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"
288 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
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"
440 Collect information on time spent by a task waiting for system
441 resources like cpu, synchronous block I/O completion and swapping
442 in pages. Such statistics can help in setting a task's priorities
443 relative to other tasks for cpu, io, rss limits etc.
448 bool "Enable extended accounting over taskstats"
451 Collect extended task accounting data and send the data
452 to userland for processing over the taskstats interface.
456 config TASK_IO_ACCOUNTING
457 bool "Enable per-task storage I/O accounting"
458 depends on TASK_XACCT
460 Collect information on the number of bytes of storage I/O which this
465 endmenu # "CPU/Task time and stats accounting"
471 default y if !PREEMPT && SMP
473 This option selects the RCU implementation that is
474 designed for very large SMP system with hundreds or
475 thousands of CPUs. It also scales down nicely to
482 This option selects the RCU implementation that is
483 designed for very large SMP systems with hundreds or
484 thousands of CPUs, but for which real-time response
485 is also required. It also scales down nicely to
488 Select this option if you are unsure.
492 default y if !PREEMPT && !SMP
494 This option selects the RCU implementation that is
495 designed for UP systems from which real-time response
496 is not required. This option greatly reduces the
497 memory footprint of RCU.
500 bool "Make expert-level adjustments to RCU configuration"
503 This option needs to be enabled if you wish to make
504 expert-level adjustments to RCU configuration. By default,
505 no such adjustments can be made, which has the often-beneficial
506 side-effect of preventing "make oldconfig" from asking you all
507 sorts of detailed questions about how you would like numerous
508 obscure RCU options to be set up.
510 Say Y if you need to make expert-level adjustments to RCU.
512 Say N if you are unsure.
517 This option selects the sleepable version of RCU. This version
518 permits arbitrary sleeping or blocking within RCU read-side critical
526 This option enables a task-based RCU implementation that uses
527 only voluntary context switch (not preemption!), idle, and
528 user-mode execution as quiescent states.
530 config RCU_STALL_COMMON
531 def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
533 This option enables RCU CPU stall code that is common between
534 the TINY and TREE variants of RCU. The purpose is to allow
535 the tiny variants to disable RCU CPU stall warnings, while
536 making these warnings mandatory for the tree variants.
538 config CONTEXT_TRACKING
541 config CONTEXT_TRACKING_FORCE
542 bool "Force context tracking"
543 depends on CONTEXT_TRACKING
544 default y if !NO_HZ_FULL
546 The major pre-requirement for full dynticks to work is to
547 support the context tracking subsystem. But there are also
548 other dependencies to provide in order to make the full
551 This option stands for testing when an arch implements the
552 context tracking backend but doesn't yet fullfill all the
553 requirements to make the full dynticks feature working.
554 Without the full dynticks, there is no way to test the support
555 for context tracking and the subsystems that rely on it: RCU
556 userspace extended quiescent state and tickless cputime
557 accounting. This option copes with the absence of the full
558 dynticks subsystem by forcing the context tracking on all
561 Say Y only if you're working on the development of an
562 architecture backend for the context tracking.
564 Say N otherwise, this option brings an overhead that you
565 don't want in production.
569 int "Tree-based hierarchical RCU fanout value"
572 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
576 This option controls the fanout of hierarchical implementations
577 of RCU, allowing RCU to work efficiently on machines with
578 large numbers of CPUs. This value must be at least the fourth
579 root of NR_CPUS, which allows NR_CPUS to be insanely large.
580 The default value of RCU_FANOUT should be used for production
581 systems, but if you are stress-testing the RCU implementation
582 itself, small RCU_FANOUT values allow you to test large-system
583 code paths on small(er) systems.
585 Select a specific number if testing RCU itself.
586 Take the default if unsure.
588 config RCU_FANOUT_LEAF
589 int "Tree-based hierarchical RCU leaf-level fanout value"
592 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
595 This option controls the leaf-level fanout of hierarchical
596 implementations of RCU, and allows trading off cache misses
597 against lock contention. Systems that synchronize their
598 scheduling-clock interrupts for energy-efficiency reasons will
599 want the default because the smaller leaf-level fanout keeps
600 lock contention levels acceptably low. Very large systems
601 (hundreds or thousands of CPUs) will instead want to set this
602 value to the maximum value possible in order to reduce the
603 number of cache misses incurred during RCU's grace-period
604 initialization. These systems tend to run CPU-bound, and thus
605 are not helped by synchronized interrupts, and thus tend to
606 skew them, which reduces lock contention enough that large
607 leaf-level fanouts work well.
609 Select a specific number if testing RCU itself.
611 Select the maximum permissible value for large systems.
613 Take the default if unsure.
615 config RCU_FAST_NO_HZ
616 bool "Accelerate last non-dyntick-idle CPU's grace periods"
617 depends on NO_HZ_COMMON && SMP && RCU_EXPERT
620 This option permits CPUs to enter dynticks-idle state even if
621 they have RCU callbacks queued, and prevents RCU from waking
622 these CPUs up more than roughly once every four jiffies (by
623 default, you can adjust this using the rcutree.rcu_idle_gp_delay
624 parameter), thus improving energy efficiency. On the other
625 hand, this option increases the duration of RCU grace periods,
626 for example, slowing down synchronize_rcu().
628 Say Y if energy efficiency is critically important, and you
629 don't care about increased grace-period durations.
631 Say N if you are unsure.
633 config TREE_RCU_TRACE
634 def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
637 This option provides tracing for the TREE_RCU and
638 PREEMPT_RCU implementations, permitting Makefile to
639 trivially select kernel/rcutree_trace.c.
642 bool "Enable RCU priority boosting"
643 depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT
646 This option boosts the priority of preempted RCU readers that
647 block the current preemptible RCU grace period for too long.
648 This option also prevents heavy loads from blocking RCU
649 callback invocation for all flavors of RCU.
651 Say Y here if you are working with real-time apps or heavy loads
652 Say N here if you are unsure.
654 config RCU_KTHREAD_PRIO
655 int "Real-time priority to use for RCU worker threads"
656 range 1 99 if RCU_BOOST
657 range 0 99 if !RCU_BOOST
658 default 1 if RCU_BOOST
659 default 0 if !RCU_BOOST
660 depends on RCU_EXPERT
662 This option specifies the SCHED_FIFO priority value that will be
663 assigned to the rcuc/n and rcub/n threads and is also the value
664 used for RCU_BOOST (if enabled). If you are working with a
665 real-time application that has one or more CPU-bound threads
666 running at a real-time priority level, you should set
667 RCU_KTHREAD_PRIO to a priority higher than the highest-priority
668 real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO
669 value of 1 is appropriate in the common case, which is real-time
670 applications that do not have any CPU-bound threads.
672 Some real-time applications might not have a single real-time
673 thread that saturates a given CPU, but instead might have
674 multiple real-time threads that, taken together, fully utilize
675 that CPU. In this case, you should set RCU_KTHREAD_PRIO to
676 a priority higher than the lowest-priority thread that is
677 conspiring to prevent the CPU from running any non-real-time
678 tasks. For example, if one thread at priority 10 and another
679 thread at priority 5 are between themselves fully consuming
680 the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
681 set to priority 6 or higher.
683 Specify the real-time priority, or take the default if unsure.
685 config RCU_BOOST_DELAY
686 int "Milliseconds to delay boosting after RCU grace-period start"
691 This option specifies the time to wait after the beginning of
692 a given grace period before priority-boosting preempted RCU
693 readers blocking that grace period. Note that any RCU reader
694 blocking an expedited RCU grace period is boosted immediately.
696 Accept the default if unsure.
699 bool "Offload RCU callback processing from boot-selected CPUs"
700 depends on TREE_RCU || PREEMPT_RCU
701 depends on RCU_EXPERT || NO_HZ_FULL
704 Use this option to reduce OS jitter for aggressive HPC or
705 real-time workloads. It can also be used to offload RCU
706 callback invocation to energy-efficient CPUs in battery-powered
707 asymmetric multiprocessors.
709 This option offloads callback invocation from the set of
710 CPUs specified at boot time by the rcu_nocbs parameter.
711 For each such CPU, a kthread ("rcuox/N") will be created to
712 invoke callbacks, where the "N" is the CPU being offloaded,
713 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
714 "s" for RCU-sched. Nothing prevents this kthread from running
715 on the specified CPUs, but (1) the kthreads may be preempted
716 between each callback, and (2) affinity or cgroups can be used
717 to force the kthreads to run on whatever set of CPUs is desired.
719 Say Y here if you want to help to debug reduced OS jitter.
720 Say N here if you are unsure.
723 prompt "Build-forced no-CBs CPUs"
724 default RCU_NOCB_CPU_NONE
725 depends on RCU_NOCB_CPU
727 This option allows no-CBs CPUs (whose RCU callbacks are invoked
728 from kthreads rather than from softirq context) to be specified
729 at build time. Additional no-CBs CPUs may be specified by
730 the rcu_nocbs= boot parameter.
732 config RCU_NOCB_CPU_NONE
733 bool "No build_forced no-CBs CPUs"
735 This option does not force any of the CPUs to be no-CBs CPUs.
736 Only CPUs designated by the rcu_nocbs= boot parameter will be
737 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
738 kthreads whose names begin with "rcuo". All other CPUs will
739 invoke their own RCU callbacks in softirq context.
741 Select this option if you want to choose no-CBs CPUs at
742 boot time, for example, to allow testing of different no-CBs
743 configurations without having to rebuild the kernel each time.
745 config RCU_NOCB_CPU_ZERO
746 bool "CPU 0 is a build_forced no-CBs CPU"
748 This option forces CPU 0 to be a no-CBs CPU, so that its RCU
749 callbacks are invoked by a per-CPU kthread whose name begins
750 with "rcuo". Additional CPUs may be designated as no-CBs
751 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
752 All other CPUs will invoke their own RCU callbacks in softirq
755 Select this if CPU 0 needs to be a no-CBs CPU for real-time
756 or energy-efficiency reasons, but the real reason it exists
757 is to ensure that randconfig testing covers mixed systems.
759 config RCU_NOCB_CPU_ALL
760 bool "All CPUs are build_forced no-CBs CPUs"
762 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
763 boot parameter will be ignored. All CPUs' RCU callbacks will
764 be executed in the context of per-CPU rcuo kthreads created for
765 this purpose. Assuming that the kthreads whose names start with
766 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
767 on the remaining CPUs, but might decrease memory locality during
768 RCU-callback invocation, thus potentially degrading throughput.
770 Select this if all CPUs need to be no-CBs CPUs for real-time
771 or energy-efficiency reasons.
775 config RCU_EXPEDITE_BOOT
779 This option enables expedited grace periods at boot time,
780 as if rcu_expedite_gp() had been invoked early in boot.
781 The corresponding rcu_unexpedite_gp() is invoked from
782 rcu_end_inkernel_boot(), which is intended to be invoked
783 at the end of the kernel-only boot sequence, just before
786 Accept the default if unsure.
788 endmenu # "RCU Subsystem"
795 tristate "Kernel .config support"
798 This option enables the complete Linux kernel ".config" file
799 contents to be saved in the kernel. It provides documentation
800 of which kernel options are used in a running kernel or in an
801 on-disk kernel. This information can be extracted from the kernel
802 image file with the script scripts/extract-ikconfig and used as
803 input to rebuild the current kernel or to build another kernel.
804 It can also be extracted from a running kernel by reading
805 /proc/config.gz if enabled (below).
808 bool "Enable access to .config through /proc/config.gz"
809 depends on IKCONFIG && PROC_FS
811 This option enables access to the kernel configuration file
812 through /proc/config.gz.
815 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
820 Select the minimal kernel log buffer size as a power of 2.
821 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
822 parameter, see below. Any higher size also might be forced
823 by "log_buf_len" boot parameter.
833 config LOG_CPU_MAX_BUF_SHIFT
834 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
837 default 12 if !BASE_SMALL
838 default 0 if BASE_SMALL
841 This option allows to increase the default ring buffer size
842 according to the number of CPUs. The value defines the contribution
843 of each CPU as a power of 2. The used space is typically only few
844 lines however it might be much more when problems are reported,
847 The increased size means that a new buffer has to be allocated and
848 the original static one is unused. It makes sense only on systems
849 with more CPUs. Therefore this value is used only when the sum of
850 contributions is greater than the half of the default kernel ring
851 buffer as defined by LOG_BUF_SHIFT. The default values are set
852 so that more than 64 CPUs are needed to trigger the allocation.
854 Also this option is ignored when "log_buf_len" kernel parameter is
855 used as it forces an exact (power of two) size of the ring buffer.
857 The number of possible CPUs is used for this computation ignoring
858 hotplugging making the compuation optimal for the the worst case
859 scenerio while allowing a simple algorithm to be used from bootup.
861 Examples shift values and their meaning:
862 17 => 128 KB for each CPU
863 16 => 64 KB for each CPU
864 15 => 32 KB for each CPU
865 14 => 16 KB for each CPU
866 13 => 8 KB for each CPU
867 12 => 4 KB for each CPU
870 # Architectures with an unreliable sched_clock() should select this:
872 config HAVE_UNSTABLE_SCHED_CLOCK
875 config GENERIC_SCHED_CLOCK
879 # For architectures that want to enable the support for NUMA-affine scheduler
882 config ARCH_SUPPORTS_NUMA_BALANCING
886 # For architectures that prefer to flush all TLBs after a number of pages
887 # are unmapped instead of sending one IPI per page to flush. The architecture
888 # must provide guarantees on what happens if a clean TLB cache entry is
889 # written after the unmap. Details are in mm/rmap.c near the check for
890 # should_defer_flush. The architecture should also consider if the full flush
891 # and the refill costs are offset by the savings of sending fewer IPIs.
892 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
896 # For architectures that know their GCC __int128 support is sound
898 config ARCH_SUPPORTS_INT128
901 # For architectures that (ab)use NUMA to represent different memory regions
902 # all cpu-local but of different latencies, such as SuperH.
904 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
907 config NUMA_BALANCING
908 bool "Memory placement aware NUMA scheduler"
909 depends on ARCH_SUPPORTS_NUMA_BALANCING
910 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
911 depends on SMP && NUMA && MIGRATION
913 This option adds support for automatic NUMA aware memory/task placement.
914 The mechanism is quite primitive and is based on migrating memory when
915 it has references to the node the task is running on.
917 This system will be inactive on UMA systems.
919 config NUMA_BALANCING_DEFAULT_ENABLED
920 bool "Automatically enable NUMA aware memory/task placement"
922 depends on NUMA_BALANCING
924 If set, automatic NUMA balancing will be enabled if running on a NUMA
928 bool "Control Group support"
931 This option adds support for grouping sets of processes together, for
932 use with process control subsystems such as Cpusets, CFS, memory
933 controls or device isolation.
935 - Documentation/scheduler/sched-design-CFS.txt (CFS)
936 - Documentation/cgroups/ (features for grouping, isolation
937 and resource control)
947 bool "Memory controller"
951 Provides control over the memory footprint of tasks in a cgroup.
954 bool "Swap controller"
955 depends on MEMCG && SWAP
957 Provides control over the swap space consumed by tasks in a cgroup.
959 config MEMCG_SWAP_ENABLED
960 bool "Swap controller enabled by default"
961 depends on MEMCG_SWAP
964 Memory Resource Controller Swap Extension comes with its price in
965 a bigger memory consumption. General purpose distribution kernels
966 which want to enable the feature but keep it disabled by default
967 and let the user enable it by swapaccount=1 boot command line
968 parameter should have this option unselected.
969 For those who want to have the feature enabled by default should
970 select this option (if, for some reason, they need to disable it
971 then swapaccount=0 does the trick).
973 bool "Memory Resource Controller Kernel Memory accounting"
975 depends on SLUB || SLAB
977 The Kernel Memory extension for Memory Resource Controller can limit
978 the amount of memory used by kernel objects in the system. Those are
979 fundamentally different from the entities handled by the standard
980 Memory Controller, which are page-based, and can be swapped. Users of
981 the kmem extension can use it to guarantee that no group of processes
982 will ever exhaust kernel resources alone.
989 Generic block IO controller cgroup interface. This is the common
990 cgroup interface which should be used by various IO controlling
993 Currently, CFQ IO scheduler uses it to recognize task groups and
994 control disk bandwidth allocation (proportional time slice allocation)
995 to such task groups. It is also used by bio throttling logic in
996 block layer to implement upper limit in IO rates on a device.
998 This option only enables generic Block IO controller infrastructure.
999 One needs to also enable actual IO controlling logic/policy. For
1000 enabling proportional weight division of disk bandwidth in CFQ, set
1001 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1002 CONFIG_BLK_DEV_THROTTLING=y.
1004 See Documentation/cgroups/blkio-controller.txt for more information.
1006 config DEBUG_BLK_CGROUP
1007 bool "IO controller debugging"
1008 depends on BLK_CGROUP
1011 Enable some debugging help. Currently it exports additional stat
1012 files in a cgroup which can be useful for debugging.
1014 config CGROUP_WRITEBACK
1016 depends on MEMCG && BLK_CGROUP
1019 menuconfig CGROUP_SCHED
1020 bool "CPU controller"
1023 This feature lets CPU scheduler recognize task groups and control CPU
1024 bandwidth allocation to such task groups. It uses cgroups to group
1028 config FAIR_GROUP_SCHED
1029 bool "Group scheduling for SCHED_OTHER"
1030 depends on CGROUP_SCHED
1031 default CGROUP_SCHED
1033 config CFS_BANDWIDTH
1034 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1035 depends on FAIR_GROUP_SCHED
1038 This option allows users to define CPU bandwidth rates (limits) for
1039 tasks running within the fair group scheduler. Groups with no limit
1040 set are considered to be unconstrained and will run with no
1042 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1044 config RT_GROUP_SCHED
1045 bool "Group scheduling for SCHED_RR/FIFO"
1046 depends on CGROUP_SCHED
1049 This feature lets you explicitly allocate real CPU bandwidth
1050 to task groups. If enabled, it will also make it impossible to
1051 schedule realtime tasks for non-root users until you allocate
1052 realtime bandwidth for them.
1053 See Documentation/scheduler/sched-rt-group.txt for more information.
1058 bool "PIDs controller"
1060 Provides enforcement of process number limits in the scope of a
1061 cgroup. Any attempt to fork more processes than is allowed in the
1062 cgroup will fail. PIDs are fundamentally a global resource because it
1063 is fairly trivial to reach PID exhaustion before you reach even a
1064 conservative kmemcg limit. As a result, it is possible to grind a
1065 system to halt without being limited by other cgroup policies. The
1066 PIDs cgroup subsystem is designed to stop this from happening.
1068 It should be noted that organisational operations (such as attaching
1069 to a cgroup hierarchy will *not* be blocked by the PIDs subsystem),
1070 since the PIDs limit only affects a process's ability to fork, not to
1073 config CGROUP_FREEZER
1074 bool "Freezer controller"
1076 Provides a way to freeze and unfreeze all tasks in a
1079 config CGROUP_HUGETLB
1080 bool "HugeTLB controller"
1081 depends on HUGETLB_PAGE
1085 Provides a cgroup controller for HugeTLB pages.
1086 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1087 The limit is enforced during page fault. Since HugeTLB doesn't
1088 support page reclaim, enforcing the limit at page fault time implies
1089 that, the application will get SIGBUS signal if it tries to access
1090 HugeTLB pages beyond its limit. This requires the application to know
1091 beforehand how much HugeTLB pages it would require for its use. The
1092 control group is tracked in the third page lru pointer. This means
1093 that we cannot use the controller with huge page less than 3 pages.
1096 bool "Cpuset controller"
1098 This option will let you create and manage CPUSETs which
1099 allow dynamically partitioning a system into sets of CPUs and
1100 Memory Nodes and assigning tasks to run only within those sets.
1101 This is primarily useful on large SMP or NUMA systems.
1105 config PROC_PID_CPUSET
1106 bool "Include legacy /proc/<pid>/cpuset file"
1110 config CGROUP_DEVICE
1111 bool "Device controller"
1113 Provides a cgroup controller implementing whitelists for
1114 devices which a process in the cgroup can mknod or open.
1116 config CGROUP_CPUACCT
1117 bool "Simple CPU accounting controller"
1119 Provides a simple controller for monitoring the
1120 total CPU consumed by the tasks in a cgroup.
1123 bool "Perf controller"
1124 depends on PERF_EVENTS
1126 This option extends the perf per-cpu mode to restrict monitoring
1127 to threads which belong to the cgroup specified and run on the
1133 bool "Example controller"
1136 This option enables a simple controller that exports
1137 debugging information about the cgroups framework.
1143 config CHECKPOINT_RESTORE
1144 bool "Checkpoint/restore support" if EXPERT
1145 select PROC_CHILDREN
1148 Enables additional kernel features in a sake of checkpoint/restore.
1149 In particular it adds auxiliary prctl codes to setup process text,
1150 data and heap segment sizes, and a few additional /proc filesystem
1153 If unsure, say N here.
1155 menuconfig NAMESPACES
1156 bool "Namespaces support" if EXPERT
1157 depends on MULTIUSER
1160 Provides the way to make tasks work with different objects using
1161 the same id. For example same IPC id may refer to different objects
1162 or same user id or pid may refer to different tasks when used in
1163 different namespaces.
1168 bool "UTS namespace"
1171 In this namespace tasks see different info provided with the
1175 bool "IPC namespace"
1176 depends on (SYSVIPC || POSIX_MQUEUE)
1179 In this namespace tasks work with IPC ids which correspond to
1180 different IPC objects in different namespaces.
1183 bool "User namespace"
1186 This allows containers, i.e. vservers, to use user namespaces
1187 to provide different user info for different servers.
1189 When user namespaces are enabled in the kernel it is
1190 recommended that the MEMCG and MEMCG_KMEM options also be
1191 enabled and that user-space use the memory control groups to
1192 limit the amount of memory a memory unprivileged users can
1198 bool "PID Namespaces"
1201 Support process id namespaces. This allows having multiple
1202 processes with the same pid as long as they are in different
1203 pid namespaces. This is a building block of containers.
1206 bool "Network namespace"
1210 Allow user space to create what appear to be multiple instances
1211 of the network stack.
1215 config SCHED_AUTOGROUP
1216 bool "Automatic process group scheduling"
1219 select FAIR_GROUP_SCHED
1221 This option optimizes the scheduler for common desktop workloads by
1222 automatically creating and populating task groups. This separation
1223 of workloads isolates aggressive CPU burners (like build jobs) from
1224 desktop applications. Task group autogeneration is currently based
1227 config SYSFS_DEPRECATED
1228 bool "Enable deprecated sysfs features to support old userspace tools"
1232 This option adds code that switches the layout of the "block" class
1233 devices, to not show up in /sys/class/block/, but only in
1236 This switch is only active when the sysfs.deprecated=1 boot option is
1237 passed or the SYSFS_DEPRECATED_V2 option is set.
1239 This option allows new kernels to run on old distributions and tools,
1240 which might get confused by /sys/class/block/. Since 2007/2008 all
1241 major distributions and tools handle this just fine.
1243 Recent distributions and userspace tools after 2009/2010 depend on
1244 the existence of /sys/class/block/, and will not work with this
1247 Only if you are using a new kernel on an old distribution, you might
1250 config SYSFS_DEPRECATED_V2
1251 bool "Enable deprecated sysfs features by default"
1254 depends on SYSFS_DEPRECATED
1256 Enable deprecated sysfs by default.
1258 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1261 Only if you are using a new kernel on an old distribution, you might
1262 need to say Y here. Even then, odds are you would not need it
1263 enabled, you can always pass the boot option if absolutely necessary.
1266 bool "Kernel->user space relay support (formerly relayfs)"
1268 This option enables support for relay interface support in
1269 certain file systems (such as debugfs).
1270 It is designed to provide an efficient mechanism for tools and
1271 facilities to relay large amounts of data from kernel space to
1276 config BLK_DEV_INITRD
1277 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1278 depends on BROKEN || !FRV
1280 The initial RAM filesystem is a ramfs which is loaded by the
1281 boot loader (loadlin or lilo) and that is mounted as root
1282 before the normal boot procedure. It is typically used to
1283 load modules needed to mount the "real" root file system,
1284 etc. See <file:Documentation/initrd.txt> for details.
1286 If RAM disk support (BLK_DEV_RAM) is also included, this
1287 also enables initial RAM disk (initrd) support and adds
1288 15 Kbytes (more on some other architectures) to the kernel size.
1294 source "usr/Kconfig"
1298 config CC_OPTIMIZE_FOR_SIZE
1299 bool "Optimize for size"
1301 Enabling this option will pass "-Os" instead of "-O2" to
1302 your compiler resulting in a smaller kernel.
1315 config SYSCTL_EXCEPTION_TRACE
1318 Enable support for /proc/sys/debug/exception-trace.
1320 config SYSCTL_ARCH_UNALIGN_NO_WARN
1323 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1324 Allows arch to define/use @no_unaligned_warning to possibly warn
1325 about unaligned access emulation going on under the hood.
1327 config SYSCTL_ARCH_UNALIGN_ALLOW
1330 Enable support for /proc/sys/kernel/unaligned-trap
1331 Allows arches to define/use @unaligned_enabled to runtime toggle
1332 the unaligned access emulation.
1333 see arch/parisc/kernel/unaligned.c for reference
1335 config HAVE_PCSPKR_PLATFORM
1338 # interpreter that classic socket filters depend on
1343 bool "Configure standard kernel features (expert users)"
1344 # Unhide debug options, to make the on-by-default options visible
1347 This option allows certain base kernel options and settings
1348 to be disabled or tweaked. This is for specialized
1349 environments which can tolerate a "non-standard" kernel.
1350 Only use this if you really know what you are doing.
1353 bool "Enable 16-bit UID system calls" if EXPERT
1354 depends on HAVE_UID16 && MULTIUSER
1357 This enables the legacy 16-bit UID syscall wrappers.
1360 bool "Multiple users, groups and capabilities support" if EXPERT
1363 This option enables support for non-root users, groups and
1366 If you say N here, all processes will run with UID 0, GID 0, and all
1367 possible capabilities. Saying N here also compiles out support for
1368 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1371 If unsure, say Y here.
1373 config SGETMASK_SYSCALL
1374 bool "sgetmask/ssetmask syscalls support" if EXPERT
1375 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1377 sys_sgetmask and sys_ssetmask are obsolete system calls
1378 no longer supported in libc but still enabled by default in some
1381 If unsure, leave the default option here.
1383 config SYSFS_SYSCALL
1384 bool "Sysfs syscall support" if EXPERT
1387 sys_sysfs is an obsolete system call no longer supported in libc.
1388 Note that disabling this option is more secure but might break
1389 compatibility with some systems.
1391 If unsure say Y here.
1393 config SYSCTL_SYSCALL
1394 bool "Sysctl syscall support" if EXPERT
1395 depends on PROC_SYSCTL
1399 sys_sysctl uses binary paths that have been found challenging
1400 to properly maintain and use. The interface in /proc/sys
1401 using paths with ascii names is now the primary path to this
1404 Almost nothing using the binary sysctl interface so if you are
1405 trying to save some space it is probably safe to disable this,
1406 making your kernel marginally smaller.
1408 If unsure say N here.
1411 bool "Load all symbols for debugging/ksymoops" if EXPERT
1414 Say Y here to let the kernel print out symbolic crash information and
1415 symbolic stack backtraces. This increases the size of the kernel
1416 somewhat, as all symbols have to be loaded into the kernel image.
1419 bool "Include all symbols in kallsyms"
1420 depends on DEBUG_KERNEL && KALLSYMS
1422 Normally kallsyms only contains the symbols of functions for nicer
1423 OOPS messages and backtraces (i.e., symbols from the text and inittext
1424 sections). This is sufficient for most cases. And only in very rare
1425 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1426 names of variables from the data sections, etc).
1428 This option makes sure that all symbols are loaded into the kernel
1429 image (i.e., symbols from all sections) in cost of increased kernel
1430 size (depending on the kernel configuration, it may be 300KiB or
1431 something like this).
1433 Say N unless you really need all symbols.
1437 bool "Enable support for printk" if EXPERT
1440 This option enables normal printk support. Removing it
1441 eliminates most of the message strings from the kernel image
1442 and makes the kernel more or less silent. As this makes it
1443 very difficult to diagnose system problems, saying N here is
1444 strongly discouraged.
1447 bool "BUG() support" if EXPERT
1450 Disabling this option eliminates support for BUG and WARN, reducing
1451 the size of your kernel image and potentially quietly ignoring
1452 numerous fatal conditions. You should only consider disabling this
1453 option for embedded systems with no facilities for reporting errors.
1459 bool "Enable ELF core dumps" if EXPERT
1461 Enable support for generating core dumps. Disabling saves about 4k.
1464 config PCSPKR_PLATFORM
1465 bool "Enable PC-Speaker support" if EXPERT
1466 depends on HAVE_PCSPKR_PLATFORM
1470 This option allows to disable the internal PC-Speaker
1471 support, saving some memory.
1475 bool "Enable full-sized data structures for core" if EXPERT
1477 Disabling this option reduces the size of miscellaneous core
1478 kernel data structures. This saves memory on small machines,
1479 but may reduce performance.
1482 bool "Enable futex support" if EXPERT
1486 Disabling this option will cause the kernel to be built without
1487 support for "fast userspace mutexes". The resulting kernel may not
1488 run glibc-based applications correctly.
1490 config HAVE_FUTEX_CMPXCHG
1494 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1495 is implemented and always working. This removes a couple of runtime
1499 bool "Enable eventpoll support" if EXPERT
1503 Disabling this option will cause the kernel to be built without
1504 support for epoll family of system calls.
1507 bool "Enable signalfd() system call" if EXPERT
1511 Enable the signalfd() system call that allows to receive signals
1512 on a file descriptor.
1517 bool "Enable timerfd() system call" if EXPERT
1521 Enable the timerfd() system call that allows to receive timer
1522 events on a file descriptor.
1527 bool "Enable eventfd() system call" if EXPERT
1531 Enable the eventfd() system call that allows to receive both
1532 kernel notification (ie. KAIO) or userspace notifications.
1536 # syscall, maps, verifier
1538 bool "Enable bpf() system call"
1543 Enable the bpf() system call that allows to manipulate eBPF
1544 programs and maps via file descriptors.
1547 bool "Use full shmem filesystem" if EXPERT
1551 The shmem is an internal filesystem used to manage shared memory.
1552 It is backed by swap and manages resource limits. It is also exported
1553 to userspace as tmpfs if TMPFS is enabled. Disabling this
1554 option replaces shmem and tmpfs with the much simpler ramfs code,
1555 which may be appropriate on small systems without swap.
1558 bool "Enable AIO support" if EXPERT
1561 This option enables POSIX asynchronous I/O which may by used
1562 by some high performance threaded applications. Disabling
1563 this option saves about 7k.
1565 config ADVISE_SYSCALLS
1566 bool "Enable madvise/fadvise syscalls" if EXPERT
1569 This option enables the madvise and fadvise syscalls, used by
1570 applications to advise the kernel about their future memory or file
1571 usage, improving performance. If building an embedded system where no
1572 applications use these syscalls, you can disable this option to save
1576 bool "Enable userfaultfd() system call"
1580 Enable the userfaultfd() system call that allows to intercept and
1581 handle page faults in userland.
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 "Enable membarrier() system call" if EXPERT
1596 Enable the membarrier() system call that allows issuing memory
1597 barriers across all running threads, which can be used to distribute
1598 the cost of user-space memory barriers asymmetrically by transforming
1599 pairs of memory barriers into pairs consisting of membarrier() and a
1605 bool "Embedded system"
1606 option allnoconfig_y
1609 This option should be enabled if compiling the kernel for
1610 an embedded system so certain expert options are available
1613 config HAVE_PERF_EVENTS
1616 See tools/perf/design.txt for details.
1618 config PERF_USE_VMALLOC
1621 See tools/perf/design.txt for details
1623 menu "Kernel Performance Events And Counters"
1626 bool "Kernel performance events and counters"
1627 default y if PROFILING
1628 depends on HAVE_PERF_EVENTS
1633 Enable kernel support for various performance events provided
1634 by software and hardware.
1636 Software events are supported either built-in or via the
1637 use of generic tracepoints.
1639 Most modern CPUs support performance events via performance
1640 counter registers. These registers count the number of certain
1641 types of hw events: such as instructions executed, cachemisses
1642 suffered, or branches mis-predicted - without slowing down the
1643 kernel or applications. These registers can also trigger interrupts
1644 when a threshold number of events have passed - and can thus be
1645 used to profile the code that runs on that CPU.
1647 The Linux Performance Event subsystem provides an abstraction of
1648 these software and hardware event capabilities, available via a
1649 system call and used by the "perf" utility in tools/perf/. It
1650 provides per task and per CPU counters, and it provides event
1651 capabilities on top of those.
1655 config DEBUG_PERF_USE_VMALLOC
1657 bool "Debug: use vmalloc to back perf mmap() buffers"
1658 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1659 select PERF_USE_VMALLOC
1661 Use vmalloc memory to back perf mmap() buffers.
1663 Mostly useful for debugging the vmalloc code on platforms
1664 that don't require it.
1670 config VM_EVENT_COUNTERS
1672 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1674 VM event counters are needed for event counts to be shown.
1675 This option allows the disabling of the VM event counters
1676 on EXPERT systems. /proc/vmstat will only show page counts
1677 if VM event counters are disabled.
1681 bool "Enable SLUB debugging support" if EXPERT
1682 depends on SLUB && SYSFS
1684 SLUB has extensive debug support features. Disabling these can
1685 result in significant savings in code size. This also disables
1686 SLUB sysfs support. /sys/slab will not exist and there will be
1687 no support for cache validation etc.
1690 bool "Disable heap randomization"
1693 Randomizing heap placement makes heap exploits harder, but it
1694 also breaks ancient binaries (including anything libc5 based).
1695 This option changes the bootup default to heap randomization
1696 disabled, and can be overridden at runtime by setting
1697 /proc/sys/kernel/randomize_va_space to 2.
1699 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1702 prompt "Choose SLAB allocator"
1705 This option allows to select a slab allocator.
1710 The regular slab allocator that is established and known to work
1711 well in all environments. It organizes cache hot objects in
1712 per cpu and per node queues.
1715 bool "SLUB (Unqueued Allocator)"
1717 SLUB is a slab allocator that minimizes cache line usage
1718 instead of managing queues of cached objects (SLAB approach).
1719 Per cpu caching is realized using slabs of objects instead
1720 of queues of objects. SLUB can use memory efficiently
1721 and has enhanced diagnostics. SLUB is the default choice for
1726 bool "SLOB (Simple Allocator)"
1728 SLOB replaces the stock allocator with a drastically simpler
1729 allocator. SLOB is generally more space efficient but
1730 does not perform as well on large systems.
1734 config SLUB_CPU_PARTIAL
1736 depends on SLUB && SMP
1737 bool "SLUB per cpu partial cache"
1739 Per cpu partial caches accellerate objects allocation and freeing
1740 that is local to a processor at the price of more indeterminism
1741 in the latency of the free. On overflow these caches will be cleared
1742 which requires the taking of locks that may cause latency spikes.
1743 Typically one would choose no for a realtime system.
1745 config MMAP_ALLOW_UNINITIALIZED
1746 bool "Allow mmapped anonymous memory to be uninitialized"
1747 depends on EXPERT && !MMU
1750 Normally, and according to the Linux spec, anonymous memory obtained
1751 from mmap() has it's contents cleared before it is passed to
1752 userspace. Enabling this config option allows you to request that
1753 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1754 providing a huge performance boost. If this option is not enabled,
1755 then the flag will be ignored.
1757 This is taken advantage of by uClibc's malloc(), and also by
1758 ELF-FDPIC binfmt's brk and stack allocator.
1760 Because of the obvious security issues, this option should only be
1761 enabled on embedded devices where you control what is run in
1762 userspace. Since that isn't generally a problem on no-MMU systems,
1763 it is normally safe to say Y here.
1765 See Documentation/nommu-mmap.txt for more information.
1767 config SYSTEM_DATA_VERIFICATION
1769 select SYSTEM_TRUSTED_KEYRING
1772 select ASYMMETRIC_KEY_TYPE
1773 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1774 select PUBLIC_KEY_ALGO_RSA
1777 select X509_CERTIFICATE_PARSER
1778 select PKCS7_MESSAGE_PARSER
1780 Provide PKCS#7 message verification using the contents of the system
1781 trusted keyring to provide public keys. This then can be used for
1782 module verification, kexec image verification and firmware blob
1786 bool "Profiling support"
1788 Say Y here to enable the extended profiling support mechanisms used
1789 by profilers such as OProfile.
1792 # Place an empty function call at each tracepoint site. Can be
1793 # dynamically changed for a probe function.
1798 source "arch/Kconfig"
1800 endmenu # General setup
1802 config HAVE_GENERIC_DMA_COHERENT
1809 depends on SLAB || SLUB_DEBUG
1817 default 0 if BASE_FULL
1818 default 1 if !BASE_FULL
1821 bool "Enable loadable module support"
1824 Kernel modules are small pieces of compiled code which can
1825 be inserted in the running kernel, rather than being
1826 permanently built into the kernel. You use the "modprobe"
1827 tool to add (and sometimes remove) them. If you say Y here,
1828 many parts of the kernel can be built as modules (by
1829 answering M instead of Y where indicated): this is most
1830 useful for infrequently used options which are not required
1831 for booting. For more information, see the man pages for
1832 modprobe, lsmod, modinfo, insmod and rmmod.
1834 If you say Y here, you will need to run "make
1835 modules_install" to put the modules under /lib/modules/
1836 where modprobe can find them (you may need to be root to do
1843 config MODULE_FORCE_LOAD
1844 bool "Forced module loading"
1847 Allow loading of modules without version information (ie. modprobe
1848 --force). Forced module loading sets the 'F' (forced) taint flag and
1849 is usually a really bad idea.
1851 config MODULE_UNLOAD
1852 bool "Module unloading"
1854 Without this option you will not be able to unload any
1855 modules (note that some modules may not be unloadable
1856 anyway), which makes your kernel smaller, faster
1857 and simpler. If unsure, say Y.
1859 config MODULE_FORCE_UNLOAD
1860 bool "Forced module unloading"
1861 depends on MODULE_UNLOAD
1863 This option allows you to force a module to unload, even if the
1864 kernel believes it is unsafe: the kernel will remove the module
1865 without waiting for anyone to stop using it (using the -f option to
1866 rmmod). This is mainly for kernel developers and desperate users.
1870 bool "Module versioning support"
1872 Usually, you have to use modules compiled with your kernel.
1873 Saying Y here makes it sometimes possible to use modules
1874 compiled for different kernels, by adding enough information
1875 to the modules to (hopefully) spot any changes which would
1876 make them incompatible with the kernel you are running. If
1879 config MODULE_SRCVERSION_ALL
1880 bool "Source checksum for all modules"
1882 Modules which contain a MODULE_VERSION get an extra "srcversion"
1883 field inserted into their modinfo section, which contains a
1884 sum of the source files which made it. This helps maintainers
1885 see exactly which source was used to build a module (since
1886 others sometimes change the module source without updating
1887 the version). With this option, such a "srcversion" field
1888 will be created for all modules. If unsure, say N.
1891 bool "Module signature verification"
1893 select SYSTEM_DATA_VERIFICATION
1895 Check modules for valid signatures upon load: the signature
1896 is simply appended to the module. For more information see
1897 Documentation/module-signing.txt.
1899 Note that this option adds the OpenSSL development packages as a
1900 kernel build dependency so that the signing tool can use its crypto
1903 !!!WARNING!!! If you enable this option, you MUST make sure that the
1904 module DOES NOT get stripped after being signed. This includes the
1905 debuginfo strip done by some packagers (such as rpmbuild) and
1906 inclusion into an initramfs that wants the module size reduced.
1908 config MODULE_SIG_FORCE
1909 bool "Require modules to be validly signed"
1910 depends on MODULE_SIG
1912 Reject unsigned modules or signed modules for which we don't have a
1913 key. Without this, such modules will simply taint the kernel.
1915 config MODULE_SIG_ALL
1916 bool "Automatically sign all modules"
1918 depends on MODULE_SIG
1920 Sign all modules during make modules_install. Without this option,
1921 modules must be signed manually, using the scripts/sign-file tool.
1923 comment "Do not forget to sign required modules with scripts/sign-file"
1924 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1927 prompt "Which hash algorithm should modules be signed with?"
1928 depends on MODULE_SIG
1930 This determines which sort of hashing algorithm will be used during
1931 signature generation. This algorithm _must_ be built into the kernel
1932 directly so that signature verification can take place. It is not
1933 possible to load a signed module containing the algorithm to check
1934 the signature on that module.
1936 config MODULE_SIG_SHA1
1937 bool "Sign modules with SHA-1"
1940 config MODULE_SIG_SHA224
1941 bool "Sign modules with SHA-224"
1942 select CRYPTO_SHA256
1944 config MODULE_SIG_SHA256
1945 bool "Sign modules with SHA-256"
1946 select CRYPTO_SHA256
1948 config MODULE_SIG_SHA384
1949 bool "Sign modules with SHA-384"
1950 select CRYPTO_SHA512
1952 config MODULE_SIG_SHA512
1953 bool "Sign modules with SHA-512"
1954 select CRYPTO_SHA512
1958 config MODULE_SIG_HASH
1960 depends on MODULE_SIG
1961 default "sha1" if MODULE_SIG_SHA1
1962 default "sha224" if MODULE_SIG_SHA224
1963 default "sha256" if MODULE_SIG_SHA256
1964 default "sha384" if MODULE_SIG_SHA384
1965 default "sha512" if MODULE_SIG_SHA512
1967 config MODULE_COMPRESS
1968 bool "Compress modules on installation"
1972 Compresses kernel modules when 'make modules_install' is run; gzip or
1973 xz depending on "Compression algorithm" below.
1975 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
1977 Out-of-tree kernel modules installed using Kbuild will also be
1978 compressed upon installation.
1980 Note: for modules inside an initrd or initramfs, it's more efficient
1981 to compress the whole initrd or initramfs instead.
1983 Note: This is fully compatible with signed modules.
1988 prompt "Compression algorithm"
1989 depends on MODULE_COMPRESS
1990 default MODULE_COMPRESS_GZIP
1992 This determines which sort of compression will be used during
1993 'make modules_install'.
1995 GZIP (default) and XZ are supported.
1997 config MODULE_COMPRESS_GZIP
2000 config MODULE_COMPRESS_XZ
2007 config MODULES_TREE_LOOKUP
2009 depends on PERF_EVENTS || TRACING
2011 config INIT_ALL_POSSIBLE
2014 Back when each arch used to define their own cpu_online_mask and
2015 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2016 with all 1s, and others with all 0s. When they were centralised,
2017 it was better to provide this option than to break all the archs
2018 and have several arch maintainers pursuing me down dark alleys.
2020 source "block/Kconfig"
2022 config PREEMPT_NOTIFIERS
2029 # Can be selected by architectures with broken toolchains
2030 # that get confused by correct const<->read_only section
2032 config BROKEN_RODATA
2038 Build a simple ASN.1 grammar compiler that produces a bytecode output
2039 that can be interpreted by the ASN.1 stream decoder and used to
2040 inform it as to what tags are to be expected in a stream and what
2041 functions to call on what tags.
2043 source "kernel/Kconfig.locks"
projects / deliverable / linux.git / blob