1 # SPDX-License-Identifier: GPL-2.0-only
6 default "/lib/modules/$(shell,uname -r)/.config"
7 default "/etc/kernel-config"
8 default "/boot/config-$(shell,uname -r)"
9 default "arch/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG)"
11 config CC_VERSION_TEXT
13 default "$(CC_VERSION_TEXT)"
15 This is used in unclear ways:
17 - Re-run Kconfig when the compiler is updated
18 The 'default' property references the environment variable,
19 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd.
20 When the compiler is updated, Kconfig will be invoked.
22 - Ensure full rebuild when the compier is updated
23 include/linux/kconfig.h contains this option in the comment line so
24 fixdep adds include/config/cc/version/text.h into the auto-generated
25 dependency. When the compiler is updated, syncconfig will touch it
26 and then every file will be rebuilt.
29 def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q gcc)
33 default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC
38 default $(shell,$(LD) --version | $(srctree)/scripts/ld-version.sh)
41 def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q clang)
44 def_bool $(success,$(LD) -v | head -n 1 | grep -q LLD)
48 default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
52 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag)) if 64BIT
53 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag))
55 config CC_CAN_LINK_STATIC
57 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static) if 64BIT
58 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag) -static)
60 config CC_HAS_ASM_GOTO
61 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
63 config CC_HAS_ASM_GOTO_OUTPUT
64 depends on CC_HAS_ASM_GOTO
65 def_bool $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null)
67 config TOOLS_SUPPORT_RELR
68 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
70 config CC_HAS_ASM_INLINE
71 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
80 config BUILDTIME_TABLE_SORT
83 config THREAD_INFO_IN_TASK
86 Select this to move thread_info off the stack into task_struct. To
87 make this work, an arch will need to remove all thread_info fields
88 except flags and fix any runtime bugs.
90 One subtle change that will be needed is to use try_get_task_stack()
91 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
100 depends on BROKEN || !SMP
103 config INIT_ENV_ARG_LIMIT
108 Maximum of each of the number of arguments and environment
109 variables passed to init from the kernel command line.
112 bool "Compile also drivers which will not load"
116 Some drivers can be compiled on a different platform than they are
117 intended to be run on. Despite they cannot be loaded there (or even
118 when they load they cannot be used due to missing HW support),
119 developers still, opposing to distributors, might want to build such
120 drivers to compile-test them.
122 If you are a developer and want to build everything available, say Y
123 here. If you are a user/distributor, say N here to exclude useless
124 drivers to be distributed.
126 config UAPI_HEADER_TEST
127 bool "Compile test UAPI headers"
128 depends on HEADERS_INSTALL && CC_CAN_LINK
130 Compile test headers exported to user-space to ensure they are
131 self-contained, i.e. compilable as standalone units.
133 If you are a developer or tester and want to ensure the exported
134 headers are self-contained, say Y here. Otherwise, choose N.
137 string "Local version - append to kernel release"
139 Append an extra string to the end of your kernel version.
140 This will show up when you type uname, for example.
141 The string you set here will be appended after the contents of
142 any files with a filename matching localversion* in your
143 object and source tree, in that order. Your total string can
144 be a maximum of 64 characters.
146 config LOCALVERSION_AUTO
147 bool "Automatically append version information to the version string"
149 depends on !COMPILE_TEST
151 This will try to automatically determine if the current tree is a
152 release tree by looking for git tags that belong to the current
153 top of tree revision.
155 A string of the format -gxxxxxxxx will be added to the localversion
156 if a git-based tree is found. The string generated by this will be
157 appended after any matching localversion* files, and after the value
158 set in CONFIG_LOCALVERSION.
160 (The actual string used here is the first eight characters produced
161 by running the command:
163 $ git rev-parse --verify HEAD
165 which is done within the script "scripts/setlocalversion".)
168 string "Build ID Salt"
171 The build ID is used to link binaries and their debug info. Setting
172 this option will use the value in the calculation of the build id.
173 This is mostly useful for distributions which want to ensure the
174 build is unique between builds. It's safe to leave the default.
176 config HAVE_KERNEL_GZIP
179 config HAVE_KERNEL_BZIP2
182 config HAVE_KERNEL_LZMA
185 config HAVE_KERNEL_XZ
188 config HAVE_KERNEL_LZO
191 config HAVE_KERNEL_LZ4
194 config HAVE_KERNEL_ZSTD
197 config HAVE_KERNEL_UNCOMPRESSED
201 prompt "Kernel compression mode"
203 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_ZSTD || HAVE_KERNEL_UNCOMPRESSED
205 The linux kernel is a kind of self-extracting executable.
206 Several compression algorithms are available, which differ
207 in efficiency, compression and decompression speed.
208 Compression speed is only relevant when building a kernel.
209 Decompression speed is relevant at each boot.
211 If you have any problems with bzip2 or lzma compressed
212 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
213 version of this functionality (bzip2 only), for 2.4, was
214 supplied by Christian Ludwig)
216 High compression options are mostly useful for users, who
217 are low on disk space (embedded systems), but for whom ram
220 If in doubt, select 'gzip'
224 depends on HAVE_KERNEL_GZIP
226 The old and tried gzip compression. It provides a good balance
227 between compression ratio and decompression speed.
231 depends on HAVE_KERNEL_BZIP2
233 Its compression ratio and speed is intermediate.
234 Decompression speed is slowest among the choices. The kernel
235 size is about 10% smaller with bzip2, in comparison to gzip.
236 Bzip2 uses a large amount of memory. For modern kernels you
237 will need at least 8MB RAM or more for booting.
241 depends on HAVE_KERNEL_LZMA
243 This compression algorithm's ratio is best. Decompression speed
244 is between gzip and bzip2. Compression is slowest.
245 The kernel size is about 33% smaller with LZMA in comparison to gzip.
249 depends on HAVE_KERNEL_XZ
251 XZ uses the LZMA2 algorithm and instruction set specific
252 BCJ filters which can improve compression ratio of executable
253 code. The size of the kernel is about 30% smaller with XZ in
254 comparison to gzip. On architectures for which there is a BCJ
255 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
256 will create a few percent smaller kernel than plain LZMA.
258 The speed is about the same as with LZMA: The decompression
259 speed of XZ is better than that of bzip2 but worse than gzip
260 and LZO. Compression is slow.
264 depends on HAVE_KERNEL_LZO
266 Its compression ratio is the poorest among the choices. The kernel
267 size is about 10% bigger than gzip; however its speed
268 (both compression and decompression) is the fastest.
272 depends on HAVE_KERNEL_LZ4
274 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
275 A preliminary version of LZ4 de/compression tool is available at
276 <https://code.google.com/p/lz4/>.
278 Its compression ratio is worse than LZO. The size of the kernel
279 is about 8% bigger than LZO. But the decompression speed is
284 depends on HAVE_KERNEL_ZSTD
286 ZSTD is a compression algorithm targeting intermediate compression
287 with fast decompression speed. It will compress better than GZIP and
288 decompress around the same speed as LZO, but slower than LZ4. You
289 will need at least 192 KB RAM or more for booting. The zstd command
290 line tool is required for compression.
292 config KERNEL_UNCOMPRESSED
294 depends on HAVE_KERNEL_UNCOMPRESSED
296 Produce uncompressed kernel image. This option is usually not what
297 you want. It is useful for debugging the kernel in slow simulation
298 environments, where decompressing and moving the kernel is awfully
299 slow. This option allows early boot code to skip the decompressor
300 and jump right at uncompressed kernel image.
305 string "Default init path"
308 This option determines the default init for the system if no init=
309 option is passed on the kernel command line. If the requested path is
310 not present, we will still then move on to attempting further
311 locations (e.g. /sbin/init, etc). If this is empty, we will just use
312 the fallback list when init= is not passed.
314 config DEFAULT_HOSTNAME
315 string "Default hostname"
318 This option determines the default system hostname before userspace
319 calls sethostname(2). The kernel traditionally uses "(none)" here,
320 but you may wish to use a different default here to make a minimal
321 system more usable with less configuration.
324 # For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
325 # add proper SWAP support to them, in which case this can be remove.
331 bool "Support for paging of anonymous memory (swap)"
332 depends on MMU && BLOCK && !ARCH_NO_SWAP
335 This option allows you to choose whether you want to have support
336 for so called swap devices or swap files in your kernel that are
337 used to provide more virtual memory than the actual RAM present
338 in your computer. If unsure say Y.
343 Inter Process Communication is a suite of library functions and
344 system calls which let processes (running programs) synchronize and
345 exchange information. It is generally considered to be a good thing,
346 and some programs won't run unless you say Y here. In particular, if
347 you want to run the DOS emulator dosemu under Linux (read the
348 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
349 you'll need to say Y here.
351 You can find documentation about IPC with "info ipc" and also in
352 section 6.4 of the Linux Programmer's Guide, available from
353 <http://www.tldp.org/guides.html>.
355 config SYSVIPC_SYSCTL
362 bool "POSIX Message Queues"
365 POSIX variant of message queues is a part of IPC. In POSIX message
366 queues every message has a priority which decides about succession
367 of receiving it by a process. If you want to compile and run
368 programs written e.g. for Solaris with use of its POSIX message
369 queues (functions mq_*) say Y here.
371 POSIX message queues are visible as a filesystem called 'mqueue'
372 and can be mounted somewhere if you want to do filesystem
373 operations on message queues.
377 config POSIX_MQUEUE_SYSCTL
379 depends on POSIX_MQUEUE
384 bool "General notification queue"
388 This is a general notification queue for the kernel to pass events to
389 userspace by splicing them into pipes. It can be used in conjunction
390 with watches for key/keyring change notifications and device
393 See Documentation/watch_queue.rst
395 config CROSS_MEMORY_ATTACH
396 bool "Enable process_vm_readv/writev syscalls"
400 Enabling this option adds the system calls process_vm_readv and
401 process_vm_writev which allow a process with the correct privileges
402 to directly read from or write to another process' address space.
403 See the man page for more details.
406 bool "uselib syscall"
407 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
409 This option enables the uselib syscall, a system call used in the
410 dynamic linker from libc5 and earlier. glibc does not use this
411 system call. If you intend to run programs built on libc5 or
412 earlier, you may need to enable this syscall. Current systems
413 running glibc can safely disable this.
416 bool "Auditing support"
419 Enable auditing infrastructure that can be used with another
420 kernel subsystem, such as SELinux (which requires this for
421 logging of avc messages output). System call auditing is included
422 on architectures which support it.
424 config HAVE_ARCH_AUDITSYSCALL
429 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
432 source "kernel/irq/Kconfig"
433 source "kernel/time/Kconfig"
434 source "kernel/Kconfig.preempt"
436 menu "CPU/Task time and stats accounting"
438 config VIRT_CPU_ACCOUNTING
442 prompt "Cputime accounting"
443 default TICK_CPU_ACCOUNTING if !PPC64
444 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
446 # Kind of a stub config for the pure tick based cputime accounting
447 config TICK_CPU_ACCOUNTING
448 bool "Simple tick based cputime accounting"
449 depends on !S390 && !NO_HZ_FULL
451 This is the basic tick based cputime accounting that maintains
452 statistics about user, system and idle time spent on per jiffies
457 config VIRT_CPU_ACCOUNTING_NATIVE
458 bool "Deterministic task and CPU time accounting"
459 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
460 select VIRT_CPU_ACCOUNTING
462 Select this option to enable more accurate task and CPU time
463 accounting. This is done by reading a CPU counter on each
464 kernel entry and exit and on transitions within the kernel
465 between system, softirq and hardirq state, so there is a
466 small performance impact. In the case of s390 or IBM POWER > 5,
467 this also enables accounting of stolen time on logically-partitioned
470 config VIRT_CPU_ACCOUNTING_GEN
471 bool "Full dynticks CPU time accounting"
472 depends on HAVE_CONTEXT_TRACKING
473 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
474 depends on GENERIC_CLOCKEVENTS
475 select VIRT_CPU_ACCOUNTING
476 select CONTEXT_TRACKING
478 Select this option to enable task and CPU time accounting on full
479 dynticks systems. This accounting is implemented by watching every
480 kernel-user boundaries using the context tracking subsystem.
481 The accounting is thus performed at the expense of some significant
484 For now this is only useful if you are working on the full
485 dynticks subsystem development.
491 config IRQ_TIME_ACCOUNTING
492 bool "Fine granularity task level IRQ time accounting"
493 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
495 Select this option to enable fine granularity task irq time
496 accounting. This is done by reading a timestamp on each
497 transitions between softirq and hardirq state, so there can be a
498 small performance impact.
500 If in doubt, say N here.
502 config HAVE_SCHED_AVG_IRQ
504 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
507 config SCHED_THERMAL_PRESSURE
508 bool "Enable periodic averaging of thermal pressure"
511 config BSD_PROCESS_ACCT
512 bool "BSD Process Accounting"
515 If you say Y here, a user level program will be able to instruct the
516 kernel (via a special system call) to write process accounting
517 information to a file: whenever a process exits, information about
518 that process will be appended to the file by the kernel. The
519 information includes things such as creation time, owning user,
520 command name, memory usage, controlling terminal etc. (the complete
521 list is in the struct acct in <file:include/linux/acct.h>). It is
522 up to the user level program to do useful things with this
523 information. This is generally a good idea, so say Y.
525 config BSD_PROCESS_ACCT_V3
526 bool "BSD Process Accounting version 3 file format"
527 depends on BSD_PROCESS_ACCT
530 If you say Y here, the process accounting information is written
531 in a new file format that also logs the process IDs of each
532 process and its parent. Note that this file format is incompatible
533 with previous v0/v1/v2 file formats, so you will need updated tools
534 for processing it. A preliminary version of these tools is available
535 at <http://www.gnu.org/software/acct/>.
538 bool "Export task/process statistics through netlink"
543 Export selected statistics for tasks/processes through the
544 generic netlink interface. Unlike BSD process accounting, the
545 statistics are available during the lifetime of tasks/processes as
546 responses to commands. Like BSD accounting, they are sent to user
551 config TASK_DELAY_ACCT
552 bool "Enable per-task delay accounting"
556 Collect information on time spent by a task waiting for system
557 resources like cpu, synchronous block I/O completion and swapping
558 in pages. Such statistics can help in setting a task's priorities
559 relative to other tasks for cpu, io, rss limits etc.
564 bool "Enable extended accounting over taskstats"
567 Collect extended task accounting data and send the data
568 to userland for processing over the taskstats interface.
572 config TASK_IO_ACCOUNTING
573 bool "Enable per-task storage I/O accounting"
574 depends on TASK_XACCT
576 Collect information on the number of bytes of storage I/O which this
582 bool "Pressure stall information tracking"
584 Collect metrics that indicate how overcommitted the CPU, memory,
585 and IO capacity are in the system.
587 If you say Y here, the kernel will create /proc/pressure/ with the
588 pressure statistics files cpu, memory, and io. These will indicate
589 the share of walltime in which some or all tasks in the system are
590 delayed due to contention of the respective resource.
592 In kernels with cgroup support, cgroups (cgroup2 only) will
593 have cpu.pressure, memory.pressure, and io.pressure files,
594 which aggregate pressure stalls for the grouped tasks only.
596 For more details see Documentation/accounting/psi.rst.
600 config PSI_DEFAULT_DISABLED
601 bool "Require boot parameter to enable pressure stall information tracking"
605 If set, pressure stall information tracking will be disabled
606 per default but can be enabled through passing psi=1 on the
607 kernel commandline during boot.
609 This feature adds some code to the task wakeup and sleep
610 paths of the scheduler. The overhead is too low to affect
611 common scheduling-intense workloads in practice (such as
612 webservers, memcache), but it does show up in artificial
613 scheduler stress tests, such as hackbench.
615 If you are paranoid and not sure what the kernel will be
620 endmenu # "CPU/Task time and stats accounting"
624 depends on SMP || COMPILE_TEST
627 Make sure that CPUs running critical tasks are not disturbed by
628 any source of "noise" such as unbound workqueues, timers, kthreads...
629 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
630 the "isolcpus=" boot parameter.
634 source "kernel/rcu/Kconfig"
641 tristate "Kernel .config support"
643 This option enables the complete Linux kernel ".config" file
644 contents to be saved in the kernel. It provides documentation
645 of which kernel options are used in a running kernel or in an
646 on-disk kernel. This information can be extracted from the kernel
647 image file with the script scripts/extract-ikconfig and used as
648 input to rebuild the current kernel or to build another kernel.
649 It can also be extracted from a running kernel by reading
650 /proc/config.gz if enabled (below).
653 bool "Enable access to .config through /proc/config.gz"
654 depends on IKCONFIG && PROC_FS
656 This option enables access to the kernel configuration file
657 through /proc/config.gz.
660 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
663 This option enables access to the in-kernel headers that are generated during
664 the build process. These can be used to build eBPF tracing programs,
665 or similar programs. If you build the headers as a module, a module called
666 kheaders.ko is built which can be loaded on-demand to get access to headers.
669 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
674 Select the minimal kernel log buffer size as a power of 2.
675 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
676 parameter, see below. Any higher size also might be forced
677 by "log_buf_len" boot parameter.
687 config LOG_CPU_MAX_BUF_SHIFT
688 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
691 default 12 if !BASE_SMALL
692 default 0 if BASE_SMALL
695 This option allows to increase the default ring buffer size
696 according to the number of CPUs. The value defines the contribution
697 of each CPU as a power of 2. The used space is typically only few
698 lines however it might be much more when problems are reported,
701 The increased size means that a new buffer has to be allocated and
702 the original static one is unused. It makes sense only on systems
703 with more CPUs. Therefore this value is used only when the sum of
704 contributions is greater than the half of the default kernel ring
705 buffer as defined by LOG_BUF_SHIFT. The default values are set
706 so that more than 64 CPUs are needed to trigger the allocation.
708 Also this option is ignored when "log_buf_len" kernel parameter is
709 used as it forces an exact (power of two) size of the ring buffer.
711 The number of possible CPUs is used for this computation ignoring
712 hotplugging making the computation optimal for the worst case
713 scenario while allowing a simple algorithm to be used from bootup.
715 Examples shift values and their meaning:
716 17 => 128 KB for each CPU
717 16 => 64 KB for each CPU
718 15 => 32 KB for each CPU
719 14 => 16 KB for each CPU
720 13 => 8 KB for each CPU
721 12 => 4 KB for each CPU
723 config PRINTK_SAFE_LOG_BUF_SHIFT
724 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
729 Select the size of an alternate printk per-CPU buffer where messages
730 printed from usafe contexts are temporary stored. One example would
731 be NMI messages, another one - printk recursion. The messages are
732 copied to the main log buffer in a safe context to avoid a deadlock.
733 The value defines the size as a power of 2.
735 Those messages are rare and limited. The largest one is when
736 a backtrace is printed. It usually fits into 4KB. Select
737 8KB if you want to be on the safe side.
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
748 # Architectures with an unreliable sched_clock() should select this:
750 config HAVE_UNSTABLE_SCHED_CLOCK
753 config GENERIC_SCHED_CLOCK
756 menu "Scheduler features"
759 bool "Enable utilization clamping for RT/FAIR tasks"
760 depends on CPU_FREQ_GOV_SCHEDUTIL
762 This feature enables the scheduler to track the clamped utilization
763 of each CPU based on RUNNABLE tasks scheduled on that CPU.
765 With this option, the user can specify the min and max CPU
766 utilization allowed for RUNNABLE tasks. The max utilization defines
767 the maximum frequency a task should use while the min utilization
768 defines the minimum frequency it should use.
770 Both min and max utilization clamp values are hints to the scheduler,
771 aiming at improving its frequency selection policy, but they do not
772 enforce or grant any specific bandwidth for tasks.
776 config UCLAMP_BUCKETS_COUNT
777 int "Number of supported utilization clamp buckets"
780 depends on UCLAMP_TASK
782 Defines the number of clamp buckets to use. The range of each bucket
783 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
784 number of clamp buckets the finer their granularity and the higher
785 the precision of clamping aggregation and tracking at run-time.
787 For example, with the minimum configuration value we will have 5
788 clamp buckets tracking 20% utilization each. A 25% boosted tasks will
789 be refcounted in the [20..39]% bucket and will set the bucket clamp
790 effective value to 25%.
791 If a second 30% boosted task should be co-scheduled on the same CPU,
792 that task will be refcounted in the same bucket of the first task and
793 it will boost the bucket clamp effective value to 30%.
794 The clamp effective value of a bucket is reset to its nominal value
795 (20% in the example above) when there are no more tasks refcounted in
798 An additional boost/capping margin can be added to some tasks. In the
799 example above the 25% task will be boosted to 30% until it exits the
800 CPU. If that should be considered not acceptable on certain systems,
801 it's always possible to reduce the margin by increasing the number of
802 clamp buckets to trade off used memory for run-time tracking
805 If in doubt, use the default value.
810 # For architectures that want to enable the support for NUMA-affine scheduler
813 config ARCH_SUPPORTS_NUMA_BALANCING
817 # For architectures that prefer to flush all TLBs after a number of pages
818 # are unmapped instead of sending one IPI per page to flush. The architecture
819 # must provide guarantees on what happens if a clean TLB cache entry is
820 # written after the unmap. Details are in mm/rmap.c near the check for
821 # should_defer_flush. The architecture should also consider if the full flush
822 # and the refill costs are offset by the savings of sending fewer IPIs.
823 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
827 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
830 # For architectures that know their GCC __int128 support is sound
832 config ARCH_SUPPORTS_INT128
835 # For architectures that (ab)use NUMA to represent different memory regions
836 # all cpu-local but of different latencies, such as SuperH.
838 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
841 config NUMA_BALANCING
842 bool "Memory placement aware NUMA scheduler"
843 depends on ARCH_SUPPORTS_NUMA_BALANCING
844 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
845 depends on SMP && NUMA && MIGRATION
847 This option adds support for automatic NUMA aware memory/task placement.
848 The mechanism is quite primitive and is based on migrating memory when
849 it has references to the node the task is running on.
851 This system will be inactive on UMA systems.
853 config NUMA_BALANCING_DEFAULT_ENABLED
854 bool "Automatically enable NUMA aware memory/task placement"
856 depends on NUMA_BALANCING
858 If set, automatic NUMA balancing will be enabled if running on a NUMA
862 bool "Control Group support"
865 This option adds support for grouping sets of processes together, for
866 use with process control subsystems such as Cpusets, CFS, memory
867 controls or device isolation.
869 - Documentation/scheduler/sched-design-CFS.rst (CFS)
870 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
871 and resource control)
881 bool "Memory controller"
885 Provides control over the memory footprint of tasks in a cgroup.
889 depends on MEMCG && SWAP
894 depends on MEMCG && !SLOB
902 Generic block IO controller cgroup interface. This is the common
903 cgroup interface which should be used by various IO controlling
906 Currently, CFQ IO scheduler uses it to recognize task groups and
907 control disk bandwidth allocation (proportional time slice allocation)
908 to such task groups. It is also used by bio throttling logic in
909 block layer to implement upper limit in IO rates on a device.
911 This option only enables generic Block IO controller infrastructure.
912 One needs to also enable actual IO controlling logic/policy. For
913 enabling proportional weight division of disk bandwidth in CFQ, set
914 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
915 CONFIG_BLK_DEV_THROTTLING=y.
917 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
919 config CGROUP_WRITEBACK
921 depends on MEMCG && BLK_CGROUP
924 menuconfig CGROUP_SCHED
925 bool "CPU controller"
928 This feature lets CPU scheduler recognize task groups and control CPU
929 bandwidth allocation to such task groups. It uses cgroups to group
933 config FAIR_GROUP_SCHED
934 bool "Group scheduling for SCHED_OTHER"
935 depends on CGROUP_SCHED
939 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
940 depends on FAIR_GROUP_SCHED
943 This option allows users to define CPU bandwidth rates (limits) for
944 tasks running within the fair group scheduler. Groups with no limit
945 set are considered to be unconstrained and will run with no
947 See Documentation/scheduler/sched-bwc.rst for more information.
949 config RT_GROUP_SCHED
950 bool "Group scheduling for SCHED_RR/FIFO"
951 depends on CGROUP_SCHED
954 This feature lets you explicitly allocate real CPU bandwidth
955 to task groups. If enabled, it will also make it impossible to
956 schedule realtime tasks for non-root users until you allocate
957 realtime bandwidth for them.
958 See Documentation/scheduler/sched-rt-group.rst for more information.
962 config UCLAMP_TASK_GROUP
963 bool "Utilization clamping per group of tasks"
964 depends on CGROUP_SCHED
965 depends on UCLAMP_TASK
968 This feature enables the scheduler to track the clamped utilization
969 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
971 When this option is enabled, the user can specify a min and max
972 CPU bandwidth which is allowed for each single task in a group.
973 The max bandwidth allows to clamp the maximum frequency a task
974 can use, while the min bandwidth allows to define a minimum
975 frequency a task will always use.
977 When task group based utilization clamping is enabled, an eventually
978 specified task-specific clamp value is constrained by the cgroup
979 specified clamp value. Both minimum and maximum task clamping cannot
980 be bigger than the corresponding clamping defined at task group level.
985 bool "PIDs controller"
987 Provides enforcement of process number limits in the scope of a
988 cgroup. Any attempt to fork more processes than is allowed in the
989 cgroup will fail. PIDs are fundamentally a global resource because it
990 is fairly trivial to reach PID exhaustion before you reach even a
991 conservative kmemcg limit. As a result, it is possible to grind a
992 system to halt without being limited by other cgroup policies. The
993 PIDs controller is designed to stop this from happening.
995 It should be noted that organisational operations (such as attaching
996 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
997 since the PIDs limit only affects a process's ability to fork, not to
1001 bool "RDMA controller"
1003 Provides enforcement of RDMA resources defined by IB stack.
1004 It is fairly easy for consumers to exhaust RDMA resources, which
1005 can result into resource unavailability to other consumers.
1006 RDMA controller is designed to stop this from happening.
1007 Attaching processes with active RDMA resources to the cgroup
1008 hierarchy is allowed even if can cross the hierarchy's limit.
1010 config CGROUP_FREEZER
1011 bool "Freezer controller"
1013 Provides a way to freeze and unfreeze all tasks in a
1016 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1017 controller includes important in-kernel memory consumers per default.
1019 If you're using cgroup2, say N.
1021 config CGROUP_HUGETLB
1022 bool "HugeTLB controller"
1023 depends on HUGETLB_PAGE
1027 Provides a cgroup controller for HugeTLB pages.
1028 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1029 The limit is enforced during page fault. Since HugeTLB doesn't
1030 support page reclaim, enforcing the limit at page fault time implies
1031 that, the application will get SIGBUS signal if it tries to access
1032 HugeTLB pages beyond its limit. This requires the application to know
1033 beforehand how much HugeTLB pages it would require for its use. The
1034 control group is tracked in the third page lru pointer. This means
1035 that we cannot use the controller with huge page less than 3 pages.
1038 bool "Cpuset controller"
1041 This option will let you create and manage CPUSETs which
1042 allow dynamically partitioning a system into sets of CPUs and
1043 Memory Nodes and assigning tasks to run only within those sets.
1044 This is primarily useful on large SMP or NUMA systems.
1048 config PROC_PID_CPUSET
1049 bool "Include legacy /proc/<pid>/cpuset file"
1053 config CGROUP_DEVICE
1054 bool "Device controller"
1056 Provides a cgroup controller implementing whitelists for
1057 devices which a process in the cgroup can mknod or open.
1059 config CGROUP_CPUACCT
1060 bool "Simple CPU accounting controller"
1062 Provides a simple controller for monitoring the
1063 total CPU consumed by the tasks in a cgroup.
1066 bool "Perf controller"
1067 depends on PERF_EVENTS
1069 This option extends the perf per-cpu mode to restrict monitoring
1070 to threads which belong to the cgroup specified and run on the
1071 designated cpu. Or this can be used to have cgroup ID in samples
1072 so that it can monitor performance events among cgroups.
1077 bool "Support for eBPF programs attached to cgroups"
1078 depends on BPF_SYSCALL
1079 select SOCK_CGROUP_DATA
1081 Allow attaching eBPF programs to a cgroup using the bpf(2)
1082 syscall command BPF_PROG_ATTACH.
1084 In which context these programs are accessed depends on the type
1085 of attachment. For instance, programs that are attached using
1086 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1090 bool "Debug controller"
1092 depends on DEBUG_KERNEL
1094 This option enables a simple controller that exports
1095 debugging information about the cgroups framework. This
1096 controller is for control cgroup debugging only. Its
1097 interfaces are not stable.
1101 config SOCK_CGROUP_DATA
1107 menuconfig NAMESPACES
1108 bool "Namespaces support" if EXPERT
1109 depends on MULTIUSER
1112 Provides the way to make tasks work with different objects using
1113 the same id. For example same IPC id may refer to different objects
1114 or same user id or pid may refer to different tasks when used in
1115 different namespaces.
1120 bool "UTS namespace"
1123 In this namespace tasks see different info provided with the
1127 bool "TIME namespace"
1128 depends on GENERIC_VDSO_TIME_NS
1131 In this namespace boottime and monotonic clocks can be set.
1132 The time will keep going with the same pace.
1135 bool "IPC namespace"
1136 depends on (SYSVIPC || POSIX_MQUEUE)
1139 In this namespace tasks work with IPC ids which correspond to
1140 different IPC objects in different namespaces.
1143 bool "User namespace"
1146 This allows containers, i.e. vservers, to use user namespaces
1147 to provide different user info for different servers.
1149 When user namespaces are enabled in the kernel it is
1150 recommended that the MEMCG option also be enabled and that
1151 user-space use the memory control groups to limit the amount
1152 of memory a memory unprivileged users can use.
1157 bool "PID Namespaces"
1160 Support process id namespaces. This allows having multiple
1161 processes with the same pid as long as they are in different
1162 pid namespaces. This is a building block of containers.
1165 bool "Network namespace"
1169 Allow user space to create what appear to be multiple instances
1170 of the network stack.
1174 config CHECKPOINT_RESTORE
1175 bool "Checkpoint/restore support"
1176 select PROC_CHILDREN
1179 Enables additional kernel features in a sake of checkpoint/restore.
1180 In particular it adds auxiliary prctl codes to setup process text,
1181 data and heap segment sizes, and a few additional /proc filesystem
1184 If unsure, say N here.
1186 config SCHED_AUTOGROUP
1187 bool "Automatic process group scheduling"
1190 select FAIR_GROUP_SCHED
1192 This option optimizes the scheduler for common desktop workloads by
1193 automatically creating and populating task groups. This separation
1194 of workloads isolates aggressive CPU burners (like build jobs) from
1195 desktop applications. Task group autogeneration is currently based
1198 config SYSFS_DEPRECATED
1199 bool "Enable deprecated sysfs features to support old userspace tools"
1203 This option adds code that switches the layout of the "block" class
1204 devices, to not show up in /sys/class/block/, but only in
1207 This switch is only active when the sysfs.deprecated=1 boot option is
1208 passed or the SYSFS_DEPRECATED_V2 option is set.
1210 This option allows new kernels to run on old distributions and tools,
1211 which might get confused by /sys/class/block/. Since 2007/2008 all
1212 major distributions and tools handle this just fine.
1214 Recent distributions and userspace tools after 2009/2010 depend on
1215 the existence of /sys/class/block/, and will not work with this
1218 Only if you are using a new kernel on an old distribution, you might
1221 config SYSFS_DEPRECATED_V2
1222 bool "Enable deprecated sysfs features by default"
1225 depends on SYSFS_DEPRECATED
1227 Enable deprecated sysfs by default.
1229 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1232 Only if you are using a new kernel on an old distribution, you might
1233 need to say Y here. Even then, odds are you would not need it
1234 enabled, you can always pass the boot option if absolutely necessary.
1237 bool "Kernel->user space relay support (formerly relayfs)"
1240 This option enables support for relay interface support in
1241 certain file systems (such as debugfs).
1242 It is designed to provide an efficient mechanism for tools and
1243 facilities to relay large amounts of data from kernel space to
1248 config BLK_DEV_INITRD
1249 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1251 The initial RAM filesystem is a ramfs which is loaded by the
1252 boot loader (loadlin or lilo) and that is mounted as root
1253 before the normal boot procedure. It is typically used to
1254 load modules needed to mount the "real" root file system,
1255 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1257 If RAM disk support (BLK_DEV_RAM) is also included, this
1258 also enables initial RAM disk (initrd) support and adds
1259 15 Kbytes (more on some other architectures) to the kernel size.
1265 source "usr/Kconfig"
1270 bool "Boot config support"
1271 select BLK_DEV_INITRD
1273 Extra boot config allows system admin to pass a config file as
1274 complemental extension of kernel cmdline when booting.
1275 The boot config file must be attached at the end of initramfs
1276 with checksum, size and magic word.
1277 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1282 prompt "Compiler optimization level"
1283 default CC_OPTIMIZE_FOR_PERFORMANCE
1285 config CC_OPTIMIZE_FOR_PERFORMANCE
1286 bool "Optimize for performance (-O2)"
1288 This is the default optimization level for the kernel, building
1289 with the "-O2" compiler flag for best performance and most
1290 helpful compile-time warnings.
1292 config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1293 bool "Optimize more for performance (-O3)"
1296 Choosing this option will pass "-O3" to your compiler to optimize
1297 the kernel yet more for performance.
1299 config CC_OPTIMIZE_FOR_SIZE
1300 bool "Optimize for size (-Os)"
1302 Choosing this option will pass "-Os" to your compiler resulting
1303 in a smaller kernel.
1307 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1310 This requires that the arch annotates or otherwise protects
1311 its external entry points from being discarded. Linker scripts
1312 must also merge .text.*, .data.*, and .bss.* correctly into
1313 output sections. Care must be taken not to pull in unrelated
1314 sections (e.g., '.text.init'). Typically '.' in section names
1315 is used to distinguish them from label names / C identifiers.
1317 config LD_DEAD_CODE_DATA_ELIMINATION
1318 bool "Dead code and data elimination (EXPERIMENTAL)"
1319 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1321 depends on $(cc-option,-ffunction-sections -fdata-sections)
1322 depends on $(ld-option,--gc-sections)
1324 Enable this if you want to do dead code and data elimination with
1325 the linker by compiling with -ffunction-sections -fdata-sections,
1326 and linking with --gc-sections.
1328 This can reduce on disk and in-memory size of the kernel
1329 code and static data, particularly for small configs and
1330 on small systems. This has the possibility of introducing
1331 silently broken kernel if the required annotations are not
1332 present. This option is not well tested yet, so use at your
1341 config SYSCTL_EXCEPTION_TRACE
1344 Enable support for /proc/sys/debug/exception-trace.
1346 config SYSCTL_ARCH_UNALIGN_NO_WARN
1349 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1350 Allows arch to define/use @no_unaligned_warning to possibly warn
1351 about unaligned access emulation going on under the hood.
1353 config SYSCTL_ARCH_UNALIGN_ALLOW
1356 Enable support for /proc/sys/kernel/unaligned-trap
1357 Allows arches to define/use @unaligned_enabled to runtime toggle
1358 the unaligned access emulation.
1359 see arch/parisc/kernel/unaligned.c for reference
1361 config HAVE_PCSPKR_PLATFORM
1364 # interpreter that classic socket filters depend on
1369 bool "Configure standard kernel features (expert users)"
1370 # Unhide debug options, to make the on-by-default options visible
1373 This option allows certain base kernel options and settings
1374 to be disabled or tweaked. This is for specialized
1375 environments which can tolerate a "non-standard" kernel.
1376 Only use this if you really know what you are doing.
1379 bool "Enable 16-bit UID system calls" if EXPERT
1380 depends on HAVE_UID16 && MULTIUSER
1383 This enables the legacy 16-bit UID syscall wrappers.
1386 bool "Multiple users, groups and capabilities support" if EXPERT
1389 This option enables support for non-root users, groups and
1392 If you say N here, all processes will run with UID 0, GID 0, and all
1393 possible capabilities. Saying N here also compiles out support for
1394 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1397 If unsure, say Y here.
1399 config SGETMASK_SYSCALL
1400 bool "sgetmask/ssetmask syscalls support" if EXPERT
1401 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1403 sys_sgetmask and sys_ssetmask are obsolete system calls
1404 no longer supported in libc but still enabled by default in some
1407 If unsure, leave the default option here.
1409 config SYSFS_SYSCALL
1410 bool "Sysfs syscall support" if EXPERT
1413 sys_sysfs is an obsolete system call no longer supported in libc.
1414 Note that disabling this option is more secure but might break
1415 compatibility with some systems.
1417 If unsure say Y here.
1420 bool "open by fhandle syscalls" if EXPERT
1424 If you say Y here, a user level program will be able to map
1425 file names to handle and then later use the handle for
1426 different file system operations. This is useful in implementing
1427 userspace file servers, which now track files using handles instead
1428 of names. The handle would remain the same even if file names
1429 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1433 bool "Posix Clocks & timers" if EXPERT
1436 This includes native support for POSIX timers to the kernel.
1437 Some embedded systems have no use for them and therefore they
1438 can be configured out to reduce the size of the kernel image.
1440 When this option is disabled, the following syscalls won't be
1441 available: timer_create, timer_gettime: timer_getoverrun,
1442 timer_settime, timer_delete, clock_adjtime, getitimer,
1443 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1444 clock_getres and clock_nanosleep syscalls will be limited to
1445 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1451 bool "Enable support for printk" if EXPERT
1454 This option enables normal printk support. Removing it
1455 eliminates most of the message strings from the kernel image
1456 and makes the kernel more or less silent. As this makes it
1457 very difficult to diagnose system problems, saying N here is
1458 strongly discouraged.
1466 bool "BUG() support" if EXPERT
1469 Disabling this option eliminates support for BUG and WARN, reducing
1470 the size of your kernel image and potentially quietly ignoring
1471 numerous fatal conditions. You should only consider disabling this
1472 option for embedded systems with no facilities for reporting errors.
1478 bool "Enable ELF core dumps" if EXPERT
1480 Enable support for generating core dumps. Disabling saves about 4k.
1483 config PCSPKR_PLATFORM
1484 bool "Enable PC-Speaker support" if EXPERT
1485 depends on HAVE_PCSPKR_PLATFORM
1489 This option allows to disable the internal PC-Speaker
1490 support, saving some memory.
1494 bool "Enable full-sized data structures for core" if EXPERT
1496 Disabling this option reduces the size of miscellaneous core
1497 kernel data structures. This saves memory on small machines,
1498 but may reduce performance.
1501 bool "Enable futex support" if EXPERT
1505 Disabling this option will cause the kernel to be built without
1506 support for "fast userspace mutexes". The resulting kernel may not
1507 run glibc-based applications correctly.
1511 depends on FUTEX && RT_MUTEXES
1514 config HAVE_FUTEX_CMPXCHG
1518 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1519 is implemented and always working. This removes a couple of runtime
1523 bool "Enable eventpoll support" if EXPERT
1526 Disabling this option will cause the kernel to be built without
1527 support for epoll family of system calls.
1530 bool "Enable signalfd() system call" if EXPERT
1533 Enable the signalfd() system call that allows to receive signals
1534 on a file descriptor.
1539 bool "Enable timerfd() system call" if EXPERT
1542 Enable the timerfd() system call that allows to receive timer
1543 events on a file descriptor.
1548 bool "Enable eventfd() system call" if EXPERT
1551 Enable the eventfd() system call that allows to receive both
1552 kernel notification (ie. KAIO) or userspace notifications.
1557 bool "Use full shmem filesystem" if EXPERT
1561 The shmem is an internal filesystem used to manage shared memory.
1562 It is backed by swap and manages resource limits. It is also exported
1563 to userspace as tmpfs if TMPFS is enabled. Disabling this
1564 option replaces shmem and tmpfs with the much simpler ramfs code,
1565 which may be appropriate on small systems without swap.
1568 bool "Enable AIO support" if EXPERT
1571 This option enables POSIX asynchronous I/O which may by used
1572 by some high performance threaded applications. Disabling
1573 this option saves about 7k.
1576 bool "Enable IO uring support" if EXPERT
1580 This option enables support for the io_uring interface, enabling
1581 applications to submit and complete IO through submission and
1582 completion rings that are shared between the kernel and application.
1584 config ADVISE_SYSCALLS
1585 bool "Enable madvise/fadvise syscalls" if EXPERT
1588 This option enables the madvise and fadvise syscalls, used by
1589 applications to advise the kernel about their future memory or file
1590 usage, improving performance. If building an embedded system where no
1591 applications use these syscalls, you can disable this option to save
1594 config HAVE_ARCH_USERFAULTFD_WP
1597 Arch has userfaultfd write protection support
1600 bool "Enable membarrier() system call" if EXPERT
1603 Enable the membarrier() system call that allows issuing memory
1604 barriers across all running threads, which can be used to distribute
1605 the cost of user-space memory barriers asymmetrically by transforming
1606 pairs of memory barriers into pairs consisting of membarrier() and a
1612 bool "Load all symbols for debugging/ksymoops" if EXPERT
1615 Say Y here to let the kernel print out symbolic crash information and
1616 symbolic stack backtraces. This increases the size of the kernel
1617 somewhat, as all symbols have to be loaded into the kernel image.
1620 bool "Include all symbols in kallsyms"
1621 depends on DEBUG_KERNEL && KALLSYMS
1623 Normally kallsyms only contains the symbols of functions for nicer
1624 OOPS messages and backtraces (i.e., symbols from the text and inittext
1625 sections). This is sufficient for most cases. And only in very rare
1626 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1627 names of variables from the data sections, etc).
1629 This option makes sure that all symbols are loaded into the kernel
1630 image (i.e., symbols from all sections) in cost of increased kernel
1631 size (depending on the kernel configuration, it may be 300KiB or
1632 something like this).
1634 Say N unless you really need all symbols.
1636 config KALLSYMS_ABSOLUTE_PERCPU
1639 default X86_64 && SMP
1641 config KALLSYMS_BASE_RELATIVE
1646 Instead of emitting them as absolute values in the native word size,
1647 emit the symbol references in the kallsyms table as 32-bit entries,
1648 each containing a relative value in the range [base, base + U32_MAX]
1649 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1650 an absolute value in the range [0, S32_MAX] or a relative value in the
1651 range [base, base + S32_MAX], where base is the lowest relative symbol
1652 address encountered in the image.
1654 On 64-bit builds, this reduces the size of the address table by 50%,
1655 but more importantly, it results in entries whose values are build
1656 time constants, and no relocation pass is required at runtime to fix
1657 up the entries based on the runtime load address of the kernel.
1659 # end of the "standard kernel features (expert users)" menu
1661 # syscall, maps, verifier
1664 bool "LSM Instrumentation with BPF"
1665 depends on BPF_EVENTS
1666 depends on BPF_SYSCALL
1670 Enables instrumentation of the security hooks with eBPF programs for
1671 implementing dynamic MAC and Audit Policies.
1673 If you are unsure how to answer this question, answer N.
1676 bool "Enable bpf() system call"
1681 Enable the bpf() system call that allows to manipulate eBPF
1682 programs and maps via file descriptors.
1684 config ARCH_WANT_DEFAULT_BPF_JIT
1687 config BPF_JIT_ALWAYS_ON
1688 bool "Permanently enable BPF JIT and remove BPF interpreter"
1689 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1691 Enables BPF JIT and removes BPF interpreter to avoid
1692 speculative execution of BPF instructions by the interpreter
1694 config BPF_JIT_DEFAULT_ON
1695 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
1696 depends on HAVE_EBPF_JIT && BPF_JIT
1699 bool "Enable userfaultfd() system call"
1702 Enable the userfaultfd() system call that allows to intercept and
1703 handle page faults in userland.
1705 config ARCH_HAS_MEMBARRIER_CALLBACKS
1708 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1712 bool "Enable rseq() system call" if EXPERT
1714 depends on HAVE_RSEQ
1717 Enable the restartable sequences system call. It provides a
1718 user-space cache for the current CPU number value, which
1719 speeds up getting the current CPU number from user-space,
1720 as well as an ABI to speed up user-space operations on
1727 bool "Enabled debugging of rseq() system call" if EXPERT
1728 depends on RSEQ && DEBUG_KERNEL
1730 Enable extra debugging checks for the rseq system call.
1735 bool "Embedded system"
1736 option allnoconfig_y
1739 This option should be enabled if compiling the kernel for
1740 an embedded system so certain expert options are available
1743 config HAVE_PERF_EVENTS
1746 See tools/perf/design.txt for details.
1748 config PERF_USE_VMALLOC
1751 See tools/perf/design.txt for details
1754 bool "PC/104 support" if EXPERT
1756 Expose PC/104 form factor device drivers and options available for
1757 selection and configuration. Enable this option if your target
1758 machine has a PC/104 bus.
1760 menu "Kernel Performance Events And Counters"
1763 bool "Kernel performance events and counters"
1764 default y if PROFILING
1765 depends on HAVE_PERF_EVENTS
1769 Enable kernel support for various performance events provided
1770 by software and hardware.
1772 Software events are supported either built-in or via the
1773 use of generic tracepoints.
1775 Most modern CPUs support performance events via performance
1776 counter registers. These registers count the number of certain
1777 types of hw events: such as instructions executed, cachemisses
1778 suffered, or branches mis-predicted - without slowing down the
1779 kernel or applications. These registers can also trigger interrupts
1780 when a threshold number of events have passed - and can thus be
1781 used to profile the code that runs on that CPU.
1783 The Linux Performance Event subsystem provides an abstraction of
1784 these software and hardware event capabilities, available via a
1785 system call and used by the "perf" utility in tools/perf/. It
1786 provides per task and per CPU counters, and it provides event
1787 capabilities on top of those.
1791 config DEBUG_PERF_USE_VMALLOC
1793 bool "Debug: use vmalloc to back perf mmap() buffers"
1794 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1795 select PERF_USE_VMALLOC
1797 Use vmalloc memory to back perf mmap() buffers.
1799 Mostly useful for debugging the vmalloc code on platforms
1800 that don't require it.
1806 config VM_EVENT_COUNTERS
1808 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1810 VM event counters are needed for event counts to be shown.
1811 This option allows the disabling of the VM event counters
1812 on EXPERT systems. /proc/vmstat will only show page counts
1813 if VM event counters are disabled.
1817 bool "Enable SLUB debugging support" if EXPERT
1818 depends on SLUB && SYSFS
1820 SLUB has extensive debug support features. Disabling these can
1821 result in significant savings in code size. This also disables
1822 SLUB sysfs support. /sys/slab will not exist and there will be
1823 no support for cache validation etc.
1825 config SLUB_MEMCG_SYSFS_ON
1827 bool "Enable memcg SLUB sysfs support by default" if EXPERT
1828 depends on SLUB && SYSFS && MEMCG
1830 SLUB creates a directory under /sys/kernel/slab for each
1831 allocation cache to host info and debug files. If memory
1832 cgroup is enabled, each cache can have per memory cgroup
1833 caches. SLUB can create the same sysfs directories for these
1834 caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1835 to a very high number of debug files being created. This is
1836 controlled by slub_memcg_sysfs boot parameter and this
1837 config option determines the parameter's default value.
1840 bool "Disable heap randomization"
1843 Randomizing heap placement makes heap exploits harder, but it
1844 also breaks ancient binaries (including anything libc5 based).
1845 This option changes the bootup default to heap randomization
1846 disabled, and can be overridden at runtime by setting
1847 /proc/sys/kernel/randomize_va_space to 2.
1849 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1852 prompt "Choose SLAB allocator"
1855 This option allows to select a slab allocator.
1859 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1861 The regular slab allocator that is established and known to work
1862 well in all environments. It organizes cache hot objects in
1863 per cpu and per node queues.
1866 bool "SLUB (Unqueued Allocator)"
1867 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1869 SLUB is a slab allocator that minimizes cache line usage
1870 instead of managing queues of cached objects (SLAB approach).
1871 Per cpu caching is realized using slabs of objects instead
1872 of queues of objects. SLUB can use memory efficiently
1873 and has enhanced diagnostics. SLUB is the default choice for
1878 bool "SLOB (Simple Allocator)"
1880 SLOB replaces the stock allocator with a drastically simpler
1881 allocator. SLOB is generally more space efficient but
1882 does not perform as well on large systems.
1886 config SLAB_MERGE_DEFAULT
1887 bool "Allow slab caches to be merged"
1890 For reduced kernel memory fragmentation, slab caches can be
1891 merged when they share the same size and other characteristics.
1892 This carries a risk of kernel heap overflows being able to
1893 overwrite objects from merged caches (and more easily control
1894 cache layout), which makes such heap attacks easier to exploit
1895 by attackers. By keeping caches unmerged, these kinds of exploits
1896 can usually only damage objects in the same cache. To disable
1897 merging at runtime, "slab_nomerge" can be passed on the kernel
1900 config SLAB_FREELIST_RANDOM
1902 depends on SLAB || SLUB
1903 bool "SLAB freelist randomization"
1905 Randomizes the freelist order used on creating new pages. This
1906 security feature reduces the predictability of the kernel slab
1907 allocator against heap overflows.
1909 config SLAB_FREELIST_HARDENED
1910 bool "Harden slab freelist metadata"
1913 Many kernel heap attacks try to target slab cache metadata and
1914 other infrastructure. This options makes minor performance
1915 sacrifices to harden the kernel slab allocator against common
1916 freelist exploit methods.
1918 config SHUFFLE_PAGE_ALLOCATOR
1919 bool "Page allocator randomization"
1920 default SLAB_FREELIST_RANDOM && ACPI_NUMA
1922 Randomization of the page allocator improves the average
1923 utilization of a direct-mapped memory-side-cache. See section
1924 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1925 6.2a specification for an example of how a platform advertises
1926 the presence of a memory-side-cache. There are also incidental
1927 security benefits as it reduces the predictability of page
1928 allocations to compliment SLAB_FREELIST_RANDOM, but the
1929 default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1930 10th order of pages is selected based on cache utilization
1933 While the randomization improves cache utilization it may
1934 negatively impact workloads on platforms without a cache. For
1935 this reason, by default, the randomization is enabled only
1936 after runtime detection of a direct-mapped memory-side-cache.
1937 Otherwise, the randomization may be force enabled with the
1938 'page_alloc.shuffle' kernel command line parameter.
1942 config SLUB_CPU_PARTIAL
1944 depends on SLUB && SMP
1945 bool "SLUB per cpu partial cache"
1947 Per cpu partial caches accelerate objects allocation and freeing
1948 that is local to a processor at the price of more indeterminism
1949 in the latency of the free. On overflow these caches will be cleared
1950 which requires the taking of locks that may cause latency spikes.
1951 Typically one would choose no for a realtime system.
1953 config MMAP_ALLOW_UNINITIALIZED
1954 bool "Allow mmapped anonymous memory to be uninitialized"
1955 depends on EXPERT && !MMU
1958 Normally, and according to the Linux spec, anonymous memory obtained
1959 from mmap() has its contents cleared before it is passed to
1960 userspace. Enabling this config option allows you to request that
1961 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1962 providing a huge performance boost. If this option is not enabled,
1963 then the flag will be ignored.
1965 This is taken advantage of by uClibc's malloc(), and also by
1966 ELF-FDPIC binfmt's brk and stack allocator.
1968 Because of the obvious security issues, this option should only be
1969 enabled on embedded devices where you control what is run in
1970 userspace. Since that isn't generally a problem on no-MMU systems,
1971 it is normally safe to say Y here.
1973 See Documentation/nommu-mmap.txt for more information.
1975 config SYSTEM_DATA_VERIFICATION
1977 select SYSTEM_TRUSTED_KEYRING
1981 select ASYMMETRIC_KEY_TYPE
1982 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1985 select X509_CERTIFICATE_PARSER
1986 select PKCS7_MESSAGE_PARSER
1988 Provide PKCS#7 message verification using the contents of the system
1989 trusted keyring to provide public keys. This then can be used for
1990 module verification, kexec image verification and firmware blob
1994 bool "Profiling support"
1996 Say Y here to enable the extended profiling support mechanisms used
1997 by profilers such as OProfile.
2000 # Place an empty function call at each tracepoint site. Can be
2001 # dynamically changed for a probe function.
2006 endmenu # General setup
2008 source "arch/Kconfig"
2015 default 0 if BASE_FULL
2016 default 1 if !BASE_FULL
2018 config MODULE_SIG_FORMAT
2020 select SYSTEM_DATA_VERIFICATION
2023 bool "Enable loadable module support"
2026 Kernel modules are small pieces of compiled code which can
2027 be inserted in the running kernel, rather than being
2028 permanently built into the kernel. You use the "modprobe"
2029 tool to add (and sometimes remove) them. If you say Y here,
2030 many parts of the kernel can be built as modules (by
2031 answering M instead of Y where indicated): this is most
2032 useful for infrequently used options which are not required
2033 for booting. For more information, see the man pages for
2034 modprobe, lsmod, modinfo, insmod and rmmod.
2036 If you say Y here, you will need to run "make
2037 modules_install" to put the modules under /lib/modules/
2038 where modprobe can find them (you may need to be root to do
2045 config MODULE_FORCE_LOAD
2046 bool "Forced module loading"
2049 Allow loading of modules without version information (ie. modprobe
2050 --force). Forced module loading sets the 'F' (forced) taint flag and
2051 is usually a really bad idea.
2053 config MODULE_UNLOAD
2054 bool "Module unloading"
2056 Without this option you will not be able to unload any
2057 modules (note that some modules may not be unloadable
2058 anyway), which makes your kernel smaller, faster
2059 and simpler. If unsure, say Y.
2061 config MODULE_FORCE_UNLOAD
2062 bool "Forced module unloading"
2063 depends on MODULE_UNLOAD
2065 This option allows you to force a module to unload, even if the
2066 kernel believes it is unsafe: the kernel will remove the module
2067 without waiting for anyone to stop using it (using the -f option to
2068 rmmod). This is mainly for kernel developers and desperate users.
2072 bool "Module versioning support"
2074 Usually, you have to use modules compiled with your kernel.
2075 Saying Y here makes it sometimes possible to use modules
2076 compiled for different kernels, by adding enough information
2077 to the modules to (hopefully) spot any changes which would
2078 make them incompatible with the kernel you are running. If
2081 config ASM_MODVERSIONS
2083 default HAVE_ASM_MODVERSIONS && MODVERSIONS
2085 This enables module versioning for exported symbols also from
2086 assembly. This can be enabled only when the target architecture
2089 config MODULE_REL_CRCS
2091 depends on MODVERSIONS
2093 config MODULE_SRCVERSION_ALL
2094 bool "Source checksum for all modules"
2096 Modules which contain a MODULE_VERSION get an extra "srcversion"
2097 field inserted into their modinfo section, which contains a
2098 sum of the source files which made it. This helps maintainers
2099 see exactly which source was used to build a module (since
2100 others sometimes change the module source without updating
2101 the version). With this option, such a "srcversion" field
2102 will be created for all modules. If unsure, say N.
2105 bool "Module signature verification"
2106 select MODULE_SIG_FORMAT
2108 Check modules for valid signatures upon load: the signature
2109 is simply appended to the module. For more information see
2110 <file:Documentation/admin-guide/module-signing.rst>.
2112 Note that this option adds the OpenSSL development packages as a
2113 kernel build dependency so that the signing tool can use its crypto
2116 You should enable this option if you wish to use either
2117 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2118 another LSM - otherwise unsigned modules will be loadable regardless
2119 of the lockdown policy.
2121 !!!WARNING!!! If you enable this option, you MUST make sure that the
2122 module DOES NOT get stripped after being signed. This includes the
2123 debuginfo strip done by some packagers (such as rpmbuild) and
2124 inclusion into an initramfs that wants the module size reduced.
2126 config MODULE_SIG_FORCE
2127 bool "Require modules to be validly signed"
2128 depends on MODULE_SIG
2130 Reject unsigned modules or signed modules for which we don't have a
2131 key. Without this, such modules will simply taint the kernel.
2133 config MODULE_SIG_ALL
2134 bool "Automatically sign all modules"
2136 depends on MODULE_SIG
2138 Sign all modules during make modules_install. Without this option,
2139 modules must be signed manually, using the scripts/sign-file tool.
2141 comment "Do not forget to sign required modules with scripts/sign-file"
2142 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2145 prompt "Which hash algorithm should modules be signed with?"
2146 depends on MODULE_SIG
2148 This determines which sort of hashing algorithm will be used during
2149 signature generation. This algorithm _must_ be built into the kernel
2150 directly so that signature verification can take place. It is not
2151 possible to load a signed module containing the algorithm to check
2152 the signature on that module.
2154 config MODULE_SIG_SHA1
2155 bool "Sign modules with SHA-1"
2158 config MODULE_SIG_SHA224
2159 bool "Sign modules with SHA-224"
2160 select CRYPTO_SHA256
2162 config MODULE_SIG_SHA256
2163 bool "Sign modules with SHA-256"
2164 select CRYPTO_SHA256
2166 config MODULE_SIG_SHA384
2167 bool "Sign modules with SHA-384"
2168 select CRYPTO_SHA512
2170 config MODULE_SIG_SHA512
2171 bool "Sign modules with SHA-512"
2172 select CRYPTO_SHA512
2176 config MODULE_SIG_HASH
2178 depends on MODULE_SIG
2179 default "sha1" if MODULE_SIG_SHA1
2180 default "sha224" if MODULE_SIG_SHA224
2181 default "sha256" if MODULE_SIG_SHA256
2182 default "sha384" if MODULE_SIG_SHA384
2183 default "sha512" if MODULE_SIG_SHA512
2185 config MODULE_COMPRESS
2186 bool "Compress modules on installation"
2189 Compresses kernel modules when 'make modules_install' is run; gzip or
2190 xz depending on "Compression algorithm" below.
2192 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2194 Out-of-tree kernel modules installed using Kbuild will also be
2195 compressed upon installation.
2197 Note: for modules inside an initrd or initramfs, it's more efficient
2198 to compress the whole initrd or initramfs instead.
2200 Note: This is fully compatible with signed modules.
2205 prompt "Compression algorithm"
2206 depends on MODULE_COMPRESS
2207 default MODULE_COMPRESS_GZIP
2209 This determines which sort of compression will be used during
2210 'make modules_install'.
2212 GZIP (default) and XZ are supported.
2214 config MODULE_COMPRESS_GZIP
2217 config MODULE_COMPRESS_XZ
2222 config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2223 bool "Allow loading of modules with missing namespace imports"
2225 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2226 a namespace. A module that makes use of a symbol exported with such a
2227 namespace is required to import the namespace via MODULE_IMPORT_NS().
2228 There is no technical reason to enforce correct namespace imports,
2229 but it creates consistency between symbols defining namespaces and
2230 users importing namespaces they make use of. This option relaxes this
2231 requirement and lifts the enforcement when loading a module.
2235 config UNUSED_SYMBOLS
2236 bool "Enable unused/obsolete exported symbols"
2239 Unused but exported symbols make the kernel needlessly bigger. For
2240 that reason most of these unused exports will soon be removed. This
2241 option is provided temporarily to provide a transition period in case
2242 some external kernel module needs one of these symbols anyway. If you
2243 encounter such a case in your module, consider if you are actually
2244 using the right API. (rationale: since nobody in the kernel is using
2245 this in a module, there is a pretty good chance it's actually the
2246 wrong interface to use). If you really need the symbol, please send a
2247 mail to the linux kernel mailing list mentioning the symbol and why
2248 you really need it, and what the merge plan to the mainline kernel for
2251 config TRIM_UNUSED_KSYMS
2252 bool "Trim unused exported kernel symbols"
2253 depends on !UNUSED_SYMBOLS
2255 The kernel and some modules make many symbols available for
2256 other modules to use via EXPORT_SYMBOL() and variants. Depending
2257 on the set of modules being selected in your kernel configuration,
2258 many of those exported symbols might never be used.
2260 This option allows for unused exported symbols to be dropped from
2261 the build. In turn, this provides the compiler more opportunities
2262 (especially when using LTO) for optimizing the code and reducing
2263 binary size. This might have some security advantages as well.
2265 If unsure, or if you need to build out-of-tree modules, say N.
2267 config UNUSED_KSYMS_WHITELIST
2268 string "Whitelist of symbols to keep in ksymtab"
2269 depends on TRIM_UNUSED_KSYMS
2271 By default, all unused exported symbols will be un-exported from the
2272 build when TRIM_UNUSED_KSYMS is selected.
2274 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
2275 exported at all times, even in absence of in-tree users. The value to
2276 set here is the path to a text file containing the list of symbols,
2277 one per line. The path can be absolute, or relative to the kernel
2282 config MODULES_TREE_LOOKUP
2284 depends on PERF_EVENTS || TRACING
2286 config INIT_ALL_POSSIBLE
2289 Back when each arch used to define their own cpu_online_mask and
2290 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2291 with all 1s, and others with all 0s. When they were centralised,
2292 it was better to provide this option than to break all the archs
2293 and have several arch maintainers pursuing me down dark alleys.
2295 source "block/Kconfig"
2297 config PREEMPT_NOTIFIERS
2307 Build a simple ASN.1 grammar compiler that produces a bytecode output
2308 that can be interpreted by the ASN.1 stream decoder and used to
2309 inform it as to what tags are to be expected in a stream and what
2310 functions to call on what tags.
2312 source "kernel/Kconfig.locks"
2314 config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2317 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2320 # It may be useful for an architecture to override the definitions of the
2321 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2322 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2323 # different calling convention for syscalls. They can also override the
2324 # macros for not-implemented syscalls in kernel/sys_ni.c and
2325 # kernel/time/posix-stubs.c. All these overrides need to be available in
2326 # <asm/syscall_wrapper.h>.
2327 config ARCH_HAS_SYSCALL_WRAPPER
projects / mirror_ubuntu-jammy-kernel.git / blob