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 TOOLS_SUPPORT_RELR
93	def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
94
95config CC_HAS_ASM_INLINE
96	def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
97
98config CC_HAS_NO_PROFILE_FN_ATTR
99	def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
100
101config PAHOLE_VERSION
102	int
103	default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))
104
105config CONSTRUCTORS
106	bool
107
108config IRQ_WORK
109	bool
110
111config BUILDTIME_TABLE_SORT
112	bool
113
114config THREAD_INFO_IN_TASK
115	bool
116	help
117	  Select this to move thread_info off the stack into task_struct.  To
118	  make this work, an arch will need to remove all thread_info fields
119	  except flags and fix any runtime bugs.
120
121	  One subtle change that will be needed is to use try_get_task_stack()
122	  and put_task_stack() in save_thread_stack_tsk() and get_wchan().
123
124menu "General setup"
125
126config BROKEN
127	bool
128
129config BROKEN_ON_SMP
130	bool
131	depends on BROKEN || !SMP
132	default y
133
134config INIT_ENV_ARG_LIMIT
135	int
136	default 32 if !UML
137	default 128 if UML
138	help
139	  Maximum of each of the number of arguments and environment
140	  variables passed to init from the kernel command line.
141
142config COMPILE_TEST
143	bool "Compile also drivers which will not load"
144	depends on HAS_IOMEM
145	help
146	  Some drivers can be compiled on a different platform than they are
147	  intended to be run on. Despite they cannot be loaded there (or even
148	  when they load they cannot be used due to missing HW support),
149	  developers still, opposing to distributors, might want to build such
150	  drivers to compile-test them.
151
152	  If you are a developer and want to build everything available, say Y
153	  here. If you are a user/distributor, say N here to exclude useless
154	  drivers to be distributed.
155
156config WERROR
157	bool "Compile the kernel with warnings as errors"
158	default COMPILE_TEST
159	help
160	  A kernel build should not cause any compiler warnings, and this
161	  enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags
162	  to enforce that rule by default.
163
164	  However, if you have a new (or very old) compiler with odd and
165	  unusual warnings, or you have some architecture with problems,
166	  you may need to disable this config option in order to
167	  successfully build the kernel.
168
169	  If in doubt, say Y.
170
171config UAPI_HEADER_TEST
172	bool "Compile test UAPI headers"
173	depends on HEADERS_INSTALL && CC_CAN_LINK
174	help
175	  Compile test headers exported to user-space to ensure they are
176	  self-contained, i.e. compilable as standalone units.
177
178	  If you are a developer or tester and want to ensure the exported
179	  headers are self-contained, say Y here. Otherwise, choose N.
180
181config LOCALVERSION
182	string "Local version - append to kernel release"
183	help
184	  Append an extra string to the end of your kernel version.
185	  This will show up when you type uname, for example.
186	  The string you set here will be appended after the contents of
187	  any files with a filename matching localversion* in your
188	  object and source tree, in that order.  Your total string can
189	  be a maximum of 64 characters.
190
191config LOCALVERSION_AUTO
192	bool "Automatically append version information to the version string"
193	default y
194	depends on !COMPILE_TEST
195	help
196	  This will try to automatically determine if the current tree is a
197	  release tree by looking for git tags that belong to the current
198	  top of tree revision.
199
200	  A string of the format -gxxxxxxxx will be added to the localversion
201	  if a git-based tree is found.  The string generated by this will be
202	  appended after any matching localversion* files, and after the value
203	  set in CONFIG_LOCALVERSION.
204
205	  (The actual string used here is the first eight characters produced
206	  by running the command:
207
208	    $ git rev-parse --verify HEAD
209
210	  which is done within the script "scripts/setlocalversion".)
211
212config BUILD_SALT
213	string "Build ID Salt"
214	default ""
215	help
216	  The build ID is used to link binaries and their debug info. Setting
217	  this option will use the value in the calculation of the build id.
218	  This is mostly useful for distributions which want to ensure the
219	  build is unique between builds. It's safe to leave the default.
220
221config HAVE_KERNEL_GZIP
222	bool
223
224config HAVE_KERNEL_BZIP2
225	bool
226
227config HAVE_KERNEL_LZMA
228	bool
229
230config HAVE_KERNEL_XZ
231	bool
232
233config HAVE_KERNEL_LZO
234	bool
235
236config HAVE_KERNEL_LZ4
237	bool
238
239config HAVE_KERNEL_ZSTD
240	bool
241
242config HAVE_KERNEL_UNCOMPRESSED
243	bool
244
245choice
246	prompt "Kernel compression mode"
247	default KERNEL_GZIP
248	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
249	help
250	  The linux kernel is a kind of self-extracting executable.
251	  Several compression algorithms are available, which differ
252	  in efficiency, compression and decompression speed.
253	  Compression speed is only relevant when building a kernel.
254	  Decompression speed is relevant at each boot.
255
256	  If you have any problems with bzip2 or lzma compressed
257	  kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
258	  version of this functionality (bzip2 only), for 2.4, was
259	  supplied by Christian Ludwig)
260
261	  High compression options are mostly useful for users, who
262	  are low on disk space (embedded systems), but for whom ram
263	  size matters less.
264
265	  If in doubt, select 'gzip'
266
267config KERNEL_GZIP
268	bool "Gzip"
269	depends on HAVE_KERNEL_GZIP
270	help
271	  The old and tried gzip compression. It provides a good balance
272	  between compression ratio and decompression speed.
273
274config KERNEL_BZIP2
275	bool "Bzip2"
276	depends on HAVE_KERNEL_BZIP2
277	help
278	  Its compression ratio and speed is intermediate.
279	  Decompression speed is slowest among the choices.  The kernel
280	  size is about 10% smaller with bzip2, in comparison to gzip.
281	  Bzip2 uses a large amount of memory. For modern kernels you
282	  will need at least 8MB RAM or more for booting.
283
284config KERNEL_LZMA
285	bool "LZMA"
286	depends on HAVE_KERNEL_LZMA
287	help
288	  This compression algorithm's ratio is best.  Decompression speed
289	  is between gzip and bzip2.  Compression is slowest.
290	  The kernel size is about 33% smaller with LZMA in comparison to gzip.
291
292config KERNEL_XZ
293	bool "XZ"
294	depends on HAVE_KERNEL_XZ
295	help
296	  XZ uses the LZMA2 algorithm and instruction set specific
297	  BCJ filters which can improve compression ratio of executable
298	  code. The size of the kernel is about 30% smaller with XZ in
299	  comparison to gzip. On architectures for which there is a BCJ
300	  filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
301	  will create a few percent smaller kernel than plain LZMA.
302
303	  The speed is about the same as with LZMA: The decompression
304	  speed of XZ is better than that of bzip2 but worse than gzip
305	  and LZO. Compression is slow.
306
307config KERNEL_LZO
308	bool "LZO"
309	depends on HAVE_KERNEL_LZO
310	help
311	  Its compression ratio is the poorest among the choices. The kernel
312	  size is about 10% bigger than gzip; however its speed
313	  (both compression and decompression) is the fastest.
314
315config KERNEL_LZ4
316	bool "LZ4"
317	depends on HAVE_KERNEL_LZ4
318	help
319	  LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
320	  A preliminary version of LZ4 de/compression tool is available at
321	  <https://code.google.com/p/lz4/>.
322
323	  Its compression ratio is worse than LZO. The size of the kernel
324	  is about 8% bigger than LZO. But the decompression speed is
325	  faster than LZO.
326
327config KERNEL_ZSTD
328	bool "ZSTD"
329	depends on HAVE_KERNEL_ZSTD
330	help
331	  ZSTD is a compression algorithm targeting intermediate compression
332	  with fast decompression speed. It will compress better than GZIP and
333	  decompress around the same speed as LZO, but slower than LZ4. You
334	  will need at least 192 KB RAM or more for booting. The zstd command
335	  line tool is required for compression.
336
337config KERNEL_UNCOMPRESSED
338	bool "None"
339	depends on HAVE_KERNEL_UNCOMPRESSED
340	help
341	  Produce uncompressed kernel image. This option is usually not what
342	  you want. It is useful for debugging the kernel in slow simulation
343	  environments, where decompressing and moving the kernel is awfully
344	  slow. This option allows early boot code to skip the decompressor
345	  and jump right at uncompressed kernel image.
346
347endchoice
348
349config DEFAULT_INIT
350	string "Default init path"
351	default ""
352	help
353	  This option determines the default init for the system if no init=
354	  option is passed on the kernel command line. If the requested path is
355	  not present, we will still then move on to attempting further
356	  locations (e.g. /sbin/init, etc). If this is empty, we will just use
357	  the fallback list when init= is not passed.
358
359config DEFAULT_HOSTNAME
360	string "Default hostname"
361	default "(none)"
362	help
363	  This option determines the default system hostname before userspace
364	  calls sethostname(2). The kernel traditionally uses "(none)" here,
365	  but you may wish to use a different default here to make a minimal
366	  system more usable with less configuration.
367
368config SYSVIPC
369	bool "System V IPC"
370	help
371	  Inter Process Communication is a suite of library functions and
372	  system calls which let processes (running programs) synchronize and
373	  exchange information. It is generally considered to be a good thing,
374	  and some programs won't run unless you say Y here. In particular, if
375	  you want to run the DOS emulator dosemu under Linux (read the
376	  DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
377	  you'll need to say Y here.
378
379	  You can find documentation about IPC with "info ipc" and also in
380	  section 6.4 of the Linux Programmer's Guide, available from
381	  <http://www.tldp.org/guides.html>.
382
383config SYSVIPC_SYSCTL
384	bool
385	depends on SYSVIPC
386	depends on SYSCTL
387	default y
388
389config SYSVIPC_COMPAT
390	def_bool y
391	depends on COMPAT && SYSVIPC
392
393config POSIX_MQUEUE
394	bool "POSIX Message Queues"
395	depends on NET
396	help
397	  POSIX variant of message queues is a part of IPC. In POSIX message
398	  queues every message has a priority which decides about succession
399	  of receiving it by a process. If you want to compile and run
400	  programs written e.g. for Solaris with use of its POSIX message
401	  queues (functions mq_*) say Y here.
402
403	  POSIX message queues are visible as a filesystem called 'mqueue'
404	  and can be mounted somewhere if you want to do filesystem
405	  operations on message queues.
406
407	  If unsure, say Y.
408
409config POSIX_MQUEUE_SYSCTL
410	bool
411	depends on POSIX_MQUEUE
412	depends on SYSCTL
413	default y
414
415config WATCH_QUEUE
416	bool "General notification queue"
417	default n
418	help
419
420	  This is a general notification queue for the kernel to pass events to
421	  userspace by splicing them into pipes.  It can be used in conjunction
422	  with watches for key/keyring change notifications and device
423	  notifications.
424
425	  See Documentation/core-api/watch_queue.rst
426
427config CROSS_MEMORY_ATTACH
428	bool "Enable process_vm_readv/writev syscalls"
429	depends on MMU
430	default y
431	help
432	  Enabling this option adds the system calls process_vm_readv and
433	  process_vm_writev which allow a process with the correct privileges
434	  to directly read from or write to another process' address space.
435	  See the man page for more details.
436
437config USELIB
438	bool "uselib syscall (for libc5 and earlier)"
439	default ALPHA || M68K || SPARC
440	help
441	  This option enables the uselib syscall, a system call used in the
442	  dynamic linker from libc5 and earlier.  glibc does not use this
443	  system call.  If you intend to run programs built on libc5 or
444	  earlier, you may need to enable this syscall.  Current systems
445	  running glibc can safely disable this.
446
447config AUDIT
448	bool "Auditing support"
449	depends on NET
450	help
451	  Enable auditing infrastructure that can be used with another
452	  kernel subsystem, such as SELinux (which requires this for
453	  logging of avc messages output).  System call auditing is included
454	  on architectures which support it.
455
456config HAVE_ARCH_AUDITSYSCALL
457	bool
458
459config AUDITSYSCALL
460	def_bool y
461	depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
462	select FSNOTIFY
463
464source "kernel/irq/Kconfig"
465source "kernel/time/Kconfig"
466source "kernel/bpf/Kconfig"
467source "kernel/Kconfig.preempt"
468
469menu "CPU/Task time and stats accounting"
470
471config VIRT_CPU_ACCOUNTING
472	bool
473
474choice
475	prompt "Cputime accounting"
476	default TICK_CPU_ACCOUNTING
477
478# Kind of a stub config for the pure tick based cputime accounting
479config TICK_CPU_ACCOUNTING
480	bool "Simple tick based cputime accounting"
481	depends on !S390 && !NO_HZ_FULL
482	help
483	  This is the basic tick based cputime accounting that maintains
484	  statistics about user, system and idle time spent on per jiffies
485	  granularity.
486
487	  If unsure, say Y.
488
489config VIRT_CPU_ACCOUNTING_NATIVE
490	bool "Deterministic task and CPU time accounting"
491	depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
492	select VIRT_CPU_ACCOUNTING
493	help
494	  Select this option to enable more accurate task and CPU time
495	  accounting.  This is done by reading a CPU counter on each
496	  kernel entry and exit and on transitions within the kernel
497	  between system, softirq and hardirq state, so there is a
498	  small performance impact.  In the case of s390 or IBM POWER > 5,
499	  this also enables accounting of stolen time on logically-partitioned
500	  systems.
501
502config VIRT_CPU_ACCOUNTING_GEN
503	bool "Full dynticks CPU time accounting"
504	depends on HAVE_CONTEXT_TRACKING_USER
505	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
506	depends on GENERIC_CLOCKEVENTS
507	select VIRT_CPU_ACCOUNTING
508	select CONTEXT_TRACKING_USER
509	help
510	  Select this option to enable task and CPU time accounting on full
511	  dynticks systems. This accounting is implemented by watching every
512	  kernel-user boundaries using the context tracking subsystem.
513	  The accounting is thus performed at the expense of some significant
514	  overhead.
515
516	  For now this is only useful if you are working on the full
517	  dynticks subsystem development.
518
519	  If unsure, say N.
520
521endchoice
522
523config IRQ_TIME_ACCOUNTING
524	bool "Fine granularity task level IRQ time accounting"
525	depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
526	help
527	  Select this option to enable fine granularity task irq time
528	  accounting. This is done by reading a timestamp on each
529	  transitions between softirq and hardirq state, so there can be a
530	  small performance impact.
531
532	  If in doubt, say N here.
533
534config HAVE_SCHED_AVG_IRQ
535	def_bool y
536	depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
537	depends on SMP
538
539config SCHED_THERMAL_PRESSURE
540	bool
541	default y if ARM && ARM_CPU_TOPOLOGY
542	default y if ARM64
543	depends on SMP
544	depends on CPU_FREQ_THERMAL
545	help
546	  Select this option to enable thermal pressure accounting in the
547	  scheduler. Thermal pressure is the value conveyed to the scheduler
548	  that reflects the reduction in CPU compute capacity resulted from
549	  thermal throttling. Thermal throttling occurs when the performance of
550	  a CPU is capped due to high operating temperatures.
551
552	  If selected, the scheduler will be able to balance tasks accordingly,
553	  i.e. put less load on throttled CPUs than on non/less throttled ones.
554
555	  This requires the architecture to implement
556	  arch_update_thermal_pressure() and arch_scale_thermal_pressure().
557
558config BSD_PROCESS_ACCT
559	bool "BSD Process Accounting"
560	depends on MULTIUSER
561	help
562	  If you say Y here, a user level program will be able to instruct the
563	  kernel (via a special system call) to write process accounting
564	  information to a file: whenever a process exits, information about
565	  that process will be appended to the file by the kernel.  The
566	  information includes things such as creation time, owning user,
567	  command name, memory usage, controlling terminal etc. (the complete
568	  list is in the struct acct in <file:include/linux/acct.h>).  It is
569	  up to the user level program to do useful things with this
570	  information.  This is generally a good idea, so say Y.
571
572config BSD_PROCESS_ACCT_V3
573	bool "BSD Process Accounting version 3 file format"
574	depends on BSD_PROCESS_ACCT
575	default n
576	help
577	  If you say Y here, the process accounting information is written
578	  in a new file format that also logs the process IDs of each
579	  process and its parent. Note that this file format is incompatible
580	  with previous v0/v1/v2 file formats, so you will need updated tools
581	  for processing it. A preliminary version of these tools is available
582	  at <http://www.gnu.org/software/acct/>.
583
584config TASKSTATS
585	bool "Export task/process statistics through netlink"
586	depends on NET
587	depends on MULTIUSER
588	default n
589	help
590	  Export selected statistics for tasks/processes through the
591	  generic netlink interface. Unlike BSD process accounting, the
592	  statistics are available during the lifetime of tasks/processes as
593	  responses to commands. Like BSD accounting, they are sent to user
594	  space on task exit.
595
596	  Say N if unsure.
597
598config TASK_DELAY_ACCT
599	bool "Enable per-task delay accounting"
600	depends on TASKSTATS
601	select SCHED_INFO
602	help
603	  Collect information on time spent by a task waiting for system
604	  resources like cpu, synchronous block I/O completion and swapping
605	  in pages. Such statistics can help in setting a task's priorities
606	  relative to other tasks for cpu, io, rss limits etc.
607
608	  Say N if unsure.
609
610config TASK_XACCT
611	bool "Enable extended accounting over taskstats"
612	depends on TASKSTATS
613	help
614	  Collect extended task accounting data and send the data
615	  to userland for processing over the taskstats interface.
616
617	  Say N if unsure.
618
619config TASK_IO_ACCOUNTING
620	bool "Enable per-task storage I/O accounting"
621	depends on TASK_XACCT
622	help
623	  Collect information on the number of bytes of storage I/O which this
624	  task has caused.
625
626	  Say N if unsure.
627
628config PSI
629	bool "Pressure stall information tracking"
630	help
631	  Collect metrics that indicate how overcommitted the CPU, memory,
632	  and IO capacity are in the system.
633
634	  If you say Y here, the kernel will create /proc/pressure/ with the
635	  pressure statistics files cpu, memory, and io. These will indicate
636	  the share of walltime in which some or all tasks in the system are
637	  delayed due to contention of the respective resource.
638
639	  In kernels with cgroup support, cgroups (cgroup2 only) will
640	  have cpu.pressure, memory.pressure, and io.pressure files,
641	  which aggregate pressure stalls for the grouped tasks only.
642
643	  For more details see Documentation/accounting/psi.rst.
644
645	  Say N if unsure.
646
647config PSI_DEFAULT_DISABLED
648	bool "Require boot parameter to enable pressure stall information tracking"
649	default n
650	depends on PSI
651	help
652	  If set, pressure stall information tracking will be disabled
653	  per default but can be enabled through passing psi=1 on the
654	  kernel commandline during boot.
655
656	  This feature adds some code to the task wakeup and sleep
657	  paths of the scheduler. The overhead is too low to affect
658	  common scheduling-intense workloads in practice (such as
659	  webservers, memcache), but it does show up in artificial
660	  scheduler stress tests, such as hackbench.
661
662	  If you are paranoid and not sure what the kernel will be
663	  used for, say Y.
664
665	  Say N if unsure.
666
667endmenu # "CPU/Task time and stats accounting"
668
669config CPU_ISOLATION
670	bool "CPU isolation"
671	depends on SMP || COMPILE_TEST
672	default y
673	help
674	  Make sure that CPUs running critical tasks are not disturbed by
675	  any source of "noise" such as unbound workqueues, timers, kthreads...
676	  Unbound jobs get offloaded to housekeeping CPUs. This is driven by
677	  the "isolcpus=" boot parameter.
678
679	  Say Y if unsure.
680
681source "kernel/rcu/Kconfig"
682
683config BUILD_BIN2C
684	bool
685	default n
686
687config IKCONFIG
688	tristate "Kernel .config support"
689	help
690	  This option enables the complete Linux kernel ".config" file
691	  contents to be saved in the kernel. It provides documentation
692	  of which kernel options are used in a running kernel or in an
693	  on-disk kernel.  This information can be extracted from the kernel
694	  image file with the script scripts/extract-ikconfig and used as
695	  input to rebuild the current kernel or to build another kernel.
696	  It can also be extracted from a running kernel by reading
697	  /proc/config.gz if enabled (below).
698
699config IKCONFIG_PROC
700	bool "Enable access to .config through /proc/config.gz"
701	depends on IKCONFIG && PROC_FS
702	help
703	  This option enables access to the kernel configuration file
704	  through /proc/config.gz.
705
706config IKHEADERS
707	tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
708	depends on SYSFS
709	help
710	  This option enables access to the in-kernel headers that are generated during
711	  the build process. These can be used to build eBPF tracing programs,
712	  or similar programs.  If you build the headers as a module, a module called
713	  kheaders.ko is built which can be loaded on-demand to get access to headers.
714
715config LOG_BUF_SHIFT
716	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
717	range 12 25
718	default 17
719	depends on PRINTK
720	help
721	  Select the minimal kernel log buffer size as a power of 2.
722	  The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
723	  parameter, see below. Any higher size also might be forced
724	  by "log_buf_len" boot parameter.
725
726	  Examples:
727		     17 => 128 KB
728		     16 => 64 KB
729		     15 => 32 KB
730		     14 => 16 KB
731		     13 =>  8 KB
732		     12 =>  4 KB
733
734config LOG_CPU_MAX_BUF_SHIFT
735	int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
736	depends on SMP
737	range 0 21
738	default 12 if !BASE_SMALL
739	default 0 if BASE_SMALL
740	depends on PRINTK
741	help
742	  This option allows to increase the default ring buffer size
743	  according to the number of CPUs. The value defines the contribution
744	  of each CPU as a power of 2. The used space is typically only few
745	  lines however it might be much more when problems are reported,
746	  e.g. backtraces.
747
748	  The increased size means that a new buffer has to be allocated and
749	  the original static one is unused. It makes sense only on systems
750	  with more CPUs. Therefore this value is used only when the sum of
751	  contributions is greater than the half of the default kernel ring
752	  buffer as defined by LOG_BUF_SHIFT. The default values are set
753	  so that more than 16 CPUs are needed to trigger the allocation.
754
755	  Also this option is ignored when "log_buf_len" kernel parameter is
756	  used as it forces an exact (power of two) size of the ring buffer.
757
758	  The number of possible CPUs is used for this computation ignoring
759	  hotplugging making the computation optimal for the worst case
760	  scenario while allowing a simple algorithm to be used from bootup.
761
762	  Examples shift values and their meaning:
763		     17 => 128 KB for each CPU
764		     16 =>  64 KB for each CPU
765		     15 =>  32 KB for each CPU
766		     14 =>  16 KB for each CPU
767		     13 =>   8 KB for each CPU
768		     12 =>   4 KB for each CPU
769
770config PRINTK_SAFE_LOG_BUF_SHIFT
771	int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
772	range 10 21
773	default 13
774	depends on PRINTK
775	help
776	  Select the size of an alternate printk per-CPU buffer where messages
777	  printed from usafe contexts are temporary stored. One example would
778	  be NMI messages, another one - printk recursion. The messages are
779	  copied to the main log buffer in a safe context to avoid a deadlock.
780	  The value defines the size as a power of 2.
781
782	  Those messages are rare and limited. The largest one is when
783	  a backtrace is printed. It usually fits into 4KB. Select
784	  8KB if you want to be on the safe side.
785
786	  Examples:
787		     17 => 128 KB for each CPU
788		     16 =>  64 KB for each CPU
789		     15 =>  32 KB for each CPU
790		     14 =>  16 KB for each CPU
791		     13 =>   8 KB for each CPU
792		     12 =>   4 KB for each CPU
793
794config PRINTK_INDEX
795	bool "Printk indexing debugfs interface"
796	depends on PRINTK && DEBUG_FS
797	help
798	  Add support for indexing of all printk formats known at compile time
799	  at <debugfs>/printk/index/<module>.
800
801	  This can be used as part of maintaining daemons which monitor
802	  /dev/kmsg, as it permits auditing the printk formats present in a
803	  kernel, allowing detection of cases where monitored printks are
804	  changed or no longer present.
805
806	  There is no additional runtime cost to printk with this enabled.
807
808#
809# Architectures with an unreliable sched_clock() should select this:
810#
811config HAVE_UNSTABLE_SCHED_CLOCK
812	bool
813
814config GENERIC_SCHED_CLOCK
815	bool
816
817menu "Scheduler features"
818
819config UCLAMP_TASK
820	bool "Enable utilization clamping for RT/FAIR tasks"
821	depends on CPU_FREQ_GOV_SCHEDUTIL
822	help
823	  This feature enables the scheduler to track the clamped utilization
824	  of each CPU based on RUNNABLE tasks scheduled on that CPU.
825
826	  With this option, the user can specify the min and max CPU
827	  utilization allowed for RUNNABLE tasks. The max utilization defines
828	  the maximum frequency a task should use while the min utilization
829	  defines the minimum frequency it should use.
830
831	  Both min and max utilization clamp values are hints to the scheduler,
832	  aiming at improving its frequency selection policy, but they do not
833	  enforce or grant any specific bandwidth for tasks.
834
835	  If in doubt, say N.
836
837config UCLAMP_BUCKETS_COUNT
838	int "Number of supported utilization clamp buckets"
839	range 5 20
840	default 5
841	depends on UCLAMP_TASK
842	help
843	  Defines the number of clamp buckets to use. The range of each bucket
844	  will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
845	  number of clamp buckets the finer their granularity and the higher
846	  the precision of clamping aggregation and tracking at run-time.
847
848	  For example, with the minimum configuration value we will have 5
849	  clamp buckets tracking 20% utilization each. A 25% boosted tasks will
850	  be refcounted in the [20..39]% bucket and will set the bucket clamp
851	  effective value to 25%.
852	  If a second 30% boosted task should be co-scheduled on the same CPU,
853	  that task will be refcounted in the same bucket of the first task and
854	  it will boost the bucket clamp effective value to 30%.
855	  The clamp effective value of a bucket is reset to its nominal value
856	  (20% in the example above) when there are no more tasks refcounted in
857	  that bucket.
858
859	  An additional boost/capping margin can be added to some tasks. In the
860	  example above the 25% task will be boosted to 30% until it exits the
861	  CPU. If that should be considered not acceptable on certain systems,
862	  it's always possible to reduce the margin by increasing the number of
863	  clamp buckets to trade off used memory for run-time tracking
864	  precision.
865
866	  If in doubt, use the default value.
867
868endmenu
869
870#
871# For architectures that want to enable the support for NUMA-affine scheduler
872# balancing logic:
873#
874config ARCH_SUPPORTS_NUMA_BALANCING
875	bool
876
877#
878# For architectures that prefer to flush all TLBs after a number of pages
879# are unmapped instead of sending one IPI per page to flush. The architecture
880# must provide guarantees on what happens if a clean TLB cache entry is
881# written after the unmap. Details are in mm/rmap.c near the check for
882# should_defer_flush. The architecture should also consider if the full flush
883# and the refill costs are offset by the savings of sending fewer IPIs.
884config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
885	bool
886
887config CC_HAS_INT128
888	def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
889
890config CC_IMPLICIT_FALLTHROUGH
891	string
892	default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
893	default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough)
894
895# Currently, disable gcc-11,12 array-bounds globally.
896# We may want to target only particular configurations some day.
897config GCC11_NO_ARRAY_BOUNDS
898	def_bool y
899
900config GCC12_NO_ARRAY_BOUNDS
901	def_bool y
902
903config CC_NO_ARRAY_BOUNDS
904	bool
905	default y if CC_IS_GCC && GCC_VERSION >= 110000 && GCC_VERSION < 120000 && GCC11_NO_ARRAY_BOUNDS
906	default y if CC_IS_GCC && GCC_VERSION >= 120000 && GCC_VERSION < 130000 && GCC12_NO_ARRAY_BOUNDS
907
908#
909# For architectures that know their GCC __int128 support is sound
910#
911config ARCH_SUPPORTS_INT128
912	bool
913
914# For architectures that (ab)use NUMA to represent different memory regions
915# all cpu-local but of different latencies, such as SuperH.
916#
917config ARCH_WANT_NUMA_VARIABLE_LOCALITY
918	bool
919
920config NUMA_BALANCING
921	bool "Memory placement aware NUMA scheduler"
922	depends on ARCH_SUPPORTS_NUMA_BALANCING
923	depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
924	depends on SMP && NUMA && MIGRATION && !PREEMPT_RT
925	help
926	  This option adds support for automatic NUMA aware memory/task placement.
927	  The mechanism is quite primitive and is based on migrating memory when
928	  it has references to the node the task is running on.
929
930	  This system will be inactive on UMA systems.
931
932config NUMA_BALANCING_DEFAULT_ENABLED
933	bool "Automatically enable NUMA aware memory/task placement"
934	default y
935	depends on NUMA_BALANCING
936	help
937	  If set, automatic NUMA balancing will be enabled if running on a NUMA
938	  machine.
939
940menuconfig CGROUPS
941	bool "Control Group support"
942	select KERNFS
943	help
944	  This option adds support for grouping sets of processes together, for
945	  use with process control subsystems such as Cpusets, CFS, memory
946	  controls or device isolation.
947	  See
948		- Documentation/scheduler/sched-design-CFS.rst	(CFS)
949		- Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
950					  and resource control)
951
952	  Say N if unsure.
953
954if CGROUPS
955
956config PAGE_COUNTER
957	bool
958
959config CGROUP_FAVOR_DYNMODS
960        bool "Favor dynamic modification latency reduction by default"
961        help
962          This option enables the "favordynmods" mount option by default
963          which reduces the latencies of dynamic cgroup modifications such
964          as task migrations and controller on/offs at the cost of making
965          hot path operations such as forks and exits more expensive.
966
967          Say N if unsure.
968
969config MEMCG
970	bool "Memory controller"
971	select PAGE_COUNTER
972	select EVENTFD
973	help
974	  Provides control over the memory footprint of tasks in a cgroup.
975
976config MEMCG_KMEM
977	bool
978	depends on MEMCG && !SLOB
979	default y
980
981config BLK_CGROUP
982	bool "IO controller"
983	depends on BLOCK
984	default n
985	help
986	Generic block IO controller cgroup interface. This is the common
987	cgroup interface which should be used by various IO controlling
988	policies.
989
990	Currently, CFQ IO scheduler uses it to recognize task groups and
991	control disk bandwidth allocation (proportional time slice allocation)
992	to such task groups. It is also used by bio throttling logic in
993	block layer to implement upper limit in IO rates on a device.
994
995	This option only enables generic Block IO controller infrastructure.
996	One needs to also enable actual IO controlling logic/policy. For
997	enabling proportional weight division of disk bandwidth in CFQ, set
998	CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
999	CONFIG_BLK_DEV_THROTTLING=y.
1000
1001	See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
1002
1003config CGROUP_WRITEBACK
1004	bool
1005	depends on MEMCG && BLK_CGROUP
1006	default y
1007
1008menuconfig CGROUP_SCHED
1009	bool "CPU controller"
1010	default n
1011	help
1012	  This feature lets CPU scheduler recognize task groups and control CPU
1013	  bandwidth allocation to such task groups. It uses cgroups to group
1014	  tasks.
1015
1016if CGROUP_SCHED
1017config FAIR_GROUP_SCHED
1018	bool "Group scheduling for SCHED_OTHER"
1019	depends on CGROUP_SCHED
1020	default CGROUP_SCHED
1021
1022config CFS_BANDWIDTH
1023	bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1024	depends on FAIR_GROUP_SCHED
1025	default n
1026	help
1027	  This option allows users to define CPU bandwidth rates (limits) for
1028	  tasks running within the fair group scheduler.  Groups with no limit
1029	  set are considered to be unconstrained and will run with no
1030	  restriction.
1031	  See Documentation/scheduler/sched-bwc.rst for more information.
1032
1033config RT_GROUP_SCHED
1034	bool "Group scheduling for SCHED_RR/FIFO"
1035	depends on CGROUP_SCHED
1036	default n
1037	help
1038	  This feature lets you explicitly allocate real CPU bandwidth
1039	  to task groups. If enabled, it will also make it impossible to
1040	  schedule realtime tasks for non-root users until you allocate
1041	  realtime bandwidth for them.
1042	  See Documentation/scheduler/sched-rt-group.rst for more information.
1043
1044endif #CGROUP_SCHED
1045
1046config UCLAMP_TASK_GROUP
1047	bool "Utilization clamping per group of tasks"
1048	depends on CGROUP_SCHED
1049	depends on UCLAMP_TASK
1050	default n
1051	help
1052	  This feature enables the scheduler to track the clamped utilization
1053	  of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
1054
1055	  When this option is enabled, the user can specify a min and max
1056	  CPU bandwidth which is allowed for each single task in a group.
1057	  The max bandwidth allows to clamp the maximum frequency a task
1058	  can use, while the min bandwidth allows to define a minimum
1059	  frequency a task will always use.
1060
1061	  When task group based utilization clamping is enabled, an eventually
1062	  specified task-specific clamp value is constrained by the cgroup
1063	  specified clamp value. Both minimum and maximum task clamping cannot
1064	  be bigger than the corresponding clamping defined at task group level.
1065
1066	  If in doubt, say N.
1067
1068config CGROUP_PIDS
1069	bool "PIDs controller"
1070	help
1071	  Provides enforcement of process number limits in the scope of a
1072	  cgroup. Any attempt to fork more processes than is allowed in the
1073	  cgroup will fail. PIDs are fundamentally a global resource because it
1074	  is fairly trivial to reach PID exhaustion before you reach even a
1075	  conservative kmemcg limit. As a result, it is possible to grind a
1076	  system to halt without being limited by other cgroup policies. The
1077	  PIDs controller is designed to stop this from happening.
1078
1079	  It should be noted that organisational operations (such as attaching
1080	  to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1081	  since the PIDs limit only affects a process's ability to fork, not to
1082	  attach to a cgroup.
1083
1084config CGROUP_RDMA
1085	bool "RDMA controller"
1086	help
1087	  Provides enforcement of RDMA resources defined by IB stack.
1088	  It is fairly easy for consumers to exhaust RDMA resources, which
1089	  can result into resource unavailability to other consumers.
1090	  RDMA controller is designed to stop this from happening.
1091	  Attaching processes with active RDMA resources to the cgroup
1092	  hierarchy is allowed even if can cross the hierarchy's limit.
1093
1094config CGROUP_FREEZER
1095	bool "Freezer controller"
1096	help
1097	  Provides a way to freeze and unfreeze all tasks in a
1098	  cgroup.
1099
1100	  This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1101	  controller includes important in-kernel memory consumers per default.
1102
1103	  If you're using cgroup2, say N.
1104
1105config CGROUP_HUGETLB
1106	bool "HugeTLB controller"
1107	depends on HUGETLB_PAGE
1108	select PAGE_COUNTER
1109	default n
1110	help
1111	  Provides a cgroup controller for HugeTLB pages.
1112	  When you enable this, you can put a per cgroup limit on HugeTLB usage.
1113	  The limit is enforced during page fault. Since HugeTLB doesn't
1114	  support page reclaim, enforcing the limit at page fault time implies
1115	  that, the application will get SIGBUS signal if it tries to access
1116	  HugeTLB pages beyond its limit. This requires the application to know
1117	  beforehand how much HugeTLB pages it would require for its use. The
1118	  control group is tracked in the third page lru pointer. This means
1119	  that we cannot use the controller with huge page less than 3 pages.
1120
1121config CPUSETS
1122	bool "Cpuset controller"
1123	depends on SMP
1124	help
1125	  This option will let you create and manage CPUSETs which
1126	  allow dynamically partitioning a system into sets of CPUs and
1127	  Memory Nodes and assigning tasks to run only within those sets.
1128	  This is primarily useful on large SMP or NUMA systems.
1129
1130	  Say N if unsure.
1131
1132config PROC_PID_CPUSET
1133	bool "Include legacy /proc/<pid>/cpuset file"
1134	depends on CPUSETS
1135	default y
1136
1137config CGROUP_DEVICE
1138	bool "Device controller"
1139	help
1140	  Provides a cgroup controller implementing whitelists for
1141	  devices which a process in the cgroup can mknod or open.
1142
1143config CGROUP_CPUACCT
1144	bool "Simple CPU accounting controller"
1145	help
1146	  Provides a simple controller for monitoring the
1147	  total CPU consumed by the tasks in a cgroup.
1148
1149config CGROUP_PERF
1150	bool "Perf controller"
1151	depends on PERF_EVENTS
1152	help
1153	  This option extends the perf per-cpu mode to restrict monitoring
1154	  to threads which belong to the cgroup specified and run on the
1155	  designated cpu.  Or this can be used to have cgroup ID in samples
1156	  so that it can monitor performance events among cgroups.
1157
1158	  Say N if unsure.
1159
1160config CGROUP_BPF
1161	bool "Support for eBPF programs attached to cgroups"
1162	depends on BPF_SYSCALL
1163	select SOCK_CGROUP_DATA
1164	help
1165	  Allow attaching eBPF programs to a cgroup using the bpf(2)
1166	  syscall command BPF_PROG_ATTACH.
1167
1168	  In which context these programs are accessed depends on the type
1169	  of attachment. For instance, programs that are attached using
1170	  BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1171	  inet sockets.
1172
1173config CGROUP_MISC
1174	bool "Misc resource controller"
1175	default n
1176	help
1177	  Provides a controller for miscellaneous resources on a host.
1178
1179	  Miscellaneous scalar resources are the resources on the host system
1180	  which cannot be abstracted like the other cgroups. This controller
1181	  tracks and limits the miscellaneous resources used by a process
1182	  attached to a cgroup hierarchy.
1183
1184	  For more information, please check misc cgroup section in
1185	  /Documentation/admin-guide/cgroup-v2.rst.
1186
1187config CGROUP_DEBUG
1188	bool "Debug controller"
1189	default n
1190	depends on DEBUG_KERNEL
1191	help
1192	  This option enables a simple controller that exports
1193	  debugging information about the cgroups framework. This
1194	  controller is for control cgroup debugging only. Its
1195	  interfaces are not stable.
1196
1197	  Say N.
1198
1199config SOCK_CGROUP_DATA
1200	bool
1201	default n
1202
1203endif # CGROUPS
1204
1205menuconfig NAMESPACES
1206	bool "Namespaces support" if EXPERT
1207	depends on MULTIUSER
1208	default !EXPERT
1209	help
1210	  Provides the way to make tasks work with different objects using
1211	  the same id. For example same IPC id may refer to different objects
1212	  or same user id or pid may refer to different tasks when used in
1213	  different namespaces.
1214
1215if NAMESPACES
1216
1217config UTS_NS
1218	bool "UTS namespace"
1219	default y
1220	help
1221	  In this namespace tasks see different info provided with the
1222	  uname() system call
1223
1224config TIME_NS
1225	bool "TIME namespace"
1226	depends on GENERIC_VDSO_TIME_NS
1227	default y
1228	help
1229	  In this namespace boottime and monotonic clocks can be set.
1230	  The time will keep going with the same pace.
1231
1232config IPC_NS
1233	bool "IPC namespace"
1234	depends on (SYSVIPC || POSIX_MQUEUE)
1235	default y
1236	help
1237	  In this namespace tasks work with IPC ids which correspond to
1238	  different IPC objects in different namespaces.
1239
1240config USER_NS
1241	bool "User namespace"
1242	default n
1243	help
1244	  This allows containers, i.e. vservers, to use user namespaces
1245	  to provide different user info for different servers.
1246
1247	  When user namespaces are enabled in the kernel it is
1248	  recommended that the MEMCG option also be enabled and that
1249	  user-space use the memory control groups to limit the amount
1250	  of memory a memory unprivileged users can use.
1251
1252	  If unsure, say N.
1253
1254config PID_NS
1255	bool "PID Namespaces"
1256	default y
1257	help
1258	  Support process id namespaces.  This allows having multiple
1259	  processes with the same pid as long as they are in different
1260	  pid namespaces.  This is a building block of containers.
1261
1262config NET_NS
1263	bool "Network namespace"
1264	depends on NET
1265	default y
1266	help
1267	  Allow user space to create what appear to be multiple instances
1268	  of the network stack.
1269
1270endif # NAMESPACES
1271
1272config CHECKPOINT_RESTORE
1273	bool "Checkpoint/restore support"
1274	depends on PROC_FS
1275	select PROC_CHILDREN
1276	select KCMP
1277	default n
1278	help
1279	  Enables additional kernel features in a sake of checkpoint/restore.
1280	  In particular it adds auxiliary prctl codes to setup process text,
1281	  data and heap segment sizes, and a few additional /proc filesystem
1282	  entries.
1283
1284	  If unsure, say N here.
1285
1286config SCHED_AUTOGROUP
1287	bool "Automatic process group scheduling"
1288	select CGROUPS
1289	select CGROUP_SCHED
1290	select FAIR_GROUP_SCHED
1291	help
1292	  This option optimizes the scheduler for common desktop workloads by
1293	  automatically creating and populating task groups.  This separation
1294	  of workloads isolates aggressive CPU burners (like build jobs) from
1295	  desktop applications.  Task group autogeneration is currently based
1296	  upon task session.
1297
1298config SYSFS_DEPRECATED
1299	bool "Enable deprecated sysfs features to support old userspace tools"
1300	depends on SYSFS
1301	default n
1302	help
1303	  This option adds code that switches the layout of the "block" class
1304	  devices, to not show up in /sys/class/block/, but only in
1305	  /sys/block/.
1306
1307	  This switch is only active when the sysfs.deprecated=1 boot option is
1308	  passed or the SYSFS_DEPRECATED_V2 option is set.
1309
1310	  This option allows new kernels to run on old distributions and tools,
1311	  which might get confused by /sys/class/block/. Since 2007/2008 all
1312	  major distributions and tools handle this just fine.
1313
1314	  Recent distributions and userspace tools after 2009/2010 depend on
1315	  the existence of /sys/class/block/, and will not work with this
1316	  option enabled.
1317
1318	  Only if you are using a new kernel on an old distribution, you might
1319	  need to say Y here.
1320
1321config SYSFS_DEPRECATED_V2
1322	bool "Enable deprecated sysfs features by default"
1323	default n
1324	depends on SYSFS
1325	depends on SYSFS_DEPRECATED
1326	help
1327	  Enable deprecated sysfs by default.
1328
1329	  See the CONFIG_SYSFS_DEPRECATED option for more details about this
1330	  option.
1331
1332	  Only if you are using a new kernel on an old distribution, you might
1333	  need to say Y here. Even then, odds are you would not need it
1334	  enabled, you can always pass the boot option if absolutely necessary.
1335
1336config RELAY
1337	bool "Kernel->user space relay support (formerly relayfs)"
1338	select IRQ_WORK
1339	help
1340	  This option enables support for relay interface support in
1341	  certain file systems (such as debugfs).
1342	  It is designed to provide an efficient mechanism for tools and
1343	  facilities to relay large amounts of data from kernel space to
1344	  user space.
1345
1346	  If unsure, say N.
1347
1348config BLK_DEV_INITRD
1349	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1350	help
1351	  The initial RAM filesystem is a ramfs which is loaded by the
1352	  boot loader (loadlin or lilo) and that is mounted as root
1353	  before the normal boot procedure. It is typically used to
1354	  load modules needed to mount the "real" root file system,
1355	  etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1356
1357	  If RAM disk support (BLK_DEV_RAM) is also included, this
1358	  also enables initial RAM disk (initrd) support and adds
1359	  15 Kbytes (more on some other architectures) to the kernel size.
1360
1361	  If unsure say Y.
1362
1363if BLK_DEV_INITRD
1364
1365source "usr/Kconfig"
1366
1367endif
1368
1369config BOOT_CONFIG
1370	bool "Boot config support"
1371	select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED
1372	help
1373	  Extra boot config allows system admin to pass a config file as
1374	  complemental extension of kernel cmdline when booting.
1375	  The boot config file must be attached at the end of initramfs
1376	  with checksum, size and magic word.
1377	  See <file:Documentation/admin-guide/bootconfig.rst> for details.
1378
1379	  If unsure, say Y.
1380
1381config BOOT_CONFIG_EMBED
1382	bool "Embed bootconfig file in the kernel"
1383	depends on BOOT_CONFIG
1384	help
1385	  Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the
1386	  kernel. Usually, the bootconfig file is loaded with the initrd
1387	  image. But if the system doesn't support initrd, this option will
1388	  help you by embedding a bootconfig file while building the kernel.
1389
1390	  If unsure, say N.
1391
1392config BOOT_CONFIG_EMBED_FILE
1393	string "Embedded bootconfig file path"
1394	depends on BOOT_CONFIG_EMBED
1395	help
1396	  Specify a bootconfig file which will be embedded to the kernel.
1397	  This bootconfig will be used if there is no initrd or no other
1398	  bootconfig in the initrd.
1399
1400config INITRAMFS_PRESERVE_MTIME
1401	bool "Preserve cpio archive mtimes in initramfs"
1402	default y
1403	help
1404	  Each entry in an initramfs cpio archive carries an mtime value. When
1405	  enabled, extracted cpio items take this mtime, with directory mtime
1406	  setting deferred until after creation of any child entries.
1407
1408	  If unsure, say Y.
1409
1410choice
1411	prompt "Compiler optimization level"
1412	default CC_OPTIMIZE_FOR_PERFORMANCE
1413
1414config CC_OPTIMIZE_FOR_PERFORMANCE
1415	bool "Optimize for performance (-O2)"
1416	help
1417	  This is the default optimization level for the kernel, building
1418	  with the "-O2" compiler flag for best performance and most
1419	  helpful compile-time warnings.
1420
1421config CC_OPTIMIZE_FOR_SIZE
1422	bool "Optimize for size (-Os)"
1423	help
1424	  Choosing this option will pass "-Os" to your compiler resulting
1425	  in a smaller kernel.
1426
1427endchoice
1428
1429config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1430	bool
1431	help
1432	  This requires that the arch annotates or otherwise protects
1433	  its external entry points from being discarded. Linker scripts
1434	  must also merge .text.*, .data.*, and .bss.* correctly into
1435	  output sections. Care must be taken not to pull in unrelated
1436	  sections (e.g., '.text.init'). Typically '.' in section names
1437	  is used to distinguish them from label names / C identifiers.
1438
1439config LD_DEAD_CODE_DATA_ELIMINATION
1440	bool "Dead code and data elimination (EXPERIMENTAL)"
1441	depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1442	depends on EXPERT
1443	depends on $(cc-option,-ffunction-sections -fdata-sections)
1444	depends on $(ld-option,--gc-sections)
1445	help
1446	  Enable this if you want to do dead code and data elimination with
1447	  the linker by compiling with -ffunction-sections -fdata-sections,
1448	  and linking with --gc-sections.
1449
1450	  This can reduce on disk and in-memory size of the kernel
1451	  code and static data, particularly for small configs and
1452	  on small systems. This has the possibility of introducing
1453	  silently broken kernel if the required annotations are not
1454	  present. This option is not well tested yet, so use at your
1455	  own risk.
1456
1457config LD_ORPHAN_WARN
1458	def_bool y
1459	depends on ARCH_WANT_LD_ORPHAN_WARN
1460	depends on $(ld-option,--orphan-handling=warn)
1461
1462config SYSCTL
1463	bool
1464
1465config HAVE_UID16
1466	bool
1467
1468config SYSCTL_EXCEPTION_TRACE
1469	bool
1470	help
1471	  Enable support for /proc/sys/debug/exception-trace.
1472
1473config SYSCTL_ARCH_UNALIGN_NO_WARN
1474	bool
1475	help
1476	  Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1477	  Allows arch to define/use @no_unaligned_warning to possibly warn
1478	  about unaligned access emulation going on under the hood.
1479
1480config SYSCTL_ARCH_UNALIGN_ALLOW
1481	bool
1482	help
1483	  Enable support for /proc/sys/kernel/unaligned-trap
1484	  Allows arches to define/use @unaligned_enabled to runtime toggle
1485	  the unaligned access emulation.
1486	  see arch/parisc/kernel/unaligned.c for reference
1487
1488config HAVE_PCSPKR_PLATFORM
1489	bool
1490
1491# interpreter that classic socket filters depend on
1492config BPF
1493	bool
1494	select CRYPTO_LIB_SHA1
1495
1496menuconfig EXPERT
1497	bool "Configure standard kernel features (expert users)"
1498	# Unhide debug options, to make the on-by-default options visible
1499	select DEBUG_KERNEL
1500	help
1501	  This option allows certain base kernel options and settings
1502	  to be disabled or tweaked. This is for specialized
1503	  environments which can tolerate a "non-standard" kernel.
1504	  Only use this if you really know what you are doing.
1505
1506config UID16
1507	bool "Enable 16-bit UID system calls" if EXPERT
1508	depends on HAVE_UID16 && MULTIUSER
1509	default y
1510	help
1511	  This enables the legacy 16-bit UID syscall wrappers.
1512
1513config MULTIUSER
1514	bool "Multiple users, groups and capabilities support" if EXPERT
1515	default y
1516	help
1517	  This option enables support for non-root users, groups and
1518	  capabilities.
1519
1520	  If you say N here, all processes will run with UID 0, GID 0, and all
1521	  possible capabilities.  Saying N here also compiles out support for
1522	  system calls related to UIDs, GIDs, and capabilities, such as setuid,
1523	  setgid, and capset.
1524
1525	  If unsure, say Y here.
1526
1527config SGETMASK_SYSCALL
1528	bool "sgetmask/ssetmask syscalls support" if EXPERT
1529	def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1530	help
1531	  sys_sgetmask and sys_ssetmask are obsolete system calls
1532	  no longer supported in libc but still enabled by default in some
1533	  architectures.
1534
1535	  If unsure, leave the default option here.
1536
1537config SYSFS_SYSCALL
1538	bool "Sysfs syscall support" if EXPERT
1539	default y
1540	help
1541	  sys_sysfs is an obsolete system call no longer supported in libc.
1542	  Note that disabling this option is more secure but might break
1543	  compatibility with some systems.
1544
1545	  If unsure say Y here.
1546
1547config FHANDLE
1548	bool "open by fhandle syscalls" if EXPERT
1549	select EXPORTFS
1550	default y
1551	help
1552	  If you say Y here, a user level program will be able to map
1553	  file names to handle and then later use the handle for
1554	  different file system operations. This is useful in implementing
1555	  userspace file servers, which now track files using handles instead
1556	  of names. The handle would remain the same even if file names
1557	  get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1558	  syscalls.
1559
1560config POSIX_TIMERS
1561	bool "Posix Clocks & timers" if EXPERT
1562	default y
1563	help
1564	  This includes native support for POSIX timers to the kernel.
1565	  Some embedded systems have no use for them and therefore they
1566	  can be configured out to reduce the size of the kernel image.
1567
1568	  When this option is disabled, the following syscalls won't be
1569	  available: timer_create, timer_gettime: timer_getoverrun,
1570	  timer_settime, timer_delete, clock_adjtime, getitimer,
1571	  setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1572	  clock_getres and clock_nanosleep syscalls will be limited to
1573	  CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1574
1575	  If unsure say y.
1576
1577config PRINTK
1578	default y
1579	bool "Enable support for printk" if EXPERT
1580	select IRQ_WORK
1581	help
1582	  This option enables normal printk support. Removing it
1583	  eliminates most of the message strings from the kernel image
1584	  and makes the kernel more or less silent. As this makes it
1585	  very difficult to diagnose system problems, saying N here is
1586	  strongly discouraged.
1587
1588config BUG
1589	bool "BUG() support" if EXPERT
1590	default y
1591	help
1592	  Disabling this option eliminates support for BUG and WARN, reducing
1593	  the size of your kernel image and potentially quietly ignoring
1594	  numerous fatal conditions. You should only consider disabling this
1595	  option for embedded systems with no facilities for reporting errors.
1596	  Just say Y.
1597
1598config ELF_CORE
1599	depends on COREDUMP
1600	default y
1601	bool "Enable ELF core dumps" if EXPERT
1602	help
1603	  Enable support for generating core dumps. Disabling saves about 4k.
1604
1605
1606config PCSPKR_PLATFORM
1607	bool "Enable PC-Speaker support" if EXPERT
1608	depends on HAVE_PCSPKR_PLATFORM
1609	select I8253_LOCK
1610	default y
1611	help
1612	  This option allows to disable the internal PC-Speaker
1613	  support, saving some memory.
1614
1615config BASE_FULL
1616	default y
1617	bool "Enable full-sized data structures for core" if EXPERT
1618	help
1619	  Disabling this option reduces the size of miscellaneous core
1620	  kernel data structures. This saves memory on small machines,
1621	  but may reduce performance.
1622
1623config FUTEX
1624	bool "Enable futex support" if EXPERT
1625	depends on !(SPARC32 && SMP)
1626	default y
1627	imply RT_MUTEXES
1628	help
1629	  Disabling this option will cause the kernel to be built without
1630	  support for "fast userspace mutexes".  The resulting kernel may not
1631	  run glibc-based applications correctly.
1632
1633config FUTEX_PI
1634	bool
1635	depends on FUTEX && RT_MUTEXES
1636	default y
1637
1638config EPOLL
1639	bool "Enable eventpoll support" if EXPERT
1640	default y
1641	help
1642	  Disabling this option will cause the kernel to be built without
1643	  support for epoll family of system calls.
1644
1645config SIGNALFD
1646	bool "Enable signalfd() system call" if EXPERT
1647	default y
1648	help
1649	  Enable the signalfd() system call that allows to receive signals
1650	  on a file descriptor.
1651
1652	  If unsure, say Y.
1653
1654config TIMERFD
1655	bool "Enable timerfd() system call" if EXPERT
1656	default y
1657	help
1658	  Enable the timerfd() system call that allows to receive timer
1659	  events on a file descriptor.
1660
1661	  If unsure, say Y.
1662
1663config EVENTFD
1664	bool "Enable eventfd() system call" if EXPERT
1665	default y
1666	help
1667	  Enable the eventfd() system call that allows to receive both
1668	  kernel notification (ie. KAIO) or userspace notifications.
1669
1670	  If unsure, say Y.
1671
1672config SHMEM
1673	bool "Use full shmem filesystem" if EXPERT
1674	default y
1675	depends on MMU
1676	help
1677	  The shmem is an internal filesystem used to manage shared memory.
1678	  It is backed by swap and manages resource limits. It is also exported
1679	  to userspace as tmpfs if TMPFS is enabled. Disabling this
1680	  option replaces shmem and tmpfs with the much simpler ramfs code,
1681	  which may be appropriate on small systems without swap.
1682
1683config AIO
1684	bool "Enable AIO support" if EXPERT
1685	default y
1686	help
1687	  This option enables POSIX asynchronous I/O which may by used
1688	  by some high performance threaded applications. Disabling
1689	  this option saves about 7k.
1690
1691config IO_URING
1692	bool "Enable IO uring support" if EXPERT
1693	select IO_WQ
1694	default y
1695	help
1696	  This option enables support for the io_uring interface, enabling
1697	  applications to submit and complete IO through submission and
1698	  completion rings that are shared between the kernel and application.
1699
1700config ADVISE_SYSCALLS
1701	bool "Enable madvise/fadvise syscalls" if EXPERT
1702	default y
1703	help
1704	  This option enables the madvise and fadvise syscalls, used by
1705	  applications to advise the kernel about their future memory or file
1706	  usage, improving performance. If building an embedded system where no
1707	  applications use these syscalls, you can disable this option to save
1708	  space.
1709
1710config MEMBARRIER
1711	bool "Enable membarrier() system call" if EXPERT
1712	default y
1713	help
1714	  Enable the membarrier() system call that allows issuing memory
1715	  barriers across all running threads, which can be used to distribute
1716	  the cost of user-space memory barriers asymmetrically by transforming
1717	  pairs of memory barriers into pairs consisting of membarrier() and a
1718	  compiler barrier.
1719
1720	  If unsure, say Y.
1721
1722config KALLSYMS
1723	bool "Load all symbols for debugging/ksymoops" if EXPERT
1724	default y
1725	help
1726	  Say Y here to let the kernel print out symbolic crash information and
1727	  symbolic stack backtraces. This increases the size of the kernel
1728	  somewhat, as all symbols have to be loaded into the kernel image.
1729
1730config KALLSYMS_ALL
1731	bool "Include all symbols in kallsyms"
1732	depends on DEBUG_KERNEL && KALLSYMS
1733	help
1734	  Normally kallsyms only contains the symbols of functions for nicer
1735	  OOPS messages and backtraces (i.e., symbols from the text and inittext
1736	  sections). This is sufficient for most cases. And only if you want to
1737	  enable kernel live patching, or other less common use cases (e.g.,
1738	  when a debugger is used) all symbols are required (i.e., names of
1739	  variables from the data sections, etc).
1740
1741	  This option makes sure that all symbols are loaded into the kernel
1742	  image (i.e., symbols from all sections) in cost of increased kernel
1743	  size (depending on the kernel configuration, it may be 300KiB or
1744	  something like this).
1745
1746	  Say N unless you really need all symbols, or kernel live patching.
1747
1748config KALLSYMS_ABSOLUTE_PERCPU
1749	bool
1750	depends on KALLSYMS
1751	default X86_64 && SMP
1752
1753config KALLSYMS_BASE_RELATIVE
1754	bool
1755	depends on KALLSYMS
1756	default !IA64
1757	help
1758	  Instead of emitting them as absolute values in the native word size,
1759	  emit the symbol references in the kallsyms table as 32-bit entries,
1760	  each containing a relative value in the range [base, base + U32_MAX]
1761	  or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1762	  an absolute value in the range [0, S32_MAX] or a relative value in the
1763	  range [base, base + S32_MAX], where base is the lowest relative symbol
1764	  address encountered in the image.
1765
1766	  On 64-bit builds, this reduces the size of the address table by 50%,
1767	  but more importantly, it results in entries whose values are build
1768	  time constants, and no relocation pass is required at runtime to fix
1769	  up the entries based on the runtime load address of the kernel.
1770
1771# end of the "standard kernel features (expert users)" menu
1772
1773# syscall, maps, verifier
1774
1775config ARCH_HAS_MEMBARRIER_CALLBACKS
1776	bool
1777
1778config ARCH_HAS_MEMBARRIER_SYNC_CORE
1779	bool
1780
1781config KCMP
1782	bool "Enable kcmp() system call" if EXPERT
1783	help
1784	  Enable the kernel resource comparison system call. It provides
1785	  user-space with the ability to compare two processes to see if they
1786	  share a common resource, such as a file descriptor or even virtual
1787	  memory space.
1788
1789	  If unsure, say N.
1790
1791config RSEQ
1792	bool "Enable rseq() system call" if EXPERT
1793	default y
1794	depends on HAVE_RSEQ
1795	select MEMBARRIER
1796	help
1797	  Enable the restartable sequences system call. It provides a
1798	  user-space cache for the current CPU number value, which
1799	  speeds up getting the current CPU number from user-space,
1800	  as well as an ABI to speed up user-space operations on
1801	  per-CPU data.
1802
1803	  If unsure, say Y.
1804
1805config DEBUG_RSEQ
1806	default n
1807	bool "Enabled debugging of rseq() system call" if EXPERT
1808	depends on RSEQ && DEBUG_KERNEL
1809	help
1810	  Enable extra debugging checks for the rseq system call.
1811
1812	  If unsure, say N.
1813
1814config EMBEDDED
1815	bool "Embedded system"
1816	select EXPERT
1817	help
1818	  This option should be enabled if compiling the kernel for
1819	  an embedded system so certain expert options are available
1820	  for configuration.
1821
1822config HAVE_PERF_EVENTS
1823	bool
1824	help
1825	  See tools/perf/design.txt for details.
1826
1827config GUEST_PERF_EVENTS
1828	bool
1829	depends on HAVE_PERF_EVENTS
1830
1831config PERF_USE_VMALLOC
1832	bool
1833	help
1834	  See tools/perf/design.txt for details
1835
1836config PC104
1837	bool "PC/104 support" if EXPERT
1838	help
1839	  Expose PC/104 form factor device drivers and options available for
1840	  selection and configuration. Enable this option if your target
1841	  machine has a PC/104 bus.
1842
1843menu "Kernel Performance Events And Counters"
1844
1845config PERF_EVENTS
1846	bool "Kernel performance events and counters"
1847	default y if PROFILING
1848	depends on HAVE_PERF_EVENTS
1849	select IRQ_WORK
1850	select SRCU
1851	help
1852	  Enable kernel support for various performance events provided
1853	  by software and hardware.
1854
1855	  Software events are supported either built-in or via the
1856	  use of generic tracepoints.
1857
1858	  Most modern CPUs support performance events via performance
1859	  counter registers. These registers count the number of certain
1860	  types of hw events: such as instructions executed, cachemisses
1861	  suffered, or branches mis-predicted - without slowing down the
1862	  kernel or applications. These registers can also trigger interrupts
1863	  when a threshold number of events have passed - and can thus be
1864	  used to profile the code that runs on that CPU.
1865
1866	  The Linux Performance Event subsystem provides an abstraction of
1867	  these software and hardware event capabilities, available via a
1868	  system call and used by the "perf" utility in tools/perf/. It
1869	  provides per task and per CPU counters, and it provides event
1870	  capabilities on top of those.
1871
1872	  Say Y if unsure.
1873
1874config DEBUG_PERF_USE_VMALLOC
1875	default n
1876	bool "Debug: use vmalloc to back perf mmap() buffers"
1877	depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1878	select PERF_USE_VMALLOC
1879	help
1880	  Use vmalloc memory to back perf mmap() buffers.
1881
1882	  Mostly useful for debugging the vmalloc code on platforms
1883	  that don't require it.
1884
1885	  Say N if unsure.
1886
1887endmenu
1888
1889config SYSTEM_DATA_VERIFICATION
1890	def_bool n
1891	select SYSTEM_TRUSTED_KEYRING
1892	select KEYS
1893	select CRYPTO
1894	select CRYPTO_RSA
1895	select ASYMMETRIC_KEY_TYPE
1896	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1897	select ASN1
1898	select OID_REGISTRY
1899	select X509_CERTIFICATE_PARSER
1900	select PKCS7_MESSAGE_PARSER
1901	help
1902	  Provide PKCS#7 message verification using the contents of the system
1903	  trusted keyring to provide public keys.  This then can be used for
1904	  module verification, kexec image verification and firmware blob
1905	  verification.
1906
1907config PROFILING
1908	bool "Profiling support"
1909	help
1910	  Say Y here to enable the extended profiling support mechanisms used
1911	  by profilers.
1912
1913config RUST
1914	bool "Rust support"
1915	depends on HAVE_RUST
1916	depends on RUST_IS_AVAILABLE
1917	depends on !MODVERSIONS
1918	depends on !GCC_PLUGINS
1919	depends on !RANDSTRUCT
1920	depends on !DEBUG_INFO_BTF
1921	select CONSTRUCTORS
1922	help
1923	  Enables Rust support in the kernel.
1924
1925	  This allows other Rust-related options, like drivers written in Rust,
1926	  to be selected.
1927
1928	  It is also required to be able to load external kernel modules
1929	  written in Rust.
1930
1931	  See Documentation/rust/ for more information.
1932
1933	  If unsure, say N.
1934
1935config RUSTC_VERSION_TEXT
1936	string
1937	depends on RUST
1938	default $(shell,command -v $(RUSTC) >/dev/null 2>&1 && $(RUSTC) --version || echo n)
1939
1940config BINDGEN_VERSION_TEXT
1941	string
1942	depends on RUST
1943	default $(shell,command -v $(BINDGEN) >/dev/null 2>&1 && $(BINDGEN) --version || echo n)
1944
1945#
1946# Place an empty function call at each tracepoint site. Can be
1947# dynamically changed for a probe function.
1948#
1949config TRACEPOINTS
1950	bool
1951
1952endmenu		# General setup
1953
1954source "arch/Kconfig"
1955
1956config RT_MUTEXES
1957	bool
1958	default y if PREEMPT_RT
1959
1960config BASE_SMALL
1961	int
1962	default 0 if BASE_FULL
1963	default 1 if !BASE_FULL
1964
1965config MODULE_SIG_FORMAT
1966	def_bool n
1967	select SYSTEM_DATA_VERIFICATION
1968
1969source "kernel/module/Kconfig"
1970
1971config INIT_ALL_POSSIBLE
1972	bool
1973	help
1974	  Back when each arch used to define their own cpu_online_mask and
1975	  cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1976	  with all 1s, and others with all 0s.  When they were centralised,
1977	  it was better to provide this option than to break all the archs
1978	  and have several arch maintainers pursuing me down dark alleys.
1979
1980source "block/Kconfig"
1981
1982config PREEMPT_NOTIFIERS
1983	bool
1984
1985config PADATA
1986	depends on SMP
1987	bool
1988
1989config ASN1
1990	tristate
1991	help
1992	  Build a simple ASN.1 grammar compiler that produces a bytecode output
1993	  that can be interpreted by the ASN.1 stream decoder and used to
1994	  inform it as to what tags are to be expected in a stream and what
1995	  functions to call on what tags.
1996
1997source "kernel/Kconfig.locks"
1998
1999config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2000	bool
2001
2002config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2003	bool
2004
2005# It may be useful for an architecture to override the definitions of the
2006# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2007# and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2008# different calling convention for syscalls. They can also override the
2009# macros for not-implemented syscalls in kernel/sys_ni.c and
2010# kernel/time/posix-stubs.c. All these overrides need to be available in
2011# <asm/syscall_wrapper.h>.
2012config ARCH_HAS_SYSCALL_WRAPPER
2013	def_bool n
2014