Version:  2.0.40 2.2.26 2.4.37 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 4.1 4.2


  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         depends on MULTIUSER
398         help
399           If you say Y here, a user level program will be able to instruct the
400           kernel (via a special system call) to write process accounting
401           information to a file: whenever a process exits, information about
402           that process will be appended to the file by the kernel.  The
403           information includes things such as creation time, owning user,
404           command name, memory usage, controlling terminal etc. (the complete
405           list is in the struct acct in <file:include/linux/acct.h>).  It is
406           up to the user level program to do useful things with this
407           information.  This is generally a good idea, so say Y.
409 config BSD_PROCESS_ACCT_V3
410         bool "BSD Process Accounting version 3 file format"
411         depends on BSD_PROCESS_ACCT
412         default n
413         help
414           If you say Y here, the process accounting information is written
415           in a new file format that also logs the process IDs of each
416           process and it's parent. Note that this file format is incompatible
417           with previous v0/v1/v2 file formats, so you will need updated tools
418           for processing it. A preliminary version of these tools is available
419           at <>.
421 config TASKSTATS
422         bool "Export task/process statistics through netlink"
423         depends on NET
424         depends on MULTIUSER
425         default n
426         help
427           Export selected statistics for tasks/processes through the
428           generic netlink interface. Unlike BSD process accounting, the
429           statistics are available during the lifetime of tasks/processes as
430           responses to commands. Like BSD accounting, they are sent to user
431           space on task exit.
433           Say N if unsure.
435 config TASK_DELAY_ACCT
436         bool "Enable per-task delay accounting"
437         depends on TASKSTATS
438         select SCHED_INFO
439         help
440           Collect information on time spent by a task waiting for system
441           resources like cpu, synchronous block I/O completion and swapping
442           in pages. Such statistics can help in setting a task's priorities
443           relative to other tasks for cpu, io, rss limits etc.
445           Say N if unsure.
447 config TASK_XACCT
448         bool "Enable extended accounting over taskstats"
449         depends on TASKSTATS
450         help
451           Collect extended task accounting data and send the data
452           to userland for processing over the taskstats interface.
454           Say N if unsure.
457         bool "Enable per-task storage I/O accounting"
458         depends on TASK_XACCT
459         help
460           Collect information on the number of bytes of storage I/O which this
461           task has caused.
463           Say N if unsure.
465 endmenu # "CPU/Task time and stats accounting"
467 menu "RCU Subsystem"
469 config TREE_RCU
470         bool
471         default y if !PREEMPT && SMP
472         help
473           This option selects the RCU implementation that is
474           designed for very large SMP system with hundreds or
475           thousands of CPUs.  It also scales down nicely to
476           smaller systems.
478 config PREEMPT_RCU
479         bool
480         default y if PREEMPT
481         help
482           This option selects the RCU implementation that is
483           designed for very large SMP systems with hundreds or
484           thousands of CPUs, but for which real-time response
485           is also required.  It also scales down nicely to
486           smaller systems.
488           Select this option if you are unsure.
490 config TINY_RCU
491         bool
492         default y if !PREEMPT && !SMP
493         help
494           This option selects the RCU implementation that is
495           designed for UP systems from which real-time response
496           is not required.  This option greatly reduces the
497           memory footprint of RCU.
499 config RCU_EXPERT
500         bool "Make expert-level adjustments to RCU configuration"
501         default n
502         help
503           This option needs to be enabled if you wish to make
504           expert-level adjustments to RCU configuration.  By default,
505           no such adjustments can be made, which has the often-beneficial
506           side-effect of preventing "make oldconfig" from asking you all
507           sorts of detailed questions about how you would like numerous
508           obscure RCU options to be set up.
510           Say Y if you need to make expert-level adjustments to RCU.
512           Say N if you are unsure.
514 config SRCU
515         bool
516         help
517           This option selects the sleepable version of RCU. This version
518           permits arbitrary sleeping or blocking within RCU read-side critical
519           sections.
521 config TASKS_RCU
522         bool
523         default n
524         select SRCU
525         help
526           This option enables a task-based RCU implementation that uses
527           only voluntary context switch (not preemption!), idle, and
528           user-mode execution as quiescent states.
531         def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
532         help
533           This option enables RCU CPU stall code that is common between
534           the TINY and TREE variants of RCU.  The purpose is to allow
535           the tiny variants to disable RCU CPU stall warnings, while
536           making these warnings mandatory for the tree variants.
539        bool
541 config RCU_USER_QS
542         bool
543         help
544           This option sets hooks on kernel / userspace boundaries and
545           puts RCU in extended quiescent state when the CPU runs in
546           userspace. It means that when a CPU runs in userspace, it is
547           excluded from the global RCU state machine and thus doesn't
548           try to keep the timer tick on for RCU.
551         bool "Force context tracking"
552         depends on CONTEXT_TRACKING
553         default y if !NO_HZ_FULL
554         help
555           The major pre-requirement for full dynticks to work is to
556           support the context tracking subsystem. But there are also
557           other dependencies to provide in order to make the full
558           dynticks working.
560           This option stands for testing when an arch implements the
561           context tracking backend but doesn't yet fullfill all the
562           requirements to make the full dynticks feature working.
563           Without the full dynticks, there is no way to test the support
564           for context tracking and the subsystems that rely on it: RCU
565           userspace extended quiescent state and tickless cputime
566           accounting. This option copes with the absence of the full
567           dynticks subsystem by forcing the context tracking on all
568           CPUs in the system.
570           Say Y only if you're working on the development of an
571           architecture backend for the context tracking.
573           Say N otherwise, this option brings an overhead that you
574           don't want in production.
577 config RCU_FANOUT
578         int "Tree-based hierarchical RCU fanout value"
579         range 2 64 if 64BIT
580         range 2 32 if !64BIT
581         depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
582         default 64 if 64BIT
583         default 32 if !64BIT
584         help
585           This option controls the fanout of hierarchical implementations
586           of RCU, allowing RCU to work efficiently on machines with
587           large numbers of CPUs.  This value must be at least the fourth
588           root of NR_CPUS, which allows NR_CPUS to be insanely large.
589           The default value of RCU_FANOUT should be used for production
590           systems, but if you are stress-testing the RCU implementation
591           itself, small RCU_FANOUT values allow you to test large-system
592           code paths on small(er) systems.
594           Select a specific number if testing RCU itself.
595           Take the default if unsure.
597 config RCU_FANOUT_LEAF
598         int "Tree-based hierarchical RCU leaf-level fanout value"
599         range 2 64 if 64BIT
600         range 2 32 if !64BIT
601         depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
602         default 16
603         help
604           This option controls the leaf-level fanout of hierarchical
605           implementations of RCU, and allows trading off cache misses
606           against lock contention.  Systems that synchronize their
607           scheduling-clock interrupts for energy-efficiency reasons will
608           want the default because the smaller leaf-level fanout keeps
609           lock contention levels acceptably low.  Very large systems
610           (hundreds or thousands of CPUs) will instead want to set this
611           value to the maximum value possible in order to reduce the
612           number of cache misses incurred during RCU's grace-period
613           initialization.  These systems tend to run CPU-bound, and thus
614           are not helped by synchronized interrupts, and thus tend to
615           skew them, which reduces lock contention enough that large
616           leaf-level fanouts work well.
618           Select a specific number if testing RCU itself.
620           Select the maximum permissible value for large systems.
622           Take the default if unsure.
624 config RCU_FAST_NO_HZ
625         bool "Accelerate last non-dyntick-idle CPU's grace periods"
626         depends on NO_HZ_COMMON && SMP && RCU_EXPERT
627         default n
628         help
629           This option permits CPUs to enter dynticks-idle state even if
630           they have RCU callbacks queued, and prevents RCU from waking
631           these CPUs up more than roughly once every four jiffies (by
632           default, you can adjust this using the rcutree.rcu_idle_gp_delay
633           parameter), thus improving energy efficiency.  On the other
634           hand, this option increases the duration of RCU grace periods,
635           for example, slowing down synchronize_rcu().
637           Say Y if energy efficiency is critically important, and you
638                 don't care about increased grace-period durations.
640           Say N if you are unsure.
642 config TREE_RCU_TRACE
643         def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
644         select DEBUG_FS
645         help
646           This option provides tracing for the TREE_RCU and
647           PREEMPT_RCU implementations, permitting Makefile to
648           trivially select kernel/rcutree_trace.c.
650 config RCU_BOOST
651         bool "Enable RCU priority boosting"
652         depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT
653         default n
654         help
655           This option boosts the priority of preempted RCU readers that
656           block the current preemptible RCU grace period for too long.
657           This option also prevents heavy loads from blocking RCU
658           callback invocation for all flavors of RCU.
660           Say Y here if you are working with real-time apps or heavy loads
661           Say N here if you are unsure.
664         int "Real-time priority to use for RCU worker threads"
665         range 1 99 if RCU_BOOST
666         range 0 99 if !RCU_BOOST
667         default 1 if RCU_BOOST
668         default 0 if !RCU_BOOST
669         depends on RCU_EXPERT
670         help
671           This option specifies the SCHED_FIFO priority value that will be
672           assigned to the rcuc/n and rcub/n threads and is also the value
673           used for RCU_BOOST (if enabled). If you are working with a
674           real-time application that has one or more CPU-bound threads
675           running at a real-time priority level, you should set
676           RCU_KTHREAD_PRIO to a priority higher than the highest-priority
677           real-time CPU-bound application thread.  The default RCU_KTHREAD_PRIO
678           value of 1 is appropriate in the common case, which is real-time
679           applications that do not have any CPU-bound threads.
681           Some real-time applications might not have a single real-time
682           thread that saturates a given CPU, but instead might have
683           multiple real-time threads that, taken together, fully utilize
684           that CPU.  In this case, you should set RCU_KTHREAD_PRIO to
685           a priority higher than the lowest-priority thread that is
686           conspiring to prevent the CPU from running any non-real-time
687           tasks.  For example, if one thread at priority 10 and another
688           thread at priority 5 are between themselves fully consuming
689           the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
690           set to priority 6 or higher.
692           Specify the real-time priority, or take the default if unsure.
694 config RCU_BOOST_DELAY
695         int "Milliseconds to delay boosting after RCU grace-period start"
696         range 0 3000
697         depends on RCU_BOOST
698         default 500
699         help
700           This option specifies the time to wait after the beginning of
701           a given grace period before priority-boosting preempted RCU
702           readers blocking that grace period.  Note that any RCU reader
703           blocking an expedited RCU grace period is boosted immediately.
705           Accept the default if unsure.
707 config RCU_NOCB_CPU
708         bool "Offload RCU callback processing from boot-selected CPUs"
709         depends on TREE_RCU || PREEMPT_RCU
710         default n
711         help
712           Use this option to reduce OS jitter for aggressive HPC or
713           real-time workloads.  It can also be used to offload RCU
714           callback invocation to energy-efficient CPUs in battery-powered
715           asymmetric multiprocessors.
717           This option offloads callback invocation from the set of
718           CPUs specified at boot time by the rcu_nocbs parameter.
719           For each such CPU, a kthread ("rcuox/N") will be created to
720           invoke callbacks, where the "N" is the CPU being offloaded,
721           and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
722           "s" for RCU-sched.  Nothing prevents this kthread from running
723           on the specified CPUs, but (1) the kthreads may be preempted
724           between each callback, and (2) affinity or cgroups can be used
725           to force the kthreads to run on whatever set of CPUs is desired.
727           Say Y here if you want to help to debug reduced OS jitter.
728           Say N here if you are unsure.
730 choice
731         prompt "Build-forced no-CBs CPUs"
732         default RCU_NOCB_CPU_NONE
733         depends on RCU_NOCB_CPU
734         help
735           This option allows no-CBs CPUs (whose RCU callbacks are invoked
736           from kthreads rather than from softirq context) to be specified
737           at build time.  Additional no-CBs CPUs may be specified by
738           the rcu_nocbs= boot parameter.
740 config RCU_NOCB_CPU_NONE
741         bool "No build_forced no-CBs CPUs"
742         help
743           This option does not force any of the CPUs to be no-CBs CPUs.
744           Only CPUs designated by the rcu_nocbs= boot parameter will be
745           no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
746           kthreads whose names begin with "rcuo".  All other CPUs will
747           invoke their own RCU callbacks in softirq context.
749           Select this option if you want to choose no-CBs CPUs at
750           boot time, for example, to allow testing of different no-CBs
751           configurations without having to rebuild the kernel each time.
753 config RCU_NOCB_CPU_ZERO
754         bool "CPU 0 is a build_forced no-CBs CPU"
755         help
756           This option forces CPU 0 to be a no-CBs CPU, so that its RCU
757           callbacks are invoked by a per-CPU kthread whose name begins
758           with "rcuo".  Additional CPUs may be designated as no-CBs
759           CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
760           All other CPUs will invoke their own RCU callbacks in softirq
761           context.
763           Select this if CPU 0 needs to be a no-CBs CPU for real-time
764           or energy-efficiency reasons, but the real reason it exists
765           is to ensure that randconfig testing covers mixed systems.
767 config RCU_NOCB_CPU_ALL
768         bool "All CPUs are build_forced no-CBs CPUs"
769         help
770           This option forces all CPUs to be no-CBs CPUs.  The rcu_nocbs=
771           boot parameter will be ignored.  All CPUs' RCU callbacks will
772           be executed in the context of per-CPU rcuo kthreads created for
773           this purpose.  Assuming that the kthreads whose names start with
774           "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
775           on the remaining CPUs, but might decrease memory locality during
776           RCU-callback invocation, thus potentially degrading throughput.
778           Select this if all CPUs need to be no-CBs CPUs for real-time
779           or energy-efficiency reasons.
781 endchoice
784         bool
785         default n
786         help
787           This option enables expedited grace periods at boot time,
788           as if rcu_expedite_gp() had been invoked early in boot.
789           The corresponding rcu_unexpedite_gp() is invoked from
790           rcu_end_inkernel_boot(), which is intended to be invoked
791           at the end of the kernel-only boot sequence, just before
792           init is exec'ed.
794           Accept the default if unsure.
796 endmenu # "RCU Subsystem"
798 config BUILD_BIN2C
799         bool
800         default n
802 config IKCONFIG
803         tristate "Kernel .config support"
804         select BUILD_BIN2C
805         ---help---
806           This option enables the complete Linux kernel ".config" file
807           contents to be saved in the kernel. It provides documentation
808           of which kernel options are used in a running kernel or in an
809           on-disk kernel.  This information can be extracted from the kernel
810           image file with the script scripts/extract-ikconfig and used as
811           input to rebuild the current kernel or to build another kernel.
812           It can also be extracted from a running kernel by reading
813           /proc/config.gz if enabled (below).
815 config IKCONFIG_PROC
816         bool "Enable access to .config through /proc/config.gz"
817         depends on IKCONFIG && PROC_FS
818         ---help---
819           This option enables access to the kernel configuration file
820           through /proc/config.gz.
822 config LOG_BUF_SHIFT
823         int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
824         range 12 25
825         default 17
826         depends on PRINTK
827         help
828           Select the minimal kernel log buffer size as a power of 2.
829           The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
830           parameter, see below. Any higher size also might be forced
831           by "log_buf_len" boot parameter.
833           Examples:
834                      17 => 128 KB
835                      16 => 64 KB
836                      15 => 32 KB
837                      14 => 16 KB
838                      13 =>  8 KB
839                      12 =>  4 KB
842         int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
843         depends on SMP
844         range 0 21
845         default 12 if !BASE_SMALL
846         default 0 if BASE_SMALL
847         depends on PRINTK
848         help
849           This option allows to increase the default ring buffer size
850           according to the number of CPUs. The value defines the contribution
851           of each CPU as a power of 2. The used space is typically only few
852           lines however it might be much more when problems are reported,
853           e.g. backtraces.
855           The increased size means that a new buffer has to be allocated and
856           the original static one is unused. It makes sense only on systems
857           with more CPUs. Therefore this value is used only when the sum of
858           contributions is greater than the half of the default kernel ring
859           buffer as defined by LOG_BUF_SHIFT. The default values are set
860           so that more than 64 CPUs are needed to trigger the allocation.
862           Also this option is ignored when "log_buf_len" kernel parameter is
863           used as it forces an exact (power of two) size of the ring buffer.
865           The number of possible CPUs is used for this computation ignoring
866           hotplugging making the compuation optimal for the the worst case
867           scenerio while allowing a simple algorithm to be used from bootup.
869           Examples shift values and their meaning:
870                      17 => 128 KB for each CPU
871                      16 =>  64 KB for each CPU
872                      15 =>  32 KB for each CPU
873                      14 =>  16 KB for each CPU
874                      13 =>   8 KB for each CPU
875                      12 =>   4 KB for each CPU
877 #
878 # Architectures with an unreliable sched_clock() should select this:
879 #
881         bool
884         bool
886 #
887 # For architectures that want to enable the support for NUMA-affine scheduler
888 # balancing logic:
889 #
891         bool
893 #
894 # For architectures that know their GCC __int128 support is sound
895 #
896 config ARCH_SUPPORTS_INT128
897         bool
899 # For architectures that (ab)use NUMA to represent different memory regions
900 # all cpu-local but of different latencies, such as SuperH.
901 #
903         bool
906         bool "Memory placement aware NUMA scheduler"
907         depends on ARCH_SUPPORTS_NUMA_BALANCING
908         depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
909         depends on SMP && NUMA && MIGRATION
910         help
911           This option adds support for automatic NUMA aware memory/task placement.
912           The mechanism is quite primitive and is based on migrating memory when
913           it has references to the node the task is running on.
915           This system will be inactive on UMA systems.
918         bool "Automatically enable NUMA aware memory/task placement"
919         default y
920         depends on NUMA_BALANCING
921         help
922           If set, automatic NUMA balancing will be enabled if running on a NUMA
923           machine.
925 menuconfig CGROUPS
926         bool "Control Group support"
927         select KERNFS
928         select PERCPU_RWSEM
929         help
930           This option adds support for grouping sets of processes together, for
931           use with process control subsystems such as Cpusets, CFS, memory
932           controls or device isolation.
933           See
934                 - Documentation/scheduler/sched-design-CFS.txt  (CFS)
935                 - Documentation/cgroups/ (features for grouping, isolation
936                                           and resource control)
938           Say N if unsure.
940 if CGROUPS
942 config CGROUP_DEBUG
943         bool "Example debug cgroup subsystem"
944         default n
945         help
946           This option enables a simple cgroup subsystem that
947           exports useful debugging information about the cgroups
948           framework.
950           Say N if unsure.
953         bool "Freezer cgroup subsystem"
954         help
955           Provides a way to freeze and unfreeze all tasks in a
956           cgroup.
958 config CGROUP_DEVICE
959         bool "Device controller for cgroups"
960         help
961           Provides a cgroup implementing whitelists for devices which
962           a process in the cgroup can mknod or open.
964 config CPUSETS
965         bool "Cpuset support"
966         help
967           This option will let you create and manage CPUSETs which
968           allow dynamically partitioning a system into sets of CPUs and
969           Memory Nodes and assigning tasks to run only within those sets.
970           This is primarily useful on large SMP or NUMA systems.
972           Say N if unsure.
974 config PROC_PID_CPUSET
975         bool "Include legacy /proc/<pid>/cpuset file"
976         depends on CPUSETS
977         default y
980         bool "Simple CPU accounting cgroup subsystem"
981         help
982           Provides a simple Resource Controller for monitoring the
983           total CPU consumed by the tasks in a cgroup.
985 config PAGE_COUNTER
986        bool
988 config MEMCG
989         bool "Memory Resource Controller for Control Groups"
990         select PAGE_COUNTER
991         select EVENTFD
992         help
993           Provides a memory resource controller that manages both anonymous
994           memory and page cache. (See Documentation/cgroups/memory.txt)
996 config MEMCG_SWAP
997         bool "Memory Resource Controller Swap Extension"
998         depends on MEMCG && SWAP
999         help
1000           Add swap management feature to memory resource controller. When you
1001           enable this, you can limit mem+swap usage per cgroup. In other words,
1002           when you disable this, memory resource controller has no cares to
1003           usage of swap...a process can exhaust all of the swap. This extension
1004           is useful when you want to avoid exhaustion swap but this itself
1005           adds more overheads and consumes memory for remembering information.
1006           Especially if you use 32bit system or small memory system, please
1007           be careful about enabling this. When memory resource controller
1008           is disabled by boot option, this will be automatically disabled and
1009           there will be no overhead from this. Even when you set this config=y,
1010           if boot option "swapaccount=0" is set, swap will not be accounted.
1011           Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
1012           size is 4096bytes, 512k per 1Gbytes of swap.
1014         bool "Memory Resource Controller Swap Extension enabled by default"
1015         depends on MEMCG_SWAP
1016         default y
1017         help
1018           Memory Resource Controller Swap Extension comes with its price in
1019           a bigger memory consumption. General purpose distribution kernels
1020           which want to enable the feature but keep it disabled by default
1021           and let the user enable it by swapaccount=1 boot command line
1022           parameter should have this option unselected.
1023           For those who want to have the feature enabled by default should
1024           select this option (if, for some reason, they need to disable it
1025           then swapaccount=0 does the trick).
1026 config MEMCG_KMEM
1027         bool "Memory Resource Controller Kernel Memory accounting"
1028         depends on MEMCG
1029         depends on SLUB || SLAB
1030         help
1031           The Kernel Memory extension for Memory Resource Controller can limit
1032           the amount of memory used by kernel objects in the system. Those are
1033           fundamentally different from the entities handled by the standard
1034           Memory Controller, which are page-based, and can be swapped. Users of
1035           the kmem extension can use it to guarantee that no group of processes
1036           will ever exhaust kernel resources alone.
1038 config CGROUP_HUGETLB
1039         bool "HugeTLB Resource Controller for Control Groups"
1040         depends on HUGETLB_PAGE
1041         select PAGE_COUNTER
1042         default n
1043         help
1044           Provides a cgroup Resource Controller for HugeTLB pages.
1045           When you enable this, you can put a per cgroup limit on HugeTLB usage.
1046           The limit is enforced during page fault. Since HugeTLB doesn't
1047           support page reclaim, enforcing the limit at page fault time implies
1048           that, the application will get SIGBUS signal if it tries to access
1049           HugeTLB pages beyond its limit. This requires the application to know
1050           beforehand how much HugeTLB pages it would require for its use. The
1051           control group is tracked in the third page lru pointer. This means
1052           that we cannot use the controller with huge page less than 3 pages.
1054 config CGROUP_PERF
1055         bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1056         depends on PERF_EVENTS && CGROUPS
1057         help
1058           This option extends the per-cpu mode to restrict monitoring to
1059           threads which belong to the cgroup specified and run on the
1060           designated cpu.
1062           Say N if unsure.
1064 menuconfig CGROUP_SCHED
1065         bool "Group CPU scheduler"
1066         default n
1067         help
1068           This feature lets CPU scheduler recognize task groups and control CPU
1069           bandwidth allocation to such task groups. It uses cgroups to group
1070           tasks.
1073 config FAIR_GROUP_SCHED
1074         bool "Group scheduling for SCHED_OTHER"
1075         depends on CGROUP_SCHED
1076         default CGROUP_SCHED
1078 config CFS_BANDWIDTH
1079         bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1080         depends on FAIR_GROUP_SCHED
1081         default n
1082         help
1083           This option allows users to define CPU bandwidth rates (limits) for
1084           tasks running within the fair group scheduler.  Groups with no limit
1085           set are considered to be unconstrained and will run with no
1086           restriction.
1087           See tip/Documentation/scheduler/sched-bwc.txt for more information.
1089 config RT_GROUP_SCHED
1090         bool "Group scheduling for SCHED_RR/FIFO"
1091         depends on CGROUP_SCHED
1092         default n
1093         help
1094           This feature lets you explicitly allocate real CPU bandwidth
1095           to task groups. If enabled, it will also make it impossible to
1096           schedule realtime tasks for non-root users until you allocate
1097           realtime bandwidth for them.
1098           See Documentation/scheduler/sched-rt-group.txt for more information.
1100 endif #CGROUP_SCHED
1102 config BLK_CGROUP
1103         bool "Block IO controller"
1104         depends on BLOCK
1105         default n
1106         ---help---
1107         Generic block IO controller cgroup interface. This is the common
1108         cgroup interface which should be used by various IO controlling
1109         policies.
1111         Currently, CFQ IO scheduler uses it to recognize task groups and
1112         control disk bandwidth allocation (proportional time slice allocation)
1113         to such task groups. It is also used by bio throttling logic in
1114         block layer to implement upper limit in IO rates on a device.
1116         This option only enables generic Block IO controller infrastructure.
1117         One needs to also enable actual IO controlling logic/policy. For
1118         enabling proportional weight division of disk bandwidth in CFQ, set
1119         CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1122         See Documentation/cgroups/blkio-controller.txt for more information.
1124 config DEBUG_BLK_CGROUP
1125         bool "Enable Block IO controller debugging"
1126         depends on BLK_CGROUP
1127         default n
1128         ---help---
1129         Enable some debugging help. Currently it exports additional stat
1130         files in a cgroup which can be useful for debugging.
1133         bool
1134         depends on MEMCG && BLK_CGROUP
1135         default y
1137 endif # CGROUPS
1140         bool "Checkpoint/restore support" if EXPERT
1141         select PROC_CHILDREN
1142         default n
1143         help
1144           Enables additional kernel features in a sake of checkpoint/restore.
1145           In particular it adds auxiliary prctl codes to setup process text,
1146           data and heap segment sizes, and a few additional /proc filesystem
1147           entries.
1149           If unsure, say N here.
1151 menuconfig NAMESPACES
1152         bool "Namespaces support" if EXPERT
1153         depends on MULTIUSER
1154         default !EXPERT
1155         help
1156           Provides the way to make tasks work with different objects using
1157           the same id. For example same IPC id may refer to different objects
1158           or same user id or pid may refer to different tasks when used in
1159           different namespaces.
1163 config UTS_NS
1164         bool "UTS namespace"
1165         default y
1166         help
1167           In this namespace tasks see different info provided with the
1168           uname() system call
1170 config IPC_NS
1171         bool "IPC namespace"
1172         depends on (SYSVIPC || POSIX_MQUEUE)
1173         default y
1174         help
1175           In this namespace tasks work with IPC ids which correspond to
1176           different IPC objects in different namespaces.
1178 config USER_NS
1179         bool "User namespace"
1180         default n
1181         help
1182           This allows containers, i.e. vservers, to use user namespaces
1183           to provide different user info for different servers.
1185           When user namespaces are enabled in the kernel it is
1186           recommended that the MEMCG and MEMCG_KMEM options also be
1187           enabled and that user-space use the memory control groups to
1188           limit the amount of memory a memory unprivileged users can
1189           use.
1191           If unsure, say N.
1193 config PID_NS
1194         bool "PID Namespaces"
1195         default y
1196         help
1197           Support process id namespaces.  This allows having multiple
1198           processes with the same pid as long as they are in different
1199           pid namespaces.  This is a building block of containers.
1201 config NET_NS
1202         bool "Network namespace"
1203         depends on NET
1204         default y
1205         help
1206           Allow user space to create what appear to be multiple instances
1207           of the network stack.
1209 endif # NAMESPACES
1212         bool "Automatic process group scheduling"
1213         select CGROUPS
1214         select CGROUP_SCHED
1215         select FAIR_GROUP_SCHED
1216         help
1217           This option optimizes the scheduler for common desktop workloads by
1218           automatically creating and populating task groups.  This separation
1219           of workloads isolates aggressive CPU burners (like build jobs) from
1220           desktop applications.  Task group autogeneration is currently based
1221           upon task session.
1224         bool "Enable deprecated sysfs features to support old userspace tools"
1225         depends on SYSFS
1226         default n
1227         help
1228           This option adds code that switches the layout of the "block" class
1229           devices, to not show up in /sys/class/block/, but only in
1230           /sys/block/.
1232           This switch is only active when the sysfs.deprecated=1 boot option is
1233           passed or the SYSFS_DEPRECATED_V2 option is set.
1235           This option allows new kernels to run on old distributions and tools,
1236           which might get confused by /sys/class/block/. Since 2007/2008 all
1237           major distributions and tools handle this just fine.
1239           Recent distributions and userspace tools after 2009/2010 depend on
1240           the existence of /sys/class/block/, and will not work with this
1241           option enabled.
1243           Only if you are using a new kernel on an old distribution, you might
1244           need to say Y here.
1247         bool "Enable deprecated sysfs features by default"
1248         default n
1249         depends on SYSFS
1250         depends on SYSFS_DEPRECATED
1251         help
1252           Enable deprecated sysfs by default.
1254           See the CONFIG_SYSFS_DEPRECATED option for more details about this
1255           option.
1257           Only if you are using a new kernel on an old distribution, you might
1258           need to say Y here. Even then, odds are you would not need it
1259           enabled, you can always pass the boot option if absolutely necessary.
1261 config RELAY
1262         bool "Kernel->user space relay support (formerly relayfs)"
1263         help
1264           This option enables support for relay interface support in
1265           certain file systems (such as debugfs).
1266           It is designed to provide an efficient mechanism for tools and
1267           facilities to relay large amounts of data from kernel space to
1268           user space.
1270           If unsure, say N.
1272 config BLK_DEV_INITRD
1273         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1274         depends on BROKEN || !FRV
1275         help
1276           The initial RAM filesystem is a ramfs which is loaded by the
1277           boot loader (loadlin or lilo) and that is mounted as root
1278           before the normal boot procedure. It is typically used to
1279           load modules needed to mount the "real" root file system,
1280           etc. See <file:Documentation/initrd.txt> for details.
1282           If RAM disk support (BLK_DEV_RAM) is also included, this
1283           also enables initial RAM disk (initrd) support and adds
1284           15 Kbytes (more on some other architectures) to the kernel size.
1286           If unsure say Y.
1290 source "usr/Kconfig"
1292 endif
1295         bool "Optimize for size"
1296         help
1297           Enabling this option will pass "-Os" instead of "-O2" to
1298           your compiler resulting in a smaller kernel.
1300           If unsure, say N.
1302 config SYSCTL
1303         bool
1305 config ANON_INODES
1306         bool
1308 config HAVE_UID16
1309         bool
1312         bool
1313         help
1314           Enable support for /proc/sys/debug/exception-trace.
1317         bool
1318         help
1319           Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1320           Allows arch to define/use @no_unaligned_warning to possibly warn
1321           about unaligned access emulation going on under the hood.
1324         bool
1325         help
1326           Enable support for /proc/sys/kernel/unaligned-trap
1327           Allows arches to define/use @unaligned_enabled to runtime toggle
1328           the unaligned access emulation.
1329           see arch/parisc/kernel/unaligned.c for reference
1332         bool
1334 # interpreter that classic socket filters depend on
1335 config BPF
1336         bool
1338 menuconfig EXPERT
1339         bool "Configure standard kernel features (expert users)"
1340         # Unhide debug options, to make the on-by-default options visible
1341         select DEBUG_KERNEL
1342         help
1343           This option allows certain base kernel options and settings
1344           to be disabled or tweaked. This is for specialized
1345           environments which can tolerate a "non-standard" kernel.
1346           Only use this if you really know what you are doing.
1348 config UID16
1349         bool "Enable 16-bit UID system calls" if EXPERT
1350         depends on HAVE_UID16 && MULTIUSER
1351         default y
1352         help
1353           This enables the legacy 16-bit UID syscall wrappers.
1355 config MULTIUSER
1356         bool "Multiple users, groups and capabilities support" if EXPERT
1357         default y
1358         help
1359           This option enables support for non-root users, groups and
1360           capabilities.
1362           If you say N here, all processes will run with UID 0, GID 0, and all
1363           possible capabilities.  Saying N here also compiles out support for
1364           system calls related to UIDs, GIDs, and capabilities, such as setuid,
1365           setgid, and capset.
1367           If unsure, say Y here.
1370         bool "sgetmask/ssetmask syscalls support" if EXPERT
1371         def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1372         ---help---
1373           sys_sgetmask and sys_ssetmask are obsolete system calls
1374           no longer supported in libc but still enabled by default in some
1375           architectures.
1377           If unsure, leave the default option here.
1379 config SYSFS_SYSCALL
1380         bool "Sysfs syscall support" if EXPERT
1381         default y
1382         ---help---
1383           sys_sysfs is an obsolete system call no longer supported in libc.
1384           Note that disabling this option is more secure but might break
1385           compatibility with some systems.
1387           If unsure say Y here.
1389 config SYSCTL_SYSCALL
1390         bool "Sysctl syscall support" if EXPERT
1391         depends on PROC_SYSCTL
1392         default n
1393         select SYSCTL
1394         ---help---
1395           sys_sysctl uses binary paths that have been found challenging
1396           to properly maintain and use.  The interface in /proc/sys
1397           using paths with ascii names is now the primary path to this
1398           information.
1400           Almost nothing using the binary sysctl interface so if you are
1401           trying to save some space it is probably safe to disable this,
1402           making your kernel marginally smaller.
1404           If unsure say N here.
1406 config KALLSYMS
1407          bool "Load all symbols for debugging/ksymoops" if EXPERT
1408          default y
1409          help
1410            Say Y here to let the kernel print out symbolic crash information and
1411            symbolic stack backtraces. This increases the size of the kernel
1412            somewhat, as all symbols have to be loaded into the kernel image.
1414 config KALLSYMS_ALL
1415         bool "Include all symbols in kallsyms"
1416         depends on DEBUG_KERNEL && KALLSYMS
1417         help
1418            Normally kallsyms only contains the symbols of functions for nicer
1419            OOPS messages and backtraces (i.e., symbols from the text and inittext
1420            sections). This is sufficient for most cases. And only in very rare
1421            cases (e.g., when a debugger is used) all symbols are required (e.g.,
1422            names of variables from the data sections, etc).
1424            This option makes sure that all symbols are loaded into the kernel
1425            image (i.e., symbols from all sections) in cost of increased kernel
1426            size (depending on the kernel configuration, it may be 300KiB or
1427            something like this).
1429            Say N unless you really need all symbols.
1431 config PRINTK
1432         default y
1433         bool "Enable support for printk" if EXPERT
1434         select IRQ_WORK
1435         help
1436           This option enables normal printk support. Removing it
1437           eliminates most of the message strings from the kernel image
1438           and makes the kernel more or less silent. As this makes it
1439           very difficult to diagnose system problems, saying N here is
1440           strongly discouraged.
1442 config BUG
1443         bool "BUG() support" if EXPERT
1444         default y
1445         help
1446           Disabling this option eliminates support for BUG and WARN, reducing
1447           the size of your kernel image and potentially quietly ignoring
1448           numerous fatal conditions. You should only consider disabling this
1449           option for embedded systems with no facilities for reporting errors.
1450           Just say Y.
1452 config ELF_CORE
1453         depends on COREDUMP
1454         default y
1455         bool "Enable ELF core dumps" if EXPERT
1456         help
1457           Enable support for generating core dumps. Disabling saves about 4k.
1461         bool "Enable PC-Speaker support" if EXPERT
1462         depends on HAVE_PCSPKR_PLATFORM
1463         select I8253_LOCK
1464         default y
1465         help
1466           This option allows to disable the internal PC-Speaker
1467           support, saving some memory.
1469 config BASE_FULL
1470         default y
1471         bool "Enable full-sized data structures for core" if EXPERT
1472         help
1473           Disabling this option reduces the size of miscellaneous core
1474           kernel data structures. This saves memory on small machines,
1475           but may reduce performance.
1477 config FUTEX
1478         bool "Enable futex support" if EXPERT
1479         default y
1480         select RT_MUTEXES
1481         help
1482           Disabling this option will cause the kernel to be built without
1483           support for "fast userspace mutexes".  The resulting kernel may not
1484           run glibc-based applications correctly.
1487         bool
1488         depends on FUTEX
1489         help
1490           Architectures should select this if futex_atomic_cmpxchg_inatomic()
1491           is implemented and always working. This removes a couple of runtime
1492           checks.
1494 config EPOLL
1495         bool "Enable eventpoll support" if EXPERT
1496         default y
1497         select ANON_INODES
1498         help
1499           Disabling this option will cause the kernel to be built without
1500           support for epoll family of system calls.
1502 config SIGNALFD
1503         bool "Enable signalfd() system call" if EXPERT
1504         select ANON_INODES
1505         default y
1506         help
1507           Enable the signalfd() system call that allows to receive signals
1508           on a file descriptor.
1510           If unsure, say Y.
1512 config TIMERFD
1513         bool "Enable timerfd() system call" if EXPERT
1514         select ANON_INODES
1515         default y
1516         help
1517           Enable the timerfd() system call that allows to receive timer
1518           events on a file descriptor.
1520           If unsure, say Y.
1522 config EVENTFD
1523         bool "Enable eventfd() system call" if EXPERT
1524         select ANON_INODES
1525         default y
1526         help
1527           Enable the eventfd() system call that allows to receive both
1528           kernel notification (ie. KAIO) or userspace notifications.
1530           If unsure, say Y.
1532 # syscall, maps, verifier
1533 config BPF_SYSCALL
1534         bool "Enable bpf() system call"
1535         select ANON_INODES
1536         select BPF
1537         default n
1538         help
1539           Enable the bpf() system call that allows to manipulate eBPF
1540           programs and maps via file descriptors.
1542 config SHMEM
1543         bool "Use full shmem filesystem" if EXPERT
1544         default y
1545         depends on MMU
1546         help
1547           The shmem is an internal filesystem used to manage shared memory.
1548           It is backed by swap and manages resource limits. It is also exported
1549           to userspace as tmpfs if TMPFS is enabled. Disabling this
1550           option replaces shmem and tmpfs with the much simpler ramfs code,
1551           which may be appropriate on small systems without swap.
1553 config AIO
1554         bool "Enable AIO support" if EXPERT
1555         default y
1556         help
1557           This option enables POSIX asynchronous I/O which may by used
1558           by some high performance threaded applications. Disabling
1559           this option saves about 7k.
1562         bool "Enable madvise/fadvise syscalls" if EXPERT
1563         default y
1564         help
1565           This option enables the madvise and fadvise syscalls, used by
1566           applications to advise the kernel about their future memory or file
1567           usage, improving performance. If building an embedded system where no
1568           applications use these syscalls, you can disable this option to save
1569           space.
1571 config PCI_QUIRKS
1572         default y
1573         bool "Enable PCI quirk workarounds" if EXPERT
1574         depends on PCI
1575         help
1576           This enables workarounds for various PCI chipset
1577           bugs/quirks. Disable this only if your target machine is
1578           unaffected by PCI quirks.
1580 config EMBEDDED
1581         bool "Embedded system"
1582         option allnoconfig_y
1583         select EXPERT
1584         help
1585           This option should be enabled if compiling the kernel for
1586           an embedded system so certain expert options are available
1587           for configuration.
1589 config HAVE_PERF_EVENTS
1590         bool
1591         help
1592           See tools/perf/design.txt for details.
1594 config PERF_USE_VMALLOC
1595         bool
1596         help
1597           See tools/perf/design.txt for details
1599 menu "Kernel Performance Events And Counters"
1601 config PERF_EVENTS
1602         bool "Kernel performance events and counters"
1603         default y if PROFILING
1604         depends on HAVE_PERF_EVENTS
1605         select ANON_INODES
1606         select IRQ_WORK
1607         select SRCU
1608         help
1609           Enable kernel support for various performance events provided
1610           by software and hardware.
1612           Software events are supported either built-in or via the
1613           use of generic tracepoints.
1615           Most modern CPUs support performance events via performance
1616           counter registers. These registers count the number of certain
1617           types of hw events: such as instructions executed, cachemisses
1618           suffered, or branches mis-predicted - without slowing down the
1619           kernel or applications. These registers can also trigger interrupts
1620           when a threshold number of events have passed - and can thus be
1621           used to profile the code that runs on that CPU.
1623           The Linux Performance Event subsystem provides an abstraction of
1624           these software and hardware event capabilities, available via a
1625           system call and used by the "perf" utility in tools/perf/. It
1626           provides per task and per CPU counters, and it provides event
1627           capabilities on top of those.
1629           Say Y if unsure.
1632         default n
1633         bool "Debug: use vmalloc to back perf mmap() buffers"
1634         depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1635         select PERF_USE_VMALLOC
1636         help
1637          Use vmalloc memory to back perf mmap() buffers.
1639          Mostly useful for debugging the vmalloc code on platforms
1640          that don't require it.
1642          Say N if unsure.
1644 endmenu
1647         default y
1648         bool "Enable VM event counters for /proc/vmstat" if EXPERT
1649         help
1650           VM event counters are needed for event counts to be shown.
1651           This option allows the disabling of the VM event counters
1652           on EXPERT systems.  /proc/vmstat will only show page counts
1653           if VM event counters are disabled.
1655 config SLUB_DEBUG
1656         default y
1657         bool "Enable SLUB debugging support" if EXPERT
1658         depends on SLUB && SYSFS
1659         help
1660           SLUB has extensive debug support features. Disabling these can
1661           result in significant savings in code size. This also disables
1662           SLUB sysfs support. /sys/slab will not exist and there will be
1663           no support for cache validation etc.
1665 config COMPAT_BRK
1666         bool "Disable heap randomization"
1667         default y
1668         help
1669           Randomizing heap placement makes heap exploits harder, but it
1670           also breaks ancient binaries (including anything libc5 based).
1671           This option changes the bootup default to heap randomization
1672           disabled, and can be overridden at runtime by setting
1673           /proc/sys/kernel/randomize_va_space to 2.
1675           On non-ancient distros (post-2000 ones) N is usually a safe choice.
1677 choice
1678         prompt "Choose SLAB allocator"
1679         default SLUB
1680         help
1681            This option allows to select a slab allocator.
1683 config SLAB
1684         bool "SLAB"
1685         help
1686           The regular slab allocator that is established and known to work
1687           well in all environments. It organizes cache hot objects in
1688           per cpu and per node queues.
1690 config SLUB
1691         bool "SLUB (Unqueued Allocator)"
1692         help
1693            SLUB is a slab allocator that minimizes cache line usage
1694            instead of managing queues of cached objects (SLAB approach).
1695            Per cpu caching is realized using slabs of objects instead
1696            of queues of objects. SLUB can use memory efficiently
1697            and has enhanced diagnostics. SLUB is the default choice for
1698            a slab allocator.
1700 config SLOB
1701         depends on EXPERT
1702         bool "SLOB (Simple Allocator)"
1703         help
1704            SLOB replaces the stock allocator with a drastically simpler
1705            allocator. SLOB is generally more space efficient but
1706            does not perform as well on large systems.
1708 endchoice
1710 config SLUB_CPU_PARTIAL
1711         default y
1712         depends on SLUB && SMP
1713         bool "SLUB per cpu partial cache"
1714         help
1715           Per cpu partial caches accellerate objects allocation and freeing
1716           that is local to a processor at the price of more indeterminism
1717           in the latency of the free. On overflow these caches will be cleared
1718           which requires the taking of locks that may cause latency spikes.
1719           Typically one would choose no for a realtime system.
1722         bool "Allow mmapped anonymous memory to be uninitialized"
1723         depends on EXPERT && !MMU
1724         default n
1725         help
1726           Normally, and according to the Linux spec, anonymous memory obtained
1727           from mmap() has it's contents cleared before it is passed to
1728           userspace.  Enabling this config option allows you to request that
1729           mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1730           providing a huge performance boost.  If this option is not enabled,
1731           then the flag will be ignored.
1733           This is taken advantage of by uClibc's malloc(), and also by
1734           ELF-FDPIC binfmt's brk and stack allocator.
1736           Because of the obvious security issues, this option should only be
1737           enabled on embedded devices where you control what is run in
1738           userspace.  Since that isn't generally a problem on no-MMU systems,
1739           it is normally safe to say Y here.
1741           See Documentation/nommu-mmap.txt for more information.
1744         bool "Provide system-wide ring of trusted keys"
1745         depends on KEYS
1746         help
1747           Provide a system keyring to which trusted keys can be added.  Keys in
1748           the keyring are considered to be trusted.  Keys may be added at will
1749           by the kernel from compiled-in data and from hardware key stores, but
1750           userspace may only add extra keys if those keys can be verified by
1751           keys already in the keyring.
1753           Keys in this keyring are used by module signature checking.
1755 config PROFILING
1756         bool "Profiling support"
1757         help
1758           Say Y here to enable the extended profiling support mechanisms used
1759           by profilers such as OProfile.
1761 #
1762 # Place an empty function call at each tracepoint site. Can be
1763 # dynamically changed for a probe function.
1764 #
1765 config TRACEPOINTS
1766         bool
1768 source "arch/Kconfig"
1770 endmenu         # General setup
1773         bool
1774         default n
1776 config SLABINFO
1777         bool
1778         depends on PROC_FS
1779         depends on SLAB || SLUB_DEBUG
1780         default y
1782 config RT_MUTEXES
1783         bool
1785 config BASE_SMALL
1786         int
1787         default 0 if BASE_FULL
1788         default 1 if !BASE_FULL
1790 menuconfig MODULES
1791         bool "Enable loadable module support"
1792         option modules
1793         help
1794           Kernel modules are small pieces of compiled code which can
1795           be inserted in the running kernel, rather than being
1796           permanently built into the kernel.  You use the "modprobe"
1797           tool to add (and sometimes remove) them.  If you say Y here,
1798           many parts of the kernel can be built as modules (by
1799           answering M instead of Y where indicated): this is most
1800           useful for infrequently used options which are not required
1801           for booting.  For more information, see the man pages for
1802           modprobe, lsmod, modinfo, insmod and rmmod.
1804           If you say Y here, you will need to run "make
1805           modules_install" to put the modules under /lib/modules/
1806           where modprobe can find them (you may need to be root to do
1807           this).
1809           If unsure, say Y.
1811 if MODULES
1814         bool "Forced module loading"
1815         default n
1816         help
1817           Allow loading of modules without version information (ie. modprobe
1818           --force).  Forced module loading sets the 'F' (forced) taint flag and
1819           is usually a really bad idea.
1821 config MODULE_UNLOAD
1822         bool "Module unloading"
1823         help
1824           Without this option you will not be able to unload any
1825           modules (note that some modules may not be unloadable
1826           anyway), which makes your kernel smaller, faster
1827           and simpler.  If unsure, say Y.
1830         bool "Forced module unloading"
1831         depends on MODULE_UNLOAD
1832         help
1833           This option allows you to force a module to unload, even if the
1834           kernel believes it is unsafe: the kernel will remove the module
1835           without waiting for anyone to stop using it (using the -f option to
1836           rmmod).  This is mainly for kernel developers and desperate users.
1837           If unsure, say N.
1839 config MODVERSIONS
1840         bool "Module versioning support"
1841         help
1842           Usually, you have to use modules compiled with your kernel.
1843           Saying Y here makes it sometimes possible to use modules
1844           compiled for different kernels, by adding enough information
1845           to the modules to (hopefully) spot any changes which would
1846           make them incompatible with the kernel you are running.  If
1847           unsure, say N.
1850         bool "Source checksum for all modules"
1851         help
1852           Modules which contain a MODULE_VERSION get an extra "srcversion"
1853           field inserted into their modinfo section, which contains a
1854           sum of the source files which made it.  This helps maintainers
1855           see exactly which source was used to build a module (since
1856           others sometimes change the module source without updating
1857           the version).  With this option, such a "srcversion" field
1858           will be created for all modules.  If unsure, say N.
1860 config MODULE_SIG
1861         bool "Module signature verification"
1862         depends on MODULES
1863         select SYSTEM_TRUSTED_KEYRING
1864         select KEYS
1865         select CRYPTO
1866         select ASYMMETRIC_KEY_TYPE
1868         select PUBLIC_KEY_ALGO_RSA
1869         select ASN1
1870         select OID_REGISTRY
1871         select X509_CERTIFICATE_PARSER
1872         help
1873           Check modules for valid signatures upon load: the signature
1874           is simply appended to the module. For more information see
1875           Documentation/module-signing.txt.
1877           !!!WARNING!!!  If you enable this option, you MUST make sure that the
1878           module DOES NOT get stripped after being signed.  This includes the
1879           debuginfo strip done by some packagers (such as rpmbuild) and
1880           inclusion into an initramfs that wants the module size reduced.
1882 config MODULE_SIG_FORCE
1883         bool "Require modules to be validly signed"
1884         depends on MODULE_SIG
1885         help
1886           Reject unsigned modules or signed modules for which we don't have a
1887           key.  Without this, such modules will simply taint the kernel.
1889 config MODULE_SIG_ALL
1890         bool "Automatically sign all modules"
1891         default y
1892         depends on MODULE_SIG
1893         help
1894           Sign all modules during make modules_install. Without this option,
1895           modules must be signed manually, using the scripts/sign-file tool.
1897 comment "Do not forget to sign required modules with scripts/sign-file"
1898         depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1900 choice
1901         prompt "Which hash algorithm should modules be signed with?"
1902         depends on MODULE_SIG
1903         help
1904           This determines which sort of hashing algorithm will be used during
1905           signature generation.  This algorithm _must_ be built into the kernel
1906           directly so that signature verification can take place.  It is not
1907           possible to load a signed module containing the algorithm to check
1908           the signature on that module.
1910 config MODULE_SIG_SHA1
1911         bool "Sign modules with SHA-1"
1912         select CRYPTO_SHA1
1914 config MODULE_SIG_SHA224
1915         bool "Sign modules with SHA-224"
1916         select CRYPTO_SHA256
1918 config MODULE_SIG_SHA256
1919         bool "Sign modules with SHA-256"
1920         select CRYPTO_SHA256
1922 config MODULE_SIG_SHA384
1923         bool "Sign modules with SHA-384"
1924         select CRYPTO_SHA512
1926 config MODULE_SIG_SHA512
1927         bool "Sign modules with SHA-512"
1928         select CRYPTO_SHA512
1930 endchoice
1932 config MODULE_SIG_HASH
1933         string
1934         depends on MODULE_SIG
1935         default "sha1" if MODULE_SIG_SHA1
1936         default "sha224" if MODULE_SIG_SHA224
1937         default "sha256" if MODULE_SIG_SHA256
1938         default "sha384" if MODULE_SIG_SHA384
1939         default "sha512" if MODULE_SIG_SHA512
1942         bool "Compress modules on installation"
1943         depends on MODULES
1944         help
1946           Compresses kernel modules when 'make modules_install' is run; gzip or
1947           xz depending on "Compression algorithm" below.
1949           module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
1951           Out-of-tree kernel modules installed using Kbuild will also be
1952           compressed upon installation.
1954           Note: for modules inside an initrd or initramfs, it's more efficient
1955           to compress the whole initrd or initramfs instead.
1957           Note: This is fully compatible with signed modules.
1959           If in doubt, say N.
1961 choice
1962         prompt "Compression algorithm"
1963         depends on MODULE_COMPRESS
1964         default MODULE_COMPRESS_GZIP
1965         help
1966           This determines which sort of compression will be used during
1967           'make modules_install'.
1969           GZIP (default) and XZ are supported.
1972         bool "GZIP"
1975         bool "XZ"
1977 endchoice
1979 endif # MODULES
1982         def_bool y
1983         depends on PERF_EVENTS || TRACING
1986         bool
1987         help
1988           Back when each arch used to define their own cpu_online_mask and
1989           cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1990           with all 1s, and others with all 0s.  When they were centralised,
1991           it was better to provide this option than to break all the archs
1992           and have several arch maintainers pursuing me down dark alleys.
1994 config STOP_MACHINE
1995         bool
1996         default y
1997         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1998         help
1999           Need stop_machine() primitive.
2001 source "block/Kconfig"
2004         bool
2006 config PADATA
2007         depends on SMP
2008         bool
2010 # Can be selected by architectures with broken toolchains
2011 # that get confused by correct const<->read_only section
2012 # mappings
2013 config BROKEN_RODATA
2014         bool
2016 config ASN1
2017         tristate
2018         help
2019           Build a simple ASN.1 grammar compiler that produces a bytecode output
2020           that can be interpreted by the ASN.1 stream decoder and used to
2021           inform it as to what tags are to be expected in a stream and what
2022           functions to call on what tags.
2024 source "kernel/Kconfig.locks"

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