xref: /openbmc/linux/init/Kconfig (revision c127d130)
1 # SPDX-License-Identifier: GPL-2.0-only
2 config 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 
19 config CC_IS_GCC
20 	def_bool $(success,test "$(cc-name)" = GCC)
21 
22 config GCC_VERSION
23 	int
24 	default $(cc-version) if CC_IS_GCC
25 	default 0
26 
27 config CC_IS_CLANG
28 	def_bool $(success,test "$(cc-name)" = Clang)
29 
30 config CLANG_VERSION
31 	int
32 	default $(cc-version) if CC_IS_CLANG
33 	default 0
34 
35 config AS_IS_GNU
36 	def_bool $(success,test "$(as-name)" = GNU)
37 
38 config AS_IS_LLVM
39 	def_bool $(success,test "$(as-name)" = LLVM)
40 
41 config AS_VERSION
42 	int
43 	# Use clang version if this is the integrated assembler
44 	default CLANG_VERSION if AS_IS_LLVM
45 	default $(as-version)
46 
47 config LD_IS_BFD
48 	def_bool $(success,test "$(ld-name)" = BFD)
49 
50 config LD_VERSION
51 	int
52 	default $(ld-version) if LD_IS_BFD
53 	default 0
54 
55 config LD_IS_LLD
56 	def_bool $(success,test "$(ld-name)" = LLD)
57 
58 config LLD_VERSION
59 	int
60 	default $(ld-version) if LD_IS_LLD
61 	default 0
62 
63 config CC_CAN_LINK
64 	bool
65 	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT
66 	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag))
67 
68 config CC_CAN_LINK_STATIC
69 	bool
70 	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT
71 	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static)
72 
73 config CC_HAS_ASM_GOTO
74 	def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
75 
76 config 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 
80 config TOOLS_SUPPORT_RELR
81 	def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
82 
83 config CC_HAS_ASM_INLINE
84 	def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
85 
86 config 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 
89 config PAHOLE_VERSION
90 	int
91 	default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))
92 
93 config CONSTRUCTORS
94 	bool
95 
96 config IRQ_WORK
97 	bool
98 
99 config BUILDTIME_TABLE_SORT
100 	bool
101 
102 config THREAD_INFO_IN_TASK
103 	bool
104 	help
105 	  Select this to move thread_info off the stack into task_struct.  To
106 	  make this work, an arch will need to remove all thread_info fields
107 	  except flags and fix any runtime bugs.
108 
109 	  One subtle change that will be needed is to use try_get_task_stack()
110 	  and put_task_stack() in save_thread_stack_tsk() and get_wchan().
111 
112 menu "General setup"
113 
114 config BROKEN
115 	bool
116 
117 config BROKEN_ON_SMP
118 	bool
119 	depends on BROKEN || !SMP
120 	default y
121 
122 config INIT_ENV_ARG_LIMIT
123 	int
124 	default 32 if !UML
125 	default 128 if UML
126 	help
127 	  Maximum of each of the number of arguments and environment
128 	  variables passed to init from the kernel command line.
129 
130 config COMPILE_TEST
131 	bool "Compile also drivers which will not load"
132 	depends on HAS_IOMEM
133 	help
134 	  Some drivers can be compiled on a different platform than they are
135 	  intended to be run on. Despite they cannot be loaded there (or even
136 	  when they load they cannot be used due to missing HW support),
137 	  developers still, opposing to distributors, might want to build such
138 	  drivers to compile-test them.
139 
140 	  If you are a developer and want to build everything available, say Y
141 	  here. If you are a user/distributor, say N here to exclude useless
142 	  drivers to be distributed.
143 
144 config WERROR
145 	bool "Compile the kernel with warnings as errors"
146 	default COMPILE_TEST
147 	help
148 	  A kernel build should not cause any compiler warnings, and this
149 	  enables the '-Werror' flag to enforce that rule by default.
150 
151 	  However, if you have a new (or very old) compiler with odd and
152 	  unusual warnings, or you have some architecture with problems,
153 	  you may need to disable this config option in order to
154 	  successfully build the kernel.
155 
156 	  If in doubt, say Y.
157 
158 config UAPI_HEADER_TEST
159 	bool "Compile test UAPI headers"
160 	depends on HEADERS_INSTALL && CC_CAN_LINK
161 	help
162 	  Compile test headers exported to user-space to ensure they are
163 	  self-contained, i.e. compilable as standalone units.
164 
165 	  If you are a developer or tester and want to ensure the exported
166 	  headers are self-contained, say Y here. Otherwise, choose N.
167 
168 config LOCALVERSION
169 	string "Local version - append to kernel release"
170 	help
171 	  Append an extra string to the end of your kernel version.
172 	  This will show up when you type uname, for example.
173 	  The string you set here will be appended after the contents of
174 	  any files with a filename matching localversion* in your
175 	  object and source tree, in that order.  Your total string can
176 	  be a maximum of 64 characters.
177 
178 config LOCALVERSION_AUTO
179 	bool "Automatically append version information to the version string"
180 	default y
181 	depends on !COMPILE_TEST
182 	help
183 	  This will try to automatically determine if the current tree is a
184 	  release tree by looking for git tags that belong to the current
185 	  top of tree revision.
186 
187 	  A string of the format -gxxxxxxxx will be added to the localversion
188 	  if a git-based tree is found.  The string generated by this will be
189 	  appended after any matching localversion* files, and after the value
190 	  set in CONFIG_LOCALVERSION.
191 
192 	  (The actual string used here is the first eight characters produced
193 	  by running the command:
194 
195 	    $ git rev-parse --verify HEAD
196 
197 	  which is done within the script "scripts/setlocalversion".)
198 
199 config BUILD_SALT
200 	string "Build ID Salt"
201 	default ""
202 	help
203 	  The build ID is used to link binaries and their debug info. Setting
204 	  this option will use the value in the calculation of the build id.
205 	  This is mostly useful for distributions which want to ensure the
206 	  build is unique between builds. It's safe to leave the default.
207 
208 config HAVE_KERNEL_GZIP
209 	bool
210 
211 config HAVE_KERNEL_BZIP2
212 	bool
213 
214 config HAVE_KERNEL_LZMA
215 	bool
216 
217 config HAVE_KERNEL_XZ
218 	bool
219 
220 config HAVE_KERNEL_LZO
221 	bool
222 
223 config HAVE_KERNEL_LZ4
224 	bool
225 
226 config HAVE_KERNEL_ZSTD
227 	bool
228 
229 config HAVE_KERNEL_UNCOMPRESSED
230 	bool
231 
232 choice
233 	prompt "Kernel compression mode"
234 	default KERNEL_GZIP
235 	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
236 	help
237 	  The linux kernel is a kind of self-extracting executable.
238 	  Several compression algorithms are available, which differ
239 	  in efficiency, compression and decompression speed.
240 	  Compression speed is only relevant when building a kernel.
241 	  Decompression speed is relevant at each boot.
242 
243 	  If you have any problems with bzip2 or lzma compressed
244 	  kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
245 	  version of this functionality (bzip2 only), for 2.4, was
246 	  supplied by Christian Ludwig)
247 
248 	  High compression options are mostly useful for users, who
249 	  are low on disk space (embedded systems), but for whom ram
250 	  size matters less.
251 
252 	  If in doubt, select 'gzip'
253 
254 config KERNEL_GZIP
255 	bool "Gzip"
256 	depends on HAVE_KERNEL_GZIP
257 	help
258 	  The old and tried gzip compression. It provides a good balance
259 	  between compression ratio and decompression speed.
260 
261 config KERNEL_BZIP2
262 	bool "Bzip2"
263 	depends on HAVE_KERNEL_BZIP2
264 	help
265 	  Its compression ratio and speed is intermediate.
266 	  Decompression speed is slowest among the choices.  The kernel
267 	  size is about 10% smaller with bzip2, in comparison to gzip.
268 	  Bzip2 uses a large amount of memory. For modern kernels you
269 	  will need at least 8MB RAM or more for booting.
270 
271 config KERNEL_LZMA
272 	bool "LZMA"
273 	depends on HAVE_KERNEL_LZMA
274 	help
275 	  This compression algorithm's ratio is best.  Decompression speed
276 	  is between gzip and bzip2.  Compression is slowest.
277 	  The kernel size is about 33% smaller with LZMA in comparison to gzip.
278 
279 config KERNEL_XZ
280 	bool "XZ"
281 	depends on HAVE_KERNEL_XZ
282 	help
283 	  XZ uses the LZMA2 algorithm and instruction set specific
284 	  BCJ filters which can improve compression ratio of executable
285 	  code. The size of the kernel is about 30% smaller with XZ in
286 	  comparison to gzip. On architectures for which there is a BCJ
287 	  filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
288 	  will create a few percent smaller kernel than plain LZMA.
289 
290 	  The speed is about the same as with LZMA: The decompression
291 	  speed of XZ is better than that of bzip2 but worse than gzip
292 	  and LZO. Compression is slow.
293 
294 config KERNEL_LZO
295 	bool "LZO"
296 	depends on HAVE_KERNEL_LZO
297 	help
298 	  Its compression ratio is the poorest among the choices. The kernel
299 	  size is about 10% bigger than gzip; however its speed
300 	  (both compression and decompression) is the fastest.
301 
302 config KERNEL_LZ4
303 	bool "LZ4"
304 	depends on HAVE_KERNEL_LZ4
305 	help
306 	  LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
307 	  A preliminary version of LZ4 de/compression tool is available at
308 	  <https://code.google.com/p/lz4/>.
309 
310 	  Its compression ratio is worse than LZO. The size of the kernel
311 	  is about 8% bigger than LZO. But the decompression speed is
312 	  faster than LZO.
313 
314 config KERNEL_ZSTD
315 	bool "ZSTD"
316 	depends on HAVE_KERNEL_ZSTD
317 	help
318 	  ZSTD is a compression algorithm targeting intermediate compression
319 	  with fast decompression speed. It will compress better than GZIP and
320 	  decompress around the same speed as LZO, but slower than LZ4. You
321 	  will need at least 192 KB RAM or more for booting. The zstd command
322 	  line tool is required for compression.
323 
324 config KERNEL_UNCOMPRESSED
325 	bool "None"
326 	depends on HAVE_KERNEL_UNCOMPRESSED
327 	help
328 	  Produce uncompressed kernel image. This option is usually not what
329 	  you want. It is useful for debugging the kernel in slow simulation
330 	  environments, where decompressing and moving the kernel is awfully
331 	  slow. This option allows early boot code to skip the decompressor
332 	  and jump right at uncompressed kernel image.
333 
334 endchoice
335 
336 config DEFAULT_INIT
337 	string "Default init path"
338 	default ""
339 	help
340 	  This option determines the default init for the system if no init=
341 	  option is passed on the kernel command line. If the requested path is
342 	  not present, we will still then move on to attempting further
343 	  locations (e.g. /sbin/init, etc). If this is empty, we will just use
344 	  the fallback list when init= is not passed.
345 
346 config DEFAULT_HOSTNAME
347 	string "Default hostname"
348 	default "(none)"
349 	help
350 	  This option determines the default system hostname before userspace
351 	  calls sethostname(2). The kernel traditionally uses "(none)" here,
352 	  but you may wish to use a different default here to make a minimal
353 	  system more usable with less configuration.
354 
355 #
356 # For some reason microblaze and nios2 hard code SWAP=n.  Hopefully we can
357 # add proper SWAP support to them, in which case this can be remove.
358 #
359 config ARCH_NO_SWAP
360 	bool
361 
362 config SWAP
363 	bool "Support for paging of anonymous memory (swap)"
364 	depends on MMU && BLOCK && !ARCH_NO_SWAP
365 	default y
366 	help
367 	  This option allows you to choose whether you want to have support
368 	  for so called swap devices or swap files in your kernel that are
369 	  used to provide more virtual memory than the actual RAM present
370 	  in your computer.  If unsure say Y.
371 
372 config SYSVIPC
373 	bool "System V IPC"
374 	help
375 	  Inter Process Communication is a suite of library functions and
376 	  system calls which let processes (running programs) synchronize and
377 	  exchange information. It is generally considered to be a good thing,
378 	  and some programs won't run unless you say Y here. In particular, if
379 	  you want to run the DOS emulator dosemu under Linux (read the
380 	  DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
381 	  you'll need to say Y here.
382 
383 	  You can find documentation about IPC with "info ipc" and also in
384 	  section 6.4 of the Linux Programmer's Guide, available from
385 	  <http://www.tldp.org/guides.html>.
386 
387 config SYSVIPC_SYSCTL
388 	bool
389 	depends on SYSVIPC
390 	depends on SYSCTL
391 	default y
392 
393 config POSIX_MQUEUE
394 	bool "POSIX Message Queues"
395 	depends on NET
396 	help
397 	  POSIX variant of message queues is a part of IPC. In POSIX message
398 	  queues every message has a priority which decides about succession
399 	  of receiving it by a process. If you want to compile and run
400 	  programs written e.g. for Solaris with use of its POSIX message
401 	  queues (functions mq_*) say Y here.
402 
403 	  POSIX message queues are visible as a filesystem called 'mqueue'
404 	  and can be mounted somewhere if you want to do filesystem
405 	  operations on message queues.
406 
407 	  If unsure, say Y.
408 
409 config POSIX_MQUEUE_SYSCTL
410 	bool
411 	depends on POSIX_MQUEUE
412 	depends on SYSCTL
413 	default y
414 
415 config WATCH_QUEUE
416 	bool "General notification queue"
417 	default n
418 	help
419 
420 	  This is a general notification queue for the kernel to pass events to
421 	  userspace by splicing them into pipes.  It can be used in conjunction
422 	  with watches for key/keyring change notifications and device
423 	  notifications.
424 
425 	  See Documentation/watch_queue.rst
426 
427 config CROSS_MEMORY_ATTACH
428 	bool "Enable process_vm_readv/writev syscalls"
429 	depends on MMU
430 	default y
431 	help
432 	  Enabling this option adds the system calls process_vm_readv and
433 	  process_vm_writev which allow a process with the correct privileges
434 	  to directly read from or write to another process' address space.
435 	  See the man page for more details.
436 
437 config USELIB
438 	bool "uselib syscall"
439 	def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
440 	help
441 	  This option enables the uselib syscall, a system call used in the
442 	  dynamic linker from libc5 and earlier.  glibc does not use this
443 	  system call.  If you intend to run programs built on libc5 or
444 	  earlier, you may need to enable this syscall.  Current systems
445 	  running glibc can safely disable this.
446 
447 config AUDIT
448 	bool "Auditing support"
449 	depends on NET
450 	help
451 	  Enable auditing infrastructure that can be used with another
452 	  kernel subsystem, such as SELinux (which requires this for
453 	  logging of avc messages output).  System call auditing is included
454 	  on architectures which support it.
455 
456 config HAVE_ARCH_AUDITSYSCALL
457 	bool
458 
459 config AUDITSYSCALL
460 	def_bool y
461 	depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
462 	select FSNOTIFY
463 
464 source "kernel/irq/Kconfig"
465 source "kernel/time/Kconfig"
466 source "kernel/bpf/Kconfig"
467 source "kernel/Kconfig.preempt"
468 
469 menu "CPU/Task time and stats accounting"
470 
471 config VIRT_CPU_ACCOUNTING
472 	bool
473 
474 choice
475 	prompt "Cputime accounting"
476 	default TICK_CPU_ACCOUNTING if !PPC64
477 	default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
478 
479 # Kind of a stub config for the pure tick based cputime accounting
480 config TICK_CPU_ACCOUNTING
481 	bool "Simple tick based cputime accounting"
482 	depends on !S390 && !NO_HZ_FULL
483 	help
484 	  This is the basic tick based cputime accounting that maintains
485 	  statistics about user, system and idle time spent on per jiffies
486 	  granularity.
487 
488 	  If unsure, say Y.
489 
490 config VIRT_CPU_ACCOUNTING_NATIVE
491 	bool "Deterministic task and CPU time accounting"
492 	depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
493 	select VIRT_CPU_ACCOUNTING
494 	help
495 	  Select this option to enable more accurate task and CPU time
496 	  accounting.  This is done by reading a CPU counter on each
497 	  kernel entry and exit and on transitions within the kernel
498 	  between system, softirq and hardirq state, so there is a
499 	  small performance impact.  In the case of s390 or IBM POWER > 5,
500 	  this also enables accounting of stolen time on logically-partitioned
501 	  systems.
502 
503 config VIRT_CPU_ACCOUNTING_GEN
504 	bool "Full dynticks CPU time accounting"
505 	depends on HAVE_CONTEXT_TRACKING
506 	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
507 	depends on GENERIC_CLOCKEVENTS
508 	select VIRT_CPU_ACCOUNTING
509 	select CONTEXT_TRACKING
510 	help
511 	  Select this option to enable task and CPU time accounting on full
512 	  dynticks systems. This accounting is implemented by watching every
513 	  kernel-user boundaries using the context tracking subsystem.
514 	  The accounting is thus performed at the expense of some significant
515 	  overhead.
516 
517 	  For now this is only useful if you are working on the full
518 	  dynticks subsystem development.
519 
520 	  If unsure, say N.
521 
522 endchoice
523 
524 config IRQ_TIME_ACCOUNTING
525 	bool "Fine granularity task level IRQ time accounting"
526 	depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
527 	help
528 	  Select this option to enable fine granularity task irq time
529 	  accounting. This is done by reading a timestamp on each
530 	  transitions between softirq and hardirq state, so there can be a
531 	  small performance impact.
532 
533 	  If in doubt, say N here.
534 
535 config HAVE_SCHED_AVG_IRQ
536 	def_bool y
537 	depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
538 	depends on SMP
539 
540 config SCHED_THERMAL_PRESSURE
541 	bool
542 	default y if ARM && ARM_CPU_TOPOLOGY
543 	default y if ARM64
544 	depends on SMP
545 	depends on CPU_FREQ_THERMAL
546 	help
547 	  Select this option to enable thermal pressure accounting in the
548 	  scheduler. Thermal pressure is the value conveyed to the scheduler
549 	  that reflects the reduction in CPU compute capacity resulted from
550 	  thermal throttling. Thermal throttling occurs when the performance of
551 	  a CPU is capped due to high operating temperatures.
552 
553 	  If selected, the scheduler will be able to balance tasks accordingly,
554 	  i.e. put less load on throttled CPUs than on non/less throttled ones.
555 
556 	  This requires the architecture to implement
557 	  arch_update_thermal_pressure() and arch_scale_thermal_pressure().
558 
559 config BSD_PROCESS_ACCT
560 	bool "BSD Process Accounting"
561 	depends on MULTIUSER
562 	help
563 	  If you say Y here, a user level program will be able to instruct the
564 	  kernel (via a special system call) to write process accounting
565 	  information to a file: whenever a process exits, information about
566 	  that process will be appended to the file by the kernel.  The
567 	  information includes things such as creation time, owning user,
568 	  command name, memory usage, controlling terminal etc. (the complete
569 	  list is in the struct acct in <file:include/linux/acct.h>).  It is
570 	  up to the user level program to do useful things with this
571 	  information.  This is generally a good idea, so say Y.
572 
573 config BSD_PROCESS_ACCT_V3
574 	bool "BSD Process Accounting version 3 file format"
575 	depends on BSD_PROCESS_ACCT
576 	default n
577 	help
578 	  If you say Y here, the process accounting information is written
579 	  in a new file format that also logs the process IDs of each
580 	  process and its parent. Note that this file format is incompatible
581 	  with previous v0/v1/v2 file formats, so you will need updated tools
582 	  for processing it. A preliminary version of these tools is available
583 	  at <http://www.gnu.org/software/acct/>.
584 
585 config TASKSTATS
586 	bool "Export task/process statistics through netlink"
587 	depends on NET
588 	depends on MULTIUSER
589 	default n
590 	help
591 	  Export selected statistics for tasks/processes through the
592 	  generic netlink interface. Unlike BSD process accounting, the
593 	  statistics are available during the lifetime of tasks/processes as
594 	  responses to commands. Like BSD accounting, they are sent to user
595 	  space on task exit.
596 
597 	  Say N if unsure.
598 
599 config TASK_DELAY_ACCT
600 	bool "Enable per-task delay accounting"
601 	depends on TASKSTATS
602 	select SCHED_INFO
603 	help
604 	  Collect information on time spent by a task waiting for system
605 	  resources like cpu, synchronous block I/O completion and swapping
606 	  in pages. Such statistics can help in setting a task's priorities
607 	  relative to other tasks for cpu, io, rss limits etc.
608 
609 	  Say N if unsure.
610 
611 config TASK_XACCT
612 	bool "Enable extended accounting over taskstats"
613 	depends on TASKSTATS
614 	help
615 	  Collect extended task accounting data and send the data
616 	  to userland for processing over the taskstats interface.
617 
618 	  Say N if unsure.
619 
620 config TASK_IO_ACCOUNTING
621 	bool "Enable per-task storage I/O accounting"
622 	depends on TASK_XACCT
623 	help
624 	  Collect information on the number of bytes of storage I/O which this
625 	  task has caused.
626 
627 	  Say N if unsure.
628 
629 config PSI
630 	bool "Pressure stall information tracking"
631 	help
632 	  Collect metrics that indicate how overcommitted the CPU, memory,
633 	  and IO capacity are in the system.
634 
635 	  If you say Y here, the kernel will create /proc/pressure/ with the
636 	  pressure statistics files cpu, memory, and io. These will indicate
637 	  the share of walltime in which some or all tasks in the system are
638 	  delayed due to contention of the respective resource.
639 
640 	  In kernels with cgroup support, cgroups (cgroup2 only) will
641 	  have cpu.pressure, memory.pressure, and io.pressure files,
642 	  which aggregate pressure stalls for the grouped tasks only.
643 
644 	  For more details see Documentation/accounting/psi.rst.
645 
646 	  Say N if unsure.
647 
648 config PSI_DEFAULT_DISABLED
649 	bool "Require boot parameter to enable pressure stall information tracking"
650 	default n
651 	depends on PSI
652 	help
653 	  If set, pressure stall information tracking will be disabled
654 	  per default but can be enabled through passing psi=1 on the
655 	  kernel commandline during boot.
656 
657 	  This feature adds some code to the task wakeup and sleep
658 	  paths of the scheduler. The overhead is too low to affect
659 	  common scheduling-intense workloads in practice (such as
660 	  webservers, memcache), but it does show up in artificial
661 	  scheduler stress tests, such as hackbench.
662 
663 	  If you are paranoid and not sure what the kernel will be
664 	  used for, say Y.
665 
666 	  Say N if unsure.
667 
668 endmenu # "CPU/Task time and stats accounting"
669 
670 config CPU_ISOLATION
671 	bool "CPU isolation"
672 	depends on SMP || COMPILE_TEST
673 	default y
674 	help
675 	  Make sure that CPUs running critical tasks are not disturbed by
676 	  any source of "noise" such as unbound workqueues, timers, kthreads...
677 	  Unbound jobs get offloaded to housekeeping CPUs. This is driven by
678 	  the "isolcpus=" boot parameter.
679 
680 	  Say Y if unsure.
681 
682 source "kernel/rcu/Kconfig"
683 
684 config BUILD_BIN2C
685 	bool
686 	default n
687 
688 config IKCONFIG
689 	tristate "Kernel .config support"
690 	help
691 	  This option enables the complete Linux kernel ".config" file
692 	  contents to be saved in the kernel. It provides documentation
693 	  of which kernel options are used in a running kernel or in an
694 	  on-disk kernel.  This information can be extracted from the kernel
695 	  image file with the script scripts/extract-ikconfig and used as
696 	  input to rebuild the current kernel or to build another kernel.
697 	  It can also be extracted from a running kernel by reading
698 	  /proc/config.gz if enabled (below).
699 
700 config IKCONFIG_PROC
701 	bool "Enable access to .config through /proc/config.gz"
702 	depends on IKCONFIG && PROC_FS
703 	help
704 	  This option enables access to the kernel configuration file
705 	  through /proc/config.gz.
706 
707 config IKHEADERS
708 	tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
709 	depends on SYSFS
710 	help
711 	  This option enables access to the in-kernel headers that are generated during
712 	  the build process. These can be used to build eBPF tracing programs,
713 	  or similar programs.  If you build the headers as a module, a module called
714 	  kheaders.ko is built which can be loaded on-demand to get access to headers.
715 
716 config LOG_BUF_SHIFT
717 	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
718 	range 12 25 if !H8300
719 	range 12 19 if H8300
720 	default 17
721 	depends on PRINTK
722 	help
723 	  Select the minimal kernel log buffer size as a power of 2.
724 	  The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
725 	  parameter, see below. Any higher size also might be forced
726 	  by "log_buf_len" boot parameter.
727 
728 	  Examples:
729 		     17 => 128 KB
730 		     16 => 64 KB
731 		     15 => 32 KB
732 		     14 => 16 KB
733 		     13 =>  8 KB
734 		     12 =>  4 KB
735 
736 config LOG_CPU_MAX_BUF_SHIFT
737 	int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
738 	depends on SMP
739 	range 0 21
740 	default 12 if !BASE_SMALL
741 	default 0 if BASE_SMALL
742 	depends on PRINTK
743 	help
744 	  This option allows to increase the default ring buffer size
745 	  according to the number of CPUs. The value defines the contribution
746 	  of each CPU as a power of 2. The used space is typically only few
747 	  lines however it might be much more when problems are reported,
748 	  e.g. backtraces.
749 
750 	  The increased size means that a new buffer has to be allocated and
751 	  the original static one is unused. It makes sense only on systems
752 	  with more CPUs. Therefore this value is used only when the sum of
753 	  contributions is greater than the half of the default kernel ring
754 	  buffer as defined by LOG_BUF_SHIFT. The default values are set
755 	  so that more than 16 CPUs are needed to trigger the allocation.
756 
757 	  Also this option is ignored when "log_buf_len" kernel parameter is
758 	  used as it forces an exact (power of two) size of the ring buffer.
759 
760 	  The number of possible CPUs is used for this computation ignoring
761 	  hotplugging making the computation optimal for the worst case
762 	  scenario while allowing a simple algorithm to be used from bootup.
763 
764 	  Examples shift values and their meaning:
765 		     17 => 128 KB for each CPU
766 		     16 =>  64 KB for each CPU
767 		     15 =>  32 KB for each CPU
768 		     14 =>  16 KB for each CPU
769 		     13 =>   8 KB for each CPU
770 		     12 =>   4 KB for each CPU
771 
772 config PRINTK_SAFE_LOG_BUF_SHIFT
773 	int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
774 	range 10 21
775 	default 13
776 	depends on PRINTK
777 	help
778 	  Select the size of an alternate printk per-CPU buffer where messages
779 	  printed from usafe contexts are temporary stored. One example would
780 	  be NMI messages, another one - printk recursion. The messages are
781 	  copied to the main log buffer in a safe context to avoid a deadlock.
782 	  The value defines the size as a power of 2.
783 
784 	  Those messages are rare and limited. The largest one is when
785 	  a backtrace is printed. It usually fits into 4KB. Select
786 	  8KB if you want to be on the safe side.
787 
788 	  Examples:
789 		     17 => 128 KB for each CPU
790 		     16 =>  64 KB for each CPU
791 		     15 =>  32 KB for each CPU
792 		     14 =>  16 KB for each CPU
793 		     13 =>   8 KB for each CPU
794 		     12 =>   4 KB for each CPU
795 
796 config PRINTK_INDEX
797 	bool "Printk indexing debugfs interface"
798 	depends on PRINTK && DEBUG_FS
799 	help
800 	  Add support for indexing of all printk formats known at compile time
801 	  at <debugfs>/printk/index/<module>.
802 
803 	  This can be used as part of maintaining daemons which monitor
804 	  /dev/kmsg, as it permits auditing the printk formats present in a
805 	  kernel, allowing detection of cases where monitored printks are
806 	  changed or no longer present.
807 
808 	  There is no additional runtime cost to printk with this enabled.
809 
810 #
811 # Architectures with an unreliable sched_clock() should select this:
812 #
813 config HAVE_UNSTABLE_SCHED_CLOCK
814 	bool
815 
816 config GENERIC_SCHED_CLOCK
817 	bool
818 
819 menu "Scheduler features"
820 
821 config UCLAMP_TASK
822 	bool "Enable utilization clamping for RT/FAIR tasks"
823 	depends on CPU_FREQ_GOV_SCHEDUTIL
824 	help
825 	  This feature enables the scheduler to track the clamped utilization
826 	  of each CPU based on RUNNABLE tasks scheduled on that CPU.
827 
828 	  With this option, the user can specify the min and max CPU
829 	  utilization allowed for RUNNABLE tasks. The max utilization defines
830 	  the maximum frequency a task should use while the min utilization
831 	  defines the minimum frequency it should use.
832 
833 	  Both min and max utilization clamp values are hints to the scheduler,
834 	  aiming at improving its frequency selection policy, but they do not
835 	  enforce or grant any specific bandwidth for tasks.
836 
837 	  If in doubt, say N.
838 
839 config UCLAMP_BUCKETS_COUNT
840 	int "Number of supported utilization clamp buckets"
841 	range 5 20
842 	default 5
843 	depends on UCLAMP_TASK
844 	help
845 	  Defines the number of clamp buckets to use. The range of each bucket
846 	  will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
847 	  number of clamp buckets the finer their granularity and the higher
848 	  the precision of clamping aggregation and tracking at run-time.
849 
850 	  For example, with the minimum configuration value we will have 5
851 	  clamp buckets tracking 20% utilization each. A 25% boosted tasks will
852 	  be refcounted in the [20..39]% bucket and will set the bucket clamp
853 	  effective value to 25%.
854 	  If a second 30% boosted task should be co-scheduled on the same CPU,
855 	  that task will be refcounted in the same bucket of the first task and
856 	  it will boost the bucket clamp effective value to 30%.
857 	  The clamp effective value of a bucket is reset to its nominal value
858 	  (20% in the example above) when there are no more tasks refcounted in
859 	  that bucket.
860 
861 	  An additional boost/capping margin can be added to some tasks. In the
862 	  example above the 25% task will be boosted to 30% until it exits the
863 	  CPU. If that should be considered not acceptable on certain systems,
864 	  it's always possible to reduce the margin by increasing the number of
865 	  clamp buckets to trade off used memory for run-time tracking
866 	  precision.
867 
868 	  If in doubt, use the default value.
869 
870 endmenu
871 
872 #
873 # For architectures that want to enable the support for NUMA-affine scheduler
874 # balancing logic:
875 #
876 config ARCH_SUPPORTS_NUMA_BALANCING
877 	bool
878 
879 #
880 # For architectures that prefer to flush all TLBs after a number of pages
881 # are unmapped instead of sending one IPI per page to flush. The architecture
882 # must provide guarantees on what happens if a clean TLB cache entry is
883 # written after the unmap. Details are in mm/rmap.c near the check for
884 # should_defer_flush. The architecture should also consider if the full flush
885 # and the refill costs are offset by the savings of sending fewer IPIs.
886 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
887 	bool
888 
889 config CC_HAS_INT128
890 	def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
891 
892 config CC_IMPLICIT_FALLTHROUGH
893 	string
894 	default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
895 	default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough)
896 
897 #
898 # For architectures that know their GCC __int128 support is sound
899 #
900 config ARCH_SUPPORTS_INT128
901 	bool
902 
903 # For architectures that (ab)use NUMA to represent different memory regions
904 # all cpu-local but of different latencies, such as SuperH.
905 #
906 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
907 	bool
908 
909 config NUMA_BALANCING
910 	bool "Memory placement aware NUMA scheduler"
911 	depends on ARCH_SUPPORTS_NUMA_BALANCING
912 	depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
913 	depends on SMP && NUMA && MIGRATION && !PREEMPT_RT
914 	help
915 	  This option adds support for automatic NUMA aware memory/task placement.
916 	  The mechanism is quite primitive and is based on migrating memory when
917 	  it has references to the node the task is running on.
918 
919 	  This system will be inactive on UMA systems.
920 
921 config NUMA_BALANCING_DEFAULT_ENABLED
922 	bool "Automatically enable NUMA aware memory/task placement"
923 	default y
924 	depends on NUMA_BALANCING
925 	help
926 	  If set, automatic NUMA balancing will be enabled if running on a NUMA
927 	  machine.
928 
929 menuconfig CGROUPS
930 	bool "Control Group support"
931 	select KERNFS
932 	help
933 	  This option adds support for grouping sets of processes together, for
934 	  use with process control subsystems such as Cpusets, CFS, memory
935 	  controls or device isolation.
936 	  See
937 		- Documentation/scheduler/sched-design-CFS.rst	(CFS)
938 		- Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
939 					  and resource control)
940 
941 	  Say N if unsure.
942 
943 if CGROUPS
944 
945 config PAGE_COUNTER
946 	bool
947 
948 config MEMCG
949 	bool "Memory controller"
950 	select PAGE_COUNTER
951 	select EVENTFD
952 	help
953 	  Provides control over the memory footprint of tasks in a cgroup.
954 
955 config MEMCG_SWAP
956 	bool
957 	depends on MEMCG && SWAP
958 	default y
959 
960 config MEMCG_KMEM
961 	bool
962 	depends on MEMCG && !SLOB
963 	default y
964 
965 config BLK_CGROUP
966 	bool "IO controller"
967 	depends on BLOCK
968 	default n
969 	help
970 	Generic block IO controller cgroup interface. This is the common
971 	cgroup interface which should be used by various IO controlling
972 	policies.
973 
974 	Currently, CFQ IO scheduler uses it to recognize task groups and
975 	control disk bandwidth allocation (proportional time slice allocation)
976 	to such task groups. It is also used by bio throttling logic in
977 	block layer to implement upper limit in IO rates on a device.
978 
979 	This option only enables generic Block IO controller infrastructure.
980 	One needs to also enable actual IO controlling logic/policy. For
981 	enabling proportional weight division of disk bandwidth in CFQ, set
982 	CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
983 	CONFIG_BLK_DEV_THROTTLING=y.
984 
985 	See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
986 
987 config CGROUP_WRITEBACK
988 	bool
989 	depends on MEMCG && BLK_CGROUP
990 	default y
991 
992 menuconfig CGROUP_SCHED
993 	bool "CPU controller"
994 	default n
995 	help
996 	  This feature lets CPU scheduler recognize task groups and control CPU
997 	  bandwidth allocation to such task groups. It uses cgroups to group
998 	  tasks.
999 
1000 if CGROUP_SCHED
1001 config FAIR_GROUP_SCHED
1002 	bool "Group scheduling for SCHED_OTHER"
1003 	depends on CGROUP_SCHED
1004 	default CGROUP_SCHED
1005 
1006 config CFS_BANDWIDTH
1007 	bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1008 	depends on FAIR_GROUP_SCHED
1009 	default n
1010 	help
1011 	  This option allows users to define CPU bandwidth rates (limits) for
1012 	  tasks running within the fair group scheduler.  Groups with no limit
1013 	  set are considered to be unconstrained and will run with no
1014 	  restriction.
1015 	  See Documentation/scheduler/sched-bwc.rst for more information.
1016 
1017 config RT_GROUP_SCHED
1018 	bool "Group scheduling for SCHED_RR/FIFO"
1019 	depends on CGROUP_SCHED
1020 	default n
1021 	help
1022 	  This feature lets you explicitly allocate real CPU bandwidth
1023 	  to task groups. If enabled, it will also make it impossible to
1024 	  schedule realtime tasks for non-root users until you allocate
1025 	  realtime bandwidth for them.
1026 	  See Documentation/scheduler/sched-rt-group.rst for more information.
1027 
1028 endif #CGROUP_SCHED
1029 
1030 config UCLAMP_TASK_GROUP
1031 	bool "Utilization clamping per group of tasks"
1032 	depends on CGROUP_SCHED
1033 	depends on UCLAMP_TASK
1034 	default n
1035 	help
1036 	  This feature enables the scheduler to track the clamped utilization
1037 	  of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
1038 
1039 	  When this option is enabled, the user can specify a min and max
1040 	  CPU bandwidth which is allowed for each single task in a group.
1041 	  The max bandwidth allows to clamp the maximum frequency a task
1042 	  can use, while the min bandwidth allows to define a minimum
1043 	  frequency a task will always use.
1044 
1045 	  When task group based utilization clamping is enabled, an eventually
1046 	  specified task-specific clamp value is constrained by the cgroup
1047 	  specified clamp value. Both minimum and maximum task clamping cannot
1048 	  be bigger than the corresponding clamping defined at task group level.
1049 
1050 	  If in doubt, say N.
1051 
1052 config CGROUP_PIDS
1053 	bool "PIDs controller"
1054 	help
1055 	  Provides enforcement of process number limits in the scope of a
1056 	  cgroup. Any attempt to fork more processes than is allowed in the
1057 	  cgroup will fail. PIDs are fundamentally a global resource because it
1058 	  is fairly trivial to reach PID exhaustion before you reach even a
1059 	  conservative kmemcg limit. As a result, it is possible to grind a
1060 	  system to halt without being limited by other cgroup policies. The
1061 	  PIDs controller is designed to stop this from happening.
1062 
1063 	  It should be noted that organisational operations (such as attaching
1064 	  to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1065 	  since the PIDs limit only affects a process's ability to fork, not to
1066 	  attach to a cgroup.
1067 
1068 config CGROUP_RDMA
1069 	bool "RDMA controller"
1070 	help
1071 	  Provides enforcement of RDMA resources defined by IB stack.
1072 	  It is fairly easy for consumers to exhaust RDMA resources, which
1073 	  can result into resource unavailability to other consumers.
1074 	  RDMA controller is designed to stop this from happening.
1075 	  Attaching processes with active RDMA resources to the cgroup
1076 	  hierarchy is allowed even if can cross the hierarchy's limit.
1077 
1078 config CGROUP_FREEZER
1079 	bool "Freezer controller"
1080 	help
1081 	  Provides a way to freeze and unfreeze all tasks in a
1082 	  cgroup.
1083 
1084 	  This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1085 	  controller includes important in-kernel memory consumers per default.
1086 
1087 	  If you're using cgroup2, say N.
1088 
1089 config CGROUP_HUGETLB
1090 	bool "HugeTLB controller"
1091 	depends on HUGETLB_PAGE
1092 	select PAGE_COUNTER
1093 	default n
1094 	help
1095 	  Provides a cgroup controller for HugeTLB pages.
1096 	  When you enable this, you can put a per cgroup limit on HugeTLB usage.
1097 	  The limit is enforced during page fault. Since HugeTLB doesn't
1098 	  support page reclaim, enforcing the limit at page fault time implies
1099 	  that, the application will get SIGBUS signal if it tries to access
1100 	  HugeTLB pages beyond its limit. This requires the application to know
1101 	  beforehand how much HugeTLB pages it would require for its use. The
1102 	  control group is tracked in the third page lru pointer. This means
1103 	  that we cannot use the controller with huge page less than 3 pages.
1104 
1105 config CPUSETS
1106 	bool "Cpuset controller"
1107 	depends on SMP
1108 	help
1109 	  This option will let you create and manage CPUSETs which
1110 	  allow dynamically partitioning a system into sets of CPUs and
1111 	  Memory Nodes and assigning tasks to run only within those sets.
1112 	  This is primarily useful on large SMP or NUMA systems.
1113 
1114 	  Say N if unsure.
1115 
1116 config PROC_PID_CPUSET
1117 	bool "Include legacy /proc/<pid>/cpuset file"
1118 	depends on CPUSETS
1119 	default y
1120 
1121 config CGROUP_DEVICE
1122 	bool "Device controller"
1123 	help
1124 	  Provides a cgroup controller implementing whitelists for
1125 	  devices which a process in the cgroup can mknod or open.
1126 
1127 config CGROUP_CPUACCT
1128 	bool "Simple CPU accounting controller"
1129 	help
1130 	  Provides a simple controller for monitoring the
1131 	  total CPU consumed by the tasks in a cgroup.
1132 
1133 config CGROUP_PERF
1134 	bool "Perf controller"
1135 	depends on PERF_EVENTS
1136 	help
1137 	  This option extends the perf per-cpu mode to restrict monitoring
1138 	  to threads which belong to the cgroup specified and run on the
1139 	  designated cpu.  Or this can be used to have cgroup ID in samples
1140 	  so that it can monitor performance events among cgroups.
1141 
1142 	  Say N if unsure.
1143 
1144 config CGROUP_BPF
1145 	bool "Support for eBPF programs attached to cgroups"
1146 	depends on BPF_SYSCALL
1147 	select SOCK_CGROUP_DATA
1148 	help
1149 	  Allow attaching eBPF programs to a cgroup using the bpf(2)
1150 	  syscall command BPF_PROG_ATTACH.
1151 
1152 	  In which context these programs are accessed depends on the type
1153 	  of attachment. For instance, programs that are attached using
1154 	  BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1155 	  inet sockets.
1156 
1157 config CGROUP_MISC
1158 	bool "Misc resource controller"
1159 	default n
1160 	help
1161 	  Provides a controller for miscellaneous resources on a host.
1162 
1163 	  Miscellaneous scalar resources are the resources on the host system
1164 	  which cannot be abstracted like the other cgroups. This controller
1165 	  tracks and limits the miscellaneous resources used by a process
1166 	  attached to a cgroup hierarchy.
1167 
1168 	  For more information, please check misc cgroup section in
1169 	  /Documentation/admin-guide/cgroup-v2.rst.
1170 
1171 config CGROUP_DEBUG
1172 	bool "Debug controller"
1173 	default n
1174 	depends on DEBUG_KERNEL
1175 	help
1176 	  This option enables a simple controller that exports
1177 	  debugging information about the cgroups framework. This
1178 	  controller is for control cgroup debugging only. Its
1179 	  interfaces are not stable.
1180 
1181 	  Say N.
1182 
1183 config SOCK_CGROUP_DATA
1184 	bool
1185 	default n
1186 
1187 endif # CGROUPS
1188 
1189 menuconfig NAMESPACES
1190 	bool "Namespaces support" if EXPERT
1191 	depends on MULTIUSER
1192 	default !EXPERT
1193 	help
1194 	  Provides the way to make tasks work with different objects using
1195 	  the same id. For example same IPC id may refer to different objects
1196 	  or same user id or pid may refer to different tasks when used in
1197 	  different namespaces.
1198 
1199 if NAMESPACES
1200 
1201 config UTS_NS
1202 	bool "UTS namespace"
1203 	default y
1204 	help
1205 	  In this namespace tasks see different info provided with the
1206 	  uname() system call
1207 
1208 config TIME_NS
1209 	bool "TIME namespace"
1210 	depends on GENERIC_VDSO_TIME_NS
1211 	default y
1212 	help
1213 	  In this namespace boottime and monotonic clocks can be set.
1214 	  The time will keep going with the same pace.
1215 
1216 config IPC_NS
1217 	bool "IPC namespace"
1218 	depends on (SYSVIPC || POSIX_MQUEUE)
1219 	default y
1220 	help
1221 	  In this namespace tasks work with IPC ids which correspond to
1222 	  different IPC objects in different namespaces.
1223 
1224 config USER_NS
1225 	bool "User namespace"
1226 	default n
1227 	help
1228 	  This allows containers, i.e. vservers, to use user namespaces
1229 	  to provide different user info for different servers.
1230 
1231 	  When user namespaces are enabled in the kernel it is
1232 	  recommended that the MEMCG option also be enabled and that
1233 	  user-space use the memory control groups to limit the amount
1234 	  of memory a memory unprivileged users can use.
1235 
1236 	  If unsure, say N.
1237 
1238 config PID_NS
1239 	bool "PID Namespaces"
1240 	default y
1241 	help
1242 	  Support process id namespaces.  This allows having multiple
1243 	  processes with the same pid as long as they are in different
1244 	  pid namespaces.  This is a building block of containers.
1245 
1246 config NET_NS
1247 	bool "Network namespace"
1248 	depends on NET
1249 	default y
1250 	help
1251 	  Allow user space to create what appear to be multiple instances
1252 	  of the network stack.
1253 
1254 endif # NAMESPACES
1255 
1256 config CHECKPOINT_RESTORE
1257 	bool "Checkpoint/restore support"
1258 	select PROC_CHILDREN
1259 	select KCMP
1260 	default n
1261 	help
1262 	  Enables additional kernel features in a sake of checkpoint/restore.
1263 	  In particular it adds auxiliary prctl codes to setup process text,
1264 	  data and heap segment sizes, and a few additional /proc filesystem
1265 	  entries.
1266 
1267 	  If unsure, say N here.
1268 
1269 config SCHED_AUTOGROUP
1270 	bool "Automatic process group scheduling"
1271 	select CGROUPS
1272 	select CGROUP_SCHED
1273 	select FAIR_GROUP_SCHED
1274 	help
1275 	  This option optimizes the scheduler for common desktop workloads by
1276 	  automatically creating and populating task groups.  This separation
1277 	  of workloads isolates aggressive CPU burners (like build jobs) from
1278 	  desktop applications.  Task group autogeneration is currently based
1279 	  upon task session.
1280 
1281 config SYSFS_DEPRECATED
1282 	bool "Enable deprecated sysfs features to support old userspace tools"
1283 	depends on SYSFS
1284 	default n
1285 	help
1286 	  This option adds code that switches the layout of the "block" class
1287 	  devices, to not show up in /sys/class/block/, but only in
1288 	  /sys/block/.
1289 
1290 	  This switch is only active when the sysfs.deprecated=1 boot option is
1291 	  passed or the SYSFS_DEPRECATED_V2 option is set.
1292 
1293 	  This option allows new kernels to run on old distributions and tools,
1294 	  which might get confused by /sys/class/block/. Since 2007/2008 all
1295 	  major distributions and tools handle this just fine.
1296 
1297 	  Recent distributions and userspace tools after 2009/2010 depend on
1298 	  the existence of /sys/class/block/, and will not work with this
1299 	  option enabled.
1300 
1301 	  Only if you are using a new kernel on an old distribution, you might
1302 	  need to say Y here.
1303 
1304 config SYSFS_DEPRECATED_V2
1305 	bool "Enable deprecated sysfs features by default"
1306 	default n
1307 	depends on SYSFS
1308 	depends on SYSFS_DEPRECATED
1309 	help
1310 	  Enable deprecated sysfs by default.
1311 
1312 	  See the CONFIG_SYSFS_DEPRECATED option for more details about this
1313 	  option.
1314 
1315 	  Only if you are using a new kernel on an old distribution, you might
1316 	  need to say Y here. Even then, odds are you would not need it
1317 	  enabled, you can always pass the boot option if absolutely necessary.
1318 
1319 config RELAY
1320 	bool "Kernel->user space relay support (formerly relayfs)"
1321 	select IRQ_WORK
1322 	help
1323 	  This option enables support for relay interface support in
1324 	  certain file systems (such as debugfs).
1325 	  It is designed to provide an efficient mechanism for tools and
1326 	  facilities to relay large amounts of data from kernel space to
1327 	  user space.
1328 
1329 	  If unsure, say N.
1330 
1331 config BLK_DEV_INITRD
1332 	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1333 	help
1334 	  The initial RAM filesystem is a ramfs which is loaded by the
1335 	  boot loader (loadlin or lilo) and that is mounted as root
1336 	  before the normal boot procedure. It is typically used to
1337 	  load modules needed to mount the "real" root file system,
1338 	  etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1339 
1340 	  If RAM disk support (BLK_DEV_RAM) is also included, this
1341 	  also enables initial RAM disk (initrd) support and adds
1342 	  15 Kbytes (more on some other architectures) to the kernel size.
1343 
1344 	  If unsure say Y.
1345 
1346 if BLK_DEV_INITRD
1347 
1348 source "usr/Kconfig"
1349 
1350 endif
1351 
1352 config BOOT_CONFIG
1353 	bool "Boot config support"
1354 	select BLK_DEV_INITRD
1355 	help
1356 	  Extra boot config allows system admin to pass a config file as
1357 	  complemental extension of kernel cmdline when booting.
1358 	  The boot config file must be attached at the end of initramfs
1359 	  with checksum, size and magic word.
1360 	  See <file:Documentation/admin-guide/bootconfig.rst> for details.
1361 
1362 	  If unsure, say Y.
1363 
1364 choice
1365 	prompt "Compiler optimization level"
1366 	default CC_OPTIMIZE_FOR_PERFORMANCE
1367 
1368 config CC_OPTIMIZE_FOR_PERFORMANCE
1369 	bool "Optimize for performance (-O2)"
1370 	help
1371 	  This is the default optimization level for the kernel, building
1372 	  with the "-O2" compiler flag for best performance and most
1373 	  helpful compile-time warnings.
1374 
1375 config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1376 	bool "Optimize more for performance (-O3)"
1377 	depends on ARC
1378 	help
1379 	  Choosing this option will pass "-O3" to your compiler to optimize
1380 	  the kernel yet more for performance.
1381 
1382 config CC_OPTIMIZE_FOR_SIZE
1383 	bool "Optimize for size (-Os)"
1384 	help
1385 	  Choosing this option will pass "-Os" to your compiler resulting
1386 	  in a smaller kernel.
1387 
1388 endchoice
1389 
1390 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1391 	bool
1392 	help
1393 	  This requires that the arch annotates or otherwise protects
1394 	  its external entry points from being discarded. Linker scripts
1395 	  must also merge .text.*, .data.*, and .bss.* correctly into
1396 	  output sections. Care must be taken not to pull in unrelated
1397 	  sections (e.g., '.text.init'). Typically '.' in section names
1398 	  is used to distinguish them from label names / C identifiers.
1399 
1400 config LD_DEAD_CODE_DATA_ELIMINATION
1401 	bool "Dead code and data elimination (EXPERIMENTAL)"
1402 	depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1403 	depends on EXPERT
1404 	depends on $(cc-option,-ffunction-sections -fdata-sections)
1405 	depends on $(ld-option,--gc-sections)
1406 	help
1407 	  Enable this if you want to do dead code and data elimination with
1408 	  the linker by compiling with -ffunction-sections -fdata-sections,
1409 	  and linking with --gc-sections.
1410 
1411 	  This can reduce on disk and in-memory size of the kernel
1412 	  code and static data, particularly for small configs and
1413 	  on small systems. This has the possibility of introducing
1414 	  silently broken kernel if the required annotations are not
1415 	  present. This option is not well tested yet, so use at your
1416 	  own risk.
1417 
1418 config LD_ORPHAN_WARN
1419 	def_bool y
1420 	depends on ARCH_WANT_LD_ORPHAN_WARN
1421 	depends on $(ld-option,--orphan-handling=warn)
1422 
1423 config SYSCTL
1424 	bool
1425 
1426 config HAVE_UID16
1427 	bool
1428 
1429 config SYSCTL_EXCEPTION_TRACE
1430 	bool
1431 	help
1432 	  Enable support for /proc/sys/debug/exception-trace.
1433 
1434 config SYSCTL_ARCH_UNALIGN_NO_WARN
1435 	bool
1436 	help
1437 	  Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1438 	  Allows arch to define/use @no_unaligned_warning to possibly warn
1439 	  about unaligned access emulation going on under the hood.
1440 
1441 config SYSCTL_ARCH_UNALIGN_ALLOW
1442 	bool
1443 	help
1444 	  Enable support for /proc/sys/kernel/unaligned-trap
1445 	  Allows arches to define/use @unaligned_enabled to runtime toggle
1446 	  the unaligned access emulation.
1447 	  see arch/parisc/kernel/unaligned.c for reference
1448 
1449 config HAVE_PCSPKR_PLATFORM
1450 	bool
1451 
1452 # interpreter that classic socket filters depend on
1453 config BPF
1454 	bool
1455 
1456 menuconfig EXPERT
1457 	bool "Configure standard kernel features (expert users)"
1458 	# Unhide debug options, to make the on-by-default options visible
1459 	select DEBUG_KERNEL
1460 	help
1461 	  This option allows certain base kernel options and settings
1462 	  to be disabled or tweaked. This is for specialized
1463 	  environments which can tolerate a "non-standard" kernel.
1464 	  Only use this if you really know what you are doing.
1465 
1466 config UID16
1467 	bool "Enable 16-bit UID system calls" if EXPERT
1468 	depends on HAVE_UID16 && MULTIUSER
1469 	default y
1470 	help
1471 	  This enables the legacy 16-bit UID syscall wrappers.
1472 
1473 config MULTIUSER
1474 	bool "Multiple users, groups and capabilities support" if EXPERT
1475 	default y
1476 	help
1477 	  This option enables support for non-root users, groups and
1478 	  capabilities.
1479 
1480 	  If you say N here, all processes will run with UID 0, GID 0, and all
1481 	  possible capabilities.  Saying N here also compiles out support for
1482 	  system calls related to UIDs, GIDs, and capabilities, such as setuid,
1483 	  setgid, and capset.
1484 
1485 	  If unsure, say Y here.
1486 
1487 config SGETMASK_SYSCALL
1488 	bool "sgetmask/ssetmask syscalls support" if EXPERT
1489 	def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1490 	help
1491 	  sys_sgetmask and sys_ssetmask are obsolete system calls
1492 	  no longer supported in libc but still enabled by default in some
1493 	  architectures.
1494 
1495 	  If unsure, leave the default option here.
1496 
1497 config SYSFS_SYSCALL
1498 	bool "Sysfs syscall support" if EXPERT
1499 	default y
1500 	help
1501 	  sys_sysfs is an obsolete system call no longer supported in libc.
1502 	  Note that disabling this option is more secure but might break
1503 	  compatibility with some systems.
1504 
1505 	  If unsure say Y here.
1506 
1507 config FHANDLE
1508 	bool "open by fhandle syscalls" if EXPERT
1509 	select EXPORTFS
1510 	default y
1511 	help
1512 	  If you say Y here, a user level program will be able to map
1513 	  file names to handle and then later use the handle for
1514 	  different file system operations. This is useful in implementing
1515 	  userspace file servers, which now track files using handles instead
1516 	  of names. The handle would remain the same even if file names
1517 	  get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1518 	  syscalls.
1519 
1520 config POSIX_TIMERS
1521 	bool "Posix Clocks & timers" if EXPERT
1522 	default y
1523 	help
1524 	  This includes native support for POSIX timers to the kernel.
1525 	  Some embedded systems have no use for them and therefore they
1526 	  can be configured out to reduce the size of the kernel image.
1527 
1528 	  When this option is disabled, the following syscalls won't be
1529 	  available: timer_create, timer_gettime: timer_getoverrun,
1530 	  timer_settime, timer_delete, clock_adjtime, getitimer,
1531 	  setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1532 	  clock_getres and clock_nanosleep syscalls will be limited to
1533 	  CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1534 
1535 	  If unsure say y.
1536 
1537 config PRINTK
1538 	default y
1539 	bool "Enable support for printk" if EXPERT
1540 	select IRQ_WORK
1541 	help
1542 	  This option enables normal printk support. Removing it
1543 	  eliminates most of the message strings from the kernel image
1544 	  and makes the kernel more or less silent. As this makes it
1545 	  very difficult to diagnose system problems, saying N here is
1546 	  strongly discouraged.
1547 
1548 config BUG
1549 	bool "BUG() support" if EXPERT
1550 	default y
1551 	help
1552 	  Disabling this option eliminates support for BUG and WARN, reducing
1553 	  the size of your kernel image and potentially quietly ignoring
1554 	  numerous fatal conditions. You should only consider disabling this
1555 	  option for embedded systems with no facilities for reporting errors.
1556 	  Just say Y.
1557 
1558 config ELF_CORE
1559 	depends on COREDUMP
1560 	default y
1561 	bool "Enable ELF core dumps" if EXPERT
1562 	help
1563 	  Enable support for generating core dumps. Disabling saves about 4k.
1564 
1565 
1566 config PCSPKR_PLATFORM
1567 	bool "Enable PC-Speaker support" if EXPERT
1568 	depends on HAVE_PCSPKR_PLATFORM
1569 	select I8253_LOCK
1570 	default y
1571 	help
1572 	  This option allows to disable the internal PC-Speaker
1573 	  support, saving some memory.
1574 
1575 config BASE_FULL
1576 	default y
1577 	bool "Enable full-sized data structures for core" if EXPERT
1578 	help
1579 	  Disabling this option reduces the size of miscellaneous core
1580 	  kernel data structures. This saves memory on small machines,
1581 	  but may reduce performance.
1582 
1583 config FUTEX
1584 	bool "Enable futex support" if EXPERT
1585 	depends on !(SPARC32 && SMP)
1586 	default y
1587 	imply RT_MUTEXES
1588 	help
1589 	  Disabling this option will cause the kernel to be built without
1590 	  support for "fast userspace mutexes".  The resulting kernel may not
1591 	  run glibc-based applications correctly.
1592 
1593 config FUTEX_PI
1594 	bool
1595 	depends on FUTEX && RT_MUTEXES
1596 	default y
1597 
1598 config EPOLL
1599 	bool "Enable eventpoll support" if EXPERT
1600 	default y
1601 	help
1602 	  Disabling this option will cause the kernel to be built without
1603 	  support for epoll family of system calls.
1604 
1605 config SIGNALFD
1606 	bool "Enable signalfd() system call" if EXPERT
1607 	default y
1608 	help
1609 	  Enable the signalfd() system call that allows to receive signals
1610 	  on a file descriptor.
1611 
1612 	  If unsure, say Y.
1613 
1614 config TIMERFD
1615 	bool "Enable timerfd() system call" if EXPERT
1616 	default y
1617 	help
1618 	  Enable the timerfd() system call that allows to receive timer
1619 	  events on a file descriptor.
1620 
1621 	  If unsure, say Y.
1622 
1623 config EVENTFD
1624 	bool "Enable eventfd() system call" if EXPERT
1625 	default y
1626 	help
1627 	  Enable the eventfd() system call that allows to receive both
1628 	  kernel notification (ie. KAIO) or userspace notifications.
1629 
1630 	  If unsure, say Y.
1631 
1632 config SHMEM
1633 	bool "Use full shmem filesystem" if EXPERT
1634 	default y
1635 	depends on MMU
1636 	help
1637 	  The shmem is an internal filesystem used to manage shared memory.
1638 	  It is backed by swap and manages resource limits. It is also exported
1639 	  to userspace as tmpfs if TMPFS is enabled. Disabling this
1640 	  option replaces shmem and tmpfs with the much simpler ramfs code,
1641 	  which may be appropriate on small systems without swap.
1642 
1643 config AIO
1644 	bool "Enable AIO support" if EXPERT
1645 	default y
1646 	help
1647 	  This option enables POSIX asynchronous I/O which may by used
1648 	  by some high performance threaded applications. Disabling
1649 	  this option saves about 7k.
1650 
1651 config IO_URING
1652 	bool "Enable IO uring support" if EXPERT
1653 	select IO_WQ
1654 	default y
1655 	help
1656 	  This option enables support for the io_uring interface, enabling
1657 	  applications to submit and complete IO through submission and
1658 	  completion rings that are shared between the kernel and application.
1659 
1660 config ADVISE_SYSCALLS
1661 	bool "Enable madvise/fadvise syscalls" if EXPERT
1662 	default y
1663 	help
1664 	  This option enables the madvise and fadvise syscalls, used by
1665 	  applications to advise the kernel about their future memory or file
1666 	  usage, improving performance. If building an embedded system where no
1667 	  applications use these syscalls, you can disable this option to save
1668 	  space.
1669 
1670 config HAVE_ARCH_USERFAULTFD_WP
1671 	bool
1672 	help
1673 	  Arch has userfaultfd write protection support
1674 
1675 config HAVE_ARCH_USERFAULTFD_MINOR
1676 	bool
1677 	help
1678 	  Arch has userfaultfd minor fault support
1679 
1680 config MEMBARRIER
1681 	bool "Enable membarrier() system call" if EXPERT
1682 	default y
1683 	help
1684 	  Enable the membarrier() system call that allows issuing memory
1685 	  barriers across all running threads, which can be used to distribute
1686 	  the cost of user-space memory barriers asymmetrically by transforming
1687 	  pairs of memory barriers into pairs consisting of membarrier() and a
1688 	  compiler barrier.
1689 
1690 	  If unsure, say Y.
1691 
1692 config KALLSYMS
1693 	bool "Load all symbols for debugging/ksymoops" if EXPERT
1694 	default y
1695 	help
1696 	  Say Y here to let the kernel print out symbolic crash information and
1697 	  symbolic stack backtraces. This increases the size of the kernel
1698 	  somewhat, as all symbols have to be loaded into the kernel image.
1699 
1700 config KALLSYMS_ALL
1701 	bool "Include all symbols in kallsyms"
1702 	depends on DEBUG_KERNEL && KALLSYMS
1703 	help
1704 	  Normally kallsyms only contains the symbols of functions for nicer
1705 	  OOPS messages and backtraces (i.e., symbols from the text and inittext
1706 	  sections). This is sufficient for most cases. And only in very rare
1707 	  cases (e.g., when a debugger is used) all symbols are required (e.g.,
1708 	  names of variables from the data sections, etc).
1709 
1710 	  This option makes sure that all symbols are loaded into the kernel
1711 	  image (i.e., symbols from all sections) in cost of increased kernel
1712 	  size (depending on the kernel configuration, it may be 300KiB or
1713 	  something like this).
1714 
1715 	  Say N unless you really need all symbols.
1716 
1717 config KALLSYMS_ABSOLUTE_PERCPU
1718 	bool
1719 	depends on KALLSYMS
1720 	default X86_64 && SMP
1721 
1722 config KALLSYMS_BASE_RELATIVE
1723 	bool
1724 	depends on KALLSYMS
1725 	default !IA64
1726 	help
1727 	  Instead of emitting them as absolute values in the native word size,
1728 	  emit the symbol references in the kallsyms table as 32-bit entries,
1729 	  each containing a relative value in the range [base, base + U32_MAX]
1730 	  or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1731 	  an absolute value in the range [0, S32_MAX] or a relative value in the
1732 	  range [base, base + S32_MAX], where base is the lowest relative symbol
1733 	  address encountered in the image.
1734 
1735 	  On 64-bit builds, this reduces the size of the address table by 50%,
1736 	  but more importantly, it results in entries whose values are build
1737 	  time constants, and no relocation pass is required at runtime to fix
1738 	  up the entries based on the runtime load address of the kernel.
1739 
1740 # end of the "standard kernel features (expert users)" menu
1741 
1742 # syscall, maps, verifier
1743 
1744 config USERFAULTFD
1745 	bool "Enable userfaultfd() system call"
1746 	depends on MMU
1747 	help
1748 	  Enable the userfaultfd() system call that allows to intercept and
1749 	  handle page faults in userland.
1750 
1751 config ARCH_HAS_MEMBARRIER_CALLBACKS
1752 	bool
1753 
1754 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1755 	bool
1756 
1757 config KCMP
1758 	bool "Enable kcmp() system call" if EXPERT
1759 	help
1760 	  Enable the kernel resource comparison system call. It provides
1761 	  user-space with the ability to compare two processes to see if they
1762 	  share a common resource, such as a file descriptor or even virtual
1763 	  memory space.
1764 
1765 	  If unsure, say N.
1766 
1767 config RSEQ
1768 	bool "Enable rseq() system call" if EXPERT
1769 	default y
1770 	depends on HAVE_RSEQ
1771 	select MEMBARRIER
1772 	help
1773 	  Enable the restartable sequences system call. It provides a
1774 	  user-space cache for the current CPU number value, which
1775 	  speeds up getting the current CPU number from user-space,
1776 	  as well as an ABI to speed up user-space operations on
1777 	  per-CPU data.
1778 
1779 	  If unsure, say Y.
1780 
1781 config DEBUG_RSEQ
1782 	default n
1783 	bool "Enabled debugging of rseq() system call" if EXPERT
1784 	depends on RSEQ && DEBUG_KERNEL
1785 	help
1786 	  Enable extra debugging checks for the rseq system call.
1787 
1788 	  If unsure, say N.
1789 
1790 config EMBEDDED
1791 	bool "Embedded system"
1792 	select EXPERT
1793 	help
1794 	  This option should be enabled if compiling the kernel for
1795 	  an embedded system so certain expert options are available
1796 	  for configuration.
1797 
1798 config HAVE_PERF_EVENTS
1799 	bool
1800 	help
1801 	  See tools/perf/design.txt for details.
1802 
1803 config GUEST_PERF_EVENTS
1804 	bool
1805 	depends on HAVE_PERF_EVENTS
1806 
1807 config PERF_USE_VMALLOC
1808 	bool
1809 	help
1810 	  See tools/perf/design.txt for details
1811 
1812 config 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 
1819 menu "Kernel Performance Events And Counters"
1820 
1821 config 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 
1850 config 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 
1863 endmenu
1864 
1865 config 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 
1874 config 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 
1884 config 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 
1896 choice
1897 	prompt "Choose SLAB allocator"
1898 	default SLUB
1899 	help
1900 	   This option allows to select a slab allocator.
1901 
1902 config 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 
1911 config 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 
1922 config 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 
1931 endchoice
1932 
1933 config SLAB_MERGE_DEFAULT
1934 	bool "Allow slab caches to be merged"
1935 	default y
1936 	depends on SLAB || SLUB
1937 	help
1938 	  For reduced kernel memory fragmentation, slab caches can be
1939 	  merged when they share the same size and other characteristics.
1940 	  This carries a risk of kernel heap overflows being able to
1941 	  overwrite objects from merged caches (and more easily control
1942 	  cache layout), which makes such heap attacks easier to exploit
1943 	  by attackers. By keeping caches unmerged, these kinds of exploits
1944 	  can usually only damage objects in the same cache. To disable
1945 	  merging at runtime, "slab_nomerge" can be passed on the kernel
1946 	  command line.
1947 
1948 config SLAB_FREELIST_RANDOM
1949 	bool "Randomize slab freelist"
1950 	depends on SLAB || SLUB
1951 	help
1952 	  Randomizes the freelist order used on creating new pages. This
1953 	  security feature reduces the predictability of the kernel slab
1954 	  allocator against heap overflows.
1955 
1956 config SLAB_FREELIST_HARDENED
1957 	bool "Harden slab freelist metadata"
1958 	depends on SLAB || SLUB
1959 	help
1960 	  Many kernel heap attacks try to target slab cache metadata and
1961 	  other infrastructure. This options makes minor performance
1962 	  sacrifices to harden the kernel slab allocator against common
1963 	  freelist exploit methods. Some slab implementations have more
1964 	  sanity-checking than others. This option is most effective with
1965 	  CONFIG_SLUB.
1966 
1967 config SHUFFLE_PAGE_ALLOCATOR
1968 	bool "Page allocator randomization"
1969 	default SLAB_FREELIST_RANDOM && ACPI_NUMA
1970 	help
1971 	  Randomization of the page allocator improves the average
1972 	  utilization of a direct-mapped memory-side-cache. See section
1973 	  5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1974 	  6.2a specification for an example of how a platform advertises
1975 	  the presence of a memory-side-cache. There are also incidental
1976 	  security benefits as it reduces the predictability of page
1977 	  allocations to compliment SLAB_FREELIST_RANDOM, but the
1978 	  default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1979 	  10th order of pages is selected based on cache utilization
1980 	  benefits on x86.
1981 
1982 	  While the randomization improves cache utilization it may
1983 	  negatively impact workloads on platforms without a cache. For
1984 	  this reason, by default, the randomization is enabled only
1985 	  after runtime detection of a direct-mapped memory-side-cache.
1986 	  Otherwise, the randomization may be force enabled with the
1987 	  'page_alloc.shuffle' kernel command line parameter.
1988 
1989 	  Say Y if unsure.
1990 
1991 config SLUB_CPU_PARTIAL
1992 	default y
1993 	depends on SLUB && SMP
1994 	bool "SLUB per cpu partial cache"
1995 	help
1996 	  Per cpu partial caches accelerate objects allocation and freeing
1997 	  that is local to a processor at the price of more indeterminism
1998 	  in the latency of the free. On overflow these caches will be cleared
1999 	  which requires the taking of locks that may cause latency spikes.
2000 	  Typically one would choose no for a realtime system.
2001 
2002 config MMAP_ALLOW_UNINITIALIZED
2003 	bool "Allow mmapped anonymous memory to be uninitialized"
2004 	depends on EXPERT && !MMU
2005 	default n
2006 	help
2007 	  Normally, and according to the Linux spec, anonymous memory obtained
2008 	  from mmap() has its contents cleared before it is passed to
2009 	  userspace.  Enabling this config option allows you to request that
2010 	  mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
2011 	  providing a huge performance boost.  If this option is not enabled,
2012 	  then the flag will be ignored.
2013 
2014 	  This is taken advantage of by uClibc's malloc(), and also by
2015 	  ELF-FDPIC binfmt's brk and stack allocator.
2016 
2017 	  Because of the obvious security issues, this option should only be
2018 	  enabled on embedded devices where you control what is run in
2019 	  userspace.  Since that isn't generally a problem on no-MMU systems,
2020 	  it is normally safe to say Y here.
2021 
2022 	  See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
2023 
2024 config SYSTEM_DATA_VERIFICATION
2025 	def_bool n
2026 	select SYSTEM_TRUSTED_KEYRING
2027 	select KEYS
2028 	select CRYPTO
2029 	select CRYPTO_RSA
2030 	select ASYMMETRIC_KEY_TYPE
2031 	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
2032 	select ASN1
2033 	select OID_REGISTRY
2034 	select X509_CERTIFICATE_PARSER
2035 	select PKCS7_MESSAGE_PARSER
2036 	help
2037 	  Provide PKCS#7 message verification using the contents of the system
2038 	  trusted keyring to provide public keys.  This then can be used for
2039 	  module verification, kexec image verification and firmware blob
2040 	  verification.
2041 
2042 config PROFILING
2043 	bool "Profiling support"
2044 	help
2045 	  Say Y here to enable the extended profiling support mechanisms used
2046 	  by profilers.
2047 
2048 #
2049 # Place an empty function call at each tracepoint site. Can be
2050 # dynamically changed for a probe function.
2051 #
2052 config TRACEPOINTS
2053 	bool
2054 
2055 endmenu		# General setup
2056 
2057 source "arch/Kconfig"
2058 
2059 config RT_MUTEXES
2060 	bool
2061 	default y if PREEMPT_RT
2062 
2063 config BASE_SMALL
2064 	int
2065 	default 0 if BASE_FULL
2066 	default 1 if !BASE_FULL
2067 
2068 config MODULE_SIG_FORMAT
2069 	def_bool n
2070 	select SYSTEM_DATA_VERIFICATION
2071 
2072 menuconfig MODULES
2073 	bool "Enable loadable module support"
2074 	modules
2075 	help
2076 	  Kernel modules are small pieces of compiled code which can
2077 	  be inserted in the running kernel, rather than being
2078 	  permanently built into the kernel.  You use the "modprobe"
2079 	  tool to add (and sometimes remove) them.  If you say Y here,
2080 	  many parts of the kernel can be built as modules (by
2081 	  answering M instead of Y where indicated): this is most
2082 	  useful for infrequently used options which are not required
2083 	  for booting.  For more information, see the man pages for
2084 	  modprobe, lsmod, modinfo, insmod and rmmod.
2085 
2086 	  If you say Y here, you will need to run "make
2087 	  modules_install" to put the modules under /lib/modules/
2088 	  where modprobe can find them (you may need to be root to do
2089 	  this).
2090 
2091 	  If unsure, say Y.
2092 
2093 if MODULES
2094 
2095 config MODULE_FORCE_LOAD
2096 	bool "Forced module loading"
2097 	default n
2098 	help
2099 	  Allow loading of modules without version information (ie. modprobe
2100 	  --force).  Forced module loading sets the 'F' (forced) taint flag and
2101 	  is usually a really bad idea.
2102 
2103 config MODULE_UNLOAD
2104 	bool "Module unloading"
2105 	help
2106 	  Without this option you will not be able to unload any
2107 	  modules (note that some modules may not be unloadable
2108 	  anyway), which makes your kernel smaller, faster
2109 	  and simpler.  If unsure, say Y.
2110 
2111 config MODULE_FORCE_UNLOAD
2112 	bool "Forced module unloading"
2113 	depends on MODULE_UNLOAD
2114 	help
2115 	  This option allows you to force a module to unload, even if the
2116 	  kernel believes it is unsafe: the kernel will remove the module
2117 	  without waiting for anyone to stop using it (using the -f option to
2118 	  rmmod).  This is mainly for kernel developers and desperate users.
2119 	  If unsure, say N.
2120 
2121 config MODVERSIONS
2122 	bool "Module versioning support"
2123 	help
2124 	  Usually, you have to use modules compiled with your kernel.
2125 	  Saying Y here makes it sometimes possible to use modules
2126 	  compiled for different kernels, by adding enough information
2127 	  to the modules to (hopefully) spot any changes which would
2128 	  make them incompatible with the kernel you are running.  If
2129 	  unsure, say N.
2130 
2131 config ASM_MODVERSIONS
2132 	bool
2133 	default HAVE_ASM_MODVERSIONS && MODVERSIONS
2134 	help
2135 	  This enables module versioning for exported symbols also from
2136 	  assembly. This can be enabled only when the target architecture
2137 	  supports it.
2138 
2139 config MODULE_REL_CRCS
2140 	bool
2141 	depends on MODVERSIONS
2142 
2143 config MODULE_SRCVERSION_ALL
2144 	bool "Source checksum for all modules"
2145 	help
2146 	  Modules which contain a MODULE_VERSION get an extra "srcversion"
2147 	  field inserted into their modinfo section, which contains a
2148     	  sum of the source files which made it.  This helps maintainers
2149 	  see exactly which source was used to build a module (since
2150 	  others sometimes change the module source without updating
2151 	  the version).  With this option, such a "srcversion" field
2152 	  will be created for all modules.  If unsure, say N.
2153 
2154 config MODULE_SIG
2155 	bool "Module signature verification"
2156 	select MODULE_SIG_FORMAT
2157 	help
2158 	  Check modules for valid signatures upon load: the signature
2159 	  is simply appended to the module. For more information see
2160 	  <file:Documentation/admin-guide/module-signing.rst>.
2161 
2162 	  Note that this option adds the OpenSSL development packages as a
2163 	  kernel build dependency so that the signing tool can use its crypto
2164 	  library.
2165 
2166 	  You should enable this option if you wish to use either
2167 	  CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2168 	  another LSM - otherwise unsigned modules will be loadable regardless
2169 	  of the lockdown policy.
2170 
2171 	  !!!WARNING!!!  If you enable this option, you MUST make sure that the
2172 	  module DOES NOT get stripped after being signed.  This includes the
2173 	  debuginfo strip done by some packagers (such as rpmbuild) and
2174 	  inclusion into an initramfs that wants the module size reduced.
2175 
2176 config MODULE_SIG_FORCE
2177 	bool "Require modules to be validly signed"
2178 	depends on MODULE_SIG
2179 	help
2180 	  Reject unsigned modules or signed modules for which we don't have a
2181 	  key.  Without this, such modules will simply taint the kernel.
2182 
2183 config MODULE_SIG_ALL
2184 	bool "Automatically sign all modules"
2185 	default y
2186 	depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2187 	help
2188 	  Sign all modules during make modules_install. Without this option,
2189 	  modules must be signed manually, using the scripts/sign-file tool.
2190 
2191 comment "Do not forget to sign required modules with scripts/sign-file"
2192 	depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2193 
2194 choice
2195 	prompt "Which hash algorithm should modules be signed with?"
2196 	depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2197 	help
2198 	  This determines which sort of hashing algorithm will be used during
2199 	  signature generation.  This algorithm _must_ be built into the kernel
2200 	  directly so that signature verification can take place.  It is not
2201 	  possible to load a signed module containing the algorithm to check
2202 	  the signature on that module.
2203 
2204 config MODULE_SIG_SHA1
2205 	bool "Sign modules with SHA-1"
2206 	select CRYPTO_SHA1
2207 
2208 config MODULE_SIG_SHA224
2209 	bool "Sign modules with SHA-224"
2210 	select CRYPTO_SHA256
2211 
2212 config MODULE_SIG_SHA256
2213 	bool "Sign modules with SHA-256"
2214 	select CRYPTO_SHA256
2215 
2216 config MODULE_SIG_SHA384
2217 	bool "Sign modules with SHA-384"
2218 	select CRYPTO_SHA512
2219 
2220 config MODULE_SIG_SHA512
2221 	bool "Sign modules with SHA-512"
2222 	select CRYPTO_SHA512
2223 
2224 endchoice
2225 
2226 config MODULE_SIG_HASH
2227 	string
2228 	depends on MODULE_SIG || IMA_APPRAISE_MODSIG
2229 	default "sha1" if MODULE_SIG_SHA1
2230 	default "sha224" if MODULE_SIG_SHA224
2231 	default "sha256" if MODULE_SIG_SHA256
2232 	default "sha384" if MODULE_SIG_SHA384
2233 	default "sha512" if MODULE_SIG_SHA512
2234 
2235 choice
2236 	prompt "Module compression mode"
2237 	help
2238 	  This option allows you to choose the algorithm which will be used to
2239 	  compress modules when 'make modules_install' is run. (or, you can
2240 	  choose to not compress modules at all.)
2241 
2242 	  External modules will also be compressed in the same way during the
2243 	  installation.
2244 
2245 	  For modules inside an initrd or initramfs, it's more efficient to
2246 	  compress the whole initrd or initramfs instead.
2247 
2248 	  This is fully compatible with signed modules.
2249 
2250 	  Please note that the tool used to load modules needs to support the
2251 	  corresponding algorithm. module-init-tools MAY support gzip, and kmod
2252 	  MAY support gzip, xz and zstd.
2253 
2254 	  Your build system needs to provide the appropriate compression tool
2255 	  to compress the modules.
2256 
2257 	  If in doubt, select 'None'.
2258 
2259 config MODULE_COMPRESS_NONE
2260 	bool "None"
2261 	help
2262 	  Do not compress modules. The installed modules are suffixed
2263 	  with .ko.
2264 
2265 config MODULE_COMPRESS_GZIP
2266 	bool "GZIP"
2267 	help
2268 	  Compress modules with GZIP. The installed modules are suffixed
2269 	  with .ko.gz.
2270 
2271 config MODULE_COMPRESS_XZ
2272 	bool "XZ"
2273 	help
2274 	  Compress modules with XZ. The installed modules are suffixed
2275 	  with .ko.xz.
2276 
2277 config MODULE_COMPRESS_ZSTD
2278 	bool "ZSTD"
2279 	help
2280 	  Compress modules with ZSTD. The installed modules are suffixed
2281 	  with .ko.zst.
2282 
2283 endchoice
2284 
2285 config MODULE_DECOMPRESS
2286 	bool "Support in-kernel module decompression"
2287 	depends on MODULE_COMPRESS_GZIP || MODULE_COMPRESS_XZ
2288 	select ZLIB_INFLATE if MODULE_COMPRESS_GZIP
2289 	select XZ_DEC if MODULE_COMPRESS_XZ
2290 	help
2291 
2292 	  Support for decompressing kernel modules by the kernel itself
2293 	  instead of relying on userspace to perform this task. Useful when
2294 	  load pinning security policy is enabled.
2295 
2296 	  If unsure, say N.
2297 
2298 config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2299 	bool "Allow loading of modules with missing namespace imports"
2300 	help
2301 	  Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2302 	  a namespace. A module that makes use of a symbol exported with such a
2303 	  namespace is required to import the namespace via MODULE_IMPORT_NS().
2304 	  There is no technical reason to enforce correct namespace imports,
2305 	  but it creates consistency between symbols defining namespaces and
2306 	  users importing namespaces they make use of. This option relaxes this
2307 	  requirement and lifts the enforcement when loading a module.
2308 
2309 	  If unsure, say N.
2310 
2311 config MODPROBE_PATH
2312 	string "Path to modprobe binary"
2313 	default "/sbin/modprobe"
2314 	help
2315 	  When kernel code requests a module, it does so by calling
2316 	  the "modprobe" userspace utility. This option allows you to
2317 	  set the path where that binary is found. This can be changed
2318 	  at runtime via the sysctl file
2319 	  /proc/sys/kernel/modprobe. Setting this to the empty string
2320 	  removes the kernel's ability to request modules (but
2321 	  userspace can still load modules explicitly).
2322 
2323 config TRIM_UNUSED_KSYMS
2324 	bool "Trim unused exported kernel symbols" if EXPERT
2325 	depends on !COMPILE_TEST
2326 	help
2327 	  The kernel and some modules make many symbols available for
2328 	  other modules to use via EXPORT_SYMBOL() and variants. Depending
2329 	  on the set of modules being selected in your kernel configuration,
2330 	  many of those exported symbols might never be used.
2331 
2332 	  This option allows for unused exported symbols to be dropped from
2333 	  the build. In turn, this provides the compiler more opportunities
2334 	  (especially when using LTO) for optimizing the code and reducing
2335 	  binary size.  This might have some security advantages as well.
2336 
2337 	  If unsure, or if you need to build out-of-tree modules, say N.
2338 
2339 config UNUSED_KSYMS_WHITELIST
2340 	string "Whitelist of symbols to keep in ksymtab"
2341 	depends on TRIM_UNUSED_KSYMS
2342 	help
2343 	  By default, all unused exported symbols will be un-exported from the
2344 	  build when TRIM_UNUSED_KSYMS is selected.
2345 
2346 	  UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
2347 	  exported at all times, even in absence of in-tree users. The value to
2348 	  set here is the path to a text file containing the list of symbols,
2349 	  one per line. The path can be absolute, or relative to the kernel
2350 	  source tree.
2351 
2352 endif # MODULES
2353 
2354 config MODULES_TREE_LOOKUP
2355 	def_bool y
2356 	depends on PERF_EVENTS || TRACING || CFI_CLANG
2357 
2358 config INIT_ALL_POSSIBLE
2359 	bool
2360 	help
2361 	  Back when each arch used to define their own cpu_online_mask and
2362 	  cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2363 	  with all 1s, and others with all 0s.  When they were centralised,
2364 	  it was better to provide this option than to break all the archs
2365 	  and have several arch maintainers pursuing me down dark alleys.
2366 
2367 source "block/Kconfig"
2368 
2369 config PREEMPT_NOTIFIERS
2370 	bool
2371 
2372 config PADATA
2373 	depends on SMP
2374 	bool
2375 
2376 config ASN1
2377 	tristate
2378 	help
2379 	  Build a simple ASN.1 grammar compiler that produces a bytecode output
2380 	  that can be interpreted by the ASN.1 stream decoder and used to
2381 	  inform it as to what tags are to be expected in a stream and what
2382 	  functions to call on what tags.
2383 
2384 source "kernel/Kconfig.locks"
2385 
2386 config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2387 	bool
2388 
2389 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2390 	bool
2391 
2392 # It may be useful for an architecture to override the definitions of the
2393 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2394 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2395 # different calling convention for syscalls. They can also override the
2396 # macros for not-implemented syscalls in kernel/sys_ni.c and
2397 # kernel/time/posix-stubs.c. All these overrides need to be available in
2398 # <asm/syscall_wrapper.h>.
2399 config ARCH_HAS_SYSCALL_WRAPPER
2400 	def_bool n
2401