xref: /openbmc/linux/init/Kconfig (revision c21b37f6)
1config DEFCONFIG_LIST
2	string
3	depends on !UML
4	option defconfig_list
5	default "/lib/modules/$UNAME_RELEASE/.config"
6	default "/etc/kernel-config"
7	default "/boot/config-$UNAME_RELEASE"
8	default "arch/$ARCH/defconfig"
9
10menu "Code maturity level options"
11
12config EXPERIMENTAL
13	bool "Prompt for development and/or incomplete code/drivers"
14	---help---
15	  Some of the various things that Linux supports (such as network
16	  drivers, file systems, network protocols, etc.) can be in a state
17	  of development where the functionality, stability, or the level of
18	  testing is not yet high enough for general use. This is usually
19	  known as the "alpha-test" phase among developers. If a feature is
20	  currently in alpha-test, then the developers usually discourage
21	  uninformed widespread use of this feature by the general public to
22	  avoid "Why doesn't this work?" type mail messages. However, active
23	  testing and use of these systems is welcomed. Just be aware that it
24	  may not meet the normal level of reliability or it may fail to work
25	  in some special cases. Detailed bug reports from people familiar
26	  with the kernel internals are usually welcomed by the developers
27	  (before submitting bug reports, please read the documents
28	  <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
29	  <file:Documentation/BUG-HUNTING>, and
30	  <file:Documentation/oops-tracing.txt> in the kernel source).
31
32	  This option will also make obsoleted drivers available. These are
33	  drivers that have been replaced by something else, and/or are
34	  scheduled to be removed in a future kernel release.
35
36	  Unless you intend to help test and develop a feature or driver that
37	  falls into this category, or you have a situation that requires
38	  using these features, you should probably say N here, which will
39	  cause the configurator to present you with fewer choices. If
40	  you say Y here, you will be offered the choice of using features or
41	  drivers that are currently considered to be in the alpha-test phase.
42
43config BROKEN
44	bool
45
46config BROKEN_ON_SMP
47	bool
48	depends on BROKEN || !SMP
49	default y
50
51config LOCK_KERNEL
52	bool
53	depends on SMP || PREEMPT
54	default y
55
56config INIT_ENV_ARG_LIMIT
57	int
58	default 32 if !UML
59	default 128 if UML
60	help
61	  Maximum of each of the number of arguments and environment
62	  variables passed to init from the kernel command line.
63
64endmenu
65
66menu "General setup"
67
68config LOCALVERSION
69	string "Local version - append to kernel release"
70	help
71	  Append an extra string to the end of your kernel version.
72	  This will show up when you type uname, for example.
73	  The string you set here will be appended after the contents of
74	  any files with a filename matching localversion* in your
75	  object and source tree, in that order.  Your total string can
76	  be a maximum of 64 characters.
77
78config LOCALVERSION_AUTO
79	bool "Automatically append version information to the version string"
80	default y
81	help
82	  This will try to automatically determine if the current tree is a
83	  release tree by looking for git tags that belong to the current
84	  top of tree revision.
85
86	  A string of the format -gxxxxxxxx will be added to the localversion
87	  if a git-based tree is found.  The string generated by this will be
88	  appended after any matching localversion* files, and after the value
89	  set in CONFIG_LOCALVERSION.
90
91	  (The actual string used here is the first eight characters produced
92	  by running the command:
93
94	    $ git rev-parse --verify HEAD
95
96	  which is done within the script "scripts/setlocalversion".)
97
98config SWAP
99	bool "Support for paging of anonymous memory (swap)"
100	depends on MMU && BLOCK
101	default y
102	help
103	  This option allows you to choose whether you want to have support
104	  for so called swap devices or swap files in your kernel that are
105	  used to provide more virtual memory than the actual RAM present
106	  in your computer.  If unsure say Y.
107
108config SYSVIPC
109	bool "System V IPC"
110	---help---
111	  Inter Process Communication is a suite of library functions and
112	  system calls which let processes (running programs) synchronize and
113	  exchange information. It is generally considered to be a good thing,
114	  and some programs won't run unless you say Y here. In particular, if
115	  you want to run the DOS emulator dosemu under Linux (read the
116	  DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
117	  you'll need to say Y here.
118
119	  You can find documentation about IPC with "info ipc" and also in
120	  section 6.4 of the Linux Programmer's Guide, available from
121	  <http://www.tldp.org/guides.html>.
122
123config SYSVIPC_SYSCTL
124	bool
125	depends on SYSVIPC
126	depends on SYSCTL
127	default y
128
129config POSIX_MQUEUE
130	bool "POSIX Message Queues"
131	depends on NET && EXPERIMENTAL
132	---help---
133	  POSIX variant of message queues is a part of IPC. In POSIX message
134	  queues every message has a priority which decides about succession
135	  of receiving it by a process. If you want to compile and run
136	  programs written e.g. for Solaris with use of its POSIX message
137	  queues (functions mq_*) say Y here.
138
139	  POSIX message queues are visible as a filesystem called 'mqueue'
140	  and can be mounted somewhere if you want to do filesystem
141	  operations on message queues.
142
143	  If unsure, say Y.
144
145config BSD_PROCESS_ACCT
146	bool "BSD Process Accounting"
147	help
148	  If you say Y here, a user level program will be able to instruct the
149	  kernel (via a special system call) to write process accounting
150	  information to a file: whenever a process exits, information about
151	  that process will be appended to the file by the kernel.  The
152	  information includes things such as creation time, owning user,
153	  command name, memory usage, controlling terminal etc. (the complete
154	  list is in the struct acct in <file:include/linux/acct.h>).  It is
155	  up to the user level program to do useful things with this
156	  information.  This is generally a good idea, so say Y.
157
158config BSD_PROCESS_ACCT_V3
159	bool "BSD Process Accounting version 3 file format"
160	depends on BSD_PROCESS_ACCT
161	default n
162	help
163	  If you say Y here, the process accounting information is written
164	  in a new file format that also logs the process IDs of each
165	  process and it's parent. Note that this file format is incompatible
166	  with previous v0/v1/v2 file formats, so you will need updated tools
167	  for processing it. A preliminary version of these tools is available
168	  at <http://www.physik3.uni-rostock.de/tim/kernel/utils/acct/>.
169
170config TASKSTATS
171	bool "Export task/process statistics through netlink (EXPERIMENTAL)"
172	depends on NET
173	default n
174	help
175	  Export selected statistics for tasks/processes through the
176	  generic netlink interface. Unlike BSD process accounting, the
177	  statistics are available during the lifetime of tasks/processes as
178	  responses to commands. Like BSD accounting, they are sent to user
179	  space on task exit.
180
181	  Say N if unsure.
182
183config TASK_DELAY_ACCT
184	bool "Enable per-task delay accounting (EXPERIMENTAL)"
185	depends on TASKSTATS
186	help
187	  Collect information on time spent by a task waiting for system
188	  resources like cpu, synchronous block I/O completion and swapping
189	  in pages. Such statistics can help in setting a task's priorities
190	  relative to other tasks for cpu, io, rss limits etc.
191
192	  Say N if unsure.
193
194config TASK_XACCT
195	bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
196	depends on TASKSTATS
197	help
198	  Collect extended task accounting data and send the data
199	  to userland for processing over the taskstats interface.
200
201	  Say N if unsure.
202
203config TASK_IO_ACCOUNTING
204	bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
205	depends on TASK_XACCT
206	help
207	  Collect information on the number of bytes of storage I/O which this
208	  task has caused.
209
210	  Say N if unsure.
211
212config USER_NS
213	bool "User Namespaces (EXPERIMENTAL)"
214	default n
215	depends on EXPERIMENTAL
216	help
217	  Support user namespaces.  This allows containers, i.e.
218	  vservers, to use user namespaces to provide different
219	  user info for different servers.  If unsure, say N.
220
221config AUDIT
222	bool "Auditing support"
223	depends on NET
224	help
225	  Enable auditing infrastructure that can be used with another
226	  kernel subsystem, such as SELinux (which requires this for
227	  logging of avc messages output).  Does not do system-call
228	  auditing without CONFIG_AUDITSYSCALL.
229
230config AUDITSYSCALL
231	bool "Enable system-call auditing support"
232	depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64)
233	default y if SECURITY_SELINUX
234	help
235	  Enable low-overhead system-call auditing infrastructure that
236	  can be used independently or with another kernel subsystem,
237	  such as SELinux.  To use audit's filesystem watch feature, please
238	  ensure that INOTIFY is configured.
239
240config IKCONFIG
241	tristate "Kernel .config support"
242	---help---
243	  This option enables the complete Linux kernel ".config" file
244	  contents to be saved in the kernel. It provides documentation
245	  of which kernel options are used in a running kernel or in an
246	  on-disk kernel.  This information can be extracted from the kernel
247	  image file with the script scripts/extract-ikconfig and used as
248	  input to rebuild the current kernel or to build another kernel.
249	  It can also be extracted from a running kernel by reading
250	  /proc/config.gz if enabled (below).
251
252config IKCONFIG_PROC
253	bool "Enable access to .config through /proc/config.gz"
254	depends on IKCONFIG && PROC_FS
255	---help---
256	  This option enables access to the kernel configuration file
257	  through /proc/config.gz.
258
259config LOG_BUF_SHIFT
260	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
261	range 12 21
262	default 17 if S390 || LOCKDEP
263	default 16 if X86_NUMAQ || IA64
264	default 15 if SMP
265	default 14
266	help
267	  Select kernel log buffer size as a power of 2.
268	  Defaults and Examples:
269	  	     17 => 128 KB for S/390
270		     16 => 64 KB for x86 NUMAQ or IA-64
271	             15 => 32 KB for SMP
272	             14 => 16 KB for uniprocessor
273		     13 =>  8 KB
274		     12 =>  4 KB
275
276config CPUSETS
277	bool "Cpuset support"
278	depends on SMP
279	help
280	  This option will let you create and manage CPUSETs which
281	  allow dynamically partitioning a system into sets of CPUs and
282	  Memory Nodes and assigning tasks to run only within those sets.
283	  This is primarily useful on large SMP or NUMA systems.
284
285	  Say N if unsure.
286
287config SYSFS_DEPRECATED
288	bool "Create deprecated sysfs files"
289	default y
290	help
291	  This option creates deprecated symlinks such as the
292	  "device"-link, the <subsystem>:<name>-link, and the
293	  "bus"-link. It may also add deprecated key in the
294	  uevent environment.
295	  None of these features or values should be used today, as
296	  they export driver core implementation details to userspace
297	  or export properties which can't be kept stable across kernel
298	  releases.
299
300	  If enabled, this option will also move any device structures
301	  that belong to a class, back into the /sys/class hierarchy, in
302	  order to support older versions of udev.
303
304	  If you are using a distro that was released in 2006 or later,
305	  it should be safe to say N here.
306
307config RELAY
308	bool "Kernel->user space relay support (formerly relayfs)"
309	help
310	  This option enables support for relay interface support in
311	  certain file systems (such as debugfs).
312	  It is designed to provide an efficient mechanism for tools and
313	  facilities to relay large amounts of data from kernel space to
314	  user space.
315
316	  If unsure, say N.
317
318config BLK_DEV_INITRD
319	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
320	depends on BROKEN || !FRV
321	help
322	  The initial RAM filesystem is a ramfs which is loaded by the
323	  boot loader (loadlin or lilo) and that is mounted as root
324	  before the normal boot procedure. It is typically used to
325	  load modules needed to mount the "real" root file system,
326	  etc. See <file:Documentation/initrd.txt> for details.
327
328	  If RAM disk support (BLK_DEV_RAM) is also included, this
329	  also enables initial RAM disk (initrd) support and adds
330	  15 Kbytes (more on some other architectures) to the kernel size.
331
332	  If unsure say Y.
333
334if BLK_DEV_INITRD
335
336source "usr/Kconfig"
337
338endif
339
340config CC_OPTIMIZE_FOR_SIZE
341	bool "Optimize for size (Look out for broken compilers!)"
342	default y
343	depends on ARM || H8300 || SUPERH || EXPERIMENTAL
344	help
345	  Enabling this option will pass "-Os" instead of "-O2" to gcc
346	  resulting in a smaller kernel.
347
348	  WARNING: some versions of gcc may generate incorrect code with this
349	  option.  If problems are observed, a gcc upgrade may be needed.
350
351	  If unsure, say N.
352
353config SYSCTL
354	bool
355
356menuconfig EMBEDDED
357	bool "Configure standard kernel features (for small systems)"
358	help
359	  This option allows certain base kernel options and settings
360          to be disabled or tweaked. This is for specialized
361          environments which can tolerate a "non-standard" kernel.
362          Only use this if you really know what you are doing.
363
364config UID16
365	bool "Enable 16-bit UID system calls" if EMBEDDED
366	depends on ARM || BFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && SPARC32_COMPAT) || UML || (X86_64 && IA32_EMULATION)
367	default y
368	help
369	  This enables the legacy 16-bit UID syscall wrappers.
370
371config SYSCTL_SYSCALL
372	bool "Sysctl syscall support" if EMBEDDED
373	default y
374	select SYSCTL
375	---help---
376	  sys_sysctl uses binary paths that have been found challenging
377	  to properly maintain and use.  The interface in /proc/sys
378	  using paths with ascii names is now the primary path to this
379	  information.
380
381	  Almost nothing using the binary sysctl interface so if you are
382	  trying to save some space it is probably safe to disable this,
383	  making your kernel marginally smaller.
384
385	  If unsure say Y here.
386
387config KALLSYMS
388	 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
389	 default y
390	 help
391	   Say Y here to let the kernel print out symbolic crash information and
392	   symbolic stack backtraces. This increases the size of the kernel
393	   somewhat, as all symbols have to be loaded into the kernel image.
394
395config KALLSYMS_ALL
396	bool "Include all symbols in kallsyms"
397	depends on DEBUG_KERNEL && KALLSYMS
398	help
399	   Normally kallsyms only contains the symbols of functions, for nicer
400	   OOPS messages.  Some debuggers can use kallsyms for other
401	   symbols too: say Y here to include all symbols, if you need them
402	   and you don't care about adding 300k to the size of your kernel.
403
404	   Say N.
405
406config KALLSYMS_EXTRA_PASS
407	bool "Do an extra kallsyms pass"
408	depends on KALLSYMS
409	help
410	   If kallsyms is not working correctly, the build will fail with
411	   inconsistent kallsyms data.  If that occurs, log a bug report and
412	   turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
413	   Always say N here unless you find a bug in kallsyms, which must be
414	   reported.  KALLSYMS_EXTRA_PASS is only a temporary workaround while
415	   you wait for kallsyms to be fixed.
416
417
418config HOTPLUG
419	bool "Support for hot-pluggable devices" if EMBEDDED
420	default y
421	help
422	  This option is provided for the case where no hotplug or uevent
423	  capabilities is wanted by the kernel.  You should only consider
424	  disabling this option for embedded systems that do not use modules, a
425	  dynamic /dev tree, or dynamic device discovery.  Just say Y.
426
427config PRINTK
428	default y
429	bool "Enable support for printk" if EMBEDDED
430	help
431	  This option enables normal printk support. Removing it
432	  eliminates most of the message strings from the kernel image
433	  and makes the kernel more or less silent. As this makes it
434	  very difficult to diagnose system problems, saying N here is
435	  strongly discouraged.
436
437config BUG
438	bool "BUG() support" if EMBEDDED
439	default y
440	help
441          Disabling this option eliminates support for BUG and WARN, reducing
442          the size of your kernel image and potentially quietly ignoring
443          numerous fatal conditions. You should only consider disabling this
444          option for embedded systems with no facilities for reporting errors.
445          Just say Y.
446
447config ELF_CORE
448	default y
449	bool "Enable ELF core dumps" if EMBEDDED
450	help
451	  Enable support for generating core dumps. Disabling saves about 4k.
452
453config BASE_FULL
454	default y
455	bool "Enable full-sized data structures for core" if EMBEDDED
456	help
457	  Disabling this option reduces the size of miscellaneous core
458	  kernel data structures. This saves memory on small machines,
459	  but may reduce performance.
460
461config FUTEX
462	bool "Enable futex support" if EMBEDDED
463	default y
464	select RT_MUTEXES
465	help
466	  Disabling this option will cause the kernel to be built without
467	  support for "fast userspace mutexes".  The resulting kernel may not
468	  run glibc-based applications correctly.
469
470config ANON_INODES
471	bool "Enable anonymous inode source" if EMBEDDED
472	default y
473	help
474	  Anonymous inode source for pseudo-files like epoll, signalfd,
475	  timerfd and eventfd.
476
477	  If unsure, say Y.
478
479config EPOLL
480	bool "Enable eventpoll support" if EMBEDDED
481	default y
482	depends on ANON_INODES
483	help
484	  Disabling this option will cause the kernel to be built without
485	  support for epoll family of system calls.
486
487config SIGNALFD
488	bool "Enable signalfd() system call" if EMBEDDED
489	depends on ANON_INODES
490	default y
491	help
492	  Enable the signalfd() system call that allows to receive signals
493	  on a file descriptor.
494
495	  If unsure, say Y.
496
497config TIMERFD
498	bool "Enable timerfd() system call" if EMBEDDED
499	depends on ANON_INODES
500	default y
501	help
502	  Enable the timerfd() system call that allows to receive timer
503	  events on a file descriptor.
504
505	  If unsure, say Y.
506
507config EVENTFD
508	bool "Enable eventfd() system call" if EMBEDDED
509	depends on ANON_INODES
510	default y
511	help
512	  Enable the eventfd() system call that allows to receive both
513	  kernel notification (ie. KAIO) or userspace notifications.
514
515	  If unsure, say Y.
516
517config SHMEM
518	bool "Use full shmem filesystem" if EMBEDDED
519	default y
520	depends on MMU
521	help
522	  The shmem is an internal filesystem used to manage shared memory.
523	  It is backed by swap and manages resource limits. It is also exported
524	  to userspace as tmpfs if TMPFS is enabled. Disabling this
525	  option replaces shmem and tmpfs with the much simpler ramfs code,
526	  which may be appropriate on small systems without swap.
527
528config VM_EVENT_COUNTERS
529	default y
530	bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
531	help
532	  VM event counters are needed for event counts to be shown.
533	  This option allows the disabling of the VM event counters
534	  on EMBEDDED systems.  /proc/vmstat will only show page counts
535	  if VM event counters are disabled.
536
537config SLUB_DEBUG
538	default y
539	bool "Enable SLUB debugging support" if EMBEDDED
540	depends on SLUB
541	help
542	  SLUB has extensive debug support features. Disabling these can
543	  result in significant savings in code size. This also disables
544	  SLUB sysfs support. /sys/slab will not exist and there will be
545	  no support for cache validation etc.
546
547choice
548	prompt "Choose SLAB allocator"
549	default SLUB
550	help
551	   This option allows to select a slab allocator.
552
553config SLAB
554	bool "SLAB"
555	help
556	  The regular slab allocator that is established and known to work
557	  well in all environments. It organizes cache hot objects in
558	  per cpu and per node queues. SLAB is the default choice for
559	  a slab allocator.
560
561config SLUB
562	bool "SLUB (Unqueued Allocator)"
563	help
564	   SLUB is a slab allocator that minimizes cache line usage
565	   instead of managing queues of cached objects (SLAB approach).
566	   Per cpu caching is realized using slabs of objects instead
567	   of queues of objects. SLUB can use memory efficiently
568	   and has enhanced diagnostics.
569
570config SLOB
571	depends on EMBEDDED
572	bool "SLOB (Simple Allocator)"
573	help
574	   SLOB replaces the SLAB allocator with a drastically simpler
575	   allocator.  SLOB is more space efficient than SLAB but does not
576	   scale well (single lock for all operations) and is also highly
577	   susceptible to fragmentation. SLUB can accomplish a higher object
578	   density. It is usually better to use SLUB instead of SLOB.
579
580endchoice
581
582endmenu		# General setup
583
584config RT_MUTEXES
585	boolean
586	select PLIST
587
588config TINY_SHMEM
589	default !SHMEM
590	bool
591
592config BASE_SMALL
593	int
594	default 0 if BASE_FULL
595	default 1 if !BASE_FULL
596
597menuconfig MODULES
598	bool "Enable loadable module support"
599	help
600	  Kernel modules are small pieces of compiled code which can
601	  be inserted in the running kernel, rather than being
602	  permanently built into the kernel.  You use the "modprobe"
603	  tool to add (and sometimes remove) them.  If you say Y here,
604	  many parts of the kernel can be built as modules (by
605	  answering M instead of Y where indicated): this is most
606	  useful for infrequently used options which are not required
607	  for booting.  For more information, see the man pages for
608	  modprobe, lsmod, modinfo, insmod and rmmod.
609
610	  If you say Y here, you will need to run "make
611	  modules_install" to put the modules under /lib/modules/
612	  where modprobe can find them (you may need to be root to do
613	  this).
614
615	  If unsure, say Y.
616
617config MODULE_UNLOAD
618	bool "Module unloading"
619	depends on MODULES
620	help
621	  Without this option you will not be able to unload any
622	  modules (note that some modules may not be unloadable
623	  anyway), which makes your kernel slightly smaller and
624	  simpler.  If unsure, say Y.
625
626config MODULE_FORCE_UNLOAD
627	bool "Forced module unloading"
628	depends on MODULE_UNLOAD && EXPERIMENTAL
629	help
630	  This option allows you to force a module to unload, even if the
631	  kernel believes it is unsafe: the kernel will remove the module
632	  without waiting for anyone to stop using it (using the -f option to
633	  rmmod).  This is mainly for kernel developers and desperate users.
634	  If unsure, say N.
635
636config MODVERSIONS
637	bool "Module versioning support"
638	depends on MODULES
639	help
640	  Usually, you have to use modules compiled with your kernel.
641	  Saying Y here makes it sometimes possible to use modules
642	  compiled for different kernels, by adding enough information
643	  to the modules to (hopefully) spot any changes which would
644	  make them incompatible with the kernel you are running.  If
645	  unsure, say N.
646
647config MODULE_SRCVERSION_ALL
648	bool "Source checksum for all modules"
649	depends on MODULES
650	help
651	  Modules which contain a MODULE_VERSION get an extra "srcversion"
652	  field inserted into their modinfo section, which contains a
653    	  sum of the source files which made it.  This helps maintainers
654	  see exactly which source was used to build a module (since
655	  others sometimes change the module source without updating
656	  the version).  With this option, such a "srcversion" field
657	  will be created for all modules.  If unsure, say N.
658
659config KMOD
660	bool "Automatic kernel module loading"
661	depends on MODULES
662	help
663	  Normally when you have selected some parts of the kernel to
664	  be created as kernel modules, you must load them (using the
665	  "modprobe" command) before you can use them. If you say Y
666	  here, some parts of the kernel will be able to load modules
667	  automatically: when a part of the kernel needs a module, it
668	  runs modprobe with the appropriate arguments, thereby
669	  loading the module if it is available.  If unsure, say Y.
670
671config STOP_MACHINE
672	bool
673	default y
674	depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
675	help
676	  Need stop_machine() primitive.
677
678source "block/Kconfig"
679