Version:  2.0.40 2.2.26 2.4.37 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 4.0


  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         help
474           This option selects the RCU implementation that is
475           designed for very large SMP system with hundreds or
476           thousands of CPUs.  It also scales down nicely to
477           smaller systems.
479 config PREEMPT_RCU
480         bool "Preemptible tree-based hierarchical RCU"
481         depends on PREEMPT
482         help
483           This option selects the RCU implementation that is
484           designed for very large SMP systems with hundreds or
485           thousands of CPUs, but for which real-time response
486           is also required.  It also scales down nicely to
487           smaller systems.
489           Select this option if you are unsure.
491 config TINY_RCU
492         bool "UP-only small-memory-footprint RCU"
493         depends on !PREEMPT && !SMP
494         help
495           This option selects the RCU implementation that is
496           designed for UP systems from which real-time response
497           is not required.  This option greatly reduces the
498           memory footprint of RCU.
500 endchoice
502 config SRCU
503         bool
504         help
505           This option selects the sleepable version of RCU. This version
506           permits arbitrary sleeping or blocking within RCU read-side critical
507           sections.
509 config TASKS_RCU
510         bool "Task_based RCU implementation using voluntary context switch"
511         default n
512         select SRCU
513         help
514           This option enables a task-based RCU implementation that uses
515           only voluntary context switch (not preemption!), idle, and
516           user-mode execution as quiescent states.
518           If unsure, say N.
521         def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
522         help
523           This option enables RCU CPU stall code that is common between
524           the TINY and TREE variants of RCU.  The purpose is to allow
525           the tiny variants to disable RCU CPU stall warnings, while
526           making these warnings mandatory for the tree variants.
529        bool
531 config RCU_USER_QS
532         bool "Consider userspace as in RCU extended quiescent state"
533         depends on HAVE_CONTEXT_TRACKING && SMP
534         select CONTEXT_TRACKING
535         help
536           This option sets hooks on kernel / userspace boundaries and
537           puts RCU in extended quiescent state when the CPU runs in
538           userspace. It means that when a CPU runs in userspace, it is
539           excluded from the global RCU state machine and thus doesn't
540           try to keep the timer tick on for RCU.
542           Unless you want to hack and help the development of the full
543           dynticks mode, you shouldn't enable this option.  It also
544           adds unnecessary overhead.
546           If unsure say N
549         bool "Force context tracking"
550         depends on CONTEXT_TRACKING
551         default y if !NO_HZ_FULL
552         help
553           The major pre-requirement for full dynticks to work is to
554           support the context tracking subsystem. But there are also
555           other dependencies to provide in order to make the full
556           dynticks working.
558           This option stands for testing when an arch implements the
559           context tracking backend but doesn't yet fullfill all the
560           requirements to make the full dynticks feature working.
561           Without the full dynticks, there is no way to test the support
562           for context tracking and the subsystems that rely on it: RCU
563           userspace extended quiescent state and tickless cputime
564           accounting. This option copes with the absence of the full
565           dynticks subsystem by forcing the context tracking on all
566           CPUs in the system.
568           Say Y only if you're working on the development of an
569           architecture backend for the context tracking.
571           Say N otherwise, this option brings an overhead that you
572           don't want in production.
575 config RCU_FANOUT
576         int "Tree-based hierarchical RCU fanout value"
577         range 2 64 if 64BIT
578         range 2 32 if !64BIT
579         depends on TREE_RCU || PREEMPT_RCU
580         default 64 if 64BIT
581         default 32 if !64BIT
582         help
583           This option controls the fanout of hierarchical implementations
584           of RCU, allowing RCU to work efficiently on machines with
585           large numbers of CPUs.  This value must be at least the fourth
586           root of NR_CPUS, which allows NR_CPUS to be insanely large.
587           The default value of RCU_FANOUT should be used for production
588           systems, but if you are stress-testing the RCU implementation
589           itself, small RCU_FANOUT values allow you to test large-system
590           code paths on small(er) systems.
592           Select a specific number if testing RCU itself.
593           Take the default if unsure.
595 config RCU_FANOUT_LEAF
596         int "Tree-based hierarchical RCU leaf-level fanout value"
597         range 2 RCU_FANOUT if 64BIT
598         range 2 RCU_FANOUT if !64BIT
599         depends on TREE_RCU || PREEMPT_RCU
600         default 16
601         help
602           This option controls the leaf-level fanout of hierarchical
603           implementations of RCU, and allows trading off cache misses
604           against lock contention.  Systems that synchronize their
605           scheduling-clock interrupts for energy-efficiency reasons will
606           want the default because the smaller leaf-level fanout keeps
607           lock contention levels acceptably low.  Very large systems
608           (hundreds or thousands of CPUs) will instead want to set this
609           value to the maximum value possible in order to reduce the
610           number of cache misses incurred during RCU's grace-period
611           initialization.  These systems tend to run CPU-bound, and thus
612           are not helped by synchronized interrupts, and thus tend to
613           skew them, which reduces lock contention enough that large
614           leaf-level fanouts work well.
616           Select a specific number if testing RCU itself.
618           Select the maximum permissible value for large systems.
620           Take the default if unsure.
623         bool "Disable tree-based hierarchical RCU auto-balancing"
624         depends on TREE_RCU || PREEMPT_RCU
625         default n
626         help
627           This option forces use of the exact RCU_FANOUT value specified,
628           regardless of imbalances in the hierarchy.  This is useful for
629           testing RCU itself, and might one day be useful on systems with
630           strong NUMA behavior.
632           Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
634           Say N if unsure.
636 config RCU_FAST_NO_HZ
637         bool "Accelerate last non-dyntick-idle CPU's grace periods"
638         depends on NO_HZ_COMMON && SMP
639         default n
640         help
641           This option permits CPUs to enter dynticks-idle state even if
642           they have RCU callbacks queued, and prevents RCU from waking
643           these CPUs up more than roughly once every four jiffies (by
644           default, you can adjust this using the rcutree.rcu_idle_gp_delay
645           parameter), thus improving energy efficiency.  On the other
646           hand, this option increases the duration of RCU grace periods,
647           for example, slowing down synchronize_rcu().
649           Say Y if energy efficiency is critically important, and you
650                 don't care about increased grace-period durations.
652           Say N if you are unsure.
654 config TREE_RCU_TRACE
655         def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
656         select DEBUG_FS
657         help
658           This option provides tracing for the TREE_RCU and
659           PREEMPT_RCU implementations, permitting Makefile to
660           trivially select kernel/rcutree_trace.c.
662 config RCU_BOOST
663         bool "Enable RCU priority boosting"
664         depends on RT_MUTEXES && PREEMPT_RCU
665         default n
666         help
667           This option boosts the priority of preempted RCU readers that
668           block the current preemptible RCU grace period for too long.
669           This option also prevents heavy loads from blocking RCU
670           callback invocation for all flavors of RCU.
672           Say Y here if you are working with real-time apps or heavy loads
673           Say N here if you are unsure.
676         int "Real-time priority to use for RCU worker threads"
677         range 1 99 if RCU_BOOST
678         range 0 99 if !RCU_BOOST
679         default 1 if RCU_BOOST
680         default 0 if !RCU_BOOST
681         help
682           This option specifies the SCHED_FIFO priority value that will be
683           assigned to the rcuc/n and rcub/n threads and is also the value
684           used for RCU_BOOST (if enabled). If you are working with a
685           real-time application that has one or more CPU-bound threads
686           running at a real-time priority level, you should set
687           RCU_KTHREAD_PRIO to a priority higher than the highest-priority
688           real-time CPU-bound application thread.  The default RCU_KTHREAD_PRIO
689           value of 1 is appropriate in the common case, which is real-time
690           applications that do not have any CPU-bound threads.
692           Some real-time applications might not have a single real-time
693           thread that saturates a given CPU, but instead might have
694           multiple real-time threads that, taken together, fully utilize
695           that CPU.  In this case, you should set RCU_KTHREAD_PRIO to
696           a priority higher than the lowest-priority thread that is
697           conspiring to prevent the CPU from running any non-real-time
698           tasks.  For example, if one thread at priority 10 and another
699           thread at priority 5 are between themselves fully consuming
700           the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
701           set to priority 6 or higher.
703           Specify the real-time priority, or take the default if unsure.
705 config RCU_BOOST_DELAY
706         int "Milliseconds to delay boosting after RCU grace-period start"
707         range 0 3000
708         depends on RCU_BOOST
709         default 500
710         help
711           This option specifies the time to wait after the beginning of
712           a given grace period before priority-boosting preempted RCU
713           readers blocking that grace period.  Note that any RCU reader
714           blocking an expedited RCU grace period is boosted immediately.
716           Accept the default if unsure.
718 config RCU_NOCB_CPU
719         bool "Offload RCU callback processing from boot-selected CPUs"
720         depends on TREE_RCU || PREEMPT_RCU
721         default n
722         help
723           Use this option to reduce OS jitter for aggressive HPC or
724           real-time workloads.  It can also be used to offload RCU
725           callback invocation to energy-efficient CPUs in battery-powered
726           asymmetric multiprocessors.
728           This option offloads callback invocation from the set of
729           CPUs specified at boot time by the rcu_nocbs parameter.
730           For each such CPU, a kthread ("rcuox/N") will be created to
731           invoke callbacks, where the "N" is the CPU being offloaded,
732           and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
733           "s" for RCU-sched.  Nothing prevents this kthread from running
734           on the specified CPUs, but (1) the kthreads may be preempted
735           between each callback, and (2) affinity or cgroups can be used
736           to force the kthreads to run on whatever set of CPUs is desired.
738           Say Y here if you want to help to debug reduced OS jitter.
739           Say N here if you are unsure.
741 choice
742         prompt "Build-forced no-CBs CPUs"
743         default RCU_NOCB_CPU_NONE
744         depends on RCU_NOCB_CPU
745         help
746           This option allows no-CBs CPUs (whose RCU callbacks are invoked
747           from kthreads rather than from softirq context) to be specified
748           at build time.  Additional no-CBs CPUs may be specified by
749           the rcu_nocbs= boot parameter.
751 config RCU_NOCB_CPU_NONE
752         bool "No build_forced no-CBs CPUs"
753         help
754           This option does not force any of the CPUs to be no-CBs CPUs.
755           Only CPUs designated by the rcu_nocbs= boot parameter will be
756           no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
757           kthreads whose names begin with "rcuo".  All other CPUs will
758           invoke their own RCU callbacks in softirq context.
760           Select this option if you want to choose no-CBs CPUs at
761           boot time, for example, to allow testing of different no-CBs
762           configurations without having to rebuild the kernel each time.
764 config RCU_NOCB_CPU_ZERO
765         bool "CPU 0 is a build_forced no-CBs CPU"
766         help
767           This option forces CPU 0 to be a no-CBs CPU, so that its RCU
768           callbacks are invoked by a per-CPU kthread whose name begins
769           with "rcuo".  Additional CPUs may be designated as no-CBs
770           CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
771           All other CPUs will invoke their own RCU callbacks in softirq
772           context.
774           Select this if CPU 0 needs to be a no-CBs CPU for real-time
775           or energy-efficiency reasons, but the real reason it exists
776           is to ensure that randconfig testing covers mixed systems.
778 config RCU_NOCB_CPU_ALL
779         bool "All CPUs are build_forced no-CBs CPUs"
780         help
781           This option forces all CPUs to be no-CBs CPUs.  The rcu_nocbs=
782           boot parameter will be ignored.  All CPUs' RCU callbacks will
783           be executed in the context of per-CPU rcuo kthreads created for
784           this purpose.  Assuming that the kthreads whose names start with
785           "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
786           on the remaining CPUs, but might decrease memory locality during
787           RCU-callback invocation, thus potentially degrading throughput.
789           Select this if all CPUs need to be no-CBs CPUs for real-time
790           or energy-efficiency reasons.
792 endchoice
794 endmenu # "RCU Subsystem"
796 config BUILD_BIN2C
797         bool
798         default n
800 config IKCONFIG
801         tristate "Kernel .config support"
802         select BUILD_BIN2C
803         ---help---
804           This option enables the complete Linux kernel ".config" file
805           contents to be saved in the kernel. It provides documentation
806           of which kernel options are used in a running kernel or in an
807           on-disk kernel.  This information can be extracted from the kernel
808           image file with the script scripts/extract-ikconfig and used as
809           input to rebuild the current kernel or to build another kernel.
810           It can also be extracted from a running kernel by reading
811           /proc/config.gz if enabled (below).
813 config IKCONFIG_PROC
814         bool "Enable access to .config through /proc/config.gz"
815         depends on IKCONFIG && PROC_FS
816         ---help---
817           This option enables access to the kernel configuration file
818           through /proc/config.gz.
820 config LOG_BUF_SHIFT
821         int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
822         range 12 21
823         default 17
824         depends on PRINTK
825         help
826           Select the minimal kernel log buffer size as a power of 2.
827           The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
828           parameter, see below. Any higher size also might be forced
829           by "log_buf_len" boot parameter.
831           Examples:
832                      17 => 128 KB
833                      16 => 64 KB
834                      15 => 32 KB
835                      14 => 16 KB
836                      13 =>  8 KB
837                      12 =>  4 KB
840         int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
841         depends on SMP
842         range 0 21
843         default 12 if !BASE_SMALL
844         default 0 if BASE_SMALL
845         depends on PRINTK
846         help
847           This option allows to increase the default ring buffer size
848           according to the number of CPUs. The value defines the contribution
849           of each CPU as a power of 2. The used space is typically only few
850           lines however it might be much more when problems are reported,
851           e.g. backtraces.
853           The increased size means that a new buffer has to be allocated and
854           the original static one is unused. It makes sense only on systems
855           with more CPUs. Therefore this value is used only when the sum of
856           contributions is greater than the half of the default kernel ring
857           buffer as defined by LOG_BUF_SHIFT. The default values are set
858           so that more than 64 CPUs are needed to trigger the allocation.
860           Also this option is ignored when "log_buf_len" kernel parameter is
861           used as it forces an exact (power of two) size of the ring buffer.
863           The number of possible CPUs is used for this computation ignoring
864           hotplugging making the compuation optimal for the the worst case
865           scenerio while allowing a simple algorithm to be used from bootup.
867           Examples shift values and their meaning:
868                      17 => 128 KB for each CPU
869                      16 =>  64 KB for each CPU
870                      15 =>  32 KB for each CPU
871                      14 =>  16 KB for each CPU
872                      13 =>   8 KB for each CPU
873                      12 =>   4 KB for each CPU
875 #
876 # Architectures with an unreliable sched_clock() should select this:
877 #
879         bool
882         bool
884 #
885 # For architectures that want to enable the support for NUMA-affine scheduler
886 # balancing logic:
887 #
889         bool
891 #
892 # For architectures that know their GCC __int128 support is sound
893 #
894 config ARCH_SUPPORTS_INT128
895         bool
897 # For architectures that (ab)use NUMA to represent different memory regions
898 # all cpu-local but of different latencies, such as SuperH.
899 #
901         bool
904         bool "Memory placement aware NUMA scheduler"
905         depends on ARCH_SUPPORTS_NUMA_BALANCING
906         depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
907         depends on SMP && NUMA && MIGRATION
908         help
909           This option adds support for automatic NUMA aware memory/task placement.
910           The mechanism is quite primitive and is based on migrating memory when
911           it has references to the node the task is running on.
913           This system will be inactive on UMA systems.
916         bool "Automatically enable NUMA aware memory/task placement"
917         default y
918         depends on NUMA_BALANCING
919         help
920           If set, automatic NUMA balancing will be enabled if running on a NUMA
921           machine.
923 menuconfig CGROUPS
924         bool "Control Group support"
925         select KERNFS
926         help
927           This option adds support for grouping sets of processes together, for
928           use with process control subsystems such as Cpusets, CFS, memory
929           controls or device isolation.
930           See
931                 - Documentation/scheduler/sched-design-CFS.txt  (CFS)
932                 - Documentation/cgroups/ (features for grouping, isolation
933                                           and resource control)
935           Say N if unsure.
937 if CGROUPS
939 config CGROUP_DEBUG
940         bool "Example debug cgroup subsystem"
941         default n
942         help
943           This option enables a simple cgroup subsystem that
944           exports useful debugging information about the cgroups
945           framework.
947           Say N if unsure.
950         bool "Freezer cgroup subsystem"
951         help
952           Provides a way to freeze and unfreeze all tasks in a
953           cgroup.
955 config CGROUP_DEVICE
956         bool "Device controller for cgroups"
957         help
958           Provides a cgroup implementing whitelists for devices which
959           a process in the cgroup can mknod or open.
961 config CPUSETS
962         bool "Cpuset support"
963         help
964           This option will let you create and manage CPUSETs which
965           allow dynamically partitioning a system into sets of CPUs and
966           Memory Nodes and assigning tasks to run only within those sets.
967           This is primarily useful on large SMP or NUMA systems.
969           Say N if unsure.
971 config PROC_PID_CPUSET
972         bool "Include legacy /proc/<pid>/cpuset file"
973         depends on CPUSETS
974         default y
977         bool "Simple CPU accounting cgroup subsystem"
978         help
979           Provides a simple Resource Controller for monitoring the
980           total CPU consumed by the tasks in a cgroup.
982 config PAGE_COUNTER
983        bool
985 config MEMCG
986         bool "Memory Resource Controller for Control Groups"
987         select PAGE_COUNTER
988         select EVENTFD
989         help
990           Provides a memory resource controller that manages both anonymous
991           memory and page cache. (See Documentation/cgroups/memory.txt)
993 config MEMCG_SWAP
994         bool "Memory Resource Controller Swap Extension"
995         depends on MEMCG && SWAP
996         help
997           Add swap management feature to memory resource controller. When you
998           enable this, you can limit mem+swap usage per cgroup. In other words,
999           when you disable this, memory resource controller has no cares to
1000           usage of swap...a process can exhaust all of the swap. This extension
1001           is useful when you want to avoid exhaustion swap but this itself
1002           adds more overheads and consumes memory for remembering information.
1003           Especially if you use 32bit system or small memory system, please
1004           be careful about enabling this. When memory resource controller
1005           is disabled by boot option, this will be automatically disabled and
1006           there will be no overhead from this. Even when you set this config=y,
1007           if boot option "swapaccount=0" is set, swap will not be accounted.
1008           Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
1009           size is 4096bytes, 512k per 1Gbytes of swap.
1011         bool "Memory Resource Controller Swap Extension enabled by default"
1012         depends on MEMCG_SWAP
1013         default y
1014         help
1015           Memory Resource Controller Swap Extension comes with its price in
1016           a bigger memory consumption. General purpose distribution kernels
1017           which want to enable the feature but keep it disabled by default
1018           and let the user enable it by swapaccount=1 boot command line
1019           parameter should have this option unselected.
1020           For those who want to have the feature enabled by default should
1021           select this option (if, for some reason, they need to disable it
1022           then swapaccount=0 does the trick).
1023 config MEMCG_KMEM
1024         bool "Memory Resource Controller Kernel Memory accounting"
1025         depends on MEMCG
1026         depends on SLUB || SLAB
1027         help
1028           The Kernel Memory extension for Memory Resource Controller can limit
1029           the amount of memory used by kernel objects in the system. Those are
1030           fundamentally different from the entities handled by the standard
1031           Memory Controller, which are page-based, and can be swapped. Users of
1032           the kmem extension can use it to guarantee that no group of processes
1033           will ever exhaust kernel resources alone.
1035           WARNING: Current implementation lacks reclaim support. That means
1036           allocation attempts will fail when close to the limit even if there
1037           are plenty of kmem available for reclaim. That makes this option
1038           unusable in real life so DO NOT SELECT IT unless for development
1039           purposes.
1041 config CGROUP_HUGETLB
1042         bool "HugeTLB Resource Controller for Control Groups"
1043         depends on HUGETLB_PAGE
1044         select PAGE_COUNTER
1045         default n
1046         help
1047           Provides a cgroup Resource Controller for HugeTLB pages.
1048           When you enable this, you can put a per cgroup limit on HugeTLB usage.
1049           The limit is enforced during page fault. Since HugeTLB doesn't
1050           support page reclaim, enforcing the limit at page fault time implies
1051           that, the application will get SIGBUS signal if it tries to access
1052           HugeTLB pages beyond its limit. This requires the application to know
1053           beforehand how much HugeTLB pages it would require for its use. The
1054           control group is tracked in the third page lru pointer. This means
1055           that we cannot use the controller with huge page less than 3 pages.
1057 config CGROUP_PERF
1058         bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1059         depends on PERF_EVENTS && CGROUPS
1060         help
1061           This option extends the per-cpu mode to restrict monitoring to
1062           threads which belong to the cgroup specified and run on the
1063           designated cpu.
1065           Say N if unsure.
1067 menuconfig CGROUP_SCHED
1068         bool "Group CPU scheduler"
1069         default n
1070         help
1071           This feature lets CPU scheduler recognize task groups and control CPU
1072           bandwidth allocation to such task groups. It uses cgroups to group
1073           tasks.
1076 config FAIR_GROUP_SCHED
1077         bool "Group scheduling for SCHED_OTHER"
1078         depends on CGROUP_SCHED
1079         default CGROUP_SCHED
1081 config CFS_BANDWIDTH
1082         bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1083         depends on FAIR_GROUP_SCHED
1084         default n
1085         help
1086           This option allows users to define CPU bandwidth rates (limits) for
1087           tasks running within the fair group scheduler.  Groups with no limit
1088           set are considered to be unconstrained and will run with no
1089           restriction.
1090           See tip/Documentation/scheduler/sched-bwc.txt for more information.
1092 config RT_GROUP_SCHED
1093         bool "Group scheduling for SCHED_RR/FIFO"
1094         depends on CGROUP_SCHED
1095         default n
1096         help
1097           This feature lets you explicitly allocate real CPU bandwidth
1098           to task groups. If enabled, it will also make it impossible to
1099           schedule realtime tasks for non-root users until you allocate
1100           realtime bandwidth for them.
1101           See Documentation/scheduler/sched-rt-group.txt for more information.
1103 endif #CGROUP_SCHED
1105 config BLK_CGROUP
1106         bool "Block IO controller"
1107         depends on BLOCK
1108         default n
1109         ---help---
1110         Generic block IO controller cgroup interface. This is the common
1111         cgroup interface which should be used by various IO controlling
1112         policies.
1114         Currently, CFQ IO scheduler uses it to recognize task groups and
1115         control disk bandwidth allocation (proportional time slice allocation)
1116         to such task groups. It is also used by bio throttling logic in
1117         block layer to implement upper limit in IO rates on a device.
1119         This option only enables generic Block IO controller infrastructure.
1120         One needs to also enable actual IO controlling logic/policy. For
1121         enabling proportional weight division of disk bandwidth in CFQ, set
1122         CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1125         See Documentation/cgroups/blkio-controller.txt for more information.
1127 config DEBUG_BLK_CGROUP
1128         bool "Enable Block IO controller debugging"
1129         depends on BLK_CGROUP
1130         default n
1131         ---help---
1132         Enable some debugging help. Currently it exports additional stat
1133         files in a cgroup which can be useful for debugging.
1135 endif # CGROUPS
1138         bool "Checkpoint/restore support" if EXPERT
1139         default n
1140         help
1141           Enables additional kernel features in a sake of checkpoint/restore.
1142           In particular it adds auxiliary prctl codes to setup process text,
1143           data and heap segment sizes, and a few additional /proc filesystem
1144           entries.
1146           If unsure, say N here.
1148 menuconfig NAMESPACES
1149         bool "Namespaces support" if EXPERT
1150         default !EXPERT
1151         help
1152           Provides the way to make tasks work with different objects using
1153           the same id. For example same IPC id may refer to different objects
1154           or same user id or pid may refer to different tasks when used in
1155           different namespaces.
1159 config UTS_NS
1160         bool "UTS namespace"
1161         default y
1162         help
1163           In this namespace tasks see different info provided with the
1164           uname() system call
1166 config IPC_NS
1167         bool "IPC namespace"
1168         depends on (SYSVIPC || POSIX_MQUEUE)
1169         default y
1170         help
1171           In this namespace tasks work with IPC ids which correspond to
1172           different IPC objects in different namespaces.
1174 config USER_NS
1175         bool "User namespace"
1176         default n
1177         help
1178           This allows containers, i.e. vservers, to use user namespaces
1179           to provide different user info for different servers.
1181           When user namespaces are enabled in the kernel it is
1182           recommended that the MEMCG and MEMCG_KMEM options also be
1183           enabled and that user-space use the memory control groups to
1184           limit the amount of memory a memory unprivileged users can
1185           use.
1187           If unsure, say N.
1189 config PID_NS
1190         bool "PID Namespaces"
1191         default y
1192         help
1193           Support process id namespaces.  This allows having multiple
1194           processes with the same pid as long as they are in different
1195           pid namespaces.  This is a building block of containers.
1197 config NET_NS
1198         bool "Network namespace"
1199         depends on NET
1200         default y
1201         help
1202           Allow user space to create what appear to be multiple instances
1203           of the network stack.
1205 endif # NAMESPACES
1208         bool "Automatic process group scheduling"
1209         select CGROUPS
1210         select CGROUP_SCHED
1211         select FAIR_GROUP_SCHED
1212         help
1213           This option optimizes the scheduler for common desktop workloads by
1214           automatically creating and populating task groups.  This separation
1215           of workloads isolates aggressive CPU burners (like build jobs) from
1216           desktop applications.  Task group autogeneration is currently based
1217           upon task session.
1220         bool "Enable deprecated sysfs features to support old userspace tools"
1221         depends on SYSFS
1222         default n
1223         help
1224           This option adds code that switches the layout of the "block" class
1225           devices, to not show up in /sys/class/block/, but only in
1226           /sys/block/.
1228           This switch is only active when the sysfs.deprecated=1 boot option is
1229           passed or the SYSFS_DEPRECATED_V2 option is set.
1231           This option allows new kernels to run on old distributions and tools,
1232           which might get confused by /sys/class/block/. Since 2007/2008 all
1233           major distributions and tools handle this just fine.
1235           Recent distributions and userspace tools after 2009/2010 depend on
1236           the existence of /sys/class/block/, and will not work with this
1237           option enabled.
1239           Only if you are using a new kernel on an old distribution, you might
1240           need to say Y here.
1243         bool "Enable deprecated sysfs features by default"
1244         default n
1245         depends on SYSFS
1246         depends on SYSFS_DEPRECATED
1247         help
1248           Enable deprecated sysfs by default.
1250           See the CONFIG_SYSFS_DEPRECATED option for more details about this
1251           option.
1253           Only if you are using a new kernel on an old distribution, you might
1254           need to say Y here. Even then, odds are you would not need it
1255           enabled, you can always pass the boot option if absolutely necessary.
1257 config RELAY
1258         bool "Kernel->user space relay support (formerly relayfs)"
1259         help
1260           This option enables support for relay interface support in
1261           certain file systems (such as debugfs).
1262           It is designed to provide an efficient mechanism for tools and
1263           facilities to relay large amounts of data from kernel space to
1264           user space.
1266           If unsure, say N.
1268 config BLK_DEV_INITRD
1269         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1270         depends on BROKEN || !FRV
1271         help
1272           The initial RAM filesystem is a ramfs which is loaded by the
1273           boot loader (loadlin or lilo) and that is mounted as root
1274           before the normal boot procedure. It is typically used to
1275           load modules needed to mount the "real" root file system,
1276           etc. See <file:Documentation/initrd.txt> for details.
1278           If RAM disk support (BLK_DEV_RAM) is also included, this
1279           also enables initial RAM disk (initrd) support and adds
1280           15 Kbytes (more on some other architectures) to the kernel size.
1282           If unsure say Y.
1286 source "usr/Kconfig"
1288 endif
1291         bool "Optimize for size"
1292         help
1293           Enabling this option will pass "-Os" instead of "-O2" to
1294           your compiler resulting in a smaller kernel.
1296           If unsure, say N.
1298 config SYSCTL
1299         bool
1301 config ANON_INODES
1302         bool
1304 config HAVE_UID16
1305         bool
1308         bool
1309         help
1310           Enable support for /proc/sys/debug/exception-trace.
1313         bool
1314         help
1315           Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1316           Allows arch to define/use @no_unaligned_warning to possibly warn
1317           about unaligned access emulation going on under the hood.
1320         bool
1321         help
1322           Enable support for /proc/sys/kernel/unaligned-trap
1323           Allows arches to define/use @unaligned_enabled to runtime toggle
1324           the unaligned access emulation.
1325           see arch/parisc/kernel/unaligned.c for reference
1328         bool
1330 # interpreter that classic socket filters depend on
1331 config BPF
1332         bool
1334 menuconfig EXPERT
1335         bool "Configure standard kernel features (expert users)"
1336         # Unhide debug options, to make the on-by-default options visible
1337         select DEBUG_KERNEL
1338         help
1339           This option allows certain base kernel options and settings
1340           to be disabled or tweaked. This is for specialized
1341           environments which can tolerate a "non-standard" kernel.
1342           Only use this if you really know what you are doing.
1344 config UID16
1345         bool "Enable 16-bit UID system calls" if EXPERT
1346         depends on HAVE_UID16
1347         default y
1348         help
1349           This enables the legacy 16-bit UID syscall wrappers.
1352         bool "sgetmask/ssetmask syscalls support" if EXPERT
1353         def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1354         ---help---
1355           sys_sgetmask and sys_ssetmask are obsolete system calls
1356           no longer supported in libc but still enabled by default in some
1357           architectures.
1359           If unsure, leave the default option here.
1361 config SYSFS_SYSCALL
1362         bool "Sysfs syscall support" if EXPERT
1363         default y
1364         ---help---
1365           sys_sysfs is an obsolete system call no longer supported in libc.
1366           Note that disabling this option is more secure but might break
1367           compatibility with some systems.
1369           If unsure say Y here.
1371 config SYSCTL_SYSCALL
1372         bool "Sysctl syscall support" if EXPERT
1373         depends on PROC_SYSCTL
1374         default n
1375         select SYSCTL
1376         ---help---
1377           sys_sysctl uses binary paths that have been found challenging
1378           to properly maintain and use.  The interface in /proc/sys
1379           using paths with ascii names is now the primary path to this
1380           information.
1382           Almost nothing using the binary sysctl interface so if you are
1383           trying to save some space it is probably safe to disable this,
1384           making your kernel marginally smaller.
1386           If unsure say N here.
1388 config KALLSYMS
1389          bool "Load all symbols for debugging/ksymoops" if EXPERT
1390          default y
1391          help
1392            Say Y here to let the kernel print out symbolic crash information and
1393            symbolic stack backtraces. This increases the size of the kernel
1394            somewhat, as all symbols have to be loaded into the kernel image.
1396 config KALLSYMS_ALL
1397         bool "Include all symbols in kallsyms"
1398         depends on DEBUG_KERNEL && KALLSYMS
1399         help
1400            Normally kallsyms only contains the symbols of functions for nicer
1401            OOPS messages and backtraces (i.e., symbols from the text and inittext
1402            sections). This is sufficient for most cases. And only in very rare
1403            cases (e.g., when a debugger is used) all symbols are required (e.g.,
1404            names of variables from the data sections, etc).
1406            This option makes sure that all symbols are loaded into the kernel
1407            image (i.e., symbols from all sections) in cost of increased kernel
1408            size (depending on the kernel configuration, it may be 300KiB or
1409            something like this).
1411            Say N unless you really need all symbols.
1413 config PRINTK
1414         default y
1415         bool "Enable support for printk" if EXPERT
1416         select IRQ_WORK
1417         help
1418           This option enables normal printk support. Removing it
1419           eliminates most of the message strings from the kernel image
1420           and makes the kernel more or less silent. As this makes it
1421           very difficult to diagnose system problems, saying N here is
1422           strongly discouraged.
1424 config BUG
1425         bool "BUG() support" if EXPERT
1426         default y
1427         help
1428           Disabling this option eliminates support for BUG and WARN, reducing
1429           the size of your kernel image and potentially quietly ignoring
1430           numerous fatal conditions. You should only consider disabling this
1431           option for embedded systems with no facilities for reporting errors.
1432           Just say Y.
1434 config ELF_CORE
1435         depends on COREDUMP
1436         default y
1437         bool "Enable ELF core dumps" if EXPERT
1438         help
1439           Enable support for generating core dumps. Disabling saves about 4k.
1443         bool "Enable PC-Speaker support" if EXPERT
1444         depends on HAVE_PCSPKR_PLATFORM
1445         select I8253_LOCK
1446         default y
1447         help
1448           This option allows to disable the internal PC-Speaker
1449           support, saving some memory.
1451 config BASE_FULL
1452         default y
1453         bool "Enable full-sized data structures for core" if EXPERT
1454         help
1455           Disabling this option reduces the size of miscellaneous core
1456           kernel data structures. This saves memory on small machines,
1457           but may reduce performance.
1459 config FUTEX
1460         bool "Enable futex support" if EXPERT
1461         default y
1462         select RT_MUTEXES
1463         help
1464           Disabling this option will cause the kernel to be built without
1465           support for "fast userspace mutexes".  The resulting kernel may not
1466           run glibc-based applications correctly.
1469         bool
1470         depends on FUTEX
1471         help
1472           Architectures should select this if futex_atomic_cmpxchg_inatomic()
1473           is implemented and always working. This removes a couple of runtime
1474           checks.
1476 config EPOLL
1477         bool "Enable eventpoll support" if EXPERT
1478         default y
1479         select ANON_INODES
1480         help
1481           Disabling this option will cause the kernel to be built without
1482           support for epoll family of system calls.
1484 config SIGNALFD
1485         bool "Enable signalfd() system call" if EXPERT
1486         select ANON_INODES
1487         default y
1488         help
1489           Enable the signalfd() system call that allows to receive signals
1490           on a file descriptor.
1492           If unsure, say Y.
1494 config TIMERFD
1495         bool "Enable timerfd() system call" if EXPERT
1496         select ANON_INODES
1497         default y
1498         help
1499           Enable the timerfd() system call that allows to receive timer
1500           events on a file descriptor.
1502           If unsure, say Y.
1504 config EVENTFD
1505         bool "Enable eventfd() system call" if EXPERT
1506         select ANON_INODES
1507         default y
1508         help
1509           Enable the eventfd() system call that allows to receive both
1510           kernel notification (ie. KAIO) or userspace notifications.
1512           If unsure, say Y.
1514 # syscall, maps, verifier
1515 config BPF_SYSCALL
1516         bool "Enable bpf() system call" if EXPERT
1517         select ANON_INODES
1518         select BPF
1519         default n
1520         help
1521           Enable the bpf() system call that allows to manipulate eBPF
1522           programs and maps via file descriptors.
1524 config SHMEM
1525         bool "Use full shmem filesystem" if EXPERT
1526         default y
1527         depends on MMU
1528         help
1529           The shmem is an internal filesystem used to manage shared memory.
1530           It is backed by swap and manages resource limits. It is also exported
1531           to userspace as tmpfs if TMPFS is enabled. Disabling this
1532           option replaces shmem and tmpfs with the much simpler ramfs code,
1533           which may be appropriate on small systems without swap.
1535 config AIO
1536         bool "Enable AIO support" if EXPERT
1537         default y
1538         help
1539           This option enables POSIX asynchronous I/O which may by used
1540           by some high performance threaded applications. Disabling
1541           this option saves about 7k.
1544         bool "Enable madvise/fadvise syscalls" if EXPERT
1545         default y
1546         help
1547           This option enables the madvise and fadvise syscalls, used by
1548           applications to advise the kernel about their future memory or file
1549           usage, improving performance. If building an embedded system where no
1550           applications use these syscalls, you can disable this option to save
1551           space.
1553 config PCI_QUIRKS
1554         default y
1555         bool "Enable PCI quirk workarounds" if EXPERT
1556         depends on PCI
1557         help
1558           This enables workarounds for various PCI chipset
1559           bugs/quirks. Disable this only if your target machine is
1560           unaffected by PCI quirks.
1562 config EMBEDDED
1563         bool "Embedded system"
1564         option allnoconfig_y
1565         select EXPERT
1566         help
1567           This option should be enabled if compiling the kernel for
1568           an embedded system so certain expert options are available
1569           for configuration.
1571 config HAVE_PERF_EVENTS
1572         bool
1573         help
1574           See tools/perf/design.txt for details.
1576 config PERF_USE_VMALLOC
1577         bool
1578         help
1579           See tools/perf/design.txt for details
1581 menu "Kernel Performance Events And Counters"
1583 config PERF_EVENTS
1584         bool "Kernel performance events and counters"
1585         default y if PROFILING
1586         depends on HAVE_PERF_EVENTS
1587         select ANON_INODES
1588         select IRQ_WORK
1589         select SRCU
1590         help
1591           Enable kernel support for various performance events provided
1592           by software and hardware.
1594           Software events are supported either built-in or via the
1595           use of generic tracepoints.
1597           Most modern CPUs support performance events via performance
1598           counter registers. These registers count the number of certain
1599           types of hw events: such as instructions executed, cachemisses
1600           suffered, or branches mis-predicted - without slowing down the
1601           kernel or applications. These registers can also trigger interrupts
1602           when a threshold number of events have passed - and can thus be
1603           used to profile the code that runs on that CPU.
1605           The Linux Performance Event subsystem provides an abstraction of
1606           these software and hardware event capabilities, available via a
1607           system call and used by the "perf" utility in tools/perf/. It
1608           provides per task and per CPU counters, and it provides event
1609           capabilities on top of those.
1611           Say Y if unsure.
1614         default n
1615         bool "Debug: use vmalloc to back perf mmap() buffers"
1616         depends on PERF_EVENTS && DEBUG_KERNEL
1617         select PERF_USE_VMALLOC
1618         help
1619          Use vmalloc memory to back perf mmap() buffers.
1621          Mostly useful for debugging the vmalloc code on platforms
1622          that don't require it.
1624          Say N if unsure.
1626 endmenu
1629         default y
1630         bool "Enable VM event counters for /proc/vmstat" if EXPERT
1631         help
1632           VM event counters are needed for event counts to be shown.
1633           This option allows the disabling of the VM event counters
1634           on EXPERT systems.  /proc/vmstat will only show page counts
1635           if VM event counters are disabled.
1637 config SLUB_DEBUG
1638         default y
1639         bool "Enable SLUB debugging support" if EXPERT
1640         depends on SLUB && SYSFS
1641         help
1642           SLUB has extensive debug support features. Disabling these can
1643           result in significant savings in code size. This also disables
1644           SLUB sysfs support. /sys/slab will not exist and there will be
1645           no support for cache validation etc.
1647 config COMPAT_BRK
1648         bool "Disable heap randomization"
1649         default y
1650         help
1651           Randomizing heap placement makes heap exploits harder, but it
1652           also breaks ancient binaries (including anything libc5 based).
1653           This option changes the bootup default to heap randomization
1654           disabled, and can be overridden at runtime by setting
1655           /proc/sys/kernel/randomize_va_space to 2.
1657           On non-ancient distros (post-2000 ones) N is usually a safe choice.
1659 choice
1660         prompt "Choose SLAB allocator"
1661         default SLUB
1662         help
1663            This option allows to select a slab allocator.
1665 config SLAB
1666         bool "SLAB"
1667         help
1668           The regular slab allocator that is established and known to work
1669           well in all environments. It organizes cache hot objects in
1670           per cpu and per node queues.
1672 config SLUB
1673         bool "SLUB (Unqueued Allocator)"
1674         help
1675            SLUB is a slab allocator that minimizes cache line usage
1676            instead of managing queues of cached objects (SLAB approach).
1677            Per cpu caching is realized using slabs of objects instead
1678            of queues of objects. SLUB can use memory efficiently
1679            and has enhanced diagnostics. SLUB is the default choice for
1680            a slab allocator.
1682 config SLOB
1683         depends on EXPERT
1684         bool "SLOB (Simple Allocator)"
1685         help
1686            SLOB replaces the stock allocator with a drastically simpler
1687            allocator. SLOB is generally more space efficient but
1688            does not perform as well on large systems.
1690 endchoice
1692 config SLUB_CPU_PARTIAL
1693         default y
1694         depends on SLUB && SMP
1695         bool "SLUB per cpu partial cache"
1696         help
1697           Per cpu partial caches accellerate objects allocation and freeing
1698           that is local to a processor at the price of more indeterminism
1699           in the latency of the free. On overflow these caches will be cleared
1700           which requires the taking of locks that may cause latency spikes.
1701           Typically one would choose no for a realtime system.
1704         bool "Allow mmapped anonymous memory to be uninitialized"
1705         depends on EXPERT && !MMU
1706         default n
1707         help
1708           Normally, and according to the Linux spec, anonymous memory obtained
1709           from mmap() has it's contents cleared before it is passed to
1710           userspace.  Enabling this config option allows you to request that
1711           mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1712           providing a huge performance boost.  If this option is not enabled,
1713           then the flag will be ignored.
1715           This is taken advantage of by uClibc's malloc(), and also by
1716           ELF-FDPIC binfmt's brk and stack allocator.
1718           Because of the obvious security issues, this option should only be
1719           enabled on embedded devices where you control what is run in
1720           userspace.  Since that isn't generally a problem on no-MMU systems,
1721           it is normally safe to say Y here.
1723           See Documentation/nommu-mmap.txt for more information.
1726         bool "Provide system-wide ring of trusted keys"
1727         depends on KEYS
1728         help
1729           Provide a system keyring to which trusted keys can be added.  Keys in
1730           the keyring are considered to be trusted.  Keys may be added at will
1731           by the kernel from compiled-in data and from hardware key stores, but
1732           userspace may only add extra keys if those keys can be verified by
1733           keys already in the keyring.
1735           Keys in this keyring are used by module signature checking.
1737 config PROFILING
1738         bool "Profiling support"
1739         help
1740           Say Y here to enable the extended profiling support mechanisms used
1741           by profilers such as OProfile.
1743 #
1744 # Place an empty function call at each tracepoint site. Can be
1745 # dynamically changed for a probe function.
1746 #
1747 config TRACEPOINTS
1748         bool
1750 source "arch/Kconfig"
1752 endmenu         # General setup
1755         bool
1756         default n
1758 config SLABINFO
1759         bool
1760         depends on PROC_FS
1761         depends on SLAB || SLUB_DEBUG
1762         default y
1764 config RT_MUTEXES
1765         bool
1767 config BASE_SMALL
1768         int
1769         default 0 if BASE_FULL
1770         default 1 if !BASE_FULL
1772 menuconfig MODULES
1773         bool "Enable loadable module support"
1774         option modules
1775         help
1776           Kernel modules are small pieces of compiled code which can
1777           be inserted in the running kernel, rather than being
1778           permanently built into the kernel.  You use the "modprobe"
1779           tool to add (and sometimes remove) them.  If you say Y here,
1780           many parts of the kernel can be built as modules (by
1781           answering M instead of Y where indicated): this is most
1782           useful for infrequently used options which are not required
1783           for booting.  For more information, see the man pages for
1784           modprobe, lsmod, modinfo, insmod and rmmod.
1786           If you say Y here, you will need to run "make
1787           modules_install" to put the modules under /lib/modules/
1788           where modprobe can find them (you may need to be root to do
1789           this).
1791           If unsure, say Y.
1793 if MODULES
1796         bool "Forced module loading"
1797         default n
1798         help
1799           Allow loading of modules without version information (ie. modprobe
1800           --force).  Forced module loading sets the 'F' (forced) taint flag and
1801           is usually a really bad idea.
1803 config MODULE_UNLOAD
1804         bool "Module unloading"
1805         help
1806           Without this option you will not be able to unload any
1807           modules (note that some modules may not be unloadable
1808           anyway), which makes your kernel smaller, faster
1809           and simpler.  If unsure, say Y.
1812         bool "Forced module unloading"
1813         depends on MODULE_UNLOAD
1814         help
1815           This option allows you to force a module to unload, even if the
1816           kernel believes it is unsafe: the kernel will remove the module
1817           without waiting for anyone to stop using it (using the -f option to
1818           rmmod).  This is mainly for kernel developers and desperate users.
1819           If unsure, say N.
1821 config MODVERSIONS
1822         bool "Module versioning support"
1823         help
1824           Usually, you have to use modules compiled with your kernel.
1825           Saying Y here makes it sometimes possible to use modules
1826           compiled for different kernels, by adding enough information
1827           to the modules to (hopefully) spot any changes which would
1828           make them incompatible with the kernel you are running.  If
1829           unsure, say N.
1832         bool "Source checksum for all modules"
1833         help
1834           Modules which contain a MODULE_VERSION get an extra "srcversion"
1835           field inserted into their modinfo section, which contains a
1836           sum of the source files which made it.  This helps maintainers
1837           see exactly which source was used to build a module (since
1838           others sometimes change the module source without updating
1839           the version).  With this option, such a "srcversion" field
1840           will be created for all modules.  If unsure, say N.
1842 config MODULE_SIG
1843         bool "Module signature verification"
1844         depends on MODULES
1845         select SYSTEM_TRUSTED_KEYRING
1846         select KEYS
1847         select CRYPTO
1848         select ASYMMETRIC_KEY_TYPE
1850         select PUBLIC_KEY_ALGO_RSA
1851         select ASN1
1852         select OID_REGISTRY
1853         select X509_CERTIFICATE_PARSER
1854         help
1855           Check modules for valid signatures upon load: the signature
1856           is simply appended to the module. For more information see
1857           Documentation/module-signing.txt.
1859           !!!WARNING!!!  If you enable this option, you MUST make sure that the
1860           module DOES NOT get stripped after being signed.  This includes the
1861           debuginfo strip done by some packagers (such as rpmbuild) and
1862           inclusion into an initramfs that wants the module size reduced.
1864 config MODULE_SIG_FORCE
1865         bool "Require modules to be validly signed"
1866         depends on MODULE_SIG
1867         help
1868           Reject unsigned modules or signed modules for which we don't have a
1869           key.  Without this, such modules will simply taint the kernel.
1871 config MODULE_SIG_ALL
1872         bool "Automatically sign all modules"
1873         default y
1874         depends on MODULE_SIG
1875         help
1876           Sign all modules during make modules_install. Without this option,
1877           modules must be signed manually, using the scripts/sign-file tool.
1879 comment "Do not forget to sign required modules with scripts/sign-file"
1880         depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1882 choice
1883         prompt "Which hash algorithm should modules be signed with?"
1884         depends on MODULE_SIG
1885         help
1886           This determines which sort of hashing algorithm will be used during
1887           signature generation.  This algorithm _must_ be built into the kernel
1888           directly so that signature verification can take place.  It is not
1889           possible to load a signed module containing the algorithm to check
1890           the signature on that module.
1892 config MODULE_SIG_SHA1
1893         bool "Sign modules with SHA-1"
1894         select CRYPTO_SHA1
1896 config MODULE_SIG_SHA224
1897         bool "Sign modules with SHA-224"
1898         select CRYPTO_SHA256
1900 config MODULE_SIG_SHA256
1901         bool "Sign modules with SHA-256"
1902         select CRYPTO_SHA256
1904 config MODULE_SIG_SHA384
1905         bool "Sign modules with SHA-384"
1906         select CRYPTO_SHA512
1908 config MODULE_SIG_SHA512
1909         bool "Sign modules with SHA-512"
1910         select CRYPTO_SHA512
1912 endchoice
1914 config MODULE_SIG_HASH
1915         string
1916         depends on MODULE_SIG
1917         default "sha1" if MODULE_SIG_SHA1
1918         default "sha224" if MODULE_SIG_SHA224
1919         default "sha256" if MODULE_SIG_SHA256
1920         default "sha384" if MODULE_SIG_SHA384
1921         default "sha512" if MODULE_SIG_SHA512
1924         bool "Compress modules on installation"
1925         depends on MODULES
1926         help
1927           This option compresses the kernel modules when 'make
1928           modules_install' is run.
1930           The modules will be compressed either using gzip or xz depend on the
1931           choice made in "Compression algorithm".
1933           module-init-tools has support for gzip format while kmod handle gzip
1934           and xz compressed modules.
1936           When a kernel module is installed from outside of the main kernel
1937           source and uses the Kbuild system for installing modules then that
1938           kernel module will also be compressed when it is installed.
1940           This option provides little benefit when the modules are to be used inside
1941           an initrd or initramfs, it generally is more efficient to compress the whole
1942           initrd or initramfs instead.
1944           This is fully compatible with signed modules while the signed module is
1945           compressed. module-init-tools or kmod handles decompression and provide to
1946           other layer the uncompressed but signed payload.
1948 choice
1949         prompt "Compression algorithm"
1950         depends on MODULE_COMPRESS
1951         default MODULE_COMPRESS_GZIP
1952         help
1953           This determines which sort of compression will be used during
1954           'make modules_install'.
1956           GZIP (default) and XZ are supported.
1959         bool "GZIP"
1962         bool "XZ"
1964 endchoice
1966 endif # MODULES
1969         bool
1970         help
1971           Back when each arch used to define their own cpu_online_mask and
1972           cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1973           with all 1s, and others with all 0s.  When they were centralised,
1974           it was better to provide this option than to break all the archs
1975           and have several arch maintainers pursuing me down dark alleys.
1977 config STOP_MACHINE
1978         bool
1979         default y
1980         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1981         help
1982           Need stop_machine() primitive.
1984 source "block/Kconfig"
1987         bool
1989 config PADATA
1990         depends on SMP
1991         bool
1993 # Can be selected by architectures with broken toolchains
1994 # that get confused by correct const<->read_only section
1995 # mappings
1996 config BROKEN_RODATA
1997         bool
1999 config ASN1
2000         tristate
2001         help
2002           Build a simple ASN.1 grammar compiler that produces a bytecode output
2003           that can be interpreted by the ASN.1 stream decoder and used to
2004           inform it as to what tags are to be expected in a stream and what
2005           functions to call on what tags.
2007 source "kernel/Kconfig.locks"

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