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)"
9 default "arch/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG)"
12 def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc)
16 default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC
21 default $(shell,$(LD) --version | $(srctree)/scripts/ld-version.sh)
24 def_bool $(success,$(CC) --version | head -n 1 | grep -q clang)
27 def_bool $(success,$(LD) -v | head -n 1 | grep -q LLD)
31 default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
34 def_bool $(success,$(srctree)/scripts/cc-can-link.sh $(CC))
36 config CC_HAS_ASM_GOTO
37 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
39 config TOOLS_SUPPORT_RELR
40 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
42 config CC_HAS_ASM_INLINE
43 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
52 config BUILDTIME_TABLE_SORT
55 config THREAD_INFO_IN_TASK
58 Select this to move thread_info off the stack into task_struct. To
59 make this work, an arch will need to remove all thread_info fields
60 except flags and fix any runtime bugs.
62 One subtle change that will be needed is to use try_get_task_stack()
63 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
72 depends on BROKEN || !SMP
75 config INIT_ENV_ARG_LIMIT
80 Maximum of each of the number of arguments and environment
81 variables passed to init from the kernel command line.
84 bool "Compile also drivers which will not load"
88 Some drivers can be compiled on a different platform than they are
89 intended to be run on. Despite they cannot be loaded there (or even
90 when they load they cannot be used due to missing HW support),
91 developers still, opposing to distributors, might want to build such
92 drivers to compile-test them.
94 If you are a developer and want to build everything available, say Y
95 here. If you are a user/distributor, say N here to exclude useless
96 drivers to be distributed.
98 config UAPI_HEADER_TEST
99 bool "Compile test UAPI headers"
100 depends on HEADERS_INSTALL && CC_CAN_LINK
102 Compile test headers exported to user-space to ensure they are
103 self-contained, i.e. compilable as standalone units.
105 If you are a developer or tester and want to ensure the exported
106 headers are self-contained, say Y here. Otherwise, choose N.
109 string "Local version - append to kernel release"
111 Append an extra string to the end of your kernel version.
112 This will show up when you type uname, for example.
113 The string you set here will be appended after the contents of
114 any files with a filename matching localversion* in your
115 object and source tree, in that order. Your total string can
116 be a maximum of 64 characters.
118 config LOCALVERSION_AUTO
119 bool "Automatically append version information to the version string"
121 depends on !COMPILE_TEST
123 This will try to automatically determine if the current tree is a
124 release tree by looking for git tags that belong to the current
125 top of tree revision.
127 A string of the format -gxxxxxxxx will be added to the localversion
128 if a git-based tree is found. The string generated by this will be
129 appended after any matching localversion* files, and after the value
130 set in CONFIG_LOCALVERSION.
132 (The actual string used here is the first eight characters produced
133 by running the command:
135 $ git rev-parse --verify HEAD
137 which is done within the script "scripts/setlocalversion".)
140 string "Build ID Salt"
143 The build ID is used to link binaries and their debug info. Setting
144 this option will use the value in the calculation of the build id.
145 This is mostly useful for distributions which want to ensure the
146 build is unique between builds. It's safe to leave the default.
148 config HAVE_KERNEL_GZIP
151 config HAVE_KERNEL_BZIP2
154 config HAVE_KERNEL_LZMA
157 config HAVE_KERNEL_XZ
160 config HAVE_KERNEL_LZO
163 config HAVE_KERNEL_LZ4
166 config HAVE_KERNEL_UNCOMPRESSED
170 prompt "Kernel compression mode"
172 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED
174 The linux kernel is a kind of self-extracting executable.
175 Several compression algorithms are available, which differ
176 in efficiency, compression and decompression speed.
177 Compression speed is only relevant when building a kernel.
178 Decompression speed is relevant at each boot.
180 If you have any problems with bzip2 or lzma compressed
181 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
182 version of this functionality (bzip2 only), for 2.4, was
183 supplied by Christian Ludwig)
185 High compression options are mostly useful for users, who
186 are low on disk space (embedded systems), but for whom ram
189 If in doubt, select 'gzip'
193 depends on HAVE_KERNEL_GZIP
195 The old and tried gzip compression. It provides a good balance
196 between compression ratio and decompression speed.
200 depends on HAVE_KERNEL_BZIP2
202 Its compression ratio and speed is intermediate.
203 Decompression speed is slowest among the choices. The kernel
204 size is about 10% smaller with bzip2, in comparison to gzip.
205 Bzip2 uses a large amount of memory. For modern kernels you
206 will need at least 8MB RAM or more for booting.
210 depends on HAVE_KERNEL_LZMA
212 This compression algorithm's ratio is best. Decompression speed
213 is between gzip and bzip2. Compression is slowest.
214 The kernel size is about 33% smaller with LZMA in comparison to gzip.
218 depends on HAVE_KERNEL_XZ
220 XZ uses the LZMA2 algorithm and instruction set specific
221 BCJ filters which can improve compression ratio of executable
222 code. The size of the kernel is about 30% smaller with XZ in
223 comparison to gzip. On architectures for which there is a BCJ
224 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
225 will create a few percent smaller kernel than plain LZMA.
227 The speed is about the same as with LZMA: The decompression
228 speed of XZ is better than that of bzip2 but worse than gzip
229 and LZO. Compression is slow.
233 depends on HAVE_KERNEL_LZO
235 Its compression ratio is the poorest among the choices. The kernel
236 size is about 10% bigger than gzip; however its speed
237 (both compression and decompression) is the fastest.
241 depends on HAVE_KERNEL_LZ4
243 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
244 A preliminary version of LZ4 de/compression tool is available at
245 <https://code.google.com/p/lz4/>.
247 Its compression ratio is worse than LZO. The size of the kernel
248 is about 8% bigger than LZO. But the decompression speed is
251 config KERNEL_UNCOMPRESSED
253 depends on HAVE_KERNEL_UNCOMPRESSED
255 Produce uncompressed kernel image. This option is usually not what
256 you want. It is useful for debugging the kernel in slow simulation
257 environments, where decompressing and moving the kernel is awfully
258 slow. This option allows early boot code to skip the decompressor
259 and jump right at uncompressed kernel image.
264 string "Default init path"
267 This option determines the default init for the system if no init=
268 option is passed on the kernel command line. If the requested path is
269 not present, we will still then move on to attempting further
270 locations (e.g. /sbin/init, etc). If this is empty, we will just use
271 the fallback list when init= is not passed.
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 SCHED_THERMAL_PRESSURE
455 bool "Enable periodic averaging of thermal pressure"
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
774 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
777 # For architectures that know their GCC __int128 support is sound
779 config ARCH_SUPPORTS_INT128
782 # For architectures that (ab)use NUMA to represent different memory regions
783 # all cpu-local but of different latencies, such as SuperH.
785 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
788 config NUMA_BALANCING
789 bool "Memory placement aware NUMA scheduler"
790 depends on ARCH_SUPPORTS_NUMA_BALANCING
791 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
792 depends on SMP && NUMA && MIGRATION
794 This option adds support for automatic NUMA aware memory/task placement.
795 The mechanism is quite primitive and is based on migrating memory when
796 it has references to the node the task is running on.
798 This system will be inactive on UMA systems.
800 config NUMA_BALANCING_DEFAULT_ENABLED
801 bool "Automatically enable NUMA aware memory/task placement"
803 depends on NUMA_BALANCING
805 If set, automatic NUMA balancing will be enabled if running on a NUMA
809 bool "Control Group support"
812 This option adds support for grouping sets of processes together, for
813 use with process control subsystems such as Cpusets, CFS, memory
814 controls or device isolation.
816 - Documentation/scheduler/sched-design-CFS.rst (CFS)
817 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
818 and resource control)
828 bool "Memory controller"
832 Provides control over the memory footprint of tasks in a cgroup.
836 depends on MEMCG && SWAP
841 depends on MEMCG && !SLOB
849 Generic block IO controller cgroup interface. This is the common
850 cgroup interface which should be used by various IO controlling
853 Currently, CFQ IO scheduler uses it to recognize task groups and
854 control disk bandwidth allocation (proportional time slice allocation)
855 to such task groups. It is also used by bio throttling logic in
856 block layer to implement upper limit in IO rates on a device.
858 This option only enables generic Block IO controller infrastructure.
859 One needs to also enable actual IO controlling logic/policy. For
860 enabling proportional weight division of disk bandwidth in CFQ, set
861 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
862 CONFIG_BLK_DEV_THROTTLING=y.
864 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
866 config CGROUP_WRITEBACK
868 depends on MEMCG && BLK_CGROUP
871 menuconfig CGROUP_SCHED
872 bool "CPU controller"
875 This feature lets CPU scheduler recognize task groups and control CPU
876 bandwidth allocation to such task groups. It uses cgroups to group
880 config FAIR_GROUP_SCHED
881 bool "Group scheduling for SCHED_OTHER"
882 depends on CGROUP_SCHED
886 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
887 depends on FAIR_GROUP_SCHED
890 This option allows users to define CPU bandwidth rates (limits) for
891 tasks running within the fair group scheduler. Groups with no limit
892 set are considered to be unconstrained and will run with no
894 See Documentation/scheduler/sched-bwc.rst for more information.
896 config RT_GROUP_SCHED
897 bool "Group scheduling for SCHED_RR/FIFO"
898 depends on CGROUP_SCHED
901 This feature lets you explicitly allocate real CPU bandwidth
902 to task groups. If enabled, it will also make it impossible to
903 schedule realtime tasks for non-root users until you allocate
904 realtime bandwidth for them.
905 See Documentation/scheduler/sched-rt-group.rst for more information.
909 config UCLAMP_TASK_GROUP
910 bool "Utilization clamping per group of tasks"
911 depends on CGROUP_SCHED
912 depends on UCLAMP_TASK
915 This feature enables the scheduler to track the clamped utilization
916 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
918 When this option is enabled, the user can specify a min and max
919 CPU bandwidth which is allowed for each single task in a group.
920 The max bandwidth allows to clamp the maximum frequency a task
921 can use, while the min bandwidth allows to define a minimum
922 frequency a task will always use.
924 When task group based utilization clamping is enabled, an eventually
925 specified task-specific clamp value is constrained by the cgroup
926 specified clamp value. Both minimum and maximum task clamping cannot
927 be bigger than the corresponding clamping defined at task group level.
932 bool "PIDs controller"
934 Provides enforcement of process number limits in the scope of a
935 cgroup. Any attempt to fork more processes than is allowed in the
936 cgroup will fail. PIDs are fundamentally a global resource because it
937 is fairly trivial to reach PID exhaustion before you reach even a
938 conservative kmemcg limit. As a result, it is possible to grind a
939 system to halt without being limited by other cgroup policies. The
940 PIDs controller is designed to stop this from happening.
942 It should be noted that organisational operations (such as attaching
943 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
944 since the PIDs limit only affects a process's ability to fork, not to
948 bool "RDMA controller"
950 Provides enforcement of RDMA resources defined by IB stack.
951 It is fairly easy for consumers to exhaust RDMA resources, which
952 can result into resource unavailability to other consumers.
953 RDMA controller is designed to stop this from happening.
954 Attaching processes with active RDMA resources to the cgroup
955 hierarchy is allowed even if can cross the hierarchy's limit.
957 config CGROUP_FREEZER
958 bool "Freezer controller"
960 Provides a way to freeze and unfreeze all tasks in a
963 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
964 controller includes important in-kernel memory consumers per default.
966 If you're using cgroup2, say N.
968 config CGROUP_HUGETLB
969 bool "HugeTLB controller"
970 depends on HUGETLB_PAGE
974 Provides a cgroup controller for HugeTLB pages.
975 When you enable this, you can put a per cgroup limit on HugeTLB usage.
976 The limit is enforced during page fault. Since HugeTLB doesn't
977 support page reclaim, enforcing the limit at page fault time implies
978 that, the application will get SIGBUS signal if it tries to access
979 HugeTLB pages beyond its limit. This requires the application to know
980 beforehand how much HugeTLB pages it would require for its use. The
981 control group is tracked in the third page lru pointer. This means
982 that we cannot use the controller with huge page less than 3 pages.
985 bool "Cpuset controller"
988 This option will let you create and manage CPUSETs which
989 allow dynamically partitioning a system into sets of CPUs and
990 Memory Nodes and assigning tasks to run only within those sets.
991 This is primarily useful on large SMP or NUMA systems.
995 config PROC_PID_CPUSET
996 bool "Include legacy /proc/<pid>/cpuset file"
1000 config CGROUP_DEVICE
1001 bool "Device controller"
1003 Provides a cgroup controller implementing whitelists for
1004 devices which a process in the cgroup can mknod or open.
1006 config CGROUP_CPUACCT
1007 bool "Simple CPU accounting controller"
1009 Provides a simple controller for monitoring the
1010 total CPU consumed by the tasks in a cgroup.
1013 bool "Perf controller"
1014 depends on PERF_EVENTS
1016 This option extends the perf per-cpu mode to restrict monitoring
1017 to threads which belong to the cgroup specified and run on the
1018 designated cpu. Or this can be used to have cgroup ID in samples
1019 so that it can monitor performance events among cgroups.
1024 bool "Support for eBPF programs attached to cgroups"
1025 depends on BPF_SYSCALL
1026 select SOCK_CGROUP_DATA
1028 Allow attaching eBPF programs to a cgroup using the bpf(2)
1029 syscall command BPF_PROG_ATTACH.
1031 In which context these programs are accessed depends on the type
1032 of attachment. For instance, programs that are attached using
1033 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1037 bool "Debug controller"
1039 depends on DEBUG_KERNEL
1041 This option enables a simple controller that exports
1042 debugging information about the cgroups framework. This
1043 controller is for control cgroup debugging only. Its
1044 interfaces are not stable.
1048 config SOCK_CGROUP_DATA
1054 menuconfig NAMESPACES
1055 bool "Namespaces support" if EXPERT
1056 depends on MULTIUSER
1059 Provides the way to make tasks work with different objects using
1060 the same id. For example same IPC id may refer to different objects
1061 or same user id or pid may refer to different tasks when used in
1062 different namespaces.
1067 bool "UTS namespace"
1070 In this namespace tasks see different info provided with the
1074 bool "TIME namespace"
1075 depends on GENERIC_VDSO_TIME_NS
1078 In this namespace boottime and monotonic clocks can be set.
1079 The time will keep going with the same pace.
1082 bool "IPC namespace"
1083 depends on (SYSVIPC || POSIX_MQUEUE)
1086 In this namespace tasks work with IPC ids which correspond to
1087 different IPC objects in different namespaces.
1090 bool "User namespace"
1093 This allows containers, i.e. vservers, to use user namespaces
1094 to provide different user info for different servers.
1096 When user namespaces are enabled in the kernel it is
1097 recommended that the MEMCG option also be enabled and that
1098 user-space use the memory control groups to limit the amount
1099 of memory a memory unprivileged users can use.
1104 bool "PID Namespaces"
1107 Support process id namespaces. This allows having multiple
1108 processes with the same pid as long as they are in different
1109 pid namespaces. This is a building block of containers.
1112 bool "Network namespace"
1116 Allow user space to create what appear to be multiple instances
1117 of the network stack.
1121 config CHECKPOINT_RESTORE
1122 bool "Checkpoint/restore support"
1123 select PROC_CHILDREN
1126 Enables additional kernel features in a sake of checkpoint/restore.
1127 In particular it adds auxiliary prctl codes to setup process text,
1128 data and heap segment sizes, and a few additional /proc filesystem
1131 If unsure, say N here.
1133 config SCHED_AUTOGROUP
1134 bool "Automatic process group scheduling"
1137 select FAIR_GROUP_SCHED
1139 This option optimizes the scheduler for common desktop workloads by
1140 automatically creating and populating task groups. This separation
1141 of workloads isolates aggressive CPU burners (like build jobs) from
1142 desktop applications. Task group autogeneration is currently based
1145 config SYSFS_DEPRECATED
1146 bool "Enable deprecated sysfs features to support old userspace tools"
1150 This option adds code that switches the layout of the "block" class
1151 devices, to not show up in /sys/class/block/, but only in
1154 This switch is only active when the sysfs.deprecated=1 boot option is
1155 passed or the SYSFS_DEPRECATED_V2 option is set.
1157 This option allows new kernels to run on old distributions and tools,
1158 which might get confused by /sys/class/block/. Since 2007/2008 all
1159 major distributions and tools handle this just fine.
1161 Recent distributions and userspace tools after 2009/2010 depend on
1162 the existence of /sys/class/block/, and will not work with this
1165 Only if you are using a new kernel on an old distribution, you might
1168 config SYSFS_DEPRECATED_V2
1169 bool "Enable deprecated sysfs features by default"
1172 depends on SYSFS_DEPRECATED
1174 Enable deprecated sysfs by default.
1176 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1179 Only if you are using a new kernel on an old distribution, you might
1180 need to say Y here. Even then, odds are you would not need it
1181 enabled, you can always pass the boot option if absolutely necessary.
1184 bool "Kernel->user space relay support (formerly relayfs)"
1187 This option enables support for relay interface support in
1188 certain file systems (such as debugfs).
1189 It is designed to provide an efficient mechanism for tools and
1190 facilities to relay large amounts of data from kernel space to
1195 config BLK_DEV_INITRD
1196 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1198 The initial RAM filesystem is a ramfs which is loaded by the
1199 boot loader (loadlin or lilo) and that is mounted as root
1200 before the normal boot procedure. It is typically used to
1201 load modules needed to mount the "real" root file system,
1202 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1204 If RAM disk support (BLK_DEV_RAM) is also included, this
1205 also enables initial RAM disk (initrd) support and adds
1206 15 Kbytes (more on some other architectures) to the kernel size.
1212 source "usr/Kconfig"
1217 bool "Boot config support"
1218 select BLK_DEV_INITRD
1220 Extra boot config allows system admin to pass a config file as
1221 complemental extension of kernel cmdline when booting.
1222 The boot config file must be attached at the end of initramfs
1223 with checksum, size and magic word.
1224 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1229 prompt "Compiler optimization level"
1230 default CC_OPTIMIZE_FOR_PERFORMANCE
1232 config CC_OPTIMIZE_FOR_PERFORMANCE
1233 bool "Optimize for performance (-O2)"
1235 This is the default optimization level for the kernel, building
1236 with the "-O2" compiler flag for best performance and most
1237 helpful compile-time warnings.
1239 config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1240 bool "Optimize more for performance (-O3)"
1243 Choosing this option will pass "-O3" to your compiler to optimize
1244 the kernel yet more for performance.
1246 config CC_OPTIMIZE_FOR_SIZE
1247 bool "Optimize for size (-Os)"
1249 Choosing this option will pass "-Os" to your compiler resulting
1250 in a smaller kernel.
1254 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1257 This requires that the arch annotates or otherwise protects
1258 its external entry points from being discarded. Linker scripts
1259 must also merge .text.*, .data.*, and .bss.* correctly into
1260 output sections. Care must be taken not to pull in unrelated
1261 sections (e.g., '.text.init'). Typically '.' in section names
1262 is used to distinguish them from label names / C identifiers.
1264 config LD_DEAD_CODE_DATA_ELIMINATION
1265 bool "Dead code and data elimination (EXPERIMENTAL)"
1266 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1268 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800)
1269 depends on $(cc-option,-ffunction-sections -fdata-sections)
1270 depends on $(ld-option,--gc-sections)
1272 Enable this if you want to do dead code and data elimination with
1273 the linker by compiling with -ffunction-sections -fdata-sections,
1274 and linking with --gc-sections.
1276 This can reduce on disk and in-memory size of the kernel
1277 code and static data, particularly for small configs and
1278 on small systems. This has the possibility of introducing
1279 silently broken kernel if the required annotations are not
1280 present. This option is not well tested yet, so use at your
1289 config SYSCTL_EXCEPTION_TRACE
1292 Enable support for /proc/sys/debug/exception-trace.
1294 config SYSCTL_ARCH_UNALIGN_NO_WARN
1297 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1298 Allows arch to define/use @no_unaligned_warning to possibly warn
1299 about unaligned access emulation going on under the hood.
1301 config SYSCTL_ARCH_UNALIGN_ALLOW
1304 Enable support for /proc/sys/kernel/unaligned-trap
1305 Allows arches to define/use @unaligned_enabled to runtime toggle
1306 the unaligned access emulation.
1307 see arch/parisc/kernel/unaligned.c for reference
1309 config HAVE_PCSPKR_PLATFORM
1312 # interpreter that classic socket filters depend on
1317 bool "Configure standard kernel features (expert users)"
1318 # Unhide debug options, to make the on-by-default options visible
1321 This option allows certain base kernel options and settings
1322 to be disabled or tweaked. This is for specialized
1323 environments which can tolerate a "non-standard" kernel.
1324 Only use this if you really know what you are doing.
1327 bool "Enable 16-bit UID system calls" if EXPERT
1328 depends on HAVE_UID16 && MULTIUSER
1331 This enables the legacy 16-bit UID syscall wrappers.
1334 bool "Multiple users, groups and capabilities support" if EXPERT
1337 This option enables support for non-root users, groups and
1340 If you say N here, all processes will run with UID 0, GID 0, and all
1341 possible capabilities. Saying N here also compiles out support for
1342 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1345 If unsure, say Y here.
1347 config SGETMASK_SYSCALL
1348 bool "sgetmask/ssetmask syscalls support" if EXPERT
1349 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1351 sys_sgetmask and sys_ssetmask are obsolete system calls
1352 no longer supported in libc but still enabled by default in some
1355 If unsure, leave the default option here.
1357 config SYSFS_SYSCALL
1358 bool "Sysfs syscall support" if EXPERT
1361 sys_sysfs is an obsolete system call no longer supported in libc.
1362 Note that disabling this option is more secure but might break
1363 compatibility with some systems.
1365 If unsure say Y here.
1368 bool "open by fhandle syscalls" if EXPERT
1372 If you say Y here, a user level program will be able to map
1373 file names to handle and then later use the handle for
1374 different file system operations. This is useful in implementing
1375 userspace file servers, which now track files using handles instead
1376 of names. The handle would remain the same even if file names
1377 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1381 bool "Posix Clocks & timers" if EXPERT
1384 This includes native support for POSIX timers to the kernel.
1385 Some embedded systems have no use for them and therefore they
1386 can be configured out to reduce the size of the kernel image.
1388 When this option is disabled, the following syscalls won't be
1389 available: timer_create, timer_gettime: timer_getoverrun,
1390 timer_settime, timer_delete, clock_adjtime, getitimer,
1391 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1392 clock_getres and clock_nanosleep syscalls will be limited to
1393 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1399 bool "Enable support for printk" if EXPERT
1402 This option enables normal printk support. Removing it
1403 eliminates most of the message strings from the kernel image
1404 and makes the kernel more or less silent. As this makes it
1405 very difficult to diagnose system problems, saying N here is
1406 strongly discouraged.
1414 bool "BUG() support" if EXPERT
1417 Disabling this option eliminates support for BUG and WARN, reducing
1418 the size of your kernel image and potentially quietly ignoring
1419 numerous fatal conditions. You should only consider disabling this
1420 option for embedded systems with no facilities for reporting errors.
1426 bool "Enable ELF core dumps" if EXPERT
1428 Enable support for generating core dumps. Disabling saves about 4k.
1431 config PCSPKR_PLATFORM
1432 bool "Enable PC-Speaker support" if EXPERT
1433 depends on HAVE_PCSPKR_PLATFORM
1437 This option allows to disable the internal PC-Speaker
1438 support, saving some memory.
1442 bool "Enable full-sized data structures for core" if EXPERT
1444 Disabling this option reduces the size of miscellaneous core
1445 kernel data structures. This saves memory on small machines,
1446 but may reduce performance.
1449 bool "Enable futex support" if EXPERT
1453 Disabling this option will cause the kernel to be built without
1454 support for "fast userspace mutexes". The resulting kernel may not
1455 run glibc-based applications correctly.
1459 depends on FUTEX && RT_MUTEXES
1462 config HAVE_FUTEX_CMPXCHG
1466 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1467 is implemented and always working. This removes a couple of runtime
1471 bool "Enable eventpoll support" if EXPERT
1474 Disabling this option will cause the kernel to be built without
1475 support for epoll family of system calls.
1478 bool "Enable signalfd() system call" if EXPERT
1481 Enable the signalfd() system call that allows to receive signals
1482 on a file descriptor.
1487 bool "Enable timerfd() system call" if EXPERT
1490 Enable the timerfd() system call that allows to receive timer
1491 events on a file descriptor.
1496 bool "Enable eventfd() system call" if EXPERT
1499 Enable the eventfd() system call that allows to receive both
1500 kernel notification (ie. KAIO) or userspace notifications.
1505 bool "Use full shmem filesystem" if EXPERT
1509 The shmem is an internal filesystem used to manage shared memory.
1510 It is backed by swap and manages resource limits. It is also exported
1511 to userspace as tmpfs if TMPFS is enabled. Disabling this
1512 option replaces shmem and tmpfs with the much simpler ramfs code,
1513 which may be appropriate on small systems without swap.
1516 bool "Enable AIO support" if EXPERT
1519 This option enables POSIX asynchronous I/O which may by used
1520 by some high performance threaded applications. Disabling
1521 this option saves about 7k.
1524 bool "Enable IO uring support" if EXPERT
1528 This option enables support for the io_uring interface, enabling
1529 applications to submit and complete IO through submission and
1530 completion rings that are shared between the kernel and application.
1532 config ADVISE_SYSCALLS
1533 bool "Enable madvise/fadvise syscalls" if EXPERT
1536 This option enables the madvise and fadvise syscalls, used by
1537 applications to advise the kernel about their future memory or file
1538 usage, improving performance. If building an embedded system where no
1539 applications use these syscalls, you can disable this option to save
1542 config HAVE_ARCH_USERFAULTFD_WP
1545 Arch has userfaultfd write protection support
1548 bool "Enable membarrier() system call" if EXPERT
1551 Enable the membarrier() system call that allows issuing memory
1552 barriers across all running threads, which can be used to distribute
1553 the cost of user-space memory barriers asymmetrically by transforming
1554 pairs of memory barriers into pairs consisting of membarrier() and a
1560 bool "Load all symbols for debugging/ksymoops" if EXPERT
1563 Say Y here to let the kernel print out symbolic crash information and
1564 symbolic stack backtraces. This increases the size of the kernel
1565 somewhat, as all symbols have to be loaded into the kernel image.
1568 bool "Include all symbols in kallsyms"
1569 depends on DEBUG_KERNEL && KALLSYMS
1571 Normally kallsyms only contains the symbols of functions for nicer
1572 OOPS messages and backtraces (i.e., symbols from the text and inittext
1573 sections). This is sufficient for most cases. And only in very rare
1574 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1575 names of variables from the data sections, etc).
1577 This option makes sure that all symbols are loaded into the kernel
1578 image (i.e., symbols from all sections) in cost of increased kernel
1579 size (depending on the kernel configuration, it may be 300KiB or
1580 something like this).
1582 Say N unless you really need all symbols.
1584 config KALLSYMS_ABSOLUTE_PERCPU
1587 default X86_64 && SMP
1589 config KALLSYMS_BASE_RELATIVE
1594 Instead of emitting them as absolute values in the native word size,
1595 emit the symbol references in the kallsyms table as 32-bit entries,
1596 each containing a relative value in the range [base, base + U32_MAX]
1597 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1598 an absolute value in the range [0, S32_MAX] or a relative value in the
1599 range [base, base + S32_MAX], where base is the lowest relative symbol
1600 address encountered in the image.
1602 On 64-bit builds, this reduces the size of the address table by 50%,
1603 but more importantly, it results in entries whose values are build
1604 time constants, and no relocation pass is required at runtime to fix
1605 up the entries based on the runtime load address of the kernel.
1607 # end of the "standard kernel features (expert users)" menu
1609 # syscall, maps, verifier
1612 bool "LSM Instrumentation with BPF"
1613 depends on BPF_EVENTS
1614 depends on BPF_SYSCALL
1618 Enables instrumentation of the security hooks with eBPF programs for
1619 implementing dynamic MAC and Audit Policies.
1621 If you are unsure how to answer this question, answer N.
1624 bool "Enable bpf() system call"
1629 Enable the bpf() system call that allows to manipulate eBPF
1630 programs and maps via file descriptors.
1632 config ARCH_WANT_DEFAULT_BPF_JIT
1635 config BPF_JIT_ALWAYS_ON
1636 bool "Permanently enable BPF JIT and remove BPF interpreter"
1637 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1639 Enables BPF JIT and removes BPF interpreter to avoid
1640 speculative execution of BPF instructions by the interpreter
1642 config BPF_JIT_DEFAULT_ON
1643 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
1644 depends on HAVE_EBPF_JIT && BPF_JIT
1647 bool "Enable userfaultfd() system call"
1650 Enable the userfaultfd() system call that allows to intercept and
1651 handle page faults in userland.
1653 config ARCH_HAS_MEMBARRIER_CALLBACKS
1656 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1660 bool "Enable rseq() system call" if EXPERT
1662 depends on HAVE_RSEQ
1665 Enable the restartable sequences system call. It provides a
1666 user-space cache for the current CPU number value, which
1667 speeds up getting the current CPU number from user-space,
1668 as well as an ABI to speed up user-space operations on
1675 bool "Enabled debugging of rseq() system call" if EXPERT
1676 depends on RSEQ && DEBUG_KERNEL
1678 Enable extra debugging checks for the rseq system call.
1683 bool "Embedded system"
1684 option allnoconfig_y
1687 This option should be enabled if compiling the kernel for
1688 an embedded system so certain expert options are available
1691 config HAVE_PERF_EVENTS
1694 See tools/perf/design.txt for details.
1696 config PERF_USE_VMALLOC
1699 See tools/perf/design.txt for details
1702 bool "PC/104 support" if EXPERT
1704 Expose PC/104 form factor device drivers and options available for
1705 selection and configuration. Enable this option if your target
1706 machine has a PC/104 bus.
1708 menu "Kernel Performance Events And Counters"
1711 bool "Kernel performance events and counters"
1712 default y if PROFILING
1713 depends on HAVE_PERF_EVENTS
1717 Enable kernel support for various performance events provided
1718 by software and hardware.
1720 Software events are supported either built-in or via the
1721 use of generic tracepoints.
1723 Most modern CPUs support performance events via performance
1724 counter registers. These registers count the number of certain
1725 types of hw events: such as instructions executed, cachemisses
1726 suffered, or branches mis-predicted - without slowing down the
1727 kernel or applications. These registers can also trigger interrupts
1728 when a threshold number of events have passed - and can thus be
1729 used to profile the code that runs on that CPU.
1731 The Linux Performance Event subsystem provides an abstraction of
1732 these software and hardware event capabilities, available via a
1733 system call and used by the "perf" utility in tools/perf/. It
1734 provides per task and per CPU counters, and it provides event
1735 capabilities on top of those.
1739 config DEBUG_PERF_USE_VMALLOC
1741 bool "Debug: use vmalloc to back perf mmap() buffers"
1742 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1743 select PERF_USE_VMALLOC
1745 Use vmalloc memory to back perf mmap() buffers.
1747 Mostly useful for debugging the vmalloc code on platforms
1748 that don't require it.
1754 config VM_EVENT_COUNTERS
1756 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1758 VM event counters are needed for event counts to be shown.
1759 This option allows the disabling of the VM event counters
1760 on EXPERT systems. /proc/vmstat will only show page counts
1761 if VM event counters are disabled.
1765 bool "Enable SLUB debugging support" if EXPERT
1766 depends on SLUB && SYSFS
1768 SLUB has extensive debug support features. Disabling these can
1769 result in significant savings in code size. This also disables
1770 SLUB sysfs support. /sys/slab will not exist and there will be
1771 no support for cache validation etc.
1773 config SLUB_MEMCG_SYSFS_ON
1775 bool "Enable memcg SLUB sysfs support by default" if EXPERT
1776 depends on SLUB && SYSFS && MEMCG
1778 SLUB creates a directory under /sys/kernel/slab for each
1779 allocation cache to host info and debug files. If memory
1780 cgroup is enabled, each cache can have per memory cgroup
1781 caches. SLUB can create the same sysfs directories for these
1782 caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1783 to a very high number of debug files being created. This is
1784 controlled by slub_memcg_sysfs boot parameter and this
1785 config option determines the parameter's default value.
1788 bool "Disable heap randomization"
1791 Randomizing heap placement makes heap exploits harder, but it
1792 also breaks ancient binaries (including anything libc5 based).
1793 This option changes the bootup default to heap randomization
1794 disabled, and can be overridden at runtime by setting
1795 /proc/sys/kernel/randomize_va_space to 2.
1797 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1800 prompt "Choose SLAB allocator"
1803 This option allows to select a slab allocator.
1807 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1809 The regular slab allocator that is established and known to work
1810 well in all environments. It organizes cache hot objects in
1811 per cpu and per node queues.
1814 bool "SLUB (Unqueued Allocator)"
1815 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1817 SLUB is a slab allocator that minimizes cache line usage
1818 instead of managing queues of cached objects (SLAB approach).
1819 Per cpu caching is realized using slabs of objects instead
1820 of queues of objects. SLUB can use memory efficiently
1821 and has enhanced diagnostics. SLUB is the default choice for
1826 bool "SLOB (Simple Allocator)"
1828 SLOB replaces the stock allocator with a drastically simpler
1829 allocator. SLOB is generally more space efficient but
1830 does not perform as well on large systems.
1834 config SLAB_MERGE_DEFAULT
1835 bool "Allow slab caches to be merged"
1838 For reduced kernel memory fragmentation, slab caches can be
1839 merged when they share the same size and other characteristics.
1840 This carries a risk of kernel heap overflows being able to
1841 overwrite objects from merged caches (and more easily control
1842 cache layout), which makes such heap attacks easier to exploit
1843 by attackers. By keeping caches unmerged, these kinds of exploits
1844 can usually only damage objects in the same cache. To disable
1845 merging at runtime, "slab_nomerge" can be passed on the kernel
1848 config SLAB_FREELIST_RANDOM
1850 depends on SLAB || SLUB
1851 bool "SLAB freelist randomization"
1853 Randomizes the freelist order used on creating new pages. This
1854 security feature reduces the predictability of the kernel slab
1855 allocator against heap overflows.
1857 config SLAB_FREELIST_HARDENED
1858 bool "Harden slab freelist metadata"
1861 Many kernel heap attacks try to target slab cache metadata and
1862 other infrastructure. This options makes minor performance
1863 sacrifices to harden the kernel slab allocator against common
1864 freelist exploit methods.
1866 config SHUFFLE_PAGE_ALLOCATOR
1867 bool "Page allocator randomization"
1868 default SLAB_FREELIST_RANDOM && ACPI_NUMA
1870 Randomization of the page allocator improves the average
1871 utilization of a direct-mapped memory-side-cache. See section
1872 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1873 6.2a specification for an example of how a platform advertises
1874 the presence of a memory-side-cache. There are also incidental
1875 security benefits as it reduces the predictability of page
1876 allocations to compliment SLAB_FREELIST_RANDOM, but the
1877 default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1878 10th order of pages is selected based on cache utilization
1881 While the randomization improves cache utilization it may
1882 negatively impact workloads on platforms without a cache. For
1883 this reason, by default, the randomization is enabled only
1884 after runtime detection of a direct-mapped memory-side-cache.
1885 Otherwise, the randomization may be force enabled with the
1886 'page_alloc.shuffle' kernel command line parameter.
1890 config SLUB_CPU_PARTIAL
1892 depends on SLUB && SMP
1893 bool "SLUB per cpu partial cache"
1895 Per cpu partial caches accelerate objects allocation and freeing
1896 that is local to a processor at the price of more indeterminism
1897 in the latency of the free. On overflow these caches will be cleared
1898 which requires the taking of locks that may cause latency spikes.
1899 Typically one would choose no for a realtime system.
1901 config MMAP_ALLOW_UNINITIALIZED
1902 bool "Allow mmapped anonymous memory to be uninitialized"
1903 depends on EXPERT && !MMU
1906 Normally, and according to the Linux spec, anonymous memory obtained
1907 from mmap() has its contents cleared before it is passed to
1908 userspace. Enabling this config option allows you to request that
1909 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1910 providing a huge performance boost. If this option is not enabled,
1911 then the flag will be ignored.
1913 This is taken advantage of by uClibc's malloc(), and also by
1914 ELF-FDPIC binfmt's brk and stack allocator.
1916 Because of the obvious security issues, this option should only be
1917 enabled on embedded devices where you control what is run in
1918 userspace. Since that isn't generally a problem on no-MMU systems,
1919 it is normally safe to say Y here.
1921 See Documentation/nommu-mmap.txt for more information.
1923 config SYSTEM_DATA_VERIFICATION
1925 select SYSTEM_TRUSTED_KEYRING
1929 select ASYMMETRIC_KEY_TYPE
1930 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1933 select X509_CERTIFICATE_PARSER
1934 select PKCS7_MESSAGE_PARSER
1936 Provide PKCS#7 message verification using the contents of the system
1937 trusted keyring to provide public keys. This then can be used for
1938 module verification, kexec image verification and firmware blob
1942 bool "Profiling support"
1944 Say Y here to enable the extended profiling support mechanisms used
1945 by profilers such as OProfile.
1948 # Place an empty function call at each tracepoint site. Can be
1949 # dynamically changed for a probe function.
1954 endmenu # General setup
1956 source "arch/Kconfig"
1963 default 0 if BASE_FULL
1964 default 1 if !BASE_FULL
1966 config MODULE_SIG_FORMAT
1968 select SYSTEM_DATA_VERIFICATION
1971 bool "Enable loadable module support"
1974 Kernel modules are small pieces of compiled code which can
1975 be inserted in the running kernel, rather than being
1976 permanently built into the kernel. You use the "modprobe"
1977 tool to add (and sometimes remove) them. If you say Y here,
1978 many parts of the kernel can be built as modules (by
1979 answering M instead of Y where indicated): this is most
1980 useful for infrequently used options which are not required
1981 for booting. For more information, see the man pages for
1982 modprobe, lsmod, modinfo, insmod and rmmod.
1984 If you say Y here, you will need to run "make
1985 modules_install" to put the modules under /lib/modules/
1986 where modprobe can find them (you may need to be root to do
1993 config MODULE_FORCE_LOAD
1994 bool "Forced module loading"
1997 Allow loading of modules without version information (ie. modprobe
1998 --force). Forced module loading sets the 'F' (forced) taint flag and
1999 is usually a really bad idea.
2001 config MODULE_UNLOAD
2002 bool "Module unloading"
2004 Without this option you will not be able to unload any
2005 modules (note that some modules may not be unloadable
2006 anyway), which makes your kernel smaller, faster
2007 and simpler. If unsure, say Y.
2009 config MODULE_FORCE_UNLOAD
2010 bool "Forced module unloading"
2011 depends on MODULE_UNLOAD
2013 This option allows you to force a module to unload, even if the
2014 kernel believes it is unsafe: the kernel will remove the module
2015 without waiting for anyone to stop using it (using the -f option to
2016 rmmod). This is mainly for kernel developers and desperate users.
2020 bool "Module versioning support"
2022 Usually, you have to use modules compiled with your kernel.
2023 Saying Y here makes it sometimes possible to use modules
2024 compiled for different kernels, by adding enough information
2025 to the modules to (hopefully) spot any changes which would
2026 make them incompatible with the kernel you are running. If
2029 config ASM_MODVERSIONS
2031 default HAVE_ASM_MODVERSIONS && MODVERSIONS
2033 This enables module versioning for exported symbols also from
2034 assembly. This can be enabled only when the target architecture
2037 config MODULE_REL_CRCS
2039 depends on MODVERSIONS
2041 config MODULE_SRCVERSION_ALL
2042 bool "Source checksum for all modules"
2044 Modules which contain a MODULE_VERSION get an extra "srcversion"
2045 field inserted into their modinfo section, which contains a
2046 sum of the source files which made it. This helps maintainers
2047 see exactly which source was used to build a module (since
2048 others sometimes change the module source without updating
2049 the version). With this option, such a "srcversion" field
2050 will be created for all modules. If unsure, say N.
2053 bool "Module signature verification"
2054 select MODULE_SIG_FORMAT
2056 Check modules for valid signatures upon load: the signature
2057 is simply appended to the module. For more information see
2058 <file:Documentation/admin-guide/module-signing.rst>.
2060 Note that this option adds the OpenSSL development packages as a
2061 kernel build dependency so that the signing tool can use its crypto
2064 You should enable this option if you wish to use either
2065 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2066 another LSM - otherwise unsigned modules will be loadable regardless
2067 of the lockdown policy.
2069 !!!WARNING!!! If you enable this option, you MUST make sure that the
2070 module DOES NOT get stripped after being signed. This includes the
2071 debuginfo strip done by some packagers (such as rpmbuild) and
2072 inclusion into an initramfs that wants the module size reduced.
2074 config MODULE_SIG_FORCE
2075 bool "Require modules to be validly signed"
2076 depends on MODULE_SIG
2078 Reject unsigned modules or signed modules for which we don't have a
2079 key. Without this, such modules will simply taint the kernel.
2081 config MODULE_SIG_ALL
2082 bool "Automatically sign all modules"
2084 depends on MODULE_SIG
2086 Sign all modules during make modules_install. Without this option,
2087 modules must be signed manually, using the scripts/sign-file tool.
2089 comment "Do not forget to sign required modules with scripts/sign-file"
2090 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2093 prompt "Which hash algorithm should modules be signed with?"
2094 depends on MODULE_SIG
2096 This determines which sort of hashing algorithm will be used during
2097 signature generation. This algorithm _must_ be built into the kernel
2098 directly so that signature verification can take place. It is not
2099 possible to load a signed module containing the algorithm to check
2100 the signature on that module.
2102 config MODULE_SIG_SHA1
2103 bool "Sign modules with SHA-1"
2106 config MODULE_SIG_SHA224
2107 bool "Sign modules with SHA-224"
2108 select CRYPTO_SHA256
2110 config MODULE_SIG_SHA256
2111 bool "Sign modules with SHA-256"
2112 select CRYPTO_SHA256
2114 config MODULE_SIG_SHA384
2115 bool "Sign modules with SHA-384"
2116 select CRYPTO_SHA512
2118 config MODULE_SIG_SHA512
2119 bool "Sign modules with SHA-512"
2120 select CRYPTO_SHA512
2124 config MODULE_SIG_HASH
2126 depends on MODULE_SIG
2127 default "sha1" if MODULE_SIG_SHA1
2128 default "sha224" if MODULE_SIG_SHA224
2129 default "sha256" if MODULE_SIG_SHA256
2130 default "sha384" if MODULE_SIG_SHA384
2131 default "sha512" if MODULE_SIG_SHA512
2133 config MODULE_COMPRESS
2134 bool "Compress modules on installation"
2137 Compresses kernel modules when 'make modules_install' is run; gzip or
2138 xz depending on "Compression algorithm" below.
2140 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2142 Out-of-tree kernel modules installed using Kbuild will also be
2143 compressed upon installation.
2145 Note: for modules inside an initrd or initramfs, it's more efficient
2146 to compress the whole initrd or initramfs instead.
2148 Note: This is fully compatible with signed modules.
2153 prompt "Compression algorithm"
2154 depends on MODULE_COMPRESS
2155 default MODULE_COMPRESS_GZIP
2157 This determines which sort of compression will be used during
2158 'make modules_install'.
2160 GZIP (default) and XZ are supported.
2162 config MODULE_COMPRESS_GZIP
2165 config MODULE_COMPRESS_XZ
2170 config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2171 bool "Allow loading of modules with missing namespace imports"
2173 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2174 a namespace. A module that makes use of a symbol exported with such a
2175 namespace is required to import the namespace via MODULE_IMPORT_NS().
2176 There is no technical reason to enforce correct namespace imports,
2177 but it creates consistency between symbols defining namespaces and
2178 users importing namespaces they make use of. This option relaxes this
2179 requirement and lifts the enforcement when loading a module.
2183 config UNUSED_SYMBOLS
2184 bool "Enable unused/obsolete exported symbols"
2187 Unused but exported symbols make the kernel needlessly bigger. For
2188 that reason most of these unused exports will soon be removed. This
2189 option is provided temporarily to provide a transition period in case
2190 some external kernel module needs one of these symbols anyway. If you
2191 encounter such a case in your module, consider if you are actually
2192 using the right API. (rationale: since nobody in the kernel is using
2193 this in a module, there is a pretty good chance it's actually the
2194 wrong interface to use). If you really need the symbol, please send a
2195 mail to the linux kernel mailing list mentioning the symbol and why
2196 you really need it, and what the merge plan to the mainline kernel for
2199 config TRIM_UNUSED_KSYMS
2200 bool "Trim unused exported kernel symbols"
2201 depends on !UNUSED_SYMBOLS
2203 The kernel and some modules make many symbols available for
2204 other modules to use via EXPORT_SYMBOL() and variants. Depending
2205 on the set of modules being selected in your kernel configuration,
2206 many of those exported symbols might never be used.
2208 This option allows for unused exported symbols to be dropped from
2209 the build. In turn, this provides the compiler more opportunities
2210 (especially when using LTO) for optimizing the code and reducing
2211 binary size. This might have some security advantages as well.
2213 If unsure, or if you need to build out-of-tree modules, say N.
2215 config UNUSED_KSYMS_WHITELIST
2216 string "Whitelist of symbols to keep in ksymtab"
2217 depends on TRIM_UNUSED_KSYMS
2219 By default, all unused exported symbols will be un-exported from the
2220 build when TRIM_UNUSED_KSYMS is selected.
2222 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
2223 exported at all times, even in absence of in-tree users. The value to
2224 set here is the path to a text file containing the list of symbols,
2225 one per line. The path can be absolute, or relative to the kernel
2230 config MODULES_TREE_LOOKUP
2232 depends on PERF_EVENTS || TRACING
2234 config INIT_ALL_POSSIBLE
2237 Back when each arch used to define their own cpu_online_mask and
2238 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2239 with all 1s, and others with all 0s. When they were centralised,
2240 it was better to provide this option than to break all the archs
2241 and have several arch maintainers pursuing me down dark alleys.
2243 source "block/Kconfig"
2245 config PREEMPT_NOTIFIERS
2255 Build a simple ASN.1 grammar compiler that produces a bytecode output
2256 that can be interpreted by the ASN.1 stream decoder and used to
2257 inform it as to what tags are to be expected in a stream and what
2258 functions to call on what tags.
2260 source "kernel/Kconfig.locks"
2262 config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2265 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2268 # It may be useful for an architecture to override the definitions of the
2269 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2270 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2271 # different calling convention for syscalls. They can also override the
2272 # macros for not-implemented syscalls in kernel/sys_ni.c and
2273 # kernel/time/posix-stubs.c. All these overrides need to be available in
2274 # <asm/syscall_wrapper.h>.
2275 config ARCH_HAS_SYSCALL_WRAPPER
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