Version:  2.0.40 2.2.26 2.4.37 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 4.3 4.4 4.5

Linux/init/Kconfig

  1 config ARCH
  2         string
  3         option env="ARCH"
  4 
  5 config KERNELVERSION
  6         string
  7         option env="KERNELVERSION"
  8 
  9 config DEFCONFIG_LIST
 10         string
 11         depends on !UML
 12         option defconfig_list
 13         default "/lib/modules/$UNAME_RELEASE/.config"
 14         default "/etc/kernel-config"
 15         default "/boot/config-$UNAME_RELEASE"
 16         default "$ARCH_DEFCONFIG"
 17         default "arch/$ARCH/defconfig"
 18 
 19 config CONSTRUCTORS
 20         bool
 21         depends on !UML
 22 
 23 config IRQ_WORK
 24         bool
 25 
 26 config BUILDTIME_EXTABLE_SORT
 27         bool
 28 
 29 menu "General setup"
 30 
 31 config BROKEN
 32         bool
 33 
 34 config BROKEN_ON_SMP
 35         bool
 36         depends on BROKEN || !SMP
 37         default y
 38 
 39 config INIT_ENV_ARG_LIMIT
 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.
 46 
 47 
 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.
 55 
 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.
 65 
 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.
 69 
 70 config LOCALVERSION
 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.
 79 
 80 config LOCALVERSION_AUTO
 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.
 87 
 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.
 92 
 93           (The actual string used here is the first eight characters produced
 94           by running the command:
 95 
 96             $ git rev-parse --verify HEAD
 97 
 98           which is done within the script "scripts/setlocalversion".)
 99 
100 config HAVE_KERNEL_GZIP
101         bool
102 
103 config HAVE_KERNEL_BZIP2
104         bool
105 
106 config HAVE_KERNEL_LZMA
107         bool
108 
109 config HAVE_KERNEL_XZ
110         bool
111 
112 config HAVE_KERNEL_LZO
113         bool
114 
115 config HAVE_KERNEL_LZ4
116         bool
117 
118 choice
119         prompt "Kernel compression mode"
120         default KERNEL_GZIP
121         depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
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.
128 
129           If you have any problems with bzip2 or lzma compressed
130           kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
131           version of this functionality (bzip2 only), for 2.4, was
132           supplied by Christian Ludwig)
133 
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.
137 
138           If in doubt, select 'gzip'
139 
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.
146 
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.
156 
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.
164 
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.
175 
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.
179 
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.
187 
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           <https://code.google.com/p/lz4/>.
195 
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.
199 
200 endchoice
201 
202 config DEFAULT_HOSTNAME
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.
210 
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.
220 
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 <http://www.tldp.org/docs.html#howto>),
230           you'll need to say Y here.
231 
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           <http://www.tldp.org/guides.html>.
235 
236 config SYSVIPC_SYSCTL
237         bool
238         depends on SYSVIPC
239         depends on SYSCTL
240         default y
241 
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.
251 
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.
255 
256           If unsure, say Y.
257 
258 config POSIX_MQUEUE_SYSCTL
259         bool
260         depends on POSIX_MQUEUE
261         depends on SYSCTL
262         default y
263 
264 config CROSS_MEMORY_ATTACH
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.
273 
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.
285 
286 config USELIB
287         bool "uselib syscall"
288         def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
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.
295 
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).  System call auditing is included
303           on architectures which support it.
304 
305 config HAVE_ARCH_AUDITSYSCALL
306         bool
307 
308 config AUDITSYSCALL
309         def_bool y
310         depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
311 
312 config AUDIT_WATCH
313         def_bool y
314         depends on AUDITSYSCALL
315         select FSNOTIFY
316 
317 config AUDIT_TREE
318         def_bool y
319         depends on AUDITSYSCALL
320         select FSNOTIFY
321 
322 source "kernel/irq/Kconfig"
323 source "kernel/time/Kconfig"
324 
325 menu "CPU/Task time and stats accounting"
326 
327 config VIRT_CPU_ACCOUNTING
328         bool
329 
330 choice
331         prompt "Cputime accounting"
332         default TICK_CPU_ACCOUNTING if !PPC64
333         default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
334 
335 # Kind of a stub config for the pure tick based cputime accounting
336 config TICK_CPU_ACCOUNTING
337         bool "Simple tick based cputime accounting"
338         depends on !S390 && !NO_HZ_FULL
339         help
340           This is the basic tick based cputime accounting that maintains
341           statistics about user, system and idle time spent on per jiffies
342           granularity.
343 
344           If unsure, say Y.
345 
346 config VIRT_CPU_ACCOUNTING_NATIVE
347         bool "Deterministic task and CPU time accounting"
348         depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
349         select VIRT_CPU_ACCOUNTING
350         help
351           Select this option to enable more accurate task and CPU time
352           accounting.  This is done by reading a CPU counter on each
353           kernel entry and exit and on transitions within the kernel
354           between system, softirq and hardirq state, so there is a
355           small performance impact.  In the case of s390 or IBM POWER > 5,
356           this also enables accounting of stolen time on logically-partitioned
357           systems.
358 
359 config VIRT_CPU_ACCOUNTING_GEN
360         bool "Full dynticks CPU time accounting"
361         depends on HAVE_CONTEXT_TRACKING
362         depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
363         select VIRT_CPU_ACCOUNTING
364         select CONTEXT_TRACKING
365         help
366           Select this option to enable task and CPU time accounting on full
367           dynticks systems. This accounting is implemented by watching every
368           kernel-user boundaries using the context tracking subsystem.
369           The accounting is thus performed at the expense of some significant
370           overhead.
371 
372           For now this is only useful if you are working on the full
373           dynticks subsystem development.
374 
375           If unsure, say N.
376 
377 config IRQ_TIME_ACCOUNTING
378         bool "Fine granularity task level IRQ time accounting"
379         depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
380         help
381           Select this option to enable fine granularity task irq time
382           accounting. This is done by reading a timestamp on each
383           transitions between softirq and hardirq state, so there can be a
384           small performance impact.
385 
386           If in doubt, say N here.
387 
388 endchoice
389 
390 config BSD_PROCESS_ACCT
391         bool "BSD Process Accounting"
392         depends on MULTIUSER
393         help
394           If you say Y here, a user level program will be able to instruct the
395           kernel (via a special system call) to write process accounting
396           information to a file: whenever a process exits, information about
397           that process will be appended to the file by the kernel.  The
398           information includes things such as creation time, owning user,
399           command name, memory usage, controlling terminal etc. (the complete
400           list is in the struct acct in <file:include/linux/acct.h>).  It is
401           up to the user level program to do useful things with this
402           information.  This is generally a good idea, so say Y.
403 
404 config BSD_PROCESS_ACCT_V3
405         bool "BSD Process Accounting version 3 file format"
406         depends on BSD_PROCESS_ACCT
407         default n
408         help
409           If you say Y here, the process accounting information is written
410           in a new file format that also logs the process IDs of each
411           process and it's parent. Note that this file format is incompatible
412           with previous v0/v1/v2 file formats, so you will need updated tools
413           for processing it. A preliminary version of these tools is available
414           at <http://www.gnu.org/software/acct/>.
415 
416 config TASKSTATS
417         bool "Export task/process statistics through netlink"
418         depends on NET
419         depends on MULTIUSER
420         default n
421         help
422           Export selected statistics for tasks/processes through the
423           generic netlink interface. Unlike BSD process accounting, the
424           statistics are available during the lifetime of tasks/processes as
425           responses to commands. Like BSD accounting, they are sent to user
426           space on task exit.
427 
428           Say N if unsure.
429 
430 config TASK_DELAY_ACCT
431         bool "Enable per-task delay accounting"
432         depends on TASKSTATS
433         select SCHED_INFO
434         help
435           Collect information on time spent by a task waiting for system
436           resources like cpu, synchronous block I/O completion and swapping
437           in pages. Such statistics can help in setting a task's priorities
438           relative to other tasks for cpu, io, rss limits etc.
439 
440           Say N if unsure.
441 
442 config TASK_XACCT
443         bool "Enable extended accounting over taskstats"
444         depends on TASKSTATS
445         help
446           Collect extended task accounting data and send the data
447           to userland for processing over the taskstats interface.
448 
449           Say N if unsure.
450 
451 config TASK_IO_ACCOUNTING
452         bool "Enable per-task storage I/O accounting"
453         depends on TASK_XACCT
454         help
455           Collect information on the number of bytes of storage I/O which this
456           task has caused.
457 
458           Say N if unsure.
459 
460 endmenu # "CPU/Task time and stats accounting"
461 
462 menu "RCU Subsystem"
463 
464 config TREE_RCU
465         bool
466         default y if !PREEMPT && SMP
467         help
468           This option selects the RCU implementation that is
469           designed for very large SMP system with hundreds or
470           thousands of CPUs.  It also scales down nicely to
471           smaller systems.
472 
473 config PREEMPT_RCU
474         bool
475         default y if PREEMPT
476         help
477           This option selects the RCU implementation that is
478           designed for very large SMP systems with hundreds or
479           thousands of CPUs, but for which real-time response
480           is also required.  It also scales down nicely to
481           smaller systems.
482 
483           Select this option if you are unsure.
484 
485 config TINY_RCU
486         bool
487         default y if !PREEMPT && !SMP
488         help
489           This option selects the RCU implementation that is
490           designed for UP systems from which real-time response
491           is not required.  This option greatly reduces the
492           memory footprint of RCU.
493 
494 config RCU_EXPERT
495         bool "Make expert-level adjustments to RCU configuration"
496         default n
497         help
498           This option needs to be enabled if you wish to make
499           expert-level adjustments to RCU configuration.  By default,
500           no such adjustments can be made, which has the often-beneficial
501           side-effect of preventing "make oldconfig" from asking you all
502           sorts of detailed questions about how you would like numerous
503           obscure RCU options to be set up.
504 
505           Say Y if you need to make expert-level adjustments to RCU.
506 
507           Say N if you are unsure.
508 
509 config SRCU
510         bool
511         help
512           This option selects the sleepable version of RCU. This version
513           permits arbitrary sleeping or blocking within RCU read-side critical
514           sections.
515 
516 config TASKS_RCU
517         bool
518         default n
519         select SRCU
520         help
521           This option enables a task-based RCU implementation that uses
522           only voluntary context switch (not preemption!), idle, and
523           user-mode execution as quiescent states.
524 
525 config RCU_STALL_COMMON
526         def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
527         help
528           This option enables RCU CPU stall code that is common between
529           the TINY and TREE variants of RCU.  The purpose is to allow
530           the tiny variants to disable RCU CPU stall warnings, while
531           making these warnings mandatory for the tree variants.
532 
533 config CONTEXT_TRACKING
534        bool
535 
536 config CONTEXT_TRACKING_FORCE
537         bool "Force context tracking"
538         depends on CONTEXT_TRACKING
539         default y if !NO_HZ_FULL
540         help
541           The major pre-requirement for full dynticks to work is to
542           support the context tracking subsystem. But there are also
543           other dependencies to provide in order to make the full
544           dynticks working.
545 
546           This option stands for testing when an arch implements the
547           context tracking backend but doesn't yet fullfill all the
548           requirements to make the full dynticks feature working.
549           Without the full dynticks, there is no way to test the support
550           for context tracking and the subsystems that rely on it: RCU
551           userspace extended quiescent state and tickless cputime
552           accounting. This option copes with the absence of the full
553           dynticks subsystem by forcing the context tracking on all
554           CPUs in the system.
555 
556           Say Y only if you're working on the development of an
557           architecture backend for the context tracking.
558 
559           Say N otherwise, this option brings an overhead that you
560           don't want in production.
561 
562 
563 config RCU_FANOUT
564         int "Tree-based hierarchical RCU fanout value"
565         range 2 64 if 64BIT
566         range 2 32 if !64BIT
567         depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
568         default 64 if 64BIT
569         default 32 if !64BIT
570         help
571           This option controls the fanout of hierarchical implementations
572           of RCU, allowing RCU to work efficiently on machines with
573           large numbers of CPUs.  This value must be at least the fourth
574           root of NR_CPUS, which allows NR_CPUS to be insanely large.
575           The default value of RCU_FANOUT should be used for production
576           systems, but if you are stress-testing the RCU implementation
577           itself, small RCU_FANOUT values allow you to test large-system
578           code paths on small(er) systems.
579 
580           Select a specific number if testing RCU itself.
581           Take the default if unsure.
582 
583 config RCU_FANOUT_LEAF
584         int "Tree-based hierarchical RCU leaf-level fanout value"
585         range 2 64 if 64BIT
586         range 2 32 if !64BIT
587         depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
588         default 16
589         help
590           This option controls the leaf-level fanout of hierarchical
591           implementations of RCU, and allows trading off cache misses
592           against lock contention.  Systems that synchronize their
593           scheduling-clock interrupts for energy-efficiency reasons will
594           want the default because the smaller leaf-level fanout keeps
595           lock contention levels acceptably low.  Very large systems
596           (hundreds or thousands of CPUs) will instead want to set this
597           value to the maximum value possible in order to reduce the
598           number of cache misses incurred during RCU's grace-period
599           initialization.  These systems tend to run CPU-bound, and thus
600           are not helped by synchronized interrupts, and thus tend to
601           skew them, which reduces lock contention enough that large
602           leaf-level fanouts work well.
603 
604           Select a specific number if testing RCU itself.
605 
606           Select the maximum permissible value for large systems.
607 
608           Take the default if unsure.
609 
610 config RCU_FAST_NO_HZ
611         bool "Accelerate last non-dyntick-idle CPU's grace periods"
612         depends on NO_HZ_COMMON && SMP && RCU_EXPERT
613         default n
614         help
615           This option permits CPUs to enter dynticks-idle state even if
616           they have RCU callbacks queued, and prevents RCU from waking
617           these CPUs up more than roughly once every four jiffies (by
618           default, you can adjust this using the rcutree.rcu_idle_gp_delay
619           parameter), thus improving energy efficiency.  On the other
620           hand, this option increases the duration of RCU grace periods,
621           for example, slowing down synchronize_rcu().
622 
623           Say Y if energy efficiency is critically important, and you
624                 don't care about increased grace-period durations.
625 
626           Say N if you are unsure.
627 
628 config TREE_RCU_TRACE
629         def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
630         select DEBUG_FS
631         help
632           This option provides tracing for the TREE_RCU and
633           PREEMPT_RCU implementations, permitting Makefile to
634           trivially select kernel/rcutree_trace.c.
635 
636 config RCU_BOOST
637         bool "Enable RCU priority boosting"
638         depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT
639         default n
640         help
641           This option boosts the priority of preempted RCU readers that
642           block the current preemptible RCU grace period for too long.
643           This option also prevents heavy loads from blocking RCU
644           callback invocation for all flavors of RCU.
645 
646           Say Y here if you are working with real-time apps or heavy loads
647           Say N here if you are unsure.
648 
649 config RCU_KTHREAD_PRIO
650         int "Real-time priority to use for RCU worker threads"
651         range 1 99 if RCU_BOOST
652         range 0 99 if !RCU_BOOST
653         default 1 if RCU_BOOST
654         default 0 if !RCU_BOOST
655         depends on RCU_EXPERT
656         help
657           This option specifies the SCHED_FIFO priority value that will be
658           assigned to the rcuc/n and rcub/n threads and is also the value
659           used for RCU_BOOST (if enabled). If you are working with a
660           real-time application that has one or more CPU-bound threads
661           running at a real-time priority level, you should set
662           RCU_KTHREAD_PRIO to a priority higher than the highest-priority
663           real-time CPU-bound application thread.  The default RCU_KTHREAD_PRIO
664           value of 1 is appropriate in the common case, which is real-time
665           applications that do not have any CPU-bound threads.
666 
667           Some real-time applications might not have a single real-time
668           thread that saturates a given CPU, but instead might have
669           multiple real-time threads that, taken together, fully utilize
670           that CPU.  In this case, you should set RCU_KTHREAD_PRIO to
671           a priority higher than the lowest-priority thread that is
672           conspiring to prevent the CPU from running any non-real-time
673           tasks.  For example, if one thread at priority 10 and another
674           thread at priority 5 are between themselves fully consuming
675           the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
676           set to priority 6 or higher.
677 
678           Specify the real-time priority, or take the default if unsure.
679 
680 config RCU_BOOST_DELAY
681         int "Milliseconds to delay boosting after RCU grace-period start"
682         range 0 3000
683         depends on RCU_BOOST
684         default 500
685         help
686           This option specifies the time to wait after the beginning of
687           a given grace period before priority-boosting preempted RCU
688           readers blocking that grace period.  Note that any RCU reader
689           blocking an expedited RCU grace period is boosted immediately.
690 
691           Accept the default if unsure.
692 
693 config RCU_NOCB_CPU
694         bool "Offload RCU callback processing from boot-selected CPUs"
695         depends on TREE_RCU || PREEMPT_RCU
696         depends on RCU_EXPERT || NO_HZ_FULL
697         default n
698         help
699           Use this option to reduce OS jitter for aggressive HPC or
700           real-time workloads.  It can also be used to offload RCU
701           callback invocation to energy-efficient CPUs in battery-powered
702           asymmetric multiprocessors.
703 
704           This option offloads callback invocation from the set of
705           CPUs specified at boot time by the rcu_nocbs parameter.
706           For each such CPU, a kthread ("rcuox/N") will be created to
707           invoke callbacks, where the "N" is the CPU being offloaded,
708           and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
709           "s" for RCU-sched.  Nothing prevents this kthread from running
710           on the specified CPUs, but (1) the kthreads may be preempted
711           between each callback, and (2) affinity or cgroups can be used
712           to force the kthreads to run on whatever set of CPUs is desired.
713 
714           Say Y here if you want to help to debug reduced OS jitter.
715           Say N here if you are unsure.
716 
717 choice
718         prompt "Build-forced no-CBs CPUs"
719         default RCU_NOCB_CPU_NONE
720         depends on RCU_NOCB_CPU
721         help
722           This option allows no-CBs CPUs (whose RCU callbacks are invoked
723           from kthreads rather than from softirq context) to be specified
724           at build time.  Additional no-CBs CPUs may be specified by
725           the rcu_nocbs= boot parameter.
726 
727 config RCU_NOCB_CPU_NONE
728         bool "No build_forced no-CBs CPUs"
729         help
730           This option does not force any of the CPUs to be no-CBs CPUs.
731           Only CPUs designated by the rcu_nocbs= boot parameter will be
732           no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
733           kthreads whose names begin with "rcuo".  All other CPUs will
734           invoke their own RCU callbacks in softirq context.
735 
736           Select this option if you want to choose no-CBs CPUs at
737           boot time, for example, to allow testing of different no-CBs
738           configurations without having to rebuild the kernel each time.
739 
740 config RCU_NOCB_CPU_ZERO
741         bool "CPU 0 is a build_forced no-CBs CPU"
742         help
743           This option forces CPU 0 to be a no-CBs CPU, so that its RCU
744           callbacks are invoked by a per-CPU kthread whose name begins
745           with "rcuo".  Additional CPUs may be designated as no-CBs
746           CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
747           All other CPUs will invoke their own RCU callbacks in softirq
748           context.
749 
750           Select this if CPU 0 needs to be a no-CBs CPU for real-time
751           or energy-efficiency reasons, but the real reason it exists
752           is to ensure that randconfig testing covers mixed systems.
753 
754 config RCU_NOCB_CPU_ALL
755         bool "All CPUs are build_forced no-CBs CPUs"
756         help
757           This option forces all CPUs to be no-CBs CPUs.  The rcu_nocbs=
758           boot parameter will be ignored.  All CPUs' RCU callbacks will
759           be executed in the context of per-CPU rcuo kthreads created for
760           this purpose.  Assuming that the kthreads whose names start with
761           "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
762           on the remaining CPUs, but might decrease memory locality during
763           RCU-callback invocation, thus potentially degrading throughput.
764 
765           Select this if all CPUs need to be no-CBs CPUs for real-time
766           or energy-efficiency reasons.
767 
768 endchoice
769 
770 config RCU_EXPEDITE_BOOT
771         bool
772         default n
773         help
774           This option enables expedited grace periods at boot time,
775           as if rcu_expedite_gp() had been invoked early in boot.
776           The corresponding rcu_unexpedite_gp() is invoked from
777           rcu_end_inkernel_boot(), which is intended to be invoked
778           at the end of the kernel-only boot sequence, just before
779           init is exec'ed.
780 
781           Accept the default if unsure.
782 
783 endmenu # "RCU Subsystem"
784 
785 config BUILD_BIN2C
786         bool
787         default n
788 
789 config IKCONFIG
790         tristate "Kernel .config support"
791         select BUILD_BIN2C
792         ---help---
793           This option enables the complete Linux kernel ".config" file
794           contents to be saved in the kernel. It provides documentation
795           of which kernel options are used in a running kernel or in an
796           on-disk kernel.  This information can be extracted from the kernel
797           image file with the script scripts/extract-ikconfig and used as
798           input to rebuild the current kernel or to build another kernel.
799           It can also be extracted from a running kernel by reading
800           /proc/config.gz if enabled (below).
801 
802 config IKCONFIG_PROC
803         bool "Enable access to .config through /proc/config.gz"
804         depends on IKCONFIG && PROC_FS
805         ---help---
806           This option enables access to the kernel configuration file
807           through /proc/config.gz.
808 
809 config LOG_BUF_SHIFT
810         int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
811         range 12 25
812         default 17
813         depends on PRINTK
814         help
815           Select the minimal kernel log buffer size as a power of 2.
816           The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
817           parameter, see below. Any higher size also might be forced
818           by "log_buf_len" boot parameter.
819 
820           Examples:
821                      17 => 128 KB
822                      16 => 64 KB
823                      15 => 32 KB
824                      14 => 16 KB
825                      13 =>  8 KB
826                      12 =>  4 KB
827 
828 config LOG_CPU_MAX_BUF_SHIFT
829         int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
830         depends on SMP
831         range 0 21
832         default 12 if !BASE_SMALL
833         default 0 if BASE_SMALL
834         depends on PRINTK
835         help
836           This option allows to increase the default ring buffer size
837           according to the number of CPUs. The value defines the contribution
838           of each CPU as a power of 2. The used space is typically only few
839           lines however it might be much more when problems are reported,
840           e.g. backtraces.
841 
842           The increased size means that a new buffer has to be allocated and
843           the original static one is unused. It makes sense only on systems
844           with more CPUs. Therefore this value is used only when the sum of
845           contributions is greater than the half of the default kernel ring
846           buffer as defined by LOG_BUF_SHIFT. The default values are set
847           so that more than 64 CPUs are needed to trigger the allocation.
848 
849           Also this option is ignored when "log_buf_len" kernel parameter is
850           used as it forces an exact (power of two) size of the ring buffer.
851 
852           The number of possible CPUs is used for this computation ignoring
853           hotplugging making the compuation optimal for the the worst case
854           scenerio while allowing a simple algorithm to be used from bootup.
855 
856           Examples shift values and their meaning:
857                      17 => 128 KB for each CPU
858                      16 =>  64 KB for each CPU
859                      15 =>  32 KB for each CPU
860                      14 =>  16 KB for each CPU
861                      13 =>   8 KB for each CPU
862                      12 =>   4 KB for each CPU
863 
864 #
865 # Architectures with an unreliable sched_clock() should select this:
866 #
867 config HAVE_UNSTABLE_SCHED_CLOCK
868         bool
869 
870 config GENERIC_SCHED_CLOCK
871         bool
872 
873 #
874 # For architectures that want to enable the support for NUMA-affine scheduler
875 # balancing logic:
876 #
877 config ARCH_SUPPORTS_NUMA_BALANCING
878         bool
879 
880 #
881 # For architectures that prefer to flush all TLBs after a number of pages
882 # are unmapped instead of sending one IPI per page to flush. The architecture
883 # must provide guarantees on what happens if a clean TLB cache entry is
884 # written after the unmap. Details are in mm/rmap.c near the check for
885 # should_defer_flush. The architecture should also consider if the full flush
886 # and the refill costs are offset by the savings of sending fewer IPIs.
887 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
888         bool
889 
890 #
891 # For architectures that know their GCC __int128 support is sound
892 #
893 config ARCH_SUPPORTS_INT128
894         bool
895 
896 # For architectures that (ab)use NUMA to represent different memory regions
897 # all cpu-local but of different latencies, such as SuperH.
898 #
899 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
900         bool
901 
902 config NUMA_BALANCING
903         bool "Memory placement aware NUMA scheduler"
904         depends on ARCH_SUPPORTS_NUMA_BALANCING
905         depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
906         depends on SMP && NUMA && MIGRATION
907         help
908           This option adds support for automatic NUMA aware memory/task placement.
909           The mechanism is quite primitive and is based on migrating memory when
910           it has references to the node the task is running on.
911 
912           This system will be inactive on UMA systems.
913 
914 config NUMA_BALANCING_DEFAULT_ENABLED
915         bool "Automatically enable NUMA aware memory/task placement"
916         default y
917         depends on NUMA_BALANCING
918         help
919           If set, automatic NUMA balancing will be enabled if running on a NUMA
920           machine.
921 
922 menuconfig CGROUPS
923         bool "Control Group support"
924         select KERNFS
925         help
926           This option adds support for grouping sets of processes together, for
927           use with process control subsystems such as Cpusets, CFS, memory
928           controls or device isolation.
929           See
930                 - Documentation/scheduler/sched-design-CFS.txt  (CFS)
931                 - Documentation/cgroups/ (features for grouping, isolation
932                                           and resource control)
933 
934           Say N if unsure.
935 
936 if CGROUPS
937 
938 config PAGE_COUNTER
939        bool
940 
941 config MEMCG
942         bool "Memory controller"
943         select PAGE_COUNTER
944         select EVENTFD
945         help
946           Provides control over the memory footprint of tasks in a cgroup.
947 
948 config MEMCG_SWAP
949         bool "Swap controller"
950         depends on MEMCG && SWAP
951         help
952           Provides control over the swap space consumed by tasks in a cgroup.
953 
954 config MEMCG_SWAP_ENABLED
955         bool "Swap controller enabled by default"
956         depends on MEMCG_SWAP
957         default y
958         help
959           Memory Resource Controller Swap Extension comes with its price in
960           a bigger memory consumption. General purpose distribution kernels
961           which want to enable the feature but keep it disabled by default
962           and let the user enable it by swapaccount=1 boot command line
963           parameter should have this option unselected.
964           For those who want to have the feature enabled by default should
965           select this option (if, for some reason, they need to disable it
966           then swapaccount=0 does the trick).
967 
968 config BLK_CGROUP
969         bool "IO controller"
970         depends on BLOCK
971         default n
972         ---help---
973         Generic block IO controller cgroup interface. This is the common
974         cgroup interface which should be used by various IO controlling
975         policies.
976 
977         Currently, CFQ IO scheduler uses it to recognize task groups and
978         control disk bandwidth allocation (proportional time slice allocation)
979         to such task groups. It is also used by bio throttling logic in
980         block layer to implement upper limit in IO rates on a device.
981 
982         This option only enables generic Block IO controller infrastructure.
983         One needs to also enable actual IO controlling logic/policy. For
984         enabling proportional weight division of disk bandwidth in CFQ, set
985         CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
986         CONFIG_BLK_DEV_THROTTLING=y.
987 
988         See Documentation/cgroups/blkio-controller.txt for more information.
989 
990 config DEBUG_BLK_CGROUP
991         bool "IO controller debugging"
992         depends on BLK_CGROUP
993         default n
994         ---help---
995         Enable some debugging help. Currently it exports additional stat
996         files in a cgroup which can be useful for debugging.
997 
998 config CGROUP_WRITEBACK
999         bool
1000         depends on MEMCG && BLK_CGROUP
1001         default y
1002 
1003 menuconfig CGROUP_SCHED
1004         bool "CPU controller"
1005         default n
1006         help
1007           This feature lets CPU scheduler recognize task groups and control CPU
1008           bandwidth allocation to such task groups. It uses cgroups to group
1009           tasks.
1010 
1011 if CGROUP_SCHED
1012 config FAIR_GROUP_SCHED
1013         bool "Group scheduling for SCHED_OTHER"
1014         depends on CGROUP_SCHED
1015         default CGROUP_SCHED
1016 
1017 config CFS_BANDWIDTH
1018         bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1019         depends on FAIR_GROUP_SCHED
1020         default n
1021         help
1022           This option allows users to define CPU bandwidth rates (limits) for
1023           tasks running within the fair group scheduler.  Groups with no limit
1024           set are considered to be unconstrained and will run with no
1025           restriction.
1026           See tip/Documentation/scheduler/sched-bwc.txt for more information.
1027 
1028 config RT_GROUP_SCHED
1029         bool "Group scheduling for SCHED_RR/FIFO"
1030         depends on CGROUP_SCHED
1031         default n
1032         help
1033           This feature lets you explicitly allocate real CPU bandwidth
1034           to task groups. If enabled, it will also make it impossible to
1035           schedule realtime tasks for non-root users until you allocate
1036           realtime bandwidth for them.
1037           See Documentation/scheduler/sched-rt-group.txt for more information.
1038 
1039 endif #CGROUP_SCHED
1040 
1041 config CGROUP_PIDS
1042         bool "PIDs controller"
1043         help
1044           Provides enforcement of process number limits in the scope of a
1045           cgroup. Any attempt to fork more processes than is allowed in the
1046           cgroup will fail. PIDs are fundamentally a global resource because it
1047           is fairly trivial to reach PID exhaustion before you reach even a
1048           conservative kmemcg limit. As a result, it is possible to grind a
1049           system to halt without being limited by other cgroup policies. The
1050           PIDs cgroup subsystem is designed to stop this from happening.
1051 
1052           It should be noted that organisational operations (such as attaching
1053           to a cgroup hierarchy will *not* be blocked by the PIDs subsystem),
1054           since the PIDs limit only affects a process's ability to fork, not to
1055           attach to a cgroup.
1056 
1057 config CGROUP_FREEZER
1058         bool "Freezer controller"
1059         help
1060           Provides a way to freeze and unfreeze all tasks in a
1061           cgroup.
1062 
1063           This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1064           controller includes important in-kernel memory consumers per default.
1065 
1066           If you're using cgroup2, say N.
1067 
1068 config CGROUP_HUGETLB
1069         bool "HugeTLB controller"
1070         depends on HUGETLB_PAGE
1071         select PAGE_COUNTER
1072         default n
1073         help
1074           Provides a cgroup controller for HugeTLB pages.
1075           When you enable this, you can put a per cgroup limit on HugeTLB usage.
1076           The limit is enforced during page fault. Since HugeTLB doesn't
1077           support page reclaim, enforcing the limit at page fault time implies
1078           that, the application will get SIGBUS signal if it tries to access
1079           HugeTLB pages beyond its limit. This requires the application to know
1080           beforehand how much HugeTLB pages it would require for its use. The
1081           control group is tracked in the third page lru pointer. This means
1082           that we cannot use the controller with huge page less than 3 pages.
1083 
1084 config CPUSETS
1085         bool "Cpuset controller"
1086         help
1087           This option will let you create and manage CPUSETs which
1088           allow dynamically partitioning a system into sets of CPUs and
1089           Memory Nodes and assigning tasks to run only within those sets.
1090           This is primarily useful on large SMP or NUMA systems.
1091 
1092           Say N if unsure.
1093 
1094 config PROC_PID_CPUSET
1095         bool "Include legacy /proc/<pid>/cpuset file"
1096         depends on CPUSETS
1097         default y
1098 
1099 config CGROUP_DEVICE
1100         bool "Device controller"
1101         help
1102           Provides a cgroup controller implementing whitelists for
1103           devices which a process in the cgroup can mknod or open.
1104 
1105 config CGROUP_CPUACCT
1106         bool "Simple CPU accounting controller"
1107         help
1108           Provides a simple controller for monitoring the
1109           total CPU consumed by the tasks in a cgroup.
1110 
1111 config CGROUP_PERF
1112         bool "Perf controller"
1113         depends on PERF_EVENTS
1114         help
1115           This option extends the perf per-cpu mode to restrict monitoring
1116           to threads which belong to the cgroup specified and run on the
1117           designated cpu.
1118 
1119           Say N if unsure.
1120 
1121 config CGROUP_DEBUG
1122         bool "Example controller"
1123         default n
1124         help
1125           This option enables a simple controller that exports
1126           debugging information about the cgroups framework.
1127 
1128           Say N.
1129 
1130 endif # CGROUPS
1131 
1132 config CHECKPOINT_RESTORE
1133         bool "Checkpoint/restore support" if EXPERT
1134         select PROC_CHILDREN
1135         default n
1136         help
1137           Enables additional kernel features in a sake of checkpoint/restore.
1138           In particular it adds auxiliary prctl codes to setup process text,
1139           data and heap segment sizes, and a few additional /proc filesystem
1140           entries.
1141 
1142           If unsure, say N here.
1143 
1144 menuconfig NAMESPACES
1145         bool "Namespaces support" if EXPERT
1146         depends on MULTIUSER
1147         default !EXPERT
1148         help
1149           Provides the way to make tasks work with different objects using
1150           the same id. For example same IPC id may refer to different objects
1151           or same user id or pid may refer to different tasks when used in
1152           different namespaces.
1153 
1154 if NAMESPACES
1155 
1156 config UTS_NS
1157         bool "UTS namespace"
1158         default y
1159         help
1160           In this namespace tasks see different info provided with the
1161           uname() system call
1162 
1163 config IPC_NS
1164         bool "IPC namespace"
1165         depends on (SYSVIPC || POSIX_MQUEUE)
1166         default y
1167         help
1168           In this namespace tasks work with IPC ids which correspond to
1169           different IPC objects in different namespaces.
1170 
1171 config USER_NS
1172         bool "User namespace"
1173         default n
1174         help
1175           This allows containers, i.e. vservers, to use user namespaces
1176           to provide different user info for different servers.
1177 
1178           When user namespaces are enabled in the kernel it is
1179           recommended that the MEMCG option also be enabled and that
1180           user-space use the memory control groups to limit the amount
1181           of memory a memory unprivileged users can use.
1182 
1183           If unsure, say N.
1184 
1185 config PID_NS
1186         bool "PID Namespaces"
1187         default y
1188         help
1189           Support process id namespaces.  This allows having multiple
1190           processes with the same pid as long as they are in different
1191           pid namespaces.  This is a building block of containers.
1192 
1193 config NET_NS
1194         bool "Network namespace"
1195         depends on NET
1196         default y
1197         help
1198           Allow user space to create what appear to be multiple instances
1199           of the network stack.
1200 
1201 endif # NAMESPACES
1202 
1203 config SCHED_AUTOGROUP
1204         bool "Automatic process group scheduling"
1205         select CGROUPS
1206         select CGROUP_SCHED
1207         select FAIR_GROUP_SCHED
1208         help
1209           This option optimizes the scheduler for common desktop workloads by
1210           automatically creating and populating task groups.  This separation
1211           of workloads isolates aggressive CPU burners (like build jobs) from
1212           desktop applications.  Task group autogeneration is currently based
1213           upon task session.
1214 
1215 config SYSFS_DEPRECATED
1216         bool "Enable deprecated sysfs features to support old userspace tools"
1217         depends on SYSFS
1218         default n
1219         help
1220           This option adds code that switches the layout of the "block" class
1221           devices, to not show up in /sys/class/block/, but only in
1222           /sys/block/.
1223 
1224           This switch is only active when the sysfs.deprecated=1 boot option is
1225           passed or the SYSFS_DEPRECATED_V2 option is set.
1226 
1227           This option allows new kernels to run on old distributions and tools,
1228           which might get confused by /sys/class/block/. Since 2007/2008 all
1229           major distributions and tools handle this just fine.
1230 
1231           Recent distributions and userspace tools after 2009/2010 depend on
1232           the existence of /sys/class/block/, and will not work with this
1233           option enabled.
1234 
1235           Only if you are using a new kernel on an old distribution, you might
1236           need to say Y here.
1237 
1238 config SYSFS_DEPRECATED_V2
1239         bool "Enable deprecated sysfs features by default"
1240         default n
1241         depends on SYSFS
1242         depends on SYSFS_DEPRECATED
1243         help
1244           Enable deprecated sysfs by default.
1245 
1246           See the CONFIG_SYSFS_DEPRECATED option for more details about this
1247           option.
1248 
1249           Only if you are using a new kernel on an old distribution, you might
1250           need to say Y here. Even then, odds are you would not need it
1251           enabled, you can always pass the boot option if absolutely necessary.
1252 
1253 config RELAY
1254         bool "Kernel->user space relay support (formerly relayfs)"
1255         help
1256           This option enables support for relay interface support in
1257           certain file systems (such as debugfs).
1258           It is designed to provide an efficient mechanism for tools and
1259           facilities to relay large amounts of data from kernel space to
1260           user space.
1261 
1262           If unsure, say N.
1263 
1264 config BLK_DEV_INITRD
1265         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1266         depends on BROKEN || !FRV
1267         help
1268           The initial RAM filesystem is a ramfs which is loaded by the
1269           boot loader (loadlin or lilo) and that is mounted as root
1270           before the normal boot procedure. It is typically used to
1271           load modules needed to mount the "real" root file system,
1272           etc. See <file:Documentation/initrd.txt> for details.
1273 
1274           If RAM disk support (BLK_DEV_RAM) is also included, this
1275           also enables initial RAM disk (initrd) support and adds
1276           15 Kbytes (more on some other architectures) to the kernel size.
1277 
1278           If unsure say Y.
1279 
1280 if BLK_DEV_INITRD
1281 
1282 source "usr/Kconfig"
1283 
1284 endif
1285 
1286 config CC_OPTIMIZE_FOR_SIZE
1287         bool "Optimize for size"
1288         help
1289           Enabling this option will pass "-Os" instead of "-O2" to
1290           your compiler resulting in a smaller kernel.
1291 
1292           If unsure, say N.
1293 
1294 config SYSCTL
1295         bool
1296 
1297 config ANON_INODES
1298         bool
1299 
1300 config HAVE_UID16
1301         bool
1302 
1303 config SYSCTL_EXCEPTION_TRACE
1304         bool
1305         help
1306           Enable support for /proc/sys/debug/exception-trace.
1307 
1308 config SYSCTL_ARCH_UNALIGN_NO_WARN
1309         bool
1310         help
1311           Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1312           Allows arch to define/use @no_unaligned_warning to possibly warn
1313           about unaligned access emulation going on under the hood.
1314 
1315 config SYSCTL_ARCH_UNALIGN_ALLOW
1316         bool
1317         help
1318           Enable support for /proc/sys/kernel/unaligned-trap
1319           Allows arches to define/use @unaligned_enabled to runtime toggle
1320           the unaligned access emulation.
1321           see arch/parisc/kernel/unaligned.c for reference
1322 
1323 config HAVE_PCSPKR_PLATFORM
1324         bool
1325 
1326 # interpreter that classic socket filters depend on
1327 config BPF
1328         bool
1329 
1330 menuconfig EXPERT
1331         bool "Configure standard kernel features (expert users)"
1332         # Unhide debug options, to make the on-by-default options visible
1333         select DEBUG_KERNEL
1334         help
1335           This option allows certain base kernel options and settings
1336           to be disabled or tweaked. This is for specialized
1337           environments which can tolerate a "non-standard" kernel.
1338           Only use this if you really know what you are doing.
1339 
1340 config UID16
1341         bool "Enable 16-bit UID system calls" if EXPERT
1342         depends on HAVE_UID16 && MULTIUSER
1343         default y
1344         help
1345           This enables the legacy 16-bit UID syscall wrappers.
1346 
1347 config MULTIUSER
1348         bool "Multiple users, groups and capabilities support" if EXPERT
1349         default y
1350         help
1351           This option enables support for non-root users, groups and
1352           capabilities.
1353 
1354           If you say N here, all processes will run with UID 0, GID 0, and all
1355           possible capabilities.  Saying N here also compiles out support for
1356           system calls related to UIDs, GIDs, and capabilities, such as setuid,
1357           setgid, and capset.
1358 
1359           If unsure, say Y here.
1360 
1361 config SGETMASK_SYSCALL
1362         bool "sgetmask/ssetmask syscalls support" if EXPERT
1363         def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1364         ---help---
1365           sys_sgetmask and sys_ssetmask are obsolete system calls
1366           no longer supported in libc but still enabled by default in some
1367           architectures.
1368 
1369           If unsure, leave the default option here.
1370 
1371 config SYSFS_SYSCALL
1372         bool "Sysfs syscall support" if EXPERT
1373         default y
1374         ---help---
1375           sys_sysfs is an obsolete system call no longer supported in libc.
1376           Note that disabling this option is more secure but might break
1377           compatibility with some systems.
1378 
1379           If unsure say Y here.
1380 
1381 config SYSCTL_SYSCALL
1382         bool "Sysctl syscall support" if EXPERT
1383         depends on PROC_SYSCTL
1384         default n
1385         select SYSCTL
1386         ---help---
1387           sys_sysctl uses binary paths that have been found challenging
1388           to properly maintain and use.  The interface in /proc/sys
1389           using paths with ascii names is now the primary path to this
1390           information.
1391 
1392           Almost nothing using the binary sysctl interface so if you are
1393           trying to save some space it is probably safe to disable this,
1394           making your kernel marginally smaller.
1395 
1396           If unsure say N here.
1397 
1398 config KALLSYMS
1399          bool "Load all symbols for debugging/ksymoops" if EXPERT
1400          default y
1401          help
1402            Say Y here to let the kernel print out symbolic crash information and
1403            symbolic stack backtraces. This increases the size of the kernel
1404            somewhat, as all symbols have to be loaded into the kernel image.
1405 
1406 config KALLSYMS_ALL
1407         bool "Include all symbols in kallsyms"
1408         depends on DEBUG_KERNEL && KALLSYMS
1409         help
1410            Normally kallsyms only contains the symbols of functions for nicer
1411            OOPS messages and backtraces (i.e., symbols from the text and inittext
1412            sections). This is sufficient for most cases. And only in very rare
1413            cases (e.g., when a debugger is used) all symbols are required (e.g.,
1414            names of variables from the data sections, etc).
1415 
1416            This option makes sure that all symbols are loaded into the kernel
1417            image (i.e., symbols from all sections) in cost of increased kernel
1418            size (depending on the kernel configuration, it may be 300KiB or
1419            something like this).
1420 
1421            Say N unless you really need all symbols.
1422 
1423 config PRINTK
1424         default y
1425         bool "Enable support for printk" if EXPERT
1426         select IRQ_WORK
1427         help
1428           This option enables normal printk support. Removing it
1429           eliminates most of the message strings from the kernel image
1430           and makes the kernel more or less silent. As this makes it
1431           very difficult to diagnose system problems, saying N here is
1432           strongly discouraged.
1433 
1434 config BUG
1435         bool "BUG() support" if EXPERT
1436         default y
1437         help
1438           Disabling this option eliminates support for BUG and WARN, reducing
1439           the size of your kernel image and potentially quietly ignoring
1440           numerous fatal conditions. You should only consider disabling this
1441           option for embedded systems with no facilities for reporting errors.
1442           Just say Y.
1443 
1444 config ELF_CORE
1445         depends on COREDUMP
1446         default y
1447         bool "Enable ELF core dumps" if EXPERT
1448         help
1449           Enable support for generating core dumps. Disabling saves about 4k.
1450 
1451 
1452 config PCSPKR_PLATFORM
1453         bool "Enable PC-Speaker support" if EXPERT
1454         depends on HAVE_PCSPKR_PLATFORM
1455         select I8253_LOCK
1456         default y
1457         help
1458           This option allows to disable the internal PC-Speaker
1459           support, saving some memory.
1460 
1461 config BASE_FULL
1462         default y
1463         bool "Enable full-sized data structures for core" if EXPERT
1464         help
1465           Disabling this option reduces the size of miscellaneous core
1466           kernel data structures. This saves memory on small machines,
1467           but may reduce performance.
1468 
1469 config FUTEX
1470         bool "Enable futex support" if EXPERT
1471         default y
1472         select RT_MUTEXES
1473         help
1474           Disabling this option will cause the kernel to be built without
1475           support for "fast userspace mutexes".  The resulting kernel may not
1476           run glibc-based applications correctly.
1477 
1478 config HAVE_FUTEX_CMPXCHG
1479         bool
1480         depends on FUTEX
1481         help
1482           Architectures should select this if futex_atomic_cmpxchg_inatomic()
1483           is implemented and always working. This removes a couple of runtime
1484           checks.
1485 
1486 config EPOLL
1487         bool "Enable eventpoll support" if EXPERT
1488         default y
1489         select ANON_INODES
1490         help
1491           Disabling this option will cause the kernel to be built without
1492           support for epoll family of system calls.
1493 
1494 config SIGNALFD
1495         bool "Enable signalfd() system call" if EXPERT
1496         select ANON_INODES
1497         default y
1498         help
1499           Enable the signalfd() system call that allows to receive signals
1500           on a file descriptor.
1501 
1502           If unsure, say Y.
1503 
1504 config TIMERFD
1505         bool "Enable timerfd() system call" if EXPERT
1506         select ANON_INODES
1507         default y
1508         help
1509           Enable the timerfd() system call that allows to receive timer
1510           events on a file descriptor.
1511 
1512           If unsure, say Y.
1513 
1514 config EVENTFD
1515         bool "Enable eventfd() system call" if EXPERT
1516         select ANON_INODES
1517         default y
1518         help
1519           Enable the eventfd() system call that allows to receive both
1520           kernel notification (ie. KAIO) or userspace notifications.
1521 
1522           If unsure, say Y.
1523 
1524 # syscall, maps, verifier
1525 config BPF_SYSCALL
1526         bool "Enable bpf() system call"
1527         select ANON_INODES
1528         select BPF
1529         default n
1530         help
1531           Enable the bpf() system call that allows to manipulate eBPF
1532           programs and maps via file descriptors.
1533 
1534 config SHMEM
1535         bool "Use full shmem filesystem" if EXPERT
1536         default y
1537         depends on MMU
1538         help
1539           The shmem is an internal filesystem used to manage shared memory.
1540           It is backed by swap and manages resource limits. It is also exported
1541           to userspace as tmpfs if TMPFS is enabled. Disabling this
1542           option replaces shmem and tmpfs with the much simpler ramfs code,
1543           which may be appropriate on small systems without swap.
1544 
1545 config AIO
1546         bool "Enable AIO support" if EXPERT
1547         default y
1548         help
1549           This option enables POSIX asynchronous I/O which may by used
1550           by some high performance threaded applications. Disabling
1551           this option saves about 7k.
1552 
1553 config ADVISE_SYSCALLS
1554         bool "Enable madvise/fadvise syscalls" if EXPERT
1555         default y
1556         help
1557           This option enables the madvise and fadvise syscalls, used by
1558           applications to advise the kernel about their future memory or file
1559           usage, improving performance. If building an embedded system where no
1560           applications use these syscalls, you can disable this option to save
1561           space.
1562 
1563 config USERFAULTFD
1564         bool "Enable userfaultfd() system call"
1565         select ANON_INODES
1566         depends on MMU
1567         help
1568           Enable the userfaultfd() system call that allows to intercept and
1569           handle page faults in userland.
1570 
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.
1579 
1580 config MEMBARRIER
1581         bool "Enable membarrier() system call" if EXPERT
1582         default y
1583         help
1584           Enable the membarrier() system call that allows issuing memory
1585           barriers across all running threads, which can be used to distribute
1586           the cost of user-space memory barriers asymmetrically by transforming
1587           pairs of memory barriers into pairs consisting of membarrier() and a
1588           compiler barrier.
1589 
1590           If unsure, say Y.
1591 
1592 config EMBEDDED
1593         bool "Embedded system"
1594         option allnoconfig_y
1595         select EXPERT
1596         help
1597           This option should be enabled if compiling the kernel for
1598           an embedded system so certain expert options are available
1599           for configuration.
1600 
1601 config HAVE_PERF_EVENTS
1602         bool
1603         help
1604           See tools/perf/design.txt for details.
1605 
1606 config PERF_USE_VMALLOC
1607         bool
1608         help
1609           See tools/perf/design.txt for details
1610 
1611 menu "Kernel Performance Events And Counters"
1612 
1613 config PERF_EVENTS
1614         bool "Kernel performance events and counters"
1615         default y if PROFILING
1616         depends on HAVE_PERF_EVENTS
1617         select ANON_INODES
1618         select IRQ_WORK
1619         select SRCU
1620         help
1621           Enable kernel support for various performance events provided
1622           by software and hardware.
1623 
1624           Software events are supported either built-in or via the
1625           use of generic tracepoints.
1626 
1627           Most modern CPUs support performance events via performance
1628           counter registers. These registers count the number of certain
1629           types of hw events: such as instructions executed, cachemisses
1630           suffered, or branches mis-predicted - without slowing down the
1631           kernel or applications. These registers can also trigger interrupts
1632           when a threshold number of events have passed - and can thus be
1633           used to profile the code that runs on that CPU.
1634 
1635           The Linux Performance Event subsystem provides an abstraction of
1636           these software and hardware event capabilities, available via a
1637           system call and used by the "perf" utility in tools/perf/. It
1638           provides per task and per CPU counters, and it provides event
1639           capabilities on top of those.
1640 
1641           Say Y if unsure.
1642 
1643 config DEBUG_PERF_USE_VMALLOC
1644         default n
1645         bool "Debug: use vmalloc to back perf mmap() buffers"
1646         depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1647         select PERF_USE_VMALLOC
1648         help
1649          Use vmalloc memory to back perf mmap() buffers.
1650 
1651          Mostly useful for debugging the vmalloc code on platforms
1652          that don't require it.
1653 
1654          Say N if unsure.
1655 
1656 endmenu
1657 
1658 config VM_EVENT_COUNTERS
1659         default y
1660         bool "Enable VM event counters for /proc/vmstat" if EXPERT
1661         help
1662           VM event counters are needed for event counts to be shown.
1663           This option allows the disabling of the VM event counters
1664           on EXPERT systems.  /proc/vmstat will only show page counts
1665           if VM event counters are disabled.
1666 
1667 config SLUB_DEBUG
1668         default y
1669         bool "Enable SLUB debugging support" if EXPERT
1670         depends on SLUB && SYSFS
1671         help
1672           SLUB has extensive debug support features. Disabling these can
1673           result in significant savings in code size. This also disables
1674           SLUB sysfs support. /sys/slab will not exist and there will be
1675           no support for cache validation etc.
1676 
1677 config COMPAT_BRK
1678         bool "Disable heap randomization"
1679         default y
1680         help
1681           Randomizing heap placement makes heap exploits harder, but it
1682           also breaks ancient binaries (including anything libc5 based).
1683           This option changes the bootup default to heap randomization
1684           disabled, and can be overridden at runtime by setting
1685           /proc/sys/kernel/randomize_va_space to 2.
1686 
1687           On non-ancient distros (post-2000 ones) N is usually a safe choice.
1688 
1689 choice
1690         prompt "Choose SLAB allocator"
1691         default SLUB
1692         help
1693            This option allows to select a slab allocator.
1694 
1695 config SLAB
1696         bool "SLAB"
1697         help
1698           The regular slab allocator that is established and known to work
1699           well in all environments. It organizes cache hot objects in
1700           per cpu and per node queues.
1701 
1702 config SLUB
1703         bool "SLUB (Unqueued Allocator)"
1704         help
1705            SLUB is a slab allocator that minimizes cache line usage
1706            instead of managing queues of cached objects (SLAB approach).
1707            Per cpu caching is realized using slabs of objects instead
1708            of queues of objects. SLUB can use memory efficiently
1709            and has enhanced diagnostics. SLUB is the default choice for
1710            a slab allocator.
1711 
1712 config SLOB
1713         depends on EXPERT
1714         bool "SLOB (Simple Allocator)"
1715         help
1716            SLOB replaces the stock allocator with a drastically simpler
1717            allocator. SLOB is generally more space efficient but
1718            does not perform as well on large systems.
1719 
1720 endchoice
1721 
1722 config SLUB_CPU_PARTIAL
1723         default y
1724         depends on SLUB && SMP
1725         bool "SLUB per cpu partial cache"
1726         help
1727           Per cpu partial caches accellerate objects allocation and freeing
1728           that is local to a processor at the price of more indeterminism
1729           in the latency of the free. On overflow these caches will be cleared
1730           which requires the taking of locks that may cause latency spikes.
1731           Typically one would choose no for a realtime system.
1732 
1733 config MMAP_ALLOW_UNINITIALIZED
1734         bool "Allow mmapped anonymous memory to be uninitialized"
1735         depends on EXPERT && !MMU
1736         default n
1737         help
1738           Normally, and according to the Linux spec, anonymous memory obtained
1739           from mmap() has it's contents cleared before it is passed to
1740           userspace.  Enabling this config option allows you to request that
1741           mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1742           providing a huge performance boost.  If this option is not enabled,
1743           then the flag will be ignored.
1744 
1745           This is taken advantage of by uClibc's malloc(), and also by
1746           ELF-FDPIC binfmt's brk and stack allocator.
1747 
1748           Because of the obvious security issues, this option should only be
1749           enabled on embedded devices where you control what is run in
1750           userspace.  Since that isn't generally a problem on no-MMU systems,
1751           it is normally safe to say Y here.
1752 
1753           See Documentation/nommu-mmap.txt for more information.
1754 
1755 config SYSTEM_DATA_VERIFICATION
1756         def_bool n
1757         select SYSTEM_TRUSTED_KEYRING
1758         select KEYS
1759         select CRYPTO
1760         select ASYMMETRIC_KEY_TYPE
1761         select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1762         select PUBLIC_KEY_ALGO_RSA
1763         select ASN1
1764         select OID_REGISTRY
1765         select X509_CERTIFICATE_PARSER
1766         select PKCS7_MESSAGE_PARSER
1767         help
1768           Provide PKCS#7 message verification using the contents of the system
1769           trusted keyring to provide public keys.  This then can be used for
1770           module verification, kexec image verification and firmware blob
1771           verification.
1772 
1773 config PROFILING
1774         bool "Profiling support"
1775         help
1776           Say Y here to enable the extended profiling support mechanisms used
1777           by profilers such as OProfile.
1778 
1779 #
1780 # Place an empty function call at each tracepoint site. Can be
1781 # dynamically changed for a probe function.
1782 #
1783 config TRACEPOINTS
1784         bool
1785 
1786 source "arch/Kconfig"
1787 
1788 endmenu         # General setup
1789 
1790 config HAVE_GENERIC_DMA_COHERENT
1791         bool
1792         default n
1793 
1794 config SLABINFO
1795         bool
1796         depends on PROC_FS
1797         depends on SLAB || SLUB_DEBUG
1798         default y
1799 
1800 config RT_MUTEXES
1801         bool
1802 
1803 config BASE_SMALL
1804         int
1805         default 0 if BASE_FULL
1806         default 1 if !BASE_FULL
1807 
1808 menuconfig MODULES
1809         bool "Enable loadable module support"
1810         option modules
1811         help
1812           Kernel modules are small pieces of compiled code which can
1813           be inserted in the running kernel, rather than being
1814           permanently built into the kernel.  You use the "modprobe"
1815           tool to add (and sometimes remove) them.  If you say Y here,
1816           many parts of the kernel can be built as modules (by
1817           answering M instead of Y where indicated): this is most
1818           useful for infrequently used options which are not required
1819           for booting.  For more information, see the man pages for
1820           modprobe, lsmod, modinfo, insmod and rmmod.
1821 
1822           If you say Y here, you will need to run "make
1823           modules_install" to put the modules under /lib/modules/
1824           where modprobe can find them (you may need to be root to do
1825           this).
1826 
1827           If unsure, say Y.
1828 
1829 if MODULES
1830 
1831 config MODULE_FORCE_LOAD
1832         bool "Forced module loading"
1833         default n
1834         help
1835           Allow loading of modules without version information (ie. modprobe
1836           --force).  Forced module loading sets the 'F' (forced) taint flag and
1837           is usually a really bad idea.
1838 
1839 config MODULE_UNLOAD
1840         bool "Module unloading"
1841         help
1842           Without this option you will not be able to unload any
1843           modules (note that some modules may not be unloadable
1844           anyway), which makes your kernel smaller, faster
1845           and simpler.  If unsure, say Y.
1846 
1847 config MODULE_FORCE_UNLOAD
1848         bool "Forced module unloading"
1849         depends on MODULE_UNLOAD
1850         help
1851           This option allows you to force a module to unload, even if the
1852           kernel believes it is unsafe: the kernel will remove the module
1853           without waiting for anyone to stop using it (using the -f option to
1854           rmmod).  This is mainly for kernel developers and desperate users.
1855           If unsure, say N.
1856 
1857 config MODVERSIONS
1858         bool "Module versioning support"
1859         help
1860           Usually, you have to use modules compiled with your kernel.
1861           Saying Y here makes it sometimes possible to use modules
1862           compiled for different kernels, by adding enough information
1863           to the modules to (hopefully) spot any changes which would
1864           make them incompatible with the kernel you are running.  If
1865           unsure, say N.
1866 
1867 config MODULE_SRCVERSION_ALL
1868         bool "Source checksum for all modules"
1869         help
1870           Modules which contain a MODULE_VERSION get an extra "srcversion"
1871           field inserted into their modinfo section, which contains a
1872           sum of the source files which made it.  This helps maintainers
1873           see exactly which source was used to build a module (since
1874           others sometimes change the module source without updating
1875           the version).  With this option, such a "srcversion" field
1876           will be created for all modules.  If unsure, say N.
1877 
1878 config MODULE_SIG
1879         bool "Module signature verification"
1880         depends on MODULES
1881         select SYSTEM_DATA_VERIFICATION
1882         help
1883           Check modules for valid signatures upon load: the signature
1884           is simply appended to the module. For more information see
1885           Documentation/module-signing.txt.
1886 
1887           Note that this option adds the OpenSSL development packages as a
1888           kernel build dependency so that the signing tool can use its crypto
1889           library.
1890 
1891           !!!WARNING!!!  If you enable this option, you MUST make sure that the
1892           module DOES NOT get stripped after being signed.  This includes the
1893           debuginfo strip done by some packagers (such as rpmbuild) and
1894           inclusion into an initramfs that wants the module size reduced.
1895 
1896 config MODULE_SIG_FORCE
1897         bool "Require modules to be validly signed"
1898         depends on MODULE_SIG
1899         help
1900           Reject unsigned modules or signed modules for which we don't have a
1901           key.  Without this, such modules will simply taint the kernel.
1902 
1903 config MODULE_SIG_ALL
1904         bool "Automatically sign all modules"
1905         default y
1906         depends on MODULE_SIG
1907         help
1908           Sign all modules during make modules_install. Without this option,
1909           modules must be signed manually, using the scripts/sign-file tool.
1910 
1911 comment "Do not forget to sign required modules with scripts/sign-file"
1912         depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1913 
1914 choice
1915         prompt "Which hash algorithm should modules be signed with?"
1916         depends on MODULE_SIG
1917         help
1918           This determines which sort of hashing algorithm will be used during
1919           signature generation.  This algorithm _must_ be built into the kernel
1920           directly so that signature verification can take place.  It is not
1921           possible to load a signed module containing the algorithm to check
1922           the signature on that module.
1923 
1924 config MODULE_SIG_SHA1
1925         bool "Sign modules with SHA-1"
1926         select CRYPTO_SHA1
1927 
1928 config MODULE_SIG_SHA224
1929         bool "Sign modules with SHA-224"
1930         select CRYPTO_SHA256
1931 
1932 config MODULE_SIG_SHA256
1933         bool "Sign modules with SHA-256"
1934         select CRYPTO_SHA256
1935 
1936 config MODULE_SIG_SHA384
1937         bool "Sign modules with SHA-384"
1938         select CRYPTO_SHA512
1939 
1940 config MODULE_SIG_SHA512
1941         bool "Sign modules with SHA-512"
1942         select CRYPTO_SHA512
1943 
1944 endchoice
1945 
1946 config MODULE_SIG_HASH
1947         string
1948         depends on MODULE_SIG
1949         default "sha1" if MODULE_SIG_SHA1
1950         default "sha224" if MODULE_SIG_SHA224
1951         default "sha256" if MODULE_SIG_SHA256
1952         default "sha384" if MODULE_SIG_SHA384
1953         default "sha512" if MODULE_SIG_SHA512
1954 
1955 config MODULE_COMPRESS
1956         bool "Compress modules on installation"
1957         depends on MODULES
1958         help
1959 
1960           Compresses kernel modules when 'make modules_install' is run; gzip or
1961           xz depending on "Compression algorithm" below.
1962 
1963           module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
1964 
1965           Out-of-tree kernel modules installed using Kbuild will also be
1966           compressed upon installation.
1967 
1968           Note: for modules inside an initrd or initramfs, it's more efficient
1969           to compress the whole initrd or initramfs instead.
1970 
1971           Note: This is fully compatible with signed modules.
1972 
1973           If in doubt, say N.
1974 
1975 choice
1976         prompt "Compression algorithm"
1977         depends on MODULE_COMPRESS
1978         default MODULE_COMPRESS_GZIP
1979         help
1980           This determines which sort of compression will be used during
1981           'make modules_install'.
1982 
1983           GZIP (default) and XZ are supported.
1984 
1985 config MODULE_COMPRESS_GZIP
1986         bool "GZIP"
1987 
1988 config MODULE_COMPRESS_XZ
1989         bool "XZ"
1990 
1991 endchoice
1992 
1993 endif # MODULES
1994 
1995 config MODULES_TREE_LOOKUP
1996         def_bool y
1997         depends on PERF_EVENTS || TRACING
1998 
1999 config INIT_ALL_POSSIBLE
2000         bool
2001         help
2002           Back when each arch used to define their own cpu_online_mask and
2003           cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2004           with all 1s, and others with all 0s.  When they were centralised,
2005           it was better to provide this option than to break all the archs
2006           and have several arch maintainers pursuing me down dark alleys.
2007 
2008 source "block/Kconfig"
2009 
2010 config PREEMPT_NOTIFIERS
2011         bool
2012 
2013 config PADATA
2014         depends on SMP
2015         bool
2016 
2017 # Can be selected by architectures with broken toolchains
2018 # that get confused by correct const<->read_only section
2019 # mappings
2020 config BROKEN_RODATA
2021         bool
2022 
2023 config ASN1
2024         tristate
2025         help
2026           Build a simple ASN.1 grammar compiler that produces a bytecode output
2027           that can be interpreted by the ASN.1 stream decoder and used to
2028           inform it as to what tags are to be expected in a stream and what
2029           functions to call on what tags.
2030 
2031 source "kernel/Kconfig.locks"

This page was automatically generated by LXR 0.3.1 (source).  •  Linux is a registered trademark of Linus Torvalds  •  Contact us