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)
889 # For architectures that know their GCC __int128 support is sound
891 config ARCH_SUPPORTS_INT128
894 # For architectures that (ab)use NUMA to represent different memory regions
895 # all cpu-local but of different latencies, such as SuperH.
897 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
900 config NUMA_BALANCING
901 bool "Memory placement aware NUMA scheduler"
902 depends on ARCH_SUPPORTS_NUMA_BALANCING
903 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
904 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT
906 This option adds support for automatic NUMA aware memory/task placement.
907 The mechanism is quite primitive and is based on migrating memory when
908 it has references to the node the task is running on.
910 This system will be inactive on UMA systems.
912 config NUMA_BALANCING_DEFAULT_ENABLED
913 bool "Automatically enable NUMA aware memory/task placement"
915 depends on NUMA_BALANCING
917 If set, automatic NUMA balancing will be enabled if running on a NUMA
921 bool "Control Group support"
924 This option adds support for grouping sets of processes together, for
925 use with process control subsystems such as Cpusets, CFS, memory
926 controls or device isolation.
928 - Documentation/scheduler/sched-design-CFS.rst (CFS)
929 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
930 and resource control)
940 bool "Memory controller"
944 Provides control over the memory footprint of tasks in a cgroup.
948 depends on MEMCG && SWAP
953 depends on MEMCG && !SLOB
961 Generic block IO controller cgroup interface. This is the common
962 cgroup interface which should be used by various IO controlling
965 Currently, CFQ IO scheduler uses it to recognize task groups and
966 control disk bandwidth allocation (proportional time slice allocation)
967 to such task groups. It is also used by bio throttling logic in
968 block layer to implement upper limit in IO rates on a device.
970 This option only enables generic Block IO controller infrastructure.
971 One needs to also enable actual IO controlling logic/policy. For
972 enabling proportional weight division of disk bandwidth in CFQ, set
973 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
974 CONFIG_BLK_DEV_THROTTLING=y.
976 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
978 config CGROUP_WRITEBACK
980 depends on MEMCG && BLK_CGROUP
983 menuconfig CGROUP_SCHED
984 bool "CPU controller"
987 This feature lets CPU scheduler recognize task groups and control CPU
988 bandwidth allocation to such task groups. It uses cgroups to group
992 config FAIR_GROUP_SCHED
993 bool "Group scheduling for SCHED_OTHER"
994 depends on CGROUP_SCHED
998 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
999 depends on FAIR_GROUP_SCHED
1002 This option allows users to define CPU bandwidth rates (limits) for
1003 tasks running within the fair group scheduler. Groups with no limit
1004 set are considered to be unconstrained and will run with no
1006 See Documentation/scheduler/sched-bwc.rst for more information.
1008 config RT_GROUP_SCHED
1009 bool "Group scheduling for SCHED_RR/FIFO"
1010 depends on CGROUP_SCHED
1013 This feature lets you explicitly allocate real CPU bandwidth
1014 to task groups. If enabled, it will also make it impossible to
1015 schedule realtime tasks for non-root users until you allocate
1016 realtime bandwidth for them.
1017 See Documentation/scheduler/sched-rt-group.rst for more information.
1021 config UCLAMP_TASK_GROUP
1022 bool "Utilization clamping per group of tasks"
1023 depends on CGROUP_SCHED
1024 depends on UCLAMP_TASK
1027 This feature enables the scheduler to track the clamped utilization
1028 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
1030 When this option is enabled, the user can specify a min and max
1031 CPU bandwidth which is allowed for each single task in a group.
1032 The max bandwidth allows to clamp the maximum frequency a task
1033 can use, while the min bandwidth allows to define a minimum
1034 frequency a task will always use.
1036 When task group based utilization clamping is enabled, an eventually
1037 specified task-specific clamp value is constrained by the cgroup
1038 specified clamp value. Both minimum and maximum task clamping cannot
1039 be bigger than the corresponding clamping defined at task group level.
1044 bool "PIDs controller"
1046 Provides enforcement of process number limits in the scope of a
1047 cgroup. Any attempt to fork more processes than is allowed in the
1048 cgroup will fail. PIDs are fundamentally a global resource because it
1049 is fairly trivial to reach PID exhaustion before you reach even a
1050 conservative kmemcg limit. As a result, it is possible to grind a
1051 system to halt without being limited by other cgroup policies. The
1052 PIDs controller is designed to stop this from happening.
1054 It should be noted that organisational operations (such as attaching
1055 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1056 since the PIDs limit only affects a process's ability to fork, not to
1060 bool "RDMA controller"
1062 Provides enforcement of RDMA resources defined by IB stack.
1063 It is fairly easy for consumers to exhaust RDMA resources, which
1064 can result into resource unavailability to other consumers.
1065 RDMA controller is designed to stop this from happening.
1066 Attaching processes with active RDMA resources to the cgroup
1067 hierarchy is allowed even if can cross the hierarchy's limit.
1069 config CGROUP_FREEZER
1070 bool "Freezer controller"
1072 Provides a way to freeze and unfreeze all tasks in a
1075 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1076 controller includes important in-kernel memory consumers per default.
1078 If you're using cgroup2, say N.
1080 config CGROUP_HUGETLB
1081 bool "HugeTLB controller"
1082 depends on HUGETLB_PAGE
1086 Provides a cgroup controller for HugeTLB pages.
1087 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1088 The limit is enforced during page fault. Since HugeTLB doesn't
1089 support page reclaim, enforcing the limit at page fault time implies
1090 that, the application will get SIGBUS signal if it tries to access
1091 HugeTLB pages beyond its limit. This requires the application to know
1092 beforehand how much HugeTLB pages it would require for its use. The
1093 control group is tracked in the third page lru pointer. This means
1094 that we cannot use the controller with huge page less than 3 pages.
1097 bool "Cpuset controller"
1100 This option will let you create and manage CPUSETs which
1101 allow dynamically partitioning a system into sets of CPUs and
1102 Memory Nodes and assigning tasks to run only within those sets.
1103 This is primarily useful on large SMP or NUMA systems.
1107 config PROC_PID_CPUSET
1108 bool "Include legacy /proc/<pid>/cpuset file"
1112 config CGROUP_DEVICE
1113 bool "Device controller"
1115 Provides a cgroup controller implementing whitelists for
1116 devices which a process in the cgroup can mknod or open.
1118 config CGROUP_CPUACCT
1119 bool "Simple CPU accounting controller"
1121 Provides a simple controller for monitoring the
1122 total CPU consumed by the tasks in a cgroup.
1125 bool "Perf controller"
1126 depends on PERF_EVENTS
1128 This option extends the perf per-cpu mode to restrict monitoring
1129 to threads which belong to the cgroup specified and run on the
1130 designated cpu. Or this can be used to have cgroup ID in samples
1131 so that it can monitor performance events among cgroups.
1136 bool "Support for eBPF programs attached to cgroups"
1137 depends on BPF_SYSCALL
1138 select SOCK_CGROUP_DATA
1140 Allow attaching eBPF programs to a cgroup using the bpf(2)
1141 syscall command BPF_PROG_ATTACH.
1143 In which context these programs are accessed depends on the type
1144 of attachment. For instance, programs that are attached using
1145 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1149 bool "Misc resource controller"
1152 Provides a controller for miscellaneous resources on a host.
1154 Miscellaneous scalar resources are the resources on the host system
1155 which cannot be abstracted like the other cgroups. This controller
1156 tracks and limits the miscellaneous resources used by a process
1157 attached to a cgroup hierarchy.
1159 For more information, please check misc cgroup section in
1160 /Documentation/admin-guide/cgroup-v2.rst.
1163 bool "Debug controller"
1165 depends on DEBUG_KERNEL
1167 This option enables a simple controller that exports
1168 debugging information about the cgroups framework. This
1169 controller is for control cgroup debugging only. Its
1170 interfaces are not stable.
1174 config SOCK_CGROUP_DATA
1180 menuconfig NAMESPACES
1181 bool "Namespaces support" if EXPERT
1182 depends on MULTIUSER
1185 Provides the way to make tasks work with different objects using
1186 the same id. For example same IPC id may refer to different objects
1187 or same user id or pid may refer to different tasks when used in
1188 different namespaces.
1193 bool "UTS namespace"
1196 In this namespace tasks see different info provided with the
1200 bool "TIME namespace"
1201 depends on GENERIC_VDSO_TIME_NS
1204 In this namespace boottime and monotonic clocks can be set.
1205 The time will keep going with the same pace.
1208 bool "IPC namespace"
1209 depends on (SYSVIPC || POSIX_MQUEUE)
1212 In this namespace tasks work with IPC ids which correspond to
1213 different IPC objects in different namespaces.
1216 bool "User namespace"
1219 This allows containers, i.e. vservers, to use user namespaces
1220 to provide different user info for different servers.
1222 When user namespaces are enabled in the kernel it is
1223 recommended that the MEMCG option also be enabled and that
1224 user-space use the memory control groups to limit the amount
1225 of memory a memory unprivileged users can use.
1230 bool "PID Namespaces"
1233 Support process id namespaces. This allows having multiple
1234 processes with the same pid as long as they are in different
1235 pid namespaces. This is a building block of containers.
1238 bool "Network namespace"
1242 Allow user space to create what appear to be multiple instances
1243 of the network stack.
1247 config CHECKPOINT_RESTORE
1248 bool "Checkpoint/restore support"
1249 select PROC_CHILDREN
1253 Enables additional kernel features in a sake of checkpoint/restore.
1254 In particular it adds auxiliary prctl codes to setup process text,
1255 data and heap segment sizes, and a few additional /proc filesystem
1258 If unsure, say N here.
1260 config SCHED_AUTOGROUP
1261 bool "Automatic process group scheduling"
1264 select FAIR_GROUP_SCHED
1266 This option optimizes the scheduler for common desktop workloads by
1267 automatically creating and populating task groups. This separation
1268 of workloads isolates aggressive CPU burners (like build jobs) from
1269 desktop applications. Task group autogeneration is currently based
1272 config SYSFS_DEPRECATED
1273 bool "Enable deprecated sysfs features to support old userspace tools"
1277 This option adds code that switches the layout of the "block" class
1278 devices, to not show up in /sys/class/block/, but only in
1281 This switch is only active when the sysfs.deprecated=1 boot option is
1282 passed or the SYSFS_DEPRECATED_V2 option is set.
1284 This option allows new kernels to run on old distributions and tools,
1285 which might get confused by /sys/class/block/. Since 2007/2008 all
1286 major distributions and tools handle this just fine.
1288 Recent distributions and userspace tools after 2009/2010 depend on
1289 the existence of /sys/class/block/, and will not work with this
1292 Only if you are using a new kernel on an old distribution, you might
1295 config SYSFS_DEPRECATED_V2
1296 bool "Enable deprecated sysfs features by default"
1299 depends on SYSFS_DEPRECATED
1301 Enable deprecated sysfs by default.
1303 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1306 Only if you are using a new kernel on an old distribution, you might
1307 need to say Y here. Even then, odds are you would not need it
1308 enabled, you can always pass the boot option if absolutely necessary.
1311 bool "Kernel->user space relay support (formerly relayfs)"
1314 This option enables support for relay interface support in
1315 certain file systems (such as debugfs).
1316 It is designed to provide an efficient mechanism for tools and
1317 facilities to relay large amounts of data from kernel space to
1322 config BLK_DEV_INITRD
1323 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1325 The initial RAM filesystem is a ramfs which is loaded by the
1326 boot loader (loadlin or lilo) and that is mounted as root
1327 before the normal boot procedure. It is typically used to
1328 load modules needed to mount the "real" root file system,
1329 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1331 If RAM disk support (BLK_DEV_RAM) is also included, this
1332 also enables initial RAM disk (initrd) support and adds
1333 15 Kbytes (more on some other architectures) to the kernel size.
1339 source "usr/Kconfig"
1344 bool "Boot config support"
1345 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED
1347 Extra boot config allows system admin to pass a config file as
1348 complemental extension of kernel cmdline when booting.
1349 The boot config file must be attached at the end of initramfs
1350 with checksum, size and magic word.
1351 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1355 config BOOT_CONFIG_EMBED
1356 bool "Embed bootconfig file in the kernel"
1357 depends on BOOT_CONFIG
1359 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the
1360 kernel. Usually, the bootconfig file is loaded with the initrd
1361 image. But if the system doesn't support initrd, this option will
1362 help you by embedding a bootconfig file while building the kernel.
1366 config BOOT_CONFIG_EMBED_FILE
1367 string "Embedded bootconfig file path"
1368 depends on BOOT_CONFIG_EMBED
1370 Specify a bootconfig file which will be embedded to the kernel.
1371 This bootconfig will be used if there is no initrd or no other
1372 bootconfig in the initrd.
1374 config INITRAMFS_PRESERVE_MTIME
1375 bool "Preserve cpio archive mtimes in initramfs"
1378 Each entry in an initramfs cpio archive carries an mtime value. When
1379 enabled, extracted cpio items take this mtime, with directory mtime
1380 setting deferred until after creation of any child entries.
1385 prompt "Compiler optimization level"
1386 default CC_OPTIMIZE_FOR_PERFORMANCE
1388 config CC_OPTIMIZE_FOR_PERFORMANCE
1389 bool "Optimize for performance (-O2)"
1391 This is the default optimization level for the kernel, building
1392 with the "-O2" compiler flag for best performance and most
1393 helpful compile-time warnings.
1395 config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1396 bool "Optimize more for performance (-O3)"
1399 Choosing this option will pass "-O3" to your compiler to optimize
1400 the kernel yet more for performance.
1402 config CC_OPTIMIZE_FOR_SIZE
1403 bool "Optimize for size (-Os)"
1405 Choosing this option will pass "-Os" to your compiler resulting
1406 in a smaller kernel.
1410 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1413 This requires that the arch annotates or otherwise protects
1414 its external entry points from being discarded. Linker scripts
1415 must also merge .text.*, .data.*, and .bss.* correctly into
1416 output sections. Care must be taken not to pull in unrelated
1417 sections (e.g., '.text.init'). Typically '.' in section names
1418 is used to distinguish them from label names / C identifiers.
1420 config LD_DEAD_CODE_DATA_ELIMINATION
1421 bool "Dead code and data elimination (EXPERIMENTAL)"
1422 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1424 depends on $(cc-option,-ffunction-sections -fdata-sections)
1425 depends on $(ld-option,--gc-sections)
1427 Enable this if you want to do dead code and data elimination with
1428 the linker by compiling with -ffunction-sections -fdata-sections,
1429 and linking with --gc-sections.
1431 This can reduce on disk and in-memory size of the kernel
1432 code and static data, particularly for small configs and
1433 on small systems. This has the possibility of introducing
1434 silently broken kernel if the required annotations are not
1435 present. This option is not well tested yet, so use at your
1438 config LD_ORPHAN_WARN
1440 depends on ARCH_WANT_LD_ORPHAN_WARN
1441 depends on $(ld-option,--orphan-handling=warn)
1449 config SYSCTL_EXCEPTION_TRACE
1452 Enable support for /proc/sys/debug/exception-trace.
1454 config SYSCTL_ARCH_UNALIGN_NO_WARN
1457 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1458 Allows arch to define/use @no_unaligned_warning to possibly warn
1459 about unaligned access emulation going on under the hood.
1461 config SYSCTL_ARCH_UNALIGN_ALLOW
1464 Enable support for /proc/sys/kernel/unaligned-trap
1465 Allows arches to define/use @unaligned_enabled to runtime toggle
1466 the unaligned access emulation.
1467 see arch/parisc/kernel/unaligned.c for reference
1469 config HAVE_PCSPKR_PLATFORM
1472 # interpreter that classic socket filters depend on
1475 select CRYPTO_LIB_SHA1
1478 bool "Configure standard kernel features (expert users)"
1479 # Unhide debug options, to make the on-by-default options visible
1482 This option allows certain base kernel options and settings
1483 to be disabled or tweaked. This is for specialized
1484 environments which can tolerate a "non-standard" kernel.
1485 Only use this if you really know what you are doing.
1488 bool "Enable 16-bit UID system calls" if EXPERT
1489 depends on HAVE_UID16 && MULTIUSER
1492 This enables the legacy 16-bit UID syscall wrappers.
1495 bool "Multiple users, groups and capabilities support" if EXPERT
1498 This option enables support for non-root users, groups and
1501 If you say N here, all processes will run with UID 0, GID 0, and all
1502 possible capabilities. Saying N here also compiles out support for
1503 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1506 If unsure, say Y here.
1508 config SGETMASK_SYSCALL
1509 bool "sgetmask/ssetmask syscalls support" if EXPERT
1510 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1512 sys_sgetmask and sys_ssetmask are obsolete system calls
1513 no longer supported in libc but still enabled by default in some
1516 If unsure, leave the default option here.
1518 config SYSFS_SYSCALL
1519 bool "Sysfs syscall support" if EXPERT
1522 sys_sysfs is an obsolete system call no longer supported in libc.
1523 Note that disabling this option is more secure but might break
1524 compatibility with some systems.
1526 If unsure say Y here.
1529 bool "open by fhandle syscalls" if EXPERT
1533 If you say Y here, a user level program will be able to map
1534 file names to handle and then later use the handle for
1535 different file system operations. This is useful in implementing
1536 userspace file servers, which now track files using handles instead
1537 of names. The handle would remain the same even if file names
1538 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1542 bool "Posix Clocks & timers" if EXPERT
1545 This includes native support for POSIX timers to the kernel.
1546 Some embedded systems have no use for them and therefore they
1547 can be configured out to reduce the size of the kernel image.
1549 When this option is disabled, the following syscalls won't be
1550 available: timer_create, timer_gettime: timer_getoverrun,
1551 timer_settime, timer_delete, clock_adjtime, getitimer,
1552 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1553 clock_getres and clock_nanosleep syscalls will be limited to
1554 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1560 bool "Enable support for printk" if EXPERT
1563 This option enables normal printk support. Removing it
1564 eliminates most of the message strings from the kernel image
1565 and makes the kernel more or less silent. As this makes it
1566 very difficult to diagnose system problems, saying N here is
1567 strongly discouraged.
1570 bool "BUG() support" if EXPERT
1573 Disabling this option eliminates support for BUG and WARN, reducing
1574 the size of your kernel image and potentially quietly ignoring
1575 numerous fatal conditions. You should only consider disabling this
1576 option for embedded systems with no facilities for reporting errors.
1582 bool "Enable ELF core dumps" if EXPERT
1584 Enable support for generating core dumps. Disabling saves about 4k.
1587 config PCSPKR_PLATFORM
1588 bool "Enable PC-Speaker support" if EXPERT
1589 depends on HAVE_PCSPKR_PLATFORM
1593 This option allows to disable the internal PC-Speaker
1594 support, saving some memory.
1598 bool "Enable full-sized data structures for core" if EXPERT
1600 Disabling this option reduces the size of miscellaneous core
1601 kernel data structures. This saves memory on small machines,
1602 but may reduce performance.
1605 bool "Enable futex support" if EXPERT
1606 depends on !(SPARC32 && SMP)
1610 Disabling this option will cause the kernel to be built without
1611 support for "fast userspace mutexes". The resulting kernel may not
1612 run glibc-based applications correctly.
1616 depends on FUTEX && RT_MUTEXES
1620 bool "Enable eventpoll support" if EXPERT
1623 Disabling this option will cause the kernel to be built without
1624 support for epoll family of system calls.
1627 bool "Enable signalfd() system call" if EXPERT
1630 Enable the signalfd() system call that allows to receive signals
1631 on a file descriptor.
1636 bool "Enable timerfd() system call" if EXPERT
1639 Enable the timerfd() system call that allows to receive timer
1640 events on a file descriptor.
1645 bool "Enable eventfd() system call" if EXPERT
1648 Enable the eventfd() system call that allows to receive both
1649 kernel notification (ie. KAIO) or userspace notifications.
1654 bool "Use full shmem filesystem" if EXPERT
1658 The shmem is an internal filesystem used to manage shared memory.
1659 It is backed by swap and manages resource limits. It is also exported
1660 to userspace as tmpfs if TMPFS is enabled. Disabling this
1661 option replaces shmem and tmpfs with the much simpler ramfs code,
1662 which may be appropriate on small systems without swap.
1665 bool "Enable AIO support" if EXPERT
1668 This option enables POSIX asynchronous I/O which may by used
1669 by some high performance threaded applications. Disabling
1670 this option saves about 7k.
1673 bool "Enable IO uring support" if EXPERT
1677 This option enables support for the io_uring interface, enabling
1678 applications to submit and complete IO through submission and
1679 completion rings that are shared between the kernel and application.
1681 config ADVISE_SYSCALLS
1682 bool "Enable madvise/fadvise syscalls" if EXPERT
1685 This option enables the madvise and fadvise syscalls, used by
1686 applications to advise the kernel about their future memory or file
1687 usage, improving performance. If building an embedded system where no
1688 applications use these syscalls, you can disable this option to save
1692 bool "Enable membarrier() system call" if EXPERT
1695 Enable the membarrier() system call that allows issuing memory
1696 barriers across all running threads, which can be used to distribute
1697 the cost of user-space memory barriers asymmetrically by transforming
1698 pairs of memory barriers into pairs consisting of membarrier() and a
1704 bool "Load all symbols for debugging/ksymoops" if EXPERT
1707 Say Y here to let the kernel print out symbolic crash information and
1708 symbolic stack backtraces. This increases the size of the kernel
1709 somewhat, as all symbols have to be loaded into the kernel image.
1712 bool "Include all symbols in kallsyms"
1713 depends on DEBUG_KERNEL && KALLSYMS
1715 Normally kallsyms only contains the symbols of functions for nicer
1716 OOPS messages and backtraces (i.e., symbols from the text and inittext
1717 sections). This is sufficient for most cases. And only in very rare
1718 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1719 names of variables from the data sections, etc).
1721 This option makes sure that all symbols are loaded into the kernel
1722 image (i.e., symbols from all sections) in cost of increased kernel
1723 size (depending on the kernel configuration, it may be 300KiB or
1724 something like this).
1726 Say N unless you really need all symbols.
1728 config KALLSYMS_ABSOLUTE_PERCPU
1731 default X86_64 && SMP
1733 config KALLSYMS_BASE_RELATIVE
1738 Instead of emitting them as absolute values in the native word size,
1739 emit the symbol references in the kallsyms table as 32-bit entries,
1740 each containing a relative value in the range [base, base + U32_MAX]
1741 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1742 an absolute value in the range [0, S32_MAX] or a relative value in the
1743 range [base, base + S32_MAX], where base is the lowest relative symbol
1744 address encountered in the image.
1746 On 64-bit builds, this reduces the size of the address table by 50%,
1747 but more importantly, it results in entries whose values are build
1748 time constants, and no relocation pass is required at runtime to fix
1749 up the entries based on the runtime load address of the kernel.
1751 # end of the "standard kernel features (expert users)" menu
1753 # syscall, maps, verifier
1755 config ARCH_HAS_MEMBARRIER_CALLBACKS
1758 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1762 bool "Enable kcmp() system call" if EXPERT
1764 Enable the kernel resource comparison system call. It provides
1765 user-space with the ability to compare two processes to see if they
1766 share a common resource, such as a file descriptor or even virtual
1772 bool "Enable rseq() system call" if EXPERT
1774 depends on HAVE_RSEQ
1777 Enable the restartable sequences system call. It provides a
1778 user-space cache for the current CPU number value, which
1779 speeds up getting the current CPU number from user-space,
1780 as well as an ABI to speed up user-space operations on
1787 bool "Enabled debugging of rseq() system call" if EXPERT
1788 depends on RSEQ && DEBUG_KERNEL
1790 Enable extra debugging checks for the rseq system call.
1795 bool "Embedded system"
1798 This option should be enabled if compiling the kernel for
1799 an embedded system so certain expert options are available
1802 config HAVE_PERF_EVENTS
1805 See tools/perf/design.txt for details.
1807 config GUEST_PERF_EVENTS
1809 depends on HAVE_PERF_EVENTS
1811 config PERF_USE_VMALLOC
1814 See tools/perf/design.txt for details
1817 bool "PC/104 support" if EXPERT
1819 Expose PC/104 form factor device drivers and options available for
1820 selection and configuration. Enable this option if your target
1821 machine has a PC/104 bus.
1823 menu "Kernel Performance Events And Counters"
1826 bool "Kernel performance events and counters"
1827 default y if PROFILING
1828 depends on HAVE_PERF_EVENTS
1832 Enable kernel support for various performance events provided
1833 by software and hardware.
1835 Software events are supported either built-in or via the
1836 use of generic tracepoints.
1838 Most modern CPUs support performance events via performance
1839 counter registers. These registers count the number of certain
1840 types of hw events: such as instructions executed, cachemisses
1841 suffered, or branches mis-predicted - without slowing down the
1842 kernel or applications. These registers can also trigger interrupts
1843 when a threshold number of events have passed - and can thus be
1844 used to profile the code that runs on that CPU.
1846 The Linux Performance Event subsystem provides an abstraction of
1847 these software and hardware event capabilities, available via a
1848 system call and used by the "perf" utility in tools/perf/. It
1849 provides per task and per CPU counters, and it provides event
1850 capabilities on top of those.
1854 config DEBUG_PERF_USE_VMALLOC
1856 bool "Debug: use vmalloc to back perf mmap() buffers"
1857 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1858 select PERF_USE_VMALLOC
1860 Use vmalloc memory to back perf mmap() buffers.
1862 Mostly useful for debugging the vmalloc code on platforms
1863 that don't require it.
1869 config SYSTEM_DATA_VERIFICATION
1871 select SYSTEM_TRUSTED_KEYRING
1875 select ASYMMETRIC_KEY_TYPE
1876 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1879 select X509_CERTIFICATE_PARSER
1880 select PKCS7_MESSAGE_PARSER
1882 Provide PKCS#7 message verification using the contents of the system
1883 trusted keyring to provide public keys. This then can be used for
1884 module verification, kexec image verification and firmware blob
1888 bool "Profiling support"
1890 Say Y here to enable the extended profiling support mechanisms used
1894 # Place an empty function call at each tracepoint site. Can be
1895 # dynamically changed for a probe function.
1900 endmenu # General setup
1902 source "arch/Kconfig"
1906 default y if PREEMPT_RT
1910 default 0 if BASE_FULL
1911 default 1 if !BASE_FULL
1913 config MODULE_SIG_FORMAT
1915 select SYSTEM_DATA_VERIFICATION
1918 bool "Enable loadable module support"
1921 Kernel modules are small pieces of compiled code which can
1922 be inserted in the running kernel, rather than being
1923 permanently built into the kernel. You use the "modprobe"
1924 tool to add (and sometimes remove) them. If you say Y here,
1925 many parts of the kernel can be built as modules (by
1926 answering M instead of Y where indicated): this is most
1927 useful for infrequently used options which are not required
1928 for booting. For more information, see the man pages for
1929 modprobe, lsmod, modinfo, insmod and rmmod.
1931 If you say Y here, you will need to run "make
1932 modules_install" to put the modules under /lib/modules/
1933 where modprobe can find them (you may need to be root to do
1940 config MODULE_FORCE_LOAD
1941 bool "Forced module loading"
1944 Allow loading of modules without version information (ie. modprobe
1945 --force). Forced module loading sets the 'F' (forced) taint flag and
1946 is usually a really bad idea.
1948 config MODULE_UNLOAD
1949 bool "Module unloading"
1951 Without this option you will not be able to unload any
1952 modules (note that some modules may not be unloadable
1953 anyway), which makes your kernel smaller, faster
1954 and simpler. If unsure, say Y.
1956 config MODULE_FORCE_UNLOAD
1957 bool "Forced module unloading"
1958 depends on MODULE_UNLOAD
1960 This option allows you to force a module to unload, even if the
1961 kernel believes it is unsafe: the kernel will remove the module
1962 without waiting for anyone to stop using it (using the -f option to
1963 rmmod). This is mainly for kernel developers and desperate users.
1966 config MODULE_UNLOAD_TAINT_TRACKING
1967 bool "Tainted module unload tracking"
1968 depends on MODULE_UNLOAD
1971 This option allows you to maintain a record of each unloaded
1972 module that tainted the kernel. In addition to displaying a
1973 list of linked (or loaded) modules e.g. on detection of a bad
1974 page (see bad_page()), the aforementioned details are also
1975 shown. If unsure, say N.
1978 bool "Module versioning support"
1980 Usually, you have to use modules compiled with your kernel.
1981 Saying Y here makes it sometimes possible to use modules
1982 compiled for different kernels, by adding enough information
1983 to the modules to (hopefully) spot any changes which would
1984 make them incompatible with the kernel you are running. If
1987 config ASM_MODVERSIONS
1989 default HAVE_ASM_MODVERSIONS && MODVERSIONS
1991 This enables module versioning for exported symbols also from
1992 assembly. This can be enabled only when the target architecture
1995 config MODULE_SRCVERSION_ALL
1996 bool "Source checksum for all modules"
1998 Modules which contain a MODULE_VERSION get an extra "srcversion"
1999 field inserted into their modinfo section, which contains a
2000 sum of the source files which made it. This helps maintainers
2001 see exactly which source was used to build a module (since
2002 others sometimes change the module source without updating
2003 the version). With this option, such a "srcversion" field
2004 will be created for all modules. If unsure, say N.
2007 bool "Module signature verification"
2008 select MODULE_SIG_FORMAT
2010 Check modules for valid signatures upon load: the signature
2011 is simply appended to the module. For more information see
2012 <file:Documentation/admin-guide/module-signing.rst>.
2014 Note that this option adds the OpenSSL development packages as a
2015 kernel build dependency so that the signing tool can use its crypto
2018 You should enable this option if you wish to use either
2019 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2020 another LSM - otherwise unsigned modules will be loadable regardless
2021 of the lockdown policy.
2023 !!!WARNING!!! If you enable this option, you MUST make sure that the
2024 module DOES NOT get stripped after being signed. This includes the
2025 debuginfo strip done by some packagers (such as rpmbuild) and
2026 inclusion into an initramfs that wants the module size reduced.
2028 config MODULE_SIG_FORCE
2029 bool "Require modules to be validly signed"
2030 depends on MODULE_SIG
2032 Reject unsigned modules or signed modules for which we don't have a
2033 key. Without this, such modules will simply taint the kernel.
2035 config MODULE_SIG_ALL
2036 bool "Automatically sign all modules"
2038 depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2040 Sign all modules during make modules_install. Without this option,
2041 modules must be signed manually, using the scripts/sign-file tool.
2043 comment "Do not forget to sign required modules with scripts/sign-file"
2044 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2047 prompt "Which hash algorithm should modules be signed with?"
2048 depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2050 This determines which sort of hashing algorithm will be used during
2051 signature generation. This algorithm _must_ be built into the kernel
2052 directly so that signature verification can take place. It is not
2053 possible to load a signed module containing the algorithm to check
2054 the signature on that module.
2056 config MODULE_SIG_SHA1
2057 bool "Sign modules with SHA-1"
2060 config MODULE_SIG_SHA224
2061 bool "Sign modules with SHA-224"
2062 select CRYPTO_SHA256
2064 config MODULE_SIG_SHA256
2065 bool "Sign modules with SHA-256"
2066 select CRYPTO_SHA256
2068 config MODULE_SIG_SHA384
2069 bool "Sign modules with SHA-384"
2070 select CRYPTO_SHA512
2072 config MODULE_SIG_SHA512
2073 bool "Sign modules with SHA-512"
2074 select CRYPTO_SHA512
2078 config MODULE_SIG_HASH
2080 depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2081 default "sha1" if MODULE_SIG_SHA1
2082 default "sha224" if MODULE_SIG_SHA224
2083 default "sha256" if MODULE_SIG_SHA256
2084 default "sha384" if MODULE_SIG_SHA384
2085 default "sha512" if MODULE_SIG_SHA512
2088 prompt "Module compression mode"
2090 This option allows you to choose the algorithm which will be used to
2091 compress modules when 'make modules_install' is run. (or, you can
2092 choose to not compress modules at all.)
2094 External modules will also be compressed in the same way during the
2097 For modules inside an initrd or initramfs, it's more efficient to
2098 compress the whole initrd or initramfs instead.
2100 This is fully compatible with signed modules.
2102 Please note that the tool used to load modules needs to support the
2103 corresponding algorithm. module-init-tools MAY support gzip, and kmod
2104 MAY support gzip, xz and zstd.
2106 Your build system needs to provide the appropriate compression tool
2107 to compress the modules.
2109 If in doubt, select 'None'.
2111 config MODULE_COMPRESS_NONE
2114 Do not compress modules. The installed modules are suffixed
2117 config MODULE_COMPRESS_GZIP
2120 Compress modules with GZIP. The installed modules are suffixed
2123 config MODULE_COMPRESS_XZ
2126 Compress modules with XZ. The installed modules are suffixed
2129 config MODULE_COMPRESS_ZSTD
2132 Compress modules with ZSTD. The installed modules are suffixed
2137 config MODULE_DECOMPRESS
2138 bool "Support in-kernel module decompression"
2139 depends on MODULE_COMPRESS_GZIP || MODULE_COMPRESS_XZ
2140 select ZLIB_INFLATE if MODULE_COMPRESS_GZIP
2141 select XZ_DEC if MODULE_COMPRESS_XZ
2144 Support for decompressing kernel modules by the kernel itself
2145 instead of relying on userspace to perform this task. Useful when
2146 load pinning security policy is enabled.
2150 config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2151 bool "Allow loading of modules with missing namespace imports"
2153 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2154 a namespace. A module that makes use of a symbol exported with such a
2155 namespace is required to import the namespace via MODULE_IMPORT_NS().
2156 There is no technical reason to enforce correct namespace imports,
2157 but it creates consistency between symbols defining namespaces and
2158 users importing namespaces they make use of. This option relaxes this
2159 requirement and lifts the enforcement when loading a module.
2163 config MODPROBE_PATH
2164 string "Path to modprobe binary"
2165 default "/sbin/modprobe"
2167 When kernel code requests a module, it does so by calling
2168 the "modprobe" userspace utility. This option allows you to
2169 set the path where that binary is found. This can be changed
2170 at runtime via the sysctl file
2171 /proc/sys/kernel/modprobe. Setting this to the empty string
2172 removes the kernel's ability to request modules (but
2173 userspace can still load modules explicitly).
2175 config TRIM_UNUSED_KSYMS
2176 bool "Trim unused exported kernel symbols" if EXPERT
2177 depends on !COMPILE_TEST
2179 The kernel and some modules make many symbols available for
2180 other modules to use via EXPORT_SYMBOL() and variants. Depending
2181 on the set of modules being selected in your kernel configuration,
2182 many of those exported symbols might never be used.
2184 This option allows for unused exported symbols to be dropped from
2185 the build. In turn, this provides the compiler more opportunities
2186 (especially when using LTO) for optimizing the code and reducing
2187 binary size. This might have some security advantages as well.
2189 If unsure, or if you need to build out-of-tree modules, say N.
2191 config UNUSED_KSYMS_WHITELIST
2192 string "Whitelist of symbols to keep in ksymtab"
2193 depends on TRIM_UNUSED_KSYMS
2195 By default, all unused exported symbols will be un-exported from the
2196 build when TRIM_UNUSED_KSYMS is selected.
2198 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
2199 exported at all times, even in absence of in-tree users. The value to
2200 set here is the path to a text file containing the list of symbols,
2201 one per line. The path can be absolute, or relative to the kernel
2206 config MODULES_TREE_LOOKUP
2208 depends on PERF_EVENTS || TRACING || CFI_CLANG
2210 config INIT_ALL_POSSIBLE
2213 Back when each arch used to define their own cpu_online_mask and
2214 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2215 with all 1s, and others with all 0s. When they were centralised,
2216 it was better to provide this option than to break all the archs
2217 and have several arch maintainers pursuing me down dark alleys.
2219 source "block/Kconfig"
2221 config PREEMPT_NOTIFIERS
2231 Build a simple ASN.1 grammar compiler that produces a bytecode output
2232 that can be interpreted by the ASN.1 stream decoder and used to
2233 inform it as to what tags are to be expected in a stream and what
2234 functions to call on what tags.
2236 source "kernel/Kconfig.locks"
2238 config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2241 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2244 # It may be useful for an architecture to override the definitions of the
2245 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2246 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2247 # different calling convention for syscalls. They can also override the
2248 # macros for not-implemented syscalls in kernel/sys_ni.c and
2249 # kernel/time/posix-stubs.c. All these overrides need to be available in
2250 # <asm/syscall_wrapper.h>.
2251 config ARCH_HAS_SYSCALL_WRAPPER
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