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 FHANDLE
287 bool "open by fhandle syscalls" if EXPERT
288 select EXPORTFS
289 default y
290 help
291 If you say Y here, a user level program will be able to map
292 file names to handle and then later use the handle for
293 different file system operations. This is useful in implementing
294 userspace file servers, which now track files using handles instead
295 of names. The handle would remain the same even if file names
296 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
297 syscalls.
298
299config USELIB
300 bool "uselib syscall"
301 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
302 help
303 This option enables the uselib syscall, a system call used in the
304 dynamic linker from libc5 and earlier. glibc does not use this
305 system call. If you intend to run programs built on libc5 or
306 earlier, you may need to enable this syscall. Current systems
307 running glibc can safely disable this.
308
309config AUDIT
310 bool "Auditing support"
311 depends on NET
312 help
313 Enable auditing infrastructure that can be used with another
314 kernel subsystem, such as SELinux (which requires this for
315 logging of avc messages output). System call auditing is included
316 on architectures which support it.
317
318config HAVE_ARCH_AUDITSYSCALL
319 bool
320
321config AUDITSYSCALL
322 def_bool y
323 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
324
325config AUDIT_WATCH
326 def_bool y
327 depends on AUDITSYSCALL
328 select FSNOTIFY
329
330config AUDIT_TREE
331 def_bool y
332 depends on AUDITSYSCALL
333 select FSNOTIFY
334
335source "kernel/irq/Kconfig"
336source "kernel/time/Kconfig"
337
338menu "CPU/Task time and stats accounting"
339
340config VIRT_CPU_ACCOUNTING
341 bool
342
343choice
344 prompt "Cputime accounting"
345 default TICK_CPU_ACCOUNTING if !PPC64
346 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
347
348
349config TICK_CPU_ACCOUNTING
350 bool "Simple tick based cputime accounting"
351 depends on !S390 && !NO_HZ_FULL
352 help
353 This is the basic tick based cputime accounting that maintains
354 statistics about user, system and idle time spent on per jiffies
355 granularity.
356
357 If unsure, say Y.
358
359config VIRT_CPU_ACCOUNTING_NATIVE
360 bool "Deterministic task and CPU time accounting"
361 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
362 select VIRT_CPU_ACCOUNTING
363 help
364 Select this option to enable more accurate task and CPU time
365 accounting. This is done by reading a CPU counter on each
366 kernel entry and exit and on transitions within the kernel
367 between system, softirq and hardirq state, so there is a
368 small performance impact. In the case of s390 or IBM POWER > 5,
369 this also enables accounting of stolen time on logically-partitioned
370 systems.
371
372config VIRT_CPU_ACCOUNTING_GEN
373 bool "Full dynticks CPU time accounting"
374 depends on HAVE_CONTEXT_TRACKING
375 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
376 select VIRT_CPU_ACCOUNTING
377 select CONTEXT_TRACKING
378 help
379 Select this option to enable task and CPU time accounting on full
380 dynticks systems. This accounting is implemented by watching every
381 kernel-user boundaries using the context tracking subsystem.
382 The accounting is thus performed at the expense of some significant
383 overhead.
384
385 For now this is only useful if you are working on the full
386 dynticks subsystem development.
387
388 If unsure, say N.
389
390endchoice
391
392config IRQ_TIME_ACCOUNTING
393 bool "Fine granularity task level IRQ time accounting"
394 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
395 help
396 Select this option to enable fine granularity task irq time
397 accounting. This is done by reading a timestamp on each
398 transitions between softirq and hardirq state, so there can be a
399 small performance impact.
400
401 If in doubt, say N here.
402
403config BSD_PROCESS_ACCT
404 bool "BSD Process Accounting"
405 depends on MULTIUSER
406 help
407 If you say Y here, a user level program will be able to instruct the
408 kernel (via a special system call) to write process accounting
409 information to a file: whenever a process exits, information about
410 that process will be appended to the file by the kernel. The
411 information includes things such as creation time, owning user,
412 command name, memory usage, controlling terminal etc. (the complete
413 list is in the struct acct in <file:include/linux/acct.h>). It is
414 up to the user level program to do useful things with this
415 information. This is generally a good idea, so say Y.
416
417config BSD_PROCESS_ACCT_V3
418 bool "BSD Process Accounting version 3 file format"
419 depends on BSD_PROCESS_ACCT
420 default n
421 help
422 If you say Y here, the process accounting information is written
423 in a new file format that also logs the process IDs of each
424 process and it's parent. Note that this file format is incompatible
425 with previous v0/v1/v2 file formats, so you will need updated tools
426 for processing it. A preliminary version of these tools is available
427 at <http://www.gnu.org/software/acct/>.
428
429config TASKSTATS
430 bool "Export task/process statistics through netlink"
431 depends on NET
432 depends on MULTIUSER
433 default n
434 help
435 Export selected statistics for tasks/processes through the
436 generic netlink interface. Unlike BSD process accounting, the
437 statistics are available during the lifetime of tasks/processes as
438 responses to commands. Like BSD accounting, they are sent to user
439 space on task exit.
440
441 Say N if unsure.
442
443config TASK_DELAY_ACCT
444 bool "Enable per-task delay accounting"
445 depends on TASKSTATS
446 select SCHED_INFO
447 help
448 Collect information on time spent by a task waiting for system
449 resources like cpu, synchronous block I/O completion and swapping
450 in pages. Such statistics can help in setting a task's priorities
451 relative to other tasks for cpu, io, rss limits etc.
452
453 Say N if unsure.
454
455config TASK_XACCT
456 bool "Enable extended accounting over taskstats"
457 depends on TASKSTATS
458 help
459 Collect extended task accounting data and send the data
460 to userland for processing over the taskstats interface.
461
462 Say N if unsure.
463
464config TASK_IO_ACCOUNTING
465 bool "Enable per-task storage I/O accounting"
466 depends on TASK_XACCT
467 help
468 Collect information on the number of bytes of storage I/O which this
469 task has caused.
470
471 Say N if unsure.
472
473endmenu
474
475source "kernel/rcu/Kconfig"
476
477config BUILD_BIN2C
478 bool
479 default n
480
481config IKCONFIG
482 tristate "Kernel .config support"
483 select BUILD_BIN2C
484 ---help---
485 This option enables the complete Linux kernel ".config" file
486 contents to be saved in the kernel. It provides documentation
487 of which kernel options are used in a running kernel or in an
488 on-disk kernel. This information can be extracted from the kernel
489 image file with the script scripts/extract-ikconfig and used as
490 input to rebuild the current kernel or to build another kernel.
491 It can also be extracted from a running kernel by reading
492 /proc/config.gz if enabled (below).
493
494config IKCONFIG_PROC
495 bool "Enable access to .config through /proc/config.gz"
496 depends on IKCONFIG && PROC_FS
497 ---help---
498 This option enables access to the kernel configuration file
499 through /proc/config.gz.
500
501config LOG_BUF_SHIFT
502 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
503 range 12 25
504 default 17
505 depends on PRINTK
506 help
507 Select the minimal kernel log buffer size as a power of 2.
508 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
509 parameter, see below. Any higher size also might be forced
510 by "log_buf_len" boot parameter.
511
512 Examples:
513 17 => 128 KB
514 16 => 64 KB
515 15 => 32 KB
516 14 => 16 KB
517 13 => 8 KB
518 12 => 4 KB
519
520config LOG_CPU_MAX_BUF_SHIFT
521 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
522 depends on SMP
523 range 0 21
524 default 12 if !BASE_SMALL
525 default 0 if BASE_SMALL
526 depends on PRINTK
527 help
528 This option allows to increase the default ring buffer size
529 according to the number of CPUs. The value defines the contribution
530 of each CPU as a power of 2. The used space is typically only few
531 lines however it might be much more when problems are reported,
532 e.g. backtraces.
533
534 The increased size means that a new buffer has to be allocated and
535 the original static one is unused. It makes sense only on systems
536 with more CPUs. Therefore this value is used only when the sum of
537 contributions is greater than the half of the default kernel ring
538 buffer as defined by LOG_BUF_SHIFT. The default values are set
539 so that more than 64 CPUs are needed to trigger the allocation.
540
541 Also this option is ignored when "log_buf_len" kernel parameter is
542 used as it forces an exact (power of two) size of the ring buffer.
543
544 The number of possible CPUs is used for this computation ignoring
545 hotplugging making the computation optimal for the worst case
546 scenario while allowing a simple algorithm to be used from bootup.
547
548 Examples shift values and their meaning:
549 17 => 128 KB for each CPU
550 16 => 64 KB for each CPU
551 15 => 32 KB for each CPU
552 14 => 16 KB for each CPU
553 13 => 8 KB for each CPU
554 12 => 4 KB for each CPU
555
556config PRINTK_SAFE_LOG_BUF_SHIFT
557 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
558 range 10 21
559 default 13
560 depends on PRINTK
561 help
562 Select the size of an alternate printk per-CPU buffer where messages
563 printed from usafe contexts are temporary stored. One example would
564 be NMI messages, another one - printk recursion. The messages are
565 copied to the main log buffer in a safe context to avoid a deadlock.
566 The value defines the size as a power of 2.
567
568 Those messages are rare and limited. The largest one is when
569 a backtrace is printed. It usually fits into 4KB. Select
570 8KB if you want to be on the safe side.
571
572 Examples:
573 17 => 128 KB for each CPU
574 16 => 64 KB for each CPU
575 15 => 32 KB for each CPU
576 14 => 16 KB for each CPU
577 13 => 8 KB for each CPU
578 12 => 4 KB for each CPU
579
580
581
582
583config HAVE_UNSTABLE_SCHED_CLOCK
584 bool
585
586config GENERIC_SCHED_CLOCK
587 bool
588
589
590
591
592
593config ARCH_SUPPORTS_NUMA_BALANCING
594 bool
595
596
597
598
599
600
601
602
603config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
604 bool
605
606
607
608
609config ARCH_SUPPORTS_INT128
610 bool
611
612
613
614
615config ARCH_WANT_NUMA_VARIABLE_LOCALITY
616 bool
617
618config NUMA_BALANCING
619 bool "Memory placement aware NUMA scheduler"
620 depends on ARCH_SUPPORTS_NUMA_BALANCING
621 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
622 depends on SMP && NUMA && MIGRATION
623 help
624 This option adds support for automatic NUMA aware memory/task placement.
625 The mechanism is quite primitive and is based on migrating memory when
626 it has references to the node the task is running on.
627
628 This system will be inactive on UMA systems.
629
630config NUMA_BALANCING_DEFAULT_ENABLED
631 bool "Automatically enable NUMA aware memory/task placement"
632 default y
633 depends on NUMA_BALANCING
634 help
635 If set, automatic NUMA balancing will be enabled if running on a NUMA
636 machine.
637
638menuconfig CGROUPS
639 bool "Control Group support"
640 select KERNFS
641 help
642 This option adds support for grouping sets of processes together, for
643 use with process control subsystems such as Cpusets, CFS, memory
644 controls or device isolation.
645 See
646 - Documentation/scheduler/sched-design-CFS.txt (CFS)
647 - Documentation/cgroup-v1/ (features for grouping, isolation
648 and resource control)
649
650 Say N if unsure.
651
652if CGROUPS
653
654config PAGE_COUNTER
655 bool
656
657config MEMCG
658 bool "Memory controller"
659 select PAGE_COUNTER
660 select EVENTFD
661 help
662 Provides control over the memory footprint of tasks in a cgroup.
663
664config MEMCG_SWAP
665 bool "Swap controller"
666 depends on MEMCG && SWAP
667 help
668 Provides control over the swap space consumed by tasks in a cgroup.
669
670config MEMCG_SWAP_ENABLED
671 bool "Swap controller enabled by default"
672 depends on MEMCG_SWAP
673 default y
674 help
675 Memory Resource Controller Swap Extension comes with its price in
676 a bigger memory consumption. General purpose distribution kernels
677 which want to enable the feature but keep it disabled by default
678 and let the user enable it by swapaccount=1 boot command line
679 parameter should have this option unselected.
680 For those who want to have the feature enabled by default should
681 select this option (if, for some reason, they need to disable it
682 then swapaccount=0 does the trick).
683
684config BLK_CGROUP
685 bool "IO controller"
686 depends on BLOCK
687 default n
688 ---help---
689 Generic block IO controller cgroup interface. This is the common
690 cgroup interface which should be used by various IO controlling
691 policies.
692
693 Currently, CFQ IO scheduler uses it to recognize task groups and
694 control disk bandwidth allocation (proportional time slice allocation)
695 to such task groups. It is also used by bio throttling logic in
696 block layer to implement upper limit in IO rates on a device.
697
698 This option only enables generic Block IO controller infrastructure.
699 One needs to also enable actual IO controlling logic/policy. For
700 enabling proportional weight division of disk bandwidth in CFQ, set
701 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
702 CONFIG_BLK_DEV_THROTTLING=y.
703
704 See Documentation/cgroup-v1/blkio-controller.txt for more information.
705
706config DEBUG_BLK_CGROUP
707 bool "IO controller debugging"
708 depends on BLK_CGROUP
709 default n
710 ---help---
711 Enable some debugging help. Currently it exports additional stat
712 files in a cgroup which can be useful for debugging.
713
714config CGROUP_WRITEBACK
715 bool
716 depends on MEMCG && BLK_CGROUP
717 default y
718
719menuconfig CGROUP_SCHED
720 bool "CPU controller"
721 default n
722 help
723 This feature lets CPU scheduler recognize task groups and control CPU
724 bandwidth allocation to such task groups. It uses cgroups to group
725 tasks.
726
727if CGROUP_SCHED
728config FAIR_GROUP_SCHED
729 bool "Group scheduling for SCHED_OTHER"
730 depends on CGROUP_SCHED
731 default CGROUP_SCHED
732
733config CFS_BANDWIDTH
734 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
735 depends on FAIR_GROUP_SCHED
736 default n
737 help
738 This option allows users to define CPU bandwidth rates (limits) for
739 tasks running within the fair group scheduler. Groups with no limit
740 set are considered to be unconstrained and will run with no
741 restriction.
742 See tip/Documentation/scheduler/sched-bwc.txt for more information.
743
744config RT_GROUP_SCHED
745 bool "Group scheduling for SCHED_RR/FIFO"
746 depends on CGROUP_SCHED
747 default n
748 help
749 This feature lets you explicitly allocate real CPU bandwidth
750 to task groups. If enabled, it will also make it impossible to
751 schedule realtime tasks for non-root users until you allocate
752 realtime bandwidth for them.
753 See Documentation/scheduler/sched-rt-group.txt for more information.
754
755endif
756
757config CGROUP_PIDS
758 bool "PIDs controller"
759 help
760 Provides enforcement of process number limits in the scope of a
761 cgroup. Any attempt to fork more processes than is allowed in the
762 cgroup will fail. PIDs are fundamentally a global resource because it
763 is fairly trivial to reach PID exhaustion before you reach even a
764 conservative kmemcg limit. As a result, it is possible to grind a
765 system to halt without being limited by other cgroup policies. The
766 PIDs controller is designed to stop this from happening.
767
768 It should be noted that organisational operations (such as attaching
769 to a cgroup hierarchy will *not* be blocked by the PIDs controller),
770 since the PIDs limit only affects a process's ability to fork, not to
771 attach to a cgroup.
772
773config CGROUP_RDMA
774 bool "RDMA controller"
775 help
776 Provides enforcement of RDMA resources defined by IB stack.
777 It is fairly easy for consumers to exhaust RDMA resources, which
778 can result into resource unavailability to other consumers.
779 RDMA controller is designed to stop this from happening.
780 Attaching processes with active RDMA resources to the cgroup
781 hierarchy is allowed even if can cross the hierarchy's limit.
782
783config CGROUP_FREEZER
784 bool "Freezer controller"
785 help
786 Provides a way to freeze and unfreeze all tasks in a
787 cgroup.
788
789 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
790 controller includes important in-kernel memory consumers per default.
791
792 If you're using cgroup2, say N.
793
794config CGROUP_HUGETLB
795 bool "HugeTLB controller"
796 depends on HUGETLB_PAGE
797 select PAGE_COUNTER
798 default n
799 help
800 Provides a cgroup controller for HugeTLB pages.
801 When you enable this, you can put a per cgroup limit on HugeTLB usage.
802 The limit is enforced during page fault. Since HugeTLB doesn't
803 support page reclaim, enforcing the limit at page fault time implies
804 that, the application will get SIGBUS signal if it tries to access
805 HugeTLB pages beyond its limit. This requires the application to know
806 beforehand how much HugeTLB pages it would require for its use. The
807 control group is tracked in the third page lru pointer. This means
808 that we cannot use the controller with huge page less than 3 pages.
809
810config CPUSETS
811 bool "Cpuset controller"
812 depends on SMP
813 help
814 This option will let you create and manage CPUSETs which
815 allow dynamically partitioning a system into sets of CPUs and
816 Memory Nodes and assigning tasks to run only within those sets.
817 This is primarily useful on large SMP or NUMA systems.
818
819 Say N if unsure.
820
821config PROC_PID_CPUSET
822 bool "Include legacy /proc/<pid>/cpuset file"
823 depends on CPUSETS
824 default y
825
826config CGROUP_DEVICE
827 bool "Device controller"
828 help
829 Provides a cgroup controller implementing whitelists for
830 devices which a process in the cgroup can mknod or open.
831
832config CGROUP_CPUACCT
833 bool "Simple CPU accounting controller"
834 help
835 Provides a simple controller for monitoring the
836 total CPU consumed by the tasks in a cgroup.
837
838config CGROUP_PERF
839 bool "Perf controller"
840 depends on PERF_EVENTS
841 help
842 This option extends the perf per-cpu mode to restrict monitoring
843 to threads which belong to the cgroup specified and run on the
844 designated cpu.
845
846 Say N if unsure.
847
848config CGROUP_BPF
849 bool "Support for eBPF programs attached to cgroups"
850 depends on BPF_SYSCALL
851 select SOCK_CGROUP_DATA
852 help
853 Allow attaching eBPF programs to a cgroup using the bpf(2)
854 syscall command BPF_PROG_ATTACH.
855
856 In which context these programs are accessed depends on the type
857 of attachment. For instance, programs that are attached using
858 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
859 inet sockets.
860
861config CGROUP_DEBUG
862 bool "Debug controller"
863 default n
864 depends on DEBUG_KERNEL
865 help
866 This option enables a simple controller that exports
867 debugging information about the cgroups framework. This
868 controller is for control cgroup debugging only. Its
869 interfaces are not stable.
870
871 Say N.
872
873config SOCK_CGROUP_DATA
874 bool
875 default n
876
877endif
878
879config CHECKPOINT_RESTORE
880 bool "Checkpoint/restore support" if EXPERT
881 select PROC_CHILDREN
882 default n
883 help
884 Enables additional kernel features in a sake of checkpoint/restore.
885 In particular it adds auxiliary prctl codes to setup process text,
886 data and heap segment sizes, and a few additional /proc filesystem
887 entries.
888
889 If unsure, say N here.
890
891menuconfig NAMESPACES
892 bool "Namespaces support" if EXPERT
893 depends on MULTIUSER
894 default !EXPERT
895 help
896 Provides the way to make tasks work with different objects using
897 the same id. For example same IPC id may refer to different objects
898 or same user id or pid may refer to different tasks when used in
899 different namespaces.
900
901if NAMESPACES
902
903config UTS_NS
904 bool "UTS namespace"
905 default y
906 help
907 In this namespace tasks see different info provided with the
908 uname() system call
909
910config IPC_NS
911 bool "IPC namespace"
912 depends on (SYSVIPC || POSIX_MQUEUE)
913 default y
914 help
915 In this namespace tasks work with IPC ids which correspond to
916 different IPC objects in different namespaces.
917
918config USER_NS
919 bool "User namespace"
920 default n
921 help
922 This allows containers, i.e. vservers, to use user namespaces
923 to provide different user info for different servers.
924
925 When user namespaces are enabled in the kernel it is
926 recommended that the MEMCG option also be enabled and that
927 user-space use the memory control groups to limit the amount
928 of memory a memory unprivileged users can use.
929
930 If unsure, say N.
931
932config PID_NS
933 bool "PID Namespaces"
934 default y
935 help
936 Support process id namespaces. This allows having multiple
937 processes with the same pid as long as they are in different
938 pid namespaces. This is a building block of containers.
939
940config NET_NS
941 bool "Network namespace"
942 depends on NET
943 default y
944 help
945 Allow user space to create what appear to be multiple instances
946 of the network stack.
947
948endif
949
950config SCHED_AUTOGROUP
951 bool "Automatic process group scheduling"
952 select CGROUPS
953 select CGROUP_SCHED
954 select FAIR_GROUP_SCHED
955 help
956 This option optimizes the scheduler for common desktop workloads by
957 automatically creating and populating task groups. This separation
958 of workloads isolates aggressive CPU burners (like build jobs) from
959 desktop applications. Task group autogeneration is currently based
960 upon task session.
961
962config SYSFS_DEPRECATED
963 bool "Enable deprecated sysfs features to support old userspace tools"
964 depends on SYSFS
965 default n
966 help
967 This option adds code that switches the layout of the "block" class
968 devices, to not show up in /sys/class/block/, but only in
969 /sys/block/.
970
971 This switch is only active when the sysfs.deprecated=1 boot option is
972 passed or the SYSFS_DEPRECATED_V2 option is set.
973
974 This option allows new kernels to run on old distributions and tools,
975 which might get confused by /sys/class/block/. Since 2007/2008 all
976 major distributions and tools handle this just fine.
977
978 Recent distributions and userspace tools after 2009/2010 depend on
979 the existence of /sys/class/block/, and will not work with this
980 option enabled.
981
982 Only if you are using a new kernel on an old distribution, you might
983 need to say Y here.
984
985config SYSFS_DEPRECATED_V2
986 bool "Enable deprecated sysfs features by default"
987 default n
988 depends on SYSFS
989 depends on SYSFS_DEPRECATED
990 help
991 Enable deprecated sysfs by default.
992
993 See the CONFIG_SYSFS_DEPRECATED option for more details about this
994 option.
995
996 Only if you are using a new kernel on an old distribution, you might
997 need to say Y here. Even then, odds are you would not need it
998 enabled, you can always pass the boot option if absolutely necessary.
999
1000config RELAY
1001 bool "Kernel->user space relay support (formerly relayfs)"
1002 select IRQ_WORK
1003 help
1004 This option enables support for relay interface support in
1005 certain file systems (such as debugfs).
1006 It is designed to provide an efficient mechanism for tools and
1007 facilities to relay large amounts of data from kernel space to
1008 user space.
1009
1010 If unsure, say N.
1011
1012config BLK_DEV_INITRD
1013 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1014 depends on BROKEN || !FRV
1015 help
1016 The initial RAM filesystem is a ramfs which is loaded by the
1017 boot loader (loadlin or lilo) and that is mounted as root
1018 before the normal boot procedure. It is typically used to
1019 load modules needed to mount the "real" root file system,
1020 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1021
1022 If RAM disk support (BLK_DEV_RAM) is also included, this
1023 also enables initial RAM disk (initrd) support and adds
1024 15 Kbytes (more on some other architectures) to the kernel size.
1025
1026 If unsure say Y.
1027
1028if BLK_DEV_INITRD
1029
1030source "usr/Kconfig"
1031
1032endif
1033
1034choice
1035 prompt "Compiler optimization level"
1036 default CC_OPTIMIZE_FOR_PERFORMANCE
1037
1038config CC_OPTIMIZE_FOR_PERFORMANCE
1039 bool "Optimize for performance"
1040 help
1041 This is the default optimization level for the kernel, building
1042 with the "-O2" compiler flag for best performance and most
1043 helpful compile-time warnings.
1044
1045config CC_OPTIMIZE_FOR_SIZE
1046 bool "Optimize for size"
1047 help
1048 Enabling this option will pass "-Os" instead of "-O2" to
1049 your compiler resulting in a smaller kernel.
1050
1051 If unsure, say N.
1052
1053endchoice
1054
1055config SYSCTL
1056 bool
1057
1058config ANON_INODES
1059 bool
1060
1061config HAVE_UID16
1062 bool
1063
1064config SYSCTL_EXCEPTION_TRACE
1065 bool
1066 help
1067 Enable support for /proc/sys/debug/exception-trace.
1068
1069config SYSCTL_ARCH_UNALIGN_NO_WARN
1070 bool
1071 help
1072 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1073 Allows arch to define/use @no_unaligned_warning to possibly warn
1074 about unaligned access emulation going on under the hood.
1075
1076config SYSCTL_ARCH_UNALIGN_ALLOW
1077 bool
1078 help
1079 Enable support for /proc/sys/kernel/unaligned-trap
1080 Allows arches to define/use @unaligned_enabled to runtime toggle
1081 the unaligned access emulation.
1082 see arch/parisc/kernel/unaligned.c for reference
1083
1084config HAVE_PCSPKR_PLATFORM
1085 bool
1086
1087
1088config BPF
1089 bool
1090
1091menuconfig EXPERT
1092 bool "Configure standard kernel features (expert users)"
1093
1094 select DEBUG_KERNEL
1095 help
1096 This option allows certain base kernel options and settings
1097 to be disabled or tweaked. This is for specialized
1098 environments which can tolerate a "non-standard" kernel.
1099 Only use this if you really know what you are doing.
1100
1101config UID16
1102 bool "Enable 16-bit UID system calls" if EXPERT
1103 depends on HAVE_UID16 && MULTIUSER
1104 default y
1105 help
1106 This enables the legacy 16-bit UID syscall wrappers.
1107
1108config MULTIUSER
1109 bool "Multiple users, groups and capabilities support" if EXPERT
1110 default y
1111 help
1112 This option enables support for non-root users, groups and
1113 capabilities.
1114
1115 If you say N here, all processes will run with UID 0, GID 0, and all
1116 possible capabilities. Saying N here also compiles out support for
1117 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1118 setgid, and capset.
1119
1120 If unsure, say Y here.
1121
1122config SGETMASK_SYSCALL
1123 bool "sgetmask/ssetmask syscalls support" if EXPERT
1124 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1125 ---help---
1126 sys_sgetmask and sys_ssetmask are obsolete system calls
1127 no longer supported in libc but still enabled by default in some
1128 architectures.
1129
1130 If unsure, leave the default option here.
1131
1132config SYSFS_SYSCALL
1133 bool "Sysfs syscall support" if EXPERT
1134 default y
1135 ---help---
1136 sys_sysfs is an obsolete system call no longer supported in libc.
1137 Note that disabling this option is more secure but might break
1138 compatibility with some systems.
1139
1140 If unsure say Y here.
1141
1142config SYSCTL_SYSCALL
1143 bool "Sysctl syscall support" if EXPERT
1144 depends on PROC_SYSCTL
1145 default n
1146 select SYSCTL
1147 ---help---
1148 sys_sysctl uses binary paths that have been found challenging
1149 to properly maintain and use. The interface in /proc/sys
1150 using paths with ascii names is now the primary path to this
1151 information.
1152
1153 Almost nothing using the binary sysctl interface so if you are
1154 trying to save some space it is probably safe to disable this,
1155 making your kernel marginally smaller.
1156
1157 If unsure say N here.
1158
1159config POSIX_TIMERS
1160 bool "Posix Clocks & timers" if EXPERT
1161 default y
1162 help
1163 This includes native support for POSIX timers to the kernel.
1164 Some embedded systems have no use for them and therefore they
1165 can be configured out to reduce the size of the kernel image.
1166
1167 When this option is disabled, the following syscalls won't be
1168 available: timer_create, timer_gettime: timer_getoverrun,
1169 timer_settime, timer_delete, clock_adjtime, getitimer,
1170 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1171 clock_getres and clock_nanosleep syscalls will be limited to
1172 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1173
1174 If unsure say y.
1175
1176config KALLSYMS
1177 bool "Load all symbols for debugging/ksymoops" if EXPERT
1178 default y
1179 help
1180 Say Y here to let the kernel print out symbolic crash information and
1181 symbolic stack backtraces. This increases the size of the kernel
1182 somewhat, as all symbols have to be loaded into the kernel image.
1183
1184config KALLSYMS_ALL
1185 bool "Include all symbols in kallsyms"
1186 depends on DEBUG_KERNEL && KALLSYMS
1187 help
1188 Normally kallsyms only contains the symbols of functions for nicer
1189 OOPS messages and backtraces (i.e., symbols from the text and inittext
1190 sections). This is sufficient for most cases. And only in very rare
1191 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1192 names of variables from the data sections, etc).
1193
1194 This option makes sure that all symbols are loaded into the kernel
1195 image (i.e., symbols from all sections) in cost of increased kernel
1196 size (depending on the kernel configuration, it may be 300KiB or
1197 something like this).
1198
1199 Say N unless you really need all symbols.
1200
1201config KALLSYMS_ABSOLUTE_PERCPU
1202 bool
1203 depends on KALLSYMS
1204 default X86_64 && SMP
1205
1206config KALLSYMS_BASE_RELATIVE
1207 bool
1208 depends on KALLSYMS
1209 default !IA64 && !(TILE && 64BIT)
1210 help
1211 Instead of emitting them as absolute values in the native word size,
1212 emit the symbol references in the kallsyms table as 32-bit entries,
1213 each containing a relative value in the range [base, base + U32_MAX]
1214 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1215 an absolute value in the range [0, S32_MAX] or a relative value in the
1216 range [base, base + S32_MAX], where base is the lowest relative symbol
1217 address encountered in the image.
1218
1219 On 64-bit builds, this reduces the size of the address table by 50%,
1220 but more importantly, it results in entries whose values are build
1221 time constants, and no relocation pass is required at runtime to fix
1222 up the entries based on the runtime load address of the kernel.
1223
1224config PRINTK
1225 default y
1226 bool "Enable support for printk" if EXPERT
1227 select IRQ_WORK
1228 help
1229 This option enables normal printk support. Removing it
1230 eliminates most of the message strings from the kernel image
1231 and makes the kernel more or less silent. As this makes it
1232 very difficult to diagnose system problems, saying N here is
1233 strongly discouraged.
1234
1235config PRINTK_NMI
1236 def_bool y
1237 depends on PRINTK
1238 depends on HAVE_NMI
1239
1240config BUG
1241 bool "BUG() support" if EXPERT
1242 default y
1243 help
1244 Disabling this option eliminates support for BUG and WARN, reducing
1245 the size of your kernel image and potentially quietly ignoring
1246 numerous fatal conditions. You should only consider disabling this
1247 option for embedded systems with no facilities for reporting errors.
1248 Just say Y.
1249
1250config ELF_CORE
1251 depends on COREDUMP
1252 default y
1253 bool "Enable ELF core dumps" if EXPERT
1254 help
1255 Enable support for generating core dumps. Disabling saves about 4k.
1256
1257
1258config PCSPKR_PLATFORM
1259 bool "Enable PC-Speaker support" if EXPERT
1260 depends on HAVE_PCSPKR_PLATFORM
1261 select I8253_LOCK
1262 default y
1263 help
1264 This option allows to disable the internal PC-Speaker
1265 support, saving some memory.
1266
1267config BASE_FULL
1268 default y
1269 bool "Enable full-sized data structures for core" if EXPERT
1270 help
1271 Disabling this option reduces the size of miscellaneous core
1272 kernel data structures. This saves memory on small machines,
1273 but may reduce performance.
1274
1275config FUTEX
1276 bool "Enable futex support" if EXPERT
1277 default y
1278 imply RT_MUTEXES
1279 help
1280 Disabling this option will cause the kernel to be built without
1281 support for "fast userspace mutexes". The resulting kernel may not
1282 run glibc-based applications correctly.
1283
1284config FUTEX_PI
1285 bool
1286 depends on FUTEX && RT_MUTEXES
1287 default y
1288
1289config HAVE_FUTEX_CMPXCHG
1290 bool
1291 depends on FUTEX
1292 help
1293 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1294 is implemented and always working. This removes a couple of runtime
1295 checks.
1296
1297config EPOLL
1298 bool "Enable eventpoll support" if EXPERT
1299 default y
1300 select ANON_INODES
1301 help
1302 Disabling this option will cause the kernel to be built without
1303 support for epoll family of system calls.
1304
1305config SIGNALFD
1306 bool "Enable signalfd() system call" if EXPERT
1307 select ANON_INODES
1308 default y
1309 help
1310 Enable the signalfd() system call that allows to receive signals
1311 on a file descriptor.
1312
1313 If unsure, say Y.
1314
1315config TIMERFD
1316 bool "Enable timerfd() system call" if EXPERT
1317 select ANON_INODES
1318 default y
1319 help
1320 Enable the timerfd() system call that allows to receive timer
1321 events on a file descriptor.
1322
1323 If unsure, say Y.
1324
1325config EVENTFD
1326 bool "Enable eventfd() system call" if EXPERT
1327 select ANON_INODES
1328 default y
1329 help
1330 Enable the eventfd() system call that allows to receive both
1331 kernel notification (ie. KAIO) or userspace notifications.
1332
1333 If unsure, say Y.
1334
1335
1336config BPF_SYSCALL
1337 bool "Enable bpf() system call"
1338 select ANON_INODES
1339 select BPF
1340 default n
1341 help
1342 Enable the bpf() system call that allows to manipulate eBPF
1343 programs and maps via file descriptors.
1344
1345config SHMEM
1346 bool "Use full shmem filesystem" if EXPERT
1347 default y
1348 depends on MMU
1349 help
1350 The shmem is an internal filesystem used to manage shared memory.
1351 It is backed by swap and manages resource limits. It is also exported
1352 to userspace as tmpfs if TMPFS is enabled. Disabling this
1353 option replaces shmem and tmpfs with the much simpler ramfs code,
1354 which may be appropriate on small systems without swap.
1355
1356config AIO
1357 bool "Enable AIO support" if EXPERT
1358 default y
1359 help
1360 This option enables POSIX asynchronous I/O which may by used
1361 by some high performance threaded applications. Disabling
1362 this option saves about 7k.
1363
1364config ADVISE_SYSCALLS
1365 bool "Enable madvise/fadvise syscalls" if EXPERT
1366 default y
1367 help
1368 This option enables the madvise and fadvise syscalls, used by
1369 applications to advise the kernel about their future memory or file
1370 usage, improving performance. If building an embedded system where no
1371 applications use these syscalls, you can disable this option to save
1372 space.
1373
1374config USERFAULTFD
1375 bool "Enable userfaultfd() system call"
1376 select ANON_INODES
1377 depends on MMU
1378 help
1379 Enable the userfaultfd() system call that allows to intercept and
1380 handle page faults in userland.
1381
1382config PCI_QUIRKS
1383 default y
1384 bool "Enable PCI quirk workarounds" if EXPERT
1385 depends on PCI
1386 help
1387 This enables workarounds for various PCI chipset
1388 bugs/quirks. Disable this only if your target machine is
1389 unaffected by PCI quirks.
1390
1391config MEMBARRIER
1392 bool "Enable membarrier() system call" if EXPERT
1393 default y
1394 help
1395 Enable the membarrier() system call that allows issuing memory
1396 barriers across all running threads, which can be used to distribute
1397 the cost of user-space memory barriers asymmetrically by transforming
1398 pairs of memory barriers into pairs consisting of membarrier() and a
1399 compiler barrier.
1400
1401 If unsure, say Y.
1402
1403config EMBEDDED
1404 bool "Embedded system"
1405 option allnoconfig_y
1406 select EXPERT
1407 help
1408 This option should be enabled if compiling the kernel for
1409 an embedded system so certain expert options are available
1410 for configuration.
1411
1412config HAVE_PERF_EVENTS
1413 bool
1414 help
1415 See tools/perf/design.txt for details.
1416
1417config PERF_USE_VMALLOC
1418 bool
1419 help
1420 See tools/perf/design.txt for details
1421
1422config PC104
1423 bool "PC/104 support"
1424 help
1425 Expose PC/104 form factor device drivers and options available for
1426 selection and configuration. Enable this option if your target
1427 machine has a PC/104 bus.
1428
1429menu "Kernel Performance Events And Counters"
1430
1431config PERF_EVENTS
1432 bool "Kernel performance events and counters"
1433 default y if PROFILING
1434 depends on HAVE_PERF_EVENTS
1435 select ANON_INODES
1436 select IRQ_WORK
1437 select SRCU
1438 help
1439 Enable kernel support for various performance events provided
1440 by software and hardware.
1441
1442 Software events are supported either built-in or via the
1443 use of generic tracepoints.
1444
1445 Most modern CPUs support performance events via performance
1446 counter registers. These registers count the number of certain
1447 types of hw events: such as instructions executed, cachemisses
1448 suffered, or branches mis-predicted - without slowing down the
1449 kernel or applications. These registers can also trigger interrupts
1450 when a threshold number of events have passed - and can thus be
1451 used to profile the code that runs on that CPU.
1452
1453 The Linux Performance Event subsystem provides an abstraction of
1454 these software and hardware event capabilities, available via a
1455 system call and used by the "perf" utility in tools/perf/. It
1456 provides per task and per CPU counters, and it provides event
1457 capabilities on top of those.
1458
1459 Say Y if unsure.
1460
1461config DEBUG_PERF_USE_VMALLOC
1462 default n
1463 bool "Debug: use vmalloc to back perf mmap() buffers"
1464 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1465 select PERF_USE_VMALLOC
1466 help
1467 Use vmalloc memory to back perf mmap() buffers.
1468
1469 Mostly useful for debugging the vmalloc code on platforms
1470 that don't require it.
1471
1472 Say N if unsure.
1473
1474endmenu
1475
1476config VM_EVENT_COUNTERS
1477 default y
1478 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1479 help
1480 VM event counters are needed for event counts to be shown.
1481 This option allows the disabling of the VM event counters
1482 on EXPERT systems. /proc/vmstat will only show page counts
1483 if VM event counters are disabled.
1484
1485config SLUB_DEBUG
1486 default y
1487 bool "Enable SLUB debugging support" if EXPERT
1488 depends on SLUB && SYSFS
1489 help
1490 SLUB has extensive debug support features. Disabling these can
1491 result in significant savings in code size. This also disables
1492 SLUB sysfs support. /sys/slab will not exist and there will be
1493 no support for cache validation etc.
1494
1495config SLUB_MEMCG_SYSFS_ON
1496 default n
1497 bool "Enable memcg SLUB sysfs support by default" if EXPERT
1498 depends on SLUB && SYSFS && MEMCG
1499 help
1500 SLUB creates a directory under /sys/kernel/slab for each
1501 allocation cache to host info and debug files. If memory
1502 cgroup is enabled, each cache can have per memory cgroup
1503 caches. SLUB can create the same sysfs directories for these
1504 caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1505 to a very high number of debug files being created. This is
1506 controlled by slub_memcg_sysfs boot parameter and this
1507 config option determines the parameter's default value.
1508
1509config COMPAT_BRK
1510 bool "Disable heap randomization"
1511 default y
1512 help
1513 Randomizing heap placement makes heap exploits harder, but it
1514 also breaks ancient binaries (including anything libc5 based).
1515 This option changes the bootup default to heap randomization
1516 disabled, and can be overridden at runtime by setting
1517 /proc/sys/kernel/randomize_va_space to 2.
1518
1519 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1520
1521choice
1522 prompt "Choose SLAB allocator"
1523 default SLUB
1524 help
1525 This option allows to select a slab allocator.
1526
1527config SLAB
1528 bool "SLAB"
1529 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1530 help
1531 The regular slab allocator that is established and known to work
1532 well in all environments. It organizes cache hot objects in
1533 per cpu and per node queues.
1534
1535config SLUB
1536 bool "SLUB (Unqueued Allocator)"
1537 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1538 help
1539 SLUB is a slab allocator that minimizes cache line usage
1540 instead of managing queues of cached objects (SLAB approach).
1541 Per cpu caching is realized using slabs of objects instead
1542 of queues of objects. SLUB can use memory efficiently
1543 and has enhanced diagnostics. SLUB is the default choice for
1544 a slab allocator.
1545
1546config SLOB
1547 depends on EXPERT
1548 bool "SLOB (Simple Allocator)"
1549 help
1550 SLOB replaces the stock allocator with a drastically simpler
1551 allocator. SLOB is generally more space efficient but
1552 does not perform as well on large systems.
1553
1554endchoice
1555
1556config SLAB_MERGE_DEFAULT
1557 bool "Allow slab caches to be merged"
1558 default y
1559 help
1560 For reduced kernel memory fragmentation, slab caches can be
1561 merged when they share the same size and other characteristics.
1562 This carries a risk of kernel heap overflows being able to
1563 overwrite objects from merged caches (and more easily control
1564 cache layout), which makes such heap attacks easier to exploit
1565 by attackers. By keeping caches unmerged, these kinds of exploits
1566 can usually only damage objects in the same cache. To disable
1567 merging at runtime, "slab_nomerge" can be passed on the kernel
1568 command line.
1569
1570config SLAB_FREELIST_RANDOM
1571 default n
1572 depends on SLAB || SLUB
1573 bool "SLAB freelist randomization"
1574 help
1575 Randomizes the freelist order used on creating new pages. This
1576 security feature reduces the predictability of the kernel slab
1577 allocator against heap overflows.
1578
1579config SLAB_FREELIST_HARDENED
1580 bool "Harden slab freelist metadata"
1581 depends on SLUB
1582 help
1583 Many kernel heap attacks try to target slab cache metadata and
1584 other infrastructure. This options makes minor performance
1585 sacrifies to harden the kernel slab allocator against common
1586 freelist exploit methods.
1587
1588config SLUB_CPU_PARTIAL
1589 default y
1590 depends on SLUB && SMP
1591 bool "SLUB per cpu partial cache"
1592 help
1593 Per cpu partial caches accellerate objects allocation and freeing
1594 that is local to a processor at the price of more indeterminism
1595 in the latency of the free. On overflow these caches will be cleared
1596 which requires the taking of locks that may cause latency spikes.
1597 Typically one would choose no for a realtime system.
1598
1599config MMAP_ALLOW_UNINITIALIZED
1600 bool "Allow mmapped anonymous memory to be uninitialized"
1601 depends on EXPERT && !MMU
1602 default n
1603 help
1604 Normally, and according to the Linux spec, anonymous memory obtained
1605 from mmap() has it's contents cleared before it is passed to
1606 userspace. Enabling this config option allows you to request that
1607 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1608 providing a huge performance boost. If this option is not enabled,
1609 then the flag will be ignored.
1610
1611 This is taken advantage of by uClibc's malloc(), and also by
1612 ELF-FDPIC binfmt's brk and stack allocator.
1613
1614 Because of the obvious security issues, this option should only be
1615 enabled on embedded devices where you control what is run in
1616 userspace. Since that isn't generally a problem on no-MMU systems,
1617 it is normally safe to say Y here.
1618
1619 See Documentation/nommu-mmap.txt for more information.
1620
1621config SYSTEM_DATA_VERIFICATION
1622 def_bool n
1623 select SYSTEM_TRUSTED_KEYRING
1624 select KEYS
1625 select CRYPTO
1626 select CRYPTO_RSA
1627 select ASYMMETRIC_KEY_TYPE
1628 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1629 select ASN1
1630 select OID_REGISTRY
1631 select X509_CERTIFICATE_PARSER
1632 select PKCS7_MESSAGE_PARSER
1633 help
1634 Provide PKCS#7 message verification using the contents of the system
1635 trusted keyring to provide public keys. This then can be used for
1636 module verification, kexec image verification and firmware blob
1637 verification.
1638
1639config PROFILING
1640 bool "Profiling support"
1641 help
1642 Say Y here to enable the extended profiling support mechanisms used
1643 by profilers such as OProfile.
1644
1645
1646
1647
1648
1649config TRACEPOINTS
1650 bool
1651
1652source "arch/Kconfig"
1653
1654endmenu
1655
1656config HAVE_GENERIC_DMA_COHERENT
1657 bool
1658 default n
1659
1660config SLABINFO
1661 bool
1662 depends on PROC_FS
1663 depends on SLAB || SLUB_DEBUG
1664 default y
1665
1666config RT_MUTEXES
1667 bool
1668
1669config BASE_SMALL
1670 int
1671 default 0 if BASE_FULL
1672 default 1 if !BASE_FULL
1673
1674menuconfig MODULES
1675 bool "Enable loadable module support"
1676 option modules
1677 help
1678 Kernel modules are small pieces of compiled code which can
1679 be inserted in the running kernel, rather than being
1680 permanently built into the kernel. You use the "modprobe"
1681 tool to add (and sometimes remove) them. If you say Y here,
1682 many parts of the kernel can be built as modules (by
1683 answering M instead of Y where indicated): this is most
1684 useful for infrequently used options which are not required
1685 for booting. For more information, see the man pages for
1686 modprobe, lsmod, modinfo, insmod and rmmod.
1687
1688 If you say Y here, you will need to run "make
1689 modules_install" to put the modules under /lib/modules/
1690 where modprobe can find them (you may need to be root to do
1691 this).
1692
1693 If unsure, say Y.
1694
1695if MODULES
1696
1697config MODULE_FORCE_LOAD
1698 bool "Forced module loading"
1699 default n
1700 help
1701 Allow loading of modules without version information (ie. modprobe
1702 --force). Forced module loading sets the 'F' (forced) taint flag and
1703 is usually a really bad idea.
1704
1705config MODULE_UNLOAD
1706 bool "Module unloading"
1707 help
1708 Without this option you will not be able to unload any
1709 modules (note that some modules may not be unloadable
1710 anyway), which makes your kernel smaller, faster
1711 and simpler. If unsure, say Y.
1712
1713config MODULE_FORCE_UNLOAD
1714 bool "Forced module unloading"
1715 depends on MODULE_UNLOAD
1716 help
1717 This option allows you to force a module to unload, even if the
1718 kernel believes it is unsafe: the kernel will remove the module
1719 without waiting for anyone to stop using it (using the -f option to
1720 rmmod). This is mainly for kernel developers and desperate users.
1721 If unsure, say N.
1722
1723config MODVERSIONS
1724 bool "Module versioning support"
1725 help
1726 Usually, you have to use modules compiled with your kernel.
1727 Saying Y here makes it sometimes possible to use modules
1728 compiled for different kernels, by adding enough information
1729 to the modules to (hopefully) spot any changes which would
1730 make them incompatible with the kernel you are running. If
1731 unsure, say N.
1732
1733config MODULE_REL_CRCS
1734 bool
1735 depends on MODVERSIONS
1736
1737config MODULE_SRCVERSION_ALL
1738 bool "Source checksum for all modules"
1739 help
1740 Modules which contain a MODULE_VERSION get an extra "srcversion"
1741 field inserted into their modinfo section, which contains a
1742 sum of the source files which made it. This helps maintainers
1743 see exactly which source was used to build a module (since
1744 others sometimes change the module source without updating
1745 the version). With this option, such a "srcversion" field
1746 will be created for all modules. If unsure, say N.
1747
1748config MODULE_SIG
1749 bool "Module signature verification"
1750 depends on MODULES
1751 select SYSTEM_DATA_VERIFICATION
1752 help
1753 Check modules for valid signatures upon load: the signature
1754 is simply appended to the module. For more information see
1755 Documentation/module-signing.txt.
1756
1757 Note that this option adds the OpenSSL development packages as a
1758 kernel build dependency so that the signing tool can use its crypto
1759 library.
1760
1761 !!!WARNING!!! If you enable this option, you MUST make sure that the
1762 module DOES NOT get stripped after being signed. This includes the
1763 debuginfo strip done by some packagers (such as rpmbuild) and
1764 inclusion into an initramfs that wants the module size reduced.
1765
1766config MODULE_SIG_FORCE
1767 bool "Require modules to be validly signed"
1768 depends on MODULE_SIG
1769 help
1770 Reject unsigned modules or signed modules for which we don't have a
1771 key. Without this, such modules will simply taint the kernel.
1772
1773config MODULE_SIG_ALL
1774 bool "Automatically sign all modules"
1775 default y
1776 depends on MODULE_SIG
1777 help
1778 Sign all modules during make modules_install. Without this option,
1779 modules must be signed manually, using the scripts/sign-file tool.
1780
1781comment "Do not forget to sign required modules with scripts/sign-file"
1782 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1783
1784choice
1785 prompt "Which hash algorithm should modules be signed with?"
1786 depends on MODULE_SIG
1787 help
1788 This determines which sort of hashing algorithm will be used during
1789 signature generation. This algorithm _must_ be built into the kernel
1790 directly so that signature verification can take place. It is not
1791 possible to load a signed module containing the algorithm to check
1792 the signature on that module.
1793
1794config MODULE_SIG_SHA1
1795 bool "Sign modules with SHA-1"
1796 select CRYPTO_SHA1
1797
1798config MODULE_SIG_SHA224
1799 bool "Sign modules with SHA-224"
1800 select CRYPTO_SHA256
1801
1802config MODULE_SIG_SHA256
1803 bool "Sign modules with SHA-256"
1804 select CRYPTO_SHA256
1805
1806config MODULE_SIG_SHA384
1807 bool "Sign modules with SHA-384"
1808 select CRYPTO_SHA512
1809
1810config MODULE_SIG_SHA512
1811 bool "Sign modules with SHA-512"
1812 select CRYPTO_SHA512
1813
1814endchoice
1815
1816config MODULE_SIG_HASH
1817 string
1818 depends on MODULE_SIG
1819 default "sha1" if MODULE_SIG_SHA1
1820 default "sha224" if MODULE_SIG_SHA224
1821 default "sha256" if MODULE_SIG_SHA256
1822 default "sha384" if MODULE_SIG_SHA384
1823 default "sha512" if MODULE_SIG_SHA512
1824
1825config MODULE_COMPRESS
1826 bool "Compress modules on installation"
1827 depends on MODULES
1828 help
1829
1830 Compresses kernel modules when 'make modules_install' is run; gzip or
1831 xz depending on "Compression algorithm" below.
1832
1833 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
1834
1835 Out-of-tree kernel modules installed using Kbuild will also be
1836 compressed upon installation.
1837
1838 Note: for modules inside an initrd or initramfs, it's more efficient
1839 to compress the whole initrd or initramfs instead.
1840
1841 Note: This is fully compatible with signed modules.
1842
1843 If in doubt, say N.
1844
1845choice
1846 prompt "Compression algorithm"
1847 depends on MODULE_COMPRESS
1848 default MODULE_COMPRESS_GZIP
1849 help
1850 This determines which sort of compression will be used during
1851 'make modules_install'.
1852
1853 GZIP (default) and XZ are supported.
1854
1855config MODULE_COMPRESS_GZIP
1856 bool "GZIP"
1857
1858config MODULE_COMPRESS_XZ
1859 bool "XZ"
1860
1861endchoice
1862
1863config TRIM_UNUSED_KSYMS
1864 bool "Trim unused exported kernel symbols"
1865 depends on MODULES && !UNUSED_SYMBOLS
1866 help
1867 The kernel and some modules make many symbols available for
1868 other modules to use via EXPORT_SYMBOL() and variants. Depending
1869 on the set of modules being selected in your kernel configuration,
1870 many of those exported symbols might never be used.
1871
1872 This option allows for unused exported symbols to be dropped from
1873 the build. In turn, this provides the compiler more opportunities
1874 (especially when using LTO) for optimizing the code and reducing
1875 binary size. This might have some security advantages as well.
1876
1877 If unsure, or if you need to build out-of-tree modules, say N.
1878
1879endif
1880
1881config MODULES_TREE_LOOKUP
1882 def_bool y
1883 depends on PERF_EVENTS || TRACING
1884
1885config INIT_ALL_POSSIBLE
1886 bool
1887 help
1888 Back when each arch used to define their own cpu_online_mask and
1889 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1890 with all 1s, and others with all 0s. When they were centralised,
1891 it was better to provide this option than to break all the archs
1892 and have several arch maintainers pursuing me down dark alleys.
1893
1894source "block/Kconfig"
1895
1896config PREEMPT_NOTIFIERS
1897 bool
1898
1899config PADATA
1900 depends on SMP
1901 bool
1902
1903config ASN1
1904 tristate
1905 help
1906 Build a simple ASN.1 grammar compiler that produces a bytecode output
1907 that can be interpreted by the ASN.1 stream decoder and used to
1908 inform it as to what tags are to be expected in a stream and what
1909 functions to call on what tags.
1910
1911source "kernel/Kconfig.locks"
1912
