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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 config THREAD_INFO_IN_TASK
30 bool
31 help
32 Select this to move thread_info off the stack into task_struct. To
33 make this work, an arch will need to remove all thread_info fields
34 except flags and fix any runtime bugs.
35
36 One subtle change that will be needed is to use try_get_task_stack()
37 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
38
39 menu "General setup"
40
41 config BROKEN
42 bool
43
44 config BROKEN_ON_SMP
45 bool
46 depends on BROKEN || !SMP
47 default y
48
49 config INIT_ENV_ARG_LIMIT
50 int
51 default 32 if !UML
52 default 128 if UML
53 help
54 Maximum of each of the number of arguments and environment
55 variables passed to init from the kernel command line.
56
57
58 config CROSS_COMPILE
59 string "Cross-compiler tool prefix"
60 help
61 Same as running 'make CROSS_COMPILE=prefix-' but stored for
62 default make runs in this kernel build directory. You don't
63 need to set this unless you want the configured kernel build
64 directory to select the cross-compiler automatically.
65
66 config COMPILE_TEST
67 bool "Compile also drivers which will not load"
68 depends on !UML
69 default n
70 help
71 Some drivers can be compiled on a different platform than they are
72 intended to be run on. Despite they cannot be loaded there (or even
73 when they load they cannot be used due to missing HW support),
74 developers still, opposing to distributors, might want to build such
75 drivers to compile-test them.
76
77 If you are a developer and want to build everything available, say Y
78 here. If you are a user/distributor, say N here to exclude useless
79 drivers to be distributed.
80
81 config LOCALVERSION
82 string "Local version - append to kernel release"
83 help
84 Append an extra string to the end of your kernel version.
85 This will show up when you type uname, for example.
86 The string you set here will be appended after the contents of
87 any files with a filename matching localversion* in your
88 object and source tree, in that order. Your total string can
89 be a maximum of 64 characters.
90
91 config LOCALVERSION_AUTO
92 bool "Automatically append version information to the version string"
93 default y
94 depends on !COMPILE_TEST
95 help
96 This will try to automatically determine if the current tree is a
97 release tree by looking for git tags that belong to the current
98 top of tree revision.
99
100 A string of the format -gxxxxxxxx will be added to the localversion
101 if a git-based tree is found. The string generated by this will be
102 appended after any matching localversion* files, and after the value
103 set in CONFIG_LOCALVERSION.
104
105 (The actual string used here is the first eight characters produced
106 by running the command:
107
108 $ git rev-parse --verify HEAD
109
110 which is done within the script "scripts/setlocalversion".)
111
112 config HAVE_KERNEL_GZIP
113 bool
114
115 config HAVE_KERNEL_BZIP2
116 bool
117
118 config HAVE_KERNEL_LZMA
119 bool
120
121 config HAVE_KERNEL_XZ
122 bool
123
124 config HAVE_KERNEL_LZO
125 bool
126
127 config HAVE_KERNEL_LZ4
128 bool
129
130 choice
131 prompt "Kernel compression mode"
132 default KERNEL_GZIP
133 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
134 help
135 The linux kernel is a kind of self-extracting executable.
136 Several compression algorithms are available, which differ
137 in efficiency, compression and decompression speed.
138 Compression speed is only relevant when building a kernel.
139 Decompression speed is relevant at each boot.
140
141 If you have any problems with bzip2 or lzma compressed
142 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
143 version of this functionality (bzip2 only), for 2.4, was
144 supplied by Christian Ludwig)
145
146 High compression options are mostly useful for users, who
147 are low on disk space (embedded systems), but for whom ram
148 size matters less.
149
150 If in doubt, select 'gzip'
151
152 config KERNEL_GZIP
153 bool "Gzip"
154 depends on HAVE_KERNEL_GZIP
155 help
156 The old and tried gzip compression. It provides a good balance
157 between compression ratio and decompression speed.
158
159 config KERNEL_BZIP2
160 bool "Bzip2"
161 depends on HAVE_KERNEL_BZIP2
162 help
163 Its compression ratio and speed is intermediate.
164 Decompression speed is slowest among the choices. The kernel
165 size is about 10% smaller with bzip2, in comparison to gzip.
166 Bzip2 uses a large amount of memory. For modern kernels you
167 will need at least 8MB RAM or more for booting.
168
169 config KERNEL_LZMA
170 bool "LZMA"
171 depends on HAVE_KERNEL_LZMA
172 help
173 This compression algorithm's ratio is best. Decompression speed
174 is between gzip and bzip2. Compression is slowest.
175 The kernel size is about 33% smaller with LZMA in comparison to gzip.
176
177 config KERNEL_XZ
178 bool "XZ"
179 depends on HAVE_KERNEL_XZ
180 help
181 XZ uses the LZMA2 algorithm and instruction set specific
182 BCJ filters which can improve compression ratio of executable
183 code. The size of the kernel is about 30% smaller with XZ in
184 comparison to gzip. On architectures for which there is a BCJ
185 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
186 will create a few percent smaller kernel than plain LZMA.
187
188 The speed is about the same as with LZMA: The decompression
189 speed of XZ is better than that of bzip2 but worse than gzip
190 and LZO. Compression is slow.
191
192 config KERNEL_LZO
193 bool "LZO"
194 depends on HAVE_KERNEL_LZO
195 help
196 Its compression ratio is the poorest among the choices. The kernel
197 size is about 10% bigger than gzip; however its speed
198 (both compression and decompression) is the fastest.
199
200 config KERNEL_LZ4
201 bool "LZ4"
202 depends on HAVE_KERNEL_LZ4
203 help
204 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
205 A preliminary version of LZ4 de/compression tool is available at
206 <https://code.google.com/p/lz4/>.
207
208 Its compression ratio is worse than LZO. The size of the kernel
209 is about 8% bigger than LZO. But the decompression speed is
210 faster than LZO.
211
212 endchoice
213
214 config DEFAULT_HOSTNAME
215 string "Default hostname"
216 default "(none)"
217 help
218 This option determines the default system hostname before userspace
219 calls sethostname(2). The kernel traditionally uses "(none)" here,
220 but you may wish to use a different default here to make a minimal
221 system more usable with less configuration.
222
223 config SWAP
224 bool "Support for paging of anonymous memory (swap)"
225 depends on MMU && BLOCK
226 default y
227 help
228 This option allows you to choose whether you want to have support
229 for so called swap devices or swap files in your kernel that are
230 used to provide more virtual memory than the actual RAM present
231 in your computer. If unsure say Y.
232
233 config SYSVIPC
234 bool "System V IPC"
235 ---help---
236 Inter Process Communication is a suite of library functions and
237 system calls which let processes (running programs) synchronize and
238 exchange information. It is generally considered to be a good thing,
239 and some programs won't run unless you say Y here. In particular, if
240 you want to run the DOS emulator dosemu under Linux (read the
241 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
242 you'll need to say Y here.
243
244 You can find documentation about IPC with "info ipc" and also in
245 section 6.4 of the Linux Programmer's Guide, available from
246 <http://www.tldp.org/guides.html>.
247
248 config SYSVIPC_SYSCTL
249 bool
250 depends on SYSVIPC
251 depends on SYSCTL
252 default y
253
254 config POSIX_MQUEUE
255 bool "POSIX Message Queues"
256 depends on NET
257 ---help---
258 POSIX variant of message queues is a part of IPC. In POSIX message
259 queues every message has a priority which decides about succession
260 of receiving it by a process. If you want to compile and run
261 programs written e.g. for Solaris with use of its POSIX message
262 queues (functions mq_*) say Y here.
263
264 POSIX message queues are visible as a filesystem called 'mqueue'
265 and can be mounted somewhere if you want to do filesystem
266 operations on message queues.
267
268 If unsure, say Y.
269
270 config POSIX_MQUEUE_SYSCTL
271 bool
272 depends on POSIX_MQUEUE
273 depends on SYSCTL
274 default y
275
276 config CROSS_MEMORY_ATTACH
277 bool "Enable process_vm_readv/writev syscalls"
278 depends on MMU
279 default y
280 help
281 Enabling this option adds the system calls process_vm_readv and
282 process_vm_writev which allow a process with the correct privileges
283 to directly read from or write to another process' address space.
284 See the man page for more details.
285
286 config FHANDLE
287 bool "open by fhandle syscalls" if EXPERT
288 select EXPORTFS
289 default y
290 help
291 If you say Y here, a user level program will be able to map
292 file names to handle and then later use the handle for
293 different file system operations. This is useful in implementing
294 userspace file servers, which now track files using handles instead
295 of names. The handle would remain the same even if file names
296 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
297 syscalls.
298
299 config USELIB
300 bool "uselib syscall"
301 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
302 help
303 This option enables the uselib syscall, a system call used in the
304 dynamic linker from libc5 and earlier. glibc does not use this
305 system call. If you intend to run programs built on libc5 or
306 earlier, you may need to enable this syscall. Current systems
307 running glibc can safely disable this.
308
309 config AUDIT
310 bool "Auditing support"
311 depends on NET
312 help
313 Enable auditing infrastructure that can be used with another
314 kernel subsystem, such as SELinux (which requires this for
315 logging of avc messages output). System call auditing is included
316 on architectures which support it.
317
318 config HAVE_ARCH_AUDITSYSCALL
319 bool
320
321 config AUDITSYSCALL
322 def_bool y
323 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
324
325 config AUDIT_WATCH
326 def_bool y
327 depends on AUDITSYSCALL
328 select FSNOTIFY
329
330 config AUDIT_TREE
331 def_bool y
332 depends on AUDITSYSCALL
333 select FSNOTIFY
334
335 source "kernel/irq/Kconfig"
336 source "kernel/time/Kconfig"
337
338 menu "CPU/Task time and stats accounting"
339
340 config VIRT_CPU_ACCOUNTING
341 bool
342
343 choice
344 prompt "Cputime accounting"
345 default TICK_CPU_ACCOUNTING if !PPC64
346 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
347
348 # Kind of a stub config for the pure tick based cputime accounting
349 config TICK_CPU_ACCOUNTING
350 bool "Simple tick based cputime accounting"
351 depends on !S390 && !NO_HZ_FULL
352 help
353 This is the basic tick based cputime accounting that maintains
354 statistics about user, system and idle time spent on per jiffies
355 granularity.
356
357 If unsure, say Y.
358
359 config VIRT_CPU_ACCOUNTING_NATIVE
360 bool "Deterministic task and CPU time accounting"
361 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
362 select VIRT_CPU_ACCOUNTING
363 help
364 Select this option to enable more accurate task and CPU time
365 accounting. This is done by reading a CPU counter on each
366 kernel entry and exit and on transitions within the kernel
367 between system, softirq and hardirq state, so there is a
368 small performance impact. In the case of s390 or IBM POWER > 5,
369 this also enables accounting of stolen time on logically-partitioned
370 systems.
371
372 config VIRT_CPU_ACCOUNTING_GEN
373 bool "Full dynticks CPU time accounting"
374 depends on HAVE_CONTEXT_TRACKING
375 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
376 select VIRT_CPU_ACCOUNTING
377 select CONTEXT_TRACKING
378 help
379 Select this option to enable task and CPU time accounting on full
380 dynticks systems. This accounting is implemented by watching every
381 kernel-user boundaries using the context tracking subsystem.
382 The accounting is thus performed at the expense of some significant
383 overhead.
384
385 For now this is only useful if you are working on the full
386 dynticks subsystem development.
387
388 If unsure, say N.
389
390 endchoice
391
392 config IRQ_TIME_ACCOUNTING
393 bool "Fine granularity task level IRQ time accounting"
394 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
395 help
396 Select this option to enable fine granularity task irq time
397 accounting. This is done by reading a timestamp on each
398 transitions between softirq and hardirq state, so there can be a
399 small performance impact.
400
401 If in doubt, say N here.
402
403 config BSD_PROCESS_ACCT
404 bool "BSD Process Accounting"
405 depends on MULTIUSER
406 help
407 If you say Y here, a user level program will be able to instruct the
408 kernel (via a special system call) to write process accounting
409 information to a file: whenever a process exits, information about
410 that process will be appended to the file by the kernel. The
411 information includes things such as creation time, owning user,
412 command name, memory usage, controlling terminal etc. (the complete
413 list is in the struct acct in <file:include/linux/acct.h>). It is
414 up to the user level program to do useful things with this
415 information. This is generally a good idea, so say Y.
416
417 config BSD_PROCESS_ACCT_V3
418 bool "BSD Process Accounting version 3 file format"
419 depends on BSD_PROCESS_ACCT
420 default n
421 help
422 If you say Y here, the process accounting information is written
423 in a new file format that also logs the process IDs of each
424 process and it's parent. Note that this file format is incompatible
425 with previous v0/v1/v2 file formats, so you will need updated tools
426 for processing it. A preliminary version of these tools is available
427 at <http://www.gnu.org/software/acct/>.
428
429 config TASKSTATS
430 bool "Export task/process statistics through netlink"
431 depends on NET
432 depends on MULTIUSER
433 default n
434 help
435 Export selected statistics for tasks/processes through the
436 generic netlink interface. Unlike BSD process accounting, the
437 statistics are available during the lifetime of tasks/processes as
438 responses to commands. Like BSD accounting, they are sent to user
439 space on task exit.
440
441 Say N if unsure.
442
443 config TASK_DELAY_ACCT
444 bool "Enable per-task delay accounting"
445 depends on TASKSTATS
446 select SCHED_INFO
447 help
448 Collect information on time spent by a task waiting for system
449 resources like cpu, synchronous block I/O completion and swapping
450 in pages. Such statistics can help in setting a task's priorities
451 relative to other tasks for cpu, io, rss limits etc.
452
453 Say N if unsure.
454
455 config TASK_XACCT
456 bool "Enable extended accounting over taskstats"
457 depends on TASKSTATS
458 help
459 Collect extended task accounting data and send the data
460 to userland for processing over the taskstats interface.
461
462 Say N if unsure.
463
464 config TASK_IO_ACCOUNTING
465 bool "Enable per-task storage I/O accounting"
466 depends on TASK_XACCT
467 help
468 Collect information on the number of bytes of storage I/O which this
469 task has caused.
470
471 Say N if unsure.
472
473 endmenu # "CPU/Task time and stats accounting"
474
475 menu "RCU Subsystem"
476
477 config TREE_RCU
478 bool
479 default y if !PREEMPT && SMP
480 help
481 This option selects the RCU implementation that is
482 designed for very large SMP system with hundreds or
483 thousands of CPUs. It also scales down nicely to
484 smaller systems.
485
486 config PREEMPT_RCU
487 bool
488 default y if PREEMPT
489 help
490 This option selects the RCU implementation that is
491 designed for very large SMP systems with hundreds or
492 thousands of CPUs, but for which real-time response
493 is also required. It also scales down nicely to
494 smaller systems.
495
496 Select this option if you are unsure.
497
498 config TINY_RCU
499 bool
500 default y if !PREEMPT && !SMP
501 help
502 This option selects the RCU implementation that is
503 designed for UP systems from which real-time response
504 is not required. This option greatly reduces the
505 memory footprint of RCU.
506
507 config RCU_EXPERT
508 bool "Make expert-level adjustments to RCU configuration"
509 default n
510 help
511 This option needs to be enabled if you wish to make
512 expert-level adjustments to RCU configuration. By default,
513 no such adjustments can be made, which has the often-beneficial
514 side-effect of preventing "make oldconfig" from asking you all
515 sorts of detailed questions about how you would like numerous
516 obscure RCU options to be set up.
517
518 Say Y if you need to make expert-level adjustments to RCU.
519
520 Say N if you are unsure.
521
522 config SRCU
523 bool
524 help
525 This option selects the sleepable version of RCU. This version
526 permits arbitrary sleeping or blocking within RCU read-side critical
527 sections.
528
529 config TASKS_RCU
530 bool
531 default n
532 select SRCU
533 help
534 This option enables a task-based RCU implementation that uses
535 only voluntary context switch (not preemption!), idle, and
536 user-mode execution as quiescent states.
537
538 config RCU_STALL_COMMON
539 def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
540 help
541 This option enables RCU CPU stall code that is common between
542 the TINY and TREE variants of RCU. The purpose is to allow
543 the tiny variants to disable RCU CPU stall warnings, while
544 making these warnings mandatory for the tree variants.
545
546 config CONTEXT_TRACKING
547 bool
548
549 config CONTEXT_TRACKING_FORCE
550 bool "Force context tracking"
551 depends on CONTEXT_TRACKING
552 default y if !NO_HZ_FULL
553 help
554 The major pre-requirement for full dynticks to work is to
555 support the context tracking subsystem. But there are also
556 other dependencies to provide in order to make the full
557 dynticks working.
558
559 This option stands for testing when an arch implements the
560 context tracking backend but doesn't yet fullfill all the
561 requirements to make the full dynticks feature working.
562 Without the full dynticks, there is no way to test the support
563 for context tracking and the subsystems that rely on it: RCU
564 userspace extended quiescent state and tickless cputime
565 accounting. This option copes with the absence of the full
566 dynticks subsystem by forcing the context tracking on all
567 CPUs in the system.
568
569 Say Y only if you're working on the development of an
570 architecture backend for the context tracking.
571
572 Say N otherwise, this option brings an overhead that you
573 don't want in production.
574
575
576 config RCU_FANOUT
577 int "Tree-based hierarchical RCU fanout value"
578 range 2 64 if 64BIT
579 range 2 32 if !64BIT
580 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
581 default 64 if 64BIT
582 default 32 if !64BIT
583 help
584 This option controls the fanout of hierarchical implementations
585 of RCU, allowing RCU to work efficiently on machines with
586 large numbers of CPUs. This value must be at least the fourth
587 root of NR_CPUS, which allows NR_CPUS to be insanely large.
588 The default value of RCU_FANOUT should be used for production
589 systems, but if you are stress-testing the RCU implementation
590 itself, small RCU_FANOUT values allow you to test large-system
591 code paths on small(er) systems.
592
593 Select a specific number if testing RCU itself.
594 Take the default if unsure.
595
596 config RCU_FANOUT_LEAF
597 int "Tree-based hierarchical RCU leaf-level fanout value"
598 range 2 64 if 64BIT
599 range 2 32 if !64BIT
600 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
601 default 16
602 help
603 This option controls the leaf-level fanout of hierarchical
604 implementations of RCU, and allows trading off cache misses
605 against lock contention. Systems that synchronize their
606 scheduling-clock interrupts for energy-efficiency reasons will
607 want the default because the smaller leaf-level fanout keeps
608 lock contention levels acceptably low. Very large systems
609 (hundreds or thousands of CPUs) will instead want to set this
610 value to the maximum value possible in order to reduce the
611 number of cache misses incurred during RCU's grace-period
612 initialization. These systems tend to run CPU-bound, and thus
613 are not helped by synchronized interrupts, and thus tend to
614 skew them, which reduces lock contention enough that large
615 leaf-level fanouts work well.
616
617 Select a specific number if testing RCU itself.
618
619 Select the maximum permissible value for large systems.
620
621 Take the default if unsure.
622
623 config RCU_FAST_NO_HZ
624 bool "Accelerate last non-dyntick-idle CPU's grace periods"
625 depends on NO_HZ_COMMON && SMP && RCU_EXPERT
626 default n
627 help
628 This option permits CPUs to enter dynticks-idle state even if
629 they have RCU callbacks queued, and prevents RCU from waking
630 these CPUs up more than roughly once every four jiffies (by
631 default, you can adjust this using the rcutree.rcu_idle_gp_delay
632 parameter), thus improving energy efficiency. On the other
633 hand, this option increases the duration of RCU grace periods,
634 for example, slowing down synchronize_rcu().
635
636 Say Y if energy efficiency is critically important, and you
637 don't care about increased grace-period durations.
638
639 Say N if you are unsure.
640
641 config TREE_RCU_TRACE
642 def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
643 select DEBUG_FS
644 help
645 This option provides tracing for the TREE_RCU and
646 PREEMPT_RCU implementations, permitting Makefile to
647 trivially select kernel/rcutree_trace.c.
648
649 config RCU_BOOST
650 bool "Enable RCU priority boosting"
651 depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT
652 default n
653 help
654 This option boosts the priority of preempted RCU readers that
655 block the current preemptible RCU grace period for too long.
656 This option also prevents heavy loads from blocking RCU
657 callback invocation for all flavors of RCU.
658
659 Say Y here if you are working with real-time apps or heavy loads
660 Say N here if you are unsure.
661
662 config RCU_KTHREAD_PRIO
663 int "Real-time priority to use for RCU worker threads"
664 range 1 99 if RCU_BOOST
665 range 0 99 if !RCU_BOOST
666 default 1 if RCU_BOOST
667 default 0 if !RCU_BOOST
668 depends on RCU_EXPERT
669 help
670 This option specifies the SCHED_FIFO priority value that will be
671 assigned to the rcuc/n and rcub/n threads and is also the value
672 used for RCU_BOOST (if enabled). If you are working with a
673 real-time application that has one or more CPU-bound threads
674 running at a real-time priority level, you should set
675 RCU_KTHREAD_PRIO to a priority higher than the highest-priority
676 real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO
677 value of 1 is appropriate in the common case, which is real-time
678 applications that do not have any CPU-bound threads.
679
680 Some real-time applications might not have a single real-time
681 thread that saturates a given CPU, but instead might have
682 multiple real-time threads that, taken together, fully utilize
683 that CPU. In this case, you should set RCU_KTHREAD_PRIO to
684 a priority higher than the lowest-priority thread that is
685 conspiring to prevent the CPU from running any non-real-time
686 tasks. For example, if one thread at priority 10 and another
687 thread at priority 5 are between themselves fully consuming
688 the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
689 set to priority 6 or higher.
690
691 Specify the real-time priority, or take the default if unsure.
692
693 config RCU_BOOST_DELAY
694 int "Milliseconds to delay boosting after RCU grace-period start"
695 range 0 3000
696 depends on RCU_BOOST
697 default 500
698 help
699 This option specifies the time to wait after the beginning of
700 a given grace period before priority-boosting preempted RCU
701 readers blocking that grace period. Note that any RCU reader
702 blocking an expedited RCU grace period is boosted immediately.
703
704 Accept the default if unsure.
705
706 config RCU_NOCB_CPU
707 bool "Offload RCU callback processing from boot-selected CPUs"
708 depends on TREE_RCU || PREEMPT_RCU
709 depends on RCU_EXPERT || NO_HZ_FULL
710 default n
711 help
712 Use this option to reduce OS jitter for aggressive HPC or
713 real-time workloads. It can also be used to offload RCU
714 callback invocation to energy-efficient CPUs in battery-powered
715 asymmetric multiprocessors.
716
717 This option offloads callback invocation from the set of
718 CPUs specified at boot time by the rcu_nocbs parameter.
719 For each such CPU, a kthread ("rcuox/N") will be created to
720 invoke callbacks, where the "N" is the CPU being offloaded,
721 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
722 "s" for RCU-sched. Nothing prevents this kthread from running
723 on the specified CPUs, but (1) the kthreads may be preempted
724 between each callback, and (2) affinity or cgroups can be used
725 to force the kthreads to run on whatever set of CPUs is desired.
726
727 Say Y here if you want to help to debug reduced OS jitter.
728 Say N here if you are unsure.
729
730 choice
731 prompt "Build-forced no-CBs CPUs"
732 default RCU_NOCB_CPU_NONE
733 depends on RCU_NOCB_CPU
734 help
735 This option allows no-CBs CPUs (whose RCU callbacks are invoked
736 from kthreads rather than from softirq context) to be specified
737 at build time. Additional no-CBs CPUs may be specified by
738 the rcu_nocbs= boot parameter.
739
740 config RCU_NOCB_CPU_NONE
741 bool "No build_forced no-CBs CPUs"
742 help
743 This option does not force any of the CPUs to be no-CBs CPUs.
744 Only CPUs designated by the rcu_nocbs= boot parameter will be
745 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
746 kthreads whose names begin with "rcuo". All other CPUs will
747 invoke their own RCU callbacks in softirq context.
748
749 Select this option if you want to choose no-CBs CPUs at
750 boot time, for example, to allow testing of different no-CBs
751 configurations without having to rebuild the kernel each time.
752
753 config RCU_NOCB_CPU_ZERO
754 bool "CPU 0 is a build_forced no-CBs CPU"
755 help
756 This option forces CPU 0 to be a no-CBs CPU, so that its RCU
757 callbacks are invoked by a per-CPU kthread whose name begins
758 with "rcuo". Additional CPUs may be designated as no-CBs
759 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
760 All other CPUs will invoke their own RCU callbacks in softirq
761 context.
762
763 Select this if CPU 0 needs to be a no-CBs CPU for real-time
764 or energy-efficiency reasons, but the real reason it exists
765 is to ensure that randconfig testing covers mixed systems.
766
767 config RCU_NOCB_CPU_ALL
768 bool "All CPUs are build_forced no-CBs CPUs"
769 help
770 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
771 boot parameter will be ignored. All CPUs' RCU callbacks will
772 be executed in the context of per-CPU rcuo kthreads created for
773 this purpose. Assuming that the kthreads whose names start with
774 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
775 on the remaining CPUs, but might decrease memory locality during
776 RCU-callback invocation, thus potentially degrading throughput.
777
778 Select this if all CPUs need to be no-CBs CPUs for real-time
779 or energy-efficiency reasons.
780
781 endchoice
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 computation optimal for the worst case
854 scenario 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 config NMI_LOG_BUF_SHIFT
865 int "Temporary per-CPU NMI log buffer size (12 => 4KB, 13 => 8KB)"
866 range 10 21
867 default 13
868 depends on PRINTK_NMI
869 help
870 Select the size of a per-CPU buffer where NMI messages are temporary
871 stored. They are copied to the main log buffer in a safe context
872 to avoid a deadlock. The value defines the size as a power of 2.
873
874 NMI messages are rare and limited. The largest one is when
875 a backtrace is printed. It usually fits into 4KB. Select
876 8KB if you want to be on the safe side.
877
878 Examples:
879 17 => 128 KB for each CPU
880 16 => 64 KB for each CPU
881 15 => 32 KB for each CPU
882 14 => 16 KB for each CPU
883 13 => 8 KB for each CPU
884 12 => 4 KB for each CPU
885
886 #
887 # Architectures with an unreliable sched_clock() should select this:
888 #
889 config HAVE_UNSTABLE_SCHED_CLOCK
890 bool
891
892 config GENERIC_SCHED_CLOCK
893 bool
894
895 #
896 # For architectures that want to enable the support for NUMA-affine scheduler
897 # balancing logic:
898 #
899 config ARCH_SUPPORTS_NUMA_BALANCING
900 bool
901
902 #
903 # For architectures that prefer to flush all TLBs after a number of pages
904 # are unmapped instead of sending one IPI per page to flush. The architecture
905 # must provide guarantees on what happens if a clean TLB cache entry is
906 # written after the unmap. Details are in mm/rmap.c near the check for
907 # should_defer_flush. The architecture should also consider if the full flush
908 # and the refill costs are offset by the savings of sending fewer IPIs.
909 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
910 bool
911
912 #
913 # For architectures that know their GCC __int128 support is sound
914 #
915 config ARCH_SUPPORTS_INT128
916 bool
917
918 # For architectures that (ab)use NUMA to represent different memory regions
919 # all cpu-local but of different latencies, such as SuperH.
920 #
921 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
922 bool
923
924 config NUMA_BALANCING
925 bool "Memory placement aware NUMA scheduler"
926 depends on ARCH_SUPPORTS_NUMA_BALANCING
927 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
928 depends on SMP && NUMA && MIGRATION
929 help
930 This option adds support for automatic NUMA aware memory/task placement.
931 The mechanism is quite primitive and is based on migrating memory when
932 it has references to the node the task is running on.
933
934 This system will be inactive on UMA systems.
935
936 config NUMA_BALANCING_DEFAULT_ENABLED
937 bool "Automatically enable NUMA aware memory/task placement"
938 default y
939 depends on NUMA_BALANCING
940 help
941 If set, automatic NUMA balancing will be enabled if running on a NUMA
942 machine.
943
944 menuconfig CGROUPS
945 bool "Control Group support"
946 select KERNFS
947 help
948 This option adds support for grouping sets of processes together, for
949 use with process control subsystems such as Cpusets, CFS, memory
950 controls or device isolation.
951 See
952 - Documentation/scheduler/sched-design-CFS.txt (CFS)
953 - Documentation/cgroup-v1/ (features for grouping, isolation
954 and resource control)
955
956 Say N if unsure.
957
958 if CGROUPS
959
960 config PAGE_COUNTER
961 bool
962
963 config MEMCG
964 bool "Memory controller"
965 select PAGE_COUNTER
966 select EVENTFD
967 help
968 Provides control over the memory footprint of tasks in a cgroup.
969
970 config MEMCG_SWAP
971 bool "Swap controller"
972 depends on MEMCG && SWAP
973 help
974 Provides control over the swap space consumed by tasks in a cgroup.
975
976 config MEMCG_SWAP_ENABLED
977 bool "Swap controller enabled by default"
978 depends on MEMCG_SWAP
979 default y
980 help
981 Memory Resource Controller Swap Extension comes with its price in
982 a bigger memory consumption. General purpose distribution kernels
983 which want to enable the feature but keep it disabled by default
984 and let the user enable it by swapaccount=1 boot command line
985 parameter should have this option unselected.
986 For those who want to have the feature enabled by default should
987 select this option (if, for some reason, they need to disable it
988 then swapaccount=0 does the trick).
989
990 config BLK_CGROUP
991 bool "IO controller"
992 depends on BLOCK
993 default n
994 ---help---
995 Generic block IO controller cgroup interface. This is the common
996 cgroup interface which should be used by various IO controlling
997 policies.
998
999 Currently, CFQ IO scheduler uses it to recognize task groups and
1000 control disk bandwidth allocation (proportional time slice allocation)
1001 to such task groups. It is also used by bio throttling logic in
1002 block layer to implement upper limit in IO rates on a device.
1003
1004 This option only enables generic Block IO controller infrastructure.
1005 One needs to also enable actual IO controlling logic/policy. For
1006 enabling proportional weight division of disk bandwidth in CFQ, set
1007 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1008 CONFIG_BLK_DEV_THROTTLING=y.
1009
1010 See Documentation/cgroup-v1/blkio-controller.txt for more information.
1011
1012 config DEBUG_BLK_CGROUP
1013 bool "IO controller debugging"
1014 depends on BLK_CGROUP
1015 default n
1016 ---help---
1017 Enable some debugging help. Currently it exports additional stat
1018 files in a cgroup which can be useful for debugging.
1019
1020 config CGROUP_WRITEBACK
1021 bool
1022 depends on MEMCG && BLK_CGROUP
1023 default y
1024
1025 menuconfig CGROUP_SCHED
1026 bool "CPU controller"
1027 default n
1028 help
1029 This feature lets CPU scheduler recognize task groups and control CPU
1030 bandwidth allocation to such task groups. It uses cgroups to group
1031 tasks.
1032
1033 if CGROUP_SCHED
1034 config FAIR_GROUP_SCHED
1035 bool "Group scheduling for SCHED_OTHER"
1036 depends on CGROUP_SCHED
1037 default CGROUP_SCHED
1038
1039 config CFS_BANDWIDTH
1040 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1041 depends on FAIR_GROUP_SCHED
1042 default n
1043 help
1044 This option allows users to define CPU bandwidth rates (limits) for
1045 tasks running within the fair group scheduler. Groups with no limit
1046 set are considered to be unconstrained and will run with no
1047 restriction.
1048 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1049
1050 config RT_GROUP_SCHED
1051 bool "Group scheduling for SCHED_RR/FIFO"
1052 depends on CGROUP_SCHED
1053 default n
1054 help
1055 This feature lets you explicitly allocate real CPU bandwidth
1056 to task groups. If enabled, it will also make it impossible to
1057 schedule realtime tasks for non-root users until you allocate
1058 realtime bandwidth for them.
1059 See Documentation/scheduler/sched-rt-group.txt for more information.
1060
1061 endif #CGROUP_SCHED
1062
1063 config CGROUP_PIDS
1064 bool "PIDs controller"
1065 help
1066 Provides enforcement of process number limits in the scope of a
1067 cgroup. Any attempt to fork more processes than is allowed in the
1068 cgroup will fail. PIDs are fundamentally a global resource because it
1069 is fairly trivial to reach PID exhaustion before you reach even a
1070 conservative kmemcg limit. As a result, it is possible to grind a
1071 system to halt without being limited by other cgroup policies. The
1072 PIDs controller is designed to stop this from happening.
1073
1074 It should be noted that organisational operations (such as attaching
1075 to a cgroup hierarchy will *not* be blocked by the PIDs controller),
1076 since the PIDs limit only affects a process's ability to fork, not to
1077 attach to a cgroup.
1078
1079 config CGROUP_FREEZER
1080 bool "Freezer controller"
1081 help
1082 Provides a way to freeze and unfreeze all tasks in a
1083 cgroup.
1084
1085 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1086 controller includes important in-kernel memory consumers per default.
1087
1088 If you're using cgroup2, say N.
1089
1090 config CGROUP_HUGETLB
1091 bool "HugeTLB controller"
1092 depends on HUGETLB_PAGE
1093 select PAGE_COUNTER
1094 default n
1095 help
1096 Provides a cgroup controller for HugeTLB pages.
1097 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1098 The limit is enforced during page fault. Since HugeTLB doesn't
1099 support page reclaim, enforcing the limit at page fault time implies
1100 that, the application will get SIGBUS signal if it tries to access
1101 HugeTLB pages beyond its limit. This requires the application to know
1102 beforehand how much HugeTLB pages it would require for its use. The
1103 control group is tracked in the third page lru pointer. This means
1104 that we cannot use the controller with huge page less than 3 pages.
1105
1106 config CPUSETS
1107 bool "Cpuset controller"
1108 help
1109 This option will let you create and manage CPUSETs which
1110 allow dynamically partitioning a system into sets of CPUs and
1111 Memory Nodes and assigning tasks to run only within those sets.
1112 This is primarily useful on large SMP or NUMA systems.
1113
1114 Say N if unsure.
1115
1116 config PROC_PID_CPUSET
1117 bool "Include legacy /proc/<pid>/cpuset file"
1118 depends on CPUSETS
1119 default y
1120
1121 config CGROUP_DEVICE
1122 bool "Device controller"
1123 help
1124 Provides a cgroup controller implementing whitelists for
1125 devices which a process in the cgroup can mknod or open.
1126
1127 config CGROUP_CPUACCT
1128 bool "Simple CPU accounting controller"
1129 help
1130 Provides a simple controller for monitoring the
1131 total CPU consumed by the tasks in a cgroup.
1132
1133 config CGROUP_PERF
1134 bool "Perf controller"
1135 depends on PERF_EVENTS
1136 help
1137 This option extends the perf per-cpu mode to restrict monitoring
1138 to threads which belong to the cgroup specified and run on the
1139 designated cpu.
1140
1141 Say N if unsure.
1142
1143 config CGROUP_BPF
1144 bool "Support for eBPF programs attached to cgroups"
1145 depends on BPF_SYSCALL
1146 select SOCK_CGROUP_DATA
1147 help
1148 Allow attaching eBPF programs to a cgroup using the bpf(2)
1149 syscall command BPF_PROG_ATTACH.
1150
1151 In which context these programs are accessed depends on the type
1152 of attachment. For instance, programs that are attached using
1153 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1154 inet sockets.
1155
1156 config CGROUP_DEBUG
1157 bool "Example controller"
1158 default n
1159 help
1160 This option enables a simple controller that exports
1161 debugging information about the cgroups framework.
1162
1163 Say N.
1164
1165 config SOCK_CGROUP_DATA
1166 bool
1167 default n
1168
1169 endif # CGROUPS
1170
1171 config CHECKPOINT_RESTORE
1172 bool "Checkpoint/restore support" if EXPERT
1173 select PROC_CHILDREN
1174 default n
1175 help
1176 Enables additional kernel features in a sake of checkpoint/restore.
1177 In particular it adds auxiliary prctl codes to setup process text,
1178 data and heap segment sizes, and a few additional /proc filesystem
1179 entries.
1180
1181 If unsure, say N here.
1182
1183 menuconfig NAMESPACES
1184 bool "Namespaces support" if EXPERT
1185 depends on MULTIUSER
1186 default !EXPERT
1187 help
1188 Provides the way to make tasks work with different objects using
1189 the same id. For example same IPC id may refer to different objects
1190 or same user id or pid may refer to different tasks when used in
1191 different namespaces.
1192
1193 if NAMESPACES
1194
1195 config UTS_NS
1196 bool "UTS namespace"
1197 default y
1198 help
1199 In this namespace tasks see different info provided with the
1200 uname() system call
1201
1202 config IPC_NS
1203 bool "IPC namespace"
1204 depends on (SYSVIPC || POSIX_MQUEUE)
1205 default y
1206 help
1207 In this namespace tasks work with IPC ids which correspond to
1208 different IPC objects in different namespaces.
1209
1210 config USER_NS
1211 bool "User namespace"
1212 default n
1213 help
1214 This allows containers, i.e. vservers, to use user namespaces
1215 to provide different user info for different servers.
1216
1217 When user namespaces are enabled in the kernel it is
1218 recommended that the MEMCG option also be enabled and that
1219 user-space use the memory control groups to limit the amount
1220 of memory a memory unprivileged users can use.
1221
1222 If unsure, say N.
1223
1224 config PID_NS
1225 bool "PID Namespaces"
1226 default y
1227 help
1228 Support process id namespaces. This allows having multiple
1229 processes with the same pid as long as they are in different
1230 pid namespaces. This is a building block of containers.
1231
1232 config NET_NS
1233 bool "Network namespace"
1234 depends on NET
1235 default y
1236 help
1237 Allow user space to create what appear to be multiple instances
1238 of the network stack.
1239
1240 endif # NAMESPACES
1241
1242 config SCHED_AUTOGROUP
1243 bool "Automatic process group scheduling"
1244 select CGROUPS
1245 select CGROUP_SCHED
1246 select FAIR_GROUP_SCHED
1247 help
1248 This option optimizes the scheduler for common desktop workloads by
1249 automatically creating and populating task groups. This separation
1250 of workloads isolates aggressive CPU burners (like build jobs) from
1251 desktop applications. Task group autogeneration is currently based
1252 upon task session.
1253
1254 config SYSFS_DEPRECATED
1255 bool "Enable deprecated sysfs features to support old userspace tools"
1256 depends on SYSFS
1257 default n
1258 help
1259 This option adds code that switches the layout of the "block" class
1260 devices, to not show up in /sys/class/block/, but only in
1261 /sys/block/.
1262
1263 This switch is only active when the sysfs.deprecated=1 boot option is
1264 passed or the SYSFS_DEPRECATED_V2 option is set.
1265
1266 This option allows new kernels to run on old distributions and tools,
1267 which might get confused by /sys/class/block/. Since 2007/2008 all
1268 major distributions and tools handle this just fine.
1269
1270 Recent distributions and userspace tools after 2009/2010 depend on
1271 the existence of /sys/class/block/, and will not work with this
1272 option enabled.
1273
1274 Only if you are using a new kernel on an old distribution, you might
1275 need to say Y here.
1276
1277 config SYSFS_DEPRECATED_V2
1278 bool "Enable deprecated sysfs features by default"
1279 default n
1280 depends on SYSFS
1281 depends on SYSFS_DEPRECATED
1282 help
1283 Enable deprecated sysfs by default.
1284
1285 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1286 option.
1287
1288 Only if you are using a new kernel on an old distribution, you might
1289 need to say Y here. Even then, odds are you would not need it
1290 enabled, you can always pass the boot option if absolutely necessary.
1291
1292 config RELAY
1293 bool "Kernel->user space relay support (formerly relayfs)"
1294 select IRQ_WORK
1295 help
1296 This option enables support for relay interface support in
1297 certain file systems (such as debugfs).
1298 It is designed to provide an efficient mechanism for tools and
1299 facilities to relay large amounts of data from kernel space to
1300 user space.
1301
1302 If unsure, say N.
1303
1304 config BLK_DEV_INITRD
1305 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1306 depends on BROKEN || !FRV
1307 help
1308 The initial RAM filesystem is a ramfs which is loaded by the
1309 boot loader (loadlin or lilo) and that is mounted as root
1310 before the normal boot procedure. It is typically used to
1311 load modules needed to mount the "real" root file system,
1312 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1313
1314 If RAM disk support (BLK_DEV_RAM) is also included, this
1315 also enables initial RAM disk (initrd) support and adds
1316 15 Kbytes (more on some other architectures) to the kernel size.
1317
1318 If unsure say Y.
1319
1320 if BLK_DEV_INITRD
1321
1322 source "usr/Kconfig"
1323
1324 endif
1325
1326 choice
1327 prompt "Compiler optimization level"
1328 default CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE
1329
1330 config CC_OPTIMIZE_FOR_PERFORMANCE
1331 bool "Optimize for performance"
1332 help
1333 This is the default optimization level for the kernel, building
1334 with the "-O2" compiler flag for best performance and most
1335 helpful compile-time warnings.
1336
1337 config CC_OPTIMIZE_FOR_SIZE
1338 bool "Optimize for size"
1339 help
1340 Enabling this option will pass "-Os" instead of "-O2" to
1341 your compiler resulting in a smaller kernel.
1342
1343 If unsure, say N.
1344
1345 endchoice
1346
1347 config SYSCTL
1348 bool
1349
1350 config ANON_INODES
1351 bool
1352
1353 config HAVE_UID16
1354 bool
1355
1356 config SYSCTL_EXCEPTION_TRACE
1357 bool
1358 help
1359 Enable support for /proc/sys/debug/exception-trace.
1360
1361 config SYSCTL_ARCH_UNALIGN_NO_WARN
1362 bool
1363 help
1364 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1365 Allows arch to define/use @no_unaligned_warning to possibly warn
1366 about unaligned access emulation going on under the hood.
1367
1368 config SYSCTL_ARCH_UNALIGN_ALLOW
1369 bool
1370 help
1371 Enable support for /proc/sys/kernel/unaligned-trap
1372 Allows arches to define/use @unaligned_enabled to runtime toggle
1373 the unaligned access emulation.
1374 see arch/parisc/kernel/unaligned.c for reference
1375
1376 config HAVE_PCSPKR_PLATFORM
1377 bool
1378
1379 # interpreter that classic socket filters depend on
1380 config BPF
1381 bool
1382
1383 menuconfig EXPERT
1384 bool "Configure standard kernel features (expert users)"
1385 # Unhide debug options, to make the on-by-default options visible
1386 select DEBUG_KERNEL
1387 help
1388 This option allows certain base kernel options and settings
1389 to be disabled or tweaked. This is for specialized
1390 environments which can tolerate a "non-standard" kernel.
1391 Only use this if you really know what you are doing.
1392
1393 config UID16
1394 bool "Enable 16-bit UID system calls" if EXPERT
1395 depends on HAVE_UID16 && MULTIUSER
1396 default y
1397 help
1398 This enables the legacy 16-bit UID syscall wrappers.
1399
1400 config MULTIUSER
1401 bool "Multiple users, groups and capabilities support" if EXPERT
1402 default y
1403 help
1404 This option enables support for non-root users, groups and
1405 capabilities.
1406
1407 If you say N here, all processes will run with UID 0, GID 0, and all
1408 possible capabilities. Saying N here also compiles out support for
1409 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1410 setgid, and capset.
1411
1412 If unsure, say Y here.
1413
1414 config SGETMASK_SYSCALL
1415 bool "sgetmask/ssetmask syscalls support" if EXPERT
1416 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1417 ---help---
1418 sys_sgetmask and sys_ssetmask are obsolete system calls
1419 no longer supported in libc but still enabled by default in some
1420 architectures.
1421
1422 If unsure, leave the default option here.
1423
1424 config SYSFS_SYSCALL
1425 bool "Sysfs syscall support" if EXPERT
1426 default y
1427 ---help---
1428 sys_sysfs is an obsolete system call no longer supported in libc.
1429 Note that disabling this option is more secure but might break
1430 compatibility with some systems.
1431
1432 If unsure say Y here.
1433
1434 config SYSCTL_SYSCALL
1435 bool "Sysctl syscall support" if EXPERT
1436 depends on PROC_SYSCTL
1437 default n
1438 select SYSCTL
1439 ---help---
1440 sys_sysctl uses binary paths that have been found challenging
1441 to properly maintain and use. The interface in /proc/sys
1442 using paths with ascii names is now the primary path to this
1443 information.
1444
1445 Almost nothing using the binary sysctl interface so if you are
1446 trying to save some space it is probably safe to disable this,
1447 making your kernel marginally smaller.
1448
1449 If unsure say N here.
1450
1451 config POSIX_TIMERS
1452 bool "Posix Clocks & timers" if EXPERT
1453 default y
1454 help
1455 This includes native support for POSIX timers to the kernel.
1456 Some embedded systems have no use for them and therefore they
1457 can be configured out to reduce the size of the kernel image.
1458
1459 When this option is disabled, the following syscalls won't be
1460 available: timer_create, timer_gettime: timer_getoverrun,
1461 timer_settime, timer_delete, clock_adjtime, getitimer,
1462 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1463 clock_getres and clock_nanosleep syscalls will be limited to
1464 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1465
1466 If unsure say y.
1467
1468 config KALLSYMS
1469 bool "Load all symbols for debugging/ksymoops" if EXPERT
1470 default y
1471 help
1472 Say Y here to let the kernel print out symbolic crash information and
1473 symbolic stack backtraces. This increases the size of the kernel
1474 somewhat, as all symbols have to be loaded into the kernel image.
1475
1476 config KALLSYMS_ALL
1477 bool "Include all symbols in kallsyms"
1478 depends on DEBUG_KERNEL && KALLSYMS
1479 help
1480 Normally kallsyms only contains the symbols of functions for nicer
1481 OOPS messages and backtraces (i.e., symbols from the text and inittext
1482 sections). This is sufficient for most cases. And only in very rare
1483 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1484 names of variables from the data sections, etc).
1485
1486 This option makes sure that all symbols are loaded into the kernel
1487 image (i.e., symbols from all sections) in cost of increased kernel
1488 size (depending on the kernel configuration, it may be 300KiB or
1489 something like this).
1490
1491 Say N unless you really need all symbols.
1492
1493 config KALLSYMS_ABSOLUTE_PERCPU
1494 bool
1495 depends on KALLSYMS
1496 default X86_64 && SMP
1497
1498 config KALLSYMS_BASE_RELATIVE
1499 bool
1500 depends on KALLSYMS
1501 default !IA64 && !(TILE && 64BIT)
1502 help
1503 Instead of emitting them as absolute values in the native word size,
1504 emit the symbol references in the kallsyms table as 32-bit entries,
1505 each containing a relative value in the range [base, base + U32_MAX]
1506 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1507 an absolute value in the range [0, S32_MAX] or a relative value in the
1508 range [base, base + S32_MAX], where base is the lowest relative symbol
1509 address encountered in the image.
1510
1511 On 64-bit builds, this reduces the size of the address table by 50%,
1512 but more importantly, it results in entries whose values are build
1513 time constants, and no relocation pass is required at runtime to fix
1514 up the entries based on the runtime load address of the kernel.
1515
1516 config PRINTK
1517 default y
1518 bool "Enable support for printk" if EXPERT
1519 select IRQ_WORK
1520 help
1521 This option enables normal printk support. Removing it
1522 eliminates most of the message strings from the kernel image
1523 and makes the kernel more or less silent. As this makes it
1524 very difficult to diagnose system problems, saying N here is
1525 strongly discouraged.
1526
1527 config PRINTK_NMI
1528 def_bool y
1529 depends on PRINTK
1530 depends on HAVE_NMI
1531
1532 config BUG
1533 bool "BUG() support" if EXPERT
1534 default y
1535 help
1536 Disabling this option eliminates support for BUG and WARN, reducing
1537 the size of your kernel image and potentially quietly ignoring
1538 numerous fatal conditions. You should only consider disabling this
1539 option for embedded systems with no facilities for reporting errors.
1540 Just say Y.
1541
1542 config ELF_CORE
1543 depends on COREDUMP
1544 default y
1545 bool "Enable ELF core dumps" if EXPERT
1546 help
1547 Enable support for generating core dumps. Disabling saves about 4k.
1548
1549
1550 config PCSPKR_PLATFORM
1551 bool "Enable PC-Speaker support" if EXPERT
1552 depends on HAVE_PCSPKR_PLATFORM
1553 select I8253_LOCK
1554 default y
1555 help
1556 This option allows to disable the internal PC-Speaker
1557 support, saving some memory.
1558
1559 config BASE_FULL
1560 default y
1561 bool "Enable full-sized data structures for core" if EXPERT
1562 help
1563 Disabling this option reduces the size of miscellaneous core
1564 kernel data structures. This saves memory on small machines,
1565 but may reduce performance.
1566
1567 config FUTEX
1568 bool "Enable futex support" if EXPERT
1569 default y
1570 select RT_MUTEXES
1571 help
1572 Disabling this option will cause the kernel to be built without
1573 support for "fast userspace mutexes". The resulting kernel may not
1574 run glibc-based applications correctly.
1575
1576 config HAVE_FUTEX_CMPXCHG
1577 bool
1578 depends on FUTEX
1579 help
1580 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1581 is implemented and always working. This removes a couple of runtime
1582 checks.
1583
1584 config EPOLL
1585 bool "Enable eventpoll support" if EXPERT
1586 default y
1587 select ANON_INODES
1588 help
1589 Disabling this option will cause the kernel to be built without
1590 support for epoll family of system calls.
1591
1592 config SIGNALFD
1593 bool "Enable signalfd() system call" if EXPERT
1594 select ANON_INODES
1595 default y
1596 help
1597 Enable the signalfd() system call that allows to receive signals
1598 on a file descriptor.
1599
1600 If unsure, say Y.
1601
1602 config TIMERFD
1603 bool "Enable timerfd() system call" if EXPERT
1604 select ANON_INODES
1605 default y
1606 help
1607 Enable the timerfd() system call that allows to receive timer
1608 events on a file descriptor.
1609
1610 If unsure, say Y.
1611
1612 config EVENTFD
1613 bool "Enable eventfd() system call" if EXPERT
1614 select ANON_INODES
1615 default y
1616 help
1617 Enable the eventfd() system call that allows to receive both
1618 kernel notification (ie. KAIO) or userspace notifications.
1619
1620 If unsure, say Y.
1621
1622 # syscall, maps, verifier
1623 config BPF_SYSCALL
1624 bool "Enable bpf() system call"
1625 select ANON_INODES
1626 select BPF
1627 default n
1628 help
1629 Enable the bpf() system call that allows to manipulate eBPF
1630 programs and maps via file descriptors.
1631
1632 config SHMEM
1633 bool "Use full shmem filesystem" if EXPERT
1634 default y
1635 depends on MMU
1636 help
1637 The shmem is an internal filesystem used to manage shared memory.
1638 It is backed by swap and manages resource limits. It is also exported
1639 to userspace as tmpfs if TMPFS is enabled. Disabling this
1640 option replaces shmem and tmpfs with the much simpler ramfs code,
1641 which may be appropriate on small systems without swap.
1642
1643 config AIO
1644 bool "Enable AIO support" if EXPERT
1645 default y
1646 help
1647 This option enables POSIX asynchronous I/O which may by used
1648 by some high performance threaded applications. Disabling
1649 this option saves about 7k.
1650
1651 config ADVISE_SYSCALLS
1652 bool "Enable madvise/fadvise syscalls" if EXPERT
1653 default y
1654 help
1655 This option enables the madvise and fadvise syscalls, used by
1656 applications to advise the kernel about their future memory or file
1657 usage, improving performance. If building an embedded system where no
1658 applications use these syscalls, you can disable this option to save
1659 space.
1660
1661 config USERFAULTFD
1662 bool "Enable userfaultfd() system call"
1663 select ANON_INODES
1664 depends on MMU
1665 help
1666 Enable the userfaultfd() system call that allows to intercept and
1667 handle page faults in userland.
1668
1669 config PCI_QUIRKS
1670 default y
1671 bool "Enable PCI quirk workarounds" if EXPERT
1672 depends on PCI
1673 help
1674 This enables workarounds for various PCI chipset
1675 bugs/quirks. Disable this only if your target machine is
1676 unaffected by PCI quirks.
1677
1678 config MEMBARRIER
1679 bool "Enable membarrier() system call" if EXPERT
1680 default y
1681 help
1682 Enable the membarrier() system call that allows issuing memory
1683 barriers across all running threads, which can be used to distribute
1684 the cost of user-space memory barriers asymmetrically by transforming
1685 pairs of memory barriers into pairs consisting of membarrier() and a
1686 compiler barrier.
1687
1688 If unsure, say Y.
1689
1690 config EMBEDDED
1691 bool "Embedded system"
1692 option allnoconfig_y
1693 select EXPERT
1694 help
1695 This option should be enabled if compiling the kernel for
1696 an embedded system so certain expert options are available
1697 for configuration.
1698
1699 config HAVE_PERF_EVENTS
1700 bool
1701 help
1702 See tools/perf/design.txt for details.
1703
1704 config PERF_USE_VMALLOC
1705 bool
1706 help
1707 See tools/perf/design.txt for details
1708
1709 menu "Kernel Performance Events And Counters"
1710
1711 config PERF_EVENTS
1712 bool "Kernel performance events and counters"
1713 default y if PROFILING
1714 depends on HAVE_PERF_EVENTS
1715 select ANON_INODES
1716 select IRQ_WORK
1717 select SRCU
1718 help
1719 Enable kernel support for various performance events provided
1720 by software and hardware.
1721
1722 Software events are supported either built-in or via the
1723 use of generic tracepoints.
1724
1725 Most modern CPUs support performance events via performance
1726 counter registers. These registers count the number of certain
1727 types of hw events: such as instructions executed, cachemisses
1728 suffered, or branches mis-predicted - without slowing down the
1729 kernel or applications. These registers can also trigger interrupts
1730 when a threshold number of events have passed - and can thus be
1731 used to profile the code that runs on that CPU.
1732
1733 The Linux Performance Event subsystem provides an abstraction of
1734 these software and hardware event capabilities, available via a
1735 system call and used by the "perf" utility in tools/perf/. It
1736 provides per task and per CPU counters, and it provides event
1737 capabilities on top of those.
1738
1739 Say Y if unsure.
1740
1741 config DEBUG_PERF_USE_VMALLOC
1742 default n
1743 bool "Debug: use vmalloc to back perf mmap() buffers"
1744 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1745 select PERF_USE_VMALLOC
1746 help
1747 Use vmalloc memory to back perf mmap() buffers.
1748
1749 Mostly useful for debugging the vmalloc code on platforms
1750 that don't require it.
1751
1752 Say N if unsure.
1753
1754 endmenu
1755
1756 config VM_EVENT_COUNTERS
1757 default y
1758 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1759 help
1760 VM event counters are needed for event counts to be shown.
1761 This option allows the disabling of the VM event counters
1762 on EXPERT systems. /proc/vmstat will only show page counts
1763 if VM event counters are disabled.
1764
1765 config SLUB_DEBUG
1766 default y
1767 bool "Enable SLUB debugging support" if EXPERT
1768 depends on SLUB && SYSFS
1769 help
1770 SLUB has extensive debug support features. Disabling these can
1771 result in significant savings in code size. This also disables
1772 SLUB sysfs support. /sys/slab will not exist and there will be
1773 no support for cache validation etc.
1774
1775 config COMPAT_BRK
1776 bool "Disable heap randomization"
1777 default y
1778 help
1779 Randomizing heap placement makes heap exploits harder, but it
1780 also breaks ancient binaries (including anything libc5 based).
1781 This option changes the bootup default to heap randomization
1782 disabled, and can be overridden at runtime by setting
1783 /proc/sys/kernel/randomize_va_space to 2.
1784
1785 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1786
1787 choice
1788 prompt "Choose SLAB allocator"
1789 default SLUB
1790 help
1791 This option allows to select a slab allocator.
1792
1793 config SLAB
1794 bool "SLAB"
1795 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1796 help
1797 The regular slab allocator that is established and known to work
1798 well in all environments. It organizes cache hot objects in
1799 per cpu and per node queues.
1800
1801 config SLUB
1802 bool "SLUB (Unqueued Allocator)"
1803 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1804 help
1805 SLUB is a slab allocator that minimizes cache line usage
1806 instead of managing queues of cached objects (SLAB approach).
1807 Per cpu caching is realized using slabs of objects instead
1808 of queues of objects. SLUB can use memory efficiently
1809 and has enhanced diagnostics. SLUB is the default choice for
1810 a slab allocator.
1811
1812 config SLOB
1813 depends on EXPERT
1814 bool "SLOB (Simple Allocator)"
1815 help
1816 SLOB replaces the stock allocator with a drastically simpler
1817 allocator. SLOB is generally more space efficient but
1818 does not perform as well on large systems.
1819
1820 endchoice
1821
1822 config SLAB_FREELIST_RANDOM
1823 default n
1824 depends on SLAB || SLUB
1825 bool "SLAB freelist randomization"
1826 help
1827 Randomizes the freelist order used on creating new pages. This
1828 security feature reduces the predictability of the kernel slab
1829 allocator against heap overflows.
1830
1831 config SLUB_CPU_PARTIAL
1832 default y
1833 depends on SLUB && SMP
1834 bool "SLUB per cpu partial cache"
1835 help
1836 Per cpu partial caches accellerate objects allocation and freeing
1837 that is local to a processor at the price of more indeterminism
1838 in the latency of the free. On overflow these caches will be cleared
1839 which requires the taking of locks that may cause latency spikes.
1840 Typically one would choose no for a realtime system.
1841
1842 config MMAP_ALLOW_UNINITIALIZED
1843 bool "Allow mmapped anonymous memory to be uninitialized"
1844 depends on EXPERT && !MMU
1845 default n
1846 help
1847 Normally, and according to the Linux spec, anonymous memory obtained
1848 from mmap() has it's contents cleared before it is passed to
1849 userspace. Enabling this config option allows you to request that
1850 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1851 providing a huge performance boost. If this option is not enabled,
1852 then the flag will be ignored.
1853
1854 This is taken advantage of by uClibc's malloc(), and also by
1855 ELF-FDPIC binfmt's brk and stack allocator.
1856
1857 Because of the obvious security issues, this option should only be
1858 enabled on embedded devices where you control what is run in
1859 userspace. Since that isn't generally a problem on no-MMU systems,
1860 it is normally safe to say Y here.
1861
1862 See Documentation/nommu-mmap.txt for more information.
1863
1864 config SYSTEM_DATA_VERIFICATION
1865 def_bool n
1866 select SYSTEM_TRUSTED_KEYRING
1867 select KEYS
1868 select CRYPTO
1869 select CRYPTO_RSA
1870 select ASYMMETRIC_KEY_TYPE
1871 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1872 select ASN1
1873 select OID_REGISTRY
1874 select X509_CERTIFICATE_PARSER
1875 select PKCS7_MESSAGE_PARSER
1876 help
1877 Provide PKCS#7 message verification using the contents of the system
1878 trusted keyring to provide public keys. This then can be used for
1879 module verification, kexec image verification and firmware blob
1880 verification.
1881
1882 config PROFILING
1883 bool "Profiling support"
1884 help
1885 Say Y here to enable the extended profiling support mechanisms used
1886 by profilers such as OProfile.
1887
1888 #
1889 # Place an empty function call at each tracepoint site. Can be
1890 # dynamically changed for a probe function.
1891 #
1892 config TRACEPOINTS
1893 bool
1894
1895 source "arch/Kconfig"
1896
1897 endmenu # General setup
1898
1899 config HAVE_GENERIC_DMA_COHERENT
1900 bool
1901 default n
1902
1903 config SLABINFO
1904 bool
1905 depends on PROC_FS
1906 depends on SLAB || SLUB_DEBUG
1907 default y
1908
1909 config RT_MUTEXES
1910 bool
1911
1912 config BASE_SMALL
1913 int
1914 default 0 if BASE_FULL
1915 default 1 if !BASE_FULL
1916
1917 menuconfig MODULES
1918 bool "Enable loadable module support"
1919 option modules
1920 help
1921 Kernel modules are small pieces of compiled code which can
1922 be inserted in the running kernel, rather than being
1923 permanently built into the kernel. You use the "modprobe"
1924 tool to add (and sometimes remove) them. If you say Y here,
1925 many parts of the kernel can be built as modules (by
1926 answering M instead of Y where indicated): this is most
1927 useful for infrequently used options which are not required
1928 for booting. For more information, see the man pages for
1929 modprobe, lsmod, modinfo, insmod and rmmod.
1930
1931 If you say Y here, you will need to run "make
1932 modules_install" to put the modules under /lib/modules/
1933 where modprobe can find them (you may need to be root to do
1934 this).
1935
1936 If unsure, say Y.
1937
1938 if MODULES
1939
1940 config MODULE_FORCE_LOAD
1941 bool "Forced module loading"
1942 default n
1943 help
1944 Allow loading of modules without version information (ie. modprobe
1945 --force). Forced module loading sets the 'F' (forced) taint flag and
1946 is usually a really bad idea.
1947
1948 config MODULE_UNLOAD
1949 bool "Module unloading"
1950 help
1951 Without this option you will not be able to unload any
1952 modules (note that some modules may not be unloadable
1953 anyway), which makes your kernel smaller, faster
1954 and simpler. If unsure, say Y.
1955
1956 config MODULE_FORCE_UNLOAD
1957 bool "Forced module unloading"
1958 depends on MODULE_UNLOAD
1959 help
1960 This option allows you to force a module to unload, even if the
1961 kernel believes it is unsafe: the kernel will remove the module
1962 without waiting for anyone to stop using it (using the -f option to
1963 rmmod). This is mainly for kernel developers and desperate users.
1964 If unsure, say N.
1965
1966 config MODVERSIONS
1967 bool "Module versioning support"
1968 help
1969 Usually, you have to use modules compiled with your kernel.
1970 Saying Y here makes it sometimes possible to use modules
1971 compiled for different kernels, by adding enough information
1972 to the modules to (hopefully) spot any changes which would
1973 make them incompatible with the kernel you are running. If
1974 unsure, say N.
1975
1976 config MODULE_REL_CRCS
1977 bool
1978 depends on MODVERSIONS
1979
1980 config MODULE_SRCVERSION_ALL
1981 bool "Source checksum for all modules"
1982 help
1983 Modules which contain a MODULE_VERSION get an extra "srcversion"
1984 field inserted into their modinfo section, which contains a
1985 sum of the source files which made it. This helps maintainers
1986 see exactly which source was used to build a module (since
1987 others sometimes change the module source without updating
1988 the version). With this option, such a "srcversion" field
1989 will be created for all modules. If unsure, say N.
1990
1991 config MODULE_SIG
1992 bool "Module signature verification"
1993 depends on MODULES
1994 select SYSTEM_DATA_VERIFICATION
1995 help
1996 Check modules for valid signatures upon load: the signature
1997 is simply appended to the module. For more information see
1998 Documentation/module-signing.txt.
1999
2000 Note that this option adds the OpenSSL development packages as a
2001 kernel build dependency so that the signing tool can use its crypto
2002 library.
2003
2004 !!!WARNING!!! If you enable this option, you MUST make sure that the
2005 module DOES NOT get stripped after being signed. This includes the
2006 debuginfo strip done by some packagers (such as rpmbuild) and
2007 inclusion into an initramfs that wants the module size reduced.
2008
2009 config MODULE_SIG_FORCE
2010 bool "Require modules to be validly signed"
2011 depends on MODULE_SIG
2012 help
2013 Reject unsigned modules or signed modules for which we don't have a
2014 key. Without this, such modules will simply taint the kernel.
2015
2016 config MODULE_SIG_ALL
2017 bool "Automatically sign all modules"
2018 default y
2019 depends on MODULE_SIG
2020 help
2021 Sign all modules during make modules_install. Without this option,
2022 modules must be signed manually, using the scripts/sign-file tool.
2023
2024 comment "Do not forget to sign required modules with scripts/sign-file"
2025 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2026
2027 choice
2028 prompt "Which hash algorithm should modules be signed with?"
2029 depends on MODULE_SIG
2030 help
2031 This determines which sort of hashing algorithm will be used during
2032 signature generation. This algorithm _must_ be built into the kernel
2033 directly so that signature verification can take place. It is not
2034 possible to load a signed module containing the algorithm to check
2035 the signature on that module.
2036
2037 config MODULE_SIG_SHA1
2038 bool "Sign modules with SHA-1"
2039 select CRYPTO_SHA1
2040
2041 config MODULE_SIG_SHA224
2042 bool "Sign modules with SHA-224"
2043 select CRYPTO_SHA256
2044
2045 config MODULE_SIG_SHA256
2046 bool "Sign modules with SHA-256"
2047 select CRYPTO_SHA256
2048
2049 config MODULE_SIG_SHA384
2050 bool "Sign modules with SHA-384"
2051 select CRYPTO_SHA512
2052
2053 config MODULE_SIG_SHA512
2054 bool "Sign modules with SHA-512"
2055 select CRYPTO_SHA512
2056
2057 endchoice
2058
2059 config MODULE_SIG_HASH
2060 string
2061 depends on MODULE_SIG
2062 default "sha1" if MODULE_SIG_SHA1
2063 default "sha224" if MODULE_SIG_SHA224
2064 default "sha256" if MODULE_SIG_SHA256
2065 default "sha384" if MODULE_SIG_SHA384
2066 default "sha512" if MODULE_SIG_SHA512
2067
2068 config MODULE_COMPRESS
2069 bool "Compress modules on installation"
2070 depends on MODULES
2071 help
2072
2073 Compresses kernel modules when 'make modules_install' is run; gzip or
2074 xz depending on "Compression algorithm" below.
2075
2076 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2077
2078 Out-of-tree kernel modules installed using Kbuild will also be
2079 compressed upon installation.
2080
2081 Note: for modules inside an initrd or initramfs, it's more efficient
2082 to compress the whole initrd or initramfs instead.
2083
2084 Note: This is fully compatible with signed modules.
2085
2086 If in doubt, say N.
2087
2088 choice
2089 prompt "Compression algorithm"
2090 depends on MODULE_COMPRESS
2091 default MODULE_COMPRESS_GZIP
2092 help
2093 This determines which sort of compression will be used during
2094 'make modules_install'.
2095
2096 GZIP (default) and XZ are supported.
2097
2098 config MODULE_COMPRESS_GZIP
2099 bool "GZIP"
2100
2101 config MODULE_COMPRESS_XZ
2102 bool "XZ"
2103
2104 endchoice
2105
2106 config TRIM_UNUSED_KSYMS
2107 bool "Trim unused exported kernel symbols"
2108 depends on MODULES && !UNUSED_SYMBOLS
2109 help
2110 The kernel and some modules make many symbols available for
2111 other modules to use via EXPORT_SYMBOL() and variants. Depending
2112 on the set of modules being selected in your kernel configuration,
2113 many of those exported symbols might never be used.
2114
2115 This option allows for unused exported symbols to be dropped from
2116 the build. In turn, this provides the compiler more opportunities
2117 (especially when using LTO) for optimizing the code and reducing
2118 binary size. This might have some security advantages as well.
2119
2120 If unsure, or if you need to build out-of-tree modules, say N.
2121
2122 endif # MODULES
2123
2124 config MODULES_TREE_LOOKUP
2125 def_bool y
2126 depends on PERF_EVENTS || TRACING
2127
2128 config INIT_ALL_POSSIBLE
2129 bool
2130 help
2131 Back when each arch used to define their own cpu_online_mask and
2132 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2133 with all 1s, and others with all 0s. When they were centralised,
2134 it was better to provide this option than to break all the archs
2135 and have several arch maintainers pursuing me down dark alleys.
2136
2137 source "block/Kconfig"
2138
2139 config PREEMPT_NOTIFIERS
2140 bool
2141
2142 config PADATA
2143 depends on SMP
2144 bool
2145
2146 config ASN1
2147 tristate
2148 help
2149 Build a simple ASN.1 grammar compiler that produces a bytecode output
2150 that can be interpreted by the ASN.1 stream decoder and used to
2151 inform it as to what tags are to be expected in a stream and what
2152 functions to call on what tags.
2153
2154 source "kernel/Kconfig.locks"