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
36 depends on BROKEN || !SMP
39 config INIT_ENV_ARG_LIMIT
44 Maximum of each of the number of arguments and environment
45 variables passed to init from the kernel command line.
49 string "Cross-compiler tool prefix"
51 Same as running 'make CROSS_COMPILE=prefix-' but stored for
52 default make runs in this kernel build directory. You don't
53 need to set this unless you want the configured kernel build
54 directory to select the cross-compiler automatically.
57 bool "Compile also drivers which will not load"
60 Some drivers can be compiled on a different platform than they are
61 intended to be run on. Despite they cannot be loaded there (or even
62 when they load they cannot be used due to missing HW support),
63 developers still, opposing to distributors, might want to build such
64 drivers to compile-test them.
66 If you are a developer and want to build everything available, say Y
67 here. If you are a user/distributor, say N here to exclude useless
68 drivers to be distributed.
71 string "Local version - append to kernel release"
73 Append an extra string to the end of your kernel version.
74 This will show up when you type uname, for example.
75 The string you set here will be appended after the contents of
76 any files with a filename matching localversion* in your
77 object and source tree, in that order. Your total string can
78 be a maximum of 64 characters.
80 config LOCALVERSION_AUTO
81 bool "Automatically append version information to the version string"
84 This will try to automatically determine if the current tree is a
85 release tree by looking for git tags that belong to the current
88 A string of the format -gxxxxxxxx will be added to the localversion
89 if a git-based tree is found. The string generated by this will be
90 appended after any matching localversion* files, and after the value
91 set in CONFIG_LOCALVERSION.
93 (The actual string used here is the first eight characters produced
94 by running the command:
96 $ git rev-parse --verify HEAD
98 which is done within the script "scripts/setlocalversion".)
100 config HAVE_KERNEL_GZIP
103 config HAVE_KERNEL_BZIP2
106 config HAVE_KERNEL_LZMA
109 config HAVE_KERNEL_XZ
112 config HAVE_KERNEL_LZO
115 config HAVE_KERNEL_LZ4
119 prompt "Kernel compression mode"
121 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
123 The linux kernel is a kind of self-extracting executable.
124 Several compression algorithms are available, which differ
125 in efficiency, compression and decompression speed.
126 Compression speed is only relevant when building a kernel.
127 Decompression speed is relevant at each boot.
129 If you have any problems with bzip2 or lzma compressed
130 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
131 version of this functionality (bzip2 only), for 2.4, was
132 supplied by Christian Ludwig)
134 High compression options are mostly useful for users, who
135 are low on disk space (embedded systems), but for whom ram
138 If in doubt, select 'gzip'
142 depends on HAVE_KERNEL_GZIP
144 The old and tried gzip compression. It provides a good balance
145 between compression ratio and decompression speed.
149 depends on HAVE_KERNEL_BZIP2
151 Its compression ratio and speed is intermediate.
152 Decompression speed is slowest among the choices. The kernel
153 size is about 10% smaller with bzip2, in comparison to gzip.
154 Bzip2 uses a large amount of memory. For modern kernels you
155 will need at least 8MB RAM or more for booting.
159 depends on HAVE_KERNEL_LZMA
161 This compression algorithm's ratio is best. Decompression speed
162 is between gzip and bzip2. Compression is slowest.
163 The kernel size is about 33% smaller with LZMA in comparison to gzip.
167 depends on HAVE_KERNEL_XZ
169 XZ uses the LZMA2 algorithm and instruction set specific
170 BCJ filters which can improve compression ratio of executable
171 code. The size of the kernel is about 30% smaller with XZ in
172 comparison to gzip. On architectures for which there is a BCJ
173 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
174 will create a few percent smaller kernel than plain LZMA.
176 The speed is about the same as with LZMA: The decompression
177 speed of XZ is better than that of bzip2 but worse than gzip
178 and LZO. Compression is slow.
182 depends on HAVE_KERNEL_LZO
184 Its compression ratio is the poorest among the choices. The kernel
185 size is about 10% bigger than gzip; however its speed
186 (both compression and decompression) is the fastest.
190 depends on HAVE_KERNEL_LZ4
192 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
193 A preliminary version of LZ4 de/compression tool is available at
194 <https://code.google.com/p/lz4/>.
196 Its compression ratio is worse than LZO. The size of the kernel
197 is about 8% bigger than LZO. But the decompression speed is
202 config DEFAULT_HOSTNAME
203 string "Default hostname"
206 This option determines the default system hostname before userspace
207 calls sethostname(2). The kernel traditionally uses "(none)" here,
208 but you may wish to use a different default here to make a minimal
209 system more usable with less configuration.
212 bool "Support for paging of anonymous memory (swap)"
213 depends on MMU && BLOCK
216 This option allows you to choose whether you want to have support
217 for so called swap devices or swap files in your kernel that are
218 used to provide more virtual memory than the actual RAM present
219 in your computer. If unsure say Y.
224 Inter Process Communication is a suite of library functions and
225 system calls which let processes (running programs) synchronize and
226 exchange information. It is generally considered to be a good thing,
227 and some programs won't run unless you say Y here. In particular, if
228 you want to run the DOS emulator dosemu under Linux (read the
229 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
230 you'll need to say Y here.
232 You can find documentation about IPC with "info ipc" and also in
233 section 6.4 of the Linux Programmer's Guide, available from
234 <http://www.tldp.org/guides.html>.
236 config SYSVIPC_SYSCTL
243 bool "POSIX Message Queues"
246 POSIX variant of message queues is a part of IPC. In POSIX message
247 queues every message has a priority which decides about succession
248 of receiving it by a process. If you want to compile and run
249 programs written e.g. for Solaris with use of its POSIX message
250 queues (functions mq_*) say Y here.
252 POSIX message queues are visible as a filesystem called 'mqueue'
253 and can be mounted somewhere if you want to do filesystem
254 operations on message queues.
258 config POSIX_MQUEUE_SYSCTL
260 depends on POSIX_MQUEUE
264 config CROSS_MEMORY_ATTACH
265 bool "Enable process_vm_readv/writev syscalls"
269 Enabling this option adds the system calls process_vm_readv and
270 process_vm_writev which allow a process with the correct privileges
271 to directly read from or write to another process' address space.
272 See the man page for more details.
275 bool "open by fhandle syscalls"
278 If you say Y here, a user level program will be able to map
279 file names to handle and then later use the handle for
280 different file system operations. This is useful in implementing
281 userspace file servers, which now track files using handles instead
282 of names. The handle would remain the same even if file names
283 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
287 bool "uselib syscall"
290 This option enables the uselib syscall, a system call used in the
291 dynamic linker from libc5 and earlier. glibc does not use this
292 system call. If you intend to run programs built on libc5 or
293 earlier, you may need to enable this syscall. Current systems
294 running glibc can safely disable this.
297 bool "Auditing support"
300 Enable auditing infrastructure that can be used with another
301 kernel subsystem, such as SELinux (which requires this for
302 logging of avc messages output). Does not do system-call
303 auditing without CONFIG_AUDITSYSCALL.
305 config HAVE_ARCH_AUDITSYSCALL
309 bool "Enable system-call auditing support"
310 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
311 default y if SECURITY_SELINUX
313 Enable low-overhead system-call auditing infrastructure that
314 can be used independently or with another kernel subsystem,
319 depends on AUDITSYSCALL
324 depends on AUDITSYSCALL
327 source "kernel/irq/Kconfig"
328 source "kernel/time/Kconfig"
330 menu "CPU/Task time and stats accounting"
332 config VIRT_CPU_ACCOUNTING
336 prompt "Cputime accounting"
337 default TICK_CPU_ACCOUNTING if !PPC64
338 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
340 # Kind of a stub config for the pure tick based cputime accounting
341 config TICK_CPU_ACCOUNTING
342 bool "Simple tick based cputime accounting"
343 depends on !S390 && !NO_HZ_FULL
345 This is the basic tick based cputime accounting that maintains
346 statistics about user, system and idle time spent on per jiffies
351 config VIRT_CPU_ACCOUNTING_NATIVE
352 bool "Deterministic task and CPU time accounting"
353 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
354 select VIRT_CPU_ACCOUNTING
356 Select this option to enable more accurate task and CPU time
357 accounting. This is done by reading a CPU counter on each
358 kernel entry and exit and on transitions within the kernel
359 between system, softirq and hardirq state, so there is a
360 small performance impact. In the case of s390 or IBM POWER > 5,
361 this also enables accounting of stolen time on logically-partitioned
364 config VIRT_CPU_ACCOUNTING_GEN
365 bool "Full dynticks CPU time accounting"
366 depends on HAVE_CONTEXT_TRACKING
367 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
368 select VIRT_CPU_ACCOUNTING
369 select CONTEXT_TRACKING
371 Select this option to enable task and CPU time accounting on full
372 dynticks systems. This accounting is implemented by watching every
373 kernel-user boundaries using the context tracking subsystem.
374 The accounting is thus performed at the expense of some significant
377 For now this is only useful if you are working on the full
378 dynticks subsystem development.
382 config IRQ_TIME_ACCOUNTING
383 bool "Fine granularity task level IRQ time accounting"
384 depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
386 Select this option to enable fine granularity task irq time
387 accounting. This is done by reading a timestamp on each
388 transitions between softirq and hardirq state, so there can be a
389 small performance impact.
391 If in doubt, say N here.
395 config BSD_PROCESS_ACCT
396 bool "BSD Process Accounting"
398 If you say Y here, a user level program will be able to instruct the
399 kernel (via a special system call) to write process accounting
400 information to a file: whenever a process exits, information about
401 that process will be appended to the file by the kernel. The
402 information includes things such as creation time, owning user,
403 command name, memory usage, controlling terminal etc. (the complete
404 list is in the struct acct in <file:include/linux/acct.h>). It is
405 up to the user level program to do useful things with this
406 information. This is generally a good idea, so say Y.
408 config BSD_PROCESS_ACCT_V3
409 bool "BSD Process Accounting version 3 file format"
410 depends on BSD_PROCESS_ACCT
413 If you say Y here, the process accounting information is written
414 in a new file format that also logs the process IDs of each
415 process and it's parent. Note that this file format is incompatible
416 with previous v0/v1/v2 file formats, so you will need updated tools
417 for processing it. A preliminary version of these tools is available
418 at <http://www.gnu.org/software/acct/>.
421 bool "Export task/process statistics through netlink"
425 Export selected statistics for tasks/processes through the
426 generic netlink interface. Unlike BSD process accounting, the
427 statistics are available during the lifetime of tasks/processes as
428 responses to commands. Like BSD accounting, they are sent to user
433 config TASK_DELAY_ACCT
434 bool "Enable per-task delay accounting"
437 Collect information on time spent by a task waiting for system
438 resources like cpu, synchronous block I/O completion and swapping
439 in pages. Such statistics can help in setting a task's priorities
440 relative to other tasks for cpu, io, rss limits etc.
445 bool "Enable extended accounting over taskstats"
448 Collect extended task accounting data and send the data
449 to userland for processing over the taskstats interface.
453 config TASK_IO_ACCOUNTING
454 bool "Enable per-task storage I/O accounting"
455 depends on TASK_XACCT
457 Collect information on the number of bytes of storage I/O which this
462 endmenu # "CPU/Task time and stats accounting"
467 prompt "RCU Implementation"
471 bool "Tree-based hierarchical RCU"
472 depends on !PREEMPT && SMP
474 This option selects the RCU implementation that is
475 designed for very large SMP system with hundreds or
476 thousands of CPUs. It also scales down nicely to
480 bool "Preemptible tree-based hierarchical RCU"
483 This option selects the RCU implementation that is
484 designed for very large SMP systems with hundreds or
485 thousands of CPUs, but for which real-time response
486 is also required. It also scales down nicely to
489 Select this option if you are unsure.
492 bool "UP-only small-memory-footprint RCU"
493 depends on !PREEMPT && !SMP
495 This option selects the RCU implementation that is
496 designed for UP systems from which real-time response
497 is not required. This option greatly reduces the
498 memory footprint of RCU.
503 bool "Task_based RCU implementation using voluntary context switch"
506 This option enables a task-based RCU implementation that uses
507 only voluntary context switch (not preemption!), idle, and
508 user-mode execution as quiescent states.
512 config RCU_STALL_COMMON
513 def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
515 This option enables RCU CPU stall code that is common between
516 the TINY and TREE variants of RCU. The purpose is to allow
517 the tiny variants to disable RCU CPU stall warnings, while
518 making these warnings mandatory for the tree variants.
520 config CONTEXT_TRACKING
524 bool "Consider userspace as in RCU extended quiescent state"
525 depends on HAVE_CONTEXT_TRACKING && SMP
526 select CONTEXT_TRACKING
528 This option sets hooks on kernel / userspace boundaries and
529 puts RCU in extended quiescent state when the CPU runs in
530 userspace. It means that when a CPU runs in userspace, it is
531 excluded from the global RCU state machine and thus doesn't
532 try to keep the timer tick on for RCU.
534 Unless you want to hack and help the development of the full
535 dynticks mode, you shouldn't enable this option. It also
536 adds unnecessary overhead.
540 config CONTEXT_TRACKING_FORCE
541 bool "Force context tracking"
542 depends on CONTEXT_TRACKING
543 default y if !NO_HZ_FULL
545 The major pre-requirement for full dynticks to work is to
546 support the context tracking subsystem. But there are also
547 other dependencies to provide in order to make the full
550 This option stands for testing when an arch implements the
551 context tracking backend but doesn't yet fullfill all the
552 requirements to make the full dynticks feature working.
553 Without the full dynticks, there is no way to test the support
554 for context tracking and the subsystems that rely on it: RCU
555 userspace extended quiescent state and tickless cputime
556 accounting. This option copes with the absence of the full
557 dynticks subsystem by forcing the context tracking on all
560 Say Y only if you're working on the development of an
561 architecture backend for the context tracking.
563 Say N otherwise, this option brings an overhead that you
564 don't want in production.
568 int "Tree-based hierarchical RCU fanout value"
571 depends on TREE_RCU || PREEMPT_RCU
575 This option controls the fanout of hierarchical implementations
576 of RCU, allowing RCU to work efficiently on machines with
577 large numbers of CPUs. This value must be at least the fourth
578 root of NR_CPUS, which allows NR_CPUS to be insanely large.
579 The default value of RCU_FANOUT should be used for production
580 systems, but if you are stress-testing the RCU implementation
581 itself, small RCU_FANOUT values allow you to test large-system
582 code paths on small(er) systems.
584 Select a specific number if testing RCU itself.
585 Take the default if unsure.
587 config RCU_FANOUT_LEAF
588 int "Tree-based hierarchical RCU leaf-level fanout value"
589 range 2 RCU_FANOUT if 64BIT
590 range 2 RCU_FANOUT if !64BIT
591 depends on TREE_RCU || PREEMPT_RCU
594 This option controls the leaf-level fanout of hierarchical
595 implementations of RCU, and allows trading off cache misses
596 against lock contention. Systems that synchronize their
597 scheduling-clock interrupts for energy-efficiency reasons will
598 want the default because the smaller leaf-level fanout keeps
599 lock contention levels acceptably low. Very large systems
600 (hundreds or thousands of CPUs) will instead want to set this
601 value to the maximum value possible in order to reduce the
602 number of cache misses incurred during RCU's grace-period
603 initialization. These systems tend to run CPU-bound, and thus
604 are not helped by synchronized interrupts, and thus tend to
605 skew them, which reduces lock contention enough that large
606 leaf-level fanouts work well.
608 Select a specific number if testing RCU itself.
610 Select the maximum permissible value for large systems.
612 Take the default if unsure.
614 config RCU_FANOUT_EXACT
615 bool "Disable tree-based hierarchical RCU auto-balancing"
616 depends on TREE_RCU || PREEMPT_RCU
619 This option forces use of the exact RCU_FANOUT value specified,
620 regardless of imbalances in the hierarchy. This is useful for
621 testing RCU itself, and might one day be useful on systems with
622 strong NUMA behavior.
624 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
628 config RCU_FAST_NO_HZ
629 bool "Accelerate last non-dyntick-idle CPU's grace periods"
630 depends on NO_HZ_COMMON && SMP
633 This option permits CPUs to enter dynticks-idle state even if
634 they have RCU callbacks queued, and prevents RCU from waking
635 these CPUs up more than roughly once every four jiffies (by
636 default, you can adjust this using the rcutree.rcu_idle_gp_delay
637 parameter), thus improving energy efficiency. On the other
638 hand, this option increases the duration of RCU grace periods,
639 for example, slowing down synchronize_rcu().
641 Say Y if energy efficiency is critically important, and you
642 don't care about increased grace-period durations.
644 Say N if you are unsure.
646 config TREE_RCU_TRACE
647 def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
650 This option provides tracing for the TREE_RCU and
651 PREEMPT_RCU implementations, permitting Makefile to
652 trivially select kernel/rcutree_trace.c.
655 bool "Enable RCU priority boosting"
656 depends on RT_MUTEXES && PREEMPT_RCU
659 This option boosts the priority of preempted RCU readers that
660 block the current preemptible RCU grace period for too long.
661 This option also prevents heavy loads from blocking RCU
662 callback invocation for all flavors of RCU.
664 Say Y here if you are working with real-time apps or heavy loads
665 Say N here if you are unsure.
667 config RCU_KTHREAD_PRIO
668 int "Real-time priority to use for RCU worker threads"
673 This option specifies the SCHED_FIFO priority value that will be
674 assigned to the rcuc/n and rcub/n threads and is also the value
675 used for RCU_BOOST (if enabled). If you are working with a
676 real-time application that has one or more CPU-bound threads
677 running at a real-time priority level, you should set
678 RCU_KTHREAD_PRIO to a priority higher than the highest-priority
679 real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO
680 value of 1 is appropriate in the common case, which is real-time
681 applications that do not have any CPU-bound threads.
683 Some real-time applications might not have a single real-time
684 thread that saturates a given CPU, but instead might have
685 multiple real-time threads that, taken together, fully utilize
686 that CPU. In this case, you should set RCU_KTHREAD_PRIO to
687 a priority higher than the lowest-priority thread that is
688 conspiring to prevent the CPU from running any non-real-time
689 tasks. For example, if one thread at priority 10 and another
690 thread at priority 5 are between themselves fully consuming
691 the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
692 set to priority 6 or higher.
694 Specify the real-time priority, or take the default if unsure.
696 config RCU_BOOST_DELAY
697 int "Milliseconds to delay boosting after RCU grace-period start"
702 This option specifies the time to wait after the beginning of
703 a given grace period before priority-boosting preempted RCU
704 readers blocking that grace period. Note that any RCU reader
705 blocking an expedited RCU grace period is boosted immediately.
707 Accept the default if unsure.
710 bool "Offload RCU callback processing from boot-selected CPUs"
711 depends on TREE_RCU || PREEMPT_RCU
714 Use this option to reduce OS jitter for aggressive HPC or
715 real-time workloads. It can also be used to offload RCU
716 callback invocation to energy-efficient CPUs in battery-powered
717 asymmetric multiprocessors.
719 This option offloads callback invocation from the set of
720 CPUs specified at boot time by the rcu_nocbs parameter.
721 For each such CPU, a kthread ("rcuox/N") will be created to
722 invoke callbacks, where the "N" is the CPU being offloaded,
723 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
724 "s" for RCU-sched. Nothing prevents this kthread from running
725 on the specified CPUs, but (1) the kthreads may be preempted
726 between each callback, and (2) affinity or cgroups can be used
727 to force the kthreads to run on whatever set of CPUs is desired.
729 Say Y here if you want to help to debug reduced OS jitter.
730 Say N here if you are unsure.
733 prompt "Build-forced no-CBs CPUs"
734 default RCU_NOCB_CPU_NONE
735 depends on RCU_NOCB_CPU
737 This option allows no-CBs CPUs (whose RCU callbacks are invoked
738 from kthreads rather than from softirq context) to be specified
739 at build time. Additional no-CBs CPUs may be specified by
740 the rcu_nocbs= boot parameter.
742 config RCU_NOCB_CPU_NONE
743 bool "No build_forced no-CBs CPUs"
745 This option does not force any of the CPUs to be no-CBs CPUs.
746 Only CPUs designated by the rcu_nocbs= boot parameter will be
747 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
748 kthreads whose names begin with "rcuo". All other CPUs will
749 invoke their own RCU callbacks in softirq context.
751 Select this option if you want to choose no-CBs CPUs at
752 boot time, for example, to allow testing of different no-CBs
753 configurations without having to rebuild the kernel each time.
755 config RCU_NOCB_CPU_ZERO
756 bool "CPU 0 is a build_forced no-CBs CPU"
758 This option forces CPU 0 to be a no-CBs CPU, so that its RCU
759 callbacks are invoked by a per-CPU kthread whose name begins
760 with "rcuo". Additional CPUs may be designated as no-CBs
761 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
762 All other CPUs will invoke their own RCU callbacks in softirq
765 Select this if CPU 0 needs to be a no-CBs CPU for real-time
766 or energy-efficiency reasons, but the real reason it exists
767 is to ensure that randconfig testing covers mixed systems.
769 config RCU_NOCB_CPU_ALL
770 bool "All CPUs are build_forced no-CBs CPUs"
772 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
773 boot parameter will be ignored. All CPUs' RCU callbacks will
774 be executed in the context of per-CPU rcuo kthreads created for
775 this purpose. Assuming that the kthreads whose names start with
776 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
777 on the remaining CPUs, but might decrease memory locality during
778 RCU-callback invocation, thus potentially degrading throughput.
780 Select this if all CPUs need to be no-CBs CPUs for real-time
781 or energy-efficiency reasons.
785 endmenu # "RCU Subsystem"
792 tristate "Kernel .config support"
795 This option enables the complete Linux kernel ".config" file
796 contents to be saved in the kernel. It provides documentation
797 of which kernel options are used in a running kernel or in an
798 on-disk kernel. This information can be extracted from the kernel
799 image file with the script scripts/extract-ikconfig and used as
800 input to rebuild the current kernel or to build another kernel.
801 It can also be extracted from a running kernel by reading
802 /proc/config.gz if enabled (below).
805 bool "Enable access to .config through /proc/config.gz"
806 depends on IKCONFIG && PROC_FS
808 This option enables access to the kernel configuration file
809 through /proc/config.gz.
812 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
817 Select the minimal kernel log buffer size as a power of 2.
818 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
819 parameter, see below. Any higher size also might be forced
820 by "log_buf_len" boot parameter.
830 config LOG_CPU_MAX_BUF_SHIFT
831 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
834 default 12 if !BASE_SMALL
835 default 0 if BASE_SMALL
838 This option allows to increase the default ring buffer size
839 according to the number of CPUs. The value defines the contribution
840 of each CPU as a power of 2. The used space is typically only few
841 lines however it might be much more when problems are reported,
844 The increased size means that a new buffer has to be allocated and
845 the original static one is unused. It makes sense only on systems
846 with more CPUs. Therefore this value is used only when the sum of
847 contributions is greater than the half of the default kernel ring
848 buffer as defined by LOG_BUF_SHIFT. The default values are set
849 so that more than 64 CPUs are needed to trigger the allocation.
851 Also this option is ignored when "log_buf_len" kernel parameter is
852 used as it forces an exact (power of two) size of the ring buffer.
854 The number of possible CPUs is used for this computation ignoring
855 hotplugging making the compuation optimal for the the worst case
856 scenerio while allowing a simple algorithm to be used from bootup.
858 Examples shift values and their meaning:
859 17 => 128 KB for each CPU
860 16 => 64 KB for each CPU
861 15 => 32 KB for each CPU
862 14 => 16 KB for each CPU
863 13 => 8 KB for each CPU
864 12 => 4 KB for each CPU
867 # Architectures with an unreliable sched_clock() should select this:
869 config HAVE_UNSTABLE_SCHED_CLOCK
872 config GENERIC_SCHED_CLOCK
876 # For architectures that want to enable the support for NUMA-affine scheduler
879 config ARCH_SUPPORTS_NUMA_BALANCING
883 # For architectures that know their GCC __int128 support is sound
885 config ARCH_SUPPORTS_INT128
888 # For architectures that (ab)use NUMA to represent different memory regions
889 # all cpu-local but of different latencies, such as SuperH.
891 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
894 config NUMA_BALANCING
895 bool "Memory placement aware NUMA scheduler"
896 depends on ARCH_SUPPORTS_NUMA_BALANCING
897 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
898 depends on SMP && NUMA && MIGRATION
900 This option adds support for automatic NUMA aware memory/task placement.
901 The mechanism is quite primitive and is based on migrating memory when
902 it has references to the node the task is running on.
904 This system will be inactive on UMA systems.
906 config NUMA_BALANCING_DEFAULT_ENABLED
907 bool "Automatically enable NUMA aware memory/task placement"
909 depends on NUMA_BALANCING
911 If set, automatic NUMA balancing will be enabled if running on a NUMA
915 boolean "Control Group support"
918 This option adds support for grouping sets of processes together, for
919 use with process control subsystems such as Cpusets, CFS, memory
920 controls or device isolation.
922 - Documentation/scheduler/sched-design-CFS.txt (CFS)
923 - Documentation/cgroups/ (features for grouping, isolation
924 and resource control)
931 bool "Example debug cgroup subsystem"
934 This option enables a simple cgroup subsystem that
935 exports useful debugging information about the cgroups
940 config CGROUP_FREEZER
941 bool "Freezer cgroup subsystem"
943 Provides a way to freeze and unfreeze all tasks in a
947 bool "Device controller for cgroups"
949 Provides a cgroup implementing whitelists for devices which
950 a process in the cgroup can mknod or open.
953 bool "Cpuset support"
955 This option will let you create and manage CPUSETs which
956 allow dynamically partitioning a system into sets of CPUs and
957 Memory Nodes and assigning tasks to run only within those sets.
958 This is primarily useful on large SMP or NUMA systems.
962 config PROC_PID_CPUSET
963 bool "Include legacy /proc/<pid>/cpuset file"
967 config CGROUP_CPUACCT
968 bool "Simple CPU accounting cgroup subsystem"
970 Provides a simple Resource Controller for monitoring the
971 total CPU consumed by the tasks in a cgroup.
977 bool "Memory Resource Controller for Control Groups"
981 Provides a memory resource controller that manages both anonymous
982 memory and page cache. (See Documentation/cgroups/memory.txt)
985 bool "Memory Resource Controller Swap Extension"
986 depends on MEMCG && SWAP
988 Add swap management feature to memory resource controller. When you
989 enable this, you can limit mem+swap usage per cgroup. In other words,
990 when you disable this, memory resource controller has no cares to
991 usage of swap...a process can exhaust all of the swap. This extension
992 is useful when you want to avoid exhaustion swap but this itself
993 adds more overheads and consumes memory for remembering information.
994 Especially if you use 32bit system or small memory system, please
995 be careful about enabling this. When memory resource controller
996 is disabled by boot option, this will be automatically disabled and
997 there will be no overhead from this. Even when you set this config=y,
998 if boot option "swapaccount=0" is set, swap will not be accounted.
999 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
1000 size is 4096bytes, 512k per 1Gbytes of swap.
1001 config MEMCG_SWAP_ENABLED
1002 bool "Memory Resource Controller Swap Extension enabled by default"
1003 depends on MEMCG_SWAP
1006 Memory Resource Controller Swap Extension comes with its price in
1007 a bigger memory consumption. General purpose distribution kernels
1008 which want to enable the feature but keep it disabled by default
1009 and let the user enable it by swapaccount=1 boot command line
1010 parameter should have this option unselected.
1011 For those who want to have the feature enabled by default should
1012 select this option (if, for some reason, they need to disable it
1013 then swapaccount=0 does the trick).
1015 bool "Memory Resource Controller Kernel Memory accounting"
1017 depends on SLUB || SLAB
1019 The Kernel Memory extension for Memory Resource Controller can limit
1020 the amount of memory used by kernel objects in the system. Those are
1021 fundamentally different from the entities handled by the standard
1022 Memory Controller, which are page-based, and can be swapped. Users of
1023 the kmem extension can use it to guarantee that no group of processes
1024 will ever exhaust kernel resources alone.
1026 WARNING: Current implementation lacks reclaim support. That means
1027 allocation attempts will fail when close to the limit even if there
1028 are plenty of kmem available for reclaim. That makes this option
1029 unusable in real life so DO NOT SELECT IT unless for development
1032 config CGROUP_HUGETLB
1033 bool "HugeTLB Resource Controller for Control Groups"
1034 depends on HUGETLB_PAGE
1038 Provides a cgroup Resource Controller for HugeTLB pages.
1039 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1040 The limit is enforced during page fault. Since HugeTLB doesn't
1041 support page reclaim, enforcing the limit at page fault time implies
1042 that, the application will get SIGBUS signal if it tries to access
1043 HugeTLB pages beyond its limit. This requires the application to know
1044 beforehand how much HugeTLB pages it would require for its use. The
1045 control group is tracked in the third page lru pointer. This means
1046 that we cannot use the controller with huge page less than 3 pages.
1049 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1050 depends on PERF_EVENTS && CGROUPS
1052 This option extends the per-cpu mode to restrict monitoring to
1053 threads which belong to the cgroup specified and run on the
1058 menuconfig CGROUP_SCHED
1059 bool "Group CPU scheduler"
1062 This feature lets CPU scheduler recognize task groups and control CPU
1063 bandwidth allocation to such task groups. It uses cgroups to group
1067 config FAIR_GROUP_SCHED
1068 bool "Group scheduling for SCHED_OTHER"
1069 depends on CGROUP_SCHED
1070 default CGROUP_SCHED
1072 config CFS_BANDWIDTH
1073 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1074 depends on FAIR_GROUP_SCHED
1077 This option allows users to define CPU bandwidth rates (limits) for
1078 tasks running within the fair group scheduler. Groups with no limit
1079 set are considered to be unconstrained and will run with no
1081 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1083 config RT_GROUP_SCHED
1084 bool "Group scheduling for SCHED_RR/FIFO"
1085 depends on CGROUP_SCHED
1088 This feature lets you explicitly allocate real CPU bandwidth
1089 to task groups. If enabled, it will also make it impossible to
1090 schedule realtime tasks for non-root users until you allocate
1091 realtime bandwidth for them.
1092 See Documentation/scheduler/sched-rt-group.txt for more information.
1097 bool "Block IO controller"
1101 Generic block IO controller cgroup interface. This is the common
1102 cgroup interface which should be used by various IO controlling
1105 Currently, CFQ IO scheduler uses it to recognize task groups and
1106 control disk bandwidth allocation (proportional time slice allocation)
1107 to such task groups. It is also used by bio throttling logic in
1108 block layer to implement upper limit in IO rates on a device.
1110 This option only enables generic Block IO controller infrastructure.
1111 One needs to also enable actual IO controlling logic/policy. For
1112 enabling proportional weight division of disk bandwidth in CFQ, set
1113 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1114 CONFIG_BLK_DEV_THROTTLING=y.
1116 See Documentation/cgroups/blkio-controller.txt for more information.
1118 config DEBUG_BLK_CGROUP
1119 bool "Enable Block IO controller debugging"
1120 depends on BLK_CGROUP
1123 Enable some debugging help. Currently it exports additional stat
1124 files in a cgroup which can be useful for debugging.
1128 config CHECKPOINT_RESTORE
1129 bool "Checkpoint/restore support" if EXPERT
1132 Enables additional kernel features in a sake of checkpoint/restore.
1133 In particular it adds auxiliary prctl codes to setup process text,
1134 data and heap segment sizes, and a few additional /proc filesystem
1137 If unsure, say N here.
1139 menuconfig NAMESPACES
1140 bool "Namespaces support" if EXPERT
1143 Provides the way to make tasks work with different objects using
1144 the same id. For example same IPC id may refer to different objects
1145 or same user id or pid may refer to different tasks when used in
1146 different namespaces.
1151 bool "UTS namespace"
1154 In this namespace tasks see different info provided with the
1158 bool "IPC namespace"
1159 depends on (SYSVIPC || POSIX_MQUEUE)
1162 In this namespace tasks work with IPC ids which correspond to
1163 different IPC objects in different namespaces.
1166 bool "User namespace"
1169 This allows containers, i.e. vservers, to use user namespaces
1170 to provide different user info for different servers.
1172 When user namespaces are enabled in the kernel it is
1173 recommended that the MEMCG and MEMCG_KMEM options also be
1174 enabled and that user-space use the memory control groups to
1175 limit the amount of memory a memory unprivileged users can
1181 bool "PID Namespaces"
1184 Support process id namespaces. This allows having multiple
1185 processes with the same pid as long as they are in different
1186 pid namespaces. This is a building block of containers.
1189 bool "Network namespace"
1193 Allow user space to create what appear to be multiple instances
1194 of the network stack.
1198 config SCHED_AUTOGROUP
1199 bool "Automatic process group scheduling"
1202 select FAIR_GROUP_SCHED
1204 This option optimizes the scheduler for common desktop workloads by
1205 automatically creating and populating task groups. This separation
1206 of workloads isolates aggressive CPU burners (like build jobs) from
1207 desktop applications. Task group autogeneration is currently based
1210 config SYSFS_DEPRECATED
1211 bool "Enable deprecated sysfs features to support old userspace tools"
1215 This option adds code that switches the layout of the "block" class
1216 devices, to not show up in /sys/class/block/, but only in
1219 This switch is only active when the sysfs.deprecated=1 boot option is
1220 passed or the SYSFS_DEPRECATED_V2 option is set.
1222 This option allows new kernels to run on old distributions and tools,
1223 which might get confused by /sys/class/block/. Since 2007/2008 all
1224 major distributions and tools handle this just fine.
1226 Recent distributions and userspace tools after 2009/2010 depend on
1227 the existence of /sys/class/block/, and will not work with this
1230 Only if you are using a new kernel on an old distribution, you might
1233 config SYSFS_DEPRECATED_V2
1234 bool "Enable deprecated sysfs features by default"
1237 depends on SYSFS_DEPRECATED
1239 Enable deprecated sysfs by default.
1241 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1244 Only if you are using a new kernel on an old distribution, you might
1245 need to say Y here. Even then, odds are you would not need it
1246 enabled, you can always pass the boot option if absolutely necessary.
1249 bool "Kernel->user space relay support (formerly relayfs)"
1251 This option enables support for relay interface support in
1252 certain file systems (such as debugfs).
1253 It is designed to provide an efficient mechanism for tools and
1254 facilities to relay large amounts of data from kernel space to
1259 config BLK_DEV_INITRD
1260 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1261 depends on BROKEN || !FRV
1263 The initial RAM filesystem is a ramfs which is loaded by the
1264 boot loader (loadlin or lilo) and that is mounted as root
1265 before the normal boot procedure. It is typically used to
1266 load modules needed to mount the "real" root file system,
1267 etc. See <file:Documentation/initrd.txt> for details.
1269 If RAM disk support (BLK_DEV_RAM) is also included, this
1270 also enables initial RAM disk (initrd) support and adds
1271 15 Kbytes (more on some other architectures) to the kernel size.
1277 source "usr/Kconfig"
1281 config INIT_FALLBACK
1282 bool "Fall back to defaults if init= parameter is bad"
1285 If enabled, the kernel will try the default init binaries if an
1286 explicit request from the init= parameter fails.
1288 This can have unexpected effects. For example, booting
1289 with init=/sbin/kiosk_app will run /sbin/init or even /bin/sh
1290 if /sbin/kiosk_app cannot be executed.
1292 The default value of Y is consistent with historical behavior.
1293 Selecting N is likely to be more appropriate for most uses,
1294 especially on kiosks and on kernels that are intended to be
1295 run under the control of a script.
1297 config CC_OPTIMIZE_FOR_SIZE
1298 bool "Optimize for size"
1300 Enabling this option will pass "-Os" instead of "-O2" to gcc
1301 resulting in a smaller kernel.
1314 config SYSCTL_EXCEPTION_TRACE
1317 Enable support for /proc/sys/debug/exception-trace.
1319 config SYSCTL_ARCH_UNALIGN_NO_WARN
1322 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1323 Allows arch to define/use @no_unaligned_warning to possibly warn
1324 about unaligned access emulation going on under the hood.
1326 config SYSCTL_ARCH_UNALIGN_ALLOW
1329 Enable support for /proc/sys/kernel/unaligned-trap
1330 Allows arches to define/use @unaligned_enabled to runtime toggle
1331 the unaligned access emulation.
1332 see arch/parisc/kernel/unaligned.c for reference
1334 config HAVE_PCSPKR_PLATFORM
1337 # interpreter that classic socket filters depend on
1342 bool "Configure standard kernel features (expert users)"
1343 # Unhide debug options, to make the on-by-default options visible
1346 This option allows certain base kernel options and settings
1347 to be disabled or tweaked. This is for specialized
1348 environments which can tolerate a "non-standard" kernel.
1349 Only use this if you really know what you are doing.
1352 bool "Enable 16-bit UID system calls" if EXPERT
1353 depends on HAVE_UID16
1356 This enables the legacy 16-bit UID syscall wrappers.
1358 config SGETMASK_SYSCALL
1359 bool "sgetmask/ssetmask syscalls support" if EXPERT
1360 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1362 sys_sgetmask and sys_ssetmask are obsolete system calls
1363 no longer supported in libc but still enabled by default in some
1366 If unsure, leave the default option here.
1368 config SYSFS_SYSCALL
1369 bool "Sysfs syscall support" if EXPERT
1372 sys_sysfs is an obsolete system call no longer supported in libc.
1373 Note that disabling this option is more secure but might break
1374 compatibility with some systems.
1376 If unsure say Y here.
1378 config SYSCTL_SYSCALL
1379 bool "Sysctl syscall support" if EXPERT
1380 depends on PROC_SYSCTL
1384 sys_sysctl uses binary paths that have been found challenging
1385 to properly maintain and use. The interface in /proc/sys
1386 using paths with ascii names is now the primary path to this
1389 Almost nothing using the binary sysctl interface so if you are
1390 trying to save some space it is probably safe to disable this,
1391 making your kernel marginally smaller.
1393 If unsure say N here.
1396 bool "Load all symbols for debugging/ksymoops" if EXPERT
1399 Say Y here to let the kernel print out symbolic crash information and
1400 symbolic stack backtraces. This increases the size of the kernel
1401 somewhat, as all symbols have to be loaded into the kernel image.
1404 bool "Include all symbols in kallsyms"
1405 depends on DEBUG_KERNEL && KALLSYMS
1407 Normally kallsyms only contains the symbols of functions for nicer
1408 OOPS messages and backtraces (i.e., symbols from the text and inittext
1409 sections). This is sufficient for most cases. And only in very rare
1410 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1411 names of variables from the data sections, etc).
1413 This option makes sure that all symbols are loaded into the kernel
1414 image (i.e., symbols from all sections) in cost of increased kernel
1415 size (depending on the kernel configuration, it may be 300KiB or
1416 something like this).
1418 Say N unless you really need all symbols.
1422 bool "Enable support for printk" if EXPERT
1425 This option enables normal printk support. Removing it
1426 eliminates most of the message strings from the kernel image
1427 and makes the kernel more or less silent. As this makes it
1428 very difficult to diagnose system problems, saying N here is
1429 strongly discouraged.
1432 bool "BUG() support" if EXPERT
1435 Disabling this option eliminates support for BUG and WARN, reducing
1436 the size of your kernel image and potentially quietly ignoring
1437 numerous fatal conditions. You should only consider disabling this
1438 option for embedded systems with no facilities for reporting errors.
1444 bool "Enable ELF core dumps" if EXPERT
1446 Enable support for generating core dumps. Disabling saves about 4k.
1449 config PCSPKR_PLATFORM
1450 bool "Enable PC-Speaker support" if EXPERT
1451 depends on HAVE_PCSPKR_PLATFORM
1455 This option allows to disable the internal PC-Speaker
1456 support, saving some memory.
1460 bool "Enable full-sized data structures for core" if EXPERT
1462 Disabling this option reduces the size of miscellaneous core
1463 kernel data structures. This saves memory on small machines,
1464 but may reduce performance.
1467 bool "Enable futex support" if EXPERT
1471 Disabling this option will cause the kernel to be built without
1472 support for "fast userspace mutexes". The resulting kernel may not
1473 run glibc-based applications correctly.
1475 config HAVE_FUTEX_CMPXCHG
1479 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1480 is implemented and always working. This removes a couple of runtime
1484 bool "Enable eventpoll support" if EXPERT
1488 Disabling this option will cause the kernel to be built without
1489 support for epoll family of system calls.
1492 bool "Enable signalfd() system call" if EXPERT
1496 Enable the signalfd() system call that allows to receive signals
1497 on a file descriptor.
1502 bool "Enable timerfd() system call" if EXPERT
1506 Enable the timerfd() system call that allows to receive timer
1507 events on a file descriptor.
1512 bool "Enable eventfd() system call" if EXPERT
1516 Enable the eventfd() system call that allows to receive both
1517 kernel notification (ie. KAIO) or userspace notifications.
1521 # syscall, maps, verifier
1523 bool "Enable bpf() system call" if EXPERT
1528 Enable the bpf() system call that allows to manipulate eBPF
1529 programs and maps via file descriptors.
1532 bool "Use full shmem filesystem" if EXPERT
1536 The shmem is an internal filesystem used to manage shared memory.
1537 It is backed by swap and manages resource limits. It is also exported
1538 to userspace as tmpfs if TMPFS is enabled. Disabling this
1539 option replaces shmem and tmpfs with the much simpler ramfs code,
1540 which may be appropriate on small systems without swap.
1543 bool "Enable AIO support" if EXPERT
1546 This option enables POSIX asynchronous I/O which may by used
1547 by some high performance threaded applications. Disabling
1548 this option saves about 7k.
1550 config ADVISE_SYSCALLS
1551 bool "Enable madvise/fadvise syscalls" if EXPERT
1554 This option enables the madvise and fadvise syscalls, used by
1555 applications to advise the kernel about their future memory or file
1556 usage, improving performance. If building an embedded system where no
1557 applications use these syscalls, you can disable this option to save
1562 bool "Enable PCI quirk workarounds" if EXPERT
1565 This enables workarounds for various PCI chipset
1566 bugs/quirks. Disable this only if your target machine is
1567 unaffected by PCI quirks.
1570 bool "Embedded system"
1571 option allnoconfig_y
1574 This option should be enabled if compiling the kernel for
1575 an embedded system so certain expert options are available
1578 config HAVE_PERF_EVENTS
1581 See tools/perf/design.txt for details.
1583 config PERF_USE_VMALLOC
1586 See tools/perf/design.txt for details
1588 menu "Kernel Performance Events And Counters"
1591 bool "Kernel performance events and counters"
1592 default y if PROFILING
1593 depends on HAVE_PERF_EVENTS
1597 Enable kernel support for various performance events provided
1598 by software and hardware.
1600 Software events are supported either built-in or via the
1601 use of generic tracepoints.
1603 Most modern CPUs support performance events via performance
1604 counter registers. These registers count the number of certain
1605 types of hw events: such as instructions executed, cachemisses
1606 suffered, or branches mis-predicted - without slowing down the
1607 kernel or applications. These registers can also trigger interrupts
1608 when a threshold number of events have passed - and can thus be
1609 used to profile the code that runs on that CPU.
1611 The Linux Performance Event subsystem provides an abstraction of
1612 these software and hardware event capabilities, available via a
1613 system call and used by the "perf" utility in tools/perf/. It
1614 provides per task and per CPU counters, and it provides event
1615 capabilities on top of those.
1619 config DEBUG_PERF_USE_VMALLOC
1621 bool "Debug: use vmalloc to back perf mmap() buffers"
1622 depends on PERF_EVENTS && DEBUG_KERNEL
1623 select PERF_USE_VMALLOC
1625 Use vmalloc memory to back perf mmap() buffers.
1627 Mostly useful for debugging the vmalloc code on platforms
1628 that don't require it.
1634 config VM_EVENT_COUNTERS
1636 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1638 VM event counters are needed for event counts to be shown.
1639 This option allows the disabling of the VM event counters
1640 on EXPERT systems. /proc/vmstat will only show page counts
1641 if VM event counters are disabled.
1645 bool "Enable SLUB debugging support" if EXPERT
1646 depends on SLUB && SYSFS
1648 SLUB has extensive debug support features. Disabling these can
1649 result in significant savings in code size. This also disables
1650 SLUB sysfs support. /sys/slab will not exist and there will be
1651 no support for cache validation etc.
1654 bool "Disable heap randomization"
1657 Randomizing heap placement makes heap exploits harder, but it
1658 also breaks ancient binaries (including anything libc5 based).
1659 This option changes the bootup default to heap randomization
1660 disabled, and can be overridden at runtime by setting
1661 /proc/sys/kernel/randomize_va_space to 2.
1663 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1666 prompt "Choose SLAB allocator"
1669 This option allows to select a slab allocator.
1674 The regular slab allocator that is established and known to work
1675 well in all environments. It organizes cache hot objects in
1676 per cpu and per node queues.
1679 bool "SLUB (Unqueued Allocator)"
1681 SLUB is a slab allocator that minimizes cache line usage
1682 instead of managing queues of cached objects (SLAB approach).
1683 Per cpu caching is realized using slabs of objects instead
1684 of queues of objects. SLUB can use memory efficiently
1685 and has enhanced diagnostics. SLUB is the default choice for
1690 bool "SLOB (Simple Allocator)"
1692 SLOB replaces the stock allocator with a drastically simpler
1693 allocator. SLOB is generally more space efficient but
1694 does not perform as well on large systems.
1698 config SLUB_CPU_PARTIAL
1700 depends on SLUB && SMP
1701 bool "SLUB per cpu partial cache"
1703 Per cpu partial caches accellerate objects allocation and freeing
1704 that is local to a processor at the price of more indeterminism
1705 in the latency of the free. On overflow these caches will be cleared
1706 which requires the taking of locks that may cause latency spikes.
1707 Typically one would choose no for a realtime system.
1709 config MMAP_ALLOW_UNINITIALIZED
1710 bool "Allow mmapped anonymous memory to be uninitialized"
1711 depends on EXPERT && !MMU
1714 Normally, and according to the Linux spec, anonymous memory obtained
1715 from mmap() has it's contents cleared before it is passed to
1716 userspace. Enabling this config option allows you to request that
1717 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1718 providing a huge performance boost. If this option is not enabled,
1719 then the flag will be ignored.
1721 This is taken advantage of by uClibc's malloc(), and also by
1722 ELF-FDPIC binfmt's brk and stack allocator.
1724 Because of the obvious security issues, this option should only be
1725 enabled on embedded devices where you control what is run in
1726 userspace. Since that isn't generally a problem on no-MMU systems,
1727 it is normally safe to say Y here.
1729 See Documentation/nommu-mmap.txt for more information.
1731 config SYSTEM_TRUSTED_KEYRING
1732 bool "Provide system-wide ring of trusted keys"
1735 Provide a system keyring to which trusted keys can be added. Keys in
1736 the keyring are considered to be trusted. Keys may be added at will
1737 by the kernel from compiled-in data and from hardware key stores, but
1738 userspace may only add extra keys if those keys can be verified by
1739 keys already in the keyring.
1741 Keys in this keyring are used by module signature checking.
1744 bool "Profiling support"
1746 Say Y here to enable the extended profiling support mechanisms used
1747 by profilers such as OProfile.
1750 # Place an empty function call at each tracepoint site. Can be
1751 # dynamically changed for a probe function.
1756 source "arch/Kconfig"
1758 endmenu # General setup
1760 config HAVE_GENERIC_DMA_COHERENT
1767 depends on SLAB || SLUB_DEBUG
1775 default 0 if BASE_FULL
1776 default 1 if !BASE_FULL
1779 bool "Enable loadable module support"
1782 Kernel modules are small pieces of compiled code which can
1783 be inserted in the running kernel, rather than being
1784 permanently built into the kernel. You use the "modprobe"
1785 tool to add (and sometimes remove) them. If you say Y here,
1786 many parts of the kernel can be built as modules (by
1787 answering M instead of Y where indicated): this is most
1788 useful for infrequently used options which are not required
1789 for booting. For more information, see the man pages for
1790 modprobe, lsmod, modinfo, insmod and rmmod.
1792 If you say Y here, you will need to run "make
1793 modules_install" to put the modules under /lib/modules/
1794 where modprobe can find them (you may need to be root to do
1801 config MODULE_FORCE_LOAD
1802 bool "Forced module loading"
1805 Allow loading of modules without version information (ie. modprobe
1806 --force). Forced module loading sets the 'F' (forced) taint flag and
1807 is usually a really bad idea.
1809 config MODULE_UNLOAD
1810 bool "Module unloading"
1812 Without this option you will not be able to unload any
1813 modules (note that some modules may not be unloadable
1814 anyway), which makes your kernel smaller, faster
1815 and simpler. If unsure, say Y.
1817 config MODULE_FORCE_UNLOAD
1818 bool "Forced module unloading"
1819 depends on MODULE_UNLOAD
1821 This option allows you to force a module to unload, even if the
1822 kernel believes it is unsafe: the kernel will remove the module
1823 without waiting for anyone to stop using it (using the -f option to
1824 rmmod). This is mainly for kernel developers and desperate users.
1828 bool "Module versioning support"
1830 Usually, you have to use modules compiled with your kernel.
1831 Saying Y here makes it sometimes possible to use modules
1832 compiled for different kernels, by adding enough information
1833 to the modules to (hopefully) spot any changes which would
1834 make them incompatible with the kernel you are running. If
1837 config MODULE_SRCVERSION_ALL
1838 bool "Source checksum for all modules"
1840 Modules which contain a MODULE_VERSION get an extra "srcversion"
1841 field inserted into their modinfo section, which contains a
1842 sum of the source files which made it. This helps maintainers
1843 see exactly which source was used to build a module (since
1844 others sometimes change the module source without updating
1845 the version). With this option, such a "srcversion" field
1846 will be created for all modules. If unsure, say N.
1849 bool "Module signature verification"
1851 select SYSTEM_TRUSTED_KEYRING
1854 select ASYMMETRIC_KEY_TYPE
1855 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1856 select PUBLIC_KEY_ALGO_RSA
1859 select X509_CERTIFICATE_PARSER
1861 Check modules for valid signatures upon load: the signature
1862 is simply appended to the module. For more information see
1863 Documentation/module-signing.txt.
1865 !!!WARNING!!! If you enable this option, you MUST make sure that the
1866 module DOES NOT get stripped after being signed. This includes the
1867 debuginfo strip done by some packagers (such as rpmbuild) and
1868 inclusion into an initramfs that wants the module size reduced.
1870 config MODULE_SIG_FORCE
1871 bool "Require modules to be validly signed"
1872 depends on MODULE_SIG
1874 Reject unsigned modules or signed modules for which we don't have a
1875 key. Without this, such modules will simply taint the kernel.
1877 config MODULE_SIG_ALL
1878 bool "Automatically sign all modules"
1880 depends on MODULE_SIG
1882 Sign all modules during make modules_install. Without this option,
1883 modules must be signed manually, using the scripts/sign-file tool.
1885 comment "Do not forget to sign required modules with scripts/sign-file"
1886 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1889 prompt "Which hash algorithm should modules be signed with?"
1890 depends on MODULE_SIG
1892 This determines which sort of hashing algorithm will be used during
1893 signature generation. This algorithm _must_ be built into the kernel
1894 directly so that signature verification can take place. It is not
1895 possible to load a signed module containing the algorithm to check
1896 the signature on that module.
1898 config MODULE_SIG_SHA1
1899 bool "Sign modules with SHA-1"
1902 config MODULE_SIG_SHA224
1903 bool "Sign modules with SHA-224"
1904 select CRYPTO_SHA256
1906 config MODULE_SIG_SHA256
1907 bool "Sign modules with SHA-256"
1908 select CRYPTO_SHA256
1910 config MODULE_SIG_SHA384
1911 bool "Sign modules with SHA-384"
1912 select CRYPTO_SHA512
1914 config MODULE_SIG_SHA512
1915 bool "Sign modules with SHA-512"
1916 select CRYPTO_SHA512
1920 config MODULE_SIG_HASH
1922 depends on MODULE_SIG
1923 default "sha1" if MODULE_SIG_SHA1
1924 default "sha224" if MODULE_SIG_SHA224
1925 default "sha256" if MODULE_SIG_SHA256
1926 default "sha384" if MODULE_SIG_SHA384
1927 default "sha512" if MODULE_SIG_SHA512
1929 config MODULE_COMPRESS
1930 bool "Compress modules on installation"
1933 This option compresses the kernel modules when 'make
1934 modules_install' is run.
1936 The modules will be compressed either using gzip or xz depend on the
1937 choice made in "Compression algorithm".
1939 module-init-tools has support for gzip format while kmod handle gzip
1940 and xz compressed modules.
1942 When a kernel module is installed from outside of the main kernel
1943 source and uses the Kbuild system for installing modules then that
1944 kernel module will also be compressed when it is installed.
1946 This option provides little benefit when the modules are to be used inside
1947 an initrd or initramfs, it generally is more efficient to compress the whole
1948 initrd or initramfs instead.
1950 This is fully compatible with signed modules while the signed module is
1951 compressed. module-init-tools or kmod handles decompression and provide to
1952 other layer the uncompressed but signed payload.
1955 prompt "Compression algorithm"
1956 depends on MODULE_COMPRESS
1957 default MODULE_COMPRESS_GZIP
1959 This determines which sort of compression will be used during
1960 'make modules_install'.
1962 GZIP (default) and XZ are supported.
1964 config MODULE_COMPRESS_GZIP
1967 config MODULE_COMPRESS_XZ
1974 config INIT_ALL_POSSIBLE
1977 Back when each arch used to define their own cpu_online_mask and
1978 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1979 with all 1s, and others with all 0s. When they were centralised,
1980 it was better to provide this option than to break all the archs
1981 and have several arch maintainers pursuing me down dark alleys.
1986 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1988 Need stop_machine() primitive.
1990 source "block/Kconfig"
1992 config PREEMPT_NOTIFIERS
1999 # Can be selected by architectures with broken toolchains
2000 # that get confused by correct const<->read_only section
2002 config BROKEN_RODATA
2008 Build a simple ASN.1 grammar compiler that produces a bytecode output
2009 that can be interpreted by the ASN.1 stream decoder and used to
2010 inform it as to what tags are to be expected in a stream and what
2011 functions to call on what tags.
2013 source "kernel/Kconfig.locks"
projects / mirror_ubuntu-jammy-kernel.git / blob