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.
211 config VERSION_SIGNATURE
212 string "Arbitrary version signature"
214 This string will be created in a file, /proc/version_signature. It
215 is useful in determining arbitrary data about your kernel. For instance,
216 if you have several kernels of the same version, but need to keep track
217 of a revision of the same kernel, but not affect it's ability to load
218 compatible modules, this is the easiest way to do that.
221 bool "Support for paging of anonymous memory (swap)"
222 depends on MMU && BLOCK
225 This option allows you to choose whether you want to have support
226 for so called swap devices or swap files in your kernel that are
227 used to provide more virtual memory than the actual RAM present
228 in your computer. If unsure say Y.
233 Inter Process Communication is a suite of library functions and
234 system calls which let processes (running programs) synchronize and
235 exchange information. It is generally considered to be a good thing,
236 and some programs won't run unless you say Y here. In particular, if
237 you want to run the DOS emulator dosemu under Linux (read the
238 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
239 you'll need to say Y here.
241 You can find documentation about IPC with "info ipc" and also in
242 section 6.4 of the Linux Programmer's Guide, available from
243 <http://www.tldp.org/guides.html>.
245 config SYSVIPC_SYSCTL
252 bool "POSIX Message Queues"
255 POSIX variant of message queues is a part of IPC. In POSIX message
256 queues every message has a priority which decides about succession
257 of receiving it by a process. If you want to compile and run
258 programs written e.g. for Solaris with use of its POSIX message
259 queues (functions mq_*) say Y here.
261 POSIX message queues are visible as a filesystem called 'mqueue'
262 and can be mounted somewhere if you want to do filesystem
263 operations on message queues.
267 config POSIX_MQUEUE_SYSCTL
269 depends on POSIX_MQUEUE
273 config CROSS_MEMORY_ATTACH
274 bool "Enable process_vm_readv/writev syscalls"
278 Enabling this option adds the system calls process_vm_readv and
279 process_vm_writev which allow a process with the correct privileges
280 to directly read from or write to another process' address space.
281 See the man page for more details.
284 bool "open by fhandle syscalls"
287 If you say Y here, a user level program will be able to map
288 file names to handle and then later use the handle for
289 different file system operations. This is useful in implementing
290 userspace file servers, which now track files using handles instead
291 of names. The handle would remain the same even if file names
292 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
296 bool "uselib syscall"
299 This option enables the uselib syscall, a system call used in the
300 dynamic linker from libc5 and earlier. glibc does not use this
301 system call. If you intend to run programs built on libc5 or
302 earlier, you may need to enable this syscall. Current systems
303 running glibc can safely disable this.
306 bool "Auditing support"
309 Enable auditing infrastructure that can be used with another
310 kernel subsystem, such as SELinux (which requires this for
311 logging of avc messages output). Does not do system-call
312 auditing without CONFIG_AUDITSYSCALL.
314 config HAVE_ARCH_AUDITSYSCALL
318 bool "Enable system-call auditing support"
319 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
320 default y if SECURITY_SELINUX
322 Enable low-overhead system-call auditing infrastructure that
323 can be used independently or with another kernel subsystem,
328 depends on AUDITSYSCALL
333 depends on AUDITSYSCALL
336 source "kernel/irq/Kconfig"
337 source "kernel/time/Kconfig"
339 menu "CPU/Task time and stats accounting"
341 config VIRT_CPU_ACCOUNTING
345 prompt "Cputime accounting"
346 default TICK_CPU_ACCOUNTING if !PPC64
347 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
349 # Kind of a stub config for the pure tick based cputime accounting
350 config TICK_CPU_ACCOUNTING
351 bool "Simple tick based cputime accounting"
352 depends on !S390 && !NO_HZ_FULL
354 This is the basic tick based cputime accounting that maintains
355 statistics about user, system and idle time spent on per jiffies
360 config VIRT_CPU_ACCOUNTING_NATIVE
361 bool "Deterministic task and CPU time accounting"
362 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
363 select VIRT_CPU_ACCOUNTING
365 Select this option to enable more accurate task and CPU time
366 accounting. This is done by reading a CPU counter on each
367 kernel entry and exit and on transitions within the kernel
368 between system, softirq and hardirq state, so there is a
369 small performance impact. In the case of s390 or IBM POWER > 5,
370 this also enables accounting of stolen time on logically-partitioned
373 config VIRT_CPU_ACCOUNTING_GEN
374 bool "Full dynticks CPU time accounting"
375 depends on HAVE_CONTEXT_TRACKING
376 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
377 select VIRT_CPU_ACCOUNTING
378 select CONTEXT_TRACKING
380 Select this option to enable task and CPU time accounting on full
381 dynticks systems. This accounting is implemented by watching every
382 kernel-user boundaries using the context tracking subsystem.
383 The accounting is thus performed at the expense of some significant
386 For now this is only useful if you are working on the full
387 dynticks subsystem development.
391 config IRQ_TIME_ACCOUNTING
392 bool "Fine granularity task level IRQ time accounting"
393 depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
395 Select this option to enable fine granularity task irq time
396 accounting. This is done by reading a timestamp on each
397 transitions between softirq and hardirq state, so there can be a
398 small performance impact.
400 If in doubt, say N here.
404 config BSD_PROCESS_ACCT
405 bool "BSD Process Accounting"
408 If you say Y here, a user level program will be able to instruct the
409 kernel (via a special system call) to write process accounting
410 information to a file: whenever a process exits, information about
411 that process will be appended to the file by the kernel. The
412 information includes things such as creation time, owning user,
413 command name, memory usage, controlling terminal etc. (the complete
414 list is in the struct acct in <file:include/linux/acct.h>). It is
415 up to the user level program to do useful things with this
416 information. This is generally a good idea, so say Y.
418 config BSD_PROCESS_ACCT_V3
419 bool "BSD Process Accounting version 3 file format"
420 depends on BSD_PROCESS_ACCT
423 If you say Y here, the process accounting information is written
424 in a new file format that also logs the process IDs of each
425 process and it's parent. Note that this file format is incompatible
426 with previous v0/v1/v2 file formats, so you will need updated tools
427 for processing it. A preliminary version of these tools is available
428 at <http://www.gnu.org/software/acct/>.
431 bool "Export task/process statistics through netlink"
436 Export selected statistics for tasks/processes through the
437 generic netlink interface. Unlike BSD process accounting, the
438 statistics are available during the lifetime of tasks/processes as
439 responses to commands. Like BSD accounting, they are sent to user
444 config TASK_DELAY_ACCT
445 bool "Enable per-task delay accounting"
449 Collect information on time spent by a task waiting for system
450 resources like cpu, synchronous block I/O completion and swapping
451 in pages. Such statistics can help in setting a task's priorities
452 relative to other tasks for cpu, io, rss limits etc.
457 bool "Enable extended accounting over taskstats"
460 Collect extended task accounting data and send the data
461 to userland for processing over the taskstats interface.
465 config TASK_IO_ACCOUNTING
466 bool "Enable per-task storage I/O accounting"
467 depends on TASK_XACCT
469 Collect information on the number of bytes of storage I/O which this
474 endmenu # "CPU/Task time and stats accounting"
480 default y if !PREEMPT && SMP
482 This option selects the RCU implementation that is
483 designed for very large SMP system with hundreds or
484 thousands of CPUs. It also scales down nicely to
491 This option selects the RCU implementation that is
492 designed for very large SMP systems with hundreds or
493 thousands of CPUs, but for which real-time response
494 is also required. It also scales down nicely to
497 Select this option if you are unsure.
501 default y if !PREEMPT && !SMP
503 This option selects the RCU implementation that is
504 designed for UP systems from which real-time response
505 is not required. This option greatly reduces the
506 memory footprint of RCU.
509 bool "Make expert-level adjustments to RCU configuration"
512 This option needs to be enabled if you wish to make
513 expert-level adjustments to RCU configuration. By default,
514 no such adjustments can be made, which has the often-beneficial
515 side-effect of preventing "make oldconfig" from asking you all
516 sorts of detailed questions about how you would like numerous
517 obscure RCU options to be set up.
519 Say Y if you need to make expert-level adjustments to RCU.
521 Say N if you are unsure.
526 This option selects the sleepable version of RCU. This version
527 permits arbitrary sleeping or blocking within RCU read-side critical
535 This option enables a task-based RCU implementation that uses
536 only voluntary context switch (not preemption!), idle, and
537 user-mode execution as quiescent states.
539 config RCU_STALL_COMMON
540 def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
542 This option enables RCU CPU stall code that is common between
543 the TINY and TREE variants of RCU. The purpose is to allow
544 the tiny variants to disable RCU CPU stall warnings, while
545 making these warnings mandatory for the tree variants.
547 config CONTEXT_TRACKING
550 config CONTEXT_TRACKING_FORCE
551 bool "Force context tracking"
552 depends on CONTEXT_TRACKING
553 default y if !NO_HZ_FULL
555 The major pre-requirement for full dynticks to work is to
556 support the context tracking subsystem. But there are also
557 other dependencies to provide in order to make the full
560 This option stands for testing when an arch implements the
561 context tracking backend but doesn't yet fullfill all the
562 requirements to make the full dynticks feature working.
563 Without the full dynticks, there is no way to test the support
564 for context tracking and the subsystems that rely on it: RCU
565 userspace extended quiescent state and tickless cputime
566 accounting. This option copes with the absence of the full
567 dynticks subsystem by forcing the context tracking on all
570 Say Y only if you're working on the development of an
571 architecture backend for the context tracking.
573 Say N otherwise, this option brings an overhead that you
574 don't want in production.
578 int "Tree-based hierarchical RCU fanout value"
581 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
585 This option controls the fanout of hierarchical implementations
586 of RCU, allowing RCU to work efficiently on machines with
587 large numbers of CPUs. This value must be at least the fourth
588 root of NR_CPUS, which allows NR_CPUS to be insanely large.
589 The default value of RCU_FANOUT should be used for production
590 systems, but if you are stress-testing the RCU implementation
591 itself, small RCU_FANOUT values allow you to test large-system
592 code paths on small(er) systems.
594 Select a specific number if testing RCU itself.
595 Take the default if unsure.
597 config RCU_FANOUT_LEAF
598 int "Tree-based hierarchical RCU leaf-level fanout value"
601 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
604 This option controls the leaf-level fanout of hierarchical
605 implementations of RCU, and allows trading off cache misses
606 against lock contention. Systems that synchronize their
607 scheduling-clock interrupts for energy-efficiency reasons will
608 want the default because the smaller leaf-level fanout keeps
609 lock contention levels acceptably low. Very large systems
610 (hundreds or thousands of CPUs) will instead want to set this
611 value to the maximum value possible in order to reduce the
612 number of cache misses incurred during RCU's grace-period
613 initialization. These systems tend to run CPU-bound, and thus
614 are not helped by synchronized interrupts, and thus tend to
615 skew them, which reduces lock contention enough that large
616 leaf-level fanouts work well.
618 Select a specific number if testing RCU itself.
620 Select the maximum permissible value for large systems.
622 Take the default if unsure.
624 config RCU_FAST_NO_HZ
625 bool "Accelerate last non-dyntick-idle CPU's grace periods"
626 depends on NO_HZ_COMMON && SMP && RCU_EXPERT
629 This option permits CPUs to enter dynticks-idle state even if
630 they have RCU callbacks queued, and prevents RCU from waking
631 these CPUs up more than roughly once every four jiffies (by
632 default, you can adjust this using the rcutree.rcu_idle_gp_delay
633 parameter), thus improving energy efficiency. On the other
634 hand, this option increases the duration of RCU grace periods,
635 for example, slowing down synchronize_rcu().
637 Say Y if energy efficiency is critically important, and you
638 don't care about increased grace-period durations.
640 Say N if you are unsure.
642 config TREE_RCU_TRACE
643 def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
646 This option provides tracing for the TREE_RCU and
647 PREEMPT_RCU implementations, permitting Makefile to
648 trivially select kernel/rcutree_trace.c.
651 bool "Enable RCU priority boosting"
652 depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT
655 This option boosts the priority of preempted RCU readers that
656 block the current preemptible RCU grace period for too long.
657 This option also prevents heavy loads from blocking RCU
658 callback invocation for all flavors of RCU.
660 Say Y here if you are working with real-time apps or heavy loads
661 Say N here if you are unsure.
663 config RCU_KTHREAD_PRIO
664 int "Real-time priority to use for RCU worker threads"
665 range 1 99 if RCU_BOOST
666 range 0 99 if !RCU_BOOST
667 default 1 if RCU_BOOST
668 default 0 if !RCU_BOOST
669 depends on RCU_EXPERT
671 This option specifies the SCHED_FIFO priority value that will be
672 assigned to the rcuc/n and rcub/n threads and is also the value
673 used for RCU_BOOST (if enabled). If you are working with a
674 real-time application that has one or more CPU-bound threads
675 running at a real-time priority level, you should set
676 RCU_KTHREAD_PRIO to a priority higher than the highest-priority
677 real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO
678 value of 1 is appropriate in the common case, which is real-time
679 applications that do not have any CPU-bound threads.
681 Some real-time applications might not have a single real-time
682 thread that saturates a given CPU, but instead might have
683 multiple real-time threads that, taken together, fully utilize
684 that CPU. In this case, you should set RCU_KTHREAD_PRIO to
685 a priority higher than the lowest-priority thread that is
686 conspiring to prevent the CPU from running any non-real-time
687 tasks. For example, if one thread at priority 10 and another
688 thread at priority 5 are between themselves fully consuming
689 the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
690 set to priority 6 or higher.
692 Specify the real-time priority, or take the default if unsure.
694 config RCU_BOOST_DELAY
695 int "Milliseconds to delay boosting after RCU grace-period start"
700 This option specifies the time to wait after the beginning of
701 a given grace period before priority-boosting preempted RCU
702 readers blocking that grace period. Note that any RCU reader
703 blocking an expedited RCU grace period is boosted immediately.
705 Accept the default if unsure.
708 bool "Offload RCU callback processing from boot-selected CPUs"
709 depends on TREE_RCU || PREEMPT_RCU
710 depends on RCU_EXPERT || NO_HZ_FULL
713 Use this option to reduce OS jitter for aggressive HPC or
714 real-time workloads. It can also be used to offload RCU
715 callback invocation to energy-efficient CPUs in battery-powered
716 asymmetric multiprocessors.
718 This option offloads callback invocation from the set of
719 CPUs specified at boot time by the rcu_nocbs parameter.
720 For each such CPU, a kthread ("rcuox/N") will be created to
721 invoke callbacks, where the "N" is the CPU being offloaded,
722 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
723 "s" for RCU-sched. Nothing prevents this kthread from running
724 on the specified CPUs, but (1) the kthreads may be preempted
725 between each callback, and (2) affinity or cgroups can be used
726 to force the kthreads to run on whatever set of CPUs is desired.
728 Say Y here if you want to help to debug reduced OS jitter.
729 Say N here if you are unsure.
732 prompt "Build-forced no-CBs CPUs"
733 default RCU_NOCB_CPU_NONE
734 depends on RCU_NOCB_CPU
736 This option allows no-CBs CPUs (whose RCU callbacks are invoked
737 from kthreads rather than from softirq context) to be specified
738 at build time. Additional no-CBs CPUs may be specified by
739 the rcu_nocbs= boot parameter.
741 config RCU_NOCB_CPU_NONE
742 bool "No build_forced no-CBs CPUs"
744 This option does not force any of the CPUs to be no-CBs CPUs.
745 Only CPUs designated by the rcu_nocbs= boot parameter will be
746 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
747 kthreads whose names begin with "rcuo". All other CPUs will
748 invoke their own RCU callbacks in softirq context.
750 Select this option if you want to choose no-CBs CPUs at
751 boot time, for example, to allow testing of different no-CBs
752 configurations without having to rebuild the kernel each time.
754 config RCU_NOCB_CPU_ZERO
755 bool "CPU 0 is a build_forced no-CBs CPU"
757 This option forces CPU 0 to be a no-CBs CPU, so that its RCU
758 callbacks are invoked by a per-CPU kthread whose name begins
759 with "rcuo". Additional CPUs may be designated as no-CBs
760 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
761 All other CPUs will invoke their own RCU callbacks in softirq
764 Select this if CPU 0 needs to be a no-CBs CPU for real-time
765 or energy-efficiency reasons, but the real reason it exists
766 is to ensure that randconfig testing covers mixed systems.
768 config RCU_NOCB_CPU_ALL
769 bool "All CPUs are build_forced no-CBs CPUs"
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 config RCU_EXPEDITE_BOOT
788 This option enables expedited grace periods at boot time,
789 as if rcu_expedite_gp() had been invoked early in boot.
790 The corresponding rcu_unexpedite_gp() is invoked from
791 rcu_end_inkernel_boot(), which is intended to be invoked
792 at the end of the kernel-only boot sequence, just before
795 Accept the default if unsure.
797 endmenu # "RCU Subsystem"
804 tristate "Kernel .config support"
807 This option enables the complete Linux kernel ".config" file
808 contents to be saved in the kernel. It provides documentation
809 of which kernel options are used in a running kernel or in an
810 on-disk kernel. This information can be extracted from the kernel
811 image file with the script scripts/extract-ikconfig and used as
812 input to rebuild the current kernel or to build another kernel.
813 It can also be extracted from a running kernel by reading
814 /proc/config.gz if enabled (below).
817 bool "Enable access to .config through /proc/config.gz"
818 depends on IKCONFIG && PROC_FS
820 This option enables access to the kernel configuration file
821 through /proc/config.gz.
824 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
829 Select the minimal kernel log buffer size as a power of 2.
830 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
831 parameter, see below. Any higher size also might be forced
832 by "log_buf_len" boot parameter.
842 config LOG_CPU_MAX_BUF_SHIFT
843 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
846 default 12 if !BASE_SMALL
847 default 0 if BASE_SMALL
850 This option allows to increase the default ring buffer size
851 according to the number of CPUs. The value defines the contribution
852 of each CPU as a power of 2. The used space is typically only few
853 lines however it might be much more when problems are reported,
856 The increased size means that a new buffer has to be allocated and
857 the original static one is unused. It makes sense only on systems
858 with more CPUs. Therefore this value is used only when the sum of
859 contributions is greater than the half of the default kernel ring
860 buffer as defined by LOG_BUF_SHIFT. The default values are set
861 so that more than 64 CPUs are needed to trigger the allocation.
863 Also this option is ignored when "log_buf_len" kernel parameter is
864 used as it forces an exact (power of two) size of the ring buffer.
866 The number of possible CPUs is used for this computation ignoring
867 hotplugging making the compuation optimal for the the worst case
868 scenerio while allowing a simple algorithm to be used from bootup.
870 Examples shift values and their meaning:
871 17 => 128 KB for each CPU
872 16 => 64 KB for each CPU
873 15 => 32 KB for each CPU
874 14 => 16 KB for each CPU
875 13 => 8 KB for each CPU
876 12 => 4 KB for each CPU
879 # Architectures with an unreliable sched_clock() should select this:
881 config HAVE_UNSTABLE_SCHED_CLOCK
884 config GENERIC_SCHED_CLOCK
888 # For architectures that want to enable the support for NUMA-affine scheduler
891 config ARCH_SUPPORTS_NUMA_BALANCING
895 # For architectures that prefer to flush all TLBs after a number of pages
896 # are unmapped instead of sending one IPI per page to flush. The architecture
897 # must provide guarantees on what happens if a clean TLB cache entry is
898 # written after the unmap. Details are in mm/rmap.c near the check for
899 # should_defer_flush. The architecture should also consider if the full flush
900 # and the refill costs are offset by the savings of sending fewer IPIs.
901 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
905 # For architectures that know their GCC __int128 support is sound
907 config ARCH_SUPPORTS_INT128
910 # For architectures that (ab)use NUMA to represent different memory regions
911 # all cpu-local but of different latencies, such as SuperH.
913 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
916 config NUMA_BALANCING
917 bool "Memory placement aware NUMA scheduler"
918 depends on ARCH_SUPPORTS_NUMA_BALANCING
919 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
920 depends on SMP && NUMA && MIGRATION
922 This option adds support for automatic NUMA aware memory/task placement.
923 The mechanism is quite primitive and is based on migrating memory when
924 it has references to the node the task is running on.
926 This system will be inactive on UMA systems.
928 config NUMA_BALANCING_DEFAULT_ENABLED
929 bool "Automatically enable NUMA aware memory/task placement"
931 depends on NUMA_BALANCING
933 If set, automatic NUMA balancing will be enabled if running on a NUMA
937 bool "Control Group support"
940 This option adds support for grouping sets of processes together, for
941 use with process control subsystems such as Cpusets, CFS, memory
942 controls or device isolation.
944 - Documentation/scheduler/sched-design-CFS.txt (CFS)
945 - Documentation/cgroups/ (features for grouping, isolation
946 and resource control)
953 bool "Example debug cgroup subsystem"
956 This option enables a simple cgroup subsystem that
957 exports useful debugging information about the cgroups
962 config CGROUP_FREEZER
963 bool "Freezer cgroup subsystem"
965 Provides a way to freeze and unfreeze all tasks in a
969 bool "PIDs cgroup subsystem"
971 Provides enforcement of process number limits in the scope of a
972 cgroup. Any attempt to fork more processes than is allowed in the
973 cgroup will fail. PIDs are fundamentally a global resource because it
974 is fairly trivial to reach PID exhaustion before you reach even a
975 conservative kmemcg limit. As a result, it is possible to grind a
976 system to halt without being limited by other cgroup policies. The
977 PIDs cgroup subsystem is designed to stop this from happening.
979 It should be noted that organisational operations (such as attaching
980 to a cgroup hierarchy will *not* be blocked by the PIDs subsystem),
981 since the PIDs limit only affects a process's ability to fork, not to
985 bool "Device controller for cgroups"
987 Provides a cgroup implementing whitelists for devices which
988 a process in the cgroup can mknod or open.
991 bool "Cpuset support"
993 This option will let you create and manage CPUSETs which
994 allow dynamically partitioning a system into sets of CPUs and
995 Memory Nodes and assigning tasks to run only within those sets.
996 This is primarily useful on large SMP or NUMA systems.
1000 config PROC_PID_CPUSET
1001 bool "Include legacy /proc/<pid>/cpuset file"
1005 config CGROUP_CPUACCT
1006 bool "Simple CPU accounting cgroup subsystem"
1008 Provides a simple Resource Controller for monitoring the
1009 total CPU consumed by the tasks in a cgroup.
1015 bool "Memory Resource Controller for Control Groups"
1019 Provides a memory resource controller that manages both anonymous
1020 memory and page cache. (See Documentation/cgroups/memory.txt)
1023 bool "Memory Resource Controller Swap Extension"
1024 depends on MEMCG && SWAP
1026 Add swap management feature to memory resource controller. When you
1027 enable this, you can limit mem+swap usage per cgroup. In other words,
1028 when you disable this, memory resource controller has no cares to
1029 usage of swap...a process can exhaust all of the swap. This extension
1030 is useful when you want to avoid exhaustion swap but this itself
1031 adds more overheads and consumes memory for remembering information.
1032 Especially if you use 32bit system or small memory system, please
1033 be careful about enabling this. When memory resource controller
1034 is disabled by boot option, this will be automatically disabled and
1035 there will be no overhead from this. Even when you set this config=y,
1036 if boot option "swapaccount=0" is set, swap will not be accounted.
1037 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
1038 size is 4096bytes, 512k per 1Gbytes of swap.
1039 config MEMCG_SWAP_ENABLED
1040 bool "Memory Resource Controller Swap Extension enabled by default"
1041 depends on MEMCG_SWAP
1044 Memory Resource Controller Swap Extension comes with its price in
1045 a bigger memory consumption. General purpose distribution kernels
1046 which want to enable the feature but keep it disabled by default
1047 and let the user enable it by swapaccount=1 boot command line
1048 parameter should have this option unselected.
1049 For those who want to have the feature enabled by default should
1050 select this option (if, for some reason, they need to disable it
1051 then swapaccount=0 does the trick).
1053 bool "Memory Resource Controller Kernel Memory accounting"
1055 depends on SLUB || SLAB
1057 The Kernel Memory extension for Memory Resource Controller can limit
1058 the amount of memory used by kernel objects in the system. Those are
1059 fundamentally different from the entities handled by the standard
1060 Memory Controller, which are page-based, and can be swapped. Users of
1061 the kmem extension can use it to guarantee that no group of processes
1062 will ever exhaust kernel resources alone.
1064 config CGROUP_HUGETLB
1065 bool "HugeTLB Resource Controller for Control Groups"
1066 depends on HUGETLB_PAGE
1070 Provides a cgroup Resource Controller for HugeTLB pages.
1071 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1072 The limit is enforced during page fault. Since HugeTLB doesn't
1073 support page reclaim, enforcing the limit at page fault time implies
1074 that, the application will get SIGBUS signal if it tries to access
1075 HugeTLB pages beyond its limit. This requires the application to know
1076 beforehand how much HugeTLB pages it would require for its use. The
1077 control group is tracked in the third page lru pointer. This means
1078 that we cannot use the controller with huge page less than 3 pages.
1081 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1082 depends on PERF_EVENTS && CGROUPS
1084 This option extends the per-cpu mode to restrict monitoring to
1085 threads which belong to the cgroup specified and run on the
1090 menuconfig CGROUP_SCHED
1091 bool "Group CPU scheduler"
1094 This feature lets CPU scheduler recognize task groups and control CPU
1095 bandwidth allocation to such task groups. It uses cgroups to group
1099 config FAIR_GROUP_SCHED
1100 bool "Group scheduling for SCHED_OTHER"
1101 depends on CGROUP_SCHED
1102 default CGROUP_SCHED
1104 config CFS_BANDWIDTH
1105 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1106 depends on FAIR_GROUP_SCHED
1109 This option allows users to define CPU bandwidth rates (limits) for
1110 tasks running within the fair group scheduler. Groups with no limit
1111 set are considered to be unconstrained and will run with no
1113 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1115 config RT_GROUP_SCHED
1116 bool "Group scheduling for SCHED_RR/FIFO"
1117 depends on CGROUP_SCHED
1120 This feature lets you explicitly allocate real CPU bandwidth
1121 to task groups. If enabled, it will also make it impossible to
1122 schedule realtime tasks for non-root users until you allocate
1123 realtime bandwidth for them.
1124 See Documentation/scheduler/sched-rt-group.txt for more information.
1129 bool "Block IO controller"
1133 Generic block IO controller cgroup interface. This is the common
1134 cgroup interface which should be used by various IO controlling
1137 Currently, CFQ IO scheduler uses it to recognize task groups and
1138 control disk bandwidth allocation (proportional time slice allocation)
1139 to such task groups. It is also used by bio throttling logic in
1140 block layer to implement upper limit in IO rates on a device.
1142 This option only enables generic Block IO controller infrastructure.
1143 One needs to also enable actual IO controlling logic/policy. For
1144 enabling proportional weight division of disk bandwidth in CFQ, set
1145 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1146 CONFIG_BLK_DEV_THROTTLING=y.
1148 See Documentation/cgroups/blkio-controller.txt for more information.
1150 config DEBUG_BLK_CGROUP
1151 bool "Enable Block IO controller debugging"
1152 depends on BLK_CGROUP
1155 Enable some debugging help. Currently it exports additional stat
1156 files in a cgroup which can be useful for debugging.
1158 config CGROUP_WRITEBACK
1160 depends on MEMCG && BLK_CGROUP
1165 config CHECKPOINT_RESTORE
1166 bool "Checkpoint/restore support" if EXPERT
1167 select PROC_CHILDREN
1170 Enables additional kernel features in a sake of checkpoint/restore.
1171 In particular it adds auxiliary prctl codes to setup process text,
1172 data and heap segment sizes, and a few additional /proc filesystem
1175 If unsure, say N here.
1177 menuconfig NAMESPACES
1178 bool "Namespaces support" if EXPERT
1179 depends on MULTIUSER
1182 Provides the way to make tasks work with different objects using
1183 the same id. For example same IPC id may refer to different objects
1184 or same user id or pid may refer to different tasks when used in
1185 different namespaces.
1190 bool "UTS namespace"
1193 In this namespace tasks see different info provided with the
1197 bool "IPC namespace"
1198 depends on (SYSVIPC || POSIX_MQUEUE)
1201 In this namespace tasks work with IPC ids which correspond to
1202 different IPC objects in different namespaces.
1205 bool "User namespace"
1208 This allows containers, i.e. vservers, to use user namespaces
1209 to provide different user info for different servers.
1211 When user namespaces are enabled in the kernel it is
1212 recommended that the MEMCG and MEMCG_KMEM options also be
1213 enabled and that user-space use the memory control groups to
1214 limit the amount of memory a memory unprivileged users can
1220 bool "PID Namespaces"
1223 Support process id namespaces. This allows having multiple
1224 processes with the same pid as long as they are in different
1225 pid namespaces. This is a building block of containers.
1228 bool "Network namespace"
1232 Allow user space to create what appear to be multiple instances
1233 of the network stack.
1237 config SCHED_AUTOGROUP
1238 bool "Automatic process group scheduling"
1241 select FAIR_GROUP_SCHED
1243 This option optimizes the scheduler for common desktop workloads by
1244 automatically creating and populating task groups. This separation
1245 of workloads isolates aggressive CPU burners (like build jobs) from
1246 desktop applications. Task group autogeneration is currently based
1249 config SYSFS_DEPRECATED
1250 bool "Enable deprecated sysfs features to support old userspace tools"
1254 This option adds code that switches the layout of the "block" class
1255 devices, to not show up in /sys/class/block/, but only in
1258 This switch is only active when the sysfs.deprecated=1 boot option is
1259 passed or the SYSFS_DEPRECATED_V2 option is set.
1261 This option allows new kernels to run on old distributions and tools,
1262 which might get confused by /sys/class/block/. Since 2007/2008 all
1263 major distributions and tools handle this just fine.
1265 Recent distributions and userspace tools after 2009/2010 depend on
1266 the existence of /sys/class/block/, and will not work with this
1269 Only if you are using a new kernel on an old distribution, you might
1272 config SYSFS_DEPRECATED_V2
1273 bool "Enable deprecated sysfs features by default"
1276 depends on SYSFS_DEPRECATED
1278 Enable deprecated sysfs by default.
1280 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1283 Only if you are using a new kernel on an old distribution, you might
1284 need to say Y here. Even then, odds are you would not need it
1285 enabled, you can always pass the boot option if absolutely necessary.
1288 bool "Kernel->user space relay support (formerly relayfs)"
1290 This option enables support for relay interface support in
1291 certain file systems (such as debugfs).
1292 It is designed to provide an efficient mechanism for tools and
1293 facilities to relay large amounts of data from kernel space to
1298 config BLK_DEV_INITRD
1299 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1300 depends on BROKEN || !FRV
1302 The initial RAM filesystem is a ramfs which is loaded by the
1303 boot loader (loadlin or lilo) and that is mounted as root
1304 before the normal boot procedure. It is typically used to
1305 load modules needed to mount the "real" root file system,
1306 etc. See <file:Documentation/initrd.txt> for details.
1308 If RAM disk support (BLK_DEV_RAM) is also included, this
1309 also enables initial RAM disk (initrd) support and adds
1310 15 Kbytes (more on some other architectures) to the kernel size.
1316 source "usr/Kconfig"
1320 config CC_OPTIMIZE_FOR_SIZE
1321 bool "Optimize for size"
1323 Enabling this option will pass "-Os" instead of "-O2" to
1324 your compiler resulting in a smaller kernel.
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
1360 # interpreter that classic socket filters depend on
1365 bool "Configure standard kernel features (expert users)"
1366 # Unhide debug options, to make the on-by-default options visible
1369 This option allows certain base kernel options and settings
1370 to be disabled or tweaked. This is for specialized
1371 environments which can tolerate a "non-standard" kernel.
1372 Only use this if you really know what you are doing.
1375 bool "Enable 16-bit UID system calls" if EXPERT
1376 depends on HAVE_UID16 && MULTIUSER
1379 This enables the legacy 16-bit UID syscall wrappers.
1382 bool "Multiple users, groups and capabilities support" if EXPERT
1385 This option enables support for non-root users, groups and
1388 If you say N here, all processes will run with UID 0, GID 0, and all
1389 possible capabilities. Saying N here also compiles out support for
1390 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1393 If unsure, say Y here.
1395 config SGETMASK_SYSCALL
1396 bool "sgetmask/ssetmask syscalls support" if EXPERT
1397 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1399 sys_sgetmask and sys_ssetmask are obsolete system calls
1400 no longer supported in libc but still enabled by default in some
1403 If unsure, leave the default option here.
1405 config SYSFS_SYSCALL
1406 bool "Sysfs syscall support" if EXPERT
1409 sys_sysfs is an obsolete system call no longer supported in libc.
1410 Note that disabling this option is more secure but might break
1411 compatibility with some systems.
1413 If unsure say Y here.
1415 config SYSCTL_SYSCALL
1416 bool "Sysctl syscall support" if EXPERT
1417 depends on PROC_SYSCTL
1421 sys_sysctl uses binary paths that have been found challenging
1422 to properly maintain and use. The interface in /proc/sys
1423 using paths with ascii names is now the primary path to this
1426 Almost nothing using the binary sysctl interface so if you are
1427 trying to save some space it is probably safe to disable this,
1428 making your kernel marginally smaller.
1430 If unsure say N here.
1433 bool "Load all symbols for debugging/ksymoops" if EXPERT
1436 Say Y here to let the kernel print out symbolic crash information and
1437 symbolic stack backtraces. This increases the size of the kernel
1438 somewhat, as all symbols have to be loaded into the kernel image.
1441 bool "Include all symbols in kallsyms"
1442 depends on DEBUG_KERNEL && KALLSYMS
1444 Normally kallsyms only contains the symbols of functions for nicer
1445 OOPS messages and backtraces (i.e., symbols from the text and inittext
1446 sections). This is sufficient for most cases. And only in very rare
1447 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1448 names of variables from the data sections, etc).
1450 This option makes sure that all symbols are loaded into the kernel
1451 image (i.e., symbols from all sections) in cost of increased kernel
1452 size (depending on the kernel configuration, it may be 300KiB or
1453 something like this).
1455 Say N unless you really need all symbols.
1459 bool "Enable support for printk" if EXPERT
1462 This option enables normal printk support. Removing it
1463 eliminates most of the message strings from the kernel image
1464 and makes the kernel more or less silent. As this makes it
1465 very difficult to diagnose system problems, saying N here is
1466 strongly discouraged.
1469 bool "BUG() support" if EXPERT
1472 Disabling this option eliminates support for BUG and WARN, reducing
1473 the size of your kernel image and potentially quietly ignoring
1474 numerous fatal conditions. You should only consider disabling this
1475 option for embedded systems with no facilities for reporting errors.
1481 bool "Enable ELF core dumps" if EXPERT
1483 Enable support for generating core dumps. Disabling saves about 4k.
1486 config PCSPKR_PLATFORM
1487 bool "Enable PC-Speaker support" if EXPERT
1488 depends on HAVE_PCSPKR_PLATFORM
1492 This option allows to disable the internal PC-Speaker
1493 support, saving some memory.
1497 bool "Enable full-sized data structures for core" if EXPERT
1499 Disabling this option reduces the size of miscellaneous core
1500 kernel data structures. This saves memory on small machines,
1501 but may reduce performance.
1504 bool "Enable futex support" if EXPERT
1508 Disabling this option will cause the kernel to be built without
1509 support for "fast userspace mutexes". The resulting kernel may not
1510 run glibc-based applications correctly.
1512 config HAVE_FUTEX_CMPXCHG
1516 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1517 is implemented and always working. This removes a couple of runtime
1521 bool "Enable eventpoll support" if EXPERT
1525 Disabling this option will cause the kernel to be built without
1526 support for epoll family of system calls.
1529 bool "Enable signalfd() system call" if EXPERT
1533 Enable the signalfd() system call that allows to receive signals
1534 on a file descriptor.
1539 bool "Enable timerfd() system call" if EXPERT
1543 Enable the timerfd() system call that allows to receive timer
1544 events on a file descriptor.
1549 bool "Enable eventfd() system call" if EXPERT
1553 Enable the eventfd() system call that allows to receive both
1554 kernel notification (ie. KAIO) or userspace notifications.
1558 # syscall, maps, verifier
1560 bool "Enable bpf() system call"
1565 Enable the bpf() system call that allows to manipulate eBPF
1566 programs and maps via file descriptors.
1568 config BPF_JIT_ALWAYS_ON
1569 bool "Permanently enable BPF JIT and remove BPF interpreter"
1570 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1572 Enables BPF JIT and removes BPF interpreter to avoid
1573 speculative execution of BPF instructions by the interpreter
1576 bool "Use full shmem filesystem" if EXPERT
1580 The shmem is an internal filesystem used to manage shared memory.
1581 It is backed by swap and manages resource limits. It is also exported
1582 to userspace as tmpfs if TMPFS is enabled. Disabling this
1583 option replaces shmem and tmpfs with the much simpler ramfs code,
1584 which may be appropriate on small systems without swap.
1587 bool "Enable AIO support" if EXPERT
1590 This option enables POSIX asynchronous I/O which may by used
1591 by some high performance threaded applications. Disabling
1592 this option saves about 7k.
1594 config ADVISE_SYSCALLS
1595 bool "Enable madvise/fadvise syscalls" if EXPERT
1598 This option enables the madvise and fadvise syscalls, used by
1599 applications to advise the kernel about their future memory or file
1600 usage, improving performance. If building an embedded system where no
1601 applications use these syscalls, you can disable this option to save
1605 bool "Enable userfaultfd() system call"
1609 Enable the userfaultfd() system call that allows to intercept and
1610 handle page faults in userland.
1614 bool "Enable PCI quirk workarounds" if EXPERT
1617 This enables workarounds for various PCI chipset
1618 bugs/quirks. Disable this only if your target machine is
1619 unaffected by PCI quirks.
1622 bool "Enable membarrier() system call" if EXPERT
1625 Enable the membarrier() system call that allows issuing memory
1626 barriers across all running threads, which can be used to distribute
1627 the cost of user-space memory barriers asymmetrically by transforming
1628 pairs of memory barriers into pairs consisting of membarrier() and a
1634 bool "Embedded system"
1635 option allnoconfig_y
1638 This option should be enabled if compiling the kernel for
1639 an embedded system so certain expert options are available
1642 config HAVE_PERF_EVENTS
1645 See tools/perf/design.txt for details.
1647 config PERF_USE_VMALLOC
1650 See tools/perf/design.txt for details
1652 menu "Kernel Performance Events And Counters"
1655 bool "Kernel performance events and counters"
1656 default y if PROFILING
1657 depends on HAVE_PERF_EVENTS
1662 Enable kernel support for various performance events provided
1663 by software and hardware.
1665 Software events are supported either built-in or via the
1666 use of generic tracepoints.
1668 Most modern CPUs support performance events via performance
1669 counter registers. These registers count the number of certain
1670 types of hw events: such as instructions executed, cachemisses
1671 suffered, or branches mis-predicted - without slowing down the
1672 kernel or applications. These registers can also trigger interrupts
1673 when a threshold number of events have passed - and can thus be
1674 used to profile the code that runs on that CPU.
1676 The Linux Performance Event subsystem provides an abstraction of
1677 these software and hardware event capabilities, available via a
1678 system call and used by the "perf" utility in tools/perf/. It
1679 provides per task and per CPU counters, and it provides event
1680 capabilities on top of those.
1684 config DEBUG_PERF_USE_VMALLOC
1686 bool "Debug: use vmalloc to back perf mmap() buffers"
1687 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1688 select PERF_USE_VMALLOC
1690 Use vmalloc memory to back perf mmap() buffers.
1692 Mostly useful for debugging the vmalloc code on platforms
1693 that don't require it.
1699 config VM_EVENT_COUNTERS
1701 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1703 VM event counters are needed for event counts to be shown.
1704 This option allows the disabling of the VM event counters
1705 on EXPERT systems. /proc/vmstat will only show page counts
1706 if VM event counters are disabled.
1710 bool "Enable SLUB debugging support" if EXPERT
1711 depends on SLUB && SYSFS
1713 SLUB has extensive debug support features. Disabling these can
1714 result in significant savings in code size. This also disables
1715 SLUB sysfs support. /sys/slab will not exist and there will be
1716 no support for cache validation etc.
1719 bool "Disable heap randomization"
1722 Randomizing heap placement makes heap exploits harder, but it
1723 also breaks ancient binaries (including anything libc5 based).
1724 This option changes the bootup default to heap randomization
1725 disabled, and can be overridden at runtime by setting
1726 /proc/sys/kernel/randomize_va_space to 2.
1728 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1731 prompt "Choose SLAB allocator"
1734 This option allows to select a slab allocator.
1739 The regular slab allocator that is established and known to work
1740 well in all environments. It organizes cache hot objects in
1741 per cpu and per node queues.
1744 bool "SLUB (Unqueued Allocator)"
1746 SLUB is a slab allocator that minimizes cache line usage
1747 instead of managing queues of cached objects (SLAB approach).
1748 Per cpu caching is realized using slabs of objects instead
1749 of queues of objects. SLUB can use memory efficiently
1750 and has enhanced diagnostics. SLUB is the default choice for
1755 bool "SLOB (Simple Allocator)"
1757 SLOB replaces the stock allocator with a drastically simpler
1758 allocator. SLOB is generally more space efficient but
1759 does not perform as well on large systems.
1763 config SLUB_CPU_PARTIAL
1765 depends on SLUB && SMP
1766 bool "SLUB per cpu partial cache"
1768 Per cpu partial caches accellerate objects allocation and freeing
1769 that is local to a processor at the price of more indeterminism
1770 in the latency of the free. On overflow these caches will be cleared
1771 which requires the taking of locks that may cause latency spikes.
1772 Typically one would choose no for a realtime system.
1774 config MMAP_ALLOW_UNINITIALIZED
1775 bool "Allow mmapped anonymous memory to be uninitialized"
1776 depends on EXPERT && !MMU
1779 Normally, and according to the Linux spec, anonymous memory obtained
1780 from mmap() has it's contents cleared before it is passed to
1781 userspace. Enabling this config option allows you to request that
1782 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1783 providing a huge performance boost. If this option is not enabled,
1784 then the flag will be ignored.
1786 This is taken advantage of by uClibc's malloc(), and also by
1787 ELF-FDPIC binfmt's brk and stack allocator.
1789 Because of the obvious security issues, this option should only be
1790 enabled on embedded devices where you control what is run in
1791 userspace. Since that isn't generally a problem on no-MMU systems,
1792 it is normally safe to say Y here.
1794 See Documentation/nommu-mmap.txt for more information.
1796 config SYSTEM_DATA_VERIFICATION
1798 select SYSTEM_TRUSTED_KEYRING
1801 select ASYMMETRIC_KEY_TYPE
1802 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1803 select PUBLIC_KEY_ALGO_RSA
1806 select X509_CERTIFICATE_PARSER
1807 select PKCS7_MESSAGE_PARSER
1809 Provide PKCS#7 message verification using the contents of the system
1810 trusted keyring to provide public keys. This then can be used for
1811 module verification, kexec image verification and firmware blob
1814 config SYSTEM_BLACKLIST_KEYRING
1815 bool "Provide system-wide ring of blacklisted keys"
1818 Provide a system keyring to which blacklisted keys can be added.
1819 Keys in the keyring are considered entirely untrusted. Keys in this
1820 keyring are used by the module signature checking to reject loading
1821 of modules signed with a blacklisted key.
1824 bool "Profiling support"
1826 Say Y here to enable the extended profiling support mechanisms used
1827 by profilers such as OProfile.
1830 # Place an empty function call at each tracepoint site. Can be
1831 # dynamically changed for a probe function.
1836 source "arch/Kconfig"
1838 endmenu # General setup
1840 config HAVE_GENERIC_DMA_COHERENT
1847 depends on SLAB || SLUB_DEBUG
1855 default 0 if BASE_FULL
1856 default 1 if !BASE_FULL
1859 bool "Enable loadable module support"
1862 Kernel modules are small pieces of compiled code which can
1863 be inserted in the running kernel, rather than being
1864 permanently built into the kernel. You use the "modprobe"
1865 tool to add (and sometimes remove) them. If you say Y here,
1866 many parts of the kernel can be built as modules (by
1867 answering M instead of Y where indicated): this is most
1868 useful for infrequently used options which are not required
1869 for booting. For more information, see the man pages for
1870 modprobe, lsmod, modinfo, insmod and rmmod.
1872 If you say Y here, you will need to run "make
1873 modules_install" to put the modules under /lib/modules/
1874 where modprobe can find them (you may need to be root to do
1881 config MODULE_FORCE_LOAD
1882 bool "Forced module loading"
1885 Allow loading of modules without version information (ie. modprobe
1886 --force). Forced module loading sets the 'F' (forced) taint flag and
1887 is usually a really bad idea.
1889 config MODULE_UNLOAD
1890 bool "Module unloading"
1892 Without this option you will not be able to unload any
1893 modules (note that some modules may not be unloadable
1894 anyway), which makes your kernel smaller, faster
1895 and simpler. If unsure, say Y.
1897 config MODULE_FORCE_UNLOAD
1898 bool "Forced module unloading"
1899 depends on MODULE_UNLOAD
1901 This option allows you to force a module to unload, even if the
1902 kernel believes it is unsafe: the kernel will remove the module
1903 without waiting for anyone to stop using it (using the -f option to
1904 rmmod). This is mainly for kernel developers and desperate users.
1908 bool "Module versioning support"
1910 Usually, you have to use modules compiled with your kernel.
1911 Saying Y here makes it sometimes possible to use modules
1912 compiled for different kernels, by adding enough information
1913 to the modules to (hopefully) spot any changes which would
1914 make them incompatible with the kernel you are running. If
1917 config MODULE_SRCVERSION_ALL
1918 bool "Source checksum for all modules"
1920 Modules which contain a MODULE_VERSION get an extra "srcversion"
1921 field inserted into their modinfo section, which contains a
1922 sum of the source files which made it. This helps maintainers
1923 see exactly which source was used to build a module (since
1924 others sometimes change the module source without updating
1925 the version). With this option, such a "srcversion" field
1926 will be created for all modules. If unsure, say N.
1929 bool "Module signature verification"
1931 select SYSTEM_DATA_VERIFICATION
1933 Check modules for valid signatures upon load: the signature
1934 is simply appended to the module. For more information see
1935 Documentation/module-signing.txt.
1937 Note that this option adds the OpenSSL development packages as a
1938 kernel build dependency so that the signing tool can use its crypto
1941 !!!WARNING!!! If you enable this option, you MUST make sure that the
1942 module DOES NOT get stripped after being signed. This includes the
1943 debuginfo strip done by some packagers (such as rpmbuild) and
1944 inclusion into an initramfs that wants the module size reduced.
1946 config MODULE_SIG_FORCE
1947 bool "Require modules to be validly signed"
1948 depends on MODULE_SIG
1950 Reject unsigned modules or signed modules for which we don't have a
1951 key. Without this, such modules will simply taint the kernel.
1953 config MODULE_SIG_ALL
1954 bool "Automatically sign all modules"
1956 depends on MODULE_SIG
1958 Sign all modules during make modules_install. Without this option,
1959 modules must be signed manually, using the scripts/sign-file tool.
1961 comment "Do not forget to sign required modules with scripts/sign-file"
1962 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1964 config MODULE_SIG_UEFI
1965 bool "Allow modules signed with certs stored in UEFI"
1966 depends on MODULE_SIG && SYSTEM_BLACKLIST_KEYRING && EFI
1967 select EFI_SIGNATURE_LIST_PARSER
1969 This will import certificates stored in UEFI and allow modules
1970 signed with those to be loaded. It will also disallow loading
1971 of modules stored in the UEFI dbx variable.
1974 prompt "Which hash algorithm should modules be signed with?"
1975 depends on MODULE_SIG
1977 This determines which sort of hashing algorithm will be used during
1978 signature generation. This algorithm _must_ be built into the kernel
1979 directly so that signature verification can take place. It is not
1980 possible to load a signed module containing the algorithm to check
1981 the signature on that module.
1983 config MODULE_SIG_SHA1
1984 bool "Sign modules with SHA-1"
1987 config MODULE_SIG_SHA224
1988 bool "Sign modules with SHA-224"
1989 select CRYPTO_SHA256
1991 config MODULE_SIG_SHA256
1992 bool "Sign modules with SHA-256"
1993 select CRYPTO_SHA256
1995 config MODULE_SIG_SHA384
1996 bool "Sign modules with SHA-384"
1997 select CRYPTO_SHA512
1999 config MODULE_SIG_SHA512
2000 bool "Sign modules with SHA-512"
2001 select CRYPTO_SHA512
2005 config MODULE_SIG_HASH
2007 depends on MODULE_SIG
2008 default "sha1" if MODULE_SIG_SHA1
2009 default "sha224" if MODULE_SIG_SHA224
2010 default "sha256" if MODULE_SIG_SHA256
2011 default "sha384" if MODULE_SIG_SHA384
2012 default "sha512" if MODULE_SIG_SHA512
2014 config MODULE_COMPRESS
2015 bool "Compress modules on installation"
2019 Compresses kernel modules when 'make modules_install' is run; gzip or
2020 xz depending on "Compression algorithm" below.
2022 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2024 Out-of-tree kernel modules installed using Kbuild will also be
2025 compressed upon installation.
2027 Note: for modules inside an initrd or initramfs, it's more efficient
2028 to compress the whole initrd or initramfs instead.
2030 Note: This is fully compatible with signed modules.
2035 prompt "Compression algorithm"
2036 depends on MODULE_COMPRESS
2037 default MODULE_COMPRESS_GZIP
2039 This determines which sort of compression will be used during
2040 'make modules_install'.
2042 GZIP (default) and XZ are supported.
2044 config MODULE_COMPRESS_GZIP
2047 config MODULE_COMPRESS_XZ
2054 config MODULES_TREE_LOOKUP
2056 depends on PERF_EVENTS || TRACING
2058 config INIT_ALL_POSSIBLE
2061 Back when each arch used to define their own cpu_online_mask and
2062 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2063 with all 1s, and others with all 0s. When they were centralised,
2064 it was better to provide this option than to break all the archs
2065 and have several arch maintainers pursuing me down dark alleys.
2067 source "block/Kconfig"
2069 config PREEMPT_NOTIFIERS
2076 # Can be selected by architectures with broken toolchains
2077 # that get confused by correct const<->read_only section
2079 config BROKEN_RODATA
2085 Build a simple ASN.1 grammar compiler that produces a bytecode output
2086 that can be interpreted by the ASN.1 stream decoder and used to
2087 inform it as to what tags are to be expected in a stream and what
2088 functions to call on what tags.
2090 source "kernel/Kconfig.locks"
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