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)"
815 Select the minimal kernel log buffer size as a power of 2.
816 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
817 parameter, see below. Any higher size also might be forced
818 by "log_buf_len" boot parameter.
828 config LOG_CPU_MAX_BUF_SHIFT
829 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
831 default 12 if !BASE_SMALL
832 default 0 if BASE_SMALL
834 This option allows to increase the default ring buffer size
835 according to the number of CPUs. The value defines the contribution
836 of each CPU as a power of 2. The used space is typically only few
837 lines however it might be much more when problems are reported,
840 The increased size means that a new buffer has to be allocated and
841 the original static one is unused. It makes sense only on systems
842 with more CPUs. Therefore this value is used only when the sum of
843 contributions is greater than the half of the default kernel ring
844 buffer as defined by LOG_BUF_SHIFT. The default values are set
845 so that more than 64 CPUs are needed to trigger the allocation.
847 Also this option is ignored when "log_buf_len" kernel parameter is
848 used as it forces an exact (power of two) size of the ring buffer.
850 The number of possible CPUs is used for this computation ignoring
851 hotplugging making the compuation optimal for the the worst case
852 scenerio while allowing a simple algorithm to be used from bootup.
854 Examples shift values and their meaning:
855 17 => 128 KB for each CPU
856 16 => 64 KB for each CPU
857 15 => 32 KB for each CPU
858 14 => 16 KB for each CPU
859 13 => 8 KB for each CPU
860 12 => 4 KB for each CPU
863 # Architectures with an unreliable sched_clock() should select this:
865 config HAVE_UNSTABLE_SCHED_CLOCK
868 config GENERIC_SCHED_CLOCK
872 # For architectures that want to enable the support for NUMA-affine scheduler
875 config ARCH_SUPPORTS_NUMA_BALANCING
879 # For architectures that know their GCC __int128 support is sound
881 config ARCH_SUPPORTS_INT128
884 # For architectures that (ab)use NUMA to represent different memory regions
885 # all cpu-local but of different latencies, such as SuperH.
887 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
891 # For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
892 config ARCH_WANTS_PROT_NUMA_PROT_NONE
895 config ARCH_USES_NUMA_PROT_NONE
898 depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
899 depends on NUMA_BALANCING
901 config NUMA_BALANCING_DEFAULT_ENABLED
902 bool "Automatically enable NUMA aware memory/task placement"
904 depends on NUMA_BALANCING
906 If set, automatic NUMA balancing will be enabled if running on a NUMA
909 config NUMA_BALANCING
910 bool "Memory placement aware NUMA scheduler"
911 depends on ARCH_SUPPORTS_NUMA_BALANCING
912 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
913 depends on SMP && NUMA && MIGRATION
915 This option adds support for automatic NUMA aware memory/task placement.
916 The mechanism is quite primitive and is based on migrating memory when
917 it has references to the node the task is running on.
919 This system will be inactive on UMA systems.
922 boolean "Control Group support"
925 This option adds support for grouping sets of processes together, for
926 use with process control subsystems such as Cpusets, CFS, memory
927 controls or device isolation.
929 - Documentation/scheduler/sched-design-CFS.txt (CFS)
930 - Documentation/cgroups/ (features for grouping, isolation
931 and resource control)
938 bool "Example debug cgroup subsystem"
941 This option enables a simple cgroup subsystem that
942 exports useful debugging information about the cgroups
947 config CGROUP_FREEZER
948 bool "Freezer cgroup subsystem"
950 Provides a way to freeze and unfreeze all tasks in a
954 bool "Device controller for cgroups"
956 Provides a cgroup implementing whitelists for devices which
957 a process in the cgroup can mknod or open.
960 bool "Cpuset support"
962 This option will let you create and manage CPUSETs which
963 allow dynamically partitioning a system into sets of CPUs and
964 Memory Nodes and assigning tasks to run only within those sets.
965 This is primarily useful on large SMP or NUMA systems.
969 config PROC_PID_CPUSET
970 bool "Include legacy /proc/<pid>/cpuset file"
974 config CGROUP_CPUACCT
975 bool "Simple CPU accounting cgroup subsystem"
977 Provides a simple Resource Controller for monitoring the
978 total CPU consumed by the tasks in a cgroup.
980 config RESOURCE_COUNTERS
981 bool "Resource counters"
983 This option enables controller independent resource accounting
984 infrastructure that works with cgroups.
987 bool "Memory Resource Controller for Control Groups"
988 depends on RESOURCE_COUNTERS
991 Provides a memory resource controller that manages both anonymous
992 memory and page cache. (See Documentation/cgroups/memory.txt)
994 Note that setting this option increases fixed memory overhead
995 associated with each page of memory in the system. By this,
996 8(16)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
997 usage tracking struct at boot. Total amount of this is printed out
1000 Only enable when you're ok with these trade offs and really
1001 sure you need the memory resource controller. Even when you enable
1002 this, you can set "cgroup_disable=memory" at your boot option to
1003 disable memory resource controller and you can avoid overheads.
1004 (and lose benefits of memory resource controller)
1007 bool "Memory Resource Controller Swap Extension"
1008 depends on MEMCG && SWAP
1010 Add swap management feature to memory resource controller. When you
1011 enable this, you can limit mem+swap usage per cgroup. In other words,
1012 when you disable this, memory resource controller has no cares to
1013 usage of swap...a process can exhaust all of the swap. This extension
1014 is useful when you want to avoid exhaustion swap but this itself
1015 adds more overheads and consumes memory for remembering information.
1016 Especially if you use 32bit system or small memory system, please
1017 be careful about enabling this. When memory resource controller
1018 is disabled by boot option, this will be automatically disabled and
1019 there will be no overhead from this. Even when you set this config=y,
1020 if boot option "swapaccount=0" is set, swap will not be accounted.
1021 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
1022 size is 4096bytes, 512k per 1Gbytes of swap.
1023 config MEMCG_SWAP_ENABLED
1024 bool "Memory Resource Controller Swap Extension enabled by default"
1025 depends on MEMCG_SWAP
1028 Memory Resource Controller Swap Extension comes with its price in
1029 a bigger memory consumption. General purpose distribution kernels
1030 which want to enable the feature but keep it disabled by default
1031 and let the user enable it by swapaccount=1 boot command line
1032 parameter should have this option unselected.
1033 For those who want to have the feature enabled by default should
1034 select this option (if, for some reason, they need to disable it
1035 then swapaccount=0 does the trick).
1037 bool "Memory Resource Controller Kernel Memory accounting"
1039 depends on SLUB || SLAB
1041 The Kernel Memory extension for Memory Resource Controller can limit
1042 the amount of memory used by kernel objects in the system. Those are
1043 fundamentally different from the entities handled by the standard
1044 Memory Controller, which are page-based, and can be swapped. Users of
1045 the kmem extension can use it to guarantee that no group of processes
1046 will ever exhaust kernel resources alone.
1048 WARNING: Current implementation lacks reclaim support. That means
1049 allocation attempts will fail when close to the limit even if there
1050 are plenty of kmem available for reclaim. That makes this option
1051 unusable in real life so DO NOT SELECT IT unless for development
1054 config CGROUP_HUGETLB
1055 bool "HugeTLB Resource Controller for Control Groups"
1056 depends on RESOURCE_COUNTERS && HUGETLB_PAGE
1059 Provides a cgroup Resource Controller for HugeTLB pages.
1060 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1061 The limit is enforced during page fault. Since HugeTLB doesn't
1062 support page reclaim, enforcing the limit at page fault time implies
1063 that, the application will get SIGBUS signal if it tries to access
1064 HugeTLB pages beyond its limit. This requires the application to know
1065 beforehand how much HugeTLB pages it would require for its use. The
1066 control group is tracked in the third page lru pointer. This means
1067 that we cannot use the controller with huge page less than 3 pages.
1070 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1071 depends on PERF_EVENTS && CGROUPS
1073 This option extends the per-cpu mode to restrict monitoring to
1074 threads which belong to the cgroup specified and run on the
1079 menuconfig CGROUP_SCHED
1080 bool "Group CPU scheduler"
1083 This feature lets CPU scheduler recognize task groups and control CPU
1084 bandwidth allocation to such task groups. It uses cgroups to group
1088 config FAIR_GROUP_SCHED
1089 bool "Group scheduling for SCHED_OTHER"
1090 depends on CGROUP_SCHED
1091 default CGROUP_SCHED
1093 config CFS_BANDWIDTH
1094 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1095 depends on FAIR_GROUP_SCHED
1098 This option allows users to define CPU bandwidth rates (limits) for
1099 tasks running within the fair group scheduler. Groups with no limit
1100 set are considered to be unconstrained and will run with no
1102 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1104 config RT_GROUP_SCHED
1105 bool "Group scheduling for SCHED_RR/FIFO"
1106 depends on CGROUP_SCHED
1109 This feature lets you explicitly allocate real CPU bandwidth
1110 to task groups. If enabled, it will also make it impossible to
1111 schedule realtime tasks for non-root users until you allocate
1112 realtime bandwidth for them.
1113 See Documentation/scheduler/sched-rt-group.txt for more information.
1118 bool "Block IO controller"
1122 Generic block IO controller cgroup interface. This is the common
1123 cgroup interface which should be used by various IO controlling
1126 Currently, CFQ IO scheduler uses it to recognize task groups and
1127 control disk bandwidth allocation (proportional time slice allocation)
1128 to such task groups. It is also used by bio throttling logic in
1129 block layer to implement upper limit in IO rates on a device.
1131 This option only enables generic Block IO controller infrastructure.
1132 One needs to also enable actual IO controlling logic/policy. For
1133 enabling proportional weight division of disk bandwidth in CFQ, set
1134 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1135 CONFIG_BLK_DEV_THROTTLING=y.
1137 See Documentation/cgroups/blkio-controller.txt for more information.
1139 config DEBUG_BLK_CGROUP
1140 bool "Enable Block IO controller debugging"
1141 depends on BLK_CGROUP
1144 Enable some debugging help. Currently it exports additional stat
1145 files in a cgroup which can be useful for debugging.
1149 config CHECKPOINT_RESTORE
1150 bool "Checkpoint/restore support" if EXPERT
1153 Enables additional kernel features in a sake of checkpoint/restore.
1154 In particular it adds auxiliary prctl codes to setup process text,
1155 data and heap segment sizes, and a few additional /proc filesystem
1158 If unsure, say N here.
1160 menuconfig NAMESPACES
1161 bool "Namespaces support" if EXPERT
1164 Provides the way to make tasks work with different objects using
1165 the same id. For example same IPC id may refer to different objects
1166 or same user id or pid may refer to different tasks when used in
1167 different namespaces.
1172 bool "UTS namespace"
1175 In this namespace tasks see different info provided with the
1179 bool "IPC namespace"
1180 depends on (SYSVIPC || POSIX_MQUEUE)
1183 In this namespace tasks work with IPC ids which correspond to
1184 different IPC objects in different namespaces.
1187 bool "User namespace"
1190 This allows containers, i.e. vservers, to use user namespaces
1191 to provide different user info for different servers.
1193 When user namespaces are enabled in the kernel it is
1194 recommended that the MEMCG and MEMCG_KMEM options also be
1195 enabled and that user-space use the memory control groups to
1196 limit the amount of memory a memory unprivileged users can
1202 bool "PID Namespaces"
1205 Support process id namespaces. This allows having multiple
1206 processes with the same pid as long as they are in different
1207 pid namespaces. This is a building block of containers.
1210 bool "Network namespace"
1214 Allow user space to create what appear to be multiple instances
1215 of the network stack.
1219 config SCHED_AUTOGROUP
1220 bool "Automatic process group scheduling"
1223 select FAIR_GROUP_SCHED
1225 This option optimizes the scheduler for common desktop workloads by
1226 automatically creating and populating task groups. This separation
1227 of workloads isolates aggressive CPU burners (like build jobs) from
1228 desktop applications. Task group autogeneration is currently based
1231 config SYSFS_DEPRECATED
1232 bool "Enable deprecated sysfs features to support old userspace tools"
1236 This option adds code that switches the layout of the "block" class
1237 devices, to not show up in /sys/class/block/, but only in
1240 This switch is only active when the sysfs.deprecated=1 boot option is
1241 passed or the SYSFS_DEPRECATED_V2 option is set.
1243 This option allows new kernels to run on old distributions and tools,
1244 which might get confused by /sys/class/block/. Since 2007/2008 all
1245 major distributions and tools handle this just fine.
1247 Recent distributions and userspace tools after 2009/2010 depend on
1248 the existence of /sys/class/block/, and will not work with this
1251 Only if you are using a new kernel on an old distribution, you might
1254 config SYSFS_DEPRECATED_V2
1255 bool "Enable deprecated sysfs features by default"
1258 depends on SYSFS_DEPRECATED
1260 Enable deprecated sysfs by default.
1262 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1265 Only if you are using a new kernel on an old distribution, you might
1266 need to say Y here. Even then, odds are you would not need it
1267 enabled, you can always pass the boot option if absolutely necessary.
1270 bool "Kernel->user space relay support (formerly relayfs)"
1272 This option enables support for relay interface support in
1273 certain file systems (such as debugfs).
1274 It is designed to provide an efficient mechanism for tools and
1275 facilities to relay large amounts of data from kernel space to
1280 config BLK_DEV_INITRD
1281 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1282 depends on BROKEN || !FRV
1284 The initial RAM filesystem is a ramfs which is loaded by the
1285 boot loader (loadlin or lilo) and that is mounted as root
1286 before the normal boot procedure. It is typically used to
1287 load modules needed to mount the "real" root file system,
1288 etc. See <file:Documentation/initrd.txt> for details.
1290 If RAM disk support (BLK_DEV_RAM) is also included, this
1291 also enables initial RAM disk (initrd) support and adds
1292 15 Kbytes (more on some other architectures) to the kernel size.
1298 source "usr/Kconfig"
1302 config CC_OPTIMIZE_FOR_SIZE
1303 bool "Optimize for size"
1305 Enabling this option will pass "-Os" instead of "-O2" to gcc
1306 resulting in a smaller kernel.
1319 config SYSCTL_EXCEPTION_TRACE
1322 Enable support for /proc/sys/debug/exception-trace.
1324 config SYSCTL_ARCH_UNALIGN_NO_WARN
1327 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1328 Allows arch to define/use @no_unaligned_warning to possibly warn
1329 about unaligned access emulation going on under the hood.
1331 config SYSCTL_ARCH_UNALIGN_ALLOW
1334 Enable support for /proc/sys/kernel/unaligned-trap
1335 Allows arches to define/use @unaligned_enabled to runtime toggle
1336 the unaligned access emulation.
1337 see arch/parisc/kernel/unaligned.c for reference
1339 config HAVE_PCSPKR_PLATFORM
1343 bool "Configure standard kernel features (expert users)"
1344 # Unhide debug options, to make the on-by-default options visible
1347 This option allows certain base kernel options and settings
1348 to be disabled or tweaked. This is for specialized
1349 environments which can tolerate a "non-standard" kernel.
1350 Only use this if you really know what you are doing.
1353 bool "Enable 16-bit UID system calls" if EXPERT
1354 depends on HAVE_UID16
1357 This enables the legacy 16-bit UID syscall wrappers.
1359 config SGETMASK_SYSCALL
1360 bool "sgetmask/ssetmask syscalls support" if EXPERT
1361 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1363 sys_sgetmask and sys_ssetmask are obsolete system calls
1364 no longer supported in libc but still enabled by default in some
1367 If unsure, leave the default option here.
1369 config SYSFS_SYSCALL
1370 bool "Sysfs syscall support" if EXPERT
1373 sys_sysfs is an obsolete system call no longer supported in libc.
1374 Note that disabling this option is more secure but might break
1375 compatibility with some systems.
1377 If unsure say Y here.
1379 config SYSCTL_SYSCALL
1380 bool "Sysctl syscall support" if EXPERT
1381 depends on PROC_SYSCTL
1385 sys_sysctl uses binary paths that have been found challenging
1386 to properly maintain and use. The interface in /proc/sys
1387 using paths with ascii names is now the primary path to this
1390 Almost nothing using the binary sysctl interface so if you are
1391 trying to save some space it is probably safe to disable this,
1392 making your kernel marginally smaller.
1394 If unsure say N here.
1397 bool "Load all symbols for debugging/ksymoops" if EXPERT
1400 Say Y here to let the kernel print out symbolic crash information and
1401 symbolic stack backtraces. This increases the size of the kernel
1402 somewhat, as all symbols have to be loaded into the kernel image.
1405 bool "Include all symbols in kallsyms"
1406 depends on DEBUG_KERNEL && KALLSYMS
1408 Normally kallsyms only contains the symbols of functions for nicer
1409 OOPS messages and backtraces (i.e., symbols from the text and inittext
1410 sections). This is sufficient for most cases. And only in very rare
1411 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1412 names of variables from the data sections, etc).
1414 This option makes sure that all symbols are loaded into the kernel
1415 image (i.e., symbols from all sections) in cost of increased kernel
1416 size (depending on the kernel configuration, it may be 300KiB or
1417 something like this).
1419 Say N unless you really need all symbols.
1423 bool "Enable support for printk" if EXPERT
1426 This option enables normal printk support. Removing it
1427 eliminates most of the message strings from the kernel image
1428 and makes the kernel more or less silent. As this makes it
1429 very difficult to diagnose system problems, saying N here is
1430 strongly discouraged.
1433 bool "BUG() support" if EXPERT
1436 Disabling this option eliminates support for BUG and WARN, reducing
1437 the size of your kernel image and potentially quietly ignoring
1438 numerous fatal conditions. You should only consider disabling this
1439 option for embedded systems with no facilities for reporting errors.
1445 bool "Enable ELF core dumps" if EXPERT
1447 Enable support for generating core dumps. Disabling saves about 4k.
1450 config PCSPKR_PLATFORM
1451 bool "Enable PC-Speaker support" if EXPERT
1452 depends on HAVE_PCSPKR_PLATFORM
1456 This option allows to disable the internal PC-Speaker
1457 support, saving some memory.
1461 bool "Enable full-sized data structures for core" if EXPERT
1463 Disabling this option reduces the size of miscellaneous core
1464 kernel data structures. This saves memory on small machines,
1465 but may reduce performance.
1468 bool "Enable futex support" if EXPERT
1472 Disabling this option will cause the kernel to be built without
1473 support for "fast userspace mutexes". The resulting kernel may not
1474 run glibc-based applications correctly.
1476 config HAVE_FUTEX_CMPXCHG
1479 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1480 is implemented and always working. This removes a couple of runtime
1484 bool "Enable eventpoll support" if EXPERT
1488 Disabling this option will cause the kernel to be built without
1489 support for epoll family of system calls.
1492 bool "Enable signalfd() system call" if EXPERT
1496 Enable the signalfd() system call that allows to receive signals
1497 on a file descriptor.
1502 bool "Enable timerfd() system call" if EXPERT
1506 Enable the timerfd() system call that allows to receive timer
1507 events on a file descriptor.
1512 bool "Enable eventfd() system call" if EXPERT
1516 Enable the eventfd() system call that allows to receive both
1517 kernel notification (ie. KAIO) or userspace notifications.
1522 bool "Use full shmem filesystem" if EXPERT
1526 The shmem is an internal filesystem used to manage shared memory.
1527 It is backed by swap and manages resource limits. It is also exported
1528 to userspace as tmpfs if TMPFS is enabled. Disabling this
1529 option replaces shmem and tmpfs with the much simpler ramfs code,
1530 which may be appropriate on small systems without swap.
1533 bool "Enable AIO support" if EXPERT
1536 This option enables POSIX asynchronous I/O which may by used
1537 by some high performance threaded applications. Disabling
1538 this option saves about 7k.
1542 bool "Enable PCI quirk workarounds" if EXPERT
1545 This enables workarounds for various PCI chipset
1546 bugs/quirks. Disable this only if your target machine is
1547 unaffected by PCI quirks.
1550 bool "Embedded system"
1551 option allnoconfig_y
1554 This option should be enabled if compiling the kernel for
1555 an embedded system so certain expert options are available
1558 config HAVE_PERF_EVENTS
1561 See tools/perf/design.txt for details.
1563 config PERF_USE_VMALLOC
1566 See tools/perf/design.txt for details
1568 menu "Kernel Performance Events And Counters"
1571 bool "Kernel performance events and counters"
1572 default y if PROFILING
1573 depends on HAVE_PERF_EVENTS
1577 Enable kernel support for various performance events provided
1578 by software and hardware.
1580 Software events are supported either built-in or via the
1581 use of generic tracepoints.
1583 Most modern CPUs support performance events via performance
1584 counter registers. These registers count the number of certain
1585 types of hw events: such as instructions executed, cachemisses
1586 suffered, or branches mis-predicted - without slowing down the
1587 kernel or applications. These registers can also trigger interrupts
1588 when a threshold number of events have passed - and can thus be
1589 used to profile the code that runs on that CPU.
1591 The Linux Performance Event subsystem provides an abstraction of
1592 these software and hardware event capabilities, available via a
1593 system call and used by the "perf" utility in tools/perf/. It
1594 provides per task and per CPU counters, and it provides event
1595 capabilities on top of those.
1599 config DEBUG_PERF_USE_VMALLOC
1601 bool "Debug: use vmalloc to back perf mmap() buffers"
1602 depends on PERF_EVENTS && DEBUG_KERNEL
1603 select PERF_USE_VMALLOC
1605 Use vmalloc memory to back perf mmap() buffers.
1607 Mostly useful for debugging the vmalloc code on platforms
1608 that don't require it.
1614 config VM_EVENT_COUNTERS
1616 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1618 VM event counters are needed for event counts to be shown.
1619 This option allows the disabling of the VM event counters
1620 on EXPERT systems. /proc/vmstat will only show page counts
1621 if VM event counters are disabled.
1625 bool "Enable SLUB debugging support" if EXPERT
1626 depends on SLUB && SYSFS
1628 SLUB has extensive debug support features. Disabling these can
1629 result in significant savings in code size. This also disables
1630 SLUB sysfs support. /sys/slab will not exist and there will be
1631 no support for cache validation etc.
1634 bool "Disable heap randomization"
1637 Randomizing heap placement makes heap exploits harder, but it
1638 also breaks ancient binaries (including anything libc5 based).
1639 This option changes the bootup default to heap randomization
1640 disabled, and can be overridden at runtime by setting
1641 /proc/sys/kernel/randomize_va_space to 2.
1643 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1646 prompt "Choose SLAB allocator"
1649 This option allows to select a slab allocator.
1654 The regular slab allocator that is established and known to work
1655 well in all environments. It organizes cache hot objects in
1656 per cpu and per node queues.
1659 bool "SLUB (Unqueued Allocator)"
1661 SLUB is a slab allocator that minimizes cache line usage
1662 instead of managing queues of cached objects (SLAB approach).
1663 Per cpu caching is realized using slabs of objects instead
1664 of queues of objects. SLUB can use memory efficiently
1665 and has enhanced diagnostics. SLUB is the default choice for
1670 bool "SLOB (Simple Allocator)"
1672 SLOB replaces the stock allocator with a drastically simpler
1673 allocator. SLOB is generally more space efficient but
1674 does not perform as well on large systems.
1678 config SLUB_CPU_PARTIAL
1680 depends on SLUB && SMP
1681 bool "SLUB per cpu partial cache"
1683 Per cpu partial caches accellerate objects allocation and freeing
1684 that is local to a processor at the price of more indeterminism
1685 in the latency of the free. On overflow these caches will be cleared
1686 which requires the taking of locks that may cause latency spikes.
1687 Typically one would choose no for a realtime system.
1689 config MMAP_ALLOW_UNINITIALIZED
1690 bool "Allow mmapped anonymous memory to be uninitialized"
1691 depends on EXPERT && !MMU
1694 Normally, and according to the Linux spec, anonymous memory obtained
1695 from mmap() has it's contents cleared before it is passed to
1696 userspace. Enabling this config option allows you to request that
1697 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1698 providing a huge performance boost. If this option is not enabled,
1699 then the flag will be ignored.
1701 This is taken advantage of by uClibc's malloc(), and also by
1702 ELF-FDPIC binfmt's brk and stack allocator.
1704 Because of the obvious security issues, this option should only be
1705 enabled on embedded devices where you control what is run in
1706 userspace. Since that isn't generally a problem on no-MMU systems,
1707 it is normally safe to say Y here.
1709 See Documentation/nommu-mmap.txt for more information.
1711 config SYSTEM_TRUSTED_KEYRING
1712 bool "Provide system-wide ring of trusted keys"
1715 Provide a system keyring to which trusted keys can be added. Keys in
1716 the keyring are considered to be trusted. Keys may be added at will
1717 by the kernel from compiled-in data and from hardware key stores, but
1718 userspace may only add extra keys if those keys can be verified by
1719 keys already in the keyring.
1721 Keys in this keyring are used by module signature checking.
1724 bool "Profiling support"
1726 Say Y here to enable the extended profiling support mechanisms used
1727 by profilers such as OProfile.
1730 # Place an empty function call at each tracepoint site. Can be
1731 # dynamically changed for a probe function.
1736 source "arch/Kconfig"
1738 endmenu # General setup
1740 config HAVE_GENERIC_DMA_COHERENT
1747 depends on SLAB || SLUB_DEBUG
1755 default 0 if BASE_FULL
1756 default 1 if !BASE_FULL
1759 bool "Enable loadable module support"
1762 Kernel modules are small pieces of compiled code which can
1763 be inserted in the running kernel, rather than being
1764 permanently built into the kernel. You use the "modprobe"
1765 tool to add (and sometimes remove) them. If you say Y here,
1766 many parts of the kernel can be built as modules (by
1767 answering M instead of Y where indicated): this is most
1768 useful for infrequently used options which are not required
1769 for booting. For more information, see the man pages for
1770 modprobe, lsmod, modinfo, insmod and rmmod.
1772 If you say Y here, you will need to run "make
1773 modules_install" to put the modules under /lib/modules/
1774 where modprobe can find them (you may need to be root to do
1781 config MODULE_FORCE_LOAD
1782 bool "Forced module loading"
1785 Allow loading of modules without version information (ie. modprobe
1786 --force). Forced module loading sets the 'F' (forced) taint flag and
1787 is usually a really bad idea.
1789 config MODULE_UNLOAD
1790 bool "Module unloading"
1792 Without this option you will not be able to unload any
1793 modules (note that some modules may not be unloadable
1794 anyway), which makes your kernel smaller, faster
1795 and simpler. If unsure, say Y.
1797 config MODULE_FORCE_UNLOAD
1798 bool "Forced module unloading"
1799 depends on MODULE_UNLOAD
1801 This option allows you to force a module to unload, even if the
1802 kernel believes it is unsafe: the kernel will remove the module
1803 without waiting for anyone to stop using it (using the -f option to
1804 rmmod). This is mainly for kernel developers and desperate users.
1808 bool "Module versioning support"
1810 Usually, you have to use modules compiled with your kernel.
1811 Saying Y here makes it sometimes possible to use modules
1812 compiled for different kernels, by adding enough information
1813 to the modules to (hopefully) spot any changes which would
1814 make them incompatible with the kernel you are running. If
1817 config MODULE_SRCVERSION_ALL
1818 bool "Source checksum for all modules"
1820 Modules which contain a MODULE_VERSION get an extra "srcversion"
1821 field inserted into their modinfo section, which contains a
1822 sum of the source files which made it. This helps maintainers
1823 see exactly which source was used to build a module (since
1824 others sometimes change the module source without updating
1825 the version). With this option, such a "srcversion" field
1826 will be created for all modules. If unsure, say N.
1829 bool "Module signature verification"
1831 select SYSTEM_TRUSTED_KEYRING
1834 select ASYMMETRIC_KEY_TYPE
1835 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1836 select PUBLIC_KEY_ALGO_RSA
1839 select X509_CERTIFICATE_PARSER
1841 Check modules for valid signatures upon load: the signature
1842 is simply appended to the module. For more information see
1843 Documentation/module-signing.txt.
1845 !!!WARNING!!! If you enable this option, you MUST make sure that the
1846 module DOES NOT get stripped after being signed. This includes the
1847 debuginfo strip done by some packagers (such as rpmbuild) and
1848 inclusion into an initramfs that wants the module size reduced.
1850 config MODULE_SIG_FORCE
1851 bool "Require modules to be validly signed"
1852 depends on MODULE_SIG
1854 Reject unsigned modules or signed modules for which we don't have a
1855 key. Without this, such modules will simply taint the kernel.
1857 config MODULE_SIG_ALL
1858 bool "Automatically sign all modules"
1860 depends on MODULE_SIG
1862 Sign all modules during make modules_install. Without this option,
1863 modules must be signed manually, using the scripts/sign-file tool.
1865 comment "Do not forget to sign required modules with scripts/sign-file"
1866 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1869 prompt "Which hash algorithm should modules be signed with?"
1870 depends on MODULE_SIG
1872 This determines which sort of hashing algorithm will be used during
1873 signature generation. This algorithm _must_ be built into the kernel
1874 directly so that signature verification can take place. It is not
1875 possible to load a signed module containing the algorithm to check
1876 the signature on that module.
1878 config MODULE_SIG_SHA1
1879 bool "Sign modules with SHA-1"
1882 config MODULE_SIG_SHA224
1883 bool "Sign modules with SHA-224"
1884 select CRYPTO_SHA256
1886 config MODULE_SIG_SHA256
1887 bool "Sign modules with SHA-256"
1888 select CRYPTO_SHA256
1890 config MODULE_SIG_SHA384
1891 bool "Sign modules with SHA-384"
1892 select CRYPTO_SHA512
1894 config MODULE_SIG_SHA512
1895 bool "Sign modules with SHA-512"
1896 select CRYPTO_SHA512
1900 config MODULE_SIG_HASH
1902 depends on MODULE_SIG
1903 default "sha1" if MODULE_SIG_SHA1
1904 default "sha224" if MODULE_SIG_SHA224
1905 default "sha256" if MODULE_SIG_SHA256
1906 default "sha384" if MODULE_SIG_SHA384
1907 default "sha512" if MODULE_SIG_SHA512
1911 config INIT_ALL_POSSIBLE
1914 Back when each arch used to define their own cpu_online_mask and
1915 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1916 with all 1s, and others with all 0s. When they were centralised,
1917 it was better to provide this option than to break all the archs
1918 and have several arch maintainers pursuing me down dark alleys.
1923 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1925 Need stop_machine() primitive.
1927 source "block/Kconfig"
1929 config PREEMPT_NOTIFIERS
1936 # Can be selected by architectures with broken toolchains
1937 # that get confused by correct const<->read_only section
1939 config BROKEN_RODATA
1945 Build a simple ASN.1 grammar compiler that produces a bytecode output
1946 that can be interpreted by the ASN.1 stream decoder and used to
1947 inform it as to what tags are to be expected in a stream and what
1948 functions to call on what tags.
1950 source "kernel/Kconfig.locks"
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