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1 # SPDX-License-Identifier: GPL-2.0-only
2 config DEFCONFIG_LIST
3 string
4 depends on !UML
5 option defconfig_list
6 default "/lib/modules/$(shell,uname -r)/.config"
7 default "/etc/kernel-config"
8 default "/boot/config-$(shell,uname -r)"
9 default "arch/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG)"
11 config CC_VERSION_TEXT
12 string
13 default "$(CC_VERSION_TEXT)"
14 help
15 This is used in unclear ways:
17 - Re-run Kconfig when the compiler is updated
18 The 'default' property references the environment variable,
19 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd.
20 When the compiler is updated, Kconfig will be invoked.
22 - Ensure full rebuild when the compier is updated
23 include/linux/kconfig.h contains this option in the comment line so
24 fixdep adds include/config/cc/version/text.h into the auto-generated
25 dependency. When the compiler is updated, syncconfig will touch it
26 and then every file will be rebuilt.
28 config CC_IS_GCC
29 def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q gcc)
31 config GCC_VERSION
32 int
33 default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC
34 default 0
36 config LD_VERSION
37 int
38 default $(shell,$(LD) --version | $(srctree)/scripts/ld-version.sh)
40 config CC_IS_CLANG
41 def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q clang)
43 config LD_IS_LLD
44 def_bool $(success,$(LD) -v | head -n 1 | grep -q LLD)
46 config CLANG_VERSION
47 int
48 default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
50 config CC_CAN_LINK
51 bool
52 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(m64-flag)) if 64BIT
53 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(m32-flag))
55 config CC_CAN_LINK_STATIC
56 bool
57 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) -static $(m64-flag)) if 64BIT
58 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) -static $(m32-flag))
60 config CC_HAS_ASM_GOTO
61 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
63 config CC_HAS_ASM_GOTO_OUTPUT
64 depends on CC_HAS_ASM_GOTO
65 def_bool $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null)
67 config TOOLS_SUPPORT_RELR
68 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
70 config CC_HAS_ASM_INLINE
71 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
73 config CONSTRUCTORS
74 bool
75 depends on !UML
77 config IRQ_WORK
78 bool
80 config BUILDTIME_TABLE_SORT
81 bool
83 config THREAD_INFO_IN_TASK
84 bool
85 help
86 Select this to move thread_info off the stack into task_struct. To
87 make this work, an arch will need to remove all thread_info fields
88 except flags and fix any runtime bugs.
90 One subtle change that will be needed is to use try_get_task_stack()
91 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
93 menu "General setup"
95 config BROKEN
96 bool
98 config BROKEN_ON_SMP
99 bool
100 depends on BROKEN || !SMP
101 default y
103 config INIT_ENV_ARG_LIMIT
104 int
105 default 32 if !UML
106 default 128 if UML
107 help
108 Maximum of each of the number of arguments and environment
109 variables passed to init from the kernel command line.
111 config COMPILE_TEST
112 bool "Compile also drivers which will not load"
113 depends on !UML
114 default n
115 help
116 Some drivers can be compiled on a different platform than they are
117 intended to be run on. Despite they cannot be loaded there (or even
118 when they load they cannot be used due to missing HW support),
119 developers still, opposing to distributors, might want to build such
120 drivers to compile-test them.
122 If you are a developer and want to build everything available, say Y
123 here. If you are a user/distributor, say N here to exclude useless
124 drivers to be distributed.
126 config UAPI_HEADER_TEST
127 bool "Compile test UAPI headers"
128 depends on HEADERS_INSTALL && CC_CAN_LINK
129 help
130 Compile test headers exported to user-space to ensure they are
131 self-contained, i.e. compilable as standalone units.
133 If you are a developer or tester and want to ensure the exported
134 headers are self-contained, say Y here. Otherwise, choose N.
136 config LOCALVERSION
137 string "Local version - append to kernel release"
138 help
139 Append an extra string to the end of your kernel version.
140 This will show up when you type uname, for example.
141 The string you set here will be appended after the contents of
142 any files with a filename matching localversion* in your
143 object and source tree, in that order. Your total string can
144 be a maximum of 64 characters.
146 config LOCALVERSION_AUTO
147 bool "Automatically append version information to the version string"
148 default y
149 depends on !COMPILE_TEST
150 help
151 This will try to automatically determine if the current tree is a
152 release tree by looking for git tags that belong to the current
153 top of tree revision.
155 A string of the format -gxxxxxxxx will be added to the localversion
156 if a git-based tree is found. The string generated by this will be
157 appended after any matching localversion* files, and after the value
158 set in CONFIG_LOCALVERSION.
160 (The actual string used here is the first eight characters produced
161 by running the command:
163 $ git rev-parse --verify HEAD
165 which is done within the script "scripts/setlocalversion".)
167 config BUILD_SALT
168 string "Build ID Salt"
169 default ""
170 help
171 The build ID is used to link binaries and their debug info. Setting
172 this option will use the value in the calculation of the build id.
173 This is mostly useful for distributions which want to ensure the
174 build is unique between builds. It's safe to leave the default.
176 config HAVE_KERNEL_GZIP
177 bool
179 config HAVE_KERNEL_BZIP2
180 bool
182 config HAVE_KERNEL_LZMA
183 bool
185 config HAVE_KERNEL_XZ
186 bool
188 config HAVE_KERNEL_LZO
189 bool
191 config HAVE_KERNEL_LZ4
192 bool
194 config HAVE_KERNEL_UNCOMPRESSED
195 bool
197 choice
198 prompt "Kernel compression mode"
199 default KERNEL_GZIP
200 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED
201 help
202 The linux kernel is a kind of self-extracting executable.
203 Several compression algorithms are available, which differ
204 in efficiency, compression and decompression speed.
205 Compression speed is only relevant when building a kernel.
206 Decompression speed is relevant at each boot.
208 If you have any problems with bzip2 or lzma compressed
209 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
210 version of this functionality (bzip2 only), for 2.4, was
211 supplied by Christian Ludwig)
213 High compression options are mostly useful for users, who
214 are low on disk space (embedded systems), but for whom ram
215 size matters less.
217 If in doubt, select 'gzip'
219 config KERNEL_GZIP
220 bool "Gzip"
221 depends on HAVE_KERNEL_GZIP
222 help
223 The old and tried gzip compression. It provides a good balance
224 between compression ratio and decompression speed.
226 config KERNEL_BZIP2
227 bool "Bzip2"
228 depends on HAVE_KERNEL_BZIP2
229 help
230 Its compression ratio and speed is intermediate.
231 Decompression speed is slowest among the choices. The kernel
232 size is about 10% smaller with bzip2, in comparison to gzip.
233 Bzip2 uses a large amount of memory. For modern kernels you
234 will need at least 8MB RAM or more for booting.
236 config KERNEL_LZMA
237 bool "LZMA"
238 depends on HAVE_KERNEL_LZMA
239 help
240 This compression algorithm's ratio is best. Decompression speed
241 is between gzip and bzip2. Compression is slowest.
242 The kernel size is about 33% smaller with LZMA in comparison to gzip.
244 config KERNEL_XZ
245 bool "XZ"
246 depends on HAVE_KERNEL_XZ
247 help
248 XZ uses the LZMA2 algorithm and instruction set specific
249 BCJ filters which can improve compression ratio of executable
250 code. The size of the kernel is about 30% smaller with XZ in
251 comparison to gzip. On architectures for which there is a BCJ
252 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
253 will create a few percent smaller kernel than plain LZMA.
255 The speed is about the same as with LZMA: The decompression
256 speed of XZ is better than that of bzip2 but worse than gzip
257 and LZO. Compression is slow.
259 config KERNEL_LZO
260 bool "LZO"
261 depends on HAVE_KERNEL_LZO
262 help
263 Its compression ratio is the poorest among the choices. The kernel
264 size is about 10% bigger than gzip; however its speed
265 (both compression and decompression) is the fastest.
267 config KERNEL_LZ4
268 bool "LZ4"
269 depends on HAVE_KERNEL_LZ4
270 help
271 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
272 A preliminary version of LZ4 de/compression tool is available at
273 <https://code.google.com/p/lz4/>.
275 Its compression ratio is worse than LZO. The size of the kernel
276 is about 8% bigger than LZO. But the decompression speed is
277 faster than LZO.
279 config KERNEL_UNCOMPRESSED
280 bool "None"
281 depends on HAVE_KERNEL_UNCOMPRESSED
282 help
283 Produce uncompressed kernel image. This option is usually not what
284 you want. It is useful for debugging the kernel in slow simulation
285 environments, where decompressing and moving the kernel is awfully
286 slow. This option allows early boot code to skip the decompressor
287 and jump right at uncompressed kernel image.
289 endchoice
291 config DEFAULT_INIT
292 string "Default init path"
293 default ""
294 help
295 This option determines the default init for the system if no init=
296 option is passed on the kernel command line. If the requested path is
297 not present, we will still then move on to attempting further
298 locations (e.g. /sbin/init, etc). If this is empty, we will just use
299 the fallback list when init= is not passed.
301 config DEFAULT_HOSTNAME
302 string "Default hostname"
303 default "(none)"
304 help
305 This option determines the default system hostname before userspace
306 calls sethostname(2). The kernel traditionally uses "(none)" here,
307 but you may wish to use a different default here to make a minimal
308 system more usable with less configuration.
310 #
311 # For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
312 # add proper SWAP support to them, in which case this can be remove.
313 #
314 config ARCH_NO_SWAP
315 bool
317 config SWAP
318 bool "Support for paging of anonymous memory (swap)"
319 depends on MMU && BLOCK && !ARCH_NO_SWAP
320 default y
321 help
322 This option allows you to choose whether you want to have support
323 for so called swap devices or swap files in your kernel that are
324 used to provide more virtual memory than the actual RAM present
325 in your computer. If unsure say Y.
327 config SYSVIPC
328 bool "System V IPC"
329 help
330 Inter Process Communication is a suite of library functions and
331 system calls which let processes (running programs) synchronize and
332 exchange information. It is generally considered to be a good thing,
333 and some programs won't run unless you say Y here. In particular, if
334 you want to run the DOS emulator dosemu under Linux (read the
335 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
336 you'll need to say Y here.
338 You can find documentation about IPC with "info ipc" and also in
339 section 6.4 of the Linux Programmer's Guide, available from
340 <http://www.tldp.org/guides.html>.
342 config SYSVIPC_SYSCTL
343 bool
344 depends on SYSVIPC
345 depends on SYSCTL
346 default y
348 config POSIX_MQUEUE
349 bool "POSIX Message Queues"
350 depends on NET
351 help
352 POSIX variant of message queues is a part of IPC. In POSIX message
353 queues every message has a priority which decides about succession
354 of receiving it by a process. If you want to compile and run
355 programs written e.g. for Solaris with use of its POSIX message
356 queues (functions mq_*) say Y here.
358 POSIX message queues are visible as a filesystem called 'mqueue'
359 and can be mounted somewhere if you want to do filesystem
360 operations on message queues.
362 If unsure, say Y.
364 config POSIX_MQUEUE_SYSCTL
365 bool
366 depends on POSIX_MQUEUE
367 depends on SYSCTL
368 default y
370 config WATCH_QUEUE
371 bool "General notification queue"
372 default n
373 help
375 This is a general notification queue for the kernel to pass events to
376 userspace by splicing them into pipes. It can be used in conjunction
377 with watches for key/keyring change notifications and device
378 notifications.
380 See Documentation/watch_queue.rst
382 config CROSS_MEMORY_ATTACH
383 bool "Enable process_vm_readv/writev syscalls"
384 depends on MMU
385 default y
386 help
387 Enabling this option adds the system calls process_vm_readv and
388 process_vm_writev which allow a process with the correct privileges
389 to directly read from or write to another process' address space.
390 See the man page for more details.
392 config USELIB
393 bool "uselib syscall"
394 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
395 help
396 This option enables the uselib syscall, a system call used in the
397 dynamic linker from libc5 and earlier. glibc does not use this
398 system call. If you intend to run programs built on libc5 or
399 earlier, you may need to enable this syscall. Current systems
400 running glibc can safely disable this.
402 config AUDIT
403 bool "Auditing support"
404 depends on NET
405 help
406 Enable auditing infrastructure that can be used with another
407 kernel subsystem, such as SELinux (which requires this for
408 logging of avc messages output). System call auditing is included
409 on architectures which support it.
411 config HAVE_ARCH_AUDITSYSCALL
412 bool
414 config AUDITSYSCALL
415 def_bool y
416 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
417 select FSNOTIFY
419 source "kernel/irq/Kconfig"
420 source "kernel/time/Kconfig"
421 source "kernel/Kconfig.preempt"
423 menu "CPU/Task time and stats accounting"
425 config VIRT_CPU_ACCOUNTING
426 bool
428 choice
429 prompt "Cputime accounting"
430 default TICK_CPU_ACCOUNTING if !PPC64
431 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
433 # Kind of a stub config for the pure tick based cputime accounting
434 config TICK_CPU_ACCOUNTING
435 bool "Simple tick based cputime accounting"
436 depends on !S390 && !NO_HZ_FULL
437 help
438 This is the basic tick based cputime accounting that maintains
439 statistics about user, system and idle time spent on per jiffies
440 granularity.
442 If unsure, say Y.
444 config VIRT_CPU_ACCOUNTING_NATIVE
445 bool "Deterministic task and CPU time accounting"
446 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
447 select VIRT_CPU_ACCOUNTING
448 help
449 Select this option to enable more accurate task and CPU time
450 accounting. This is done by reading a CPU counter on each
451 kernel entry and exit and on transitions within the kernel
452 between system, softirq and hardirq state, so there is a
453 small performance impact. In the case of s390 or IBM POWER > 5,
454 this also enables accounting of stolen time on logically-partitioned
455 systems.
457 config VIRT_CPU_ACCOUNTING_GEN
458 bool "Full dynticks CPU time accounting"
459 depends on HAVE_CONTEXT_TRACKING
460 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
461 depends on GENERIC_CLOCKEVENTS
462 select VIRT_CPU_ACCOUNTING
463 select CONTEXT_TRACKING
464 help
465 Select this option to enable task and CPU time accounting on full
466 dynticks systems. This accounting is implemented by watching every
467 kernel-user boundaries using the context tracking subsystem.
468 The accounting is thus performed at the expense of some significant
469 overhead.
471 For now this is only useful if you are working on the full
472 dynticks subsystem development.
474 If unsure, say N.
476 endchoice
478 config IRQ_TIME_ACCOUNTING
479 bool "Fine granularity task level IRQ time accounting"
480 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
481 help
482 Select this option to enable fine granularity task irq time
483 accounting. This is done by reading a timestamp on each
484 transitions between softirq and hardirq state, so there can be a
485 small performance impact.
487 If in doubt, say N here.
489 config HAVE_SCHED_AVG_IRQ
490 def_bool y
491 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
492 depends on SMP
494 config SCHED_THERMAL_PRESSURE
495 bool "Enable periodic averaging of thermal pressure"
496 depends on SMP
498 config BSD_PROCESS_ACCT
499 bool "BSD Process Accounting"
500 depends on MULTIUSER
501 help
502 If you say Y here, a user level program will be able to instruct the
503 kernel (via a special system call) to write process accounting
504 information to a file: whenever a process exits, information about
505 that process will be appended to the file by the kernel. The
506 information includes things such as creation time, owning user,
507 command name, memory usage, controlling terminal etc. (the complete
508 list is in the struct acct in <file:include/linux/acct.h>). It is
509 up to the user level program to do useful things with this
510 information. This is generally a good idea, so say Y.
512 config BSD_PROCESS_ACCT_V3
513 bool "BSD Process Accounting version 3 file format"
514 depends on BSD_PROCESS_ACCT
515 default n
516 help
517 If you say Y here, the process accounting information is written
518 in a new file format that also logs the process IDs of each
519 process and its parent. Note that this file format is incompatible
520 with previous v0/v1/v2 file formats, so you will need updated tools
521 for processing it. A preliminary version of these tools is available
522 at <http://www.gnu.org/software/acct/>.
524 config TASKSTATS
525 bool "Export task/process statistics through netlink"
526 depends on NET
527 depends on MULTIUSER
528 default n
529 help
530 Export selected statistics for tasks/processes through the
531 generic netlink interface. Unlike BSD process accounting, the
532 statistics are available during the lifetime of tasks/processes as
533 responses to commands. Like BSD accounting, they are sent to user
534 space on task exit.
536 Say N if unsure.
538 config TASK_DELAY_ACCT
539 bool "Enable per-task delay accounting"
540 depends on TASKSTATS
541 select SCHED_INFO
542 help
543 Collect information on time spent by a task waiting for system
544 resources like cpu, synchronous block I/O completion and swapping
545 in pages. Such statistics can help in setting a task's priorities
546 relative to other tasks for cpu, io, rss limits etc.
548 Say N if unsure.
550 config TASK_XACCT
551 bool "Enable extended accounting over taskstats"
552 depends on TASKSTATS
553 help
554 Collect extended task accounting data and send the data
555 to userland for processing over the taskstats interface.
557 Say N if unsure.
559 config TASK_IO_ACCOUNTING
560 bool "Enable per-task storage I/O accounting"
561 depends on TASK_XACCT
562 help
563 Collect information on the number of bytes of storage I/O which this
564 task has caused.
566 Say N if unsure.
568 config PSI
569 bool "Pressure stall information tracking"
570 help
571 Collect metrics that indicate how overcommitted the CPU, memory,
572 and IO capacity are in the system.
574 If you say Y here, the kernel will create /proc/pressure/ with the
575 pressure statistics files cpu, memory, and io. These will indicate
576 the share of walltime in which some or all tasks in the system are
577 delayed due to contention of the respective resource.
579 In kernels with cgroup support, cgroups (cgroup2 only) will
580 have cpu.pressure, memory.pressure, and io.pressure files,
581 which aggregate pressure stalls for the grouped tasks only.
583 For more details see Documentation/accounting/psi.rst.
585 Say N if unsure.
587 config PSI_DEFAULT_DISABLED
588 bool "Require boot parameter to enable pressure stall information tracking"
589 default n
590 depends on PSI
591 help
592 If set, pressure stall information tracking will be disabled
593 per default but can be enabled through passing psi=1 on the
594 kernel commandline during boot.
596 This feature adds some code to the task wakeup and sleep
597 paths of the scheduler. The overhead is too low to affect
598 common scheduling-intense workloads in practice (such as
599 webservers, memcache), but it does show up in artificial
600 scheduler stress tests, such as hackbench.
602 If you are paranoid and not sure what the kernel will be
603 used for, say Y.
605 Say N if unsure.
607 endmenu # "CPU/Task time and stats accounting"
609 config CPU_ISOLATION
610 bool "CPU isolation"
611 depends on SMP || COMPILE_TEST
612 default y
613 help
614 Make sure that CPUs running critical tasks are not disturbed by
615 any source of "noise" such as unbound workqueues, timers, kthreads...
616 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
617 the "isolcpus=" boot parameter.
619 Say Y if unsure.
621 source "kernel/rcu/Kconfig"
623 config BUILD_BIN2C
624 bool
625 default n
627 config IKCONFIG
628 tristate "Kernel .config support"
629 help
630 This option enables the complete Linux kernel ".config" file
631 contents to be saved in the kernel. It provides documentation
632 of which kernel options are used in a running kernel or in an
633 on-disk kernel. This information can be extracted from the kernel
634 image file with the script scripts/extract-ikconfig and used as
635 input to rebuild the current kernel or to build another kernel.
636 It can also be extracted from a running kernel by reading
637 /proc/config.gz if enabled (below).
639 config IKCONFIG_PROC
640 bool "Enable access to .config through /proc/config.gz"
641 depends on IKCONFIG && PROC_FS
642 help
643 This option enables access to the kernel configuration file
644 through /proc/config.gz.
646 config IKHEADERS
647 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
648 depends on SYSFS
649 help
650 This option enables access to the in-kernel headers that are generated during
651 the build process. These can be used to build eBPF tracing programs,
652 or similar programs. If you build the headers as a module, a module called
653 kheaders.ko is built which can be loaded on-demand to get access to headers.
655 config LOG_BUF_SHIFT
656 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
657 range 12 25
658 default 17
659 depends on PRINTK
660 help
661 Select the minimal kernel log buffer size as a power of 2.
662 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
663 parameter, see below. Any higher size also might be forced
664 by "log_buf_len" boot parameter.
666 Examples:
667 17 => 128 KB
668 16 => 64 KB
669 15 => 32 KB
670 14 => 16 KB
671 13 => 8 KB
672 12 => 4 KB
674 config LOG_CPU_MAX_BUF_SHIFT
675 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
676 depends on SMP
677 range 0 21
678 default 12 if !BASE_SMALL
679 default 0 if BASE_SMALL
680 depends on PRINTK
681 help
682 This option allows to increase the default ring buffer size
683 according to the number of CPUs. The value defines the contribution
684 of each CPU as a power of 2. The used space is typically only few
685 lines however it might be much more when problems are reported,
686 e.g. backtraces.
688 The increased size means that a new buffer has to be allocated and
689 the original static one is unused. It makes sense only on systems
690 with more CPUs. Therefore this value is used only when the sum of
691 contributions is greater than the half of the default kernel ring
692 buffer as defined by LOG_BUF_SHIFT. The default values are set
693 so that more than 64 CPUs are needed to trigger the allocation.
695 Also this option is ignored when "log_buf_len" kernel parameter is
696 used as it forces an exact (power of two) size of the ring buffer.
698 The number of possible CPUs is used for this computation ignoring
699 hotplugging making the computation optimal for the worst case
700 scenario while allowing a simple algorithm to be used from bootup.
702 Examples shift values and their meaning:
703 17 => 128 KB for each CPU
704 16 => 64 KB for each CPU
705 15 => 32 KB for each CPU
706 14 => 16 KB for each CPU
707 13 => 8 KB for each CPU
708 12 => 4 KB for each CPU
710 config PRINTK_SAFE_LOG_BUF_SHIFT
711 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
712 range 10 21
713 default 13
714 depends on PRINTK
715 help
716 Select the size of an alternate printk per-CPU buffer where messages
717 printed from usafe contexts are temporary stored. One example would
718 be NMI messages, another one - printk recursion. The messages are
719 copied to the main log buffer in a safe context to avoid a deadlock.
720 The value defines the size as a power of 2.
722 Those messages are rare and limited. The largest one is when
723 a backtrace is printed. It usually fits into 4KB. Select
724 8KB if you want to be on the safe side.
726 Examples:
727 17 => 128 KB for each CPU
728 16 => 64 KB for each CPU
729 15 => 32 KB for each CPU
730 14 => 16 KB for each CPU
731 13 => 8 KB for each CPU
732 12 => 4 KB for each CPU
734 #
735 # Architectures with an unreliable sched_clock() should select this:
736 #
737 config HAVE_UNSTABLE_SCHED_CLOCK
738 bool
740 config GENERIC_SCHED_CLOCK
741 bool
743 menu "Scheduler features"
745 config UCLAMP_TASK
746 bool "Enable utilization clamping for RT/FAIR tasks"
747 depends on CPU_FREQ_GOV_SCHEDUTIL
748 help
749 This feature enables the scheduler to track the clamped utilization
750 of each CPU based on RUNNABLE tasks scheduled on that CPU.
752 With this option, the user can specify the min and max CPU
753 utilization allowed for RUNNABLE tasks. The max utilization defines
754 the maximum frequency a task should use while the min utilization
755 defines the minimum frequency it should use.
757 Both min and max utilization clamp values are hints to the scheduler,
758 aiming at improving its frequency selection policy, but they do not
759 enforce or grant any specific bandwidth for tasks.
761 If in doubt, say N.
763 config UCLAMP_BUCKETS_COUNT
764 int "Number of supported utilization clamp buckets"
765 range 5 20
766 default 5
767 depends on UCLAMP_TASK
768 help
769 Defines the number of clamp buckets to use. The range of each bucket
770 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
771 number of clamp buckets the finer their granularity and the higher
772 the precision of clamping aggregation and tracking at run-time.
774 For example, with the minimum configuration value we will have 5
775 clamp buckets tracking 20% utilization each. A 25% boosted tasks will
776 be refcounted in the [20..39]% bucket and will set the bucket clamp
777 effective value to 25%.
778 If a second 30% boosted task should be co-scheduled on the same CPU,
779 that task will be refcounted in the same bucket of the first task and
780 it will boost the bucket clamp effective value to 30%.
781 The clamp effective value of a bucket is reset to its nominal value
782 (20% in the example above) when there are no more tasks refcounted in
783 that bucket.
785 An additional boost/capping margin can be added to some tasks. In the
786 example above the 25% task will be boosted to 30% until it exits the
787 CPU. If that should be considered not acceptable on certain systems,
788 it's always possible to reduce the margin by increasing the number of
789 clamp buckets to trade off used memory for run-time tracking
790 precision.
792 If in doubt, use the default value.
794 endmenu
796 #
797 # For architectures that want to enable the support for NUMA-affine scheduler
798 # balancing logic:
799 #
800 config ARCH_SUPPORTS_NUMA_BALANCING
801 bool
803 #
804 # For architectures that prefer to flush all TLBs after a number of pages
805 # are unmapped instead of sending one IPI per page to flush. The architecture
806 # must provide guarantees on what happens if a clean TLB cache entry is
807 # written after the unmap. Details are in mm/rmap.c near the check for
808 # should_defer_flush. The architecture should also consider if the full flush
809 # and the refill costs are offset by the savings of sending fewer IPIs.
810 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
811 bool
813 config CC_HAS_INT128
814 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
816 #
817 # For architectures that know their GCC __int128 support is sound
818 #
819 config ARCH_SUPPORTS_INT128
820 bool
822 # For architectures that (ab)use NUMA to represent different memory regions
823 # all cpu-local but of different latencies, such as SuperH.
824 #
825 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
826 bool
828 config NUMA_BALANCING
829 bool "Memory placement aware NUMA scheduler"
830 depends on ARCH_SUPPORTS_NUMA_BALANCING
831 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
832 depends on SMP && NUMA && MIGRATION
833 help
834 This option adds support for automatic NUMA aware memory/task placement.
835 The mechanism is quite primitive and is based on migrating memory when
836 it has references to the node the task is running on.
838 This system will be inactive on UMA systems.
840 config NUMA_BALANCING_DEFAULT_ENABLED
841 bool "Automatically enable NUMA aware memory/task placement"
842 default y
843 depends on NUMA_BALANCING
844 help
845 If set, automatic NUMA balancing will be enabled if running on a NUMA
846 machine.
848 menuconfig CGROUPS
849 bool "Control Group support"
850 select KERNFS
851 help
852 This option adds support for grouping sets of processes together, for
853 use with process control subsystems such as Cpusets, CFS, memory
854 controls or device isolation.
855 See
856 - Documentation/scheduler/sched-design-CFS.rst (CFS)
857 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
858 and resource control)
860 Say N if unsure.
862 if CGROUPS
864 config PAGE_COUNTER
865 bool
867 config MEMCG
868 bool "Memory controller"
869 select PAGE_COUNTER
870 select EVENTFD
871 help
872 Provides control over the memory footprint of tasks in a cgroup.
874 config MEMCG_SWAP
875 bool
876 depends on MEMCG && SWAP
877 default y
879 config MEMCG_KMEM
880 bool
881 depends on MEMCG && !SLOB
882 default y
884 config BLK_CGROUP
885 bool "IO controller"
886 depends on BLOCK
887 default n
888 help
889 Generic block IO controller cgroup interface. This is the common
890 cgroup interface which should be used by various IO controlling
891 policies.
893 Currently, CFQ IO scheduler uses it to recognize task groups and
894 control disk bandwidth allocation (proportional time slice allocation)
895 to such task groups. It is also used by bio throttling logic in
896 block layer to implement upper limit in IO rates on a device.
898 This option only enables generic Block IO controller infrastructure.
899 One needs to also enable actual IO controlling logic/policy. For
900 enabling proportional weight division of disk bandwidth in CFQ, set
901 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
902 CONFIG_BLK_DEV_THROTTLING=y.
904 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
906 config CGROUP_WRITEBACK
907 bool
908 depends on MEMCG && BLK_CGROUP
909 default y
911 menuconfig CGROUP_SCHED
912 bool "CPU controller"
913 default n
914 help
915 This feature lets CPU scheduler recognize task groups and control CPU
916 bandwidth allocation to such task groups. It uses cgroups to group
917 tasks.
919 if CGROUP_SCHED
920 config FAIR_GROUP_SCHED
921 bool "Group scheduling for SCHED_OTHER"
922 depends on CGROUP_SCHED
923 default CGROUP_SCHED
925 config CFS_BANDWIDTH
926 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
927 depends on FAIR_GROUP_SCHED
928 default n
929 help
930 This option allows users to define CPU bandwidth rates (limits) for
931 tasks running within the fair group scheduler. Groups with no limit
932 set are considered to be unconstrained and will run with no
933 restriction.
934 See Documentation/scheduler/sched-bwc.rst for more information.
936 config RT_GROUP_SCHED
937 bool "Group scheduling for SCHED_RR/FIFO"
938 depends on CGROUP_SCHED
939 default n
940 help
941 This feature lets you explicitly allocate real CPU bandwidth
942 to task groups. If enabled, it will also make it impossible to
943 schedule realtime tasks for non-root users until you allocate
944 realtime bandwidth for them.
945 See Documentation/scheduler/sched-rt-group.rst for more information.
947 endif #CGROUP_SCHED
949 config UCLAMP_TASK_GROUP
950 bool "Utilization clamping per group of tasks"
951 depends on CGROUP_SCHED
952 depends on UCLAMP_TASK
953 default n
954 help
955 This feature enables the scheduler to track the clamped utilization
956 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
958 When this option is enabled, the user can specify a min and max
959 CPU bandwidth which is allowed for each single task in a group.
960 The max bandwidth allows to clamp the maximum frequency a task
961 can use, while the min bandwidth allows to define a minimum
962 frequency a task will always use.
964 When task group based utilization clamping is enabled, an eventually
965 specified task-specific clamp value is constrained by the cgroup
966 specified clamp value. Both minimum and maximum task clamping cannot
967 be bigger than the corresponding clamping defined at task group level.
969 If in doubt, say N.
971 config CGROUP_PIDS
972 bool "PIDs controller"
973 help
974 Provides enforcement of process number limits in the scope of a
975 cgroup. Any attempt to fork more processes than is allowed in the
976 cgroup will fail. PIDs are fundamentally a global resource because it
977 is fairly trivial to reach PID exhaustion before you reach even a
978 conservative kmemcg limit. As a result, it is possible to grind a
979 system to halt without being limited by other cgroup policies. The
980 PIDs controller is designed to stop this from happening.
982 It should be noted that organisational operations (such as attaching
983 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
984 since the PIDs limit only affects a process's ability to fork, not to
985 attach to a cgroup.
987 config CGROUP_RDMA
988 bool "RDMA controller"
989 help
990 Provides enforcement of RDMA resources defined by IB stack.
991 It is fairly easy for consumers to exhaust RDMA resources, which
992 can result into resource unavailability to other consumers.
993 RDMA controller is designed to stop this from happening.
994 Attaching processes with active RDMA resources to the cgroup
995 hierarchy is allowed even if can cross the hierarchy's limit.
997 config CGROUP_FREEZER
998 bool "Freezer controller"
999 help
1000 Provides a way to freeze and unfreeze all tasks in a
1001 cgroup.
1003 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1004 controller includes important in-kernel memory consumers per default.
1006 If you're using cgroup2, say N.
1008 config CGROUP_HUGETLB
1009 bool "HugeTLB controller"
1010 depends on HUGETLB_PAGE
1011 select PAGE_COUNTER
1012 default n
1013 help
1014 Provides a cgroup controller for HugeTLB pages.
1015 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1016 The limit is enforced during page fault. Since HugeTLB doesn't
1017 support page reclaim, enforcing the limit at page fault time implies
1018 that, the application will get SIGBUS signal if it tries to access
1019 HugeTLB pages beyond its limit. This requires the application to know
1020 beforehand how much HugeTLB pages it would require for its use. The
1021 control group is tracked in the third page lru pointer. This means
1022 that we cannot use the controller with huge page less than 3 pages.
1024 config CPUSETS
1025 bool "Cpuset controller"
1026 depends on SMP
1027 help
1028 This option will let you create and manage CPUSETs which
1029 allow dynamically partitioning a system into sets of CPUs and
1030 Memory Nodes and assigning tasks to run only within those sets.
1031 This is primarily useful on large SMP or NUMA systems.
1033 Say N if unsure.
1035 config PROC_PID_CPUSET
1036 bool "Include legacy /proc/<pid>/cpuset file"
1037 depends on CPUSETS
1038 default y
1040 config CGROUP_DEVICE
1041 bool "Device controller"
1042 help
1043 Provides a cgroup controller implementing whitelists for
1044 devices which a process in the cgroup can mknod or open.
1046 config CGROUP_CPUACCT
1047 bool "Simple CPU accounting controller"
1048 help
1049 Provides a simple controller for monitoring the
1050 total CPU consumed by the tasks in a cgroup.
1052 config CGROUP_PERF
1053 bool "Perf controller"
1054 depends on PERF_EVENTS
1055 help
1056 This option extends the perf per-cpu mode to restrict monitoring
1057 to threads which belong to the cgroup specified and run on the
1058 designated cpu. Or this can be used to have cgroup ID in samples
1059 so that it can monitor performance events among cgroups.
1061 Say N if unsure.
1063 config CGROUP_BPF
1064 bool "Support for eBPF programs attached to cgroups"
1065 depends on BPF_SYSCALL
1066 select SOCK_CGROUP_DATA
1067 help
1068 Allow attaching eBPF programs to a cgroup using the bpf(2)
1069 syscall command BPF_PROG_ATTACH.
1071 In which context these programs are accessed depends on the type
1072 of attachment. For instance, programs that are attached using
1073 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1074 inet sockets.
1076 config CGROUP_DEBUG
1077 bool "Debug controller"
1078 default n
1079 depends on DEBUG_KERNEL
1080 help
1081 This option enables a simple controller that exports
1082 debugging information about the cgroups framework. This
1083 controller is for control cgroup debugging only. Its
1084 interfaces are not stable.
1086 Say N.
1088 config SOCK_CGROUP_DATA
1089 bool
1090 default n
1092 endif # CGROUPS
1094 menuconfig NAMESPACES
1095 bool "Namespaces support" if EXPERT
1096 depends on MULTIUSER
1097 default !EXPERT
1098 help
1099 Provides the way to make tasks work with different objects using
1100 the same id. For example same IPC id may refer to different objects
1101 or same user id or pid may refer to different tasks when used in
1102 different namespaces.
1104 if NAMESPACES
1106 config UTS_NS
1107 bool "UTS namespace"
1108 default y
1109 help
1110 In this namespace tasks see different info provided with the
1111 uname() system call
1113 config TIME_NS
1114 bool "TIME namespace"
1115 depends on GENERIC_VDSO_TIME_NS
1116 default y
1117 help
1118 In this namespace boottime and monotonic clocks can be set.
1119 The time will keep going with the same pace.
1121 config IPC_NS
1122 bool "IPC namespace"
1123 depends on (SYSVIPC || POSIX_MQUEUE)
1124 default y
1125 help
1126 In this namespace tasks work with IPC ids which correspond to
1127 different IPC objects in different namespaces.
1129 config USER_NS
1130 bool "User namespace"
1131 default n
1132 help
1133 This allows containers, i.e. vservers, to use user namespaces
1134 to provide different user info for different servers.
1136 When user namespaces are enabled in the kernel it is
1137 recommended that the MEMCG option also be enabled and that
1138 user-space use the memory control groups to limit the amount
1139 of memory a memory unprivileged users can use.
1141 If unsure, say N.
1143 config PID_NS
1144 bool "PID Namespaces"
1145 default y
1146 help
1147 Support process id namespaces. This allows having multiple
1148 processes with the same pid as long as they are in different
1149 pid namespaces. This is a building block of containers.
1151 config NET_NS
1152 bool "Network namespace"
1153 depends on NET
1154 default y
1155 help
1156 Allow user space to create what appear to be multiple instances
1157 of the network stack.
1159 endif # NAMESPACES
1161 config CHECKPOINT_RESTORE
1162 bool "Checkpoint/restore support"
1163 select PROC_CHILDREN
1164 default n
1165 help
1166 Enables additional kernel features in a sake of checkpoint/restore.
1167 In particular it adds auxiliary prctl codes to setup process text,
1168 data and heap segment sizes, and a few additional /proc filesystem
1169 entries.
1171 If unsure, say N here.
1173 config SCHED_AUTOGROUP
1174 bool "Automatic process group scheduling"
1175 select CGROUPS
1176 select CGROUP_SCHED
1177 select FAIR_GROUP_SCHED
1178 help
1179 This option optimizes the scheduler for common desktop workloads by
1180 automatically creating and populating task groups. This separation
1181 of workloads isolates aggressive CPU burners (like build jobs) from
1182 desktop applications. Task group autogeneration is currently based
1183 upon task session.
1185 config SYSFS_DEPRECATED
1186 bool "Enable deprecated sysfs features to support old userspace tools"
1187 depends on SYSFS
1188 default n
1189 help
1190 This option adds code that switches the layout of the "block" class
1191 devices, to not show up in /sys/class/block/, but only in
1192 /sys/block/.
1194 This switch is only active when the sysfs.deprecated=1 boot option is
1195 passed or the SYSFS_DEPRECATED_V2 option is set.
1197 This option allows new kernels to run on old distributions and tools,
1198 which might get confused by /sys/class/block/. Since 2007/2008 all
1199 major distributions and tools handle this just fine.
1201 Recent distributions and userspace tools after 2009/2010 depend on
1202 the existence of /sys/class/block/, and will not work with this
1203 option enabled.
1205 Only if you are using a new kernel on an old distribution, you might
1206 need to say Y here.
1208 config SYSFS_DEPRECATED_V2
1209 bool "Enable deprecated sysfs features by default"
1210 default n
1211 depends on SYSFS
1212 depends on SYSFS_DEPRECATED
1213 help
1214 Enable deprecated sysfs by default.
1216 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1217 option.
1219 Only if you are using a new kernel on an old distribution, you might
1220 need to say Y here. Even then, odds are you would not need it
1221 enabled, you can always pass the boot option if absolutely necessary.
1223 config RELAY
1224 bool "Kernel->user space relay support (formerly relayfs)"
1225 select IRQ_WORK
1226 help
1227 This option enables support for relay interface support in
1228 certain file systems (such as debugfs).
1229 It is designed to provide an efficient mechanism for tools and
1230 facilities to relay large amounts of data from kernel space to
1231 user space.
1233 If unsure, say N.
1235 config BLK_DEV_INITRD
1236 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1237 help
1238 The initial RAM filesystem is a ramfs which is loaded by the
1239 boot loader (loadlin or lilo) and that is mounted as root
1240 before the normal boot procedure. It is typically used to
1241 load modules needed to mount the "real" root file system,
1242 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1244 If RAM disk support (BLK_DEV_RAM) is also included, this
1245 also enables initial RAM disk (initrd) support and adds
1246 15 Kbytes (more on some other architectures) to the kernel size.
1248 If unsure say Y.
1250 if BLK_DEV_INITRD
1252 source "usr/Kconfig"
1254 endif
1256 config BOOT_CONFIG
1257 bool "Boot config support"
1258 select BLK_DEV_INITRD
1259 help
1260 Extra boot config allows system admin to pass a config file as
1261 complemental extension of kernel cmdline when booting.
1262 The boot config file must be attached at the end of initramfs
1263 with checksum, size and magic word.
1264 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1266 If unsure, say Y.
1268 choice
1269 prompt "Compiler optimization level"
1270 default CC_OPTIMIZE_FOR_PERFORMANCE
1272 config CC_OPTIMIZE_FOR_PERFORMANCE
1273 bool "Optimize for performance (-O2)"
1274 help
1275 This is the default optimization level for the kernel, building
1276 with the "-O2" compiler flag for best performance and most
1277 helpful compile-time warnings.
1279 config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1280 bool "Optimize more for performance (-O3)"
1281 depends on ARC
1282 help
1283 Choosing this option will pass "-O3" to your compiler to optimize
1284 the kernel yet more for performance.
1286 config CC_OPTIMIZE_FOR_SIZE
1287 bool "Optimize for size (-Os)"
1288 help
1289 Choosing this option will pass "-Os" to your compiler resulting
1290 in a smaller kernel.
1292 endchoice
1294 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1295 bool
1296 help
1297 This requires that the arch annotates or otherwise protects
1298 its external entry points from being discarded. Linker scripts
1299 must also merge .text.*, .data.*, and .bss.* correctly into
1300 output sections. Care must be taken not to pull in unrelated
1301 sections (e.g., '.text.init'). Typically '.' in section names
1302 is used to distinguish them from label names / C identifiers.
1304 config LD_DEAD_CODE_DATA_ELIMINATION
1305 bool "Dead code and data elimination (EXPERIMENTAL)"
1306 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1307 depends on EXPERT
1308 depends on $(cc-option,-ffunction-sections -fdata-sections)
1309 depends on $(ld-option,--gc-sections)
1310 help
1311 Enable this if you want to do dead code and data elimination with
1312 the linker by compiling with -ffunction-sections -fdata-sections,
1313 and linking with --gc-sections.
1315 This can reduce on disk and in-memory size of the kernel
1316 code and static data, particularly for small configs and
1317 on small systems. This has the possibility of introducing
1318 silently broken kernel if the required annotations are not
1319 present. This option is not well tested yet, so use at your
1320 own risk.
1322 config SYSCTL
1323 bool
1325 config HAVE_UID16
1326 bool
1328 config SYSCTL_EXCEPTION_TRACE
1329 bool
1330 help
1331 Enable support for /proc/sys/debug/exception-trace.
1333 config SYSCTL_ARCH_UNALIGN_NO_WARN
1334 bool
1335 help
1336 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1337 Allows arch to define/use @no_unaligned_warning to possibly warn
1338 about unaligned access emulation going on under the hood.
1340 config SYSCTL_ARCH_UNALIGN_ALLOW
1341 bool
1342 help
1343 Enable support for /proc/sys/kernel/unaligned-trap
1344 Allows arches to define/use @unaligned_enabled to runtime toggle
1345 the unaligned access emulation.
1346 see arch/parisc/kernel/unaligned.c for reference
1348 config HAVE_PCSPKR_PLATFORM
1349 bool
1351 # interpreter that classic socket filters depend on
1352 config BPF
1353 bool
1355 menuconfig EXPERT
1356 bool "Configure standard kernel features (expert users)"
1357 # Unhide debug options, to make the on-by-default options visible
1358 select DEBUG_KERNEL
1359 help
1360 This option allows certain base kernel options and settings
1361 to be disabled or tweaked. This is for specialized
1362 environments which can tolerate a "non-standard" kernel.
1363 Only use this if you really know what you are doing.
1365 config UID16
1366 bool "Enable 16-bit UID system calls" if EXPERT
1367 depends on HAVE_UID16 && MULTIUSER
1368 default y
1369 help
1370 This enables the legacy 16-bit UID syscall wrappers.
1372 config MULTIUSER
1373 bool "Multiple users, groups and capabilities support" if EXPERT
1374 default y
1375 help
1376 This option enables support for non-root users, groups and
1377 capabilities.
1379 If you say N here, all processes will run with UID 0, GID 0, and all
1380 possible capabilities. Saying N here also compiles out support for
1381 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1382 setgid, and capset.
1384 If unsure, say Y here.
1386 config SGETMASK_SYSCALL
1387 bool "sgetmask/ssetmask syscalls support" if EXPERT
1388 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1389 help
1390 sys_sgetmask and sys_ssetmask are obsolete system calls
1391 no longer supported in libc but still enabled by default in some
1392 architectures.
1394 If unsure, leave the default option here.
1396 config SYSFS_SYSCALL
1397 bool "Sysfs syscall support" if EXPERT
1398 default y
1399 help
1400 sys_sysfs is an obsolete system call no longer supported in libc.
1401 Note that disabling this option is more secure but might break
1402 compatibility with some systems.
1404 If unsure say Y here.
1406 config FHANDLE
1407 bool "open by fhandle syscalls" if EXPERT
1408 select EXPORTFS
1409 default y
1410 help
1411 If you say Y here, a user level program will be able to map
1412 file names to handle and then later use the handle for
1413 different file system operations. This is useful in implementing
1414 userspace file servers, which now track files using handles instead
1415 of names. The handle would remain the same even if file names
1416 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1417 syscalls.
1419 config POSIX_TIMERS
1420 bool "Posix Clocks & timers" if EXPERT
1421 default y
1422 help
1423 This includes native support for POSIX timers to the kernel.
1424 Some embedded systems have no use for them and therefore they
1425 can be configured out to reduce the size of the kernel image.
1427 When this option is disabled, the following syscalls won't be
1428 available: timer_create, timer_gettime: timer_getoverrun,
1429 timer_settime, timer_delete, clock_adjtime, getitimer,
1430 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1431 clock_getres and clock_nanosleep syscalls will be limited to
1432 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1434 If unsure say y.
1436 config PRINTK
1437 default y
1438 bool "Enable support for printk" if EXPERT
1439 select IRQ_WORK
1440 help
1441 This option enables normal printk support. Removing it
1442 eliminates most of the message strings from the kernel image
1443 and makes the kernel more or less silent. As this makes it
1444 very difficult to diagnose system problems, saying N here is
1445 strongly discouraged.
1447 config PRINTK_NMI
1448 def_bool y
1449 depends on PRINTK
1450 depends on HAVE_NMI
1452 config BUG
1453 bool "BUG() support" if EXPERT
1454 default y
1455 help
1456 Disabling this option eliminates support for BUG and WARN, reducing
1457 the size of your kernel image and potentially quietly ignoring
1458 numerous fatal conditions. You should only consider disabling this
1459 option for embedded systems with no facilities for reporting errors.
1460 Just say Y.
1462 config ELF_CORE
1463 depends on COREDUMP
1464 default y
1465 bool "Enable ELF core dumps" if EXPERT
1466 help
1467 Enable support for generating core dumps. Disabling saves about 4k.
1470 config PCSPKR_PLATFORM
1471 bool "Enable PC-Speaker support" if EXPERT
1472 depends on HAVE_PCSPKR_PLATFORM
1473 select I8253_LOCK
1474 default y
1475 help
1476 This option allows to disable the internal PC-Speaker
1477 support, saving some memory.
1479 config BASE_FULL
1480 default y
1481 bool "Enable full-sized data structures for core" if EXPERT
1482 help
1483 Disabling this option reduces the size of miscellaneous core
1484 kernel data structures. This saves memory on small machines,
1485 but may reduce performance.
1487 config FUTEX
1488 bool "Enable futex support" if EXPERT
1489 default y
1490 imply RT_MUTEXES
1491 help
1492 Disabling this option will cause the kernel to be built without
1493 support for "fast userspace mutexes". The resulting kernel may not
1494 run glibc-based applications correctly.
1496 config FUTEX_PI
1497 bool
1498 depends on FUTEX && RT_MUTEXES
1499 default y
1501 config HAVE_FUTEX_CMPXCHG
1502 bool
1503 depends on FUTEX
1504 help
1505 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1506 is implemented and always working. This removes a couple of runtime
1507 checks.
1509 config EPOLL
1510 bool "Enable eventpoll support" if EXPERT
1511 default y
1512 help
1513 Disabling this option will cause the kernel to be built without
1514 support for epoll family of system calls.
1516 config SIGNALFD
1517 bool "Enable signalfd() system call" if EXPERT
1518 default y
1519 help
1520 Enable the signalfd() system call that allows to receive signals
1521 on a file descriptor.
1523 If unsure, say Y.
1525 config TIMERFD
1526 bool "Enable timerfd() system call" if EXPERT
1527 default y
1528 help
1529 Enable the timerfd() system call that allows to receive timer
1530 events on a file descriptor.
1532 If unsure, say Y.
1534 config EVENTFD
1535 bool "Enable eventfd() system call" if EXPERT
1536 default y
1537 help
1538 Enable the eventfd() system call that allows to receive both
1539 kernel notification (ie. KAIO) or userspace notifications.
1541 If unsure, say Y.
1543 config SHMEM
1544 bool "Use full shmem filesystem" if EXPERT
1545 default y
1546 depends on MMU
1547 help
1548 The shmem is an internal filesystem used to manage shared memory.
1549 It is backed by swap and manages resource limits. It is also exported
1550 to userspace as tmpfs if TMPFS is enabled. Disabling this
1551 option replaces shmem and tmpfs with the much simpler ramfs code,
1552 which may be appropriate on small systems without swap.
1554 config AIO
1555 bool "Enable AIO support" if EXPERT
1556 default y
1557 help
1558 This option enables POSIX asynchronous I/O which may by used
1559 by some high performance threaded applications. Disabling
1560 this option saves about 7k.
1562 config IO_URING
1563 bool "Enable IO uring support" if EXPERT
1564 select IO_WQ
1565 default y
1566 help
1567 This option enables support for the io_uring interface, enabling
1568 applications to submit and complete IO through submission and
1569 completion rings that are shared between the kernel and application.
1571 config ADVISE_SYSCALLS
1572 bool "Enable madvise/fadvise syscalls" if EXPERT
1573 default y
1574 help
1575 This option enables the madvise and fadvise syscalls, used by
1576 applications to advise the kernel about their future memory or file
1577 usage, improving performance. If building an embedded system where no
1578 applications use these syscalls, you can disable this option to save
1579 space.
1581 config HAVE_ARCH_USERFAULTFD_WP
1582 bool
1583 help
1584 Arch has userfaultfd write protection support
1586 config MEMBARRIER
1587 bool "Enable membarrier() system call" if EXPERT
1588 default y
1589 help
1590 Enable the membarrier() system call that allows issuing memory
1591 barriers across all running threads, which can be used to distribute
1592 the cost of user-space memory barriers asymmetrically by transforming
1593 pairs of memory barriers into pairs consisting of membarrier() and a
1594 compiler barrier.
1596 If unsure, say Y.
1598 config KALLSYMS
1599 bool "Load all symbols for debugging/ksymoops" if EXPERT
1600 default y
1601 help
1602 Say Y here to let the kernel print out symbolic crash information and
1603 symbolic stack backtraces. This increases the size of the kernel
1604 somewhat, as all symbols have to be loaded into the kernel image.
1606 config KALLSYMS_ALL
1607 bool "Include all symbols in kallsyms"
1608 depends on DEBUG_KERNEL && KALLSYMS
1609 help
1610 Normally kallsyms only contains the symbols of functions for nicer
1611 OOPS messages and backtraces (i.e., symbols from the text and inittext
1612 sections). This is sufficient for most cases. And only in very rare
1613 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1614 names of variables from the data sections, etc).
1616 This option makes sure that all symbols are loaded into the kernel
1617 image (i.e., symbols from all sections) in cost of increased kernel
1618 size (depending on the kernel configuration, it may be 300KiB or
1619 something like this).
1621 Say N unless you really need all symbols.
1623 config KALLSYMS_ABSOLUTE_PERCPU
1624 bool
1625 depends on KALLSYMS
1626 default X86_64 && SMP
1628 config KALLSYMS_BASE_RELATIVE
1629 bool
1630 depends on KALLSYMS
1631 default !IA64
1632 help
1633 Instead of emitting them as absolute values in the native word size,
1634 emit the symbol references in the kallsyms table as 32-bit entries,
1635 each containing a relative value in the range [base, base + U32_MAX]
1636 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1637 an absolute value in the range [0, S32_MAX] or a relative value in the
1638 range [base, base + S32_MAX], where base is the lowest relative symbol
1639 address encountered in the image.
1641 On 64-bit builds, this reduces the size of the address table by 50%,
1642 but more importantly, it results in entries whose values are build
1643 time constants, and no relocation pass is required at runtime to fix
1644 up the entries based on the runtime load address of the kernel.
1646 # end of the "standard kernel features (expert users)" menu
1648 # syscall, maps, verifier
1650 config BPF_LSM
1651 bool "LSM Instrumentation with BPF"
1652 depends on BPF_EVENTS
1653 depends on BPF_SYSCALL
1654 depends on SECURITY
1655 depends on BPF_JIT
1656 help
1657 Enables instrumentation of the security hooks with eBPF programs for
1658 implementing dynamic MAC and Audit Policies.
1660 If you are unsure how to answer this question, answer N.
1662 config BPF_SYSCALL
1663 bool "Enable bpf() system call"
1664 select BPF
1665 select IRQ_WORK
1666 default n
1667 help
1668 Enable the bpf() system call that allows to manipulate eBPF
1669 programs and maps via file descriptors.
1671 config ARCH_WANT_DEFAULT_BPF_JIT
1672 bool
1674 config BPF_JIT_ALWAYS_ON
1675 bool "Permanently enable BPF JIT and remove BPF interpreter"
1676 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1677 help
1678 Enables BPF JIT and removes BPF interpreter to avoid
1679 speculative execution of BPF instructions by the interpreter
1681 config BPF_JIT_DEFAULT_ON
1682 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
1683 depends on HAVE_EBPF_JIT && BPF_JIT
1685 config USERFAULTFD
1686 bool "Enable userfaultfd() system call"
1687 depends on MMU
1688 help
1689 Enable the userfaultfd() system call that allows to intercept and
1690 handle page faults in userland.
1692 config ARCH_HAS_MEMBARRIER_CALLBACKS
1693 bool
1695 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1696 bool
1698 config RSEQ
1699 bool "Enable rseq() system call" if EXPERT
1700 default y
1701 depends on HAVE_RSEQ
1702 select MEMBARRIER
1703 help
1704 Enable the restartable sequences system call. It provides a
1705 user-space cache for the current CPU number value, which
1706 speeds up getting the current CPU number from user-space,
1707 as well as an ABI to speed up user-space operations on
1708 per-CPU data.
1710 If unsure, say Y.
1712 config DEBUG_RSEQ
1713 default n
1714 bool "Enabled debugging of rseq() system call" if EXPERT
1715 depends on RSEQ && DEBUG_KERNEL
1716 help
1717 Enable extra debugging checks for the rseq system call.
1719 If unsure, say N.
1721 config EMBEDDED
1722 bool "Embedded system"
1723 option allnoconfig_y
1724 select EXPERT
1725 help
1726 This option should be enabled if compiling the kernel for
1727 an embedded system so certain expert options are available
1728 for configuration.
1730 config HAVE_PERF_EVENTS
1731 bool
1732 help
1733 See tools/perf/design.txt for details.
1735 config PERF_USE_VMALLOC
1736 bool
1737 help
1738 See tools/perf/design.txt for details
1740 config PC104
1741 bool "PC/104 support" if EXPERT
1742 help
1743 Expose PC/104 form factor device drivers and options available for
1744 selection and configuration. Enable this option if your target
1745 machine has a PC/104 bus.
1747 menu "Kernel Performance Events And Counters"
1749 config PERF_EVENTS
1750 bool "Kernel performance events and counters"
1751 default y if PROFILING
1752 depends on HAVE_PERF_EVENTS
1753 select IRQ_WORK
1754 select SRCU
1755 help
1756 Enable kernel support for various performance events provided
1757 by software and hardware.
1759 Software events are supported either built-in or via the
1760 use of generic tracepoints.
1762 Most modern CPUs support performance events via performance
1763 counter registers. These registers count the number of certain
1764 types of hw events: such as instructions executed, cachemisses
1765 suffered, or branches mis-predicted - without slowing down the
1766 kernel or applications. These registers can also trigger interrupts
1767 when a threshold number of events have passed - and can thus be
1768 used to profile the code that runs on that CPU.
1770 The Linux Performance Event subsystem provides an abstraction of
1771 these software and hardware event capabilities, available via a
1772 system call and used by the "perf" utility in tools/perf/. It
1773 provides per task and per CPU counters, and it provides event
1774 capabilities on top of those.
1776 Say Y if unsure.
1778 config DEBUG_PERF_USE_VMALLOC
1779 default n
1780 bool "Debug: use vmalloc to back perf mmap() buffers"
1781 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1782 select PERF_USE_VMALLOC
1783 help
1784 Use vmalloc memory to back perf mmap() buffers.
1786 Mostly useful for debugging the vmalloc code on platforms
1787 that don't require it.
1789 Say N if unsure.
1791 endmenu
1793 config VM_EVENT_COUNTERS
1794 default y
1795 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1796 help
1797 VM event counters are needed for event counts to be shown.
1798 This option allows the disabling of the VM event counters
1799 on EXPERT systems. /proc/vmstat will only show page counts
1800 if VM event counters are disabled.
1802 config SLUB_DEBUG
1803 default y
1804 bool "Enable SLUB debugging support" if EXPERT
1805 depends on SLUB && SYSFS
1806 help
1807 SLUB has extensive debug support features. Disabling these can
1808 result in significant savings in code size. This also disables
1809 SLUB sysfs support. /sys/slab will not exist and there will be
1810 no support for cache validation etc.
1812 config SLUB_MEMCG_SYSFS_ON
1813 default n
1814 bool "Enable memcg SLUB sysfs support by default" if EXPERT
1815 depends on SLUB && SYSFS && MEMCG
1816 help
1817 SLUB creates a directory under /sys/kernel/slab for each
1818 allocation cache to host info and debug files. If memory
1819 cgroup is enabled, each cache can have per memory cgroup
1820 caches. SLUB can create the same sysfs directories for these
1821 caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1822 to a very high number of debug files being created. This is
1823 controlled by slub_memcg_sysfs boot parameter and this
1824 config option determines the parameter's default value.
1826 config COMPAT_BRK
1827 bool "Disable heap randomization"
1828 default y
1829 help
1830 Randomizing heap placement makes heap exploits harder, but it
1831 also breaks ancient binaries (including anything libc5 based).
1832 This option changes the bootup default to heap randomization
1833 disabled, and can be overridden at runtime by setting
1834 /proc/sys/kernel/randomize_va_space to 2.
1836 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1838 choice
1839 prompt "Choose SLAB allocator"
1840 default SLUB
1841 help
1842 This option allows to select a slab allocator.
1844 config SLAB
1845 bool "SLAB"
1846 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1847 help
1848 The regular slab allocator that is established and known to work
1849 well in all environments. It organizes cache hot objects in
1850 per cpu and per node queues.
1852 config SLUB
1853 bool "SLUB (Unqueued Allocator)"
1854 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1855 help
1856 SLUB is a slab allocator that minimizes cache line usage
1857 instead of managing queues of cached objects (SLAB approach).
1858 Per cpu caching is realized using slabs of objects instead
1859 of queues of objects. SLUB can use memory efficiently
1860 and has enhanced diagnostics. SLUB is the default choice for
1861 a slab allocator.
1863 config SLOB
1864 depends on EXPERT
1865 bool "SLOB (Simple Allocator)"
1866 help
1867 SLOB replaces the stock allocator with a drastically simpler
1868 allocator. SLOB is generally more space efficient but
1869 does not perform as well on large systems.
1871 endchoice
1873 config SLAB_MERGE_DEFAULT
1874 bool "Allow slab caches to be merged"
1875 default y
1876 help
1877 For reduced kernel memory fragmentation, slab caches can be
1878 merged when they share the same size and other characteristics.
1879 This carries a risk of kernel heap overflows being able to
1880 overwrite objects from merged caches (and more easily control
1881 cache layout), which makes such heap attacks easier to exploit
1882 by attackers. By keeping caches unmerged, these kinds of exploits
1883 can usually only damage objects in the same cache. To disable
1884 merging at runtime, "slab_nomerge" can be passed on the kernel
1885 command line.
1887 config SLAB_FREELIST_RANDOM
1888 default n
1889 depends on SLAB || SLUB
1890 bool "SLAB freelist randomization"
1891 help
1892 Randomizes the freelist order used on creating new pages. This
1893 security feature reduces the predictability of the kernel slab
1894 allocator against heap overflows.
1896 config SLAB_FREELIST_HARDENED
1897 bool "Harden slab freelist metadata"
1898 depends on SLUB
1899 help
1900 Many kernel heap attacks try to target slab cache metadata and
1901 other infrastructure. This options makes minor performance
1902 sacrifices to harden the kernel slab allocator against common
1903 freelist exploit methods.
1905 config SHUFFLE_PAGE_ALLOCATOR
1906 bool "Page allocator randomization"
1907 default SLAB_FREELIST_RANDOM && ACPI_NUMA
1908 help
1909 Randomization of the page allocator improves the average
1910 utilization of a direct-mapped memory-side-cache. See section
1911 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1912 6.2a specification for an example of how a platform advertises
1913 the presence of a memory-side-cache. There are also incidental
1914 security benefits as it reduces the predictability of page
1915 allocations to compliment SLAB_FREELIST_RANDOM, but the
1916 default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1917 10th order of pages is selected based on cache utilization
1918 benefits on x86.
1920 While the randomization improves cache utilization it may
1921 negatively impact workloads on platforms without a cache. For
1922 this reason, by default, the randomization is enabled only
1923 after runtime detection of a direct-mapped memory-side-cache.
1924 Otherwise, the randomization may be force enabled with the
1925 'page_alloc.shuffle' kernel command line parameter.
1927 Say Y if unsure.
1929 config SLUB_CPU_PARTIAL
1930 default y
1931 depends on SLUB && SMP
1932 bool "SLUB per cpu partial cache"
1933 help
1934 Per cpu partial caches accelerate objects allocation and freeing
1935 that is local to a processor at the price of more indeterminism
1936 in the latency of the free. On overflow these caches will be cleared
1937 which requires the taking of locks that may cause latency spikes.
1938 Typically one would choose no for a realtime system.
1940 config MMAP_ALLOW_UNINITIALIZED
1941 bool "Allow mmapped anonymous memory to be uninitialized"
1942 depends on EXPERT && !MMU
1943 default n
1944 help
1945 Normally, and according to the Linux spec, anonymous memory obtained
1946 from mmap() has its contents cleared before it is passed to
1947 userspace. Enabling this config option allows you to request that
1948 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1949 providing a huge performance boost. If this option is not enabled,
1950 then the flag will be ignored.
1952 This is taken advantage of by uClibc's malloc(), and also by
1953 ELF-FDPIC binfmt's brk and stack allocator.
1955 Because of the obvious security issues, this option should only be
1956 enabled on embedded devices where you control what is run in
1957 userspace. Since that isn't generally a problem on no-MMU systems,
1958 it is normally safe to say Y here.
1960 See Documentation/nommu-mmap.txt for more information.
1962 config SYSTEM_DATA_VERIFICATION
1963 def_bool n
1964 select SYSTEM_TRUSTED_KEYRING
1965 select KEYS
1966 select CRYPTO
1967 select CRYPTO_RSA
1968 select ASYMMETRIC_KEY_TYPE
1969 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1970 select ASN1
1971 select OID_REGISTRY
1972 select X509_CERTIFICATE_PARSER
1973 select PKCS7_MESSAGE_PARSER
1974 help
1975 Provide PKCS#7 message verification using the contents of the system
1976 trusted keyring to provide public keys. This then can be used for
1977 module verification, kexec image verification and firmware blob
1978 verification.
1980 config PROFILING
1981 bool "Profiling support"
1982 help
1983 Say Y here to enable the extended profiling support mechanisms used
1984 by profilers such as OProfile.
1986 #
1987 # Place an empty function call at each tracepoint site. Can be
1988 # dynamically changed for a probe function.
1989 #
1990 config TRACEPOINTS
1991 bool
1993 endmenu # General setup
1995 source "arch/Kconfig"
1997 config RT_MUTEXES
1998 bool
2000 config BASE_SMALL
2001 int
2002 default 0 if BASE_FULL
2003 default 1 if !BASE_FULL
2005 config MODULE_SIG_FORMAT
2006 def_bool n
2007 select SYSTEM_DATA_VERIFICATION
2009 menuconfig MODULES
2010 bool "Enable loadable module support"
2011 option modules
2012 help
2013 Kernel modules are small pieces of compiled code which can
2014 be inserted in the running kernel, rather than being
2015 permanently built into the kernel. You use the "modprobe"
2016 tool to add (and sometimes remove) them. If you say Y here,
2017 many parts of the kernel can be built as modules (by
2018 answering M instead of Y where indicated): this is most
2019 useful for infrequently used options which are not required
2020 for booting. For more information, see the man pages for
2021 modprobe, lsmod, modinfo, insmod and rmmod.
2023 If you say Y here, you will need to run "make
2024 modules_install" to put the modules under /lib/modules/
2025 where modprobe can find them (you may need to be root to do
2026 this).
2028 If unsure, say Y.
2030 if MODULES
2032 config MODULE_FORCE_LOAD
2033 bool "Forced module loading"
2034 default n
2035 help
2036 Allow loading of modules without version information (ie. modprobe
2037 --force). Forced module loading sets the 'F' (forced) taint flag and
2038 is usually a really bad idea.
2040 config MODULE_UNLOAD
2041 bool "Module unloading"
2042 help
2043 Without this option you will not be able to unload any
2044 modules (note that some modules may not be unloadable
2045 anyway), which makes your kernel smaller, faster
2046 and simpler. If unsure, say Y.
2048 config MODULE_FORCE_UNLOAD
2049 bool "Forced module unloading"
2050 depends on MODULE_UNLOAD
2051 help
2052 This option allows you to force a module to unload, even if the
2053 kernel believes it is unsafe: the kernel will remove the module
2054 without waiting for anyone to stop using it (using the -f option to
2055 rmmod). This is mainly for kernel developers and desperate users.
2056 If unsure, say N.
2058 config MODVERSIONS
2059 bool "Module versioning support"
2060 help
2061 Usually, you have to use modules compiled with your kernel.
2062 Saying Y here makes it sometimes possible to use modules
2063 compiled for different kernels, by adding enough information
2064 to the modules to (hopefully) spot any changes which would
2065 make them incompatible with the kernel you are running. If
2066 unsure, say N.
2068 config ASM_MODVERSIONS
2069 bool
2070 default HAVE_ASM_MODVERSIONS && MODVERSIONS
2071 help
2072 This enables module versioning for exported symbols also from
2073 assembly. This can be enabled only when the target architecture
2074 supports it.
2076 config MODULE_REL_CRCS
2077 bool
2078 depends on MODVERSIONS
2080 config MODULE_SRCVERSION_ALL
2081 bool "Source checksum for all modules"
2082 help
2083 Modules which contain a MODULE_VERSION get an extra "srcversion"
2084 field inserted into their modinfo section, which contains a
2085 sum of the source files which made it. This helps maintainers
2086 see exactly which source was used to build a module (since
2087 others sometimes change the module source without updating
2088 the version). With this option, such a "srcversion" field
2089 will be created for all modules. If unsure, say N.
2091 config MODULE_SIG
2092 bool "Module signature verification"
2093 select MODULE_SIG_FORMAT
2094 help
2095 Check modules for valid signatures upon load: the signature
2096 is simply appended to the module. For more information see
2097 <file:Documentation/admin-guide/module-signing.rst>.
2099 Note that this option adds the OpenSSL development packages as a
2100 kernel build dependency so that the signing tool can use its crypto
2101 library.
2103 You should enable this option if you wish to use either
2104 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2105 another LSM - otherwise unsigned modules will be loadable regardless
2106 of the lockdown policy.
2108 !!!WARNING!!! If you enable this option, you MUST make sure that the
2109 module DOES NOT get stripped after being signed. This includes the
2110 debuginfo strip done by some packagers (such as rpmbuild) and
2111 inclusion into an initramfs that wants the module size reduced.
2113 config MODULE_SIG_FORCE
2114 bool "Require modules to be validly signed"
2115 depends on MODULE_SIG
2116 help
2117 Reject unsigned modules or signed modules for which we don't have a
2118 key. Without this, such modules will simply taint the kernel.
2120 config MODULE_SIG_ALL
2121 bool "Automatically sign all modules"
2122 default y
2123 depends on MODULE_SIG
2124 help
2125 Sign all modules during make modules_install. Without this option,
2126 modules must be signed manually, using the scripts/sign-file tool.
2128 comment "Do not forget to sign required modules with scripts/sign-file"
2129 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2131 choice
2132 prompt "Which hash algorithm should modules be signed with?"
2133 depends on MODULE_SIG
2134 help
2135 This determines which sort of hashing algorithm will be used during
2136 signature generation. This algorithm _must_ be built into the kernel
2137 directly so that signature verification can take place. It is not
2138 possible to load a signed module containing the algorithm to check
2139 the signature on that module.
2141 config MODULE_SIG_SHA1
2142 bool "Sign modules with SHA-1"
2143 select CRYPTO_SHA1
2145 config MODULE_SIG_SHA224
2146 bool "Sign modules with SHA-224"
2147 select CRYPTO_SHA256
2149 config MODULE_SIG_SHA256
2150 bool "Sign modules with SHA-256"
2151 select CRYPTO_SHA256
2153 config MODULE_SIG_SHA384
2154 bool "Sign modules with SHA-384"
2155 select CRYPTO_SHA512
2157 config MODULE_SIG_SHA512
2158 bool "Sign modules with SHA-512"
2159 select CRYPTO_SHA512
2161 endchoice
2163 config MODULE_SIG_HASH
2164 string
2165 depends on MODULE_SIG
2166 default "sha1" if MODULE_SIG_SHA1
2167 default "sha224" if MODULE_SIG_SHA224
2168 default "sha256" if MODULE_SIG_SHA256
2169 default "sha384" if MODULE_SIG_SHA384
2170 default "sha512" if MODULE_SIG_SHA512
2172 config MODULE_COMPRESS
2173 bool "Compress modules on installation"
2174 help
2176 Compresses kernel modules when 'make modules_install' is run; gzip or
2177 xz depending on "Compression algorithm" below.
2179 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2181 Out-of-tree kernel modules installed using Kbuild will also be
2182 compressed upon installation.
2184 Note: for modules inside an initrd or initramfs, it's more efficient
2185 to compress the whole initrd or initramfs instead.
2187 Note: This is fully compatible with signed modules.
2189 If in doubt, say N.
2191 choice
2192 prompt "Compression algorithm"
2193 depends on MODULE_COMPRESS
2194 default MODULE_COMPRESS_GZIP
2195 help
2196 This determines which sort of compression will be used during
2197 'make modules_install'.
2199 GZIP (default) and XZ are supported.
2201 config MODULE_COMPRESS_GZIP
2202 bool "GZIP"
2204 config MODULE_COMPRESS_XZ
2205 bool "XZ"
2207 endchoice
2209 config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2210 bool "Allow loading of modules with missing namespace imports"
2211 help
2212 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2213 a namespace. A module that makes use of a symbol exported with such a
2214 namespace is required to import the namespace via MODULE_IMPORT_NS().
2215 There is no technical reason to enforce correct namespace imports,
2216 but it creates consistency between symbols defining namespaces and
2217 users importing namespaces they make use of. This option relaxes this
2218 requirement and lifts the enforcement when loading a module.
2220 If unsure, say N.
2222 config UNUSED_SYMBOLS
2223 bool "Enable unused/obsolete exported symbols"
2224 default y if X86
2225 help
2226 Unused but exported symbols make the kernel needlessly bigger. For
2227 that reason most of these unused exports will soon be removed. This
2228 option is provided temporarily to provide a transition period in case
2229 some external kernel module needs one of these symbols anyway. If you
2230 encounter such a case in your module, consider if you are actually
2231 using the right API. (rationale: since nobody in the kernel is using
2232 this in a module, there is a pretty good chance it's actually the
2233 wrong interface to use). If you really need the symbol, please send a
2234 mail to the linux kernel mailing list mentioning the symbol and why
2235 you really need it, and what the merge plan to the mainline kernel for
2236 your module is.
2238 config TRIM_UNUSED_KSYMS
2239 bool "Trim unused exported kernel symbols"
2240 depends on !UNUSED_SYMBOLS
2241 help
2242 The kernel and some modules make many symbols available for
2243 other modules to use via EXPORT_SYMBOL() and variants. Depending
2244 on the set of modules being selected in your kernel configuration,
2245 many of those exported symbols might never be used.
2247 This option allows for unused exported symbols to be dropped from
2248 the build. In turn, this provides the compiler more opportunities
2249 (especially when using LTO) for optimizing the code and reducing
2250 binary size. This might have some security advantages as well.
2252 If unsure, or if you need to build out-of-tree modules, say N.
2254 config UNUSED_KSYMS_WHITELIST
2255 string "Whitelist of symbols to keep in ksymtab"
2256 depends on TRIM_UNUSED_KSYMS
2257 help
2258 By default, all unused exported symbols will be un-exported from the
2259 build when TRIM_UNUSED_KSYMS is selected.
2261 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
2262 exported at all times, even in absence of in-tree users. The value to
2263 set here is the path to a text file containing the list of symbols,
2264 one per line. The path can be absolute, or relative to the kernel
2265 source tree.
2267 endif # MODULES
2269 config MODULES_TREE_LOOKUP
2270 def_bool y
2271 depends on PERF_EVENTS || TRACING
2273 config INIT_ALL_POSSIBLE
2274 bool
2275 help
2276 Back when each arch used to define their own cpu_online_mask and
2277 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2278 with all 1s, and others with all 0s. When they were centralised,
2279 it was better to provide this option than to break all the archs
2280 and have several arch maintainers pursuing me down dark alleys.
2282 source "block/Kconfig"
2284 config PREEMPT_NOTIFIERS
2285 bool
2287 config PADATA
2288 depends on SMP
2289 bool
2291 config ASN1
2292 tristate
2293 help
2294 Build a simple ASN.1 grammar compiler that produces a bytecode output
2295 that can be interpreted by the ASN.1 stream decoder and used to
2296 inform it as to what tags are to be expected in a stream and what
2297 functions to call on what tags.
2299 source "kernel/Kconfig.locks"
2301 config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2302 bool
2304 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2305 bool
2307 # It may be useful for an architecture to override the definitions of the
2308 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2309 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2310 # different calling convention for syscalls. They can also override the
2311 # macros for not-implemented syscalls in kernel/sys_ni.c and
2312 # kernel/time/posix-stubs.c. All these overrides need to be available in
2313 # <asm/syscall_wrapper.h>.
2314 config ARCH_HAS_SYSCALL_WRAPPER
2315 def_bool n