xref: /openbmc/linux/init/Kconfig (revision 877d95dc)
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 CC_CAN_LINK
64	bool
65	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT
66	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag))
67
68config CC_CAN_LINK_STATIC
69	bool
70	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT
71	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static)
72
73config CC_HAS_ASM_GOTO
74	def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
75
76config CC_HAS_ASM_GOTO_OUTPUT
77	depends on CC_HAS_ASM_GOTO
78	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)
79
80config CC_HAS_ASM_GOTO_TIED_OUTPUT
81	depends on CC_HAS_ASM_GOTO_OUTPUT
82	# Detect buggy gcc and clang, fixed in gcc-11 clang-14.
83	def_bool $(success,echo 'int foo(int *x) { asm goto (".long (%l[bar]) - .\n": "+m"(*x) ::: bar); return *x; bar: return 0; }' | $CC -x c - -c -o /dev/null)
84
85config TOOLS_SUPPORT_RELR
86	def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
87
88config CC_HAS_ASM_INLINE
89	def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
90
91config CC_HAS_NO_PROFILE_FN_ATTR
92	def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
93
94config PAHOLE_VERSION
95	int
96	default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))
97
98config CONSTRUCTORS
99	bool
100
101config IRQ_WORK
102	bool
103
104config BUILDTIME_TABLE_SORT
105	bool
106
107config THREAD_INFO_IN_TASK
108	bool
109	help
110	  Select this to move thread_info off the stack into task_struct.  To
111	  make this work, an arch will need to remove all thread_info fields
112	  except flags and fix any runtime bugs.
113
114	  One subtle change that will be needed is to use try_get_task_stack()
115	  and put_task_stack() in save_thread_stack_tsk() and get_wchan().
116
117menu "General setup"
118
119config BROKEN
120	bool
121
122config BROKEN_ON_SMP
123	bool
124	depends on BROKEN || !SMP
125	default y
126
127config INIT_ENV_ARG_LIMIT
128	int
129	default 32 if !UML
130	default 128 if UML
131	help
132	  Maximum of each of the number of arguments and environment
133	  variables passed to init from the kernel command line.
134
135config COMPILE_TEST
136	bool "Compile also drivers which will not load"
137	depends on HAS_IOMEM
138	help
139	  Some drivers can be compiled on a different platform than they are
140	  intended to be run on. Despite they cannot be loaded there (or even
141	  when they load they cannot be used due to missing HW support),
142	  developers still, opposing to distributors, might want to build such
143	  drivers to compile-test them.
144
145	  If you are a developer and want to build everything available, say Y
146	  here. If you are a user/distributor, say N here to exclude useless
147	  drivers to be distributed.
148
149config WERROR
150	bool "Compile the kernel with warnings as errors"
151	default COMPILE_TEST
152	help
153	  A kernel build should not cause any compiler warnings, and this
154	  enables the '-Werror' flag to enforce that rule by default.
155
156	  However, if you have a new (or very old) compiler with odd and
157	  unusual warnings, or you have some architecture with problems,
158	  you may need to disable this config option in order to
159	  successfully build the kernel.
160
161	  If in doubt, say Y.
162
163config UAPI_HEADER_TEST
164	bool "Compile test UAPI headers"
165	depends on HEADERS_INSTALL && CC_CAN_LINK
166	help
167	  Compile test headers exported to user-space to ensure they are
168	  self-contained, i.e. compilable as standalone units.
169
170	  If you are a developer or tester and want to ensure the exported
171	  headers are self-contained, say Y here. Otherwise, choose N.
172
173config LOCALVERSION
174	string "Local version - append to kernel release"
175	help
176	  Append an extra string to the end of your kernel version.
177	  This will show up when you type uname, for example.
178	  The string you set here will be appended after the contents of
179	  any files with a filename matching localversion* in your
180	  object and source tree, in that order.  Your total string can
181	  be a maximum of 64 characters.
182
183config LOCALVERSION_AUTO
184	bool "Automatically append version information to the version string"
185	default y
186	depends on !COMPILE_TEST
187	help
188	  This will try to automatically determine if the current tree is a
189	  release tree by looking for git tags that belong to the current
190	  top of tree revision.
191
192	  A string of the format -gxxxxxxxx will be added to the localversion
193	  if a git-based tree is found.  The string generated by this will be
194	  appended after any matching localversion* files, and after the value
195	  set in CONFIG_LOCALVERSION.
196
197	  (The actual string used here is the first eight characters produced
198	  by running the command:
199
200	    $ git rev-parse --verify HEAD
201
202	  which is done within the script "scripts/setlocalversion".)
203
204config BUILD_SALT
205	string "Build ID Salt"
206	default ""
207	help
208	  The build ID is used to link binaries and their debug info. Setting
209	  this option will use the value in the calculation of the build id.
210	  This is mostly useful for distributions which want to ensure the
211	  build is unique between builds. It's safe to leave the default.
212
213config HAVE_KERNEL_GZIP
214	bool
215
216config HAVE_KERNEL_BZIP2
217	bool
218
219config HAVE_KERNEL_LZMA
220	bool
221
222config HAVE_KERNEL_XZ
223	bool
224
225config HAVE_KERNEL_LZO
226	bool
227
228config HAVE_KERNEL_LZ4
229	bool
230
231config HAVE_KERNEL_ZSTD
232	bool
233
234config HAVE_KERNEL_UNCOMPRESSED
235	bool
236
237choice
238	prompt "Kernel compression mode"
239	default KERNEL_GZIP
240	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
241	help
242	  The linux kernel is a kind of self-extracting executable.
243	  Several compression algorithms are available, which differ
244	  in efficiency, compression and decompression speed.
245	  Compression speed is only relevant when building a kernel.
246	  Decompression speed is relevant at each boot.
247
248	  If you have any problems with bzip2 or lzma compressed
249	  kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
250	  version of this functionality (bzip2 only), for 2.4, was
251	  supplied by Christian Ludwig)
252
253	  High compression options are mostly useful for users, who
254	  are low on disk space (embedded systems), but for whom ram
255	  size matters less.
256
257	  If in doubt, select 'gzip'
258
259config KERNEL_GZIP
260	bool "Gzip"
261	depends on HAVE_KERNEL_GZIP
262	help
263	  The old and tried gzip compression. It provides a good balance
264	  between compression ratio and decompression speed.
265
266config KERNEL_BZIP2
267	bool "Bzip2"
268	depends on HAVE_KERNEL_BZIP2
269	help
270	  Its compression ratio and speed is intermediate.
271	  Decompression speed is slowest among the choices.  The kernel
272	  size is about 10% smaller with bzip2, in comparison to gzip.
273	  Bzip2 uses a large amount of memory. For modern kernels you
274	  will need at least 8MB RAM or more for booting.
275
276config KERNEL_LZMA
277	bool "LZMA"
278	depends on HAVE_KERNEL_LZMA
279	help
280	  This compression algorithm's ratio is best.  Decompression speed
281	  is between gzip and bzip2.  Compression is slowest.
282	  The kernel size is about 33% smaller with LZMA in comparison to gzip.
283
284config KERNEL_XZ
285	bool "XZ"
286	depends on HAVE_KERNEL_XZ
287	help
288	  XZ uses the LZMA2 algorithm and instruction set specific
289	  BCJ filters which can improve compression ratio of executable
290	  code. The size of the kernel is about 30% smaller with XZ in
291	  comparison to gzip. On architectures for which there is a BCJ
292	  filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
293	  will create a few percent smaller kernel than plain LZMA.
294
295	  The speed is about the same as with LZMA: The decompression
296	  speed of XZ is better than that of bzip2 but worse than gzip
297	  and LZO. Compression is slow.
298
299config KERNEL_LZO
300	bool "LZO"
301	depends on HAVE_KERNEL_LZO
302	help
303	  Its compression ratio is the poorest among the choices. The kernel
304	  size is about 10% bigger than gzip; however its speed
305	  (both compression and decompression) is the fastest.
306
307config KERNEL_LZ4
308	bool "LZ4"
309	depends on HAVE_KERNEL_LZ4
310	help
311	  LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
312	  A preliminary version of LZ4 de/compression tool is available at
313	  <https://code.google.com/p/lz4/>.
314
315	  Its compression ratio is worse than LZO. The size of the kernel
316	  is about 8% bigger than LZO. But the decompression speed is
317	  faster than LZO.
318
319config KERNEL_ZSTD
320	bool "ZSTD"
321	depends on HAVE_KERNEL_ZSTD
322	help
323	  ZSTD is a compression algorithm targeting intermediate compression
324	  with fast decompression speed. It will compress better than GZIP and
325	  decompress around the same speed as LZO, but slower than LZ4. You
326	  will need at least 192 KB RAM or more for booting. The zstd command
327	  line tool is required for compression.
328
329config KERNEL_UNCOMPRESSED
330	bool "None"
331	depends on HAVE_KERNEL_UNCOMPRESSED
332	help
333	  Produce uncompressed kernel image. This option is usually not what
334	  you want. It is useful for debugging the kernel in slow simulation
335	  environments, where decompressing and moving the kernel is awfully
336	  slow. This option allows early boot code to skip the decompressor
337	  and jump right at uncompressed kernel image.
338
339endchoice
340
341config DEFAULT_INIT
342	string "Default init path"
343	default ""
344	help
345	  This option determines the default init for the system if no init=
346	  option is passed on the kernel command line. If the requested path is
347	  not present, we will still then move on to attempting further
348	  locations (e.g. /sbin/init, etc). If this is empty, we will just use
349	  the fallback list when init= is not passed.
350
351config DEFAULT_HOSTNAME
352	string "Default hostname"
353	default "(none)"
354	help
355	  This option determines the default system hostname before userspace
356	  calls sethostname(2). The kernel traditionally uses "(none)" here,
357	  but you may wish to use a different default here to make a minimal
358	  system more usable with less configuration.
359
360config SYSVIPC
361	bool "System V IPC"
362	help
363	  Inter Process Communication is a suite of library functions and
364	  system calls which let processes (running programs) synchronize and
365	  exchange information. It is generally considered to be a good thing,
366	  and some programs won't run unless you say Y here. In particular, if
367	  you want to run the DOS emulator dosemu under Linux (read the
368	  DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
369	  you'll need to say Y here.
370
371	  You can find documentation about IPC with "info ipc" and also in
372	  section 6.4 of the Linux Programmer's Guide, available from
373	  <http://www.tldp.org/guides.html>.
374
375config SYSVIPC_SYSCTL
376	bool
377	depends on SYSVIPC
378	depends on SYSCTL
379	default y
380
381config SYSVIPC_COMPAT
382	def_bool y
383	depends on COMPAT && SYSVIPC
384
385config POSIX_MQUEUE
386	bool "POSIX Message Queues"
387	depends on NET
388	help
389	  POSIX variant of message queues is a part of IPC. In POSIX message
390	  queues every message has a priority which decides about succession
391	  of receiving it by a process. If you want to compile and run
392	  programs written e.g. for Solaris with use of its POSIX message
393	  queues (functions mq_*) say Y here.
394
395	  POSIX message queues are visible as a filesystem called 'mqueue'
396	  and can be mounted somewhere if you want to do filesystem
397	  operations on message queues.
398
399	  If unsure, say Y.
400
401config POSIX_MQUEUE_SYSCTL
402	bool
403	depends on POSIX_MQUEUE
404	depends on SYSCTL
405	default y
406
407config WATCH_QUEUE
408	bool "General notification queue"
409	default n
410	help
411
412	  This is a general notification queue for the kernel to pass events to
413	  userspace by splicing them into pipes.  It can be used in conjunction
414	  with watches for key/keyring change notifications and device
415	  notifications.
416
417	  See Documentation/core-api/watch_queue.rst
418
419config CROSS_MEMORY_ATTACH
420	bool "Enable process_vm_readv/writev syscalls"
421	depends on MMU
422	default y
423	help
424	  Enabling this option adds the system calls process_vm_readv and
425	  process_vm_writev which allow a process with the correct privileges
426	  to directly read from or write to another process' address space.
427	  See the man page for more details.
428
429config USELIB
430	bool "uselib syscall (for libc5 and earlier)"
431	default ALPHA || M68K || SPARC
432	help
433	  This option enables the uselib syscall, a system call used in the
434	  dynamic linker from libc5 and earlier.  glibc does not use this
435	  system call.  If you intend to run programs built on libc5 or
436	  earlier, you may need to enable this syscall.  Current systems
437	  running glibc can safely disable this.
438
439config AUDIT
440	bool "Auditing support"
441	depends on NET
442	help
443	  Enable auditing infrastructure that can be used with another
444	  kernel subsystem, such as SELinux (which requires this for
445	  logging of avc messages output).  System call auditing is included
446	  on architectures which support it.
447
448config HAVE_ARCH_AUDITSYSCALL
449	bool
450
451config AUDITSYSCALL
452	def_bool y
453	depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
454	select FSNOTIFY
455
456source "kernel/irq/Kconfig"
457source "kernel/time/Kconfig"
458source "kernel/bpf/Kconfig"
459source "kernel/Kconfig.preempt"
460
461menu "CPU/Task time and stats accounting"
462
463config VIRT_CPU_ACCOUNTING
464	bool
465
466choice
467	prompt "Cputime accounting"
468	default TICK_CPU_ACCOUNTING if !PPC64
469	default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
470
471# Kind of a stub config for the pure tick based cputime accounting
472config TICK_CPU_ACCOUNTING
473	bool "Simple tick based cputime accounting"
474	depends on !S390 && !NO_HZ_FULL
475	help
476	  This is the basic tick based cputime accounting that maintains
477	  statistics about user, system and idle time spent on per jiffies
478	  granularity.
479
480	  If unsure, say Y.
481
482config VIRT_CPU_ACCOUNTING_NATIVE
483	bool "Deterministic task and CPU time accounting"
484	depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
485	select VIRT_CPU_ACCOUNTING
486	help
487	  Select this option to enable more accurate task and CPU time
488	  accounting.  This is done by reading a CPU counter on each
489	  kernel entry and exit and on transitions within the kernel
490	  between system, softirq and hardirq state, so there is a
491	  small performance impact.  In the case of s390 or IBM POWER > 5,
492	  this also enables accounting of stolen time on logically-partitioned
493	  systems.
494
495config VIRT_CPU_ACCOUNTING_GEN
496	bool "Full dynticks CPU time accounting"
497	depends on HAVE_CONTEXT_TRACKING_USER
498	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
499	depends on GENERIC_CLOCKEVENTS
500	select VIRT_CPU_ACCOUNTING
501	select CONTEXT_TRACKING_USER
502	help
503	  Select this option to enable task and CPU time accounting on full
504	  dynticks systems. This accounting is implemented by watching every
505	  kernel-user boundaries using the context tracking subsystem.
506	  The accounting is thus performed at the expense of some significant
507	  overhead.
508
509	  For now this is only useful if you are working on the full
510	  dynticks subsystem development.
511
512	  If unsure, say N.
513
514endchoice
515
516config IRQ_TIME_ACCOUNTING
517	bool "Fine granularity task level IRQ time accounting"
518	depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
519	help
520	  Select this option to enable fine granularity task irq time
521	  accounting. This is done by reading a timestamp on each
522	  transitions between softirq and hardirq state, so there can be a
523	  small performance impact.
524
525	  If in doubt, say N here.
526
527config HAVE_SCHED_AVG_IRQ
528	def_bool y
529	depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
530	depends on SMP
531
532config SCHED_THERMAL_PRESSURE
533	bool
534	default y if ARM && ARM_CPU_TOPOLOGY
535	default y if ARM64
536	depends on SMP
537	depends on CPU_FREQ_THERMAL
538	help
539	  Select this option to enable thermal pressure accounting in the
540	  scheduler. Thermal pressure is the value conveyed to the scheduler
541	  that reflects the reduction in CPU compute capacity resulted from
542	  thermal throttling. Thermal throttling occurs when the performance of
543	  a CPU is capped due to high operating temperatures.
544
545	  If selected, the scheduler will be able to balance tasks accordingly,
546	  i.e. put less load on throttled CPUs than on non/less throttled ones.
547
548	  This requires the architecture to implement
549	  arch_update_thermal_pressure() and arch_scale_thermal_pressure().
550
551config BSD_PROCESS_ACCT
552	bool "BSD Process Accounting"
553	depends on MULTIUSER
554	help
555	  If you say Y here, a user level program will be able to instruct the
556	  kernel (via a special system call) to write process accounting
557	  information to a file: whenever a process exits, information about
558	  that process will be appended to the file by the kernel.  The
559	  information includes things such as creation time, owning user,
560	  command name, memory usage, controlling terminal etc. (the complete
561	  list is in the struct acct in <file:include/linux/acct.h>).  It is
562	  up to the user level program to do useful things with this
563	  information.  This is generally a good idea, so say Y.
564
565config BSD_PROCESS_ACCT_V3
566	bool "BSD Process Accounting version 3 file format"
567	depends on BSD_PROCESS_ACCT
568	default n
569	help
570	  If you say Y here, the process accounting information is written
571	  in a new file format that also logs the process IDs of each
572	  process and its parent. Note that this file format is incompatible
573	  with previous v0/v1/v2 file formats, so you will need updated tools
574	  for processing it. A preliminary version of these tools is available
575	  at <http://www.gnu.org/software/acct/>.
576
577config TASKSTATS
578	bool "Export task/process statistics through netlink"
579	depends on NET
580	depends on MULTIUSER
581	default n
582	help
583	  Export selected statistics for tasks/processes through the
584	  generic netlink interface. Unlike BSD process accounting, the
585	  statistics are available during the lifetime of tasks/processes as
586	  responses to commands. Like BSD accounting, they are sent to user
587	  space on task exit.
588
589	  Say N if unsure.
590
591config TASK_DELAY_ACCT
592	bool "Enable per-task delay accounting"
593	depends on TASKSTATS
594	select SCHED_INFO
595	help
596	  Collect information on time spent by a task waiting for system
597	  resources like cpu, synchronous block I/O completion and swapping
598	  in pages. Such statistics can help in setting a task's priorities
599	  relative to other tasks for cpu, io, rss limits etc.
600
601	  Say N if unsure.
602
603config TASK_XACCT
604	bool "Enable extended accounting over taskstats"
605	depends on TASKSTATS
606	help
607	  Collect extended task accounting data and send the data
608	  to userland for processing over the taskstats interface.
609
610	  Say N if unsure.
611
612config TASK_IO_ACCOUNTING
613	bool "Enable per-task storage I/O accounting"
614	depends on TASK_XACCT
615	help
616	  Collect information on the number of bytes of storage I/O which this
617	  task has caused.
618
619	  Say N if unsure.
620
621config PSI
622	bool "Pressure stall information tracking"
623	help
624	  Collect metrics that indicate how overcommitted the CPU, memory,
625	  and IO capacity are in the system.
626
627	  If you say Y here, the kernel will create /proc/pressure/ with the
628	  pressure statistics files cpu, memory, and io. These will indicate
629	  the share of walltime in which some or all tasks in the system are
630	  delayed due to contention of the respective resource.
631
632	  In kernels with cgroup support, cgroups (cgroup2 only) will
633	  have cpu.pressure, memory.pressure, and io.pressure files,
634	  which aggregate pressure stalls for the grouped tasks only.
635
636	  For more details see Documentation/accounting/psi.rst.
637
638	  Say N if unsure.
639
640config PSI_DEFAULT_DISABLED
641	bool "Require boot parameter to enable pressure stall information tracking"
642	default n
643	depends on PSI
644	help
645	  If set, pressure stall information tracking will be disabled
646	  per default but can be enabled through passing psi=1 on the
647	  kernel commandline during boot.
648
649	  This feature adds some code to the task wakeup and sleep
650	  paths of the scheduler. The overhead is too low to affect
651	  common scheduling-intense workloads in practice (such as
652	  webservers, memcache), but it does show up in artificial
653	  scheduler stress tests, such as hackbench.
654
655	  If you are paranoid and not sure what the kernel will be
656	  used for, say Y.
657
658	  Say N if unsure.
659
660endmenu # "CPU/Task time and stats accounting"
661
662config CPU_ISOLATION
663	bool "CPU isolation"
664	depends on SMP || COMPILE_TEST
665	default y
666	help
667	  Make sure that CPUs running critical tasks are not disturbed by
668	  any source of "noise" such as unbound workqueues, timers, kthreads...
669	  Unbound jobs get offloaded to housekeeping CPUs. This is driven by
670	  the "isolcpus=" boot parameter.
671
672	  Say Y if unsure.
673
674source "kernel/rcu/Kconfig"
675
676config BUILD_BIN2C
677	bool
678	default n
679
680config IKCONFIG
681	tristate "Kernel .config support"
682	help
683	  This option enables the complete Linux kernel ".config" file
684	  contents to be saved in the kernel. It provides documentation
685	  of which kernel options are used in a running kernel or in an
686	  on-disk kernel.  This information can be extracted from the kernel
687	  image file with the script scripts/extract-ikconfig and used as
688	  input to rebuild the current kernel or to build another kernel.
689	  It can also be extracted from a running kernel by reading
690	  /proc/config.gz if enabled (below).
691
692config IKCONFIG_PROC
693	bool "Enable access to .config through /proc/config.gz"
694	depends on IKCONFIG && PROC_FS
695	help
696	  This option enables access to the kernel configuration file
697	  through /proc/config.gz.
698
699config IKHEADERS
700	tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
701	depends on SYSFS
702	help
703	  This option enables access to the in-kernel headers that are generated during
704	  the build process. These can be used to build eBPF tracing programs,
705	  or similar programs.  If you build the headers as a module, a module called
706	  kheaders.ko is built which can be loaded on-demand to get access to headers.
707
708config LOG_BUF_SHIFT
709	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
710	range 12 25
711	default 17
712	depends on PRINTK
713	help
714	  Select the minimal kernel log buffer size as a power of 2.
715	  The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
716	  parameter, see below. Any higher size also might be forced
717	  by "log_buf_len" boot parameter.
718
719	  Examples:
720		     17 => 128 KB
721		     16 => 64 KB
722		     15 => 32 KB
723		     14 => 16 KB
724		     13 =>  8 KB
725		     12 =>  4 KB
726
727config LOG_CPU_MAX_BUF_SHIFT
728	int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
729	depends on SMP
730	range 0 21
731	default 12 if !BASE_SMALL
732	default 0 if BASE_SMALL
733	depends on PRINTK
734	help
735	  This option allows to increase the default ring buffer size
736	  according to the number of CPUs. The value defines the contribution
737	  of each CPU as a power of 2. The used space is typically only few
738	  lines however it might be much more when problems are reported,
739	  e.g. backtraces.
740
741	  The increased size means that a new buffer has to be allocated and
742	  the original static one is unused. It makes sense only on systems
743	  with more CPUs. Therefore this value is used only when the sum of
744	  contributions is greater than the half of the default kernel ring
745	  buffer as defined by LOG_BUF_SHIFT. The default values are set
746	  so that more than 16 CPUs are needed to trigger the allocation.
747
748	  Also this option is ignored when "log_buf_len" kernel parameter is
749	  used as it forces an exact (power of two) size of the ring buffer.
750
751	  The number of possible CPUs is used for this computation ignoring
752	  hotplugging making the computation optimal for the worst case
753	  scenario while allowing a simple algorithm to be used from bootup.
754
755	  Examples shift values and their meaning:
756		     17 => 128 KB for each CPU
757		     16 =>  64 KB for each CPU
758		     15 =>  32 KB for each CPU
759		     14 =>  16 KB for each CPU
760		     13 =>   8 KB for each CPU
761		     12 =>   4 KB for each CPU
762
763config PRINTK_SAFE_LOG_BUF_SHIFT
764	int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
765	range 10 21
766	default 13
767	depends on PRINTK
768	help
769	  Select the size of an alternate printk per-CPU buffer where messages
770	  printed from usafe contexts are temporary stored. One example would
771	  be NMI messages, another one - printk recursion. The messages are
772	  copied to the main log buffer in a safe context to avoid a deadlock.
773	  The value defines the size as a power of 2.
774
775	  Those messages are rare and limited. The largest one is when
776	  a backtrace is printed. It usually fits into 4KB. Select
777	  8KB if you want to be on the safe side.
778
779	  Examples:
780		     17 => 128 KB for each CPU
781		     16 =>  64 KB for each CPU
782		     15 =>  32 KB for each CPU
783		     14 =>  16 KB for each CPU
784		     13 =>   8 KB for each CPU
785		     12 =>   4 KB for each CPU
786
787config PRINTK_INDEX
788	bool "Printk indexing debugfs interface"
789	depends on PRINTK && DEBUG_FS
790	help
791	  Add support for indexing of all printk formats known at compile time
792	  at <debugfs>/printk/index/<module>.
793
794	  This can be used as part of maintaining daemons which monitor
795	  /dev/kmsg, as it permits auditing the printk formats present in a
796	  kernel, allowing detection of cases where monitored printks are
797	  changed or no longer present.
798
799	  There is no additional runtime cost to printk with this enabled.
800
801#
802# Architectures with an unreliable sched_clock() should select this:
803#
804config HAVE_UNSTABLE_SCHED_CLOCK
805	bool
806
807config GENERIC_SCHED_CLOCK
808	bool
809
810menu "Scheduler features"
811
812config UCLAMP_TASK
813	bool "Enable utilization clamping for RT/FAIR tasks"
814	depends on CPU_FREQ_GOV_SCHEDUTIL
815	help
816	  This feature enables the scheduler to track the clamped utilization
817	  of each CPU based on RUNNABLE tasks scheduled on that CPU.
818
819	  With this option, the user can specify the min and max CPU
820	  utilization allowed for RUNNABLE tasks. The max utilization defines
821	  the maximum frequency a task should use while the min utilization
822	  defines the minimum frequency it should use.
823
824	  Both min and max utilization clamp values are hints to the scheduler,
825	  aiming at improving its frequency selection policy, but they do not
826	  enforce or grant any specific bandwidth for tasks.
827
828	  If in doubt, say N.
829
830config UCLAMP_BUCKETS_COUNT
831	int "Number of supported utilization clamp buckets"
832	range 5 20
833	default 5
834	depends on UCLAMP_TASK
835	help
836	  Defines the number of clamp buckets to use. The range of each bucket
837	  will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
838	  number of clamp buckets the finer their granularity and the higher
839	  the precision of clamping aggregation and tracking at run-time.
840
841	  For example, with the minimum configuration value we will have 5
842	  clamp buckets tracking 20% utilization each. A 25% boosted tasks will
843	  be refcounted in the [20..39]% bucket and will set the bucket clamp
844	  effective value to 25%.
845	  If a second 30% boosted task should be co-scheduled on the same CPU,
846	  that task will be refcounted in the same bucket of the first task and
847	  it will boost the bucket clamp effective value to 30%.
848	  The clamp effective value of a bucket is reset to its nominal value
849	  (20% in the example above) when there are no more tasks refcounted in
850	  that bucket.
851
852	  An additional boost/capping margin can be added to some tasks. In the
853	  example above the 25% task will be boosted to 30% until it exits the
854	  CPU. If that should be considered not acceptable on certain systems,
855	  it's always possible to reduce the margin by increasing the number of
856	  clamp buckets to trade off used memory for run-time tracking
857	  precision.
858
859	  If in doubt, use the default value.
860
861endmenu
862
863#
864# For architectures that want to enable the support for NUMA-affine scheduler
865# balancing logic:
866#
867config ARCH_SUPPORTS_NUMA_BALANCING
868	bool
869
870#
871# For architectures that prefer to flush all TLBs after a number of pages
872# are unmapped instead of sending one IPI per page to flush. The architecture
873# must provide guarantees on what happens if a clean TLB cache entry is
874# written after the unmap. Details are in mm/rmap.c near the check for
875# should_defer_flush. The architecture should also consider if the full flush
876# and the refill costs are offset by the savings of sending fewer IPIs.
877config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
878	bool
879
880config CC_HAS_INT128
881	def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
882
883config CC_IMPLICIT_FALLTHROUGH
884	string
885	default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
886	default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough)
887
888# Currently, disable gcc-12 array-bounds globally.
889# We may want to target only particular configurations some day.
890config GCC12_NO_ARRAY_BOUNDS
891	def_bool y
892
893config CC_NO_ARRAY_BOUNDS
894	bool
895	default y if CC_IS_GCC && GCC_VERSION >= 120000 && GCC_VERSION < 130000 && GCC12_NO_ARRAY_BOUNDS
896
897#
898# For architectures that know their GCC __int128 support is sound
899#
900config ARCH_SUPPORTS_INT128
901	bool
902
903# For architectures that (ab)use NUMA to represent different memory regions
904# all cpu-local but of different latencies, such as SuperH.
905#
906config ARCH_WANT_NUMA_VARIABLE_LOCALITY
907	bool
908
909config NUMA_BALANCING
910	bool "Memory placement aware NUMA scheduler"
911	depends on ARCH_SUPPORTS_NUMA_BALANCING
912	depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
913	depends on SMP && NUMA && MIGRATION && !PREEMPT_RT
914	help
915	  This option adds support for automatic NUMA aware memory/task placement.
916	  The mechanism is quite primitive and is based on migrating memory when
917	  it has references to the node the task is running on.
918
919	  This system will be inactive on UMA systems.
920
921config NUMA_BALANCING_DEFAULT_ENABLED
922	bool "Automatically enable NUMA aware memory/task placement"
923	default y
924	depends on NUMA_BALANCING
925	help
926	  If set, automatic NUMA balancing will be enabled if running on a NUMA
927	  machine.
928
929menuconfig CGROUPS
930	bool "Control Group support"
931	select KERNFS
932	help
933	  This option adds support for grouping sets of processes together, for
934	  use with process control subsystems such as Cpusets, CFS, memory
935	  controls or device isolation.
936	  See
937		- Documentation/scheduler/sched-design-CFS.rst	(CFS)
938		- Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
939					  and resource control)
940
941	  Say N if unsure.
942
943if CGROUPS
944
945config PAGE_COUNTER
946	bool
947
948config CGROUP_FAVOR_DYNMODS
949        bool "Favor dynamic modification latency reduction by default"
950        help
951          This option enables the "favordynmods" mount option by default
952          which reduces the latencies of dynamic cgroup modifications such
953          as task migrations and controller on/offs at the cost of making
954          hot path operations such as forks and exits more expensive.
955
956          Say N if unsure.
957
958config MEMCG
959	bool "Memory controller"
960	select PAGE_COUNTER
961	select EVENTFD
962	help
963	  Provides control over the memory footprint of tasks in a cgroup.
964
965config MEMCG_SWAP
966	bool
967	depends on MEMCG && SWAP
968	default y
969
970config MEMCG_KMEM
971	bool
972	depends on MEMCG && !SLOB
973	default y
974
975config BLK_CGROUP
976	bool "IO controller"
977	depends on BLOCK
978	default n
979	help
980	Generic block IO controller cgroup interface. This is the common
981	cgroup interface which should be used by various IO controlling
982	policies.
983
984	Currently, CFQ IO scheduler uses it to recognize task groups and
985	control disk bandwidth allocation (proportional time slice allocation)
986	to such task groups. It is also used by bio throttling logic in
987	block layer to implement upper limit in IO rates on a device.
988
989	This option only enables generic Block IO controller infrastructure.
990	One needs to also enable actual IO controlling logic/policy. For
991	enabling proportional weight division of disk bandwidth in CFQ, set
992	CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
993	CONFIG_BLK_DEV_THROTTLING=y.
994
995	See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
996
997config CGROUP_WRITEBACK
998	bool
999	depends on MEMCG && BLK_CGROUP
1000	default y
1001
1002menuconfig CGROUP_SCHED
1003	bool "CPU controller"
1004	default n
1005	help
1006	  This feature lets CPU scheduler recognize task groups and control CPU
1007	  bandwidth allocation to such task groups. It uses cgroups to group
1008	  tasks.
1009
1010if CGROUP_SCHED
1011config FAIR_GROUP_SCHED
1012	bool "Group scheduling for SCHED_OTHER"
1013	depends on CGROUP_SCHED
1014	default CGROUP_SCHED
1015
1016config CFS_BANDWIDTH
1017	bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1018	depends on FAIR_GROUP_SCHED
1019	default n
1020	help
1021	  This option allows users to define CPU bandwidth rates (limits) for
1022	  tasks running within the fair group scheduler.  Groups with no limit
1023	  set are considered to be unconstrained and will run with no
1024	  restriction.
1025	  See Documentation/scheduler/sched-bwc.rst for more information.
1026
1027config RT_GROUP_SCHED
1028	bool "Group scheduling for SCHED_RR/FIFO"
1029	depends on CGROUP_SCHED
1030	default n
1031	help
1032	  This feature lets you explicitly allocate real CPU bandwidth
1033	  to task groups. If enabled, it will also make it impossible to
1034	  schedule realtime tasks for non-root users until you allocate
1035	  realtime bandwidth for them.
1036	  See Documentation/scheduler/sched-rt-group.rst for more information.
1037
1038endif #CGROUP_SCHED
1039
1040config UCLAMP_TASK_GROUP
1041	bool "Utilization clamping per group of tasks"
1042	depends on CGROUP_SCHED
1043	depends on UCLAMP_TASK
1044	default n
1045	help
1046	  This feature enables the scheduler to track the clamped utilization
1047	  of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
1048
1049	  When this option is enabled, the user can specify a min and max
1050	  CPU bandwidth which is allowed for each single task in a group.
1051	  The max bandwidth allows to clamp the maximum frequency a task
1052	  can use, while the min bandwidth allows to define a minimum
1053	  frequency a task will always use.
1054
1055	  When task group based utilization clamping is enabled, an eventually
1056	  specified task-specific clamp value is constrained by the cgroup
1057	  specified clamp value. Both minimum and maximum task clamping cannot
1058	  be bigger than the corresponding clamping defined at task group level.
1059
1060	  If in doubt, say N.
1061
1062config CGROUP_PIDS
1063	bool "PIDs controller"
1064	help
1065	  Provides enforcement of process number limits in the scope of a
1066	  cgroup. Any attempt to fork more processes than is allowed in the
1067	  cgroup will fail. PIDs are fundamentally a global resource because it
1068	  is fairly trivial to reach PID exhaustion before you reach even a
1069	  conservative kmemcg limit. As a result, it is possible to grind a
1070	  system to halt without being limited by other cgroup policies. The
1071	  PIDs controller is designed to stop this from happening.
1072
1073	  It should be noted that organisational operations (such as attaching
1074	  to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1075	  since the PIDs limit only affects a process's ability to fork, not to
1076	  attach to a cgroup.
1077
1078config CGROUP_RDMA
1079	bool "RDMA controller"
1080	help
1081	  Provides enforcement of RDMA resources defined by IB stack.
1082	  It is fairly easy for consumers to exhaust RDMA resources, which
1083	  can result into resource unavailability to other consumers.
1084	  RDMA controller is designed to stop this from happening.
1085	  Attaching processes with active RDMA resources to the cgroup
1086	  hierarchy is allowed even if can cross the hierarchy's limit.
1087
1088config CGROUP_FREEZER
1089	bool "Freezer controller"
1090	help
1091	  Provides a way to freeze and unfreeze all tasks in a
1092	  cgroup.
1093
1094	  This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1095	  controller includes important in-kernel memory consumers per default.
1096
1097	  If you're using cgroup2, say N.
1098
1099config CGROUP_HUGETLB
1100	bool "HugeTLB controller"
1101	depends on HUGETLB_PAGE
1102	select PAGE_COUNTER
1103	default n
1104	help
1105	  Provides a cgroup controller for HugeTLB pages.
1106	  When you enable this, you can put a per cgroup limit on HugeTLB usage.
1107	  The limit is enforced during page fault. Since HugeTLB doesn't
1108	  support page reclaim, enforcing the limit at page fault time implies
1109	  that, the application will get SIGBUS signal if it tries to access
1110	  HugeTLB pages beyond its limit. This requires the application to know
1111	  beforehand how much HugeTLB pages it would require for its use. The
1112	  control group is tracked in the third page lru pointer. This means
1113	  that we cannot use the controller with huge page less than 3 pages.
1114
1115config CPUSETS
1116	bool "Cpuset controller"
1117	depends on SMP
1118	help
1119	  This option will let you create and manage CPUSETs which
1120	  allow dynamically partitioning a system into sets of CPUs and
1121	  Memory Nodes and assigning tasks to run only within those sets.
1122	  This is primarily useful on large SMP or NUMA systems.
1123
1124	  Say N if unsure.
1125
1126config PROC_PID_CPUSET
1127	bool "Include legacy /proc/<pid>/cpuset file"
1128	depends on CPUSETS
1129	default y
1130
1131config CGROUP_DEVICE
1132	bool "Device controller"
1133	help
1134	  Provides a cgroup controller implementing whitelists for
1135	  devices which a process in the cgroup can mknod or open.
1136
1137config CGROUP_CPUACCT
1138	bool "Simple CPU accounting controller"
1139	help
1140	  Provides a simple controller for monitoring the
1141	  total CPU consumed by the tasks in a cgroup.
1142
1143config CGROUP_PERF
1144	bool "Perf controller"
1145	depends on PERF_EVENTS
1146	help
1147	  This option extends the perf per-cpu mode to restrict monitoring
1148	  to threads which belong to the cgroup specified and run on the
1149	  designated cpu.  Or this can be used to have cgroup ID in samples
1150	  so that it can monitor performance events among cgroups.
1151
1152	  Say N if unsure.
1153
1154config CGROUP_BPF
1155	bool "Support for eBPF programs attached to cgroups"
1156	depends on BPF_SYSCALL
1157	select SOCK_CGROUP_DATA
1158	help
1159	  Allow attaching eBPF programs to a cgroup using the bpf(2)
1160	  syscall command BPF_PROG_ATTACH.
1161
1162	  In which context these programs are accessed depends on the type
1163	  of attachment. For instance, programs that are attached using
1164	  BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1165	  inet sockets.
1166
1167config CGROUP_MISC
1168	bool "Misc resource controller"
1169	default n
1170	help
1171	  Provides a controller for miscellaneous resources on a host.
1172
1173	  Miscellaneous scalar resources are the resources on the host system
1174	  which cannot be abstracted like the other cgroups. This controller
1175	  tracks and limits the miscellaneous resources used by a process
1176	  attached to a cgroup hierarchy.
1177
1178	  For more information, please check misc cgroup section in
1179	  /Documentation/admin-guide/cgroup-v2.rst.
1180
1181config CGROUP_DEBUG
1182	bool "Debug controller"
1183	default n
1184	depends on DEBUG_KERNEL
1185	help
1186	  This option enables a simple controller that exports
1187	  debugging information about the cgroups framework. This
1188	  controller is for control cgroup debugging only. Its
1189	  interfaces are not stable.
1190
1191	  Say N.
1192
1193config SOCK_CGROUP_DATA
1194	bool
1195	default n
1196
1197endif # CGROUPS
1198
1199menuconfig NAMESPACES
1200	bool "Namespaces support" if EXPERT
1201	depends on MULTIUSER
1202	default !EXPERT
1203	help
1204	  Provides the way to make tasks work with different objects using
1205	  the same id. For example same IPC id may refer to different objects
1206	  or same user id or pid may refer to different tasks when used in
1207	  different namespaces.
1208
1209if NAMESPACES
1210
1211config UTS_NS
1212	bool "UTS namespace"
1213	default y
1214	help
1215	  In this namespace tasks see different info provided with the
1216	  uname() system call
1217
1218config TIME_NS
1219	bool "TIME namespace"
1220	depends on GENERIC_VDSO_TIME_NS
1221	default y
1222	help
1223	  In this namespace boottime and monotonic clocks can be set.
1224	  The time will keep going with the same pace.
1225
1226config IPC_NS
1227	bool "IPC namespace"
1228	depends on (SYSVIPC || POSIX_MQUEUE)
1229	default y
1230	help
1231	  In this namespace tasks work with IPC ids which correspond to
1232	  different IPC objects in different namespaces.
1233
1234config USER_NS
1235	bool "User namespace"
1236	default n
1237	help
1238	  This allows containers, i.e. vservers, to use user namespaces
1239	  to provide different user info for different servers.
1240
1241	  When user namespaces are enabled in the kernel it is
1242	  recommended that the MEMCG option also be enabled and that
1243	  user-space use the memory control groups to limit the amount
1244	  of memory a memory unprivileged users can use.
1245
1246	  If unsure, say N.
1247
1248config PID_NS
1249	bool "PID Namespaces"
1250	default y
1251	help
1252	  Support process id namespaces.  This allows having multiple
1253	  processes with the same pid as long as they are in different
1254	  pid namespaces.  This is a building block of containers.
1255
1256config NET_NS
1257	bool "Network namespace"
1258	depends on NET
1259	default y
1260	help
1261	  Allow user space to create what appear to be multiple instances
1262	  of the network stack.
1263
1264endif # NAMESPACES
1265
1266config CHECKPOINT_RESTORE
1267	bool "Checkpoint/restore support"
1268	select PROC_CHILDREN
1269	select KCMP
1270	default n
1271	help
1272	  Enables additional kernel features in a sake of checkpoint/restore.
1273	  In particular it adds auxiliary prctl codes to setup process text,
1274	  data and heap segment sizes, and a few additional /proc filesystem
1275	  entries.
1276
1277	  If unsure, say N here.
1278
1279config SCHED_AUTOGROUP
1280	bool "Automatic process group scheduling"
1281	select CGROUPS
1282	select CGROUP_SCHED
1283	select FAIR_GROUP_SCHED
1284	help
1285	  This option optimizes the scheduler for common desktop workloads by
1286	  automatically creating and populating task groups.  This separation
1287	  of workloads isolates aggressive CPU burners (like build jobs) from
1288	  desktop applications.  Task group autogeneration is currently based
1289	  upon task session.
1290
1291config SYSFS_DEPRECATED
1292	bool "Enable deprecated sysfs features to support old userspace tools"
1293	depends on SYSFS
1294	default n
1295	help
1296	  This option adds code that switches the layout of the "block" class
1297	  devices, to not show up in /sys/class/block/, but only in
1298	  /sys/block/.
1299
1300	  This switch is only active when the sysfs.deprecated=1 boot option is
1301	  passed or the SYSFS_DEPRECATED_V2 option is set.
1302
1303	  This option allows new kernels to run on old distributions and tools,
1304	  which might get confused by /sys/class/block/. Since 2007/2008 all
1305	  major distributions and tools handle this just fine.
1306
1307	  Recent distributions and userspace tools after 2009/2010 depend on
1308	  the existence of /sys/class/block/, and will not work with this
1309	  option enabled.
1310
1311	  Only if you are using a new kernel on an old distribution, you might
1312	  need to say Y here.
1313
1314config SYSFS_DEPRECATED_V2
1315	bool "Enable deprecated sysfs features by default"
1316	default n
1317	depends on SYSFS
1318	depends on SYSFS_DEPRECATED
1319	help
1320	  Enable deprecated sysfs by default.
1321
1322	  See the CONFIG_SYSFS_DEPRECATED option for more details about this
1323	  option.
1324
1325	  Only if you are using a new kernel on an old distribution, you might
1326	  need to say Y here. Even then, odds are you would not need it
1327	  enabled, you can always pass the boot option if absolutely necessary.
1328
1329config RELAY
1330	bool "Kernel->user space relay support (formerly relayfs)"
1331	select IRQ_WORK
1332	help
1333	  This option enables support for relay interface support in
1334	  certain file systems (such as debugfs).
1335	  It is designed to provide an efficient mechanism for tools and
1336	  facilities to relay large amounts of data from kernel space to
1337	  user space.
1338
1339	  If unsure, say N.
1340
1341config BLK_DEV_INITRD
1342	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1343	help
1344	  The initial RAM filesystem is a ramfs which is loaded by the
1345	  boot loader (loadlin or lilo) and that is mounted as root
1346	  before the normal boot procedure. It is typically used to
1347	  load modules needed to mount the "real" root file system,
1348	  etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1349
1350	  If RAM disk support (BLK_DEV_RAM) is also included, this
1351	  also enables initial RAM disk (initrd) support and adds
1352	  15 Kbytes (more on some other architectures) to the kernel size.
1353
1354	  If unsure say Y.
1355
1356if BLK_DEV_INITRD
1357
1358source "usr/Kconfig"
1359
1360endif
1361
1362config BOOT_CONFIG
1363	bool "Boot config support"
1364	select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED
1365	help
1366	  Extra boot config allows system admin to pass a config file as
1367	  complemental extension of kernel cmdline when booting.
1368	  The boot config file must be attached at the end of initramfs
1369	  with checksum, size and magic word.
1370	  See <file:Documentation/admin-guide/bootconfig.rst> for details.
1371
1372	  If unsure, say Y.
1373
1374config BOOT_CONFIG_EMBED
1375	bool "Embed bootconfig file in the kernel"
1376	depends on BOOT_CONFIG
1377	help
1378	  Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the
1379	  kernel. Usually, the bootconfig file is loaded with the initrd
1380	  image. But if the system doesn't support initrd, this option will
1381	  help you by embedding a bootconfig file while building the kernel.
1382
1383	  If unsure, say N.
1384
1385config BOOT_CONFIG_EMBED_FILE
1386	string "Embedded bootconfig file path"
1387	depends on BOOT_CONFIG_EMBED
1388	help
1389	  Specify a bootconfig file which will be embedded to the kernel.
1390	  This bootconfig will be used if there is no initrd or no other
1391	  bootconfig in the initrd.
1392
1393config INITRAMFS_PRESERVE_MTIME
1394	bool "Preserve cpio archive mtimes in initramfs"
1395	default y
1396	help
1397	  Each entry in an initramfs cpio archive carries an mtime value. When
1398	  enabled, extracted cpio items take this mtime, with directory mtime
1399	  setting deferred until after creation of any child entries.
1400
1401	  If unsure, say Y.
1402
1403choice
1404	prompt "Compiler optimization level"
1405	default CC_OPTIMIZE_FOR_PERFORMANCE
1406
1407config CC_OPTIMIZE_FOR_PERFORMANCE
1408	bool "Optimize for performance (-O2)"
1409	help
1410	  This is the default optimization level for the kernel, building
1411	  with the "-O2" compiler flag for best performance and most
1412	  helpful compile-time warnings.
1413
1414config CC_OPTIMIZE_FOR_SIZE
1415	bool "Optimize for size (-Os)"
1416	help
1417	  Choosing this option will pass "-Os" to your compiler resulting
1418	  in a smaller kernel.
1419
1420endchoice
1421
1422config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1423	bool
1424	help
1425	  This requires that the arch annotates or otherwise protects
1426	  its external entry points from being discarded. Linker scripts
1427	  must also merge .text.*, .data.*, and .bss.* correctly into
1428	  output sections. Care must be taken not to pull in unrelated
1429	  sections (e.g., '.text.init'). Typically '.' in section names
1430	  is used to distinguish them from label names / C identifiers.
1431
1432config LD_DEAD_CODE_DATA_ELIMINATION
1433	bool "Dead code and data elimination (EXPERIMENTAL)"
1434	depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1435	depends on EXPERT
1436	depends on $(cc-option,-ffunction-sections -fdata-sections)
1437	depends on $(ld-option,--gc-sections)
1438	help
1439	  Enable this if you want to do dead code and data elimination with
1440	  the linker by compiling with -ffunction-sections -fdata-sections,
1441	  and linking with --gc-sections.
1442
1443	  This can reduce on disk and in-memory size of the kernel
1444	  code and static data, particularly for small configs and
1445	  on small systems. This has the possibility of introducing
1446	  silently broken kernel if the required annotations are not
1447	  present. This option is not well tested yet, so use at your
1448	  own risk.
1449
1450config LD_ORPHAN_WARN
1451	def_bool y
1452	depends on ARCH_WANT_LD_ORPHAN_WARN
1453	depends on $(ld-option,--orphan-handling=warn)
1454
1455config SYSCTL
1456	bool
1457
1458config HAVE_UID16
1459	bool
1460
1461config SYSCTL_EXCEPTION_TRACE
1462	bool
1463	help
1464	  Enable support for /proc/sys/debug/exception-trace.
1465
1466config SYSCTL_ARCH_UNALIGN_NO_WARN
1467	bool
1468	help
1469	  Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1470	  Allows arch to define/use @no_unaligned_warning to possibly warn
1471	  about unaligned access emulation going on under the hood.
1472
1473config SYSCTL_ARCH_UNALIGN_ALLOW
1474	bool
1475	help
1476	  Enable support for /proc/sys/kernel/unaligned-trap
1477	  Allows arches to define/use @unaligned_enabled to runtime toggle
1478	  the unaligned access emulation.
1479	  see arch/parisc/kernel/unaligned.c for reference
1480
1481config HAVE_PCSPKR_PLATFORM
1482	bool
1483
1484# interpreter that classic socket filters depend on
1485config BPF
1486	bool
1487	select CRYPTO_LIB_SHA1
1488
1489menuconfig EXPERT
1490	bool "Configure standard kernel features (expert users)"
1491	# Unhide debug options, to make the on-by-default options visible
1492	select DEBUG_KERNEL
1493	help
1494	  This option allows certain base kernel options and settings
1495	  to be disabled or tweaked. This is for specialized
1496	  environments which can tolerate a "non-standard" kernel.
1497	  Only use this if you really know what you are doing.
1498
1499config UID16
1500	bool "Enable 16-bit UID system calls" if EXPERT
1501	depends on HAVE_UID16 && MULTIUSER
1502	default y
1503	help
1504	  This enables the legacy 16-bit UID syscall wrappers.
1505
1506config MULTIUSER
1507	bool "Multiple users, groups and capabilities support" if EXPERT
1508	default y
1509	help
1510	  This option enables support for non-root users, groups and
1511	  capabilities.
1512
1513	  If you say N here, all processes will run with UID 0, GID 0, and all
1514	  possible capabilities.  Saying N here also compiles out support for
1515	  system calls related to UIDs, GIDs, and capabilities, such as setuid,
1516	  setgid, and capset.
1517
1518	  If unsure, say Y here.
1519
1520config SGETMASK_SYSCALL
1521	bool "sgetmask/ssetmask syscalls support" if EXPERT
1522	def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1523	help
1524	  sys_sgetmask and sys_ssetmask are obsolete system calls
1525	  no longer supported in libc but still enabled by default in some
1526	  architectures.
1527
1528	  If unsure, leave the default option here.
1529
1530config SYSFS_SYSCALL
1531	bool "Sysfs syscall support" if EXPERT
1532	default y
1533	help
1534	  sys_sysfs is an obsolete system call no longer supported in libc.
1535	  Note that disabling this option is more secure but might break
1536	  compatibility with some systems.
1537
1538	  If unsure say Y here.
1539
1540config FHANDLE
1541	bool "open by fhandle syscalls" if EXPERT
1542	select EXPORTFS
1543	default y
1544	help
1545	  If you say Y here, a user level program will be able to map
1546	  file names to handle and then later use the handle for
1547	  different file system operations. This is useful in implementing
1548	  userspace file servers, which now track files using handles instead
1549	  of names. The handle would remain the same even if file names
1550	  get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1551	  syscalls.
1552
1553config POSIX_TIMERS
1554	bool "Posix Clocks & timers" if EXPERT
1555	default y
1556	help
1557	  This includes native support for POSIX timers to the kernel.
1558	  Some embedded systems have no use for them and therefore they
1559	  can be configured out to reduce the size of the kernel image.
1560
1561	  When this option is disabled, the following syscalls won't be
1562	  available: timer_create, timer_gettime: timer_getoverrun,
1563	  timer_settime, timer_delete, clock_adjtime, getitimer,
1564	  setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1565	  clock_getres and clock_nanosleep syscalls will be limited to
1566	  CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1567
1568	  If unsure say y.
1569
1570config PRINTK
1571	default y
1572	bool "Enable support for printk" if EXPERT
1573	select IRQ_WORK
1574	help
1575	  This option enables normal printk support. Removing it
1576	  eliminates most of the message strings from the kernel image
1577	  and makes the kernel more or less silent. As this makes it
1578	  very difficult to diagnose system problems, saying N here is
1579	  strongly discouraged.
1580
1581config BUG
1582	bool "BUG() support" if EXPERT
1583	default y
1584	help
1585	  Disabling this option eliminates support for BUG and WARN, reducing
1586	  the size of your kernel image and potentially quietly ignoring
1587	  numerous fatal conditions. You should only consider disabling this
1588	  option for embedded systems with no facilities for reporting errors.
1589	  Just say Y.
1590
1591config ELF_CORE
1592	depends on COREDUMP
1593	default y
1594	bool "Enable ELF core dumps" if EXPERT
1595	help
1596	  Enable support for generating core dumps. Disabling saves about 4k.
1597
1598
1599config PCSPKR_PLATFORM
1600	bool "Enable PC-Speaker support" if EXPERT
1601	depends on HAVE_PCSPKR_PLATFORM
1602	select I8253_LOCK
1603	default y
1604	help
1605	  This option allows to disable the internal PC-Speaker
1606	  support, saving some memory.
1607
1608config BASE_FULL
1609	default y
1610	bool "Enable full-sized data structures for core" if EXPERT
1611	help
1612	  Disabling this option reduces the size of miscellaneous core
1613	  kernel data structures. This saves memory on small machines,
1614	  but may reduce performance.
1615
1616config FUTEX
1617	bool "Enable futex support" if EXPERT
1618	depends on !(SPARC32 && SMP)
1619	default y
1620	imply RT_MUTEXES
1621	help
1622	  Disabling this option will cause the kernel to be built without
1623	  support for "fast userspace mutexes".  The resulting kernel may not
1624	  run glibc-based applications correctly.
1625
1626config FUTEX_PI
1627	bool
1628	depends on FUTEX && RT_MUTEXES
1629	default y
1630
1631config EPOLL
1632	bool "Enable eventpoll support" if EXPERT
1633	default y
1634	help
1635	  Disabling this option will cause the kernel to be built without
1636	  support for epoll family of system calls.
1637
1638config SIGNALFD
1639	bool "Enable signalfd() system call" if EXPERT
1640	default y
1641	help
1642	  Enable the signalfd() system call that allows to receive signals
1643	  on a file descriptor.
1644
1645	  If unsure, say Y.
1646
1647config TIMERFD
1648	bool "Enable timerfd() system call" if EXPERT
1649	default y
1650	help
1651	  Enable the timerfd() system call that allows to receive timer
1652	  events on a file descriptor.
1653
1654	  If unsure, say Y.
1655
1656config EVENTFD
1657	bool "Enable eventfd() system call" if EXPERT
1658	default y
1659	help
1660	  Enable the eventfd() system call that allows to receive both
1661	  kernel notification (ie. KAIO) or userspace notifications.
1662
1663	  If unsure, say Y.
1664
1665config SHMEM
1666	bool "Use full shmem filesystem" if EXPERT
1667	default y
1668	depends on MMU
1669	help
1670	  The shmem is an internal filesystem used to manage shared memory.
1671	  It is backed by swap and manages resource limits. It is also exported
1672	  to userspace as tmpfs if TMPFS is enabled. Disabling this
1673	  option replaces shmem and tmpfs with the much simpler ramfs code,
1674	  which may be appropriate on small systems without swap.
1675
1676config AIO
1677	bool "Enable AIO support" if EXPERT
1678	default y
1679	help
1680	  This option enables POSIX asynchronous I/O which may by used
1681	  by some high performance threaded applications. Disabling
1682	  this option saves about 7k.
1683
1684config IO_URING
1685	bool "Enable IO uring support" if EXPERT
1686	select IO_WQ
1687	default y
1688	help
1689	  This option enables support for the io_uring interface, enabling
1690	  applications to submit and complete IO through submission and
1691	  completion rings that are shared between the kernel and application.
1692
1693config ADVISE_SYSCALLS
1694	bool "Enable madvise/fadvise syscalls" if EXPERT
1695	default y
1696	help
1697	  This option enables the madvise and fadvise syscalls, used by
1698	  applications to advise the kernel about their future memory or file
1699	  usage, improving performance. If building an embedded system where no
1700	  applications use these syscalls, you can disable this option to save
1701	  space.
1702
1703config MEMBARRIER
1704	bool "Enable membarrier() system call" if EXPERT
1705	default y
1706	help
1707	  Enable the membarrier() system call that allows issuing memory
1708	  barriers across all running threads, which can be used to distribute
1709	  the cost of user-space memory barriers asymmetrically by transforming
1710	  pairs of memory barriers into pairs consisting of membarrier() and a
1711	  compiler barrier.
1712
1713	  If unsure, say Y.
1714
1715config KALLSYMS
1716	bool "Load all symbols for debugging/ksymoops" if EXPERT
1717	default y
1718	help
1719	  Say Y here to let the kernel print out symbolic crash information and
1720	  symbolic stack backtraces. This increases the size of the kernel
1721	  somewhat, as all symbols have to be loaded into the kernel image.
1722
1723config KALLSYMS_ALL
1724	bool "Include all symbols in kallsyms"
1725	depends on DEBUG_KERNEL && KALLSYMS
1726	help
1727	  Normally kallsyms only contains the symbols of functions for nicer
1728	  OOPS messages and backtraces (i.e., symbols from the text and inittext
1729	  sections). This is sufficient for most cases. And only if you want to
1730	  enable kernel live patching, or other less common use cases (e.g.,
1731	  when a debugger is used) all symbols are required (i.e., names of
1732	  variables from the data sections, etc).
1733
1734	  This option makes sure that all symbols are loaded into the kernel
1735	  image (i.e., symbols from all sections) in cost of increased kernel
1736	  size (depending on the kernel configuration, it may be 300KiB or
1737	  something like this).
1738
1739	  Say N unless you really need all symbols, or kernel live patching.
1740
1741config KALLSYMS_ABSOLUTE_PERCPU
1742	bool
1743	depends on KALLSYMS
1744	default X86_64 && SMP
1745
1746config KALLSYMS_BASE_RELATIVE
1747	bool
1748	depends on KALLSYMS
1749	default !IA64
1750	help
1751	  Instead of emitting them as absolute values in the native word size,
1752	  emit the symbol references in the kallsyms table as 32-bit entries,
1753	  each containing a relative value in the range [base, base + U32_MAX]
1754	  or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1755	  an absolute value in the range [0, S32_MAX] or a relative value in the
1756	  range [base, base + S32_MAX], where base is the lowest relative symbol
1757	  address encountered in the image.
1758
1759	  On 64-bit builds, this reduces the size of the address table by 50%,
1760	  but more importantly, it results in entries whose values are build
1761	  time constants, and no relocation pass is required at runtime to fix
1762	  up the entries based on the runtime load address of the kernel.
1763
1764# end of the "standard kernel features (expert users)" menu
1765
1766# syscall, maps, verifier
1767
1768config ARCH_HAS_MEMBARRIER_CALLBACKS
1769	bool
1770
1771config ARCH_HAS_MEMBARRIER_SYNC_CORE
1772	bool
1773
1774config KCMP
1775	bool "Enable kcmp() system call" if EXPERT
1776	help
1777	  Enable the kernel resource comparison system call. It provides
1778	  user-space with the ability to compare two processes to see if they
1779	  share a common resource, such as a file descriptor or even virtual
1780	  memory space.
1781
1782	  If unsure, say N.
1783
1784config RSEQ
1785	bool "Enable rseq() system call" if EXPERT
1786	default y
1787	depends on HAVE_RSEQ
1788	select MEMBARRIER
1789	help
1790	  Enable the restartable sequences system call. It provides a
1791	  user-space cache for the current CPU number value, which
1792	  speeds up getting the current CPU number from user-space,
1793	  as well as an ABI to speed up user-space operations on
1794	  per-CPU data.
1795
1796	  If unsure, say Y.
1797
1798config DEBUG_RSEQ
1799	default n
1800	bool "Enabled debugging of rseq() system call" if EXPERT
1801	depends on RSEQ && DEBUG_KERNEL
1802	help
1803	  Enable extra debugging checks for the rseq system call.
1804
1805	  If unsure, say N.
1806
1807config EMBEDDED
1808	bool "Embedded system"
1809	select EXPERT
1810	help
1811	  This option should be enabled if compiling the kernel for
1812	  an embedded system so certain expert options are available
1813	  for configuration.
1814
1815config HAVE_PERF_EVENTS
1816	bool
1817	help
1818	  See tools/perf/design.txt for details.
1819
1820config GUEST_PERF_EVENTS
1821	bool
1822	depends on HAVE_PERF_EVENTS
1823
1824config PERF_USE_VMALLOC
1825	bool
1826	help
1827	  See tools/perf/design.txt for details
1828
1829config PC104
1830	bool "PC/104 support" if EXPERT
1831	help
1832	  Expose PC/104 form factor device drivers and options available for
1833	  selection and configuration. Enable this option if your target
1834	  machine has a PC/104 bus.
1835
1836menu "Kernel Performance Events And Counters"
1837
1838config PERF_EVENTS
1839	bool "Kernel performance events and counters"
1840	default y if PROFILING
1841	depends on HAVE_PERF_EVENTS
1842	select IRQ_WORK
1843	select SRCU
1844	help
1845	  Enable kernel support for various performance events provided
1846	  by software and hardware.
1847
1848	  Software events are supported either built-in or via the
1849	  use of generic tracepoints.
1850
1851	  Most modern CPUs support performance events via performance
1852	  counter registers. These registers count the number of certain
1853	  types of hw events: such as instructions executed, cachemisses
1854	  suffered, or branches mis-predicted - without slowing down the
1855	  kernel or applications. These registers can also trigger interrupts
1856	  when a threshold number of events have passed - and can thus be
1857	  used to profile the code that runs on that CPU.
1858
1859	  The Linux Performance Event subsystem provides an abstraction of
1860	  these software and hardware event capabilities, available via a
1861	  system call and used by the "perf" utility in tools/perf/. It
1862	  provides per task and per CPU counters, and it provides event
1863	  capabilities on top of those.
1864
1865	  Say Y if unsure.
1866
1867config DEBUG_PERF_USE_VMALLOC
1868	default n
1869	bool "Debug: use vmalloc to back perf mmap() buffers"
1870	depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1871	select PERF_USE_VMALLOC
1872	help
1873	  Use vmalloc memory to back perf mmap() buffers.
1874
1875	  Mostly useful for debugging the vmalloc code on platforms
1876	  that don't require it.
1877
1878	  Say N if unsure.
1879
1880endmenu
1881
1882config SYSTEM_DATA_VERIFICATION
1883	def_bool n
1884	select SYSTEM_TRUSTED_KEYRING
1885	select KEYS
1886	select CRYPTO
1887	select CRYPTO_RSA
1888	select ASYMMETRIC_KEY_TYPE
1889	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1890	select ASN1
1891	select OID_REGISTRY
1892	select X509_CERTIFICATE_PARSER
1893	select PKCS7_MESSAGE_PARSER
1894	help
1895	  Provide PKCS#7 message verification using the contents of the system
1896	  trusted keyring to provide public keys.  This then can be used for
1897	  module verification, kexec image verification and firmware blob
1898	  verification.
1899
1900config PROFILING
1901	bool "Profiling support"
1902	help
1903	  Say Y here to enable the extended profiling support mechanisms used
1904	  by profilers.
1905
1906#
1907# Place an empty function call at each tracepoint site. Can be
1908# dynamically changed for a probe function.
1909#
1910config TRACEPOINTS
1911	bool
1912
1913endmenu		# General setup
1914
1915source "arch/Kconfig"
1916
1917config RT_MUTEXES
1918	bool
1919	default y if PREEMPT_RT
1920
1921config BASE_SMALL
1922	int
1923	default 0 if BASE_FULL
1924	default 1 if !BASE_FULL
1925
1926config MODULE_SIG_FORMAT
1927	def_bool n
1928	select SYSTEM_DATA_VERIFICATION
1929
1930source "kernel/module/Kconfig"
1931
1932config INIT_ALL_POSSIBLE
1933	bool
1934	help
1935	  Back when each arch used to define their own cpu_online_mask and
1936	  cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1937	  with all 1s, and others with all 0s.  When they were centralised,
1938	  it was better to provide this option than to break all the archs
1939	  and have several arch maintainers pursuing me down dark alleys.
1940
1941source "block/Kconfig"
1942
1943config PREEMPT_NOTIFIERS
1944	bool
1945
1946config PADATA
1947	depends on SMP
1948	bool
1949
1950config ASN1
1951	tristate
1952	help
1953	  Build a simple ASN.1 grammar compiler that produces a bytecode output
1954	  that can be interpreted by the ASN.1 stream decoder and used to
1955	  inform it as to what tags are to be expected in a stream and what
1956	  functions to call on what tags.
1957
1958source "kernel/Kconfig.locks"
1959
1960config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
1961	bool
1962
1963config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
1964	bool
1965
1966# It may be useful for an architecture to override the definitions of the
1967# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
1968# and the COMPAT_ variants in <linux/compat.h>, in particular to use a
1969# different calling convention for syscalls. They can also override the
1970# macros for not-implemented syscalls in kernel/sys_ni.c and
1971# kernel/time/posix-stubs.c. All these overrides need to be available in
1972# <asm/syscall_wrapper.h>.
1973config ARCH_HAS_SYSCALL_WRAPPER
1974	def_bool n
1975