xref: /openbmc/linux/init/Kconfig (revision f7875966)
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. Certain warnings from other tools
163	  such as the linker may be upgraded to errors with this option as
164	  well.
165
166	  However, if you have a new (or very old) compiler or linker with odd
167	  and unusual warnings, or you have some architecture with problems,
168	  you may need to disable this config option in order to
169	  successfully build the kernel.
170
171	  If in doubt, say Y.
172
173config UAPI_HEADER_TEST
174	bool "Compile test UAPI headers"
175	depends on HEADERS_INSTALL && CC_CAN_LINK
176	help
177	  Compile test headers exported to user-space to ensure they are
178	  self-contained, i.e. compilable as standalone units.
179
180	  If you are a developer or tester and want to ensure the exported
181	  headers are self-contained, say Y here. Otherwise, choose N.
182
183config LOCALVERSION
184	string "Local version - append to kernel release"
185	help
186	  Append an extra string to the end of your kernel version.
187	  This will show up when you type uname, for example.
188	  The string you set here will be appended after the contents of
189	  any files with a filename matching localversion* in your
190	  object and source tree, in that order.  Your total string can
191	  be a maximum of 64 characters.
192
193config LOCALVERSION_AUTO
194	bool "Automatically append version information to the version string"
195	default y
196	depends on !COMPILE_TEST
197	help
198	  This will try to automatically determine if the current tree is a
199	  release tree by looking for git tags that belong to the current
200	  top of tree revision.
201
202	  A string of the format -gxxxxxxxx will be added to the localversion
203	  if a git-based tree is found.  The string generated by this will be
204	  appended after any matching localversion* files, and after the value
205	  set in CONFIG_LOCALVERSION.
206
207	  (The actual string used here is the first 12 characters produced
208	  by running the command:
209
210	    $ git rev-parse --verify HEAD
211
212	  which is done within the script "scripts/setlocalversion".)
213
214config BUILD_SALT
215	string "Build ID Salt"
216	default ""
217	help
218	  The build ID is used to link binaries and their debug info. Setting
219	  this option will use the value in the calculation of the build id.
220	  This is mostly useful for distributions which want to ensure the
221	  build is unique between builds. It's safe to leave the default.
222
223config HAVE_KERNEL_GZIP
224	bool
225
226config HAVE_KERNEL_BZIP2
227	bool
228
229config HAVE_KERNEL_LZMA
230	bool
231
232config HAVE_KERNEL_XZ
233	bool
234
235config HAVE_KERNEL_LZO
236	bool
237
238config HAVE_KERNEL_LZ4
239	bool
240
241config HAVE_KERNEL_ZSTD
242	bool
243
244config HAVE_KERNEL_UNCOMPRESSED
245	bool
246
247choice
248	prompt "Kernel compression mode"
249	default KERNEL_GZIP
250	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
251	help
252	  The linux kernel is a kind of self-extracting executable.
253	  Several compression algorithms are available, which differ
254	  in efficiency, compression and decompression speed.
255	  Compression speed is only relevant when building a kernel.
256	  Decompression speed is relevant at each boot.
257
258	  If you have any problems with bzip2 or lzma compressed
259	  kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
260	  version of this functionality (bzip2 only), for 2.4, was
261	  supplied by Christian Ludwig)
262
263	  High compression options are mostly useful for users, who
264	  are low on disk space (embedded systems), but for whom ram
265	  size matters less.
266
267	  If in doubt, select 'gzip'
268
269config KERNEL_GZIP
270	bool "Gzip"
271	depends on HAVE_KERNEL_GZIP
272	help
273	  The old and tried gzip compression. It provides a good balance
274	  between compression ratio and decompression speed.
275
276config KERNEL_BZIP2
277	bool "Bzip2"
278	depends on HAVE_KERNEL_BZIP2
279	help
280	  Its compression ratio and speed is intermediate.
281	  Decompression speed is slowest among the choices.  The kernel
282	  size is about 10% smaller with bzip2, in comparison to gzip.
283	  Bzip2 uses a large amount of memory. For modern kernels you
284	  will need at least 8MB RAM or more for booting.
285
286config KERNEL_LZMA
287	bool "LZMA"
288	depends on HAVE_KERNEL_LZMA
289	help
290	  This compression algorithm's ratio is best.  Decompression speed
291	  is between gzip and bzip2.  Compression is slowest.
292	  The kernel size is about 33% smaller with LZMA in comparison to gzip.
293
294config KERNEL_XZ
295	bool "XZ"
296	depends on HAVE_KERNEL_XZ
297	help
298	  XZ uses the LZMA2 algorithm and instruction set specific
299	  BCJ filters which can improve compression ratio of executable
300	  code. The size of the kernel is about 30% smaller with XZ in
301	  comparison to gzip. On architectures for which there is a BCJ
302	  filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
303	  will create a few percent smaller kernel than plain LZMA.
304
305	  The speed is about the same as with LZMA: The decompression
306	  speed of XZ is better than that of bzip2 but worse than gzip
307	  and LZO. Compression is slow.
308
309config KERNEL_LZO
310	bool "LZO"
311	depends on HAVE_KERNEL_LZO
312	help
313	  Its compression ratio is the poorest among the choices. The kernel
314	  size is about 10% bigger than gzip; however its speed
315	  (both compression and decompression) is the fastest.
316
317config KERNEL_LZ4
318	bool "LZ4"
319	depends on HAVE_KERNEL_LZ4
320	help
321	  LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
322	  A preliminary version of LZ4 de/compression tool is available at
323	  <https://code.google.com/p/lz4/>.
324
325	  Its compression ratio is worse than LZO. The size of the kernel
326	  is about 8% bigger than LZO. But the decompression speed is
327	  faster than LZO.
328
329config KERNEL_ZSTD
330	bool "ZSTD"
331	depends on HAVE_KERNEL_ZSTD
332	help
333	  ZSTD is a compression algorithm targeting intermediate compression
334	  with fast decompression speed. It will compress better than GZIP and
335	  decompress around the same speed as LZO, but slower than LZ4. You
336	  will need at least 192 KB RAM or more for booting. The zstd command
337	  line tool is required for compression.
338
339config KERNEL_UNCOMPRESSED
340	bool "None"
341	depends on HAVE_KERNEL_UNCOMPRESSED
342	help
343	  Produce uncompressed kernel image. This option is usually not what
344	  you want. It is useful for debugging the kernel in slow simulation
345	  environments, where decompressing and moving the kernel is awfully
346	  slow. This option allows early boot code to skip the decompressor
347	  and jump right at uncompressed kernel image.
348
349endchoice
350
351config DEFAULT_INIT
352	string "Default init path"
353	default ""
354	help
355	  This option determines the default init for the system if no init=
356	  option is passed on the kernel command line. If the requested path is
357	  not present, we will still then move on to attempting further
358	  locations (e.g. /sbin/init, etc). If this is empty, we will just use
359	  the fallback list when init= is not passed.
360
361config DEFAULT_HOSTNAME
362	string "Default hostname"
363	default "(none)"
364	help
365	  This option determines the default system hostname before userspace
366	  calls sethostname(2). The kernel traditionally uses "(none)" here,
367	  but you may wish to use a different default here to make a minimal
368	  system more usable with less configuration.
369
370config SYSVIPC
371	bool "System V IPC"
372	help
373	  Inter Process Communication is a suite of library functions and
374	  system calls which let processes (running programs) synchronize and
375	  exchange information. It is generally considered to be a good thing,
376	  and some programs won't run unless you say Y here. In particular, if
377	  you want to run the DOS emulator dosemu under Linux (read the
378	  DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
379	  you'll need to say Y here.
380
381	  You can find documentation about IPC with "info ipc" and also in
382	  section 6.4 of the Linux Programmer's Guide, available from
383	  <http://www.tldp.org/guides.html>.
384
385config SYSVIPC_SYSCTL
386	bool
387	depends on SYSVIPC
388	depends on SYSCTL
389	default y
390
391config SYSVIPC_COMPAT
392	def_bool y
393	depends on COMPAT && SYSVIPC
394
395config POSIX_MQUEUE
396	bool "POSIX Message Queues"
397	depends on NET
398	help
399	  POSIX variant of message queues is a part of IPC. In POSIX message
400	  queues every message has a priority which decides about succession
401	  of receiving it by a process. If you want to compile and run
402	  programs written e.g. for Solaris with use of its POSIX message
403	  queues (functions mq_*) say Y here.
404
405	  POSIX message queues are visible as a filesystem called 'mqueue'
406	  and can be mounted somewhere if you want to do filesystem
407	  operations on message queues.
408
409	  If unsure, say Y.
410
411config POSIX_MQUEUE_SYSCTL
412	bool
413	depends on POSIX_MQUEUE
414	depends on SYSCTL
415	default y
416
417config WATCH_QUEUE
418	bool "General notification queue"
419	default n
420	help
421
422	  This is a general notification queue for the kernel to pass events to
423	  userspace by splicing them into pipes.  It can be used in conjunction
424	  with watches for key/keyring change notifications and device
425	  notifications.
426
427	  See Documentation/core-api/watch_queue.rst
428
429config CROSS_MEMORY_ATTACH
430	bool "Enable process_vm_readv/writev syscalls"
431	depends on MMU
432	default y
433	help
434	  Enabling this option adds the system calls process_vm_readv and
435	  process_vm_writev which allow a process with the correct privileges
436	  to directly read from or write to another process' address space.
437	  See the man page for more details.
438
439config USELIB
440	bool "uselib syscall (for libc5 and earlier)"
441	default ALPHA || M68K || SPARC
442	help
443	  This option enables the uselib syscall, a system call used in the
444	  dynamic linker from libc5 and earlier.  glibc does not use this
445	  system call.  If you intend to run programs built on libc5 or
446	  earlier, you may need to enable this syscall.  Current systems
447	  running glibc can safely disable this.
448
449config AUDIT
450	bool "Auditing support"
451	depends on NET
452	help
453	  Enable auditing infrastructure that can be used with another
454	  kernel subsystem, such as SELinux (which requires this for
455	  logging of avc messages output).  System call auditing is included
456	  on architectures which support it.
457
458config HAVE_ARCH_AUDITSYSCALL
459	bool
460
461config AUDITSYSCALL
462	def_bool y
463	depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
464	select FSNOTIFY
465
466source "kernel/irq/Kconfig"
467source "kernel/time/Kconfig"
468source "kernel/bpf/Kconfig"
469source "kernel/Kconfig.preempt"
470
471menu "CPU/Task time and stats accounting"
472
473config VIRT_CPU_ACCOUNTING
474	bool
475
476choice
477	prompt "Cputime accounting"
478	default TICK_CPU_ACCOUNTING
479
480# Kind of a stub config for the pure tick based cputime accounting
481config TICK_CPU_ACCOUNTING
482	bool "Simple tick based cputime accounting"
483	depends on !S390 && !NO_HZ_FULL
484	help
485	  This is the basic tick based cputime accounting that maintains
486	  statistics about user, system and idle time spent on per jiffies
487	  granularity.
488
489	  If unsure, say Y.
490
491config VIRT_CPU_ACCOUNTING_NATIVE
492	bool "Deterministic task and CPU time accounting"
493	depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
494	select VIRT_CPU_ACCOUNTING
495	help
496	  Select this option to enable more accurate task and CPU time
497	  accounting.  This is done by reading a CPU counter on each
498	  kernel entry and exit and on transitions within the kernel
499	  between system, softirq and hardirq state, so there is a
500	  small performance impact.  In the case of s390 or IBM POWER > 5,
501	  this also enables accounting of stolen time on logically-partitioned
502	  systems.
503
504config VIRT_CPU_ACCOUNTING_GEN
505	bool "Full dynticks CPU time accounting"
506	depends on HAVE_CONTEXT_TRACKING_USER
507	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
508	depends on GENERIC_CLOCKEVENTS
509	select VIRT_CPU_ACCOUNTING
510	select CONTEXT_TRACKING_USER
511	help
512	  Select this option to enable task and CPU time accounting on full
513	  dynticks systems. This accounting is implemented by watching every
514	  kernel-user boundaries using the context tracking subsystem.
515	  The accounting is thus performed at the expense of some significant
516	  overhead.
517
518	  For now this is only useful if you are working on the full
519	  dynticks subsystem development.
520
521	  If unsure, say N.
522
523endchoice
524
525config IRQ_TIME_ACCOUNTING
526	bool "Fine granularity task level IRQ time accounting"
527	depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
528	help
529	  Select this option to enable fine granularity task irq time
530	  accounting. This is done by reading a timestamp on each
531	  transitions between softirq and hardirq state, so there can be a
532	  small performance impact.
533
534	  If in doubt, say N here.
535
536config HAVE_SCHED_AVG_IRQ
537	def_bool y
538	depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
539	depends on SMP
540
541config SCHED_THERMAL_PRESSURE
542	bool
543	default y if ARM && ARM_CPU_TOPOLOGY
544	default y if ARM64
545	depends on SMP
546	depends on CPU_FREQ_THERMAL
547	help
548	  Select this option to enable thermal pressure accounting in the
549	  scheduler. Thermal pressure is the value conveyed to the scheduler
550	  that reflects the reduction in CPU compute capacity resulted from
551	  thermal throttling. Thermal throttling occurs when the performance of
552	  a CPU is capped due to high operating temperatures.
553
554	  If selected, the scheduler will be able to balance tasks accordingly,
555	  i.e. put less load on throttled CPUs than on non/less throttled ones.
556
557	  This requires the architecture to implement
558	  arch_update_thermal_pressure() and arch_scale_thermal_pressure().
559
560config BSD_PROCESS_ACCT
561	bool "BSD Process Accounting"
562	depends on MULTIUSER
563	help
564	  If you say Y here, a user level program will be able to instruct the
565	  kernel (via a special system call) to write process accounting
566	  information to a file: whenever a process exits, information about
567	  that process will be appended to the file by the kernel.  The
568	  information includes things such as creation time, owning user,
569	  command name, memory usage, controlling terminal etc. (the complete
570	  list is in the struct acct in <file:include/linux/acct.h>).  It is
571	  up to the user level program to do useful things with this
572	  information.  This is generally a good idea, so say Y.
573
574config BSD_PROCESS_ACCT_V3
575	bool "BSD Process Accounting version 3 file format"
576	depends on BSD_PROCESS_ACCT
577	default n
578	help
579	  If you say Y here, the process accounting information is written
580	  in a new file format that also logs the process IDs of each
581	  process and its parent. Note that this file format is incompatible
582	  with previous v0/v1/v2 file formats, so you will need updated tools
583	  for processing it. A preliminary version of these tools is available
584	  at <http://www.gnu.org/software/acct/>.
585
586config TASKSTATS
587	bool "Export task/process statistics through netlink"
588	depends on NET
589	depends on MULTIUSER
590	default n
591	help
592	  Export selected statistics for tasks/processes through the
593	  generic netlink interface. Unlike BSD process accounting, the
594	  statistics are available during the lifetime of tasks/processes as
595	  responses to commands. Like BSD accounting, they are sent to user
596	  space on task exit.
597
598	  Say N if unsure.
599
600config TASK_DELAY_ACCT
601	bool "Enable per-task delay accounting"
602	depends on TASKSTATS
603	select SCHED_INFO
604	help
605	  Collect information on time spent by a task waiting for system
606	  resources like cpu, synchronous block I/O completion and swapping
607	  in pages. Such statistics can help in setting a task's priorities
608	  relative to other tasks for cpu, io, rss limits etc.
609
610	  Say N if unsure.
611
612config TASK_XACCT
613	bool "Enable extended accounting over taskstats"
614	depends on TASKSTATS
615	help
616	  Collect extended task accounting data and send the data
617	  to userland for processing over the taskstats interface.
618
619	  Say N if unsure.
620
621config TASK_IO_ACCOUNTING
622	bool "Enable per-task storage I/O accounting"
623	depends on TASK_XACCT
624	help
625	  Collect information on the number of bytes of storage I/O which this
626	  task has caused.
627
628	  Say N if unsure.
629
630config PSI
631	bool "Pressure stall information tracking"
632	select KERNFS
633	help
634	  Collect metrics that indicate how overcommitted the CPU, memory,
635	  and IO capacity are in the system.
636
637	  If you say Y here, the kernel will create /proc/pressure/ with the
638	  pressure statistics files cpu, memory, and io. These will indicate
639	  the share of walltime in which some or all tasks in the system are
640	  delayed due to contention of the respective resource.
641
642	  In kernels with cgroup support, cgroups (cgroup2 only) will
643	  have cpu.pressure, memory.pressure, and io.pressure files,
644	  which aggregate pressure stalls for the grouped tasks only.
645
646	  For more details see Documentation/accounting/psi.rst.
647
648	  Say N if unsure.
649
650config PSI_DEFAULT_DISABLED
651	bool "Require boot parameter to enable pressure stall information tracking"
652	default n
653	depends on PSI
654	help
655	  If set, pressure stall information tracking will be disabled
656	  per default but can be enabled through passing psi=1 on the
657	  kernel commandline during boot.
658
659	  This feature adds some code to the task wakeup and sleep
660	  paths of the scheduler. The overhead is too low to affect
661	  common scheduling-intense workloads in practice (such as
662	  webservers, memcache), but it does show up in artificial
663	  scheduler stress tests, such as hackbench.
664
665	  If you are paranoid and not sure what the kernel will be
666	  used for, say Y.
667
668	  Say N if unsure.
669
670endmenu # "CPU/Task time and stats accounting"
671
672config CPU_ISOLATION
673	bool "CPU isolation"
674	depends on SMP || COMPILE_TEST
675	default y
676	help
677	  Make sure that CPUs running critical tasks are not disturbed by
678	  any source of "noise" such as unbound workqueues, timers, kthreads...
679	  Unbound jobs get offloaded to housekeeping CPUs. This is driven by
680	  the "isolcpus=" boot parameter.
681
682	  Say Y if unsure.
683
684source "kernel/rcu/Kconfig"
685
686config IKCONFIG
687	tristate "Kernel .config support"
688	help
689	  This option enables the complete Linux kernel ".config" file
690	  contents to be saved in the kernel. It provides documentation
691	  of which kernel options are used in a running kernel or in an
692	  on-disk kernel.  This information can be extracted from the kernel
693	  image file with the script scripts/extract-ikconfig and used as
694	  input to rebuild the current kernel or to build another kernel.
695	  It can also be extracted from a running kernel by reading
696	  /proc/config.gz if enabled (below).
697
698config IKCONFIG_PROC
699	bool "Enable access to .config through /proc/config.gz"
700	depends on IKCONFIG && PROC_FS
701	help
702	  This option enables access to the kernel configuration file
703	  through /proc/config.gz.
704
705config IKHEADERS
706	tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
707	depends on SYSFS
708	help
709	  This option enables access to the in-kernel headers that are generated during
710	  the build process. These can be used to build eBPF tracing programs,
711	  or similar programs.  If you build the headers as a module, a module called
712	  kheaders.ko is built which can be loaded on-demand to get access to headers.
713
714config LOG_BUF_SHIFT
715	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
716	range 12 25
717	default 17
718	depends on PRINTK
719	help
720	  Select the minimal kernel log buffer size as a power of 2.
721	  The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
722	  parameter, see below. Any higher size also might be forced
723	  by "log_buf_len" boot parameter.
724
725	  Examples:
726		     17 => 128 KB
727		     16 => 64 KB
728		     15 => 32 KB
729		     14 => 16 KB
730		     13 =>  8 KB
731		     12 =>  4 KB
732
733config LOG_CPU_MAX_BUF_SHIFT
734	int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
735	depends on SMP
736	range 0 21
737	default 12 if !BASE_SMALL
738	default 0 if BASE_SMALL
739	depends on PRINTK
740	help
741	  This option allows to increase the default ring buffer size
742	  according to the number of CPUs. The value defines the contribution
743	  of each CPU as a power of 2. The used space is typically only few
744	  lines however it might be much more when problems are reported,
745	  e.g. backtraces.
746
747	  The increased size means that a new buffer has to be allocated and
748	  the original static one is unused. It makes sense only on systems
749	  with more CPUs. Therefore this value is used only when the sum of
750	  contributions is greater than the half of the default kernel ring
751	  buffer as defined by LOG_BUF_SHIFT. The default values are set
752	  so that more than 16 CPUs are needed to trigger the allocation.
753
754	  Also this option is ignored when "log_buf_len" kernel parameter is
755	  used as it forces an exact (power of two) size of the ring buffer.
756
757	  The number of possible CPUs is used for this computation ignoring
758	  hotplugging making the computation optimal for the worst case
759	  scenario while allowing a simple algorithm to be used from bootup.
760
761	  Examples shift values and their meaning:
762		     17 => 128 KB for each CPU
763		     16 =>  64 KB for each CPU
764		     15 =>  32 KB for each CPU
765		     14 =>  16 KB for each CPU
766		     13 =>   8 KB for each CPU
767		     12 =>   4 KB for each CPU
768
769config PRINTK_INDEX
770	bool "Printk indexing debugfs interface"
771	depends on PRINTK && DEBUG_FS
772	help
773	  Add support for indexing of all printk formats known at compile time
774	  at <debugfs>/printk/index/<module>.
775
776	  This can be used as part of maintaining daemons which monitor
777	  /dev/kmsg, as it permits auditing the printk formats present in a
778	  kernel, allowing detection of cases where monitored printks are
779	  changed or no longer present.
780
781	  There is no additional runtime cost to printk with this enabled.
782
783#
784# Architectures with an unreliable sched_clock() should select this:
785#
786config HAVE_UNSTABLE_SCHED_CLOCK
787	bool
788
789config GENERIC_SCHED_CLOCK
790	bool
791
792menu "Scheduler features"
793
794config UCLAMP_TASK
795	bool "Enable utilization clamping for RT/FAIR tasks"
796	depends on CPU_FREQ_GOV_SCHEDUTIL
797	help
798	  This feature enables the scheduler to track the clamped utilization
799	  of each CPU based on RUNNABLE tasks scheduled on that CPU.
800
801	  With this option, the user can specify the min and max CPU
802	  utilization allowed for RUNNABLE tasks. The max utilization defines
803	  the maximum frequency a task should use while the min utilization
804	  defines the minimum frequency it should use.
805
806	  Both min and max utilization clamp values are hints to the scheduler,
807	  aiming at improving its frequency selection policy, but they do not
808	  enforce or grant any specific bandwidth for tasks.
809
810	  If in doubt, say N.
811
812config UCLAMP_BUCKETS_COUNT
813	int "Number of supported utilization clamp buckets"
814	range 5 20
815	default 5
816	depends on UCLAMP_TASK
817	help
818	  Defines the number of clamp buckets to use. The range of each bucket
819	  will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
820	  number of clamp buckets the finer their granularity and the higher
821	  the precision of clamping aggregation and tracking at run-time.
822
823	  For example, with the minimum configuration value we will have 5
824	  clamp buckets tracking 20% utilization each. A 25% boosted tasks will
825	  be refcounted in the [20..39]% bucket and will set the bucket clamp
826	  effective value to 25%.
827	  If a second 30% boosted task should be co-scheduled on the same CPU,
828	  that task will be refcounted in the same bucket of the first task and
829	  it will boost the bucket clamp effective value to 30%.
830	  The clamp effective value of a bucket is reset to its nominal value
831	  (20% in the example above) when there are no more tasks refcounted in
832	  that bucket.
833
834	  An additional boost/capping margin can be added to some tasks. In the
835	  example above the 25% task will be boosted to 30% until it exits the
836	  CPU. If that should be considered not acceptable on certain systems,
837	  it's always possible to reduce the margin by increasing the number of
838	  clamp buckets to trade off used memory for run-time tracking
839	  precision.
840
841	  If in doubt, use the default value.
842
843endmenu
844
845#
846# For architectures that want to enable the support for NUMA-affine scheduler
847# balancing logic:
848#
849config ARCH_SUPPORTS_NUMA_BALANCING
850	bool
851
852#
853# For architectures that prefer to flush all TLBs after a number of pages
854# are unmapped instead of sending one IPI per page to flush. The architecture
855# must provide guarantees on what happens if a clean TLB cache entry is
856# written after the unmap. Details are in mm/rmap.c near the check for
857# should_defer_flush. The architecture should also consider if the full flush
858# and the refill costs are offset by the savings of sending fewer IPIs.
859config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
860	bool
861
862config CC_HAS_INT128
863	def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
864
865config CC_IMPLICIT_FALLTHROUGH
866	string
867	default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
868	default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough)
869
870# Currently, disable gcc-11+ array-bounds globally.
871# It's still broken in gcc-13, so no upper bound yet.
872config GCC11_NO_ARRAY_BOUNDS
873	def_bool y
874
875config CC_NO_ARRAY_BOUNDS
876	bool
877	default y if CC_IS_GCC && GCC_VERSION >= 110000 && GCC11_NO_ARRAY_BOUNDS
878
879#
880# For architectures that know their GCC __int128 support is sound
881#
882config ARCH_SUPPORTS_INT128
883	bool
884
885# For architectures that (ab)use NUMA to represent different memory regions
886# all cpu-local but of different latencies, such as SuperH.
887#
888config ARCH_WANT_NUMA_VARIABLE_LOCALITY
889	bool
890
891config NUMA_BALANCING
892	bool "Memory placement aware NUMA scheduler"
893	depends on ARCH_SUPPORTS_NUMA_BALANCING
894	depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
895	depends on SMP && NUMA && MIGRATION && !PREEMPT_RT
896	help
897	  This option adds support for automatic NUMA aware memory/task placement.
898	  The mechanism is quite primitive and is based on migrating memory when
899	  it has references to the node the task is running on.
900
901	  This system will be inactive on UMA systems.
902
903config NUMA_BALANCING_DEFAULT_ENABLED
904	bool "Automatically enable NUMA aware memory/task placement"
905	default y
906	depends on NUMA_BALANCING
907	help
908	  If set, automatic NUMA balancing will be enabled if running on a NUMA
909	  machine.
910
911menuconfig CGROUPS
912	bool "Control Group support"
913	select KERNFS
914	help
915	  This option adds support for grouping sets of processes together, for
916	  use with process control subsystems such as Cpusets, CFS, memory
917	  controls or device isolation.
918	  See
919		- Documentation/scheduler/sched-design-CFS.rst	(CFS)
920		- Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
921					  and resource control)
922
923	  Say N if unsure.
924
925if CGROUPS
926
927config PAGE_COUNTER
928	bool
929
930config CGROUP_FAVOR_DYNMODS
931        bool "Favor dynamic modification latency reduction by default"
932        help
933          This option enables the "favordynmods" mount option by default
934          which reduces the latencies of dynamic cgroup modifications such
935          as task migrations and controller on/offs at the cost of making
936          hot path operations such as forks and exits more expensive.
937
938          Say N if unsure.
939
940config MEMCG
941	bool "Memory controller"
942	select PAGE_COUNTER
943	select EVENTFD
944	help
945	  Provides control over the memory footprint of tasks in a cgroup.
946
947config MEMCG_KMEM
948	bool
949	depends on MEMCG
950	default y
951
952config BLK_CGROUP
953	bool "IO controller"
954	depends on BLOCK
955	default n
956	help
957	Generic block IO controller cgroup interface. This is the common
958	cgroup interface which should be used by various IO controlling
959	policies.
960
961	Currently, CFQ IO scheduler uses it to recognize task groups and
962	control disk bandwidth allocation (proportional time slice allocation)
963	to such task groups. It is also used by bio throttling logic in
964	block layer to implement upper limit in IO rates on a device.
965
966	This option only enables generic Block IO controller infrastructure.
967	One needs to also enable actual IO controlling logic/policy. For
968	enabling proportional weight division of disk bandwidth in CFQ, set
969	CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
970	CONFIG_BLK_DEV_THROTTLING=y.
971
972	See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
973
974config CGROUP_WRITEBACK
975	bool
976	depends on MEMCG && BLK_CGROUP
977	default y
978
979menuconfig CGROUP_SCHED
980	bool "CPU controller"
981	default n
982	help
983	  This feature lets CPU scheduler recognize task groups and control CPU
984	  bandwidth allocation to such task groups. It uses cgroups to group
985	  tasks.
986
987if CGROUP_SCHED
988config FAIR_GROUP_SCHED
989	bool "Group scheduling for SCHED_OTHER"
990	depends on CGROUP_SCHED
991	default CGROUP_SCHED
992
993config CFS_BANDWIDTH
994	bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
995	depends on FAIR_GROUP_SCHED
996	default n
997	help
998	  This option allows users to define CPU bandwidth rates (limits) for
999	  tasks running within the fair group scheduler.  Groups with no limit
1000	  set are considered to be unconstrained and will run with no
1001	  restriction.
1002	  See Documentation/scheduler/sched-bwc.rst for more information.
1003
1004config RT_GROUP_SCHED
1005	bool "Group scheduling for SCHED_RR/FIFO"
1006	depends on CGROUP_SCHED
1007	default n
1008	help
1009	  This feature lets you explicitly allocate real CPU bandwidth
1010	  to task groups. If enabled, it will also make it impossible to
1011	  schedule realtime tasks for non-root users until you allocate
1012	  realtime bandwidth for them.
1013	  See Documentation/scheduler/sched-rt-group.rst for more information.
1014
1015endif #CGROUP_SCHED
1016
1017config SCHED_MM_CID
1018	def_bool y
1019	depends on SMP && RSEQ
1020
1021config UCLAMP_TASK_GROUP
1022	bool "Utilization clamping per group of tasks"
1023	depends on CGROUP_SCHED
1024	depends on UCLAMP_TASK
1025	default n
1026	help
1027	  This feature enables the scheduler to track the clamped utilization
1028	  of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
1029
1030	  When this option is enabled, the user can specify a min and max
1031	  CPU bandwidth which is allowed for each single task in a group.
1032	  The max bandwidth allows to clamp the maximum frequency a task
1033	  can use, while the min bandwidth allows to define a minimum
1034	  frequency a task will always use.
1035
1036	  When task group based utilization clamping is enabled, an eventually
1037	  specified task-specific clamp value is constrained by the cgroup
1038	  specified clamp value. Both minimum and maximum task clamping cannot
1039	  be bigger than the corresponding clamping defined at task group level.
1040
1041	  If in doubt, say N.
1042
1043config CGROUP_PIDS
1044	bool "PIDs controller"
1045	help
1046	  Provides enforcement of process number limits in the scope of a
1047	  cgroup. Any attempt to fork more processes than is allowed in the
1048	  cgroup will fail. PIDs are fundamentally a global resource because it
1049	  is fairly trivial to reach PID exhaustion before you reach even a
1050	  conservative kmemcg limit. As a result, it is possible to grind a
1051	  system to halt without being limited by other cgroup policies. The
1052	  PIDs controller is designed to stop this from happening.
1053
1054	  It should be noted that organisational operations (such as attaching
1055	  to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1056	  since the PIDs limit only affects a process's ability to fork, not to
1057	  attach to a cgroup.
1058
1059config CGROUP_RDMA
1060	bool "RDMA controller"
1061	help
1062	  Provides enforcement of RDMA resources defined by IB stack.
1063	  It is fairly easy for consumers to exhaust RDMA resources, which
1064	  can result into resource unavailability to other consumers.
1065	  RDMA controller is designed to stop this from happening.
1066	  Attaching processes with active RDMA resources to the cgroup
1067	  hierarchy is allowed even if can cross the hierarchy's limit.
1068
1069config CGROUP_FREEZER
1070	bool "Freezer controller"
1071	help
1072	  Provides a way to freeze and unfreeze all tasks in a
1073	  cgroup.
1074
1075	  This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1076	  controller includes important in-kernel memory consumers per default.
1077
1078	  If you're using cgroup2, say N.
1079
1080config CGROUP_HUGETLB
1081	bool "HugeTLB controller"
1082	depends on HUGETLB_PAGE
1083	select PAGE_COUNTER
1084	default n
1085	help
1086	  Provides a cgroup controller for HugeTLB pages.
1087	  When you enable this, you can put a per cgroup limit on HugeTLB usage.
1088	  The limit is enforced during page fault. Since HugeTLB doesn't
1089	  support page reclaim, enforcing the limit at page fault time implies
1090	  that, the application will get SIGBUS signal if it tries to access
1091	  HugeTLB pages beyond its limit. This requires the application to know
1092	  beforehand how much HugeTLB pages it would require for its use. The
1093	  control group is tracked in the third page lru pointer. This means
1094	  that we cannot use the controller with huge page less than 3 pages.
1095
1096config CPUSETS
1097	bool "Cpuset controller"
1098	depends on SMP
1099	help
1100	  This option will let you create and manage CPUSETs which
1101	  allow dynamically partitioning a system into sets of CPUs and
1102	  Memory Nodes and assigning tasks to run only within those sets.
1103	  This is primarily useful on large SMP or NUMA systems.
1104
1105	  Say N if unsure.
1106
1107config PROC_PID_CPUSET
1108	bool "Include legacy /proc/<pid>/cpuset file"
1109	depends on CPUSETS
1110	default y
1111
1112config CGROUP_DEVICE
1113	bool "Device controller"
1114	help
1115	  Provides a cgroup controller implementing whitelists for
1116	  devices which a process in the cgroup can mknod or open.
1117
1118config CGROUP_CPUACCT
1119	bool "Simple CPU accounting controller"
1120	help
1121	  Provides a simple controller for monitoring the
1122	  total CPU consumed by the tasks in a cgroup.
1123
1124config CGROUP_PERF
1125	bool "Perf controller"
1126	depends on PERF_EVENTS
1127	help
1128	  This option extends the perf per-cpu mode to restrict monitoring
1129	  to threads which belong to the cgroup specified and run on the
1130	  designated cpu.  Or this can be used to have cgroup ID in samples
1131	  so that it can monitor performance events among cgroups.
1132
1133	  Say N if unsure.
1134
1135config CGROUP_BPF
1136	bool "Support for eBPF programs attached to cgroups"
1137	depends on BPF_SYSCALL
1138	select SOCK_CGROUP_DATA
1139	help
1140	  Allow attaching eBPF programs to a cgroup using the bpf(2)
1141	  syscall command BPF_PROG_ATTACH.
1142
1143	  In which context these programs are accessed depends on the type
1144	  of attachment. For instance, programs that are attached using
1145	  BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1146	  inet sockets.
1147
1148config CGROUP_MISC
1149	bool "Misc resource controller"
1150	default n
1151	help
1152	  Provides a controller for miscellaneous resources on a host.
1153
1154	  Miscellaneous scalar resources are the resources on the host system
1155	  which cannot be abstracted like the other cgroups. This controller
1156	  tracks and limits the miscellaneous resources used by a process
1157	  attached to a cgroup hierarchy.
1158
1159	  For more information, please check misc cgroup section in
1160	  /Documentation/admin-guide/cgroup-v2.rst.
1161
1162config CGROUP_DEBUG
1163	bool "Debug controller"
1164	default n
1165	depends on DEBUG_KERNEL
1166	help
1167	  This option enables a simple controller that exports
1168	  debugging information about the cgroups framework. This
1169	  controller is for control cgroup debugging only. Its
1170	  interfaces are not stable.
1171
1172	  Say N.
1173
1174config SOCK_CGROUP_DATA
1175	bool
1176	default n
1177
1178endif # CGROUPS
1179
1180menuconfig NAMESPACES
1181	bool "Namespaces support" if EXPERT
1182	depends on MULTIUSER
1183	default !EXPERT
1184	help
1185	  Provides the way to make tasks work with different objects using
1186	  the same id. For example same IPC id may refer to different objects
1187	  or same user id or pid may refer to different tasks when used in
1188	  different namespaces.
1189
1190if NAMESPACES
1191
1192config UTS_NS
1193	bool "UTS namespace"
1194	default y
1195	help
1196	  In this namespace tasks see different info provided with the
1197	  uname() system call
1198
1199config TIME_NS
1200	bool "TIME namespace"
1201	depends on GENERIC_VDSO_TIME_NS
1202	default y
1203	help
1204	  In this namespace boottime and monotonic clocks can be set.
1205	  The time will keep going with the same pace.
1206
1207config IPC_NS
1208	bool "IPC namespace"
1209	depends on (SYSVIPC || POSIX_MQUEUE)
1210	default y
1211	help
1212	  In this namespace tasks work with IPC ids which correspond to
1213	  different IPC objects in different namespaces.
1214
1215config USER_NS
1216	bool "User namespace"
1217	default n
1218	help
1219	  This allows containers, i.e. vservers, to use user namespaces
1220	  to provide different user info for different servers.
1221
1222	  When user namespaces are enabled in the kernel it is
1223	  recommended that the MEMCG option also be enabled and that
1224	  user-space use the memory control groups to limit the amount
1225	  of memory a memory unprivileged users can use.
1226
1227	  If unsure, say N.
1228
1229config PID_NS
1230	bool "PID Namespaces"
1231	default y
1232	help
1233	  Support process id namespaces.  This allows having multiple
1234	  processes with the same pid as long as they are in different
1235	  pid namespaces.  This is a building block of containers.
1236
1237config NET_NS
1238	bool "Network namespace"
1239	depends on NET
1240	default y
1241	help
1242	  Allow user space to create what appear to be multiple instances
1243	  of the network stack.
1244
1245endif # NAMESPACES
1246
1247config CHECKPOINT_RESTORE
1248	bool "Checkpoint/restore support"
1249	depends on PROC_FS
1250	select PROC_CHILDREN
1251	select KCMP
1252	default n
1253	help
1254	  Enables additional kernel features in a sake of checkpoint/restore.
1255	  In particular it adds auxiliary prctl codes to setup process text,
1256	  data and heap segment sizes, and a few additional /proc filesystem
1257	  entries.
1258
1259	  If unsure, say N here.
1260
1261config SCHED_AUTOGROUP
1262	bool "Automatic process group scheduling"
1263	select CGROUPS
1264	select CGROUP_SCHED
1265	select FAIR_GROUP_SCHED
1266	help
1267	  This option optimizes the scheduler for common desktop workloads by
1268	  automatically creating and populating task groups.  This separation
1269	  of workloads isolates aggressive CPU burners (like build jobs) from
1270	  desktop applications.  Task group autogeneration is currently based
1271	  upon task session.
1272
1273config RELAY
1274	bool "Kernel->user space relay support (formerly relayfs)"
1275	select IRQ_WORK
1276	help
1277	  This option enables support for relay interface support in
1278	  certain file systems (such as debugfs).
1279	  It is designed to provide an efficient mechanism for tools and
1280	  facilities to relay large amounts of data from kernel space to
1281	  user space.
1282
1283	  If unsure, say N.
1284
1285config BLK_DEV_INITRD
1286	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1287	help
1288	  The initial RAM filesystem is a ramfs which is loaded by the
1289	  boot loader (loadlin or lilo) and that is mounted as root
1290	  before the normal boot procedure. It is typically used to
1291	  load modules needed to mount the "real" root file system,
1292	  etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1293
1294	  If RAM disk support (BLK_DEV_RAM) is also included, this
1295	  also enables initial RAM disk (initrd) support and adds
1296	  15 Kbytes (more on some other architectures) to the kernel size.
1297
1298	  If unsure say Y.
1299
1300if BLK_DEV_INITRD
1301
1302source "usr/Kconfig"
1303
1304endif
1305
1306config BOOT_CONFIG
1307	bool "Boot config support"
1308	select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED
1309	help
1310	  Extra boot config allows system admin to pass a config file as
1311	  complemental extension of kernel cmdline when booting.
1312	  The boot config file must be attached at the end of initramfs
1313	  with checksum, size and magic word.
1314	  See <file:Documentation/admin-guide/bootconfig.rst> for details.
1315
1316	  If unsure, say Y.
1317
1318config BOOT_CONFIG_FORCE
1319	bool "Force unconditional bootconfig processing"
1320	depends on BOOT_CONFIG
1321	default y if BOOT_CONFIG_EMBED
1322	help
1323	  With this Kconfig option set, BOOT_CONFIG processing is carried
1324	  out even when the "bootconfig" kernel-boot parameter is omitted.
1325	  In fact, with this Kconfig option set, there is no way to
1326	  make the kernel ignore the BOOT_CONFIG-supplied kernel-boot
1327	  parameters.
1328
1329	  If unsure, say N.
1330
1331config BOOT_CONFIG_EMBED
1332	bool "Embed bootconfig file in the kernel"
1333	depends on BOOT_CONFIG
1334	help
1335	  Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the
1336	  kernel. Usually, the bootconfig file is loaded with the initrd
1337	  image. But if the system doesn't support initrd, this option will
1338	  help you by embedding a bootconfig file while building the kernel.
1339
1340	  If unsure, say N.
1341
1342config BOOT_CONFIG_EMBED_FILE
1343	string "Embedded bootconfig file path"
1344	depends on BOOT_CONFIG_EMBED
1345	help
1346	  Specify a bootconfig file which will be embedded to the kernel.
1347	  This bootconfig will be used if there is no initrd or no other
1348	  bootconfig in the initrd.
1349
1350config INITRAMFS_PRESERVE_MTIME
1351	bool "Preserve cpio archive mtimes in initramfs"
1352	default y
1353	help
1354	  Each entry in an initramfs cpio archive carries an mtime value. When
1355	  enabled, extracted cpio items take this mtime, with directory mtime
1356	  setting deferred until after creation of any child entries.
1357
1358	  If unsure, say Y.
1359
1360choice
1361	prompt "Compiler optimization level"
1362	default CC_OPTIMIZE_FOR_PERFORMANCE
1363
1364config CC_OPTIMIZE_FOR_PERFORMANCE
1365	bool "Optimize for performance (-O2)"
1366	help
1367	  This is the default optimization level for the kernel, building
1368	  with the "-O2" compiler flag for best performance and most
1369	  helpful compile-time warnings.
1370
1371config CC_OPTIMIZE_FOR_SIZE
1372	bool "Optimize for size (-Os)"
1373	help
1374	  Choosing this option will pass "-Os" to your compiler resulting
1375	  in a smaller kernel.
1376
1377endchoice
1378
1379config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1380	bool
1381	help
1382	  This requires that the arch annotates or otherwise protects
1383	  its external entry points from being discarded. Linker scripts
1384	  must also merge .text.*, .data.*, and .bss.* correctly into
1385	  output sections. Care must be taken not to pull in unrelated
1386	  sections (e.g., '.text.init'). Typically '.' in section names
1387	  is used to distinguish them from label names / C identifiers.
1388
1389config LD_DEAD_CODE_DATA_ELIMINATION
1390	bool "Dead code and data elimination (EXPERIMENTAL)"
1391	depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1392	depends on EXPERT
1393	depends on $(cc-option,-ffunction-sections -fdata-sections)
1394	depends on $(ld-option,--gc-sections)
1395	help
1396	  Enable this if you want to do dead code and data elimination with
1397	  the linker by compiling with -ffunction-sections -fdata-sections,
1398	  and linking with --gc-sections.
1399
1400	  This can reduce on disk and in-memory size of the kernel
1401	  code and static data, particularly for small configs and
1402	  on small systems. This has the possibility of introducing
1403	  silently broken kernel if the required annotations are not
1404	  present. This option is not well tested yet, so use at your
1405	  own risk.
1406
1407config LD_ORPHAN_WARN
1408	def_bool y
1409	depends on ARCH_WANT_LD_ORPHAN_WARN
1410	depends on $(ld-option,--orphan-handling=warn)
1411	depends on $(ld-option,--orphan-handling=error)
1412
1413config LD_ORPHAN_WARN_LEVEL
1414        string
1415        depends on LD_ORPHAN_WARN
1416        default "error" if WERROR
1417        default "warn"
1418
1419config SYSCTL
1420	bool
1421
1422config HAVE_UID16
1423	bool
1424
1425config SYSCTL_EXCEPTION_TRACE
1426	bool
1427	help
1428	  Enable support for /proc/sys/debug/exception-trace.
1429
1430config SYSCTL_ARCH_UNALIGN_NO_WARN
1431	bool
1432	help
1433	  Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1434	  Allows arch to define/use @no_unaligned_warning to possibly warn
1435	  about unaligned access emulation going on under the hood.
1436
1437config SYSCTL_ARCH_UNALIGN_ALLOW
1438	bool
1439	help
1440	  Enable support for /proc/sys/kernel/unaligned-trap
1441	  Allows arches to define/use @unaligned_enabled to runtime toggle
1442	  the unaligned access emulation.
1443	  see arch/parisc/kernel/unaligned.c for reference
1444
1445config HAVE_PCSPKR_PLATFORM
1446	bool
1447
1448# interpreter that classic socket filters depend on
1449config BPF
1450	bool
1451	select CRYPTO_LIB_SHA1
1452
1453menuconfig EXPERT
1454	bool "Configure standard kernel features (expert users)"
1455	# Unhide debug options, to make the on-by-default options visible
1456	select DEBUG_KERNEL
1457	help
1458	  This option allows certain base kernel options and settings
1459	  to be disabled or tweaked. This is for specialized
1460	  environments which can tolerate a "non-standard" kernel.
1461	  Only use this if you really know what you are doing.
1462
1463config UID16
1464	bool "Enable 16-bit UID system calls" if EXPERT
1465	depends on HAVE_UID16 && MULTIUSER
1466	default y
1467	help
1468	  This enables the legacy 16-bit UID syscall wrappers.
1469
1470config MULTIUSER
1471	bool "Multiple users, groups and capabilities support" if EXPERT
1472	default y
1473	help
1474	  This option enables support for non-root users, groups and
1475	  capabilities.
1476
1477	  If you say N here, all processes will run with UID 0, GID 0, and all
1478	  possible capabilities.  Saying N here also compiles out support for
1479	  system calls related to UIDs, GIDs, and capabilities, such as setuid,
1480	  setgid, and capset.
1481
1482	  If unsure, say Y here.
1483
1484config SGETMASK_SYSCALL
1485	bool "sgetmask/ssetmask syscalls support" if EXPERT
1486	def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1487	help
1488	  sys_sgetmask and sys_ssetmask are obsolete system calls
1489	  no longer supported in libc but still enabled by default in some
1490	  architectures.
1491
1492	  If unsure, leave the default option here.
1493
1494config SYSFS_SYSCALL
1495	bool "Sysfs syscall support" if EXPERT
1496	default y
1497	help
1498	  sys_sysfs is an obsolete system call no longer supported in libc.
1499	  Note that disabling this option is more secure but might break
1500	  compatibility with some systems.
1501
1502	  If unsure say Y here.
1503
1504config FHANDLE
1505	bool "open by fhandle syscalls" if EXPERT
1506	select EXPORTFS
1507	default y
1508	help
1509	  If you say Y here, a user level program will be able to map
1510	  file names to handle and then later use the handle for
1511	  different file system operations. This is useful in implementing
1512	  userspace file servers, which now track files using handles instead
1513	  of names. The handle would remain the same even if file names
1514	  get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1515	  syscalls.
1516
1517config POSIX_TIMERS
1518	bool "Posix Clocks & timers" if EXPERT
1519	default y
1520	help
1521	  This includes native support for POSIX timers to the kernel.
1522	  Some embedded systems have no use for them and therefore they
1523	  can be configured out to reduce the size of the kernel image.
1524
1525	  When this option is disabled, the following syscalls won't be
1526	  available: timer_create, timer_gettime: timer_getoverrun,
1527	  timer_settime, timer_delete, clock_adjtime, getitimer,
1528	  setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1529	  clock_getres and clock_nanosleep syscalls will be limited to
1530	  CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1531
1532	  If unsure say y.
1533
1534config PRINTK
1535	default y
1536	bool "Enable support for printk" if EXPERT
1537	select IRQ_WORK
1538	help
1539	  This option enables normal printk support. Removing it
1540	  eliminates most of the message strings from the kernel image
1541	  and makes the kernel more or less silent. As this makes it
1542	  very difficult to diagnose system problems, saying N here is
1543	  strongly discouraged.
1544
1545config BUG
1546	bool "BUG() support" if EXPERT
1547	default y
1548	help
1549	  Disabling this option eliminates support for BUG and WARN, reducing
1550	  the size of your kernel image and potentially quietly ignoring
1551	  numerous fatal conditions. You should only consider disabling this
1552	  option for embedded systems with no facilities for reporting errors.
1553	  Just say Y.
1554
1555config ELF_CORE
1556	depends on COREDUMP
1557	default y
1558	bool "Enable ELF core dumps" if EXPERT
1559	help
1560	  Enable support for generating core dumps. Disabling saves about 4k.
1561
1562
1563config PCSPKR_PLATFORM
1564	bool "Enable PC-Speaker support" if EXPERT
1565	depends on HAVE_PCSPKR_PLATFORM
1566	select I8253_LOCK
1567	default y
1568	help
1569	  This option allows to disable the internal PC-Speaker
1570	  support, saving some memory.
1571
1572config BASE_FULL
1573	default y
1574	bool "Enable full-sized data structures for core" if EXPERT
1575	help
1576	  Disabling this option reduces the size of miscellaneous core
1577	  kernel data structures. This saves memory on small machines,
1578	  but may reduce performance.
1579
1580config FUTEX
1581	bool "Enable futex support" if EXPERT
1582	depends on !(SPARC32 && SMP)
1583	default y
1584	imply RT_MUTEXES
1585	help
1586	  Disabling this option will cause the kernel to be built without
1587	  support for "fast userspace mutexes".  The resulting kernel may not
1588	  run glibc-based applications correctly.
1589
1590config FUTEX_PI
1591	bool
1592	depends on FUTEX && RT_MUTEXES
1593	default y
1594
1595config EPOLL
1596	bool "Enable eventpoll support" if EXPERT
1597	default y
1598	help
1599	  Disabling this option will cause the kernel to be built without
1600	  support for epoll family of system calls.
1601
1602config SIGNALFD
1603	bool "Enable signalfd() system call" if EXPERT
1604	default y
1605	help
1606	  Enable the signalfd() system call that allows to receive signals
1607	  on a file descriptor.
1608
1609	  If unsure, say Y.
1610
1611config TIMERFD
1612	bool "Enable timerfd() system call" if EXPERT
1613	default y
1614	help
1615	  Enable the timerfd() system call that allows to receive timer
1616	  events on a file descriptor.
1617
1618	  If unsure, say Y.
1619
1620config EVENTFD
1621	bool "Enable eventfd() system call" if EXPERT
1622	default y
1623	help
1624	  Enable the eventfd() system call that allows to receive both
1625	  kernel notification (ie. KAIO) or userspace notifications.
1626
1627	  If unsure, say Y.
1628
1629config SHMEM
1630	bool "Use full shmem filesystem" if EXPERT
1631	default y
1632	depends on MMU
1633	help
1634	  The shmem is an internal filesystem used to manage shared memory.
1635	  It is backed by swap and manages resource limits. It is also exported
1636	  to userspace as tmpfs if TMPFS is enabled. Disabling this
1637	  option replaces shmem and tmpfs with the much simpler ramfs code,
1638	  which may be appropriate on small systems without swap.
1639
1640config AIO
1641	bool "Enable AIO support" if EXPERT
1642	default y
1643	help
1644	  This option enables POSIX asynchronous I/O which may by used
1645	  by some high performance threaded applications. Disabling
1646	  this option saves about 7k.
1647
1648config IO_URING
1649	bool "Enable IO uring support" if EXPERT
1650	select IO_WQ
1651	default y
1652	help
1653	  This option enables support for the io_uring interface, enabling
1654	  applications to submit and complete IO through submission and
1655	  completion rings that are shared between the kernel and application.
1656
1657config ADVISE_SYSCALLS
1658	bool "Enable madvise/fadvise syscalls" if EXPERT
1659	default y
1660	help
1661	  This option enables the madvise and fadvise syscalls, used by
1662	  applications to advise the kernel about their future memory or file
1663	  usage, improving performance. If building an embedded system where no
1664	  applications use these syscalls, you can disable this option to save
1665	  space.
1666
1667config MEMBARRIER
1668	bool "Enable membarrier() system call" if EXPERT
1669	default y
1670	help
1671	  Enable the membarrier() system call that allows issuing memory
1672	  barriers across all running threads, which can be used to distribute
1673	  the cost of user-space memory barriers asymmetrically by transforming
1674	  pairs of memory barriers into pairs consisting of membarrier() and a
1675	  compiler barrier.
1676
1677	  If unsure, say Y.
1678
1679config KALLSYMS
1680	bool "Load all symbols for debugging/ksymoops" if EXPERT
1681	default y
1682	help
1683	  Say Y here to let the kernel print out symbolic crash information and
1684	  symbolic stack backtraces. This increases the size of the kernel
1685	  somewhat, as all symbols have to be loaded into the kernel image.
1686
1687config KALLSYMS_SELFTEST
1688	bool "Test the basic functions and performance of kallsyms"
1689	depends on KALLSYMS
1690	default n
1691	help
1692	  Test the basic functions and performance of some interfaces, such as
1693	  kallsyms_lookup_name. It also calculates the compression rate of the
1694	  kallsyms compression algorithm for the current symbol set.
1695
1696	  Start self-test automatically after system startup. Suggest executing
1697	  "dmesg | grep kallsyms_selftest" to collect test results. "finish" is
1698	  displayed in the last line, indicating that the test is complete.
1699
1700config KALLSYMS_ALL
1701	bool "Include all symbols in kallsyms"
1702	depends on DEBUG_KERNEL && KALLSYMS
1703	help
1704	  Normally kallsyms only contains the symbols of functions for nicer
1705	  OOPS messages and backtraces (i.e., symbols from the text and inittext
1706	  sections). This is sufficient for most cases. And only if you want to
1707	  enable kernel live patching, or other less common use cases (e.g.,
1708	  when a debugger is used) all symbols are required (i.e., names of
1709	  variables from the data sections, etc).
1710
1711	  This option makes sure that all symbols are loaded into the kernel
1712	  image (i.e., symbols from all sections) in cost of increased kernel
1713	  size (depending on the kernel configuration, it may be 300KiB or
1714	  something like this).
1715
1716	  Say N unless you really need all symbols, or kernel live patching.
1717
1718config KALLSYMS_ABSOLUTE_PERCPU
1719	bool
1720	depends on KALLSYMS
1721	default X86_64 && SMP
1722
1723config KALLSYMS_BASE_RELATIVE
1724	bool
1725	depends on KALLSYMS
1726	default !IA64
1727	help
1728	  Instead of emitting them as absolute values in the native word size,
1729	  emit the symbol references in the kallsyms table as 32-bit entries,
1730	  each containing a relative value in the range [base, base + U32_MAX]
1731	  or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1732	  an absolute value in the range [0, S32_MAX] or a relative value in the
1733	  range [base, base + S32_MAX], where base is the lowest relative symbol
1734	  address encountered in the image.
1735
1736	  On 64-bit builds, this reduces the size of the address table by 50%,
1737	  but more importantly, it results in entries whose values are build
1738	  time constants, and no relocation pass is required at runtime to fix
1739	  up the entries based on the runtime load address of the kernel.
1740
1741# end of the "standard kernel features (expert users)" menu
1742
1743# syscall, maps, verifier
1744
1745config ARCH_HAS_MEMBARRIER_CALLBACKS
1746	bool
1747
1748config ARCH_HAS_MEMBARRIER_SYNC_CORE
1749	bool
1750
1751config KCMP
1752	bool "Enable kcmp() system call" if EXPERT
1753	help
1754	  Enable the kernel resource comparison system call. It provides
1755	  user-space with the ability to compare two processes to see if they
1756	  share a common resource, such as a file descriptor or even virtual
1757	  memory space.
1758
1759	  If unsure, say N.
1760
1761config RSEQ
1762	bool "Enable rseq() system call" if EXPERT
1763	default y
1764	depends on HAVE_RSEQ
1765	select MEMBARRIER
1766	help
1767	  Enable the restartable sequences system call. It provides a
1768	  user-space cache for the current CPU number value, which
1769	  speeds up getting the current CPU number from user-space,
1770	  as well as an ABI to speed up user-space operations on
1771	  per-CPU data.
1772
1773	  If unsure, say Y.
1774
1775config CACHESTAT_SYSCALL
1776	bool "Enable cachestat() system call" if EXPERT
1777	default y
1778	help
1779	  Enable the cachestat system call, which queries the page cache
1780	  statistics of a file (number of cached pages, dirty pages,
1781	  pages marked for writeback, (recently) evicted pages).
1782
1783	  If unsure say Y here.
1784
1785config DEBUG_RSEQ
1786	default n
1787	bool "Enabled debugging of rseq() system call" if EXPERT
1788	depends on RSEQ && DEBUG_KERNEL
1789	help
1790	  Enable extra debugging checks for the rseq system call.
1791
1792	  If unsure, say N.
1793
1794config HAVE_PERF_EVENTS
1795	bool
1796	help
1797	  See tools/perf/design.txt for details.
1798
1799config GUEST_PERF_EVENTS
1800	bool
1801	depends on HAVE_PERF_EVENTS
1802
1803config PERF_USE_VMALLOC
1804	bool
1805	help
1806	  See tools/perf/design.txt for details
1807
1808config PC104
1809	bool "PC/104 support" if EXPERT
1810	help
1811	  Expose PC/104 form factor device drivers and options available for
1812	  selection and configuration. Enable this option if your target
1813	  machine has a PC/104 bus.
1814
1815menu "Kernel Performance Events And Counters"
1816
1817config PERF_EVENTS
1818	bool "Kernel performance events and counters"
1819	default y if PROFILING
1820	depends on HAVE_PERF_EVENTS
1821	select IRQ_WORK
1822	help
1823	  Enable kernel support for various performance events provided
1824	  by software and hardware.
1825
1826	  Software events are supported either built-in or via the
1827	  use of generic tracepoints.
1828
1829	  Most modern CPUs support performance events via performance
1830	  counter registers. These registers count the number of certain
1831	  types of hw events: such as instructions executed, cachemisses
1832	  suffered, or branches mis-predicted - without slowing down the
1833	  kernel or applications. These registers can also trigger interrupts
1834	  when a threshold number of events have passed - and can thus be
1835	  used to profile the code that runs on that CPU.
1836
1837	  The Linux Performance Event subsystem provides an abstraction of
1838	  these software and hardware event capabilities, available via a
1839	  system call and used by the "perf" utility in tools/perf/. It
1840	  provides per task and per CPU counters, and it provides event
1841	  capabilities on top of those.
1842
1843	  Say Y if unsure.
1844
1845config DEBUG_PERF_USE_VMALLOC
1846	default n
1847	bool "Debug: use vmalloc to back perf mmap() buffers"
1848	depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1849	select PERF_USE_VMALLOC
1850	help
1851	  Use vmalloc memory to back perf mmap() buffers.
1852
1853	  Mostly useful for debugging the vmalloc code on platforms
1854	  that don't require it.
1855
1856	  Say N if unsure.
1857
1858endmenu
1859
1860config SYSTEM_DATA_VERIFICATION
1861	def_bool n
1862	select SYSTEM_TRUSTED_KEYRING
1863	select KEYS
1864	select CRYPTO
1865	select CRYPTO_RSA
1866	select ASYMMETRIC_KEY_TYPE
1867	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1868	select ASN1
1869	select OID_REGISTRY
1870	select X509_CERTIFICATE_PARSER
1871	select PKCS7_MESSAGE_PARSER
1872	help
1873	  Provide PKCS#7 message verification using the contents of the system
1874	  trusted keyring to provide public keys.  This then can be used for
1875	  module verification, kexec image verification and firmware blob
1876	  verification.
1877
1878config PROFILING
1879	bool "Profiling support"
1880	help
1881	  Say Y here to enable the extended profiling support mechanisms used
1882	  by profilers.
1883
1884config RUST
1885	bool "Rust support"
1886	depends on HAVE_RUST
1887	depends on RUST_IS_AVAILABLE
1888	depends on !MODVERSIONS
1889	depends on !GCC_PLUGINS
1890	depends on !RANDSTRUCT
1891	depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE
1892	select CONSTRUCTORS
1893	help
1894	  Enables Rust support in the kernel.
1895
1896	  This allows other Rust-related options, like drivers written in Rust,
1897	  to be selected.
1898
1899	  It is also required to be able to load external kernel modules
1900	  written in Rust.
1901
1902	  See Documentation/rust/ for more information.
1903
1904	  If unsure, say N.
1905
1906config RUSTC_VERSION_TEXT
1907	string
1908	depends on RUST
1909	default $(shell,command -v $(RUSTC) >/dev/null 2>&1 && $(RUSTC) --version || echo n)
1910
1911config BINDGEN_VERSION_TEXT
1912	string
1913	depends on RUST
1914	default $(shell,command -v $(BINDGEN) >/dev/null 2>&1 && $(BINDGEN) --version || echo n)
1915
1916#
1917# Place an empty function call at each tracepoint site. Can be
1918# dynamically changed for a probe function.
1919#
1920config TRACEPOINTS
1921	bool
1922
1923source "kernel/Kconfig.kexec"
1924
1925endmenu		# General setup
1926
1927source "arch/Kconfig"
1928
1929config RT_MUTEXES
1930	bool
1931	default y if PREEMPT_RT
1932
1933config BASE_SMALL
1934	int
1935	default 0 if BASE_FULL
1936	default 1 if !BASE_FULL
1937
1938config MODULE_SIG_FORMAT
1939	def_bool n
1940	select SYSTEM_DATA_VERIFICATION
1941
1942source "kernel/module/Kconfig"
1943
1944config INIT_ALL_POSSIBLE
1945	bool
1946	help
1947	  Back when each arch used to define their own cpu_online_mask and
1948	  cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1949	  with all 1s, and others with all 0s.  When they were centralised,
1950	  it was better to provide this option than to break all the archs
1951	  and have several arch maintainers pursuing me down dark alleys.
1952
1953source "block/Kconfig"
1954
1955config PREEMPT_NOTIFIERS
1956	bool
1957
1958config PADATA
1959	depends on SMP
1960	bool
1961
1962config ASN1
1963	tristate
1964	help
1965	  Build a simple ASN.1 grammar compiler that produces a bytecode output
1966	  that can be interpreted by the ASN.1 stream decoder and used to
1967	  inform it as to what tags are to be expected in a stream and what
1968	  functions to call on what tags.
1969
1970source "kernel/Kconfig.locks"
1971
1972config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
1973	bool
1974
1975config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
1976	bool
1977
1978# It may be useful for an architecture to override the definitions of the
1979# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
1980# and the COMPAT_ variants in <linux/compat.h>, in particular to use a
1981# different calling convention for syscalls. They can also override the
1982# macros for not-implemented syscalls in kernel/sys_ni.c and
1983# kernel/time/posix-stubs.c. All these overrides need to be available in
1984# <asm/syscall_wrapper.h>.
1985config ARCH_HAS_SYSCALL_WRAPPER
1986	def_bool n
1987