1 # SPDX-License-Identifier: GPL-2.0-only
6 default "/lib/modules/$(shell,uname -r)/.config"
7 default "/etc/kernel-config"
8 default "/boot/config-$(shell,uname -r)"
9 default "arch/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG)"
11 config CC_VERSION_TEXT
13 default "$(CC_VERSION_TEXT)"
15 This is used in unclear ways:
17 - Re-run Kconfig when the compiler is updated
18 The 'default' property references the environment variable,
19 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd.
20 When the compiler is updated, Kconfig will be invoked.
22 - Ensure full rebuild when the compier is updated
23 include/linux/kconfig.h contains this option in the comment line so
24 fixdep adds include/config/cc/version/text.h into the auto-generated
25 dependency. When the compiler is updated, syncconfig will touch it
26 and then every file will be rebuilt.
29 def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q gcc)
33 default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC
38 default $(shell,$(LD) --version | $(srctree)/scripts/ld-version.sh)
41 def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q clang)
44 def_bool $(success,$(LD) -v | head -n 1 | grep -q LLD)
48 default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
52 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag)) if 64BIT
53 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag))
55 config CC_CAN_LINK_STATIC
57 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static) if 64BIT
58 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag) -static)
60 config CC_HAS_ASM_GOTO
61 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
63 config CC_HAS_ASM_GOTO_OUTPUT
64 depends on CC_HAS_ASM_GOTO
65 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)
67 config TOOLS_SUPPORT_RELR
68 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
70 config CC_HAS_ASM_INLINE
71 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
80 config BUILDTIME_TABLE_SORT
83 config THREAD_INFO_IN_TASK
86 Select this to move thread_info off the stack into task_struct. To
87 make this work, an arch will need to remove all thread_info fields
88 except flags and fix any runtime bugs.
90 One subtle change that will be needed is to use try_get_task_stack()
91 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
100 depends on BROKEN || !SMP
103 config INIT_ENV_ARG_LIMIT
108 Maximum of each of the number of arguments and environment
109 variables passed to init from the kernel command line.
112 bool "Compile also drivers which will not load"
116 Some drivers can be compiled on a different platform than they are
117 intended to be run on. Despite they cannot be loaded there (or even
118 when they load they cannot be used due to missing HW support),
119 developers still, opposing to distributors, might want to build such
120 drivers to compile-test them.
122 If you are a developer and want to build everything available, say Y
123 here. If you are a user/distributor, say N here to exclude useless
124 drivers to be distributed.
126 config UAPI_HEADER_TEST
127 bool "Compile test UAPI headers"
128 depends on HEADERS_INSTALL && CC_CAN_LINK
130 Compile test headers exported to user-space to ensure they are
131 self-contained, i.e. compilable as standalone units.
133 If you are a developer or tester and want to ensure the exported
134 headers are self-contained, say Y here. Otherwise, choose N.
137 string "Local version - append to kernel release"
139 Append an extra string to the end of your kernel version.
140 This will show up when you type uname, for example.
141 The string you set here will be appended after the contents of
142 any files with a filename matching localversion* in your
143 object and source tree, in that order. Your total string can
144 be a maximum of 64 characters.
146 config LOCALVERSION_AUTO
147 bool "Automatically append version information to the version string"
149 depends on !COMPILE_TEST
151 This will try to automatically determine if the current tree is a
152 release tree by looking for git tags that belong to the current
153 top of tree revision.
155 A string of the format -gxxxxxxxx will be added to the localversion
156 if a git-based tree is found. The string generated by this will be
157 appended after any matching localversion* files, and after the value
158 set in CONFIG_LOCALVERSION.
160 (The actual string used here is the first eight characters produced
161 by running the command:
163 $ git rev-parse --verify HEAD
165 which is done within the script "scripts/setlocalversion".)
168 string "Build ID Salt"
171 The build ID is used to link binaries and their debug info. Setting
172 this option will use the value in the calculation of the build id.
173 This is mostly useful for distributions which want to ensure the
174 build is unique between builds. It's safe to leave the default.
176 config HAVE_KERNEL_GZIP
179 config HAVE_KERNEL_BZIP2
182 config HAVE_KERNEL_LZMA
185 config HAVE_KERNEL_XZ
188 config HAVE_KERNEL_LZO
191 config HAVE_KERNEL_LZ4
194 config HAVE_KERNEL_ZSTD
197 config HAVE_KERNEL_UNCOMPRESSED
201 prompt "Kernel compression mode"
203 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
205 The linux kernel is a kind of self-extracting executable.
206 Several compression algorithms are available, which differ
207 in efficiency, compression and decompression speed.
208 Compression speed is only relevant when building a kernel.
209 Decompression speed is relevant at each boot.
211 If you have any problems with bzip2 or lzma compressed
212 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
213 version of this functionality (bzip2 only), for 2.4, was
214 supplied by Christian Ludwig)
216 High compression options are mostly useful for users, who
217 are low on disk space (embedded systems), but for whom ram
220 If in doubt, select 'gzip'
224 depends on HAVE_KERNEL_GZIP
226 The old and tried gzip compression. It provides a good balance
227 between compression ratio and decompression speed.
231 depends on HAVE_KERNEL_BZIP2
233 Its compression ratio and speed is intermediate.
234 Decompression speed is slowest among the choices. The kernel
235 size is about 10% smaller with bzip2, in comparison to gzip.
236 Bzip2 uses a large amount of memory. For modern kernels you
237 will need at least 8MB RAM or more for booting.
241 depends on HAVE_KERNEL_LZMA
243 This compression algorithm's ratio is best. Decompression speed
244 is between gzip and bzip2. Compression is slowest.
245 The kernel size is about 33% smaller with LZMA in comparison to gzip.
249 depends on HAVE_KERNEL_XZ
251 XZ uses the LZMA2 algorithm and instruction set specific
252 BCJ filters which can improve compression ratio of executable
253 code. The size of the kernel is about 30% smaller with XZ in
254 comparison to gzip. On architectures for which there is a BCJ
255 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
256 will create a few percent smaller kernel than plain LZMA.
258 The speed is about the same as with LZMA: The decompression
259 speed of XZ is better than that of bzip2 but worse than gzip
260 and LZO. Compression is slow.
264 depends on HAVE_KERNEL_LZO
266 Its compression ratio is the poorest among the choices. The kernel
267 size is about 10% bigger than gzip; however its speed
268 (both compression and decompression) is the fastest.
272 depends on HAVE_KERNEL_LZ4
274 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
275 A preliminary version of LZ4 de/compression tool is available at
276 <https://code.google.com/p/lz4/>.
278 Its compression ratio is worse than LZO. The size of the kernel
279 is about 8% bigger than LZO. But the decompression speed is
284 depends on HAVE_KERNEL_ZSTD
286 ZSTD is a compression algorithm targeting intermediate compression
287 with fast decompression speed. It will compress better than GZIP and
288 decompress around the same speed as LZO, but slower than LZ4. You
289 will need at least 192 KB RAM or more for booting. The zstd command
290 line tool is required for compression.
292 config KERNEL_UNCOMPRESSED
294 depends on HAVE_KERNEL_UNCOMPRESSED
296 Produce uncompressed kernel image. This option is usually not what
297 you want. It is useful for debugging the kernel in slow simulation
298 environments, where decompressing and moving the kernel is awfully
299 slow. This option allows early boot code to skip the decompressor
300 and jump right at uncompressed kernel image.
305 string "Default init path"
308 This option determines the default init for the system if no init=
309 option is passed on the kernel command line. If the requested path is
310 not present, we will still then move on to attempting further
311 locations (e.g. /sbin/init, etc). If this is empty, we will just use
312 the fallback list when init= is not passed.
314 config DEFAULT_HOSTNAME
315 string "Default hostname"
318 This option determines the default system hostname before userspace
319 calls sethostname(2). The kernel traditionally uses "(none)" here,
320 but you may wish to use a different default here to make a minimal
321 system more usable with less configuration.
324 # For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
325 # add proper SWAP support to them, in which case this can be remove.
331 bool "Support for paging of anonymous memory (swap)"
332 depends on MMU && BLOCK && !ARCH_NO_SWAP
335 This option allows you to choose whether you want to have support
336 for so called swap devices or swap files in your kernel that are
337 used to provide more virtual memory than the actual RAM present
338 in your computer. If unsure say Y.
343 Inter Process Communication is a suite of library functions and
344 system calls which let processes (running programs) synchronize and
345 exchange information. It is generally considered to be a good thing,
346 and some programs won't run unless you say Y here. In particular, if
347 you want to run the DOS emulator dosemu under Linux (read the
348 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
349 you'll need to say Y here.
351 You can find documentation about IPC with "info ipc" and also in
352 section 6.4 of the Linux Programmer's Guide, available from
353 <http://www.tldp.org/guides.html>.
355 config SYSVIPC_SYSCTL
362 bool "POSIX Message Queues"
365 POSIX variant of message queues is a part of IPC. In POSIX message
366 queues every message has a priority which decides about succession
367 of receiving it by a process. If you want to compile and run
368 programs written e.g. for Solaris with use of its POSIX message
369 queues (functions mq_*) say Y here.
371 POSIX message queues are visible as a filesystem called 'mqueue'
372 and can be mounted somewhere if you want to do filesystem
373 operations on message queues.
377 config POSIX_MQUEUE_SYSCTL
379 depends on POSIX_MQUEUE
384 bool "General notification queue"
388 This is a general notification queue for the kernel to pass events to
389 userspace by splicing them into pipes. It can be used in conjunction
390 with watches for key/keyring change notifications and device
393 See Documentation/watch_queue.rst
395 config CROSS_MEMORY_ATTACH
396 bool "Enable process_vm_readv/writev syscalls"
400 Enabling this option adds the system calls process_vm_readv and
401 process_vm_writev which allow a process with the correct privileges
402 to directly read from or write to another process' address space.
403 See the man page for more details.
406 bool "uselib syscall"
407 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
409 This option enables the uselib syscall, a system call used in the
410 dynamic linker from libc5 and earlier. glibc does not use this
411 system call. If you intend to run programs built on libc5 or
412 earlier, you may need to enable this syscall. Current systems
413 running glibc can safely disable this.
416 bool "Auditing support"
419 Enable auditing infrastructure that can be used with another
420 kernel subsystem, such as SELinux (which requires this for
421 logging of avc messages output). System call auditing is included
422 on architectures which support it.
424 config HAVE_ARCH_AUDITSYSCALL
429 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
432 source "kernel/irq/Kconfig"
433 source "kernel/time/Kconfig"
434 source "kernel/Kconfig.preempt"
436 menu "CPU/Task time and stats accounting"
438 config VIRT_CPU_ACCOUNTING
442 prompt "Cputime accounting"
443 default TICK_CPU_ACCOUNTING if !PPC64
444 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
446 # Kind of a stub config for the pure tick based cputime accounting
447 config TICK_CPU_ACCOUNTING
448 bool "Simple tick based cputime accounting"
449 depends on !S390 && !NO_HZ_FULL
451 This is the basic tick based cputime accounting that maintains
452 statistics about user, system and idle time spent on per jiffies
457 config VIRT_CPU_ACCOUNTING_NATIVE
458 bool "Deterministic task and CPU time accounting"
459 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
460 select VIRT_CPU_ACCOUNTING
462 Select this option to enable more accurate task and CPU time
463 accounting. This is done by reading a CPU counter on each
464 kernel entry and exit and on transitions within the kernel
465 between system, softirq and hardirq state, so there is a
466 small performance impact. In the case of s390 or IBM POWER > 5,
467 this also enables accounting of stolen time on logically-partitioned
470 config VIRT_CPU_ACCOUNTING_GEN
471 bool "Full dynticks CPU time accounting"
472 depends on HAVE_CONTEXT_TRACKING
473 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
474 depends on GENERIC_CLOCKEVENTS
475 select VIRT_CPU_ACCOUNTING
476 select CONTEXT_TRACKING
478 Select this option to enable task and CPU time accounting on full
479 dynticks systems. This accounting is implemented by watching every
480 kernel-user boundaries using the context tracking subsystem.
481 The accounting is thus performed at the expense of some significant
484 For now this is only useful if you are working on the full
485 dynticks subsystem development.
491 config IRQ_TIME_ACCOUNTING
492 bool "Fine granularity task level IRQ time accounting"
493 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
495 Select this option to enable fine granularity task irq time
496 accounting. This is done by reading a timestamp on each
497 transitions between softirq and hardirq state, so there can be a
498 small performance impact.
500 If in doubt, say N here.
502 config HAVE_SCHED_AVG_IRQ
504 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
507 config SCHED_THERMAL_PRESSURE
509 default y if ARM && ARM_CPU_TOPOLOGY
512 depends on CPU_FREQ_THERMAL
514 Select this option to enable thermal pressure accounting in the
515 scheduler. Thermal pressure is the value conveyed to the scheduler
516 that reflects the reduction in CPU compute capacity resulted from
517 thermal throttling. Thermal throttling occurs when the performance of
518 a CPU is capped due to high operating temperatures.
520 If selected, the scheduler will be able to balance tasks accordingly,
521 i.e. put less load on throttled CPUs than on non/less throttled ones.
523 This requires the architecture to implement
524 arch_set_thermal_pressure() and arch_get_thermal_pressure().
526 config BSD_PROCESS_ACCT
527 bool "BSD Process Accounting"
530 If you say Y here, a user level program will be able to instruct the
531 kernel (via a special system call) to write process accounting
532 information to a file: whenever a process exits, information about
533 that process will be appended to the file by the kernel. The
534 information includes things such as creation time, owning user,
535 command name, memory usage, controlling terminal etc. (the complete
536 list is in the struct acct in <file:include/linux/acct.h>). It is
537 up to the user level program to do useful things with this
538 information. This is generally a good idea, so say Y.
540 config BSD_PROCESS_ACCT_V3
541 bool "BSD Process Accounting version 3 file format"
542 depends on BSD_PROCESS_ACCT
545 If you say Y here, the process accounting information is written
546 in a new file format that also logs the process IDs of each
547 process and its parent. Note that this file format is incompatible
548 with previous v0/v1/v2 file formats, so you will need updated tools
549 for processing it. A preliminary version of these tools is available
550 at <http://www.gnu.org/software/acct/>.
553 bool "Export task/process statistics through netlink"
558 Export selected statistics for tasks/processes through the
559 generic netlink interface. Unlike BSD process accounting, the
560 statistics are available during the lifetime of tasks/processes as
561 responses to commands. Like BSD accounting, they are sent to user
566 config TASK_DELAY_ACCT
567 bool "Enable per-task delay accounting"
571 Collect information on time spent by a task waiting for system
572 resources like cpu, synchronous block I/O completion and swapping
573 in pages. Such statistics can help in setting a task's priorities
574 relative to other tasks for cpu, io, rss limits etc.
579 bool "Enable extended accounting over taskstats"
582 Collect extended task accounting data and send the data
583 to userland for processing over the taskstats interface.
587 config TASK_IO_ACCOUNTING
588 bool "Enable per-task storage I/O accounting"
589 depends on TASK_XACCT
591 Collect information on the number of bytes of storage I/O which this
597 bool "Pressure stall information tracking"
599 Collect metrics that indicate how overcommitted the CPU, memory,
600 and IO capacity are in the system.
602 If you say Y here, the kernel will create /proc/pressure/ with the
603 pressure statistics files cpu, memory, and io. These will indicate
604 the share of walltime in which some or all tasks in the system are
605 delayed due to contention of the respective resource.
607 In kernels with cgroup support, cgroups (cgroup2 only) will
608 have cpu.pressure, memory.pressure, and io.pressure files,
609 which aggregate pressure stalls for the grouped tasks only.
611 For more details see Documentation/accounting/psi.rst.
615 config PSI_DEFAULT_DISABLED
616 bool "Require boot parameter to enable pressure stall information tracking"
620 If set, pressure stall information tracking will be disabled
621 per default but can be enabled through passing psi=1 on the
622 kernel commandline during boot.
624 This feature adds some code to the task wakeup and sleep
625 paths of the scheduler. The overhead is too low to affect
626 common scheduling-intense workloads in practice (such as
627 webservers, memcache), but it does show up in artificial
628 scheduler stress tests, such as hackbench.
630 If you are paranoid and not sure what the kernel will be
635 endmenu # "CPU/Task time and stats accounting"
639 depends on SMP || COMPILE_TEST
642 Make sure that CPUs running critical tasks are not disturbed by
643 any source of "noise" such as unbound workqueues, timers, kthreads...
644 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
645 the "isolcpus=" boot parameter.
649 source "kernel/rcu/Kconfig"
656 tristate "Kernel .config support"
658 This option enables the complete Linux kernel ".config" file
659 contents to be saved in the kernel. It provides documentation
660 of which kernel options are used in a running kernel or in an
661 on-disk kernel. This information can be extracted from the kernel
662 image file with the script scripts/extract-ikconfig and used as
663 input to rebuild the current kernel or to build another kernel.
664 It can also be extracted from a running kernel by reading
665 /proc/config.gz if enabled (below).
668 bool "Enable access to .config through /proc/config.gz"
669 depends on IKCONFIG && PROC_FS
671 This option enables access to the kernel configuration file
672 through /proc/config.gz.
675 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
678 This option enables access to the in-kernel headers that are generated during
679 the build process. These can be used to build eBPF tracing programs,
680 or similar programs. If you build the headers as a module, a module called
681 kheaders.ko is built which can be loaded on-demand to get access to headers.
684 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
685 range 12 25 if !H8300
690 Select the minimal kernel log buffer size as a power of 2.
691 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
692 parameter, see below. Any higher size also might be forced
693 by "log_buf_len" boot parameter.
703 config LOG_CPU_MAX_BUF_SHIFT
704 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
707 default 12 if !BASE_SMALL
708 default 0 if BASE_SMALL
711 This option allows to increase the default ring buffer size
712 according to the number of CPUs. The value defines the contribution
713 of each CPU as a power of 2. The used space is typically only few
714 lines however it might be much more when problems are reported,
717 The increased size means that a new buffer has to be allocated and
718 the original static one is unused. It makes sense only on systems
719 with more CPUs. Therefore this value is used only when the sum of
720 contributions is greater than the half of the default kernel ring
721 buffer as defined by LOG_BUF_SHIFT. The default values are set
722 so that more than 64 CPUs are needed to trigger the allocation.
724 Also this option is ignored when "log_buf_len" kernel parameter is
725 used as it forces an exact (power of two) size of the ring buffer.
727 The number of possible CPUs is used for this computation ignoring
728 hotplugging making the computation optimal for the worst case
729 scenario while allowing a simple algorithm to be used from bootup.
731 Examples shift values and their meaning:
732 17 => 128 KB for each CPU
733 16 => 64 KB for each CPU
734 15 => 32 KB for each CPU
735 14 => 16 KB for each CPU
736 13 => 8 KB for each CPU
737 12 => 4 KB for each CPU
739 config PRINTK_SAFE_LOG_BUF_SHIFT
740 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
745 Select the size of an alternate printk per-CPU buffer where messages
746 printed from usafe contexts are temporary stored. One example would
747 be NMI messages, another one - printk recursion. The messages are
748 copied to the main log buffer in a safe context to avoid a deadlock.
749 The value defines the size as a power of 2.
751 Those messages are rare and limited. The largest one is when
752 a backtrace is printed. It usually fits into 4KB. Select
753 8KB if you want to be on the safe side.
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
764 # Architectures with an unreliable sched_clock() should select this:
766 config HAVE_UNSTABLE_SCHED_CLOCK
769 config GENERIC_SCHED_CLOCK
772 menu "Scheduler features"
775 bool "Enable utilization clamping for RT/FAIR tasks"
776 depends on CPU_FREQ_GOV_SCHEDUTIL
778 This feature enables the scheduler to track the clamped utilization
779 of each CPU based on RUNNABLE tasks scheduled on that CPU.
781 With this option, the user can specify the min and max CPU
782 utilization allowed for RUNNABLE tasks. The max utilization defines
783 the maximum frequency a task should use while the min utilization
784 defines the minimum frequency it should use.
786 Both min and max utilization clamp values are hints to the scheduler,
787 aiming at improving its frequency selection policy, but they do not
788 enforce or grant any specific bandwidth for tasks.
792 config UCLAMP_BUCKETS_COUNT
793 int "Number of supported utilization clamp buckets"
796 depends on UCLAMP_TASK
798 Defines the number of clamp buckets to use. The range of each bucket
799 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
800 number of clamp buckets the finer their granularity and the higher
801 the precision of clamping aggregation and tracking at run-time.
803 For example, with the minimum configuration value we will have 5
804 clamp buckets tracking 20% utilization each. A 25% boosted tasks will
805 be refcounted in the [20..39]% bucket and will set the bucket clamp
806 effective value to 25%.
807 If a second 30% boosted task should be co-scheduled on the same CPU,
808 that task will be refcounted in the same bucket of the first task and
809 it will boost the bucket clamp effective value to 30%.
810 The clamp effective value of a bucket is reset to its nominal value
811 (20% in the example above) when there are no more tasks refcounted in
814 An additional boost/capping margin can be added to some tasks. In the
815 example above the 25% task will be boosted to 30% until it exits the
816 CPU. If that should be considered not acceptable on certain systems,
817 it's always possible to reduce the margin by increasing the number of
818 clamp buckets to trade off used memory for run-time tracking
821 If in doubt, use the default value.
826 # For architectures that want to enable the support for NUMA-affine scheduler
829 config ARCH_SUPPORTS_NUMA_BALANCING
833 # For architectures that prefer to flush all TLBs after a number of pages
834 # are unmapped instead of sending one IPI per page to flush. The architecture
835 # must provide guarantees on what happens if a clean TLB cache entry is
836 # written after the unmap. Details are in mm/rmap.c near the check for
837 # should_defer_flush. The architecture should also consider if the full flush
838 # and the refill costs are offset by the savings of sending fewer IPIs.
839 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
843 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
846 # For architectures that know their GCC __int128 support is sound
848 config ARCH_SUPPORTS_INT128
851 # For architectures that (ab)use NUMA to represent different memory regions
852 # all cpu-local but of different latencies, such as SuperH.
854 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
857 config NUMA_BALANCING
858 bool "Memory placement aware NUMA scheduler"
859 depends on ARCH_SUPPORTS_NUMA_BALANCING
860 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
861 depends on SMP && NUMA && MIGRATION
863 This option adds support for automatic NUMA aware memory/task placement.
864 The mechanism is quite primitive and is based on migrating memory when
865 it has references to the node the task is running on.
867 This system will be inactive on UMA systems.
869 config NUMA_BALANCING_DEFAULT_ENABLED
870 bool "Automatically enable NUMA aware memory/task placement"
872 depends on NUMA_BALANCING
874 If set, automatic NUMA balancing will be enabled if running on a NUMA
878 bool "Control Group support"
881 This option adds support for grouping sets of processes together, for
882 use with process control subsystems such as Cpusets, CFS, memory
883 controls or device isolation.
885 - Documentation/scheduler/sched-design-CFS.rst (CFS)
886 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
887 and resource control)
897 bool "Memory controller"
901 Provides control over the memory footprint of tasks in a cgroup.
905 depends on MEMCG && SWAP
910 depends on MEMCG && !SLOB
918 Generic block IO controller cgroup interface. This is the common
919 cgroup interface which should be used by various IO controlling
922 Currently, CFQ IO scheduler uses it to recognize task groups and
923 control disk bandwidth allocation (proportional time slice allocation)
924 to such task groups. It is also used by bio throttling logic in
925 block layer to implement upper limit in IO rates on a device.
927 This option only enables generic Block IO controller infrastructure.
928 One needs to also enable actual IO controlling logic/policy. For
929 enabling proportional weight division of disk bandwidth in CFQ, set
930 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
931 CONFIG_BLK_DEV_THROTTLING=y.
933 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
935 config CGROUP_WRITEBACK
937 depends on MEMCG && BLK_CGROUP
940 menuconfig CGROUP_SCHED
941 bool "CPU controller"
944 This feature lets CPU scheduler recognize task groups and control CPU
945 bandwidth allocation to such task groups. It uses cgroups to group
949 config FAIR_GROUP_SCHED
950 bool "Group scheduling for SCHED_OTHER"
951 depends on CGROUP_SCHED
955 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
956 depends on FAIR_GROUP_SCHED
959 This option allows users to define CPU bandwidth rates (limits) for
960 tasks running within the fair group scheduler. Groups with no limit
961 set are considered to be unconstrained and will run with no
963 See Documentation/scheduler/sched-bwc.rst for more information.
965 config RT_GROUP_SCHED
966 bool "Group scheduling for SCHED_RR/FIFO"
967 depends on CGROUP_SCHED
970 This feature lets you explicitly allocate real CPU bandwidth
971 to task groups. If enabled, it will also make it impossible to
972 schedule realtime tasks for non-root users until you allocate
973 realtime bandwidth for them.
974 See Documentation/scheduler/sched-rt-group.rst for more information.
978 config UCLAMP_TASK_GROUP
979 bool "Utilization clamping per group of tasks"
980 depends on CGROUP_SCHED
981 depends on UCLAMP_TASK
984 This feature enables the scheduler to track the clamped utilization
985 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
987 When this option is enabled, the user can specify a min and max
988 CPU bandwidth which is allowed for each single task in a group.
989 The max bandwidth allows to clamp the maximum frequency a task
990 can use, while the min bandwidth allows to define a minimum
991 frequency a task will always use.
993 When task group based utilization clamping is enabled, an eventually
994 specified task-specific clamp value is constrained by the cgroup
995 specified clamp value. Both minimum and maximum task clamping cannot
996 be bigger than the corresponding clamping defined at task group level.
1001 bool "PIDs controller"
1003 Provides enforcement of process number limits in the scope of a
1004 cgroup. Any attempt to fork more processes than is allowed in the
1005 cgroup will fail. PIDs are fundamentally a global resource because it
1006 is fairly trivial to reach PID exhaustion before you reach even a
1007 conservative kmemcg limit. As a result, it is possible to grind a
1008 system to halt without being limited by other cgroup policies. The
1009 PIDs controller is designed to stop this from happening.
1011 It should be noted that organisational operations (such as attaching
1012 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1013 since the PIDs limit only affects a process's ability to fork, not to
1017 bool "RDMA controller"
1019 Provides enforcement of RDMA resources defined by IB stack.
1020 It is fairly easy for consumers to exhaust RDMA resources, which
1021 can result into resource unavailability to other consumers.
1022 RDMA controller is designed to stop this from happening.
1023 Attaching processes with active RDMA resources to the cgroup
1024 hierarchy is allowed even if can cross the hierarchy's limit.
1026 config CGROUP_FREEZER
1027 bool "Freezer controller"
1029 Provides a way to freeze and unfreeze all tasks in a
1032 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1033 controller includes important in-kernel memory consumers per default.
1035 If you're using cgroup2, say N.
1037 config CGROUP_HUGETLB
1038 bool "HugeTLB controller"
1039 depends on HUGETLB_PAGE
1043 Provides a cgroup controller for HugeTLB pages.
1044 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1045 The limit is enforced during page fault. Since HugeTLB doesn't
1046 support page reclaim, enforcing the limit at page fault time implies
1047 that, the application will get SIGBUS signal if it tries to access
1048 HugeTLB pages beyond its limit. This requires the application to know
1049 beforehand how much HugeTLB pages it would require for its use. The
1050 control group is tracked in the third page lru pointer. This means
1051 that we cannot use the controller with huge page less than 3 pages.
1054 bool "Cpuset controller"
1057 This option will let you create and manage CPUSETs which
1058 allow dynamically partitioning a system into sets of CPUs and
1059 Memory Nodes and assigning tasks to run only within those sets.
1060 This is primarily useful on large SMP or NUMA systems.
1064 config PROC_PID_CPUSET
1065 bool "Include legacy /proc/<pid>/cpuset file"
1069 config CGROUP_DEVICE
1070 bool "Device controller"
1072 Provides a cgroup controller implementing whitelists for
1073 devices which a process in the cgroup can mknod or open.
1075 config CGROUP_CPUACCT
1076 bool "Simple CPU accounting controller"
1078 Provides a simple controller for monitoring the
1079 total CPU consumed by the tasks in a cgroup.
1082 bool "Perf controller"
1083 depends on PERF_EVENTS
1085 This option extends the perf per-cpu mode to restrict monitoring
1086 to threads which belong to the cgroup specified and run on the
1087 designated cpu. Or this can be used to have cgroup ID in samples
1088 so that it can monitor performance events among cgroups.
1093 bool "Support for eBPF programs attached to cgroups"
1094 depends on BPF_SYSCALL
1095 select SOCK_CGROUP_DATA
1097 Allow attaching eBPF programs to a cgroup using the bpf(2)
1098 syscall command BPF_PROG_ATTACH.
1100 In which context these programs are accessed depends on the type
1101 of attachment. For instance, programs that are attached using
1102 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1106 bool "Debug controller"
1108 depends on DEBUG_KERNEL
1110 This option enables a simple controller that exports
1111 debugging information about the cgroups framework. This
1112 controller is for control cgroup debugging only. Its
1113 interfaces are not stable.
1117 config SOCK_CGROUP_DATA
1123 menuconfig NAMESPACES
1124 bool "Namespaces support" if EXPERT
1125 depends on MULTIUSER
1128 Provides the way to make tasks work with different objects using
1129 the same id. For example same IPC id may refer to different objects
1130 or same user id or pid may refer to different tasks when used in
1131 different namespaces.
1136 bool "UTS namespace"
1139 In this namespace tasks see different info provided with the
1143 bool "TIME namespace"
1144 depends on GENERIC_VDSO_TIME_NS
1147 In this namespace boottime and monotonic clocks can be set.
1148 The time will keep going with the same pace.
1151 bool "IPC namespace"
1152 depends on (SYSVIPC || POSIX_MQUEUE)
1155 In this namespace tasks work with IPC ids which correspond to
1156 different IPC objects in different namespaces.
1159 bool "User namespace"
1162 This allows containers, i.e. vservers, to use user namespaces
1163 to provide different user info for different servers.
1165 When user namespaces are enabled in the kernel it is
1166 recommended that the MEMCG option also be enabled and that
1167 user-space use the memory control groups to limit the amount
1168 of memory a memory unprivileged users can use.
1173 bool "PID Namespaces"
1176 Support process id namespaces. This allows having multiple
1177 processes with the same pid as long as they are in different
1178 pid namespaces. This is a building block of containers.
1181 bool "Network namespace"
1185 Allow user space to create what appear to be multiple instances
1186 of the network stack.
1190 config CHECKPOINT_RESTORE
1191 bool "Checkpoint/restore support"
1192 select PROC_CHILDREN
1195 Enables additional kernel features in a sake of checkpoint/restore.
1196 In particular it adds auxiliary prctl codes to setup process text,
1197 data and heap segment sizes, and a few additional /proc filesystem
1200 If unsure, say N here.
1202 config SCHED_AUTOGROUP
1203 bool "Automatic process group scheduling"
1206 select FAIR_GROUP_SCHED
1208 This option optimizes the scheduler for common desktop workloads by
1209 automatically creating and populating task groups. This separation
1210 of workloads isolates aggressive CPU burners (like build jobs) from
1211 desktop applications. Task group autogeneration is currently based
1214 config SYSFS_DEPRECATED
1215 bool "Enable deprecated sysfs features to support old userspace tools"
1219 This option adds code that switches the layout of the "block" class
1220 devices, to not show up in /sys/class/block/, but only in
1223 This switch is only active when the sysfs.deprecated=1 boot option is
1224 passed or the SYSFS_DEPRECATED_V2 option is set.
1226 This option allows new kernels to run on old distributions and tools,
1227 which might get confused by /sys/class/block/. Since 2007/2008 all
1228 major distributions and tools handle this just fine.
1230 Recent distributions and userspace tools after 2009/2010 depend on
1231 the existence of /sys/class/block/, and will not work with this
1234 Only if you are using a new kernel on an old distribution, you might
1237 config SYSFS_DEPRECATED_V2
1238 bool "Enable deprecated sysfs features by default"
1241 depends on SYSFS_DEPRECATED
1243 Enable deprecated sysfs by default.
1245 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1248 Only if you are using a new kernel on an old distribution, you might
1249 need to say Y here. Even then, odds are you would not need it
1250 enabled, you can always pass the boot option if absolutely necessary.
1253 bool "Kernel->user space relay support (formerly relayfs)"
1256 This option enables support for relay interface support in
1257 certain file systems (such as debugfs).
1258 It is designed to provide an efficient mechanism for tools and
1259 facilities to relay large amounts of data from kernel space to
1264 config BLK_DEV_INITRD
1265 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1267 The initial RAM filesystem is a ramfs which is loaded by the
1268 boot loader (loadlin or lilo) and that is mounted as root
1269 before the normal boot procedure. It is typically used to
1270 load modules needed to mount the "real" root file system,
1271 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1273 If RAM disk support (BLK_DEV_RAM) is also included, this
1274 also enables initial RAM disk (initrd) support and adds
1275 15 Kbytes (more on some other architectures) to the kernel size.
1281 source "usr/Kconfig"
1286 bool "Boot config support"
1287 select BLK_DEV_INITRD
1289 Extra boot config allows system admin to pass a config file as
1290 complemental extension of kernel cmdline when booting.
1291 The boot config file must be attached at the end of initramfs
1292 with checksum, size and magic word.
1293 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1298 prompt "Compiler optimization level"
1299 default CC_OPTIMIZE_FOR_PERFORMANCE
1301 config CC_OPTIMIZE_FOR_PERFORMANCE
1302 bool "Optimize for performance (-O2)"
1304 This is the default optimization level for the kernel, building
1305 with the "-O2" compiler flag for best performance and most
1306 helpful compile-time warnings.
1308 config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1309 bool "Optimize more for performance (-O3)"
1312 Choosing this option will pass "-O3" to your compiler to optimize
1313 the kernel yet more for performance.
1315 config CC_OPTIMIZE_FOR_SIZE
1316 bool "Optimize for size (-Os)"
1318 Choosing this option will pass "-Os" to your compiler resulting
1319 in a smaller kernel.
1323 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1326 This requires that the arch annotates or otherwise protects
1327 its external entry points from being discarded. Linker scripts
1328 must also merge .text.*, .data.*, and .bss.* correctly into
1329 output sections. Care must be taken not to pull in unrelated
1330 sections (e.g., '.text.init'). Typically '.' in section names
1331 is used to distinguish them from label names / C identifiers.
1333 config LD_DEAD_CODE_DATA_ELIMINATION
1334 bool "Dead code and data elimination (EXPERIMENTAL)"
1335 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1337 depends on $(cc-option,-ffunction-sections -fdata-sections)
1338 depends on $(ld-option,--gc-sections)
1340 Enable this if you want to do dead code and data elimination with
1341 the linker by compiling with -ffunction-sections -fdata-sections,
1342 and linking with --gc-sections.
1344 This can reduce on disk and in-memory size of the kernel
1345 code and static data, particularly for small configs and
1346 on small systems. This has the possibility of introducing
1347 silently broken kernel if the required annotations are not
1348 present. This option is not well tested yet, so use at your
1357 config SYSCTL_EXCEPTION_TRACE
1360 Enable support for /proc/sys/debug/exception-trace.
1362 config SYSCTL_ARCH_UNALIGN_NO_WARN
1365 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1366 Allows arch to define/use @no_unaligned_warning to possibly warn
1367 about unaligned access emulation going on under the hood.
1369 config SYSCTL_ARCH_UNALIGN_ALLOW
1372 Enable support for /proc/sys/kernel/unaligned-trap
1373 Allows arches to define/use @unaligned_enabled to runtime toggle
1374 the unaligned access emulation.
1375 see arch/parisc/kernel/unaligned.c for reference
1377 config HAVE_PCSPKR_PLATFORM
1380 # interpreter that classic socket filters depend on
1385 bool "Configure standard kernel features (expert users)"
1386 # Unhide debug options, to make the on-by-default options visible
1389 This option allows certain base kernel options and settings
1390 to be disabled or tweaked. This is for specialized
1391 environments which can tolerate a "non-standard" kernel.
1392 Only use this if you really know what you are doing.
1395 bool "Enable 16-bit UID system calls" if EXPERT
1396 depends on HAVE_UID16 && MULTIUSER
1399 This enables the legacy 16-bit UID syscall wrappers.
1402 bool "Multiple users, groups and capabilities support" if EXPERT
1405 This option enables support for non-root users, groups and
1408 If you say N here, all processes will run with UID 0, GID 0, and all
1409 possible capabilities. Saying N here also compiles out support for
1410 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1413 If unsure, say Y here.
1415 config SGETMASK_SYSCALL
1416 bool "sgetmask/ssetmask syscalls support" if EXPERT
1417 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1419 sys_sgetmask and sys_ssetmask are obsolete system calls
1420 no longer supported in libc but still enabled by default in some
1423 If unsure, leave the default option here.
1425 config SYSFS_SYSCALL
1426 bool "Sysfs syscall support" if EXPERT
1429 sys_sysfs is an obsolete system call no longer supported in libc.
1430 Note that disabling this option is more secure but might break
1431 compatibility with some systems.
1433 If unsure say Y here.
1436 bool "open by fhandle syscalls" if EXPERT
1440 If you say Y here, a user level program will be able to map
1441 file names to handle and then later use the handle for
1442 different file system operations. This is useful in implementing
1443 userspace file servers, which now track files using handles instead
1444 of names. The handle would remain the same even if file names
1445 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1449 bool "Posix Clocks & timers" if EXPERT
1452 This includes native support for POSIX timers to the kernel.
1453 Some embedded systems have no use for them and therefore they
1454 can be configured out to reduce the size of the kernel image.
1456 When this option is disabled, the following syscalls won't be
1457 available: timer_create, timer_gettime: timer_getoverrun,
1458 timer_settime, timer_delete, clock_adjtime, getitimer,
1459 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1460 clock_getres and clock_nanosleep syscalls will be limited to
1461 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1467 bool "Enable support for printk" if EXPERT
1470 This option enables normal printk support. Removing it
1471 eliminates most of the message strings from the kernel image
1472 and makes the kernel more or less silent. As this makes it
1473 very difficult to diagnose system problems, saying N here is
1474 strongly discouraged.
1482 bool "BUG() support" if EXPERT
1485 Disabling this option eliminates support for BUG and WARN, reducing
1486 the size of your kernel image and potentially quietly ignoring
1487 numerous fatal conditions. You should only consider disabling this
1488 option for embedded systems with no facilities for reporting errors.
1494 bool "Enable ELF core dumps" if EXPERT
1496 Enable support for generating core dumps. Disabling saves about 4k.
1499 config PCSPKR_PLATFORM
1500 bool "Enable PC-Speaker support" if EXPERT
1501 depends on HAVE_PCSPKR_PLATFORM
1505 This option allows to disable the internal PC-Speaker
1506 support, saving some memory.
1510 bool "Enable full-sized data structures for core" if EXPERT
1512 Disabling this option reduces the size of miscellaneous core
1513 kernel data structures. This saves memory on small machines,
1514 but may reduce performance.
1517 bool "Enable futex support" if EXPERT
1521 Disabling this option will cause the kernel to be built without
1522 support for "fast userspace mutexes". The resulting kernel may not
1523 run glibc-based applications correctly.
1527 depends on FUTEX && RT_MUTEXES
1530 config HAVE_FUTEX_CMPXCHG
1534 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1535 is implemented and always working. This removes a couple of runtime
1539 bool "Enable eventpoll support" if EXPERT
1542 Disabling this option will cause the kernel to be built without
1543 support for epoll family of system calls.
1546 bool "Enable signalfd() system call" if EXPERT
1549 Enable the signalfd() system call that allows to receive signals
1550 on a file descriptor.
1555 bool "Enable timerfd() system call" if EXPERT
1558 Enable the timerfd() system call that allows to receive timer
1559 events on a file descriptor.
1564 bool "Enable eventfd() system call" if EXPERT
1567 Enable the eventfd() system call that allows to receive both
1568 kernel notification (ie. KAIO) or userspace notifications.
1573 bool "Use full shmem filesystem" if EXPERT
1577 The shmem is an internal filesystem used to manage shared memory.
1578 It is backed by swap and manages resource limits. It is also exported
1579 to userspace as tmpfs if TMPFS is enabled. Disabling this
1580 option replaces shmem and tmpfs with the much simpler ramfs code,
1581 which may be appropriate on small systems without swap.
1584 bool "Enable AIO support" if EXPERT
1587 This option enables POSIX asynchronous I/O which may by used
1588 by some high performance threaded applications. Disabling
1589 this option saves about 7k.
1592 bool "Enable IO uring support" if EXPERT
1596 This option enables support for the io_uring interface, enabling
1597 applications to submit and complete IO through submission and
1598 completion rings that are shared between the kernel and application.
1600 config ADVISE_SYSCALLS
1601 bool "Enable madvise/fadvise syscalls" if EXPERT
1604 This option enables the madvise and fadvise syscalls, used by
1605 applications to advise the kernel about their future memory or file
1606 usage, improving performance. If building an embedded system where no
1607 applications use these syscalls, you can disable this option to save
1610 config HAVE_ARCH_USERFAULTFD_WP
1613 Arch has userfaultfd write protection support
1616 bool "Enable membarrier() system call" if EXPERT
1619 Enable the membarrier() system call that allows issuing memory
1620 barriers across all running threads, which can be used to distribute
1621 the cost of user-space memory barriers asymmetrically by transforming
1622 pairs of memory barriers into pairs consisting of membarrier() and a
1628 bool "Load all symbols for debugging/ksymoops" if EXPERT
1631 Say Y here to let the kernel print out symbolic crash information and
1632 symbolic stack backtraces. This increases the size of the kernel
1633 somewhat, as all symbols have to be loaded into the kernel image.
1636 bool "Include all symbols in kallsyms"
1637 depends on DEBUG_KERNEL && KALLSYMS
1639 Normally kallsyms only contains the symbols of functions for nicer
1640 OOPS messages and backtraces (i.e., symbols from the text and inittext
1641 sections). This is sufficient for most cases. And only in very rare
1642 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1643 names of variables from the data sections, etc).
1645 This option makes sure that all symbols are loaded into the kernel
1646 image (i.e., symbols from all sections) in cost of increased kernel
1647 size (depending on the kernel configuration, it may be 300KiB or
1648 something like this).
1650 Say N unless you really need all symbols.
1652 config KALLSYMS_ABSOLUTE_PERCPU
1655 default X86_64 && SMP
1657 config KALLSYMS_BASE_RELATIVE
1662 Instead of emitting them as absolute values in the native word size,
1663 emit the symbol references in the kallsyms table as 32-bit entries,
1664 each containing a relative value in the range [base, base + U32_MAX]
1665 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1666 an absolute value in the range [0, S32_MAX] or a relative value in the
1667 range [base, base + S32_MAX], where base is the lowest relative symbol
1668 address encountered in the image.
1670 On 64-bit builds, this reduces the size of the address table by 50%,
1671 but more importantly, it results in entries whose values are build
1672 time constants, and no relocation pass is required at runtime to fix
1673 up the entries based on the runtime load address of the kernel.
1675 # end of the "standard kernel features (expert users)" menu
1677 # syscall, maps, verifier
1680 bool "LSM Instrumentation with BPF"
1681 depends on BPF_EVENTS
1682 depends on BPF_SYSCALL
1686 Enables instrumentation of the security hooks with eBPF programs for
1687 implementing dynamic MAC and Audit Policies.
1689 If you are unsure how to answer this question, answer N.
1692 bool "Enable bpf() system call"
1695 select TASKS_TRACE_RCU
1698 Enable the bpf() system call that allows to manipulate eBPF
1699 programs and maps via file descriptors.
1701 config ARCH_WANT_DEFAULT_BPF_JIT
1704 config BPF_JIT_ALWAYS_ON
1705 bool "Permanently enable BPF JIT and remove BPF interpreter"
1706 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1708 Enables BPF JIT and removes BPF interpreter to avoid
1709 speculative execution of BPF instructions by the interpreter
1711 config BPF_JIT_DEFAULT_ON
1712 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
1713 depends on HAVE_EBPF_JIT && BPF_JIT
1715 source "kernel/bpf/preload/Kconfig"
1718 bool "Enable userfaultfd() system call"
1721 Enable the userfaultfd() system call that allows to intercept and
1722 handle page faults in userland.
1724 config ARCH_HAS_MEMBARRIER_CALLBACKS
1727 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1731 bool "Enable rseq() system call" if EXPERT
1733 depends on HAVE_RSEQ
1736 Enable the restartable sequences system call. It provides a
1737 user-space cache for the current CPU number value, which
1738 speeds up getting the current CPU number from user-space,
1739 as well as an ABI to speed up user-space operations on
1746 bool "Enabled debugging of rseq() system call" if EXPERT
1747 depends on RSEQ && DEBUG_KERNEL
1749 Enable extra debugging checks for the rseq system call.
1754 bool "Embedded system"
1755 option allnoconfig_y
1758 This option should be enabled if compiling the kernel for
1759 an embedded system so certain expert options are available
1762 config HAVE_PERF_EVENTS
1765 See tools/perf/design.txt for details.
1767 config PERF_USE_VMALLOC
1770 See tools/perf/design.txt for details
1773 bool "PC/104 support" if EXPERT
1775 Expose PC/104 form factor device drivers and options available for
1776 selection and configuration. Enable this option if your target
1777 machine has a PC/104 bus.
1779 menu "Kernel Performance Events And Counters"
1782 bool "Kernel performance events and counters"
1783 default y if PROFILING
1784 depends on HAVE_PERF_EVENTS
1788 Enable kernel support for various performance events provided
1789 by software and hardware.
1791 Software events are supported either built-in or via the
1792 use of generic tracepoints.
1794 Most modern CPUs support performance events via performance
1795 counter registers. These registers count the number of certain
1796 types of hw events: such as instructions executed, cachemisses
1797 suffered, or branches mis-predicted - without slowing down the
1798 kernel or applications. These registers can also trigger interrupts
1799 when a threshold number of events have passed - and can thus be
1800 used to profile the code that runs on that CPU.
1802 The Linux Performance Event subsystem provides an abstraction of
1803 these software and hardware event capabilities, available via a
1804 system call and used by the "perf" utility in tools/perf/. It
1805 provides per task and per CPU counters, and it provides event
1806 capabilities on top of those.
1810 config DEBUG_PERF_USE_VMALLOC
1812 bool "Debug: use vmalloc to back perf mmap() buffers"
1813 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1814 select PERF_USE_VMALLOC
1816 Use vmalloc memory to back perf mmap() buffers.
1818 Mostly useful for debugging the vmalloc code on platforms
1819 that don't require it.
1825 config VM_EVENT_COUNTERS
1827 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1829 VM event counters are needed for event counts to be shown.
1830 This option allows the disabling of the VM event counters
1831 on EXPERT systems. /proc/vmstat will only show page counts
1832 if VM event counters are disabled.
1836 bool "Enable SLUB debugging support" if EXPERT
1837 depends on SLUB && SYSFS
1839 SLUB has extensive debug support features. Disabling these can
1840 result in significant savings in code size. This also disables
1841 SLUB sysfs support. /sys/slab will not exist and there will be
1842 no support for cache validation etc.
1844 config SLUB_MEMCG_SYSFS_ON
1846 bool "Enable memcg SLUB sysfs support by default" if EXPERT
1847 depends on SLUB && SYSFS && MEMCG
1849 SLUB creates a directory under /sys/kernel/slab for each
1850 allocation cache to host info and debug files. If memory
1851 cgroup is enabled, each cache can have per memory cgroup
1852 caches. SLUB can create the same sysfs directories for these
1853 caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1854 to a very high number of debug files being created. This is
1855 controlled by slub_memcg_sysfs boot parameter and this
1856 config option determines the parameter's default value.
1859 bool "Disable heap randomization"
1862 Randomizing heap placement makes heap exploits harder, but it
1863 also breaks ancient binaries (including anything libc5 based).
1864 This option changes the bootup default to heap randomization
1865 disabled, and can be overridden at runtime by setting
1866 /proc/sys/kernel/randomize_va_space to 2.
1868 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1871 prompt "Choose SLAB allocator"
1874 This option allows to select a slab allocator.
1878 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1880 The regular slab allocator that is established and known to work
1881 well in all environments. It organizes cache hot objects in
1882 per cpu and per node queues.
1885 bool "SLUB (Unqueued Allocator)"
1886 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1888 SLUB is a slab allocator that minimizes cache line usage
1889 instead of managing queues of cached objects (SLAB approach).
1890 Per cpu caching is realized using slabs of objects instead
1891 of queues of objects. SLUB can use memory efficiently
1892 and has enhanced diagnostics. SLUB is the default choice for
1897 bool "SLOB (Simple Allocator)"
1899 SLOB replaces the stock allocator with a drastically simpler
1900 allocator. SLOB is generally more space efficient but
1901 does not perform as well on large systems.
1905 config SLAB_MERGE_DEFAULT
1906 bool "Allow slab caches to be merged"
1909 For reduced kernel memory fragmentation, slab caches can be
1910 merged when they share the same size and other characteristics.
1911 This carries a risk of kernel heap overflows being able to
1912 overwrite objects from merged caches (and more easily control
1913 cache layout), which makes such heap attacks easier to exploit
1914 by attackers. By keeping caches unmerged, these kinds of exploits
1915 can usually only damage objects in the same cache. To disable
1916 merging at runtime, "slab_nomerge" can be passed on the kernel
1919 config SLAB_FREELIST_RANDOM
1920 bool "Randomize slab freelist"
1921 depends on SLAB || SLUB
1923 Randomizes the freelist order used on creating new pages. This
1924 security feature reduces the predictability of the kernel slab
1925 allocator against heap overflows.
1927 config SLAB_FREELIST_HARDENED
1928 bool "Harden slab freelist metadata"
1929 depends on SLAB || SLUB
1931 Many kernel heap attacks try to target slab cache metadata and
1932 other infrastructure. This options makes minor performance
1933 sacrifices to harden the kernel slab allocator against common
1934 freelist exploit methods. Some slab implementations have more
1935 sanity-checking than others. This option is most effective with
1938 config SHUFFLE_PAGE_ALLOCATOR
1939 bool "Page allocator randomization"
1940 default SLAB_FREELIST_RANDOM && ACPI_NUMA
1942 Randomization of the page allocator improves the average
1943 utilization of a direct-mapped memory-side-cache. See section
1944 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1945 6.2a specification for an example of how a platform advertises
1946 the presence of a memory-side-cache. There are also incidental
1947 security benefits as it reduces the predictability of page
1948 allocations to compliment SLAB_FREELIST_RANDOM, but the
1949 default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1950 10th order of pages is selected based on cache utilization
1953 While the randomization improves cache utilization it may
1954 negatively impact workloads on platforms without a cache. For
1955 this reason, by default, the randomization is enabled only
1956 after runtime detection of a direct-mapped memory-side-cache.
1957 Otherwise, the randomization may be force enabled with the
1958 'page_alloc.shuffle' kernel command line parameter.
1962 config SLUB_CPU_PARTIAL
1964 depends on SLUB && SMP
1965 bool "SLUB per cpu partial cache"
1967 Per cpu partial caches accelerate objects allocation and freeing
1968 that is local to a processor at the price of more indeterminism
1969 in the latency of the free. On overflow these caches will be cleared
1970 which requires the taking of locks that may cause latency spikes.
1971 Typically one would choose no for a realtime system.
1973 config MMAP_ALLOW_UNINITIALIZED
1974 bool "Allow mmapped anonymous memory to be uninitialized"
1975 depends on EXPERT && !MMU
1978 Normally, and according to the Linux spec, anonymous memory obtained
1979 from mmap() has its contents cleared before it is passed to
1980 userspace. Enabling this config option allows you to request that
1981 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1982 providing a huge performance boost. If this option is not enabled,
1983 then the flag will be ignored.
1985 This is taken advantage of by uClibc's malloc(), and also by
1986 ELF-FDPIC binfmt's brk and stack allocator.
1988 Because of the obvious security issues, this option should only be
1989 enabled on embedded devices where you control what is run in
1990 userspace. Since that isn't generally a problem on no-MMU systems,
1991 it is normally safe to say Y here.
1993 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
1995 config SYSTEM_DATA_VERIFICATION
1997 select SYSTEM_TRUSTED_KEYRING
2001 select ASYMMETRIC_KEY_TYPE
2002 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
2005 select X509_CERTIFICATE_PARSER
2006 select PKCS7_MESSAGE_PARSER
2008 Provide PKCS#7 message verification using the contents of the system
2009 trusted keyring to provide public keys. This then can be used for
2010 module verification, kexec image verification and firmware blob
2014 bool "Profiling support"
2016 Say Y here to enable the extended profiling support mechanisms used
2017 by profilers such as OProfile.
2020 # Place an empty function call at each tracepoint site. Can be
2021 # dynamically changed for a probe function.
2026 endmenu # General setup
2028 source "arch/Kconfig"
2035 default 0 if BASE_FULL
2036 default 1 if !BASE_FULL
2038 config MODULE_SIG_FORMAT
2040 select SYSTEM_DATA_VERIFICATION
2043 bool "Enable loadable module support"
2046 Kernel modules are small pieces of compiled code which can
2047 be inserted in the running kernel, rather than being
2048 permanently built into the kernel. You use the "modprobe"
2049 tool to add (and sometimes remove) them. If you say Y here,
2050 many parts of the kernel can be built as modules (by
2051 answering M instead of Y where indicated): this is most
2052 useful for infrequently used options which are not required
2053 for booting. For more information, see the man pages for
2054 modprobe, lsmod, modinfo, insmod and rmmod.
2056 If you say Y here, you will need to run "make
2057 modules_install" to put the modules under /lib/modules/
2058 where modprobe can find them (you may need to be root to do
2065 config MODULE_FORCE_LOAD
2066 bool "Forced module loading"
2069 Allow loading of modules without version information (ie. modprobe
2070 --force). Forced module loading sets the 'F' (forced) taint flag and
2071 is usually a really bad idea.
2073 config MODULE_UNLOAD
2074 bool "Module unloading"
2076 Without this option you will not be able to unload any
2077 modules (note that some modules may not be unloadable
2078 anyway), which makes your kernel smaller, faster
2079 and simpler. If unsure, say Y.
2081 config MODULE_FORCE_UNLOAD
2082 bool "Forced module unloading"
2083 depends on MODULE_UNLOAD
2085 This option allows you to force a module to unload, even if the
2086 kernel believes it is unsafe: the kernel will remove the module
2087 without waiting for anyone to stop using it (using the -f option to
2088 rmmod). This is mainly for kernel developers and desperate users.
2092 bool "Module versioning support"
2094 Usually, you have to use modules compiled with your kernel.
2095 Saying Y here makes it sometimes possible to use modules
2096 compiled for different kernels, by adding enough information
2097 to the modules to (hopefully) spot any changes which would
2098 make them incompatible with the kernel you are running. If
2101 config ASM_MODVERSIONS
2103 default HAVE_ASM_MODVERSIONS && MODVERSIONS
2105 This enables module versioning for exported symbols also from
2106 assembly. This can be enabled only when the target architecture
2109 config MODULE_REL_CRCS
2111 depends on MODVERSIONS
2113 config MODULE_SRCVERSION_ALL
2114 bool "Source checksum for all modules"
2116 Modules which contain a MODULE_VERSION get an extra "srcversion"
2117 field inserted into their modinfo section, which contains a
2118 sum of the source files which made it. This helps maintainers
2119 see exactly which source was used to build a module (since
2120 others sometimes change the module source without updating
2121 the version). With this option, such a "srcversion" field
2122 will be created for all modules. If unsure, say N.
2125 bool "Module signature verification"
2126 select MODULE_SIG_FORMAT
2128 Check modules for valid signatures upon load: the signature
2129 is simply appended to the module. For more information see
2130 <file:Documentation/admin-guide/module-signing.rst>.
2132 Note that this option adds the OpenSSL development packages as a
2133 kernel build dependency so that the signing tool can use its crypto
2136 You should enable this option if you wish to use either
2137 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2138 another LSM - otherwise unsigned modules will be loadable regardless
2139 of the lockdown policy.
2141 !!!WARNING!!! If you enable this option, you MUST make sure that the
2142 module DOES NOT get stripped after being signed. This includes the
2143 debuginfo strip done by some packagers (such as rpmbuild) and
2144 inclusion into an initramfs that wants the module size reduced.
2146 config MODULE_SIG_FORCE
2147 bool "Require modules to be validly signed"
2148 depends on MODULE_SIG
2150 Reject unsigned modules or signed modules for which we don't have a
2151 key. Without this, such modules will simply taint the kernel.
2153 config MODULE_SIG_ALL
2154 bool "Automatically sign all modules"
2156 depends on MODULE_SIG
2158 Sign all modules during make modules_install. Without this option,
2159 modules must be signed manually, using the scripts/sign-file tool.
2161 comment "Do not forget to sign required modules with scripts/sign-file"
2162 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2165 prompt "Which hash algorithm should modules be signed with?"
2166 depends on MODULE_SIG
2168 This determines which sort of hashing algorithm will be used during
2169 signature generation. This algorithm _must_ be built into the kernel
2170 directly so that signature verification can take place. It is not
2171 possible to load a signed module containing the algorithm to check
2172 the signature on that module.
2174 config MODULE_SIG_SHA1
2175 bool "Sign modules with SHA-1"
2178 config MODULE_SIG_SHA224
2179 bool "Sign modules with SHA-224"
2180 select CRYPTO_SHA256
2182 config MODULE_SIG_SHA256
2183 bool "Sign modules with SHA-256"
2184 select CRYPTO_SHA256
2186 config MODULE_SIG_SHA384
2187 bool "Sign modules with SHA-384"
2188 select CRYPTO_SHA512
2190 config MODULE_SIG_SHA512
2191 bool "Sign modules with SHA-512"
2192 select CRYPTO_SHA512
2196 config MODULE_SIG_HASH
2198 depends on MODULE_SIG
2199 default "sha1" if MODULE_SIG_SHA1
2200 default "sha224" if MODULE_SIG_SHA224
2201 default "sha256" if MODULE_SIG_SHA256
2202 default "sha384" if MODULE_SIG_SHA384
2203 default "sha512" if MODULE_SIG_SHA512
2205 config MODULE_COMPRESS
2206 bool "Compress modules on installation"
2209 Compresses kernel modules when 'make modules_install' is run; gzip or
2210 xz depending on "Compression algorithm" below.
2212 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2214 Out-of-tree kernel modules installed using Kbuild will also be
2215 compressed upon installation.
2217 Note: for modules inside an initrd or initramfs, it's more efficient
2218 to compress the whole initrd or initramfs instead.
2220 Note: This is fully compatible with signed modules.
2225 prompt "Compression algorithm"
2226 depends on MODULE_COMPRESS
2227 default MODULE_COMPRESS_GZIP
2229 This determines which sort of compression will be used during
2230 'make modules_install'.
2232 GZIP (default) and XZ are supported.
2234 config MODULE_COMPRESS_GZIP
2237 config MODULE_COMPRESS_XZ
2242 config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2243 bool "Allow loading of modules with missing namespace imports"
2245 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2246 a namespace. A module that makes use of a symbol exported with such a
2247 namespace is required to import the namespace via MODULE_IMPORT_NS().
2248 There is no technical reason to enforce correct namespace imports,
2249 but it creates consistency between symbols defining namespaces and
2250 users importing namespaces they make use of. This option relaxes this
2251 requirement and lifts the enforcement when loading a module.
2255 config UNUSED_SYMBOLS
2256 bool "Enable unused/obsolete exported symbols"
2259 Unused but exported symbols make the kernel needlessly bigger. For
2260 that reason most of these unused exports will soon be removed. This
2261 option is provided temporarily to provide a transition period in case
2262 some external kernel module needs one of these symbols anyway. If you
2263 encounter such a case in your module, consider if you are actually
2264 using the right API. (rationale: since nobody in the kernel is using
2265 this in a module, there is a pretty good chance it's actually the
2266 wrong interface to use). If you really need the symbol, please send a
2267 mail to the linux kernel mailing list mentioning the symbol and why
2268 you really need it, and what the merge plan to the mainline kernel for
2271 config TRIM_UNUSED_KSYMS
2272 bool "Trim unused exported kernel symbols"
2273 depends on !UNUSED_SYMBOLS
2275 The kernel and some modules make many symbols available for
2276 other modules to use via EXPORT_SYMBOL() and variants. Depending
2277 on the set of modules being selected in your kernel configuration,
2278 many of those exported symbols might never be used.
2280 This option allows for unused exported symbols to be dropped from
2281 the build. In turn, this provides the compiler more opportunities
2282 (especially when using LTO) for optimizing the code and reducing
2283 binary size. This might have some security advantages as well.
2285 If unsure, or if you need to build out-of-tree modules, say N.
2287 config UNUSED_KSYMS_WHITELIST
2288 string "Whitelist of symbols to keep in ksymtab"
2289 depends on TRIM_UNUSED_KSYMS
2291 By default, all unused exported symbols will be un-exported from the
2292 build when TRIM_UNUSED_KSYMS is selected.
2294 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
2295 exported at all times, even in absence of in-tree users. The value to
2296 set here is the path to a text file containing the list of symbols,
2297 one per line. The path can be absolute, or relative to the kernel
2302 config MODULES_TREE_LOOKUP
2304 depends on PERF_EVENTS || TRACING
2306 config INIT_ALL_POSSIBLE
2309 Back when each arch used to define their own cpu_online_mask and
2310 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2311 with all 1s, and others with all 0s. When they were centralised,
2312 it was better to provide this option than to break all the archs
2313 and have several arch maintainers pursuing me down dark alleys.
2315 source "block/Kconfig"
2317 config PREEMPT_NOTIFIERS
2327 Build a simple ASN.1 grammar compiler that produces a bytecode output
2328 that can be interpreted by the ASN.1 stream decoder and used to
2329 inform it as to what tags are to be expected in a stream and what
2330 functions to call on what tags.
2332 source "kernel/Kconfig.locks"
2334 config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2337 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2340 # It may be useful for an architecture to override the definitions of the
2341 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2342 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2343 # different calling convention for syscalls. They can also override the
2344 # macros for not-implemented syscalls in kernel/sys_ni.c and
2345 # kernel/time/posix-stubs.c. All these overrides need to be available in
2346 # <asm/syscall_wrapper.h>.
2347 config ARCH_HAS_SYSCALL_WRAPPER
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