xref: /openbmc/linux/init/Kconfig (revision d198b34f3855eee2571dda03eea75a09c7c31480)
1# SPDX-License-Identifier: GPL-2.0-only
2config DEFCONFIG_LIST
3	string
4	depends on !UML
5	option defconfig_list
6	default "/lib/modules/$(shell,uname -r)/.config"
7	default "/etc/kernel-config"
8	default "/boot/config-$(shell,uname -r)"
9	default ARCH_DEFCONFIG
10	default "arch/$(ARCH)/defconfig"
11
12config CC_IS_GCC
13	def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc)
14
15config GCC_VERSION
16	int
17	default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC
18	default 0
19
20config CC_IS_CLANG
21	def_bool $(success,$(CC) --version | head -n 1 | grep -q clang)
22
23config CLANG_VERSION
24	int
25	default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
26
27config CC_CAN_LINK
28	def_bool $(success,$(srctree)/scripts/cc-can-link.sh $(CC))
29
30config CC_HAS_ASM_GOTO
31	def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
32
33config TOOLS_SUPPORT_RELR
34	def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
35
36config CC_HAS_ASM_INLINE
37	def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
38
39config CC_HAS_WARN_MAYBE_UNINITIALIZED
40	def_bool $(cc-option,-Wmaybe-uninitialized)
41	help
42	  GCC >= 4.7 supports this option.
43
44config CC_DISABLE_WARN_MAYBE_UNINITIALIZED
45	bool
46	depends on CC_HAS_WARN_MAYBE_UNINITIALIZED
47	default CC_IS_GCC && GCC_VERSION < 40900  # unreliable for GCC < 4.9
48	help
49	  GCC's -Wmaybe-uninitialized is not reliable by definition.
50	  Lots of false positive warnings are produced in some cases.
51
52	  If this option is enabled, -Wno-maybe-uninitialzed is passed
53	  to the compiler to suppress maybe-uninitialized warnings.
54
55config CONSTRUCTORS
56	bool
57	depends on !UML
58
59config IRQ_WORK
60	bool
61
62config BUILDTIME_TABLE_SORT
63	bool
64
65config THREAD_INFO_IN_TASK
66	bool
67	help
68	  Select this to move thread_info off the stack into task_struct.  To
69	  make this work, an arch will need to remove all thread_info fields
70	  except flags and fix any runtime bugs.
71
72	  One subtle change that will be needed is to use try_get_task_stack()
73	  and put_task_stack() in save_thread_stack_tsk() and get_wchan().
74
75menu "General setup"
76
77config BROKEN
78	bool
79
80config BROKEN_ON_SMP
81	bool
82	depends on BROKEN || !SMP
83	default y
84
85config INIT_ENV_ARG_LIMIT
86	int
87	default 32 if !UML
88	default 128 if UML
89	help
90	  Maximum of each of the number of arguments and environment
91	  variables passed to init from the kernel command line.
92
93config COMPILE_TEST
94	bool "Compile also drivers which will not load"
95	depends on !UML
96	default n
97	help
98	  Some drivers can be compiled on a different platform than they are
99	  intended to be run on. Despite they cannot be loaded there (or even
100	  when they load they cannot be used due to missing HW support),
101	  developers still, opposing to distributors, might want to build such
102	  drivers to compile-test them.
103
104	  If you are a developer and want to build everything available, say Y
105	  here. If you are a user/distributor, say N here to exclude useless
106	  drivers to be distributed.
107
108config UAPI_HEADER_TEST
109	bool "Compile test UAPI headers"
110	depends on HEADERS_INSTALL && CC_CAN_LINK
111	help
112	  Compile test headers exported to user-space to ensure they are
113	  self-contained, i.e. compilable as standalone units.
114
115	  If you are a developer or tester and want to ensure the exported
116	  headers are self-contained, say Y here. Otherwise, choose N.
117
118config LOCALVERSION
119	string "Local version - append to kernel release"
120	help
121	  Append an extra string to the end of your kernel version.
122	  This will show up when you type uname, for example.
123	  The string you set here will be appended after the contents of
124	  any files with a filename matching localversion* in your
125	  object and source tree, in that order.  Your total string can
126	  be a maximum of 64 characters.
127
128config LOCALVERSION_AUTO
129	bool "Automatically append version information to the version string"
130	default y
131	depends on !COMPILE_TEST
132	help
133	  This will try to automatically determine if the current tree is a
134	  release tree by looking for git tags that belong to the current
135	  top of tree revision.
136
137	  A string of the format -gxxxxxxxx will be added to the localversion
138	  if a git-based tree is found.  The string generated by this will be
139	  appended after any matching localversion* files, and after the value
140	  set in CONFIG_LOCALVERSION.
141
142	  (The actual string used here is the first eight characters produced
143	  by running the command:
144
145	    $ git rev-parse --verify HEAD
146
147	  which is done within the script "scripts/setlocalversion".)
148
149config BUILD_SALT
150	string "Build ID Salt"
151	default ""
152	help
153	  The build ID is used to link binaries and their debug info. Setting
154	  this option will use the value in the calculation of the build id.
155	  This is mostly useful for distributions which want to ensure the
156	  build is unique between builds. It's safe to leave the default.
157
158config HAVE_KERNEL_GZIP
159	bool
160
161config HAVE_KERNEL_BZIP2
162	bool
163
164config HAVE_KERNEL_LZMA
165	bool
166
167config HAVE_KERNEL_XZ
168	bool
169
170config HAVE_KERNEL_LZO
171	bool
172
173config HAVE_KERNEL_LZ4
174	bool
175
176config HAVE_KERNEL_UNCOMPRESSED
177	bool
178
179choice
180	prompt "Kernel compression mode"
181	default KERNEL_GZIP
182	depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED
183	help
184	  The linux kernel is a kind of self-extracting executable.
185	  Several compression algorithms are available, which differ
186	  in efficiency, compression and decompression speed.
187	  Compression speed is only relevant when building a kernel.
188	  Decompression speed is relevant at each boot.
189
190	  If you have any problems with bzip2 or lzma compressed
191	  kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
192	  version of this functionality (bzip2 only), for 2.4, was
193	  supplied by Christian Ludwig)
194
195	  High compression options are mostly useful for users, who
196	  are low on disk space (embedded systems), but for whom ram
197	  size matters less.
198
199	  If in doubt, select 'gzip'
200
201config KERNEL_GZIP
202	bool "Gzip"
203	depends on HAVE_KERNEL_GZIP
204	help
205	  The old and tried gzip compression. It provides a good balance
206	  between compression ratio and decompression speed.
207
208config KERNEL_BZIP2
209	bool "Bzip2"
210	depends on HAVE_KERNEL_BZIP2
211	help
212	  Its compression ratio and speed is intermediate.
213	  Decompression speed is slowest among the choices.  The kernel
214	  size is about 10% smaller with bzip2, in comparison to gzip.
215	  Bzip2 uses a large amount of memory. For modern kernels you
216	  will need at least 8MB RAM or more for booting.
217
218config KERNEL_LZMA
219	bool "LZMA"
220	depends on HAVE_KERNEL_LZMA
221	help
222	  This compression algorithm's ratio is best.  Decompression speed
223	  is between gzip and bzip2.  Compression is slowest.
224	  The kernel size is about 33% smaller with LZMA in comparison to gzip.
225
226config KERNEL_XZ
227	bool "XZ"
228	depends on HAVE_KERNEL_XZ
229	help
230	  XZ uses the LZMA2 algorithm and instruction set specific
231	  BCJ filters which can improve compression ratio of executable
232	  code. The size of the kernel is about 30% smaller with XZ in
233	  comparison to gzip. On architectures for which there is a BCJ
234	  filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
235	  will create a few percent smaller kernel than plain LZMA.
236
237	  The speed is about the same as with LZMA: The decompression
238	  speed of XZ is better than that of bzip2 but worse than gzip
239	  and LZO. Compression is slow.
240
241config KERNEL_LZO
242	bool "LZO"
243	depends on HAVE_KERNEL_LZO
244	help
245	  Its compression ratio is the poorest among the choices. The kernel
246	  size is about 10% bigger than gzip; however its speed
247	  (both compression and decompression) is the fastest.
248
249config KERNEL_LZ4
250	bool "LZ4"
251	depends on HAVE_KERNEL_LZ4
252	help
253	  LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
254	  A preliminary version of LZ4 de/compression tool is available at
255	  <https://code.google.com/p/lz4/>.
256
257	  Its compression ratio is worse than LZO. The size of the kernel
258	  is about 8% bigger than LZO. But the decompression speed is
259	  faster than LZO.
260
261config KERNEL_UNCOMPRESSED
262	bool "None"
263	depends on HAVE_KERNEL_UNCOMPRESSED
264	help
265	  Produce uncompressed kernel image. This option is usually not what
266	  you want. It is useful for debugging the kernel in slow simulation
267	  environments, where decompressing and moving the kernel is awfully
268	  slow. This option allows early boot code to skip the decompressor
269	  and jump right at uncompressed kernel image.
270
271endchoice
272
273config DEFAULT_HOSTNAME
274	string "Default hostname"
275	default "(none)"
276	help
277	  This option determines the default system hostname before userspace
278	  calls sethostname(2). The kernel traditionally uses "(none)" here,
279	  but you may wish to use a different default here to make a minimal
280	  system more usable with less configuration.
281
282#
283# For some reason microblaze and nios2 hard code SWAP=n.  Hopefully we can
284# add proper SWAP support to them, in which case this can be remove.
285#
286config ARCH_NO_SWAP
287	bool
288
289config SWAP
290	bool "Support for paging of anonymous memory (swap)"
291	depends on MMU && BLOCK && !ARCH_NO_SWAP
292	default y
293	help
294	  This option allows you to choose whether you want to have support
295	  for so called swap devices or swap files in your kernel that are
296	  used to provide more virtual memory than the actual RAM present
297	  in your computer.  If unsure say Y.
298
299config SYSVIPC
300	bool "System V IPC"
301	---help---
302	  Inter Process Communication is a suite of library functions and
303	  system calls which let processes (running programs) synchronize and
304	  exchange information. It is generally considered to be a good thing,
305	  and some programs won't run unless you say Y here. In particular, if
306	  you want to run the DOS emulator dosemu under Linux (read the
307	  DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
308	  you'll need to say Y here.
309
310	  You can find documentation about IPC with "info ipc" and also in
311	  section 6.4 of the Linux Programmer's Guide, available from
312	  <http://www.tldp.org/guides.html>.
313
314config SYSVIPC_SYSCTL
315	bool
316	depends on SYSVIPC
317	depends on SYSCTL
318	default y
319
320config POSIX_MQUEUE
321	bool "POSIX Message Queues"
322	depends on NET
323	---help---
324	  POSIX variant of message queues is a part of IPC. In POSIX message
325	  queues every message has a priority which decides about succession
326	  of receiving it by a process. If you want to compile and run
327	  programs written e.g. for Solaris with use of its POSIX message
328	  queues (functions mq_*) say Y here.
329
330	  POSIX message queues are visible as a filesystem called 'mqueue'
331	  and can be mounted somewhere if you want to do filesystem
332	  operations on message queues.
333
334	  If unsure, say Y.
335
336config POSIX_MQUEUE_SYSCTL
337	bool
338	depends on POSIX_MQUEUE
339	depends on SYSCTL
340	default y
341
342config CROSS_MEMORY_ATTACH
343	bool "Enable process_vm_readv/writev syscalls"
344	depends on MMU
345	default y
346	help
347	  Enabling this option adds the system calls process_vm_readv and
348	  process_vm_writev which allow a process with the correct privileges
349	  to directly read from or write to another process' address space.
350	  See the man page for more details.
351
352config USELIB
353	bool "uselib syscall"
354	def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
355	help
356	  This option enables the uselib syscall, a system call used in the
357	  dynamic linker from libc5 and earlier.  glibc does not use this
358	  system call.  If you intend to run programs built on libc5 or
359	  earlier, you may need to enable this syscall.  Current systems
360	  running glibc can safely disable this.
361
362config AUDIT
363	bool "Auditing support"
364	depends on NET
365	help
366	  Enable auditing infrastructure that can be used with another
367	  kernel subsystem, such as SELinux (which requires this for
368	  logging of avc messages output).  System call auditing is included
369	  on architectures which support it.
370
371config HAVE_ARCH_AUDITSYSCALL
372	bool
373
374config AUDITSYSCALL
375	def_bool y
376	depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
377	select FSNOTIFY
378
379source "kernel/irq/Kconfig"
380source "kernel/time/Kconfig"
381source "kernel/Kconfig.preempt"
382
383menu "CPU/Task time and stats accounting"
384
385config VIRT_CPU_ACCOUNTING
386	bool
387
388choice
389	prompt "Cputime accounting"
390	default TICK_CPU_ACCOUNTING if !PPC64
391	default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
392
393# Kind of a stub config for the pure tick based cputime accounting
394config TICK_CPU_ACCOUNTING
395	bool "Simple tick based cputime accounting"
396	depends on !S390 && !NO_HZ_FULL
397	help
398	  This is the basic tick based cputime accounting that maintains
399	  statistics about user, system and idle time spent on per jiffies
400	  granularity.
401
402	  If unsure, say Y.
403
404config VIRT_CPU_ACCOUNTING_NATIVE
405	bool "Deterministic task and CPU time accounting"
406	depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
407	select VIRT_CPU_ACCOUNTING
408	help
409	  Select this option to enable more accurate task and CPU time
410	  accounting.  This is done by reading a CPU counter on each
411	  kernel entry and exit and on transitions within the kernel
412	  between system, softirq and hardirq state, so there is a
413	  small performance impact.  In the case of s390 or IBM POWER > 5,
414	  this also enables accounting of stolen time on logically-partitioned
415	  systems.
416
417config VIRT_CPU_ACCOUNTING_GEN
418	bool "Full dynticks CPU time accounting"
419	depends on HAVE_CONTEXT_TRACKING
420	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
421	depends on GENERIC_CLOCKEVENTS
422	select VIRT_CPU_ACCOUNTING
423	select CONTEXT_TRACKING
424	help
425	  Select this option to enable task and CPU time accounting on full
426	  dynticks systems. This accounting is implemented by watching every
427	  kernel-user boundaries using the context tracking subsystem.
428	  The accounting is thus performed at the expense of some significant
429	  overhead.
430
431	  For now this is only useful if you are working on the full
432	  dynticks subsystem development.
433
434	  If unsure, say N.
435
436endchoice
437
438config IRQ_TIME_ACCOUNTING
439	bool "Fine granularity task level IRQ time accounting"
440	depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
441	help
442	  Select this option to enable fine granularity task irq time
443	  accounting. This is done by reading a timestamp on each
444	  transitions between softirq and hardirq state, so there can be a
445	  small performance impact.
446
447	  If in doubt, say N here.
448
449config HAVE_SCHED_AVG_IRQ
450	def_bool y
451	depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
452	depends on SMP
453
454config BSD_PROCESS_ACCT
455	bool "BSD Process Accounting"
456	depends on MULTIUSER
457	help
458	  If you say Y here, a user level program will be able to instruct the
459	  kernel (via a special system call) to write process accounting
460	  information to a file: whenever a process exits, information about
461	  that process will be appended to the file by the kernel.  The
462	  information includes things such as creation time, owning user,
463	  command name, memory usage, controlling terminal etc. (the complete
464	  list is in the struct acct in <file:include/linux/acct.h>).  It is
465	  up to the user level program to do useful things with this
466	  information.  This is generally a good idea, so say Y.
467
468config BSD_PROCESS_ACCT_V3
469	bool "BSD Process Accounting version 3 file format"
470	depends on BSD_PROCESS_ACCT
471	default n
472	help
473	  If you say Y here, the process accounting information is written
474	  in a new file format that also logs the process IDs of each
475	  process and its parent. Note that this file format is incompatible
476	  with previous v0/v1/v2 file formats, so you will need updated tools
477	  for processing it. A preliminary version of these tools is available
478	  at <http://www.gnu.org/software/acct/>.
479
480config TASKSTATS
481	bool "Export task/process statistics through netlink"
482	depends on NET
483	depends on MULTIUSER
484	default n
485	help
486	  Export selected statistics for tasks/processes through the
487	  generic netlink interface. Unlike BSD process accounting, the
488	  statistics are available during the lifetime of tasks/processes as
489	  responses to commands. Like BSD accounting, they are sent to user
490	  space on task exit.
491
492	  Say N if unsure.
493
494config TASK_DELAY_ACCT
495	bool "Enable per-task delay accounting"
496	depends on TASKSTATS
497	select SCHED_INFO
498	help
499	  Collect information on time spent by a task waiting for system
500	  resources like cpu, synchronous block I/O completion and swapping
501	  in pages. Such statistics can help in setting a task's priorities
502	  relative to other tasks for cpu, io, rss limits etc.
503
504	  Say N if unsure.
505
506config TASK_XACCT
507	bool "Enable extended accounting over taskstats"
508	depends on TASKSTATS
509	help
510	  Collect extended task accounting data and send the data
511	  to userland for processing over the taskstats interface.
512
513	  Say N if unsure.
514
515config TASK_IO_ACCOUNTING
516	bool "Enable per-task storage I/O accounting"
517	depends on TASK_XACCT
518	help
519	  Collect information on the number of bytes of storage I/O which this
520	  task has caused.
521
522	  Say N if unsure.
523
524config PSI
525	bool "Pressure stall information tracking"
526	help
527	  Collect metrics that indicate how overcommitted the CPU, memory,
528	  and IO capacity are in the system.
529
530	  If you say Y here, the kernel will create /proc/pressure/ with the
531	  pressure statistics files cpu, memory, and io. These will indicate
532	  the share of walltime in which some or all tasks in the system are
533	  delayed due to contention of the respective resource.
534
535	  In kernels with cgroup support, cgroups (cgroup2 only) will
536	  have cpu.pressure, memory.pressure, and io.pressure files,
537	  which aggregate pressure stalls for the grouped tasks only.
538
539	  For more details see Documentation/accounting/psi.rst.
540
541	  Say N if unsure.
542
543config PSI_DEFAULT_DISABLED
544	bool "Require boot parameter to enable pressure stall information tracking"
545	default n
546	depends on PSI
547	help
548	  If set, pressure stall information tracking will be disabled
549	  per default but can be enabled through passing psi=1 on the
550	  kernel commandline during boot.
551
552	  This feature adds some code to the task wakeup and sleep
553	  paths of the scheduler. The overhead is too low to affect
554	  common scheduling-intense workloads in practice (such as
555	  webservers, memcache), but it does show up in artificial
556	  scheduler stress tests, such as hackbench.
557
558	  If you are paranoid and not sure what the kernel will be
559	  used for, say Y.
560
561	  Say N if unsure.
562
563endmenu # "CPU/Task time and stats accounting"
564
565config CPU_ISOLATION
566	bool "CPU isolation"
567	depends on SMP || COMPILE_TEST
568	default y
569	help
570	  Make sure that CPUs running critical tasks are not disturbed by
571	  any source of "noise" such as unbound workqueues, timers, kthreads...
572	  Unbound jobs get offloaded to housekeeping CPUs. This is driven by
573	  the "isolcpus=" boot parameter.
574
575	  Say Y if unsure.
576
577source "kernel/rcu/Kconfig"
578
579config BUILD_BIN2C
580	bool
581	default n
582
583config IKCONFIG
584	tristate "Kernel .config support"
585	---help---
586	  This option enables the complete Linux kernel ".config" file
587	  contents to be saved in the kernel. It provides documentation
588	  of which kernel options are used in a running kernel or in an
589	  on-disk kernel.  This information can be extracted from the kernel
590	  image file with the script scripts/extract-ikconfig and used as
591	  input to rebuild the current kernel or to build another kernel.
592	  It can also be extracted from a running kernel by reading
593	  /proc/config.gz if enabled (below).
594
595config IKCONFIG_PROC
596	bool "Enable access to .config through /proc/config.gz"
597	depends on IKCONFIG && PROC_FS
598	---help---
599	  This option enables access to the kernel configuration file
600	  through /proc/config.gz.
601
602config IKHEADERS
603	tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
604	depends on SYSFS
605	help
606	  This option enables access to the in-kernel headers that are generated during
607	  the build process. These can be used to build eBPF tracing programs,
608	  or similar programs.  If you build the headers as a module, a module called
609	  kheaders.ko is built which can be loaded on-demand to get access to headers.
610
611config LOG_BUF_SHIFT
612	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
613	range 12 25
614	default 17
615	depends on PRINTK
616	help
617	  Select the minimal kernel log buffer size as a power of 2.
618	  The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
619	  parameter, see below. Any higher size also might be forced
620	  by "log_buf_len" boot parameter.
621
622	  Examples:
623		     17 => 128 KB
624		     16 => 64 KB
625		     15 => 32 KB
626		     14 => 16 KB
627		     13 =>  8 KB
628		     12 =>  4 KB
629
630config LOG_CPU_MAX_BUF_SHIFT
631	int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
632	depends on SMP
633	range 0 21
634	default 12 if !BASE_SMALL
635	default 0 if BASE_SMALL
636	depends on PRINTK
637	help
638	  This option allows to increase the default ring buffer size
639	  according to the number of CPUs. The value defines the contribution
640	  of each CPU as a power of 2. The used space is typically only few
641	  lines however it might be much more when problems are reported,
642	  e.g. backtraces.
643
644	  The increased size means that a new buffer has to be allocated and
645	  the original static one is unused. It makes sense only on systems
646	  with more CPUs. Therefore this value is used only when the sum of
647	  contributions is greater than the half of the default kernel ring
648	  buffer as defined by LOG_BUF_SHIFT. The default values are set
649	  so that more than 64 CPUs are needed to trigger the allocation.
650
651	  Also this option is ignored when "log_buf_len" kernel parameter is
652	  used as it forces an exact (power of two) size of the ring buffer.
653
654	  The number of possible CPUs is used for this computation ignoring
655	  hotplugging making the computation optimal for the worst case
656	  scenario while allowing a simple algorithm to be used from bootup.
657
658	  Examples shift values and their meaning:
659		     17 => 128 KB for each CPU
660		     16 =>  64 KB for each CPU
661		     15 =>  32 KB for each CPU
662		     14 =>  16 KB for each CPU
663		     13 =>   8 KB for each CPU
664		     12 =>   4 KB for each CPU
665
666config PRINTK_SAFE_LOG_BUF_SHIFT
667	int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
668	range 10 21
669	default 13
670	depends on PRINTK
671	help
672	  Select the size of an alternate printk per-CPU buffer where messages
673	  printed from usafe contexts are temporary stored. One example would
674	  be NMI messages, another one - printk recursion. The messages are
675	  copied to the main log buffer in a safe context to avoid a deadlock.
676	  The value defines the size as a power of 2.
677
678	  Those messages are rare and limited. The largest one is when
679	  a backtrace is printed. It usually fits into 4KB. Select
680	  8KB if you want to be on the safe side.
681
682	  Examples:
683		     17 => 128 KB for each CPU
684		     16 =>  64 KB for each CPU
685		     15 =>  32 KB for each CPU
686		     14 =>  16 KB for each CPU
687		     13 =>   8 KB for each CPU
688		     12 =>   4 KB for each CPU
689
690#
691# Architectures with an unreliable sched_clock() should select this:
692#
693config HAVE_UNSTABLE_SCHED_CLOCK
694	bool
695
696config GENERIC_SCHED_CLOCK
697	bool
698
699menu "Scheduler features"
700
701config UCLAMP_TASK
702	bool "Enable utilization clamping for RT/FAIR tasks"
703	depends on CPU_FREQ_GOV_SCHEDUTIL
704	help
705	  This feature enables the scheduler to track the clamped utilization
706	  of each CPU based on RUNNABLE tasks scheduled on that CPU.
707
708	  With this option, the user can specify the min and max CPU
709	  utilization allowed for RUNNABLE tasks. The max utilization defines
710	  the maximum frequency a task should use while the min utilization
711	  defines the minimum frequency it should use.
712
713	  Both min and max utilization clamp values are hints to the scheduler,
714	  aiming at improving its frequency selection policy, but they do not
715	  enforce or grant any specific bandwidth for tasks.
716
717	  If in doubt, say N.
718
719config UCLAMP_BUCKETS_COUNT
720	int "Number of supported utilization clamp buckets"
721	range 5 20
722	default 5
723	depends on UCLAMP_TASK
724	help
725	  Defines the number of clamp buckets to use. The range of each bucket
726	  will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
727	  number of clamp buckets the finer their granularity and the higher
728	  the precision of clamping aggregation and tracking at run-time.
729
730	  For example, with the minimum configuration value we will have 5
731	  clamp buckets tracking 20% utilization each. A 25% boosted tasks will
732	  be refcounted in the [20..39]% bucket and will set the bucket clamp
733	  effective value to 25%.
734	  If a second 30% boosted task should be co-scheduled on the same CPU,
735	  that task will be refcounted in the same bucket of the first task and
736	  it will boost the bucket clamp effective value to 30%.
737	  The clamp effective value of a bucket is reset to its nominal value
738	  (20% in the example above) when there are no more tasks refcounted in
739	  that bucket.
740
741	  An additional boost/capping margin can be added to some tasks. In the
742	  example above the 25% task will be boosted to 30% until it exits the
743	  CPU. If that should be considered not acceptable on certain systems,
744	  it's always possible to reduce the margin by increasing the number of
745	  clamp buckets to trade off used memory for run-time tracking
746	  precision.
747
748	  If in doubt, use the default value.
749
750endmenu
751
752#
753# For architectures that want to enable the support for NUMA-affine scheduler
754# balancing logic:
755#
756config ARCH_SUPPORTS_NUMA_BALANCING
757	bool
758
759#
760# For architectures that prefer to flush all TLBs after a number of pages
761# are unmapped instead of sending one IPI per page to flush. The architecture
762# must provide guarantees on what happens if a clean TLB cache entry is
763# written after the unmap. Details are in mm/rmap.c near the check for
764# should_defer_flush. The architecture should also consider if the full flush
765# and the refill costs are offset by the savings of sending fewer IPIs.
766config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
767	bool
768
769config CC_HAS_INT128
770	def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
771
772#
773# For architectures that know their GCC __int128 support is sound
774#
775config ARCH_SUPPORTS_INT128
776	bool
777
778# For architectures that (ab)use NUMA to represent different memory regions
779# all cpu-local but of different latencies, such as SuperH.
780#
781config ARCH_WANT_NUMA_VARIABLE_LOCALITY
782	bool
783
784config NUMA_BALANCING
785	bool "Memory placement aware NUMA scheduler"
786	depends on ARCH_SUPPORTS_NUMA_BALANCING
787	depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
788	depends on SMP && NUMA && MIGRATION
789	help
790	  This option adds support for automatic NUMA aware memory/task placement.
791	  The mechanism is quite primitive and is based on migrating memory when
792	  it has references to the node the task is running on.
793
794	  This system will be inactive on UMA systems.
795
796config NUMA_BALANCING_DEFAULT_ENABLED
797	bool "Automatically enable NUMA aware memory/task placement"
798	default y
799	depends on NUMA_BALANCING
800	help
801	  If set, automatic NUMA balancing will be enabled if running on a NUMA
802	  machine.
803
804menuconfig CGROUPS
805	bool "Control Group support"
806	select KERNFS
807	help
808	  This option adds support for grouping sets of processes together, for
809	  use with process control subsystems such as Cpusets, CFS, memory
810	  controls or device isolation.
811	  See
812		- Documentation/scheduler/sched-design-CFS.rst	(CFS)
813		- Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
814					  and resource control)
815
816	  Say N if unsure.
817
818if CGROUPS
819
820config PAGE_COUNTER
821	bool
822
823config MEMCG
824	bool "Memory controller"
825	select PAGE_COUNTER
826	select EVENTFD
827	help
828	  Provides control over the memory footprint of tasks in a cgroup.
829
830config MEMCG_SWAP
831	bool "Swap controller"
832	depends on MEMCG && SWAP
833	help
834	  Provides control over the swap space consumed by tasks in a cgroup.
835
836config MEMCG_SWAP_ENABLED
837	bool "Swap controller enabled by default"
838	depends on MEMCG_SWAP
839	default y
840	help
841	  Memory Resource Controller Swap Extension comes with its price in
842	  a bigger memory consumption. General purpose distribution kernels
843	  which want to enable the feature but keep it disabled by default
844	  and let the user enable it by swapaccount=1 boot command line
845	  parameter should have this option unselected.
846	  For those who want to have the feature enabled by default should
847	  select this option (if, for some reason, they need to disable it
848	  then swapaccount=0 does the trick).
849
850config MEMCG_KMEM
851	bool
852	depends on MEMCG && !SLOB
853	default y
854
855config BLK_CGROUP
856	bool "IO controller"
857	depends on BLOCK
858	default n
859	---help---
860	Generic block IO controller cgroup interface. This is the common
861	cgroup interface which should be used by various IO controlling
862	policies.
863
864	Currently, CFQ IO scheduler uses it to recognize task groups and
865	control disk bandwidth allocation (proportional time slice allocation)
866	to such task groups. It is also used by bio throttling logic in
867	block layer to implement upper limit in IO rates on a device.
868
869	This option only enables generic Block IO controller infrastructure.
870	One needs to also enable actual IO controlling logic/policy. For
871	enabling proportional weight division of disk bandwidth in CFQ, set
872	CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
873	CONFIG_BLK_DEV_THROTTLING=y.
874
875	See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
876
877config CGROUP_WRITEBACK
878	bool
879	depends on MEMCG && BLK_CGROUP
880	default y
881
882menuconfig CGROUP_SCHED
883	bool "CPU controller"
884	default n
885	help
886	  This feature lets CPU scheduler recognize task groups and control CPU
887	  bandwidth allocation to such task groups. It uses cgroups to group
888	  tasks.
889
890if CGROUP_SCHED
891config FAIR_GROUP_SCHED
892	bool "Group scheduling for SCHED_OTHER"
893	depends on CGROUP_SCHED
894	default CGROUP_SCHED
895
896config CFS_BANDWIDTH
897	bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
898	depends on FAIR_GROUP_SCHED
899	default n
900	help
901	  This option allows users to define CPU bandwidth rates (limits) for
902	  tasks running within the fair group scheduler.  Groups with no limit
903	  set are considered to be unconstrained and will run with no
904	  restriction.
905	  See Documentation/scheduler/sched-bwc.rst for more information.
906
907config RT_GROUP_SCHED
908	bool "Group scheduling for SCHED_RR/FIFO"
909	depends on CGROUP_SCHED
910	default n
911	help
912	  This feature lets you explicitly allocate real CPU bandwidth
913	  to task groups. If enabled, it will also make it impossible to
914	  schedule realtime tasks for non-root users until you allocate
915	  realtime bandwidth for them.
916	  See Documentation/scheduler/sched-rt-group.rst for more information.
917
918endif #CGROUP_SCHED
919
920config UCLAMP_TASK_GROUP
921	bool "Utilization clamping per group of tasks"
922	depends on CGROUP_SCHED
923	depends on UCLAMP_TASK
924	default n
925	help
926	  This feature enables the scheduler to track the clamped utilization
927	  of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
928
929	  When this option is enabled, the user can specify a min and max
930	  CPU bandwidth which is allowed for each single task in a group.
931	  The max bandwidth allows to clamp the maximum frequency a task
932	  can use, while the min bandwidth allows to define a minimum
933	  frequency a task will always use.
934
935	  When task group based utilization clamping is enabled, an eventually
936	  specified task-specific clamp value is constrained by the cgroup
937	  specified clamp value. Both minimum and maximum task clamping cannot
938	  be bigger than the corresponding clamping defined at task group level.
939
940	  If in doubt, say N.
941
942config CGROUP_PIDS
943	bool "PIDs controller"
944	help
945	  Provides enforcement of process number limits in the scope of a
946	  cgroup. Any attempt to fork more processes than is allowed in the
947	  cgroup will fail. PIDs are fundamentally a global resource because it
948	  is fairly trivial to reach PID exhaustion before you reach even a
949	  conservative kmemcg limit. As a result, it is possible to grind a
950	  system to halt without being limited by other cgroup policies. The
951	  PIDs controller is designed to stop this from happening.
952
953	  It should be noted that organisational operations (such as attaching
954	  to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
955	  since the PIDs limit only affects a process's ability to fork, not to
956	  attach to a cgroup.
957
958config CGROUP_RDMA
959	bool "RDMA controller"
960	help
961	  Provides enforcement of RDMA resources defined by IB stack.
962	  It is fairly easy for consumers to exhaust RDMA resources, which
963	  can result into resource unavailability to other consumers.
964	  RDMA controller is designed to stop this from happening.
965	  Attaching processes with active RDMA resources to the cgroup
966	  hierarchy is allowed even if can cross the hierarchy's limit.
967
968config CGROUP_FREEZER
969	bool "Freezer controller"
970	help
971	  Provides a way to freeze and unfreeze all tasks in a
972	  cgroup.
973
974	  This option affects the ORIGINAL cgroup interface. The cgroup2 memory
975	  controller includes important in-kernel memory consumers per default.
976
977	  If you're using cgroup2, say N.
978
979config CGROUP_HUGETLB
980	bool "HugeTLB controller"
981	depends on HUGETLB_PAGE
982	select PAGE_COUNTER
983	default n
984	help
985	  Provides a cgroup controller for HugeTLB pages.
986	  When you enable this, you can put a per cgroup limit on HugeTLB usage.
987	  The limit is enforced during page fault. Since HugeTLB doesn't
988	  support page reclaim, enforcing the limit at page fault time implies
989	  that, the application will get SIGBUS signal if it tries to access
990	  HugeTLB pages beyond its limit. This requires the application to know
991	  beforehand how much HugeTLB pages it would require for its use. The
992	  control group is tracked in the third page lru pointer. This means
993	  that we cannot use the controller with huge page less than 3 pages.
994
995config CPUSETS
996	bool "Cpuset controller"
997	depends on SMP
998	help
999	  This option will let you create and manage CPUSETs which
1000	  allow dynamically partitioning a system into sets of CPUs and
1001	  Memory Nodes and assigning tasks to run only within those sets.
1002	  This is primarily useful on large SMP or NUMA systems.
1003
1004	  Say N if unsure.
1005
1006config PROC_PID_CPUSET
1007	bool "Include legacy /proc/<pid>/cpuset file"
1008	depends on CPUSETS
1009	default y
1010
1011config CGROUP_DEVICE
1012	bool "Device controller"
1013	help
1014	  Provides a cgroup controller implementing whitelists for
1015	  devices which a process in the cgroup can mknod or open.
1016
1017config CGROUP_CPUACCT
1018	bool "Simple CPU accounting controller"
1019	help
1020	  Provides a simple controller for monitoring the
1021	  total CPU consumed by the tasks in a cgroup.
1022
1023config CGROUP_PERF
1024	bool "Perf controller"
1025	depends on PERF_EVENTS
1026	help
1027	  This option extends the perf per-cpu mode to restrict monitoring
1028	  to threads which belong to the cgroup specified and run on the
1029	  designated cpu.
1030
1031	  Say N if unsure.
1032
1033config CGROUP_BPF
1034	bool "Support for eBPF programs attached to cgroups"
1035	depends on BPF_SYSCALL
1036	select SOCK_CGROUP_DATA
1037	help
1038	  Allow attaching eBPF programs to a cgroup using the bpf(2)
1039	  syscall command BPF_PROG_ATTACH.
1040
1041	  In which context these programs are accessed depends on the type
1042	  of attachment. For instance, programs that are attached using
1043	  BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1044	  inet sockets.
1045
1046config CGROUP_DEBUG
1047	bool "Debug controller"
1048	default n
1049	depends on DEBUG_KERNEL
1050	help
1051	  This option enables a simple controller that exports
1052	  debugging information about the cgroups framework. This
1053	  controller is for control cgroup debugging only. Its
1054	  interfaces are not stable.
1055
1056	  Say N.
1057
1058config SOCK_CGROUP_DATA
1059	bool
1060	default n
1061
1062endif # CGROUPS
1063
1064menuconfig NAMESPACES
1065	bool "Namespaces support" if EXPERT
1066	depends on MULTIUSER
1067	default !EXPERT
1068	help
1069	  Provides the way to make tasks work with different objects using
1070	  the same id. For example same IPC id may refer to different objects
1071	  or same user id or pid may refer to different tasks when used in
1072	  different namespaces.
1073
1074if NAMESPACES
1075
1076config UTS_NS
1077	bool "UTS namespace"
1078	default y
1079	help
1080	  In this namespace tasks see different info provided with the
1081	  uname() system call
1082
1083config TIME_NS
1084	bool "TIME namespace"
1085	depends on GENERIC_VDSO_TIME_NS
1086	default y
1087	help
1088	  In this namespace boottime and monotonic clocks can be set.
1089	  The time will keep going with the same pace.
1090
1091config IPC_NS
1092	bool "IPC namespace"
1093	depends on (SYSVIPC || POSIX_MQUEUE)
1094	default y
1095	help
1096	  In this namespace tasks work with IPC ids which correspond to
1097	  different IPC objects in different namespaces.
1098
1099config USER_NS
1100	bool "User namespace"
1101	default n
1102	help
1103	  This allows containers, i.e. vservers, to use user namespaces
1104	  to provide different user info for different servers.
1105
1106	  When user namespaces are enabled in the kernel it is
1107	  recommended that the MEMCG option also be enabled and that
1108	  user-space use the memory control groups to limit the amount
1109	  of memory a memory unprivileged users can use.
1110
1111	  If unsure, say N.
1112
1113config PID_NS
1114	bool "PID Namespaces"
1115	default y
1116	help
1117	  Support process id namespaces.  This allows having multiple
1118	  processes with the same pid as long as they are in different
1119	  pid namespaces.  This is a building block of containers.
1120
1121config NET_NS
1122	bool "Network namespace"
1123	depends on NET
1124	default y
1125	help
1126	  Allow user space to create what appear to be multiple instances
1127	  of the network stack.
1128
1129endif # NAMESPACES
1130
1131config CHECKPOINT_RESTORE
1132	bool "Checkpoint/restore support"
1133	select PROC_CHILDREN
1134	default n
1135	help
1136	  Enables additional kernel features in a sake of checkpoint/restore.
1137	  In particular it adds auxiliary prctl codes to setup process text,
1138	  data and heap segment sizes, and a few additional /proc filesystem
1139	  entries.
1140
1141	  If unsure, say N here.
1142
1143config SCHED_AUTOGROUP
1144	bool "Automatic process group scheduling"
1145	select CGROUPS
1146	select CGROUP_SCHED
1147	select FAIR_GROUP_SCHED
1148	help
1149	  This option optimizes the scheduler for common desktop workloads by
1150	  automatically creating and populating task groups.  This separation
1151	  of workloads isolates aggressive CPU burners (like build jobs) from
1152	  desktop applications.  Task group autogeneration is currently based
1153	  upon task session.
1154
1155config SYSFS_DEPRECATED
1156	bool "Enable deprecated sysfs features to support old userspace tools"
1157	depends on SYSFS
1158	default n
1159	help
1160	  This option adds code that switches the layout of the "block" class
1161	  devices, to not show up in /sys/class/block/, but only in
1162	  /sys/block/.
1163
1164	  This switch is only active when the sysfs.deprecated=1 boot option is
1165	  passed or the SYSFS_DEPRECATED_V2 option is set.
1166
1167	  This option allows new kernels to run on old distributions and tools,
1168	  which might get confused by /sys/class/block/. Since 2007/2008 all
1169	  major distributions and tools handle this just fine.
1170
1171	  Recent distributions and userspace tools after 2009/2010 depend on
1172	  the existence of /sys/class/block/, and will not work with this
1173	  option enabled.
1174
1175	  Only if you are using a new kernel on an old distribution, you might
1176	  need to say Y here.
1177
1178config SYSFS_DEPRECATED_V2
1179	bool "Enable deprecated sysfs features by default"
1180	default n
1181	depends on SYSFS
1182	depends on SYSFS_DEPRECATED
1183	help
1184	  Enable deprecated sysfs by default.
1185
1186	  See the CONFIG_SYSFS_DEPRECATED option for more details about this
1187	  option.
1188
1189	  Only if you are using a new kernel on an old distribution, you might
1190	  need to say Y here. Even then, odds are you would not need it
1191	  enabled, you can always pass the boot option if absolutely necessary.
1192
1193config RELAY
1194	bool "Kernel->user space relay support (formerly relayfs)"
1195	select IRQ_WORK
1196	help
1197	  This option enables support for relay interface support in
1198	  certain file systems (such as debugfs).
1199	  It is designed to provide an efficient mechanism for tools and
1200	  facilities to relay large amounts of data from kernel space to
1201	  user space.
1202
1203	  If unsure, say N.
1204
1205config BLK_DEV_INITRD
1206	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1207	help
1208	  The initial RAM filesystem is a ramfs which is loaded by the
1209	  boot loader (loadlin or lilo) and that is mounted as root
1210	  before the normal boot procedure. It is typically used to
1211	  load modules needed to mount the "real" root file system,
1212	  etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1213
1214	  If RAM disk support (BLK_DEV_RAM) is also included, this
1215	  also enables initial RAM disk (initrd) support and adds
1216	  15 Kbytes (more on some other architectures) to the kernel size.
1217
1218	  If unsure say Y.
1219
1220if BLK_DEV_INITRD
1221
1222source "usr/Kconfig"
1223
1224endif
1225
1226config BOOT_CONFIG
1227	bool "Boot config support"
1228	select BLK_DEV_INITRD
1229	help
1230	  Extra boot config allows system admin to pass a config file as
1231	  complemental extension of kernel cmdline when booting.
1232	  The boot config file must be attached at the end of initramfs
1233	  with checksum, size and magic word.
1234	  See <file:Documentation/admin-guide/bootconfig.rst> for details.
1235
1236	  If unsure, say Y.
1237
1238choice
1239	prompt "Compiler optimization level"
1240	default CC_OPTIMIZE_FOR_PERFORMANCE
1241
1242config CC_OPTIMIZE_FOR_PERFORMANCE
1243	bool "Optimize for performance (-O2)"
1244	help
1245	  This is the default optimization level for the kernel, building
1246	  with the "-O2" compiler flag for best performance and most
1247	  helpful compile-time warnings.
1248
1249config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1250	bool "Optimize more for performance (-O3)"
1251	depends on ARC
1252	imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED  # avoid false positives
1253	help
1254	  Choosing this option will pass "-O3" to your compiler to optimize
1255	  the kernel yet more for performance.
1256
1257config CC_OPTIMIZE_FOR_SIZE
1258	bool "Optimize for size (-Os)"
1259	imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED  # avoid false positives
1260	help
1261	  Choosing this option will pass "-Os" to your compiler resulting
1262	  in a smaller kernel.
1263
1264endchoice
1265
1266config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1267	bool
1268	help
1269	  This requires that the arch annotates or otherwise protects
1270	  its external entry points from being discarded. Linker scripts
1271	  must also merge .text.*, .data.*, and .bss.* correctly into
1272	  output sections. Care must be taken not to pull in unrelated
1273	  sections (e.g., '.text.init'). Typically '.' in section names
1274	  is used to distinguish them from label names / C identifiers.
1275
1276config LD_DEAD_CODE_DATA_ELIMINATION
1277	bool "Dead code and data elimination (EXPERIMENTAL)"
1278	depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1279	depends on EXPERT
1280	depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800)
1281	depends on $(cc-option,-ffunction-sections -fdata-sections)
1282	depends on $(ld-option,--gc-sections)
1283	help
1284	  Enable this if you want to do dead code and data elimination with
1285	  the linker by compiling with -ffunction-sections -fdata-sections,
1286	  and linking with --gc-sections.
1287
1288	  This can reduce on disk and in-memory size of the kernel
1289	  code and static data, particularly for small configs and
1290	  on small systems. This has the possibility of introducing
1291	  silently broken kernel if the required annotations are not
1292	  present. This option is not well tested yet, so use at your
1293	  own risk.
1294
1295config SYSCTL
1296	bool
1297
1298config HAVE_UID16
1299	bool
1300
1301config SYSCTL_EXCEPTION_TRACE
1302	bool
1303	help
1304	  Enable support for /proc/sys/debug/exception-trace.
1305
1306config SYSCTL_ARCH_UNALIGN_NO_WARN
1307	bool
1308	help
1309	  Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1310	  Allows arch to define/use @no_unaligned_warning to possibly warn
1311	  about unaligned access emulation going on under the hood.
1312
1313config SYSCTL_ARCH_UNALIGN_ALLOW
1314	bool
1315	help
1316	  Enable support for /proc/sys/kernel/unaligned-trap
1317	  Allows arches to define/use @unaligned_enabled to runtime toggle
1318	  the unaligned access emulation.
1319	  see arch/parisc/kernel/unaligned.c for reference
1320
1321config HAVE_PCSPKR_PLATFORM
1322	bool
1323
1324# interpreter that classic socket filters depend on
1325config BPF
1326	bool
1327
1328menuconfig EXPERT
1329	bool "Configure standard kernel features (expert users)"
1330	# Unhide debug options, to make the on-by-default options visible
1331	select DEBUG_KERNEL
1332	help
1333	  This option allows certain base kernel options and settings
1334	  to be disabled or tweaked. This is for specialized
1335	  environments which can tolerate a "non-standard" kernel.
1336	  Only use this if you really know what you are doing.
1337
1338config UID16
1339	bool "Enable 16-bit UID system calls" if EXPERT
1340	depends on HAVE_UID16 && MULTIUSER
1341	default y
1342	help
1343	  This enables the legacy 16-bit UID syscall wrappers.
1344
1345config MULTIUSER
1346	bool "Multiple users, groups and capabilities support" if EXPERT
1347	default y
1348	help
1349	  This option enables support for non-root users, groups and
1350	  capabilities.
1351
1352	  If you say N here, all processes will run with UID 0, GID 0, and all
1353	  possible capabilities.  Saying N here also compiles out support for
1354	  system calls related to UIDs, GIDs, and capabilities, such as setuid,
1355	  setgid, and capset.
1356
1357	  If unsure, say Y here.
1358
1359config SGETMASK_SYSCALL
1360	bool "sgetmask/ssetmask syscalls support" if EXPERT
1361	def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1362	---help---
1363	  sys_sgetmask and sys_ssetmask are obsolete system calls
1364	  no longer supported in libc but still enabled by default in some
1365	  architectures.
1366
1367	  If unsure, leave the default option here.
1368
1369config SYSFS_SYSCALL
1370	bool "Sysfs syscall support" if EXPERT
1371	default y
1372	---help---
1373	  sys_sysfs is an obsolete system call no longer supported in libc.
1374	  Note that disabling this option is more secure but might break
1375	  compatibility with some systems.
1376
1377	  If unsure say Y here.
1378
1379config FHANDLE
1380	bool "open by fhandle syscalls" if EXPERT
1381	select EXPORTFS
1382	default y
1383	help
1384	  If you say Y here, a user level program will be able to map
1385	  file names to handle and then later use the handle for
1386	  different file system operations. This is useful in implementing
1387	  userspace file servers, which now track files using handles instead
1388	  of names. The handle would remain the same even if file names
1389	  get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1390	  syscalls.
1391
1392config POSIX_TIMERS
1393	bool "Posix Clocks & timers" if EXPERT
1394	default y
1395	help
1396	  This includes native support for POSIX timers to the kernel.
1397	  Some embedded systems have no use for them and therefore they
1398	  can be configured out to reduce the size of the kernel image.
1399
1400	  When this option is disabled, the following syscalls won't be
1401	  available: timer_create, timer_gettime: timer_getoverrun,
1402	  timer_settime, timer_delete, clock_adjtime, getitimer,
1403	  setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1404	  clock_getres and clock_nanosleep syscalls will be limited to
1405	  CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1406
1407	  If unsure say y.
1408
1409config PRINTK
1410	default y
1411	bool "Enable support for printk" if EXPERT
1412	select IRQ_WORK
1413	help
1414	  This option enables normal printk support. Removing it
1415	  eliminates most of the message strings from the kernel image
1416	  and makes the kernel more or less silent. As this makes it
1417	  very difficult to diagnose system problems, saying N here is
1418	  strongly discouraged.
1419
1420config PRINTK_NMI
1421	def_bool y
1422	depends on PRINTK
1423	depends on HAVE_NMI
1424
1425config BUG
1426	bool "BUG() support" if EXPERT
1427	default y
1428	help
1429	  Disabling this option eliminates support for BUG and WARN, reducing
1430	  the size of your kernel image and potentially quietly ignoring
1431	  numerous fatal conditions. You should only consider disabling this
1432	  option for embedded systems with no facilities for reporting errors.
1433	  Just say Y.
1434
1435config ELF_CORE
1436	depends on COREDUMP
1437	default y
1438	bool "Enable ELF core dumps" if EXPERT
1439	help
1440	  Enable support for generating core dumps. Disabling saves about 4k.
1441
1442
1443config PCSPKR_PLATFORM
1444	bool "Enable PC-Speaker support" if EXPERT
1445	depends on HAVE_PCSPKR_PLATFORM
1446	select I8253_LOCK
1447	default y
1448	help
1449	  This option allows to disable the internal PC-Speaker
1450	  support, saving some memory.
1451
1452config BASE_FULL
1453	default y
1454	bool "Enable full-sized data structures for core" if EXPERT
1455	help
1456	  Disabling this option reduces the size of miscellaneous core
1457	  kernel data structures. This saves memory on small machines,
1458	  but may reduce performance.
1459
1460config FUTEX
1461	bool "Enable futex support" if EXPERT
1462	default y
1463	imply RT_MUTEXES
1464	help
1465	  Disabling this option will cause the kernel to be built without
1466	  support for "fast userspace mutexes".  The resulting kernel may not
1467	  run glibc-based applications correctly.
1468
1469config FUTEX_PI
1470	bool
1471	depends on FUTEX && RT_MUTEXES
1472	default y
1473
1474config HAVE_FUTEX_CMPXCHG
1475	bool
1476	depends on FUTEX
1477	help
1478	  Architectures should select this if futex_atomic_cmpxchg_inatomic()
1479	  is implemented and always working. This removes a couple of runtime
1480	  checks.
1481
1482config EPOLL
1483	bool "Enable eventpoll support" if EXPERT
1484	default y
1485	help
1486	  Disabling this option will cause the kernel to be built without
1487	  support for epoll family of system calls.
1488
1489config SIGNALFD
1490	bool "Enable signalfd() system call" if EXPERT
1491	default y
1492	help
1493	  Enable the signalfd() system call that allows to receive signals
1494	  on a file descriptor.
1495
1496	  If unsure, say Y.
1497
1498config TIMERFD
1499	bool "Enable timerfd() system call" if EXPERT
1500	default y
1501	help
1502	  Enable the timerfd() system call that allows to receive timer
1503	  events on a file descriptor.
1504
1505	  If unsure, say Y.
1506
1507config EVENTFD
1508	bool "Enable eventfd() system call" if EXPERT
1509	default y
1510	help
1511	  Enable the eventfd() system call that allows to receive both
1512	  kernel notification (ie. KAIO) or userspace notifications.
1513
1514	  If unsure, say Y.
1515
1516config SHMEM
1517	bool "Use full shmem filesystem" if EXPERT
1518	default y
1519	depends on MMU
1520	help
1521	  The shmem is an internal filesystem used to manage shared memory.
1522	  It is backed by swap and manages resource limits. It is also exported
1523	  to userspace as tmpfs if TMPFS is enabled. Disabling this
1524	  option replaces shmem and tmpfs with the much simpler ramfs code,
1525	  which may be appropriate on small systems without swap.
1526
1527config AIO
1528	bool "Enable AIO support" if EXPERT
1529	default y
1530	help
1531	  This option enables POSIX asynchronous I/O which may by used
1532	  by some high performance threaded applications. Disabling
1533	  this option saves about 7k.
1534
1535config IO_URING
1536	bool "Enable IO uring support" if EXPERT
1537	select ANON_INODES
1538	select IO_WQ
1539	default y
1540	help
1541	  This option enables support for the io_uring interface, enabling
1542	  applications to submit and complete IO through submission and
1543	  completion rings that are shared between the kernel and application.
1544
1545config ADVISE_SYSCALLS
1546	bool "Enable madvise/fadvise syscalls" if EXPERT
1547	default y
1548	help
1549	  This option enables the madvise and fadvise syscalls, used by
1550	  applications to advise the kernel about their future memory or file
1551	  usage, improving performance. If building an embedded system where no
1552	  applications use these syscalls, you can disable this option to save
1553	  space.
1554
1555config MEMBARRIER
1556	bool "Enable membarrier() system call" if EXPERT
1557	default y
1558	help
1559	  Enable the membarrier() system call that allows issuing memory
1560	  barriers across all running threads, which can be used to distribute
1561	  the cost of user-space memory barriers asymmetrically by transforming
1562	  pairs of memory barriers into pairs consisting of membarrier() and a
1563	  compiler barrier.
1564
1565	  If unsure, say Y.
1566
1567config KALLSYMS
1568	bool "Load all symbols for debugging/ksymoops" if EXPERT
1569	default y
1570	help
1571	  Say Y here to let the kernel print out symbolic crash information and
1572	  symbolic stack backtraces. This increases the size of the kernel
1573	  somewhat, as all symbols have to be loaded into the kernel image.
1574
1575config KALLSYMS_ALL
1576	bool "Include all symbols in kallsyms"
1577	depends on DEBUG_KERNEL && KALLSYMS
1578	help
1579	  Normally kallsyms only contains the symbols of functions for nicer
1580	  OOPS messages and backtraces (i.e., symbols from the text and inittext
1581	  sections). This is sufficient for most cases. And only in very rare
1582	  cases (e.g., when a debugger is used) all symbols are required (e.g.,
1583	  names of variables from the data sections, etc).
1584
1585	  This option makes sure that all symbols are loaded into the kernel
1586	  image (i.e., symbols from all sections) in cost of increased kernel
1587	  size (depending on the kernel configuration, it may be 300KiB or
1588	  something like this).
1589
1590	  Say N unless you really need all symbols.
1591
1592config KALLSYMS_ABSOLUTE_PERCPU
1593	bool
1594	depends on KALLSYMS
1595	default X86_64 && SMP
1596
1597config KALLSYMS_BASE_RELATIVE
1598	bool
1599	depends on KALLSYMS
1600	default !IA64
1601	help
1602	  Instead of emitting them as absolute values in the native word size,
1603	  emit the symbol references in the kallsyms table as 32-bit entries,
1604	  each containing a relative value in the range [base, base + U32_MAX]
1605	  or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1606	  an absolute value in the range [0, S32_MAX] or a relative value in the
1607	  range [base, base + S32_MAX], where base is the lowest relative symbol
1608	  address encountered in the image.
1609
1610	  On 64-bit builds, this reduces the size of the address table by 50%,
1611	  but more importantly, it results in entries whose values are build
1612	  time constants, and no relocation pass is required at runtime to fix
1613	  up the entries based on the runtime load address of the kernel.
1614
1615# end of the "standard kernel features (expert users)" menu
1616
1617# syscall, maps, verifier
1618config BPF_SYSCALL
1619	bool "Enable bpf() system call"
1620	select BPF
1621	select IRQ_WORK
1622	default n
1623	help
1624	  Enable the bpf() system call that allows to manipulate eBPF
1625	  programs and maps via file descriptors.
1626
1627config ARCH_WANT_DEFAULT_BPF_JIT
1628	bool
1629
1630config BPF_JIT_ALWAYS_ON
1631	bool "Permanently enable BPF JIT and remove BPF interpreter"
1632	depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1633	help
1634	  Enables BPF JIT and removes BPF interpreter to avoid
1635	  speculative execution of BPF instructions by the interpreter
1636
1637config BPF_JIT_DEFAULT_ON
1638	def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
1639	depends on HAVE_EBPF_JIT && BPF_JIT
1640
1641config USERFAULTFD
1642	bool "Enable userfaultfd() system call"
1643	depends on MMU
1644	help
1645	  Enable the userfaultfd() system call that allows to intercept and
1646	  handle page faults in userland.
1647
1648config ARCH_HAS_MEMBARRIER_CALLBACKS
1649	bool
1650
1651config ARCH_HAS_MEMBARRIER_SYNC_CORE
1652	bool
1653
1654config RSEQ
1655	bool "Enable rseq() system call" if EXPERT
1656	default y
1657	depends on HAVE_RSEQ
1658	select MEMBARRIER
1659	help
1660	  Enable the restartable sequences system call. It provides a
1661	  user-space cache for the current CPU number value, which
1662	  speeds up getting the current CPU number from user-space,
1663	  as well as an ABI to speed up user-space operations on
1664	  per-CPU data.
1665
1666	  If unsure, say Y.
1667
1668config DEBUG_RSEQ
1669	default n
1670	bool "Enabled debugging of rseq() system call" if EXPERT
1671	depends on RSEQ && DEBUG_KERNEL
1672	help
1673	  Enable extra debugging checks for the rseq system call.
1674
1675	  If unsure, say N.
1676
1677config EMBEDDED
1678	bool "Embedded system"
1679	option allnoconfig_y
1680	select EXPERT
1681	help
1682	  This option should be enabled if compiling the kernel for
1683	  an embedded system so certain expert options are available
1684	  for configuration.
1685
1686config HAVE_PERF_EVENTS
1687	bool
1688	help
1689	  See tools/perf/design.txt for details.
1690
1691config PERF_USE_VMALLOC
1692	bool
1693	help
1694	  See tools/perf/design.txt for details
1695
1696config PC104
1697	bool "PC/104 support" if EXPERT
1698	help
1699	  Expose PC/104 form factor device drivers and options available for
1700	  selection and configuration. Enable this option if your target
1701	  machine has a PC/104 bus.
1702
1703menu "Kernel Performance Events And Counters"
1704
1705config PERF_EVENTS
1706	bool "Kernel performance events and counters"
1707	default y if PROFILING
1708	depends on HAVE_PERF_EVENTS
1709	select IRQ_WORK
1710	select SRCU
1711	help
1712	  Enable kernel support for various performance events provided
1713	  by software and hardware.
1714
1715	  Software events are supported either built-in or via the
1716	  use of generic tracepoints.
1717
1718	  Most modern CPUs support performance events via performance
1719	  counter registers. These registers count the number of certain
1720	  types of hw events: such as instructions executed, cachemisses
1721	  suffered, or branches mis-predicted - without slowing down the
1722	  kernel or applications. These registers can also trigger interrupts
1723	  when a threshold number of events have passed - and can thus be
1724	  used to profile the code that runs on that CPU.
1725
1726	  The Linux Performance Event subsystem provides an abstraction of
1727	  these software and hardware event capabilities, available via a
1728	  system call and used by the "perf" utility in tools/perf/. It
1729	  provides per task and per CPU counters, and it provides event
1730	  capabilities on top of those.
1731
1732	  Say Y if unsure.
1733
1734config DEBUG_PERF_USE_VMALLOC
1735	default n
1736	bool "Debug: use vmalloc to back perf mmap() buffers"
1737	depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1738	select PERF_USE_VMALLOC
1739	help
1740	  Use vmalloc memory to back perf mmap() buffers.
1741
1742	  Mostly useful for debugging the vmalloc code on platforms
1743	  that don't require it.
1744
1745	  Say N if unsure.
1746
1747endmenu
1748
1749config VM_EVENT_COUNTERS
1750	default y
1751	bool "Enable VM event counters for /proc/vmstat" if EXPERT
1752	help
1753	  VM event counters are needed for event counts to be shown.
1754	  This option allows the disabling of the VM event counters
1755	  on EXPERT systems.  /proc/vmstat will only show page counts
1756	  if VM event counters are disabled.
1757
1758config SLUB_DEBUG
1759	default y
1760	bool "Enable SLUB debugging support" if EXPERT
1761	depends on SLUB && SYSFS
1762	help
1763	  SLUB has extensive debug support features. Disabling these can
1764	  result in significant savings in code size. This also disables
1765	  SLUB sysfs support. /sys/slab will not exist and there will be
1766	  no support for cache validation etc.
1767
1768config SLUB_MEMCG_SYSFS_ON
1769	default n
1770	bool "Enable memcg SLUB sysfs support by default" if EXPERT
1771	depends on SLUB && SYSFS && MEMCG
1772	help
1773	  SLUB creates a directory under /sys/kernel/slab for each
1774	  allocation cache to host info and debug files. If memory
1775	  cgroup is enabled, each cache can have per memory cgroup
1776	  caches. SLUB can create the same sysfs directories for these
1777	  caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1778	  to a very high number of debug files being created. This is
1779	  controlled by slub_memcg_sysfs boot parameter and this
1780	  config option determines the parameter's default value.
1781
1782config COMPAT_BRK
1783	bool "Disable heap randomization"
1784	default y
1785	help
1786	  Randomizing heap placement makes heap exploits harder, but it
1787	  also breaks ancient binaries (including anything libc5 based).
1788	  This option changes the bootup default to heap randomization
1789	  disabled, and can be overridden at runtime by setting
1790	  /proc/sys/kernel/randomize_va_space to 2.
1791
1792	  On non-ancient distros (post-2000 ones) N is usually a safe choice.
1793
1794choice
1795	prompt "Choose SLAB allocator"
1796	default SLUB
1797	help
1798	   This option allows to select a slab allocator.
1799
1800config SLAB
1801	bool "SLAB"
1802	select HAVE_HARDENED_USERCOPY_ALLOCATOR
1803	help
1804	  The regular slab allocator that is established and known to work
1805	  well in all environments. It organizes cache hot objects in
1806	  per cpu and per node queues.
1807
1808config SLUB
1809	bool "SLUB (Unqueued Allocator)"
1810	select HAVE_HARDENED_USERCOPY_ALLOCATOR
1811	help
1812	   SLUB is a slab allocator that minimizes cache line usage
1813	   instead of managing queues of cached objects (SLAB approach).
1814	   Per cpu caching is realized using slabs of objects instead
1815	   of queues of objects. SLUB can use memory efficiently
1816	   and has enhanced diagnostics. SLUB is the default choice for
1817	   a slab allocator.
1818
1819config SLOB
1820	depends on EXPERT
1821	bool "SLOB (Simple Allocator)"
1822	help
1823	   SLOB replaces the stock allocator with a drastically simpler
1824	   allocator. SLOB is generally more space efficient but
1825	   does not perform as well on large systems.
1826
1827endchoice
1828
1829config SLAB_MERGE_DEFAULT
1830	bool "Allow slab caches to be merged"
1831	default y
1832	help
1833	  For reduced kernel memory fragmentation, slab caches can be
1834	  merged when they share the same size and other characteristics.
1835	  This carries a risk of kernel heap overflows being able to
1836	  overwrite objects from merged caches (and more easily control
1837	  cache layout), which makes such heap attacks easier to exploit
1838	  by attackers. By keeping caches unmerged, these kinds of exploits
1839	  can usually only damage objects in the same cache. To disable
1840	  merging at runtime, "slab_nomerge" can be passed on the kernel
1841	  command line.
1842
1843config SLAB_FREELIST_RANDOM
1844	default n
1845	depends on SLAB || SLUB
1846	bool "SLAB freelist randomization"
1847	help
1848	  Randomizes the freelist order used on creating new pages. This
1849	  security feature reduces the predictability of the kernel slab
1850	  allocator against heap overflows.
1851
1852config SLAB_FREELIST_HARDENED
1853	bool "Harden slab freelist metadata"
1854	depends on SLUB
1855	help
1856	  Many kernel heap attacks try to target slab cache metadata and
1857	  other infrastructure. This options makes minor performance
1858	  sacrifices to harden the kernel slab allocator against common
1859	  freelist exploit methods.
1860
1861config SHUFFLE_PAGE_ALLOCATOR
1862	bool "Page allocator randomization"
1863	default SLAB_FREELIST_RANDOM && ACPI_NUMA
1864	help
1865	  Randomization of the page allocator improves the average
1866	  utilization of a direct-mapped memory-side-cache. See section
1867	  5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1868	  6.2a specification for an example of how a platform advertises
1869	  the presence of a memory-side-cache. There are also incidental
1870	  security benefits as it reduces the predictability of page
1871	  allocations to compliment SLAB_FREELIST_RANDOM, but the
1872	  default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1873	  10th order of pages is selected based on cache utilization
1874	  benefits on x86.
1875
1876	  While the randomization improves cache utilization it may
1877	  negatively impact workloads on platforms without a cache. For
1878	  this reason, by default, the randomization is enabled only
1879	  after runtime detection of a direct-mapped memory-side-cache.
1880	  Otherwise, the randomization may be force enabled with the
1881	  'page_alloc.shuffle' kernel command line parameter.
1882
1883	  Say Y if unsure.
1884
1885config SLUB_CPU_PARTIAL
1886	default y
1887	depends on SLUB && SMP
1888	bool "SLUB per cpu partial cache"
1889	help
1890	  Per cpu partial caches accelerate objects allocation and freeing
1891	  that is local to a processor at the price of more indeterminism
1892	  in the latency of the free. On overflow these caches will be cleared
1893	  which requires the taking of locks that may cause latency spikes.
1894	  Typically one would choose no for a realtime system.
1895
1896config MMAP_ALLOW_UNINITIALIZED
1897	bool "Allow mmapped anonymous memory to be uninitialized"
1898	depends on EXPERT && !MMU
1899	default n
1900	help
1901	  Normally, and according to the Linux spec, anonymous memory obtained
1902	  from mmap() has its contents cleared before it is passed to
1903	  userspace.  Enabling this config option allows you to request that
1904	  mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1905	  providing a huge performance boost.  If this option is not enabled,
1906	  then the flag will be ignored.
1907
1908	  This is taken advantage of by uClibc's malloc(), and also by
1909	  ELF-FDPIC binfmt's brk and stack allocator.
1910
1911	  Because of the obvious security issues, this option should only be
1912	  enabled on embedded devices where you control what is run in
1913	  userspace.  Since that isn't generally a problem on no-MMU systems,
1914	  it is normally safe to say Y here.
1915
1916	  See Documentation/nommu-mmap.txt for more information.
1917
1918config SYSTEM_DATA_VERIFICATION
1919	def_bool n
1920	select SYSTEM_TRUSTED_KEYRING
1921	select KEYS
1922	select CRYPTO
1923	select CRYPTO_RSA
1924	select ASYMMETRIC_KEY_TYPE
1925	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1926	select ASN1
1927	select OID_REGISTRY
1928	select X509_CERTIFICATE_PARSER
1929	select PKCS7_MESSAGE_PARSER
1930	help
1931	  Provide PKCS#7 message verification using the contents of the system
1932	  trusted keyring to provide public keys.  This then can be used for
1933	  module verification, kexec image verification and firmware blob
1934	  verification.
1935
1936config PROFILING
1937	bool "Profiling support"
1938	help
1939	  Say Y here to enable the extended profiling support mechanisms used
1940	  by profilers such as OProfile.
1941
1942#
1943# Place an empty function call at each tracepoint site. Can be
1944# dynamically changed for a probe function.
1945#
1946config TRACEPOINTS
1947	bool
1948
1949endmenu		# General setup
1950
1951source "arch/Kconfig"
1952
1953config RT_MUTEXES
1954	bool
1955
1956config BASE_SMALL
1957	int
1958	default 0 if BASE_FULL
1959	default 1 if !BASE_FULL
1960
1961config MODULE_SIG_FORMAT
1962	def_bool n
1963	select SYSTEM_DATA_VERIFICATION
1964
1965menuconfig MODULES
1966	bool "Enable loadable module support"
1967	option modules
1968	help
1969	  Kernel modules are small pieces of compiled code which can
1970	  be inserted in the running kernel, rather than being
1971	  permanently built into the kernel.  You use the "modprobe"
1972	  tool to add (and sometimes remove) them.  If you say Y here,
1973	  many parts of the kernel can be built as modules (by
1974	  answering M instead of Y where indicated): this is most
1975	  useful for infrequently used options which are not required
1976	  for booting.  For more information, see the man pages for
1977	  modprobe, lsmod, modinfo, insmod and rmmod.
1978
1979	  If you say Y here, you will need to run "make
1980	  modules_install" to put the modules under /lib/modules/
1981	  where modprobe can find them (you may need to be root to do
1982	  this).
1983
1984	  If unsure, say Y.
1985
1986if MODULES
1987
1988config MODULE_FORCE_LOAD
1989	bool "Forced module loading"
1990	default n
1991	help
1992	  Allow loading of modules without version information (ie. modprobe
1993	  --force).  Forced module loading sets the 'F' (forced) taint flag and
1994	  is usually a really bad idea.
1995
1996config MODULE_UNLOAD
1997	bool "Module unloading"
1998	help
1999	  Without this option you will not be able to unload any
2000	  modules (note that some modules may not be unloadable
2001	  anyway), which makes your kernel smaller, faster
2002	  and simpler.  If unsure, say Y.
2003
2004config MODULE_FORCE_UNLOAD
2005	bool "Forced module unloading"
2006	depends on MODULE_UNLOAD
2007	help
2008	  This option allows you to force a module to unload, even if the
2009	  kernel believes it is unsafe: the kernel will remove the module
2010	  without waiting for anyone to stop using it (using the -f option to
2011	  rmmod).  This is mainly for kernel developers and desperate users.
2012	  If unsure, say N.
2013
2014config MODVERSIONS
2015	bool "Module versioning support"
2016	help
2017	  Usually, you have to use modules compiled with your kernel.
2018	  Saying Y here makes it sometimes possible to use modules
2019	  compiled for different kernels, by adding enough information
2020	  to the modules to (hopefully) spot any changes which would
2021	  make them incompatible with the kernel you are running.  If
2022	  unsure, say N.
2023
2024config ASM_MODVERSIONS
2025	bool
2026	default HAVE_ASM_MODVERSIONS && MODVERSIONS
2027	help
2028	  This enables module versioning for exported symbols also from
2029	  assembly. This can be enabled only when the target architecture
2030	  supports it.
2031
2032config MODULE_REL_CRCS
2033	bool
2034	depends on MODVERSIONS
2035
2036config MODULE_SRCVERSION_ALL
2037	bool "Source checksum for all modules"
2038	help
2039	  Modules which contain a MODULE_VERSION get an extra "srcversion"
2040	  field inserted into their modinfo section, which contains a
2041    	  sum of the source files which made it.  This helps maintainers
2042	  see exactly which source was used to build a module (since
2043	  others sometimes change the module source without updating
2044	  the version).  With this option, such a "srcversion" field
2045	  will be created for all modules.  If unsure, say N.
2046
2047config MODULE_SIG
2048	bool "Module signature verification"
2049	select MODULE_SIG_FORMAT
2050	help
2051	  Check modules for valid signatures upon load: the signature
2052	  is simply appended to the module. For more information see
2053	  <file:Documentation/admin-guide/module-signing.rst>.
2054
2055	  Note that this option adds the OpenSSL development packages as a
2056	  kernel build dependency so that the signing tool can use its crypto
2057	  library.
2058
2059	  You should enable this option if you wish to use either
2060	  CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2061	  another LSM - otherwise unsigned modules will be loadable regardless
2062	  of the lockdown policy.
2063
2064	  !!!WARNING!!!  If you enable this option, you MUST make sure that the
2065	  module DOES NOT get stripped after being signed.  This includes the
2066	  debuginfo strip done by some packagers (such as rpmbuild) and
2067	  inclusion into an initramfs that wants the module size reduced.
2068
2069config MODULE_SIG_FORCE
2070	bool "Require modules to be validly signed"
2071	depends on MODULE_SIG
2072	help
2073	  Reject unsigned modules or signed modules for which we don't have a
2074	  key.  Without this, such modules will simply taint the kernel.
2075
2076config MODULE_SIG_ALL
2077	bool "Automatically sign all modules"
2078	default y
2079	depends on MODULE_SIG
2080	help
2081	  Sign all modules during make modules_install. Without this option,
2082	  modules must be signed manually, using the scripts/sign-file tool.
2083
2084comment "Do not forget to sign required modules with scripts/sign-file"
2085	depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2086
2087choice
2088	prompt "Which hash algorithm should modules be signed with?"
2089	depends on MODULE_SIG
2090	help
2091	  This determines which sort of hashing algorithm will be used during
2092	  signature generation.  This algorithm _must_ be built into the kernel
2093	  directly so that signature verification can take place.  It is not
2094	  possible to load a signed module containing the algorithm to check
2095	  the signature on that module.
2096
2097config MODULE_SIG_SHA1
2098	bool "Sign modules with SHA-1"
2099	select CRYPTO_SHA1
2100
2101config MODULE_SIG_SHA224
2102	bool "Sign modules with SHA-224"
2103	select CRYPTO_SHA256
2104
2105config MODULE_SIG_SHA256
2106	bool "Sign modules with SHA-256"
2107	select CRYPTO_SHA256
2108
2109config MODULE_SIG_SHA384
2110	bool "Sign modules with SHA-384"
2111	select CRYPTO_SHA512
2112
2113config MODULE_SIG_SHA512
2114	bool "Sign modules with SHA-512"
2115	select CRYPTO_SHA512
2116
2117endchoice
2118
2119config MODULE_SIG_HASH
2120	string
2121	depends on MODULE_SIG
2122	default "sha1" if MODULE_SIG_SHA1
2123	default "sha224" if MODULE_SIG_SHA224
2124	default "sha256" if MODULE_SIG_SHA256
2125	default "sha384" if MODULE_SIG_SHA384
2126	default "sha512" if MODULE_SIG_SHA512
2127
2128config MODULE_COMPRESS
2129	bool "Compress modules on installation"
2130	help
2131
2132	  Compresses kernel modules when 'make modules_install' is run; gzip or
2133	  xz depending on "Compression algorithm" below.
2134
2135	  module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2136
2137	  Out-of-tree kernel modules installed using Kbuild will also be
2138	  compressed upon installation.
2139
2140	  Note: for modules inside an initrd or initramfs, it's more efficient
2141	  to compress the whole initrd or initramfs instead.
2142
2143	  Note: This is fully compatible with signed modules.
2144
2145	  If in doubt, say N.
2146
2147choice
2148	prompt "Compression algorithm"
2149	depends on MODULE_COMPRESS
2150	default MODULE_COMPRESS_GZIP
2151	help
2152	  This determines which sort of compression will be used during
2153	  'make modules_install'.
2154
2155	  GZIP (default) and XZ are supported.
2156
2157config MODULE_COMPRESS_GZIP
2158	bool "GZIP"
2159
2160config MODULE_COMPRESS_XZ
2161	bool "XZ"
2162
2163endchoice
2164
2165config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2166	bool "Allow loading of modules with missing namespace imports"
2167	help
2168	  Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2169	  a namespace. A module that makes use of a symbol exported with such a
2170	  namespace is required to import the namespace via MODULE_IMPORT_NS().
2171	  There is no technical reason to enforce correct namespace imports,
2172	  but it creates consistency between symbols defining namespaces and
2173	  users importing namespaces they make use of. This option relaxes this
2174	  requirement and lifts the enforcement when loading a module.
2175
2176	  If unsure, say N.
2177
2178config UNUSED_SYMBOLS
2179	bool "Enable unused/obsolete exported symbols"
2180	default y if X86
2181	help
2182	  Unused but exported symbols make the kernel needlessly bigger.  For
2183	  that reason most of these unused exports will soon be removed.  This
2184	  option is provided temporarily to provide a transition period in case
2185	  some external kernel module needs one of these symbols anyway. If you
2186	  encounter such a case in your module, consider if you are actually
2187	  using the right API.  (rationale: since nobody in the kernel is using
2188	  this in a module, there is a pretty good chance it's actually the
2189	  wrong interface to use).  If you really need the symbol, please send a
2190	  mail to the linux kernel mailing list mentioning the symbol and why
2191	  you really need it, and what the merge plan to the mainline kernel for
2192	  your module is.
2193
2194config TRIM_UNUSED_KSYMS
2195	bool "Trim unused exported kernel symbols"
2196	depends on !UNUSED_SYMBOLS
2197	help
2198	  The kernel and some modules make many symbols available for
2199	  other modules to use via EXPORT_SYMBOL() and variants. Depending
2200	  on the set of modules being selected in your kernel configuration,
2201	  many of those exported symbols might never be used.
2202
2203	  This option allows for unused exported symbols to be dropped from
2204	  the build. In turn, this provides the compiler more opportunities
2205	  (especially when using LTO) for optimizing the code and reducing
2206	  binary size.  This might have some security advantages as well.
2207
2208	  If unsure, or if you need to build out-of-tree modules, say N.
2209
2210endif # MODULES
2211
2212config MODULES_TREE_LOOKUP
2213	def_bool y
2214	depends on PERF_EVENTS || TRACING
2215
2216config INIT_ALL_POSSIBLE
2217	bool
2218	help
2219	  Back when each arch used to define their own cpu_online_mask and
2220	  cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2221	  with all 1s, and others with all 0s.  When they were centralised,
2222	  it was better to provide this option than to break all the archs
2223	  and have several arch maintainers pursuing me down dark alleys.
2224
2225source "block/Kconfig"
2226
2227config PREEMPT_NOTIFIERS
2228	bool
2229
2230config PADATA
2231	depends on SMP
2232	bool
2233
2234config ASN1
2235	tristate
2236	help
2237	  Build a simple ASN.1 grammar compiler that produces a bytecode output
2238	  that can be interpreted by the ASN.1 stream decoder and used to
2239	  inform it as to what tags are to be expected in a stream and what
2240	  functions to call on what tags.
2241
2242source "kernel/Kconfig.locks"
2243
2244config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2245	bool
2246
2247# It may be useful for an architecture to override the definitions of the
2248# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2249# and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2250# different calling convention for syscalls. They can also override the
2251# macros for not-implemented syscalls in kernel/sys_ni.c and
2252# kernel/time/posix-stubs.c. All these overrides need to be available in
2253# <asm/syscall_wrapper.h>.
2254config ARCH_HAS_SYSCALL_WRAPPER
2255	def_bool n
2256