1 # SPDX-License-Identifier: GPL-2.0-only
6 default "/lib/modules/$(shell,uname -r)/.config"
7 default "/etc/kernel-config"
8 default "/boot/config-$(shell,uname -r)"
10 default "arch/$(ARCH)/defconfig"
13 def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc)
17 default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC
21 def_bool $(success,$(CC) --version | head -n 1 | grep -q clang)
25 default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
28 def_bool $(success,$(srctree)/scripts/cc-can-link.sh $(CC))
30 config CC_HAS_ASM_GOTO
31 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
33 config TOOLS_SUPPORT_RELR
34 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
36 config CC_HAS_ASM_INLINE
37 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
39 config CC_HAS_WARN_MAYBE_UNINITIALIZED
40 def_bool $(cc-option,-Wmaybe-uninitialized)
42 GCC >= 4.7 supports this option.
44 config CC_DISABLE_WARN_MAYBE_UNINITIALIZED
46 depends on CC_HAS_WARN_MAYBE_UNINITIALIZED
47 default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9
49 GCC's -Wmaybe-uninitialized is not reliable by definition.
50 Lots of false positive warnings are produced in some cases.
52 If this option is enabled, -Wno-maybe-uninitialzed is passed
53 to the compiler to suppress maybe-uninitialized warnings.
62 config BUILDTIME_TABLE_SORT
65 config THREAD_INFO_IN_TASK
68 Select this to move thread_info off the stack into task_struct. To
69 make this work, an arch will need to remove all thread_info fields
70 except flags and fix any runtime bugs.
72 One subtle change that will be needed is to use try_get_task_stack()
73 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
82 depends on BROKEN || !SMP
85 config INIT_ENV_ARG_LIMIT
90 Maximum of each of the number of arguments and environment
91 variables passed to init from the kernel command line.
94 bool "Compile also drivers which will not load"
98 Some drivers can be compiled on a different platform than they are
99 intended to be run on. Despite they cannot be loaded there (or even
100 when they load they cannot be used due to missing HW support),
101 developers still, opposing to distributors, might want to build such
102 drivers to compile-test them.
104 If you are a developer and want to build everything available, say Y
105 here. If you are a user/distributor, say N here to exclude useless
106 drivers to be distributed.
108 config UAPI_HEADER_TEST
109 bool "Compile test UAPI headers"
110 depends on HEADERS_INSTALL && CC_CAN_LINK
112 Compile test headers exported to user-space to ensure they are
113 self-contained, i.e. compilable as standalone units.
115 If you are a developer or tester and want to ensure the exported
116 headers are self-contained, say Y here. Otherwise, choose N.
119 string "Local version - append to kernel release"
121 Append an extra string to the end of your kernel version.
122 This will show up when you type uname, for example.
123 The string you set here will be appended after the contents of
124 any files with a filename matching localversion* in your
125 object and source tree, in that order. Your total string can
126 be a maximum of 64 characters.
128 config LOCALVERSION_AUTO
129 bool "Automatically append version information to the version string"
131 depends on !COMPILE_TEST
133 This will try to automatically determine if the current tree is a
134 release tree by looking for git tags that belong to the current
135 top of tree revision.
137 A string of the format -gxxxxxxxx will be added to the localversion
138 if a git-based tree is found. The string generated by this will be
139 appended after any matching localversion* files, and after the value
140 set in CONFIG_LOCALVERSION.
142 (The actual string used here is the first eight characters produced
143 by running the command:
145 $ git rev-parse --verify HEAD
147 which is done within the script "scripts/setlocalversion".)
150 string "Build ID Salt"
153 The build ID is used to link binaries and their debug info. Setting
154 this option will use the value in the calculation of the build id.
155 This is mostly useful for distributions which want to ensure the
156 build is unique between builds. It's safe to leave the default.
158 config HAVE_KERNEL_GZIP
161 config HAVE_KERNEL_BZIP2
164 config HAVE_KERNEL_LZMA
167 config HAVE_KERNEL_XZ
170 config HAVE_KERNEL_LZO
173 config HAVE_KERNEL_LZ4
176 config HAVE_KERNEL_UNCOMPRESSED
180 prompt "Kernel compression mode"
182 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED
184 The linux kernel is a kind of self-extracting executable.
185 Several compression algorithms are available, which differ
186 in efficiency, compression and decompression speed.
187 Compression speed is only relevant when building a kernel.
188 Decompression speed is relevant at each boot.
190 If you have any problems with bzip2 or lzma compressed
191 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
192 version of this functionality (bzip2 only), for 2.4, was
193 supplied by Christian Ludwig)
195 High compression options are mostly useful for users, who
196 are low on disk space (embedded systems), but for whom ram
199 If in doubt, select 'gzip'
203 depends on HAVE_KERNEL_GZIP
205 The old and tried gzip compression. It provides a good balance
206 between compression ratio and decompression speed.
210 depends on HAVE_KERNEL_BZIP2
212 Its compression ratio and speed is intermediate.
213 Decompression speed is slowest among the choices. The kernel
214 size is about 10% smaller with bzip2, in comparison to gzip.
215 Bzip2 uses a large amount of memory. For modern kernels you
216 will need at least 8MB RAM or more for booting.
220 depends on HAVE_KERNEL_LZMA
222 This compression algorithm's ratio is best. Decompression speed
223 is between gzip and bzip2. Compression is slowest.
224 The kernel size is about 33% smaller with LZMA in comparison to gzip.
228 depends on HAVE_KERNEL_XZ
230 XZ uses the LZMA2 algorithm and instruction set specific
231 BCJ filters which can improve compression ratio of executable
232 code. The size of the kernel is about 30% smaller with XZ in
233 comparison to gzip. On architectures for which there is a BCJ
234 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
235 will create a few percent smaller kernel than plain LZMA.
237 The speed is about the same as with LZMA: The decompression
238 speed of XZ is better than that of bzip2 but worse than gzip
239 and LZO. Compression is slow.
243 depends on HAVE_KERNEL_LZO
245 Its compression ratio is the poorest among the choices. The kernel
246 size is about 10% bigger than gzip; however its speed
247 (both compression and decompression) is the fastest.
251 depends on HAVE_KERNEL_LZ4
253 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
254 A preliminary version of LZ4 de/compression tool is available at
255 <https://code.google.com/p/lz4/>.
257 Its compression ratio is worse than LZO. The size of the kernel
258 is about 8% bigger than LZO. But the decompression speed is
261 config KERNEL_UNCOMPRESSED
263 depends on HAVE_KERNEL_UNCOMPRESSED
265 Produce uncompressed kernel image. This option is usually not what
266 you want. It is useful for debugging the kernel in slow simulation
267 environments, where decompressing and moving the kernel is awfully
268 slow. This option allows early boot code to skip the decompressor
269 and jump right at uncompressed kernel image.
273 config DEFAULT_HOSTNAME
274 string "Default hostname"
277 This option determines the default system hostname before userspace
278 calls sethostname(2). The kernel traditionally uses "(none)" here,
279 but you may wish to use a different default here to make a minimal
280 system more usable with less configuration.
283 # For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
284 # add proper SWAP support to them, in which case this can be remove.
290 bool "Support for paging of anonymous memory (swap)"
291 depends on MMU && BLOCK && !ARCH_NO_SWAP
294 This option allows you to choose whether you want to have support
295 for so called swap devices or swap files in your kernel that are
296 used to provide more virtual memory than the actual RAM present
297 in your computer. If unsure say Y.
302 Inter Process Communication is a suite of library functions and
303 system calls which let processes (running programs) synchronize and
304 exchange information. It is generally considered to be a good thing,
305 and some programs won't run unless you say Y here. In particular, if
306 you want to run the DOS emulator dosemu under Linux (read the
307 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
308 you'll need to say Y here.
310 You can find documentation about IPC with "info ipc" and also in
311 section 6.4 of the Linux Programmer's Guide, available from
312 <http://www.tldp.org/guides.html>.
314 config SYSVIPC_SYSCTL
321 bool "POSIX Message Queues"
324 POSIX variant of message queues is a part of IPC. In POSIX message
325 queues every message has a priority which decides about succession
326 of receiving it by a process. If you want to compile and run
327 programs written e.g. for Solaris with use of its POSIX message
328 queues (functions mq_*) say Y here.
330 POSIX message queues are visible as a filesystem called 'mqueue'
331 and can be mounted somewhere if you want to do filesystem
332 operations on message queues.
336 config POSIX_MQUEUE_SYSCTL
338 depends on POSIX_MQUEUE
342 config CROSS_MEMORY_ATTACH
343 bool "Enable process_vm_readv/writev syscalls"
347 Enabling this option adds the system calls process_vm_readv and
348 process_vm_writev which allow a process with the correct privileges
349 to directly read from or write to another process' address space.
350 See the man page for more details.
353 bool "uselib syscall"
354 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
356 This option enables the uselib syscall, a system call used in the
357 dynamic linker from libc5 and earlier. glibc does not use this
358 system call. If you intend to run programs built on libc5 or
359 earlier, you may need to enable this syscall. Current systems
360 running glibc can safely disable this.
363 bool "Auditing support"
366 Enable auditing infrastructure that can be used with another
367 kernel subsystem, such as SELinux (which requires this for
368 logging of avc messages output). System call auditing is included
369 on architectures which support it.
371 config HAVE_ARCH_AUDITSYSCALL
376 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
379 source "kernel/irq/Kconfig"
380 source "kernel/time/Kconfig"
381 source "kernel/Kconfig.preempt"
383 menu "CPU/Task time and stats accounting"
385 config VIRT_CPU_ACCOUNTING
389 prompt "Cputime accounting"
390 default TICK_CPU_ACCOUNTING if !PPC64
391 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
393 # Kind of a stub config for the pure tick based cputime accounting
394 config TICK_CPU_ACCOUNTING
395 bool "Simple tick based cputime accounting"
396 depends on !S390 && !NO_HZ_FULL
398 This is the basic tick based cputime accounting that maintains
399 statistics about user, system and idle time spent on per jiffies
404 config VIRT_CPU_ACCOUNTING_NATIVE
405 bool "Deterministic task and CPU time accounting"
406 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
407 select VIRT_CPU_ACCOUNTING
409 Select this option to enable more accurate task and CPU time
410 accounting. This is done by reading a CPU counter on each
411 kernel entry and exit and on transitions within the kernel
412 between system, softirq and hardirq state, so there is a
413 small performance impact. In the case of s390 or IBM POWER > 5,
414 this also enables accounting of stolen time on logically-partitioned
417 config VIRT_CPU_ACCOUNTING_GEN
418 bool "Full dynticks CPU time accounting"
419 depends on HAVE_CONTEXT_TRACKING
420 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
421 depends on GENERIC_CLOCKEVENTS
422 select VIRT_CPU_ACCOUNTING
423 select CONTEXT_TRACKING
425 Select this option to enable task and CPU time accounting on full
426 dynticks systems. This accounting is implemented by watching every
427 kernel-user boundaries using the context tracking subsystem.
428 The accounting is thus performed at the expense of some significant
431 For now this is only useful if you are working on the full
432 dynticks subsystem development.
438 config IRQ_TIME_ACCOUNTING
439 bool "Fine granularity task level IRQ time accounting"
440 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
442 Select this option to enable fine granularity task irq time
443 accounting. This is done by reading a timestamp on each
444 transitions between softirq and hardirq state, so there can be a
445 small performance impact.
447 If in doubt, say N here.
449 config HAVE_SCHED_AVG_IRQ
451 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
454 config BSD_PROCESS_ACCT
455 bool "BSD Process Accounting"
458 If you say Y here, a user level program will be able to instruct the
459 kernel (via a special system call) to write process accounting
460 information to a file: whenever a process exits, information about
461 that process will be appended to the file by the kernel. The
462 information includes things such as creation time, owning user,
463 command name, memory usage, controlling terminal etc. (the complete
464 list is in the struct acct in <file:include/linux/acct.h>). It is
465 up to the user level program to do useful things with this
466 information. This is generally a good idea, so say Y.
468 config BSD_PROCESS_ACCT_V3
469 bool "BSD Process Accounting version 3 file format"
470 depends on BSD_PROCESS_ACCT
473 If you say Y here, the process accounting information is written
474 in a new file format that also logs the process IDs of each
475 process and its parent. Note that this file format is incompatible
476 with previous v0/v1/v2 file formats, so you will need updated tools
477 for processing it. A preliminary version of these tools is available
478 at <http://www.gnu.org/software/acct/>.
481 bool "Export task/process statistics through netlink"
486 Export selected statistics for tasks/processes through the
487 generic netlink interface. Unlike BSD process accounting, the
488 statistics are available during the lifetime of tasks/processes as
489 responses to commands. Like BSD accounting, they are sent to user
494 config TASK_DELAY_ACCT
495 bool "Enable per-task delay accounting"
499 Collect information on time spent by a task waiting for system
500 resources like cpu, synchronous block I/O completion and swapping
501 in pages. Such statistics can help in setting a task's priorities
502 relative to other tasks for cpu, io, rss limits etc.
507 bool "Enable extended accounting over taskstats"
510 Collect extended task accounting data and send the data
511 to userland for processing over the taskstats interface.
515 config TASK_IO_ACCOUNTING
516 bool "Enable per-task storage I/O accounting"
517 depends on TASK_XACCT
519 Collect information on the number of bytes of storage I/O which this
525 bool "Pressure stall information tracking"
527 Collect metrics that indicate how overcommitted the CPU, memory,
528 and IO capacity are in the system.
530 If you say Y here, the kernel will create /proc/pressure/ with the
531 pressure statistics files cpu, memory, and io. These will indicate
532 the share of walltime in which some or all tasks in the system are
533 delayed due to contention of the respective resource.
535 In kernels with cgroup support, cgroups (cgroup2 only) will
536 have cpu.pressure, memory.pressure, and io.pressure files,
537 which aggregate pressure stalls for the grouped tasks only.
539 For more details see Documentation/accounting/psi.rst.
543 config PSI_DEFAULT_DISABLED
544 bool "Require boot parameter to enable pressure stall information tracking"
548 If set, pressure stall information tracking will be disabled
549 per default but can be enabled through passing psi=1 on the
550 kernel commandline during boot.
552 This feature adds some code to the task wakeup and sleep
553 paths of the scheduler. The overhead is too low to affect
554 common scheduling-intense workloads in practice (such as
555 webservers, memcache), but it does show up in artificial
556 scheduler stress tests, such as hackbench.
558 If you are paranoid and not sure what the kernel will be
563 endmenu # "CPU/Task time and stats accounting"
567 depends on SMP || COMPILE_TEST
570 Make sure that CPUs running critical tasks are not disturbed by
571 any source of "noise" such as unbound workqueues, timers, kthreads...
572 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
573 the "isolcpus=" boot parameter.
577 source "kernel/rcu/Kconfig"
584 tristate "Kernel .config support"
586 This option enables the complete Linux kernel ".config" file
587 contents to be saved in the kernel. It provides documentation
588 of which kernel options are used in a running kernel or in an
589 on-disk kernel. This information can be extracted from the kernel
590 image file with the script scripts/extract-ikconfig and used as
591 input to rebuild the current kernel or to build another kernel.
592 It can also be extracted from a running kernel by reading
593 /proc/config.gz if enabled (below).
596 bool "Enable access to .config through /proc/config.gz"
597 depends on IKCONFIG && PROC_FS
599 This option enables access to the kernel configuration file
600 through /proc/config.gz.
603 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
606 This option enables access to the in-kernel headers that are generated during
607 the build process. These can be used to build eBPF tracing programs,
608 or similar programs. If you build the headers as a module, a module called
609 kheaders.ko is built which can be loaded on-demand to get access to headers.
612 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
617 Select the minimal kernel log buffer size as a power of 2.
618 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
619 parameter, see below. Any higher size also might be forced
620 by "log_buf_len" boot parameter.
630 config LOG_CPU_MAX_BUF_SHIFT
631 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
634 default 12 if !BASE_SMALL
635 default 0 if BASE_SMALL
638 This option allows to increase the default ring buffer size
639 according to the number of CPUs. The value defines the contribution
640 of each CPU as a power of 2. The used space is typically only few
641 lines however it might be much more when problems are reported,
644 The increased size means that a new buffer has to be allocated and
645 the original static one is unused. It makes sense only on systems
646 with more CPUs. Therefore this value is used only when the sum of
647 contributions is greater than the half of the default kernel ring
648 buffer as defined by LOG_BUF_SHIFT. The default values are set
649 so that more than 64 CPUs are needed to trigger the allocation.
651 Also this option is ignored when "log_buf_len" kernel parameter is
652 used as it forces an exact (power of two) size of the ring buffer.
654 The number of possible CPUs is used for this computation ignoring
655 hotplugging making the computation optimal for the worst case
656 scenario while allowing a simple algorithm to be used from bootup.
658 Examples shift values and their meaning:
659 17 => 128 KB for each CPU
660 16 => 64 KB for each CPU
661 15 => 32 KB for each CPU
662 14 => 16 KB for each CPU
663 13 => 8 KB for each CPU
664 12 => 4 KB for each CPU
666 config PRINTK_SAFE_LOG_BUF_SHIFT
667 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
672 Select the size of an alternate printk per-CPU buffer where messages
673 printed from usafe contexts are temporary stored. One example would
674 be NMI messages, another one - printk recursion. The messages are
675 copied to the main log buffer in a safe context to avoid a deadlock.
676 The value defines the size as a power of 2.
678 Those messages are rare and limited. The largest one is when
679 a backtrace is printed. It usually fits into 4KB. Select
680 8KB if you want to be on the safe side.
683 17 => 128 KB for each CPU
684 16 => 64 KB for each CPU
685 15 => 32 KB for each CPU
686 14 => 16 KB for each CPU
687 13 => 8 KB for each CPU
688 12 => 4 KB for each CPU
691 # Architectures with an unreliable sched_clock() should select this:
693 config HAVE_UNSTABLE_SCHED_CLOCK
696 config GENERIC_SCHED_CLOCK
699 menu "Scheduler features"
702 bool "Enable utilization clamping for RT/FAIR tasks"
703 depends on CPU_FREQ_GOV_SCHEDUTIL
705 This feature enables the scheduler to track the clamped utilization
706 of each CPU based on RUNNABLE tasks scheduled on that CPU.
708 With this option, the user can specify the min and max CPU
709 utilization allowed for RUNNABLE tasks. The max utilization defines
710 the maximum frequency a task should use while the min utilization
711 defines the minimum frequency it should use.
713 Both min and max utilization clamp values are hints to the scheduler,
714 aiming at improving its frequency selection policy, but they do not
715 enforce or grant any specific bandwidth for tasks.
719 config UCLAMP_BUCKETS_COUNT
720 int "Number of supported utilization clamp buckets"
723 depends on UCLAMP_TASK
725 Defines the number of clamp buckets to use. The range of each bucket
726 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
727 number of clamp buckets the finer their granularity and the higher
728 the precision of clamping aggregation and tracking at run-time.
730 For example, with the minimum configuration value we will have 5
731 clamp buckets tracking 20% utilization each. A 25% boosted tasks will
732 be refcounted in the [20..39]% bucket and will set the bucket clamp
733 effective value to 25%.
734 If a second 30% boosted task should be co-scheduled on the same CPU,
735 that task will be refcounted in the same bucket of the first task and
736 it will boost the bucket clamp effective value to 30%.
737 The clamp effective value of a bucket is reset to its nominal value
738 (20% in the example above) when there are no more tasks refcounted in
741 An additional boost/capping margin can be added to some tasks. In the
742 example above the 25% task will be boosted to 30% until it exits the
743 CPU. If that should be considered not acceptable on certain systems,
744 it's always possible to reduce the margin by increasing the number of
745 clamp buckets to trade off used memory for run-time tracking
748 If in doubt, use the default value.
753 # For architectures that want to enable the support for NUMA-affine scheduler
756 config ARCH_SUPPORTS_NUMA_BALANCING
760 # For architectures that prefer to flush all TLBs after a number of pages
761 # are unmapped instead of sending one IPI per page to flush. The architecture
762 # must provide guarantees on what happens if a clean TLB cache entry is
763 # written after the unmap. Details are in mm/rmap.c near the check for
764 # should_defer_flush. The architecture should also consider if the full flush
765 # and the refill costs are offset by the savings of sending fewer IPIs.
766 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
771 depends on !$(cc-option,-D__SIZEOF_INT128__=0)
774 # For architectures that know their GCC __int128 support is sound
776 config ARCH_SUPPORTS_INT128
779 # For architectures that (ab)use NUMA to represent different memory regions
780 # all cpu-local but of different latencies, such as SuperH.
782 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
785 config NUMA_BALANCING
786 bool "Memory placement aware NUMA scheduler"
787 depends on ARCH_SUPPORTS_NUMA_BALANCING
788 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
789 depends on SMP && NUMA && MIGRATION
791 This option adds support for automatic NUMA aware memory/task placement.
792 The mechanism is quite primitive and is based on migrating memory when
793 it has references to the node the task is running on.
795 This system will be inactive on UMA systems.
797 config NUMA_BALANCING_DEFAULT_ENABLED
798 bool "Automatically enable NUMA aware memory/task placement"
800 depends on NUMA_BALANCING
802 If set, automatic NUMA balancing will be enabled if running on a NUMA
806 bool "Control Group support"
809 This option adds support for grouping sets of processes together, for
810 use with process control subsystems such as Cpusets, CFS, memory
811 controls or device isolation.
813 - Documentation/scheduler/sched-design-CFS.rst (CFS)
814 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
815 and resource control)
825 bool "Memory controller"
829 Provides control over the memory footprint of tasks in a cgroup.
832 bool "Swap controller"
833 depends on MEMCG && SWAP
835 Provides control over the swap space consumed by tasks in a cgroup.
837 config MEMCG_SWAP_ENABLED
838 bool "Swap controller enabled by default"
839 depends on MEMCG_SWAP
842 Memory Resource Controller Swap Extension comes with its price in
843 a bigger memory consumption. General purpose distribution kernels
844 which want to enable the feature but keep it disabled by default
845 and let the user enable it by swapaccount=1 boot command line
846 parameter should have this option unselected.
847 For those who want to have the feature enabled by default should
848 select this option (if, for some reason, they need to disable it
849 then swapaccount=0 does the trick).
853 depends on MEMCG && !SLOB
861 Generic block IO controller cgroup interface. This is the common
862 cgroup interface which should be used by various IO controlling
865 Currently, CFQ IO scheduler uses it to recognize task groups and
866 control disk bandwidth allocation (proportional time slice allocation)
867 to such task groups. It is also used by bio throttling logic in
868 block layer to implement upper limit in IO rates on a device.
870 This option only enables generic Block IO controller infrastructure.
871 One needs to also enable actual IO controlling logic/policy. For
872 enabling proportional weight division of disk bandwidth in CFQ, set
873 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
874 CONFIG_BLK_DEV_THROTTLING=y.
876 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
878 config CGROUP_WRITEBACK
880 depends on MEMCG && BLK_CGROUP
883 menuconfig CGROUP_SCHED
884 bool "CPU controller"
887 This feature lets CPU scheduler recognize task groups and control CPU
888 bandwidth allocation to such task groups. It uses cgroups to group
892 config FAIR_GROUP_SCHED
893 bool "Group scheduling for SCHED_OTHER"
894 depends on CGROUP_SCHED
898 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
899 depends on FAIR_GROUP_SCHED
902 This option allows users to define CPU bandwidth rates (limits) for
903 tasks running within the fair group scheduler. Groups with no limit
904 set are considered to be unconstrained and will run with no
906 See Documentation/scheduler/sched-bwc.rst for more information.
908 config RT_GROUP_SCHED
909 bool "Group scheduling for SCHED_RR/FIFO"
910 depends on CGROUP_SCHED
913 This feature lets you explicitly allocate real CPU bandwidth
914 to task groups. If enabled, it will also make it impossible to
915 schedule realtime tasks for non-root users until you allocate
916 realtime bandwidth for them.
917 See Documentation/scheduler/sched-rt-group.rst for more information.
921 config UCLAMP_TASK_GROUP
922 bool "Utilization clamping per group of tasks"
923 depends on CGROUP_SCHED
924 depends on UCLAMP_TASK
927 This feature enables the scheduler to track the clamped utilization
928 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
930 When this option is enabled, the user can specify a min and max
931 CPU bandwidth which is allowed for each single task in a group.
932 The max bandwidth allows to clamp the maximum frequency a task
933 can use, while the min bandwidth allows to define a minimum
934 frequency a task will always use.
936 When task group based utilization clamping is enabled, an eventually
937 specified task-specific clamp value is constrained by the cgroup
938 specified clamp value. Both minimum and maximum task clamping cannot
939 be bigger than the corresponding clamping defined at task group level.
944 bool "PIDs controller"
946 Provides enforcement of process number limits in the scope of a
947 cgroup. Any attempt to fork more processes than is allowed in the
948 cgroup will fail. PIDs are fundamentally a global resource because it
949 is fairly trivial to reach PID exhaustion before you reach even a
950 conservative kmemcg limit. As a result, it is possible to grind a
951 system to halt without being limited by other cgroup policies. The
952 PIDs controller is designed to stop this from happening.
954 It should be noted that organisational operations (such as attaching
955 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
956 since the PIDs limit only affects a process's ability to fork, not to
960 bool "RDMA controller"
962 Provides enforcement of RDMA resources defined by IB stack.
963 It is fairly easy for consumers to exhaust RDMA resources, which
964 can result into resource unavailability to other consumers.
965 RDMA controller is designed to stop this from happening.
966 Attaching processes with active RDMA resources to the cgroup
967 hierarchy is allowed even if can cross the hierarchy's limit.
969 config CGROUP_FREEZER
970 bool "Freezer controller"
972 Provides a way to freeze and unfreeze all tasks in a
975 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
976 controller includes important in-kernel memory consumers per default.
978 If you're using cgroup2, say N.
980 config CGROUP_HUGETLB
981 bool "HugeTLB controller"
982 depends on HUGETLB_PAGE
986 Provides a cgroup controller for HugeTLB pages.
987 When you enable this, you can put a per cgroup limit on HugeTLB usage.
988 The limit is enforced during page fault. Since HugeTLB doesn't
989 support page reclaim, enforcing the limit at page fault time implies
990 that, the application will get SIGBUS signal if it tries to access
991 HugeTLB pages beyond its limit. This requires the application to know
992 beforehand how much HugeTLB pages it would require for its use. The
993 control group is tracked in the third page lru pointer. This means
994 that we cannot use the controller with huge page less than 3 pages.
997 bool "Cpuset controller"
1000 This option will let you create and manage CPUSETs which
1001 allow dynamically partitioning a system into sets of CPUs and
1002 Memory Nodes and assigning tasks to run only within those sets.
1003 This is primarily useful on large SMP or NUMA systems.
1007 config PROC_PID_CPUSET
1008 bool "Include legacy /proc/<pid>/cpuset file"
1012 config CGROUP_DEVICE
1013 bool "Device controller"
1015 Provides a cgroup controller implementing whitelists for
1016 devices which a process in the cgroup can mknod or open.
1018 config CGROUP_CPUACCT
1019 bool "Simple CPU accounting controller"
1021 Provides a simple controller for monitoring the
1022 total CPU consumed by the tasks in a cgroup.
1025 bool "Perf controller"
1026 depends on PERF_EVENTS
1028 This option extends the perf per-cpu mode to restrict monitoring
1029 to threads which belong to the cgroup specified and run on the
1035 bool "Support for eBPF programs attached to cgroups"
1036 depends on BPF_SYSCALL
1037 select SOCK_CGROUP_DATA
1039 Allow attaching eBPF programs to a cgroup using the bpf(2)
1040 syscall command BPF_PROG_ATTACH.
1042 In which context these programs are accessed depends on the type
1043 of attachment. For instance, programs that are attached using
1044 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1048 bool "Debug controller"
1050 depends on DEBUG_KERNEL
1052 This option enables a simple controller that exports
1053 debugging information about the cgroups framework. This
1054 controller is for control cgroup debugging only. Its
1055 interfaces are not stable.
1059 config SOCK_CGROUP_DATA
1065 menuconfig NAMESPACES
1066 bool "Namespaces support" if EXPERT
1067 depends on MULTIUSER
1070 Provides the way to make tasks work with different objects using
1071 the same id. For example same IPC id may refer to different objects
1072 or same user id or pid may refer to different tasks when used in
1073 different namespaces.
1078 bool "UTS namespace"
1081 In this namespace tasks see different info provided with the
1085 bool "TIME namespace"
1086 depends on GENERIC_VDSO_TIME_NS
1089 In this namespace boottime and monotonic clocks can be set.
1090 The time will keep going with the same pace.
1093 bool "IPC namespace"
1094 depends on (SYSVIPC || POSIX_MQUEUE)
1097 In this namespace tasks work with IPC ids which correspond to
1098 different IPC objects in different namespaces.
1101 bool "User namespace"
1104 This allows containers, i.e. vservers, to use user namespaces
1105 to provide different user info for different servers.
1107 When user namespaces are enabled in the kernel it is
1108 recommended that the MEMCG option also be enabled and that
1109 user-space use the memory control groups to limit the amount
1110 of memory a memory unprivileged users can use.
1115 bool "PID Namespaces"
1118 Support process id namespaces. This allows having multiple
1119 processes with the same pid as long as they are in different
1120 pid namespaces. This is a building block of containers.
1123 bool "Network namespace"
1127 Allow user space to create what appear to be multiple instances
1128 of the network stack.
1132 config CHECKPOINT_RESTORE
1133 bool "Checkpoint/restore support"
1134 select PROC_CHILDREN
1137 Enables additional kernel features in a sake of checkpoint/restore.
1138 In particular it adds auxiliary prctl codes to setup process text,
1139 data and heap segment sizes, and a few additional /proc filesystem
1142 If unsure, say N here.
1144 config SCHED_AUTOGROUP
1145 bool "Automatic process group scheduling"
1148 select FAIR_GROUP_SCHED
1150 This option optimizes the scheduler for common desktop workloads by
1151 automatically creating and populating task groups. This separation
1152 of workloads isolates aggressive CPU burners (like build jobs) from
1153 desktop applications. Task group autogeneration is currently based
1156 config SYSFS_DEPRECATED
1157 bool "Enable deprecated sysfs features to support old userspace tools"
1161 This option adds code that switches the layout of the "block" class
1162 devices, to not show up in /sys/class/block/, but only in
1165 This switch is only active when the sysfs.deprecated=1 boot option is
1166 passed or the SYSFS_DEPRECATED_V2 option is set.
1168 This option allows new kernels to run on old distributions and tools,
1169 which might get confused by /sys/class/block/. Since 2007/2008 all
1170 major distributions and tools handle this just fine.
1172 Recent distributions and userspace tools after 2009/2010 depend on
1173 the existence of /sys/class/block/, and will not work with this
1176 Only if you are using a new kernel on an old distribution, you might
1179 config SYSFS_DEPRECATED_V2
1180 bool "Enable deprecated sysfs features by default"
1183 depends on SYSFS_DEPRECATED
1185 Enable deprecated sysfs by default.
1187 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1190 Only if you are using a new kernel on an old distribution, you might
1191 need to say Y here. Even then, odds are you would not need it
1192 enabled, you can always pass the boot option if absolutely necessary.
1195 bool "Kernel->user space relay support (formerly relayfs)"
1198 This option enables support for relay interface support in
1199 certain file systems (such as debugfs).
1200 It is designed to provide an efficient mechanism for tools and
1201 facilities to relay large amounts of data from kernel space to
1206 config BLK_DEV_INITRD
1207 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1209 The initial RAM filesystem is a ramfs which is loaded by the
1210 boot loader (loadlin or lilo) and that is mounted as root
1211 before the normal boot procedure. It is typically used to
1212 load modules needed to mount the "real" root file system,
1213 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1215 If RAM disk support (BLK_DEV_RAM) is also included, this
1216 also enables initial RAM disk (initrd) support and adds
1217 15 Kbytes (more on some other architectures) to the kernel size.
1223 source "usr/Kconfig"
1228 bool "Boot config support"
1229 depends on BLK_DEV_INITRD
1233 Extra boot config allows system admin to pass a config file as
1234 complemental extension of kernel cmdline when booting.
1235 The boot config file must be attached at the end of initramfs
1236 with checksum and size.
1237 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1242 prompt "Compiler optimization level"
1243 default CC_OPTIMIZE_FOR_PERFORMANCE
1245 config CC_OPTIMIZE_FOR_PERFORMANCE
1246 bool "Optimize for performance (-O2)"
1248 This is the default optimization level for the kernel, building
1249 with the "-O2" compiler flag for best performance and most
1250 helpful compile-time warnings.
1252 config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1253 bool "Optimize more for performance (-O3)"
1255 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives
1257 Choosing this option will pass "-O3" to your compiler to optimize
1258 the kernel yet more for performance.
1260 config CC_OPTIMIZE_FOR_SIZE
1261 bool "Optimize for size (-Os)"
1262 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives
1264 Choosing this option will pass "-Os" to your compiler resulting
1265 in a smaller kernel.
1269 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1272 This requires that the arch annotates or otherwise protects
1273 its external entry points from being discarded. Linker scripts
1274 must also merge .text.*, .data.*, and .bss.* correctly into
1275 output sections. Care must be taken not to pull in unrelated
1276 sections (e.g., '.text.init'). Typically '.' in section names
1277 is used to distinguish them from label names / C identifiers.
1279 config LD_DEAD_CODE_DATA_ELIMINATION
1280 bool "Dead code and data elimination (EXPERIMENTAL)"
1281 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1283 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800)
1284 depends on $(cc-option,-ffunction-sections -fdata-sections)
1285 depends on $(ld-option,--gc-sections)
1287 Enable this if you want to do dead code and data elimination with
1288 the linker by compiling with -ffunction-sections -fdata-sections,
1289 and linking with --gc-sections.
1291 This can reduce on disk and in-memory size of the kernel
1292 code and static data, particularly for small configs and
1293 on small systems. This has the possibility of introducing
1294 silently broken kernel if the required annotations are not
1295 present. This option is not well tested yet, so use at your
1304 config SYSCTL_EXCEPTION_TRACE
1307 Enable support for /proc/sys/debug/exception-trace.
1309 config SYSCTL_ARCH_UNALIGN_NO_WARN
1312 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1313 Allows arch to define/use @no_unaligned_warning to possibly warn
1314 about unaligned access emulation going on under the hood.
1316 config SYSCTL_ARCH_UNALIGN_ALLOW
1319 Enable support for /proc/sys/kernel/unaligned-trap
1320 Allows arches to define/use @unaligned_enabled to runtime toggle
1321 the unaligned access emulation.
1322 see arch/parisc/kernel/unaligned.c for reference
1324 config HAVE_PCSPKR_PLATFORM
1327 # interpreter that classic socket filters depend on
1332 bool "Configure standard kernel features (expert users)"
1333 # Unhide debug options, to make the on-by-default options visible
1336 This option allows certain base kernel options and settings
1337 to be disabled or tweaked. This is for specialized
1338 environments which can tolerate a "non-standard" kernel.
1339 Only use this if you really know what you are doing.
1342 bool "Enable 16-bit UID system calls" if EXPERT
1343 depends on HAVE_UID16 && MULTIUSER
1346 This enables the legacy 16-bit UID syscall wrappers.
1349 bool "Multiple users, groups and capabilities support" if EXPERT
1352 This option enables support for non-root users, groups and
1355 If you say N here, all processes will run with UID 0, GID 0, and all
1356 possible capabilities. Saying N here also compiles out support for
1357 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1360 If unsure, say Y here.
1362 config SGETMASK_SYSCALL
1363 bool "sgetmask/ssetmask syscalls support" if EXPERT
1364 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1366 sys_sgetmask and sys_ssetmask are obsolete system calls
1367 no longer supported in libc but still enabled by default in some
1370 If unsure, leave the default option here.
1372 config SYSFS_SYSCALL
1373 bool "Sysfs syscall support" if EXPERT
1376 sys_sysfs is an obsolete system call no longer supported in libc.
1377 Note that disabling this option is more secure but might break
1378 compatibility with some systems.
1380 If unsure say Y here.
1383 bool "open by fhandle syscalls" if EXPERT
1387 If you say Y here, a user level program will be able to map
1388 file names to handle and then later use the handle for
1389 different file system operations. This is useful in implementing
1390 userspace file servers, which now track files using handles instead
1391 of names. The handle would remain the same even if file names
1392 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1396 bool "Posix Clocks & timers" if EXPERT
1399 This includes native support for POSIX timers to the kernel.
1400 Some embedded systems have no use for them and therefore they
1401 can be configured out to reduce the size of the kernel image.
1403 When this option is disabled, the following syscalls won't be
1404 available: timer_create, timer_gettime: timer_getoverrun,
1405 timer_settime, timer_delete, clock_adjtime, getitimer,
1406 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1407 clock_getres and clock_nanosleep syscalls will be limited to
1408 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1414 bool "Enable support for printk" if EXPERT
1417 This option enables normal printk support. Removing it
1418 eliminates most of the message strings from the kernel image
1419 and makes the kernel more or less silent. As this makes it
1420 very difficult to diagnose system problems, saying N here is
1421 strongly discouraged.
1429 bool "BUG() support" if EXPERT
1432 Disabling this option eliminates support for BUG and WARN, reducing
1433 the size of your kernel image and potentially quietly ignoring
1434 numerous fatal conditions. You should only consider disabling this
1435 option for embedded systems with no facilities for reporting errors.
1441 bool "Enable ELF core dumps" if EXPERT
1443 Enable support for generating core dumps. Disabling saves about 4k.
1446 config PCSPKR_PLATFORM
1447 bool "Enable PC-Speaker support" if EXPERT
1448 depends on HAVE_PCSPKR_PLATFORM
1452 This option allows to disable the internal PC-Speaker
1453 support, saving some memory.
1457 bool "Enable full-sized data structures for core" if EXPERT
1459 Disabling this option reduces the size of miscellaneous core
1460 kernel data structures. This saves memory on small machines,
1461 but may reduce performance.
1464 bool "Enable futex support" if EXPERT
1468 Disabling this option will cause the kernel to be built without
1469 support for "fast userspace mutexes". The resulting kernel may not
1470 run glibc-based applications correctly.
1474 depends on FUTEX && RT_MUTEXES
1477 config HAVE_FUTEX_CMPXCHG
1481 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1482 is implemented and always working. This removes a couple of runtime
1486 bool "Enable eventpoll support" if EXPERT
1489 Disabling this option will cause the kernel to be built without
1490 support for epoll family of system calls.
1493 bool "Enable signalfd() system call" if EXPERT
1496 Enable the signalfd() system call that allows to receive signals
1497 on a file descriptor.
1502 bool "Enable timerfd() system call" if EXPERT
1505 Enable the timerfd() system call that allows to receive timer
1506 events on a file descriptor.
1511 bool "Enable eventfd() system call" if EXPERT
1514 Enable the eventfd() system call that allows to receive both
1515 kernel notification (ie. KAIO) or userspace notifications.
1520 bool "Use full shmem filesystem" if EXPERT
1524 The shmem is an internal filesystem used to manage shared memory.
1525 It is backed by swap and manages resource limits. It is also exported
1526 to userspace as tmpfs if TMPFS is enabled. Disabling this
1527 option replaces shmem and tmpfs with the much simpler ramfs code,
1528 which may be appropriate on small systems without swap.
1531 bool "Enable AIO support" if EXPERT
1534 This option enables POSIX asynchronous I/O which may by used
1535 by some high performance threaded applications. Disabling
1536 this option saves about 7k.
1539 bool "Enable IO uring support" if EXPERT
1544 This option enables support for the io_uring interface, enabling
1545 applications to submit and complete IO through submission and
1546 completion rings that are shared between the kernel and application.
1548 config ADVISE_SYSCALLS
1549 bool "Enable madvise/fadvise syscalls" if EXPERT
1552 This option enables the madvise and fadvise syscalls, used by
1553 applications to advise the kernel about their future memory or file
1554 usage, improving performance. If building an embedded system where no
1555 applications use these syscalls, you can disable this option to save
1559 bool "Enable membarrier() system call" if EXPERT
1562 Enable the membarrier() system call that allows issuing memory
1563 barriers across all running threads, which can be used to distribute
1564 the cost of user-space memory barriers asymmetrically by transforming
1565 pairs of memory barriers into pairs consisting of membarrier() and a
1571 bool "Load all symbols for debugging/ksymoops" if EXPERT
1574 Say Y here to let the kernel print out symbolic crash information and
1575 symbolic stack backtraces. This increases the size of the kernel
1576 somewhat, as all symbols have to be loaded into the kernel image.
1579 bool "Include all symbols in kallsyms"
1580 depends on DEBUG_KERNEL && KALLSYMS
1582 Normally kallsyms only contains the symbols of functions for nicer
1583 OOPS messages and backtraces (i.e., symbols from the text and inittext
1584 sections). This is sufficient for most cases. And only in very rare
1585 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1586 names of variables from the data sections, etc).
1588 This option makes sure that all symbols are loaded into the kernel
1589 image (i.e., symbols from all sections) in cost of increased kernel
1590 size (depending on the kernel configuration, it may be 300KiB or
1591 something like this).
1593 Say N unless you really need all symbols.
1595 config KALLSYMS_ABSOLUTE_PERCPU
1598 default X86_64 && SMP
1600 config KALLSYMS_BASE_RELATIVE
1605 Instead of emitting them as absolute values in the native word size,
1606 emit the symbol references in the kallsyms table as 32-bit entries,
1607 each containing a relative value in the range [base, base + U32_MAX]
1608 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1609 an absolute value in the range [0, S32_MAX] or a relative value in the
1610 range [base, base + S32_MAX], where base is the lowest relative symbol
1611 address encountered in the image.
1613 On 64-bit builds, this reduces the size of the address table by 50%,
1614 but more importantly, it results in entries whose values are build
1615 time constants, and no relocation pass is required at runtime to fix
1616 up the entries based on the runtime load address of the kernel.
1618 # end of the "standard kernel features (expert users)" menu
1620 # syscall, maps, verifier
1622 bool "Enable bpf() system call"
1627 Enable the bpf() system call that allows to manipulate eBPF
1628 programs and maps via file descriptors.
1630 config ARCH_WANT_DEFAULT_BPF_JIT
1633 config BPF_JIT_ALWAYS_ON
1634 bool "Permanently enable BPF JIT and remove BPF interpreter"
1635 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1637 Enables BPF JIT and removes BPF interpreter to avoid
1638 speculative execution of BPF instructions by the interpreter
1640 config BPF_JIT_DEFAULT_ON
1641 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
1642 depends on HAVE_EBPF_JIT && BPF_JIT
1645 bool "Enable userfaultfd() system call"
1648 Enable the userfaultfd() system call that allows to intercept and
1649 handle page faults in userland.
1651 config ARCH_HAS_MEMBARRIER_CALLBACKS
1654 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1658 bool "Enable rseq() system call" if EXPERT
1660 depends on HAVE_RSEQ
1663 Enable the restartable sequences system call. It provides a
1664 user-space cache for the current CPU number value, which
1665 speeds up getting the current CPU number from user-space,
1666 as well as an ABI to speed up user-space operations on
1673 bool "Enabled debugging of rseq() system call" if EXPERT
1674 depends on RSEQ && DEBUG_KERNEL
1676 Enable extra debugging checks for the rseq system call.
1681 bool "Embedded system"
1682 option allnoconfig_y
1685 This option should be enabled if compiling the kernel for
1686 an embedded system so certain expert options are available
1689 config HAVE_PERF_EVENTS
1692 See tools/perf/design.txt for details.
1694 config PERF_USE_VMALLOC
1697 See tools/perf/design.txt for details
1700 bool "PC/104 support" if EXPERT
1702 Expose PC/104 form factor device drivers and options available for
1703 selection and configuration. Enable this option if your target
1704 machine has a PC/104 bus.
1706 menu "Kernel Performance Events And Counters"
1709 bool "Kernel performance events and counters"
1710 default y if PROFILING
1711 depends on HAVE_PERF_EVENTS
1715 Enable kernel support for various performance events provided
1716 by software and hardware.
1718 Software events are supported either built-in or via the
1719 use of generic tracepoints.
1721 Most modern CPUs support performance events via performance
1722 counter registers. These registers count the number of certain
1723 types of hw events: such as instructions executed, cachemisses
1724 suffered, or branches mis-predicted - without slowing down the
1725 kernel or applications. These registers can also trigger interrupts
1726 when a threshold number of events have passed - and can thus be
1727 used to profile the code that runs on that CPU.
1729 The Linux Performance Event subsystem provides an abstraction of
1730 these software and hardware event capabilities, available via a
1731 system call and used by the "perf" utility in tools/perf/. It
1732 provides per task and per CPU counters, and it provides event
1733 capabilities on top of those.
1737 config DEBUG_PERF_USE_VMALLOC
1739 bool "Debug: use vmalloc to back perf mmap() buffers"
1740 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1741 select PERF_USE_VMALLOC
1743 Use vmalloc memory to back perf mmap() buffers.
1745 Mostly useful for debugging the vmalloc code on platforms
1746 that don't require it.
1752 config VM_EVENT_COUNTERS
1754 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1756 VM event counters are needed for event counts to be shown.
1757 This option allows the disabling of the VM event counters
1758 on EXPERT systems. /proc/vmstat will only show page counts
1759 if VM event counters are disabled.
1763 bool "Enable SLUB debugging support" if EXPERT
1764 depends on SLUB && SYSFS
1766 SLUB has extensive debug support features. Disabling these can
1767 result in significant savings in code size. This also disables
1768 SLUB sysfs support. /sys/slab will not exist and there will be
1769 no support for cache validation etc.
1771 config SLUB_MEMCG_SYSFS_ON
1773 bool "Enable memcg SLUB sysfs support by default" if EXPERT
1774 depends on SLUB && SYSFS && MEMCG
1776 SLUB creates a directory under /sys/kernel/slab for each
1777 allocation cache to host info and debug files. If memory
1778 cgroup is enabled, each cache can have per memory cgroup
1779 caches. SLUB can create the same sysfs directories for these
1780 caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1781 to a very high number of debug files being created. This is
1782 controlled by slub_memcg_sysfs boot parameter and this
1783 config option determines the parameter's default value.
1786 bool "Disable heap randomization"
1789 Randomizing heap placement makes heap exploits harder, but it
1790 also breaks ancient binaries (including anything libc5 based).
1791 This option changes the bootup default to heap randomization
1792 disabled, and can be overridden at runtime by setting
1793 /proc/sys/kernel/randomize_va_space to 2.
1795 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1798 prompt "Choose SLAB allocator"
1801 This option allows to select a slab allocator.
1805 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1807 The regular slab allocator that is established and known to work
1808 well in all environments. It organizes cache hot objects in
1809 per cpu and per node queues.
1812 bool "SLUB (Unqueued Allocator)"
1813 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1815 SLUB is a slab allocator that minimizes cache line usage
1816 instead of managing queues of cached objects (SLAB approach).
1817 Per cpu caching is realized using slabs of objects instead
1818 of queues of objects. SLUB can use memory efficiently
1819 and has enhanced diagnostics. SLUB is the default choice for
1824 bool "SLOB (Simple Allocator)"
1826 SLOB replaces the stock allocator with a drastically simpler
1827 allocator. SLOB is generally more space efficient but
1828 does not perform as well on large systems.
1832 config SLAB_MERGE_DEFAULT
1833 bool "Allow slab caches to be merged"
1836 For reduced kernel memory fragmentation, slab caches can be
1837 merged when they share the same size and other characteristics.
1838 This carries a risk of kernel heap overflows being able to
1839 overwrite objects from merged caches (and more easily control
1840 cache layout), which makes such heap attacks easier to exploit
1841 by attackers. By keeping caches unmerged, these kinds of exploits
1842 can usually only damage objects in the same cache. To disable
1843 merging at runtime, "slab_nomerge" can be passed on the kernel
1846 config SLAB_FREELIST_RANDOM
1848 depends on SLAB || SLUB
1849 bool "SLAB freelist randomization"
1851 Randomizes the freelist order used on creating new pages. This
1852 security feature reduces the predictability of the kernel slab
1853 allocator against heap overflows.
1855 config SLAB_FREELIST_HARDENED
1856 bool "Harden slab freelist metadata"
1859 Many kernel heap attacks try to target slab cache metadata and
1860 other infrastructure. This options makes minor performance
1861 sacrifices to harden the kernel slab allocator against common
1862 freelist exploit methods.
1864 config SHUFFLE_PAGE_ALLOCATOR
1865 bool "Page allocator randomization"
1866 default SLAB_FREELIST_RANDOM && ACPI_NUMA
1868 Randomization of the page allocator improves the average
1869 utilization of a direct-mapped memory-side-cache. See section
1870 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1871 6.2a specification for an example of how a platform advertises
1872 the presence of a memory-side-cache. There are also incidental
1873 security benefits as it reduces the predictability of page
1874 allocations to compliment SLAB_FREELIST_RANDOM, but the
1875 default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1876 10th order of pages is selected based on cache utilization
1879 While the randomization improves cache utilization it may
1880 negatively impact workloads on platforms without a cache. For
1881 this reason, by default, the randomization is enabled only
1882 after runtime detection of a direct-mapped memory-side-cache.
1883 Otherwise, the randomization may be force enabled with the
1884 'page_alloc.shuffle' kernel command line parameter.
1888 config SLUB_CPU_PARTIAL
1890 depends on SLUB && SMP
1891 bool "SLUB per cpu partial cache"
1893 Per cpu partial caches accelerate objects allocation and freeing
1894 that is local to a processor at the price of more indeterminism
1895 in the latency of the free. On overflow these caches will be cleared
1896 which requires the taking of locks that may cause latency spikes.
1897 Typically one would choose no for a realtime system.
1899 config MMAP_ALLOW_UNINITIALIZED
1900 bool "Allow mmapped anonymous memory to be uninitialized"
1901 depends on EXPERT && !MMU
1904 Normally, and according to the Linux spec, anonymous memory obtained
1905 from mmap() has its contents cleared before it is passed to
1906 userspace. Enabling this config option allows you to request that
1907 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1908 providing a huge performance boost. If this option is not enabled,
1909 then the flag will be ignored.
1911 This is taken advantage of by uClibc's malloc(), and also by
1912 ELF-FDPIC binfmt's brk and stack allocator.
1914 Because of the obvious security issues, this option should only be
1915 enabled on embedded devices where you control what is run in
1916 userspace. Since that isn't generally a problem on no-MMU systems,
1917 it is normally safe to say Y here.
1919 See Documentation/nommu-mmap.txt for more information.
1921 config SYSTEM_DATA_VERIFICATION
1923 select SYSTEM_TRUSTED_KEYRING
1927 select ASYMMETRIC_KEY_TYPE
1928 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1931 select X509_CERTIFICATE_PARSER
1932 select PKCS7_MESSAGE_PARSER
1934 Provide PKCS#7 message verification using the contents of the system
1935 trusted keyring to provide public keys. This then can be used for
1936 module verification, kexec image verification and firmware blob
1940 bool "Profiling support"
1942 Say Y here to enable the extended profiling support mechanisms used
1943 by profilers such as OProfile.
1946 # Place an empty function call at each tracepoint site. Can be
1947 # dynamically changed for a probe function.
1952 endmenu # General setup
1954 source "arch/Kconfig"
1961 default 0 if BASE_FULL
1962 default 1 if !BASE_FULL
1964 config MODULE_SIG_FORMAT
1966 select SYSTEM_DATA_VERIFICATION
1969 bool "Enable loadable module support"
1972 Kernel modules are small pieces of compiled code which can
1973 be inserted in the running kernel, rather than being
1974 permanently built into the kernel. You use the "modprobe"
1975 tool to add (and sometimes remove) them. If you say Y here,
1976 many parts of the kernel can be built as modules (by
1977 answering M instead of Y where indicated): this is most
1978 useful for infrequently used options which are not required
1979 for booting. For more information, see the man pages for
1980 modprobe, lsmod, modinfo, insmod and rmmod.
1982 If you say Y here, you will need to run "make
1983 modules_install" to put the modules under /lib/modules/
1984 where modprobe can find them (you may need to be root to do
1991 config MODULE_FORCE_LOAD
1992 bool "Forced module loading"
1995 Allow loading of modules without version information (ie. modprobe
1996 --force). Forced module loading sets the 'F' (forced) taint flag and
1997 is usually a really bad idea.
1999 config MODULE_UNLOAD
2000 bool "Module unloading"
2002 Without this option you will not be able to unload any
2003 modules (note that some modules may not be unloadable
2004 anyway), which makes your kernel smaller, faster
2005 and simpler. If unsure, say Y.
2007 config MODULE_FORCE_UNLOAD
2008 bool "Forced module unloading"
2009 depends on MODULE_UNLOAD
2011 This option allows you to force a module to unload, even if the
2012 kernel believes it is unsafe: the kernel will remove the module
2013 without waiting for anyone to stop using it (using the -f option to
2014 rmmod). This is mainly for kernel developers and desperate users.
2018 bool "Module versioning support"
2020 Usually, you have to use modules compiled with your kernel.
2021 Saying Y here makes it sometimes possible to use modules
2022 compiled for different kernels, by adding enough information
2023 to the modules to (hopefully) spot any changes which would
2024 make them incompatible with the kernel you are running. If
2027 config ASM_MODVERSIONS
2029 default HAVE_ASM_MODVERSIONS && MODVERSIONS
2031 This enables module versioning for exported symbols also from
2032 assembly. This can be enabled only when the target architecture
2035 config MODULE_REL_CRCS
2037 depends on MODVERSIONS
2039 config MODULE_SRCVERSION_ALL
2040 bool "Source checksum for all modules"
2042 Modules which contain a MODULE_VERSION get an extra "srcversion"
2043 field inserted into their modinfo section, which contains a
2044 sum of the source files which made it. This helps maintainers
2045 see exactly which source was used to build a module (since
2046 others sometimes change the module source without updating
2047 the version). With this option, such a "srcversion" field
2048 will be created for all modules. If unsure, say N.
2051 bool "Module signature verification"
2052 select MODULE_SIG_FORMAT
2054 Check modules for valid signatures upon load: the signature
2055 is simply appended to the module. For more information see
2056 <file:Documentation/admin-guide/module-signing.rst>.
2058 Note that this option adds the OpenSSL development packages as a
2059 kernel build dependency so that the signing tool can use its crypto
2062 You should enable this option if you wish to use either
2063 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2064 another LSM - otherwise unsigned modules will be loadable regardless
2065 of the lockdown policy.
2067 !!!WARNING!!! If you enable this option, you MUST make sure that the
2068 module DOES NOT get stripped after being signed. This includes the
2069 debuginfo strip done by some packagers (such as rpmbuild) and
2070 inclusion into an initramfs that wants the module size reduced.
2072 config MODULE_SIG_FORCE
2073 bool "Require modules to be validly signed"
2074 depends on MODULE_SIG
2076 Reject unsigned modules or signed modules for which we don't have a
2077 key. Without this, such modules will simply taint the kernel.
2079 config MODULE_SIG_ALL
2080 bool "Automatically sign all modules"
2082 depends on MODULE_SIG
2084 Sign all modules during make modules_install. Without this option,
2085 modules must be signed manually, using the scripts/sign-file tool.
2087 comment "Do not forget to sign required modules with scripts/sign-file"
2088 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2091 prompt "Which hash algorithm should modules be signed with?"
2092 depends on MODULE_SIG
2094 This determines which sort of hashing algorithm will be used during
2095 signature generation. This algorithm _must_ be built into the kernel
2096 directly so that signature verification can take place. It is not
2097 possible to load a signed module containing the algorithm to check
2098 the signature on that module.
2100 config MODULE_SIG_SHA1
2101 bool "Sign modules with SHA-1"
2104 config MODULE_SIG_SHA224
2105 bool "Sign modules with SHA-224"
2106 select CRYPTO_SHA256
2108 config MODULE_SIG_SHA256
2109 bool "Sign modules with SHA-256"
2110 select CRYPTO_SHA256
2112 config MODULE_SIG_SHA384
2113 bool "Sign modules with SHA-384"
2114 select CRYPTO_SHA512
2116 config MODULE_SIG_SHA512
2117 bool "Sign modules with SHA-512"
2118 select CRYPTO_SHA512
2122 config MODULE_SIG_HASH
2124 depends on MODULE_SIG
2125 default "sha1" if MODULE_SIG_SHA1
2126 default "sha224" if MODULE_SIG_SHA224
2127 default "sha256" if MODULE_SIG_SHA256
2128 default "sha384" if MODULE_SIG_SHA384
2129 default "sha512" if MODULE_SIG_SHA512
2131 config MODULE_COMPRESS
2132 bool "Compress modules on installation"
2135 Compresses kernel modules when 'make modules_install' is run; gzip or
2136 xz depending on "Compression algorithm" below.
2138 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2140 Out-of-tree kernel modules installed using Kbuild will also be
2141 compressed upon installation.
2143 Note: for modules inside an initrd or initramfs, it's more efficient
2144 to compress the whole initrd or initramfs instead.
2146 Note: This is fully compatible with signed modules.
2151 prompt "Compression algorithm"
2152 depends on MODULE_COMPRESS
2153 default MODULE_COMPRESS_GZIP
2155 This determines which sort of compression will be used during
2156 'make modules_install'.
2158 GZIP (default) and XZ are supported.
2160 config MODULE_COMPRESS_GZIP
2163 config MODULE_COMPRESS_XZ
2168 config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2169 bool "Allow loading of modules with missing namespace imports"
2171 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2172 a namespace. A module that makes use of a symbol exported with such a
2173 namespace is required to import the namespace via MODULE_IMPORT_NS().
2174 There is no technical reason to enforce correct namespace imports,
2175 but it creates consistency between symbols defining namespaces and
2176 users importing namespaces they make use of. This option relaxes this
2177 requirement and lifts the enforcement when loading a module.
2181 config UNUSED_SYMBOLS
2182 bool "Enable unused/obsolete exported symbols"
2185 Unused but exported symbols make the kernel needlessly bigger. For
2186 that reason most of these unused exports will soon be removed. This
2187 option is provided temporarily to provide a transition period in case
2188 some external kernel module needs one of these symbols anyway. If you
2189 encounter such a case in your module, consider if you are actually
2190 using the right API. (rationale: since nobody in the kernel is using
2191 this in a module, there is a pretty good chance it's actually the
2192 wrong interface to use). If you really need the symbol, please send a
2193 mail to the linux kernel mailing list mentioning the symbol and why
2194 you really need it, and what the merge plan to the mainline kernel for
2197 config TRIM_UNUSED_KSYMS
2198 bool "Trim unused exported kernel symbols"
2199 depends on !UNUSED_SYMBOLS
2201 The kernel and some modules make many symbols available for
2202 other modules to use via EXPORT_SYMBOL() and variants. Depending
2203 on the set of modules being selected in your kernel configuration,
2204 many of those exported symbols might never be used.
2206 This option allows for unused exported symbols to be dropped from
2207 the build. In turn, this provides the compiler more opportunities
2208 (especially when using LTO) for optimizing the code and reducing
2209 binary size. This might have some security advantages as well.
2211 If unsure, or if you need to build out-of-tree modules, say N.
2215 config MODULES_TREE_LOOKUP
2217 depends on PERF_EVENTS || TRACING
2219 config INIT_ALL_POSSIBLE
2222 Back when each arch used to define their own cpu_online_mask and
2223 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2224 with all 1s, and others with all 0s. When they were centralised,
2225 it was better to provide this option than to break all the archs
2226 and have several arch maintainers pursuing me down dark alleys.
2228 source "block/Kconfig"
2230 config PREEMPT_NOTIFIERS
2240 Build a simple ASN.1 grammar compiler that produces a bytecode output
2241 that can be interpreted by the ASN.1 stream decoder and used to
2242 inform it as to what tags are to be expected in a stream and what
2243 functions to call on what tags.
2245 source "kernel/Kconfig.locks"
2247 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2250 # It may be useful for an architecture to override the definitions of the
2251 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2252 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2253 # different calling convention for syscalls. They can also override the
2254 # macros for not-implemented syscalls in kernel/sys_ni.c and
2255 # kernel/time/posix-stubs.c. All these overrides need to be available in
2256 # <asm/syscall_wrapper.h>.
2257 config ARCH_HAS_SYSCALL_WRAPPER
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