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
265 tristate "kdbus interprocess communication"
268 D-Bus is a system for low-latency, low-overhead, easy to use
269 interprocess communication (IPC).
271 See the man-pages and HTML files in Documentation/kdbus/
272 that are generated by 'make mandocs' and 'make htmldocs'.
274 If you have an ordinary machine, select M here. The module
275 will be called kdbus.
277 config CROSS_MEMORY_ATTACH
278 bool "Enable process_vm_readv/writev syscalls"
282 Enabling this option adds the system calls process_vm_readv and
283 process_vm_writev which allow a process with the correct privileges
284 to directly read from or write to another process' address space.
285 See the man page for more details.
288 bool "open by fhandle syscalls"
291 If you say Y here, a user level program will be able to map
292 file names to handle and then later use the handle for
293 different file system operations. This is useful in implementing
294 userspace file servers, which now track files using handles instead
295 of names. The handle would remain the same even if file names
296 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
300 bool "uselib syscall"
303 This option enables the uselib syscall, a system call used in the
304 dynamic linker from libc5 and earlier. glibc does not use this
305 system call. If you intend to run programs built on libc5 or
306 earlier, you may need to enable this syscall. Current systems
307 running glibc can safely disable this.
310 bool "Auditing support"
313 Enable auditing infrastructure that can be used with another
314 kernel subsystem, such as SELinux (which requires this for
315 logging of avc messages output). Does not do system-call
316 auditing without CONFIG_AUDITSYSCALL.
318 config HAVE_ARCH_AUDITSYSCALL
322 bool "Enable system-call auditing support"
323 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
324 default y if SECURITY_SELINUX
326 Enable low-overhead system-call auditing infrastructure that
327 can be used independently or with another kernel subsystem,
332 depends on AUDITSYSCALL
337 depends on AUDITSYSCALL
340 source "kernel/irq/Kconfig"
341 source "kernel/time/Kconfig"
343 menu "CPU/Task time and stats accounting"
345 config VIRT_CPU_ACCOUNTING
349 prompt "Cputime accounting"
350 default TICK_CPU_ACCOUNTING if !PPC64
351 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
353 # Kind of a stub config for the pure tick based cputime accounting
354 config TICK_CPU_ACCOUNTING
355 bool "Simple tick based cputime accounting"
356 depends on !S390 && !NO_HZ_FULL
358 This is the basic tick based cputime accounting that maintains
359 statistics about user, system and idle time spent on per jiffies
364 config VIRT_CPU_ACCOUNTING_NATIVE
365 bool "Deterministic task and CPU time accounting"
366 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
367 select VIRT_CPU_ACCOUNTING
369 Select this option to enable more accurate task and CPU time
370 accounting. This is done by reading a CPU counter on each
371 kernel entry and exit and on transitions within the kernel
372 between system, softirq and hardirq state, so there is a
373 small performance impact. In the case of s390 or IBM POWER > 5,
374 this also enables accounting of stolen time on logically-partitioned
377 config VIRT_CPU_ACCOUNTING_GEN
378 bool "Full dynticks CPU time accounting"
379 depends on HAVE_CONTEXT_TRACKING
380 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
381 select VIRT_CPU_ACCOUNTING
382 select CONTEXT_TRACKING
384 Select this option to enable task and CPU time accounting on full
385 dynticks systems. This accounting is implemented by watching every
386 kernel-user boundaries using the context tracking subsystem.
387 The accounting is thus performed at the expense of some significant
390 For now this is only useful if you are working on the full
391 dynticks subsystem development.
395 config IRQ_TIME_ACCOUNTING
396 bool "Fine granularity task level IRQ time accounting"
397 depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
399 Select this option to enable fine granularity task irq time
400 accounting. This is done by reading a timestamp on each
401 transitions between softirq and hardirq state, so there can be a
402 small performance impact.
404 If in doubt, say N here.
408 config BSD_PROCESS_ACCT
409 bool "BSD Process Accounting"
412 If you say Y here, a user level program will be able to instruct the
413 kernel (via a special system call) to write process accounting
414 information to a file: whenever a process exits, information about
415 that process will be appended to the file by the kernel. The
416 information includes things such as creation time, owning user,
417 command name, memory usage, controlling terminal etc. (the complete
418 list is in the struct acct in <file:include/linux/acct.h>). It is
419 up to the user level program to do useful things with this
420 information. This is generally a good idea, so say Y.
422 config BSD_PROCESS_ACCT_V3
423 bool "BSD Process Accounting version 3 file format"
424 depends on BSD_PROCESS_ACCT
427 If you say Y here, the process accounting information is written
428 in a new file format that also logs the process IDs of each
429 process and it's parent. Note that this file format is incompatible
430 with previous v0/v1/v2 file formats, so you will need updated tools
431 for processing it. A preliminary version of these tools is available
432 at <http://www.gnu.org/software/acct/>.
435 bool "Export task/process statistics through netlink"
440 Export selected statistics for tasks/processes through the
441 generic netlink interface. Unlike BSD process accounting, the
442 statistics are available during the lifetime of tasks/processes as
443 responses to commands. Like BSD accounting, they are sent to user
448 config TASK_DELAY_ACCT
449 bool "Enable per-task delay accounting"
452 Collect information on time spent by a task waiting for system
453 resources like cpu, synchronous block I/O completion and swapping
454 in pages. Such statistics can help in setting a task's priorities
455 relative to other tasks for cpu, io, rss limits etc.
460 bool "Enable extended accounting over taskstats"
463 Collect extended task accounting data and send the data
464 to userland for processing over the taskstats interface.
468 config TASK_IO_ACCOUNTING
469 bool "Enable per-task storage I/O accounting"
470 depends on TASK_XACCT
472 Collect information on the number of bytes of storage I/O which this
477 endmenu # "CPU/Task time and stats accounting"
482 prompt "RCU Implementation"
486 bool "Tree-based hierarchical RCU"
487 depends on !PREEMPT && SMP
489 This option selects the RCU implementation that is
490 designed for very large SMP system with hundreds or
491 thousands of CPUs. It also scales down nicely to
495 bool "Preemptible tree-based hierarchical RCU"
498 This option selects the RCU implementation that is
499 designed for very large SMP systems with hundreds or
500 thousands of CPUs, but for which real-time response
501 is also required. It also scales down nicely to
504 Select this option if you are unsure.
507 bool "UP-only small-memory-footprint RCU"
508 depends on !PREEMPT && !SMP
510 This option selects the RCU implementation that is
511 designed for UP systems from which real-time response
512 is not required. This option greatly reduces the
513 memory footprint of RCU.
520 This option selects the sleepable version of RCU. This version
521 permits arbitrary sleeping or blocking within RCU read-side critical
525 bool "Task_based RCU implementation using voluntary context switch"
529 This option enables a task-based RCU implementation that uses
530 only voluntary context switch (not preemption!), idle, and
531 user-mode execution as quiescent states.
535 config RCU_STALL_COMMON
536 def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
538 This option enables RCU CPU stall code that is common between
539 the TINY and TREE variants of RCU. The purpose is to allow
540 the tiny variants to disable RCU CPU stall warnings, while
541 making these warnings mandatory for the tree variants.
543 config CONTEXT_TRACKING
547 bool "Consider userspace as in RCU extended quiescent state"
548 depends on HAVE_CONTEXT_TRACKING && SMP
549 select CONTEXT_TRACKING
551 This option sets hooks on kernel / userspace boundaries and
552 puts RCU in extended quiescent state when the CPU runs in
553 userspace. It means that when a CPU runs in userspace, it is
554 excluded from the global RCU state machine and thus doesn't
555 try to keep the timer tick on for RCU.
557 Unless you want to hack and help the development of the full
558 dynticks mode, you shouldn't enable this option. It also
559 adds unnecessary overhead.
563 config CONTEXT_TRACKING_FORCE
564 bool "Force context tracking"
565 depends on CONTEXT_TRACKING
566 default y if !NO_HZ_FULL
568 The major pre-requirement for full dynticks to work is to
569 support the context tracking subsystem. But there are also
570 other dependencies to provide in order to make the full
573 This option stands for testing when an arch implements the
574 context tracking backend but doesn't yet fullfill all the
575 requirements to make the full dynticks feature working.
576 Without the full dynticks, there is no way to test the support
577 for context tracking and the subsystems that rely on it: RCU
578 userspace extended quiescent state and tickless cputime
579 accounting. This option copes with the absence of the full
580 dynticks subsystem by forcing the context tracking on all
583 Say Y only if you're working on the development of an
584 architecture backend for the context tracking.
586 Say N otherwise, this option brings an overhead that you
587 don't want in production.
591 int "Tree-based hierarchical RCU fanout value"
594 depends on TREE_RCU || PREEMPT_RCU
598 This option controls the fanout of hierarchical implementations
599 of RCU, allowing RCU to work efficiently on machines with
600 large numbers of CPUs. This value must be at least the fourth
601 root of NR_CPUS, which allows NR_CPUS to be insanely large.
602 The default value of RCU_FANOUT should be used for production
603 systems, but if you are stress-testing the RCU implementation
604 itself, small RCU_FANOUT values allow you to test large-system
605 code paths on small(er) systems.
607 Select a specific number if testing RCU itself.
608 Take the default if unsure.
610 config RCU_FANOUT_LEAF
611 int "Tree-based hierarchical RCU leaf-level fanout value"
612 range 2 RCU_FANOUT if 64BIT
613 range 2 RCU_FANOUT if !64BIT
614 depends on TREE_RCU || PREEMPT_RCU
617 This option controls the leaf-level fanout of hierarchical
618 implementations of RCU, and allows trading off cache misses
619 against lock contention. Systems that synchronize their
620 scheduling-clock interrupts for energy-efficiency reasons will
621 want the default because the smaller leaf-level fanout keeps
622 lock contention levels acceptably low. Very large systems
623 (hundreds or thousands of CPUs) will instead want to set this
624 value to the maximum value possible in order to reduce the
625 number of cache misses incurred during RCU's grace-period
626 initialization. These systems tend to run CPU-bound, and thus
627 are not helped by synchronized interrupts, and thus tend to
628 skew them, which reduces lock contention enough that large
629 leaf-level fanouts work well.
631 Select a specific number if testing RCU itself.
633 Select the maximum permissible value for large systems.
635 Take the default if unsure.
637 config RCU_FANOUT_EXACT
638 bool "Disable tree-based hierarchical RCU auto-balancing"
639 depends on TREE_RCU || PREEMPT_RCU
642 This option forces use of the exact RCU_FANOUT value specified,
643 regardless of imbalances in the hierarchy. This is useful for
644 testing RCU itself, and might one day be useful on systems with
645 strong NUMA behavior.
647 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
651 config RCU_FAST_NO_HZ
652 bool "Accelerate last non-dyntick-idle CPU's grace periods"
653 depends on NO_HZ_COMMON && SMP
656 This option permits CPUs to enter dynticks-idle state even if
657 they have RCU callbacks queued, and prevents RCU from waking
658 these CPUs up more than roughly once every four jiffies (by
659 default, you can adjust this using the rcutree.rcu_idle_gp_delay
660 parameter), thus improving energy efficiency. On the other
661 hand, this option increases the duration of RCU grace periods,
662 for example, slowing down synchronize_rcu().
664 Say Y if energy efficiency is critically important, and you
665 don't care about increased grace-period durations.
667 Say N if you are unsure.
669 config TREE_RCU_TRACE
670 def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
673 This option provides tracing for the TREE_RCU and
674 PREEMPT_RCU implementations, permitting Makefile to
675 trivially select kernel/rcutree_trace.c.
678 bool "Enable RCU priority boosting"
679 depends on RT_MUTEXES && PREEMPT_RCU
682 This option boosts the priority of preempted RCU readers that
683 block the current preemptible RCU grace period for too long.
684 This option also prevents heavy loads from blocking RCU
685 callback invocation for all flavors of RCU.
687 Say Y here if you are working with real-time apps or heavy loads
688 Say N here if you are unsure.
690 config RCU_KTHREAD_PRIO
691 int "Real-time priority to use for RCU worker threads"
692 range 1 99 if RCU_BOOST
693 range 0 99 if !RCU_BOOST
694 default 1 if RCU_BOOST
695 default 0 if !RCU_BOOST
697 This option specifies the SCHED_FIFO priority value that will be
698 assigned to the rcuc/n and rcub/n threads and is also the value
699 used for RCU_BOOST (if enabled). If you are working with a
700 real-time application that has one or more CPU-bound threads
701 running at a real-time priority level, you should set
702 RCU_KTHREAD_PRIO to a priority higher than the highest-priority
703 real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO
704 value of 1 is appropriate in the common case, which is real-time
705 applications that do not have any CPU-bound threads.
707 Some real-time applications might not have a single real-time
708 thread that saturates a given CPU, but instead might have
709 multiple real-time threads that, taken together, fully utilize
710 that CPU. In this case, you should set RCU_KTHREAD_PRIO to
711 a priority higher than the lowest-priority thread that is
712 conspiring to prevent the CPU from running any non-real-time
713 tasks. For example, if one thread at priority 10 and another
714 thread at priority 5 are between themselves fully consuming
715 the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
716 set to priority 6 or higher.
718 Specify the real-time priority, or take the default if unsure.
720 config RCU_BOOST_DELAY
721 int "Milliseconds to delay boosting after RCU grace-period start"
726 This option specifies the time to wait after the beginning of
727 a given grace period before priority-boosting preempted RCU
728 readers blocking that grace period. Note that any RCU reader
729 blocking an expedited RCU grace period is boosted immediately.
731 Accept the default if unsure.
734 bool "Offload RCU callback processing from boot-selected CPUs"
735 depends on TREE_RCU || PREEMPT_RCU
738 Use this option to reduce OS jitter for aggressive HPC or
739 real-time workloads. It can also be used to offload RCU
740 callback invocation to energy-efficient CPUs in battery-powered
741 asymmetric multiprocessors.
743 This option offloads callback invocation from the set of
744 CPUs specified at boot time by the rcu_nocbs parameter.
745 For each such CPU, a kthread ("rcuox/N") will be created to
746 invoke callbacks, where the "N" is the CPU being offloaded,
747 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
748 "s" for RCU-sched. Nothing prevents this kthread from running
749 on the specified CPUs, but (1) the kthreads may be preempted
750 between each callback, and (2) affinity or cgroups can be used
751 to force the kthreads to run on whatever set of CPUs is desired.
753 Say Y here if you want to help to debug reduced OS jitter.
754 Say N here if you are unsure.
757 prompt "Build-forced no-CBs CPUs"
758 default RCU_NOCB_CPU_NONE
759 depends on RCU_NOCB_CPU
761 This option allows no-CBs CPUs (whose RCU callbacks are invoked
762 from kthreads rather than from softirq context) to be specified
763 at build time. Additional no-CBs CPUs may be specified by
764 the rcu_nocbs= boot parameter.
766 config RCU_NOCB_CPU_NONE
767 bool "No build_forced no-CBs CPUs"
769 This option does not force any of the CPUs to be no-CBs CPUs.
770 Only CPUs designated by the rcu_nocbs= boot parameter will be
771 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
772 kthreads whose names begin with "rcuo". All other CPUs will
773 invoke their own RCU callbacks in softirq context.
775 Select this option if you want to choose no-CBs CPUs at
776 boot time, for example, to allow testing of different no-CBs
777 configurations without having to rebuild the kernel each time.
779 config RCU_NOCB_CPU_ZERO
780 bool "CPU 0 is a build_forced no-CBs CPU"
782 This option forces CPU 0 to be a no-CBs CPU, so that its RCU
783 callbacks are invoked by a per-CPU kthread whose name begins
784 with "rcuo". Additional CPUs may be designated as no-CBs
785 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
786 All other CPUs will invoke their own RCU callbacks in softirq
789 Select this if CPU 0 needs to be a no-CBs CPU for real-time
790 or energy-efficiency reasons, but the real reason it exists
791 is to ensure that randconfig testing covers mixed systems.
793 config RCU_NOCB_CPU_ALL
794 bool "All CPUs are build_forced no-CBs CPUs"
796 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
797 boot parameter will be ignored. All CPUs' RCU callbacks will
798 be executed in the context of per-CPU rcuo kthreads created for
799 this purpose. Assuming that the kthreads whose names start with
800 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
801 on the remaining CPUs, but might decrease memory locality during
802 RCU-callback invocation, thus potentially degrading throughput.
804 Select this if all CPUs need to be no-CBs CPUs for real-time
805 or energy-efficiency reasons.
809 config RCU_EXPEDITE_BOOT
813 This option enables expedited grace periods at boot time,
814 as if rcu_expedite_gp() had been invoked early in boot.
815 The corresponding rcu_unexpedite_gp() is invoked from
816 rcu_end_inkernel_boot(), which is intended to be invoked
817 at the end of the kernel-only boot sequence, just before
820 Accept the default if unsure.
822 endmenu # "RCU Subsystem"
829 tristate "Kernel .config support"
832 This option enables the complete Linux kernel ".config" file
833 contents to be saved in the kernel. It provides documentation
834 of which kernel options are used in a running kernel or in an
835 on-disk kernel. This information can be extracted from the kernel
836 image file with the script scripts/extract-ikconfig and used as
837 input to rebuild the current kernel or to build another kernel.
838 It can also be extracted from a running kernel by reading
839 /proc/config.gz if enabled (below).
842 bool "Enable access to .config through /proc/config.gz"
843 depends on IKCONFIG && PROC_FS
845 This option enables access to the kernel configuration file
846 through /proc/config.gz.
849 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
854 Select the minimal kernel log buffer size as a power of 2.
855 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
856 parameter, see below. Any higher size also might be forced
857 by "log_buf_len" boot parameter.
867 config LOG_CPU_MAX_BUF_SHIFT
868 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
871 default 12 if !BASE_SMALL
872 default 0 if BASE_SMALL
875 This option allows to increase the default ring buffer size
876 according to the number of CPUs. The value defines the contribution
877 of each CPU as a power of 2. The used space is typically only few
878 lines however it might be much more when problems are reported,
881 The increased size means that a new buffer has to be allocated and
882 the original static one is unused. It makes sense only on systems
883 with more CPUs. Therefore this value is used only when the sum of
884 contributions is greater than the half of the default kernel ring
885 buffer as defined by LOG_BUF_SHIFT. The default values are set
886 so that more than 64 CPUs are needed to trigger the allocation.
888 Also this option is ignored when "log_buf_len" kernel parameter is
889 used as it forces an exact (power of two) size of the ring buffer.
891 The number of possible CPUs is used for this computation ignoring
892 hotplugging making the compuation optimal for the the worst case
893 scenerio while allowing a simple algorithm to be used from bootup.
895 Examples shift values and their meaning:
896 17 => 128 KB for each CPU
897 16 => 64 KB for each CPU
898 15 => 32 KB for each CPU
899 14 => 16 KB for each CPU
900 13 => 8 KB for each CPU
901 12 => 4 KB for each CPU
904 # Architectures with an unreliable sched_clock() should select this:
906 config HAVE_UNSTABLE_SCHED_CLOCK
909 config GENERIC_SCHED_CLOCK
913 # For architectures that want to enable the support for NUMA-affine scheduler
916 config ARCH_SUPPORTS_NUMA_BALANCING
920 # For architectures that know their GCC __int128 support is sound
922 config ARCH_SUPPORTS_INT128
925 # For architectures that (ab)use NUMA to represent different memory regions
926 # all cpu-local but of different latencies, such as SuperH.
928 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
931 config NUMA_BALANCING
932 bool "Memory placement aware NUMA scheduler"
933 depends on ARCH_SUPPORTS_NUMA_BALANCING
934 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
935 depends on SMP && NUMA && MIGRATION
937 This option adds support for automatic NUMA aware memory/task placement.
938 The mechanism is quite primitive and is based on migrating memory when
939 it has references to the node the task is running on.
941 This system will be inactive on UMA systems.
943 config NUMA_BALANCING_DEFAULT_ENABLED
944 bool "Automatically enable NUMA aware memory/task placement"
946 depends on NUMA_BALANCING
948 If set, automatic NUMA balancing will be enabled if running on a NUMA
952 bool "Control Group support"
955 This option adds support for grouping sets of processes together, for
956 use with process control subsystems such as Cpusets, CFS, memory
957 controls or device isolation.
959 - Documentation/scheduler/sched-design-CFS.txt (CFS)
960 - Documentation/cgroups/ (features for grouping, isolation
961 and resource control)
968 bool "Example debug cgroup subsystem"
971 This option enables a simple cgroup subsystem that
972 exports useful debugging information about the cgroups
977 config CGROUP_FREEZER
978 bool "Freezer cgroup subsystem"
980 Provides a way to freeze and unfreeze all tasks in a
984 bool "Device controller for cgroups"
986 Provides a cgroup implementing whitelists for devices which
987 a process in the cgroup can mknod or open.
990 bool "Cpuset support"
992 This option will let you create and manage CPUSETs which
993 allow dynamically partitioning a system into sets of CPUs and
994 Memory Nodes and assigning tasks to run only within those sets.
995 This is primarily useful on large SMP or NUMA systems.
999 config PROC_PID_CPUSET
1000 bool "Include legacy /proc/<pid>/cpuset file"
1004 config CGROUP_CPUACCT
1005 bool "Simple CPU accounting cgroup subsystem"
1007 Provides a simple Resource Controller for monitoring the
1008 total CPU consumed by the tasks in a cgroup.
1014 bool "Memory Resource Controller for Control Groups"
1018 Provides a memory resource controller that manages both anonymous
1019 memory and page cache. (See Documentation/cgroups/memory.txt)
1022 bool "Memory Resource Controller Swap Extension"
1023 depends on MEMCG && SWAP
1025 Add swap management feature to memory resource controller. When you
1026 enable this, you can limit mem+swap usage per cgroup. In other words,
1027 when you disable this, memory resource controller has no cares to
1028 usage of swap...a process can exhaust all of the swap. This extension
1029 is useful when you want to avoid exhaustion swap but this itself
1030 adds more overheads and consumes memory for remembering information.
1031 Especially if you use 32bit system or small memory system, please
1032 be careful about enabling this. When memory resource controller
1033 is disabled by boot option, this will be automatically disabled and
1034 there will be no overhead from this. Even when you set this config=y,
1035 if boot option "swapaccount=0" is set, swap will not be accounted.
1036 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
1037 size is 4096bytes, 512k per 1Gbytes of swap.
1038 config MEMCG_SWAP_ENABLED
1039 bool "Memory Resource Controller Swap Extension enabled by default"
1040 depends on MEMCG_SWAP
1043 Memory Resource Controller Swap Extension comes with its price in
1044 a bigger memory consumption. General purpose distribution kernels
1045 which want to enable the feature but keep it disabled by default
1046 and let the user enable it by swapaccount=1 boot command line
1047 parameter should have this option unselected.
1048 For those who want to have the feature enabled by default should
1049 select this option (if, for some reason, they need to disable it
1050 then swapaccount=0 does the trick).
1052 bool "Memory Resource Controller Kernel Memory accounting"
1054 depends on SLUB || SLAB
1056 The Kernel Memory extension for Memory Resource Controller can limit
1057 the amount of memory used by kernel objects in the system. Those are
1058 fundamentally different from the entities handled by the standard
1059 Memory Controller, which are page-based, and can be swapped. Users of
1060 the kmem extension can use it to guarantee that no group of processes
1061 will ever exhaust kernel resources alone.
1063 config CGROUP_HUGETLB
1064 bool "HugeTLB Resource Controller for Control Groups"
1065 depends on HUGETLB_PAGE
1069 Provides a cgroup Resource Controller for HugeTLB pages.
1070 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1071 The limit is enforced during page fault. Since HugeTLB doesn't
1072 support page reclaim, enforcing the limit at page fault time implies
1073 that, the application will get SIGBUS signal if it tries to access
1074 HugeTLB pages beyond its limit. This requires the application to know
1075 beforehand how much HugeTLB pages it would require for its use. The
1076 control group is tracked in the third page lru pointer. This means
1077 that we cannot use the controller with huge page less than 3 pages.
1080 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1081 depends on PERF_EVENTS && CGROUPS
1083 This option extends the per-cpu mode to restrict monitoring to
1084 threads which belong to the cgroup specified and run on the
1089 menuconfig CGROUP_SCHED
1090 bool "Group CPU scheduler"
1093 This feature lets CPU scheduler recognize task groups and control CPU
1094 bandwidth allocation to such task groups. It uses cgroups to group
1098 config FAIR_GROUP_SCHED
1099 bool "Group scheduling for SCHED_OTHER"
1100 depends on CGROUP_SCHED
1101 default CGROUP_SCHED
1103 config CFS_BANDWIDTH
1104 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1105 depends on FAIR_GROUP_SCHED
1108 This option allows users to define CPU bandwidth rates (limits) for
1109 tasks running within the fair group scheduler. Groups with no limit
1110 set are considered to be unconstrained and will run with no
1112 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1114 config RT_GROUP_SCHED
1115 bool "Group scheduling for SCHED_RR/FIFO"
1116 depends on CGROUP_SCHED
1119 This feature lets you explicitly allocate real CPU bandwidth
1120 to task groups. If enabled, it will also make it impossible to
1121 schedule realtime tasks for non-root users until you allocate
1122 realtime bandwidth for them.
1123 See Documentation/scheduler/sched-rt-group.txt for more information.
1128 bool "Block IO controller"
1132 Generic block IO controller cgroup interface. This is the common
1133 cgroup interface which should be used by various IO controlling
1136 Currently, CFQ IO scheduler uses it to recognize task groups and
1137 control disk bandwidth allocation (proportional time slice allocation)
1138 to such task groups. It is also used by bio throttling logic in
1139 block layer to implement upper limit in IO rates on a device.
1141 This option only enables generic Block IO controller infrastructure.
1142 One needs to also enable actual IO controlling logic/policy. For
1143 enabling proportional weight division of disk bandwidth in CFQ, set
1144 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1145 CONFIG_BLK_DEV_THROTTLING=y.
1147 See Documentation/cgroups/blkio-controller.txt for more information.
1149 config DEBUG_BLK_CGROUP
1150 bool "Enable Block IO controller debugging"
1151 depends on BLK_CGROUP
1154 Enable some debugging help. Currently it exports additional stat
1155 files in a cgroup which can be useful for debugging.
1159 config CHECKPOINT_RESTORE
1160 bool "Checkpoint/restore support" if EXPERT
1163 Enables additional kernel features in a sake of checkpoint/restore.
1164 In particular it adds auxiliary prctl codes to setup process text,
1165 data and heap segment sizes, and a few additional /proc filesystem
1168 If unsure, say N here.
1170 menuconfig NAMESPACES
1171 bool "Namespaces support" if EXPERT
1172 depends on MULTIUSER
1175 Provides the way to make tasks work with different objects using
1176 the same id. For example same IPC id may refer to different objects
1177 or same user id or pid may refer to different tasks when used in
1178 different namespaces.
1183 bool "UTS namespace"
1186 In this namespace tasks see different info provided with the
1190 bool "IPC namespace"
1191 depends on (SYSVIPC || POSIX_MQUEUE)
1194 In this namespace tasks work with IPC ids which correspond to
1195 different IPC objects in different namespaces.
1198 bool "User namespace"
1201 This allows containers, i.e. vservers, to use user namespaces
1202 to provide different user info for different servers.
1204 When user namespaces are enabled in the kernel it is
1205 recommended that the MEMCG and MEMCG_KMEM options also be
1206 enabled and that user-space use the memory control groups to
1207 limit the amount of memory a memory unprivileged users can
1213 bool "PID Namespaces"
1216 Support process id namespaces. This allows having multiple
1217 processes with the same pid as long as they are in different
1218 pid namespaces. This is a building block of containers.
1221 bool "Network namespace"
1225 Allow user space to create what appear to be multiple instances
1226 of the network stack.
1230 config SCHED_AUTOGROUP
1231 bool "Automatic process group scheduling"
1234 select FAIR_GROUP_SCHED
1236 This option optimizes the scheduler for common desktop workloads by
1237 automatically creating and populating task groups. This separation
1238 of workloads isolates aggressive CPU burners (like build jobs) from
1239 desktop applications. Task group autogeneration is currently based
1242 config SYSFS_DEPRECATED
1243 bool "Enable deprecated sysfs features to support old userspace tools"
1247 This option adds code that switches the layout of the "block" class
1248 devices, to not show up in /sys/class/block/, but only in
1251 This switch is only active when the sysfs.deprecated=1 boot option is
1252 passed or the SYSFS_DEPRECATED_V2 option is set.
1254 This option allows new kernels to run on old distributions and tools,
1255 which might get confused by /sys/class/block/. Since 2007/2008 all
1256 major distributions and tools handle this just fine.
1258 Recent distributions and userspace tools after 2009/2010 depend on
1259 the existence of /sys/class/block/, and will not work with this
1262 Only if you are using a new kernel on an old distribution, you might
1265 config SYSFS_DEPRECATED_V2
1266 bool "Enable deprecated sysfs features by default"
1269 depends on SYSFS_DEPRECATED
1271 Enable deprecated sysfs by default.
1273 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1276 Only if you are using a new kernel on an old distribution, you might
1277 need to say Y here. Even then, odds are you would not need it
1278 enabled, you can always pass the boot option if absolutely necessary.
1281 bool "Kernel->user space relay support (formerly relayfs)"
1283 This option enables support for relay interface support in
1284 certain file systems (such as debugfs).
1285 It is designed to provide an efficient mechanism for tools and
1286 facilities to relay large amounts of data from kernel space to
1291 config BLK_DEV_INITRD
1292 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1293 depends on BROKEN || !FRV
1295 The initial RAM filesystem is a ramfs which is loaded by the
1296 boot loader (loadlin or lilo) and that is mounted as root
1297 before the normal boot procedure. It is typically used to
1298 load modules needed to mount the "real" root file system,
1299 etc. See <file:Documentation/initrd.txt> for details.
1301 If RAM disk support (BLK_DEV_RAM) is also included, this
1302 also enables initial RAM disk (initrd) support and adds
1303 15 Kbytes (more on some other architectures) to the kernel size.
1309 source "usr/Kconfig"
1313 config CC_OPTIMIZE_FOR_SIZE
1314 bool "Optimize for size"
1316 Enabling this option will pass "-Os" instead of "-O2" to
1317 your compiler resulting in a smaller kernel.
1322 bool "Enable gcc link time optimization (LTO)"
1323 # Only tested on X86 for now. For other architectures you likely
1324 # have to fix some things first, like adding asmlinkages etc.
1326 # lto does not support excluding flags for specific files
1327 # right now. Can be removed if that is fixed.
1328 depends on !FUNCTION_TRACER
1330 With this option gcc will do whole program optimizations for
1331 the whole kernel and module. This increases compile time, but can
1332 lead to better code. It allows gcc to inline functions between
1333 different files and do other optimization. It might also trigger
1334 bugs due to more aggressive optimization. It allows gcc to drop unused
1335 code. On smaller monolithic kernel configurations
1336 it usually leads to smaller kernels, especially when modules
1339 With this option gcc will also do some global checking over
1340 different source files. It also disables a number of kernel
1343 This option is recommended for release builds. With LTO
1344 the kernel always has to be re-optimized (but not re-parsed)
1347 This requires a gcc 4.8 or later compiler and
1348 Linux binutils 2.21.51.0.3 or later. gcc 4.9 builds significantly
1349 faster than 4.8 It does not currently work with a FSF release of
1350 binutils or with the gold linker.
1352 On larger configurations this may need more than 4GB of RAM.
1353 It will likely not work on those with a 32bit compiler.
1355 When the toolchain support is not available this will (hopefully)
1356 be automatically disabled.
1358 For more information see Documentation/lto-build
1361 bool "Disable LTO again"
1365 This option is merely here so that allyesconfig or allmodconfig do
1366 not enable LTO. If you want to actually use LTO do not enable.
1371 depends on LTO_MENU && !LTO_DISABLE
1374 bool "Enable LTO compile time debugging"
1377 Enable LTO debugging in the compiler. The compiler dumps
1378 some log files that make it easier to figure out LTO
1379 behavior. The log files also allow to reconstruct
1380 the global inlining and a global callgraph.
1381 They however add some (single threaded) cost to the
1382 compilation. When in doubt do not enable.
1385 bool "Allow aggressive cloning for function specialization"
1388 Allow the compiler to clone and specialize functions for specific
1389 arguments when it determines these arguments are very commonly
1390 called. Experimential. Will increase text size.
1401 config SYSCTL_EXCEPTION_TRACE
1404 Enable support for /proc/sys/debug/exception-trace.
1406 config SYSCTL_ARCH_UNALIGN_NO_WARN
1409 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1410 Allows arch to define/use @no_unaligned_warning to possibly warn
1411 about unaligned access emulation going on under the hood.
1413 config SYSCTL_ARCH_UNALIGN_ALLOW
1416 Enable support for /proc/sys/kernel/unaligned-trap
1417 Allows arches to define/use @unaligned_enabled to runtime toggle
1418 the unaligned access emulation.
1419 see arch/parisc/kernel/unaligned.c for reference
1421 config HAVE_PCSPKR_PLATFORM
1424 # interpreter that classic socket filters depend on
1429 bool "Configure standard kernel features (expert users)"
1430 # Unhide debug options, to make the on-by-default options visible
1433 This option allows certain base kernel options and settings
1434 to be disabled or tweaked. This is for specialized
1435 environments which can tolerate a "non-standard" kernel.
1436 Only use this if you really know what you are doing.
1439 bool "Enable 16-bit UID system calls" if EXPERT
1440 depends on HAVE_UID16 && MULTIUSER
1443 This enables the legacy 16-bit UID syscall wrappers.
1446 bool "Multiple users, groups and capabilities support" if EXPERT
1449 This option enables support for non-root users, groups and
1452 If you say N here, all processes will run with UID 0, GID 0, and all
1453 possible capabilities. Saying N here also compiles out support for
1454 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1457 If unsure, say Y here.
1459 config SGETMASK_SYSCALL
1460 bool "sgetmask/ssetmask syscalls support" if EXPERT
1461 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1463 sys_sgetmask and sys_ssetmask are obsolete system calls
1464 no longer supported in libc but still enabled by default in some
1467 If unsure, leave the default option here.
1469 config SYSFS_SYSCALL
1470 bool "Sysfs syscall support" if EXPERT
1473 sys_sysfs is an obsolete system call no longer supported in libc.
1474 Note that disabling this option is more secure but might break
1475 compatibility with some systems.
1477 If unsure say Y here.
1479 config SYSCTL_SYSCALL
1480 bool "Sysctl syscall support" if EXPERT
1481 depends on PROC_SYSCTL
1485 sys_sysctl uses binary paths that have been found challenging
1486 to properly maintain and use. The interface in /proc/sys
1487 using paths with ascii names is now the primary path to this
1490 Almost nothing using the binary sysctl interface so if you are
1491 trying to save some space it is probably safe to disable this,
1492 making your kernel marginally smaller.
1494 If unsure say N here.
1497 bool "Load all symbols for debugging/ksymoops" if EXPERT
1500 Say Y here to let the kernel print out symbolic crash information and
1501 symbolic stack backtraces. This increases the size of the kernel
1502 somewhat, as all symbols have to be loaded into the kernel image.
1505 bool "Include all symbols in kallsyms"
1506 depends on DEBUG_KERNEL && KALLSYMS
1508 Normally kallsyms only contains the symbols of functions for nicer
1509 OOPS messages and backtraces (i.e., symbols from the text and inittext
1510 sections). This is sufficient for most cases. And only in very rare
1511 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1512 names of variables from the data sections, etc).
1514 This option makes sure that all symbols are loaded into the kernel
1515 image (i.e., symbols from all sections) in cost of increased kernel
1516 size (depending on the kernel configuration, it may be 300KiB or
1517 something like this).
1519 Say N unless you really need all symbols.
1523 bool "Enable support for printk" if EXPERT
1526 This option enables normal printk support. Removing it
1527 eliminates most of the message strings from the kernel image
1528 and makes the kernel more or less silent. As this makes it
1529 very difficult to diagnose system problems, saying N here is
1530 strongly discouraged.
1533 bool "BUG() support" if EXPERT
1536 Disabling this option eliminates support for BUG and WARN, reducing
1537 the size of your kernel image and potentially quietly ignoring
1538 numerous fatal conditions. You should only consider disabling this
1539 option for embedded systems with no facilities for reporting errors.
1545 bool "Enable ELF core dumps" if EXPERT
1547 Enable support for generating core dumps. Disabling saves about 4k.
1550 config PCSPKR_PLATFORM
1551 bool "Enable PC-Speaker support" if EXPERT
1552 depends on HAVE_PCSPKR_PLATFORM
1556 This option allows to disable the internal PC-Speaker
1557 support, saving some memory.
1561 bool "Enable full-sized data structures for core" if EXPERT
1563 Disabling this option reduces the size of miscellaneous core
1564 kernel data structures. This saves memory on small machines,
1565 but may reduce performance.
1568 bool "Enable futex support" if EXPERT
1572 Disabling this option will cause the kernel to be built without
1573 support for "fast userspace mutexes". The resulting kernel may not
1574 run glibc-based applications correctly.
1576 config HAVE_FUTEX_CMPXCHG
1580 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1581 is implemented and always working. This removes a couple of runtime
1585 bool "Enable eventpoll support" if EXPERT
1589 Disabling this option will cause the kernel to be built without
1590 support for epoll family of system calls.
1593 bool "Enable signalfd() system call" if EXPERT
1597 Enable the signalfd() system call that allows to receive signals
1598 on a file descriptor.
1603 bool "Enable timerfd() system call" if EXPERT
1607 Enable the timerfd() system call that allows to receive timer
1608 events on a file descriptor.
1613 bool "Enable eventfd() system call" if EXPERT
1617 Enable the eventfd() system call that allows to receive both
1618 kernel notification (ie. KAIO) or userspace notifications.
1622 # syscall, maps, verifier
1624 bool "Enable bpf() system call"
1629 Enable the bpf() system call that allows to manipulate eBPF
1630 programs and maps via file descriptors.
1633 bool "Use full shmem filesystem" if EXPERT
1637 The shmem is an internal filesystem used to manage shared memory.
1638 It is backed by swap and manages resource limits. It is also exported
1639 to userspace as tmpfs if TMPFS is enabled. Disabling this
1640 option replaces shmem and tmpfs with the much simpler ramfs code,
1641 which may be appropriate on small systems without swap.
1644 bool "Enable AIO support" if EXPERT
1647 This option enables POSIX asynchronous I/O which may by used
1648 by some high performance threaded applications. Disabling
1649 this option saves about 7k.
1651 config ADVISE_SYSCALLS
1652 bool "Enable madvise/fadvise syscalls" if EXPERT
1655 This option enables the madvise and fadvise syscalls, used by
1656 applications to advise the kernel about their future memory or file
1657 usage, improving performance. If building an embedded system where no
1658 applications use these syscalls, you can disable this option to save
1663 bool "Enable PCI quirk workarounds" if EXPERT
1666 This enables workarounds for various PCI chipset
1667 bugs/quirks. Disable this only if your target machine is
1668 unaffected by PCI quirks.
1671 bool "Embedded system"
1672 option allnoconfig_y
1675 This option should be enabled if compiling the kernel for
1676 an embedded system so certain expert options are available
1679 config HAVE_PERF_EVENTS
1682 See tools/perf/design.txt for details.
1684 config PERF_USE_VMALLOC
1687 See tools/perf/design.txt for details
1689 menu "Kernel Performance Events And Counters"
1692 bool "Kernel performance events and counters"
1693 default y if PROFILING
1694 depends on HAVE_PERF_EVENTS
1699 Enable kernel support for various performance events provided
1700 by software and hardware.
1702 Software events are supported either built-in or via the
1703 use of generic tracepoints.
1705 Most modern CPUs support performance events via performance
1706 counter registers. These registers count the number of certain
1707 types of hw events: such as instructions executed, cachemisses
1708 suffered, or branches mis-predicted - without slowing down the
1709 kernel or applications. These registers can also trigger interrupts
1710 when a threshold number of events have passed - and can thus be
1711 used to profile the code that runs on that CPU.
1713 The Linux Performance Event subsystem provides an abstraction of
1714 these software and hardware event capabilities, available via a
1715 system call and used by the "perf" utility in tools/perf/. It
1716 provides per task and per CPU counters, and it provides event
1717 capabilities on top of those.
1721 config DEBUG_PERF_USE_VMALLOC
1723 bool "Debug: use vmalloc to back perf mmap() buffers"
1724 depends on PERF_EVENTS && DEBUG_KERNEL
1725 select PERF_USE_VMALLOC
1727 Use vmalloc memory to back perf mmap() buffers.
1729 Mostly useful for debugging the vmalloc code on platforms
1730 that don't require it.
1736 config VM_EVENT_COUNTERS
1738 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1740 VM event counters are needed for event counts to be shown.
1741 This option allows the disabling of the VM event counters
1742 on EXPERT systems. /proc/vmstat will only show page counts
1743 if VM event counters are disabled.
1747 bool "Enable SLUB debugging support" if EXPERT
1748 depends on SLUB && SYSFS
1750 SLUB has extensive debug support features. Disabling these can
1751 result in significant savings in code size. This also disables
1752 SLUB sysfs support. /sys/slab will not exist and there will be
1753 no support for cache validation etc.
1756 bool "Disable heap randomization"
1759 Randomizing heap placement makes heap exploits harder, but it
1760 also breaks ancient binaries (including anything libc5 based).
1761 This option changes the bootup default to heap randomization
1762 disabled, and can be overridden at runtime by setting
1763 /proc/sys/kernel/randomize_va_space to 2.
1765 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1768 prompt "Choose SLAB allocator"
1771 This option allows to select a slab allocator.
1776 The regular slab allocator that is established and known to work
1777 well in all environments. It organizes cache hot objects in
1778 per cpu and per node queues.
1781 bool "SLUB (Unqueued Allocator)"
1783 SLUB is a slab allocator that minimizes cache line usage
1784 instead of managing queues of cached objects (SLAB approach).
1785 Per cpu caching is realized using slabs of objects instead
1786 of queues of objects. SLUB can use memory efficiently
1787 and has enhanced diagnostics. SLUB is the default choice for
1792 bool "SLOB (Simple Allocator)"
1794 SLOB replaces the stock allocator with a drastically simpler
1795 allocator. SLOB is generally more space efficient but
1796 does not perform as well on large systems.
1800 config SLUB_CPU_PARTIAL
1802 depends on SLUB && SMP
1803 bool "SLUB per cpu partial cache"
1805 Per cpu partial caches accellerate objects allocation and freeing
1806 that is local to a processor at the price of more indeterminism
1807 in the latency of the free. On overflow these caches will be cleared
1808 which requires the taking of locks that may cause latency spikes.
1809 Typically one would choose no for a realtime system.
1811 config MMAP_ALLOW_UNINITIALIZED
1812 bool "Allow mmapped anonymous memory to be uninitialized"
1813 depends on EXPERT && !MMU
1816 Normally, and according to the Linux spec, anonymous memory obtained
1817 from mmap() has it's contents cleared before it is passed to
1818 userspace. Enabling this config option allows you to request that
1819 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1820 providing a huge performance boost. If this option is not enabled,
1821 then the flag will be ignored.
1823 This is taken advantage of by uClibc's malloc(), and also by
1824 ELF-FDPIC binfmt's brk and stack allocator.
1826 Because of the obvious security issues, this option should only be
1827 enabled on embedded devices where you control what is run in
1828 userspace. Since that isn't generally a problem on no-MMU systems,
1829 it is normally safe to say Y here.
1831 See Documentation/nommu-mmap.txt for more information.
1833 config SYSTEM_TRUSTED_KEYRING
1834 bool "Provide system-wide ring of trusted keys"
1837 Provide a system keyring to which trusted keys can be added. Keys in
1838 the keyring are considered to be trusted. Keys may be added at will
1839 by the kernel from compiled-in data and from hardware key stores, but
1840 userspace may only add extra keys if those keys can be verified by
1841 keys already in the keyring.
1843 Keys in this keyring are used by module signature checking.
1846 bool "Profiling support"
1848 Say Y here to enable the extended profiling support mechanisms used
1849 by profilers such as OProfile.
1852 # Place an empty function call at each tracepoint site. Can be
1853 # dynamically changed for a probe function.
1858 source "arch/Kconfig"
1860 endmenu # General setup
1862 config HAVE_GENERIC_DMA_COHERENT
1869 depends on SLAB || SLUB_DEBUG
1877 default 0 if BASE_FULL
1878 default 1 if !BASE_FULL
1881 bool "Enable loadable module support"
1884 Kernel modules are small pieces of compiled code which can
1885 be inserted in the running kernel, rather than being
1886 permanently built into the kernel. You use the "modprobe"
1887 tool to add (and sometimes remove) them. If you say Y here,
1888 many parts of the kernel can be built as modules (by
1889 answering M instead of Y where indicated): this is most
1890 useful for infrequently used options which are not required
1891 for booting. For more information, see the man pages for
1892 modprobe, lsmod, modinfo, insmod and rmmod.
1894 If you say Y here, you will need to run "make
1895 modules_install" to put the modules under /lib/modules/
1896 where modprobe can find them (you may need to be root to do
1903 config MODULE_FORCE_LOAD
1904 bool "Forced module loading"
1907 Allow loading of modules without version information (ie. modprobe
1908 --force). Forced module loading sets the 'F' (forced) taint flag and
1909 is usually a really bad idea.
1911 config MODULE_UNLOAD
1912 bool "Module unloading"
1914 Without this option you will not be able to unload any
1915 modules (note that some modules may not be unloadable
1916 anyway), which makes your kernel smaller, faster
1917 and simpler. If unsure, say Y.
1919 config MODULE_FORCE_UNLOAD
1920 bool "Forced module unloading"
1921 depends on MODULE_UNLOAD
1923 This option allows you to force a module to unload, even if the
1924 kernel believes it is unsafe: the kernel will remove the module
1925 without waiting for anyone to stop using it (using the -f option to
1926 rmmod). This is mainly for kernel developers and desperate users.
1930 bool "Module versioning support"
1931 # LTO should work with gcc 4.9
1934 Usually, you have to use modules compiled with your kernel.
1935 Saying Y here makes it sometimes possible to use modules
1936 compiled for different kernels, by adding enough information
1937 to the modules to (hopefully) spot any changes which would
1938 make them incompatible with the kernel you are running. If
1941 config MODULE_SRCVERSION_ALL
1942 bool "Source checksum for all modules"
1944 Modules which contain a MODULE_VERSION get an extra "srcversion"
1945 field inserted into their modinfo section, which contains a
1946 sum of the source files which made it. This helps maintainers
1947 see exactly which source was used to build a module (since
1948 others sometimes change the module source without updating
1949 the version). With this option, such a "srcversion" field
1950 will be created for all modules. If unsure, say N.
1953 bool "Module signature verification"
1955 select SYSTEM_TRUSTED_KEYRING
1958 select ASYMMETRIC_KEY_TYPE
1959 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1960 select PUBLIC_KEY_ALGO_RSA
1963 select X509_CERTIFICATE_PARSER
1965 Check modules for valid signatures upon load: the signature
1966 is simply appended to the module. For more information see
1967 Documentation/module-signing.txt.
1969 !!!WARNING!!! If you enable this option, you MUST make sure that the
1970 module DOES NOT get stripped after being signed. This includes the
1971 debuginfo strip done by some packagers (such as rpmbuild) and
1972 inclusion into an initramfs that wants the module size reduced.
1974 config MODULE_SIG_FORCE
1975 bool "Require modules to be validly signed"
1976 depends on MODULE_SIG
1978 Reject unsigned modules or signed modules for which we don't have a
1979 key. Without this, such modules will simply taint the kernel.
1981 config MODULE_SIG_ALL
1982 bool "Automatically sign all modules"
1984 depends on MODULE_SIG
1986 Sign all modules during make modules_install. Without this option,
1987 modules must be signed manually, using the scripts/sign-file tool.
1989 comment "Do not forget to sign required modules with scripts/sign-file"
1990 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1993 prompt "Which hash algorithm should modules be signed with?"
1994 depends on MODULE_SIG
1996 This determines which sort of hashing algorithm will be used during
1997 signature generation. This algorithm _must_ be built into the kernel
1998 directly so that signature verification can take place. It is not
1999 possible to load a signed module containing the algorithm to check
2000 the signature on that module.
2002 config MODULE_SIG_SHA1
2003 bool "Sign modules with SHA-1"
2006 config MODULE_SIG_SHA224
2007 bool "Sign modules with SHA-224"
2008 select CRYPTO_SHA256
2010 config MODULE_SIG_SHA256
2011 bool "Sign modules with SHA-256"
2012 select CRYPTO_SHA256
2014 config MODULE_SIG_SHA384
2015 bool "Sign modules with SHA-384"
2016 select CRYPTO_SHA512
2018 config MODULE_SIG_SHA512
2019 bool "Sign modules with SHA-512"
2020 select CRYPTO_SHA512
2024 config MODULE_SIG_HASH
2026 depends on MODULE_SIG
2027 default "sha1" if MODULE_SIG_SHA1
2028 default "sha224" if MODULE_SIG_SHA224
2029 default "sha256" if MODULE_SIG_SHA256
2030 default "sha384" if MODULE_SIG_SHA384
2031 default "sha512" if MODULE_SIG_SHA512
2033 config MODULE_COMPRESS
2034 bool "Compress modules on installation"
2037 This option compresses the kernel modules when 'make
2038 modules_install' is run.
2040 The modules will be compressed either using gzip or xz depend on the
2041 choice made in "Compression algorithm".
2043 module-init-tools has support for gzip format while kmod handle gzip
2044 and xz compressed modules.
2046 When a kernel module is installed from outside of the main kernel
2047 source and uses the Kbuild system for installing modules then that
2048 kernel module will also be compressed when it is installed.
2050 This option provides little benefit when the modules are to be used inside
2051 an initrd or initramfs, it generally is more efficient to compress the whole
2052 initrd or initramfs instead.
2054 This is fully compatible with signed modules while the signed module is
2055 compressed. module-init-tools or kmod handles decompression and provide to
2056 other layer the uncompressed but signed payload.
2059 prompt "Compression algorithm"
2060 depends on MODULE_COMPRESS
2061 default MODULE_COMPRESS_GZIP
2063 This determines which sort of compression will be used during
2064 'make modules_install'.
2066 GZIP (default) and XZ are supported.
2068 config MODULE_COMPRESS_GZIP
2071 config MODULE_COMPRESS_XZ
2078 config INIT_ALL_POSSIBLE
2081 Back when each arch used to define their own cpu_online_mask and
2082 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2083 with all 1s, and others with all 0s. When they were centralised,
2084 it was better to provide this option than to break all the archs
2085 and have several arch maintainers pursuing me down dark alleys.
2090 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
2092 Need stop_machine() primitive.
2094 source "block/Kconfig"
2096 config PREEMPT_NOTIFIERS
2103 # Can be selected by architectures with broken toolchains
2104 # that get confused by correct const<->read_only section
2106 config BROKEN_RODATA
2112 Build a simple ASN.1 grammar compiler that produces a bytecode output
2113 that can be interpreted by the ASN.1 stream decoder and used to
2114 inform it as to what tags are to be expected in a stream and what
2115 functions to call on what tags.
2117 source "kernel/Kconfig.locks"
projects / karo-tx-linux.git / blob