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
63 config RUST_IS_AVAILABLE
64 def_bool $(success,$(srctree)/scripts/rust_is_available.sh)
66 This shows whether a suitable Rust toolchain is available (found).
68 Please see Documentation/rust/quick-start.rst for instructions on how
69 to satisfy the build requirements of Rust support.
71 In particular, the Makefile target 'rustavailable' is useful to check
72 why the Rust toolchain is not being detected.
76 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT
77 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag))
79 config CC_CAN_LINK_STATIC
81 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT
82 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static)
84 config CC_HAS_ASM_GOTO_OUTPUT
85 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)
87 config CC_HAS_ASM_GOTO_TIED_OUTPUT
88 depends on CC_HAS_ASM_GOTO_OUTPUT
89 # Detect buggy gcc and clang, fixed in gcc-11 clang-14.
90 def_bool $(success,echo 'int foo(int *x) { asm goto (".long (%l[bar]) - .": "+m"(*x) ::: bar); return *x; bar: return 0; }' | $CC -x c - -c -o /dev/null)
92 config GCC_ASM_GOTO_OUTPUT_WORKAROUND
94 depends on CC_IS_GCC && CC_HAS_ASM_GOTO_OUTPUT
95 # Fixed in GCC 14, 13.3, 12.4 and 11.5
96 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113921
97 default y if GCC_VERSION < 110500
98 default y if GCC_VERSION >= 120000 && GCC_VERSION < 120400
99 default y if GCC_VERSION >= 130000 && GCC_VERSION < 130300
101 config TOOLS_SUPPORT_RELR
102 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
104 config CC_HAS_ASM_INLINE
105 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
107 config CC_HAS_NO_PROFILE_FN_ATTR
108 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
110 config PAHOLE_VERSION
112 default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))
120 config BUILDTIME_TABLE_SORT
123 config THREAD_INFO_IN_TASK
126 Select this to move thread_info off the stack into task_struct. To
127 make this work, an arch will need to remove all thread_info fields
128 except flags and fix any runtime bugs.
130 One subtle change that will be needed is to use try_get_task_stack()
131 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
140 depends on BROKEN || !SMP
143 config INIT_ENV_ARG_LIMIT
148 Maximum of each of the number of arguments and environment
149 variables passed to init from the kernel command line.
152 bool "Compile also drivers which will not load"
155 Some drivers can be compiled on a different platform than they are
156 intended to be run on. Despite they cannot be loaded there (or even
157 when they load they cannot be used due to missing HW support),
158 developers still, opposing to distributors, might want to build such
159 drivers to compile-test them.
161 If you are a developer and want to build everything available, say Y
162 here. If you are a user/distributor, say N here to exclude useless
163 drivers to be distributed.
166 bool "Compile the kernel with warnings as errors"
169 A kernel build should not cause any compiler warnings, and this
170 enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags
171 to enforce that rule by default.
173 However, if you have a new (or very old) compiler with odd and
174 unusual warnings, or you have some architecture with problems,
175 you may need to disable this config option in order to
176 successfully build the kernel.
180 config UAPI_HEADER_TEST
181 bool "Compile test UAPI headers"
182 depends on HEADERS_INSTALL && CC_CAN_LINK
184 Compile test headers exported to user-space to ensure they are
185 self-contained, i.e. compilable as standalone units.
187 If you are a developer or tester and want to ensure the exported
188 headers are self-contained, say Y here. Otherwise, choose N.
191 string "Local version - append to kernel release"
193 Append an extra string to the end of your kernel version.
194 This will show up when you type uname, for example.
195 The string you set here will be appended after the contents of
196 any files with a filename matching localversion* in your
197 object and source tree, in that order. Your total string can
198 be a maximum of 64 characters.
200 config LOCALVERSION_AUTO
201 bool "Automatically append version information to the version string"
203 depends on !COMPILE_TEST
205 This will try to automatically determine if the current tree is a
206 release tree by looking for git tags that belong to the current
207 top of tree revision.
209 A string of the format -gxxxxxxxx will be added to the localversion
210 if a git-based tree is found. The string generated by this will be
211 appended after any matching localversion* files, and after the value
212 set in CONFIG_LOCALVERSION.
214 (The actual string used here is the first eight characters produced
215 by running the command:
217 $ git rev-parse --verify HEAD
219 which is done within the script "scripts/setlocalversion".)
222 string "Build ID Salt"
225 The build ID is used to link binaries and their debug info. Setting
226 this option will use the value in the calculation of the build id.
227 This is mostly useful for distributions which want to ensure the
228 build is unique between builds. It's safe to leave the default.
230 config HAVE_KERNEL_GZIP
233 config HAVE_KERNEL_BZIP2
236 config HAVE_KERNEL_LZMA
239 config HAVE_KERNEL_XZ
242 config HAVE_KERNEL_LZO
245 config HAVE_KERNEL_LZ4
248 config HAVE_KERNEL_ZSTD
251 config HAVE_KERNEL_UNCOMPRESSED
255 prompt "Kernel compression mode"
257 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
259 The linux kernel is a kind of self-extracting executable.
260 Several compression algorithms are available, which differ
261 in efficiency, compression and decompression speed.
262 Compression speed is only relevant when building a kernel.
263 Decompression speed is relevant at each boot.
265 If you have any problems with bzip2 or lzma compressed
266 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
267 version of this functionality (bzip2 only), for 2.4, was
268 supplied by Christian Ludwig)
270 High compression options are mostly useful for users, who
271 are low on disk space (embedded systems), but for whom ram
274 If in doubt, select 'gzip'
278 depends on HAVE_KERNEL_GZIP
280 The old and tried gzip compression. It provides a good balance
281 between compression ratio and decompression speed.
285 depends on HAVE_KERNEL_BZIP2
287 Its compression ratio and speed is intermediate.
288 Decompression speed is slowest among the choices. The kernel
289 size is about 10% smaller with bzip2, in comparison to gzip.
290 Bzip2 uses a large amount of memory. For modern kernels you
291 will need at least 8MB RAM or more for booting.
295 depends on HAVE_KERNEL_LZMA
297 This compression algorithm's ratio is best. Decompression speed
298 is between gzip and bzip2. Compression is slowest.
299 The kernel size is about 33% smaller with LZMA in comparison to gzip.
303 depends on HAVE_KERNEL_XZ
305 XZ uses the LZMA2 algorithm and instruction set specific
306 BCJ filters which can improve compression ratio of executable
307 code. The size of the kernel is about 30% smaller with XZ in
308 comparison to gzip. On architectures for which there is a BCJ
309 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
310 will create a few percent smaller kernel than plain LZMA.
312 The speed is about the same as with LZMA: The decompression
313 speed of XZ is better than that of bzip2 but worse than gzip
314 and LZO. Compression is slow.
318 depends on HAVE_KERNEL_LZO
320 Its compression ratio is the poorest among the choices. The kernel
321 size is about 10% bigger than gzip; however its speed
322 (both compression and decompression) is the fastest.
326 depends on HAVE_KERNEL_LZ4
328 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
329 A preliminary version of LZ4 de/compression tool is available at
330 <https://code.google.com/p/lz4/>.
332 Its compression ratio is worse than LZO. The size of the kernel
333 is about 8% bigger than LZO. But the decompression speed is
338 depends on HAVE_KERNEL_ZSTD
340 ZSTD is a compression algorithm targeting intermediate compression
341 with fast decompression speed. It will compress better than GZIP and
342 decompress around the same speed as LZO, but slower than LZ4. You
343 will need at least 192 KB RAM or more for booting. The zstd command
344 line tool is required for compression.
346 config KERNEL_UNCOMPRESSED
348 depends on HAVE_KERNEL_UNCOMPRESSED
350 Produce uncompressed kernel image. This option is usually not what
351 you want. It is useful for debugging the kernel in slow simulation
352 environments, where decompressing and moving the kernel is awfully
353 slow. This option allows early boot code to skip the decompressor
354 and jump right at uncompressed kernel image.
359 string "Default init path"
362 This option determines the default init for the system if no init=
363 option is passed on the kernel command line. If the requested path is
364 not present, we will still then move on to attempting further
365 locations (e.g. /sbin/init, etc). If this is empty, we will just use
366 the fallback list when init= is not passed.
368 config DEFAULT_HOSTNAME
369 string "Default hostname"
372 This option determines the default system hostname before userspace
373 calls sethostname(2). The kernel traditionally uses "(none)" here,
374 but you may wish to use a different default here to make a minimal
375 system more usable with less configuration.
380 Inter Process Communication is a suite of library functions and
381 system calls which let processes (running programs) synchronize and
382 exchange information. It is generally considered to be a good thing,
383 and some programs won't run unless you say Y here. In particular, if
384 you want to run the DOS emulator dosemu under Linux (read the
385 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
386 you'll need to say Y here.
388 You can find documentation about IPC with "info ipc" and also in
389 section 6.4 of the Linux Programmer's Guide, available from
390 <http://www.tldp.org/guides.html>.
392 config SYSVIPC_SYSCTL
398 config SYSVIPC_COMPAT
400 depends on COMPAT && SYSVIPC
403 bool "POSIX Message Queues"
406 POSIX variant of message queues is a part of IPC. In POSIX message
407 queues every message has a priority which decides about succession
408 of receiving it by a process. If you want to compile and run
409 programs written e.g. for Solaris with use of its POSIX message
410 queues (functions mq_*) say Y here.
412 POSIX message queues are visible as a filesystem called 'mqueue'
413 and can be mounted somewhere if you want to do filesystem
414 operations on message queues.
418 config POSIX_MQUEUE_SYSCTL
420 depends on POSIX_MQUEUE
425 bool "General notification queue"
429 This is a general notification queue for the kernel to pass events to
430 userspace by splicing them into pipes. It can be used in conjunction
431 with watches for key/keyring change notifications and device
434 See Documentation/core-api/watch_queue.rst
436 config CROSS_MEMORY_ATTACH
437 bool "Enable process_vm_readv/writev syscalls"
441 Enabling this option adds the system calls process_vm_readv and
442 process_vm_writev which allow a process with the correct privileges
443 to directly read from or write to another process' address space.
444 See the man page for more details.
447 bool "uselib syscall (for libc5 and earlier)"
448 default ALPHA || M68K || SPARC
450 This option enables the uselib syscall, a system call used in the
451 dynamic linker from libc5 and earlier. glibc does not use this
452 system call. If you intend to run programs built on libc5 or
453 earlier, you may need to enable this syscall. Current systems
454 running glibc can safely disable this.
457 bool "Auditing support"
460 Enable auditing infrastructure that can be used with another
461 kernel subsystem, such as SELinux (which requires this for
462 logging of avc messages output). System call auditing is included
463 on architectures which support it.
465 config HAVE_ARCH_AUDITSYSCALL
470 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
473 source "kernel/irq/Kconfig"
474 source "kernel/time/Kconfig"
475 source "kernel/bpf/Kconfig"
476 source "kernel/Kconfig.preempt"
478 menu "CPU/Task time and stats accounting"
480 config VIRT_CPU_ACCOUNTING
484 prompt "Cputime accounting"
485 default TICK_CPU_ACCOUNTING
487 # Kind of a stub config for the pure tick based cputime accounting
488 config TICK_CPU_ACCOUNTING
489 bool "Simple tick based cputime accounting"
490 depends on !S390 && !NO_HZ_FULL
492 This is the basic tick based cputime accounting that maintains
493 statistics about user, system and idle time spent on per jiffies
498 config VIRT_CPU_ACCOUNTING_NATIVE
499 bool "Deterministic task and CPU time accounting"
500 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
501 select VIRT_CPU_ACCOUNTING
503 Select this option to enable more accurate task and CPU time
504 accounting. This is done by reading a CPU counter on each
505 kernel entry and exit and on transitions within the kernel
506 between system, softirq and hardirq state, so there is a
507 small performance impact. In the case of s390 or IBM POWER > 5,
508 this also enables accounting of stolen time on logically-partitioned
511 config VIRT_CPU_ACCOUNTING_GEN
512 bool "Full dynticks CPU time accounting"
513 depends on HAVE_CONTEXT_TRACKING_USER
514 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
515 depends on GENERIC_CLOCKEVENTS
516 select VIRT_CPU_ACCOUNTING
517 select CONTEXT_TRACKING_USER
519 Select this option to enable task and CPU time accounting on full
520 dynticks systems. This accounting is implemented by watching every
521 kernel-user boundaries using the context tracking subsystem.
522 The accounting is thus performed at the expense of some significant
525 For now this is only useful if you are working on the full
526 dynticks subsystem development.
532 config IRQ_TIME_ACCOUNTING
533 bool "Fine granularity task level IRQ time accounting"
534 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
536 Select this option to enable fine granularity task irq time
537 accounting. This is done by reading a timestamp on each
538 transitions between softirq and hardirq state, so there can be a
539 small performance impact.
541 If in doubt, say N here.
543 config HAVE_SCHED_AVG_IRQ
545 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
548 config SCHED_THERMAL_PRESSURE
550 default y if ARM && ARM_CPU_TOPOLOGY
553 depends on CPU_FREQ_THERMAL
555 Select this option to enable thermal pressure accounting in the
556 scheduler. Thermal pressure is the value conveyed to the scheduler
557 that reflects the reduction in CPU compute capacity resulted from
558 thermal throttling. Thermal throttling occurs when the performance of
559 a CPU is capped due to high operating temperatures.
561 If selected, the scheduler will be able to balance tasks accordingly,
562 i.e. put less load on throttled CPUs than on non/less throttled ones.
564 This requires the architecture to implement
565 arch_update_thermal_pressure() and arch_scale_thermal_pressure().
567 config BSD_PROCESS_ACCT
568 bool "BSD Process Accounting"
571 If you say Y here, a user level program will be able to instruct the
572 kernel (via a special system call) to write process accounting
573 information to a file: whenever a process exits, information about
574 that process will be appended to the file by the kernel. The
575 information includes things such as creation time, owning user,
576 command name, memory usage, controlling terminal etc. (the complete
577 list is in the struct acct in <file:include/linux/acct.h>). It is
578 up to the user level program to do useful things with this
579 information. This is generally a good idea, so say Y.
581 config BSD_PROCESS_ACCT_V3
582 bool "BSD Process Accounting version 3 file format"
583 depends on BSD_PROCESS_ACCT
586 If you say Y here, the process accounting information is written
587 in a new file format that also logs the process IDs of each
588 process and its parent. Note that this file format is incompatible
589 with previous v0/v1/v2 file formats, so you will need updated tools
590 for processing it. A preliminary version of these tools is available
591 at <http://www.gnu.org/software/acct/>.
594 bool "Export task/process statistics through netlink"
599 Export selected statistics for tasks/processes through the
600 generic netlink interface. Unlike BSD process accounting, the
601 statistics are available during the lifetime of tasks/processes as
602 responses to commands. Like BSD accounting, they are sent to user
607 config TASK_DELAY_ACCT
608 bool "Enable per-task delay accounting"
612 Collect information on time spent by a task waiting for system
613 resources like cpu, synchronous block I/O completion and swapping
614 in pages. Such statistics can help in setting a task's priorities
615 relative to other tasks for cpu, io, rss limits etc.
620 bool "Enable extended accounting over taskstats"
623 Collect extended task accounting data and send the data
624 to userland for processing over the taskstats interface.
628 config TASK_IO_ACCOUNTING
629 bool "Enable per-task storage I/O accounting"
630 depends on TASK_XACCT
632 Collect information on the number of bytes of storage I/O which this
638 bool "Pressure stall information tracking"
641 Collect metrics that indicate how overcommitted the CPU, memory,
642 and IO capacity are in the system.
644 If you say Y here, the kernel will create /proc/pressure/ with the
645 pressure statistics files cpu, memory, and io. These will indicate
646 the share of walltime in which some or all tasks in the system are
647 delayed due to contention of the respective resource.
649 In kernels with cgroup support, cgroups (cgroup2 only) will
650 have cpu.pressure, memory.pressure, and io.pressure files,
651 which aggregate pressure stalls for the grouped tasks only.
653 For more details see Documentation/accounting/psi.rst.
657 config PSI_DEFAULT_DISABLED
658 bool "Require boot parameter to enable pressure stall information tracking"
662 If set, pressure stall information tracking will be disabled
663 per default but can be enabled through passing psi=1 on the
664 kernel commandline during boot.
666 This feature adds some code to the task wakeup and sleep
667 paths of the scheduler. The overhead is too low to affect
668 common scheduling-intense workloads in practice (such as
669 webservers, memcache), but it does show up in artificial
670 scheduler stress tests, such as hackbench.
672 If you are paranoid and not sure what the kernel will be
677 endmenu # "CPU/Task time and stats accounting"
681 depends on SMP || COMPILE_TEST
684 Make sure that CPUs running critical tasks are not disturbed by
685 any source of "noise" such as unbound workqueues, timers, kthreads...
686 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
687 the "isolcpus=" boot parameter.
691 source "kernel/rcu/Kconfig"
698 tristate "Kernel .config support"
700 This option enables the complete Linux kernel ".config" file
701 contents to be saved in the kernel. It provides documentation
702 of which kernel options are used in a running kernel or in an
703 on-disk kernel. This information can be extracted from the kernel
704 image file with the script scripts/extract-ikconfig and used as
705 input to rebuild the current kernel or to build another kernel.
706 It can also be extracted from a running kernel by reading
707 /proc/config.gz if enabled (below).
710 bool "Enable access to .config through /proc/config.gz"
711 depends on IKCONFIG && PROC_FS
713 This option enables access to the kernel configuration file
714 through /proc/config.gz.
717 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
720 This option enables access to the in-kernel headers that are generated during
721 the build process. These can be used to build eBPF tracing programs,
722 or similar programs. If you build the headers as a module, a module called
723 kheaders.ko is built which can be loaded on-demand to get access to headers.
726 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
731 Select the minimal kernel log buffer size as a power of 2.
732 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
733 parameter, see below. Any higher size also might be forced
734 by "log_buf_len" boot parameter.
744 config LOG_CPU_MAX_BUF_SHIFT
745 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
748 default 12 if !BASE_SMALL
749 default 0 if BASE_SMALL
752 This option allows to increase the default ring buffer size
753 according to the number of CPUs. The value defines the contribution
754 of each CPU as a power of 2. The used space is typically only few
755 lines however it might be much more when problems are reported,
758 The increased size means that a new buffer has to be allocated and
759 the original static one is unused. It makes sense only on systems
760 with more CPUs. Therefore this value is used only when the sum of
761 contributions is greater than the half of the default kernel ring
762 buffer as defined by LOG_BUF_SHIFT. The default values are set
763 so that more than 16 CPUs are needed to trigger the allocation.
765 Also this option is ignored when "log_buf_len" kernel parameter is
766 used as it forces an exact (power of two) size of the ring buffer.
768 The number of possible CPUs is used for this computation ignoring
769 hotplugging making the computation optimal for the worst case
770 scenario while allowing a simple algorithm to be used from bootup.
772 Examples shift values and their meaning:
773 17 => 128 KB for each CPU
774 16 => 64 KB for each CPU
775 15 => 32 KB for each CPU
776 14 => 16 KB for each CPU
777 13 => 8 KB for each CPU
778 12 => 4 KB for each CPU
780 config PRINTK_SAFE_LOG_BUF_SHIFT
781 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
786 Select the size of an alternate printk per-CPU buffer where messages
787 printed from usafe contexts are temporary stored. One example would
788 be NMI messages, another one - printk recursion. The messages are
789 copied to the main log buffer in a safe context to avoid a deadlock.
790 The value defines the size as a power of 2.
792 Those messages are rare and limited. The largest one is when
793 a backtrace is printed. It usually fits into 4KB. Select
794 8KB if you want to be on the safe side.
797 17 => 128 KB for each CPU
798 16 => 64 KB for each CPU
799 15 => 32 KB for each CPU
800 14 => 16 KB for each CPU
801 13 => 8 KB for each CPU
802 12 => 4 KB for each CPU
805 bool "Printk indexing debugfs interface"
806 depends on PRINTK && DEBUG_FS
808 Add support for indexing of all printk formats known at compile time
809 at <debugfs>/printk/index/<module>.
811 This can be used as part of maintaining daemons which monitor
812 /dev/kmsg, as it permits auditing the printk formats present in a
813 kernel, allowing detection of cases where monitored printks are
814 changed or no longer present.
816 There is no additional runtime cost to printk with this enabled.
819 # Architectures with an unreliable sched_clock() should select this:
821 config HAVE_UNSTABLE_SCHED_CLOCK
824 config GENERIC_SCHED_CLOCK
827 menu "Scheduler features"
830 bool "Enable utilization clamping for RT/FAIR tasks"
831 depends on CPU_FREQ_GOV_SCHEDUTIL
833 This feature enables the scheduler to track the clamped utilization
834 of each CPU based on RUNNABLE tasks scheduled on that CPU.
836 With this option, the user can specify the min and max CPU
837 utilization allowed for RUNNABLE tasks. The max utilization defines
838 the maximum frequency a task should use while the min utilization
839 defines the minimum frequency it should use.
841 Both min and max utilization clamp values are hints to the scheduler,
842 aiming at improving its frequency selection policy, but they do not
843 enforce or grant any specific bandwidth for tasks.
847 config UCLAMP_BUCKETS_COUNT
848 int "Number of supported utilization clamp buckets"
851 depends on UCLAMP_TASK
853 Defines the number of clamp buckets to use. The range of each bucket
854 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
855 number of clamp buckets the finer their granularity and the higher
856 the precision of clamping aggregation and tracking at run-time.
858 For example, with the minimum configuration value we will have 5
859 clamp buckets tracking 20% utilization each. A 25% boosted tasks will
860 be refcounted in the [20..39]% bucket and will set the bucket clamp
861 effective value to 25%.
862 If a second 30% boosted task should be co-scheduled on the same CPU,
863 that task will be refcounted in the same bucket of the first task and
864 it will boost the bucket clamp effective value to 30%.
865 The clamp effective value of a bucket is reset to its nominal value
866 (20% in the example above) when there are no more tasks refcounted in
869 An additional boost/capping margin can be added to some tasks. In the
870 example above the 25% task will be boosted to 30% until it exits the
871 CPU. If that should be considered not acceptable on certain systems,
872 it's always possible to reduce the margin by increasing the number of
873 clamp buckets to trade off used memory for run-time tracking
876 If in doubt, use the default value.
881 # For architectures that want to enable the support for NUMA-affine scheduler
884 config ARCH_SUPPORTS_NUMA_BALANCING
888 # For architectures that prefer to flush all TLBs after a number of pages
889 # are unmapped instead of sending one IPI per page to flush. The architecture
890 # must provide guarantees on what happens if a clean TLB cache entry is
891 # written after the unmap. Details are in mm/rmap.c near the check for
892 # should_defer_flush. The architecture should also consider if the full flush
893 # and the refill costs are offset by the savings of sending fewer IPIs.
894 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
898 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
900 config CC_IMPLICIT_FALLTHROUGH
902 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
903 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough)
905 # Currently, disable gcc-10+ array-bounds globally.
906 # It's still broken in gcc-13, so no upper bound yet.
907 config GCC10_NO_ARRAY_BOUNDS
910 config CC_NO_ARRAY_BOUNDS
912 default y if CC_IS_GCC && GCC_VERSION >= 100000 && GCC10_NO_ARRAY_BOUNDS
915 # For architectures that know their GCC __int128 support is sound
917 config ARCH_SUPPORTS_INT128
920 # For architectures that (ab)use NUMA to represent different memory regions
921 # all cpu-local but of different latencies, such as SuperH.
923 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
926 config NUMA_BALANCING
927 bool "Memory placement aware NUMA scheduler"
928 depends on ARCH_SUPPORTS_NUMA_BALANCING
929 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
930 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT
932 This option adds support for automatic NUMA aware memory/task placement.
933 The mechanism is quite primitive and is based on migrating memory when
934 it has references to the node the task is running on.
936 This system will be inactive on UMA systems.
938 config NUMA_BALANCING_DEFAULT_ENABLED
939 bool "Automatically enable NUMA aware memory/task placement"
941 depends on NUMA_BALANCING
943 If set, automatic NUMA balancing will be enabled if running on a NUMA
947 bool "Control Group support"
950 This option adds support for grouping sets of processes together, for
951 use with process control subsystems such as Cpusets, CFS, memory
952 controls or device isolation.
954 - Documentation/scheduler/sched-design-CFS.rst (CFS)
955 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
956 and resource control)
965 config CGROUP_FAVOR_DYNMODS
966 bool "Favor dynamic modification latency reduction by default"
968 This option enables the "favordynmods" mount option by default
969 which reduces the latencies of dynamic cgroup modifications such
970 as task migrations and controller on/offs at the cost of making
971 hot path operations such as forks and exits more expensive.
976 bool "Memory controller"
980 Provides control over the memory footprint of tasks in a cgroup.
984 depends on MEMCG && !SLOB
992 Generic block IO controller cgroup interface. This is the common
993 cgroup interface which should be used by various IO controlling
996 Currently, CFQ IO scheduler uses it to recognize task groups and
997 control disk bandwidth allocation (proportional time slice allocation)
998 to such task groups. It is also used by bio throttling logic in
999 block layer to implement upper limit in IO rates on a device.
1001 This option only enables generic Block IO controller infrastructure.
1002 One needs to also enable actual IO controlling logic/policy. For
1003 enabling proportional weight division of disk bandwidth in CFQ, set
1004 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1005 CONFIG_BLK_DEV_THROTTLING=y.
1007 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
1009 config CGROUP_WRITEBACK
1011 depends on MEMCG && BLK_CGROUP
1014 menuconfig CGROUP_SCHED
1015 bool "CPU controller"
1018 This feature lets CPU scheduler recognize task groups and control CPU
1019 bandwidth allocation to such task groups. It uses cgroups to group
1023 config FAIR_GROUP_SCHED
1024 bool "Group scheduling for SCHED_OTHER"
1025 depends on CGROUP_SCHED
1026 default CGROUP_SCHED
1028 config CFS_BANDWIDTH
1029 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1030 depends on FAIR_GROUP_SCHED
1033 This option allows users to define CPU bandwidth rates (limits) for
1034 tasks running within the fair group scheduler. Groups with no limit
1035 set are considered to be unconstrained and will run with no
1037 See Documentation/scheduler/sched-bwc.rst for more information.
1039 config RT_GROUP_SCHED
1040 bool "Group scheduling for SCHED_RR/FIFO"
1041 depends on CGROUP_SCHED
1044 This feature lets you explicitly allocate real CPU bandwidth
1045 to task groups. If enabled, it will also make it impossible to
1046 schedule realtime tasks for non-root users until you allocate
1047 realtime bandwidth for them.
1048 See Documentation/scheduler/sched-rt-group.rst for more information.
1052 config UCLAMP_TASK_GROUP
1053 bool "Utilization clamping per group of tasks"
1054 depends on CGROUP_SCHED
1055 depends on UCLAMP_TASK
1058 This feature enables the scheduler to track the clamped utilization
1059 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
1061 When this option is enabled, the user can specify a min and max
1062 CPU bandwidth which is allowed for each single task in a group.
1063 The max bandwidth allows to clamp the maximum frequency a task
1064 can use, while the min bandwidth allows to define a minimum
1065 frequency a task will always use.
1067 When task group based utilization clamping is enabled, an eventually
1068 specified task-specific clamp value is constrained by the cgroup
1069 specified clamp value. Both minimum and maximum task clamping cannot
1070 be bigger than the corresponding clamping defined at task group level.
1075 bool "PIDs controller"
1077 Provides enforcement of process number limits in the scope of a
1078 cgroup. Any attempt to fork more processes than is allowed in the
1079 cgroup will fail. PIDs are fundamentally a global resource because it
1080 is fairly trivial to reach PID exhaustion before you reach even a
1081 conservative kmemcg limit. As a result, it is possible to grind a
1082 system to halt without being limited by other cgroup policies. The
1083 PIDs controller is designed to stop this from happening.
1085 It should be noted that organisational operations (such as attaching
1086 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1087 since the PIDs limit only affects a process's ability to fork, not to
1091 bool "RDMA controller"
1093 Provides enforcement of RDMA resources defined by IB stack.
1094 It is fairly easy for consumers to exhaust RDMA resources, which
1095 can result into resource unavailability to other consumers.
1096 RDMA controller is designed to stop this from happening.
1097 Attaching processes with active RDMA resources to the cgroup
1098 hierarchy is allowed even if can cross the hierarchy's limit.
1100 config CGROUP_FREEZER
1101 bool "Freezer controller"
1103 Provides a way to freeze and unfreeze all tasks in a
1106 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1107 controller includes important in-kernel memory consumers per default.
1109 If you're using cgroup2, say N.
1111 config CGROUP_HUGETLB
1112 bool "HugeTLB controller"
1113 depends on HUGETLB_PAGE
1117 Provides a cgroup controller for HugeTLB pages.
1118 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1119 The limit is enforced during page fault. Since HugeTLB doesn't
1120 support page reclaim, enforcing the limit at page fault time implies
1121 that, the application will get SIGBUS signal if it tries to access
1122 HugeTLB pages beyond its limit. This requires the application to know
1123 beforehand how much HugeTLB pages it would require for its use. The
1124 control group is tracked in the third page lru pointer. This means
1125 that we cannot use the controller with huge page less than 3 pages.
1128 bool "Cpuset controller"
1131 This option will let you create and manage CPUSETs which
1132 allow dynamically partitioning a system into sets of CPUs and
1133 Memory Nodes and assigning tasks to run only within those sets.
1134 This is primarily useful on large SMP or NUMA systems.
1138 config PROC_PID_CPUSET
1139 bool "Include legacy /proc/<pid>/cpuset file"
1143 config CGROUP_DEVICE
1144 bool "Device controller"
1146 Provides a cgroup controller implementing whitelists for
1147 devices which a process in the cgroup can mknod or open.
1149 config CGROUP_CPUACCT
1150 bool "Simple CPU accounting controller"
1152 Provides a simple controller for monitoring the
1153 total CPU consumed by the tasks in a cgroup.
1156 bool "Perf controller"
1157 depends on PERF_EVENTS
1159 This option extends the perf per-cpu mode to restrict monitoring
1160 to threads which belong to the cgroup specified and run on the
1161 designated cpu. Or this can be used to have cgroup ID in samples
1162 so that it can monitor performance events among cgroups.
1167 bool "Support for eBPF programs attached to cgroups"
1168 depends on BPF_SYSCALL
1169 select SOCK_CGROUP_DATA
1171 Allow attaching eBPF programs to a cgroup using the bpf(2)
1172 syscall command BPF_PROG_ATTACH.
1174 In which context these programs are accessed depends on the type
1175 of attachment. For instance, programs that are attached using
1176 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1180 bool "Misc resource controller"
1183 Provides a controller for miscellaneous resources on a host.
1185 Miscellaneous scalar resources are the resources on the host system
1186 which cannot be abstracted like the other cgroups. This controller
1187 tracks and limits the miscellaneous resources used by a process
1188 attached to a cgroup hierarchy.
1190 For more information, please check misc cgroup section in
1191 /Documentation/admin-guide/cgroup-v2.rst.
1194 bool "Debug controller"
1196 depends on DEBUG_KERNEL
1198 This option enables a simple controller that exports
1199 debugging information about the cgroups framework. This
1200 controller is for control cgroup debugging only. Its
1201 interfaces are not stable.
1205 config SOCK_CGROUP_DATA
1211 menuconfig NAMESPACES
1212 bool "Namespaces support" if EXPERT
1213 depends on MULTIUSER
1216 Provides the way to make tasks work with different objects using
1217 the same id. For example same IPC id may refer to different objects
1218 or same user id or pid may refer to different tasks when used in
1219 different namespaces.
1224 bool "UTS namespace"
1227 In this namespace tasks see different info provided with the
1231 bool "TIME namespace"
1232 depends on GENERIC_VDSO_TIME_NS
1235 In this namespace boottime and monotonic clocks can be set.
1236 The time will keep going with the same pace.
1239 bool "IPC namespace"
1240 depends on (SYSVIPC || POSIX_MQUEUE)
1243 In this namespace tasks work with IPC ids which correspond to
1244 different IPC objects in different namespaces.
1247 bool "User namespace"
1250 This allows containers, i.e. vservers, to use user namespaces
1251 to provide different user info for different servers.
1253 When user namespaces are enabled in the kernel it is
1254 recommended that the MEMCG option also be enabled and that
1255 user-space use the memory control groups to limit the amount
1256 of memory a memory unprivileged users can use.
1261 bool "PID Namespaces"
1264 Support process id namespaces. This allows having multiple
1265 processes with the same pid as long as they are in different
1266 pid namespaces. This is a building block of containers.
1269 bool "Network namespace"
1273 Allow user space to create what appear to be multiple instances
1274 of the network stack.
1278 config CHECKPOINT_RESTORE
1279 bool "Checkpoint/restore support"
1281 select PROC_CHILDREN
1285 Enables additional kernel features in a sake of checkpoint/restore.
1286 In particular it adds auxiliary prctl codes to setup process text,
1287 data and heap segment sizes, and a few additional /proc filesystem
1290 If unsure, say N here.
1292 config SCHED_AUTOGROUP
1293 bool "Automatic process group scheduling"
1296 select FAIR_GROUP_SCHED
1298 This option optimizes the scheduler for common desktop workloads by
1299 automatically creating and populating task groups. This separation
1300 of workloads isolates aggressive CPU burners (like build jobs) from
1301 desktop applications. Task group autogeneration is currently based
1304 config SYSFS_DEPRECATED
1305 bool "Enable deprecated sysfs features to support old userspace tools"
1309 This option adds code that switches the layout of the "block" class
1310 devices, to not show up in /sys/class/block/, but only in
1313 This switch is only active when the sysfs.deprecated=1 boot option is
1314 passed or the SYSFS_DEPRECATED_V2 option is set.
1316 This option allows new kernels to run on old distributions and tools,
1317 which might get confused by /sys/class/block/. Since 2007/2008 all
1318 major distributions and tools handle this just fine.
1320 Recent distributions and userspace tools after 2009/2010 depend on
1321 the existence of /sys/class/block/, and will not work with this
1324 Only if you are using a new kernel on an old distribution, you might
1327 config SYSFS_DEPRECATED_V2
1328 bool "Enable deprecated sysfs features by default"
1331 depends on SYSFS_DEPRECATED
1333 Enable deprecated sysfs by default.
1335 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1338 Only if you are using a new kernel on an old distribution, you might
1339 need to say Y here. Even then, odds are you would not need it
1340 enabled, you can always pass the boot option if absolutely necessary.
1343 bool "Kernel->user space relay support (formerly relayfs)"
1346 This option enables support for relay interface support in
1347 certain file systems (such as debugfs).
1348 It is designed to provide an efficient mechanism for tools and
1349 facilities to relay large amounts of data from kernel space to
1354 config BLK_DEV_INITRD
1355 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1357 The initial RAM filesystem is a ramfs which is loaded by the
1358 boot loader (loadlin or lilo) and that is mounted as root
1359 before the normal boot procedure. It is typically used to
1360 load modules needed to mount the "real" root file system,
1361 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1363 If RAM disk support (BLK_DEV_RAM) is also included, this
1364 also enables initial RAM disk (initrd) support and adds
1365 15 Kbytes (more on some other architectures) to the kernel size.
1371 source "usr/Kconfig"
1376 bool "Boot config support"
1377 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED
1379 Extra boot config allows system admin to pass a config file as
1380 complemental extension of kernel cmdline when booting.
1381 The boot config file must be attached at the end of initramfs
1382 with checksum, size and magic word.
1383 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1387 config BOOT_CONFIG_EMBED
1388 bool "Embed bootconfig file in the kernel"
1389 depends on BOOT_CONFIG
1391 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the
1392 kernel. Usually, the bootconfig file is loaded with the initrd
1393 image. But if the system doesn't support initrd, this option will
1394 help you by embedding a bootconfig file while building the kernel.
1398 config BOOT_CONFIG_EMBED_FILE
1399 string "Embedded bootconfig file path"
1400 depends on BOOT_CONFIG_EMBED
1402 Specify a bootconfig file which will be embedded to the kernel.
1403 This bootconfig will be used if there is no initrd or no other
1404 bootconfig in the initrd.
1406 config INITRAMFS_PRESERVE_MTIME
1407 bool "Preserve cpio archive mtimes in initramfs"
1410 Each entry in an initramfs cpio archive carries an mtime value. When
1411 enabled, extracted cpio items take this mtime, with directory mtime
1412 setting deferred until after creation of any child entries.
1417 prompt "Compiler optimization level"
1418 default CC_OPTIMIZE_FOR_PERFORMANCE
1420 config CC_OPTIMIZE_FOR_PERFORMANCE
1421 bool "Optimize for performance (-O2)"
1423 This is the default optimization level for the kernel, building
1424 with the "-O2" compiler flag for best performance and most
1425 helpful compile-time warnings.
1427 config CC_OPTIMIZE_FOR_SIZE
1428 bool "Optimize for size (-Os)"
1430 Choosing this option will pass "-Os" to your compiler resulting
1431 in a smaller kernel.
1435 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1438 This requires that the arch annotates or otherwise protects
1439 its external entry points from being discarded. Linker scripts
1440 must also merge .text.*, .data.*, and .bss.* correctly into
1441 output sections. Care must be taken not to pull in unrelated
1442 sections (e.g., '.text.init'). Typically '.' in section names
1443 is used to distinguish them from label names / C identifiers.
1445 config LD_DEAD_CODE_DATA_ELIMINATION
1446 bool "Dead code and data elimination (EXPERIMENTAL)"
1447 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1449 depends on $(cc-option,-ffunction-sections -fdata-sections)
1450 depends on $(ld-option,--gc-sections)
1452 Enable this if you want to do dead code and data elimination with
1453 the linker by compiling with -ffunction-sections -fdata-sections,
1454 and linking with --gc-sections.
1456 This can reduce on disk and in-memory size of the kernel
1457 code and static data, particularly for small configs and
1458 on small systems. This has the possibility of introducing
1459 silently broken kernel if the required annotations are not
1460 present. This option is not well tested yet, so use at your
1463 config LD_ORPHAN_WARN
1465 depends on ARCH_WANT_LD_ORPHAN_WARN
1466 depends on $(ld-option,--orphan-handling=warn)
1474 config SYSCTL_EXCEPTION_TRACE
1477 Enable support for /proc/sys/debug/exception-trace.
1479 config SYSCTL_ARCH_UNALIGN_NO_WARN
1482 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1483 Allows arch to define/use @no_unaligned_warning to possibly warn
1484 about unaligned access emulation going on under the hood.
1486 config SYSCTL_ARCH_UNALIGN_ALLOW
1489 Enable support for /proc/sys/kernel/unaligned-trap
1490 Allows arches to define/use @unaligned_enabled to runtime toggle
1491 the unaligned access emulation.
1492 see arch/parisc/kernel/unaligned.c for reference
1494 config HAVE_PCSPKR_PLATFORM
1497 # interpreter that classic socket filters depend on
1500 select CRYPTO_LIB_SHA1
1503 bool "Configure standard kernel features (expert users)"
1504 # Unhide debug options, to make the on-by-default options visible
1507 This option allows certain base kernel options and settings
1508 to be disabled or tweaked. This is for specialized
1509 environments which can tolerate a "non-standard" kernel.
1510 Only use this if you really know what you are doing.
1513 bool "Enable 16-bit UID system calls" if EXPERT
1514 depends on HAVE_UID16 && MULTIUSER
1517 This enables the legacy 16-bit UID syscall wrappers.
1520 bool "Multiple users, groups and capabilities support" if EXPERT
1523 This option enables support for non-root users, groups and
1526 If you say N here, all processes will run with UID 0, GID 0, and all
1527 possible capabilities. Saying N here also compiles out support for
1528 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1531 If unsure, say Y here.
1533 config SGETMASK_SYSCALL
1534 bool "sgetmask/ssetmask syscalls support" if EXPERT
1535 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1537 sys_sgetmask and sys_ssetmask are obsolete system calls
1538 no longer supported in libc but still enabled by default in some
1541 If unsure, leave the default option here.
1543 config SYSFS_SYSCALL
1544 bool "Sysfs syscall support" if EXPERT
1547 sys_sysfs is an obsolete system call no longer supported in libc.
1548 Note that disabling this option is more secure but might break
1549 compatibility with some systems.
1551 If unsure say Y here.
1554 bool "open by fhandle syscalls" if EXPERT
1558 If you say Y here, a user level program will be able to map
1559 file names to handle and then later use the handle for
1560 different file system operations. This is useful in implementing
1561 userspace file servers, which now track files using handles instead
1562 of names. The handle would remain the same even if file names
1563 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1567 bool "Posix Clocks & timers" if EXPERT
1570 This includes native support for POSIX timers to the kernel.
1571 Some embedded systems have no use for them and therefore they
1572 can be configured out to reduce the size of the kernel image.
1574 When this option is disabled, the following syscalls won't be
1575 available: timer_create, timer_gettime: timer_getoverrun,
1576 timer_settime, timer_delete, clock_adjtime, getitimer,
1577 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1578 clock_getres and clock_nanosleep syscalls will be limited to
1579 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1585 bool "Enable support for printk" if EXPERT
1588 This option enables normal printk support. Removing it
1589 eliminates most of the message strings from the kernel image
1590 and makes the kernel more or less silent. As this makes it
1591 very difficult to diagnose system problems, saying N here is
1592 strongly discouraged.
1595 bool "BUG() support" if EXPERT
1598 Disabling this option eliminates support for BUG and WARN, reducing
1599 the size of your kernel image and potentially quietly ignoring
1600 numerous fatal conditions. You should only consider disabling this
1601 option for embedded systems with no facilities for reporting errors.
1607 bool "Enable ELF core dumps" if EXPERT
1609 Enable support for generating core dumps. Disabling saves about 4k.
1612 config PCSPKR_PLATFORM
1613 bool "Enable PC-Speaker support" if EXPERT
1614 depends on HAVE_PCSPKR_PLATFORM
1618 This option allows to disable the internal PC-Speaker
1619 support, saving some memory.
1623 bool "Enable full-sized data structures for core" if EXPERT
1625 Disabling this option reduces the size of miscellaneous core
1626 kernel data structures. This saves memory on small machines,
1627 but may reduce performance.
1630 bool "Enable futex support" if EXPERT
1631 depends on !(SPARC32 && SMP)
1635 Disabling this option will cause the kernel to be built without
1636 support for "fast userspace mutexes". The resulting kernel may not
1637 run glibc-based applications correctly.
1641 depends on FUTEX && RT_MUTEXES
1645 bool "Enable eventpoll support" if EXPERT
1648 Disabling this option will cause the kernel to be built without
1649 support for epoll family of system calls.
1652 bool "Enable signalfd() system call" if EXPERT
1655 Enable the signalfd() system call that allows to receive signals
1656 on a file descriptor.
1661 bool "Enable timerfd() system call" if EXPERT
1664 Enable the timerfd() system call that allows to receive timer
1665 events on a file descriptor.
1670 bool "Enable eventfd() system call" if EXPERT
1673 Enable the eventfd() system call that allows to receive both
1674 kernel notification (ie. KAIO) or userspace notifications.
1679 bool "Use full shmem filesystem" if EXPERT
1683 The shmem is an internal filesystem used to manage shared memory.
1684 It is backed by swap and manages resource limits. It is also exported
1685 to userspace as tmpfs if TMPFS is enabled. Disabling this
1686 option replaces shmem and tmpfs with the much simpler ramfs code,
1687 which may be appropriate on small systems without swap.
1690 bool "Enable AIO support" if EXPERT
1693 This option enables POSIX asynchronous I/O which may by used
1694 by some high performance threaded applications. Disabling
1695 this option saves about 7k.
1698 bool "Enable IO uring support" if EXPERT
1702 This option enables support for the io_uring interface, enabling
1703 applications to submit and complete IO through submission and
1704 completion rings that are shared between the kernel and application.
1706 config ADVISE_SYSCALLS
1707 bool "Enable madvise/fadvise syscalls" if EXPERT
1710 This option enables the madvise and fadvise syscalls, used by
1711 applications to advise the kernel about their future memory or file
1712 usage, improving performance. If building an embedded system where no
1713 applications use these syscalls, you can disable this option to save
1717 bool "Enable membarrier() system call" if EXPERT
1720 Enable the membarrier() system call that allows issuing memory
1721 barriers across all running threads, which can be used to distribute
1722 the cost of user-space memory barriers asymmetrically by transforming
1723 pairs of memory barriers into pairs consisting of membarrier() and a
1729 bool "Load all symbols for debugging/ksymoops" if EXPERT
1732 Say Y here to let the kernel print out symbolic crash information and
1733 symbolic stack backtraces. This increases the size of the kernel
1734 somewhat, as all symbols have to be loaded into the kernel image.
1737 bool "Include all symbols in kallsyms"
1738 depends on DEBUG_KERNEL && KALLSYMS
1740 Normally kallsyms only contains the symbols of functions for nicer
1741 OOPS messages and backtraces (i.e., symbols from the text and inittext
1742 sections). This is sufficient for most cases. And only if you want to
1743 enable kernel live patching, or other less common use cases (e.g.,
1744 when a debugger is used) all symbols are required (i.e., names of
1745 variables from the data sections, etc).
1747 This option makes sure that all symbols are loaded into the kernel
1748 image (i.e., symbols from all sections) in cost of increased kernel
1749 size (depending on the kernel configuration, it may be 300KiB or
1750 something like this).
1752 Say N unless you really need all symbols, or kernel live patching.
1754 config KALLSYMS_ABSOLUTE_PERCPU
1757 default X86_64 && SMP
1759 config KALLSYMS_BASE_RELATIVE
1764 Instead of emitting them as absolute values in the native word size,
1765 emit the symbol references in the kallsyms table as 32-bit entries,
1766 each containing a relative value in the range [base, base + U32_MAX]
1767 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1768 an absolute value in the range [0, S32_MAX] or a relative value in the
1769 range [base, base + S32_MAX], where base is the lowest relative symbol
1770 address encountered in the image.
1772 On 64-bit builds, this reduces the size of the address table by 50%,
1773 but more importantly, it results in entries whose values are build
1774 time constants, and no relocation pass is required at runtime to fix
1775 up the entries based on the runtime load address of the kernel.
1777 # end of the "standard kernel features (expert users)" menu
1779 # syscall, maps, verifier
1781 config ARCH_HAS_MEMBARRIER_CALLBACKS
1784 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1788 bool "Enable kcmp() system call" if EXPERT
1790 Enable the kernel resource comparison system call. It provides
1791 user-space with the ability to compare two processes to see if they
1792 share a common resource, such as a file descriptor or even virtual
1798 bool "Enable rseq() system call" if EXPERT
1800 depends on HAVE_RSEQ
1803 Enable the restartable sequences system call. It provides a
1804 user-space cache for the current CPU number value, which
1805 speeds up getting the current CPU number from user-space,
1806 as well as an ABI to speed up user-space operations on
1813 bool "Enabled debugging of rseq() system call" if EXPERT
1814 depends on RSEQ && DEBUG_KERNEL
1816 Enable extra debugging checks for the rseq system call.
1821 bool "Embedded system"
1824 This option should be enabled if compiling the kernel for
1825 an embedded system so certain expert options are available
1828 config HAVE_PERF_EVENTS
1831 See tools/perf/design.txt for details.
1833 config GUEST_PERF_EVENTS
1835 depends on HAVE_PERF_EVENTS
1837 config PERF_USE_VMALLOC
1840 See tools/perf/design.txt for details
1843 bool "PC/104 support" if EXPERT
1845 Expose PC/104 form factor device drivers and options available for
1846 selection and configuration. Enable this option if your target
1847 machine has a PC/104 bus.
1849 menu "Kernel Performance Events And Counters"
1852 bool "Kernel performance events and counters"
1853 default y if PROFILING
1854 depends on HAVE_PERF_EVENTS
1858 Enable kernel support for various performance events provided
1859 by software and hardware.
1861 Software events are supported either built-in or via the
1862 use of generic tracepoints.
1864 Most modern CPUs support performance events via performance
1865 counter registers. These registers count the number of certain
1866 types of hw events: such as instructions executed, cachemisses
1867 suffered, or branches mis-predicted - without slowing down the
1868 kernel or applications. These registers can also trigger interrupts
1869 when a threshold number of events have passed - and can thus be
1870 used to profile the code that runs on that CPU.
1872 The Linux Performance Event subsystem provides an abstraction of
1873 these software and hardware event capabilities, available via a
1874 system call and used by the "perf" utility in tools/perf/. It
1875 provides per task and per CPU counters, and it provides event
1876 capabilities on top of those.
1880 config DEBUG_PERF_USE_VMALLOC
1882 bool "Debug: use vmalloc to back perf mmap() buffers"
1883 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1884 select PERF_USE_VMALLOC
1886 Use vmalloc memory to back perf mmap() buffers.
1888 Mostly useful for debugging the vmalloc code on platforms
1889 that don't require it.
1895 config SYSTEM_DATA_VERIFICATION
1897 select SYSTEM_TRUSTED_KEYRING
1901 select ASYMMETRIC_KEY_TYPE
1902 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1905 select X509_CERTIFICATE_PARSER
1906 select PKCS7_MESSAGE_PARSER
1908 Provide PKCS#7 message verification using the contents of the system
1909 trusted keyring to provide public keys. This then can be used for
1910 module verification, kexec image verification and firmware blob
1914 bool "Profiling support"
1916 Say Y here to enable the extended profiling support mechanisms used
1921 depends on HAVE_RUST
1922 depends on RUST_IS_AVAILABLE
1923 depends on !CFI_CLANG
1924 depends on !MODVERSIONS
1925 depends on !GCC_PLUGINS
1926 depends on !RANDSTRUCT
1927 depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE
1929 Enables Rust support in the kernel.
1931 This allows other Rust-related options, like drivers written in Rust,
1934 It is also required to be able to load external kernel modules
1937 See Documentation/rust/ for more information.
1941 config RUSTC_VERSION_TEXT
1944 default $(shell,command -v $(RUSTC) >/dev/null 2>&1 && $(RUSTC) --version || echo n)
1946 config BINDGEN_VERSION_TEXT
1949 default $(shell,command -v $(BINDGEN) >/dev/null 2>&1 && $(BINDGEN) --version || echo n)
1952 # Place an empty function call at each tracepoint site. Can be
1953 # dynamically changed for a probe function.
1958 endmenu # General setup
1960 source "arch/Kconfig"
1964 default y if PREEMPT_RT
1968 default 0 if BASE_FULL
1969 default 1 if !BASE_FULL
1971 config MODULE_SIG_FORMAT
1973 select SYSTEM_DATA_VERIFICATION
1975 source "kernel/module/Kconfig"
1977 config INIT_ALL_POSSIBLE
1980 Back when each arch used to define their own cpu_online_mask and
1981 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1982 with all 1s, and others with all 0s. When they were centralised,
1983 it was better to provide this option than to break all the archs
1984 and have several arch maintainers pursuing me down dark alleys.
1986 source "block/Kconfig"
1988 config PREEMPT_NOTIFIERS
1998 Build a simple ASN.1 grammar compiler that produces a bytecode output
1999 that can be interpreted by the ASN.1 stream decoder and used to
2000 inform it as to what tags are to be expected in a stream and what
2001 functions to call on what tags.
2003 source "kernel/Kconfig.locks"
2005 config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2008 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2011 # It may be useful for an architecture to override the definitions of the
2012 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2013 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2014 # different calling convention for syscalls. They can also override the
2015 # macros for not-implemented syscalls in kernel/sys_ni.c and
2016 # kernel/time/posix-stubs.c. All these overrides need to be available in
2017 # <asm/syscall_wrapper.h>.
2018 config ARCH_HAS_SYSCALL_WRAPPER
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