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1config DEFCONFIG_LIST
2 string
b2670eac 3 depends on !UML
face4374 4 option defconfig_list
47f38ae0 5 default "/lib/modules/$(shell,uname -r)/.config"
face4374 6 default "/etc/kernel-config"
47f38ae0 7 default "/boot/config-$(shell,uname -r)"
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8 default ARCH_DEFCONFIG
9 default "arch/$(ARCH)/defconfig"
face4374 10
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11config CC_IS_GCC
12 def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc)
13
14config GCC_VERSION
15 int
16 default $(shell,$(srctree)/scripts/gcc-version.sh -p $(CC) | sed 's/^0*//') if CC_IS_GCC
17 default 0
18
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19config CC_IS_CLANG
20 def_bool $(success,$(CC) --version | head -n 1 | grep -q clang)
21
22config CLANG_VERSION
23 int
24 default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
25
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26config CC_HAS_ASM_GOTO
27 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
28
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29config CONSTRUCTORS
30 bool
31 depends on !UML
b99b87f7 32
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33config IRQ_WORK
34 bool
e360adbe 35
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36config BUILDTIME_EXTABLE_SORT
37 bool
38
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39config THREAD_INFO_IN_TASK
40 bool
41 help
42 Select this to move thread_info off the stack into task_struct. To
43 make this work, an arch will need to remove all thread_info fields
44 except flags and fix any runtime bugs.
45
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46 One subtle change that will be needed is to use try_get_task_stack()
47 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
48
ff0cfc66 49menu "General setup"
1da177e4 50
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51config BROKEN
52 bool
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53
54config BROKEN_ON_SMP
55 bool
56 depends on BROKEN || !SMP
57 default y
58
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59config INIT_ENV_ARG_LIMIT
60 int
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61 default 32 if !UML
62 default 128 if UML
1da177e4 63 help
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64 Maximum of each of the number of arguments and environment
65 variables passed to init from the kernel command line.
1da177e4 66
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67config COMPILE_TEST
68 bool "Compile also drivers which will not load"
bc083a64 69 depends on !UML
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70 default n
71 help
72 Some drivers can be compiled on a different platform than they are
73 intended to be run on. Despite they cannot be loaded there (or even
74 when they load they cannot be used due to missing HW support),
75 developers still, opposing to distributors, might want to build such
76 drivers to compile-test them.
77
78 If you are a developer and want to build everything available, say Y
79 here. If you are a user/distributor, say N here to exclude useless
80 drivers to be distributed.
81
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82config LOCALVERSION
83 string "Local version - append to kernel release"
84 help
85 Append an extra string to the end of your kernel version.
86 This will show up when you type uname, for example.
87 The string you set here will be appended after the contents of
88 any files with a filename matching localversion* in your
89 object and source tree, in that order. Your total string can
90 be a maximum of 64 characters.
91
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92config LOCALVERSION_AUTO
93 bool "Automatically append version information to the version string"
94 default y
ac3339ba 95 depends on !COMPILE_TEST
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96 help
97 This will try to automatically determine if the current tree is a
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98 release tree by looking for git tags that belong to the current
99 top of tree revision.
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100
101 A string of the format -gxxxxxxxx will be added to the localversion
6e5a5420 102 if a git-based tree is found. The string generated by this will be
aaebf433 103 appended after any matching localversion* files, and after the value
6e5a5420 104 set in CONFIG_LOCALVERSION.
aaebf433 105
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106 (The actual string used here is the first eight characters produced
107 by running the command:
108
109 $ git rev-parse --verify HEAD
110
111 which is done within the script "scripts/setlocalversion".)
aaebf433 112
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113config BUILD_SALT
114 string "Build ID Salt"
115 default ""
116 help
117 The build ID is used to link binaries and their debug info. Setting
118 this option will use the value in the calculation of the build id.
119 This is mostly useful for distributions which want to ensure the
120 build is unique between builds. It's safe to leave the default.
121
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122config HAVE_KERNEL_GZIP
123 bool
124
125config HAVE_KERNEL_BZIP2
126 bool
127
128config HAVE_KERNEL_LZMA
129 bool
130
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131config HAVE_KERNEL_XZ
132 bool
133
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134config HAVE_KERNEL_LZO
135 bool
136
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137config HAVE_KERNEL_LZ4
138 bool
139
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140config HAVE_KERNEL_UNCOMPRESSED
141 bool
142
30d65dbf 143choice
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144 prompt "Kernel compression mode"
145 default KERNEL_GZIP
f16466af 146 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED
2e9f3bdd 147 help
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148 The linux kernel is a kind of self-extracting executable.
149 Several compression algorithms are available, which differ
150 in efficiency, compression and decompression speed.
151 Compression speed is only relevant when building a kernel.
152 Decompression speed is relevant at each boot.
153
154 If you have any problems with bzip2 or lzma compressed
155 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
156 version of this functionality (bzip2 only), for 2.4, was
157 supplied by Christian Ludwig)
158
159 High compression options are mostly useful for users, who
160 are low on disk space (embedded systems), but for whom ram
161 size matters less.
162
163 If in doubt, select 'gzip'
164
165config KERNEL_GZIP
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166 bool "Gzip"
167 depends on HAVE_KERNEL_GZIP
168 help
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169 The old and tried gzip compression. It provides a good balance
170 between compression ratio and decompression speed.
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171
172config KERNEL_BZIP2
173 bool "Bzip2"
2e9f3bdd 174 depends on HAVE_KERNEL_BZIP2
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175 help
176 Its compression ratio and speed is intermediate.
0a4dd35c 177 Decompression speed is slowest among the choices. The kernel
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178 size is about 10% smaller with bzip2, in comparison to gzip.
179 Bzip2 uses a large amount of memory. For modern kernels you
180 will need at least 8MB RAM or more for booting.
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181
182config KERNEL_LZMA
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183 bool "LZMA"
184 depends on HAVE_KERNEL_LZMA
185 help
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186 This compression algorithm's ratio is best. Decompression speed
187 is between gzip and bzip2. Compression is slowest.
188 The kernel size is about 33% smaller with LZMA in comparison to gzip.
30d65dbf 189
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190config KERNEL_XZ
191 bool "XZ"
192 depends on HAVE_KERNEL_XZ
193 help
194 XZ uses the LZMA2 algorithm and instruction set specific
195 BCJ filters which can improve compression ratio of executable
196 code. The size of the kernel is about 30% smaller with XZ in
197 comparison to gzip. On architectures for which there is a BCJ
198 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
199 will create a few percent smaller kernel than plain LZMA.
200
201 The speed is about the same as with LZMA: The decompression
202 speed of XZ is better than that of bzip2 but worse than gzip
203 and LZO. Compression is slow.
204
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205config KERNEL_LZO
206 bool "LZO"
207 depends on HAVE_KERNEL_LZO
208 help
0a4dd35c 209 Its compression ratio is the poorest among the choices. The kernel
681b3049 210 size is about 10% bigger than gzip; however its speed
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211 (both compression and decompression) is the fastest.
212
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213config KERNEL_LZ4
214 bool "LZ4"
215 depends on HAVE_KERNEL_LZ4
216 help
217 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
218 A preliminary version of LZ4 de/compression tool is available at
219 <https://code.google.com/p/lz4/>.
220
221 Its compression ratio is worse than LZO. The size of the kernel
222 is about 8% bigger than LZO. But the decompression speed is
223 faster than LZO.
224
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225config KERNEL_UNCOMPRESSED
226 bool "None"
227 depends on HAVE_KERNEL_UNCOMPRESSED
228 help
229 Produce uncompressed kernel image. This option is usually not what
230 you want. It is useful for debugging the kernel in slow simulation
231 environments, where decompressing and moving the kernel is awfully
232 slow. This option allows early boot code to skip the decompressor
233 and jump right at uncompressed kernel image.
234
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235endchoice
236
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237config DEFAULT_HOSTNAME
238 string "Default hostname"
239 default "(none)"
240 help
241 This option determines the default system hostname before userspace
242 calls sethostname(2). The kernel traditionally uses "(none)" here,
243 but you may wish to use a different default here to make a minimal
244 system more usable with less configuration.
245
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246#
247# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
248# add proper SWAP support to them, in which case this can be remove.
249#
250config ARCH_NO_SWAP
251 bool
252
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253config SWAP
254 bool "Support for paging of anonymous memory (swap)"
17c46a6a 255 depends on MMU && BLOCK && !ARCH_NO_SWAP
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256 default y
257 help
258 This option allows you to choose whether you want to have support
92c3504e 259 for so called swap devices or swap files in your kernel that are
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260 used to provide more virtual memory than the actual RAM present
261 in your computer. If unsure say Y.
262
263config SYSVIPC
264 bool "System V IPC"
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265 ---help---
266 Inter Process Communication is a suite of library functions and
267 system calls which let processes (running programs) synchronize and
268 exchange information. It is generally considered to be a good thing,
269 and some programs won't run unless you say Y here. In particular, if
270 you want to run the DOS emulator dosemu under Linux (read the
271 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
272 you'll need to say Y here.
273
274 You can find documentation about IPC with "info ipc" and also in
275 section 6.4 of the Linux Programmer's Guide, available from
276 <http://www.tldp.org/guides.html>.
277
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278config SYSVIPC_SYSCTL
279 bool
280 depends on SYSVIPC
281 depends on SYSCTL
282 default y
283
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284config POSIX_MQUEUE
285 bool "POSIX Message Queues"
19c92399 286 depends on NET
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287 ---help---
288 POSIX variant of message queues is a part of IPC. In POSIX message
289 queues every message has a priority which decides about succession
290 of receiving it by a process. If you want to compile and run
291 programs written e.g. for Solaris with use of its POSIX message
b0e37650 292 queues (functions mq_*) say Y here.
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293
294 POSIX message queues are visible as a filesystem called 'mqueue'
295 and can be mounted somewhere if you want to do filesystem
296 operations on message queues.
297
298 If unsure, say Y.
299
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300config POSIX_MQUEUE_SYSCTL
301 bool
302 depends on POSIX_MQUEUE
303 depends on SYSCTL
304 default y
305
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306config CROSS_MEMORY_ATTACH
307 bool "Enable process_vm_readv/writev syscalls"
308 depends on MMU
309 default y
310 help
311 Enabling this option adds the system calls process_vm_readv and
312 process_vm_writev which allow a process with the correct privileges
a2a368d9 313 to directly read from or write to another process' address space.
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314 See the man page for more details.
315
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316config USELIB
317 bool "uselib syscall"
b2113a41 318 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
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319 help
320 This option enables the uselib syscall, a system call used in the
321 dynamic linker from libc5 and earlier. glibc does not use this
322 system call. If you intend to run programs built on libc5 or
323 earlier, you may need to enable this syscall. Current systems
324 running glibc can safely disable this.
325
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326config AUDIT
327 bool "Auditing support"
328 depends on NET
329 help
330 Enable auditing infrastructure that can be used with another
331 kernel subsystem, such as SELinux (which requires this for
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332 logging of avc messages output). System call auditing is included
333 on architectures which support it.
391dc69c 334
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335config HAVE_ARCH_AUDITSYSCALL
336 bool
337
391dc69c 338config AUDITSYSCALL
cb74ed27 339 def_bool y
7a017721 340 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
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341
342config AUDIT_WATCH
343 def_bool y
344 depends on AUDITSYSCALL
345 select FSNOTIFY
346
347config AUDIT_TREE
348 def_bool y
349 depends on AUDITSYSCALL
350 select FSNOTIFY
351
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352source "kernel/irq/Kconfig"
353source "kernel/time/Kconfig"
87a4c375 354source "kernel/Kconfig.preempt"
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355
356menu "CPU/Task time and stats accounting"
357
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358config VIRT_CPU_ACCOUNTING
359 bool
360
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361choice
362 prompt "Cputime accounting"
363 default TICK_CPU_ACCOUNTING if !PPC64
02fc8d37 364 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
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365
366# Kind of a stub config for the pure tick based cputime accounting
367config TICK_CPU_ACCOUNTING
368 bool "Simple tick based cputime accounting"
c58b0df1 369 depends on !S390 && !NO_HZ_FULL
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370 help
371 This is the basic tick based cputime accounting that maintains
372 statistics about user, system and idle time spent on per jiffies
373 granularity.
374
375 If unsure, say Y.
376
abf917cd 377config VIRT_CPU_ACCOUNTING_NATIVE
b952741c 378 bool "Deterministic task and CPU time accounting"
c58b0df1 379 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
abf917cd 380 select VIRT_CPU_ACCOUNTING
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381 help
382 Select this option to enable more accurate task and CPU time
383 accounting. This is done by reading a CPU counter on each
384 kernel entry and exit and on transitions within the kernel
385 between system, softirq and hardirq state, so there is a
386 small performance impact. In the case of s390 or IBM POWER > 5,
387 this also enables accounting of stolen time on logically-partitioned
388 systems.
389
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390config VIRT_CPU_ACCOUNTING_GEN
391 bool "Full dynticks CPU time accounting"
ff3fb254 392 depends on HAVE_CONTEXT_TRACKING
554b0004 393 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
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394 select VIRT_CPU_ACCOUNTING
395 select CONTEXT_TRACKING
396 help
397 Select this option to enable task and CPU time accounting on full
398 dynticks systems. This accounting is implemented by watching every
399 kernel-user boundaries using the context tracking subsystem.
400 The accounting is thus performed at the expense of some significant
401 overhead.
402
403 For now this is only useful if you are working on the full
404 dynticks subsystem development.
405
406 If unsure, say N.
407
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408endchoice
409
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410config IRQ_TIME_ACCOUNTING
411 bool "Fine granularity task level IRQ time accounting"
b58c3584 412 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
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413 help
414 Select this option to enable fine granularity task irq time
415 accounting. This is done by reading a timestamp on each
416 transitions between softirq and hardirq state, so there can be a
417 small performance impact.
418
419 If in doubt, say N here.
420
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421config HAVE_SCHED_AVG_IRQ
422 def_bool y
423 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
424 depends on SMP
425
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426config BSD_PROCESS_ACCT
427 bool "BSD Process Accounting"
2813893f 428 depends on MULTIUSER
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429 help
430 If you say Y here, a user level program will be able to instruct the
431 kernel (via a special system call) to write process accounting
432 information to a file: whenever a process exits, information about
433 that process will be appended to the file by the kernel. The
434 information includes things such as creation time, owning user,
435 command name, memory usage, controlling terminal etc. (the complete
436 list is in the struct acct in <file:include/linux/acct.h>). It is
437 up to the user level program to do useful things with this
438 information. This is generally a good idea, so say Y.
439
440config BSD_PROCESS_ACCT_V3
441 bool "BSD Process Accounting version 3 file format"
442 depends on BSD_PROCESS_ACCT
443 default n
444 help
445 If you say Y here, the process accounting information is written
446 in a new file format that also logs the process IDs of each
3903bf94 447 process and its parent. Note that this file format is incompatible
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448 with previous v0/v1/v2 file formats, so you will need updated tools
449 for processing it. A preliminary version of these tools is available
37a4c940 450 at <http://www.gnu.org/software/acct/>.
1da177e4 451
c757249a 452config TASKSTATS
19c92399 453 bool "Export task/process statistics through netlink"
c757249a 454 depends on NET
2813893f 455 depends on MULTIUSER
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456 default n
457 help
458 Export selected statistics for tasks/processes through the
459 generic netlink interface. Unlike BSD process accounting, the
460 statistics are available during the lifetime of tasks/processes as
461 responses to commands. Like BSD accounting, they are sent to user
462 space on task exit.
463
464 Say N if unsure.
465
ca74e92b 466config TASK_DELAY_ACCT
19c92399 467 bool "Enable per-task delay accounting"
6f44993f 468 depends on TASKSTATS
f6db8347 469 select SCHED_INFO
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470 help
471 Collect information on time spent by a task waiting for system
472 resources like cpu, synchronous block I/O completion and swapping
473 in pages. Such statistics can help in setting a task's priorities
474 relative to other tasks for cpu, io, rss limits etc.
475
476 Say N if unsure.
477
18f705f4 478config TASK_XACCT
19c92399 479 bool "Enable extended accounting over taskstats"
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480 depends on TASKSTATS
481 help
482 Collect extended task accounting data and send the data
483 to userland for processing over the taskstats interface.
484
485 Say N if unsure.
486
487config TASK_IO_ACCOUNTING
19c92399 488 bool "Enable per-task storage I/O accounting"
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489 depends on TASK_XACCT
490 help
491 Collect information on the number of bytes of storage I/O which this
492 task has caused.
493
494 Say N if unsure.
495
391dc69c 496endmenu # "CPU/Task time and stats accounting"
d9817ebe 497
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498config CPU_ISOLATION
499 bool "CPU isolation"
414a2dc1 500 depends on SMP || COMPILE_TEST
2c43838c 501 default y
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502 help
503 Make sure that CPUs running critical tasks are not disturbed by
504 any source of "noise" such as unbound workqueues, timers, kthreads...
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505 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
506 the "isolcpus=" boot parameter.
507
508 Say Y if unsure.
5c4991e2 509
0af92d46 510source "kernel/rcu/Kconfig"
c903ff83 511
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512config BUILD_BIN2C
513 bool
514 default n
515
1da177e4 516config IKCONFIG
f2443ab6 517 tristate "Kernel .config support"
de5b56ba 518 select BUILD_BIN2C
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519 ---help---
520 This option enables the complete Linux kernel ".config" file
521 contents to be saved in the kernel. It provides documentation
522 of which kernel options are used in a running kernel or in an
523 on-disk kernel. This information can be extracted from the kernel
524 image file with the script scripts/extract-ikconfig and used as
525 input to rebuild the current kernel or to build another kernel.
526 It can also be extracted from a running kernel by reading
527 /proc/config.gz if enabled (below).
528
529config IKCONFIG_PROC
530 bool "Enable access to .config through /proc/config.gz"
531 depends on IKCONFIG && PROC_FS
532 ---help---
533 This option enables access to the kernel configuration file
534 through /proc/config.gz.
535
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536config LOG_BUF_SHIFT
537 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
fb39f98d 538 range 12 25
f17a32e9 539 default 17
361e9dfb 540 depends on PRINTK
794543a2 541 help
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542 Select the minimal kernel log buffer size as a power of 2.
543 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
544 parameter, see below. Any higher size also might be forced
545 by "log_buf_len" boot parameter.
546
f17a32e9 547 Examples:
23b2899f 548 17 => 128 KB
f17a32e9 549 16 => 64 KB
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550 15 => 32 KB
551 14 => 16 KB
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552 13 => 8 KB
553 12 => 4 KB
554
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555config LOG_CPU_MAX_BUF_SHIFT
556 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
2240a31d 557 depends on SMP
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558 range 0 21
559 default 12 if !BASE_SMALL
560 default 0 if BASE_SMALL
361e9dfb 561 depends on PRINTK
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562 help
563 This option allows to increase the default ring buffer size
564 according to the number of CPUs. The value defines the contribution
565 of each CPU as a power of 2. The used space is typically only few
566 lines however it might be much more when problems are reported,
567 e.g. backtraces.
568
569 The increased size means that a new buffer has to be allocated and
570 the original static one is unused. It makes sense only on systems
571 with more CPUs. Therefore this value is used only when the sum of
572 contributions is greater than the half of the default kernel ring
573 buffer as defined by LOG_BUF_SHIFT. The default values are set
574 so that more than 64 CPUs are needed to trigger the allocation.
575
576 Also this option is ignored when "log_buf_len" kernel parameter is
577 used as it forces an exact (power of two) size of the ring buffer.
578
579 The number of possible CPUs is used for this computation ignoring
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580 hotplugging making the computation optimal for the worst case
581 scenario while allowing a simple algorithm to be used from bootup.
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582
583 Examples shift values and their meaning:
584 17 => 128 KB for each CPU
585 16 => 64 KB for each CPU
586 15 => 32 KB for each CPU
587 14 => 16 KB for each CPU
588 13 => 8 KB for each CPU
589 12 => 4 KB for each CPU
590
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591config PRINTK_SAFE_LOG_BUF_SHIFT
592 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
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593 range 10 21
594 default 13
f92bac3b 595 depends on PRINTK
427934b8 596 help
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597 Select the size of an alternate printk per-CPU buffer where messages
598 printed from usafe contexts are temporary stored. One example would
599 be NMI messages, another one - printk recursion. The messages are
600 copied to the main log buffer in a safe context to avoid a deadlock.
601 The value defines the size as a power of 2.
427934b8 602
f92bac3b 603 Those messages are rare and limited. The largest one is when
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604 a backtrace is printed. It usually fits into 4KB. Select
605 8KB if you want to be on the safe side.
606
607 Examples:
608 17 => 128 KB for each CPU
609 16 => 64 KB for each CPU
610 15 => 32 KB for each CPU
611 14 => 16 KB for each CPU
612 13 => 8 KB for each CPU
613 12 => 4 KB for each CPU
614
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615#
616# Architectures with an unreliable sched_clock() should select this:
617#
618config HAVE_UNSTABLE_SCHED_CLOCK
619 bool
620
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621config GENERIC_SCHED_CLOCK
622 bool
623
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624#
625# For architectures that want to enable the support for NUMA-affine scheduler
626# balancing logic:
627#
628config ARCH_SUPPORTS_NUMA_BALANCING
629 bool
630
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631#
632# For architectures that prefer to flush all TLBs after a number of pages
633# are unmapped instead of sending one IPI per page to flush. The architecture
634# must provide guarantees on what happens if a clean TLB cache entry is
635# written after the unmap. Details are in mm/rmap.c near the check for
636# should_defer_flush. The architecture should also consider if the full flush
637# and the refill costs are offset by the savings of sending fewer IPIs.
638config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
639 bool
640
be5e610c
PZ
641#
642# For architectures that know their GCC __int128 support is sound
643#
644config ARCH_SUPPORTS_INT128
645 bool
646
be3a7284
AA
647# For architectures that (ab)use NUMA to represent different memory regions
648# all cpu-local but of different latencies, such as SuperH.
649#
650config ARCH_WANT_NUMA_VARIABLE_LOCALITY
651 bool
652
be3a7284
AA
653config NUMA_BALANCING
654 bool "Memory placement aware NUMA scheduler"
be3a7284
AA
655 depends on ARCH_SUPPORTS_NUMA_BALANCING
656 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
657 depends on SMP && NUMA && MIGRATION
658 help
659 This option adds support for automatic NUMA aware memory/task placement.
660 The mechanism is quite primitive and is based on migrating memory when
6d56a410 661 it has references to the node the task is running on.
be3a7284
AA
662
663 This system will be inactive on UMA systems.
664
6f7c97e8
AK
665config NUMA_BALANCING_DEFAULT_ENABLED
666 bool "Automatically enable NUMA aware memory/task placement"
667 default y
668 depends on NUMA_BALANCING
669 help
670 If set, automatic NUMA balancing will be enabled if running on a NUMA
671 machine.
672
23964d2d 673menuconfig CGROUPS
6341e62b 674 bool "Control Group support"
2bd59d48 675 select KERNFS
5cdc38f9 676 help
23964d2d 677 This option adds support for grouping sets of processes together, for
5cdc38f9
KH
678 use with process control subsystems such as Cpusets, CFS, memory
679 controls or device isolation.
680 See
5cdc38f9 681 - Documentation/scheduler/sched-design-CFS.txt (CFS)
9991a9c8 682 - Documentation/cgroup-v1/ (features for grouping, isolation
45ce80fb 683 and resource control)
5cdc38f9
KH
684
685 Say N if unsure.
686
23964d2d
LZ
687if CGROUPS
688
3e32cb2e
JW
689config PAGE_COUNTER
690 bool
691
c255a458 692config MEMCG
a0166ec4 693 bool "Memory controller"
3e32cb2e 694 select PAGE_COUNTER
79bd9814 695 select EVENTFD
00f0b825 696 help
a0166ec4 697 Provides control over the memory footprint of tasks in a cgroup.
00f0b825 698
c255a458 699config MEMCG_SWAP
a0166ec4 700 bool "Swap controller"
c255a458 701 depends on MEMCG && SWAP
c077719b 702 help
a0166ec4
JW
703 Provides control over the swap space consumed by tasks in a cgroup.
704
c255a458 705config MEMCG_SWAP_ENABLED
a0166ec4 706 bool "Swap controller enabled by default"
c255a458 707 depends on MEMCG_SWAP
a42c390c
MH
708 default y
709 help
710 Memory Resource Controller Swap Extension comes with its price in
711 a bigger memory consumption. General purpose distribution kernels
43d547f9 712 which want to enable the feature but keep it disabled by default
07555ac1 713 and let the user enable it by swapaccount=1 boot command line
a42c390c
MH
714 parameter should have this option unselected.
715 For those who want to have the feature enabled by default should
716 select this option (if, for some reason, they need to disable it
00a66d29 717 then swapaccount=0 does the trick).
c077719b 718
84c07d11
KT
719config MEMCG_KMEM
720 bool
721 depends on MEMCG && !SLOB
722 default y
723
6bf024e6
JW
724config BLK_CGROUP
725 bool "IO controller"
726 depends on BLOCK
2bc64a20 727 default n
6bf024e6
JW
728 ---help---
729 Generic block IO controller cgroup interface. This is the common
730 cgroup interface which should be used by various IO controlling
731 policies.
2bc64a20 732
6bf024e6
JW
733 Currently, CFQ IO scheduler uses it to recognize task groups and
734 control disk bandwidth allocation (proportional time slice allocation)
735 to such task groups. It is also used by bio throttling logic in
736 block layer to implement upper limit in IO rates on a device.
e5d1367f 737
6bf024e6
JW
738 This option only enables generic Block IO controller infrastructure.
739 One needs to also enable actual IO controlling logic/policy. For
740 enabling proportional weight division of disk bandwidth in CFQ, set
741 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
742 CONFIG_BLK_DEV_THROTTLING=y.
743
9991a9c8 744 See Documentation/cgroup-v1/blkio-controller.txt for more information.
6bf024e6
JW
745
746config DEBUG_BLK_CGROUP
747 bool "IO controller debugging"
748 depends on BLK_CGROUP
749 default n
750 ---help---
751 Enable some debugging help. Currently it exports additional stat
752 files in a cgroup which can be useful for debugging.
753
754config CGROUP_WRITEBACK
755 bool
756 depends on MEMCG && BLK_CGROUP
757 default y
e5d1367f 758
7c941438 759menuconfig CGROUP_SCHED
a0166ec4 760 bool "CPU controller"
7c941438
DG
761 default n
762 help
763 This feature lets CPU scheduler recognize task groups and control CPU
764 bandwidth allocation to such task groups. It uses cgroups to group
765 tasks.
766
767if CGROUP_SCHED
768config FAIR_GROUP_SCHED
769 bool "Group scheduling for SCHED_OTHER"
770 depends on CGROUP_SCHED
771 default CGROUP_SCHED
772
ab84d31e
PT
773config CFS_BANDWIDTH
774 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
ab84d31e
PT
775 depends on FAIR_GROUP_SCHED
776 default n
777 help
778 This option allows users to define CPU bandwidth rates (limits) for
779 tasks running within the fair group scheduler. Groups with no limit
780 set are considered to be unconstrained and will run with no
781 restriction.
cd33d880 782 See Documentation/scheduler/sched-bwc.txt for more information.
ab84d31e 783
7c941438
DG
784config RT_GROUP_SCHED
785 bool "Group scheduling for SCHED_RR/FIFO"
7c941438
DG
786 depends on CGROUP_SCHED
787 default n
788 help
789 This feature lets you explicitly allocate real CPU bandwidth
32bd7eb5 790 to task groups. If enabled, it will also make it impossible to
7c941438
DG
791 schedule realtime tasks for non-root users until you allocate
792 realtime bandwidth for them.
793 See Documentation/scheduler/sched-rt-group.txt for more information.
794
795endif #CGROUP_SCHED
796
6bf024e6
JW
797config CGROUP_PIDS
798 bool "PIDs controller"
799 help
800 Provides enforcement of process number limits in the scope of a
801 cgroup. Any attempt to fork more processes than is allowed in the
802 cgroup will fail. PIDs are fundamentally a global resource because it
803 is fairly trivial to reach PID exhaustion before you reach even a
804 conservative kmemcg limit. As a result, it is possible to grind a
805 system to halt without being limited by other cgroup policies. The
6cc578df 806 PIDs controller is designed to stop this from happening.
6bf024e6
JW
807
808 It should be noted that organisational operations (such as attaching
6cc578df 809 to a cgroup hierarchy will *not* be blocked by the PIDs controller),
6bf024e6
JW
810 since the PIDs limit only affects a process's ability to fork, not to
811 attach to a cgroup.
812
39d3e758
PP
813config CGROUP_RDMA
814 bool "RDMA controller"
815 help
816 Provides enforcement of RDMA resources defined by IB stack.
817 It is fairly easy for consumers to exhaust RDMA resources, which
818 can result into resource unavailability to other consumers.
819 RDMA controller is designed to stop this from happening.
820 Attaching processes with active RDMA resources to the cgroup
821 hierarchy is allowed even if can cross the hierarchy's limit.
822
6bf024e6
JW
823config CGROUP_FREEZER
824 bool "Freezer controller"
825 help
826 Provides a way to freeze and unfreeze all tasks in a
827 cgroup.
828
489c2a20
JW
829 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
830 controller includes important in-kernel memory consumers per default.
831
832 If you're using cgroup2, say N.
833
6bf024e6
JW
834config CGROUP_HUGETLB
835 bool "HugeTLB controller"
836 depends on HUGETLB_PAGE
837 select PAGE_COUNTER
afc24d49 838 default n
6bf024e6
JW
839 help
840 Provides a cgroup controller for HugeTLB pages.
841 When you enable this, you can put a per cgroup limit on HugeTLB usage.
842 The limit is enforced during page fault. Since HugeTLB doesn't
843 support page reclaim, enforcing the limit at page fault time implies
844 that, the application will get SIGBUS signal if it tries to access
845 HugeTLB pages beyond its limit. This requires the application to know
846 beforehand how much HugeTLB pages it would require for its use. The
847 control group is tracked in the third page lru pointer. This means
848 that we cannot use the controller with huge page less than 3 pages.
afc24d49 849
6bf024e6
JW
850config CPUSETS
851 bool "Cpuset controller"
e1d4eeec 852 depends on SMP
6bf024e6
JW
853 help
854 This option will let you create and manage CPUSETs which
855 allow dynamically partitioning a system into sets of CPUs and
856 Memory Nodes and assigning tasks to run only within those sets.
857 This is primarily useful on large SMP or NUMA systems.
afc24d49 858
6bf024e6 859 Say N if unsure.
afc24d49 860
6bf024e6
JW
861config PROC_PID_CPUSET
862 bool "Include legacy /proc/<pid>/cpuset file"
863 depends on CPUSETS
864 default y
afc24d49 865
6bf024e6
JW
866config CGROUP_DEVICE
867 bool "Device controller"
868 help
869 Provides a cgroup controller implementing whitelists for
870 devices which a process in the cgroup can mknod or open.
871
872config CGROUP_CPUACCT
873 bool "Simple CPU accounting controller"
874 help
875 Provides a simple controller for monitoring the
876 total CPU consumed by the tasks in a cgroup.
877
878config CGROUP_PERF
879 bool "Perf controller"
880 depends on PERF_EVENTS
881 help
882 This option extends the perf per-cpu mode to restrict monitoring
883 to threads which belong to the cgroup specified and run on the
884 designated cpu.
885
886 Say N if unsure.
887
30070984
DM
888config CGROUP_BPF
889 bool "Support for eBPF programs attached to cgroups"
483c4933
AL
890 depends on BPF_SYSCALL
891 select SOCK_CGROUP_DATA
30070984
DM
892 help
893 Allow attaching eBPF programs to a cgroup using the bpf(2)
894 syscall command BPF_PROG_ATTACH.
895
896 In which context these programs are accessed depends on the type
897 of attachment. For instance, programs that are attached using
898 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
899 inet sockets.
900
6bf024e6 901config CGROUP_DEBUG
23b0be48 902 bool "Debug controller"
afc24d49 903 default n
23b0be48 904 depends on DEBUG_KERNEL
6bf024e6
JW
905 help
906 This option enables a simple controller that exports
23b0be48
WL
907 debugging information about the cgroups framework. This
908 controller is for control cgroup debugging only. Its
909 interfaces are not stable.
afc24d49 910
6bf024e6 911 Say N.
89e9b9e0 912
73b35147
AB
913config SOCK_CGROUP_DATA
914 bool
915 default n
916
23964d2d 917endif # CGROUPS
c077719b 918
8dd2a82c 919menuconfig NAMESPACES
6a108a14 920 bool "Namespaces support" if EXPERT
2813893f 921 depends on MULTIUSER
6a108a14 922 default !EXPERT
c5289a69
PE
923 help
924 Provides the way to make tasks work with different objects using
925 the same id. For example same IPC id may refer to different objects
926 or same user id or pid may refer to different tasks when used in
927 different namespaces.
928
8dd2a82c
DL
929if NAMESPACES
930
58bfdd6d
PE
931config UTS_NS
932 bool "UTS namespace"
17a6d441 933 default y
58bfdd6d
PE
934 help
935 In this namespace tasks see different info provided with the
936 uname() system call
937
ae5e1b22
PE
938config IPC_NS
939 bool "IPC namespace"
8dd2a82c 940 depends on (SYSVIPC || POSIX_MQUEUE)
17a6d441 941 default y
ae5e1b22
PE
942 help
943 In this namespace tasks work with IPC ids which correspond to
614b84cf 944 different IPC objects in different namespaces.
ae5e1b22 945
aee16ce7 946config USER_NS
19c92399 947 bool "User namespace"
5673a94c 948 default n
aee16ce7
PE
949 help
950 This allows containers, i.e. vservers, to use user namespaces
951 to provide different user info for different servers.
e11f0ae3
EB
952
953 When user namespaces are enabled in the kernel it is
d886f4e4
JW
954 recommended that the MEMCG option also be enabled and that
955 user-space use the memory control groups to limit the amount
956 of memory a memory unprivileged users can use.
e11f0ae3 957
aee16ce7
PE
958 If unsure, say N.
959
74bd59bb 960config PID_NS
9bd38c2c 961 bool "PID Namespaces"
17a6d441 962 default y
74bd59bb 963 help
12d2b8f9 964 Support process id namespaces. This allows having multiple
692105b8 965 processes with the same pid as long as they are in different
74bd59bb
PE
966 pid namespaces. This is a building block of containers.
967
d6eb633f
MH
968config NET_NS
969 bool "Network namespace"
8dd2a82c 970 depends on NET
17a6d441 971 default y
d6eb633f
MH
972 help
973 Allow user space to create what appear to be multiple instances
974 of the network stack.
975
8dd2a82c
DL
976endif # NAMESPACES
977
5cb366bb
AR
978config CHECKPOINT_RESTORE
979 bool "Checkpoint/restore support"
980 select PROC_CHILDREN
981 default n
982 help
983 Enables additional kernel features in a sake of checkpoint/restore.
984 In particular it adds auxiliary prctl codes to setup process text,
985 data and heap segment sizes, and a few additional /proc filesystem
986 entries.
987
988 If unsure, say N here.
989
5091faa4
MG
990config SCHED_AUTOGROUP
991 bool "Automatic process group scheduling"
5091faa4
MG
992 select CGROUPS
993 select CGROUP_SCHED
994 select FAIR_GROUP_SCHED
995 help
996 This option optimizes the scheduler for common desktop workloads by
997 automatically creating and populating task groups. This separation
998 of workloads isolates aggressive CPU burners (like build jobs) from
999 desktop applications. Task group autogeneration is currently based
1000 upon task session.
1001
7af37bec 1002config SYSFS_DEPRECATED
5d6a4ea5 1003 bool "Enable deprecated sysfs features to support old userspace tools"
7af37bec
DL
1004 depends on SYSFS
1005 default n
1006 help
1007 This option adds code that switches the layout of the "block" class
1008 devices, to not show up in /sys/class/block/, but only in
1009 /sys/block/.
1010
1011 This switch is only active when the sysfs.deprecated=1 boot option is
1012 passed or the SYSFS_DEPRECATED_V2 option is set.
1013
1014 This option allows new kernels to run on old distributions and tools,
1015 which might get confused by /sys/class/block/. Since 2007/2008 all
1016 major distributions and tools handle this just fine.
1017
1018 Recent distributions and userspace tools after 2009/2010 depend on
1019 the existence of /sys/class/block/, and will not work with this
1020 option enabled.
1021
1022 Only if you are using a new kernel on an old distribution, you might
1023 need to say Y here.
1024
1025config SYSFS_DEPRECATED_V2
5d6a4ea5 1026 bool "Enable deprecated sysfs features by default"
7af37bec
DL
1027 default n
1028 depends on SYSFS
1029 depends on SYSFS_DEPRECATED
1030 help
1031 Enable deprecated sysfs by default.
1032
1033 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1034 option.
1035
1036 Only if you are using a new kernel on an old distribution, you might
1037 need to say Y here. Even then, odds are you would not need it
1038 enabled, you can always pass the boot option if absolutely necessary.
1039
1040config RELAY
1041 bool "Kernel->user space relay support (formerly relayfs)"
26b5679e 1042 select IRQ_WORK
7af37bec
DL
1043 help
1044 This option enables support for relay interface support in
1045 certain file systems (such as debugfs).
1046 It is designed to provide an efficient mechanism for tools and
1047 facilities to relay large amounts of data from kernel space to
1048 user space.
1049
1050 If unsure, say N.
1051
f991633d
DG
1052config BLK_DEV_INITRD
1053 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
f991633d
DG
1054 help
1055 The initial RAM filesystem is a ramfs which is loaded by the
1056 boot loader (loadlin or lilo) and that is mounted as root
1057 before the normal boot procedure. It is typically used to
1058 load modules needed to mount the "real" root file system,
8c27ceff 1059 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
f991633d
DG
1060
1061 If RAM disk support (BLK_DEV_RAM) is also included, this
1062 also enables initial RAM disk (initrd) support and adds
1063 15 Kbytes (more on some other architectures) to the kernel size.
1064
1065 If unsure say Y.
1066
c33df4ea
JPS
1067if BLK_DEV_INITRD
1068
dbec4866
SR
1069source "usr/Kconfig"
1070
c33df4ea
JPS
1071endif
1072
877417e6
AB
1073choice
1074 prompt "Compiler optimization level"
2cc3ce24 1075 default CC_OPTIMIZE_FOR_PERFORMANCE
877417e6
AB
1076
1077config CC_OPTIMIZE_FOR_PERFORMANCE
1078 bool "Optimize for performance"
1079 help
1080 This is the default optimization level for the kernel, building
1081 with the "-O2" compiler flag for best performance and most
1082 helpful compile-time warnings.
1083
c45b4f1f 1084config CC_OPTIMIZE_FOR_SIZE
96fffeb4 1085 bool "Optimize for size"
c45b4f1f 1086 help
31a4af7f
MY
1087 Enabling this option will pass "-Os" instead of "-O2" to
1088 your compiler resulting in a smaller kernel.
c45b4f1f 1089
3a55fb0d 1090 If unsure, say N.
c45b4f1f 1091
877417e6
AB
1092endchoice
1093
5d20ee31
NP
1094config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1095 bool
1096 help
1097 This requires that the arch annotates or otherwise protects
1098 its external entry points from being discarded. Linker scripts
1099 must also merge .text.*, .data.*, and .bss.* correctly into
1100 output sections. Care must be taken not to pull in unrelated
1101 sections (e.g., '.text.init'). Typically '.' in section names
1102 is used to distinguish them from label names / C identifiers.
1103
1104config LD_DEAD_CODE_DATA_ELIMINATION
1105 bool "Dead code and data elimination (EXPERIMENTAL)"
1106 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1107 depends on EXPERT
0098f2e7 1108 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800)
e85d1d65
MY
1109 depends on $(cc-option,-ffunction-sections -fdata-sections)
1110 depends on $(ld-option,--gc-sections)
5d20ee31 1111 help
8b9d2712
MY
1112 Enable this if you want to do dead code and data elimination with
1113 the linker by compiling with -ffunction-sections -fdata-sections,
1114 and linking with --gc-sections.
5d20ee31
NP
1115
1116 This can reduce on disk and in-memory size of the kernel
1117 code and static data, particularly for small configs and
1118 on small systems. This has the possibility of introducing
1119 silently broken kernel if the required annotations are not
1120 present. This option is not well tested yet, so use at your
1121 own risk.
1122
0847062a
RD
1123config SYSCTL
1124 bool
1125
b943c460
RD
1126config ANON_INODES
1127 bool
1128
657a5209
MF
1129config HAVE_UID16
1130 bool
1131
1132config SYSCTL_EXCEPTION_TRACE
1133 bool
1134 help
1135 Enable support for /proc/sys/debug/exception-trace.
1136
1137config SYSCTL_ARCH_UNALIGN_NO_WARN
1138 bool
1139 help
1140 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1141 Allows arch to define/use @no_unaligned_warning to possibly warn
1142 about unaligned access emulation going on under the hood.
1143
1144config SYSCTL_ARCH_UNALIGN_ALLOW
1145 bool
1146 help
1147 Enable support for /proc/sys/kernel/unaligned-trap
1148 Allows arches to define/use @unaligned_enabled to runtime toggle
1149 the unaligned access emulation.
1150 see arch/parisc/kernel/unaligned.c for reference
1151
657a5209
MF
1152config HAVE_PCSPKR_PLATFORM
1153 bool
1154
f89b7755
AS
1155# interpreter that classic socket filters depend on
1156config BPF
1157 bool
1158
6a108a14
DR
1159menuconfig EXPERT
1160 bool "Configure standard kernel features (expert users)"
f505c553
JT
1161 # Unhide debug options, to make the on-by-default options visible
1162 select DEBUG_KERNEL
1da177e4
LT
1163 help
1164 This option allows certain base kernel options and settings
1165 to be disabled or tweaked. This is for specialized
1166 environments which can tolerate a "non-standard" kernel.
1167 Only use this if you really know what you are doing.
1168
ae81f9e3 1169config UID16
6a108a14 1170 bool "Enable 16-bit UID system calls" if EXPERT
2813893f 1171 depends on HAVE_UID16 && MULTIUSER
ae81f9e3
CE
1172 default y
1173 help
1174 This enables the legacy 16-bit UID syscall wrappers.
1175
2813893f
IM
1176config MULTIUSER
1177 bool "Multiple users, groups and capabilities support" if EXPERT
1178 default y
1179 help
1180 This option enables support for non-root users, groups and
1181 capabilities.
1182
1183 If you say N here, all processes will run with UID 0, GID 0, and all
1184 possible capabilities. Saying N here also compiles out support for
1185 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1186 setgid, and capset.
1187
1188 If unsure, say Y here.
1189
f6187769
FF
1190config SGETMASK_SYSCALL
1191 bool "sgetmask/ssetmask syscalls support" if EXPERT
a687a533 1192 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
f6187769
FF
1193 ---help---
1194 sys_sgetmask and sys_ssetmask are obsolete system calls
1195 no longer supported in libc but still enabled by default in some
1196 architectures.
1197
1198 If unsure, leave the default option here.
1199
6af9f7bf
FF
1200config SYSFS_SYSCALL
1201 bool "Sysfs syscall support" if EXPERT
1202 default y
1203 ---help---
1204 sys_sysfs is an obsolete system call no longer supported in libc.
1205 Note that disabling this option is more secure but might break
1206 compatibility with some systems.
1207
1208 If unsure say Y here.
1209
b89a8171 1210config SYSCTL_SYSCALL
6a108a14 1211 bool "Sysctl syscall support" if EXPERT
26a7034b 1212 depends on PROC_SYSCTL
c736de60 1213 default n
b89a8171 1214 select SYSCTL
ae81f9e3 1215 ---help---
13bb7e37
EB
1216 sys_sysctl uses binary paths that have been found challenging
1217 to properly maintain and use. The interface in /proc/sys
1218 using paths with ascii names is now the primary path to this
1219 information.
b89a8171 1220
13bb7e37
EB
1221 Almost nothing using the binary sysctl interface so if you are
1222 trying to save some space it is probably safe to disable this,
1223 making your kernel marginally smaller.
b89a8171 1224
c736de60 1225 If unsure say N here.
ae81f9e3 1226
d1b069f5
RD
1227config FHANDLE
1228 bool "open by fhandle syscalls" if EXPERT
1229 select EXPORTFS
1230 default y
1231 help
1232 If you say Y here, a user level program will be able to map
1233 file names to handle and then later use the handle for
1234 different file system operations. This is useful in implementing
1235 userspace file servers, which now track files using handles instead
1236 of names. The handle would remain the same even if file names
1237 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1238 syscalls.
1239
baa73d9e
NP
1240config POSIX_TIMERS
1241 bool "Posix Clocks & timers" if EXPERT
1242 default y
1243 help
1244 This includes native support for POSIX timers to the kernel.
1245 Some embedded systems have no use for them and therefore they
1246 can be configured out to reduce the size of the kernel image.
1247
1248 When this option is disabled, the following syscalls won't be
1249 available: timer_create, timer_gettime: timer_getoverrun,
1250 timer_settime, timer_delete, clock_adjtime, getitimer,
1251 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1252 clock_getres and clock_nanosleep syscalls will be limited to
1253 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1254
1255 If unsure say y.
1256
d59745ce
MM
1257config PRINTK
1258 default y
6a108a14 1259 bool "Enable support for printk" if EXPERT
74876a98 1260 select IRQ_WORK
d59745ce
MM
1261 help
1262 This option enables normal printk support. Removing it
1263 eliminates most of the message strings from the kernel image
1264 and makes the kernel more or less silent. As this makes it
1265 very difficult to diagnose system problems, saying N here is
1266 strongly discouraged.
1267
42a0bb3f
PM
1268config PRINTK_NMI
1269 def_bool y
1270 depends on PRINTK
1271 depends on HAVE_NMI
1272
c8538a7a 1273config BUG
6a108a14 1274 bool "BUG() support" if EXPERT
c8538a7a
MM
1275 default y
1276 help
1277 Disabling this option eliminates support for BUG and WARN, reducing
1278 the size of your kernel image and potentially quietly ignoring
1279 numerous fatal conditions. You should only consider disabling this
1280 option for embedded systems with no facilities for reporting errors.
1281 Just say Y.
1282
708e9a79 1283config ELF_CORE
046d662f 1284 depends on COREDUMP
708e9a79 1285 default y
6a108a14 1286 bool "Enable ELF core dumps" if EXPERT
708e9a79
MM
1287 help
1288 Enable support for generating core dumps. Disabling saves about 4k.
1289
8761f1ab 1290
e5e1d3cb 1291config PCSPKR_PLATFORM
6a108a14 1292 bool "Enable PC-Speaker support" if EXPERT
8761f1ab 1293 depends on HAVE_PCSPKR_PLATFORM
15f304b6 1294 select I8253_LOCK
e5e1d3cb
SS
1295 default y
1296 help
1297 This option allows to disable the internal PC-Speaker
1298 support, saving some memory.
1299
1da177e4
LT
1300config BASE_FULL
1301 default y
6a108a14 1302 bool "Enable full-sized data structures for core" if EXPERT
1da177e4
LT
1303 help
1304 Disabling this option reduces the size of miscellaneous core
1305 kernel data structures. This saves memory on small machines,
1306 but may reduce performance.
1307
1308config FUTEX
6a108a14 1309 bool "Enable futex support" if EXPERT
1da177e4 1310 default y
bc2eecd7 1311 imply RT_MUTEXES
1da177e4
LT
1312 help
1313 Disabling this option will cause the kernel to be built without
1314 support for "fast userspace mutexes". The resulting kernel may not
1315 run glibc-based applications correctly.
1316
bc2eecd7
NP
1317config FUTEX_PI
1318 bool
1319 depends on FUTEX && RT_MUTEXES
1320 default y
1321
03b8c7b6
HC
1322config HAVE_FUTEX_CMPXCHG
1323 bool
62b4d204 1324 depends on FUTEX
03b8c7b6
HC
1325 help
1326 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1327 is implemented and always working. This removes a couple of runtime
1328 checks.
1329
1da177e4 1330config EPOLL
6a108a14 1331 bool "Enable eventpoll support" if EXPERT
1da177e4 1332 default y
448e3cee 1333 select ANON_INODES
1da177e4
LT
1334 help
1335 Disabling this option will cause the kernel to be built without
1336 support for epoll family of system calls.
1337
fba2afaa 1338config SIGNALFD
6a108a14 1339 bool "Enable signalfd() system call" if EXPERT
448e3cee 1340 select ANON_INODES
fba2afaa
DL
1341 default y
1342 help
1343 Enable the signalfd() system call that allows to receive signals
1344 on a file descriptor.
1345
1346 If unsure, say Y.
1347
b215e283 1348config TIMERFD
6a108a14 1349 bool "Enable timerfd() system call" if EXPERT
448e3cee 1350 select ANON_INODES
b215e283
DL
1351 default y
1352 help
1353 Enable the timerfd() system call that allows to receive timer
1354 events on a file descriptor.
1355
1356 If unsure, say Y.
1357
e1ad7468 1358config EVENTFD
6a108a14 1359 bool "Enable eventfd() system call" if EXPERT
448e3cee 1360 select ANON_INODES
e1ad7468
DL
1361 default y
1362 help
1363 Enable the eventfd() system call that allows to receive both
1364 kernel notification (ie. KAIO) or userspace notifications.
1365
1366 If unsure, say Y.
1367
1da177e4 1368config SHMEM
6a108a14 1369 bool "Use full shmem filesystem" if EXPERT
1da177e4
LT
1370 default y
1371 depends on MMU
1372 help
1373 The shmem is an internal filesystem used to manage shared memory.
1374 It is backed by swap and manages resource limits. It is also exported
1375 to userspace as tmpfs if TMPFS is enabled. Disabling this
1376 option replaces shmem and tmpfs with the much simpler ramfs code,
1377 which may be appropriate on small systems without swap.
1378
ebf3f09c 1379config AIO
6a108a14 1380 bool "Enable AIO support" if EXPERT
ebf3f09c
TP
1381 default y
1382 help
1383 This option enables POSIX asynchronous I/O which may by used
657a5209
MF
1384 by some high performance threaded applications. Disabling
1385 this option saves about 7k.
1386
d3ac21ca
JT
1387config ADVISE_SYSCALLS
1388 bool "Enable madvise/fadvise syscalls" if EXPERT
1389 default y
1390 help
1391 This option enables the madvise and fadvise syscalls, used by
1392 applications to advise the kernel about their future memory or file
1393 usage, improving performance. If building an embedded system where no
1394 applications use these syscalls, you can disable this option to save
1395 space.
1396
5b25b13a
MD
1397config MEMBARRIER
1398 bool "Enable membarrier() system call" if EXPERT
1399 default y
1400 help
1401 Enable the membarrier() system call that allows issuing memory
1402 barriers across all running threads, which can be used to distribute
1403 the cost of user-space memory barriers asymmetrically by transforming
1404 pairs of memory barriers into pairs consisting of membarrier() and a
1405 compiler barrier.
1406
1407 If unsure, say Y.
1408
d1b069f5
RD
1409config KALLSYMS
1410 bool "Load all symbols for debugging/ksymoops" if EXPERT
1411 default y
1412 help
1413 Say Y here to let the kernel print out symbolic crash information and
1414 symbolic stack backtraces. This increases the size of the kernel
1415 somewhat, as all symbols have to be loaded into the kernel image.
1416
1417config KALLSYMS_ALL
1418 bool "Include all symbols in kallsyms"
1419 depends on DEBUG_KERNEL && KALLSYMS
1420 help
1421 Normally kallsyms only contains the symbols of functions for nicer
1422 OOPS messages and backtraces (i.e., symbols from the text and inittext
1423 sections). This is sufficient for most cases. And only in very rare
1424 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1425 names of variables from the data sections, etc).
1426
1427 This option makes sure that all symbols are loaded into the kernel
1428 image (i.e., symbols from all sections) in cost of increased kernel
1429 size (depending on the kernel configuration, it may be 300KiB or
1430 something like this).
1431
1432 Say N unless you really need all symbols.
1433
1434config KALLSYMS_ABSOLUTE_PERCPU
1435 bool
1436 depends on KALLSYMS
1437 default X86_64 && SMP
1438
1439config KALLSYMS_BASE_RELATIVE
1440 bool
1441 depends on KALLSYMS
a687a533 1442 default !IA64
d1b069f5
RD
1443 help
1444 Instead of emitting them as absolute values in the native word size,
1445 emit the symbol references in the kallsyms table as 32-bit entries,
1446 each containing a relative value in the range [base, base + U32_MAX]
1447 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1448 an absolute value in the range [0, S32_MAX] or a relative value in the
1449 range [base, base + S32_MAX], where base is the lowest relative symbol
1450 address encountered in the image.
1451
1452 On 64-bit builds, this reduces the size of the address table by 50%,
1453 but more importantly, it results in entries whose values are build
1454 time constants, and no relocation pass is required at runtime to fix
1455 up the entries based on the runtime load address of the kernel.
1456
1457# end of the "standard kernel features (expert users)" menu
1458
1459# syscall, maps, verifier
1460config BPF_SYSCALL
1461 bool "Enable bpf() system call"
1462 select ANON_INODES
1463 select BPF
bae77c5e 1464 select IRQ_WORK
d1b069f5
RD
1465 default n
1466 help
1467 Enable the bpf() system call that allows to manipulate eBPF
1468 programs and maps via file descriptors.
1469
290af866
AS
1470config BPF_JIT_ALWAYS_ON
1471 bool "Permanently enable BPF JIT and remove BPF interpreter"
1472 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1473 help
1474 Enables BPF JIT and removes BPF interpreter to avoid
1475 speculative execution of BPF instructions by the interpreter
1476
d1b069f5
RD
1477config USERFAULTFD
1478 bool "Enable userfaultfd() system call"
1479 select ANON_INODES
1480 depends on MMU
1481 help
1482 Enable the userfaultfd() system call that allows to intercept and
1483 handle page faults in userland.
1484
3ccfebed
MD
1485config ARCH_HAS_MEMBARRIER_CALLBACKS
1486 bool
1487
70216e18
MD
1488config ARCH_HAS_MEMBARRIER_SYNC_CORE
1489 bool
1490
d7822b1e
MD
1491config RSEQ
1492 bool "Enable rseq() system call" if EXPERT
1493 default y
1494 depends on HAVE_RSEQ
1495 select MEMBARRIER
1496 help
1497 Enable the restartable sequences system call. It provides a
1498 user-space cache for the current CPU number value, which
1499 speeds up getting the current CPU number from user-space,
1500 as well as an ABI to speed up user-space operations on
1501 per-CPU data.
1502
1503 If unsure, say Y.
1504
1505config DEBUG_RSEQ
1506 default n
1507 bool "Enabled debugging of rseq() system call" if EXPERT
1508 depends on RSEQ && DEBUG_KERNEL
1509 help
1510 Enable extra debugging checks for the rseq system call.
1511
1512 If unsure, say N.
1513
6befe5f6
RD
1514config EMBEDDED
1515 bool "Embedded system"
5d2acfc7 1516 option allnoconfig_y
6befe5f6
RD
1517 select EXPERT
1518 help
1519 This option should be enabled if compiling the kernel for
1520 an embedded system so certain expert options are available
1521 for configuration.
1522
cdd6c482 1523config HAVE_PERF_EVENTS
0793a61d 1524 bool
018df72d
MF
1525 help
1526 See tools/perf/design.txt for details.
0793a61d 1527
906010b2
PZ
1528config PERF_USE_VMALLOC
1529 bool
1530 help
1531 See tools/perf/design.txt for details
1532
ad90a3de 1533config PC104
424529fb 1534 bool "PC/104 support" if EXPERT
ad90a3de
WBG
1535 help
1536 Expose PC/104 form factor device drivers and options available for
1537 selection and configuration. Enable this option if your target
1538 machine has a PC/104 bus.
1539
57c0c15b 1540menu "Kernel Performance Events And Counters"
0793a61d 1541
cdd6c482 1542config PERF_EVENTS
57c0c15b 1543 bool "Kernel performance events and counters"
392d65a9 1544 default y if PROFILING
cdd6c482 1545 depends on HAVE_PERF_EVENTS
4c59e467 1546 select ANON_INODES
e360adbe 1547 select IRQ_WORK
83fe27ea 1548 select SRCU
0793a61d 1549 help
57c0c15b
IM
1550 Enable kernel support for various performance events provided
1551 by software and hardware.
0793a61d 1552
dd77038d 1553 Software events are supported either built-in or via the
57c0c15b 1554 use of generic tracepoints.
0793a61d 1555
57c0c15b
IM
1556 Most modern CPUs support performance events via performance
1557 counter registers. These registers count the number of certain
0793a61d
TG
1558 types of hw events: such as instructions executed, cachemisses
1559 suffered, or branches mis-predicted - without slowing down the
1560 kernel or applications. These registers can also trigger interrupts
1561 when a threshold number of events have passed - and can thus be
1562 used to profile the code that runs on that CPU.
1563
57c0c15b 1564 The Linux Performance Event subsystem provides an abstraction of
dd77038d 1565 these software and hardware event capabilities, available via a
57c0c15b 1566 system call and used by the "perf" utility in tools/perf/. It
0793a61d
TG
1567 provides per task and per CPU counters, and it provides event
1568 capabilities on top of those.
1569
1570 Say Y if unsure.
1571
906010b2
PZ
1572config DEBUG_PERF_USE_VMALLOC
1573 default n
1574 bool "Debug: use vmalloc to back perf mmap() buffers"
cb307113 1575 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
906010b2
PZ
1576 select PERF_USE_VMALLOC
1577 help
1578 Use vmalloc memory to back perf mmap() buffers.
1579
1580 Mostly useful for debugging the vmalloc code on platforms
1581 that don't require it.
1582
1583 Say N if unsure.
1584
0793a61d
TG
1585endmenu
1586
f8891e5e
CL
1587config VM_EVENT_COUNTERS
1588 default y
6a108a14 1589 bool "Enable VM event counters for /proc/vmstat" if EXPERT
f8891e5e 1590 help
2aea4fb6
PJ
1591 VM event counters are needed for event counts to be shown.
1592 This option allows the disabling of the VM event counters
6a108a14 1593 on EXPERT systems. /proc/vmstat will only show page counts
2aea4fb6 1594 if VM event counters are disabled.
f8891e5e 1595
41ecc55b
CL
1596config SLUB_DEBUG
1597 default y
6a108a14 1598 bool "Enable SLUB debugging support" if EXPERT
f6acb635 1599 depends on SLUB && SYSFS
41ecc55b
CL
1600 help
1601 SLUB has extensive debug support features. Disabling these can
1602 result in significant savings in code size. This also disables
1603 SLUB sysfs support. /sys/slab will not exist and there will be
1604 no support for cache validation etc.
1605
1663f26d
TH
1606config SLUB_MEMCG_SYSFS_ON
1607 default n
1608 bool "Enable memcg SLUB sysfs support by default" if EXPERT
1609 depends on SLUB && SYSFS && MEMCG
1610 help
1611 SLUB creates a directory under /sys/kernel/slab for each
1612 allocation cache to host info and debug files. If memory
1613 cgroup is enabled, each cache can have per memory cgroup
1614 caches. SLUB can create the same sysfs directories for these
1615 caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1616 to a very high number of debug files being created. This is
1617 controlled by slub_memcg_sysfs boot parameter and this
1618 config option determines the parameter's default value.
1619
b943c460
RD
1620config COMPAT_BRK
1621 bool "Disable heap randomization"
1622 default y
1623 help
1624 Randomizing heap placement makes heap exploits harder, but it
1625 also breaks ancient binaries (including anything libc5 based).
1626 This option changes the bootup default to heap randomization
692105b8 1627 disabled, and can be overridden at runtime by setting
b943c460
RD
1628 /proc/sys/kernel/randomize_va_space to 2.
1629
1630 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1631
81819f0f
CL
1632choice
1633 prompt "Choose SLAB allocator"
a0acd820 1634 default SLUB
81819f0f
CL
1635 help
1636 This option allows to select a slab allocator.
1637
1638config SLAB
1639 bool "SLAB"
04385fc5 1640 select HAVE_HARDENED_USERCOPY_ALLOCATOR
81819f0f
CL
1641 help
1642 The regular slab allocator that is established and known to work
34013886 1643 well in all environments. It organizes cache hot objects in
02f56210 1644 per cpu and per node queues.
81819f0f
CL
1645
1646config SLUB
81819f0f 1647 bool "SLUB (Unqueued Allocator)"
ed18adc1 1648 select HAVE_HARDENED_USERCOPY_ALLOCATOR
81819f0f
CL
1649 help
1650 SLUB is a slab allocator that minimizes cache line usage
1651 instead of managing queues of cached objects (SLAB approach).
1652 Per cpu caching is realized using slabs of objects instead
1653 of queues of objects. SLUB can use memory efficiently
02f56210
SA
1654 and has enhanced diagnostics. SLUB is the default choice for
1655 a slab allocator.
81819f0f
CL
1656
1657config SLOB
6a108a14 1658 depends on EXPERT
81819f0f
CL
1659 bool "SLOB (Simple Allocator)"
1660 help
37291458
MM
1661 SLOB replaces the stock allocator with a drastically simpler
1662 allocator. SLOB is generally more space efficient but
1663 does not perform as well on large systems.
81819f0f
CL
1664
1665endchoice
1666
7660a6fd
KC
1667config SLAB_MERGE_DEFAULT
1668 bool "Allow slab caches to be merged"
1669 default y
1670 help
1671 For reduced kernel memory fragmentation, slab caches can be
1672 merged when they share the same size and other characteristics.
1673 This carries a risk of kernel heap overflows being able to
1674 overwrite objects from merged caches (and more easily control
1675 cache layout), which makes such heap attacks easier to exploit
1676 by attackers. By keeping caches unmerged, these kinds of exploits
1677 can usually only damage objects in the same cache. To disable
1678 merging at runtime, "slab_nomerge" can be passed on the kernel
1679 command line.
1680
c7ce4f60
TG
1681config SLAB_FREELIST_RANDOM
1682 default n
210e7a43 1683 depends on SLAB || SLUB
c7ce4f60
TG
1684 bool "SLAB freelist randomization"
1685 help
210e7a43 1686 Randomizes the freelist order used on creating new pages. This
c7ce4f60
TG
1687 security feature reduces the predictability of the kernel slab
1688 allocator against heap overflows.
1689
2482ddec
KC
1690config SLAB_FREELIST_HARDENED
1691 bool "Harden slab freelist metadata"
1692 depends on SLUB
1693 help
1694 Many kernel heap attacks try to target slab cache metadata and
1695 other infrastructure. This options makes minor performance
1696 sacrifies to harden the kernel slab allocator against common
1697 freelist exploit methods.
1698
345c905d
JK
1699config SLUB_CPU_PARTIAL
1700 default y
b39ffbf8 1701 depends on SLUB && SMP
345c905d
JK
1702 bool "SLUB per cpu partial cache"
1703 help
1704 Per cpu partial caches accellerate objects allocation and freeing
1705 that is local to a processor at the price of more indeterminism
1706 in the latency of the free. On overflow these caches will be cleared
1707 which requires the taking of locks that may cause latency spikes.
1708 Typically one would choose no for a realtime system.
1709
ea637639
JZ
1710config MMAP_ALLOW_UNINITIALIZED
1711 bool "Allow mmapped anonymous memory to be uninitialized"
6a108a14 1712 depends on EXPERT && !MMU
ea637639
JZ
1713 default n
1714 help
1715 Normally, and according to the Linux spec, anonymous memory obtained
3903bf94 1716 from mmap() has its contents cleared before it is passed to
ea637639
JZ
1717 userspace. Enabling this config option allows you to request that
1718 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1719 providing a huge performance boost. If this option is not enabled,
1720 then the flag will be ignored.
1721
1722 This is taken advantage of by uClibc's malloc(), and also by
1723 ELF-FDPIC binfmt's brk and stack allocator.
1724
1725 Because of the obvious security issues, this option should only be
1726 enabled on embedded devices where you control what is run in
1727 userspace. Since that isn't generally a problem on no-MMU systems,
1728 it is normally safe to say Y here.
1729
1730 See Documentation/nommu-mmap.txt for more information.
1731
091f6e26
DH
1732config SYSTEM_DATA_VERIFICATION
1733 def_bool n
1734 select SYSTEM_TRUSTED_KEYRING
1735 select KEYS
1736 select CRYPTO
d43de6c7 1737 select CRYPTO_RSA
091f6e26
DH
1738 select ASYMMETRIC_KEY_TYPE
1739 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
091f6e26
DH
1740 select ASN1
1741 select OID_REGISTRY
1742 select X509_CERTIFICATE_PARSER
1743 select PKCS7_MESSAGE_PARSER
82c04ff8 1744 help
091f6e26
DH
1745 Provide PKCS#7 message verification using the contents of the system
1746 trusted keyring to provide public keys. This then can be used for
1747 module verification, kexec image verification and firmware blob
1748 verification.
82c04ff8 1749
125e5645 1750config PROFILING
b309a294 1751 bool "Profiling support"
125e5645
MD
1752 help
1753 Say Y here to enable the extended profiling support mechanisms used
1754 by profilers such as OProfile.
1755
5f87f112
IM
1756#
1757# Place an empty function call at each tracepoint site. Can be
1758# dynamically changed for a probe function.
1759#
97e1c18e 1760config TRACEPOINTS
5f87f112 1761 bool
97e1c18e 1762
1da177e4
LT
1763endmenu # General setup
1764
1572497c
CH
1765source "arch/Kconfig"
1766
ae81f9e3 1767config RT_MUTEXES
6341e62b 1768 bool
ae81f9e3 1769
1da177e4
LT
1770config BASE_SMALL
1771 int
1772 default 0 if BASE_FULL
1773 default 1 if !BASE_FULL
1774
66da5733 1775menuconfig MODULES
1da177e4 1776 bool "Enable loadable module support"
11097a03 1777 option modules
1da177e4
LT
1778 help
1779 Kernel modules are small pieces of compiled code which can
1780 be inserted in the running kernel, rather than being
1781 permanently built into the kernel. You use the "modprobe"
1782 tool to add (and sometimes remove) them. If you say Y here,
1783 many parts of the kernel can be built as modules (by
1784 answering M instead of Y where indicated): this is most
1785 useful for infrequently used options which are not required
1786 for booting. For more information, see the man pages for
1787 modprobe, lsmod, modinfo, insmod and rmmod.
1788
1789 If you say Y here, you will need to run "make
1790 modules_install" to put the modules under /lib/modules/
1791 where modprobe can find them (you may need to be root to do
1792 this).
1793
1794 If unsure, say Y.
1795
0b0de144
RD
1796if MODULES
1797
826e4506
LT
1798config MODULE_FORCE_LOAD
1799 bool "Forced module loading"
826e4506
LT
1800 default n
1801 help
91e37a79
RR
1802 Allow loading of modules without version information (ie. modprobe
1803 --force). Forced module loading sets the 'F' (forced) taint flag and
1804 is usually a really bad idea.
826e4506 1805
1da177e4
LT
1806config MODULE_UNLOAD
1807 bool "Module unloading"
1da177e4
LT
1808 help
1809 Without this option you will not be able to unload any
1810 modules (note that some modules may not be unloadable
f7f5b675
DV
1811 anyway), which makes your kernel smaller, faster
1812 and simpler. If unsure, say Y.
1da177e4
LT
1813
1814config MODULE_FORCE_UNLOAD
1815 bool "Forced module unloading"
19c92399 1816 depends on MODULE_UNLOAD
1da177e4
LT
1817 help
1818 This option allows you to force a module to unload, even if the
1819 kernel believes it is unsafe: the kernel will remove the module
1820 without waiting for anyone to stop using it (using the -f option to
1821 rmmod). This is mainly for kernel developers and desperate users.
1822 If unsure, say N.
1823
1da177e4 1824config MODVERSIONS
0d541643 1825 bool "Module versioning support"
1da177e4
LT
1826 help
1827 Usually, you have to use modules compiled with your kernel.
1828 Saying Y here makes it sometimes possible to use modules
1829 compiled for different kernels, by adding enough information
1830 to the modules to (hopefully) spot any changes which would
1831 make them incompatible with the kernel you are running. If
1832 unsure, say N.
1833
56067812
AB
1834config MODULE_REL_CRCS
1835 bool
1836 depends on MODVERSIONS
1837
1da177e4
LT
1838config MODULE_SRCVERSION_ALL
1839 bool "Source checksum for all modules"
1da177e4
LT
1840 help
1841 Modules which contain a MODULE_VERSION get an extra "srcversion"
1842 field inserted into their modinfo section, which contains a
1843 sum of the source files which made it. This helps maintainers
1844 see exactly which source was used to build a module (since
1845 others sometimes change the module source without updating
1846 the version). With this option, such a "srcversion" field
1847 will be created for all modules. If unsure, say N.
1848
106a4ee2
RR
1849config MODULE_SIG
1850 bool "Module signature verification"
1851 depends on MODULES
091f6e26 1852 select SYSTEM_DATA_VERIFICATION
106a4ee2
RR
1853 help
1854 Check modules for valid signatures upon load: the signature
1855 is simply appended to the module. For more information see
cbdc8217 1856 <file:Documentation/admin-guide/module-signing.rst>.
106a4ee2 1857
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1858 Note that this option adds the OpenSSL development packages as a
1859 kernel build dependency so that the signing tool can use its crypto
1860 library.
1861
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1862 !!!WARNING!!! If you enable this option, you MUST make sure that the
1863 module DOES NOT get stripped after being signed. This includes the
1864 debuginfo strip done by some packagers (such as rpmbuild) and
1865 inclusion into an initramfs that wants the module size reduced.
1866
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1867config MODULE_SIG_FORCE
1868 bool "Require modules to be validly signed"
1869 depends on MODULE_SIG
1870 help
1871 Reject unsigned modules or signed modules for which we don't have a
1872 key. Without this, such modules will simply taint the kernel.
ea0b6dcf 1873
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1874config MODULE_SIG_ALL
1875 bool "Automatically sign all modules"
1876 default y
1877 depends on MODULE_SIG
1878 help
1879 Sign all modules during make modules_install. Without this option,
1880 modules must be signed manually, using the scripts/sign-file tool.
1881
1882comment "Do not forget to sign required modules with scripts/sign-file"
1883 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1884
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1885choice
1886 prompt "Which hash algorithm should modules be signed with?"
1887 depends on MODULE_SIG
1888 help
1889 This determines which sort of hashing algorithm will be used during
1890 signature generation. This algorithm _must_ be built into the kernel
1891 directly so that signature verification can take place. It is not
1892 possible to load a signed module containing the algorithm to check
1893 the signature on that module.
1894
1895config MODULE_SIG_SHA1
1896 bool "Sign modules with SHA-1"
1897 select CRYPTO_SHA1
1898
1899config MODULE_SIG_SHA224
1900 bool "Sign modules with SHA-224"
1901 select CRYPTO_SHA256
1902
1903config MODULE_SIG_SHA256
1904 bool "Sign modules with SHA-256"
1905 select CRYPTO_SHA256
1906
1907config MODULE_SIG_SHA384
1908 bool "Sign modules with SHA-384"
1909 select CRYPTO_SHA512
1910
1911config MODULE_SIG_SHA512
1912 bool "Sign modules with SHA-512"
1913 select CRYPTO_SHA512
1914
1915endchoice
1916
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1917config MODULE_SIG_HASH
1918 string
1919 depends on MODULE_SIG
1920 default "sha1" if MODULE_SIG_SHA1
1921 default "sha224" if MODULE_SIG_SHA224
1922 default "sha256" if MODULE_SIG_SHA256
1923 default "sha384" if MODULE_SIG_SHA384
1924 default "sha512" if MODULE_SIG_SHA512
1925
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1926config MODULE_COMPRESS
1927 bool "Compress modules on installation"
1928 depends on MODULES
1929 help
beb50df3 1930
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1931 Compresses kernel modules when 'make modules_install' is run; gzip or
1932 xz depending on "Compression algorithm" below.
beb50df3 1933
b6c09b51 1934 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
beb50df3 1935
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1936 Out-of-tree kernel modules installed using Kbuild will also be
1937 compressed upon installation.
beb50df3 1938
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1939 Note: for modules inside an initrd or initramfs, it's more efficient
1940 to compress the whole initrd or initramfs instead.
beb50df3 1941
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1942 Note: This is fully compatible with signed modules.
1943
1944 If in doubt, say N.
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1945
1946choice
1947 prompt "Compression algorithm"
1948 depends on MODULE_COMPRESS
1949 default MODULE_COMPRESS_GZIP
1950 help
1951 This determines which sort of compression will be used during
1952 'make modules_install'.
1953
1954 GZIP (default) and XZ are supported.
1955
1956config MODULE_COMPRESS_GZIP
1957 bool "GZIP"
1958
1959config MODULE_COMPRESS_XZ
1960 bool "XZ"
1961
1962endchoice
1963
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1964config TRIM_UNUSED_KSYMS
1965 bool "Trim unused exported kernel symbols"
1966 depends on MODULES && !UNUSED_SYMBOLS
1967 help
1968 The kernel and some modules make many symbols available for
1969 other modules to use via EXPORT_SYMBOL() and variants. Depending
1970 on the set of modules being selected in your kernel configuration,
1971 many of those exported symbols might never be used.
1972
1973 This option allows for unused exported symbols to be dropped from
1974 the build. In turn, this provides the compiler more opportunities
1975 (especially when using LTO) for optimizing the code and reducing
1976 binary size. This might have some security advantages as well.
1977
f1cb637e 1978 If unsure, or if you need to build out-of-tree modules, say N.
dbacb0ef 1979
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1980endif # MODULES
1981
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1982config MODULES_TREE_LOOKUP
1983 def_bool y
1984 depends on PERF_EVENTS || TRACING
1985
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1986config INIT_ALL_POSSIBLE
1987 bool
1988 help
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1989 Back when each arch used to define their own cpu_online_mask and
1990 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
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1991 with all 1s, and others with all 0s. When they were centralised,
1992 it was better to provide this option than to break all the archs
692105b8 1993 and have several arch maintainers pursuing me down dark alleys.
98a79d6a 1994
3a65dfe8 1995source "block/Kconfig"
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1996
1997config PREEMPT_NOTIFIERS
1998 bool
e260be67 1999
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2000config PADATA
2001 depends on SMP
2002 bool
2003
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2004config ASN1
2005 tristate
2006 help
2007 Build a simple ASN.1 grammar compiler that produces a bytecode output
2008 that can be interpreted by the ASN.1 stream decoder and used to
2009 inform it as to what tags are to be expected in a stream and what
2010 functions to call on what tags.
2011
6beb0009 2012source "kernel/Kconfig.locks"
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2013
2014config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2015 bool
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2016
2017# It may be useful for an architecture to override the definitions of the
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2018# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2019# and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2020# different calling convention for syscalls. They can also override the
2021# macros for not-implemented syscalls in kernel/sys_ni.c and
2022# kernel/time/posix-stubs.c. All these overrides need to be available in
2023# <asm/syscall_wrapper.h>.
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2024config ARCH_HAS_SYSCALL_WRAPPER
2025 def_bool n