7 option env="KERNELVERSION"
13 default "/lib/modules/$UNAME_RELEASE/.config"
14 default "/etc/kernel-config"
15 default "/boot/config-$UNAME_RELEASE"
16 default "$ARCH_DEFCONFIG"
17 default "arch/$ARCH/defconfig"
26 config BUILDTIME_EXTABLE_SORT
29 config THREAD_INFO_IN_TASK
32 Select this to move thread_info off the stack into task_struct. To
33 make this work, an arch will need to remove all thread_info fields
34 except flags and fix any runtime bugs.
36 One subtle change that will be needed is to use try_get_task_stack()
37 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
46 depends on BROKEN || !SMP
49 config INIT_ENV_ARG_LIMIT
54 Maximum of each of the number of arguments and environment
55 variables passed to init from the kernel command line.
59 string "Cross-compiler tool prefix"
61 Same as running 'make CROSS_COMPILE=prefix-' but stored for
62 default make runs in this kernel build directory. You don't
63 need to set this unless you want the configured kernel build
64 directory to select the cross-compiler automatically.
67 bool "Compile also drivers which will not load"
71 Some drivers can be compiled on a different platform than they are
72 intended to be run on. Despite they cannot be loaded there (or even
73 when they load they cannot be used due to missing HW support),
74 developers still, opposing to distributors, might want to build such
75 drivers to compile-test them.
77 If you are a developer and want to build everything available, say Y
78 here. If you are a user/distributor, say N here to exclude useless
79 drivers to be distributed.
82 string "Local version - append to kernel release"
84 Append an extra string to the end of your kernel version.
85 This will show up when you type uname, for example.
86 The string you set here will be appended after the contents of
87 any files with a filename matching localversion* in your
88 object and source tree, in that order. Your total string can
89 be a maximum of 64 characters.
91 config LOCALVERSION_AUTO
92 bool "Automatically append version information to the version string"
94 depends on !COMPILE_TEST
96 This will try to automatically determine if the current tree is a
97 release tree by looking for git tags that belong to the current
100 A string of the format -gxxxxxxxx will be added to the localversion
101 if a git-based tree is found. The string generated by this will be
102 appended after any matching localversion* files, and after the value
103 set in CONFIG_LOCALVERSION.
105 (The actual string used here is the first eight characters produced
106 by running the command:
108 $ git rev-parse --verify HEAD
110 which is done within the script "scripts/setlocalversion".)
112 config HAVE_KERNEL_GZIP
115 config HAVE_KERNEL_BZIP2
118 config HAVE_KERNEL_LZMA
121 config HAVE_KERNEL_XZ
124 config HAVE_KERNEL_LZO
127 config HAVE_KERNEL_LZ4
131 prompt "Kernel compression mode"
133 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
135 The linux kernel is a kind of self-extracting executable.
136 Several compression algorithms are available, which differ
137 in efficiency, compression and decompression speed.
138 Compression speed is only relevant when building a kernel.
139 Decompression speed is relevant at each boot.
141 If you have any problems with bzip2 or lzma compressed
142 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
143 version of this functionality (bzip2 only), for 2.4, was
144 supplied by Christian Ludwig)
146 High compression options are mostly useful for users, who
147 are low on disk space (embedded systems), but for whom ram
150 If in doubt, select 'gzip'
154 depends on HAVE_KERNEL_GZIP
156 The old and tried gzip compression. It provides a good balance
157 between compression ratio and decompression speed.
161 depends on HAVE_KERNEL_BZIP2
163 Its compression ratio and speed is intermediate.
164 Decompression speed is slowest among the choices. The kernel
165 size is about 10% smaller with bzip2, in comparison to gzip.
166 Bzip2 uses a large amount of memory. For modern kernels you
167 will need at least 8MB RAM or more for booting.
171 depends on HAVE_KERNEL_LZMA
173 This compression algorithm's ratio is best. Decompression speed
174 is between gzip and bzip2. Compression is slowest.
175 The kernel size is about 33% smaller with LZMA in comparison to gzip.
179 depends on HAVE_KERNEL_XZ
181 XZ uses the LZMA2 algorithm and instruction set specific
182 BCJ filters which can improve compression ratio of executable
183 code. The size of the kernel is about 30% smaller with XZ in
184 comparison to gzip. On architectures for which there is a BCJ
185 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
186 will create a few percent smaller kernel than plain LZMA.
188 The speed is about the same as with LZMA: The decompression
189 speed of XZ is better than that of bzip2 but worse than gzip
190 and LZO. Compression is slow.
194 depends on HAVE_KERNEL_LZO
196 Its compression ratio is the poorest among the choices. The kernel
197 size is about 10% bigger than gzip; however its speed
198 (both compression and decompression) is the fastest.
202 depends on HAVE_KERNEL_LZ4
204 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
205 A preliminary version of LZ4 de/compression tool is available at
206 <https://code.google.com/p/lz4/>.
208 Its compression ratio is worse than LZO. The size of the kernel
209 is about 8% bigger than LZO. But the decompression speed is
214 config DEFAULT_HOSTNAME
215 string "Default hostname"
218 This option determines the default system hostname before userspace
219 calls sethostname(2). The kernel traditionally uses "(none)" here,
220 but you may wish to use a different default here to make a minimal
221 system more usable with less configuration.
224 bool "Support for paging of anonymous memory (swap)"
225 depends on MMU && BLOCK
228 This option allows you to choose whether you want to have support
229 for so called swap devices or swap files in your kernel that are
230 used to provide more virtual memory than the actual RAM present
231 in your computer. If unsure say Y.
236 Inter Process Communication is a suite of library functions and
237 system calls which let processes (running programs) synchronize and
238 exchange information. It is generally considered to be a good thing,
239 and some programs won't run unless you say Y here. In particular, if
240 you want to run the DOS emulator dosemu under Linux (read the
241 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
242 you'll need to say Y here.
244 You can find documentation about IPC with "info ipc" and also in
245 section 6.4 of the Linux Programmer's Guide, available from
246 <http://www.tldp.org/guides.html>.
248 config SYSVIPC_SYSCTL
255 bool "POSIX Message Queues"
258 POSIX variant of message queues is a part of IPC. In POSIX message
259 queues every message has a priority which decides about succession
260 of receiving it by a process. If you want to compile and run
261 programs written e.g. for Solaris with use of its POSIX message
262 queues (functions mq_*) say Y here.
264 POSIX message queues are visible as a filesystem called 'mqueue'
265 and can be mounted somewhere if you want to do filesystem
266 operations on message queues.
270 config POSIX_MQUEUE_SYSCTL
272 depends on POSIX_MQUEUE
276 config CROSS_MEMORY_ATTACH
277 bool "Enable process_vm_readv/writev syscalls"
281 Enabling this option adds the system calls process_vm_readv and
282 process_vm_writev which allow a process with the correct privileges
283 to directly read from or write to another process' address space.
284 See the man page for more details.
287 bool "open by fhandle syscalls" if EXPERT
291 If you say Y here, a user level program will be able to map
292 file names to handle and then later use the handle for
293 different file system operations. This is useful in implementing
294 userspace file servers, which now track files using handles instead
295 of names. The handle would remain the same even if file names
296 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
300 bool "uselib syscall"
301 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
303 This option enables the uselib syscall, a system call used in the
304 dynamic linker from libc5 and earlier. glibc does not use this
305 system call. If you intend to run programs built on libc5 or
306 earlier, you may need to enable this syscall. Current systems
307 running glibc can safely disable this.
310 bool "Auditing support"
313 Enable auditing infrastructure that can be used with another
314 kernel subsystem, such as SELinux (which requires this for
315 logging of avc messages output). System call auditing is included
316 on architectures which support it.
318 config HAVE_ARCH_AUDITSYSCALL
323 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
327 depends on AUDITSYSCALL
332 depends on AUDITSYSCALL
335 source "kernel/irq/Kconfig"
336 source "kernel/time/Kconfig"
338 menu "CPU/Task time and stats accounting"
340 config VIRT_CPU_ACCOUNTING
344 prompt "Cputime accounting"
345 default TICK_CPU_ACCOUNTING if !PPC64
346 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
348 # Kind of a stub config for the pure tick based cputime accounting
349 config TICK_CPU_ACCOUNTING
350 bool "Simple tick based cputime accounting"
351 depends on !S390 && !NO_HZ_FULL
353 This is the basic tick based cputime accounting that maintains
354 statistics about user, system and idle time spent on per jiffies
359 config VIRT_CPU_ACCOUNTING_NATIVE
360 bool "Deterministic task and CPU time accounting"
361 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
362 select VIRT_CPU_ACCOUNTING
364 Select this option to enable more accurate task and CPU time
365 accounting. This is done by reading a CPU counter on each
366 kernel entry and exit and on transitions within the kernel
367 between system, softirq and hardirq state, so there is a
368 small performance impact. In the case of s390 or IBM POWER > 5,
369 this also enables accounting of stolen time on logically-partitioned
372 config VIRT_CPU_ACCOUNTING_GEN
373 bool "Full dynticks CPU time accounting"
374 depends on HAVE_CONTEXT_TRACKING
375 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
376 select VIRT_CPU_ACCOUNTING
377 select CONTEXT_TRACKING
379 Select this option to enable task and CPU time accounting on full
380 dynticks systems. This accounting is implemented by watching every
381 kernel-user boundaries using the context tracking subsystem.
382 The accounting is thus performed at the expense of some significant
385 For now this is only useful if you are working on the full
386 dynticks subsystem development.
392 config IRQ_TIME_ACCOUNTING
393 bool "Fine granularity task level IRQ time accounting"
394 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
396 Select this option to enable fine granularity task irq time
397 accounting. This is done by reading a timestamp on each
398 transitions between softirq and hardirq state, so there can be a
399 small performance impact.
401 If in doubt, say N here.
404 bool "Support window based load tracking"
407 This feature will allow the scheduler to maintain a tunable window
408 based set of metrics for tasks and runqueues. These metrics can be
409 used to guide task placement as well as task frequency requirements
410 for cpufreq governors.
412 config BSD_PROCESS_ACCT
413 bool "BSD Process Accounting"
416 If you say Y here, a user level program will be able to instruct the
417 kernel (via a special system call) to write process accounting
418 information to a file: whenever a process exits, information about
419 that process will be appended to the file by the kernel. The
420 information includes things such as creation time, owning user,
421 command name, memory usage, controlling terminal etc. (the complete
422 list is in the struct acct in <file:include/linux/acct.h>). It is
423 up to the user level program to do useful things with this
424 information. This is generally a good idea, so say Y.
426 config BSD_PROCESS_ACCT_V3
427 bool "BSD Process Accounting version 3 file format"
428 depends on BSD_PROCESS_ACCT
431 If you say Y here, the process accounting information is written
432 in a new file format that also logs the process IDs of each
433 process and it's parent. Note that this file format is incompatible
434 with previous v0/v1/v2 file formats, so you will need updated tools
435 for processing it. A preliminary version of these tools is available
436 at <http://www.gnu.org/software/acct/>.
439 bool "Export task/process statistics through netlink"
444 Export selected statistics for tasks/processes through the
445 generic netlink interface. Unlike BSD process accounting, the
446 statistics are available during the lifetime of tasks/processes as
447 responses to commands. Like BSD accounting, they are sent to user
452 config TASK_DELAY_ACCT
453 bool "Enable per-task delay accounting"
457 Collect information on time spent by a task waiting for system
458 resources like cpu, synchronous block I/O completion and swapping
459 in pages. Such statistics can help in setting a task's priorities
460 relative to other tasks for cpu, io, rss limits etc.
465 bool "Enable extended accounting over taskstats"
468 Collect extended task accounting data and send the data
469 to userland for processing over the taskstats interface.
473 config TASK_IO_ACCOUNTING
474 bool "Enable per-task storage I/O accounting"
475 depends on TASK_XACCT
477 Collect information on the number of bytes of storage I/O which this
482 endmenu # "CPU/Task time and stats accounting"
484 source "kernel/rcu/Kconfig"
491 tristate "Kernel .config support"
494 This option enables the complete Linux kernel ".config" file
495 contents to be saved in the kernel. It provides documentation
496 of which kernel options are used in a running kernel or in an
497 on-disk kernel. This information can be extracted from the kernel
498 image file with the script scripts/extract-ikconfig and used as
499 input to rebuild the current kernel or to build another kernel.
500 It can also be extracted from a running kernel by reading
501 /proc/config.gz if enabled (below).
504 bool "Enable access to .config through /proc/config.gz"
505 depends on IKCONFIG && PROC_FS
507 This option enables access to the kernel configuration file
508 through /proc/config.gz.
511 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
516 Select the minimal kernel log buffer size as a power of 2.
517 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
518 parameter, see below. Any higher size also might be forced
519 by "log_buf_len" boot parameter.
529 config LOG_CPU_MAX_BUF_SHIFT
530 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
533 default 12 if !BASE_SMALL
534 default 0 if BASE_SMALL
537 This option allows to increase the default ring buffer size
538 according to the number of CPUs. The value defines the contribution
539 of each CPU as a power of 2. The used space is typically only few
540 lines however it might be much more when problems are reported,
543 The increased size means that a new buffer has to be allocated and
544 the original static one is unused. It makes sense only on systems
545 with more CPUs. Therefore this value is used only when the sum of
546 contributions is greater than the half of the default kernel ring
547 buffer as defined by LOG_BUF_SHIFT. The default values are set
548 so that more than 64 CPUs are needed to trigger the allocation.
550 Also this option is ignored when "log_buf_len" kernel parameter is
551 used as it forces an exact (power of two) size of the ring buffer.
553 The number of possible CPUs is used for this computation ignoring
554 hotplugging making the computation optimal for the worst case
555 scenario while allowing a simple algorithm to be used from bootup.
557 Examples shift values and their meaning:
558 17 => 128 KB for each CPU
559 16 => 64 KB for each CPU
560 15 => 32 KB for each CPU
561 14 => 16 KB for each CPU
562 13 => 8 KB for each CPU
563 12 => 4 KB for each CPU
565 config PRINTK_SAFE_LOG_BUF_SHIFT
566 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
571 Select the size of an alternate printk per-CPU buffer where messages
572 printed from usafe contexts are temporary stored. One example would
573 be NMI messages, another one - printk recursion. The messages are
574 copied to the main log buffer in a safe context to avoid a deadlock.
575 The value defines the size as a power of 2.
577 Those messages are rare and limited. The largest one is when
578 a backtrace is printed. It usually fits into 4KB. Select
579 8KB if you want to be on the safe side.
582 17 => 128 KB for each CPU
583 16 => 64 KB for each CPU
584 15 => 32 KB for each CPU
585 14 => 16 KB for each CPU
586 13 => 8 KB for each CPU
587 12 => 4 KB for each CPU
590 # Architectures with an unreliable sched_clock() should select this:
592 config HAVE_UNSTABLE_SCHED_CLOCK
595 config GENERIC_SCHED_CLOCK
599 # For architectures that want to enable the support for NUMA-affine scheduler
602 config ARCH_SUPPORTS_NUMA_BALANCING
606 # For architectures that prefer to flush all TLBs after a number of pages
607 # are unmapped instead of sending one IPI per page to flush. The architecture
608 # must provide guarantees on what happens if a clean TLB cache entry is
609 # written after the unmap. Details are in mm/rmap.c near the check for
610 # should_defer_flush. The architecture should also consider if the full flush
611 # and the refill costs are offset by the savings of sending fewer IPIs.
612 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
616 # For architectures that know their GCC __int128 support is sound
618 config ARCH_SUPPORTS_INT128
621 # For architectures that (ab)use NUMA to represent different memory regions
622 # all cpu-local but of different latencies, such as SuperH.
624 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
627 config NUMA_BALANCING
628 bool "Memory placement aware NUMA scheduler"
629 depends on ARCH_SUPPORTS_NUMA_BALANCING
630 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
631 depends on SMP && NUMA && MIGRATION
633 This option adds support for automatic NUMA aware memory/task placement.
634 The mechanism is quite primitive and is based on migrating memory when
635 it has references to the node the task is running on.
637 This system will be inactive on UMA systems.
639 config NUMA_BALANCING_DEFAULT_ENABLED
640 bool "Automatically enable NUMA aware memory/task placement"
642 depends on NUMA_BALANCING
644 If set, automatic NUMA balancing will be enabled if running on a NUMA
648 bool "Control Group support"
651 This option adds support for grouping sets of processes together, for
652 use with process control subsystems such as Cpusets, CFS, memory
653 controls or device isolation.
655 - Documentation/scheduler/sched-design-CFS.txt (CFS)
656 - Documentation/cgroup-v1/ (features for grouping, isolation
657 and resource control)
667 bool "Memory controller"
671 Provides control over the memory footprint of tasks in a cgroup.
674 bool "Swap controller"
675 depends on MEMCG && SWAP
677 Provides control over the swap space consumed by tasks in a cgroup.
679 config MEMCG_SWAP_ENABLED
680 bool "Swap controller enabled by default"
681 depends on MEMCG_SWAP
684 Memory Resource Controller Swap Extension comes with its price in
685 a bigger memory consumption. General purpose distribution kernels
686 which want to enable the feature but keep it disabled by default
687 and let the user enable it by swapaccount=1 boot command line
688 parameter should have this option unselected.
689 For those who want to have the feature enabled by default should
690 select this option (if, for some reason, they need to disable it
691 then swapaccount=0 does the trick).
698 Generic block IO controller cgroup interface. This is the common
699 cgroup interface which should be used by various IO controlling
702 Currently, CFQ IO scheduler uses it to recognize task groups and
703 control disk bandwidth allocation (proportional time slice allocation)
704 to such task groups. It is also used by bio throttling logic in
705 block layer to implement upper limit in IO rates on a device.
707 This option only enables generic Block IO controller infrastructure.
708 One needs to also enable actual IO controlling logic/policy. For
709 enabling proportional weight division of disk bandwidth in CFQ, set
710 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
711 CONFIG_BLK_DEV_THROTTLING=y.
713 See Documentation/cgroup-v1/blkio-controller.txt for more information.
715 config DEBUG_BLK_CGROUP
716 bool "IO controller debugging"
717 depends on BLK_CGROUP
720 Enable some debugging help. Currently it exports additional stat
721 files in a cgroup which can be useful for debugging.
723 config CGROUP_WRITEBACK
725 depends on MEMCG && BLK_CGROUP
728 menuconfig CGROUP_SCHED
729 bool "CPU controller"
732 This feature lets CPU scheduler recognize task groups and control CPU
733 bandwidth allocation to such task groups. It uses cgroups to group
737 config FAIR_GROUP_SCHED
738 bool "Group scheduling for SCHED_OTHER"
739 depends on CGROUP_SCHED
743 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
744 depends on FAIR_GROUP_SCHED
747 This option allows users to define CPU bandwidth rates (limits) for
748 tasks running within the fair group scheduler. Groups with no limit
749 set are considered to be unconstrained and will run with no
751 See tip/Documentation/scheduler/sched-bwc.txt for more information.
753 config RT_GROUP_SCHED
754 bool "Group scheduling for SCHED_RR/FIFO"
755 depends on CGROUP_SCHED
758 This feature lets you explicitly allocate real CPU bandwidth
759 to task groups. If enabled, it will also make it impossible to
760 schedule realtime tasks for non-root users until you allocate
761 realtime bandwidth for them.
762 See Documentation/scheduler/sched-rt-group.txt for more information.
767 bool "PIDs controller"
769 Provides enforcement of process number limits in the scope of a
770 cgroup. Any attempt to fork more processes than is allowed in the
771 cgroup will fail. PIDs are fundamentally a global resource because it
772 is fairly trivial to reach PID exhaustion before you reach even a
773 conservative kmemcg limit. As a result, it is possible to grind a
774 system to halt without being limited by other cgroup policies. The
775 PIDs controller is designed to stop this from happening.
777 It should be noted that organisational operations (such as attaching
778 to a cgroup hierarchy will *not* be blocked by the PIDs controller),
779 since the PIDs limit only affects a process's ability to fork, not to
783 bool "RDMA controller"
785 Provides enforcement of RDMA resources defined by IB stack.
786 It is fairly easy for consumers to exhaust RDMA resources, which
787 can result into resource unavailability to other consumers.
788 RDMA controller is designed to stop this from happening.
789 Attaching processes with active RDMA resources to the cgroup
790 hierarchy is allowed even if can cross the hierarchy's limit.
792 config CGROUP_FREEZER
793 bool "Freezer controller"
795 Provides a way to freeze and unfreeze all tasks in a
798 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
799 controller includes important in-kernel memory consumers per default.
801 If you're using cgroup2, say N.
803 config CGROUP_HUGETLB
804 bool "HugeTLB controller"
805 depends on HUGETLB_PAGE
809 Provides a cgroup controller for HugeTLB pages.
810 When you enable this, you can put a per cgroup limit on HugeTLB usage.
811 The limit is enforced during page fault. Since HugeTLB doesn't
812 support page reclaim, enforcing the limit at page fault time implies
813 that, the application will get SIGBUS signal if it tries to access
814 HugeTLB pages beyond its limit. This requires the application to know
815 beforehand how much HugeTLB pages it would require for its use. The
816 control group is tracked in the third page lru pointer. This means
817 that we cannot use the controller with huge page less than 3 pages.
820 bool "Cpuset controller"
823 This option will let you create and manage CPUSETs which
824 allow dynamically partitioning a system into sets of CPUs and
825 Memory Nodes and assigning tasks to run only within those sets.
826 This is primarily useful on large SMP or NUMA systems.
830 config PROC_PID_CPUSET
831 bool "Include legacy /proc/<pid>/cpuset file"
836 bool "Device controller"
838 Provides a cgroup controller implementing whitelists for
839 devices which a process in the cgroup can mknod or open.
841 config CGROUP_CPUACCT
842 bool "Simple CPU accounting controller"
844 Provides a simple controller for monitoring the
845 total CPU consumed by the tasks in a cgroup.
848 bool "Perf controller"
849 depends on PERF_EVENTS
851 This option extends the perf per-cpu mode to restrict monitoring
852 to threads which belong to the cgroup specified and run on the
858 bool "Support for eBPF programs attached to cgroups"
859 depends on BPF_SYSCALL
860 select SOCK_CGROUP_DATA
862 Allow attaching eBPF programs to a cgroup using the bpf(2)
863 syscall command BPF_PROG_ATTACH.
865 In which context these programs are accessed depends on the type
866 of attachment. For instance, programs that are attached using
867 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
871 bool "Debug controller"
873 depends on DEBUG_KERNEL
875 This option enables a simple controller that exports
876 debugging information about the cgroups framework. This
877 controller is for control cgroup debugging only. Its
878 interfaces are not stable.
882 config SOCK_CGROUP_DATA
888 config CHECKPOINT_RESTORE
889 bool "Checkpoint/restore support" if EXPERT
893 Enables additional kernel features in a sake of checkpoint/restore.
894 In particular it adds auxiliary prctl codes to setup process text,
895 data and heap segment sizes, and a few additional /proc filesystem
898 If unsure, say N here.
900 menuconfig NAMESPACES
901 bool "Namespaces support" if EXPERT
905 Provides the way to make tasks work with different objects using
906 the same id. For example same IPC id may refer to different objects
907 or same user id or pid may refer to different tasks when used in
908 different namespaces.
916 In this namespace tasks see different info provided with the
921 depends on (SYSVIPC || POSIX_MQUEUE)
924 In this namespace tasks work with IPC ids which correspond to
925 different IPC objects in different namespaces.
928 bool "User namespace"
931 This allows containers, i.e. vservers, to use user namespaces
932 to provide different user info for different servers.
934 When user namespaces are enabled in the kernel it is
935 recommended that the MEMCG option also be enabled and that
936 user-space use the memory control groups to limit the amount
937 of memory a memory unprivileged users can use.
942 bool "PID Namespaces"
945 Support process id namespaces. This allows having multiple
946 processes with the same pid as long as they are in different
947 pid namespaces. This is a building block of containers.
950 bool "Network namespace"
954 Allow user space to create what appear to be multiple instances
955 of the network stack.
959 config SCHED_AUTOGROUP
960 bool "Automatic process group scheduling"
963 select FAIR_GROUP_SCHED
965 This option optimizes the scheduler for common desktop workloads by
966 automatically creating and populating task groups. This separation
967 of workloads isolates aggressive CPU burners (like build jobs) from
968 desktop applications. Task group autogeneration is currently based
972 bool "Boosting for CFS tasks (EXPERIMENTAL)"
975 This option enables support for task classification using a new
976 cgroup controller, schedtune. Schedtune allows tasks to be given
977 a boost value and marked as latency-sensitive or not. This option
978 provides the "schedtune" controller.
981 1. allows only a two layers hierarchy, where the root defines the
982 system-wide boost value and its direct childrens define each one a
983 different "class of tasks" to be boosted with a different value
984 2. supports up to 16 different task classes, each one which could be
985 configured with a different boost value
987 Latency-sensitive tasks are not subject to energy-aware wakeup
988 task placement. The boost value assigned to tasks is used to
989 influence task placement and CPU frequency selection (if
990 utilization-driven frequency selection is in use).
994 config DEFAULT_USE_ENERGY_AWARE
995 bool "Default to enabling the Energy Aware Scheduler feature"
998 This option defaults the ENERGY_AWARE scheduling feature to true,
999 as without SCHED_DEBUG set this feature can't be enabled or disabled
1004 config SYSFS_DEPRECATED
1005 bool "Enable deprecated sysfs features to support old userspace tools"
1009 This option adds code that switches the layout of the "block" class
1010 devices, to not show up in /sys/class/block/, but only in
1013 This switch is only active when the sysfs.deprecated=1 boot option is
1014 passed or the SYSFS_DEPRECATED_V2 option is set.
1016 This option allows new kernels to run on old distributions and tools,
1017 which might get confused by /sys/class/block/. Since 2007/2008 all
1018 major distributions and tools handle this just fine.
1020 Recent distributions and userspace tools after 2009/2010 depend on
1021 the existence of /sys/class/block/, and will not work with this
1024 Only if you are using a new kernel on an old distribution, you might
1027 config SYSFS_DEPRECATED_V2
1028 bool "Enable deprecated sysfs features by default"
1031 depends on SYSFS_DEPRECATED
1033 Enable deprecated sysfs by default.
1035 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1038 Only if you are using a new kernel on an old distribution, you might
1039 need to say Y here. Even then, odds are you would not need it
1040 enabled, you can always pass the boot option if absolutely necessary.
1043 bool "Kernel->user space relay support (formerly relayfs)"
1046 This option enables support for relay interface support in
1047 certain file systems (such as debugfs).
1048 It is designed to provide an efficient mechanism for tools and
1049 facilities to relay large amounts of data from kernel space to
1054 config BLK_DEV_INITRD
1055 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1056 depends on BROKEN || !FRV
1058 The initial RAM filesystem is a ramfs which is loaded by the
1059 boot loader (loadlin or lilo) and that is mounted as root
1060 before the normal boot procedure. It is typically used to
1061 load modules needed to mount the "real" root file system,
1062 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1064 If RAM disk support (BLK_DEV_RAM) is also included, this
1065 also enables initial RAM disk (initrd) support and adds
1066 15 Kbytes (more on some other architectures) to the kernel size.
1072 source "usr/Kconfig"
1077 prompt "Compiler optimization level"
1078 default CC_OPTIMIZE_FOR_PERFORMANCE
1080 config CC_OPTIMIZE_FOR_PERFORMANCE
1081 bool "Optimize for performance"
1083 This is the default optimization level for the kernel, building
1084 with the "-O2" compiler flag for best performance and most
1085 helpful compile-time warnings.
1087 config CC_OPTIMIZE_FOR_SIZE
1088 bool "Optimize for size"
1090 Enabling this option will pass "-Os" instead of "-O2" to
1091 your compiler resulting in a smaller kernel.
1106 config SYSCTL_EXCEPTION_TRACE
1109 Enable support for /proc/sys/debug/exception-trace.
1111 config SYSCTL_ARCH_UNALIGN_NO_WARN
1114 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1115 Allows arch to define/use @no_unaligned_warning to possibly warn
1116 about unaligned access emulation going on under the hood.
1118 config SYSCTL_ARCH_UNALIGN_ALLOW
1121 Enable support for /proc/sys/kernel/unaligned-trap
1122 Allows arches to define/use @unaligned_enabled to runtime toggle
1123 the unaligned access emulation.
1124 see arch/parisc/kernel/unaligned.c for reference
1126 config HAVE_PCSPKR_PLATFORM
1129 # interpreter that classic socket filters depend on
1134 bool "Configure standard kernel features (expert users)"
1135 # Unhide debug options, to make the on-by-default options visible
1138 This option allows certain base kernel options and settings
1139 to be disabled or tweaked. This is for specialized
1140 environments which can tolerate a "non-standard" kernel.
1141 Only use this if you really know what you are doing.
1144 bool "Enable 16-bit UID system calls" if EXPERT
1145 depends on HAVE_UID16 && MULTIUSER
1148 This enables the legacy 16-bit UID syscall wrappers.
1151 bool "Multiple users, groups and capabilities support" if EXPERT
1154 This option enables support for non-root users, groups and
1157 If you say N here, all processes will run with UID 0, GID 0, and all
1158 possible capabilities. Saying N here also compiles out support for
1159 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1162 If unsure, say Y here.
1164 config SGETMASK_SYSCALL
1165 bool "sgetmask/ssetmask syscalls support" if EXPERT
1166 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1168 sys_sgetmask and sys_ssetmask are obsolete system calls
1169 no longer supported in libc but still enabled by default in some
1172 If unsure, leave the default option here.
1174 config SYSFS_SYSCALL
1175 bool "Sysfs syscall support" if EXPERT
1178 sys_sysfs is an obsolete system call no longer supported in libc.
1179 Note that disabling this option is more secure but might break
1180 compatibility with some systems.
1182 If unsure say Y here.
1184 config SYSCTL_SYSCALL
1185 bool "Sysctl syscall support" if EXPERT
1186 depends on PROC_SYSCTL
1190 sys_sysctl uses binary paths that have been found challenging
1191 to properly maintain and use. The interface in /proc/sys
1192 using paths with ascii names is now the primary path to this
1195 Almost nothing using the binary sysctl interface so if you are
1196 trying to save some space it is probably safe to disable this,
1197 making your kernel marginally smaller.
1199 If unsure say N here.
1202 bool "Posix Clocks & timers" if EXPERT
1205 This includes native support for POSIX timers to the kernel.
1206 Some embedded systems have no use for them and therefore they
1207 can be configured out to reduce the size of the kernel image.
1209 When this option is disabled, the following syscalls won't be
1210 available: timer_create, timer_gettime: timer_getoverrun,
1211 timer_settime, timer_delete, clock_adjtime, getitimer,
1212 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1213 clock_getres and clock_nanosleep syscalls will be limited to
1214 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1219 bool "Load all symbols for debugging/ksymoops" if EXPERT
1222 Say Y here to let the kernel print out symbolic crash information and
1223 symbolic stack backtraces. This increases the size of the kernel
1224 somewhat, as all symbols have to be loaded into the kernel image.
1227 bool "Include all symbols in kallsyms"
1228 depends on DEBUG_KERNEL && KALLSYMS
1230 Normally kallsyms only contains the symbols of functions for nicer
1231 OOPS messages and backtraces (i.e., symbols from the text and inittext
1232 sections). This is sufficient for most cases. And only in very rare
1233 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1234 names of variables from the data sections, etc).
1236 This option makes sure that all symbols are loaded into the kernel
1237 image (i.e., symbols from all sections) in cost of increased kernel
1238 size (depending on the kernel configuration, it may be 300KiB or
1239 something like this).
1241 Say N unless you really need all symbols.
1243 config KALLSYMS_ABSOLUTE_PERCPU
1246 default X86_64 && SMP
1248 config KALLSYMS_BASE_RELATIVE
1251 default !IA64 && !(TILE && 64BIT)
1253 Instead of emitting them as absolute values in the native word size,
1254 emit the symbol references in the kallsyms table as 32-bit entries,
1255 each containing a relative value in the range [base, base + U32_MAX]
1256 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1257 an absolute value in the range [0, S32_MAX] or a relative value in the
1258 range [base, base + S32_MAX], where base is the lowest relative symbol
1259 address encountered in the image.
1261 On 64-bit builds, this reduces the size of the address table by 50%,
1262 but more importantly, it results in entries whose values are build
1263 time constants, and no relocation pass is required at runtime to fix
1264 up the entries based on the runtime load address of the kernel.
1268 bool "Enable support for printk" if EXPERT
1271 This option enables normal printk support. Removing it
1272 eliminates most of the message strings from the kernel image
1273 and makes the kernel more or less silent. As this makes it
1274 very difficult to diagnose system problems, saying N here is
1275 strongly discouraged.
1283 bool "BUG() support" if EXPERT
1286 Disabling this option eliminates support for BUG and WARN, reducing
1287 the size of your kernel image and potentially quietly ignoring
1288 numerous fatal conditions. You should only consider disabling this
1289 option for embedded systems with no facilities for reporting errors.
1295 bool "Enable ELF core dumps" if EXPERT
1297 Enable support for generating core dumps. Disabling saves about 4k.
1300 config PCSPKR_PLATFORM
1301 bool "Enable PC-Speaker support" if EXPERT
1302 depends on HAVE_PCSPKR_PLATFORM
1306 This option allows to disable the internal PC-Speaker
1307 support, saving some memory.
1311 bool "Enable full-sized data structures for core" if EXPERT
1313 Disabling this option reduces the size of miscellaneous core
1314 kernel data structures. This saves memory on small machines,
1315 but may reduce performance.
1318 bool "Enable futex support" if EXPERT
1322 Disabling this option will cause the kernel to be built without
1323 support for "fast userspace mutexes". The resulting kernel may not
1324 run glibc-based applications correctly.
1328 depends on FUTEX && RT_MUTEXES
1331 config HAVE_FUTEX_CMPXCHG
1335 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1336 is implemented and always working. This removes a couple of runtime
1340 bool "Enable eventpoll support" if EXPERT
1344 Disabling this option will cause the kernel to be built without
1345 support for epoll family of system calls.
1348 bool "Enable signalfd() system call" if EXPERT
1352 Enable the signalfd() system call that allows to receive signals
1353 on a file descriptor.
1358 bool "Enable timerfd() system call" if EXPERT
1362 Enable the timerfd() system call that allows to receive timer
1363 events on a file descriptor.
1368 bool "Enable eventfd() system call" if EXPERT
1372 Enable the eventfd() system call that allows to receive both
1373 kernel notification (ie. KAIO) or userspace notifications.
1377 # syscall, maps, verifier
1379 bool "Enable bpf() system call"
1384 Enable the bpf() system call that allows to manipulate eBPF
1385 programs and maps via file descriptors.
1387 config BPF_JIT_ALWAYS_ON
1388 bool "Permanently enable BPF JIT and remove BPF interpreter"
1389 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1391 Enables BPF JIT and removes BPF interpreter to avoid
1392 speculative execution of BPF instructions by the interpreter
1395 bool "Use full shmem filesystem" if EXPERT
1399 The shmem is an internal filesystem used to manage shared memory.
1400 It is backed by swap and manages resource limits. It is also exported
1401 to userspace as tmpfs if TMPFS is enabled. Disabling this
1402 option replaces shmem and tmpfs with the much simpler ramfs code,
1403 which may be appropriate on small systems without swap.
1406 bool "Enable AIO support" if EXPERT
1409 This option enables POSIX asynchronous I/O which may by used
1410 by some high performance threaded applications. Disabling
1411 this option saves about 7k.
1413 config ADVISE_SYSCALLS
1414 bool "Enable madvise/fadvise syscalls" if EXPERT
1417 This option enables the madvise and fadvise syscalls, used by
1418 applications to advise the kernel about their future memory or file
1419 usage, improving performance. If building an embedded system where no
1420 applications use these syscalls, you can disable this option to save
1424 bool "Enable userfaultfd() system call"
1428 Enable the userfaultfd() system call that allows to intercept and
1429 handle page faults in userland.
1433 bool "Enable PCI quirk workarounds" if EXPERT
1436 This enables workarounds for various PCI chipset
1437 bugs/quirks. Disable this only if your target machine is
1438 unaffected by PCI quirks.
1441 bool "Enable membarrier() system call" if EXPERT
1444 Enable the membarrier() system call that allows issuing memory
1445 barriers across all running threads, which can be used to distribute
1446 the cost of user-space memory barriers asymmetrically by transforming
1447 pairs of memory barriers into pairs consisting of membarrier() and a
1453 bool "Embedded system"
1454 option allnoconfig_y
1457 This option should be enabled if compiling the kernel for
1458 an embedded system so certain expert options are available
1461 config HAVE_PERF_EVENTS
1464 See tools/perf/design.txt for details.
1466 config PERF_USE_VMALLOC
1469 See tools/perf/design.txt for details
1472 bool "PC/104 support"
1474 Expose PC/104 form factor device drivers and options available for
1475 selection and configuration. Enable this option if your target
1476 machine has a PC/104 bus.
1478 menu "Kernel Performance Events And Counters"
1481 bool "Kernel performance events and counters"
1482 default y if PROFILING
1483 depends on HAVE_PERF_EVENTS
1488 Enable kernel support for various performance events provided
1489 by software and hardware.
1491 Software events are supported either built-in or via the
1492 use of generic tracepoints.
1494 Most modern CPUs support performance events via performance
1495 counter registers. These registers count the number of certain
1496 types of hw events: such as instructions executed, cachemisses
1497 suffered, or branches mis-predicted - without slowing down the
1498 kernel or applications. These registers can also trigger interrupts
1499 when a threshold number of events have passed - and can thus be
1500 used to profile the code that runs on that CPU.
1502 The Linux Performance Event subsystem provides an abstraction of
1503 these software and hardware event capabilities, available via a
1504 system call and used by the "perf" utility in tools/perf/. It
1505 provides per task and per CPU counters, and it provides event
1506 capabilities on top of those.
1510 config DEBUG_PERF_USE_VMALLOC
1512 bool "Debug: use vmalloc to back perf mmap() buffers"
1513 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1514 select PERF_USE_VMALLOC
1516 Use vmalloc memory to back perf mmap() buffers.
1518 Mostly useful for debugging the vmalloc code on platforms
1519 that don't require it.
1525 config VM_EVENT_COUNTERS
1527 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1529 VM event counters are needed for event counts to be shown.
1530 This option allows the disabling of the VM event counters
1531 on EXPERT systems. /proc/vmstat will only show page counts
1532 if VM event counters are disabled.
1536 bool "Enable SLUB debugging support" if EXPERT
1537 depends on SLUB && SYSFS
1539 SLUB has extensive debug support features. Disabling these can
1540 result in significant savings in code size. This also disables
1541 SLUB sysfs support. /sys/slab will not exist and there will be
1542 no support for cache validation etc.
1544 config SLUB_MEMCG_SYSFS_ON
1546 bool "Enable memcg SLUB sysfs support by default" if EXPERT
1547 depends on SLUB && SYSFS && MEMCG
1549 SLUB creates a directory under /sys/kernel/slab for each
1550 allocation cache to host info and debug files. If memory
1551 cgroup is enabled, each cache can have per memory cgroup
1552 caches. SLUB can create the same sysfs directories for these
1553 caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1554 to a very high number of debug files being created. This is
1555 controlled by slub_memcg_sysfs boot parameter and this
1556 config option determines the parameter's default value.
1559 bool "Disable heap randomization"
1562 Randomizing heap placement makes heap exploits harder, but it
1563 also breaks ancient binaries (including anything libc5 based).
1564 This option changes the bootup default to heap randomization
1565 disabled, and can be overridden at runtime by setting
1566 /proc/sys/kernel/randomize_va_space to 2.
1568 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1571 prompt "Choose SLAB allocator"
1574 This option allows to select a slab allocator.
1578 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1580 The regular slab allocator that is established and known to work
1581 well in all environments. It organizes cache hot objects in
1582 per cpu and per node queues.
1585 bool "SLUB (Unqueued Allocator)"
1586 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1588 SLUB is a slab allocator that minimizes cache line usage
1589 instead of managing queues of cached objects (SLAB approach).
1590 Per cpu caching is realized using slabs of objects instead
1591 of queues of objects. SLUB can use memory efficiently
1592 and has enhanced diagnostics. SLUB is the default choice for
1597 bool "SLOB (Simple Allocator)"
1599 SLOB replaces the stock allocator with a drastically simpler
1600 allocator. SLOB is generally more space efficient but
1601 does not perform as well on large systems.
1605 config SLAB_MERGE_DEFAULT
1606 bool "Allow slab caches to be merged"
1609 For reduced kernel memory fragmentation, slab caches can be
1610 merged when they share the same size and other characteristics.
1611 This carries a risk of kernel heap overflows being able to
1612 overwrite objects from merged caches (and more easily control
1613 cache layout), which makes such heap attacks easier to exploit
1614 by attackers. By keeping caches unmerged, these kinds of exploits
1615 can usually only damage objects in the same cache. To disable
1616 merging at runtime, "slab_nomerge" can be passed on the kernel
1619 config SLAB_FREELIST_RANDOM
1621 depends on SLAB || SLUB
1622 bool "SLAB freelist randomization"
1624 Randomizes the freelist order used on creating new pages. This
1625 security feature reduces the predictability of the kernel slab
1626 allocator against heap overflows.
1628 config SLAB_FREELIST_HARDENED
1629 bool "Harden slab freelist metadata"
1632 Many kernel heap attacks try to target slab cache metadata and
1633 other infrastructure. This options makes minor performance
1634 sacrifies to harden the kernel slab allocator against common
1635 freelist exploit methods.
1637 config SLUB_CPU_PARTIAL
1639 depends on SLUB && SMP
1640 bool "SLUB per cpu partial cache"
1642 Per cpu partial caches accellerate objects allocation and freeing
1643 that is local to a processor at the price of more indeterminism
1644 in the latency of the free. On overflow these caches will be cleared
1645 which requires the taking of locks that may cause latency spikes.
1646 Typically one would choose no for a realtime system.
1648 config MMAP_ALLOW_UNINITIALIZED
1649 bool "Allow mmapped anonymous memory to be uninitialized"
1650 depends on EXPERT && !MMU
1653 Normally, and according to the Linux spec, anonymous memory obtained
1654 from mmap() has it's contents cleared before it is passed to
1655 userspace. Enabling this config option allows you to request that
1656 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1657 providing a huge performance boost. If this option is not enabled,
1658 then the flag will be ignored.
1660 This is taken advantage of by uClibc's malloc(), and also by
1661 ELF-FDPIC binfmt's brk and stack allocator.
1663 Because of the obvious security issues, this option should only be
1664 enabled on embedded devices where you control what is run in
1665 userspace. Since that isn't generally a problem on no-MMU systems,
1666 it is normally safe to say Y here.
1668 See Documentation/nommu-mmap.txt for more information.
1670 config SYSTEM_DATA_VERIFICATION
1672 select SYSTEM_TRUSTED_KEYRING
1676 select ASYMMETRIC_KEY_TYPE
1677 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1680 select X509_CERTIFICATE_PARSER
1681 select PKCS7_MESSAGE_PARSER
1683 Provide PKCS#7 message verification using the contents of the system
1684 trusted keyring to provide public keys. This then can be used for
1685 module verification, kexec image verification and firmware blob
1689 bool "Profiling support"
1691 Say Y here to enable the extended profiling support mechanisms used
1692 by profilers such as OProfile.
1695 # Place an empty function call at each tracepoint site. Can be
1696 # dynamically changed for a probe function.
1701 source "arch/Kconfig"
1703 endmenu # General setup
1705 config HAVE_GENERIC_DMA_COHERENT
1712 depends on SLAB || SLUB_DEBUG
1720 default 0 if BASE_FULL
1721 default 1 if !BASE_FULL
1724 bool "Enable loadable module support"
1727 Kernel modules are small pieces of compiled code which can
1728 be inserted in the running kernel, rather than being
1729 permanently built into the kernel. You use the "modprobe"
1730 tool to add (and sometimes remove) them. If you say Y here,
1731 many parts of the kernel can be built as modules (by
1732 answering M instead of Y where indicated): this is most
1733 useful for infrequently used options which are not required
1734 for booting. For more information, see the man pages for
1735 modprobe, lsmod, modinfo, insmod and rmmod.
1737 If you say Y here, you will need to run "make
1738 modules_install" to put the modules under /lib/modules/
1739 where modprobe can find them (you may need to be root to do
1746 config MODULE_FORCE_LOAD
1747 bool "Forced module loading"
1750 Allow loading of modules without version information (ie. modprobe
1751 --force). Forced module loading sets the 'F' (forced) taint flag and
1752 is usually a really bad idea.
1754 config MODULE_UNLOAD
1755 bool "Module unloading"
1757 Without this option you will not be able to unload any
1758 modules (note that some modules may not be unloadable
1759 anyway), which makes your kernel smaller, faster
1760 and simpler. If unsure, say Y.
1762 config MODULE_FORCE_UNLOAD
1763 bool "Forced module unloading"
1764 depends on MODULE_UNLOAD
1766 This option allows you to force a module to unload, even if the
1767 kernel believes it is unsafe: the kernel will remove the module
1768 without waiting for anyone to stop using it (using the -f option to
1769 rmmod). This is mainly for kernel developers and desperate users.
1773 bool "Module versioning support"
1775 Usually, you have to use modules compiled with your kernel.
1776 Saying Y here makes it sometimes possible to use modules
1777 compiled for different kernels, by adding enough information
1778 to the modules to (hopefully) spot any changes which would
1779 make them incompatible with the kernel you are running. If
1782 config MODULE_REL_CRCS
1784 depends on MODVERSIONS
1786 config MODULE_SRCVERSION_ALL
1787 bool "Source checksum for all modules"
1789 Modules which contain a MODULE_VERSION get an extra "srcversion"
1790 field inserted into their modinfo section, which contains a
1791 sum of the source files which made it. This helps maintainers
1792 see exactly which source was used to build a module (since
1793 others sometimes change the module source without updating
1794 the version). With this option, such a "srcversion" field
1795 will be created for all modules. If unsure, say N.
1798 bool "Module signature verification"
1800 select SYSTEM_DATA_VERIFICATION
1802 Check modules for valid signatures upon load: the signature
1803 is simply appended to the module. For more information see
1804 Documentation/module-signing.txt.
1806 Note that this option adds the OpenSSL development packages as a
1807 kernel build dependency so that the signing tool can use its crypto
1810 !!!WARNING!!! If you enable this option, you MUST make sure that the
1811 module DOES NOT get stripped after being signed. This includes the
1812 debuginfo strip done by some packagers (such as rpmbuild) and
1813 inclusion into an initramfs that wants the module size reduced.
1815 config MODULE_SIG_FORCE
1816 bool "Require modules to be validly signed"
1817 depends on MODULE_SIG
1819 Reject unsigned modules or signed modules for which we don't have a
1820 key. Without this, such modules will simply taint the kernel.
1822 config MODULE_SIG_ALL
1823 bool "Automatically sign all modules"
1825 depends on MODULE_SIG
1827 Sign all modules during make modules_install. Without this option,
1828 modules must be signed manually, using the scripts/sign-file tool.
1830 comment "Do not forget to sign required modules with scripts/sign-file"
1831 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1834 prompt "Which hash algorithm should modules be signed with?"
1835 depends on MODULE_SIG
1837 This determines which sort of hashing algorithm will be used during
1838 signature generation. This algorithm _must_ be built into the kernel
1839 directly so that signature verification can take place. It is not
1840 possible to load a signed module containing the algorithm to check
1841 the signature on that module.
1843 config MODULE_SIG_SHA1
1844 bool "Sign modules with SHA-1"
1847 config MODULE_SIG_SHA224
1848 bool "Sign modules with SHA-224"
1849 select CRYPTO_SHA256
1851 config MODULE_SIG_SHA256
1852 bool "Sign modules with SHA-256"
1853 select CRYPTO_SHA256
1855 config MODULE_SIG_SHA384
1856 bool "Sign modules with SHA-384"
1857 select CRYPTO_SHA512
1859 config MODULE_SIG_SHA512
1860 bool "Sign modules with SHA-512"
1861 select CRYPTO_SHA512
1865 config MODULE_SIG_HASH
1867 depends on MODULE_SIG
1868 default "sha1" if MODULE_SIG_SHA1
1869 default "sha224" if MODULE_SIG_SHA224
1870 default "sha256" if MODULE_SIG_SHA256
1871 default "sha384" if MODULE_SIG_SHA384
1872 default "sha512" if MODULE_SIG_SHA512
1874 config MODULE_COMPRESS
1875 bool "Compress modules on installation"
1879 Compresses kernel modules when 'make modules_install' is run; gzip or
1880 xz depending on "Compression algorithm" below.
1882 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
1884 Out-of-tree kernel modules installed using Kbuild will also be
1885 compressed upon installation.
1887 Note: for modules inside an initrd or initramfs, it's more efficient
1888 to compress the whole initrd or initramfs instead.
1890 Note: This is fully compatible with signed modules.
1895 prompt "Compression algorithm"
1896 depends on MODULE_COMPRESS
1897 default MODULE_COMPRESS_GZIP
1899 This determines which sort of compression will be used during
1900 'make modules_install'.
1902 GZIP (default) and XZ are supported.
1904 config MODULE_COMPRESS_GZIP
1907 config MODULE_COMPRESS_XZ
1912 config TRIM_UNUSED_KSYMS
1913 bool "Trim unused exported kernel symbols"
1914 depends on MODULES && !UNUSED_SYMBOLS
1916 The kernel and some modules make many symbols available for
1917 other modules to use via EXPORT_SYMBOL() and variants. Depending
1918 on the set of modules being selected in your kernel configuration,
1919 many of those exported symbols might never be used.
1921 This option allows for unused exported symbols to be dropped from
1922 the build. In turn, this provides the compiler more opportunities
1923 (especially when using LTO) for optimizing the code and reducing
1924 binary size. This might have some security advantages as well.
1926 If unsure, or if you need to build out-of-tree modules, say N.
1930 config MODULES_TREE_LOOKUP
1932 depends on PERF_EVENTS || TRACING
1934 config INIT_ALL_POSSIBLE
1937 Back when each arch used to define their own cpu_online_mask and
1938 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1939 with all 1s, and others with all 0s. When they were centralised,
1940 it was better to provide this option than to break all the archs
1941 and have several arch maintainers pursuing me down dark alleys.
1943 source "block/Kconfig"
1945 config PREEMPT_NOTIFIERS
1955 Build a simple ASN.1 grammar compiler that produces a bytecode output
1956 that can be interpreted by the ASN.1 stream decoder and used to
1957 inform it as to what tags are to be expected in a stream and what
1958 functions to call on what tags.
1960 source "kernel/Kconfig.locks"
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