1config DEFCONFIG_LIST
2 string
3 depends on !UML
4 option defconfig_list
5 default "/lib/modules/$(shell,uname -r)/.config"
6 default "/etc/kernel-config"
7 default "/boot/config-$(shell,uname -r)"
8 default ARCH_DEFCONFIG
9 default "arch/$(ARCH)/defconfig"
10
11config CC_IS_GCC
12 def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc)
13
14config GCC_VERSION
15 int
16 default $(shell,$(srctree)/scripts/gcc-version.sh -p $(CC) | sed 's/^0*//') if CC_IS_GCC
17 default 0
18
19config CC_IS_CLANG
20 def_bool $(success,$(CC) --version | head -n 1 | grep -q clang)
21
22config CLANG_VERSION
23 int
24 default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
25
26config CONSTRUCTORS
27 bool
28 depends on !UML
29
30config IRQ_WORK
31 bool
32
33config BUILDTIME_EXTABLE_SORT
34 bool
35
36config THREAD_INFO_IN_TASK
37 bool
38 help
39 Select this to move thread_info off the stack into task_struct. To
40 make this work, an arch will need to remove all thread_info fields
41 except flags and fix any runtime bugs.
42
43 One subtle change that will be needed is to use try_get_task_stack()
44 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
45
46menu "General setup"
47
48config BROKEN
49 bool
50
51config BROKEN_ON_SMP
52 bool
53 depends on BROKEN || !SMP
54 default y
55
56config INIT_ENV_ARG_LIMIT
57 int
58 default 32 if !UML
59 default 128 if UML
60 help
61 Maximum of each of the number of arguments and environment
62 variables passed to init from the kernel command line.
63
64config COMPILE_TEST
65 bool "Compile also drivers which will not load"
66 depends on !UML
67 default n
68 help
69 Some drivers can be compiled on a different platform than they are
70 intended to be run on. Despite they cannot be loaded there (or even
71 when they load they cannot be used due to missing HW support),
72 developers still, opposing to distributors, might want to build such
73 drivers to compile-test them.
74
75 If you are a developer and want to build everything available, say Y
76 here. If you are a user/distributor, say N here to exclude useless
77 drivers to be distributed.
78
79config LOCALVERSION
80 string "Local version - append to kernel release"
81 help
82 Append an extra string to the end of your kernel version.
83 This will show up when you type uname, for example.
84 The string you set here will be appended after the contents of
85 any files with a filename matching localversion* in your
86 object and source tree, in that order. Your total string can
87 be a maximum of 64 characters.
88
89config LOCALVERSION_AUTO
90 bool "Automatically append version information to the version string"
91 default y
92 depends on !COMPILE_TEST
93 help
94 This will try to automatically determine if the current tree is a
95 release tree by looking for git tags that belong to the current
96 top of tree revision.
97
98 A string of the format -gxxxxxxxx will be added to the localversion
99 if a git-based tree is found. The string generated by this will be
100 appended after any matching localversion* files, and after the value
101 set in CONFIG_LOCALVERSION.
102
103 (The actual string used here is the first eight characters produced
104 by running the command:
105
106 $ git rev-parse --verify HEAD
107
108 which is done within the script "scripts/setlocalversion".)
109
110config BUILD_SALT
111 string "Build ID Salt"
112 default ""
113 help
114 The build ID is used to link binaries and their debug info. Setting
115 this option will use the value in the calculation of the build id.
116 This is mostly useful for distributions which want to ensure the
117 build is unique between builds. It's safe to leave the default.
118
119config HAVE_KERNEL_GZIP
120 bool
121
122config HAVE_KERNEL_BZIP2
123 bool
124
125config HAVE_KERNEL_LZMA
126 bool
127
128config HAVE_KERNEL_XZ
129 bool
130
131config HAVE_KERNEL_LZO
132 bool
133
134config HAVE_KERNEL_LZ4
135 bool
136
137config HAVE_KERNEL_UNCOMPRESSED
138 bool
139
140choice
141 prompt "Kernel compression mode"
142 default KERNEL_GZIP
143 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED
144 help
145 The linux kernel is a kind of self-extracting executable.
146 Several compression algorithms are available, which differ
147 in efficiency, compression and decompression speed.
148 Compression speed is only relevant when building a kernel.
149 Decompression speed is relevant at each boot.
150
151 If you have any problems with bzip2 or lzma compressed
152 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
153 version of this functionality (bzip2 only), for 2.4, was
154 supplied by Christian Ludwig)
155
156 High compression options are mostly useful for users, who
157 are low on disk space (embedded systems), but for whom ram
158 size matters less.
159
160 If in doubt, select 'gzip'
161
162config KERNEL_GZIP
163 bool "Gzip"
164 depends on HAVE_KERNEL_GZIP
165 help
166 The old and tried gzip compression. It provides a good balance
167 between compression ratio and decompression speed.
168
169config KERNEL_BZIP2
170 bool "Bzip2"
171 depends on HAVE_KERNEL_BZIP2
172 help
173 Its compression ratio and speed is intermediate.
174 Decompression speed is slowest among the choices. The kernel
175 size is about 10% smaller with bzip2, in comparison to gzip.
176 Bzip2 uses a large amount of memory. For modern kernels you
177 will need at least 8MB RAM or more for booting.
178
179config KERNEL_LZMA
180 bool "LZMA"
181 depends on HAVE_KERNEL_LZMA
182 help
183 This compression algorithm's ratio is best. Decompression speed
184 is between gzip and bzip2. Compression is slowest.
185 The kernel size is about 33% smaller with LZMA in comparison to gzip.
186
187config KERNEL_XZ
188 bool "XZ"
189 depends on HAVE_KERNEL_XZ
190 help
191 XZ uses the LZMA2 algorithm and instruction set specific
192 BCJ filters which can improve compression ratio of executable
193 code. The size of the kernel is about 30% smaller with XZ in
194 comparison to gzip. On architectures for which there is a BCJ
195 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
196 will create a few percent smaller kernel than plain LZMA.
197
198 The speed is about the same as with LZMA: The decompression
199 speed of XZ is better than that of bzip2 but worse than gzip
200 and LZO. Compression is slow.
201
202config KERNEL_LZO
203 bool "LZO"
204 depends on HAVE_KERNEL_LZO
205 help
206 Its compression ratio is the poorest among the choices. The kernel
207 size is about 10% bigger than gzip; however its speed
208 (both compression and decompression) is the fastest.
209
210config KERNEL_LZ4
211 bool "LZ4"
212 depends on HAVE_KERNEL_LZ4
213 help
214 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
215 A preliminary version of LZ4 de/compression tool is available at
216 <https://code.google.com/p/lz4/>.
217
218 Its compression ratio is worse than LZO. The size of the kernel
219 is about 8% bigger than LZO. But the decompression speed is
220 faster than LZO.
221
222config KERNEL_UNCOMPRESSED
223 bool "None"
224 depends on HAVE_KERNEL_UNCOMPRESSED
225 help
226 Produce uncompressed kernel image. This option is usually not what
227 you want. It is useful for debugging the kernel in slow simulation
228 environments, where decompressing and moving the kernel is awfully
229 slow. This option allows early boot code to skip the decompressor
230 and jump right at uncompressed kernel image.
231
232endchoice
233
234config DEFAULT_HOSTNAME
235 string "Default hostname"
236 default "(none)"
237 help
238 This option determines the default system hostname before userspace
239 calls sethostname(2). The kernel traditionally uses "(none)" here,
240 but you may wish to use a different default here to make a minimal
241 system more usable with less configuration.
242
243
244
245
246
247config ARCH_NO_SWAP
248 bool
249
250config SWAP
251 bool "Support for paging of anonymous memory (swap)"
252 depends on MMU && BLOCK && !ARCH_NO_SWAP
253 default y
254 help
255 This option allows you to choose whether you want to have support
256 for so called swap devices or swap files in your kernel that are
257 used to provide more virtual memory than the actual RAM present
258 in your computer. If unsure say Y.
259
260config SYSVIPC
261 bool "System V IPC"
262 ---help---
263 Inter Process Communication is a suite of library functions and
264 system calls which let processes (running programs) synchronize and
265 exchange information. It is generally considered to be a good thing,
266 and some programs won't run unless you say Y here. In particular, if
267 you want to run the DOS emulator dosemu under Linux (read the
268 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html
269 you'll need to say Y here.
270
271 You can find documentation about IPC with "info ipc" and also in
272 section 6.4 of the Linux Programmer's Guide, available from
273 <http://www.tldp.org/guides.html>.
274
275config SYSVIPC_SYSCTL
276 bool
277 depends on SYSVIPC
278 depends on SYSCTL
279 default y
280
281config POSIX_MQUEUE
282 bool "POSIX Message Queues"
283 depends on NET
284 ---help---
285 POSIX variant of message queues is a part of IPC. In POSIX message
286 queues every message has a priority which decides about succession
287 of receiving it by a process. If you want to compile and run
288 programs written e.g. for Solaris with use of its POSIX message
289 queues (functions mq_*) say Y here.
290
291 POSIX message queues are visible as a filesystem called 'mqueue'
292 and can be mounted somewhere if you want to do filesystem
293 operations on message queues.
294
295 If unsure, say Y.
296
297config POSIX_MQUEUE_SYSCTL
298 bool
299 depends on POSIX_MQUEUE
300 depends on SYSCTL
301 default y
302
303config CROSS_MEMORY_ATTACH
304 bool "Enable process_vm_readv/writev syscalls"
305 depends on MMU
306 default y
307 help
308 Enabling this option adds the system calls process_vm_readv and
309 process_vm_writev which allow a process with the correct privileges
310 to directly read from or write to another process' address space.
311 See the man page for more details.
312
313config USELIB
314 bool "uselib syscall"
315 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
316 help
317 This option enables the uselib syscall, a system call used in the
318 dynamic linker from libc5 and earlier. glibc does not use this
319 system call. If you intend to run programs built on libc5 or
320 earlier, you may need to enable this syscall. Current systems
321 running glibc can safely disable this.
322
323config AUDIT
324 bool "Auditing support"
325 depends on NET
326 help
327 Enable auditing infrastructure that can be used with another
328 kernel subsystem, such as SELinux (which requires this for
329 logging of avc messages output). System call auditing is included
330 on architectures which support it.
331
332config HAVE_ARCH_AUDITSYSCALL
333 bool
334
335config AUDITSYSCALL
336 def_bool y
337 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
338
339config AUDIT_WATCH
340 def_bool y
341 depends on AUDITSYSCALL
342 select FSNOTIFY
343
344config AUDIT_TREE
345 def_bool y
346 depends on AUDITSYSCALL
347 select FSNOTIFY
348
349source "kernel/irq/Kconfig"
350source "kernel/time/Kconfig"
351source "kernel/Kconfig.preempt"
352
353menu "CPU/Task time and stats accounting"
354
355config VIRT_CPU_ACCOUNTING
356 bool
357
358choice
359 prompt "Cputime accounting"
360 default TICK_CPU_ACCOUNTING if !PPC64
361 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
362
363
364config TICK_CPU_ACCOUNTING
365 bool "Simple tick based cputime accounting"
366 depends on !S390 && !NO_HZ_FULL
367 help
368 This is the basic tick based cputime accounting that maintains
369 statistics about user, system and idle time spent on per jiffies
370 granularity.
371
372 If unsure, say Y.
373
374config VIRT_CPU_ACCOUNTING_NATIVE
375 bool "Deterministic task and CPU time accounting"
376 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
377 select VIRT_CPU_ACCOUNTING
378 help
379 Select this option to enable more accurate task and CPU time
380 accounting. This is done by reading a CPU counter on each
381 kernel entry and exit and on transitions within the kernel
382 between system, softirq and hardirq state, so there is a
383 small performance impact. In the case of s390 or IBM POWER > 5,
384 this also enables accounting of stolen time on logically-partitioned
385 systems.
386
387config VIRT_CPU_ACCOUNTING_GEN
388 bool "Full dynticks CPU time accounting"
389 depends on HAVE_CONTEXT_TRACKING
390 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
391 select VIRT_CPU_ACCOUNTING
392 select CONTEXT_TRACKING
393 help
394 Select this option to enable task and CPU time accounting on full
395 dynticks systems. This accounting is implemented by watching every
396 kernel-user boundaries using the context tracking subsystem.
397 The accounting is thus performed at the expense of some significant
398 overhead.
399
400 For now this is only useful if you are working on the full
401 dynticks subsystem development.
402
403 If unsure, say N.
404
405endchoice
406
407config IRQ_TIME_ACCOUNTING
408 bool "Fine granularity task level IRQ time accounting"
409 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
410 help
411 Select this option to enable fine granularity task irq time
412 accounting. This is done by reading a timestamp on each
413 transitions between softirq and hardirq state, so there can be a
414 small performance impact.
415
416 If in doubt, say N here.
417
418config BSD_PROCESS_ACCT
419 bool "BSD Process Accounting"
420 depends on MULTIUSER
421 help
422 If you say Y here, a user level program will be able to instruct the
423 kernel (via a special system call) to write process accounting
424 information to a file: whenever a process exits, information about
425 that process will be appended to the file by the kernel. The
426 information includes things such as creation time, owning user,
427 command name, memory usage, controlling terminal etc. (the complete
428 list is in the struct acct in <file:include/linux/acct.h>). It is
429 up to the user level program to do useful things with this
430 information. This is generally a good idea, so say Y.
431
432config BSD_PROCESS_ACCT_V3
433 bool "BSD Process Accounting version 3 file format"
434 depends on BSD_PROCESS_ACCT
435 default n
436 help
437 If you say Y here, the process accounting information is written
438 in a new file format that also logs the process IDs of each
439 process and its parent. Note that this file format is incompatible
440 with previous v0/v1/v2 file formats, so you will need updated tools
441 for processing it. A preliminary version of these tools is available
442 at <http://www.gnu.org/software/acct/>.
443
444config TASKSTATS
445 bool "Export task/process statistics through netlink"
446 depends on NET
447 depends on MULTIUSER
448 default n
449 help
450 Export selected statistics for tasks/processes through the
451 generic netlink interface. Unlike BSD process accounting, the
452 statistics are available during the lifetime of tasks/processes as
453 responses to commands. Like BSD accounting, they are sent to user
454 space on task exit.
455
456 Say N if unsure.
457
458config TASK_DELAY_ACCT
459 bool "Enable per-task delay accounting"
460 depends on TASKSTATS
461 select SCHED_INFO
462 help
463 Collect information on time spent by a task waiting for system
464 resources like cpu, synchronous block I/O completion and swapping
465 in pages. Such statistics can help in setting a task's priorities
466 relative to other tasks for cpu, io, rss limits etc.
467
468 Say N if unsure.
469
470config TASK_XACCT
471 bool "Enable extended accounting over taskstats"
472 depends on TASKSTATS
473 help
474 Collect extended task accounting data and send the data
475 to userland for processing over the taskstats interface.
476
477 Say N if unsure.
478
479config TASK_IO_ACCOUNTING
480 bool "Enable per-task storage I/O accounting"
481 depends on TASK_XACCT
482 help
483 Collect information on the number of bytes of storage I/O which this
484 task has caused.
485
486 Say N if unsure.
487
488endmenu
489
490config CPU_ISOLATION
491 bool "CPU isolation"
492 depends on SMP || COMPILE_TEST
493 default y
494 help
495 Make sure that CPUs running critical tasks are not disturbed by
496 any source of "noise" such as unbound workqueues, timers, kthreads...
497 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
498 the "isolcpus=" boot parameter.
499
500 Say Y if unsure.
501
502source "kernel/rcu/Kconfig"
503
504config BUILD_BIN2C
505 bool
506 default n
507
508config IKCONFIG
509 tristate "Kernel .config support"
510 select BUILD_BIN2C
511 ---help---
512 This option enables the complete Linux kernel ".config" file
513 contents to be saved in the kernel. It provides documentation
514 of which kernel options are used in a running kernel or in an
515 on-disk kernel. This information can be extracted from the kernel
516 image file with the script scripts/extract-ikconfig and used as
517 input to rebuild the current kernel or to build another kernel.
518 It can also be extracted from a running kernel by reading
519 /proc/config.gz if enabled (below).
520
521config IKCONFIG_PROC
522 bool "Enable access to .config through /proc/config.gz"
523 depends on IKCONFIG && PROC_FS
524 ---help---
525 This option enables access to the kernel configuration file
526 through /proc/config.gz.
527
528config LOG_BUF_SHIFT
529 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
530 range 12 25
531 default 17
532 depends on PRINTK
533 help
534 Select the minimal kernel log buffer size as a power of 2.
535 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
536 parameter, see below. Any higher size also might be forced
537 by "log_buf_len" boot parameter.
538
539 Examples:
540 17 => 128 KB
541 16 => 64 KB
542 15 => 32 KB
543 14 => 16 KB
544 13 => 8 KB
545 12 => 4 KB
546
547config LOG_CPU_MAX_BUF_SHIFT
548 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
549 depends on SMP
550 range 0 21
551 default 12 if !BASE_SMALL
552 default 0 if BASE_SMALL
553 depends on PRINTK
554 help
555 This option allows to increase the default ring buffer size
556 according to the number of CPUs. The value defines the contribution
557 of each CPU as a power of 2. The used space is typically only few
558 lines however it might be much more when problems are reported,
559 e.g. backtraces.
560
561 The increased size means that a new buffer has to be allocated and
562 the original static one is unused. It makes sense only on systems
563 with more CPUs. Therefore this value is used only when the sum of
564 contributions is greater than the half of the default kernel ring
565 buffer as defined by LOG_BUF_SHIFT. The default values are set
566 so that more than 64 CPUs are needed to trigger the allocation.
567
568 Also this option is ignored when "log_buf_len" kernel parameter is
569 used as it forces an exact (power of two) size of the ring buffer.
570
571 The number of possible CPUs is used for this computation ignoring
572 hotplugging making the computation optimal for the worst case
573 scenario while allowing a simple algorithm to be used from bootup.
574
575 Examples shift values and their meaning:
576 17 => 128 KB for each CPU
577 16 => 64 KB for each CPU
578 15 => 32 KB for each CPU
579 14 => 16 KB for each CPU
580 13 => 8 KB for each CPU
581 12 => 4 KB for each CPU
582
583config PRINTK_SAFE_LOG_BUF_SHIFT
584 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
585 range 10 21
586 default 13
587 depends on PRINTK
588 help
589 Select the size of an alternate printk per-CPU buffer where messages
590 printed from usafe contexts are temporary stored. One example would
591 be NMI messages, another one - printk recursion. The messages are
592 copied to the main log buffer in a safe context to avoid a deadlock.
593 The value defines the size as a power of 2.
594
595 Those messages are rare and limited. The largest one is when
596 a backtrace is printed. It usually fits into 4KB. Select
597 8KB if you want to be on the safe side.
598
599 Examples:
600 17 => 128 KB for each CPU
601 16 => 64 KB for each CPU
602 15 => 32 KB for each CPU
603 14 => 16 KB for each CPU
604 13 => 8 KB for each CPU
605 12 => 4 KB for each CPU
606
607
608
609
610config HAVE_UNSTABLE_SCHED_CLOCK
611 bool
612
613config GENERIC_SCHED_CLOCK
614 bool
615
616
617
618
619
620config ARCH_SUPPORTS_NUMA_BALANCING
621 bool
622
623
624
625
626
627
628
629
630config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
631 bool
632
633
634
635
636config ARCH_SUPPORTS_INT128
637 bool
638
639
640
641
642config ARCH_WANT_NUMA_VARIABLE_LOCALITY
643 bool
644
645config NUMA_BALANCING
646 bool "Memory placement aware NUMA scheduler"
647 depends on ARCH_SUPPORTS_NUMA_BALANCING
648 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
649 depends on SMP && NUMA && MIGRATION
650 help
651 This option adds support for automatic NUMA aware memory/task placement.
652 The mechanism is quite primitive and is based on migrating memory when
653 it has references to the node the task is running on.
654
655 This system will be inactive on UMA systems.
656
657config NUMA_BALANCING_DEFAULT_ENABLED
658 bool "Automatically enable NUMA aware memory/task placement"
659 default y
660 depends on NUMA_BALANCING
661 help
662 If set, automatic NUMA balancing will be enabled if running on a NUMA
663 machine.
664
665menuconfig CGROUPS
666 bool "Control Group support"
667 select KERNFS
668 help
669 This option adds support for grouping sets of processes together, for
670 use with process control subsystems such as Cpusets, CFS, memory
671 controls or device isolation.
672 See
673 - Documentation/scheduler/sched-design-CFS.txt (CFS)
674 - Documentation/cgroup-v1/ (features for grouping, isolation
675 and resource control)
676
677 Say N if unsure.
678
679if CGROUPS
680
681config PAGE_COUNTER
682 bool
683
684config MEMCG
685 bool "Memory controller"
686 select PAGE_COUNTER
687 select EVENTFD
688 help
689 Provides control over the memory footprint of tasks in a cgroup.
690
691config MEMCG_SWAP
692 bool "Swap controller"
693 depends on MEMCG && SWAP
694 help
695 Provides control over the swap space consumed by tasks in a cgroup.
696
697config MEMCG_SWAP_ENABLED
698 bool "Swap controller enabled by default"
699 depends on MEMCG_SWAP
700 default y
701 help
702 Memory Resource Controller Swap Extension comes with its price in
703 a bigger memory consumption. General purpose distribution kernels
704 which want to enable the feature but keep it disabled by default
705 and let the user enable it by swapaccount=1 boot command line
706 parameter should have this option unselected.
707 For those who want to have the feature enabled by default should
708 select this option (if, for some reason, they need to disable it
709 then swapaccount=0 does the trick).
710
711config MEMCG_KMEM
712 bool
713 depends on MEMCG && !SLOB
714 default y
715
716config BLK_CGROUP
717 bool "IO controller"
718 depends on BLOCK
719 default n
720 ---help---
721 Generic block IO controller cgroup interface. This is the common
722 cgroup interface which should be used by various IO controlling
723 policies.
724
725 Currently, CFQ IO scheduler uses it to recognize task groups and
726 control disk bandwidth allocation (proportional time slice allocation)
727 to such task groups. It is also used by bio throttling logic in
728 block layer to implement upper limit in IO rates on a device.
729
730 This option only enables generic Block IO controller infrastructure.
731 One needs to also enable actual IO controlling logic/policy. For
732 enabling proportional weight division of disk bandwidth in CFQ, set
733 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
734 CONFIG_BLK_DEV_THROTTLING=y.
735
736 See Documentation/cgroup-v1/blkio-controller.txt for more information.
737
738config DEBUG_BLK_CGROUP
739 bool "IO controller debugging"
740 depends on BLK_CGROUP
741 default n
742 ---help---
743 Enable some debugging help. Currently it exports additional stat
744 files in a cgroup which can be useful for debugging.
745
746config CGROUP_WRITEBACK
747 bool
748 depends on MEMCG && BLK_CGROUP
749 default y
750
751menuconfig CGROUP_SCHED
752 bool "CPU controller"
753 default n
754 help
755 This feature lets CPU scheduler recognize task groups and control CPU
756 bandwidth allocation to such task groups. It uses cgroups to group
757 tasks.
758
759if CGROUP_SCHED
760config FAIR_GROUP_SCHED
761 bool "Group scheduling for SCHED_OTHER"
762 depends on CGROUP_SCHED
763 default CGROUP_SCHED
764
765config CFS_BANDWIDTH
766 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
767 depends on FAIR_GROUP_SCHED
768 default n
769 help
770 This option allows users to define CPU bandwidth rates (limits) for
771 tasks running within the fair group scheduler. Groups with no limit
772 set are considered to be unconstrained and will run with no
773 restriction.
774 See Documentation/scheduler/sched-bwc.txt for more information.
775
776config RT_GROUP_SCHED
777 bool "Group scheduling for SCHED_RR/FIFO"
778 depends on CGROUP_SCHED
779 default n
780 help
781 This feature lets you explicitly allocate real CPU bandwidth
782 to task groups. If enabled, it will also make it impossible to
783 schedule realtime tasks for non-root users until you allocate
784 realtime bandwidth for them.
785 See Documentation/scheduler/sched-rt-group.txt for more information.
786
787endif
788
789config CGROUP_PIDS
790 bool "PIDs controller"
791 help
792 Provides enforcement of process number limits in the scope of a
793 cgroup. Any attempt to fork more processes than is allowed in the
794 cgroup will fail. PIDs are fundamentally a global resource because it
795 is fairly trivial to reach PID exhaustion before you reach even a
796 conservative kmemcg limit. As a result, it is possible to grind a
797 system to halt without being limited by other cgroup policies. The
798 PIDs controller is designed to stop this from happening.
799
800 It should be noted that organisational operations (such as attaching
801 to a cgroup hierarchy will *not* be blocked by the PIDs controller),
802 since the PIDs limit only affects a process's ability to fork, not to
803 attach to a cgroup.
804
805config CGROUP_RDMA
806 bool "RDMA controller"
807 help
808 Provides enforcement of RDMA resources defined by IB stack.
809 It is fairly easy for consumers to exhaust RDMA resources, which
810 can result into resource unavailability to other consumers.
811 RDMA controller is designed to stop this from happening.
812 Attaching processes with active RDMA resources to the cgroup
813 hierarchy is allowed even if can cross the hierarchy's limit.
814
815config CGROUP_FREEZER
816 bool "Freezer controller"
817 help
818 Provides a way to freeze and unfreeze all tasks in a
819 cgroup.
820
821 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
822 controller includes important in-kernel memory consumers per default.
823
824 If you're using cgroup2, say N.
825
826config CGROUP_HUGETLB
827 bool "HugeTLB controller"
828 depends on HUGETLB_PAGE
829 select PAGE_COUNTER
830 default n
831 help
832 Provides a cgroup controller for HugeTLB pages.
833 When you enable this, you can put a per cgroup limit on HugeTLB usage.
834 The limit is enforced during page fault. Since HugeTLB doesn't
835 support page reclaim, enforcing the limit at page fault time implies
836 that, the application will get SIGBUS signal if it tries to access
837 HugeTLB pages beyond its limit. This requires the application to know
838 beforehand how much HugeTLB pages it would require for its use. The
839 control group is tracked in the third page lru pointer. This means
840 that we cannot use the controller with huge page less than 3 pages.
841
842config CPUSETS
843 bool "Cpuset controller"
844 depends on SMP
845 help
846 This option will let you create and manage CPUSETs which
847 allow dynamically partitioning a system into sets of CPUs and
848 Memory Nodes and assigning tasks to run only within those sets.
849 This is primarily useful on large SMP or NUMA systems.
850
851 Say N if unsure.
852
853config PROC_PID_CPUSET
854 bool "Include legacy /proc/<pid>/cpuset file"
855 depends on CPUSETS
856 default y
857
858config CGROUP_DEVICE
859 bool "Device controller"
860 help
861 Provides a cgroup controller implementing whitelists for
862 devices which a process in the cgroup can mknod or open.
863
864config CGROUP_CPUACCT
865 bool "Simple CPU accounting controller"
866 help
867 Provides a simple controller for monitoring the
868 total CPU consumed by the tasks in a cgroup.
869
870config CGROUP_PERF
871 bool "Perf controller"
872 depends on PERF_EVENTS
873 help
874 This option extends the perf per-cpu mode to restrict monitoring
875 to threads which belong to the cgroup specified and run on the
876 designated cpu.
877
878 Say N if unsure.
879
880config CGROUP_BPF
881 bool "Support for eBPF programs attached to cgroups"
882 depends on BPF_SYSCALL
883 select SOCK_CGROUP_DATA
884 help
885 Allow attaching eBPF programs to a cgroup using the bpf(2)
886 syscall command BPF_PROG_ATTACH.
887
888 In which context these programs are accessed depends on the type
889 of attachment. For instance, programs that are attached using
890 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
891 inet sockets.
892
893config CGROUP_DEBUG
894 bool "Debug controller"
895 default n
896 depends on DEBUG_KERNEL
897 help
898 This option enables a simple controller that exports
899 debugging information about the cgroups framework. This
900 controller is for control cgroup debugging only. Its
901 interfaces are not stable.
902
903 Say N.
904
905config SOCK_CGROUP_DATA
906 bool
907 default n
908
909endif
910
911menuconfig NAMESPACES
912 bool "Namespaces support" if EXPERT
913 depends on MULTIUSER
914 default !EXPERT
915 help
916 Provides the way to make tasks work with different objects using
917 the same id. For example same IPC id may refer to different objects
918 or same user id or pid may refer to different tasks when used in
919 different namespaces.
920
921if NAMESPACES
922
923config UTS_NS
924 bool "UTS namespace"
925 default y
926 help
927 In this namespace tasks see different info provided with the
928 uname() system call
929
930config IPC_NS
931 bool "IPC namespace"
932 depends on (SYSVIPC || POSIX_MQUEUE)
933 default y
934 help
935 In this namespace tasks work with IPC ids which correspond to
936 different IPC objects in different namespaces.
937
938config USER_NS
939 bool "User namespace"
940 default n
941 help
942 This allows containers, i.e. vservers, to use user namespaces
943 to provide different user info for different servers.
944
945 When user namespaces are enabled in the kernel it is
946 recommended that the MEMCG option also be enabled and that
947 user-space use the memory control groups to limit the amount
948 of memory a memory unprivileged users can use.
949
950 If unsure, say N.
951
952config PID_NS
953 bool "PID Namespaces"
954 default y
955 help
956 Support process id namespaces. This allows having multiple
957 processes with the same pid as long as they are in different
958 pid namespaces. This is a building block of containers.
959
960config NET_NS
961 bool "Network namespace"
962 depends on NET
963 default y
964 help
965 Allow user space to create what appear to be multiple instances
966 of the network stack.
967
968endif
969
970config CHECKPOINT_RESTORE
971 bool "Checkpoint/restore support"
972 select PROC_CHILDREN
973 default n
974 help
975 Enables additional kernel features in a sake of checkpoint/restore.
976 In particular it adds auxiliary prctl codes to setup process text,
977 data and heap segment sizes, and a few additional /proc filesystem
978 entries.
979
980 If unsure, say N here.
981
982config SCHED_AUTOGROUP
983 bool "Automatic process group scheduling"
984 select CGROUPS
985 select CGROUP_SCHED
986 select FAIR_GROUP_SCHED
987 help
988 This option optimizes the scheduler for common desktop workloads by
989 automatically creating and populating task groups. This separation
990 of workloads isolates aggressive CPU burners (like build jobs) from
991 desktop applications. Task group autogeneration is currently based
992 upon task session.
993
994config SYSFS_DEPRECATED
995 bool "Enable deprecated sysfs features to support old userspace tools"
996 depends on SYSFS
997 default n
998 help
999 This option adds code that switches the layout of the "block" class
1000 devices, to not show up in /sys/class/block/, but only in
1001 /sys/block/.
1002
1003 This switch is only active when the sysfs.deprecated=1 boot option is
1004 passed or the SYSFS_DEPRECATED_V2 option is set.
1005
1006 This option allows new kernels to run on old distributions and tools,
1007 which might get confused by /sys/class/block/. Since 2007/2008 all
1008 major distributions and tools handle this just fine.
1009
1010 Recent distributions and userspace tools after 2009/2010 depend on
1011 the existence of /sys/class/block/, and will not work with this
1012 option enabled.
1013
1014 Only if you are using a new kernel on an old distribution, you might
1015 need to say Y here.
1016
1017config SYSFS_DEPRECATED_V2
1018 bool "Enable deprecated sysfs features by default"
1019 default n
1020 depends on SYSFS
1021 depends on SYSFS_DEPRECATED
1022 help
1023 Enable deprecated sysfs by default.
1024
1025 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1026 option.
1027
1028 Only if you are using a new kernel on an old distribution, you might
1029 need to say Y here. Even then, odds are you would not need it
1030 enabled, you can always pass the boot option if absolutely necessary.
1031
1032config RELAY
1033 bool "Kernel->user space relay support (formerly relayfs)"
1034 select IRQ_WORK
1035 help
1036 This option enables support for relay interface support in
1037 certain file systems (such as debugfs).
1038 It is designed to provide an efficient mechanism for tools and
1039 facilities to relay large amounts of data from kernel space to
1040 user space.
1041
1042 If unsure, say N.
1043
1044config BLK_DEV_INITRD
1045 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1046 help
1047 The initial RAM filesystem is a ramfs which is loaded by the
1048 boot loader (loadlin or lilo) and that is mounted as root
1049 before the normal boot procedure. It is typically used to
1050 load modules needed to mount the "real" root file system,
1051 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1052
1053 If RAM disk support (BLK_DEV_RAM) is also included, this
1054 also enables initial RAM disk (initrd) support and adds
1055 15 Kbytes (more on some other architectures) to the kernel size.
1056
1057 If unsure say Y.
1058
1059if BLK_DEV_INITRD
1060
1061source "usr/Kconfig"
1062
1063endif
1064
1065choice
1066 prompt "Compiler optimization level"
1067 default CC_OPTIMIZE_FOR_PERFORMANCE
1068
1069config CC_OPTIMIZE_FOR_PERFORMANCE
1070 bool "Optimize for performance"
1071 help
1072 This is the default optimization level for the kernel, building
1073 with the "-O2" compiler flag for best performance and most
1074 helpful compile-time warnings.
1075
1076config CC_OPTIMIZE_FOR_SIZE
1077 bool "Optimize for size"
1078 help
1079 Enabling this option will pass "-Os" instead of "-O2" to
1080 your compiler resulting in a smaller kernel.
1081
1082 If unsure, say N.
1083
1084endchoice
1085
1086config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1087 bool
1088 help
1089 This requires that the arch annotates or otherwise protects
1090 its external entry points from being discarded. Linker scripts
1091 must also merge .text.*, .data.*, and .bss.* correctly into
1092 output sections. Care must be taken not to pull in unrelated
1093 sections (e.g., '.text.init'). Typically '.' in section names
1094 is used to distinguish them from label names / C identifiers.
1095
1096config LD_DEAD_CODE_DATA_ELIMINATION
1097 bool "Dead code and data elimination (EXPERIMENTAL)"
1098 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1099 depends on EXPERT
1100 depends on $(cc-option,-ffunction-sections -fdata-sections)
1101 depends on $(ld-option,--gc-sections)
1102 help
1103 Enable this if you want to do dead code and data elimination with
1104 the linker by compiling with -ffunction-sections -fdata-sections,
1105 and linking with --gc-sections.
1106
1107 This can reduce on disk and in-memory size of the kernel
1108 code and static data, particularly for small configs and
1109 on small systems. This has the possibility of introducing
1110 silently broken kernel if the required annotations are not
1111 present. This option is not well tested yet, so use at your
1112 own risk.
1113
1114config SYSCTL
1115 bool
1116
1117config ANON_INODES
1118 bool
1119
1120config HAVE_UID16
1121 bool
1122
1123config SYSCTL_EXCEPTION_TRACE
1124 bool
1125 help
1126 Enable support for /proc/sys/debug/exception-trace.
1127
1128config SYSCTL_ARCH_UNALIGN_NO_WARN
1129 bool
1130 help
1131 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1132 Allows arch to define/use @no_unaligned_warning to possibly warn
1133 about unaligned access emulation going on under the hood.
1134
1135config SYSCTL_ARCH_UNALIGN_ALLOW
1136 bool
1137 help
1138 Enable support for /proc/sys/kernel/unaligned-trap
1139 Allows arches to define/use @unaligned_enabled to runtime toggle
1140 the unaligned access emulation.
1141 see arch/parisc/kernel/unaligned.c for reference
1142
1143config HAVE_PCSPKR_PLATFORM
1144 bool
1145
1146
1147config BPF
1148 bool
1149
1150menuconfig EXPERT
1151 bool "Configure standard kernel features (expert users)"
1152
1153 select DEBUG_KERNEL
1154 help
1155 This option allows certain base kernel options and settings
1156 to be disabled or tweaked. This is for specialized
1157 environments which can tolerate a "non-standard" kernel.
1158 Only use this if you really know what you are doing.
1159
1160config UID16
1161 bool "Enable 16-bit UID system calls" if EXPERT
1162 depends on HAVE_UID16 && MULTIUSER
1163 default y
1164 help
1165 This enables the legacy 16-bit UID syscall wrappers.
1166
1167config MULTIUSER
1168 bool "Multiple users, groups and capabilities support" if EXPERT
1169 default y
1170 help
1171 This option enables support for non-root users, groups and
1172 capabilities.
1173
1174 If you say N here, all processes will run with UID 0, GID 0, and all
1175 possible capabilities. Saying N here also compiles out support for
1176 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1177 setgid, and capset.
1178
1179 If unsure, say Y here.
1180
1181config SGETMASK_SYSCALL
1182 bool "sgetmask/ssetmask syscalls support" if EXPERT
1183 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1184 ---help---
1185 sys_sgetmask and sys_ssetmask are obsolete system calls
1186 no longer supported in libc but still enabled by default in some
1187 architectures.
1188
1189 If unsure, leave the default option here.
1190
1191config SYSFS_SYSCALL
1192 bool "Sysfs syscall support" if EXPERT
1193 default y
1194 ---help---
1195 sys_sysfs is an obsolete system call no longer supported in libc.
1196 Note that disabling this option is more secure but might break
1197 compatibility with some systems.
1198
1199 If unsure say Y here.
1200
1201config SYSCTL_SYSCALL
1202 bool "Sysctl syscall support" if EXPERT
1203 depends on PROC_SYSCTL
1204 default n
1205 select SYSCTL
1206 ---help---
1207 sys_sysctl uses binary paths that have been found challenging
1208 to properly maintain and use. The interface in /proc/sys
1209 using paths with ascii names is now the primary path to this
1210 information.
1211
1212 Almost nothing using the binary sysctl interface so if you are
1213 trying to save some space it is probably safe to disable this,
1214 making your kernel marginally smaller.
1215
1216 If unsure say N here.
1217
1218config FHANDLE
1219 bool "open by fhandle syscalls" if EXPERT
1220 select EXPORTFS
1221 default y
1222 help
1223 If you say Y here, a user level program will be able to map
1224 file names to handle and then later use the handle for
1225 different file system operations. This is useful in implementing
1226 userspace file servers, which now track files using handles instead
1227 of names. The handle would remain the same even if file names
1228 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1229 syscalls.
1230
1231config POSIX_TIMERS
1232 bool "Posix Clocks & timers" if EXPERT
1233 default y
1234 help
1235 This includes native support for POSIX timers to the kernel.
1236 Some embedded systems have no use for them and therefore they
1237 can be configured out to reduce the size of the kernel image.
1238
1239 When this option is disabled, the following syscalls won't be
1240 available: timer_create, timer_gettime: timer_getoverrun,
1241 timer_settime, timer_delete, clock_adjtime, getitimer,
1242 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1243 clock_getres and clock_nanosleep syscalls will be limited to
1244 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1245
1246 If unsure say y.
1247
1248config PRINTK
1249 default y
1250 bool "Enable support for printk" if EXPERT
1251 select IRQ_WORK
1252 help
1253 This option enables normal printk support. Removing it
1254 eliminates most of the message strings from the kernel image
1255 and makes the kernel more or less silent. As this makes it
1256 very difficult to diagnose system problems, saying N here is
1257 strongly discouraged.
1258
1259config PRINTK_NMI
1260 def_bool y
1261 depends on PRINTK
1262 depends on HAVE_NMI
1263
1264config BUG
1265 bool "BUG() support" if EXPERT
1266 default y
1267 help
1268 Disabling this option eliminates support for BUG and WARN, reducing
1269 the size of your kernel image and potentially quietly ignoring
1270 numerous fatal conditions. You should only consider disabling this
1271 option for embedded systems with no facilities for reporting errors.
1272 Just say Y.
1273
1274config ELF_CORE
1275 depends on COREDUMP
1276 default y
1277 bool "Enable ELF core dumps" if EXPERT
1278 help
1279 Enable support for generating core dumps. Disabling saves about 4k.
1280
1281
1282config PCSPKR_PLATFORM
1283 bool "Enable PC-Speaker support" if EXPERT
1284 depends on HAVE_PCSPKR_PLATFORM
1285 select I8253_LOCK
1286 default y
1287 help
1288 This option allows to disable the internal PC-Speaker
1289 support, saving some memory.
1290
1291config BASE_FULL
1292 default y
1293 bool "Enable full-sized data structures for core" if EXPERT
1294 help
1295 Disabling this option reduces the size of miscellaneous core
1296 kernel data structures. This saves memory on small machines,
1297 but may reduce performance.
1298
1299config FUTEX
1300 bool "Enable futex support" if EXPERT
1301 default y
1302 imply RT_MUTEXES
1303 help
1304 Disabling this option will cause the kernel to be built without
1305 support for "fast userspace mutexes". The resulting kernel may not
1306 run glibc-based applications correctly.
1307
1308config FUTEX_PI
1309 bool
1310 depends on FUTEX && RT_MUTEXES
1311 default y
1312
1313config HAVE_FUTEX_CMPXCHG
1314 bool
1315 depends on FUTEX
1316 help
1317 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1318 is implemented and always working. This removes a couple of runtime
1319 checks.
1320
1321config EPOLL
1322 bool "Enable eventpoll support" if EXPERT
1323 default y
1324 select ANON_INODES
1325 help
1326 Disabling this option will cause the kernel to be built without
1327 support for epoll family of system calls.
1328
1329config SIGNALFD
1330 bool "Enable signalfd() system call" if EXPERT
1331 select ANON_INODES
1332 default y
1333 help
1334 Enable the signalfd() system call that allows to receive signals
1335 on a file descriptor.
1336
1337 If unsure, say Y.
1338
1339config TIMERFD
1340 bool "Enable timerfd() system call" if EXPERT
1341 select ANON_INODES
1342 default y
1343 help
1344 Enable the timerfd() system call that allows to receive timer
1345 events on a file descriptor.
1346
1347 If unsure, say Y.
1348
1349config EVENTFD
1350 bool "Enable eventfd() system call" if EXPERT
1351 select ANON_INODES
1352 default y
1353 help
1354 Enable the eventfd() system call that allows to receive both
1355 kernel notification (ie. KAIO) or userspace notifications.
1356
1357 If unsure, say Y.
1358
1359config SHMEM
1360 bool "Use full shmem filesystem" if EXPERT
1361 default y
1362 depends on MMU
1363 help
1364 The shmem is an internal filesystem used to manage shared memory.
1365 It is backed by swap and manages resource limits. It is also exported
1366 to userspace as tmpfs if TMPFS is enabled. Disabling this
1367 option replaces shmem and tmpfs with the much simpler ramfs code,
1368 which may be appropriate on small systems without swap.
1369
1370config AIO
1371 bool "Enable AIO support" if EXPERT
1372 default y
1373 help
1374 This option enables POSIX asynchronous I/O which may by used
1375 by some high performance threaded applications. Disabling
1376 this option saves about 7k.
1377
1378config ADVISE_SYSCALLS
1379 bool "Enable madvise/fadvise syscalls" if EXPERT
1380 default y
1381 help
1382 This option enables the madvise and fadvise syscalls, used by
1383 applications to advise the kernel about their future memory or file
1384 usage, improving performance. If building an embedded system where no
1385 applications use these syscalls, you can disable this option to save
1386 space.
1387
1388config MEMBARRIER
1389 bool "Enable membarrier() system call" if EXPERT
1390 default y
1391 help
1392 Enable the membarrier() system call that allows issuing memory
1393 barriers across all running threads, which can be used to distribute
1394 the cost of user-space memory barriers asymmetrically by transforming
1395 pairs of memory barriers into pairs consisting of membarrier() and a
1396 compiler barrier.
1397
1398 If unsure, say Y.
1399
1400config KALLSYMS
1401 bool "Load all symbols for debugging/ksymoops" if EXPERT
1402 default y
1403 help
1404 Say Y here to let the kernel print out symbolic crash information and
1405 symbolic stack backtraces. This increases the size of the kernel
1406 somewhat, as all symbols have to be loaded into the kernel image.
1407
1408config KALLSYMS_ALL
1409 bool "Include all symbols in kallsyms"
1410 depends on DEBUG_KERNEL && KALLSYMS
1411 help
1412 Normally kallsyms only contains the symbols of functions for nicer
1413 OOPS messages and backtraces (i.e., symbols from the text and inittext
1414 sections). This is sufficient for most cases. And only in very rare
1415 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1416 names of variables from the data sections, etc).
1417
1418 This option makes sure that all symbols are loaded into the kernel
1419 image (i.e., symbols from all sections) in cost of increased kernel
1420 size (depending on the kernel configuration, it may be 300KiB or
1421 something like this).
1422
1423 Say N unless you really need all symbols.
1424
1425config KALLSYMS_ABSOLUTE_PERCPU
1426 bool
1427 depends on KALLSYMS
1428 default X86_64 && SMP
1429
1430config KALLSYMS_BASE_RELATIVE
1431 bool
1432 depends on KALLSYMS
1433 default !IA64
1434 help
1435 Instead of emitting them as absolute values in the native word size,
1436 emit the symbol references in the kallsyms table as 32-bit entries,
1437 each containing a relative value in the range [base, base + U32_MAX]
1438 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1439 an absolute value in the range [0, S32_MAX] or a relative value in the
1440 range [base, base + S32_MAX], where base is the lowest relative symbol
1441 address encountered in the image.
1442
1443 On 64-bit builds, this reduces the size of the address table by 50%,
1444 but more importantly, it results in entries whose values are build
1445 time constants, and no relocation pass is required at runtime to fix
1446 up the entries based on the runtime load address of the kernel.
1447
1448
1449
1450
1451config BPF_SYSCALL
1452 bool "Enable bpf() system call"
1453 select ANON_INODES
1454 select BPF
1455 select IRQ_WORK
1456 default n
1457 help
1458 Enable the bpf() system call that allows to manipulate eBPF
1459 programs and maps via file descriptors.
1460
1461config BPF_JIT_ALWAYS_ON
1462 bool "Permanently enable BPF JIT and remove BPF interpreter"
1463 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1464 help
1465 Enables BPF JIT and removes BPF interpreter to avoid
1466 speculative execution of BPF instructions by the interpreter
1467
1468config USERFAULTFD
1469 bool "Enable userfaultfd() system call"
1470 select ANON_INODES
1471 depends on MMU
1472 help
1473 Enable the userfaultfd() system call that allows to intercept and
1474 handle page faults in userland.
1475
1476config ARCH_HAS_MEMBARRIER_CALLBACKS
1477 bool
1478
1479config ARCH_HAS_MEMBARRIER_SYNC_CORE
1480 bool
1481
1482config RSEQ
1483 bool "Enable rseq() system call" if EXPERT
1484 default y
1485 depends on HAVE_RSEQ
1486 select MEMBARRIER
1487 help
1488 Enable the restartable sequences system call. It provides a
1489 user-space cache for the current CPU number value, which
1490 speeds up getting the current CPU number from user-space,
1491 as well as an ABI to speed up user-space operations on
1492 per-CPU data.
1493
1494 If unsure, say Y.
1495
1496config DEBUG_RSEQ
1497 default n
1498 bool "Enabled debugging of rseq() system call" if EXPERT
1499 depends on RSEQ && DEBUG_KERNEL
1500 help
1501 Enable extra debugging checks for the rseq system call.
1502
1503 If unsure, say N.
1504
1505config EMBEDDED
1506 bool "Embedded system"
1507 option allnoconfig_y
1508 select EXPERT
1509 help
1510 This option should be enabled if compiling the kernel for
1511 an embedded system so certain expert options are available
1512 for configuration.
1513
1514config HAVE_PERF_EVENTS
1515 bool
1516 help
1517 See tools/perf/design.txt for details.
1518
1519config PERF_USE_VMALLOC
1520 bool
1521 help
1522 See tools/perf/design.txt for details
1523
1524config PC104
1525 bool "PC/104 support" if EXPERT
1526 help
1527 Expose PC/104 form factor device drivers and options available for
1528 selection and configuration. Enable this option if your target
1529 machine has a PC/104 bus.
1530
1531menu "Kernel Performance Events And Counters"
1532
1533config PERF_EVENTS
1534 bool "Kernel performance events and counters"
1535 default y if PROFILING
1536 depends on HAVE_PERF_EVENTS
1537 select ANON_INODES
1538 select IRQ_WORK
1539 select SRCU
1540 help
1541 Enable kernel support for various performance events provided
1542 by software and hardware.
1543
1544 Software events are supported either built-in or via the
1545 use of generic tracepoints.
1546
1547 Most modern CPUs support performance events via performance
1548 counter registers. These registers count the number of certain
1549 types of hw events: such as instructions executed, cachemisses
1550 suffered, or branches mis-predicted - without slowing down the
1551 kernel or applications. These registers can also trigger interrupts
1552 when a threshold number of events have passed - and can thus be
1553 used to profile the code that runs on that CPU.
1554
1555 The Linux Performance Event subsystem provides an abstraction of
1556 these software and hardware event capabilities, available via a
1557 system call and used by the "perf" utility in tools/perf/. It
1558 provides per task and per CPU counters, and it provides event
1559 capabilities on top of those.
1560
1561 Say Y if unsure.
1562
1563config DEBUG_PERF_USE_VMALLOC
1564 default n
1565 bool "Debug: use vmalloc to back perf mmap() buffers"
1566 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1567 select PERF_USE_VMALLOC
1568 help
1569 Use vmalloc memory to back perf mmap() buffers.
1570
1571 Mostly useful for debugging the vmalloc code on platforms
1572 that don't require it.
1573
1574 Say N if unsure.
1575
1576endmenu
1577
1578config VM_EVENT_COUNTERS
1579 default y
1580 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1581 help
1582 VM event counters are needed for event counts to be shown.
1583 This option allows the disabling of the VM event counters
1584 on EXPERT systems. /proc/vmstat will only show page counts
1585 if VM event counters are disabled.
1586
1587config SLUB_DEBUG
1588 default y
1589 bool "Enable SLUB debugging support" if EXPERT
1590 depends on SLUB && SYSFS
1591 help
1592 SLUB has extensive debug support features. Disabling these can
1593 result in significant savings in code size. This also disables
1594 SLUB sysfs support. /sys/slab will not exist and there will be
1595 no support for cache validation etc.
1596
1597config SLUB_MEMCG_SYSFS_ON
1598 default n
1599 bool "Enable memcg SLUB sysfs support by default" if EXPERT
1600 depends on SLUB && SYSFS && MEMCG
1601 help
1602 SLUB creates a directory under /sys/kernel/slab for each
1603 allocation cache to host info and debug files. If memory
1604 cgroup is enabled, each cache can have per memory cgroup
1605 caches. SLUB can create the same sysfs directories for these
1606 caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1607 to a very high number of debug files being created. This is
1608 controlled by slub_memcg_sysfs boot parameter and this
1609 config option determines the parameter's default value.
1610
1611config COMPAT_BRK
1612 bool "Disable heap randomization"
1613 default y
1614 help
1615 Randomizing heap placement makes heap exploits harder, but it
1616 also breaks ancient binaries (including anything libc5 based).
1617 This option changes the bootup default to heap randomization
1618 disabled, and can be overridden at runtime by setting
1619 /proc/sys/kernel/randomize_va_space to 2.
1620
1621 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1622
1623choice
1624 prompt "Choose SLAB allocator"
1625 default SLUB
1626 help
1627 This option allows to select a slab allocator.
1628
1629config SLAB
1630 bool "SLAB"
1631 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1632 help
1633 The regular slab allocator that is established and known to work
1634 well in all environments. It organizes cache hot objects in
1635 per cpu and per node queues.
1636
1637config SLUB
1638 bool "SLUB (Unqueued Allocator)"
1639 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1640 help
1641 SLUB is a slab allocator that minimizes cache line usage
1642 instead of managing queues of cached objects (SLAB approach).
1643 Per cpu caching is realized using slabs of objects instead
1644 of queues of objects. SLUB can use memory efficiently
1645 and has enhanced diagnostics. SLUB is the default choice for
1646 a slab allocator.
1647
1648config SLOB
1649 depends on EXPERT
1650 bool "SLOB (Simple Allocator)"
1651 help
1652 SLOB replaces the stock allocator with a drastically simpler
1653 allocator. SLOB is generally more space efficient but
1654 does not perform as well on large systems.
1655
1656endchoice
1657
1658config SLAB_MERGE_DEFAULT
1659 bool "Allow slab caches to be merged"
1660 default y
1661 help
1662 For reduced kernel memory fragmentation, slab caches can be
1663 merged when they share the same size and other characteristics.
1664 This carries a risk of kernel heap overflows being able to
1665 overwrite objects from merged caches (and more easily control
1666 cache layout), which makes such heap attacks easier to exploit
1667 by attackers. By keeping caches unmerged, these kinds of exploits
1668 can usually only damage objects in the same cache. To disable
1669 merging at runtime, "slab_nomerge" can be passed on the kernel
1670 command line.
1671
1672config SLAB_FREELIST_RANDOM
1673 default n
1674 depends on SLAB || SLUB
1675 bool "SLAB freelist randomization"
1676 help
1677 Randomizes the freelist order used on creating new pages. This
1678 security feature reduces the predictability of the kernel slab
1679 allocator against heap overflows.
1680
1681config SLAB_FREELIST_HARDENED
1682 bool "Harden slab freelist metadata"
1683 depends on SLUB
1684 help
1685 Many kernel heap attacks try to target slab cache metadata and
1686 other infrastructure. This options makes minor performance
1687 sacrifies to harden the kernel slab allocator against common
1688 freelist exploit methods.
1689
1690config SLUB_CPU_PARTIAL
1691 default y
1692 depends on SLUB && SMP
1693 bool "SLUB per cpu partial cache"
1694 help
1695 Per cpu partial caches accellerate objects allocation and freeing
1696 that is local to a processor at the price of more indeterminism
1697 in the latency of the free. On overflow these caches will be cleared
1698 which requires the taking of locks that may cause latency spikes.
1699 Typically one would choose no for a realtime system.
1700
1701config MMAP_ALLOW_UNINITIALIZED
1702 bool "Allow mmapped anonymous memory to be uninitialized"
1703 depends on EXPERT && !MMU
1704 default n
1705 help
1706 Normally, and according to the Linux spec, anonymous memory obtained
1707 from mmap() has its contents cleared before it is passed to
1708 userspace. Enabling this config option allows you to request that
1709 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1710 providing a huge performance boost. If this option is not enabled,
1711 then the flag will be ignored.
1712
1713 This is taken advantage of by uClibc's malloc(), and also by
1714 ELF-FDPIC binfmt's brk and stack allocator.
1715
1716 Because of the obvious security issues, this option should only be
1717 enabled on embedded devices where you control what is run in
1718 userspace. Since that isn't generally a problem on no-MMU systems,
1719 it is normally safe to say Y here.
1720
1721 See Documentation/nommu-mmap.txt for more information.
1722
1723config SYSTEM_DATA_VERIFICATION
1724 def_bool n
1725 select SYSTEM_TRUSTED_KEYRING
1726 select KEYS
1727 select CRYPTO
1728 select CRYPTO_RSA
1729 select ASYMMETRIC_KEY_TYPE
1730 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1731 select ASN1
1732 select OID_REGISTRY
1733 select X509_CERTIFICATE_PARSER
1734 select PKCS7_MESSAGE_PARSER
1735 help
1736 Provide PKCS#7 message verification using the contents of the system
1737 trusted keyring to provide public keys. This then can be used for
1738 module verification, kexec image verification and firmware blob
1739 verification.
1740
1741config PROFILING
1742 bool "Profiling support"
1743 help
1744 Say Y here to enable the extended profiling support mechanisms used
1745 by profilers such as OProfile.
1746
1747
1748
1749
1750
1751config TRACEPOINTS
1752 bool
1753
1754endmenu
1755
1756source "arch/Kconfig"
1757
1758config RT_MUTEXES
1759 bool
1760
1761config BASE_SMALL
1762 int
1763 default 0 if BASE_FULL
1764 default 1 if !BASE_FULL
1765
1766menuconfig MODULES
1767 bool "Enable loadable module support"
1768 option modules
1769 help
1770 Kernel modules are small pieces of compiled code which can
1771 be inserted in the running kernel, rather than being
1772 permanently built into the kernel. You use the "modprobe"
1773 tool to add (and sometimes remove) them. If you say Y here,
1774 many parts of the kernel can be built as modules (by
1775 answering M instead of Y where indicated): this is most
1776 useful for infrequently used options which are not required
1777 for booting. For more information, see the man pages for
1778 modprobe, lsmod, modinfo, insmod and rmmod.
1779
1780 If you say Y here, you will need to run "make
1781 modules_install" to put the modules under /lib/modules/
1782 where modprobe can find them (you may need to be root to do
1783 this).
1784
1785 If unsure, say Y.
1786
1787if MODULES
1788
1789config MODULE_FORCE_LOAD
1790 bool "Forced module loading"
1791 default n
1792 help
1793 Allow loading of modules without version information (ie. modprobe
1794 --force). Forced module loading sets the 'F' (forced) taint flag and
1795 is usually a really bad idea.
1796
1797config MODULE_UNLOAD
1798 bool "Module unloading"
1799 help
1800 Without this option you will not be able to unload any
1801 modules (note that some modules may not be unloadable
1802 anyway), which makes your kernel smaller, faster
1803 and simpler. If unsure, say Y.
1804
1805config MODULE_FORCE_UNLOAD
1806 bool "Forced module unloading"
1807 depends on MODULE_UNLOAD
1808 help
1809 This option allows you to force a module to unload, even if the
1810 kernel believes it is unsafe: the kernel will remove the module
1811 without waiting for anyone to stop using it (using the -f option to
1812 rmmod). This is mainly for kernel developers and desperate users.
1813 If unsure, say N.
1814
1815config MODVERSIONS
1816 bool "Module versioning support"
1817 help
1818 Usually, you have to use modules compiled with your kernel.
1819 Saying Y here makes it sometimes possible to use modules
1820 compiled for different kernels, by adding enough information
1821 to the modules to (hopefully) spot any changes which would
1822 make them incompatible with the kernel you are running. If
1823 unsure, say N.
1824
1825config MODULE_REL_CRCS
1826 bool
1827 depends on MODVERSIONS
1828
1829config MODULE_SRCVERSION_ALL
1830 bool "Source checksum for all modules"
1831 help
1832 Modules which contain a MODULE_VERSION get an extra "srcversion"
1833 field inserted into their modinfo section, which contains a
1834 sum of the source files which made it. This helps maintainers
1835 see exactly which source was used to build a module (since
1836 others sometimes change the module source without updating
1837 the version). With this option, such a "srcversion" field
1838 will be created for all modules. If unsure, say N.
1839
1840config MODULE_SIG
1841 bool "Module signature verification"
1842 depends on MODULES
1843 select SYSTEM_DATA_VERIFICATION
1844 help
1845 Check modules for valid signatures upon load: the signature
1846 is simply appended to the module. For more information see
1847 <file:Documentation/admin-guide/module-signing.rst>.
1848
1849 Note that this option adds the OpenSSL development packages as a
1850 kernel build dependency so that the signing tool can use its crypto
1851 library.
1852
1853 !!!WARNING!!! If you enable this option, you MUST make sure that the
1854 module DOES NOT get stripped after being signed. This includes the
1855 debuginfo strip done by some packagers (such as rpmbuild) and
1856 inclusion into an initramfs that wants the module size reduced.
1857
1858config MODULE_SIG_FORCE
1859 bool "Require modules to be validly signed"
1860 depends on MODULE_SIG
1861 help
1862 Reject unsigned modules or signed modules for which we don't have a
1863 key. Without this, such modules will simply taint the kernel.
1864
1865config MODULE_SIG_ALL
1866 bool "Automatically sign all modules"
1867 default y
1868 depends on MODULE_SIG
1869 help
1870 Sign all modules during make modules_install. Without this option,
1871 modules must be signed manually, using the scripts/sign-file tool.
1872
1873comment "Do not forget to sign required modules with scripts/sign-file"
1874 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1875
1876choice
1877 prompt "Which hash algorithm should modules be signed with?"
1878 depends on MODULE_SIG
1879 help
1880 This determines which sort of hashing algorithm will be used during
1881 signature generation. This algorithm _must_ be built into the kernel
1882 directly so that signature verification can take place. It is not
1883 possible to load a signed module containing the algorithm to check
1884 the signature on that module.
1885
1886config MODULE_SIG_SHA1
1887 bool "Sign modules with SHA-1"
1888 select CRYPTO_SHA1
1889
1890config MODULE_SIG_SHA224
1891 bool "Sign modules with SHA-224"
1892 select CRYPTO_SHA256
1893
1894config MODULE_SIG_SHA256
1895 bool "Sign modules with SHA-256"
1896 select CRYPTO_SHA256
1897
1898config MODULE_SIG_SHA384
1899 bool "Sign modules with SHA-384"
1900 select CRYPTO_SHA512
1901
1902config MODULE_SIG_SHA512
1903 bool "Sign modules with SHA-512"
1904 select CRYPTO_SHA512
1905
1906endchoice
1907
1908config MODULE_SIG_HASH
1909 string
1910 depends on MODULE_SIG
1911 default "sha1" if MODULE_SIG_SHA1
1912 default "sha224" if MODULE_SIG_SHA224
1913 default "sha256" if MODULE_SIG_SHA256
1914 default "sha384" if MODULE_SIG_SHA384
1915 default "sha512" if MODULE_SIG_SHA512
1916
1917config MODULE_COMPRESS
1918 bool "Compress modules on installation"
1919 depends on MODULES
1920 help
1921
1922 Compresses kernel modules when 'make modules_install' is run; gzip or
1923 xz depending on "Compression algorithm" below.
1924
1925 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
1926
1927 Out-of-tree kernel modules installed using Kbuild will also be
1928 compressed upon installation.
1929
1930 Note: for modules inside an initrd or initramfs, it's more efficient
1931 to compress the whole initrd or initramfs instead.
1932
1933 Note: This is fully compatible with signed modules.
1934
1935 If in doubt, say N.
1936
1937choice
1938 prompt "Compression algorithm"
1939 depends on MODULE_COMPRESS
1940 default MODULE_COMPRESS_GZIP
1941 help
1942 This determines which sort of compression will be used during
1943 'make modules_install'.
1944
1945 GZIP (default) and XZ are supported.
1946
1947config MODULE_COMPRESS_GZIP
1948 bool "GZIP"
1949
1950config MODULE_COMPRESS_XZ
1951 bool "XZ"
1952
1953endchoice
1954
1955config TRIM_UNUSED_KSYMS
1956 bool "Trim unused exported kernel symbols"
1957 depends on MODULES && !UNUSED_SYMBOLS
1958 help
1959 The kernel and some modules make many symbols available for
1960 other modules to use via EXPORT_SYMBOL() and variants. Depending
1961 on the set of modules being selected in your kernel configuration,
1962 many of those exported symbols might never be used.
1963
1964 This option allows for unused exported symbols to be dropped from
1965 the build. In turn, this provides the compiler more opportunities
1966 (especially when using LTO) for optimizing the code and reducing
1967 binary size. This might have some security advantages as well.
1968
1969 If unsure, or if you need to build out-of-tree modules, say N.
1970
1971endif
1972
1973config MODULES_TREE_LOOKUP
1974 def_bool y
1975 depends on PERF_EVENTS || TRACING
1976
1977config INIT_ALL_POSSIBLE
1978 bool
1979 help
1980 Back when each arch used to define their own cpu_online_mask and
1981 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1982 with all 1s, and others with all 0s. When they were centralised,
1983 it was better to provide this option than to break all the archs
1984 and have several arch maintainers pursuing me down dark alleys.
1985
1986source "block/Kconfig"
1987
1988config PREEMPT_NOTIFIERS
1989 bool
1990
1991config PADATA
1992 depends on SMP
1993 bool
1994
1995config ASN1
1996 tristate
1997 help
1998 Build a simple ASN.1 grammar compiler that produces a bytecode output
1999 that can be interpreted by the ASN.1 stream decoder and used to
2000 inform it as to what tags are to be expected in a stream and what
2001 functions to call on what tags.
2002
2003source "kernel/Kconfig.locks"
2004
2005config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2006 bool
2007
2008
2009
2010
2011
2012
2013
2014
2015config ARCH_HAS_SYSCALL_WRAPPER
2016 def_bool n
2017
