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
172 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
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.
583 config IKHEADERS_PROC
584 tristate "Enable kernel header artifacts through /proc/kheaders.tar.xz"
587 This option enables access to the kernel header and other artifacts that
588 are generated during the build process. These can be used to build eBPF
589 tracing programs, or similar programs. If you build the headers as a
590 module, a module called kheaders.ko is built which can be loaded on-demand
591 to get access to the headers.
594 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
599 Select the minimal kernel log buffer size as a power of 2.
600 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
601 parameter, see below. Any higher size also might be forced
602 by "log_buf_len" boot parameter.
612 config LOG_CPU_MAX_BUF_SHIFT
613 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
616 default 12 if !BASE_SMALL
617 default 0 if BASE_SMALL
620 This option allows to increase the default ring buffer size
621 according to the number of CPUs. The value defines the contribution
622 of each CPU as a power of 2. The used space is typically only few
623 lines however it might be much more when problems are reported,
626 The increased size means that a new buffer has to be allocated and
627 the original static one is unused. It makes sense only on systems
628 with more CPUs. Therefore this value is used only when the sum of
629 contributions is greater than the half of the default kernel ring
630 buffer as defined by LOG_BUF_SHIFT. The default values are set
631 so that more than 64 CPUs are needed to trigger the allocation.
633 Also this option is ignored when "log_buf_len" kernel parameter is
634 used as it forces an exact (power of two) size of the ring buffer.
636 The number of possible CPUs is used for this computation ignoring
637 hotplugging making the computation optimal for the worst case
638 scenario while allowing a simple algorithm to be used from bootup.
640 Examples shift values and their meaning:
641 17 => 128 KB for each CPU
642 16 => 64 KB for each CPU
643 15 => 32 KB for each CPU
644 14 => 16 KB for each CPU
645 13 => 8 KB for each CPU
646 12 => 4 KB for each CPU
648 config PRINTK_SAFE_LOG_BUF_SHIFT
649 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
654 Select the size of an alternate printk per-CPU buffer where messages
655 printed from usafe contexts are temporary stored. One example would
656 be NMI messages, another one - printk recursion. The messages are
657 copied to the main log buffer in a safe context to avoid a deadlock.
658 The value defines the size as a power of 2.
660 Those messages are rare and limited. The largest one is when
661 a backtrace is printed. It usually fits into 4KB. Select
662 8KB if you want to be on the safe side.
665 17 => 128 KB for each CPU
666 16 => 64 KB for each CPU
667 15 => 32 KB for each CPU
668 14 => 16 KB for each CPU
669 13 => 8 KB for each CPU
670 12 => 4 KB for each CPU
673 # Architectures with an unreliable sched_clock() should select this:
675 config HAVE_UNSTABLE_SCHED_CLOCK
678 config GENERIC_SCHED_CLOCK
682 # For architectures that want to enable the support for NUMA-affine scheduler
685 config ARCH_SUPPORTS_NUMA_BALANCING
689 # For architectures that prefer to flush all TLBs after a number of pages
690 # are unmapped instead of sending one IPI per page to flush. The architecture
691 # must provide guarantees on what happens if a clean TLB cache entry is
692 # written after the unmap. Details are in mm/rmap.c near the check for
693 # should_defer_flush. The architecture should also consider if the full flush
694 # and the refill costs are offset by the savings of sending fewer IPIs.
695 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
699 # For architectures that know their GCC __int128 support is sound
701 config ARCH_SUPPORTS_INT128
704 # For architectures that (ab)use NUMA to represent different memory regions
705 # all cpu-local but of different latencies, such as SuperH.
707 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
710 config NUMA_BALANCING
711 bool "Memory placement aware NUMA scheduler"
712 depends on ARCH_SUPPORTS_NUMA_BALANCING
713 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
714 depends on SMP && NUMA && MIGRATION
716 This option adds support for automatic NUMA aware memory/task placement.
717 The mechanism is quite primitive and is based on migrating memory when
718 it has references to the node the task is running on.
720 This system will be inactive on UMA systems.
722 config NUMA_BALANCING_DEFAULT_ENABLED
723 bool "Automatically enable NUMA aware memory/task placement"
725 depends on NUMA_BALANCING
727 If set, automatic NUMA balancing will be enabled if running on a NUMA
731 bool "Control Group support"
734 This option adds support for grouping sets of processes together, for
735 use with process control subsystems such as Cpusets, CFS, memory
736 controls or device isolation.
738 - Documentation/scheduler/sched-design-CFS.txt (CFS)
739 - Documentation/cgroup-v1/ (features for grouping, isolation
740 and resource control)
750 bool "Memory controller"
754 Provides control over the memory footprint of tasks in a cgroup.
757 bool "Swap controller"
758 depends on MEMCG && SWAP
760 Provides control over the swap space consumed by tasks in a cgroup.
762 config MEMCG_SWAP_ENABLED
763 bool "Swap controller enabled by default"
764 depends on MEMCG_SWAP
767 Memory Resource Controller Swap Extension comes with its price in
768 a bigger memory consumption. General purpose distribution kernels
769 which want to enable the feature but keep it disabled by default
770 and let the user enable it by swapaccount=1 boot command line
771 parameter should have this option unselected.
772 For those who want to have the feature enabled by default should
773 select this option (if, for some reason, they need to disable it
774 then swapaccount=0 does the trick).
778 depends on MEMCG && !SLOB
786 Generic block IO controller cgroup interface. This is the common
787 cgroup interface which should be used by various IO controlling
790 Currently, CFQ IO scheduler uses it to recognize task groups and
791 control disk bandwidth allocation (proportional time slice allocation)
792 to such task groups. It is also used by bio throttling logic in
793 block layer to implement upper limit in IO rates on a device.
795 This option only enables generic Block IO controller infrastructure.
796 One needs to also enable actual IO controlling logic/policy. For
797 enabling proportional weight division of disk bandwidth in CFQ, set
798 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
799 CONFIG_BLK_DEV_THROTTLING=y.
801 See Documentation/cgroup-v1/blkio-controller.txt for more information.
803 config DEBUG_BLK_CGROUP
804 bool "IO controller debugging"
805 depends on BLK_CGROUP
808 Enable some debugging help. Currently it exports additional stat
809 files in a cgroup which can be useful for debugging.
811 config CGROUP_WRITEBACK
813 depends on MEMCG && BLK_CGROUP
816 menuconfig CGROUP_SCHED
817 bool "CPU controller"
820 This feature lets CPU scheduler recognize task groups and control CPU
821 bandwidth allocation to such task groups. It uses cgroups to group
825 config FAIR_GROUP_SCHED
826 bool "Group scheduling for SCHED_OTHER"
827 depends on CGROUP_SCHED
831 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
832 depends on FAIR_GROUP_SCHED
835 This option allows users to define CPU bandwidth rates (limits) for
836 tasks running within the fair group scheduler. Groups with no limit
837 set are considered to be unconstrained and will run with no
839 See Documentation/scheduler/sched-bwc.txt for more information.
841 config RT_GROUP_SCHED
842 bool "Group scheduling for SCHED_RR/FIFO"
843 depends on CGROUP_SCHED
846 This feature lets you explicitly allocate real CPU bandwidth
847 to task groups. If enabled, it will also make it impossible to
848 schedule realtime tasks for non-root users until you allocate
849 realtime bandwidth for them.
850 See Documentation/scheduler/sched-rt-group.txt for more information.
855 bool "PIDs controller"
857 Provides enforcement of process number limits in the scope of a
858 cgroup. Any attempt to fork more processes than is allowed in the
859 cgroup will fail. PIDs are fundamentally a global resource because it
860 is fairly trivial to reach PID exhaustion before you reach even a
861 conservative kmemcg limit. As a result, it is possible to grind a
862 system to halt without being limited by other cgroup policies. The
863 PIDs controller is designed to stop this from happening.
865 It should be noted that organisational operations (such as attaching
866 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
867 since the PIDs limit only affects a process's ability to fork, not to
871 bool "RDMA controller"
873 Provides enforcement of RDMA resources defined by IB stack.
874 It is fairly easy for consumers to exhaust RDMA resources, which
875 can result into resource unavailability to other consumers.
876 RDMA controller is designed to stop this from happening.
877 Attaching processes with active RDMA resources to the cgroup
878 hierarchy is allowed even if can cross the hierarchy's limit.
880 config CGROUP_FREEZER
881 bool "Freezer controller"
883 Provides a way to freeze and unfreeze all tasks in a
886 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
887 controller includes important in-kernel memory consumers per default.
889 If you're using cgroup2, say N.
891 config CGROUP_HUGETLB
892 bool "HugeTLB controller"
893 depends on HUGETLB_PAGE
897 Provides a cgroup controller for HugeTLB pages.
898 When you enable this, you can put a per cgroup limit on HugeTLB usage.
899 The limit is enforced during page fault. Since HugeTLB doesn't
900 support page reclaim, enforcing the limit at page fault time implies
901 that, the application will get SIGBUS signal if it tries to access
902 HugeTLB pages beyond its limit. This requires the application to know
903 beforehand how much HugeTLB pages it would require for its use. The
904 control group is tracked in the third page lru pointer. This means
905 that we cannot use the controller with huge page less than 3 pages.
908 bool "Cpuset controller"
911 This option will let you create and manage CPUSETs which
912 allow dynamically partitioning a system into sets of CPUs and
913 Memory Nodes and assigning tasks to run only within those sets.
914 This is primarily useful on large SMP or NUMA systems.
918 config PROC_PID_CPUSET
919 bool "Include legacy /proc/<pid>/cpuset file"
924 bool "Device controller"
926 Provides a cgroup controller implementing whitelists for
927 devices which a process in the cgroup can mknod or open.
929 config CGROUP_CPUACCT
930 bool "Simple CPU accounting controller"
932 Provides a simple controller for monitoring the
933 total CPU consumed by the tasks in a cgroup.
936 bool "Perf controller"
937 depends on PERF_EVENTS
939 This option extends the perf per-cpu mode to restrict monitoring
940 to threads which belong to the cgroup specified and run on the
946 bool "Support for eBPF programs attached to cgroups"
947 depends on BPF_SYSCALL
948 select SOCK_CGROUP_DATA
950 Allow attaching eBPF programs to a cgroup using the bpf(2)
951 syscall command BPF_PROG_ATTACH.
953 In which context these programs are accessed depends on the type
954 of attachment. For instance, programs that are attached using
955 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
959 bool "Debug controller"
961 depends on DEBUG_KERNEL
963 This option enables a simple controller that exports
964 debugging information about the cgroups framework. This
965 controller is for control cgroup debugging only. Its
966 interfaces are not stable.
970 config SOCK_CGROUP_DATA
976 menuconfig NAMESPACES
977 bool "Namespaces support" if EXPERT
981 Provides the way to make tasks work with different objects using
982 the same id. For example same IPC id may refer to different objects
983 or same user id or pid may refer to different tasks when used in
984 different namespaces.
992 In this namespace tasks see different info provided with the
997 depends on (SYSVIPC || POSIX_MQUEUE)
1000 In this namespace tasks work with IPC ids which correspond to
1001 different IPC objects in different namespaces.
1004 bool "User namespace"
1007 This allows containers, i.e. vservers, to use user namespaces
1008 to provide different user info for different servers.
1010 When user namespaces are enabled in the kernel it is
1011 recommended that the MEMCG option also be enabled and that
1012 user-space use the memory control groups to limit the amount
1013 of memory a memory unprivileged users can use.
1018 bool "PID Namespaces"
1021 Support process id namespaces. This allows having multiple
1022 processes with the same pid as long as they are in different
1023 pid namespaces. This is a building block of containers.
1026 bool "Network namespace"
1030 Allow user space to create what appear to be multiple instances
1031 of the network stack.
1035 config CHECKPOINT_RESTORE
1036 bool "Checkpoint/restore support"
1037 select PROC_CHILDREN
1040 Enables additional kernel features in a sake of checkpoint/restore.
1041 In particular it adds auxiliary prctl codes to setup process text,
1042 data and heap segment sizes, and a few additional /proc filesystem
1045 If unsure, say N here.
1047 config SCHED_AUTOGROUP
1048 bool "Automatic process group scheduling"
1051 select FAIR_GROUP_SCHED
1053 This option optimizes the scheduler for common desktop workloads by
1054 automatically creating and populating task groups. This separation
1055 of workloads isolates aggressive CPU burners (like build jobs) from
1056 desktop applications. Task group autogeneration is currently based
1059 config SYSFS_DEPRECATED
1060 bool "Enable deprecated sysfs features to support old userspace tools"
1064 This option adds code that switches the layout of the "block" class
1065 devices, to not show up in /sys/class/block/, but only in
1068 This switch is only active when the sysfs.deprecated=1 boot option is
1069 passed or the SYSFS_DEPRECATED_V2 option is set.
1071 This option allows new kernels to run on old distributions and tools,
1072 which might get confused by /sys/class/block/. Since 2007/2008 all
1073 major distributions and tools handle this just fine.
1075 Recent distributions and userspace tools after 2009/2010 depend on
1076 the existence of /sys/class/block/, and will not work with this
1079 Only if you are using a new kernel on an old distribution, you might
1082 config SYSFS_DEPRECATED_V2
1083 bool "Enable deprecated sysfs features by default"
1086 depends on SYSFS_DEPRECATED
1088 Enable deprecated sysfs by default.
1090 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1093 Only if you are using a new kernel on an old distribution, you might
1094 need to say Y here. Even then, odds are you would not need it
1095 enabled, you can always pass the boot option if absolutely necessary.
1098 bool "Kernel->user space relay support (formerly relayfs)"
1101 This option enables support for relay interface support in
1102 certain file systems (such as debugfs).
1103 It is designed to provide an efficient mechanism for tools and
1104 facilities to relay large amounts of data from kernel space to
1109 config BLK_DEV_INITRD
1110 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1112 The initial RAM filesystem is a ramfs which is loaded by the
1113 boot loader (loadlin or lilo) and that is mounted as root
1114 before the normal boot procedure. It is typically used to
1115 load modules needed to mount the "real" root file system,
1116 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1118 If RAM disk support (BLK_DEV_RAM) is also included, this
1119 also enables initial RAM disk (initrd) support and adds
1120 15 Kbytes (more on some other architectures) to the kernel size.
1126 source "usr/Kconfig"
1131 prompt "Compiler optimization level"
1132 default CC_OPTIMIZE_FOR_PERFORMANCE
1134 config CC_OPTIMIZE_FOR_PERFORMANCE
1135 bool "Optimize for performance"
1137 This is the default optimization level for the kernel, building
1138 with the "-O2" compiler flag for best performance and most
1139 helpful compile-time warnings.
1141 config CC_OPTIMIZE_FOR_SIZE
1142 bool "Optimize for size"
1143 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives
1145 Enabling this option will pass "-Os" instead of "-O2" to
1146 your compiler resulting in a smaller kernel.
1152 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1155 This requires that the arch annotates or otherwise protects
1156 its external entry points from being discarded. Linker scripts
1157 must also merge .text.*, .data.*, and .bss.* correctly into
1158 output sections. Care must be taken not to pull in unrelated
1159 sections (e.g., '.text.init'). Typically '.' in section names
1160 is used to distinguish them from label names / C identifiers.
1162 config LD_DEAD_CODE_DATA_ELIMINATION
1163 bool "Dead code and data elimination (EXPERIMENTAL)"
1164 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1166 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800)
1167 depends on $(cc-option,-ffunction-sections -fdata-sections)
1168 depends on $(ld-option,--gc-sections)
1170 Enable this if you want to do dead code and data elimination with
1171 the linker by compiling with -ffunction-sections -fdata-sections,
1172 and linking with --gc-sections.
1174 This can reduce on disk and in-memory size of the kernel
1175 code and static data, particularly for small configs and
1176 on small systems. This has the possibility of introducing
1177 silently broken kernel if the required annotations are not
1178 present. This option is not well tested yet, so use at your
1187 config SYSCTL_EXCEPTION_TRACE
1190 Enable support for /proc/sys/debug/exception-trace.
1192 config SYSCTL_ARCH_UNALIGN_NO_WARN
1195 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1196 Allows arch to define/use @no_unaligned_warning to possibly warn
1197 about unaligned access emulation going on under the hood.
1199 config SYSCTL_ARCH_UNALIGN_ALLOW
1202 Enable support for /proc/sys/kernel/unaligned-trap
1203 Allows arches to define/use @unaligned_enabled to runtime toggle
1204 the unaligned access emulation.
1205 see arch/parisc/kernel/unaligned.c for reference
1207 config HAVE_PCSPKR_PLATFORM
1210 # interpreter that classic socket filters depend on
1215 bool "Configure standard kernel features (expert users)"
1216 # Unhide debug options, to make the on-by-default options visible
1219 This option allows certain base kernel options and settings
1220 to be disabled or tweaked. This is for specialized
1221 environments which can tolerate a "non-standard" kernel.
1222 Only use this if you really know what you are doing.
1225 bool "Enable 16-bit UID system calls" if EXPERT
1226 depends on HAVE_UID16 && MULTIUSER
1229 This enables the legacy 16-bit UID syscall wrappers.
1232 bool "Multiple users, groups and capabilities support" if EXPERT
1235 This option enables support for non-root users, groups and
1238 If you say N here, all processes will run with UID 0, GID 0, and all
1239 possible capabilities. Saying N here also compiles out support for
1240 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1243 If unsure, say Y here.
1245 config SGETMASK_SYSCALL
1246 bool "sgetmask/ssetmask syscalls support" if EXPERT
1247 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1249 sys_sgetmask and sys_ssetmask are obsolete system calls
1250 no longer supported in libc but still enabled by default in some
1253 If unsure, leave the default option here.
1255 config SYSFS_SYSCALL
1256 bool "Sysfs syscall support" if EXPERT
1259 sys_sysfs is an obsolete system call no longer supported in libc.
1260 Note that disabling this option is more secure but might break
1261 compatibility with some systems.
1263 If unsure say Y here.
1265 config SYSCTL_SYSCALL
1266 bool "Sysctl syscall support" if EXPERT
1267 depends on PROC_SYSCTL
1271 sys_sysctl uses binary paths that have been found challenging
1272 to properly maintain and use. The interface in /proc/sys
1273 using paths with ascii names is now the primary path to this
1276 Almost nothing using the binary sysctl interface so if you are
1277 trying to save some space it is probably safe to disable this,
1278 making your kernel marginally smaller.
1280 If unsure say N here.
1283 bool "open by fhandle syscalls" if EXPERT
1287 If you say Y here, a user level program will be able to map
1288 file names to handle and then later use the handle for
1289 different file system operations. This is useful in implementing
1290 userspace file servers, which now track files using handles instead
1291 of names. The handle would remain the same even if file names
1292 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1296 bool "Posix Clocks & timers" if EXPERT
1299 This includes native support for POSIX timers to the kernel.
1300 Some embedded systems have no use for them and therefore they
1301 can be configured out to reduce the size of the kernel image.
1303 When this option is disabled, the following syscalls won't be
1304 available: timer_create, timer_gettime: timer_getoverrun,
1305 timer_settime, timer_delete, clock_adjtime, getitimer,
1306 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1307 clock_getres and clock_nanosleep syscalls will be limited to
1308 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1314 bool "Enable support for printk" if EXPERT
1317 This option enables normal printk support. Removing it
1318 eliminates most of the message strings from the kernel image
1319 and makes the kernel more or less silent. As this makes it
1320 very difficult to diagnose system problems, saying N here is
1321 strongly discouraged.
1329 bool "BUG() support" if EXPERT
1332 Disabling this option eliminates support for BUG and WARN, reducing
1333 the size of your kernel image and potentially quietly ignoring
1334 numerous fatal conditions. You should only consider disabling this
1335 option for embedded systems with no facilities for reporting errors.
1341 bool "Enable ELF core dumps" if EXPERT
1343 Enable support for generating core dumps. Disabling saves about 4k.
1346 config PCSPKR_PLATFORM
1347 bool "Enable PC-Speaker support" if EXPERT
1348 depends on HAVE_PCSPKR_PLATFORM
1352 This option allows to disable the internal PC-Speaker
1353 support, saving some memory.
1357 bool "Enable full-sized data structures for core" if EXPERT
1359 Disabling this option reduces the size of miscellaneous core
1360 kernel data structures. This saves memory on small machines,
1361 but may reduce performance.
1364 bool "Enable futex support" if EXPERT
1368 Disabling this option will cause the kernel to be built without
1369 support for "fast userspace mutexes". The resulting kernel may not
1370 run glibc-based applications correctly.
1374 depends on FUTEX && RT_MUTEXES
1377 config HAVE_FUTEX_CMPXCHG
1381 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1382 is implemented and always working. This removes a couple of runtime
1386 bool "Enable eventpoll support" if EXPERT
1389 Disabling this option will cause the kernel to be built without
1390 support for epoll family of system calls.
1393 bool "Enable signalfd() system call" if EXPERT
1396 Enable the signalfd() system call that allows to receive signals
1397 on a file descriptor.
1402 bool "Enable timerfd() system call" if EXPERT
1405 Enable the timerfd() system call that allows to receive timer
1406 events on a file descriptor.
1411 bool "Enable eventfd() system call" if EXPERT
1414 Enable the eventfd() system call that allows to receive both
1415 kernel notification (ie. KAIO) or userspace notifications.
1420 bool "Use full shmem filesystem" if EXPERT
1424 The shmem is an internal filesystem used to manage shared memory.
1425 It is backed by swap and manages resource limits. It is also exported
1426 to userspace as tmpfs if TMPFS is enabled. Disabling this
1427 option replaces shmem and tmpfs with the much simpler ramfs code,
1428 which may be appropriate on small systems without swap.
1431 bool "Enable AIO support" if EXPERT
1434 This option enables POSIX asynchronous I/O which may by used
1435 by some high performance threaded applications. Disabling
1436 this option saves about 7k.
1439 bool "Enable IO uring support" if EXPERT
1443 This option enables support for the io_uring interface, enabling
1444 applications to submit and complete IO through submission and
1445 completion rings that are shared between the kernel and application.
1447 config ADVISE_SYSCALLS
1448 bool "Enable madvise/fadvise syscalls" if EXPERT
1451 This option enables the madvise and fadvise syscalls, used by
1452 applications to advise the kernel about their future memory or file
1453 usage, improving performance. If building an embedded system where no
1454 applications use these syscalls, you can disable this option to save
1458 bool "Enable membarrier() system call" if EXPERT
1461 Enable the membarrier() system call that allows issuing memory
1462 barriers across all running threads, which can be used to distribute
1463 the cost of user-space memory barriers asymmetrically by transforming
1464 pairs of memory barriers into pairs consisting of membarrier() and a
1470 bool "Load all symbols for debugging/ksymoops" if EXPERT
1473 Say Y here to let the kernel print out symbolic crash information and
1474 symbolic stack backtraces. This increases the size of the kernel
1475 somewhat, as all symbols have to be loaded into the kernel image.
1478 bool "Include all symbols in kallsyms"
1479 depends on DEBUG_KERNEL && KALLSYMS
1481 Normally kallsyms only contains the symbols of functions for nicer
1482 OOPS messages and backtraces (i.e., symbols from the text and inittext
1483 sections). This is sufficient for most cases. And only in very rare
1484 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1485 names of variables from the data sections, etc).
1487 This option makes sure that all symbols are loaded into the kernel
1488 image (i.e., symbols from all sections) in cost of increased kernel
1489 size (depending on the kernel configuration, it may be 300KiB or
1490 something like this).
1492 Say N unless you really need all symbols.
1494 config KALLSYMS_ABSOLUTE_PERCPU
1497 default X86_64 && SMP
1499 config KALLSYMS_BASE_RELATIVE
1504 Instead of emitting them as absolute values in the native word size,
1505 emit the symbol references in the kallsyms table as 32-bit entries,
1506 each containing a relative value in the range [base, base + U32_MAX]
1507 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1508 an absolute value in the range [0, S32_MAX] or a relative value in the
1509 range [base, base + S32_MAX], where base is the lowest relative symbol
1510 address encountered in the image.
1512 On 64-bit builds, this reduces the size of the address table by 50%,
1513 but more importantly, it results in entries whose values are build
1514 time constants, and no relocation pass is required at runtime to fix
1515 up the entries based on the runtime load address of the kernel.
1517 # end of the "standard kernel features (expert users)" menu
1519 # syscall, maps, verifier
1521 bool "Enable bpf() system call"
1526 Enable the bpf() system call that allows to manipulate eBPF
1527 programs and maps via file descriptors.
1529 config BPF_JIT_ALWAYS_ON
1530 bool "Permanently enable BPF JIT and remove BPF interpreter"
1531 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1533 Enables BPF JIT and removes BPF interpreter to avoid
1534 speculative execution of BPF instructions by the interpreter
1537 bool "Enable userfaultfd() system call"
1540 Enable the userfaultfd() system call that allows to intercept and
1541 handle page faults in userland.
1543 config ARCH_HAS_MEMBARRIER_CALLBACKS
1546 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1550 bool "Enable rseq() system call" if EXPERT
1552 depends on HAVE_RSEQ
1555 Enable the restartable sequences system call. It provides a
1556 user-space cache for the current CPU number value, which
1557 speeds up getting the current CPU number from user-space,
1558 as well as an ABI to speed up user-space operations on
1565 bool "Enabled debugging of rseq() system call" if EXPERT
1566 depends on RSEQ && DEBUG_KERNEL
1568 Enable extra debugging checks for the rseq system call.
1573 bool "Embedded system"
1574 option allnoconfig_y
1577 This option should be enabled if compiling the kernel for
1578 an embedded system so certain expert options are available
1581 config HAVE_PERF_EVENTS
1584 See tools/perf/design.txt for details.
1586 config PERF_USE_VMALLOC
1589 See tools/perf/design.txt for details
1592 bool "PC/104 support" if EXPERT
1594 Expose PC/104 form factor device drivers and options available for
1595 selection and configuration. Enable this option if your target
1596 machine has a PC/104 bus.
1598 menu "Kernel Performance Events And Counters"
1601 bool "Kernel performance events and counters"
1602 default y if PROFILING
1603 depends on HAVE_PERF_EVENTS
1607 Enable kernel support for various performance events provided
1608 by software and hardware.
1610 Software events are supported either built-in or via the
1611 use of generic tracepoints.
1613 Most modern CPUs support performance events via performance
1614 counter registers. These registers count the number of certain
1615 types of hw events: such as instructions executed, cachemisses
1616 suffered, or branches mis-predicted - without slowing down the
1617 kernel or applications. These registers can also trigger interrupts
1618 when a threshold number of events have passed - and can thus be
1619 used to profile the code that runs on that CPU.
1621 The Linux Performance Event subsystem provides an abstraction of
1622 these software and hardware event capabilities, available via a
1623 system call and used by the "perf" utility in tools/perf/. It
1624 provides per task and per CPU counters, and it provides event
1625 capabilities on top of those.
1629 config DEBUG_PERF_USE_VMALLOC
1631 bool "Debug: use vmalloc to back perf mmap() buffers"
1632 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1633 select PERF_USE_VMALLOC
1635 Use vmalloc memory to back perf mmap() buffers.
1637 Mostly useful for debugging the vmalloc code on platforms
1638 that don't require it.
1644 config VM_EVENT_COUNTERS
1646 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1648 VM event counters are needed for event counts to be shown.
1649 This option allows the disabling of the VM event counters
1650 on EXPERT systems. /proc/vmstat will only show page counts
1651 if VM event counters are disabled.
1655 bool "Enable SLUB debugging support" if EXPERT
1656 depends on SLUB && SYSFS
1658 SLUB has extensive debug support features. Disabling these can
1659 result in significant savings in code size. This also disables
1660 SLUB sysfs support. /sys/slab will not exist and there will be
1661 no support for cache validation etc.
1663 config SLUB_MEMCG_SYSFS_ON
1665 bool "Enable memcg SLUB sysfs support by default" if EXPERT
1666 depends on SLUB && SYSFS && MEMCG
1668 SLUB creates a directory under /sys/kernel/slab for each
1669 allocation cache to host info and debug files. If memory
1670 cgroup is enabled, each cache can have per memory cgroup
1671 caches. SLUB can create the same sysfs directories for these
1672 caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1673 to a very high number of debug files being created. This is
1674 controlled by slub_memcg_sysfs boot parameter and this
1675 config option determines the parameter's default value.
1678 bool "Disable heap randomization"
1681 Randomizing heap placement makes heap exploits harder, but it
1682 also breaks ancient binaries (including anything libc5 based).
1683 This option changes the bootup default to heap randomization
1684 disabled, and can be overridden at runtime by setting
1685 /proc/sys/kernel/randomize_va_space to 2.
1687 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1690 prompt "Choose SLAB allocator"
1693 This option allows to select a slab allocator.
1697 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1699 The regular slab allocator that is established and known to work
1700 well in all environments. It organizes cache hot objects in
1701 per cpu and per node queues.
1704 bool "SLUB (Unqueued Allocator)"
1705 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1707 SLUB is a slab allocator that minimizes cache line usage
1708 instead of managing queues of cached objects (SLAB approach).
1709 Per cpu caching is realized using slabs of objects instead
1710 of queues of objects. SLUB can use memory efficiently
1711 and has enhanced diagnostics. SLUB is the default choice for
1716 bool "SLOB (Simple Allocator)"
1718 SLOB replaces the stock allocator with a drastically simpler
1719 allocator. SLOB is generally more space efficient but
1720 does not perform as well on large systems.
1724 config SLAB_MERGE_DEFAULT
1725 bool "Allow slab caches to be merged"
1728 For reduced kernel memory fragmentation, slab caches can be
1729 merged when they share the same size and other characteristics.
1730 This carries a risk of kernel heap overflows being able to
1731 overwrite objects from merged caches (and more easily control
1732 cache layout), which makes such heap attacks easier to exploit
1733 by attackers. By keeping caches unmerged, these kinds of exploits
1734 can usually only damage objects in the same cache. To disable
1735 merging at runtime, "slab_nomerge" can be passed on the kernel
1738 config SLAB_FREELIST_RANDOM
1740 depends on SLAB || SLUB
1741 bool "SLAB freelist randomization"
1743 Randomizes the freelist order used on creating new pages. This
1744 security feature reduces the predictability of the kernel slab
1745 allocator against heap overflows.
1747 config SLAB_FREELIST_HARDENED
1748 bool "Harden slab freelist metadata"
1751 Many kernel heap attacks try to target slab cache metadata and
1752 other infrastructure. This options makes minor performance
1753 sacrifies to harden the kernel slab allocator against common
1754 freelist exploit methods.
1756 config SHUFFLE_PAGE_ALLOCATOR
1757 bool "Page allocator randomization"
1758 default SLAB_FREELIST_RANDOM && ACPI_NUMA
1760 Randomization of the page allocator improves the average
1761 utilization of a direct-mapped memory-side-cache. See section
1762 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1763 6.2a specification for an example of how a platform advertises
1764 the presence of a memory-side-cache. There are also incidental
1765 security benefits as it reduces the predictability of page
1766 allocations to compliment SLAB_FREELIST_RANDOM, but the
1767 default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1768 10th order of pages is selected based on cache utilization
1771 While the randomization improves cache utilization it may
1772 negatively impact workloads on platforms without a cache. For
1773 this reason, by default, the randomization is enabled only
1774 after runtime detection of a direct-mapped memory-side-cache.
1775 Otherwise, the randomization may be force enabled with the
1776 'page_alloc.shuffle' kernel command line parameter.
1780 config SLUB_CPU_PARTIAL
1782 depends on SLUB && SMP
1783 bool "SLUB per cpu partial cache"
1785 Per cpu partial caches accellerate objects allocation and freeing
1786 that is local to a processor at the price of more indeterminism
1787 in the latency of the free. On overflow these caches will be cleared
1788 which requires the taking of locks that may cause latency spikes.
1789 Typically one would choose no for a realtime system.
1791 config MMAP_ALLOW_UNINITIALIZED
1792 bool "Allow mmapped anonymous memory to be uninitialized"
1793 depends on EXPERT && !MMU
1796 Normally, and according to the Linux spec, anonymous memory obtained
1797 from mmap() has its contents cleared before it is passed to
1798 userspace. Enabling this config option allows you to request that
1799 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1800 providing a huge performance boost. If this option is not enabled,
1801 then the flag will be ignored.
1803 This is taken advantage of by uClibc's malloc(), and also by
1804 ELF-FDPIC binfmt's brk and stack allocator.
1806 Because of the obvious security issues, this option should only be
1807 enabled on embedded devices where you control what is run in
1808 userspace. Since that isn't generally a problem on no-MMU systems,
1809 it is normally safe to say Y here.
1811 See Documentation/nommu-mmap.txt for more information.
1813 config SYSTEM_DATA_VERIFICATION
1815 select SYSTEM_TRUSTED_KEYRING
1819 select ASYMMETRIC_KEY_TYPE
1820 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1823 select X509_CERTIFICATE_PARSER
1824 select PKCS7_MESSAGE_PARSER
1826 Provide PKCS#7 message verification using the contents of the system
1827 trusted keyring to provide public keys. This then can be used for
1828 module verification, kexec image verification and firmware blob
1832 bool "Profiling support"
1834 Say Y here to enable the extended profiling support mechanisms used
1835 by profilers such as OProfile.
1838 # Place an empty function call at each tracepoint site. Can be
1839 # dynamically changed for a probe function.
1844 endmenu # General setup
1846 source "arch/Kconfig"
1853 default 0 if BASE_FULL
1854 default 1 if !BASE_FULL
1857 bool "Enable loadable module support"
1860 Kernel modules are small pieces of compiled code which can
1861 be inserted in the running kernel, rather than being
1862 permanently built into the kernel. You use the "modprobe"
1863 tool to add (and sometimes remove) them. If you say Y here,
1864 many parts of the kernel can be built as modules (by
1865 answering M instead of Y where indicated): this is most
1866 useful for infrequently used options which are not required
1867 for booting. For more information, see the man pages for
1868 modprobe, lsmod, modinfo, insmod and rmmod.
1870 If you say Y here, you will need to run "make
1871 modules_install" to put the modules under /lib/modules/
1872 where modprobe can find them (you may need to be root to do
1879 config MODULE_FORCE_LOAD
1880 bool "Forced module loading"
1883 Allow loading of modules without version information (ie. modprobe
1884 --force). Forced module loading sets the 'F' (forced) taint flag and
1885 is usually a really bad idea.
1887 config MODULE_UNLOAD
1888 bool "Module unloading"
1890 Without this option you will not be able to unload any
1891 modules (note that some modules may not be unloadable
1892 anyway), which makes your kernel smaller, faster
1893 and simpler. If unsure, say Y.
1895 config MODULE_FORCE_UNLOAD
1896 bool "Forced module unloading"
1897 depends on MODULE_UNLOAD
1899 This option allows you to force a module to unload, even if the
1900 kernel believes it is unsafe: the kernel will remove the module
1901 without waiting for anyone to stop using it (using the -f option to
1902 rmmod). This is mainly for kernel developers and desperate users.
1906 bool "Module versioning support"
1908 Usually, you have to use modules compiled with your kernel.
1909 Saying Y here makes it sometimes possible to use modules
1910 compiled for different kernels, by adding enough information
1911 to the modules to (hopefully) spot any changes which would
1912 make them incompatible with the kernel you are running. If
1915 config MODULE_REL_CRCS
1917 depends on MODVERSIONS
1919 config MODULE_SRCVERSION_ALL
1920 bool "Source checksum for all modules"
1922 Modules which contain a MODULE_VERSION get an extra "srcversion"
1923 field inserted into their modinfo section, which contains a
1924 sum of the source files which made it. This helps maintainers
1925 see exactly which source was used to build a module (since
1926 others sometimes change the module source without updating
1927 the version). With this option, such a "srcversion" field
1928 will be created for all modules. If unsure, say N.
1931 bool "Module signature verification"
1933 select SYSTEM_DATA_VERIFICATION
1935 Check modules for valid signatures upon load: the signature
1936 is simply appended to the module. For more information see
1937 <file:Documentation/admin-guide/module-signing.rst>.
1939 Note that this option adds the OpenSSL development packages as a
1940 kernel build dependency so that the signing tool can use its crypto
1943 !!!WARNING!!! If you enable this option, you MUST make sure that the
1944 module DOES NOT get stripped after being signed. This includes the
1945 debuginfo strip done by some packagers (such as rpmbuild) and
1946 inclusion into an initramfs that wants the module size reduced.
1948 config MODULE_SIG_FORCE
1949 bool "Require modules to be validly signed"
1950 depends on MODULE_SIG
1952 Reject unsigned modules or signed modules for which we don't have a
1953 key. Without this, such modules will simply taint the kernel.
1955 config MODULE_SIG_ALL
1956 bool "Automatically sign all modules"
1958 depends on MODULE_SIG
1960 Sign all modules during make modules_install. Without this option,
1961 modules must be signed manually, using the scripts/sign-file tool.
1963 comment "Do not forget to sign required modules with scripts/sign-file"
1964 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1967 prompt "Which hash algorithm should modules be signed with?"
1968 depends on MODULE_SIG
1970 This determines which sort of hashing algorithm will be used during
1971 signature generation. This algorithm _must_ be built into the kernel
1972 directly so that signature verification can take place. It is not
1973 possible to load a signed module containing the algorithm to check
1974 the signature on that module.
1976 config MODULE_SIG_SHA1
1977 bool "Sign modules with SHA-1"
1980 config MODULE_SIG_SHA224
1981 bool "Sign modules with SHA-224"
1982 select CRYPTO_SHA256
1984 config MODULE_SIG_SHA256
1985 bool "Sign modules with SHA-256"
1986 select CRYPTO_SHA256
1988 config MODULE_SIG_SHA384
1989 bool "Sign modules with SHA-384"
1990 select CRYPTO_SHA512
1992 config MODULE_SIG_SHA512
1993 bool "Sign modules with SHA-512"
1994 select CRYPTO_SHA512
1998 config MODULE_SIG_HASH
2000 depends on MODULE_SIG
2001 default "sha1" if MODULE_SIG_SHA1
2002 default "sha224" if MODULE_SIG_SHA224
2003 default "sha256" if MODULE_SIG_SHA256
2004 default "sha384" if MODULE_SIG_SHA384
2005 default "sha512" if MODULE_SIG_SHA512
2007 config MODULE_COMPRESS
2008 bool "Compress modules on installation"
2012 Compresses kernel modules when 'make modules_install' is run; gzip or
2013 xz depending on "Compression algorithm" below.
2015 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2017 Out-of-tree kernel modules installed using Kbuild will also be
2018 compressed upon installation.
2020 Note: for modules inside an initrd or initramfs, it's more efficient
2021 to compress the whole initrd or initramfs instead.
2023 Note: This is fully compatible with signed modules.
2028 prompt "Compression algorithm"
2029 depends on MODULE_COMPRESS
2030 default MODULE_COMPRESS_GZIP
2032 This determines which sort of compression will be used during
2033 'make modules_install'.
2035 GZIP (default) and XZ are supported.
2037 config MODULE_COMPRESS_GZIP
2040 config MODULE_COMPRESS_XZ
2045 config TRIM_UNUSED_KSYMS
2046 bool "Trim unused exported kernel symbols"
2047 depends on MODULES && !UNUSED_SYMBOLS
2049 The kernel and some modules make many symbols available for
2050 other modules to use via EXPORT_SYMBOL() and variants. Depending
2051 on the set of modules being selected in your kernel configuration,
2052 many of those exported symbols might never be used.
2054 This option allows for unused exported symbols to be dropped from
2055 the build. In turn, this provides the compiler more opportunities
2056 (especially when using LTO) for optimizing the code and reducing
2057 binary size. This might have some security advantages as well.
2059 If unsure, or if you need to build out-of-tree modules, say N.
2063 config MODULES_TREE_LOOKUP
2065 depends on PERF_EVENTS || TRACING
2067 config INIT_ALL_POSSIBLE
2070 Back when each arch used to define their own cpu_online_mask and
2071 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2072 with all 1s, and others with all 0s. When they were centralised,
2073 it was better to provide this option than to break all the archs
2074 and have several arch maintainers pursuing me down dark alleys.
2076 source "block/Kconfig"
2078 config PREEMPT_NOTIFIERS
2088 Build a simple ASN.1 grammar compiler that produces a bytecode output
2089 that can be interpreted by the ASN.1 stream decoder and used to
2090 inform it as to what tags are to be expected in a stream and what
2091 functions to call on what tags.
2093 source "kernel/Kconfig.locks"
2095 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2098 # It may be useful for an architecture to override the definitions of the
2099 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2100 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2101 # different calling convention for syscalls. They can also override the
2102 # macros for not-implemented syscalls in kernel/sys_ni.c and
2103 # kernel/time/posix-stubs.c. All these overrides need to be available in
2104 # <asm/syscall_wrapper.h>.
2105 config ARCH_HAS_SYSCALL_WRAPPER
projects / mirror_ubuntu-eoan-kernel.git / blob