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47      drivers that have been replaced by something else, and/or are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

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