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
22 default $(shell,$(LD) --version | $(srctree)/scripts/ld-version.sh)
25 def_bool $(success,$(CC) --version | head -n 1 | grep -q clang)
29 default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
32 def_bool $(success,$(srctree)/scripts/cc-can-link.sh $(CC))
34 config CC_HAS_ASM_GOTO
35 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
37 config TOOLS_SUPPORT_RELR
38 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
40 config CC_HAS_ASM_INLINE
41 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
43 config CC_HAS_WARN_MAYBE_UNINITIALIZED
44 def_bool $(cc-option,-Wmaybe-uninitialized)
46 GCC >= 4.7 supports this option.
48 config CC_DISABLE_WARN_MAYBE_UNINITIALIZED
50 depends on CC_HAS_WARN_MAYBE_UNINITIALIZED
51 default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9
53 GCC's -Wmaybe-uninitialized is not reliable by definition.
54 Lots of false positive warnings are produced in some cases.
56 If this option is enabled, -Wno-maybe-uninitialzed is passed
57 to the compiler to suppress maybe-uninitialized warnings.
66 config BUILDTIME_TABLE_SORT
69 config THREAD_INFO_IN_TASK
72 Select this to move thread_info off the stack into task_struct. To
73 make this work, an arch will need to remove all thread_info fields
74 except flags and fix any runtime bugs.
76 One subtle change that will be needed is to use try_get_task_stack()
77 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
86 depends on BROKEN || !SMP
89 config INIT_ENV_ARG_LIMIT
94 Maximum of each of the number of arguments and environment
95 variables passed to init from the kernel command line.
98 bool "Compile also drivers which will not load"
102 Some drivers can be compiled on a different platform than they are
103 intended to be run on. Despite they cannot be loaded there (or even
104 when they load they cannot be used due to missing HW support),
105 developers still, opposing to distributors, might want to build such
106 drivers to compile-test them.
108 If you are a developer and want to build everything available, say Y
109 here. If you are a user/distributor, say N here to exclude useless
110 drivers to be distributed.
112 config UAPI_HEADER_TEST
113 bool "Compile test UAPI headers"
114 depends on HEADERS_INSTALL && CC_CAN_LINK
116 Compile test headers exported to user-space to ensure they are
117 self-contained, i.e. compilable as standalone units.
119 If you are a developer or tester and want to ensure the exported
120 headers are self-contained, say Y here. Otherwise, choose N.
123 string "Local version - append to kernel release"
125 Append an extra string to the end of your kernel version.
126 This will show up when you type uname, for example.
127 The string you set here will be appended after the contents of
128 any files with a filename matching localversion* in your
129 object and source tree, in that order. Your total string can
130 be a maximum of 64 characters.
132 config LOCALVERSION_AUTO
133 bool "Automatically append version information to the version string"
135 depends on !COMPILE_TEST
137 This will try to automatically determine if the current tree is a
138 release tree by looking for git tags that belong to the current
139 top of tree revision.
141 A string of the format -gxxxxxxxx will be added to the localversion
142 if a git-based tree is found. The string generated by this will be
143 appended after any matching localversion* files, and after the value
144 set in CONFIG_LOCALVERSION.
146 (The actual string used here is the first eight characters produced
147 by running the command:
149 $ git rev-parse --verify HEAD
151 which is done within the script "scripts/setlocalversion".)
154 string "Build ID Salt"
157 The build ID is used to link binaries and their debug info. Setting
158 this option will use the value in the calculation of the build id.
159 This is mostly useful for distributions which want to ensure the
160 build is unique between builds. It's safe to leave the default.
162 config HAVE_KERNEL_GZIP
165 config HAVE_KERNEL_BZIP2
168 config HAVE_KERNEL_LZMA
171 config HAVE_KERNEL_XZ
174 config HAVE_KERNEL_LZO
177 config HAVE_KERNEL_LZ4
180 config HAVE_KERNEL_UNCOMPRESSED
184 prompt "Kernel compression mode"
186 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED
188 The linux kernel is a kind of self-extracting executable.
189 Several compression algorithms are available, which differ
190 in efficiency, compression and decompression speed.
191 Compression speed is only relevant when building a kernel.
192 Decompression speed is relevant at each boot.
194 If you have any problems with bzip2 or lzma compressed
196 version of this functionality (bzip2 only), for 2.4, was
197 supplied by Christian Ludwig)
199 High compression options are mostly useful for users, who
200 are low on disk space (embedded systems), but for whom ram
203 If in doubt, select 'gzip'
207 depends on HAVE_KERNEL_GZIP
209 The old and tried gzip compression. It provides a good balance
210 between compression ratio and decompression speed.
214 depends on HAVE_KERNEL_BZIP2
216 Its compression ratio and speed is intermediate.
217 Decompression speed is slowest among the choices. The kernel
218 size is about 10% smaller with bzip2, in comparison to gzip.
219 Bzip2 uses a large amount of memory. For modern kernels you
220 will need at least 8MB RAM or more for booting.
224 depends on HAVE_KERNEL_LZMA
226 This compression algorithm's ratio is best. Decompression speed
227 is between gzip and bzip2. Compression is slowest.
228 The kernel size is about 33% smaller with LZMA in comparison to gzip.
232 depends on HAVE_KERNEL_XZ
234 XZ uses the LZMA2 algorithm and instruction set specific
235 BCJ filters which can improve compression ratio of executable
236 code. The size of the kernel is about 30% smaller with XZ in
237 comparison to gzip. On architectures for which there is a BCJ
238 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
239 will create a few percent smaller kernel than plain LZMA.
241 The speed is about the same as with LZMA: The decompression
242 speed of XZ is better than that of bzip2 but worse than gzip
243 and LZO. Compression is slow.
247 depends on HAVE_KERNEL_LZO
249 Its compression ratio is the poorest among the choices. The kernel
250 size is about 10% bigger than gzip; however its speed
251 (both compression and decompression) is the fastest.
255 depends on HAVE_KERNEL_LZ4
257 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
258 A preliminary version of LZ4 de/compression tool is available at
259 <https://code.google.com/p/lz4/>.
261 Its compression ratio is worse than LZO. The size of the kernel
262 is about 8% bigger than LZO. But the decompression speed is
265 config KERNEL_UNCOMPRESSED
267 depends on HAVE_KERNEL_UNCOMPRESSED
269 Produce uncompressed kernel image. This option is usually not what
270 you want. It is useful for debugging the kernel in slow simulation
271 environments, where decompressing and moving the kernel is awfully
272 slow. This option allows early boot code to skip the decompressor
273 and jump right at uncompressed kernel image.
277 config DEFAULT_HOSTNAME
278 string "Default hostname"
281 This option determines the default system hostname before userspace
282 calls sethostname(2). The kernel traditionally uses "(none)" here,
283 but you may wish to use a different default here to make a minimal
284 system more usable with less configuration.
287 # For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
288 # add proper SWAP support to them, in which case this can be remove.
294 bool "Support for paging of anonymous memory (swap)"
295 depends on MMU && BLOCK && !ARCH_NO_SWAP
298 This option allows you to choose whether you want to have support
299 for so called swap devices or swap files in your kernel that are
300 used to provide more virtual memory than the actual RAM present
301 in your computer. If unsure say Y.
306 Inter Process Communication is a suite of library functions and
307 system calls which let processes (running programs) synchronize and
308 exchange information. It is generally considered to be a good thing,
309 and some programs won't run unless you say Y here. In particular, if
310 you want to run the DOS emulator dosemu under Linux (read the
311 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
312 you'll need to say Y here.
314 You can find documentation about IPC with "info ipc" and also in
315 section 6.4 of the Linux Programmer's Guide, available from
316 <http://www.tldp.org/guides.html>.
318 config SYSVIPC_SYSCTL
325 bool "POSIX Message Queues"
328 POSIX variant of message queues is a part of IPC. In POSIX message
329 queues every message has a priority which decides about succession
330 of receiving it by a process. If you want to compile and run
331 programs written e.g. for Solaris with use of its POSIX message
332 queues (functions mq_*) say Y here.
334 POSIX message queues are visible as a filesystem called 'mqueue'
335 and can be mounted somewhere if you want to do filesystem
336 operations on message queues.
340 config POSIX_MQUEUE_SYSCTL
342 depends on POSIX_MQUEUE
346 config CROSS_MEMORY_ATTACH
347 bool "Enable process_vm_readv/writev syscalls"
351 Enabling this option adds the system calls process_vm_readv and
352 process_vm_writev which allow a process with the correct privileges
353 to directly read from or write to another process' address space.
354 See the man page for more details.
357 bool "uselib syscall"
358 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
360 This option enables the uselib syscall, a system call used in the
361 dynamic linker from libc5 and earlier. glibc does not use this
362 system call. If you intend to run programs built on libc5 or
363 earlier, you may need to enable this syscall. Current systems
364 running glibc can safely disable this.
367 bool "Auditing support"
370 Enable auditing infrastructure that can be used with another
371 kernel subsystem, such as SELinux (which requires this for
372 logging of avc messages output). System call auditing is included
373 on architectures which support it.
375 config HAVE_ARCH_AUDITSYSCALL
380 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
383 source "kernel/irq/Kconfig"
384 source "kernel/time/Kconfig"
385 source "kernel/Kconfig.preempt"
387 menu "CPU/Task time and stats accounting"
389 config VIRT_CPU_ACCOUNTING
393 prompt "Cputime accounting"
394 default TICK_CPU_ACCOUNTING if !PPC64
395 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
397 # Kind of a stub config for the pure tick based cputime accounting
398 config TICK_CPU_ACCOUNTING
399 bool "Simple tick based cputime accounting"
400 depends on !S390 && !NO_HZ_FULL
402 This is the basic tick based cputime accounting that maintains
403 statistics about user, system and idle time spent on per jiffies
408 config VIRT_CPU_ACCOUNTING_NATIVE
409 bool "Deterministic task and CPU time accounting"
410 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
411 select VIRT_CPU_ACCOUNTING
413 Select this option to enable more accurate task and CPU time
414 accounting. This is done by reading a CPU counter on each
415 kernel entry and exit and on transitions within the kernel
416 between system, softirq and hardirq state, so there is a
417 small performance impact. In the case of s390 or IBM POWER > 5,
418 this also enables accounting of stolen time on logically-partitioned
421 config VIRT_CPU_ACCOUNTING_GEN
422 bool "Full dynticks CPU time accounting"
423 depends on HAVE_CONTEXT_TRACKING
424 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
425 depends on GENERIC_CLOCKEVENTS
426 select VIRT_CPU_ACCOUNTING
427 select CONTEXT_TRACKING
429 Select this option to enable task and CPU time accounting on full
430 dynticks systems. This accounting is implemented by watching every
431 kernel-user boundaries using the context tracking subsystem.
432 The accounting is thus performed at the expense of some significant
435 For now this is only useful if you are working on the full
436 dynticks subsystem development.
442 config IRQ_TIME_ACCOUNTING
443 bool "Fine granularity task level IRQ time accounting"
444 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
446 Select this option to enable fine granularity task irq time
447 accounting. This is done by reading a timestamp on each
448 transitions between softirq and hardirq state, so there can be a
449 small performance impact.
451 If in doubt, say N here.
453 config HAVE_SCHED_AVG_IRQ
455 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
458 config BSD_PROCESS_ACCT
459 bool "BSD Process Accounting"
462 If you say Y here, a user level program will be able to instruct the
463 kernel (via a special system call) to write process accounting
464 information to a file: whenever a process exits, information about
465 that process will be appended to the file by the kernel. The
466 information includes things such as creation time, owning user,
467 command name, memory usage, controlling terminal etc. (the complete
468 list is in the struct acct in <file:include/linux/acct.h>). It is
469 up to the user level program to do useful things with this
470 information. This is generally a good idea, so say Y.
472 config BSD_PROCESS_ACCT_V3
473 bool "BSD Process Accounting version 3 file format"
474 depends on BSD_PROCESS_ACCT
477 If you say Y here, the process accounting information is written
478 in a new file format that also logs the process IDs of each
479 process and its parent. Note that this file format is incompatible
480 with previous v0/v1/v2 file formats, so you will need updated tools
481 for processing it. A preliminary version of these tools is available
482 at <http://www.gnu.org/software/acct/>.
485 bool "Export task/process statistics through netlink"
490 Export selected statistics for tasks/processes through the
491 generic netlink interface. Unlike BSD process accounting, the
492 statistics are available during the lifetime of tasks/processes as
493 responses to commands. Like BSD accounting, they are sent to user
498 config TASK_DELAY_ACCT
499 bool "Enable per-task delay accounting"
503 Collect information on time spent by a task waiting for system
504 resources like cpu, synchronous block I/O completion and swapping
505 in pages. Such statistics can help in setting a task's priorities
506 relative to other tasks for cpu, io, rss limits etc.
511 bool "Enable extended accounting over taskstats"
514 Collect extended task accounting data and send the data
515 to userland for processing over the taskstats interface.
519 config TASK_IO_ACCOUNTING
520 bool "Enable per-task storage I/O accounting"
521 depends on TASK_XACCT
523 Collect information on the number of bytes of storage I/O which this
529 bool "Pressure stall information tracking"
531 Collect metrics that indicate how overcommitted the CPU, memory,
532 and IO capacity are in the system.
534 If you say Y here, the kernel will create /proc/pressure/ with the
535 pressure statistics files cpu, memory, and io. These will indicate
536 the share of walltime in which some or all tasks in the system are
537 delayed due to contention of the respective resource.
539 In kernels with cgroup support, cgroups (cgroup2 only) will
540 have cpu.pressure, memory.pressure, and io.pressure files,
541 which aggregate pressure stalls for the grouped tasks only.
543 For more details see Documentation/accounting/psi.rst.
547 config PSI_DEFAULT_DISABLED
548 bool "Require boot parameter to enable pressure stall information tracking"
552 If set, pressure stall information tracking will be disabled
553 per default but can be enabled through passing psi=1 on the
554 kernel commandline during boot.
556 This feature adds some code to the task wakeup and sleep
557 paths of the scheduler. The overhead is too low to affect
558 common scheduling-intense workloads in practice (such as
559 webservers, memcache), but it does show up in artificial
560 scheduler stress tests, such as hackbench.
562 If you are paranoid and not sure what the kernel will be
567 endmenu # "CPU/Task time and stats accounting"
571 depends on SMP || COMPILE_TEST
574 Make sure that CPUs running critical tasks are not disturbed by
575 any source of "noise" such as unbound workqueues, timers, kthreads...
576 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
577 the "isolcpus=" boot parameter.
581 source "kernel/rcu/Kconfig"
588 tristate "Kernel .config support"
590 This option enables the complete Linux kernel ".config" file
591 contents to be saved in the kernel. It provides documentation
592 of which kernel options are used in a running kernel or in an
593 on-disk kernel. This information can be extracted from the kernel
594 image file with the script scripts/extract-ikconfig and used as
595 input to rebuild the current kernel or to build another kernel.
596 It can also be extracted from a running kernel by reading
597 /proc/config.gz if enabled (below).
600 bool "Enable access to .config through /proc/config.gz"
601 depends on IKCONFIG && PROC_FS
603 This option enables access to the kernel configuration file
604 through /proc/config.gz.
607 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
610 This option enables access to the in-kernel headers that are generated during
611 the build process. These can be used to build eBPF tracing programs,
612 or similar programs. If you build the headers as a module, a module called
613 kheaders.ko is built which can be loaded on-demand to get access to headers.
616 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
621 Select the minimal kernel log buffer size as a power of 2.
622 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
623 parameter, see below. Any higher size also might be forced
624 by "log_buf_len" boot parameter.
634 config LOG_CPU_MAX_BUF_SHIFT
635 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
638 default 12 if !BASE_SMALL
639 default 0 if BASE_SMALL
642 This option allows to increase the default ring buffer size
643 according to the number of CPUs. The value defines the contribution
644 of each CPU as a power of 2. The used space is typically only few
645 lines however it might be much more when problems are reported,
648 The increased size means that a new buffer has to be allocated and
649 the original static one is unused. It makes sense only on systems
650 with more CPUs. Therefore this value is used only when the sum of
651 contributions is greater than the half of the default kernel ring
652 buffer as defined by LOG_BUF_SHIFT. The default values are set
653 so that more than 64 CPUs are needed to trigger the allocation.
655 Also this option is ignored when "log_buf_len" kernel parameter is
656 used as it forces an exact (power of two) size of the ring buffer.
658 The number of possible CPUs is used for this computation ignoring
659 hotplugging making the computation optimal for the worst case
660 scenario while allowing a simple algorithm to be used from bootup.
662 Examples shift values and their meaning:
663 17 => 128 KB for each CPU
664 16 => 64 KB for each CPU
665 15 => 32 KB for each CPU
666 14 => 16 KB for each CPU
667 13 => 8 KB for each CPU
668 12 => 4 KB for each CPU
670 config PRINTK_SAFE_LOG_BUF_SHIFT
671 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
676 Select the size of an alternate printk per-CPU buffer where messages
677 printed from usafe contexts are temporary stored. One example would
678 be NMI messages, another one - printk recursion. The messages are
679 copied to the main log buffer in a safe context to avoid a deadlock.
680 The value defines the size as a power of 2.
682 Those messages are rare and limited. The largest one is when
683 a backtrace is printed. It usually fits into 4KB. Select
684 8KB if you want to be on the safe side.
687 17 => 128 KB for each CPU
688 16 => 64 KB for each CPU
689 15 => 32 KB for each CPU
690 14 => 16 KB for each CPU
691 13 => 8 KB for each CPU
692 12 => 4 KB for each CPU
695 # Architectures with an unreliable sched_clock() should select this:
697 config HAVE_UNSTABLE_SCHED_CLOCK
700 config GENERIC_SCHED_CLOCK
703 menu "Scheduler features"
706 bool "Enable utilization clamping for RT/FAIR tasks"
707 depends on CPU_FREQ_GOV_SCHEDUTIL
709 This feature enables the scheduler to track the clamped utilization
710 of each CPU based on RUNNABLE tasks scheduled on that CPU.
712 With this option, the user can specify the min and max CPU
713 utilization allowed for RUNNABLE tasks. The max utilization defines
714 the maximum frequency a task should use while the min utilization
715 defines the minimum frequency it should use.
717 Both min and max utilization clamp values are hints to the scheduler,
718 aiming at improving its frequency selection policy, but they do not
719 enforce or grant any specific bandwidth for tasks.
723 config UCLAMP_BUCKETS_COUNT
724 int "Number of supported utilization clamp buckets"
727 depends on UCLAMP_TASK
729 Defines the number of clamp buckets to use. The range of each bucket
730 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
731 number of clamp buckets the finer their granularity and the higher
732 the precision of clamping aggregation and tracking at run-time.
734 For example, with the minimum configuration value we will have 5
735 clamp buckets tracking 20% utilization each. A 25% boosted tasks will
736 be refcounted in the [20..39]% bucket and will set the bucket clamp
737 effective value to 25%.
738 If a second 30% boosted task should be co-scheduled on the same CPU,
739 that task will be refcounted in the same bucket of the first task and
740 it will boost the bucket clamp effective value to 30%.
741 The clamp effective value of a bucket is reset to its nominal value
742 (20% in the example above) when there are no more tasks refcounted in
745 An additional boost/capping margin can be added to some tasks. In the
746 example above the 25% task will be boosted to 30% until it exits the
747 CPU. If that should be considered not acceptable on certain systems,
748 it's always possible to reduce the margin by increasing the number of
749 clamp buckets to trade off used memory for run-time tracking
752 If in doubt, use the default value.
757 # For architectures that want to enable the support for NUMA-affine scheduler
760 config ARCH_SUPPORTS_NUMA_BALANCING
764 # For architectures that prefer to flush all TLBs after a number of pages
765 # are unmapped instead of sending one IPI per page to flush. The architecture
766 # must provide guarantees on what happens if a clean TLB cache entry is
767 # written after the unmap. Details are in mm/rmap.c near the check for
768 # should_defer_flush. The architecture should also consider if the full flush
769 # and the refill costs are offset by the savings of sending fewer IPIs.
770 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
775 depends on !$(cc-option,-D__SIZEOF_INT128__=0)
778 # For architectures that know their GCC __int128 support is sound
780 config ARCH_SUPPORTS_INT128
783 # For architectures that (ab)use NUMA to represent different memory regions
784 # all cpu-local but of different latencies, such as SuperH.
786 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
789 config NUMA_BALANCING
790 bool "Memory placement aware NUMA scheduler"
791 depends on ARCH_SUPPORTS_NUMA_BALANCING
792 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
793 depends on SMP && NUMA && MIGRATION
795 This option adds support for automatic NUMA aware memory/task placement.
796 The mechanism is quite primitive and is based on migrating memory when
797 it has references to the node the task is running on.
799 This system will be inactive on UMA systems.
801 config NUMA_BALANCING_DEFAULT_ENABLED
802 bool "Automatically enable NUMA aware memory/task placement"
804 depends on NUMA_BALANCING
806 If set, automatic NUMA balancing will be enabled if running on a NUMA
810 bool "Control Group support"
813 This option adds support for grouping sets of processes together, for
814 use with process control subsystems such as Cpusets, CFS, memory
815 controls or device isolation.
817 - Documentation/scheduler/sched-design-CFS.rst (CFS)
818 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
819 and resource control)
829 bool "Memory controller"
833 Provides control over the memory footprint of tasks in a cgroup.
836 bool "Swap controller"
837 depends on MEMCG && SWAP
839 Provides control over the swap space consumed by tasks in a cgroup.
841 config MEMCG_SWAP_ENABLED
842 bool "Swap controller enabled by default"
843 depends on MEMCG_SWAP
846 Memory Resource Controller Swap Extension comes with its price in
847 a bigger memory consumption. General purpose distribution kernels
848 which want to enable the feature but keep it disabled by default
849 and let the user enable it by swapaccount=1 boot command line
850 parameter should have this option unselected.
851 For those who want to have the feature enabled by default should
852 select this option (if, for some reason, they need to disable it
853 then swapaccount=0 does the trick).
857 depends on MEMCG && !SLOB
865 Generic block IO controller cgroup interface. This is the common
866 cgroup interface which should be used by various IO controlling
869 Currently, CFQ IO scheduler uses it to recognize task groups and
870 control disk bandwidth allocation (proportional time slice allocation)
871 to such task groups. It is also used by bio throttling logic in
872 block layer to implement upper limit in IO rates on a device.
874 This option only enables generic Block IO controller infrastructure.
875 One needs to also enable actual IO controlling logic/policy. For
876 enabling proportional weight division of disk bandwidth in CFQ, set
877 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
878 CONFIG_BLK_DEV_THROTTLING=y.
880 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
882 config CGROUP_WRITEBACK
884 depends on MEMCG && BLK_CGROUP
887 menuconfig CGROUP_SCHED
888 bool "CPU controller"
891 This feature lets CPU scheduler recognize task groups and control CPU
892 bandwidth allocation to such task groups. It uses cgroups to group
896 config FAIR_GROUP_SCHED
897 bool "Group scheduling for SCHED_OTHER"
898 depends on CGROUP_SCHED
902 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
903 depends on FAIR_GROUP_SCHED
906 This option allows users to define CPU bandwidth rates (limits) for
907 tasks running within the fair group scheduler. Groups with no limit
908 set are considered to be unconstrained and will run with no
910 See Documentation/scheduler/sched-bwc.rst for more information.
912 config RT_GROUP_SCHED
913 bool "Group scheduling for SCHED_RR/FIFO"
914 depends on CGROUP_SCHED
917 This feature lets you explicitly allocate real CPU bandwidth
918 to task groups. If enabled, it will also make it impossible to
919 schedule realtime tasks for non-root users until you allocate
920 realtime bandwidth for them.
921 See Documentation/scheduler/sched-rt-group.rst for more information.
925 config UCLAMP_TASK_GROUP
926 bool "Utilization clamping per group of tasks"
927 depends on CGROUP_SCHED
928 depends on UCLAMP_TASK
931 This feature enables the scheduler to track the clamped utilization
932 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
934 When this option is enabled, the user can specify a min and max
935 CPU bandwidth which is allowed for each single task in a group.
936 The max bandwidth allows to clamp the maximum frequency a task
937 can use, while the min bandwidth allows to define a minimum
938 frequency a task will always use.
940 When task group based utilization clamping is enabled, an eventually
941 specified task-specific clamp value is constrained by the cgroup
942 specified clamp value. Both minimum and maximum task clamping cannot
943 be bigger than the corresponding clamping defined at task group level.
948 bool "PIDs controller"
950 Provides enforcement of process number limits in the scope of a
951 cgroup. Any attempt to fork more processes than is allowed in the
952 cgroup will fail. PIDs are fundamentally a global resource because it
953 is fairly trivial to reach PID exhaustion before you reach even a
954 conservative kmemcg limit. As a result, it is possible to grind a
955 system to halt without being limited by other cgroup policies. The
956 PIDs controller is designed to stop this from happening.
958 It should be noted that organisational operations (such as attaching
959 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
960 since the PIDs limit only affects a process's ability to fork, not to
964 bool "RDMA controller"
966 Provides enforcement of RDMA resources defined by IB stack.
967 It is fairly easy for consumers to exhaust RDMA resources, which
968 can result into resource unavailability to other consumers.
969 RDMA controller is designed to stop this from happening.
970 Attaching processes with active RDMA resources to the cgroup
971 hierarchy is allowed even if can cross the hierarchy's limit.
973 config CGROUP_FREEZER
974 bool "Freezer controller"
976 Provides a way to freeze and unfreeze all tasks in a
979 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
980 controller includes important in-kernel memory consumers per default.
982 If you're using cgroup2, say N.
984 config CGROUP_HUGETLB
985 bool "HugeTLB controller"
986 depends on HUGETLB_PAGE
990 Provides a cgroup controller for HugeTLB pages.
991 When you enable this, you can put a per cgroup limit on HugeTLB usage.
992 The limit is enforced during page fault. Since HugeTLB doesn't
993 support page reclaim, enforcing the limit at page fault time implies
994 that, the application will get SIGBUS signal if it tries to access
995 HugeTLB pages beyond its limit. This requires the application to know
996 beforehand how much HugeTLB pages it would require for its use. The
997 control group is tracked in the third page lru pointer. This means
998 that we cannot use the controller with huge page less than 3 pages.
1001 bool "Cpuset controller"
1004 This option will let you create and manage CPUSETs which
1005 allow dynamically partitioning a system into sets of CPUs and
1006 Memory Nodes and assigning tasks to run only within those sets.
1007 This is primarily useful on large SMP or NUMA systems.
1011 config PROC_PID_CPUSET
1012 bool "Include legacy /proc/<pid>/cpuset file"
1016 config CGROUP_DEVICE
1017 bool "Device controller"
1019 Provides a cgroup controller implementing whitelists for
1020 devices which a process in the cgroup can mknod or open.
1022 config CGROUP_CPUACCT
1023 bool "Simple CPU accounting controller"
1025 Provides a simple controller for monitoring the
1026 total CPU consumed by the tasks in a cgroup.
1029 bool "Perf controller"
1030 depends on PERF_EVENTS
1032 This option extends the perf per-cpu mode to restrict monitoring
1033 to threads which belong to the cgroup specified and run on the
1039 bool "Support for eBPF programs attached to cgroups"
1040 depends on BPF_SYSCALL
1041 select SOCK_CGROUP_DATA
1043 Allow attaching eBPF programs to a cgroup using the bpf(2)
1044 syscall command BPF_PROG_ATTACH.
1046 In which context these programs are accessed depends on the type
1047 of attachment. For instance, programs that are attached using
1048 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1052 bool "Debug controller"
1054 depends on DEBUG_KERNEL
1056 This option enables a simple controller that exports
1057 debugging information about the cgroups framework. This
1058 controller is for control cgroup debugging only. Its
1059 interfaces are not stable.
1063 config SOCK_CGROUP_DATA
1069 menuconfig NAMESPACES
1070 bool "Namespaces support" if EXPERT
1071 depends on MULTIUSER
1074 Provides the way to make tasks work with different objects using
1075 the same id. For example same IPC id may refer to different objects
1076 or same user id or pid may refer to different tasks when used in
1077 different namespaces.
1082 bool "UTS namespace"
1085 In this namespace tasks see different info provided with the
1089 bool "TIME namespace"
1090 depends on GENERIC_VDSO_TIME_NS
1093 In this namespace boottime and monotonic clocks can be set.
1094 The time will keep going with the same pace.
1097 bool "IPC namespace"
1098 depends on (SYSVIPC || POSIX_MQUEUE)
1101 In this namespace tasks work with IPC ids which correspond to
1102 different IPC objects in different namespaces.
1105 bool "User namespace"
1108 This allows containers, i.e. vservers, to use user namespaces
1109 to provide different user info for different servers.
1111 When user namespaces are enabled in the kernel it is
1112 recommended that the MEMCG option also be enabled and that
1113 user-space use the memory control groups to limit the amount
1114 of memory a memory unprivileged users can use.
1119 bool "PID Namespaces"
1122 Support process id namespaces. This allows having multiple
1123 processes with the same pid as long as they are in different
1124 pid namespaces. This is a building block of containers.
1127 bool "Network namespace"
1131 Allow user space to create what appear to be multiple instances
1132 of the network stack.
1136 config CHECKPOINT_RESTORE
1137 bool "Checkpoint/restore support"
1138 select PROC_CHILDREN
1141 Enables additional kernel features in a sake of checkpoint/restore.
1142 In particular it adds auxiliary prctl codes to setup process text,
1143 data and heap segment sizes, and a few additional /proc filesystem
1146 If unsure, say N here.
1148 config SCHED_AUTOGROUP
1149 bool "Automatic process group scheduling"
1152 select FAIR_GROUP_SCHED
1154 This option optimizes the scheduler for common desktop workloads by
1155 automatically creating and populating task groups. This separation
1156 of workloads isolates aggressive CPU burners (like build jobs) from
1157 desktop applications. Task group autogeneration is currently based
1160 config SYSFS_DEPRECATED
1161 bool "Enable deprecated sysfs features to support old userspace tools"
1165 This option adds code that switches the layout of the "block" class
1166 devices, to not show up in /sys/class/block/, but only in
1169 This switch is only active when the sysfs.deprecated=1 boot option is
1170 passed or the SYSFS_DEPRECATED_V2 option is set.
1172 This option allows new kernels to run on old distributions and tools,
1173 which might get confused by /sys/class/block/. Since 2007/2008 all
1174 major distributions and tools handle this just fine.
1176 Recent distributions and userspace tools after 2009/2010 depend on
1177 the existence of /sys/class/block/, and will not work with this
1180 Only if you are using a new kernel on an old distribution, you might
1183 config SYSFS_DEPRECATED_V2
1184 bool "Enable deprecated sysfs features by default"
1187 depends on SYSFS_DEPRECATED
1189 Enable deprecated sysfs by default.
1191 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1194 Only if you are using a new kernel on an old distribution, you might
1195 need to say Y here. Even then, odds are you would not need it
1196 enabled, you can always pass the boot option if absolutely necessary.
1199 bool "Kernel->user space relay support (formerly relayfs)"
1202 This option enables support for relay interface support in
1203 certain file systems (such as debugfs).
1204 It is designed to provide an efficient mechanism for tools and
1205 facilities to relay large amounts of data from kernel space to
1210 config BLK_DEV_INITRD
1211 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1213 The initial RAM filesystem is a ramfs which is loaded by the
1214 boot loader (loadlin or lilo) and that is mounted as root
1215 before the normal boot procedure. It is typically used to
1216 load modules needed to mount the "real" root file system,
1217 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1219 If RAM disk support (BLK_DEV_RAM) is also included, this
1220 also enables initial RAM disk (initrd) support and adds
1221 15 Kbytes (more on some other architectures) to the kernel size.
1227 source "usr/Kconfig"
1232 bool "Boot config support"
1233 depends on BLK_DEV_INITRD
1236 Extra boot config allows system admin to pass a config file as
1237 complemental extension of kernel cmdline when booting.
1238 The boot config file must be attached at the end of initramfs
1239 with checksum and size.
1240 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1245 prompt "Compiler optimization level"
1246 default CC_OPTIMIZE_FOR_PERFORMANCE
1248 config CC_OPTIMIZE_FOR_PERFORMANCE
1249 bool "Optimize for performance (-O2)"
1251 This is the default optimization level for the kernel, building
1252 with the "-O2" compiler flag for best performance and most
1253 helpful compile-time warnings.
1255 config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1256 bool "Optimize more for performance (-O3)"
1258 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives
1260 Choosing this option will pass "-O3" to your compiler to optimize
1261 the kernel yet more for performance.
1263 config CC_OPTIMIZE_FOR_SIZE
1264 bool "Optimize for size (-Os)"
1265 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives
1267 Choosing this option will pass "-Os" to your compiler resulting
1268 in a smaller kernel.
1272 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1275 This requires that the arch annotates or otherwise protects
1276 its external entry points from being discarded. Linker scripts
1277 must also merge .text.*, .data.*, and .bss.* correctly into
1278 output sections. Care must be taken not to pull in unrelated
1279 sections (e.g., '.text.init'). Typically '.' in section names
1280 is used to distinguish them from label names / C identifiers.
1282 config LD_DEAD_CODE_DATA_ELIMINATION
1283 bool "Dead code and data elimination (EXPERIMENTAL)"
1284 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1286 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800)
1287 depends on $(cc-option,-ffunction-sections -fdata-sections)
1288 depends on $(ld-option,--gc-sections)
1290 Enable this if you want to do dead code and data elimination with
1291 the linker by compiling with -ffunction-sections -fdata-sections,
1292 and linking with --gc-sections.
1294 This can reduce on disk and in-memory size of the kernel
1295 code and static data, particularly for small configs and
1296 on small systems. This has the possibility of introducing
1297 silently broken kernel if the required annotations are not
1298 present. This option is not well tested yet, so use at your
1307 config SYSCTL_EXCEPTION_TRACE
1310 Enable support for /proc/sys/debug/exception-trace.
1312 config SYSCTL_ARCH_UNALIGN_NO_WARN
1315 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1316 Allows arch to define/use @no_unaligned_warning to possibly warn
1317 about unaligned access emulation going on under the hood.
1319 config SYSCTL_ARCH_UNALIGN_ALLOW
1322 Enable support for /proc/sys/kernel/unaligned-trap
1323 Allows arches to define/use @unaligned_enabled to runtime toggle
1324 the unaligned access emulation.
1325 see arch/parisc/kernel/unaligned.c for reference
1327 config HAVE_PCSPKR_PLATFORM
1330 # interpreter that classic socket filters depend on
1335 bool "Configure standard kernel features (expert users)"
1336 # Unhide debug options, to make the on-by-default options visible
1339 This option allows certain base kernel options and settings
1340 to be disabled or tweaked. This is for specialized
1341 environments which can tolerate a "non-standard" kernel.
1342 Only use this if you really know what you are doing.
1345 bool "Enable 16-bit UID system calls" if EXPERT
1346 depends on HAVE_UID16 && MULTIUSER
1349 This enables the legacy 16-bit UID syscall wrappers.
1352 bool "Multiple users, groups and capabilities support" if EXPERT
1355 This option enables support for non-root users, groups and
1358 If you say N here, all processes will run with UID 0, GID 0, and all
1359 possible capabilities. Saying N here also compiles out support for
1360 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1363 If unsure, say Y here.
1365 config SGETMASK_SYSCALL
1366 bool "sgetmask/ssetmask syscalls support" if EXPERT
1367 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1369 sys_sgetmask and sys_ssetmask are obsolete system calls
1370 no longer supported in libc but still enabled by default in some
1373 If unsure, leave the default option here.
1375 config SYSFS_SYSCALL
1376 bool "Sysfs syscall support" if EXPERT
1379 sys_sysfs is an obsolete system call no longer supported in libc.
1380 Note that disabling this option is more secure but might break
1381 compatibility with some systems.
1383 If unsure say Y here.
1386 bool "open by fhandle syscalls" if EXPERT
1390 If you say Y here, a user level program will be able to map
1391 file names to handle and then later use the handle for
1392 different file system operations. This is useful in implementing
1393 userspace file servers, which now track files using handles instead
1394 of names. The handle would remain the same even if file names
1395 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1399 bool "Posix Clocks & timers" if EXPERT
1402 This includes native support for POSIX timers to the kernel.
1403 Some embedded systems have no use for them and therefore they
1404 can be configured out to reduce the size of the kernel image.
1406 When this option is disabled, the following syscalls won't be
1407 available: timer_create, timer_gettime: timer_getoverrun,
1408 timer_settime, timer_delete, clock_adjtime, getitimer,
1409 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1410 clock_getres and clock_nanosleep syscalls will be limited to
1411 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1417 bool "Enable support for printk" if EXPERT
1420 This option enables normal printk support. Removing it
1421 eliminates most of the message strings from the kernel image
1422 and makes the kernel more or less silent. As this makes it
1423 very difficult to diagnose system problems, saying N here is
1424 strongly discouraged.
1432 bool "BUG() support" if EXPERT
1435 Disabling this option eliminates support for BUG and WARN, reducing
1436 the size of your kernel image and potentially quietly ignoring
1437 numerous fatal conditions. You should only consider disabling this
1438 option for embedded systems with no facilities for reporting errors.
1444 bool "Enable ELF core dumps" if EXPERT
1446 Enable support for generating core dumps. Disabling saves about 4k.
1449 config PCSPKR_PLATFORM
1450 bool "Enable PC-Speaker support" if EXPERT
1451 depends on HAVE_PCSPKR_PLATFORM
1455 This option allows to disable the internal PC-Speaker
1456 support, saving some memory.
1460 bool "Enable full-sized data structures for core" if EXPERT
1462 Disabling this option reduces the size of miscellaneous core
1463 kernel data structures. This saves memory on small machines,
1464 but may reduce performance.
1467 bool "Enable futex support" if EXPERT
1471 Disabling this option will cause the kernel to be built without
1472 support for "fast userspace mutexes". The resulting kernel may not
1473 run glibc-based applications correctly.
1477 depends on FUTEX && RT_MUTEXES
1480 config HAVE_FUTEX_CMPXCHG
1484 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1485 is implemented and always working. This removes a couple of runtime
1489 bool "Enable eventpoll support" if EXPERT
1492 Disabling this option will cause the kernel to be built without
1493 support for epoll family of system calls.
1496 bool "Enable signalfd() system call" if EXPERT
1499 Enable the signalfd() system call that allows to receive signals
1500 on a file descriptor.
1505 bool "Enable timerfd() system call" if EXPERT
1508 Enable the timerfd() system call that allows to receive timer
1509 events on a file descriptor.
1514 bool "Enable eventfd() system call" if EXPERT
1517 Enable the eventfd() system call that allows to receive both
1518 kernel notification (ie. KAIO) or userspace notifications.
1523 bool "Use full shmem filesystem" if EXPERT
1527 The shmem is an internal filesystem used to manage shared memory.
1528 It is backed by swap and manages resource limits. It is also exported
1529 to userspace as tmpfs if TMPFS is enabled. Disabling this
1530 option replaces shmem and tmpfs with the much simpler ramfs code,
1531 which may be appropriate on small systems without swap.
1534 bool "Enable AIO support" if EXPERT
1537 This option enables POSIX asynchronous I/O which may by used
1538 by some high performance threaded applications. Disabling
1539 this option saves about 7k.
1542 bool "Enable IO uring support" if EXPERT
1547 This option enables support for the io_uring interface, enabling
1548 applications to submit and complete IO through submission and
1549 completion rings that are shared between the kernel and application.
1551 config ADVISE_SYSCALLS
1552 bool "Enable madvise/fadvise syscalls" if EXPERT
1555 This option enables the madvise and fadvise syscalls, used by
1556 applications to advise the kernel about their future memory or file
1557 usage, improving performance. If building an embedded system where no
1558 applications use these syscalls, you can disable this option to save
1562 bool "Enable membarrier() system call" if EXPERT
1565 Enable the membarrier() system call that allows issuing memory
1566 barriers across all running threads, which can be used to distribute
1567 the cost of user-space memory barriers asymmetrically by transforming
1568 pairs of memory barriers into pairs consisting of membarrier() and a
1574 bool "Load all symbols for debugging/ksymoops" if EXPERT
1577 Say Y here to let the kernel print out symbolic crash information and
1578 symbolic stack backtraces. This increases the size of the kernel
1579 somewhat, as all symbols have to be loaded into the kernel image.
1582 bool "Include all symbols in kallsyms"
1583 depends on DEBUG_KERNEL && KALLSYMS
1585 Normally kallsyms only contains the symbols of functions for nicer
1586 OOPS messages and backtraces (i.e., symbols from the text and inittext
1587 sections). This is sufficient for most cases. And only in very rare
1588 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1589 names of variables from the data sections, etc).
1591 This option makes sure that all symbols are loaded into the kernel
1592 image (i.e., symbols from all sections) in cost of increased kernel
1593 size (depending on the kernel configuration, it may be 300KiB or
1594 something like this).
1596 Say N unless you really need all symbols.
1598 config KALLSYMS_ABSOLUTE_PERCPU
1601 default X86_64 && SMP
1603 config KALLSYMS_BASE_RELATIVE
1608 Instead of emitting them as absolute values in the native word size,
1609 emit the symbol references in the kallsyms table as 32-bit entries,
1610 each containing a relative value in the range [base, base + U32_MAX]
1611 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1612 an absolute value in the range [0, S32_MAX] or a relative value in the
1613 range [base, base + S32_MAX], where base is the lowest relative symbol
1614 address encountered in the image.
1616 On 64-bit builds, this reduces the size of the address table by 50%,
1617 but more importantly, it results in entries whose values are build
1618 time constants, and no relocation pass is required at runtime to fix
1619 up the entries based on the runtime load address of the kernel.
1621 # end of the "standard kernel features (expert users)" menu
1623 # syscall, maps, verifier
1625 bool "Enable bpf() system call"
1630 Enable the bpf() system call that allows to manipulate eBPF
1631 programs and maps via file descriptors.
1633 config ARCH_WANT_DEFAULT_BPF_JIT
1636 config BPF_JIT_ALWAYS_ON
1637 bool "Permanently enable BPF JIT and remove BPF interpreter"
1638 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1640 Enables BPF JIT and removes BPF interpreter to avoid
1641 speculative execution of BPF instructions by the interpreter
1643 config BPF_JIT_DEFAULT_ON
1644 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
1645 depends on HAVE_EBPF_JIT && BPF_JIT
1648 bool "Enable userfaultfd() system call"
1651 Enable the userfaultfd() system call that allows to intercept and
1652 handle page faults in userland.
1654 config ARCH_HAS_MEMBARRIER_CALLBACKS
1657 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1661 bool "Enable rseq() system call" if EXPERT
1663 depends on HAVE_RSEQ
1666 Enable the restartable sequences system call. It provides a
1667 user-space cache for the current CPU number value, which
1668 speeds up getting the current CPU number from user-space,
1669 as well as an ABI to speed up user-space operations on
1676 bool "Enabled debugging of rseq() system call" if EXPERT
1677 depends on RSEQ && DEBUG_KERNEL
1679 Enable extra debugging checks for the rseq system call.
1684 bool "Embedded system"
1685 option allnoconfig_y
1688 This option should be enabled if compiling the kernel for
1689 an embedded system so certain expert options are available
1692 config HAVE_PERF_EVENTS
1695 See tools/perf/design.txt for details.
1697 config PERF_USE_VMALLOC
1700 See tools/perf/design.txt for details
1703 bool "PC/104 support" if EXPERT
1705 Expose PC/104 form factor device drivers and options available for
1706 selection and configuration. Enable this option if your target
1707 machine has a PC/104 bus.
1709 menu "Kernel Performance Events And Counters"
1712 bool "Kernel performance events and counters"
1713 default y if PROFILING
1714 depends on HAVE_PERF_EVENTS
1718 Enable kernel support for various performance events provided
1719 by software and hardware.
1721 Software events are supported either built-in or via the
1722 use of generic tracepoints.
1724 Most modern CPUs support performance events via performance
1725 counter registers. These registers count the number of certain
1726 types of hw events: such as instructions executed, cachemisses
1727 suffered, or branches mis-predicted - without slowing down the
1728 kernel or applications. These registers can also trigger interrupts
1729 when a threshold number of events have passed - and can thus be
1730 used to profile the code that runs on that CPU.
1732 The Linux Performance Event subsystem provides an abstraction of
1733 these software and hardware event capabilities, available via a
1734 system call and used by the "perf" utility in tools/perf/. It
1735 provides per task and per CPU counters, and it provides event
1736 capabilities on top of those.
1740 config DEBUG_PERF_USE_VMALLOC
1742 bool "Debug: use vmalloc to back perf mmap() buffers"
1743 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1744 select PERF_USE_VMALLOC
1746 Use vmalloc memory to back perf mmap() buffers.
1748 Mostly useful for debugging the vmalloc code on platforms
1749 that don't require it.
1755 config VM_EVENT_COUNTERS
1757 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1759 VM event counters are needed for event counts to be shown.
1760 This option allows the disabling of the VM event counters
1761 on EXPERT systems. /proc/vmstat will only show page counts
1762 if VM event counters are disabled.
1766 bool "Enable SLUB debugging support" if EXPERT
1767 depends on SLUB && SYSFS
1769 SLUB has extensive debug support features. Disabling these can
1770 result in significant savings in code size. This also disables
1771 SLUB sysfs support. /sys/slab will not exist and there will be
1772 no support for cache validation etc.
1774 config SLUB_MEMCG_SYSFS_ON
1776 bool "Enable memcg SLUB sysfs support by default" if EXPERT
1777 depends on SLUB && SYSFS && MEMCG
1779 SLUB creates a directory under /sys/kernel/slab for each
1780 allocation cache to host info and debug files. If memory
1781 cgroup is enabled, each cache can have per memory cgroup
1782 caches. SLUB can create the same sysfs directories for these
1783 caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1784 to a very high number of debug files being created. This is
1785 controlled by slub_memcg_sysfs boot parameter and this
1786 config option determines the parameter's default value.
1789 bool "Disable heap randomization"
1792 Randomizing heap placement makes heap exploits harder, but it
1793 also breaks ancient binaries (including anything libc5 based).
1794 This option changes the bootup default to heap randomization
1795 disabled, and can be overridden at runtime by setting
1796 /proc/sys/kernel/randomize_va_space to 2.
1798 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1801 prompt "Choose SLAB allocator"
1804 This option allows to select a slab allocator.
1808 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1810 The regular slab allocator that is established and known to work
1811 well in all environments. It organizes cache hot objects in
1812 per cpu and per node queues.
1815 bool "SLUB (Unqueued Allocator)"
1816 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1818 SLUB is a slab allocator that minimizes cache line usage
1819 instead of managing queues of cached objects (SLAB approach).
1820 Per cpu caching is realized using slabs of objects instead
1821 of queues of objects. SLUB can use memory efficiently
1822 and has enhanced diagnostics. SLUB is the default choice for
1827 bool "SLOB (Simple Allocator)"
1829 SLOB replaces the stock allocator with a drastically simpler
1830 allocator. SLOB is generally more space efficient but
1831 does not perform as well on large systems.
1835 config SLAB_MERGE_DEFAULT
1836 bool "Allow slab caches to be merged"
1839 For reduced kernel memory fragmentation, slab caches can be
1840 merged when they share the same size and other characteristics.
1841 This carries a risk of kernel heap overflows being able to
1842 overwrite objects from merged caches (and more easily control
1843 cache layout), which makes such heap attacks easier to exploit
1844 by attackers. By keeping caches unmerged, these kinds of exploits
1845 can usually only damage objects in the same cache. To disable
1846 merging at runtime, "slab_nomerge" can be passed on the kernel
1849 config SLAB_FREELIST_RANDOM
1851 depends on SLAB || SLUB
1852 bool "SLAB freelist randomization"
1854 Randomizes the freelist order used on creating new pages. This
1855 security feature reduces the predictability of the kernel slab
1856 allocator against heap overflows.
1858 config SLAB_FREELIST_HARDENED
1859 bool "Harden slab freelist metadata"
1862 Many kernel heap attacks try to target slab cache metadata and
1863 other infrastructure. This options makes minor performance
1864 sacrifices to harden the kernel slab allocator against common
1865 freelist exploit methods.
1867 config SHUFFLE_PAGE_ALLOCATOR
1868 bool "Page allocator randomization"
1869 default SLAB_FREELIST_RANDOM && ACPI_NUMA
1871 Randomization of the page allocator improves the average
1872 utilization of a direct-mapped memory-side-cache. See section
1873 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1874 6.2a specification for an example of how a platform advertises
1875 the presence of a memory-side-cache. There are also incidental
1876 security benefits as it reduces the predictability of page
1877 allocations to compliment SLAB_FREELIST_RANDOM, but the
1878 default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1879 10th order of pages is selected based on cache utilization
1882 While the randomization improves cache utilization it may
1883 negatively impact workloads on platforms without a cache. For
1884 this reason, by default, the randomization is enabled only
1885 after runtime detection of a direct-mapped memory-side-cache.
1886 Otherwise, the randomization may be force enabled with the
1887 'page_alloc.shuffle' kernel command line parameter.
1891 config SLUB_CPU_PARTIAL
1893 depends on SLUB && SMP
1894 bool "SLUB per cpu partial cache"
1896 Per cpu partial caches accelerate objects allocation and freeing
1897 that is local to a processor at the price of more indeterminism
1898 in the latency of the free. On overflow these caches will be cleared
1899 which requires the taking of locks that may cause latency spikes.
1900 Typically one would choose no for a realtime system.
1902 config MMAP_ALLOW_UNINITIALIZED
1903 bool "Allow mmapped anonymous memory to be uninitialized"
1904 depends on EXPERT && !MMU
1907 Normally, and according to the Linux spec, anonymous memory obtained
1908 from mmap() has its contents cleared before it is passed to
1909 userspace. Enabling this config option allows you to request that
1910 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1911 providing a huge performance boost. If this option is not enabled,
1912 then the flag will be ignored.
1914 This is taken advantage of by uClibc's malloc(), and also by
1915 ELF-FDPIC binfmt's brk and stack allocator.
1917 Because of the obvious security issues, this option should only be
1918 enabled on embedded devices where you control what is run in
1919 userspace. Since that isn't generally a problem on no-MMU systems,
1920 it is normally safe to say Y here.
1922 See Documentation/nommu-mmap.txt for more information.
1924 config SYSTEM_DATA_VERIFICATION
1926 select SYSTEM_TRUSTED_KEYRING
1930 select ASYMMETRIC_KEY_TYPE
1931 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1934 select X509_CERTIFICATE_PARSER
1935 select PKCS7_MESSAGE_PARSER
1937 Provide PKCS#7 message verification using the contents of the system
1938 trusted keyring to provide public keys. This then can be used for
1939 module verification, kexec image verification and firmware blob
1943 bool "Profiling support"
1945 Say Y here to enable the extended profiling support mechanisms used
1946 by profilers such as OProfile.
1949 # Place an empty function call at each tracepoint site. Can be
1950 # dynamically changed for a probe function.
1955 endmenu # General setup
1957 source "arch/Kconfig"
1964 default 0 if BASE_FULL
1965 default 1 if !BASE_FULL
1967 config MODULE_SIG_FORMAT
1969 select SYSTEM_DATA_VERIFICATION
1972 bool "Enable loadable module support"
1975 Kernel modules are small pieces of compiled code which can
1976 be inserted in the running kernel, rather than being
1977 permanently built into the kernel. You use the "modprobe"
1978 tool to add (and sometimes remove) them. If you say Y here,
1979 many parts of the kernel can be built as modules (by
1980 answering M instead of Y where indicated): this is most
1981 useful for infrequently used options which are not required
1982 for booting. For more information, see the man pages for
1983 modprobe, lsmod, modinfo, insmod and rmmod.
1985 If you say Y here, you will need to run "make
1986 modules_install" to put the modules under /lib/modules/
1987 where modprobe can find them (you may need to be root to do
1994 config MODULE_FORCE_LOAD
1995 bool "Forced module loading"
1998 Allow loading of modules without version information (ie. modprobe
1999 --force). Forced module loading sets the 'F' (forced) taint flag and
2000 is usually a really bad idea.
2002 config MODULE_UNLOAD
2003 bool "Module unloading"
2005 Without this option you will not be able to unload any
2006 modules (note that some modules may not be unloadable
2007 anyway), which makes your kernel smaller, faster
2008 and simpler. If unsure, say Y.
2010 config MODULE_FORCE_UNLOAD
2011 bool "Forced module unloading"
2012 depends on MODULE_UNLOAD
2014 This option allows you to force a module to unload, even if the
2015 kernel believes it is unsafe: the kernel will remove the module
2016 without waiting for anyone to stop using it (using the -f option to
2017 rmmod). This is mainly for kernel developers and desperate users.
2021 bool "Module versioning support"
2023 Usually, you have to use modules compiled with your kernel.
2024 Saying Y here makes it sometimes possible to use modules
2025 compiled for different kernels, by adding enough information
2026 to the modules to (hopefully) spot any changes which would
2027 make them incompatible with the kernel you are running. If
2030 config ASM_MODVERSIONS
2032 default HAVE_ASM_MODVERSIONS && MODVERSIONS
2034 This enables module versioning for exported symbols also from
2035 assembly. This can be enabled only when the target architecture
2038 config MODULE_REL_CRCS
2040 depends on MODVERSIONS
2042 config MODULE_SRCVERSION_ALL
2043 bool "Source checksum for all modules"
2045 Modules which contain a MODULE_VERSION get an extra "srcversion"
2046 field inserted into their modinfo section, which contains a
2047 sum of the source files which made it. This helps maintainers
2048 see exactly which source was used to build a module (since
2049 others sometimes change the module source without updating
2050 the version). With this option, such a "srcversion" field
2051 will be created for all modules. If unsure, say N.
2054 bool "Module signature verification"
2055 select MODULE_SIG_FORMAT
2057 Check modules for valid signatures upon load: the signature
2058 is simply appended to the module. For more information see
2059 <file:Documentation/admin-guide/module-signing.rst>.
2061 Note that this option adds the OpenSSL development packages as a
2062 kernel build dependency so that the signing tool can use its crypto
2065 You should enable this option if you wish to use either
2066 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2067 another LSM - otherwise unsigned modules will be loadable regardless
2068 of the lockdown policy.
2070 !!!WARNING!!! If you enable this option, you MUST make sure that the
2071 module DOES NOT get stripped after being signed. This includes the
2072 debuginfo strip done by some packagers (such as rpmbuild) and
2073 inclusion into an initramfs that wants the module size reduced.
2075 config MODULE_SIG_FORCE
2076 bool "Require modules to be validly signed"
2077 depends on MODULE_SIG
2079 Reject unsigned modules or signed modules for which we don't have a
2080 key. Without this, such modules will simply taint the kernel.
2082 config MODULE_SIG_ALL
2083 bool "Automatically sign all modules"
2085 depends on MODULE_SIG
2087 Sign all modules during make modules_install. Without this option,
2088 modules must be signed manually, using the scripts/sign-file tool.
2090 comment "Do not forget to sign required modules with scripts/sign-file"
2091 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2094 prompt "Which hash algorithm should modules be signed with?"
2095 depends on MODULE_SIG
2097 This determines which sort of hashing algorithm will be used during
2098 signature generation. This algorithm _must_ be built into the kernel
2099 directly so that signature verification can take place. It is not
2100 possible to load a signed module containing the algorithm to check
2101 the signature on that module.
2103 config MODULE_SIG_SHA1
2104 bool "Sign modules with SHA-1"
2107 config MODULE_SIG_SHA224
2108 bool "Sign modules with SHA-224"
2109 select CRYPTO_SHA256
2111 config MODULE_SIG_SHA256
2112 bool "Sign modules with SHA-256"
2113 select CRYPTO_SHA256
2115 config MODULE_SIG_SHA384
2116 bool "Sign modules with SHA-384"
2117 select CRYPTO_SHA512
2119 config MODULE_SIG_SHA512
2120 bool "Sign modules with SHA-512"
2121 select CRYPTO_SHA512
2125 config MODULE_SIG_HASH
2127 depends on MODULE_SIG
2128 default "sha1" if MODULE_SIG_SHA1
2129 default "sha224" if MODULE_SIG_SHA224
2130 default "sha256" if MODULE_SIG_SHA256
2131 default "sha384" if MODULE_SIG_SHA384
2132 default "sha512" if MODULE_SIG_SHA512
2134 config MODULE_COMPRESS
2135 bool "Compress modules on installation"
2138 Compresses kernel modules when 'make modules_install' is run; gzip or
2139 xz depending on "Compression algorithm" below.
2141 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2143 Out-of-tree kernel modules installed using Kbuild will also be
2144 compressed upon installation.
2146 Note: for modules inside an initrd or initramfs, it's more efficient
2147 to compress the whole initrd or initramfs instead.
2149 Note: This is fully compatible with signed modules.
2154 prompt "Compression algorithm"
2155 depends on MODULE_COMPRESS
2156 default MODULE_COMPRESS_GZIP
2158 This determines which sort of compression will be used during
2159 'make modules_install'.
2161 GZIP (default) and XZ are supported.
2163 config MODULE_COMPRESS_GZIP
2166 config MODULE_COMPRESS_XZ
2171 config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2172 bool "Allow loading of modules with missing namespace imports"
2174 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2175 a namespace. A module that makes use of a symbol exported with such a
2176 namespace is required to import the namespace via MODULE_IMPORT_NS().
2177 There is no technical reason to enforce correct namespace imports,
2178 but it creates consistency between symbols defining namespaces and
2179 users importing namespaces they make use of. This option relaxes this
2180 requirement and lifts the enforcement when loading a module.
2184 config UNUSED_SYMBOLS
2185 bool "Enable unused/obsolete exported symbols"
2188 Unused but exported symbols make the kernel needlessly bigger. For
2189 that reason most of these unused exports will soon be removed. This
2190 option is provided temporarily to provide a transition period in case
2191 some external kernel module needs one of these symbols anyway. If you
2192 encounter such a case in your module, consider if you are actually
2193 using the right API. (rationale: since nobody in the kernel is using
2194 this in a module, there is a pretty good chance it's actually the
2195 wrong interface to use). If you really need the symbol, please send a
2196 mail to the linux kernel mailing list mentioning the symbol and why
2197 you really need it, and what the merge plan to the mainline kernel for
2200 config TRIM_UNUSED_KSYMS
2201 bool "Trim unused exported kernel symbols"
2202 depends on !UNUSED_SYMBOLS
2204 The kernel and some modules make many symbols available for
2205 other modules to use via EXPORT_SYMBOL() and variants. Depending
2206 on the set of modules being selected in your kernel configuration,
2207 many of those exported symbols might never be used.
2209 This option allows for unused exported symbols to be dropped from
2210 the build. In turn, this provides the compiler more opportunities
2211 (especially when using LTO) for optimizing the code and reducing
2212 binary size. This might have some security advantages as well.
2214 If unsure, or if you need to build out-of-tree modules, say N.
2218 config MODULES_TREE_LOOKUP
2220 depends on PERF_EVENTS || TRACING
2222 config INIT_ALL_POSSIBLE
2225 Back when each arch used to define their own cpu_online_mask and
2226 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2227 with all 1s, and others with all 0s. When they were centralised,
2228 it was better to provide this option than to break all the archs
2229 and have several arch maintainers pursuing me down dark alleys.
2231 source "block/Kconfig"
2233 config PREEMPT_NOTIFIERS
2243 Build a simple ASN.1 grammar compiler that produces a bytecode output
2244 that can be interpreted by the ASN.1 stream decoder and used to
2245 inform it as to what tags are to be expected in a stream and what
2246 functions to call on what tags.
2248 source "kernel/Kconfig.locks"
2250 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2253 # It may be useful for an architecture to override the definitions of the
2254 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2255 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2256 # different calling convention for syscalls. They can also override the
2257 # macros for not-implemented syscalls in kernel/sys_ni.c and
2258 # kernel/time/posix-stubs.c. All these overrides need to be available in
2259 # <asm/syscall_wrapper.h>.
2260 config ARCH_HAS_SYSCALL_WRAPPER
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