xref: /openbmc/linux/init/Kconfig (revision 9ac17575)
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/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG)"
10
11config CC_IS_GCC
12	def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc)
13
14config GCC_VERSION
15	int
16	default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC
17	default 0
18
19config LD_VERSION
20	int
21	default $(shell,$(LD) --version | $(srctree)/scripts/ld-version.sh)
22
23config CC_IS_CLANG
24	def_bool $(success,$(CC) --version | head -n 1 | grep -q clang)
25
26config LD_IS_LLD
27	def_bool $(success,$(LD) -v | head -n 1 | grep -q LLD)
28
29config CLANG_VERSION
30	int
31	default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
32
33config CC_CAN_LINK
34	def_bool $(success,$(srctree)/scripts/cc-can-link.sh $(CC))
35
36config CC_HAS_ASM_GOTO
37	def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
38
39config TOOLS_SUPPORT_RELR
40	def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
41
42config CC_HAS_ASM_INLINE
43	def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
44
45config CONSTRUCTORS
46	bool
47	depends on !UML
48
49config IRQ_WORK
50	bool
51
52config BUILDTIME_TABLE_SORT
53	bool
54
55config THREAD_INFO_IN_TASK
56	bool
57	help
58	  Select this to move thread_info off the stack into task_struct.  To
59	  make this work, an arch will need to remove all thread_info fields
60	  except flags and fix any runtime bugs.
61
62	  One subtle change that will be needed is to use try_get_task_stack()
63	  and put_task_stack() in save_thread_stack_tsk() and get_wchan().
64
65menu "General setup"
66
67config BROKEN
68	bool
69
70config BROKEN_ON_SMP
71	bool
72	depends on BROKEN || !SMP
73	default y
74
75config INIT_ENV_ARG_LIMIT
76	int
77	default 32 if !UML
78	default 128 if UML
79	help
80	  Maximum of each of the number of arguments and environment
81	  variables passed to init from the kernel command line.
82
83config COMPILE_TEST
84	bool "Compile also drivers which will not load"
85	depends on !UML
86	default n
87	help
88	  Some drivers can be compiled on a different platform than they are
89	  intended to be run on. Despite they cannot be loaded there (or even
90	  when they load they cannot be used due to missing HW support),
91	  developers still, opposing to distributors, might want to build such
92	  drivers to compile-test them.
93
94	  If you are a developer and want to build everything available, say Y
95	  here. If you are a user/distributor, say N here to exclude useless
96	  drivers to be distributed.
97
98config UAPI_HEADER_TEST
99	bool "Compile test UAPI headers"
100	depends on HEADERS_INSTALL && CC_CAN_LINK
101	help
102	  Compile test headers exported to user-space to ensure they are
103	  self-contained, i.e. compilable as standalone units.
104
105	  If you are a developer or tester and want to ensure the exported
106	  headers are self-contained, say Y here. Otherwise, choose N.
107
108config LOCALVERSION
109	string "Local version - append to kernel release"
110	help
111	  Append an extra string to the end of your kernel version.
112	  This will show up when you type uname, for example.
113	  The string you set here will be appended after the contents of
114	  any files with a filename matching localversion* in your
115	  object and source tree, in that order.  Your total string can
116	  be a maximum of 64 characters.
117
118config LOCALVERSION_AUTO
119	bool "Automatically append version information to the version string"
120	default y
121	depends on !COMPILE_TEST
122	help
123	  This will try to automatically determine if the current tree is a
124	  release tree by looking for git tags that belong to the current
125	  top of tree revision.
126
127	  A string of the format -gxxxxxxxx will be added to the localversion
128	  if a git-based tree is found.  The string generated by this will be
129	  appended after any matching localversion* files, and after the value
130	  set in CONFIG_LOCALVERSION.
131
132	  (The actual string used here is the first eight characters produced
133	  by running the command:
134
135	    $ git rev-parse --verify HEAD
136
137	  which is done within the script "scripts/setlocalversion".)
138
139config BUILD_SALT
140	string "Build ID Salt"
141	default ""
142	help
143	  The build ID is used to link binaries and their debug info. Setting
144	  this option will use the value in the calculation of the build id.
145	  This is mostly useful for distributions which want to ensure the
146	  build is unique between builds. It's safe to leave the default.
147
148config HAVE_KERNEL_GZIP
149	bool
150
151config HAVE_KERNEL_BZIP2
152	bool
153
154config HAVE_KERNEL_LZMA
155	bool
156
157config HAVE_KERNEL_XZ
158	bool
159
160config HAVE_KERNEL_LZO
161	bool
162
163config HAVE_KERNEL_LZ4
164	bool
165
166config HAVE_KERNEL_UNCOMPRESSED
167	bool
168
169choice
170	prompt "Kernel compression mode"
171	default KERNEL_GZIP
172	depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED
173	help
174	  The linux kernel is a kind of self-extracting executable.
175	  Several compression algorithms are available, which differ
176	  in efficiency, compression and decompression speed.
177	  Compression speed is only relevant when building a kernel.
178	  Decompression speed is relevant at each boot.
179
180	  If you have any problems with bzip2 or lzma compressed
181	  kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
182	  version of this functionality (bzip2 only), for 2.4, was
183	  supplied by Christian Ludwig)
184
185	  High compression options are mostly useful for users, who
186	  are low on disk space (embedded systems), but for whom ram
187	  size matters less.
188
189	  If in doubt, select 'gzip'
190
191config KERNEL_GZIP
192	bool "Gzip"
193	depends on HAVE_KERNEL_GZIP
194	help
195	  The old and tried gzip compression. It provides a good balance
196	  between compression ratio and decompression speed.
197
198config KERNEL_BZIP2
199	bool "Bzip2"
200	depends on HAVE_KERNEL_BZIP2
201	help
202	  Its compression ratio and speed is intermediate.
203	  Decompression speed is slowest among the choices.  The kernel
204	  size is about 10% smaller with bzip2, in comparison to gzip.
205	  Bzip2 uses a large amount of memory. For modern kernels you
206	  will need at least 8MB RAM or more for booting.
207
208config KERNEL_LZMA
209	bool "LZMA"
210	depends on HAVE_KERNEL_LZMA
211	help
212	  This compression algorithm's ratio is best.  Decompression speed
213	  is between gzip and bzip2.  Compression is slowest.
214	  The kernel size is about 33% smaller with LZMA in comparison to gzip.
215
216config KERNEL_XZ
217	bool "XZ"
218	depends on HAVE_KERNEL_XZ
219	help
220	  XZ uses the LZMA2 algorithm and instruction set specific
221	  BCJ filters which can improve compression ratio of executable
222	  code. The size of the kernel is about 30% smaller with XZ in
223	  comparison to gzip. On architectures for which there is a BCJ
224	  filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
225	  will create a few percent smaller kernel than plain LZMA.
226
227	  The speed is about the same as with LZMA: The decompression
228	  speed of XZ is better than that of bzip2 but worse than gzip
229	  and LZO. Compression is slow.
230
231config KERNEL_LZO
232	bool "LZO"
233	depends on HAVE_KERNEL_LZO
234	help
235	  Its compression ratio is the poorest among the choices. The kernel
236	  size is about 10% bigger than gzip; however its speed
237	  (both compression and decompression) is the fastest.
238
239config KERNEL_LZ4
240	bool "LZ4"
241	depends on HAVE_KERNEL_LZ4
242	help
243	  LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
244	  A preliminary version of LZ4 de/compression tool is available at
245	  <https://code.google.com/p/lz4/>.
246
247	  Its compression ratio is worse than LZO. The size of the kernel
248	  is about 8% bigger than LZO. But the decompression speed is
249	  faster than LZO.
250
251config KERNEL_UNCOMPRESSED
252	bool "None"
253	depends on HAVE_KERNEL_UNCOMPRESSED
254	help
255	  Produce uncompressed kernel image. This option is usually not what
256	  you want. It is useful for debugging the kernel in slow simulation
257	  environments, where decompressing and moving the kernel is awfully
258	  slow. This option allows early boot code to skip the decompressor
259	  and jump right at uncompressed kernel image.
260
261endchoice
262
263config DEFAULT_HOSTNAME
264	string "Default hostname"
265	default "(none)"
266	help
267	  This option determines the default system hostname before userspace
268	  calls sethostname(2). The kernel traditionally uses "(none)" here,
269	  but you may wish to use a different default here to make a minimal
270	  system more usable with less configuration.
271
272#
273# For some reason microblaze and nios2 hard code SWAP=n.  Hopefully we can
274# add proper SWAP support to them, in which case this can be remove.
275#
276config ARCH_NO_SWAP
277	bool
278
279config SWAP
280	bool "Support for paging of anonymous memory (swap)"
281	depends on MMU && BLOCK && !ARCH_NO_SWAP
282	default y
283	help
284	  This option allows you to choose whether you want to have support
285	  for so called swap devices or swap files in your kernel that are
286	  used to provide more virtual memory than the actual RAM present
287	  in your computer.  If unsure say Y.
288
289config SYSVIPC
290	bool "System V IPC"
291	---help---
292	  Inter Process Communication is a suite of library functions and
293	  system calls which let processes (running programs) synchronize and
294	  exchange information. It is generally considered to be a good thing,
295	  and some programs won't run unless you say Y here. In particular, if
296	  you want to run the DOS emulator dosemu under Linux (read the
297	  DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
298	  you'll need to say Y here.
299
300	  You can find documentation about IPC with "info ipc" and also in
301	  section 6.4 of the Linux Programmer's Guide, available from
302	  <http://www.tldp.org/guides.html>.
303
304config SYSVIPC_SYSCTL
305	bool
306	depends on SYSVIPC
307	depends on SYSCTL
308	default y
309
310config POSIX_MQUEUE
311	bool "POSIX Message Queues"
312	depends on NET
313	---help---
314	  POSIX variant of message queues is a part of IPC. In POSIX message
315	  queues every message has a priority which decides about succession
316	  of receiving it by a process. If you want to compile and run
317	  programs written e.g. for Solaris with use of its POSIX message
318	  queues (functions mq_*) say Y here.
319
320	  POSIX message queues are visible as a filesystem called 'mqueue'
321	  and can be mounted somewhere if you want to do filesystem
322	  operations on message queues.
323
324	  If unsure, say Y.
325
326config POSIX_MQUEUE_SYSCTL
327	bool
328	depends on POSIX_MQUEUE
329	depends on SYSCTL
330	default y
331
332config CROSS_MEMORY_ATTACH
333	bool "Enable process_vm_readv/writev syscalls"
334	depends on MMU
335	default y
336	help
337	  Enabling this option adds the system calls process_vm_readv and
338	  process_vm_writev which allow a process with the correct privileges
339	  to directly read from or write to another process' address space.
340	  See the man page for more details.
341
342config USELIB
343	bool "uselib syscall"
344	def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
345	help
346	  This option enables the uselib syscall, a system call used in the
347	  dynamic linker from libc5 and earlier.  glibc does not use this
348	  system call.  If you intend to run programs built on libc5 or
349	  earlier, you may need to enable this syscall.  Current systems
350	  running glibc can safely disable this.
351
352config AUDIT
353	bool "Auditing support"
354	depends on NET
355	help
356	  Enable auditing infrastructure that can be used with another
357	  kernel subsystem, such as SELinux (which requires this for
358	  logging of avc messages output).  System call auditing is included
359	  on architectures which support it.
360
361config HAVE_ARCH_AUDITSYSCALL
362	bool
363
364config AUDITSYSCALL
365	def_bool y
366	depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
367	select FSNOTIFY
368
369source "kernel/irq/Kconfig"
370source "kernel/time/Kconfig"
371source "kernel/Kconfig.preempt"
372
373menu "CPU/Task time and stats accounting"
374
375config VIRT_CPU_ACCOUNTING
376	bool
377
378choice
379	prompt "Cputime accounting"
380	default TICK_CPU_ACCOUNTING if !PPC64
381	default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
382
383# Kind of a stub config for the pure tick based cputime accounting
384config TICK_CPU_ACCOUNTING
385	bool "Simple tick based cputime accounting"
386	depends on !S390 && !NO_HZ_FULL
387	help
388	  This is the basic tick based cputime accounting that maintains
389	  statistics about user, system and idle time spent on per jiffies
390	  granularity.
391
392	  If unsure, say Y.
393
394config VIRT_CPU_ACCOUNTING_NATIVE
395	bool "Deterministic task and CPU time accounting"
396	depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
397	select VIRT_CPU_ACCOUNTING
398	help
399	  Select this option to enable more accurate task and CPU time
400	  accounting.  This is done by reading a CPU counter on each
401	  kernel entry and exit and on transitions within the kernel
402	  between system, softirq and hardirq state, so there is a
403	  small performance impact.  In the case of s390 or IBM POWER > 5,
404	  this also enables accounting of stolen time on logically-partitioned
405	  systems.
406
407config VIRT_CPU_ACCOUNTING_GEN
408	bool "Full dynticks CPU time accounting"
409	depends on HAVE_CONTEXT_TRACKING
410	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
411	depends on GENERIC_CLOCKEVENTS
412	select VIRT_CPU_ACCOUNTING
413	select CONTEXT_TRACKING
414	help
415	  Select this option to enable task and CPU time accounting on full
416	  dynticks systems. This accounting is implemented by watching every
417	  kernel-user boundaries using the context tracking subsystem.
418	  The accounting is thus performed at the expense of some significant
419	  overhead.
420
421	  For now this is only useful if you are working on the full
422	  dynticks subsystem development.
423
424	  If unsure, say N.
425
426endchoice
427
428config IRQ_TIME_ACCOUNTING
429	bool "Fine granularity task level IRQ time accounting"
430	depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
431	help
432	  Select this option to enable fine granularity task irq time
433	  accounting. This is done by reading a timestamp on each
434	  transitions between softirq and hardirq state, so there can be a
435	  small performance impact.
436
437	  If in doubt, say N here.
438
439config HAVE_SCHED_AVG_IRQ
440	def_bool y
441	depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
442	depends on SMP
443
444config SCHED_THERMAL_PRESSURE
445	bool "Enable periodic averaging of thermal pressure"
446	depends on SMP
447
448config BSD_PROCESS_ACCT
449	bool "BSD Process Accounting"
450	depends on MULTIUSER
451	help
452	  If you say Y here, a user level program will be able to instruct the
453	  kernel (via a special system call) to write process accounting
454	  information to a file: whenever a process exits, information about
455	  that process will be appended to the file by the kernel.  The
456	  information includes things such as creation time, owning user,
457	  command name, memory usage, controlling terminal etc. (the complete
458	  list is in the struct acct in <file:include/linux/acct.h>).  It is
459	  up to the user level program to do useful things with this
460	  information.  This is generally a good idea, so say Y.
461
462config BSD_PROCESS_ACCT_V3
463	bool "BSD Process Accounting version 3 file format"
464	depends on BSD_PROCESS_ACCT
465	default n
466	help
467	  If you say Y here, the process accounting information is written
468	  in a new file format that also logs the process IDs of each
469	  process and its parent. Note that this file format is incompatible
470	  with previous v0/v1/v2 file formats, so you will need updated tools
471	  for processing it. A preliminary version of these tools is available
472	  at <http://www.gnu.org/software/acct/>.
473
474config TASKSTATS
475	bool "Export task/process statistics through netlink"
476	depends on NET
477	depends on MULTIUSER
478	default n
479	help
480	  Export selected statistics for tasks/processes through the
481	  generic netlink interface. Unlike BSD process accounting, the
482	  statistics are available during the lifetime of tasks/processes as
483	  responses to commands. Like BSD accounting, they are sent to user
484	  space on task exit.
485
486	  Say N if unsure.
487
488config TASK_DELAY_ACCT
489	bool "Enable per-task delay accounting"
490	depends on TASKSTATS
491	select SCHED_INFO
492	help
493	  Collect information on time spent by a task waiting for system
494	  resources like cpu, synchronous block I/O completion and swapping
495	  in pages. Such statistics can help in setting a task's priorities
496	  relative to other tasks for cpu, io, rss limits etc.
497
498	  Say N if unsure.
499
500config TASK_XACCT
501	bool "Enable extended accounting over taskstats"
502	depends on TASKSTATS
503	help
504	  Collect extended task accounting data and send the data
505	  to userland for processing over the taskstats interface.
506
507	  Say N if unsure.
508
509config TASK_IO_ACCOUNTING
510	bool "Enable per-task storage I/O accounting"
511	depends on TASK_XACCT
512	help
513	  Collect information on the number of bytes of storage I/O which this
514	  task has caused.
515
516	  Say N if unsure.
517
518config PSI
519	bool "Pressure stall information tracking"
520	help
521	  Collect metrics that indicate how overcommitted the CPU, memory,
522	  and IO capacity are in the system.
523
524	  If you say Y here, the kernel will create /proc/pressure/ with the
525	  pressure statistics files cpu, memory, and io. These will indicate
526	  the share of walltime in which some or all tasks in the system are
527	  delayed due to contention of the respective resource.
528
529	  In kernels with cgroup support, cgroups (cgroup2 only) will
530	  have cpu.pressure, memory.pressure, and io.pressure files,
531	  which aggregate pressure stalls for the grouped tasks only.
532
533	  For more details see Documentation/accounting/psi.rst.
534
535	  Say N if unsure.
536
537config PSI_DEFAULT_DISABLED
538	bool "Require boot parameter to enable pressure stall information tracking"
539	default n
540	depends on PSI
541	help
542	  If set, pressure stall information tracking will be disabled
543	  per default but can be enabled through passing psi=1 on the
544	  kernel commandline during boot.
545
546	  This feature adds some code to the task wakeup and sleep
547	  paths of the scheduler. The overhead is too low to affect
548	  common scheduling-intense workloads in practice (such as
549	  webservers, memcache), but it does show up in artificial
550	  scheduler stress tests, such as hackbench.
551
552	  If you are paranoid and not sure what the kernel will be
553	  used for, say Y.
554
555	  Say N if unsure.
556
557endmenu # "CPU/Task time and stats accounting"
558
559config CPU_ISOLATION
560	bool "CPU isolation"
561	depends on SMP || COMPILE_TEST
562	default y
563	help
564	  Make sure that CPUs running critical tasks are not disturbed by
565	  any source of "noise" such as unbound workqueues, timers, kthreads...
566	  Unbound jobs get offloaded to housekeeping CPUs. This is driven by
567	  the "isolcpus=" boot parameter.
568
569	  Say Y if unsure.
570
571source "kernel/rcu/Kconfig"
572
573config BUILD_BIN2C
574	bool
575	default n
576
577config IKCONFIG
578	tristate "Kernel .config support"
579	---help---
580	  This option enables the complete Linux kernel ".config" file
581	  contents to be saved in the kernel. It provides documentation
582	  of which kernel options are used in a running kernel or in an
583	  on-disk kernel.  This information can be extracted from the kernel
584	  image file with the script scripts/extract-ikconfig and used as
585	  input to rebuild the current kernel or to build another kernel.
586	  It can also be extracted from a running kernel by reading
587	  /proc/config.gz if enabled (below).
588
589config IKCONFIG_PROC
590	bool "Enable access to .config through /proc/config.gz"
591	depends on IKCONFIG && PROC_FS
592	---help---
593	  This option enables access to the kernel configuration file
594	  through /proc/config.gz.
595
596config IKHEADERS
597	tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
598	depends on SYSFS
599	help
600	  This option enables access to the in-kernel headers that are generated during
601	  the build process. These can be used to build eBPF tracing programs,
602	  or similar programs.  If you build the headers as a module, a module called
603	  kheaders.ko is built which can be loaded on-demand to get access to headers.
604
605config LOG_BUF_SHIFT
606	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
607	range 12 25
608	default 17
609	depends on PRINTK
610	help
611	  Select the minimal kernel log buffer size as a power of 2.
612	  The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
613	  parameter, see below. Any higher size also might be forced
614	  by "log_buf_len" boot parameter.
615
616	  Examples:
617		     17 => 128 KB
618		     16 => 64 KB
619		     15 => 32 KB
620		     14 => 16 KB
621		     13 =>  8 KB
622		     12 =>  4 KB
623
624config LOG_CPU_MAX_BUF_SHIFT
625	int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
626	depends on SMP
627	range 0 21
628	default 12 if !BASE_SMALL
629	default 0 if BASE_SMALL
630	depends on PRINTK
631	help
632	  This option allows to increase the default ring buffer size
633	  according to the number of CPUs. The value defines the contribution
634	  of each CPU as a power of 2. The used space is typically only few
635	  lines however it might be much more when problems are reported,
636	  e.g. backtraces.
637
638	  The increased size means that a new buffer has to be allocated and
639	  the original static one is unused. It makes sense only on systems
640	  with more CPUs. Therefore this value is used only when the sum of
641	  contributions is greater than the half of the default kernel ring
642	  buffer as defined by LOG_BUF_SHIFT. The default values are set
643	  so that more than 64 CPUs are needed to trigger the allocation.
644
645	  Also this option is ignored when "log_buf_len" kernel parameter is
646	  used as it forces an exact (power of two) size of the ring buffer.
647
648	  The number of possible CPUs is used for this computation ignoring
649	  hotplugging making the computation optimal for the worst case
650	  scenario while allowing a simple algorithm to be used from bootup.
651
652	  Examples shift values and their meaning:
653		     17 => 128 KB for each CPU
654		     16 =>  64 KB for each CPU
655		     15 =>  32 KB for each CPU
656		     14 =>  16 KB for each CPU
657		     13 =>   8 KB for each CPU
658		     12 =>   4 KB for each CPU
659
660config PRINTK_SAFE_LOG_BUF_SHIFT
661	int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
662	range 10 21
663	default 13
664	depends on PRINTK
665	help
666	  Select the size of an alternate printk per-CPU buffer where messages
667	  printed from usafe contexts are temporary stored. One example would
668	  be NMI messages, another one - printk recursion. The messages are
669	  copied to the main log buffer in a safe context to avoid a deadlock.
670	  The value defines the size as a power of 2.
671
672	  Those messages are rare and limited. The largest one is when
673	  a backtrace is printed. It usually fits into 4KB. Select
674	  8KB if you want to be on the safe side.
675
676	  Examples:
677		     17 => 128 KB for each CPU
678		     16 =>  64 KB for each CPU
679		     15 =>  32 KB for each CPU
680		     14 =>  16 KB for each CPU
681		     13 =>   8 KB for each CPU
682		     12 =>   4 KB for each CPU
683
684#
685# Architectures with an unreliable sched_clock() should select this:
686#
687config HAVE_UNSTABLE_SCHED_CLOCK
688	bool
689
690config GENERIC_SCHED_CLOCK
691	bool
692
693menu "Scheduler features"
694
695config UCLAMP_TASK
696	bool "Enable utilization clamping for RT/FAIR tasks"
697	depends on CPU_FREQ_GOV_SCHEDUTIL
698	help
699	  This feature enables the scheduler to track the clamped utilization
700	  of each CPU based on RUNNABLE tasks scheduled on that CPU.
701
702	  With this option, the user can specify the min and max CPU
703	  utilization allowed for RUNNABLE tasks. The max utilization defines
704	  the maximum frequency a task should use while the min utilization
705	  defines the minimum frequency it should use.
706
707	  Both min and max utilization clamp values are hints to the scheduler,
708	  aiming at improving its frequency selection policy, but they do not
709	  enforce or grant any specific bandwidth for tasks.
710
711	  If in doubt, say N.
712
713config UCLAMP_BUCKETS_COUNT
714	int "Number of supported utilization clamp buckets"
715	range 5 20
716	default 5
717	depends on UCLAMP_TASK
718	help
719	  Defines the number of clamp buckets to use. The range of each bucket
720	  will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
721	  number of clamp buckets the finer their granularity and the higher
722	  the precision of clamping aggregation and tracking at run-time.
723
724	  For example, with the minimum configuration value we will have 5
725	  clamp buckets tracking 20% utilization each. A 25% boosted tasks will
726	  be refcounted in the [20..39]% bucket and will set the bucket clamp
727	  effective value to 25%.
728	  If a second 30% boosted task should be co-scheduled on the same CPU,
729	  that task will be refcounted in the same bucket of the first task and
730	  it will boost the bucket clamp effective value to 30%.
731	  The clamp effective value of a bucket is reset to its nominal value
732	  (20% in the example above) when there are no more tasks refcounted in
733	  that bucket.
734
735	  An additional boost/capping margin can be added to some tasks. In the
736	  example above the 25% task will be boosted to 30% until it exits the
737	  CPU. If that should be considered not acceptable on certain systems,
738	  it's always possible to reduce the margin by increasing the number of
739	  clamp buckets to trade off used memory for run-time tracking
740	  precision.
741
742	  If in doubt, use the default value.
743
744endmenu
745
746#
747# For architectures that want to enable the support for NUMA-affine scheduler
748# balancing logic:
749#
750config ARCH_SUPPORTS_NUMA_BALANCING
751	bool
752
753#
754# For architectures that prefer to flush all TLBs after a number of pages
755# are unmapped instead of sending one IPI per page to flush. The architecture
756# must provide guarantees on what happens if a clean TLB cache entry is
757# written after the unmap. Details are in mm/rmap.c near the check for
758# should_defer_flush. The architecture should also consider if the full flush
759# and the refill costs are offset by the savings of sending fewer IPIs.
760config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
761	bool
762
763config CC_HAS_INT128
764	def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
765
766#
767# For architectures that know their GCC __int128 support is sound
768#
769config ARCH_SUPPORTS_INT128
770	bool
771
772# For architectures that (ab)use NUMA to represent different memory regions
773# all cpu-local but of different latencies, such as SuperH.
774#
775config ARCH_WANT_NUMA_VARIABLE_LOCALITY
776	bool
777
778config NUMA_BALANCING
779	bool "Memory placement aware NUMA scheduler"
780	depends on ARCH_SUPPORTS_NUMA_BALANCING
781	depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
782	depends on SMP && NUMA && MIGRATION
783	help
784	  This option adds support for automatic NUMA aware memory/task placement.
785	  The mechanism is quite primitive and is based on migrating memory when
786	  it has references to the node the task is running on.
787
788	  This system will be inactive on UMA systems.
789
790config NUMA_BALANCING_DEFAULT_ENABLED
791	bool "Automatically enable NUMA aware memory/task placement"
792	default y
793	depends on NUMA_BALANCING
794	help
795	  If set, automatic NUMA balancing will be enabled if running on a NUMA
796	  machine.
797
798menuconfig CGROUPS
799	bool "Control Group support"
800	select KERNFS
801	help
802	  This option adds support for grouping sets of processes together, for
803	  use with process control subsystems such as Cpusets, CFS, memory
804	  controls or device isolation.
805	  See
806		- Documentation/scheduler/sched-design-CFS.rst	(CFS)
807		- Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
808					  and resource control)
809
810	  Say N if unsure.
811
812if CGROUPS
813
814config PAGE_COUNTER
815	bool
816
817config MEMCG
818	bool "Memory controller"
819	select PAGE_COUNTER
820	select EVENTFD
821	help
822	  Provides control over the memory footprint of tasks in a cgroup.
823
824config MEMCG_SWAP
825	bool
826	depends on MEMCG && SWAP
827	default y
828
829config MEMCG_KMEM
830	bool
831	depends on MEMCG && !SLOB
832	default y
833
834config BLK_CGROUP
835	bool "IO controller"
836	depends on BLOCK
837	default n
838	---help---
839	Generic block IO controller cgroup interface. This is the common
840	cgroup interface which should be used by various IO controlling
841	policies.
842
843	Currently, CFQ IO scheduler uses it to recognize task groups and
844	control disk bandwidth allocation (proportional time slice allocation)
845	to such task groups. It is also used by bio throttling logic in
846	block layer to implement upper limit in IO rates on a device.
847
848	This option only enables generic Block IO controller infrastructure.
849	One needs to also enable actual IO controlling logic/policy. For
850	enabling proportional weight division of disk bandwidth in CFQ, set
851	CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
852	CONFIG_BLK_DEV_THROTTLING=y.
853
854	See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
855
856config CGROUP_WRITEBACK
857	bool
858	depends on MEMCG && BLK_CGROUP
859	default y
860
861menuconfig CGROUP_SCHED
862	bool "CPU controller"
863	default n
864	help
865	  This feature lets CPU scheduler recognize task groups and control CPU
866	  bandwidth allocation to such task groups. It uses cgroups to group
867	  tasks.
868
869if CGROUP_SCHED
870config FAIR_GROUP_SCHED
871	bool "Group scheduling for SCHED_OTHER"
872	depends on CGROUP_SCHED
873	default CGROUP_SCHED
874
875config CFS_BANDWIDTH
876	bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
877	depends on FAIR_GROUP_SCHED
878	default n
879	help
880	  This option allows users to define CPU bandwidth rates (limits) for
881	  tasks running within the fair group scheduler.  Groups with no limit
882	  set are considered to be unconstrained and will run with no
883	  restriction.
884	  See Documentation/scheduler/sched-bwc.rst for more information.
885
886config RT_GROUP_SCHED
887	bool "Group scheduling for SCHED_RR/FIFO"
888	depends on CGROUP_SCHED
889	default n
890	help
891	  This feature lets you explicitly allocate real CPU bandwidth
892	  to task groups. If enabled, it will also make it impossible to
893	  schedule realtime tasks for non-root users until you allocate
894	  realtime bandwidth for them.
895	  See Documentation/scheduler/sched-rt-group.rst for more information.
896
897endif #CGROUP_SCHED
898
899config UCLAMP_TASK_GROUP
900	bool "Utilization clamping per group of tasks"
901	depends on CGROUP_SCHED
902	depends on UCLAMP_TASK
903	default n
904	help
905	  This feature enables the scheduler to track the clamped utilization
906	  of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
907
908	  When this option is enabled, the user can specify a min and max
909	  CPU bandwidth which is allowed for each single task in a group.
910	  The max bandwidth allows to clamp the maximum frequency a task
911	  can use, while the min bandwidth allows to define a minimum
912	  frequency a task will always use.
913
914	  When task group based utilization clamping is enabled, an eventually
915	  specified task-specific clamp value is constrained by the cgroup
916	  specified clamp value. Both minimum and maximum task clamping cannot
917	  be bigger than the corresponding clamping defined at task group level.
918
919	  If in doubt, say N.
920
921config CGROUP_PIDS
922	bool "PIDs controller"
923	help
924	  Provides enforcement of process number limits in the scope of a
925	  cgroup. Any attempt to fork more processes than is allowed in the
926	  cgroup will fail. PIDs are fundamentally a global resource because it
927	  is fairly trivial to reach PID exhaustion before you reach even a
928	  conservative kmemcg limit. As a result, it is possible to grind a
929	  system to halt without being limited by other cgroup policies. The
930	  PIDs controller is designed to stop this from happening.
931
932	  It should be noted that organisational operations (such as attaching
933	  to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
934	  since the PIDs limit only affects a process's ability to fork, not to
935	  attach to a cgroup.
936
937config CGROUP_RDMA
938	bool "RDMA controller"
939	help
940	  Provides enforcement of RDMA resources defined by IB stack.
941	  It is fairly easy for consumers to exhaust RDMA resources, which
942	  can result into resource unavailability to other consumers.
943	  RDMA controller is designed to stop this from happening.
944	  Attaching processes with active RDMA resources to the cgroup
945	  hierarchy is allowed even if can cross the hierarchy's limit.
946
947config CGROUP_FREEZER
948	bool "Freezer controller"
949	help
950	  Provides a way to freeze and unfreeze all tasks in a
951	  cgroup.
952
953	  This option affects the ORIGINAL cgroup interface. The cgroup2 memory
954	  controller includes important in-kernel memory consumers per default.
955
956	  If you're using cgroup2, say N.
957
958config CGROUP_HUGETLB
959	bool "HugeTLB controller"
960	depends on HUGETLB_PAGE
961	select PAGE_COUNTER
962	default n
963	help
964	  Provides a cgroup controller for HugeTLB pages.
965	  When you enable this, you can put a per cgroup limit on HugeTLB usage.
966	  The limit is enforced during page fault. Since HugeTLB doesn't
967	  support page reclaim, enforcing the limit at page fault time implies
968	  that, the application will get SIGBUS signal if it tries to access
969	  HugeTLB pages beyond its limit. This requires the application to know
970	  beforehand how much HugeTLB pages it would require for its use. The
971	  control group is tracked in the third page lru pointer. This means
972	  that we cannot use the controller with huge page less than 3 pages.
973
974config CPUSETS
975	bool "Cpuset controller"
976	depends on SMP
977	help
978	  This option will let you create and manage CPUSETs which
979	  allow dynamically partitioning a system into sets of CPUs and
980	  Memory Nodes and assigning tasks to run only within those sets.
981	  This is primarily useful on large SMP or NUMA systems.
982
983	  Say N if unsure.
984
985config PROC_PID_CPUSET
986	bool "Include legacy /proc/<pid>/cpuset file"
987	depends on CPUSETS
988	default y
989
990config CGROUP_DEVICE
991	bool "Device controller"
992	help
993	  Provides a cgroup controller implementing whitelists for
994	  devices which a process in the cgroup can mknod or open.
995
996config CGROUP_CPUACCT
997	bool "Simple CPU accounting controller"
998	help
999	  Provides a simple controller for monitoring the
1000	  total CPU consumed by the tasks in a cgroup.
1001
1002config CGROUP_PERF
1003	bool "Perf controller"
1004	depends on PERF_EVENTS
1005	help
1006	  This option extends the perf per-cpu mode to restrict monitoring
1007	  to threads which belong to the cgroup specified and run on the
1008	  designated cpu.  Or this can be used to have cgroup ID in samples
1009	  so that it can monitor performance events among cgroups.
1010
1011	  Say N if unsure.
1012
1013config CGROUP_BPF
1014	bool "Support for eBPF programs attached to cgroups"
1015	depends on BPF_SYSCALL
1016	select SOCK_CGROUP_DATA
1017	help
1018	  Allow attaching eBPF programs to a cgroup using the bpf(2)
1019	  syscall command BPF_PROG_ATTACH.
1020
1021	  In which context these programs are accessed depends on the type
1022	  of attachment. For instance, programs that are attached using
1023	  BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1024	  inet sockets.
1025
1026config CGROUP_DEBUG
1027	bool "Debug controller"
1028	default n
1029	depends on DEBUG_KERNEL
1030	help
1031	  This option enables a simple controller that exports
1032	  debugging information about the cgroups framework. This
1033	  controller is for control cgroup debugging only. Its
1034	  interfaces are not stable.
1035
1036	  Say N.
1037
1038config SOCK_CGROUP_DATA
1039	bool
1040	default n
1041
1042endif # CGROUPS
1043
1044menuconfig NAMESPACES
1045	bool "Namespaces support" if EXPERT
1046	depends on MULTIUSER
1047	default !EXPERT
1048	help
1049	  Provides the way to make tasks work with different objects using
1050	  the same id. For example same IPC id may refer to different objects
1051	  or same user id or pid may refer to different tasks when used in
1052	  different namespaces.
1053
1054if NAMESPACES
1055
1056config UTS_NS
1057	bool "UTS namespace"
1058	default y
1059	help
1060	  In this namespace tasks see different info provided with the
1061	  uname() system call
1062
1063config TIME_NS
1064	bool "TIME namespace"
1065	depends on GENERIC_VDSO_TIME_NS
1066	default y
1067	help
1068	  In this namespace boottime and monotonic clocks can be set.
1069	  The time will keep going with the same pace.
1070
1071config IPC_NS
1072	bool "IPC namespace"
1073	depends on (SYSVIPC || POSIX_MQUEUE)
1074	default y
1075	help
1076	  In this namespace tasks work with IPC ids which correspond to
1077	  different IPC objects in different namespaces.
1078
1079config USER_NS
1080	bool "User namespace"
1081	default n
1082	help
1083	  This allows containers, i.e. vservers, to use user namespaces
1084	  to provide different user info for different servers.
1085
1086	  When user namespaces are enabled in the kernel it is
1087	  recommended that the MEMCG option also be enabled and that
1088	  user-space use the memory control groups to limit the amount
1089	  of memory a memory unprivileged users can use.
1090
1091	  If unsure, say N.
1092
1093config PID_NS
1094	bool "PID Namespaces"
1095	default y
1096	help
1097	  Support process id namespaces.  This allows having multiple
1098	  processes with the same pid as long as they are in different
1099	  pid namespaces.  This is a building block of containers.
1100
1101config NET_NS
1102	bool "Network namespace"
1103	depends on NET
1104	default y
1105	help
1106	  Allow user space to create what appear to be multiple instances
1107	  of the network stack.
1108
1109endif # NAMESPACES
1110
1111config CHECKPOINT_RESTORE
1112	bool "Checkpoint/restore support"
1113	select PROC_CHILDREN
1114	default n
1115	help
1116	  Enables additional kernel features in a sake of checkpoint/restore.
1117	  In particular it adds auxiliary prctl codes to setup process text,
1118	  data and heap segment sizes, and a few additional /proc filesystem
1119	  entries.
1120
1121	  If unsure, say N here.
1122
1123config SCHED_AUTOGROUP
1124	bool "Automatic process group scheduling"
1125	select CGROUPS
1126	select CGROUP_SCHED
1127	select FAIR_GROUP_SCHED
1128	help
1129	  This option optimizes the scheduler for common desktop workloads by
1130	  automatically creating and populating task groups.  This separation
1131	  of workloads isolates aggressive CPU burners (like build jobs) from
1132	  desktop applications.  Task group autogeneration is currently based
1133	  upon task session.
1134
1135config SYSFS_DEPRECATED
1136	bool "Enable deprecated sysfs features to support old userspace tools"
1137	depends on SYSFS
1138	default n
1139	help
1140	  This option adds code that switches the layout of the "block" class
1141	  devices, to not show up in /sys/class/block/, but only in
1142	  /sys/block/.
1143
1144	  This switch is only active when the sysfs.deprecated=1 boot option is
1145	  passed or the SYSFS_DEPRECATED_V2 option is set.
1146
1147	  This option allows new kernels to run on old distributions and tools,
1148	  which might get confused by /sys/class/block/. Since 2007/2008 all
1149	  major distributions and tools handle this just fine.
1150
1151	  Recent distributions and userspace tools after 2009/2010 depend on
1152	  the existence of /sys/class/block/, and will not work with this
1153	  option enabled.
1154
1155	  Only if you are using a new kernel on an old distribution, you might
1156	  need to say Y here.
1157
1158config SYSFS_DEPRECATED_V2
1159	bool "Enable deprecated sysfs features by default"
1160	default n
1161	depends on SYSFS
1162	depends on SYSFS_DEPRECATED
1163	help
1164	  Enable deprecated sysfs by default.
1165
1166	  See the CONFIG_SYSFS_DEPRECATED option for more details about this
1167	  option.
1168
1169	  Only if you are using a new kernel on an old distribution, you might
1170	  need to say Y here. Even then, odds are you would not need it
1171	  enabled, you can always pass the boot option if absolutely necessary.
1172
1173config RELAY
1174	bool "Kernel->user space relay support (formerly relayfs)"
1175	select IRQ_WORK
1176	help
1177	  This option enables support for relay interface support in
1178	  certain file systems (such as debugfs).
1179	  It is designed to provide an efficient mechanism for tools and
1180	  facilities to relay large amounts of data from kernel space to
1181	  user space.
1182
1183	  If unsure, say N.
1184
1185config BLK_DEV_INITRD
1186	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1187	help
1188	  The initial RAM filesystem is a ramfs which is loaded by the
1189	  boot loader (loadlin or lilo) and that is mounted as root
1190	  before the normal boot procedure. It is typically used to
1191	  load modules needed to mount the "real" root file system,
1192	  etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1193
1194	  If RAM disk support (BLK_DEV_RAM) is also included, this
1195	  also enables initial RAM disk (initrd) support and adds
1196	  15 Kbytes (more on some other architectures) to the kernel size.
1197
1198	  If unsure say Y.
1199
1200if BLK_DEV_INITRD
1201
1202source "usr/Kconfig"
1203
1204endif
1205
1206config BOOT_CONFIG
1207	bool "Boot config support"
1208	select BLK_DEV_INITRD
1209	help
1210	  Extra boot config allows system admin to pass a config file as
1211	  complemental extension of kernel cmdline when booting.
1212	  The boot config file must be attached at the end of initramfs
1213	  with checksum, size and magic word.
1214	  See <file:Documentation/admin-guide/bootconfig.rst> for details.
1215
1216	  If unsure, say Y.
1217
1218choice
1219	prompt "Compiler optimization level"
1220	default CC_OPTIMIZE_FOR_PERFORMANCE
1221
1222config CC_OPTIMIZE_FOR_PERFORMANCE
1223	bool "Optimize for performance (-O2)"
1224	help
1225	  This is the default optimization level for the kernel, building
1226	  with the "-O2" compiler flag for best performance and most
1227	  helpful compile-time warnings.
1228
1229config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1230	bool "Optimize more for performance (-O3)"
1231	depends on ARC
1232	help
1233	  Choosing this option will pass "-O3" to your compiler to optimize
1234	  the kernel yet more for performance.
1235
1236config CC_OPTIMIZE_FOR_SIZE
1237	bool "Optimize for size (-Os)"
1238	help
1239	  Choosing this option will pass "-Os" to your compiler resulting
1240	  in a smaller kernel.
1241
1242endchoice
1243
1244config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1245	bool
1246	help
1247	  This requires that the arch annotates or otherwise protects
1248	  its external entry points from being discarded. Linker scripts
1249	  must also merge .text.*, .data.*, and .bss.* correctly into
1250	  output sections. Care must be taken not to pull in unrelated
1251	  sections (e.g., '.text.init'). Typically '.' in section names
1252	  is used to distinguish them from label names / C identifiers.
1253
1254config LD_DEAD_CODE_DATA_ELIMINATION
1255	bool "Dead code and data elimination (EXPERIMENTAL)"
1256	depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1257	depends on EXPERT
1258	depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800)
1259	depends on $(cc-option,-ffunction-sections -fdata-sections)
1260	depends on $(ld-option,--gc-sections)
1261	help
1262	  Enable this if you want to do dead code and data elimination with
1263	  the linker by compiling with -ffunction-sections -fdata-sections,
1264	  and linking with --gc-sections.
1265
1266	  This can reduce on disk and in-memory size of the kernel
1267	  code and static data, particularly for small configs and
1268	  on small systems. This has the possibility of introducing
1269	  silently broken kernel if the required annotations are not
1270	  present. This option is not well tested yet, so use at your
1271	  own risk.
1272
1273config SYSCTL
1274	bool
1275
1276config HAVE_UID16
1277	bool
1278
1279config SYSCTL_EXCEPTION_TRACE
1280	bool
1281	help
1282	  Enable support for /proc/sys/debug/exception-trace.
1283
1284config SYSCTL_ARCH_UNALIGN_NO_WARN
1285	bool
1286	help
1287	  Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1288	  Allows arch to define/use @no_unaligned_warning to possibly warn
1289	  about unaligned access emulation going on under the hood.
1290
1291config SYSCTL_ARCH_UNALIGN_ALLOW
1292	bool
1293	help
1294	  Enable support for /proc/sys/kernel/unaligned-trap
1295	  Allows arches to define/use @unaligned_enabled to runtime toggle
1296	  the unaligned access emulation.
1297	  see arch/parisc/kernel/unaligned.c for reference
1298
1299config HAVE_PCSPKR_PLATFORM
1300	bool
1301
1302# interpreter that classic socket filters depend on
1303config BPF
1304	bool
1305
1306menuconfig EXPERT
1307	bool "Configure standard kernel features (expert users)"
1308	# Unhide debug options, to make the on-by-default options visible
1309	select DEBUG_KERNEL
1310	help
1311	  This option allows certain base kernel options and settings
1312	  to be disabled or tweaked. This is for specialized
1313	  environments which can tolerate a "non-standard" kernel.
1314	  Only use this if you really know what you are doing.
1315
1316config UID16
1317	bool "Enable 16-bit UID system calls" if EXPERT
1318	depends on HAVE_UID16 && MULTIUSER
1319	default y
1320	help
1321	  This enables the legacy 16-bit UID syscall wrappers.
1322
1323config MULTIUSER
1324	bool "Multiple users, groups and capabilities support" if EXPERT
1325	default y
1326	help
1327	  This option enables support for non-root users, groups and
1328	  capabilities.
1329
1330	  If you say N here, all processes will run with UID 0, GID 0, and all
1331	  possible capabilities.  Saying N here also compiles out support for
1332	  system calls related to UIDs, GIDs, and capabilities, such as setuid,
1333	  setgid, and capset.
1334
1335	  If unsure, say Y here.
1336
1337config SGETMASK_SYSCALL
1338	bool "sgetmask/ssetmask syscalls support" if EXPERT
1339	def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1340	---help---
1341	  sys_sgetmask and sys_ssetmask are obsolete system calls
1342	  no longer supported in libc but still enabled by default in some
1343	  architectures.
1344
1345	  If unsure, leave the default option here.
1346
1347config SYSFS_SYSCALL
1348	bool "Sysfs syscall support" if EXPERT
1349	default y
1350	---help---
1351	  sys_sysfs is an obsolete system call no longer supported in libc.
1352	  Note that disabling this option is more secure but might break
1353	  compatibility with some systems.
1354
1355	  If unsure say Y here.
1356
1357config FHANDLE
1358	bool "open by fhandle syscalls" if EXPERT
1359	select EXPORTFS
1360	default y
1361	help
1362	  If you say Y here, a user level program will be able to map
1363	  file names to handle and then later use the handle for
1364	  different file system operations. This is useful in implementing
1365	  userspace file servers, which now track files using handles instead
1366	  of names. The handle would remain the same even if file names
1367	  get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1368	  syscalls.
1369
1370config POSIX_TIMERS
1371	bool "Posix Clocks & timers" if EXPERT
1372	default y
1373	help
1374	  This includes native support for POSIX timers to the kernel.
1375	  Some embedded systems have no use for them and therefore they
1376	  can be configured out to reduce the size of the kernel image.
1377
1378	  When this option is disabled, the following syscalls won't be
1379	  available: timer_create, timer_gettime: timer_getoverrun,
1380	  timer_settime, timer_delete, clock_adjtime, getitimer,
1381	  setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1382	  clock_getres and clock_nanosleep syscalls will be limited to
1383	  CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1384
1385	  If unsure say y.
1386
1387config PRINTK
1388	default y
1389	bool "Enable support for printk" if EXPERT
1390	select IRQ_WORK
1391	help
1392	  This option enables normal printk support. Removing it
1393	  eliminates most of the message strings from the kernel image
1394	  and makes the kernel more or less silent. As this makes it
1395	  very difficult to diagnose system problems, saying N here is
1396	  strongly discouraged.
1397
1398config PRINTK_NMI
1399	def_bool y
1400	depends on PRINTK
1401	depends on HAVE_NMI
1402
1403config BUG
1404	bool "BUG() support" if EXPERT
1405	default y
1406	help
1407	  Disabling this option eliminates support for BUG and WARN, reducing
1408	  the size of your kernel image and potentially quietly ignoring
1409	  numerous fatal conditions. You should only consider disabling this
1410	  option for embedded systems with no facilities for reporting errors.
1411	  Just say Y.
1412
1413config ELF_CORE
1414	depends on COREDUMP
1415	default y
1416	bool "Enable ELF core dumps" if EXPERT
1417	help
1418	  Enable support for generating core dumps. Disabling saves about 4k.
1419
1420
1421config PCSPKR_PLATFORM
1422	bool "Enable PC-Speaker support" if EXPERT
1423	depends on HAVE_PCSPKR_PLATFORM
1424	select I8253_LOCK
1425	default y
1426	help
1427	  This option allows to disable the internal PC-Speaker
1428	  support, saving some memory.
1429
1430config BASE_FULL
1431	default y
1432	bool "Enable full-sized data structures for core" if EXPERT
1433	help
1434	  Disabling this option reduces the size of miscellaneous core
1435	  kernel data structures. This saves memory on small machines,
1436	  but may reduce performance.
1437
1438config FUTEX
1439	bool "Enable futex support" if EXPERT
1440	default y
1441	imply RT_MUTEXES
1442	help
1443	  Disabling this option will cause the kernel to be built without
1444	  support for "fast userspace mutexes".  The resulting kernel may not
1445	  run glibc-based applications correctly.
1446
1447config FUTEX_PI
1448	bool
1449	depends on FUTEX && RT_MUTEXES
1450	default y
1451
1452config HAVE_FUTEX_CMPXCHG
1453	bool
1454	depends on FUTEX
1455	help
1456	  Architectures should select this if futex_atomic_cmpxchg_inatomic()
1457	  is implemented and always working. This removes a couple of runtime
1458	  checks.
1459
1460config EPOLL
1461	bool "Enable eventpoll support" if EXPERT
1462	default y
1463	help
1464	  Disabling this option will cause the kernel to be built without
1465	  support for epoll family of system calls.
1466
1467config SIGNALFD
1468	bool "Enable signalfd() system call" if EXPERT
1469	default y
1470	help
1471	  Enable the signalfd() system call that allows to receive signals
1472	  on a file descriptor.
1473
1474	  If unsure, say Y.
1475
1476config TIMERFD
1477	bool "Enable timerfd() system call" if EXPERT
1478	default y
1479	help
1480	  Enable the timerfd() system call that allows to receive timer
1481	  events on a file descriptor.
1482
1483	  If unsure, say Y.
1484
1485config EVENTFD
1486	bool "Enable eventfd() system call" if EXPERT
1487	default y
1488	help
1489	  Enable the eventfd() system call that allows to receive both
1490	  kernel notification (ie. KAIO) or userspace notifications.
1491
1492	  If unsure, say Y.
1493
1494config SHMEM
1495	bool "Use full shmem filesystem" if EXPERT
1496	default y
1497	depends on MMU
1498	help
1499	  The shmem is an internal filesystem used to manage shared memory.
1500	  It is backed by swap and manages resource limits. It is also exported
1501	  to userspace as tmpfs if TMPFS is enabled. Disabling this
1502	  option replaces shmem and tmpfs with the much simpler ramfs code,
1503	  which may be appropriate on small systems without swap.
1504
1505config AIO
1506	bool "Enable AIO support" if EXPERT
1507	default y
1508	help
1509	  This option enables POSIX asynchronous I/O which may by used
1510	  by some high performance threaded applications. Disabling
1511	  this option saves about 7k.
1512
1513config IO_URING
1514	bool "Enable IO uring support" if EXPERT
1515	select IO_WQ
1516	default y
1517	help
1518	  This option enables support for the io_uring interface, enabling
1519	  applications to submit and complete IO through submission and
1520	  completion rings that are shared between the kernel and application.
1521
1522config ADVISE_SYSCALLS
1523	bool "Enable madvise/fadvise syscalls" if EXPERT
1524	default y
1525	help
1526	  This option enables the madvise and fadvise syscalls, used by
1527	  applications to advise the kernel about their future memory or file
1528	  usage, improving performance. If building an embedded system where no
1529	  applications use these syscalls, you can disable this option to save
1530	  space.
1531
1532config HAVE_ARCH_USERFAULTFD_WP
1533	bool
1534	help
1535	  Arch has userfaultfd write protection support
1536
1537config MEMBARRIER
1538	bool "Enable membarrier() system call" if EXPERT
1539	default y
1540	help
1541	  Enable the membarrier() system call that allows issuing memory
1542	  barriers across all running threads, which can be used to distribute
1543	  the cost of user-space memory barriers asymmetrically by transforming
1544	  pairs of memory barriers into pairs consisting of membarrier() and a
1545	  compiler barrier.
1546
1547	  If unsure, say Y.
1548
1549config KALLSYMS
1550	bool "Load all symbols for debugging/ksymoops" if EXPERT
1551	default y
1552	help
1553	  Say Y here to let the kernel print out symbolic crash information and
1554	  symbolic stack backtraces. This increases the size of the kernel
1555	  somewhat, as all symbols have to be loaded into the kernel image.
1556
1557config KALLSYMS_ALL
1558	bool "Include all symbols in kallsyms"
1559	depends on DEBUG_KERNEL && KALLSYMS
1560	help
1561	  Normally kallsyms only contains the symbols of functions for nicer
1562	  OOPS messages and backtraces (i.e., symbols from the text and inittext
1563	  sections). This is sufficient for most cases. And only in very rare
1564	  cases (e.g., when a debugger is used) all symbols are required (e.g.,
1565	  names of variables from the data sections, etc).
1566
1567	  This option makes sure that all symbols are loaded into the kernel
1568	  image (i.e., symbols from all sections) in cost of increased kernel
1569	  size (depending on the kernel configuration, it may be 300KiB or
1570	  something like this).
1571
1572	  Say N unless you really need all symbols.
1573
1574config KALLSYMS_ABSOLUTE_PERCPU
1575	bool
1576	depends on KALLSYMS
1577	default X86_64 && SMP
1578
1579config KALLSYMS_BASE_RELATIVE
1580	bool
1581	depends on KALLSYMS
1582	default !IA64
1583	help
1584	  Instead of emitting them as absolute values in the native word size,
1585	  emit the symbol references in the kallsyms table as 32-bit entries,
1586	  each containing a relative value in the range [base, base + U32_MAX]
1587	  or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1588	  an absolute value in the range [0, S32_MAX] or a relative value in the
1589	  range [base, base + S32_MAX], where base is the lowest relative symbol
1590	  address encountered in the image.
1591
1592	  On 64-bit builds, this reduces the size of the address table by 50%,
1593	  but more importantly, it results in entries whose values are build
1594	  time constants, and no relocation pass is required at runtime to fix
1595	  up the entries based on the runtime load address of the kernel.
1596
1597# end of the "standard kernel features (expert users)" menu
1598
1599# syscall, maps, verifier
1600
1601config BPF_LSM
1602	bool "LSM Instrumentation with BPF"
1603	depends on BPF_EVENTS
1604	depends on BPF_SYSCALL
1605	depends on SECURITY
1606	depends on BPF_JIT
1607	help
1608	  Enables instrumentation of the security hooks with eBPF programs for
1609	  implementing dynamic MAC and Audit Policies.
1610
1611	  If you are unsure how to answer this question, answer N.
1612
1613config BPF_SYSCALL
1614	bool "Enable bpf() system call"
1615	select BPF
1616	select IRQ_WORK
1617	default n
1618	help
1619	  Enable the bpf() system call that allows to manipulate eBPF
1620	  programs and maps via file descriptors.
1621
1622config ARCH_WANT_DEFAULT_BPF_JIT
1623	bool
1624
1625config BPF_JIT_ALWAYS_ON
1626	bool "Permanently enable BPF JIT and remove BPF interpreter"
1627	depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1628	help
1629	  Enables BPF JIT and removes BPF interpreter to avoid
1630	  speculative execution of BPF instructions by the interpreter
1631
1632config BPF_JIT_DEFAULT_ON
1633	def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
1634	depends on HAVE_EBPF_JIT && BPF_JIT
1635
1636config USERFAULTFD
1637	bool "Enable userfaultfd() system call"
1638	depends on MMU
1639	help
1640	  Enable the userfaultfd() system call that allows to intercept and
1641	  handle page faults in userland.
1642
1643config ARCH_HAS_MEMBARRIER_CALLBACKS
1644	bool
1645
1646config ARCH_HAS_MEMBARRIER_SYNC_CORE
1647	bool
1648
1649config RSEQ
1650	bool "Enable rseq() system call" if EXPERT
1651	default y
1652	depends on HAVE_RSEQ
1653	select MEMBARRIER
1654	help
1655	  Enable the restartable sequences system call. It provides a
1656	  user-space cache for the current CPU number value, which
1657	  speeds up getting the current CPU number from user-space,
1658	  as well as an ABI to speed up user-space operations on
1659	  per-CPU data.
1660
1661	  If unsure, say Y.
1662
1663config DEBUG_RSEQ
1664	default n
1665	bool "Enabled debugging of rseq() system call" if EXPERT
1666	depends on RSEQ && DEBUG_KERNEL
1667	help
1668	  Enable extra debugging checks for the rseq system call.
1669
1670	  If unsure, say N.
1671
1672config EMBEDDED
1673	bool "Embedded system"
1674	option allnoconfig_y
1675	select EXPERT
1676	help
1677	  This option should be enabled if compiling the kernel for
1678	  an embedded system so certain expert options are available
1679	  for configuration.
1680
1681config HAVE_PERF_EVENTS
1682	bool
1683	help
1684	  See tools/perf/design.txt for details.
1685
1686config PERF_USE_VMALLOC
1687	bool
1688	help
1689	  See tools/perf/design.txt for details
1690
1691config PC104
1692	bool "PC/104 support" if EXPERT
1693	help
1694	  Expose PC/104 form factor device drivers and options available for
1695	  selection and configuration. Enable this option if your target
1696	  machine has a PC/104 bus.
1697
1698menu "Kernel Performance Events And Counters"
1699
1700config PERF_EVENTS
1701	bool "Kernel performance events and counters"
1702	default y if PROFILING
1703	depends on HAVE_PERF_EVENTS
1704	select IRQ_WORK
1705	select SRCU
1706	help
1707	  Enable kernel support for various performance events provided
1708	  by software and hardware.
1709
1710	  Software events are supported either built-in or via the
1711	  use of generic tracepoints.
1712
1713	  Most modern CPUs support performance events via performance
1714	  counter registers. These registers count the number of certain
1715	  types of hw events: such as instructions executed, cachemisses
1716	  suffered, or branches mis-predicted - without slowing down the
1717	  kernel or applications. These registers can also trigger interrupts
1718	  when a threshold number of events have passed - and can thus be
1719	  used to profile the code that runs on that CPU.
1720
1721	  The Linux Performance Event subsystem provides an abstraction of
1722	  these software and hardware event capabilities, available via a
1723	  system call and used by the "perf" utility in tools/perf/. It
1724	  provides per task and per CPU counters, and it provides event
1725	  capabilities on top of those.
1726
1727	  Say Y if unsure.
1728
1729config DEBUG_PERF_USE_VMALLOC
1730	default n
1731	bool "Debug: use vmalloc to back perf mmap() buffers"
1732	depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1733	select PERF_USE_VMALLOC
1734	help
1735	  Use vmalloc memory to back perf mmap() buffers.
1736
1737	  Mostly useful for debugging the vmalloc code on platforms
1738	  that don't require it.
1739
1740	  Say N if unsure.
1741
1742endmenu
1743
1744config VM_EVENT_COUNTERS
1745	default y
1746	bool "Enable VM event counters for /proc/vmstat" if EXPERT
1747	help
1748	  VM event counters are needed for event counts to be shown.
1749	  This option allows the disabling of the VM event counters
1750	  on EXPERT systems.  /proc/vmstat will only show page counts
1751	  if VM event counters are disabled.
1752
1753config SLUB_DEBUG
1754	default y
1755	bool "Enable SLUB debugging support" if EXPERT
1756	depends on SLUB && SYSFS
1757	help
1758	  SLUB has extensive debug support features. Disabling these can
1759	  result in significant savings in code size. This also disables
1760	  SLUB sysfs support. /sys/slab will not exist and there will be
1761	  no support for cache validation etc.
1762
1763config SLUB_MEMCG_SYSFS_ON
1764	default n
1765	bool "Enable memcg SLUB sysfs support by default" if EXPERT
1766	depends on SLUB && SYSFS && MEMCG
1767	help
1768	  SLUB creates a directory under /sys/kernel/slab for each
1769	  allocation cache to host info and debug files. If memory
1770	  cgroup is enabled, each cache can have per memory cgroup
1771	  caches. SLUB can create the same sysfs directories for these
1772	  caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1773	  to a very high number of debug files being created. This is
1774	  controlled by slub_memcg_sysfs boot parameter and this
1775	  config option determines the parameter's default value.
1776
1777config COMPAT_BRK
1778	bool "Disable heap randomization"
1779	default y
1780	help
1781	  Randomizing heap placement makes heap exploits harder, but it
1782	  also breaks ancient binaries (including anything libc5 based).
1783	  This option changes the bootup default to heap randomization
1784	  disabled, and can be overridden at runtime by setting
1785	  /proc/sys/kernel/randomize_va_space to 2.
1786
1787	  On non-ancient distros (post-2000 ones) N is usually a safe choice.
1788
1789choice
1790	prompt "Choose SLAB allocator"
1791	default SLUB
1792	help
1793	   This option allows to select a slab allocator.
1794
1795config SLAB
1796	bool "SLAB"
1797	select HAVE_HARDENED_USERCOPY_ALLOCATOR
1798	help
1799	  The regular slab allocator that is established and known to work
1800	  well in all environments. It organizes cache hot objects in
1801	  per cpu and per node queues.
1802
1803config SLUB
1804	bool "SLUB (Unqueued Allocator)"
1805	select HAVE_HARDENED_USERCOPY_ALLOCATOR
1806	help
1807	   SLUB is a slab allocator that minimizes cache line usage
1808	   instead of managing queues of cached objects (SLAB approach).
1809	   Per cpu caching is realized using slabs of objects instead
1810	   of queues of objects. SLUB can use memory efficiently
1811	   and has enhanced diagnostics. SLUB is the default choice for
1812	   a slab allocator.
1813
1814config SLOB
1815	depends on EXPERT
1816	bool "SLOB (Simple Allocator)"
1817	help
1818	   SLOB replaces the stock allocator with a drastically simpler
1819	   allocator. SLOB is generally more space efficient but
1820	   does not perform as well on large systems.
1821
1822endchoice
1823
1824config SLAB_MERGE_DEFAULT
1825	bool "Allow slab caches to be merged"
1826	default y
1827	help
1828	  For reduced kernel memory fragmentation, slab caches can be
1829	  merged when they share the same size and other characteristics.
1830	  This carries a risk of kernel heap overflows being able to
1831	  overwrite objects from merged caches (and more easily control
1832	  cache layout), which makes such heap attacks easier to exploit
1833	  by attackers. By keeping caches unmerged, these kinds of exploits
1834	  can usually only damage objects in the same cache. To disable
1835	  merging at runtime, "slab_nomerge" can be passed on the kernel
1836	  command line.
1837
1838config SLAB_FREELIST_RANDOM
1839	default n
1840	depends on SLAB || SLUB
1841	bool "SLAB freelist randomization"
1842	help
1843	  Randomizes the freelist order used on creating new pages. This
1844	  security feature reduces the predictability of the kernel slab
1845	  allocator against heap overflows.
1846
1847config SLAB_FREELIST_HARDENED
1848	bool "Harden slab freelist metadata"
1849	depends on SLUB
1850	help
1851	  Many kernel heap attacks try to target slab cache metadata and
1852	  other infrastructure. This options makes minor performance
1853	  sacrifices to harden the kernel slab allocator against common
1854	  freelist exploit methods.
1855
1856config SHUFFLE_PAGE_ALLOCATOR
1857	bool "Page allocator randomization"
1858	default SLAB_FREELIST_RANDOM && ACPI_NUMA
1859	help
1860	  Randomization of the page allocator improves the average
1861	  utilization of a direct-mapped memory-side-cache. See section
1862	  5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1863	  6.2a specification for an example of how a platform advertises
1864	  the presence of a memory-side-cache. There are also incidental
1865	  security benefits as it reduces the predictability of page
1866	  allocations to compliment SLAB_FREELIST_RANDOM, but the
1867	  default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1868	  10th order of pages is selected based on cache utilization
1869	  benefits on x86.
1870
1871	  While the randomization improves cache utilization it may
1872	  negatively impact workloads on platforms without a cache. For
1873	  this reason, by default, the randomization is enabled only
1874	  after runtime detection of a direct-mapped memory-side-cache.
1875	  Otherwise, the randomization may be force enabled with the
1876	  'page_alloc.shuffle' kernel command line parameter.
1877
1878	  Say Y if unsure.
1879
1880config SLUB_CPU_PARTIAL
1881	default y
1882	depends on SLUB && SMP
1883	bool "SLUB per cpu partial cache"
1884	help
1885	  Per cpu partial caches accelerate objects allocation and freeing
1886	  that is local to a processor at the price of more indeterminism
1887	  in the latency of the free. On overflow these caches will be cleared
1888	  which requires the taking of locks that may cause latency spikes.
1889	  Typically one would choose no for a realtime system.
1890
1891config MMAP_ALLOW_UNINITIALIZED
1892	bool "Allow mmapped anonymous memory to be uninitialized"
1893	depends on EXPERT && !MMU
1894	default n
1895	help
1896	  Normally, and according to the Linux spec, anonymous memory obtained
1897	  from mmap() has its contents cleared before it is passed to
1898	  userspace.  Enabling this config option allows you to request that
1899	  mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1900	  providing a huge performance boost.  If this option is not enabled,
1901	  then the flag will be ignored.
1902
1903	  This is taken advantage of by uClibc's malloc(), and also by
1904	  ELF-FDPIC binfmt's brk and stack allocator.
1905
1906	  Because of the obvious security issues, this option should only be
1907	  enabled on embedded devices where you control what is run in
1908	  userspace.  Since that isn't generally a problem on no-MMU systems,
1909	  it is normally safe to say Y here.
1910
1911	  See Documentation/nommu-mmap.txt for more information.
1912
1913config SYSTEM_DATA_VERIFICATION
1914	def_bool n
1915	select SYSTEM_TRUSTED_KEYRING
1916	select KEYS
1917	select CRYPTO
1918	select CRYPTO_RSA
1919	select ASYMMETRIC_KEY_TYPE
1920	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1921	select ASN1
1922	select OID_REGISTRY
1923	select X509_CERTIFICATE_PARSER
1924	select PKCS7_MESSAGE_PARSER
1925	help
1926	  Provide PKCS#7 message verification using the contents of the system
1927	  trusted keyring to provide public keys.  This then can be used for
1928	  module verification, kexec image verification and firmware blob
1929	  verification.
1930
1931config PROFILING
1932	bool "Profiling support"
1933	help
1934	  Say Y here to enable the extended profiling support mechanisms used
1935	  by profilers such as OProfile.
1936
1937#
1938# Place an empty function call at each tracepoint site. Can be
1939# dynamically changed for a probe function.
1940#
1941config TRACEPOINTS
1942	bool
1943
1944endmenu		# General setup
1945
1946source "arch/Kconfig"
1947
1948config RT_MUTEXES
1949	bool
1950
1951config BASE_SMALL
1952	int
1953	default 0 if BASE_FULL
1954	default 1 if !BASE_FULL
1955
1956config MODULE_SIG_FORMAT
1957	def_bool n
1958	select SYSTEM_DATA_VERIFICATION
1959
1960menuconfig MODULES
1961	bool "Enable loadable module support"
1962	option modules
1963	help
1964	  Kernel modules are small pieces of compiled code which can
1965	  be inserted in the running kernel, rather than being
1966	  permanently built into the kernel.  You use the "modprobe"
1967	  tool to add (and sometimes remove) them.  If you say Y here,
1968	  many parts of the kernel can be built as modules (by
1969	  answering M instead of Y where indicated): this is most
1970	  useful for infrequently used options which are not required
1971	  for booting.  For more information, see the man pages for
1972	  modprobe, lsmod, modinfo, insmod and rmmod.
1973
1974	  If you say Y here, you will need to run "make
1975	  modules_install" to put the modules under /lib/modules/
1976	  where modprobe can find them (you may need to be root to do
1977	  this).
1978
1979	  If unsure, say Y.
1980
1981if MODULES
1982
1983config MODULE_FORCE_LOAD
1984	bool "Forced module loading"
1985	default n
1986	help
1987	  Allow loading of modules without version information (ie. modprobe
1988	  --force).  Forced module loading sets the 'F' (forced) taint flag and
1989	  is usually a really bad idea.
1990
1991config MODULE_UNLOAD
1992	bool "Module unloading"
1993	help
1994	  Without this option you will not be able to unload any
1995	  modules (note that some modules may not be unloadable
1996	  anyway), which makes your kernel smaller, faster
1997	  and simpler.  If unsure, say Y.
1998
1999config MODULE_FORCE_UNLOAD
2000	bool "Forced module unloading"
2001	depends on MODULE_UNLOAD
2002	help
2003	  This option allows you to force a module to unload, even if the
2004	  kernel believes it is unsafe: the kernel will remove the module
2005	  without waiting for anyone to stop using it (using the -f option to
2006	  rmmod).  This is mainly for kernel developers and desperate users.
2007	  If unsure, say N.
2008
2009config MODVERSIONS
2010	bool "Module versioning support"
2011	help
2012	  Usually, you have to use modules compiled with your kernel.
2013	  Saying Y here makes it sometimes possible to use modules
2014	  compiled for different kernels, by adding enough information
2015	  to the modules to (hopefully) spot any changes which would
2016	  make them incompatible with the kernel you are running.  If
2017	  unsure, say N.
2018
2019config ASM_MODVERSIONS
2020	bool
2021	default HAVE_ASM_MODVERSIONS && MODVERSIONS
2022	help
2023	  This enables module versioning for exported symbols also from
2024	  assembly. This can be enabled only when the target architecture
2025	  supports it.
2026
2027config MODULE_REL_CRCS
2028	bool
2029	depends on MODVERSIONS
2030
2031config MODULE_SRCVERSION_ALL
2032	bool "Source checksum for all modules"
2033	help
2034	  Modules which contain a MODULE_VERSION get an extra "srcversion"
2035	  field inserted into their modinfo section, which contains a
2036    	  sum of the source files which made it.  This helps maintainers
2037	  see exactly which source was used to build a module (since
2038	  others sometimes change the module source without updating
2039	  the version).  With this option, such a "srcversion" field
2040	  will be created for all modules.  If unsure, say N.
2041
2042config MODULE_SIG
2043	bool "Module signature verification"
2044	select MODULE_SIG_FORMAT
2045	help
2046	  Check modules for valid signatures upon load: the signature
2047	  is simply appended to the module. For more information see
2048	  <file:Documentation/admin-guide/module-signing.rst>.
2049
2050	  Note that this option adds the OpenSSL development packages as a
2051	  kernel build dependency so that the signing tool can use its crypto
2052	  library.
2053
2054	  You should enable this option if you wish to use either
2055	  CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2056	  another LSM - otherwise unsigned modules will be loadable regardless
2057	  of the lockdown policy.
2058
2059	  !!!WARNING!!!  If you enable this option, you MUST make sure that the
2060	  module DOES NOT get stripped after being signed.  This includes the
2061	  debuginfo strip done by some packagers (such as rpmbuild) and
2062	  inclusion into an initramfs that wants the module size reduced.
2063
2064config MODULE_SIG_FORCE
2065	bool "Require modules to be validly signed"
2066	depends on MODULE_SIG
2067	help
2068	  Reject unsigned modules or signed modules for which we don't have a
2069	  key.  Without this, such modules will simply taint the kernel.
2070
2071config MODULE_SIG_ALL
2072	bool "Automatically sign all modules"
2073	default y
2074	depends on MODULE_SIG
2075	help
2076	  Sign all modules during make modules_install. Without this option,
2077	  modules must be signed manually, using the scripts/sign-file tool.
2078
2079comment "Do not forget to sign required modules with scripts/sign-file"
2080	depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2081
2082choice
2083	prompt "Which hash algorithm should modules be signed with?"
2084	depends on MODULE_SIG
2085	help
2086	  This determines which sort of hashing algorithm will be used during
2087	  signature generation.  This algorithm _must_ be built into the kernel
2088	  directly so that signature verification can take place.  It is not
2089	  possible to load a signed module containing the algorithm to check
2090	  the signature on that module.
2091
2092config MODULE_SIG_SHA1
2093	bool "Sign modules with SHA-1"
2094	select CRYPTO_SHA1
2095
2096config MODULE_SIG_SHA224
2097	bool "Sign modules with SHA-224"
2098	select CRYPTO_SHA256
2099
2100config MODULE_SIG_SHA256
2101	bool "Sign modules with SHA-256"
2102	select CRYPTO_SHA256
2103
2104config MODULE_SIG_SHA384
2105	bool "Sign modules with SHA-384"
2106	select CRYPTO_SHA512
2107
2108config MODULE_SIG_SHA512
2109	bool "Sign modules with SHA-512"
2110	select CRYPTO_SHA512
2111
2112endchoice
2113
2114config MODULE_SIG_HASH
2115	string
2116	depends on MODULE_SIG
2117	default "sha1" if MODULE_SIG_SHA1
2118	default "sha224" if MODULE_SIG_SHA224
2119	default "sha256" if MODULE_SIG_SHA256
2120	default "sha384" if MODULE_SIG_SHA384
2121	default "sha512" if MODULE_SIG_SHA512
2122
2123config MODULE_COMPRESS
2124	bool "Compress modules on installation"
2125	help
2126
2127	  Compresses kernel modules when 'make modules_install' is run; gzip or
2128	  xz depending on "Compression algorithm" below.
2129
2130	  module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2131
2132	  Out-of-tree kernel modules installed using Kbuild will also be
2133	  compressed upon installation.
2134
2135	  Note: for modules inside an initrd or initramfs, it's more efficient
2136	  to compress the whole initrd or initramfs instead.
2137
2138	  Note: This is fully compatible with signed modules.
2139
2140	  If in doubt, say N.
2141
2142choice
2143	prompt "Compression algorithm"
2144	depends on MODULE_COMPRESS
2145	default MODULE_COMPRESS_GZIP
2146	help
2147	  This determines which sort of compression will be used during
2148	  'make modules_install'.
2149
2150	  GZIP (default) and XZ are supported.
2151
2152config MODULE_COMPRESS_GZIP
2153	bool "GZIP"
2154
2155config MODULE_COMPRESS_XZ
2156	bool "XZ"
2157
2158endchoice
2159
2160config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2161	bool "Allow loading of modules with missing namespace imports"
2162	help
2163	  Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2164	  a namespace. A module that makes use of a symbol exported with such a
2165	  namespace is required to import the namespace via MODULE_IMPORT_NS().
2166	  There is no technical reason to enforce correct namespace imports,
2167	  but it creates consistency between symbols defining namespaces and
2168	  users importing namespaces they make use of. This option relaxes this
2169	  requirement and lifts the enforcement when loading a module.
2170
2171	  If unsure, say N.
2172
2173config UNUSED_SYMBOLS
2174	bool "Enable unused/obsolete exported symbols"
2175	default y if X86
2176	help
2177	  Unused but exported symbols make the kernel needlessly bigger.  For
2178	  that reason most of these unused exports will soon be removed.  This
2179	  option is provided temporarily to provide a transition period in case
2180	  some external kernel module needs one of these symbols anyway. If you
2181	  encounter such a case in your module, consider if you are actually
2182	  using the right API.  (rationale: since nobody in the kernel is using
2183	  this in a module, there is a pretty good chance it's actually the
2184	  wrong interface to use).  If you really need the symbol, please send a
2185	  mail to the linux kernel mailing list mentioning the symbol and why
2186	  you really need it, and what the merge plan to the mainline kernel for
2187	  your module is.
2188
2189config TRIM_UNUSED_KSYMS
2190	bool "Trim unused exported kernel symbols"
2191	depends on !UNUSED_SYMBOLS
2192	help
2193	  The kernel and some modules make many symbols available for
2194	  other modules to use via EXPORT_SYMBOL() and variants. Depending
2195	  on the set of modules being selected in your kernel configuration,
2196	  many of those exported symbols might never be used.
2197
2198	  This option allows for unused exported symbols to be dropped from
2199	  the build. In turn, this provides the compiler more opportunities
2200	  (especially when using LTO) for optimizing the code and reducing
2201	  binary size.  This might have some security advantages as well.
2202
2203	  If unsure, or if you need to build out-of-tree modules, say N.
2204
2205config UNUSED_KSYMS_WHITELIST
2206	string "Whitelist of symbols to keep in ksymtab"
2207	depends on TRIM_UNUSED_KSYMS
2208	help
2209	  By default, all unused exported symbols will be un-exported from the
2210	  build when TRIM_UNUSED_KSYMS is selected.
2211
2212	  UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
2213	  exported at all times, even in absence of in-tree users. The value to
2214	  set here is the path to a text file containing the list of symbols,
2215	  one per line. The path can be absolute, or relative to the kernel
2216	  source tree.
2217
2218endif # MODULES
2219
2220config MODULES_TREE_LOOKUP
2221	def_bool y
2222	depends on PERF_EVENTS || TRACING
2223
2224config INIT_ALL_POSSIBLE
2225	bool
2226	help
2227	  Back when each arch used to define their own cpu_online_mask and
2228	  cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2229	  with all 1s, and others with all 0s.  When they were centralised,
2230	  it was better to provide this option than to break all the archs
2231	  and have several arch maintainers pursuing me down dark alleys.
2232
2233source "block/Kconfig"
2234
2235config PREEMPT_NOTIFIERS
2236	bool
2237
2238config PADATA
2239	depends on SMP
2240	bool
2241
2242config ASN1
2243	tristate
2244	help
2245	  Build a simple ASN.1 grammar compiler that produces a bytecode output
2246	  that can be interpreted by the ASN.1 stream decoder and used to
2247	  inform it as to what tags are to be expected in a stream and what
2248	  functions to call on what tags.
2249
2250source "kernel/Kconfig.locks"
2251
2252config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2253	bool
2254
2255config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2256	bool
2257
2258# It may be useful for an architecture to override the definitions of the
2259# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2260# and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2261# different calling convention for syscalls. They can also override the
2262# macros for not-implemented syscalls in kernel/sys_ni.c and
2263# kernel/time/posix-stubs.c. All these overrides need to be available in
2264# <asm/syscall_wrapper.h>.
2265config ARCH_HAS_SYSCALL_WRAPPER
2266	def_bool n
2267