer.
855
856	The number of possible CPUs is used for this computation ignoring
857	hotplugging making the computation optimal for the worst case
858	scenario while allowing a simple algorithm to be used from bootup.
859
860	Examples shift values and their meaning:
861	17 => 128 KB for each CPU
862	16 => 64 KB for each CPU
863	15 => 32 KB for each CPU
864	14 => 16 KB for each CPU
865	13 => 8 KB for each CPU
866	12 => 4 KB for each CPU
867
868	config PRINTK_INDEX
869	bool "Printk indexing debugfs interface"
870	depends on PRINTK && DEBUG_FS
871	help
872	Add support for indexing of all printk formats known at compile time
873	at <debugfs>/printk/index/<module>.
874
875	This can be used as part of maintaining daemons which monitor
876	/dev/kmsg, as it permits auditing the printk formats present in a
877	kernel, allowing detection of cases where monitored printks are
878	changed or no longer present.
879
880	There is no additional runtime cost to printk with this enabled.
881
882	#
883	# Architectures with an unreliable sched_clock() should select this:
884	#
885	config HAVE_UNSTABLE_SCHED_CLOCK
886	bool
887
888	config GENERIC_SCHED_CLOCK
889	bool
890
891	menu "Scheduler features"
892
893	config UCLAMP_TASK
894	bool "Enable utilization clamping for RT/FAIR tasks"
895	depends on CPU_FREQ_GOV_SCHEDUTIL
896	help
897	This feature enables the scheduler to track the clamped utilization
898	of each CPU based on RUNNABLE tasks scheduled on that CPU.
899
900	With this option, the user can specify the min and max CPU
901	utilization allowed for RUNNABLE tasks. The max utilization defines
902	the maximum frequency a task should use while the min utilization
903	defines the minimum frequency it should use.
904
905	Both min and max utilization clamp values are hints to the scheduler,
906	aiming at improving its frequency selection policy, but they do not
907	enforce or grant any specific bandwidth for tasks.
908
909	If in doubt, say N.
910
911	config UCLAMP_BUCKETS_COUNT
912	int "Number of supported utilization clamp buckets"
913	range 5 20
914	default 5
915	depends on UCLAMP_TASK
916	help
917	Defines the number of clamp buckets to use. The range of each bucket
918	will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
919	number of clamp buckets the finer their granularity and the higher
920	the precision of clamping aggregation and tracking at run-time.
921
922	For example, with the minimum configuration value we will have 5
923	clamp buckets tracking 20% utilization each. A 25% boosted tasks will
924	be refcounted in the [20..39]% bucket and will set the bucket clamp
925	effective value to 25%.
926	If a second 30% boosted task should be co-scheduled on the same CPU,
927	that task will be refcounted in the same bucket of the first task and
928	it will boost the bucket clamp effective value to 30%.
929	The clamp effective value of a bucket is reset to its nominal value
930	(20% in the example above) when there are no more tasks refcounted in
931	that bucket.
932
933	An additional boost/capping margin can be added to some tasks. In the
934	example above the 25% task will be boosted to 30% until it exits the
935	CPU. If that should be considered not acceptable on certain systems,
936	it's always possible to reduce the margin by increasing the number of
937	clamp buckets to trade off used memory for run-time tracking
938	precision.
939
940	If in doubt, use the default value.
941
942	config SCHED_PROXY_EXEC
943	bool "Proxy Execution"
944	# Avoid some build failures w/ PREEMPT_RT until it can be fixed
945	depends on !PREEMPT_RT
946	# Need to investigate how to inform sched_ext of split contexts
947	depends on !SCHED_CLASS_EXT
948	# Not particularly useful until we get to multi-rq proxying
949	depends on EXPERT
950	help
951	This option enables proxy execution, a mechanism for mutex-owning
952	tasks to inherit the scheduling context of higher priority waiters.
953
954	endmenu
955
956	#
957	# For architectures that support present-but-inaccessible (PROT_NONE) page
958	# table entries detectable via pte_protnone() / pmd_protnone():
959	#
960	config ARCH_HAS_PTE_PROTNONE
961	bool
962
963	#
964	# For architectures that want to enable the support for NUMA-affine scheduler
965	# balancing logic:
966	#
967	config ARCH_SUPPORTS_NUMA_BALANCING
968	bool
969
970	#
971	# For architectures that prefer to flush all TLBs after a number of pages
972	# are unmapped instead of sending one IPI per page to flush. The architecture
973	# must provide guarantees on what happens if a clean TLB cache entry is
974	# written after the unmap. Details are in mm/rmap.c near the check for
975	# should_defer_flush. The architecture should also consider if the full flush
976	# and the refill costs are offset by the savings of sending fewer IPIs.
977	config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
978	bool
979
980	config CC_HAS_INT128
981	def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
982
983	config CC_IMPLICIT_FALLTHROUGH
984	string
985	default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
986	default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough)
987
988	config CC_MS_EXTENSIONS
989	string
990	default "-fms-anonymous-structs" if $(cc-option,-fms-anonymous-structs)
991	default "-fms-extensions"
992
993	# Currently, disable gcc-10+ array-bounds globally.
994	# It's still broken in gcc-13, so no upper bound yet.
995	config GCC10_NO_ARRAY_BOUNDS
996	def_bool y
997
998	config CC_NO_ARRAY_BOUNDS
999	bool
1000	default y if CC_IS_GCC && GCC_VERSION >= 90000 && GCC10_NO_ARRAY_BOUNDS
1001
1002	# Currently, disable -Wstringop-overflow for GCC globally.
1003	config GCC_NO_STRINGOP_OVERFLOW
1004	def_bool y
1005
1006	config CC_NO_STRINGOP_OVERFLOW
1007	bool
1008	default y if CC_IS_GCC && GCC_NO_STRINGOP_OVERFLOW
1009
1010	config CC_STRINGOP_OVERFLOW
1011	bool
1012	default y if CC_IS_GCC && !CC_NO_STRINGOP_OVERFLOW
1013
1014	#
1015	# For architectures that know their GCC __int128 support is sound
1016	#
1017	config ARCH_SUPPORTS_INT128
1018	bool
1019
1020	# For architectures that (ab)use NUMA to represent different memory regions
1021	# all cpu-local but of different latencies, such as SuperH.
1022	#
1023	config ARCH_WANT_NUMA_VARIABLE_LOCALITY
1024	bool
1025
1026	config NUMA_BALANCING
1027	bool "Memory placement aware NUMA scheduler"
1028	depends on ARCH_SUPPORTS_NUMA_BALANCING
1029	depends on ARCH_HAS_PTE_PROTNONE
1030	depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
1031	depends on SMP && NUMA_MIGRATION && !PREEMPT_RT
1032	help
1033	This option adds support for automatic NUMA aware memory/task placement.
1034	The mechanism is quite primitive and is based on migrating memory when
1035	it has references to the node the task is running on.
1036
1037	This system will be inactive on UMA systems.
1038
1039	config SCHED_CACHE
1040	bool "Cache aware load balance"
1041	default y
1042	depends on SMP
1043	help
1044	When enabled, the scheduler will attempt to aggregate tasks from
1045	the same process onto a single Last Level Cache (LLC) domain when
1046	possible. This improves cache locality by keeping tasks that share
1047	resources within the same cache domain, reducing cache misses and
1048	lowering data access latency.
1049
1050	config NUMA_BALANCING_DEFAULT_ENABLED
1051	bool "Automatically enable NUMA aware memory/task placement"
1052	default y
1053	depends on NUMA_BALANCING
1054	help
1055	If set, automatic NUMA balancing will be enabled if running on a NUMA
1056	machine.
1057
1058	config SLAB_OBJ_EXT
1059	bool
1060
1061	menuconfig CGROUPS
1062	bool "Control Group support"
1063	select KERNFS
1064	help
1065	This option adds support for grouping sets of processes together, for
1066	use with process control subsystems such as Cpusets, CFS, memory
1067	controls or device isolation.
1068	See
1069	- Documentation/scheduler/sched-design-CFS.rst (CFS)
1070	- Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
1071	and resource control)
1072
1073	Say N if unsure.
1074
1075	if CGROUPS
1076
1077	config PAGE_COUNTER
1078	bool
1079
1080	config CGROUP_FAVOR_DYNMODS
1081	bool "Favor dynamic modification latency reduction by default"
1082	help
1083	This option enables the "favordynmods" mount option by default
1084	which reduces the latencies of dynamic cgroup modifications such
1085	as task migrations and controller on/offs at the cost of making
1086	hot path operations such as forks and exits more expensive.
1087
1088	Say N if unsure.
1089
1090	config MEMCG
1091	bool "Memory controller"
1092	select PAGE_COUNTER
1093	select EVENTFD
1094	select SLAB_OBJ_EXT
1095	select VM_EVENT_COUNTERS
1096	help
1097	Provides control over the memory footprint of tasks in a cgroup.
1098
1099	config MEMCG_NMI_UNSAFE
1100	bool
1101	depends on MEMCG
1102	depends on HAVE_NMI
1103	depends on !ARCH_HAS_NMI_SAFE_THIS_CPU_OPS && !ARCH_HAVE_NMI_SAFE_CMPXCHG
1104	default y
1105
1106	config MEMCG_NMI_SAFETY_REQUIRES_ATOMIC
1107	bool
1108	depends on MEMCG
1109	depends on HAVE_NMI
1110	depends on !ARCH_HAS_NMI_SAFE_THIS_CPU_OPS && ARCH_HAVE_NMI_SAFE_CMPXCHG
1111	default y
1112
1113	config MEMCG_V1
1114	bool "Legacy cgroup v1 memory controller"
1115	depends on MEMCG
1116	default n
1117	help
1118	Legacy cgroup v1 memory controller which has been deprecated by
1119	cgroup v2 implementation. The v1 is there for legacy applications
1120	which haven't migrated to the new cgroup v2 interface yet. If you
1121	do not have any such application then you are completely fine leaving
1122	this option disabled.
1123
1124	Please note that feature set of the legacy memory controller is likely
1125	going to shrink due to deprecation process. New deployments with v1
1126	controller are highly discouraged.
1127
1128	Say N if unsure.
1129
1130	config BLK_CGROUP
1131	bool "IO controller"
1132	depends on BLOCK
1133	default n
1134	help
1135	Generic block IO controller cgroup interface. This is the common
1136	cgroup interface which should be used by various IO controlling
1137	policies.
1138
1139	Currently, CFQ IO scheduler uses it to recognize task groups and
1140	control disk bandwidth allocation (proportional time slice allocation)
1141	to such task groups. It is also used by bio throttling logic in
1142	block layer to implement upper limit in IO rates on a device.
1143
1144	This option only enables generic Block IO controller infrastructure.
1145	One needs to also enable actual IO controlling logic/policy. For
1146	enabling proportional weight division of disk bandwidth in CFQ, set
1147	CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1148	CONFIG_BLK_DEV_THROTTLING=y.
1149
1150	See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
1151
1152	config CGROUP_WRITEBACK
1153	bool
1154	depends on MEMCG && BLK_CGROUP
1155	default y
1156
1157	menuconfig CGROUP_SCHED
1158	bool "CPU controller"
1159	default n
1160	help
1161	This feature lets CPU scheduler recognize task groups and control CPU
1162	bandwidth allocation to such task groups. It uses cgroups to group
1163	tasks.
1164
1165	if CGROUP_SCHED
1166	config GROUP_SCHED_WEIGHT
1167	def_bool n
1168
1169	config GROUP_SCHED_BANDWIDTH
1170	def_bool n
1171
1172	config FAIR_GROUP_SCHED
1173	bool "Group scheduling for SCHED_OTHER"
1174	depends on CGROUP_SCHED
1175	select GROUP_SCHED_WEIGHT
1176	default CGROUP_SCHED
1177
1178	config CFS_BANDWIDTH
1179	bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1180	depends on FAIR_GROUP_SCHED
1181	select GROUP_SCHED_BANDWIDTH
1182	default n
1183	help
1184	This option allows users to define CPU bandwidth rates (limits) for
1185	tasks running within the fair group scheduler. Groups with no limit
1186	set are considered to be unconstrained and will run with no
1187	restriction.
1188	See Documentation/scheduler/sched-bwc.rst for more information.
1189
1190	config RT_GROUP_SCHED
1191	bool "Group scheduling for SCHED_RR/FIFO"
1192	depends on CGROUP_SCHED
1193	default n
1194	help
1195	This feature lets you explicitly allocate real CPU bandwidth
1196	to task groups. If enabled, it will also make it impossible to
1197	schedule realtime tasks for non-root users until you allocate
1198	realtime bandwidth for them.
1199	See Documentation/scheduler/sched-rt-group.rst for more information.
1200
1201	config RT_GROUP_SCHED_DEFAULT_DISABLED
1202	bool "Require boot parameter to enable group scheduling for SCHED_RR/FIFO"
1203	depends on RT_GROUP_SCHED
1204	default n
1205	help
1206	When set, the RT group scheduling is disabled by default. The option
1207	is in inverted form so that mere RT_GROUP_SCHED enables the group
1208	scheduling.
1209
1210	Say N if unsure.
1211
1212	config EXT_GROUP_SCHED
1213	bool
1214	depends on SCHED_CLASS_EXT && CGROUP_SCHED
1215	select GROUP_SCHED_WEIGHT
1216	select GROUP_SCHED_BANDWIDTH
1217	default y
1218
1219	endif #CGROUP_SCHED
1220
1221	config EXT_SUB_SCHED
1222	def_bool y
1223	depends on SCHED_CLASS_EXT && CGROUPS
1224
1225	config SCHED_MM_CID
1226	def_bool y
1227	depends on SMP && RSEQ
1228
1229	config UCLAMP_TASK_GROUP
1230	bool "Utilization clamping per group of tasks"
1231	depends on CGROUP_SCHED
1232	depends on UCLAMP_TASK
1233	default n
1234	help
1235	This feature enables the scheduler to track the clamped utilization
1236	of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
1237
1238	When this option is enabled, the user can specify a min and max
1239	CPU bandwidth which is allowed for each single task in a group.
1240	The max bandwidth allows to clamp the maximum frequency a task
1241	can use, while the min bandwidth allows to define a minimum
1242	frequency a task will always use.
1243
1244	When task group based utilization clamping is enabled, an eventually
1245	specified task-specific clamp value is constrained by the cgroup
1246	specified clamp value. Both minimum and maximum task clamping cannot
1247	be bigger than the corresponding clamping defined at task group level.
1248
1249	If in doubt, say N.
1250
1251	config CGROUP_PIDS
1252	bool "PIDs controller"
1253	help
1254	Provides enforcement of process number limits in the scope of a
1255	cgroup. Any attempt to fork more processes than is allowed in the
1256	cgroup will fail. PIDs are fundamentally a global resource because it
1257	is fairly trivial to reach PID exhaustion before you reach even a
1258	conservative kmemcg limit. As a result, it is possible to grind a
1259	system to halt without being limited by other cgroup policies. The
1260	PIDs controller is designed to stop this from happening.
1261
1262	It should be noted that organisational operations (such as attaching
1263	to a cgroup hierarchy) will not be blocked by the PIDs controller,
1264	since the PIDs limit only affects a process's ability to fork, not to
1265	attach to a cgroup.
1266
1267	config CGROUP_RDMA
1268	bool "RDMA controller"
1269	help
1270	Provides enforcement of RDMA resources defined by IB stack.
1271	It is fairly easy for consumers to exhaust RDMA resources, which
1272	can result into resource unavailability to other consumers.
1273	RDMA controller is designed to stop this from happening.
1274	Attaching processes with active RDMA resources to the cgroup
1275	hierarchy is allowed even if can cross the hierarchy's limit.
1276
1277	config CGROUP_DMEM
1278	bool "Device memory controller (DMEM)"
1279	select PAGE_COUNTER
1280	help
1281	The DMEM controller allows compatible devices to restrict device
1282	memory usage based on the cgroup hierarchy.
1283
1284	As an example, it allows you to restrict VRAM usage for applications
1285	in the DRM subsystem.
1286
1287	config CGROUP_FREEZER
1288	bool "Freezer controller"
1289	help
1290	Provides a way to freeze and unfreeze all tasks in a
1291	cgroup.
1292
1293	This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1294	controller includes important in-kernel memory consumers per default.
1295
1296	If you're using cgroup2, say N.
1297
1298	config CGROUP_HUGETLB
1299	bool "HugeTLB controller"
1300	depends on HUGETLB_PAGE
1301	select PAGE_COUNTER
1302	default n
1303	help
1304	Provides a cgroup controller for HugeTLB pages.
1305	When you enable this, you can put a per cgroup limit on HugeTLB usage.
1306	The limit is enforced during page fault. Since HugeTLB doesn't
1307	support page reclaim, enforcing the limit at page fault time implies
1308	that, the application will get SIGBUS signal if it tries to access
1309	HugeTLB pages beyond its limit. This requires the application to know
1310	beforehand how much HugeTLB pages it would require for its use. The
1311	control group is tracked in the third page lru pointer. This means
1312	that we cannot use the controller with huge page less than 3 pages.
1313
1314	config CPUSETS
1315	bool "Cpuset controller"
1316	depends on SMP
1317	select UNION_FIND
1318	select CPU_ISOLATION
1319	help
1320	This option will let you create and manage CPUSETs which
1321	allow dynamically partitioning a system into sets of CPUs and
1322	Memory Nodes and assigning tasks to run only within those sets.
1323	This is primarily useful on large SMP or NUMA systems.
1324
1325	Say N if unsure.
1326
1327	config CPUSETS_V1
1328	bool "Legacy cgroup v1 cpusets controller"
1329	depends on CPUSETS
1330	default n
1331	help
1332	Legacy cgroup v1 cpusets controller which has been deprecated by
1333	cgroup v2 implementation. The v1 is there for legacy applications
1334	which haven't migrated to the new cgroup v2 interface yet. Legacy
1335	interface includes cpuset filesystem and /proc/<pid>/cpuset. If you
1336	do not have any such application then you are completely fine leaving
1337	this option disabled.
1338
1339	Say N if unsure.
1340
1341	config PROC_PID_CPUSET
1342	bool "Include legacy /proc/<pid>/cpuset file"
1343	depends on CPUSETS_V1
1344	default y
1345
1346	config CGROUP_DEVICE
1347	bool "Device controller"
1348	help
1349	Provides a cgroup controller implementing whitelists for
1350	devices which a process in the cgroup can mknod or open.
1351
1352	config CGROUP_CPUACCT
1353	bool "Simple CPU accounting controller"
1354	help
1355	Provides a simple controller for monitoring the
1356	total CPU consumed by the tasks in a cgroup.
1357
1358	config CGROUP_PERF
1359	bool "Perf controller"
1360	depends on PERF_EVENTS
1361	help
1362	This option extends the perf per-cpu mode to restrict monitoring
1363	to threads which belong to the cgroup specified and run on the
1364	designated cpu. Or this can be used to have cgroup ID in samples
1365	so that it can monitor performance events among cgroups.
1366
1367	Say N if unsure.
1368
1369	config CGROUP_BPF
1370	bool "Support for eBPF programs attached to cgroups"
1371	depends on BPF_SYSCALL
1372	select SOCK_CGROUP_DATA
1373	help
1374	Allow attaching eBPF programs to a cgroup using the bpf(2)
1375	syscall command BPF_PROG_ATTACH.
1376
1377	In which context these programs are accessed depends on the type
1378	of attachment. For instance, programs that are attached using
1379	BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1380	inet sockets.
1381
1382	config CGROUP_MISC
1383	bool "Misc resource controller"
1384	default n
1385	help
1386	Provides a controller for miscellaneous resources on a host.
1387
1388	Miscellaneous scalar resources are the resources on the host system
1389	which cannot be abstracted like the other cgroups. This controller
1390	tracks and limits the miscellaneous resources used by a process
1391	attached to a cgroup hierarchy.
1392
1393	For more information, please check misc cgroup section in
1394	/Documentation/admin-guide/cgroup-v2.rst.
1395
1396	config CGROUP_DEBUG
1397	bool "Debug controller"
1398	default n
1399	depends on DEBUG_KERNEL
1400	help
1401	This option enables a simple controller that exports
1402	debugging information about the cgroups framework. This
1403	controller is for control cgroup debugging only. Its
1404	interfaces are not stable.
1405
1406	Say N.
1407
1408	config SOCK_CGROUP_DATA
1409	bool
1410	default n
1411
1412	endif # CGROUPS
1413
1414	menuconfig NAMESPACES
1415	bool "Namespaces support" if EXPERT
1416	depends on MULTIUSER
1417	default !EXPERT
1418	help
1419	Provides the way to make tasks work with different objects using
1420	the same id. For example same IPC id may refer to different objects
1421	or same user id or pid may refer to different tasks when used in
1422	different namespaces.
1423
1424	if NAMESPACES
1425
1426	config UTS_NS
1427	bool "UTS namespace"
1428	default y
1429	help
1430	In this namespace tasks see different info provided with the
1431	uname() system call
1432
1433	config TIME_NS
1434	bool "TIME namespace"
1435	default y
1436	help
1437	In this namespace boottime and monotonic clocks can be set.
1438	The time will keep going with the same pace.
1439
1440	config TIME_NS_VDSO
1441	def_bool TIME_NS && GENERIC_GETTIMEOFDAY
1442
1443	config IPC_NS
1444	bool "IPC namespace"
1445	depends on (SYSVIPC \|\| POSIX_MQUEUE)
1446	default y
1447	help
1448	In this namespace tasks work with IPC ids which correspond to
1449	different IPC objects in different namespaces.
1450
1451	config USER_NS
1452	bool "User namespace"
1453	default n
1454	help
1455	This allows containers, i.e. vservers, to use user namespaces
1456	to provide different user info for different servers.
1457
1458	When user namespaces are enabled in the kernel it is
1459	recommended that the MEMCG option also be enabled and that
1460	user-space use the memory control groups to limit the amount
1461	of memory a memory unprivileged users can use.
1462
1463	If unsure, say N.
1464
1465	config PID_NS
1466	bool "PID Namespaces"
1467	default y
1468	help
1469	Support process id namespaces. This allows having multiple
1470	processes with the same pid as long as they are in different
1471	pid namespaces. This is a building block of containers.
1472
1473	config NET_NS
1474	bool "Network namespace"
1475	depends on NET
1476	default y
1477	help
1478	Allow user space to create what appear to be multiple instances
1479	of the network stack.
1480
1481	endif # NAMESPACES
1482
1483	config CHECKPOINT_RESTORE
1484	bool "Checkpoint/restore support"
1485	depends on PROC_FS
1486	select PROC_CHILDREN
1487	select KCMP
1488	default n
1489	help
1490	Enables additional kernel features in a sake of checkpoint/restore.
1491	In particular it adds auxiliary prctl codes to setup process text,
1492	data and heap segment sizes, and a few additional /proc filesystem
1493	entries.
1494
1495	If unsure, say N here.
1496
1497	config SCHED_AUTOGROUP
1498	bool "Automatic process group scheduling"
1499	select CGROUPS
1500	select CGROUP_SCHED
1501	select FAIR_GROUP_SCHED
1502	help
1503	This option optimizes the scheduler for common desktop workloads by
1504	automatically creating and populating task groups. This separation
1505	of workloads isolates aggressive CPU burners (like build jobs) from
1506	desktop applications. Task group autogeneration is currently based
1507	upon task session.
1508
1509	config RELAY
1510	bool "Kernel->user space relay support (formerly relayfs)"
1511	select IRQ_WORK
1512	help
1513	This option enables support for relay interface support in
1514	certain file systems (such as debugfs).
1515	It is designed to provide an efficient mechanism for tools and
1516	facilities to relay large amounts of data from kernel space to
1517	user space.
1518
1519	If unsure, say N.
1520
1521	config BLK_DEV_INITRD
1522	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1523	help
1524	The initial RAM filesystem is a ramfs which is loaded by the
1525	boot loader (loadlin or lilo) and that is mounted as root
1526	before the normal boot procedure. It is typically used to
1527	load modules needed to mount the "real" root file system,
1528	etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1529
1530	If RAM disk support (BLK_DEV_RAM) is also included, this
1531	also enables initial RAM disk (initrd) support and adds
1532	15 Kbytes (more on some other architectures) to the kernel size.
1533
1534	If unsure say Y.
1535
1536	if BLK_DEV_INITRD
1537
1538	source "usr/Kconfig"
1539
1540	endif
1541
1542	config BOOT_CONFIG
1543	bool "Boot config support"
1544	select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED
1545	help
1546	Extra boot config allows system admin to pass a config file as
1547	complemental extension of kernel cmdline when booting.
1548	The boot config file must be attached at the end of initramfs
1549	with checksum, size and magic word.
1550	See <file:Documentation/admin-guide/bootconfig.rst> for details.
1551
1552	If unsure, say Y.
1553
1554	config BOOT_CONFIG_FORCE
1555	bool "Force unconditional bootconfig processing"
1556	depends on BOOT_CONFIG
1557	default y if BOOT_CONFIG_EMBED
1558	help
1559	With this Kconfig option set, BOOT_CONFIG processing is carried
1560	out even when the "bootconfig" kernel-boot parameter is omitted.
1561	In fact, with this Kconfig option set, there is no way to
1562	make the kernel ignore the BOOT_CONFIG-supplied kernel-boot
1563	parameters.
1564
1565	If unsure, say N.
1566
1567	config BOOT_CONFIG_EMBED
1568	bool "Embed bootconfig file in the kernel"
1569	depends on BOOT_CONFIG
1570	help
1571	Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the
1572	kernel. Usually, the bootconfig file is loaded with the initrd
1573	image. But if the system doesn't support initrd, this option will
1574	help you by embedding a bootconfig file while building the kernel.
1575
1576	If unsure, say N.
1577
1578	config BOOT_CONFIG_EMBED_FILE
1579	string "Embedded bootconfig file path"
1580	depends on BOOT_CONFIG_EMBED
1581	help
1582	Specify a bootconfig file which will be embedded to the kernel.
1583	This bootconfig will be used if there is no initrd or no other
1584	bootconfig in the initrd.
1585
1586	config ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG
1587	bool
1588	help
1589	Silent symbol; no C code reads it directly. Architectures
1590	select it once their setup_arch() calls
1591	xbc_prepend_embedded_cmdline() before parse_early_param().
1592	Its only role is to gate the user-visible
1593	CMDLINE_FROM_BOOTCONFIG option per-arch, the same
1594	ARCH_SUPPORTS_* idiom used by ARCH_SUPPORTS_CFI, etc.
1595
1596	config CMDLINE_FROM_BOOTCONFIG
1597	bool "Render embedded bootconfig as kernel cmdline at build time"
1598	depends on BOOT_CONFIG_EMBED_FILE != ""
1599	depends on ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG
1600	depends on CMDLINE = ""
1601	default n
1602	help
1603	Render the "kernel" subtree of the embedded bootconfig file into a
1604	flat cmdline string at kernel build time and prepend it to
1605	boot_command_line during early architecture setup. This makes
1606	early_param() handlers (e.g. mem=, earlycon=, loglevel=) see the
1607	values supplied via the embedded bootconfig.
1608
1609	The runtime bootconfig parser is unaffected, so tree-structured
1610	consumers such as ftrace boot-time tracing keep working.
1611
1612	Note: when an initrd also carries a bootconfig, its "kernel"
1613	subtree is still parsed at runtime, but the embedded "kernel"
1614	keys remain in boot_command_line for parse_early_param() and
1615	end up later than the initrd keys in saved_command_line, so
1616	parse_args() last-wins favors the embedded values. If you need
1617	initrd to override embedded kernel.* keys, leave this option
1618	off.
1619
1620	If unsure, say N.
1621
1622	config CMDLINE_LOG_WRAP_IDEAL_LEN
1623	int "Length to try to wrap the cmdline when logged at boot"
1624	default 1021
1625	range 0 1021
1626	help
1627	At boot time, the kernel command line is logged to the console.
1628	The log message will start with the prefix "Kernel command line: ".
1629	The log message will attempt to be wrapped (split into multiple log
1630	messages) at spaces based on CMDLINE_LOG_WRAP_IDEAL_LEN characters.
1631	If wrapping happens, each log message will start with the prefix and
1632	all but the last message will end with " \". Messages may exceed the
1633	ideal length if a place to wrap isn't found before the specified
1634	number of characters.
1635
1636	A value of 0 disables wrapping, though be warned that the maximum
1637	length of a log message (1021 characters) may cause the cmdline to
1638	be truncated.
1639
1640	config INITRAMFS_PRESERVE_MTIME
1641	bool "Preserve cpio archive mtimes in initramfs"
1642	depends on BLK_DEV_INITRD
1643	default y
1644	help
1645	Each entry in an initramfs cpio archive carries an mtime value. When
1646	enabled, extracted cpio items take this mtime, with directory mtime
1647	setting deferred until after creation of any child entries.
1648
1649	If unsure, say Y.
1650
1651	config INITRAMFS_TEST
1652	bool "Test initramfs cpio archive extraction" if !KUNIT_ALL_TESTS
1653	depends on BLK_DEV_INITRD && KUNIT=y
1654	default KUNIT_ALL_TESTS
1655	help
1656	Build KUnit tests for initramfs. See Documentation/dev-tools/kunit
1657
1658	choice
1659	prompt "Compiler optimization level"
1660	default CC_OPTIMIZE_FOR_PERFORMANCE
1661
1662	config CC_OPTIMIZE_FOR_PERFORMANCE
1663	bool "Optimize for performance (-O2)"
1664	help
1665	This is the default optimization level for the kernel, building
1666	with the "-O2" compiler flag for best performance and most
1667	helpful compile-time warnings.
1668
1669	config CC_OPTIMIZE_FOR_SIZE
1670	bool "Optimize for size (-Os)"
1671	help
1672	Choosing this option will pass "-Os" to your compiler resulting
1673	in a smaller kernel.
1674
1675	endchoice
1676
1677	config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1678	bool
1679	help
1680	This requires that the arch annotates or otherwise protects
1681	its external entry points from being discarded. Linker scripts
1682	must also merge .text., .data., and .bss.* correctly into
1683	output sections. Care must be taken not to pull in unrelated
1684	sections (e.g., '.text.init'). Typically '.' in section names
1685	is used to distinguish them from label names / C identifiers.
1686
1687	config LD_DEAD_CODE_DATA_ELIMINATION
1688	bool "Dead code and data elimination (EXPERIMENTAL)"
1689	depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1690	depends on EXPERT
1691	depends on $(cc-option,-ffunction-sections -fdata-sections)
1692	depends on $(ld-option,--gc-sections)
1693	help
1694	Enable this if you want to do dead code and data elimination with
1695	the linker by compiling with -ffunction-sections -fdata-sections,
1696	and linking with --gc-sections.
1697
1698	This can reduce on disk and in-memory size of the kernel
1699	code and static data, particularly for small configs and
1700	on small systems. This has the possibility of introducing
1701	silently broken kernel if the required annotations are not
1702	present. This option is not well tested yet, so use at your
1703	own risk.
1704
1705	config LD_ORPHAN_WARN
1706	def_bool y
1707	depends on ARCH_WANT_LD_ORPHAN_WARN
1708	depends on $(ld-option,--orphan-handling=warn)
1709	depends on $(ld-option,--orphan-handling=error)
1710
1711	config LD_ORPHAN_WARN_LEVEL
1712	string
1713	depends on LD_ORPHAN_WARN
1714	default "error" if WERROR
1715	default "warn"
1716
1717	config HAVE_UID16
1718	bool
1719
1720	config SYSCTL_EXCEPTION_TRACE
1721	bool
1722	help
1723	Enable support for /proc/sys/debug/exception-trace.
1724
1725	config SYSCTL_ARCH_UNALIGN_NO_WARN
1726	bool
1727	help
1728	Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1729	Allows arch to define/use @no_unaligned_warning to possibly warn
1730	about unaligned access emulation going on under the hood.
1731
1732	config SYSCTL_ARCH_UNALIGN_ALLOW
1733	bool
1734	help
1735	Enable support for /proc/sys/kernel/unaligned-trap
1736	Allows arches to define/use @unaligned_enabled to runtime toggle
1737	the unaligned access emulation.
1738	see arch/parisc/kernel/unaligned.c for reference
1739
1740	config SYSFS_SYSCALL
1741	bool "Sysfs syscall support"
1742	default n
1743	help
1744	sys_sysfs is an obsolete system call no longer supported in libc.
1745	Note that disabling this option is more secure but might break
1746	compatibility with some systems.
1747
1748	If unsure say N here.
1749
1750	config HAVE_PCSPKR_PLATFORM
1751	bool
1752
1753	menuconfig EXPERT
1754	bool "Configure standard kernel features (expert users)"
1755	# Unhide debug options, to make the on-by-default options visible
1756	select DEBUG_KERNEL
1757	help
1758	This option allows certain base kernel options and settings
1759	to be disabled or tweaked. This is for specialized
1760	environments which can tolerate a "non-standard" kernel.
1761	Only use this if you really know what you are doing.
1762
1763	config UID16
1764	bool "Enable 16-bit UID system calls" if EXPERT
1765	depends on HAVE_UID16 && MULTIUSER
1766	default y
1767	help
1768	This enables the legacy 16-bit UID syscall wrappers.
1769
1770	config MULTIUSER
1771	bool "Multiple users, groups and capabilities support" if EXPERT
1772	default y
1773	help
1774	This option enables support for non-root users, groups and
1775	capabilities.
1776
1777	If you say N here, all processes will run with UID 0, GID 0, and all
1778	possible capabilities. Saying N here also compiles out support for
1779	system calls related to UIDs, GIDs, and capabilities, such as setuid,
1780	setgid, and capset.
1781
1782	If unsure, say Y here.
1783
1784	config SGETMASK_SYSCALL
1785	bool "sgetmask/ssetmask syscalls support" if EXPERT
1786	default PARISC \|\| M68K \|\| PPC \|\| MIPS \|\| X86 \|\| SPARC \|\| MICROBLAZE \|\| SUPERH
1787	help
1788	sys_sgetmask and sys_ssetmask are obsolete system calls
1789	no longer supported in libc but still enabled by default in some
1790	architectures.
1791
1792	If unsure, leave the default option here.
1793
1794	config FHANDLE
1795	bool "open by fhandle syscalls" if EXPERT
1796	select EXPORTFS
1797	default y
1798	help
1799	If you say Y here, a user level program will be able to map
1800	file names to handle and then later use the handle for
1801	different file system operations. This is useful in implementing
1802	userspace file servers, which now track files using handles instead
1803	of names. The handle would remain the same even if file names
1804	get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1805	syscalls.
1806
1807	config POSIX_TIMERS
1808	bool "Posix Clocks & timers" if EXPERT
1809	default y
1810	help
1811	This includes native support for POSIX timers to the kernel.
1812	Some embedded systems have no use for them and therefore they
1813	can be configured out to reduce the size of the kernel image.
1814
1815	When this option is disabled, the following syscalls won't be
1816	available: timer_create, timer_gettime: timer_getoverrun,
1817	timer_settime, timer_delete, clock_adjtime, getitimer,
1818	setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1819	clock_getres and clock_nanosleep syscalls will be limited to
1820	CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1821
1822	If unsure say y.
1823
1824	config PRINTK
1825	default y
1826	bool "Enable support for printk" if EXPERT
1827	select IRQ_WORK
1828	help
1829	This option enables normal printk support. Removing it
1830	eliminates most of the message strings from the kernel image
1831	and makes the kernel more or less silent. As this makes it
1832	very difficult to diagnose system problems, saying N here is
1833	strongly discouraged.
1834
1835	config PRINTK_RINGBUFFER_KUNIT_TEST
1836	tristate "KUnit Test for the printk ringbuffer" if !KUNIT_ALL_TESTS
1837	depends on PRINTK && KUNIT
1838	default KUNIT_ALL_TESTS
1839	help
1840	This builds the printk ringbuffer KUnit test suite.
1841
1842	For more information on KUnit and unit tests in general, please refer
1843	to the KUnit documentation.
1844
1845	If unsure, say N.
1846
1847	config BUG
1848	bool "BUG() support" if EXPERT
1849	default y
1850	help
1851	Disabling this option eliminates support for BUG and WARN, reducing
1852	the size of your kernel image and potentially quietly ignoring
1853	numerous fatal conditions. You should only consider disabling this
1854	option for embedded systems with no facilities for reporting errors.
1855	Just say Y.
1856
1857	config ELF_CORE
1858	depends on COREDUMP
1859	default y
1860	bool "Enable ELF core dumps" if EXPERT
1861	help
1862	Enable support for generating core dumps. Disabling saves about 4k.
1863
1864
1865	config PCSPKR_PLATFORM
1866	bool "Enable PC-Speaker support" if EXPERT
1867	depends on HAVE_PCSPKR_PLATFORM
1868	select I8253_LOCK
1869	default y
1870	help
1871	This option allows to disable the internal PC-Speaker
1872	support, saving some memory.
1873
1874	config BASE_SMALL
1875	bool "Enable smaller-sized data structures for core" if EXPERT
1876	help
1877	Enabling this option reduces the size of miscellaneous core
1878	kernel data structures. This saves memory on small machines,
1879	but may reduce performance.
1880
1881	config FUTEX
1882	bool "Enable futex support" if EXPERT
1883	depends on !(SPARC32 && SMP)
1884	default y
1885	imply RT_MUTEXES
1886	help
1887	Disabling this option will cause the kernel to be built without
1888	support for "fast userspace mutexes". The resulting kernel may not
1889	run glibc-based applications correctly.
1890
1891	config FUTEX_PI
1892	bool
1893	depends on FUTEX && RT_MUTEXES
1894	default y
1895
1896	config FUTEX_PRIVATE_HASH
1897	bool
1898	depends on FUTEX && !BASE_SMALL && MMU
1899	default y
1900
1901	config FUTEX_MPOL
1902	bool
1903	depends on FUTEX && NUMA
1904	default y
1905
1906	config HAVE_FUTEX_ROBUST_UNLOCK
1907	bool
1908
1909	config FUTEX_ROBUST_UNLOCK
1910	def_bool FUTEX && GENERIC_IRQ_ENTRY && RSEQ && HAVE_FUTEX_ROBUST_UNLOCK
1911
1912	config EPOLL
1913	bool "Enable eventpoll support" if EXPERT
1914	default y
1915	help
1916	Disabling this option will cause the kernel to be built without
1917	support for epoll family of system calls.
1918
1919	config SIGNALFD
1920	bool "Enable signalfd() system call" if EXPERT
1921	default y
1922	help
1923	Enable the signalfd() system call that allows to receive signals
1924	on a file descriptor.
1925
1926	If unsure, say Y.
1927
1928	config TIMERFD
1929	bool "Enable timerfd() system call" if EXPERT
1930	default y
1931	help
1932	Enable the timerfd() system call that allows to receive timer
1933	events on a file descriptor.
1934
1935	If unsure, say Y.
1936
1937	config EVENTFD
1938	bool "Enable eventfd() system call" if EXPERT
1939	default y
1940	help
1941	Enable the eventfd() system call that allows to receive both
1942	kernel notification (ie. KAIO) or userspace notifications.
1943
1944	If unsure, say Y.
1945
1946	config SHMEM
1947	bool "Use full shmem filesystem" if EXPERT
1948	default y
1949	depends on MMU
1950	help
1951	The shmem is an internal filesystem used to manage shared memory.
1952	It is backed by swap and manages resource limits. It is also exported
1953	to userspace as tmpfs if TMPFS is enabled. Disabling this
1954	option replaces shmem and tmpfs with the much simpler ramfs code,
1955	which may be appropriate on small systems without swap.
1956
1957	config AIO
1958	bool "Enable AIO support" if EXPERT
1959	default y
1960	help
1961	This option enables POSIX asynchronous I/O which may by used
1962	by some high performance threaded applications. Disabling
1963	this option saves about 7k.
1964
1965	config IO_URING
1966	bool "Enable IO uring support" if EXPERT
1967	select IO_WQ
1968	default y
1969	help
1970	This option enables support for the io_uring interface, enabling
1971	applications to submit and complete IO through submission and
1972	completion rings that are shared between the kernel and application.
1973
1974	config GCOV_PROFILE_URING
1975	bool "Enable GCOV profiling on the io_uring subsystem"
1976	depends on IO_URING && GCOV_KERNEL
1977	help
1978	Enable GCOV profiling on the io_uring subsystem, to facilitate
1979	code coverage testing.
1980
1981	If unsure, say N.
1982
1983	Note that this will have a negative impact on the performance of
1984	the io_uring subsystem, hence this should only be enabled for
1985	specific test purposes.
1986
1987	config IO_URING_MOCK_FILE
1988	tristate "Enable io_uring mock files (Experimental)" if EXPERT
1989	default n
1990	depends on IO_URING
1991	help
1992	Enable mock files for io_uring subsystem testing. The ABI might
1993	still change, so it's still experimental and should only be enabled
1994	for specific test purposes.
1995
1996	If unsure, say N.
1997
1998	config ADVISE_SYSCALLS
1999	bool "Enable madvise/fadvise syscalls" if EXPERT
2000	default y
2001	help
2002	This option enables the madvise and fadvise syscalls, used by
2003	applications to advise the kernel about their future memory or file
2004	usage, improving performance. If building an embedded system where no
2005	applications use these syscalls, you can disable this option to save
2006	space.
2007
2008	config MEMBARRIER
2009	bool "Enable membarrier() system call" if EXPERT
2010	default y
2011	help
2012	Enable the membarrier() system call that allows issuing memory
2013	barriers across all running threads, which can be used to distribute
2014	the cost of user-space memory barriers asymmetrically by transforming
2015	pairs of memory barriers into pairs consisting of membarrier() and a
2016	compiler barrier.
2017
2018	If unsure, say Y.
2019
2020	config KCMP
2021	bool "Enable kcmp() system call" if EXPERT
2022	help
2023	Enable the kernel resource comparison system call. It provides
2024	user-space with the ability to compare two processes to see if they
2025	share a common resource, such as a file descriptor or even virtual
2026	memory space.
2027
2028	If unsure, say N.
2029
2030	config RSEQ
2031	bool "Enable rseq() system call" if EXPERT
2032	default y
2033	depends on HAVE_RSEQ
2034	select MEMBARRIER
2035	help
2036	Enable the restartable sequences system call. It provides a
2037	user-space cache for the current CPU number value, which
2038	speeds up getting the current CPU number from user-space,
2039	as well as an ABI to speed up user-space operations on
2040	per-CPU data.
2041
2042	If unsure, say Y.
2043
2044	config RSEQ_SLICE_EXTENSION
2045	bool "Enable rseq-based time slice extension mechanism"
2046	depends on RSEQ && HIGH_RES_TIMERS && GENERIC_ENTRY && HAVE_GENERIC_TIF_BITS
2047	help
2048	Allows userspace to request a limited time slice extension when
2049	returning from an interrupt to user space via the RSEQ shared
2050	data ABI. If granted, that allows to complete a critical section,
2051	so that other threads are not stuck on a conflicted resource,
2052	while the task is scheduled out.
2053
2054	If unsure, say N.
2055
2056	config RSEQ_STATS
2057	default n
2058	bool "Enable lightweight statistics of restartable sequences" if EXPERT
2059	depends on RSEQ && DEBUG_FS
2060	help
2061	Enable lightweight counters which expose information about the
2062	frequency of RSEQ operations via debugfs. Mostly interesting for
2063	kernel debugging or performance analysis. While lightweight it's
2064	still adding code into the user/kernel mode transitions.
2065
2066	If unsure, say N.
2067
2068	config RSEQ_DEBUG_DEFAULT_ENABLE
2069	default n
2070	bool "Enable restartable sequences debug mode by default" if EXPERT
2071	depends on RSEQ
2072	help
2073	This enables the static branch for debug mode of restartable
2074	sequences.
2075
2076	This also can be controlled on the kernel command line via the
2077	command line parameter "rseq_debug=0/1" and through debugfs.
2078
2079	If unsure, say N.
2080
2081	config DEBUG_RSEQ
2082	default n
2083	bool "Enable debugging of rseq() system call" if EXPERT
2084	depends on RSEQ && DEBUG_KERNEL && !GENERIC_ENTRY
2085	select RSEQ_DEBUG_DEFAULT_ENABLE
2086	help
2087	Enable extra debugging checks for the rseq system call.
2088
2089	If unsure, say N.
2090
2091	config CACHESTAT_SYSCALL
2092	bool "Enable cachestat() system call" if EXPERT
2093	default y
2094	help
2095	Enable the cachestat system call, which queries the page cache
2096	statistics of a file (number of cached pages, dirty pages,
2097	pages marked for writeback, (recently) evicted pages).
2098
2099	If unsure say Y here.
2100
2101	config KALLSYMS
2102	bool "Load all symbols for debugging/ksymoops" if EXPERT
2103	default y
2104	help
2105	Say Y here to let the kernel print out symbolic crash information and
2106	symbolic stack backtraces. This increases the size of the kernel
2107	somewhat, as all symbols have to be loaded into the kernel image.
2108
2109	config KALLSYMS_SELFTEST
2110	bool "Test the basic functions and performance of kallsyms"
2111	depends on KALLSYMS
2112	default n
2113	help
2114	Test the basic functions and performance of some interfaces, such as
2115	kallsyms_lookup_name. It also calculates the compression rate of the
2116	kallsyms compression algorithm for the current symbol set.
2117
2118	Start self-test automatically after system startup. Suggest executing
2119	"dmesg \| grep kallsyms_selftest" to collect test results. "finish" is
2120	displayed in the last line, indicating that the test is complete.
2121
2122	config KALLSYMS_ALL
2123	bool "Include all symbols in kallsyms"
2124	depends on DEBUG_KERNEL && KALLSYMS
2125	help
2126	Normally kallsyms only contains the symbols of functions for nicer
2127	OOPS messages and backtraces (i.e., symbols from the text and inittext
2128	sections). This is sufficient for most cases. And only if you want to
2129	enable kernel live patching, or other less common use cases (e.g.,
2130	when a debugger is used) all symbols are required (i.e., names of
2131	variables from the data sections, etc).
2132
2133	This option makes sure that all symbols are loaded into the kernel
2134	image (i.e., symbols from all sections) in cost of increased kernel
2135	size (depending on the kernel configuration, it may be 300KiB or
2136	something like this).
2137
2138	Say N unless you really need all symbols, or kernel live patching.
2139
2140	# end of the "standard kernel features (expert users)" menu
2141
2142	config ARCH_HAS_MEMBARRIER_CALLBACKS
2143	bool
2144
2145	config ARCH_HAS_MEMBARRIER_SYNC_CORE
2146	bool
2147
2148	config ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS
2149	bool
2150	help
2151	Control MSEAL_SYSTEM_MAPPINGS access based on architecture.
2152
2153	A 64-bit kernel is required for the memory sealing feature.
2154	No specific hardware features from the CPU are needed.
2155
2156	To enable this feature, the architecture needs to update their
2157	special mappings calls to include the sealing flag and confirm
2158	that it doesn't unmap/remap system mappings during the life
2159	time of the process. The existence of this flag for an architecture
2160	implies that it does not require the remapping of the system
2161	mappings during process lifetime, so sealing these mappings is safe
2162	from a kernel perspective.
2163
2164	After the architecture enables this, a distribution can set
2165	CONFIG_MSEAL_SYSTEM_MAPPINGS to manage access to the feature.
2166
2167	For complete descriptions of memory sealing, please see
2168	Documentation/userspace-api/mseal.rst
2169
2170	config HAVE_PERF_EVENTS
2171	bool
2172	help
2173	See tools/perf/design.txt for details.
2174
2175	config GUEST_PERF_EVENTS
2176	bool
2177	depends on HAVE_PERF_EVENTS
2178
2179	config PERF_GUEST_MEDIATED_PMU
2180	bool
2181	depends on GUEST_PERF_EVENTS
2182
2183	config PERF_USE_VMALLOC
2184	bool
2185	help
2186	See tools/perf/design.txt for details
2187
2188	menu "Kernel Performance Events And Counters"
2189
2190	config PERF_EVENTS
2191	bool "Kernel performance events and counters"
2192	default y if PROFILING
2193	depends on HAVE_PERF_EVENTS
2194	select IRQ_WORK
2195	help
2196	Enable kernel support for various performance events provided
2197	by software and hardware.
2198
2199	Software events are supported either built-in or via the
2200	use of generic tracepoints.
2201
2202	Most modern CPUs support performance events via performance
2203	counter registers. These registers count the number of certain
2204	types of hw events: such as instructions executed, cachemisses
2205	suffered, or branches mis-predicted - without slowing down the
2206	kernel or applications. These registers can also trigger interrupts
2207	when a threshold number of events have passed - and can thus be
2208	used to profile the code that runs on that CPU.
2209
2210	The Linux Performance Event subsystem provides an abstraction of
2211	these software and hardware event capabilities, available via a
2212	system call and used by the "perf" utility in tools/perf/. It
2213	provides per task and per CPU counters, and it provides event
2214	capabilities on top of those.
2215
2216	Say Y if unsure.
2217
2218	config DEBUG_PERF_USE_VMALLOC
2219	default n
2220	bool "Debug: use vmalloc to back perf mmap() buffers"
2221	depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
2222	select PERF_USE_VMALLOC
2223	help
2224	Use vmalloc memory to back perf mmap() buffers.
2225
2226	Mostly useful for debugging the vmalloc code on platforms
2227	that don't require it.
2228
2229	Say N if unsure.
2230
2231	endmenu
2232
2233	config SYSTEM_DATA_VERIFICATION
2234	def_bool n
2235	select SYSTEM_TRUSTED_KEYRING
2236	select KEYS
2237	select CRYPTO
2238	select CRYPTO_RSA
2239	select ASYMMETRIC_KEY_TYPE
2240	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
2241	select ASN1
2242	select OID_REGISTRY
2243	select X509_CERTIFICATE_PARSER
2244	select PKCS7_MESSAGE_PARSER
2245	help
2246	Provide PKCS#7 message verification using the contents of the system
2247	trusted keyring to provide public keys. This then can be used for
2248	module verification, kexec image verification and firmware blob
2249	verification.
2250
2251	config PROFILING
2252	bool "Profiling support"
2253	help
2254	Say Y here to enable the extended profiling support mechanisms used
2255	by profilers.
2256
2257	config RUST
2258	bool "Rust support"
2259	depends on HAVE_RUST
2260	depends on RUST_IS_AVAILABLE
2261	select EXTENDED_MODVERSIONS if MODVERSIONS
2262	depends on !MODVERSIONS \|\| GENDWARFKSYMS
2263	depends on !GCC_PLUGIN_RANDSTRUCT
2264	depends on !RANDSTRUCT
2265	depends on !DEBUG_INFO_BTF \|\| (PAHOLE_HAS_LANG_EXCLUDE && !LTO)
2266	depends on !CFI \|\| HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC
2267	select CFI_ICALL_NORMALIZE_INTEGERS if CFI
2268	depends on !KASAN \|\| CC_IS_CLANG
2269	depends on !KASAN_SW_TAGS \|\| RUSTC_VERSION >= 109600
2270	help
2271	Enables Rust support in the kernel.
2272
2273	This allows other Rust-related options, like drivers written in Rust,
2274	to be selected.
2275
2276	It is also required to be able to load external kernel modules
2277	written in Rust.
2278
2279	See Documentation/rust/ for more information.
2280
2281	If unsure, say N.
2282
2283	source "rust/kernel/Kconfig.test"
2284
2285	config RUSTC_VERSION_TEXT
2286	string
2287	depends on RUST
2288	default "$(RUSTC_VERSION_TEXT)"
2289	help
2290	See `CC_VERSION_TEXT`.
2291
2292	config BINDGEN_VERSION_TEXT
2293	string
2294	depends on RUST
2295	default "$(shell,$(BINDGEN) --version 2>/dev/null)"
2296
2297	#
2298	# Place an empty function call at each tracepoint site. Can be
2299	# dynamically changed for a probe function.
2300	#
2301	config TRACEPOINTS
2302	bool
2303	select TASKS_TRACE_RCU
2304
2305	source "kernel/Kconfig.kexec"
2306
2307	source "kernel/liveupdate/Kconfig"
2308
2309	endmenu # General setup
2310
2311	source "arch/Kconfig"
2312
2313	config RT_MUTEXES
2314	bool
2315	default y if PREEMPT_RT
2316
2317	config MODULE_SIG_FORMAT
2318	def_bool n
2319	select SYSTEM_DATA_VERIFICATION
2320
2321	source "kernel/module/Kconfig"
2322
2323	config INIT_ALL_POSSIBLE
2324	bool
2325	help
2326	Back when each arch used to define their own cpu_online_mask and
2327	cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2328	with all 1s, and others with all 0s. When they were centralised,
2329	it was better to provide this option than to break all the archs
2330	and have several arch maintainers pursuing me down dark alleys.
2331
2332	source "block/Kconfig"
2333
2334	config PREEMPT_NOTIFIERS
2335	bool
2336
2337	config PADATA
2338	depends on SMP
2339	bool
2340
2341	config ASN1
2342	tristate
2343	help
2344	Build a simple ASN.1 grammar compiler that produces a bytecode output
2345	that can be interpreted by the ASN.1 stream decoder and used to
2346	inform it as to what tags are to be expected in a stream and what
2347	functions to call on what tags.
2348
2349	source "kernel/Kconfig.locks"
2350
2351	config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2352	bool
2353
2354	config ARCH_HAS_PREPARE_SYNC_CORE_CMD
2355	bool
2356
2357	config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2358	bool
2359
2360	# It may be useful for an architecture to override the definitions of the
2361	# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2362	# and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2363	# different calling convention for syscalls. They can also override the
2364	# macros for not-implemented syscalls in kernel/sys_ni.c and
2365	# kernel/time/posix-stubs.c. All these overrides need to be available in
2366	# <asm/syscall_wrapper.h>.
2367	config ARCH_HAS_SYSCALL_WRAPPER
2368	def_bool n