xref: /openbmc/linux/init/Kconfig (revision d8bcaabe)
1config ARCH
2	string
3	option env="ARCH"
4
5config KERNELVERSION
6	string
7	option env="KERNELVERSION"
8
9config DEFCONFIG_LIST
10	string
11	depends on !UML
12	option defconfig_list
13	default "/lib/modules/$UNAME_RELEASE/.config"
14	default "/etc/kernel-config"
15	default "/boot/config-$UNAME_RELEASE"
16	default "$ARCH_DEFCONFIG"
17	default "arch/$ARCH/defconfig"
18
19config CONSTRUCTORS
20	bool
21	depends on !UML
22
23config IRQ_WORK
24	bool
25
26config BUILDTIME_EXTABLE_SORT
27	bool
28
29config THREAD_INFO_IN_TASK
30	bool
31	help
32	  Select this to move thread_info off the stack into task_struct.  To
33	  make this work, an arch will need to remove all thread_info fields
34	  except flags and fix any runtime bugs.
35
36	  One subtle change that will be needed is to use try_get_task_stack()
37	  and put_task_stack() in save_thread_stack_tsk() and get_wchan().
38
39menu "General setup"
40
41config BROKEN
42	bool
43
44config BROKEN_ON_SMP
45	bool
46	depends on BROKEN || !SMP
47	default y
48
49config INIT_ENV_ARG_LIMIT
50	int
51	default 32 if !UML
52	default 128 if UML
53	help
54	  Maximum of each of the number of arguments and environment
55	  variables passed to init from the kernel command line.
56
57
58config CROSS_COMPILE
59	string "Cross-compiler tool prefix"
60	help
61	  Same as running 'make CROSS_COMPILE=prefix-' but stored for
62	  default make runs in this kernel build directory.  You don't
63	  need to set this unless you want the configured kernel build
64	  directory to select the cross-compiler automatically.
65
66config COMPILE_TEST
67	bool "Compile also drivers which will not load"
68	depends on !UML
69	default n
70	help
71	  Some drivers can be compiled on a different platform than they are
72	  intended to be run on. Despite they cannot be loaded there (or even
73	  when they load they cannot be used due to missing HW support),
74	  developers still, opposing to distributors, might want to build such
75	  drivers to compile-test them.
76
77	  If you are a developer and want to build everything available, say Y
78	  here. If you are a user/distributor, say N here to exclude useless
79	  drivers to be distributed.
80
81config LOCALVERSION
82	string "Local version - append to kernel release"
83	help
84	  Append an extra string to the end of your kernel version.
85	  This will show up when you type uname, for example.
86	  The string you set here will be appended after the contents of
87	  any files with a filename matching localversion* in your
88	  object and source tree, in that order.  Your total string can
89	  be a maximum of 64 characters.
90
91config LOCALVERSION_AUTO
92	bool "Automatically append version information to the version string"
93	default y
94	depends on !COMPILE_TEST
95	help
96	  This will try to automatically determine if the current tree is a
97	  release tree by looking for git tags that belong to the current
98	  top of tree revision.
99
100	  A string of the format -gxxxxxxxx will be added to the localversion
101	  if a git-based tree is found.  The string generated by this will be
102	  appended after any matching localversion* files, and after the value
103	  set in CONFIG_LOCALVERSION.
104
105	  (The actual string used here is the first eight characters produced
106	  by running the command:
107
108	    $ git rev-parse --verify HEAD
109
110	  which is done within the script "scripts/setlocalversion".)
111
112config HAVE_KERNEL_GZIP
113	bool
114
115config HAVE_KERNEL_BZIP2
116	bool
117
118config HAVE_KERNEL_LZMA
119	bool
120
121config HAVE_KERNEL_XZ
122	bool
123
124config HAVE_KERNEL_LZO
125	bool
126
127config HAVE_KERNEL_LZ4
128	bool
129
130choice
131	prompt "Kernel compression mode"
132	default KERNEL_GZIP
133	depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
134	help
135	  The linux kernel is a kind of self-extracting executable.
136	  Several compression algorithms are available, which differ
137	  in efficiency, compression and decompression speed.
138	  Compression speed is only relevant when building a kernel.
139	  Decompression speed is relevant at each boot.
140
141	  If you have any problems with bzip2 or lzma compressed
142	  kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
143	  version of this functionality (bzip2 only), for 2.4, was
144	  supplied by Christian Ludwig)
145
146	  High compression options are mostly useful for users, who
147	  are low on disk space (embedded systems), but for whom ram
148	  size matters less.
149
150	  If in doubt, select 'gzip'
151
152config KERNEL_GZIP
153	bool "Gzip"
154	depends on HAVE_KERNEL_GZIP
155	help
156	  The old and tried gzip compression. It provides a good balance
157	  between compression ratio and decompression speed.
158
159config KERNEL_BZIP2
160	bool "Bzip2"
161	depends on HAVE_KERNEL_BZIP2
162	help
163	  Its compression ratio and speed is intermediate.
164	  Decompression speed is slowest among the choices.  The kernel
165	  size is about 10% smaller with bzip2, in comparison to gzip.
166	  Bzip2 uses a large amount of memory. For modern kernels you
167	  will need at least 8MB RAM or more for booting.
168
169config KERNEL_LZMA
170	bool "LZMA"
171	depends on HAVE_KERNEL_LZMA
172	help
173	  This compression algorithm's ratio is best.  Decompression speed
174	  is between gzip and bzip2.  Compression is slowest.
175	  The kernel size is about 33% smaller with LZMA in comparison to gzip.
176
177config KERNEL_XZ
178	bool "XZ"
179	depends on HAVE_KERNEL_XZ
180	help
181	  XZ uses the LZMA2 algorithm and instruction set specific
182	  BCJ filters which can improve compression ratio of executable
183	  code. The size of the kernel is about 30% smaller with XZ in
184	  comparison to gzip. On architectures for which there is a BCJ
185	  filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
186	  will create a few percent smaller kernel than plain LZMA.
187
188	  The speed is about the same as with LZMA: The decompression
189	  speed of XZ is better than that of bzip2 but worse than gzip
190	  and LZO. Compression is slow.
191
192config KERNEL_LZO
193	bool "LZO"
194	depends on HAVE_KERNEL_LZO
195	help
196	  Its compression ratio is the poorest among the choices. The kernel
197	  size is about 10% bigger than gzip; however its speed
198	  (both compression and decompression) is the fastest.
199
200config KERNEL_LZ4
201	bool "LZ4"
202	depends on HAVE_KERNEL_LZ4
203	help
204	  LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
205	  A preliminary version of LZ4 de/compression tool is available at
206	  <https://code.google.com/p/lz4/>.
207
208	  Its compression ratio is worse than LZO. The size of the kernel
209	  is about 8% bigger than LZO. But the decompression speed is
210	  faster than LZO.
211
212endchoice
213
214config DEFAULT_HOSTNAME
215	string "Default hostname"
216	default "(none)"
217	help
218	  This option determines the default system hostname before userspace
219	  calls sethostname(2). The kernel traditionally uses "(none)" here,
220	  but you may wish to use a different default here to make a minimal
221	  system more usable with less configuration.
222
223config SWAP
224	bool "Support for paging of anonymous memory (swap)"
225	depends on MMU && BLOCK
226	default y
227	help
228	  This option allows you to choose whether you want to have support
229	  for so called swap devices or swap files in your kernel that are
230	  used to provide more virtual memory than the actual RAM present
231	  in your computer.  If unsure say Y.
232
233config SYSVIPC
234	bool "System V IPC"
235	---help---
236	  Inter Process Communication is a suite of library functions and
237	  system calls which let processes (running programs) synchronize and
238	  exchange information. It is generally considered to be a good thing,
239	  and some programs won't run unless you say Y here. In particular, if
240	  you want to run the DOS emulator dosemu under Linux (read the
241	  DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
242	  you'll need to say Y here.
243
244	  You can find documentation about IPC with "info ipc" and also in
245	  section 6.4 of the Linux Programmer's Guide, available from
246	  <http://www.tldp.org/guides.html>.
247
248config SYSVIPC_SYSCTL
249	bool
250	depends on SYSVIPC
251	depends on SYSCTL
252	default y
253
254config POSIX_MQUEUE
255	bool "POSIX Message Queues"
256	depends on NET
257	---help---
258	  POSIX variant of message queues is a part of IPC. In POSIX message
259	  queues every message has a priority which decides about succession
260	  of receiving it by a process. If you want to compile and run
261	  programs written e.g. for Solaris with use of its POSIX message
262	  queues (functions mq_*) say Y here.
263
264	  POSIX message queues are visible as a filesystem called 'mqueue'
265	  and can be mounted somewhere if you want to do filesystem
266	  operations on message queues.
267
268	  If unsure, say Y.
269
270config POSIX_MQUEUE_SYSCTL
271	bool
272	depends on POSIX_MQUEUE
273	depends on SYSCTL
274	default y
275
276config CROSS_MEMORY_ATTACH
277	bool "Enable process_vm_readv/writev syscalls"
278	depends on MMU
279	default y
280	help
281	  Enabling this option adds the system calls process_vm_readv and
282	  process_vm_writev which allow a process with the correct privileges
283	  to directly read from or write to another process' address space.
284	  See the man page for more details.
285
286config FHANDLE
287	bool "open by fhandle syscalls" if EXPERT
288	select EXPORTFS
289	default y
290	help
291	  If you say Y here, a user level program will be able to map
292	  file names to handle and then later use the handle for
293	  different file system operations. This is useful in implementing
294	  userspace file servers, which now track files using handles instead
295	  of names. The handle would remain the same even if file names
296	  get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
297	  syscalls.
298
299config USELIB
300	bool "uselib syscall"
301	def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
302	help
303	  This option enables the uselib syscall, a system call used in the
304	  dynamic linker from libc5 and earlier.  glibc does not use this
305	  system call.  If you intend to run programs built on libc5 or
306	  earlier, you may need to enable this syscall.  Current systems
307	  running glibc can safely disable this.
308
309config AUDIT
310	bool "Auditing support"
311	depends on NET
312	help
313	  Enable auditing infrastructure that can be used with another
314	  kernel subsystem, such as SELinux (which requires this for
315	  logging of avc messages output).  System call auditing is included
316	  on architectures which support it.
317
318config HAVE_ARCH_AUDITSYSCALL
319	bool
320
321config AUDITSYSCALL
322	def_bool y
323	depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
324
325config AUDIT_WATCH
326	def_bool y
327	depends on AUDITSYSCALL
328	select FSNOTIFY
329
330config AUDIT_TREE
331	def_bool y
332	depends on AUDITSYSCALL
333	select FSNOTIFY
334
335source "kernel/irq/Kconfig"
336source "kernel/time/Kconfig"
337
338menu "CPU/Task time and stats accounting"
339
340config VIRT_CPU_ACCOUNTING
341	bool
342
343choice
344	prompt "Cputime accounting"
345	default TICK_CPU_ACCOUNTING if !PPC64
346	default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
347
348# Kind of a stub config for the pure tick based cputime accounting
349config TICK_CPU_ACCOUNTING
350	bool "Simple tick based cputime accounting"
351	depends on !S390 && !NO_HZ_FULL
352	help
353	  This is the basic tick based cputime accounting that maintains
354	  statistics about user, system and idle time spent on per jiffies
355	  granularity.
356
357	  If unsure, say Y.
358
359config VIRT_CPU_ACCOUNTING_NATIVE
360	bool "Deterministic task and CPU time accounting"
361	depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
362	select VIRT_CPU_ACCOUNTING
363	help
364	  Select this option to enable more accurate task and CPU time
365	  accounting.  This is done by reading a CPU counter on each
366	  kernel entry and exit and on transitions within the kernel
367	  between system, softirq and hardirq state, so there is a
368	  small performance impact.  In the case of s390 or IBM POWER > 5,
369	  this also enables accounting of stolen time on logically-partitioned
370	  systems.
371
372config VIRT_CPU_ACCOUNTING_GEN
373	bool "Full dynticks CPU time accounting"
374	depends on HAVE_CONTEXT_TRACKING
375	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
376	select VIRT_CPU_ACCOUNTING
377	select CONTEXT_TRACKING
378	help
379	  Select this option to enable task and CPU time accounting on full
380	  dynticks systems. This accounting is implemented by watching every
381	  kernel-user boundaries using the context tracking subsystem.
382	  The accounting is thus performed at the expense of some significant
383	  overhead.
384
385	  For now this is only useful if you are working on the full
386	  dynticks subsystem development.
387
388	  If unsure, say N.
389
390endchoice
391
392config IRQ_TIME_ACCOUNTING
393	bool "Fine granularity task level IRQ time accounting"
394	depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
395	help
396	  Select this option to enable fine granularity task irq time
397	  accounting. This is done by reading a timestamp on each
398	  transitions between softirq and hardirq state, so there can be a
399	  small performance impact.
400
401	  If in doubt, say N here.
402
403config BSD_PROCESS_ACCT
404	bool "BSD Process Accounting"
405	depends on MULTIUSER
406	help
407	  If you say Y here, a user level program will be able to instruct the
408	  kernel (via a special system call) to write process accounting
409	  information to a file: whenever a process exits, information about
410	  that process will be appended to the file by the kernel.  The
411	  information includes things such as creation time, owning user,
412	  command name, memory usage, controlling terminal etc. (the complete
413	  list is in the struct acct in <file:include/linux/acct.h>).  It is
414	  up to the user level program to do useful things with this
415	  information.  This is generally a good idea, so say Y.
416
417config BSD_PROCESS_ACCT_V3
418	bool "BSD Process Accounting version 3 file format"
419	depends on BSD_PROCESS_ACCT
420	default n
421	help
422	  If you say Y here, the process accounting information is written
423	  in a new file format that also logs the process IDs of each
424	  process and it's parent. Note that this file format is incompatible
425	  with previous v0/v1/v2 file formats, so you will need updated tools
426	  for processing it. A preliminary version of these tools is available
427	  at <http://www.gnu.org/software/acct/>.
428
429config TASKSTATS
430	bool "Export task/process statistics through netlink"
431	depends on NET
432	depends on MULTIUSER
433	default n
434	help
435	  Export selected statistics for tasks/processes through the
436	  generic netlink interface. Unlike BSD process accounting, the
437	  statistics are available during the lifetime of tasks/processes as
438	  responses to commands. Like BSD accounting, they are sent to user
439	  space on task exit.
440
441	  Say N if unsure.
442
443config TASK_DELAY_ACCT
444	bool "Enable per-task delay accounting"
445	depends on TASKSTATS
446	select SCHED_INFO
447	help
448	  Collect information on time spent by a task waiting for system
449	  resources like cpu, synchronous block I/O completion and swapping
450	  in pages. Such statistics can help in setting a task's priorities
451	  relative to other tasks for cpu, io, rss limits etc.
452
453	  Say N if unsure.
454
455config TASK_XACCT
456	bool "Enable extended accounting over taskstats"
457	depends on TASKSTATS
458	help
459	  Collect extended task accounting data and send the data
460	  to userland for processing over the taskstats interface.
461
462	  Say N if unsure.
463
464config TASK_IO_ACCOUNTING
465	bool "Enable per-task storage I/O accounting"
466	depends on TASK_XACCT
467	help
468	  Collect information on the number of bytes of storage I/O which this
469	  task has caused.
470
471	  Say N if unsure.
472
473endmenu # "CPU/Task time and stats accounting"
474
475source "kernel/rcu/Kconfig"
476
477config BUILD_BIN2C
478	bool
479	default n
480
481config IKCONFIG
482	tristate "Kernel .config support"
483	select BUILD_BIN2C
484	---help---
485	  This option enables the complete Linux kernel ".config" file
486	  contents to be saved in the kernel. It provides documentation
487	  of which kernel options are used in a running kernel or in an
488	  on-disk kernel.  This information can be extracted from the kernel
489	  image file with the script scripts/extract-ikconfig and used as
490	  input to rebuild the current kernel or to build another kernel.
491	  It can also be extracted from a running kernel by reading
492	  /proc/config.gz if enabled (below).
493
494config IKCONFIG_PROC
495	bool "Enable access to .config through /proc/config.gz"
496	depends on IKCONFIG && PROC_FS
497	---help---
498	  This option enables access to the kernel configuration file
499	  through /proc/config.gz.
500
501config LOG_BUF_SHIFT
502	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
503	range 12 25
504	default 17
505	depends on PRINTK
506	help
507	  Select the minimal kernel log buffer size as a power of 2.
508	  The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
509	  parameter, see below. Any higher size also might be forced
510	  by "log_buf_len" boot parameter.
511
512	  Examples:
513		     17 => 128 KB
514		     16 => 64 KB
515		     15 => 32 KB
516		     14 => 16 KB
517		     13 =>  8 KB
518		     12 =>  4 KB
519
520config LOG_CPU_MAX_BUF_SHIFT
521	int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
522	depends on SMP
523	range 0 21
524	default 12 if !BASE_SMALL
525	default 0 if BASE_SMALL
526	depends on PRINTK
527	help
528	  This option allows to increase the default ring buffer size
529	  according to the number of CPUs. The value defines the contribution
530	  of each CPU as a power of 2. The used space is typically only few
531	  lines however it might be much more when problems are reported,
532	  e.g. backtraces.
533
534	  The increased size means that a new buffer has to be allocated and
535	  the original static one is unused. It makes sense only on systems
536	  with more CPUs. Therefore this value is used only when the sum of
537	  contributions is greater than the half of the default kernel ring
538	  buffer as defined by LOG_BUF_SHIFT. The default values are set
539	  so that more than 64 CPUs are needed to trigger the allocation.
540
541	  Also this option is ignored when "log_buf_len" kernel parameter is
542	  used as it forces an exact (power of two) size of the ring buffer.
543
544	  The number of possible CPUs is used for this computation ignoring
545	  hotplugging making the computation optimal for the worst case
546	  scenario while allowing a simple algorithm to be used from bootup.
547
548	  Examples shift values and their meaning:
549		     17 => 128 KB for each CPU
550		     16 =>  64 KB for each CPU
551		     15 =>  32 KB for each CPU
552		     14 =>  16 KB for each CPU
553		     13 =>   8 KB for each CPU
554		     12 =>   4 KB for each CPU
555
556config PRINTK_SAFE_LOG_BUF_SHIFT
557	int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
558	range 10 21
559	default 13
560	depends on PRINTK
561	help
562	  Select the size of an alternate printk per-CPU buffer where messages
563	  printed from usafe contexts are temporary stored. One example would
564	  be NMI messages, another one - printk recursion. The messages are
565	  copied to the main log buffer in a safe context to avoid a deadlock.
566	  The value defines the size as a power of 2.
567
568	  Those messages are rare and limited. The largest one is when
569	  a backtrace is printed. It usually fits into 4KB. Select
570	  8KB if you want to be on the safe side.
571
572	  Examples:
573		     17 => 128 KB for each CPU
574		     16 =>  64 KB for each CPU
575		     15 =>  32 KB for each CPU
576		     14 =>  16 KB for each CPU
577		     13 =>   8 KB for each CPU
578		     12 =>   4 KB for each CPU
579
580#
581# Architectures with an unreliable sched_clock() should select this:
582#
583config HAVE_UNSTABLE_SCHED_CLOCK
584	bool
585
586config GENERIC_SCHED_CLOCK
587	bool
588
589#
590# For architectures that want to enable the support for NUMA-affine scheduler
591# balancing logic:
592#
593config ARCH_SUPPORTS_NUMA_BALANCING
594	bool
595
596#
597# For architectures that prefer to flush all TLBs after a number of pages
598# are unmapped instead of sending one IPI per page to flush. The architecture
599# must provide guarantees on what happens if a clean TLB cache entry is
600# written after the unmap. Details are in mm/rmap.c near the check for
601# should_defer_flush. The architecture should also consider if the full flush
602# and the refill costs are offset by the savings of sending fewer IPIs.
603config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
604	bool
605
606#
607# For architectures that know their GCC __int128 support is sound
608#
609config ARCH_SUPPORTS_INT128
610	bool
611
612# For architectures that (ab)use NUMA to represent different memory regions
613# all cpu-local but of different latencies, such as SuperH.
614#
615config ARCH_WANT_NUMA_VARIABLE_LOCALITY
616	bool
617
618config NUMA_BALANCING
619	bool "Memory placement aware NUMA scheduler"
620	depends on ARCH_SUPPORTS_NUMA_BALANCING
621	depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
622	depends on SMP && NUMA && MIGRATION
623	help
624	  This option adds support for automatic NUMA aware memory/task placement.
625	  The mechanism is quite primitive and is based on migrating memory when
626	  it has references to the node the task is running on.
627
628	  This system will be inactive on UMA systems.
629
630config NUMA_BALANCING_DEFAULT_ENABLED
631	bool "Automatically enable NUMA aware memory/task placement"
632	default y
633	depends on NUMA_BALANCING
634	help
635	  If set, automatic NUMA balancing will be enabled if running on a NUMA
636	  machine.
637
638menuconfig CGROUPS
639	bool "Control Group support"
640	select KERNFS
641	help
642	  This option adds support for grouping sets of processes together, for
643	  use with process control subsystems such as Cpusets, CFS, memory
644	  controls or device isolation.
645	  See
646		- Documentation/scheduler/sched-design-CFS.txt	(CFS)
647		- Documentation/cgroup-v1/ (features for grouping, isolation
648					  and resource control)
649
650	  Say N if unsure.
651
652if CGROUPS
653
654config PAGE_COUNTER
655       bool
656
657config MEMCG
658	bool "Memory controller"
659	select PAGE_COUNTER
660	select EVENTFD
661	help
662	  Provides control over the memory footprint of tasks in a cgroup.
663
664config MEMCG_SWAP
665	bool "Swap controller"
666	depends on MEMCG && SWAP
667	help
668	  Provides control over the swap space consumed by tasks in a cgroup.
669
670config MEMCG_SWAP_ENABLED
671	bool "Swap controller enabled by default"
672	depends on MEMCG_SWAP
673	default y
674	help
675	  Memory Resource Controller Swap Extension comes with its price in
676	  a bigger memory consumption. General purpose distribution kernels
677	  which want to enable the feature but keep it disabled by default
678	  and let the user enable it by swapaccount=1 boot command line
679	  parameter should have this option unselected.
680	  For those who want to have the feature enabled by default should
681	  select this option (if, for some reason, they need to disable it
682	  then swapaccount=0 does the trick).
683
684config BLK_CGROUP
685	bool "IO controller"
686	depends on BLOCK
687	default n
688	---help---
689	Generic block IO controller cgroup interface. This is the common
690	cgroup interface which should be used by various IO controlling
691	policies.
692
693	Currently, CFQ IO scheduler uses it to recognize task groups and
694	control disk bandwidth allocation (proportional time slice allocation)
695	to such task groups. It is also used by bio throttling logic in
696	block layer to implement upper limit in IO rates on a device.
697
698	This option only enables generic Block IO controller infrastructure.
699	One needs to also enable actual IO controlling logic/policy. For
700	enabling proportional weight division of disk bandwidth in CFQ, set
701	CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
702	CONFIG_BLK_DEV_THROTTLING=y.
703
704	See Documentation/cgroup-v1/blkio-controller.txt for more information.
705
706config DEBUG_BLK_CGROUP
707	bool "IO controller debugging"
708	depends on BLK_CGROUP
709	default n
710	---help---
711	Enable some debugging help. Currently it exports additional stat
712	files in a cgroup which can be useful for debugging.
713
714config CGROUP_WRITEBACK
715	bool
716	depends on MEMCG && BLK_CGROUP
717	default y
718
719menuconfig CGROUP_SCHED
720	bool "CPU controller"
721	default n
722	help
723	  This feature lets CPU scheduler recognize task groups and control CPU
724	  bandwidth allocation to such task groups. It uses cgroups to group
725	  tasks.
726
727if CGROUP_SCHED
728config FAIR_GROUP_SCHED
729	bool "Group scheduling for SCHED_OTHER"
730	depends on CGROUP_SCHED
731	default CGROUP_SCHED
732
733config CFS_BANDWIDTH
734	bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
735	depends on FAIR_GROUP_SCHED
736	default n
737	help
738	  This option allows users to define CPU bandwidth rates (limits) for
739	  tasks running within the fair group scheduler.  Groups with no limit
740	  set are considered to be unconstrained and will run with no
741	  restriction.
742	  See tip/Documentation/scheduler/sched-bwc.txt for more information.
743
744config RT_GROUP_SCHED
745	bool "Group scheduling for SCHED_RR/FIFO"
746	depends on CGROUP_SCHED
747	default n
748	help
749	  This feature lets you explicitly allocate real CPU bandwidth
750	  to task groups. If enabled, it will also make it impossible to
751	  schedule realtime tasks for non-root users until you allocate
752	  realtime bandwidth for them.
753	  See Documentation/scheduler/sched-rt-group.txt for more information.
754
755endif #CGROUP_SCHED
756
757config CGROUP_PIDS
758	bool "PIDs controller"
759	help
760	  Provides enforcement of process number limits in the scope of a
761	  cgroup. Any attempt to fork more processes than is allowed in the
762	  cgroup will fail. PIDs are fundamentally a global resource because it
763	  is fairly trivial to reach PID exhaustion before you reach even a
764	  conservative kmemcg limit. As a result, it is possible to grind a
765	  system to halt without being limited by other cgroup policies. The
766	  PIDs controller is designed to stop this from happening.
767
768	  It should be noted that organisational operations (such as attaching
769	  to a cgroup hierarchy will *not* be blocked by the PIDs controller),
770	  since the PIDs limit only affects a process's ability to fork, not to
771	  attach to a cgroup.
772
773config CGROUP_RDMA
774	bool "RDMA controller"
775	help
776	  Provides enforcement of RDMA resources defined by IB stack.
777	  It is fairly easy for consumers to exhaust RDMA resources, which
778	  can result into resource unavailability to other consumers.
779	  RDMA controller is designed to stop this from happening.
780	  Attaching processes with active RDMA resources to the cgroup
781	  hierarchy is allowed even if can cross the hierarchy's limit.
782
783config CGROUP_FREEZER
784	bool "Freezer controller"
785	help
786	  Provides a way to freeze and unfreeze all tasks in a
787	  cgroup.
788
789	  This option affects the ORIGINAL cgroup interface. The cgroup2 memory
790	  controller includes important in-kernel memory consumers per default.
791
792	  If you're using cgroup2, say N.
793
794config CGROUP_HUGETLB
795	bool "HugeTLB controller"
796	depends on HUGETLB_PAGE
797	select PAGE_COUNTER
798	default n
799	help
800	  Provides a cgroup controller for HugeTLB pages.
801	  When you enable this, you can put a per cgroup limit on HugeTLB usage.
802	  The limit is enforced during page fault. Since HugeTLB doesn't
803	  support page reclaim, enforcing the limit at page fault time implies
804	  that, the application will get SIGBUS signal if it tries to access
805	  HugeTLB pages beyond its limit. This requires the application to know
806	  beforehand how much HugeTLB pages it would require for its use. The
807	  control group is tracked in the third page lru pointer. This means
808	  that we cannot use the controller with huge page less than 3 pages.
809
810config CPUSETS
811	bool "Cpuset controller"
812	depends on SMP
813	help
814	  This option will let you create and manage CPUSETs which
815	  allow dynamically partitioning a system into sets of CPUs and
816	  Memory Nodes and assigning tasks to run only within those sets.
817	  This is primarily useful on large SMP or NUMA systems.
818
819	  Say N if unsure.
820
821config PROC_PID_CPUSET
822	bool "Include legacy /proc/<pid>/cpuset file"
823	depends on CPUSETS
824	default y
825
826config CGROUP_DEVICE
827	bool "Device controller"
828	help
829	  Provides a cgroup controller implementing whitelists for
830	  devices which a process in the cgroup can mknod or open.
831
832config CGROUP_CPUACCT
833	bool "Simple CPU accounting controller"
834	help
835	  Provides a simple controller for monitoring the
836	  total CPU consumed by the tasks in a cgroup.
837
838config CGROUP_PERF
839	bool "Perf controller"
840	depends on PERF_EVENTS
841	help
842	  This option extends the perf per-cpu mode to restrict monitoring
843	  to threads which belong to the cgroup specified and run on the
844	  designated cpu.
845
846	  Say N if unsure.
847
848config CGROUP_BPF
849	bool "Support for eBPF programs attached to cgroups"
850	depends on BPF_SYSCALL
851	select SOCK_CGROUP_DATA
852	help
853	  Allow attaching eBPF programs to a cgroup using the bpf(2)
854	  syscall command BPF_PROG_ATTACH.
855
856	  In which context these programs are accessed depends on the type
857	  of attachment. For instance, programs that are attached using
858	  BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
859	  inet sockets.
860
861config CGROUP_DEBUG
862	bool "Debug controller"
863	default n
864	depends on DEBUG_KERNEL
865	help
866	  This option enables a simple controller that exports
867	  debugging information about the cgroups framework. This
868	  controller is for control cgroup debugging only. Its
869	  interfaces are not stable.
870
871	  Say N.
872
873config SOCK_CGROUP_DATA
874	bool
875	default n
876
877endif # CGROUPS
878
879config CHECKPOINT_RESTORE
880	bool "Checkpoint/restore support" if EXPERT
881	select PROC_CHILDREN
882	default n
883	help
884	  Enables additional kernel features in a sake of checkpoint/restore.
885	  In particular it adds auxiliary prctl codes to setup process text,
886	  data and heap segment sizes, and a few additional /proc filesystem
887	  entries.
888
889	  If unsure, say N here.
890
891menuconfig NAMESPACES
892	bool "Namespaces support" if EXPERT
893	depends on MULTIUSER
894	default !EXPERT
895	help
896	  Provides the way to make tasks work with different objects using
897	  the same id. For example same IPC id may refer to different objects
898	  or same user id or pid may refer to different tasks when used in
899	  different namespaces.
900
901if NAMESPACES
902
903config UTS_NS
904	bool "UTS namespace"
905	default y
906	help
907	  In this namespace tasks see different info provided with the
908	  uname() system call
909
910config IPC_NS
911	bool "IPC namespace"
912	depends on (SYSVIPC || POSIX_MQUEUE)
913	default y
914	help
915	  In this namespace tasks work with IPC ids which correspond to
916	  different IPC objects in different namespaces.
917
918config USER_NS
919	bool "User namespace"
920	default n
921	help
922	  This allows containers, i.e. vservers, to use user namespaces
923	  to provide different user info for different servers.
924
925	  When user namespaces are enabled in the kernel it is
926	  recommended that the MEMCG option also be enabled and that
927	  user-space use the memory control groups to limit the amount
928	  of memory a memory unprivileged users can use.
929
930	  If unsure, say N.
931
932config PID_NS
933	bool "PID Namespaces"
934	default y
935	help
936	  Support process id namespaces.  This allows having multiple
937	  processes with the same pid as long as they are in different
938	  pid namespaces.  This is a building block of containers.
939
940config NET_NS
941	bool "Network namespace"
942	depends on NET
943	default y
944	help
945	  Allow user space to create what appear to be multiple instances
946	  of the network stack.
947
948endif # NAMESPACES
949
950config SCHED_AUTOGROUP
951	bool "Automatic process group scheduling"
952	select CGROUPS
953	select CGROUP_SCHED
954	select FAIR_GROUP_SCHED
955	help
956	  This option optimizes the scheduler for common desktop workloads by
957	  automatically creating and populating task groups.  This separation
958	  of workloads isolates aggressive CPU burners (like build jobs) from
959	  desktop applications.  Task group autogeneration is currently based
960	  upon task session.
961
962config SYSFS_DEPRECATED
963	bool "Enable deprecated sysfs features to support old userspace tools"
964	depends on SYSFS
965	default n
966	help
967	  This option adds code that switches the layout of the "block" class
968	  devices, to not show up in /sys/class/block/, but only in
969	  /sys/block/.
970
971	  This switch is only active when the sysfs.deprecated=1 boot option is
972	  passed or the SYSFS_DEPRECATED_V2 option is set.
973
974	  This option allows new kernels to run on old distributions and tools,
975	  which might get confused by /sys/class/block/. Since 2007/2008 all
976	  major distributions and tools handle this just fine.
977
978	  Recent distributions and userspace tools after 2009/2010 depend on
979	  the existence of /sys/class/block/, and will not work with this
980	  option enabled.
981
982	  Only if you are using a new kernel on an old distribution, you might
983	  need to say Y here.
984
985config SYSFS_DEPRECATED_V2
986	bool "Enable deprecated sysfs features by default"
987	default n
988	depends on SYSFS
989	depends on SYSFS_DEPRECATED
990	help
991	  Enable deprecated sysfs by default.
992
993	  See the CONFIG_SYSFS_DEPRECATED option for more details about this
994	  option.
995
996	  Only if you are using a new kernel on an old distribution, you might
997	  need to say Y here. Even then, odds are you would not need it
998	  enabled, you can always pass the boot option if absolutely necessary.
999
1000config RELAY
1001	bool "Kernel->user space relay support (formerly relayfs)"
1002	select IRQ_WORK
1003	help
1004	  This option enables support for relay interface support in
1005	  certain file systems (such as debugfs).
1006	  It is designed to provide an efficient mechanism for tools and
1007	  facilities to relay large amounts of data from kernel space to
1008	  user space.
1009
1010	  If unsure, say N.
1011
1012config BLK_DEV_INITRD
1013	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1014	depends on BROKEN || !FRV
1015	help
1016	  The initial RAM filesystem is a ramfs which is loaded by the
1017	  boot loader (loadlin or lilo) and that is mounted as root
1018	  before the normal boot procedure. It is typically used to
1019	  load modules needed to mount the "real" root file system,
1020	  etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1021
1022	  If RAM disk support (BLK_DEV_RAM) is also included, this
1023	  also enables initial RAM disk (initrd) support and adds
1024	  15 Kbytes (more on some other architectures) to the kernel size.
1025
1026	  If unsure say Y.
1027
1028if BLK_DEV_INITRD
1029
1030source "usr/Kconfig"
1031
1032endif
1033
1034choice
1035	prompt "Compiler optimization level"
1036	default CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE
1037
1038config CC_OPTIMIZE_FOR_PERFORMANCE
1039	bool "Optimize for performance"
1040	help
1041	  This is the default optimization level for the kernel, building
1042	  with the "-O2" compiler flag for best performance and most
1043	  helpful compile-time warnings.
1044
1045config CC_OPTIMIZE_FOR_SIZE
1046	bool "Optimize for size"
1047	help
1048	  Enabling this option will pass "-Os" instead of "-O2" to
1049	  your compiler resulting in a smaller kernel.
1050
1051	  If unsure, say N.
1052
1053endchoice
1054
1055config SYSCTL
1056	bool
1057
1058config ANON_INODES
1059	bool
1060
1061config HAVE_UID16
1062	bool
1063
1064config SYSCTL_EXCEPTION_TRACE
1065	bool
1066	help
1067	  Enable support for /proc/sys/debug/exception-trace.
1068
1069config SYSCTL_ARCH_UNALIGN_NO_WARN
1070	bool
1071	help
1072	  Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1073	  Allows arch to define/use @no_unaligned_warning to possibly warn
1074	  about unaligned access emulation going on under the hood.
1075
1076config SYSCTL_ARCH_UNALIGN_ALLOW
1077	bool
1078	help
1079	  Enable support for /proc/sys/kernel/unaligned-trap
1080	  Allows arches to define/use @unaligned_enabled to runtime toggle
1081	  the unaligned access emulation.
1082	  see arch/parisc/kernel/unaligned.c for reference
1083
1084config HAVE_PCSPKR_PLATFORM
1085	bool
1086
1087# interpreter that classic socket filters depend on
1088config BPF
1089	bool
1090
1091menuconfig EXPERT
1092	bool "Configure standard kernel features (expert users)"
1093	# Unhide debug options, to make the on-by-default options visible
1094	select DEBUG_KERNEL
1095	help
1096	  This option allows certain base kernel options and settings
1097          to be disabled or tweaked. This is for specialized
1098          environments which can tolerate a "non-standard" kernel.
1099          Only use this if you really know what you are doing.
1100
1101config UID16
1102	bool "Enable 16-bit UID system calls" if EXPERT
1103	depends on HAVE_UID16 && MULTIUSER
1104	default y
1105	help
1106	  This enables the legacy 16-bit UID syscall wrappers.
1107
1108config MULTIUSER
1109	bool "Multiple users, groups and capabilities support" if EXPERT
1110	default y
1111	help
1112	  This option enables support for non-root users, groups and
1113	  capabilities.
1114
1115	  If you say N here, all processes will run with UID 0, GID 0, and all
1116	  possible capabilities.  Saying N here also compiles out support for
1117	  system calls related to UIDs, GIDs, and capabilities, such as setuid,
1118	  setgid, and capset.
1119
1120	  If unsure, say Y here.
1121
1122config SGETMASK_SYSCALL
1123	bool "sgetmask/ssetmask syscalls support" if EXPERT
1124	def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1125	---help---
1126	  sys_sgetmask and sys_ssetmask are obsolete system calls
1127	  no longer supported in libc but still enabled by default in some
1128	  architectures.
1129
1130	  If unsure, leave the default option here.
1131
1132config SYSFS_SYSCALL
1133	bool "Sysfs syscall support" if EXPERT
1134	default y
1135	---help---
1136	  sys_sysfs is an obsolete system call no longer supported in libc.
1137	  Note that disabling this option is more secure but might break
1138	  compatibility with some systems.
1139
1140	  If unsure say Y here.
1141
1142config SYSCTL_SYSCALL
1143	bool "Sysctl syscall support" if EXPERT
1144	depends on PROC_SYSCTL
1145	default n
1146	select SYSCTL
1147	---help---
1148	  sys_sysctl uses binary paths that have been found challenging
1149	  to properly maintain and use.  The interface in /proc/sys
1150	  using paths with ascii names is now the primary path to this
1151	  information.
1152
1153	  Almost nothing using the binary sysctl interface so if you are
1154	  trying to save some space it is probably safe to disable this,
1155	  making your kernel marginally smaller.
1156
1157	  If unsure say N here.
1158
1159config POSIX_TIMERS
1160	bool "Posix Clocks & timers" if EXPERT
1161	default y
1162	help
1163	  This includes native support for POSIX timers to the kernel.
1164	  Some embedded systems have no use for them and therefore they
1165	  can be configured out to reduce the size of the kernel image.
1166
1167	  When this option is disabled, the following syscalls won't be
1168	  available: timer_create, timer_gettime: timer_getoverrun,
1169	  timer_settime, timer_delete, clock_adjtime, getitimer,
1170	  setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1171	  clock_getres and clock_nanosleep syscalls will be limited to
1172	  CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1173
1174	  If unsure say y.
1175
1176config KALLSYMS
1177	 bool "Load all symbols for debugging/ksymoops" if EXPERT
1178	 default y
1179	 help
1180	   Say Y here to let the kernel print out symbolic crash information and
1181	   symbolic stack backtraces. This increases the size of the kernel
1182	   somewhat, as all symbols have to be loaded into the kernel image.
1183
1184config KALLSYMS_ALL
1185	bool "Include all symbols in kallsyms"
1186	depends on DEBUG_KERNEL && KALLSYMS
1187	help
1188	   Normally kallsyms only contains the symbols of functions for nicer
1189	   OOPS messages and backtraces (i.e., symbols from the text and inittext
1190	   sections). This is sufficient for most cases. And only in very rare
1191	   cases (e.g., when a debugger is used) all symbols are required (e.g.,
1192	   names of variables from the data sections, etc).
1193
1194	   This option makes sure that all symbols are loaded into the kernel
1195	   image (i.e., symbols from all sections) in cost of increased kernel
1196	   size (depending on the kernel configuration, it may be 300KiB or
1197	   something like this).
1198
1199	   Say N unless you really need all symbols.
1200
1201config KALLSYMS_ABSOLUTE_PERCPU
1202	bool
1203	depends on KALLSYMS
1204	default X86_64 && SMP
1205
1206config KALLSYMS_BASE_RELATIVE
1207	bool
1208	depends on KALLSYMS
1209	default !IA64 && !(TILE && 64BIT)
1210	help
1211	  Instead of emitting them as absolute values in the native word size,
1212	  emit the symbol references in the kallsyms table as 32-bit entries,
1213	  each containing a relative value in the range [base, base + U32_MAX]
1214	  or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1215	  an absolute value in the range [0, S32_MAX] or a relative value in the
1216	  range [base, base + S32_MAX], where base is the lowest relative symbol
1217	  address encountered in the image.
1218
1219	  On 64-bit builds, this reduces the size of the address table by 50%,
1220	  but more importantly, it results in entries whose values are build
1221	  time constants, and no relocation pass is required at runtime to fix
1222	  up the entries based on the runtime load address of the kernel.
1223
1224config PRINTK
1225	default y
1226	bool "Enable support for printk" if EXPERT
1227	select IRQ_WORK
1228	help
1229	  This option enables normal printk support. Removing it
1230	  eliminates most of the message strings from the kernel image
1231	  and makes the kernel more or less silent. As this makes it
1232	  very difficult to diagnose system problems, saying N here is
1233	  strongly discouraged.
1234
1235config PRINTK_NMI
1236	def_bool y
1237	depends on PRINTK
1238	depends on HAVE_NMI
1239
1240config BUG
1241	bool "BUG() support" if EXPERT
1242	default y
1243	help
1244          Disabling this option eliminates support for BUG and WARN, reducing
1245          the size of your kernel image and potentially quietly ignoring
1246          numerous fatal conditions. You should only consider disabling this
1247          option for embedded systems with no facilities for reporting errors.
1248          Just say Y.
1249
1250config ELF_CORE
1251	depends on COREDUMP
1252	default y
1253	bool "Enable ELF core dumps" if EXPERT
1254	help
1255	  Enable support for generating core dumps. Disabling saves about 4k.
1256
1257
1258config PCSPKR_PLATFORM
1259	bool "Enable PC-Speaker support" if EXPERT
1260	depends on HAVE_PCSPKR_PLATFORM
1261	select I8253_LOCK
1262	default y
1263	help
1264          This option allows to disable the internal PC-Speaker
1265          support, saving some memory.
1266
1267config BASE_FULL
1268	default y
1269	bool "Enable full-sized data structures for core" if EXPERT
1270	help
1271	  Disabling this option reduces the size of miscellaneous core
1272	  kernel data structures. This saves memory on small machines,
1273	  but may reduce performance.
1274
1275config FUTEX
1276	bool "Enable futex support" if EXPERT
1277	default y
1278	imply RT_MUTEXES
1279	help
1280	  Disabling this option will cause the kernel to be built without
1281	  support for "fast userspace mutexes".  The resulting kernel may not
1282	  run glibc-based applications correctly.
1283
1284config FUTEX_PI
1285	bool
1286	depends on FUTEX && RT_MUTEXES
1287	default y
1288
1289config HAVE_FUTEX_CMPXCHG
1290	bool
1291	depends on FUTEX
1292	help
1293	  Architectures should select this if futex_atomic_cmpxchg_inatomic()
1294	  is implemented and always working. This removes a couple of runtime
1295	  checks.
1296
1297config EPOLL
1298	bool "Enable eventpoll support" if EXPERT
1299	default y
1300	select ANON_INODES
1301	help
1302	  Disabling this option will cause the kernel to be built without
1303	  support for epoll family of system calls.
1304
1305config SIGNALFD
1306	bool "Enable signalfd() system call" if EXPERT
1307	select ANON_INODES
1308	default y
1309	help
1310	  Enable the signalfd() system call that allows to receive signals
1311	  on a file descriptor.
1312
1313	  If unsure, say Y.
1314
1315config TIMERFD
1316	bool "Enable timerfd() system call" if EXPERT
1317	select ANON_INODES
1318	default y
1319	help
1320	  Enable the timerfd() system call that allows to receive timer
1321	  events on a file descriptor.
1322
1323	  If unsure, say Y.
1324
1325config EVENTFD
1326	bool "Enable eventfd() system call" if EXPERT
1327	select ANON_INODES
1328	default y
1329	help
1330	  Enable the eventfd() system call that allows to receive both
1331	  kernel notification (ie. KAIO) or userspace notifications.
1332
1333	  If unsure, say Y.
1334
1335# syscall, maps, verifier
1336config BPF_SYSCALL
1337	bool "Enable bpf() system call"
1338	select ANON_INODES
1339	select BPF
1340	default n
1341	help
1342	  Enable the bpf() system call that allows to manipulate eBPF
1343	  programs and maps via file descriptors.
1344
1345config SHMEM
1346	bool "Use full shmem filesystem" if EXPERT
1347	default y
1348	depends on MMU
1349	help
1350	  The shmem is an internal filesystem used to manage shared memory.
1351	  It is backed by swap and manages resource limits. It is also exported
1352	  to userspace as tmpfs if TMPFS is enabled. Disabling this
1353	  option replaces shmem and tmpfs with the much simpler ramfs code,
1354	  which may be appropriate on small systems without swap.
1355
1356config AIO
1357	bool "Enable AIO support" if EXPERT
1358	default y
1359	help
1360	  This option enables POSIX asynchronous I/O which may by used
1361	  by some high performance threaded applications. Disabling
1362	  this option saves about 7k.
1363
1364config ADVISE_SYSCALLS
1365	bool "Enable madvise/fadvise syscalls" if EXPERT
1366	default y
1367	help
1368	  This option enables the madvise and fadvise syscalls, used by
1369	  applications to advise the kernel about their future memory or file
1370	  usage, improving performance. If building an embedded system where no
1371	  applications use these syscalls, you can disable this option to save
1372	  space.
1373
1374config USERFAULTFD
1375	bool "Enable userfaultfd() system call"
1376	select ANON_INODES
1377	depends on MMU
1378	help
1379	  Enable the userfaultfd() system call that allows to intercept and
1380	  handle page faults in userland.
1381
1382config PCI_QUIRKS
1383	default y
1384	bool "Enable PCI quirk workarounds" if EXPERT
1385	depends on PCI
1386	help
1387	  This enables workarounds for various PCI chipset
1388	  bugs/quirks. Disable this only if your target machine is
1389	  unaffected by PCI quirks.
1390
1391config MEMBARRIER
1392	bool "Enable membarrier() system call" if EXPERT
1393	default y
1394	help
1395	  Enable the membarrier() system call that allows issuing memory
1396	  barriers across all running threads, which can be used to distribute
1397	  the cost of user-space memory barriers asymmetrically by transforming
1398	  pairs of memory barriers into pairs consisting of membarrier() and a
1399	  compiler barrier.
1400
1401	  If unsure, say Y.
1402
1403config EMBEDDED
1404	bool "Embedded system"
1405	option allnoconfig_y
1406	select EXPERT
1407	help
1408	  This option should be enabled if compiling the kernel for
1409	  an embedded system so certain expert options are available
1410	  for configuration.
1411
1412config HAVE_PERF_EVENTS
1413	bool
1414	help
1415	  See tools/perf/design.txt for details.
1416
1417config PERF_USE_VMALLOC
1418	bool
1419	help
1420	  See tools/perf/design.txt for details
1421
1422config PC104
1423	bool "PC/104 support"
1424	help
1425	  Expose PC/104 form factor device drivers and options available for
1426	  selection and configuration. Enable this option if your target
1427	  machine has a PC/104 bus.
1428
1429menu "Kernel Performance Events And Counters"
1430
1431config PERF_EVENTS
1432	bool "Kernel performance events and counters"
1433	default y if PROFILING
1434	depends on HAVE_PERF_EVENTS
1435	select ANON_INODES
1436	select IRQ_WORK
1437	select SRCU
1438	help
1439	  Enable kernel support for various performance events provided
1440	  by software and hardware.
1441
1442	  Software events are supported either built-in or via the
1443	  use of generic tracepoints.
1444
1445	  Most modern CPUs support performance events via performance
1446	  counter registers. These registers count the number of certain
1447	  types of hw events: such as instructions executed, cachemisses
1448	  suffered, or branches mis-predicted - without slowing down the
1449	  kernel or applications. These registers can also trigger interrupts
1450	  when a threshold number of events have passed - and can thus be
1451	  used to profile the code that runs on that CPU.
1452
1453	  The Linux Performance Event subsystem provides an abstraction of
1454	  these software and hardware event capabilities, available via a
1455	  system call and used by the "perf" utility in tools/perf/. It
1456	  provides per task and per CPU counters, and it provides event
1457	  capabilities on top of those.
1458
1459	  Say Y if unsure.
1460
1461config DEBUG_PERF_USE_VMALLOC
1462	default n
1463	bool "Debug: use vmalloc to back perf mmap() buffers"
1464	depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1465	select PERF_USE_VMALLOC
1466	help
1467	 Use vmalloc memory to back perf mmap() buffers.
1468
1469	 Mostly useful for debugging the vmalloc code on platforms
1470	 that don't require it.
1471
1472	 Say N if unsure.
1473
1474endmenu
1475
1476config VM_EVENT_COUNTERS
1477	default y
1478	bool "Enable VM event counters for /proc/vmstat" if EXPERT
1479	help
1480	  VM event counters are needed for event counts to be shown.
1481	  This option allows the disabling of the VM event counters
1482	  on EXPERT systems.  /proc/vmstat will only show page counts
1483	  if VM event counters are disabled.
1484
1485config SLUB_DEBUG
1486	default y
1487	bool "Enable SLUB debugging support" if EXPERT
1488	depends on SLUB && SYSFS
1489	help
1490	  SLUB has extensive debug support features. Disabling these can
1491	  result in significant savings in code size. This also disables
1492	  SLUB sysfs support. /sys/slab will not exist and there will be
1493	  no support for cache validation etc.
1494
1495config SLUB_MEMCG_SYSFS_ON
1496	default n
1497	bool "Enable memcg SLUB sysfs support by default" if EXPERT
1498	depends on SLUB && SYSFS && MEMCG
1499	help
1500	  SLUB creates a directory under /sys/kernel/slab for each
1501	  allocation cache to host info and debug files. If memory
1502	  cgroup is enabled, each cache can have per memory cgroup
1503	  caches. SLUB can create the same sysfs directories for these
1504	  caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1505	  to a very high number of debug files being created. This is
1506	  controlled by slub_memcg_sysfs boot parameter and this
1507	  config option determines the parameter's default value.
1508
1509config COMPAT_BRK
1510	bool "Disable heap randomization"
1511	default y
1512	help
1513	  Randomizing heap placement makes heap exploits harder, but it
1514	  also breaks ancient binaries (including anything libc5 based).
1515	  This option changes the bootup default to heap randomization
1516	  disabled, and can be overridden at runtime by setting
1517	  /proc/sys/kernel/randomize_va_space to 2.
1518
1519	  On non-ancient distros (post-2000 ones) N is usually a safe choice.
1520
1521choice
1522	prompt "Choose SLAB allocator"
1523	default SLUB
1524	help
1525	   This option allows to select a slab allocator.
1526
1527config SLAB
1528	bool "SLAB"
1529	select HAVE_HARDENED_USERCOPY_ALLOCATOR
1530	help
1531	  The regular slab allocator that is established and known to work
1532	  well in all environments. It organizes cache hot objects in
1533	  per cpu and per node queues.
1534
1535config SLUB
1536	bool "SLUB (Unqueued Allocator)"
1537	select HAVE_HARDENED_USERCOPY_ALLOCATOR
1538	help
1539	   SLUB is a slab allocator that minimizes cache line usage
1540	   instead of managing queues of cached objects (SLAB approach).
1541	   Per cpu caching is realized using slabs of objects instead
1542	   of queues of objects. SLUB can use memory efficiently
1543	   and has enhanced diagnostics. SLUB is the default choice for
1544	   a slab allocator.
1545
1546config SLOB
1547	depends on EXPERT
1548	bool "SLOB (Simple Allocator)"
1549	help
1550	   SLOB replaces the stock allocator with a drastically simpler
1551	   allocator. SLOB is generally more space efficient but
1552	   does not perform as well on large systems.
1553
1554endchoice
1555
1556config SLAB_MERGE_DEFAULT
1557	bool "Allow slab caches to be merged"
1558	default y
1559	help
1560	  For reduced kernel memory fragmentation, slab caches can be
1561	  merged when they share the same size and other characteristics.
1562	  This carries a risk of kernel heap overflows being able to
1563	  overwrite objects from merged caches (and more easily control
1564	  cache layout), which makes such heap attacks easier to exploit
1565	  by attackers. By keeping caches unmerged, these kinds of exploits
1566	  can usually only damage objects in the same cache. To disable
1567	  merging at runtime, "slab_nomerge" can be passed on the kernel
1568	  command line.
1569
1570config SLAB_FREELIST_RANDOM
1571	default n
1572	depends on SLAB || SLUB
1573	bool "SLAB freelist randomization"
1574	help
1575	  Randomizes the freelist order used on creating new pages. This
1576	  security feature reduces the predictability of the kernel slab
1577	  allocator against heap overflows.
1578
1579config SLAB_FREELIST_HARDENED
1580	bool "Harden slab freelist metadata"
1581	depends on SLUB
1582	help
1583	  Many kernel heap attacks try to target slab cache metadata and
1584	  other infrastructure. This options makes minor performance
1585	  sacrifies to harden the kernel slab allocator against common
1586	  freelist exploit methods.
1587
1588config SLUB_CPU_PARTIAL
1589	default y
1590	depends on SLUB && SMP
1591	bool "SLUB per cpu partial cache"
1592	help
1593	  Per cpu partial caches accellerate objects allocation and freeing
1594	  that is local to a processor at the price of more indeterminism
1595	  in the latency of the free. On overflow these caches will be cleared
1596	  which requires the taking of locks that may cause latency spikes.
1597	  Typically one would choose no for a realtime system.
1598
1599config MMAP_ALLOW_UNINITIALIZED
1600	bool "Allow mmapped anonymous memory to be uninitialized"
1601	depends on EXPERT && !MMU
1602	default n
1603	help
1604	  Normally, and according to the Linux spec, anonymous memory obtained
1605	  from mmap() has it's contents cleared before it is passed to
1606	  userspace.  Enabling this config option allows you to request that
1607	  mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1608	  providing a huge performance boost.  If this option is not enabled,
1609	  then the flag will be ignored.
1610
1611	  This is taken advantage of by uClibc's malloc(), and also by
1612	  ELF-FDPIC binfmt's brk and stack allocator.
1613
1614	  Because of the obvious security issues, this option should only be
1615	  enabled on embedded devices where you control what is run in
1616	  userspace.  Since that isn't generally a problem on no-MMU systems,
1617	  it is normally safe to say Y here.
1618
1619	  See Documentation/nommu-mmap.txt for more information.
1620
1621config SYSTEM_DATA_VERIFICATION
1622	def_bool n
1623	select SYSTEM_TRUSTED_KEYRING
1624	select KEYS
1625	select CRYPTO
1626	select CRYPTO_RSA
1627	select ASYMMETRIC_KEY_TYPE
1628	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1629	select ASN1
1630	select OID_REGISTRY
1631	select X509_CERTIFICATE_PARSER
1632	select PKCS7_MESSAGE_PARSER
1633	help
1634	  Provide PKCS#7 message verification using the contents of the system
1635	  trusted keyring to provide public keys.  This then can be used for
1636	  module verification, kexec image verification and firmware blob
1637	  verification.
1638
1639config PROFILING
1640	bool "Profiling support"
1641	help
1642	  Say Y here to enable the extended profiling support mechanisms used
1643	  by profilers such as OProfile.
1644
1645#
1646# Place an empty function call at each tracepoint site. Can be
1647# dynamically changed for a probe function.
1648#
1649config TRACEPOINTS
1650	bool
1651
1652source "arch/Kconfig"
1653
1654endmenu		# General setup
1655
1656config HAVE_GENERIC_DMA_COHERENT
1657	bool
1658	default n
1659
1660config SLABINFO
1661	bool
1662	depends on PROC_FS
1663	depends on SLAB || SLUB_DEBUG
1664	default y
1665
1666config RT_MUTEXES
1667	bool
1668
1669config BASE_SMALL
1670	int
1671	default 0 if BASE_FULL
1672	default 1 if !BASE_FULL
1673
1674menuconfig MODULES
1675	bool "Enable loadable module support"
1676	option modules
1677	help
1678	  Kernel modules are small pieces of compiled code which can
1679	  be inserted in the running kernel, rather than being
1680	  permanently built into the kernel.  You use the "modprobe"
1681	  tool to add (and sometimes remove) them.  If you say Y here,
1682	  many parts of the kernel can be built as modules (by
1683	  answering M instead of Y where indicated): this is most
1684	  useful for infrequently used options which are not required
1685	  for booting.  For more information, see the man pages for
1686	  modprobe, lsmod, modinfo, insmod and rmmod.
1687
1688	  If you say Y here, you will need to run "make
1689	  modules_install" to put the modules under /lib/modules/
1690	  where modprobe can find them (you may need to be root to do
1691	  this).
1692
1693	  If unsure, say Y.
1694
1695if MODULES
1696
1697config MODULE_FORCE_LOAD
1698	bool "Forced module loading"
1699	default n
1700	help
1701	  Allow loading of modules without version information (ie. modprobe
1702	  --force).  Forced module loading sets the 'F' (forced) taint flag and
1703	  is usually a really bad idea.
1704
1705config MODULE_UNLOAD
1706	bool "Module unloading"
1707	help
1708	  Without this option you will not be able to unload any
1709	  modules (note that some modules may not be unloadable
1710	  anyway), which makes your kernel smaller, faster
1711	  and simpler.  If unsure, say Y.
1712
1713config MODULE_FORCE_UNLOAD
1714	bool "Forced module unloading"
1715	depends on MODULE_UNLOAD
1716	help
1717	  This option allows you to force a module to unload, even if the
1718	  kernel believes it is unsafe: the kernel will remove the module
1719	  without waiting for anyone to stop using it (using the -f option to
1720	  rmmod).  This is mainly for kernel developers and desperate users.
1721	  If unsure, say N.
1722
1723config MODVERSIONS
1724	bool "Module versioning support"
1725	help
1726	  Usually, you have to use modules compiled with your kernel.
1727	  Saying Y here makes it sometimes possible to use modules
1728	  compiled for different kernels, by adding enough information
1729	  to the modules to (hopefully) spot any changes which would
1730	  make them incompatible with the kernel you are running.  If
1731	  unsure, say N.
1732
1733config MODULE_REL_CRCS
1734	bool
1735	depends on MODVERSIONS
1736
1737config MODULE_SRCVERSION_ALL
1738	bool "Source checksum for all modules"
1739	help
1740	  Modules which contain a MODULE_VERSION get an extra "srcversion"
1741	  field inserted into their modinfo section, which contains a
1742    	  sum of the source files which made it.  This helps maintainers
1743	  see exactly which source was used to build a module (since
1744	  others sometimes change the module source without updating
1745	  the version).  With this option, such a "srcversion" field
1746	  will be created for all modules.  If unsure, say N.
1747
1748config MODULE_SIG
1749	bool "Module signature verification"
1750	depends on MODULES
1751	select SYSTEM_DATA_VERIFICATION
1752	help
1753	  Check modules for valid signatures upon load: the signature
1754	  is simply appended to the module. For more information see
1755	  Documentation/module-signing.txt.
1756
1757	  Note that this option adds the OpenSSL development packages as a
1758	  kernel build dependency so that the signing tool can use its crypto
1759	  library.
1760
1761	  !!!WARNING!!!  If you enable this option, you MUST make sure that the
1762	  module DOES NOT get stripped after being signed.  This includes the
1763	  debuginfo strip done by some packagers (such as rpmbuild) and
1764	  inclusion into an initramfs that wants the module size reduced.
1765
1766config MODULE_SIG_FORCE
1767	bool "Require modules to be validly signed"
1768	depends on MODULE_SIG
1769	help
1770	  Reject unsigned modules or signed modules for which we don't have a
1771	  key.  Without this, such modules will simply taint the kernel.
1772
1773config MODULE_SIG_ALL
1774	bool "Automatically sign all modules"
1775	default y
1776	depends on MODULE_SIG
1777	help
1778	  Sign all modules during make modules_install. Without this option,
1779	  modules must be signed manually, using the scripts/sign-file tool.
1780
1781comment "Do not forget to sign required modules with scripts/sign-file"
1782	depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1783
1784choice
1785	prompt "Which hash algorithm should modules be signed with?"
1786	depends on MODULE_SIG
1787	help
1788	  This determines which sort of hashing algorithm will be used during
1789	  signature generation.  This algorithm _must_ be built into the kernel
1790	  directly so that signature verification can take place.  It is not
1791	  possible to load a signed module containing the algorithm to check
1792	  the signature on that module.
1793
1794config MODULE_SIG_SHA1
1795	bool "Sign modules with SHA-1"
1796	select CRYPTO_SHA1
1797
1798config MODULE_SIG_SHA224
1799	bool "Sign modules with SHA-224"
1800	select CRYPTO_SHA256
1801
1802config MODULE_SIG_SHA256
1803	bool "Sign modules with SHA-256"
1804	select CRYPTO_SHA256
1805
1806config MODULE_SIG_SHA384
1807	bool "Sign modules with SHA-384"
1808	select CRYPTO_SHA512
1809
1810config MODULE_SIG_SHA512
1811	bool "Sign modules with SHA-512"
1812	select CRYPTO_SHA512
1813
1814endchoice
1815
1816config MODULE_SIG_HASH
1817	string
1818	depends on MODULE_SIG
1819	default "sha1" if MODULE_SIG_SHA1
1820	default "sha224" if MODULE_SIG_SHA224
1821	default "sha256" if MODULE_SIG_SHA256
1822	default "sha384" if MODULE_SIG_SHA384
1823	default "sha512" if MODULE_SIG_SHA512
1824
1825config MODULE_COMPRESS
1826	bool "Compress modules on installation"
1827	depends on MODULES
1828	help
1829
1830	  Compresses kernel modules when 'make modules_install' is run; gzip or
1831	  xz depending on "Compression algorithm" below.
1832
1833	  module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
1834
1835	  Out-of-tree kernel modules installed using Kbuild will also be
1836	  compressed upon installation.
1837
1838	  Note: for modules inside an initrd or initramfs, it's more efficient
1839	  to compress the whole initrd or initramfs instead.
1840
1841	  Note: This is fully compatible with signed modules.
1842
1843	  If in doubt, say N.
1844
1845choice
1846	prompt "Compression algorithm"
1847	depends on MODULE_COMPRESS
1848	default MODULE_COMPRESS_GZIP
1849	help
1850	  This determines which sort of compression will be used during
1851	  'make modules_install'.
1852
1853	  GZIP (default) and XZ are supported.
1854
1855config MODULE_COMPRESS_GZIP
1856	bool "GZIP"
1857
1858config MODULE_COMPRESS_XZ
1859	bool "XZ"
1860
1861endchoice
1862
1863config TRIM_UNUSED_KSYMS
1864	bool "Trim unused exported kernel symbols"
1865	depends on MODULES && !UNUSED_SYMBOLS
1866	help
1867	  The kernel and some modules make many symbols available for
1868	  other modules to use via EXPORT_SYMBOL() and variants. Depending
1869	  on the set of modules being selected in your kernel configuration,
1870	  many of those exported symbols might never be used.
1871
1872	  This option allows for unused exported symbols to be dropped from
1873	  the build. In turn, this provides the compiler more opportunities
1874	  (especially when using LTO) for optimizing the code and reducing
1875	  binary size.  This might have some security advantages as well.
1876
1877	  If unsure, or if you need to build out-of-tree modules, say N.
1878
1879endif # MODULES
1880
1881config MODULES_TREE_LOOKUP
1882	def_bool y
1883	depends on PERF_EVENTS || TRACING
1884
1885config INIT_ALL_POSSIBLE
1886	bool
1887	help
1888	  Back when each arch used to define their own cpu_online_mask and
1889	  cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1890	  with all 1s, and others with all 0s.  When they were centralised,
1891	  it was better to provide this option than to break all the archs
1892	  and have several arch maintainers pursuing me down dark alleys.
1893
1894source "block/Kconfig"
1895
1896config PREEMPT_NOTIFIERS
1897	bool
1898
1899config PADATA
1900	depends on SMP
1901	bool
1902
1903config ASN1
1904	tristate
1905	help
1906	  Build a simple ASN.1 grammar compiler that produces a bytecode output
1907	  that can be interpreted by the ASN.1 stream decoder and used to
1908	  inform it as to what tags are to be expected in a stream and what
1909	  functions to call on what tags.
1910
1911source "kernel/Kconfig.locks"
1912