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 bool "open by fhandle syscalls"
268 If you say Y here, a user level program will be able to map
269 file names to handle and then later use the handle for
270 different file system operations. This is useful in implementing
271 userspace file servers, which now track files using handles instead
272 of names. The handle would remain the same even if file names
273 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
277 bool "uselib syscall"
280 This option enables the uselib syscall, a system call used in the
281 dynamic linker from libc5 and earlier. glibc does not use this
282 system call. If you intend to run programs built on libc5 or
283 earlier, you may need to enable this syscall. Current systems
284 running glibc can safely disable this.
287 bool "Auditing support"
290 Enable auditing infrastructure that can be used with another
291 kernel subsystem, such as SELinux (which requires this for
292 logging of avc messages output). Does not do system-call
293 auditing without CONFIG_AUDITSYSCALL.
295 config HAVE_ARCH_AUDITSYSCALL
299 bool "Enable system-call auditing support"
300 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
301 default y if SECURITY_SELINUX
303 Enable low-overhead system-call auditing infrastructure that
304 can be used independently or with another kernel subsystem,
309 depends on AUDITSYSCALL
314 depends on AUDITSYSCALL
317 source "kernel/irq/Kconfig"
318 source "kernel/time/Kconfig"
320 menu "CPU/Task time and stats accounting"
322 config VIRT_CPU_ACCOUNTING
326 prompt "Cputime accounting"
327 default TICK_CPU_ACCOUNTING if !PPC64
328 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
330 # Kind of a stub config for the pure tick based cputime accounting
331 config TICK_CPU_ACCOUNTING
332 bool "Simple tick based cputime accounting"
333 depends on !S390 && !NO_HZ_FULL
335 This is the basic tick based cputime accounting that maintains
336 statistics about user, system and idle time spent on per jiffies
341 config VIRT_CPU_ACCOUNTING_NATIVE
342 bool "Deterministic task and CPU time accounting"
343 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
344 select VIRT_CPU_ACCOUNTING
346 Select this option to enable more accurate task and CPU time
347 accounting. This is done by reading a CPU counter on each
348 kernel entry and exit and on transitions within the kernel
349 between system, softirq and hardirq state, so there is a
350 small performance impact. In the case of s390 or IBM POWER > 5,
351 this also enables accounting of stolen time on logically-partitioned
354 config VIRT_CPU_ACCOUNTING_GEN
355 bool "Full dynticks CPU time accounting"
356 depends on HAVE_CONTEXT_TRACKING
357 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
358 select VIRT_CPU_ACCOUNTING
359 select CONTEXT_TRACKING
361 Select this option to enable task and CPU time accounting on full
362 dynticks systems. This accounting is implemented by watching every
363 kernel-user boundaries using the context tracking subsystem.
364 The accounting is thus performed at the expense of some significant
367 For now this is only useful if you are working on the full
368 dynticks subsystem development.
372 config IRQ_TIME_ACCOUNTING
373 bool "Fine granularity task level IRQ time accounting"
374 depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
376 Select this option to enable fine granularity task irq time
377 accounting. This is done by reading a timestamp on each
378 transitions between softirq and hardirq state, so there can be a
379 small performance impact.
381 If in doubt, say N here.
385 config BSD_PROCESS_ACCT
386 bool "BSD Process Accounting"
388 If you say Y here, a user level program will be able to instruct the
389 kernel (via a special system call) to write process accounting
390 information to a file: whenever a process exits, information about
391 that process will be appended to the file by the kernel. The
392 information includes things such as creation time, owning user,
393 command name, memory usage, controlling terminal etc. (the complete
394 list is in the struct acct in <file:include/linux/acct.h>). It is
395 up to the user level program to do useful things with this
396 information. This is generally a good idea, so say Y.
398 config BSD_PROCESS_ACCT_V3
399 bool "BSD Process Accounting version 3 file format"
400 depends on BSD_PROCESS_ACCT
403 If you say Y here, the process accounting information is written
404 in a new file format that also logs the process IDs of each
405 process and it's parent. Note that this file format is incompatible
406 with previous v0/v1/v2 file formats, so you will need updated tools
407 for processing it. A preliminary version of these tools is available
408 at <http://www.gnu.org/software/acct/>.
411 bool "Export task/process statistics through netlink"
415 Export selected statistics for tasks/processes through the
416 generic netlink interface. Unlike BSD process accounting, the
417 statistics are available during the lifetime of tasks/processes as
418 responses to commands. Like BSD accounting, they are sent to user
423 config TASK_DELAY_ACCT
424 bool "Enable per-task delay accounting"
427 Collect information on time spent by a task waiting for system
428 resources like cpu, synchronous block I/O completion and swapping
429 in pages. Such statistics can help in setting a task's priorities
430 relative to other tasks for cpu, io, rss limits etc.
435 bool "Enable extended accounting over taskstats"
438 Collect extended task accounting data and send the data
439 to userland for processing over the taskstats interface.
443 config TASK_IO_ACCOUNTING
444 bool "Enable per-task storage I/O accounting"
445 depends on TASK_XACCT
447 Collect information on the number of bytes of storage I/O which this
452 endmenu # "CPU/Task time and stats accounting"
457 prompt "RCU Implementation"
461 bool "Tree-based hierarchical RCU"
462 depends on !PREEMPT && SMP
465 This option selects the RCU implementation that is
466 designed for very large SMP system with hundreds or
467 thousands of CPUs. It also scales down nicely to
470 config TREE_PREEMPT_RCU
471 bool "Preemptible tree-based hierarchical RCU"
475 This option selects the RCU implementation that is
476 designed for very large SMP systems with hundreds or
477 thousands of CPUs, but for which real-time response
478 is also required. It also scales down nicely to
481 Select this option if you are unsure.
484 bool "UP-only small-memory-footprint RCU"
485 depends on !PREEMPT && !SMP
487 This option selects the RCU implementation that is
488 designed for UP systems from which real-time response
489 is not required. This option greatly reduces the
490 memory footprint of RCU.
495 def_bool TREE_PREEMPT_RCU
497 This option enables preemptible-RCU code that is common between
498 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
500 config RCU_STALL_COMMON
501 def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
503 This option enables RCU CPU stall code that is common between
504 the TINY and TREE variants of RCU. The purpose is to allow
505 the tiny variants to disable RCU CPU stall warnings, while
506 making these warnings mandatory for the tree variants.
508 config CONTEXT_TRACKING
512 bool "Consider userspace as in RCU extended quiescent state"
513 depends on HAVE_CONTEXT_TRACKING && SMP
514 select CONTEXT_TRACKING
516 This option sets hooks on kernel / userspace boundaries and
517 puts RCU in extended quiescent state when the CPU runs in
518 userspace. It means that when a CPU runs in userspace, it is
519 excluded from the global RCU state machine and thus doesn't
520 try to keep the timer tick on for RCU.
522 Unless you want to hack and help the development of the full
523 dynticks mode, you shouldn't enable this option. It also
524 adds unnecessary overhead.
528 config CONTEXT_TRACKING_FORCE
529 bool "Force context tracking"
530 depends on CONTEXT_TRACKING
531 default y if !NO_HZ_FULL
533 The major pre-requirement for full dynticks to work is to
534 support the context tracking subsystem. But there are also
535 other dependencies to provide in order to make the full
538 This option stands for testing when an arch implements the
539 context tracking backend but doesn't yet fullfill all the
540 requirements to make the full dynticks feature working.
541 Without the full dynticks, there is no way to test the support
542 for context tracking and the subsystems that rely on it: RCU
543 userspace extended quiescent state and tickless cputime
544 accounting. This option copes with the absence of the full
545 dynticks subsystem by forcing the context tracking on all
548 Say Y only if you're working on the development of an
549 architecture backend for the context tracking.
551 Say N otherwise, this option brings an overhead that you
552 don't want in production.
556 int "Tree-based hierarchical RCU fanout value"
559 depends on TREE_RCU || TREE_PREEMPT_RCU
563 This option controls the fanout of hierarchical implementations
564 of RCU, allowing RCU to work efficiently on machines with
565 large numbers of CPUs. This value must be at least the fourth
566 root of NR_CPUS, which allows NR_CPUS to be insanely large.
567 The default value of RCU_FANOUT should be used for production
568 systems, but if you are stress-testing the RCU implementation
569 itself, small RCU_FANOUT values allow you to test large-system
570 code paths on small(er) systems.
572 Select a specific number if testing RCU itself.
573 Take the default if unsure.
575 config RCU_FANOUT_LEAF
576 int "Tree-based hierarchical RCU leaf-level fanout value"
577 range 2 RCU_FANOUT if 64BIT
578 range 2 RCU_FANOUT if !64BIT
579 depends on TREE_RCU || TREE_PREEMPT_RCU
582 This option controls the leaf-level fanout of hierarchical
583 implementations of RCU, and allows trading off cache misses
584 against lock contention. Systems that synchronize their
585 scheduling-clock interrupts for energy-efficiency reasons will
586 want the default because the smaller leaf-level fanout keeps
587 lock contention levels acceptably low. Very large systems
588 (hundreds or thousands of CPUs) will instead want to set this
589 value to the maximum value possible in order to reduce the
590 number of cache misses incurred during RCU's grace-period
591 initialization. These systems tend to run CPU-bound, and thus
592 are not helped by synchronized interrupts, and thus tend to
593 skew them, which reduces lock contention enough that large
594 leaf-level fanouts work well.
596 Select a specific number if testing RCU itself.
598 Select the maximum permissible value for large systems.
600 Take the default if unsure.
602 config RCU_FANOUT_EXACT
603 bool "Disable tree-based hierarchical RCU auto-balancing"
604 depends on TREE_RCU || TREE_PREEMPT_RCU
607 This option forces use of the exact RCU_FANOUT value specified,
608 regardless of imbalances in the hierarchy. This is useful for
609 testing RCU itself, and might one day be useful on systems with
610 strong NUMA behavior.
612 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
616 config RCU_FAST_NO_HZ
617 bool "Accelerate last non-dyntick-idle CPU's grace periods"
618 depends on NO_HZ_COMMON && SMP
621 This option permits CPUs to enter dynticks-idle state even if
622 they have RCU callbacks queued, and prevents RCU from waking
623 these CPUs up more than roughly once every four jiffies (by
624 default, you can adjust this using the rcutree.rcu_idle_gp_delay
625 parameter), thus improving energy efficiency. On the other
626 hand, this option increases the duration of RCU grace periods,
627 for example, slowing down synchronize_rcu().
629 Say Y if energy efficiency is critically important, and you
630 don't care about increased grace-period durations.
632 Say N if you are unsure.
634 config TREE_RCU_TRACE
635 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
638 This option provides tracing for the TREE_RCU and
639 TREE_PREEMPT_RCU implementations, permitting Makefile to
640 trivially select kernel/rcutree_trace.c.
643 bool "Enable RCU priority boosting"
644 depends on RT_MUTEXES && PREEMPT_RCU
647 This option boosts the priority of preempted RCU readers that
648 block the current preemptible RCU grace period for too long.
649 This option also prevents heavy loads from blocking RCU
650 callback invocation for all flavors of RCU.
652 Say Y here if you are working with real-time apps or heavy loads
653 Say N here if you are unsure.
655 config RCU_BOOST_PRIO
656 int "Real-time priority to boost RCU readers to"
661 This option specifies the real-time priority to which long-term
662 preempted RCU readers are to be boosted. If you are working
663 with a real-time application that has one or more CPU-bound
664 threads running at a real-time priority level, you should set
665 RCU_BOOST_PRIO to a priority higher then the highest-priority
666 real-time CPU-bound thread. The default RCU_BOOST_PRIO value
667 of 1 is appropriate in the common case, which is real-time
668 applications that do not have any CPU-bound threads.
670 Some real-time applications might not have a single real-time
671 thread that saturates a given CPU, but instead might have
672 multiple real-time threads that, taken together, fully utilize
673 that CPU. In this case, you should set RCU_BOOST_PRIO to
674 a priority higher than the lowest-priority thread that is
675 conspiring to prevent the CPU from running any non-real-time
676 tasks. For example, if one thread at priority 10 and another
677 thread at priority 5 are between themselves fully consuming
678 the CPU time on a given CPU, then RCU_BOOST_PRIO should be
679 set to priority 6 or higher.
681 Specify the real-time priority, or take the default if unsure.
683 config RCU_BOOST_DELAY
684 int "Milliseconds to delay boosting after RCU grace-period start"
689 This option specifies the time to wait after the beginning of
690 a given grace period before priority-boosting preempted RCU
691 readers blocking that grace period. Note that any RCU reader
692 blocking an expedited RCU grace period is boosted immediately.
694 Accept the default if unsure.
697 bool "Offload RCU callback processing from boot-selected CPUs"
698 depends on TREE_RCU || TREE_PREEMPT_RCU
701 Use this option to reduce OS jitter for aggressive HPC or
702 real-time workloads. It can also be used to offload RCU
703 callback invocation to energy-efficient CPUs in battery-powered
704 asymmetric multiprocessors.
706 This option offloads callback invocation from the set of
707 CPUs specified at boot time by the rcu_nocbs parameter.
708 For each such CPU, a kthread ("rcuox/N") will be created to
709 invoke callbacks, where the "N" is the CPU being offloaded,
710 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
711 "s" for RCU-sched. Nothing prevents this kthread from running
712 on the specified CPUs, but (1) the kthreads may be preempted
713 between each callback, and (2) affinity or cgroups can be used
714 to force the kthreads to run on whatever set of CPUs is desired.
716 Say Y here if you want to help to debug reduced OS jitter.
717 Say N here if you are unsure.
720 prompt "Build-forced no-CBs CPUs"
721 default RCU_NOCB_CPU_NONE
723 This option allows no-CBs CPUs (whose RCU callbacks are invoked
724 from kthreads rather than from softirq context) to be specified
725 at build time. Additional no-CBs CPUs may be specified by
726 the rcu_nocbs= boot parameter.
728 config RCU_NOCB_CPU_NONE
729 bool "No build_forced no-CBs CPUs"
730 depends on RCU_NOCB_CPU && !NO_HZ_FULL
732 This option does not force any of the CPUs to be no-CBs CPUs.
733 Only CPUs designated by the rcu_nocbs= boot parameter will be
734 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
735 kthreads whose names begin with "rcuo". All other CPUs will
736 invoke their own RCU callbacks in softirq context.
738 Select this option if you want to choose no-CBs CPUs at
739 boot time, for example, to allow testing of different no-CBs
740 configurations without having to rebuild the kernel each time.
742 config RCU_NOCB_CPU_ZERO
743 bool "CPU 0 is a build_forced no-CBs CPU"
744 depends on RCU_NOCB_CPU && !NO_HZ_FULL
746 This option forces CPU 0 to be a no-CBs CPU, so that its RCU
747 callbacks are invoked by a per-CPU kthread whose name begins
748 with "rcuo". Additional CPUs may be designated as no-CBs
749 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
750 All other CPUs will invoke their own RCU callbacks in softirq
753 Select this if CPU 0 needs to be a no-CBs CPU for real-time
754 or energy-efficiency reasons, but the real reason it exists
755 is to ensure that randconfig testing covers mixed systems.
757 config RCU_NOCB_CPU_ALL
758 bool "All CPUs are build_forced no-CBs CPUs"
759 depends on RCU_NOCB_CPU
761 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
762 boot parameter will be ignored. All CPUs' RCU callbacks will
763 be executed in the context of per-CPU rcuo kthreads created for
764 this purpose. Assuming that the kthreads whose names start with
765 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
766 on the remaining CPUs, but might decrease memory locality during
767 RCU-callback invocation, thus potentially degrading throughput.
769 Select this if all CPUs need to be no-CBs CPUs for real-time
770 or energy-efficiency reasons.
774 endmenu # "RCU Subsystem"
777 tristate "Kernel .config support"
779 This option enables the complete Linux kernel ".config" file
780 contents to be saved in the kernel. It provides documentation
781 of which kernel options are used in a running kernel or in an
782 on-disk kernel. This information can be extracted from the kernel
783 image file with the script scripts/extract-ikconfig and used as
784 input to rebuild the current kernel or to build another kernel.
785 It can also be extracted from a running kernel by reading
786 /proc/config.gz if enabled (below).
789 bool "Enable access to .config through /proc/config.gz"
790 depends on IKCONFIG && PROC_FS
792 This option enables access to the kernel configuration file
793 through /proc/config.gz.
796 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
800 Select kernel log buffer size as a power of 2.
810 # Architectures with an unreliable sched_clock() should select this:
812 config HAVE_UNSTABLE_SCHED_CLOCK
815 config GENERIC_SCHED_CLOCK
819 # For architectures that want to enable the support for NUMA-affine scheduler
822 config ARCH_SUPPORTS_NUMA_BALANCING
826 # For architectures that know their GCC __int128 support is sound
828 config ARCH_SUPPORTS_INT128
831 # For architectures that (ab)use NUMA to represent different memory regions
832 # all cpu-local but of different latencies, such as SuperH.
834 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
838 # For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
839 config ARCH_WANTS_PROT_NUMA_PROT_NONE
842 config ARCH_USES_NUMA_PROT_NONE
845 depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
846 depends on NUMA_BALANCING
848 config NUMA_BALANCING_DEFAULT_ENABLED
849 bool "Automatically enable NUMA aware memory/task placement"
851 depends on NUMA_BALANCING
853 If set, automatic NUMA balancing will be enabled if running on a NUMA
856 config NUMA_BALANCING
857 bool "Memory placement aware NUMA scheduler"
858 depends on ARCH_SUPPORTS_NUMA_BALANCING
859 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
860 depends on SMP && NUMA && MIGRATION
862 This option adds support for automatic NUMA aware memory/task placement.
863 The mechanism is quite primitive and is based on migrating memory when
864 it has references to the node the task is running on.
866 This system will be inactive on UMA systems.
869 boolean "Control Group support"
872 This option adds support for grouping sets of processes together, for
873 use with process control subsystems such as Cpusets, CFS, memory
874 controls or device isolation.
876 - Documentation/scheduler/sched-design-CFS.txt (CFS)
877 - Documentation/cgroups/ (features for grouping, isolation
878 and resource control)
885 bool "Example debug cgroup subsystem"
888 This option enables a simple cgroup subsystem that
889 exports useful debugging information about the cgroups
894 config CGROUP_FREEZER
895 bool "Freezer cgroup subsystem"
897 Provides a way to freeze and unfreeze all tasks in a
901 bool "Device controller for cgroups"
903 Provides a cgroup implementing whitelists for devices which
904 a process in the cgroup can mknod or open.
907 bool "Cpuset support"
909 This option will let you create and manage CPUSETs which
910 allow dynamically partitioning a system into sets of CPUs and
911 Memory Nodes and assigning tasks to run only within those sets.
912 This is primarily useful on large SMP or NUMA systems.
916 config PROC_PID_CPUSET
917 bool "Include legacy /proc/<pid>/cpuset file"
921 config CGROUP_CPUACCT
922 bool "Simple CPU accounting cgroup subsystem"
924 Provides a simple Resource Controller for monitoring the
925 total CPU consumed by the tasks in a cgroup.
927 config RESOURCE_COUNTERS
928 bool "Resource counters"
930 This option enables controller independent resource accounting
931 infrastructure that works with cgroups.
934 bool "Memory Resource Controller for Control Groups"
935 depends on RESOURCE_COUNTERS
938 Provides a memory resource controller that manages both anonymous
939 memory and page cache. (See Documentation/cgroups/memory.txt)
941 Note that setting this option increases fixed memory overhead
942 associated with each page of memory in the system. By this,
943 8(16)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
944 usage tracking struct at boot. Total amount of this is printed out
947 Only enable when you're ok with these trade offs and really
948 sure you need the memory resource controller. Even when you enable
949 this, you can set "cgroup_disable=memory" at your boot option to
950 disable memory resource controller and you can avoid overheads.
951 (and lose benefits of memory resource controller)
954 bool "Memory Resource Controller Swap Extension"
955 depends on MEMCG && SWAP
957 Add swap management feature to memory resource controller. When you
958 enable this, you can limit mem+swap usage per cgroup. In other words,
959 when you disable this, memory resource controller has no cares to
960 usage of swap...a process can exhaust all of the swap. This extension
961 is useful when you want to avoid exhaustion swap but this itself
962 adds more overheads and consumes memory for remembering information.
963 Especially if you use 32bit system or small memory system, please
964 be careful about enabling this. When memory resource controller
965 is disabled by boot option, this will be automatically disabled and
966 there will be no overhead from this. Even when you set this config=y,
967 if boot option "swapaccount=0" is set, swap will not be accounted.
968 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
969 size is 4096bytes, 512k per 1Gbytes of swap.
970 config MEMCG_SWAP_ENABLED
971 bool "Memory Resource Controller Swap Extension enabled by default"
972 depends on MEMCG_SWAP
975 Memory Resource Controller Swap Extension comes with its price in
976 a bigger memory consumption. General purpose distribution kernels
977 which want to enable the feature but keep it disabled by default
978 and let the user enable it by swapaccount=1 boot command line
979 parameter should have this option unselected.
980 For those who want to have the feature enabled by default should
981 select this option (if, for some reason, they need to disable it
982 then swapaccount=0 does the trick).
984 bool "Memory Resource Controller Kernel Memory accounting"
986 depends on SLUB || SLAB
988 The Kernel Memory extension for Memory Resource Controller can limit
989 the amount of memory used by kernel objects in the system. Those are
990 fundamentally different from the entities handled by the standard
991 Memory Controller, which are page-based, and can be swapped. Users of
992 the kmem extension can use it to guarantee that no group of processes
993 will ever exhaust kernel resources alone.
995 WARNING: Current implementation lacks reclaim support. That means
996 allocation attempts will fail when close to the limit even if there
997 are plenty of kmem available for reclaim. That makes this option
998 unusable in real life so DO NOT SELECT IT unless for development
1001 config CGROUP_HUGETLB
1002 bool "HugeTLB Resource Controller for Control Groups"
1003 depends on RESOURCE_COUNTERS && HUGETLB_PAGE
1006 Provides a cgroup Resource Controller for HugeTLB pages.
1007 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1008 The limit is enforced during page fault. Since HugeTLB doesn't
1009 support page reclaim, enforcing the limit at page fault time implies
1010 that, the application will get SIGBUS signal if it tries to access
1011 HugeTLB pages beyond its limit. This requires the application to know
1012 beforehand how much HugeTLB pages it would require for its use. The
1013 control group is tracked in the third page lru pointer. This means
1014 that we cannot use the controller with huge page less than 3 pages.
1017 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1018 depends on PERF_EVENTS && CGROUPS
1020 This option extends the per-cpu mode to restrict monitoring to
1021 threads which belong to the cgroup specified and run on the
1026 menuconfig CGROUP_SCHED
1027 bool "Group CPU scheduler"
1030 This feature lets CPU scheduler recognize task groups and control CPU
1031 bandwidth allocation to such task groups. It uses cgroups to group
1035 config FAIR_GROUP_SCHED
1036 bool "Group scheduling for SCHED_OTHER"
1037 depends on CGROUP_SCHED
1038 default CGROUP_SCHED
1040 config CFS_BANDWIDTH
1041 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1042 depends on FAIR_GROUP_SCHED
1045 This option allows users to define CPU bandwidth rates (limits) for
1046 tasks running within the fair group scheduler. Groups with no limit
1047 set are considered to be unconstrained and will run with no
1049 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1051 config RT_GROUP_SCHED
1052 bool "Group scheduling for SCHED_RR/FIFO"
1053 depends on CGROUP_SCHED
1056 This feature lets you explicitly allocate real CPU bandwidth
1057 to task groups. If enabled, it will also make it impossible to
1058 schedule realtime tasks for non-root users until you allocate
1059 realtime bandwidth for them.
1060 See Documentation/scheduler/sched-rt-group.txt for more information.
1065 bool "Block IO controller"
1069 Generic block IO controller cgroup interface. This is the common
1070 cgroup interface which should be used by various IO controlling
1073 Currently, CFQ IO scheduler uses it to recognize task groups and
1074 control disk bandwidth allocation (proportional time slice allocation)
1075 to such task groups. It is also used by bio throttling logic in
1076 block layer to implement upper limit in IO rates on a device.
1078 This option only enables generic Block IO controller infrastructure.
1079 One needs to also enable actual IO controlling logic/policy. For
1080 enabling proportional weight division of disk bandwidth in CFQ, set
1081 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1082 CONFIG_BLK_DEV_THROTTLING=y.
1084 See Documentation/cgroups/blkio-controller.txt for more information.
1086 config DEBUG_BLK_CGROUP
1087 bool "Enable Block IO controller debugging"
1088 depends on BLK_CGROUP
1091 Enable some debugging help. Currently it exports additional stat
1092 files in a cgroup which can be useful for debugging.
1096 config CHECKPOINT_RESTORE
1097 bool "Checkpoint/restore support" if EXPERT
1100 Enables additional kernel features in a sake of checkpoint/restore.
1101 In particular it adds auxiliary prctl codes to setup process text,
1102 data and heap segment sizes, and a few additional /proc filesystem
1105 If unsure, say N here.
1107 menuconfig NAMESPACES
1108 bool "Namespaces support" if EXPERT
1111 Provides the way to make tasks work with different objects using
1112 the same id. For example same IPC id may refer to different objects
1113 or same user id or pid may refer to different tasks when used in
1114 different namespaces.
1119 bool "UTS namespace"
1122 In this namespace tasks see different info provided with the
1126 bool "IPC namespace"
1127 depends on (SYSVIPC || POSIX_MQUEUE)
1130 In this namespace tasks work with IPC ids which correspond to
1131 different IPC objects in different namespaces.
1134 bool "User namespace"
1137 This allows containers, i.e. vservers, to use user namespaces
1138 to provide different user info for different servers.
1140 When user namespaces are enabled in the kernel it is
1141 recommended that the MEMCG and MEMCG_KMEM options also be
1142 enabled and that user-space use the memory control groups to
1143 limit the amount of memory a memory unprivileged users can
1149 bool "PID Namespaces"
1152 Support process id namespaces. This allows having multiple
1153 processes with the same pid as long as they are in different
1154 pid namespaces. This is a building block of containers.
1157 bool "Network namespace"
1161 Allow user space to create what appear to be multiple instances
1162 of the network stack.
1166 config SCHED_AUTOGROUP
1167 bool "Automatic process group scheduling"
1170 select FAIR_GROUP_SCHED
1172 This option optimizes the scheduler for common desktop workloads by
1173 automatically creating and populating task groups. This separation
1174 of workloads isolates aggressive CPU burners (like build jobs) from
1175 desktop applications. Task group autogeneration is currently based
1178 config SYSFS_DEPRECATED
1179 bool "Enable deprecated sysfs features to support old userspace tools"
1183 This option adds code that switches the layout of the "block" class
1184 devices, to not show up in /sys/class/block/, but only in
1187 This switch is only active when the sysfs.deprecated=1 boot option is
1188 passed or the SYSFS_DEPRECATED_V2 option is set.
1190 This option allows new kernels to run on old distributions and tools,
1191 which might get confused by /sys/class/block/. Since 2007/2008 all
1192 major distributions and tools handle this just fine.
1194 Recent distributions and userspace tools after 2009/2010 depend on
1195 the existence of /sys/class/block/, and will not work with this
1198 Only if you are using a new kernel on an old distribution, you might
1201 config SYSFS_DEPRECATED_V2
1202 bool "Enable deprecated sysfs features by default"
1205 depends on SYSFS_DEPRECATED
1207 Enable deprecated sysfs by default.
1209 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1212 Only if you are using a new kernel on an old distribution, you might
1213 need to say Y here. Even then, odds are you would not need it
1214 enabled, you can always pass the boot option if absolutely necessary.
1217 bool "Kernel->user space relay support (formerly relayfs)"
1219 This option enables support for relay interface support in
1220 certain file systems (such as debugfs).
1221 It is designed to provide an efficient mechanism for tools and
1222 facilities to relay large amounts of data from kernel space to
1227 config BLK_DEV_INITRD
1228 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1229 depends on BROKEN || !FRV
1231 The initial RAM filesystem is a ramfs which is loaded by the
1232 boot loader (loadlin or lilo) and that is mounted as root
1233 before the normal boot procedure. It is typically used to
1234 load modules needed to mount the "real" root file system,
1235 etc. See <file:Documentation/initrd.txt> for details.
1237 If RAM disk support (BLK_DEV_RAM) is also included, this
1238 also enables initial RAM disk (initrd) support and adds
1239 15 Kbytes (more on some other architectures) to the kernel size.
1245 source "usr/Kconfig"
1249 config CC_OPTIMIZE_FOR_SIZE
1250 bool "Optimize for size"
1252 Enabling this option will pass "-Os" instead of "-O2" to gcc
1253 resulting in a smaller kernel.
1258 bool "Enable gcc link time optimization (LTO)"
1259 # Only tested on X86 for now. For other architectures you likely
1260 # have to fix some things first, like adding asmlinkages etc.
1262 # lto does not support excluding flags for specific files
1263 # right now. Can be removed if that is fixed.
1264 depends on !FUNCTION_TRACER
1266 With this option gcc will do whole program optimizations for
1267 the whole kernel and module. This increases compile time, but can
1268 lead to better code. It allows gcc to inline functions between
1269 different files and do other optimization. It might also trigger
1270 bugs due to more aggressive optimization. It allows gcc to drop unused
1271 code. On smaller monolithic kernel configurations
1272 it usually leads to smaller kernels, especially when modules
1275 With this option gcc will also do some global checking over
1276 different source files. It also disables a number of kernel
1279 This option is recommended for release builds. With LTO
1280 the kernel always has to be re-optimized (but not re-parsed)
1283 This requires a gcc 4.8 or later compiler and
1284 Linux binutils 2.21.51.0.3 or later. gcc 4.9 builds significantly
1285 faster than 4.8 It does not currently work with a FSF release of
1286 binutils or with the gold linker.
1288 On larger configurations this may need more than 4GB of RAM.
1289 It will likely not work on those with a 32bit compiler.
1291 When the toolchain support is not available this will (hopefully)
1292 be automatically disabled.
1294 For more information see Documentation/lto-build
1297 bool "Disable LTO again"
1301 This option is merely here so that allyesconfig or allmodconfig do
1302 not enable LTO. If you want to actually use LTO do not enable.
1307 depends on LTO_MENU && !LTO_DISABLE
1310 bool "Enable LTO compile time debugging"
1313 Enable LTO debugging in the compiler. The compiler dumps
1314 some log files that make it easier to figure out LTO
1315 behavior. The log files also allow to reconstruct
1316 the global inlining and a global callgraph.
1317 They however add some (single threaded) cost to the
1318 compilation. When in doubt do not enable.
1321 bool "Allow aggressive cloning for function specialization"
1324 Allow the compiler to clone and specialize functions for specific
1325 arguments when it determines these arguments are very commonly
1326 called. Experimential. Will increase text size.
1337 config SYSCTL_EXCEPTION_TRACE
1340 Enable support for /proc/sys/debug/exception-trace.
1342 config SYSCTL_ARCH_UNALIGN_NO_WARN
1345 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1346 Allows arch to define/use @no_unaligned_warning to possibly warn
1347 about unaligned access emulation going on under the hood.
1349 config SYSCTL_ARCH_UNALIGN_ALLOW
1352 Enable support for /proc/sys/kernel/unaligned-trap
1353 Allows arches to define/use @unaligned_enabled to runtime toggle
1354 the unaligned access emulation.
1355 see arch/parisc/kernel/unaligned.c for reference
1357 config HAVE_PCSPKR_PLATFORM
1361 bool "Configure standard kernel features (expert users)"
1362 # Unhide debug options, to make the on-by-default options visible
1365 This option allows certain base kernel options and settings
1366 to be disabled or tweaked. This is for specialized
1367 environments which can tolerate a "non-standard" kernel.
1368 Only use this if you really know what you are doing.
1371 bool "Enable 16-bit UID system calls" if EXPERT
1372 depends on HAVE_UID16
1375 This enables the legacy 16-bit UID syscall wrappers.
1377 config SGETMASK_SYSCALL
1378 bool "sgetmask/ssetmask syscalls support" if EXPERT
1379 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1381 sys_sgetmask and sys_ssetmask are obsolete system calls
1382 no longer supported in libc but still enabled by default in some
1385 If unsure, leave the default option here.
1387 config SYSFS_SYSCALL
1388 bool "Sysfs syscall support" if EXPERT
1391 sys_sysfs is an obsolete system call no longer supported in libc.
1392 Note that disabling this option is more secure but might break
1393 compatibility with some systems.
1395 If unsure say Y here.
1397 config SYSCTL_SYSCALL
1398 bool "Sysctl syscall support" if EXPERT
1399 depends on PROC_SYSCTL
1403 sys_sysctl uses binary paths that have been found challenging
1404 to properly maintain and use. The interface in /proc/sys
1405 using paths with ascii names is now the primary path to this
1408 Almost nothing using the binary sysctl interface so if you are
1409 trying to save some space it is probably safe to disable this,
1410 making your kernel marginally smaller.
1412 If unsure say N here.
1415 bool "Load all symbols for debugging/ksymoops" if EXPERT
1418 Say Y here to let the kernel print out symbolic crash information and
1419 symbolic stack backtraces. This increases the size of the kernel
1420 somewhat, as all symbols have to be loaded into the kernel image.
1423 bool "Include all symbols in kallsyms"
1424 depends on DEBUG_KERNEL && KALLSYMS
1426 Normally kallsyms only contains the symbols of functions for nicer
1427 OOPS messages and backtraces (i.e., symbols from the text and inittext
1428 sections). This is sufficient for most cases. And only in very rare
1429 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1430 names of variables from the data sections, etc).
1432 This option makes sure that all symbols are loaded into the kernel
1433 image (i.e., symbols from all sections) in cost of increased kernel
1434 size (depending on the kernel configuration, it may be 300KiB or
1435 something like this).
1437 Say N unless you really need all symbols.
1441 bool "Enable support for printk" if EXPERT
1444 This option enables normal printk support. Removing it
1445 eliminates most of the message strings from the kernel image
1446 and makes the kernel more or less silent. As this makes it
1447 very difficult to diagnose system problems, saying N here is
1448 strongly discouraged.
1451 bool "BUG() support" if EXPERT
1454 Disabling this option eliminates support for BUG and WARN, reducing
1455 the size of your kernel image and potentially quietly ignoring
1456 numerous fatal conditions. You should only consider disabling this
1457 option for embedded systems with no facilities for reporting errors.
1463 bool "Enable ELF core dumps" if EXPERT
1465 Enable support for generating core dumps. Disabling saves about 4k.
1468 config PCSPKR_PLATFORM
1469 bool "Enable PC-Speaker support" if EXPERT
1470 depends on HAVE_PCSPKR_PLATFORM
1474 This option allows to disable the internal PC-Speaker
1475 support, saving some memory.
1479 bool "Enable full-sized data structures for core" if EXPERT
1481 Disabling this option reduces the size of miscellaneous core
1482 kernel data structures. This saves memory on small machines,
1483 but may reduce performance.
1486 bool "Enable futex support" if EXPERT
1490 Disabling this option will cause the kernel to be built without
1491 support for "fast userspace mutexes". The resulting kernel may not
1492 run glibc-based applications correctly.
1494 config HAVE_FUTEX_CMPXCHG
1497 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1498 is implemented and always working. This removes a couple of runtime
1502 bool "Enable eventpoll support" if EXPERT
1506 Disabling this option will cause the kernel to be built without
1507 support for epoll family of system calls.
1510 bool "Enable signalfd() system call" if EXPERT
1514 Enable the signalfd() system call that allows to receive signals
1515 on a file descriptor.
1520 bool "Enable timerfd() system call" if EXPERT
1524 Enable the timerfd() system call that allows to receive timer
1525 events on a file descriptor.
1530 bool "Enable eventfd() system call" if EXPERT
1534 Enable the eventfd() system call that allows to receive both
1535 kernel notification (ie. KAIO) or userspace notifications.
1540 bool "Use full shmem filesystem" if EXPERT
1544 The shmem is an internal filesystem used to manage shared memory.
1545 It is backed by swap and manages resource limits. It is also exported
1546 to userspace as tmpfs if TMPFS is enabled. Disabling this
1547 option replaces shmem and tmpfs with the much simpler ramfs code,
1548 which may be appropriate on small systems without swap.
1551 bool "Enable AIO support" if EXPERT
1554 This option enables POSIX asynchronous I/O which may by used
1555 by some high performance threaded applications. Disabling
1556 this option saves about 7k.
1560 bool "Enable PCI quirk workarounds" if EXPERT
1563 This enables workarounds for various PCI chipset
1564 bugs/quirks. Disable this only if your target machine is
1565 unaffected by PCI quirks.
1568 bool "Embedded system"
1569 option allnoconfig_y
1572 This option should be enabled if compiling the kernel for
1573 an embedded system so certain expert options are available
1576 config HAVE_PERF_EVENTS
1579 See tools/perf/design.txt for details.
1581 config PERF_USE_VMALLOC
1584 See tools/perf/design.txt for details
1586 menu "Kernel Performance Events And Counters"
1589 bool "Kernel performance events and counters"
1590 default y if PROFILING
1591 depends on HAVE_PERF_EVENTS
1595 Enable kernel support for various performance events provided
1596 by software and hardware.
1598 Software events are supported either built-in or via the
1599 use of generic tracepoints.
1601 Most modern CPUs support performance events via performance
1602 counter registers. These registers count the number of certain
1603 types of hw events: such as instructions executed, cachemisses
1604 suffered, or branches mis-predicted - without slowing down the
1605 kernel or applications. These registers can also trigger interrupts
1606 when a threshold number of events have passed - and can thus be
1607 used to profile the code that runs on that CPU.
1609 The Linux Performance Event subsystem provides an abstraction of
1610 these software and hardware event capabilities, available via a
1611 system call and used by the "perf" utility in tools/perf/. It
1612 provides per task and per CPU counters, and it provides event
1613 capabilities on top of those.
1617 config DEBUG_PERF_USE_VMALLOC
1619 bool "Debug: use vmalloc to back perf mmap() buffers"
1620 depends on PERF_EVENTS && DEBUG_KERNEL
1621 select PERF_USE_VMALLOC
1623 Use vmalloc memory to back perf mmap() buffers.
1625 Mostly useful for debugging the vmalloc code on platforms
1626 that don't require it.
1632 config VM_EVENT_COUNTERS
1634 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1636 VM event counters are needed for event counts to be shown.
1637 This option allows the disabling of the VM event counters
1638 on EXPERT systems. /proc/vmstat will only show page counts
1639 if VM event counters are disabled.
1643 bool "Enable SLUB debugging support" if EXPERT
1644 depends on SLUB && SYSFS
1646 SLUB has extensive debug support features. Disabling these can
1647 result in significant savings in code size. This also disables
1648 SLUB sysfs support. /sys/slab will not exist and there will be
1649 no support for cache validation etc.
1652 bool "Disable heap randomization"
1655 Randomizing heap placement makes heap exploits harder, but it
1656 also breaks ancient binaries (including anything libc5 based).
1657 This option changes the bootup default to heap randomization
1658 disabled, and can be overridden at runtime by setting
1659 /proc/sys/kernel/randomize_va_space to 2.
1661 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1664 prompt "Choose SLAB allocator"
1667 This option allows to select a slab allocator.
1672 The regular slab allocator that is established and known to work
1673 well in all environments. It organizes cache hot objects in
1674 per cpu and per node queues.
1677 bool "SLUB (Unqueued Allocator)"
1679 SLUB is a slab allocator that minimizes cache line usage
1680 instead of managing queues of cached objects (SLAB approach).
1681 Per cpu caching is realized using slabs of objects instead
1682 of queues of objects. SLUB can use memory efficiently
1683 and has enhanced diagnostics. SLUB is the default choice for
1688 bool "SLOB (Simple Allocator)"
1690 SLOB replaces the stock allocator with a drastically simpler
1691 allocator. SLOB is generally more space efficient but
1692 does not perform as well on large systems.
1696 config SLUB_CPU_PARTIAL
1698 depends on SLUB && SMP
1699 bool "SLUB per cpu partial cache"
1701 Per cpu partial caches accellerate objects allocation and freeing
1702 that is local to a processor at the price of more indeterminism
1703 in the latency of the free. On overflow these caches will be cleared
1704 which requires the taking of locks that may cause latency spikes.
1705 Typically one would choose no for a realtime system.
1707 config MMAP_ALLOW_UNINITIALIZED
1708 bool "Allow mmapped anonymous memory to be uninitialized"
1709 depends on EXPERT && !MMU
1712 Normally, and according to the Linux spec, anonymous memory obtained
1713 from mmap() has it's contents cleared before it is passed to
1714 userspace. Enabling this config option allows you to request that
1715 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1716 providing a huge performance boost. If this option is not enabled,
1717 then the flag will be ignored.
1719 This is taken advantage of by uClibc's malloc(), and also by
1720 ELF-FDPIC binfmt's brk and stack allocator.
1722 Because of the obvious security issues, this option should only be
1723 enabled on embedded devices where you control what is run in
1724 userspace. Since that isn't generally a problem on no-MMU systems,
1725 it is normally safe to say Y here.
1727 See Documentation/nommu-mmap.txt for more information.
1729 config SYSTEM_TRUSTED_KEYRING
1730 bool "Provide system-wide ring of trusted keys"
1733 Provide a system keyring to which trusted keys can be added. Keys in
1734 the keyring are considered to be trusted. Keys may be added at will
1735 by the kernel from compiled-in data and from hardware key stores, but
1736 userspace may only add extra keys if those keys can be verified by
1737 keys already in the keyring.
1739 Keys in this keyring are used by module signature checking.
1742 bool "Profiling support"
1744 Say Y here to enable the extended profiling support mechanisms used
1745 by profilers such as OProfile.
1748 # Place an empty function call at each tracepoint site. Can be
1749 # dynamically changed for a probe function.
1754 source "arch/Kconfig"
1756 endmenu # General setup
1758 config HAVE_GENERIC_DMA_COHERENT
1765 depends on SLAB || SLUB_DEBUG
1773 default 0 if BASE_FULL
1774 default 1 if !BASE_FULL
1777 bool "Enable loadable module support"
1780 Kernel modules are small pieces of compiled code which can
1781 be inserted in the running kernel, rather than being
1782 permanently built into the kernel. You use the "modprobe"
1783 tool to add (and sometimes remove) them. If you say Y here,
1784 many parts of the kernel can be built as modules (by
1785 answering M instead of Y where indicated): this is most
1786 useful for infrequently used options which are not required
1787 for booting. For more information, see the man pages for
1788 modprobe, lsmod, modinfo, insmod and rmmod.
1790 If you say Y here, you will need to run "make
1791 modules_install" to put the modules under /lib/modules/
1792 where modprobe can find them (you may need to be root to do
1799 config MODULE_FORCE_LOAD
1800 bool "Forced module loading"
1803 Allow loading of modules without version information (ie. modprobe
1804 --force). Forced module loading sets the 'F' (forced) taint flag and
1805 is usually a really bad idea.
1807 config MODULE_UNLOAD
1808 bool "Module unloading"
1810 Without this option you will not be able to unload any
1811 modules (note that some modules may not be unloadable
1812 anyway), which makes your kernel smaller, faster
1813 and simpler. If unsure, say Y.
1815 config MODULE_FORCE_UNLOAD
1816 bool "Forced module unloading"
1817 depends on MODULE_UNLOAD
1819 This option allows you to force a module to unload, even if the
1820 kernel believes it is unsafe: the kernel will remove the module
1821 without waiting for anyone to stop using it (using the -f option to
1822 rmmod). This is mainly for kernel developers and desperate users.
1826 bool "Module versioning support"
1827 # LTO should work with gcc 4.9
1830 Usually, you have to use modules compiled with your kernel.
1831 Saying Y here makes it sometimes possible to use modules
1832 compiled for different kernels, by adding enough information
1833 to the modules to (hopefully) spot any changes which would
1834 make them incompatible with the kernel you are running. If
1837 config MODULE_SRCVERSION_ALL
1838 bool "Source checksum for all modules"
1840 Modules which contain a MODULE_VERSION get an extra "srcversion"
1841 field inserted into their modinfo section, which contains a
1842 sum of the source files which made it. This helps maintainers
1843 see exactly which source was used to build a module (since
1844 others sometimes change the module source without updating
1845 the version). With this option, such a "srcversion" field
1846 will be created for all modules. If unsure, say N.
1849 bool "Module signature verification"
1851 select SYSTEM_TRUSTED_KEYRING
1854 select ASYMMETRIC_KEY_TYPE
1855 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1856 select PUBLIC_KEY_ALGO_RSA
1859 select X509_CERTIFICATE_PARSER
1861 Check modules for valid signatures upon load: the signature
1862 is simply appended to the module. For more information see
1863 Documentation/module-signing.txt.
1865 !!!WARNING!!! If you enable this option, you MUST make sure that the
1866 module DOES NOT get stripped after being signed. This includes the
1867 debuginfo strip done by some packagers (such as rpmbuild) and
1868 inclusion into an initramfs that wants the module size reduced.
1870 config MODULE_SIG_FORCE
1871 bool "Require modules to be validly signed"
1872 depends on MODULE_SIG
1874 Reject unsigned modules or signed modules for which we don't have a
1875 key. Without this, such modules will simply taint the kernel.
1877 config MODULE_SIG_ALL
1878 bool "Automatically sign all modules"
1880 depends on MODULE_SIG
1882 Sign all modules during make modules_install. Without this option,
1883 modules must be signed manually, using the scripts/sign-file tool.
1885 comment "Do not forget to sign required modules with scripts/sign-file"
1886 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1889 prompt "Which hash algorithm should modules be signed with?"
1890 depends on MODULE_SIG
1892 This determines which sort of hashing algorithm will be used during
1893 signature generation. This algorithm _must_ be built into the kernel
1894 directly so that signature verification can take place. It is not
1895 possible to load a signed module containing the algorithm to check
1896 the signature on that module.
1898 config MODULE_SIG_SHA1
1899 bool "Sign modules with SHA-1"
1902 config MODULE_SIG_SHA224
1903 bool "Sign modules with SHA-224"
1904 select CRYPTO_SHA256
1906 config MODULE_SIG_SHA256
1907 bool "Sign modules with SHA-256"
1908 select CRYPTO_SHA256
1910 config MODULE_SIG_SHA384
1911 bool "Sign modules with SHA-384"
1912 select CRYPTO_SHA512
1914 config MODULE_SIG_SHA512
1915 bool "Sign modules with SHA-512"
1916 select CRYPTO_SHA512
1920 config MODULE_SIG_HASH
1922 depends on MODULE_SIG
1923 default "sha1" if MODULE_SIG_SHA1
1924 default "sha224" if MODULE_SIG_SHA224
1925 default "sha256" if MODULE_SIG_SHA256
1926 default "sha384" if MODULE_SIG_SHA384
1927 default "sha512" if MODULE_SIG_SHA512
1931 config INIT_ALL_POSSIBLE
1934 Back when each arch used to define their own cpu_online_mask and
1935 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1936 with all 1s, and others with all 0s. When they were centralised,
1937 it was better to provide this option than to break all the archs
1938 and have several arch maintainers pursuing me down dark alleys.
1943 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1945 Need stop_machine() primitive.
1947 source "block/Kconfig"
1949 config PREEMPT_NOTIFIERS
1956 # Can be selected by architectures with broken toolchains
1957 # that get confused by correct const<->read_only section
1959 config BROKEN_RODATA
1965 Build a simple ASN.1 grammar compiler that produces a bytecode output
1966 that can be interpreted by the ASN.1 stream decoder and used to
1967 inform it as to what tags are to be expected in a stream and what
1968 functions to call on what tags.
1970 source "kernel/Kconfig.locks"