Version:  2.0.40 2.2.26 2.4.37 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19


  1 config ARCH
  2         string
  3         option env="ARCH"
  6         string
  7         option env="KERNELVERSION"
 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"
 20         bool
 21         depends on !UML
 23 config IRQ_WORK
 24         bool
 27         bool
 29 menu "General setup"
 31 config BROKEN
 32         bool
 34 config BROKEN_ON_SMP
 35         bool
 36         depends on BROKEN || !SMP
 37         default y
 40         int
 41         default 32 if !UML
 42         default 128 if UML
 43         help
 44           Maximum of each of the number of arguments and environment
 45           variables passed to init from the kernel command line.
 48 config CROSS_COMPILE
 49         string "Cross-compiler tool prefix"
 50         help
 51           Same as running 'make CROSS_COMPILE=prefix-' but stored for
 52           default make runs in this kernel build directory.  You don't
 53           need to set this unless you want the configured kernel build
 54           directory to select the cross-compiler automatically.
 56 config COMPILE_TEST
 57         bool "Compile also drivers which will not load"
 58         default n
 59         help
 60           Some drivers can be compiled on a different platform than they are
 61           intended to be run on. Despite they cannot be loaded there (or even
 62           when they load they cannot be used due to missing HW support),
 63           developers still, opposing to distributors, might want to build such
 64           drivers to compile-test them.
 66           If you are a developer and want to build everything available, say Y
 67           here. If you are a user/distributor, say N here to exclude useless
 68           drivers to be distributed.
 71         string "Local version - append to kernel release"
 72         help
 73           Append an extra string to the end of your kernel version.
 74           This will show up when you type uname, for example.
 75           The string you set here will be appended after the contents of
 76           any files with a filename matching localversion* in your
 77           object and source tree, in that order.  Your total string can
 78           be a maximum of 64 characters.
 81         bool "Automatically append version information to the version string"
 82         default y
 83         help
 84           This will try to automatically determine if the current tree is a
 85           release tree by looking for git tags that belong to the current
 86           top of tree revision.
 88           A string of the format -gxxxxxxxx will be added to the localversion
 89           if a git-based tree is found.  The string generated by this will be
 90           appended after any matching localversion* files, and after the value
 91           set in CONFIG_LOCALVERSION.
 93           (The actual string used here is the first eight characters produced
 94           by running the command:
 96             $ git rev-parse --verify HEAD
 98           which is done within the script "scripts/setlocalversion".)
101         bool
103 config HAVE_KERNEL_BZIP2
104         bool
107         bool
109 config HAVE_KERNEL_XZ
110         bool
112 config HAVE_KERNEL_LZO
113         bool
115 config HAVE_KERNEL_LZ4
116         bool
118 choice
119         prompt "Kernel compression mode"
120         default KERNEL_GZIP
122         help
123           The linux kernel is a kind of self-extracting executable.
124           Several compression algorithms are available, which differ
125           in efficiency, compression and decompression speed.
126           Compression speed is only relevant when building a kernel.
127           Decompression speed is relevant at each boot.
129           If you have any problems with bzip2 or lzma compressed
130           kernels, mail me (Alain Knaff) <>. (An older
131           version of this functionality (bzip2 only), for 2.4, was
132           supplied by Christian Ludwig)
134           High compression options are mostly useful for users, who
135           are low on disk space (embedded systems), but for whom ram
136           size matters less.
138           If in doubt, select 'gzip'
140 config KERNEL_GZIP
141         bool "Gzip"
142         depends on HAVE_KERNEL_GZIP
143         help
144           The old and tried gzip compression. It provides a good balance
145           between compression ratio and decompression speed.
147 config KERNEL_BZIP2
148         bool "Bzip2"
149         depends on HAVE_KERNEL_BZIP2
150         help
151           Its compression ratio and speed is intermediate.
152           Decompression speed is slowest among the choices.  The kernel
153           size is about 10% smaller with bzip2, in comparison to gzip.
154           Bzip2 uses a large amount of memory. For modern kernels you
155           will need at least 8MB RAM or more for booting.
157 config KERNEL_LZMA
158         bool "LZMA"
159         depends on HAVE_KERNEL_LZMA
160         help
161           This compression algorithm's ratio is best.  Decompression speed
162           is between gzip and bzip2.  Compression is slowest.
163           The kernel size is about 33% smaller with LZMA in comparison to gzip.
165 config KERNEL_XZ
166         bool "XZ"
167         depends on HAVE_KERNEL_XZ
168         help
169           XZ uses the LZMA2 algorithm and instruction set specific
170           BCJ filters which can improve compression ratio of executable
171           code. The size of the kernel is about 30% smaller with XZ in
172           comparison to gzip. On architectures for which there is a BCJ
173           filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
174           will create a few percent smaller kernel than plain LZMA.
176           The speed is about the same as with LZMA: The decompression
177           speed of XZ is better than that of bzip2 but worse than gzip
178           and LZO. Compression is slow.
180 config KERNEL_LZO
181         bool "LZO"
182         depends on HAVE_KERNEL_LZO
183         help
184           Its compression ratio is the poorest among the choices. The kernel
185           size is about 10% bigger than gzip; however its speed
186           (both compression and decompression) is the fastest.
188 config KERNEL_LZ4
189         bool "LZ4"
190         depends on HAVE_KERNEL_LZ4
191         help
192           LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
193           A preliminary version of LZ4 de/compression tool is available at
194           <>.
196           Its compression ratio is worse than LZO. The size of the kernel
197           is about 8% bigger than LZO. But the decompression speed is
198           faster than LZO.
200 endchoice
203         string "Default hostname"
204         default "(none)"
205         help
206           This option determines the default system hostname before userspace
207           calls sethostname(2). The kernel traditionally uses "(none)" here,
208           but you may wish to use a different default here to make a minimal
209           system more usable with less configuration.
211 config SWAP
212         bool "Support for paging of anonymous memory (swap)"
213         depends on MMU && BLOCK
214         default y
215         help
216           This option allows you to choose whether you want to have support
217           for so called swap devices or swap files in your kernel that are
218           used to provide more virtual memory than the actual RAM present
219           in your computer.  If unsure say Y.
221 config SYSVIPC
222         bool "System V IPC"
223         ---help---
224           Inter Process Communication is a suite of library functions and
225           system calls which let processes (running programs) synchronize and
226           exchange information. It is generally considered to be a good thing,
227           and some programs won't run unless you say Y here. In particular, if
228           you want to run the DOS emulator dosemu under Linux (read the
229           DOSEMU-HOWTO, available from <>),
230           you'll need to say Y here.
232           You can find documentation about IPC with "info ipc" and also in
233           section 6.4 of the Linux Programmer's Guide, available from
234           <>.
237         bool
238         depends on SYSVIPC
239         depends on SYSCTL
240         default y
242 config POSIX_MQUEUE
243         bool "POSIX Message Queues"
244         depends on NET
245         ---help---
246           POSIX variant of message queues is a part of IPC. In POSIX message
247           queues every message has a priority which decides about succession
248           of receiving it by a process. If you want to compile and run
249           programs written e.g. for Solaris with use of its POSIX message
250           queues (functions mq_*) say Y here.
252           POSIX message queues are visible as a filesystem called 'mqueue'
253           and can be mounted somewhere if you want to do filesystem
254           operations on message queues.
256           If unsure, say Y.
259         bool
260         depends on POSIX_MQUEUE
261         depends on SYSCTL
262         default y
265         bool "Enable process_vm_readv/writev syscalls"
266         depends on MMU
267         default y
268         help
269           Enabling this option adds the system calls process_vm_readv and
270           process_vm_writev which allow a process with the correct privileges
271           to directly read from or write to another process' address space.
272           See the man page for more details.
274 config FHANDLE
275         bool "open by fhandle syscalls"
276         select EXPORTFS
277         help
278           If you say Y here, a user level program will be able to map
279           file names to handle and then later use the handle for
280           different file system operations. This is useful in implementing
281           userspace file servers, which now track files using handles instead
282           of names. The handle would remain the same even if file names
283           get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
284           syscalls.
286 config USELIB
287         bool "uselib syscall"
288         default y
289         help
290           This option enables the uselib syscall, a system call used in the
291           dynamic linker from libc5 and earlier.  glibc does not use this
292           system call.  If you intend to run programs built on libc5 or
293           earlier, you may need to enable this syscall.  Current systems
294           running glibc can safely disable this.
296 config AUDIT
297         bool "Auditing support"
298         depends on NET
299         help
300           Enable auditing infrastructure that can be used with another
301           kernel subsystem, such as SELinux (which requires this for
302           logging of avc messages output).  Does not do system-call
303           auditing without CONFIG_AUDITSYSCALL.
306         bool
309         bool "Enable system-call auditing support"
310         depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
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.
317 config AUDIT_WATCH
318         def_bool y
319         depends on AUDITSYSCALL
320         select FSNOTIFY
322 config AUDIT_TREE
323         def_bool y
324         depends on AUDITSYSCALL
325         select FSNOTIFY
327 source "kernel/irq/Kconfig"
328 source "kernel/time/Kconfig"
330 menu "CPU/Task time and stats accounting"
333         bool
335 choice
336         prompt "Cputime accounting"
337         default TICK_CPU_ACCOUNTING if !PPC64
338         default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
340 # Kind of a stub config for the pure tick based cputime accounting
342         bool "Simple tick based cputime accounting"
343         depends on !S390 && !NO_HZ_FULL
344         help
345           This is the basic tick based cputime accounting that maintains
346           statistics about user, system and idle time spent on per jiffies
347           granularity.
349           If unsure, say Y.
352         bool "Deterministic task and CPU time accounting"
353         depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
354         select VIRT_CPU_ACCOUNTING
355         help
356           Select this option to enable more accurate task and CPU time
357           accounting.  This is done by reading a CPU counter on each
358           kernel entry and exit and on transitions within the kernel
359           between system, softirq and hardirq state, so there is a
360           small performance impact.  In the case of s390 or IBM POWER > 5,
361           this also enables accounting of stolen time on logically-partitioned
362           systems.
365         bool "Full dynticks CPU time accounting"
366         depends on HAVE_CONTEXT_TRACKING
367         depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
368         select VIRT_CPU_ACCOUNTING
369         select CONTEXT_TRACKING
370         help
371           Select this option to enable task and CPU time accounting on full
372           dynticks systems. This accounting is implemented by watching every
373           kernel-user boundaries using the context tracking subsystem.
374           The accounting is thus performed at the expense of some significant
375           overhead.
377           For now this is only useful if you are working on the full
378           dynticks subsystem development.
380           If unsure, say N.
383         bool "Fine granularity task level IRQ time accounting"
384         depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
385         help
386           Select this option to enable fine granularity task irq time
387           accounting. This is done by reading a timestamp on each
388           transitions between softirq and hardirq state, so there can be a
389           small performance impact.
391           If in doubt, say N here.
393 endchoice
396         bool "BSD Process Accounting"
397         help
398           If you say Y here, a user level program will be able to instruct the
399           kernel (via a special system call) to write process accounting
400           information to a file: whenever a process exits, information about
401           that process will be appended to the file by the kernel.  The
402           information includes things such as creation time, owning user,
403           command name, memory usage, controlling terminal etc. (the complete
404           list is in the struct acct in <file:include/linux/acct.h>).  It is
405           up to the user level program to do useful things with this
406           information.  This is generally a good idea, so say Y.
408 config BSD_PROCESS_ACCT_V3
409         bool "BSD Process Accounting version 3 file format"
410         depends on BSD_PROCESS_ACCT
411         default n
412         help
413           If you say Y here, the process accounting information is written
414           in a new file format that also logs the process IDs of each
415           process and it's parent. Note that this file format is incompatible
416           with previous v0/v1/v2 file formats, so you will need updated tools
417           for processing it. A preliminary version of these tools is available
418           at <>.
420 config TASKSTATS
421         bool "Export task/process statistics through netlink"
422         depends on NET
423         default n
424         help
425           Export selected statistics for tasks/processes through the
426           generic netlink interface. Unlike BSD process accounting, the
427           statistics are available during the lifetime of tasks/processes as
428           responses to commands. Like BSD accounting, they are sent to user
429           space on task exit.
431           Say N if unsure.
433 config TASK_DELAY_ACCT
434         bool "Enable per-task delay accounting"
435         depends on TASKSTATS
436         help
437           Collect information on time spent by a task waiting for system
438           resources like cpu, synchronous block I/O completion and swapping
439           in pages. Such statistics can help in setting a task's priorities
440           relative to other tasks for cpu, io, rss limits etc.
442           Say N if unsure.
444 config TASK_XACCT
445         bool "Enable extended accounting over taskstats"
446         depends on TASKSTATS
447         help
448           Collect extended task accounting data and send the data
449           to userland for processing over the taskstats interface.
451           Say N if unsure.
454         bool "Enable per-task storage I/O accounting"
455         depends on TASK_XACCT
456         help
457           Collect information on the number of bytes of storage I/O which this
458           task has caused.
460           Say N if unsure.
462 endmenu # "CPU/Task time and stats accounting"
464 menu "RCU Subsystem"
466 choice
467         prompt "RCU Implementation"
468         default TREE_RCU
470 config TREE_RCU
471         bool "Tree-based hierarchical RCU"
472         depends on !PREEMPT && SMP
473         select IRQ_WORK
474         help
475           This option selects the RCU implementation that is
476           designed for very large SMP system with hundreds or
477           thousands of CPUs.  It also scales down nicely to
478           smaller systems.
480 config PREEMPT_RCU
481         bool "Preemptible tree-based hierarchical RCU"
482         depends on PREEMPT
483         select IRQ_WORK
484         help
485           This option selects the RCU implementation that is
486           designed for very large SMP systems with hundreds or
487           thousands of CPUs, but for which real-time response
488           is also required.  It also scales down nicely to
489           smaller systems.
491           Select this option if you are unsure.
493 config TINY_RCU
494         bool "UP-only small-memory-footprint RCU"
495         depends on !PREEMPT && !SMP
496         help
497           This option selects the RCU implementation that is
498           designed for UP systems from which real-time response
499           is not required.  This option greatly reduces the
500           memory footprint of RCU.
502 endchoice
504 config TASKS_RCU
505         bool "Task_based RCU implementation using voluntary context switch"
506         default n
507         help
508           This option enables a task-based RCU implementation that uses
509           only voluntary context switch (not preemption!), idle, and
510           user-mode execution as quiescent states.
512           If unsure, say N.
515         def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
516         help
517           This option enables RCU CPU stall code that is common between
518           the TINY and TREE variants of RCU.  The purpose is to allow
519           the tiny variants to disable RCU CPU stall warnings, while
520           making these warnings mandatory for the tree variants.
523        bool
525 config RCU_USER_QS
526         bool "Consider userspace as in RCU extended quiescent state"
527         depends on HAVE_CONTEXT_TRACKING && SMP
528         select CONTEXT_TRACKING
529         help
530           This option sets hooks on kernel / userspace boundaries and
531           puts RCU in extended quiescent state when the CPU runs in
532           userspace. It means that when a CPU runs in userspace, it is
533           excluded from the global RCU state machine and thus doesn't
534           try to keep the timer tick on for RCU.
536           Unless you want to hack and help the development of the full
537           dynticks mode, you shouldn't enable this option.  It also
538           adds unnecessary overhead.
540           If unsure say N
543         bool "Force context tracking"
544         depends on CONTEXT_TRACKING
545         default y if !NO_HZ_FULL
546         help
547           The major pre-requirement for full dynticks to work is to
548           support the context tracking subsystem. But there are also
549           other dependencies to provide in order to make the full
550           dynticks working.
552           This option stands for testing when an arch implements the
553           context tracking backend but doesn't yet fullfill all the
554           requirements to make the full dynticks feature working.
555           Without the full dynticks, there is no way to test the support
556           for context tracking and the subsystems that rely on it: RCU
557           userspace extended quiescent state and tickless cputime
558           accounting. This option copes with the absence of the full
559           dynticks subsystem by forcing the context tracking on all
560           CPUs in the system.
562           Say Y only if you're working on the development of an
563           architecture backend for the context tracking.
565           Say N otherwise, this option brings an overhead that you
566           don't want in production.
569 config RCU_FANOUT
570         int "Tree-based hierarchical RCU fanout value"
571         range 2 64 if 64BIT
572         range 2 32 if !64BIT
573         depends on TREE_RCU || PREEMPT_RCU
574         default 64 if 64BIT
575         default 32 if !64BIT
576         help
577           This option controls the fanout of hierarchical implementations
578           of RCU, allowing RCU to work efficiently on machines with
579           large numbers of CPUs.  This value must be at least the fourth
580           root of NR_CPUS, which allows NR_CPUS to be insanely large.
581           The default value of RCU_FANOUT should be used for production
582           systems, but if you are stress-testing the RCU implementation
583           itself, small RCU_FANOUT values allow you to test large-system
584           code paths on small(er) systems.
586           Select a specific number if testing RCU itself.
587           Take the default if unsure.
589 config RCU_FANOUT_LEAF
590         int "Tree-based hierarchical RCU leaf-level fanout value"
591         range 2 RCU_FANOUT if 64BIT
592         range 2 RCU_FANOUT if !64BIT
593         depends on TREE_RCU || PREEMPT_RCU
594         default 16
595         help
596           This option controls the leaf-level fanout of hierarchical
597           implementations of RCU, and allows trading off cache misses
598           against lock contention.  Systems that synchronize their
599           scheduling-clock interrupts for energy-efficiency reasons will
600           want the default because the smaller leaf-level fanout keeps
601           lock contention levels acceptably low.  Very large systems
602           (hundreds or thousands of CPUs) will instead want to set this
603           value to the maximum value possible in order to reduce the
604           number of cache misses incurred during RCU's grace-period
605           initialization.  These systems tend to run CPU-bound, and thus
606           are not helped by synchronized interrupts, and thus tend to
607           skew them, which reduces lock contention enough that large
608           leaf-level fanouts work well.
610           Select a specific number if testing RCU itself.
612           Select the maximum permissible value for large systems.
614           Take the default if unsure.
617         bool "Disable tree-based hierarchical RCU auto-balancing"
618         depends on TREE_RCU || PREEMPT_RCU
619         default n
620         help
621           This option forces use of the exact RCU_FANOUT value specified,
622           regardless of imbalances in the hierarchy.  This is useful for
623           testing RCU itself, and might one day be useful on systems with
624           strong NUMA behavior.
626           Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
628           Say N if unsure.
630 config RCU_FAST_NO_HZ
631         bool "Accelerate last non-dyntick-idle CPU's grace periods"
632         depends on NO_HZ_COMMON && SMP
633         default n
634         help
635           This option permits CPUs to enter dynticks-idle state even if
636           they have RCU callbacks queued, and prevents RCU from waking
637           these CPUs up more than roughly once every four jiffies (by
638           default, you can adjust this using the rcutree.rcu_idle_gp_delay
639           parameter), thus improving energy efficiency.  On the other
640           hand, this option increases the duration of RCU grace periods,
641           for example, slowing down synchronize_rcu().
643           Say Y if energy efficiency is critically important, and you
644                 don't care about increased grace-period durations.
646           Say N if you are unsure.
648 config TREE_RCU_TRACE
649         def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
650         select DEBUG_FS
651         help
652           This option provides tracing for the TREE_RCU and
653           PREEMPT_RCU implementations, permitting Makefile to
654           trivially select kernel/rcutree_trace.c.
656 config RCU_BOOST
657         bool "Enable RCU priority boosting"
658         depends on RT_MUTEXES && PREEMPT_RCU
659         default n
660         help
661           This option boosts the priority of preempted RCU readers that
662           block the current preemptible RCU grace period for too long.
663           This option also prevents heavy loads from blocking RCU
664           callback invocation for all flavors of RCU.
666           Say Y here if you are working with real-time apps or heavy loads
667           Say N here if you are unsure.
670         int "Real-time priority to use for RCU worker threads"
671         range 1 99
672         depends on RCU_BOOST
673         default 1
674         help
675           This option specifies the SCHED_FIFO priority value that will be
676           assigned to the rcuc/n and rcub/n threads and is also the value
677           used for RCU_BOOST (if enabled). If you are working with a
678           real-time application that has one or more CPU-bound threads
679           running at a real-time priority level, you should set
680           RCU_KTHREAD_PRIO to a priority higher than the highest-priority
681           real-time CPU-bound application thread.  The default RCU_KTHREAD_PRIO
682           value of 1 is appropriate in the common case, which is real-time
683           applications that do not have any CPU-bound threads.
685           Some real-time applications might not have a single real-time
686           thread that saturates a given CPU, but instead might have
687           multiple real-time threads that, taken together, fully utilize
688           that CPU.  In this case, you should set RCU_KTHREAD_PRIO to
689           a priority higher than the lowest-priority thread that is
690           conspiring to prevent the CPU from running any non-real-time
691           tasks.  For example, if one thread at priority 10 and another
692           thread at priority 5 are between themselves fully consuming
693           the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
694           set to priority 6 or higher.
696           Specify the real-time priority, or take the default if unsure.
698 config RCU_BOOST_DELAY
699         int "Milliseconds to delay boosting after RCU grace-period start"
700         range 0 3000
701         depends on RCU_BOOST
702         default 500
703         help
704           This option specifies the time to wait after the beginning of
705           a given grace period before priority-boosting preempted RCU
706           readers blocking that grace period.  Note that any RCU reader
707           blocking an expedited RCU grace period is boosted immediately.
709           Accept the default if unsure.
711 config RCU_NOCB_CPU
712         bool "Offload RCU callback processing from boot-selected CPUs"
713         depends on TREE_RCU || PREEMPT_RCU
714         default n
715         help
716           Use this option to reduce OS jitter for aggressive HPC or
717           real-time workloads.  It can also be used to offload RCU
718           callback invocation to energy-efficient CPUs in battery-powered
719           asymmetric multiprocessors.
721           This option offloads callback invocation from the set of
722           CPUs specified at boot time by the rcu_nocbs parameter.
723           For each such CPU, a kthread ("rcuox/N") will be created to
724           invoke callbacks, where the "N" is the CPU being offloaded,
725           and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
726           "s" for RCU-sched.  Nothing prevents this kthread from running
727           on the specified CPUs, but (1) the kthreads may be preempted
728           between each callback, and (2) affinity or cgroups can be used
729           to force the kthreads to run on whatever set of CPUs is desired.
731           Say Y here if you want to help to debug reduced OS jitter.
732           Say N here if you are unsure.
734 choice
735         prompt "Build-forced no-CBs CPUs"
736         default RCU_NOCB_CPU_NONE
737         depends on RCU_NOCB_CPU
738         help
739           This option allows no-CBs CPUs (whose RCU callbacks are invoked
740           from kthreads rather than from softirq context) to be specified
741           at build time.  Additional no-CBs CPUs may be specified by
742           the rcu_nocbs= boot parameter.
744 config RCU_NOCB_CPU_NONE
745         bool "No build_forced no-CBs CPUs"
746         help
747           This option does not force any of the CPUs to be no-CBs CPUs.
748           Only CPUs designated by the rcu_nocbs= boot parameter will be
749           no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
750           kthreads whose names begin with "rcuo".  All other CPUs will
751           invoke their own RCU callbacks in softirq context.
753           Select this option if you want to choose no-CBs CPUs at
754           boot time, for example, to allow testing of different no-CBs
755           configurations without having to rebuild the kernel each time.
757 config RCU_NOCB_CPU_ZERO
758         bool "CPU 0 is a build_forced no-CBs CPU"
759         help
760           This option forces CPU 0 to be a no-CBs CPU, so that its RCU
761           callbacks are invoked by a per-CPU kthread whose name begins
762           with "rcuo".  Additional CPUs may be designated as no-CBs
763           CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
764           All other CPUs will invoke their own RCU callbacks in softirq
765           context.
767           Select this if CPU 0 needs to be a no-CBs CPU for real-time
768           or energy-efficiency reasons, but the real reason it exists
769           is to ensure that randconfig testing covers mixed systems.
771 config RCU_NOCB_CPU_ALL
772         bool "All CPUs are build_forced no-CBs CPUs"
773         help
774           This option forces all CPUs to be no-CBs CPUs.  The rcu_nocbs=
775           boot parameter will be ignored.  All CPUs' RCU callbacks will
776           be executed in the context of per-CPU rcuo kthreads created for
777           this purpose.  Assuming that the kthreads whose names start with
778           "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
779           on the remaining CPUs, but might decrease memory locality during
780           RCU-callback invocation, thus potentially degrading throughput.
782           Select this if all CPUs need to be no-CBs CPUs for real-time
783           or energy-efficiency reasons.
785 endchoice
787 endmenu # "RCU Subsystem"
789 config BUILD_BIN2C
790         bool
791         default n
793 config IKCONFIG
794         tristate "Kernel .config support"
795         select BUILD_BIN2C
796         ---help---
797           This option enables the complete Linux kernel ".config" file
798           contents to be saved in the kernel. It provides documentation
799           of which kernel options are used in a running kernel or in an
800           on-disk kernel.  This information can be extracted from the kernel
801           image file with the script scripts/extract-ikconfig and used as
802           input to rebuild the current kernel or to build another kernel.
803           It can also be extracted from a running kernel by reading
804           /proc/config.gz if enabled (below).
806 config IKCONFIG_PROC
807         bool "Enable access to .config through /proc/config.gz"
808         depends on IKCONFIG && PROC_FS
809         ---help---
810           This option enables access to the kernel configuration file
811           through /proc/config.gz.
813 config LOG_BUF_SHIFT
814         int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
815         range 12 21
816         default 17
817         depends on PRINTK
818         help
819           Select the minimal kernel log buffer size as a power of 2.
820           The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
821           parameter, see below. Any higher size also might be forced
822           by "log_buf_len" boot parameter.
824           Examples:
825                      17 => 128 KB
826                      16 => 64 KB
827                      15 => 32 KB
828                      14 => 16 KB
829                      13 =>  8 KB
830                      12 =>  4 KB
833         int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
834         depends on SMP
835         range 0 21
836         default 12 if !BASE_SMALL
837         default 0 if BASE_SMALL
838         depends on PRINTK
839         help
840           This option allows to increase the default ring buffer size
841           according to the number of CPUs. The value defines the contribution
842           of each CPU as a power of 2. The used space is typically only few
843           lines however it might be much more when problems are reported,
844           e.g. backtraces.
846           The increased size means that a new buffer has to be allocated and
847           the original static one is unused. It makes sense only on systems
848           with more CPUs. Therefore this value is used only when the sum of
849           contributions is greater than the half of the default kernel ring
850           buffer as defined by LOG_BUF_SHIFT. The default values are set
851           so that more than 64 CPUs are needed to trigger the allocation.
853           Also this option is ignored when "log_buf_len" kernel parameter is
854           used as it forces an exact (power of two) size of the ring buffer.
856           The number of possible CPUs is used for this computation ignoring
857           hotplugging making the compuation optimal for the the worst case
858           scenerio while allowing a simple algorithm to be used from bootup.
860           Examples shift values and their meaning:
861                      17 => 128 KB for each CPU
862                      16 =>  64 KB for each CPU
863                      15 =>  32 KB for each CPU
864                      14 =>  16 KB for each CPU
865                      13 =>   8 KB for each CPU
866                      12 =>   4 KB for each CPU
868 #
869 # Architectures with an unreliable sched_clock() should select this:
870 #
872         bool
875         bool
877 #
878 # For architectures that want to enable the support for NUMA-affine scheduler
879 # balancing logic:
880 #
882         bool
884 #
885 # For architectures that know their GCC __int128 support is sound
886 #
887 config ARCH_SUPPORTS_INT128
888         bool
890 # For architectures that (ab)use NUMA to represent different memory regions
891 # all cpu-local but of different latencies, such as SuperH.
892 #
894         bool
897         bool "Memory placement aware NUMA scheduler"
898         depends on ARCH_SUPPORTS_NUMA_BALANCING
899         depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
900         depends on SMP && NUMA && MIGRATION
901         help
902           This option adds support for automatic NUMA aware memory/task placement.
903           The mechanism is quite primitive and is based on migrating memory when
904           it has references to the node the task is running on.
906           This system will be inactive on UMA systems.
909         bool "Automatically enable NUMA aware memory/task placement"
910         default y
911         depends on NUMA_BALANCING
912         help
913           If set, automatic NUMA balancing will be enabled if running on a NUMA
914           machine.
916 menuconfig CGROUPS
917         boolean "Control Group support"
918         select KERNFS
919         help
920           This option adds support for grouping sets of processes together, for
921           use with process control subsystems such as Cpusets, CFS, memory
922           controls or device isolation.
923           See
924                 - Documentation/scheduler/sched-design-CFS.txt  (CFS)
925                 - Documentation/cgroups/ (features for grouping, isolation
926                                           and resource control)
928           Say N if unsure.
930 if CGROUPS
932 config CGROUP_DEBUG
933         bool "Example debug cgroup subsystem"
934         default n
935         help
936           This option enables a simple cgroup subsystem that
937           exports useful debugging information about the cgroups
938           framework.
940           Say N if unsure.
943         bool "Freezer cgroup subsystem"
944         help
945           Provides a way to freeze and unfreeze all tasks in a
946           cgroup.
948 config CGROUP_DEVICE
949         bool "Device controller for cgroups"
950         help
951           Provides a cgroup implementing whitelists for devices which
952           a process in the cgroup can mknod or open.
954 config CPUSETS
955         bool "Cpuset support"
956         help
957           This option will let you create and manage CPUSETs which
958           allow dynamically partitioning a system into sets of CPUs and
959           Memory Nodes and assigning tasks to run only within those sets.
960           This is primarily useful on large SMP or NUMA systems.
962           Say N if unsure.
964 config PROC_PID_CPUSET
965         bool "Include legacy /proc/<pid>/cpuset file"
966         depends on CPUSETS
967         default y
970         bool "Simple CPU accounting cgroup subsystem"
971         help
972           Provides a simple Resource Controller for monitoring the
973           total CPU consumed by the tasks in a cgroup.
975 config PAGE_COUNTER
976        bool
978 config MEMCG
979         bool "Memory Resource Controller for Control Groups"
980         select PAGE_COUNTER
981         select EVENTFD
982         help
983           Provides a memory resource controller that manages both anonymous
984           memory and page cache. (See Documentation/cgroups/memory.txt)
986 config MEMCG_SWAP
987         bool "Memory Resource Controller Swap Extension"
988         depends on MEMCG && SWAP
989         help
990           Add swap management feature to memory resource controller. When you
991           enable this, you can limit mem+swap usage per cgroup. In other words,
992           when you disable this, memory resource controller has no cares to
993           usage of swap...a process can exhaust all of the swap. This extension
994           is useful when you want to avoid exhaustion swap but this itself
995           adds more overheads and consumes memory for remembering information.
996           Especially if you use 32bit system or small memory system, please
997           be careful about enabling this. When memory resource controller
998           is disabled by boot option, this will be automatically disabled and
999           there will be no overhead from this. Even when you set this config=y,
1000           if boot option "swapaccount=0" is set, swap will not be accounted.
1001           Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
1002           size is 4096bytes, 512k per 1Gbytes of swap.
1004         bool "Memory Resource Controller Swap Extension enabled by default"
1005         depends on MEMCG_SWAP
1006         default y
1007         help
1008           Memory Resource Controller Swap Extension comes with its price in
1009           a bigger memory consumption. General purpose distribution kernels
1010           which want to enable the feature but keep it disabled by default
1011           and let the user enable it by swapaccount=1 boot command line
1012           parameter should have this option unselected.
1013           For those who want to have the feature enabled by default should
1014           select this option (if, for some reason, they need to disable it
1015           then swapaccount=0 does the trick).
1016 config MEMCG_KMEM
1017         bool "Memory Resource Controller Kernel Memory accounting"
1018         depends on MEMCG
1019         depends on SLUB || SLAB
1020         help
1021           The Kernel Memory extension for Memory Resource Controller can limit
1022           the amount of memory used by kernel objects in the system. Those are
1023           fundamentally different from the entities handled by the standard
1024           Memory Controller, which are page-based, and can be swapped. Users of
1025           the kmem extension can use it to guarantee that no group of processes
1026           will ever exhaust kernel resources alone.
1028           WARNING: Current implementation lacks reclaim support. That means
1029           allocation attempts will fail when close to the limit even if there
1030           are plenty of kmem available for reclaim. That makes this option
1031           unusable in real life so DO NOT SELECT IT unless for development
1032           purposes.
1034 config CGROUP_HUGETLB
1035         bool "HugeTLB Resource Controller for Control Groups"
1036         depends on HUGETLB_PAGE
1037         select PAGE_COUNTER
1038         default n
1039         help
1040           Provides a cgroup Resource Controller for HugeTLB pages.
1041           When you enable this, you can put a per cgroup limit on HugeTLB usage.
1042           The limit is enforced during page fault. Since HugeTLB doesn't
1043           support page reclaim, enforcing the limit at page fault time implies
1044           that, the application will get SIGBUS signal if it tries to access
1045           HugeTLB pages beyond its limit. This requires the application to know
1046           beforehand how much HugeTLB pages it would require for its use. The
1047           control group is tracked in the third page lru pointer. This means
1048           that we cannot use the controller with huge page less than 3 pages.
1050 config CGROUP_PERF
1051         bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1052         depends on PERF_EVENTS && CGROUPS
1053         help
1054           This option extends the per-cpu mode to restrict monitoring to
1055           threads which belong to the cgroup specified and run on the
1056           designated cpu.
1058           Say N if unsure.
1060 menuconfig CGROUP_SCHED
1061         bool "Group CPU scheduler"
1062         default n
1063         help
1064           This feature lets CPU scheduler recognize task groups and control CPU
1065           bandwidth allocation to such task groups. It uses cgroups to group
1066           tasks.
1069 config FAIR_GROUP_SCHED
1070         bool "Group scheduling for SCHED_OTHER"
1071         depends on CGROUP_SCHED
1072         default CGROUP_SCHED
1074 config CFS_BANDWIDTH
1075         bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1076         depends on FAIR_GROUP_SCHED
1077         default n
1078         help
1079           This option allows users to define CPU bandwidth rates (limits) for
1080           tasks running within the fair group scheduler.  Groups with no limit
1081           set are considered to be unconstrained and will run with no
1082           restriction.
1083           See tip/Documentation/scheduler/sched-bwc.txt for more information.
1085 config RT_GROUP_SCHED
1086         bool "Group scheduling for SCHED_RR/FIFO"
1087         depends on CGROUP_SCHED
1088         default n
1089         help
1090           This feature lets you explicitly allocate real CPU bandwidth
1091           to task groups. If enabled, it will also make it impossible to
1092           schedule realtime tasks for non-root users until you allocate
1093           realtime bandwidth for them.
1094           See Documentation/scheduler/sched-rt-group.txt for more information.
1096 endif #CGROUP_SCHED
1098 config BLK_CGROUP
1099         bool "Block IO controller"
1100         depends on BLOCK
1101         default n
1102         ---help---
1103         Generic block IO controller cgroup interface. This is the common
1104         cgroup interface which should be used by various IO controlling
1105         policies.
1107         Currently, CFQ IO scheduler uses it to recognize task groups and
1108         control disk bandwidth allocation (proportional time slice allocation)
1109         to such task groups. It is also used by bio throttling logic in
1110         block layer to implement upper limit in IO rates on a device.
1112         This option only enables generic Block IO controller infrastructure.
1113         One needs to also enable actual IO controlling logic/policy. For
1114         enabling proportional weight division of disk bandwidth in CFQ, set
1115         CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1118         See Documentation/cgroups/blkio-controller.txt for more information.
1120 config DEBUG_BLK_CGROUP
1121         bool "Enable Block IO controller debugging"
1122         depends on BLK_CGROUP
1123         default n
1124         ---help---
1125         Enable some debugging help. Currently it exports additional stat
1126         files in a cgroup which can be useful for debugging.
1128 endif # CGROUPS
1131         bool "Checkpoint/restore support" if EXPERT
1132         default n
1133         help
1134           Enables additional kernel features in a sake of checkpoint/restore.
1135           In particular it adds auxiliary prctl codes to setup process text,
1136           data and heap segment sizes, and a few additional /proc filesystem
1137           entries.
1139           If unsure, say N here.
1141 menuconfig NAMESPACES
1142         bool "Namespaces support" if EXPERT
1143         default !EXPERT
1144         help
1145           Provides the way to make tasks work with different objects using
1146           the same id. For example same IPC id may refer to different objects
1147           or same user id or pid may refer to different tasks when used in
1148           different namespaces.
1152 config UTS_NS
1153         bool "UTS namespace"
1154         default y
1155         help
1156           In this namespace tasks see different info provided with the
1157           uname() system call
1159 config IPC_NS
1160         bool "IPC namespace"
1161         depends on (SYSVIPC || POSIX_MQUEUE)
1162         default y
1163         help
1164           In this namespace tasks work with IPC ids which correspond to
1165           different IPC objects in different namespaces.
1167 config USER_NS
1168         bool "User namespace"
1169         default n
1170         help
1171           This allows containers, i.e. vservers, to use user namespaces
1172           to provide different user info for different servers.
1174           When user namespaces are enabled in the kernel it is
1175           recommended that the MEMCG and MEMCG_KMEM options also be
1176           enabled and that user-space use the memory control groups to
1177           limit the amount of memory a memory unprivileged users can
1178           use.
1180           If unsure, say N.
1182 config PID_NS
1183         bool "PID Namespaces"
1184         default y
1185         help
1186           Support process id namespaces.  This allows having multiple
1187           processes with the same pid as long as they are in different
1188           pid namespaces.  This is a building block of containers.
1190 config NET_NS
1191         bool "Network namespace"
1192         depends on NET
1193         default y
1194         help
1195           Allow user space to create what appear to be multiple instances
1196           of the network stack.
1198 endif # NAMESPACES
1201         bool "Automatic process group scheduling"
1202         select CGROUPS
1203         select CGROUP_SCHED
1204         select FAIR_GROUP_SCHED
1205         help
1206           This option optimizes the scheduler for common desktop workloads by
1207           automatically creating and populating task groups.  This separation
1208           of workloads isolates aggressive CPU burners (like build jobs) from
1209           desktop applications.  Task group autogeneration is currently based
1210           upon task session.
1213         bool "Enable deprecated sysfs features to support old userspace tools"
1214         depends on SYSFS
1215         default n
1216         help
1217           This option adds code that switches the layout of the "block" class
1218           devices, to not show up in /sys/class/block/, but only in
1219           /sys/block/.
1221           This switch is only active when the sysfs.deprecated=1 boot option is
1222           passed or the SYSFS_DEPRECATED_V2 option is set.
1224           This option allows new kernels to run on old distributions and tools,
1225           which might get confused by /sys/class/block/. Since 2007/2008 all
1226           major distributions and tools handle this just fine.
1228           Recent distributions and userspace tools after 2009/2010 depend on
1229           the existence of /sys/class/block/, and will not work with this
1230           option enabled.
1232           Only if you are using a new kernel on an old distribution, you might
1233           need to say Y here.
1236         bool "Enable deprecated sysfs features by default"
1237         default n
1238         depends on SYSFS
1239         depends on SYSFS_DEPRECATED
1240         help
1241           Enable deprecated sysfs by default.
1243           See the CONFIG_SYSFS_DEPRECATED option for more details about this
1244           option.
1246           Only if you are using a new kernel on an old distribution, you might
1247           need to say Y here. Even then, odds are you would not need it
1248           enabled, you can always pass the boot option if absolutely necessary.
1250 config RELAY
1251         bool "Kernel->user space relay support (formerly relayfs)"
1252         help
1253           This option enables support for relay interface support in
1254           certain file systems (such as debugfs).
1255           It is designed to provide an efficient mechanism for tools and
1256           facilities to relay large amounts of data from kernel space to
1257           user space.
1259           If unsure, say N.
1261 config BLK_DEV_INITRD
1262         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1263         depends on BROKEN || !FRV
1264         help
1265           The initial RAM filesystem is a ramfs which is loaded by the
1266           boot loader (loadlin or lilo) and that is mounted as root
1267           before the normal boot procedure. It is typically used to
1268           load modules needed to mount the "real" root file system,
1269           etc. See <file:Documentation/initrd.txt> for details.
1271           If RAM disk support (BLK_DEV_RAM) is also included, this
1272           also enables initial RAM disk (initrd) support and adds
1273           15 Kbytes (more on some other architectures) to the kernel size.
1275           If unsure say Y.
1279 source "usr/Kconfig"
1281 endif
1283 config INIT_FALLBACK
1284         bool "Fall back to defaults if init= parameter is bad"
1285         default y
1286         help
1287           If enabled, the kernel will try the default init binaries if an
1288           explicit request from the init= parameter fails.
1290           This can have unexpected effects.  For example, booting
1291           with init=/sbin/kiosk_app will run /sbin/init or even /bin/sh
1292           if /sbin/kiosk_app cannot be executed.
1294           The default value of Y is consistent with historical behavior.
1295           Selecting N is likely to be more appropriate for most uses,
1296           especially on kiosks and on kernels that are intended to be
1297           run under the control of a script.
1300         bool "Optimize for size"
1301         help
1302           Enabling this option will pass "-Os" instead of "-O2" to gcc
1303           resulting in a smaller kernel.
1305           If unsure, say N.
1307 config SYSCTL
1308         bool
1310 config ANON_INODES
1311         bool
1313 config HAVE_UID16
1314         bool
1317         bool
1318         help
1319           Enable support for /proc/sys/debug/exception-trace.
1322         bool
1323         help
1324           Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1325           Allows arch to define/use @no_unaligned_warning to possibly warn
1326           about unaligned access emulation going on under the hood.
1329         bool
1330         help
1331           Enable support for /proc/sys/kernel/unaligned-trap
1332           Allows arches to define/use @unaligned_enabled to runtime toggle
1333           the unaligned access emulation.
1334           see arch/parisc/kernel/unaligned.c for reference
1337         bool
1339 # interpreter that classic socket filters depend on
1340 config BPF
1341         bool
1343 menuconfig EXPERT
1344         bool "Configure standard kernel features (expert users)"
1345         # Unhide debug options, to make the on-by-default options visible
1346         select DEBUG_KERNEL
1347         help
1348           This option allows certain base kernel options and settings
1349           to be disabled or tweaked. This is for specialized
1350           environments which can tolerate a "non-standard" kernel.
1351           Only use this if you really know what you are doing.
1353 config UID16
1354         bool "Enable 16-bit UID system calls" if EXPERT
1355         depends on HAVE_UID16
1356         default y
1357         help
1358           This enables the legacy 16-bit UID syscall wrappers.
1361         bool "sgetmask/ssetmask syscalls support" if EXPERT
1362         def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1363         ---help---
1364           sys_sgetmask and sys_ssetmask are obsolete system calls
1365           no longer supported in libc but still enabled by default in some
1366           architectures.
1368           If unsure, leave the default option here.
1370 config SYSFS_SYSCALL
1371         bool "Sysfs syscall support" if EXPERT
1372         default y
1373         ---help---
1374           sys_sysfs is an obsolete system call no longer supported in libc.
1375           Note that disabling this option is more secure but might break
1376           compatibility with some systems.
1378           If unsure say Y here.
1380 config SYSCTL_SYSCALL
1381         bool "Sysctl syscall support" if EXPERT
1382         depends on PROC_SYSCTL
1383         default n
1384         select SYSCTL
1385         ---help---
1386           sys_sysctl uses binary paths that have been found challenging
1387           to properly maintain and use.  The interface in /proc/sys
1388           using paths with ascii names is now the primary path to this
1389           information.
1391           Almost nothing using the binary sysctl interface so if you are
1392           trying to save some space it is probably safe to disable this,
1393           making your kernel marginally smaller.
1395           If unsure say N here.
1397 config KALLSYMS
1398          bool "Load all symbols for debugging/ksymoops" if EXPERT
1399          default y
1400          help
1401            Say Y here to let the kernel print out symbolic crash information and
1402            symbolic stack backtraces. This increases the size of the kernel
1403            somewhat, as all symbols have to be loaded into the kernel image.
1405 config KALLSYMS_ALL
1406         bool "Include all symbols in kallsyms"
1407         depends on DEBUG_KERNEL && KALLSYMS
1408         help
1409            Normally kallsyms only contains the symbols of functions for nicer
1410            OOPS messages and backtraces (i.e., symbols from the text and inittext
1411            sections). This is sufficient for most cases. And only in very rare
1412            cases (e.g., when a debugger is used) all symbols are required (e.g.,
1413            names of variables from the data sections, etc).
1415            This option makes sure that all symbols are loaded into the kernel
1416            image (i.e., symbols from all sections) in cost of increased kernel
1417            size (depending on the kernel configuration, it may be 300KiB or
1418            something like this).
1420            Say N unless you really need all symbols.
1422 config PRINTK
1423         default y
1424         bool "Enable support for printk" if EXPERT
1425         select IRQ_WORK
1426         help
1427           This option enables normal printk support. Removing it
1428           eliminates most of the message strings from the kernel image
1429           and makes the kernel more or less silent. As this makes it
1430           very difficult to diagnose system problems, saying N here is
1431           strongly discouraged.
1433 config BUG
1434         bool "BUG() support" if EXPERT
1435         default y
1436         help
1437           Disabling this option eliminates support for BUG and WARN, reducing
1438           the size of your kernel image and potentially quietly ignoring
1439           numerous fatal conditions. You should only consider disabling this
1440           option for embedded systems with no facilities for reporting errors.
1441           Just say Y.
1443 config ELF_CORE
1444         depends on COREDUMP
1445         default y
1446         bool "Enable ELF core dumps" if EXPERT
1447         help
1448           Enable support for generating core dumps. Disabling saves about 4k.
1452         bool "Enable PC-Speaker support" if EXPERT
1453         depends on HAVE_PCSPKR_PLATFORM
1454         select I8253_LOCK
1455         default y
1456         help
1457           This option allows to disable the internal PC-Speaker
1458           support, saving some memory.
1460 config BASE_FULL
1461         default y
1462         bool "Enable full-sized data structures for core" if EXPERT
1463         help
1464           Disabling this option reduces the size of miscellaneous core
1465           kernel data structures. This saves memory on small machines,
1466           but may reduce performance.
1468 config FUTEX
1469         bool "Enable futex support" if EXPERT
1470         default y
1471         select RT_MUTEXES
1472         help
1473           Disabling this option will cause the kernel to be built without
1474           support for "fast userspace mutexes".  The resulting kernel may not
1475           run glibc-based applications correctly.
1478         bool
1479         depends on FUTEX
1480         help
1481           Architectures should select this if futex_atomic_cmpxchg_inatomic()
1482           is implemented and always working. This removes a couple of runtime
1483           checks.
1485 config EPOLL
1486         bool "Enable eventpoll support" if EXPERT
1487         default y
1488         select ANON_INODES
1489         help
1490           Disabling this option will cause the kernel to be built without
1491           support for epoll family of system calls.
1493 config SIGNALFD
1494         bool "Enable signalfd() system call" if EXPERT
1495         select ANON_INODES
1496         default y
1497         help
1498           Enable the signalfd() system call that allows to receive signals
1499           on a file descriptor.
1501           If unsure, say Y.
1503 config TIMERFD
1504         bool "Enable timerfd() system call" if EXPERT
1505         select ANON_INODES
1506         default y
1507         help
1508           Enable the timerfd() system call that allows to receive timer
1509           events on a file descriptor.
1511           If unsure, say Y.
1513 config EVENTFD
1514         bool "Enable eventfd() system call" if EXPERT
1515         select ANON_INODES
1516         default y
1517         help
1518           Enable the eventfd() system call that allows to receive both
1519           kernel notification (ie. KAIO) or userspace notifications.
1521           If unsure, say Y.
1523 # syscall, maps, verifier
1524 config BPF_SYSCALL
1525         bool "Enable bpf() system call" if EXPERT
1526         select ANON_INODES
1527         select BPF
1528         default n
1529         help
1530           Enable the bpf() system call that allows to manipulate eBPF
1531           programs and maps via file descriptors.
1533 config SHMEM
1534         bool "Use full shmem filesystem" if EXPERT
1535         default y
1536         depends on MMU
1537         help
1538           The shmem is an internal filesystem used to manage shared memory.
1539           It is backed by swap and manages resource limits. It is also exported
1540           to userspace as tmpfs if TMPFS is enabled. Disabling this
1541           option replaces shmem and tmpfs with the much simpler ramfs code,
1542           which may be appropriate on small systems without swap.
1544 config AIO
1545         bool "Enable AIO support" if EXPERT
1546         default y
1547         help
1548           This option enables POSIX asynchronous I/O which may by used
1549           by some high performance threaded applications. Disabling
1550           this option saves about 7k.
1553         bool "Enable madvise/fadvise syscalls" if EXPERT
1554         default y
1555         help
1556           This option enables the madvise and fadvise syscalls, used by
1557           applications to advise the kernel about their future memory or file
1558           usage, improving performance. If building an embedded system where no
1559           applications use these syscalls, you can disable this option to save
1560           space.
1562 config PCI_QUIRKS
1563         default y
1564         bool "Enable PCI quirk workarounds" if EXPERT
1565         depends on PCI
1566         help
1567           This enables workarounds for various PCI chipset
1568           bugs/quirks. Disable this only if your target machine is
1569           unaffected by PCI quirks.
1571 config EMBEDDED
1572         bool "Embedded system"
1573         option allnoconfig_y
1574         select EXPERT
1575         help
1576           This option should be enabled if compiling the kernel for
1577           an embedded system so certain expert options are available
1578           for configuration.
1580 config HAVE_PERF_EVENTS
1581         bool
1582         help
1583           See tools/perf/design.txt for details.
1585 config PERF_USE_VMALLOC
1586         bool
1587         help
1588           See tools/perf/design.txt for details
1590 menu "Kernel Performance Events And Counters"
1592 config PERF_EVENTS
1593         bool "Kernel performance events and counters"
1594         default y if PROFILING
1595         depends on HAVE_PERF_EVENTS
1596         select ANON_INODES
1597         select IRQ_WORK
1598         help
1599           Enable kernel support for various performance events provided
1600           by software and hardware.
1602           Software events are supported either built-in or via the
1603           use of generic tracepoints.
1605           Most modern CPUs support performance events via performance
1606           counter registers. These registers count the number of certain
1607           types of hw events: such as instructions executed, cachemisses
1608           suffered, or branches mis-predicted - without slowing down the
1609           kernel or applications. These registers can also trigger interrupts
1610           when a threshold number of events have passed - and can thus be
1611           used to profile the code that runs on that CPU.
1613           The Linux Performance Event subsystem provides an abstraction of
1614           these software and hardware event capabilities, available via a
1615           system call and used by the "perf" utility in tools/perf/. It
1616           provides per task and per CPU counters, and it provides event
1617           capabilities on top of those.
1619           Say Y if unsure.
1622         default n
1623         bool "Debug: use vmalloc to back perf mmap() buffers"
1624         depends on PERF_EVENTS && DEBUG_KERNEL
1625         select PERF_USE_VMALLOC
1626         help
1627          Use vmalloc memory to back perf mmap() buffers.
1629          Mostly useful for debugging the vmalloc code on platforms
1630          that don't require it.
1632          Say N if unsure.
1634 endmenu
1637         default y
1638         bool "Enable VM event counters for /proc/vmstat" if EXPERT
1639         help
1640           VM event counters are needed for event counts to be shown.
1641           This option allows the disabling of the VM event counters
1642           on EXPERT systems.  /proc/vmstat will only show page counts
1643           if VM event counters are disabled.
1645 config SLUB_DEBUG
1646         default y
1647         bool "Enable SLUB debugging support" if EXPERT
1648         depends on SLUB && SYSFS
1649         help
1650           SLUB has extensive debug support features. Disabling these can
1651           result in significant savings in code size. This also disables
1652           SLUB sysfs support. /sys/slab will not exist and there will be
1653           no support for cache validation etc.
1655 config COMPAT_BRK
1656         bool "Disable heap randomization"
1657         default y
1658         help
1659           Randomizing heap placement makes heap exploits harder, but it
1660           also breaks ancient binaries (including anything libc5 based).
1661           This option changes the bootup default to heap randomization
1662           disabled, and can be overridden at runtime by setting
1663           /proc/sys/kernel/randomize_va_space to 2.
1665           On non-ancient distros (post-2000 ones) N is usually a safe choice.
1667 choice
1668         prompt "Choose SLAB allocator"
1669         default SLUB
1670         help
1671            This option allows to select a slab allocator.
1673 config SLAB
1674         bool "SLAB"
1675         help
1676           The regular slab allocator that is established and known to work
1677           well in all environments. It organizes cache hot objects in
1678           per cpu and per node queues.
1680 config SLUB
1681         bool "SLUB (Unqueued Allocator)"
1682         help
1683            SLUB is a slab allocator that minimizes cache line usage
1684            instead of managing queues of cached objects (SLAB approach).
1685            Per cpu caching is realized using slabs of objects instead
1686            of queues of objects. SLUB can use memory efficiently
1687            and has enhanced diagnostics. SLUB is the default choice for
1688            a slab allocator.
1690 config SLOB
1691         depends on EXPERT
1692         bool "SLOB (Simple Allocator)"
1693         help
1694            SLOB replaces the stock allocator with a drastically simpler
1695            allocator. SLOB is generally more space efficient but
1696            does not perform as well on large systems.
1698 endchoice
1700 config SLUB_CPU_PARTIAL
1701         default y
1702         depends on SLUB && SMP
1703         bool "SLUB per cpu partial cache"
1704         help
1705           Per cpu partial caches accellerate objects allocation and freeing
1706           that is local to a processor at the price of more indeterminism
1707           in the latency of the free. On overflow these caches will be cleared
1708           which requires the taking of locks that may cause latency spikes.
1709           Typically one would choose no for a realtime system.
1712         bool "Allow mmapped anonymous memory to be uninitialized"
1713         depends on EXPERT && !MMU
1714         default n
1715         help
1716           Normally, and according to the Linux spec, anonymous memory obtained
1717           from mmap() has it's contents cleared before it is passed to
1718           userspace.  Enabling this config option allows you to request that
1719           mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1720           providing a huge performance boost.  If this option is not enabled,
1721           then the flag will be ignored.
1723           This is taken advantage of by uClibc's malloc(), and also by
1724           ELF-FDPIC binfmt's brk and stack allocator.
1726           Because of the obvious security issues, this option should only be
1727           enabled on embedded devices where you control what is run in
1728           userspace.  Since that isn't generally a problem on no-MMU systems,
1729           it is normally safe to say Y here.
1731           See Documentation/nommu-mmap.txt for more information.
1734         bool "Provide system-wide ring of trusted keys"
1735         depends on KEYS
1736         help
1737           Provide a system keyring to which trusted keys can be added.  Keys in
1738           the keyring are considered to be trusted.  Keys may be added at will
1739           by the kernel from compiled-in data and from hardware key stores, but
1740           userspace may only add extra keys if those keys can be verified by
1741           keys already in the keyring.
1743           Keys in this keyring are used by module signature checking.
1745 config PROFILING
1746         bool "Profiling support"
1747         help
1748           Say Y here to enable the extended profiling support mechanisms used
1749           by profilers such as OProfile.
1751 #
1752 # Place an empty function call at each tracepoint site. Can be
1753 # dynamically changed for a probe function.
1754 #
1755 config TRACEPOINTS
1756         bool
1758 source "arch/Kconfig"
1760 endmenu         # General setup
1763         bool
1764         default n
1766 config SLABINFO
1767         bool
1768         depends on PROC_FS
1769         depends on SLAB || SLUB_DEBUG
1770         default y
1772 config RT_MUTEXES
1773         boolean
1775 config BASE_SMALL
1776         int
1777         default 0 if BASE_FULL
1778         default 1 if !BASE_FULL
1780 menuconfig MODULES
1781         bool "Enable loadable module support"
1782         option modules
1783         help
1784           Kernel modules are small pieces of compiled code which can
1785           be inserted in the running kernel, rather than being
1786           permanently built into the kernel.  You use the "modprobe"
1787           tool to add (and sometimes remove) them.  If you say Y here,
1788           many parts of the kernel can be built as modules (by
1789           answering M instead of Y where indicated): this is most
1790           useful for infrequently used options which are not required
1791           for booting.  For more information, see the man pages for
1792           modprobe, lsmod, modinfo, insmod and rmmod.
1794           If you say Y here, you will need to run "make
1795           modules_install" to put the modules under /lib/modules/
1796           where modprobe can find them (you may need to be root to do
1797           this).
1799           If unsure, say Y.
1801 if MODULES
1804         bool "Forced module loading"
1805         default n
1806         help
1807           Allow loading of modules without version information (ie. modprobe
1808           --force).  Forced module loading sets the 'F' (forced) taint flag and
1809           is usually a really bad idea.
1811 config MODULE_UNLOAD
1812         bool "Module unloading"
1813         help
1814           Without this option you will not be able to unload any
1815           modules (note that some modules may not be unloadable
1816           anyway), which makes your kernel smaller, faster
1817           and simpler.  If unsure, say Y.
1820         bool "Forced module unloading"
1821         depends on MODULE_UNLOAD
1822         help
1823           This option allows you to force a module to unload, even if the
1824           kernel believes it is unsafe: the kernel will remove the module
1825           without waiting for anyone to stop using it (using the -f option to
1826           rmmod).  This is mainly for kernel developers and desperate users.
1827           If unsure, say N.
1829 config MODVERSIONS
1830         bool "Module versioning support"
1831         help
1832           Usually, you have to use modules compiled with your kernel.
1833           Saying Y here makes it sometimes possible to use modules
1834           compiled for different kernels, by adding enough information
1835           to the modules to (hopefully) spot any changes which would
1836           make them incompatible with the kernel you are running.  If
1837           unsure, say N.
1840         bool "Source checksum for all modules"
1841         help
1842           Modules which contain a MODULE_VERSION get an extra "srcversion"
1843           field inserted into their modinfo section, which contains a
1844           sum of the source files which made it.  This helps maintainers
1845           see exactly which source was used to build a module (since
1846           others sometimes change the module source without updating
1847           the version).  With this option, such a "srcversion" field
1848           will be created for all modules.  If unsure, say N.
1850 config MODULE_SIG
1851         bool "Module signature verification"
1852         depends on MODULES
1853         select SYSTEM_TRUSTED_KEYRING
1854         select KEYS
1855         select CRYPTO
1856         select ASYMMETRIC_KEY_TYPE
1858         select PUBLIC_KEY_ALGO_RSA
1859         select ASN1
1860         select OID_REGISTRY
1861         select X509_CERTIFICATE_PARSER
1862         help
1863           Check modules for valid signatures upon load: the signature
1864           is simply appended to the module. For more information see
1865           Documentation/module-signing.txt.
1867           !!!WARNING!!!  If you enable this option, you MUST make sure that the
1868           module DOES NOT get stripped after being signed.  This includes the
1869           debuginfo strip done by some packagers (such as rpmbuild) and
1870           inclusion into an initramfs that wants the module size reduced.
1872 config MODULE_SIG_FORCE
1873         bool "Require modules to be validly signed"
1874         depends on MODULE_SIG
1875         help
1876           Reject unsigned modules or signed modules for which we don't have a
1877           key.  Without this, such modules will simply taint the kernel.
1879 config MODULE_SIG_ALL
1880         bool "Automatically sign all modules"
1881         default y
1882         depends on MODULE_SIG
1883         help
1884           Sign all modules during make modules_install. Without this option,
1885           modules must be signed manually, using the scripts/sign-file tool.
1887 comment "Do not forget to sign required modules with scripts/sign-file"
1888         depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1890 choice
1891         prompt "Which hash algorithm should modules be signed with?"
1892         depends on MODULE_SIG
1893         help
1894           This determines which sort of hashing algorithm will be used during
1895           signature generation.  This algorithm _must_ be built into the kernel
1896           directly so that signature verification can take place.  It is not
1897           possible to load a signed module containing the algorithm to check
1898           the signature on that module.
1900 config MODULE_SIG_SHA1
1901         bool "Sign modules with SHA-1"
1902         select CRYPTO_SHA1
1904 config MODULE_SIG_SHA224
1905         bool "Sign modules with SHA-224"
1906         select CRYPTO_SHA256
1908 config MODULE_SIG_SHA256
1909         bool "Sign modules with SHA-256"
1910         select CRYPTO_SHA256
1912 config MODULE_SIG_SHA384
1913         bool "Sign modules with SHA-384"
1914         select CRYPTO_SHA512
1916 config MODULE_SIG_SHA512
1917         bool "Sign modules with SHA-512"
1918         select CRYPTO_SHA512
1920 endchoice
1922 config MODULE_SIG_HASH
1923         string
1924         depends on MODULE_SIG
1925         default "sha1" if MODULE_SIG_SHA1
1926         default "sha224" if MODULE_SIG_SHA224
1927         default "sha256" if MODULE_SIG_SHA256
1928         default "sha384" if MODULE_SIG_SHA384
1929         default "sha512" if MODULE_SIG_SHA512
1932         bool "Compress modules on installation"
1933         depends on MODULES
1934         help
1935           This option compresses the kernel modules when 'make
1936           modules_install' is run.
1938           The modules will be compressed either using gzip or xz depend on the
1939           choice made in "Compression algorithm".
1941           module-init-tools has support for gzip format while kmod handle gzip
1942           and xz compressed modules.
1944           When a kernel module is installed from outside of the main kernel
1945           source and uses the Kbuild system for installing modules then that
1946           kernel module will also be compressed when it is installed.
1948           This option provides little benefit when the modules are to be used inside
1949           an initrd or initramfs, it generally is more efficient to compress the whole
1950           initrd or initramfs instead.
1952           This is fully compatible with signed modules while the signed module is
1953           compressed. module-init-tools or kmod handles decompression and provide to
1954           other layer the uncompressed but signed payload.
1956 choice
1957         prompt "Compression algorithm"
1958         depends on MODULE_COMPRESS
1959         default MODULE_COMPRESS_GZIP
1960         help
1961           This determines which sort of compression will be used during
1962           'make modules_install'.
1964           GZIP (default) and XZ are supported.
1967         bool "GZIP"
1970         bool "XZ"
1972 endchoice
1974 endif # MODULES
1977         bool
1978         help
1979           Back when each arch used to define their own cpu_online_mask and
1980           cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1981           with all 1s, and others with all 0s.  When they were centralised,
1982           it was better to provide this option than to break all the archs
1983           and have several arch maintainers pursuing me down dark alleys.
1985 config STOP_MACHINE
1986         bool
1987         default y
1988         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1989         help
1990           Need stop_machine() primitive.
1992 source "block/Kconfig"
1995         bool
1997 config PADATA
1998         depends on SMP
1999         bool
2001 # Can be selected by architectures with broken toolchains
2002 # that get confused by correct const<->read_only section
2003 # mappings
2004 config BROKEN_RODATA
2005         bool
2007 config ASN1
2008         tristate
2009         help
2010           Build a simple ASN.1 grammar compiler that produces a bytecode output
2011           that can be interpreted by the ASN.1 stream decoder and used to
2012           inform it as to what tags are to be expected in a stream and what
2013           functions to call on what tags.
2015 source "kernel/Kconfig.locks"

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