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
220 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
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 "Debug controller"
1116 depends on DEBUG_KERNEL
1118 This option enables a simple controller that exports
1119 debugging information about the cgroups framework. This
1120 controller is for control cgroup debugging only. Its
1121 interfaces are not stable.
1125 config SOCK_CGROUP_DATA
1131 menuconfig NAMESPACES
1132 bool "Namespaces support" if EXPERT
1133 depends on MULTIUSER
1136 Provides the way to make tasks work with different objects using
1137 the same id. For example same IPC id may refer to different objects
1138 or same user id or pid may refer to different tasks when used in
1139 different namespaces.
1144 bool "UTS namespace"
1147 In this namespace tasks see different info provided with the
1151 bool "TIME namespace"
1152 depends on GENERIC_VDSO_TIME_NS
1155 In this namespace boottime and monotonic clocks can be set.
1156 The time will keep going with the same pace.
1159 bool "IPC namespace"
1160 depends on (SYSVIPC || POSIX_MQUEUE)
1163 In this namespace tasks work with IPC ids which correspond to
1164 different IPC objects in different namespaces.
1167 bool "User namespace"
1170 This allows containers, i.e. vservers, to use user namespaces
1171 to provide different user info for different servers.
1173 When user namespaces are enabled in the kernel it is
1174 recommended that the MEMCG option also be enabled and that
1175 user-space use the memory control groups to limit the amount
1176 of memory a memory unprivileged users can use.
1181 bool "PID Namespaces"
1184 Support process id namespaces. This allows having multiple
1185 processes with the same pid as long as they are in different
1186 pid namespaces. This is a building block of containers.
1189 bool "Network namespace"
1193 Allow user space to create what appear to be multiple instances
1194 of the network stack.
1198 config CHECKPOINT_RESTORE
1199 bool "Checkpoint/restore support"
1200 select PROC_CHILDREN
1204 Enables additional kernel features in a sake of checkpoint/restore.
1205 In particular it adds auxiliary prctl codes to setup process text,
1206 data and heap segment sizes, and a few additional /proc filesystem
1209 If unsure, say N here.
1211 config SCHED_AUTOGROUP
1212 bool "Automatic process group scheduling"
1215 select FAIR_GROUP_SCHED
1217 This option optimizes the scheduler for common desktop workloads by
1218 automatically creating and populating task groups. This separation
1219 of workloads isolates aggressive CPU burners (like build jobs) from
1220 desktop applications. Task group autogeneration is currently based
1223 config SYSFS_DEPRECATED
1224 bool "Enable deprecated sysfs features to support old userspace tools"
1228 This option adds code that switches the layout of the "block" class
1229 devices, to not show up in /sys/class/block/, but only in
1232 This switch is only active when the sysfs.deprecated=1 boot option is
1233 passed or the SYSFS_DEPRECATED_V2 option is set.
1235 This option allows new kernels to run on old distributions and tools,
1236 which might get confused by /sys/class/block/. Since 2007/2008 all
1237 major distributions and tools handle this just fine.
1239 Recent distributions and userspace tools after 2009/2010 depend on
1240 the existence of /sys/class/block/, and will not work with this
1243 Only if you are using a new kernel on an old distribution, you might
1246 config SYSFS_DEPRECATED_V2
1247 bool "Enable deprecated sysfs features by default"
1250 depends on SYSFS_DEPRECATED
1252 Enable deprecated sysfs by default.
1254 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1257 Only if you are using a new kernel on an old distribution, you might
1258 need to say Y here. Even then, odds are you would not need it
1259 enabled, you can always pass the boot option if absolutely necessary.
1262 bool "Kernel->user space relay support (formerly relayfs)"
1265 This option enables support for relay interface support in
1266 certain file systems (such as debugfs).
1267 It is designed to provide an efficient mechanism for tools and
1268 facilities to relay large amounts of data from kernel space to
1273 config BLK_DEV_INITRD
1274 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1276 The initial RAM filesystem is a ramfs which is loaded by the
1277 boot loader (loadlin or lilo) and that is mounted as root
1278 before the normal boot procedure. It is typically used to
1279 load modules needed to mount the "real" root file system,
1280 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1282 If RAM disk support (BLK_DEV_RAM) is also included, this
1283 also enables initial RAM disk (initrd) support and adds
1284 15 Kbytes (more on some other architectures) to the kernel size.
1290 source "usr/Kconfig"
1295 bool "Boot config support"
1296 select BLK_DEV_INITRD
1298 Extra boot config allows system admin to pass a config file as
1299 complemental extension of kernel cmdline when booting.
1300 The boot config file must be attached at the end of initramfs
1301 with checksum, size and magic word.
1302 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1307 prompt "Compiler optimization level"
1308 default CC_OPTIMIZE_FOR_PERFORMANCE
1310 config CC_OPTIMIZE_FOR_PERFORMANCE
1311 bool "Optimize for performance (-O2)"
1313 This is the default optimization level for the kernel, building
1314 with the "-O2" compiler flag for best performance and most
1315 helpful compile-time warnings.
1317 config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1318 bool "Optimize more for performance (-O3)"
1321 Choosing this option will pass "-O3" to your compiler to optimize
1322 the kernel yet more for performance.
1324 config CC_OPTIMIZE_FOR_SIZE
1325 bool "Optimize for size (-Os)"
1327 Choosing this option will pass "-Os" to your compiler resulting
1328 in a smaller kernel.
1332 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1335 This requires that the arch annotates or otherwise protects
1336 its external entry points from being discarded. Linker scripts
1337 must also merge .text.*, .data.*, and .bss.* correctly into
1338 output sections. Care must be taken not to pull in unrelated
1339 sections (e.g., '.text.init'). Typically '.' in section names
1340 is used to distinguish them from label names / C identifiers.
1342 config LD_DEAD_CODE_DATA_ELIMINATION
1343 bool "Dead code and data elimination (EXPERIMENTAL)"
1344 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1346 depends on $(cc-option,-ffunction-sections -fdata-sections)
1347 depends on $(ld-option,--gc-sections)
1349 Enable this if you want to do dead code and data elimination with
1350 the linker by compiling with -ffunction-sections -fdata-sections,
1351 and linking with --gc-sections.
1353 This can reduce on disk and in-memory size of the kernel
1354 code and static data, particularly for small configs and
1355 on small systems. This has the possibility of introducing
1356 silently broken kernel if the required annotations are not
1357 present. This option is not well tested yet, so use at your
1360 config LD_ORPHAN_WARN
1362 depends on ARCH_WANT_LD_ORPHAN_WARN
1363 depends on !LD_IS_LLD || LLD_VERSION >= 110000
1364 depends on $(ld-option,--orphan-handling=warn)
1372 config SYSCTL_EXCEPTION_TRACE
1375 Enable support for /proc/sys/debug/exception-trace.
1377 config SYSCTL_ARCH_UNALIGN_NO_WARN
1380 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1381 Allows arch to define/use @no_unaligned_warning to possibly warn
1382 about unaligned access emulation going on under the hood.
1384 config SYSCTL_ARCH_UNALIGN_ALLOW
1387 Enable support for /proc/sys/kernel/unaligned-trap
1388 Allows arches to define/use @unaligned_enabled to runtime toggle
1389 the unaligned access emulation.
1390 see arch/parisc/kernel/unaligned.c for reference
1392 config HAVE_PCSPKR_PLATFORM
1395 # interpreter that classic socket filters depend on
1400 bool "Configure standard kernel features (expert users)"
1401 # Unhide debug options, to make the on-by-default options visible
1404 This option allows certain base kernel options and settings
1405 to be disabled or tweaked. This is for specialized
1406 environments which can tolerate a "non-standard" kernel.
1407 Only use this if you really know what you are doing.
1410 bool "Enable 16-bit UID system calls" if EXPERT
1411 depends on HAVE_UID16 && MULTIUSER
1414 This enables the legacy 16-bit UID syscall wrappers.
1417 bool "Multiple users, groups and capabilities support" if EXPERT
1420 This option enables support for non-root users, groups and
1423 If you say N here, all processes will run with UID 0, GID 0, and all
1424 possible capabilities. Saying N here also compiles out support for
1425 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1428 If unsure, say Y here.
1430 config SGETMASK_SYSCALL
1431 bool "sgetmask/ssetmask syscalls support" if EXPERT
1432 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1434 sys_sgetmask and sys_ssetmask are obsolete system calls
1435 no longer supported in libc but still enabled by default in some
1438 If unsure, leave the default option here.
1440 config SYSFS_SYSCALL
1441 bool "Sysfs syscall support" if EXPERT
1444 sys_sysfs is an obsolete system call no longer supported in libc.
1445 Note that disabling this option is more secure but might break
1446 compatibility with some systems.
1448 If unsure say Y here.
1451 bool "open by fhandle syscalls" if EXPERT
1455 If you say Y here, a user level program will be able to map
1456 file names to handle and then later use the handle for
1457 different file system operations. This is useful in implementing
1458 userspace file servers, which now track files using handles instead
1459 of names. The handle would remain the same even if file names
1460 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1464 bool "Posix Clocks & timers" if EXPERT
1467 This includes native support for POSIX timers to the kernel.
1468 Some embedded systems have no use for them and therefore they
1469 can be configured out to reduce the size of the kernel image.
1471 When this option is disabled, the following syscalls won't be
1472 available: timer_create, timer_gettime: timer_getoverrun,
1473 timer_settime, timer_delete, clock_adjtime, getitimer,
1474 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1475 clock_getres and clock_nanosleep syscalls will be limited to
1476 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1482 bool "Enable support for printk" if EXPERT
1485 This option enables normal printk support. Removing it
1486 eliminates most of the message strings from the kernel image
1487 and makes the kernel more or less silent. As this makes it
1488 very difficult to diagnose system problems, saying N here is
1489 strongly discouraged.
1497 bool "BUG() support" if EXPERT
1500 Disabling this option eliminates support for BUG and WARN, reducing
1501 the size of your kernel image and potentially quietly ignoring
1502 numerous fatal conditions. You should only consider disabling this
1503 option for embedded systems with no facilities for reporting errors.
1509 bool "Enable ELF core dumps" if EXPERT
1511 Enable support for generating core dumps. Disabling saves about 4k.
1514 config PCSPKR_PLATFORM
1515 bool "Enable PC-Speaker support" if EXPERT
1516 depends on HAVE_PCSPKR_PLATFORM
1520 This option allows to disable the internal PC-Speaker
1521 support, saving some memory.
1525 bool "Enable full-sized data structures for core" if EXPERT
1527 Disabling this option reduces the size of miscellaneous core
1528 kernel data structures. This saves memory on small machines,
1529 but may reduce performance.
1532 bool "Enable futex support" if EXPERT
1536 Disabling this option will cause the kernel to be built without
1537 support for "fast userspace mutexes". The resulting kernel may not
1538 run glibc-based applications correctly.
1542 depends on FUTEX && RT_MUTEXES
1545 config HAVE_FUTEX_CMPXCHG
1549 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1550 is implemented and always working. This removes a couple of runtime
1554 bool "Enable eventpoll support" if EXPERT
1557 Disabling this option will cause the kernel to be built without
1558 support for epoll family of system calls.
1561 bool "Enable signalfd() system call" if EXPERT
1564 Enable the signalfd() system call that allows to receive signals
1565 on a file descriptor.
1570 bool "Enable timerfd() system call" if EXPERT
1573 Enable the timerfd() system call that allows to receive timer
1574 events on a file descriptor.
1579 bool "Enable eventfd() system call" if EXPERT
1582 Enable the eventfd() system call that allows to receive both
1583 kernel notification (ie. KAIO) or userspace notifications.
1588 bool "Use full shmem filesystem" if EXPERT
1592 The shmem is an internal filesystem used to manage shared memory.
1593 It is backed by swap and manages resource limits. It is also exported
1594 to userspace as tmpfs if TMPFS is enabled. Disabling this
1595 option replaces shmem and tmpfs with the much simpler ramfs code,
1596 which may be appropriate on small systems without swap.
1599 bool "Enable AIO support" if EXPERT
1602 This option enables POSIX asynchronous I/O which may by used
1603 by some high performance threaded applications. Disabling
1604 this option saves about 7k.
1607 bool "Enable IO uring support" if EXPERT
1611 This option enables support for the io_uring interface, enabling
1612 applications to submit and complete IO through submission and
1613 completion rings that are shared between the kernel and application.
1615 config ADVISE_SYSCALLS
1616 bool "Enable madvise/fadvise syscalls" if EXPERT
1619 This option enables the madvise and fadvise syscalls, used by
1620 applications to advise the kernel about their future memory or file
1621 usage, improving performance. If building an embedded system where no
1622 applications use these syscalls, you can disable this option to save
1625 config HAVE_ARCH_USERFAULTFD_WP
1628 Arch has userfaultfd write protection support
1631 bool "Enable membarrier() system call" if EXPERT
1634 Enable the membarrier() system call that allows issuing memory
1635 barriers across all running threads, which can be used to distribute
1636 the cost of user-space memory barriers asymmetrically by transforming
1637 pairs of memory barriers into pairs consisting of membarrier() and a
1643 bool "Load all symbols for debugging/ksymoops" if EXPERT
1646 Say Y here to let the kernel print out symbolic crash information and
1647 symbolic stack backtraces. This increases the size of the kernel
1648 somewhat, as all symbols have to be loaded into the kernel image.
1651 bool "Include all symbols in kallsyms"
1652 depends on DEBUG_KERNEL && KALLSYMS
1654 Normally kallsyms only contains the symbols of functions for nicer
1655 OOPS messages and backtraces (i.e., symbols from the text and inittext
1656 sections). This is sufficient for most cases. And only in very rare
1657 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1658 names of variables from the data sections, etc).
1660 This option makes sure that all symbols are loaded into the kernel
1661 image (i.e., symbols from all sections) in cost of increased kernel
1662 size (depending on the kernel configuration, it may be 300KiB or
1663 something like this).
1665 Say N unless you really need all symbols.
1667 config KALLSYMS_ABSOLUTE_PERCPU
1670 default X86_64 && SMP
1672 config KALLSYMS_BASE_RELATIVE
1677 Instead of emitting them as absolute values in the native word size,
1678 emit the symbol references in the kallsyms table as 32-bit entries,
1679 each containing a relative value in the range [base, base + U32_MAX]
1680 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1681 an absolute value in the range [0, S32_MAX] or a relative value in the
1682 range [base, base + S32_MAX], where base is the lowest relative symbol
1683 address encountered in the image.
1685 On 64-bit builds, this reduces the size of the address table by 50%,
1686 but more importantly, it results in entries whose values are build
1687 time constants, and no relocation pass is required at runtime to fix
1688 up the entries based on the runtime load address of the kernel.
1690 # end of the "standard kernel features (expert users)" menu
1692 # syscall, maps, verifier
1695 bool "LSM Instrumentation with BPF"
1696 depends on BPF_EVENTS
1697 depends on BPF_SYSCALL
1701 Enables instrumentation of the security hooks with eBPF programs for
1702 implementing dynamic MAC and Audit Policies.
1704 If you are unsure how to answer this question, answer N.
1707 bool "Enable bpf() system call"
1710 select TASKS_TRACE_RCU
1713 Enable the bpf() system call that allows to manipulate eBPF
1714 programs and maps via file descriptors.
1716 config ARCH_WANT_DEFAULT_BPF_JIT
1719 config BPF_JIT_ALWAYS_ON
1720 bool "Permanently enable BPF JIT and remove BPF interpreter"
1721 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1723 Enables BPF JIT and removes BPF interpreter to avoid
1724 speculative execution of BPF instructions by the interpreter
1726 config BPF_JIT_DEFAULT_ON
1727 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
1728 depends on HAVE_EBPF_JIT && BPF_JIT
1730 source "kernel/bpf/preload/Kconfig"
1733 bool "Enable userfaultfd() system call"
1736 Enable the userfaultfd() system call that allows to intercept and
1737 handle page faults in userland.
1739 config ARCH_HAS_MEMBARRIER_CALLBACKS
1742 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1746 bool "Enable kcmp() system call" if EXPERT
1748 Enable the kernel resource comparison system call. It provides
1749 user-space with the ability to compare two processes to see if they
1750 share a common resource, such as a file descriptor or even virtual
1756 bool "Enable rseq() system call" if EXPERT
1758 depends on HAVE_RSEQ
1761 Enable the restartable sequences system call. It provides a
1762 user-space cache for the current CPU number value, which
1763 speeds up getting the current CPU number from user-space,
1764 as well as an ABI to speed up user-space operations on
1771 bool "Enabled debugging of rseq() system call" if EXPERT
1772 depends on RSEQ && DEBUG_KERNEL
1774 Enable extra debugging checks for the rseq system call.
1779 bool "Embedded system"
1780 option allnoconfig_y
1783 This option should be enabled if compiling the kernel for
1784 an embedded system so certain expert options are available
1787 config HAVE_PERF_EVENTS
1790 See tools/perf/design.txt for details.
1792 config PERF_USE_VMALLOC
1795 See tools/perf/design.txt for details
1798 bool "PC/104 support" if EXPERT
1800 Expose PC/104 form factor device drivers and options available for
1801 selection and configuration. Enable this option if your target
1802 machine has a PC/104 bus.
1804 menu "Kernel Performance Events And Counters"
1807 bool "Kernel performance events and counters"
1808 default y if PROFILING
1809 depends on HAVE_PERF_EVENTS
1813 Enable kernel support for various performance events provided
1814 by software and hardware.
1816 Software events are supported either built-in or via the
1817 use of generic tracepoints.
1819 Most modern CPUs support performance events via performance
1820 counter registers. These registers count the number of certain
1821 types of hw events: such as instructions executed, cachemisses
1822 suffered, or branches mis-predicted - without slowing down the
1823 kernel or applications. These registers can also trigger interrupts
1824 when a threshold number of events have passed - and can thus be
1825 used to profile the code that runs on that CPU.
1827 The Linux Performance Event subsystem provides an abstraction of
1828 these software and hardware event capabilities, available via a
1829 system call and used by the "perf" utility in tools/perf/. It
1830 provides per task and per CPU counters, and it provides event
1831 capabilities on top of those.
1835 config DEBUG_PERF_USE_VMALLOC
1837 bool "Debug: use vmalloc to back perf mmap() buffers"
1838 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1839 select PERF_USE_VMALLOC
1841 Use vmalloc memory to back perf mmap() buffers.
1843 Mostly useful for debugging the vmalloc code on platforms
1844 that don't require it.
1850 config VM_EVENT_COUNTERS
1852 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1854 VM event counters are needed for event counts to be shown.
1855 This option allows the disabling of the VM event counters
1856 on EXPERT systems. /proc/vmstat will only show page counts
1857 if VM event counters are disabled.
1861 bool "Enable SLUB debugging support" if EXPERT
1862 depends on SLUB && SYSFS
1864 SLUB has extensive debug support features. Disabling these can
1865 result in significant savings in code size. This also disables
1866 SLUB sysfs support. /sys/slab will not exist and there will be
1867 no support for cache validation etc.
1870 bool "Disable heap randomization"
1873 Randomizing heap placement makes heap exploits harder, but it
1874 also breaks ancient binaries (including anything libc5 based).
1875 This option changes the bootup default to heap randomization
1876 disabled, and can be overridden at runtime by setting
1877 /proc/sys/kernel/randomize_va_space to 2.
1879 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1882 prompt "Choose SLAB allocator"
1885 This option allows to select a slab allocator.
1889 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1891 The regular slab allocator that is established and known to work
1892 well in all environments. It organizes cache hot objects in
1893 per cpu and per node queues.
1896 bool "SLUB (Unqueued Allocator)"
1897 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1899 SLUB is a slab allocator that minimizes cache line usage
1900 instead of managing queues of cached objects (SLAB approach).
1901 Per cpu caching is realized using slabs of objects instead
1902 of queues of objects. SLUB can use memory efficiently
1903 and has enhanced diagnostics. SLUB is the default choice for
1908 bool "SLOB (Simple Allocator)"
1910 SLOB replaces the stock allocator with a drastically simpler
1911 allocator. SLOB is generally more space efficient but
1912 does not perform as well on large systems.
1916 config SLAB_MERGE_DEFAULT
1917 bool "Allow slab caches to be merged"
1920 For reduced kernel memory fragmentation, slab caches can be
1921 merged when they share the same size and other characteristics.
1922 This carries a risk of kernel heap overflows being able to
1923 overwrite objects from merged caches (and more easily control
1924 cache layout), which makes such heap attacks easier to exploit
1925 by attackers. By keeping caches unmerged, these kinds of exploits
1926 can usually only damage objects in the same cache. To disable
1927 merging at runtime, "slab_nomerge" can be passed on the kernel
1930 config SLAB_FREELIST_RANDOM
1931 bool "Randomize slab freelist"
1932 depends on SLAB || SLUB
1934 Randomizes the freelist order used on creating new pages. This
1935 security feature reduces the predictability of the kernel slab
1936 allocator against heap overflows.
1938 config SLAB_FREELIST_HARDENED
1939 bool "Harden slab freelist metadata"
1940 depends on SLAB || SLUB
1942 Many kernel heap attacks try to target slab cache metadata and
1943 other infrastructure. This options makes minor performance
1944 sacrifices to harden the kernel slab allocator against common
1945 freelist exploit methods. Some slab implementations have more
1946 sanity-checking than others. This option is most effective with
1949 config SHUFFLE_PAGE_ALLOCATOR
1950 bool "Page allocator randomization"
1951 default SLAB_FREELIST_RANDOM && ACPI_NUMA
1953 Randomization of the page allocator improves the average
1954 utilization of a direct-mapped memory-side-cache. See section
1955 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1956 6.2a specification for an example of how a platform advertises
1957 the presence of a memory-side-cache. There are also incidental
1958 security benefits as it reduces the predictability of page
1959 allocations to compliment SLAB_FREELIST_RANDOM, but the
1960 default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1961 10th order of pages is selected based on cache utilization
1964 While the randomization improves cache utilization it may
1965 negatively impact workloads on platforms without a cache. For
1966 this reason, by default, the randomization is enabled only
1967 after runtime detection of a direct-mapped memory-side-cache.
1968 Otherwise, the randomization may be force enabled with the
1969 'page_alloc.shuffle' kernel command line parameter.
1973 config SLUB_CPU_PARTIAL
1975 depends on SLUB && SMP
1976 bool "SLUB per cpu partial cache"
1978 Per cpu partial caches accelerate objects allocation and freeing
1979 that is local to a processor at the price of more indeterminism
1980 in the latency of the free. On overflow these caches will be cleared
1981 which requires the taking of locks that may cause latency spikes.
1982 Typically one would choose no for a realtime system.
1984 config MMAP_ALLOW_UNINITIALIZED
1985 bool "Allow mmapped anonymous memory to be uninitialized"
1986 depends on EXPERT && !MMU
1989 Normally, and according to the Linux spec, anonymous memory obtained
1990 from mmap() has its contents cleared before it is passed to
1991 userspace. Enabling this config option allows you to request that
1992 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1993 providing a huge performance boost. If this option is not enabled,
1994 then the flag will be ignored.
1996 This is taken advantage of by uClibc's malloc(), and also by
1997 ELF-FDPIC binfmt's brk and stack allocator.
1999 Because of the obvious security issues, this option should only be
2000 enabled on embedded devices where you control what is run in
2001 userspace. Since that isn't generally a problem on no-MMU systems,
2002 it is normally safe to say Y here.
2004 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
2006 config SYSTEM_DATA_VERIFICATION
2008 select SYSTEM_TRUSTED_KEYRING
2012 select ASYMMETRIC_KEY_TYPE
2013 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
2016 select X509_CERTIFICATE_PARSER
2017 select PKCS7_MESSAGE_PARSER
2019 Provide PKCS#7 message verification using the contents of the system
2020 trusted keyring to provide public keys. This then can be used for
2021 module verification, kexec image verification and firmware blob
2025 bool "Profiling support"
2027 Say Y here to enable the extended profiling support mechanisms used
2031 # Place an empty function call at each tracepoint site. Can be
2032 # dynamically changed for a probe function.
2037 endmenu # General setup
2039 source "arch/Kconfig"
2046 default 0 if BASE_FULL
2047 default 1 if !BASE_FULL
2049 config MODULE_SIG_FORMAT
2051 select SYSTEM_DATA_VERIFICATION
2054 bool "Enable loadable module support"
2057 Kernel modules are small pieces of compiled code which can
2058 be inserted in the running kernel, rather than being
2059 permanently built into the kernel. You use the "modprobe"
2060 tool to add (and sometimes remove) them. If you say Y here,
2061 many parts of the kernel can be built as modules (by
2062 answering M instead of Y where indicated): this is most
2063 useful for infrequently used options which are not required
2064 for booting. For more information, see the man pages for
2065 modprobe, lsmod, modinfo, insmod and rmmod.
2067 If you say Y here, you will need to run "make
2068 modules_install" to put the modules under /lib/modules/
2069 where modprobe can find them (you may need to be root to do
2076 config MODULE_FORCE_LOAD
2077 bool "Forced module loading"
2080 Allow loading of modules without version information (ie. modprobe
2081 --force). Forced module loading sets the 'F' (forced) taint flag and
2082 is usually a really bad idea.
2084 config MODULE_UNLOAD
2085 bool "Module unloading"
2087 Without this option you will not be able to unload any
2088 modules (note that some modules may not be unloadable
2089 anyway), which makes your kernel smaller, faster
2090 and simpler. If unsure, say Y.
2092 config MODULE_FORCE_UNLOAD
2093 bool "Forced module unloading"
2094 depends on MODULE_UNLOAD
2096 This option allows you to force a module to unload, even if the
2097 kernel believes it is unsafe: the kernel will remove the module
2098 without waiting for anyone to stop using it (using the -f option to
2099 rmmod). This is mainly for kernel developers and desperate users.
2103 bool "Module versioning support"
2105 Usually, you have to use modules compiled with your kernel.
2106 Saying Y here makes it sometimes possible to use modules
2107 compiled for different kernels, by adding enough information
2108 to the modules to (hopefully) spot any changes which would
2109 make them incompatible with the kernel you are running. If
2112 config ASM_MODVERSIONS
2114 default HAVE_ASM_MODVERSIONS && MODVERSIONS
2116 This enables module versioning for exported symbols also from
2117 assembly. This can be enabled only when the target architecture
2120 config MODULE_REL_CRCS
2122 depends on MODVERSIONS
2124 config MODULE_SRCVERSION_ALL
2125 bool "Source checksum for all modules"
2127 Modules which contain a MODULE_VERSION get an extra "srcversion"
2128 field inserted into their modinfo section, which contains a
2129 sum of the source files which made it. This helps maintainers
2130 see exactly which source was used to build a module (since
2131 others sometimes change the module source without updating
2132 the version). With this option, such a "srcversion" field
2133 will be created for all modules. If unsure, say N.
2136 bool "Module signature verification"
2137 select MODULE_SIG_FORMAT
2139 Check modules for valid signatures upon load: the signature
2140 is simply appended to the module. For more information see
2141 <file:Documentation/admin-guide/module-signing.rst>.
2143 Note that this option adds the OpenSSL development packages as a
2144 kernel build dependency so that the signing tool can use its crypto
2147 You should enable this option if you wish to use either
2148 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2149 another LSM - otherwise unsigned modules will be loadable regardless
2150 of the lockdown policy.
2152 !!!WARNING!!! If you enable this option, you MUST make sure that the
2153 module DOES NOT get stripped after being signed. This includes the
2154 debuginfo strip done by some packagers (such as rpmbuild) and
2155 inclusion into an initramfs that wants the module size reduced.
2157 config MODULE_SIG_FORCE
2158 bool "Require modules to be validly signed"
2159 depends on MODULE_SIG
2161 Reject unsigned modules or signed modules for which we don't have a
2162 key. Without this, such modules will simply taint the kernel.
2164 config MODULE_SIG_ALL
2165 bool "Automatically sign all modules"
2167 depends on MODULE_SIG
2169 Sign all modules during make modules_install. Without this option,
2170 modules must be signed manually, using the scripts/sign-file tool.
2172 comment "Do not forget to sign required modules with scripts/sign-file"
2173 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2176 prompt "Which hash algorithm should modules be signed with?"
2177 depends on MODULE_SIG
2179 This determines which sort of hashing algorithm will be used during
2180 signature generation. This algorithm _must_ be built into the kernel
2181 directly so that signature verification can take place. It is not
2182 possible to load a signed module containing the algorithm to check
2183 the signature on that module.
2185 config MODULE_SIG_SHA1
2186 bool "Sign modules with SHA-1"
2189 config MODULE_SIG_SHA224
2190 bool "Sign modules with SHA-224"
2191 select CRYPTO_SHA256
2193 config MODULE_SIG_SHA256
2194 bool "Sign modules with SHA-256"
2195 select CRYPTO_SHA256
2197 config MODULE_SIG_SHA384
2198 bool "Sign modules with SHA-384"
2199 select CRYPTO_SHA512
2201 config MODULE_SIG_SHA512
2202 bool "Sign modules with SHA-512"
2203 select CRYPTO_SHA512
2207 config MODULE_SIG_HASH
2209 depends on MODULE_SIG
2210 default "sha1" if MODULE_SIG_SHA1
2211 default "sha224" if MODULE_SIG_SHA224
2212 default "sha256" if MODULE_SIG_SHA256
2213 default "sha384" if MODULE_SIG_SHA384
2214 default "sha512" if MODULE_SIG_SHA512
2216 config MODULE_COMPRESS
2217 bool "Compress modules on installation"
2220 Compresses kernel modules when 'make modules_install' is run; gzip or
2221 xz depending on "Compression algorithm" below.
2223 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2225 Out-of-tree kernel modules installed using Kbuild will also be
2226 compressed upon installation.
2228 Note: for modules inside an initrd or initramfs, it's more efficient
2229 to compress the whole initrd or initramfs instead.
2231 Note: This is fully compatible with signed modules.
2236 prompt "Compression algorithm"
2237 depends on MODULE_COMPRESS
2238 default MODULE_COMPRESS_GZIP
2240 This determines which sort of compression will be used during
2241 'make modules_install'.
2243 GZIP (default) and XZ are supported.
2245 config MODULE_COMPRESS_GZIP
2248 config MODULE_COMPRESS_XZ
2253 config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2254 bool "Allow loading of modules with missing namespace imports"
2256 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2257 a namespace. A module that makes use of a symbol exported with such a
2258 namespace is required to import the namespace via MODULE_IMPORT_NS().
2259 There is no technical reason to enforce correct namespace imports,
2260 but it creates consistency between symbols defining namespaces and
2261 users importing namespaces they make use of. This option relaxes this
2262 requirement and lifts the enforcement when loading a module.
2266 config TRIM_UNUSED_KSYMS
2267 bool "Trim unused exported kernel symbols" if EXPERT
2268 depends on !COMPILE_TEST
2270 The kernel and some modules make many symbols available for
2271 other modules to use via EXPORT_SYMBOL() and variants. Depending
2272 on the set of modules being selected in your kernel configuration,
2273 many of those exported symbols might never be used.
2275 This option allows for unused exported symbols to be dropped from
2276 the build. In turn, this provides the compiler more opportunities
2277 (especially when using LTO) for optimizing the code and reducing
2278 binary size. This might have some security advantages as well.
2280 If unsure, or if you need to build out-of-tree modules, say N.
2282 config UNUSED_KSYMS_WHITELIST
2283 string "Whitelist of symbols to keep in ksymtab"
2284 depends on TRIM_UNUSED_KSYMS
2286 By default, all unused exported symbols will be un-exported from the
2287 build when TRIM_UNUSED_KSYMS is selected.
2289 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
2290 exported at all times, even in absence of in-tree users. The value to
2291 set here is the path to a text file containing the list of symbols,
2292 one per line. The path can be absolute, or relative to the kernel
2297 config MODULES_TREE_LOOKUP
2299 depends on PERF_EVENTS || TRACING
2301 config INIT_ALL_POSSIBLE
2304 Back when each arch used to define their own cpu_online_mask and
2305 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2306 with all 1s, and others with all 0s. When they were centralised,
2307 it was better to provide this option than to break all the archs
2308 and have several arch maintainers pursuing me down dark alleys.
2310 source "block/Kconfig"
2312 config PREEMPT_NOTIFIERS
2322 Build a simple ASN.1 grammar compiler that produces a bytecode output
2323 that can be interpreted by the ASN.1 stream decoder and used to
2324 inform it as to what tags are to be expected in a stream and what
2325 functions to call on what tags.
2327 source "kernel/Kconfig.locks"
2329 config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2332 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2335 # It may be useful for an architecture to override the definitions of the
2336 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2337 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2338 # different calling convention for syscalls. They can also override the
2339 # macros for not-implemented syscalls in kernel/sys_ni.c and
2340 # kernel/time/posix-stubs.c. All these overrides need to be available in
2341 # <asm/syscall_wrapper.h>.
2342 config ARCH_HAS_SYSCALL_WRAPPER
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