xref: /openbmc/linux/init/Kconfig (revision 93d90ad7)
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
29menu "General setup"
30
31config BROKEN
32	bool
33
34config BROKEN_ON_SMP
35	bool
36	depends on BROKEN || !SMP
37	default y
38
39config INIT_ENV_ARG_LIMIT
40	int
41	default 32 if !UML
42	default 128 if UML
43	help
44	  Maximum of each of the number of arguments and environment
45	  variables passed to init from the kernel command line.
46
47
48config CROSS_COMPILE
49	string "Cross-compiler tool prefix"
50	help
51	  Same as running 'make CROSS_COMPILE=prefix-' but stored for
52	  default make runs in this kernel build directory.  You don't
53	  need to set this unless you want the configured kernel build
54	  directory to select the cross-compiler automatically.
55
56config COMPILE_TEST
57	bool "Compile also drivers which will not load"
58	default n
59	help
60	  Some drivers can be compiled on a different platform than they are
61	  intended to be run on. Despite they cannot be loaded there (or even
62	  when they load they cannot be used due to missing HW support),
63	  developers still, opposing to distributors, might want to build such
64	  drivers to compile-test them.
65
66	  If you are a developer and want to build everything available, say Y
67	  here. If you are a user/distributor, say N here to exclude useless
68	  drivers to be distributed.
69
70config LOCALVERSION
71	string "Local version - append to kernel release"
72	help
73	  Append an extra string to the end of your kernel version.
74	  This will show up when you type uname, for example.
75	  The string you set here will be appended after the contents of
76	  any files with a filename matching localversion* in your
77	  object and source tree, in that order.  Your total string can
78	  be a maximum of 64 characters.
79
80config LOCALVERSION_AUTO
81	bool "Automatically append version information to the version string"
82	default y
83	help
84	  This will try to automatically determine if the current tree is a
85	  release tree by looking for git tags that belong to the current
86	  top of tree revision.
87
88	  A string of the format -gxxxxxxxx will be added to the localversion
89	  if a git-based tree is found.  The string generated by this will be
90	  appended after any matching localversion* files, and after the value
91	  set in CONFIG_LOCALVERSION.
92
93	  (The actual string used here is the first eight characters produced
94	  by running the command:
95
96	    $ git rev-parse --verify HEAD
97
98	  which is done within the script "scripts/setlocalversion".)
99
100config HAVE_KERNEL_GZIP
101	bool
102
103config HAVE_KERNEL_BZIP2
104	bool
105
106config HAVE_KERNEL_LZMA
107	bool
108
109config HAVE_KERNEL_XZ
110	bool
111
112config HAVE_KERNEL_LZO
113	bool
114
115config HAVE_KERNEL_LZ4
116	bool
117
118choice
119	prompt "Kernel compression mode"
120	default KERNEL_GZIP
121	depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
122	help
123	  The linux kernel is a kind of self-extracting executable.
124	  Several compression algorithms are available, which differ
125	  in efficiency, compression and decompression speed.
126	  Compression speed is only relevant when building a kernel.
127	  Decompression speed is relevant at each boot.
128
129	  If you have any problems with bzip2 or lzma compressed
130	  kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
131	  version of this functionality (bzip2 only), for 2.4, was
132	  supplied by Christian Ludwig)
133
134	  High compression options are mostly useful for users, who
135	  are low on disk space (embedded systems), but for whom ram
136	  size matters less.
137
138	  If in doubt, select 'gzip'
139
140config KERNEL_GZIP
141	bool "Gzip"
142	depends on HAVE_KERNEL_GZIP
143	help
144	  The old and tried gzip compression. It provides a good balance
145	  between compression ratio and decompression speed.
146
147config KERNEL_BZIP2
148	bool "Bzip2"
149	depends on HAVE_KERNEL_BZIP2
150	help
151	  Its compression ratio and speed is intermediate.
152	  Decompression speed is slowest among the choices.  The kernel
153	  size is about 10% smaller with bzip2, in comparison to gzip.
154	  Bzip2 uses a large amount of memory. For modern kernels you
155	  will need at least 8MB RAM or more for booting.
156
157config KERNEL_LZMA
158	bool "LZMA"
159	depends on HAVE_KERNEL_LZMA
160	help
161	  This compression algorithm's ratio is best.  Decompression speed
162	  is between gzip and bzip2.  Compression is slowest.
163	  The kernel size is about 33% smaller with LZMA in comparison to gzip.
164
165config KERNEL_XZ
166	bool "XZ"
167	depends on HAVE_KERNEL_XZ
168	help
169	  XZ uses the LZMA2 algorithm and instruction set specific
170	  BCJ filters which can improve compression ratio of executable
171	  code. The size of the kernel is about 30% smaller with XZ in
172	  comparison to gzip. On architectures for which there is a BCJ
173	  filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
174	  will create a few percent smaller kernel than plain LZMA.
175
176	  The speed is about the same as with LZMA: The decompression
177	  speed of XZ is better than that of bzip2 but worse than gzip
178	  and LZO. Compression is slow.
179
180config KERNEL_LZO
181	bool "LZO"
182	depends on HAVE_KERNEL_LZO
183	help
184	  Its compression ratio is the poorest among the choices. The kernel
185	  size is about 10% bigger than gzip; however its speed
186	  (both compression and decompression) is the fastest.
187
188config KERNEL_LZ4
189	bool "LZ4"
190	depends on HAVE_KERNEL_LZ4
191	help
192	  LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
193	  A preliminary version of LZ4 de/compression tool is available at
194	  <https://code.google.com/p/lz4/>.
195
196	  Its compression ratio is worse than LZO. The size of the kernel
197	  is about 8% bigger than LZO. But the decompression speed is
198	  faster than LZO.
199
200endchoice
201
202config DEFAULT_HOSTNAME
203	string "Default hostname"
204	default "(none)"
205	help
206	  This option determines the default system hostname before userspace
207	  calls sethostname(2). The kernel traditionally uses "(none)" here,
208	  but you may wish to use a different default here to make a minimal
209	  system more usable with less configuration.
210
211config SWAP
212	bool "Support for paging of anonymous memory (swap)"
213	depends on MMU && BLOCK
214	default y
215	help
216	  This option allows you to choose whether you want to have support
217	  for so called swap devices or swap files in your kernel that are
218	  used to provide more virtual memory than the actual RAM present
219	  in your computer.  If unsure say Y.
220
221config SYSVIPC
222	bool "System V IPC"
223	---help---
224	  Inter Process Communication is a suite of library functions and
225	  system calls which let processes (running programs) synchronize and
226	  exchange information. It is generally considered to be a good thing,
227	  and some programs won't run unless you say Y here. In particular, if
228	  you want to run the DOS emulator dosemu under Linux (read the
229	  DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
230	  you'll need to say Y here.
231
232	  You can find documentation about IPC with "info ipc" and also in
233	  section 6.4 of the Linux Programmer's Guide, available from
234	  <http://www.tldp.org/guides.html>.
235
236config SYSVIPC_SYSCTL
237	bool
238	depends on SYSVIPC
239	depends on SYSCTL
240	default y
241
242config POSIX_MQUEUE
243	bool "POSIX Message Queues"
244	depends on NET
245	---help---
246	  POSIX variant of message queues is a part of IPC. In POSIX message
247	  queues every message has a priority which decides about succession
248	  of receiving it by a process. If you want to compile and run
249	  programs written e.g. for Solaris with use of its POSIX message
250	  queues (functions mq_*) say Y here.
251
252	  POSIX message queues are visible as a filesystem called 'mqueue'
253	  and can be mounted somewhere if you want to do filesystem
254	  operations on message queues.
255
256	  If unsure, say Y.
257
258config POSIX_MQUEUE_SYSCTL
259	bool
260	depends on POSIX_MQUEUE
261	depends on SYSCTL
262	default y
263
264config CROSS_MEMORY_ATTACH
265	bool "Enable process_vm_readv/writev syscalls"
266	depends on MMU
267	default y
268	help
269	  Enabling this option adds the system calls process_vm_readv and
270	  process_vm_writev which allow a process with the correct privileges
271	  to directly read from or write to another process' address space.
272	  See the man page for more details.
273
274config FHANDLE
275	bool "open by fhandle syscalls"
276	select EXPORTFS
277	help
278	  If you say Y here, a user level program will be able to map
279	  file names to handle and then later use the handle for
280	  different file system operations. This is useful in implementing
281	  userspace file servers, which now track files using handles instead
282	  of names. The handle would remain the same even if file names
283	  get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
284	  syscalls.
285
286config USELIB
287	bool "uselib syscall"
288	default y
289	help
290	  This option enables the uselib syscall, a system call used in the
291	  dynamic linker from libc5 and earlier.  glibc does not use this
292	  system call.  If you intend to run programs built on libc5 or
293	  earlier, you may need to enable this syscall.  Current systems
294	  running glibc can safely disable this.
295
296config AUDIT
297	bool "Auditing support"
298	depends on NET
299	help
300	  Enable auditing infrastructure that can be used with another
301	  kernel subsystem, such as SELinux (which requires this for
302	  logging of avc messages output).  Does not do system-call
303	  auditing without CONFIG_AUDITSYSCALL.
304
305config HAVE_ARCH_AUDITSYSCALL
306	bool
307
308config AUDITSYSCALL
309	bool "Enable system-call auditing support"
310	depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
311	default y if SECURITY_SELINUX
312	help
313	  Enable low-overhead system-call auditing infrastructure that
314	  can be used independently or with another kernel subsystem,
315	  such as SELinux.
316
317config AUDIT_WATCH
318	def_bool y
319	depends on AUDITSYSCALL
320	select FSNOTIFY
321
322config AUDIT_TREE
323	def_bool y
324	depends on AUDITSYSCALL
325	select FSNOTIFY
326
327source "kernel/irq/Kconfig"
328source "kernel/time/Kconfig"
329
330menu "CPU/Task time and stats accounting"
331
332config VIRT_CPU_ACCOUNTING
333	bool
334
335choice
336	prompt "Cputime accounting"
337	default TICK_CPU_ACCOUNTING if !PPC64
338	default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
339
340# Kind of a stub config for the pure tick based cputime accounting
341config TICK_CPU_ACCOUNTING
342	bool "Simple tick based cputime accounting"
343	depends on !S390 && !NO_HZ_FULL
344	help
345	  This is the basic tick based cputime accounting that maintains
346	  statistics about user, system and idle time spent on per jiffies
347	  granularity.
348
349	  If unsure, say Y.
350
351config VIRT_CPU_ACCOUNTING_NATIVE
352	bool "Deterministic task and CPU time accounting"
353	depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
354	select VIRT_CPU_ACCOUNTING
355	help
356	  Select this option to enable more accurate task and CPU time
357	  accounting.  This is done by reading a CPU counter on each
358	  kernel entry and exit and on transitions within the kernel
359	  between system, softirq and hardirq state, so there is a
360	  small performance impact.  In the case of s390 or IBM POWER > 5,
361	  this also enables accounting of stolen time on logically-partitioned
362	  systems.
363
364config VIRT_CPU_ACCOUNTING_GEN
365	bool "Full dynticks CPU time accounting"
366	depends on HAVE_CONTEXT_TRACKING
367	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
368	select VIRT_CPU_ACCOUNTING
369	select CONTEXT_TRACKING
370	help
371	  Select this option to enable task and CPU time accounting on full
372	  dynticks systems. This accounting is implemented by watching every
373	  kernel-user boundaries using the context tracking subsystem.
374	  The accounting is thus performed at the expense of some significant
375	  overhead.
376
377	  For now this is only useful if you are working on the full
378	  dynticks subsystem development.
379
380	  If unsure, say N.
381
382config IRQ_TIME_ACCOUNTING
383	bool "Fine granularity task level IRQ time accounting"
384	depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
385	help
386	  Select this option to enable fine granularity task irq time
387	  accounting. This is done by reading a timestamp on each
388	  transitions between softirq and hardirq state, so there can be a
389	  small performance impact.
390
391	  If in doubt, say N here.
392
393endchoice
394
395config BSD_PROCESS_ACCT
396	bool "BSD Process Accounting"
397	help
398	  If you say Y here, a user level program will be able to instruct the
399	  kernel (via a special system call) to write process accounting
400	  information to a file: whenever a process exits, information about
401	  that process will be appended to the file by the kernel.  The
402	  information includes things such as creation time, owning user,
403	  command name, memory usage, controlling terminal etc. (the complete
404	  list is in the struct acct in <file:include/linux/acct.h>).  It is
405	  up to the user level program to do useful things with this
406	  information.  This is generally a good idea, so say Y.
407
408config BSD_PROCESS_ACCT_V3
409	bool "BSD Process Accounting version 3 file format"
410	depends on BSD_PROCESS_ACCT
411	default n
412	help
413	  If you say Y here, the process accounting information is written
414	  in a new file format that also logs the process IDs of each
415	  process and it's parent. Note that this file format is incompatible
416	  with previous v0/v1/v2 file formats, so you will need updated tools
417	  for processing it. A preliminary version of these tools is available
418	  at <http://www.gnu.org/software/acct/>.
419
420config TASKSTATS
421	bool "Export task/process statistics through netlink"
422	depends on NET
423	default n
424	help
425	  Export selected statistics for tasks/processes through the
426	  generic netlink interface. Unlike BSD process accounting, the
427	  statistics are available during the lifetime of tasks/processes as
428	  responses to commands. Like BSD accounting, they are sent to user
429	  space on task exit.
430
431	  Say N if unsure.
432
433config TASK_DELAY_ACCT
434	bool "Enable per-task delay accounting"
435	depends on TASKSTATS
436	help
437	  Collect information on time spent by a task waiting for system
438	  resources like cpu, synchronous block I/O completion and swapping
439	  in pages. Such statistics can help in setting a task's priorities
440	  relative to other tasks for cpu, io, rss limits etc.
441
442	  Say N if unsure.
443
444config TASK_XACCT
445	bool "Enable extended accounting over taskstats"
446	depends on TASKSTATS
447	help
448	  Collect extended task accounting data and send the data
449	  to userland for processing over the taskstats interface.
450
451	  Say N if unsure.
452
453config TASK_IO_ACCOUNTING
454	bool "Enable per-task storage I/O accounting"
455	depends on TASK_XACCT
456	help
457	  Collect information on the number of bytes of storage I/O which this
458	  task has caused.
459
460	  Say N if unsure.
461
462endmenu # "CPU/Task time and stats accounting"
463
464menu "RCU Subsystem"
465
466choice
467	prompt "RCU Implementation"
468	default TREE_RCU
469
470config TREE_RCU
471	bool "Tree-based hierarchical RCU"
472	depends on !PREEMPT && SMP
473	select IRQ_WORK
474	help
475	  This option selects the RCU implementation that is
476	  designed for very large SMP system with hundreds or
477	  thousands of CPUs.  It also scales down nicely to
478	  smaller systems.
479
480config PREEMPT_RCU
481	bool "Preemptible tree-based hierarchical RCU"
482	depends on PREEMPT
483	select IRQ_WORK
484	help
485	  This option selects the RCU implementation that is
486	  designed for very large SMP systems with hundreds or
487	  thousands of CPUs, but for which real-time response
488	  is also required.  It also scales down nicely to
489	  smaller systems.
490
491	  Select this option if you are unsure.
492
493config TINY_RCU
494	bool "UP-only small-memory-footprint RCU"
495	depends on !PREEMPT && !SMP
496	help
497	  This option selects the RCU implementation that is
498	  designed for UP systems from which real-time response
499	  is not required.  This option greatly reduces the
500	  memory footprint of RCU.
501
502endchoice
503
504config TASKS_RCU
505	bool "Task_based RCU implementation using voluntary context switch"
506	default n
507	help
508	  This option enables a task-based RCU implementation that uses
509	  only voluntary context switch (not preemption!), idle, and
510	  user-mode execution as quiescent states.
511
512	  If unsure, say N.
513
514config RCU_STALL_COMMON
515	def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
516	help
517	  This option enables RCU CPU stall code that is common between
518	  the TINY and TREE variants of RCU.  The purpose is to allow
519	  the tiny variants to disable RCU CPU stall warnings, while
520	  making these warnings mandatory for the tree variants.
521
522config CONTEXT_TRACKING
523       bool
524
525config RCU_USER_QS
526	bool "Consider userspace as in RCU extended quiescent state"
527	depends on HAVE_CONTEXT_TRACKING && SMP
528	select CONTEXT_TRACKING
529	help
530	  This option sets hooks on kernel / userspace boundaries and
531	  puts RCU in extended quiescent state when the CPU runs in
532	  userspace. It means that when a CPU runs in userspace, it is
533	  excluded from the global RCU state machine and thus doesn't
534	  try to keep the timer tick on for RCU.
535
536	  Unless you want to hack and help the development of the full
537	  dynticks mode, you shouldn't enable this option.  It also
538	  adds unnecessary overhead.
539
540	  If unsure say N
541
542config CONTEXT_TRACKING_FORCE
543	bool "Force context tracking"
544	depends on CONTEXT_TRACKING
545	default y if !NO_HZ_FULL
546	help
547	  The major pre-requirement for full dynticks to work is to
548	  support the context tracking subsystem. But there are also
549	  other dependencies to provide in order to make the full
550	  dynticks working.
551
552	  This option stands for testing when an arch implements the
553	  context tracking backend but doesn't yet fullfill all the
554	  requirements to make the full dynticks feature working.
555	  Without the full dynticks, there is no way to test the support
556	  for context tracking and the subsystems that rely on it: RCU
557	  userspace extended quiescent state and tickless cputime
558	  accounting. This option copes with the absence of the full
559	  dynticks subsystem by forcing the context tracking on all
560	  CPUs in the system.
561
562	  Say Y only if you're working on the development of an
563	  architecture backend for the context tracking.
564
565	  Say N otherwise, this option brings an overhead that you
566	  don't want in production.
567
568
569config RCU_FANOUT
570	int "Tree-based hierarchical RCU fanout value"
571	range 2 64 if 64BIT
572	range 2 32 if !64BIT
573	depends on TREE_RCU || PREEMPT_RCU
574	default 64 if 64BIT
575	default 32 if !64BIT
576	help
577	  This option controls the fanout of hierarchical implementations
578	  of RCU, allowing RCU to work efficiently on machines with
579	  large numbers of CPUs.  This value must be at least the fourth
580	  root of NR_CPUS, which allows NR_CPUS to be insanely large.
581	  The default value of RCU_FANOUT should be used for production
582	  systems, but if you are stress-testing the RCU implementation
583	  itself, small RCU_FANOUT values allow you to test large-system
584	  code paths on small(er) systems.
585
586	  Select a specific number if testing RCU itself.
587	  Take the default if unsure.
588
589config RCU_FANOUT_LEAF
590	int "Tree-based hierarchical RCU leaf-level fanout value"
591	range 2 RCU_FANOUT if 64BIT
592	range 2 RCU_FANOUT if !64BIT
593	depends on TREE_RCU || PREEMPT_RCU
594	default 16
595	help
596	  This option controls the leaf-level fanout of hierarchical
597	  implementations of RCU, and allows trading off cache misses
598	  against lock contention.  Systems that synchronize their
599	  scheduling-clock interrupts for energy-efficiency reasons will
600	  want the default because the smaller leaf-level fanout keeps
601	  lock contention levels acceptably low.  Very large systems
602	  (hundreds or thousands of CPUs) will instead want to set this
603	  value to the maximum value possible in order to reduce the
604	  number of cache misses incurred during RCU's grace-period
605	  initialization.  These systems tend to run CPU-bound, and thus
606	  are not helped by synchronized interrupts, and thus tend to
607	  skew them, which reduces lock contention enough that large
608	  leaf-level fanouts work well.
609
610	  Select a specific number if testing RCU itself.
611
612	  Select the maximum permissible value for large systems.
613
614	  Take the default if unsure.
615
616config RCU_FANOUT_EXACT
617	bool "Disable tree-based hierarchical RCU auto-balancing"
618	depends on TREE_RCU || PREEMPT_RCU
619	default n
620	help
621	  This option forces use of the exact RCU_FANOUT value specified,
622	  regardless of imbalances in the hierarchy.  This is useful for
623	  testing RCU itself, and might one day be useful on systems with
624	  strong NUMA behavior.
625
626	  Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
627
628	  Say N if unsure.
629
630config RCU_FAST_NO_HZ
631	bool "Accelerate last non-dyntick-idle CPU's grace periods"
632	depends on NO_HZ_COMMON && SMP
633	default n
634	help
635	  This option permits CPUs to enter dynticks-idle state even if
636	  they have RCU callbacks queued, and prevents RCU from waking
637	  these CPUs up more than roughly once every four jiffies (by
638	  default, you can adjust this using the rcutree.rcu_idle_gp_delay
639	  parameter), thus improving energy efficiency.  On the other
640	  hand, this option increases the duration of RCU grace periods,
641	  for example, slowing down synchronize_rcu().
642
643	  Say Y if energy efficiency is critically important, and you
644	  	don't care about increased grace-period durations.
645
646	  Say N if you are unsure.
647
648config TREE_RCU_TRACE
649	def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
650	select DEBUG_FS
651	help
652	  This option provides tracing for the TREE_RCU and
653	  PREEMPT_RCU implementations, permitting Makefile to
654	  trivially select kernel/rcutree_trace.c.
655
656config RCU_BOOST
657	bool "Enable RCU priority boosting"
658	depends on RT_MUTEXES && PREEMPT_RCU
659	default n
660	help
661	  This option boosts the priority of preempted RCU readers that
662	  block the current preemptible RCU grace period for too long.
663	  This option also prevents heavy loads from blocking RCU
664	  callback invocation for all flavors of RCU.
665
666	  Say Y here if you are working with real-time apps or heavy loads
667	  Say N here if you are unsure.
668
669config RCU_KTHREAD_PRIO
670	int "Real-time priority to use for RCU worker threads"
671	range 1 99
672	depends on RCU_BOOST
673	default 1
674	help
675	  This option specifies the SCHED_FIFO priority value that will be
676	  assigned to the rcuc/n and rcub/n threads and is also the value
677	  used for RCU_BOOST (if enabled). If you are working with a
678	  real-time application that has one or more CPU-bound threads
679	  running at a real-time priority level, you should set
680	  RCU_KTHREAD_PRIO to a priority higher than the highest-priority
681	  real-time CPU-bound application thread.  The default RCU_KTHREAD_PRIO
682	  value of 1 is appropriate in the common case, which is real-time
683	  applications that do not have any CPU-bound threads.
684
685	  Some real-time applications might not have a single real-time
686	  thread that saturates a given CPU, but instead might have
687	  multiple real-time threads that, taken together, fully utilize
688	  that CPU.  In this case, you should set RCU_KTHREAD_PRIO to
689	  a priority higher than the lowest-priority thread that is
690	  conspiring to prevent the CPU from running any non-real-time
691	  tasks.  For example, if one thread at priority 10 and another
692	  thread at priority 5 are between themselves fully consuming
693	  the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
694	  set to priority 6 or higher.
695
696	  Specify the real-time priority, or take the default if unsure.
697
698config RCU_BOOST_DELAY
699	int "Milliseconds to delay boosting after RCU grace-period start"
700	range 0 3000
701	depends on RCU_BOOST
702	default 500
703	help
704	  This option specifies the time to wait after the beginning of
705	  a given grace period before priority-boosting preempted RCU
706	  readers blocking that grace period.  Note that any RCU reader
707	  blocking an expedited RCU grace period is boosted immediately.
708
709	  Accept the default if unsure.
710
711config RCU_NOCB_CPU
712	bool "Offload RCU callback processing from boot-selected CPUs"
713	depends on TREE_RCU || PREEMPT_RCU
714	default n
715	help
716	  Use this option to reduce OS jitter for aggressive HPC or
717	  real-time workloads.	It can also be used to offload RCU
718	  callback invocation to energy-efficient CPUs in battery-powered
719	  asymmetric multiprocessors.
720
721	  This option offloads callback invocation from the set of
722	  CPUs specified at boot time by the rcu_nocbs parameter.
723	  For each such CPU, a kthread ("rcuox/N") will be created to
724	  invoke callbacks, where the "N" is the CPU being offloaded,
725	  and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
726	  "s" for RCU-sched.  Nothing prevents this kthread from running
727	  on the specified CPUs, but (1) the kthreads may be preempted
728	  between each callback, and (2) affinity or cgroups can be used
729	  to force the kthreads to run on whatever set of CPUs is desired.
730
731	  Say Y here if you want to help to debug reduced OS jitter.
732	  Say N here if you are unsure.
733
734choice
735	prompt "Build-forced no-CBs CPUs"
736	default RCU_NOCB_CPU_NONE
737	depends on RCU_NOCB_CPU
738	help
739	  This option allows no-CBs CPUs (whose RCU callbacks are invoked
740	  from kthreads rather than from softirq context) to be specified
741	  at build time.  Additional no-CBs CPUs may be specified by
742	  the rcu_nocbs= boot parameter.
743
744config RCU_NOCB_CPU_NONE
745	bool "No build_forced no-CBs CPUs"
746	help
747	  This option does not force any of the CPUs to be no-CBs CPUs.
748	  Only CPUs designated by the rcu_nocbs= boot parameter will be
749	  no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
750	  kthreads whose names begin with "rcuo".  All other CPUs will
751	  invoke their own RCU callbacks in softirq context.
752
753	  Select this option if you want to choose no-CBs CPUs at
754	  boot time, for example, to allow testing of different no-CBs
755	  configurations without having to rebuild the kernel each time.
756
757config RCU_NOCB_CPU_ZERO
758	bool "CPU 0 is a build_forced no-CBs CPU"
759	help
760	  This option forces CPU 0 to be a no-CBs CPU, so that its RCU
761	  callbacks are invoked by a per-CPU kthread whose name begins
762	  with "rcuo".	Additional CPUs may be designated as no-CBs
763	  CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
764	  All other CPUs will invoke their own RCU callbacks in softirq
765	  context.
766
767	  Select this if CPU 0 needs to be a no-CBs CPU for real-time
768	  or energy-efficiency reasons, but the real reason it exists
769	  is to ensure that randconfig testing covers mixed systems.
770
771config RCU_NOCB_CPU_ALL
772	bool "All CPUs are build_forced no-CBs CPUs"
773	help
774	  This option forces all CPUs to be no-CBs CPUs.  The rcu_nocbs=
775	  boot parameter will be ignored.  All CPUs' RCU callbacks will
776	  be executed in the context of per-CPU rcuo kthreads created for
777	  this purpose.  Assuming that the kthreads whose names start with
778	  "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
779	  on the remaining CPUs, but might decrease memory locality during
780	  RCU-callback invocation, thus potentially degrading throughput.
781
782	  Select this if all CPUs need to be no-CBs CPUs for real-time
783	  or energy-efficiency reasons.
784
785endchoice
786
787endmenu # "RCU Subsystem"
788
789config BUILD_BIN2C
790	bool
791	default n
792
793config IKCONFIG
794	tristate "Kernel .config support"
795	select BUILD_BIN2C
796	---help---
797	  This option enables the complete Linux kernel ".config" file
798	  contents to be saved in the kernel. It provides documentation
799	  of which kernel options are used in a running kernel or in an
800	  on-disk kernel.  This information can be extracted from the kernel
801	  image file with the script scripts/extract-ikconfig and used as
802	  input to rebuild the current kernel or to build another kernel.
803	  It can also be extracted from a running kernel by reading
804	  /proc/config.gz if enabled (below).
805
806config IKCONFIG_PROC
807	bool "Enable access to .config through /proc/config.gz"
808	depends on IKCONFIG && PROC_FS
809	---help---
810	  This option enables access to the kernel configuration file
811	  through /proc/config.gz.
812
813config LOG_BUF_SHIFT
814	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
815	range 12 21
816	default 17
817	depends on PRINTK
818	help
819	  Select the minimal kernel log buffer size as a power of 2.
820	  The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
821	  parameter, see below. Any higher size also might be forced
822	  by "log_buf_len" boot parameter.
823
824	  Examples:
825		     17 => 128 KB
826		     16 => 64 KB
827		     15 => 32 KB
828		     14 => 16 KB
829		     13 =>  8 KB
830		     12 =>  4 KB
831
832config LOG_CPU_MAX_BUF_SHIFT
833	int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
834	depends on SMP
835	range 0 21
836	default 12 if !BASE_SMALL
837	default 0 if BASE_SMALL
838	depends on PRINTK
839	help
840	  This option allows to increase the default ring buffer size
841	  according to the number of CPUs. The value defines the contribution
842	  of each CPU as a power of 2. The used space is typically only few
843	  lines however it might be much more when problems are reported,
844	  e.g. backtraces.
845
846	  The increased size means that a new buffer has to be allocated and
847	  the original static one is unused. It makes sense only on systems
848	  with more CPUs. Therefore this value is used only when the sum of
849	  contributions is greater than the half of the default kernel ring
850	  buffer as defined by LOG_BUF_SHIFT. The default values are set
851	  so that more than 64 CPUs are needed to trigger the allocation.
852
853	  Also this option is ignored when "log_buf_len" kernel parameter is
854	  used as it forces an exact (power of two) size of the ring buffer.
855
856	  The number of possible CPUs is used for this computation ignoring
857	  hotplugging making the compuation optimal for the the worst case
858	  scenerio while allowing a simple algorithm to be used from bootup.
859
860	  Examples shift values and their meaning:
861		     17 => 128 KB for each CPU
862		     16 =>  64 KB for each CPU
863		     15 =>  32 KB for each CPU
864		     14 =>  16 KB for each CPU
865		     13 =>   8 KB for each CPU
866		     12 =>   4 KB for each CPU
867
868#
869# Architectures with an unreliable sched_clock() should select this:
870#
871config HAVE_UNSTABLE_SCHED_CLOCK
872	bool
873
874config GENERIC_SCHED_CLOCK
875	bool
876
877#
878# For architectures that want to enable the support for NUMA-affine scheduler
879# balancing logic:
880#
881config ARCH_SUPPORTS_NUMA_BALANCING
882	bool
883
884#
885# For architectures that know their GCC __int128 support is sound
886#
887config ARCH_SUPPORTS_INT128
888	bool
889
890# For architectures that (ab)use NUMA to represent different memory regions
891# all cpu-local but of different latencies, such as SuperH.
892#
893config ARCH_WANT_NUMA_VARIABLE_LOCALITY
894	bool
895
896config NUMA_BALANCING
897	bool "Memory placement aware NUMA scheduler"
898	depends on ARCH_SUPPORTS_NUMA_BALANCING
899	depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
900	depends on SMP && NUMA && MIGRATION
901	help
902	  This option adds support for automatic NUMA aware memory/task placement.
903	  The mechanism is quite primitive and is based on migrating memory when
904	  it has references to the node the task is running on.
905
906	  This system will be inactive on UMA systems.
907
908config NUMA_BALANCING_DEFAULT_ENABLED
909	bool "Automatically enable NUMA aware memory/task placement"
910	default y
911	depends on NUMA_BALANCING
912	help
913	  If set, automatic NUMA balancing will be enabled if running on a NUMA
914	  machine.
915
916menuconfig CGROUPS
917	boolean "Control Group support"
918	select KERNFS
919	help
920	  This option adds support for grouping sets of processes together, for
921	  use with process control subsystems such as Cpusets, CFS, memory
922	  controls or device isolation.
923	  See
924		- Documentation/scheduler/sched-design-CFS.txt	(CFS)
925		- Documentation/cgroups/ (features for grouping, isolation
926					  and resource control)
927
928	  Say N if unsure.
929
930if CGROUPS
931
932config CGROUP_DEBUG
933	bool "Example debug cgroup subsystem"
934	default n
935	help
936	  This option enables a simple cgroup subsystem that
937	  exports useful debugging information about the cgroups
938	  framework.
939
940	  Say N if unsure.
941
942config CGROUP_FREEZER
943	bool "Freezer cgroup subsystem"
944	help
945	  Provides a way to freeze and unfreeze all tasks in a
946	  cgroup.
947
948config CGROUP_DEVICE
949	bool "Device controller for cgroups"
950	help
951	  Provides a cgroup implementing whitelists for devices which
952	  a process in the cgroup can mknod or open.
953
954config CPUSETS
955	bool "Cpuset support"
956	help
957	  This option will let you create and manage CPUSETs which
958	  allow dynamically partitioning a system into sets of CPUs and
959	  Memory Nodes and assigning tasks to run only within those sets.
960	  This is primarily useful on large SMP or NUMA systems.
961
962	  Say N if unsure.
963
964config PROC_PID_CPUSET
965	bool "Include legacy /proc/<pid>/cpuset file"
966	depends on CPUSETS
967	default y
968
969config CGROUP_CPUACCT
970	bool "Simple CPU accounting cgroup subsystem"
971	help
972	  Provides a simple Resource Controller for monitoring the
973	  total CPU consumed by the tasks in a cgroup.
974
975config PAGE_COUNTER
976       bool
977
978config MEMCG
979	bool "Memory Resource Controller for Control Groups"
980	select PAGE_COUNTER
981	select EVENTFD
982	help
983	  Provides a memory resource controller that manages both anonymous
984	  memory and page cache. (See Documentation/cgroups/memory.txt)
985
986config MEMCG_SWAP
987	bool "Memory Resource Controller Swap Extension"
988	depends on MEMCG && SWAP
989	help
990	  Add swap management feature to memory resource controller. When you
991	  enable this, you can limit mem+swap usage per cgroup. In other words,
992	  when you disable this, memory resource controller has no cares to
993	  usage of swap...a process can exhaust all of the swap. This extension
994	  is useful when you want to avoid exhaustion swap but this itself
995	  adds more overheads and consumes memory for remembering information.
996	  Especially if you use 32bit system or small memory system, please
997	  be careful about enabling this. When memory resource controller
998	  is disabled by boot option, this will be automatically disabled and
999	  there will be no overhead from this. Even when you set this config=y,
1000	  if boot option "swapaccount=0" is set, swap will not be accounted.
1001	  Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
1002	  size is 4096bytes, 512k per 1Gbytes of swap.
1003config MEMCG_SWAP_ENABLED
1004	bool "Memory Resource Controller Swap Extension enabled by default"
1005	depends on MEMCG_SWAP
1006	default y
1007	help
1008	  Memory Resource Controller Swap Extension comes with its price in
1009	  a bigger memory consumption. General purpose distribution kernels
1010	  which want to enable the feature but keep it disabled by default
1011	  and let the user enable it by swapaccount=1 boot command line
1012	  parameter should have this option unselected.
1013	  For those who want to have the feature enabled by default should
1014	  select this option (if, for some reason, they need to disable it
1015	  then swapaccount=0 does the trick).
1016config MEMCG_KMEM
1017	bool "Memory Resource Controller Kernel Memory accounting"
1018	depends on MEMCG
1019	depends on SLUB || SLAB
1020	help
1021	  The Kernel Memory extension for Memory Resource Controller can limit
1022	  the amount of memory used by kernel objects in the system. Those are
1023	  fundamentally different from the entities handled by the standard
1024	  Memory Controller, which are page-based, and can be swapped. Users of
1025	  the kmem extension can use it to guarantee that no group of processes
1026	  will ever exhaust kernel resources alone.
1027
1028	  WARNING: Current implementation lacks reclaim support. That means
1029	  allocation attempts will fail when close to the limit even if there
1030	  are plenty of kmem available for reclaim. That makes this option
1031	  unusable in real life so DO NOT SELECT IT unless for development
1032	  purposes.
1033
1034config CGROUP_HUGETLB
1035	bool "HugeTLB Resource Controller for Control Groups"
1036	depends on HUGETLB_PAGE
1037	select PAGE_COUNTER
1038	default n
1039	help
1040	  Provides a cgroup Resource Controller for HugeTLB pages.
1041	  When you enable this, you can put a per cgroup limit on HugeTLB usage.
1042	  The limit is enforced during page fault. Since HugeTLB doesn't
1043	  support page reclaim, enforcing the limit at page fault time implies
1044	  that, the application will get SIGBUS signal if it tries to access
1045	  HugeTLB pages beyond its limit. This requires the application to know
1046	  beforehand how much HugeTLB pages it would require for its use. The
1047	  control group is tracked in the third page lru pointer. This means
1048	  that we cannot use the controller with huge page less than 3 pages.
1049
1050config CGROUP_PERF
1051	bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1052	depends on PERF_EVENTS && CGROUPS
1053	help
1054	  This option extends the per-cpu mode to restrict monitoring to
1055	  threads which belong to the cgroup specified and run on the
1056	  designated cpu.
1057
1058	  Say N if unsure.
1059
1060menuconfig CGROUP_SCHED
1061	bool "Group CPU scheduler"
1062	default n
1063	help
1064	  This feature lets CPU scheduler recognize task groups and control CPU
1065	  bandwidth allocation to such task groups. It uses cgroups to group
1066	  tasks.
1067
1068if CGROUP_SCHED
1069config FAIR_GROUP_SCHED
1070	bool "Group scheduling for SCHED_OTHER"
1071	depends on CGROUP_SCHED
1072	default CGROUP_SCHED
1073
1074config CFS_BANDWIDTH
1075	bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1076	depends on FAIR_GROUP_SCHED
1077	default n
1078	help
1079	  This option allows users to define CPU bandwidth rates (limits) for
1080	  tasks running within the fair group scheduler.  Groups with no limit
1081	  set are considered to be unconstrained and will run with no
1082	  restriction.
1083	  See tip/Documentation/scheduler/sched-bwc.txt for more information.
1084
1085config RT_GROUP_SCHED
1086	bool "Group scheduling for SCHED_RR/FIFO"
1087	depends on CGROUP_SCHED
1088	default n
1089	help
1090	  This feature lets you explicitly allocate real CPU bandwidth
1091	  to task groups. If enabled, it will also make it impossible to
1092	  schedule realtime tasks for non-root users until you allocate
1093	  realtime bandwidth for them.
1094	  See Documentation/scheduler/sched-rt-group.txt for more information.
1095
1096endif #CGROUP_SCHED
1097
1098config BLK_CGROUP
1099	bool "Block IO controller"
1100	depends on BLOCK
1101	default n
1102	---help---
1103	Generic block IO controller cgroup interface. This is the common
1104	cgroup interface which should be used by various IO controlling
1105	policies.
1106
1107	Currently, CFQ IO scheduler uses it to recognize task groups and
1108	control disk bandwidth allocation (proportional time slice allocation)
1109	to such task groups. It is also used by bio throttling logic in
1110	block layer to implement upper limit in IO rates on a device.
1111
1112	This option only enables generic Block IO controller infrastructure.
1113	One needs to also enable actual IO controlling logic/policy. For
1114	enabling proportional weight division of disk bandwidth in CFQ, set
1115	CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1116	CONFIG_BLK_DEV_THROTTLING=y.
1117
1118	See Documentation/cgroups/blkio-controller.txt for more information.
1119
1120config DEBUG_BLK_CGROUP
1121	bool "Enable Block IO controller debugging"
1122	depends on BLK_CGROUP
1123	default n
1124	---help---
1125	Enable some debugging help. Currently it exports additional stat
1126	files in a cgroup which can be useful for debugging.
1127
1128endif # CGROUPS
1129
1130config CHECKPOINT_RESTORE
1131	bool "Checkpoint/restore support" if EXPERT
1132	default n
1133	help
1134	  Enables additional kernel features in a sake of checkpoint/restore.
1135	  In particular it adds auxiliary prctl codes to setup process text,
1136	  data and heap segment sizes, and a few additional /proc filesystem
1137	  entries.
1138
1139	  If unsure, say N here.
1140
1141menuconfig NAMESPACES
1142	bool "Namespaces support" if EXPERT
1143	default !EXPERT
1144	help
1145	  Provides the way to make tasks work with different objects using
1146	  the same id. For example same IPC id may refer to different objects
1147	  or same user id or pid may refer to different tasks when used in
1148	  different namespaces.
1149
1150if NAMESPACES
1151
1152config UTS_NS
1153	bool "UTS namespace"
1154	default y
1155	help
1156	  In this namespace tasks see different info provided with the
1157	  uname() system call
1158
1159config IPC_NS
1160	bool "IPC namespace"
1161	depends on (SYSVIPC || POSIX_MQUEUE)
1162	default y
1163	help
1164	  In this namespace tasks work with IPC ids which correspond to
1165	  different IPC objects in different namespaces.
1166
1167config USER_NS
1168	bool "User namespace"
1169	default n
1170	help
1171	  This allows containers, i.e. vservers, to use user namespaces
1172	  to provide different user info for different servers.
1173
1174	  When user namespaces are enabled in the kernel it is
1175	  recommended that the MEMCG and MEMCG_KMEM options also be
1176	  enabled and that user-space use the memory control groups to
1177	  limit the amount of memory a memory unprivileged users can
1178	  use.
1179
1180	  If unsure, say N.
1181
1182config PID_NS
1183	bool "PID Namespaces"
1184	default y
1185	help
1186	  Support process id namespaces.  This allows having multiple
1187	  processes with the same pid as long as they are in different
1188	  pid namespaces.  This is a building block of containers.
1189
1190config NET_NS
1191	bool "Network namespace"
1192	depends on NET
1193	default y
1194	help
1195	  Allow user space to create what appear to be multiple instances
1196	  of the network stack.
1197
1198endif # NAMESPACES
1199
1200config SCHED_AUTOGROUP
1201	bool "Automatic process group scheduling"
1202	select CGROUPS
1203	select CGROUP_SCHED
1204	select FAIR_GROUP_SCHED
1205	help
1206	  This option optimizes the scheduler for common desktop workloads by
1207	  automatically creating and populating task groups.  This separation
1208	  of workloads isolates aggressive CPU burners (like build jobs) from
1209	  desktop applications.  Task group autogeneration is currently based
1210	  upon task session.
1211
1212config SYSFS_DEPRECATED
1213	bool "Enable deprecated sysfs features to support old userspace tools"
1214	depends on SYSFS
1215	default n
1216	help
1217	  This option adds code that switches the layout of the "block" class
1218	  devices, to not show up in /sys/class/block/, but only in
1219	  /sys/block/.
1220
1221	  This switch is only active when the sysfs.deprecated=1 boot option is
1222	  passed or the SYSFS_DEPRECATED_V2 option is set.
1223
1224	  This option allows new kernels to run on old distributions and tools,
1225	  which might get confused by /sys/class/block/. Since 2007/2008 all
1226	  major distributions and tools handle this just fine.
1227
1228	  Recent distributions and userspace tools after 2009/2010 depend on
1229	  the existence of /sys/class/block/, and will not work with this
1230	  option enabled.
1231
1232	  Only if you are using a new kernel on an old distribution, you might
1233	  need to say Y here.
1234
1235config SYSFS_DEPRECATED_V2
1236	bool "Enable deprecated sysfs features by default"
1237	default n
1238	depends on SYSFS
1239	depends on SYSFS_DEPRECATED
1240	help
1241	  Enable deprecated sysfs by default.
1242
1243	  See the CONFIG_SYSFS_DEPRECATED option for more details about this
1244	  option.
1245
1246	  Only if you are using a new kernel on an old distribution, you might
1247	  need to say Y here. Even then, odds are you would not need it
1248	  enabled, you can always pass the boot option if absolutely necessary.
1249
1250config RELAY
1251	bool "Kernel->user space relay support (formerly relayfs)"
1252	help
1253	  This option enables support for relay interface support in
1254	  certain file systems (such as debugfs).
1255	  It is designed to provide an efficient mechanism for tools and
1256	  facilities to relay large amounts of data from kernel space to
1257	  user space.
1258
1259	  If unsure, say N.
1260
1261config BLK_DEV_INITRD
1262	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1263	depends on BROKEN || !FRV
1264	help
1265	  The initial RAM filesystem is a ramfs which is loaded by the
1266	  boot loader (loadlin or lilo) and that is mounted as root
1267	  before the normal boot procedure. It is typically used to
1268	  load modules needed to mount the "real" root file system,
1269	  etc. See <file:Documentation/initrd.txt> for details.
1270
1271	  If RAM disk support (BLK_DEV_RAM) is also included, this
1272	  also enables initial RAM disk (initrd) support and adds
1273	  15 Kbytes (more on some other architectures) to the kernel size.
1274
1275	  If unsure say Y.
1276
1277if BLK_DEV_INITRD
1278
1279source "usr/Kconfig"
1280
1281endif
1282
1283config INIT_FALLBACK
1284	bool "Fall back to defaults if init= parameter is bad"
1285	default y
1286	help
1287	  If enabled, the kernel will try the default init binaries if an
1288	  explicit request from the init= parameter fails.
1289
1290	  This can have unexpected effects.  For example, booting
1291	  with init=/sbin/kiosk_app will run /sbin/init or even /bin/sh
1292	  if /sbin/kiosk_app cannot be executed.
1293
1294	  The default value of Y is consistent with historical behavior.
1295	  Selecting N is likely to be more appropriate for most uses,
1296	  especially on kiosks and on kernels that are intended to be
1297	  run under the control of a script.
1298
1299config CC_OPTIMIZE_FOR_SIZE
1300	bool "Optimize for size"
1301	help
1302	  Enabling this option will pass "-Os" instead of "-O2" to gcc
1303	  resulting in a smaller kernel.
1304
1305	  If unsure, say N.
1306
1307config SYSCTL
1308	bool
1309
1310config ANON_INODES
1311	bool
1312
1313config HAVE_UID16
1314	bool
1315
1316config SYSCTL_EXCEPTION_TRACE
1317	bool
1318	help
1319	  Enable support for /proc/sys/debug/exception-trace.
1320
1321config SYSCTL_ARCH_UNALIGN_NO_WARN
1322	bool
1323	help
1324	  Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1325	  Allows arch to define/use @no_unaligned_warning to possibly warn
1326	  about unaligned access emulation going on under the hood.
1327
1328config SYSCTL_ARCH_UNALIGN_ALLOW
1329	bool
1330	help
1331	  Enable support for /proc/sys/kernel/unaligned-trap
1332	  Allows arches to define/use @unaligned_enabled to runtime toggle
1333	  the unaligned access emulation.
1334	  see arch/parisc/kernel/unaligned.c for reference
1335
1336config HAVE_PCSPKR_PLATFORM
1337	bool
1338
1339# interpreter that classic socket filters depend on
1340config BPF
1341	bool
1342
1343menuconfig EXPERT
1344	bool "Configure standard kernel features (expert users)"
1345	# Unhide debug options, to make the on-by-default options visible
1346	select DEBUG_KERNEL
1347	help
1348	  This option allows certain base kernel options and settings
1349          to be disabled or tweaked. This is for specialized
1350          environments which can tolerate a "non-standard" kernel.
1351          Only use this if you really know what you are doing.
1352
1353config UID16
1354	bool "Enable 16-bit UID system calls" if EXPERT
1355	depends on HAVE_UID16
1356	default y
1357	help
1358	  This enables the legacy 16-bit UID syscall wrappers.
1359
1360config SGETMASK_SYSCALL
1361	bool "sgetmask/ssetmask syscalls support" if EXPERT
1362	def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1363	---help---
1364	  sys_sgetmask and sys_ssetmask are obsolete system calls
1365	  no longer supported in libc but still enabled by default in some
1366	  architectures.
1367
1368	  If unsure, leave the default option here.
1369
1370config SYSFS_SYSCALL
1371	bool "Sysfs syscall support" if EXPERT
1372	default y
1373	---help---
1374	  sys_sysfs is an obsolete system call no longer supported in libc.
1375	  Note that disabling this option is more secure but might break
1376	  compatibility with some systems.
1377
1378	  If unsure say Y here.
1379
1380config SYSCTL_SYSCALL
1381	bool "Sysctl syscall support" if EXPERT
1382	depends on PROC_SYSCTL
1383	default n
1384	select SYSCTL
1385	---help---
1386	  sys_sysctl uses binary paths that have been found challenging
1387	  to properly maintain and use.  The interface in /proc/sys
1388	  using paths with ascii names is now the primary path to this
1389	  information.
1390
1391	  Almost nothing using the binary sysctl interface so if you are
1392	  trying to save some space it is probably safe to disable this,
1393	  making your kernel marginally smaller.
1394
1395	  If unsure say N here.
1396
1397config KALLSYMS
1398	 bool "Load all symbols for debugging/ksymoops" if EXPERT
1399	 default y
1400	 help
1401	   Say Y here to let the kernel print out symbolic crash information and
1402	   symbolic stack backtraces. This increases the size of the kernel
1403	   somewhat, as all symbols have to be loaded into the kernel image.
1404
1405config KALLSYMS_ALL
1406	bool "Include all symbols in kallsyms"
1407	depends on DEBUG_KERNEL && KALLSYMS
1408	help
1409	   Normally kallsyms only contains the symbols of functions for nicer
1410	   OOPS messages and backtraces (i.e., symbols from the text and inittext
1411	   sections). This is sufficient for most cases. And only in very rare
1412	   cases (e.g., when a debugger is used) all symbols are required (e.g.,
1413	   names of variables from the data sections, etc).
1414
1415	   This option makes sure that all symbols are loaded into the kernel
1416	   image (i.e., symbols from all sections) in cost of increased kernel
1417	   size (depending on the kernel configuration, it may be 300KiB or
1418	   something like this).
1419
1420	   Say N unless you really need all symbols.
1421
1422config PRINTK
1423	default y
1424	bool "Enable support for printk" if EXPERT
1425	select IRQ_WORK
1426	help
1427	  This option enables normal printk support. Removing it
1428	  eliminates most of the message strings from the kernel image
1429	  and makes the kernel more or less silent. As this makes it
1430	  very difficult to diagnose system problems, saying N here is
1431	  strongly discouraged.
1432
1433config BUG
1434	bool "BUG() support" if EXPERT
1435	default y
1436	help
1437          Disabling this option eliminates support for BUG and WARN, reducing
1438          the size of your kernel image and potentially quietly ignoring
1439          numerous fatal conditions. You should only consider disabling this
1440          option for embedded systems with no facilities for reporting errors.
1441          Just say Y.
1442
1443config ELF_CORE
1444	depends on COREDUMP
1445	default y
1446	bool "Enable ELF core dumps" if EXPERT
1447	help
1448	  Enable support for generating core dumps. Disabling saves about 4k.
1449
1450
1451config PCSPKR_PLATFORM
1452	bool "Enable PC-Speaker support" if EXPERT
1453	depends on HAVE_PCSPKR_PLATFORM
1454	select I8253_LOCK
1455	default y
1456	help
1457          This option allows to disable the internal PC-Speaker
1458          support, saving some memory.
1459
1460config BASE_FULL
1461	default y
1462	bool "Enable full-sized data structures for core" if EXPERT
1463	help
1464	  Disabling this option reduces the size of miscellaneous core
1465	  kernel data structures. This saves memory on small machines,
1466	  but may reduce performance.
1467
1468config FUTEX
1469	bool "Enable futex support" if EXPERT
1470	default y
1471	select RT_MUTEXES
1472	help
1473	  Disabling this option will cause the kernel to be built without
1474	  support for "fast userspace mutexes".  The resulting kernel may not
1475	  run glibc-based applications correctly.
1476
1477config HAVE_FUTEX_CMPXCHG
1478	bool
1479	depends on FUTEX
1480	help
1481	  Architectures should select this if futex_atomic_cmpxchg_inatomic()
1482	  is implemented and always working. This removes a couple of runtime
1483	  checks.
1484
1485config EPOLL
1486	bool "Enable eventpoll support" if EXPERT
1487	default y
1488	select ANON_INODES
1489	help
1490	  Disabling this option will cause the kernel to be built without
1491	  support for epoll family of system calls.
1492
1493config SIGNALFD
1494	bool "Enable signalfd() system call" if EXPERT
1495	select ANON_INODES
1496	default y
1497	help
1498	  Enable the signalfd() system call that allows to receive signals
1499	  on a file descriptor.
1500
1501	  If unsure, say Y.
1502
1503config TIMERFD
1504	bool "Enable timerfd() system call" if EXPERT
1505	select ANON_INODES
1506	default y
1507	help
1508	  Enable the timerfd() system call that allows to receive timer
1509	  events on a file descriptor.
1510
1511	  If unsure, say Y.
1512
1513config EVENTFD
1514	bool "Enable eventfd() system call" if EXPERT
1515	select ANON_INODES
1516	default y
1517	help
1518	  Enable the eventfd() system call that allows to receive both
1519	  kernel notification (ie. KAIO) or userspace notifications.
1520
1521	  If unsure, say Y.
1522
1523# syscall, maps, verifier
1524config BPF_SYSCALL
1525	bool "Enable bpf() system call" if EXPERT
1526	select ANON_INODES
1527	select BPF
1528	default n
1529	help
1530	  Enable the bpf() system call that allows to manipulate eBPF
1531	  programs and maps via file descriptors.
1532
1533config SHMEM
1534	bool "Use full shmem filesystem" if EXPERT
1535	default y
1536	depends on MMU
1537	help
1538	  The shmem is an internal filesystem used to manage shared memory.
1539	  It is backed by swap and manages resource limits. It is also exported
1540	  to userspace as tmpfs if TMPFS is enabled. Disabling this
1541	  option replaces shmem and tmpfs with the much simpler ramfs code,
1542	  which may be appropriate on small systems without swap.
1543
1544config AIO
1545	bool "Enable AIO support" if EXPERT
1546	default y
1547	help
1548	  This option enables POSIX asynchronous I/O which may by used
1549	  by some high performance threaded applications. Disabling
1550	  this option saves about 7k.
1551
1552config ADVISE_SYSCALLS
1553	bool "Enable madvise/fadvise syscalls" if EXPERT
1554	default y
1555	help
1556	  This option enables the madvise and fadvise syscalls, used by
1557	  applications to advise the kernel about their future memory or file
1558	  usage, improving performance. If building an embedded system where no
1559	  applications use these syscalls, you can disable this option to save
1560	  space.
1561
1562config PCI_QUIRKS
1563	default y
1564	bool "Enable PCI quirk workarounds" if EXPERT
1565	depends on PCI
1566	help
1567	  This enables workarounds for various PCI chipset
1568	  bugs/quirks. Disable this only if your target machine is
1569	  unaffected by PCI quirks.
1570
1571config EMBEDDED
1572	bool "Embedded system"
1573	option allnoconfig_y
1574	select EXPERT
1575	help
1576	  This option should be enabled if compiling the kernel for
1577	  an embedded system so certain expert options are available
1578	  for configuration.
1579
1580config HAVE_PERF_EVENTS
1581	bool
1582	help
1583	  See tools/perf/design.txt for details.
1584
1585config PERF_USE_VMALLOC
1586	bool
1587	help
1588	  See tools/perf/design.txt for details
1589
1590menu "Kernel Performance Events And Counters"
1591
1592config PERF_EVENTS
1593	bool "Kernel performance events and counters"
1594	default y if PROFILING
1595	depends on HAVE_PERF_EVENTS
1596	select ANON_INODES
1597	select IRQ_WORK
1598	help
1599	  Enable kernel support for various performance events provided
1600	  by software and hardware.
1601
1602	  Software events are supported either built-in or via the
1603	  use of generic tracepoints.
1604
1605	  Most modern CPUs support performance events via performance
1606	  counter registers. These registers count the number of certain
1607	  types of hw events: such as instructions executed, cachemisses
1608	  suffered, or branches mis-predicted - without slowing down the
1609	  kernel or applications. These registers can also trigger interrupts
1610	  when a threshold number of events have passed - and can thus be
1611	  used to profile the code that runs on that CPU.
1612
1613	  The Linux Performance Event subsystem provides an abstraction of
1614	  these software and hardware event capabilities, available via a
1615	  system call and used by the "perf" utility in tools/perf/. It
1616	  provides per task and per CPU counters, and it provides event
1617	  capabilities on top of those.
1618
1619	  Say Y if unsure.
1620
1621config DEBUG_PERF_USE_VMALLOC
1622	default n
1623	bool "Debug: use vmalloc to back perf mmap() buffers"
1624	depends on PERF_EVENTS && DEBUG_KERNEL
1625	select PERF_USE_VMALLOC
1626	help
1627	 Use vmalloc memory to back perf mmap() buffers.
1628
1629	 Mostly useful for debugging the vmalloc code on platforms
1630	 that don't require it.
1631
1632	 Say N if unsure.
1633
1634endmenu
1635
1636config VM_EVENT_COUNTERS
1637	default y
1638	bool "Enable VM event counters for /proc/vmstat" if EXPERT
1639	help
1640	  VM event counters are needed for event counts to be shown.
1641	  This option allows the disabling of the VM event counters
1642	  on EXPERT systems.  /proc/vmstat will only show page counts
1643	  if VM event counters are disabled.
1644
1645config SLUB_DEBUG
1646	default y
1647	bool "Enable SLUB debugging support" if EXPERT
1648	depends on SLUB && SYSFS
1649	help
1650	  SLUB has extensive debug support features. Disabling these can
1651	  result in significant savings in code size. This also disables
1652	  SLUB sysfs support. /sys/slab will not exist and there will be
1653	  no support for cache validation etc.
1654
1655config COMPAT_BRK
1656	bool "Disable heap randomization"
1657	default y
1658	help
1659	  Randomizing heap placement makes heap exploits harder, but it
1660	  also breaks ancient binaries (including anything libc5 based).
1661	  This option changes the bootup default to heap randomization
1662	  disabled, and can be overridden at runtime by setting
1663	  /proc/sys/kernel/randomize_va_space to 2.
1664
1665	  On non-ancient distros (post-2000 ones) N is usually a safe choice.
1666
1667choice
1668	prompt "Choose SLAB allocator"
1669	default SLUB
1670	help
1671	   This option allows to select a slab allocator.
1672
1673config SLAB
1674	bool "SLAB"
1675	help
1676	  The regular slab allocator that is established and known to work
1677	  well in all environments. It organizes cache hot objects in
1678	  per cpu and per node queues.
1679
1680config SLUB
1681	bool "SLUB (Unqueued Allocator)"
1682	help
1683	   SLUB is a slab allocator that minimizes cache line usage
1684	   instead of managing queues of cached objects (SLAB approach).
1685	   Per cpu caching is realized using slabs of objects instead
1686	   of queues of objects. SLUB can use memory efficiently
1687	   and has enhanced diagnostics. SLUB is the default choice for
1688	   a slab allocator.
1689
1690config SLOB
1691	depends on EXPERT
1692	bool "SLOB (Simple Allocator)"
1693	help
1694	   SLOB replaces the stock allocator with a drastically simpler
1695	   allocator. SLOB is generally more space efficient but
1696	   does not perform as well on large systems.
1697
1698endchoice
1699
1700config SLUB_CPU_PARTIAL
1701	default y
1702	depends on SLUB && SMP
1703	bool "SLUB per cpu partial cache"
1704	help
1705	  Per cpu partial caches accellerate objects allocation and freeing
1706	  that is local to a processor at the price of more indeterminism
1707	  in the latency of the free. On overflow these caches will be cleared
1708	  which requires the taking of locks that may cause latency spikes.
1709	  Typically one would choose no for a realtime system.
1710
1711config MMAP_ALLOW_UNINITIALIZED
1712	bool "Allow mmapped anonymous memory to be uninitialized"
1713	depends on EXPERT && !MMU
1714	default n
1715	help
1716	  Normally, and according to the Linux spec, anonymous memory obtained
1717	  from mmap() has it's contents cleared before it is passed to
1718	  userspace.  Enabling this config option allows you to request that
1719	  mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1720	  providing a huge performance boost.  If this option is not enabled,
1721	  then the flag will be ignored.
1722
1723	  This is taken advantage of by uClibc's malloc(), and also by
1724	  ELF-FDPIC binfmt's brk and stack allocator.
1725
1726	  Because of the obvious security issues, this option should only be
1727	  enabled on embedded devices where you control what is run in
1728	  userspace.  Since that isn't generally a problem on no-MMU systems,
1729	  it is normally safe to say Y here.
1730
1731	  See Documentation/nommu-mmap.txt for more information.
1732
1733config SYSTEM_TRUSTED_KEYRING
1734	bool "Provide system-wide ring of trusted keys"
1735	depends on KEYS
1736	help
1737	  Provide a system keyring to which trusted keys can be added.  Keys in
1738	  the keyring are considered to be trusted.  Keys may be added at will
1739	  by the kernel from compiled-in data and from hardware key stores, but
1740	  userspace may only add extra keys if those keys can be verified by
1741	  keys already in the keyring.
1742
1743	  Keys in this keyring are used by module signature checking.
1744
1745config PROFILING
1746	bool "Profiling support"
1747	help
1748	  Say Y here to enable the extended profiling support mechanisms used
1749	  by profilers such as OProfile.
1750
1751#
1752# Place an empty function call at each tracepoint site. Can be
1753# dynamically changed for a probe function.
1754#
1755config TRACEPOINTS
1756	bool
1757
1758source "arch/Kconfig"
1759
1760endmenu		# General setup
1761
1762config HAVE_GENERIC_DMA_COHERENT
1763	bool
1764	default n
1765
1766config SLABINFO
1767	bool
1768	depends on PROC_FS
1769	depends on SLAB || SLUB_DEBUG
1770	default y
1771
1772config RT_MUTEXES
1773	boolean
1774
1775config BASE_SMALL
1776	int
1777	default 0 if BASE_FULL
1778	default 1 if !BASE_FULL
1779
1780menuconfig MODULES
1781	bool "Enable loadable module support"
1782	option modules
1783	help
1784	  Kernel modules are small pieces of compiled code which can
1785	  be inserted in the running kernel, rather than being
1786	  permanently built into the kernel.  You use the "modprobe"
1787	  tool to add (and sometimes remove) them.  If you say Y here,
1788	  many parts of the kernel can be built as modules (by
1789	  answering M instead of Y where indicated): this is most
1790	  useful for infrequently used options which are not required
1791	  for booting.  For more information, see the man pages for
1792	  modprobe, lsmod, modinfo, insmod and rmmod.
1793
1794	  If you say Y here, you will need to run "make
1795	  modules_install" to put the modules under /lib/modules/
1796	  where modprobe can find them (you may need to be root to do
1797	  this).
1798
1799	  If unsure, say Y.
1800
1801if MODULES
1802
1803config MODULE_FORCE_LOAD
1804	bool "Forced module loading"
1805	default n
1806	help
1807	  Allow loading of modules without version information (ie. modprobe
1808	  --force).  Forced module loading sets the 'F' (forced) taint flag and
1809	  is usually a really bad idea.
1810
1811config MODULE_UNLOAD
1812	bool "Module unloading"
1813	help
1814	  Without this option you will not be able to unload any
1815	  modules (note that some modules may not be unloadable
1816	  anyway), which makes your kernel smaller, faster
1817	  and simpler.  If unsure, say Y.
1818
1819config MODULE_FORCE_UNLOAD
1820	bool "Forced module unloading"
1821	depends on MODULE_UNLOAD
1822	help
1823	  This option allows you to force a module to unload, even if the
1824	  kernel believes it is unsafe: the kernel will remove the module
1825	  without waiting for anyone to stop using it (using the -f option to
1826	  rmmod).  This is mainly for kernel developers and desperate users.
1827	  If unsure, say N.
1828
1829config MODVERSIONS
1830	bool "Module versioning support"
1831	help
1832	  Usually, you have to use modules compiled with your kernel.
1833	  Saying Y here makes it sometimes possible to use modules
1834	  compiled for different kernels, by adding enough information
1835	  to the modules to (hopefully) spot any changes which would
1836	  make them incompatible with the kernel you are running.  If
1837	  unsure, say N.
1838
1839config MODULE_SRCVERSION_ALL
1840	bool "Source checksum for all modules"
1841	help
1842	  Modules which contain a MODULE_VERSION get an extra "srcversion"
1843	  field inserted into their modinfo section, which contains a
1844    	  sum of the source files which made it.  This helps maintainers
1845	  see exactly which source was used to build a module (since
1846	  others sometimes change the module source without updating
1847	  the version).  With this option, such a "srcversion" field
1848	  will be created for all modules.  If unsure, say N.
1849
1850config MODULE_SIG
1851	bool "Module signature verification"
1852	depends on MODULES
1853	select SYSTEM_TRUSTED_KEYRING
1854	select KEYS
1855	select CRYPTO
1856	select ASYMMETRIC_KEY_TYPE
1857	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1858	select PUBLIC_KEY_ALGO_RSA
1859	select ASN1
1860	select OID_REGISTRY
1861	select X509_CERTIFICATE_PARSER
1862	help
1863	  Check modules for valid signatures upon load: the signature
1864	  is simply appended to the module. For more information see
1865	  Documentation/module-signing.txt.
1866
1867	  !!!WARNING!!!  If you enable this option, you MUST make sure that the
1868	  module DOES NOT get stripped after being signed.  This includes the
1869	  debuginfo strip done by some packagers (such as rpmbuild) and
1870	  inclusion into an initramfs that wants the module size reduced.
1871
1872config MODULE_SIG_FORCE
1873	bool "Require modules to be validly signed"
1874	depends on MODULE_SIG
1875	help
1876	  Reject unsigned modules or signed modules for which we don't have a
1877	  key.  Without this, such modules will simply taint the kernel.
1878
1879config MODULE_SIG_ALL
1880	bool "Automatically sign all modules"
1881	default y
1882	depends on MODULE_SIG
1883	help
1884	  Sign all modules during make modules_install. Without this option,
1885	  modules must be signed manually, using the scripts/sign-file tool.
1886
1887comment "Do not forget to sign required modules with scripts/sign-file"
1888	depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1889
1890choice
1891	prompt "Which hash algorithm should modules be signed with?"
1892	depends on MODULE_SIG
1893	help
1894	  This determines which sort of hashing algorithm will be used during
1895	  signature generation.  This algorithm _must_ be built into the kernel
1896	  directly so that signature verification can take place.  It is not
1897	  possible to load a signed module containing the algorithm to check
1898	  the signature on that module.
1899
1900config MODULE_SIG_SHA1
1901	bool "Sign modules with SHA-1"
1902	select CRYPTO_SHA1
1903
1904config MODULE_SIG_SHA224
1905	bool "Sign modules with SHA-224"
1906	select CRYPTO_SHA256
1907
1908config MODULE_SIG_SHA256
1909	bool "Sign modules with SHA-256"
1910	select CRYPTO_SHA256
1911
1912config MODULE_SIG_SHA384
1913	bool "Sign modules with SHA-384"
1914	select CRYPTO_SHA512
1915
1916config MODULE_SIG_SHA512
1917	bool "Sign modules with SHA-512"
1918	select CRYPTO_SHA512
1919
1920endchoice
1921
1922config MODULE_SIG_HASH
1923	string
1924	depends on MODULE_SIG
1925	default "sha1" if MODULE_SIG_SHA1
1926	default "sha224" if MODULE_SIG_SHA224
1927	default "sha256" if MODULE_SIG_SHA256
1928	default "sha384" if MODULE_SIG_SHA384
1929	default "sha512" if MODULE_SIG_SHA512
1930
1931config MODULE_COMPRESS
1932	bool "Compress modules on installation"
1933	depends on MODULES
1934	help
1935	  This option compresses the kernel modules when 'make
1936	  modules_install' is run.
1937
1938	  The modules will be compressed either using gzip or xz depend on the
1939	  choice made in "Compression algorithm".
1940
1941	  module-init-tools has support for gzip format while kmod handle gzip
1942	  and xz compressed modules.
1943
1944	  When a kernel module is installed from outside of the main kernel
1945	  source and uses the Kbuild system for installing modules then that
1946	  kernel module will also be compressed when it is installed.
1947
1948	  This option provides little benefit when the modules are to be used inside
1949	  an initrd or initramfs, it generally is more efficient to compress the whole
1950	  initrd or initramfs instead.
1951
1952	  This is fully compatible with signed modules while the signed module is
1953	  compressed. module-init-tools or kmod handles decompression and provide to
1954	  other layer the uncompressed but signed payload.
1955
1956choice
1957	prompt "Compression algorithm"
1958	depends on MODULE_COMPRESS
1959	default MODULE_COMPRESS_GZIP
1960	help
1961	  This determines which sort of compression will be used during
1962	  'make modules_install'.
1963
1964	  GZIP (default) and XZ are supported.
1965
1966config MODULE_COMPRESS_GZIP
1967	bool "GZIP"
1968
1969config MODULE_COMPRESS_XZ
1970	bool "XZ"
1971
1972endchoice
1973
1974endif # MODULES
1975
1976config INIT_ALL_POSSIBLE
1977	bool
1978	help
1979	  Back when each arch used to define their own cpu_online_mask and
1980	  cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1981	  with all 1s, and others with all 0s.  When they were centralised,
1982	  it was better to provide this option than to break all the archs
1983	  and have several arch maintainers pursuing me down dark alleys.
1984
1985config STOP_MACHINE
1986	bool
1987	default y
1988	depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1989	help
1990	  Need stop_machine() primitive.
1991
1992source "block/Kconfig"
1993
1994config PREEMPT_NOTIFIERS
1995	bool
1996
1997config PADATA
1998	depends on SMP
1999	bool
2000
2001# Can be selected by architectures with broken toolchains
2002# that get confused by correct const<->read_only section
2003# mappings
2004config BROKEN_RODATA
2005	bool
2006
2007config ASN1
2008	tristate
2009	help
2010	  Build a simple ASN.1 grammar compiler that produces a bytecode output
2011	  that can be interpreted by the ASN.1 stream decoder and used to
2012	  inform it as to what tags are to be expected in a stream and what
2013	  functions to call on what tags.
2014
2015source "kernel/Kconfig.locks"
2016