xref: /openbmc/linux/init/Kconfig (revision 4e1a33b1)
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
475menu "RCU Subsystem"
476
477config TREE_RCU
478	bool
479	default y if !PREEMPT && SMP
480	help
481	  This option selects the RCU implementation that is
482	  designed for very large SMP system with hundreds or
483	  thousands of CPUs.  It also scales down nicely to
484	  smaller systems.
485
486config PREEMPT_RCU
487	bool
488	default y if PREEMPT
489	help
490	  This option selects the RCU implementation that is
491	  designed for very large SMP systems with hundreds or
492	  thousands of CPUs, but for which real-time response
493	  is also required.  It also scales down nicely to
494	  smaller systems.
495
496	  Select this option if you are unsure.
497
498config TINY_RCU
499	bool
500	default y if !PREEMPT && !SMP
501	help
502	  This option selects the RCU implementation that is
503	  designed for UP systems from which real-time response
504	  is not required.  This option greatly reduces the
505	  memory footprint of RCU.
506
507config RCU_EXPERT
508	bool "Make expert-level adjustments to RCU configuration"
509	default n
510	help
511	  This option needs to be enabled if you wish to make
512	  expert-level adjustments to RCU configuration.  By default,
513	  no such adjustments can be made, which has the often-beneficial
514	  side-effect of preventing "make oldconfig" from asking you all
515	  sorts of detailed questions about how you would like numerous
516	  obscure RCU options to be set up.
517
518	  Say Y if you need to make expert-level adjustments to RCU.
519
520	  Say N if you are unsure.
521
522config SRCU
523	bool
524	help
525	  This option selects the sleepable version of RCU. This version
526	  permits arbitrary sleeping or blocking within RCU read-side critical
527	  sections.
528
529config TASKS_RCU
530	bool
531	default n
532	select SRCU
533	help
534	  This option enables a task-based RCU implementation that uses
535	  only voluntary context switch (not preemption!), idle, and
536	  user-mode execution as quiescent states.
537
538config RCU_STALL_COMMON
539	def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
540	help
541	  This option enables RCU CPU stall code that is common between
542	  the TINY and TREE variants of RCU.  The purpose is to allow
543	  the tiny variants to disable RCU CPU stall warnings, while
544	  making these warnings mandatory for the tree variants.
545
546config CONTEXT_TRACKING
547       bool
548
549config CONTEXT_TRACKING_FORCE
550	bool "Force context tracking"
551	depends on CONTEXT_TRACKING
552	default y if !NO_HZ_FULL
553	help
554	  The major pre-requirement for full dynticks to work is to
555	  support the context tracking subsystem. But there are also
556	  other dependencies to provide in order to make the full
557	  dynticks working.
558
559	  This option stands for testing when an arch implements the
560	  context tracking backend but doesn't yet fullfill all the
561	  requirements to make the full dynticks feature working.
562	  Without the full dynticks, there is no way to test the support
563	  for context tracking and the subsystems that rely on it: RCU
564	  userspace extended quiescent state and tickless cputime
565	  accounting. This option copes with the absence of the full
566	  dynticks subsystem by forcing the context tracking on all
567	  CPUs in the system.
568
569	  Say Y only if you're working on the development of an
570	  architecture backend for the context tracking.
571
572	  Say N otherwise, this option brings an overhead that you
573	  don't want in production.
574
575
576config RCU_FANOUT
577	int "Tree-based hierarchical RCU fanout value"
578	range 2 64 if 64BIT
579	range 2 32 if !64BIT
580	depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
581	default 64 if 64BIT
582	default 32 if !64BIT
583	help
584	  This option controls the fanout of hierarchical implementations
585	  of RCU, allowing RCU to work efficiently on machines with
586	  large numbers of CPUs.  This value must be at least the fourth
587	  root of NR_CPUS, which allows NR_CPUS to be insanely large.
588	  The default value of RCU_FANOUT should be used for production
589	  systems, but if you are stress-testing the RCU implementation
590	  itself, small RCU_FANOUT values allow you to test large-system
591	  code paths on small(er) systems.
592
593	  Select a specific number if testing RCU itself.
594	  Take the default if unsure.
595
596config RCU_FANOUT_LEAF
597	int "Tree-based hierarchical RCU leaf-level fanout value"
598	range 2 64 if 64BIT
599	range 2 32 if !64BIT
600	depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
601	default 16
602	help
603	  This option controls the leaf-level fanout of hierarchical
604	  implementations of RCU, and allows trading off cache misses
605	  against lock contention.  Systems that synchronize their
606	  scheduling-clock interrupts for energy-efficiency reasons will
607	  want the default because the smaller leaf-level fanout keeps
608	  lock contention levels acceptably low.  Very large systems
609	  (hundreds or thousands of CPUs) will instead want to set this
610	  value to the maximum value possible in order to reduce the
611	  number of cache misses incurred during RCU's grace-period
612	  initialization.  These systems tend to run CPU-bound, and thus
613	  are not helped by synchronized interrupts, and thus tend to
614	  skew them, which reduces lock contention enough that large
615	  leaf-level fanouts work well.
616
617	  Select a specific number if testing RCU itself.
618
619	  Select the maximum permissible value for large systems.
620
621	  Take the default if unsure.
622
623config RCU_FAST_NO_HZ
624	bool "Accelerate last non-dyntick-idle CPU's grace periods"
625	depends on NO_HZ_COMMON && SMP && RCU_EXPERT
626	default n
627	help
628	  This option permits CPUs to enter dynticks-idle state even if
629	  they have RCU callbacks queued, and prevents RCU from waking
630	  these CPUs up more than roughly once every four jiffies (by
631	  default, you can adjust this using the rcutree.rcu_idle_gp_delay
632	  parameter), thus improving energy efficiency.  On the other
633	  hand, this option increases the duration of RCU grace periods,
634	  for example, slowing down synchronize_rcu().
635
636	  Say Y if energy efficiency is critically important, and you
637	  	don't care about increased grace-period durations.
638
639	  Say N if you are unsure.
640
641config TREE_RCU_TRACE
642	def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
643	select DEBUG_FS
644	help
645	  This option provides tracing for the TREE_RCU and
646	  PREEMPT_RCU implementations, permitting Makefile to
647	  trivially select kernel/rcutree_trace.c.
648
649config RCU_BOOST
650	bool "Enable RCU priority boosting"
651	depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT
652	default n
653	help
654	  This option boosts the priority of preempted RCU readers that
655	  block the current preemptible RCU grace period for too long.
656	  This option also prevents heavy loads from blocking RCU
657	  callback invocation for all flavors of RCU.
658
659	  Say Y here if you are working with real-time apps or heavy loads
660	  Say N here if you are unsure.
661
662config RCU_KTHREAD_PRIO
663	int "Real-time priority to use for RCU worker threads"
664	range 1 99 if RCU_BOOST
665	range 0 99 if !RCU_BOOST
666	default 1 if RCU_BOOST
667	default 0 if !RCU_BOOST
668	depends on RCU_EXPERT
669	help
670	  This option specifies the SCHED_FIFO priority value that will be
671	  assigned to the rcuc/n and rcub/n threads and is also the value
672	  used for RCU_BOOST (if enabled). If you are working with a
673	  real-time application that has one or more CPU-bound threads
674	  running at a real-time priority level, you should set
675	  RCU_KTHREAD_PRIO to a priority higher than the highest-priority
676	  real-time CPU-bound application thread.  The default RCU_KTHREAD_PRIO
677	  value of 1 is appropriate in the common case, which is real-time
678	  applications that do not have any CPU-bound threads.
679
680	  Some real-time applications might not have a single real-time
681	  thread that saturates a given CPU, but instead might have
682	  multiple real-time threads that, taken together, fully utilize
683	  that CPU.  In this case, you should set RCU_KTHREAD_PRIO to
684	  a priority higher than the lowest-priority thread that is
685	  conspiring to prevent the CPU from running any non-real-time
686	  tasks.  For example, if one thread at priority 10 and another
687	  thread at priority 5 are between themselves fully consuming
688	  the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
689	  set to priority 6 or higher.
690
691	  Specify the real-time priority, or take the default if unsure.
692
693config RCU_BOOST_DELAY
694	int "Milliseconds to delay boosting after RCU grace-period start"
695	range 0 3000
696	depends on RCU_BOOST
697	default 500
698	help
699	  This option specifies the time to wait after the beginning of
700	  a given grace period before priority-boosting preempted RCU
701	  readers blocking that grace period.  Note that any RCU reader
702	  blocking an expedited RCU grace period is boosted immediately.
703
704	  Accept the default if unsure.
705
706config RCU_NOCB_CPU
707	bool "Offload RCU callback processing from boot-selected CPUs"
708	depends on TREE_RCU || PREEMPT_RCU
709	depends on RCU_EXPERT || NO_HZ_FULL
710	default n
711	help
712	  Use this option to reduce OS jitter for aggressive HPC or
713	  real-time workloads.	It can also be used to offload RCU
714	  callback invocation to energy-efficient CPUs in battery-powered
715	  asymmetric multiprocessors.
716
717	  This option offloads callback invocation from the set of
718	  CPUs specified at boot time by the rcu_nocbs parameter.
719	  For each such CPU, a kthread ("rcuox/N") will be created to
720	  invoke callbacks, where the "N" is the CPU being offloaded,
721	  and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
722	  "s" for RCU-sched.  Nothing prevents this kthread from running
723	  on the specified CPUs, but (1) the kthreads may be preempted
724	  between each callback, and (2) affinity or cgroups can be used
725	  to force the kthreads to run on whatever set of CPUs is desired.
726
727	  Say Y here if you want to help to debug reduced OS jitter.
728	  Say N here if you are unsure.
729
730choice
731	prompt "Build-forced no-CBs CPUs"
732	default RCU_NOCB_CPU_NONE
733	depends on RCU_NOCB_CPU
734	help
735	  This option allows no-CBs CPUs (whose RCU callbacks are invoked
736	  from kthreads rather than from softirq context) to be specified
737	  at build time.  Additional no-CBs CPUs may be specified by
738	  the rcu_nocbs= boot parameter.
739
740config RCU_NOCB_CPU_NONE
741	bool "No build_forced no-CBs CPUs"
742	help
743	  This option does not force any of the CPUs to be no-CBs CPUs.
744	  Only CPUs designated by the rcu_nocbs= boot parameter will be
745	  no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
746	  kthreads whose names begin with "rcuo".  All other CPUs will
747	  invoke their own RCU callbacks in softirq context.
748
749	  Select this option if you want to choose no-CBs CPUs at
750	  boot time, for example, to allow testing of different no-CBs
751	  configurations without having to rebuild the kernel each time.
752
753config RCU_NOCB_CPU_ZERO
754	bool "CPU 0 is a build_forced no-CBs CPU"
755	help
756	  This option forces CPU 0 to be a no-CBs CPU, so that its RCU
757	  callbacks are invoked by a per-CPU kthread whose name begins
758	  with "rcuo".	Additional CPUs may be designated as no-CBs
759	  CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
760	  All other CPUs will invoke their own RCU callbacks in softirq
761	  context.
762
763	  Select this if CPU 0 needs to be a no-CBs CPU for real-time
764	  or energy-efficiency reasons, but the real reason it exists
765	  is to ensure that randconfig testing covers mixed systems.
766
767config RCU_NOCB_CPU_ALL
768	bool "All CPUs are build_forced no-CBs CPUs"
769	help
770	  This option forces all CPUs to be no-CBs CPUs.  The rcu_nocbs=
771	  boot parameter will be ignored.  All CPUs' RCU callbacks will
772	  be executed in the context of per-CPU rcuo kthreads created for
773	  this purpose.  Assuming that the kthreads whose names start with
774	  "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
775	  on the remaining CPUs, but might decrease memory locality during
776	  RCU-callback invocation, thus potentially degrading throughput.
777
778	  Select this if all CPUs need to be no-CBs CPUs for real-time
779	  or energy-efficiency reasons.
780
781endchoice
782
783endmenu # "RCU Subsystem"
784
785config BUILD_BIN2C
786	bool
787	default n
788
789config IKCONFIG
790	tristate "Kernel .config support"
791	select BUILD_BIN2C
792	---help---
793	  This option enables the complete Linux kernel ".config" file
794	  contents to be saved in the kernel. It provides documentation
795	  of which kernel options are used in a running kernel or in an
796	  on-disk kernel.  This information can be extracted from the kernel
797	  image file with the script scripts/extract-ikconfig and used as
798	  input to rebuild the current kernel or to build another kernel.
799	  It can also be extracted from a running kernel by reading
800	  /proc/config.gz if enabled (below).
801
802config IKCONFIG_PROC
803	bool "Enable access to .config through /proc/config.gz"
804	depends on IKCONFIG && PROC_FS
805	---help---
806	  This option enables access to the kernel configuration file
807	  through /proc/config.gz.
808
809config LOG_BUF_SHIFT
810	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
811	range 12 25
812	default 17
813	depends on PRINTK
814	help
815	  Select the minimal kernel log buffer size as a power of 2.
816	  The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
817	  parameter, see below. Any higher size also might be forced
818	  by "log_buf_len" boot parameter.
819
820	  Examples:
821		     17 => 128 KB
822		     16 => 64 KB
823		     15 => 32 KB
824		     14 => 16 KB
825		     13 =>  8 KB
826		     12 =>  4 KB
827
828config LOG_CPU_MAX_BUF_SHIFT
829	int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
830	depends on SMP
831	range 0 21
832	default 12 if !BASE_SMALL
833	default 0 if BASE_SMALL
834	depends on PRINTK
835	help
836	  This option allows to increase the default ring buffer size
837	  according to the number of CPUs. The value defines the contribution
838	  of each CPU as a power of 2. The used space is typically only few
839	  lines however it might be much more when problems are reported,
840	  e.g. backtraces.
841
842	  The increased size means that a new buffer has to be allocated and
843	  the original static one is unused. It makes sense only on systems
844	  with more CPUs. Therefore this value is used only when the sum of
845	  contributions is greater than the half of the default kernel ring
846	  buffer as defined by LOG_BUF_SHIFT. The default values are set
847	  so that more than 64 CPUs are needed to trigger the allocation.
848
849	  Also this option is ignored when "log_buf_len" kernel parameter is
850	  used as it forces an exact (power of two) size of the ring buffer.
851
852	  The number of possible CPUs is used for this computation ignoring
853	  hotplugging making the computation optimal for the worst case
854	  scenario while allowing a simple algorithm to be used from bootup.
855
856	  Examples shift values and their meaning:
857		     17 => 128 KB for each CPU
858		     16 =>  64 KB for each CPU
859		     15 =>  32 KB for each CPU
860		     14 =>  16 KB for each CPU
861		     13 =>   8 KB for each CPU
862		     12 =>   4 KB for each CPU
863
864config PRINTK_SAFE_LOG_BUF_SHIFT
865	int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
866	range 10 21
867	default 13
868	depends on PRINTK
869	help
870	  Select the size of an alternate printk per-CPU buffer where messages
871	  printed from usafe contexts are temporary stored. One example would
872	  be NMI messages, another one - printk recursion. The messages are
873	  copied to the main log buffer in a safe context to avoid a deadlock.
874	  The value defines the size as a power of 2.
875
876	  Those messages are rare and limited. The largest one is when
877	  a backtrace is printed. It usually fits into 4KB. Select
878	  8KB if you want to be on the safe side.
879
880	  Examples:
881		     17 => 128 KB for each CPU
882		     16 =>  64 KB for each CPU
883		     15 =>  32 KB for each CPU
884		     14 =>  16 KB for each CPU
885		     13 =>   8 KB for each CPU
886		     12 =>   4 KB for each CPU
887
888#
889# Architectures with an unreliable sched_clock() should select this:
890#
891config HAVE_UNSTABLE_SCHED_CLOCK
892	bool
893
894config GENERIC_SCHED_CLOCK
895	bool
896
897#
898# For architectures that want to enable the support for NUMA-affine scheduler
899# balancing logic:
900#
901config ARCH_SUPPORTS_NUMA_BALANCING
902	bool
903
904#
905# For architectures that prefer to flush all TLBs after a number of pages
906# are unmapped instead of sending one IPI per page to flush. The architecture
907# must provide guarantees on what happens if a clean TLB cache entry is
908# written after the unmap. Details are in mm/rmap.c near the check for
909# should_defer_flush. The architecture should also consider if the full flush
910# and the refill costs are offset by the savings of sending fewer IPIs.
911config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
912	bool
913
914#
915# For architectures that know their GCC __int128 support is sound
916#
917config ARCH_SUPPORTS_INT128
918	bool
919
920# For architectures that (ab)use NUMA to represent different memory regions
921# all cpu-local but of different latencies, such as SuperH.
922#
923config ARCH_WANT_NUMA_VARIABLE_LOCALITY
924	bool
925
926config NUMA_BALANCING
927	bool "Memory placement aware NUMA scheduler"
928	depends on ARCH_SUPPORTS_NUMA_BALANCING
929	depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
930	depends on SMP && NUMA && MIGRATION
931	help
932	  This option adds support for automatic NUMA aware memory/task placement.
933	  The mechanism is quite primitive and is based on migrating memory when
934	  it has references to the node the task is running on.
935
936	  This system will be inactive on UMA systems.
937
938config NUMA_BALANCING_DEFAULT_ENABLED
939	bool "Automatically enable NUMA aware memory/task placement"
940	default y
941	depends on NUMA_BALANCING
942	help
943	  If set, automatic NUMA balancing will be enabled if running on a NUMA
944	  machine.
945
946menuconfig CGROUPS
947	bool "Control Group support"
948	select KERNFS
949	help
950	  This option adds support for grouping sets of processes together, for
951	  use with process control subsystems such as Cpusets, CFS, memory
952	  controls or device isolation.
953	  See
954		- Documentation/scheduler/sched-design-CFS.txt	(CFS)
955		- Documentation/cgroup-v1/ (features for grouping, isolation
956					  and resource control)
957
958	  Say N if unsure.
959
960if CGROUPS
961
962config PAGE_COUNTER
963       bool
964
965config MEMCG
966	bool "Memory controller"
967	select PAGE_COUNTER
968	select EVENTFD
969	help
970	  Provides control over the memory footprint of tasks in a cgroup.
971
972config MEMCG_SWAP
973	bool "Swap controller"
974	depends on MEMCG && SWAP
975	help
976	  Provides control over the swap space consumed by tasks in a cgroup.
977
978config MEMCG_SWAP_ENABLED
979	bool "Swap controller enabled by default"
980	depends on MEMCG_SWAP
981	default y
982	help
983	  Memory Resource Controller Swap Extension comes with its price in
984	  a bigger memory consumption. General purpose distribution kernels
985	  which want to enable the feature but keep it disabled by default
986	  and let the user enable it by swapaccount=1 boot command line
987	  parameter should have this option unselected.
988	  For those who want to have the feature enabled by default should
989	  select this option (if, for some reason, they need to disable it
990	  then swapaccount=0 does the trick).
991
992config BLK_CGROUP
993	bool "IO controller"
994	depends on BLOCK
995	default n
996	---help---
997	Generic block IO controller cgroup interface. This is the common
998	cgroup interface which should be used by various IO controlling
999	policies.
1000
1001	Currently, CFQ IO scheduler uses it to recognize task groups and
1002	control disk bandwidth allocation (proportional time slice allocation)
1003	to such task groups. It is also used by bio throttling logic in
1004	block layer to implement upper limit in IO rates on a device.
1005
1006	This option only enables generic Block IO controller infrastructure.
1007	One needs to also enable actual IO controlling logic/policy. For
1008	enabling proportional weight division of disk bandwidth in CFQ, set
1009	CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1010	CONFIG_BLK_DEV_THROTTLING=y.
1011
1012	See Documentation/cgroup-v1/blkio-controller.txt for more information.
1013
1014config DEBUG_BLK_CGROUP
1015	bool "IO controller debugging"
1016	depends on BLK_CGROUP
1017	default n
1018	---help---
1019	Enable some debugging help. Currently it exports additional stat
1020	files in a cgroup which can be useful for debugging.
1021
1022config CGROUP_WRITEBACK
1023	bool
1024	depends on MEMCG && BLK_CGROUP
1025	default y
1026
1027menuconfig CGROUP_SCHED
1028	bool "CPU controller"
1029	default n
1030	help
1031	  This feature lets CPU scheduler recognize task groups and control CPU
1032	  bandwidth allocation to such task groups. It uses cgroups to group
1033	  tasks.
1034
1035if CGROUP_SCHED
1036config FAIR_GROUP_SCHED
1037	bool "Group scheduling for SCHED_OTHER"
1038	depends on CGROUP_SCHED
1039	default CGROUP_SCHED
1040
1041config CFS_BANDWIDTH
1042	bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1043	depends on FAIR_GROUP_SCHED
1044	default n
1045	help
1046	  This option allows users to define CPU bandwidth rates (limits) for
1047	  tasks running within the fair group scheduler.  Groups with no limit
1048	  set are considered to be unconstrained and will run with no
1049	  restriction.
1050	  See tip/Documentation/scheduler/sched-bwc.txt for more information.
1051
1052config RT_GROUP_SCHED
1053	bool "Group scheduling for SCHED_RR/FIFO"
1054	depends on CGROUP_SCHED
1055	default n
1056	help
1057	  This feature lets you explicitly allocate real CPU bandwidth
1058	  to task groups. If enabled, it will also make it impossible to
1059	  schedule realtime tasks for non-root users until you allocate
1060	  realtime bandwidth for them.
1061	  See Documentation/scheduler/sched-rt-group.txt for more information.
1062
1063endif #CGROUP_SCHED
1064
1065config CGROUP_PIDS
1066	bool "PIDs controller"
1067	help
1068	  Provides enforcement of process number limits in the scope of a
1069	  cgroup. Any attempt to fork more processes than is allowed in the
1070	  cgroup will fail. PIDs are fundamentally a global resource because it
1071	  is fairly trivial to reach PID exhaustion before you reach even a
1072	  conservative kmemcg limit. As a result, it is possible to grind a
1073	  system to halt without being limited by other cgroup policies. The
1074	  PIDs controller is designed to stop this from happening.
1075
1076	  It should be noted that organisational operations (such as attaching
1077	  to a cgroup hierarchy will *not* be blocked by the PIDs controller),
1078	  since the PIDs limit only affects a process's ability to fork, not to
1079	  attach to a cgroup.
1080
1081config CGROUP_FREEZER
1082	bool "Freezer controller"
1083	help
1084	  Provides a way to freeze and unfreeze all tasks in a
1085	  cgroup.
1086
1087	  This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1088	  controller includes important in-kernel memory consumers per default.
1089
1090	  If you're using cgroup2, say N.
1091
1092config CGROUP_HUGETLB
1093	bool "HugeTLB controller"
1094	depends on HUGETLB_PAGE
1095	select PAGE_COUNTER
1096	default n
1097	help
1098	  Provides a cgroup controller for HugeTLB pages.
1099	  When you enable this, you can put a per cgroup limit on HugeTLB usage.
1100	  The limit is enforced during page fault. Since HugeTLB doesn't
1101	  support page reclaim, enforcing the limit at page fault time implies
1102	  that, the application will get SIGBUS signal if it tries to access
1103	  HugeTLB pages beyond its limit. This requires the application to know
1104	  beforehand how much HugeTLB pages it would require for its use. The
1105	  control group is tracked in the third page lru pointer. This means
1106	  that we cannot use the controller with huge page less than 3 pages.
1107
1108config CPUSETS
1109	bool "Cpuset controller"
1110	help
1111	  This option will let you create and manage CPUSETs which
1112	  allow dynamically partitioning a system into sets of CPUs and
1113	  Memory Nodes and assigning tasks to run only within those sets.
1114	  This is primarily useful on large SMP or NUMA systems.
1115
1116	  Say N if unsure.
1117
1118config PROC_PID_CPUSET
1119	bool "Include legacy /proc/<pid>/cpuset file"
1120	depends on CPUSETS
1121	default y
1122
1123config CGROUP_DEVICE
1124	bool "Device controller"
1125	help
1126	  Provides a cgroup controller implementing whitelists for
1127	  devices which a process in the cgroup can mknod or open.
1128
1129config CGROUP_CPUACCT
1130	bool "Simple CPU accounting controller"
1131	help
1132	  Provides a simple controller for monitoring the
1133	  total CPU consumed by the tasks in a cgroup.
1134
1135config CGROUP_PERF
1136	bool "Perf controller"
1137	depends on PERF_EVENTS
1138	help
1139	  This option extends the perf per-cpu mode to restrict monitoring
1140	  to threads which belong to the cgroup specified and run on the
1141	  designated cpu.
1142
1143	  Say N if unsure.
1144
1145config CGROUP_BPF
1146	bool "Support for eBPF programs attached to cgroups"
1147	depends on BPF_SYSCALL
1148	select SOCK_CGROUP_DATA
1149	help
1150	  Allow attaching eBPF programs to a cgroup using the bpf(2)
1151	  syscall command BPF_PROG_ATTACH.
1152
1153	  In which context these programs are accessed depends on the type
1154	  of attachment. For instance, programs that are attached using
1155	  BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1156	  inet sockets.
1157
1158config CGROUP_DEBUG
1159	bool "Example controller"
1160	default n
1161	help
1162	  This option enables a simple controller that exports
1163	  debugging information about the cgroups framework.
1164
1165	  Say N.
1166
1167config SOCK_CGROUP_DATA
1168	bool
1169	default n
1170
1171endif # CGROUPS
1172
1173config CHECKPOINT_RESTORE
1174	bool "Checkpoint/restore support" if EXPERT
1175	select PROC_CHILDREN
1176	default n
1177	help
1178	  Enables additional kernel features in a sake of checkpoint/restore.
1179	  In particular it adds auxiliary prctl codes to setup process text,
1180	  data and heap segment sizes, and a few additional /proc filesystem
1181	  entries.
1182
1183	  If unsure, say N here.
1184
1185menuconfig NAMESPACES
1186	bool "Namespaces support" if EXPERT
1187	depends on MULTIUSER
1188	default !EXPERT
1189	help
1190	  Provides the way to make tasks work with different objects using
1191	  the same id. For example same IPC id may refer to different objects
1192	  or same user id or pid may refer to different tasks when used in
1193	  different namespaces.
1194
1195if NAMESPACES
1196
1197config UTS_NS
1198	bool "UTS namespace"
1199	default y
1200	help
1201	  In this namespace tasks see different info provided with the
1202	  uname() system call
1203
1204config IPC_NS
1205	bool "IPC namespace"
1206	depends on (SYSVIPC || POSIX_MQUEUE)
1207	default y
1208	help
1209	  In this namespace tasks work with IPC ids which correspond to
1210	  different IPC objects in different namespaces.
1211
1212config USER_NS
1213	bool "User namespace"
1214	default n
1215	help
1216	  This allows containers, i.e. vservers, to use user namespaces
1217	  to provide different user info for different servers.
1218
1219	  When user namespaces are enabled in the kernel it is
1220	  recommended that the MEMCG option also be enabled and that
1221	  user-space use the memory control groups to limit the amount
1222	  of memory a memory unprivileged users can use.
1223
1224	  If unsure, say N.
1225
1226config PID_NS
1227	bool "PID Namespaces"
1228	default y
1229	help
1230	  Support process id namespaces.  This allows having multiple
1231	  processes with the same pid as long as they are in different
1232	  pid namespaces.  This is a building block of containers.
1233
1234config NET_NS
1235	bool "Network namespace"
1236	depends on NET
1237	default y
1238	help
1239	  Allow user space to create what appear to be multiple instances
1240	  of the network stack.
1241
1242endif # NAMESPACES
1243
1244config SCHED_AUTOGROUP
1245	bool "Automatic process group scheduling"
1246	select CGROUPS
1247	select CGROUP_SCHED
1248	select FAIR_GROUP_SCHED
1249	help
1250	  This option optimizes the scheduler for common desktop workloads by
1251	  automatically creating and populating task groups.  This separation
1252	  of workloads isolates aggressive CPU burners (like build jobs) from
1253	  desktop applications.  Task group autogeneration is currently based
1254	  upon task session.
1255
1256config SYSFS_DEPRECATED
1257	bool "Enable deprecated sysfs features to support old userspace tools"
1258	depends on SYSFS
1259	default n
1260	help
1261	  This option adds code that switches the layout of the "block" class
1262	  devices, to not show up in /sys/class/block/, but only in
1263	  /sys/block/.
1264
1265	  This switch is only active when the sysfs.deprecated=1 boot option is
1266	  passed or the SYSFS_DEPRECATED_V2 option is set.
1267
1268	  This option allows new kernels to run on old distributions and tools,
1269	  which might get confused by /sys/class/block/. Since 2007/2008 all
1270	  major distributions and tools handle this just fine.
1271
1272	  Recent distributions and userspace tools after 2009/2010 depend on
1273	  the existence of /sys/class/block/, and will not work with this
1274	  option enabled.
1275
1276	  Only if you are using a new kernel on an old distribution, you might
1277	  need to say Y here.
1278
1279config SYSFS_DEPRECATED_V2
1280	bool "Enable deprecated sysfs features by default"
1281	default n
1282	depends on SYSFS
1283	depends on SYSFS_DEPRECATED
1284	help
1285	  Enable deprecated sysfs by default.
1286
1287	  See the CONFIG_SYSFS_DEPRECATED option for more details about this
1288	  option.
1289
1290	  Only if you are using a new kernel on an old distribution, you might
1291	  need to say Y here. Even then, odds are you would not need it
1292	  enabled, you can always pass the boot option if absolutely necessary.
1293
1294config RELAY
1295	bool "Kernel->user space relay support (formerly relayfs)"
1296	select IRQ_WORK
1297	help
1298	  This option enables support for relay interface support in
1299	  certain file systems (such as debugfs).
1300	  It is designed to provide an efficient mechanism for tools and
1301	  facilities to relay large amounts of data from kernel space to
1302	  user space.
1303
1304	  If unsure, say N.
1305
1306config BLK_DEV_INITRD
1307	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1308	depends on BROKEN || !FRV
1309	help
1310	  The initial RAM filesystem is a ramfs which is loaded by the
1311	  boot loader (loadlin or lilo) and that is mounted as root
1312	  before the normal boot procedure. It is typically used to
1313	  load modules needed to mount the "real" root file system,
1314	  etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1315
1316	  If RAM disk support (BLK_DEV_RAM) is also included, this
1317	  also enables initial RAM disk (initrd) support and adds
1318	  15 Kbytes (more on some other architectures) to the kernel size.
1319
1320	  If unsure say Y.
1321
1322if BLK_DEV_INITRD
1323
1324source "usr/Kconfig"
1325
1326endif
1327
1328choice
1329	prompt "Compiler optimization level"
1330	default CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE
1331
1332config CC_OPTIMIZE_FOR_PERFORMANCE
1333	bool "Optimize for performance"
1334	help
1335	  This is the default optimization level for the kernel, building
1336	  with the "-O2" compiler flag for best performance and most
1337	  helpful compile-time warnings.
1338
1339config CC_OPTIMIZE_FOR_SIZE
1340	bool "Optimize for size"
1341	help
1342	  Enabling this option will pass "-Os" instead of "-O2" to
1343	  your compiler resulting in a smaller kernel.
1344
1345	  If unsure, say N.
1346
1347endchoice
1348
1349config SYSCTL
1350	bool
1351
1352config ANON_INODES
1353	bool
1354
1355config HAVE_UID16
1356	bool
1357
1358config SYSCTL_EXCEPTION_TRACE
1359	bool
1360	help
1361	  Enable support for /proc/sys/debug/exception-trace.
1362
1363config SYSCTL_ARCH_UNALIGN_NO_WARN
1364	bool
1365	help
1366	  Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1367	  Allows arch to define/use @no_unaligned_warning to possibly warn
1368	  about unaligned access emulation going on under the hood.
1369
1370config SYSCTL_ARCH_UNALIGN_ALLOW
1371	bool
1372	help
1373	  Enable support for /proc/sys/kernel/unaligned-trap
1374	  Allows arches to define/use @unaligned_enabled to runtime toggle
1375	  the unaligned access emulation.
1376	  see arch/parisc/kernel/unaligned.c for reference
1377
1378config HAVE_PCSPKR_PLATFORM
1379	bool
1380
1381# interpreter that classic socket filters depend on
1382config BPF
1383	bool
1384
1385menuconfig EXPERT
1386	bool "Configure standard kernel features (expert users)"
1387	# Unhide debug options, to make the on-by-default options visible
1388	select DEBUG_KERNEL
1389	help
1390	  This option allows certain base kernel options and settings
1391          to be disabled or tweaked. This is for specialized
1392          environments which can tolerate a "non-standard" kernel.
1393          Only use this if you really know what you are doing.
1394
1395config UID16
1396	bool "Enable 16-bit UID system calls" if EXPERT
1397	depends on HAVE_UID16 && MULTIUSER
1398	default y
1399	help
1400	  This enables the legacy 16-bit UID syscall wrappers.
1401
1402config MULTIUSER
1403	bool "Multiple users, groups and capabilities support" if EXPERT
1404	default y
1405	help
1406	  This option enables support for non-root users, groups and
1407	  capabilities.
1408
1409	  If you say N here, all processes will run with UID 0, GID 0, and all
1410	  possible capabilities.  Saying N here also compiles out support for
1411	  system calls related to UIDs, GIDs, and capabilities, such as setuid,
1412	  setgid, and capset.
1413
1414	  If unsure, say Y here.
1415
1416config SGETMASK_SYSCALL
1417	bool "sgetmask/ssetmask syscalls support" if EXPERT
1418	def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1419	---help---
1420	  sys_sgetmask and sys_ssetmask are obsolete system calls
1421	  no longer supported in libc but still enabled by default in some
1422	  architectures.
1423
1424	  If unsure, leave the default option here.
1425
1426config SYSFS_SYSCALL
1427	bool "Sysfs syscall support" if EXPERT
1428	default y
1429	---help---
1430	  sys_sysfs is an obsolete system call no longer supported in libc.
1431	  Note that disabling this option is more secure but might break
1432	  compatibility with some systems.
1433
1434	  If unsure say Y here.
1435
1436config SYSCTL_SYSCALL
1437	bool "Sysctl syscall support" if EXPERT
1438	depends on PROC_SYSCTL
1439	default n
1440	select SYSCTL
1441	---help---
1442	  sys_sysctl uses binary paths that have been found challenging
1443	  to properly maintain and use.  The interface in /proc/sys
1444	  using paths with ascii names is now the primary path to this
1445	  information.
1446
1447	  Almost nothing using the binary sysctl interface so if you are
1448	  trying to save some space it is probably safe to disable this,
1449	  making your kernel marginally smaller.
1450
1451	  If unsure say N here.
1452
1453config POSIX_TIMERS
1454	bool "Posix Clocks & timers" if EXPERT
1455	default y
1456	help
1457	  This includes native support for POSIX timers to the kernel.
1458	  Some embedded systems have no use for them and therefore they
1459	  can be configured out to reduce the size of the kernel image.
1460
1461	  When this option is disabled, the following syscalls won't be
1462	  available: timer_create, timer_gettime: timer_getoverrun,
1463	  timer_settime, timer_delete, clock_adjtime, getitimer,
1464	  setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1465	  clock_getres and clock_nanosleep syscalls will be limited to
1466	  CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1467
1468	  If unsure say y.
1469
1470config KALLSYMS
1471	 bool "Load all symbols for debugging/ksymoops" if EXPERT
1472	 default y
1473	 help
1474	   Say Y here to let the kernel print out symbolic crash information and
1475	   symbolic stack backtraces. This increases the size of the kernel
1476	   somewhat, as all symbols have to be loaded into the kernel image.
1477
1478config KALLSYMS_ALL
1479	bool "Include all symbols in kallsyms"
1480	depends on DEBUG_KERNEL && KALLSYMS
1481	help
1482	   Normally kallsyms only contains the symbols of functions for nicer
1483	   OOPS messages and backtraces (i.e., symbols from the text and inittext
1484	   sections). This is sufficient for most cases. And only in very rare
1485	   cases (e.g., when a debugger is used) all symbols are required (e.g.,
1486	   names of variables from the data sections, etc).
1487
1488	   This option makes sure that all symbols are loaded into the kernel
1489	   image (i.e., symbols from all sections) in cost of increased kernel
1490	   size (depending on the kernel configuration, it may be 300KiB or
1491	   something like this).
1492
1493	   Say N unless you really need all symbols.
1494
1495config KALLSYMS_ABSOLUTE_PERCPU
1496	bool
1497	depends on KALLSYMS
1498	default X86_64 && SMP
1499
1500config KALLSYMS_BASE_RELATIVE
1501	bool
1502	depends on KALLSYMS
1503	default !IA64 && !(TILE && 64BIT)
1504	help
1505	  Instead of emitting them as absolute values in the native word size,
1506	  emit the symbol references in the kallsyms table as 32-bit entries,
1507	  each containing a relative value in the range [base, base + U32_MAX]
1508	  or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1509	  an absolute value in the range [0, S32_MAX] or a relative value in the
1510	  range [base, base + S32_MAX], where base is the lowest relative symbol
1511	  address encountered in the image.
1512
1513	  On 64-bit builds, this reduces the size of the address table by 50%,
1514	  but more importantly, it results in entries whose values are build
1515	  time constants, and no relocation pass is required at runtime to fix
1516	  up the entries based on the runtime load address of the kernel.
1517
1518config PRINTK
1519	default y
1520	bool "Enable support for printk" if EXPERT
1521	select IRQ_WORK
1522	help
1523	  This option enables normal printk support. Removing it
1524	  eliminates most of the message strings from the kernel image
1525	  and makes the kernel more or less silent. As this makes it
1526	  very difficult to diagnose system problems, saying N here is
1527	  strongly discouraged.
1528
1529config PRINTK_NMI
1530	def_bool y
1531	depends on PRINTK
1532	depends on HAVE_NMI
1533
1534config BUG
1535	bool "BUG() support" if EXPERT
1536	default y
1537	help
1538          Disabling this option eliminates support for BUG and WARN, reducing
1539          the size of your kernel image and potentially quietly ignoring
1540          numerous fatal conditions. You should only consider disabling this
1541          option for embedded systems with no facilities for reporting errors.
1542          Just say Y.
1543
1544config ELF_CORE
1545	depends on COREDUMP
1546	default y
1547	bool "Enable ELF core dumps" if EXPERT
1548	help
1549	  Enable support for generating core dumps. Disabling saves about 4k.
1550
1551
1552config PCSPKR_PLATFORM
1553	bool "Enable PC-Speaker support" if EXPERT
1554	depends on HAVE_PCSPKR_PLATFORM
1555	select I8253_LOCK
1556	default y
1557	help
1558          This option allows to disable the internal PC-Speaker
1559          support, saving some memory.
1560
1561config BASE_FULL
1562	default y
1563	bool "Enable full-sized data structures for core" if EXPERT
1564	help
1565	  Disabling this option reduces the size of miscellaneous core
1566	  kernel data structures. This saves memory on small machines,
1567	  but may reduce performance.
1568
1569config FUTEX
1570	bool "Enable futex support" if EXPERT
1571	default y
1572	select RT_MUTEXES
1573	help
1574	  Disabling this option will cause the kernel to be built without
1575	  support for "fast userspace mutexes".  The resulting kernel may not
1576	  run glibc-based applications correctly.
1577
1578config HAVE_FUTEX_CMPXCHG
1579	bool
1580	depends on FUTEX
1581	help
1582	  Architectures should select this if futex_atomic_cmpxchg_inatomic()
1583	  is implemented and always working. This removes a couple of runtime
1584	  checks.
1585
1586config EPOLL
1587	bool "Enable eventpoll support" if EXPERT
1588	default y
1589	select ANON_INODES
1590	help
1591	  Disabling this option will cause the kernel to be built without
1592	  support for epoll family of system calls.
1593
1594config SIGNALFD
1595	bool "Enable signalfd() system call" if EXPERT
1596	select ANON_INODES
1597	default y
1598	help
1599	  Enable the signalfd() system call that allows to receive signals
1600	  on a file descriptor.
1601
1602	  If unsure, say Y.
1603
1604config TIMERFD
1605	bool "Enable timerfd() system call" if EXPERT
1606	select ANON_INODES
1607	default y
1608	help
1609	  Enable the timerfd() system call that allows to receive timer
1610	  events on a file descriptor.
1611
1612	  If unsure, say Y.
1613
1614config EVENTFD
1615	bool "Enable eventfd() system call" if EXPERT
1616	select ANON_INODES
1617	default y
1618	help
1619	  Enable the eventfd() system call that allows to receive both
1620	  kernel notification (ie. KAIO) or userspace notifications.
1621
1622	  If unsure, say Y.
1623
1624# syscall, maps, verifier
1625config BPF_SYSCALL
1626	bool "Enable bpf() system call"
1627	select ANON_INODES
1628	select BPF
1629	default n
1630	help
1631	  Enable the bpf() system call that allows to manipulate eBPF
1632	  programs and maps via file descriptors.
1633
1634config SHMEM
1635	bool "Use full shmem filesystem" if EXPERT
1636	default y
1637	depends on MMU
1638	help
1639	  The shmem is an internal filesystem used to manage shared memory.
1640	  It is backed by swap and manages resource limits. It is also exported
1641	  to userspace as tmpfs if TMPFS is enabled. Disabling this
1642	  option replaces shmem and tmpfs with the much simpler ramfs code,
1643	  which may be appropriate on small systems without swap.
1644
1645config AIO
1646	bool "Enable AIO support" if EXPERT
1647	default y
1648	help
1649	  This option enables POSIX asynchronous I/O which may by used
1650	  by some high performance threaded applications. Disabling
1651	  this option saves about 7k.
1652
1653config ADVISE_SYSCALLS
1654	bool "Enable madvise/fadvise syscalls" if EXPERT
1655	default y
1656	help
1657	  This option enables the madvise and fadvise syscalls, used by
1658	  applications to advise the kernel about their future memory or file
1659	  usage, improving performance. If building an embedded system where no
1660	  applications use these syscalls, you can disable this option to save
1661	  space.
1662
1663config USERFAULTFD
1664	bool "Enable userfaultfd() system call"
1665	select ANON_INODES
1666	depends on MMU
1667	help
1668	  Enable the userfaultfd() system call that allows to intercept and
1669	  handle page faults in userland.
1670
1671config PCI_QUIRKS
1672	default y
1673	bool "Enable PCI quirk workarounds" if EXPERT
1674	depends on PCI
1675	help
1676	  This enables workarounds for various PCI chipset
1677	  bugs/quirks. Disable this only if your target machine is
1678	  unaffected by PCI quirks.
1679
1680config MEMBARRIER
1681	bool "Enable membarrier() system call" if EXPERT
1682	default y
1683	help
1684	  Enable the membarrier() system call that allows issuing memory
1685	  barriers across all running threads, which can be used to distribute
1686	  the cost of user-space memory barriers asymmetrically by transforming
1687	  pairs of memory barriers into pairs consisting of membarrier() and a
1688	  compiler barrier.
1689
1690	  If unsure, say Y.
1691
1692config EMBEDDED
1693	bool "Embedded system"
1694	option allnoconfig_y
1695	select EXPERT
1696	help
1697	  This option should be enabled if compiling the kernel for
1698	  an embedded system so certain expert options are available
1699	  for configuration.
1700
1701config HAVE_PERF_EVENTS
1702	bool
1703	help
1704	  See tools/perf/design.txt for details.
1705
1706config PERF_USE_VMALLOC
1707	bool
1708	help
1709	  See tools/perf/design.txt for details
1710
1711config PC104
1712	bool "PC/104 support"
1713	help
1714	  Expose PC/104 form factor device drivers and options available for
1715	  selection and configuration. Enable this option if your target
1716	  machine has a PC/104 bus.
1717
1718menu "Kernel Performance Events And Counters"
1719
1720config PERF_EVENTS
1721	bool "Kernel performance events and counters"
1722	default y if PROFILING
1723	depends on HAVE_PERF_EVENTS
1724	select ANON_INODES
1725	select IRQ_WORK
1726	select SRCU
1727	help
1728	  Enable kernel support for various performance events provided
1729	  by software and hardware.
1730
1731	  Software events are supported either built-in or via the
1732	  use of generic tracepoints.
1733
1734	  Most modern CPUs support performance events via performance
1735	  counter registers. These registers count the number of certain
1736	  types of hw events: such as instructions executed, cachemisses
1737	  suffered, or branches mis-predicted - without slowing down the
1738	  kernel or applications. These registers can also trigger interrupts
1739	  when a threshold number of events have passed - and can thus be
1740	  used to profile the code that runs on that CPU.
1741
1742	  The Linux Performance Event subsystem provides an abstraction of
1743	  these software and hardware event capabilities, available via a
1744	  system call and used by the "perf" utility in tools/perf/. It
1745	  provides per task and per CPU counters, and it provides event
1746	  capabilities on top of those.
1747
1748	  Say Y if unsure.
1749
1750config DEBUG_PERF_USE_VMALLOC
1751	default n
1752	bool "Debug: use vmalloc to back perf mmap() buffers"
1753	depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1754	select PERF_USE_VMALLOC
1755	help
1756	 Use vmalloc memory to back perf mmap() buffers.
1757
1758	 Mostly useful for debugging the vmalloc code on platforms
1759	 that don't require it.
1760
1761	 Say N if unsure.
1762
1763endmenu
1764
1765config VM_EVENT_COUNTERS
1766	default y
1767	bool "Enable VM event counters for /proc/vmstat" if EXPERT
1768	help
1769	  VM event counters are needed for event counts to be shown.
1770	  This option allows the disabling of the VM event counters
1771	  on EXPERT systems.  /proc/vmstat will only show page counts
1772	  if VM event counters are disabled.
1773
1774config SLUB_DEBUG
1775	default y
1776	bool "Enable SLUB debugging support" if EXPERT
1777	depends on SLUB && SYSFS
1778	help
1779	  SLUB has extensive debug support features. Disabling these can
1780	  result in significant savings in code size. This also disables
1781	  SLUB sysfs support. /sys/slab will not exist and there will be
1782	  no support for cache validation etc.
1783
1784config SLUB_MEMCG_SYSFS_ON
1785	default n
1786	bool "Enable memcg SLUB sysfs support by default" if EXPERT
1787	depends on SLUB && SYSFS && MEMCG
1788	help
1789	  SLUB creates a directory under /sys/kernel/slab for each
1790	  allocation cache to host info and debug files. If memory
1791	  cgroup is enabled, each cache can have per memory cgroup
1792	  caches. SLUB can create the same sysfs directories for these
1793	  caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1794	  to a very high number of debug files being created. This is
1795	  controlled by slub_memcg_sysfs boot parameter and this
1796	  config option determines the parameter's default value.
1797
1798config COMPAT_BRK
1799	bool "Disable heap randomization"
1800	default y
1801	help
1802	  Randomizing heap placement makes heap exploits harder, but it
1803	  also breaks ancient binaries (including anything libc5 based).
1804	  This option changes the bootup default to heap randomization
1805	  disabled, and can be overridden at runtime by setting
1806	  /proc/sys/kernel/randomize_va_space to 2.
1807
1808	  On non-ancient distros (post-2000 ones) N is usually a safe choice.
1809
1810choice
1811	prompt "Choose SLAB allocator"
1812	default SLUB
1813	help
1814	   This option allows to select a slab allocator.
1815
1816config SLAB
1817	bool "SLAB"
1818	select HAVE_HARDENED_USERCOPY_ALLOCATOR
1819	help
1820	  The regular slab allocator that is established and known to work
1821	  well in all environments. It organizes cache hot objects in
1822	  per cpu and per node queues.
1823
1824config SLUB
1825	bool "SLUB (Unqueued Allocator)"
1826	select HAVE_HARDENED_USERCOPY_ALLOCATOR
1827	help
1828	   SLUB is a slab allocator that minimizes cache line usage
1829	   instead of managing queues of cached objects (SLAB approach).
1830	   Per cpu caching is realized using slabs of objects instead
1831	   of queues of objects. SLUB can use memory efficiently
1832	   and has enhanced diagnostics. SLUB is the default choice for
1833	   a slab allocator.
1834
1835config SLOB
1836	depends on EXPERT
1837	bool "SLOB (Simple Allocator)"
1838	help
1839	   SLOB replaces the stock allocator with a drastically simpler
1840	   allocator. SLOB is generally more space efficient but
1841	   does not perform as well on large systems.
1842
1843endchoice
1844
1845config SLAB_FREELIST_RANDOM
1846	default n
1847	depends on SLAB || SLUB
1848	bool "SLAB freelist randomization"
1849	help
1850	  Randomizes the freelist order used on creating new pages. This
1851	  security feature reduces the predictability of the kernel slab
1852	  allocator against heap overflows.
1853
1854config SLUB_CPU_PARTIAL
1855	default y
1856	depends on SLUB && SMP
1857	bool "SLUB per cpu partial cache"
1858	help
1859	  Per cpu partial caches accellerate objects allocation and freeing
1860	  that is local to a processor at the price of more indeterminism
1861	  in the latency of the free. On overflow these caches will be cleared
1862	  which requires the taking of locks that may cause latency spikes.
1863	  Typically one would choose no for a realtime system.
1864
1865config MMAP_ALLOW_UNINITIALIZED
1866	bool "Allow mmapped anonymous memory to be uninitialized"
1867	depends on EXPERT && !MMU
1868	default n
1869	help
1870	  Normally, and according to the Linux spec, anonymous memory obtained
1871	  from mmap() has it's contents cleared before it is passed to
1872	  userspace.  Enabling this config option allows you to request that
1873	  mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1874	  providing a huge performance boost.  If this option is not enabled,
1875	  then the flag will be ignored.
1876
1877	  This is taken advantage of by uClibc's malloc(), and also by
1878	  ELF-FDPIC binfmt's brk and stack allocator.
1879
1880	  Because of the obvious security issues, this option should only be
1881	  enabled on embedded devices where you control what is run in
1882	  userspace.  Since that isn't generally a problem on no-MMU systems,
1883	  it is normally safe to say Y here.
1884
1885	  See Documentation/nommu-mmap.txt for more information.
1886
1887config SYSTEM_DATA_VERIFICATION
1888	def_bool n
1889	select SYSTEM_TRUSTED_KEYRING
1890	select KEYS
1891	select CRYPTO
1892	select CRYPTO_RSA
1893	select ASYMMETRIC_KEY_TYPE
1894	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1895	select ASN1
1896	select OID_REGISTRY
1897	select X509_CERTIFICATE_PARSER
1898	select PKCS7_MESSAGE_PARSER
1899	help
1900	  Provide PKCS#7 message verification using the contents of the system
1901	  trusted keyring to provide public keys.  This then can be used for
1902	  module verification, kexec image verification and firmware blob
1903	  verification.
1904
1905config PROFILING
1906	bool "Profiling support"
1907	help
1908	  Say Y here to enable the extended profiling support mechanisms used
1909	  by profilers such as OProfile.
1910
1911#
1912# Place an empty function call at each tracepoint site. Can be
1913# dynamically changed for a probe function.
1914#
1915config TRACEPOINTS
1916	bool
1917
1918source "arch/Kconfig"
1919
1920endmenu		# General setup
1921
1922config HAVE_GENERIC_DMA_COHERENT
1923	bool
1924	default n
1925
1926config SLABINFO
1927	bool
1928	depends on PROC_FS
1929	depends on SLAB || SLUB_DEBUG
1930	default y
1931
1932config RT_MUTEXES
1933	bool
1934
1935config BASE_SMALL
1936	int
1937	default 0 if BASE_FULL
1938	default 1 if !BASE_FULL
1939
1940menuconfig MODULES
1941	bool "Enable loadable module support"
1942	option modules
1943	help
1944	  Kernel modules are small pieces of compiled code which can
1945	  be inserted in the running kernel, rather than being
1946	  permanently built into the kernel.  You use the "modprobe"
1947	  tool to add (and sometimes remove) them.  If you say Y here,
1948	  many parts of the kernel can be built as modules (by
1949	  answering M instead of Y where indicated): this is most
1950	  useful for infrequently used options which are not required
1951	  for booting.  For more information, see the man pages for
1952	  modprobe, lsmod, modinfo, insmod and rmmod.
1953
1954	  If you say Y here, you will need to run "make
1955	  modules_install" to put the modules under /lib/modules/
1956	  where modprobe can find them (you may need to be root to do
1957	  this).
1958
1959	  If unsure, say Y.
1960
1961if MODULES
1962
1963config MODULE_FORCE_LOAD
1964	bool "Forced module loading"
1965	default n
1966	help
1967	  Allow loading of modules without version information (ie. modprobe
1968	  --force).  Forced module loading sets the 'F' (forced) taint flag and
1969	  is usually a really bad idea.
1970
1971config MODULE_UNLOAD
1972	bool "Module unloading"
1973	help
1974	  Without this option you will not be able to unload any
1975	  modules (note that some modules may not be unloadable
1976	  anyway), which makes your kernel smaller, faster
1977	  and simpler.  If unsure, say Y.
1978
1979config MODULE_FORCE_UNLOAD
1980	bool "Forced module unloading"
1981	depends on MODULE_UNLOAD
1982	help
1983	  This option allows you to force a module to unload, even if the
1984	  kernel believes it is unsafe: the kernel will remove the module
1985	  without waiting for anyone to stop using it (using the -f option to
1986	  rmmod).  This is mainly for kernel developers and desperate users.
1987	  If unsure, say N.
1988
1989config MODVERSIONS
1990	bool "Module versioning support"
1991	help
1992	  Usually, you have to use modules compiled with your kernel.
1993	  Saying Y here makes it sometimes possible to use modules
1994	  compiled for different kernels, by adding enough information
1995	  to the modules to (hopefully) spot any changes which would
1996	  make them incompatible with the kernel you are running.  If
1997	  unsure, say N.
1998
1999config MODULE_REL_CRCS
2000	bool
2001	depends on MODVERSIONS
2002
2003config MODULE_SRCVERSION_ALL
2004	bool "Source checksum for all modules"
2005	help
2006	  Modules which contain a MODULE_VERSION get an extra "srcversion"
2007	  field inserted into their modinfo section, which contains a
2008    	  sum of the source files which made it.  This helps maintainers
2009	  see exactly which source was used to build a module (since
2010	  others sometimes change the module source without updating
2011	  the version).  With this option, such a "srcversion" field
2012	  will be created for all modules.  If unsure, say N.
2013
2014config MODULE_SIG
2015	bool "Module signature verification"
2016	depends on MODULES
2017	select SYSTEM_DATA_VERIFICATION
2018	help
2019	  Check modules for valid signatures upon load: the signature
2020	  is simply appended to the module. For more information see
2021	  Documentation/module-signing.txt.
2022
2023	  Note that this option adds the OpenSSL development packages as a
2024	  kernel build dependency so that the signing tool can use its crypto
2025	  library.
2026
2027	  !!!WARNING!!!  If you enable this option, you MUST make sure that the
2028	  module DOES NOT get stripped after being signed.  This includes the
2029	  debuginfo strip done by some packagers (such as rpmbuild) and
2030	  inclusion into an initramfs that wants the module size reduced.
2031
2032config MODULE_SIG_FORCE
2033	bool "Require modules to be validly signed"
2034	depends on MODULE_SIG
2035	help
2036	  Reject unsigned modules or signed modules for which we don't have a
2037	  key.  Without this, such modules will simply taint the kernel.
2038
2039config MODULE_SIG_ALL
2040	bool "Automatically sign all modules"
2041	default y
2042	depends on MODULE_SIG
2043	help
2044	  Sign all modules during make modules_install. Without this option,
2045	  modules must be signed manually, using the scripts/sign-file tool.
2046
2047comment "Do not forget to sign required modules with scripts/sign-file"
2048	depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2049
2050choice
2051	prompt "Which hash algorithm should modules be signed with?"
2052	depends on MODULE_SIG
2053	help
2054	  This determines which sort of hashing algorithm will be used during
2055	  signature generation.  This algorithm _must_ be built into the kernel
2056	  directly so that signature verification can take place.  It is not
2057	  possible to load a signed module containing the algorithm to check
2058	  the signature on that module.
2059
2060config MODULE_SIG_SHA1
2061	bool "Sign modules with SHA-1"
2062	select CRYPTO_SHA1
2063
2064config MODULE_SIG_SHA224
2065	bool "Sign modules with SHA-224"
2066	select CRYPTO_SHA256
2067
2068config MODULE_SIG_SHA256
2069	bool "Sign modules with SHA-256"
2070	select CRYPTO_SHA256
2071
2072config MODULE_SIG_SHA384
2073	bool "Sign modules with SHA-384"
2074	select CRYPTO_SHA512
2075
2076config MODULE_SIG_SHA512
2077	bool "Sign modules with SHA-512"
2078	select CRYPTO_SHA512
2079
2080endchoice
2081
2082config MODULE_SIG_HASH
2083	string
2084	depends on MODULE_SIG
2085	default "sha1" if MODULE_SIG_SHA1
2086	default "sha224" if MODULE_SIG_SHA224
2087	default "sha256" if MODULE_SIG_SHA256
2088	default "sha384" if MODULE_SIG_SHA384
2089	default "sha512" if MODULE_SIG_SHA512
2090
2091config MODULE_COMPRESS
2092	bool "Compress modules on installation"
2093	depends on MODULES
2094	help
2095
2096	  Compresses kernel modules when 'make modules_install' is run; gzip or
2097	  xz depending on "Compression algorithm" below.
2098
2099	  module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2100
2101	  Out-of-tree kernel modules installed using Kbuild will also be
2102	  compressed upon installation.
2103
2104	  Note: for modules inside an initrd or initramfs, it's more efficient
2105	  to compress the whole initrd or initramfs instead.
2106
2107	  Note: This is fully compatible with signed modules.
2108
2109	  If in doubt, say N.
2110
2111choice
2112	prompt "Compression algorithm"
2113	depends on MODULE_COMPRESS
2114	default MODULE_COMPRESS_GZIP
2115	help
2116	  This determines which sort of compression will be used during
2117	  'make modules_install'.
2118
2119	  GZIP (default) and XZ are supported.
2120
2121config MODULE_COMPRESS_GZIP
2122	bool "GZIP"
2123
2124config MODULE_COMPRESS_XZ
2125	bool "XZ"
2126
2127endchoice
2128
2129config TRIM_UNUSED_KSYMS
2130	bool "Trim unused exported kernel symbols"
2131	depends on MODULES && !UNUSED_SYMBOLS
2132	help
2133	  The kernel and some modules make many symbols available for
2134	  other modules to use via EXPORT_SYMBOL() and variants. Depending
2135	  on the set of modules being selected in your kernel configuration,
2136	  many of those exported symbols might never be used.
2137
2138	  This option allows for unused exported symbols to be dropped from
2139	  the build. In turn, this provides the compiler more opportunities
2140	  (especially when using LTO) for optimizing the code and reducing
2141	  binary size.  This might have some security advantages as well.
2142
2143	  If unsure, or if you need to build out-of-tree modules, say N.
2144
2145endif # MODULES
2146
2147config MODULES_TREE_LOOKUP
2148	def_bool y
2149	depends on PERF_EVENTS || TRACING
2150
2151config INIT_ALL_POSSIBLE
2152	bool
2153	help
2154	  Back when each arch used to define their own cpu_online_mask and
2155	  cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2156	  with all 1s, and others with all 0s.  When they were centralised,
2157	  it was better to provide this option than to break all the archs
2158	  and have several arch maintainers pursuing me down dark alleys.
2159
2160source "block/Kconfig"
2161
2162config PREEMPT_NOTIFIERS
2163	bool
2164
2165config PADATA
2166	depends on SMP
2167	bool
2168
2169config ASN1
2170	tristate
2171	help
2172	  Build a simple ASN.1 grammar compiler that produces a bytecode output
2173	  that can be interpreted by the ASN.1 stream decoder and used to
2174	  inform it as to what tags are to be expected in a stream and what
2175	  functions to call on what tags.
2176
2177source "kernel/Kconfig.locks"
2178