Version:  2.0.40 2.2.26 2.4.37 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1

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         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.
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).  Does not do system-call
303           auditing without CONFIG_AUDITSYSCALL.
304 
305 config HAVE_ARCH_AUDITSYSCALL
306         bool
307 
308 config AUDITSYSCALL
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.
316 
317 config AUDIT_WATCH
318         def_bool y
319         depends on AUDITSYSCALL
320         select FSNOTIFY
321 
322 config AUDIT_TREE
323         def_bool y
324         depends on AUDITSYSCALL
325         select FSNOTIFY
326 
327 source "kernel/irq/Kconfig"
328 source "kernel/time/Kconfig"
329 
330 menu "CPU/Task time and stats accounting"
331 
332 config VIRT_CPU_ACCOUNTING
333         bool
334 
335 choice
336         prompt "Cputime accounting"
337         default TICK_CPU_ACCOUNTING if !PPC64
338         default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
339 
340 # Kind of a stub config for the pure tick based cputime accounting
341 config TICK_CPU_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.
348 
349           If unsure, say Y.
350 
351 config VIRT_CPU_ACCOUNTING_NATIVE
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.
363 
364 config VIRT_CPU_ACCOUNTING_GEN
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.
376 
377           For now this is only useful if you are working on the full
378           dynticks subsystem development.
379 
380           If unsure, say N.
381 
382 config IRQ_TIME_ACCOUNTING
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.
390 
391           If in doubt, say N here.
392 
393 endchoice
394 
395 config BSD_PROCESS_ACCT
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.
408 
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 <http://www.gnu.org/software/acct/>.
420 
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.
432 
433           Say N if unsure.
434 
435 config TASK_DELAY_ACCT
436         bool "Enable per-task delay accounting"
437         depends on TASKSTATS
438         help
439           Collect information on time spent by a task waiting for system
440           resources like cpu, synchronous block I/O completion and swapping
441           in pages. Such statistics can help in setting a task's priorities
442           relative to other tasks for cpu, io, rss limits etc.
443 
444           Say N if unsure.
445 
446 config TASK_XACCT
447         bool "Enable extended accounting over taskstats"
448         depends on TASKSTATS
449         help
450           Collect extended task accounting data and send the data
451           to userland for processing over the taskstats interface.
452 
453           Say N if unsure.
454 
455 config TASK_IO_ACCOUNTING
456         bool "Enable per-task storage I/O accounting"
457         depends on TASK_XACCT
458         help
459           Collect information on the number of bytes of storage I/O which this
460           task has caused.
461 
462           Say N if unsure.
463 
464 endmenu # "CPU/Task time and stats accounting"
465 
466 menu "RCU Subsystem"
467 
468 choice
469         prompt "RCU Implementation"
470         default TREE_RCU
471 
472 config TREE_RCU
473         bool "Tree-based hierarchical RCU"
474         depends on !PREEMPT && SMP
475         help
476           This option selects the RCU implementation that is
477           designed for very large SMP system with hundreds or
478           thousands of CPUs.  It also scales down nicely to
479           smaller systems.
480 
481 config PREEMPT_RCU
482         bool "Preemptible tree-based hierarchical RCU"
483         depends on PREEMPT
484         help
485           This option selects the RCU implementation that is
486           designed for very large SMP systems with hundreds or
487           thousands of CPUs, but for which real-time response
488           is also required.  It also scales down nicely to
489           smaller systems.
490 
491           Select this option if you are unsure.
492 
493 config TINY_RCU
494         bool "UP-only small-memory-footprint RCU"
495         depends on !PREEMPT && !SMP
496         help
497           This option selects the RCU implementation that is
498           designed for UP systems from which real-time response
499           is not required.  This option greatly reduces the
500           memory footprint of RCU.
501 
502 endchoice
503 
504 config SRCU
505         bool
506         help
507           This option selects the sleepable version of RCU. This version
508           permits arbitrary sleeping or blocking within RCU read-side critical
509           sections.
510 
511 config TASKS_RCU
512         bool "Task_based RCU implementation using voluntary context switch"
513         default n
514         select SRCU
515         help
516           This option enables a task-based RCU implementation that uses
517           only voluntary context switch (not preemption!), idle, and
518           user-mode execution as quiescent states.
519 
520           If unsure, say N.
521 
522 config RCU_STALL_COMMON
523         def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
524         help
525           This option enables RCU CPU stall code that is common between
526           the TINY and TREE variants of RCU.  The purpose is to allow
527           the tiny variants to disable RCU CPU stall warnings, while
528           making these warnings mandatory for the tree variants.
529 
530 config CONTEXT_TRACKING
531        bool
532 
533 config RCU_USER_QS
534         bool "Consider userspace as in RCU extended quiescent state"
535         depends on HAVE_CONTEXT_TRACKING && SMP
536         select CONTEXT_TRACKING
537         help
538           This option sets hooks on kernel / userspace boundaries and
539           puts RCU in extended quiescent state when the CPU runs in
540           userspace. It means that when a CPU runs in userspace, it is
541           excluded from the global RCU state machine and thus doesn't
542           try to keep the timer tick on for RCU.
543 
544           Unless you want to hack and help the development of the full
545           dynticks mode, you shouldn't enable this option.  It also
546           adds unnecessary overhead.
547 
548           If unsure say N
549 
550 config CONTEXT_TRACKING_FORCE
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.
559 
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.
569 
570           Say Y only if you're working on the development of an
571           architecture backend for the context tracking.
572 
573           Say N otherwise, this option brings an overhead that you
574           don't want in production.
575 
576 
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
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.
593 
594           Select a specific number if testing RCU itself.
595           Take the default if unsure.
596 
597 config RCU_FANOUT_LEAF
598         int "Tree-based hierarchical RCU leaf-level fanout value"
599         range 2 RCU_FANOUT if 64BIT
600         range 2 RCU_FANOUT if !64BIT
601         depends on TREE_RCU || PREEMPT_RCU
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.
617 
618           Select a specific number if testing RCU itself.
619 
620           Select the maximum permissible value for large systems.
621 
622           Take the default if unsure.
623 
624 config RCU_FANOUT_EXACT
625         bool "Disable tree-based hierarchical RCU auto-balancing"
626         depends on TREE_RCU || PREEMPT_RCU
627         default n
628         help
629           This option forces use of the exact RCU_FANOUT value specified,
630           regardless of imbalances in the hierarchy.  This is useful for
631           testing RCU itself, and might one day be useful on systems with
632           strong NUMA behavior.
633 
634           Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
635 
636           Say N if unsure.
637 
638 config RCU_FAST_NO_HZ
639         bool "Accelerate last non-dyntick-idle CPU's grace periods"
640         depends on NO_HZ_COMMON && SMP
641         default n
642         help
643           This option permits CPUs to enter dynticks-idle state even if
644           they have RCU callbacks queued, and prevents RCU from waking
645           these CPUs up more than roughly once every four jiffies (by
646           default, you can adjust this using the rcutree.rcu_idle_gp_delay
647           parameter), thus improving energy efficiency.  On the other
648           hand, this option increases the duration of RCU grace periods,
649           for example, slowing down synchronize_rcu().
650 
651           Say Y if energy efficiency is critically important, and you
652                 don't care about increased grace-period durations.
653 
654           Say N if you are unsure.
655 
656 config TREE_RCU_TRACE
657         def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
658         select DEBUG_FS
659         help
660           This option provides tracing for the TREE_RCU and
661           PREEMPT_RCU implementations, permitting Makefile to
662           trivially select kernel/rcutree_trace.c.
663 
664 config RCU_BOOST
665         bool "Enable RCU priority boosting"
666         depends on RT_MUTEXES && PREEMPT_RCU
667         default n
668         help
669           This option boosts the priority of preempted RCU readers that
670           block the current preemptible RCU grace period for too long.
671           This option also prevents heavy loads from blocking RCU
672           callback invocation for all flavors of RCU.
673 
674           Say Y here if you are working with real-time apps or heavy loads
675           Say N here if you are unsure.
676 
677 config RCU_KTHREAD_PRIO
678         int "Real-time priority to use for RCU worker threads"
679         range 1 99 if RCU_BOOST
680         range 0 99 if !RCU_BOOST
681         default 1 if RCU_BOOST
682         default 0 if !RCU_BOOST
683         help
684           This option specifies the SCHED_FIFO priority value that will be
685           assigned to the rcuc/n and rcub/n threads and is also the value
686           used for RCU_BOOST (if enabled). If you are working with a
687           real-time application that has one or more CPU-bound threads
688           running at a real-time priority level, you should set
689           RCU_KTHREAD_PRIO to a priority higher than the highest-priority
690           real-time CPU-bound application thread.  The default RCU_KTHREAD_PRIO
691           value of 1 is appropriate in the common case, which is real-time
692           applications that do not have any CPU-bound threads.
693 
694           Some real-time applications might not have a single real-time
695           thread that saturates a given CPU, but instead might have
696           multiple real-time threads that, taken together, fully utilize
697           that CPU.  In this case, you should set RCU_KTHREAD_PRIO to
698           a priority higher than the lowest-priority thread that is
699           conspiring to prevent the CPU from running any non-real-time
700           tasks.  For example, if one thread at priority 10 and another
701           thread at priority 5 are between themselves fully consuming
702           the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
703           set to priority 6 or higher.
704 
705           Specify the real-time priority, or take the default if unsure.
706 
707 config RCU_BOOST_DELAY
708         int "Milliseconds to delay boosting after RCU grace-period start"
709         range 0 3000
710         depends on RCU_BOOST
711         default 500
712         help
713           This option specifies the time to wait after the beginning of
714           a given grace period before priority-boosting preempted RCU
715           readers blocking that grace period.  Note that any RCU reader
716           blocking an expedited RCU grace period is boosted immediately.
717 
718           Accept the default if unsure.
719 
720 config RCU_NOCB_CPU
721         bool "Offload RCU callback processing from boot-selected CPUs"
722         depends on TREE_RCU || PREEMPT_RCU
723         default n
724         help
725           Use this option to reduce OS jitter for aggressive HPC or
726           real-time workloads.  It can also be used to offload RCU
727           callback invocation to energy-efficient CPUs in battery-powered
728           asymmetric multiprocessors.
729 
730           This option offloads callback invocation from the set of
731           CPUs specified at boot time by the rcu_nocbs parameter.
732           For each such CPU, a kthread ("rcuox/N") will be created to
733           invoke callbacks, where the "N" is the CPU being offloaded,
734           and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
735           "s" for RCU-sched.  Nothing prevents this kthread from running
736           on the specified CPUs, but (1) the kthreads may be preempted
737           between each callback, and (2) affinity or cgroups can be used
738           to force the kthreads to run on whatever set of CPUs is desired.
739 
740           Say Y here if you want to help to debug reduced OS jitter.
741           Say N here if you are unsure.
742 
743 choice
744         prompt "Build-forced no-CBs CPUs"
745         default RCU_NOCB_CPU_NONE
746         depends on RCU_NOCB_CPU
747         help
748           This option allows no-CBs CPUs (whose RCU callbacks are invoked
749           from kthreads rather than from softirq context) to be specified
750           at build time.  Additional no-CBs CPUs may be specified by
751           the rcu_nocbs= boot parameter.
752 
753 config RCU_NOCB_CPU_NONE
754         bool "No build_forced no-CBs CPUs"
755         help
756           This option does not force any of the CPUs to be no-CBs CPUs.
757           Only CPUs designated by the rcu_nocbs= boot parameter will be
758           no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
759           kthreads whose names begin with "rcuo".  All other CPUs will
760           invoke their own RCU callbacks in softirq context.
761 
762           Select this option if you want to choose no-CBs CPUs at
763           boot time, for example, to allow testing of different no-CBs
764           configurations without having to rebuild the kernel each time.
765 
766 config RCU_NOCB_CPU_ZERO
767         bool "CPU 0 is a build_forced no-CBs CPU"
768         help
769           This option forces CPU 0 to be a no-CBs CPU, so that its RCU
770           callbacks are invoked by a per-CPU kthread whose name begins
771           with "rcuo".  Additional CPUs may be designated as no-CBs
772           CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
773           All other CPUs will invoke their own RCU callbacks in softirq
774           context.
775 
776           Select this if CPU 0 needs to be a no-CBs CPU for real-time
777           or energy-efficiency reasons, but the real reason it exists
778           is to ensure that randconfig testing covers mixed systems.
779 
780 config RCU_NOCB_CPU_ALL
781         bool "All CPUs are build_forced no-CBs CPUs"
782         help
783           This option forces all CPUs to be no-CBs CPUs.  The rcu_nocbs=
784           boot parameter will be ignored.  All CPUs' RCU callbacks will
785           be executed in the context of per-CPU rcuo kthreads created for
786           this purpose.  Assuming that the kthreads whose names start with
787           "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
788           on the remaining CPUs, but might decrease memory locality during
789           RCU-callback invocation, thus potentially degrading throughput.
790 
791           Select this if all CPUs need to be no-CBs CPUs for real-time
792           or energy-efficiency reasons.
793 
794 endchoice
795 
796 config RCU_EXPEDITE_BOOT
797         bool
798         default n
799         help
800           This option enables expedited grace periods at boot time,
801           as if rcu_expedite_gp() had been invoked early in boot.
802           The corresponding rcu_unexpedite_gp() is invoked from
803           rcu_end_inkernel_boot(), which is intended to be invoked
804           at the end of the kernel-only boot sequence, just before
805           init is exec'ed.
806 
807           Accept the default if unsure.
808 
809 endmenu # "RCU Subsystem"
810 
811 config BUILD_BIN2C
812         bool
813         default n
814 
815 config IKCONFIG
816         tristate "Kernel .config support"
817         select BUILD_BIN2C
818         ---help---
819           This option enables the complete Linux kernel ".config" file
820           contents to be saved in the kernel. It provides documentation
821           of which kernel options are used in a running kernel or in an
822           on-disk kernel.  This information can be extracted from the kernel
823           image file with the script scripts/extract-ikconfig and used as
824           input to rebuild the current kernel or to build another kernel.
825           It can also be extracted from a running kernel by reading
826           /proc/config.gz if enabled (below).
827 
828 config IKCONFIG_PROC
829         bool "Enable access to .config through /proc/config.gz"
830         depends on IKCONFIG && PROC_FS
831         ---help---
832           This option enables access to the kernel configuration file
833           through /proc/config.gz.
834 
835 config LOG_BUF_SHIFT
836         int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
837         range 12 21
838         default 17
839         depends on PRINTK
840         help
841           Select the minimal kernel log buffer size as a power of 2.
842           The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
843           parameter, see below. Any higher size also might be forced
844           by "log_buf_len" boot parameter.
845 
846           Examples:
847                      17 => 128 KB
848                      16 => 64 KB
849                      15 => 32 KB
850                      14 => 16 KB
851                      13 =>  8 KB
852                      12 =>  4 KB
853 
854 config LOG_CPU_MAX_BUF_SHIFT
855         int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
856         depends on SMP
857         range 0 21
858         default 12 if !BASE_SMALL
859         default 0 if BASE_SMALL
860         depends on PRINTK
861         help
862           This option allows to increase the default ring buffer size
863           according to the number of CPUs. The value defines the contribution
864           of each CPU as a power of 2. The used space is typically only few
865           lines however it might be much more when problems are reported,
866           e.g. backtraces.
867 
868           The increased size means that a new buffer has to be allocated and
869           the original static one is unused. It makes sense only on systems
870           with more CPUs. Therefore this value is used only when the sum of
871           contributions is greater than the half of the default kernel ring
872           buffer as defined by LOG_BUF_SHIFT. The default values are set
873           so that more than 64 CPUs are needed to trigger the allocation.
874 
875           Also this option is ignored when "log_buf_len" kernel parameter is
876           used as it forces an exact (power of two) size of the ring buffer.
877 
878           The number of possible CPUs is used for this computation ignoring
879           hotplugging making the compuation optimal for the the worst case
880           scenerio while allowing a simple algorithm to be used from bootup.
881 
882           Examples shift values and their meaning:
883                      17 => 128 KB for each CPU
884                      16 =>  64 KB for each CPU
885                      15 =>  32 KB for each CPU
886                      14 =>  16 KB for each CPU
887                      13 =>   8 KB for each CPU
888                      12 =>   4 KB for each CPU
889 
890 #
891 # Architectures with an unreliable sched_clock() should select this:
892 #
893 config HAVE_UNSTABLE_SCHED_CLOCK
894         bool
895 
896 config GENERIC_SCHED_CLOCK
897         bool
898 
899 #
900 # For architectures that want to enable the support for NUMA-affine scheduler
901 # balancing logic:
902 #
903 config ARCH_SUPPORTS_NUMA_BALANCING
904         bool
905 
906 #
907 # For architectures that know their GCC __int128 support is sound
908 #
909 config ARCH_SUPPORTS_INT128
910         bool
911 
912 # For architectures that (ab)use NUMA to represent different memory regions
913 # all cpu-local but of different latencies, such as SuperH.
914 #
915 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
916         bool
917 
918 config NUMA_BALANCING
919         bool "Memory placement aware NUMA scheduler"
920         depends on ARCH_SUPPORTS_NUMA_BALANCING
921         depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
922         depends on SMP && NUMA && MIGRATION
923         help
924           This option adds support for automatic NUMA aware memory/task placement.
925           The mechanism is quite primitive and is based on migrating memory when
926           it has references to the node the task is running on.
927 
928           This system will be inactive on UMA systems.
929 
930 config NUMA_BALANCING_DEFAULT_ENABLED
931         bool "Automatically enable NUMA aware memory/task placement"
932         default y
933         depends on NUMA_BALANCING
934         help
935           If set, automatic NUMA balancing will be enabled if running on a NUMA
936           machine.
937 
938 menuconfig CGROUPS
939         bool "Control Group support"
940         select KERNFS
941         help
942           This option adds support for grouping sets of processes together, for
943           use with process control subsystems such as Cpusets, CFS, memory
944           controls or device isolation.
945           See
946                 - Documentation/scheduler/sched-design-CFS.txt  (CFS)
947                 - Documentation/cgroups/ (features for grouping, isolation
948                                           and resource control)
949 
950           Say N if unsure.
951 
952 if CGROUPS
953 
954 config CGROUP_DEBUG
955         bool "Example debug cgroup subsystem"
956         default n
957         help
958           This option enables a simple cgroup subsystem that
959           exports useful debugging information about the cgroups
960           framework.
961 
962           Say N if unsure.
963 
964 config CGROUP_FREEZER
965         bool "Freezer cgroup subsystem"
966         help
967           Provides a way to freeze and unfreeze all tasks in a
968           cgroup.
969 
970 config CGROUP_DEVICE
971         bool "Device controller for cgroups"
972         help
973           Provides a cgroup implementing whitelists for devices which
974           a process in the cgroup can mknod or open.
975 
976 config CPUSETS
977         bool "Cpuset support"
978         help
979           This option will let you create and manage CPUSETs which
980           allow dynamically partitioning a system into sets of CPUs and
981           Memory Nodes and assigning tasks to run only within those sets.
982           This is primarily useful on large SMP or NUMA systems.
983 
984           Say N if unsure.
985 
986 config PROC_PID_CPUSET
987         bool "Include legacy /proc/<pid>/cpuset file"
988         depends on CPUSETS
989         default y
990 
991 config CGROUP_CPUACCT
992         bool "Simple CPU accounting cgroup subsystem"
993         help
994           Provides a simple Resource Controller for monitoring the
995           total CPU consumed by the tasks in a cgroup.
996 
997 config PAGE_COUNTER
998        bool
999 
1000 config MEMCG
1001         bool "Memory Resource Controller for Control Groups"
1002         select PAGE_COUNTER
1003         select EVENTFD
1004         help
1005           Provides a memory resource controller that manages both anonymous
1006           memory and page cache. (See Documentation/cgroups/memory.txt)
1007 
1008 config MEMCG_SWAP
1009         bool "Memory Resource Controller Swap Extension"
1010         depends on MEMCG && SWAP
1011         help
1012           Add swap management feature to memory resource controller. When you
1013           enable this, you can limit mem+swap usage per cgroup. In other words,
1014           when you disable this, memory resource controller has no cares to
1015           usage of swap...a process can exhaust all of the swap. This extension
1016           is useful when you want to avoid exhaustion swap but this itself
1017           adds more overheads and consumes memory for remembering information.
1018           Especially if you use 32bit system or small memory system, please
1019           be careful about enabling this. When memory resource controller
1020           is disabled by boot option, this will be automatically disabled and
1021           there will be no overhead from this. Even when you set this config=y,
1022           if boot option "swapaccount=0" is set, swap will not be accounted.
1023           Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
1024           size is 4096bytes, 512k per 1Gbytes of swap.
1025 config MEMCG_SWAP_ENABLED
1026         bool "Memory Resource Controller Swap Extension enabled by default"
1027         depends on MEMCG_SWAP
1028         default y
1029         help
1030           Memory Resource Controller Swap Extension comes with its price in
1031           a bigger memory consumption. General purpose distribution kernels
1032           which want to enable the feature but keep it disabled by default
1033           and let the user enable it by swapaccount=1 boot command line
1034           parameter should have this option unselected.
1035           For those who want to have the feature enabled by default should
1036           select this option (if, for some reason, they need to disable it
1037           then swapaccount=0 does the trick).
1038 config MEMCG_KMEM
1039         bool "Memory Resource Controller Kernel Memory accounting"
1040         depends on MEMCG
1041         depends on SLUB || SLAB
1042         help
1043           The Kernel Memory extension for Memory Resource Controller can limit
1044           the amount of memory used by kernel objects in the system. Those are
1045           fundamentally different from the entities handled by the standard
1046           Memory Controller, which are page-based, and can be swapped. Users of
1047           the kmem extension can use it to guarantee that no group of processes
1048           will ever exhaust kernel resources alone.
1049 
1050 config CGROUP_HUGETLB
1051         bool "HugeTLB Resource Controller for Control Groups"
1052         depends on HUGETLB_PAGE
1053         select PAGE_COUNTER
1054         default n
1055         help
1056           Provides a cgroup Resource Controller for HugeTLB pages.
1057           When you enable this, you can put a per cgroup limit on HugeTLB usage.
1058           The limit is enforced during page fault. Since HugeTLB doesn't
1059           support page reclaim, enforcing the limit at page fault time implies
1060           that, the application will get SIGBUS signal if it tries to access
1061           HugeTLB pages beyond its limit. This requires the application to know
1062           beforehand how much HugeTLB pages it would require for its use. The
1063           control group is tracked in the third page lru pointer. This means
1064           that we cannot use the controller with huge page less than 3 pages.
1065 
1066 config CGROUP_PERF
1067         bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1068         depends on PERF_EVENTS && CGROUPS
1069         help
1070           This option extends the per-cpu mode to restrict monitoring to
1071           threads which belong to the cgroup specified and run on the
1072           designated cpu.
1073 
1074           Say N if unsure.
1075 
1076 menuconfig CGROUP_SCHED
1077         bool "Group CPU scheduler"
1078         default n
1079         help
1080           This feature lets CPU scheduler recognize task groups and control CPU
1081           bandwidth allocation to such task groups. It uses cgroups to group
1082           tasks.
1083 
1084 if CGROUP_SCHED
1085 config FAIR_GROUP_SCHED
1086         bool "Group scheduling for SCHED_OTHER"
1087         depends on CGROUP_SCHED
1088         default CGROUP_SCHED
1089 
1090 config CFS_BANDWIDTH
1091         bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1092         depends on FAIR_GROUP_SCHED
1093         default n
1094         help
1095           This option allows users to define CPU bandwidth rates (limits) for
1096           tasks running within the fair group scheduler.  Groups with no limit
1097           set are considered to be unconstrained and will run with no
1098           restriction.
1099           See tip/Documentation/scheduler/sched-bwc.txt for more information.
1100 
1101 config RT_GROUP_SCHED
1102         bool "Group scheduling for SCHED_RR/FIFO"
1103         depends on CGROUP_SCHED
1104         default n
1105         help
1106           This feature lets you explicitly allocate real CPU bandwidth
1107           to task groups. If enabled, it will also make it impossible to
1108           schedule realtime tasks for non-root users until you allocate
1109           realtime bandwidth for them.
1110           See Documentation/scheduler/sched-rt-group.txt for more information.
1111 
1112 endif #CGROUP_SCHED
1113 
1114 config BLK_CGROUP
1115         bool "Block IO controller"
1116         depends on BLOCK
1117         default n
1118         ---help---
1119         Generic block IO controller cgroup interface. This is the common
1120         cgroup interface which should be used by various IO controlling
1121         policies.
1122 
1123         Currently, CFQ IO scheduler uses it to recognize task groups and
1124         control disk bandwidth allocation (proportional time slice allocation)
1125         to such task groups. It is also used by bio throttling logic in
1126         block layer to implement upper limit in IO rates on a device.
1127 
1128         This option only enables generic Block IO controller infrastructure.
1129         One needs to also enable actual IO controlling logic/policy. For
1130         enabling proportional weight division of disk bandwidth in CFQ, set
1131         CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1132         CONFIG_BLK_DEV_THROTTLING=y.
1133 
1134         See Documentation/cgroups/blkio-controller.txt for more information.
1135 
1136 config DEBUG_BLK_CGROUP
1137         bool "Enable Block IO controller debugging"
1138         depends on BLK_CGROUP
1139         default n
1140         ---help---
1141         Enable some debugging help. Currently it exports additional stat
1142         files in a cgroup which can be useful for debugging.
1143 
1144 endif # CGROUPS
1145 
1146 config CHECKPOINT_RESTORE
1147         bool "Checkpoint/restore support" if EXPERT
1148         default n
1149         help
1150           Enables additional kernel features in a sake of checkpoint/restore.
1151           In particular it adds auxiliary prctl codes to setup process text,
1152           data and heap segment sizes, and a few additional /proc filesystem
1153           entries.
1154 
1155           If unsure, say N here.
1156 
1157 menuconfig NAMESPACES
1158         bool "Namespaces support" if EXPERT
1159         depends on MULTIUSER
1160         default !EXPERT
1161         help
1162           Provides the way to make tasks work with different objects using
1163           the same id. For example same IPC id may refer to different objects
1164           or same user id or pid may refer to different tasks when used in
1165           different namespaces.
1166 
1167 if NAMESPACES
1168 
1169 config UTS_NS
1170         bool "UTS namespace"
1171         default y
1172         help
1173           In this namespace tasks see different info provided with the
1174           uname() system call
1175 
1176 config IPC_NS
1177         bool "IPC namespace"
1178         depends on (SYSVIPC || POSIX_MQUEUE)
1179         default y
1180         help
1181           In this namespace tasks work with IPC ids which correspond to
1182           different IPC objects in different namespaces.
1183 
1184 config USER_NS
1185         bool "User namespace"
1186         default n
1187         help
1188           This allows containers, i.e. vservers, to use user namespaces
1189           to provide different user info for different servers.
1190 
1191           When user namespaces are enabled in the kernel it is
1192           recommended that the MEMCG and MEMCG_KMEM options also be
1193           enabled and that user-space use the memory control groups to
1194           limit the amount of memory a memory unprivileged users can
1195           use.
1196 
1197           If unsure, say N.
1198 
1199 config PID_NS
1200         bool "PID Namespaces"
1201         default y
1202         help
1203           Support process id namespaces.  This allows having multiple
1204           processes with the same pid as long as they are in different
1205           pid namespaces.  This is a building block of containers.
1206 
1207 config NET_NS
1208         bool "Network namespace"
1209         depends on NET
1210         default y
1211         help
1212           Allow user space to create what appear to be multiple instances
1213           of the network stack.
1214 
1215 endif # NAMESPACES
1216 
1217 config SCHED_AUTOGROUP
1218         bool "Automatic process group scheduling"
1219         select CGROUPS
1220         select CGROUP_SCHED
1221         select FAIR_GROUP_SCHED
1222         help
1223           This option optimizes the scheduler for common desktop workloads by
1224           automatically creating and populating task groups.  This separation
1225           of workloads isolates aggressive CPU burners (like build jobs) from
1226           desktop applications.  Task group autogeneration is currently based
1227           upon task session.
1228 
1229 config SYSFS_DEPRECATED
1230         bool "Enable deprecated sysfs features to support old userspace tools"
1231         depends on SYSFS
1232         default n
1233         help
1234           This option adds code that switches the layout of the "block" class
1235           devices, to not show up in /sys/class/block/, but only in
1236           /sys/block/.
1237 
1238           This switch is only active when the sysfs.deprecated=1 boot option is
1239           passed or the SYSFS_DEPRECATED_V2 option is set.
1240 
1241           This option allows new kernels to run on old distributions and tools,
1242           which might get confused by /sys/class/block/. Since 2007/2008 all
1243           major distributions and tools handle this just fine.
1244 
1245           Recent distributions and userspace tools after 2009/2010 depend on
1246           the existence of /sys/class/block/, and will not work with this
1247           option enabled.
1248 
1249           Only if you are using a new kernel on an old distribution, you might
1250           need to say Y here.
1251 
1252 config SYSFS_DEPRECATED_V2
1253         bool "Enable deprecated sysfs features by default"
1254         default n
1255         depends on SYSFS
1256         depends on SYSFS_DEPRECATED
1257         help
1258           Enable deprecated sysfs by default.
1259 
1260           See the CONFIG_SYSFS_DEPRECATED option for more details about this
1261           option.
1262 
1263           Only if you are using a new kernel on an old distribution, you might
1264           need to say Y here. Even then, odds are you would not need it
1265           enabled, you can always pass the boot option if absolutely necessary.
1266 
1267 config RELAY
1268         bool "Kernel->user space relay support (formerly relayfs)"
1269         help
1270           This option enables support for relay interface support in
1271           certain file systems (such as debugfs).
1272           It is designed to provide an efficient mechanism for tools and
1273           facilities to relay large amounts of data from kernel space to
1274           user space.
1275 
1276           If unsure, say N.
1277 
1278 config BLK_DEV_INITRD
1279         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1280         depends on BROKEN || !FRV
1281         help
1282           The initial RAM filesystem is a ramfs which is loaded by the
1283           boot loader (loadlin or lilo) and that is mounted as root
1284           before the normal boot procedure. It is typically used to
1285           load modules needed to mount the "real" root file system,
1286           etc. See <file:Documentation/initrd.txt> for details.
1287 
1288           If RAM disk support (BLK_DEV_RAM) is also included, this
1289           also enables initial RAM disk (initrd) support and adds
1290           15 Kbytes (more on some other architectures) to the kernel size.
1291 
1292           If unsure say Y.
1293 
1294 if BLK_DEV_INITRD
1295 
1296 source "usr/Kconfig"
1297 
1298 endif
1299 
1300 config CC_OPTIMIZE_FOR_SIZE
1301         bool "Optimize for size"
1302         help
1303           Enabling this option will pass "-Os" instead of "-O2" to
1304           your compiler resulting in a smaller kernel.
1305 
1306           If unsure, say N.
1307 
1308 config SYSCTL
1309         bool
1310 
1311 config ANON_INODES
1312         bool
1313 
1314 config HAVE_UID16
1315         bool
1316 
1317 config SYSCTL_EXCEPTION_TRACE
1318         bool
1319         help
1320           Enable support for /proc/sys/debug/exception-trace.
1321 
1322 config SYSCTL_ARCH_UNALIGN_NO_WARN
1323         bool
1324         help
1325           Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1326           Allows arch to define/use @no_unaligned_warning to possibly warn
1327           about unaligned access emulation going on under the hood.
1328 
1329 config SYSCTL_ARCH_UNALIGN_ALLOW
1330         bool
1331         help
1332           Enable support for /proc/sys/kernel/unaligned-trap
1333           Allows arches to define/use @unaligned_enabled to runtime toggle
1334           the unaligned access emulation.
1335           see arch/parisc/kernel/unaligned.c for reference
1336 
1337 config HAVE_PCSPKR_PLATFORM
1338         bool
1339 
1340 # interpreter that classic socket filters depend on
1341 config BPF
1342         bool
1343 
1344 menuconfig EXPERT
1345         bool "Configure standard kernel features (expert users)"
1346         # Unhide debug options, to make the on-by-default options visible
1347         select DEBUG_KERNEL
1348         help
1349           This option allows certain base kernel options and settings
1350           to be disabled or tweaked. This is for specialized
1351           environments which can tolerate a "non-standard" kernel.
1352           Only use this if you really know what you are doing.
1353 
1354 config UID16
1355         bool "Enable 16-bit UID system calls" if EXPERT
1356         depends on HAVE_UID16 && MULTIUSER
1357         default y
1358         help
1359           This enables the legacy 16-bit UID syscall wrappers.
1360 
1361 config MULTIUSER
1362         bool "Multiple users, groups and capabilities support" if EXPERT
1363         default y
1364         help
1365           This option enables support for non-root users, groups and
1366           capabilities.
1367 
1368           If you say N here, all processes will run with UID 0, GID 0, and all
1369           possible capabilities.  Saying N here also compiles out support for
1370           system calls related to UIDs, GIDs, and capabilities, such as setuid,
1371           setgid, and capset.
1372 
1373           If unsure, say Y here.
1374 
1375 config SGETMASK_SYSCALL
1376         bool "sgetmask/ssetmask syscalls support" if EXPERT
1377         def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1378         ---help---
1379           sys_sgetmask and sys_ssetmask are obsolete system calls
1380           no longer supported in libc but still enabled by default in some
1381           architectures.
1382 
1383           If unsure, leave the default option here.
1384 
1385 config SYSFS_SYSCALL
1386         bool "Sysfs syscall support" if EXPERT
1387         default y
1388         ---help---
1389           sys_sysfs is an obsolete system call no longer supported in libc.
1390           Note that disabling this option is more secure but might break
1391           compatibility with some systems.
1392 
1393           If unsure say Y here.
1394 
1395 config SYSCTL_SYSCALL
1396         bool "Sysctl syscall support" if EXPERT
1397         depends on PROC_SYSCTL
1398         default n
1399         select SYSCTL
1400         ---help---
1401           sys_sysctl uses binary paths that have been found challenging
1402           to properly maintain and use.  The interface in /proc/sys
1403           using paths with ascii names is now the primary path to this
1404           information.
1405 
1406           Almost nothing using the binary sysctl interface so if you are
1407           trying to save some space it is probably safe to disable this,
1408           making your kernel marginally smaller.
1409 
1410           If unsure say N here.
1411 
1412 config KALLSYMS
1413          bool "Load all symbols for debugging/ksymoops" if EXPERT
1414          default y
1415          help
1416            Say Y here to let the kernel print out symbolic crash information and
1417            symbolic stack backtraces. This increases the size of the kernel
1418            somewhat, as all symbols have to be loaded into the kernel image.
1419 
1420 config KALLSYMS_ALL
1421         bool "Include all symbols in kallsyms"
1422         depends on DEBUG_KERNEL && KALLSYMS
1423         help
1424            Normally kallsyms only contains the symbols of functions for nicer
1425            OOPS messages and backtraces (i.e., symbols from the text and inittext
1426            sections). This is sufficient for most cases. And only in very rare
1427            cases (e.g., when a debugger is used) all symbols are required (e.g.,
1428            names of variables from the data sections, etc).
1429 
1430            This option makes sure that all symbols are loaded into the kernel
1431            image (i.e., symbols from all sections) in cost of increased kernel
1432            size (depending on the kernel configuration, it may be 300KiB or
1433            something like this).
1434 
1435            Say N unless you really need all symbols.
1436 
1437 config PRINTK
1438         default y
1439         bool "Enable support for printk" if EXPERT
1440         select IRQ_WORK
1441         help
1442           This option enables normal printk support. Removing it
1443           eliminates most of the message strings from the kernel image
1444           and makes the kernel more or less silent. As this makes it
1445           very difficult to diagnose system problems, saying N here is
1446           strongly discouraged.
1447 
1448 config BUG
1449         bool "BUG() support" if EXPERT
1450         default y
1451         help
1452           Disabling this option eliminates support for BUG and WARN, reducing
1453           the size of your kernel image and potentially quietly ignoring
1454           numerous fatal conditions. You should only consider disabling this
1455           option for embedded systems with no facilities for reporting errors.
1456           Just say Y.
1457 
1458 config ELF_CORE
1459         depends on COREDUMP
1460         default y
1461         bool "Enable ELF core dumps" if EXPERT
1462         help
1463           Enable support for generating core dumps. Disabling saves about 4k.
1464 
1465 
1466 config PCSPKR_PLATFORM
1467         bool "Enable PC-Speaker support" if EXPERT
1468         depends on HAVE_PCSPKR_PLATFORM
1469         select I8253_LOCK
1470         default y
1471         help
1472           This option allows to disable the internal PC-Speaker
1473           support, saving some memory.
1474 
1475 config BASE_FULL
1476         default y
1477         bool "Enable full-sized data structures for core" if EXPERT
1478         help
1479           Disabling this option reduces the size of miscellaneous core
1480           kernel data structures. This saves memory on small machines,
1481           but may reduce performance.
1482 
1483 config FUTEX
1484         bool "Enable futex support" if EXPERT
1485         default y
1486         select RT_MUTEXES
1487         help
1488           Disabling this option will cause the kernel to be built without
1489           support for "fast userspace mutexes".  The resulting kernel may not
1490           run glibc-based applications correctly.
1491 
1492 config HAVE_FUTEX_CMPXCHG
1493         bool
1494         depends on FUTEX
1495         help
1496           Architectures should select this if futex_atomic_cmpxchg_inatomic()
1497           is implemented and always working. This removes a couple of runtime
1498           checks.
1499 
1500 config EPOLL
1501         bool "Enable eventpoll support" if EXPERT
1502         default y
1503         select ANON_INODES
1504         help
1505           Disabling this option will cause the kernel to be built without
1506           support for epoll family of system calls.
1507 
1508 config SIGNALFD
1509         bool "Enable signalfd() system call" if EXPERT
1510         select ANON_INODES
1511         default y
1512         help
1513           Enable the signalfd() system call that allows to receive signals
1514           on a file descriptor.
1515 
1516           If unsure, say Y.
1517 
1518 config TIMERFD
1519         bool "Enable timerfd() system call" if EXPERT
1520         select ANON_INODES
1521         default y
1522         help
1523           Enable the timerfd() system call that allows to receive timer
1524           events on a file descriptor.
1525 
1526           If unsure, say Y.
1527 
1528 config EVENTFD
1529         bool "Enable eventfd() system call" if EXPERT
1530         select ANON_INODES
1531         default y
1532         help
1533           Enable the eventfd() system call that allows to receive both
1534           kernel notification (ie. KAIO) or userspace notifications.
1535 
1536           If unsure, say Y.
1537 
1538 # syscall, maps, verifier
1539 config BPF_SYSCALL
1540         bool "Enable bpf() system call"
1541         select ANON_INODES
1542         select BPF
1543         default n
1544         help
1545           Enable the bpf() system call that allows to manipulate eBPF
1546           programs and maps via file descriptors.
1547 
1548 config SHMEM
1549         bool "Use full shmem filesystem" if EXPERT
1550         default y
1551         depends on MMU
1552         help
1553           The shmem is an internal filesystem used to manage shared memory.
1554           It is backed by swap and manages resource limits. It is also exported
1555           to userspace as tmpfs if TMPFS is enabled. Disabling this
1556           option replaces shmem and tmpfs with the much simpler ramfs code,
1557           which may be appropriate on small systems without swap.
1558 
1559 config AIO
1560         bool "Enable AIO support" if EXPERT
1561         default y
1562         help
1563           This option enables POSIX asynchronous I/O which may by used
1564           by some high performance threaded applications. Disabling
1565           this option saves about 7k.
1566 
1567 config ADVISE_SYSCALLS
1568         bool "Enable madvise/fadvise syscalls" if EXPERT
1569         default y
1570         help
1571           This option enables the madvise and fadvise syscalls, used by
1572           applications to advise the kernel about their future memory or file
1573           usage, improving performance. If building an embedded system where no
1574           applications use these syscalls, you can disable this option to save
1575           space.
1576 
1577 config PCI_QUIRKS
1578         default y
1579         bool "Enable PCI quirk workarounds" if EXPERT
1580         depends on PCI
1581         help
1582           This enables workarounds for various PCI chipset
1583           bugs/quirks. Disable this only if your target machine is
1584           unaffected by PCI quirks.
1585 
1586 config EMBEDDED
1587         bool "Embedded system"
1588         option allnoconfig_y
1589         select EXPERT
1590         help
1591           This option should be enabled if compiling the kernel for
1592           an embedded system so certain expert options are available
1593           for configuration.
1594 
1595 config HAVE_PERF_EVENTS
1596         bool
1597         help
1598           See tools/perf/design.txt for details.
1599 
1600 config PERF_USE_VMALLOC
1601         bool
1602         help
1603           See tools/perf/design.txt for details
1604 
1605 menu "Kernel Performance Events And Counters"
1606 
1607 config PERF_EVENTS
1608         bool "Kernel performance events and counters"
1609         default y if PROFILING
1610         depends on HAVE_PERF_EVENTS
1611         select ANON_INODES
1612         select IRQ_WORK
1613         select SRCU
1614         help
1615           Enable kernel support for various performance events provided
1616           by software and hardware.
1617 
1618           Software events are supported either built-in or via the
1619           use of generic tracepoints.
1620 
1621           Most modern CPUs support performance events via performance
1622           counter registers. These registers count the number of certain
1623           types of hw events: such as instructions executed, cachemisses
1624           suffered, or branches mis-predicted - without slowing down the
1625           kernel or applications. These registers can also trigger interrupts
1626           when a threshold number of events have passed - and can thus be
1627           used to profile the code that runs on that CPU.
1628 
1629           The Linux Performance Event subsystem provides an abstraction of
1630           these software and hardware event capabilities, available via a
1631           system call and used by the "perf" utility in tools/perf/. It
1632           provides per task and per CPU counters, and it provides event
1633           capabilities on top of those.
1634 
1635           Say Y if unsure.
1636 
1637 config DEBUG_PERF_USE_VMALLOC
1638         default n
1639         bool "Debug: use vmalloc to back perf mmap() buffers"
1640         depends on PERF_EVENTS && DEBUG_KERNEL
1641         select PERF_USE_VMALLOC
1642         help
1643          Use vmalloc memory to back perf mmap() buffers.
1644 
1645          Mostly useful for debugging the vmalloc code on platforms
1646          that don't require it.
1647 
1648          Say N if unsure.
1649 
1650 endmenu
1651 
1652 config VM_EVENT_COUNTERS
1653         default y
1654         bool "Enable VM event counters for /proc/vmstat" if EXPERT
1655         help
1656           VM event counters are needed for event counts to be shown.
1657           This option allows the disabling of the VM event counters
1658           on EXPERT systems.  /proc/vmstat will only show page counts
1659           if VM event counters are disabled.
1660 
1661 config SLUB_DEBUG
1662         default y
1663         bool "Enable SLUB debugging support" if EXPERT
1664         depends on SLUB && SYSFS
1665         help
1666           SLUB has extensive debug support features. Disabling these can
1667           result in significant savings in code size. This also disables
1668           SLUB sysfs support. /sys/slab will not exist and there will be
1669           no support for cache validation etc.
1670 
1671 config COMPAT_BRK
1672         bool "Disable heap randomization"
1673         default y
1674         help
1675           Randomizing heap placement makes heap exploits harder, but it
1676           also breaks ancient binaries (including anything libc5 based).
1677           This option changes the bootup default to heap randomization
1678           disabled, and can be overridden at runtime by setting
1679           /proc/sys/kernel/randomize_va_space to 2.
1680 
1681           On non-ancient distros (post-2000 ones) N is usually a safe choice.
1682 
1683 choice
1684         prompt "Choose SLAB allocator"
1685         default SLUB
1686         help
1687            This option allows to select a slab allocator.
1688 
1689 config SLAB
1690         bool "SLAB"
1691         help
1692           The regular slab allocator that is established and known to work
1693           well in all environments. It organizes cache hot objects in
1694           per cpu and per node queues.
1695 
1696 config SLUB
1697         bool "SLUB (Unqueued Allocator)"
1698         help
1699            SLUB is a slab allocator that minimizes cache line usage
1700            instead of managing queues of cached objects (SLAB approach).
1701            Per cpu caching is realized using slabs of objects instead
1702            of queues of objects. SLUB can use memory efficiently
1703            and has enhanced diagnostics. SLUB is the default choice for
1704            a slab allocator.
1705 
1706 config SLOB
1707         depends on EXPERT
1708         bool "SLOB (Simple Allocator)"
1709         help
1710            SLOB replaces the stock allocator with a drastically simpler
1711            allocator. SLOB is generally more space efficient but
1712            does not perform as well on large systems.
1713 
1714 endchoice
1715 
1716 config SLUB_CPU_PARTIAL
1717         default y
1718         depends on SLUB && SMP
1719         bool "SLUB per cpu partial cache"
1720         help
1721           Per cpu partial caches accellerate objects allocation and freeing
1722           that is local to a processor at the price of more indeterminism
1723           in the latency of the free. On overflow these caches will be cleared
1724           which requires the taking of locks that may cause latency spikes.
1725           Typically one would choose no for a realtime system.
1726 
1727 config MMAP_ALLOW_UNINITIALIZED
1728         bool "Allow mmapped anonymous memory to be uninitialized"
1729         depends on EXPERT && !MMU
1730         default n
1731         help
1732           Normally, and according to the Linux spec, anonymous memory obtained
1733           from mmap() has it's contents cleared before it is passed to
1734           userspace.  Enabling this config option allows you to request that
1735           mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1736           providing a huge performance boost.  If this option is not enabled,
1737           then the flag will be ignored.
1738 
1739           This is taken advantage of by uClibc's malloc(), and also by
1740           ELF-FDPIC binfmt's brk and stack allocator.
1741 
1742           Because of the obvious security issues, this option should only be
1743           enabled on embedded devices where you control what is run in
1744           userspace.  Since that isn't generally a problem on no-MMU systems,
1745           it is normally safe to say Y here.
1746 
1747           See Documentation/nommu-mmap.txt for more information.
1748 
1749 config SYSTEM_TRUSTED_KEYRING
1750         bool "Provide system-wide ring of trusted keys"
1751         depends on KEYS
1752         help
1753           Provide a system keyring to which trusted keys can be added.  Keys in
1754           the keyring are considered to be trusted.  Keys may be added at will
1755           by the kernel from compiled-in data and from hardware key stores, but
1756           userspace may only add extra keys if those keys can be verified by
1757           keys already in the keyring.
1758 
1759           Keys in this keyring are used by module signature checking.
1760 
1761 config PROFILING
1762         bool "Profiling support"
1763         help
1764           Say Y here to enable the extended profiling support mechanisms used
1765           by profilers such as OProfile.
1766 
1767 #
1768 # Place an empty function call at each tracepoint site. Can be
1769 # dynamically changed for a probe function.
1770 #
1771 config TRACEPOINTS
1772         bool
1773 
1774 source "arch/Kconfig"
1775 
1776 endmenu         # General setup
1777 
1778 config HAVE_GENERIC_DMA_COHERENT
1779         bool
1780         default n
1781 
1782 config SLABINFO
1783         bool
1784         depends on PROC_FS
1785         depends on SLAB || SLUB_DEBUG
1786         default y
1787 
1788 config RT_MUTEXES
1789         bool
1790 
1791 config BASE_SMALL
1792         int
1793         default 0 if BASE_FULL
1794         default 1 if !BASE_FULL
1795 
1796 menuconfig MODULES
1797         bool "Enable loadable module support"
1798         option modules
1799         help
1800           Kernel modules are small pieces of compiled code which can
1801           be inserted in the running kernel, rather than being
1802           permanently built into the kernel.  You use the "modprobe"
1803           tool to add (and sometimes remove) them.  If you say Y here,
1804           many parts of the kernel can be built as modules (by
1805           answering M instead of Y where indicated): this is most
1806           useful for infrequently used options which are not required
1807           for booting.  For more information, see the man pages for
1808           modprobe, lsmod, modinfo, insmod and rmmod.
1809 
1810           If you say Y here, you will need to run "make
1811           modules_install" to put the modules under /lib/modules/
1812           where modprobe can find them (you may need to be root to do
1813           this).
1814 
1815           If unsure, say Y.
1816 
1817 if MODULES
1818 
1819 config MODULE_FORCE_LOAD
1820         bool "Forced module loading"
1821         default n
1822         help
1823           Allow loading of modules without version information (ie. modprobe
1824           --force).  Forced module loading sets the 'F' (forced) taint flag and
1825           is usually a really bad idea.
1826 
1827 config MODULE_UNLOAD
1828         bool "Module unloading"
1829         help
1830           Without this option you will not be able to unload any
1831           modules (note that some modules may not be unloadable
1832           anyway), which makes your kernel smaller, faster
1833           and simpler.  If unsure, say Y.
1834 
1835 config MODULE_FORCE_UNLOAD
1836         bool "Forced module unloading"
1837         depends on MODULE_UNLOAD
1838         help
1839           This option allows you to force a module to unload, even if the
1840           kernel believes it is unsafe: the kernel will remove the module
1841           without waiting for anyone to stop using it (using the -f option to
1842           rmmod).  This is mainly for kernel developers and desperate users.
1843           If unsure, say N.
1844 
1845 config MODVERSIONS
1846         bool "Module versioning support"
1847         help
1848           Usually, you have to use modules compiled with your kernel.
1849           Saying Y here makes it sometimes possible to use modules
1850           compiled for different kernels, by adding enough information
1851           to the modules to (hopefully) spot any changes which would
1852           make them incompatible with the kernel you are running.  If
1853           unsure, say N.
1854 
1855 config MODULE_SRCVERSION_ALL
1856         bool "Source checksum for all modules"
1857         help
1858           Modules which contain a MODULE_VERSION get an extra "srcversion"
1859           field inserted into their modinfo section, which contains a
1860           sum of the source files which made it.  This helps maintainers
1861           see exactly which source was used to build a module (since
1862           others sometimes change the module source without updating
1863           the version).  With this option, such a "srcversion" field
1864           will be created for all modules.  If unsure, say N.
1865 
1866 config MODULE_SIG
1867         bool "Module signature verification"
1868         depends on MODULES
1869         select SYSTEM_TRUSTED_KEYRING
1870         select KEYS
1871         select CRYPTO
1872         select ASYMMETRIC_KEY_TYPE
1873         select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1874         select PUBLIC_KEY_ALGO_RSA
1875         select ASN1
1876         select OID_REGISTRY
1877         select X509_CERTIFICATE_PARSER
1878         help
1879           Check modules for valid signatures upon load: the signature
1880           is simply appended to the module. For more information see
1881           Documentation/module-signing.txt.
1882 
1883           !!!WARNING!!!  If you enable this option, you MUST make sure that the
1884           module DOES NOT get stripped after being signed.  This includes the
1885           debuginfo strip done by some packagers (such as rpmbuild) and
1886           inclusion into an initramfs that wants the module size reduced.
1887 
1888 config MODULE_SIG_FORCE
1889         bool "Require modules to be validly signed"
1890         depends on MODULE_SIG
1891         help
1892           Reject unsigned modules or signed modules for which we don't have a
1893           key.  Without this, such modules will simply taint the kernel.
1894 
1895 config MODULE_SIG_ALL
1896         bool "Automatically sign all modules"
1897         default y
1898         depends on MODULE_SIG
1899         help
1900           Sign all modules during make modules_install. Without this option,
1901           modules must be signed manually, using the scripts/sign-file tool.
1902 
1903 comment "Do not forget to sign required modules with scripts/sign-file"
1904         depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1905 
1906 choice
1907         prompt "Which hash algorithm should modules be signed with?"
1908         depends on MODULE_SIG
1909         help
1910           This determines which sort of hashing algorithm will be used during
1911           signature generation.  This algorithm _must_ be built into the kernel
1912           directly so that signature verification can take place.  It is not
1913           possible to load a signed module containing the algorithm to check
1914           the signature on that module.
1915 
1916 config MODULE_SIG_SHA1
1917         bool "Sign modules with SHA-1"
1918         select CRYPTO_SHA1
1919 
1920 config MODULE_SIG_SHA224
1921         bool "Sign modules with SHA-224"
1922         select CRYPTO_SHA256
1923 
1924 config MODULE_SIG_SHA256
1925         bool "Sign modules with SHA-256"
1926         select CRYPTO_SHA256
1927 
1928 config MODULE_SIG_SHA384
1929         bool "Sign modules with SHA-384"
1930         select CRYPTO_SHA512
1931 
1932 config MODULE_SIG_SHA512
1933         bool "Sign modules with SHA-512"
1934         select CRYPTO_SHA512
1935 
1936 endchoice
1937 
1938 config MODULE_SIG_HASH
1939         string
1940         depends on MODULE_SIG
1941         default "sha1" if MODULE_SIG_SHA1
1942         default "sha224" if MODULE_SIG_SHA224
1943         default "sha256" if MODULE_SIG_SHA256
1944         default "sha384" if MODULE_SIG_SHA384
1945         default "sha512" if MODULE_SIG_SHA512
1946 
1947 config MODULE_COMPRESS
1948         bool "Compress modules on installation"
1949         depends on MODULES
1950         help
1951           This option compresses the kernel modules when 'make
1952           modules_install' is run.
1953 
1954           The modules will be compressed either using gzip or xz depend on the
1955           choice made in "Compression algorithm".
1956 
1957           module-init-tools has support for gzip format while kmod handle gzip
1958           and xz compressed modules.
1959 
1960           When a kernel module is installed from outside of the main kernel
1961           source and uses the Kbuild system for installing modules then that
1962           kernel module will also be compressed when it is installed.
1963 
1964           This option provides little benefit when the modules are to be used inside
1965           an initrd or initramfs, it generally is more efficient to compress the whole
1966           initrd or initramfs instead.
1967 
1968           This is fully compatible with signed modules while the signed module is
1969           compressed. module-init-tools or kmod handles decompression and provide to
1970           other layer the uncompressed but signed payload.
1971 
1972 choice
1973         prompt "Compression algorithm"
1974         depends on MODULE_COMPRESS
1975         default MODULE_COMPRESS_GZIP
1976         help
1977           This determines which sort of compression will be used during
1978           'make modules_install'.
1979 
1980           GZIP (default) and XZ are supported.
1981 
1982 config MODULE_COMPRESS_GZIP
1983         bool "GZIP"
1984 
1985 config MODULE_COMPRESS_XZ
1986         bool "XZ"
1987 
1988 endchoice
1989 
1990 endif # MODULES
1991 
1992 config INIT_ALL_POSSIBLE
1993         bool
1994         help
1995           Back when each arch used to define their own cpu_online_mask and
1996           cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1997           with all 1s, and others with all 0s.  When they were centralised,
1998           it was better to provide this option than to break all the archs
1999           and have several arch maintainers pursuing me down dark alleys.
2000 
2001 config STOP_MACHINE
2002         bool
2003         default y
2004         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
2005         help
2006           Need stop_machine() primitive.
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"

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