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