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 compiler is updated
23 include/linux/compiler-version.h contains this option in the comment
24 line so fixdep adds include/config/cc/version/text.h into the
25 auto-generated dependency. When the compiler is updated, syncconfig
26 will touch it and then every file will be rebuilt.
29 def_bool $(success,test "$(cc-name)" = GCC)
33 default $(cc-version) if CC_IS_GCC
37 def_bool $(success,test "$(cc-name)" = Clang)
41 default $(cc-version) if CC_IS_CLANG
45 def_bool $(success,test "$(ld-name)" = BFD)
49 default $(ld-version) if LD_IS_BFD
53 def_bool $(success,test "$(ld-name)" = LLD)
57 default $(ld-version) if LD_IS_LLD
62 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag)) if 64BIT
63 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag))
65 config CC_CAN_LINK_STATIC
67 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static) if 64BIT
68 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag) -static)
70 config CC_HAS_ASM_GOTO
71 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
73 config CC_HAS_ASM_GOTO_OUTPUT
74 depends on CC_HAS_ASM_GOTO
75 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)
77 config TOOLS_SUPPORT_RELR
78 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
80 config CC_HAS_ASM_INLINE
81 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
89 config BUILDTIME_TABLE_SORT
92 config THREAD_INFO_IN_TASK
95 Select this to move thread_info off the stack into task_struct. To
96 make this work, an arch will need to remove all thread_info fields
97 except flags and fix any runtime bugs.
99 One subtle change that will be needed is to use try_get_task_stack()
100 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
109 depends on BROKEN || !SMP
112 config INIT_ENV_ARG_LIMIT
117 Maximum of each of the number of arguments and environment
118 variables passed to init from the kernel command line.
121 bool "Compile also drivers which will not load"
124 Some drivers can be compiled on a different platform than they are
125 intended to be run on. Despite they cannot be loaded there (or even
126 when they load they cannot be used due to missing HW support),
127 developers still, opposing to distributors, might want to build such
128 drivers to compile-test them.
130 If you are a developer and want to build everything available, say Y
131 here. If you are a user/distributor, say N here to exclude useless
132 drivers to be distributed.
134 config UAPI_HEADER_TEST
135 bool "Compile test UAPI headers"
136 depends on HEADERS_INSTALL && CC_CAN_LINK
138 Compile test headers exported to user-space to ensure they are
139 self-contained, i.e. compilable as standalone units.
141 If you are a developer or tester and want to ensure the exported
142 headers are self-contained, say Y here. Otherwise, choose N.
145 string "Local version - append to kernel release"
147 Append an extra string to the end of your kernel version.
148 This will show up when you type uname, for example.
149 The string you set here will be appended after the contents of
150 any files with a filename matching localversion* in your
151 object and source tree, in that order. Your total string can
152 be a maximum of 64 characters.
154 config LOCALVERSION_AUTO
155 bool "Automatically append version information to the version string"
157 depends on !COMPILE_TEST
159 This will try to automatically determine if the current tree is a
160 release tree by looking for git tags that belong to the current
161 top of tree revision.
163 A string of the format -gxxxxxxxx will be added to the localversion
164 if a git-based tree is found. The string generated by this will be
165 appended after any matching localversion* files, and after the value
166 set in CONFIG_LOCALVERSION.
168 (The actual string used here is the first eight characters produced
169 by running the command:
171 $ git rev-parse --verify HEAD
173 which is done within the script "scripts/setlocalversion".)
176 string "Build ID Salt"
179 The build ID is used to link binaries and their debug info. Setting
180 this option will use the value in the calculation of the build id.
181 This is mostly useful for distributions which want to ensure the
182 build is unique between builds. It's safe to leave the default.
184 config HAVE_KERNEL_GZIP
187 config HAVE_KERNEL_BZIP2
190 config HAVE_KERNEL_LZMA
193 config HAVE_KERNEL_XZ
196 config HAVE_KERNEL_LZO
199 config HAVE_KERNEL_LZ4
202 config HAVE_KERNEL_ZSTD
205 config HAVE_KERNEL_UNCOMPRESSED
209 prompt "Kernel compression mode"
211 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
213 The linux kernel is a kind of self-extracting executable.
214 Several compression algorithms are available, which differ
215 in efficiency, compression and decompression speed.
216 Compression speed is only relevant when building a kernel.
217 Decompression speed is relevant at each boot.
219 If you have any problems with bzip2 or lzma compressed
221 version of this functionality (bzip2 only), for 2.4, was
222 supplied by Christian Ludwig)
224 High compression options are mostly useful for users, who
225 are low on disk space (embedded systems), but for whom ram
228 If in doubt, select 'gzip'
232 depends on HAVE_KERNEL_GZIP
234 The old and tried gzip compression. It provides a good balance
235 between compression ratio and decompression speed.
239 depends on HAVE_KERNEL_BZIP2
241 Its compression ratio and speed is intermediate.
242 Decompression speed is slowest among the choices. The kernel
243 size is about 10% smaller with bzip2, in comparison to gzip.
244 Bzip2 uses a large amount of memory. For modern kernels you
245 will need at least 8MB RAM or more for booting.
249 depends on HAVE_KERNEL_LZMA
251 This compression algorithm's ratio is best. Decompression speed
252 is between gzip and bzip2. Compression is slowest.
253 The kernel size is about 33% smaller with LZMA in comparison to gzip.
257 depends on HAVE_KERNEL_XZ
259 XZ uses the LZMA2 algorithm and instruction set specific
260 BCJ filters which can improve compression ratio of executable
261 code. The size of the kernel is about 30% smaller with XZ in
262 comparison to gzip. On architectures for which there is a BCJ
263 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
264 will create a few percent smaller kernel than plain LZMA.
266 The speed is about the same as with LZMA: The decompression
267 speed of XZ is better than that of bzip2 but worse than gzip
268 and LZO. Compression is slow.
272 depends on HAVE_KERNEL_LZO
274 Its compression ratio is the poorest among the choices. The kernel
275 size is about 10% bigger than gzip; however its speed
276 (both compression and decompression) is the fastest.
280 depends on HAVE_KERNEL_LZ4
282 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
283 A preliminary version of LZ4 de/compression tool is available at
284 <https://code.google.com/p/lz4/>.
286 Its compression ratio is worse than LZO. The size of the kernel
287 is about 8% bigger than LZO. But the decompression speed is
292 depends on HAVE_KERNEL_ZSTD
294 ZSTD is a compression algorithm targeting intermediate compression
295 with fast decompression speed. It will compress better than GZIP and
296 decompress around the same speed as LZO, but slower than LZ4. You
297 will need at least 192 KB RAM or more for booting. The zstd command
298 line tool is required for compression.
300 config KERNEL_UNCOMPRESSED
302 depends on HAVE_KERNEL_UNCOMPRESSED
304 Produce uncompressed kernel image. This option is usually not what
305 you want. It is useful for debugging the kernel in slow simulation
306 environments, where decompressing and moving the kernel is awfully
307 slow. This option allows early boot code to skip the decompressor
308 and jump right at uncompressed kernel image.
313 string "Default init path"
316 This option determines the default init for the system if no init=
317 option is passed on the kernel command line. If the requested path is
318 not present, we will still then move on to attempting further
319 locations (e.g. /sbin/init, etc). If this is empty, we will just use
320 the fallback list when init= is not passed.
322 config DEFAULT_HOSTNAME
323 string "Default hostname"
326 This option determines the default system hostname before userspace
327 calls sethostname(2). The kernel traditionally uses "(none)" here,
328 but you may wish to use a different default here to make a minimal
329 system more usable with less configuration.
332 # For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
333 # add proper SWAP support to them, in which case this can be remove.
339 bool "Support for paging of anonymous memory (swap)"
340 depends on MMU && BLOCK && !ARCH_NO_SWAP
343 This option allows you to choose whether you want to have support
344 for so called swap devices or swap files in your kernel that are
345 used to provide more virtual memory than the actual RAM present
346 in your computer. If unsure say Y.
351 Inter Process Communication is a suite of library functions and
352 system calls which let processes (running programs) synchronize and
353 exchange information. It is generally considered to be a good thing,
354 and some programs won't run unless you say Y here. In particular, if
355 you want to run the DOS emulator dosemu under Linux (read the
356 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
357 you'll need to say Y here.
359 You can find documentation about IPC with "info ipc" and also in
360 section 6.4 of the Linux Programmer's Guide, available from
361 <http://www.tldp.org/guides.html>.
363 config SYSVIPC_SYSCTL
370 bool "POSIX Message Queues"
373 POSIX variant of message queues is a part of IPC. In POSIX message
374 queues every message has a priority which decides about succession
375 of receiving it by a process. If you want to compile and run
376 programs written e.g. for Solaris with use of its POSIX message
377 queues (functions mq_*) say Y here.
379 POSIX message queues are visible as a filesystem called 'mqueue'
380 and can be mounted somewhere if you want to do filesystem
381 operations on message queues.
385 config POSIX_MQUEUE_SYSCTL
387 depends on POSIX_MQUEUE
392 bool "General notification queue"
396 This is a general notification queue for the kernel to pass events to
397 userspace by splicing them into pipes. It can be used in conjunction
398 with watches for key/keyring change notifications and device
401 See Documentation/watch_queue.rst
403 config CROSS_MEMORY_ATTACH
404 bool "Enable process_vm_readv/writev syscalls"
408 Enabling this option adds the system calls process_vm_readv and
409 process_vm_writev which allow a process with the correct privileges
410 to directly read from or write to another process' address space.
411 See the man page for more details.
414 bool "uselib syscall"
415 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
417 This option enables the uselib syscall, a system call used in the
418 dynamic linker from libc5 and earlier. glibc does not use this
419 system call. If you intend to run programs built on libc5 or
420 earlier, you may need to enable this syscall. Current systems
421 running glibc can safely disable this.
424 bool "Auditing support"
427 Enable auditing infrastructure that can be used with another
428 kernel subsystem, such as SELinux (which requires this for
429 logging of avc messages output). System call auditing is included
430 on architectures which support it.
432 config HAVE_ARCH_AUDITSYSCALL
437 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
440 source "kernel/irq/Kconfig"
441 source "kernel/time/Kconfig"
442 source "kernel/Kconfig.preempt"
444 menu "CPU/Task time and stats accounting"
446 config VIRT_CPU_ACCOUNTING
450 prompt "Cputime accounting"
451 default TICK_CPU_ACCOUNTING if !PPC64
452 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
454 # Kind of a stub config for the pure tick based cputime accounting
455 config TICK_CPU_ACCOUNTING
456 bool "Simple tick based cputime accounting"
457 depends on !S390 && !NO_HZ_FULL
459 This is the basic tick based cputime accounting that maintains
460 statistics about user, system and idle time spent on per jiffies
465 config VIRT_CPU_ACCOUNTING_NATIVE
466 bool "Deterministic task and CPU time accounting"
467 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
468 select VIRT_CPU_ACCOUNTING
470 Select this option to enable more accurate task and CPU time
471 accounting. This is done by reading a CPU counter on each
472 kernel entry and exit and on transitions within the kernel
473 between system, softirq and hardirq state, so there is a
474 small performance impact. In the case of s390 or IBM POWER > 5,
475 this also enables accounting of stolen time on logically-partitioned
478 config VIRT_CPU_ACCOUNTING_GEN
479 bool "Full dynticks CPU time accounting"
480 depends on HAVE_CONTEXT_TRACKING
481 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
482 depends on GENERIC_CLOCKEVENTS
483 select VIRT_CPU_ACCOUNTING
484 select CONTEXT_TRACKING
486 Select this option to enable task and CPU time accounting on full
487 dynticks systems. This accounting is implemented by watching every
488 kernel-user boundaries using the context tracking subsystem.
489 The accounting is thus performed at the expense of some significant
492 For now this is only useful if you are working on the full
493 dynticks subsystem development.
499 config IRQ_TIME_ACCOUNTING
500 bool "Fine granularity task level IRQ time accounting"
501 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
503 Select this option to enable fine granularity task irq time
504 accounting. This is done by reading a timestamp on each
505 transitions between softirq and hardirq state, so there can be a
506 small performance impact.
508 If in doubt, say N here.
510 config HAVE_SCHED_AVG_IRQ
512 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
515 config SCHED_THERMAL_PRESSURE
517 default y if ARM && ARM_CPU_TOPOLOGY
520 depends on CPU_FREQ_THERMAL
522 Select this option to enable thermal pressure accounting in the
523 scheduler. Thermal pressure is the value conveyed to the scheduler
524 that reflects the reduction in CPU compute capacity resulted from
525 thermal throttling. Thermal throttling occurs when the performance of
526 a CPU is capped due to high operating temperatures.
528 If selected, the scheduler will be able to balance tasks accordingly,
529 i.e. put less load on throttled CPUs than on non/less throttled ones.
531 This requires the architecture to implement
532 arch_set_thermal_pressure() and arch_scale_thermal_pressure().
534 config BSD_PROCESS_ACCT
535 bool "BSD Process Accounting"
538 If you say Y here, a user level program will be able to instruct the
539 kernel (via a special system call) to write process accounting
540 information to a file: whenever a process exits, information about
541 that process will be appended to the file by the kernel. The
542 information includes things such as creation time, owning user,
543 command name, memory usage, controlling terminal etc. (the complete
544 list is in the struct acct in <file:include/linux/acct.h>). It is
545 up to the user level program to do useful things with this
546 information. This is generally a good idea, so say Y.
548 config BSD_PROCESS_ACCT_V3
549 bool "BSD Process Accounting version 3 file format"
550 depends on BSD_PROCESS_ACCT
553 If you say Y here, the process accounting information is written
554 in a new file format that also logs the process IDs of each
555 process and its parent. Note that this file format is incompatible
556 with previous v0/v1/v2 file formats, so you will need updated tools
557 for processing it. A preliminary version of these tools is available
558 at <http://www.gnu.org/software/acct/>.
561 bool "Export task/process statistics through netlink"
566 Export selected statistics for tasks/processes through the
567 generic netlink interface. Unlike BSD process accounting, the
568 statistics are available during the lifetime of tasks/processes as
569 responses to commands. Like BSD accounting, they are sent to user
574 config TASK_DELAY_ACCT
575 bool "Enable per-task delay accounting"
579 Collect information on time spent by a task waiting for system
580 resources like cpu, synchronous block I/O completion and swapping
581 in pages. Such statistics can help in setting a task's priorities
582 relative to other tasks for cpu, io, rss limits etc.
587 bool "Enable extended accounting over taskstats"
590 Collect extended task accounting data and send the data
591 to userland for processing over the taskstats interface.
595 config TASK_IO_ACCOUNTING
596 bool "Enable per-task storage I/O accounting"
597 depends on TASK_XACCT
599 Collect information on the number of bytes of storage I/O which this
605 bool "Pressure stall information tracking"
607 Collect metrics that indicate how overcommitted the CPU, memory,
608 and IO capacity are in the system.
610 If you say Y here, the kernel will create /proc/pressure/ with the
611 pressure statistics files cpu, memory, and io. These will indicate
612 the share of walltime in which some or all tasks in the system are
613 delayed due to contention of the respective resource.
615 In kernels with cgroup support, cgroups (cgroup2 only) will
616 have cpu.pressure, memory.pressure, and io.pressure files,
617 which aggregate pressure stalls for the grouped tasks only.
619 For more details see Documentation/accounting/psi.rst.
623 config PSI_DEFAULT_DISABLED
624 bool "Require boot parameter to enable pressure stall information tracking"
628 If set, pressure stall information tracking will be disabled
629 per default but can be enabled through passing psi=1 on the
630 kernel commandline during boot.
632 This feature adds some code to the task wakeup and sleep
633 paths of the scheduler. The overhead is too low to affect
634 common scheduling-intense workloads in practice (such as
635 webservers, memcache), but it does show up in artificial
636 scheduler stress tests, such as hackbench.
638 If you are paranoid and not sure what the kernel will be
643 endmenu # "CPU/Task time and stats accounting"
647 depends on SMP || COMPILE_TEST
650 Make sure that CPUs running critical tasks are not disturbed by
651 any source of "noise" such as unbound workqueues, timers, kthreads...
652 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
653 the "isolcpus=" boot parameter.
657 source "kernel/rcu/Kconfig"
664 tristate "Kernel .config support"
666 This option enables the complete Linux kernel ".config" file
667 contents to be saved in the kernel. It provides documentation
668 of which kernel options are used in a running kernel or in an
669 on-disk kernel. This information can be extracted from the kernel
670 image file with the script scripts/extract-ikconfig and used as
671 input to rebuild the current kernel or to build another kernel.
672 It can also be extracted from a running kernel by reading
673 /proc/config.gz if enabled (below).
676 bool "Enable access to .config through /proc/config.gz"
677 depends on IKCONFIG && PROC_FS
679 This option enables access to the kernel configuration file
680 through /proc/config.gz.
683 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
686 This option enables access to the in-kernel headers that are generated during
687 the build process. These can be used to build eBPF tracing programs,
688 or similar programs. If you build the headers as a module, a module called
689 kheaders.ko is built which can be loaded on-demand to get access to headers.
692 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
693 range 12 25 if !H8300
698 Select the minimal kernel log buffer size as a power of 2.
699 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
700 parameter, see below. Any higher size also might be forced
701 by "log_buf_len" boot parameter.
711 config LOG_CPU_MAX_BUF_SHIFT
712 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
715 default 12 if !BASE_SMALL
716 default 0 if BASE_SMALL
719 This option allows to increase the default ring buffer size
720 according to the number of CPUs. The value defines the contribution
721 of each CPU as a power of 2. The used space is typically only few
722 lines however it might be much more when problems are reported,
725 The increased size means that a new buffer has to be allocated and
726 the original static one is unused. It makes sense only on systems
727 with more CPUs. Therefore this value is used only when the sum of
728 contributions is greater than the half of the default kernel ring
729 buffer as defined by LOG_BUF_SHIFT. The default values are set
730 so that more than 16 CPUs are needed to trigger the allocation.
732 Also this option is ignored when "log_buf_len" kernel parameter is
733 used as it forces an exact (power of two) size of the ring buffer.
735 The number of possible CPUs is used for this computation ignoring
736 hotplugging making the computation optimal for the worst case
737 scenario while allowing a simple algorithm to be used from bootup.
739 Examples shift values and their meaning:
740 17 => 128 KB for each CPU
741 16 => 64 KB for each CPU
742 15 => 32 KB for each CPU
743 14 => 16 KB for each CPU
744 13 => 8 KB for each CPU
745 12 => 4 KB for each CPU
747 config PRINTK_SAFE_LOG_BUF_SHIFT
748 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
753 Select the size of an alternate printk per-CPU buffer where messages
754 printed from usafe contexts are temporary stored. One example would
755 be NMI messages, another one - printk recursion. The messages are
756 copied to the main log buffer in a safe context to avoid a deadlock.
757 The value defines the size as a power of 2.
759 Those messages are rare and limited. The largest one is when
760 a backtrace is printed. It usually fits into 4KB. Select
761 8KB if you want to be on the safe side.
764 17 => 128 KB for each CPU
765 16 => 64 KB for each CPU
766 15 => 32 KB for each CPU
767 14 => 16 KB for each CPU
768 13 => 8 KB for each CPU
769 12 => 4 KB for each CPU
772 # Architectures with an unreliable sched_clock() should select this:
774 config HAVE_UNSTABLE_SCHED_CLOCK
777 config GENERIC_SCHED_CLOCK
780 menu "Scheduler features"
783 bool "Enable utilization clamping for RT/FAIR tasks"
784 depends on CPU_FREQ_GOV_SCHEDUTIL
786 This feature enables the scheduler to track the clamped utilization
787 of each CPU based on RUNNABLE tasks scheduled on that CPU.
789 With this option, the user can specify the min and max CPU
790 utilization allowed for RUNNABLE tasks. The max utilization defines
791 the maximum frequency a task should use while the min utilization
792 defines the minimum frequency it should use.
794 Both min and max utilization clamp values are hints to the scheduler,
795 aiming at improving its frequency selection policy, but they do not
796 enforce or grant any specific bandwidth for tasks.
800 config UCLAMP_BUCKETS_COUNT
801 int "Number of supported utilization clamp buckets"
804 depends on UCLAMP_TASK
806 Defines the number of clamp buckets to use. The range of each bucket
807 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
808 number of clamp buckets the finer their granularity and the higher
809 the precision of clamping aggregation and tracking at run-time.
811 For example, with the minimum configuration value we will have 5
812 clamp buckets tracking 20% utilization each. A 25% boosted tasks will
813 be refcounted in the [20..39]% bucket and will set the bucket clamp
814 effective value to 25%.
815 If a second 30% boosted task should be co-scheduled on the same CPU,
816 that task will be refcounted in the same bucket of the first task and
817 it will boost the bucket clamp effective value to 30%.
818 The clamp effective value of a bucket is reset to its nominal value
819 (20% in the example above) when there are no more tasks refcounted in
822 An additional boost/capping margin can be added to some tasks. In the
823 example above the 25% task will be boosted to 30% until it exits the
824 CPU. If that should be considered not acceptable on certain systems,
825 it's always possible to reduce the margin by increasing the number of
826 clamp buckets to trade off used memory for run-time tracking
829 If in doubt, use the default value.
834 # For architectures that want to enable the support for NUMA-affine scheduler
837 config ARCH_SUPPORTS_NUMA_BALANCING
841 # For architectures that prefer to flush all TLBs after a number of pages
842 # are unmapped instead of sending one IPI per page to flush. The architecture
843 # must provide guarantees on what happens if a clean TLB cache entry is
844 # written after the unmap. Details are in mm/rmap.c near the check for
845 # should_defer_flush. The architecture should also consider if the full flush
846 # and the refill costs are offset by the savings of sending fewer IPIs.
847 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
851 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
854 # For architectures that know their GCC __int128 support is sound
856 config ARCH_SUPPORTS_INT128
859 # For architectures that (ab)use NUMA to represent different memory regions
860 # all cpu-local but of different latencies, such as SuperH.
862 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
865 config NUMA_BALANCING
866 bool "Memory placement aware NUMA scheduler"
867 depends on ARCH_SUPPORTS_NUMA_BALANCING
868 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
869 depends on SMP && NUMA && MIGRATION
871 This option adds support for automatic NUMA aware memory/task placement.
872 The mechanism is quite primitive and is based on migrating memory when
873 it has references to the node the task is running on.
875 This system will be inactive on UMA systems.
877 config NUMA_BALANCING_DEFAULT_ENABLED
878 bool "Automatically enable NUMA aware memory/task placement"
880 depends on NUMA_BALANCING
882 If set, automatic NUMA balancing will be enabled if running on a NUMA
886 bool "Control Group support"
889 This option adds support for grouping sets of processes together, for
890 use with process control subsystems such as Cpusets, CFS, memory
891 controls or device isolation.
893 - Documentation/scheduler/sched-design-CFS.rst (CFS)
894 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
895 and resource control)
905 bool "Memory controller"
909 Provides control over the memory footprint of tasks in a cgroup.
913 depends on MEMCG && SWAP
918 depends on MEMCG && !SLOB
926 Generic block IO controller cgroup interface. This is the common
927 cgroup interface which should be used by various IO controlling
930 Currently, CFQ IO scheduler uses it to recognize task groups and
931 control disk bandwidth allocation (proportional time slice allocation)
932 to such task groups. It is also used by bio throttling logic in
933 block layer to implement upper limit in IO rates on a device.
935 This option only enables generic Block IO controller infrastructure.
936 One needs to also enable actual IO controlling logic/policy. For
937 enabling proportional weight division of disk bandwidth in CFQ, set
938 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
939 CONFIG_BLK_DEV_THROTTLING=y.
941 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
943 config CGROUP_WRITEBACK
945 depends on MEMCG && BLK_CGROUP
948 menuconfig CGROUP_SCHED
949 bool "CPU controller"
952 This feature lets CPU scheduler recognize task groups and control CPU
953 bandwidth allocation to such task groups. It uses cgroups to group
957 config FAIR_GROUP_SCHED
958 bool "Group scheduling for SCHED_OTHER"
959 depends on CGROUP_SCHED
963 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
964 depends on FAIR_GROUP_SCHED
967 This option allows users to define CPU bandwidth rates (limits) for
968 tasks running within the fair group scheduler. Groups with no limit
969 set are considered to be unconstrained and will run with no
971 See Documentation/scheduler/sched-bwc.rst for more information.
973 config RT_GROUP_SCHED
974 bool "Group scheduling for SCHED_RR/FIFO"
975 depends on CGROUP_SCHED
978 This feature lets you explicitly allocate real CPU bandwidth
979 to task groups. If enabled, it will also make it impossible to
980 schedule realtime tasks for non-root users until you allocate
981 realtime bandwidth for them.
982 See Documentation/scheduler/sched-rt-group.rst for more information.
986 config UCLAMP_TASK_GROUP
987 bool "Utilization clamping per group of tasks"
988 depends on CGROUP_SCHED
989 depends on UCLAMP_TASK
992 This feature enables the scheduler to track the clamped utilization
993 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
995 When this option is enabled, the user can specify a min and max
996 CPU bandwidth which is allowed for each single task in a group.
997 The max bandwidth allows to clamp the maximum frequency a task
998 can use, while the min bandwidth allows to define a minimum
999 frequency a task will always use.
1001 When task group based utilization clamping is enabled, an eventually
1002 specified task-specific clamp value is constrained by the cgroup
1003 specified clamp value. Both minimum and maximum task clamping cannot
1004 be bigger than the corresponding clamping defined at task group level.
1009 bool "PIDs controller"
1011 Provides enforcement of process number limits in the scope of a
1012 cgroup. Any attempt to fork more processes than is allowed in the
1013 cgroup will fail. PIDs are fundamentally a global resource because it
1014 is fairly trivial to reach PID exhaustion before you reach even a
1015 conservative kmemcg limit. As a result, it is possible to grind a
1016 system to halt without being limited by other cgroup policies. The
1017 PIDs controller is designed to stop this from happening.
1019 It should be noted that organisational operations (such as attaching
1020 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1021 since the PIDs limit only affects a process's ability to fork, not to
1025 bool "RDMA controller"
1027 Provides enforcement of RDMA resources defined by IB stack.
1028 It is fairly easy for consumers to exhaust RDMA resources, which
1029 can result into resource unavailability to other consumers.
1030 RDMA controller is designed to stop this from happening.
1031 Attaching processes with active RDMA resources to the cgroup
1032 hierarchy is allowed even if can cross the hierarchy's limit.
1034 config CGROUP_FREEZER
1035 bool "Freezer controller"
1037 Provides a way to freeze and unfreeze all tasks in a
1040 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1041 controller includes important in-kernel memory consumers per default.
1043 If you're using cgroup2, say N.
1045 config CGROUP_HUGETLB
1046 bool "HugeTLB controller"
1047 depends on HUGETLB_PAGE
1051 Provides a cgroup controller for HugeTLB pages.
1052 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1053 The limit is enforced during page fault. Since HugeTLB doesn't
1054 support page reclaim, enforcing the limit at page fault time implies
1055 that, the application will get SIGBUS signal if it tries to access
1056 HugeTLB pages beyond its limit. This requires the application to know
1057 beforehand how much HugeTLB pages it would require for its use. The
1058 control group is tracked in the third page lru pointer. This means
1059 that we cannot use the controller with huge page less than 3 pages.
1062 bool "Cpuset controller"
1065 This option will let you create and manage CPUSETs which
1066 allow dynamically partitioning a system into sets of CPUs and
1067 Memory Nodes and assigning tasks to run only within those sets.
1068 This is primarily useful on large SMP or NUMA systems.
1072 config PROC_PID_CPUSET
1073 bool "Include legacy /proc/<pid>/cpuset file"
1077 config CGROUP_DEVICE
1078 bool "Device controller"
1080 Provides a cgroup controller implementing whitelists for
1081 devices which a process in the cgroup can mknod or open.
1083 config CGROUP_CPUACCT
1084 bool "Simple CPU accounting controller"
1086 Provides a simple controller for monitoring the
1087 total CPU consumed by the tasks in a cgroup.
1090 bool "Perf controller"
1091 depends on PERF_EVENTS
1093 This option extends the perf per-cpu mode to restrict monitoring
1094 to threads which belong to the cgroup specified and run on the
1095 designated cpu. Or this can be used to have cgroup ID in samples
1096 so that it can monitor performance events among cgroups.
1101 bool "Support for eBPF programs attached to cgroups"
1102 depends on BPF_SYSCALL
1103 select SOCK_CGROUP_DATA
1105 Allow attaching eBPF programs to a cgroup using the bpf(2)
1106 syscall command BPF_PROG_ATTACH.
1108 In which context these programs are accessed depends on the type
1109 of attachment. For instance, programs that are attached using
1110 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1114 bool "Misc resource controller"
1117 Provides a controller for miscellaneous resources on a host.
1119 Miscellaneous scalar resources are the resources on the host system
1120 which cannot be abstracted like the other cgroups. This controller
1121 tracks and limits the miscellaneous resources used by a process
1122 attached to a cgroup hierarchy.
1124 For more information, please check misc cgroup section in
1125 /Documentation/admin-guide/cgroup-v2.rst.
1128 bool "Debug controller"
1130 depends on DEBUG_KERNEL
1132 This option enables a simple controller that exports
1133 debugging information about the cgroups framework. This
1134 controller is for control cgroup debugging only. Its
1135 interfaces are not stable.
1139 config SOCK_CGROUP_DATA
1145 menuconfig NAMESPACES
1146 bool "Namespaces support" if EXPERT
1147 depends on MULTIUSER
1150 Provides the way to make tasks work with different objects using
1151 the same id. For example same IPC id may refer to different objects
1152 or same user id or pid may refer to different tasks when used in
1153 different namespaces.
1158 bool "UTS namespace"
1161 In this namespace tasks see different info provided with the
1165 bool "TIME namespace"
1166 depends on GENERIC_VDSO_TIME_NS
1169 In this namespace boottime and monotonic clocks can be set.
1170 The time will keep going with the same pace.
1173 bool "IPC namespace"
1174 depends on (SYSVIPC || POSIX_MQUEUE)
1177 In this namespace tasks work with IPC ids which correspond to
1178 different IPC objects in different namespaces.
1181 bool "User namespace"
1184 This allows containers, i.e. vservers, to use user namespaces
1185 to provide different user info for different servers.
1187 When user namespaces are enabled in the kernel it is
1188 recommended that the MEMCG option also be enabled and that
1189 user-space use the memory control groups to limit the amount
1190 of memory a memory unprivileged users can use.
1195 bool "PID Namespaces"
1198 Support process id namespaces. This allows having multiple
1199 processes with the same pid as long as they are in different
1200 pid namespaces. This is a building block of containers.
1203 bool "Network namespace"
1207 Allow user space to create what appear to be multiple instances
1208 of the network stack.
1212 config CHECKPOINT_RESTORE
1213 bool "Checkpoint/restore support"
1214 select PROC_CHILDREN
1218 Enables additional kernel features in a sake of checkpoint/restore.
1219 In particular it adds auxiliary prctl codes to setup process text,
1220 data and heap segment sizes, and a few additional /proc filesystem
1223 If unsure, say N here.
1225 config SCHED_AUTOGROUP
1226 bool "Automatic process group scheduling"
1229 select FAIR_GROUP_SCHED
1231 This option optimizes the scheduler for common desktop workloads by
1232 automatically creating and populating task groups. This separation
1233 of workloads isolates aggressive CPU burners (like build jobs) from
1234 desktop applications. Task group autogeneration is currently based
1237 config SYSFS_DEPRECATED
1238 bool "Enable deprecated sysfs features to support old userspace tools"
1242 This option adds code that switches the layout of the "block" class
1243 devices, to not show up in /sys/class/block/, but only in
1246 This switch is only active when the sysfs.deprecated=1 boot option is
1247 passed or the SYSFS_DEPRECATED_V2 option is set.
1249 This option allows new kernels to run on old distributions and tools,
1250 which might get confused by /sys/class/block/. Since 2007/2008 all
1251 major distributions and tools handle this just fine.
1253 Recent distributions and userspace tools after 2009/2010 depend on
1254 the existence of /sys/class/block/, and will not work with this
1257 Only if you are using a new kernel on an old distribution, you might
1260 config SYSFS_DEPRECATED_V2
1261 bool "Enable deprecated sysfs features by default"
1264 depends on SYSFS_DEPRECATED
1266 Enable deprecated sysfs by default.
1268 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1271 Only if you are using a new kernel on an old distribution, you might
1272 need to say Y here. Even then, odds are you would not need it
1273 enabled, you can always pass the boot option if absolutely necessary.
1276 bool "Kernel->user space relay support (formerly relayfs)"
1279 This option enables support for relay interface support in
1280 certain file systems (such as debugfs).
1281 It is designed to provide an efficient mechanism for tools and
1282 facilities to relay large amounts of data from kernel space to
1287 config BLK_DEV_INITRD
1288 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1290 The initial RAM filesystem is a ramfs which is loaded by the
1291 boot loader (loadlin or lilo) and that is mounted as root
1292 before the normal boot procedure. It is typically used to
1293 load modules needed to mount the "real" root file system,
1294 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1296 If RAM disk support (BLK_DEV_RAM) is also included, this
1297 also enables initial RAM disk (initrd) support and adds
1298 15 Kbytes (more on some other architectures) to the kernel size.
1304 source "usr/Kconfig"
1309 bool "Boot config support"
1310 select BLK_DEV_INITRD
1312 Extra boot config allows system admin to pass a config file as
1313 complemental extension of kernel cmdline when booting.
1314 The boot config file must be attached at the end of initramfs
1315 with checksum, size and magic word.
1316 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1321 prompt "Compiler optimization level"
1322 default CC_OPTIMIZE_FOR_PERFORMANCE
1324 config CC_OPTIMIZE_FOR_PERFORMANCE
1325 bool "Optimize for performance (-O2)"
1327 This is the default optimization level for the kernel, building
1328 with the "-O2" compiler flag for best performance and most
1329 helpful compile-time warnings.
1331 config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1332 bool "Optimize more for performance (-O3)"
1335 Choosing this option will pass "-O3" to your compiler to optimize
1336 the kernel yet more for performance.
1338 config CC_OPTIMIZE_FOR_SIZE
1339 bool "Optimize for size (-Os)"
1341 Choosing this option will pass "-Os" to your compiler resulting
1342 in a smaller kernel.
1346 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1349 This requires that the arch annotates or otherwise protects
1350 its external entry points from being discarded. Linker scripts
1351 must also merge .text.*, .data.*, and .bss.* correctly into
1352 output sections. Care must be taken not to pull in unrelated
1353 sections (e.g., '.text.init'). Typically '.' in section names
1354 is used to distinguish them from label names / C identifiers.
1356 config LD_DEAD_CODE_DATA_ELIMINATION
1357 bool "Dead code and data elimination (EXPERIMENTAL)"
1358 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1360 depends on $(cc-option,-ffunction-sections -fdata-sections)
1361 depends on $(ld-option,--gc-sections)
1363 Enable this if you want to do dead code and data elimination with
1364 the linker by compiling with -ffunction-sections -fdata-sections,
1365 and linking with --gc-sections.
1367 This can reduce on disk and in-memory size of the kernel
1368 code and static data, particularly for small configs and
1369 on small systems. This has the possibility of introducing
1370 silently broken kernel if the required annotations are not
1371 present. This option is not well tested yet, so use at your
1374 config LD_ORPHAN_WARN
1376 depends on ARCH_WANT_LD_ORPHAN_WARN
1377 depends on !LD_IS_LLD || LLD_VERSION >= 110000
1378 depends on $(ld-option,--orphan-handling=warn)
1386 config SYSCTL_EXCEPTION_TRACE
1389 Enable support for /proc/sys/debug/exception-trace.
1391 config SYSCTL_ARCH_UNALIGN_NO_WARN
1394 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1395 Allows arch to define/use @no_unaligned_warning to possibly warn
1396 about unaligned access emulation going on under the hood.
1398 config SYSCTL_ARCH_UNALIGN_ALLOW
1401 Enable support for /proc/sys/kernel/unaligned-trap
1402 Allows arches to define/use @unaligned_enabled to runtime toggle
1403 the unaligned access emulation.
1404 see arch/parisc/kernel/unaligned.c for reference
1406 config HAVE_PCSPKR_PLATFORM
1409 # interpreter that classic socket filters depend on
1414 bool "Configure standard kernel features (expert users)"
1415 # Unhide debug options, to make the on-by-default options visible
1418 This option allows certain base kernel options and settings
1419 to be disabled or tweaked. This is for specialized
1420 environments which can tolerate a "non-standard" kernel.
1421 Only use this if you really know what you are doing.
1424 bool "Enable 16-bit UID system calls" if EXPERT
1425 depends on HAVE_UID16 && MULTIUSER
1428 This enables the legacy 16-bit UID syscall wrappers.
1431 bool "Multiple users, groups and capabilities support" if EXPERT
1434 This option enables support for non-root users, groups and
1437 If you say N here, all processes will run with UID 0, GID 0, and all
1438 possible capabilities. Saying N here also compiles out support for
1439 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1442 If unsure, say Y here.
1444 config SGETMASK_SYSCALL
1445 bool "sgetmask/ssetmask syscalls support" if EXPERT
1446 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1448 sys_sgetmask and sys_ssetmask are obsolete system calls
1449 no longer supported in libc but still enabled by default in some
1452 If unsure, leave the default option here.
1454 config SYSFS_SYSCALL
1455 bool "Sysfs syscall support" if EXPERT
1458 sys_sysfs is an obsolete system call no longer supported in libc.
1459 Note that disabling this option is more secure but might break
1460 compatibility with some systems.
1462 If unsure say Y here.
1465 bool "open by fhandle syscalls" if EXPERT
1469 If you say Y here, a user level program will be able to map
1470 file names to handle and then later use the handle for
1471 different file system operations. This is useful in implementing
1472 userspace file servers, which now track files using handles instead
1473 of names. The handle would remain the same even if file names
1474 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1478 bool "Posix Clocks & timers" if EXPERT
1481 This includes native support for POSIX timers to the kernel.
1482 Some embedded systems have no use for them and therefore they
1483 can be configured out to reduce the size of the kernel image.
1485 When this option is disabled, the following syscalls won't be
1486 available: timer_create, timer_gettime: timer_getoverrun,
1487 timer_settime, timer_delete, clock_adjtime, getitimer,
1488 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1489 clock_getres and clock_nanosleep syscalls will be limited to
1490 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1496 bool "Enable support for printk" if EXPERT
1499 This option enables normal printk support. Removing it
1500 eliminates most of the message strings from the kernel image
1501 and makes the kernel more or less silent. As this makes it
1502 very difficult to diagnose system problems, saying N here is
1503 strongly discouraged.
1511 bool "BUG() support" if EXPERT
1514 Disabling this option eliminates support for BUG and WARN, reducing
1515 the size of your kernel image and potentially quietly ignoring
1516 numerous fatal conditions. You should only consider disabling this
1517 option for embedded systems with no facilities for reporting errors.
1523 bool "Enable ELF core dumps" if EXPERT
1525 Enable support for generating core dumps. Disabling saves about 4k.
1528 config PCSPKR_PLATFORM
1529 bool "Enable PC-Speaker support" if EXPERT
1530 depends on HAVE_PCSPKR_PLATFORM
1534 This option allows to disable the internal PC-Speaker
1535 support, saving some memory.
1539 bool "Enable full-sized data structures for core" if EXPERT
1541 Disabling this option reduces the size of miscellaneous core
1542 kernel data structures. This saves memory on small machines,
1543 but may reduce performance.
1546 bool "Enable futex support" if EXPERT
1550 Disabling this option will cause the kernel to be built without
1551 support for "fast userspace mutexes". The resulting kernel may not
1552 run glibc-based applications correctly.
1556 depends on FUTEX && RT_MUTEXES
1559 config HAVE_FUTEX_CMPXCHG
1563 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1564 is implemented and always working. This removes a couple of runtime
1568 bool "Enable eventpoll support" if EXPERT
1571 Disabling this option will cause the kernel to be built without
1572 support for epoll family of system calls.
1575 bool "Enable signalfd() system call" if EXPERT
1578 Enable the signalfd() system call that allows to receive signals
1579 on a file descriptor.
1584 bool "Enable timerfd() system call" if EXPERT
1587 Enable the timerfd() system call that allows to receive timer
1588 events on a file descriptor.
1593 bool "Enable eventfd() system call" if EXPERT
1596 Enable the eventfd() system call that allows to receive both
1597 kernel notification (ie. KAIO) or userspace notifications.
1602 bool "Use full shmem filesystem" if EXPERT
1606 The shmem is an internal filesystem used to manage shared memory.
1607 It is backed by swap and manages resource limits. It is also exported
1608 to userspace as tmpfs if TMPFS is enabled. Disabling this
1609 option replaces shmem and tmpfs with the much simpler ramfs code,
1610 which may be appropriate on small systems without swap.
1613 bool "Enable AIO support" if EXPERT
1616 This option enables POSIX asynchronous I/O which may by used
1617 by some high performance threaded applications. Disabling
1618 this option saves about 7k.
1621 bool "Enable IO uring support" if EXPERT
1625 This option enables support for the io_uring interface, enabling
1626 applications to submit and complete IO through submission and
1627 completion rings that are shared between the kernel and application.
1629 config ADVISE_SYSCALLS
1630 bool "Enable madvise/fadvise syscalls" if EXPERT
1633 This option enables the madvise and fadvise syscalls, used by
1634 applications to advise the kernel about their future memory or file
1635 usage, improving performance. If building an embedded system where no
1636 applications use these syscalls, you can disable this option to save
1639 config HAVE_ARCH_USERFAULTFD_WP
1642 Arch has userfaultfd write protection support
1645 bool "Enable membarrier() system call" if EXPERT
1648 Enable the membarrier() system call that allows issuing memory
1649 barriers across all running threads, which can be used to distribute
1650 the cost of user-space memory barriers asymmetrically by transforming
1651 pairs of memory barriers into pairs consisting of membarrier() and a
1657 bool "Load all symbols for debugging/ksymoops" if EXPERT
1660 Say Y here to let the kernel print out symbolic crash information and
1661 symbolic stack backtraces. This increases the size of the kernel
1662 somewhat, as all symbols have to be loaded into the kernel image.
1665 bool "Include all symbols in kallsyms"
1666 depends on DEBUG_KERNEL && KALLSYMS
1668 Normally kallsyms only contains the symbols of functions for nicer
1669 OOPS messages and backtraces (i.e., symbols from the text and inittext
1670 sections). This is sufficient for most cases. And only in very rare
1671 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1672 names of variables from the data sections, etc).
1674 This option makes sure that all symbols are loaded into the kernel
1675 image (i.e., symbols from all sections) in cost of increased kernel
1676 size (depending on the kernel configuration, it may be 300KiB or
1677 something like this).
1679 Say N unless you really need all symbols.
1681 config KALLSYMS_ABSOLUTE_PERCPU
1684 default X86_64 && SMP
1686 config KALLSYMS_BASE_RELATIVE
1691 Instead of emitting them as absolute values in the native word size,
1692 emit the symbol references in the kallsyms table as 32-bit entries,
1693 each containing a relative value in the range [base, base + U32_MAX]
1694 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1695 an absolute value in the range [0, S32_MAX] or a relative value in the
1696 range [base, base + S32_MAX], where base is the lowest relative symbol
1697 address encountered in the image.
1699 On 64-bit builds, this reduces the size of the address table by 50%,
1700 but more importantly, it results in entries whose values are build
1701 time constants, and no relocation pass is required at runtime to fix
1702 up the entries based on the runtime load address of the kernel.
1704 # end of the "standard kernel features (expert users)" menu
1706 # syscall, maps, verifier
1709 bool "LSM Instrumentation with BPF"
1710 depends on BPF_EVENTS
1711 depends on BPF_SYSCALL
1715 Enables instrumentation of the security hooks with eBPF programs for
1716 implementing dynamic MAC and Audit Policies.
1718 If you are unsure how to answer this question, answer N.
1721 bool "Enable bpf() system call"
1724 select TASKS_TRACE_RCU
1727 Enable the bpf() system call that allows to manipulate eBPF
1728 programs and maps via file descriptors.
1730 config ARCH_WANT_DEFAULT_BPF_JIT
1733 config BPF_JIT_ALWAYS_ON
1734 bool "Permanently enable BPF JIT and remove BPF interpreter"
1735 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1737 Enables BPF JIT and removes BPF interpreter to avoid
1738 speculative execution of BPF instructions by the interpreter
1740 config BPF_JIT_DEFAULT_ON
1741 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
1742 depends on HAVE_EBPF_JIT && BPF_JIT
1744 source "kernel/bpf/preload/Kconfig"
1747 bool "Enable userfaultfd() system call"
1750 Enable the userfaultfd() system call that allows to intercept and
1751 handle page faults in userland.
1753 config ARCH_HAS_MEMBARRIER_CALLBACKS
1756 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1760 bool "Enable kcmp() system call" if EXPERT
1762 Enable the kernel resource comparison system call. It provides
1763 user-space with the ability to compare two processes to see if they
1764 share a common resource, such as a file descriptor or even virtual
1770 bool "Enable rseq() system call" if EXPERT
1772 depends on HAVE_RSEQ
1775 Enable the restartable sequences system call. It provides a
1776 user-space cache for the current CPU number value, which
1777 speeds up getting the current CPU number from user-space,
1778 as well as an ABI to speed up user-space operations on
1785 bool "Enabled debugging of rseq() system call" if EXPERT
1786 depends on RSEQ && DEBUG_KERNEL
1788 Enable extra debugging checks for the rseq system call.
1793 bool "Embedded system"
1794 option allnoconfig_y
1797 This option should be enabled if compiling the kernel for
1798 an embedded system so certain expert options are available
1801 config HAVE_PERF_EVENTS
1804 See tools/perf/design.txt for details.
1806 config PERF_USE_VMALLOC
1809 See tools/perf/design.txt for details
1812 bool "PC/104 support" if EXPERT
1814 Expose PC/104 form factor device drivers and options available for
1815 selection and configuration. Enable this option if your target
1816 machine has a PC/104 bus.
1818 menu "Kernel Performance Events And Counters"
1821 bool "Kernel performance events and counters"
1822 default y if PROFILING
1823 depends on HAVE_PERF_EVENTS
1827 Enable kernel support for various performance events provided
1828 by software and hardware.
1830 Software events are supported either built-in or via the
1831 use of generic tracepoints.
1833 Most modern CPUs support performance events via performance
1834 counter registers. These registers count the number of certain
1835 types of hw events: such as instructions executed, cachemisses
1836 suffered, or branches mis-predicted - without slowing down the
1837 kernel or applications. These registers can also trigger interrupts
1838 when a threshold number of events have passed - and can thus be
1839 used to profile the code that runs on that CPU.
1841 The Linux Performance Event subsystem provides an abstraction of
1842 these software and hardware event capabilities, available via a
1843 system call and used by the "perf" utility in tools/perf/. It
1844 provides per task and per CPU counters, and it provides event
1845 capabilities on top of those.
1849 config DEBUG_PERF_USE_VMALLOC
1851 bool "Debug: use vmalloc to back perf mmap() buffers"
1852 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1853 select PERF_USE_VMALLOC
1855 Use vmalloc memory to back perf mmap() buffers.
1857 Mostly useful for debugging the vmalloc code on platforms
1858 that don't require it.
1864 config VM_EVENT_COUNTERS
1866 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1868 VM event counters are needed for event counts to be shown.
1869 This option allows the disabling of the VM event counters
1870 on EXPERT systems. /proc/vmstat will only show page counts
1871 if VM event counters are disabled.
1875 bool "Enable SLUB debugging support" if EXPERT
1876 depends on SLUB && SYSFS
1878 SLUB has extensive debug support features. Disabling these can
1879 result in significant savings in code size. This also disables
1880 SLUB sysfs support. /sys/slab will not exist and there will be
1881 no support for cache validation etc.
1884 bool "Disable heap randomization"
1887 Randomizing heap placement makes heap exploits harder, but it
1888 also breaks ancient binaries (including anything libc5 based).
1889 This option changes the bootup default to heap randomization
1890 disabled, and can be overridden at runtime by setting
1891 /proc/sys/kernel/randomize_va_space to 2.
1893 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1896 prompt "Choose SLAB allocator"
1899 This option allows to select a slab allocator.
1903 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1905 The regular slab allocator that is established and known to work
1906 well in all environments. It organizes cache hot objects in
1907 per cpu and per node queues.
1910 bool "SLUB (Unqueued Allocator)"
1911 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1913 SLUB is a slab allocator that minimizes cache line usage
1914 instead of managing queues of cached objects (SLAB approach).
1915 Per cpu caching is realized using slabs of objects instead
1916 of queues of objects. SLUB can use memory efficiently
1917 and has enhanced diagnostics. SLUB is the default choice for
1922 bool "SLOB (Simple Allocator)"
1924 SLOB replaces the stock allocator with a drastically simpler
1925 allocator. SLOB is generally more space efficient but
1926 does not perform as well on large systems.
1930 config SLAB_MERGE_DEFAULT
1931 bool "Allow slab caches to be merged"
1934 For reduced kernel memory fragmentation, slab caches can be
1935 merged when they share the same size and other characteristics.
1936 This carries a risk of kernel heap overflows being able to
1937 overwrite objects from merged caches (and more easily control
1938 cache layout), which makes such heap attacks easier to exploit
1939 by attackers. By keeping caches unmerged, these kinds of exploits
1940 can usually only damage objects in the same cache. To disable
1941 merging at runtime, "slab_nomerge" can be passed on the kernel
1944 config SLAB_FREELIST_RANDOM
1945 bool "Randomize slab freelist"
1946 depends on SLAB || SLUB
1948 Randomizes the freelist order used on creating new pages. This
1949 security feature reduces the predictability of the kernel slab
1950 allocator against heap overflows.
1952 config SLAB_FREELIST_HARDENED
1953 bool "Harden slab freelist metadata"
1954 depends on SLAB || SLUB
1956 Many kernel heap attacks try to target slab cache metadata and
1957 other infrastructure. This options makes minor performance
1958 sacrifices to harden the kernel slab allocator against common
1959 freelist exploit methods. Some slab implementations have more
1960 sanity-checking than others. This option is most effective with
1963 config SHUFFLE_PAGE_ALLOCATOR
1964 bool "Page allocator randomization"
1965 default SLAB_FREELIST_RANDOM && ACPI_NUMA
1967 Randomization of the page allocator improves the average
1968 utilization of a direct-mapped memory-side-cache. See section
1969 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1970 6.2a specification for an example of how a platform advertises
1971 the presence of a memory-side-cache. There are also incidental
1972 security benefits as it reduces the predictability of page
1973 allocations to compliment SLAB_FREELIST_RANDOM, but the
1974 default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1975 10th order of pages is selected based on cache utilization
1978 While the randomization improves cache utilization it may
1979 negatively impact workloads on platforms without a cache. For
1980 this reason, by default, the randomization is enabled only
1981 after runtime detection of a direct-mapped memory-side-cache.
1982 Otherwise, the randomization may be force enabled with the
1983 'page_alloc.shuffle' kernel command line parameter.
1987 config SLUB_CPU_PARTIAL
1989 depends on SLUB && SMP
1990 bool "SLUB per cpu partial cache"
1992 Per cpu partial caches accelerate objects allocation and freeing
1993 that is local to a processor at the price of more indeterminism
1994 in the latency of the free. On overflow these caches will be cleared
1995 which requires the taking of locks that may cause latency spikes.
1996 Typically one would choose no for a realtime system.
1998 config MMAP_ALLOW_UNINITIALIZED
1999 bool "Allow mmapped anonymous memory to be uninitialized"
2000 depends on EXPERT && !MMU
2003 Normally, and according to the Linux spec, anonymous memory obtained
2004 from mmap() has its contents cleared before it is passed to
2005 userspace. Enabling this config option allows you to request that
2006 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
2007 providing a huge performance boost. If this option is not enabled,
2008 then the flag will be ignored.
2010 This is taken advantage of by uClibc's malloc(), and also by
2011 ELF-FDPIC binfmt's brk and stack allocator.
2013 Because of the obvious security issues, this option should only be
2014 enabled on embedded devices where you control what is run in
2015 userspace. Since that isn't generally a problem on no-MMU systems,
2016 it is normally safe to say Y here.
2018 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
2020 config SYSTEM_DATA_VERIFICATION
2022 select SYSTEM_TRUSTED_KEYRING
2026 select ASYMMETRIC_KEY_TYPE
2027 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
2030 select X509_CERTIFICATE_PARSER
2031 select PKCS7_MESSAGE_PARSER
2033 Provide PKCS#7 message verification using the contents of the system
2034 trusted keyring to provide public keys. This then can be used for
2035 module verification, kexec image verification and firmware blob
2039 bool "Profiling support"
2041 Say Y here to enable the extended profiling support mechanisms used
2045 # Place an empty function call at each tracepoint site. Can be
2046 # dynamically changed for a probe function.
2051 endmenu # General setup
2053 source "arch/Kconfig"
2060 default 0 if BASE_FULL
2061 default 1 if !BASE_FULL
2063 config MODULE_SIG_FORMAT
2065 select SYSTEM_DATA_VERIFICATION
2068 bool "Enable loadable module support"
2071 Kernel modules are small pieces of compiled code which can
2072 be inserted in the running kernel, rather than being
2073 permanently built into the kernel. You use the "modprobe"
2074 tool to add (and sometimes remove) them. If you say Y here,
2075 many parts of the kernel can be built as modules (by
2076 answering M instead of Y where indicated): this is most
2077 useful for infrequently used options which are not required
2078 for booting. For more information, see the man pages for
2079 modprobe, lsmod, modinfo, insmod and rmmod.
2081 If you say Y here, you will need to run "make
2082 modules_install" to put the modules under /lib/modules/
2083 where modprobe can find them (you may need to be root to do
2090 config MODULE_FORCE_LOAD
2091 bool "Forced module loading"
2094 Allow loading of modules without version information (ie. modprobe
2095 --force). Forced module loading sets the 'F' (forced) taint flag and
2096 is usually a really bad idea.
2098 config MODULE_UNLOAD
2099 bool "Module unloading"
2101 Without this option you will not be able to unload any
2102 modules (note that some modules may not be unloadable
2103 anyway), which makes your kernel smaller, faster
2104 and simpler. If unsure, say Y.
2106 config MODULE_FORCE_UNLOAD
2107 bool "Forced module unloading"
2108 depends on MODULE_UNLOAD
2110 This option allows you to force a module to unload, even if the
2111 kernel believes it is unsafe: the kernel will remove the module
2112 without waiting for anyone to stop using it (using the -f option to
2113 rmmod). This is mainly for kernel developers and desperate users.
2117 bool "Module versioning support"
2119 Usually, you have to use modules compiled with your kernel.
2120 Saying Y here makes it sometimes possible to use modules
2121 compiled for different kernels, by adding enough information
2122 to the modules to (hopefully) spot any changes which would
2123 make them incompatible with the kernel you are running. If
2126 config ASM_MODVERSIONS
2128 default HAVE_ASM_MODVERSIONS && MODVERSIONS
2130 This enables module versioning for exported symbols also from
2131 assembly. This can be enabled only when the target architecture
2134 config MODULE_REL_CRCS
2136 depends on MODVERSIONS
2138 config MODULE_SRCVERSION_ALL
2139 bool "Source checksum for all modules"
2141 Modules which contain a MODULE_VERSION get an extra "srcversion"
2142 field inserted into their modinfo section, which contains a
2143 sum of the source files which made it. This helps maintainers
2144 see exactly which source was used to build a module (since
2145 others sometimes change the module source without updating
2146 the version). With this option, such a "srcversion" field
2147 will be created for all modules. If unsure, say N.
2150 bool "Module signature verification"
2151 select MODULE_SIG_FORMAT
2153 Check modules for valid signatures upon load: the signature
2154 is simply appended to the module. For more information see
2155 <file:Documentation/admin-guide/module-signing.rst>.
2157 Note that this option adds the OpenSSL development packages as a
2158 kernel build dependency so that the signing tool can use its crypto
2161 You should enable this option if you wish to use either
2162 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2163 another LSM - otherwise unsigned modules will be loadable regardless
2164 of the lockdown policy.
2166 !!!WARNING!!! If you enable this option, you MUST make sure that the
2167 module DOES NOT get stripped after being signed. This includes the
2168 debuginfo strip done by some packagers (such as rpmbuild) and
2169 inclusion into an initramfs that wants the module size reduced.
2171 config MODULE_SIG_FORCE
2172 bool "Require modules to be validly signed"
2173 depends on MODULE_SIG
2175 Reject unsigned modules or signed modules for which we don't have a
2176 key. Without this, such modules will simply taint the kernel.
2178 config MODULE_SIG_ALL
2179 bool "Automatically sign all modules"
2181 depends on MODULE_SIG
2183 Sign all modules during make modules_install. Without this option,
2184 modules must be signed manually, using the scripts/sign-file tool.
2186 comment "Do not forget to sign required modules with scripts/sign-file"
2187 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2190 prompt "Which hash algorithm should modules be signed with?"
2191 depends on MODULE_SIG
2193 This determines which sort of hashing algorithm will be used during
2194 signature generation. This algorithm _must_ be built into the kernel
2195 directly so that signature verification can take place. It is not
2196 possible to load a signed module containing the algorithm to check
2197 the signature on that module.
2199 config MODULE_SIG_SHA1
2200 bool "Sign modules with SHA-1"
2203 config MODULE_SIG_SHA224
2204 bool "Sign modules with SHA-224"
2205 select CRYPTO_SHA256
2207 config MODULE_SIG_SHA256
2208 bool "Sign modules with SHA-256"
2209 select CRYPTO_SHA256
2211 config MODULE_SIG_SHA384
2212 bool "Sign modules with SHA-384"
2213 select CRYPTO_SHA512
2215 config MODULE_SIG_SHA512
2216 bool "Sign modules with SHA-512"
2217 select CRYPTO_SHA512
2221 config MODULE_SIG_HASH
2223 depends on MODULE_SIG
2224 default "sha1" if MODULE_SIG_SHA1
2225 default "sha224" if MODULE_SIG_SHA224
2226 default "sha256" if MODULE_SIG_SHA256
2227 default "sha384" if MODULE_SIG_SHA384
2228 default "sha512" if MODULE_SIG_SHA512
2230 config MODULE_COMPRESS
2231 bool "Compress modules on installation"
2234 Compresses kernel modules when 'make modules_install' is run; gzip or
2235 xz depending on "Compression algorithm" below.
2237 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2239 Out-of-tree kernel modules installed using Kbuild will also be
2240 compressed upon installation.
2242 Note: for modules inside an initrd or initramfs, it's more efficient
2243 to compress the whole initrd or initramfs instead.
2245 Note: This is fully compatible with signed modules.
2250 prompt "Compression algorithm"
2251 depends on MODULE_COMPRESS
2252 default MODULE_COMPRESS_GZIP
2254 This determines which sort of compression will be used during
2255 'make modules_install'.
2257 GZIP (default) and XZ are supported.
2259 config MODULE_COMPRESS_GZIP
2262 config MODULE_COMPRESS_XZ
2267 config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2268 bool "Allow loading of modules with missing namespace imports"
2270 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2271 a namespace. A module that makes use of a symbol exported with such a
2272 namespace is required to import the namespace via MODULE_IMPORT_NS().
2273 There is no technical reason to enforce correct namespace imports,
2274 but it creates consistency between symbols defining namespaces and
2275 users importing namespaces they make use of. This option relaxes this
2276 requirement and lifts the enforcement when loading a module.
2280 config TRIM_UNUSED_KSYMS
2281 bool "Trim unused exported kernel symbols" if EXPERT
2282 depends on !COMPILE_TEST
2284 The kernel and some modules make many symbols available for
2285 other modules to use via EXPORT_SYMBOL() and variants. Depending
2286 on the set of modules being selected in your kernel configuration,
2287 many of those exported symbols might never be used.
2289 This option allows for unused exported symbols to be dropped from
2290 the build. In turn, this provides the compiler more opportunities
2291 (especially when using LTO) for optimizing the code and reducing
2292 binary size. This might have some security advantages as well.
2294 If unsure, or if you need to build out-of-tree modules, say N.
2296 config UNUSED_KSYMS_WHITELIST
2297 string "Whitelist of symbols to keep in ksymtab"
2298 depends on TRIM_UNUSED_KSYMS
2300 By default, all unused exported symbols will be un-exported from the
2301 build when TRIM_UNUSED_KSYMS is selected.
2303 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
2304 exported at all times, even in absence of in-tree users. The value to
2305 set here is the path to a text file containing the list of symbols,
2306 one per line. The path can be absolute, or relative to the kernel
2311 config MODULES_TREE_LOOKUP
2313 depends on PERF_EVENTS || TRACING || CFI_CLANG
2315 config INIT_ALL_POSSIBLE
2318 Back when each arch used to define their own cpu_online_mask and
2319 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2320 with all 1s, and others with all 0s. When they were centralised,
2321 it was better to provide this option than to break all the archs
2322 and have several arch maintainers pursuing me down dark alleys.
2324 source "block/Kconfig"
2326 config PREEMPT_NOTIFIERS
2336 Build a simple ASN.1 grammar compiler that produces a bytecode output
2337 that can be interpreted by the ASN.1 stream decoder and used to
2338 inform it as to what tags are to be expected in a stream and what
2339 functions to call on what tags.
2341 source "kernel/Kconfig.locks"
2343 config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2346 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2349 # It may be useful for an architecture to override the definitions of the
2350 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2351 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2352 # different calling convention for syscalls. They can also override the
2353 # macros for not-implemented syscalls in kernel/sys_ni.c and
2354 # kernel/time/posix-stubs.c. All these overrides need to be available in
2355 # <asm/syscall_wrapper.h>.
2356 config ARCH_HAS_SYSCALL_WRAPPER
projects / linux.git / blob