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
888config CC_IMPLICIT_FALLTHROUGH
889	string
890	default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
891	default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough)
892
893#
894# For architectures that know their GCC __int128 support is sound
895#
896config ARCH_SUPPORTS_INT128
897	bool
898
899# For architectures that (ab)use NUMA to represent different memory regions
900# all cpu-local but of different latencies, such as SuperH.
901#
902config ARCH_WANT_NUMA_VARIABLE_LOCALITY
903	bool
904
905config NUMA_BALANCING
906	bool "Memory placement aware NUMA scheduler"
907	depends on ARCH_SUPPORTS_NUMA_BALANCING
908	depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
909	depends on SMP && NUMA && MIGRATION && !PREEMPT_RT
910	help
911	  This option adds support for automatic NUMA aware memory/task placement.
912	  The mechanism is quite primitive and is based on migrating memory when
913	  it has references to the node the task is running on.
914
915	  This system will be inactive on UMA systems.
916
917config NUMA_BALANCING_DEFAULT_ENABLED
918	bool "Automatically enable NUMA aware memory/task placement"
919	default y
920	depends on NUMA_BALANCING
921	help
922	  If set, automatic NUMA balancing will be enabled if running on a NUMA
923	  machine.
924
925menuconfig CGROUPS
926	bool "Control Group support"
927	select KERNFS
928	help
929	  This option adds support for grouping sets of processes together, for
930	  use with process control subsystems such as Cpusets, CFS, memory
931	  controls or device isolation.
932	  See
933		- Documentation/scheduler/sched-design-CFS.rst	(CFS)
934		- Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
935					  and resource control)
936
937	  Say N if unsure.
938
939if CGROUPS
940
941config PAGE_COUNTER
942	bool
943
944config MEMCG
945	bool "Memory controller"
946	select PAGE_COUNTER
947	select EVENTFD
948	help
949	  Provides control over the memory footprint of tasks in a cgroup.
950
951config MEMCG_SWAP
952	bool
953	depends on MEMCG && SWAP
954	default y
955
956config MEMCG_KMEM
957	bool
958	depends on MEMCG && !SLOB
959	default y
960
961config BLK_CGROUP
962	bool "IO controller"
963	depends on BLOCK
964	default n
965	help
966	Generic block IO controller cgroup interface. This is the common
967	cgroup interface which should be used by various IO controlling
968	policies.
969
970	Currently, CFQ IO scheduler uses it to recognize task groups and
971	control disk bandwidth allocation (proportional time slice allocation)
972	to such task groups. It is also used by bio throttling logic in
973	block layer to implement upper limit in IO rates on a device.
974
975	This option only enables generic Block IO controller infrastructure.
976	One needs to also enable actual IO controlling logic/policy. For
977	enabling proportional weight division of disk bandwidth in CFQ, set
978	CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
979	CONFIG_BLK_DEV_THROTTLING=y.
980
981	See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
982
983config CGROUP_WRITEBACK
984	bool
985	depends on MEMCG && BLK_CGROUP
986	default y
987
988menuconfig CGROUP_SCHED
989	bool "CPU controller"
990	default n
991	help
992	  This feature lets CPU scheduler recognize task groups and control CPU
993	  bandwidth allocation to such task groups. It uses cgroups to group
994	  tasks.
995
996if CGROUP_SCHED
997config FAIR_GROUP_SCHED
998	bool "Group scheduling for SCHED_OTHER"
999	depends on CGROUP_SCHED
1000	default CGROUP_SCHED
1001
1002config CFS_BANDWIDTH
1003	bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1004	depends on FAIR_GROUP_SCHED
1005	default n
1006	help
1007	  This option allows users to define CPU bandwidth rates (limits) for
1008	  tasks running within the fair group scheduler.  Groups with no limit
1009	  set are considered to be unconstrained and will run with no
1010	  restriction.
1011	  See Documentation/scheduler/sched-bwc.rst for more information.
1012
1013config RT_GROUP_SCHED
1014	bool "Group scheduling for SCHED_RR/FIFO"
1015	depends on CGROUP_SCHED
1016	default n
1017	help
1018	  This feature lets you explicitly allocate real CPU bandwidth
1019	  to task groups. If enabled, it will also make it impossible to
1020	  schedule realtime tasks for non-root users until you allocate
1021	  realtime bandwidth for them.
1022	  See Documentation/scheduler/sched-rt-group.rst for more information.
1023
1024endif #CGROUP_SCHED
1025
1026config UCLAMP_TASK_GROUP
1027	bool "Utilization clamping per group of tasks"
1028	depends on CGROUP_SCHED
1029	depends on UCLAMP_TASK
1030	default n
1031	help
1032	  This feature enables the scheduler to track the clamped utilization
1033	  of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
1034
1035	  When this option is enabled, the user can specify a min and max
1036	  CPU bandwidth which is allowed for each single task in a group.
1037	  The max bandwidth allows to clamp the maximum frequency a task
1038	  can use, while the min bandwidth allows to define a minimum
1039	  frequency a task will always use.
1040
1041	  When task group based utilization clamping is enabled, an eventually
1042	  specified task-specific clamp value is constrained by the cgroup
1043	  specified clamp value. Both minimum and maximum task clamping cannot
1044	  be bigger than the corresponding clamping defined at task group level.
1045
1046	  If in doubt, say N.
1047
1048config CGROUP_PIDS
1049	bool "PIDs controller"
1050	help
1051	  Provides enforcement of process number limits in the scope of a
1052	  cgroup. Any attempt to fork more processes than is allowed in the
1053	  cgroup will fail. PIDs are fundamentally a global resource because it
1054	  is fairly trivial to reach PID exhaustion before you reach even a
1055	  conservative kmemcg limit. As a result, it is possible to grind a
1056	  system to halt without being limited by other cgroup policies. The
1057	  PIDs controller is designed to stop this from happening.
1058
1059	  It should be noted that organisational operations (such as attaching
1060	  to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1061	  since the PIDs limit only affects a process's ability to fork, not to
1062	  attach to a cgroup.
1063
1064config CGROUP_RDMA
1065	bool "RDMA controller"
1066	help
1067	  Provides enforcement of RDMA resources defined by IB stack.
1068	  It is fairly easy for consumers to exhaust RDMA resources, which
1069	  can result into resource unavailability to other consumers.
1070	  RDMA controller is designed to stop this from happening.
1071	  Attaching processes with active RDMA resources to the cgroup
1072	  hierarchy is allowed even if can cross the hierarchy's limit.
1073
1074config CGROUP_FREEZER
1075	bool "Freezer controller"
1076	help
1077	  Provides a way to freeze and unfreeze all tasks in a
1078	  cgroup.
1079
1080	  This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1081	  controller includes important in-kernel memory consumers per default.
1082
1083	  If you're using cgroup2, say N.
1084
1085config CGROUP_HUGETLB
1086	bool "HugeTLB controller"
1087	depends on HUGETLB_PAGE
1088	select PAGE_COUNTER
1089	default n
1090	help
1091	  Provides a cgroup controller for HugeTLB pages.
1092	  When you enable this, you can put a per cgroup limit on HugeTLB usage.
1093	  The limit is enforced during page fault. Since HugeTLB doesn't
1094	  support page reclaim, enforcing the limit at page fault time implies
1095	  that, the application will get SIGBUS signal if it tries to access
1096	  HugeTLB pages beyond its limit. This requires the application to know
1097	  beforehand how much HugeTLB pages it would require for its use. The
1098	  control group is tracked in the third page lru pointer. This means
1099	  that we cannot use the controller with huge page less than 3 pages.
1100
1101config CPUSETS
1102	bool "Cpuset controller"
1103	depends on SMP
1104	help
1105	  This option will let you create and manage CPUSETs which
1106	  allow dynamically partitioning a system into sets of CPUs and
1107	  Memory Nodes and assigning tasks to run only within those sets.
1108	  This is primarily useful on large SMP or NUMA systems.
1109
1110	  Say N if unsure.
1111
1112config PROC_PID_CPUSET
1113	bool "Include legacy /proc/<pid>/cpuset file"
1114	depends on CPUSETS
1115	default y
1116
1117config CGROUP_DEVICE
1118	bool "Device controller"
1119	help
1120	  Provides a cgroup controller implementing whitelists for
1121	  devices which a process in the cgroup can mknod or open.
1122
1123config CGROUP_CPUACCT
1124	bool "Simple CPU accounting controller"
1125	help
1126	  Provides a simple controller for monitoring the
1127	  total CPU consumed by the tasks in a cgroup.
1128
1129config CGROUP_PERF
1130	bool "Perf controller"
1131	depends on PERF_EVENTS
1132	help
1133	  This option extends the perf per-cpu mode to restrict monitoring
1134	  to threads which belong to the cgroup specified and run on the
1135	  designated cpu.  Or this can be used to have cgroup ID in samples
1136	  so that it can monitor performance events among cgroups.
1137
1138	  Say N if unsure.
1139
1140config CGROUP_BPF
1141	bool "Support for eBPF programs attached to cgroups"
1142	depends on BPF_SYSCALL
1143	select SOCK_CGROUP_DATA
1144	help
1145	  Allow attaching eBPF programs to a cgroup using the bpf(2)
1146	  syscall command BPF_PROG_ATTACH.
1147
1148	  In which context these programs are accessed depends on the type
1149	  of attachment. For instance, programs that are attached using
1150	  BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1151	  inet sockets.
1152
1153config CGROUP_MISC
1154	bool "Misc resource controller"
1155	default n
1156	help
1157	  Provides a controller for miscellaneous resources on a host.
1158
1159	  Miscellaneous scalar resources are the resources on the host system
1160	  which cannot be abstracted like the other cgroups. This controller
1161	  tracks and limits the miscellaneous resources used by a process
1162	  attached to a cgroup hierarchy.
1163
1164	  For more information, please check misc cgroup section in
1165	  /Documentation/admin-guide/cgroup-v2.rst.
1166
1167config CGROUP_DEBUG
1168	bool "Debug controller"
1169	default n
1170	depends on DEBUG_KERNEL
1171	help
1172	  This option enables a simple controller that exports
1173	  debugging information about the cgroups framework. This
1174	  controller is for control cgroup debugging only. Its
1175	  interfaces are not stable.
1176
1177	  Say N.
1178
1179config SOCK_CGROUP_DATA
1180	bool
1181	default n
1182
1183endif # CGROUPS
1184
1185menuconfig NAMESPACES
1186	bool "Namespaces support" if EXPERT
1187	depends on MULTIUSER
1188	default !EXPERT
1189	help
1190	  Provides the way to make tasks work with different objects using
1191	  the same id. For example same IPC id may refer to different objects
1192	  or same user id or pid may refer to different tasks when used in
1193	  different namespaces.
1194
1195if NAMESPACES
1196
1197config UTS_NS
1198	bool "UTS namespace"
1199	default y
1200	help
1201	  In this namespace tasks see different info provided with the
1202	  uname() system call
1203
1204config TIME_NS
1205	bool "TIME namespace"
1206	depends on GENERIC_VDSO_TIME_NS
1207	default y
1208	help
1209	  In this namespace boottime and monotonic clocks can be set.
1210	  The time will keep going with the same pace.
1211
1212config IPC_NS
1213	bool "IPC namespace"
1214	depends on (SYSVIPC || POSIX_MQUEUE)
1215	default y
1216	help
1217	  In this namespace tasks work with IPC ids which correspond to
1218	  different IPC objects in different namespaces.
1219
1220config USER_NS
1221	bool "User namespace"
1222	default n
1223	help
1224	  This allows containers, i.e. vservers, to use user namespaces
1225	  to provide different user info for different servers.
1226
1227	  When user namespaces are enabled in the kernel it is
1228	  recommended that the MEMCG option also be enabled and that
1229	  user-space use the memory control groups to limit the amount
1230	  of memory a memory unprivileged users can use.
1231
1232	  If unsure, say N.
1233
1234config PID_NS
1235	bool "PID Namespaces"
1236	default y
1237	help
1238	  Support process id namespaces.  This allows having multiple
1239	  processes with the same pid as long as they are in different
1240	  pid namespaces.  This is a building block of containers.
1241
1242config NET_NS
1243	bool "Network namespace"
1244	depends on NET
1245	default y
1246	help
1247	  Allow user space to create what appear to be multiple instances
1248	  of the network stack.
1249
1250endif # NAMESPACES
1251
1252config CHECKPOINT_RESTORE
1253	bool "Checkpoint/restore support"
1254	select PROC_CHILDREN
1255	select KCMP
1256	default n
1257	help
1258	  Enables additional kernel features in a sake of checkpoint/restore.
1259	  In particular it adds auxiliary prctl codes to setup process text,
1260	  data and heap segment sizes, and a few additional /proc filesystem
1261	  entries.
1262
1263	  If unsure, say N here.
1264
1265config SCHED_AUTOGROUP
1266	bool "Automatic process group scheduling"
1267	select CGROUPS
1268	select CGROUP_SCHED
1269	select FAIR_GROUP_SCHED
1270	help
1271	  This option optimizes the scheduler for common desktop workloads by
1272	  automatically creating and populating task groups.  This separation
1273	  of workloads isolates aggressive CPU burners (like build jobs) from
1274	  desktop applications.  Task group autogeneration is currently based
1275	  upon task session.
1276
1277config SYSFS_DEPRECATED
1278	bool "Enable deprecated sysfs features to support old userspace tools"
1279	depends on SYSFS
1280	default n
1281	help
1282	  This option adds code that switches the layout of the "block" class
1283	  devices, to not show up in /sys/class/block/, but only in
1284	  /sys/block/.
1285
1286	  This switch is only active when the sysfs.deprecated=1 boot option is
1287	  passed or the SYSFS_DEPRECATED_V2 option is set.
1288
1289	  This option allows new kernels to run on old distributions and tools,
1290	  which might get confused by /sys/class/block/. Since 2007/2008 all
1291	  major distributions and tools handle this just fine.
1292
1293	  Recent distributions and userspace tools after 2009/2010 depend on
1294	  the existence of /sys/class/block/, and will not work with this
1295	  option enabled.
1296
1297	  Only if you are using a new kernel on an old distribution, you might
1298	  need to say Y here.
1299
1300config SYSFS_DEPRECATED_V2
1301	bool "Enable deprecated sysfs features by default"
1302	default n
1303	depends on SYSFS
1304	depends on SYSFS_DEPRECATED
1305	help
1306	  Enable deprecated sysfs by default.
1307
1308	  See the CONFIG_SYSFS_DEPRECATED option for more details about this
1309	  option.
1310
1311	  Only if you are using a new kernel on an old distribution, you might
1312	  need to say Y here. Even then, odds are you would not need it
1313	  enabled, you can always pass the boot option if absolutely necessary.
1314
1315config RELAY
1316	bool "Kernel->user space relay support (formerly relayfs)"
1317	select IRQ_WORK
1318	help
1319	  This option enables support for relay interface support in
1320	  certain file systems (such as debugfs).
1321	  It is designed to provide an efficient mechanism for tools and
1322	  facilities to relay large amounts of data from kernel space to
1323	  user space.
1324
1325	  If unsure, say N.
1326
1327config BLK_DEV_INITRD
1328	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1329	help
1330	  The initial RAM filesystem is a ramfs which is loaded by the
1331	  boot loader (loadlin or lilo) and that is mounted as root
1332	  before the normal boot procedure. It is typically used to
1333	  load modules needed to mount the "real" root file system,
1334	  etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1335
1336	  If RAM disk support (BLK_DEV_RAM) is also included, this
1337	  also enables initial RAM disk (initrd) support and adds
1338	  15 Kbytes (more on some other architectures) to the kernel size.
1339
1340	  If unsure say Y.
1341
1342if BLK_DEV_INITRD
1343
1344source "usr/Kconfig"
1345
1346endif
1347
1348config BOOT_CONFIG
1349	bool "Boot config support"
1350	select BLK_DEV_INITRD
1351	help
1352	  Extra boot config allows system admin to pass a config file as
1353	  complemental extension of kernel cmdline when booting.
1354	  The boot config file must be attached at the end of initramfs
1355	  with checksum, size and magic word.
1356	  See <file:Documentation/admin-guide/bootconfig.rst> for details.
1357
1358	  If unsure, say Y.
1359
1360choice
1361	prompt "Compiler optimization level"
1362	default CC_OPTIMIZE_FOR_PERFORMANCE
1363
1364config CC_OPTIMIZE_FOR_PERFORMANCE
1365	bool "Optimize for performance (-O2)"
1366	help
1367	  This is the default optimization level for the kernel, building
1368	  with the "-O2" compiler flag for best performance and most
1369	  helpful compile-time warnings.
1370
1371config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1372	bool "Optimize more for performance (-O3)"
1373	depends on ARC
1374	help
1375	  Choosing this option will pass "-O3" to your compiler to optimize
1376	  the kernel yet more for performance.
1377
1378config CC_OPTIMIZE_FOR_SIZE
1379	bool "Optimize for size (-Os)"
1380	help
1381	  Choosing this option will pass "-Os" to your compiler resulting
1382	  in a smaller kernel.
1383
1384endchoice
1385
1386config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1387	bool
1388	help
1389	  This requires that the arch annotates or otherwise protects
1390	  its external entry points from being discarded. Linker scripts
1391	  must also merge .text.*, .data.*, and .bss.* correctly into
1392	  output sections. Care must be taken not to pull in unrelated
1393	  sections (e.g., '.text.init'). Typically '.' in section names
1394	  is used to distinguish them from label names / C identifiers.
1395
1396config LD_DEAD_CODE_DATA_ELIMINATION
1397	bool "Dead code and data elimination (EXPERIMENTAL)"
1398	depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1399	depends on EXPERT
1400	depends on $(cc-option,-ffunction-sections -fdata-sections)
1401	depends on $(ld-option,--gc-sections)
1402	help
1403	  Enable this if you want to do dead code and data elimination with
1404	  the linker by compiling with -ffunction-sections -fdata-sections,
1405	  and linking with --gc-sections.
1406
1407	  This can reduce on disk and in-memory size of the kernel
1408	  code and static data, particularly for small configs and
1409	  on small systems. This has the possibility of introducing
1410	  silently broken kernel if the required annotations are not
1411	  present. This option is not well tested yet, so use at your
1412	  own risk.
1413
1414config LD_ORPHAN_WARN
1415	def_bool y
1416	depends on ARCH_WANT_LD_ORPHAN_WARN
1417	depends on !LD_IS_LLD || LLD_VERSION >= 110000
1418	depends on $(ld-option,--orphan-handling=warn)
1419
1420config SYSCTL
1421	bool
1422
1423config HAVE_UID16
1424	bool
1425
1426config SYSCTL_EXCEPTION_TRACE
1427	bool
1428	help
1429	  Enable support for /proc/sys/debug/exception-trace.
1430
1431config SYSCTL_ARCH_UNALIGN_NO_WARN
1432	bool
1433	help
1434	  Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1435	  Allows arch to define/use @no_unaligned_warning to possibly warn
1436	  about unaligned access emulation going on under the hood.
1437
1438config SYSCTL_ARCH_UNALIGN_ALLOW
1439	bool
1440	help
1441	  Enable support for /proc/sys/kernel/unaligned-trap
1442	  Allows arches to define/use @unaligned_enabled to runtime toggle
1443	  the unaligned access emulation.
1444	  see arch/parisc/kernel/unaligned.c for reference
1445
1446config HAVE_PCSPKR_PLATFORM
1447	bool
1448
1449# interpreter that classic socket filters depend on
1450config BPF
1451	bool
1452
1453menuconfig EXPERT
1454	bool "Configure standard kernel features (expert users)"
1455	# Unhide debug options, to make the on-by-default options visible
1456	select DEBUG_KERNEL
1457	help
1458	  This option allows certain base kernel options and settings
1459	  to be disabled or tweaked. This is for specialized
1460	  environments which can tolerate a "non-standard" kernel.
1461	  Only use this if you really know what you are doing.
1462
1463config UID16
1464	bool "Enable 16-bit UID system calls" if EXPERT
1465	depends on HAVE_UID16 && MULTIUSER
1466	default y
1467	help
1468	  This enables the legacy 16-bit UID syscall wrappers.
1469
1470config MULTIUSER
1471	bool "Multiple users, groups and capabilities support" if EXPERT
1472	default y
1473	help
1474	  This option enables support for non-root users, groups and
1475	  capabilities.
1476
1477	  If you say N here, all processes will run with UID 0, GID 0, and all
1478	  possible capabilities.  Saying N here also compiles out support for
1479	  system calls related to UIDs, GIDs, and capabilities, such as setuid,
1480	  setgid, and capset.
1481
1482	  If unsure, say Y here.
1483
1484config SGETMASK_SYSCALL
1485	bool "sgetmask/ssetmask syscalls support" if EXPERT
1486	def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1487	help
1488	  sys_sgetmask and sys_ssetmask are obsolete system calls
1489	  no longer supported in libc but still enabled by default in some
1490	  architectures.
1491
1492	  If unsure, leave the default option here.
1493
1494config SYSFS_SYSCALL
1495	bool "Sysfs syscall support" if EXPERT
1496	default y
1497	help
1498	  sys_sysfs is an obsolete system call no longer supported in libc.
1499	  Note that disabling this option is more secure but might break
1500	  compatibility with some systems.
1501
1502	  If unsure say Y here.
1503
1504config FHANDLE
1505	bool "open by fhandle syscalls" if EXPERT
1506	select EXPORTFS
1507	default y
1508	help
1509	  If you say Y here, a user level program will be able to map
1510	  file names to handle and then later use the handle for
1511	  different file system operations. This is useful in implementing
1512	  userspace file servers, which now track files using handles instead
1513	  of names. The handle would remain the same even if file names
1514	  get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1515	  syscalls.
1516
1517config POSIX_TIMERS
1518	bool "Posix Clocks & timers" if EXPERT
1519	default y
1520	help
1521	  This includes native support for POSIX timers to the kernel.
1522	  Some embedded systems have no use for them and therefore they
1523	  can be configured out to reduce the size of the kernel image.
1524
1525	  When this option is disabled, the following syscalls won't be
1526	  available: timer_create, timer_gettime: timer_getoverrun,
1527	  timer_settime, timer_delete, clock_adjtime, getitimer,
1528	  setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1529	  clock_getres and clock_nanosleep syscalls will be limited to
1530	  CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1531
1532	  If unsure say y.
1533
1534config PRINTK
1535	default y
1536	bool "Enable support for printk" if EXPERT
1537	select IRQ_WORK
1538	help
1539	  This option enables normal printk support. Removing it
1540	  eliminates most of the message strings from the kernel image
1541	  and makes the kernel more or less silent. As this makes it
1542	  very difficult to diagnose system problems, saying N here is
1543	  strongly discouraged.
1544
1545config BUG
1546	bool "BUG() support" if EXPERT
1547	default y
1548	help
1549	  Disabling this option eliminates support for BUG and WARN, reducing
1550	  the size of your kernel image and potentially quietly ignoring
1551	  numerous fatal conditions. You should only consider disabling this
1552	  option for embedded systems with no facilities for reporting errors.
1553	  Just say Y.
1554
1555config ELF_CORE
1556	depends on COREDUMP
1557	default y
1558	bool "Enable ELF core dumps" if EXPERT
1559	help
1560	  Enable support for generating core dumps. Disabling saves about 4k.
1561
1562
1563config PCSPKR_PLATFORM
1564	bool "Enable PC-Speaker support" if EXPERT
1565	depends on HAVE_PCSPKR_PLATFORM
1566	select I8253_LOCK
1567	default y
1568	help
1569	  This option allows to disable the internal PC-Speaker
1570	  support, saving some memory.
1571
1572config BASE_FULL
1573	default y
1574	bool "Enable full-sized data structures for core" if EXPERT
1575	help
1576	  Disabling this option reduces the size of miscellaneous core
1577	  kernel data structures. This saves memory on small machines,
1578	  but may reduce performance.
1579
1580config FUTEX
1581	bool "Enable futex support" if EXPERT
1582	default y
1583	imply RT_MUTEXES
1584	help
1585	  Disabling this option will cause the kernel to be built without
1586	  support for "fast userspace mutexes".  The resulting kernel may not
1587	  run glibc-based applications correctly.
1588
1589config FUTEX_PI
1590	bool
1591	depends on FUTEX && RT_MUTEXES
1592	default y
1593
1594config HAVE_FUTEX_CMPXCHG
1595	bool
1596	depends on FUTEX
1597	help
1598	  Architectures should select this if futex_atomic_cmpxchg_inatomic()
1599	  is implemented and always working. This removes a couple of runtime
1600	  checks.
1601
1602config EPOLL
1603	bool "Enable eventpoll support" if EXPERT
1604	default y
1605	help
1606	  Disabling this option will cause the kernel to be built without
1607	  support for epoll family of system calls.
1608
1609config SIGNALFD
1610	bool "Enable signalfd() system call" if EXPERT
1611	default y
1612	help
1613	  Enable the signalfd() system call that allows to receive signals
1614	  on a file descriptor.
1615
1616	  If unsure, say Y.
1617
1618config TIMERFD
1619	bool "Enable timerfd() system call" if EXPERT
1620	default y
1621	help
1622	  Enable the timerfd() system call that allows to receive timer
1623	  events on a file descriptor.
1624
1625	  If unsure, say Y.
1626
1627config EVENTFD
1628	bool "Enable eventfd() system call" if EXPERT
1629	default y
1630	help
1631	  Enable the eventfd() system call that allows to receive both
1632	  kernel notification (ie. KAIO) or userspace notifications.
1633
1634	  If unsure, say Y.
1635
1636config SHMEM
1637	bool "Use full shmem filesystem" if EXPERT
1638	default y
1639	depends on MMU
1640	help
1641	  The shmem is an internal filesystem used to manage shared memory.
1642	  It is backed by swap and manages resource limits. It is also exported
1643	  to userspace as tmpfs if TMPFS is enabled. Disabling this
1644	  option replaces shmem and tmpfs with the much simpler ramfs code,
1645	  which may be appropriate on small systems without swap.
1646
1647config AIO
1648	bool "Enable AIO support" if EXPERT
1649	default y
1650	help
1651	  This option enables POSIX asynchronous I/O which may by used
1652	  by some high performance threaded applications. Disabling
1653	  this option saves about 7k.
1654
1655config IO_URING
1656	bool "Enable IO uring support" if EXPERT
1657	select IO_WQ
1658	default y
1659	help
1660	  This option enables support for the io_uring interface, enabling
1661	  applications to submit and complete IO through submission and
1662	  completion rings that are shared between the kernel and application.
1663
1664config ADVISE_SYSCALLS
1665	bool "Enable madvise/fadvise syscalls" if EXPERT
1666	default y
1667	help
1668	  This option enables the madvise and fadvise syscalls, used by
1669	  applications to advise the kernel about their future memory or file
1670	  usage, improving performance. If building an embedded system where no
1671	  applications use these syscalls, you can disable this option to save
1672	  space.
1673
1674config HAVE_ARCH_USERFAULTFD_WP
1675	bool
1676	help
1677	  Arch has userfaultfd write protection support
1678
1679config HAVE_ARCH_USERFAULTFD_MINOR
1680	bool
1681	help
1682	  Arch has userfaultfd minor fault support
1683
1684config MEMBARRIER
1685	bool "Enable membarrier() system call" if EXPERT
1686	default y
1687	help
1688	  Enable the membarrier() system call that allows issuing memory
1689	  barriers across all running threads, which can be used to distribute
1690	  the cost of user-space memory barriers asymmetrically by transforming
1691	  pairs of memory barriers into pairs consisting of membarrier() and a
1692	  compiler barrier.
1693
1694	  If unsure, say Y.
1695
1696config KALLSYMS
1697	bool "Load all symbols for debugging/ksymoops" if EXPERT
1698	default y
1699	help
1700	  Say Y here to let the kernel print out symbolic crash information and
1701	  symbolic stack backtraces. This increases the size of the kernel
1702	  somewhat, as all symbols have to be loaded into the kernel image.
1703
1704config KALLSYMS_ALL
1705	bool "Include all symbols in kallsyms"
1706	depends on DEBUG_KERNEL && KALLSYMS
1707	help
1708	  Normally kallsyms only contains the symbols of functions for nicer
1709	  OOPS messages and backtraces (i.e., symbols from the text and inittext
1710	  sections). This is sufficient for most cases. And only in very rare
1711	  cases (e.g., when a debugger is used) all symbols are required (e.g.,
1712	  names of variables from the data sections, etc).
1713
1714	  This option makes sure that all symbols are loaded into the kernel
1715	  image (i.e., symbols from all sections) in cost of increased kernel
1716	  size (depending on the kernel configuration, it may be 300KiB or
1717	  something like this).
1718
1719	  Say N unless you really need all symbols.
1720
1721config KALLSYMS_ABSOLUTE_PERCPU
1722	bool
1723	depends on KALLSYMS
1724	default X86_64 && SMP
1725
1726config KALLSYMS_BASE_RELATIVE
1727	bool
1728	depends on KALLSYMS
1729	default !IA64
1730	help
1731	  Instead of emitting them as absolute values in the native word size,
1732	  emit the symbol references in the kallsyms table as 32-bit entries,
1733	  each containing a relative value in the range [base, base + U32_MAX]
1734	  or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1735	  an absolute value in the range [0, S32_MAX] or a relative value in the
1736	  range [base, base + S32_MAX], where base is the lowest relative symbol
1737	  address encountered in the image.
1738
1739	  On 64-bit builds, this reduces the size of the address table by 50%,
1740	  but more importantly, it results in entries whose values are build
1741	  time constants, and no relocation pass is required at runtime to fix
1742	  up the entries based on the runtime load address of the kernel.
1743
1744# end of the "standard kernel features (expert users)" menu
1745
1746# syscall, maps, verifier
1747
1748config USERFAULTFD
1749	bool "Enable userfaultfd() system call"
1750	depends on MMU
1751	help
1752	  Enable the userfaultfd() system call that allows to intercept and
1753	  handle page faults in userland.
1754
1755config ARCH_HAS_MEMBARRIER_CALLBACKS
1756	bool
1757
1758config ARCH_HAS_MEMBARRIER_SYNC_CORE
1759	bool
1760
1761config KCMP
1762	bool "Enable kcmp() system call" if EXPERT
1763	help
1764	  Enable the kernel resource comparison system call. It provides
1765	  user-space with the ability to compare two processes to see if they
1766	  share a common resource, such as a file descriptor or even virtual
1767	  memory space.
1768
1769	  If unsure, say N.
1770
1771config RSEQ
1772	bool "Enable rseq() system call" if EXPERT
1773	default y
1774	depends on HAVE_RSEQ
1775	select MEMBARRIER
1776	help
1777	  Enable the restartable sequences system call. It provides a
1778	  user-space cache for the current CPU number value, which
1779	  speeds up getting the current CPU number from user-space,
1780	  as well as an ABI to speed up user-space operations on
1781	  per-CPU data.
1782
1783	  If unsure, say Y.
1784
1785config DEBUG_RSEQ
1786	default n
1787	bool "Enabled debugging of rseq() system call" if EXPERT
1788	depends on RSEQ && DEBUG_KERNEL
1789	help
1790	  Enable extra debugging checks for the rseq system call.
1791
1792	  If unsure, say N.
1793
1794config EMBEDDED
1795	bool "Embedded system"
1796	select EXPERT
1797	help
1798	  This option should be enabled if compiling the kernel for
1799	  an embedded system so certain expert options are available
1800	  for configuration.
1801
1802config HAVE_PERF_EVENTS
1803	bool
1804	help
1805	  See tools/perf/design.txt for details.
1806
1807config PERF_USE_VMALLOC
1808	bool
1809	help
1810	  See tools/perf/design.txt for details
1811
1812config PC104
1813	bool "PC/104 support" if EXPERT
1814	help
1815	  Expose PC/104 form factor device drivers and options available for
1816	  selection and configuration. Enable this option if your target
1817	  machine has a PC/104 bus.
1818
1819menu "Kernel Performance Events And Counters"
1820
1821config PERF_EVENTS
1822	bool "Kernel performance events and counters"
1823	default y if PROFILING
1824	depends on HAVE_PERF_EVENTS
1825	select IRQ_WORK
1826	select SRCU
1827	help
1828	  Enable kernel support for various performance events provided
1829	  by software and hardware.
1830
1831	  Software events are supported either built-in or via the
1832	  use of generic tracepoints.
1833
1834	  Most modern CPUs support performance events via performance
1835	  counter registers. These registers count the number of certain
1836	  types of hw events: such as instructions executed, cachemisses
1837	  suffered, or branches mis-predicted - without slowing down the
1838	  kernel or applications. These registers can also trigger interrupts
1839	  when a threshold number of events have passed - and can thus be
1840	  used to profile the code that runs on that CPU.
1841
1842	  The Linux Performance Event subsystem provides an abstraction of
1843	  these software and hardware event capabilities, available via a
1844	  system call and used by the "perf" utility in tools/perf/. It
1845	  provides per task and per CPU counters, and it provides event
1846	  capabilities on top of those.
1847
1848	  Say Y if unsure.
1849
1850config DEBUG_PERF_USE_VMALLOC
1851	default n
1852	bool "Debug: use vmalloc to back perf mmap() buffers"
1853	depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1854	select PERF_USE_VMALLOC
1855	help
1856	  Use vmalloc memory to back perf mmap() buffers.
1857
1858	  Mostly useful for debugging the vmalloc code on platforms
1859	  that don't require it.
1860
1861	  Say N if unsure.
1862
1863endmenu
1864
1865config VM_EVENT_COUNTERS
1866	default y
1867	bool "Enable VM event counters for /proc/vmstat" if EXPERT
1868	help
1869	  VM event counters are needed for event counts to be shown.
1870	  This option allows the disabling of the VM event counters
1871	  on EXPERT systems.  /proc/vmstat will only show page counts
1872	  if VM event counters are disabled.
1873
1874config SLUB_DEBUG
1875	default y
1876	bool "Enable SLUB debugging support" if EXPERT
1877	depends on SLUB && SYSFS
1878	help
1879	  SLUB has extensive debug support features. Disabling these can
1880	  result in significant savings in code size. This also disables
1881	  SLUB sysfs support. /sys/slab will not exist and there will be
1882	  no support for cache validation etc.
1883
1884config COMPAT_BRK
1885	bool "Disable heap randomization"
1886	default y
1887	help
1888	  Randomizing heap placement makes heap exploits harder, but it
1889	  also breaks ancient binaries (including anything libc5 based).
1890	  This option changes the bootup default to heap randomization
1891	  disabled, and can be overridden at runtime by setting
1892	  /proc/sys/kernel/randomize_va_space to 2.
1893
1894	  On non-ancient distros (post-2000 ones) N is usually a safe choice.
1895
1896choice
1897	prompt "Choose SLAB allocator"
1898	default SLUB
1899	help
1900	   This option allows to select a slab allocator.
1901
1902config SLAB
1903	bool "SLAB"
1904	depends on !PREEMPT_RT
1905	select HAVE_HARDENED_USERCOPY_ALLOCATOR
1906	help
1907	  The regular slab allocator that is established and known to work
1908	  well in all environments. It organizes cache hot objects in
1909	  per cpu and per node queues.
1910
1911config SLUB
1912	bool "SLUB (Unqueued Allocator)"
1913	select HAVE_HARDENED_USERCOPY_ALLOCATOR
1914	help
1915	   SLUB is a slab allocator that minimizes cache line usage
1916	   instead of managing queues of cached objects (SLAB approach).
1917	   Per cpu caching is realized using slabs of objects instead
1918	   of queues of objects. SLUB can use memory efficiently
1919	   and has enhanced diagnostics. SLUB is the default choice for
1920	   a slab allocator.
1921
1922config SLOB
1923	depends on EXPERT
1924	bool "SLOB (Simple Allocator)"
1925	depends on !PREEMPT_RT
1926	help
1927	   SLOB replaces the stock allocator with a drastically simpler
1928	   allocator. SLOB is generally more space efficient but
1929	   does not perform as well on large systems.
1930
1931endchoice
1932
1933config SLAB_MERGE_DEFAULT
1934	bool "Allow slab caches to be merged"
1935	default y
1936	help
1937	  For reduced kernel memory fragmentation, slab caches can be
1938	  merged when they share the same size and other characteristics.
1939	  This carries a risk of kernel heap overflows being able to
1940	  overwrite objects from merged caches (and more easily control
1941	  cache layout), which makes such heap attacks easier to exploit
1942	  by attackers. By keeping caches unmerged, these kinds of exploits
1943	  can usually only damage objects in the same cache. To disable
1944	  merging at runtime, "slab_nomerge" can be passed on the kernel
1945	  command line.
1946
1947config SLAB_FREELIST_RANDOM
1948	bool "Randomize slab freelist"
1949	depends on SLAB || SLUB
1950	help
1951	  Randomizes the freelist order used on creating new pages. This
1952	  security feature reduces the predictability of the kernel slab
1953	  allocator against heap overflows.
1954
1955config SLAB_FREELIST_HARDENED
1956	bool "Harden slab freelist metadata"
1957	depends on SLAB || SLUB
1958	help
1959	  Many kernel heap attacks try to target slab cache metadata and
1960	  other infrastructure. This options makes minor performance
1961	  sacrifices to harden the kernel slab allocator against common
1962	  freelist exploit methods. Some slab implementations have more
1963	  sanity-checking than others. This option is most effective with
1964	  CONFIG_SLUB.
1965
1966config SHUFFLE_PAGE_ALLOCATOR
1967	bool "Page allocator randomization"
1968	default SLAB_FREELIST_RANDOM && ACPI_NUMA
1969	help
1970	  Randomization of the page allocator improves the average
1971	  utilization of a direct-mapped memory-side-cache. See section
1972	  5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1973	  6.2a specification for an example of how a platform advertises
1974	  the presence of a memory-side-cache. There are also incidental
1975	  security benefits as it reduces the predictability of page
1976	  allocations to compliment SLAB_FREELIST_RANDOM, but the
1977	  default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1978	  10th order of pages is selected based on cache utilization
1979	  benefits on x86.
1980
1981	  While the randomization improves cache utilization it may
1982	  negatively impact workloads on platforms without a cache. For
1983	  this reason, by default, the randomization is enabled only
1984	  after runtime detection of a direct-mapped memory-side-cache.
1985	  Otherwise, the randomization may be force enabled with the
1986	  'page_alloc.shuffle' kernel command line parameter.
1987
1988	  Say Y if unsure.
1989
1990config SLUB_CPU_PARTIAL
1991	default y
1992	depends on SLUB && SMP
1993	bool "SLUB per cpu partial cache"
1994	help
1995	  Per cpu partial caches accelerate objects allocation and freeing
1996	  that is local to a processor at the price of more indeterminism
1997	  in the latency of the free. On overflow these caches will be cleared
1998	  which requires the taking of locks that may cause latency spikes.
1999	  Typically one would choose no for a realtime system.
2000
2001config MMAP_ALLOW_UNINITIALIZED
2002	bool "Allow mmapped anonymous memory to be uninitialized"
2003	depends on EXPERT && !MMU
2004	default n
2005	help
2006	  Normally, and according to the Linux spec, anonymous memory obtained
2007	  from mmap() has its contents cleared before it is passed to
2008	  userspace.  Enabling this config option allows you to request that
2009	  mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
2010	  providing a huge performance boost.  If this option is not enabled,
2011	  then the flag will be ignored.
2012
2013	  This is taken advantage of by uClibc's malloc(), and also by
2014	  ELF-FDPIC binfmt's brk and stack allocator.
2015
2016	  Because of the obvious security issues, this option should only be
2017	  enabled on embedded devices where you control what is run in
2018	  userspace.  Since that isn't generally a problem on no-MMU systems,
2019	  it is normally safe to say Y here.
2020
2021	  See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
2022
2023config SYSTEM_DATA_VERIFICATION
2024	def_bool n
2025	select SYSTEM_TRUSTED_KEYRING
2026	select KEYS
2027	select CRYPTO
2028	select CRYPTO_RSA
2029	select ASYMMETRIC_KEY_TYPE
2030	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
2031	select ASN1
2032	select OID_REGISTRY
2033	select X509_CERTIFICATE_PARSER
2034	select PKCS7_MESSAGE_PARSER
2035	help
2036	  Provide PKCS#7 message verification using the contents of the system
2037	  trusted keyring to provide public keys.  This then can be used for
2038	  module verification, kexec image verification and firmware blob
2039	  verification.
2040
2041config PROFILING
2042	bool "Profiling support"
2043	help
2044	  Say Y here to enable the extended profiling support mechanisms used
2045	  by profilers.
2046
2047#
2048# Place an empty function call at each tracepoint site. Can be
2049# dynamically changed for a probe function.
2050#
2051config TRACEPOINTS
2052	bool
2053
2054endmenu		# General setup
2055
2056source "arch/Kconfig"
2057
2058config RT_MUTEXES
2059	bool
2060
2061config BASE_SMALL
2062	int
2063	default 0 if BASE_FULL
2064	default 1 if !BASE_FULL
2065
2066config MODULE_SIG_FORMAT
2067	def_bool n
2068	select SYSTEM_DATA_VERIFICATION
2069
2070menuconfig MODULES
2071	bool "Enable loadable module support"
2072	modules
2073	help
2074	  Kernel modules are small pieces of compiled code which can
2075	  be inserted in the running kernel, rather than being
2076	  permanently built into the kernel.  You use the "modprobe"
2077	  tool to add (and sometimes remove) them.  If you say Y here,
2078	  many parts of the kernel can be built as modules (by
2079	  answering M instead of Y where indicated): this is most
2080	  useful for infrequently used options which are not required
2081	  for booting.  For more information, see the man pages for
2082	  modprobe, lsmod, modinfo, insmod and rmmod.
2083
2084	  If you say Y here, you will need to run "make
2085	  modules_install" to put the modules under /lib/modules/
2086	  where modprobe can find them (you may need to be root to do
2087	  this).
2088
2089	  If unsure, say Y.
2090
2091if MODULES
2092
2093config MODULE_FORCE_LOAD
2094	bool "Forced module loading"
2095	default n
2096	help
2097	  Allow loading of modules without version information (ie. modprobe
2098	  --force).  Forced module loading sets the 'F' (forced) taint flag and
2099	  is usually a really bad idea.
2100
2101config MODULE_UNLOAD
2102	bool "Module unloading"
2103	help
2104	  Without this option you will not be able to unload any
2105	  modules (note that some modules may not be unloadable
2106	  anyway), which makes your kernel smaller, faster
2107	  and simpler.  If unsure, say Y.
2108
2109config MODULE_FORCE_UNLOAD
2110	bool "Forced module unloading"
2111	depends on MODULE_UNLOAD
2112	help
2113	  This option allows you to force a module to unload, even if the
2114	  kernel believes it is unsafe: the kernel will remove the module
2115	  without waiting for anyone to stop using it (using the -f option to
2116	  rmmod).  This is mainly for kernel developers and desperate users.
2117	  If unsure, say N.
2118
2119config MODVERSIONS
2120	bool "Module versioning support"
2121	help
2122	  Usually, you have to use modules compiled with your kernel.
2123	  Saying Y here makes it sometimes possible to use modules
2124	  compiled for different kernels, by adding enough information
2125	  to the modules to (hopefully) spot any changes which would
2126	  make them incompatible with the kernel you are running.  If
2127	  unsure, say N.
2128
2129config ASM_MODVERSIONS
2130	bool
2131	default HAVE_ASM_MODVERSIONS && MODVERSIONS
2132	help
2133	  This enables module versioning for exported symbols also from
2134	  assembly. This can be enabled only when the target architecture
2135	  supports it.
2136
2137config MODULE_REL_CRCS
2138	bool
2139	depends on MODVERSIONS
2140
2141config MODULE_SRCVERSION_ALL
2142	bool "Source checksum for all modules"
2143	help
2144	  Modules which contain a MODULE_VERSION get an extra "srcversion"
2145	  field inserted into their modinfo section, which contains a
2146    	  sum of the source files which made it.  This helps maintainers
2147	  see exactly which source was used to build a module (since
2148	  others sometimes change the module source without updating
2149	  the version).  With this option, such a "srcversion" field
2150	  will be created for all modules.  If unsure, say N.
2151
2152config MODULE_SIG
2153	bool "Module signature verification"
2154	select MODULE_SIG_FORMAT
2155	help
2156	  Check modules for valid signatures upon load: the signature
2157	  is simply appended to the module. For more information see
2158	  <file:Documentation/admin-guide/module-signing.rst>.
2159
2160	  Note that this option adds the OpenSSL development packages as a
2161	  kernel build dependency so that the signing tool can use its crypto
2162	  library.
2163
2164	  You should enable this option if you wish to use either
2165	  CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2166	  another LSM - otherwise unsigned modules will be loadable regardless
2167	  of the lockdown policy.
2168
2169	  !!!WARNING!!!  If you enable this option, you MUST make sure that the
2170	  module DOES NOT get stripped after being signed.  This includes the
2171	  debuginfo strip done by some packagers (such as rpmbuild) and
2172	  inclusion into an initramfs that wants the module size reduced.
2173
2174config MODULE_SIG_FORCE
2175	bool "Require modules to be validly signed"
2176	depends on MODULE_SIG
2177	help
2178	  Reject unsigned modules or signed modules for which we don't have a
2179	  key.  Without this, such modules will simply taint the kernel.
2180
2181config MODULE_SIG_ALL
2182	bool "Automatically sign all modules"
2183	default y
2184	depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2185	help
2186	  Sign all modules during make modules_install. Without this option,
2187	  modules must be signed manually, using the scripts/sign-file tool.
2188
2189comment "Do not forget to sign required modules with scripts/sign-file"
2190	depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2191
2192choice
2193	prompt "Which hash algorithm should modules be signed with?"
2194	depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2195	help
2196	  This determines which sort of hashing algorithm will be used during
2197	  signature generation.  This algorithm _must_ be built into the kernel
2198	  directly so that signature verification can take place.  It is not
2199	  possible to load a signed module containing the algorithm to check
2200	  the signature on that module.
2201
2202config MODULE_SIG_SHA1
2203	bool "Sign modules with SHA-1"
2204	select CRYPTO_SHA1
2205
2206config MODULE_SIG_SHA224
2207	bool "Sign modules with SHA-224"
2208	select CRYPTO_SHA256
2209
2210config MODULE_SIG_SHA256
2211	bool "Sign modules with SHA-256"
2212	select CRYPTO_SHA256
2213
2214config MODULE_SIG_SHA384
2215	bool "Sign modules with SHA-384"
2216	select CRYPTO_SHA512
2217
2218config MODULE_SIG_SHA512
2219	bool "Sign modules with SHA-512"
2220	select CRYPTO_SHA512
2221
2222endchoice
2223
2224config MODULE_SIG_HASH
2225	string
2226	depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2227	default "sha1" if MODULE_SIG_SHA1
2228	default "sha224" if MODULE_SIG_SHA224
2229	default "sha256" if MODULE_SIG_SHA256
2230	default "sha384" if MODULE_SIG_SHA384
2231	default "sha512" if MODULE_SIG_SHA512
2232
2233choice
2234	prompt "Module compression mode"
2235	help
2236	  This option allows you to choose the algorithm which will be used to
2237	  compress modules when 'make modules_install' is run. (or, you can
2238	  choose to not compress modules at all.)
2239
2240	  External modules will also be compressed in the same way during the
2241	  installation.
2242
2243	  For modules inside an initrd or initramfs, it's more efficient to
2244	  compress the whole initrd or initramfs instead.
2245
2246	  This is fully compatible with signed modules.
2247
2248	  Please note that the tool used to load modules needs to support the
2249	  corresponding algorithm. module-init-tools MAY support gzip, and kmod
2250	  MAY support gzip, xz and zstd.
2251
2252	  Your build system needs to provide the appropriate compression tool
2253	  to compress the modules.
2254
2255	  If in doubt, select 'None'.
2256
2257config MODULE_COMPRESS_NONE
2258	bool "None"
2259	help
2260	  Do not compress modules. The installed modules are suffixed
2261	  with .ko.
2262
2263config MODULE_COMPRESS_GZIP
2264	bool "GZIP"
2265	help
2266	  Compress modules with GZIP. The installed modules are suffixed
2267	  with .ko.gz.
2268
2269config MODULE_COMPRESS_XZ
2270	bool "XZ"
2271	help
2272	  Compress modules with XZ. The installed modules are suffixed
2273	  with .ko.xz.
2274
2275config MODULE_COMPRESS_ZSTD
2276	bool "ZSTD"
2277	help
2278	  Compress modules with ZSTD. The installed modules are suffixed
2279	  with .ko.zst.
2280
2281endchoice
2282
2283config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2284	bool "Allow loading of modules with missing namespace imports"
2285	help
2286	  Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2287	  a namespace. A module that makes use of a symbol exported with such a
2288	  namespace is required to import the namespace via MODULE_IMPORT_NS().
2289	  There is no technical reason to enforce correct namespace imports,
2290	  but it creates consistency between symbols defining namespaces and
2291	  users importing namespaces they make use of. This option relaxes this
2292	  requirement and lifts the enforcement when loading a module.
2293
2294	  If unsure, say N.
2295
2296config MODPROBE_PATH
2297	string "Path to modprobe binary"
2298	default "/sbin/modprobe"
2299	help
2300	  When kernel code requests a module, it does so by calling
2301	  the "modprobe" userspace utility. This option allows you to
2302	  set the path where that binary is found. This can be changed
2303	  at runtime via the sysctl file
2304	  /proc/sys/kernel/modprobe. Setting this to the empty string
2305	  removes the kernel's ability to request modules (but
2306	  userspace can still load modules explicitly).
2307
2308config TRIM_UNUSED_KSYMS
2309	bool "Trim unused exported kernel symbols" if EXPERT
2310	depends on !COMPILE_TEST
2311	help
2312	  The kernel and some modules make many symbols available for
2313	  other modules to use via EXPORT_SYMBOL() and variants. Depending
2314	  on the set of modules being selected in your kernel configuration,
2315	  many of those exported symbols might never be used.
2316
2317	  This option allows for unused exported symbols to be dropped from
2318	  the build. In turn, this provides the compiler more opportunities
2319	  (especially when using LTO) for optimizing the code and reducing
2320	  binary size.  This might have some security advantages as well.
2321
2322	  If unsure, or if you need to build out-of-tree modules, say N.
2323
2324config UNUSED_KSYMS_WHITELIST
2325	string "Whitelist of symbols to keep in ksymtab"
2326	depends on TRIM_UNUSED_KSYMS
2327	help
2328	  By default, all unused exported symbols will be un-exported from the
2329	  build when TRIM_UNUSED_KSYMS is selected.
2330
2331	  UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
2332	  exported at all times, even in absence of in-tree users. The value to
2333	  set here is the path to a text file containing the list of symbols,
2334	  one per line. The path can be absolute, or relative to the kernel
2335	  source tree.
2336
2337endif # MODULES
2338
2339config MODULES_TREE_LOOKUP
2340	def_bool y
2341	depends on PERF_EVENTS || TRACING || CFI_CLANG
2342
2343config INIT_ALL_POSSIBLE
2344	bool
2345	help
2346	  Back when each arch used to define their own cpu_online_mask and
2347	  cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2348	  with all 1s, and others with all 0s.  When they were centralised,
2349	  it was better to provide this option than to break all the archs
2350	  and have several arch maintainers pursuing me down dark alleys.
2351
2352source "block/Kconfig"
2353
2354config PREEMPT_NOTIFIERS
2355	bool
2356
2357config PADATA
2358	depends on SMP
2359	bool
2360
2361config ASN1
2362	tristate
2363	help
2364	  Build a simple ASN.1 grammar compiler that produces a bytecode output
2365	  that can be interpreted by the ASN.1 stream decoder and used to
2366	  inform it as to what tags are to be expected in a stream and what
2367	  functions to call on what tags.
2368
2369source "kernel/Kconfig.locks"
2370
2371config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2372	bool
2373
2374config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2375	bool
2376
2377# It may be useful for an architecture to override the definitions of the
2378# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2379# and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2380# different calling convention for syscalls. They can also override the
2381# macros for not-implemented syscalls in kernel/sys_ni.c and
2382# kernel/time/posix-stubs.c. All these overrides need to be available in
2383# <asm/syscall_wrapper.h>.
2384config ARCH_HAS_SYSCALL_WRAPPER
2385	def_bool n
2386