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
1232 Extra boot config allows system admin to pass a config file as
1233 complemental extension of kernel cmdline when booting.
1234 The boot config file must be attached at the end of initramfs
1235 with checksum and size.
1236 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1241 prompt "Compiler optimization level"
1242 default CC_OPTIMIZE_FOR_PERFORMANCE
1244 config CC_OPTIMIZE_FOR_PERFORMANCE
1245 bool "Optimize for performance (-O2)"
1247 This is the default optimization level for the kernel, building
1248 with the "-O2" compiler flag for best performance and most
1249 helpful compile-time warnings.
1251 config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1252 bool "Optimize more for performance (-O3)"
1254 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives
1256 Choosing this option will pass "-O3" to your compiler to optimize
1257 the kernel yet more for performance.
1259 config CC_OPTIMIZE_FOR_SIZE
1260 bool "Optimize for size (-Os)"
1261 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives
1263 Choosing this option will pass "-Os" to your compiler resulting
1264 in a smaller kernel.
1268 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1271 This requires that the arch annotates or otherwise protects
1272 its external entry points from being discarded. Linker scripts
1273 must also merge .text.*, .data.*, and .bss.* correctly into
1274 output sections. Care must be taken not to pull in unrelated
1275 sections (e.g., '.text.init'). Typically '.' in section names
1276 is used to distinguish them from label names / C identifiers.
1278 config LD_DEAD_CODE_DATA_ELIMINATION
1279 bool "Dead code and data elimination (EXPERIMENTAL)"
1280 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1282 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800)
1283 depends on $(cc-option,-ffunction-sections -fdata-sections)
1284 depends on $(ld-option,--gc-sections)
1286 Enable this if you want to do dead code and data elimination with
1287 the linker by compiling with -ffunction-sections -fdata-sections,
1288 and linking with --gc-sections.
1290 This can reduce on disk and in-memory size of the kernel
1291 code and static data, particularly for small configs and
1292 on small systems. This has the possibility of introducing
1293 silently broken kernel if the required annotations are not
1294 present. This option is not well tested yet, so use at your
1303 config SYSCTL_EXCEPTION_TRACE
1306 Enable support for /proc/sys/debug/exception-trace.
1308 config SYSCTL_ARCH_UNALIGN_NO_WARN
1311 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1312 Allows arch to define/use @no_unaligned_warning to possibly warn
1313 about unaligned access emulation going on under the hood.
1315 config SYSCTL_ARCH_UNALIGN_ALLOW
1318 Enable support for /proc/sys/kernel/unaligned-trap
1319 Allows arches to define/use @unaligned_enabled to runtime toggle
1320 the unaligned access emulation.
1321 see arch/parisc/kernel/unaligned.c for reference
1323 config HAVE_PCSPKR_PLATFORM
1326 # interpreter that classic socket filters depend on
1331 bool "Configure standard kernel features (expert users)"
1332 # Unhide debug options, to make the on-by-default options visible
1335 This option allows certain base kernel options and settings
1336 to be disabled or tweaked. This is for specialized
1337 environments which can tolerate a "non-standard" kernel.
1338 Only use this if you really know what you are doing.
1341 bool "Enable 16-bit UID system calls" if EXPERT
1342 depends on HAVE_UID16 && MULTIUSER
1345 This enables the legacy 16-bit UID syscall wrappers.
1348 bool "Multiple users, groups and capabilities support" if EXPERT
1351 This option enables support for non-root users, groups and
1354 If you say N here, all processes will run with UID 0, GID 0, and all
1355 possible capabilities. Saying N here also compiles out support for
1356 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1359 If unsure, say Y here.
1361 config SGETMASK_SYSCALL
1362 bool "sgetmask/ssetmask syscalls support" if EXPERT
1363 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1365 sys_sgetmask and sys_ssetmask are obsolete system calls
1366 no longer supported in libc but still enabled by default in some
1369 If unsure, leave the default option here.
1371 config SYSFS_SYSCALL
1372 bool "Sysfs syscall support" if EXPERT
1375 sys_sysfs is an obsolete system call no longer supported in libc.
1376 Note that disabling this option is more secure but might break
1377 compatibility with some systems.
1379 If unsure say Y here.
1382 bool "open by fhandle syscalls" if EXPERT
1386 If you say Y here, a user level program will be able to map
1387 file names to handle and then later use the handle for
1388 different file system operations. This is useful in implementing
1389 userspace file servers, which now track files using handles instead
1390 of names. The handle would remain the same even if file names
1391 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1395 bool "Posix Clocks & timers" if EXPERT
1398 This includes native support for POSIX timers to the kernel.
1399 Some embedded systems have no use for them and therefore they
1400 can be configured out to reduce the size of the kernel image.
1402 When this option is disabled, the following syscalls won't be
1403 available: timer_create, timer_gettime: timer_getoverrun,
1404 timer_settime, timer_delete, clock_adjtime, getitimer,
1405 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1406 clock_getres and clock_nanosleep syscalls will be limited to
1407 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1413 bool "Enable support for printk" if EXPERT
1416 This option enables normal printk support. Removing it
1417 eliminates most of the message strings from the kernel image
1418 and makes the kernel more or less silent. As this makes it
1419 very difficult to diagnose system problems, saying N here is
1420 strongly discouraged.
1428 bool "BUG() support" if EXPERT
1431 Disabling this option eliminates support for BUG and WARN, reducing
1432 the size of your kernel image and potentially quietly ignoring
1433 numerous fatal conditions. You should only consider disabling this
1434 option for embedded systems with no facilities for reporting errors.
1440 bool "Enable ELF core dumps" if EXPERT
1442 Enable support for generating core dumps. Disabling saves about 4k.
1445 config PCSPKR_PLATFORM
1446 bool "Enable PC-Speaker support" if EXPERT
1447 depends on HAVE_PCSPKR_PLATFORM
1451 This option allows to disable the internal PC-Speaker
1452 support, saving some memory.
1456 bool "Enable full-sized data structures for core" if EXPERT
1458 Disabling this option reduces the size of miscellaneous core
1459 kernel data structures. This saves memory on small machines,
1460 but may reduce performance.
1463 bool "Enable futex support" if EXPERT
1467 Disabling this option will cause the kernel to be built without
1468 support for "fast userspace mutexes". The resulting kernel may not
1469 run glibc-based applications correctly.
1473 depends on FUTEX && RT_MUTEXES
1476 config HAVE_FUTEX_CMPXCHG
1480 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1481 is implemented and always working. This removes a couple of runtime
1485 bool "Enable eventpoll support" if EXPERT
1488 Disabling this option will cause the kernel to be built without
1489 support for epoll family of system calls.
1492 bool "Enable signalfd() system call" if EXPERT
1495 Enable the signalfd() system call that allows to receive signals
1496 on a file descriptor.
1501 bool "Enable timerfd() system call" if EXPERT
1504 Enable the timerfd() system call that allows to receive timer
1505 events on a file descriptor.
1510 bool "Enable eventfd() system call" if EXPERT
1513 Enable the eventfd() system call that allows to receive both
1514 kernel notification (ie. KAIO) or userspace notifications.
1519 bool "Use full shmem filesystem" if EXPERT
1523 The shmem is an internal filesystem used to manage shared memory.
1524 It is backed by swap and manages resource limits. It is also exported
1525 to userspace as tmpfs if TMPFS is enabled. Disabling this
1526 option replaces shmem and tmpfs with the much simpler ramfs code,
1527 which may be appropriate on small systems without swap.
1530 bool "Enable AIO support" if EXPERT
1533 This option enables POSIX asynchronous I/O which may by used
1534 by some high performance threaded applications. Disabling
1535 this option saves about 7k.
1538 bool "Enable IO uring support" if EXPERT
1543 This option enables support for the io_uring interface, enabling
1544 applications to submit and complete IO through submission and
1545 completion rings that are shared between the kernel and application.
1547 config ADVISE_SYSCALLS
1548 bool "Enable madvise/fadvise syscalls" if EXPERT
1551 This option enables the madvise and fadvise syscalls, used by
1552 applications to advise the kernel about their future memory or file
1553 usage, improving performance. If building an embedded system where no
1554 applications use these syscalls, you can disable this option to save
1558 bool "Enable membarrier() system call" if EXPERT
1561 Enable the membarrier() system call that allows issuing memory
1562 barriers across all running threads, which can be used to distribute
1563 the cost of user-space memory barriers asymmetrically by transforming
1564 pairs of memory barriers into pairs consisting of membarrier() and a
1570 bool "Load all symbols for debugging/ksymoops" if EXPERT
1573 Say Y here to let the kernel print out symbolic crash information and
1574 symbolic stack backtraces. This increases the size of the kernel
1575 somewhat, as all symbols have to be loaded into the kernel image.
1578 bool "Include all symbols in kallsyms"
1579 depends on DEBUG_KERNEL && KALLSYMS
1581 Normally kallsyms only contains the symbols of functions for nicer
1582 OOPS messages and backtraces (i.e., symbols from the text and inittext
1583 sections). This is sufficient for most cases. And only in very rare
1584 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1585 names of variables from the data sections, etc).
1587 This option makes sure that all symbols are loaded into the kernel
1588 image (i.e., symbols from all sections) in cost of increased kernel
1589 size (depending on the kernel configuration, it may be 300KiB or
1590 something like this).
1592 Say N unless you really need all symbols.
1594 config KALLSYMS_ABSOLUTE_PERCPU
1597 default X86_64 && SMP
1599 config KALLSYMS_BASE_RELATIVE
1604 Instead of emitting them as absolute values in the native word size,
1605 emit the symbol references in the kallsyms table as 32-bit entries,
1606 each containing a relative value in the range [base, base + U32_MAX]
1607 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1608 an absolute value in the range [0, S32_MAX] or a relative value in the
1609 range [base, base + S32_MAX], where base is the lowest relative symbol
1610 address encountered in the image.
1612 On 64-bit builds, this reduces the size of the address table by 50%,
1613 but more importantly, it results in entries whose values are build
1614 time constants, and no relocation pass is required at runtime to fix
1615 up the entries based on the runtime load address of the kernel.
1617 # end of the "standard kernel features (expert users)" menu
1619 # syscall, maps, verifier
1621 bool "Enable bpf() system call"
1626 Enable the bpf() system call that allows to manipulate eBPF
1627 programs and maps via file descriptors.
1629 config ARCH_WANT_DEFAULT_BPF_JIT
1632 config BPF_JIT_ALWAYS_ON
1633 bool "Permanently enable BPF JIT and remove BPF interpreter"
1634 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1636 Enables BPF JIT and removes BPF interpreter to avoid
1637 speculative execution of BPF instructions by the interpreter
1639 config BPF_JIT_DEFAULT_ON
1640 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
1641 depends on HAVE_EBPF_JIT && BPF_JIT
1644 bool "Enable userfaultfd() system call"
1647 Enable the userfaultfd() system call that allows to intercept and
1648 handle page faults in userland.
1650 config ARCH_HAS_MEMBARRIER_CALLBACKS
1653 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1657 bool "Enable rseq() system call" if EXPERT
1659 depends on HAVE_RSEQ
1662 Enable the restartable sequences system call. It provides a
1663 user-space cache for the current CPU number value, which
1664 speeds up getting the current CPU number from user-space,
1665 as well as an ABI to speed up user-space operations on
1672 bool "Enabled debugging of rseq() system call" if EXPERT
1673 depends on RSEQ && DEBUG_KERNEL
1675 Enable extra debugging checks for the rseq system call.
1680 bool "Embedded system"
1681 option allnoconfig_y
1684 This option should be enabled if compiling the kernel for
1685 an embedded system so certain expert options are available
1688 config HAVE_PERF_EVENTS
1691 See tools/perf/design.txt for details.
1693 config PERF_USE_VMALLOC
1696 See tools/perf/design.txt for details
1699 bool "PC/104 support" if EXPERT
1701 Expose PC/104 form factor device drivers and options available for
1702 selection and configuration. Enable this option if your target
1703 machine has a PC/104 bus.
1705 menu "Kernel Performance Events And Counters"
1708 bool "Kernel performance events and counters"
1709 default y if PROFILING
1710 depends on HAVE_PERF_EVENTS
1714 Enable kernel support for various performance events provided
1715 by software and hardware.
1717 Software events are supported either built-in or via the
1718 use of generic tracepoints.
1720 Most modern CPUs support performance events via performance
1721 counter registers. These registers count the number of certain
1722 types of hw events: such as instructions executed, cachemisses
1723 suffered, or branches mis-predicted - without slowing down the
1724 kernel or applications. These registers can also trigger interrupts
1725 when a threshold number of events have passed - and can thus be
1726 used to profile the code that runs on that CPU.
1728 The Linux Performance Event subsystem provides an abstraction of
1729 these software and hardware event capabilities, available via a
1730 system call and used by the "perf" utility in tools/perf/. It
1731 provides per task and per CPU counters, and it provides event
1732 capabilities on top of those.
1736 config DEBUG_PERF_USE_VMALLOC
1738 bool "Debug: use vmalloc to back perf mmap() buffers"
1739 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1740 select PERF_USE_VMALLOC
1742 Use vmalloc memory to back perf mmap() buffers.
1744 Mostly useful for debugging the vmalloc code on platforms
1745 that don't require it.
1751 config VM_EVENT_COUNTERS
1753 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1755 VM event counters are needed for event counts to be shown.
1756 This option allows the disabling of the VM event counters
1757 on EXPERT systems. /proc/vmstat will only show page counts
1758 if VM event counters are disabled.
1762 bool "Enable SLUB debugging support" if EXPERT
1763 depends on SLUB && SYSFS
1765 SLUB has extensive debug support features. Disabling these can
1766 result in significant savings in code size. This also disables
1767 SLUB sysfs support. /sys/slab will not exist and there will be
1768 no support for cache validation etc.
1770 config SLUB_MEMCG_SYSFS_ON
1772 bool "Enable memcg SLUB sysfs support by default" if EXPERT
1773 depends on SLUB && SYSFS && MEMCG
1775 SLUB creates a directory under /sys/kernel/slab for each
1776 allocation cache to host info and debug files. If memory
1777 cgroup is enabled, each cache can have per memory cgroup
1778 caches. SLUB can create the same sysfs directories for these
1779 caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1780 to a very high number of debug files being created. This is
1781 controlled by slub_memcg_sysfs boot parameter and this
1782 config option determines the parameter's default value.
1785 bool "Disable heap randomization"
1788 Randomizing heap placement makes heap exploits harder, but it
1789 also breaks ancient binaries (including anything libc5 based).
1790 This option changes the bootup default to heap randomization
1791 disabled, and can be overridden at runtime by setting
1792 /proc/sys/kernel/randomize_va_space to 2.
1794 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1797 prompt "Choose SLAB allocator"
1800 This option allows to select a slab allocator.
1804 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1806 The regular slab allocator that is established and known to work
1807 well in all environments. It organizes cache hot objects in
1808 per cpu and per node queues.
1811 bool "SLUB (Unqueued Allocator)"
1812 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1814 SLUB is a slab allocator that minimizes cache line usage
1815 instead of managing queues of cached objects (SLAB approach).
1816 Per cpu caching is realized using slabs of objects instead
1817 of queues of objects. SLUB can use memory efficiently
1818 and has enhanced diagnostics. SLUB is the default choice for
1823 bool "SLOB (Simple Allocator)"
1825 SLOB replaces the stock allocator with a drastically simpler
1826 allocator. SLOB is generally more space efficient but
1827 does not perform as well on large systems.
1831 config SLAB_MERGE_DEFAULT
1832 bool "Allow slab caches to be merged"
1835 For reduced kernel memory fragmentation, slab caches can be
1836 merged when they share the same size and other characteristics.
1837 This carries a risk of kernel heap overflows being able to
1838 overwrite objects from merged caches (and more easily control
1839 cache layout), which makes such heap attacks easier to exploit
1840 by attackers. By keeping caches unmerged, these kinds of exploits
1841 can usually only damage objects in the same cache. To disable
1842 merging at runtime, "slab_nomerge" can be passed on the kernel
1845 config SLAB_FREELIST_RANDOM
1847 depends on SLAB || SLUB
1848 bool "SLAB freelist randomization"
1850 Randomizes the freelist order used on creating new pages. This
1851 security feature reduces the predictability of the kernel slab
1852 allocator against heap overflows.
1854 config SLAB_FREELIST_HARDENED
1855 bool "Harden slab freelist metadata"
1858 Many kernel heap attacks try to target slab cache metadata and
1859 other infrastructure. This options makes minor performance
1860 sacrifices to harden the kernel slab allocator against common
1861 freelist exploit methods.
1863 config SHUFFLE_PAGE_ALLOCATOR
1864 bool "Page allocator randomization"
1865 default SLAB_FREELIST_RANDOM && ACPI_NUMA
1867 Randomization of the page allocator improves the average
1868 utilization of a direct-mapped memory-side-cache. See section
1869 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1870 6.2a specification for an example of how a platform advertises
1871 the presence of a memory-side-cache. There are also incidental
1872 security benefits as it reduces the predictability of page
1873 allocations to compliment SLAB_FREELIST_RANDOM, but the
1874 default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1875 10th order of pages is selected based on cache utilization
1878 While the randomization improves cache utilization it may
1879 negatively impact workloads on platforms without a cache. For
1880 this reason, by default, the randomization is enabled only
1881 after runtime detection of a direct-mapped memory-side-cache.
1882 Otherwise, the randomization may be force enabled with the
1883 'page_alloc.shuffle' kernel command line parameter.
1887 config SLUB_CPU_PARTIAL
1889 depends on SLUB && SMP
1890 bool "SLUB per cpu partial cache"
1892 Per cpu partial caches accelerate objects allocation and freeing
1893 that is local to a processor at the price of more indeterminism
1894 in the latency of the free. On overflow these caches will be cleared
1895 which requires the taking of locks that may cause latency spikes.
1896 Typically one would choose no for a realtime system.
1898 config MMAP_ALLOW_UNINITIALIZED
1899 bool "Allow mmapped anonymous memory to be uninitialized"
1900 depends on EXPERT && !MMU
1903 Normally, and according to the Linux spec, anonymous memory obtained
1904 from mmap() has its contents cleared before it is passed to
1905 userspace. Enabling this config option allows you to request that
1906 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1907 providing a huge performance boost. If this option is not enabled,
1908 then the flag will be ignored.
1910 This is taken advantage of by uClibc's malloc(), and also by
1911 ELF-FDPIC binfmt's brk and stack allocator.
1913 Because of the obvious security issues, this option should only be
1914 enabled on embedded devices where you control what is run in
1915 userspace. Since that isn't generally a problem on no-MMU systems,
1916 it is normally safe to say Y here.
1918 See Documentation/nommu-mmap.txt for more information.
1920 config SYSTEM_DATA_VERIFICATION
1922 select SYSTEM_TRUSTED_KEYRING
1926 select ASYMMETRIC_KEY_TYPE
1927 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1930 select X509_CERTIFICATE_PARSER
1931 select PKCS7_MESSAGE_PARSER
1933 Provide PKCS#7 message verification using the contents of the system
1934 trusted keyring to provide public keys. This then can be used for
1935 module verification, kexec image verification and firmware blob
1939 bool "Profiling support"
1941 Say Y here to enable the extended profiling support mechanisms used
1942 by profilers such as OProfile.
1945 # Place an empty function call at each tracepoint site. Can be
1946 # dynamically changed for a probe function.
1951 endmenu # General setup
1953 source "arch/Kconfig"
1960 default 0 if BASE_FULL
1961 default 1 if !BASE_FULL
1963 config MODULE_SIG_FORMAT
1965 select SYSTEM_DATA_VERIFICATION
1968 bool "Enable loadable module support"
1971 Kernel modules are small pieces of compiled code which can
1972 be inserted in the running kernel, rather than being
1973 permanently built into the kernel. You use the "modprobe"
1974 tool to add (and sometimes remove) them. If you say Y here,
1975 many parts of the kernel can be built as modules (by
1976 answering M instead of Y where indicated): this is most
1977 useful for infrequently used options which are not required
1978 for booting. For more information, see the man pages for
1979 modprobe, lsmod, modinfo, insmod and rmmod.
1981 If you say Y here, you will need to run "make
1982 modules_install" to put the modules under /lib/modules/
1983 where modprobe can find them (you may need to be root to do
1990 config MODULE_FORCE_LOAD
1991 bool "Forced module loading"
1994 Allow loading of modules without version information (ie. modprobe
1995 --force). Forced module loading sets the 'F' (forced) taint flag and
1996 is usually a really bad idea.
1998 config MODULE_UNLOAD
1999 bool "Module unloading"
2001 Without this option you will not be able to unload any
2002 modules (note that some modules may not be unloadable
2003 anyway), which makes your kernel smaller, faster
2004 and simpler. If unsure, say Y.
2006 config MODULE_FORCE_UNLOAD
2007 bool "Forced module unloading"
2008 depends on MODULE_UNLOAD
2010 This option allows you to force a module to unload, even if the
2011 kernel believes it is unsafe: the kernel will remove the module
2012 without waiting for anyone to stop using it (using the -f option to
2013 rmmod). This is mainly for kernel developers and desperate users.
2017 bool "Module versioning support"
2019 Usually, you have to use modules compiled with your kernel.
2020 Saying Y here makes it sometimes possible to use modules
2021 compiled for different kernels, by adding enough information
2022 to the modules to (hopefully) spot any changes which would
2023 make them incompatible with the kernel you are running. If
2026 config ASM_MODVERSIONS
2028 default HAVE_ASM_MODVERSIONS && MODVERSIONS
2030 This enables module versioning for exported symbols also from
2031 assembly. This can be enabled only when the target architecture
2034 config MODULE_REL_CRCS
2036 depends on MODVERSIONS
2038 config MODULE_SRCVERSION_ALL
2039 bool "Source checksum for all modules"
2041 Modules which contain a MODULE_VERSION get an extra "srcversion"
2042 field inserted into their modinfo section, which contains a
2043 sum of the source files which made it. This helps maintainers
2044 see exactly which source was used to build a module (since
2045 others sometimes change the module source without updating
2046 the version). With this option, such a "srcversion" field
2047 will be created for all modules. If unsure, say N.
2050 bool "Module signature verification"
2051 select MODULE_SIG_FORMAT
2053 Check modules for valid signatures upon load: the signature
2054 is simply appended to the module. For more information see
2055 <file:Documentation/admin-guide/module-signing.rst>.
2057 Note that this option adds the OpenSSL development packages as a
2058 kernel build dependency so that the signing tool can use its crypto
2061 You should enable this option if you wish to use either
2062 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2063 another LSM - otherwise unsigned modules will be loadable regardless
2064 of the lockdown policy.
2066 !!!WARNING!!! If you enable this option, you MUST make sure that the
2067 module DOES NOT get stripped after being signed. This includes the
2068 debuginfo strip done by some packagers (such as rpmbuild) and
2069 inclusion into an initramfs that wants the module size reduced.
2071 config MODULE_SIG_FORCE
2072 bool "Require modules to be validly signed"
2073 depends on MODULE_SIG
2075 Reject unsigned modules or signed modules for which we don't have a
2076 key. Without this, such modules will simply taint the kernel.
2078 config MODULE_SIG_ALL
2079 bool "Automatically sign all modules"
2081 depends on MODULE_SIG
2083 Sign all modules during make modules_install. Without this option,
2084 modules must be signed manually, using the scripts/sign-file tool.
2086 comment "Do not forget to sign required modules with scripts/sign-file"
2087 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2090 prompt "Which hash algorithm should modules be signed with?"
2091 depends on MODULE_SIG
2093 This determines which sort of hashing algorithm will be used during
2094 signature generation. This algorithm _must_ be built into the kernel
2095 directly so that signature verification can take place. It is not
2096 possible to load a signed module containing the algorithm to check
2097 the signature on that module.
2099 config MODULE_SIG_SHA1
2100 bool "Sign modules with SHA-1"
2103 config MODULE_SIG_SHA224
2104 bool "Sign modules with SHA-224"
2105 select CRYPTO_SHA256
2107 config MODULE_SIG_SHA256
2108 bool "Sign modules with SHA-256"
2109 select CRYPTO_SHA256
2111 config MODULE_SIG_SHA384
2112 bool "Sign modules with SHA-384"
2113 select CRYPTO_SHA512
2115 config MODULE_SIG_SHA512
2116 bool "Sign modules with SHA-512"
2117 select CRYPTO_SHA512
2121 config MODULE_SIG_HASH
2123 depends on MODULE_SIG
2124 default "sha1" if MODULE_SIG_SHA1
2125 default "sha224" if MODULE_SIG_SHA224
2126 default "sha256" if MODULE_SIG_SHA256
2127 default "sha384" if MODULE_SIG_SHA384
2128 default "sha512" if MODULE_SIG_SHA512
2130 config MODULE_COMPRESS
2131 bool "Compress modules on installation"
2134 Compresses kernel modules when 'make modules_install' is run; gzip or
2135 xz depending on "Compression algorithm" below.
2137 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2139 Out-of-tree kernel modules installed using Kbuild will also be
2140 compressed upon installation.
2142 Note: for modules inside an initrd or initramfs, it's more efficient
2143 to compress the whole initrd or initramfs instead.
2145 Note: This is fully compatible with signed modules.
2150 prompt "Compression algorithm"
2151 depends on MODULE_COMPRESS
2152 default MODULE_COMPRESS_GZIP
2154 This determines which sort of compression will be used during
2155 'make modules_install'.
2157 GZIP (default) and XZ are supported.
2159 config MODULE_COMPRESS_GZIP
2162 config MODULE_COMPRESS_XZ
2167 config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2168 bool "Allow loading of modules with missing namespace imports"
2170 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2171 a namespace. A module that makes use of a symbol exported with such a
2172 namespace is required to import the namespace via MODULE_IMPORT_NS().
2173 There is no technical reason to enforce correct namespace imports,
2174 but it creates consistency between symbols defining namespaces and
2175 users importing namespaces they make use of. This option relaxes this
2176 requirement and lifts the enforcement when loading a module.
2180 config UNUSED_SYMBOLS
2181 bool "Enable unused/obsolete exported symbols"
2184 Unused but exported symbols make the kernel needlessly bigger. For
2185 that reason most of these unused exports will soon be removed. This
2186 option is provided temporarily to provide a transition period in case
2187 some external kernel module needs one of these symbols anyway. If you
2188 encounter such a case in your module, consider if you are actually
2189 using the right API. (rationale: since nobody in the kernel is using
2190 this in a module, there is a pretty good chance it's actually the
2191 wrong interface to use). If you really need the symbol, please send a
2192 mail to the linux kernel mailing list mentioning the symbol and why
2193 you really need it, and what the merge plan to the mainline kernel for
2196 config TRIM_UNUSED_KSYMS
2197 bool "Trim unused exported kernel symbols"
2198 depends on !UNUSED_SYMBOLS
2200 The kernel and some modules make many symbols available for
2201 other modules to use via EXPORT_SYMBOL() and variants. Depending
2202 on the set of modules being selected in your kernel configuration,
2203 many of those exported symbols might never be used.
2205 This option allows for unused exported symbols to be dropped from
2206 the build. In turn, this provides the compiler more opportunities
2207 (especially when using LTO) for optimizing the code and reducing
2208 binary size. This might have some security advantages as well.
2210 If unsure, or if you need to build out-of-tree modules, say N.
2214 config MODULES_TREE_LOOKUP
2216 depends on PERF_EVENTS || TRACING
2218 config INIT_ALL_POSSIBLE
2221 Back when each arch used to define their own cpu_online_mask and
2222 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2223 with all 1s, and others with all 0s. When they were centralised,
2224 it was better to provide this option than to break all the archs
2225 and have several arch maintainers pursuing me down dark alleys.
2227 source "block/Kconfig"
2229 config PREEMPT_NOTIFIERS
2239 Build a simple ASN.1 grammar compiler that produces a bytecode output
2240 that can be interpreted by the ASN.1 stream decoder and used to
2241 inform it as to what tags are to be expected in a stream and what
2242 functions to call on what tags.
2244 source "kernel/Kconfig.locks"
2246 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2249 # It may be useful for an architecture to override the definitions of the
2250 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2251 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2252 # different calling convention for syscalls. They can also override the
2253 # macros for not-implemented syscalls in kernel/sys_ni.c and
2254 # kernel/time/posix-stubs.c. All these overrides need to be available in
2255 # <asm/syscall_wrapper.h>.
2256 config ARCH_HAS_SYSCALL_WRAPPER
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