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))
28 def_bool $(success,$(srctree)/scripts/cc-can-link.sh $(CC))
30 config CC_HAS_ASM_GOTO
31 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
33 config CC_HAS_WARN_MAYBE_UNINITIALIZED
34 def_bool $(cc-option,-Wmaybe-uninitialized)
36 GCC >= 4.7 supports this option.
38 config CC_DISABLE_WARN_MAYBE_UNINITIALIZED
40 depends on CC_HAS_WARN_MAYBE_UNINITIALIZED
41 default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9
43 GCC's -Wmaybe-uninitialized is not reliable by definition.
44 Lots of false positive warnings are produced in some cases.
46 If this option is enabled, -Wno-maybe-uninitialzed is passed
47 to the compiler to suppress maybe-uninitialized warnings.
56 config BUILDTIME_EXTABLE_SORT
59 config THREAD_INFO_IN_TASK
62 Select this to move thread_info off the stack into task_struct. To
63 make this work, an arch will need to remove all thread_info fields
64 except flags and fix any runtime bugs.
66 One subtle change that will be needed is to use try_get_task_stack()
67 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
76 depends on BROKEN || !SMP
79 config INIT_ENV_ARG_LIMIT
84 Maximum of each of the number of arguments and environment
85 variables passed to init from the kernel command line.
88 bool "Compile also drivers which will not load"
92 Some drivers can be compiled on a different platform than they are
93 intended to be run on. Despite they cannot be loaded there (or even
94 when they load they cannot be used due to missing HW support),
95 developers still, opposing to distributors, might want to build such
96 drivers to compile-test them.
98 If you are a developer and want to build everything available, say Y
99 here. If you are a user/distributor, say N here to exclude useless
100 drivers to be distributed.
103 bool "Compile test headers that should be standalone compilable"
105 Compile test headers listed in header-test-y target to ensure they are
106 self-contained, i.e. compilable as standalone units.
108 If you are a developer or tester and want to ensure the requested
109 headers are self-contained, say Y here. Otherwise, choose N.
111 config UAPI_HEADER_TEST
112 bool "Compile test UAPI headers"
113 depends on HEADER_TEST && HEADERS_INSTALL && CC_CAN_LINK
115 Compile test headers exported to user-space to ensure they are
116 self-contained, i.e. compilable as standalone units.
118 If you are a developer or tester and want to ensure the exported
119 headers are self-contained, say Y here. Otherwise, choose N.
122 string "Local version - append to kernel release"
124 Append an extra string to the end of your kernel version.
125 This will show up when you type uname, for example.
126 The string you set here will be appended after the contents of
127 any files with a filename matching localversion* in your
128 object and source tree, in that order. Your total string can
129 be a maximum of 64 characters.
131 config LOCALVERSION_AUTO
132 bool "Automatically append version information to the version string"
134 depends on !COMPILE_TEST
136 This will try to automatically determine if the current tree is a
137 release tree by looking for git tags that belong to the current
138 top of tree revision.
140 A string of the format -gxxxxxxxx will be added to the localversion
141 if a git-based tree is found. The string generated by this will be
142 appended after any matching localversion* files, and after the value
143 set in CONFIG_LOCALVERSION.
145 (The actual string used here is the first eight characters produced
146 by running the command:
148 $ git rev-parse --verify HEAD
150 which is done within the script "scripts/setlocalversion".)
153 string "Build ID Salt"
156 The build ID is used to link binaries and their debug info. Setting
157 this option will use the value in the calculation of the build id.
158 This is mostly useful for distributions which want to ensure the
159 build is unique between builds. It's safe to leave the default.
161 config HAVE_KERNEL_GZIP
164 config HAVE_KERNEL_BZIP2
167 config HAVE_KERNEL_LZMA
170 config HAVE_KERNEL_XZ
173 config HAVE_KERNEL_LZO
176 config HAVE_KERNEL_LZ4
179 config HAVE_KERNEL_UNCOMPRESSED
183 prompt "Kernel compression mode"
185 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED
187 The linux kernel is a kind of self-extracting executable.
188 Several compression algorithms are available, which differ
189 in efficiency, compression and decompression speed.
190 Compression speed is only relevant when building a kernel.
191 Decompression speed is relevant at each boot.
193 If you have any problems with bzip2 or lzma compressed
195 version of this functionality (bzip2 only), for 2.4, was
196 supplied by Christian Ludwig)
198 High compression options are mostly useful for users, who
199 are low on disk space (embedded systems), but for whom ram
202 If in doubt, select 'gzip'
206 depends on HAVE_KERNEL_GZIP
208 The old and tried gzip compression. It provides a good balance
209 between compression ratio and decompression speed.
213 depends on HAVE_KERNEL_BZIP2
215 Its compression ratio and speed is intermediate.
216 Decompression speed is slowest among the choices. The kernel
217 size is about 10% smaller with bzip2, in comparison to gzip.
218 Bzip2 uses a large amount of memory. For modern kernels you
219 will need at least 8MB RAM or more for booting.
223 depends on HAVE_KERNEL_LZMA
225 This compression algorithm's ratio is best. Decompression speed
226 is between gzip and bzip2. Compression is slowest.
227 The kernel size is about 33% smaller with LZMA in comparison to gzip.
231 depends on HAVE_KERNEL_XZ
233 XZ uses the LZMA2 algorithm and instruction set specific
234 BCJ filters which can improve compression ratio of executable
235 code. The size of the kernel is about 30% smaller with XZ in
236 comparison to gzip. On architectures for which there is a BCJ
237 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
238 will create a few percent smaller kernel than plain LZMA.
240 The speed is about the same as with LZMA: The decompression
241 speed of XZ is better than that of bzip2 but worse than gzip
242 and LZO. Compression is slow.
246 depends on HAVE_KERNEL_LZO
248 Its compression ratio is the poorest among the choices. The kernel
249 size is about 10% bigger than gzip; however its speed
250 (both compression and decompression) is the fastest.
254 depends on HAVE_KERNEL_LZ4
256 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
257 A preliminary version of LZ4 de/compression tool is available at
258 <https://code.google.com/p/lz4/>.
260 Its compression ratio is worse than LZO. The size of the kernel
261 is about 8% bigger than LZO. But the decompression speed is
264 config KERNEL_UNCOMPRESSED
266 depends on HAVE_KERNEL_UNCOMPRESSED
268 Produce uncompressed kernel image. This option is usually not what
269 you want. It is useful for debugging the kernel in slow simulation
270 environments, where decompressing and moving the kernel is awfully
271 slow. This option allows early boot code to skip the decompressor
272 and jump right at uncompressed kernel image.
276 config DEFAULT_HOSTNAME
277 string "Default hostname"
280 This option determines the default system hostname before userspace
281 calls sethostname(2). The kernel traditionally uses "(none)" here,
282 but you may wish to use a different default here to make a minimal
283 system more usable with less configuration.
286 # For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
287 # add proper SWAP support to them, in which case this can be remove.
293 bool "Support for paging of anonymous memory (swap)"
294 depends on MMU && BLOCK && !ARCH_NO_SWAP
297 This option allows you to choose whether you want to have support
298 for so called swap devices or swap files in your kernel that are
299 used to provide more virtual memory than the actual RAM present
300 in your computer. If unsure say Y.
305 Inter Process Communication is a suite of library functions and
306 system calls which let processes (running programs) synchronize and
307 exchange information. It is generally considered to be a good thing,
308 and some programs won't run unless you say Y here. In particular, if
309 you want to run the DOS emulator dosemu under Linux (read the
310 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
311 you'll need to say Y here.
313 You can find documentation about IPC with "info ipc" and also in
314 section 6.4 of the Linux Programmer's Guide, available from
315 <http://www.tldp.org/guides.html>.
317 config SYSVIPC_SYSCTL
324 bool "POSIX Message Queues"
327 POSIX variant of message queues is a part of IPC. In POSIX message
328 queues every message has a priority which decides about succession
329 of receiving it by a process. If you want to compile and run
330 programs written e.g. for Solaris with use of its POSIX message
331 queues (functions mq_*) say Y here.
333 POSIX message queues are visible as a filesystem called 'mqueue'
334 and can be mounted somewhere if you want to do filesystem
335 operations on message queues.
339 config POSIX_MQUEUE_SYSCTL
341 depends on POSIX_MQUEUE
345 config CROSS_MEMORY_ATTACH
346 bool "Enable process_vm_readv/writev syscalls"
350 Enabling this option adds the system calls process_vm_readv and
351 process_vm_writev which allow a process with the correct privileges
352 to directly read from or write to another process' address space.
353 See the man page for more details.
356 bool "uselib syscall"
357 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
359 This option enables the uselib syscall, a system call used in the
360 dynamic linker from libc5 and earlier. glibc does not use this
361 system call. If you intend to run programs built on libc5 or
362 earlier, you may need to enable this syscall. Current systems
363 running glibc can safely disable this.
366 bool "Auditing support"
369 Enable auditing infrastructure that can be used with another
370 kernel subsystem, such as SELinux (which requires this for
371 logging of avc messages output). System call auditing is included
372 on architectures which support it.
374 config HAVE_ARCH_AUDITSYSCALL
379 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
382 source "kernel/irq/Kconfig"
383 source "kernel/time/Kconfig"
384 source "kernel/Kconfig.preempt"
386 menu "CPU/Task time and stats accounting"
388 config VIRT_CPU_ACCOUNTING
392 prompt "Cputime accounting"
393 default TICK_CPU_ACCOUNTING if !PPC64
394 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
396 # Kind of a stub config for the pure tick based cputime accounting
397 config TICK_CPU_ACCOUNTING
398 bool "Simple tick based cputime accounting"
399 depends on !S390 && !NO_HZ_FULL
401 This is the basic tick based cputime accounting that maintains
402 statistics about user, system and idle time spent on per jiffies
407 config VIRT_CPU_ACCOUNTING_NATIVE
408 bool "Deterministic task and CPU time accounting"
409 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
410 select VIRT_CPU_ACCOUNTING
412 Select this option to enable more accurate task and CPU time
413 accounting. This is done by reading a CPU counter on each
414 kernel entry and exit and on transitions within the kernel
415 between system, softirq and hardirq state, so there is a
416 small performance impact. In the case of s390 or IBM POWER > 5,
417 this also enables accounting of stolen time on logically-partitioned
420 config VIRT_CPU_ACCOUNTING_GEN
421 bool "Full dynticks CPU time accounting"
422 depends on HAVE_CONTEXT_TRACKING
423 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
424 depends on GENERIC_CLOCKEVENTS
425 select VIRT_CPU_ACCOUNTING
426 select CONTEXT_TRACKING
428 Select this option to enable task and CPU time accounting on full
429 dynticks systems. This accounting is implemented by watching every
430 kernel-user boundaries using the context tracking subsystem.
431 The accounting is thus performed at the expense of some significant
434 For now this is only useful if you are working on the full
435 dynticks subsystem development.
441 config IRQ_TIME_ACCOUNTING
442 bool "Fine granularity task level IRQ time accounting"
443 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
445 Select this option to enable fine granularity task irq time
446 accounting. This is done by reading a timestamp on each
447 transitions between softirq and hardirq state, so there can be a
448 small performance impact.
450 If in doubt, say N here.
452 config HAVE_SCHED_AVG_IRQ
454 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
457 config BSD_PROCESS_ACCT
458 bool "BSD Process Accounting"
461 If you say Y here, a user level program will be able to instruct the
462 kernel (via a special system call) to write process accounting
463 information to a file: whenever a process exits, information about
464 that process will be appended to the file by the kernel. The
465 information includes things such as creation time, owning user,
466 command name, memory usage, controlling terminal etc. (the complete
467 list is in the struct acct in <file:include/linux/acct.h>). It is
468 up to the user level program to do useful things with this
469 information. This is generally a good idea, so say Y.
471 config BSD_PROCESS_ACCT_V3
472 bool "BSD Process Accounting version 3 file format"
473 depends on BSD_PROCESS_ACCT
476 If you say Y here, the process accounting information is written
477 in a new file format that also logs the process IDs of each
478 process and its parent. Note that this file format is incompatible
479 with previous v0/v1/v2 file formats, so you will need updated tools
480 for processing it. A preliminary version of these tools is available
481 at <http://www.gnu.org/software/acct/>.
484 bool "Export task/process statistics through netlink"
489 Export selected statistics for tasks/processes through the
490 generic netlink interface. Unlike BSD process accounting, the
491 statistics are available during the lifetime of tasks/processes as
492 responses to commands. Like BSD accounting, they are sent to user
497 config TASK_DELAY_ACCT
498 bool "Enable per-task delay accounting"
502 Collect information on time spent by a task waiting for system
503 resources like cpu, synchronous block I/O completion and swapping
504 in pages. Such statistics can help in setting a task's priorities
505 relative to other tasks for cpu, io, rss limits etc.
510 bool "Enable extended accounting over taskstats"
513 Collect extended task accounting data and send the data
514 to userland for processing over the taskstats interface.
518 config TASK_IO_ACCOUNTING
519 bool "Enable per-task storage I/O accounting"
520 depends on TASK_XACCT
522 Collect information on the number of bytes of storage I/O which this
528 bool "Pressure stall information tracking"
530 Collect metrics that indicate how overcommitted the CPU, memory,
531 and IO capacity are in the system.
533 If you say Y here, the kernel will create /proc/pressure/ with the
534 pressure statistics files cpu, memory, and io. These will indicate
535 the share of walltime in which some or all tasks in the system are
536 delayed due to contention of the respective resource.
538 In kernels with cgroup support, cgroups (cgroup2 only) will
539 have cpu.pressure, memory.pressure, and io.pressure files,
540 which aggregate pressure stalls for the grouped tasks only.
542 For more details see Documentation/accounting/psi.txt.
546 config PSI_DEFAULT_DISABLED
547 bool "Require boot parameter to enable pressure stall information tracking"
551 If set, pressure stall information tracking will be disabled
552 per default but can be enabled through passing psi=1 on the
553 kernel commandline during boot.
555 This feature adds some code to the task wakeup and sleep
556 paths of the scheduler. The overhead is too low to affect
557 common scheduling-intense workloads in practice (such as
558 webservers, memcache), but it does show up in artificial
559 scheduler stress tests, such as hackbench.
561 If you are paranoid and not sure what the kernel will be
566 endmenu # "CPU/Task time and stats accounting"
570 depends on SMP || COMPILE_TEST
573 Make sure that CPUs running critical tasks are not disturbed by
574 any source of "noise" such as unbound workqueues, timers, kthreads...
575 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
576 the "isolcpus=" boot parameter.
580 source "kernel/rcu/Kconfig"
587 tristate "Kernel .config support"
589 This option enables the complete Linux kernel ".config" file
590 contents to be saved in the kernel. It provides documentation
591 of which kernel options are used in a running kernel or in an
592 on-disk kernel. This information can be extracted from the kernel
593 image file with the script scripts/extract-ikconfig and used as
594 input to rebuild the current kernel or to build another kernel.
595 It can also be extracted from a running kernel by reading
596 /proc/config.gz if enabled (below).
599 bool "Enable access to .config through /proc/config.gz"
600 depends on IKCONFIG && PROC_FS
602 This option enables access to the kernel configuration file
603 through /proc/config.gz.
606 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
609 This option enables access to the in-kernel headers that are generated during
610 the build process. These can be used to build eBPF tracing programs,
611 or similar programs. If you build the headers as a module, a module called
612 kheaders.ko is built which can be loaded on-demand to get access to headers.
615 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
620 Select the minimal kernel log buffer size as a power of 2.
621 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
622 parameter, see below. Any higher size also might be forced
623 by "log_buf_len" boot parameter.
633 config LOG_CPU_MAX_BUF_SHIFT
634 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
637 default 12 if !BASE_SMALL
638 default 0 if BASE_SMALL
641 This option allows to increase the default ring buffer size
642 according to the number of CPUs. The value defines the contribution
643 of each CPU as a power of 2. The used space is typically only few
644 lines however it might be much more when problems are reported,
647 The increased size means that a new buffer has to be allocated and
648 the original static one is unused. It makes sense only on systems
649 with more CPUs. Therefore this value is used only when the sum of
650 contributions is greater than the half of the default kernel ring
651 buffer as defined by LOG_BUF_SHIFT. The default values are set
652 so that more than 64 CPUs are needed to trigger the allocation.
654 Also this option is ignored when "log_buf_len" kernel parameter is
655 used as it forces an exact (power of two) size of the ring buffer.
657 The number of possible CPUs is used for this computation ignoring
658 hotplugging making the computation optimal for the worst case
659 scenario while allowing a simple algorithm to be used from bootup.
661 Examples shift values and their meaning:
662 17 => 128 KB for each CPU
663 16 => 64 KB for each CPU
664 15 => 32 KB for each CPU
665 14 => 16 KB for each CPU
666 13 => 8 KB for each CPU
667 12 => 4 KB for each CPU
669 config PRINTK_SAFE_LOG_BUF_SHIFT
670 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
675 Select the size of an alternate printk per-CPU buffer where messages
676 printed from usafe contexts are temporary stored. One example would
677 be NMI messages, another one - printk recursion. The messages are
678 copied to the main log buffer in a safe context to avoid a deadlock.
679 The value defines the size as a power of 2.
681 Those messages are rare and limited. The largest one is when
682 a backtrace is printed. It usually fits into 4KB. Select
683 8KB if you want to be on the safe side.
686 17 => 128 KB for each CPU
687 16 => 64 KB for each CPU
688 15 => 32 KB for each CPU
689 14 => 16 KB for each CPU
690 13 => 8 KB for each CPU
691 12 => 4 KB for each CPU
694 # Architectures with an unreliable sched_clock() should select this:
696 config HAVE_UNSTABLE_SCHED_CLOCK
699 config GENERIC_SCHED_CLOCK
703 # For architectures that want to enable the support for NUMA-affine scheduler
706 config ARCH_SUPPORTS_NUMA_BALANCING
710 # For architectures that prefer to flush all TLBs after a number of pages
711 # are unmapped instead of sending one IPI per page to flush. The architecture
712 # must provide guarantees on what happens if a clean TLB cache entry is
713 # written after the unmap. Details are in mm/rmap.c near the check for
714 # should_defer_flush. The architecture should also consider if the full flush
715 # and the refill costs are offset by the savings of sending fewer IPIs.
716 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
720 # For architectures that know their GCC __int128 support is sound
722 config ARCH_SUPPORTS_INT128
725 # For architectures that (ab)use NUMA to represent different memory regions
726 # all cpu-local but of different latencies, such as SuperH.
728 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
731 config NUMA_BALANCING
732 bool "Memory placement aware NUMA scheduler"
733 depends on ARCH_SUPPORTS_NUMA_BALANCING
734 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
735 depends on SMP && NUMA && MIGRATION
737 This option adds support for automatic NUMA aware memory/task placement.
738 The mechanism is quite primitive and is based on migrating memory when
739 it has references to the node the task is running on.
741 This system will be inactive on UMA systems.
743 config NUMA_BALANCING_DEFAULT_ENABLED
744 bool "Automatically enable NUMA aware memory/task placement"
746 depends on NUMA_BALANCING
748 If set, automatic NUMA balancing will be enabled if running on a NUMA
752 bool "Control Group support"
755 This option adds support for grouping sets of processes together, for
756 use with process control subsystems such as Cpusets, CFS, memory
757 controls or device isolation.
759 - Documentation/scheduler/sched-design-CFS.txt (CFS)
760 - Documentation/cgroup-v1/ (features for grouping, isolation
761 and resource control)
771 bool "Memory controller"
775 Provides control over the memory footprint of tasks in a cgroup.
778 bool "Swap controller"
779 depends on MEMCG && SWAP
781 Provides control over the swap space consumed by tasks in a cgroup.
783 config MEMCG_SWAP_ENABLED
784 bool "Swap controller enabled by default"
785 depends on MEMCG_SWAP
788 Memory Resource Controller Swap Extension comes with its price in
789 a bigger memory consumption. General purpose distribution kernels
790 which want to enable the feature but keep it disabled by default
791 and let the user enable it by swapaccount=1 boot command line
792 parameter should have this option unselected.
793 For those who want to have the feature enabled by default should
794 select this option (if, for some reason, they need to disable it
795 then swapaccount=0 does the trick).
799 depends on MEMCG && !SLOB
807 Generic block IO controller cgroup interface. This is the common
808 cgroup interface which should be used by various IO controlling
811 Currently, CFQ IO scheduler uses it to recognize task groups and
812 control disk bandwidth allocation (proportional time slice allocation)
813 to such task groups. It is also used by bio throttling logic in
814 block layer to implement upper limit in IO rates on a device.
816 This option only enables generic Block IO controller infrastructure.
817 One needs to also enable actual IO controlling logic/policy. For
818 enabling proportional weight division of disk bandwidth in CFQ, set
819 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
820 CONFIG_BLK_DEV_THROTTLING=y.
822 See Documentation/cgroup-v1/blkio-controller.txt for more information.
824 config DEBUG_BLK_CGROUP
825 bool "IO controller debugging"
826 depends on BLK_CGROUP
829 Enable some debugging help. Currently it exports additional stat
830 files in a cgroup which can be useful for debugging.
832 config CGROUP_WRITEBACK
834 depends on MEMCG && BLK_CGROUP
837 menuconfig CGROUP_SCHED
838 bool "CPU controller"
841 This feature lets CPU scheduler recognize task groups and control CPU
842 bandwidth allocation to such task groups. It uses cgroups to group
846 config FAIR_GROUP_SCHED
847 bool "Group scheduling for SCHED_OTHER"
848 depends on CGROUP_SCHED
852 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
853 depends on FAIR_GROUP_SCHED
856 This option allows users to define CPU bandwidth rates (limits) for
857 tasks running within the fair group scheduler. Groups with no limit
858 set are considered to be unconstrained and will run with no
860 See Documentation/scheduler/sched-bwc.txt for more information.
862 config RT_GROUP_SCHED
863 bool "Group scheduling for SCHED_RR/FIFO"
864 depends on CGROUP_SCHED
867 This feature lets you explicitly allocate real CPU bandwidth
868 to task groups. If enabled, it will also make it impossible to
869 schedule realtime tasks for non-root users until you allocate
870 realtime bandwidth for them.
871 See Documentation/scheduler/sched-rt-group.txt for more information.
876 bool "PIDs controller"
878 Provides enforcement of process number limits in the scope of a
879 cgroup. Any attempt to fork more processes than is allowed in the
880 cgroup will fail. PIDs are fundamentally a global resource because it
881 is fairly trivial to reach PID exhaustion before you reach even a
882 conservative kmemcg limit. As a result, it is possible to grind a
883 system to halt without being limited by other cgroup policies. The
884 PIDs controller is designed to stop this from happening.
886 It should be noted that organisational operations (such as attaching
887 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
888 since the PIDs limit only affects a process's ability to fork, not to
892 bool "RDMA controller"
894 Provides enforcement of RDMA resources defined by IB stack.
895 It is fairly easy for consumers to exhaust RDMA resources, which
896 can result into resource unavailability to other consumers.
897 RDMA controller is designed to stop this from happening.
898 Attaching processes with active RDMA resources to the cgroup
899 hierarchy is allowed even if can cross the hierarchy's limit.
901 config CGROUP_FREEZER
902 bool "Freezer controller"
904 Provides a way to freeze and unfreeze all tasks in a
907 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
908 controller includes important in-kernel memory consumers per default.
910 If you're using cgroup2, say N.
912 config CGROUP_HUGETLB
913 bool "HugeTLB controller"
914 depends on HUGETLB_PAGE
918 Provides a cgroup controller for HugeTLB pages.
919 When you enable this, you can put a per cgroup limit on HugeTLB usage.
920 The limit is enforced during page fault. Since HugeTLB doesn't
921 support page reclaim, enforcing the limit at page fault time implies
922 that, the application will get SIGBUS signal if it tries to access
923 HugeTLB pages beyond its limit. This requires the application to know
924 beforehand how much HugeTLB pages it would require for its use. The
925 control group is tracked in the third page lru pointer. This means
926 that we cannot use the controller with huge page less than 3 pages.
929 bool "Cpuset controller"
932 This option will let you create and manage CPUSETs which
933 allow dynamically partitioning a system into sets of CPUs and
934 Memory Nodes and assigning tasks to run only within those sets.
935 This is primarily useful on large SMP or NUMA systems.
939 config PROC_PID_CPUSET
940 bool "Include legacy /proc/<pid>/cpuset file"
945 bool "Device controller"
947 Provides a cgroup controller implementing whitelists for
948 devices which a process in the cgroup can mknod or open.
950 config CGROUP_CPUACCT
951 bool "Simple CPU accounting controller"
953 Provides a simple controller for monitoring the
954 total CPU consumed by the tasks in a cgroup.
957 bool "Perf controller"
958 depends on PERF_EVENTS
960 This option extends the perf per-cpu mode to restrict monitoring
961 to threads which belong to the cgroup specified and run on the
967 bool "Support for eBPF programs attached to cgroups"
968 depends on BPF_SYSCALL
969 select SOCK_CGROUP_DATA
971 Allow attaching eBPF programs to a cgroup using the bpf(2)
972 syscall command BPF_PROG_ATTACH.
974 In which context these programs are accessed depends on the type
975 of attachment. For instance, programs that are attached using
976 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
980 bool "Debug controller"
982 depends on DEBUG_KERNEL
984 This option enables a simple controller that exports
985 debugging information about the cgroups framework. This
986 controller is for control cgroup debugging only. Its
987 interfaces are not stable.
991 config SOCK_CGROUP_DATA
997 menuconfig NAMESPACES
998 bool "Namespaces support" if EXPERT
1002 Provides the way to make tasks work with different objects using
1003 the same id. For example same IPC id may refer to different objects
1004 or same user id or pid may refer to different tasks when used in
1005 different namespaces.
1010 bool "UTS namespace"
1013 In this namespace tasks see different info provided with the
1017 bool "IPC namespace"
1018 depends on (SYSVIPC || POSIX_MQUEUE)
1021 In this namespace tasks work with IPC ids which correspond to
1022 different IPC objects in different namespaces.
1025 bool "User namespace"
1028 This allows containers, i.e. vservers, to use user namespaces
1029 to provide different user info for different servers.
1031 When user namespaces are enabled in the kernel it is
1032 recommended that the MEMCG option also be enabled and that
1033 user-space use the memory control groups to limit the amount
1034 of memory a memory unprivileged users can use.
1039 bool "PID Namespaces"
1042 Support process id namespaces. This allows having multiple
1043 processes with the same pid as long as they are in different
1044 pid namespaces. This is a building block of containers.
1047 bool "Network namespace"
1051 Allow user space to create what appear to be multiple instances
1052 of the network stack.
1056 config CHECKPOINT_RESTORE
1057 bool "Checkpoint/restore support"
1058 select PROC_CHILDREN
1061 Enables additional kernel features in a sake of checkpoint/restore.
1062 In particular it adds auxiliary prctl codes to setup process text,
1063 data and heap segment sizes, and a few additional /proc filesystem
1066 If unsure, say N here.
1068 config SCHED_AUTOGROUP
1069 bool "Automatic process group scheduling"
1072 select FAIR_GROUP_SCHED
1074 This option optimizes the scheduler for common desktop workloads by
1075 automatically creating and populating task groups. This separation
1076 of workloads isolates aggressive CPU burners (like build jobs) from
1077 desktop applications. Task group autogeneration is currently based
1080 config SYSFS_DEPRECATED
1081 bool "Enable deprecated sysfs features to support old userspace tools"
1085 This option adds code that switches the layout of the "block" class
1086 devices, to not show up in /sys/class/block/, but only in
1089 This switch is only active when the sysfs.deprecated=1 boot option is
1090 passed or the SYSFS_DEPRECATED_V2 option is set.
1092 This option allows new kernels to run on old distributions and tools,
1093 which might get confused by /sys/class/block/. Since 2007/2008 all
1094 major distributions and tools handle this just fine.
1096 Recent distributions and userspace tools after 2009/2010 depend on
1097 the existence of /sys/class/block/, and will not work with this
1100 Only if you are using a new kernel on an old distribution, you might
1103 config SYSFS_DEPRECATED_V2
1104 bool "Enable deprecated sysfs features by default"
1107 depends on SYSFS_DEPRECATED
1109 Enable deprecated sysfs by default.
1111 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1114 Only if you are using a new kernel on an old distribution, you might
1115 need to say Y here. Even then, odds are you would not need it
1116 enabled, you can always pass the boot option if absolutely necessary.
1119 bool "Kernel->user space relay support (formerly relayfs)"
1122 This option enables support for relay interface support in
1123 certain file systems (such as debugfs).
1124 It is designed to provide an efficient mechanism for tools and
1125 facilities to relay large amounts of data from kernel space to
1130 config BLK_DEV_INITRD
1131 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1133 The initial RAM filesystem is a ramfs which is loaded by the
1134 boot loader (loadlin or lilo) and that is mounted as root
1135 before the normal boot procedure. It is typically used to
1136 load modules needed to mount the "real" root file system,
1137 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1139 If RAM disk support (BLK_DEV_RAM) is also included, this
1140 also enables initial RAM disk (initrd) support and adds
1141 15 Kbytes (more on some other architectures) to the kernel size.
1147 source "usr/Kconfig"
1152 prompt "Compiler optimization level"
1153 default CC_OPTIMIZE_FOR_PERFORMANCE
1155 config CC_OPTIMIZE_FOR_PERFORMANCE
1156 bool "Optimize for performance"
1158 This is the default optimization level for the kernel, building
1159 with the "-O2" compiler flag for best performance and most
1160 helpful compile-time warnings.
1162 config CC_OPTIMIZE_FOR_SIZE
1163 bool "Optimize for size"
1164 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives
1166 Enabling this option will pass "-Os" instead of "-O2" to
1167 your compiler resulting in a smaller kernel.
1173 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1176 This requires that the arch annotates or otherwise protects
1177 its external entry points from being discarded. Linker scripts
1178 must also merge .text.*, .data.*, and .bss.* correctly into
1179 output sections. Care must be taken not to pull in unrelated
1180 sections (e.g., '.text.init'). Typically '.' in section names
1181 is used to distinguish them from label names / C identifiers.
1183 config LD_DEAD_CODE_DATA_ELIMINATION
1184 bool "Dead code and data elimination (EXPERIMENTAL)"
1185 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1187 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800)
1188 depends on $(cc-option,-ffunction-sections -fdata-sections)
1189 depends on $(ld-option,--gc-sections)
1191 Enable this if you want to do dead code and data elimination with
1192 the linker by compiling with -ffunction-sections -fdata-sections,
1193 and linking with --gc-sections.
1195 This can reduce on disk and in-memory size of the kernel
1196 code and static data, particularly for small configs and
1197 on small systems. This has the possibility of introducing
1198 silently broken kernel if the required annotations are not
1199 present. This option is not well tested yet, so use at your
1208 config SYSCTL_EXCEPTION_TRACE
1211 Enable support for /proc/sys/debug/exception-trace.
1213 config SYSCTL_ARCH_UNALIGN_NO_WARN
1216 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1217 Allows arch to define/use @no_unaligned_warning to possibly warn
1218 about unaligned access emulation going on under the hood.
1220 config SYSCTL_ARCH_UNALIGN_ALLOW
1223 Enable support for /proc/sys/kernel/unaligned-trap
1224 Allows arches to define/use @unaligned_enabled to runtime toggle
1225 the unaligned access emulation.
1226 see arch/parisc/kernel/unaligned.c for reference
1228 config HAVE_PCSPKR_PLATFORM
1231 # interpreter that classic socket filters depend on
1236 bool "Configure standard kernel features (expert users)"
1237 # Unhide debug options, to make the on-by-default options visible
1240 This option allows certain base kernel options and settings
1241 to be disabled or tweaked. This is for specialized
1242 environments which can tolerate a "non-standard" kernel.
1243 Only use this if you really know what you are doing.
1246 bool "Enable 16-bit UID system calls" if EXPERT
1247 depends on HAVE_UID16 && MULTIUSER
1250 This enables the legacy 16-bit UID syscall wrappers.
1253 bool "Multiple users, groups and capabilities support" if EXPERT
1256 This option enables support for non-root users, groups and
1259 If you say N here, all processes will run with UID 0, GID 0, and all
1260 possible capabilities. Saying N here also compiles out support for
1261 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1264 If unsure, say Y here.
1266 config SGETMASK_SYSCALL
1267 bool "sgetmask/ssetmask syscalls support" if EXPERT
1268 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1270 sys_sgetmask and sys_ssetmask are obsolete system calls
1271 no longer supported in libc but still enabled by default in some
1274 If unsure, leave the default option here.
1276 config SYSFS_SYSCALL
1277 bool "Sysfs syscall support" if EXPERT
1280 sys_sysfs is an obsolete system call no longer supported in libc.
1281 Note that disabling this option is more secure but might break
1282 compatibility with some systems.
1284 If unsure say Y here.
1286 config SYSCTL_SYSCALL
1287 bool "Sysctl syscall support" if EXPERT
1288 depends on PROC_SYSCTL
1292 sys_sysctl uses binary paths that have been found challenging
1293 to properly maintain and use. The interface in /proc/sys
1294 using paths with ascii names is now the primary path to this
1297 Almost nothing using the binary sysctl interface so if you are
1298 trying to save some space it is probably safe to disable this,
1299 making your kernel marginally smaller.
1301 If unsure say N here.
1304 bool "open by fhandle syscalls" if EXPERT
1308 If you say Y here, a user level program will be able to map
1309 file names to handle and then later use the handle for
1310 different file system operations. This is useful in implementing
1311 userspace file servers, which now track files using handles instead
1312 of names. The handle would remain the same even if file names
1313 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1317 bool "Posix Clocks & timers" if EXPERT
1320 This includes native support for POSIX timers to the kernel.
1321 Some embedded systems have no use for them and therefore they
1322 can be configured out to reduce the size of the kernel image.
1324 When this option is disabled, the following syscalls won't be
1325 available: timer_create, timer_gettime: timer_getoverrun,
1326 timer_settime, timer_delete, clock_adjtime, getitimer,
1327 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1328 clock_getres and clock_nanosleep syscalls will be limited to
1329 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1335 bool "Enable support for printk" if EXPERT
1338 This option enables normal printk support. Removing it
1339 eliminates most of the message strings from the kernel image
1340 and makes the kernel more or less silent. As this makes it
1341 very difficult to diagnose system problems, saying N here is
1342 strongly discouraged.
1350 bool "BUG() support" if EXPERT
1353 Disabling this option eliminates support for BUG and WARN, reducing
1354 the size of your kernel image and potentially quietly ignoring
1355 numerous fatal conditions. You should only consider disabling this
1356 option for embedded systems with no facilities for reporting errors.
1362 bool "Enable ELF core dumps" if EXPERT
1364 Enable support for generating core dumps. Disabling saves about 4k.
1367 config PCSPKR_PLATFORM
1368 bool "Enable PC-Speaker support" if EXPERT
1369 depends on HAVE_PCSPKR_PLATFORM
1373 This option allows to disable the internal PC-Speaker
1374 support, saving some memory.
1378 bool "Enable full-sized data structures for core" if EXPERT
1380 Disabling this option reduces the size of miscellaneous core
1381 kernel data structures. This saves memory on small machines,
1382 but may reduce performance.
1385 bool "Enable futex support" if EXPERT
1389 Disabling this option will cause the kernel to be built without
1390 support for "fast userspace mutexes". The resulting kernel may not
1391 run glibc-based applications correctly.
1395 depends on FUTEX && RT_MUTEXES
1398 config HAVE_FUTEX_CMPXCHG
1402 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1403 is implemented and always working. This removes a couple of runtime
1407 bool "Enable eventpoll support" if EXPERT
1410 Disabling this option will cause the kernel to be built without
1411 support for epoll family of system calls.
1414 bool "Enable signalfd() system call" if EXPERT
1417 Enable the signalfd() system call that allows to receive signals
1418 on a file descriptor.
1423 bool "Enable timerfd() system call" if EXPERT
1426 Enable the timerfd() system call that allows to receive timer
1427 events on a file descriptor.
1432 bool "Enable eventfd() system call" if EXPERT
1435 Enable the eventfd() system call that allows to receive both
1436 kernel notification (ie. KAIO) or userspace notifications.
1441 bool "Use full shmem filesystem" if EXPERT
1445 The shmem is an internal filesystem used to manage shared memory.
1446 It is backed by swap and manages resource limits. It is also exported
1447 to userspace as tmpfs if TMPFS is enabled. Disabling this
1448 option replaces shmem and tmpfs with the much simpler ramfs code,
1449 which may be appropriate on small systems without swap.
1452 bool "Enable AIO support" if EXPERT
1455 This option enables POSIX asynchronous I/O which may by used
1456 by some high performance threaded applications. Disabling
1457 this option saves about 7k.
1460 bool "Enable IO uring support" if EXPERT
1464 This option enables support for the io_uring interface, enabling
1465 applications to submit and complete IO through submission and
1466 completion rings that are shared between the kernel and application.
1468 config ADVISE_SYSCALLS
1469 bool "Enable madvise/fadvise syscalls" if EXPERT
1472 This option enables the madvise and fadvise syscalls, used by
1473 applications to advise the kernel about their future memory or file
1474 usage, improving performance. If building an embedded system where no
1475 applications use these syscalls, you can disable this option to save
1479 bool "Enable membarrier() system call" if EXPERT
1482 Enable the membarrier() system call that allows issuing memory
1483 barriers across all running threads, which can be used to distribute
1484 the cost of user-space memory barriers asymmetrically by transforming
1485 pairs of memory barriers into pairs consisting of membarrier() and a
1491 bool "Load all symbols for debugging/ksymoops" if EXPERT
1494 Say Y here to let the kernel print out symbolic crash information and
1495 symbolic stack backtraces. This increases the size of the kernel
1496 somewhat, as all symbols have to be loaded into the kernel image.
1499 bool "Include all symbols in kallsyms"
1500 depends on DEBUG_KERNEL && KALLSYMS
1502 Normally kallsyms only contains the symbols of functions for nicer
1503 OOPS messages and backtraces (i.e., symbols from the text and inittext
1504 sections). This is sufficient for most cases. And only in very rare
1505 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1506 names of variables from the data sections, etc).
1508 This option makes sure that all symbols are loaded into the kernel
1509 image (i.e., symbols from all sections) in cost of increased kernel
1510 size (depending on the kernel configuration, it may be 300KiB or
1511 something like this).
1513 Say N unless you really need all symbols.
1515 config KALLSYMS_ABSOLUTE_PERCPU
1518 default X86_64 && SMP
1520 config KALLSYMS_BASE_RELATIVE
1525 Instead of emitting them as absolute values in the native word size,
1526 emit the symbol references in the kallsyms table as 32-bit entries,
1527 each containing a relative value in the range [base, base + U32_MAX]
1528 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1529 an absolute value in the range [0, S32_MAX] or a relative value in the
1530 range [base, base + S32_MAX], where base is the lowest relative symbol
1531 address encountered in the image.
1533 On 64-bit builds, this reduces the size of the address table by 50%,
1534 but more importantly, it results in entries whose values are build
1535 time constants, and no relocation pass is required at runtime to fix
1536 up the entries based on the runtime load address of the kernel.
1538 # end of the "standard kernel features (expert users)" menu
1540 # syscall, maps, verifier
1542 bool "Enable bpf() system call"
1547 Enable the bpf() system call that allows to manipulate eBPF
1548 programs and maps via file descriptors.
1550 config BPF_JIT_ALWAYS_ON
1551 bool "Permanently enable BPF JIT and remove BPF interpreter"
1552 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1554 Enables BPF JIT and removes BPF interpreter to avoid
1555 speculative execution of BPF instructions by the interpreter
1558 bool "Enable userfaultfd() system call"
1561 Enable the userfaultfd() system call that allows to intercept and
1562 handle page faults in userland.
1564 config ARCH_HAS_MEMBARRIER_CALLBACKS
1567 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1571 bool "Enable rseq() system call" if EXPERT
1573 depends on HAVE_RSEQ
1576 Enable the restartable sequences system call. It provides a
1577 user-space cache for the current CPU number value, which
1578 speeds up getting the current CPU number from user-space,
1579 as well as an ABI to speed up user-space operations on
1586 bool "Enabled debugging of rseq() system call" if EXPERT
1587 depends on RSEQ && DEBUG_KERNEL
1589 Enable extra debugging checks for the rseq system call.
1594 bool "Embedded system"
1595 option allnoconfig_y
1598 This option should be enabled if compiling the kernel for
1599 an embedded system so certain expert options are available
1602 config HAVE_PERF_EVENTS
1605 See tools/perf/design.txt for details.
1607 config PERF_USE_VMALLOC
1610 See tools/perf/design.txt for details
1613 bool "PC/104 support" if EXPERT
1615 Expose PC/104 form factor device drivers and options available for
1616 selection and configuration. Enable this option if your target
1617 machine has a PC/104 bus.
1619 menu "Kernel Performance Events And Counters"
1622 bool "Kernel performance events and counters"
1623 default y if PROFILING
1624 depends on HAVE_PERF_EVENTS
1628 Enable kernel support for various performance events provided
1629 by software and hardware.
1631 Software events are supported either built-in or via the
1632 use of generic tracepoints.
1634 Most modern CPUs support performance events via performance
1635 counter registers. These registers count the number of certain
1636 types of hw events: such as instructions executed, cachemisses
1637 suffered, or branches mis-predicted - without slowing down the
1638 kernel or applications. These registers can also trigger interrupts
1639 when a threshold number of events have passed - and can thus be
1640 used to profile the code that runs on that CPU.
1642 The Linux Performance Event subsystem provides an abstraction of
1643 these software and hardware event capabilities, available via a
1644 system call and used by the "perf" utility in tools/perf/. It
1645 provides per task and per CPU counters, and it provides event
1646 capabilities on top of those.
1650 config DEBUG_PERF_USE_VMALLOC
1652 bool "Debug: use vmalloc to back perf mmap() buffers"
1653 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1654 select PERF_USE_VMALLOC
1656 Use vmalloc memory to back perf mmap() buffers.
1658 Mostly useful for debugging the vmalloc code on platforms
1659 that don't require it.
1665 config VM_EVENT_COUNTERS
1667 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1669 VM event counters are needed for event counts to be shown.
1670 This option allows the disabling of the VM event counters
1671 on EXPERT systems. /proc/vmstat will only show page counts
1672 if VM event counters are disabled.
1676 bool "Enable SLUB debugging support" if EXPERT
1677 depends on SLUB && SYSFS
1679 SLUB has extensive debug support features. Disabling these can
1680 result in significant savings in code size. This also disables
1681 SLUB sysfs support. /sys/slab will not exist and there will be
1682 no support for cache validation etc.
1684 config SLUB_MEMCG_SYSFS_ON
1686 bool "Enable memcg SLUB sysfs support by default" if EXPERT
1687 depends on SLUB && SYSFS && MEMCG
1689 SLUB creates a directory under /sys/kernel/slab for each
1690 allocation cache to host info and debug files. If memory
1691 cgroup is enabled, each cache can have per memory cgroup
1692 caches. SLUB can create the same sysfs directories for these
1693 caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1694 to a very high number of debug files being created. This is
1695 controlled by slub_memcg_sysfs boot parameter and this
1696 config option determines the parameter's default value.
1699 bool "Disable heap randomization"
1702 Randomizing heap placement makes heap exploits harder, but it
1703 also breaks ancient binaries (including anything libc5 based).
1704 This option changes the bootup default to heap randomization
1705 disabled, and can be overridden at runtime by setting
1706 /proc/sys/kernel/randomize_va_space to 2.
1708 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1711 prompt "Choose SLAB allocator"
1714 This option allows to select a slab allocator.
1718 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1720 The regular slab allocator that is established and known to work
1721 well in all environments. It organizes cache hot objects in
1722 per cpu and per node queues.
1725 bool "SLUB (Unqueued Allocator)"
1726 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1728 SLUB is a slab allocator that minimizes cache line usage
1729 instead of managing queues of cached objects (SLAB approach).
1730 Per cpu caching is realized using slabs of objects instead
1731 of queues of objects. SLUB can use memory efficiently
1732 and has enhanced diagnostics. SLUB is the default choice for
1737 bool "SLOB (Simple Allocator)"
1739 SLOB replaces the stock allocator with a drastically simpler
1740 allocator. SLOB is generally more space efficient but
1741 does not perform as well on large systems.
1745 config SLAB_MERGE_DEFAULT
1746 bool "Allow slab caches to be merged"
1749 For reduced kernel memory fragmentation, slab caches can be
1750 merged when they share the same size and other characteristics.
1751 This carries a risk of kernel heap overflows being able to
1752 overwrite objects from merged caches (and more easily control
1753 cache layout), which makes such heap attacks easier to exploit
1754 by attackers. By keeping caches unmerged, these kinds of exploits
1755 can usually only damage objects in the same cache. To disable
1756 merging at runtime, "slab_nomerge" can be passed on the kernel
1759 config SLAB_FREELIST_RANDOM
1761 depends on SLAB || SLUB
1762 bool "SLAB freelist randomization"
1764 Randomizes the freelist order used on creating new pages. This
1765 security feature reduces the predictability of the kernel slab
1766 allocator against heap overflows.
1768 config SLAB_FREELIST_HARDENED
1769 bool "Harden slab freelist metadata"
1772 Many kernel heap attacks try to target slab cache metadata and
1773 other infrastructure. This options makes minor performance
1774 sacrifies to harden the kernel slab allocator against common
1775 freelist exploit methods.
1777 config SHUFFLE_PAGE_ALLOCATOR
1778 bool "Page allocator randomization"
1779 default SLAB_FREELIST_RANDOM && ACPI_NUMA
1781 Randomization of the page allocator improves the average
1782 utilization of a direct-mapped memory-side-cache. See section
1783 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1784 6.2a specification for an example of how a platform advertises
1785 the presence of a memory-side-cache. There are also incidental
1786 security benefits as it reduces the predictability of page
1787 allocations to compliment SLAB_FREELIST_RANDOM, but the
1788 default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1789 10th order of pages is selected based on cache utilization
1792 While the randomization improves cache utilization it may
1793 negatively impact workloads on platforms without a cache. For
1794 this reason, by default, the randomization is enabled only
1795 after runtime detection of a direct-mapped memory-side-cache.
1796 Otherwise, the randomization may be force enabled with the
1797 'page_alloc.shuffle' kernel command line parameter.
1801 config SLUB_CPU_PARTIAL
1803 depends on SLUB && SMP
1804 bool "SLUB per cpu partial cache"
1806 Per cpu partial caches accellerate objects allocation and freeing
1807 that is local to a processor at the price of more indeterminism
1808 in the latency of the free. On overflow these caches will be cleared
1809 which requires the taking of locks that may cause latency spikes.
1810 Typically one would choose no for a realtime system.
1812 config MMAP_ALLOW_UNINITIALIZED
1813 bool "Allow mmapped anonymous memory to be uninitialized"
1814 depends on EXPERT && !MMU
1817 Normally, and according to the Linux spec, anonymous memory obtained
1818 from mmap() has its contents cleared before it is passed to
1819 userspace. Enabling this config option allows you to request that
1820 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1821 providing a huge performance boost. If this option is not enabled,
1822 then the flag will be ignored.
1824 This is taken advantage of by uClibc's malloc(), and also by
1825 ELF-FDPIC binfmt's brk and stack allocator.
1827 Because of the obvious security issues, this option should only be
1828 enabled on embedded devices where you control what is run in
1829 userspace. Since that isn't generally a problem on no-MMU systems,
1830 it is normally safe to say Y here.
1832 See Documentation/nommu-mmap.txt for more information.
1834 config SYSTEM_DATA_VERIFICATION
1836 select SYSTEM_TRUSTED_KEYRING
1840 select ASYMMETRIC_KEY_TYPE
1841 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1844 select X509_CERTIFICATE_PARSER
1845 select PKCS7_MESSAGE_PARSER
1847 Provide PKCS#7 message verification using the contents of the system
1848 trusted keyring to provide public keys. This then can be used for
1849 module verification, kexec image verification and firmware blob
1853 bool "Profiling support"
1855 Say Y here to enable the extended profiling support mechanisms used
1856 by profilers such as OProfile.
1859 # Place an empty function call at each tracepoint site. Can be
1860 # dynamically changed for a probe function.
1865 endmenu # General setup
1867 source "arch/Kconfig"
1874 default 0 if BASE_FULL
1875 default 1 if !BASE_FULL
1878 bool "Enable loadable module support"
1881 Kernel modules are small pieces of compiled code which can
1882 be inserted in the running kernel, rather than being
1883 permanently built into the kernel. You use the "modprobe"
1884 tool to add (and sometimes remove) them. If you say Y here,
1885 many parts of the kernel can be built as modules (by
1886 answering M instead of Y where indicated): this is most
1887 useful for infrequently used options which are not required
1888 for booting. For more information, see the man pages for
1889 modprobe, lsmod, modinfo, insmod and rmmod.
1891 If you say Y here, you will need to run "make
1892 modules_install" to put the modules under /lib/modules/
1893 where modprobe can find them (you may need to be root to do
1900 config MODULE_FORCE_LOAD
1901 bool "Forced module loading"
1904 Allow loading of modules without version information (ie. modprobe
1905 --force). Forced module loading sets the 'F' (forced) taint flag and
1906 is usually a really bad idea.
1908 config MODULE_UNLOAD
1909 bool "Module unloading"
1911 Without this option you will not be able to unload any
1912 modules (note that some modules may not be unloadable
1913 anyway), which makes your kernel smaller, faster
1914 and simpler. If unsure, say Y.
1916 config MODULE_FORCE_UNLOAD
1917 bool "Forced module unloading"
1918 depends on MODULE_UNLOAD
1920 This option allows you to force a module to unload, even if the
1921 kernel believes it is unsafe: the kernel will remove the module
1922 without waiting for anyone to stop using it (using the -f option to
1923 rmmod). This is mainly for kernel developers and desperate users.
1927 bool "Module versioning support"
1929 Usually, you have to use modules compiled with your kernel.
1930 Saying Y here makes it sometimes possible to use modules
1931 compiled for different kernels, by adding enough information
1932 to the modules to (hopefully) spot any changes which would
1933 make them incompatible with the kernel you are running. If
1936 config MODULE_REL_CRCS
1938 depends on MODVERSIONS
1940 config MODULE_SRCVERSION_ALL
1941 bool "Source checksum for all modules"
1943 Modules which contain a MODULE_VERSION get an extra "srcversion"
1944 field inserted into their modinfo section, which contains a
1945 sum of the source files which made it. This helps maintainers
1946 see exactly which source was used to build a module (since
1947 others sometimes change the module source without updating
1948 the version). With this option, such a "srcversion" field
1949 will be created for all modules. If unsure, say N.
1952 bool "Module signature verification"
1954 select SYSTEM_DATA_VERIFICATION
1956 Check modules for valid signatures upon load: the signature
1957 is simply appended to the module. For more information see
1958 <file:Documentation/admin-guide/module-signing.rst>.
1960 Note that this option adds the OpenSSL development packages as a
1961 kernel build dependency so that the signing tool can use its crypto
1964 !!!WARNING!!! If you enable this option, you MUST make sure that the
1965 module DOES NOT get stripped after being signed. This includes the
1966 debuginfo strip done by some packagers (such as rpmbuild) and
1967 inclusion into an initramfs that wants the module size reduced.
1969 config MODULE_SIG_FORCE
1970 bool "Require modules to be validly signed"
1971 depends on MODULE_SIG
1973 Reject unsigned modules or signed modules for which we don't have a
1974 key. Without this, such modules will simply taint the kernel.
1976 config MODULE_SIG_ALL
1977 bool "Automatically sign all modules"
1979 depends on MODULE_SIG
1981 Sign all modules during make modules_install. Without this option,
1982 modules must be signed manually, using the scripts/sign-file tool.
1984 comment "Do not forget to sign required modules with scripts/sign-file"
1985 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1988 prompt "Which hash algorithm should modules be signed with?"
1989 depends on MODULE_SIG
1991 This determines which sort of hashing algorithm will be used during
1992 signature generation. This algorithm _must_ be built into the kernel
1993 directly so that signature verification can take place. It is not
1994 possible to load a signed module containing the algorithm to check
1995 the signature on that module.
1997 config MODULE_SIG_SHA1
1998 bool "Sign modules with SHA-1"
2001 config MODULE_SIG_SHA224
2002 bool "Sign modules with SHA-224"
2003 select CRYPTO_SHA256
2005 config MODULE_SIG_SHA256
2006 bool "Sign modules with SHA-256"
2007 select CRYPTO_SHA256
2009 config MODULE_SIG_SHA384
2010 bool "Sign modules with SHA-384"
2011 select CRYPTO_SHA512
2013 config MODULE_SIG_SHA512
2014 bool "Sign modules with SHA-512"
2015 select CRYPTO_SHA512
2019 config MODULE_SIG_HASH
2021 depends on MODULE_SIG
2022 default "sha1" if MODULE_SIG_SHA1
2023 default "sha224" if MODULE_SIG_SHA224
2024 default "sha256" if MODULE_SIG_SHA256
2025 default "sha384" if MODULE_SIG_SHA384
2026 default "sha512" if MODULE_SIG_SHA512
2028 config MODULE_COMPRESS
2029 bool "Compress modules on installation"
2033 Compresses kernel modules when 'make modules_install' is run; gzip or
2034 xz depending on "Compression algorithm" below.
2036 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2038 Out-of-tree kernel modules installed using Kbuild will also be
2039 compressed upon installation.
2041 Note: for modules inside an initrd or initramfs, it's more efficient
2042 to compress the whole initrd or initramfs instead.
2044 Note: This is fully compatible with signed modules.
2049 prompt "Compression algorithm"
2050 depends on MODULE_COMPRESS
2051 default MODULE_COMPRESS_GZIP
2053 This determines which sort of compression will be used during
2054 'make modules_install'.
2056 GZIP (default) and XZ are supported.
2058 config MODULE_COMPRESS_GZIP
2061 config MODULE_COMPRESS_XZ
2066 config TRIM_UNUSED_KSYMS
2067 bool "Trim unused exported kernel symbols"
2068 depends on MODULES && !UNUSED_SYMBOLS
2070 The kernel and some modules make many symbols available for
2071 other modules to use via EXPORT_SYMBOL() and variants. Depending
2072 on the set of modules being selected in your kernel configuration,
2073 many of those exported symbols might never be used.
2075 This option allows for unused exported symbols to be dropped from
2076 the build. In turn, this provides the compiler more opportunities
2077 (especially when using LTO) for optimizing the code and reducing
2078 binary size. This might have some security advantages as well.
2080 If unsure, or if you need to build out-of-tree modules, say N.
2084 config MODULES_TREE_LOOKUP
2086 depends on PERF_EVENTS || TRACING
2088 config INIT_ALL_POSSIBLE
2091 Back when each arch used to define their own cpu_online_mask and
2092 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2093 with all 1s, and others with all 0s. When they were centralised,
2094 it was better to provide this option than to break all the archs
2095 and have several arch maintainers pursuing me down dark alleys.
2097 source "block/Kconfig"
2099 config PREEMPT_NOTIFIERS
2109 Build a simple ASN.1 grammar compiler that produces a bytecode output
2110 that can be interpreted by the ASN.1 stream decoder and used to
2111 inform it as to what tags are to be expected in a stream and what
2112 functions to call on what tags.
2114 source "kernel/Kconfig.locks"
2116 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2119 # It may be useful for an architecture to override the definitions of the
2120 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2121 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2122 # different calling convention for syscalls. They can also override the
2123 # macros for not-implemented syscalls in kernel/sys_ni.c and
2124 # kernel/time/posix-stubs.c. All these overrides need to be available in
2125 # <asm/syscall_wrapper.h>.
2126 config ARCH_HAS_SYSCALL_WRAPPER
projects / linux.git / blob