1 # SPDX-License-Identifier: GPL-2.0-only
6 default "/lib/modules/$(shell,uname -r)/.config"
7 default "/etc/kernel-config"
8 default "/boot/config-$(shell,uname -r)"
9 default "arch/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG)"
11 config CC_VERSION_TEXT
13 default "$(CC_VERSION_TEXT)"
15 This is used in unclear ways:
17 - Re-run Kconfig when the compiler is updated
18 The 'default' property references the environment variable,
19 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd.
20 When the compiler is updated, Kconfig will be invoked.
22 - Ensure full rebuild when the compier is updated
23 include/linux/kconfig.h contains this option in the comment line so
24 fixdep adds include/config/cc/version/text.h into the auto-generated
25 dependency. When the compiler is updated, syncconfig will touch it
26 and then every file will be rebuilt.
29 def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q gcc)
33 default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC
38 default $(shell,$(LD) --version | $(srctree)/scripts/ld-version.sh)
41 def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q clang)
44 def_bool $(success,$(LD) -v | head -n 1 | grep -q LLD)
48 default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
52 default $(shell,$(srctree)/scripts/lld-version.sh $(LD))
56 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag)) if 64BIT
57 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag))
59 config CC_CAN_LINK_STATIC
61 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static) if 64BIT
62 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag) -static)
64 config CC_HAS_ASM_GOTO
65 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
67 config CC_HAS_ASM_GOTO_OUTPUT
68 depends on CC_HAS_ASM_GOTO
69 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)
71 config TOOLS_SUPPORT_RELR
72 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
74 config CC_HAS_ASM_INLINE
75 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
83 config BUILDTIME_TABLE_SORT
86 config THREAD_INFO_IN_TASK
89 Select this to move thread_info off the stack into task_struct. To
90 make this work, an arch will need to remove all thread_info fields
91 except flags and fix any runtime bugs.
93 One subtle change that will be needed is to use try_get_task_stack()
94 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
103 depends on BROKEN || !SMP
106 config INIT_ENV_ARG_LIMIT
111 Maximum of each of the number of arguments and environment
112 variables passed to init from the kernel command line.
115 bool "Compile also drivers which will not load"
118 Some drivers can be compiled on a different platform than they are
119 intended to be run on. Despite they cannot be loaded there (or even
120 when they load they cannot be used due to missing HW support),
121 developers still, opposing to distributors, might want to build such
122 drivers to compile-test them.
124 If you are a developer and want to build everything available, say Y
125 here. If you are a user/distributor, say N here to exclude useless
126 drivers to be distributed.
128 config UAPI_HEADER_TEST
129 bool "Compile test UAPI headers"
130 depends on HEADERS_INSTALL && CC_CAN_LINK
132 Compile test headers exported to user-space to ensure they are
133 self-contained, i.e. compilable as standalone units.
135 If you are a developer or tester and want to ensure the exported
136 headers are self-contained, say Y here. Otherwise, choose N.
139 string "Local version - append to kernel release"
141 Append an extra string to the end of your kernel version.
142 This will show up when you type uname, for example.
143 The string you set here will be appended after the contents of
144 any files with a filename matching localversion* in your
145 object and source tree, in that order. Your total string can
146 be a maximum of 64 characters.
148 config LOCALVERSION_AUTO
149 bool "Automatically append version information to the version string"
151 depends on !COMPILE_TEST
153 This will try to automatically determine if the current tree is a
154 release tree by looking for git tags that belong to the current
155 top of tree revision.
157 A string of the format -gxxxxxxxx will be added to the localversion
158 if a git-based tree is found. The string generated by this will be
159 appended after any matching localversion* files, and after the value
160 set in CONFIG_LOCALVERSION.
162 (The actual string used here is the first eight characters produced
163 by running the command:
165 $ git rev-parse --verify HEAD
167 which is done within the script "scripts/setlocalversion".)
170 string "Build ID Salt"
173 The build ID is used to link binaries and their debug info. Setting
174 this option will use the value in the calculation of the build id.
175 This is mostly useful for distributions which want to ensure the
176 build is unique between builds. It's safe to leave the default.
178 config HAVE_KERNEL_GZIP
181 config HAVE_KERNEL_BZIP2
184 config HAVE_KERNEL_LZMA
187 config HAVE_KERNEL_XZ
190 config HAVE_KERNEL_LZO
193 config HAVE_KERNEL_LZ4
196 config HAVE_KERNEL_ZSTD
199 config HAVE_KERNEL_UNCOMPRESSED
203 prompt "Kernel compression mode"
205 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
207 The linux kernel is a kind of self-extracting executable.
208 Several compression algorithms are available, which differ
209 in efficiency, compression and decompression speed.
210 Compression speed is only relevant when building a kernel.
211 Decompression speed is relevant at each boot.
213 If you have any problems with bzip2 or lzma compressed
214 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
215 version of this functionality (bzip2 only), for 2.4, was
216 supplied by Christian Ludwig)
218 High compression options are mostly useful for users, who
219 are low on disk space (embedded systems), but for whom ram
222 If in doubt, select 'gzip'
226 depends on HAVE_KERNEL_GZIP
228 The old and tried gzip compression. It provides a good balance
229 between compression ratio and decompression speed.
233 depends on HAVE_KERNEL_BZIP2
235 Its compression ratio and speed is intermediate.
236 Decompression speed is slowest among the choices. The kernel
237 size is about 10% smaller with bzip2, in comparison to gzip.
238 Bzip2 uses a large amount of memory. For modern kernels you
239 will need at least 8MB RAM or more for booting.
243 depends on HAVE_KERNEL_LZMA
245 This compression algorithm's ratio is best. Decompression speed
246 is between gzip and bzip2. Compression is slowest.
247 The kernel size is about 33% smaller with LZMA in comparison to gzip.
251 depends on HAVE_KERNEL_XZ
253 XZ uses the LZMA2 algorithm and instruction set specific
254 BCJ filters which can improve compression ratio of executable
255 code. The size of the kernel is about 30% smaller with XZ in
256 comparison to gzip. On architectures for which there is a BCJ
257 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
258 will create a few percent smaller kernel than plain LZMA.
260 The speed is about the same as with LZMA: The decompression
261 speed of XZ is better than that of bzip2 but worse than gzip
262 and LZO. Compression is slow.
266 depends on HAVE_KERNEL_LZO
268 Its compression ratio is the poorest among the choices. The kernel
269 size is about 10% bigger than gzip; however its speed
270 (both compression and decompression) is the fastest.
274 depends on HAVE_KERNEL_LZ4
276 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
277 A preliminary version of LZ4 de/compression tool is available at
278 <https://code.google.com/p/lz4/>.
280 Its compression ratio is worse than LZO. The size of the kernel
281 is about 8% bigger than LZO. But the decompression speed is
286 depends on HAVE_KERNEL_ZSTD
288 ZSTD is a compression algorithm targeting intermediate compression
289 with fast decompression speed. It will compress better than GZIP and
290 decompress around the same speed as LZO, but slower than LZ4. You
291 will need at least 192 KB RAM or more for booting. The zstd command
292 line tool is required for compression.
294 config KERNEL_UNCOMPRESSED
296 depends on HAVE_KERNEL_UNCOMPRESSED
298 Produce uncompressed kernel image. This option is usually not what
299 you want. It is useful for debugging the kernel in slow simulation
300 environments, where decompressing and moving the kernel is awfully
301 slow. This option allows early boot code to skip the decompressor
302 and jump right at uncompressed kernel image.
307 string "Default init path"
310 This option determines the default init for the system if no init=
311 option is passed on the kernel command line. If the requested path is
312 not present, we will still then move on to attempting further
313 locations (e.g. /sbin/init, etc). If this is empty, we will just use
314 the fallback list when init= is not passed.
316 config DEFAULT_HOSTNAME
317 string "Default hostname"
320 This option determines the default system hostname before userspace
321 calls sethostname(2). The kernel traditionally uses "(none)" here,
322 but you may wish to use a different default here to make a minimal
323 system more usable with less configuration.
326 # For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
327 # add proper SWAP support to them, in which case this can be remove.
332 config VERSION_SIGNATURE
333 string "Arbitrary version signature"
335 This string will be created in a file, /proc/version_signature. It
336 is useful in determining arbitrary data about your kernel. For instance,
337 if you have several kernels of the same version, but need to keep track
338 of a revision of the same kernel, but not affect it's ability to load
339 compatible modules, this is the easiest way to do that.
342 bool "Support for paging of anonymous memory (swap)"
343 depends on MMU && BLOCK && !ARCH_NO_SWAP
346 This option allows you to choose whether you want to have support
347 for so called swap devices or swap files in your kernel that are
348 used to provide more virtual memory than the actual RAM present
349 in your computer. If unsure say Y.
354 Inter Process Communication is a suite of library functions and
355 system calls which let processes (running programs) synchronize and
356 exchange information. It is generally considered to be a good thing,
357 and some programs won't run unless you say Y here. In particular, if
358 you want to run the DOS emulator dosemu under Linux (read the
359 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
360 you'll need to say Y here.
362 You can find documentation about IPC with "info ipc" and also in
363 section 6.4 of the Linux Programmer's Guide, available from
364 <http://www.tldp.org/guides.html>.
366 config SYSVIPC_SYSCTL
373 bool "POSIX Message Queues"
376 POSIX variant of message queues is a part of IPC. In POSIX message
377 queues every message has a priority which decides about succession
378 of receiving it by a process. If you want to compile and run
379 programs written e.g. for Solaris with use of its POSIX message
380 queues (functions mq_*) say Y here.
382 POSIX message queues are visible as a filesystem called 'mqueue'
383 and can be mounted somewhere if you want to do filesystem
384 operations on message queues.
388 config POSIX_MQUEUE_SYSCTL
390 depends on POSIX_MQUEUE
395 bool "General notification queue"
399 This is a general notification queue for the kernel to pass events to
400 userspace by splicing them into pipes. It can be used in conjunction
401 with watches for key/keyring change notifications and device
404 See Documentation/watch_queue.rst
406 config CROSS_MEMORY_ATTACH
407 bool "Enable process_vm_readv/writev syscalls"
411 Enabling this option adds the system calls process_vm_readv and
412 process_vm_writev which allow a process with the correct privileges
413 to directly read from or write to another process' address space.
414 See the man page for more details.
417 bool "uselib syscall"
418 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
420 This option enables the uselib syscall, a system call used in the
421 dynamic linker from libc5 and earlier. glibc does not use this
422 system call. If you intend to run programs built on libc5 or
423 earlier, you may need to enable this syscall. Current systems
424 running glibc can safely disable this.
427 bool "Auditing support"
430 Enable auditing infrastructure that can be used with another
431 kernel subsystem, such as SELinux (which requires this for
432 logging of avc messages output). System call auditing is included
433 on architectures which support it.
435 config HAVE_ARCH_AUDITSYSCALL
440 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
443 source "kernel/irq/Kconfig"
444 source "kernel/time/Kconfig"
445 source "kernel/Kconfig.preempt"
447 menu "CPU/Task time and stats accounting"
449 config VIRT_CPU_ACCOUNTING
453 prompt "Cputime accounting"
454 default TICK_CPU_ACCOUNTING if !PPC64
455 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
457 # Kind of a stub config for the pure tick based cputime accounting
458 config TICK_CPU_ACCOUNTING
459 bool "Simple tick based cputime accounting"
460 depends on !S390 && !NO_HZ_FULL
462 This is the basic tick based cputime accounting that maintains
463 statistics about user, system and idle time spent on per jiffies
468 config VIRT_CPU_ACCOUNTING_NATIVE
469 bool "Deterministic task and CPU time accounting"
470 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
471 select VIRT_CPU_ACCOUNTING
473 Select this option to enable more accurate task and CPU time
474 accounting. This is done by reading a CPU counter on each
475 kernel entry and exit and on transitions within the kernel
476 between system, softirq and hardirq state, so there is a
477 small performance impact. In the case of s390 or IBM POWER > 5,
478 this also enables accounting of stolen time on logically-partitioned
481 config VIRT_CPU_ACCOUNTING_GEN
482 bool "Full dynticks CPU time accounting"
483 depends on HAVE_CONTEXT_TRACKING
484 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
485 depends on GENERIC_CLOCKEVENTS
486 select VIRT_CPU_ACCOUNTING
487 select CONTEXT_TRACKING
489 Select this option to enable task and CPU time accounting on full
490 dynticks systems. This accounting is implemented by watching every
491 kernel-user boundaries using the context tracking subsystem.
492 The accounting is thus performed at the expense of some significant
495 For now this is only useful if you are working on the full
496 dynticks subsystem development.
502 config IRQ_TIME_ACCOUNTING
503 bool "Fine granularity task level IRQ time accounting"
504 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
506 Select this option to enable fine granularity task irq time
507 accounting. This is done by reading a timestamp on each
508 transitions between softirq and hardirq state, so there can be a
509 small performance impact.
511 If in doubt, say N here.
513 config HAVE_SCHED_AVG_IRQ
515 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
518 config SCHED_THERMAL_PRESSURE
520 default y if ARM && ARM_CPU_TOPOLOGY
523 depends on CPU_FREQ_THERMAL
525 Select this option to enable thermal pressure accounting in the
526 scheduler. Thermal pressure is the value conveyed to the scheduler
527 that reflects the reduction in CPU compute capacity resulted from
528 thermal throttling. Thermal throttling occurs when the performance of
529 a CPU is capped due to high operating temperatures.
531 If selected, the scheduler will be able to balance tasks accordingly,
532 i.e. put less load on throttled CPUs than on non/less throttled ones.
534 This requires the architecture to implement
535 arch_set_thermal_pressure() and arch_get_thermal_pressure().
537 config BSD_PROCESS_ACCT
538 bool "BSD Process Accounting"
541 If you say Y here, a user level program will be able to instruct the
542 kernel (via a special system call) to write process accounting
543 information to a file: whenever a process exits, information about
544 that process will be appended to the file by the kernel. The
545 information includes things such as creation time, owning user,
546 command name, memory usage, controlling terminal etc. (the complete
547 list is in the struct acct in <file:include/linux/acct.h>). It is
548 up to the user level program to do useful things with this
549 information. This is generally a good idea, so say Y.
551 config BSD_PROCESS_ACCT_V3
552 bool "BSD Process Accounting version 3 file format"
553 depends on BSD_PROCESS_ACCT
556 If you say Y here, the process accounting information is written
557 in a new file format that also logs the process IDs of each
558 process and its parent. Note that this file format is incompatible
559 with previous v0/v1/v2 file formats, so you will need updated tools
560 for processing it. A preliminary version of these tools is available
561 at <http://www.gnu.org/software/acct/>.
564 bool "Export task/process statistics through netlink"
569 Export selected statistics for tasks/processes through the
570 generic netlink interface. Unlike BSD process accounting, the
571 statistics are available during the lifetime of tasks/processes as
572 responses to commands. Like BSD accounting, they are sent to user
577 config TASK_DELAY_ACCT
578 bool "Enable per-task delay accounting"
582 Collect information on time spent by a task waiting for system
583 resources like cpu, synchronous block I/O completion and swapping
584 in pages. Such statistics can help in setting a task's priorities
585 relative to other tasks for cpu, io, rss limits etc.
590 bool "Enable extended accounting over taskstats"
593 Collect extended task accounting data and send the data
594 to userland for processing over the taskstats interface.
598 config TASK_IO_ACCOUNTING
599 bool "Enable per-task storage I/O accounting"
600 depends on TASK_XACCT
602 Collect information on the number of bytes of storage I/O which this
608 bool "Pressure stall information tracking"
610 Collect metrics that indicate how overcommitted the CPU, memory,
611 and IO capacity are in the system.
613 If you say Y here, the kernel will create /proc/pressure/ with the
614 pressure statistics files cpu, memory, and io. These will indicate
615 the share of walltime in which some or all tasks in the system are
616 delayed due to contention of the respective resource.
618 In kernels with cgroup support, cgroups (cgroup2 only) will
619 have cpu.pressure, memory.pressure, and io.pressure files,
620 which aggregate pressure stalls for the grouped tasks only.
622 For more details see Documentation/accounting/psi.rst.
626 config PSI_DEFAULT_DISABLED
627 bool "Require boot parameter to enable pressure stall information tracking"
631 If set, pressure stall information tracking will be disabled
632 per default but can be enabled through passing psi=1 on the
633 kernel commandline during boot.
635 This feature adds some code to the task wakeup and sleep
636 paths of the scheduler. The overhead is too low to affect
637 common scheduling-intense workloads in practice (such as
638 webservers, memcache), but it does show up in artificial
639 scheduler stress tests, such as hackbench.
641 If you are paranoid and not sure what the kernel will be
646 endmenu # "CPU/Task time and stats accounting"
650 depends on SMP || COMPILE_TEST
653 Make sure that CPUs running critical tasks are not disturbed by
654 any source of "noise" such as unbound workqueues, timers, kthreads...
655 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
656 the "isolcpus=" boot parameter.
660 source "kernel/rcu/Kconfig"
667 tristate "Kernel .config support"
669 This option enables the complete Linux kernel ".config" file
670 contents to be saved in the kernel. It provides documentation
671 of which kernel options are used in a running kernel or in an
672 on-disk kernel. This information can be extracted from the kernel
673 image file with the script scripts/extract-ikconfig and used as
674 input to rebuild the current kernel or to build another kernel.
675 It can also be extracted from a running kernel by reading
676 /proc/config.gz if enabled (below).
679 bool "Enable access to .config through /proc/config.gz"
680 depends on IKCONFIG && PROC_FS
682 This option enables access to the kernel configuration file
683 through /proc/config.gz.
686 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
689 This option enables access to the in-kernel headers that are generated during
690 the build process. These can be used to build eBPF tracing programs,
691 or similar programs. If you build the headers as a module, a module called
692 kheaders.ko is built which can be loaded on-demand to get access to headers.
695 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
696 range 12 25 if !H8300
701 Select the minimal kernel log buffer size as a power of 2.
702 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
703 parameter, see below. Any higher size also might be forced
704 by "log_buf_len" boot parameter.
714 config LOG_CPU_MAX_BUF_SHIFT
715 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
718 default 12 if !BASE_SMALL
719 default 0 if BASE_SMALL
722 This option allows to increase the default ring buffer size
723 according to the number of CPUs. The value defines the contribution
724 of each CPU as a power of 2. The used space is typically only few
725 lines however it might be much more when problems are reported,
728 The increased size means that a new buffer has to be allocated and
729 the original static one is unused. It makes sense only on systems
730 with more CPUs. Therefore this value is used only when the sum of
731 contributions is greater than the half of the default kernel ring
732 buffer as defined by LOG_BUF_SHIFT. The default values are set
733 so that more than 16 CPUs are needed to trigger the allocation.
735 Also this option is ignored when "log_buf_len" kernel parameter is
736 used as it forces an exact (power of two) size of the ring buffer.
738 The number of possible CPUs is used for this computation ignoring
739 hotplugging making the computation optimal for the worst case
740 scenario while allowing a simple algorithm to be used from bootup.
742 Examples shift values and their meaning:
743 17 => 128 KB for each CPU
744 16 => 64 KB for each CPU
745 15 => 32 KB for each CPU
746 14 => 16 KB for each CPU
747 13 => 8 KB for each CPU
748 12 => 4 KB for each CPU
750 config PRINTK_SAFE_LOG_BUF_SHIFT
751 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
756 Select the size of an alternate printk per-CPU buffer where messages
757 printed from usafe contexts are temporary stored. One example would
758 be NMI messages, another one - printk recursion. The messages are
759 copied to the main log buffer in a safe context to avoid a deadlock.
760 The value defines the size as a power of 2.
762 Those messages are rare and limited. The largest one is when
763 a backtrace is printed. It usually fits into 4KB. Select
764 8KB if you want to be on the safe side.
767 17 => 128 KB for each CPU
768 16 => 64 KB for each CPU
769 15 => 32 KB for each CPU
770 14 => 16 KB for each CPU
771 13 => 8 KB for each CPU
772 12 => 4 KB for each CPU
775 # Architectures with an unreliable sched_clock() should select this:
777 config HAVE_UNSTABLE_SCHED_CLOCK
780 config GENERIC_SCHED_CLOCK
783 menu "Scheduler features"
786 bool "Enable utilization clamping for RT/FAIR tasks"
787 depends on CPU_FREQ_GOV_SCHEDUTIL
789 This feature enables the scheduler to track the clamped utilization
790 of each CPU based on RUNNABLE tasks scheduled on that CPU.
792 With this option, the user can specify the min and max CPU
793 utilization allowed for RUNNABLE tasks. The max utilization defines
794 the maximum frequency a task should use while the min utilization
795 defines the minimum frequency it should use.
797 Both min and max utilization clamp values are hints to the scheduler,
798 aiming at improving its frequency selection policy, but they do not
799 enforce or grant any specific bandwidth for tasks.
803 config UCLAMP_BUCKETS_COUNT
804 int "Number of supported utilization clamp buckets"
807 depends on UCLAMP_TASK
809 Defines the number of clamp buckets to use. The range of each bucket
810 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
811 number of clamp buckets the finer their granularity and the higher
812 the precision of clamping aggregation and tracking at run-time.
814 For example, with the minimum configuration value we will have 5
815 clamp buckets tracking 20% utilization each. A 25% boosted tasks will
816 be refcounted in the [20..39]% bucket and will set the bucket clamp
817 effective value to 25%.
818 If a second 30% boosted task should be co-scheduled on the same CPU,
819 that task will be refcounted in the same bucket of the first task and
820 it will boost the bucket clamp effective value to 30%.
821 The clamp effective value of a bucket is reset to its nominal value
822 (20% in the example above) when there are no more tasks refcounted in
825 An additional boost/capping margin can be added to some tasks. In the
826 example above the 25% task will be boosted to 30% until it exits the
827 CPU. If that should be considered not acceptable on certain systems,
828 it's always possible to reduce the margin by increasing the number of
829 clamp buckets to trade off used memory for run-time tracking
832 If in doubt, use the default value.
837 # For architectures that want to enable the support for NUMA-affine scheduler
840 config ARCH_SUPPORTS_NUMA_BALANCING
844 # For architectures that prefer to flush all TLBs after a number of pages
845 # are unmapped instead of sending one IPI per page to flush. The architecture
846 # must provide guarantees on what happens if a clean TLB cache entry is
847 # written after the unmap. Details are in mm/rmap.c near the check for
848 # should_defer_flush. The architecture should also consider if the full flush
849 # and the refill costs are offset by the savings of sending fewer IPIs.
850 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
854 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
857 # For architectures that know their GCC __int128 support is sound
859 config ARCH_SUPPORTS_INT128
862 # For architectures that (ab)use NUMA to represent different memory regions
863 # all cpu-local but of different latencies, such as SuperH.
865 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
868 config NUMA_BALANCING
869 bool "Memory placement aware NUMA scheduler"
870 depends on ARCH_SUPPORTS_NUMA_BALANCING
871 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
872 depends on SMP && NUMA && MIGRATION
874 This option adds support for automatic NUMA aware memory/task placement.
875 The mechanism is quite primitive and is based on migrating memory when
876 it has references to the node the task is running on.
878 This system will be inactive on UMA systems.
880 config NUMA_BALANCING_DEFAULT_ENABLED
881 bool "Automatically enable NUMA aware memory/task placement"
883 depends on NUMA_BALANCING
885 If set, automatic NUMA balancing will be enabled if running on a NUMA
889 bool "Control Group support"
892 This option adds support for grouping sets of processes together, for
893 use with process control subsystems such as Cpusets, CFS, memory
894 controls or device isolation.
896 - Documentation/scheduler/sched-design-CFS.rst (CFS)
897 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
898 and resource control)
908 bool "Memory controller"
912 Provides control over the memory footprint of tasks in a cgroup.
916 depends on MEMCG && SWAP
921 depends on MEMCG && !SLOB
929 Generic block IO controller cgroup interface. This is the common
930 cgroup interface which should be used by various IO controlling
933 Currently, CFQ IO scheduler uses it to recognize task groups and
934 control disk bandwidth allocation (proportional time slice allocation)
935 to such task groups. It is also used by bio throttling logic in
936 block layer to implement upper limit in IO rates on a device.
938 This option only enables generic Block IO controller infrastructure.
939 One needs to also enable actual IO controlling logic/policy. For
940 enabling proportional weight division of disk bandwidth in CFQ, set
941 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
942 CONFIG_BLK_DEV_THROTTLING=y.
944 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
946 config CGROUP_WRITEBACK
948 depends on MEMCG && BLK_CGROUP
951 menuconfig CGROUP_SCHED
952 bool "CPU controller"
955 This feature lets CPU scheduler recognize task groups and control CPU
956 bandwidth allocation to such task groups. It uses cgroups to group
960 config FAIR_GROUP_SCHED
961 bool "Group scheduling for SCHED_OTHER"
962 depends on CGROUP_SCHED
966 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
967 depends on FAIR_GROUP_SCHED
970 This option allows users to define CPU bandwidth rates (limits) for
971 tasks running within the fair group scheduler. Groups with no limit
972 set are considered to be unconstrained and will run with no
974 See Documentation/scheduler/sched-bwc.rst for more information.
976 config RT_GROUP_SCHED
977 bool "Group scheduling for SCHED_RR/FIFO"
978 depends on CGROUP_SCHED
981 This feature lets you explicitly allocate real CPU bandwidth
982 to task groups. If enabled, it will also make it impossible to
983 schedule realtime tasks for non-root users until you allocate
984 realtime bandwidth for them.
985 See Documentation/scheduler/sched-rt-group.rst for more information.
989 config UCLAMP_TASK_GROUP
990 bool "Utilization clamping per group of tasks"
991 depends on CGROUP_SCHED
992 depends on UCLAMP_TASK
995 This feature enables the scheduler to track the clamped utilization
996 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
998 When this option is enabled, the user can specify a min and max
999 CPU bandwidth which is allowed for each single task in a group.
1000 The max bandwidth allows to clamp the maximum frequency a task
1001 can use, while the min bandwidth allows to define a minimum
1002 frequency a task will always use.
1004 When task group based utilization clamping is enabled, an eventually
1005 specified task-specific clamp value is constrained by the cgroup
1006 specified clamp value. Both minimum and maximum task clamping cannot
1007 be bigger than the corresponding clamping defined at task group level.
1012 bool "PIDs controller"
1014 Provides enforcement of process number limits in the scope of a
1015 cgroup. Any attempt to fork more processes than is allowed in the
1016 cgroup will fail. PIDs are fundamentally a global resource because it
1017 is fairly trivial to reach PID exhaustion before you reach even a
1018 conservative kmemcg limit. As a result, it is possible to grind a
1019 system to halt without being limited by other cgroup policies. The
1020 PIDs controller is designed to stop this from happening.
1022 It should be noted that organisational operations (such as attaching
1023 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1024 since the PIDs limit only affects a process's ability to fork, not to
1028 bool "RDMA controller"
1030 Provides enforcement of RDMA resources defined by IB stack.
1031 It is fairly easy for consumers to exhaust RDMA resources, which
1032 can result into resource unavailability to other consumers.
1033 RDMA controller is designed to stop this from happening.
1034 Attaching processes with active RDMA resources to the cgroup
1035 hierarchy is allowed even if can cross the hierarchy's limit.
1037 config CGROUP_FREEZER
1038 bool "Freezer controller"
1040 Provides a way to freeze and unfreeze all tasks in a
1043 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1044 controller includes important in-kernel memory consumers per default.
1046 If you're using cgroup2, say N.
1048 config CGROUP_HUGETLB
1049 bool "HugeTLB controller"
1050 depends on HUGETLB_PAGE
1054 Provides a cgroup controller for HugeTLB pages.
1055 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1056 The limit is enforced during page fault. Since HugeTLB doesn't
1057 support page reclaim, enforcing the limit at page fault time implies
1058 that, the application will get SIGBUS signal if it tries to access
1059 HugeTLB pages beyond its limit. This requires the application to know
1060 beforehand how much HugeTLB pages it would require for its use. The
1061 control group is tracked in the third page lru pointer. This means
1062 that we cannot use the controller with huge page less than 3 pages.
1065 bool "Cpuset controller"
1068 This option will let you create and manage CPUSETs which
1069 allow dynamically partitioning a system into sets of CPUs and
1070 Memory Nodes and assigning tasks to run only within those sets.
1071 This is primarily useful on large SMP or NUMA systems.
1075 config PROC_PID_CPUSET
1076 bool "Include legacy /proc/<pid>/cpuset file"
1080 config CGROUP_DEVICE
1081 bool "Device controller"
1083 Provides a cgroup controller implementing whitelists for
1084 devices which a process in the cgroup can mknod or open.
1086 config CGROUP_CPUACCT
1087 bool "Simple CPU accounting controller"
1089 Provides a simple controller for monitoring the
1090 total CPU consumed by the tasks in a cgroup.
1093 bool "Perf controller"
1094 depends on PERF_EVENTS
1096 This option extends the perf per-cpu mode to restrict monitoring
1097 to threads which belong to the cgroup specified and run on the
1098 designated cpu. Or this can be used to have cgroup ID in samples
1099 so that it can monitor performance events among cgroups.
1104 bool "Support for eBPF programs attached to cgroups"
1105 depends on BPF_SYSCALL
1106 select SOCK_CGROUP_DATA
1108 Allow attaching eBPF programs to a cgroup using the bpf(2)
1109 syscall command BPF_PROG_ATTACH.
1111 In which context these programs are accessed depends on the type
1112 of attachment. For instance, programs that are attached using
1113 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1117 bool "Debug controller"
1119 depends on DEBUG_KERNEL
1121 This option enables a simple controller that exports
1122 debugging information about the cgroups framework. This
1123 controller is for control cgroup debugging only. Its
1124 interfaces are not stable.
1128 config SOCK_CGROUP_DATA
1134 menuconfig NAMESPACES
1135 bool "Namespaces support" if EXPERT
1136 depends on MULTIUSER
1139 Provides the way to make tasks work with different objects using
1140 the same id. For example same IPC id may refer to different objects
1141 or same user id or pid may refer to different tasks when used in
1142 different namespaces.
1147 bool "UTS namespace"
1150 In this namespace tasks see different info provided with the
1154 bool "TIME namespace"
1155 depends on GENERIC_VDSO_TIME_NS
1158 In this namespace boottime and monotonic clocks can be set.
1159 The time will keep going with the same pace.
1162 bool "IPC namespace"
1163 depends on (SYSVIPC || POSIX_MQUEUE)
1166 In this namespace tasks work with IPC ids which correspond to
1167 different IPC objects in different namespaces.
1170 bool "User namespace"
1173 This allows containers, i.e. vservers, to use user namespaces
1174 to provide different user info for different servers.
1176 When user namespaces are enabled in the kernel it is
1177 recommended that the MEMCG option also be enabled and that
1178 user-space use the memory control groups to limit the amount
1179 of memory a memory unprivileged users can use.
1184 bool "PID Namespaces"
1187 Support process id namespaces. This allows having multiple
1188 processes with the same pid as long as they are in different
1189 pid namespaces. This is a building block of containers.
1192 bool "Network namespace"
1196 Allow user space to create what appear to be multiple instances
1197 of the network stack.
1201 config CHECKPOINT_RESTORE
1202 bool "Checkpoint/restore support"
1203 select PROC_CHILDREN
1207 Enables additional kernel features in a sake of checkpoint/restore.
1208 In particular it adds auxiliary prctl codes to setup process text,
1209 data and heap segment sizes, and a few additional /proc filesystem
1212 If unsure, say N here.
1214 config SCHED_AUTOGROUP
1215 bool "Automatic process group scheduling"
1218 select FAIR_GROUP_SCHED
1220 This option optimizes the scheduler for common desktop workloads by
1221 automatically creating and populating task groups. This separation
1222 of workloads isolates aggressive CPU burners (like build jobs) from
1223 desktop applications. Task group autogeneration is currently based
1226 config SYSFS_DEPRECATED
1227 bool "Enable deprecated sysfs features to support old userspace tools"
1231 This option adds code that switches the layout of the "block" class
1232 devices, to not show up in /sys/class/block/, but only in
1235 This switch is only active when the sysfs.deprecated=1 boot option is
1236 passed or the SYSFS_DEPRECATED_V2 option is set.
1238 This option allows new kernels to run on old distributions and tools,
1239 which might get confused by /sys/class/block/. Since 2007/2008 all
1240 major distributions and tools handle this just fine.
1242 Recent distributions and userspace tools after 2009/2010 depend on
1243 the existence of /sys/class/block/, and will not work with this
1246 Only if you are using a new kernel on an old distribution, you might
1249 config SYSFS_DEPRECATED_V2
1250 bool "Enable deprecated sysfs features by default"
1253 depends on SYSFS_DEPRECATED
1255 Enable deprecated sysfs by default.
1257 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1260 Only if you are using a new kernel on an old distribution, you might
1261 need to say Y here. Even then, odds are you would not need it
1262 enabled, you can always pass the boot option if absolutely necessary.
1265 bool "Kernel->user space relay support (formerly relayfs)"
1268 This option enables support for relay interface support in
1269 certain file systems (such as debugfs).
1270 It is designed to provide an efficient mechanism for tools and
1271 facilities to relay large amounts of data from kernel space to
1276 config BLK_DEV_INITRD
1277 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1279 The initial RAM filesystem is a ramfs which is loaded by the
1280 boot loader (loadlin or lilo) and that is mounted as root
1281 before the normal boot procedure. It is typically used to
1282 load modules needed to mount the "real" root file system,
1283 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1285 If RAM disk support (BLK_DEV_RAM) is also included, this
1286 also enables initial RAM disk (initrd) support and adds
1287 15 Kbytes (more on some other architectures) to the kernel size.
1293 source "usr/Kconfig"
1298 bool "Boot config support"
1299 select BLK_DEV_INITRD
1301 Extra boot config allows system admin to pass a config file as
1302 complemental extension of kernel cmdline when booting.
1303 The boot config file must be attached at the end of initramfs
1304 with checksum, size and magic word.
1305 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1310 prompt "Compiler optimization level"
1311 default CC_OPTIMIZE_FOR_PERFORMANCE
1313 config CC_OPTIMIZE_FOR_PERFORMANCE
1314 bool "Optimize for performance (-O2)"
1316 This is the default optimization level for the kernel, building
1317 with the "-O2" compiler flag for best performance and most
1318 helpful compile-time warnings.
1320 config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1321 bool "Optimize more for performance (-O3)"
1324 Choosing this option will pass "-O3" to your compiler to optimize
1325 the kernel yet more for performance.
1327 config CC_OPTIMIZE_FOR_SIZE
1328 bool "Optimize for size (-Os)"
1330 Choosing this option will pass "-Os" to your compiler resulting
1331 in a smaller kernel.
1335 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1338 This requires that the arch annotates or otherwise protects
1339 its external entry points from being discarded. Linker scripts
1340 must also merge .text.*, .data.*, and .bss.* correctly into
1341 output sections. Care must be taken not to pull in unrelated
1342 sections (e.g., '.text.init'). Typically '.' in section names
1343 is used to distinguish them from label names / C identifiers.
1345 config LD_DEAD_CODE_DATA_ELIMINATION
1346 bool "Dead code and data elimination (EXPERIMENTAL)"
1347 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1349 depends on $(cc-option,-ffunction-sections -fdata-sections)
1350 depends on $(ld-option,--gc-sections)
1352 Enable this if you want to do dead code and data elimination with
1353 the linker by compiling with -ffunction-sections -fdata-sections,
1354 and linking with --gc-sections.
1356 This can reduce on disk and in-memory size of the kernel
1357 code and static data, particularly for small configs and
1358 on small systems. This has the possibility of introducing
1359 silently broken kernel if the required annotations are not
1360 present. This option is not well tested yet, so use at your
1363 config LD_ORPHAN_WARN
1365 depends on ARCH_WANT_LD_ORPHAN_WARN
1366 depends on !LD_IS_LLD || LLD_VERSION >= 110000
1367 depends on $(ld-option,--orphan-handling=warn)
1375 config SYSCTL_EXCEPTION_TRACE
1378 Enable support for /proc/sys/debug/exception-trace.
1380 config SYSCTL_ARCH_UNALIGN_NO_WARN
1383 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1384 Allows arch to define/use @no_unaligned_warning to possibly warn
1385 about unaligned access emulation going on under the hood.
1387 config SYSCTL_ARCH_UNALIGN_ALLOW
1390 Enable support for /proc/sys/kernel/unaligned-trap
1391 Allows arches to define/use @unaligned_enabled to runtime toggle
1392 the unaligned access emulation.
1393 see arch/parisc/kernel/unaligned.c for reference
1395 config HAVE_PCSPKR_PLATFORM
1398 # interpreter that classic socket filters depend on
1403 bool "Configure standard kernel features (expert users)"
1404 # Unhide debug options, to make the on-by-default options visible
1407 This option allows certain base kernel options and settings
1408 to be disabled or tweaked. This is for specialized
1409 environments which can tolerate a "non-standard" kernel.
1410 Only use this if you really know what you are doing.
1413 bool "Enable 16-bit UID system calls" if EXPERT
1414 depends on HAVE_UID16 && MULTIUSER
1417 This enables the legacy 16-bit UID syscall wrappers.
1420 bool "Multiple users, groups and capabilities support" if EXPERT
1423 This option enables support for non-root users, groups and
1426 If you say N here, all processes will run with UID 0, GID 0, and all
1427 possible capabilities. Saying N here also compiles out support for
1428 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1431 If unsure, say Y here.
1433 config SGETMASK_SYSCALL
1434 bool "sgetmask/ssetmask syscalls support" if EXPERT
1435 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1437 sys_sgetmask and sys_ssetmask are obsolete system calls
1438 no longer supported in libc but still enabled by default in some
1441 If unsure, leave the default option here.
1443 config SYSFS_SYSCALL
1444 bool "Sysfs syscall support" if EXPERT
1447 sys_sysfs is an obsolete system call no longer supported in libc.
1448 Note that disabling this option is more secure but might break
1449 compatibility with some systems.
1451 If unsure say Y here.
1454 bool "open by fhandle syscalls" if EXPERT
1458 If you say Y here, a user level program will be able to map
1459 file names to handle and then later use the handle for
1460 different file system operations. This is useful in implementing
1461 userspace file servers, which now track files using handles instead
1462 of names. The handle would remain the same even if file names
1463 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1467 bool "Posix Clocks & timers" if EXPERT
1470 This includes native support for POSIX timers to the kernel.
1471 Some embedded systems have no use for them and therefore they
1472 can be configured out to reduce the size of the kernel image.
1474 When this option is disabled, the following syscalls won't be
1475 available: timer_create, timer_gettime: timer_getoverrun,
1476 timer_settime, timer_delete, clock_adjtime, getitimer,
1477 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1478 clock_getres and clock_nanosleep syscalls will be limited to
1479 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1485 bool "Enable support for printk" if EXPERT
1488 This option enables normal printk support. Removing it
1489 eliminates most of the message strings from the kernel image
1490 and makes the kernel more or less silent. As this makes it
1491 very difficult to diagnose system problems, saying N here is
1492 strongly discouraged.
1500 bool "BUG() support" if EXPERT
1503 Disabling this option eliminates support for BUG and WARN, reducing
1504 the size of your kernel image and potentially quietly ignoring
1505 numerous fatal conditions. You should only consider disabling this
1506 option for embedded systems with no facilities for reporting errors.
1512 bool "Enable ELF core dumps" if EXPERT
1514 Enable support for generating core dumps. Disabling saves about 4k.
1517 config PCSPKR_PLATFORM
1518 bool "Enable PC-Speaker support" if EXPERT
1519 depends on HAVE_PCSPKR_PLATFORM
1523 This option allows to disable the internal PC-Speaker
1524 support, saving some memory.
1528 bool "Enable full-sized data structures for core" if EXPERT
1530 Disabling this option reduces the size of miscellaneous core
1531 kernel data structures. This saves memory on small machines,
1532 but may reduce performance.
1535 bool "Enable futex support" if EXPERT
1539 Disabling this option will cause the kernel to be built without
1540 support for "fast userspace mutexes". The resulting kernel may not
1541 run glibc-based applications correctly.
1545 depends on FUTEX && RT_MUTEXES
1548 config HAVE_FUTEX_CMPXCHG
1552 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1553 is implemented and always working. This removes a couple of runtime
1557 bool "Enable eventpoll support" if EXPERT
1560 Disabling this option will cause the kernel to be built without
1561 support for epoll family of system calls.
1564 bool "Enable signalfd() system call" if EXPERT
1567 Enable the signalfd() system call that allows to receive signals
1568 on a file descriptor.
1573 bool "Enable timerfd() system call" if EXPERT
1576 Enable the timerfd() system call that allows to receive timer
1577 events on a file descriptor.
1582 bool "Enable eventfd() system call" if EXPERT
1585 Enable the eventfd() system call that allows to receive both
1586 kernel notification (ie. KAIO) or userspace notifications.
1591 bool "Use full shmem filesystem" if EXPERT
1595 The shmem is an internal filesystem used to manage shared memory.
1596 It is backed by swap and manages resource limits. It is also exported
1597 to userspace as tmpfs if TMPFS is enabled. Disabling this
1598 option replaces shmem and tmpfs with the much simpler ramfs code,
1599 which may be appropriate on small systems without swap.
1602 bool "Enable AIO support" if EXPERT
1605 This option enables POSIX asynchronous I/O which may by used
1606 by some high performance threaded applications. Disabling
1607 this option saves about 7k.
1610 bool "Enable IO uring support" if EXPERT
1614 This option enables support for the io_uring interface, enabling
1615 applications to submit and complete IO through submission and
1616 completion rings that are shared between the kernel and application.
1618 config ADVISE_SYSCALLS
1619 bool "Enable madvise/fadvise syscalls" if EXPERT
1622 This option enables the madvise and fadvise syscalls, used by
1623 applications to advise the kernel about their future memory or file
1624 usage, improving performance. If building an embedded system where no
1625 applications use these syscalls, you can disable this option to save
1628 config HAVE_ARCH_USERFAULTFD_WP
1631 Arch has userfaultfd write protection support
1634 bool "Enable membarrier() system call" if EXPERT
1637 Enable the membarrier() system call that allows issuing memory
1638 barriers across all running threads, which can be used to distribute
1639 the cost of user-space memory barriers asymmetrically by transforming
1640 pairs of memory barriers into pairs consisting of membarrier() and a
1646 bool "Load all symbols for debugging/ksymoops" if EXPERT
1649 Say Y here to let the kernel print out symbolic crash information and
1650 symbolic stack backtraces. This increases the size of the kernel
1651 somewhat, as all symbols have to be loaded into the kernel image.
1654 bool "Include all symbols in kallsyms"
1655 depends on DEBUG_KERNEL && KALLSYMS
1657 Normally kallsyms only contains the symbols of functions for nicer
1658 OOPS messages and backtraces (i.e., symbols from the text and inittext
1659 sections). This is sufficient for most cases. And only in very rare
1660 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1661 names of variables from the data sections, etc).
1663 This option makes sure that all symbols are loaded into the kernel
1664 image (i.e., symbols from all sections) in cost of increased kernel
1665 size (depending on the kernel configuration, it may be 300KiB or
1666 something like this).
1668 Say N unless you really need all symbols.
1670 config KALLSYMS_ABSOLUTE_PERCPU
1673 default X86_64 && SMP
1675 config KALLSYMS_BASE_RELATIVE
1680 Instead of emitting them as absolute values in the native word size,
1681 emit the symbol references in the kallsyms table as 32-bit entries,
1682 each containing a relative value in the range [base, base + U32_MAX]
1683 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1684 an absolute value in the range [0, S32_MAX] or a relative value in the
1685 range [base, base + S32_MAX], where base is the lowest relative symbol
1686 address encountered in the image.
1688 On 64-bit builds, this reduces the size of the address table by 50%,
1689 but more importantly, it results in entries whose values are build
1690 time constants, and no relocation pass is required at runtime to fix
1691 up the entries based on the runtime load address of the kernel.
1693 # end of the "standard kernel features (expert users)" menu
1695 # syscall, maps, verifier
1698 bool "LSM Instrumentation with BPF"
1699 depends on BPF_EVENTS
1700 depends on BPF_SYSCALL
1704 Enables instrumentation of the security hooks with eBPF programs for
1705 implementing dynamic MAC and Audit Policies.
1707 If you are unsure how to answer this question, answer N.
1710 bool "Enable bpf() system call"
1713 select TASKS_TRACE_RCU
1716 Enable the bpf() system call that allows to manipulate eBPF
1717 programs and maps via file descriptors.
1719 config ARCH_WANT_DEFAULT_BPF_JIT
1722 config BPF_JIT_ALWAYS_ON
1723 bool "Permanently enable BPF JIT and remove BPF interpreter"
1724 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1726 Enables BPF JIT and removes BPF interpreter to avoid
1727 speculative execution of BPF instructions by the interpreter
1729 config BPF_JIT_DEFAULT_ON
1730 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
1731 depends on HAVE_EBPF_JIT && BPF_JIT
1733 source "kernel/bpf/preload/Kconfig"
1736 bool "Enable userfaultfd() system call"
1739 Enable the userfaultfd() system call that allows to intercept and
1740 handle page faults in userland.
1742 config ARCH_HAS_MEMBARRIER_CALLBACKS
1745 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1749 bool "Enable kcmp() system call" if EXPERT
1751 Enable the kernel resource comparison system call. It provides
1752 user-space with the ability to compare two processes to see if they
1753 share a common resource, such as a file descriptor or even virtual
1759 bool "Enable rseq() system call" if EXPERT
1761 depends on HAVE_RSEQ
1764 Enable the restartable sequences system call. It provides a
1765 user-space cache for the current CPU number value, which
1766 speeds up getting the current CPU number from user-space,
1767 as well as an ABI to speed up user-space operations on
1774 bool "Enabled debugging of rseq() system call" if EXPERT
1775 depends on RSEQ && DEBUG_KERNEL
1777 Enable extra debugging checks for the rseq system call.
1782 bool "Embedded system"
1783 option allnoconfig_y
1786 This option should be enabled if compiling the kernel for
1787 an embedded system so certain expert options are available
1790 config HAVE_PERF_EVENTS
1793 See tools/perf/design.txt for details.
1795 config PERF_USE_VMALLOC
1798 See tools/perf/design.txt for details
1801 bool "PC/104 support" if EXPERT
1803 Expose PC/104 form factor device drivers and options available for
1804 selection and configuration. Enable this option if your target
1805 machine has a PC/104 bus.
1807 menu "Kernel Performance Events And Counters"
1810 bool "Kernel performance events and counters"
1811 default y if PROFILING
1812 depends on HAVE_PERF_EVENTS
1816 Enable kernel support for various performance events provided
1817 by software and hardware.
1819 Software events are supported either built-in or via the
1820 use of generic tracepoints.
1822 Most modern CPUs support performance events via performance
1823 counter registers. These registers count the number of certain
1824 types of hw events: such as instructions executed, cachemisses
1825 suffered, or branches mis-predicted - without slowing down the
1826 kernel or applications. These registers can also trigger interrupts
1827 when a threshold number of events have passed - and can thus be
1828 used to profile the code that runs on that CPU.
1830 The Linux Performance Event subsystem provides an abstraction of
1831 these software and hardware event capabilities, available via a
1832 system call and used by the "perf" utility in tools/perf/. It
1833 provides per task and per CPU counters, and it provides event
1834 capabilities on top of those.
1838 config DEBUG_PERF_USE_VMALLOC
1840 bool "Debug: use vmalloc to back perf mmap() buffers"
1841 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1842 select PERF_USE_VMALLOC
1844 Use vmalloc memory to back perf mmap() buffers.
1846 Mostly useful for debugging the vmalloc code on platforms
1847 that don't require it.
1853 config VM_EVENT_COUNTERS
1855 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1857 VM event counters are needed for event counts to be shown.
1858 This option allows the disabling of the VM event counters
1859 on EXPERT systems. /proc/vmstat will only show page counts
1860 if VM event counters are disabled.
1864 bool "Enable SLUB debugging support" if EXPERT
1865 depends on SLUB && SYSFS
1867 SLUB has extensive debug support features. Disabling these can
1868 result in significant savings in code size. This also disables
1869 SLUB sysfs support. /sys/slab will not exist and there will be
1870 no support for cache validation etc.
1872 config SLUB_MEMCG_SYSFS_ON
1874 bool "Enable memcg SLUB sysfs support by default" if EXPERT
1875 depends on SLUB && SYSFS && MEMCG
1877 SLUB creates a directory under /sys/kernel/slab for each
1878 allocation cache to host info and debug files. If memory
1879 cgroup is enabled, each cache can have per memory cgroup
1880 caches. SLUB can create the same sysfs directories for these
1881 caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1882 to a very high number of debug files being created. This is
1883 controlled by slub_memcg_sysfs boot parameter and this
1884 config option determines the parameter's default value.
1887 bool "Disable heap randomization"
1890 Randomizing heap placement makes heap exploits harder, but it
1891 also breaks ancient binaries (including anything libc5 based).
1892 This option changes the bootup default to heap randomization
1893 disabled, and can be overridden at runtime by setting
1894 /proc/sys/kernel/randomize_va_space to 2.
1896 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1899 prompt "Choose SLAB allocator"
1902 This option allows to select a slab allocator.
1906 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1908 The regular slab allocator that is established and known to work
1909 well in all environments. It organizes cache hot objects in
1910 per cpu and per node queues.
1913 bool "SLUB (Unqueued Allocator)"
1914 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1916 SLUB is a slab allocator that minimizes cache line usage
1917 instead of managing queues of cached objects (SLAB approach).
1918 Per cpu caching is realized using slabs of objects instead
1919 of queues of objects. SLUB can use memory efficiently
1920 and has enhanced diagnostics. SLUB is the default choice for
1925 bool "SLOB (Simple Allocator)"
1927 SLOB replaces the stock allocator with a drastically simpler
1928 allocator. SLOB is generally more space efficient but
1929 does not perform as well on large systems.
1933 config SLAB_MERGE_DEFAULT
1934 bool "Allow slab caches to be merged"
1937 For reduced kernel memory fragmentation, slab caches can be
1938 merged when they share the same size and other characteristics.
1939 This carries a risk of kernel heap overflows being able to
1940 overwrite objects from merged caches (and more easily control
1941 cache layout), which makes such heap attacks easier to exploit
1942 by attackers. By keeping caches unmerged, these kinds of exploits
1943 can usually only damage objects in the same cache. To disable
1944 merging at runtime, "slab_nomerge" can be passed on the kernel
1947 config SLAB_FREELIST_RANDOM
1948 bool "Randomize slab freelist"
1949 depends on SLAB || SLUB
1951 Randomizes the freelist order used on creating new pages. This
1952 security feature reduces the predictability of the kernel slab
1953 allocator against heap overflows.
1955 config SLAB_FREELIST_HARDENED
1956 bool "Harden slab freelist metadata"
1957 depends on SLAB || SLUB
1959 Many kernel heap attacks try to target slab cache metadata and
1960 other infrastructure. This options makes minor performance
1961 sacrifices to harden the kernel slab allocator against common
1962 freelist exploit methods. Some slab implementations have more
1963 sanity-checking than others. This option is most effective with
1966 config SHUFFLE_PAGE_ALLOCATOR
1967 bool "Page allocator randomization"
1968 default SLAB_FREELIST_RANDOM && ACPI_NUMA
1970 Randomization of the page allocator improves the average
1971 utilization of a direct-mapped memory-side-cache. See section
1972 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1973 6.2a specification for an example of how a platform advertises
1974 the presence of a memory-side-cache. There are also incidental
1975 security benefits as it reduces the predictability of page
1976 allocations to compliment SLAB_FREELIST_RANDOM, but the
1977 default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1978 10th order of pages is selected based on cache utilization
1981 While the randomization improves cache utilization it may
1982 negatively impact workloads on platforms without a cache. For
1983 this reason, by default, the randomization is enabled only
1984 after runtime detection of a direct-mapped memory-side-cache.
1985 Otherwise, the randomization may be force enabled with the
1986 'page_alloc.shuffle' kernel command line parameter.
1990 config SLUB_CPU_PARTIAL
1992 depends on SLUB && SMP
1993 bool "SLUB per cpu partial cache"
1995 Per cpu partial caches accelerate objects allocation and freeing
1996 that is local to a processor at the price of more indeterminism
1997 in the latency of the free. On overflow these caches will be cleared
1998 which requires the taking of locks that may cause latency spikes.
1999 Typically one would choose no for a realtime system.
2001 config MMAP_ALLOW_UNINITIALIZED
2002 bool "Allow mmapped anonymous memory to be uninitialized"
2003 depends on EXPERT && !MMU
2006 Normally, and according to the Linux spec, anonymous memory obtained
2007 from mmap() has its contents cleared before it is passed to
2008 userspace. Enabling this config option allows you to request that
2009 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
2010 providing a huge performance boost. If this option is not enabled,
2011 then the flag will be ignored.
2013 This is taken advantage of by uClibc's malloc(), and also by
2014 ELF-FDPIC binfmt's brk and stack allocator.
2016 Because of the obvious security issues, this option should only be
2017 enabled on embedded devices where you control what is run in
2018 userspace. Since that isn't generally a problem on no-MMU systems,
2019 it is normally safe to say Y here.
2021 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
2023 config SYSTEM_DATA_VERIFICATION
2025 select SYSTEM_TRUSTED_KEYRING
2029 select ASYMMETRIC_KEY_TYPE
2030 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
2033 select X509_CERTIFICATE_PARSER
2034 select PKCS7_MESSAGE_PARSER
2036 Provide PKCS#7 message verification using the contents of the system
2037 trusted keyring to provide public keys. This then can be used for
2038 module verification, kexec image verification and firmware blob
2042 bool "Profiling support"
2044 Say Y here to enable the extended profiling support mechanisms used
2045 by profilers such as OProfile.
2048 # Place an empty function call at each tracepoint site. Can be
2049 # dynamically changed for a probe function.
2054 endmenu # General setup
2056 source "arch/Kconfig"
2063 default 0 if BASE_FULL
2064 default 1 if !BASE_FULL
2066 config MODULE_SIG_FORMAT
2068 select SYSTEM_DATA_VERIFICATION
2071 bool "Enable loadable module support"
2074 Kernel modules are small pieces of compiled code which can
2075 be inserted in the running kernel, rather than being
2076 permanently built into the kernel. You use the "modprobe"
2077 tool to add (and sometimes remove) them. If you say Y here,
2078 many parts of the kernel can be built as modules (by
2079 answering M instead of Y where indicated): this is most
2080 useful for infrequently used options which are not required
2081 for booting. For more information, see the man pages for
2082 modprobe, lsmod, modinfo, insmod and rmmod.
2084 If you say Y here, you will need to run "make
2085 modules_install" to put the modules under /lib/modules/
2086 where modprobe can find them (you may need to be root to do
2093 config MODULE_FORCE_LOAD
2094 bool "Forced module loading"
2097 Allow loading of modules without version information (ie. modprobe
2098 --force). Forced module loading sets the 'F' (forced) taint flag and
2099 is usually a really bad idea.
2101 config MODULE_UNLOAD
2102 bool "Module unloading"
2104 Without this option you will not be able to unload any
2105 modules (note that some modules may not be unloadable
2106 anyway), which makes your kernel smaller, faster
2107 and simpler. If unsure, say Y.
2109 config MODULE_FORCE_UNLOAD
2110 bool "Forced module unloading"
2111 depends on MODULE_UNLOAD
2113 This option allows you to force a module to unload, even if the
2114 kernel believes it is unsafe: the kernel will remove the module
2115 without waiting for anyone to stop using it (using the -f option to
2116 rmmod). This is mainly for kernel developers and desperate users.
2120 bool "Module versioning support"
2122 Usually, you have to use modules compiled with your kernel.
2123 Saying Y here makes it sometimes possible to use modules
2124 compiled for different kernels, by adding enough information
2125 to the modules to (hopefully) spot any changes which would
2126 make them incompatible with the kernel you are running. If
2129 config ASM_MODVERSIONS
2131 default HAVE_ASM_MODVERSIONS && MODVERSIONS
2133 This enables module versioning for exported symbols also from
2134 assembly. This can be enabled only when the target architecture
2137 config MODULE_REL_CRCS
2139 depends on MODVERSIONS
2141 config MODULE_SRCVERSION_ALL
2142 bool "Source checksum for all modules"
2144 Modules which contain a MODULE_VERSION get an extra "srcversion"
2145 field inserted into their modinfo section, which contains a
2146 sum of the source files which made it. This helps maintainers
2147 see exactly which source was used to build a module (since
2148 others sometimes change the module source without updating
2149 the version). With this option, such a "srcversion" field
2150 will be created for all modules. If unsure, say N.
2153 bool "Module signature verification"
2154 select MODULE_SIG_FORMAT
2156 Check modules for valid signatures upon load: the signature
2157 is simply appended to the module. For more information see
2158 <file:Documentation/admin-guide/module-signing.rst>.
2160 Note that this option adds the OpenSSL development packages as a
2161 kernel build dependency so that the signing tool can use its crypto
2164 You should enable this option if you wish to use either
2165 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2166 another LSM - otherwise unsigned modules will be loadable regardless
2167 of the lockdown policy.
2169 !!!WARNING!!! If you enable this option, you MUST make sure that the
2170 module DOES NOT get stripped after being signed. This includes the
2171 debuginfo strip done by some packagers (such as rpmbuild) and
2172 inclusion into an initramfs that wants the module size reduced.
2174 config MODULE_SIG_FORCE
2175 bool "Require modules to be validly signed"
2176 depends on MODULE_SIG
2178 Reject unsigned modules or signed modules for which we don't have a
2179 key. Without this, such modules will simply taint the kernel.
2181 config MODULE_SIG_ALL
2182 bool "Automatically sign all modules"
2184 depends on MODULE_SIG
2186 Sign all modules during make modules_install. Without this option,
2187 modules must be signed manually, using the scripts/sign-file tool.
2189 comment "Do not forget to sign required modules with scripts/sign-file"
2190 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2193 prompt "Which hash algorithm should modules be signed with?"
2194 depends on MODULE_SIG
2196 This determines which sort of hashing algorithm will be used during
2197 signature generation. This algorithm _must_ be built into the kernel
2198 directly so that signature verification can take place. It is not
2199 possible to load a signed module containing the algorithm to check
2200 the signature on that module.
2202 config MODULE_SIG_SHA1
2203 bool "Sign modules with SHA-1"
2206 config MODULE_SIG_SHA224
2207 bool "Sign modules with SHA-224"
2208 select CRYPTO_SHA256
2210 config MODULE_SIG_SHA256
2211 bool "Sign modules with SHA-256"
2212 select CRYPTO_SHA256
2214 config MODULE_SIG_SHA384
2215 bool "Sign modules with SHA-384"
2216 select CRYPTO_SHA512
2218 config MODULE_SIG_SHA512
2219 bool "Sign modules with SHA-512"
2220 select CRYPTO_SHA512
2224 config MODULE_SIG_HASH
2226 depends on MODULE_SIG
2227 default "sha1" if MODULE_SIG_SHA1
2228 default "sha224" if MODULE_SIG_SHA224
2229 default "sha256" if MODULE_SIG_SHA256
2230 default "sha384" if MODULE_SIG_SHA384
2231 default "sha512" if MODULE_SIG_SHA512
2233 config MODULE_COMPRESS
2234 bool "Compress modules on installation"
2237 Compresses kernel modules when 'make modules_install' is run; gzip or
2238 xz depending on "Compression algorithm" below.
2240 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2242 Out-of-tree kernel modules installed using Kbuild will also be
2243 compressed upon installation.
2245 Note: for modules inside an initrd or initramfs, it's more efficient
2246 to compress the whole initrd or initramfs instead.
2248 Note: This is fully compatible with signed modules.
2253 prompt "Compression algorithm"
2254 depends on MODULE_COMPRESS
2255 default MODULE_COMPRESS_GZIP
2257 This determines which sort of compression will be used during
2258 'make modules_install'.
2260 GZIP (default) and XZ are supported.
2262 config MODULE_COMPRESS_GZIP
2265 config MODULE_COMPRESS_XZ
2270 config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2271 bool "Allow loading of modules with missing namespace imports"
2273 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2274 a namespace. A module that makes use of a symbol exported with such a
2275 namespace is required to import the namespace via MODULE_IMPORT_NS().
2276 There is no technical reason to enforce correct namespace imports,
2277 but it creates consistency between symbols defining namespaces and
2278 users importing namespaces they make use of. This option relaxes this
2279 requirement and lifts the enforcement when loading a module.
2283 config UNUSED_SYMBOLS
2284 bool "Enable unused/obsolete exported symbols"
2287 Unused but exported symbols make the kernel needlessly bigger. For
2288 that reason most of these unused exports will soon be removed. This
2289 option is provided temporarily to provide a transition period in case
2290 some external kernel module needs one of these symbols anyway. If you
2291 encounter such a case in your module, consider if you are actually
2292 using the right API. (rationale: since nobody in the kernel is using
2293 this in a module, there is a pretty good chance it's actually the
2294 wrong interface to use). If you really need the symbol, please send a
2295 mail to the linux kernel mailing list mentioning the symbol and why
2296 you really need it, and what the merge plan to the mainline kernel for
2299 config TRIM_UNUSED_KSYMS
2300 bool "Trim unused exported kernel symbols"
2301 depends on !UNUSED_SYMBOLS
2303 The kernel and some modules make many symbols available for
2304 other modules to use via EXPORT_SYMBOL() and variants. Depending
2305 on the set of modules being selected in your kernel configuration,
2306 many of those exported symbols might never be used.
2308 This option allows for unused exported symbols to be dropped from
2309 the build. In turn, this provides the compiler more opportunities
2310 (especially when using LTO) for optimizing the code and reducing
2311 binary size. This might have some security advantages as well.
2313 If unsure, or if you need to build out-of-tree modules, say N.
2315 config UNUSED_KSYMS_WHITELIST
2316 string "Whitelist of symbols to keep in ksymtab"
2317 depends on TRIM_UNUSED_KSYMS
2319 By default, all unused exported symbols will be un-exported from the
2320 build when TRIM_UNUSED_KSYMS is selected.
2322 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
2323 exported at all times, even in absence of in-tree users. The value to
2324 set here is the path to a text file containing the list of symbols,
2325 one per line. The path can be absolute, or relative to the kernel
2330 config MODULES_TREE_LOOKUP
2332 depends on PERF_EVENTS || TRACING
2334 config INIT_ALL_POSSIBLE
2337 Back when each arch used to define their own cpu_online_mask and
2338 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2339 with all 1s, and others with all 0s. When they were centralised,
2340 it was better to provide this option than to break all the archs
2341 and have several arch maintainers pursuing me down dark alleys.
2343 source "block/Kconfig"
2345 config PREEMPT_NOTIFIERS
2355 Build a simple ASN.1 grammar compiler that produces a bytecode output
2356 that can be interpreted by the ASN.1 stream decoder and used to
2357 inform it as to what tags are to be expected in a stream and what
2358 functions to call on what tags.
2360 source "kernel/Kconfig.locks"
2362 config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2365 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2368 # It may be useful for an architecture to override the definitions of the
2369 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2370 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2371 # different calling convention for syscalls. They can also override the
2372 # macros for not-implemented syscalls in kernel/sys_ni.c and
2373 # kernel/time/posix-stubs.c. All these overrides need to be available in
2374 # <asm/syscall_wrapper.h>.
2375 config ARCH_HAS_SYSCALL_WRAPPER
projects / mirror_ubuntu-hirsute-kernel.git / blob