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)"
10 default "arch/$(ARCH)/defconfig"
13 def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc)
17 default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC
21 def_bool $(success,$(CC) --version | head -n 1 | grep -q clang)
25 default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
27 config CC_HAS_ASM_GOTO
28 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
30 config CC_HAS_WARN_MAYBE_UNINITIALIZED
31 def_bool $(cc-option,-Wmaybe-uninitialized)
33 GCC >= 4.7 supports this option.
35 config CC_DISABLE_WARN_MAYBE_UNINITIALIZED
37 depends on CC_HAS_WARN_MAYBE_UNINITIALIZED
38 default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9
40 GCC's -Wmaybe-uninitialized is not reliable by definition.
41 Lots of false positive warnings are produced in some cases.
43 If this option is enabled, -Wno-maybe-uninitialzed is passed
44 to the compiler to suppress maybe-uninitialized warnings.
53 config BUILDTIME_EXTABLE_SORT
56 config THREAD_INFO_IN_TASK
59 Select this to move thread_info off the stack into task_struct. To
60 make this work, an arch will need to remove all thread_info fields
61 except flags and fix any runtime bugs.
63 One subtle change that will be needed is to use try_get_task_stack()
64 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
73 depends on BROKEN || !SMP
76 config INIT_ENV_ARG_LIMIT
81 Maximum of each of the number of arguments and environment
82 variables passed to init from the kernel command line.
85 bool "Compile also drivers which will not load"
89 Some drivers can be compiled on a different platform than they are
90 intended to be run on. Despite they cannot be loaded there (or even
91 when they load they cannot be used due to missing HW support),
92 developers still, opposing to distributors, might want to build such
93 drivers to compile-test them.
95 If you are a developer and want to build everything available, say Y
96 here. If you are a user/distributor, say N here to exclude useless
97 drivers to be distributed.
100 string "Local version - append to kernel release"
102 Append an extra string to the end of your kernel version.
103 This will show up when you type uname, for example.
104 The string you set here will be appended after the contents of
105 any files with a filename matching localversion* in your
106 object and source tree, in that order. Your total string can
107 be a maximum of 64 characters.
109 config LOCALVERSION_AUTO
110 bool "Automatically append version information to the version string"
112 depends on !COMPILE_TEST
114 This will try to automatically determine if the current tree is a
115 release tree by looking for git tags that belong to the current
116 top of tree revision.
118 A string of the format -gxxxxxxxx will be added to the localversion
119 if a git-based tree is found. The string generated by this will be
120 appended after any matching localversion* files, and after the value
121 set in CONFIG_LOCALVERSION.
123 (The actual string used here is the first eight characters produced
124 by running the command:
126 $ git rev-parse --verify HEAD
128 which is done within the script "scripts/setlocalversion".)
131 string "Build ID Salt"
134 The build ID is used to link binaries and their debug info. Setting
135 this option will use the value in the calculation of the build id.
136 This is mostly useful for distributions which want to ensure the
137 build is unique between builds. It's safe to leave the default.
139 config HAVE_KERNEL_GZIP
142 config HAVE_KERNEL_BZIP2
145 config HAVE_KERNEL_LZMA
148 config HAVE_KERNEL_XZ
151 config HAVE_KERNEL_LZO
154 config HAVE_KERNEL_LZ4
157 config HAVE_KERNEL_UNCOMPRESSED
161 prompt "Kernel compression mode"
163 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED
165 The linux kernel is a kind of self-extracting executable.
166 Several compression algorithms are available, which differ
167 in efficiency, compression and decompression speed.
168 Compression speed is only relevant when building a kernel.
169 Decompression speed is relevant at each boot.
171 If you have any problems with bzip2 or lzma compressed
173 version of this functionality (bzip2 only), for 2.4, was
174 supplied by Christian Ludwig)
176 High compression options are mostly useful for users, who
177 are low on disk space (embedded systems), but for whom ram
180 If in doubt, select 'gzip'
184 depends on HAVE_KERNEL_GZIP
186 The old and tried gzip compression. It provides a good balance
187 between compression ratio and decompression speed.
191 depends on HAVE_KERNEL_BZIP2
193 Its compression ratio and speed is intermediate.
194 Decompression speed is slowest among the choices. The kernel
195 size is about 10% smaller with bzip2, in comparison to gzip.
196 Bzip2 uses a large amount of memory. For modern kernels you
197 will need at least 8MB RAM or more for booting.
201 depends on HAVE_KERNEL_LZMA
203 This compression algorithm's ratio is best. Decompression speed
204 is between gzip and bzip2. Compression is slowest.
205 The kernel size is about 33% smaller with LZMA in comparison to gzip.
209 depends on HAVE_KERNEL_XZ
211 XZ uses the LZMA2 algorithm and instruction set specific
212 BCJ filters which can improve compression ratio of executable
213 code. The size of the kernel is about 30% smaller with XZ in
214 comparison to gzip. On architectures for which there is a BCJ
215 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
216 will create a few percent smaller kernel than plain LZMA.
218 The speed is about the same as with LZMA: The decompression
219 speed of XZ is better than that of bzip2 but worse than gzip
220 and LZO. Compression is slow.
224 depends on HAVE_KERNEL_LZO
226 Its compression ratio is the poorest among the choices. The kernel
227 size is about 10% bigger than gzip; however its speed
228 (both compression and decompression) is the fastest.
232 depends on HAVE_KERNEL_LZ4
234 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
235 A preliminary version of LZ4 de/compression tool is available at
236 <https://code.google.com/p/lz4/>.
238 Its compression ratio is worse than LZO. The size of the kernel
239 is about 8% bigger than LZO. But the decompression speed is
242 config KERNEL_UNCOMPRESSED
244 depends on HAVE_KERNEL_UNCOMPRESSED
246 Produce uncompressed kernel image. This option is usually not what
247 you want. It is useful for debugging the kernel in slow simulation
248 environments, where decompressing and moving the kernel is awfully
249 slow. This option allows early boot code to skip the decompressor
250 and jump right at uncompressed kernel image.
254 config DEFAULT_HOSTNAME
255 string "Default hostname"
258 This option determines the default system hostname before userspace
259 calls sethostname(2). The kernel traditionally uses "(none)" here,
260 but you may wish to use a different default here to make a minimal
261 system more usable with less configuration.
264 # For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
265 # add proper SWAP support to them, in which case this can be remove.
271 bool "Support for paging of anonymous memory (swap)"
272 depends on MMU && BLOCK && !ARCH_NO_SWAP
275 This option allows you to choose whether you want to have support
276 for so called swap devices or swap files in your kernel that are
277 used to provide more virtual memory than the actual RAM present
278 in your computer. If unsure say Y.
283 Inter Process Communication is a suite of library functions and
284 system calls which let processes (running programs) synchronize and
285 exchange information. It is generally considered to be a good thing,
286 and some programs won't run unless you say Y here. In particular, if
287 you want to run the DOS emulator dosemu under Linux (read the
288 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
289 you'll need to say Y here.
291 You can find documentation about IPC with "info ipc" and also in
292 section 6.4 of the Linux Programmer's Guide, available from
293 <http://www.tldp.org/guides.html>.
295 config SYSVIPC_SYSCTL
302 bool "POSIX Message Queues"
305 POSIX variant of message queues is a part of IPC. In POSIX message
306 queues every message has a priority which decides about succession
307 of receiving it by a process. If you want to compile and run
308 programs written e.g. for Solaris with use of its POSIX message
309 queues (functions mq_*) say Y here.
311 POSIX message queues are visible as a filesystem called 'mqueue'
312 and can be mounted somewhere if you want to do filesystem
313 operations on message queues.
317 config POSIX_MQUEUE_SYSCTL
319 depends on POSIX_MQUEUE
323 config CROSS_MEMORY_ATTACH
324 bool "Enable process_vm_readv/writev syscalls"
328 Enabling this option adds the system calls process_vm_readv and
329 process_vm_writev which allow a process with the correct privileges
330 to directly read from or write to another process' address space.
331 See the man page for more details.
334 bool "uselib syscall"
335 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
337 This option enables the uselib syscall, a system call used in the
338 dynamic linker from libc5 and earlier. glibc does not use this
339 system call. If you intend to run programs built on libc5 or
340 earlier, you may need to enable this syscall. Current systems
341 running glibc can safely disable this.
344 bool "Auditing support"
347 Enable auditing infrastructure that can be used with another
348 kernel subsystem, such as SELinux (which requires this for
349 logging of avc messages output). System call auditing is included
350 on architectures which support it.
352 config HAVE_ARCH_AUDITSYSCALL
357 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
360 source "kernel/irq/Kconfig"
361 source "kernel/time/Kconfig"
362 source "kernel/Kconfig.preempt"
364 menu "CPU/Task time and stats accounting"
366 config VIRT_CPU_ACCOUNTING
370 prompt "Cputime accounting"
371 default TICK_CPU_ACCOUNTING if !PPC64
372 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
374 # Kind of a stub config for the pure tick based cputime accounting
375 config TICK_CPU_ACCOUNTING
376 bool "Simple tick based cputime accounting"
377 depends on !S390 && !NO_HZ_FULL
379 This is the basic tick based cputime accounting that maintains
380 statistics about user, system and idle time spent on per jiffies
385 config VIRT_CPU_ACCOUNTING_NATIVE
386 bool "Deterministic task and CPU time accounting"
387 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
388 select VIRT_CPU_ACCOUNTING
390 Select this option to enable more accurate task and CPU time
391 accounting. This is done by reading a CPU counter on each
392 kernel entry and exit and on transitions within the kernel
393 between system, softirq and hardirq state, so there is a
394 small performance impact. In the case of s390 or IBM POWER > 5,
395 this also enables accounting of stolen time on logically-partitioned
398 config VIRT_CPU_ACCOUNTING_GEN
399 bool "Full dynticks CPU time accounting"
400 depends on HAVE_CONTEXT_TRACKING
401 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
402 depends on GENERIC_CLOCKEVENTS
403 select VIRT_CPU_ACCOUNTING
404 select CONTEXT_TRACKING
406 Select this option to enable task and CPU time accounting on full
407 dynticks systems. This accounting is implemented by watching every
408 kernel-user boundaries using the context tracking subsystem.
409 The accounting is thus performed at the expense of some significant
412 For now this is only useful if you are working on the full
413 dynticks subsystem development.
419 config IRQ_TIME_ACCOUNTING
420 bool "Fine granularity task level IRQ time accounting"
421 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
423 Select this option to enable fine granularity task irq time
424 accounting. This is done by reading a timestamp on each
425 transitions between softirq and hardirq state, so there can be a
426 small performance impact.
428 If in doubt, say N here.
430 config HAVE_SCHED_AVG_IRQ
432 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
435 config BSD_PROCESS_ACCT
436 bool "BSD Process Accounting"
439 If you say Y here, a user level program will be able to instruct the
440 kernel (via a special system call) to write process accounting
441 information to a file: whenever a process exits, information about
442 that process will be appended to the file by the kernel. The
443 information includes things such as creation time, owning user,
444 command name, memory usage, controlling terminal etc. (the complete
445 list is in the struct acct in <file:include/linux/acct.h>). It is
446 up to the user level program to do useful things with this
447 information. This is generally a good idea, so say Y.
449 config BSD_PROCESS_ACCT_V3
450 bool "BSD Process Accounting version 3 file format"
451 depends on BSD_PROCESS_ACCT
454 If you say Y here, the process accounting information is written
455 in a new file format that also logs the process IDs of each
456 process and its parent. Note that this file format is incompatible
457 with previous v0/v1/v2 file formats, so you will need updated tools
458 for processing it. A preliminary version of these tools is available
459 at <http://www.gnu.org/software/acct/>.
462 bool "Export task/process statistics through netlink"
467 Export selected statistics for tasks/processes through the
468 generic netlink interface. Unlike BSD process accounting, the
469 statistics are available during the lifetime of tasks/processes as
470 responses to commands. Like BSD accounting, they are sent to user
475 config TASK_DELAY_ACCT
476 bool "Enable per-task delay accounting"
480 Collect information on time spent by a task waiting for system
481 resources like cpu, synchronous block I/O completion and swapping
482 in pages. Such statistics can help in setting a task's priorities
483 relative to other tasks for cpu, io, rss limits etc.
488 bool "Enable extended accounting over taskstats"
491 Collect extended task accounting data and send the data
492 to userland for processing over the taskstats interface.
496 config TASK_IO_ACCOUNTING
497 bool "Enable per-task storage I/O accounting"
498 depends on TASK_XACCT
500 Collect information on the number of bytes of storage I/O which this
506 bool "Pressure stall information tracking"
508 Collect metrics that indicate how overcommitted the CPU, memory,
509 and IO capacity are in the system.
511 If you say Y here, the kernel will create /proc/pressure/ with the
512 pressure statistics files cpu, memory, and io. These will indicate
513 the share of walltime in which some or all tasks in the system are
514 delayed due to contention of the respective resource.
516 In kernels with cgroup support, cgroups (cgroup2 only) will
517 have cpu.pressure, memory.pressure, and io.pressure files,
518 which aggregate pressure stalls for the grouped tasks only.
520 For more details see Documentation/accounting/psi.txt.
524 config PSI_DEFAULT_DISABLED
525 bool "Require boot parameter to enable pressure stall information tracking"
529 If set, pressure stall information tracking will be disabled
530 per default but can be enabled through passing psi=1 on the
531 kernel commandline during boot.
533 This feature adds some code to the task wakeup and sleep
534 paths of the scheduler. The overhead is too low to affect
535 common scheduling-intense workloads in practice (such as
536 webservers, memcache), but it does show up in artificial
537 scheduler stress tests, such as hackbench.
539 If you are paranoid and not sure what the kernel will be
544 endmenu # "CPU/Task time and stats accounting"
548 depends on SMP || COMPILE_TEST
551 Make sure that CPUs running critical tasks are not disturbed by
552 any source of "noise" such as unbound workqueues, timers, kthreads...
553 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
554 the "isolcpus=" boot parameter.
558 source "kernel/rcu/Kconfig"
565 tristate "Kernel .config support"
567 This option enables the complete Linux kernel ".config" file
568 contents to be saved in the kernel. It provides documentation
569 of which kernel options are used in a running kernel or in an
570 on-disk kernel. This information can be extracted from the kernel
571 image file with the script scripts/extract-ikconfig and used as
572 input to rebuild the current kernel or to build another kernel.
573 It can also be extracted from a running kernel by reading
574 /proc/config.gz if enabled (below).
577 bool "Enable access to .config through /proc/config.gz"
578 depends on IKCONFIG && PROC_FS
580 This option enables access to the kernel configuration file
581 through /proc/config.gz.
584 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
587 This option enables access to the in-kernel headers that are generated during
588 the build process. These can be used to build eBPF tracing programs,
589 or similar programs. If you build the headers as a module, a module called
590 kheaders.ko is built which can be loaded on-demand to get access to headers.
593 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
598 Select the minimal kernel log buffer size as a power of 2.
599 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
600 parameter, see below. Any higher size also might be forced
601 by "log_buf_len" boot parameter.
611 config LOG_CPU_MAX_BUF_SHIFT
612 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
615 default 12 if !BASE_SMALL
616 default 0 if BASE_SMALL
619 This option allows to increase the default ring buffer size
620 according to the number of CPUs. The value defines the contribution
621 of each CPU as a power of 2. The used space is typically only few
622 lines however it might be much more when problems are reported,
625 The increased size means that a new buffer has to be allocated and
626 the original static one is unused. It makes sense only on systems
627 with more CPUs. Therefore this value is used only when the sum of
628 contributions is greater than the half of the default kernel ring
629 buffer as defined by LOG_BUF_SHIFT. The default values are set
630 so that more than 64 CPUs are needed to trigger the allocation.
632 Also this option is ignored when "log_buf_len" kernel parameter is
633 used as it forces an exact (power of two) size of the ring buffer.
635 The number of possible CPUs is used for this computation ignoring
636 hotplugging making the computation optimal for the worst case
637 scenario while allowing a simple algorithm to be used from bootup.
639 Examples shift values and their meaning:
640 17 => 128 KB for each CPU
641 16 => 64 KB for each CPU
642 15 => 32 KB for each CPU
643 14 => 16 KB for each CPU
644 13 => 8 KB for each CPU
645 12 => 4 KB for each CPU
647 config PRINTK_SAFE_LOG_BUF_SHIFT
648 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
653 Select the size of an alternate printk per-CPU buffer where messages
654 printed from usafe contexts are temporary stored. One example would
655 be NMI messages, another one - printk recursion. The messages are
656 copied to the main log buffer in a safe context to avoid a deadlock.
657 The value defines the size as a power of 2.
659 Those messages are rare and limited. The largest one is when
660 a backtrace is printed. It usually fits into 4KB. Select
661 8KB if you want to be on the safe side.
664 17 => 128 KB for each CPU
665 16 => 64 KB for each CPU
666 15 => 32 KB for each CPU
667 14 => 16 KB for each CPU
668 13 => 8 KB for each CPU
669 12 => 4 KB for each CPU
672 # Architectures with an unreliable sched_clock() should select this:
674 config HAVE_UNSTABLE_SCHED_CLOCK
677 config GENERIC_SCHED_CLOCK
680 menu "Scheduler features"
683 bool "Enable utilization clamping for RT/FAIR tasks"
684 depends on CPU_FREQ_GOV_SCHEDUTIL
686 This feature enables the scheduler to track the clamped utilization
687 of each CPU based on RUNNABLE tasks scheduled on that CPU.
689 With this option, the user can specify the min and max CPU
690 utilization allowed for RUNNABLE tasks. The max utilization defines
691 the maximum frequency a task should use while the min utilization
692 defines the minimum frequency it should use.
694 Both min and max utilization clamp values are hints to the scheduler,
695 aiming at improving its frequency selection policy, but they do not
696 enforce or grant any specific bandwidth for tasks.
700 config UCLAMP_BUCKETS_COUNT
701 int "Number of supported utilization clamp buckets"
704 depends on UCLAMP_TASK
706 Defines the number of clamp buckets to use. The range of each bucket
707 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
708 number of clamp buckets the finer their granularity and the higher
709 the precision of clamping aggregation and tracking at run-time.
711 For example, with the minimum configuration value we will have 5
712 clamp buckets tracking 20% utilization each. A 25% boosted tasks will
713 be refcounted in the [20..39]% bucket and will set the bucket clamp
714 effective value to 25%.
715 If a second 30% boosted task should be co-scheduled on the same CPU,
716 that task will be refcounted in the same bucket of the first task and
717 it will boost the bucket clamp effective value to 30%.
718 The clamp effective value of a bucket is reset to its nominal value
719 (20% in the example above) when there are no more tasks refcounted in
722 An additional boost/capping margin can be added to some tasks. In the
723 example above the 25% task will be boosted to 30% until it exits the
724 CPU. If that should be considered not acceptable on certain systems,
725 it's always possible to reduce the margin by increasing the number of
726 clamp buckets to trade off used memory for run-time tracking
729 If in doubt, use the default value.
734 # For architectures that want to enable the support for NUMA-affine scheduler
737 config ARCH_SUPPORTS_NUMA_BALANCING
741 # For architectures that prefer to flush all TLBs after a number of pages
742 # are unmapped instead of sending one IPI per page to flush. The architecture
743 # must provide guarantees on what happens if a clean TLB cache entry is
744 # written after the unmap. Details are in mm/rmap.c near the check for
745 # should_defer_flush. The architecture should also consider if the full flush
746 # and the refill costs are offset by the savings of sending fewer IPIs.
747 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
751 # For architectures that know their GCC __int128 support is sound
753 config ARCH_SUPPORTS_INT128
756 # For architectures that (ab)use NUMA to represent different memory regions
757 # all cpu-local but of different latencies, such as SuperH.
759 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
762 config NUMA_BALANCING
763 bool "Memory placement aware NUMA scheduler"
764 depends on ARCH_SUPPORTS_NUMA_BALANCING
765 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
766 depends on SMP && NUMA && MIGRATION
768 This option adds support for automatic NUMA aware memory/task placement.
769 The mechanism is quite primitive and is based on migrating memory when
770 it has references to the node the task is running on.
772 This system will be inactive on UMA systems.
774 config NUMA_BALANCING_DEFAULT_ENABLED
775 bool "Automatically enable NUMA aware memory/task placement"
777 depends on NUMA_BALANCING
779 If set, automatic NUMA balancing will be enabled if running on a NUMA
783 bool "Control Group support"
786 This option adds support for grouping sets of processes together, for
787 use with process control subsystems such as Cpusets, CFS, memory
788 controls or device isolation.
790 - Documentation/scheduler/sched-design-CFS.rst (CFS)
791 - Documentation/cgroup-v1/ (features for grouping, isolation
792 and resource control)
802 bool "Memory controller"
806 Provides control over the memory footprint of tasks in a cgroup.
809 bool "Swap controller"
810 depends on MEMCG && SWAP
812 Provides control over the swap space consumed by tasks in a cgroup.
814 config MEMCG_SWAP_ENABLED
815 bool "Swap controller enabled by default"
816 depends on MEMCG_SWAP
819 Memory Resource Controller Swap Extension comes with its price in
820 a bigger memory consumption. General purpose distribution kernels
821 which want to enable the feature but keep it disabled by default
822 and let the user enable it by swapaccount=1 boot command line
823 parameter should have this option unselected.
824 For those who want to have the feature enabled by default should
825 select this option (if, for some reason, they need to disable it
826 then swapaccount=0 does the trick).
830 depends on MEMCG && !SLOB
838 Generic block IO controller cgroup interface. This is the common
839 cgroup interface which should be used by various IO controlling
842 Currently, CFQ IO scheduler uses it to recognize task groups and
843 control disk bandwidth allocation (proportional time slice allocation)
844 to such task groups. It is also used by bio throttling logic in
845 block layer to implement upper limit in IO rates on a device.
847 This option only enables generic Block IO controller infrastructure.
848 One needs to also enable actual IO controlling logic/policy. For
849 enabling proportional weight division of disk bandwidth in CFQ, set
850 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
851 CONFIG_BLK_DEV_THROTTLING=y.
853 See Documentation/cgroup-v1/blkio-controller.rst for more information.
855 config CGROUP_WRITEBACK
857 depends on MEMCG && BLK_CGROUP
860 menuconfig CGROUP_SCHED
861 bool "CPU controller"
864 This feature lets CPU scheduler recognize task groups and control CPU
865 bandwidth allocation to such task groups. It uses cgroups to group
869 config FAIR_GROUP_SCHED
870 bool "Group scheduling for SCHED_OTHER"
871 depends on CGROUP_SCHED
875 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
876 depends on FAIR_GROUP_SCHED
879 This option allows users to define CPU bandwidth rates (limits) for
880 tasks running within the fair group scheduler. Groups with no limit
881 set are considered to be unconstrained and will run with no
883 See Documentation/scheduler/sched-bwc.rst for more information.
885 config RT_GROUP_SCHED
886 bool "Group scheduling for SCHED_RR/FIFO"
887 depends on CGROUP_SCHED
890 This feature lets you explicitly allocate real CPU bandwidth
891 to task groups. If enabled, it will also make it impossible to
892 schedule realtime tasks for non-root users until you allocate
893 realtime bandwidth for them.
894 See Documentation/scheduler/sched-rt-group.rst for more information.
899 bool "PIDs controller"
901 Provides enforcement of process number limits in the scope of a
902 cgroup. Any attempt to fork more processes than is allowed in the
903 cgroup will fail. PIDs are fundamentally a global resource because it
904 is fairly trivial to reach PID exhaustion before you reach even a
905 conservative kmemcg limit. As a result, it is possible to grind a
906 system to halt without being limited by other cgroup policies. The
907 PIDs controller is designed to stop this from happening.
909 It should be noted that organisational operations (such as attaching
910 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
911 since the PIDs limit only affects a process's ability to fork, not to
915 bool "RDMA controller"
917 Provides enforcement of RDMA resources defined by IB stack.
918 It is fairly easy for consumers to exhaust RDMA resources, which
919 can result into resource unavailability to other consumers.
920 RDMA controller is designed to stop this from happening.
921 Attaching processes with active RDMA resources to the cgroup
922 hierarchy is allowed even if can cross the hierarchy's limit.
924 config CGROUP_FREEZER
925 bool "Freezer controller"
927 Provides a way to freeze and unfreeze all tasks in a
930 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
931 controller includes important in-kernel memory consumers per default.
933 If you're using cgroup2, say N.
935 config CGROUP_HUGETLB
936 bool "HugeTLB controller"
937 depends on HUGETLB_PAGE
941 Provides a cgroup controller for HugeTLB pages.
942 When you enable this, you can put a per cgroup limit on HugeTLB usage.
943 The limit is enforced during page fault. Since HugeTLB doesn't
944 support page reclaim, enforcing the limit at page fault time implies
945 that, the application will get SIGBUS signal if it tries to access
946 HugeTLB pages beyond its limit. This requires the application to know
947 beforehand how much HugeTLB pages it would require for its use. The
948 control group is tracked in the third page lru pointer. This means
949 that we cannot use the controller with huge page less than 3 pages.
952 bool "Cpuset controller"
955 This option will let you create and manage CPUSETs which
956 allow dynamically partitioning a system into sets of CPUs and
957 Memory Nodes and assigning tasks to run only within those sets.
958 This is primarily useful on large SMP or NUMA systems.
962 config PROC_PID_CPUSET
963 bool "Include legacy /proc/<pid>/cpuset file"
968 bool "Device controller"
970 Provides a cgroup controller implementing whitelists for
971 devices which a process in the cgroup can mknod or open.
973 config CGROUP_CPUACCT
974 bool "Simple CPU accounting controller"
976 Provides a simple controller for monitoring the
977 total CPU consumed by the tasks in a cgroup.
980 bool "Perf controller"
981 depends on PERF_EVENTS
983 This option extends the perf per-cpu mode to restrict monitoring
984 to threads which belong to the cgroup specified and run on the
990 bool "Support for eBPF programs attached to cgroups"
991 depends on BPF_SYSCALL
992 select SOCK_CGROUP_DATA
994 Allow attaching eBPF programs to a cgroup using the bpf(2)
995 syscall command BPF_PROG_ATTACH.
997 In which context these programs are accessed depends on the type
998 of attachment. For instance, programs that are attached using
999 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1003 bool "Debug controller"
1005 depends on DEBUG_KERNEL
1007 This option enables a simple controller that exports
1008 debugging information about the cgroups framework. This
1009 controller is for control cgroup debugging only. Its
1010 interfaces are not stable.
1014 config SOCK_CGROUP_DATA
1020 menuconfig NAMESPACES
1021 bool "Namespaces support" if EXPERT
1022 depends on MULTIUSER
1025 Provides the way to make tasks work with different objects using
1026 the same id. For example same IPC id may refer to different objects
1027 or same user id or pid may refer to different tasks when used in
1028 different namespaces.
1033 bool "UTS namespace"
1036 In this namespace tasks see different info provided with the
1040 bool "IPC namespace"
1041 depends on (SYSVIPC || POSIX_MQUEUE)
1044 In this namespace tasks work with IPC ids which correspond to
1045 different IPC objects in different namespaces.
1048 bool "User namespace"
1051 This allows containers, i.e. vservers, to use user namespaces
1052 to provide different user info for different servers.
1054 When user namespaces are enabled in the kernel it is
1055 recommended that the MEMCG option also be enabled and that
1056 user-space use the memory control groups to limit the amount
1057 of memory a memory unprivileged users can use.
1062 bool "PID Namespaces"
1065 Support process id namespaces. This allows having multiple
1066 processes with the same pid as long as they are in different
1067 pid namespaces. This is a building block of containers.
1070 bool "Network namespace"
1074 Allow user space to create what appear to be multiple instances
1075 of the network stack.
1079 config CHECKPOINT_RESTORE
1080 bool "Checkpoint/restore support"
1081 select PROC_CHILDREN
1084 Enables additional kernel features in a sake of checkpoint/restore.
1085 In particular it adds auxiliary prctl codes to setup process text,
1086 data and heap segment sizes, and a few additional /proc filesystem
1089 If unsure, say N here.
1091 config SCHED_AUTOGROUP
1092 bool "Automatic process group scheduling"
1095 select FAIR_GROUP_SCHED
1097 This option optimizes the scheduler for common desktop workloads by
1098 automatically creating and populating task groups. This separation
1099 of workloads isolates aggressive CPU burners (like build jobs) from
1100 desktop applications. Task group autogeneration is currently based
1103 config SYSFS_DEPRECATED
1104 bool "Enable deprecated sysfs features to support old userspace tools"
1108 This option adds code that switches the layout of the "block" class
1109 devices, to not show up in /sys/class/block/, but only in
1112 This switch is only active when the sysfs.deprecated=1 boot option is
1113 passed or the SYSFS_DEPRECATED_V2 option is set.
1115 This option allows new kernels to run on old distributions and tools,
1116 which might get confused by /sys/class/block/. Since 2007/2008 all
1117 major distributions and tools handle this just fine.
1119 Recent distributions and userspace tools after 2009/2010 depend on
1120 the existence of /sys/class/block/, and will not work with this
1123 Only if you are using a new kernel on an old distribution, you might
1126 config SYSFS_DEPRECATED_V2
1127 bool "Enable deprecated sysfs features by default"
1130 depends on SYSFS_DEPRECATED
1132 Enable deprecated sysfs by default.
1134 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1137 Only if you are using a new kernel on an old distribution, you might
1138 need to say Y here. Even then, odds are you would not need it
1139 enabled, you can always pass the boot option if absolutely necessary.
1142 bool "Kernel->user space relay support (formerly relayfs)"
1145 This option enables support for relay interface support in
1146 certain file systems (such as debugfs).
1147 It is designed to provide an efficient mechanism for tools and
1148 facilities to relay large amounts of data from kernel space to
1153 config BLK_DEV_INITRD
1154 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1156 The initial RAM filesystem is a ramfs which is loaded by the
1157 boot loader (loadlin or lilo) and that is mounted as root
1158 before the normal boot procedure. It is typically used to
1159 load modules needed to mount the "real" root file system,
1160 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1162 If RAM disk support (BLK_DEV_RAM) is also included, this
1163 also enables initial RAM disk (initrd) support and adds
1164 15 Kbytes (more on some other architectures) to the kernel size.
1170 source "usr/Kconfig"
1175 prompt "Compiler optimization level"
1176 default CC_OPTIMIZE_FOR_PERFORMANCE
1178 config CC_OPTIMIZE_FOR_PERFORMANCE
1179 bool "Optimize for performance"
1181 This is the default optimization level for the kernel, building
1182 with the "-O2" compiler flag for best performance and most
1183 helpful compile-time warnings.
1185 config CC_OPTIMIZE_FOR_SIZE
1186 bool "Optimize for size"
1187 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives
1189 Enabling this option will pass "-Os" instead of "-O2" to
1190 your compiler resulting in a smaller kernel.
1196 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1199 This requires that the arch annotates or otherwise protects
1200 its external entry points from being discarded. Linker scripts
1201 must also merge .text.*, .data.*, and .bss.* correctly into
1202 output sections. Care must be taken not to pull in unrelated
1203 sections (e.g., '.text.init'). Typically '.' in section names
1204 is used to distinguish them from label names / C identifiers.
1206 config LD_DEAD_CODE_DATA_ELIMINATION
1207 bool "Dead code and data elimination (EXPERIMENTAL)"
1208 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1210 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800)
1211 depends on $(cc-option,-ffunction-sections -fdata-sections)
1212 depends on $(ld-option,--gc-sections)
1214 Enable this if you want to do dead code and data elimination with
1215 the linker by compiling with -ffunction-sections -fdata-sections,
1216 and linking with --gc-sections.
1218 This can reduce on disk and in-memory size of the kernel
1219 code and static data, particularly for small configs and
1220 on small systems. This has the possibility of introducing
1221 silently broken kernel if the required annotations are not
1222 present. This option is not well tested yet, so use at your
1231 config SYSCTL_EXCEPTION_TRACE
1234 Enable support for /proc/sys/debug/exception-trace.
1236 config SYSCTL_ARCH_UNALIGN_NO_WARN
1239 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1240 Allows arch to define/use @no_unaligned_warning to possibly warn
1241 about unaligned access emulation going on under the hood.
1243 config SYSCTL_ARCH_UNALIGN_ALLOW
1246 Enable support for /proc/sys/kernel/unaligned-trap
1247 Allows arches to define/use @unaligned_enabled to runtime toggle
1248 the unaligned access emulation.
1249 see arch/parisc/kernel/unaligned.c for reference
1251 config HAVE_PCSPKR_PLATFORM
1254 # interpreter that classic socket filters depend on
1259 bool "Configure standard kernel features (expert users)"
1260 # Unhide debug options, to make the on-by-default options visible
1263 This option allows certain base kernel options and settings
1264 to be disabled or tweaked. This is for specialized
1265 environments which can tolerate a "non-standard" kernel.
1266 Only use this if you really know what you are doing.
1269 bool "Enable 16-bit UID system calls" if EXPERT
1270 depends on HAVE_UID16 && MULTIUSER
1273 This enables the legacy 16-bit UID syscall wrappers.
1276 bool "Multiple users, groups and capabilities support" if EXPERT
1279 This option enables support for non-root users, groups and
1282 If you say N here, all processes will run with UID 0, GID 0, and all
1283 possible capabilities. Saying N here also compiles out support for
1284 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1287 If unsure, say Y here.
1289 config SGETMASK_SYSCALL
1290 bool "sgetmask/ssetmask syscalls support" if EXPERT
1291 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1293 sys_sgetmask and sys_ssetmask are obsolete system calls
1294 no longer supported in libc but still enabled by default in some
1297 If unsure, leave the default option here.
1299 config SYSFS_SYSCALL
1300 bool "Sysfs syscall support" if EXPERT
1303 sys_sysfs is an obsolete system call no longer supported in libc.
1304 Note that disabling this option is more secure but might break
1305 compatibility with some systems.
1307 If unsure say Y here.
1309 config SYSCTL_SYSCALL
1310 bool "Sysctl syscall support" if EXPERT
1311 depends on PROC_SYSCTL
1315 sys_sysctl uses binary paths that have been found challenging
1316 to properly maintain and use. The interface in /proc/sys
1317 using paths with ascii names is now the primary path to this
1320 Almost nothing using the binary sysctl interface so if you are
1321 trying to save some space it is probably safe to disable this,
1322 making your kernel marginally smaller.
1324 If unsure say N here.
1327 bool "open by fhandle syscalls" if EXPERT
1331 If you say Y here, a user level program will be able to map
1332 file names to handle and then later use the handle for
1333 different file system operations. This is useful in implementing
1334 userspace file servers, which now track files using handles instead
1335 of names. The handle would remain the same even if file names
1336 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1340 bool "Posix Clocks & timers" if EXPERT
1343 This includes native support for POSIX timers to the kernel.
1344 Some embedded systems have no use for them and therefore they
1345 can be configured out to reduce the size of the kernel image.
1347 When this option is disabled, the following syscalls won't be
1348 available: timer_create, timer_gettime: timer_getoverrun,
1349 timer_settime, timer_delete, clock_adjtime, getitimer,
1350 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1351 clock_getres and clock_nanosleep syscalls will be limited to
1352 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1358 bool "Enable support for printk" if EXPERT
1361 This option enables normal printk support. Removing it
1362 eliminates most of the message strings from the kernel image
1363 and makes the kernel more or less silent. As this makes it
1364 very difficult to diagnose system problems, saying N here is
1365 strongly discouraged.
1373 bool "BUG() support" if EXPERT
1376 Disabling this option eliminates support for BUG and WARN, reducing
1377 the size of your kernel image and potentially quietly ignoring
1378 numerous fatal conditions. You should only consider disabling this
1379 option for embedded systems with no facilities for reporting errors.
1385 bool "Enable ELF core dumps" if EXPERT
1387 Enable support for generating core dumps. Disabling saves about 4k.
1390 config PCSPKR_PLATFORM
1391 bool "Enable PC-Speaker support" if EXPERT
1392 depends on HAVE_PCSPKR_PLATFORM
1396 This option allows to disable the internal PC-Speaker
1397 support, saving some memory.
1401 bool "Enable full-sized data structures for core" if EXPERT
1403 Disabling this option reduces the size of miscellaneous core
1404 kernel data structures. This saves memory on small machines,
1405 but may reduce performance.
1408 bool "Enable futex support" if EXPERT
1412 Disabling this option will cause the kernel to be built without
1413 support for "fast userspace mutexes". The resulting kernel may not
1414 run glibc-based applications correctly.
1418 depends on FUTEX && RT_MUTEXES
1421 config HAVE_FUTEX_CMPXCHG
1425 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1426 is implemented and always working. This removes a couple of runtime
1430 bool "Enable eventpoll support" if EXPERT
1433 Disabling this option will cause the kernel to be built without
1434 support for epoll family of system calls.
1437 bool "Enable signalfd() system call" if EXPERT
1440 Enable the signalfd() system call that allows to receive signals
1441 on a file descriptor.
1446 bool "Enable timerfd() system call" if EXPERT
1449 Enable the timerfd() system call that allows to receive timer
1450 events on a file descriptor.
1455 bool "Enable eventfd() system call" if EXPERT
1458 Enable the eventfd() system call that allows to receive both
1459 kernel notification (ie. KAIO) or userspace notifications.
1464 bool "Use full shmem filesystem" if EXPERT
1468 The shmem is an internal filesystem used to manage shared memory.
1469 It is backed by swap and manages resource limits. It is also exported
1470 to userspace as tmpfs if TMPFS is enabled. Disabling this
1471 option replaces shmem and tmpfs with the much simpler ramfs code,
1472 which may be appropriate on small systems without swap.
1475 bool "Enable AIO support" if EXPERT
1478 This option enables POSIX asynchronous I/O which may by used
1479 by some high performance threaded applications. Disabling
1480 this option saves about 7k.
1483 bool "Enable IO uring support" if EXPERT
1487 This option enables support for the io_uring interface, enabling
1488 applications to submit and complete IO through submission and
1489 completion rings that are shared between the kernel and application.
1491 config ADVISE_SYSCALLS
1492 bool "Enable madvise/fadvise syscalls" if EXPERT
1495 This option enables the madvise and fadvise syscalls, used by
1496 applications to advise the kernel about their future memory or file
1497 usage, improving performance. If building an embedded system where no
1498 applications use these syscalls, you can disable this option to save
1502 bool "Enable membarrier() system call" if EXPERT
1505 Enable the membarrier() system call that allows issuing memory
1506 barriers across all running threads, which can be used to distribute
1507 the cost of user-space memory barriers asymmetrically by transforming
1508 pairs of memory barriers into pairs consisting of membarrier() and a
1514 bool "Load all symbols for debugging/ksymoops" if EXPERT
1517 Say Y here to let the kernel print out symbolic crash information and
1518 symbolic stack backtraces. This increases the size of the kernel
1519 somewhat, as all symbols have to be loaded into the kernel image.
1522 bool "Include all symbols in kallsyms"
1523 depends on DEBUG_KERNEL && KALLSYMS
1525 Normally kallsyms only contains the symbols of functions for nicer
1526 OOPS messages and backtraces (i.e., symbols from the text and inittext
1527 sections). This is sufficient for most cases. And only in very rare
1528 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1529 names of variables from the data sections, etc).
1531 This option makes sure that all symbols are loaded into the kernel
1532 image (i.e., symbols from all sections) in cost of increased kernel
1533 size (depending on the kernel configuration, it may be 300KiB or
1534 something like this).
1536 Say N unless you really need all symbols.
1538 config KALLSYMS_ABSOLUTE_PERCPU
1541 default X86_64 && SMP
1543 config KALLSYMS_BASE_RELATIVE
1548 Instead of emitting them as absolute values in the native word size,
1549 emit the symbol references in the kallsyms table as 32-bit entries,
1550 each containing a relative value in the range [base, base + U32_MAX]
1551 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1552 an absolute value in the range [0, S32_MAX] or a relative value in the
1553 range [base, base + S32_MAX], where base is the lowest relative symbol
1554 address encountered in the image.
1556 On 64-bit builds, this reduces the size of the address table by 50%,
1557 but more importantly, it results in entries whose values are build
1558 time constants, and no relocation pass is required at runtime to fix
1559 up the entries based on the runtime load address of the kernel.
1561 # end of the "standard kernel features (expert users)" menu
1563 # syscall, maps, verifier
1565 bool "Enable bpf() system call"
1570 Enable the bpf() system call that allows to manipulate eBPF
1571 programs and maps via file descriptors.
1573 config BPF_JIT_ALWAYS_ON
1574 bool "Permanently enable BPF JIT and remove BPF interpreter"
1575 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1577 Enables BPF JIT and removes BPF interpreter to avoid
1578 speculative execution of BPF instructions by the interpreter
1581 bool "Enable userfaultfd() system call"
1584 Enable the userfaultfd() system call that allows to intercept and
1585 handle page faults in userland.
1587 config ARCH_HAS_MEMBARRIER_CALLBACKS
1590 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1594 bool "Enable rseq() system call" if EXPERT
1596 depends on HAVE_RSEQ
1599 Enable the restartable sequences system call. It provides a
1600 user-space cache for the current CPU number value, which
1601 speeds up getting the current CPU number from user-space,
1602 as well as an ABI to speed up user-space operations on
1609 bool "Enabled debugging of rseq() system call" if EXPERT
1610 depends on RSEQ && DEBUG_KERNEL
1612 Enable extra debugging checks for the rseq system call.
1617 bool "Embedded system"
1618 option allnoconfig_y
1621 This option should be enabled if compiling the kernel for
1622 an embedded system so certain expert options are available
1625 config HAVE_PERF_EVENTS
1628 See tools/perf/design.txt for details.
1630 config PERF_USE_VMALLOC
1633 See tools/perf/design.txt for details
1636 bool "PC/104 support" if EXPERT
1638 Expose PC/104 form factor device drivers and options available for
1639 selection and configuration. Enable this option if your target
1640 machine has a PC/104 bus.
1642 menu "Kernel Performance Events And Counters"
1645 bool "Kernel performance events and counters"
1646 default y if PROFILING
1647 depends on HAVE_PERF_EVENTS
1651 Enable kernel support for various performance events provided
1652 by software and hardware.
1654 Software events are supported either built-in or via the
1655 use of generic tracepoints.
1657 Most modern CPUs support performance events via performance
1658 counter registers. These registers count the number of certain
1659 types of hw events: such as instructions executed, cachemisses
1660 suffered, or branches mis-predicted - without slowing down the
1661 kernel or applications. These registers can also trigger interrupts
1662 when a threshold number of events have passed - and can thus be
1663 used to profile the code that runs on that CPU.
1665 The Linux Performance Event subsystem provides an abstraction of
1666 these software and hardware event capabilities, available via a
1667 system call and used by the "perf" utility in tools/perf/. It
1668 provides per task and per CPU counters, and it provides event
1669 capabilities on top of those.
1673 config DEBUG_PERF_USE_VMALLOC
1675 bool "Debug: use vmalloc to back perf mmap() buffers"
1676 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1677 select PERF_USE_VMALLOC
1679 Use vmalloc memory to back perf mmap() buffers.
1681 Mostly useful for debugging the vmalloc code on platforms
1682 that don't require it.
1688 config VM_EVENT_COUNTERS
1690 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1692 VM event counters are needed for event counts to be shown.
1693 This option allows the disabling of the VM event counters
1694 on EXPERT systems. /proc/vmstat will only show page counts
1695 if VM event counters are disabled.
1699 bool "Enable SLUB debugging support" if EXPERT
1700 depends on SLUB && SYSFS
1702 SLUB has extensive debug support features. Disabling these can
1703 result in significant savings in code size. This also disables
1704 SLUB sysfs support. /sys/slab will not exist and there will be
1705 no support for cache validation etc.
1707 config SLUB_MEMCG_SYSFS_ON
1709 bool "Enable memcg SLUB sysfs support by default" if EXPERT
1710 depends on SLUB && SYSFS && MEMCG
1712 SLUB creates a directory under /sys/kernel/slab for each
1713 allocation cache to host info and debug files. If memory
1714 cgroup is enabled, each cache can have per memory cgroup
1715 caches. SLUB can create the same sysfs directories for these
1716 caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1717 to a very high number of debug files being created. This is
1718 controlled by slub_memcg_sysfs boot parameter and this
1719 config option determines the parameter's default value.
1722 bool "Disable heap randomization"
1725 Randomizing heap placement makes heap exploits harder, but it
1726 also breaks ancient binaries (including anything libc5 based).
1727 This option changes the bootup default to heap randomization
1728 disabled, and can be overridden at runtime by setting
1729 /proc/sys/kernel/randomize_va_space to 2.
1731 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1734 prompt "Choose SLAB allocator"
1737 This option allows to select a slab allocator.
1741 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1743 The regular slab allocator that is established and known to work
1744 well in all environments. It organizes cache hot objects in
1745 per cpu and per node queues.
1748 bool "SLUB (Unqueued Allocator)"
1749 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1751 SLUB is a slab allocator that minimizes cache line usage
1752 instead of managing queues of cached objects (SLAB approach).
1753 Per cpu caching is realized using slabs of objects instead
1754 of queues of objects. SLUB can use memory efficiently
1755 and has enhanced diagnostics. SLUB is the default choice for
1760 bool "SLOB (Simple Allocator)"
1762 SLOB replaces the stock allocator with a drastically simpler
1763 allocator. SLOB is generally more space efficient but
1764 does not perform as well on large systems.
1768 config SLAB_MERGE_DEFAULT
1769 bool "Allow slab caches to be merged"
1772 For reduced kernel memory fragmentation, slab caches can be
1773 merged when they share the same size and other characteristics.
1774 This carries a risk of kernel heap overflows being able to
1775 overwrite objects from merged caches (and more easily control
1776 cache layout), which makes such heap attacks easier to exploit
1777 by attackers. By keeping caches unmerged, these kinds of exploits
1778 can usually only damage objects in the same cache. To disable
1779 merging at runtime, "slab_nomerge" can be passed on the kernel
1782 config SLAB_FREELIST_RANDOM
1784 depends on SLAB || SLUB
1785 bool "SLAB freelist randomization"
1787 Randomizes the freelist order used on creating new pages. This
1788 security feature reduces the predictability of the kernel slab
1789 allocator against heap overflows.
1791 config SLAB_FREELIST_HARDENED
1792 bool "Harden slab freelist metadata"
1795 Many kernel heap attacks try to target slab cache metadata and
1796 other infrastructure. This options makes minor performance
1797 sacrifies to harden the kernel slab allocator against common
1798 freelist exploit methods.
1800 config SHUFFLE_PAGE_ALLOCATOR
1801 bool "Page allocator randomization"
1802 default SLAB_FREELIST_RANDOM && ACPI_NUMA
1804 Randomization of the page allocator improves the average
1805 utilization of a direct-mapped memory-side-cache. See section
1806 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1807 6.2a specification for an example of how a platform advertises
1808 the presence of a memory-side-cache. There are also incidental
1809 security benefits as it reduces the predictability of page
1810 allocations to compliment SLAB_FREELIST_RANDOM, but the
1811 default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1812 10th order of pages is selected based on cache utilization
1815 While the randomization improves cache utilization it may
1816 negatively impact workloads on platforms without a cache. For
1817 this reason, by default, the randomization is enabled only
1818 after runtime detection of a direct-mapped memory-side-cache.
1819 Otherwise, the randomization may be force enabled with the
1820 'page_alloc.shuffle' kernel command line parameter.
1824 config SLUB_CPU_PARTIAL
1826 depends on SLUB && SMP
1827 bool "SLUB per cpu partial cache"
1829 Per cpu partial caches accellerate objects allocation and freeing
1830 that is local to a processor at the price of more indeterminism
1831 in the latency of the free. On overflow these caches will be cleared
1832 which requires the taking of locks that may cause latency spikes.
1833 Typically one would choose no for a realtime system.
1835 config MMAP_ALLOW_UNINITIALIZED
1836 bool "Allow mmapped anonymous memory to be uninitialized"
1837 depends on EXPERT && !MMU
1840 Normally, and according to the Linux spec, anonymous memory obtained
1841 from mmap() has its contents cleared before it is passed to
1842 userspace. Enabling this config option allows you to request that
1843 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1844 providing a huge performance boost. If this option is not enabled,
1845 then the flag will be ignored.
1847 This is taken advantage of by uClibc's malloc(), and also by
1848 ELF-FDPIC binfmt's brk and stack allocator.
1850 Because of the obvious security issues, this option should only be
1851 enabled on embedded devices where you control what is run in
1852 userspace. Since that isn't generally a problem on no-MMU systems,
1853 it is normally safe to say Y here.
1855 See Documentation/nommu-mmap.txt for more information.
1857 config SYSTEM_DATA_VERIFICATION
1859 select SYSTEM_TRUSTED_KEYRING
1863 select ASYMMETRIC_KEY_TYPE
1864 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1867 select X509_CERTIFICATE_PARSER
1868 select PKCS7_MESSAGE_PARSER
1870 Provide PKCS#7 message verification using the contents of the system
1871 trusted keyring to provide public keys. This then can be used for
1872 module verification, kexec image verification and firmware blob
1876 bool "Profiling support"
1878 Say Y here to enable the extended profiling support mechanisms used
1879 by profilers such as OProfile.
1882 # Place an empty function call at each tracepoint site. Can be
1883 # dynamically changed for a probe function.
1888 endmenu # General setup
1890 source "arch/Kconfig"
1897 default 0 if BASE_FULL
1898 default 1 if !BASE_FULL
1901 bool "Enable loadable module support"
1904 Kernel modules are small pieces of compiled code which can
1905 be inserted in the running kernel, rather than being
1906 permanently built into the kernel. You use the "modprobe"
1907 tool to add (and sometimes remove) them. If you say Y here,
1908 many parts of the kernel can be built as modules (by
1909 answering M instead of Y where indicated): this is most
1910 useful for infrequently used options which are not required
1911 for booting. For more information, see the man pages for
1912 modprobe, lsmod, modinfo, insmod and rmmod.
1914 If you say Y here, you will need to run "make
1915 modules_install" to put the modules under /lib/modules/
1916 where modprobe can find them (you may need to be root to do
1923 config MODULE_FORCE_LOAD
1924 bool "Forced module loading"
1927 Allow loading of modules without version information (ie. modprobe
1928 --force). Forced module loading sets the 'F' (forced) taint flag and
1929 is usually a really bad idea.
1931 config MODULE_UNLOAD
1932 bool "Module unloading"
1934 Without this option you will not be able to unload any
1935 modules (note that some modules may not be unloadable
1936 anyway), which makes your kernel smaller, faster
1937 and simpler. If unsure, say Y.
1939 config MODULE_FORCE_UNLOAD
1940 bool "Forced module unloading"
1941 depends on MODULE_UNLOAD
1943 This option allows you to force a module to unload, even if the
1944 kernel believes it is unsafe: the kernel will remove the module
1945 without waiting for anyone to stop using it (using the -f option to
1946 rmmod). This is mainly for kernel developers and desperate users.
1950 bool "Module versioning support"
1952 Usually, you have to use modules compiled with your kernel.
1953 Saying Y here makes it sometimes possible to use modules
1954 compiled for different kernels, by adding enough information
1955 to the modules to (hopefully) spot any changes which would
1956 make them incompatible with the kernel you are running. If
1959 config MODULE_REL_CRCS
1961 depends on MODVERSIONS
1963 config MODULE_SRCVERSION_ALL
1964 bool "Source checksum for all modules"
1966 Modules which contain a MODULE_VERSION get an extra "srcversion"
1967 field inserted into their modinfo section, which contains a
1968 sum of the source files which made it. This helps maintainers
1969 see exactly which source was used to build a module (since
1970 others sometimes change the module source without updating
1971 the version). With this option, such a "srcversion" field
1972 will be created for all modules. If unsure, say N.
1975 bool "Module signature verification"
1977 select SYSTEM_DATA_VERIFICATION
1979 Check modules for valid signatures upon load: the signature
1980 is simply appended to the module. For more information see
1981 <file:Documentation/admin-guide/module-signing.rst>.
1983 Note that this option adds the OpenSSL development packages as a
1984 kernel build dependency so that the signing tool can use its crypto
1987 !!!WARNING!!! If you enable this option, you MUST make sure that the
1988 module DOES NOT get stripped after being signed. This includes the
1989 debuginfo strip done by some packagers (such as rpmbuild) and
1990 inclusion into an initramfs that wants the module size reduced.
1992 config MODULE_SIG_FORCE
1993 bool "Require modules to be validly signed"
1994 depends on MODULE_SIG
1996 Reject unsigned modules or signed modules for which we don't have a
1997 key. Without this, such modules will simply taint the kernel.
1999 config MODULE_SIG_ALL
2000 bool "Automatically sign all modules"
2002 depends on MODULE_SIG
2004 Sign all modules during make modules_install. Without this option,
2005 modules must be signed manually, using the scripts/sign-file tool.
2007 comment "Do not forget to sign required modules with scripts/sign-file"
2008 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2011 prompt "Which hash algorithm should modules be signed with?"
2012 depends on MODULE_SIG
2014 This determines which sort of hashing algorithm will be used during
2015 signature generation. This algorithm _must_ be built into the kernel
2016 directly so that signature verification can take place. It is not
2017 possible to load a signed module containing the algorithm to check
2018 the signature on that module.
2020 config MODULE_SIG_SHA1
2021 bool "Sign modules with SHA-1"
2024 config MODULE_SIG_SHA224
2025 bool "Sign modules with SHA-224"
2026 select CRYPTO_SHA256
2028 config MODULE_SIG_SHA256
2029 bool "Sign modules with SHA-256"
2030 select CRYPTO_SHA256
2032 config MODULE_SIG_SHA384
2033 bool "Sign modules with SHA-384"
2034 select CRYPTO_SHA512
2036 config MODULE_SIG_SHA512
2037 bool "Sign modules with SHA-512"
2038 select CRYPTO_SHA512
2042 config MODULE_SIG_HASH
2044 depends on MODULE_SIG
2045 default "sha1" if MODULE_SIG_SHA1
2046 default "sha224" if MODULE_SIG_SHA224
2047 default "sha256" if MODULE_SIG_SHA256
2048 default "sha384" if MODULE_SIG_SHA384
2049 default "sha512" if MODULE_SIG_SHA512
2051 config MODULE_COMPRESS
2052 bool "Compress modules on installation"
2056 Compresses kernel modules when 'make modules_install' is run; gzip or
2057 xz depending on "Compression algorithm" below.
2059 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2061 Out-of-tree kernel modules installed using Kbuild will also be
2062 compressed upon installation.
2064 Note: for modules inside an initrd or initramfs, it's more efficient
2065 to compress the whole initrd or initramfs instead.
2067 Note: This is fully compatible with signed modules.
2072 prompt "Compression algorithm"
2073 depends on MODULE_COMPRESS
2074 default MODULE_COMPRESS_GZIP
2076 This determines which sort of compression will be used during
2077 'make modules_install'.
2079 GZIP (default) and XZ are supported.
2081 config MODULE_COMPRESS_GZIP
2084 config MODULE_COMPRESS_XZ
2089 config TRIM_UNUSED_KSYMS
2090 bool "Trim unused exported kernel symbols"
2091 depends on MODULES && !UNUSED_SYMBOLS
2093 The kernel and some modules make many symbols available for
2094 other modules to use via EXPORT_SYMBOL() and variants. Depending
2095 on the set of modules being selected in your kernel configuration,
2096 many of those exported symbols might never be used.
2098 This option allows for unused exported symbols to be dropped from
2099 the build. In turn, this provides the compiler more opportunities
2100 (especially when using LTO) for optimizing the code and reducing
2101 binary size. This might have some security advantages as well.
2103 If unsure, or if you need to build out-of-tree modules, say N.
2107 config MODULES_TREE_LOOKUP
2109 depends on PERF_EVENTS || TRACING
2111 config INIT_ALL_POSSIBLE
2114 Back when each arch used to define their own cpu_online_mask and
2115 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2116 with all 1s, and others with all 0s. When they were centralised,
2117 it was better to provide this option than to break all the archs
2118 and have several arch maintainers pursuing me down dark alleys.
2120 source "block/Kconfig"
2122 config PREEMPT_NOTIFIERS
2132 Build a simple ASN.1 grammar compiler that produces a bytecode output
2133 that can be interpreted by the ASN.1 stream decoder and used to
2134 inform it as to what tags are to be expected in a stream and what
2135 functions to call on what tags.
2137 source "kernel/Kconfig.locks"
2139 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2142 # It may be useful for an architecture to override the definitions of the
2143 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2144 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2145 # different calling convention for syscalls. They can also override the
2146 # macros for not-implemented syscalls in kernel/sys_ni.c and
2147 # kernel/time/posix-stubs.c. All these overrides need to be available in
2148 # <asm/syscall_wrapper.h>.
2149 config ARCH_HAS_SYSCALL_WRAPPER
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