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"
399 If you say Y here, a user level program will be able to instruct the
400 kernel (via a special system call) to write process accounting
401 information to a file: whenever a process exits, information about
402 that process will be appended to the file by the kernel. The
403 information includes things such as creation time, owning user,
404 command name, memory usage, controlling terminal etc. (the complete
405 list is in the struct acct in <file:include/linux/acct.h>). It is
406 up to the user level program to do useful things with this
407 information. This is generally a good idea, so say Y.
409 config BSD_PROCESS_ACCT_V3
410 bool "BSD Process Accounting version 3 file format"
411 depends on BSD_PROCESS_ACCT
414 If you say Y here, the process accounting information is written
415 in a new file format that also logs the process IDs of each
416 process and it's parent. Note that this file format is incompatible
417 with previous v0/v1/v2 file formats, so you will need updated tools
418 for processing it. A preliminary version of these tools is available
419 at <http://www.gnu.org/software/acct/>.
422 bool "Export task/process statistics through netlink"
427 Export selected statistics for tasks/processes through the
428 generic netlink interface. Unlike BSD process accounting, the
429 statistics are available during the lifetime of tasks/processes as
430 responses to commands. Like BSD accounting, they are sent to user
435 config TASK_DELAY_ACCT
436 bool "Enable per-task delay accounting"
439 Collect information on time spent by a task waiting for system
440 resources like cpu, synchronous block I/O completion and swapping
441 in pages. Such statistics can help in setting a task's priorities
442 relative to other tasks for cpu, io, rss limits etc.
447 bool "Enable extended accounting over taskstats"
450 Collect extended task accounting data and send the data
451 to userland for processing over the taskstats interface.
455 config TASK_IO_ACCOUNTING
456 bool "Enable per-task storage I/O accounting"
457 depends on TASK_XACCT
459 Collect information on the number of bytes of storage I/O which this
464 endmenu # "CPU/Task time and stats accounting"
469 prompt "RCU Implementation"
473 bool "Tree-based hierarchical RCU"
474 depends on !PREEMPT && SMP
476 This option selects the RCU implementation that is
477 designed for very large SMP system with hundreds or
478 thousands of CPUs. It also scales down nicely to
482 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 bool "Make expert-level adjustments to RCU configuration"
508 This option needs to be enabled if you wish to make
509 expert-level adjustments to RCU configuration. By default,
510 no such adjustments can be made, which has the often-beneficial
511 side-effect of preventing "make oldconfig" from asking you all
512 sorts of detailed questions about how you would like numerous
513 obscure RCU options to be set up.
515 Say Y if you need to make expert-level adjustments to RCU.
517 Say N if you are unsure.
522 This option selects the sleepable version of RCU. This version
523 permits arbitrary sleeping or blocking within RCU read-side critical
531 This option enables a task-based RCU implementation that uses
532 only voluntary context switch (not preemption!), idle, and
533 user-mode execution as quiescent states.
535 config RCU_STALL_COMMON
536 def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
538 This option enables RCU CPU stall code that is common between
539 the TINY and TREE variants of RCU. The purpose is to allow
540 the tiny variants to disable RCU CPU stall warnings, while
541 making these warnings mandatory for the tree variants.
543 config CONTEXT_TRACKING
549 This option sets hooks on kernel / userspace boundaries and
550 puts RCU in extended quiescent state when the CPU runs in
551 userspace. It means that when a CPU runs in userspace, it is
552 excluded from the global RCU state machine and thus doesn't
553 try to keep the timer tick on for RCU.
555 config CONTEXT_TRACKING_FORCE
556 bool "Force context tracking"
557 depends on CONTEXT_TRACKING
558 default y if !NO_HZ_FULL
560 The major pre-requirement for full dynticks to work is to
561 support the context tracking subsystem. But there are also
562 other dependencies to provide in order to make the full
565 This option stands for testing when an arch implements the
566 context tracking backend but doesn't yet fullfill all the
567 requirements to make the full dynticks feature working.
568 Without the full dynticks, there is no way to test the support
569 for context tracking and the subsystems that rely on it: RCU
570 userspace extended quiescent state and tickless cputime
571 accounting. This option copes with the absence of the full
572 dynticks subsystem by forcing the context tracking on all
575 Say Y only if you're working on the development of an
576 architecture backend for the context tracking.
578 Say N otherwise, this option brings an overhead that you
579 don't want in production.
583 int "Tree-based hierarchical RCU fanout value"
586 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
590 This option controls the fanout of hierarchical implementations
591 of RCU, allowing RCU to work efficiently on machines with
592 large numbers of CPUs. This value must be at least the fourth
593 root of NR_CPUS, which allows NR_CPUS to be insanely large.
594 The default value of RCU_FANOUT should be used for production
595 systems, but if you are stress-testing the RCU implementation
596 itself, small RCU_FANOUT values allow you to test large-system
597 code paths on small(er) systems.
599 Select a specific number if testing RCU itself.
600 Take the default if unsure.
602 config RCU_FANOUT_LEAF
603 int "Tree-based hierarchical RCU leaf-level fanout value"
606 depends on TREE_RCU || PREEMPT_RCU
609 This option controls the leaf-level fanout of hierarchical
610 implementations of RCU, and allows trading off cache misses
611 against lock contention. Systems that synchronize their
612 scheduling-clock interrupts for energy-efficiency reasons will
613 want the default because the smaller leaf-level fanout keeps
614 lock contention levels acceptably low. Very large systems
615 (hundreds or thousands of CPUs) will instead want to set this
616 value to the maximum value possible in order to reduce the
617 number of cache misses incurred during RCU's grace-period
618 initialization. These systems tend to run CPU-bound, and thus
619 are not helped by synchronized interrupts, and thus tend to
620 skew them, which reduces lock contention enough that large
621 leaf-level fanouts work well.
623 Select a specific number if testing RCU itself.
625 Select the maximum permissible value for large systems.
627 Take the default if unsure.
629 config RCU_FAST_NO_HZ
630 bool "Accelerate last non-dyntick-idle CPU's grace periods"
631 depends on NO_HZ_COMMON && SMP && RCU_EXPERT
634 This option permits CPUs to enter dynticks-idle state even if
635 they have RCU callbacks queued, and prevents RCU from waking
636 these CPUs up more than roughly once every four jiffies (by
637 default, you can adjust this using the rcutree.rcu_idle_gp_delay
638 parameter), thus improving energy efficiency. On the other
639 hand, this option increases the duration of RCU grace periods,
640 for example, slowing down synchronize_rcu().
642 Say Y if energy efficiency is critically important, and you
643 don't care about increased grace-period durations.
645 Say N if you are unsure.
647 config TREE_RCU_TRACE
648 def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
651 This option provides tracing for the TREE_RCU and
652 PREEMPT_RCU implementations, permitting Makefile to
653 trivially select kernel/rcutree_trace.c.
656 bool "Enable RCU priority boosting"
657 depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT
660 This option boosts the priority of preempted RCU readers that
661 block the current preemptible RCU grace period for too long.
662 This option also prevents heavy loads from blocking RCU
663 callback invocation for all flavors of RCU.
665 Say Y here if you are working with real-time apps or heavy loads
666 Say N here if you are unsure.
668 config RCU_KTHREAD_PRIO
669 int "Real-time priority to use for RCU worker threads"
670 range 1 99 if RCU_BOOST
671 range 0 99 if !RCU_BOOST
672 default 1 if RCU_BOOST
673 default 0 if !RCU_BOOST
675 This option specifies the SCHED_FIFO priority value that will be
676 assigned to the rcuc/n and rcub/n threads and is also the value
677 used for RCU_BOOST (if enabled). If you are working with a
678 real-time application that has one or more CPU-bound threads
679 running at a real-time priority level, you should set
680 RCU_KTHREAD_PRIO to a priority higher than the highest-priority
681 real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO
682 value of 1 is appropriate in the common case, which is real-time
683 applications that do not have any CPU-bound threads.
685 Some real-time applications might not have a single real-time
686 thread that saturates a given CPU, but instead might have
687 multiple real-time threads that, taken together, fully utilize
688 that CPU. In this case, you should set RCU_KTHREAD_PRIO to
689 a priority higher than the lowest-priority thread that is
690 conspiring to prevent the CPU from running any non-real-time
691 tasks. For example, if one thread at priority 10 and another
692 thread at priority 5 are between themselves fully consuming
693 the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
694 set to priority 6 or higher.
696 Specify the real-time priority, or take the default if unsure.
698 config RCU_BOOST_DELAY
699 int "Milliseconds to delay boosting after RCU grace-period start"
704 This option specifies the time to wait after the beginning of
705 a given grace period before priority-boosting preempted RCU
706 readers blocking that grace period. Note that any RCU reader
707 blocking an expedited RCU grace period is boosted immediately.
709 Accept the default if unsure.
712 bool "Offload RCU callback processing from boot-selected CPUs"
713 depends on TREE_RCU || PREEMPT_RCU
716 Use this option to reduce OS jitter for aggressive HPC or
717 real-time workloads. It can also be used to offload RCU
718 callback invocation to energy-efficient CPUs in battery-powered
719 asymmetric multiprocessors.
721 This option offloads callback invocation from the set of
722 CPUs specified at boot time by the rcu_nocbs parameter.
723 For each such CPU, a kthread ("rcuox/N") will be created to
724 invoke callbacks, where the "N" is the CPU being offloaded,
725 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
726 "s" for RCU-sched. Nothing prevents this kthread from running
727 on the specified CPUs, but (1) the kthreads may be preempted
728 between each callback, and (2) affinity or cgroups can be used
729 to force the kthreads to run on whatever set of CPUs is desired.
731 Say Y here if you want to help to debug reduced OS jitter.
732 Say N here if you are unsure.
735 prompt "Build-forced no-CBs CPUs"
736 default RCU_NOCB_CPU_NONE
737 depends on RCU_NOCB_CPU
739 This option allows no-CBs CPUs (whose RCU callbacks are invoked
740 from kthreads rather than from softirq context) to be specified
741 at build time. Additional no-CBs CPUs may be specified by
742 the rcu_nocbs= boot parameter.
744 config RCU_NOCB_CPU_NONE
745 bool "No build_forced no-CBs CPUs"
747 This option does not force any of the CPUs to be no-CBs CPUs.
748 Only CPUs designated by the rcu_nocbs= boot parameter will be
749 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
750 kthreads whose names begin with "rcuo". All other CPUs will
751 invoke their own RCU callbacks in softirq context.
753 Select this option if you want to choose no-CBs CPUs at
754 boot time, for example, to allow testing of different no-CBs
755 configurations without having to rebuild the kernel each time.
757 config RCU_NOCB_CPU_ZERO
758 bool "CPU 0 is a build_forced no-CBs CPU"
760 This option forces CPU 0 to be a no-CBs CPU, so that its RCU
761 callbacks are invoked by a per-CPU kthread whose name begins
762 with "rcuo". Additional CPUs may be designated as no-CBs
763 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
764 All other CPUs will invoke their own RCU callbacks in softirq
767 Select this if CPU 0 needs to be a no-CBs CPU for real-time
768 or energy-efficiency reasons, but the real reason it exists
769 is to ensure that randconfig testing covers mixed systems.
771 config RCU_NOCB_CPU_ALL
772 bool "All CPUs are build_forced no-CBs CPUs"
774 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
775 boot parameter will be ignored. All CPUs' RCU callbacks will
776 be executed in the context of per-CPU rcuo kthreads created for
777 this purpose. Assuming that the kthreads whose names start with
778 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
779 on the remaining CPUs, but might decrease memory locality during
780 RCU-callback invocation, thus potentially degrading throughput.
782 Select this if all CPUs need to be no-CBs CPUs for real-time
783 or energy-efficiency reasons.
787 config RCU_EXPEDITE_BOOT
791 This option enables expedited grace periods at boot time,
792 as if rcu_expedite_gp() had been invoked early in boot.
793 The corresponding rcu_unexpedite_gp() is invoked from
794 rcu_end_inkernel_boot(), which is intended to be invoked
795 at the end of the kernel-only boot sequence, just before
798 Accept the default if unsure.
800 endmenu # "RCU Subsystem"
807 tristate "Kernel .config support"
810 This option enables the complete Linux kernel ".config" file
811 contents to be saved in the kernel. It provides documentation
812 of which kernel options are used in a running kernel or in an
813 on-disk kernel. This information can be extracted from the kernel
814 image file with the script scripts/extract-ikconfig and used as
815 input to rebuild the current kernel or to build another kernel.
816 It can also be extracted from a running kernel by reading
817 /proc/config.gz if enabled (below).
820 bool "Enable access to .config through /proc/config.gz"
821 depends on IKCONFIG && PROC_FS
823 This option enables access to the kernel configuration file
824 through /proc/config.gz.
827 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
832 Select the minimal kernel log buffer size as a power of 2.
833 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
834 parameter, see below. Any higher size also might be forced
835 by "log_buf_len" boot parameter.
845 config LOG_CPU_MAX_BUF_SHIFT
846 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
849 default 12 if !BASE_SMALL
850 default 0 if BASE_SMALL
853 This option allows to increase the default ring buffer size
854 according to the number of CPUs. The value defines the contribution
855 of each CPU as a power of 2. The used space is typically only few
856 lines however it might be much more when problems are reported,
859 The increased size means that a new buffer has to be allocated and
860 the original static one is unused. It makes sense only on systems
861 with more CPUs. Therefore this value is used only when the sum of
862 contributions is greater than the half of the default kernel ring
863 buffer as defined by LOG_BUF_SHIFT. The default values are set
864 so that more than 64 CPUs are needed to trigger the allocation.
866 Also this option is ignored when "log_buf_len" kernel parameter is
867 used as it forces an exact (power of two) size of the ring buffer.
869 The number of possible CPUs is used for this computation ignoring
870 hotplugging making the compuation optimal for the the worst case
871 scenerio while allowing a simple algorithm to be used from bootup.
873 Examples shift values and their meaning:
874 17 => 128 KB for each CPU
875 16 => 64 KB for each CPU
876 15 => 32 KB for each CPU
877 14 => 16 KB for each CPU
878 13 => 8 KB for each CPU
879 12 => 4 KB for each CPU
882 # Architectures with an unreliable sched_clock() should select this:
884 config HAVE_UNSTABLE_SCHED_CLOCK
887 config GENERIC_SCHED_CLOCK
891 # For architectures that want to enable the support for NUMA-affine scheduler
894 config ARCH_SUPPORTS_NUMA_BALANCING
898 # For architectures that know their GCC __int128 support is sound
900 config ARCH_SUPPORTS_INT128
903 # For architectures that (ab)use NUMA to represent different memory regions
904 # all cpu-local but of different latencies, such as SuperH.
906 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
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.
921 config NUMA_BALANCING_DEFAULT_ENABLED
922 bool "Automatically enable NUMA aware memory/task placement"
924 depends on NUMA_BALANCING
926 If set, automatic NUMA balancing will be enabled if running on a NUMA
930 bool "Control Group support"
933 This option adds support for grouping sets of processes together, for
934 use with process control subsystems such as Cpusets, CFS, memory
935 controls or device isolation.
937 - Documentation/scheduler/sched-design-CFS.txt (CFS)
938 - Documentation/cgroups/ (features for grouping, isolation
939 and resource control)
946 bool "Example debug cgroup subsystem"
949 This option enables a simple cgroup subsystem that
950 exports useful debugging information about the cgroups
955 config CGROUP_FREEZER
956 bool "Freezer cgroup subsystem"
958 Provides a way to freeze and unfreeze all tasks in a
962 bool "Device controller for cgroups"
964 Provides a cgroup implementing whitelists for devices which
965 a process in the cgroup can mknod or open.
968 bool "Cpuset support"
970 This option will let you create and manage CPUSETs which
971 allow dynamically partitioning a system into sets of CPUs and
972 Memory Nodes and assigning tasks to run only within those sets.
973 This is primarily useful on large SMP or NUMA systems.
977 config PROC_PID_CPUSET
978 bool "Include legacy /proc/<pid>/cpuset file"
982 config CGROUP_CPUACCT
983 bool "Simple CPU accounting cgroup subsystem"
985 Provides a simple Resource Controller for monitoring the
986 total CPU consumed by the tasks in a cgroup.
992 bool "Memory Resource Controller for Control Groups"
996 Provides a memory resource controller that manages both anonymous
997 memory and page cache. (See Documentation/cgroups/memory.txt)
1000 bool "Memory Resource Controller Swap Extension"
1001 depends on MEMCG && SWAP
1003 Add swap management feature to memory resource controller. When you
1004 enable this, you can limit mem+swap usage per cgroup. In other words,
1005 when you disable this, memory resource controller has no cares to
1006 usage of swap...a process can exhaust all of the swap. This extension
1007 is useful when you want to avoid exhaustion swap but this itself
1008 adds more overheads and consumes memory for remembering information.
1009 Especially if you use 32bit system or small memory system, please
1010 be careful about enabling this. When memory resource controller
1011 is disabled by boot option, this will be automatically disabled and
1012 there will be no overhead from this. Even when you set this config=y,
1013 if boot option "swapaccount=0" is set, swap will not be accounted.
1014 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
1015 size is 4096bytes, 512k per 1Gbytes of swap.
1016 config MEMCG_SWAP_ENABLED
1017 bool "Memory Resource Controller Swap Extension enabled by default"
1018 depends on MEMCG_SWAP
1021 Memory Resource Controller Swap Extension comes with its price in
1022 a bigger memory consumption. General purpose distribution kernels
1023 which want to enable the feature but keep it disabled by default
1024 and let the user enable it by swapaccount=1 boot command line
1025 parameter should have this option unselected.
1026 For those who want to have the feature enabled by default should
1027 select this option (if, for some reason, they need to disable it
1028 then swapaccount=0 does the trick).
1030 bool "Memory Resource Controller Kernel Memory accounting"
1032 depends on SLUB || SLAB
1034 The Kernel Memory extension for Memory Resource Controller can limit
1035 the amount of memory used by kernel objects in the system. Those are
1036 fundamentally different from the entities handled by the standard
1037 Memory Controller, which are page-based, and can be swapped. Users of
1038 the kmem extension can use it to guarantee that no group of processes
1039 will ever exhaust kernel resources alone.
1041 config CGROUP_HUGETLB
1042 bool "HugeTLB Resource Controller for Control Groups"
1043 depends on HUGETLB_PAGE
1047 Provides a cgroup Resource Controller for HugeTLB pages.
1048 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1049 The limit is enforced during page fault. Since HugeTLB doesn't
1050 support page reclaim, enforcing the limit at page fault time implies
1051 that, the application will get SIGBUS signal if it tries to access
1052 HugeTLB pages beyond its limit. This requires the application to know
1053 beforehand how much HugeTLB pages it would require for its use. The
1054 control group is tracked in the third page lru pointer. This means
1055 that we cannot use the controller with huge page less than 3 pages.
1058 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1059 depends on PERF_EVENTS && CGROUPS
1061 This option extends the per-cpu mode to restrict monitoring to
1062 threads which belong to the cgroup specified and run on the
1067 menuconfig CGROUP_SCHED
1068 bool "Group CPU scheduler"
1071 This feature lets CPU scheduler recognize task groups and control CPU
1072 bandwidth allocation to such task groups. It uses cgroups to group
1076 config FAIR_GROUP_SCHED
1077 bool "Group scheduling for SCHED_OTHER"
1078 depends on CGROUP_SCHED
1079 default CGROUP_SCHED
1081 config CFS_BANDWIDTH
1082 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1083 depends on FAIR_GROUP_SCHED
1086 This option allows users to define CPU bandwidth rates (limits) for
1087 tasks running within the fair group scheduler. Groups with no limit
1088 set are considered to be unconstrained and will run with no
1090 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1092 config RT_GROUP_SCHED
1093 bool "Group scheduling for SCHED_RR/FIFO"
1094 depends on CGROUP_SCHED
1097 This feature lets you explicitly allocate real CPU bandwidth
1098 to task groups. If enabled, it will also make it impossible to
1099 schedule realtime tasks for non-root users until you allocate
1100 realtime bandwidth for them.
1101 See Documentation/scheduler/sched-rt-group.txt for more information.
1106 bool "Block IO controller"
1110 Generic block IO controller cgroup interface. This is the common
1111 cgroup interface which should be used by various IO controlling
1114 Currently, CFQ IO scheduler uses it to recognize task groups and
1115 control disk bandwidth allocation (proportional time slice allocation)
1116 to such task groups. It is also used by bio throttling logic in
1117 block layer to implement upper limit in IO rates on a device.
1119 This option only enables generic Block IO controller infrastructure.
1120 One needs to also enable actual IO controlling logic/policy. For
1121 enabling proportional weight division of disk bandwidth in CFQ, set
1122 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1123 CONFIG_BLK_DEV_THROTTLING=y.
1125 See Documentation/cgroups/blkio-controller.txt for more information.
1127 config DEBUG_BLK_CGROUP
1128 bool "Enable Block IO controller debugging"
1129 depends on BLK_CGROUP
1132 Enable some debugging help. Currently it exports additional stat
1133 files in a cgroup which can be useful for debugging.
1137 config CHECKPOINT_RESTORE
1138 bool "Checkpoint/restore support" if EXPERT
1141 Enables additional kernel features in a sake of checkpoint/restore.
1142 In particular it adds auxiliary prctl codes to setup process text,
1143 data and heap segment sizes, and a few additional /proc filesystem
1146 If unsure, say N here.
1148 menuconfig NAMESPACES
1149 bool "Namespaces support" if EXPERT
1150 depends on MULTIUSER
1153 Provides the way to make tasks work with different objects using
1154 the same id. For example same IPC id may refer to different objects
1155 or same user id or pid may refer to different tasks when used in
1156 different namespaces.
1161 bool "UTS namespace"
1164 In this namespace tasks see different info provided with the
1168 bool "IPC namespace"
1169 depends on (SYSVIPC || POSIX_MQUEUE)
1172 In this namespace tasks work with IPC ids which correspond to
1173 different IPC objects in different namespaces.
1176 bool "User namespace"
1179 This allows containers, i.e. vservers, to use user namespaces
1180 to provide different user info for different servers.
1182 When user namespaces are enabled in the kernel it is
1183 recommended that the MEMCG and MEMCG_KMEM options also be
1184 enabled and that user-space use the memory control groups to
1185 limit the amount of memory a memory unprivileged users can
1191 bool "PID Namespaces"
1194 Support process id namespaces. This allows having multiple
1195 processes with the same pid as long as they are in different
1196 pid namespaces. This is a building block of containers.
1199 bool "Network namespace"
1203 Allow user space to create what appear to be multiple instances
1204 of the network stack.
1208 config SCHED_AUTOGROUP
1209 bool "Automatic process group scheduling"
1212 select FAIR_GROUP_SCHED
1214 This option optimizes the scheduler for common desktop workloads by
1215 automatically creating and populating task groups. This separation
1216 of workloads isolates aggressive CPU burners (like build jobs) from
1217 desktop applications. Task group autogeneration is currently based
1220 config SYSFS_DEPRECATED
1221 bool "Enable deprecated sysfs features to support old userspace tools"
1225 This option adds code that switches the layout of the "block" class
1226 devices, to not show up in /sys/class/block/, but only in
1229 This switch is only active when the sysfs.deprecated=1 boot option is
1230 passed or the SYSFS_DEPRECATED_V2 option is set.
1232 This option allows new kernels to run on old distributions and tools,
1233 which might get confused by /sys/class/block/. Since 2007/2008 all
1234 major distributions and tools handle this just fine.
1236 Recent distributions and userspace tools after 2009/2010 depend on
1237 the existence of /sys/class/block/, and will not work with this
1240 Only if you are using a new kernel on an old distribution, you might
1243 config SYSFS_DEPRECATED_V2
1244 bool "Enable deprecated sysfs features by default"
1247 depends on SYSFS_DEPRECATED
1249 Enable deprecated sysfs by default.
1251 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1254 Only if you are using a new kernel on an old distribution, you might
1255 need to say Y here. Even then, odds are you would not need it
1256 enabled, you can always pass the boot option if absolutely necessary.
1259 bool "Kernel->user space relay support (formerly relayfs)"
1261 This option enables support for relay interface support in
1262 certain file systems (such as debugfs).
1263 It is designed to provide an efficient mechanism for tools and
1264 facilities to relay large amounts of data from kernel space to
1269 config BLK_DEV_INITRD
1270 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1271 depends on BROKEN || !FRV
1273 The initial RAM filesystem is a ramfs which is loaded by the
1274 boot loader (loadlin or lilo) and that is mounted as root
1275 before the normal boot procedure. It is typically used to
1276 load modules needed to mount the "real" root file system,
1277 etc. See <file:Documentation/initrd.txt> for details.
1279 If RAM disk support (BLK_DEV_RAM) is also included, this
1280 also enables initial RAM disk (initrd) support and adds
1281 15 Kbytes (more on some other architectures) to the kernel size.
1287 source "usr/Kconfig"
1291 config CC_OPTIMIZE_FOR_SIZE
1292 bool "Optimize for size"
1294 Enabling this option will pass "-Os" instead of "-O2" to
1295 your compiler resulting in a smaller kernel.
1308 config SYSCTL_EXCEPTION_TRACE
1311 Enable support for /proc/sys/debug/exception-trace.
1313 config SYSCTL_ARCH_UNALIGN_NO_WARN
1316 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1317 Allows arch to define/use @no_unaligned_warning to possibly warn
1318 about unaligned access emulation going on under the hood.
1320 config SYSCTL_ARCH_UNALIGN_ALLOW
1323 Enable support for /proc/sys/kernel/unaligned-trap
1324 Allows arches to define/use @unaligned_enabled to runtime toggle
1325 the unaligned access emulation.
1326 see arch/parisc/kernel/unaligned.c for reference
1328 config HAVE_PCSPKR_PLATFORM
1331 # interpreter that classic socket filters depend on
1336 bool "Configure standard kernel features (expert users)"
1337 # Unhide debug options, to make the on-by-default options visible
1340 This option allows certain base kernel options and settings
1341 to be disabled or tweaked. This is for specialized
1342 environments which can tolerate a "non-standard" kernel.
1343 Only use this if you really know what you are doing.
1346 bool "Enable 16-bit UID system calls" if EXPERT
1347 depends on HAVE_UID16 && MULTIUSER
1350 This enables the legacy 16-bit UID syscall wrappers.
1353 bool "Multiple users, groups and capabilities support" if EXPERT
1356 This option enables support for non-root users, groups and
1359 If you say N here, all processes will run with UID 0, GID 0, and all
1360 possible capabilities. Saying N here also compiles out support for
1361 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1364 If unsure, say Y here.
1366 config SGETMASK_SYSCALL
1367 bool "sgetmask/ssetmask syscalls support" if EXPERT
1368 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1370 sys_sgetmask and sys_ssetmask are obsolete system calls
1371 no longer supported in libc but still enabled by default in some
1374 If unsure, leave the default option here.
1376 config SYSFS_SYSCALL
1377 bool "Sysfs syscall support" if EXPERT
1380 sys_sysfs is an obsolete system call no longer supported in libc.
1381 Note that disabling this option is more secure but might break
1382 compatibility with some systems.
1384 If unsure say Y here.
1386 config SYSCTL_SYSCALL
1387 bool "Sysctl syscall support" if EXPERT
1388 depends on PROC_SYSCTL
1392 sys_sysctl uses binary paths that have been found challenging
1393 to properly maintain and use. The interface in /proc/sys
1394 using paths with ascii names is now the primary path to this
1397 Almost nothing using the binary sysctl interface so if you are
1398 trying to save some space it is probably safe to disable this,
1399 making your kernel marginally smaller.
1401 If unsure say N here.
1404 bool "Load all symbols for debugging/ksymoops" if EXPERT
1407 Say Y here to let the kernel print out symbolic crash information and
1408 symbolic stack backtraces. This increases the size of the kernel
1409 somewhat, as all symbols have to be loaded into the kernel image.
1412 bool "Include all symbols in kallsyms"
1413 depends on DEBUG_KERNEL && KALLSYMS
1415 Normally kallsyms only contains the symbols of functions for nicer
1416 OOPS messages and backtraces (i.e., symbols from the text and inittext
1417 sections). This is sufficient for most cases. And only in very rare
1418 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1419 names of variables from the data sections, etc).
1421 This option makes sure that all symbols are loaded into the kernel
1422 image (i.e., symbols from all sections) in cost of increased kernel
1423 size (depending on the kernel configuration, it may be 300KiB or
1424 something like this).
1426 Say N unless you really need all symbols.
1430 bool "Enable support for printk" if EXPERT
1433 This option enables normal printk support. Removing it
1434 eliminates most of the message strings from the kernel image
1435 and makes the kernel more or less silent. As this makes it
1436 very difficult to diagnose system problems, saying N here is
1437 strongly discouraged.
1440 bool "BUG() support" if EXPERT
1443 Disabling this option eliminates support for BUG and WARN, reducing
1444 the size of your kernel image and potentially quietly ignoring
1445 numerous fatal conditions. You should only consider disabling this
1446 option for embedded systems with no facilities for reporting errors.
1452 bool "Enable ELF core dumps" if EXPERT
1454 Enable support for generating core dumps. Disabling saves about 4k.
1457 config PCSPKR_PLATFORM
1458 bool "Enable PC-Speaker support" if EXPERT
1459 depends on HAVE_PCSPKR_PLATFORM
1463 This option allows to disable the internal PC-Speaker
1464 support, saving some memory.
1468 bool "Enable full-sized data structures for core" if EXPERT
1470 Disabling this option reduces the size of miscellaneous core
1471 kernel data structures. This saves memory on small machines,
1472 but may reduce performance.
1475 bool "Enable futex support" if EXPERT
1479 Disabling this option will cause the kernel to be built without
1480 support for "fast userspace mutexes". The resulting kernel may not
1481 run glibc-based applications correctly.
1483 config HAVE_FUTEX_CMPXCHG
1487 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1488 is implemented and always working. This removes a couple of runtime
1492 bool "Enable eventpoll support" if EXPERT
1496 Disabling this option will cause the kernel to be built without
1497 support for epoll family of system calls.
1500 bool "Enable signalfd() system call" if EXPERT
1504 Enable the signalfd() system call that allows to receive signals
1505 on a file descriptor.
1510 bool "Enable timerfd() system call" if EXPERT
1514 Enable the timerfd() system call that allows to receive timer
1515 events on a file descriptor.
1520 bool "Enable eventfd() system call" if EXPERT
1524 Enable the eventfd() system call that allows to receive both
1525 kernel notification (ie. KAIO) or userspace notifications.
1529 # syscall, maps, verifier
1531 bool "Enable bpf() system call"
1536 Enable the bpf() system call that allows to manipulate eBPF
1537 programs and maps via file descriptors.
1540 bool "Use full shmem filesystem" if EXPERT
1544 The shmem is an internal filesystem used to manage shared memory.
1545 It is backed by swap and manages resource limits. It is also exported
1546 to userspace as tmpfs if TMPFS is enabled. Disabling this
1547 option replaces shmem and tmpfs with the much simpler ramfs code,
1548 which may be appropriate on small systems without swap.
1551 bool "Enable AIO support" if EXPERT
1554 This option enables POSIX asynchronous I/O which may by used
1555 by some high performance threaded applications. Disabling
1556 this option saves about 7k.
1558 config ADVISE_SYSCALLS
1559 bool "Enable madvise/fadvise syscalls" if EXPERT
1562 This option enables the madvise and fadvise syscalls, used by
1563 applications to advise the kernel about their future memory or file
1564 usage, improving performance. If building an embedded system where no
1565 applications use these syscalls, you can disable this option to save
1570 bool "Enable PCI quirk workarounds" if EXPERT
1573 This enables workarounds for various PCI chipset
1574 bugs/quirks. Disable this only if your target machine is
1575 unaffected by PCI quirks.
1578 bool "Embedded system"
1579 option allnoconfig_y
1582 This option should be enabled if compiling the kernel for
1583 an embedded system so certain expert options are available
1586 config HAVE_PERF_EVENTS
1589 See tools/perf/design.txt for details.
1591 config PERF_USE_VMALLOC
1594 See tools/perf/design.txt for details
1596 menu "Kernel Performance Events And Counters"
1599 bool "Kernel performance events and counters"
1600 default y if PROFILING
1601 depends on HAVE_PERF_EVENTS
1606 Enable kernel support for various performance events provided
1607 by software and hardware.
1609 Software events are supported either built-in or via the
1610 use of generic tracepoints.
1612 Most modern CPUs support performance events via performance
1613 counter registers. These registers count the number of certain
1614 types of hw events: such as instructions executed, cachemisses
1615 suffered, or branches mis-predicted - without slowing down the
1616 kernel or applications. These registers can also trigger interrupts
1617 when a threshold number of events have passed - and can thus be
1618 used to profile the code that runs on that CPU.
1620 The Linux Performance Event subsystem provides an abstraction of
1621 these software and hardware event capabilities, available via a
1622 system call and used by the "perf" utility in tools/perf/. It
1623 provides per task and per CPU counters, and it provides event
1624 capabilities on top of those.
1628 config DEBUG_PERF_USE_VMALLOC
1630 bool "Debug: use vmalloc to back perf mmap() buffers"
1631 depends on PERF_EVENTS && DEBUG_KERNEL
1632 select PERF_USE_VMALLOC
1634 Use vmalloc memory to back perf mmap() buffers.
1636 Mostly useful for debugging the vmalloc code on platforms
1637 that don't require it.
1643 config VM_EVENT_COUNTERS
1645 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1647 VM event counters are needed for event counts to be shown.
1648 This option allows the disabling of the VM event counters
1649 on EXPERT systems. /proc/vmstat will only show page counts
1650 if VM event counters are disabled.
1654 bool "Enable SLUB debugging support" if EXPERT
1655 depends on SLUB && SYSFS
1657 SLUB has extensive debug support features. Disabling these can
1658 result in significant savings in code size. This also disables
1659 SLUB sysfs support. /sys/slab will not exist and there will be
1660 no support for cache validation etc.
1663 bool "Disable heap randomization"
1666 Randomizing heap placement makes heap exploits harder, but it
1667 also breaks ancient binaries (including anything libc5 based).
1668 This option changes the bootup default to heap randomization
1669 disabled, and can be overridden at runtime by setting
1670 /proc/sys/kernel/randomize_va_space to 2.
1672 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1675 prompt "Choose SLAB allocator"
1678 This option allows to select a slab allocator.
1683 The regular slab allocator that is established and known to work
1684 well in all environments. It organizes cache hot objects in
1685 per cpu and per node queues.
1688 bool "SLUB (Unqueued Allocator)"
1690 SLUB is a slab allocator that minimizes cache line usage
1691 instead of managing queues of cached objects (SLAB approach).
1692 Per cpu caching is realized using slabs of objects instead
1693 of queues of objects. SLUB can use memory efficiently
1694 and has enhanced diagnostics. SLUB is the default choice for
1699 bool "SLOB (Simple Allocator)"
1701 SLOB replaces the stock allocator with a drastically simpler
1702 allocator. SLOB is generally more space efficient but
1703 does not perform as well on large systems.
1707 config SLUB_CPU_PARTIAL
1709 depends on SLUB && SMP
1710 bool "SLUB per cpu partial cache"
1712 Per cpu partial caches accellerate objects allocation and freeing
1713 that is local to a processor at the price of more indeterminism
1714 in the latency of the free. On overflow these caches will be cleared
1715 which requires the taking of locks that may cause latency spikes.
1716 Typically one would choose no for a realtime system.
1718 config MMAP_ALLOW_UNINITIALIZED
1719 bool "Allow mmapped anonymous memory to be uninitialized"
1720 depends on EXPERT && !MMU
1723 Normally, and according to the Linux spec, anonymous memory obtained
1724 from mmap() has it's contents cleared before it is passed to
1725 userspace. Enabling this config option allows you to request that
1726 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1727 providing a huge performance boost. If this option is not enabled,
1728 then the flag will be ignored.
1730 This is taken advantage of by uClibc's malloc(), and also by
1731 ELF-FDPIC binfmt's brk and stack allocator.
1733 Because of the obvious security issues, this option should only be
1734 enabled on embedded devices where you control what is run in
1735 userspace. Since that isn't generally a problem on no-MMU systems,
1736 it is normally safe to say Y here.
1738 See Documentation/nommu-mmap.txt for more information.
1740 config SYSTEM_TRUSTED_KEYRING
1741 bool "Provide system-wide ring of trusted keys"
1744 Provide a system keyring to which trusted keys can be added. Keys in
1745 the keyring are considered to be trusted. Keys may be added at will
1746 by the kernel from compiled-in data and from hardware key stores, but
1747 userspace may only add extra keys if those keys can be verified by
1748 keys already in the keyring.
1750 Keys in this keyring are used by module signature checking.
1753 bool "Profiling support"
1755 Say Y here to enable the extended profiling support mechanisms used
1756 by profilers such as OProfile.
1759 # Place an empty function call at each tracepoint site. Can be
1760 # dynamically changed for a probe function.
1765 source "arch/Kconfig"
1767 endmenu # General setup
1769 config HAVE_GENERIC_DMA_COHERENT
1776 depends on SLAB || SLUB_DEBUG
1784 default 0 if BASE_FULL
1785 default 1 if !BASE_FULL
1788 bool "Enable loadable module support"
1791 Kernel modules are small pieces of compiled code which can
1792 be inserted in the running kernel, rather than being
1793 permanently built into the kernel. You use the "modprobe"
1794 tool to add (and sometimes remove) them. If you say Y here,
1795 many parts of the kernel can be built as modules (by
1796 answering M instead of Y where indicated): this is most
1797 useful for infrequently used options which are not required
1798 for booting. For more information, see the man pages for
1799 modprobe, lsmod, modinfo, insmod and rmmod.
1801 If you say Y here, you will need to run "make
1802 modules_install" to put the modules under /lib/modules/
1803 where modprobe can find them (you may need to be root to do
1810 config MODULE_FORCE_LOAD
1811 bool "Forced module loading"
1814 Allow loading of modules without version information (ie. modprobe
1815 --force). Forced module loading sets the 'F' (forced) taint flag and
1816 is usually a really bad idea.
1818 config MODULE_UNLOAD
1819 bool "Module unloading"
1821 Without this option you will not be able to unload any
1822 modules (note that some modules may not be unloadable
1823 anyway), which makes your kernel smaller, faster
1824 and simpler. If unsure, say Y.
1826 config MODULE_FORCE_UNLOAD
1827 bool "Forced module unloading"
1828 depends on MODULE_UNLOAD
1830 This option allows you to force a module to unload, even if the
1831 kernel believes it is unsafe: the kernel will remove the module
1832 without waiting for anyone to stop using it (using the -f option to
1833 rmmod). This is mainly for kernel developers and desperate users.
1837 bool "Module versioning support"
1839 Usually, you have to use modules compiled with your kernel.
1840 Saying Y here makes it sometimes possible to use modules
1841 compiled for different kernels, by adding enough information
1842 to the modules to (hopefully) spot any changes which would
1843 make them incompatible with the kernel you are running. If
1846 config MODULE_SRCVERSION_ALL
1847 bool "Source checksum for all modules"
1849 Modules which contain a MODULE_VERSION get an extra "srcversion"
1850 field inserted into their modinfo section, which contains a
1851 sum of the source files which made it. This helps maintainers
1852 see exactly which source was used to build a module (since
1853 others sometimes change the module source without updating
1854 the version). With this option, such a "srcversion" field
1855 will be created for all modules. If unsure, say N.
1858 bool "Module signature verification"
1860 select SYSTEM_TRUSTED_KEYRING
1863 select ASYMMETRIC_KEY_TYPE
1864 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1865 select PUBLIC_KEY_ALGO_RSA
1868 select X509_CERTIFICATE_PARSER
1870 Check modules for valid signatures upon load: the signature
1871 is simply appended to the module. For more information see
1872 Documentation/module-signing.txt.
1874 !!!WARNING!!! If you enable this option, you MUST make sure that the
1875 module DOES NOT get stripped after being signed. This includes the
1876 debuginfo strip done by some packagers (such as rpmbuild) and
1877 inclusion into an initramfs that wants the module size reduced.
1879 config MODULE_SIG_FORCE
1880 bool "Require modules to be validly signed"
1881 depends on MODULE_SIG
1883 Reject unsigned modules or signed modules for which we don't have a
1884 key. Without this, such modules will simply taint the kernel.
1886 config MODULE_SIG_ALL
1887 bool "Automatically sign all modules"
1889 depends on MODULE_SIG
1891 Sign all modules during make modules_install. Without this option,
1892 modules must be signed manually, using the scripts/sign-file tool.
1894 comment "Do not forget to sign required modules with scripts/sign-file"
1895 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1898 prompt "Which hash algorithm should modules be signed with?"
1899 depends on MODULE_SIG
1901 This determines which sort of hashing algorithm will be used during
1902 signature generation. This algorithm _must_ be built into the kernel
1903 directly so that signature verification can take place. It is not
1904 possible to load a signed module containing the algorithm to check
1905 the signature on that module.
1907 config MODULE_SIG_SHA1
1908 bool "Sign modules with SHA-1"
1911 config MODULE_SIG_SHA224
1912 bool "Sign modules with SHA-224"
1913 select CRYPTO_SHA256
1915 config MODULE_SIG_SHA256
1916 bool "Sign modules with SHA-256"
1917 select CRYPTO_SHA256
1919 config MODULE_SIG_SHA384
1920 bool "Sign modules with SHA-384"
1921 select CRYPTO_SHA512
1923 config MODULE_SIG_SHA512
1924 bool "Sign modules with SHA-512"
1925 select CRYPTO_SHA512
1929 config MODULE_SIG_HASH
1931 depends on MODULE_SIG
1932 default "sha1" if MODULE_SIG_SHA1
1933 default "sha224" if MODULE_SIG_SHA224
1934 default "sha256" if MODULE_SIG_SHA256
1935 default "sha384" if MODULE_SIG_SHA384
1936 default "sha512" if MODULE_SIG_SHA512
1938 config MODULE_COMPRESS
1939 bool "Compress modules on installation"
1942 This option compresses the kernel modules when 'make
1943 modules_install' is run.
1945 The modules will be compressed either using gzip or xz depend on the
1946 choice made in "Compression algorithm".
1948 module-init-tools has support for gzip format while kmod handle gzip
1949 and xz compressed modules.
1951 When a kernel module is installed from outside of the main kernel
1952 source and uses the Kbuild system for installing modules then that
1953 kernel module will also be compressed when it is installed.
1955 This option provides little benefit when the modules are to be used inside
1956 an initrd or initramfs, it generally is more efficient to compress the whole
1957 initrd or initramfs instead.
1959 This is fully compatible with signed modules while the signed module is
1960 compressed. module-init-tools or kmod handles decompression and provide to
1961 other layer the uncompressed but signed payload.
1964 prompt "Compression algorithm"
1965 depends on MODULE_COMPRESS
1966 default MODULE_COMPRESS_GZIP
1968 This determines which sort of compression will be used during
1969 'make modules_install'.
1971 GZIP (default) and XZ are supported.
1973 config MODULE_COMPRESS_GZIP
1976 config MODULE_COMPRESS_XZ
1983 config INIT_ALL_POSSIBLE
1986 Back when each arch used to define their own cpu_online_mask and
1987 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1988 with all 1s, and others with all 0s. When they were centralised,
1989 it was better to provide this option than to break all the archs
1990 and have several arch maintainers pursuing me down dark alleys.
1995 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1997 Need stop_machine() primitive.
1999 source "block/Kconfig"
2001 config PREEMPT_NOTIFIERS
2008 # Can be selected by architectures with broken toolchains
2009 # that get confused by correct const<->read_only section
2011 config BROKEN_RODATA
2017 Build a simple ASN.1 grammar compiler that produces a bytecode output
2018 that can be interpreted by the ASN.1 stream decoder and used to
2019 inform it as to what tags are to be expected in a stream and what
2020 functions to call on what tags.
2022 source "kernel/Kconfig.locks"
projects / mirror_ubuntu-bionic-kernel.git / blob