1
2config CC_VERSION_TEXT
3 string
4 default "$(CC_VERSION_TEXT)"
5 help
6 This is used in unclear ways:
7
8 - Re-run Kconfig when the compiler is updated
9 The 'default' property references the environment variable,
10 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd.
11 When the compiler is updated, Kconfig will be invoked.
12
13 - Ensure full rebuild when the compiler is updated
14 include/linux/compiler-version.h contains this option in the comment
15 line so fixdep adds include/config/CC_VERSION_TEXT into the
16 auto-generated dependency. When the compiler is updated, syncconfig
17 will touch it and then every file will be rebuilt.
18
19config CC_IS_GCC
20 def_bool $(success,test "$(cc-name)" = GCC)
21
22config GCC_VERSION
23 int
24 default $(cc-version) if CC_IS_GCC
25 default 0
26
27config CC_IS_CLANG
28 def_bool $(success,test "$(cc-name)" = Clang)
29
30config CLANG_VERSION
31 int
32 default $(cc-version) if CC_IS_CLANG
33 default 0
34
35config AS_IS_GNU
36 def_bool $(success,test "$(as-name)" = GNU)
37
38config AS_IS_LLVM
39 def_bool $(success,test "$(as-name)" = LLVM)
40
41config AS_VERSION
42 int
43
44 default CLANG_VERSION if AS_IS_LLVM
45 default $(as-version)
46
47config LD_IS_BFD
48 def_bool $(success,test "$(ld-name)" = BFD)
49
50config LD_VERSION
51 int
52 default $(ld-version) if LD_IS_BFD
53 default 0
54
55config LD_IS_LLD
56 def_bool $(success,test "$(ld-name)" = LLD)
57
58config LLD_VERSION
59 int
60 default $(ld-version) if LD_IS_LLD
61 default 0
62
63config CC_CAN_LINK
64 bool
65 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag)) if 64BIT
66 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag))
67
68config CC_CAN_LINK_STATIC
69 bool
70 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static) if 64BIT
71 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag) -static)
72
73config CC_HAS_ASM_GOTO
74 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
75
76config CC_HAS_ASM_GOTO_OUTPUT
77 depends on CC_HAS_ASM_GOTO
78 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)
79
80config TOOLS_SUPPORT_RELR
81 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
82
83config CC_HAS_ASM_INLINE
84 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
85
86config CC_HAS_NO_PROFILE_FN_ATTR
87 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
88
89config CONSTRUCTORS
90 bool
91
92config IRQ_WORK
93 bool
94
95config BUILDTIME_TABLE_SORT
96 bool
97
98config THREAD_INFO_IN_TASK
99 bool
100 help
101 Select this to move thread_info off the stack into task_struct. To
102 make this work, an arch will need to remove all thread_info fields
103 except flags and fix any runtime bugs.
104
105 One subtle change that will be needed is to use try_get_task_stack()
106 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
107
108menu "General setup"
109
110config BROKEN
111 bool
112
113config BROKEN_ON_SMP
114 bool
115 depends on BROKEN || !SMP
116 default y
117
118config INIT_ENV_ARG_LIMIT
119 int
120 default 32 if !UML
121 default 128 if UML
122 help
123 Maximum of each of the number of arguments and environment
124 variables passed to init from the kernel command line.
125
126config COMPILE_TEST
127 bool "Compile also drivers which will not load"
128 depends on HAS_IOMEM
129 help
130 Some drivers can be compiled on a different platform than they are
131 intended to be run on. Despite they cannot be loaded there (or even
132 when they load they cannot be used due to missing HW support),
133 developers still, opposing to distributors, might want to build such
134 drivers to compile-test them.
135
136 If you are a developer and want to build everything available, say Y
137 here. If you are a user/distributor, say N here to exclude useless
138 drivers to be distributed.
139
140config WERROR
141 bool "Compile the kernel with warnings as errors"
142 default COMPILE_TEST
143 help
144 A kernel build should not cause any compiler warnings, and this
145 enables the '-Werror' flag to enforce that rule by default.
146
147 However, if you have a new (or very old) compiler with odd and
148 unusual warnings, or you have some architecture with problems,
149 you may need to disable this config option in order to
150 successfully build the kernel.
151
152 If in doubt, say Y.
153
154config UAPI_HEADER_TEST
155 bool "Compile test UAPI headers"
156 depends on HEADERS_INSTALL && CC_CAN_LINK
157 help
158 Compile test headers exported to user-space to ensure they are
159 self-contained, i.e. compilable as standalone units.
160
161 If you are a developer or tester and want to ensure the exported
162 headers are self-contained, say Y here. Otherwise, choose N.
163
164config LOCALVERSION
165 string "Local version - append to kernel release"
166 help
167 Append an extra string to the end of your kernel version.
168 This will show up when you type uname, for example.
169 The string you set here will be appended after the contents of
170 any files with a filename matching localversion* in your
171 object and source tree, in that order. Your total string can
172 be a maximum of 64 characters.
173
174config LOCALVERSION_AUTO
175 bool "Automatically append version information to the version string"
176 default y
177 depends on !COMPILE_TEST
178 help
179 This will try to automatically determine if the current tree is a
180 release tree by looking for git tags that belong to the current
181 top of tree revision.
182
183 A string of the format -gxxxxxxxx will be added to the localversion
184 if a git-based tree is found. The string generated by this will be
185 appended after any matching localversion* files, and after the value
186 set in CONFIG_LOCALVERSION.
187
188 (The actual string used here is the first eight characters produced
189 by running the command:
190
191 $ git rev-parse --verify HEAD
192
193 which is done within the script "scripts/setlocalversion".)
194
195config BUILD_SALT
196 string "Build ID Salt"
197 default ""
198 help
199 The build ID is used to link binaries and their debug info. Setting
200 this option will use the value in the calculation of the build id.
201 This is mostly useful for distributions which want to ensure the
202 build is unique between builds. It's safe to leave the default.
203
204config HAVE_KERNEL_GZIP
205 bool
206
207config HAVE_KERNEL_BZIP2
208 bool
209
210config HAVE_KERNEL_LZMA
211 bool
212
213config HAVE_KERNEL_XZ
214 bool
215
216config HAVE_KERNEL_LZO
217 bool
218
219config HAVE_KERNEL_LZ4
220 bool
221
222config HAVE_KERNEL_ZSTD
223 bool
224
225config HAVE_KERNEL_UNCOMPRESSED
226 bool
227
228choice
229 prompt "Kernel compression mode"
230 default KERNEL_GZIP
231 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_ZSTD || HAVE_KERNEL_UNCOMPRESSED
232 help
233 The linux kernel is a kind of self-extracting executable.
234 Several compression algorithms are available, which differ
235 in efficiency, compression and decompression speed.
236 Compression speed is only relevant when building a kernel.
237 Decompression speed is relevant at each boot.
238
239 If you have any problems with bzip2 or lzma compressed
240 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
241 version of this functionality (bzip2 only), for 2.4, was
242 supplied by Christian Ludwig)
243
244 High compression options are mostly useful for users, who
245 are low on disk space (embedded systems), but for whom ram
246 size matters less.
247
248 If in doubt, select 'gzip'
249
250config KERNEL_GZIP
251 bool "Gzip"
252 depends on HAVE_KERNEL_GZIP
253 help
254 The old and tried gzip compression. It provides a good balance
255 between compression ratio and decompression speed.
256
257config KERNEL_BZIP2
258 bool "Bzip2"
259 depends on HAVE_KERNEL_BZIP2
260 help
261 Its compression ratio and speed is intermediate.
262 Decompression speed is slowest among the choices. The kernel
263 size is about 10% smaller with bzip2, in comparison to gzip.
264 Bzip2 uses a large amount of memory. For modern kernels you
265 will need at least 8MB RAM or more for booting.
266
267config KERNEL_LZMA
268 bool "LZMA"
269 depends on HAVE_KERNEL_LZMA
270 help
271 This compression algorithm's ratio is best. Decompression speed
272 is between gzip and bzip2. Compression is slowest.
273 The kernel size is about 33% smaller with LZMA in comparison to gzip.
274
275config KERNEL_XZ
276 bool "XZ"
277 depends on HAVE_KERNEL_XZ
278 help
279 XZ uses the LZMA2 algorithm and instruction set specific
280 BCJ filters which can improve compression ratio of executable
281 code. The size of the kernel is about 30% smaller with XZ in
282 comparison to gzip. On architectures for which there is a BCJ
283 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
284 will create a few percent smaller kernel than plain LZMA.
285
286 The speed is about the same as with LZMA: The decompression
287 speed of XZ is better than that of bzip2 but worse than gzip
288 and LZO. Compression is slow.
289
290config KERNEL_LZO
291 bool "LZO"
292 depends on HAVE_KERNEL_LZO
293 help
294 Its compression ratio is the poorest among the choices. The kernel
295 size is about 10% bigger than gzip; however its speed
296 (both compression and decompression) is the fastest.
297
298config KERNEL_LZ4
299 bool "LZ4"
300 depends on HAVE_KERNEL_LZ4
301 help
302 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
303 A preliminary version of LZ4 de/compression tool is available at
304 <https://code.google.com/p/lz4/>.
305
306 Its compression ratio is worse than LZO. The size of the kernel
307 is about 8% bigger than LZO. But the decompression speed is
308 faster than LZO.
309
310config KERNEL_ZSTD
311 bool "ZSTD"
312 depends on HAVE_KERNEL_ZSTD
313 help
314 ZSTD is a compression algorithm targeting intermediate compression
315 with fast decompression speed. It will compress better than GZIP and
316 decompress around the same speed as LZO, but slower than LZ4. You
317 will need at least 192 KB RAM or more for booting. The zstd command
318 line tool is required for compression.
319
320config KERNEL_UNCOMPRESSED
321 bool "None"
322 depends on HAVE_KERNEL_UNCOMPRESSED
323 help
324 Produce uncompressed kernel image. This option is usually not what
325 you want. It is useful for debugging the kernel in slow simulation
326 environments, where decompressing and moving the kernel is awfully
327 slow. This option allows early boot code to skip the decompressor
328 and jump right at uncompressed kernel image.
329
330endchoice
331
332config DEFAULT_INIT
333 string "Default init path"
334 default ""
335 help
336 This option determines the default init for the system if no init=
337 option is passed on the kernel command line. If the requested path is
338 not present, we will still then move on to attempting further
339 locations (e.g. /sbin/init, etc). If this is empty, we will just use
340 the fallback list when init= is not passed.
341
342config DEFAULT_HOSTNAME
343 string "Default hostname"
344 default "(none)"
345 help
346 This option determines the default system hostname before userspace
347 calls sethostname(2). The kernel traditionally uses "(none)" here,
348 but you may wish to use a different default here to make a minimal
349 system more usable with less configuration.
350
351
352
353
354
355config ARCH_NO_SWAP
356 bool
357
358config SWAP
359 bool "Support for paging of anonymous memory (swap)"
360 depends on MMU && BLOCK && !ARCH_NO_SWAP
361 default y
362 help
363 This option allows you to choose whether you want to have support
364 for so called swap devices or swap files in your kernel that are
365 used to provide more virtual memory than the actual RAM present
366 in your computer. If unsure say Y.
367
368config SYSVIPC
369 bool "System V IPC"
370 help
371 Inter Process Communication is a suite of library functions and
372 system calls which let processes (running programs) synchronize and
373 exchange information. It is generally considered to be a good thing,
374 and some programs won't run unless you say Y here. In particular, if
375 you want to run the DOS emulator dosemu under Linux (read the
376 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
377 you'll need to say Y here.
378
379 You can find documentation about IPC with "info ipc" and also in
380 section 6.4 of the Linux Programmer's Guide, available from
381 <http://www.tldp.org/guides.html>.
382
383config SYSVIPC_SYSCTL
384 bool
385 depends on SYSVIPC
386 depends on SYSCTL
387 default y
388
389config POSIX_MQUEUE
390 bool "POSIX Message Queues"
391 depends on NET
392 help
393 POSIX variant of message queues is a part of IPC. In POSIX message
394 queues every message has a priority which decides about succession
395 of receiving it by a process. If you want to compile and run
396 programs written e.g. for Solaris with use of its POSIX message
397 queues (functions mq_*) say Y here.
398
399 POSIX message queues are visible as a filesystem called 'mqueue'
400 and can be mounted somewhere if you want to do filesystem
401 operations on message queues.
402
403 If unsure, say Y.
404
405config POSIX_MQUEUE_SYSCTL
406 bool
407 depends on POSIX_MQUEUE
408 depends on SYSCTL
409 default y
410
411config WATCH_QUEUE
412 bool "General notification queue"
413 default n
414 help
415
416 This is a general notification queue for the kernel to pass events to
417 userspace by splicing them into pipes. It can be used in conjunction
418 with watches for key/keyring change notifications and device
419 notifications.
420
421 See Documentation/watch_queue.rst
422
423config CROSS_MEMORY_ATTACH
424 bool "Enable process_vm_readv/writev syscalls"
425 depends on MMU
426 default y
427 help
428 Enabling this option adds the system calls process_vm_readv and
429 process_vm_writev which allow a process with the correct privileges
430 to directly read from or write to another process' address space.
431 See the man page for more details.
432
433config USELIB
434 bool "uselib syscall"
435 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
436 help
437 This option enables the uselib syscall, a system call used in the
438 dynamic linker from libc5 and earlier. glibc does not use this
439 system call. If you intend to run programs built on libc5 or
440 earlier, you may need to enable this syscall. Current systems
441 running glibc can safely disable this.
442
443config AUDIT
444 bool "Auditing support"
445 depends on NET
446 help
447 Enable auditing infrastructure that can be used with another
448 kernel subsystem, such as SELinux (which requires this for
449 logging of avc messages output). System call auditing is included
450 on architectures which support it.
451
452config HAVE_ARCH_AUDITSYSCALL
453 bool
454
455config AUDITSYSCALL
456 def_bool y
457 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
458 select FSNOTIFY
459
460source "kernel/irq/Kconfig"
461source "kernel/time/Kconfig"
462source "kernel/bpf/Kconfig"
463source "kernel/Kconfig.preempt"
464
465menu "CPU/Task time and stats accounting"
466
467config VIRT_CPU_ACCOUNTING
468 bool
469
470choice
471 prompt "Cputime accounting"
472 default TICK_CPU_ACCOUNTING if !PPC64
473 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
474
475
476config TICK_CPU_ACCOUNTING
477 bool "Simple tick based cputime accounting"
478 depends on !S390 && !NO_HZ_FULL
479 help
480 This is the basic tick based cputime accounting that maintains
481 statistics about user, system and idle time spent on per jiffies
482 granularity.
483
484 If unsure, say Y.
485
486config VIRT_CPU_ACCOUNTING_NATIVE
487 bool "Deterministic task and CPU time accounting"
488 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
489 select VIRT_CPU_ACCOUNTING
490 help
491 Select this option to enable more accurate task and CPU time
492 accounting. This is done by reading a CPU counter on each
493 kernel entry and exit and on transitions within the kernel
494 between system, softirq and hardirq state, so there is a
495 small performance impact. In the case of s390 or IBM POWER > 5,
496 this also enables accounting of stolen time on logically-partitioned
497 systems.
498
499config VIRT_CPU_ACCOUNTING_GEN
500 bool "Full dynticks CPU time accounting"
501 depends on HAVE_CONTEXT_TRACKING
502 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
503 depends on GENERIC_CLOCKEVENTS
504 select VIRT_CPU_ACCOUNTING
505 select CONTEXT_TRACKING
506 help
507 Select this option to enable task and CPU time accounting on full
508 dynticks systems. This accounting is implemented by watching every
509 kernel-user boundaries using the context tracking subsystem.
510 The accounting is thus performed at the expense of some significant
511 overhead.
512
513 For now this is only useful if you are working on the full
514 dynticks subsystem development.
515
516 If unsure, say N.
517
518endchoice
519
520config IRQ_TIME_ACCOUNTING
521 bool "Fine granularity task level IRQ time accounting"
522 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
523 help
524 Select this option to enable fine granularity task irq time
525 accounting. This is done by reading a timestamp on each
526 transitions between softirq and hardirq state, so there can be a
527 small performance impact.
528
529 If in doubt, say N here.
530
531config HAVE_SCHED_AVG_IRQ
532 def_bool y
533 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
534 depends on SMP
535
536config SCHED_THERMAL_PRESSURE
537 bool
538 default y if ARM && ARM_CPU_TOPOLOGY
539 default y if ARM64
540 depends on SMP
541 depends on CPU_FREQ_THERMAL
542 help
543 Select this option to enable thermal pressure accounting in the
544 scheduler. Thermal pressure is the value conveyed to the scheduler
545 that reflects the reduction in CPU compute capacity resulted from
546 thermal throttling. Thermal throttling occurs when the performance of
547 a CPU is capped due to high operating temperatures.
548
549 If selected, the scheduler will be able to balance tasks accordingly,
550 i.e. put less load on throttled CPUs than on non/less throttled ones.
551
552 This requires the architecture to implement
553 arch_set_thermal_pressure() and arch_scale_thermal_pressure().
554
555config BSD_PROCESS_ACCT
556 bool "BSD Process Accounting"
557 depends on MULTIUSER
558 help
559 If you say Y here, a user level program will be able to instruct the
560 kernel (via a special system call) to write process accounting
561 information to a file: whenever a process exits, information about
562 that process will be appended to the file by the kernel. The
563 information includes things such as creation time, owning user,
564 command name, memory usage, controlling terminal etc. (the complete
565 list is in the struct acct in <file:include/linux/acct.h>). It is
566 up to the user level program to do useful things with this
567 information. This is generally a good idea, so say Y.
568
569config BSD_PROCESS_ACCT_V3
570 bool "BSD Process Accounting version 3 file format"
571 depends on BSD_PROCESS_ACCT
572 default n
573 help
574 If you say Y here, the process accounting information is written
575 in a new file format that also logs the process IDs of each
576 process and its parent. Note that this file format is incompatible
577 with previous v0/v1/v2 file formats, so you will need updated tools
578 for processing it. A preliminary version of these tools is available
579 at <http://www.gnu.org/software/acct/>.
580
581config TASKSTATS
582 bool "Export task/process statistics through netlink"
583 depends on NET
584 depends on MULTIUSER
585 default n
586 help
587 Export selected statistics for tasks/processes through the
588 generic netlink interface. Unlike BSD process accounting, the
589 statistics are available during the lifetime of tasks/processes as
590 responses to commands. Like BSD accounting, they are sent to user
591 space on task exit.
592
593 Say N if unsure.
594
595config TASK_DELAY_ACCT
596 bool "Enable per-task delay accounting"
597 depends on TASKSTATS
598 select SCHED_INFO
599 help
600 Collect information on time spent by a task waiting for system
601 resources like cpu, synchronous block I/O completion and swapping
602 in pages. Such statistics can help in setting a task's priorities
603 relative to other tasks for cpu, io, rss limits etc.
604
605 Say N if unsure.
606
607config TASK_XACCT
608 bool "Enable extended accounting over taskstats"
609 depends on TASKSTATS
610 help
611 Collect extended task accounting data and send the data
612 to userland for processing over the taskstats interface.
613
614 Say N if unsure.
615
616config TASK_IO_ACCOUNTING
617 bool "Enable per-task storage I/O accounting"
618 depends on TASK_XACCT
619 help
620 Collect information on the number of bytes of storage I/O which this
621 task has caused.
622
623 Say N if unsure.
624
625config PSI
626 bool "Pressure stall information tracking"
627 help
628 Collect metrics that indicate how overcommitted the CPU, memory,
629 and IO capacity are in the system.
630
631 If you say Y here, the kernel will create /proc/pressure/ with the
632 pressure statistics files cpu, memory, and io. These will indicate
633 the share of walltime in which some or all tasks in the system are
634 delayed due to contention of the respective resource.
635
636 In kernels with cgroup support, cgroups (cgroup2 only) will
637 have cpu.pressure, memory.pressure, and io.pressure files,
638 which aggregate pressure stalls for the grouped tasks only.
639
640 For more details see Documentation/accounting/psi.rst.
641
642 Say N if unsure.
643
644config PSI_DEFAULT_DISABLED
645 bool "Require boot parameter to enable pressure stall information tracking"
646 default n
647 depends on PSI
648 help
649 If set, pressure stall information tracking will be disabled
650 per default but can be enabled through passing psi=1 on the
651 kernel commandline during boot.
652
653 This feature adds some code to the task wakeup and sleep
654 paths of the scheduler. The overhead is too low to affect
655 common scheduling-intense workloads in practice (such as
656 webservers, memcache), but it does show up in artificial
657 scheduler stress tests, such as hackbench.
658
659 If you are paranoid and not sure what the kernel will be
660 used for, say Y.
661
662 Say N if unsure.
663
664endmenu
665
666config CPU_ISOLATION
667 bool "CPU isolation"
668 depends on SMP || COMPILE_TEST
669 default y
670 help
671 Make sure that CPUs running critical tasks are not disturbed by
672 any source of "noise" such as unbound workqueues, timers, kthreads...
673 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
674 the "isolcpus=" boot parameter.
675
676 Say Y if unsure.
677
678source "kernel/rcu/Kconfig"
679
680config BUILD_BIN2C
681 bool
682 default n
683
684config IKCONFIG
685 tristate "Kernel .config support"
686 help
687 This option enables the complete Linux kernel ".config" file
688 contents to be saved in the kernel. It provides documentation
689 of which kernel options are used in a running kernel or in an
690 on-disk kernel. This information can be extracted from the kernel
691 image file with the script scripts/extract-ikconfig and used as
692 input to rebuild the current kernel or to build another kernel.
693 It can also be extracted from a running kernel by reading
694 /proc/config.gz if enabled (below).
695
696config IKCONFIG_PROC
697 bool "Enable access to .config through /proc/config.gz"
698 depends on IKCONFIG && PROC_FS
699 help
700 This option enables access to the kernel configuration file
701 through /proc/config.gz.
702
703config IKHEADERS
704 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
705 depends on SYSFS
706 help
707 This option enables access to the in-kernel headers that are generated during
708 the build process. These can be used to build eBPF tracing programs,
709 or similar programs. If you build the headers as a module, a module called
710 kheaders.ko is built which can be loaded on-demand to get access to headers.
711
712config LOG_BUF_SHIFT
713 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
714 range 12 25 if !H8300
715 range 12 19 if H8300
716 default 17
717 depends on PRINTK
718 help
719 Select the minimal kernel log buffer size as a power of 2.
720 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
721 parameter, see below. Any higher size also might be forced
722 by "log_buf_len" boot parameter.
723
724 Examples:
725 17 => 128 KB
726 16 => 64 KB
727 15 => 32 KB
728 14 => 16 KB
729 13 => 8 KB
730 12 => 4 KB
731
732config LOG_CPU_MAX_BUF_SHIFT
733 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
734 depends on SMP
735 range 0 21
736 default 12 if !BASE_SMALL
737 default 0 if BASE_SMALL
738 depends on PRINTK
739 help
740 This option allows to increase the default ring buffer size
741 according to the number of CPUs. The value defines the contribution
742 of each CPU as a power of 2. The used space is typically only few
743 lines however it might be much more when problems are reported,
744 e.g. backtraces.
745
746 The increased size means that a new buffer has to be allocated and
747 the original static one is unused. It makes sense only on systems
748 with more CPUs. Therefore this value is used only when the sum of
749 contributions is greater than the half of the default kernel ring
750 buffer as defined by LOG_BUF_SHIFT. The default values are set
751 so that more than 16 CPUs are needed to trigger the allocation.
752
753 Also this option is ignored when "log_buf_len" kernel parameter is
754 used as it forces an exact (power of two) size of the ring buffer.
755
756 The number of possible CPUs is used for this computation ignoring
757 hotplugging making the computation optimal for the worst case
758 scenario while allowing a simple algorithm to be used from bootup.
759
760 Examples shift values and their meaning:
761 17 => 128 KB for each CPU
762 16 => 64 KB for each CPU
763 15 => 32 KB for each CPU
764 14 => 16 KB for each CPU
765 13 => 8 KB for each CPU
766 12 => 4 KB for each CPU
767
768config PRINTK_SAFE_LOG_BUF_SHIFT
769 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
770 range 10 21
771 default 13
772 depends on PRINTK
773 help
774 Select the size of an alternate printk per-CPU buffer where messages
775 printed from usafe contexts are temporary stored. One example would
776 be NMI messages, another one - printk recursion. The messages are
777 copied to the main log buffer in a safe context to avoid a deadlock.
778 The value defines the size as a power of 2.
779
780 Those messages are rare and limited. The largest one is when
781 a backtrace is printed. It usually fits into 4KB. Select
782 8KB if you want to be on the safe side.
783
784 Examples:
785 17 => 128 KB for each CPU
786 16 => 64 KB for each CPU
787 15 => 32 KB for each CPU
788 14 => 16 KB for each CPU
789 13 => 8 KB for each CPU
790 12 => 4 KB for each CPU
791
792config PRINTK_INDEX
793 bool "Printk indexing debugfs interface"
794 depends on PRINTK && DEBUG_FS
795 help
796 Add support for indexing of all printk formats known at compile time
797 at <debugfs>/printk/index/<module>.
798
799 This can be used as part of maintaining daemons which monitor
800 /dev/kmsg, as it permits auditing the printk formats present in a
801 kernel, allowing detection of cases where monitored printks are
802 changed or no longer present.
803
804 There is no additional runtime cost to printk with this enabled.
805
806
807
808
809config HAVE_UNSTABLE_SCHED_CLOCK
810 bool
811
812config GENERIC_SCHED_CLOCK
813 bool
814
815menu "Scheduler features"
816
817config UCLAMP_TASK
818 bool "Enable utilization clamping for RT/FAIR tasks"
819 depends on CPU_FREQ_GOV_SCHEDUTIL
820 help
821 This feature enables the scheduler to track the clamped utilization
822 of each CPU based on RUNNABLE tasks scheduled on that CPU.
823
824 With this option, the user can specify the min and max CPU
825 utilization allowed for RUNNABLE tasks. The max utilization defines
826 the maximum frequency a task should use while the min utilization
827 defines the minimum frequency it should use.
828
829 Both min and max utilization clamp values are hints to the scheduler,
830 aiming at improving its frequency selection policy, but they do not
831 enforce or grant any specific bandwidth for tasks.
832
833 If in doubt, say N.
834
835config UCLAMP_BUCKETS_COUNT
836 int "Number of supported utilization clamp buckets"
837 range 5 20
838 default 5
839 depends on UCLAMP_TASK
840 help
841 Defines the number of clamp buckets to use. The range of each bucket
842 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
843 number of clamp buckets the finer their granularity and the higher
844 the precision of clamping aggregation and tracking at run-time.
845
846 For example, with the minimum configuration value we will have 5
847 clamp buckets tracking 20% utilization each. A 25% boosted tasks will
848 be refcounted in the [20..39]% bucket and will set the bucket clamp
849 effective value to 25%.
850 If a second 30% boosted task should be co-scheduled on the same CPU,
851 that task will be refcounted in the same bucket of the first task and
852 it will boost the bucket clamp effective value to 30%.
853 The clamp effective value of a bucket is reset to its nominal value
854 (20% in the example above) when there are no more tasks refcounted in
855 that bucket.
856
857 An additional boost/capping margin can be added to some tasks. In the
858 example above the 25% task will be boosted to 30% until it exits the
859 CPU. If that should be considered not acceptable on certain systems,
860 it's always possible to reduce the margin by increasing the number of
861 clamp buckets to trade off used memory for run-time tracking
862 precision.
863
864 If in doubt, use the default value.
865
866endmenu
867
868
869
870
871
872config ARCH_SUPPORTS_NUMA_BALANCING
873 bool
874
875
876
877
878
879
880
881
882config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
883 bool
884
885config CC_HAS_INT128
886 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
887
888config CC_IMPLICIT_FALLTHROUGH
889 string
890 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
891 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough)
892
893
894
895
896config ARCH_SUPPORTS_INT128
897 bool
898
899
900
901
902config ARCH_WANT_NUMA_VARIABLE_LOCALITY
903 bool
904
905config NUMA_BALANCING
906 bool "Memory placement aware NUMA scheduler"
907 depends on ARCH_SUPPORTS_NUMA_BALANCING
908 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
909 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT
910 help
911 This option adds support for automatic NUMA aware memory/task placement.
912 The mechanism is quite primitive and is based on migrating memory when
913 it has references to the node the task is running on.
914
915 This system will be inactive on UMA systems.
916
917config NUMA_BALANCING_DEFAULT_ENABLED
918 bool "Automatically enable NUMA aware memory/task placement"
919 default y
920 depends on NUMA_BALANCING
921 help
922 If set, automatic NUMA balancing will be enabled if running on a NUMA
923 machine.
924
925menuconfig CGROUPS
926 bool "Control Group support"
927 select KERNFS
928 help
929 This option adds support for grouping sets of processes together, for
930 use with process control subsystems such as Cpusets, CFS, memory
931 controls or device isolation.
932 See
933 - Documentation/scheduler/sched-design-CFS.rst (CFS)
934 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
935 and resource control)
936
937 Say N if unsure.
938
939if CGROUPS
940
941config PAGE_COUNTER
942 bool
943
944config MEMCG
945 bool "Memory controller"
946 select PAGE_COUNTER
947 select EVENTFD
948 help
949 Provides control over the memory footprint of tasks in a cgroup.
950
951config MEMCG_SWAP
952 bool
953 depends on MEMCG && SWAP
954 default y
955
956config MEMCG_KMEM
957 bool
958 depends on MEMCG && !SLOB
959 default y
960
961config BLK_CGROUP
962 bool "IO controller"
963 depends on BLOCK
964 default n
965 help
966 Generic block IO controller cgroup interface. This is the common
967 cgroup interface which should be used by various IO controlling
968 policies.
969
970 Currently, CFQ IO scheduler uses it to recognize task groups and
971 control disk bandwidth allocation (proportional time slice allocation)
972 to such task groups. It is also used by bio throttling logic in
973 block layer to implement upper limit in IO rates on a device.
974
975 This option only enables generic Block IO controller infrastructure.
976 One needs to also enable actual IO controlling logic/policy. For
977 enabling proportional weight division of disk bandwidth in CFQ, set
978 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
979 CONFIG_BLK_DEV_THROTTLING=y.
980
981 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
982
983config CGROUP_WRITEBACK
984 bool
985 depends on MEMCG && BLK_CGROUP
986 default y
987
988menuconfig CGROUP_SCHED
989 bool "CPU controller"
990 default n
991 help
992 This feature lets CPU scheduler recognize task groups and control CPU
993 bandwidth allocation to such task groups. It uses cgroups to group
994 tasks.
995
996if CGROUP_SCHED
997config FAIR_GROUP_SCHED
998 bool "Group scheduling for SCHED_OTHER"
999 depends on CGROUP_SCHED
1000 default CGROUP_SCHED
1001
1002config CFS_BANDWIDTH
1003 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1004 depends on FAIR_GROUP_SCHED
1005 default n
1006 help
1007 This option allows users to define CPU bandwidth rates (limits) for
1008 tasks running within the fair group scheduler. Groups with no limit
1009 set are considered to be unconstrained and will run with no
1010 restriction.
1011 See Documentation/scheduler/sched-bwc.rst for more information.
1012
1013config RT_GROUP_SCHED
1014 bool "Group scheduling for SCHED_RR/FIFO"
1015 depends on CGROUP_SCHED
1016 default n
1017 help
1018 This feature lets you explicitly allocate real CPU bandwidth
1019 to task groups. If enabled, it will also make it impossible to
1020 schedule realtime tasks for non-root users until you allocate
1021 realtime bandwidth for them.
1022 See Documentation/scheduler/sched-rt-group.rst for more information.
1023
1024endif
1025
1026config UCLAMP_TASK_GROUP
1027 bool "Utilization clamping per group of tasks"
1028 depends on CGROUP_SCHED
1029 depends on UCLAMP_TASK
1030 default n
1031 help
1032 This feature enables the scheduler to track the clamped utilization
1033 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
1034
1035 When this option is enabled, the user can specify a min and max
1036 CPU bandwidth which is allowed for each single task in a group.
1037 The max bandwidth allows to clamp the maximum frequency a task
1038 can use, while the min bandwidth allows to define a minimum
1039 frequency a task will always use.
1040
1041 When task group based utilization clamping is enabled, an eventually
1042 specified task-specific clamp value is constrained by the cgroup
1043 specified clamp value. Both minimum and maximum task clamping cannot
1044 be bigger than the corresponding clamping defined at task group level.
1045
1046 If in doubt, say N.
1047
1048config CGROUP_PIDS
1049 bool "PIDs controller"
1050 help
1051 Provides enforcement of process number limits in the scope of a
1052 cgroup. Any attempt to fork more processes than is allowed in the
1053 cgroup will fail. PIDs are fundamentally a global resource because it
1054 is fairly trivial to reach PID exhaustion before you reach even a
1055 conservative kmemcg limit. As a result, it is possible to grind a
1056 system to halt without being limited by other cgroup policies. The
1057 PIDs controller is designed to stop this from happening.
1058
1059 It should be noted that organisational operations (such as attaching
1060 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1061 since the PIDs limit only affects a process's ability to fork, not to
1062 attach to a cgroup.
1063
1064config CGROUP_RDMA
1065 bool "RDMA controller"
1066 help
1067 Provides enforcement of RDMA resources defined by IB stack.
1068 It is fairly easy for consumers to exhaust RDMA resources, which
1069 can result into resource unavailability to other consumers.
1070 RDMA controller is designed to stop this from happening.
1071 Attaching processes with active RDMA resources to the cgroup
1072 hierarchy is allowed even if can cross the hierarchy's limit.
1073
1074config CGROUP_FREEZER
1075 bool "Freezer controller"
1076 help
1077 Provides a way to freeze and unfreeze all tasks in a
1078 cgroup.
1079
1080 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1081 controller includes important in-kernel memory consumers per default.
1082
1083 If you're using cgroup2, say N.
1084
1085config CGROUP_HUGETLB
1086 bool "HugeTLB controller"
1087 depends on HUGETLB_PAGE
1088 select PAGE_COUNTER
1089 default n
1090 help
1091 Provides a cgroup controller for HugeTLB pages.
1092 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1093 The limit is enforced during page fault. Since HugeTLB doesn't
1094 support page reclaim, enforcing the limit at page fault time implies
1095 that, the application will get SIGBUS signal if it tries to access
1096 HugeTLB pages beyond its limit. This requires the application to know
1097 beforehand how much HugeTLB pages it would require for its use. The
1098 control group is tracked in the third page lru pointer. This means
1099 that we cannot use the controller with huge page less than 3 pages.
1100
1101config CPUSETS
1102 bool "Cpuset controller"
1103 depends on SMP
1104 help
1105 This option will let you create and manage CPUSETs which
1106 allow dynamically partitioning a system into sets of CPUs and
1107 Memory Nodes and assigning tasks to run only within those sets.
1108 This is primarily useful on large SMP or NUMA systems.
1109
1110 Say N if unsure.
1111
1112config PROC_PID_CPUSET
1113 bool "Include legacy /proc/<pid>/cpuset file"
1114 depends on CPUSETS
1115 default y
1116
1117config CGROUP_DEVICE
1118 bool "Device controller"
1119 help
1120 Provides a cgroup controller implementing whitelists for
1121 devices which a process in the cgroup can mknod or open.
1122
1123config CGROUP_CPUACCT
1124 bool "Simple CPU accounting controller"
1125 help
1126 Provides a simple controller for monitoring the
1127 total CPU consumed by the tasks in a cgroup.
1128
1129config CGROUP_PERF
1130 bool "Perf controller"
1131 depends on PERF_EVENTS
1132 help
1133 This option extends the perf per-cpu mode to restrict monitoring
1134 to threads which belong to the cgroup specified and run on the
1135 designated cpu. Or this can be used to have cgroup ID in samples
1136 so that it can monitor performance events among cgroups.
1137
1138 Say N if unsure.
1139
1140config CGROUP_BPF
1141 bool "Support for eBPF programs attached to cgroups"
1142 depends on BPF_SYSCALL
1143 select SOCK_CGROUP_DATA
1144 help
1145 Allow attaching eBPF programs to a cgroup using the bpf(2)
1146 syscall command BPF_PROG_ATTACH.
1147
1148 In which context these programs are accessed depends on the type
1149 of attachment. For instance, programs that are attached using
1150 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1151 inet sockets.
1152
1153config CGROUP_MISC
1154 bool "Misc resource controller"
1155 default n
1156 help
1157 Provides a controller for miscellaneous resources on a host.
1158
1159 Miscellaneous scalar resources are the resources on the host system
1160 which cannot be abstracted like the other cgroups. This controller
1161 tracks and limits the miscellaneous resources used by a process
1162 attached to a cgroup hierarchy.
1163
1164 For more information, please check misc cgroup section in
1165 /Documentation/admin-guide/cgroup-v2.rst.
1166
1167config CGROUP_DEBUG
1168 bool "Debug controller"
1169 default n
1170 depends on DEBUG_KERNEL
1171 help
1172 This option enables a simple controller that exports
1173 debugging information about the cgroups framework. This
1174 controller is for control cgroup debugging only. Its
1175 interfaces are not stable.
1176
1177 Say N.
1178
1179config SOCK_CGROUP_DATA
1180 bool
1181 default n
1182
1183endif
1184
1185menuconfig NAMESPACES
1186 bool "Namespaces support" if EXPERT
1187 depends on MULTIUSER
1188 default !EXPERT
1189 help
1190 Provides the way to make tasks work with different objects using
1191 the same id. For example same IPC id may refer to different objects
1192 or same user id or pid may refer to different tasks when used in
1193 different namespaces.
1194
1195if NAMESPACES
1196
1197config UTS_NS
1198 bool "UTS namespace"
1199 default y
1200 help
1201 In this namespace tasks see different info provided with the
1202 uname() system call
1203
1204config TIME_NS
1205 bool "TIME namespace"
1206 depends on GENERIC_VDSO_TIME_NS
1207 default y
1208 help
1209 In this namespace boottime and monotonic clocks can be set.
1210 The time will keep going with the same pace.
1211
1212config IPC_NS
1213 bool "IPC namespace"
1214 depends on (SYSVIPC || POSIX_MQUEUE)
1215 default y
1216 help
1217 In this namespace tasks work with IPC ids which correspond to
1218 different IPC objects in different namespaces.
1219
1220config USER_NS
1221 bool "User namespace"
1222 default n
1223 help
1224 This allows containers, i.e. vservers, to use user namespaces
1225 to provide different user info for different servers.
1226
1227 When user namespaces are enabled in the kernel it is
1228 recommended that the MEMCG option also be enabled and that
1229 user-space use the memory control groups to limit the amount
1230 of memory a memory unprivileged users can use.
1231
1232 If unsure, say N.
1233
1234config PID_NS
1235 bool "PID Namespaces"
1236 default y
1237 help
1238 Support process id namespaces. This allows having multiple
1239 processes with the same pid as long as they are in different
1240 pid namespaces. This is a building block of containers.
1241
1242config NET_NS
1243 bool "Network namespace"
1244 depends on NET
1245 default y
1246 help
1247 Allow user space to create what appear to be multiple instances
1248 of the network stack.
1249
1250endif
1251
1252config CHECKPOINT_RESTORE
1253 bool "Checkpoint/restore support"
1254 select PROC_CHILDREN
1255 select KCMP
1256 default n
1257 help
1258 Enables additional kernel features in a sake of checkpoint/restore.
1259 In particular it adds auxiliary prctl codes to setup process text,
1260 data and heap segment sizes, and a few additional /proc filesystem
1261 entries.
1262
1263 If unsure, say N here.
1264
1265config SCHED_AUTOGROUP
1266 bool "Automatic process group scheduling"
1267 select CGROUPS
1268 select CGROUP_SCHED
1269 select FAIR_GROUP_SCHED
1270 help
1271 This option optimizes the scheduler for common desktop workloads by
1272 automatically creating and populating task groups. This separation
1273 of workloads isolates aggressive CPU burners (like build jobs) from
1274 desktop applications. Task group autogeneration is currently based
1275 upon task session.
1276
1277config SYSFS_DEPRECATED
1278 bool "Enable deprecated sysfs features to support old userspace tools"
1279 depends on SYSFS
1280 default n
1281 help
1282 This option adds code that switches the layout of the "block" class
1283 devices, to not show up in /sys/class/block/, but only in
1284 /sys/block/.
1285
1286 This switch is only active when the sysfs.deprecated=1 boot option is
1287 passed or the SYSFS_DEPRECATED_V2 option is set.
1288
1289 This option allows new kernels to run on old distributions and tools,
1290 which might get confused by /sys/class/block/. Since 2007/2008 all
1291 major distributions and tools handle this just fine.
1292
1293 Recent distributions and userspace tools after 2009/2010 depend on
1294 the existence of /sys/class/block/, and will not work with this
1295 option enabled.
1296
1297 Only if you are using a new kernel on an old distribution, you might
1298 need to say Y here.
1299
1300config SYSFS_DEPRECATED_V2
1301 bool "Enable deprecated sysfs features by default"
1302 default n
1303 depends on SYSFS
1304 depends on SYSFS_DEPRECATED
1305 help
1306 Enable deprecated sysfs by default.
1307
1308 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1309 option.
1310
1311 Only if you are using a new kernel on an old distribution, you might
1312 need to say Y here. Even then, odds are you would not need it
1313 enabled, you can always pass the boot option if absolutely necessary.
1314
1315config RELAY
1316 bool "Kernel->user space relay support (formerly relayfs)"
1317 select IRQ_WORK
1318 help
1319 This option enables support for relay interface support in
1320 certain file systems (such as debugfs).
1321 It is designed to provide an efficient mechanism for tools and
1322 facilities to relay large amounts of data from kernel space to
1323 user space.
1324
1325 If unsure, say N.
1326
1327config BLK_DEV_INITRD
1328 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1329 help
1330 The initial RAM filesystem is a ramfs which is loaded by the
1331 boot loader (loadlin or lilo) and that is mounted as root
1332 before the normal boot procedure. It is typically used to
1333 load modules needed to mount the "real" root file system,
1334 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1335
1336 If RAM disk support (BLK_DEV_RAM) is also included, this
1337 also enables initial RAM disk (initrd) support and adds
1338 15 Kbytes (more on some other architectures) to the kernel size.
1339
1340 If unsure say Y.
1341
1342if BLK_DEV_INITRD
1343
1344source "usr/Kconfig"
1345
1346endif
1347
1348config BOOT_CONFIG
1349 bool "Boot config support"
1350 select BLK_DEV_INITRD
1351 help
1352 Extra boot config allows system admin to pass a config file as
1353 complemental extension of kernel cmdline when booting.
1354 The boot config file must be attached at the end of initramfs
1355 with checksum, size and magic word.
1356 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1357
1358 If unsure, say Y.
1359
1360choice
1361 prompt "Compiler optimization level"
1362 default CC_OPTIMIZE_FOR_PERFORMANCE
1363
1364config CC_OPTIMIZE_FOR_PERFORMANCE
1365 bool "Optimize for performance (-O2)"
1366 help
1367 This is the default optimization level for the kernel, building
1368 with the "-O2" compiler flag for best performance and most
1369 helpful compile-time warnings.
1370
1371config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1372 bool "Optimize more for performance (-O3)"
1373 depends on ARC
1374 help
1375 Choosing this option will pass "-O3" to your compiler to optimize
1376 the kernel yet more for performance.
1377
1378config CC_OPTIMIZE_FOR_SIZE
1379 bool "Optimize for size (-Os)"
1380 help
1381 Choosing this option will pass "-Os" to your compiler resulting
1382 in a smaller kernel.
1383
1384endchoice
1385
1386config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1387 bool
1388 help
1389 This requires that the arch annotates or otherwise protects
1390 its external entry points from being discarded. Linker scripts
1391 must also merge .text.*, .data.*, and .bss.* correctly into
1392 output sections. Care must be taken not to pull in unrelated
1393 sections (e.g., '.text.init'). Typically '.' in section names
1394 is used to distinguish them from label names / C identifiers.
1395
1396config LD_DEAD_CODE_DATA_ELIMINATION
1397 bool "Dead code and data elimination (EXPERIMENTAL)"
1398 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1399 depends on EXPERT
1400 depends on $(cc-option,-ffunction-sections -fdata-sections)
1401 depends on $(ld-option,--gc-sections)
1402 help
1403 Enable this if you want to do dead code and data elimination with
1404 the linker by compiling with -ffunction-sections -fdata-sections,
1405 and linking with --gc-sections.
1406
1407 This can reduce on disk and in-memory size of the kernel
1408 code and static data, particularly for small configs and
1409 on small systems. This has the possibility of introducing
1410 silently broken kernel if the required annotations are not
1411 present. This option is not well tested yet, so use at your
1412 own risk.
1413
1414config LD_ORPHAN_WARN
1415 def_bool y
1416 depends on ARCH_WANT_LD_ORPHAN_WARN
1417 depends on !LD_IS_LLD || LLD_VERSION >= 110000
1418 depends on $(ld-option,--orphan-handling=warn)
1419
1420config SYSCTL
1421 bool
1422
1423config HAVE_UID16
1424 bool
1425
1426config SYSCTL_EXCEPTION_TRACE
1427 bool
1428 help
1429 Enable support for /proc/sys/debug/exception-trace.
1430
1431config SYSCTL_ARCH_UNALIGN_NO_WARN
1432 bool
1433 help
1434 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1435 Allows arch to define/use @no_unaligned_warning to possibly warn
1436 about unaligned access emulation going on under the hood.
1437
1438config SYSCTL_ARCH_UNALIGN_ALLOW
1439 bool
1440 help
1441 Enable support for /proc/sys/kernel/unaligned-trap
1442 Allows arches to define/use @unaligned_enabled to runtime toggle
1443 the unaligned access emulation.
1444 see arch/parisc/kernel/unaligned.c for reference
1445
1446config HAVE_PCSPKR_PLATFORM
1447 bool
1448
1449
1450config BPF
1451 bool
1452
1453menuconfig EXPERT
1454 bool "Configure standard kernel features (expert users)"
1455
1456 select DEBUG_KERNEL
1457 help
1458 This option allows certain base kernel options and settings
1459 to be disabled or tweaked. This is for specialized
1460 environments which can tolerate a "non-standard" kernel.
1461 Only use this if you really know what you are doing.
1462
1463config UID16
1464 bool "Enable 16-bit UID system calls" if EXPERT
1465 depends on HAVE_UID16 && MULTIUSER
1466 default y
1467 help
1468 This enables the legacy 16-bit UID syscall wrappers.
1469
1470config MULTIUSER
1471 bool "Multiple users, groups and capabilities support" if EXPERT
1472 default y
1473 help
1474 This option enables support for non-root users, groups and
1475 capabilities.
1476
1477 If you say N here, all processes will run with UID 0, GID 0, and all
1478 possible capabilities. Saying N here also compiles out support for
1479 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1480 setgid, and capset.
1481
1482 If unsure, say Y here.
1483
1484config SGETMASK_SYSCALL
1485 bool "sgetmask/ssetmask syscalls support" if EXPERT
1486 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1487 help
1488 sys_sgetmask and sys_ssetmask are obsolete system calls
1489 no longer supported in libc but still enabled by default in some
1490 architectures.
1491
1492 If unsure, leave the default option here.
1493
1494config SYSFS_SYSCALL
1495 bool "Sysfs syscall support" if EXPERT
1496 default y
1497 help
1498 sys_sysfs is an obsolete system call no longer supported in libc.
1499 Note that disabling this option is more secure but might break
1500 compatibility with some systems.
1501
1502 If unsure say Y here.
1503
1504config FHANDLE
1505 bool "open by fhandle syscalls" if EXPERT
1506 select EXPORTFS
1507 default y
1508 help
1509 If you say Y here, a user level program will be able to map
1510 file names to handle and then later use the handle for
1511 different file system operations. This is useful in implementing
1512 userspace file servers, which now track files using handles instead
1513 of names. The handle would remain the same even if file names
1514 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1515 syscalls.
1516
1517config POSIX_TIMERS
1518 bool "Posix Clocks & timers" if EXPERT
1519 default y
1520 help
1521 This includes native support for POSIX timers to the kernel.
1522 Some embedded systems have no use for them and therefore they
1523 can be configured out to reduce the size of the kernel image.
1524
1525 When this option is disabled, the following syscalls won't be
1526 available: timer_create, timer_gettime: timer_getoverrun,
1527 timer_settime, timer_delete, clock_adjtime, getitimer,
1528 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1529 clock_getres and clock_nanosleep syscalls will be limited to
1530 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1531
1532 If unsure say y.
1533
1534config PRINTK
1535 default y
1536 bool "Enable support for printk" if EXPERT
1537 select IRQ_WORK
1538 help
1539 This option enables normal printk support. Removing it
1540 eliminates most of the message strings from the kernel image
1541 and makes the kernel more or less silent. As this makes it
1542 very difficult to diagnose system problems, saying N here is
1543 strongly discouraged.
1544
1545config BUG
1546 bool "BUG() support" if EXPERT
1547 default y
1548 help
1549 Disabling this option eliminates support for BUG and WARN, reducing
1550 the size of your kernel image and potentially quietly ignoring
1551 numerous fatal conditions. You should only consider disabling this
1552 option for embedded systems with no facilities for reporting errors.
1553 Just say Y.
1554
1555config ELF_CORE
1556 depends on COREDUMP
1557 default y
1558 bool "Enable ELF core dumps" if EXPERT
1559 help
1560 Enable support for generating core dumps. Disabling saves about 4k.
1561
1562
1563config PCSPKR_PLATFORM
1564 bool "Enable PC-Speaker support" if EXPERT
1565 depends on HAVE_PCSPKR_PLATFORM
1566 select I8253_LOCK
1567 default y
1568 help
1569 This option allows to disable the internal PC-Speaker
1570 support, saving some memory.
1571
1572config BASE_FULL
1573 default y
1574 bool "Enable full-sized data structures for core" if EXPERT
1575 help
1576 Disabling this option reduces the size of miscellaneous core
1577 kernel data structures. This saves memory on small machines,
1578 but may reduce performance.
1579
1580config FUTEX
1581 bool "Enable futex support" if EXPERT
1582 default y
1583 imply RT_MUTEXES
1584 help
1585 Disabling this option will cause the kernel to be built without
1586 support for "fast userspace mutexes". The resulting kernel may not
1587 run glibc-based applications correctly.
1588
1589config FUTEX_PI
1590 bool
1591 depends on FUTEX && RT_MUTEXES
1592 default y
1593
1594config HAVE_FUTEX_CMPXCHG
1595 bool
1596 depends on FUTEX
1597 help
1598 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1599 is implemented and always working. This removes a couple of runtime
1600 checks.
1601
1602config EPOLL
1603 bool "Enable eventpoll support" if EXPERT
1604 default y
1605 help
1606 Disabling this option will cause the kernel to be built without
1607 support for epoll family of system calls.
1608
1609config SIGNALFD
1610 bool "Enable signalfd() system call" if EXPERT
1611 default y
1612 help
1613 Enable the signalfd() system call that allows to receive signals
1614 on a file descriptor.
1615
1616 If unsure, say Y.
1617
1618config TIMERFD
1619 bool "Enable timerfd() system call" if EXPERT
1620 default y
1621 help
1622 Enable the timerfd() system call that allows to receive timer
1623 events on a file descriptor.
1624
1625 If unsure, say Y.
1626
1627config EVENTFD
1628 bool "Enable eventfd() system call" if EXPERT
1629 default y
1630 help
1631 Enable the eventfd() system call that allows to receive both
1632 kernel notification (ie. KAIO) or userspace notifications.
1633
1634 If unsure, say Y.
1635
1636config SHMEM
1637 bool "Use full shmem filesystem" if EXPERT
1638 default y
1639 depends on MMU
1640 help
1641 The shmem is an internal filesystem used to manage shared memory.
1642 It is backed by swap and manages resource limits. It is also exported
1643 to userspace as tmpfs if TMPFS is enabled. Disabling this
1644 option replaces shmem and tmpfs with the much simpler ramfs code,
1645 which may be appropriate on small systems without swap.
1646
1647config AIO
1648 bool "Enable AIO support" if EXPERT
1649 default y
1650 help
1651 This option enables POSIX asynchronous I/O which may by used
1652 by some high performance threaded applications. Disabling
1653 this option saves about 7k.
1654
1655config IO_URING
1656 bool "Enable IO uring support" if EXPERT
1657 select IO_WQ
1658 default y
1659 help
1660 This option enables support for the io_uring interface, enabling
1661 applications to submit and complete IO through submission and
1662 completion rings that are shared between the kernel and application.
1663
1664config ADVISE_SYSCALLS
1665 bool "Enable madvise/fadvise syscalls" if EXPERT
1666 default y
1667 help
1668 This option enables the madvise and fadvise syscalls, used by
1669 applications to advise the kernel about their future memory or file
1670 usage, improving performance. If building an embedded system where no
1671 applications use these syscalls, you can disable this option to save
1672 space.
1673
1674config HAVE_ARCH_USERFAULTFD_WP
1675 bool
1676 help
1677 Arch has userfaultfd write protection support
1678
1679config HAVE_ARCH_USERFAULTFD_MINOR
1680 bool
1681 help
1682 Arch has userfaultfd minor fault support
1683
1684config MEMBARRIER
1685 bool "Enable membarrier() system call" if EXPERT
1686 default y
1687 help
1688 Enable the membarrier() system call that allows issuing memory
1689 barriers across all running threads, which can be used to distribute
1690 the cost of user-space memory barriers asymmetrically by transforming
1691 pairs of memory barriers into pairs consisting of membarrier() and a
1692 compiler barrier.
1693
1694 If unsure, say Y.
1695
1696config KALLSYMS
1697 bool "Load all symbols for debugging/ksymoops" if EXPERT
1698 default y
1699 help
1700 Say Y here to let the kernel print out symbolic crash information and
1701 symbolic stack backtraces. This increases the size of the kernel
1702 somewhat, as all symbols have to be loaded into the kernel image.
1703
1704config KALLSYMS_ALL
1705 bool "Include all symbols in kallsyms"
1706 depends on DEBUG_KERNEL && KALLSYMS
1707 help
1708 Normally kallsyms only contains the symbols of functions for nicer
1709 OOPS messages and backtraces (i.e., symbols from the text and inittext
1710 sections). This is sufficient for most cases. And only in very rare
1711 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1712 names of variables from the data sections, etc).
1713
1714 This option makes sure that all symbols are loaded into the kernel
1715 image (i.e., symbols from all sections) in cost of increased kernel
1716 size (depending on the kernel configuration, it may be 300KiB or
1717 something like this).
1718
1719 Say N unless you really need all symbols.
1720
1721config KALLSYMS_ABSOLUTE_PERCPU
1722 bool
1723 depends on KALLSYMS
1724 default X86_64 && SMP
1725
1726config KALLSYMS_BASE_RELATIVE
1727 bool
1728 depends on KALLSYMS
1729 default !IA64
1730 help
1731 Instead of emitting them as absolute values in the native word size,
1732 emit the symbol references in the kallsyms table as 32-bit entries,
1733 each containing a relative value in the range [base, base + U32_MAX]
1734 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1735 an absolute value in the range [0, S32_MAX] or a relative value in the
1736 range [base, base + S32_MAX], where base is the lowest relative symbol
1737 address encountered in the image.
1738
1739 On 64-bit builds, this reduces the size of the address table by 50%,
1740 but more importantly, it results in entries whose values are build
1741 time constants, and no relocation pass is required at runtime to fix
1742 up the entries based on the runtime load address of the kernel.
1743
1744
1745
1746
1747
1748config USERFAULTFD
1749 bool "Enable userfaultfd() system call"
1750 depends on MMU
1751 help
1752 Enable the userfaultfd() system call that allows to intercept and
1753 handle page faults in userland.
1754
1755config ARCH_HAS_MEMBARRIER_CALLBACKS
1756 bool
1757
1758config ARCH_HAS_MEMBARRIER_SYNC_CORE
1759 bool
1760
1761config KCMP
1762 bool "Enable kcmp() system call" if EXPERT
1763 help
1764 Enable the kernel resource comparison system call. It provides
1765 user-space with the ability to compare two processes to see if they
1766 share a common resource, such as a file descriptor or even virtual
1767 memory space.
1768
1769 If unsure, say N.
1770
1771config RSEQ
1772 bool "Enable rseq() system call" if EXPERT
1773 default y
1774 depends on HAVE_RSEQ
1775 select MEMBARRIER
1776 help
1777 Enable the restartable sequences system call. It provides a
1778 user-space cache for the current CPU number value, which
1779 speeds up getting the current CPU number from user-space,
1780 as well as an ABI to speed up user-space operations on
1781 per-CPU data.
1782
1783 If unsure, say Y.
1784
1785config DEBUG_RSEQ
1786 default n
1787 bool "Enabled debugging of rseq() system call" if EXPERT
1788 depends on RSEQ && DEBUG_KERNEL
1789 help
1790 Enable extra debugging checks for the rseq system call.
1791
1792 If unsure, say N.
1793
1794config EMBEDDED
1795 bool "Embedded system"
1796 select EXPERT
1797 help
1798 This option should be enabled if compiling the kernel for
1799 an embedded system so certain expert options are available
1800 for configuration.
1801
1802config HAVE_PERF_EVENTS
1803 bool
1804 help
1805 See tools/perf/design.txt for details.
1806
1807config PERF_USE_VMALLOC
1808 bool
1809 help
1810 See tools/perf/design.txt for details
1811
1812config PC104
1813 bool "PC/104 support" if EXPERT
1814 help
1815 Expose PC/104 form factor device drivers and options available for
1816 selection and configuration. Enable this option if your target
1817 machine has a PC/104 bus.
1818
1819menu "Kernel Performance Events And Counters"
1820
1821config PERF_EVENTS
1822 bool "Kernel performance events and counters"
1823 default y if PROFILING
1824 depends on HAVE_PERF_EVENTS
1825 select IRQ_WORK
1826 select SRCU
1827 help
1828 Enable kernel support for various performance events provided
1829 by software and hardware.
1830
1831 Software events are supported either built-in or via the
1832 use of generic tracepoints.
1833
1834 Most modern CPUs support performance events via performance
1835 counter registers. These registers count the number of certain
1836 types of hw events: such as instructions executed, cachemisses
1837 suffered, or branches mis-predicted - without slowing down the
1838 kernel or applications. These registers can also trigger interrupts
1839 when a threshold number of events have passed - and can thus be
1840 used to profile the code that runs on that CPU.
1841
1842 The Linux Performance Event subsystem provides an abstraction of
1843 these software and hardware event capabilities, available via a
1844 system call and used by the "perf" utility in tools/perf/. It
1845 provides per task and per CPU counters, and it provides event
1846 capabilities on top of those.
1847
1848 Say Y if unsure.
1849
1850config DEBUG_PERF_USE_VMALLOC
1851 default n
1852 bool "Debug: use vmalloc to back perf mmap() buffers"
1853 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1854 select PERF_USE_VMALLOC
1855 help
1856 Use vmalloc memory to back perf mmap() buffers.
1857
1858 Mostly useful for debugging the vmalloc code on platforms
1859 that don't require it.
1860
1861 Say N if unsure.
1862
1863endmenu
1864
1865config VM_EVENT_COUNTERS
1866 default y
1867 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1868 help
1869 VM event counters are needed for event counts to be shown.
1870 This option allows the disabling of the VM event counters
1871 on EXPERT systems. /proc/vmstat will only show page counts
1872 if VM event counters are disabled.
1873
1874config SLUB_DEBUG
1875 default y
1876 bool "Enable SLUB debugging support" if EXPERT
1877 depends on SLUB && SYSFS
1878 help
1879 SLUB has extensive debug support features. Disabling these can
1880 result in significant savings in code size. This also disables
1881 SLUB sysfs support. /sys/slab will not exist and there will be
1882 no support for cache validation etc.
1883
1884config COMPAT_BRK
1885 bool "Disable heap randomization"
1886 default y
1887 help
1888 Randomizing heap placement makes heap exploits harder, but it
1889 also breaks ancient binaries (including anything libc5 based).
1890 This option changes the bootup default to heap randomization
1891 disabled, and can be overridden at runtime by setting
1892 /proc/sys/kernel/randomize_va_space to 2.
1893
1894 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1895
1896choice
1897 prompt "Choose SLAB allocator"
1898 default SLUB
1899 help
1900 This option allows to select a slab allocator.
1901
1902config SLAB
1903 bool "SLAB"
1904 depends on !PREEMPT_RT
1905 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1906 help
1907 The regular slab allocator that is established and known to work
1908 well in all environments. It organizes cache hot objects in
1909 per cpu and per node queues.
1910
1911config SLUB
1912 bool "SLUB (Unqueued Allocator)"
1913 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1914 help
1915 SLUB is a slab allocator that minimizes cache line usage
1916 instead of managing queues of cached objects (SLAB approach).
1917 Per cpu caching is realized using slabs of objects instead
1918 of queues of objects. SLUB can use memory efficiently
1919 and has enhanced diagnostics. SLUB is the default choice for
1920 a slab allocator.
1921
1922config SLOB
1923 depends on EXPERT
1924 bool "SLOB (Simple Allocator)"
1925 depends on !PREEMPT_RT
1926 help
1927 SLOB replaces the stock allocator with a drastically simpler
1928 allocator. SLOB is generally more space efficient but
1929 does not perform as well on large systems.
1930
1931endchoice
1932
1933config SLAB_MERGE_DEFAULT
1934 bool "Allow slab caches to be merged"
1935 default y
1936 help
1937 For reduced kernel memory fragmentation, slab caches can be
1938 merged when they share the same size and other characteristics.
1939 This carries a risk of kernel heap overflows being able to
1940 overwrite objects from merged caches (and more easily control
1941 cache layout), which makes such heap attacks easier to exploit
1942 by attackers. By keeping caches unmerged, these kinds of exploits
1943 can usually only damage objects in the same cache. To disable
1944 merging at runtime, "slab_nomerge" can be passed on the kernel
1945 command line.
1946
1947config SLAB_FREELIST_RANDOM
1948 bool "Randomize slab freelist"
1949 depends on SLAB || SLUB
1950 help
1951 Randomizes the freelist order used on creating new pages. This
1952 security feature reduces the predictability of the kernel slab
1953 allocator against heap overflows.
1954
1955config SLAB_FREELIST_HARDENED
1956 bool "Harden slab freelist metadata"
1957 depends on SLAB || SLUB
1958 help
1959 Many kernel heap attacks try to target slab cache metadata and
1960 other infrastructure. This options makes minor performance
1961 sacrifices to harden the kernel slab allocator against common
1962 freelist exploit methods. Some slab implementations have more
1963 sanity-checking than others. This option is most effective with
1964 CONFIG_SLUB.
1965
1966config SHUFFLE_PAGE_ALLOCATOR
1967 bool "Page allocator randomization"
1968 default SLAB_FREELIST_RANDOM && ACPI_NUMA
1969 help
1970 Randomization of the page allocator improves the average
1971 utilization of a direct-mapped memory-side-cache. See section
1972 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1973 6.2a specification for an example of how a platform advertises
1974 the presence of a memory-side-cache. There are also incidental
1975 security benefits as it reduces the predictability of page
1976 allocations to compliment SLAB_FREELIST_RANDOM, but the
1977 default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1978 10th order of pages is selected based on cache utilization
1979 benefits on x86.
1980
1981 While the randomization improves cache utilization it may
1982 negatively impact workloads on platforms without a cache. For
1983 this reason, by default, the randomization is enabled only
1984 after runtime detection of a direct-mapped memory-side-cache.
1985 Otherwise, the randomization may be force enabled with the
1986 'page_alloc.shuffle' kernel command line parameter.
1987
1988 Say Y if unsure.
1989
1990config SLUB_CPU_PARTIAL
1991 default y
1992 depends on SLUB && SMP
1993 bool "SLUB per cpu partial cache"
1994 help
1995 Per cpu partial caches accelerate objects allocation and freeing
1996 that is local to a processor at the price of more indeterminism
1997 in the latency of the free. On overflow these caches will be cleared
1998 which requires the taking of locks that may cause latency spikes.
1999 Typically one would choose no for a realtime system.
2000
2001config MMAP_ALLOW_UNINITIALIZED
2002 bool "Allow mmapped anonymous memory to be uninitialized"
2003 depends on EXPERT && !MMU
2004 default n
2005 help
2006 Normally, and according to the Linux spec, anonymous memory obtained
2007 from mmap() has its contents cleared before it is passed to
2008 userspace. Enabling this config option allows you to request that
2009 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
2010 providing a huge performance boost. If this option is not enabled,
2011 then the flag will be ignored.
2012
2013 This is taken advantage of by uClibc's malloc(), and also by
2014 ELF-FDPIC binfmt's brk and stack allocator.
2015
2016 Because of the obvious security issues, this option should only be
2017 enabled on embedded devices where you control what is run in
2018 userspace. Since that isn't generally a problem on no-MMU systems,
2019 it is normally safe to say Y here.
2020
2021 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
2022
2023config SYSTEM_DATA_VERIFICATION
2024 def_bool n
2025 select SYSTEM_TRUSTED_KEYRING
2026 select KEYS
2027 select CRYPTO
2028 select CRYPTO_RSA
2029 select ASYMMETRIC_KEY_TYPE
2030 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
2031 select ASN1
2032 select OID_REGISTRY
2033 select X509_CERTIFICATE_PARSER
2034 select PKCS7_MESSAGE_PARSER
2035 help
2036 Provide PKCS#7 message verification using the contents of the system
2037 trusted keyring to provide public keys. This then can be used for
2038 module verification, kexec image verification and firmware blob
2039 verification.
2040
2041config PROFILING
2042 bool "Profiling support"
2043 help
2044 Say Y here to enable the extended profiling support mechanisms used
2045 by profilers.
2046
2047
2048
2049
2050
2051config TRACEPOINTS
2052 bool
2053
2054endmenu
2055
2056source "arch/Kconfig"
2057
2058config RT_MUTEXES
2059 bool
2060
2061config BASE_SMALL
2062 int
2063 default 0 if BASE_FULL
2064 default 1 if !BASE_FULL
2065
2066config MODULE_SIG_FORMAT
2067 def_bool n
2068 select SYSTEM_DATA_VERIFICATION
2069
2070menuconfig MODULES
2071 bool "Enable loadable module support"
2072 modules
2073 help
2074 Kernel modules are small pieces of compiled code which can
2075 be inserted in the running kernel, rather than being
2076 permanently built into the kernel. You use the "modprobe"
2077 tool to add (and sometimes remove) them. If you say Y here,
2078 many parts of the kernel can be built as modules (by
2079 answering M instead of Y where indicated): this is most
2080 useful for infrequently used options which are not required
2081 for booting. For more information, see the man pages for
2082 modprobe, lsmod, modinfo, insmod and rmmod.
2083
2084 If you say Y here, you will need to run "make
2085 modules_install" to put the modules under /lib/modules/
2086 where modprobe can find them (you may need to be root to do
2087 this).
2088
2089 If unsure, say Y.
2090
2091if MODULES
2092
2093config MODULE_FORCE_LOAD
2094 bool "Forced module loading"
2095 default n
2096 help
2097 Allow loading of modules without version information (ie. modprobe
2098 --force). Forced module loading sets the 'F' (forced) taint flag and
2099 is usually a really bad idea.
2100
2101config MODULE_UNLOAD
2102 bool "Module unloading"
2103 help
2104 Without this option you will not be able to unload any
2105 modules (note that some modules may not be unloadable
2106 anyway), which makes your kernel smaller, faster
2107 and simpler. If unsure, say Y.
2108
2109config MODULE_FORCE_UNLOAD
2110 bool "Forced module unloading"
2111 depends on MODULE_UNLOAD
2112 help
2113 This option allows you to force a module to unload, even if the
2114 kernel believes it is unsafe: the kernel will remove the module
2115 without waiting for anyone to stop using it (using the -f option to
2116 rmmod). This is mainly for kernel developers and desperate users.
2117 If unsure, say N.
2118
2119config MODVERSIONS
2120 bool "Module versioning support"
2121 help
2122 Usually, you have to use modules compiled with your kernel.
2123 Saying Y here makes it sometimes possible to use modules
2124 compiled for different kernels, by adding enough information
2125 to the modules to (hopefully) spot any changes which would
2126 make them incompatible with the kernel you are running. If
2127 unsure, say N.
2128
2129config ASM_MODVERSIONS
2130 bool
2131 default HAVE_ASM_MODVERSIONS && MODVERSIONS
2132 help
2133 This enables module versioning for exported symbols also from
2134 assembly. This can be enabled only when the target architecture
2135 supports it.
2136
2137config MODULE_REL_CRCS
2138 bool
2139 depends on MODVERSIONS
2140
2141config MODULE_SRCVERSION_ALL
2142 bool "Source checksum for all modules"
2143 help
2144 Modules which contain a MODULE_VERSION get an extra "srcversion"
2145 field inserted into their modinfo section, which contains a
2146 sum of the source files which made it. This helps maintainers
2147 see exactly which source was used to build a module (since
2148 others sometimes change the module source without updating
2149 the version). With this option, such a "srcversion" field
2150 will be created for all modules. If unsure, say N.
2151
2152config MODULE_SIG
2153 bool "Module signature verification"
2154 select MODULE_SIG_FORMAT
2155 help
2156 Check modules for valid signatures upon load: the signature
2157 is simply appended to the module. For more information see
2158 <file:Documentation/admin-guide/module-signing.rst>.
2159
2160 Note that this option adds the OpenSSL development packages as a
2161 kernel build dependency so that the signing tool can use its crypto
2162 library.
2163
2164 You should enable this option if you wish to use either
2165 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2166 another LSM - otherwise unsigned modules will be loadable regardless
2167 of the lockdown policy.
2168
2169 !!!WARNING!!! If you enable this option, you MUST make sure that the
2170 module DOES NOT get stripped after being signed. This includes the
2171 debuginfo strip done by some packagers (such as rpmbuild) and
2172 inclusion into an initramfs that wants the module size reduced.
2173
2174config MODULE_SIG_FORCE
2175 bool "Require modules to be validly signed"
2176 depends on MODULE_SIG
2177 help
2178 Reject unsigned modules or signed modules for which we don't have a
2179 key. Without this, such modules will simply taint the kernel.
2180
2181config MODULE_SIG_ALL
2182 bool "Automatically sign all modules"
2183 default y
2184 depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2185 help
2186 Sign all modules during make modules_install. Without this option,
2187 modules must be signed manually, using the scripts/sign-file tool.
2188
2189comment "Do not forget to sign required modules with scripts/sign-file"
2190 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2191
2192choice
2193 prompt "Which hash algorithm should modules be signed with?"
2194 depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2195 help
2196 This determines which sort of hashing algorithm will be used during
2197 signature generation. This algorithm _must_ be built into the kernel
2198 directly so that signature verification can take place. It is not
2199 possible to load a signed module containing the algorithm to check
2200 the signature on that module.
2201
2202config MODULE_SIG_SHA1
2203 bool "Sign modules with SHA-1"
2204 select CRYPTO_SHA1
2205
2206config MODULE_SIG_SHA224
2207 bool "Sign modules with SHA-224"
2208 select CRYPTO_SHA256
2209
2210config MODULE_SIG_SHA256
2211 bool "Sign modules with SHA-256"
2212 select CRYPTO_SHA256
2213
2214config MODULE_SIG_SHA384
2215 bool "Sign modules with SHA-384"
2216 select CRYPTO_SHA512
2217
2218config MODULE_SIG_SHA512
2219 bool "Sign modules with SHA-512"
2220 select CRYPTO_SHA512
2221
2222endchoice
2223
2224config MODULE_SIG_HASH
2225 string
2226 depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2227 default "sha1" if MODULE_SIG_SHA1
2228 default "sha224" if MODULE_SIG_SHA224
2229 default "sha256" if MODULE_SIG_SHA256
2230 default "sha384" if MODULE_SIG_SHA384
2231 default "sha512" if MODULE_SIG_SHA512
2232
2233choice
2234 prompt "Module compression mode"
2235 help
2236 This option allows you to choose the algorithm which will be used to
2237 compress modules when 'make modules_install' is run. (or, you can
2238 choose to not compress modules at all.)
2239
2240 External modules will also be compressed in the same way during the
2241 installation.
2242
2243 For modules inside an initrd or initramfs, it's more efficient to
2244 compress the whole initrd or initramfs instead.
2245
2246 This is fully compatible with signed modules.
2247
2248 Please note that the tool used to load modules needs to support the
2249 corresponding algorithm. module-init-tools MAY support gzip, and kmod
2250 MAY support gzip, xz and zstd.
2251
2252 Your build system needs to provide the appropriate compression tool
2253 to compress the modules.
2254
2255 If in doubt, select 'None'.
2256
2257config MODULE_COMPRESS_NONE
2258 bool "None"
2259 help
2260 Do not compress modules. The installed modules are suffixed
2261 with .ko.
2262
2263config MODULE_COMPRESS_GZIP
2264 bool "GZIP"
2265 help
2266 Compress modules with GZIP. The installed modules are suffixed
2267 with .ko.gz.
2268
2269config MODULE_COMPRESS_XZ
2270 bool "XZ"
2271 help
2272 Compress modules with XZ. The installed modules are suffixed
2273 with .ko.xz.
2274
2275config MODULE_COMPRESS_ZSTD
2276 bool "ZSTD"
2277 help
2278 Compress modules with ZSTD. The installed modules are suffixed
2279 with .ko.zst.
2280
2281endchoice
2282
2283config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2284 bool "Allow loading of modules with missing namespace imports"
2285 help
2286 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2287 a namespace. A module that makes use of a symbol exported with such a
2288 namespace is required to import the namespace via MODULE_IMPORT_NS().
2289 There is no technical reason to enforce correct namespace imports,
2290 but it creates consistency between symbols defining namespaces and
2291 users importing namespaces they make use of. This option relaxes this
2292 requirement and lifts the enforcement when loading a module.
2293
2294 If unsure, say N.
2295
2296config MODPROBE_PATH
2297 string "Path to modprobe binary"
2298 default "/sbin/modprobe"
2299 help
2300 When kernel code requests a module, it does so by calling
2301 the "modprobe" userspace utility. This option allows you to
2302 set the path where that binary is found. This can be changed
2303 at runtime via the sysctl file
2304 /proc/sys/kernel/modprobe. Setting this to the empty string
2305 removes the kernel's ability to request modules (but
2306 userspace can still load modules explicitly).
2307
2308config TRIM_UNUSED_KSYMS
2309 bool "Trim unused exported kernel symbols" if EXPERT
2310 depends on !COMPILE_TEST
2311 help
2312 The kernel and some modules make many symbols available for
2313 other modules to use via EXPORT_SYMBOL() and variants. Depending
2314 on the set of modules being selected in your kernel configuration,
2315 many of those exported symbols might never be used.
2316
2317 This option allows for unused exported symbols to be dropped from
2318 the build. In turn, this provides the compiler more opportunities
2319 (especially when using LTO) for optimizing the code and reducing
2320 binary size. This might have some security advantages as well.
2321
2322 If unsure, or if you need to build out-of-tree modules, say N.
2323
2324config UNUSED_KSYMS_WHITELIST
2325 string "Whitelist of symbols to keep in ksymtab"
2326 depends on TRIM_UNUSED_KSYMS
2327 help
2328 By default, all unused exported symbols will be un-exported from the
2329 build when TRIM_UNUSED_KSYMS is selected.
2330
2331 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
2332 exported at all times, even in absence of in-tree users. The value to
2333 set here is the path to a text file containing the list of symbols,
2334 one per line. The path can be absolute, or relative to the kernel
2335 source tree.
2336
2337endif
2338
2339config MODULES_TREE_LOOKUP
2340 def_bool y
2341 depends on PERF_EVENTS || TRACING || CFI_CLANG
2342
2343config INIT_ALL_POSSIBLE
2344 bool
2345 help
2346 Back when each arch used to define their own cpu_online_mask and
2347 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2348 with all 1s, and others with all 0s. When they were centralised,
2349 it was better to provide this option than to break all the archs
2350 and have several arch maintainers pursuing me down dark alleys.
2351
2352source "block/Kconfig"
2353
2354config PREEMPT_NOTIFIERS
2355 bool
2356
2357config PADATA
2358 depends on SMP
2359 bool
2360
2361config ASN1
2362 tristate
2363 help
2364 Build a simple ASN.1 grammar compiler that produces a bytecode output
2365 that can be interpreted by the ASN.1 stream decoder and used to
2366 inform it as to what tags are to be expected in a stream and what
2367 functions to call on what tags.
2368
2369source "kernel/Kconfig.locks"
2370
2371config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2372 bool
2373
2374config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2375 bool
2376
2377
2378
2379
2380
2381
2382
2383
2384config ARCH_HAS_SYSCALL_WRAPPER
2385 def_bool n
2386