xref: /openbmc/linux/init/Kconfig (revision 25b892b5)
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) $(m64-flag)) if 64BIT
66	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag))
67
68config CC_CAN_LINK_STATIC
69	bool
70	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static) if 64BIT
71	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(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 TOOLS_SUPPORT_RELR
81	def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
82
83config CC_HAS_ASM_INLINE
84	def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
85
86config CC_HAS_NO_PROFILE_FN_ATTR
87	def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
88
89config CONSTRUCTORS
90	bool
91
92config IRQ_WORK
93	bool
94
95config BUILDTIME_TABLE_SORT
96	bool
97
98config THREAD_INFO_IN_TASK
99	bool
100	help
101	  Select this to move thread_info off the stack into task_struct.  To
102	  make this work, an arch will need to remove all thread_info fields
103	  except flags and fix any runtime bugs.
104
105	  One subtle change that will be needed is to use try_get_task_stack()
106	  and put_task_stack() in save_thread_stack_tsk() and get_wchan().
107
108menu "General setup"
109
110config BROKEN
111	bool
112
113config BROKEN_ON_SMP
114	bool
115	depends on BROKEN || !SMP
116	default y
117
118config INIT_ENV_ARG_LIMIT
119	int
120	default 32 if !UML
121	default 128 if UML
122	help
123	  Maximum of each of the number of arguments and environment
124	  variables passed to init from the kernel command line.
125
126config COMPILE_TEST
127	bool "Compile also drivers which will not load"
128	depends on HAS_IOMEM
129	help
130	  Some drivers can be compiled on a different platform than they are
131	  intended to be run on. Despite they cannot be loaded there (or even
132	  when they load they cannot be used due to missing HW support),
133	  developers still, opposing to distributors, might want to build such
134	  drivers to compile-test them.
135
136	  If you are a developer and want to build everything available, say Y
137	  here. If you are a user/distributor, say N here to exclude useless
138	  drivers to be distributed.
139
140config WERROR
141	bool "Compile the kernel with warnings as errors"
142	default COMPILE_TEST
143	help
144	  A kernel build should not cause any compiler warnings, and this
145	  enables the '-Werror' flag to enforce that rule by default.
146
147	  However, if you have a new (or very old) compiler with odd and
148	  unusual warnings, or you have some architecture with problems,
149	  you may need to disable this config option in order to
150	  successfully build the kernel.
151
152	  If in doubt, say Y.
153
154config UAPI_HEADER_TEST
155	bool "Compile test UAPI headers"
156	depends on HEADERS_INSTALL && CC_CAN_LINK
157	help
158	  Compile test headers exported to user-space to ensure they are
159	  self-contained, i.e. compilable as standalone units.
160
161	  If you are a developer or tester and want to ensure the exported
162	  headers are self-contained, say Y here. Otherwise, choose N.
163
164config LOCALVERSION
165	string "Local version - append to kernel release"
166	help
167	  Append an extra string to the end of your kernel version.
168	  This will show up when you type uname, for example.
169	  The string you set here will be appended after the contents of
170	  any files with a filename matching localversion* in your
171	  object and source tree, in that order.  Your total string can
172	  be a maximum of 64 characters.
173
174config LOCALVERSION_AUTO
175	bool "Automatically append version information to the version string"
176	default y
177	depends on !COMPILE_TEST
178	help
179	  This will try to automatically determine if the current tree is a
180	  release tree by looking for git tags that belong to the current
181	  top of tree revision.
182
183	  A string of the format -gxxxxxxxx will be added to the localversion
184	  if a git-based tree is found.  The string generated by this will be
185	  appended after any matching localversion* files, and after the value
186	  set in CONFIG_LOCALVERSION.
187
188	  (The actual string used here is the first eight characters produced
189	  by running the command:
190
191	    $ git rev-parse --verify HEAD
192
193	  which is done within the script "scripts/setlocalversion".)
194
195config BUILD_SALT
196	string "Build ID Salt"
197	default ""
198	help
199	  The build ID is used to link binaries and their debug info. Setting
200	  this option will use the value in the calculation of the build id.
201	  This is mostly useful for distributions which want to ensure the
202	  build is unique between builds. It's safe to leave the default.
203
204config HAVE_KERNEL_GZIP
205	bool
206
207config HAVE_KERNEL_BZIP2
208	bool
209
210config HAVE_KERNEL_LZMA
211	bool
212
213config HAVE_KERNEL_XZ
214	bool
215
216config HAVE_KERNEL_LZO
217	bool
218
219config HAVE_KERNEL_LZ4
220	bool
221
222config HAVE_KERNEL_ZSTD
223	bool
224
225config HAVE_KERNEL_UNCOMPRESSED
226	bool
227
228choice
229	prompt "Kernel compression mode"
230	default KERNEL_GZIP
231	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
232	help
233	  The linux kernel is a kind of self-extracting executable.
234	  Several compression algorithms are available, which differ
235	  in efficiency, compression and decompression speed.
236	  Compression speed is only relevant when building a kernel.
237	  Decompression speed is relevant at each boot.
238
239	  If you have any problems with bzip2 or lzma compressed
240	  kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
241	  version of this functionality (bzip2 only), for 2.4, was
242	  supplied by Christian Ludwig)
243
244	  High compression options are mostly useful for users, who
245	  are low on disk space (embedded systems), but for whom ram
246	  size matters less.
247
248	  If in doubt, select 'gzip'
249
250config KERNEL_GZIP
251	bool "Gzip"
252	depends on HAVE_KERNEL_GZIP
253	help
254	  The old and tried gzip compression. It provides a good balance
255	  between compression ratio and decompression speed.
256
257config KERNEL_BZIP2
258	bool "Bzip2"
259	depends on HAVE_KERNEL_BZIP2
260	help
261	  Its compression ratio and speed is intermediate.
262	  Decompression speed is slowest among the choices.  The kernel
263	  size is about 10% smaller with bzip2, in comparison to gzip.
264	  Bzip2 uses a large amount of memory. For modern kernels you
265	  will need at least 8MB RAM or more for booting.
266
267config KERNEL_LZMA
268	bool "LZMA"
269	depends on HAVE_KERNEL_LZMA
270	help
271	  This compression algorithm's ratio is best.  Decompression speed
272	  is between gzip and bzip2.  Compression is slowest.
273	  The kernel size is about 33% smaller with LZMA in comparison to gzip.
274
275config KERNEL_XZ
276	bool "XZ"
277	depends on HAVE_KERNEL_XZ
278	help
279	  XZ uses the LZMA2 algorithm and instruction set specific
280	  BCJ filters which can improve compression ratio of executable
281	  code. The size of the kernel is about 30% smaller with XZ in
282	  comparison to gzip. On architectures for which there is a BCJ
283	  filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
284	  will create a few percent smaller kernel than plain LZMA.
285
286	  The speed is about the same as with LZMA: The decompression
287	  speed of XZ is better than that of bzip2 but worse than gzip
288	  and LZO. Compression is slow.
289
290config KERNEL_LZO
291	bool "LZO"
292	depends on HAVE_KERNEL_LZO
293	help
294	  Its compression ratio is the poorest among the choices. The kernel
295	  size is about 10% bigger than gzip; however its speed
296	  (both compression and decompression) is the fastest.
297
298config KERNEL_LZ4
299	bool "LZ4"
300	depends on HAVE_KERNEL_LZ4
301	help
302	  LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
303	  A preliminary version of LZ4 de/compression tool is available at
304	  <https://code.google.com/p/lz4/>.
305
306	  Its compression ratio is worse than LZO. The size of the kernel
307	  is about 8% bigger than LZO. But the decompression speed is
308	  faster than LZO.
309
310config KERNEL_ZSTD
311	bool "ZSTD"
312	depends on HAVE_KERNEL_ZSTD
313	help
314	  ZSTD is a compression algorithm targeting intermediate compression
315	  with fast decompression speed. It will compress better than GZIP and
316	  decompress around the same speed as LZO, but slower than LZ4. You
317	  will need at least 192 KB RAM or more for booting. The zstd command
318	  line tool is required for compression.
319
320config KERNEL_UNCOMPRESSED
321	bool "None"
322	depends on HAVE_KERNEL_UNCOMPRESSED
323	help
324	  Produce uncompressed kernel image. This option is usually not what
325	  you want. It is useful for debugging the kernel in slow simulation
326	  environments, where decompressing and moving the kernel is awfully
327	  slow. This option allows early boot code to skip the decompressor
328	  and jump right at uncompressed kernel image.
329
330endchoice
331
332config DEFAULT_INIT
333	string "Default init path"
334	default ""
335	help
336	  This option determines the default init for the system if no init=
337	  option is passed on the kernel command line. If the requested path is
338	  not present, we will still then move on to attempting further
339	  locations (e.g. /sbin/init, etc). If this is empty, we will just use
340	  the fallback list when init= is not passed.
341
342config DEFAULT_HOSTNAME
343	string "Default hostname"
344	default "(none)"
345	help
346	  This option determines the default system hostname before userspace
347	  calls sethostname(2). The kernel traditionally uses "(none)" here,
348	  but you may wish to use a different default here to make a minimal
349	  system more usable with less configuration.
350
351#
352# For some reason microblaze and nios2 hard code SWAP=n.  Hopefully we can
353# add proper SWAP support to them, in which case this can be remove.
354#
355config ARCH_NO_SWAP
356	bool
357
358config SWAP
359	bool "Support for paging of anonymous memory (swap)"
360	depends on MMU && BLOCK && !ARCH_NO_SWAP
361	default y
362	help
363	  This option allows you to choose whether you want to have support
364	  for so called swap devices or swap files in your kernel that are
365	  used to provide more virtual memory than the actual RAM present
366	  in your computer.  If unsure say Y.
367
368config SYSVIPC
369	bool "System V IPC"
370	help
371	  Inter Process Communication is a suite of library functions and
372	  system calls which let processes (running programs) synchronize and
373	  exchange information. It is generally considered to be a good thing,
374	  and some programs won't run unless you say Y here. In particular, if
375	  you want to run the DOS emulator dosemu under Linux (read the
376	  DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
377	  you'll need to say Y here.
378
379	  You can find documentation about IPC with "info ipc" and also in
380	  section 6.4 of the Linux Programmer's Guide, available from
381	  <http://www.tldp.org/guides.html>.
382
383config SYSVIPC_SYSCTL
384	bool
385	depends on SYSVIPC
386	depends on SYSCTL
387	default y
388
389config POSIX_MQUEUE
390	bool "POSIX Message Queues"
391	depends on NET
392	help
393	  POSIX variant of message queues is a part of IPC. In POSIX message
394	  queues every message has a priority which decides about succession
395	  of receiving it by a process. If you want to compile and run
396	  programs written e.g. for Solaris with use of its POSIX message
397	  queues (functions mq_*) say Y here.
398
399	  POSIX message queues are visible as a filesystem called 'mqueue'
400	  and can be mounted somewhere if you want to do filesystem
401	  operations on message queues.
402
403	  If unsure, say Y.
404
405config POSIX_MQUEUE_SYSCTL
406	bool
407	depends on POSIX_MQUEUE
408	depends on SYSCTL
409	default y
410
411config WATCH_QUEUE
412	bool "General notification queue"
413	default n
414	help
415
416	  This is a general notification queue for the kernel to pass events to
417	  userspace by splicing them into pipes.  It can be used in conjunction
418	  with watches for key/keyring change notifications and device
419	  notifications.
420
421	  See Documentation/watch_queue.rst
422
423config CROSS_MEMORY_ATTACH
424	bool "Enable process_vm_readv/writev syscalls"
425	depends on MMU
426	default y
427	help
428	  Enabling this option adds the system calls process_vm_readv and
429	  process_vm_writev which allow a process with the correct privileges
430	  to directly read from or write to another process' address space.
431	  See the man page for more details.
432
433config USELIB
434	bool "uselib syscall"
435	def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
436	help
437	  This option enables the uselib syscall, a system call used in the
438	  dynamic linker from libc5 and earlier.  glibc does not use this
439	  system call.  If you intend to run programs built on libc5 or
440	  earlier, you may need to enable this syscall.  Current systems
441	  running glibc can safely disable this.
442
443config AUDIT
444	bool "Auditing support"
445	depends on NET
446	help
447	  Enable auditing infrastructure that can be used with another
448	  kernel subsystem, such as SELinux (which requires this for
449	  logging of avc messages output).  System call auditing is included
450	  on architectures which support it.
451
452config HAVE_ARCH_AUDITSYSCALL
453	bool
454
455config AUDITSYSCALL
456	def_bool y
457	depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
458	select FSNOTIFY
459
460source "kernel/irq/Kconfig"
461source "kernel/time/Kconfig"
462source "kernel/bpf/Kconfig"
463source "kernel/Kconfig.preempt"
464
465menu "CPU/Task time and stats accounting"
466
467config VIRT_CPU_ACCOUNTING
468	bool
469
470choice
471	prompt "Cputime accounting"
472	default TICK_CPU_ACCOUNTING if !PPC64
473	default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
474
475# Kind of a stub config for the pure tick based cputime accounting
476config TICK_CPU_ACCOUNTING
477	bool "Simple tick based cputime accounting"
478	depends on !S390 && !NO_HZ_FULL
479	help
480	  This is the basic tick based cputime accounting that maintains
481	  statistics about user, system and idle time spent on per jiffies
482	  granularity.
483
484	  If unsure, say Y.
485
486config VIRT_CPU_ACCOUNTING_NATIVE
487	bool "Deterministic task and CPU time accounting"
488	depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
489	select VIRT_CPU_ACCOUNTING
490	help
491	  Select this option to enable more accurate task and CPU time
492	  accounting.  This is done by reading a CPU counter on each
493	  kernel entry and exit and on transitions within the kernel
494	  between system, softirq and hardirq state, so there is a
495	  small performance impact.  In the case of s390 or IBM POWER > 5,
496	  this also enables accounting of stolen time on logically-partitioned
497	  systems.
498
499config VIRT_CPU_ACCOUNTING_GEN
500	bool "Full dynticks CPU time accounting"
501	depends on HAVE_CONTEXT_TRACKING
502	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
503	depends on GENERIC_CLOCKEVENTS
504	select VIRT_CPU_ACCOUNTING
505	select CONTEXT_TRACKING
506	help
507	  Select this option to enable task and CPU time accounting on full
508	  dynticks systems. This accounting is implemented by watching every
509	  kernel-user boundaries using the context tracking subsystem.
510	  The accounting is thus performed at the expense of some significant
511	  overhead.
512
513	  For now this is only useful if you are working on the full
514	  dynticks subsystem development.
515
516	  If unsure, say N.
517
518endchoice
519
520config IRQ_TIME_ACCOUNTING
521	bool "Fine granularity task level IRQ time accounting"
522	depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
523	help
524	  Select this option to enable fine granularity task irq time
525	  accounting. This is done by reading a timestamp on each
526	  transitions between softirq and hardirq state, so there can be a
527	  small performance impact.
528
529	  If in doubt, say N here.
530
531config HAVE_SCHED_AVG_IRQ
532	def_bool y
533	depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
534	depends on SMP
535
536config SCHED_THERMAL_PRESSURE
537	bool
538	default y if ARM && ARM_CPU_TOPOLOGY
539	default y if ARM64
540	depends on SMP
541	depends on CPU_FREQ_THERMAL
542	help
543	  Select this option to enable thermal pressure accounting in the
544	  scheduler. Thermal pressure is the value conveyed to the scheduler
545	  that reflects the reduction in CPU compute capacity resulted from
546	  thermal throttling. Thermal throttling occurs when the performance of
547	  a CPU is capped due to high operating temperatures.
548
549	  If selected, the scheduler will be able to balance tasks accordingly,
550	  i.e. put less load on throttled CPUs than on non/less throttled ones.
551
552	  This requires the architecture to implement
553	  arch_set_thermal_pressure() and arch_scale_thermal_pressure().
554
555config BSD_PROCESS_ACCT
556	bool "BSD Process Accounting"
557	depends on MULTIUSER
558	help
559	  If you say Y here, a user level program will be able to instruct the
560	  kernel (via a special system call) to write process accounting
561	  information to a file: whenever a process exits, information about
562	  that process will be appended to the file by the kernel.  The
563	  information includes things such as creation time, owning user,
564	  command name, memory usage, controlling terminal etc. (the complete
565	  list is in the struct acct in <file:include/linux/acct.h>).  It is
566	  up to the user level program to do useful things with this
567	  information.  This is generally a good idea, so say Y.
568
569config BSD_PROCESS_ACCT_V3
570	bool "BSD Process Accounting version 3 file format"
571	depends on BSD_PROCESS_ACCT
572	default n
573	help
574	  If you say Y here, the process accounting information is written
575	  in a new file format that also logs the process IDs of each
576	  process and its parent. Note that this file format is incompatible
577	  with previous v0/v1/v2 file formats, so you will need updated tools
578	  for processing it. A preliminary version of these tools is available
579	  at <http://www.gnu.org/software/acct/>.
580
581config TASKSTATS
582	bool "Export task/process statistics through netlink"
583	depends on NET
584	depends on MULTIUSER
585	default n
586	help
587	  Export selected statistics for tasks/processes through the
588	  generic netlink interface. Unlike BSD process accounting, the
589	  statistics are available during the lifetime of tasks/processes as
590	  responses to commands. Like BSD accounting, they are sent to user
591	  space on task exit.
592
593	  Say N if unsure.
594
595config TASK_DELAY_ACCT
596	bool "Enable per-task delay accounting"
597	depends on TASKSTATS
598	select SCHED_INFO
599	help
600	  Collect information on time spent by a task waiting for system
601	  resources like cpu, synchronous block I/O completion and swapping
602	  in pages. Such statistics can help in setting a task's priorities
603	  relative to other tasks for cpu, io, rss limits etc.
604
605	  Say N if unsure.
606
607config TASK_XACCT
608	bool "Enable extended accounting over taskstats"
609	depends on TASKSTATS
610	help
611	  Collect extended task accounting data and send the data
612	  to userland for processing over the taskstats interface.
613
614	  Say N if unsure.
615
616config TASK_IO_ACCOUNTING
617	bool "Enable per-task storage I/O accounting"
618	depends on TASK_XACCT
619	help
620	  Collect information on the number of bytes of storage I/O which this
621	  task has caused.
622
623	  Say N if unsure.
624
625config PSI
626	bool "Pressure stall information tracking"
627	help
628	  Collect metrics that indicate how overcommitted the CPU, memory,
629	  and IO capacity are in the system.
630
631	  If you say Y here, the kernel will create /proc/pressure/ with the
632	  pressure statistics files cpu, memory, and io. These will indicate
633	  the share of walltime in which some or all tasks in the system are
634	  delayed due to contention of the respective resource.
635
636	  In kernels with cgroup support, cgroups (cgroup2 only) will
637	  have cpu.pressure, memory.pressure, and io.pressure files,
638	  which aggregate pressure stalls for the grouped tasks only.
639
640	  For more details see Documentation/accounting/psi.rst.
641
642	  Say N if unsure.
643
644config PSI_DEFAULT_DISABLED
645	bool "Require boot parameter to enable pressure stall information tracking"
646	default n
647	depends on PSI
648	help
649	  If set, pressure stall information tracking will be disabled
650	  per default but can be enabled through passing psi=1 on the
651	  kernel commandline during boot.
652
653	  This feature adds some code to the task wakeup and sleep
654	  paths of the scheduler. The overhead is too low to affect
655	  common scheduling-intense workloads in practice (such as
656	  webservers, memcache), but it does show up in artificial
657	  scheduler stress tests, such as hackbench.
658
659	  If you are paranoid and not sure what the kernel will be
660	  used for, say Y.
661
662	  Say N if unsure.
663
664endmenu # "CPU/Task time and stats accounting"
665
666config CPU_ISOLATION
667	bool "CPU isolation"
668	depends on SMP || COMPILE_TEST
669	default y
670	help
671	  Make sure that CPUs running critical tasks are not disturbed by
672	  any source of "noise" such as unbound workqueues, timers, kthreads...
673	  Unbound jobs get offloaded to housekeeping CPUs. This is driven by
674	  the "isolcpus=" boot parameter.
675
676	  Say Y if unsure.
677
678source "kernel/rcu/Kconfig"
679
680config BUILD_BIN2C
681	bool
682	default n
683
684config IKCONFIG
685	tristate "Kernel .config support"
686	help
687	  This option enables the complete Linux kernel ".config" file
688	  contents to be saved in the kernel. It provides documentation
689	  of which kernel options are used in a running kernel or in an
690	  on-disk kernel.  This information can be extracted from the kernel
691	  image file with the script scripts/extract-ikconfig and used as
692	  input to rebuild the current kernel or to build another kernel.
693	  It can also be extracted from a running kernel by reading
694	  /proc/config.gz if enabled (below).
695
696config IKCONFIG_PROC
697	bool "Enable access to .config through /proc/config.gz"
698	depends on IKCONFIG && PROC_FS
699	help
700	  This option enables access to the kernel configuration file
701	  through /proc/config.gz.
702
703config IKHEADERS
704	tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
705	depends on SYSFS
706	help
707	  This option enables access to the in-kernel headers that are generated during
708	  the build process. These can be used to build eBPF tracing programs,
709	  or similar programs.  If you build the headers as a module, a module called
710	  kheaders.ko is built which can be loaded on-demand to get access to headers.
711
712config LOG_BUF_SHIFT
713	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
714	range 12 25 if !H8300
715	range 12 19 if H8300
716	default 17
717	depends on PRINTK
718	help
719	  Select the minimal kernel log buffer size as a power of 2.
720	  The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
721	  parameter, see below. Any higher size also might be forced
722	  by "log_buf_len" boot parameter.
723
724	  Examples:
725		     17 => 128 KB
726		     16 => 64 KB
727		     15 => 32 KB
728		     14 => 16 KB
729		     13 =>  8 KB
730		     12 =>  4 KB
731
732config LOG_CPU_MAX_BUF_SHIFT
733	int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
734	depends on SMP
735	range 0 21
736	default 12 if !BASE_SMALL
737	default 0 if BASE_SMALL
738	depends on PRINTK
739	help
740	  This option allows to increase the default ring buffer size
741	  according to the number of CPUs. The value defines the contribution
742	  of each CPU as a power of 2. The used space is typically only few
743	  lines however it might be much more when problems are reported,
744	  e.g. backtraces.
745
746	  The increased size means that a new buffer has to be allocated and
747	  the original static one is unused. It makes sense only on systems
748	  with more CPUs. Therefore this value is used only when the sum of
749	  contributions is greater than the half of the default kernel ring
750	  buffer as defined by LOG_BUF_SHIFT. The default values are set
751	  so that more than 16 CPUs are needed to trigger the allocation.
752
753	  Also this option is ignored when "log_buf_len" kernel parameter is
754	  used as it forces an exact (power of two) size of the ring buffer.
755
756	  The number of possible CPUs is used for this computation ignoring
757	  hotplugging making the computation optimal for the worst case
758	  scenario while allowing a simple algorithm to be used from bootup.
759
760	  Examples shift values and their meaning:
761		     17 => 128 KB for each CPU
762		     16 =>  64 KB for each CPU
763		     15 =>  32 KB for each CPU
764		     14 =>  16 KB for each CPU
765		     13 =>   8 KB for each CPU
766		     12 =>   4 KB for each CPU
767
768config PRINTK_SAFE_LOG_BUF_SHIFT
769	int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
770	range 10 21
771	default 13
772	depends on PRINTK
773	help
774	  Select the size of an alternate printk per-CPU buffer where messages
775	  printed from usafe contexts are temporary stored. One example would
776	  be NMI messages, another one - printk recursion. The messages are
777	  copied to the main log buffer in a safe context to avoid a deadlock.
778	  The value defines the size as a power of 2.
779
780	  Those messages are rare and limited. The largest one is when
781	  a backtrace is printed. It usually fits into 4KB. Select
782	  8KB if you want to be on the safe side.
783
784	  Examples:
785		     17 => 128 KB for each CPU
786		     16 =>  64 KB for each CPU
787		     15 =>  32 KB for each CPU
788		     14 =>  16 KB for each CPU
789		     13 =>   8 KB for each CPU
790		     12 =>   4 KB for each CPU
791
792config PRINTK_INDEX
793	bool "Printk indexing debugfs interface"
794	depends on PRINTK && DEBUG_FS
795	help
796	  Add support for indexing of all printk formats known at compile time
797	  at <debugfs>/printk/index/<module>.
798
799	  This can be used as part of maintaining daemons which monitor
800	  /dev/kmsg, as it permits auditing the printk formats present in a
801	  kernel, allowing detection of cases where monitored printks are
802	  changed or no longer present.
803
804	  There is no additional runtime cost to printk with this enabled.
805
806#
807# Architectures with an unreliable sched_clock() should select this:
808#
809config HAVE_UNSTABLE_SCHED_CLOCK
810	bool
811
812config GENERIC_SCHED_CLOCK
813	bool
814
815menu "Scheduler features"
816
817config UCLAMP_TASK
818	bool "Enable utilization clamping for RT/FAIR tasks"
819	depends on CPU_FREQ_GOV_SCHEDUTIL
820	help
821	  This feature enables the scheduler to track the clamped utilization
822	  of each CPU based on RUNNABLE tasks scheduled on that CPU.
823
824	  With this option, the user can specify the min and max CPU
825	  utilization allowed for RUNNABLE tasks. The max utilization defines
826	  the maximum frequency a task should use while the min utilization
827	  defines the minimum frequency it should use.
828
829	  Both min and max utilization clamp values are hints to the scheduler,
830	  aiming at improving its frequency selection policy, but they do not
831	  enforce or grant any specific bandwidth for tasks.
832
833	  If in doubt, say N.
834
835config UCLAMP_BUCKETS_COUNT
836	int "Number of supported utilization clamp buckets"
837	range 5 20
838	default 5
839	depends on UCLAMP_TASK
840	help
841	  Defines the number of clamp buckets to use. The range of each bucket
842	  will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
843	  number of clamp buckets the finer their granularity and the higher
844	  the precision of clamping aggregation and tracking at run-time.
845
846	  For example, with the minimum configuration value we will have 5
847	  clamp buckets tracking 20% utilization each. A 25% boosted tasks will
848	  be refcounted in the [20..39]% bucket and will set the bucket clamp
849	  effective value to 25%.
850	  If a second 30% boosted task should be co-scheduled on the same CPU,
851	  that task will be refcounted in the same bucket of the first task and
852	  it will boost the bucket clamp effective value to 30%.
853	  The clamp effective value of a bucket is reset to its nominal value
854	  (20% in the example above) when there are no more tasks refcounted in
855	  that bucket.
856
857	  An additional boost/capping margin can be added to some tasks. In the
858	  example above the 25% task will be boosted to 30% until it exits the
859	  CPU. If that should be considered not acceptable on certain systems,
860	  it's always possible to reduce the margin by increasing the number of
861	  clamp buckets to trade off used memory for run-time tracking
862	  precision.
863
864	  If in doubt, use the default value.
865
866endmenu
867
868#
869# For architectures that want to enable the support for NUMA-affine scheduler
870# balancing logic:
871#
872config ARCH_SUPPORTS_NUMA_BALANCING
873	bool
874
875#
876# For architectures that prefer to flush all TLBs after a number of pages
877# are unmapped instead of sending one IPI per page to flush. The architecture
878# must provide guarantees on what happens if a clean TLB cache entry is
879# written after the unmap. Details are in mm/rmap.c near the check for
880# should_defer_flush. The architecture should also consider if the full flush
881# and the refill costs are offset by the savings of sending fewer IPIs.
882config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
883	bool
884
885config CC_HAS_INT128
886	def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
887
888#
889# For architectures that know their GCC __int128 support is sound
890#
891config ARCH_SUPPORTS_INT128
892	bool
893
894# For architectures that (ab)use NUMA to represent different memory regions
895# all cpu-local but of different latencies, such as SuperH.
896#
897config ARCH_WANT_NUMA_VARIABLE_LOCALITY
898	bool
899
900config NUMA_BALANCING
901	bool "Memory placement aware NUMA scheduler"
902	depends on ARCH_SUPPORTS_NUMA_BALANCING
903	depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
904	depends on SMP && NUMA && MIGRATION
905	help
906	  This option adds support for automatic NUMA aware memory/task placement.
907	  The mechanism is quite primitive and is based on migrating memory when
908	  it has references to the node the task is running on.
909
910	  This system will be inactive on UMA systems.
911
912config NUMA_BALANCING_DEFAULT_ENABLED
913	bool "Automatically enable NUMA aware memory/task placement"
914	default y
915	depends on NUMA_BALANCING
916	help
917	  If set, automatic NUMA balancing will be enabled if running on a NUMA
918	  machine.
919
920menuconfig CGROUPS
921	bool "Control Group support"
922	select KERNFS
923	help
924	  This option adds support for grouping sets of processes together, for
925	  use with process control subsystems such as Cpusets, CFS, memory
926	  controls or device isolation.
927	  See
928		- Documentation/scheduler/sched-design-CFS.rst	(CFS)
929		- Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
930					  and resource control)
931
932	  Say N if unsure.
933
934if CGROUPS
935
936config PAGE_COUNTER
937	bool
938
939config MEMCG
940	bool "Memory controller"
941	select PAGE_COUNTER
942	select EVENTFD
943	help
944	  Provides control over the memory footprint of tasks in a cgroup.
945
946config MEMCG_SWAP
947	bool
948	depends on MEMCG && SWAP
949	default y
950
951config MEMCG_KMEM
952	bool
953	depends on MEMCG && !SLOB
954	default y
955
956config BLK_CGROUP
957	bool "IO controller"
958	depends on BLOCK
959	default n
960	help
961	Generic block IO controller cgroup interface. This is the common
962	cgroup interface which should be used by various IO controlling
963	policies.
964
965	Currently, CFQ IO scheduler uses it to recognize task groups and
966	control disk bandwidth allocation (proportional time slice allocation)
967	to such task groups. It is also used by bio throttling logic in
968	block layer to implement upper limit in IO rates on a device.
969
970	This option only enables generic Block IO controller infrastructure.
971	One needs to also enable actual IO controlling logic/policy. For
972	enabling proportional weight division of disk bandwidth in CFQ, set
973	CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
974	CONFIG_BLK_DEV_THROTTLING=y.
975
976	See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
977
978config CGROUP_WRITEBACK
979	bool
980	depends on MEMCG && BLK_CGROUP
981	default y
982
983menuconfig CGROUP_SCHED
984	bool "CPU controller"
985	default n
986	help
987	  This feature lets CPU scheduler recognize task groups and control CPU
988	  bandwidth allocation to such task groups. It uses cgroups to group
989	  tasks.
990
991if CGROUP_SCHED
992config FAIR_GROUP_SCHED
993	bool "Group scheduling for SCHED_OTHER"
994	depends on CGROUP_SCHED
995	default CGROUP_SCHED
996
997config CFS_BANDWIDTH
998	bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
999	depends on FAIR_GROUP_SCHED
1000	default n
1001	help
1002	  This option allows users to define CPU bandwidth rates (limits) for
1003	  tasks running within the fair group scheduler.  Groups with no limit
1004	  set are considered to be unconstrained and will run with no
1005	  restriction.
1006	  See Documentation/scheduler/sched-bwc.rst for more information.
1007
1008config RT_GROUP_SCHED
1009	bool "Group scheduling for SCHED_RR/FIFO"
1010	depends on CGROUP_SCHED
1011	default n
1012	help
1013	  This feature lets you explicitly allocate real CPU bandwidth
1014	  to task groups. If enabled, it will also make it impossible to
1015	  schedule realtime tasks for non-root users until you allocate
1016	  realtime bandwidth for them.
1017	  See Documentation/scheduler/sched-rt-group.rst for more information.
1018
1019endif #CGROUP_SCHED
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	select PROC_CHILDREN
1250	select KCMP
1251	default n
1252	help
1253	  Enables additional kernel features in a sake of checkpoint/restore.
1254	  In particular it adds auxiliary prctl codes to setup process text,
1255	  data and heap segment sizes, and a few additional /proc filesystem
1256	  entries.
1257
1258	  If unsure, say N here.
1259
1260config SCHED_AUTOGROUP
1261	bool "Automatic process group scheduling"
1262	select CGROUPS
1263	select CGROUP_SCHED
1264	select FAIR_GROUP_SCHED
1265	help
1266	  This option optimizes the scheduler for common desktop workloads by
1267	  automatically creating and populating task groups.  This separation
1268	  of workloads isolates aggressive CPU burners (like build jobs) from
1269	  desktop applications.  Task group autogeneration is currently based
1270	  upon task session.
1271
1272config SYSFS_DEPRECATED
1273	bool "Enable deprecated sysfs features to support old userspace tools"
1274	depends on SYSFS
1275	default n
1276	help
1277	  This option adds code that switches the layout of the "block" class
1278	  devices, to not show up in /sys/class/block/, but only in
1279	  /sys/block/.
1280
1281	  This switch is only active when the sysfs.deprecated=1 boot option is
1282	  passed or the SYSFS_DEPRECATED_V2 option is set.
1283
1284	  This option allows new kernels to run on old distributions and tools,
1285	  which might get confused by /sys/class/block/. Since 2007/2008 all
1286	  major distributions and tools handle this just fine.
1287
1288	  Recent distributions and userspace tools after 2009/2010 depend on
1289	  the existence of /sys/class/block/, and will not work with this
1290	  option enabled.
1291
1292	  Only if you are using a new kernel on an old distribution, you might
1293	  need to say Y here.
1294
1295config SYSFS_DEPRECATED_V2
1296	bool "Enable deprecated sysfs features by default"
1297	default n
1298	depends on SYSFS
1299	depends on SYSFS_DEPRECATED
1300	help
1301	  Enable deprecated sysfs by default.
1302
1303	  See the CONFIG_SYSFS_DEPRECATED option for more details about this
1304	  option.
1305
1306	  Only if you are using a new kernel on an old distribution, you might
1307	  need to say Y here. Even then, odds are you would not need it
1308	  enabled, you can always pass the boot option if absolutely necessary.
1309
1310config RELAY
1311	bool "Kernel->user space relay support (formerly relayfs)"
1312	select IRQ_WORK
1313	help
1314	  This option enables support for relay interface support in
1315	  certain file systems (such as debugfs).
1316	  It is designed to provide an efficient mechanism for tools and
1317	  facilities to relay large amounts of data from kernel space to
1318	  user space.
1319
1320	  If unsure, say N.
1321
1322config BLK_DEV_INITRD
1323	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1324	help
1325	  The initial RAM filesystem is a ramfs which is loaded by the
1326	  boot loader (loadlin or lilo) and that is mounted as root
1327	  before the normal boot procedure. It is typically used to
1328	  load modules needed to mount the "real" root file system,
1329	  etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1330
1331	  If RAM disk support (BLK_DEV_RAM) is also included, this
1332	  also enables initial RAM disk (initrd) support and adds
1333	  15 Kbytes (more on some other architectures) to the kernel size.
1334
1335	  If unsure say Y.
1336
1337if BLK_DEV_INITRD
1338
1339source "usr/Kconfig"
1340
1341endif
1342
1343config BOOT_CONFIG
1344	bool "Boot config support"
1345	select BLK_DEV_INITRD
1346	help
1347	  Extra boot config allows system admin to pass a config file as
1348	  complemental extension of kernel cmdline when booting.
1349	  The boot config file must be attached at the end of initramfs
1350	  with checksum, size and magic word.
1351	  See <file:Documentation/admin-guide/bootconfig.rst> for details.
1352
1353	  If unsure, say Y.
1354
1355choice
1356	prompt "Compiler optimization level"
1357	default CC_OPTIMIZE_FOR_PERFORMANCE
1358
1359config CC_OPTIMIZE_FOR_PERFORMANCE
1360	bool "Optimize for performance (-O2)"
1361	help
1362	  This is the default optimization level for the kernel, building
1363	  with the "-O2" compiler flag for best performance and most
1364	  helpful compile-time warnings.
1365
1366config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1367	bool "Optimize more for performance (-O3)"
1368	depends on ARC
1369	help
1370	  Choosing this option will pass "-O3" to your compiler to optimize
1371	  the kernel yet more for performance.
1372
1373config CC_OPTIMIZE_FOR_SIZE
1374	bool "Optimize for size (-Os)"
1375	help
1376	  Choosing this option will pass "-Os" to your compiler resulting
1377	  in a smaller kernel.
1378
1379endchoice
1380
1381config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1382	bool
1383	help
1384	  This requires that the arch annotates or otherwise protects
1385	  its external entry points from being discarded. Linker scripts
1386	  must also merge .text.*, .data.*, and .bss.* correctly into
1387	  output sections. Care must be taken not to pull in unrelated
1388	  sections (e.g., '.text.init'). Typically '.' in section names
1389	  is used to distinguish them from label names / C identifiers.
1390
1391config LD_DEAD_CODE_DATA_ELIMINATION
1392	bool "Dead code and data elimination (EXPERIMENTAL)"
1393	depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1394	depends on EXPERT
1395	depends on $(cc-option,-ffunction-sections -fdata-sections)
1396	depends on $(ld-option,--gc-sections)
1397	help
1398	  Enable this if you want to do dead code and data elimination with
1399	  the linker by compiling with -ffunction-sections -fdata-sections,
1400	  and linking with --gc-sections.
1401
1402	  This can reduce on disk and in-memory size of the kernel
1403	  code and static data, particularly for small configs and
1404	  on small systems. This has the possibility of introducing
1405	  silently broken kernel if the required annotations are not
1406	  present. This option is not well tested yet, so use at your
1407	  own risk.
1408
1409config LD_ORPHAN_WARN
1410	def_bool y
1411	depends on ARCH_WANT_LD_ORPHAN_WARN
1412	depends on !LD_IS_LLD || LLD_VERSION >= 110000
1413	depends on $(ld-option,--orphan-handling=warn)
1414
1415config SYSCTL
1416	bool
1417
1418config HAVE_UID16
1419	bool
1420
1421config SYSCTL_EXCEPTION_TRACE
1422	bool
1423	help
1424	  Enable support for /proc/sys/debug/exception-trace.
1425
1426config SYSCTL_ARCH_UNALIGN_NO_WARN
1427	bool
1428	help
1429	  Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1430	  Allows arch to define/use @no_unaligned_warning to possibly warn
1431	  about unaligned access emulation going on under the hood.
1432
1433config SYSCTL_ARCH_UNALIGN_ALLOW
1434	bool
1435	help
1436	  Enable support for /proc/sys/kernel/unaligned-trap
1437	  Allows arches to define/use @unaligned_enabled to runtime toggle
1438	  the unaligned access emulation.
1439	  see arch/parisc/kernel/unaligned.c for reference
1440
1441config HAVE_PCSPKR_PLATFORM
1442	bool
1443
1444# interpreter that classic socket filters depend on
1445config BPF
1446	bool
1447
1448menuconfig EXPERT
1449	bool "Configure standard kernel features (expert users)"
1450	# Unhide debug options, to make the on-by-default options visible
1451	select DEBUG_KERNEL
1452	help
1453	  This option allows certain base kernel options and settings
1454	  to be disabled or tweaked. This is for specialized
1455	  environments which can tolerate a "non-standard" kernel.
1456	  Only use this if you really know what you are doing.
1457
1458config UID16
1459	bool "Enable 16-bit UID system calls" if EXPERT
1460	depends on HAVE_UID16 && MULTIUSER
1461	default y
1462	help
1463	  This enables the legacy 16-bit UID syscall wrappers.
1464
1465config MULTIUSER
1466	bool "Multiple users, groups and capabilities support" if EXPERT
1467	default y
1468	help
1469	  This option enables support for non-root users, groups and
1470	  capabilities.
1471
1472	  If you say N here, all processes will run with UID 0, GID 0, and all
1473	  possible capabilities.  Saying N here also compiles out support for
1474	  system calls related to UIDs, GIDs, and capabilities, such as setuid,
1475	  setgid, and capset.
1476
1477	  If unsure, say Y here.
1478
1479config SGETMASK_SYSCALL
1480	bool "sgetmask/ssetmask syscalls support" if EXPERT
1481	def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1482	help
1483	  sys_sgetmask and sys_ssetmask are obsolete system calls
1484	  no longer supported in libc but still enabled by default in some
1485	  architectures.
1486
1487	  If unsure, leave the default option here.
1488
1489config SYSFS_SYSCALL
1490	bool "Sysfs syscall support" if EXPERT
1491	default y
1492	help
1493	  sys_sysfs is an obsolete system call no longer supported in libc.
1494	  Note that disabling this option is more secure but might break
1495	  compatibility with some systems.
1496
1497	  If unsure say Y here.
1498
1499config FHANDLE
1500	bool "open by fhandle syscalls" if EXPERT
1501	select EXPORTFS
1502	default y
1503	help
1504	  If you say Y here, a user level program will be able to map
1505	  file names to handle and then later use the handle for
1506	  different file system operations. This is useful in implementing
1507	  userspace file servers, which now track files using handles instead
1508	  of names. The handle would remain the same even if file names
1509	  get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1510	  syscalls.
1511
1512config POSIX_TIMERS
1513	bool "Posix Clocks & timers" if EXPERT
1514	default y
1515	help
1516	  This includes native support for POSIX timers to the kernel.
1517	  Some embedded systems have no use for them and therefore they
1518	  can be configured out to reduce the size of the kernel image.
1519
1520	  When this option is disabled, the following syscalls won't be
1521	  available: timer_create, timer_gettime: timer_getoverrun,
1522	  timer_settime, timer_delete, clock_adjtime, getitimer,
1523	  setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1524	  clock_getres and clock_nanosleep syscalls will be limited to
1525	  CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1526
1527	  If unsure say y.
1528
1529config PRINTK
1530	default y
1531	bool "Enable support for printk" if EXPERT
1532	select IRQ_WORK
1533	help
1534	  This option enables normal printk support. Removing it
1535	  eliminates most of the message strings from the kernel image
1536	  and makes the kernel more or less silent. As this makes it
1537	  very difficult to diagnose system problems, saying N here is
1538	  strongly discouraged.
1539
1540config BUG
1541	bool "BUG() support" if EXPERT
1542	default y
1543	help
1544	  Disabling this option eliminates support for BUG and WARN, reducing
1545	  the size of your kernel image and potentially quietly ignoring
1546	  numerous fatal conditions. You should only consider disabling this
1547	  option for embedded systems with no facilities for reporting errors.
1548	  Just say Y.
1549
1550config ELF_CORE
1551	depends on COREDUMP
1552	default y
1553	bool "Enable ELF core dumps" if EXPERT
1554	help
1555	  Enable support for generating core dumps. Disabling saves about 4k.
1556
1557
1558config PCSPKR_PLATFORM
1559	bool "Enable PC-Speaker support" if EXPERT
1560	depends on HAVE_PCSPKR_PLATFORM
1561	select I8253_LOCK
1562	default y
1563	help
1564	  This option allows to disable the internal PC-Speaker
1565	  support, saving some memory.
1566
1567config BASE_FULL
1568	default y
1569	bool "Enable full-sized data structures for core" if EXPERT
1570	help
1571	  Disabling this option reduces the size of miscellaneous core
1572	  kernel data structures. This saves memory on small machines,
1573	  but may reduce performance.
1574
1575config FUTEX
1576	bool "Enable futex support" if EXPERT
1577	default y
1578	imply RT_MUTEXES
1579	help
1580	  Disabling this option will cause the kernel to be built without
1581	  support for "fast userspace mutexes".  The resulting kernel may not
1582	  run glibc-based applications correctly.
1583
1584config FUTEX_PI
1585	bool
1586	depends on FUTEX && RT_MUTEXES
1587	default y
1588
1589config HAVE_FUTEX_CMPXCHG
1590	bool
1591	depends on FUTEX
1592	help
1593	  Architectures should select this if futex_atomic_cmpxchg_inatomic()
1594	  is implemented and always working. This removes a couple of runtime
1595	  checks.
1596
1597config EPOLL
1598	bool "Enable eventpoll support" if EXPERT
1599	default y
1600	help
1601	  Disabling this option will cause the kernel to be built without
1602	  support for epoll family of system calls.
1603
1604config SIGNALFD
1605	bool "Enable signalfd() system call" if EXPERT
1606	default y
1607	help
1608	  Enable the signalfd() system call that allows to receive signals
1609	  on a file descriptor.
1610
1611	  If unsure, say Y.
1612
1613config TIMERFD
1614	bool "Enable timerfd() system call" if EXPERT
1615	default y
1616	help
1617	  Enable the timerfd() system call that allows to receive timer
1618	  events on a file descriptor.
1619
1620	  If unsure, say Y.
1621
1622config EVENTFD
1623	bool "Enable eventfd() system call" if EXPERT
1624	default y
1625	help
1626	  Enable the eventfd() system call that allows to receive both
1627	  kernel notification (ie. KAIO) or userspace notifications.
1628
1629	  If unsure, say Y.
1630
1631config SHMEM
1632	bool "Use full shmem filesystem" if EXPERT
1633	default y
1634	depends on MMU
1635	help
1636	  The shmem is an internal filesystem used to manage shared memory.
1637	  It is backed by swap and manages resource limits. It is also exported
1638	  to userspace as tmpfs if TMPFS is enabled. Disabling this
1639	  option replaces shmem and tmpfs with the much simpler ramfs code,
1640	  which may be appropriate on small systems without swap.
1641
1642config AIO
1643	bool "Enable AIO support" if EXPERT
1644	default y
1645	help
1646	  This option enables POSIX asynchronous I/O which may by used
1647	  by some high performance threaded applications. Disabling
1648	  this option saves about 7k.
1649
1650config IO_URING
1651	bool "Enable IO uring support" if EXPERT
1652	select IO_WQ
1653	default y
1654	help
1655	  This option enables support for the io_uring interface, enabling
1656	  applications to submit and complete IO through submission and
1657	  completion rings that are shared between the kernel and application.
1658
1659config ADVISE_SYSCALLS
1660	bool "Enable madvise/fadvise syscalls" if EXPERT
1661	default y
1662	help
1663	  This option enables the madvise and fadvise syscalls, used by
1664	  applications to advise the kernel about their future memory or file
1665	  usage, improving performance. If building an embedded system where no
1666	  applications use these syscalls, you can disable this option to save
1667	  space.
1668
1669config HAVE_ARCH_USERFAULTFD_WP
1670	bool
1671	help
1672	  Arch has userfaultfd write protection support
1673
1674config HAVE_ARCH_USERFAULTFD_MINOR
1675	bool
1676	help
1677	  Arch has userfaultfd minor fault support
1678
1679config MEMBARRIER
1680	bool "Enable membarrier() system call" if EXPERT
1681	default y
1682	help
1683	  Enable the membarrier() system call that allows issuing memory
1684	  barriers across all running threads, which can be used to distribute
1685	  the cost of user-space memory barriers asymmetrically by transforming
1686	  pairs of memory barriers into pairs consisting of membarrier() and a
1687	  compiler barrier.
1688
1689	  If unsure, say Y.
1690
1691config KALLSYMS
1692	bool "Load all symbols for debugging/ksymoops" if EXPERT
1693	default y
1694	help
1695	  Say Y here to let the kernel print out symbolic crash information and
1696	  symbolic stack backtraces. This increases the size of the kernel
1697	  somewhat, as all symbols have to be loaded into the kernel image.
1698
1699config KALLSYMS_ALL
1700	bool "Include all symbols in kallsyms"
1701	depends on DEBUG_KERNEL && KALLSYMS
1702	help
1703	  Normally kallsyms only contains the symbols of functions for nicer
1704	  OOPS messages and backtraces (i.e., symbols from the text and inittext
1705	  sections). This is sufficient for most cases. And only in very rare
1706	  cases (e.g., when a debugger is used) all symbols are required (e.g.,
1707	  names of variables from the data sections, etc).
1708
1709	  This option makes sure that all symbols are loaded into the kernel
1710	  image (i.e., symbols from all sections) in cost of increased kernel
1711	  size (depending on the kernel configuration, it may be 300KiB or
1712	  something like this).
1713
1714	  Say N unless you really need all symbols.
1715
1716config KALLSYMS_ABSOLUTE_PERCPU
1717	bool
1718	depends on KALLSYMS
1719	default X86_64 && SMP
1720
1721config KALLSYMS_BASE_RELATIVE
1722	bool
1723	depends on KALLSYMS
1724	default !IA64
1725	help
1726	  Instead of emitting them as absolute values in the native word size,
1727	  emit the symbol references in the kallsyms table as 32-bit entries,
1728	  each containing a relative value in the range [base, base + U32_MAX]
1729	  or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1730	  an absolute value in the range [0, S32_MAX] or a relative value in the
1731	  range [base, base + S32_MAX], where base is the lowest relative symbol
1732	  address encountered in the image.
1733
1734	  On 64-bit builds, this reduces the size of the address table by 50%,
1735	  but more importantly, it results in entries whose values are build
1736	  time constants, and no relocation pass is required at runtime to fix
1737	  up the entries based on the runtime load address of the kernel.
1738
1739# end of the "standard kernel features (expert users)" menu
1740
1741# syscall, maps, verifier
1742
1743config USERFAULTFD
1744	bool "Enable userfaultfd() system call"
1745	depends on MMU
1746	help
1747	  Enable the userfaultfd() system call that allows to intercept and
1748	  handle page faults in userland.
1749
1750config ARCH_HAS_MEMBARRIER_CALLBACKS
1751	bool
1752
1753config ARCH_HAS_MEMBARRIER_SYNC_CORE
1754	bool
1755
1756config KCMP
1757	bool "Enable kcmp() system call" if EXPERT
1758	help
1759	  Enable the kernel resource comparison system call. It provides
1760	  user-space with the ability to compare two processes to see if they
1761	  share a common resource, such as a file descriptor or even virtual
1762	  memory space.
1763
1764	  If unsure, say N.
1765
1766config RSEQ
1767	bool "Enable rseq() system call" if EXPERT
1768	default y
1769	depends on HAVE_RSEQ
1770	select MEMBARRIER
1771	help
1772	  Enable the restartable sequences system call. It provides a
1773	  user-space cache for the current CPU number value, which
1774	  speeds up getting the current CPU number from user-space,
1775	  as well as an ABI to speed up user-space operations on
1776	  per-CPU data.
1777
1778	  If unsure, say Y.
1779
1780config DEBUG_RSEQ
1781	default n
1782	bool "Enabled debugging of rseq() system call" if EXPERT
1783	depends on RSEQ && DEBUG_KERNEL
1784	help
1785	  Enable extra debugging checks for the rseq system call.
1786
1787	  If unsure, say N.
1788
1789config EMBEDDED
1790	bool "Embedded system"
1791	select EXPERT
1792	help
1793	  This option should be enabled if compiling the kernel for
1794	  an embedded system so certain expert options are available
1795	  for configuration.
1796
1797config HAVE_PERF_EVENTS
1798	bool
1799	help
1800	  See tools/perf/design.txt for details.
1801
1802config PERF_USE_VMALLOC
1803	bool
1804	help
1805	  See tools/perf/design.txt for details
1806
1807config PC104
1808	bool "PC/104 support" if EXPERT
1809	help
1810	  Expose PC/104 form factor device drivers and options available for
1811	  selection and configuration. Enable this option if your target
1812	  machine has a PC/104 bus.
1813
1814menu "Kernel Performance Events And Counters"
1815
1816config PERF_EVENTS
1817	bool "Kernel performance events and counters"
1818	default y if PROFILING
1819	depends on HAVE_PERF_EVENTS
1820	select IRQ_WORK
1821	select SRCU
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 VM_EVENT_COUNTERS
1861	default y
1862	bool "Enable VM event counters for /proc/vmstat" if EXPERT
1863	help
1864	  VM event counters are needed for event counts to be shown.
1865	  This option allows the disabling of the VM event counters
1866	  on EXPERT systems.  /proc/vmstat will only show page counts
1867	  if VM event counters are disabled.
1868
1869config SLUB_DEBUG
1870	default y
1871	bool "Enable SLUB debugging support" if EXPERT
1872	depends on SLUB && SYSFS
1873	help
1874	  SLUB has extensive debug support features. Disabling these can
1875	  result in significant savings in code size. This also disables
1876	  SLUB sysfs support. /sys/slab will not exist and there will be
1877	  no support for cache validation etc.
1878
1879config COMPAT_BRK
1880	bool "Disable heap randomization"
1881	default y
1882	help
1883	  Randomizing heap placement makes heap exploits harder, but it
1884	  also breaks ancient binaries (including anything libc5 based).
1885	  This option changes the bootup default to heap randomization
1886	  disabled, and can be overridden at runtime by setting
1887	  /proc/sys/kernel/randomize_va_space to 2.
1888
1889	  On non-ancient distros (post-2000 ones) N is usually a safe choice.
1890
1891choice
1892	prompt "Choose SLAB allocator"
1893	default SLUB
1894	help
1895	   This option allows to select a slab allocator.
1896
1897config SLAB
1898	bool "SLAB"
1899	select HAVE_HARDENED_USERCOPY_ALLOCATOR
1900	help
1901	  The regular slab allocator that is established and known to work
1902	  well in all environments. It organizes cache hot objects in
1903	  per cpu and per node queues.
1904
1905config SLUB
1906	bool "SLUB (Unqueued Allocator)"
1907	select HAVE_HARDENED_USERCOPY_ALLOCATOR
1908	help
1909	   SLUB is a slab allocator that minimizes cache line usage
1910	   instead of managing queues of cached objects (SLAB approach).
1911	   Per cpu caching is realized using slabs of objects instead
1912	   of queues of objects. SLUB can use memory efficiently
1913	   and has enhanced diagnostics. SLUB is the default choice for
1914	   a slab allocator.
1915
1916config SLOB
1917	depends on EXPERT
1918	bool "SLOB (Simple Allocator)"
1919	help
1920	   SLOB replaces the stock allocator with a drastically simpler
1921	   allocator. SLOB is generally more space efficient but
1922	   does not perform as well on large systems.
1923
1924endchoice
1925
1926config SLAB_MERGE_DEFAULT
1927	bool "Allow slab caches to be merged"
1928	default y
1929	help
1930	  For reduced kernel memory fragmentation, slab caches can be
1931	  merged when they share the same size and other characteristics.
1932	  This carries a risk of kernel heap overflows being able to
1933	  overwrite objects from merged caches (and more easily control
1934	  cache layout), which makes such heap attacks easier to exploit
1935	  by attackers. By keeping caches unmerged, these kinds of exploits
1936	  can usually only damage objects in the same cache. To disable
1937	  merging at runtime, "slab_nomerge" can be passed on the kernel
1938	  command line.
1939
1940config SLAB_FREELIST_RANDOM
1941	bool "Randomize slab freelist"
1942	depends on SLAB || SLUB
1943	help
1944	  Randomizes the freelist order used on creating new pages. This
1945	  security feature reduces the predictability of the kernel slab
1946	  allocator against heap overflows.
1947
1948config SLAB_FREELIST_HARDENED
1949	bool "Harden slab freelist metadata"
1950	depends on SLAB || SLUB
1951	help
1952	  Many kernel heap attacks try to target slab cache metadata and
1953	  other infrastructure. This options makes minor performance
1954	  sacrifices to harden the kernel slab allocator against common
1955	  freelist exploit methods. Some slab implementations have more
1956	  sanity-checking than others. This option is most effective with
1957	  CONFIG_SLUB.
1958
1959config SHUFFLE_PAGE_ALLOCATOR
1960	bool "Page allocator randomization"
1961	default SLAB_FREELIST_RANDOM && ACPI_NUMA
1962	help
1963	  Randomization of the page allocator improves the average
1964	  utilization of a direct-mapped memory-side-cache. See section
1965	  5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1966	  6.2a specification for an example of how a platform advertises
1967	  the presence of a memory-side-cache. There are also incidental
1968	  security benefits as it reduces the predictability of page
1969	  allocations to compliment SLAB_FREELIST_RANDOM, but the
1970	  default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1971	  10th order of pages is selected based on cache utilization
1972	  benefits on x86.
1973
1974	  While the randomization improves cache utilization it may
1975	  negatively impact workloads on platforms without a cache. For
1976	  this reason, by default, the randomization is enabled only
1977	  after runtime detection of a direct-mapped memory-side-cache.
1978	  Otherwise, the randomization may be force enabled with the
1979	  'page_alloc.shuffle' kernel command line parameter.
1980
1981	  Say Y if unsure.
1982
1983config SLUB_CPU_PARTIAL
1984	default y
1985	depends on SLUB && SMP
1986	bool "SLUB per cpu partial cache"
1987	help
1988	  Per cpu partial caches accelerate objects allocation and freeing
1989	  that is local to a processor at the price of more indeterminism
1990	  in the latency of the free. On overflow these caches will be cleared
1991	  which requires the taking of locks that may cause latency spikes.
1992	  Typically one would choose no for a realtime system.
1993
1994config MMAP_ALLOW_UNINITIALIZED
1995	bool "Allow mmapped anonymous memory to be uninitialized"
1996	depends on EXPERT && !MMU
1997	default n
1998	help
1999	  Normally, and according to the Linux spec, anonymous memory obtained
2000	  from mmap() has its contents cleared before it is passed to
2001	  userspace.  Enabling this config option allows you to request that
2002	  mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
2003	  providing a huge performance boost.  If this option is not enabled,
2004	  then the flag will be ignored.
2005
2006	  This is taken advantage of by uClibc's malloc(), and also by
2007	  ELF-FDPIC binfmt's brk and stack allocator.
2008
2009	  Because of the obvious security issues, this option should only be
2010	  enabled on embedded devices where you control what is run in
2011	  userspace.  Since that isn't generally a problem on no-MMU systems,
2012	  it is normally safe to say Y here.
2013
2014	  See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
2015
2016config SYSTEM_DATA_VERIFICATION
2017	def_bool n
2018	select SYSTEM_TRUSTED_KEYRING
2019	select KEYS
2020	select CRYPTO
2021	select CRYPTO_RSA
2022	select ASYMMETRIC_KEY_TYPE
2023	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
2024	select ASN1
2025	select OID_REGISTRY
2026	select X509_CERTIFICATE_PARSER
2027	select PKCS7_MESSAGE_PARSER
2028	help
2029	  Provide PKCS#7 message verification using the contents of the system
2030	  trusted keyring to provide public keys.  This then can be used for
2031	  module verification, kexec image verification and firmware blob
2032	  verification.
2033
2034config PROFILING
2035	bool "Profiling support"
2036	help
2037	  Say Y here to enable the extended profiling support mechanisms used
2038	  by profilers.
2039
2040#
2041# Place an empty function call at each tracepoint site. Can be
2042# dynamically changed for a probe function.
2043#
2044config TRACEPOINTS
2045	bool
2046
2047endmenu		# General setup
2048
2049source "arch/Kconfig"
2050
2051config RT_MUTEXES
2052	bool
2053
2054config BASE_SMALL
2055	int
2056	default 0 if BASE_FULL
2057	default 1 if !BASE_FULL
2058
2059config MODULE_SIG_FORMAT
2060	def_bool n
2061	select SYSTEM_DATA_VERIFICATION
2062
2063menuconfig MODULES
2064	bool "Enable loadable module support"
2065	modules
2066	help
2067	  Kernel modules are small pieces of compiled code which can
2068	  be inserted in the running kernel, rather than being
2069	  permanently built into the kernel.  You use the "modprobe"
2070	  tool to add (and sometimes remove) them.  If you say Y here,
2071	  many parts of the kernel can be built as modules (by
2072	  answering M instead of Y where indicated): this is most
2073	  useful for infrequently used options which are not required
2074	  for booting.  For more information, see the man pages for
2075	  modprobe, lsmod, modinfo, insmod and rmmod.
2076
2077	  If you say Y here, you will need to run "make
2078	  modules_install" to put the modules under /lib/modules/
2079	  where modprobe can find them (you may need to be root to do
2080	  this).
2081
2082	  If unsure, say Y.
2083
2084if MODULES
2085
2086config MODULE_FORCE_LOAD
2087	bool "Forced module loading"
2088	default n
2089	help
2090	  Allow loading of modules without version information (ie. modprobe
2091	  --force).  Forced module loading sets the 'F' (forced) taint flag and
2092	  is usually a really bad idea.
2093
2094config MODULE_UNLOAD
2095	bool "Module unloading"
2096	help
2097	  Without this option you will not be able to unload any
2098	  modules (note that some modules may not be unloadable
2099	  anyway), which makes your kernel smaller, faster
2100	  and simpler.  If unsure, say Y.
2101
2102config MODULE_FORCE_UNLOAD
2103	bool "Forced module unloading"
2104	depends on MODULE_UNLOAD
2105	help
2106	  This option allows you to force a module to unload, even if the
2107	  kernel believes it is unsafe: the kernel will remove the module
2108	  without waiting for anyone to stop using it (using the -f option to
2109	  rmmod).  This is mainly for kernel developers and desperate users.
2110	  If unsure, say N.
2111
2112config MODVERSIONS
2113	bool "Module versioning support"
2114	help
2115	  Usually, you have to use modules compiled with your kernel.
2116	  Saying Y here makes it sometimes possible to use modules
2117	  compiled for different kernels, by adding enough information
2118	  to the modules to (hopefully) spot any changes which would
2119	  make them incompatible with the kernel you are running.  If
2120	  unsure, say N.
2121
2122config ASM_MODVERSIONS
2123	bool
2124	default HAVE_ASM_MODVERSIONS && MODVERSIONS
2125	help
2126	  This enables module versioning for exported symbols also from
2127	  assembly. This can be enabled only when the target architecture
2128	  supports it.
2129
2130config MODULE_REL_CRCS
2131	bool
2132	depends on MODVERSIONS
2133
2134config MODULE_SRCVERSION_ALL
2135	bool "Source checksum for all modules"
2136	help
2137	  Modules which contain a MODULE_VERSION get an extra "srcversion"
2138	  field inserted into their modinfo section, which contains a
2139    	  sum of the source files which made it.  This helps maintainers
2140	  see exactly which source was used to build a module (since
2141	  others sometimes change the module source without updating
2142	  the version).  With this option, such a "srcversion" field
2143	  will be created for all modules.  If unsure, say N.
2144
2145config MODULE_SIG
2146	bool "Module signature verification"
2147	select MODULE_SIG_FORMAT
2148	help
2149	  Check modules for valid signatures upon load: the signature
2150	  is simply appended to the module. For more information see
2151	  <file:Documentation/admin-guide/module-signing.rst>.
2152
2153	  Note that this option adds the OpenSSL development packages as a
2154	  kernel build dependency so that the signing tool can use its crypto
2155	  library.
2156
2157	  You should enable this option if you wish to use either
2158	  CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2159	  another LSM - otherwise unsigned modules will be loadable regardless
2160	  of the lockdown policy.
2161
2162	  !!!WARNING!!!  If you enable this option, you MUST make sure that the
2163	  module DOES NOT get stripped after being signed.  This includes the
2164	  debuginfo strip done by some packagers (such as rpmbuild) and
2165	  inclusion into an initramfs that wants the module size reduced.
2166
2167config MODULE_SIG_FORCE
2168	bool "Require modules to be validly signed"
2169	depends on MODULE_SIG
2170	help
2171	  Reject unsigned modules or signed modules for which we don't have a
2172	  key.  Without this, such modules will simply taint the kernel.
2173
2174config MODULE_SIG_ALL
2175	bool "Automatically sign all modules"
2176	default y
2177	depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2178	help
2179	  Sign all modules during make modules_install. Without this option,
2180	  modules must be signed manually, using the scripts/sign-file tool.
2181
2182comment "Do not forget to sign required modules with scripts/sign-file"
2183	depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2184
2185choice
2186	prompt "Which hash algorithm should modules be signed with?"
2187	depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2188	help
2189	  This determines which sort of hashing algorithm will be used during
2190	  signature generation.  This algorithm _must_ be built into the kernel
2191	  directly so that signature verification can take place.  It is not
2192	  possible to load a signed module containing the algorithm to check
2193	  the signature on that module.
2194
2195config MODULE_SIG_SHA1
2196	bool "Sign modules with SHA-1"
2197	select CRYPTO_SHA1
2198
2199config MODULE_SIG_SHA224
2200	bool "Sign modules with SHA-224"
2201	select CRYPTO_SHA256
2202
2203config MODULE_SIG_SHA256
2204	bool "Sign modules with SHA-256"
2205	select CRYPTO_SHA256
2206
2207config MODULE_SIG_SHA384
2208	bool "Sign modules with SHA-384"
2209	select CRYPTO_SHA512
2210
2211config MODULE_SIG_SHA512
2212	bool "Sign modules with SHA-512"
2213	select CRYPTO_SHA512
2214
2215endchoice
2216
2217config MODULE_SIG_HASH
2218	string
2219	depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2220	default "sha1" if MODULE_SIG_SHA1
2221	default "sha224" if MODULE_SIG_SHA224
2222	default "sha256" if MODULE_SIG_SHA256
2223	default "sha384" if MODULE_SIG_SHA384
2224	default "sha512" if MODULE_SIG_SHA512
2225
2226choice
2227	prompt "Module compression mode"
2228	help
2229	  This option allows you to choose the algorithm which will be used to
2230	  compress modules when 'make modules_install' is run. (or, you can
2231	  choose to not compress modules at all.)
2232
2233	  External modules will also be compressed in the same way during the
2234	  installation.
2235
2236	  For modules inside an initrd or initramfs, it's more efficient to
2237	  compress the whole initrd or initramfs instead.
2238
2239	  This is fully compatible with signed modules.
2240
2241	  Please note that the tool used to load modules needs to support the
2242	  corresponding algorithm. module-init-tools MAY support gzip, and kmod
2243	  MAY support gzip, xz and zstd.
2244
2245	  Your build system needs to provide the appropriate compression tool
2246	  to compress the modules.
2247
2248	  If in doubt, select 'None'.
2249
2250config MODULE_COMPRESS_NONE
2251	bool "None"
2252	help
2253	  Do not compress modules. The installed modules are suffixed
2254	  with .ko.
2255
2256config MODULE_COMPRESS_GZIP
2257	bool "GZIP"
2258	help
2259	  Compress modules with GZIP. The installed modules are suffixed
2260	  with .ko.gz.
2261
2262config MODULE_COMPRESS_XZ
2263	bool "XZ"
2264	help
2265	  Compress modules with XZ. The installed modules are suffixed
2266	  with .ko.xz.
2267
2268config MODULE_COMPRESS_ZSTD
2269	bool "ZSTD"
2270	help
2271	  Compress modules with ZSTD. The installed modules are suffixed
2272	  with .ko.zst.
2273
2274endchoice
2275
2276config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2277	bool "Allow loading of modules with missing namespace imports"
2278	help
2279	  Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2280	  a namespace. A module that makes use of a symbol exported with such a
2281	  namespace is required to import the namespace via MODULE_IMPORT_NS().
2282	  There is no technical reason to enforce correct namespace imports,
2283	  but it creates consistency between symbols defining namespaces and
2284	  users importing namespaces they make use of. This option relaxes this
2285	  requirement and lifts the enforcement when loading a module.
2286
2287	  If unsure, say N.
2288
2289config MODPROBE_PATH
2290	string "Path to modprobe binary"
2291	default "/sbin/modprobe"
2292	help
2293	  When kernel code requests a module, it does so by calling
2294	  the "modprobe" userspace utility. This option allows you to
2295	  set the path where that binary is found. This can be changed
2296	  at runtime via the sysctl file
2297	  /proc/sys/kernel/modprobe. Setting this to the empty string
2298	  removes the kernel's ability to request modules (but
2299	  userspace can still load modules explicitly).
2300
2301config TRIM_UNUSED_KSYMS
2302	bool "Trim unused exported kernel symbols" if EXPERT
2303	depends on !COMPILE_TEST
2304	help
2305	  The kernel and some modules make many symbols available for
2306	  other modules to use via EXPORT_SYMBOL() and variants. Depending
2307	  on the set of modules being selected in your kernel configuration,
2308	  many of those exported symbols might never be used.
2309
2310	  This option allows for unused exported symbols to be dropped from
2311	  the build. In turn, this provides the compiler more opportunities
2312	  (especially when using LTO) for optimizing the code and reducing
2313	  binary size.  This might have some security advantages as well.
2314
2315	  If unsure, or if you need to build out-of-tree modules, say N.
2316
2317config UNUSED_KSYMS_WHITELIST
2318	string "Whitelist of symbols to keep in ksymtab"
2319	depends on TRIM_UNUSED_KSYMS
2320	help
2321	  By default, all unused exported symbols will be un-exported from the
2322	  build when TRIM_UNUSED_KSYMS is selected.
2323
2324	  UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
2325	  exported at all times, even in absence of in-tree users. The value to
2326	  set here is the path to a text file containing the list of symbols,
2327	  one per line. The path can be absolute, or relative to the kernel
2328	  source tree.
2329
2330endif # MODULES
2331
2332config MODULES_TREE_LOOKUP
2333	def_bool y
2334	depends on PERF_EVENTS || TRACING || CFI_CLANG
2335
2336config INIT_ALL_POSSIBLE
2337	bool
2338	help
2339	  Back when each arch used to define their own cpu_online_mask and
2340	  cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2341	  with all 1s, and others with all 0s.  When they were centralised,
2342	  it was better to provide this option than to break all the archs
2343	  and have several arch maintainers pursuing me down dark alleys.
2344
2345source "block/Kconfig"
2346
2347config PREEMPT_NOTIFIERS
2348	bool
2349
2350config PADATA
2351	depends on SMP
2352	bool
2353
2354config ASN1
2355	tristate
2356	help
2357	  Build a simple ASN.1 grammar compiler that produces a bytecode output
2358	  that can be interpreted by the ASN.1 stream decoder and used to
2359	  inform it as to what tags are to be expected in a stream and what
2360	  functions to call on what tags.
2361
2362source "kernel/Kconfig.locks"
2363
2364config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2365	bool
2366
2367config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2368	bool
2369
2370# It may be useful for an architecture to override the definitions of the
2371# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2372# and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2373# different calling convention for syscalls. They can also override the
2374# macros for not-implemented syscalls in kernel/sys_ni.c and
2375# kernel/time/posix-stubs.c. All these overrides need to be available in
2376# <asm/syscall_wrapper.h>.
2377config ARCH_HAS_SYSCALL_WRAPPER
2378	def_bool n
2379