Kconfig 63 KB

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