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 -p $(CC) | sed 's/^0*//') 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))
33 config BUILDTIME_EXTABLE_SORT
36 config THREAD_INFO_IN_TASK
39 Select this to move thread_info off the stack into task_struct. To
40 make this work, an arch will need to remove all thread_info fields
41 except flags and fix any runtime bugs.
43 One subtle change that will be needed is to use try_get_task_stack()
44 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
53 depends on BROKEN || !SMP
56 config INIT_ENV_ARG_LIMIT
61 Maximum of each of the number of arguments and environment
62 variables passed to init from the kernel command line.
65 bool "Compile also drivers which will not load"
69 Some drivers can be compiled on a different platform than they are
70 intended to be run on. Despite they cannot be loaded there (or even
71 when they load they cannot be used due to missing HW support),
72 developers still, opposing to distributors, might want to build such
73 drivers to compile-test them.
75 If you are a developer and want to build everything available, say Y
76 here. If you are a user/distributor, say N here to exclude useless
77 drivers to be distributed.
80 string "Local version - append to kernel release"
82 Append an extra string to the end of your kernel version.
83 This will show up when you type uname, for example.
84 The string you set here will be appended after the contents of
85 any files with a filename matching localversion* in your
86 object and source tree, in that order. Your total string can
87 be a maximum of 64 characters.
89 config LOCALVERSION_AUTO
90 bool "Automatically append version information to the version string"
92 depends on !COMPILE_TEST
94 This will try to automatically determine if the current tree is a
95 release tree by looking for git tags that belong to the current
98 A string of the format -gxxxxxxxx will be added to the localversion
99 if a git-based tree is found. The string generated by this will be
100 appended after any matching localversion* files, and after the value
101 set in CONFIG_LOCALVERSION.
103 (The actual string used here is the first eight characters produced
104 by running the command:
106 $ git rev-parse --verify HEAD
108 which is done within the script "scripts/setlocalversion".)
111 string "Build ID Salt"
114 The build ID is used to link binaries and their debug info. Setting
115 this option will use the value in the calculation of the build id.
116 This is mostly useful for distributions which want to ensure the
117 build is unique between builds. It's safe to leave the default.
119 config HAVE_KERNEL_GZIP
122 config HAVE_KERNEL_BZIP2
125 config HAVE_KERNEL_LZMA
128 config HAVE_KERNEL_XZ
131 config HAVE_KERNEL_LZO
134 config HAVE_KERNEL_LZ4
137 config HAVE_KERNEL_UNCOMPRESSED
141 prompt "Kernel compression mode"
143 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED
145 The linux kernel is a kind of self-extracting executable.
146 Several compression algorithms are available, which differ
147 in efficiency, compression and decompression speed.
148 Compression speed is only relevant when building a kernel.
149 Decompression speed is relevant at each boot.
151 If you have any problems with bzip2 or lzma compressed
152 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
153 version of this functionality (bzip2 only), for 2.4, was
154 supplied by Christian Ludwig)
156 High compression options are mostly useful for users, who
157 are low on disk space (embedded systems), but for whom ram
160 If in doubt, select 'gzip'
164 depends on HAVE_KERNEL_GZIP
166 The old and tried gzip compression. It provides a good balance
167 between compression ratio and decompression speed.
171 depends on HAVE_KERNEL_BZIP2
173 Its compression ratio and speed is intermediate.
174 Decompression speed is slowest among the choices. The kernel
175 size is about 10% smaller with bzip2, in comparison to gzip.
176 Bzip2 uses a large amount of memory. For modern kernels you
177 will need at least 8MB RAM or more for booting.
181 depends on HAVE_KERNEL_LZMA
183 This compression algorithm's ratio is best. Decompression speed
184 is between gzip and bzip2. Compression is slowest.
185 The kernel size is about 33% smaller with LZMA in comparison to gzip.
189 depends on HAVE_KERNEL_XZ
191 XZ uses the LZMA2 algorithm and instruction set specific
192 BCJ filters which can improve compression ratio of executable
193 code. The size of the kernel is about 30% smaller with XZ in
194 comparison to gzip. On architectures for which there is a BCJ
195 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
196 will create a few percent smaller kernel than plain LZMA.
198 The speed is about the same as with LZMA: The decompression
199 speed of XZ is better than that of bzip2 but worse than gzip
200 and LZO. Compression is slow.
204 depends on HAVE_KERNEL_LZO
206 Its compression ratio is the poorest among the choices. The kernel
207 size is about 10% bigger than gzip; however its speed
208 (both compression and decompression) is the fastest.
212 depends on HAVE_KERNEL_LZ4
214 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
215 A preliminary version of LZ4 de/compression tool is available at
216 <https://code.google.com/p/lz4/>.
218 Its compression ratio is worse than LZO. The size of the kernel
219 is about 8% bigger than LZO. But the decompression speed is
222 config KERNEL_UNCOMPRESSED
224 depends on HAVE_KERNEL_UNCOMPRESSED
226 Produce uncompressed kernel image. This option is usually not what
227 you want. It is useful for debugging the kernel in slow simulation
228 environments, where decompressing and moving the kernel is awfully
229 slow. This option allows early boot code to skip the decompressor
230 and jump right at uncompressed kernel image.
234 config DEFAULT_HOSTNAME
235 string "Default hostname"
238 This option determines the default system hostname before userspace
239 calls sethostname(2). The kernel traditionally uses "(none)" here,
240 but you may wish to use a different default here to make a minimal
241 system more usable with less configuration.
244 # For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
245 # add proper SWAP support to them, in which case this can be remove.
251 bool "Support for paging of anonymous memory (swap)"
252 depends on MMU && BLOCK && !ARCH_NO_SWAP
255 This option allows you to choose whether you want to have support
256 for so called swap devices or swap files in your kernel that are
257 used to provide more virtual memory than the actual RAM present
258 in your computer. If unsure say Y.
263 Inter Process Communication is a suite of library functions and
264 system calls which let processes (running programs) synchronize and
265 exchange information. It is generally considered to be a good thing,
266 and some programs won't run unless you say Y here. In particular, if
267 you want to run the DOS emulator dosemu under Linux (read the
268 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
269 you'll need to say Y here.
271 You can find documentation about IPC with "info ipc" and also in
272 section 6.4 of the Linux Programmer's Guide, available from
273 <http://www.tldp.org/guides.html>.
275 config SYSVIPC_SYSCTL
282 bool "POSIX Message Queues"
285 POSIX variant of message queues is a part of IPC. In POSIX message
286 queues every message has a priority which decides about succession
287 of receiving it by a process. If you want to compile and run
288 programs written e.g. for Solaris with use of its POSIX message
289 queues (functions mq_*) say Y here.
291 POSIX message queues are visible as a filesystem called 'mqueue'
292 and can be mounted somewhere if you want to do filesystem
293 operations on message queues.
297 config POSIX_MQUEUE_SYSCTL
299 depends on POSIX_MQUEUE
303 config CROSS_MEMORY_ATTACH
304 bool "Enable process_vm_readv/writev syscalls"
308 Enabling this option adds the system calls process_vm_readv and
309 process_vm_writev which allow a process with the correct privileges
310 to directly read from or write to another process' address space.
311 See the man page for more details.
314 bool "uselib syscall"
315 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
317 This option enables the uselib syscall, a system call used in the
318 dynamic linker from libc5 and earlier. glibc does not use this
319 system call. If you intend to run programs built on libc5 or
320 earlier, you may need to enable this syscall. Current systems
321 running glibc can safely disable this.
324 bool "Auditing support"
327 Enable auditing infrastructure that can be used with another
328 kernel subsystem, such as SELinux (which requires this for
329 logging of avc messages output). System call auditing is included
330 on architectures which support it.
332 config HAVE_ARCH_AUDITSYSCALL
337 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
341 depends on AUDITSYSCALL
346 depends on AUDITSYSCALL
349 source "kernel/irq/Kconfig"
350 source "kernel/time/Kconfig"
351 source "kernel/Kconfig.preempt"
353 menu "CPU/Task time and stats accounting"
355 config VIRT_CPU_ACCOUNTING
359 prompt "Cputime accounting"
360 default TICK_CPU_ACCOUNTING if !PPC64
361 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
363 # Kind of a stub config for the pure tick based cputime accounting
364 config TICK_CPU_ACCOUNTING
365 bool "Simple tick based cputime accounting"
366 depends on !S390 && !NO_HZ_FULL
368 This is the basic tick based cputime accounting that maintains
369 statistics about user, system and idle time spent on per jiffies
374 config VIRT_CPU_ACCOUNTING_NATIVE
375 bool "Deterministic task and CPU time accounting"
376 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
377 select VIRT_CPU_ACCOUNTING
379 Select this option to enable more accurate task and CPU time
380 accounting. This is done by reading a CPU counter on each
381 kernel entry and exit and on transitions within the kernel
382 between system, softirq and hardirq state, so there is a
383 small performance impact. In the case of s390 or IBM POWER > 5,
384 this also enables accounting of stolen time on logically-partitioned
387 config VIRT_CPU_ACCOUNTING_GEN
388 bool "Full dynticks CPU time accounting"
389 depends on HAVE_CONTEXT_TRACKING
390 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
391 select VIRT_CPU_ACCOUNTING
392 select CONTEXT_TRACKING
394 Select this option to enable task and CPU time accounting on full
395 dynticks systems. This accounting is implemented by watching every
396 kernel-user boundaries using the context tracking subsystem.
397 The accounting is thus performed at the expense of some significant
400 For now this is only useful if you are working on the full
401 dynticks subsystem development.
407 config IRQ_TIME_ACCOUNTING
408 bool "Fine granularity task level IRQ time accounting"
409 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
411 Select this option to enable fine granularity task irq time
412 accounting. This is done by reading a timestamp on each
413 transitions between softirq and hardirq state, so there can be a
414 small performance impact.
416 If in doubt, say N here.
418 config BSD_PROCESS_ACCT
419 bool "BSD Process Accounting"
422 If you say Y here, a user level program will be able to instruct the
423 kernel (via a special system call) to write process accounting
424 information to a file: whenever a process exits, information about
425 that process will be appended to the file by the kernel. The
426 information includes things such as creation time, owning user,
427 command name, memory usage, controlling terminal etc. (the complete
428 list is in the struct acct in <file:include/linux/acct.h>). It is
429 up to the user level program to do useful things with this
430 information. This is generally a good idea, so say Y.
432 config BSD_PROCESS_ACCT_V3
433 bool "BSD Process Accounting version 3 file format"
434 depends on BSD_PROCESS_ACCT
437 If you say Y here, the process accounting information is written
438 in a new file format that also logs the process IDs of each
439 process and it's parent. Note that this file format is incompatible
440 with previous v0/v1/v2 file formats, so you will need updated tools
441 for processing it. A preliminary version of these tools is available
442 at <http://www.gnu.org/software/acct/>.
445 bool "Export task/process statistics through netlink"
450 Export selected statistics for tasks/processes through the
451 generic netlink interface. Unlike BSD process accounting, the
452 statistics are available during the lifetime of tasks/processes as
453 responses to commands. Like BSD accounting, they are sent to user
458 config TASK_DELAY_ACCT
459 bool "Enable per-task delay accounting"
463 Collect information on time spent by a task waiting for system
464 resources like cpu, synchronous block I/O completion and swapping
465 in pages. Such statistics can help in setting a task's priorities
466 relative to other tasks for cpu, io, rss limits etc.
471 bool "Enable extended accounting over taskstats"
474 Collect extended task accounting data and send the data
475 to userland for processing over the taskstats interface.
479 config TASK_IO_ACCOUNTING
480 bool "Enable per-task storage I/O accounting"
481 depends on TASK_XACCT
483 Collect information on the number of bytes of storage I/O which this
488 endmenu # "CPU/Task time and stats accounting"
492 depends on SMP || COMPILE_TEST
495 Make sure that CPUs running critical tasks are not disturbed by
496 any source of "noise" such as unbound workqueues, timers, kthreads...
497 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
498 the "isolcpus=" boot parameter.
502 source "kernel/rcu/Kconfig"
509 tristate "Kernel .config support"
512 This option enables the complete Linux kernel ".config" file
513 contents to be saved in the kernel. It provides documentation
514 of which kernel options are used in a running kernel or in an
515 on-disk kernel. This information can be extracted from the kernel
516 image file with the script scripts/extract-ikconfig and used as
517 input to rebuild the current kernel or to build another kernel.
518 It can also be extracted from a running kernel by reading
519 /proc/config.gz if enabled (below).
522 bool "Enable access to .config through /proc/config.gz"
523 depends on IKCONFIG && PROC_FS
525 This option enables access to the kernel configuration file
526 through /proc/config.gz.
529 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
534 Select the minimal kernel log buffer size as a power of 2.
535 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
536 parameter, see below. Any higher size also might be forced
537 by "log_buf_len" boot parameter.
547 config LOG_CPU_MAX_BUF_SHIFT
548 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
551 default 12 if !BASE_SMALL
552 default 0 if BASE_SMALL
555 This option allows to increase the default ring buffer size
556 according to the number of CPUs. The value defines the contribution
557 of each CPU as a power of 2. The used space is typically only few
558 lines however it might be much more when problems are reported,
561 The increased size means that a new buffer has to be allocated and
562 the original static one is unused. It makes sense only on systems
563 with more CPUs. Therefore this value is used only when the sum of
564 contributions is greater than the half of the default kernel ring
565 buffer as defined by LOG_BUF_SHIFT. The default values are set
566 so that more than 64 CPUs are needed to trigger the allocation.
568 Also this option is ignored when "log_buf_len" kernel parameter is
569 used as it forces an exact (power of two) size of the ring buffer.
571 The number of possible CPUs is used for this computation ignoring
572 hotplugging making the computation optimal for the worst case
573 scenario while allowing a simple algorithm to be used from bootup.
575 Examples shift values and their meaning:
576 17 => 128 KB for each CPU
577 16 => 64 KB for each CPU
578 15 => 32 KB for each CPU
579 14 => 16 KB for each CPU
580 13 => 8 KB for each CPU
581 12 => 4 KB for each CPU
583 config PRINTK_SAFE_LOG_BUF_SHIFT
584 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
589 Select the size of an alternate printk per-CPU buffer where messages
590 printed from usafe contexts are temporary stored. One example would
591 be NMI messages, another one - printk recursion. The messages are
592 copied to the main log buffer in a safe context to avoid a deadlock.
593 The value defines the size as a power of 2.
595 Those messages are rare and limited. The largest one is when
596 a backtrace is printed. It usually fits into 4KB. Select
597 8KB if you want to be on the safe side.
600 17 => 128 KB for each CPU
601 16 => 64 KB for each CPU
602 15 => 32 KB for each CPU
603 14 => 16 KB for each CPU
604 13 => 8 KB for each CPU
605 12 => 4 KB for each CPU
608 # Architectures with an unreliable sched_clock() should select this:
610 config HAVE_UNSTABLE_SCHED_CLOCK
613 config GENERIC_SCHED_CLOCK
617 # For architectures that want to enable the support for NUMA-affine scheduler
620 config ARCH_SUPPORTS_NUMA_BALANCING
624 # For architectures that prefer to flush all TLBs after a number of pages
625 # are unmapped instead of sending one IPI per page to flush. The architecture
626 # must provide guarantees on what happens if a clean TLB cache entry is
627 # written after the unmap. Details are in mm/rmap.c near the check for
628 # should_defer_flush. The architecture should also consider if the full flush
629 # and the refill costs are offset by the savings of sending fewer IPIs.
630 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
634 # For architectures that know their GCC __int128 support is sound
636 config ARCH_SUPPORTS_INT128
639 # For architectures that (ab)use NUMA to represent different memory regions
640 # all cpu-local but of different latencies, such as SuperH.
642 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
645 config NUMA_BALANCING
646 bool "Memory placement aware NUMA scheduler"
647 depends on ARCH_SUPPORTS_NUMA_BALANCING
648 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
649 depends on SMP && NUMA && MIGRATION
651 This option adds support for automatic NUMA aware memory/task placement.
652 The mechanism is quite primitive and is based on migrating memory when
653 it has references to the node the task is running on.
655 This system will be inactive on UMA systems.
657 config NUMA_BALANCING_DEFAULT_ENABLED
658 bool "Automatically enable NUMA aware memory/task placement"
660 depends on NUMA_BALANCING
662 If set, automatic NUMA balancing will be enabled if running on a NUMA
666 bool "Control Group support"
669 This option adds support for grouping sets of processes together, for
670 use with process control subsystems such as Cpusets, CFS, memory
671 controls or device isolation.
673 - Documentation/scheduler/sched-design-CFS.txt (CFS)
674 - Documentation/cgroup-v1/ (features for grouping, isolation
675 and resource control)
685 bool "Memory controller"
689 Provides control over the memory footprint of tasks in a cgroup.
692 bool "Swap controller"
693 depends on MEMCG && SWAP
695 Provides control over the swap space consumed by tasks in a cgroup.
697 config MEMCG_SWAP_ENABLED
698 bool "Swap controller enabled by default"
699 depends on MEMCG_SWAP
702 Memory Resource Controller Swap Extension comes with its price in
703 a bigger memory consumption. General purpose distribution kernels
704 which want to enable the feature but keep it disabled by default
705 and let the user enable it by swapaccount=1 boot command line
706 parameter should have this option unselected.
707 For those who want to have the feature enabled by default should
708 select this option (if, for some reason, they need to disable it
709 then swapaccount=0 does the trick).
716 Generic block IO controller cgroup interface. This is the common
717 cgroup interface which should be used by various IO controlling
720 Currently, CFQ IO scheduler uses it to recognize task groups and
721 control disk bandwidth allocation (proportional time slice allocation)
722 to such task groups. It is also used by bio throttling logic in
723 block layer to implement upper limit in IO rates on a device.
725 This option only enables generic Block IO controller infrastructure.
726 One needs to also enable actual IO controlling logic/policy. For
727 enabling proportional weight division of disk bandwidth in CFQ, set
728 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
729 CONFIG_BLK_DEV_THROTTLING=y.
731 See Documentation/cgroup-v1/blkio-controller.txt for more information.
733 config DEBUG_BLK_CGROUP
734 bool "IO controller debugging"
735 depends on BLK_CGROUP
738 Enable some debugging help. Currently it exports additional stat
739 files in a cgroup which can be useful for debugging.
741 config CGROUP_WRITEBACK
743 depends on MEMCG && BLK_CGROUP
746 menuconfig CGROUP_SCHED
747 bool "CPU controller"
750 This feature lets CPU scheduler recognize task groups and control CPU
751 bandwidth allocation to such task groups. It uses cgroups to group
755 config FAIR_GROUP_SCHED
756 bool "Group scheduling for SCHED_OTHER"
757 depends on CGROUP_SCHED
761 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
762 depends on FAIR_GROUP_SCHED
765 This option allows users to define CPU bandwidth rates (limits) for
766 tasks running within the fair group scheduler. Groups with no limit
767 set are considered to be unconstrained and will run with no
769 See Documentation/scheduler/sched-bwc.txt for more information.
771 config RT_GROUP_SCHED
772 bool "Group scheduling for SCHED_RR/FIFO"
773 depends on CGROUP_SCHED
776 This feature lets you explicitly allocate real CPU bandwidth
777 to task groups. If enabled, it will also make it impossible to
778 schedule realtime tasks for non-root users until you allocate
779 realtime bandwidth for them.
780 See Documentation/scheduler/sched-rt-group.txt for more information.
785 bool "PIDs controller"
787 Provides enforcement of process number limits in the scope of a
788 cgroup. Any attempt to fork more processes than is allowed in the
789 cgroup will fail. PIDs are fundamentally a global resource because it
790 is fairly trivial to reach PID exhaustion before you reach even a
791 conservative kmemcg limit. As a result, it is possible to grind a
792 system to halt without being limited by other cgroup policies. The
793 PIDs controller is designed to stop this from happening.
795 It should be noted that organisational operations (such as attaching
796 to a cgroup hierarchy will *not* be blocked by the PIDs controller),
797 since the PIDs limit only affects a process's ability to fork, not to
801 bool "RDMA controller"
803 Provides enforcement of RDMA resources defined by IB stack.
804 It is fairly easy for consumers to exhaust RDMA resources, which
805 can result into resource unavailability to other consumers.
806 RDMA controller is designed to stop this from happening.
807 Attaching processes with active RDMA resources to the cgroup
808 hierarchy is allowed even if can cross the hierarchy's limit.
810 config CGROUP_FREEZER
811 bool "Freezer controller"
813 Provides a way to freeze and unfreeze all tasks in a
816 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
817 controller includes important in-kernel memory consumers per default.
819 If you're using cgroup2, say N.
821 config CGROUP_HUGETLB
822 bool "HugeTLB controller"
823 depends on HUGETLB_PAGE
827 Provides a cgroup controller for HugeTLB pages.
828 When you enable this, you can put a per cgroup limit on HugeTLB usage.
829 The limit is enforced during page fault. Since HugeTLB doesn't
830 support page reclaim, enforcing the limit at page fault time implies
831 that, the application will get SIGBUS signal if it tries to access
832 HugeTLB pages beyond its limit. This requires the application to know
833 beforehand how much HugeTLB pages it would require for its use. The
834 control group is tracked in the third page lru pointer. This means
835 that we cannot use the controller with huge page less than 3 pages.
838 bool "Cpuset controller"
841 This option will let you create and manage CPUSETs which
842 allow dynamically partitioning a system into sets of CPUs and
843 Memory Nodes and assigning tasks to run only within those sets.
844 This is primarily useful on large SMP or NUMA systems.
848 config PROC_PID_CPUSET
849 bool "Include legacy /proc/<pid>/cpuset file"
854 bool "Device controller"
856 Provides a cgroup controller implementing whitelists for
857 devices which a process in the cgroup can mknod or open.
859 config CGROUP_CPUACCT
860 bool "Simple CPU accounting controller"
862 Provides a simple controller for monitoring the
863 total CPU consumed by the tasks in a cgroup.
866 bool "Perf controller"
867 depends on PERF_EVENTS
869 This option extends the perf per-cpu mode to restrict monitoring
870 to threads which belong to the cgroup specified and run on the
876 bool "Support for eBPF programs attached to cgroups"
877 depends on BPF_SYSCALL
878 select SOCK_CGROUP_DATA
880 Allow attaching eBPF programs to a cgroup using the bpf(2)
881 syscall command BPF_PROG_ATTACH.
883 In which context these programs are accessed depends on the type
884 of attachment. For instance, programs that are attached using
885 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
889 bool "Debug controller"
891 depends on DEBUG_KERNEL
893 This option enables a simple controller that exports
894 debugging information about the cgroups framework. This
895 controller is for control cgroup debugging only. Its
896 interfaces are not stable.
900 config SOCK_CGROUP_DATA
906 menuconfig NAMESPACES
907 bool "Namespaces support" if EXPERT
911 Provides the way to make tasks work with different objects using
912 the same id. For example same IPC id may refer to different objects
913 or same user id or pid may refer to different tasks when used in
914 different namespaces.
922 In this namespace tasks see different info provided with the
927 depends on (SYSVIPC || POSIX_MQUEUE)
930 In this namespace tasks work with IPC ids which correspond to
931 different IPC objects in different namespaces.
934 bool "User namespace"
937 This allows containers, i.e. vservers, to use user namespaces
938 to provide different user info for different servers.
940 When user namespaces are enabled in the kernel it is
941 recommended that the MEMCG option also be enabled and that
942 user-space use the memory control groups to limit the amount
943 of memory a memory unprivileged users can use.
948 bool "PID Namespaces"
951 Support process id namespaces. This allows having multiple
952 processes with the same pid as long as they are in different
953 pid namespaces. This is a building block of containers.
956 bool "Network namespace"
960 Allow user space to create what appear to be multiple instances
961 of the network stack.
965 config SCHED_AUTOGROUP
966 bool "Automatic process group scheduling"
969 select FAIR_GROUP_SCHED
971 This option optimizes the scheduler for common desktop workloads by
972 automatically creating and populating task groups. This separation
973 of workloads isolates aggressive CPU burners (like build jobs) from
974 desktop applications. Task group autogeneration is currently based
977 config SYSFS_DEPRECATED
978 bool "Enable deprecated sysfs features to support old userspace tools"
982 This option adds code that switches the layout of the "block" class
983 devices, to not show up in /sys/class/block/, but only in
986 This switch is only active when the sysfs.deprecated=1 boot option is
987 passed or the SYSFS_DEPRECATED_V2 option is set.
989 This option allows new kernels to run on old distributions and tools,
990 which might get confused by /sys/class/block/. Since 2007/2008 all
991 major distributions and tools handle this just fine.
993 Recent distributions and userspace tools after 2009/2010 depend on
994 the existence of /sys/class/block/, and will not work with this
997 Only if you are using a new kernel on an old distribution, you might
1000 config SYSFS_DEPRECATED_V2
1001 bool "Enable deprecated sysfs features by default"
1004 depends on SYSFS_DEPRECATED
1006 Enable deprecated sysfs by default.
1008 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1011 Only if you are using a new kernel on an old distribution, you might
1012 need to say Y here. Even then, odds are you would not need it
1013 enabled, you can always pass the boot option if absolutely necessary.
1016 bool "Kernel->user space relay support (formerly relayfs)"
1019 This option enables support for relay interface support in
1020 certain file systems (such as debugfs).
1021 It is designed to provide an efficient mechanism for tools and
1022 facilities to relay large amounts of data from kernel space to
1027 config BLK_DEV_INITRD
1028 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1030 The initial RAM filesystem is a ramfs which is loaded by the
1031 boot loader (loadlin or lilo) and that is mounted as root
1032 before the normal boot procedure. It is typically used to
1033 load modules needed to mount the "real" root file system,
1034 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1036 If RAM disk support (BLK_DEV_RAM) is also included, this
1037 also enables initial RAM disk (initrd) support and adds
1038 15 Kbytes (more on some other architectures) to the kernel size.
1044 source "usr/Kconfig"
1049 prompt "Compiler optimization level"
1050 default CC_OPTIMIZE_FOR_PERFORMANCE
1052 config CC_OPTIMIZE_FOR_PERFORMANCE
1053 bool "Optimize for performance"
1055 This is the default optimization level for the kernel, building
1056 with the "-O2" compiler flag for best performance and most
1057 helpful compile-time warnings.
1059 config CC_OPTIMIZE_FOR_SIZE
1060 bool "Optimize for size"
1062 Enabling this option will pass "-Os" instead of "-O2" to
1063 your compiler resulting in a smaller kernel.
1069 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1072 This requires that the arch annotates or otherwise protects
1073 its external entry points from being discarded. Linker scripts
1074 must also merge .text.*, .data.*, and .bss.* correctly into
1075 output sections. Care must be taken not to pull in unrelated
1076 sections (e.g., '.text.init'). Typically '.' in section names
1077 is used to distinguish them from label names / C identifiers.
1079 config LD_DEAD_CODE_DATA_ELIMINATION
1080 bool "Dead code and data elimination (EXPERIMENTAL)"
1081 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1084 Enable this if you want to do dead code and data elimination with
1085 the linker by compiling with -ffunction-sections -fdata-sections,
1086 and linking with --gc-sections.
1088 This can reduce on disk and in-memory size of the kernel
1089 code and static data, particularly for small configs and
1090 on small systems. This has the possibility of introducing
1091 silently broken kernel if the required annotations are not
1092 present. This option is not well tested yet, so use at your
1104 config SYSCTL_EXCEPTION_TRACE
1107 Enable support for /proc/sys/debug/exception-trace.
1109 config SYSCTL_ARCH_UNALIGN_NO_WARN
1112 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1113 Allows arch to define/use @no_unaligned_warning to possibly warn
1114 about unaligned access emulation going on under the hood.
1116 config SYSCTL_ARCH_UNALIGN_ALLOW
1119 Enable support for /proc/sys/kernel/unaligned-trap
1120 Allows arches to define/use @unaligned_enabled to runtime toggle
1121 the unaligned access emulation.
1122 see arch/parisc/kernel/unaligned.c for reference
1124 config HAVE_PCSPKR_PLATFORM
1127 # interpreter that classic socket filters depend on
1132 bool "Configure standard kernel features (expert users)"
1133 # Unhide debug options, to make the on-by-default options visible
1136 This option allows certain base kernel options and settings
1137 to be disabled or tweaked. This is for specialized
1138 environments which can tolerate a "non-standard" kernel.
1139 Only use this if you really know what you are doing.
1142 bool "Enable 16-bit UID system calls" if EXPERT
1143 depends on HAVE_UID16 && MULTIUSER
1146 This enables the legacy 16-bit UID syscall wrappers.
1149 bool "Multiple users, groups and capabilities support" if EXPERT
1152 This option enables support for non-root users, groups and
1155 If you say N here, all processes will run with UID 0, GID 0, and all
1156 possible capabilities. Saying N here also compiles out support for
1157 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1160 If unsure, say Y here.
1162 config SGETMASK_SYSCALL
1163 bool "sgetmask/ssetmask syscalls support" if EXPERT
1164 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1166 sys_sgetmask and sys_ssetmask are obsolete system calls
1167 no longer supported in libc but still enabled by default in some
1170 If unsure, leave the default option here.
1172 config SYSFS_SYSCALL
1173 bool "Sysfs syscall support" if EXPERT
1176 sys_sysfs is an obsolete system call no longer supported in libc.
1177 Note that disabling this option is more secure but might break
1178 compatibility with some systems.
1180 If unsure say Y here.
1182 config SYSCTL_SYSCALL
1183 bool "Sysctl syscall support" if EXPERT
1184 depends on PROC_SYSCTL
1188 sys_sysctl uses binary paths that have been found challenging
1189 to properly maintain and use. The interface in /proc/sys
1190 using paths with ascii names is now the primary path to this
1193 Almost nothing using the binary sysctl interface so if you are
1194 trying to save some space it is probably safe to disable this,
1195 making your kernel marginally smaller.
1197 If unsure say N here.
1200 bool "open by fhandle syscalls" if EXPERT
1204 If you say Y here, a user level program will be able to map
1205 file names to handle and then later use the handle for
1206 different file system operations. This is useful in implementing
1207 userspace file servers, which now track files using handles instead
1208 of names. The handle would remain the same even if file names
1209 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1213 bool "Posix Clocks & timers" if EXPERT
1216 This includes native support for POSIX timers to the kernel.
1217 Some embedded systems have no use for them and therefore they
1218 can be configured out to reduce the size of the kernel image.
1220 When this option is disabled, the following syscalls won't be
1221 available: timer_create, timer_gettime: timer_getoverrun,
1222 timer_settime, timer_delete, clock_adjtime, getitimer,
1223 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1224 clock_getres and clock_nanosleep syscalls will be limited to
1225 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1231 bool "Enable support for printk" if EXPERT
1234 This option enables normal printk support. Removing it
1235 eliminates most of the message strings from the kernel image
1236 and makes the kernel more or less silent. As this makes it
1237 very difficult to diagnose system problems, saying N here is
1238 strongly discouraged.
1246 bool "BUG() support" if EXPERT
1249 Disabling this option eliminates support for BUG and WARN, reducing
1250 the size of your kernel image and potentially quietly ignoring
1251 numerous fatal conditions. You should only consider disabling this
1252 option for embedded systems with no facilities for reporting errors.
1258 bool "Enable ELF core dumps" if EXPERT
1260 Enable support for generating core dumps. Disabling saves about 4k.
1263 config PCSPKR_PLATFORM
1264 bool "Enable PC-Speaker support" if EXPERT
1265 depends on HAVE_PCSPKR_PLATFORM
1269 This option allows to disable the internal PC-Speaker
1270 support, saving some memory.
1274 bool "Enable full-sized data structures for core" if EXPERT
1276 Disabling this option reduces the size of miscellaneous core
1277 kernel data structures. This saves memory on small machines,
1278 but may reduce performance.
1281 bool "Enable futex support" if EXPERT
1285 Disabling this option will cause the kernel to be built without
1286 support for "fast userspace mutexes". The resulting kernel may not
1287 run glibc-based applications correctly.
1291 depends on FUTEX && RT_MUTEXES
1294 config HAVE_FUTEX_CMPXCHG
1298 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1299 is implemented and always working. This removes a couple of runtime
1303 bool "Enable eventpoll support" if EXPERT
1307 Disabling this option will cause the kernel to be built without
1308 support for epoll family of system calls.
1311 bool "Enable signalfd() system call" if EXPERT
1315 Enable the signalfd() system call that allows to receive signals
1316 on a file descriptor.
1321 bool "Enable timerfd() system call" if EXPERT
1325 Enable the timerfd() system call that allows to receive timer
1326 events on a file descriptor.
1331 bool "Enable eventfd() system call" if EXPERT
1335 Enable the eventfd() system call that allows to receive both
1336 kernel notification (ie. KAIO) or userspace notifications.
1341 bool "Use full shmem filesystem" if EXPERT
1345 The shmem is an internal filesystem used to manage shared memory.
1346 It is backed by swap and manages resource limits. It is also exported
1347 to userspace as tmpfs if TMPFS is enabled. Disabling this
1348 option replaces shmem and tmpfs with the much simpler ramfs code,
1349 which may be appropriate on small systems without swap.
1352 bool "Enable AIO support" if EXPERT
1355 This option enables POSIX asynchronous I/O which may by used
1356 by some high performance threaded applications. Disabling
1357 this option saves about 7k.
1359 config ADVISE_SYSCALLS
1360 bool "Enable madvise/fadvise syscalls" if EXPERT
1363 This option enables the madvise and fadvise syscalls, used by
1364 applications to advise the kernel about their future memory or file
1365 usage, improving performance. If building an embedded system where no
1366 applications use these syscalls, you can disable this option to save
1370 bool "Enable membarrier() system call" if EXPERT
1373 Enable the membarrier() system call that allows issuing memory
1374 barriers across all running threads, which can be used to distribute
1375 the cost of user-space memory barriers asymmetrically by transforming
1376 pairs of memory barriers into pairs consisting of membarrier() and a
1381 config CHECKPOINT_RESTORE
1382 bool "Checkpoint/restore support" if EXPERT
1383 select PROC_CHILDREN
1386 Enables additional kernel features in a sake of checkpoint/restore.
1387 In particular it adds auxiliary prctl codes to setup process text,
1388 data and heap segment sizes, and a few additional /proc filesystem
1391 If unsure, say N here.
1394 bool "Load all symbols for debugging/ksymoops" if EXPERT
1397 Say Y here to let the kernel print out symbolic crash information and
1398 symbolic stack backtraces. This increases the size of the kernel
1399 somewhat, as all symbols have to be loaded into the kernel image.
1402 bool "Include all symbols in kallsyms"
1403 depends on DEBUG_KERNEL && KALLSYMS
1405 Normally kallsyms only contains the symbols of functions for nicer
1406 OOPS messages and backtraces (i.e., symbols from the text and inittext
1407 sections). This is sufficient for most cases. And only in very rare
1408 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1409 names of variables from the data sections, etc).
1411 This option makes sure that all symbols are loaded into the kernel
1412 image (i.e., symbols from all sections) in cost of increased kernel
1413 size (depending on the kernel configuration, it may be 300KiB or
1414 something like this).
1416 Say N unless you really need all symbols.
1418 config KALLSYMS_ABSOLUTE_PERCPU
1421 default X86_64 && SMP
1423 config KALLSYMS_BASE_RELATIVE
1428 Instead of emitting them as absolute values in the native word size,
1429 emit the symbol references in the kallsyms table as 32-bit entries,
1430 each containing a relative value in the range [base, base + U32_MAX]
1431 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1432 an absolute value in the range [0, S32_MAX] or a relative value in the
1433 range [base, base + S32_MAX], where base is the lowest relative symbol
1434 address encountered in the image.
1436 On 64-bit builds, this reduces the size of the address table by 50%,
1437 but more importantly, it results in entries whose values are build
1438 time constants, and no relocation pass is required at runtime to fix
1439 up the entries based on the runtime load address of the kernel.
1441 # end of the "standard kernel features (expert users)" menu
1443 # syscall, maps, verifier
1445 bool "Enable bpf() system call"
1451 Enable the bpf() system call that allows to manipulate eBPF
1452 programs and maps via file descriptors.
1454 config BPF_JIT_ALWAYS_ON
1455 bool "Permanently enable BPF JIT and remove BPF interpreter"
1456 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1458 Enables BPF JIT and removes BPF interpreter to avoid
1459 speculative execution of BPF instructions by the interpreter
1462 bool "Enable userfaultfd() system call"
1466 Enable the userfaultfd() system call that allows to intercept and
1467 handle page faults in userland.
1469 config ARCH_HAS_MEMBARRIER_CALLBACKS
1472 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1476 bool "Enable rseq() system call" if EXPERT
1478 depends on HAVE_RSEQ
1481 Enable the restartable sequences system call. It provides a
1482 user-space cache for the current CPU number value, which
1483 speeds up getting the current CPU number from user-space,
1484 as well as an ABI to speed up user-space operations on
1491 bool "Enabled debugging of rseq() system call" if EXPERT
1492 depends on RSEQ && DEBUG_KERNEL
1494 Enable extra debugging checks for the rseq system call.
1499 bool "Embedded system"
1500 option allnoconfig_y
1503 This option should be enabled if compiling the kernel for
1504 an embedded system so certain expert options are available
1507 config HAVE_PERF_EVENTS
1510 See tools/perf/design.txt for details.
1512 config PERF_USE_VMALLOC
1515 See tools/perf/design.txt for details
1518 bool "PC/104 support" if EXPERT
1520 Expose PC/104 form factor device drivers and options available for
1521 selection and configuration. Enable this option if your target
1522 machine has a PC/104 bus.
1524 menu "Kernel Performance Events And Counters"
1527 bool "Kernel performance events and counters"
1528 default y if PROFILING
1529 depends on HAVE_PERF_EVENTS
1534 Enable kernel support for various performance events provided
1535 by software and hardware.
1537 Software events are supported either built-in or via the
1538 use of generic tracepoints.
1540 Most modern CPUs support performance events via performance
1541 counter registers. These registers count the number of certain
1542 types of hw events: such as instructions executed, cachemisses
1543 suffered, or branches mis-predicted - without slowing down the
1544 kernel or applications. These registers can also trigger interrupts
1545 when a threshold number of events have passed - and can thus be
1546 used to profile the code that runs on that CPU.
1548 The Linux Performance Event subsystem provides an abstraction of
1549 these software and hardware event capabilities, available via a
1550 system call and used by the "perf" utility in tools/perf/. It
1551 provides per task and per CPU counters, and it provides event
1552 capabilities on top of those.
1556 config DEBUG_PERF_USE_VMALLOC
1558 bool "Debug: use vmalloc to back perf mmap() buffers"
1559 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1560 select PERF_USE_VMALLOC
1562 Use vmalloc memory to back perf mmap() buffers.
1564 Mostly useful for debugging the vmalloc code on platforms
1565 that don't require it.
1571 config VM_EVENT_COUNTERS
1573 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1575 VM event counters are needed for event counts to be shown.
1576 This option allows the disabling of the VM event counters
1577 on EXPERT systems. /proc/vmstat will only show page counts
1578 if VM event counters are disabled.
1582 bool "Enable SLUB debugging support" if EXPERT
1583 depends on SLUB && SYSFS
1585 SLUB has extensive debug support features. Disabling these can
1586 result in significant savings in code size. This also disables
1587 SLUB sysfs support. /sys/slab will not exist and there will be
1588 no support for cache validation etc.
1590 config SLUB_MEMCG_SYSFS_ON
1592 bool "Enable memcg SLUB sysfs support by default" if EXPERT
1593 depends on SLUB && SYSFS && MEMCG
1595 SLUB creates a directory under /sys/kernel/slab for each
1596 allocation cache to host info and debug files. If memory
1597 cgroup is enabled, each cache can have per memory cgroup
1598 caches. SLUB can create the same sysfs directories for these
1599 caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1600 to a very high number of debug files being created. This is
1601 controlled by slub_memcg_sysfs boot parameter and this
1602 config option determines the parameter's default value.
1605 bool "Disable heap randomization"
1608 Randomizing heap placement makes heap exploits harder, but it
1609 also breaks ancient binaries (including anything libc5 based).
1610 This option changes the bootup default to heap randomization
1611 disabled, and can be overridden at runtime by setting
1612 /proc/sys/kernel/randomize_va_space to 2.
1614 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1617 prompt "Choose SLAB allocator"
1620 This option allows to select a slab allocator.
1624 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1626 The regular slab allocator that is established and known to work
1627 well in all environments. It organizes cache hot objects in
1628 per cpu and per node queues.
1631 bool "SLUB (Unqueued Allocator)"
1632 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1634 SLUB is a slab allocator that minimizes cache line usage
1635 instead of managing queues of cached objects (SLAB approach).
1636 Per cpu caching is realized using slabs of objects instead
1637 of queues of objects. SLUB can use memory efficiently
1638 and has enhanced diagnostics. SLUB is the default choice for
1643 bool "SLOB (Simple Allocator)"
1645 SLOB replaces the stock allocator with a drastically simpler
1646 allocator. SLOB is generally more space efficient but
1647 does not perform as well on large systems.
1651 config SLAB_MERGE_DEFAULT
1652 bool "Allow slab caches to be merged"
1655 For reduced kernel memory fragmentation, slab caches can be
1656 merged when they share the same size and other characteristics.
1657 This carries a risk of kernel heap overflows being able to
1658 overwrite objects from merged caches (and more easily control
1659 cache layout), which makes such heap attacks easier to exploit
1660 by attackers. By keeping caches unmerged, these kinds of exploits
1661 can usually only damage objects in the same cache. To disable
1662 merging at runtime, "slab_nomerge" can be passed on the kernel
1665 config SLAB_FREELIST_RANDOM
1667 depends on SLAB || SLUB
1668 bool "SLAB freelist randomization"
1670 Randomizes the freelist order used on creating new pages. This
1671 security feature reduces the predictability of the kernel slab
1672 allocator against heap overflows.
1674 config SLAB_FREELIST_HARDENED
1675 bool "Harden slab freelist metadata"
1678 Many kernel heap attacks try to target slab cache metadata and
1679 other infrastructure. This options makes minor performance
1680 sacrifies to harden the kernel slab allocator against common
1681 freelist exploit methods.
1683 config SLUB_CPU_PARTIAL
1685 depends on SLUB && SMP
1686 bool "SLUB per cpu partial cache"
1688 Per cpu partial caches accellerate objects allocation and freeing
1689 that is local to a processor at the price of more indeterminism
1690 in the latency of the free. On overflow these caches will be cleared
1691 which requires the taking of locks that may cause latency spikes.
1692 Typically one would choose no for a realtime system.
1694 config MMAP_ALLOW_UNINITIALIZED
1695 bool "Allow mmapped anonymous memory to be uninitialized"
1696 depends on EXPERT && !MMU
1699 Normally, and according to the Linux spec, anonymous memory obtained
1700 from mmap() has it's contents cleared before it is passed to
1701 userspace. Enabling this config option allows you to request that
1702 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1703 providing a huge performance boost. If this option is not enabled,
1704 then the flag will be ignored.
1706 This is taken advantage of by uClibc's malloc(), and also by
1707 ELF-FDPIC binfmt's brk and stack allocator.
1709 Because of the obvious security issues, this option should only be
1710 enabled on embedded devices where you control what is run in
1711 userspace. Since that isn't generally a problem on no-MMU systems,
1712 it is normally safe to say Y here.
1714 See Documentation/nommu-mmap.txt for more information.
1716 config SYSTEM_DATA_VERIFICATION
1718 select SYSTEM_TRUSTED_KEYRING
1722 select ASYMMETRIC_KEY_TYPE
1723 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1726 select X509_CERTIFICATE_PARSER
1727 select PKCS7_MESSAGE_PARSER
1729 Provide PKCS#7 message verification using the contents of the system
1730 trusted keyring to provide public keys. This then can be used for
1731 module verification, kexec image verification and firmware blob
1735 bool "Profiling support"
1737 Say Y here to enable the extended profiling support mechanisms used
1738 by profilers such as OProfile.
1741 # Place an empty function call at each tracepoint site. Can be
1742 # dynamically changed for a probe function.
1747 endmenu # General setup
1749 source "arch/Kconfig"
1756 default 0 if BASE_FULL
1757 default 1 if !BASE_FULL
1760 bool "Enable loadable module support"
1763 Kernel modules are small pieces of compiled code which can
1764 be inserted in the running kernel, rather than being
1765 permanently built into the kernel. You use the "modprobe"
1766 tool to add (and sometimes remove) them. If you say Y here,
1767 many parts of the kernel can be built as modules (by
1768 answering M instead of Y where indicated): this is most
1769 useful for infrequently used options which are not required
1770 for booting. For more information, see the man pages for
1771 modprobe, lsmod, modinfo, insmod and rmmod.
1773 If you say Y here, you will need to run "make
1774 modules_install" to put the modules under /lib/modules/
1775 where modprobe can find them (you may need to be root to do
1782 config MODULE_FORCE_LOAD
1783 bool "Forced module loading"
1786 Allow loading of modules without version information (ie. modprobe
1787 --force). Forced module loading sets the 'F' (forced) taint flag and
1788 is usually a really bad idea.
1790 config MODULE_UNLOAD
1791 bool "Module unloading"
1793 Without this option you will not be able to unload any
1794 modules (note that some modules may not be unloadable
1795 anyway), which makes your kernel smaller, faster
1796 and simpler. If unsure, say Y.
1798 config MODULE_FORCE_UNLOAD
1799 bool "Forced module unloading"
1800 depends on MODULE_UNLOAD
1802 This option allows you to force a module to unload, even if the
1803 kernel believes it is unsafe: the kernel will remove the module
1804 without waiting for anyone to stop using it (using the -f option to
1805 rmmod). This is mainly for kernel developers and desperate users.
1809 bool "Module versioning support"
1811 Usually, you have to use modules compiled with your kernel.
1812 Saying Y here makes it sometimes possible to use modules
1813 compiled for different kernels, by adding enough information
1814 to the modules to (hopefully) spot any changes which would
1815 make them incompatible with the kernel you are running. If
1818 config MODULE_REL_CRCS
1820 depends on MODVERSIONS
1822 config MODULE_SRCVERSION_ALL
1823 bool "Source checksum for all modules"
1825 Modules which contain a MODULE_VERSION get an extra "srcversion"
1826 field inserted into their modinfo section, which contains a
1827 sum of the source files which made it. This helps maintainers
1828 see exactly which source was used to build a module (since
1829 others sometimes change the module source without updating
1830 the version). With this option, such a "srcversion" field
1831 will be created for all modules. If unsure, say N.
1834 bool "Module signature verification"
1836 select SYSTEM_DATA_VERIFICATION
1838 Check modules for valid signatures upon load: the signature
1839 is simply appended to the module. For more information see
1840 <file:Documentation/admin-guide/module-signing.rst>.
1842 Note that this option adds the OpenSSL development packages as a
1843 kernel build dependency so that the signing tool can use its crypto
1846 !!!WARNING!!! If you enable this option, you MUST make sure that the
1847 module DOES NOT get stripped after being signed. This includes the
1848 debuginfo strip done by some packagers (such as rpmbuild) and
1849 inclusion into an initramfs that wants the module size reduced.
1851 config MODULE_SIG_FORCE
1852 bool "Require modules to be validly signed"
1853 depends on MODULE_SIG
1855 Reject unsigned modules or signed modules for which we don't have a
1856 key. Without this, such modules will simply taint the kernel.
1858 config MODULE_SIG_ALL
1859 bool "Automatically sign all modules"
1861 depends on MODULE_SIG
1863 Sign all modules during make modules_install. Without this option,
1864 modules must be signed manually, using the scripts/sign-file tool.
1866 comment "Do not forget to sign required modules with scripts/sign-file"
1867 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1870 prompt "Which hash algorithm should modules be signed with?"
1871 depends on MODULE_SIG
1873 This determines which sort of hashing algorithm will be used during
1874 signature generation. This algorithm _must_ be built into the kernel
1875 directly so that signature verification can take place. It is not
1876 possible to load a signed module containing the algorithm to check
1877 the signature on that module.
1879 config MODULE_SIG_SHA1
1880 bool "Sign modules with SHA-1"
1883 config MODULE_SIG_SHA224
1884 bool "Sign modules with SHA-224"
1885 select CRYPTO_SHA256
1887 config MODULE_SIG_SHA256
1888 bool "Sign modules with SHA-256"
1889 select CRYPTO_SHA256
1891 config MODULE_SIG_SHA384
1892 bool "Sign modules with SHA-384"
1893 select CRYPTO_SHA512
1895 config MODULE_SIG_SHA512
1896 bool "Sign modules with SHA-512"
1897 select CRYPTO_SHA512
1901 config MODULE_SIG_HASH
1903 depends on MODULE_SIG
1904 default "sha1" if MODULE_SIG_SHA1
1905 default "sha224" if MODULE_SIG_SHA224
1906 default "sha256" if MODULE_SIG_SHA256
1907 default "sha384" if MODULE_SIG_SHA384
1908 default "sha512" if MODULE_SIG_SHA512
1910 config MODULE_COMPRESS
1911 bool "Compress modules on installation"
1915 Compresses kernel modules when 'make modules_install' is run; gzip or
1916 xz depending on "Compression algorithm" below.
1918 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
1920 Out-of-tree kernel modules installed using Kbuild will also be
1921 compressed upon installation.
1923 Note: for modules inside an initrd or initramfs, it's more efficient
1924 to compress the whole initrd or initramfs instead.
1926 Note: This is fully compatible with signed modules.
1931 prompt "Compression algorithm"
1932 depends on MODULE_COMPRESS
1933 default MODULE_COMPRESS_GZIP
1935 This determines which sort of compression will be used during
1936 'make modules_install'.
1938 GZIP (default) and XZ are supported.
1940 config MODULE_COMPRESS_GZIP
1943 config MODULE_COMPRESS_XZ
1948 config TRIM_UNUSED_KSYMS
1949 bool "Trim unused exported kernel symbols"
1950 depends on MODULES && !UNUSED_SYMBOLS
1952 The kernel and some modules make many symbols available for
1953 other modules to use via EXPORT_SYMBOL() and variants. Depending
1954 on the set of modules being selected in your kernel configuration,
1955 many of those exported symbols might never be used.
1957 This option allows for unused exported symbols to be dropped from
1958 the build. In turn, this provides the compiler more opportunities
1959 (especially when using LTO) for optimizing the code and reducing
1960 binary size. This might have some security advantages as well.
1962 If unsure, or if you need to build out-of-tree modules, say N.
1966 config MODULES_TREE_LOOKUP
1968 depends on PERF_EVENTS || TRACING
1970 config INIT_ALL_POSSIBLE
1973 Back when each arch used to define their own cpu_online_mask and
1974 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1975 with all 1s, and others with all 0s. When they were centralised,
1976 it was better to provide this option than to break all the archs
1977 and have several arch maintainers pursuing me down dark alleys.
1979 source "block/Kconfig"
1981 config PREEMPT_NOTIFIERS
1991 Build a simple ASN.1 grammar compiler that produces a bytecode output
1992 that can be interpreted by the ASN.1 stream decoder and used to
1993 inform it as to what tags are to be expected in a stream and what
1994 functions to call on what tags.
1996 source "kernel/Kconfig.locks"
1998 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2001 # It may be useful for an architecture to override the definitions of the
2002 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2003 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2004 # different calling convention for syscalls. They can also override the
2005 # macros for not-implemented syscalls in kernel/sys_ni.c and
2006 # kernel/time/posix-stubs.c. All these overrides need to be available in
2007 # <asm/syscall_wrapper.h>.
2008 config ARCH_HAS_SYSCALL_WRAPPER
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