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
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"
399 If you say Y here, a user level program will be able to instruct the
400 kernel (via a special system call) to write process accounting
401 information to a file: whenever a process exits, information about
402 that process will be appended to the file by the kernel. The
403 information includes things such as creation time, owning user,
404 command name, memory usage, controlling terminal etc. (the complete
405 list is in the struct acct in <file:include/linux/acct.h>). It is
406 up to the user level program to do useful things with this
407 information. This is generally a good idea, so say Y.
409 config BSD_PROCESS_ACCT_V3
410 bool "BSD Process Accounting version 3 file format"
411 depends on BSD_PROCESS_ACCT
414 If you say Y here, the process accounting information is written
415 in a new file format that also logs the process IDs of each
416 process and it's parent. Note that this file format is incompatible
417 with previous v0/v1/v2 file formats, so you will need updated tools
418 for processing it. A preliminary version of these tools is available
419 at <http://www.gnu.org/software/acct/>.
422 bool "Export task/process statistics through netlink"
427 Export selected statistics for tasks/processes through the
428 generic netlink interface. Unlike BSD process accounting, the
429 statistics are available during the lifetime of tasks/processes as
430 responses to commands. Like BSD accounting, they are sent to user
435 config TASK_DELAY_ACCT
436 bool "Enable per-task delay accounting"
439 Collect information on time spent by a task waiting for system
440 resources like cpu, synchronous block I/O completion and swapping
441 in pages. Such statistics can help in setting a task's priorities
442 relative to other tasks for cpu, io, rss limits etc.
447 bool "Enable extended accounting over taskstats"
450 Collect extended task accounting data and send the data
451 to userland for processing over the taskstats interface.
455 config TASK_IO_ACCOUNTING
456 bool "Enable per-task storage I/O accounting"
457 depends on TASK_XACCT
459 Collect information on the number of bytes of storage I/O which this
464 endmenu # "CPU/Task time and stats accounting"
469 prompt "RCU Implementation"
473 bool "Tree-based hierarchical RCU"
474 depends on !PREEMPT && SMP
476 This option selects the RCU implementation that is
477 designed for very large SMP system with hundreds or
478 thousands of CPUs. It also scales down nicely to
482 bool "Preemptible tree-based hierarchical RCU"
485 This option selects the RCU implementation that is
486 designed for very large SMP systems with hundreds or
487 thousands of CPUs, but for which real-time response
488 is also required. It also scales down nicely to
491 Select this option if you are unsure.
494 bool "UP-only small-memory-footprint RCU"
495 depends on !PREEMPT && !SMP
497 This option selects the RCU implementation that is
498 designed for UP systems from which real-time response
499 is not required. This option greatly reduces the
500 memory footprint of RCU.
507 This option selects the sleepable version of RCU. This version
508 permits arbitrary sleeping or blocking within RCU read-side critical
512 bool "Task_based RCU implementation using voluntary context switch"
516 This option enables a task-based RCU implementation that uses
517 only voluntary context switch (not preemption!), idle, and
518 user-mode execution as quiescent states.
522 config RCU_STALL_COMMON
523 def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
525 This option enables RCU CPU stall code that is common between
526 the TINY and TREE variants of RCU. The purpose is to allow
527 the tiny variants to disable RCU CPU stall warnings, while
528 making these warnings mandatory for the tree variants.
530 config CONTEXT_TRACKING
534 bool "Consider userspace as in RCU extended quiescent state"
535 depends on HAVE_CONTEXT_TRACKING && SMP
536 select CONTEXT_TRACKING
538 This option sets hooks on kernel / userspace boundaries and
539 puts RCU in extended quiescent state when the CPU runs in
540 userspace. It means that when a CPU runs in userspace, it is
541 excluded from the global RCU state machine and thus doesn't
542 try to keep the timer tick on for RCU.
544 Unless you want to hack and help the development of the full
545 dynticks mode, you shouldn't enable this option. It also
546 adds unnecessary overhead.
550 config CONTEXT_TRACKING_FORCE
551 bool "Force context tracking"
552 depends on CONTEXT_TRACKING
553 default y if !NO_HZ_FULL
555 The major pre-requirement for full dynticks to work is to
556 support the context tracking subsystem. But there are also
557 other dependencies to provide in order to make the full
560 This option stands for testing when an arch implements the
561 context tracking backend but doesn't yet fullfill all the
562 requirements to make the full dynticks feature working.
563 Without the full dynticks, there is no way to test the support
564 for context tracking and the subsystems that rely on it: RCU
565 userspace extended quiescent state and tickless cputime
566 accounting. This option copes with the absence of the full
567 dynticks subsystem by forcing the context tracking on all
570 Say Y only if you're working on the development of an
571 architecture backend for the context tracking.
573 Say N otherwise, this option brings an overhead that you
574 don't want in production.
578 int "Tree-based hierarchical RCU fanout value"
581 depends on TREE_RCU || PREEMPT_RCU
585 This option controls the fanout of hierarchical implementations
586 of RCU, allowing RCU to work efficiently on machines with
587 large numbers of CPUs. This value must be at least the fourth
588 root of NR_CPUS, which allows NR_CPUS to be insanely large.
589 The default value of RCU_FANOUT should be used for production
590 systems, but if you are stress-testing the RCU implementation
591 itself, small RCU_FANOUT values allow you to test large-system
592 code paths on small(er) systems.
594 Select a specific number if testing RCU itself.
595 Take the default if unsure.
597 config RCU_FANOUT_LEAF
598 int "Tree-based hierarchical RCU leaf-level fanout value"
599 range 2 RCU_FANOUT if 64BIT
600 range 2 RCU_FANOUT if !64BIT
601 depends on TREE_RCU || PREEMPT_RCU
604 This option controls the leaf-level fanout of hierarchical
605 implementations of RCU, and allows trading off cache misses
606 against lock contention. Systems that synchronize their
607 scheduling-clock interrupts for energy-efficiency reasons will
608 want the default because the smaller leaf-level fanout keeps
609 lock contention levels acceptably low. Very large systems
610 (hundreds or thousands of CPUs) will instead want to set this
611 value to the maximum value possible in order to reduce the
612 number of cache misses incurred during RCU's grace-period
613 initialization. These systems tend to run CPU-bound, and thus
614 are not helped by synchronized interrupts, and thus tend to
615 skew them, which reduces lock contention enough that large
616 leaf-level fanouts work well.
618 Select a specific number if testing RCU itself.
620 Select the maximum permissible value for large systems.
622 Take the default if unsure.
624 config RCU_FANOUT_EXACT
625 bool "Disable tree-based hierarchical RCU auto-balancing"
626 depends on TREE_RCU || PREEMPT_RCU
629 This option forces use of the exact RCU_FANOUT value specified,
630 regardless of imbalances in the hierarchy. This is useful for
631 testing RCU itself, and might one day be useful on systems with
632 strong NUMA behavior.
634 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
638 config RCU_FAST_NO_HZ
639 bool "Accelerate last non-dyntick-idle CPU's grace periods"
640 depends on NO_HZ_COMMON && SMP
643 This option permits CPUs to enter dynticks-idle state even if
644 they have RCU callbacks queued, and prevents RCU from waking
645 these CPUs up more than roughly once every four jiffies (by
646 default, you can adjust this using the rcutree.rcu_idle_gp_delay
647 parameter), thus improving energy efficiency. On the other
648 hand, this option increases the duration of RCU grace periods,
649 for example, slowing down synchronize_rcu().
651 Say Y if energy efficiency is critically important, and you
652 don't care about increased grace-period durations.
654 Say N if you are unsure.
656 config TREE_RCU_TRACE
657 def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
660 This option provides tracing for the TREE_RCU and
661 PREEMPT_RCU implementations, permitting Makefile to
662 trivially select kernel/rcutree_trace.c.
665 bool "Enable RCU priority boosting"
666 depends on RT_MUTEXES && PREEMPT_RCU
669 This option boosts the priority of preempted RCU readers that
670 block the current preemptible RCU grace period for too long.
671 This option also prevents heavy loads from blocking RCU
672 callback invocation for all flavors of RCU.
674 Say Y here if you are working with real-time apps or heavy loads
675 Say N here if you are unsure.
677 config RCU_KTHREAD_PRIO
678 int "Real-time priority to use for RCU worker threads"
679 range 1 99 if RCU_BOOST
680 range 0 99 if !RCU_BOOST
681 default 1 if RCU_BOOST
682 default 0 if !RCU_BOOST
684 This option specifies the SCHED_FIFO priority value that will be
685 assigned to the rcuc/n and rcub/n threads and is also the value
686 used for RCU_BOOST (if enabled). If you are working with a
687 real-time application that has one or more CPU-bound threads
688 running at a real-time priority level, you should set
689 RCU_KTHREAD_PRIO to a priority higher than the highest-priority
690 real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO
691 value of 1 is appropriate in the common case, which is real-time
692 applications that do not have any CPU-bound threads.
694 Some real-time applications might not have a single real-time
695 thread that saturates a given CPU, but instead might have
696 multiple real-time threads that, taken together, fully utilize
697 that CPU. In this case, you should set RCU_KTHREAD_PRIO to
698 a priority higher than the lowest-priority thread that is
699 conspiring to prevent the CPU from running any non-real-time
700 tasks. For example, if one thread at priority 10 and another
701 thread at priority 5 are between themselves fully consuming
702 the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
703 set to priority 6 or higher.
705 Specify the real-time priority, or take the default if unsure.
707 config RCU_BOOST_DELAY
708 int "Milliseconds to delay boosting after RCU grace-period start"
713 This option specifies the time to wait after the beginning of
714 a given grace period before priority-boosting preempted RCU
715 readers blocking that grace period. Note that any RCU reader
716 blocking an expedited RCU grace period is boosted immediately.
718 Accept the default if unsure.
721 bool "Offload RCU callback processing from boot-selected CPUs"
722 depends on TREE_RCU || PREEMPT_RCU
725 Use this option to reduce OS jitter for aggressive HPC or
726 real-time workloads. It can also be used to offload RCU
727 callback invocation to energy-efficient CPUs in battery-powered
728 asymmetric multiprocessors.
730 This option offloads callback invocation from the set of
731 CPUs specified at boot time by the rcu_nocbs parameter.
732 For each such CPU, a kthread ("rcuox/N") will be created to
733 invoke callbacks, where the "N" is the CPU being offloaded,
734 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
735 "s" for RCU-sched. Nothing prevents this kthread from running
736 on the specified CPUs, but (1) the kthreads may be preempted
737 between each callback, and (2) affinity or cgroups can be used
738 to force the kthreads to run on whatever set of CPUs is desired.
740 Say Y here if you want to help to debug reduced OS jitter.
741 Say N here if you are unsure.
744 prompt "Build-forced no-CBs CPUs"
745 default RCU_NOCB_CPU_NONE
746 depends on RCU_NOCB_CPU
748 This option allows no-CBs CPUs (whose RCU callbacks are invoked
749 from kthreads rather than from softirq context) to be specified
750 at build time. Additional no-CBs CPUs may be specified by
751 the rcu_nocbs= boot parameter.
753 config RCU_NOCB_CPU_NONE
754 bool "No build_forced no-CBs CPUs"
756 This option does not force any of the CPUs to be no-CBs CPUs.
757 Only CPUs designated by the rcu_nocbs= boot parameter will be
758 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
759 kthreads whose names begin with "rcuo". All other CPUs will
760 invoke their own RCU callbacks in softirq context.
762 Select this option if you want to choose no-CBs CPUs at
763 boot time, for example, to allow testing of different no-CBs
764 configurations without having to rebuild the kernel each time.
766 config RCU_NOCB_CPU_ZERO
767 bool "CPU 0 is a build_forced no-CBs CPU"
769 This option forces CPU 0 to be a no-CBs CPU, so that its RCU
770 callbacks are invoked by a per-CPU kthread whose name begins
771 with "rcuo". Additional CPUs may be designated as no-CBs
772 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
773 All other CPUs will invoke their own RCU callbacks in softirq
776 Select this if CPU 0 needs to be a no-CBs CPU for real-time
777 or energy-efficiency reasons, but the real reason it exists
778 is to ensure that randconfig testing covers mixed systems.
780 config RCU_NOCB_CPU_ALL
781 bool "All CPUs are build_forced no-CBs CPUs"
783 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
784 boot parameter will be ignored. All CPUs' RCU callbacks will
785 be executed in the context of per-CPU rcuo kthreads created for
786 this purpose. Assuming that the kthreads whose names start with
787 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
788 on the remaining CPUs, but might decrease memory locality during
789 RCU-callback invocation, thus potentially degrading throughput.
791 Select this if all CPUs need to be no-CBs CPUs for real-time
792 or energy-efficiency reasons.
796 config RCU_EXPEDITE_BOOT
800 This option enables expedited grace periods at boot time,
801 as if rcu_expedite_gp() had been invoked early in boot.
802 The corresponding rcu_unexpedite_gp() is invoked from
803 rcu_end_inkernel_boot(), which is intended to be invoked
804 at the end of the kernel-only boot sequence, just before
807 Accept the default if unsure.
809 endmenu # "RCU Subsystem"
816 tristate "Kernel .config support"
819 This option enables the complete Linux kernel ".config" file
820 contents to be saved in the kernel. It provides documentation
821 of which kernel options are used in a running kernel or in an
822 on-disk kernel. This information can be extracted from the kernel
823 image file with the script scripts/extract-ikconfig and used as
824 input to rebuild the current kernel or to build another kernel.
825 It can also be extracted from a running kernel by reading
826 /proc/config.gz if enabled (below).
829 bool "Enable access to .config through /proc/config.gz"
830 depends on IKCONFIG && PROC_FS
832 This option enables access to the kernel configuration file
833 through /proc/config.gz.
836 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
841 Select the minimal kernel log buffer size as a power of 2.
842 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
843 parameter, see below. Any higher size also might be forced
844 by "log_buf_len" boot parameter.
854 config LOG_CPU_MAX_BUF_SHIFT
855 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
858 default 12 if !BASE_SMALL
859 default 0 if BASE_SMALL
862 This option allows to increase the default ring buffer size
863 according to the number of CPUs. The value defines the contribution
864 of each CPU as a power of 2. The used space is typically only few
865 lines however it might be much more when problems are reported,
868 The increased size means that a new buffer has to be allocated and
869 the original static one is unused. It makes sense only on systems
870 with more CPUs. Therefore this value is used only when the sum of
871 contributions is greater than the half of the default kernel ring
872 buffer as defined by LOG_BUF_SHIFT. The default values are set
873 so that more than 64 CPUs are needed to trigger the allocation.
875 Also this option is ignored when "log_buf_len" kernel parameter is
876 used as it forces an exact (power of two) size of the ring buffer.
878 The number of possible CPUs is used for this computation ignoring
879 hotplugging making the compuation optimal for the the worst case
880 scenerio while allowing a simple algorithm to be used from bootup.
882 Examples shift values and their meaning:
883 17 => 128 KB for each CPU
884 16 => 64 KB for each CPU
885 15 => 32 KB for each CPU
886 14 => 16 KB for each CPU
887 13 => 8 KB for each CPU
888 12 => 4 KB for each CPU
891 # Architectures with an unreliable sched_clock() should select this:
893 config HAVE_UNSTABLE_SCHED_CLOCK
896 config GENERIC_SCHED_CLOCK
900 # For architectures that want to enable the support for NUMA-affine scheduler
903 config ARCH_SUPPORTS_NUMA_BALANCING
907 # For architectures that know their GCC __int128 support is sound
909 config ARCH_SUPPORTS_INT128
912 # For architectures that (ab)use NUMA to represent different memory regions
913 # all cpu-local but of different latencies, such as SuperH.
915 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
918 config NUMA_BALANCING
919 bool "Memory placement aware NUMA scheduler"
920 depends on ARCH_SUPPORTS_NUMA_BALANCING
921 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
922 depends on SMP && NUMA && MIGRATION
924 This option adds support for automatic NUMA aware memory/task placement.
925 The mechanism is quite primitive and is based on migrating memory when
926 it has references to the node the task is running on.
928 This system will be inactive on UMA systems.
930 config NUMA_BALANCING_DEFAULT_ENABLED
931 bool "Automatically enable NUMA aware memory/task placement"
933 depends on NUMA_BALANCING
935 If set, automatic NUMA balancing will be enabled if running on a NUMA
939 bool "Control Group support"
942 This option adds support for grouping sets of processes together, for
943 use with process control subsystems such as Cpusets, CFS, memory
944 controls or device isolation.
946 - Documentation/scheduler/sched-design-CFS.txt (CFS)
947 - Documentation/cgroups/ (features for grouping, isolation
948 and resource control)
955 bool "Example debug cgroup subsystem"
958 This option enables a simple cgroup subsystem that
959 exports useful debugging information about the cgroups
964 config CGROUP_FREEZER
965 bool "Freezer cgroup subsystem"
967 Provides a way to freeze and unfreeze all tasks in a
971 bool "Device controller for cgroups"
973 Provides a cgroup implementing whitelists for devices which
974 a process in the cgroup can mknod or open.
977 bool "Cpuset support"
979 This option will let you create and manage CPUSETs which
980 allow dynamically partitioning a system into sets of CPUs and
981 Memory Nodes and assigning tasks to run only within those sets.
982 This is primarily useful on large SMP or NUMA systems.
986 config PROC_PID_CPUSET
987 bool "Include legacy /proc/<pid>/cpuset file"
991 config CGROUP_CPUACCT
992 bool "Simple CPU accounting cgroup subsystem"
994 Provides a simple Resource Controller for monitoring the
995 total CPU consumed by the tasks in a cgroup.
1001 bool "Memory Resource Controller for Control Groups"
1005 Provides a memory resource controller that manages both anonymous
1006 memory and page cache. (See Documentation/cgroups/memory.txt)
1009 bool "Memory Resource Controller Swap Extension"
1010 depends on MEMCG && SWAP
1012 Add swap management feature to memory resource controller. When you
1013 enable this, you can limit mem+swap usage per cgroup. In other words,
1014 when you disable this, memory resource controller has no cares to
1015 usage of swap...a process can exhaust all of the swap. This extension
1016 is useful when you want to avoid exhaustion swap but this itself
1017 adds more overheads and consumes memory for remembering information.
1018 Especially if you use 32bit system or small memory system, please
1019 be careful about enabling this. When memory resource controller
1020 is disabled by boot option, this will be automatically disabled and
1021 there will be no overhead from this. Even when you set this config=y,
1022 if boot option "swapaccount=0" is set, swap will not be accounted.
1023 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
1024 size is 4096bytes, 512k per 1Gbytes of swap.
1025 config MEMCG_SWAP_ENABLED
1026 bool "Memory Resource Controller Swap Extension enabled by default"
1027 depends on MEMCG_SWAP
1030 Memory Resource Controller Swap Extension comes with its price in
1031 a bigger memory consumption. General purpose distribution kernels
1032 which want to enable the feature but keep it disabled by default
1033 and let the user enable it by swapaccount=1 boot command line
1034 parameter should have this option unselected.
1035 For those who want to have the feature enabled by default should
1036 select this option (if, for some reason, they need to disable it
1037 then swapaccount=0 does the trick).
1039 bool "Memory Resource Controller Kernel Memory accounting"
1041 depends on SLUB || SLAB
1043 The Kernel Memory extension for Memory Resource Controller can limit
1044 the amount of memory used by kernel objects in the system. Those are
1045 fundamentally different from the entities handled by the standard
1046 Memory Controller, which are page-based, and can be swapped. Users of
1047 the kmem extension can use it to guarantee that no group of processes
1048 will ever exhaust kernel resources alone.
1050 WARNING: Current implementation lacks reclaim support. That means
1051 allocation attempts will fail when close to the limit even if there
1052 are plenty of kmem available for reclaim. That makes this option
1053 unusable in real life so DO NOT SELECT IT unless for development
1056 config CGROUP_HUGETLB
1057 bool "HugeTLB Resource Controller for Control Groups"
1058 depends on HUGETLB_PAGE
1062 Provides a cgroup Resource Controller for HugeTLB pages.
1063 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1064 The limit is enforced during page fault. Since HugeTLB doesn't
1065 support page reclaim, enforcing the limit at page fault time implies
1066 that, the application will get SIGBUS signal if it tries to access
1067 HugeTLB pages beyond its limit. This requires the application to know
1068 beforehand how much HugeTLB pages it would require for its use. The
1069 control group is tracked in the third page lru pointer. This means
1070 that we cannot use the controller with huge page less than 3 pages.
1073 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1074 depends on PERF_EVENTS && CGROUPS
1076 This option extends the per-cpu mode to restrict monitoring to
1077 threads which belong to the cgroup specified and run on the
1082 menuconfig CGROUP_SCHED
1083 bool "Group CPU scheduler"
1086 This feature lets CPU scheduler recognize task groups and control CPU
1087 bandwidth allocation to such task groups. It uses cgroups to group
1091 config FAIR_GROUP_SCHED
1092 bool "Group scheduling for SCHED_OTHER"
1093 depends on CGROUP_SCHED
1094 default CGROUP_SCHED
1096 config CFS_BANDWIDTH
1097 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1098 depends on FAIR_GROUP_SCHED
1101 This option allows users to define CPU bandwidth rates (limits) for
1102 tasks running within the fair group scheduler. Groups with no limit
1103 set are considered to be unconstrained and will run with no
1105 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1107 config RT_GROUP_SCHED
1108 bool "Group scheduling for SCHED_RR/FIFO"
1109 depends on CGROUP_SCHED
1112 This feature lets you explicitly allocate real CPU bandwidth
1113 to task groups. If enabled, it will also make it impossible to
1114 schedule realtime tasks for non-root users until you allocate
1115 realtime bandwidth for them.
1116 See Documentation/scheduler/sched-rt-group.txt for more information.
1121 bool "Block IO controller"
1125 Generic block IO controller cgroup interface. This is the common
1126 cgroup interface which should be used by various IO controlling
1129 Currently, CFQ IO scheduler uses it to recognize task groups and
1130 control disk bandwidth allocation (proportional time slice allocation)
1131 to such task groups. It is also used by bio throttling logic in
1132 block layer to implement upper limit in IO rates on a device.
1134 This option only enables generic Block IO controller infrastructure.
1135 One needs to also enable actual IO controlling logic/policy. For
1136 enabling proportional weight division of disk bandwidth in CFQ, set
1137 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1138 CONFIG_BLK_DEV_THROTTLING=y.
1140 See Documentation/cgroups/blkio-controller.txt for more information.
1142 config DEBUG_BLK_CGROUP
1143 bool "Enable Block IO controller debugging"
1144 depends on BLK_CGROUP
1147 Enable some debugging help. Currently it exports additional stat
1148 files in a cgroup which can be useful for debugging.
1152 config CHECKPOINT_RESTORE
1153 bool "Checkpoint/restore support" if EXPERT
1156 Enables additional kernel features in a sake of checkpoint/restore.
1157 In particular it adds auxiliary prctl codes to setup process text,
1158 data and heap segment sizes, and a few additional /proc filesystem
1161 If unsure, say N here.
1163 menuconfig NAMESPACES
1164 bool "Namespaces support" if EXPERT
1165 depends on MULTIUSER
1168 Provides the way to make tasks work with different objects using
1169 the same id. For example same IPC id may refer to different objects
1170 or same user id or pid may refer to different tasks when used in
1171 different namespaces.
1176 bool "UTS namespace"
1179 In this namespace tasks see different info provided with the
1183 bool "IPC namespace"
1184 depends on (SYSVIPC || POSIX_MQUEUE)
1187 In this namespace tasks work with IPC ids which correspond to
1188 different IPC objects in different namespaces.
1191 bool "User namespace"
1194 This allows containers, i.e. vservers, to use user namespaces
1195 to provide different user info for different servers.
1197 When user namespaces are enabled in the kernel it is
1198 recommended that the MEMCG and MEMCG_KMEM options also be
1199 enabled and that user-space use the memory control groups to
1200 limit the amount of memory a memory unprivileged users can
1206 bool "PID Namespaces"
1209 Support process id namespaces. This allows having multiple
1210 processes with the same pid as long as they are in different
1211 pid namespaces. This is a building block of containers.
1214 bool "Network namespace"
1218 Allow user space to create what appear to be multiple instances
1219 of the network stack.
1223 config SCHED_AUTOGROUP
1224 bool "Automatic process group scheduling"
1227 select FAIR_GROUP_SCHED
1229 This option optimizes the scheduler for common desktop workloads by
1230 automatically creating and populating task groups. This separation
1231 of workloads isolates aggressive CPU burners (like build jobs) from
1232 desktop applications. Task group autogeneration is currently based
1235 config SYSFS_DEPRECATED
1236 bool "Enable deprecated sysfs features to support old userspace tools"
1240 This option adds code that switches the layout of the "block" class
1241 devices, to not show up in /sys/class/block/, but only in
1244 This switch is only active when the sysfs.deprecated=1 boot option is
1245 passed or the SYSFS_DEPRECATED_V2 option is set.
1247 This option allows new kernels to run on old distributions and tools,
1248 which might get confused by /sys/class/block/. Since 2007/2008 all
1249 major distributions and tools handle this just fine.
1251 Recent distributions and userspace tools after 2009/2010 depend on
1252 the existence of /sys/class/block/, and will not work with this
1255 Only if you are using a new kernel on an old distribution, you might
1258 config SYSFS_DEPRECATED_V2
1259 bool "Enable deprecated sysfs features by default"
1262 depends on SYSFS_DEPRECATED
1264 Enable deprecated sysfs by default.
1266 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1269 Only if you are using a new kernel on an old distribution, you might
1270 need to say Y here. Even then, odds are you would not need it
1271 enabled, you can always pass the boot option if absolutely necessary.
1274 bool "Kernel->user space relay support (formerly relayfs)"
1276 This option enables support for relay interface support in
1277 certain file systems (such as debugfs).
1278 It is designed to provide an efficient mechanism for tools and
1279 facilities to relay large amounts of data from kernel space to
1284 config BLK_DEV_INITRD
1285 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1286 depends on BROKEN || !FRV
1288 The initial RAM filesystem is a ramfs which is loaded by the
1289 boot loader (loadlin or lilo) and that is mounted as root
1290 before the normal boot procedure. It is typically used to
1291 load modules needed to mount the "real" root file system,
1292 etc. See <file:Documentation/initrd.txt> for details.
1294 If RAM disk support (BLK_DEV_RAM) is also included, this
1295 also enables initial RAM disk (initrd) support and adds
1296 15 Kbytes (more on some other architectures) to the kernel size.
1302 source "usr/Kconfig"
1306 config CC_OPTIMIZE_FOR_SIZE
1307 bool "Optimize for size"
1309 Enabling this option will pass "-Os" instead of "-O2" to
1310 your compiler resulting in a smaller kernel.
1323 config SYSCTL_EXCEPTION_TRACE
1326 Enable support for /proc/sys/debug/exception-trace.
1328 config SYSCTL_ARCH_UNALIGN_NO_WARN
1331 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1332 Allows arch to define/use @no_unaligned_warning to possibly warn
1333 about unaligned access emulation going on under the hood.
1335 config SYSCTL_ARCH_UNALIGN_ALLOW
1338 Enable support for /proc/sys/kernel/unaligned-trap
1339 Allows arches to define/use @unaligned_enabled to runtime toggle
1340 the unaligned access emulation.
1341 see arch/parisc/kernel/unaligned.c for reference
1343 config HAVE_PCSPKR_PLATFORM
1346 # interpreter that classic socket filters depend on
1351 bool "Configure standard kernel features (expert users)"
1352 # Unhide debug options, to make the on-by-default options visible
1355 This option allows certain base kernel options and settings
1356 to be disabled or tweaked. This is for specialized
1357 environments which can tolerate a "non-standard" kernel.
1358 Only use this if you really know what you are doing.
1361 bool "Enable 16-bit UID system calls" if EXPERT
1362 depends on HAVE_UID16 && MULTIUSER
1365 This enables the legacy 16-bit UID syscall wrappers.
1368 bool "Multiple users, groups and capabilities support" if EXPERT
1371 This option enables support for non-root users, groups and
1374 If you say N here, all processes will run with UID 0, GID 0, and all
1375 possible capabilities. Saying N here also compiles out support for
1376 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1379 If unsure, say Y here.
1381 config SGETMASK_SYSCALL
1382 bool "sgetmask/ssetmask syscalls support" if EXPERT
1383 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1385 sys_sgetmask and sys_ssetmask are obsolete system calls
1386 no longer supported in libc but still enabled by default in some
1389 If unsure, leave the default option here.
1391 config SYSFS_SYSCALL
1392 bool "Sysfs syscall support" if EXPERT
1395 sys_sysfs is an obsolete system call no longer supported in libc.
1396 Note that disabling this option is more secure but might break
1397 compatibility with some systems.
1399 If unsure say Y here.
1401 config SYSCTL_SYSCALL
1402 bool "Sysctl syscall support" if EXPERT
1403 depends on PROC_SYSCTL
1407 sys_sysctl uses binary paths that have been found challenging
1408 to properly maintain and use. The interface in /proc/sys
1409 using paths with ascii names is now the primary path to this
1412 Almost nothing using the binary sysctl interface so if you are
1413 trying to save some space it is probably safe to disable this,
1414 making your kernel marginally smaller.
1416 If unsure say N here.
1419 bool "Load all symbols for debugging/ksymoops" if EXPERT
1422 Say Y here to let the kernel print out symbolic crash information and
1423 symbolic stack backtraces. This increases the size of the kernel
1424 somewhat, as all symbols have to be loaded into the kernel image.
1427 bool "Include all symbols in kallsyms"
1428 depends on DEBUG_KERNEL && KALLSYMS
1430 Normally kallsyms only contains the symbols of functions for nicer
1431 OOPS messages and backtraces (i.e., symbols from the text and inittext
1432 sections). This is sufficient for most cases. And only in very rare
1433 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1434 names of variables from the data sections, etc).
1436 This option makes sure that all symbols are loaded into the kernel
1437 image (i.e., symbols from all sections) in cost of increased kernel
1438 size (depending on the kernel configuration, it may be 300KiB or
1439 something like this).
1441 Say N unless you really need all symbols.
1445 bool "Enable support for printk" if EXPERT
1448 This option enables normal printk support. Removing it
1449 eliminates most of the message strings from the kernel image
1450 and makes the kernel more or less silent. As this makes it
1451 very difficult to diagnose system problems, saying N here is
1452 strongly discouraged.
1455 bool "BUG() support" if EXPERT
1458 Disabling this option eliminates support for BUG and WARN, reducing
1459 the size of your kernel image and potentially quietly ignoring
1460 numerous fatal conditions. You should only consider disabling this
1461 option for embedded systems with no facilities for reporting errors.
1467 bool "Enable ELF core dumps" if EXPERT
1469 Enable support for generating core dumps. Disabling saves about 4k.
1472 config PCSPKR_PLATFORM
1473 bool "Enable PC-Speaker support" if EXPERT
1474 depends on HAVE_PCSPKR_PLATFORM
1478 This option allows to disable the internal PC-Speaker
1479 support, saving some memory.
1483 bool "Enable full-sized data structures for core" if EXPERT
1485 Disabling this option reduces the size of miscellaneous core
1486 kernel data structures. This saves memory on small machines,
1487 but may reduce performance.
1490 bool "Enable futex support" if EXPERT
1494 Disabling this option will cause the kernel to be built without
1495 support for "fast userspace mutexes". The resulting kernel may not
1496 run glibc-based applications correctly.
1498 config HAVE_FUTEX_CMPXCHG
1502 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1503 is implemented and always working. This removes a couple of runtime
1507 bool "Enable eventpoll support" if EXPERT
1511 Disabling this option will cause the kernel to be built without
1512 support for epoll family of system calls.
1515 bool "Enable signalfd() system call" if EXPERT
1519 Enable the signalfd() system call that allows to receive signals
1520 on a file descriptor.
1525 bool "Enable timerfd() system call" if EXPERT
1529 Enable the timerfd() system call that allows to receive timer
1530 events on a file descriptor.
1535 bool "Enable eventfd() system call" if EXPERT
1539 Enable the eventfd() system call that allows to receive both
1540 kernel notification (ie. KAIO) or userspace notifications.
1544 # syscall, maps, verifier
1546 bool "Enable bpf() system call"
1551 Enable the bpf() system call that allows to manipulate eBPF
1552 programs and maps via file descriptors.
1555 bool "Use full shmem filesystem" if EXPERT
1559 The shmem is an internal filesystem used to manage shared memory.
1560 It is backed by swap and manages resource limits. It is also exported
1561 to userspace as tmpfs if TMPFS is enabled. Disabling this
1562 option replaces shmem and tmpfs with the much simpler ramfs code,
1563 which may be appropriate on small systems without swap.
1566 bool "Enable AIO support" if EXPERT
1569 This option enables POSIX asynchronous I/O which may by used
1570 by some high performance threaded applications. Disabling
1571 this option saves about 7k.
1573 config ADVISE_SYSCALLS
1574 bool "Enable madvise/fadvise syscalls" if EXPERT
1577 This option enables the madvise and fadvise syscalls, used by
1578 applications to advise the kernel about their future memory or file
1579 usage, improving performance. If building an embedded system where no
1580 applications use these syscalls, you can disable this option to save
1585 bool "Enable PCI quirk workarounds" if EXPERT
1588 This enables workarounds for various PCI chipset
1589 bugs/quirks. Disable this only if your target machine is
1590 unaffected by PCI quirks.
1593 bool "Embedded system"
1594 option allnoconfig_y
1597 This option should be enabled if compiling the kernel for
1598 an embedded system so certain expert options are available
1601 config HAVE_PERF_EVENTS
1604 See tools/perf/design.txt for details.
1606 config PERF_USE_VMALLOC
1609 See tools/perf/design.txt for details
1611 menu "Kernel Performance Events And Counters"
1614 bool "Kernel performance events and counters"
1615 default y if PROFILING
1616 depends on HAVE_PERF_EVENTS
1621 Enable kernel support for various performance events provided
1622 by software and hardware.
1624 Software events are supported either built-in or via the
1625 use of generic tracepoints.
1627 Most modern CPUs support performance events via performance
1628 counter registers. These registers count the number of certain
1629 types of hw events: such as instructions executed, cachemisses
1630 suffered, or branches mis-predicted - without slowing down the
1631 kernel or applications. These registers can also trigger interrupts
1632 when a threshold number of events have passed - and can thus be
1633 used to profile the code that runs on that CPU.
1635 The Linux Performance Event subsystem provides an abstraction of
1636 these software and hardware event capabilities, available via a
1637 system call and used by the "perf" utility in tools/perf/. It
1638 provides per task and per CPU counters, and it provides event
1639 capabilities on top of those.
1643 config DEBUG_PERF_USE_VMALLOC
1645 bool "Debug: use vmalloc to back perf mmap() buffers"
1646 depends on PERF_EVENTS && DEBUG_KERNEL
1647 select PERF_USE_VMALLOC
1649 Use vmalloc memory to back perf mmap() buffers.
1651 Mostly useful for debugging the vmalloc code on platforms
1652 that don't require it.
1658 config VM_EVENT_COUNTERS
1660 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1662 VM event counters are needed for event counts to be shown.
1663 This option allows the disabling of the VM event counters
1664 on EXPERT systems. /proc/vmstat will only show page counts
1665 if VM event counters are disabled.
1669 bool "Enable SLUB debugging support" if EXPERT
1670 depends on SLUB && SYSFS
1672 SLUB has extensive debug support features. Disabling these can
1673 result in significant savings in code size. This also disables
1674 SLUB sysfs support. /sys/slab will not exist and there will be
1675 no support for cache validation etc.
1678 bool "Disable heap randomization"
1681 Randomizing heap placement makes heap exploits harder, but it
1682 also breaks ancient binaries (including anything libc5 based).
1683 This option changes the bootup default to heap randomization
1684 disabled, and can be overridden at runtime by setting
1685 /proc/sys/kernel/randomize_va_space to 2.
1687 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1690 prompt "Choose SLAB allocator"
1693 This option allows to select a slab allocator.
1698 The regular slab allocator that is established and known to work
1699 well in all environments. It organizes cache hot objects in
1700 per cpu and per node queues.
1703 bool "SLUB (Unqueued Allocator)"
1705 SLUB is a slab allocator that minimizes cache line usage
1706 instead of managing queues of cached objects (SLAB approach).
1707 Per cpu caching is realized using slabs of objects instead
1708 of queues of objects. SLUB can use memory efficiently
1709 and has enhanced diagnostics. SLUB is the default choice for
1714 bool "SLOB (Simple Allocator)"
1716 SLOB replaces the stock allocator with a drastically simpler
1717 allocator. SLOB is generally more space efficient but
1718 does not perform as well on large systems.
1722 config SLUB_CPU_PARTIAL
1724 depends on SLUB && SMP
1725 bool "SLUB per cpu partial cache"
1727 Per cpu partial caches accellerate objects allocation and freeing
1728 that is local to a processor at the price of more indeterminism
1729 in the latency of the free. On overflow these caches will be cleared
1730 which requires the taking of locks that may cause latency spikes.
1731 Typically one would choose no for a realtime system.
1733 config MMAP_ALLOW_UNINITIALIZED
1734 bool "Allow mmapped anonymous memory to be uninitialized"
1735 depends on EXPERT && !MMU
1738 Normally, and according to the Linux spec, anonymous memory obtained
1739 from mmap() has it's contents cleared before it is passed to
1740 userspace. Enabling this config option allows you to request that
1741 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1742 providing a huge performance boost. If this option is not enabled,
1743 then the flag will be ignored.
1745 This is taken advantage of by uClibc's malloc(), and also by
1746 ELF-FDPIC binfmt's brk and stack allocator.
1748 Because of the obvious security issues, this option should only be
1749 enabled on embedded devices where you control what is run in
1750 userspace. Since that isn't generally a problem on no-MMU systems,
1751 it is normally safe to say Y here.
1753 See Documentation/nommu-mmap.txt for more information.
1755 config SYSTEM_TRUSTED_KEYRING
1756 bool "Provide system-wide ring of trusted keys"
1759 Provide a system keyring to which trusted keys can be added. Keys in
1760 the keyring are considered to be trusted. Keys may be added at will
1761 by the kernel from compiled-in data and from hardware key stores, but
1762 userspace may only add extra keys if those keys can be verified by
1763 keys already in the keyring.
1765 Keys in this keyring are used by module signature checking.
1768 bool "Profiling support"
1770 Say Y here to enable the extended profiling support mechanisms used
1771 by profilers such as OProfile.
1774 # Place an empty function call at each tracepoint site. Can be
1775 # dynamically changed for a probe function.
1780 source "arch/Kconfig"
1782 endmenu # General setup
1784 config HAVE_GENERIC_DMA_COHERENT
1791 depends on SLAB || SLUB_DEBUG
1799 default 0 if BASE_FULL
1800 default 1 if !BASE_FULL
1803 bool "Enable loadable module support"
1806 Kernel modules are small pieces of compiled code which can
1807 be inserted in the running kernel, rather than being
1808 permanently built into the kernel. You use the "modprobe"
1809 tool to add (and sometimes remove) them. If you say Y here,
1810 many parts of the kernel can be built as modules (by
1811 answering M instead of Y where indicated): this is most
1812 useful for infrequently used options which are not required
1813 for booting. For more information, see the man pages for
1814 modprobe, lsmod, modinfo, insmod and rmmod.
1816 If you say Y here, you will need to run "make
1817 modules_install" to put the modules under /lib/modules/
1818 where modprobe can find them (you may need to be root to do
1825 config MODULE_FORCE_LOAD
1826 bool "Forced module loading"
1829 Allow loading of modules without version information (ie. modprobe
1830 --force). Forced module loading sets the 'F' (forced) taint flag and
1831 is usually a really bad idea.
1833 config MODULE_UNLOAD
1834 bool "Module unloading"
1836 Without this option you will not be able to unload any
1837 modules (note that some modules may not be unloadable
1838 anyway), which makes your kernel smaller, faster
1839 and simpler. If unsure, say Y.
1841 config MODULE_FORCE_UNLOAD
1842 bool "Forced module unloading"
1843 depends on MODULE_UNLOAD
1845 This option allows you to force a module to unload, even if the
1846 kernel believes it is unsafe: the kernel will remove the module
1847 without waiting for anyone to stop using it (using the -f option to
1848 rmmod). This is mainly for kernel developers and desperate users.
1852 bool "Module versioning support"
1854 Usually, you have to use modules compiled with your kernel.
1855 Saying Y here makes it sometimes possible to use modules
1856 compiled for different kernels, by adding enough information
1857 to the modules to (hopefully) spot any changes which would
1858 make them incompatible with the kernel you are running. If
1861 config MODULE_SRCVERSION_ALL
1862 bool "Source checksum for all modules"
1864 Modules which contain a MODULE_VERSION get an extra "srcversion"
1865 field inserted into their modinfo section, which contains a
1866 sum of the source files which made it. This helps maintainers
1867 see exactly which source was used to build a module (since
1868 others sometimes change the module source without updating
1869 the version). With this option, such a "srcversion" field
1870 will be created for all modules. If unsure, say N.
1873 bool "Module signature verification"
1875 select SYSTEM_TRUSTED_KEYRING
1878 select ASYMMETRIC_KEY_TYPE
1879 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1880 select PUBLIC_KEY_ALGO_RSA
1883 select X509_CERTIFICATE_PARSER
1885 Check modules for valid signatures upon load: the signature
1886 is simply appended to the module. For more information see
1887 Documentation/module-signing.txt.
1889 !!!WARNING!!! If you enable this option, you MUST make sure that the
1890 module DOES NOT get stripped after being signed. This includes the
1891 debuginfo strip done by some packagers (such as rpmbuild) and
1892 inclusion into an initramfs that wants the module size reduced.
1894 config MODULE_SIG_FORCE
1895 bool "Require modules to be validly signed"
1896 depends on MODULE_SIG
1898 Reject unsigned modules or signed modules for which we don't have a
1899 key. Without this, such modules will simply taint the kernel.
1901 config MODULE_SIG_ALL
1902 bool "Automatically sign all modules"
1904 depends on MODULE_SIG
1906 Sign all modules during make modules_install. Without this option,
1907 modules must be signed manually, using the scripts/sign-file tool.
1909 comment "Do not forget to sign required modules with scripts/sign-file"
1910 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1913 prompt "Which hash algorithm should modules be signed with?"
1914 depends on MODULE_SIG
1916 This determines which sort of hashing algorithm will be used during
1917 signature generation. This algorithm _must_ be built into the kernel
1918 directly so that signature verification can take place. It is not
1919 possible to load a signed module containing the algorithm to check
1920 the signature on that module.
1922 config MODULE_SIG_SHA1
1923 bool "Sign modules with SHA-1"
1926 config MODULE_SIG_SHA224
1927 bool "Sign modules with SHA-224"
1928 select CRYPTO_SHA256
1930 config MODULE_SIG_SHA256
1931 bool "Sign modules with SHA-256"
1932 select CRYPTO_SHA256
1934 config MODULE_SIG_SHA384
1935 bool "Sign modules with SHA-384"
1936 select CRYPTO_SHA512
1938 config MODULE_SIG_SHA512
1939 bool "Sign modules with SHA-512"
1940 select CRYPTO_SHA512
1944 config MODULE_SIG_HASH
1946 depends on MODULE_SIG
1947 default "sha1" if MODULE_SIG_SHA1
1948 default "sha224" if MODULE_SIG_SHA224
1949 default "sha256" if MODULE_SIG_SHA256
1950 default "sha384" if MODULE_SIG_SHA384
1951 default "sha512" if MODULE_SIG_SHA512
1953 config MODULE_COMPRESS
1954 bool "Compress modules on installation"
1957 This option compresses the kernel modules when 'make
1958 modules_install' is run.
1960 The modules will be compressed either using gzip or xz depend on the
1961 choice made in "Compression algorithm".
1963 module-init-tools has support for gzip format while kmod handle gzip
1964 and xz compressed modules.
1966 When a kernel module is installed from outside of the main kernel
1967 source and uses the Kbuild system for installing modules then that
1968 kernel module will also be compressed when it is installed.
1970 This option provides little benefit when the modules are to be used inside
1971 an initrd or initramfs, it generally is more efficient to compress the whole
1972 initrd or initramfs instead.
1974 This is fully compatible with signed modules while the signed module is
1975 compressed. module-init-tools or kmod handles decompression and provide to
1976 other layer the uncompressed but signed payload.
1979 prompt "Compression algorithm"
1980 depends on MODULE_COMPRESS
1981 default MODULE_COMPRESS_GZIP
1983 This determines which sort of compression will be used during
1984 'make modules_install'.
1986 GZIP (default) and XZ are supported.
1988 config MODULE_COMPRESS_GZIP
1991 config MODULE_COMPRESS_XZ
1998 config INIT_ALL_POSSIBLE
2001 Back when each arch used to define their own cpu_online_mask and
2002 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2003 with all 1s, and others with all 0s. When they were centralised,
2004 it was better to provide this option than to break all the archs
2005 and have several arch maintainers pursuing me down dark alleys.
2010 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
2012 Need stop_machine() primitive.
2014 source "block/Kconfig"
2016 config PREEMPT_NOTIFIERS
2023 # Can be selected by architectures with broken toolchains
2024 # that get confused by correct const<->read_only section
2026 config BROKEN_RODATA
2032 Build a simple ASN.1 grammar compiler that produces a bytecode output
2033 that can be interpreted by the ASN.1 stream decoder and used to
2034 inform it as to what tags are to be expected in a stream and what
2035 functions to call on what tags.
2037 source "kernel/Kconfig.locks"
projects / linux.git / blob