7 option env="KERNELVERSION"
13 default "/lib/modules/$UNAME_RELEASE/.config"
14 default "/etc/kernel-config"
15 default "/boot/config-$UNAME_RELEASE"
16 default "$ARCH_DEFCONFIG"
17 default "arch/$ARCH/defconfig"
26 config BUILDTIME_EXTABLE_SORT
36 depends on BROKEN || !SMP
39 config INIT_ENV_ARG_LIMIT
44 Maximum of each of the number of arguments and environment
45 variables passed to init from the kernel command line.
49 string "Cross-compiler tool prefix"
51 Same as running 'make CROSS_COMPILE=prefix-' but stored for
52 default make runs in this kernel build directory. You don't
53 need to set this unless you want the configured kernel build
54 directory to select the cross-compiler automatically.
57 bool "Compile also drivers which will not load"
60 Some drivers can be compiled on a different platform than they are
61 intended to be run on. Despite they cannot be loaded there (or even
62 when they load they cannot be used due to missing HW support),
63 developers still, opposing to distributors, might want to build such
64 drivers to compile-test them.
66 If you are a developer and want to build everything available, say Y
67 here. If you are a user/distributor, say N here to exclude useless
68 drivers to be distributed.
71 string "Local version - append to kernel release"
73 Append an extra string to the end of your kernel version.
74 This will show up when you type uname, for example.
75 The string you set here will be appended after the contents of
76 any files with a filename matching localversion* in your
77 object and source tree, in that order. Your total string can
78 be a maximum of 64 characters.
80 config LOCALVERSION_AUTO
81 bool "Automatically append version information to the version string"
84 This will try to automatically determine if the current tree is a
85 release tree by looking for git tags that belong to the current
88 A string of the format -gxxxxxxxx will be added to the localversion
89 if a git-based tree is found. The string generated by this will be
90 appended after any matching localversion* files, and after the value
91 set in CONFIG_LOCALVERSION.
93 (The actual string used here is the first eight characters produced
94 by running the command:
96 $ git rev-parse --verify HEAD
98 which is done within the script "scripts/setlocalversion".)
100 config HAVE_KERNEL_GZIP
103 config HAVE_KERNEL_BZIP2
106 config HAVE_KERNEL_LZMA
109 config HAVE_KERNEL_XZ
112 config HAVE_KERNEL_LZO
115 config HAVE_KERNEL_LZ4
119 prompt "Kernel compression mode"
121 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
123 The linux kernel is a kind of self-extracting executable.
124 Several compression algorithms are available, which differ
125 in efficiency, compression and decompression speed.
126 Compression speed is only relevant when building a kernel.
127 Decompression speed is relevant at each boot.
129 If you have any problems with bzip2 or lzma compressed
130 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
131 version of this functionality (bzip2 only), for 2.4, was
132 supplied by Christian Ludwig)
134 High compression options are mostly useful for users, who
135 are low on disk space (embedded systems), but for whom ram
138 If in doubt, select 'gzip'
142 depends on HAVE_KERNEL_GZIP
144 The old and tried gzip compression. It provides a good balance
145 between compression ratio and decompression speed.
149 depends on HAVE_KERNEL_BZIP2
151 Its compression ratio and speed is intermediate.
152 Decompression speed is slowest among the choices. The kernel
153 size is about 10% smaller with bzip2, in comparison to gzip.
154 Bzip2 uses a large amount of memory. For modern kernels you
155 will need at least 8MB RAM or more for booting.
159 depends on HAVE_KERNEL_LZMA
161 This compression algorithm's ratio is best. Decompression speed
162 is between gzip and bzip2. Compression is slowest.
163 The kernel size is about 33% smaller with LZMA in comparison to gzip.
167 depends on HAVE_KERNEL_XZ
169 XZ uses the LZMA2 algorithm and instruction set specific
170 BCJ filters which can improve compression ratio of executable
171 code. The size of the kernel is about 30% smaller with XZ in
172 comparison to gzip. On architectures for which there is a BCJ
173 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
174 will create a few percent smaller kernel than plain LZMA.
176 The speed is about the same as with LZMA: The decompression
177 speed of XZ is better than that of bzip2 but worse than gzip
178 and LZO. Compression is slow.
182 depends on HAVE_KERNEL_LZO
184 Its compression ratio is the poorest among the choices. The kernel
185 size is about 10% bigger than gzip; however its speed
186 (both compression and decompression) is the fastest.
190 depends on HAVE_KERNEL_LZ4
192 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
193 A preliminary version of LZ4 de/compression tool is available at
194 <https://code.google.com/p/lz4/>.
196 Its compression ratio is worse than LZO. The size of the kernel
197 is about 8% bigger than LZO. But the decompression speed is
202 config DEFAULT_HOSTNAME
203 string "Default hostname"
206 This option determines the default system hostname before userspace
207 calls sethostname(2). The kernel traditionally uses "(none)" here,
208 but you may wish to use a different default here to make a minimal
209 system more usable with less configuration.
212 bool "Support for paging of anonymous memory (swap)"
213 depends on MMU && BLOCK
216 This option allows you to choose whether you want to have support
217 for so called swap devices or swap files in your kernel that are
218 used to provide more virtual memory than the actual RAM present
219 in your computer. If unsure say Y.
224 Inter Process Communication is a suite of library functions and
225 system calls which let processes (running programs) synchronize and
226 exchange information. It is generally considered to be a good thing,
227 and some programs won't run unless you say Y here. In particular, if
228 you want to run the DOS emulator dosemu under Linux (read the
229 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
230 you'll need to say Y here.
232 You can find documentation about IPC with "info ipc" and also in
233 section 6.4 of the Linux Programmer's Guide, available from
234 <http://www.tldp.org/guides.html>.
236 config SYSVIPC_SYSCTL
243 bool "POSIX Message Queues"
246 POSIX variant of message queues is a part of IPC. In POSIX message
247 queues every message has a priority which decides about succession
248 of receiving it by a process. If you want to compile and run
249 programs written e.g. for Solaris with use of its POSIX message
250 queues (functions mq_*) say Y here.
252 POSIX message queues are visible as a filesystem called 'mqueue'
253 and can be mounted somewhere if you want to do filesystem
254 operations on message queues.
258 config POSIX_MQUEUE_SYSCTL
260 depends on POSIX_MQUEUE
264 config CROSS_MEMORY_ATTACH
265 bool "Enable process_vm_readv/writev syscalls"
269 Enabling this option adds the system calls process_vm_readv and
270 process_vm_writev which allow a process with the correct privileges
271 to directly read from or write to another process' address space.
272 See the man page for more details.
275 bool "open by fhandle syscalls"
278 If you say Y here, a user level program will be able to map
279 file names to handle and then later use the handle for
280 different file system operations. This is useful in implementing
281 userspace file servers, which now track files using handles instead
282 of names. The handle would remain the same even if file names
283 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
287 bool "uselib syscall"
290 This option enables the uselib syscall, a system call used in the
291 dynamic linker from libc5 and earlier. glibc does not use this
292 system call. If you intend to run programs built on libc5 or
293 earlier, you may need to enable this syscall. Current systems
294 running glibc can safely disable this.
297 bool "Auditing support"
300 Enable auditing infrastructure that can be used with another
301 kernel subsystem, such as SELinux (which requires this for
302 logging of avc messages output). Does not do system-call
303 auditing without CONFIG_AUDITSYSCALL.
305 config HAVE_ARCH_AUDITSYSCALL
309 bool "Enable system-call auditing support"
310 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
311 default y if SECURITY_SELINUX
313 Enable low-overhead system-call auditing infrastructure that
314 can be used independently or with another kernel subsystem,
319 depends on AUDITSYSCALL
324 depends on AUDITSYSCALL
327 source "kernel/irq/Kconfig"
328 source "kernel/time/Kconfig"
330 menu "CPU/Task time and stats accounting"
332 config VIRT_CPU_ACCOUNTING
336 prompt "Cputime accounting"
337 default TICK_CPU_ACCOUNTING if !PPC64
338 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
340 # Kind of a stub config for the pure tick based cputime accounting
341 config TICK_CPU_ACCOUNTING
342 bool "Simple tick based cputime accounting"
343 depends on !S390 && !NO_HZ_FULL
345 This is the basic tick based cputime accounting that maintains
346 statistics about user, system and idle time spent on per jiffies
351 config VIRT_CPU_ACCOUNTING_NATIVE
352 bool "Deterministic task and CPU time accounting"
353 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
354 select VIRT_CPU_ACCOUNTING
356 Select this option to enable more accurate task and CPU time
357 accounting. This is done by reading a CPU counter on each
358 kernel entry and exit and on transitions within the kernel
359 between system, softirq and hardirq state, so there is a
360 small performance impact. In the case of s390 or IBM POWER > 5,
361 this also enables accounting of stolen time on logically-partitioned
364 config VIRT_CPU_ACCOUNTING_GEN
365 bool "Full dynticks CPU time accounting"
366 depends on HAVE_CONTEXT_TRACKING
367 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
368 select VIRT_CPU_ACCOUNTING
369 select CONTEXT_TRACKING
371 Select this option to enable task and CPU time accounting on full
372 dynticks systems. This accounting is implemented by watching every
373 kernel-user boundaries using the context tracking subsystem.
374 The accounting is thus performed at the expense of some significant
377 For now this is only useful if you are working on the full
378 dynticks subsystem development.
382 config IRQ_TIME_ACCOUNTING
383 bool "Fine granularity task level IRQ time accounting"
384 depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
386 Select this option to enable fine granularity task irq time
387 accounting. This is done by reading a timestamp on each
388 transitions between softirq and hardirq state, so there can be a
389 small performance impact.
391 If in doubt, say N here.
395 config BSD_PROCESS_ACCT
396 bool "BSD Process Accounting"
398 If you say Y here, a user level program will be able to instruct the
399 kernel (via a special system call) to write process accounting
400 information to a file: whenever a process exits, information about
401 that process will be appended to the file by the kernel. The
402 information includes things such as creation time, owning user,
403 command name, memory usage, controlling terminal etc. (the complete
404 list is in the struct acct in <file:include/linux/acct.h>). It is
405 up to the user level program to do useful things with this
406 information. This is generally a good idea, so say Y.
408 config BSD_PROCESS_ACCT_V3
409 bool "BSD Process Accounting version 3 file format"
410 depends on BSD_PROCESS_ACCT
413 If you say Y here, the process accounting information is written
414 in a new file format that also logs the process IDs of each
415 process and it's parent. Note that this file format is incompatible
416 with previous v0/v1/v2 file formats, so you will need updated tools
417 for processing it. A preliminary version of these tools is available
418 at <http://www.gnu.org/software/acct/>.
421 bool "Export task/process statistics through netlink"
425 Export selected statistics for tasks/processes through the
426 generic netlink interface. Unlike BSD process accounting, the
427 statistics are available during the lifetime of tasks/processes as
428 responses to commands. Like BSD accounting, they are sent to user
433 config TASK_DELAY_ACCT
434 bool "Enable per-task delay accounting"
437 Collect information on time spent by a task waiting for system
438 resources like cpu, synchronous block I/O completion and swapping
439 in pages. Such statistics can help in setting a task's priorities
440 relative to other tasks for cpu, io, rss limits etc.
445 bool "Enable extended accounting over taskstats"
448 Collect extended task accounting data and send the data
449 to userland for processing over the taskstats interface.
453 config TASK_IO_ACCOUNTING
454 bool "Enable per-task storage I/O accounting"
455 depends on TASK_XACCT
457 Collect information on the number of bytes of storage I/O which this
462 endmenu # "CPU/Task time and stats accounting"
467 prompt "RCU Implementation"
471 bool "Tree-based hierarchical RCU"
472 depends on !PREEMPT && SMP
475 This option selects the RCU implementation that is
476 designed for very large SMP system with hundreds or
477 thousands of CPUs. It also scales down nicely to
480 config TREE_PREEMPT_RCU
481 bool "Preemptible tree-based hierarchical RCU"
485 This option selects the RCU implementation that is
486 designed for very large SMP systems with hundreds or
487 thousands of CPUs, but for which real-time response
488 is also required. It also scales down nicely to
491 Select this option if you are unsure.
494 bool "UP-only small-memory-footprint RCU"
495 depends on !PREEMPT && !SMP
497 This option selects the RCU implementation that is
498 designed for UP systems from which real-time response
499 is not required. This option greatly reduces the
500 memory footprint of RCU.
505 def_bool TREE_PREEMPT_RCU
507 This option enables preemptible-RCU code that is common between
508 TREE_PREEMPT_RCU and, in the old days, TINY_PREEMPT_RCU.
510 config RCU_STALL_COMMON
511 def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
513 This option enables RCU CPU stall code that is common between
514 the TINY and TREE variants of RCU. The purpose is to allow
515 the tiny variants to disable RCU CPU stall warnings, while
516 making these warnings mandatory for the tree variants.
518 config CONTEXT_TRACKING
522 bool "Consider userspace as in RCU extended quiescent state"
523 depends on HAVE_CONTEXT_TRACKING && SMP
524 select CONTEXT_TRACKING
526 This option sets hooks on kernel / userspace boundaries and
527 puts RCU in extended quiescent state when the CPU runs in
528 userspace. It means that when a CPU runs in userspace, it is
529 excluded from the global RCU state machine and thus doesn't
530 try to keep the timer tick on for RCU.
532 Unless you want to hack and help the development of the full
533 dynticks mode, you shouldn't enable this option. It also
534 adds unnecessary overhead.
538 config CONTEXT_TRACKING_FORCE
539 bool "Force context tracking"
540 depends on CONTEXT_TRACKING
541 default y if !NO_HZ_FULL
543 The major pre-requirement for full dynticks to work is to
544 support the context tracking subsystem. But there are also
545 other dependencies to provide in order to make the full
548 This option stands for testing when an arch implements the
549 context tracking backend but doesn't yet fullfill all the
550 requirements to make the full dynticks feature working.
551 Without the full dynticks, there is no way to test the support
552 for context tracking and the subsystems that rely on it: RCU
553 userspace extended quiescent state and tickless cputime
554 accounting. This option copes with the absence of the full
555 dynticks subsystem by forcing the context tracking on all
558 Say Y only if you're working on the development of an
559 architecture backend for the context tracking.
561 Say N otherwise, this option brings an overhead that you
562 don't want in production.
566 int "Tree-based hierarchical RCU fanout value"
569 depends on TREE_RCU || TREE_PREEMPT_RCU
573 This option controls the fanout of hierarchical implementations
574 of RCU, allowing RCU to work efficiently on machines with
575 large numbers of CPUs. This value must be at least the fourth
576 root of NR_CPUS, which allows NR_CPUS to be insanely large.
577 The default value of RCU_FANOUT should be used for production
578 systems, but if you are stress-testing the RCU implementation
579 itself, small RCU_FANOUT values allow you to test large-system
580 code paths on small(er) systems.
582 Select a specific number if testing RCU itself.
583 Take the default if unsure.
585 config RCU_FANOUT_LEAF
586 int "Tree-based hierarchical RCU leaf-level fanout value"
587 range 2 RCU_FANOUT if 64BIT
588 range 2 RCU_FANOUT if !64BIT
589 depends on TREE_RCU || TREE_PREEMPT_RCU
592 This option controls the leaf-level fanout of hierarchical
593 implementations of RCU, and allows trading off cache misses
594 against lock contention. Systems that synchronize their
595 scheduling-clock interrupts for energy-efficiency reasons will
596 want the default because the smaller leaf-level fanout keeps
597 lock contention levels acceptably low. Very large systems
598 (hundreds or thousands of CPUs) will instead want to set this
599 value to the maximum value possible in order to reduce the
600 number of cache misses incurred during RCU's grace-period
601 initialization. These systems tend to run CPU-bound, and thus
602 are not helped by synchronized interrupts, and thus tend to
603 skew them, which reduces lock contention enough that large
604 leaf-level fanouts work well.
606 Select a specific number if testing RCU itself.
608 Select the maximum permissible value for large systems.
610 Take the default if unsure.
612 config RCU_FANOUT_EXACT
613 bool "Disable tree-based hierarchical RCU auto-balancing"
614 depends on TREE_RCU || TREE_PREEMPT_RCU
617 This option forces use of the exact RCU_FANOUT value specified,
618 regardless of imbalances in the hierarchy. This is useful for
619 testing RCU itself, and might one day be useful on systems with
620 strong NUMA behavior.
622 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
626 config RCU_FAST_NO_HZ
627 bool "Accelerate last non-dyntick-idle CPU's grace periods"
628 depends on NO_HZ_COMMON && SMP
631 This option permits CPUs to enter dynticks-idle state even if
632 they have RCU callbacks queued, and prevents RCU from waking
633 these CPUs up more than roughly once every four jiffies (by
634 default, you can adjust this using the rcutree.rcu_idle_gp_delay
635 parameter), thus improving energy efficiency. On the other
636 hand, this option increases the duration of RCU grace periods,
637 for example, slowing down synchronize_rcu().
639 Say Y if energy efficiency is critically important, and you
640 don't care about increased grace-period durations.
642 Say N if you are unsure.
644 config TREE_RCU_TRACE
645 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
648 This option provides tracing for the TREE_RCU and
649 TREE_PREEMPT_RCU implementations, permitting Makefile to
650 trivially select kernel/rcutree_trace.c.
653 bool "Enable RCU priority boosting"
654 depends on RT_MUTEXES && PREEMPT_RCU
657 This option boosts the priority of preempted RCU readers that
658 block the current preemptible RCU grace period for too long.
659 This option also prevents heavy loads from blocking RCU
660 callback invocation for all flavors of RCU.
662 Say Y here if you are working with real-time apps or heavy loads
663 Say N here if you are unsure.
665 config RCU_BOOST_PRIO
666 int "Real-time priority to boost RCU readers to"
671 This option specifies the real-time priority to which long-term
672 preempted RCU readers are to be boosted. If you are working
673 with a real-time application that has one or more CPU-bound
674 threads running at a real-time priority level, you should set
675 RCU_BOOST_PRIO to a priority higher then the highest-priority
676 real-time CPU-bound thread. The default RCU_BOOST_PRIO value
677 of 1 is appropriate in the common case, which is real-time
678 applications that do not have any CPU-bound threads.
680 Some real-time applications might not have a single real-time
681 thread that saturates a given CPU, but instead might have
682 multiple real-time threads that, taken together, fully utilize
683 that CPU. In this case, you should set RCU_BOOST_PRIO to
684 a priority higher than the lowest-priority thread that is
685 conspiring to prevent the CPU from running any non-real-time
686 tasks. For example, if one thread at priority 10 and another
687 thread at priority 5 are between themselves fully consuming
688 the CPU time on a given CPU, then RCU_BOOST_PRIO should be
689 set to priority 6 or higher.
691 Specify the real-time priority, or take the default if unsure.
693 config RCU_BOOST_DELAY
694 int "Milliseconds to delay boosting after RCU grace-period start"
699 This option specifies the time to wait after the beginning of
700 a given grace period before priority-boosting preempted RCU
701 readers blocking that grace period. Note that any RCU reader
702 blocking an expedited RCU grace period is boosted immediately.
704 Accept the default if unsure.
707 bool "Offload RCU callback processing from boot-selected CPUs"
708 depends on TREE_RCU || TREE_PREEMPT_RCU
711 Use this option to reduce OS jitter for aggressive HPC or
712 real-time workloads. It can also be used to offload RCU
713 callback invocation to energy-efficient CPUs in battery-powered
714 asymmetric multiprocessors.
716 This option offloads callback invocation from the set of
717 CPUs specified at boot time by the rcu_nocbs parameter.
718 For each such CPU, a kthread ("rcuox/N") will be created to
719 invoke callbacks, where the "N" is the CPU being offloaded,
720 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
721 "s" for RCU-sched. Nothing prevents this kthread from running
722 on the specified CPUs, but (1) the kthreads may be preempted
723 between each callback, and (2) affinity or cgroups can be used
724 to force the kthreads to run on whatever set of CPUs is desired.
726 Say Y here if you want to help to debug reduced OS jitter.
727 Say N here if you are unsure.
730 prompt "Build-forced no-CBs CPUs"
731 default RCU_NOCB_CPU_NONE
733 This option allows no-CBs CPUs (whose RCU callbacks are invoked
734 from kthreads rather than from softirq context) to be specified
735 at build time. Additional no-CBs CPUs may be specified by
736 the rcu_nocbs= boot parameter.
738 config RCU_NOCB_CPU_NONE
739 bool "No build_forced no-CBs CPUs"
740 depends on RCU_NOCB_CPU && !NO_HZ_FULL_ALL
742 This option does not force any of the CPUs to be no-CBs CPUs.
743 Only CPUs designated by the rcu_nocbs= boot parameter will be
744 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
745 kthreads whose names begin with "rcuo". All other CPUs will
746 invoke their own RCU callbacks in softirq context.
748 Select this option if you want to choose no-CBs CPUs at
749 boot time, for example, to allow testing of different no-CBs
750 configurations without having to rebuild the kernel each time.
752 config RCU_NOCB_CPU_ZERO
753 bool "CPU 0 is a build_forced no-CBs CPU"
754 depends on RCU_NOCB_CPU && !NO_HZ_FULL_ALL
756 This option forces CPU 0 to be a no-CBs CPU, so that its RCU
757 callbacks are invoked by a per-CPU kthread whose name begins
758 with "rcuo". Additional CPUs may be designated as no-CBs
759 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
760 All other CPUs will invoke their own RCU callbacks in softirq
763 Select this if CPU 0 needs to be a no-CBs CPU for real-time
764 or energy-efficiency reasons, but the real reason it exists
765 is to ensure that randconfig testing covers mixed systems.
767 config RCU_NOCB_CPU_ALL
768 bool "All CPUs are build_forced no-CBs CPUs"
769 depends on RCU_NOCB_CPU
771 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
772 boot parameter will be ignored. All CPUs' RCU callbacks will
773 be executed in the context of per-CPU rcuo kthreads created for
774 this purpose. Assuming that the kthreads whose names start with
775 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
776 on the remaining CPUs, but might decrease memory locality during
777 RCU-callback invocation, thus potentially degrading throughput.
779 Select this if all CPUs need to be no-CBs CPUs for real-time
780 or energy-efficiency reasons.
784 endmenu # "RCU Subsystem"
791 tristate "Kernel .config support"
794 This option enables the complete Linux kernel ".config" file
795 contents to be saved in the kernel. It provides documentation
796 of which kernel options are used in a running kernel or in an
797 on-disk kernel. This information can be extracted from the kernel
798 image file with the script scripts/extract-ikconfig and used as
799 input to rebuild the current kernel or to build another kernel.
800 It can also be extracted from a running kernel by reading
801 /proc/config.gz if enabled (below).
804 bool "Enable access to .config through /proc/config.gz"
805 depends on IKCONFIG && PROC_FS
807 This option enables access to the kernel configuration file
808 through /proc/config.gz.
811 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
816 Select the minimal kernel log buffer size as a power of 2.
817 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
818 parameter, see below. Any higher size also might be forced
819 by "log_buf_len" boot parameter.
829 config LOG_CPU_MAX_BUF_SHIFT
830 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
832 default 12 if !BASE_SMALL
833 default 0 if BASE_SMALL
836 This option allows to increase the default ring buffer size
837 according to the number of CPUs. The value defines the contribution
838 of each CPU as a power of 2. The used space is typically only few
839 lines however it might be much more when problems are reported,
842 The increased size means that a new buffer has to be allocated and
843 the original static one is unused. It makes sense only on systems
844 with more CPUs. Therefore this value is used only when the sum of
845 contributions is greater than the half of the default kernel ring
846 buffer as defined by LOG_BUF_SHIFT. The default values are set
847 so that more than 64 CPUs are needed to trigger the allocation.
849 Also this option is ignored when "log_buf_len" kernel parameter is
850 used as it forces an exact (power of two) size of the ring buffer.
852 The number of possible CPUs is used for this computation ignoring
853 hotplugging making the compuation optimal for the the worst case
854 scenerio while allowing a simple algorithm to be used from bootup.
856 Examples shift values and their meaning:
857 17 => 128 KB for each CPU
858 16 => 64 KB for each CPU
859 15 => 32 KB for each CPU
860 14 => 16 KB for each CPU
861 13 => 8 KB for each CPU
862 12 => 4 KB for each CPU
865 # Architectures with an unreliable sched_clock() should select this:
867 config HAVE_UNSTABLE_SCHED_CLOCK
870 config GENERIC_SCHED_CLOCK
874 # For architectures that want to enable the support for NUMA-affine scheduler
877 config ARCH_SUPPORTS_NUMA_BALANCING
881 # For architectures that know their GCC __int128 support is sound
883 config ARCH_SUPPORTS_INT128
886 # For architectures that (ab)use NUMA to represent different memory regions
887 # all cpu-local but of different latencies, such as SuperH.
889 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
892 config NUMA_BALANCING_DEFAULT_ENABLED
893 bool "Automatically enable NUMA aware memory/task placement"
895 depends on NUMA_BALANCING
897 If set, automatic NUMA balancing will be enabled if running on a NUMA
900 config NUMA_BALANCING
901 bool "Memory placement aware NUMA scheduler"
902 depends on ARCH_SUPPORTS_NUMA_BALANCING
903 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
904 depends on SMP && NUMA && MIGRATION
906 This option adds support for automatic NUMA aware memory/task placement.
907 The mechanism is quite primitive and is based on migrating memory when
908 it has references to the node the task is running on.
910 This system will be inactive on UMA systems.
913 boolean "Control Group support"
916 This option adds support for grouping sets of processes together, for
917 use with process control subsystems such as Cpusets, CFS, memory
918 controls or device isolation.
920 - Documentation/scheduler/sched-design-CFS.txt (CFS)
921 - Documentation/cgroups/ (features for grouping, isolation
922 and resource control)
929 bool "Example debug cgroup subsystem"
932 This option enables a simple cgroup subsystem that
933 exports useful debugging information about the cgroups
938 config CGROUP_FREEZER
939 bool "Freezer cgroup subsystem"
941 Provides a way to freeze and unfreeze all tasks in a
945 bool "Device controller for cgroups"
947 Provides a cgroup implementing whitelists for devices which
948 a process in the cgroup can mknod or open.
951 bool "Cpuset support"
953 This option will let you create and manage CPUSETs which
954 allow dynamically partitioning a system into sets of CPUs and
955 Memory Nodes and assigning tasks to run only within those sets.
956 This is primarily useful on large SMP or NUMA systems.
960 config PROC_PID_CPUSET
961 bool "Include legacy /proc/<pid>/cpuset file"
965 config CGROUP_CPUACCT
966 bool "Simple CPU accounting cgroup subsystem"
968 Provides a simple Resource Controller for monitoring the
969 total CPU consumed by the tasks in a cgroup.
971 config RESOURCE_COUNTERS
972 bool "Resource counters"
974 This option enables controller independent resource accounting
975 infrastructure that works with cgroups.
978 bool "Memory Resource Controller for Control Groups"
979 depends on RESOURCE_COUNTERS
982 Provides a memory resource controller that manages both anonymous
983 memory and page cache. (See Documentation/cgroups/memory.txt)
985 Note that setting this option increases fixed memory overhead
986 associated with each page of memory in the system. By this,
987 8(16)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
988 usage tracking struct at boot. Total amount of this is printed out
991 Only enable when you're ok with these trade offs and really
992 sure you need the memory resource controller. Even when you enable
993 this, you can set "cgroup_disable=memory" at your boot option to
994 disable memory resource controller and you can avoid overheads.
995 (and lose benefits of memory resource controller)
998 bool "Memory Resource Controller Swap Extension"
999 depends on MEMCG && SWAP
1001 Add swap management feature to memory resource controller. When you
1002 enable this, you can limit mem+swap usage per cgroup. In other words,
1003 when you disable this, memory resource controller has no cares to
1004 usage of swap...a process can exhaust all of the swap. This extension
1005 is useful when you want to avoid exhaustion swap but this itself
1006 adds more overheads and consumes memory for remembering information.
1007 Especially if you use 32bit system or small memory system, please
1008 be careful about enabling this. When memory resource controller
1009 is disabled by boot option, this will be automatically disabled and
1010 there will be no overhead from this. Even when you set this config=y,
1011 if boot option "swapaccount=0" is set, swap will not be accounted.
1012 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
1013 size is 4096bytes, 512k per 1Gbytes of swap.
1014 config MEMCG_SWAP_ENABLED
1015 bool "Memory Resource Controller Swap Extension enabled by default"
1016 depends on MEMCG_SWAP
1019 Memory Resource Controller Swap Extension comes with its price in
1020 a bigger memory consumption. General purpose distribution kernels
1021 which want to enable the feature but keep it disabled by default
1022 and let the user enable it by swapaccount=1 boot command line
1023 parameter should have this option unselected.
1024 For those who want to have the feature enabled by default should
1025 select this option (if, for some reason, they need to disable it
1026 then swapaccount=0 does the trick).
1028 bool "Memory Resource Controller Kernel Memory accounting"
1030 depends on SLUB || SLAB
1032 The Kernel Memory extension for Memory Resource Controller can limit
1033 the amount of memory used by kernel objects in the system. Those are
1034 fundamentally different from the entities handled by the standard
1035 Memory Controller, which are page-based, and can be swapped. Users of
1036 the kmem extension can use it to guarantee that no group of processes
1037 will ever exhaust kernel resources alone.
1039 WARNING: Current implementation lacks reclaim support. That means
1040 allocation attempts will fail when close to the limit even if there
1041 are plenty of kmem available for reclaim. That makes this option
1042 unusable in real life so DO NOT SELECT IT unless for development
1045 config CGROUP_HUGETLB
1046 bool "HugeTLB Resource Controller for Control Groups"
1047 depends on RESOURCE_COUNTERS && HUGETLB_PAGE
1050 Provides a cgroup Resource Controller for HugeTLB pages.
1051 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1052 The limit is enforced during page fault. Since HugeTLB doesn't
1053 support page reclaim, enforcing the limit at page fault time implies
1054 that, the application will get SIGBUS signal if it tries to access
1055 HugeTLB pages beyond its limit. This requires the application to know
1056 beforehand how much HugeTLB pages it would require for its use. The
1057 control group is tracked in the third page lru pointer. This means
1058 that we cannot use the controller with huge page less than 3 pages.
1061 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1062 depends on PERF_EVENTS && CGROUPS
1064 This option extends the per-cpu mode to restrict monitoring to
1065 threads which belong to the cgroup specified and run on the
1070 menuconfig CGROUP_SCHED
1071 bool "Group CPU scheduler"
1074 This feature lets CPU scheduler recognize task groups and control CPU
1075 bandwidth allocation to such task groups. It uses cgroups to group
1079 config FAIR_GROUP_SCHED
1080 bool "Group scheduling for SCHED_OTHER"
1081 depends on CGROUP_SCHED
1082 default CGROUP_SCHED
1084 config CFS_BANDWIDTH
1085 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1086 depends on FAIR_GROUP_SCHED
1089 This option allows users to define CPU bandwidth rates (limits) for
1090 tasks running within the fair group scheduler. Groups with no limit
1091 set are considered to be unconstrained and will run with no
1093 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1095 config RT_GROUP_SCHED
1096 bool "Group scheduling for SCHED_RR/FIFO"
1097 depends on CGROUP_SCHED
1100 This feature lets you explicitly allocate real CPU bandwidth
1101 to task groups. If enabled, it will also make it impossible to
1102 schedule realtime tasks for non-root users until you allocate
1103 realtime bandwidth for them.
1104 See Documentation/scheduler/sched-rt-group.txt for more information.
1109 bool "Block IO controller"
1113 Generic block IO controller cgroup interface. This is the common
1114 cgroup interface which should be used by various IO controlling
1117 Currently, CFQ IO scheduler uses it to recognize task groups and
1118 control disk bandwidth allocation (proportional time slice allocation)
1119 to such task groups. It is also used by bio throttling logic in
1120 block layer to implement upper limit in IO rates on a device.
1122 This option only enables generic Block IO controller infrastructure.
1123 One needs to also enable actual IO controlling logic/policy. For
1124 enabling proportional weight division of disk bandwidth in CFQ, set
1125 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1126 CONFIG_BLK_DEV_THROTTLING=y.
1128 See Documentation/cgroups/blkio-controller.txt for more information.
1130 config DEBUG_BLK_CGROUP
1131 bool "Enable Block IO controller debugging"
1132 depends on BLK_CGROUP
1135 Enable some debugging help. Currently it exports additional stat
1136 files in a cgroup which can be useful for debugging.
1140 config CHECKPOINT_RESTORE
1141 bool "Checkpoint/restore support" if EXPERT
1144 Enables additional kernel features in a sake of checkpoint/restore.
1145 In particular it adds auxiliary prctl codes to setup process text,
1146 data and heap segment sizes, and a few additional /proc filesystem
1149 If unsure, say N here.
1151 menuconfig NAMESPACES
1152 bool "Namespaces support" if EXPERT
1155 Provides the way to make tasks work with different objects using
1156 the same id. For example same IPC id may refer to different objects
1157 or same user id or pid may refer to different tasks when used in
1158 different namespaces.
1163 bool "UTS namespace"
1166 In this namespace tasks see different info provided with the
1170 bool "IPC namespace"
1171 depends on (SYSVIPC || POSIX_MQUEUE)
1174 In this namespace tasks work with IPC ids which correspond to
1175 different IPC objects in different namespaces.
1178 bool "User namespace"
1181 This allows containers, i.e. vservers, to use user namespaces
1182 to provide different user info for different servers.
1184 When user namespaces are enabled in the kernel it is
1185 recommended that the MEMCG and MEMCG_KMEM options also be
1186 enabled and that user-space use the memory control groups to
1187 limit the amount of memory a memory unprivileged users can
1193 bool "PID Namespaces"
1196 Support process id namespaces. This allows having multiple
1197 processes with the same pid as long as they are in different
1198 pid namespaces. This is a building block of containers.
1201 bool "Network namespace"
1205 Allow user space to create what appear to be multiple instances
1206 of the network stack.
1210 config SCHED_AUTOGROUP
1211 bool "Automatic process group scheduling"
1214 select FAIR_GROUP_SCHED
1216 This option optimizes the scheduler for common desktop workloads by
1217 automatically creating and populating task groups. This separation
1218 of workloads isolates aggressive CPU burners (like build jobs) from
1219 desktop applications. Task group autogeneration is currently based
1222 config SYSFS_DEPRECATED
1223 bool "Enable deprecated sysfs features to support old userspace tools"
1227 This option adds code that switches the layout of the "block" class
1228 devices, to not show up in /sys/class/block/, but only in
1231 This switch is only active when the sysfs.deprecated=1 boot option is
1232 passed or the SYSFS_DEPRECATED_V2 option is set.
1234 This option allows new kernels to run on old distributions and tools,
1235 which might get confused by /sys/class/block/. Since 2007/2008 all
1236 major distributions and tools handle this just fine.
1238 Recent distributions and userspace tools after 2009/2010 depend on
1239 the existence of /sys/class/block/, and will not work with this
1242 Only if you are using a new kernel on an old distribution, you might
1245 config SYSFS_DEPRECATED_V2
1246 bool "Enable deprecated sysfs features by default"
1249 depends on SYSFS_DEPRECATED
1251 Enable deprecated sysfs by default.
1253 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1256 Only if you are using a new kernel on an old distribution, you might
1257 need to say Y here. Even then, odds are you would not need it
1258 enabled, you can always pass the boot option if absolutely necessary.
1261 bool "Kernel->user space relay support (formerly relayfs)"
1263 This option enables support for relay interface support in
1264 certain file systems (such as debugfs).
1265 It is designed to provide an efficient mechanism for tools and
1266 facilities to relay large amounts of data from kernel space to
1271 config BLK_DEV_INITRD
1272 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1273 depends on BROKEN || !FRV
1275 The initial RAM filesystem is a ramfs which is loaded by the
1276 boot loader (loadlin or lilo) and that is mounted as root
1277 before the normal boot procedure. It is typically used to
1278 load modules needed to mount the "real" root file system,
1279 etc. See <file:Documentation/initrd.txt> for details.
1281 If RAM disk support (BLK_DEV_RAM) is also included, this
1282 also enables initial RAM disk (initrd) support and adds
1283 15 Kbytes (more on some other architectures) to the kernel size.
1289 source "usr/Kconfig"
1293 config CC_OPTIMIZE_FOR_SIZE
1294 bool "Optimize for size"
1296 Enabling this option will pass "-Os" instead of "-O2" to gcc
1297 resulting in a smaller kernel.
1310 config SYSCTL_EXCEPTION_TRACE
1313 Enable support for /proc/sys/debug/exception-trace.
1315 config SYSCTL_ARCH_UNALIGN_NO_WARN
1318 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1319 Allows arch to define/use @no_unaligned_warning to possibly warn
1320 about unaligned access emulation going on under the hood.
1322 config SYSCTL_ARCH_UNALIGN_ALLOW
1325 Enable support for /proc/sys/kernel/unaligned-trap
1326 Allows arches to define/use @unaligned_enabled to runtime toggle
1327 the unaligned access emulation.
1328 see arch/parisc/kernel/unaligned.c for reference
1330 config HAVE_PCSPKR_PLATFORM
1334 bool "Configure standard kernel features (expert users)"
1335 # Unhide debug options, to make the on-by-default options visible
1338 This option allows certain base kernel options and settings
1339 to be disabled or tweaked. This is for specialized
1340 environments which can tolerate a "non-standard" kernel.
1341 Only use this if you really know what you are doing.
1344 bool "Enable 16-bit UID system calls" if EXPERT
1345 depends on HAVE_UID16
1348 This enables the legacy 16-bit UID syscall wrappers.
1350 config SGETMASK_SYSCALL
1351 bool "sgetmask/ssetmask syscalls support" if EXPERT
1352 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1354 sys_sgetmask and sys_ssetmask are obsolete system calls
1355 no longer supported in libc but still enabled by default in some
1358 If unsure, leave the default option here.
1360 config SYSFS_SYSCALL
1361 bool "Sysfs syscall support" if EXPERT
1364 sys_sysfs is an obsolete system call no longer supported in libc.
1365 Note that disabling this option is more secure but might break
1366 compatibility with some systems.
1368 If unsure say Y here.
1370 config SYSCTL_SYSCALL
1371 bool "Sysctl syscall support" if EXPERT
1372 depends on PROC_SYSCTL
1376 sys_sysctl uses binary paths that have been found challenging
1377 to properly maintain and use. The interface in /proc/sys
1378 using paths with ascii names is now the primary path to this
1381 Almost nothing using the binary sysctl interface so if you are
1382 trying to save some space it is probably safe to disable this,
1383 making your kernel marginally smaller.
1385 If unsure say N here.
1388 bool "Load all symbols for debugging/ksymoops" if EXPERT
1391 Say Y here to let the kernel print out symbolic crash information and
1392 symbolic stack backtraces. This increases the size of the kernel
1393 somewhat, as all symbols have to be loaded into the kernel image.
1396 bool "Include all symbols in kallsyms"
1397 depends on DEBUG_KERNEL && KALLSYMS
1399 Normally kallsyms only contains the symbols of functions for nicer
1400 OOPS messages and backtraces (i.e., symbols from the text and inittext
1401 sections). This is sufficient for most cases. And only in very rare
1402 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1403 names of variables from the data sections, etc).
1405 This option makes sure that all symbols are loaded into the kernel
1406 image (i.e., symbols from all sections) in cost of increased kernel
1407 size (depending on the kernel configuration, it may be 300KiB or
1408 something like this).
1410 Say N unless you really need all symbols.
1414 bool "Enable support for printk" if EXPERT
1417 This option enables normal printk support. Removing it
1418 eliminates most of the message strings from the kernel image
1419 and makes the kernel more or less silent. As this makes it
1420 very difficult to diagnose system problems, saying N here is
1421 strongly discouraged.
1424 bool "BUG() support" if EXPERT
1427 Disabling this option eliminates support for BUG and WARN, reducing
1428 the size of your kernel image and potentially quietly ignoring
1429 numerous fatal conditions. You should only consider disabling this
1430 option for embedded systems with no facilities for reporting errors.
1436 bool "Enable ELF core dumps" if EXPERT
1438 Enable support for generating core dumps. Disabling saves about 4k.
1441 config PCSPKR_PLATFORM
1442 bool "Enable PC-Speaker support" if EXPERT
1443 depends on HAVE_PCSPKR_PLATFORM
1447 This option allows to disable the internal PC-Speaker
1448 support, saving some memory.
1452 bool "Enable full-sized data structures for core" if EXPERT
1454 Disabling this option reduces the size of miscellaneous core
1455 kernel data structures. This saves memory on small machines,
1456 but may reduce performance.
1459 bool "Enable futex support" if EXPERT
1463 Disabling this option will cause the kernel to be built without
1464 support for "fast userspace mutexes". The resulting kernel may not
1465 run glibc-based applications correctly.
1467 config HAVE_FUTEX_CMPXCHG
1471 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1472 is implemented and always working. This removes a couple of runtime
1476 bool "Enable eventpoll support" if EXPERT
1480 Disabling this option will cause the kernel to be built without
1481 support for epoll family of system calls.
1484 bool "Enable signalfd() system call" if EXPERT
1488 Enable the signalfd() system call that allows to receive signals
1489 on a file descriptor.
1494 bool "Enable timerfd() system call" if EXPERT
1498 Enable the timerfd() system call that allows to receive timer
1499 events on a file descriptor.
1504 bool "Enable eventfd() system call" if EXPERT
1508 Enable the eventfd() system call that allows to receive both
1509 kernel notification (ie. KAIO) or userspace notifications.
1514 bool "Use full shmem filesystem" if EXPERT
1518 The shmem is an internal filesystem used to manage shared memory.
1519 It is backed by swap and manages resource limits. It is also exported
1520 to userspace as tmpfs if TMPFS is enabled. Disabling this
1521 option replaces shmem and tmpfs with the much simpler ramfs code,
1522 which may be appropriate on small systems without swap.
1525 bool "Enable AIO support" if EXPERT
1528 This option enables POSIX asynchronous I/O which may by used
1529 by some high performance threaded applications. Disabling
1530 this option saves about 7k.
1532 config ADVISE_SYSCALLS
1533 bool "Enable madvise/fadvise syscalls" if EXPERT
1536 This option enables the madvise and fadvise syscalls, used by
1537 applications to advise the kernel about their future memory or file
1538 usage, improving performance. If building an embedded system where no
1539 applications use these syscalls, you can disable this option to save
1544 bool "Enable PCI quirk workarounds" if EXPERT
1547 This enables workarounds for various PCI chipset
1548 bugs/quirks. Disable this only if your target machine is
1549 unaffected by PCI quirks.
1552 bool "Embedded system"
1553 option allnoconfig_y
1556 This option should be enabled if compiling the kernel for
1557 an embedded system so certain expert options are available
1560 config HAVE_PERF_EVENTS
1563 See tools/perf/design.txt for details.
1565 config PERF_USE_VMALLOC
1568 See tools/perf/design.txt for details
1570 menu "Kernel Performance Events And Counters"
1573 bool "Kernel performance events and counters"
1574 default y if PROFILING
1575 depends on HAVE_PERF_EVENTS
1579 Enable kernel support for various performance events provided
1580 by software and hardware.
1582 Software events are supported either built-in or via the
1583 use of generic tracepoints.
1585 Most modern CPUs support performance events via performance
1586 counter registers. These registers count the number of certain
1587 types of hw events: such as instructions executed, cachemisses
1588 suffered, or branches mis-predicted - without slowing down the
1589 kernel or applications. These registers can also trigger interrupts
1590 when a threshold number of events have passed - and can thus be
1591 used to profile the code that runs on that CPU.
1593 The Linux Performance Event subsystem provides an abstraction of
1594 these software and hardware event capabilities, available via a
1595 system call and used by the "perf" utility in tools/perf/. It
1596 provides per task and per CPU counters, and it provides event
1597 capabilities on top of those.
1601 config DEBUG_PERF_USE_VMALLOC
1603 bool "Debug: use vmalloc to back perf mmap() buffers"
1604 depends on PERF_EVENTS && DEBUG_KERNEL
1605 select PERF_USE_VMALLOC
1607 Use vmalloc memory to back perf mmap() buffers.
1609 Mostly useful for debugging the vmalloc code on platforms
1610 that don't require it.
1616 config VM_EVENT_COUNTERS
1618 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1620 VM event counters are needed for event counts to be shown.
1621 This option allows the disabling of the VM event counters
1622 on EXPERT systems. /proc/vmstat will only show page counts
1623 if VM event counters are disabled.
1627 bool "Enable SLUB debugging support" if EXPERT
1628 depends on SLUB && SYSFS
1630 SLUB has extensive debug support features. Disabling these can
1631 result in significant savings in code size. This also disables
1632 SLUB sysfs support. /sys/slab will not exist and there will be
1633 no support for cache validation etc.
1636 bool "Disable heap randomization"
1639 Randomizing heap placement makes heap exploits harder, but it
1640 also breaks ancient binaries (including anything libc5 based).
1641 This option changes the bootup default to heap randomization
1642 disabled, and can be overridden at runtime by setting
1643 /proc/sys/kernel/randomize_va_space to 2.
1645 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1648 prompt "Choose SLAB allocator"
1651 This option allows to select a slab allocator.
1656 The regular slab allocator that is established and known to work
1657 well in all environments. It organizes cache hot objects in
1658 per cpu and per node queues.
1661 bool "SLUB (Unqueued Allocator)"
1663 SLUB is a slab allocator that minimizes cache line usage
1664 instead of managing queues of cached objects (SLAB approach).
1665 Per cpu caching is realized using slabs of objects instead
1666 of queues of objects. SLUB can use memory efficiently
1667 and has enhanced diagnostics. SLUB is the default choice for
1672 bool "SLOB (Simple Allocator)"
1674 SLOB replaces the stock allocator with a drastically simpler
1675 allocator. SLOB is generally more space efficient but
1676 does not perform as well on large systems.
1680 config SLUB_CPU_PARTIAL
1682 depends on SLUB && SMP
1683 bool "SLUB per cpu partial cache"
1685 Per cpu partial caches accellerate objects allocation and freeing
1686 that is local to a processor at the price of more indeterminism
1687 in the latency of the free. On overflow these caches will be cleared
1688 which requires the taking of locks that may cause latency spikes.
1689 Typically one would choose no for a realtime system.
1691 config MMAP_ALLOW_UNINITIALIZED
1692 bool "Allow mmapped anonymous memory to be uninitialized"
1693 depends on EXPERT && !MMU
1696 Normally, and according to the Linux spec, anonymous memory obtained
1697 from mmap() has it's contents cleared before it is passed to
1698 userspace. Enabling this config option allows you to request that
1699 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1700 providing a huge performance boost. If this option is not enabled,
1701 then the flag will be ignored.
1703 This is taken advantage of by uClibc's malloc(), and also by
1704 ELF-FDPIC binfmt's brk and stack allocator.
1706 Because of the obvious security issues, this option should only be
1707 enabled on embedded devices where you control what is run in
1708 userspace. Since that isn't generally a problem on no-MMU systems,
1709 it is normally safe to say Y here.
1711 See Documentation/nommu-mmap.txt for more information.
1713 config SYSTEM_TRUSTED_KEYRING
1714 bool "Provide system-wide ring of trusted keys"
1717 Provide a system keyring to which trusted keys can be added. Keys in
1718 the keyring are considered to be trusted. Keys may be added at will
1719 by the kernel from compiled-in data and from hardware key stores, but
1720 userspace may only add extra keys if those keys can be verified by
1721 keys already in the keyring.
1723 Keys in this keyring are used by module signature checking.
1726 bool "Profiling support"
1728 Say Y here to enable the extended profiling support mechanisms used
1729 by profilers such as OProfile.
1732 # Place an empty function call at each tracepoint site. Can be
1733 # dynamically changed for a probe function.
1738 source "arch/Kconfig"
1740 endmenu # General setup
1742 config HAVE_GENERIC_DMA_COHERENT
1749 depends on SLAB || SLUB_DEBUG
1757 default 0 if BASE_FULL
1758 default 1 if !BASE_FULL
1761 bool "Enable loadable module support"
1764 Kernel modules are small pieces of compiled code which can
1765 be inserted in the running kernel, rather than being
1766 permanently built into the kernel. You use the "modprobe"
1767 tool to add (and sometimes remove) them. If you say Y here,
1768 many parts of the kernel can be built as modules (by
1769 answering M instead of Y where indicated): this is most
1770 useful for infrequently used options which are not required
1771 for booting. For more information, see the man pages for
1772 modprobe, lsmod, modinfo, insmod and rmmod.
1774 If you say Y here, you will need to run "make
1775 modules_install" to put the modules under /lib/modules/
1776 where modprobe can find them (you may need to be root to do
1783 config MODULE_FORCE_LOAD
1784 bool "Forced module loading"
1787 Allow loading of modules without version information (ie. modprobe
1788 --force). Forced module loading sets the 'F' (forced) taint flag and
1789 is usually a really bad idea.
1791 config MODULE_UNLOAD
1792 bool "Module unloading"
1794 Without this option you will not be able to unload any
1795 modules (note that some modules may not be unloadable
1796 anyway), which makes your kernel smaller, faster
1797 and simpler. If unsure, say Y.
1799 config MODULE_FORCE_UNLOAD
1800 bool "Forced module unloading"
1801 depends on MODULE_UNLOAD
1803 This option allows you to force a module to unload, even if the
1804 kernel believes it is unsafe: the kernel will remove the module
1805 without waiting for anyone to stop using it (using the -f option to
1806 rmmod). This is mainly for kernel developers and desperate users.
1810 bool "Module versioning support"
1812 Usually, you have to use modules compiled with your kernel.
1813 Saying Y here makes it sometimes possible to use modules
1814 compiled for different kernels, by adding enough information
1815 to the modules to (hopefully) spot any changes which would
1816 make them incompatible with the kernel you are running. If
1819 config MODULE_SRCVERSION_ALL
1820 bool "Source checksum for all modules"
1822 Modules which contain a MODULE_VERSION get an extra "srcversion"
1823 field inserted into their modinfo section, which contains a
1824 sum of the source files which made it. This helps maintainers
1825 see exactly which source was used to build a module (since
1826 others sometimes change the module source without updating
1827 the version). With this option, such a "srcversion" field
1828 will be created for all modules. If unsure, say N.
1831 bool "Module signature verification"
1833 select SYSTEM_TRUSTED_KEYRING
1836 select ASYMMETRIC_KEY_TYPE
1837 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1838 select PUBLIC_KEY_ALGO_RSA
1841 select X509_CERTIFICATE_PARSER
1843 Check modules for valid signatures upon load: the signature
1844 is simply appended to the module. For more information see
1845 Documentation/module-signing.txt.
1847 !!!WARNING!!! If you enable this option, you MUST make sure that the
1848 module DOES NOT get stripped after being signed. This includes the
1849 debuginfo strip done by some packagers (such as rpmbuild) and
1850 inclusion into an initramfs that wants the module size reduced.
1852 config MODULE_SIG_FORCE
1853 bool "Require modules to be validly signed"
1854 depends on MODULE_SIG
1856 Reject unsigned modules or signed modules for which we don't have a
1857 key. Without this, such modules will simply taint the kernel.
1859 config MODULE_SIG_ALL
1860 bool "Automatically sign all modules"
1862 depends on MODULE_SIG
1864 Sign all modules during make modules_install. Without this option,
1865 modules must be signed manually, using the scripts/sign-file tool.
1867 comment "Do not forget to sign required modules with scripts/sign-file"
1868 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1871 prompt "Which hash algorithm should modules be signed with?"
1872 depends on MODULE_SIG
1874 This determines which sort of hashing algorithm will be used during
1875 signature generation. This algorithm _must_ be built into the kernel
1876 directly so that signature verification can take place. It is not
1877 possible to load a signed module containing the algorithm to check
1878 the signature on that module.
1880 config MODULE_SIG_SHA1
1881 bool "Sign modules with SHA-1"
1884 config MODULE_SIG_SHA224
1885 bool "Sign modules with SHA-224"
1886 select CRYPTO_SHA256
1888 config MODULE_SIG_SHA256
1889 bool "Sign modules with SHA-256"
1890 select CRYPTO_SHA256
1892 config MODULE_SIG_SHA384
1893 bool "Sign modules with SHA-384"
1894 select CRYPTO_SHA512
1896 config MODULE_SIG_SHA512
1897 bool "Sign modules with SHA-512"
1898 select CRYPTO_SHA512
1902 config MODULE_SIG_HASH
1904 depends on MODULE_SIG
1905 default "sha1" if MODULE_SIG_SHA1
1906 default "sha224" if MODULE_SIG_SHA224
1907 default "sha256" if MODULE_SIG_SHA256
1908 default "sha384" if MODULE_SIG_SHA384
1909 default "sha512" if MODULE_SIG_SHA512
1911 config MODULE_COMPRESS
1912 bool "Compress modules on installation"
1915 This option compresses the kernel modules when 'make
1916 modules_install' is run.
1918 The modules will be compressed either using gzip or xz depend on the
1919 choice made in "Compression algorithm".
1921 module-init-tools has support for gzip format while kmod handle gzip
1922 and xz compressed modules.
1924 When a kernel module is installed from outside of the main kernel
1925 source and uses the Kbuild system for installing modules then that
1926 kernel module will also be compressed when it is installed.
1928 This option provides little benefit when the modules are to be used inside
1929 an initrd or initramfs, it generally is more efficient to compress the whole
1930 initrd or initramfs instead.
1932 This is fully compatible with signed modules while the signed module is
1933 compressed. module-init-tools or kmod handles decompression and provide to
1934 other layer the uncompressed but signed payload.
1937 prompt "Compression algorithm"
1938 depends on MODULE_COMPRESS
1939 default MODULE_COMPRESS_GZIP
1941 This determines which sort of compression will be used during
1942 'make modules_install'.
1944 GZIP (default) and XZ are supported.
1946 config MODULE_COMPRESS_GZIP
1949 config MODULE_COMPRESS_XZ
1956 config INIT_ALL_POSSIBLE
1959 Back when each arch used to define their own cpu_online_mask and
1960 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1961 with all 1s, and others with all 0s. When they were centralised,
1962 it was better to provide this option than to break all the archs
1963 and have several arch maintainers pursuing me down dark alleys.
1968 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1970 Need stop_machine() primitive.
1972 source "block/Kconfig"
1974 config PREEMPT_NOTIFIERS
1981 # Can be selected by architectures with broken toolchains
1982 # that get confused by correct const<->read_only section
1984 config BROKEN_RODATA
1990 Build a simple ASN.1 grammar compiler that produces a bytecode output
1991 that can be interpreted by the ASN.1 stream decoder and used to
1992 inform it as to what tags are to be expected in a stream and what
1993 functions to call on what tags.
1995 source "kernel/Kconfig.locks"
projects / deliverable / linux.git / blob