1 # SPDX-License-Identifier: GPL-2.0-only
4 default "$(CC_VERSION_TEXT)"
6 This is used in unclear ways:
8 - Re-run Kconfig when the compiler is updated
9 The 'default' property references the environment variable,
10 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd.
11 When the compiler is updated, Kconfig will be invoked.
13 - Ensure full rebuild when the compiler is updated
14 include/linux/compiler-version.h contains this option in the comment
15 line so fixdep adds include/config/CC_VERSION_TEXT into the
16 auto-generated dependency. When the compiler is updated, syncconfig
17 will touch it and then every file will be rebuilt.
20 def_bool $(success,test "$(cc-name)" = GCC)
24 default $(cc-version) if CC_IS_GCC
28 def_bool $(success,test "$(cc-name)" = Clang)
32 default $(cc-version) if CC_IS_CLANG
36 def_bool $(success,test "$(as-name)" = GNU)
39 def_bool $(success,test "$(as-name)" = LLVM)
43 # Use clang version if this is the integrated assembler
44 default CLANG_VERSION if AS_IS_LLVM
48 def_bool $(success,test "$(ld-name)" = BFD)
52 default $(ld-version) if LD_IS_BFD
56 def_bool $(success,test "$(ld-name)" = LLD)
60 default $(ld-version) if LD_IS_LLD
65 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT
66 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag))
68 config CC_CAN_LINK_STATIC
70 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT
71 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static)
73 config CC_HAS_ASM_GOTO
74 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
76 config CC_HAS_ASM_GOTO_OUTPUT
77 depends on CC_HAS_ASM_GOTO
78 def_bool $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null)
80 config CC_HAS_ASM_GOTO_TIED_OUTPUT
81 depends on CC_HAS_ASM_GOTO_OUTPUT
82 # Detect buggy gcc and clang, fixed in gcc-11 clang-14.
83 def_bool $(success,echo 'int foo(int *x) { asm goto (".long (%l[bar]) - .\n": "+m"(*x) ::: bar); return *x; bar: return 0; }' | $CC -x c - -c -o /dev/null)
85 config TOOLS_SUPPORT_RELR
86 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
88 config CC_HAS_ASM_INLINE
89 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
91 config CC_HAS_NO_PROFILE_FN_ATTR
92 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
96 default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))
104 config BUILDTIME_TABLE_SORT
107 config THREAD_INFO_IN_TASK
110 Select this to move thread_info off the stack into task_struct. To
111 make this work, an arch will need to remove all thread_info fields
112 except flags and fix any runtime bugs.
114 One subtle change that will be needed is to use try_get_task_stack()
115 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
124 depends on BROKEN || !SMP
127 config INIT_ENV_ARG_LIMIT
132 Maximum of each of the number of arguments and environment
133 variables passed to init from the kernel command line.
136 bool "Compile also drivers which will not load"
139 Some drivers can be compiled on a different platform than they are
140 intended to be run on. Despite they cannot be loaded there (or even
141 when they load they cannot be used due to missing HW support),
142 developers still, opposing to distributors, might want to build such
143 drivers to compile-test them.
145 If you are a developer and want to build everything available, say Y
146 here. If you are a user/distributor, say N here to exclude useless
147 drivers to be distributed.
150 bool "Compile the kernel with warnings as errors"
153 A kernel build should not cause any compiler warnings, and this
154 enables the '-Werror' flag to enforce that rule by default.
156 However, if you have a new (or very old) compiler with odd and
157 unusual warnings, or you have some architecture with problems,
158 you may need to disable this config option in order to
159 successfully build the kernel.
163 config UAPI_HEADER_TEST
164 bool "Compile test UAPI headers"
165 depends on HEADERS_INSTALL && CC_CAN_LINK
167 Compile test headers exported to user-space to ensure they are
168 self-contained, i.e. compilable as standalone units.
170 If you are a developer or tester and want to ensure the exported
171 headers are self-contained, say Y here. Otherwise, choose N.
174 string "Local version - append to kernel release"
176 Append an extra string to the end of your kernel version.
177 This will show up when you type uname, for example.
178 The string you set here will be appended after the contents of
179 any files with a filename matching localversion* in your
180 object and source tree, in that order. Your total string can
181 be a maximum of 64 characters.
183 config LOCALVERSION_AUTO
184 bool "Automatically append version information to the version string"
186 depends on !COMPILE_TEST
188 This will try to automatically determine if the current tree is a
189 release tree by looking for git tags that belong to the current
190 top of tree revision.
192 A string of the format -gxxxxxxxx will be added to the localversion
193 if a git-based tree is found. The string generated by this will be
194 appended after any matching localversion* files, and after the value
195 set in CONFIG_LOCALVERSION.
197 (The actual string used here is the first eight characters produced
198 by running the command:
200 $ git rev-parse --verify HEAD
202 which is done within the script "scripts/setlocalversion".)
205 string "Build ID Salt"
208 The build ID is used to link binaries and their debug info. Setting
209 this option will use the value in the calculation of the build id.
210 This is mostly useful for distributions which want to ensure the
211 build is unique between builds. It's safe to leave the default.
213 config HAVE_KERNEL_GZIP
216 config HAVE_KERNEL_BZIP2
219 config HAVE_KERNEL_LZMA
222 config HAVE_KERNEL_XZ
225 config HAVE_KERNEL_LZO
228 config HAVE_KERNEL_LZ4
231 config HAVE_KERNEL_ZSTD
234 config HAVE_KERNEL_UNCOMPRESSED
238 prompt "Kernel compression mode"
240 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_ZSTD || HAVE_KERNEL_UNCOMPRESSED
242 The linux kernel is a kind of self-extracting executable.
243 Several compression algorithms are available, which differ
244 in efficiency, compression and decompression speed.
245 Compression speed is only relevant when building a kernel.
246 Decompression speed is relevant at each boot.
248 If you have any problems with bzip2 or lzma compressed
249 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
250 version of this functionality (bzip2 only), for 2.4, was
251 supplied by Christian Ludwig)
253 High compression options are mostly useful for users, who
254 are low on disk space (embedded systems), but for whom ram
257 If in doubt, select 'gzip'
261 depends on HAVE_KERNEL_GZIP
263 The old and tried gzip compression. It provides a good balance
264 between compression ratio and decompression speed.
268 depends on HAVE_KERNEL_BZIP2
270 Its compression ratio and speed is intermediate.
271 Decompression speed is slowest among the choices. The kernel
272 size is about 10% smaller with bzip2, in comparison to gzip.
273 Bzip2 uses a large amount of memory. For modern kernels you
274 will need at least 8MB RAM or more for booting.
278 depends on HAVE_KERNEL_LZMA
280 This compression algorithm's ratio is best. Decompression speed
281 is between gzip and bzip2. Compression is slowest.
282 The kernel size is about 33% smaller with LZMA in comparison to gzip.
286 depends on HAVE_KERNEL_XZ
288 XZ uses the LZMA2 algorithm and instruction set specific
289 BCJ filters which can improve compression ratio of executable
290 code. The size of the kernel is about 30% smaller with XZ in
291 comparison to gzip. On architectures for which there is a BCJ
292 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
293 will create a few percent smaller kernel than plain LZMA.
295 The speed is about the same as with LZMA: The decompression
296 speed of XZ is better than that of bzip2 but worse than gzip
297 and LZO. Compression is slow.
301 depends on HAVE_KERNEL_LZO
303 Its compression ratio is the poorest among the choices. The kernel
304 size is about 10% bigger than gzip; however its speed
305 (both compression and decompression) is the fastest.
309 depends on HAVE_KERNEL_LZ4
311 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
312 A preliminary version of LZ4 de/compression tool is available at
313 <https://code.google.com/p/lz4/>.
315 Its compression ratio is worse than LZO. The size of the kernel
316 is about 8% bigger than LZO. But the decompression speed is
321 depends on HAVE_KERNEL_ZSTD
323 ZSTD is a compression algorithm targeting intermediate compression
324 with fast decompression speed. It will compress better than GZIP and
325 decompress around the same speed as LZO, but slower than LZ4. You
326 will need at least 192 KB RAM or more for booting. The zstd command
327 line tool is required for compression.
329 config KERNEL_UNCOMPRESSED
331 depends on HAVE_KERNEL_UNCOMPRESSED
333 Produce uncompressed kernel image. This option is usually not what
334 you want. It is useful for debugging the kernel in slow simulation
335 environments, where decompressing and moving the kernel is awfully
336 slow. This option allows early boot code to skip the decompressor
337 and jump right at uncompressed kernel image.
342 string "Default init path"
345 This option determines the default init for the system if no init=
346 option is passed on the kernel command line. If the requested path is
347 not present, we will still then move on to attempting further
348 locations (e.g. /sbin/init, etc). If this is empty, we will just use
349 the fallback list when init= is not passed.
351 config DEFAULT_HOSTNAME
352 string "Default hostname"
355 This option determines the default system hostname before userspace
356 calls sethostname(2). The kernel traditionally uses "(none)" here,
357 but you may wish to use a different default here to make a minimal
358 system more usable with less configuration.
363 Inter Process Communication is a suite of library functions and
364 system calls which let processes (running programs) synchronize and
365 exchange information. It is generally considered to be a good thing,
366 and some programs won't run unless you say Y here. In particular, if
367 you want to run the DOS emulator dosemu under Linux (read the
368 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
369 you'll need to say Y here.
371 You can find documentation about IPC with "info ipc" and also in
372 section 6.4 of the Linux Programmer's Guide, available from
373 <http://www.tldp.org/guides.html>.
375 config SYSVIPC_SYSCTL
381 config SYSVIPC_COMPAT
383 depends on COMPAT && SYSVIPC
386 bool "POSIX Message Queues"
389 POSIX variant of message queues is a part of IPC. In POSIX message
390 queues every message has a priority which decides about succession
391 of receiving it by a process. If you want to compile and run
392 programs written e.g. for Solaris with use of its POSIX message
393 queues (functions mq_*) say Y here.
395 POSIX message queues are visible as a filesystem called 'mqueue'
396 and can be mounted somewhere if you want to do filesystem
397 operations on message queues.
401 config POSIX_MQUEUE_SYSCTL
403 depends on POSIX_MQUEUE
408 bool "General notification queue"
412 This is a general notification queue for the kernel to pass events to
413 userspace by splicing them into pipes. It can be used in conjunction
414 with watches for key/keyring change notifications and device
417 See Documentation/core-api/watch_queue.rst
419 config CROSS_MEMORY_ATTACH
420 bool "Enable process_vm_readv/writev syscalls"
424 Enabling this option adds the system calls process_vm_readv and
425 process_vm_writev which allow a process with the correct privileges
426 to directly read from or write to another process' address space.
427 See the man page for more details.
430 bool "uselib syscall (for libc5 and earlier)"
431 default ALPHA || M68K || SPARC
433 This option enables the uselib syscall, a system call used in the
434 dynamic linker from libc5 and earlier. glibc does not use this
435 system call. If you intend to run programs built on libc5 or
436 earlier, you may need to enable this syscall. Current systems
437 running glibc can safely disable this.
440 bool "Auditing support"
443 Enable auditing infrastructure that can be used with another
444 kernel subsystem, such as SELinux (which requires this for
445 logging of avc messages output). System call auditing is included
446 on architectures which support it.
448 config HAVE_ARCH_AUDITSYSCALL
453 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
456 source "kernel/irq/Kconfig"
457 source "kernel/time/Kconfig"
458 source "kernel/bpf/Kconfig"
459 source "kernel/Kconfig.preempt"
461 menu "CPU/Task time and stats accounting"
463 config VIRT_CPU_ACCOUNTING
467 prompt "Cputime accounting"
468 default TICK_CPU_ACCOUNTING if !PPC64
469 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
471 # Kind of a stub config for the pure tick based cputime accounting
472 config TICK_CPU_ACCOUNTING
473 bool "Simple tick based cputime accounting"
474 depends on !S390 && !NO_HZ_FULL
476 This is the basic tick based cputime accounting that maintains
477 statistics about user, system and idle time spent on per jiffies
482 config VIRT_CPU_ACCOUNTING_NATIVE
483 bool "Deterministic task and CPU time accounting"
484 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
485 select VIRT_CPU_ACCOUNTING
487 Select this option to enable more accurate task and CPU time
488 accounting. This is done by reading a CPU counter on each
489 kernel entry and exit and on transitions within the kernel
490 between system, softirq and hardirq state, so there is a
491 small performance impact. In the case of s390 or IBM POWER > 5,
492 this also enables accounting of stolen time on logically-partitioned
495 config VIRT_CPU_ACCOUNTING_GEN
496 bool "Full dynticks CPU time accounting"
497 depends on HAVE_CONTEXT_TRACKING_USER
498 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
499 depends on GENERIC_CLOCKEVENTS
500 select VIRT_CPU_ACCOUNTING
501 select CONTEXT_TRACKING_USER
503 Select this option to enable task and CPU time accounting on full
504 dynticks systems. This accounting is implemented by watching every
505 kernel-user boundaries using the context tracking subsystem.
506 The accounting is thus performed at the expense of some significant
509 For now this is only useful if you are working on the full
510 dynticks subsystem development.
516 config IRQ_TIME_ACCOUNTING
517 bool "Fine granularity task level IRQ time accounting"
518 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
520 Select this option to enable fine granularity task irq time
521 accounting. This is done by reading a timestamp on each
522 transitions between softirq and hardirq state, so there can be a
523 small performance impact.
525 If in doubt, say N here.
527 config HAVE_SCHED_AVG_IRQ
529 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
532 config SCHED_THERMAL_PRESSURE
534 default y if ARM && ARM_CPU_TOPOLOGY
537 depends on CPU_FREQ_THERMAL
539 Select this option to enable thermal pressure accounting in the
540 scheduler. Thermal pressure is the value conveyed to the scheduler
541 that reflects the reduction in CPU compute capacity resulted from
542 thermal throttling. Thermal throttling occurs when the performance of
543 a CPU is capped due to high operating temperatures.
545 If selected, the scheduler will be able to balance tasks accordingly,
546 i.e. put less load on throttled CPUs than on non/less throttled ones.
548 This requires the architecture to implement
549 arch_update_thermal_pressure() and arch_scale_thermal_pressure().
551 config BSD_PROCESS_ACCT
552 bool "BSD Process Accounting"
555 If you say Y here, a user level program will be able to instruct the
556 kernel (via a special system call) to write process accounting
557 information to a file: whenever a process exits, information about
558 that process will be appended to the file by the kernel. The
559 information includes things such as creation time, owning user,
560 command name, memory usage, controlling terminal etc. (the complete
561 list is in the struct acct in <file:include/linux/acct.h>). It is
562 up to the user level program to do useful things with this
563 information. This is generally a good idea, so say Y.
565 config BSD_PROCESS_ACCT_V3
566 bool "BSD Process Accounting version 3 file format"
567 depends on BSD_PROCESS_ACCT
570 If you say Y here, the process accounting information is written
571 in a new file format that also logs the process IDs of each
572 process and its parent. Note that this file format is incompatible
573 with previous v0/v1/v2 file formats, so you will need updated tools
574 for processing it. A preliminary version of these tools is available
575 at <http://www.gnu.org/software/acct/>.
578 bool "Export task/process statistics through netlink"
583 Export selected statistics for tasks/processes through the
584 generic netlink interface. Unlike BSD process accounting, the
585 statistics are available during the lifetime of tasks/processes as
586 responses to commands. Like BSD accounting, they are sent to user
591 config TASK_DELAY_ACCT
592 bool "Enable per-task delay accounting"
596 Collect information on time spent by a task waiting for system
597 resources like cpu, synchronous block I/O completion and swapping
598 in pages. Such statistics can help in setting a task's priorities
599 relative to other tasks for cpu, io, rss limits etc.
604 bool "Enable extended accounting over taskstats"
607 Collect extended task accounting data and send the data
608 to userland for processing over the taskstats interface.
612 config TASK_IO_ACCOUNTING
613 bool "Enable per-task storage I/O accounting"
614 depends on TASK_XACCT
616 Collect information on the number of bytes of storage I/O which this
622 bool "Pressure stall information tracking"
624 Collect metrics that indicate how overcommitted the CPU, memory,
625 and IO capacity are in the system.
627 If you say Y here, the kernel will create /proc/pressure/ with the
628 pressure statistics files cpu, memory, and io. These will indicate
629 the share of walltime in which some or all tasks in the system are
630 delayed due to contention of the respective resource.
632 In kernels with cgroup support, cgroups (cgroup2 only) will
633 have cpu.pressure, memory.pressure, and io.pressure files,
634 which aggregate pressure stalls for the grouped tasks only.
636 For more details see Documentation/accounting/psi.rst.
640 config PSI_DEFAULT_DISABLED
641 bool "Require boot parameter to enable pressure stall information tracking"
645 If set, pressure stall information tracking will be disabled
646 per default but can be enabled through passing psi=1 on the
647 kernel commandline during boot.
649 This feature adds some code to the task wakeup and sleep
650 paths of the scheduler. The overhead is too low to affect
651 common scheduling-intense workloads in practice (such as
652 webservers, memcache), but it does show up in artificial
653 scheduler stress tests, such as hackbench.
655 If you are paranoid and not sure what the kernel will be
660 endmenu # "CPU/Task time and stats accounting"
664 depends on SMP || COMPILE_TEST
667 Make sure that CPUs running critical tasks are not disturbed by
668 any source of "noise" such as unbound workqueues, timers, kthreads...
669 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
670 the "isolcpus=" boot parameter.
674 source "kernel/rcu/Kconfig"
681 tristate "Kernel .config support"
683 This option enables the complete Linux kernel ".config" file
684 contents to be saved in the kernel. It provides documentation
685 of which kernel options are used in a running kernel or in an
686 on-disk kernel. This information can be extracted from the kernel
687 image file with the script scripts/extract-ikconfig and used as
688 input to rebuild the current kernel or to build another kernel.
689 It can also be extracted from a running kernel by reading
690 /proc/config.gz if enabled (below).
693 bool "Enable access to .config through /proc/config.gz"
694 depends on IKCONFIG && PROC_FS
696 This option enables access to the kernel configuration file
697 through /proc/config.gz.
700 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
703 This option enables access to the in-kernel headers that are generated during
704 the build process. These can be used to build eBPF tracing programs,
705 or similar programs. If you build the headers as a module, a module called
706 kheaders.ko is built which can be loaded on-demand to get access to headers.
709 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
714 Select the minimal kernel log buffer size as a power of 2.
715 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
716 parameter, see below. Any higher size also might be forced
717 by "log_buf_len" boot parameter.
727 config LOG_CPU_MAX_BUF_SHIFT
728 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
731 default 12 if !BASE_SMALL
732 default 0 if BASE_SMALL
735 This option allows to increase the default ring buffer size
736 according to the number of CPUs. The value defines the contribution
737 of each CPU as a power of 2. The used space is typically only few
738 lines however it might be much more when problems are reported,
741 The increased size means that a new buffer has to be allocated and
742 the original static one is unused. It makes sense only on systems
743 with more CPUs. Therefore this value is used only when the sum of
744 contributions is greater than the half of the default kernel ring
745 buffer as defined by LOG_BUF_SHIFT. The default values are set
746 so that more than 16 CPUs are needed to trigger the allocation.
748 Also this option is ignored when "log_buf_len" kernel parameter is
749 used as it forces an exact (power of two) size of the ring buffer.
751 The number of possible CPUs is used for this computation ignoring
752 hotplugging making the computation optimal for the worst case
753 scenario while allowing a simple algorithm to be used from bootup.
755 Examples shift values and their meaning:
756 17 => 128 KB for each CPU
757 16 => 64 KB for each CPU
758 15 => 32 KB for each CPU
759 14 => 16 KB for each CPU
760 13 => 8 KB for each CPU
761 12 => 4 KB for each CPU
763 config PRINTK_SAFE_LOG_BUF_SHIFT
764 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
769 Select the size of an alternate printk per-CPU buffer where messages
770 printed from usafe contexts are temporary stored. One example would
771 be NMI messages, another one - printk recursion. The messages are
772 copied to the main log buffer in a safe context to avoid a deadlock.
773 The value defines the size as a power of 2.
775 Those messages are rare and limited. The largest one is when
776 a backtrace is printed. It usually fits into 4KB. Select
777 8KB if you want to be on the safe side.
780 17 => 128 KB for each CPU
781 16 => 64 KB for each CPU
782 15 => 32 KB for each CPU
783 14 => 16 KB for each CPU
784 13 => 8 KB for each CPU
785 12 => 4 KB for each CPU
788 bool "Printk indexing debugfs interface"
789 depends on PRINTK && DEBUG_FS
791 Add support for indexing of all printk formats known at compile time
792 at <debugfs>/printk/index/<module>.
794 This can be used as part of maintaining daemons which monitor
795 /dev/kmsg, as it permits auditing the printk formats present in a
796 kernel, allowing detection of cases where monitored printks are
797 changed or no longer present.
799 There is no additional runtime cost to printk with this enabled.
802 # Architectures with an unreliable sched_clock() should select this:
804 config HAVE_UNSTABLE_SCHED_CLOCK
807 config GENERIC_SCHED_CLOCK
810 menu "Scheduler features"
813 bool "Enable utilization clamping for RT/FAIR tasks"
814 depends on CPU_FREQ_GOV_SCHEDUTIL
816 This feature enables the scheduler to track the clamped utilization
817 of each CPU based on RUNNABLE tasks scheduled on that CPU.
819 With this option, the user can specify the min and max CPU
820 utilization allowed for RUNNABLE tasks. The max utilization defines
821 the maximum frequency a task should use while the min utilization
822 defines the minimum frequency it should use.
824 Both min and max utilization clamp values are hints to the scheduler,
825 aiming at improving its frequency selection policy, but they do not
826 enforce or grant any specific bandwidth for tasks.
830 config UCLAMP_BUCKETS_COUNT
831 int "Number of supported utilization clamp buckets"
834 depends on UCLAMP_TASK
836 Defines the number of clamp buckets to use. The range of each bucket
837 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
838 number of clamp buckets the finer their granularity and the higher
839 the precision of clamping aggregation and tracking at run-time.
841 For example, with the minimum configuration value we will have 5
842 clamp buckets tracking 20% utilization each. A 25% boosted tasks will
843 be refcounted in the [20..39]% bucket and will set the bucket clamp
844 effective value to 25%.
845 If a second 30% boosted task should be co-scheduled on the same CPU,
846 that task will be refcounted in the same bucket of the first task and
847 it will boost the bucket clamp effective value to 30%.
848 The clamp effective value of a bucket is reset to its nominal value
849 (20% in the example above) when there are no more tasks refcounted in
852 An additional boost/capping margin can be added to some tasks. In the
853 example above the 25% task will be boosted to 30% until it exits the
854 CPU. If that should be considered not acceptable on certain systems,
855 it's always possible to reduce the margin by increasing the number of
856 clamp buckets to trade off used memory for run-time tracking
859 If in doubt, use the default value.
864 # For architectures that want to enable the support for NUMA-affine scheduler
867 config ARCH_SUPPORTS_NUMA_BALANCING
871 # For architectures that prefer to flush all TLBs after a number of pages
872 # are unmapped instead of sending one IPI per page to flush. The architecture
873 # must provide guarantees on what happens if a clean TLB cache entry is
874 # written after the unmap. Details are in mm/rmap.c near the check for
875 # should_defer_flush. The architecture should also consider if the full flush
876 # and the refill costs are offset by the savings of sending fewer IPIs.
877 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
881 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
883 config CC_IMPLICIT_FALLTHROUGH
885 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
886 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough)
888 # Currently, disable gcc-12 array-bounds globally.
889 # We may want to target only particular configurations some day.
890 config GCC12_NO_ARRAY_BOUNDS
893 config CC_NO_ARRAY_BOUNDS
895 default y if CC_IS_GCC && GCC_VERSION >= 120000 && GCC_VERSION < 130000 && GCC12_NO_ARRAY_BOUNDS
898 # For architectures that know their GCC __int128 support is sound
900 config ARCH_SUPPORTS_INT128
903 # For architectures that (ab)use NUMA to represent different memory regions
904 # all cpu-local but of different latencies, such as SuperH.
906 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
909 config NUMA_BALANCING
910 bool "Memory placement aware NUMA scheduler"
911 depends on ARCH_SUPPORTS_NUMA_BALANCING
912 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
913 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT
915 This option adds support for automatic NUMA aware memory/task placement.
916 The mechanism is quite primitive and is based on migrating memory when
917 it has references to the node the task is running on.
919 This system will be inactive on UMA systems.
921 config NUMA_BALANCING_DEFAULT_ENABLED
922 bool "Automatically enable NUMA aware memory/task placement"
924 depends on NUMA_BALANCING
926 If set, automatic NUMA balancing will be enabled if running on a NUMA
930 bool "Control Group support"
933 This option adds support for grouping sets of processes together, for
934 use with process control subsystems such as Cpusets, CFS, memory
935 controls or device isolation.
937 - Documentation/scheduler/sched-design-CFS.rst (CFS)
938 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
939 and resource control)
948 config CGROUP_FAVOR_DYNMODS
949 bool "Favor dynamic modification latency reduction by default"
951 This option enables the "favordynmods" mount option by default
952 which reduces the latencies of dynamic cgroup modifications such
953 as task migrations and controller on/offs at the cost of making
954 hot path operations such as forks and exits more expensive.
959 bool "Memory controller"
963 Provides control over the memory footprint of tasks in a cgroup.
967 depends on MEMCG && SWAP
972 depends on MEMCG && !SLOB
980 Generic block IO controller cgroup interface. This is the common
981 cgroup interface which should be used by various IO controlling
984 Currently, CFQ IO scheduler uses it to recognize task groups and
985 control disk bandwidth allocation (proportional time slice allocation)
986 to such task groups. It is also used by bio throttling logic in
987 block layer to implement upper limit in IO rates on a device.
989 This option only enables generic Block IO controller infrastructure.
990 One needs to also enable actual IO controlling logic/policy. For
991 enabling proportional weight division of disk bandwidth in CFQ, set
992 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
993 CONFIG_BLK_DEV_THROTTLING=y.
995 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
997 config CGROUP_WRITEBACK
999 depends on MEMCG && BLK_CGROUP
1002 menuconfig CGROUP_SCHED
1003 bool "CPU controller"
1006 This feature lets CPU scheduler recognize task groups and control CPU
1007 bandwidth allocation to such task groups. It uses cgroups to group
1011 config FAIR_GROUP_SCHED
1012 bool "Group scheduling for SCHED_OTHER"
1013 depends on CGROUP_SCHED
1014 default CGROUP_SCHED
1016 config CFS_BANDWIDTH
1017 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1018 depends on FAIR_GROUP_SCHED
1021 This option allows users to define CPU bandwidth rates (limits) for
1022 tasks running within the fair group scheduler. Groups with no limit
1023 set are considered to be unconstrained and will run with no
1025 See Documentation/scheduler/sched-bwc.rst for more information.
1027 config RT_GROUP_SCHED
1028 bool "Group scheduling for SCHED_RR/FIFO"
1029 depends on CGROUP_SCHED
1032 This feature lets you explicitly allocate real CPU bandwidth
1033 to task groups. If enabled, it will also make it impossible to
1034 schedule realtime tasks for non-root users until you allocate
1035 realtime bandwidth for them.
1036 See Documentation/scheduler/sched-rt-group.rst for more information.
1040 config UCLAMP_TASK_GROUP
1041 bool "Utilization clamping per group of tasks"
1042 depends on CGROUP_SCHED
1043 depends on UCLAMP_TASK
1046 This feature enables the scheduler to track the clamped utilization
1047 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
1049 When this option is enabled, the user can specify a min and max
1050 CPU bandwidth which is allowed for each single task in a group.
1051 The max bandwidth allows to clamp the maximum frequency a task
1052 can use, while the min bandwidth allows to define a minimum
1053 frequency a task will always use.
1055 When task group based utilization clamping is enabled, an eventually
1056 specified task-specific clamp value is constrained by the cgroup
1057 specified clamp value. Both minimum and maximum task clamping cannot
1058 be bigger than the corresponding clamping defined at task group level.
1063 bool "PIDs controller"
1065 Provides enforcement of process number limits in the scope of a
1066 cgroup. Any attempt to fork more processes than is allowed in the
1067 cgroup will fail. PIDs are fundamentally a global resource because it
1068 is fairly trivial to reach PID exhaustion before you reach even a
1069 conservative kmemcg limit. As a result, it is possible to grind a
1070 system to halt without being limited by other cgroup policies. The
1071 PIDs controller is designed to stop this from happening.
1073 It should be noted that organisational operations (such as attaching
1074 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1075 since the PIDs limit only affects a process's ability to fork, not to
1079 bool "RDMA controller"
1081 Provides enforcement of RDMA resources defined by IB stack.
1082 It is fairly easy for consumers to exhaust RDMA resources, which
1083 can result into resource unavailability to other consumers.
1084 RDMA controller is designed to stop this from happening.
1085 Attaching processes with active RDMA resources to the cgroup
1086 hierarchy is allowed even if can cross the hierarchy's limit.
1088 config CGROUP_FREEZER
1089 bool "Freezer controller"
1091 Provides a way to freeze and unfreeze all tasks in a
1094 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1095 controller includes important in-kernel memory consumers per default.
1097 If you're using cgroup2, say N.
1099 config CGROUP_HUGETLB
1100 bool "HugeTLB controller"
1101 depends on HUGETLB_PAGE
1105 Provides a cgroup controller for HugeTLB pages.
1106 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1107 The limit is enforced during page fault. Since HugeTLB doesn't
1108 support page reclaim, enforcing the limit at page fault time implies
1109 that, the application will get SIGBUS signal if it tries to access
1110 HugeTLB pages beyond its limit. This requires the application to know
1111 beforehand how much HugeTLB pages it would require for its use. The
1112 control group is tracked in the third page lru pointer. This means
1113 that we cannot use the controller with huge page less than 3 pages.
1116 bool "Cpuset controller"
1119 This option will let you create and manage CPUSETs which
1120 allow dynamically partitioning a system into sets of CPUs and
1121 Memory Nodes and assigning tasks to run only within those sets.
1122 This is primarily useful on large SMP or NUMA systems.
1126 config PROC_PID_CPUSET
1127 bool "Include legacy /proc/<pid>/cpuset file"
1131 config CGROUP_DEVICE
1132 bool "Device controller"
1134 Provides a cgroup controller implementing whitelists for
1135 devices which a process in the cgroup can mknod or open.
1137 config CGROUP_CPUACCT
1138 bool "Simple CPU accounting controller"
1140 Provides a simple controller for monitoring the
1141 total CPU consumed by the tasks in a cgroup.
1144 bool "Perf controller"
1145 depends on PERF_EVENTS
1147 This option extends the perf per-cpu mode to restrict monitoring
1148 to threads which belong to the cgroup specified and run on the
1149 designated cpu. Or this can be used to have cgroup ID in samples
1150 so that it can monitor performance events among cgroups.
1155 bool "Support for eBPF programs attached to cgroups"
1156 depends on BPF_SYSCALL
1157 select SOCK_CGROUP_DATA
1159 Allow attaching eBPF programs to a cgroup using the bpf(2)
1160 syscall command BPF_PROG_ATTACH.
1162 In which context these programs are accessed depends on the type
1163 of attachment. For instance, programs that are attached using
1164 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1168 bool "Misc resource controller"
1171 Provides a controller for miscellaneous resources on a host.
1173 Miscellaneous scalar resources are the resources on the host system
1174 which cannot be abstracted like the other cgroups. This controller
1175 tracks and limits the miscellaneous resources used by a process
1176 attached to a cgroup hierarchy.
1178 For more information, please check misc cgroup section in
1179 /Documentation/admin-guide/cgroup-v2.rst.
1182 bool "Debug controller"
1184 depends on DEBUG_KERNEL
1186 This option enables a simple controller that exports
1187 debugging information about the cgroups framework. This
1188 controller is for control cgroup debugging only. Its
1189 interfaces are not stable.
1193 config SOCK_CGROUP_DATA
1199 menuconfig NAMESPACES
1200 bool "Namespaces support" if EXPERT
1201 depends on MULTIUSER
1204 Provides the way to make tasks work with different objects using
1205 the same id. For example same IPC id may refer to different objects
1206 or same user id or pid may refer to different tasks when used in
1207 different namespaces.
1212 bool "UTS namespace"
1215 In this namespace tasks see different info provided with the
1219 bool "TIME namespace"
1220 depends on GENERIC_VDSO_TIME_NS
1223 In this namespace boottime and monotonic clocks can be set.
1224 The time will keep going with the same pace.
1227 bool "IPC namespace"
1228 depends on (SYSVIPC || POSIX_MQUEUE)
1231 In this namespace tasks work with IPC ids which correspond to
1232 different IPC objects in different namespaces.
1235 bool "User namespace"
1238 This allows containers, i.e. vservers, to use user namespaces
1239 to provide different user info for different servers.
1241 When user namespaces are enabled in the kernel it is
1242 recommended that the MEMCG option also be enabled and that
1243 user-space use the memory control groups to limit the amount
1244 of memory a memory unprivileged users can use.
1249 bool "PID Namespaces"
1252 Support process id namespaces. This allows having multiple
1253 processes with the same pid as long as they are in different
1254 pid namespaces. This is a building block of containers.
1257 bool "Network namespace"
1261 Allow user space to create what appear to be multiple instances
1262 of the network stack.
1266 config CHECKPOINT_RESTORE
1267 bool "Checkpoint/restore support"
1268 select PROC_CHILDREN
1272 Enables additional kernel features in a sake of checkpoint/restore.
1273 In particular it adds auxiliary prctl codes to setup process text,
1274 data and heap segment sizes, and a few additional /proc filesystem
1277 If unsure, say N here.
1279 config SCHED_AUTOGROUP
1280 bool "Automatic process group scheduling"
1283 select FAIR_GROUP_SCHED
1285 This option optimizes the scheduler for common desktop workloads by
1286 automatically creating and populating task groups. This separation
1287 of workloads isolates aggressive CPU burners (like build jobs) from
1288 desktop applications. Task group autogeneration is currently based
1291 config SYSFS_DEPRECATED
1292 bool "Enable deprecated sysfs features to support old userspace tools"
1296 This option adds code that switches the layout of the "block" class
1297 devices, to not show up in /sys/class/block/, but only in
1300 This switch is only active when the sysfs.deprecated=1 boot option is
1301 passed or the SYSFS_DEPRECATED_V2 option is set.
1303 This option allows new kernels to run on old distributions and tools,
1304 which might get confused by /sys/class/block/. Since 2007/2008 all
1305 major distributions and tools handle this just fine.
1307 Recent distributions and userspace tools after 2009/2010 depend on
1308 the existence of /sys/class/block/, and will not work with this
1311 Only if you are using a new kernel on an old distribution, you might
1314 config SYSFS_DEPRECATED_V2
1315 bool "Enable deprecated sysfs features by default"
1318 depends on SYSFS_DEPRECATED
1320 Enable deprecated sysfs by default.
1322 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1325 Only if you are using a new kernel on an old distribution, you might
1326 need to say Y here. Even then, odds are you would not need it
1327 enabled, you can always pass the boot option if absolutely necessary.
1330 bool "Kernel->user space relay support (formerly relayfs)"
1333 This option enables support for relay interface support in
1334 certain file systems (such as debugfs).
1335 It is designed to provide an efficient mechanism for tools and
1336 facilities to relay large amounts of data from kernel space to
1341 config BLK_DEV_INITRD
1342 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1344 The initial RAM filesystem is a ramfs which is loaded by the
1345 boot loader (loadlin or lilo) and that is mounted as root
1346 before the normal boot procedure. It is typically used to
1347 load modules needed to mount the "real" root file system,
1348 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1350 If RAM disk support (BLK_DEV_RAM) is also included, this
1351 also enables initial RAM disk (initrd) support and adds
1352 15 Kbytes (more on some other architectures) to the kernel size.
1358 source "usr/Kconfig"
1363 bool "Boot config support"
1364 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED
1366 Extra boot config allows system admin to pass a config file as
1367 complemental extension of kernel cmdline when booting.
1368 The boot config file must be attached at the end of initramfs
1369 with checksum, size and magic word.
1370 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1374 config BOOT_CONFIG_EMBED
1375 bool "Embed bootconfig file in the kernel"
1376 depends on BOOT_CONFIG
1378 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the
1379 kernel. Usually, the bootconfig file is loaded with the initrd
1380 image. But if the system doesn't support initrd, this option will
1381 help you by embedding a bootconfig file while building the kernel.
1385 config BOOT_CONFIG_EMBED_FILE
1386 string "Embedded bootconfig file path"
1387 depends on BOOT_CONFIG_EMBED
1389 Specify a bootconfig file which will be embedded to the kernel.
1390 This bootconfig will be used if there is no initrd or no other
1391 bootconfig in the initrd.
1393 config INITRAMFS_PRESERVE_MTIME
1394 bool "Preserve cpio archive mtimes in initramfs"
1397 Each entry in an initramfs cpio archive carries an mtime value. When
1398 enabled, extracted cpio items take this mtime, with directory mtime
1399 setting deferred until after creation of any child entries.
1404 prompt "Compiler optimization level"
1405 default CC_OPTIMIZE_FOR_PERFORMANCE
1407 config CC_OPTIMIZE_FOR_PERFORMANCE
1408 bool "Optimize for performance (-O2)"
1410 This is the default optimization level for the kernel, building
1411 with the "-O2" compiler flag for best performance and most
1412 helpful compile-time warnings.
1414 config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1415 bool "Optimize more for performance (-O3)"
1418 Choosing this option will pass "-O3" to your compiler to optimize
1419 the kernel yet more for performance.
1421 config CC_OPTIMIZE_FOR_SIZE
1422 bool "Optimize for size (-Os)"
1424 Choosing this option will pass "-Os" to your compiler resulting
1425 in a smaller kernel.
1429 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1432 This requires that the arch annotates or otherwise protects
1433 its external entry points from being discarded. Linker scripts
1434 must also merge .text.*, .data.*, and .bss.* correctly into
1435 output sections. Care must be taken not to pull in unrelated
1436 sections (e.g., '.text.init'). Typically '.' in section names
1437 is used to distinguish them from label names / C identifiers.
1439 config LD_DEAD_CODE_DATA_ELIMINATION
1440 bool "Dead code and data elimination (EXPERIMENTAL)"
1441 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1443 depends on $(cc-option,-ffunction-sections -fdata-sections)
1444 depends on $(ld-option,--gc-sections)
1446 Enable this if you want to do dead code and data elimination with
1447 the linker by compiling with -ffunction-sections -fdata-sections,
1448 and linking with --gc-sections.
1450 This can reduce on disk and in-memory size of the kernel
1451 code and static data, particularly for small configs and
1452 on small systems. This has the possibility of introducing
1453 silently broken kernel if the required annotations are not
1454 present. This option is not well tested yet, so use at your
1457 config LD_ORPHAN_WARN
1459 depends on ARCH_WANT_LD_ORPHAN_WARN
1460 depends on $(ld-option,--orphan-handling=warn)
1468 config SYSCTL_EXCEPTION_TRACE
1471 Enable support for /proc/sys/debug/exception-trace.
1473 config SYSCTL_ARCH_UNALIGN_NO_WARN
1476 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1477 Allows arch to define/use @no_unaligned_warning to possibly warn
1478 about unaligned access emulation going on under the hood.
1480 config SYSCTL_ARCH_UNALIGN_ALLOW
1483 Enable support for /proc/sys/kernel/unaligned-trap
1484 Allows arches to define/use @unaligned_enabled to runtime toggle
1485 the unaligned access emulation.
1486 see arch/parisc/kernel/unaligned.c for reference
1488 config HAVE_PCSPKR_PLATFORM
1491 # interpreter that classic socket filters depend on
1494 select CRYPTO_LIB_SHA1
1497 bool "Configure standard kernel features (expert users)"
1498 # Unhide debug options, to make the on-by-default options visible
1501 This option allows certain base kernel options and settings
1502 to be disabled or tweaked. This is for specialized
1503 environments which can tolerate a "non-standard" kernel.
1504 Only use this if you really know what you are doing.
1507 bool "Enable 16-bit UID system calls" if EXPERT
1508 depends on HAVE_UID16 && MULTIUSER
1511 This enables the legacy 16-bit UID syscall wrappers.
1514 bool "Multiple users, groups and capabilities support" if EXPERT
1517 This option enables support for non-root users, groups and
1520 If you say N here, all processes will run with UID 0, GID 0, and all
1521 possible capabilities. Saying N here also compiles out support for
1522 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1525 If unsure, say Y here.
1527 config SGETMASK_SYSCALL
1528 bool "sgetmask/ssetmask syscalls support" if EXPERT
1529 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1531 sys_sgetmask and sys_ssetmask are obsolete system calls
1532 no longer supported in libc but still enabled by default in some
1535 If unsure, leave the default option here.
1537 config SYSFS_SYSCALL
1538 bool "Sysfs syscall support" if EXPERT
1541 sys_sysfs is an obsolete system call no longer supported in libc.
1542 Note that disabling this option is more secure but might break
1543 compatibility with some systems.
1545 If unsure say Y here.
1548 bool "open by fhandle syscalls" if EXPERT
1552 If you say Y here, a user level program will be able to map
1553 file names to handle and then later use the handle for
1554 different file system operations. This is useful in implementing
1555 userspace file servers, which now track files using handles instead
1556 of names. The handle would remain the same even if file names
1557 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1561 bool "Posix Clocks & timers" if EXPERT
1564 This includes native support for POSIX timers to the kernel.
1565 Some embedded systems have no use for them and therefore they
1566 can be configured out to reduce the size of the kernel image.
1568 When this option is disabled, the following syscalls won't be
1569 available: timer_create, timer_gettime: timer_getoverrun,
1570 timer_settime, timer_delete, clock_adjtime, getitimer,
1571 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1572 clock_getres and clock_nanosleep syscalls will be limited to
1573 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1579 bool "Enable support for printk" if EXPERT
1582 This option enables normal printk support. Removing it
1583 eliminates most of the message strings from the kernel image
1584 and makes the kernel more or less silent. As this makes it
1585 very difficult to diagnose system problems, saying N here is
1586 strongly discouraged.
1589 bool "BUG() support" if EXPERT
1592 Disabling this option eliminates support for BUG and WARN, reducing
1593 the size of your kernel image and potentially quietly ignoring
1594 numerous fatal conditions. You should only consider disabling this
1595 option for embedded systems with no facilities for reporting errors.
1601 bool "Enable ELF core dumps" if EXPERT
1603 Enable support for generating core dumps. Disabling saves about 4k.
1606 config PCSPKR_PLATFORM
1607 bool "Enable PC-Speaker support" if EXPERT
1608 depends on HAVE_PCSPKR_PLATFORM
1612 This option allows to disable the internal PC-Speaker
1613 support, saving some memory.
1617 bool "Enable full-sized data structures for core" if EXPERT
1619 Disabling this option reduces the size of miscellaneous core
1620 kernel data structures. This saves memory on small machines,
1621 but may reduce performance.
1624 bool "Enable futex support" if EXPERT
1625 depends on !(SPARC32 && SMP)
1629 Disabling this option will cause the kernel to be built without
1630 support for "fast userspace mutexes". The resulting kernel may not
1631 run glibc-based applications correctly.
1635 depends on FUTEX && RT_MUTEXES
1639 bool "Enable eventpoll support" if EXPERT
1642 Disabling this option will cause the kernel to be built without
1643 support for epoll family of system calls.
1646 bool "Enable signalfd() system call" if EXPERT
1649 Enable the signalfd() system call that allows to receive signals
1650 on a file descriptor.
1655 bool "Enable timerfd() system call" if EXPERT
1658 Enable the timerfd() system call that allows to receive timer
1659 events on a file descriptor.
1664 bool "Enable eventfd() system call" if EXPERT
1667 Enable the eventfd() system call that allows to receive both
1668 kernel notification (ie. KAIO) or userspace notifications.
1673 bool "Use full shmem filesystem" if EXPERT
1677 The shmem is an internal filesystem used to manage shared memory.
1678 It is backed by swap and manages resource limits. It is also exported
1679 to userspace as tmpfs if TMPFS is enabled. Disabling this
1680 option replaces shmem and tmpfs with the much simpler ramfs code,
1681 which may be appropriate on small systems without swap.
1684 bool "Enable AIO support" if EXPERT
1687 This option enables POSIX asynchronous I/O which may by used
1688 by some high performance threaded applications. Disabling
1689 this option saves about 7k.
1692 bool "Enable IO uring support" if EXPERT
1696 This option enables support for the io_uring interface, enabling
1697 applications to submit and complete IO through submission and
1698 completion rings that are shared between the kernel and application.
1700 config ADVISE_SYSCALLS
1701 bool "Enable madvise/fadvise syscalls" if EXPERT
1704 This option enables the madvise and fadvise syscalls, used by
1705 applications to advise the kernel about their future memory or file
1706 usage, improving performance. If building an embedded system where no
1707 applications use these syscalls, you can disable this option to save
1711 bool "Enable membarrier() system call" if EXPERT
1714 Enable the membarrier() system call that allows issuing memory
1715 barriers across all running threads, which can be used to distribute
1716 the cost of user-space memory barriers asymmetrically by transforming
1717 pairs of memory barriers into pairs consisting of membarrier() and a
1723 bool "Load all symbols for debugging/ksymoops" if EXPERT
1726 Say Y here to let the kernel print out symbolic crash information and
1727 symbolic stack backtraces. This increases the size of the kernel
1728 somewhat, as all symbols have to be loaded into the kernel image.
1731 bool "Include all symbols in kallsyms"
1732 depends on DEBUG_KERNEL && KALLSYMS
1734 Normally kallsyms only contains the symbols of functions for nicer
1735 OOPS messages and backtraces (i.e., symbols from the text and inittext
1736 sections). This is sufficient for most cases. And only in very rare
1737 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1738 names of variables from the data sections, etc).
1740 This option makes sure that all symbols are loaded into the kernel
1741 image (i.e., symbols from all sections) in cost of increased kernel
1742 size (depending on the kernel configuration, it may be 300KiB or
1743 something like this).
1745 Say N unless you really need all symbols.
1747 config KALLSYMS_ABSOLUTE_PERCPU
1750 default X86_64 && SMP
1752 config KALLSYMS_BASE_RELATIVE
1757 Instead of emitting them as absolute values in the native word size,
1758 emit the symbol references in the kallsyms table as 32-bit entries,
1759 each containing a relative value in the range [base, base + U32_MAX]
1760 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1761 an absolute value in the range [0, S32_MAX] or a relative value in the
1762 range [base, base + S32_MAX], where base is the lowest relative symbol
1763 address encountered in the image.
1765 On 64-bit builds, this reduces the size of the address table by 50%,
1766 but more importantly, it results in entries whose values are build
1767 time constants, and no relocation pass is required at runtime to fix
1768 up the entries based on the runtime load address of the kernel.
1770 # end of the "standard kernel features (expert users)" menu
1772 # syscall, maps, verifier
1774 config ARCH_HAS_MEMBARRIER_CALLBACKS
1777 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1781 bool "Enable kcmp() system call" if EXPERT
1783 Enable the kernel resource comparison system call. It provides
1784 user-space with the ability to compare two processes to see if they
1785 share a common resource, such as a file descriptor or even virtual
1791 bool "Enable rseq() system call" if EXPERT
1793 depends on HAVE_RSEQ
1796 Enable the restartable sequences system call. It provides a
1797 user-space cache for the current CPU number value, which
1798 speeds up getting the current CPU number from user-space,
1799 as well as an ABI to speed up user-space operations on
1806 bool "Enabled debugging of rseq() system call" if EXPERT
1807 depends on RSEQ && DEBUG_KERNEL
1809 Enable extra debugging checks for the rseq system call.
1814 bool "Embedded system"
1817 This option should be enabled if compiling the kernel for
1818 an embedded system so certain expert options are available
1821 config HAVE_PERF_EVENTS
1824 See tools/perf/design.txt for details.
1826 config GUEST_PERF_EVENTS
1828 depends on HAVE_PERF_EVENTS
1830 config PERF_USE_VMALLOC
1833 See tools/perf/design.txt for details
1836 bool "PC/104 support" if EXPERT
1838 Expose PC/104 form factor device drivers and options available for
1839 selection and configuration. Enable this option if your target
1840 machine has a PC/104 bus.
1842 menu "Kernel Performance Events And Counters"
1845 bool "Kernel performance events and counters"
1846 default y if PROFILING
1847 depends on HAVE_PERF_EVENTS
1851 Enable kernel support for various performance events provided
1852 by software and hardware.
1854 Software events are supported either built-in or via the
1855 use of generic tracepoints.
1857 Most modern CPUs support performance events via performance
1858 counter registers. These registers count the number of certain
1859 types of hw events: such as instructions executed, cachemisses
1860 suffered, or branches mis-predicted - without slowing down the
1861 kernel or applications. These registers can also trigger interrupts
1862 when a threshold number of events have passed - and can thus be
1863 used to profile the code that runs on that CPU.
1865 The Linux Performance Event subsystem provides an abstraction of
1866 these software and hardware event capabilities, available via a
1867 system call and used by the "perf" utility in tools/perf/. It
1868 provides per task and per CPU counters, and it provides event
1869 capabilities on top of those.
1873 config DEBUG_PERF_USE_VMALLOC
1875 bool "Debug: use vmalloc to back perf mmap() buffers"
1876 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1877 select PERF_USE_VMALLOC
1879 Use vmalloc memory to back perf mmap() buffers.
1881 Mostly useful for debugging the vmalloc code on platforms
1882 that don't require it.
1888 config SYSTEM_DATA_VERIFICATION
1890 select SYSTEM_TRUSTED_KEYRING
1894 select ASYMMETRIC_KEY_TYPE
1895 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1898 select X509_CERTIFICATE_PARSER
1899 select PKCS7_MESSAGE_PARSER
1901 Provide PKCS#7 message verification using the contents of the system
1902 trusted keyring to provide public keys. This then can be used for
1903 module verification, kexec image verification and firmware blob
1907 bool "Profiling support"
1909 Say Y here to enable the extended profiling support mechanisms used
1913 # Place an empty function call at each tracepoint site. Can be
1914 # dynamically changed for a probe function.
1919 endmenu # General setup
1921 source "arch/Kconfig"
1925 default y if PREEMPT_RT
1929 default 0 if BASE_FULL
1930 default 1 if !BASE_FULL
1932 config MODULE_SIG_FORMAT
1934 select SYSTEM_DATA_VERIFICATION
1937 bool "Enable loadable module support"
1940 Kernel modules are small pieces of compiled code which can
1941 be inserted in the running kernel, rather than being
1942 permanently built into the kernel. You use the "modprobe"
1943 tool to add (and sometimes remove) them. If you say Y here,
1944 many parts of the kernel can be built as modules (by
1945 answering M instead of Y where indicated): this is most
1946 useful for infrequently used options which are not required
1947 for booting. For more information, see the man pages for
1948 modprobe, lsmod, modinfo, insmod and rmmod.
1950 If you say Y here, you will need to run "make
1951 modules_install" to put the modules under /lib/modules/
1952 where modprobe can find them (you may need to be root to do
1959 config MODULE_FORCE_LOAD
1960 bool "Forced module loading"
1963 Allow loading of modules without version information (ie. modprobe
1964 --force). Forced module loading sets the 'F' (forced) taint flag and
1965 is usually a really bad idea.
1967 config MODULE_UNLOAD
1968 bool "Module unloading"
1970 Without this option you will not be able to unload any
1971 modules (note that some modules may not be unloadable
1972 anyway), which makes your kernel smaller, faster
1973 and simpler. If unsure, say Y.
1975 config MODULE_FORCE_UNLOAD
1976 bool "Forced module unloading"
1977 depends on MODULE_UNLOAD
1979 This option allows you to force a module to unload, even if the
1980 kernel believes it is unsafe: the kernel will remove the module
1981 without waiting for anyone to stop using it (using the -f option to
1982 rmmod). This is mainly for kernel developers and desperate users.
1985 config MODULE_UNLOAD_TAINT_TRACKING
1986 bool "Tainted module unload tracking"
1987 depends on MODULE_UNLOAD
1990 This option allows you to maintain a record of each unloaded
1991 module that tainted the kernel. In addition to displaying a
1992 list of linked (or loaded) modules e.g. on detection of a bad
1993 page (see bad_page()), the aforementioned details are also
1994 shown. If unsure, say N.
1997 bool "Module versioning support"
1999 Usually, you have to use modules compiled with your kernel.
2000 Saying Y here makes it sometimes possible to use modules
2001 compiled for different kernels, by adding enough information
2002 to the modules to (hopefully) spot any changes which would
2003 make them incompatible with the kernel you are running. If
2006 config ASM_MODVERSIONS
2008 default HAVE_ASM_MODVERSIONS && MODVERSIONS
2010 This enables module versioning for exported symbols also from
2011 assembly. This can be enabled only when the target architecture
2014 config MODULE_SRCVERSION_ALL
2015 bool "Source checksum for all modules"
2017 Modules which contain a MODULE_VERSION get an extra "srcversion"
2018 field inserted into their modinfo section, which contains a
2019 sum of the source files which made it. This helps maintainers
2020 see exactly which source was used to build a module (since
2021 others sometimes change the module source without updating
2022 the version). With this option, such a "srcversion" field
2023 will be created for all modules. If unsure, say N.
2026 bool "Module signature verification"
2027 select MODULE_SIG_FORMAT
2029 Check modules for valid signatures upon load: the signature
2030 is simply appended to the module. For more information see
2031 <file:Documentation/admin-guide/module-signing.rst>.
2033 Note that this option adds the OpenSSL development packages as a
2034 kernel build dependency so that the signing tool can use its crypto
2037 You should enable this option if you wish to use either
2038 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2039 another LSM - otherwise unsigned modules will be loadable regardless
2040 of the lockdown policy.
2042 !!!WARNING!!! If you enable this option, you MUST make sure that the
2043 module DOES NOT get stripped after being signed. This includes the
2044 debuginfo strip done by some packagers (such as rpmbuild) and
2045 inclusion into an initramfs that wants the module size reduced.
2047 config MODULE_SIG_FORCE
2048 bool "Require modules to be validly signed"
2049 depends on MODULE_SIG
2051 Reject unsigned modules or signed modules for which we don't have a
2052 key. Without this, such modules will simply taint the kernel.
2054 config MODULE_SIG_ALL
2055 bool "Automatically sign all modules"
2057 depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2059 Sign all modules during make modules_install. Without this option,
2060 modules must be signed manually, using the scripts/sign-file tool.
2062 comment "Do not forget to sign required modules with scripts/sign-file"
2063 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2066 prompt "Which hash algorithm should modules be signed with?"
2067 depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2069 This determines which sort of hashing algorithm will be used during
2070 signature generation. This algorithm _must_ be built into the kernel
2071 directly so that signature verification can take place. It is not
2072 possible to load a signed module containing the algorithm to check
2073 the signature on that module.
2075 config MODULE_SIG_SHA1
2076 bool "Sign modules with SHA-1"
2079 config MODULE_SIG_SHA224
2080 bool "Sign modules with SHA-224"
2081 select CRYPTO_SHA256
2083 config MODULE_SIG_SHA256
2084 bool "Sign modules with SHA-256"
2085 select CRYPTO_SHA256
2087 config MODULE_SIG_SHA384
2088 bool "Sign modules with SHA-384"
2089 select CRYPTO_SHA512
2091 config MODULE_SIG_SHA512
2092 bool "Sign modules with SHA-512"
2093 select CRYPTO_SHA512
2097 config MODULE_SIG_HASH
2099 depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2100 default "sha1" if MODULE_SIG_SHA1
2101 default "sha224" if MODULE_SIG_SHA224
2102 default "sha256" if MODULE_SIG_SHA256
2103 default "sha384" if MODULE_SIG_SHA384
2104 default "sha512" if MODULE_SIG_SHA512
2107 prompt "Module compression mode"
2109 This option allows you to choose the algorithm which will be used to
2110 compress modules when 'make modules_install' is run. (or, you can
2111 choose to not compress modules at all.)
2113 External modules will also be compressed in the same way during the
2116 For modules inside an initrd or initramfs, it's more efficient to
2117 compress the whole initrd or initramfs instead.
2119 This is fully compatible with signed modules.
2121 Please note that the tool used to load modules needs to support the
2122 corresponding algorithm. module-init-tools MAY support gzip, and kmod
2123 MAY support gzip, xz and zstd.
2125 Your build system needs to provide the appropriate compression tool
2126 to compress the modules.
2128 If in doubt, select 'None'.
2130 config MODULE_COMPRESS_NONE
2133 Do not compress modules. The installed modules are suffixed
2136 config MODULE_COMPRESS_GZIP
2139 Compress modules with GZIP. The installed modules are suffixed
2142 config MODULE_COMPRESS_XZ
2145 Compress modules with XZ. The installed modules are suffixed
2148 config MODULE_COMPRESS_ZSTD
2151 Compress modules with ZSTD. The installed modules are suffixed
2156 config MODULE_DECOMPRESS
2157 bool "Support in-kernel module decompression"
2158 depends on MODULE_COMPRESS_GZIP || MODULE_COMPRESS_XZ
2159 select ZLIB_INFLATE if MODULE_COMPRESS_GZIP
2160 select XZ_DEC if MODULE_COMPRESS_XZ
2163 Support for decompressing kernel modules by the kernel itself
2164 instead of relying on userspace to perform this task. Useful when
2165 load pinning security policy is enabled.
2169 config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2170 bool "Allow loading of modules with missing namespace imports"
2172 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2173 a namespace. A module that makes use of a symbol exported with such a
2174 namespace is required to import the namespace via MODULE_IMPORT_NS().
2175 There is no technical reason to enforce correct namespace imports,
2176 but it creates consistency between symbols defining namespaces and
2177 users importing namespaces they make use of. This option relaxes this
2178 requirement and lifts the enforcement when loading a module.
2182 config MODPROBE_PATH
2183 string "Path to modprobe binary"
2184 default "/sbin/modprobe"
2186 When kernel code requests a module, it does so by calling
2187 the "modprobe" userspace utility. This option allows you to
2188 set the path where that binary is found. This can be changed
2189 at runtime via the sysctl file
2190 /proc/sys/kernel/modprobe. Setting this to the empty string
2191 removes the kernel's ability to request modules (but
2192 userspace can still load modules explicitly).
2194 config TRIM_UNUSED_KSYMS
2195 bool "Trim unused exported kernel symbols" if EXPERT
2196 depends on !COMPILE_TEST
2198 The kernel and some modules make many symbols available for
2199 other modules to use via EXPORT_SYMBOL() and variants. Depending
2200 on the set of modules being selected in your kernel configuration,
2201 many of those exported symbols might never be used.
2203 This option allows for unused exported symbols to be dropped from
2204 the build. In turn, this provides the compiler more opportunities
2205 (especially when using LTO) for optimizing the code and reducing
2206 binary size. This might have some security advantages as well.
2208 If unsure, or if you need to build out-of-tree modules, say N.
2210 config UNUSED_KSYMS_WHITELIST
2211 string "Whitelist of symbols to keep in ksymtab"
2212 depends on TRIM_UNUSED_KSYMS
2214 By default, all unused exported symbols will be un-exported from the
2215 build when TRIM_UNUSED_KSYMS is selected.
2217 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
2218 exported at all times, even in absence of in-tree users. The value to
2219 set here is the path to a text file containing the list of symbols,
2220 one per line. The path can be absolute, or relative to the kernel
2225 config MODULES_TREE_LOOKUP
2227 depends on PERF_EVENTS || TRACING || CFI_CLANG
2229 config INIT_ALL_POSSIBLE
2232 Back when each arch used to define their own cpu_online_mask and
2233 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2234 with all 1s, and others with all 0s. When they were centralised,
2235 it was better to provide this option than to break all the archs
2236 and have several arch maintainers pursuing me down dark alleys.
2238 source "block/Kconfig"
2240 config PREEMPT_NOTIFIERS
2250 Build a simple ASN.1 grammar compiler that produces a bytecode output
2251 that can be interpreted by the ASN.1 stream decoder and used to
2252 inform it as to what tags are to be expected in a stream and what
2253 functions to call on what tags.
2255 source "kernel/Kconfig.locks"
2257 config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2260 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2263 # It may be useful for an architecture to override the definitions of the
2264 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2265 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2266 # different calling convention for syscalls. They can also override the
2267 # macros for not-implemented syscalls in kernel/sys_ni.c and
2268 # kernel/time/posix-stubs.c. All these overrides need to be available in
2269 # <asm/syscall_wrapper.h>.
2270 config ARCH_HAS_SYSCALL_WRAPPER
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