xref: /openbmc/linux/init/Kconfig (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
1menu "Code maturity level options"
2
3config EXPERIMENTAL
4	bool "Prompt for development and/or incomplete code/drivers"
5	---help---
6	  Some of the various things that Linux supports (such as network
7	  drivers, file systems, network protocols, etc.) can be in a state
8	  of development where the functionality, stability, or the level of
9	  testing is not yet high enough for general use. This is usually
10	  known as the "alpha-test" phase among developers. If a feature is
11	  currently in alpha-test, then the developers usually discourage
12	  uninformed widespread use of this feature by the general public to
13	  avoid "Why doesn't this work?" type mail messages. However, active
14	  testing and use of these systems is welcomed. Just be aware that it
15	  may not meet the normal level of reliability or it may fail to work
16	  in some special cases. Detailed bug reports from people familiar
17	  with the kernel internals are usually welcomed by the developers
18	  (before submitting bug reports, please read the documents
19	  <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
20	  <file:Documentation/BUG-HUNTING>, and
21	  <file:Documentation/oops-tracing.txt> in the kernel source).
22
23	  This option will also make obsoleted drivers available. These are
24	  drivers that have been replaced by something else, and/or are
25	  scheduled to be removed in a future kernel release.
26
27	  Unless you intend to help test and develop a feature or driver that
28	  falls into this category, or you have a situation that requires
29	  using these features, you should probably say N here, which will
30	  cause the configurator to present you with fewer choices. If
31	  you say Y here, you will be offered the choice of using features or
32	  drivers that are currently considered to be in the alpha-test phase.
33
34config CLEAN_COMPILE
35	bool "Select only drivers expected to compile cleanly" if EXPERIMENTAL
36	default y
37	help
38	  Select this option if you don't even want to see the option
39	  to configure known-broken drivers.
40
41	  If unsure, say Y
42
43config BROKEN
44	bool
45	depends on !CLEAN_COMPILE
46	default y
47
48config BROKEN_ON_SMP
49	bool
50	depends on BROKEN || !SMP
51	default y
52
53config LOCK_KERNEL
54	bool
55	depends on SMP || PREEMPT
56	default y
57
58config INIT_ENV_ARG_LIMIT
59	int
60	default 32 if !USERMODE
61	default 128 if USERMODE
62	help
63	  Maximum of each of the number of arguments and environment
64	  variables passed to init from the kernel command line.
65
66endmenu
67
68menu "General setup"
69
70config LOCALVERSION
71	string "Local version - append to kernel release"
72	help
73	  Append an extra string to the end of your kernel version.
74	  This will show up when you type uname, for example.
75	  The string you set here will be appended after the contents of
76	  any files with a filename matching localversion* in your
77	  object and source tree, in that order.  Your total string can
78	  be a maximum of 64 characters.
79
80config LOCALVERSION_AUTO
81	bool "Automatically append version information to the version string"
82	default y
83	help
84	  This will try to automatically determine if the current tree is a
85	  release tree by looking for git tags that
86	  belong to the current top of tree revision.
87
88	  A string of the format -gxxxxxxxx will be added to the localversion
89	  if a git based tree is found.  The string generated by this will be
90	  appended after any matching localversion* files, and after the value
91	  set in CONFIG_LOCALVERSION
92
93	  Note: This requires Perl, and a git repository, but not necessarily
94	  the git or cogito tools to be installed.
95
96config SWAP
97	bool "Support for paging of anonymous memory (swap)"
98	depends on MMU
99	default y
100	help
101	  This option allows you to choose whether you want to have support
102	  for socalled swap devices or swap files in your kernel that are
103	  used to provide more virtual memory than the actual RAM present
104	  in your computer.  If unsure say Y.
105
106config SYSVIPC
107	bool "System V IPC"
108	depends on MMU
109	---help---
110	  Inter Process Communication is a suite of library functions and
111	  system calls which let processes (running programs) synchronize and
112	  exchange information. It is generally considered to be a good thing,
113	  and some programs won't run unless you say Y here. In particular, if
114	  you want to run the DOS emulator dosemu under Linux (read the
115	  DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
116	  you'll need to say Y here.
117
118	  You can find documentation about IPC with "info ipc" and also in
119	  section 6.4 of the Linux Programmer's Guide, available from
120	  <http://www.tldp.org/guides.html>.
121
122config POSIX_MQUEUE
123	bool "POSIX Message Queues"
124	depends on NET && EXPERIMENTAL
125	---help---
126	  POSIX variant of message queues is a part of IPC. In POSIX message
127	  queues every message has a priority which decides about succession
128	  of receiving it by a process. If you want to compile and run
129	  programs written e.g. for Solaris with use of its POSIX message
130	  queues (functions mq_*) say Y here. To use this feature you will
131	  also need mqueue library, available from
132	  <http://www.mat.uni.torun.pl/~wrona/posix_ipc/>
133
134	  POSIX message queues are visible as a filesystem called 'mqueue'
135	  and can be mounted somewhere if you want to do filesystem
136	  operations on message queues.
137
138	  If unsure, say Y.
139
140config BSD_PROCESS_ACCT
141	bool "BSD Process Accounting"
142	help
143	  If you say Y here, a user level program will be able to instruct the
144	  kernel (via a special system call) to write process accounting
145	  information to a file: whenever a process exits, information about
146	  that process will be appended to the file by the kernel.  The
147	  information includes things such as creation time, owning user,
148	  command name, memory usage, controlling terminal etc. (the complete
149	  list is in the struct acct in <file:include/linux/acct.h>).  It is
150	  up to the user level program to do useful things with this
151	  information.  This is generally a good idea, so say Y.
152
153config BSD_PROCESS_ACCT_V3
154	bool "BSD Process Accounting version 3 file format"
155	depends on BSD_PROCESS_ACCT
156	default n
157	help
158	  If you say Y here, the process accounting information is written
159	  in a new file format that also logs the process IDs of each
160	  process and it's parent. Note that this file format is incompatible
161	  with previous v0/v1/v2 file formats, so you will need updated tools
162	  for processing it. A preliminary version of these tools is available
163	  at <http://www.physik3.uni-rostock.de/tim/kernel/utils/acct/>.
164
165config SYSCTL
166	bool "Sysctl support"
167	---help---
168	  The sysctl interface provides a means of dynamically changing
169	  certain kernel parameters and variables on the fly without requiring
170	  a recompile of the kernel or reboot of the system.  The primary
171	  interface consists of a system call, but if you say Y to "/proc
172	  file system support", a tree of modifiable sysctl entries will be
173	  generated beneath the /proc/sys directory. They are explained in the
174	  files in <file:Documentation/sysctl/>.  Note that enabling this
175	  option will enlarge the kernel by at least 8 KB.
176
177	  As it is generally a good thing, you should say Y here unless
178	  building a kernel for install/rescue disks or your system is very
179	  limited in memory.
180
181config AUDIT
182	bool "Auditing support"
183	depends on NET
184	default y if SECURITY_SELINUX
185	help
186	  Enable auditing infrastructure that can be used with another
187	  kernel subsystem, such as SELinux (which requires this for
188	  logging of avc messages output).  Does not do system-call
189	  auditing without CONFIG_AUDITSYSCALL.
190
191config AUDITSYSCALL
192	bool "Enable system-call auditing support"
193	depends on AUDIT && (X86 || PPC || PPC64 || ARCH_S390 || IA64 || UML || SPARC64)
194	default y if SECURITY_SELINUX
195	help
196	  Enable low-overhead system-call auditing infrastructure that
197	  can be used independently or with another kernel subsystem,
198	  such as SELinux.
199
200config HOTPLUG
201	bool "Support for hot-pluggable devices" if !ARCH_S390
202	default ARCH_S390
203	help
204	  This option is provided for the case where no in-kernel-tree
205	  modules require HOTPLUG functionality, but a module built
206	  outside the kernel tree does. Such modules require Y here.
207
208config KOBJECT_UEVENT
209	bool "Kernel Userspace Events"
210	depends on NET
211	default y
212	help
213	  This option enables the kernel userspace event layer, which is a
214	  simple mechanism for kernel-to-user communication over a netlink
215	  socket.
216	  The goal of the kernel userspace events layer is to provide a simple
217	  and efficient events system, that notifies userspace about kobject
218	  state changes. This will enable applications to just listen for
219	  events instead of polling system devices and files.
220	  Hotplug events (kobject addition and removal) are also available on
221	  the netlink socket in addition to the execution of /sbin/hotplug if
222	  CONFIG_HOTPLUG is enabled.
223
224	  Say Y, unless you are building a system requiring minimal memory
225	  consumption.
226
227config IKCONFIG
228	bool "Kernel .config support"
229	---help---
230	  This option enables the complete Linux kernel ".config" file
231	  contents to be saved in the kernel. It provides documentation
232	  of which kernel options are used in a running kernel or in an
233	  on-disk kernel.  This information can be extracted from the kernel
234	  image file with the script scripts/extract-ikconfig and used as
235	  input to rebuild the current kernel or to build another kernel.
236	  It can also be extracted from a running kernel by reading
237	  /proc/config.gz if enabled (below).
238
239config IKCONFIG_PROC
240	bool "Enable access to .config through /proc/config.gz"
241	depends on IKCONFIG && PROC_FS
242	---help---
243	  This option enables access to the kernel configuration file
244	  through /proc/config.gz.
245
246config CPUSETS
247	bool "Cpuset support"
248	depends on SMP
249	help
250	  This option will let you create and manage CPUSETs which
251	  allow dynamically partitioning a system into sets of CPUs and
252	  Memory Nodes and assigning tasks to run only within those sets.
253	  This is primarily useful on large SMP or NUMA systems.
254
255	  Say N if unsure.
256
257source "usr/Kconfig"
258
259menuconfig EMBEDDED
260	bool "Configure standard kernel features (for small systems)"
261	help
262	  This option allows certain base kernel options and settings
263          to be disabled or tweaked. This is for specialized
264          environments which can tolerate a "non-standard" kernel.
265          Only use this if you really know what you are doing.
266
267config KALLSYMS
268	 bool "Load all symbols for debugging/kksymoops" if EMBEDDED
269	 default y
270	 help
271	   Say Y here to let the kernel print out symbolic crash information and
272	   symbolic stack backtraces. This increases the size of the kernel
273	   somewhat, as all symbols have to be loaded into the kernel image.
274
275config KALLSYMS_ALL
276	bool "Include all symbols in kallsyms"
277	depends on DEBUG_KERNEL && KALLSYMS
278	help
279	   Normally kallsyms only contains the symbols of functions, for nicer
280	   OOPS messages.  Some debuggers can use kallsyms for other
281	   symbols too: say Y here to include all symbols, if you need them
282	   and you don't care about adding 300k to the size of your kernel.
283
284	   Say N.
285
286config KALLSYMS_EXTRA_PASS
287	bool "Do an extra kallsyms pass"
288	depends on KALLSYMS
289	help
290	   If kallsyms is not working correctly, the build will fail with
291	   inconsistent kallsyms data.  If that occurs, log a bug report and
292	   turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
293	   Always say N here unless you find a bug in kallsyms, which must be
294	   reported.  KALLSYMS_EXTRA_PASS is only a temporary workaround while
295	   you wait for kallsyms to be fixed.
296
297
298config PRINTK
299	default y
300	bool "Enable support for printk" if EMBEDDED
301	help
302	  This option enables normal printk support. Removing it
303	  eliminates most of the message strings from the kernel image
304	  and makes the kernel more or less silent. As this makes it
305	  very difficult to diagnose system problems, saying N here is
306	  strongly discouraged.
307
308config BUG
309	bool "BUG() support" if EMBEDDED
310	default y
311	help
312          Disabling this option eliminates support for BUG and WARN, reducing
313          the size of your kernel image and potentially quietly ignoring
314          numerous fatal conditions. You should only consider disabling this
315          option for embedded systems with no facilities for reporting errors.
316          Just say Y.
317
318config BASE_FULL
319	default y
320	bool "Enable full-sized data structures for core" if EMBEDDED
321	help
322	  Disabling this option reduces the size of miscellaneous core
323	  kernel data structures. This saves memory on small machines,
324	  but may reduce performance.
325
326config FUTEX
327	bool "Enable futex support" if EMBEDDED
328	default y
329	help
330	  Disabling this option will cause the kernel to be built without
331	  support for "fast userspace mutexes".  The resulting kernel may not
332	  run glibc-based applications correctly.
333
334config EPOLL
335	bool "Enable eventpoll support" if EMBEDDED
336	default y
337	help
338	  Disabling this option will cause the kernel to be built without
339	  support for epoll family of system calls.
340
341config CC_OPTIMIZE_FOR_SIZE
342	bool "Optimize for size" if EMBEDDED
343	default y if ARM || H8300
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 SHMEM
354	bool "Use full shmem filesystem" if EMBEDDED
355	default y
356	depends on MMU
357	help
358	  The shmem is an internal filesystem used to manage shared memory.
359	  It is backed by swap and manages resource limits. It is also exported
360	  to userspace as tmpfs if TMPFS is enabled. Disabling this
361	  option replaces shmem and tmpfs with the much simpler ramfs code,
362	  which may be appropriate on small systems without swap.
363
364config CC_ALIGN_FUNCTIONS
365	int "Function alignment" if EMBEDDED
366	default 0
367	help
368	  Align the start of functions to the next power-of-two greater than n,
369	  skipping up to n bytes.  For instance, 32 aligns functions
370	  to the next 32-byte boundary, but 24 would align to the next
371	  32-byte boundary only if this can be done by skipping 23 bytes or less.
372	  Zero means use compiler's default.
373
374config CC_ALIGN_LABELS
375	int "Label alignment" if EMBEDDED
376	default 0
377	help
378	  Align all branch targets to a power-of-two boundary, skipping
379	  up to n bytes like ALIGN_FUNCTIONS.  This option can easily
380	  make code slower, because it must insert dummy operations for
381	  when the branch target is reached in the usual flow of the code.
382	  Zero means use compiler's default.
383
384config CC_ALIGN_LOOPS
385	int "Loop alignment" if EMBEDDED
386	default 0
387	help
388	  Align loops to a power-of-two boundary, skipping up to n bytes.
389	  Zero means use compiler's default.
390
391config CC_ALIGN_JUMPS
392	int "Jump alignment" if EMBEDDED
393	default 0
394	help
395	  Align branch targets to a power-of-two boundary, for branch
396	  targets where the targets can only be reached by jumping,
397	  skipping up to n bytes like ALIGN_FUNCTIONS.  In this case,
398	  no dummy operations need be executed.
399	  Zero means use compiler's default.
400
401endmenu		# General setup
402
403config TINY_SHMEM
404	default !SHMEM
405	bool
406
407config BASE_SMALL
408	int
409	default 0 if BASE_FULL
410	default 1 if !BASE_FULL
411
412menu "Loadable module support"
413
414config MODULES
415	bool "Enable loadable module support"
416	help
417	  Kernel modules are small pieces of compiled code which can
418	  be inserted in the running kernel, rather than being
419	  permanently built into the kernel.  You use the "modprobe"
420	  tool to add (and sometimes remove) them.  If you say Y here,
421	  many parts of the kernel can be built as modules (by
422	  answering M instead of Y where indicated): this is most
423	  useful for infrequently used options which are not required
424	  for booting.  For more information, see the man pages for
425	  modprobe, lsmod, modinfo, insmod and rmmod.
426
427	  If you say Y here, you will need to run "make
428	  modules_install" to put the modules under /lib/modules/
429	  where modprobe can find them (you may need to be root to do
430	  this).
431
432	  If unsure, say Y.
433
434config MODULE_UNLOAD
435	bool "Module unloading"
436	depends on MODULES
437	help
438	  Without this option you will not be able to unload any
439	  modules (note that some modules may not be unloadable
440	  anyway), which makes your kernel slightly smaller and
441	  simpler.  If unsure, say Y.
442
443config MODULE_FORCE_UNLOAD
444	bool "Forced module unloading"
445	depends on MODULE_UNLOAD && EXPERIMENTAL
446	help
447	  This option allows you to force a module to unload, even if the
448	  kernel believes it is unsafe: the kernel will remove the module
449	  without waiting for anyone to stop using it (using the -f option to
450	  rmmod).  This is mainly for kernel developers and desperate users.
451	  If unsure, say N.
452
453config OBSOLETE_MODPARM
454	bool
455	default y
456	depends on MODULES
457	help
458	  You need this option to use module parameters on modules which
459	  have not been converted to the new module parameter system yet.
460	  If unsure, say Y.
461
462config MODVERSIONS
463	bool "Module versioning support (EXPERIMENTAL)"
464	depends on MODULES && EXPERIMENTAL
465	help
466	  Usually, you have to use modules compiled with your kernel.
467	  Saying Y here makes it sometimes possible to use modules
468	  compiled for different kernels, by adding enough information
469	  to the modules to (hopefully) spot any changes which would
470	  make them incompatible with the kernel you are running.  If
471	  unsure, say N.
472
473config MODULE_SRCVERSION_ALL
474	bool "Source checksum for all modules"
475	depends on MODULES
476	help
477	  Modules which contain a MODULE_VERSION get an extra "srcversion"
478	  field inserted into their modinfo section, which contains a
479    	  sum of the source files which made it.  This helps maintainers
480	  see exactly which source was used to build a module (since
481	  others sometimes change the module source without updating
482	  the version).  With this option, such a "srcversion" field
483	  will be created for all modules.  If unsure, say N.
484
485config KMOD
486	bool "Automatic kernel module loading"
487	depends on MODULES
488	help
489	  Normally when you have selected some parts of the kernel to
490	  be created as kernel modules, you must load them (using the
491	  "modprobe" command) before you can use them. If you say Y
492	  here, some parts of the kernel will be able to load modules
493	  automatically: when a part of the kernel needs a module, it
494	  runs modprobe with the appropriate arguments, thereby
495	  loading the module if it is available.  If unsure, say Y.
496
497config STOP_MACHINE
498	bool
499	default y
500	depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
501	help
502	  Need stop_machine() primitive.
503endmenu
504