5 default "/lib/modules/$(shell,uname -r)/.config"
6 default "/etc/kernel-config"
7 default "/boot/config-$(shell,uname -r)"
9 default "arch/$(ARCH)/defconfig"
12 def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc)
16 default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC
20 def_bool $(success,$(CC) --version | head -n 1 | grep -q clang)
24 default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
26 config CC_HAS_ASM_GOTO
27 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
29 config CC_HAS_WARN_MAYBE_UNINITIALIZED
30 def_bool $(cc-option,-Wmaybe-uninitialized)
32 GCC >= 4.7 supports this option.
34 config CC_DISABLE_WARN_MAYBE_UNINITIALIZED
36 depends on CC_HAS_WARN_MAYBE_UNINITIALIZED
37 default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9
39 GCC's -Wmaybe-uninitialized is not reliable by definition.
40 Lots of false positive warnings are produced in some cases.
42 If this option is enabled, -Wno-maybe-uninitialzed is passed
43 to the compiler to suppress maybe-uninitialized warnings.
52 config BUILDTIME_EXTABLE_SORT
55 config THREAD_INFO_IN_TASK
58 Select this to move thread_info off the stack into task_struct. To
59 make this work, an arch will need to remove all thread_info fields
60 except flags and fix any runtime bugs.
62 One subtle change that will be needed is to use try_get_task_stack()
63 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
72 depends on BROKEN || !SMP
75 config INIT_ENV_ARG_LIMIT
80 Maximum of each of the number of arguments and environment
81 variables passed to init from the kernel command line.
84 bool "Compile also drivers which will not load"
88 Some drivers can be compiled on a different platform than they are
89 intended to be run on. Despite they cannot be loaded there (or even
90 when they load they cannot be used due to missing HW support),
91 developers still, opposing to distributors, might want to build such
92 drivers to compile-test them.
94 If you are a developer and want to build everything available, say Y
95 here. If you are a user/distributor, say N here to exclude useless
96 drivers to be distributed.
99 string "Local version - append to kernel release"
101 Append an extra string to the end of your kernel version.
102 This will show up when you type uname, for example.
103 The string you set here will be appended after the contents of
104 any files with a filename matching localversion* in your
105 object and source tree, in that order. Your total string can
106 be a maximum of 64 characters.
108 config LOCALVERSION_AUTO
109 bool "Automatically append version information to the version string"
111 depends on !COMPILE_TEST
113 This will try to automatically determine if the current tree is a
114 release tree by looking for git tags that belong to the current
115 top of tree revision.
117 A string of the format -gxxxxxxxx will be added to the localversion
118 if a git-based tree is found. The string generated by this will be
119 appended after any matching localversion* files, and after the value
120 set in CONFIG_LOCALVERSION.
122 (The actual string used here is the first eight characters produced
123 by running the command:
125 $ git rev-parse --verify HEAD
127 which is done within the script "scripts/setlocalversion".)
130 string "Build ID Salt"
133 The build ID is used to link binaries and their debug info. Setting
134 this option will use the value in the calculation of the build id.
135 This is mostly useful for distributions which want to ensure the
136 build is unique between builds. It's safe to leave the default.
138 config HAVE_KERNEL_GZIP
141 config HAVE_KERNEL_BZIP2
144 config HAVE_KERNEL_LZMA
147 config HAVE_KERNEL_XZ
150 config HAVE_KERNEL_LZO
153 config HAVE_KERNEL_LZ4
156 config HAVE_KERNEL_UNCOMPRESSED
160 prompt "Kernel compression mode"
162 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED
164 The linux kernel is a kind of self-extracting executable.
165 Several compression algorithms are available, which differ
166 in efficiency, compression and decompression speed.
167 Compression speed is only relevant when building a kernel.
168 Decompression speed is relevant at each boot.
170 If you have any problems with bzip2 or lzma compressed
171 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
172 version of this functionality (bzip2 only), for 2.4, was
173 supplied by Christian Ludwig)
175 High compression options are mostly useful for users, who
176 are low on disk space (embedded systems), but for whom ram
179 If in doubt, select 'gzip'
183 depends on HAVE_KERNEL_GZIP
185 The old and tried gzip compression. It provides a good balance
186 between compression ratio and decompression speed.
190 depends on HAVE_KERNEL_BZIP2
192 Its compression ratio and speed is intermediate.
193 Decompression speed is slowest among the choices. The kernel
194 size is about 10% smaller with bzip2, in comparison to gzip.
195 Bzip2 uses a large amount of memory. For modern kernels you
196 will need at least 8MB RAM or more for booting.
200 depends on HAVE_KERNEL_LZMA
202 This compression algorithm's ratio is best. Decompression speed
203 is between gzip and bzip2. Compression is slowest.
204 The kernel size is about 33% smaller with LZMA in comparison to gzip.
208 depends on HAVE_KERNEL_XZ
210 XZ uses the LZMA2 algorithm and instruction set specific
211 BCJ filters which can improve compression ratio of executable
212 code. The size of the kernel is about 30% smaller with XZ in
213 comparison to gzip. On architectures for which there is a BCJ
214 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
215 will create a few percent smaller kernel than plain LZMA.
217 The speed is about the same as with LZMA: The decompression
218 speed of XZ is better than that of bzip2 but worse than gzip
219 and LZO. Compression is slow.
223 depends on HAVE_KERNEL_LZO
225 Its compression ratio is the poorest among the choices. The kernel
226 size is about 10% bigger than gzip; however its speed
227 (both compression and decompression) is the fastest.
231 depends on HAVE_KERNEL_LZ4
233 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
234 A preliminary version of LZ4 de/compression tool is available at
235 <https://code.google.com/p/lz4/>.
237 Its compression ratio is worse than LZO. The size of the kernel
238 is about 8% bigger than LZO. But the decompression speed is
241 config KERNEL_UNCOMPRESSED
243 depends on HAVE_KERNEL_UNCOMPRESSED
245 Produce uncompressed kernel image. This option is usually not what
246 you want. It is useful for debugging the kernel in slow simulation
247 environments, where decompressing and moving the kernel is awfully
248 slow. This option allows early boot code to skip the decompressor
249 and jump right at uncompressed kernel image.
253 config DEFAULT_HOSTNAME
254 string "Default hostname"
257 This option determines the default system hostname before userspace
258 calls sethostname(2). The kernel traditionally uses "(none)" here,
259 but you may wish to use a different default here to make a minimal
260 system more usable with less configuration.
263 # For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
264 # add proper SWAP support to them, in which case this can be remove.
270 bool "Support for paging of anonymous memory (swap)"
271 depends on MMU && BLOCK && !ARCH_NO_SWAP
274 This option allows you to choose whether you want to have support
275 for so called swap devices or swap files in your kernel that are
276 used to provide more virtual memory than the actual RAM present
277 in your computer. If unsure say Y.
282 Inter Process Communication is a suite of library functions and
283 system calls which let processes (running programs) synchronize and
284 exchange information. It is generally considered to be a good thing,
285 and some programs won't run unless you say Y here. In particular, if
286 you want to run the DOS emulator dosemu under Linux (read the
287 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
288 you'll need to say Y here.
290 You can find documentation about IPC with "info ipc" and also in
291 section 6.4 of the Linux Programmer's Guide, available from
292 <http://www.tldp.org/guides.html>.
294 config SYSVIPC_SYSCTL
301 bool "POSIX Message Queues"
304 POSIX variant of message queues is a part of IPC. In POSIX message
305 queues every message has a priority which decides about succession
306 of receiving it by a process. If you want to compile and run
307 programs written e.g. for Solaris with use of its POSIX message
308 queues (functions mq_*) say Y here.
310 POSIX message queues are visible as a filesystem called 'mqueue'
311 and can be mounted somewhere if you want to do filesystem
312 operations on message queues.
316 config POSIX_MQUEUE_SYSCTL
318 depends on POSIX_MQUEUE
322 config CROSS_MEMORY_ATTACH
323 bool "Enable process_vm_readv/writev syscalls"
327 Enabling this option adds the system calls process_vm_readv and
328 process_vm_writev which allow a process with the correct privileges
329 to directly read from or write to another process' address space.
330 See the man page for more details.
333 bool "uselib syscall"
334 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
336 This option enables the uselib syscall, a system call used in the
337 dynamic linker from libc5 and earlier. glibc does not use this
338 system call. If you intend to run programs built on libc5 or
339 earlier, you may need to enable this syscall. Current systems
340 running glibc can safely disable this.
343 bool "Auditing support"
346 Enable auditing infrastructure that can be used with another
347 kernel subsystem, such as SELinux (which requires this for
348 logging of avc messages output). System call auditing is included
349 on architectures which support it.
351 config HAVE_ARCH_AUDITSYSCALL
356 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
359 source "kernel/irq/Kconfig"
360 source "kernel/time/Kconfig"
361 source "kernel/Kconfig.preempt"
363 menu "CPU/Task time and stats accounting"
365 config VIRT_CPU_ACCOUNTING
369 prompt "Cputime accounting"
370 default TICK_CPU_ACCOUNTING if !PPC64
371 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
373 # Kind of a stub config for the pure tick based cputime accounting
374 config TICK_CPU_ACCOUNTING
375 bool "Simple tick based cputime accounting"
376 depends on !S390 && !NO_HZ_FULL
378 This is the basic tick based cputime accounting that maintains
379 statistics about user, system and idle time spent on per jiffies
384 config VIRT_CPU_ACCOUNTING_NATIVE
385 bool "Deterministic task and CPU time accounting"
386 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
387 select VIRT_CPU_ACCOUNTING
389 Select this option to enable more accurate task and CPU time
390 accounting. This is done by reading a CPU counter on each
391 kernel entry and exit and on transitions within the kernel
392 between system, softirq and hardirq state, so there is a
393 small performance impact. In the case of s390 or IBM POWER > 5,
394 this also enables accounting of stolen time on logically-partitioned
397 config VIRT_CPU_ACCOUNTING_GEN
398 bool "Full dynticks CPU time accounting"
399 depends on HAVE_CONTEXT_TRACKING
400 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
401 depends on GENERIC_CLOCKEVENTS
402 select VIRT_CPU_ACCOUNTING
403 select CONTEXT_TRACKING
405 Select this option to enable task and CPU time accounting on full
406 dynticks systems. This accounting is implemented by watching every
407 kernel-user boundaries using the context tracking subsystem.
408 The accounting is thus performed at the expense of some significant
411 For now this is only useful if you are working on the full
412 dynticks subsystem development.
418 config IRQ_TIME_ACCOUNTING
419 bool "Fine granularity task level IRQ time accounting"
420 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
422 Select this option to enable fine granularity task irq time
423 accounting. This is done by reading a timestamp on each
424 transitions between softirq and hardirq state, so there can be a
425 small performance impact.
427 If in doubt, say N here.
429 config HAVE_SCHED_AVG_IRQ
431 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
434 config BSD_PROCESS_ACCT
435 bool "BSD Process Accounting"
438 If you say Y here, a user level program will be able to instruct the
439 kernel (via a special system call) to write process accounting
440 information to a file: whenever a process exits, information about
441 that process will be appended to the file by the kernel. The
442 information includes things such as creation time, owning user,
443 command name, memory usage, controlling terminal etc. (the complete
444 list is in the struct acct in <file:include/linux/acct.h>). It is
445 up to the user level program to do useful things with this
446 information. This is generally a good idea, so say Y.
448 config BSD_PROCESS_ACCT_V3
449 bool "BSD Process Accounting version 3 file format"
450 depends on BSD_PROCESS_ACCT
453 If you say Y here, the process accounting information is written
454 in a new file format that also logs the process IDs of each
455 process and its parent. Note that this file format is incompatible
456 with previous v0/v1/v2 file formats, so you will need updated tools
457 for processing it. A preliminary version of these tools is available
458 at <http://www.gnu.org/software/acct/>.
461 bool "Export task/process statistics through netlink"
466 Export selected statistics for tasks/processes through the
467 generic netlink interface. Unlike BSD process accounting, the
468 statistics are available during the lifetime of tasks/processes as
469 responses to commands. Like BSD accounting, they are sent to user
474 config TASK_DELAY_ACCT
475 bool "Enable per-task delay accounting"
479 Collect information on time spent by a task waiting for system
480 resources like cpu, synchronous block I/O completion and swapping
481 in pages. Such statistics can help in setting a task's priorities
482 relative to other tasks for cpu, io, rss limits etc.
487 bool "Enable extended accounting over taskstats"
490 Collect extended task accounting data and send the data
491 to userland for processing over the taskstats interface.
495 config TASK_IO_ACCOUNTING
496 bool "Enable per-task storage I/O accounting"
497 depends on TASK_XACCT
499 Collect information on the number of bytes of storage I/O which this
505 bool "Pressure stall information tracking"
507 Collect metrics that indicate how overcommitted the CPU, memory,
508 and IO capacity are in the system.
510 If you say Y here, the kernel will create /proc/pressure/ with the
511 pressure statistics files cpu, memory, and io. These will indicate
512 the share of walltime in which some or all tasks in the system are
513 delayed due to contention of the respective resource.
515 In kernels with cgroup support, cgroups (cgroup2 only) will
516 have cpu.pressure, memory.pressure, and io.pressure files,
517 which aggregate pressure stalls for the grouped tasks only.
519 For more details see Documentation/accounting/psi.txt.
523 config PSI_DEFAULT_DISABLED
524 bool "Require boot parameter to enable pressure stall information tracking"
528 If set, pressure stall information tracking will be disabled
529 per default but can be enabled through passing psi=1 on the
530 kernel commandline during boot.
532 This feature adds some code to the task wakeup and sleep
533 paths of the scheduler. The overhead is too low to affect
534 common scheduling-intense workloads in practice (such as
535 webservers, memcache), but it does show up in artificial
536 scheduler stress tests, such as hackbench.
538 If you are paranoid and not sure what the kernel will be
543 endmenu # "CPU/Task time and stats accounting"
547 depends on SMP || COMPILE_TEST
550 Make sure that CPUs running critical tasks are not disturbed by
551 any source of "noise" such as unbound workqueues, timers, kthreads...
552 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
553 the "isolcpus=" boot parameter.
557 source "kernel/rcu/Kconfig"
564 tristate "Kernel .config support"
566 This option enables the complete Linux kernel ".config" file
567 contents to be saved in the kernel. It provides documentation
568 of which kernel options are used in a running kernel or in an
569 on-disk kernel. This information can be extracted from the kernel
570 image file with the script scripts/extract-ikconfig and used as
571 input to rebuild the current kernel or to build another kernel.
572 It can also be extracted from a running kernel by reading
573 /proc/config.gz if enabled (below).
576 bool "Enable access to .config through /proc/config.gz"
577 depends on IKCONFIG && PROC_FS
579 This option enables access to the kernel configuration file
580 through /proc/config.gz.
582 config IKHEADERS_PROC
583 tristate "Enable kernel header artifacts through /proc/kheaders.tar.xz"
586 This option enables access to the kernel header and other artifacts that
587 are generated during the build process. These can be used to build eBPF
588 tracing programs, or similar programs. If you build the headers as a
589 module, a module called kheaders.ko is built which can be loaded on-demand
590 to get access to the headers.
593 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
598 Select the minimal kernel log buffer size as a power of 2.
599 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
600 parameter, see below. Any higher size also might be forced
601 by "log_buf_len" boot parameter.
611 config LOG_CPU_MAX_BUF_SHIFT
612 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
615 default 12 if !BASE_SMALL
616 default 0 if BASE_SMALL
619 This option allows to increase the default ring buffer size
620 according to the number of CPUs. The value defines the contribution
621 of each CPU as a power of 2. The used space is typically only few
622 lines however it might be much more when problems are reported,
625 The increased size means that a new buffer has to be allocated and
626 the original static one is unused. It makes sense only on systems
627 with more CPUs. Therefore this value is used only when the sum of
628 contributions is greater than the half of the default kernel ring
629 buffer as defined by LOG_BUF_SHIFT. The default values are set
630 so that more than 64 CPUs are needed to trigger the allocation.
632 Also this option is ignored when "log_buf_len" kernel parameter is
633 used as it forces an exact (power of two) size of the ring buffer.
635 The number of possible CPUs is used for this computation ignoring
636 hotplugging making the computation optimal for the worst case
637 scenario while allowing a simple algorithm to be used from bootup.
639 Examples shift values and their meaning:
640 17 => 128 KB for each CPU
641 16 => 64 KB for each CPU
642 15 => 32 KB for each CPU
643 14 => 16 KB for each CPU
644 13 => 8 KB for each CPU
645 12 => 4 KB for each CPU
647 config PRINTK_SAFE_LOG_BUF_SHIFT
648 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
653 Select the size of an alternate printk per-CPU buffer where messages
654 printed from usafe contexts are temporary stored. One example would
655 be NMI messages, another one - printk recursion. The messages are
656 copied to the main log buffer in a safe context to avoid a deadlock.
657 The value defines the size as a power of 2.
659 Those messages are rare and limited. The largest one is when
660 a backtrace is printed. It usually fits into 4KB. Select
661 8KB if you want to be on the safe side.
664 17 => 128 KB for each CPU
665 16 => 64 KB for each CPU
666 15 => 32 KB for each CPU
667 14 => 16 KB for each CPU
668 13 => 8 KB for each CPU
669 12 => 4 KB for each CPU
672 # Architectures with an unreliable sched_clock() should select this:
674 config HAVE_UNSTABLE_SCHED_CLOCK
677 config GENERIC_SCHED_CLOCK
681 # For architectures that want to enable the support for NUMA-affine scheduler
684 config ARCH_SUPPORTS_NUMA_BALANCING
688 # For architectures that prefer to flush all TLBs after a number of pages
689 # are unmapped instead of sending one IPI per page to flush. The architecture
690 # must provide guarantees on what happens if a clean TLB cache entry is
691 # written after the unmap. Details are in mm/rmap.c near the check for
692 # should_defer_flush. The architecture should also consider if the full flush
693 # and the refill costs are offset by the savings of sending fewer IPIs.
694 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
698 # For architectures that know their GCC __int128 support is sound
700 config ARCH_SUPPORTS_INT128
703 # For architectures that (ab)use NUMA to represent different memory regions
704 # all cpu-local but of different latencies, such as SuperH.
706 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
709 config NUMA_BALANCING
710 bool "Memory placement aware NUMA scheduler"
711 depends on ARCH_SUPPORTS_NUMA_BALANCING
712 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
713 depends on SMP && NUMA && MIGRATION
715 This option adds support for automatic NUMA aware memory/task placement.
716 The mechanism is quite primitive and is based on migrating memory when
717 it has references to the node the task is running on.
719 This system will be inactive on UMA systems.
721 config NUMA_BALANCING_DEFAULT_ENABLED
722 bool "Automatically enable NUMA aware memory/task placement"
724 depends on NUMA_BALANCING
726 If set, automatic NUMA balancing will be enabled if running on a NUMA
730 bool "Control Group support"
733 This option adds support for grouping sets of processes together, for
734 use with process control subsystems such as Cpusets, CFS, memory
735 controls or device isolation.
737 - Documentation/scheduler/sched-design-CFS.txt (CFS)
738 - Documentation/cgroup-v1/ (features for grouping, isolation
739 and resource control)
749 bool "Memory controller"
753 Provides control over the memory footprint of tasks in a cgroup.
756 bool "Swap controller"
757 depends on MEMCG && SWAP
759 Provides control over the swap space consumed by tasks in a cgroup.
761 config MEMCG_SWAP_ENABLED
762 bool "Swap controller enabled by default"
763 depends on MEMCG_SWAP
766 Memory Resource Controller Swap Extension comes with its price in
767 a bigger memory consumption. General purpose distribution kernels
768 which want to enable the feature but keep it disabled by default
769 and let the user enable it by swapaccount=1 boot command line
770 parameter should have this option unselected.
771 For those who want to have the feature enabled by default should
772 select this option (if, for some reason, they need to disable it
773 then swapaccount=0 does the trick).
777 depends on MEMCG && !SLOB
785 Generic block IO controller cgroup interface. This is the common
786 cgroup interface which should be used by various IO controlling
789 Currently, CFQ IO scheduler uses it to recognize task groups and
790 control disk bandwidth allocation (proportional time slice allocation)
791 to such task groups. It is also used by bio throttling logic in
792 block layer to implement upper limit in IO rates on a device.
794 This option only enables generic Block IO controller infrastructure.
795 One needs to also enable actual IO controlling logic/policy. For
796 enabling proportional weight division of disk bandwidth in CFQ, set
797 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
798 CONFIG_BLK_DEV_THROTTLING=y.
800 See Documentation/cgroup-v1/blkio-controller.txt for more information.
802 config DEBUG_BLK_CGROUP
803 bool "IO controller debugging"
804 depends on BLK_CGROUP
807 Enable some debugging help. Currently it exports additional stat
808 files in a cgroup which can be useful for debugging.
810 config CGROUP_WRITEBACK
812 depends on MEMCG && BLK_CGROUP
815 menuconfig CGROUP_SCHED
816 bool "CPU controller"
819 This feature lets CPU scheduler recognize task groups and control CPU
820 bandwidth allocation to such task groups. It uses cgroups to group
824 config FAIR_GROUP_SCHED
825 bool "Group scheduling for SCHED_OTHER"
826 depends on CGROUP_SCHED
830 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
831 depends on FAIR_GROUP_SCHED
834 This option allows users to define CPU bandwidth rates (limits) for
835 tasks running within the fair group scheduler. Groups with no limit
836 set are considered to be unconstrained and will run with no
838 See Documentation/scheduler/sched-bwc.txt for more information.
840 config RT_GROUP_SCHED
841 bool "Group scheduling for SCHED_RR/FIFO"
842 depends on CGROUP_SCHED
845 This feature lets you explicitly allocate real CPU bandwidth
846 to task groups. If enabled, it will also make it impossible to
847 schedule realtime tasks for non-root users until you allocate
848 realtime bandwidth for them.
849 See Documentation/scheduler/sched-rt-group.txt for more information.
854 bool "PIDs controller"
856 Provides enforcement of process number limits in the scope of a
857 cgroup. Any attempt to fork more processes than is allowed in the
858 cgroup will fail. PIDs are fundamentally a global resource because it
859 is fairly trivial to reach PID exhaustion before you reach even a
860 conservative kmemcg limit. As a result, it is possible to grind a
861 system to halt without being limited by other cgroup policies. The
862 PIDs controller is designed to stop this from happening.
864 It should be noted that organisational operations (such as attaching
865 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
866 since the PIDs limit only affects a process's ability to fork, not to
870 bool "RDMA controller"
872 Provides enforcement of RDMA resources defined by IB stack.
873 It is fairly easy for consumers to exhaust RDMA resources, which
874 can result into resource unavailability to other consumers.
875 RDMA controller is designed to stop this from happening.
876 Attaching processes with active RDMA resources to the cgroup
877 hierarchy is allowed even if can cross the hierarchy's limit.
879 config CGROUP_FREEZER
880 bool "Freezer controller"
882 Provides a way to freeze and unfreeze all tasks in a
885 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
886 controller includes important in-kernel memory consumers per default.
888 If you're using cgroup2, say N.
890 config CGROUP_HUGETLB
891 bool "HugeTLB controller"
892 depends on HUGETLB_PAGE
896 Provides a cgroup controller for HugeTLB pages.
897 When you enable this, you can put a per cgroup limit on HugeTLB usage.
898 The limit is enforced during page fault. Since HugeTLB doesn't
899 support page reclaim, enforcing the limit at page fault time implies
900 that, the application will get SIGBUS signal if it tries to access
901 HugeTLB pages beyond its limit. This requires the application to know
902 beforehand how much HugeTLB pages it would require for its use. The
903 control group is tracked in the third page lru pointer. This means
904 that we cannot use the controller with huge page less than 3 pages.
907 bool "Cpuset controller"
910 This option will let you create and manage CPUSETs which
911 allow dynamically partitioning a system into sets of CPUs and
912 Memory Nodes and assigning tasks to run only within those sets.
913 This is primarily useful on large SMP or NUMA systems.
917 config PROC_PID_CPUSET
918 bool "Include legacy /proc/<pid>/cpuset file"
923 bool "Device controller"
925 Provides a cgroup controller implementing whitelists for
926 devices which a process in the cgroup can mknod or open.
928 config CGROUP_CPUACCT
929 bool "Simple CPU accounting controller"
931 Provides a simple controller for monitoring the
932 total CPU consumed by the tasks in a cgroup.
935 bool "Perf controller"
936 depends on PERF_EVENTS
938 This option extends the perf per-cpu mode to restrict monitoring
939 to threads which belong to the cgroup specified and run on the
945 bool "Support for eBPF programs attached to cgroups"
946 depends on BPF_SYSCALL
947 select SOCK_CGROUP_DATA
949 Allow attaching eBPF programs to a cgroup using the bpf(2)
950 syscall command BPF_PROG_ATTACH.
952 In which context these programs are accessed depends on the type
953 of attachment. For instance, programs that are attached using
954 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
958 bool "Debug controller"
960 depends on DEBUG_KERNEL
962 This option enables a simple controller that exports
963 debugging information about the cgroups framework. This
964 controller is for control cgroup debugging only. Its
965 interfaces are not stable.
969 config SOCK_CGROUP_DATA
975 menuconfig NAMESPACES
976 bool "Namespaces support" if EXPERT
980 Provides the way to make tasks work with different objects using
981 the same id. For example same IPC id may refer to different objects
982 or same user id or pid may refer to different tasks when used in
983 different namespaces.
991 In this namespace tasks see different info provided with the
996 depends on (SYSVIPC || POSIX_MQUEUE)
999 In this namespace tasks work with IPC ids which correspond to
1000 different IPC objects in different namespaces.
1003 bool "User namespace"
1006 This allows containers, i.e. vservers, to use user namespaces
1007 to provide different user info for different servers.
1009 When user namespaces are enabled in the kernel it is
1010 recommended that the MEMCG option also be enabled and that
1011 user-space use the memory control groups to limit the amount
1012 of memory a memory unprivileged users can use.
1017 bool "PID Namespaces"
1020 Support process id namespaces. This allows having multiple
1021 processes with the same pid as long as they are in different
1022 pid namespaces. This is a building block of containers.
1025 bool "Network namespace"
1029 Allow user space to create what appear to be multiple instances
1030 of the network stack.
1034 config CHECKPOINT_RESTORE
1035 bool "Checkpoint/restore support"
1036 select PROC_CHILDREN
1039 Enables additional kernel features in a sake of checkpoint/restore.
1040 In particular it adds auxiliary prctl codes to setup process text,
1041 data and heap segment sizes, and a few additional /proc filesystem
1044 If unsure, say N here.
1046 config SCHED_AUTOGROUP
1047 bool "Automatic process group scheduling"
1050 select FAIR_GROUP_SCHED
1052 This option optimizes the scheduler for common desktop workloads by
1053 automatically creating and populating task groups. This separation
1054 of workloads isolates aggressive CPU burners (like build jobs) from
1055 desktop applications. Task group autogeneration is currently based
1058 config SYSFS_DEPRECATED
1059 bool "Enable deprecated sysfs features to support old userspace tools"
1063 This option adds code that switches the layout of the "block" class
1064 devices, to not show up in /sys/class/block/, but only in
1067 This switch is only active when the sysfs.deprecated=1 boot option is
1068 passed or the SYSFS_DEPRECATED_V2 option is set.
1070 This option allows new kernels to run on old distributions and tools,
1071 which might get confused by /sys/class/block/. Since 2007/2008 all
1072 major distributions and tools handle this just fine.
1074 Recent distributions and userspace tools after 2009/2010 depend on
1075 the existence of /sys/class/block/, and will not work with this
1078 Only if you are using a new kernel on an old distribution, you might
1081 config SYSFS_DEPRECATED_V2
1082 bool "Enable deprecated sysfs features by default"
1085 depends on SYSFS_DEPRECATED
1087 Enable deprecated sysfs by default.
1089 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1092 Only if you are using a new kernel on an old distribution, you might
1093 need to say Y here. Even then, odds are you would not need it
1094 enabled, you can always pass the boot option if absolutely necessary.
1097 bool "Kernel->user space relay support (formerly relayfs)"
1100 This option enables support for relay interface support in
1101 certain file systems (such as debugfs).
1102 It is designed to provide an efficient mechanism for tools and
1103 facilities to relay large amounts of data from kernel space to
1108 config BLK_DEV_INITRD
1109 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1111 The initial RAM filesystem is a ramfs which is loaded by the
1112 boot loader (loadlin or lilo) and that is mounted as root
1113 before the normal boot procedure. It is typically used to
1114 load modules needed to mount the "real" root file system,
1115 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1117 If RAM disk support (BLK_DEV_RAM) is also included, this
1118 also enables initial RAM disk (initrd) support and adds
1119 15 Kbytes (more on some other architectures) to the kernel size.
1125 source "usr/Kconfig"
1130 prompt "Compiler optimization level"
1131 default CC_OPTIMIZE_FOR_PERFORMANCE
1133 config CC_OPTIMIZE_FOR_PERFORMANCE
1134 bool "Optimize for performance"
1136 This is the default optimization level for the kernel, building
1137 with the "-O2" compiler flag for best performance and most
1138 helpful compile-time warnings.
1140 config CC_OPTIMIZE_FOR_SIZE
1141 bool "Optimize for size"
1142 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives
1144 Enabling this option will pass "-Os" instead of "-O2" to
1145 your compiler resulting in a smaller kernel.
1151 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1154 This requires that the arch annotates or otherwise protects
1155 its external entry points from being discarded. Linker scripts
1156 must also merge .text.*, .data.*, and .bss.* correctly into
1157 output sections. Care must be taken not to pull in unrelated
1158 sections (e.g., '.text.init'). Typically '.' in section names
1159 is used to distinguish them from label names / C identifiers.
1161 config LD_DEAD_CODE_DATA_ELIMINATION
1162 bool "Dead code and data elimination (EXPERIMENTAL)"
1163 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1165 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800)
1166 depends on $(cc-option,-ffunction-sections -fdata-sections)
1167 depends on $(ld-option,--gc-sections)
1169 Enable this if you want to do dead code and data elimination with
1170 the linker by compiling with -ffunction-sections -fdata-sections,
1171 and linking with --gc-sections.
1173 This can reduce on disk and in-memory size of the kernel
1174 code and static data, particularly for small configs and
1175 on small systems. This has the possibility of introducing
1176 silently broken kernel if the required annotations are not
1177 present. This option is not well tested yet, so use at your
1186 config SYSCTL_EXCEPTION_TRACE
1189 Enable support for /proc/sys/debug/exception-trace.
1191 config SYSCTL_ARCH_UNALIGN_NO_WARN
1194 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1195 Allows arch to define/use @no_unaligned_warning to possibly warn
1196 about unaligned access emulation going on under the hood.
1198 config SYSCTL_ARCH_UNALIGN_ALLOW
1201 Enable support for /proc/sys/kernel/unaligned-trap
1202 Allows arches to define/use @unaligned_enabled to runtime toggle
1203 the unaligned access emulation.
1204 see arch/parisc/kernel/unaligned.c for reference
1206 config HAVE_PCSPKR_PLATFORM
1209 # interpreter that classic socket filters depend on
1214 bool "Configure standard kernel features (expert users)"
1215 # Unhide debug options, to make the on-by-default options visible
1218 This option allows certain base kernel options and settings
1219 to be disabled or tweaked. This is for specialized
1220 environments which can tolerate a "non-standard" kernel.
1221 Only use this if you really know what you are doing.
1224 bool "Enable 16-bit UID system calls" if EXPERT
1225 depends on HAVE_UID16 && MULTIUSER
1228 This enables the legacy 16-bit UID syscall wrappers.
1231 bool "Multiple users, groups and capabilities support" if EXPERT
1234 This option enables support for non-root users, groups and
1237 If you say N here, all processes will run with UID 0, GID 0, and all
1238 possible capabilities. Saying N here also compiles out support for
1239 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1242 If unsure, say Y here.
1244 config SGETMASK_SYSCALL
1245 bool "sgetmask/ssetmask syscalls support" if EXPERT
1246 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1248 sys_sgetmask and sys_ssetmask are obsolete system calls
1249 no longer supported in libc but still enabled by default in some
1252 If unsure, leave the default option here.
1254 config SYSFS_SYSCALL
1255 bool "Sysfs syscall support" if EXPERT
1258 sys_sysfs is an obsolete system call no longer supported in libc.
1259 Note that disabling this option is more secure but might break
1260 compatibility with some systems.
1262 If unsure say Y here.
1264 config SYSCTL_SYSCALL
1265 bool "Sysctl syscall support" if EXPERT
1266 depends on PROC_SYSCTL
1270 sys_sysctl uses binary paths that have been found challenging
1271 to properly maintain and use. The interface in /proc/sys
1272 using paths with ascii names is now the primary path to this
1275 Almost nothing using the binary sysctl interface so if you are
1276 trying to save some space it is probably safe to disable this,
1277 making your kernel marginally smaller.
1279 If unsure say N here.
1282 bool "open by fhandle syscalls" if EXPERT
1286 If you say Y here, a user level program will be able to map
1287 file names to handle and then later use the handle for
1288 different file system operations. This is useful in implementing
1289 userspace file servers, which now track files using handles instead
1290 of names. The handle would remain the same even if file names
1291 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1295 bool "Posix Clocks & timers" if EXPERT
1298 This includes native support for POSIX timers to the kernel.
1299 Some embedded systems have no use for them and therefore they
1300 can be configured out to reduce the size of the kernel image.
1302 When this option is disabled, the following syscalls won't be
1303 available: timer_create, timer_gettime: timer_getoverrun,
1304 timer_settime, timer_delete, clock_adjtime, getitimer,
1305 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1306 clock_getres and clock_nanosleep syscalls will be limited to
1307 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1313 bool "Enable support for printk" if EXPERT
1316 This option enables normal printk support. Removing it
1317 eliminates most of the message strings from the kernel image
1318 and makes the kernel more or less silent. As this makes it
1319 very difficult to diagnose system problems, saying N here is
1320 strongly discouraged.
1328 bool "BUG() support" if EXPERT
1331 Disabling this option eliminates support for BUG and WARN, reducing
1332 the size of your kernel image and potentially quietly ignoring
1333 numerous fatal conditions. You should only consider disabling this
1334 option for embedded systems with no facilities for reporting errors.
1340 bool "Enable ELF core dumps" if EXPERT
1342 Enable support for generating core dumps. Disabling saves about 4k.
1345 config PCSPKR_PLATFORM
1346 bool "Enable PC-Speaker support" if EXPERT
1347 depends on HAVE_PCSPKR_PLATFORM
1351 This option allows to disable the internal PC-Speaker
1352 support, saving some memory.
1356 bool "Enable full-sized data structures for core" if EXPERT
1358 Disabling this option reduces the size of miscellaneous core
1359 kernel data structures. This saves memory on small machines,
1360 but may reduce performance.
1363 bool "Enable futex support" if EXPERT
1367 Disabling this option will cause the kernel to be built without
1368 support for "fast userspace mutexes". The resulting kernel may not
1369 run glibc-based applications correctly.
1373 depends on FUTEX && RT_MUTEXES
1376 config HAVE_FUTEX_CMPXCHG
1380 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1381 is implemented and always working. This removes a couple of runtime
1385 bool "Enable eventpoll support" if EXPERT
1388 Disabling this option will cause the kernel to be built without
1389 support for epoll family of system calls.
1392 bool "Enable signalfd() system call" if EXPERT
1395 Enable the signalfd() system call that allows to receive signals
1396 on a file descriptor.
1401 bool "Enable timerfd() system call" if EXPERT
1404 Enable the timerfd() system call that allows to receive timer
1405 events on a file descriptor.
1410 bool "Enable eventfd() system call" if EXPERT
1413 Enable the eventfd() system call that allows to receive both
1414 kernel notification (ie. KAIO) or userspace notifications.
1419 bool "Use full shmem filesystem" if EXPERT
1423 The shmem is an internal filesystem used to manage shared memory.
1424 It is backed by swap and manages resource limits. It is also exported
1425 to userspace as tmpfs if TMPFS is enabled. Disabling this
1426 option replaces shmem and tmpfs with the much simpler ramfs code,
1427 which may be appropriate on small systems without swap.
1430 bool "Enable AIO support" if EXPERT
1433 This option enables POSIX asynchronous I/O which may by used
1434 by some high performance threaded applications. Disabling
1435 this option saves about 7k.
1438 bool "Enable IO uring support" if EXPERT
1442 This option enables support for the io_uring interface, enabling
1443 applications to submit and complete IO through submission and
1444 completion rings that are shared between the kernel and application.
1446 config ADVISE_SYSCALLS
1447 bool "Enable madvise/fadvise syscalls" if EXPERT
1450 This option enables the madvise and fadvise syscalls, used by
1451 applications to advise the kernel about their future memory or file
1452 usage, improving performance. If building an embedded system where no
1453 applications use these syscalls, you can disable this option to save
1457 bool "Enable membarrier() system call" if EXPERT
1460 Enable the membarrier() system call that allows issuing memory
1461 barriers across all running threads, which can be used to distribute
1462 the cost of user-space memory barriers asymmetrically by transforming
1463 pairs of memory barriers into pairs consisting of membarrier() and a
1469 bool "Load all symbols for debugging/ksymoops" if EXPERT
1472 Say Y here to let the kernel print out symbolic crash information and
1473 symbolic stack backtraces. This increases the size of the kernel
1474 somewhat, as all symbols have to be loaded into the kernel image.
1477 bool "Include all symbols in kallsyms"
1478 depends on DEBUG_KERNEL && KALLSYMS
1480 Normally kallsyms only contains the symbols of functions for nicer
1481 OOPS messages and backtraces (i.e., symbols from the text and inittext
1482 sections). This is sufficient for most cases. And only in very rare
1483 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1484 names of variables from the data sections, etc).
1486 This option makes sure that all symbols are loaded into the kernel
1487 image (i.e., symbols from all sections) in cost of increased kernel
1488 size (depending on the kernel configuration, it may be 300KiB or
1489 something like this).
1491 Say N unless you really need all symbols.
1493 config KALLSYMS_ABSOLUTE_PERCPU
1496 default X86_64 && SMP
1498 config KALLSYMS_BASE_RELATIVE
1503 Instead of emitting them as absolute values in the native word size,
1504 emit the symbol references in the kallsyms table as 32-bit entries,
1505 each containing a relative value in the range [base, base + U32_MAX]
1506 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1507 an absolute value in the range [0, S32_MAX] or a relative value in the
1508 range [base, base + S32_MAX], where base is the lowest relative symbol
1509 address encountered in the image.
1511 On 64-bit builds, this reduces the size of the address table by 50%,
1512 but more importantly, it results in entries whose values are build
1513 time constants, and no relocation pass is required at runtime to fix
1514 up the entries based on the runtime load address of the kernel.
1516 # end of the "standard kernel features (expert users)" menu
1518 # syscall, maps, verifier
1520 bool "Enable bpf() system call"
1525 Enable the bpf() system call that allows to manipulate eBPF
1526 programs and maps via file descriptors.
1528 config BPF_JIT_ALWAYS_ON
1529 bool "Permanently enable BPF JIT and remove BPF interpreter"
1530 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1532 Enables BPF JIT and removes BPF interpreter to avoid
1533 speculative execution of BPF instructions by the interpreter
1536 bool "Enable userfaultfd() system call"
1539 Enable the userfaultfd() system call that allows to intercept and
1540 handle page faults in userland.
1542 config ARCH_HAS_MEMBARRIER_CALLBACKS
1545 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1549 bool "Enable rseq() system call" if EXPERT
1551 depends on HAVE_RSEQ
1554 Enable the restartable sequences system call. It provides a
1555 user-space cache for the current CPU number value, which
1556 speeds up getting the current CPU number from user-space,
1557 as well as an ABI to speed up user-space operations on
1564 bool "Enabled debugging of rseq() system call" if EXPERT
1565 depends on RSEQ && DEBUG_KERNEL
1567 Enable extra debugging checks for the rseq system call.
1572 bool "Embedded system"
1573 option allnoconfig_y
1576 This option should be enabled if compiling the kernel for
1577 an embedded system so certain expert options are available
1580 config HAVE_PERF_EVENTS
1583 See tools/perf/design.txt for details.
1585 config PERF_USE_VMALLOC
1588 See tools/perf/design.txt for details
1591 bool "PC/104 support" if EXPERT
1593 Expose PC/104 form factor device drivers and options available for
1594 selection and configuration. Enable this option if your target
1595 machine has a PC/104 bus.
1597 menu "Kernel Performance Events And Counters"
1600 bool "Kernel performance events and counters"
1601 default y if PROFILING
1602 depends on HAVE_PERF_EVENTS
1606 Enable kernel support for various performance events provided
1607 by software and hardware.
1609 Software events are supported either built-in or via the
1610 use of generic tracepoints.
1612 Most modern CPUs support performance events via performance
1613 counter registers. These registers count the number of certain
1614 types of hw events: such as instructions executed, cachemisses
1615 suffered, or branches mis-predicted - without slowing down the
1616 kernel or applications. These registers can also trigger interrupts
1617 when a threshold number of events have passed - and can thus be
1618 used to profile the code that runs on that CPU.
1620 The Linux Performance Event subsystem provides an abstraction of
1621 these software and hardware event capabilities, available via a
1622 system call and used by the "perf" utility in tools/perf/. It
1623 provides per task and per CPU counters, and it provides event
1624 capabilities on top of those.
1628 config DEBUG_PERF_USE_VMALLOC
1630 bool "Debug: use vmalloc to back perf mmap() buffers"
1631 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1632 select PERF_USE_VMALLOC
1634 Use vmalloc memory to back perf mmap() buffers.
1636 Mostly useful for debugging the vmalloc code on platforms
1637 that don't require it.
1643 config VM_EVENT_COUNTERS
1645 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1647 VM event counters are needed for event counts to be shown.
1648 This option allows the disabling of the VM event counters
1649 on EXPERT systems. /proc/vmstat will only show page counts
1650 if VM event counters are disabled.
1654 bool "Enable SLUB debugging support" if EXPERT
1655 depends on SLUB && SYSFS
1657 SLUB has extensive debug support features. Disabling these can
1658 result in significant savings in code size. This also disables
1659 SLUB sysfs support. /sys/slab will not exist and there will be
1660 no support for cache validation etc.
1662 config SLUB_MEMCG_SYSFS_ON
1664 bool "Enable memcg SLUB sysfs support by default" if EXPERT
1665 depends on SLUB && SYSFS && MEMCG
1667 SLUB creates a directory under /sys/kernel/slab for each
1668 allocation cache to host info and debug files. If memory
1669 cgroup is enabled, each cache can have per memory cgroup
1670 caches. SLUB can create the same sysfs directories for these
1671 caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1672 to a very high number of debug files being created. This is
1673 controlled by slub_memcg_sysfs boot parameter and this
1674 config option determines the parameter's default value.
1677 bool "Disable heap randomization"
1680 Randomizing heap placement makes heap exploits harder, but it
1681 also breaks ancient binaries (including anything libc5 based).
1682 This option changes the bootup default to heap randomization
1683 disabled, and can be overridden at runtime by setting
1684 /proc/sys/kernel/randomize_va_space to 2.
1686 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1689 prompt "Choose SLAB allocator"
1692 This option allows to select a slab allocator.
1696 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1698 The regular slab allocator that is established and known to work
1699 well in all environments. It organizes cache hot objects in
1700 per cpu and per node queues.
1703 bool "SLUB (Unqueued Allocator)"
1704 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1706 SLUB is a slab allocator that minimizes cache line usage
1707 instead of managing queues of cached objects (SLAB approach).
1708 Per cpu caching is realized using slabs of objects instead
1709 of queues of objects. SLUB can use memory efficiently
1710 and has enhanced diagnostics. SLUB is the default choice for
1715 bool "SLOB (Simple Allocator)"
1717 SLOB replaces the stock allocator with a drastically simpler
1718 allocator. SLOB is generally more space efficient but
1719 does not perform as well on large systems.
1723 config SLAB_MERGE_DEFAULT
1724 bool "Allow slab caches to be merged"
1727 For reduced kernel memory fragmentation, slab caches can be
1728 merged when they share the same size and other characteristics.
1729 This carries a risk of kernel heap overflows being able to
1730 overwrite objects from merged caches (and more easily control
1731 cache layout), which makes such heap attacks easier to exploit
1732 by attackers. By keeping caches unmerged, these kinds of exploits
1733 can usually only damage objects in the same cache. To disable
1734 merging at runtime, "slab_nomerge" can be passed on the kernel
1737 config SLAB_FREELIST_RANDOM
1739 depends on SLAB || SLUB
1740 bool "SLAB freelist randomization"
1742 Randomizes the freelist order used on creating new pages. This
1743 security feature reduces the predictability of the kernel slab
1744 allocator against heap overflows.
1746 config SLAB_FREELIST_HARDENED
1747 bool "Harden slab freelist metadata"
1750 Many kernel heap attacks try to target slab cache metadata and
1751 other infrastructure. This options makes minor performance
1752 sacrifies to harden the kernel slab allocator against common
1753 freelist exploit methods.
1755 config SHUFFLE_PAGE_ALLOCATOR
1756 bool "Page allocator randomization"
1757 default SLAB_FREELIST_RANDOM && ACPI_NUMA
1759 Randomization of the page allocator improves the average
1760 utilization of a direct-mapped memory-side-cache. See section
1761 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1762 6.2a specification for an example of how a platform advertises
1763 the presence of a memory-side-cache. There are also incidental
1764 security benefits as it reduces the predictability of page
1765 allocations to compliment SLAB_FREELIST_RANDOM, but the
1766 default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1767 10th order of pages is selected based on cache utilization
1770 While the randomization improves cache utilization it may
1771 negatively impact workloads on platforms without a cache. For
1772 this reason, by default, the randomization is enabled only
1773 after runtime detection of a direct-mapped memory-side-cache.
1774 Otherwise, the randomization may be force enabled with the
1775 'page_alloc.shuffle' kernel command line parameter.
1779 config SLUB_CPU_PARTIAL
1781 depends on SLUB && SMP
1782 bool "SLUB per cpu partial cache"
1784 Per cpu partial caches accellerate objects allocation and freeing
1785 that is local to a processor at the price of more indeterminism
1786 in the latency of the free. On overflow these caches will be cleared
1787 which requires the taking of locks that may cause latency spikes.
1788 Typically one would choose no for a realtime system.
1790 config MMAP_ALLOW_UNINITIALIZED
1791 bool "Allow mmapped anonymous memory to be uninitialized"
1792 depends on EXPERT && !MMU
1795 Normally, and according to the Linux spec, anonymous memory obtained
1796 from mmap() has its contents cleared before it is passed to
1797 userspace. Enabling this config option allows you to request that
1798 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1799 providing a huge performance boost. If this option is not enabled,
1800 then the flag will be ignored.
1802 This is taken advantage of by uClibc's malloc(), and also by
1803 ELF-FDPIC binfmt's brk and stack allocator.
1805 Because of the obvious security issues, this option should only be
1806 enabled on embedded devices where you control what is run in
1807 userspace. Since that isn't generally a problem on no-MMU systems,
1808 it is normally safe to say Y here.
1810 See Documentation/nommu-mmap.txt for more information.
1812 config SYSTEM_DATA_VERIFICATION
1814 select SYSTEM_TRUSTED_KEYRING
1818 select ASYMMETRIC_KEY_TYPE
1819 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1822 select X509_CERTIFICATE_PARSER
1823 select PKCS7_MESSAGE_PARSER
1825 Provide PKCS#7 message verification using the contents of the system
1826 trusted keyring to provide public keys. This then can be used for
1827 module verification, kexec image verification and firmware blob
1831 bool "Profiling support"
1833 Say Y here to enable the extended profiling support mechanisms used
1834 by profilers such as OProfile.
1837 # Place an empty function call at each tracepoint site. Can be
1838 # dynamically changed for a probe function.
1843 endmenu # General setup
1845 source "arch/Kconfig"
1852 default 0 if BASE_FULL
1853 default 1 if !BASE_FULL
1856 bool "Enable loadable module support"
1859 Kernel modules are small pieces of compiled code which can
1860 be inserted in the running kernel, rather than being
1861 permanently built into the kernel. You use the "modprobe"
1862 tool to add (and sometimes remove) them. If you say Y here,
1863 many parts of the kernel can be built as modules (by
1864 answering M instead of Y where indicated): this is most
1865 useful for infrequently used options which are not required
1866 for booting. For more information, see the man pages for
1867 modprobe, lsmod, modinfo, insmod and rmmod.
1869 If you say Y here, you will need to run "make
1870 modules_install" to put the modules under /lib/modules/
1871 where modprobe can find them (you may need to be root to do
1878 config MODULE_FORCE_LOAD
1879 bool "Forced module loading"
1882 Allow loading of modules without version information (ie. modprobe
1883 --force). Forced module loading sets the 'F' (forced) taint flag and
1884 is usually a really bad idea.
1886 config MODULE_UNLOAD
1887 bool "Module unloading"
1889 Without this option you will not be able to unload any
1890 modules (note that some modules may not be unloadable
1891 anyway), which makes your kernel smaller, faster
1892 and simpler. If unsure, say Y.
1894 config MODULE_FORCE_UNLOAD
1895 bool "Forced module unloading"
1896 depends on MODULE_UNLOAD
1898 This option allows you to force a module to unload, even if the
1899 kernel believes it is unsafe: the kernel will remove the module
1900 without waiting for anyone to stop using it (using the -f option to
1901 rmmod). This is mainly for kernel developers and desperate users.
1905 bool "Module versioning support"
1907 Usually, you have to use modules compiled with your kernel.
1908 Saying Y here makes it sometimes possible to use modules
1909 compiled for different kernels, by adding enough information
1910 to the modules to (hopefully) spot any changes which would
1911 make them incompatible with the kernel you are running. If
1914 config MODULE_REL_CRCS
1916 depends on MODVERSIONS
1918 config MODULE_SRCVERSION_ALL
1919 bool "Source checksum for all modules"
1921 Modules which contain a MODULE_VERSION get an extra "srcversion"
1922 field inserted into their modinfo section, which contains a
1923 sum of the source files which made it. This helps maintainers
1924 see exactly which source was used to build a module (since
1925 others sometimes change the module source without updating
1926 the version). With this option, such a "srcversion" field
1927 will be created for all modules. If unsure, say N.
1930 bool "Module signature verification"
1932 select SYSTEM_DATA_VERIFICATION
1934 Check modules for valid signatures upon load: the signature
1935 is simply appended to the module. For more information see
1936 <file:Documentation/admin-guide/module-signing.rst>.
1938 Note that this option adds the OpenSSL development packages as a
1939 kernel build dependency so that the signing tool can use its crypto
1942 !!!WARNING!!! If you enable this option, you MUST make sure that the
1943 module DOES NOT get stripped after being signed. This includes the
1944 debuginfo strip done by some packagers (such as rpmbuild) and
1945 inclusion into an initramfs that wants the module size reduced.
1947 config MODULE_SIG_FORCE
1948 bool "Require modules to be validly signed"
1949 depends on MODULE_SIG
1951 Reject unsigned modules or signed modules for which we don't have a
1952 key. Without this, such modules will simply taint the kernel.
1954 config MODULE_SIG_ALL
1955 bool "Automatically sign all modules"
1957 depends on MODULE_SIG
1959 Sign all modules during make modules_install. Without this option,
1960 modules must be signed manually, using the scripts/sign-file tool.
1962 comment "Do not forget to sign required modules with scripts/sign-file"
1963 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1966 prompt "Which hash algorithm should modules be signed with?"
1967 depends on MODULE_SIG
1969 This determines which sort of hashing algorithm will be used during
1970 signature generation. This algorithm _must_ be built into the kernel
1971 directly so that signature verification can take place. It is not
1972 possible to load a signed module containing the algorithm to check
1973 the signature on that module.
1975 config MODULE_SIG_SHA1
1976 bool "Sign modules with SHA-1"
1979 config MODULE_SIG_SHA224
1980 bool "Sign modules with SHA-224"
1981 select CRYPTO_SHA256
1983 config MODULE_SIG_SHA256
1984 bool "Sign modules with SHA-256"
1985 select CRYPTO_SHA256
1987 config MODULE_SIG_SHA384
1988 bool "Sign modules with SHA-384"
1989 select CRYPTO_SHA512
1991 config MODULE_SIG_SHA512
1992 bool "Sign modules with SHA-512"
1993 select CRYPTO_SHA512
1997 config MODULE_SIG_HASH
1999 depends on MODULE_SIG
2000 default "sha1" if MODULE_SIG_SHA1
2001 default "sha224" if MODULE_SIG_SHA224
2002 default "sha256" if MODULE_SIG_SHA256
2003 default "sha384" if MODULE_SIG_SHA384
2004 default "sha512" if MODULE_SIG_SHA512
2006 config MODULE_COMPRESS
2007 bool "Compress modules on installation"
2011 Compresses kernel modules when 'make modules_install' is run; gzip or
2012 xz depending on "Compression algorithm" below.
2014 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2016 Out-of-tree kernel modules installed using Kbuild will also be
2017 compressed upon installation.
2019 Note: for modules inside an initrd or initramfs, it's more efficient
2020 to compress the whole initrd or initramfs instead.
2022 Note: This is fully compatible with signed modules.
2027 prompt "Compression algorithm"
2028 depends on MODULE_COMPRESS
2029 default MODULE_COMPRESS_GZIP
2031 This determines which sort of compression will be used during
2032 'make modules_install'.
2034 GZIP (default) and XZ are supported.
2036 config MODULE_COMPRESS_GZIP
2039 config MODULE_COMPRESS_XZ
2044 config TRIM_UNUSED_KSYMS
2045 bool "Trim unused exported kernel symbols"
2046 depends on MODULES && !UNUSED_SYMBOLS
2048 The kernel and some modules make many symbols available for
2049 other modules to use via EXPORT_SYMBOL() and variants. Depending
2050 on the set of modules being selected in your kernel configuration,
2051 many of those exported symbols might never be used.
2053 This option allows for unused exported symbols to be dropped from
2054 the build. In turn, this provides the compiler more opportunities
2055 (especially when using LTO) for optimizing the code and reducing
2056 binary size. This might have some security advantages as well.
2058 If unsure, or if you need to build out-of-tree modules, say N.
2062 config MODULES_TREE_LOOKUP
2064 depends on PERF_EVENTS || TRACING
2066 config INIT_ALL_POSSIBLE
2069 Back when each arch used to define their own cpu_online_mask and
2070 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2071 with all 1s, and others with all 0s. When they were centralised,
2072 it was better to provide this option than to break all the archs
2073 and have several arch maintainers pursuing me down dark alleys.
2075 source "block/Kconfig"
2077 config PREEMPT_NOTIFIERS
2087 Build a simple ASN.1 grammar compiler that produces a bytecode output
2088 that can be interpreted by the ASN.1 stream decoder and used to
2089 inform it as to what tags are to be expected in a stream and what
2090 functions to call on what tags.
2092 source "kernel/Kconfig.locks"
2094 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2097 # It may be useful for an architecture to override the definitions of the
2098 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2099 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2100 # different calling convention for syscalls. They can also override the
2101 # macros for not-implemented syscalls in kernel/sys_ni.c and
2102 # kernel/time/posix-stubs.c. All these overrides need to be available in
2103 # <asm/syscall_wrapper.h>.
2104 config ARCH_HAS_SYSCALL_WRAPPER
projects / platform / kernel / linux-rpi.git / blob