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"
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"
470 default y if !PREEMPT && SMP
472 This option selects the RCU implementation that is
473 designed for very large SMP system with hundreds or
474 thousands of CPUs. It also scales down nicely to
481 This option selects the RCU implementation that is
482 designed for very large SMP systems with hundreds or
483 thousands of CPUs, but for which real-time response
484 is also required. It also scales down nicely to
487 Select this option if you are unsure.
491 default y if !PREEMPT && !SMP
493 This option selects the RCU implementation that is
494 designed for UP systems from which real-time response
495 is not required. This option greatly reduces the
496 memory footprint of RCU.
499 bool "Make expert-level adjustments to RCU configuration"
502 This option needs to be enabled if you wish to make
503 expert-level adjustments to RCU configuration. By default,
504 no such adjustments can be made, which has the often-beneficial
505 side-effect of preventing "make oldconfig" from asking you all
506 sorts of detailed questions about how you would like numerous
507 obscure RCU options to be set up.
509 Say Y if you need to make expert-level adjustments to RCU.
511 Say N if you are unsure.
516 This option selects the sleepable version of RCU. This version
517 permits arbitrary sleeping or blocking within RCU read-side critical
525 This option enables a task-based RCU implementation that uses
526 only voluntary context switch (not preemption!), idle, and
527 user-mode execution as quiescent states.
529 config RCU_STALL_COMMON
530 def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
532 This option enables RCU CPU stall code that is common between
533 the TINY and TREE variants of RCU. The purpose is to allow
534 the tiny variants to disable RCU CPU stall warnings, while
535 making these warnings mandatory for the tree variants.
537 config CONTEXT_TRACKING
543 This option sets hooks on kernel / userspace boundaries and
544 puts RCU in extended quiescent state when the CPU runs in
545 userspace. It means that when a CPU runs in userspace, it is
546 excluded from the global RCU state machine and thus doesn't
547 try to keep the timer tick on for RCU.
549 config CONTEXT_TRACKING_FORCE
550 bool "Force context tracking"
551 depends on CONTEXT_TRACKING
552 default y if !NO_HZ_FULL
554 The major pre-requirement for full dynticks to work is to
555 support the context tracking subsystem. But there are also
556 other dependencies to provide in order to make the full
559 This option stands for testing when an arch implements the
560 context tracking backend but doesn't yet fullfill all the
561 requirements to make the full dynticks feature working.
562 Without the full dynticks, there is no way to test the support
563 for context tracking and the subsystems that rely on it: RCU
564 userspace extended quiescent state and tickless cputime
565 accounting. This option copes with the absence of the full
566 dynticks subsystem by forcing the context tracking on all
569 Say Y only if you're working on the development of an
570 architecture backend for the context tracking.
572 Say N otherwise, this option brings an overhead that you
573 don't want in production.
577 int "Tree-based hierarchical RCU fanout value"
580 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
584 This option controls the fanout of hierarchical implementations
585 of RCU, allowing RCU to work efficiently on machines with
586 large numbers of CPUs. This value must be at least the fourth
587 root of NR_CPUS, which allows NR_CPUS to be insanely large.
588 The default value of RCU_FANOUT should be used for production
589 systems, but if you are stress-testing the RCU implementation
590 itself, small RCU_FANOUT values allow you to test large-system
591 code paths on small(er) systems.
593 Select a specific number if testing RCU itself.
594 Take the default if unsure.
596 config RCU_FANOUT_LEAF
597 int "Tree-based hierarchical RCU leaf-level fanout value"
600 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
603 This option controls the leaf-level fanout of hierarchical
604 implementations of RCU, and allows trading off cache misses
605 against lock contention. Systems that synchronize their
606 scheduling-clock interrupts for energy-efficiency reasons will
607 want the default because the smaller leaf-level fanout keeps
608 lock contention levels acceptably low. Very large systems
609 (hundreds or thousands of CPUs) will instead want to set this
610 value to the maximum value possible in order to reduce the
611 number of cache misses incurred during RCU's grace-period
612 initialization. These systems tend to run CPU-bound, and thus
613 are not helped by synchronized interrupts, and thus tend to
614 skew them, which reduces lock contention enough that large
615 leaf-level fanouts work well.
617 Select a specific number if testing RCU itself.
619 Select the maximum permissible value for large systems.
621 Take the default if unsure.
623 config RCU_FAST_NO_HZ
624 bool "Accelerate last non-dyntick-idle CPU's grace periods"
625 depends on NO_HZ_COMMON && SMP && RCU_EXPERT
628 This option permits CPUs to enter dynticks-idle state even if
629 they have RCU callbacks queued, and prevents RCU from waking
630 these CPUs up more than roughly once every four jiffies (by
631 default, you can adjust this using the rcutree.rcu_idle_gp_delay
632 parameter), thus improving energy efficiency. On the other
633 hand, this option increases the duration of RCU grace periods,
634 for example, slowing down synchronize_rcu().
636 Say Y if energy efficiency is critically important, and you
637 don't care about increased grace-period durations.
639 Say N if you are unsure.
641 config TREE_RCU_TRACE
642 def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
645 This option provides tracing for the TREE_RCU and
646 PREEMPT_RCU implementations, permitting Makefile to
647 trivially select kernel/rcutree_trace.c.
650 bool "Enable RCU priority boosting"
651 depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT
654 This option boosts the priority of preempted RCU readers that
655 block the current preemptible RCU grace period for too long.
656 This option also prevents heavy loads from blocking RCU
657 callback invocation for all flavors of RCU.
659 Say Y here if you are working with real-time apps or heavy loads
660 Say N here if you are unsure.
662 config RCU_KTHREAD_PRIO
663 int "Real-time priority to use for RCU worker threads"
664 range 1 99 if RCU_BOOST
665 range 0 99 if !RCU_BOOST
666 default 1 if RCU_BOOST
667 default 0 if !RCU_BOOST
668 depends on RCU_EXPERT
670 This option specifies the SCHED_FIFO priority value that will be
671 assigned to the rcuc/n and rcub/n threads and is also the value
672 used for RCU_BOOST (if enabled). If you are working with a
673 real-time application that has one or more CPU-bound threads
674 running at a real-time priority level, you should set
675 RCU_KTHREAD_PRIO to a priority higher than the highest-priority
676 real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO
677 value of 1 is appropriate in the common case, which is real-time
678 applications that do not have any CPU-bound threads.
680 Some real-time applications might not have a single real-time
681 thread that saturates a given CPU, but instead might have
682 multiple real-time threads that, taken together, fully utilize
683 that CPU. In this case, you should set RCU_KTHREAD_PRIO to
684 a priority higher than the lowest-priority thread that is
685 conspiring to prevent the CPU from running any non-real-time
686 tasks. For example, if one thread at priority 10 and another
687 thread at priority 5 are between themselves fully consuming
688 the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
689 set to priority 6 or higher.
691 Specify the real-time priority, or take the default if unsure.
693 config RCU_BOOST_DELAY
694 int "Milliseconds to delay boosting after RCU grace-period start"
699 This option specifies the time to wait after the beginning of
700 a given grace period before priority-boosting preempted RCU
701 readers blocking that grace period. Note that any RCU reader
702 blocking an expedited RCU grace period is boosted immediately.
704 Accept the default if unsure.
707 bool "Offload RCU callback processing from boot-selected CPUs"
708 depends on TREE_RCU || PREEMPT_RCU
711 Use this option to reduce OS jitter for aggressive HPC or
712 real-time workloads. It can also be used to offload RCU
713 callback invocation to energy-efficient CPUs in battery-powered
714 asymmetric multiprocessors.
716 This option offloads callback invocation from the set of
717 CPUs specified at boot time by the rcu_nocbs parameter.
718 For each such CPU, a kthread ("rcuox/N") will be created to
719 invoke callbacks, where the "N" is the CPU being offloaded,
720 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
721 "s" for RCU-sched. Nothing prevents this kthread from running
722 on the specified CPUs, but (1) the kthreads may be preempted
723 between each callback, and (2) affinity or cgroups can be used
724 to force the kthreads to run on whatever set of CPUs is desired.
726 Say Y here if you want to help to debug reduced OS jitter.
727 Say N here if you are unsure.
730 prompt "Build-forced no-CBs CPUs"
731 default RCU_NOCB_CPU_NONE
732 depends on RCU_NOCB_CPU
734 This option allows no-CBs CPUs (whose RCU callbacks are invoked
735 from kthreads rather than from softirq context) to be specified
736 at build time. Additional no-CBs CPUs may be specified by
737 the rcu_nocbs= boot parameter.
739 config RCU_NOCB_CPU_NONE
740 bool "No build_forced no-CBs CPUs"
742 This option does not force any of the CPUs to be no-CBs CPUs.
743 Only CPUs designated by the rcu_nocbs= boot parameter will be
744 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
745 kthreads whose names begin with "rcuo". All other CPUs will
746 invoke their own RCU callbacks in softirq context.
748 Select this option if you want to choose no-CBs CPUs at
749 boot time, for example, to allow testing of different no-CBs
750 configurations without having to rebuild the kernel each time.
752 config RCU_NOCB_CPU_ZERO
753 bool "CPU 0 is a build_forced no-CBs CPU"
755 This option forces CPU 0 to be a no-CBs CPU, so that its RCU
756 callbacks are invoked by a per-CPU kthread whose name begins
757 with "rcuo". Additional CPUs may be designated as no-CBs
758 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
759 All other CPUs will invoke their own RCU callbacks in softirq
762 Select this if CPU 0 needs to be a no-CBs CPU for real-time
763 or energy-efficiency reasons, but the real reason it exists
764 is to ensure that randconfig testing covers mixed systems.
766 config RCU_NOCB_CPU_ALL
767 bool "All CPUs are build_forced no-CBs CPUs"
769 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
770 boot parameter will be ignored. All CPUs' RCU callbacks will
771 be executed in the context of per-CPU rcuo kthreads created for
772 this purpose. Assuming that the kthreads whose names start with
773 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
774 on the remaining CPUs, but might decrease memory locality during
775 RCU-callback invocation, thus potentially degrading throughput.
777 Select this if all CPUs need to be no-CBs CPUs for real-time
778 or energy-efficiency reasons.
782 config RCU_EXPEDITE_BOOT
786 This option enables expedited grace periods at boot time,
787 as if rcu_expedite_gp() had been invoked early in boot.
788 The corresponding rcu_unexpedite_gp() is invoked from
789 rcu_end_inkernel_boot(), which is intended to be invoked
790 at the end of the kernel-only boot sequence, just before
793 Accept the default if unsure.
795 endmenu # "RCU Subsystem"
802 tristate "Kernel .config support"
805 This option enables the complete Linux kernel ".config" file
806 contents to be saved in the kernel. It provides documentation
807 of which kernel options are used in a running kernel or in an
808 on-disk kernel. This information can be extracted from the kernel
809 image file with the script scripts/extract-ikconfig and used as
810 input to rebuild the current kernel or to build another kernel.
811 It can also be extracted from a running kernel by reading
812 /proc/config.gz if enabled (below).
815 bool "Enable access to .config through /proc/config.gz"
816 depends on IKCONFIG && PROC_FS
818 This option enables access to the kernel configuration file
819 through /proc/config.gz.
822 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
827 Select the minimal kernel log buffer size as a power of 2.
828 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
829 parameter, see below. Any higher size also might be forced
830 by "log_buf_len" boot parameter.
840 config LOG_CPU_MAX_BUF_SHIFT
841 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
844 default 12 if !BASE_SMALL
845 default 0 if BASE_SMALL
848 This option allows to increase the default ring buffer size
849 according to the number of CPUs. The value defines the contribution
850 of each CPU as a power of 2. The used space is typically only few
851 lines however it might be much more when problems are reported,
854 The increased size means that a new buffer has to be allocated and
855 the original static one is unused. It makes sense only on systems
856 with more CPUs. Therefore this value is used only when the sum of
857 contributions is greater than the half of the default kernel ring
858 buffer as defined by LOG_BUF_SHIFT. The default values are set
859 so that more than 64 CPUs are needed to trigger the allocation.
861 Also this option is ignored when "log_buf_len" kernel parameter is
862 used as it forces an exact (power of two) size of the ring buffer.
864 The number of possible CPUs is used for this computation ignoring
865 hotplugging making the compuation optimal for the the worst case
866 scenerio while allowing a simple algorithm to be used from bootup.
868 Examples shift values and their meaning:
869 17 => 128 KB for each CPU
870 16 => 64 KB for each CPU
871 15 => 32 KB for each CPU
872 14 => 16 KB for each CPU
873 13 => 8 KB for each CPU
874 12 => 4 KB for each CPU
877 # Architectures with an unreliable sched_clock() should select this:
879 config HAVE_UNSTABLE_SCHED_CLOCK
882 config GENERIC_SCHED_CLOCK
886 # For architectures that want to enable the support for NUMA-affine scheduler
889 config ARCH_SUPPORTS_NUMA_BALANCING
893 # For architectures that know their GCC __int128 support is sound
895 config ARCH_SUPPORTS_INT128
898 # For architectures that (ab)use NUMA to represent different memory regions
899 # all cpu-local but of different latencies, such as SuperH.
901 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
904 config NUMA_BALANCING
905 bool "Memory placement aware NUMA scheduler"
906 depends on ARCH_SUPPORTS_NUMA_BALANCING
907 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
908 depends on SMP && NUMA && MIGRATION
910 This option adds support for automatic NUMA aware memory/task placement.
911 The mechanism is quite primitive and is based on migrating memory when
912 it has references to the node the task is running on.
914 This system will be inactive on UMA systems.
916 config NUMA_BALANCING_DEFAULT_ENABLED
917 bool "Automatically enable NUMA aware memory/task placement"
919 depends on NUMA_BALANCING
921 If set, automatic NUMA balancing will be enabled if running on a NUMA
925 bool "Control Group support"
929 This option adds support for grouping sets of processes together, for
930 use with process control subsystems such as Cpusets, CFS, memory
931 controls or device isolation.
933 - Documentation/scheduler/sched-design-CFS.txt (CFS)
934 - Documentation/cgroups/ (features for grouping, isolation
935 and resource control)
942 bool "Example debug cgroup subsystem"
945 This option enables a simple cgroup subsystem that
946 exports useful debugging information about the cgroups
951 config CGROUP_FREEZER
952 bool "Freezer cgroup subsystem"
954 Provides a way to freeze and unfreeze all tasks in a
958 bool "Device controller for cgroups"
960 Provides a cgroup implementing whitelists for devices which
961 a process in the cgroup can mknod or open.
964 bool "Cpuset support"
966 This option will let you create and manage CPUSETs which
967 allow dynamically partitioning a system into sets of CPUs and
968 Memory Nodes and assigning tasks to run only within those sets.
969 This is primarily useful on large SMP or NUMA systems.
973 config PROC_PID_CPUSET
974 bool "Include legacy /proc/<pid>/cpuset file"
978 config CGROUP_CPUACCT
979 bool "Simple CPU accounting cgroup subsystem"
981 Provides a simple Resource Controller for monitoring the
982 total CPU consumed by the tasks in a cgroup.
988 bool "Memory Resource Controller for Control Groups"
992 Provides a memory resource controller that manages both anonymous
993 memory and page cache. (See Documentation/cgroups/memory.txt)
996 bool "Memory Resource Controller Swap Extension"
997 depends on MEMCG && SWAP
999 Add swap management feature to memory resource controller. When you
1000 enable this, you can limit mem+swap usage per cgroup. In other words,
1001 when you disable this, memory resource controller has no cares to
1002 usage of swap...a process can exhaust all of the swap. This extension
1003 is useful when you want to avoid exhaustion swap but this itself
1004 adds more overheads and consumes memory for remembering information.
1005 Especially if you use 32bit system or small memory system, please
1006 be careful about enabling this. When memory resource controller
1007 is disabled by boot option, this will be automatically disabled and
1008 there will be no overhead from this. Even when you set this config=y,
1009 if boot option "swapaccount=0" is set, swap will not be accounted.
1010 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
1011 size is 4096bytes, 512k per 1Gbytes of swap.
1012 config MEMCG_SWAP_ENABLED
1013 bool "Memory Resource Controller Swap Extension enabled by default"
1014 depends on MEMCG_SWAP
1017 Memory Resource Controller Swap Extension comes with its price in
1018 a bigger memory consumption. General purpose distribution kernels
1019 which want to enable the feature but keep it disabled by default
1020 and let the user enable it by swapaccount=1 boot command line
1021 parameter should have this option unselected.
1022 For those who want to have the feature enabled by default should
1023 select this option (if, for some reason, they need to disable it
1024 then swapaccount=0 does the trick).
1026 bool "Memory Resource Controller Kernel Memory accounting"
1028 depends on SLUB || SLAB
1030 The Kernel Memory extension for Memory Resource Controller can limit
1031 the amount of memory used by kernel objects in the system. Those are
1032 fundamentally different from the entities handled by the standard
1033 Memory Controller, which are page-based, and can be swapped. Users of
1034 the kmem extension can use it to guarantee that no group of processes
1035 will ever exhaust kernel resources alone.
1037 config CGROUP_HUGETLB
1038 bool "HugeTLB Resource Controller for Control Groups"
1039 depends on HUGETLB_PAGE
1043 Provides a cgroup Resource Controller for HugeTLB pages.
1044 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1045 The limit is enforced during page fault. Since HugeTLB doesn't
1046 support page reclaim, enforcing the limit at page fault time implies
1047 that, the application will get SIGBUS signal if it tries to access
1048 HugeTLB pages beyond its limit. This requires the application to know
1049 beforehand how much HugeTLB pages it would require for its use. The
1050 control group is tracked in the third page lru pointer. This means
1051 that we cannot use the controller with huge page less than 3 pages.
1054 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1055 depends on PERF_EVENTS && CGROUPS
1057 This option extends the per-cpu mode to restrict monitoring to
1058 threads which belong to the cgroup specified and run on the
1063 menuconfig CGROUP_SCHED
1064 bool "Group CPU scheduler"
1067 This feature lets CPU scheduler recognize task groups and control CPU
1068 bandwidth allocation to such task groups. It uses cgroups to group
1072 config FAIR_GROUP_SCHED
1073 bool "Group scheduling for SCHED_OTHER"
1074 depends on CGROUP_SCHED
1075 default CGROUP_SCHED
1077 config CFS_BANDWIDTH
1078 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1079 depends on FAIR_GROUP_SCHED
1082 This option allows users to define CPU bandwidth rates (limits) for
1083 tasks running within the fair group scheduler. Groups with no limit
1084 set are considered to be unconstrained and will run with no
1086 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1088 config RT_GROUP_SCHED
1089 bool "Group scheduling for SCHED_RR/FIFO"
1090 depends on CGROUP_SCHED
1093 This feature lets you explicitly allocate real CPU bandwidth
1094 to task groups. If enabled, it will also make it impossible to
1095 schedule realtime tasks for non-root users until you allocate
1096 realtime bandwidth for them.
1097 See Documentation/scheduler/sched-rt-group.txt for more information.
1102 bool "Block IO controller"
1106 Generic block IO controller cgroup interface. This is the common
1107 cgroup interface which should be used by various IO controlling
1110 Currently, CFQ IO scheduler uses it to recognize task groups and
1111 control disk bandwidth allocation (proportional time slice allocation)
1112 to such task groups. It is also used by bio throttling logic in
1113 block layer to implement upper limit in IO rates on a device.
1115 This option only enables generic Block IO controller infrastructure.
1116 One needs to also enable actual IO controlling logic/policy. For
1117 enabling proportional weight division of disk bandwidth in CFQ, set
1118 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1119 CONFIG_BLK_DEV_THROTTLING=y.
1121 See Documentation/cgroups/blkio-controller.txt for more information.
1123 config DEBUG_BLK_CGROUP
1124 bool "Enable Block IO controller debugging"
1125 depends on BLK_CGROUP
1128 Enable some debugging help. Currently it exports additional stat
1129 files in a cgroup which can be useful for debugging.
1131 config CGROUP_WRITEBACK
1133 depends on MEMCG && BLK_CGROUP
1138 config CHECKPOINT_RESTORE
1139 bool "Checkpoint/restore support" if EXPERT
1140 select PROC_CHILDREN
1143 Enables additional kernel features in a sake of checkpoint/restore.
1144 In particular it adds auxiliary prctl codes to setup process text,
1145 data and heap segment sizes, and a few additional /proc filesystem
1148 If unsure, say N here.
1150 menuconfig NAMESPACES
1151 bool "Namespaces support" if EXPERT
1152 depends on MULTIUSER
1155 Provides the way to make tasks work with different objects using
1156 the same id. For example same IPC id may refer to different objects
1157 or same user id or pid may refer to different tasks when used in
1158 different namespaces.
1163 bool "UTS namespace"
1166 In this namespace tasks see different info provided with the
1170 bool "IPC namespace"
1171 depends on (SYSVIPC || POSIX_MQUEUE)
1174 In this namespace tasks work with IPC ids which correspond to
1175 different IPC objects in different namespaces.
1178 bool "User namespace"
1181 This allows containers, i.e. vservers, to use user namespaces
1182 to provide different user info for different servers.
1184 When user namespaces are enabled in the kernel it is
1185 recommended that the MEMCG and MEMCG_KMEM options also be
1186 enabled and that user-space use the memory control groups to
1187 limit the amount of memory a memory unprivileged users can
1193 bool "PID Namespaces"
1196 Support process id namespaces. This allows having multiple
1197 processes with the same pid as long as they are in different
1198 pid namespaces. This is a building block of containers.
1201 bool "Network namespace"
1205 Allow user space to create what appear to be multiple instances
1206 of the network stack.
1210 config SCHED_AUTOGROUP
1211 bool "Automatic process group scheduling"
1214 select FAIR_GROUP_SCHED
1216 This option optimizes the scheduler for common desktop workloads by
1217 automatically creating and populating task groups. This separation
1218 of workloads isolates aggressive CPU burners (like build jobs) from
1219 desktop applications. Task group autogeneration is currently based
1222 config SYSFS_DEPRECATED
1223 bool "Enable deprecated sysfs features to support old userspace tools"
1227 This option adds code that switches the layout of the "block" class
1228 devices, to not show up in /sys/class/block/, but only in
1231 This switch is only active when the sysfs.deprecated=1 boot option is
1232 passed or the SYSFS_DEPRECATED_V2 option is set.
1234 This option allows new kernels to run on old distributions and tools,
1235 which might get confused by /sys/class/block/. Since 2007/2008 all
1236 major distributions and tools handle this just fine.
1238 Recent distributions and userspace tools after 2009/2010 depend on
1239 the existence of /sys/class/block/, and will not work with this
1242 Only if you are using a new kernel on an old distribution, you might
1245 config SYSFS_DEPRECATED_V2
1246 bool "Enable deprecated sysfs features by default"
1249 depends on SYSFS_DEPRECATED
1251 Enable deprecated sysfs by default.
1253 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1256 Only if you are using a new kernel on an old distribution, you might
1257 need to say Y here. Even then, odds are you would not need it
1258 enabled, you can always pass the boot option if absolutely necessary.
1261 bool "Kernel->user space relay support (formerly relayfs)"
1263 This option enables support for relay interface support in
1264 certain file systems (such as debugfs).
1265 It is designed to provide an efficient mechanism for tools and
1266 facilities to relay large amounts of data from kernel space to
1271 config BLK_DEV_INITRD
1272 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1273 depends on BROKEN || !FRV
1275 The initial RAM filesystem is a ramfs which is loaded by the
1276 boot loader (loadlin or lilo) and that is mounted as root
1277 before the normal boot procedure. It is typically used to
1278 load modules needed to mount the "real" root file system,
1279 etc. See <file:Documentation/initrd.txt> for details.
1281 If RAM disk support (BLK_DEV_RAM) is also included, this
1282 also enables initial RAM disk (initrd) support and adds
1283 15 Kbytes (more on some other architectures) to the kernel size.
1289 source "usr/Kconfig"
1293 config CC_OPTIMIZE_FOR_SIZE
1294 bool "Optimize for size"
1296 Enabling this option will pass "-Os" instead of "-O2" to
1297 your compiler resulting in a smaller kernel.
1310 config SYSCTL_EXCEPTION_TRACE
1313 Enable support for /proc/sys/debug/exception-trace.
1315 config SYSCTL_ARCH_UNALIGN_NO_WARN
1318 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1319 Allows arch to define/use @no_unaligned_warning to possibly warn
1320 about unaligned access emulation going on under the hood.
1322 config SYSCTL_ARCH_UNALIGN_ALLOW
1325 Enable support for /proc/sys/kernel/unaligned-trap
1326 Allows arches to define/use @unaligned_enabled to runtime toggle
1327 the unaligned access emulation.
1328 see arch/parisc/kernel/unaligned.c for reference
1330 config HAVE_PCSPKR_PLATFORM
1333 # interpreter that classic socket filters depend on
1338 bool "Configure standard kernel features (expert users)"
1339 # Unhide debug options, to make the on-by-default options visible
1342 This option allows certain base kernel options and settings
1343 to be disabled or tweaked. This is for specialized
1344 environments which can tolerate a "non-standard" kernel.
1345 Only use this if you really know what you are doing.
1348 bool "Enable 16-bit UID system calls" if EXPERT
1349 depends on HAVE_UID16 && MULTIUSER
1352 This enables the legacy 16-bit UID syscall wrappers.
1355 bool "Multiple users, groups and capabilities support" if EXPERT
1358 This option enables support for non-root users, groups and
1361 If you say N here, all processes will run with UID 0, GID 0, and all
1362 possible capabilities. Saying N here also compiles out support for
1363 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1366 If unsure, say Y here.
1368 config SGETMASK_SYSCALL
1369 bool "sgetmask/ssetmask syscalls support" if EXPERT
1370 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1372 sys_sgetmask and sys_ssetmask are obsolete system calls
1373 no longer supported in libc but still enabled by default in some
1376 If unsure, leave the default option here.
1378 config SYSFS_SYSCALL
1379 bool "Sysfs syscall support" if EXPERT
1382 sys_sysfs is an obsolete system call no longer supported in libc.
1383 Note that disabling this option is more secure but might break
1384 compatibility with some systems.
1386 If unsure say Y here.
1388 config SYSCTL_SYSCALL
1389 bool "Sysctl syscall support" if EXPERT
1390 depends on PROC_SYSCTL
1394 sys_sysctl uses binary paths that have been found challenging
1395 to properly maintain and use. The interface in /proc/sys
1396 using paths with ascii names is now the primary path to this
1399 Almost nothing using the binary sysctl interface so if you are
1400 trying to save some space it is probably safe to disable this,
1401 making your kernel marginally smaller.
1403 If unsure say N here.
1406 bool "Load all symbols for debugging/ksymoops" if EXPERT
1409 Say Y here to let the kernel print out symbolic crash information and
1410 symbolic stack backtraces. This increases the size of the kernel
1411 somewhat, as all symbols have to be loaded into the kernel image.
1414 bool "Include all symbols in kallsyms"
1415 depends on DEBUG_KERNEL && KALLSYMS
1417 Normally kallsyms only contains the symbols of functions for nicer
1418 OOPS messages and backtraces (i.e., symbols from the text and inittext
1419 sections). This is sufficient for most cases. And only in very rare
1420 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1421 names of variables from the data sections, etc).
1423 This option makes sure that all symbols are loaded into the kernel
1424 image (i.e., symbols from all sections) in cost of increased kernel
1425 size (depending on the kernel configuration, it may be 300KiB or
1426 something like this).
1428 Say N unless you really need all symbols.
1432 bool "Enable support for printk" if EXPERT
1435 This option enables normal printk support. Removing it
1436 eliminates most of the message strings from the kernel image
1437 and makes the kernel more or less silent. As this makes it
1438 very difficult to diagnose system problems, saying N here is
1439 strongly discouraged.
1442 bool "BUG() support" if EXPERT
1445 Disabling this option eliminates support for BUG and WARN, reducing
1446 the size of your kernel image and potentially quietly ignoring
1447 numerous fatal conditions. You should only consider disabling this
1448 option for embedded systems with no facilities for reporting errors.
1454 bool "Enable ELF core dumps" if EXPERT
1456 Enable support for generating core dumps. Disabling saves about 4k.
1459 config PCSPKR_PLATFORM
1460 bool "Enable PC-Speaker support" if EXPERT
1461 depends on HAVE_PCSPKR_PLATFORM
1465 This option allows to disable the internal PC-Speaker
1466 support, saving some memory.
1470 bool "Enable full-sized data structures for core" if EXPERT
1472 Disabling this option reduces the size of miscellaneous core
1473 kernel data structures. This saves memory on small machines,
1474 but may reduce performance.
1477 bool "Enable futex support" if EXPERT
1481 Disabling this option will cause the kernel to be built without
1482 support for "fast userspace mutexes". The resulting kernel may not
1483 run glibc-based applications correctly.
1485 config HAVE_FUTEX_CMPXCHG
1489 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1490 is implemented and always working. This removes a couple of runtime
1494 bool "Enable eventpoll support" if EXPERT
1498 Disabling this option will cause the kernel to be built without
1499 support for epoll family of system calls.
1502 bool "Enable signalfd() system call" if EXPERT
1506 Enable the signalfd() system call that allows to receive signals
1507 on a file descriptor.
1512 bool "Enable timerfd() system call" if EXPERT
1516 Enable the timerfd() system call that allows to receive timer
1517 events on a file descriptor.
1522 bool "Enable eventfd() system call" if EXPERT
1526 Enable the eventfd() system call that allows to receive both
1527 kernel notification (ie. KAIO) or userspace notifications.
1531 # syscall, maps, verifier
1533 bool "Enable bpf() system call"
1538 Enable the bpf() system call that allows to manipulate eBPF
1539 programs and maps via file descriptors.
1542 bool "Use full shmem filesystem" if EXPERT
1546 The shmem is an internal filesystem used to manage shared memory.
1547 It is backed by swap and manages resource limits. It is also exported
1548 to userspace as tmpfs if TMPFS is enabled. Disabling this
1549 option replaces shmem and tmpfs with the much simpler ramfs code,
1550 which may be appropriate on small systems without swap.
1553 bool "Enable AIO support" if EXPERT
1556 This option enables POSIX asynchronous I/O which may by used
1557 by some high performance threaded applications. Disabling
1558 this option saves about 7k.
1560 config ADVISE_SYSCALLS
1561 bool "Enable madvise/fadvise syscalls" if EXPERT
1564 This option enables the madvise and fadvise syscalls, used by
1565 applications to advise the kernel about their future memory or file
1566 usage, improving performance. If building an embedded system where no
1567 applications use these syscalls, you can disable this option to save
1572 bool "Enable PCI quirk workarounds" if EXPERT
1575 This enables workarounds for various PCI chipset
1576 bugs/quirks. Disable this only if your target machine is
1577 unaffected by PCI quirks.
1580 bool "Embedded system"
1581 option allnoconfig_y
1584 This option should be enabled if compiling the kernel for
1585 an embedded system so certain expert options are available
1588 config HAVE_PERF_EVENTS
1591 See tools/perf/design.txt for details.
1593 config PERF_USE_VMALLOC
1596 See tools/perf/design.txt for details
1598 menu "Kernel Performance Events And Counters"
1601 bool "Kernel performance events and counters"
1602 default y if PROFILING
1603 depends on HAVE_PERF_EVENTS
1608 Enable kernel support for various performance events provided
1609 by software and hardware.
1611 Software events are supported either built-in or via the
1612 use of generic tracepoints.
1614 Most modern CPUs support performance events via performance
1615 counter registers. These registers count the number of certain
1616 types of hw events: such as instructions executed, cachemisses
1617 suffered, or branches mis-predicted - without slowing down the
1618 kernel or applications. These registers can also trigger interrupts
1619 when a threshold number of events have passed - and can thus be
1620 used to profile the code that runs on that CPU.
1622 The Linux Performance Event subsystem provides an abstraction of
1623 these software and hardware event capabilities, available via a
1624 system call and used by the "perf" utility in tools/perf/. It
1625 provides per task and per CPU counters, and it provides event
1626 capabilities on top of those.
1630 config DEBUG_PERF_USE_VMALLOC
1632 bool "Debug: use vmalloc to back perf mmap() buffers"
1633 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1634 select PERF_USE_VMALLOC
1636 Use vmalloc memory to back perf mmap() buffers.
1638 Mostly useful for debugging the vmalloc code on platforms
1639 that don't require it.
1645 config VM_EVENT_COUNTERS
1647 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1649 VM event counters are needed for event counts to be shown.
1650 This option allows the disabling of the VM event counters
1651 on EXPERT systems. /proc/vmstat will only show page counts
1652 if VM event counters are disabled.
1656 bool "Enable SLUB debugging support" if EXPERT
1657 depends on SLUB && SYSFS
1659 SLUB has extensive debug support features. Disabling these can
1660 result in significant savings in code size. This also disables
1661 SLUB sysfs support. /sys/slab will not exist and there will be
1662 no support for cache validation etc.
1665 bool "Disable heap randomization"
1668 Randomizing heap placement makes heap exploits harder, but it
1669 also breaks ancient binaries (including anything libc5 based).
1670 This option changes the bootup default to heap randomization
1671 disabled, and can be overridden at runtime by setting
1672 /proc/sys/kernel/randomize_va_space to 2.
1674 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1677 prompt "Choose SLAB allocator"
1680 This option allows to select a slab allocator.
1685 The regular slab allocator that is established and known to work
1686 well in all environments. It organizes cache hot objects in
1687 per cpu and per node queues.
1690 bool "SLUB (Unqueued Allocator)"
1692 SLUB is a slab allocator that minimizes cache line usage
1693 instead of managing queues of cached objects (SLAB approach).
1694 Per cpu caching is realized using slabs of objects instead
1695 of queues of objects. SLUB can use memory efficiently
1696 and has enhanced diagnostics. SLUB is the default choice for
1701 bool "SLOB (Simple Allocator)"
1703 SLOB replaces the stock allocator with a drastically simpler
1704 allocator. SLOB is generally more space efficient but
1705 does not perform as well on large systems.
1709 config SLUB_CPU_PARTIAL
1711 depends on SLUB && SMP
1712 bool "SLUB per cpu partial cache"
1714 Per cpu partial caches accellerate objects allocation and freeing
1715 that is local to a processor at the price of more indeterminism
1716 in the latency of the free. On overflow these caches will be cleared
1717 which requires the taking of locks that may cause latency spikes.
1718 Typically one would choose no for a realtime system.
1720 config MMAP_ALLOW_UNINITIALIZED
1721 bool "Allow mmapped anonymous memory to be uninitialized"
1722 depends on EXPERT && !MMU
1725 Normally, and according to the Linux spec, anonymous memory obtained
1726 from mmap() has it's contents cleared before it is passed to
1727 userspace. Enabling this config option allows you to request that
1728 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1729 providing a huge performance boost. If this option is not enabled,
1730 then the flag will be ignored.
1732 This is taken advantage of by uClibc's malloc(), and also by
1733 ELF-FDPIC binfmt's brk and stack allocator.
1735 Because of the obvious security issues, this option should only be
1736 enabled on embedded devices where you control what is run in
1737 userspace. Since that isn't generally a problem on no-MMU systems,
1738 it is normally safe to say Y here.
1740 See Documentation/nommu-mmap.txt for more information.
1742 config SYSTEM_TRUSTED_KEYRING
1743 bool "Provide system-wide ring of trusted keys"
1746 Provide a system keyring to which trusted keys can be added. Keys in
1747 the keyring are considered to be trusted. Keys may be added at will
1748 by the kernel from compiled-in data and from hardware key stores, but
1749 userspace may only add extra keys if those keys can be verified by
1750 keys already in the keyring.
1752 Keys in this keyring are used by module signature checking.
1755 bool "Profiling support"
1757 Say Y here to enable the extended profiling support mechanisms used
1758 by profilers such as OProfile.
1761 # Place an empty function call at each tracepoint site. Can be
1762 # dynamically changed for a probe function.
1767 source "arch/Kconfig"
1769 endmenu # General setup
1771 config HAVE_GENERIC_DMA_COHERENT
1778 depends on SLAB || SLUB_DEBUG
1786 default 0 if BASE_FULL
1787 default 1 if !BASE_FULL
1790 bool "Enable loadable module support"
1793 Kernel modules are small pieces of compiled code which can
1794 be inserted in the running kernel, rather than being
1795 permanently built into the kernel. You use the "modprobe"
1796 tool to add (and sometimes remove) them. If you say Y here,
1797 many parts of the kernel can be built as modules (by
1798 answering M instead of Y where indicated): this is most
1799 useful for infrequently used options which are not required
1800 for booting. For more information, see the man pages for
1801 modprobe, lsmod, modinfo, insmod and rmmod.
1803 If you say Y here, you will need to run "make
1804 modules_install" to put the modules under /lib/modules/
1805 where modprobe can find them (you may need to be root to do
1812 config MODULE_FORCE_LOAD
1813 bool "Forced module loading"
1816 Allow loading of modules without version information (ie. modprobe
1817 --force). Forced module loading sets the 'F' (forced) taint flag and
1818 is usually a really bad idea.
1820 config MODULE_UNLOAD
1821 bool "Module unloading"
1823 Without this option you will not be able to unload any
1824 modules (note that some modules may not be unloadable
1825 anyway), which makes your kernel smaller, faster
1826 and simpler. If unsure, say Y.
1828 config MODULE_FORCE_UNLOAD
1829 bool "Forced module unloading"
1830 depends on MODULE_UNLOAD
1832 This option allows you to force a module to unload, even if the
1833 kernel believes it is unsafe: the kernel will remove the module
1834 without waiting for anyone to stop using it (using the -f option to
1835 rmmod). This is mainly for kernel developers and desperate users.
1839 bool "Module versioning support"
1841 Usually, you have to use modules compiled with your kernel.
1842 Saying Y here makes it sometimes possible to use modules
1843 compiled for different kernels, by adding enough information
1844 to the modules to (hopefully) spot any changes which would
1845 make them incompatible with the kernel you are running. If
1848 config MODULE_SRCVERSION_ALL
1849 bool "Source checksum for all modules"
1851 Modules which contain a MODULE_VERSION get an extra "srcversion"
1852 field inserted into their modinfo section, which contains a
1853 sum of the source files which made it. This helps maintainers
1854 see exactly which source was used to build a module (since
1855 others sometimes change the module source without updating
1856 the version). With this option, such a "srcversion" field
1857 will be created for all modules. If unsure, say N.
1860 bool "Module signature verification"
1862 select SYSTEM_TRUSTED_KEYRING
1865 select ASYMMETRIC_KEY_TYPE
1866 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1867 select PUBLIC_KEY_ALGO_RSA
1870 select X509_CERTIFICATE_PARSER
1872 Check modules for valid signatures upon load: the signature
1873 is simply appended to the module. For more information see
1874 Documentation/module-signing.txt.
1876 !!!WARNING!!! If you enable this option, you MUST make sure that the
1877 module DOES NOT get stripped after being signed. This includes the
1878 debuginfo strip done by some packagers (such as rpmbuild) and
1879 inclusion into an initramfs that wants the module size reduced.
1881 config MODULE_SIG_FORCE
1882 bool "Require modules to be validly signed"
1883 depends on MODULE_SIG
1885 Reject unsigned modules or signed modules for which we don't have a
1886 key. Without this, such modules will simply taint the kernel.
1888 config MODULE_SIG_ALL
1889 bool "Automatically sign all modules"
1891 depends on MODULE_SIG
1893 Sign all modules during make modules_install. Without this option,
1894 modules must be signed manually, using the scripts/sign-file tool.
1896 comment "Do not forget to sign required modules with scripts/sign-file"
1897 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1900 prompt "Which hash algorithm should modules be signed with?"
1901 depends on MODULE_SIG
1903 This determines which sort of hashing algorithm will be used during
1904 signature generation. This algorithm _must_ be built into the kernel
1905 directly so that signature verification can take place. It is not
1906 possible to load a signed module containing the algorithm to check
1907 the signature on that module.
1909 config MODULE_SIG_SHA1
1910 bool "Sign modules with SHA-1"
1913 config MODULE_SIG_SHA224
1914 bool "Sign modules with SHA-224"
1915 select CRYPTO_SHA256
1917 config MODULE_SIG_SHA256
1918 bool "Sign modules with SHA-256"
1919 select CRYPTO_SHA256
1921 config MODULE_SIG_SHA384
1922 bool "Sign modules with SHA-384"
1923 select CRYPTO_SHA512
1925 config MODULE_SIG_SHA512
1926 bool "Sign modules with SHA-512"
1927 select CRYPTO_SHA512
1931 config MODULE_SIG_HASH
1933 depends on MODULE_SIG
1934 default "sha1" if MODULE_SIG_SHA1
1935 default "sha224" if MODULE_SIG_SHA224
1936 default "sha256" if MODULE_SIG_SHA256
1937 default "sha384" if MODULE_SIG_SHA384
1938 default "sha512" if MODULE_SIG_SHA512
1940 config MODULE_COMPRESS
1941 bool "Compress modules on installation"
1945 Compresses kernel modules when 'make modules_install' is run; gzip or
1946 xz depending on "Compression algorithm" below.
1948 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
1950 Out-of-tree kernel modules installed using Kbuild will also be
1951 compressed upon installation.
1953 Note: for modules inside an initrd or initramfs, it's more efficient
1954 to compress the whole initrd or initramfs instead.
1956 Note: This is fully compatible with signed modules.
1961 prompt "Compression algorithm"
1962 depends on MODULE_COMPRESS
1963 default MODULE_COMPRESS_GZIP
1965 This determines which sort of compression will be used during
1966 'make modules_install'.
1968 GZIP (default) and XZ are supported.
1970 config MODULE_COMPRESS_GZIP
1973 config MODULE_COMPRESS_XZ
1980 config MODULES_TREE_LOOKUP
1982 depends on PERF_EVENTS || TRACING
1984 config INIT_ALL_POSSIBLE
1987 Back when each arch used to define their own cpu_online_mask and
1988 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1989 with all 1s, and others with all 0s. When they were centralised,
1990 it was better to provide this option than to break all the archs
1991 and have several arch maintainers pursuing me down dark alleys.
1996 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1998 Need stop_machine() primitive.
2000 source "block/Kconfig"
2002 config PREEMPT_NOTIFIERS
2009 # Can be selected by architectures with broken toolchains
2010 # that get confused by correct const<->read_only section
2012 config BROKEN_RODATA
2018 Build a simple ASN.1 grammar compiler that produces a bytecode output
2019 that can be interpreted by the ASN.1 stream decoder and used to
2020 inform it as to what tags are to be expected in a stream and what
2021 functions to call on what tags.
2023 source "kernel/Kconfig.locks"
projects / deliverable / linux.git / blob