Root/init/Kconfig

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    default y
23
24menu "General setup"
25
26config EXPERIMENTAL
27    bool "Prompt for development and/or incomplete code/drivers"
28    ---help---
29      Some of the various things that Linux supports (such as network
30      drivers, file systems, network protocols, etc.) can be in a state
31      of development where the functionality, stability, or the level of
32      testing is not yet high enough for general use. This is usually
33      known as the "alpha-test" phase among developers. If a feature is
34      currently in alpha-test, then the developers usually discourage
35      uninformed widespread use of this feature by the general public to
36      avoid "Why doesn't this work?" type mail messages. However, active
37      testing and use of these systems is welcomed. Just be aware that it
38      may not meet the normal level of reliability or it may fail to work
39      in some special cases. Detailed bug reports from people familiar
40      with the kernel internals are usually welcomed by the developers
41      (before submitting bug reports, please read the documents
42      <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
43      <file:Documentation/BUG-HUNTING>, and
44      <file:Documentation/oops-tracing.txt> in the kernel source).
45
46      This option will also make obsoleted drivers available. These are
47      drivers that have been replaced by something else, and/or are
48      scheduled to be removed in a future kernel release.
49
50      Unless you intend to help test and develop a feature or driver that
51      falls into this category, or you have a situation that requires
52      using these features, you should probably say N here, which will
53      cause the configurator to present you with fewer choices. If
54      you say Y here, you will be offered the choice of using features or
55      drivers that are currently considered to be in the alpha-test phase.
56
57config BROKEN
58    bool
59
60config BROKEN_ON_SMP
61    bool
62    depends on BROKEN || !SMP
63    default y
64
65config LOCK_KERNEL
66    bool
67    depends on SMP || PREEMPT
68    default y
69
70config INIT_ENV_ARG_LIMIT
71    int
72    default 32 if !UML
73    default 128 if UML
74    help
75      Maximum of each of the number of arguments and environment
76      variables passed to init from the kernel command line.
77
78
79config CROSS_COMPILE
80    string "Cross-compiler tool prefix"
81    help
82      Same as running 'make CROSS_COMPILE=prefix-' but stored for
83      default make runs in this kernel build directory. You don't
84      need to set this unless you want the configured kernel build
85      directory to select the cross-compiler automatically.
86
87config LOCALVERSION
88    string "Local version - append to kernel release"
89    help
90      Append an extra string to the end of your kernel version.
91      This will show up when you type uname, for example.
92      The string you set here will be appended after the contents of
93      any files with a filename matching localversion* in your
94      object and source tree, in that order. Your total string can
95      be a maximum of 64 characters.
96
97config LOCALVERSION_AUTO
98    bool "Automatically append version information to the version string"
99    default y
100    help
101      This will try to automatically determine if the current tree is a
102      release tree by looking for git tags that belong to the current
103      top of tree revision.
104
105      A string of the format -gxxxxxxxx will be added to the localversion
106      if a git-based tree is found. The string generated by this will be
107      appended after any matching localversion* files, and after the value
108      set in CONFIG_LOCALVERSION.
109
110      (The actual string used here is the first eight characters produced
111      by running the command:
112
113        $ git rev-parse --verify HEAD
114
115      which is done within the script "scripts/setlocalversion".)
116
117config HAVE_KERNEL_GZIP
118    bool
119
120config HAVE_KERNEL_BZIP2
121    bool
122
123config HAVE_KERNEL_LZMA
124    bool
125
126config HAVE_KERNEL_LZO
127    bool
128
129choice
130    prompt "Kernel compression mode"
131    default KERNEL_GZIP
132    depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_LZO
133    help
134      The linux kernel is a kind of self-extracting executable.
135      Several compression algorithms are available, which differ
136      in efficiency, compression and decompression speed.
137      Compression speed is only relevant when building a kernel.
138      Decompression speed is relevant at each boot.
139
140      If you have any problems with bzip2 or lzma compressed
141      kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
142      version of this functionality (bzip2 only), for 2.4, was
143      supplied by Christian Ludwig)
144
145      High compression options are mostly useful for users, who
146      are low on disk space (embedded systems), but for whom ram
147      size matters less.
148
149      If in doubt, select 'gzip'
150
151config KERNEL_GZIP
152    bool "Gzip"
153    depends on HAVE_KERNEL_GZIP
154    help
155      The old and tried gzip compression. It provides a good balance
156      between compression ratio and decompression speed.
157
158config KERNEL_BZIP2
159    bool "Bzip2"
160    depends on HAVE_KERNEL_BZIP2
161    help
162      Its compression ratio and speed is intermediate.
163      Decompression speed is slowest among the three. The kernel
164      size is about 10% smaller with bzip2, in comparison to gzip.
165      Bzip2 uses a large amount of memory. For modern kernels you
166      will need at least 8MB RAM or more for booting.
167
168config KERNEL_LZMA
169    bool "LZMA"
170    depends on HAVE_KERNEL_LZMA
171    help
172      The most recent compression algorithm.
173      Its ratio is best, decompression speed is between the other
174      two. Compression is slowest. The kernel size is about 33%
175      smaller with LZMA in comparison to gzip.
176
177config KERNEL_LZO
178    bool "LZO"
179    depends on HAVE_KERNEL_LZO
180    help
181      Its compression ratio is the poorest among the 4. The kernel
182      size is about about 10% bigger than gzip; however its speed
183      (both compression and decompression) is the fastest.
184
185endchoice
186
187config SWAP
188    bool "Support for paging of anonymous memory (swap)"
189    depends on MMU && BLOCK
190    default y
191    help
192      This option allows you to choose whether you want to have support
193      for so called swap devices or swap files in your kernel that are
194      used to provide more virtual memory than the actual RAM present
195      in your computer. If unsure say Y.
196
197config SYSVIPC
198    bool "System V IPC"
199    ---help---
200      Inter Process Communication is a suite of library functions and
201      system calls which let processes (running programs) synchronize and
202      exchange information. It is generally considered to be a good thing,
203      and some programs won't run unless you say Y here. In particular, if
204      you want to run the DOS emulator dosemu under Linux (read the
205      DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
206      you'll need to say Y here.
207
208      You can find documentation about IPC with "info ipc" and also in
209      section 6.4 of the Linux Programmer's Guide, available from
210      <http://www.tldp.org/guides.html>.
211
212config SYSVIPC_SYSCTL
213    bool
214    depends on SYSVIPC
215    depends on SYSCTL
216    default y
217
218config POSIX_MQUEUE
219    bool "POSIX Message Queues"
220    depends on NET && EXPERIMENTAL
221    ---help---
222      POSIX variant of message queues is a part of IPC. In POSIX message
223      queues every message has a priority which decides about succession
224      of receiving it by a process. If you want to compile and run
225      programs written e.g. for Solaris with use of its POSIX message
226      queues (functions mq_*) say Y here.
227
228      POSIX message queues are visible as a filesystem called 'mqueue'
229      and can be mounted somewhere if you want to do filesystem
230      operations on message queues.
231
232      If unsure, say Y.
233
234config POSIX_MQUEUE_SYSCTL
235    bool
236    depends on POSIX_MQUEUE
237    depends on SYSCTL
238    default y
239
240config BSD_PROCESS_ACCT
241    bool "BSD Process Accounting"
242    help
243      If you say Y here, a user level program will be able to instruct the
244      kernel (via a special system call) to write process accounting
245      information to a file: whenever a process exits, information about
246      that process will be appended to the file by the kernel. The
247      information includes things such as creation time, owning user,
248      command name, memory usage, controlling terminal etc. (the complete
249      list is in the struct acct in <file:include/linux/acct.h>). It is
250      up to the user level program to do useful things with this
251      information. This is generally a good idea, so say Y.
252
253config BSD_PROCESS_ACCT_V3
254    bool "BSD Process Accounting version 3 file format"
255    depends on BSD_PROCESS_ACCT
256    default n
257    help
258      If you say Y here, the process accounting information is written
259      in a new file format that also logs the process IDs of each
260      process and it's parent. Note that this file format is incompatible
261      with previous v0/v1/v2 file formats, so you will need updated tools
262      for processing it. A preliminary version of these tools is available
263      at <http://www.gnu.org/software/acct/>.
264
265config TASKSTATS
266    bool "Export task/process statistics through netlink (EXPERIMENTAL)"
267    depends on NET
268    default n
269    help
270      Export selected statistics for tasks/processes through the
271      generic netlink interface. Unlike BSD process accounting, the
272      statistics are available during the lifetime of tasks/processes as
273      responses to commands. Like BSD accounting, they are sent to user
274      space on task exit.
275
276      Say N if unsure.
277
278config TASK_DELAY_ACCT
279    bool "Enable per-task delay accounting (EXPERIMENTAL)"
280    depends on TASKSTATS
281    help
282      Collect information on time spent by a task waiting for system
283      resources like cpu, synchronous block I/O completion and swapping
284      in pages. Such statistics can help in setting a task's priorities
285      relative to other tasks for cpu, io, rss limits etc.
286
287      Say N if unsure.
288
289config TASK_XACCT
290    bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
291    depends on TASKSTATS
292    help
293      Collect extended task accounting data and send the data
294      to userland for processing over the taskstats interface.
295
296      Say N if unsure.
297
298config TASK_IO_ACCOUNTING
299    bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
300    depends on TASK_XACCT
301    help
302      Collect information on the number of bytes of storage I/O which this
303      task has caused.
304
305      Say N if unsure.
306
307config AUDIT
308    bool "Auditing support"
309    depends on NET
310    help
311      Enable auditing infrastructure that can be used with another
312      kernel subsystem, such as SELinux (which requires this for
313      logging of avc messages output). Does not do system-call
314      auditing without CONFIG_AUDITSYSCALL.
315
316config AUDITSYSCALL
317    bool "Enable system-call auditing support"
318    depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
319    default y if SECURITY_SELINUX
320    help
321      Enable low-overhead system-call auditing infrastructure that
322      can be used independently or with another kernel subsystem,
323      such as SELinux. To use audit's filesystem watch feature, please
324      ensure that INOTIFY is configured.
325
326config AUDIT_TREE
327    def_bool y
328    depends on AUDITSYSCALL
329    select INOTIFY
330
331menu "RCU Subsystem"
332
333choice
334    prompt "RCU Implementation"
335    default TREE_RCU
336
337config TREE_RCU
338    bool "Tree-based hierarchical RCU"
339    help
340      This option selects the RCU implementation that is
341      designed for very large SMP system with hundreds or
342      thousands of CPUs. It also scales down nicely to
343      smaller systems.
344
345config TREE_PREEMPT_RCU
346    bool "Preemptable tree-based hierarchical RCU"
347    depends on PREEMPT
348    help
349      This option selects the RCU implementation that is
350      designed for very large SMP systems with hundreds or
351      thousands of CPUs, but for which real-time response
352      is also required. It also scales down nicely to
353      smaller systems.
354
355config TINY_RCU
356    bool "UP-only small-memory-footprint RCU"
357    depends on !SMP
358    help
359      This option selects the RCU implementation that is
360      designed for UP systems from which real-time response
361      is not required. This option greatly reduces the
362      memory footprint of RCU.
363
364endchoice
365
366config RCU_TRACE
367    bool "Enable tracing for RCU"
368    depends on TREE_RCU || TREE_PREEMPT_RCU
369    help
370      This option provides tracing in RCU which presents stats
371      in debugfs for debugging RCU implementation.
372
373      Say Y here if you want to enable RCU tracing
374      Say N if you are unsure.
375
376config RCU_FANOUT
377    int "Tree-based hierarchical RCU fanout value"
378    range 2 64 if 64BIT
379    range 2 32 if !64BIT
380    depends on TREE_RCU || TREE_PREEMPT_RCU
381    default 64 if 64BIT
382    default 32 if !64BIT
383    help
384      This option controls the fanout of hierarchical implementations
385      of RCU, allowing RCU to work efficiently on machines with
386      large numbers of CPUs. This value must be at least the cube
387      root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
388      systems and up to 262,144 for 64-bit systems.
389
390      Select a specific number if testing RCU itself.
391      Take the default if unsure.
392
393config RCU_FANOUT_EXACT
394    bool "Disable tree-based hierarchical RCU auto-balancing"
395    depends on TREE_RCU || TREE_PREEMPT_RCU
396    default n
397    help
398      This option forces use of the exact RCU_FANOUT value specified,
399      regardless of imbalances in the hierarchy. This is useful for
400      testing RCU itself, and might one day be useful on systems with
401      strong NUMA behavior.
402
403      Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
404
405      Say N if unsure.
406
407config RCU_FAST_NO_HZ
408    bool "Accelerate last non-dyntick-idle CPU's grace periods"
409    depends on TREE_RCU && NO_HZ && SMP
410    default n
411    help
412      This option causes RCU to attempt to accelerate grace periods
413      in order to allow the final CPU to enter dynticks-idle state
414      more quickly. On the other hand, this option increases the
415      overhead of the dynticks-idle checking, particularly on systems
416      with large numbers of CPUs.
417
418      Say Y if energy efficiency is critically important, particularly
419          if you have relatively few CPUs.
420
421      Say N if you are unsure.
422
423config TREE_RCU_TRACE
424    def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
425    select DEBUG_FS
426    help
427      This option provides tracing for the TREE_RCU and
428      TREE_PREEMPT_RCU implementations, permitting Makefile to
429      trivially select kernel/rcutree_trace.c.
430
431endmenu # "RCU Subsystem"
432
433config IKCONFIG
434    tristate "Kernel .config support"
435    ---help---
436      This option enables the complete Linux kernel ".config" file
437      contents to be saved in the kernel. It provides documentation
438      of which kernel options are used in a running kernel or in an
439      on-disk kernel. This information can be extracted from the kernel
440      image file with the script scripts/extract-ikconfig and used as
441      input to rebuild the current kernel or to build another kernel.
442      It can also be extracted from a running kernel by reading
443      /proc/config.gz if enabled (below).
444
445config IKCONFIG_PROC
446    bool "Enable access to .config through /proc/config.gz"
447    depends on IKCONFIG && PROC_FS
448    ---help---
449      This option enables access to the kernel configuration file
450      through /proc/config.gz.
451
452config LOG_BUF_SHIFT
453    int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
454    range 12 21
455    default 17
456    help
457      Select kernel log buffer size as a power of 2.
458      Examples:
459               17 => 128 KB
460             16 => 64 KB
461                 15 => 32 KB
462                 14 => 16 KB
463             13 => 8 KB
464             12 => 4 KB
465
466#
467# Architectures with an unreliable sched_clock() should select this:
468#
469config HAVE_UNSTABLE_SCHED_CLOCK
470    bool
471
472menuconfig CGROUPS
473    boolean "Control Group support"
474    depends on EVENTFD
475    help
476      This option adds support for grouping sets of processes together, for
477      use with process control subsystems such as Cpusets, CFS, memory
478      controls or device isolation.
479      See
480        - Documentation/scheduler/sched-design-CFS.txt (CFS)
481        - Documentation/cgroups/ (features for grouping, isolation
482                      and resource control)
483
484      Say N if unsure.
485
486if CGROUPS
487
488config CGROUP_DEBUG
489    bool "Example debug cgroup subsystem"
490    depends on CGROUPS
491    default n
492    help
493      This option enables a simple cgroup subsystem that
494      exports useful debugging information about the cgroups
495      framework.
496
497      Say N if unsure.
498
499config CGROUP_NS
500    bool "Namespace cgroup subsystem"
501    depends on CGROUPS
502    help
503      Provides a simple namespace cgroup subsystem to
504      provide hierarchical naming of sets of namespaces,
505      for instance virtual servers and checkpoint/restart
506      jobs.
507
508config CGROUP_FREEZER
509    bool "Freezer cgroup subsystem"
510    depends on CGROUPS
511    help
512      Provides a way to freeze and unfreeze all tasks in a
513      cgroup.
514
515config CGROUP_DEVICE
516    bool "Device controller for cgroups"
517    depends on CGROUPS && EXPERIMENTAL
518    help
519      Provides a cgroup implementing whitelists for devices which
520      a process in the cgroup can mknod or open.
521
522config CPUSETS
523    bool "Cpuset support"
524    depends on CGROUPS
525    help
526      This option will let you create and manage CPUSETs which
527      allow dynamically partitioning a system into sets of CPUs and
528      Memory Nodes and assigning tasks to run only within those sets.
529      This is primarily useful on large SMP or NUMA systems.
530
531      Say N if unsure.
532
533config PROC_PID_CPUSET
534    bool "Include legacy /proc/<pid>/cpuset file"
535    depends on CPUSETS
536    default y
537
538config CGROUP_CPUACCT
539    bool "Simple CPU accounting cgroup subsystem"
540    depends on CGROUPS
541    help
542      Provides a simple Resource Controller for monitoring the
543      total CPU consumed by the tasks in a cgroup.
544
545config RESOURCE_COUNTERS
546    bool "Resource counters"
547    help
548      This option enables controller independent resource accounting
549      infrastructure that works with cgroups.
550    depends on CGROUPS
551
552config CGROUP_MEM_RES_CTLR
553    bool "Memory Resource Controller for Control Groups"
554    depends on CGROUPS && RESOURCE_COUNTERS
555    select MM_OWNER
556    help
557      Provides a memory resource controller that manages both anonymous
558      memory and page cache. (See Documentation/cgroups/memory.txt)
559
560      Note that setting this option increases fixed memory overhead
561      associated with each page of memory in the system. By this,
562      20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
563      usage tracking struct at boot. Total amount of this is printed out
564      at boot.
565
566      Only enable when you're ok with these trade offs and really
567      sure you need the memory resource controller. Even when you enable
568      this, you can set "cgroup_disable=memory" at your boot option to
569      disable memory resource controller and you can avoid overheads.
570      (and lose benefits of memory resource controller)
571
572      This config option also selects MM_OWNER config option, which
573      could in turn add some fork/exit overhead.
574
575config CGROUP_MEM_RES_CTLR_SWAP
576    bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
577    depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
578    help
579      Add swap management feature to memory resource controller. When you
580      enable this, you can limit mem+swap usage per cgroup. In other words,
581      when you disable this, memory resource controller has no cares to
582      usage of swap...a process can exhaust all of the swap. This extension
583      is useful when you want to avoid exhaustion swap but this itself
584      adds more overheads and consumes memory for remembering information.
585      Especially if you use 32bit system or small memory system, please
586      be careful about enabling this. When memory resource controller
587      is disabled by boot option, this will be automatically disabled and
588      there will be no overhead from this. Even when you set this config=y,
589      if boot option "noswapaccount" is set, swap will not be accounted.
590      Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
591      size is 4096bytes, 512k per 1Gbytes of swap.
592
593menuconfig CGROUP_SCHED
594    bool "Group CPU scheduler"
595    depends on EXPERIMENTAL && CGROUPS
596    default n
597    help
598      This feature lets CPU scheduler recognize task groups and control CPU
599      bandwidth allocation to such task groups. It uses cgroups to group
600      tasks.
601
602if CGROUP_SCHED
603config FAIR_GROUP_SCHED
604    bool "Group scheduling for SCHED_OTHER"
605    depends on CGROUP_SCHED
606    default CGROUP_SCHED
607
608config RT_GROUP_SCHED
609    bool "Group scheduling for SCHED_RR/FIFO"
610    depends on EXPERIMENTAL
611    depends on CGROUP_SCHED
612    default n
613    help
614      This feature lets you explicitly allocate real CPU bandwidth
615      to task groups. If enabled, it will also make it impossible to
616      schedule realtime tasks for non-root users until you allocate
617      realtime bandwidth for them.
618      See Documentation/scheduler/sched-rt-group.txt for more information.
619
620endif #CGROUP_SCHED
621
622config BLK_CGROUP
623    tristate "Block IO controller"
624    depends on CGROUPS && BLOCK
625    default n
626    ---help---
627    Generic block IO controller cgroup interface. This is the common
628    cgroup interface which should be used by various IO controlling
629    policies.
630
631    Currently, CFQ IO scheduler uses it to recognize task groups and
632    control disk bandwidth allocation (proportional time slice allocation)
633    to such task groups.
634
635    This option only enables generic Block IO controller infrastructure.
636    One needs to also enable actual IO controlling logic in CFQ for it
637    to take effect. (CONFIG_CFQ_GROUP_IOSCHED=y).
638
639    See Documentation/cgroups/blkio-controller.txt for more information.
640
641config DEBUG_BLK_CGROUP
642    bool "Enable Block IO controller debugging"
643    depends on BLK_CGROUP
644    default n
645    ---help---
646    Enable some debugging help. Currently it exports additional stat
647    files in a cgroup which can be useful for debugging.
648
649endif # CGROUPS
650
651config MM_OWNER
652    bool
653
654config SYSFS_DEPRECATED
655    bool
656
657config SYSFS_DEPRECATED_V2
658    bool "enable deprecated sysfs features to support old userspace tools"
659    depends on SYSFS
660    default n
661    select SYSFS_DEPRECATED
662    help
663      This option switches the layout of sysfs to the deprecated
664      version. Do not use it on recent distributions.
665
666      The current sysfs layout features a unified device tree at
667      /sys/devices/, which is able to express a hierarchy between
668      class devices. If the deprecated option is set to Y, the
669      unified device tree is split into a bus device tree at
670      /sys/devices/ and several individual class device trees at
671      /sys/class/. The class and bus devices will be connected by
672      "<subsystem>:<name>" and the "device" links. The "block"
673      class devices, will not show up in /sys/class/block/. Some
674      subsystems will suppress the creation of some devices which
675      depend on the unified device tree.
676
677      This option is not a pure compatibility option that can
678      be safely enabled on newer distributions. It will change the
679      layout of sysfs to the non-extensible deprecated version,
680      and disable some features, which can not be exported without
681      confusing older userspace tools. Since 2007/2008 all major
682      distributions do not enable this option, and ship no tools which
683      depend on the deprecated layout or this option.
684
685      If you are using a new kernel on an older distribution, or use
686      older userspace tools, you might need to say Y here. Do not say Y,
687      if the original kernel, that came with your distribution, has
688      this option set to N.
689
690config RELAY
691    bool "Kernel->user space relay support (formerly relayfs)"
692    help
693      This option enables support for relay interface support in
694      certain file systems (such as debugfs).
695      It is designed to provide an efficient mechanism for tools and
696      facilities to relay large amounts of data from kernel space to
697      user space.
698
699      If unsure, say N.
700
701config NAMESPACES
702    bool "Namespaces support" if EMBEDDED
703    default !EMBEDDED
704    help
705      Provides the way to make tasks work with different objects using
706      the same id. For example same IPC id may refer to different objects
707      or same user id or pid may refer to different tasks when used in
708      different namespaces.
709
710config UTS_NS
711    bool "UTS namespace"
712    depends on NAMESPACES
713    help
714      In this namespace tasks see different info provided with the
715      uname() system call
716
717config IPC_NS
718    bool "IPC namespace"
719    depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
720    help
721      In this namespace tasks work with IPC ids which correspond to
722      different IPC objects in different namespaces.
723
724config USER_NS
725    bool "User namespace (EXPERIMENTAL)"
726    depends on NAMESPACES && EXPERIMENTAL
727    help
728      This allows containers, i.e. vservers, to use user namespaces
729      to provide different user info for different servers.
730      If unsure, say N.
731
732config PID_NS
733    bool "PID Namespaces (EXPERIMENTAL)"
734    default n
735    depends on NAMESPACES && EXPERIMENTAL
736    help
737      Support process id namespaces. This allows having multiple
738      processes with the same pid as long as they are in different
739      pid namespaces. This is a building block of containers.
740
741      Unless you want to work with an experimental feature
742      say N here.
743
744config NET_NS
745    bool "Network namespace"
746    default n
747    depends on NAMESPACES && EXPERIMENTAL && NET
748    help
749      Allow user space to create what appear to be multiple instances
750      of the network stack.
751
752config BLK_DEV_INITRD
753    bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
754    depends on BROKEN || !FRV
755    help
756      The initial RAM filesystem is a ramfs which is loaded by the
757      boot loader (loadlin or lilo) and that is mounted as root
758      before the normal boot procedure. It is typically used to
759      load modules needed to mount the "real" root file system,
760      etc. See <file:Documentation/initrd.txt> for details.
761
762      If RAM disk support (BLK_DEV_RAM) is also included, this
763      also enables initial RAM disk (initrd) support and adds
764      15 Kbytes (more on some other architectures) to the kernel size.
765
766      If unsure say Y.
767
768if BLK_DEV_INITRD
769
770source "usr/Kconfig"
771
772endif
773
774config CC_OPTIMIZE_FOR_SIZE
775    bool "Optimize for size"
776    default y
777    help
778      Enabling this option will pass "-Os" instead of "-O2" to gcc
779      resulting in a smaller kernel.
780
781      If unsure, say Y.
782
783config SYSCTL
784    bool
785
786config ANON_INODES
787    bool
788
789menuconfig EMBEDDED
790    bool "Configure standard kernel features (for small systems)"
791    help
792      This option allows certain base kernel options and settings
793          to be disabled or tweaked. This is for specialized
794          environments which can tolerate a "non-standard" kernel.
795          Only use this if you really know what you are doing.
796
797config UID16
798    bool "Enable 16-bit UID system calls" if EMBEDDED
799    depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
800    default y
801    help
802      This enables the legacy 16-bit UID syscall wrappers.
803
804config SYSCTL_SYSCALL
805    bool "Sysctl syscall support" if EMBEDDED
806    depends on PROC_SYSCTL
807    default y
808    select SYSCTL
809    ---help---
810      sys_sysctl uses binary paths that have been found challenging
811      to properly maintain and use. The interface in /proc/sys
812      using paths with ascii names is now the primary path to this
813      information.
814
815      Almost nothing using the binary sysctl interface so if you are
816      trying to save some space it is probably safe to disable this,
817      making your kernel marginally smaller.
818
819      If unsure say Y here.
820
821config KALLSYMS
822     bool "Load all symbols for debugging/ksymoops" if EMBEDDED
823     default y
824     help
825       Say Y here to let the kernel print out symbolic crash information and
826       symbolic stack backtraces. This increases the size of the kernel
827       somewhat, as all symbols have to be loaded into the kernel image.
828
829config KALLSYMS_ALL
830    bool "Include all symbols in kallsyms"
831    depends on DEBUG_KERNEL && KALLSYMS
832    help
833       Normally kallsyms only contains the symbols of functions, for nicer
834       OOPS messages. Some debuggers can use kallsyms for other
835       symbols too: say Y here to include all symbols, if you need them
836       and you don't care about adding 300k to the size of your kernel.
837
838       Say N.
839
840config KALLSYMS_EXTRA_PASS
841    bool "Do an extra kallsyms pass"
842    depends on KALLSYMS
843    help
844       If kallsyms is not working correctly, the build will fail with
845       inconsistent kallsyms data. If that occurs, log a bug report and
846       turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
847       Always say N here unless you find a bug in kallsyms, which must be
848       reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
849       you wait for kallsyms to be fixed.
850
851
852config HOTPLUG
853    bool "Support for hot-pluggable devices" if EMBEDDED
854    default y
855    help
856      This option is provided for the case where no hotplug or uevent
857      capabilities is wanted by the kernel. You should only consider
858      disabling this option for embedded systems that do not use modules, a
859      dynamic /dev tree, or dynamic device discovery. Just say Y.
860
861config PRINTK
862    default y
863    bool "Enable support for printk" if EMBEDDED
864    help
865      This option enables normal printk support. Removing it
866      eliminates most of the message strings from the kernel image
867      and makes the kernel more or less silent. As this makes it
868      very difficult to diagnose system problems, saying N here is
869      strongly discouraged.
870
871config BUG
872    bool "BUG() support" if EMBEDDED
873    default y
874    help
875          Disabling this option eliminates support for BUG and WARN, reducing
876          the size of your kernel image and potentially quietly ignoring
877          numerous fatal conditions. You should only consider disabling this
878          option for embedded systems with no facilities for reporting errors.
879          Just say Y.
880
881config ELF_CORE
882    default y
883    bool "Enable ELF core dumps" if EMBEDDED
884    help
885      Enable support for generating core dumps. Disabling saves about 4k.
886
887config PCSPKR_PLATFORM
888    bool "Enable PC-Speaker support" if EMBEDDED
889    depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
890    default y
891    help
892          This option allows to disable the internal PC-Speaker
893          support, saving some memory.
894
895config BASE_FULL
896    default y
897    bool "Enable full-sized data structures for core" if EMBEDDED
898    help
899      Disabling this option reduces the size of miscellaneous core
900      kernel data structures. This saves memory on small machines,
901      but may reduce performance.
902
903config FUTEX
904    bool "Enable futex support" if EMBEDDED
905    default y
906    select RT_MUTEXES
907    help
908      Disabling this option will cause the kernel to be built without
909      support for "fast userspace mutexes". The resulting kernel may not
910      run glibc-based applications correctly.
911
912config EPOLL
913    bool "Enable eventpoll support" if EMBEDDED
914    default y
915    select ANON_INODES
916    help
917      Disabling this option will cause the kernel to be built without
918      support for epoll family of system calls.
919
920config SIGNALFD
921    bool "Enable signalfd() system call" if EMBEDDED
922    select ANON_INODES
923    default y
924    help
925      Enable the signalfd() system call that allows to receive signals
926      on a file descriptor.
927
928      If unsure, say Y.
929
930config TIMERFD
931    bool "Enable timerfd() system call" if EMBEDDED
932    select ANON_INODES
933    default y
934    help
935      Enable the timerfd() system call that allows to receive timer
936      events on a file descriptor.
937
938      If unsure, say Y.
939
940config EVENTFD
941    bool "Enable eventfd() system call" if EMBEDDED
942    select ANON_INODES
943    default y
944    help
945      Enable the eventfd() system call that allows to receive both
946      kernel notification (ie. KAIO) or userspace notifications.
947
948      If unsure, say Y.
949
950config SHMEM
951    bool "Use full shmem filesystem" if EMBEDDED
952    default y
953    depends on MMU
954    help
955      The shmem is an internal filesystem used to manage shared memory.
956      It is backed by swap and manages resource limits. It is also exported
957      to userspace as tmpfs if TMPFS is enabled. Disabling this
958      option replaces shmem and tmpfs with the much simpler ramfs code,
959      which may be appropriate on small systems without swap.
960
961config AIO
962    bool "Enable AIO support" if EMBEDDED
963    default y
964    help
965      This option enables POSIX asynchronous I/O which may by used
966          by some high performance threaded applications. Disabling
967          this option saves about 7k.
968
969config HAVE_PERF_EVENTS
970    bool
971    help
972      See tools/perf/design.txt for details.
973
974config PERF_USE_VMALLOC
975    bool
976    help
977      See tools/perf/design.txt for details
978
979menu "Kernel Performance Events And Counters"
980
981config PERF_EVENTS
982    bool "Kernel performance events and counters"
983    default y if (PROFILING || PERF_COUNTERS)
984    depends on HAVE_PERF_EVENTS
985    select ANON_INODES
986    help
987      Enable kernel support for various performance events provided
988      by software and hardware.
989
990      Software events are supported either built-in or via the
991      use of generic tracepoints.
992
993      Most modern CPUs support performance events via performance
994      counter registers. These registers count the number of certain
995      types of hw events: such as instructions executed, cachemisses
996      suffered, or branches mis-predicted - without slowing down the
997      kernel or applications. These registers can also trigger interrupts
998      when a threshold number of events have passed - and can thus be
999      used to profile the code that runs on that CPU.
1000
1001      The Linux Performance Event subsystem provides an abstraction of
1002      these software and hardware event capabilities, available via a
1003      system call and used by the "perf" utility in tools/perf/. It
1004      provides per task and per CPU counters, and it provides event
1005      capabilities on top of those.
1006
1007      Say Y if unsure.
1008
1009config PERF_COUNTERS
1010    bool "Kernel performance counters (old config option)"
1011    depends on HAVE_PERF_EVENTS
1012    help
1013      This config has been obsoleted by the PERF_EVENTS
1014      config option - please see that one for details.
1015
1016      It has no effect on the kernel whether you enable
1017      it or not, it is a compatibility placeholder.
1018
1019      Say N if unsure.
1020
1021config DEBUG_PERF_USE_VMALLOC
1022    default n
1023    bool "Debug: use vmalloc to back perf mmap() buffers"
1024    depends on PERF_EVENTS && DEBUG_KERNEL
1025    select PERF_USE_VMALLOC
1026    help
1027     Use vmalloc memory to back perf mmap() buffers.
1028
1029     Mostly useful for debugging the vmalloc code on platforms
1030     that don't require it.
1031
1032     Say N if unsure.
1033
1034endmenu
1035
1036config VM_EVENT_COUNTERS
1037    default y
1038    bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
1039    help
1040      VM event counters are needed for event counts to be shown.
1041      This option allows the disabling of the VM event counters
1042      on EMBEDDED systems. /proc/vmstat will only show page counts
1043      if VM event counters are disabled.
1044
1045config PCI_QUIRKS
1046    default y
1047    bool "Enable PCI quirk workarounds" if EMBEDDED
1048    depends on PCI
1049    help
1050      This enables workarounds for various PCI chipset
1051          bugs/quirks. Disable this only if your target machine is
1052          unaffected by PCI quirks.
1053
1054config SLUB_DEBUG
1055    default y
1056    bool "Enable SLUB debugging support" if EMBEDDED
1057    depends on SLUB && SYSFS
1058    help
1059      SLUB has extensive debug support features. Disabling these can
1060      result in significant savings in code size. This also disables
1061      SLUB sysfs support. /sys/slab will not exist and there will be
1062      no support for cache validation etc.
1063
1064config COMPAT_BRK
1065    bool "Disable heap randomization"
1066    default y
1067    help
1068      Randomizing heap placement makes heap exploits harder, but it
1069      also breaks ancient binaries (including anything libc5 based).
1070      This option changes the bootup default to heap randomization
1071      disabled, and can be overridden at runtime by setting
1072      /proc/sys/kernel/randomize_va_space to 2.
1073
1074      On non-ancient distros (post-2000 ones) N is usually a safe choice.
1075
1076choice
1077    prompt "Choose SLAB allocator"
1078    default SLUB
1079    help
1080       This option allows to select a slab allocator.
1081
1082config SLAB
1083    bool "SLAB"
1084    help
1085      The regular slab allocator that is established and known to work
1086      well in all environments. It organizes cache hot objects in
1087      per cpu and per node queues.
1088
1089config SLUB
1090    bool "SLUB (Unqueued Allocator)"
1091    help
1092       SLUB is a slab allocator that minimizes cache line usage
1093       instead of managing queues of cached objects (SLAB approach).
1094       Per cpu caching is realized using slabs of objects instead
1095       of queues of objects. SLUB can use memory efficiently
1096       and has enhanced diagnostics. SLUB is the default choice for
1097       a slab allocator.
1098
1099config SLOB
1100    depends on EMBEDDED
1101    bool "SLOB (Simple Allocator)"
1102    help
1103       SLOB replaces the stock allocator with a drastically simpler
1104       allocator. SLOB is generally more space efficient but
1105       does not perform as well on large systems.
1106
1107endchoice
1108
1109config MMAP_ALLOW_UNINITIALIZED
1110    bool "Allow mmapped anonymous memory to be uninitialized"
1111    depends on EMBEDDED && !MMU
1112    default n
1113    help
1114      Normally, and according to the Linux spec, anonymous memory obtained
1115      from mmap() has it's contents cleared before it is passed to
1116      userspace. Enabling this config option allows you to request that
1117      mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1118      providing a huge performance boost. If this option is not enabled,
1119      then the flag will be ignored.
1120
1121      This is taken advantage of by uClibc's malloc(), and also by
1122      ELF-FDPIC binfmt's brk and stack allocator.
1123
1124      Because of the obvious security issues, this option should only be
1125      enabled on embedded devices where you control what is run in
1126      userspace. Since that isn't generally a problem on no-MMU systems,
1127      it is normally safe to say Y here.
1128
1129      See Documentation/nommu-mmap.txt for more information.
1130
1131config PROFILING
1132    bool "Profiling support"
1133    help
1134      Say Y here to enable the extended profiling support mechanisms used
1135      by profilers such as OProfile.
1136
1137#
1138# Place an empty function call at each tracepoint site. Can be
1139# dynamically changed for a probe function.
1140#
1141config TRACEPOINTS
1142    bool
1143
1144source "arch/Kconfig"
1145
1146config SLOW_WORK
1147    default n
1148    bool
1149    help
1150      The slow work thread pool provides a number of dynamically allocated
1151      threads that can be used by the kernel to perform operations that
1152      take a relatively long time.
1153
1154      An example of this would be CacheFiles doing a path lookup followed
1155      by a series of mkdirs and a create call, all of which have to touch
1156      disk.
1157
1158      See Documentation/slow-work.txt.
1159
1160config SLOW_WORK_DEBUG
1161    bool "Slow work debugging through debugfs"
1162    default n
1163    depends on SLOW_WORK && DEBUG_FS
1164    help
1165      Display the contents of the slow work run queue through debugfs,
1166      including items currently executing.
1167
1168      See Documentation/slow-work.txt.
1169
1170endmenu # General setup
1171
1172config HAVE_GENERIC_DMA_COHERENT
1173    bool
1174    default n
1175
1176config SLABINFO
1177    bool
1178    depends on PROC_FS
1179    depends on SLAB || SLUB_DEBUG
1180    default y
1181
1182config RT_MUTEXES
1183    boolean
1184
1185config BASE_SMALL
1186    int
1187    default 0 if BASE_FULL
1188    default 1 if !BASE_FULL
1189
1190menuconfig MODULES
1191    bool "Enable loadable module support"
1192    help
1193      Kernel modules are small pieces of compiled code which can
1194      be inserted in the running kernel, rather than being
1195      permanently built into the kernel. You use the "modprobe"
1196      tool to add (and sometimes remove) them. If you say Y here,
1197      many parts of the kernel can be built as modules (by
1198      answering M instead of Y where indicated): this is most
1199      useful for infrequently used options which are not required
1200      for booting. For more information, see the man pages for
1201      modprobe, lsmod, modinfo, insmod and rmmod.
1202
1203      If you say Y here, you will need to run "make
1204      modules_install" to put the modules under /lib/modules/
1205      where modprobe can find them (you may need to be root to do
1206      this).
1207
1208      If unsure, say Y.
1209
1210if MODULES
1211
1212config MODULE_FORCE_LOAD
1213    bool "Forced module loading"
1214    default n
1215    help
1216      Allow loading of modules without version information (ie. modprobe
1217      --force). Forced module loading sets the 'F' (forced) taint flag and
1218      is usually a really bad idea.
1219
1220config MODULE_UNLOAD
1221    bool "Module unloading"
1222    help
1223      Without this option you will not be able to unload any
1224      modules (note that some modules may not be unloadable
1225      anyway), which makes your kernel smaller, faster
1226      and simpler. If unsure, say Y.
1227
1228config MODULE_FORCE_UNLOAD
1229    bool "Forced module unloading"
1230    depends on MODULE_UNLOAD && EXPERIMENTAL
1231    help
1232      This option allows you to force a module to unload, even if the
1233      kernel believes it is unsafe: the kernel will remove the module
1234      without waiting for anyone to stop using it (using the -f option to
1235      rmmod). This is mainly for kernel developers and desperate users.
1236      If unsure, say N.
1237
1238config MODVERSIONS
1239    bool "Module versioning support"
1240    help
1241      Usually, you have to use modules compiled with your kernel.
1242      Saying Y here makes it sometimes possible to use modules
1243      compiled for different kernels, by adding enough information
1244      to the modules to (hopefully) spot any changes which would
1245      make them incompatible with the kernel you are running. If
1246      unsure, say N.
1247
1248config MODULE_SRCVERSION_ALL
1249    bool "Source checksum for all modules"
1250    help
1251      Modules which contain a MODULE_VERSION get an extra "srcversion"
1252      field inserted into their modinfo section, which contains a
1253          sum of the source files which made it. This helps maintainers
1254      see exactly which source was used to build a module (since
1255      others sometimes change the module source without updating
1256      the version). With this option, such a "srcversion" field
1257      will be created for all modules. If unsure, say N.
1258
1259endif # MODULES
1260
1261config INIT_ALL_POSSIBLE
1262    bool
1263    help
1264      Back when each arch used to define their own cpu_online_map and
1265      cpu_possible_map, some of them chose to initialize cpu_possible_map
1266      with all 1s, and others with all 0s. When they were centralised,
1267      it was better to provide this option than to break all the archs
1268      and have several arch maintainers pursuing me down dark alleys.
1269
1270config STOP_MACHINE
1271    bool
1272    default y
1273    depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1274    help
1275      Need stop_machine() primitive.
1276
1277source "block/Kconfig"
1278
1279config PREEMPT_NOTIFIERS
1280    bool
1281
1282config PADATA
1283    depends on SMP
1284    bool
1285
1286source "kernel/Kconfig.locks"
1287

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