xref: /openbmc/linux/init/Kconfig (revision 37744fee)
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 CLANG_VERSION
27	int
28	default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
29
30config CC_CAN_LINK
31	def_bool $(success,$(srctree)/scripts/cc-can-link.sh $(CC))
32
33config CC_HAS_ASM_GOTO
34	def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
35
36config TOOLS_SUPPORT_RELR
37	def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
38
39config CC_HAS_ASM_INLINE
40	def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
41
42config CONSTRUCTORS
43	bool
44	depends on !UML
45
46config IRQ_WORK
47	bool
48
49config BUILDTIME_TABLE_SORT
50	bool
51
52config THREAD_INFO_IN_TASK
53	bool
54	help
55	  Select this to move thread_info off the stack into task_struct.  To
56	  make this work, an arch will need to remove all thread_info fields
57	  except flags and fix any runtime bugs.
58
59	  One subtle change that will be needed is to use try_get_task_stack()
60	  and put_task_stack() in save_thread_stack_tsk() and get_wchan().
61
62menu "General setup"
63
64config BROKEN
65	bool
66
67config BROKEN_ON_SMP
68	bool
69	depends on BROKEN || !SMP
70	default y
71
72config INIT_ENV_ARG_LIMIT
73	int
74	default 32 if !UML
75	default 128 if UML
76	help
77	  Maximum of each of the number of arguments and environment
78	  variables passed to init from the kernel command line.
79
80config COMPILE_TEST
81	bool "Compile also drivers which will not load"
82	depends on !UML
83	default n
84	help
85	  Some drivers can be compiled on a different platform than they are
86	  intended to be run on. Despite they cannot be loaded there (or even
87	  when they load they cannot be used due to missing HW support),
88	  developers still, opposing to distributors, might want to build such
89	  drivers to compile-test them.
90
91	  If you are a developer and want to build everything available, say Y
92	  here. If you are a user/distributor, say N here to exclude useless
93	  drivers to be distributed.
94
95config UAPI_HEADER_TEST
96	bool "Compile test UAPI headers"
97	depends on HEADERS_INSTALL && CC_CAN_LINK
98	help
99	  Compile test headers exported to user-space to ensure they are
100	  self-contained, i.e. compilable as standalone units.
101
102	  If you are a developer or tester and want to ensure the exported
103	  headers are self-contained, say Y here. Otherwise, choose N.
104
105config LOCALVERSION
106	string "Local version - append to kernel release"
107	help
108	  Append an extra string to the end of your kernel version.
109	  This will show up when you type uname, for example.
110	  The string you set here will be appended after the contents of
111	  any files with a filename matching localversion* in your
112	  object and source tree, in that order.  Your total string can
113	  be a maximum of 64 characters.
114
115config LOCALVERSION_AUTO
116	bool "Automatically append version information to the version string"
117	default y
118	depends on !COMPILE_TEST
119	help
120	  This will try to automatically determine if the current tree is a
121	  release tree by looking for git tags that belong to the current
122	  top of tree revision.
123
124	  A string of the format -gxxxxxxxx will be added to the localversion
125	  if a git-based tree is found.  The string generated by this will be
126	  appended after any matching localversion* files, and after the value
127	  set in CONFIG_LOCALVERSION.
128
129	  (The actual string used here is the first eight characters produced
130	  by running the command:
131
132	    $ git rev-parse --verify HEAD
133
134	  which is done within the script "scripts/setlocalversion".)
135
136config BUILD_SALT
137	string "Build ID Salt"
138	default ""
139	help
140	  The build ID is used to link binaries and their debug info. Setting
141	  this option will use the value in the calculation of the build id.
142	  This is mostly useful for distributions which want to ensure the
143	  build is unique between builds. It's safe to leave the default.
144
145config HAVE_KERNEL_GZIP
146	bool
147
148config HAVE_KERNEL_BZIP2
149	bool
150
151config HAVE_KERNEL_LZMA
152	bool
153
154config HAVE_KERNEL_XZ
155	bool
156
157config HAVE_KERNEL_LZO
158	bool
159
160config HAVE_KERNEL_LZ4
161	bool
162
163config HAVE_KERNEL_UNCOMPRESSED
164	bool
165
166choice
167	prompt "Kernel compression mode"
168	default KERNEL_GZIP
169	depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED
170	help
171	  The linux kernel is a kind of self-extracting executable.
172	  Several compression algorithms are available, which differ
173	  in efficiency, compression and decompression speed.
174	  Compression speed is only relevant when building a kernel.
175	  Decompression speed is relevant at each boot.
176
177	  If you have any problems with bzip2 or lzma compressed
178	  kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
179	  version of this functionality (bzip2 only), for 2.4, was
180	  supplied by Christian Ludwig)
181
182	  High compression options are mostly useful for users, who
183	  are low on disk space (embedded systems), but for whom ram
184	  size matters less.
185
186	  If in doubt, select 'gzip'
187
188config KERNEL_GZIP
189	bool "Gzip"
190	depends on HAVE_KERNEL_GZIP
191	help
192	  The old and tried gzip compression. It provides a good balance
193	  between compression ratio and decompression speed.
194
195config KERNEL_BZIP2
196	bool "Bzip2"
197	depends on HAVE_KERNEL_BZIP2
198	help
199	  Its compression ratio and speed is intermediate.
200	  Decompression speed is slowest among the choices.  The kernel
201	  size is about 10% smaller with bzip2, in comparison to gzip.
202	  Bzip2 uses a large amount of memory. For modern kernels you
203	  will need at least 8MB RAM or more for booting.
204
205config KERNEL_LZMA
206	bool "LZMA"
207	depends on HAVE_KERNEL_LZMA
208	help
209	  This compression algorithm's ratio is best.  Decompression speed
210	  is between gzip and bzip2.  Compression is slowest.
211	  The kernel size is about 33% smaller with LZMA in comparison to gzip.
212
213config KERNEL_XZ
214	bool "XZ"
215	depends on HAVE_KERNEL_XZ
216	help
217	  XZ uses the LZMA2 algorithm and instruction set specific
218	  BCJ filters which can improve compression ratio of executable
219	  code. The size of the kernel is about 30% smaller with XZ in
220	  comparison to gzip. On architectures for which there is a BCJ
221	  filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
222	  will create a few percent smaller kernel than plain LZMA.
223
224	  The speed is about the same as with LZMA: The decompression
225	  speed of XZ is better than that of bzip2 but worse than gzip
226	  and LZO. Compression is slow.
227
228config KERNEL_LZO
229	bool "LZO"
230	depends on HAVE_KERNEL_LZO
231	help
232	  Its compression ratio is the poorest among the choices. The kernel
233	  size is about 10% bigger than gzip; however its speed
234	  (both compression and decompression) is the fastest.
235
236config KERNEL_LZ4
237	bool "LZ4"
238	depends on HAVE_KERNEL_LZ4
239	help
240	  LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
241	  A preliminary version of LZ4 de/compression tool is available at
242	  <https://code.google.com/p/lz4/>.
243
244	  Its compression ratio is worse than LZO. The size of the kernel
245	  is about 8% bigger than LZO. But the decompression speed is
246	  faster than LZO.
247
248config KERNEL_UNCOMPRESSED
249	bool "None"
250	depends on HAVE_KERNEL_UNCOMPRESSED
251	help
252	  Produce uncompressed kernel image. This option is usually not what
253	  you want. It is useful for debugging the kernel in slow simulation
254	  environments, where decompressing and moving the kernel is awfully
255	  slow. This option allows early boot code to skip the decompressor
256	  and jump right at uncompressed kernel image.
257
258endchoice
259
260config DEFAULT_HOSTNAME
261	string "Default hostname"
262	default "(none)"
263	help
264	  This option determines the default system hostname before userspace
265	  calls sethostname(2). The kernel traditionally uses "(none)" here,
266	  but you may wish to use a different default here to make a minimal
267	  system more usable with less configuration.
268
269#
270# For some reason microblaze and nios2 hard code SWAP=n.  Hopefully we can
271# add proper SWAP support to them, in which case this can be remove.
272#
273config ARCH_NO_SWAP
274	bool
275
276config SWAP
277	bool "Support for paging of anonymous memory (swap)"
278	depends on MMU && BLOCK && !ARCH_NO_SWAP
279	default y
280	help
281	  This option allows you to choose whether you want to have support
282	  for so called swap devices or swap files in your kernel that are
283	  used to provide more virtual memory than the actual RAM present
284	  in your computer.  If unsure say Y.
285
286config SYSVIPC
287	bool "System V IPC"
288	---help---
289	  Inter Process Communication is a suite of library functions and
290	  system calls which let processes (running programs) synchronize and
291	  exchange information. It is generally considered to be a good thing,
292	  and some programs won't run unless you say Y here. In particular, if
293	  you want to run the DOS emulator dosemu under Linux (read the
294	  DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
295	  you'll need to say Y here.
296
297	  You can find documentation about IPC with "info ipc" and also in
298	  section 6.4 of the Linux Programmer's Guide, available from
299	  <http://www.tldp.org/guides.html>.
300
301config SYSVIPC_SYSCTL
302	bool
303	depends on SYSVIPC
304	depends on SYSCTL
305	default y
306
307config POSIX_MQUEUE
308	bool "POSIX Message Queues"
309	depends on NET
310	---help---
311	  POSIX variant of message queues is a part of IPC. In POSIX message
312	  queues every message has a priority which decides about succession
313	  of receiving it by a process. If you want to compile and run
314	  programs written e.g. for Solaris with use of its POSIX message
315	  queues (functions mq_*) say Y here.
316
317	  POSIX message queues are visible as a filesystem called 'mqueue'
318	  and can be mounted somewhere if you want to do filesystem
319	  operations on message queues.
320
321	  If unsure, say Y.
322
323config POSIX_MQUEUE_SYSCTL
324	bool
325	depends on POSIX_MQUEUE
326	depends on SYSCTL
327	default y
328
329config CROSS_MEMORY_ATTACH
330	bool "Enable process_vm_readv/writev syscalls"
331	depends on MMU
332	default y
333	help
334	  Enabling this option adds the system calls process_vm_readv and
335	  process_vm_writev which allow a process with the correct privileges
336	  to directly read from or write to another process' address space.
337	  See the man page for more details.
338
339config USELIB
340	bool "uselib syscall"
341	def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
342	help
343	  This option enables the uselib syscall, a system call used in the
344	  dynamic linker from libc5 and earlier.  glibc does not use this
345	  system call.  If you intend to run programs built on libc5 or
346	  earlier, you may need to enable this syscall.  Current systems
347	  running glibc can safely disable this.
348
349config AUDIT
350	bool "Auditing support"
351	depends on NET
352	help
353	  Enable auditing infrastructure that can be used with another
354	  kernel subsystem, such as SELinux (which requires this for
355	  logging of avc messages output).  System call auditing is included
356	  on architectures which support it.
357
358config HAVE_ARCH_AUDITSYSCALL
359	bool
360
361config AUDITSYSCALL
362	def_bool y
363	depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
364	select FSNOTIFY
365
366source "kernel/irq/Kconfig"
367source "kernel/time/Kconfig"
368source "kernel/Kconfig.preempt"
369
370menu "CPU/Task time and stats accounting"
371
372config VIRT_CPU_ACCOUNTING
373	bool
374
375choice
376	prompt "Cputime accounting"
377	default TICK_CPU_ACCOUNTING if !PPC64
378	default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
379
380# Kind of a stub config for the pure tick based cputime accounting
381config TICK_CPU_ACCOUNTING
382	bool "Simple tick based cputime accounting"
383	depends on !S390 && !NO_HZ_FULL
384	help
385	  This is the basic tick based cputime accounting that maintains
386	  statistics about user, system and idle time spent on per jiffies
387	  granularity.
388
389	  If unsure, say Y.
390
391config VIRT_CPU_ACCOUNTING_NATIVE
392	bool "Deterministic task and CPU time accounting"
393	depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
394	select VIRT_CPU_ACCOUNTING
395	help
396	  Select this option to enable more accurate task and CPU time
397	  accounting.  This is done by reading a CPU counter on each
398	  kernel entry and exit and on transitions within the kernel
399	  between system, softirq and hardirq state, so there is a
400	  small performance impact.  In the case of s390 or IBM POWER > 5,
401	  this also enables accounting of stolen time on logically-partitioned
402	  systems.
403
404config VIRT_CPU_ACCOUNTING_GEN
405	bool "Full dynticks CPU time accounting"
406	depends on HAVE_CONTEXT_TRACKING
407	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
408	depends on GENERIC_CLOCKEVENTS
409	select VIRT_CPU_ACCOUNTING
410	select CONTEXT_TRACKING
411	help
412	  Select this option to enable task and CPU time accounting on full
413	  dynticks systems. This accounting is implemented by watching every
414	  kernel-user boundaries using the context tracking subsystem.
415	  The accounting is thus performed at the expense of some significant
416	  overhead.
417
418	  For now this is only useful if you are working on the full
419	  dynticks subsystem development.
420
421	  If unsure, say N.
422
423endchoice
424
425config IRQ_TIME_ACCOUNTING
426	bool "Fine granularity task level IRQ time accounting"
427	depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
428	help
429	  Select this option to enable fine granularity task irq time
430	  accounting. This is done by reading a timestamp on each
431	  transitions between softirq and hardirq state, so there can be a
432	  small performance impact.
433
434	  If in doubt, say N here.
435
436config HAVE_SCHED_AVG_IRQ
437	def_bool y
438	depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
439	depends on SMP
440
441config SCHED_THERMAL_PRESSURE
442	bool "Enable periodic averaging of thermal pressure"
443	depends on SMP
444
445config BSD_PROCESS_ACCT
446	bool "BSD Process Accounting"
447	depends on MULTIUSER
448	help
449	  If you say Y here, a user level program will be able to instruct the
450	  kernel (via a special system call) to write process accounting
451	  information to a file: whenever a process exits, information about
452	  that process will be appended to the file by the kernel.  The
453	  information includes things such as creation time, owning user,
454	  command name, memory usage, controlling terminal etc. (the complete
455	  list is in the struct acct in <file:include/linux/acct.h>).  It is
456	  up to the user level program to do useful things with this
457	  information.  This is generally a good idea, so say Y.
458
459config BSD_PROCESS_ACCT_V3
460	bool "BSD Process Accounting version 3 file format"
461	depends on BSD_PROCESS_ACCT
462	default n
463	help
464	  If you say Y here, the process accounting information is written
465	  in a new file format that also logs the process IDs of each
466	  process and its parent. Note that this file format is incompatible
467	  with previous v0/v1/v2 file formats, so you will need updated tools
468	  for processing it. A preliminary version of these tools is available
469	  at <http://www.gnu.org/software/acct/>.
470
471config TASKSTATS
472	bool "Export task/process statistics through netlink"
473	depends on NET
474	depends on MULTIUSER
475	default n
476	help
477	  Export selected statistics for tasks/processes through the
478	  generic netlink interface. Unlike BSD process accounting, the
479	  statistics are available during the lifetime of tasks/processes as
480	  responses to commands. Like BSD accounting, they are sent to user
481	  space on task exit.
482
483	  Say N if unsure.
484
485config TASK_DELAY_ACCT
486	bool "Enable per-task delay accounting"
487	depends on TASKSTATS
488	select SCHED_INFO
489	help
490	  Collect information on time spent by a task waiting for system
491	  resources like cpu, synchronous block I/O completion and swapping
492	  in pages. Such statistics can help in setting a task's priorities
493	  relative to other tasks for cpu, io, rss limits etc.
494
495	  Say N if unsure.
496
497config TASK_XACCT
498	bool "Enable extended accounting over taskstats"
499	depends on TASKSTATS
500	help
501	  Collect extended task accounting data and send the data
502	  to userland for processing over the taskstats interface.
503
504	  Say N if unsure.
505
506config TASK_IO_ACCOUNTING
507	bool "Enable per-task storage I/O accounting"
508	depends on TASK_XACCT
509	help
510	  Collect information on the number of bytes of storage I/O which this
511	  task has caused.
512
513	  Say N if unsure.
514
515config PSI
516	bool "Pressure stall information tracking"
517	help
518	  Collect metrics that indicate how overcommitted the CPU, memory,
519	  and IO capacity are in the system.
520
521	  If you say Y here, the kernel will create /proc/pressure/ with the
522	  pressure statistics files cpu, memory, and io. These will indicate
523	  the share of walltime in which some or all tasks in the system are
524	  delayed due to contention of the respective resource.
525
526	  In kernels with cgroup support, cgroups (cgroup2 only) will
527	  have cpu.pressure, memory.pressure, and io.pressure files,
528	  which aggregate pressure stalls for the grouped tasks only.
529
530	  For more details see Documentation/accounting/psi.rst.
531
532	  Say N if unsure.
533
534config PSI_DEFAULT_DISABLED
535	bool "Require boot parameter to enable pressure stall information tracking"
536	default n
537	depends on PSI
538	help
539	  If set, pressure stall information tracking will be disabled
540	  per default but can be enabled through passing psi=1 on the
541	  kernel commandline during boot.
542
543	  This feature adds some code to the task wakeup and sleep
544	  paths of the scheduler. The overhead is too low to affect
545	  common scheduling-intense workloads in practice (such as
546	  webservers, memcache), but it does show up in artificial
547	  scheduler stress tests, such as hackbench.
548
549	  If you are paranoid and not sure what the kernel will be
550	  used for, say Y.
551
552	  Say N if unsure.
553
554endmenu # "CPU/Task time and stats accounting"
555
556config CPU_ISOLATION
557	bool "CPU isolation"
558	depends on SMP || COMPILE_TEST
559	default y
560	help
561	  Make sure that CPUs running critical tasks are not disturbed by
562	  any source of "noise" such as unbound workqueues, timers, kthreads...
563	  Unbound jobs get offloaded to housekeeping CPUs. This is driven by
564	  the "isolcpus=" boot parameter.
565
566	  Say Y if unsure.
567
568source "kernel/rcu/Kconfig"
569
570config BUILD_BIN2C
571	bool
572	default n
573
574config IKCONFIG
575	tristate "Kernel .config support"
576	---help---
577	  This option enables the complete Linux kernel ".config" file
578	  contents to be saved in the kernel. It provides documentation
579	  of which kernel options are used in a running kernel or in an
580	  on-disk kernel.  This information can be extracted from the kernel
581	  image file with the script scripts/extract-ikconfig and used as
582	  input to rebuild the current kernel or to build another kernel.
583	  It can also be extracted from a running kernel by reading
584	  /proc/config.gz if enabled (below).
585
586config IKCONFIG_PROC
587	bool "Enable access to .config through /proc/config.gz"
588	depends on IKCONFIG && PROC_FS
589	---help---
590	  This option enables access to the kernel configuration file
591	  through /proc/config.gz.
592
593config IKHEADERS
594	tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
595	depends on SYSFS
596	help
597	  This option enables access to the in-kernel headers that are generated during
598	  the build process. These can be used to build eBPF tracing programs,
599	  or similar programs.  If you build the headers as a module, a module called
600	  kheaders.ko is built which can be loaded on-demand to get access to headers.
601
602config LOG_BUF_SHIFT
603	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
604	range 12 25
605	default 17
606	depends on PRINTK
607	help
608	  Select the minimal kernel log buffer size as a power of 2.
609	  The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
610	  parameter, see below. Any higher size also might be forced
611	  by "log_buf_len" boot parameter.
612
613	  Examples:
614		     17 => 128 KB
615		     16 => 64 KB
616		     15 => 32 KB
617		     14 => 16 KB
618		     13 =>  8 KB
619		     12 =>  4 KB
620
621config LOG_CPU_MAX_BUF_SHIFT
622	int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
623	depends on SMP
624	range 0 21
625	default 12 if !BASE_SMALL
626	default 0 if BASE_SMALL
627	depends on PRINTK
628	help
629	  This option allows to increase the default ring buffer size
630	  according to the number of CPUs. The value defines the contribution
631	  of each CPU as a power of 2. The used space is typically only few
632	  lines however it might be much more when problems are reported,
633	  e.g. backtraces.
634
635	  The increased size means that a new buffer has to be allocated and
636	  the original static one is unused. It makes sense only on systems
637	  with more CPUs. Therefore this value is used only when the sum of
638	  contributions is greater than the half of the default kernel ring
639	  buffer as defined by LOG_BUF_SHIFT. The default values are set
640	  so that more than 64 CPUs are needed to trigger the allocation.
641
642	  Also this option is ignored when "log_buf_len" kernel parameter is
643	  used as it forces an exact (power of two) size of the ring buffer.
644
645	  The number of possible CPUs is used for this computation ignoring
646	  hotplugging making the computation optimal for the worst case
647	  scenario while allowing a simple algorithm to be used from bootup.
648
649	  Examples shift values and their meaning:
650		     17 => 128 KB for each CPU
651		     16 =>  64 KB for each CPU
652		     15 =>  32 KB for each CPU
653		     14 =>  16 KB for each CPU
654		     13 =>   8 KB for each CPU
655		     12 =>   4 KB for each CPU
656
657config PRINTK_SAFE_LOG_BUF_SHIFT
658	int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
659	range 10 21
660	default 13
661	depends on PRINTK
662	help
663	  Select the size of an alternate printk per-CPU buffer where messages
664	  printed from usafe contexts are temporary stored. One example would
665	  be NMI messages, another one - printk recursion. The messages are
666	  copied to the main log buffer in a safe context to avoid a deadlock.
667	  The value defines the size as a power of 2.
668
669	  Those messages are rare and limited. The largest one is when
670	  a backtrace is printed. It usually fits into 4KB. Select
671	  8KB if you want to be on the safe side.
672
673	  Examples:
674		     17 => 128 KB for each CPU
675		     16 =>  64 KB for each CPU
676		     15 =>  32 KB for each CPU
677		     14 =>  16 KB for each CPU
678		     13 =>   8 KB for each CPU
679		     12 =>   4 KB for each CPU
680
681#
682# Architectures with an unreliable sched_clock() should select this:
683#
684config HAVE_UNSTABLE_SCHED_CLOCK
685	bool
686
687config GENERIC_SCHED_CLOCK
688	bool
689
690menu "Scheduler features"
691
692config UCLAMP_TASK
693	bool "Enable utilization clamping for RT/FAIR tasks"
694	depends on CPU_FREQ_GOV_SCHEDUTIL
695	help
696	  This feature enables the scheduler to track the clamped utilization
697	  of each CPU based on RUNNABLE tasks scheduled on that CPU.
698
699	  With this option, the user can specify the min and max CPU
700	  utilization allowed for RUNNABLE tasks. The max utilization defines
701	  the maximum frequency a task should use while the min utilization
702	  defines the minimum frequency it should use.
703
704	  Both min and max utilization clamp values are hints to the scheduler,
705	  aiming at improving its frequency selection policy, but they do not
706	  enforce or grant any specific bandwidth for tasks.
707
708	  If in doubt, say N.
709
710config UCLAMP_BUCKETS_COUNT
711	int "Number of supported utilization clamp buckets"
712	range 5 20
713	default 5
714	depends on UCLAMP_TASK
715	help
716	  Defines the number of clamp buckets to use. The range of each bucket
717	  will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
718	  number of clamp buckets the finer their granularity and the higher
719	  the precision of clamping aggregation and tracking at run-time.
720
721	  For example, with the minimum configuration value we will have 5
722	  clamp buckets tracking 20% utilization each. A 25% boosted tasks will
723	  be refcounted in the [20..39]% bucket and will set the bucket clamp
724	  effective value to 25%.
725	  If a second 30% boosted task should be co-scheduled on the same CPU,
726	  that task will be refcounted in the same bucket of the first task and
727	  it will boost the bucket clamp effective value to 30%.
728	  The clamp effective value of a bucket is reset to its nominal value
729	  (20% in the example above) when there are no more tasks refcounted in
730	  that bucket.
731
732	  An additional boost/capping margin can be added to some tasks. In the
733	  example above the 25% task will be boosted to 30% until it exits the
734	  CPU. If that should be considered not acceptable on certain systems,
735	  it's always possible to reduce the margin by increasing the number of
736	  clamp buckets to trade off used memory for run-time tracking
737	  precision.
738
739	  If in doubt, use the default value.
740
741endmenu
742
743#
744# For architectures that want to enable the support for NUMA-affine scheduler
745# balancing logic:
746#
747config ARCH_SUPPORTS_NUMA_BALANCING
748	bool
749
750#
751# For architectures that prefer to flush all TLBs after a number of pages
752# are unmapped instead of sending one IPI per page to flush. The architecture
753# must provide guarantees on what happens if a clean TLB cache entry is
754# written after the unmap. Details are in mm/rmap.c near the check for
755# should_defer_flush. The architecture should also consider if the full flush
756# and the refill costs are offset by the savings of sending fewer IPIs.
757config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
758	bool
759
760config CC_HAS_INT128
761	def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
762
763#
764# For architectures that know their GCC __int128 support is sound
765#
766config ARCH_SUPPORTS_INT128
767	bool
768
769# For architectures that (ab)use NUMA to represent different memory regions
770# all cpu-local but of different latencies, such as SuperH.
771#
772config ARCH_WANT_NUMA_VARIABLE_LOCALITY
773	bool
774
775config NUMA_BALANCING
776	bool "Memory placement aware NUMA scheduler"
777	depends on ARCH_SUPPORTS_NUMA_BALANCING
778	depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
779	depends on SMP && NUMA && MIGRATION
780	help
781	  This option adds support for automatic NUMA aware memory/task placement.
782	  The mechanism is quite primitive and is based on migrating memory when
783	  it has references to the node the task is running on.
784
785	  This system will be inactive on UMA systems.
786
787config NUMA_BALANCING_DEFAULT_ENABLED
788	bool "Automatically enable NUMA aware memory/task placement"
789	default y
790	depends on NUMA_BALANCING
791	help
792	  If set, automatic NUMA balancing will be enabled if running on a NUMA
793	  machine.
794
795menuconfig CGROUPS
796	bool "Control Group support"
797	select KERNFS
798	help
799	  This option adds support for grouping sets of processes together, for
800	  use with process control subsystems such as Cpusets, CFS, memory
801	  controls or device isolation.
802	  See
803		- Documentation/scheduler/sched-design-CFS.rst	(CFS)
804		- Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
805					  and resource control)
806
807	  Say N if unsure.
808
809if CGROUPS
810
811config PAGE_COUNTER
812	bool
813
814config MEMCG
815	bool "Memory controller"
816	select PAGE_COUNTER
817	select EVENTFD
818	help
819	  Provides control over the memory footprint of tasks in a cgroup.
820
821config MEMCG_SWAP
822	bool "Swap controller"
823	depends on MEMCG && SWAP
824	help
825	  Provides control over the swap space consumed by tasks in a cgroup.
826
827config MEMCG_SWAP_ENABLED
828	bool "Swap controller enabled by default"
829	depends on MEMCG_SWAP
830	default y
831	help
832	  Memory Resource Controller Swap Extension comes with its price in
833	  a bigger memory consumption. General purpose distribution kernels
834	  which want to enable the feature but keep it disabled by default
835	  and let the user enable it by swapaccount=1 boot command line
836	  parameter should have this option unselected.
837	  For those who want to have the feature enabled by default should
838	  select this option (if, for some reason, they need to disable it
839	  then swapaccount=0 does the trick).
840
841config MEMCG_KMEM
842	bool
843	depends on MEMCG && !SLOB
844	default y
845
846config BLK_CGROUP
847	bool "IO controller"
848	depends on BLOCK
849	default n
850	---help---
851	Generic block IO controller cgroup interface. This is the common
852	cgroup interface which should be used by various IO controlling
853	policies.
854
855	Currently, CFQ IO scheduler uses it to recognize task groups and
856	control disk bandwidth allocation (proportional time slice allocation)
857	to such task groups. It is also used by bio throttling logic in
858	block layer to implement upper limit in IO rates on a device.
859
860	This option only enables generic Block IO controller infrastructure.
861	One needs to also enable actual IO controlling logic/policy. For
862	enabling proportional weight division of disk bandwidth in CFQ, set
863	CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
864	CONFIG_BLK_DEV_THROTTLING=y.
865
866	See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
867
868config CGROUP_WRITEBACK
869	bool
870	depends on MEMCG && BLK_CGROUP
871	default y
872
873menuconfig CGROUP_SCHED
874	bool "CPU controller"
875	default n
876	help
877	  This feature lets CPU scheduler recognize task groups and control CPU
878	  bandwidth allocation to such task groups. It uses cgroups to group
879	  tasks.
880
881if CGROUP_SCHED
882config FAIR_GROUP_SCHED
883	bool "Group scheduling for SCHED_OTHER"
884	depends on CGROUP_SCHED
885	default CGROUP_SCHED
886
887config CFS_BANDWIDTH
888	bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
889	depends on FAIR_GROUP_SCHED
890	default n
891	help
892	  This option allows users to define CPU bandwidth rates (limits) for
893	  tasks running within the fair group scheduler.  Groups with no limit
894	  set are considered to be unconstrained and will run with no
895	  restriction.
896	  See Documentation/scheduler/sched-bwc.rst for more information.
897
898config RT_GROUP_SCHED
899	bool "Group scheduling for SCHED_RR/FIFO"
900	depends on CGROUP_SCHED
901	default n
902	help
903	  This feature lets you explicitly allocate real CPU bandwidth
904	  to task groups. If enabled, it will also make it impossible to
905	  schedule realtime tasks for non-root users until you allocate
906	  realtime bandwidth for them.
907	  See Documentation/scheduler/sched-rt-group.rst for more information.
908
909endif #CGROUP_SCHED
910
911config UCLAMP_TASK_GROUP
912	bool "Utilization clamping per group of tasks"
913	depends on CGROUP_SCHED
914	depends on UCLAMP_TASK
915	default n
916	help
917	  This feature enables the scheduler to track the clamped utilization
918	  of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
919
920	  When this option is enabled, the user can specify a min and max
921	  CPU bandwidth which is allowed for each single task in a group.
922	  The max bandwidth allows to clamp the maximum frequency a task
923	  can use, while the min bandwidth allows to define a minimum
924	  frequency a task will always use.
925
926	  When task group based utilization clamping is enabled, an eventually
927	  specified task-specific clamp value is constrained by the cgroup
928	  specified clamp value. Both minimum and maximum task clamping cannot
929	  be bigger than the corresponding clamping defined at task group level.
930
931	  If in doubt, say N.
932
933config CGROUP_PIDS
934	bool "PIDs controller"
935	help
936	  Provides enforcement of process number limits in the scope of a
937	  cgroup. Any attempt to fork more processes than is allowed in the
938	  cgroup will fail. PIDs are fundamentally a global resource because it
939	  is fairly trivial to reach PID exhaustion before you reach even a
940	  conservative kmemcg limit. As a result, it is possible to grind a
941	  system to halt without being limited by other cgroup policies. The
942	  PIDs controller is designed to stop this from happening.
943
944	  It should be noted that organisational operations (such as attaching
945	  to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
946	  since the PIDs limit only affects a process's ability to fork, not to
947	  attach to a cgroup.
948
949config CGROUP_RDMA
950	bool "RDMA controller"
951	help
952	  Provides enforcement of RDMA resources defined by IB stack.
953	  It is fairly easy for consumers to exhaust RDMA resources, which
954	  can result into resource unavailability to other consumers.
955	  RDMA controller is designed to stop this from happening.
956	  Attaching processes with active RDMA resources to the cgroup
957	  hierarchy is allowed even if can cross the hierarchy's limit.
958
959config CGROUP_FREEZER
960	bool "Freezer controller"
961	help
962	  Provides a way to freeze and unfreeze all tasks in a
963	  cgroup.
964
965	  This option affects the ORIGINAL cgroup interface. The cgroup2 memory
966	  controller includes important in-kernel memory consumers per default.
967
968	  If you're using cgroup2, say N.
969
970config CGROUP_HUGETLB
971	bool "HugeTLB controller"
972	depends on HUGETLB_PAGE
973	select PAGE_COUNTER
974	default n
975	help
976	  Provides a cgroup controller for HugeTLB pages.
977	  When you enable this, you can put a per cgroup limit on HugeTLB usage.
978	  The limit is enforced during page fault. Since HugeTLB doesn't
979	  support page reclaim, enforcing the limit at page fault time implies
980	  that, the application will get SIGBUS signal if it tries to access
981	  HugeTLB pages beyond its limit. This requires the application to know
982	  beforehand how much HugeTLB pages it would require for its use. The
983	  control group is tracked in the third page lru pointer. This means
984	  that we cannot use the controller with huge page less than 3 pages.
985
986config CPUSETS
987	bool "Cpuset controller"
988	depends on SMP
989	help
990	  This option will let you create and manage CPUSETs which
991	  allow dynamically partitioning a system into sets of CPUs and
992	  Memory Nodes and assigning tasks to run only within those sets.
993	  This is primarily useful on large SMP or NUMA systems.
994
995	  Say N if unsure.
996
997config PROC_PID_CPUSET
998	bool "Include legacy /proc/<pid>/cpuset file"
999	depends on CPUSETS
1000	default y
1001
1002config CGROUP_DEVICE
1003	bool "Device controller"
1004	help
1005	  Provides a cgroup controller implementing whitelists for
1006	  devices which a process in the cgroup can mknod or open.
1007
1008config CGROUP_CPUACCT
1009	bool "Simple CPU accounting controller"
1010	help
1011	  Provides a simple controller for monitoring the
1012	  total CPU consumed by the tasks in a cgroup.
1013
1014config CGROUP_PERF
1015	bool "Perf controller"
1016	depends on PERF_EVENTS
1017	help
1018	  This option extends the perf per-cpu mode to restrict monitoring
1019	  to threads which belong to the cgroup specified and run on the
1020	  designated cpu.  Or this can be used to have cgroup ID in samples
1021	  so that it can monitor performance events among cgroups.
1022
1023	  Say N if unsure.
1024
1025config CGROUP_BPF
1026	bool "Support for eBPF programs attached to cgroups"
1027	depends on BPF_SYSCALL
1028	select SOCK_CGROUP_DATA
1029	help
1030	  Allow attaching eBPF programs to a cgroup using the bpf(2)
1031	  syscall command BPF_PROG_ATTACH.
1032
1033	  In which context these programs are accessed depends on the type
1034	  of attachment. For instance, programs that are attached using
1035	  BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1036	  inet sockets.
1037
1038config CGROUP_DEBUG
1039	bool "Debug controller"
1040	default n
1041	depends on DEBUG_KERNEL
1042	help
1043	  This option enables a simple controller that exports
1044	  debugging information about the cgroups framework. This
1045	  controller is for control cgroup debugging only. Its
1046	  interfaces are not stable.
1047
1048	  Say N.
1049
1050config SOCK_CGROUP_DATA
1051	bool
1052	default n
1053
1054endif # CGROUPS
1055
1056menuconfig NAMESPACES
1057	bool "Namespaces support" if EXPERT
1058	depends on MULTIUSER
1059	default !EXPERT
1060	help
1061	  Provides the way to make tasks work with different objects using
1062	  the same id. For example same IPC id may refer to different objects
1063	  or same user id or pid may refer to different tasks when used in
1064	  different namespaces.
1065
1066if NAMESPACES
1067
1068config UTS_NS
1069	bool "UTS namespace"
1070	default y
1071	help
1072	  In this namespace tasks see different info provided with the
1073	  uname() system call
1074
1075config TIME_NS
1076	bool "TIME namespace"
1077	depends on GENERIC_VDSO_TIME_NS
1078	default y
1079	help
1080	  In this namespace boottime and monotonic clocks can be set.
1081	  The time will keep going with the same pace.
1082
1083config IPC_NS
1084	bool "IPC namespace"
1085	depends on (SYSVIPC || POSIX_MQUEUE)
1086	default y
1087	help
1088	  In this namespace tasks work with IPC ids which correspond to
1089	  different IPC objects in different namespaces.
1090
1091config USER_NS
1092	bool "User namespace"
1093	default n
1094	help
1095	  This allows containers, i.e. vservers, to use user namespaces
1096	  to provide different user info for different servers.
1097
1098	  When user namespaces are enabled in the kernel it is
1099	  recommended that the MEMCG option also be enabled and that
1100	  user-space use the memory control groups to limit the amount
1101	  of memory a memory unprivileged users can use.
1102
1103	  If unsure, say N.
1104
1105config PID_NS
1106	bool "PID Namespaces"
1107	default y
1108	help
1109	  Support process id namespaces.  This allows having multiple
1110	  processes with the same pid as long as they are in different
1111	  pid namespaces.  This is a building block of containers.
1112
1113config NET_NS
1114	bool "Network namespace"
1115	depends on NET
1116	default y
1117	help
1118	  Allow user space to create what appear to be multiple instances
1119	  of the network stack.
1120
1121endif # NAMESPACES
1122
1123config CHECKPOINT_RESTORE
1124	bool "Checkpoint/restore support"
1125	select PROC_CHILDREN
1126	default n
1127	help
1128	  Enables additional kernel features in a sake of checkpoint/restore.
1129	  In particular it adds auxiliary prctl codes to setup process text,
1130	  data and heap segment sizes, and a few additional /proc filesystem
1131	  entries.
1132
1133	  If unsure, say N here.
1134
1135config SCHED_AUTOGROUP
1136	bool "Automatic process group scheduling"
1137	select CGROUPS
1138	select CGROUP_SCHED
1139	select FAIR_GROUP_SCHED
1140	help
1141	  This option optimizes the scheduler for common desktop workloads by
1142	  automatically creating and populating task groups.  This separation
1143	  of workloads isolates aggressive CPU burners (like build jobs) from
1144	  desktop applications.  Task group autogeneration is currently based
1145	  upon task session.
1146
1147config SYSFS_DEPRECATED
1148	bool "Enable deprecated sysfs features to support old userspace tools"
1149	depends on SYSFS
1150	default n
1151	help
1152	  This option adds code that switches the layout of the "block" class
1153	  devices, to not show up in /sys/class/block/, but only in
1154	  /sys/block/.
1155
1156	  This switch is only active when the sysfs.deprecated=1 boot option is
1157	  passed or the SYSFS_DEPRECATED_V2 option is set.
1158
1159	  This option allows new kernels to run on old distributions and tools,
1160	  which might get confused by /sys/class/block/. Since 2007/2008 all
1161	  major distributions and tools handle this just fine.
1162
1163	  Recent distributions and userspace tools after 2009/2010 depend on
1164	  the existence of /sys/class/block/, and will not work with this
1165	  option enabled.
1166
1167	  Only if you are using a new kernel on an old distribution, you might
1168	  need to say Y here.
1169
1170config SYSFS_DEPRECATED_V2
1171	bool "Enable deprecated sysfs features by default"
1172	default n
1173	depends on SYSFS
1174	depends on SYSFS_DEPRECATED
1175	help
1176	  Enable deprecated sysfs by default.
1177
1178	  See the CONFIG_SYSFS_DEPRECATED option for more details about this
1179	  option.
1180
1181	  Only if you are using a new kernel on an old distribution, you might
1182	  need to say Y here. Even then, odds are you would not need it
1183	  enabled, you can always pass the boot option if absolutely necessary.
1184
1185config RELAY
1186	bool "Kernel->user space relay support (formerly relayfs)"
1187	select IRQ_WORK
1188	help
1189	  This option enables support for relay interface support in
1190	  certain file systems (such as debugfs).
1191	  It is designed to provide an efficient mechanism for tools and
1192	  facilities to relay large amounts of data from kernel space to
1193	  user space.
1194
1195	  If unsure, say N.
1196
1197config BLK_DEV_INITRD
1198	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1199	help
1200	  The initial RAM filesystem is a ramfs which is loaded by the
1201	  boot loader (loadlin or lilo) and that is mounted as root
1202	  before the normal boot procedure. It is typically used to
1203	  load modules needed to mount the "real" root file system,
1204	  etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1205
1206	  If RAM disk support (BLK_DEV_RAM) is also included, this
1207	  also enables initial RAM disk (initrd) support and adds
1208	  15 Kbytes (more on some other architectures) to the kernel size.
1209
1210	  If unsure say Y.
1211
1212if BLK_DEV_INITRD
1213
1214source "usr/Kconfig"
1215
1216endif
1217
1218config BOOT_CONFIG
1219	bool "Boot config support"
1220	select BLK_DEV_INITRD
1221	help
1222	  Extra boot config allows system admin to pass a config file as
1223	  complemental extension of kernel cmdline when booting.
1224	  The boot config file must be attached at the end of initramfs
1225	  with checksum, size and magic word.
1226	  See <file:Documentation/admin-guide/bootconfig.rst> for details.
1227
1228	  If unsure, say Y.
1229
1230choice
1231	prompt "Compiler optimization level"
1232	default CC_OPTIMIZE_FOR_PERFORMANCE
1233
1234config CC_OPTIMIZE_FOR_PERFORMANCE
1235	bool "Optimize for performance (-O2)"
1236	help
1237	  This is the default optimization level for the kernel, building
1238	  with the "-O2" compiler flag for best performance and most
1239	  helpful compile-time warnings.
1240
1241config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1242	bool "Optimize more for performance (-O3)"
1243	depends on ARC
1244	help
1245	  Choosing this option will pass "-O3" to your compiler to optimize
1246	  the kernel yet more for performance.
1247
1248config CC_OPTIMIZE_FOR_SIZE
1249	bool "Optimize for size (-Os)"
1250	help
1251	  Choosing this option will pass "-Os" to your compiler resulting
1252	  in a smaller kernel.
1253
1254endchoice
1255
1256config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1257	bool
1258	help
1259	  This requires that the arch annotates or otherwise protects
1260	  its external entry points from being discarded. Linker scripts
1261	  must also merge .text.*, .data.*, and .bss.* correctly into
1262	  output sections. Care must be taken not to pull in unrelated
1263	  sections (e.g., '.text.init'). Typically '.' in section names
1264	  is used to distinguish them from label names / C identifiers.
1265
1266config LD_DEAD_CODE_DATA_ELIMINATION
1267	bool "Dead code and data elimination (EXPERIMENTAL)"
1268	depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1269	depends on EXPERT
1270	depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800)
1271	depends on $(cc-option,-ffunction-sections -fdata-sections)
1272	depends on $(ld-option,--gc-sections)
1273	help
1274	  Enable this if you want to do dead code and data elimination with
1275	  the linker by compiling with -ffunction-sections -fdata-sections,
1276	  and linking with --gc-sections.
1277
1278	  This can reduce on disk and in-memory size of the kernel
1279	  code and static data, particularly for small configs and
1280	  on small systems. This has the possibility of introducing
1281	  silently broken kernel if the required annotations are not
1282	  present. This option is not well tested yet, so use at your
1283	  own risk.
1284
1285config SYSCTL
1286	bool
1287
1288config HAVE_UID16
1289	bool
1290
1291config SYSCTL_EXCEPTION_TRACE
1292	bool
1293	help
1294	  Enable support for /proc/sys/debug/exception-trace.
1295
1296config SYSCTL_ARCH_UNALIGN_NO_WARN
1297	bool
1298	help
1299	  Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1300	  Allows arch to define/use @no_unaligned_warning to possibly warn
1301	  about unaligned access emulation going on under the hood.
1302
1303config SYSCTL_ARCH_UNALIGN_ALLOW
1304	bool
1305	help
1306	  Enable support for /proc/sys/kernel/unaligned-trap
1307	  Allows arches to define/use @unaligned_enabled to runtime toggle
1308	  the unaligned access emulation.
1309	  see arch/parisc/kernel/unaligned.c for reference
1310
1311config HAVE_PCSPKR_PLATFORM
1312	bool
1313
1314# interpreter that classic socket filters depend on
1315config BPF
1316	bool
1317
1318menuconfig EXPERT
1319	bool "Configure standard kernel features (expert users)"
1320	# Unhide debug options, to make the on-by-default options visible
1321	select DEBUG_KERNEL
1322	help
1323	  This option allows certain base kernel options and settings
1324	  to be disabled or tweaked. This is for specialized
1325	  environments which can tolerate a "non-standard" kernel.
1326	  Only use this if you really know what you are doing.
1327
1328config UID16
1329	bool "Enable 16-bit UID system calls" if EXPERT
1330	depends on HAVE_UID16 && MULTIUSER
1331	default y
1332	help
1333	  This enables the legacy 16-bit UID syscall wrappers.
1334
1335config MULTIUSER
1336	bool "Multiple users, groups and capabilities support" if EXPERT
1337	default y
1338	help
1339	  This option enables support for non-root users, groups and
1340	  capabilities.
1341
1342	  If you say N here, all processes will run with UID 0, GID 0, and all
1343	  possible capabilities.  Saying N here also compiles out support for
1344	  system calls related to UIDs, GIDs, and capabilities, such as setuid,
1345	  setgid, and capset.
1346
1347	  If unsure, say Y here.
1348
1349config SGETMASK_SYSCALL
1350	bool "sgetmask/ssetmask syscalls support" if EXPERT
1351	def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1352	---help---
1353	  sys_sgetmask and sys_ssetmask are obsolete system calls
1354	  no longer supported in libc but still enabled by default in some
1355	  architectures.
1356
1357	  If unsure, leave the default option here.
1358
1359config SYSFS_SYSCALL
1360	bool "Sysfs syscall support" if EXPERT
1361	default y
1362	---help---
1363	  sys_sysfs is an obsolete system call no longer supported in libc.
1364	  Note that disabling this option is more secure but might break
1365	  compatibility with some systems.
1366
1367	  If unsure say Y here.
1368
1369config FHANDLE
1370	bool "open by fhandle syscalls" if EXPERT
1371	select EXPORTFS
1372	default y
1373	help
1374	  If you say Y here, a user level program will be able to map
1375	  file names to handle and then later use the handle for
1376	  different file system operations. This is useful in implementing
1377	  userspace file servers, which now track files using handles instead
1378	  of names. The handle would remain the same even if file names
1379	  get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1380	  syscalls.
1381
1382config POSIX_TIMERS
1383	bool "Posix Clocks & timers" if EXPERT
1384	default y
1385	help
1386	  This includes native support for POSIX timers to the kernel.
1387	  Some embedded systems have no use for them and therefore they
1388	  can be configured out to reduce the size of the kernel image.
1389
1390	  When this option is disabled, the following syscalls won't be
1391	  available: timer_create, timer_gettime: timer_getoverrun,
1392	  timer_settime, timer_delete, clock_adjtime, getitimer,
1393	  setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1394	  clock_getres and clock_nanosleep syscalls will be limited to
1395	  CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1396
1397	  If unsure say y.
1398
1399config PRINTK
1400	default y
1401	bool "Enable support for printk" if EXPERT
1402	select IRQ_WORK
1403	help
1404	  This option enables normal printk support. Removing it
1405	  eliminates most of the message strings from the kernel image
1406	  and makes the kernel more or less silent. As this makes it
1407	  very difficult to diagnose system problems, saying N here is
1408	  strongly discouraged.
1409
1410config PRINTK_NMI
1411	def_bool y
1412	depends on PRINTK
1413	depends on HAVE_NMI
1414
1415config BUG
1416	bool "BUG() support" if EXPERT
1417	default y
1418	help
1419	  Disabling this option eliminates support for BUG and WARN, reducing
1420	  the size of your kernel image and potentially quietly ignoring
1421	  numerous fatal conditions. You should only consider disabling this
1422	  option for embedded systems with no facilities for reporting errors.
1423	  Just say Y.
1424
1425config ELF_CORE
1426	depends on COREDUMP
1427	default y
1428	bool "Enable ELF core dumps" if EXPERT
1429	help
1430	  Enable support for generating core dumps. Disabling saves about 4k.
1431
1432
1433config PCSPKR_PLATFORM
1434	bool "Enable PC-Speaker support" if EXPERT
1435	depends on HAVE_PCSPKR_PLATFORM
1436	select I8253_LOCK
1437	default y
1438	help
1439	  This option allows to disable the internal PC-Speaker
1440	  support, saving some memory.
1441
1442config BASE_FULL
1443	default y
1444	bool "Enable full-sized data structures for core" if EXPERT
1445	help
1446	  Disabling this option reduces the size of miscellaneous core
1447	  kernel data structures. This saves memory on small machines,
1448	  but may reduce performance.
1449
1450config FUTEX
1451	bool "Enable futex support" if EXPERT
1452	default y
1453	imply RT_MUTEXES
1454	help
1455	  Disabling this option will cause the kernel to be built without
1456	  support for "fast userspace mutexes".  The resulting kernel may not
1457	  run glibc-based applications correctly.
1458
1459config FUTEX_PI
1460	bool
1461	depends on FUTEX && RT_MUTEXES
1462	default y
1463
1464config HAVE_FUTEX_CMPXCHG
1465	bool
1466	depends on FUTEX
1467	help
1468	  Architectures should select this if futex_atomic_cmpxchg_inatomic()
1469	  is implemented and always working. This removes a couple of runtime
1470	  checks.
1471
1472config EPOLL
1473	bool "Enable eventpoll support" if EXPERT
1474	default y
1475	help
1476	  Disabling this option will cause the kernel to be built without
1477	  support for epoll family of system calls.
1478
1479config SIGNALFD
1480	bool "Enable signalfd() system call" if EXPERT
1481	default y
1482	help
1483	  Enable the signalfd() system call that allows to receive signals
1484	  on a file descriptor.
1485
1486	  If unsure, say Y.
1487
1488config TIMERFD
1489	bool "Enable timerfd() system call" if EXPERT
1490	default y
1491	help
1492	  Enable the timerfd() system call that allows to receive timer
1493	  events on a file descriptor.
1494
1495	  If unsure, say Y.
1496
1497config EVENTFD
1498	bool "Enable eventfd() system call" if EXPERT
1499	default y
1500	help
1501	  Enable the eventfd() system call that allows to receive both
1502	  kernel notification (ie. KAIO) or userspace notifications.
1503
1504	  If unsure, say Y.
1505
1506config SHMEM
1507	bool "Use full shmem filesystem" if EXPERT
1508	default y
1509	depends on MMU
1510	help
1511	  The shmem is an internal filesystem used to manage shared memory.
1512	  It is backed by swap and manages resource limits. It is also exported
1513	  to userspace as tmpfs if TMPFS is enabled. Disabling this
1514	  option replaces shmem and tmpfs with the much simpler ramfs code,
1515	  which may be appropriate on small systems without swap.
1516
1517config AIO
1518	bool "Enable AIO support" if EXPERT
1519	default y
1520	help
1521	  This option enables POSIX asynchronous I/O which may by used
1522	  by some high performance threaded applications. Disabling
1523	  this option saves about 7k.
1524
1525config IO_URING
1526	bool "Enable IO uring support" if EXPERT
1527	select IO_WQ
1528	default y
1529	help
1530	  This option enables support for the io_uring interface, enabling
1531	  applications to submit and complete IO through submission and
1532	  completion rings that are shared between the kernel and application.
1533
1534config ADVISE_SYSCALLS
1535	bool "Enable madvise/fadvise syscalls" if EXPERT
1536	default y
1537	help
1538	  This option enables the madvise and fadvise syscalls, used by
1539	  applications to advise the kernel about their future memory or file
1540	  usage, improving performance. If building an embedded system where no
1541	  applications use these syscalls, you can disable this option to save
1542	  space.
1543
1544config HAVE_ARCH_USERFAULTFD_WP
1545	bool
1546	help
1547	  Arch has userfaultfd write protection support
1548
1549config MEMBARRIER
1550	bool "Enable membarrier() system call" if EXPERT
1551	default y
1552	help
1553	  Enable the membarrier() system call that allows issuing memory
1554	  barriers across all running threads, which can be used to distribute
1555	  the cost of user-space memory barriers asymmetrically by transforming
1556	  pairs of memory barriers into pairs consisting of membarrier() and a
1557	  compiler barrier.
1558
1559	  If unsure, say Y.
1560
1561config KALLSYMS
1562	bool "Load all symbols for debugging/ksymoops" if EXPERT
1563	default y
1564	help
1565	  Say Y here to let the kernel print out symbolic crash information and
1566	  symbolic stack backtraces. This increases the size of the kernel
1567	  somewhat, as all symbols have to be loaded into the kernel image.
1568
1569config KALLSYMS_ALL
1570	bool "Include all symbols in kallsyms"
1571	depends on DEBUG_KERNEL && KALLSYMS
1572	help
1573	  Normally kallsyms only contains the symbols of functions for nicer
1574	  OOPS messages and backtraces (i.e., symbols from the text and inittext
1575	  sections). This is sufficient for most cases. And only in very rare
1576	  cases (e.g., when a debugger is used) all symbols are required (e.g.,
1577	  names of variables from the data sections, etc).
1578
1579	  This option makes sure that all symbols are loaded into the kernel
1580	  image (i.e., symbols from all sections) in cost of increased kernel
1581	  size (depending on the kernel configuration, it may be 300KiB or
1582	  something like this).
1583
1584	  Say N unless you really need all symbols.
1585
1586config KALLSYMS_ABSOLUTE_PERCPU
1587	bool
1588	depends on KALLSYMS
1589	default X86_64 && SMP
1590
1591config KALLSYMS_BASE_RELATIVE
1592	bool
1593	depends on KALLSYMS
1594	default !IA64
1595	help
1596	  Instead of emitting them as absolute values in the native word size,
1597	  emit the symbol references in the kallsyms table as 32-bit entries,
1598	  each containing a relative value in the range [base, base + U32_MAX]
1599	  or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1600	  an absolute value in the range [0, S32_MAX] or a relative value in the
1601	  range [base, base + S32_MAX], where base is the lowest relative symbol
1602	  address encountered in the image.
1603
1604	  On 64-bit builds, this reduces the size of the address table by 50%,
1605	  but more importantly, it results in entries whose values are build
1606	  time constants, and no relocation pass is required at runtime to fix
1607	  up the entries based on the runtime load address of the kernel.
1608
1609# end of the "standard kernel features (expert users)" menu
1610
1611# syscall, maps, verifier
1612
1613config BPF_LSM
1614	bool "LSM Instrumentation with BPF"
1615	depends on BPF_EVENTS
1616	depends on BPF_SYSCALL
1617	depends on SECURITY
1618	depends on BPF_JIT
1619	help
1620	  Enables instrumentation of the security hooks with eBPF programs for
1621	  implementing dynamic MAC and Audit Policies.
1622
1623	  If you are unsure how to answer this question, answer N.
1624
1625config BPF_SYSCALL
1626	bool "Enable bpf() system call"
1627	select BPF
1628	select IRQ_WORK
1629	default n
1630	help
1631	  Enable the bpf() system call that allows to manipulate eBPF
1632	  programs and maps via file descriptors.
1633
1634config ARCH_WANT_DEFAULT_BPF_JIT
1635	bool
1636
1637config BPF_JIT_ALWAYS_ON
1638	bool "Permanently enable BPF JIT and remove BPF interpreter"
1639	depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1640	help
1641	  Enables BPF JIT and removes BPF interpreter to avoid
1642	  speculative execution of BPF instructions by the interpreter
1643
1644config BPF_JIT_DEFAULT_ON
1645	def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
1646	depends on HAVE_EBPF_JIT && BPF_JIT
1647
1648config USERFAULTFD
1649	bool "Enable userfaultfd() system call"
1650	depends on MMU
1651	help
1652	  Enable the userfaultfd() system call that allows to intercept and
1653	  handle page faults in userland.
1654
1655config ARCH_HAS_MEMBARRIER_CALLBACKS
1656	bool
1657
1658config ARCH_HAS_MEMBARRIER_SYNC_CORE
1659	bool
1660
1661config RSEQ
1662	bool "Enable rseq() system call" if EXPERT
1663	default y
1664	depends on HAVE_RSEQ
1665	select MEMBARRIER
1666	help
1667	  Enable the restartable sequences system call. It provides a
1668	  user-space cache for the current CPU number value, which
1669	  speeds up getting the current CPU number from user-space,
1670	  as well as an ABI to speed up user-space operations on
1671	  per-CPU data.
1672
1673	  If unsure, say Y.
1674
1675config DEBUG_RSEQ
1676	default n
1677	bool "Enabled debugging of rseq() system call" if EXPERT
1678	depends on RSEQ && DEBUG_KERNEL
1679	help
1680	  Enable extra debugging checks for the rseq system call.
1681
1682	  If unsure, say N.
1683
1684config EMBEDDED
1685	bool "Embedded system"
1686	option allnoconfig_y
1687	select EXPERT
1688	help
1689	  This option should be enabled if compiling the kernel for
1690	  an embedded system so certain expert options are available
1691	  for configuration.
1692
1693config HAVE_PERF_EVENTS
1694	bool
1695	help
1696	  See tools/perf/design.txt for details.
1697
1698config PERF_USE_VMALLOC
1699	bool
1700	help
1701	  See tools/perf/design.txt for details
1702
1703config PC104
1704	bool "PC/104 support" if EXPERT
1705	help
1706	  Expose PC/104 form factor device drivers and options available for
1707	  selection and configuration. Enable this option if your target
1708	  machine has a PC/104 bus.
1709
1710menu "Kernel Performance Events And Counters"
1711
1712config PERF_EVENTS
1713	bool "Kernel performance events and counters"
1714	default y if PROFILING
1715	depends on HAVE_PERF_EVENTS
1716	select IRQ_WORK
1717	select SRCU
1718	help
1719	  Enable kernel support for various performance events provided
1720	  by software and hardware.
1721
1722	  Software events are supported either built-in or via the
1723	  use of generic tracepoints.
1724
1725	  Most modern CPUs support performance events via performance
1726	  counter registers. These registers count the number of certain
1727	  types of hw events: such as instructions executed, cachemisses
1728	  suffered, or branches mis-predicted - without slowing down the
1729	  kernel or applications. These registers can also trigger interrupts
1730	  when a threshold number of events have passed - and can thus be
1731	  used to profile the code that runs on that CPU.
1732
1733	  The Linux Performance Event subsystem provides an abstraction of
1734	  these software and hardware event capabilities, available via a
1735	  system call and used by the "perf" utility in tools/perf/. It
1736	  provides per task and per CPU counters, and it provides event
1737	  capabilities on top of those.
1738
1739	  Say Y if unsure.
1740
1741config DEBUG_PERF_USE_VMALLOC
1742	default n
1743	bool "Debug: use vmalloc to back perf mmap() buffers"
1744	depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1745	select PERF_USE_VMALLOC
1746	help
1747	  Use vmalloc memory to back perf mmap() buffers.
1748
1749	  Mostly useful for debugging the vmalloc code on platforms
1750	  that don't require it.
1751
1752	  Say N if unsure.
1753
1754endmenu
1755
1756config VM_EVENT_COUNTERS
1757	default y
1758	bool "Enable VM event counters for /proc/vmstat" if EXPERT
1759	help
1760	  VM event counters are needed for event counts to be shown.
1761	  This option allows the disabling of the VM event counters
1762	  on EXPERT systems.  /proc/vmstat will only show page counts
1763	  if VM event counters are disabled.
1764
1765config SLUB_DEBUG
1766	default y
1767	bool "Enable SLUB debugging support" if EXPERT
1768	depends on SLUB && SYSFS
1769	help
1770	  SLUB has extensive debug support features. Disabling these can
1771	  result in significant savings in code size. This also disables
1772	  SLUB sysfs support. /sys/slab will not exist and there will be
1773	  no support for cache validation etc.
1774
1775config SLUB_MEMCG_SYSFS_ON
1776	default n
1777	bool "Enable memcg SLUB sysfs support by default" if EXPERT
1778	depends on SLUB && SYSFS && MEMCG
1779	help
1780	  SLUB creates a directory under /sys/kernel/slab for each
1781	  allocation cache to host info and debug files. If memory
1782	  cgroup is enabled, each cache can have per memory cgroup
1783	  caches. SLUB can create the same sysfs directories for these
1784	  caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1785	  to a very high number of debug files being created. This is
1786	  controlled by slub_memcg_sysfs boot parameter and this
1787	  config option determines the parameter's default value.
1788
1789config COMPAT_BRK
1790	bool "Disable heap randomization"
1791	default y
1792	help
1793	  Randomizing heap placement makes heap exploits harder, but it
1794	  also breaks ancient binaries (including anything libc5 based).
1795	  This option changes the bootup default to heap randomization
1796	  disabled, and can be overridden at runtime by setting
1797	  /proc/sys/kernel/randomize_va_space to 2.
1798
1799	  On non-ancient distros (post-2000 ones) N is usually a safe choice.
1800
1801choice
1802	prompt "Choose SLAB allocator"
1803	default SLUB
1804	help
1805	   This option allows to select a slab allocator.
1806
1807config SLAB
1808	bool "SLAB"
1809	select HAVE_HARDENED_USERCOPY_ALLOCATOR
1810	help
1811	  The regular slab allocator that is established and known to work
1812	  well in all environments. It organizes cache hot objects in
1813	  per cpu and per node queues.
1814
1815config SLUB
1816	bool "SLUB (Unqueued Allocator)"
1817	select HAVE_HARDENED_USERCOPY_ALLOCATOR
1818	help
1819	   SLUB is a slab allocator that minimizes cache line usage
1820	   instead of managing queues of cached objects (SLAB approach).
1821	   Per cpu caching is realized using slabs of objects instead
1822	   of queues of objects. SLUB can use memory efficiently
1823	   and has enhanced diagnostics. SLUB is the default choice for
1824	   a slab allocator.
1825
1826config SLOB
1827	depends on EXPERT
1828	bool "SLOB (Simple Allocator)"
1829	help
1830	   SLOB replaces the stock allocator with a drastically simpler
1831	   allocator. SLOB is generally more space efficient but
1832	   does not perform as well on large systems.
1833
1834endchoice
1835
1836config SLAB_MERGE_DEFAULT
1837	bool "Allow slab caches to be merged"
1838	default y
1839	help
1840	  For reduced kernel memory fragmentation, slab caches can be
1841	  merged when they share the same size and other characteristics.
1842	  This carries a risk of kernel heap overflows being able to
1843	  overwrite objects from merged caches (and more easily control
1844	  cache layout), which makes such heap attacks easier to exploit
1845	  by attackers. By keeping caches unmerged, these kinds of exploits
1846	  can usually only damage objects in the same cache. To disable
1847	  merging at runtime, "slab_nomerge" can be passed on the kernel
1848	  command line.
1849
1850config SLAB_FREELIST_RANDOM
1851	default n
1852	depends on SLAB || SLUB
1853	bool "SLAB freelist randomization"
1854	help
1855	  Randomizes the freelist order used on creating new pages. This
1856	  security feature reduces the predictability of the kernel slab
1857	  allocator against heap overflows.
1858
1859config SLAB_FREELIST_HARDENED
1860	bool "Harden slab freelist metadata"
1861	depends on SLUB
1862	help
1863	  Many kernel heap attacks try to target slab cache metadata and
1864	  other infrastructure. This options makes minor performance
1865	  sacrifices to harden the kernel slab allocator against common
1866	  freelist exploit methods.
1867
1868config SHUFFLE_PAGE_ALLOCATOR
1869	bool "Page allocator randomization"
1870	default SLAB_FREELIST_RANDOM && ACPI_NUMA
1871	help
1872	  Randomization of the page allocator improves the average
1873	  utilization of a direct-mapped memory-side-cache. See section
1874	  5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1875	  6.2a specification for an example of how a platform advertises
1876	  the presence of a memory-side-cache. There are also incidental
1877	  security benefits as it reduces the predictability of page
1878	  allocations to compliment SLAB_FREELIST_RANDOM, but the
1879	  default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1880	  10th order of pages is selected based on cache utilization
1881	  benefits on x86.
1882
1883	  While the randomization improves cache utilization it may
1884	  negatively impact workloads on platforms without a cache. For
1885	  this reason, by default, the randomization is enabled only
1886	  after runtime detection of a direct-mapped memory-side-cache.
1887	  Otherwise, the randomization may be force enabled with the
1888	  'page_alloc.shuffle' kernel command line parameter.
1889
1890	  Say Y if unsure.
1891
1892config SLUB_CPU_PARTIAL
1893	default y
1894	depends on SLUB && SMP
1895	bool "SLUB per cpu partial cache"
1896	help
1897	  Per cpu partial caches accelerate objects allocation and freeing
1898	  that is local to a processor at the price of more indeterminism
1899	  in the latency of the free. On overflow these caches will be cleared
1900	  which requires the taking of locks that may cause latency spikes.
1901	  Typically one would choose no for a realtime system.
1902
1903config MMAP_ALLOW_UNINITIALIZED
1904	bool "Allow mmapped anonymous memory to be uninitialized"
1905	depends on EXPERT && !MMU
1906	default n
1907	help
1908	  Normally, and according to the Linux spec, anonymous memory obtained
1909	  from mmap() has its contents cleared before it is passed to
1910	  userspace.  Enabling this config option allows you to request that
1911	  mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1912	  providing a huge performance boost.  If this option is not enabled,
1913	  then the flag will be ignored.
1914
1915	  This is taken advantage of by uClibc's malloc(), and also by
1916	  ELF-FDPIC binfmt's brk and stack allocator.
1917
1918	  Because of the obvious security issues, this option should only be
1919	  enabled on embedded devices where you control what is run in
1920	  userspace.  Since that isn't generally a problem on no-MMU systems,
1921	  it is normally safe to say Y here.
1922
1923	  See Documentation/nommu-mmap.txt for more information.
1924
1925config SYSTEM_DATA_VERIFICATION
1926	def_bool n
1927	select SYSTEM_TRUSTED_KEYRING
1928	select KEYS
1929	select CRYPTO
1930	select CRYPTO_RSA
1931	select ASYMMETRIC_KEY_TYPE
1932	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1933	select ASN1
1934	select OID_REGISTRY
1935	select X509_CERTIFICATE_PARSER
1936	select PKCS7_MESSAGE_PARSER
1937	help
1938	  Provide PKCS#7 message verification using the contents of the system
1939	  trusted keyring to provide public keys.  This then can be used for
1940	  module verification, kexec image verification and firmware blob
1941	  verification.
1942
1943config PROFILING
1944	bool "Profiling support"
1945	help
1946	  Say Y here to enable the extended profiling support mechanisms used
1947	  by profilers such as OProfile.
1948
1949#
1950# Place an empty function call at each tracepoint site. Can be
1951# dynamically changed for a probe function.
1952#
1953config TRACEPOINTS
1954	bool
1955
1956endmenu		# General setup
1957
1958source "arch/Kconfig"
1959
1960config RT_MUTEXES
1961	bool
1962
1963config BASE_SMALL
1964	int
1965	default 0 if BASE_FULL
1966	default 1 if !BASE_FULL
1967
1968config MODULE_SIG_FORMAT
1969	def_bool n
1970	select SYSTEM_DATA_VERIFICATION
1971
1972menuconfig MODULES
1973	bool "Enable loadable module support"
1974	option modules
1975	help
1976	  Kernel modules are small pieces of compiled code which can
1977	  be inserted in the running kernel, rather than being
1978	  permanently built into the kernel.  You use the "modprobe"
1979	  tool to add (and sometimes remove) them.  If you say Y here,
1980	  many parts of the kernel can be built as modules (by
1981	  answering M instead of Y where indicated): this is most
1982	  useful for infrequently used options which are not required
1983	  for booting.  For more information, see the man pages for
1984	  modprobe, lsmod, modinfo, insmod and rmmod.
1985
1986	  If you say Y here, you will need to run "make
1987	  modules_install" to put the modules under /lib/modules/
1988	  where modprobe can find them (you may need to be root to do
1989	  this).
1990
1991	  If unsure, say Y.
1992
1993if MODULES
1994
1995config MODULE_FORCE_LOAD
1996	bool "Forced module loading"
1997	default n
1998	help
1999	  Allow loading of modules without version information (ie. modprobe
2000	  --force).  Forced module loading sets the 'F' (forced) taint flag and
2001	  is usually a really bad idea.
2002
2003config MODULE_UNLOAD
2004	bool "Module unloading"
2005	help
2006	  Without this option you will not be able to unload any
2007	  modules (note that some modules may not be unloadable
2008	  anyway), which makes your kernel smaller, faster
2009	  and simpler.  If unsure, say Y.
2010
2011config MODULE_FORCE_UNLOAD
2012	bool "Forced module unloading"
2013	depends on MODULE_UNLOAD
2014	help
2015	  This option allows you to force a module to unload, even if the
2016	  kernel believes it is unsafe: the kernel will remove the module
2017	  without waiting for anyone to stop using it (using the -f option to
2018	  rmmod).  This is mainly for kernel developers and desperate users.
2019	  If unsure, say N.
2020
2021config MODVERSIONS
2022	bool "Module versioning support"
2023	help
2024	  Usually, you have to use modules compiled with your kernel.
2025	  Saying Y here makes it sometimes possible to use modules
2026	  compiled for different kernels, by adding enough information
2027	  to the modules to (hopefully) spot any changes which would
2028	  make them incompatible with the kernel you are running.  If
2029	  unsure, say N.
2030
2031config ASM_MODVERSIONS
2032	bool
2033	default HAVE_ASM_MODVERSIONS && MODVERSIONS
2034	help
2035	  This enables module versioning for exported symbols also from
2036	  assembly. This can be enabled only when the target architecture
2037	  supports it.
2038
2039config MODULE_REL_CRCS
2040	bool
2041	depends on MODVERSIONS
2042
2043config MODULE_SRCVERSION_ALL
2044	bool "Source checksum for all modules"
2045	help
2046	  Modules which contain a MODULE_VERSION get an extra "srcversion"
2047	  field inserted into their modinfo section, which contains a
2048    	  sum of the source files which made it.  This helps maintainers
2049	  see exactly which source was used to build a module (since
2050	  others sometimes change the module source without updating
2051	  the version).  With this option, such a "srcversion" field
2052	  will be created for all modules.  If unsure, say N.
2053
2054config MODULE_SIG
2055	bool "Module signature verification"
2056	select MODULE_SIG_FORMAT
2057	help
2058	  Check modules for valid signatures upon load: the signature
2059	  is simply appended to the module. For more information see
2060	  <file:Documentation/admin-guide/module-signing.rst>.
2061
2062	  Note that this option adds the OpenSSL development packages as a
2063	  kernel build dependency so that the signing tool can use its crypto
2064	  library.
2065
2066	  You should enable this option if you wish to use either
2067	  CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2068	  another LSM - otherwise unsigned modules will be loadable regardless
2069	  of the lockdown policy.
2070
2071	  !!!WARNING!!!  If you enable this option, you MUST make sure that the
2072	  module DOES NOT get stripped after being signed.  This includes the
2073	  debuginfo strip done by some packagers (such as rpmbuild) and
2074	  inclusion into an initramfs that wants the module size reduced.
2075
2076config MODULE_SIG_FORCE
2077	bool "Require modules to be validly signed"
2078	depends on MODULE_SIG
2079	help
2080	  Reject unsigned modules or signed modules for which we don't have a
2081	  key.  Without this, such modules will simply taint the kernel.
2082
2083config MODULE_SIG_ALL
2084	bool "Automatically sign all modules"
2085	default y
2086	depends on MODULE_SIG
2087	help
2088	  Sign all modules during make modules_install. Without this option,
2089	  modules must be signed manually, using the scripts/sign-file tool.
2090
2091comment "Do not forget to sign required modules with scripts/sign-file"
2092	depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2093
2094choice
2095	prompt "Which hash algorithm should modules be signed with?"
2096	depends on MODULE_SIG
2097	help
2098	  This determines which sort of hashing algorithm will be used during
2099	  signature generation.  This algorithm _must_ be built into the kernel
2100	  directly so that signature verification can take place.  It is not
2101	  possible to load a signed module containing the algorithm to check
2102	  the signature on that module.
2103
2104config MODULE_SIG_SHA1
2105	bool "Sign modules with SHA-1"
2106	select CRYPTO_SHA1
2107
2108config MODULE_SIG_SHA224
2109	bool "Sign modules with SHA-224"
2110	select CRYPTO_SHA256
2111
2112config MODULE_SIG_SHA256
2113	bool "Sign modules with SHA-256"
2114	select CRYPTO_SHA256
2115
2116config MODULE_SIG_SHA384
2117	bool "Sign modules with SHA-384"
2118	select CRYPTO_SHA512
2119
2120config MODULE_SIG_SHA512
2121	bool "Sign modules with SHA-512"
2122	select CRYPTO_SHA512
2123
2124endchoice
2125
2126config MODULE_SIG_HASH
2127	string
2128	depends on MODULE_SIG
2129	default "sha1" if MODULE_SIG_SHA1
2130	default "sha224" if MODULE_SIG_SHA224
2131	default "sha256" if MODULE_SIG_SHA256
2132	default "sha384" if MODULE_SIG_SHA384
2133	default "sha512" if MODULE_SIG_SHA512
2134
2135config MODULE_COMPRESS
2136	bool "Compress modules on installation"
2137	help
2138
2139	  Compresses kernel modules when 'make modules_install' is run; gzip or
2140	  xz depending on "Compression algorithm" below.
2141
2142	  module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2143
2144	  Out-of-tree kernel modules installed using Kbuild will also be
2145	  compressed upon installation.
2146
2147	  Note: for modules inside an initrd or initramfs, it's more efficient
2148	  to compress the whole initrd or initramfs instead.
2149
2150	  Note: This is fully compatible with signed modules.
2151
2152	  If in doubt, say N.
2153
2154choice
2155	prompt "Compression algorithm"
2156	depends on MODULE_COMPRESS
2157	default MODULE_COMPRESS_GZIP
2158	help
2159	  This determines which sort of compression will be used during
2160	  'make modules_install'.
2161
2162	  GZIP (default) and XZ are supported.
2163
2164config MODULE_COMPRESS_GZIP
2165	bool "GZIP"
2166
2167config MODULE_COMPRESS_XZ
2168	bool "XZ"
2169
2170endchoice
2171
2172config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2173	bool "Allow loading of modules with missing namespace imports"
2174	help
2175	  Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2176	  a namespace. A module that makes use of a symbol exported with such a
2177	  namespace is required to import the namespace via MODULE_IMPORT_NS().
2178	  There is no technical reason to enforce correct namespace imports,
2179	  but it creates consistency between symbols defining namespaces and
2180	  users importing namespaces they make use of. This option relaxes this
2181	  requirement and lifts the enforcement when loading a module.
2182
2183	  If unsure, say N.
2184
2185config UNUSED_SYMBOLS
2186	bool "Enable unused/obsolete exported symbols"
2187	default y if X86
2188	help
2189	  Unused but exported symbols make the kernel needlessly bigger.  For
2190	  that reason most of these unused exports will soon be removed.  This
2191	  option is provided temporarily to provide a transition period in case
2192	  some external kernel module needs one of these symbols anyway. If you
2193	  encounter such a case in your module, consider if you are actually
2194	  using the right API.  (rationale: since nobody in the kernel is using
2195	  this in a module, there is a pretty good chance it's actually the
2196	  wrong interface to use).  If you really need the symbol, please send a
2197	  mail to the linux kernel mailing list mentioning the symbol and why
2198	  you really need it, and what the merge plan to the mainline kernel for
2199	  your module is.
2200
2201config TRIM_UNUSED_KSYMS
2202	bool "Trim unused exported kernel symbols"
2203	depends on !UNUSED_SYMBOLS
2204	help
2205	  The kernel and some modules make many symbols available for
2206	  other modules to use via EXPORT_SYMBOL() and variants. Depending
2207	  on the set of modules being selected in your kernel configuration,
2208	  many of those exported symbols might never be used.
2209
2210	  This option allows for unused exported symbols to be dropped from
2211	  the build. In turn, this provides the compiler more opportunities
2212	  (especially when using LTO) for optimizing the code and reducing
2213	  binary size.  This might have some security advantages as well.
2214
2215	  If unsure, or if you need to build out-of-tree modules, say N.
2216
2217config UNUSED_KSYMS_WHITELIST
2218	string "Whitelist of symbols to keep in ksymtab"
2219	depends on TRIM_UNUSED_KSYMS
2220	help
2221	  By default, all unused exported symbols will be un-exported from the
2222	  build when TRIM_UNUSED_KSYMS is selected.
2223
2224	  UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
2225	  exported at all times, even in absence of in-tree users. The value to
2226	  set here is the path to a text file containing the list of symbols,
2227	  one per line. The path can be absolute, or relative to the kernel
2228	  source tree.
2229
2230endif # MODULES
2231
2232config MODULES_TREE_LOOKUP
2233	def_bool y
2234	depends on PERF_EVENTS || TRACING
2235
2236config INIT_ALL_POSSIBLE
2237	bool
2238	help
2239	  Back when each arch used to define their own cpu_online_mask and
2240	  cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2241	  with all 1s, and others with all 0s.  When they were centralised,
2242	  it was better to provide this option than to break all the archs
2243	  and have several arch maintainers pursuing me down dark alleys.
2244
2245source "block/Kconfig"
2246
2247config PREEMPT_NOTIFIERS
2248	bool
2249
2250config PADATA
2251	depends on SMP
2252	bool
2253
2254config ASN1
2255	tristate
2256	help
2257	  Build a simple ASN.1 grammar compiler that produces a bytecode output
2258	  that can be interpreted by the ASN.1 stream decoder and used to
2259	  inform it as to what tags are to be expected in a stream and what
2260	  functions to call on what tags.
2261
2262source "kernel/Kconfig.locks"
2263
2264config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2265	bool
2266
2267config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2268	bool
2269
2270# It may be useful for an architecture to override the definitions of the
2271# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2272# and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2273# different calling convention for syscalls. They can also override the
2274# macros for not-implemented syscalls in kernel/sys_ni.c and
2275# kernel/time/posix-stubs.c. All these overrides need to be available in
2276# <asm/syscall_wrapper.h>.
2277config ARCH_HAS_SYSCALL_WRAPPER
2278	def_bool n
2279