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/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
498 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
499 depends on GENERIC_CLOCKEVENTS
500 select VIRT_CPU_ACCOUNTING
501 select CONTEXT_TRACKING
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)
949 bool "Memory controller"
953 Provides control over the memory footprint of tasks in a cgroup.
957 depends on MEMCG && SWAP
962 depends on MEMCG && !SLOB
970 Generic block IO controller cgroup interface. This is the common
971 cgroup interface which should be used by various IO controlling
974 Currently, CFQ IO scheduler uses it to recognize task groups and
975 control disk bandwidth allocation (proportional time slice allocation)
976 to such task groups. It is also used by bio throttling logic in
977 block layer to implement upper limit in IO rates on a device.
979 This option only enables generic Block IO controller infrastructure.
980 One needs to also enable actual IO controlling logic/policy. For
981 enabling proportional weight division of disk bandwidth in CFQ, set
982 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
983 CONFIG_BLK_DEV_THROTTLING=y.
985 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
987 config CGROUP_WRITEBACK
989 depends on MEMCG && BLK_CGROUP
992 menuconfig CGROUP_SCHED
993 bool "CPU controller"
996 This feature lets CPU scheduler recognize task groups and control CPU
997 bandwidth allocation to such task groups. It uses cgroups to group
1001 config FAIR_GROUP_SCHED
1002 bool "Group scheduling for SCHED_OTHER"
1003 depends on CGROUP_SCHED
1004 default CGROUP_SCHED
1006 config CFS_BANDWIDTH
1007 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1008 depends on FAIR_GROUP_SCHED
1011 This option allows users to define CPU bandwidth rates (limits) for
1012 tasks running within the fair group scheduler. Groups with no limit
1013 set are considered to be unconstrained and will run with no
1015 See Documentation/scheduler/sched-bwc.rst for more information.
1017 config RT_GROUP_SCHED
1018 bool "Group scheduling for SCHED_RR/FIFO"
1019 depends on CGROUP_SCHED
1022 This feature lets you explicitly allocate real CPU bandwidth
1023 to task groups. If enabled, it will also make it impossible to
1024 schedule realtime tasks for non-root users until you allocate
1025 realtime bandwidth for them.
1026 See Documentation/scheduler/sched-rt-group.rst for more information.
1030 config UCLAMP_TASK_GROUP
1031 bool "Utilization clamping per group of tasks"
1032 depends on CGROUP_SCHED
1033 depends on UCLAMP_TASK
1036 This feature enables the scheduler to track the clamped utilization
1037 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
1039 When this option is enabled, the user can specify a min and max
1040 CPU bandwidth which is allowed for each single task in a group.
1041 The max bandwidth allows to clamp the maximum frequency a task
1042 can use, while the min bandwidth allows to define a minimum
1043 frequency a task will always use.
1045 When task group based utilization clamping is enabled, an eventually
1046 specified task-specific clamp value is constrained by the cgroup
1047 specified clamp value. Both minimum and maximum task clamping cannot
1048 be bigger than the corresponding clamping defined at task group level.
1053 bool "PIDs controller"
1055 Provides enforcement of process number limits in the scope of a
1056 cgroup. Any attempt to fork more processes than is allowed in the
1057 cgroup will fail. PIDs are fundamentally a global resource because it
1058 is fairly trivial to reach PID exhaustion before you reach even a
1059 conservative kmemcg limit. As a result, it is possible to grind a
1060 system to halt without being limited by other cgroup policies. The
1061 PIDs controller is designed to stop this from happening.
1063 It should be noted that organisational operations (such as attaching
1064 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1065 since the PIDs limit only affects a process's ability to fork, not to
1069 bool "RDMA controller"
1071 Provides enforcement of RDMA resources defined by IB stack.
1072 It is fairly easy for consumers to exhaust RDMA resources, which
1073 can result into resource unavailability to other consumers.
1074 RDMA controller is designed to stop this from happening.
1075 Attaching processes with active RDMA resources to the cgroup
1076 hierarchy is allowed even if can cross the hierarchy's limit.
1078 config CGROUP_FREEZER
1079 bool "Freezer controller"
1081 Provides a way to freeze and unfreeze all tasks in a
1084 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1085 controller includes important in-kernel memory consumers per default.
1087 If you're using cgroup2, say N.
1089 config CGROUP_HUGETLB
1090 bool "HugeTLB controller"
1091 depends on HUGETLB_PAGE
1095 Provides a cgroup controller for HugeTLB pages.
1096 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1097 The limit is enforced during page fault. Since HugeTLB doesn't
1098 support page reclaim, enforcing the limit at page fault time implies
1099 that, the application will get SIGBUS signal if it tries to access
1100 HugeTLB pages beyond its limit. This requires the application to know
1101 beforehand how much HugeTLB pages it would require for its use. The
1102 control group is tracked in the third page lru pointer. This means
1103 that we cannot use the controller with huge page less than 3 pages.
1106 bool "Cpuset controller"
1109 This option will let you create and manage CPUSETs which
1110 allow dynamically partitioning a system into sets of CPUs and
1111 Memory Nodes and assigning tasks to run only within those sets.
1112 This is primarily useful on large SMP or NUMA systems.
1116 config PROC_PID_CPUSET
1117 bool "Include legacy /proc/<pid>/cpuset file"
1121 config CGROUP_DEVICE
1122 bool "Device controller"
1124 Provides a cgroup controller implementing whitelists for
1125 devices which a process in the cgroup can mknod or open.
1127 config CGROUP_CPUACCT
1128 bool "Simple CPU accounting controller"
1130 Provides a simple controller for monitoring the
1131 total CPU consumed by the tasks in a cgroup.
1134 bool "Perf controller"
1135 depends on PERF_EVENTS
1137 This option extends the perf per-cpu mode to restrict monitoring
1138 to threads which belong to the cgroup specified and run on the
1139 designated cpu. Or this can be used to have cgroup ID in samples
1140 so that it can monitor performance events among cgroups.
1145 bool "Support for eBPF programs attached to cgroups"
1146 depends on BPF_SYSCALL
1147 select SOCK_CGROUP_DATA
1149 Allow attaching eBPF programs to a cgroup using the bpf(2)
1150 syscall command BPF_PROG_ATTACH.
1152 In which context these programs are accessed depends on the type
1153 of attachment. For instance, programs that are attached using
1154 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1158 bool "Misc resource controller"
1161 Provides a controller for miscellaneous resources on a host.
1163 Miscellaneous scalar resources are the resources on the host system
1164 which cannot be abstracted like the other cgroups. This controller
1165 tracks and limits the miscellaneous resources used by a process
1166 attached to a cgroup hierarchy.
1168 For more information, please check misc cgroup section in
1169 /Documentation/admin-guide/cgroup-v2.rst.
1172 bool "Debug controller"
1174 depends on DEBUG_KERNEL
1176 This option enables a simple controller that exports
1177 debugging information about the cgroups framework. This
1178 controller is for control cgroup debugging only. Its
1179 interfaces are not stable.
1183 config SOCK_CGROUP_DATA
1189 menuconfig NAMESPACES
1190 bool "Namespaces support" if EXPERT
1191 depends on MULTIUSER
1194 Provides the way to make tasks work with different objects using
1195 the same id. For example same IPC id may refer to different objects
1196 or same user id or pid may refer to different tasks when used in
1197 different namespaces.
1202 bool "UTS namespace"
1205 In this namespace tasks see different info provided with the
1209 bool "TIME namespace"
1210 depends on GENERIC_VDSO_TIME_NS
1213 In this namespace boottime and monotonic clocks can be set.
1214 The time will keep going with the same pace.
1217 bool "IPC namespace"
1218 depends on (SYSVIPC || POSIX_MQUEUE)
1221 In this namespace tasks work with IPC ids which correspond to
1222 different IPC objects in different namespaces.
1225 bool "User namespace"
1228 This allows containers, i.e. vservers, to use user namespaces
1229 to provide different user info for different servers.
1231 When user namespaces are enabled in the kernel it is
1232 recommended that the MEMCG option also be enabled and that
1233 user-space use the memory control groups to limit the amount
1234 of memory a memory unprivileged users can use.
1239 bool "PID Namespaces"
1242 Support process id namespaces. This allows having multiple
1243 processes with the same pid as long as they are in different
1244 pid namespaces. This is a building block of containers.
1247 bool "Network namespace"
1251 Allow user space to create what appear to be multiple instances
1252 of the network stack.
1256 config CHECKPOINT_RESTORE
1257 bool "Checkpoint/restore support"
1258 select PROC_CHILDREN
1262 Enables additional kernel features in a sake of checkpoint/restore.
1263 In particular it adds auxiliary prctl codes to setup process text,
1264 data and heap segment sizes, and a few additional /proc filesystem
1267 If unsure, say N here.
1269 config SCHED_AUTOGROUP
1270 bool "Automatic process group scheduling"
1273 select FAIR_GROUP_SCHED
1275 This option optimizes the scheduler for common desktop workloads by
1276 automatically creating and populating task groups. This separation
1277 of workloads isolates aggressive CPU burners (like build jobs) from
1278 desktop applications. Task group autogeneration is currently based
1281 config SYSFS_DEPRECATED
1282 bool "Enable deprecated sysfs features to support old userspace tools"
1286 This option adds code that switches the layout of the "block" class
1287 devices, to not show up in /sys/class/block/, but only in
1290 This switch is only active when the sysfs.deprecated=1 boot option is
1291 passed or the SYSFS_DEPRECATED_V2 option is set.
1293 This option allows new kernels to run on old distributions and tools,
1294 which might get confused by /sys/class/block/. Since 2007/2008 all
1295 major distributions and tools handle this just fine.
1297 Recent distributions and userspace tools after 2009/2010 depend on
1298 the existence of /sys/class/block/, and will not work with this
1301 Only if you are using a new kernel on an old distribution, you might
1304 config SYSFS_DEPRECATED_V2
1305 bool "Enable deprecated sysfs features by default"
1308 depends on SYSFS_DEPRECATED
1310 Enable deprecated sysfs by default.
1312 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1315 Only if you are using a new kernel on an old distribution, you might
1316 need to say Y here. Even then, odds are you would not need it
1317 enabled, you can always pass the boot option if absolutely necessary.
1320 bool "Kernel->user space relay support (formerly relayfs)"
1323 This option enables support for relay interface support in
1324 certain file systems (such as debugfs).
1325 It is designed to provide an efficient mechanism for tools and
1326 facilities to relay large amounts of data from kernel space to
1331 config BLK_DEV_INITRD
1332 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1334 The initial RAM filesystem is a ramfs which is loaded by the
1335 boot loader (loadlin or lilo) and that is mounted as root
1336 before the normal boot procedure. It is typically used to
1337 load modules needed to mount the "real" root file system,
1338 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1340 If RAM disk support (BLK_DEV_RAM) is also included, this
1341 also enables initial RAM disk (initrd) support and adds
1342 15 Kbytes (more on some other architectures) to the kernel size.
1348 source "usr/Kconfig"
1353 bool "Boot config support"
1354 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED
1356 Extra boot config allows system admin to pass a config file as
1357 complemental extension of kernel cmdline when booting.
1358 The boot config file must be attached at the end of initramfs
1359 with checksum, size and magic word.
1360 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1364 config BOOT_CONFIG_EMBED
1365 bool "Embed bootconfig file in the kernel"
1366 depends on BOOT_CONFIG
1368 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the
1369 kernel. Usually, the bootconfig file is loaded with the initrd
1370 image. But if the system doesn't support initrd, this option will
1371 help you by embedding a bootconfig file while building the kernel.
1375 config BOOT_CONFIG_EMBED_FILE
1376 string "Embedded bootconfig file path"
1377 depends on BOOT_CONFIG_EMBED
1379 Specify a bootconfig file which will be embedded to the kernel.
1380 This bootconfig will be used if there is no initrd or no other
1381 bootconfig in the initrd.
1383 config INITRAMFS_PRESERVE_MTIME
1384 bool "Preserve cpio archive mtimes in initramfs"
1387 Each entry in an initramfs cpio archive carries an mtime value. When
1388 enabled, extracted cpio items take this mtime, with directory mtime
1389 setting deferred until after creation of any child entries.
1394 prompt "Compiler optimization level"
1395 default CC_OPTIMIZE_FOR_PERFORMANCE
1397 config CC_OPTIMIZE_FOR_PERFORMANCE
1398 bool "Optimize for performance (-O2)"
1400 This is the default optimization level for the kernel, building
1401 with the "-O2" compiler flag for best performance and most
1402 helpful compile-time warnings.
1404 config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1405 bool "Optimize more for performance (-O3)"
1408 Choosing this option will pass "-O3" to your compiler to optimize
1409 the kernel yet more for performance.
1411 config CC_OPTIMIZE_FOR_SIZE
1412 bool "Optimize for size (-Os)"
1414 Choosing this option will pass "-Os" to your compiler resulting
1415 in a smaller kernel.
1419 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1422 This requires that the arch annotates or otherwise protects
1423 its external entry points from being discarded. Linker scripts
1424 must also merge .text.*, .data.*, and .bss.* correctly into
1425 output sections. Care must be taken not to pull in unrelated
1426 sections (e.g., '.text.init'). Typically '.' in section names
1427 is used to distinguish them from label names / C identifiers.
1429 config LD_DEAD_CODE_DATA_ELIMINATION
1430 bool "Dead code and data elimination (EXPERIMENTAL)"
1431 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1433 depends on $(cc-option,-ffunction-sections -fdata-sections)
1434 depends on $(ld-option,--gc-sections)
1436 Enable this if you want to do dead code and data elimination with
1437 the linker by compiling with -ffunction-sections -fdata-sections,
1438 and linking with --gc-sections.
1440 This can reduce on disk and in-memory size of the kernel
1441 code and static data, particularly for small configs and
1442 on small systems. This has the possibility of introducing
1443 silently broken kernel if the required annotations are not
1444 present. This option is not well tested yet, so use at your
1447 config LD_ORPHAN_WARN
1449 depends on ARCH_WANT_LD_ORPHAN_WARN
1450 depends on $(ld-option,--orphan-handling=warn)
1458 config SYSCTL_EXCEPTION_TRACE
1461 Enable support for /proc/sys/debug/exception-trace.
1463 config SYSCTL_ARCH_UNALIGN_NO_WARN
1466 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1467 Allows arch to define/use @no_unaligned_warning to possibly warn
1468 about unaligned access emulation going on under the hood.
1470 config SYSCTL_ARCH_UNALIGN_ALLOW
1473 Enable support for /proc/sys/kernel/unaligned-trap
1474 Allows arches to define/use @unaligned_enabled to runtime toggle
1475 the unaligned access emulation.
1476 see arch/parisc/kernel/unaligned.c for reference
1478 config HAVE_PCSPKR_PLATFORM
1481 # interpreter that classic socket filters depend on
1486 bool "Configure standard kernel features (expert users)"
1487 # Unhide debug options, to make the on-by-default options visible
1490 This option allows certain base kernel options and settings
1491 to be disabled or tweaked. This is for specialized
1492 environments which can tolerate a "non-standard" kernel.
1493 Only use this if you really know what you are doing.
1496 bool "Enable 16-bit UID system calls" if EXPERT
1497 depends on HAVE_UID16 && MULTIUSER
1500 This enables the legacy 16-bit UID syscall wrappers.
1503 bool "Multiple users, groups and capabilities support" if EXPERT
1506 This option enables support for non-root users, groups and
1509 If you say N here, all processes will run with UID 0, GID 0, and all
1510 possible capabilities. Saying N here also compiles out support for
1511 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1514 If unsure, say Y here.
1516 config SGETMASK_SYSCALL
1517 bool "sgetmask/ssetmask syscalls support" if EXPERT
1518 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1520 sys_sgetmask and sys_ssetmask are obsolete system calls
1521 no longer supported in libc but still enabled by default in some
1524 If unsure, leave the default option here.
1526 config SYSFS_SYSCALL
1527 bool "Sysfs syscall support" if EXPERT
1530 sys_sysfs is an obsolete system call no longer supported in libc.
1531 Note that disabling this option is more secure but might break
1532 compatibility with some systems.
1534 If unsure say Y here.
1537 bool "open by fhandle syscalls" if EXPERT
1541 If you say Y here, a user level program will be able to map
1542 file names to handle and then later use the handle for
1543 different file system operations. This is useful in implementing
1544 userspace file servers, which now track files using handles instead
1545 of names. The handle would remain the same even if file names
1546 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1550 bool "Posix Clocks & timers" if EXPERT
1553 This includes native support for POSIX timers to the kernel.
1554 Some embedded systems have no use for them and therefore they
1555 can be configured out to reduce the size of the kernel image.
1557 When this option is disabled, the following syscalls won't be
1558 available: timer_create, timer_gettime: timer_getoverrun,
1559 timer_settime, timer_delete, clock_adjtime, getitimer,
1560 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1561 clock_getres and clock_nanosleep syscalls will be limited to
1562 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1568 bool "Enable support for printk" if EXPERT
1571 This option enables normal printk support. Removing it
1572 eliminates most of the message strings from the kernel image
1573 and makes the kernel more or less silent. As this makes it
1574 very difficult to diagnose system problems, saying N here is
1575 strongly discouraged.
1578 bool "BUG() support" if EXPERT
1581 Disabling this option eliminates support for BUG and WARN, reducing
1582 the size of your kernel image and potentially quietly ignoring
1583 numerous fatal conditions. You should only consider disabling this
1584 option for embedded systems with no facilities for reporting errors.
1590 bool "Enable ELF core dumps" if EXPERT
1592 Enable support for generating core dumps. Disabling saves about 4k.
1595 config PCSPKR_PLATFORM
1596 bool "Enable PC-Speaker support" if EXPERT
1597 depends on HAVE_PCSPKR_PLATFORM
1601 This option allows to disable the internal PC-Speaker
1602 support, saving some memory.
1606 bool "Enable full-sized data structures for core" if EXPERT
1608 Disabling this option reduces the size of miscellaneous core
1609 kernel data structures. This saves memory on small machines,
1610 but may reduce performance.
1613 bool "Enable futex support" if EXPERT
1614 depends on !(SPARC32 && SMP)
1618 Disabling this option will cause the kernel to be built without
1619 support for "fast userspace mutexes". The resulting kernel may not
1620 run glibc-based applications correctly.
1624 depends on FUTEX && RT_MUTEXES
1628 bool "Enable eventpoll support" if EXPERT
1631 Disabling this option will cause the kernel to be built without
1632 support for epoll family of system calls.
1635 bool "Enable signalfd() system call" if EXPERT
1638 Enable the signalfd() system call that allows to receive signals
1639 on a file descriptor.
1644 bool "Enable timerfd() system call" if EXPERT
1647 Enable the timerfd() system call that allows to receive timer
1648 events on a file descriptor.
1653 bool "Enable eventfd() system call" if EXPERT
1656 Enable the eventfd() system call that allows to receive both
1657 kernel notification (ie. KAIO) or userspace notifications.
1662 bool "Use full shmem filesystem" if EXPERT
1666 The shmem is an internal filesystem used to manage shared memory.
1667 It is backed by swap and manages resource limits. It is also exported
1668 to userspace as tmpfs if TMPFS is enabled. Disabling this
1669 option replaces shmem and tmpfs with the much simpler ramfs code,
1670 which may be appropriate on small systems without swap.
1673 bool "Enable AIO support" if EXPERT
1676 This option enables POSIX asynchronous I/O which may by used
1677 by some high performance threaded applications. Disabling
1678 this option saves about 7k.
1681 bool "Enable IO uring support" if EXPERT
1685 This option enables support for the io_uring interface, enabling
1686 applications to submit and complete IO through submission and
1687 completion rings that are shared between the kernel and application.
1689 config ADVISE_SYSCALLS
1690 bool "Enable madvise/fadvise syscalls" if EXPERT
1693 This option enables the madvise and fadvise syscalls, used by
1694 applications to advise the kernel about their future memory or file
1695 usage, improving performance. If building an embedded system where no
1696 applications use these syscalls, you can disable this option to save
1700 bool "Enable membarrier() system call" if EXPERT
1703 Enable the membarrier() system call that allows issuing memory
1704 barriers across all running threads, which can be used to distribute
1705 the cost of user-space memory barriers asymmetrically by transforming
1706 pairs of memory barriers into pairs consisting of membarrier() and a
1712 bool "Load all symbols for debugging/ksymoops" if EXPERT
1715 Say Y here to let the kernel print out symbolic crash information and
1716 symbolic stack backtraces. This increases the size of the kernel
1717 somewhat, as all symbols have to be loaded into the kernel image.
1720 bool "Include all symbols in kallsyms"
1721 depends on DEBUG_KERNEL && KALLSYMS
1723 Normally kallsyms only contains the symbols of functions for nicer
1724 OOPS messages and backtraces (i.e., symbols from the text and inittext
1725 sections). This is sufficient for most cases. And only in very rare
1726 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1727 names of variables from the data sections, etc).
1729 This option makes sure that all symbols are loaded into the kernel
1730 image (i.e., symbols from all sections) in cost of increased kernel
1731 size (depending on the kernel configuration, it may be 300KiB or
1732 something like this).
1734 Say N unless you really need all symbols.
1736 config KALLSYMS_ABSOLUTE_PERCPU
1739 default X86_64 && SMP
1741 config KALLSYMS_BASE_RELATIVE
1746 Instead of emitting them as absolute values in the native word size,
1747 emit the symbol references in the kallsyms table as 32-bit entries,
1748 each containing a relative value in the range [base, base + U32_MAX]
1749 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1750 an absolute value in the range [0, S32_MAX] or a relative value in the
1751 range [base, base + S32_MAX], where base is the lowest relative symbol
1752 address encountered in the image.
1754 On 64-bit builds, this reduces the size of the address table by 50%,
1755 but more importantly, it results in entries whose values are build
1756 time constants, and no relocation pass is required at runtime to fix
1757 up the entries based on the runtime load address of the kernel.
1759 # end of the "standard kernel features (expert users)" menu
1761 # syscall, maps, verifier
1763 config ARCH_HAS_MEMBARRIER_CALLBACKS
1766 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1770 bool "Enable kcmp() system call" if EXPERT
1772 Enable the kernel resource comparison system call. It provides
1773 user-space with the ability to compare two processes to see if they
1774 share a common resource, such as a file descriptor or even virtual
1780 bool "Enable rseq() system call" if EXPERT
1782 depends on HAVE_RSEQ
1785 Enable the restartable sequences system call. It provides a
1786 user-space cache for the current CPU number value, which
1787 speeds up getting the current CPU number from user-space,
1788 as well as an ABI to speed up user-space operations on
1795 bool "Enabled debugging of rseq() system call" if EXPERT
1796 depends on RSEQ && DEBUG_KERNEL
1798 Enable extra debugging checks for the rseq system call.
1803 bool "Embedded system"
1806 This option should be enabled if compiling the kernel for
1807 an embedded system so certain expert options are available
1810 config HAVE_PERF_EVENTS
1813 See tools/perf/design.txt for details.
1815 config GUEST_PERF_EVENTS
1817 depends on HAVE_PERF_EVENTS
1819 config PERF_USE_VMALLOC
1822 See tools/perf/design.txt for details
1825 bool "PC/104 support" if EXPERT
1827 Expose PC/104 form factor device drivers and options available for
1828 selection and configuration. Enable this option if your target
1829 machine has a PC/104 bus.
1831 menu "Kernel Performance Events And Counters"
1834 bool "Kernel performance events and counters"
1835 default y if PROFILING
1836 depends on HAVE_PERF_EVENTS
1840 Enable kernel support for various performance events provided
1841 by software and hardware.
1843 Software events are supported either built-in or via the
1844 use of generic tracepoints.
1846 Most modern CPUs support performance events via performance
1847 counter registers. These registers count the number of certain
1848 types of hw events: such as instructions executed, cachemisses
1849 suffered, or branches mis-predicted - without slowing down the
1850 kernel or applications. These registers can also trigger interrupts
1851 when a threshold number of events have passed - and can thus be
1852 used to profile the code that runs on that CPU.
1854 The Linux Performance Event subsystem provides an abstraction of
1855 these software and hardware event capabilities, available via a
1856 system call and used by the "perf" utility in tools/perf/. It
1857 provides per task and per CPU counters, and it provides event
1858 capabilities on top of those.
1862 config DEBUG_PERF_USE_VMALLOC
1864 bool "Debug: use vmalloc to back perf mmap() buffers"
1865 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1866 select PERF_USE_VMALLOC
1868 Use vmalloc memory to back perf mmap() buffers.
1870 Mostly useful for debugging the vmalloc code on platforms
1871 that don't require it.
1877 config SYSTEM_DATA_VERIFICATION
1879 select SYSTEM_TRUSTED_KEYRING
1883 select ASYMMETRIC_KEY_TYPE
1884 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1887 select X509_CERTIFICATE_PARSER
1888 select PKCS7_MESSAGE_PARSER
1890 Provide PKCS#7 message verification using the contents of the system
1891 trusted keyring to provide public keys. This then can be used for
1892 module verification, kexec image verification and firmware blob
1896 bool "Profiling support"
1898 Say Y here to enable the extended profiling support mechanisms used
1902 # Place an empty function call at each tracepoint site. Can be
1903 # dynamically changed for a probe function.
1908 endmenu # General setup
1910 source "arch/Kconfig"
1914 default y if PREEMPT_RT
1918 default 0 if BASE_FULL
1919 default 1 if !BASE_FULL
1921 config MODULE_SIG_FORMAT
1923 select SYSTEM_DATA_VERIFICATION
1926 bool "Enable loadable module support"
1929 Kernel modules are small pieces of compiled code which can
1930 be inserted in the running kernel, rather than being
1931 permanently built into the kernel. You use the "modprobe"
1932 tool to add (and sometimes remove) them. If you say Y here,
1933 many parts of the kernel can be built as modules (by
1934 answering M instead of Y where indicated): this is most
1935 useful for infrequently used options which are not required
1936 for booting. For more information, see the man pages for
1937 modprobe, lsmod, modinfo, insmod and rmmod.
1939 If you say Y here, you will need to run "make
1940 modules_install" to put the modules under /lib/modules/
1941 where modprobe can find them (you may need to be root to do
1948 config MODULE_FORCE_LOAD
1949 bool "Forced module loading"
1952 Allow loading of modules without version information (ie. modprobe
1953 --force). Forced module loading sets the 'F' (forced) taint flag and
1954 is usually a really bad idea.
1956 config MODULE_UNLOAD
1957 bool "Module unloading"
1959 Without this option you will not be able to unload any
1960 modules (note that some modules may not be unloadable
1961 anyway), which makes your kernel smaller, faster
1962 and simpler. If unsure, say Y.
1964 config MODULE_FORCE_UNLOAD
1965 bool "Forced module unloading"
1966 depends on MODULE_UNLOAD
1968 This option allows you to force a module to unload, even if the
1969 kernel believes it is unsafe: the kernel will remove the module
1970 without waiting for anyone to stop using it (using the -f option to
1971 rmmod). This is mainly for kernel developers and desperate users.
1974 config MODULE_UNLOAD_TAINT_TRACKING
1975 bool "Tainted module unload tracking"
1976 depends on MODULE_UNLOAD
1979 This option allows you to maintain a record of each unloaded
1980 module that tainted the kernel. In addition to displaying a
1981 list of linked (or loaded) modules e.g. on detection of a bad
1982 page (see bad_page()), the aforementioned details are also
1983 shown. If unsure, say N.
1986 bool "Module versioning support"
1988 Usually, you have to use modules compiled with your kernel.
1989 Saying Y here makes it sometimes possible to use modules
1990 compiled for different kernels, by adding enough information
1991 to the modules to (hopefully) spot any changes which would
1992 make them incompatible with the kernel you are running. If
1995 config ASM_MODVERSIONS
1997 default HAVE_ASM_MODVERSIONS && MODVERSIONS
1999 This enables module versioning for exported symbols also from
2000 assembly. This can be enabled only when the target architecture
2003 config MODULE_SRCVERSION_ALL
2004 bool "Source checksum for all modules"
2006 Modules which contain a MODULE_VERSION get an extra "srcversion"
2007 field inserted into their modinfo section, which contains a
2008 sum of the source files which made it. This helps maintainers
2009 see exactly which source was used to build a module (since
2010 others sometimes change the module source without updating
2011 the version). With this option, such a "srcversion" field
2012 will be created for all modules. If unsure, say N.
2015 bool "Module signature verification"
2016 select MODULE_SIG_FORMAT
2018 Check modules for valid signatures upon load: the signature
2019 is simply appended to the module. For more information see
2020 <file:Documentation/admin-guide/module-signing.rst>.
2022 Note that this option adds the OpenSSL development packages as a
2023 kernel build dependency so that the signing tool can use its crypto
2026 You should enable this option if you wish to use either
2027 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2028 another LSM - otherwise unsigned modules will be loadable regardless
2029 of the lockdown policy.
2031 !!!WARNING!!! If you enable this option, you MUST make sure that the
2032 module DOES NOT get stripped after being signed. This includes the
2033 debuginfo strip done by some packagers (such as rpmbuild) and
2034 inclusion into an initramfs that wants the module size reduced.
2036 config MODULE_SIG_FORCE
2037 bool "Require modules to be validly signed"
2038 depends on MODULE_SIG
2040 Reject unsigned modules or signed modules for which we don't have a
2041 key. Without this, such modules will simply taint the kernel.
2043 config MODULE_SIG_ALL
2044 bool "Automatically sign all modules"
2046 depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2048 Sign all modules during make modules_install. Without this option,
2049 modules must be signed manually, using the scripts/sign-file tool.
2051 comment "Do not forget to sign required modules with scripts/sign-file"
2052 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2055 prompt "Which hash algorithm should modules be signed with?"
2056 depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2058 This determines which sort of hashing algorithm will be used during
2059 signature generation. This algorithm _must_ be built into the kernel
2060 directly so that signature verification can take place. It is not
2061 possible to load a signed module containing the algorithm to check
2062 the signature on that module.
2064 config MODULE_SIG_SHA1
2065 bool "Sign modules with SHA-1"
2068 config MODULE_SIG_SHA224
2069 bool "Sign modules with SHA-224"
2070 select CRYPTO_SHA256
2072 config MODULE_SIG_SHA256
2073 bool "Sign modules with SHA-256"
2074 select CRYPTO_SHA256
2076 config MODULE_SIG_SHA384
2077 bool "Sign modules with SHA-384"
2078 select CRYPTO_SHA512
2080 config MODULE_SIG_SHA512
2081 bool "Sign modules with SHA-512"
2082 select CRYPTO_SHA512
2086 config MODULE_SIG_HASH
2088 depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2089 default "sha1" if MODULE_SIG_SHA1
2090 default "sha224" if MODULE_SIG_SHA224
2091 default "sha256" if MODULE_SIG_SHA256
2092 default "sha384" if MODULE_SIG_SHA384
2093 default "sha512" if MODULE_SIG_SHA512
2096 prompt "Module compression mode"
2098 This option allows you to choose the algorithm which will be used to
2099 compress modules when 'make modules_install' is run. (or, you can
2100 choose to not compress modules at all.)
2102 External modules will also be compressed in the same way during the
2105 For modules inside an initrd or initramfs, it's more efficient to
2106 compress the whole initrd or initramfs instead.
2108 This is fully compatible with signed modules.
2110 Please note that the tool used to load modules needs to support the
2111 corresponding algorithm. module-init-tools MAY support gzip, and kmod
2112 MAY support gzip, xz and zstd.
2114 Your build system needs to provide the appropriate compression tool
2115 to compress the modules.
2117 If in doubt, select 'None'.
2119 config MODULE_COMPRESS_NONE
2122 Do not compress modules. The installed modules are suffixed
2125 config MODULE_COMPRESS_GZIP
2128 Compress modules with GZIP. The installed modules are suffixed
2131 config MODULE_COMPRESS_XZ
2134 Compress modules with XZ. The installed modules are suffixed
2137 config MODULE_COMPRESS_ZSTD
2140 Compress modules with ZSTD. The installed modules are suffixed
2145 config MODULE_DECOMPRESS
2146 bool "Support in-kernel module decompression"
2147 depends on MODULE_COMPRESS_GZIP || MODULE_COMPRESS_XZ
2148 select ZLIB_INFLATE if MODULE_COMPRESS_GZIP
2149 select XZ_DEC if MODULE_COMPRESS_XZ
2152 Support for decompressing kernel modules by the kernel itself
2153 instead of relying on userspace to perform this task. Useful when
2154 load pinning security policy is enabled.
2158 config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2159 bool "Allow loading of modules with missing namespace imports"
2161 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2162 a namespace. A module that makes use of a symbol exported with such a
2163 namespace is required to import the namespace via MODULE_IMPORT_NS().
2164 There is no technical reason to enforce correct namespace imports,
2165 but it creates consistency between symbols defining namespaces and
2166 users importing namespaces they make use of. This option relaxes this
2167 requirement and lifts the enforcement when loading a module.
2171 config MODPROBE_PATH
2172 string "Path to modprobe binary"
2173 default "/sbin/modprobe"
2175 When kernel code requests a module, it does so by calling
2176 the "modprobe" userspace utility. This option allows you to
2177 set the path where that binary is found. This can be changed
2178 at runtime via the sysctl file
2179 /proc/sys/kernel/modprobe. Setting this to the empty string
2180 removes the kernel's ability to request modules (but
2181 userspace can still load modules explicitly).
2183 config TRIM_UNUSED_KSYMS
2184 bool "Trim unused exported kernel symbols" if EXPERT
2185 depends on !COMPILE_TEST
2187 The kernel and some modules make many symbols available for
2188 other modules to use via EXPORT_SYMBOL() and variants. Depending
2189 on the set of modules being selected in your kernel configuration,
2190 many of those exported symbols might never be used.
2192 This option allows for unused exported symbols to be dropped from
2193 the build. In turn, this provides the compiler more opportunities
2194 (especially when using LTO) for optimizing the code and reducing
2195 binary size. This might have some security advantages as well.
2197 If unsure, or if you need to build out-of-tree modules, say N.
2199 config UNUSED_KSYMS_WHITELIST
2200 string "Whitelist of symbols to keep in ksymtab"
2201 depends on TRIM_UNUSED_KSYMS
2203 By default, all unused exported symbols will be un-exported from the
2204 build when TRIM_UNUSED_KSYMS is selected.
2206 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
2207 exported at all times, even in absence of in-tree users. The value to
2208 set here is the path to a text file containing the list of symbols,
2209 one per line. The path can be absolute, or relative to the kernel
2214 config MODULES_TREE_LOOKUP
2216 depends on PERF_EVENTS || TRACING || CFI_CLANG
2218 config INIT_ALL_POSSIBLE
2221 Back when each arch used to define their own cpu_online_mask and
2222 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2223 with all 1s, and others with all 0s. When they were centralised,
2224 it was better to provide this option than to break all the archs
2225 and have several arch maintainers pursuing me down dark alleys.
2227 source "block/Kconfig"
2229 config PREEMPT_NOTIFIERS
2239 Build a simple ASN.1 grammar compiler that produces a bytecode output
2240 that can be interpreted by the ASN.1 stream decoder and used to
2241 inform it as to what tags are to be expected in a stream and what
2242 functions to call on what tags.
2244 source "kernel/Kconfig.locks"
2246 config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2249 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2252 # It may be useful for an architecture to override the definitions of the
2253 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2254 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2255 # different calling convention for syscalls. They can also override the
2256 # macros for not-implemented syscalls in kernel/sys_ni.c and
2257 # kernel/time/posix-stubs.c. All these overrides need to be available in
2258 # <asm/syscall_wrapper.h>.
2259 config ARCH_HAS_SYSCALL_WRAPPER
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