Kconfig 64 KB

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  1. config ARCH
  2. string
  3. option env="ARCH"
  4. config KERNELVERSION
  5. string
  6. option env="KERNELVERSION"
  7. config DEFCONFIG_LIST
  8. string
  9. depends on !UML
  10. option defconfig_list
  11. default "/lib/modules/$UNAME_RELEASE/.config"
  12. default "/etc/kernel-config"
  13. default "/boot/config-$UNAME_RELEASE"
  14. default "$ARCH_DEFCONFIG"
  15. default "arch/$ARCH/defconfig"
  16. config CONSTRUCTORS
  17. bool
  18. depends on !UML
  19. config IRQ_WORK
  20. bool
  21. config BUILDTIME_EXTABLE_SORT
  22. bool
  23. menu "General setup"
  24. config BROKEN
  25. bool
  26. config BROKEN_ON_SMP
  27. bool
  28. depends on BROKEN || !SMP
  29. default y
  30. config INIT_ENV_ARG_LIMIT
  31. int
  32. default 32 if !UML
  33. default 128 if UML
  34. help
  35. Maximum of each of the number of arguments and environment
  36. variables passed to init from the kernel command line.
  37. config CROSS_COMPILE
  38. string "Cross-compiler tool prefix"
  39. help
  40. Same as running 'make CROSS_COMPILE=prefix-' but stored for
  41. default make runs in this kernel build directory. You don't
  42. need to set this unless you want the configured kernel build
  43. directory to select the cross-compiler automatically.
  44. config COMPILE_TEST
  45. bool "Compile also drivers which will not load"
  46. default n
  47. help
  48. Some drivers can be compiled on a different platform than they are
  49. intended to be run on. Despite they cannot be loaded there (or even
  50. when they load they cannot be used due to missing HW support),
  51. developers still, opposing to distributors, might want to build such
  52. drivers to compile-test them.
  53. If you are a developer and want to build everything available, say Y
  54. here. If you are a user/distributor, say N here to exclude useless
  55. drivers to be distributed.
  56. config LOCALVERSION
  57. string "Local version - append to kernel release"
  58. help
  59. Append an extra string to the end of your kernel version.
  60. This will show up when you type uname, for example.
  61. The string you set here will be appended after the contents of
  62. any files with a filename matching localversion* in your
  63. object and source tree, in that order. Your total string can
  64. be a maximum of 64 characters.
  65. config LOCALVERSION_AUTO
  66. bool "Automatically append version information to the version string"
  67. default y
  68. help
  69. This will try to automatically determine if the current tree is a
  70. release tree by looking for git tags that belong to the current
  71. top of tree revision.
  72. A string of the format -gxxxxxxxx will be added to the localversion
  73. if a git-based tree is found. The string generated by this will be
  74. appended after any matching localversion* files, and after the value
  75. set in CONFIG_LOCALVERSION.
  76. (The actual string used here is the first eight characters produced
  77. by running the command:
  78. $ git rev-parse --verify HEAD
  79. which is done within the script "scripts/setlocalversion".)
  80. config HAVE_KERNEL_GZIP
  81. bool
  82. config HAVE_KERNEL_BZIP2
  83. bool
  84. config HAVE_KERNEL_LZMA
  85. bool
  86. config HAVE_KERNEL_XZ
  87. bool
  88. config HAVE_KERNEL_LZO
  89. bool
  90. config HAVE_KERNEL_LZ4
  91. bool
  92. choice
  93. prompt "Kernel compression mode"
  94. default KERNEL_GZIP
  95. depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
  96. help
  97. The linux kernel is a kind of self-extracting executable.
  98. Several compression algorithms are available, which differ
  99. in efficiency, compression and decompression speed.
  100. Compression speed is only relevant when building a kernel.
  101. Decompression speed is relevant at each boot.
  102. If you have any problems with bzip2 or lzma compressed
  103. kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
  104. version of this functionality (bzip2 only), for 2.4, was
  105. supplied by Christian Ludwig)
  106. High compression options are mostly useful for users, who
  107. are low on disk space (embedded systems), but for whom ram
  108. size matters less.
  109. If in doubt, select 'gzip'
  110. config KERNEL_GZIP
  111. bool "Gzip"
  112. depends on HAVE_KERNEL_GZIP
  113. help
  114. The old and tried gzip compression. It provides a good balance
  115. between compression ratio and decompression speed.
  116. config KERNEL_BZIP2
  117. bool "Bzip2"
  118. depends on HAVE_KERNEL_BZIP2
  119. help
  120. Its compression ratio and speed is intermediate.
  121. Decompression speed is slowest among the choices. The kernel
  122. size is about 10% smaller with bzip2, in comparison to gzip.
  123. Bzip2 uses a large amount of memory. For modern kernels you
  124. will need at least 8MB RAM or more for booting.
  125. config KERNEL_LZMA
  126. bool "LZMA"
  127. depends on HAVE_KERNEL_LZMA
  128. help
  129. This compression algorithm's ratio is best. Decompression speed
  130. is between gzip and bzip2. Compression is slowest.
  131. The kernel size is about 33% smaller with LZMA in comparison to gzip.
  132. config KERNEL_XZ
  133. bool "XZ"
  134. depends on HAVE_KERNEL_XZ
  135. help
  136. XZ uses the LZMA2 algorithm and instruction set specific
  137. BCJ filters which can improve compression ratio of executable
  138. code. The size of the kernel is about 30% smaller with XZ in
  139. comparison to gzip. On architectures for which there is a BCJ
  140. filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
  141. will create a few percent smaller kernel than plain LZMA.
  142. The speed is about the same as with LZMA: The decompression
  143. speed of XZ is better than that of bzip2 but worse than gzip
  144. and LZO. Compression is slow.
  145. config KERNEL_LZO
  146. bool "LZO"
  147. depends on HAVE_KERNEL_LZO
  148. help
  149. Its compression ratio is the poorest among the choices. The kernel
  150. size is about 10% bigger than gzip; however its speed
  151. (both compression and decompression) is the fastest.
  152. config KERNEL_LZ4
  153. bool "LZ4"
  154. depends on HAVE_KERNEL_LZ4
  155. help
  156. LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
  157. A preliminary version of LZ4 de/compression tool is available at
  158. <https://code.google.com/p/lz4/>.
  159. Its compression ratio is worse than LZO. The size of the kernel
  160. is about 8% bigger than LZO. But the decompression speed is
  161. faster than LZO.
  162. endchoice
  163. config DEFAULT_HOSTNAME
  164. string "Default hostname"
  165. default "(none)"
  166. help
  167. This option determines the default system hostname before userspace
  168. calls sethostname(2). The kernel traditionally uses "(none)" here,
  169. but you may wish to use a different default here to make a minimal
  170. system more usable with less configuration.
  171. config SWAP
  172. bool "Support for paging of anonymous memory (swap)"
  173. depends on MMU && BLOCK
  174. default y
  175. help
  176. This option allows you to choose whether you want to have support
  177. for so called swap devices or swap files in your kernel that are
  178. used to provide more virtual memory than the actual RAM present
  179. in your computer. If unsure say Y.
  180. config SYSVIPC
  181. bool "System V IPC"
  182. ---help---
  183. Inter Process Communication is a suite of library functions and
  184. system calls which let processes (running programs) synchronize and
  185. exchange information. It is generally considered to be a good thing,
  186. and some programs won't run unless you say Y here. In particular, if
  187. you want to run the DOS emulator dosemu under Linux (read the
  188. DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
  189. you'll need to say Y here.
  190. You can find documentation about IPC with "info ipc" and also in
  191. section 6.4 of the Linux Programmer's Guide, available from
  192. <http://www.tldp.org/guides.html>.
  193. config SYSVIPC_SYSCTL
  194. bool
  195. depends on SYSVIPC
  196. depends on SYSCTL
  197. default y
  198. config POSIX_MQUEUE
  199. bool "POSIX Message Queues"
  200. depends on NET
  201. ---help---
  202. POSIX variant of message queues is a part of IPC. In POSIX message
  203. queues every message has a priority which decides about succession
  204. of receiving it by a process. If you want to compile and run
  205. programs written e.g. for Solaris with use of its POSIX message
  206. queues (functions mq_*) say Y here.
  207. POSIX message queues are visible as a filesystem called 'mqueue'
  208. and can be mounted somewhere if you want to do filesystem
  209. operations on message queues.
  210. If unsure, say Y.
  211. config POSIX_MQUEUE_SYSCTL
  212. bool
  213. depends on POSIX_MQUEUE
  214. depends on SYSCTL
  215. default y
  216. config CROSS_MEMORY_ATTACH
  217. bool "Enable process_vm_readv/writev syscalls"
  218. depends on MMU
  219. default y
  220. help
  221. Enabling this option adds the system calls process_vm_readv and
  222. process_vm_writev which allow a process with the correct privileges
  223. to directly read from or write to another process' address space.
  224. See the man page for more details.
  225. config FHANDLE
  226. bool "open by fhandle syscalls"
  227. select EXPORTFS
  228. help
  229. If you say Y here, a user level program will be able to map
  230. file names to handle and then later use the handle for
  231. different file system operations. This is useful in implementing
  232. userspace file servers, which now track files using handles instead
  233. of names. The handle would remain the same even if file names
  234. get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
  235. syscalls.
  236. config USELIB
  237. bool "uselib syscall"
  238. def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
  239. help
  240. This option enables the uselib syscall, a system call used in the
  241. dynamic linker from libc5 and earlier. glibc does not use this
  242. system call. If you intend to run programs built on libc5 or
  243. earlier, you may need to enable this syscall. Current systems
  244. running glibc can safely disable this.
  245. config AUDIT
  246. bool "Auditing support"
  247. depends on NET
  248. help
  249. Enable auditing infrastructure that can be used with another
  250. kernel subsystem, such as SELinux (which requires this for
  251. logging of avc messages output). System call auditing is included
  252. on architectures which support it.
  253. config HAVE_ARCH_AUDITSYSCALL
  254. bool
  255. config AUDITSYSCALL
  256. def_bool y
  257. depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
  258. config AUDIT_WATCH
  259. def_bool y
  260. depends on AUDITSYSCALL
  261. select FSNOTIFY
  262. config AUDIT_TREE
  263. def_bool y
  264. depends on AUDITSYSCALL
  265. select FSNOTIFY
  266. source "kernel/irq/Kconfig"
  267. source "kernel/time/Kconfig"
  268. menu "CPU/Task time and stats accounting"
  269. config VIRT_CPU_ACCOUNTING
  270. bool
  271. choice
  272. prompt "Cputime accounting"
  273. default TICK_CPU_ACCOUNTING if !PPC64
  274. default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
  275. # Kind of a stub config for the pure tick based cputime accounting
  276. config TICK_CPU_ACCOUNTING
  277. bool "Simple tick based cputime accounting"
  278. depends on !S390 && !NO_HZ_FULL
  279. help
  280. This is the basic tick based cputime accounting that maintains
  281. statistics about user, system and idle time spent on per jiffies
  282. granularity.
  283. If unsure, say Y.
  284. config VIRT_CPU_ACCOUNTING_NATIVE
  285. bool "Deterministic task and CPU time accounting"
  286. depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
  287. select VIRT_CPU_ACCOUNTING
  288. help
  289. Select this option to enable more accurate task and CPU time
  290. accounting. This is done by reading a CPU counter on each
  291. kernel entry and exit and on transitions within the kernel
  292. between system, softirq and hardirq state, so there is a
  293. small performance impact. In the case of s390 or IBM POWER > 5,
  294. this also enables accounting of stolen time on logically-partitioned
  295. systems.
  296. config VIRT_CPU_ACCOUNTING_GEN
  297. bool "Full dynticks CPU time accounting"
  298. depends on HAVE_CONTEXT_TRACKING
  299. depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
  300. select VIRT_CPU_ACCOUNTING
  301. select CONTEXT_TRACKING
  302. help
  303. Select this option to enable task and CPU time accounting on full
  304. dynticks systems. This accounting is implemented by watching every
  305. kernel-user boundaries using the context tracking subsystem.
  306. The accounting is thus performed at the expense of some significant
  307. overhead.
  308. For now this is only useful if you are working on the full
  309. dynticks subsystem development.
  310. If unsure, say N.
  311. config IRQ_TIME_ACCOUNTING
  312. bool "Fine granularity task level IRQ time accounting"
  313. depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
  314. help
  315. Select this option to enable fine granularity task irq time
  316. accounting. This is done by reading a timestamp on each
  317. transitions between softirq and hardirq state, so there can be a
  318. small performance impact.
  319. If in doubt, say N here.
  320. endchoice
  321. config BSD_PROCESS_ACCT
  322. bool "BSD Process Accounting"
  323. depends on MULTIUSER
  324. help
  325. If you say Y here, a user level program will be able to instruct the
  326. kernel (via a special system call) to write process accounting
  327. information to a file: whenever a process exits, information about
  328. that process will be appended to the file by the kernel. The
  329. information includes things such as creation time, owning user,
  330. command name, memory usage, controlling terminal etc. (the complete
  331. list is in the struct acct in <file:include/linux/acct.h>). It is
  332. up to the user level program to do useful things with this
  333. information. This is generally a good idea, so say Y.
  334. config BSD_PROCESS_ACCT_V3
  335. bool "BSD Process Accounting version 3 file format"
  336. depends on BSD_PROCESS_ACCT
  337. default n
  338. help
  339. If you say Y here, the process accounting information is written
  340. in a new file format that also logs the process IDs of each
  341. process and it's parent. Note that this file format is incompatible
  342. with previous v0/v1/v2 file formats, so you will need updated tools
  343. for processing it. A preliminary version of these tools is available
  344. at <http://www.gnu.org/software/acct/>.
  345. config TASKSTATS
  346. bool "Export task/process statistics through netlink"
  347. depends on NET
  348. depends on MULTIUSER
  349. default n
  350. help
  351. Export selected statistics for tasks/processes through the
  352. generic netlink interface. Unlike BSD process accounting, the
  353. statistics are available during the lifetime of tasks/processes as
  354. responses to commands. Like BSD accounting, they are sent to user
  355. space on task exit.
  356. Say N if unsure.
  357. config TASK_DELAY_ACCT
  358. bool "Enable per-task delay accounting"
  359. depends on TASKSTATS
  360. select SCHED_INFO
  361. help
  362. Collect information on time spent by a task waiting for system
  363. resources like cpu, synchronous block I/O completion and swapping
  364. in pages. Such statistics can help in setting a task's priorities
  365. relative to other tasks for cpu, io, rss limits etc.
  366. Say N if unsure.
  367. config TASK_XACCT
  368. bool "Enable extended accounting over taskstats"
  369. depends on TASKSTATS
  370. help
  371. Collect extended task accounting data and send the data
  372. to userland for processing over the taskstats interface.
  373. Say N if unsure.
  374. config TASK_IO_ACCOUNTING
  375. bool "Enable per-task storage I/O accounting"
  376. depends on TASK_XACCT
  377. help
  378. Collect information on the number of bytes of storage I/O which this
  379. task has caused.
  380. Say N if unsure.
  381. endmenu # "CPU/Task time and stats accounting"
  382. menu "RCU Subsystem"
  383. config TREE_RCU
  384. bool
  385. default y if !PREEMPT && SMP
  386. help
  387. This option selects the RCU implementation that is
  388. designed for very large SMP system with hundreds or
  389. thousands of CPUs. It also scales down nicely to
  390. smaller systems.
  391. config PREEMPT_RCU
  392. bool
  393. default y if PREEMPT
  394. help
  395. This option selects the RCU implementation that is
  396. designed for very large SMP systems with hundreds or
  397. thousands of CPUs, but for which real-time response
  398. is also required. It also scales down nicely to
  399. smaller systems.
  400. Select this option if you are unsure.
  401. config TINY_RCU
  402. bool
  403. default y if !PREEMPT && !SMP
  404. help
  405. This option selects the RCU implementation that is
  406. designed for UP systems from which real-time response
  407. is not required. This option greatly reduces the
  408. memory footprint of RCU.
  409. config RCU_EXPERT
  410. bool "Make expert-level adjustments to RCU configuration"
  411. default n
  412. help
  413. This option needs to be enabled if you wish to make
  414. expert-level adjustments to RCU configuration. By default,
  415. no such adjustments can be made, which has the often-beneficial
  416. side-effect of preventing "make oldconfig" from asking you all
  417. sorts of detailed questions about how you would like numerous
  418. obscure RCU options to be set up.
  419. Say Y if you need to make expert-level adjustments to RCU.
  420. Say N if you are unsure.
  421. config SRCU
  422. bool
  423. help
  424. This option selects the sleepable version of RCU. This version
  425. permits arbitrary sleeping or blocking within RCU read-side critical
  426. sections.
  427. config TASKS_RCU
  428. bool
  429. default n
  430. select SRCU
  431. help
  432. This option enables a task-based RCU implementation that uses
  433. only voluntary context switch (not preemption!), idle, and
  434. user-mode execution as quiescent states.
  435. config RCU_STALL_COMMON
  436. def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
  437. help
  438. This option enables RCU CPU stall code that is common between
  439. the TINY and TREE variants of RCU. The purpose is to allow
  440. the tiny variants to disable RCU CPU stall warnings, while
  441. making these warnings mandatory for the tree variants.
  442. config CONTEXT_TRACKING
  443. bool
  444. config CONTEXT_TRACKING_FORCE
  445. bool "Force context tracking"
  446. depends on CONTEXT_TRACKING
  447. default y if !NO_HZ_FULL
  448. help
  449. The major pre-requirement for full dynticks to work is to
  450. support the context tracking subsystem. But there are also
  451. other dependencies to provide in order to make the full
  452. dynticks working.
  453. This option stands for testing when an arch implements the
  454. context tracking backend but doesn't yet fullfill all the
  455. requirements to make the full dynticks feature working.
  456. Without the full dynticks, there is no way to test the support
  457. for context tracking and the subsystems that rely on it: RCU
  458. userspace extended quiescent state and tickless cputime
  459. accounting. This option copes with the absence of the full
  460. dynticks subsystem by forcing the context tracking on all
  461. CPUs in the system.
  462. Say Y only if you're working on the development of an
  463. architecture backend for the context tracking.
  464. Say N otherwise, this option brings an overhead that you
  465. don't want in production.
  466. config RCU_FANOUT
  467. int "Tree-based hierarchical RCU fanout value"
  468. range 2 64 if 64BIT
  469. range 2 32 if !64BIT
  470. depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
  471. default 64 if 64BIT
  472. default 32 if !64BIT
  473. help
  474. This option controls the fanout of hierarchical implementations
  475. of RCU, allowing RCU to work efficiently on machines with
  476. large numbers of CPUs. This value must be at least the fourth
  477. root of NR_CPUS, which allows NR_CPUS to be insanely large.
  478. The default value of RCU_FANOUT should be used for production
  479. systems, but if you are stress-testing the RCU implementation
  480. itself, small RCU_FANOUT values allow you to test large-system
  481. code paths on small(er) systems.
  482. Select a specific number if testing RCU itself.
  483. Take the default if unsure.
  484. config RCU_FANOUT_LEAF
  485. int "Tree-based hierarchical RCU leaf-level fanout value"
  486. range 2 64 if 64BIT
  487. range 2 32 if !64BIT
  488. depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
  489. default 16
  490. help
  491. This option controls the leaf-level fanout of hierarchical
  492. implementations of RCU, and allows trading off cache misses
  493. against lock contention. Systems that synchronize their
  494. scheduling-clock interrupts for energy-efficiency reasons will
  495. want the default because the smaller leaf-level fanout keeps
  496. lock contention levels acceptably low. Very large systems
  497. (hundreds or thousands of CPUs) will instead want to set this
  498. value to the maximum value possible in order to reduce the
  499. number of cache misses incurred during RCU's grace-period
  500. initialization. These systems tend to run CPU-bound, and thus
  501. are not helped by synchronized interrupts, and thus tend to
  502. skew them, which reduces lock contention enough that large
  503. leaf-level fanouts work well.
  504. Select a specific number if testing RCU itself.
  505. Select the maximum permissible value for large systems.
  506. Take the default if unsure.
  507. config RCU_FAST_NO_HZ
  508. bool "Accelerate last non-dyntick-idle CPU's grace periods"
  509. depends on NO_HZ_COMMON && SMP && RCU_EXPERT
  510. default n
  511. help
  512. This option permits CPUs to enter dynticks-idle state even if
  513. they have RCU callbacks queued, and prevents RCU from waking
  514. these CPUs up more than roughly once every four jiffies (by
  515. default, you can adjust this using the rcutree.rcu_idle_gp_delay
  516. parameter), thus improving energy efficiency. On the other
  517. hand, this option increases the duration of RCU grace periods,
  518. for example, slowing down synchronize_rcu().
  519. Say Y if energy efficiency is critically important, and you
  520. don't care about increased grace-period durations.
  521. Say N if you are unsure.
  522. config TREE_RCU_TRACE
  523. def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
  524. select DEBUG_FS
  525. help
  526. This option provides tracing for the TREE_RCU and
  527. PREEMPT_RCU implementations, permitting Makefile to
  528. trivially select kernel/rcutree_trace.c.
  529. config RCU_BOOST
  530. bool "Enable RCU priority boosting"
  531. depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT
  532. default n
  533. help
  534. This option boosts the priority of preempted RCU readers that
  535. block the current preemptible RCU grace period for too long.
  536. This option also prevents heavy loads from blocking RCU
  537. callback invocation for all flavors of RCU.
  538. Say Y here if you are working with real-time apps or heavy loads
  539. Say N here if you are unsure.
  540. config RCU_KTHREAD_PRIO
  541. int "Real-time priority to use for RCU worker threads"
  542. range 1 99 if RCU_BOOST
  543. range 0 99 if !RCU_BOOST
  544. default 1 if RCU_BOOST
  545. default 0 if !RCU_BOOST
  546. depends on RCU_EXPERT
  547. help
  548. This option specifies the SCHED_FIFO priority value that will be
  549. assigned to the rcuc/n and rcub/n threads and is also the value
  550. used for RCU_BOOST (if enabled). If you are working with a
  551. real-time application that has one or more CPU-bound threads
  552. running at a real-time priority level, you should set
  553. RCU_KTHREAD_PRIO to a priority higher than the highest-priority
  554. real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO
  555. value of 1 is appropriate in the common case, which is real-time
  556. applications that do not have any CPU-bound threads.
  557. Some real-time applications might not have a single real-time
  558. thread that saturates a given CPU, but instead might have
  559. multiple real-time threads that, taken together, fully utilize
  560. that CPU. In this case, you should set RCU_KTHREAD_PRIO to
  561. a priority higher than the lowest-priority thread that is
  562. conspiring to prevent the CPU from running any non-real-time
  563. tasks. For example, if one thread at priority 10 and another
  564. thread at priority 5 are between themselves fully consuming
  565. the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
  566. set to priority 6 or higher.
  567. Specify the real-time priority, or take the default if unsure.
  568. config RCU_BOOST_DELAY
  569. int "Milliseconds to delay boosting after RCU grace-period start"
  570. range 0 3000
  571. depends on RCU_BOOST
  572. default 500
  573. help
  574. This option specifies the time to wait after the beginning of
  575. a given grace period before priority-boosting preempted RCU
  576. readers blocking that grace period. Note that any RCU reader
  577. blocking an expedited RCU grace period is boosted immediately.
  578. Accept the default if unsure.
  579. config RCU_NOCB_CPU
  580. bool "Offload RCU callback processing from boot-selected CPUs"
  581. depends on TREE_RCU || PREEMPT_RCU
  582. depends on RCU_EXPERT || NO_HZ_FULL
  583. default n
  584. help
  585. Use this option to reduce OS jitter for aggressive HPC or
  586. real-time workloads. It can also be used to offload RCU
  587. callback invocation to energy-efficient CPUs in battery-powered
  588. asymmetric multiprocessors.
  589. This option offloads callback invocation from the set of
  590. CPUs specified at boot time by the rcu_nocbs parameter.
  591. For each such CPU, a kthread ("rcuox/N") will be created to
  592. invoke callbacks, where the "N" is the CPU being offloaded,
  593. and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
  594. "s" for RCU-sched. Nothing prevents this kthread from running
  595. on the specified CPUs, but (1) the kthreads may be preempted
  596. between each callback, and (2) affinity or cgroups can be used
  597. to force the kthreads to run on whatever set of CPUs is desired.
  598. Say Y here if you want to help to debug reduced OS jitter.
  599. Say N here if you are unsure.
  600. choice
  601. prompt "Build-forced no-CBs CPUs"
  602. default RCU_NOCB_CPU_NONE
  603. depends on RCU_NOCB_CPU
  604. help
  605. This option allows no-CBs CPUs (whose RCU callbacks are invoked
  606. from kthreads rather than from softirq context) to be specified
  607. at build time. Additional no-CBs CPUs may be specified by
  608. the rcu_nocbs= boot parameter.
  609. config RCU_NOCB_CPU_NONE
  610. bool "No build_forced no-CBs CPUs"
  611. help
  612. This option does not force any of the CPUs to be no-CBs CPUs.
  613. Only CPUs designated by the rcu_nocbs= boot parameter will be
  614. no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
  615. kthreads whose names begin with "rcuo". All other CPUs will
  616. invoke their own RCU callbacks in softirq context.
  617. Select this option if you want to choose no-CBs CPUs at
  618. boot time, for example, to allow testing of different no-CBs
  619. configurations without having to rebuild the kernel each time.
  620. config RCU_NOCB_CPU_ZERO
  621. bool "CPU 0 is a build_forced no-CBs CPU"
  622. help
  623. This option forces CPU 0 to be a no-CBs CPU, so that its RCU
  624. callbacks are invoked by a per-CPU kthread whose name begins
  625. with "rcuo". Additional CPUs may be designated as no-CBs
  626. CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
  627. All other CPUs will invoke their own RCU callbacks in softirq
  628. context.
  629. Select this if CPU 0 needs to be a no-CBs CPU for real-time
  630. or energy-efficiency reasons, but the real reason it exists
  631. is to ensure that randconfig testing covers mixed systems.
  632. config RCU_NOCB_CPU_ALL
  633. bool "All CPUs are build_forced no-CBs CPUs"
  634. help
  635. This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
  636. boot parameter will be ignored. All CPUs' RCU callbacks will
  637. be executed in the context of per-CPU rcuo kthreads created for
  638. this purpose. Assuming that the kthreads whose names start with
  639. "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
  640. on the remaining CPUs, but might decrease memory locality during
  641. RCU-callback invocation, thus potentially degrading throughput.
  642. Select this if all CPUs need to be no-CBs CPUs for real-time
  643. or energy-efficiency reasons.
  644. endchoice
  645. config RCU_EXPEDITE_BOOT
  646. bool
  647. default n
  648. help
  649. This option enables expedited grace periods at boot time,
  650. as if rcu_expedite_gp() had been invoked early in boot.
  651. The corresponding rcu_unexpedite_gp() is invoked from
  652. rcu_end_inkernel_boot(), which is intended to be invoked
  653. at the end of the kernel-only boot sequence, just before
  654. init is exec'ed.
  655. Accept the default if unsure.
  656. endmenu # "RCU Subsystem"
  657. config BUILD_BIN2C
  658. bool
  659. default n
  660. config IKCONFIG
  661. tristate "Kernel .config support"
  662. select BUILD_BIN2C
  663. ---help---
  664. This option enables the complete Linux kernel ".config" file
  665. contents to be saved in the kernel. It provides documentation
  666. of which kernel options are used in a running kernel or in an
  667. on-disk kernel. This information can be extracted from the kernel
  668. image file with the script scripts/extract-ikconfig and used as
  669. input to rebuild the current kernel or to build another kernel.
  670. It can also be extracted from a running kernel by reading
  671. /proc/config.gz if enabled (below).
  672. config IKCONFIG_PROC
  673. bool "Enable access to .config through /proc/config.gz"
  674. depends on IKCONFIG && PROC_FS
  675. ---help---
  676. This option enables access to the kernel configuration file
  677. through /proc/config.gz.
  678. config LOG_BUF_SHIFT
  679. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  680. range 12 25
  681. default 17
  682. depends on PRINTK
  683. help
  684. Select the minimal kernel log buffer size as a power of 2.
  685. The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
  686. parameter, see below. Any higher size also might be forced
  687. by "log_buf_len" boot parameter.
  688. Examples:
  689. 17 => 128 KB
  690. 16 => 64 KB
  691. 15 => 32 KB
  692. 14 => 16 KB
  693. 13 => 8 KB
  694. 12 => 4 KB
  695. config LOG_CPU_MAX_BUF_SHIFT
  696. int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
  697. depends on SMP
  698. range 0 21
  699. default 12 if !BASE_SMALL
  700. default 0 if BASE_SMALL
  701. depends on PRINTK
  702. help
  703. This option allows to increase the default ring buffer size
  704. according to the number of CPUs. The value defines the contribution
  705. of each CPU as a power of 2. The used space is typically only few
  706. lines however it might be much more when problems are reported,
  707. e.g. backtraces.
  708. The increased size means that a new buffer has to be allocated and
  709. the original static one is unused. It makes sense only on systems
  710. with more CPUs. Therefore this value is used only when the sum of
  711. contributions is greater than the half of the default kernel ring
  712. buffer as defined by LOG_BUF_SHIFT. The default values are set
  713. so that more than 64 CPUs are needed to trigger the allocation.
  714. Also this option is ignored when "log_buf_len" kernel parameter is
  715. used as it forces an exact (power of two) size of the ring buffer.
  716. The number of possible CPUs is used for this computation ignoring
  717. hotplugging making the compuation optimal for the the worst case
  718. scenerio while allowing a simple algorithm to be used from bootup.
  719. Examples shift values and their meaning:
  720. 17 => 128 KB for each CPU
  721. 16 => 64 KB for each CPU
  722. 15 => 32 KB for each CPU
  723. 14 => 16 KB for each CPU
  724. 13 => 8 KB for each CPU
  725. 12 => 4 KB for each CPU
  726. #
  727. # Architectures with an unreliable sched_clock() should select this:
  728. #
  729. config HAVE_UNSTABLE_SCHED_CLOCK
  730. bool
  731. config GENERIC_SCHED_CLOCK
  732. bool
  733. #
  734. # For architectures that want to enable the support for NUMA-affine scheduler
  735. # balancing logic:
  736. #
  737. config ARCH_SUPPORTS_NUMA_BALANCING
  738. bool
  739. #
  740. # For architectures that prefer to flush all TLBs after a number of pages
  741. # are unmapped instead of sending one IPI per page to flush. The architecture
  742. # must provide guarantees on what happens if a clean TLB cache entry is
  743. # written after the unmap. Details are in mm/rmap.c near the check for
  744. # should_defer_flush. The architecture should also consider if the full flush
  745. # and the refill costs are offset by the savings of sending fewer IPIs.
  746. config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
  747. bool
  748. #
  749. # For architectures that know their GCC __int128 support is sound
  750. #
  751. config ARCH_SUPPORTS_INT128
  752. bool
  753. # For architectures that (ab)use NUMA to represent different memory regions
  754. # all cpu-local but of different latencies, such as SuperH.
  755. #
  756. config ARCH_WANT_NUMA_VARIABLE_LOCALITY
  757. bool
  758. config NUMA_BALANCING
  759. bool "Memory placement aware NUMA scheduler"
  760. depends on ARCH_SUPPORTS_NUMA_BALANCING
  761. depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
  762. depends on SMP && NUMA && MIGRATION
  763. help
  764. This option adds support for automatic NUMA aware memory/task placement.
  765. The mechanism is quite primitive and is based on migrating memory when
  766. it has references to the node the task is running on.
  767. This system will be inactive on UMA systems.
  768. config NUMA_BALANCING_DEFAULT_ENABLED
  769. bool "Automatically enable NUMA aware memory/task placement"
  770. default y
  771. depends on NUMA_BALANCING
  772. help
  773. If set, automatic NUMA balancing will be enabled if running on a NUMA
  774. machine.
  775. menuconfig CGROUPS
  776. bool "Control Group support"
  777. select KERNFS
  778. help
  779. This option adds support for grouping sets of processes together, for
  780. use with process control subsystems such as Cpusets, CFS, memory
  781. controls or device isolation.
  782. See
  783. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  784. - Documentation/cgroups/ (features for grouping, isolation
  785. and resource control)
  786. Say N if unsure.
  787. if CGROUPS
  788. config PAGE_COUNTER
  789. bool
  790. config MEMCG
  791. bool "Memory controller"
  792. select PAGE_COUNTER
  793. select EVENTFD
  794. help
  795. Provides control over the memory footprint of tasks in a cgroup.
  796. config MEMCG_SWAP
  797. bool "Swap controller"
  798. depends on MEMCG && SWAP
  799. help
  800. Provides control over the swap space consumed by tasks in a cgroup.
  801. config MEMCG_SWAP_ENABLED
  802. bool "Swap controller enabled by default"
  803. depends on MEMCG_SWAP
  804. default y
  805. help
  806. Memory Resource Controller Swap Extension comes with its price in
  807. a bigger memory consumption. General purpose distribution kernels
  808. which want to enable the feature but keep it disabled by default
  809. and let the user enable it by swapaccount=1 boot command line
  810. parameter should have this option unselected.
  811. For those who want to have the feature enabled by default should
  812. select this option (if, for some reason, they need to disable it
  813. then swapaccount=0 does the trick).
  814. config BLK_CGROUP
  815. bool "IO controller"
  816. depends on BLOCK
  817. default n
  818. ---help---
  819. Generic block IO controller cgroup interface. This is the common
  820. cgroup interface which should be used by various IO controlling
  821. policies.
  822. Currently, CFQ IO scheduler uses it to recognize task groups and
  823. control disk bandwidth allocation (proportional time slice allocation)
  824. to such task groups. It is also used by bio throttling logic in
  825. block layer to implement upper limit in IO rates on a device.
  826. This option only enables generic Block IO controller infrastructure.
  827. One needs to also enable actual IO controlling logic/policy. For
  828. enabling proportional weight division of disk bandwidth in CFQ, set
  829. CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
  830. CONFIG_BLK_DEV_THROTTLING=y.
  831. See Documentation/cgroups/blkio-controller.txt for more information.
  832. config DEBUG_BLK_CGROUP
  833. bool "IO controller debugging"
  834. depends on BLK_CGROUP
  835. default n
  836. ---help---
  837. Enable some debugging help. Currently it exports additional stat
  838. files in a cgroup which can be useful for debugging.
  839. config CGROUP_WRITEBACK
  840. bool
  841. depends on MEMCG && BLK_CGROUP
  842. default y
  843. menuconfig CGROUP_SCHED
  844. bool "CPU controller"
  845. default n
  846. help
  847. This feature lets CPU scheduler recognize task groups and control CPU
  848. bandwidth allocation to such task groups. It uses cgroups to group
  849. tasks.
  850. if CGROUP_SCHED
  851. config FAIR_GROUP_SCHED
  852. bool "Group scheduling for SCHED_OTHER"
  853. depends on CGROUP_SCHED
  854. default CGROUP_SCHED
  855. config CFS_BANDWIDTH
  856. bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
  857. depends on FAIR_GROUP_SCHED
  858. default n
  859. help
  860. This option allows users to define CPU bandwidth rates (limits) for
  861. tasks running within the fair group scheduler. Groups with no limit
  862. set are considered to be unconstrained and will run with no
  863. restriction.
  864. See tip/Documentation/scheduler/sched-bwc.txt for more information.
  865. config RT_GROUP_SCHED
  866. bool "Group scheduling for SCHED_RR/FIFO"
  867. depends on CGROUP_SCHED
  868. default n
  869. help
  870. This feature lets you explicitly allocate real CPU bandwidth
  871. to task groups. If enabled, it will also make it impossible to
  872. schedule realtime tasks for non-root users until you allocate
  873. realtime bandwidth for them.
  874. See Documentation/scheduler/sched-rt-group.txt for more information.
  875. endif #CGROUP_SCHED
  876. config CGROUP_PIDS
  877. bool "PIDs controller"
  878. help
  879. Provides enforcement of process number limits in the scope of a
  880. cgroup. Any attempt to fork more processes than is allowed in the
  881. cgroup will fail. PIDs are fundamentally a global resource because it
  882. is fairly trivial to reach PID exhaustion before you reach even a
  883. conservative kmemcg limit. As a result, it is possible to grind a
  884. system to halt without being limited by other cgroup policies. The
  885. PIDs cgroup subsystem is designed to stop this from happening.
  886. It should be noted that organisational operations (such as attaching
  887. to a cgroup hierarchy will *not* be blocked by the PIDs subsystem),
  888. since the PIDs limit only affects a process's ability to fork, not to
  889. attach to a cgroup.
  890. config CGROUP_FREEZER
  891. bool "Freezer controller"
  892. help
  893. Provides a way to freeze and unfreeze all tasks in a
  894. cgroup.
  895. This option affects the ORIGINAL cgroup interface. The cgroup2 memory
  896. controller includes important in-kernel memory consumers per default.
  897. If you're using cgroup2, say N.
  898. config CGROUP_HUGETLB
  899. bool "HugeTLB controller"
  900. depends on HUGETLB_PAGE
  901. select PAGE_COUNTER
  902. default n
  903. help
  904. Provides a cgroup controller for HugeTLB pages.
  905. When you enable this, you can put a per cgroup limit on HugeTLB usage.
  906. The limit is enforced during page fault. Since HugeTLB doesn't
  907. support page reclaim, enforcing the limit at page fault time implies
  908. that, the application will get SIGBUS signal if it tries to access
  909. HugeTLB pages beyond its limit. This requires the application to know
  910. beforehand how much HugeTLB pages it would require for its use. The
  911. control group is tracked in the third page lru pointer. This means
  912. that we cannot use the controller with huge page less than 3 pages.
  913. config CPUSETS
  914. bool "Cpuset controller"
  915. help
  916. This option will let you create and manage CPUSETs which
  917. allow dynamically partitioning a system into sets of CPUs and
  918. Memory Nodes and assigning tasks to run only within those sets.
  919. This is primarily useful on large SMP or NUMA systems.
  920. Say N if unsure.
  921. config PROC_PID_CPUSET
  922. bool "Include legacy /proc/<pid>/cpuset file"
  923. depends on CPUSETS
  924. default y
  925. config CGROUP_DEVICE
  926. bool "Device controller"
  927. help
  928. Provides a cgroup controller implementing whitelists for
  929. devices which a process in the cgroup can mknod or open.
  930. config CGROUP_CPUACCT
  931. bool "Simple CPU accounting controller"
  932. help
  933. Provides a simple controller for monitoring the
  934. total CPU consumed by the tasks in a cgroup.
  935. config CGROUP_PERF
  936. bool "Perf controller"
  937. depends on PERF_EVENTS
  938. help
  939. This option extends the perf per-cpu mode to restrict monitoring
  940. to threads which belong to the cgroup specified and run on the
  941. designated cpu.
  942. Say N if unsure.
  943. config CGROUP_DEBUG
  944. bool "Example controller"
  945. default n
  946. help
  947. This option enables a simple controller that exports
  948. debugging information about the cgroups framework.
  949. Say N.
  950. endif # CGROUPS
  951. config CHECKPOINT_RESTORE
  952. bool "Checkpoint/restore support" if EXPERT
  953. select PROC_CHILDREN
  954. default n
  955. help
  956. Enables additional kernel features in a sake of checkpoint/restore.
  957. In particular it adds auxiliary prctl codes to setup process text,
  958. data and heap segment sizes, and a few additional /proc filesystem
  959. entries.
  960. If unsure, say N here.
  961. menuconfig NAMESPACES
  962. bool "Namespaces support" if EXPERT
  963. depends on MULTIUSER
  964. default !EXPERT
  965. help
  966. Provides the way to make tasks work with different objects using
  967. the same id. For example same IPC id may refer to different objects
  968. or same user id or pid may refer to different tasks when used in
  969. different namespaces.
  970. if NAMESPACES
  971. config UTS_NS
  972. bool "UTS namespace"
  973. default y
  974. help
  975. In this namespace tasks see different info provided with the
  976. uname() system call
  977. config IPC_NS
  978. bool "IPC namespace"
  979. depends on (SYSVIPC || POSIX_MQUEUE)
  980. default y
  981. help
  982. In this namespace tasks work with IPC ids which correspond to
  983. different IPC objects in different namespaces.
  984. config USER_NS
  985. bool "User namespace"
  986. default n
  987. help
  988. This allows containers, i.e. vservers, to use user namespaces
  989. to provide different user info for different servers.
  990. When user namespaces are enabled in the kernel it is
  991. recommended that the MEMCG option also be enabled and that
  992. user-space use the memory control groups to limit the amount
  993. of memory a memory unprivileged users can use.
  994. If unsure, say N.
  995. config PID_NS
  996. bool "PID Namespaces"
  997. default y
  998. help
  999. Support process id namespaces. This allows having multiple
  1000. processes with the same pid as long as they are in different
  1001. pid namespaces. This is a building block of containers.
  1002. config NET_NS
  1003. bool "Network namespace"
  1004. depends on NET
  1005. default y
  1006. help
  1007. Allow user space to create what appear to be multiple instances
  1008. of the network stack.
  1009. endif # NAMESPACES
  1010. config SCHED_AUTOGROUP
  1011. bool "Automatic process group scheduling"
  1012. select CGROUPS
  1013. select CGROUP_SCHED
  1014. select FAIR_GROUP_SCHED
  1015. help
  1016. This option optimizes the scheduler for common desktop workloads by
  1017. automatically creating and populating task groups. This separation
  1018. of workloads isolates aggressive CPU burners (like build jobs) from
  1019. desktop applications. Task group autogeneration is currently based
  1020. upon task session.
  1021. config SYSFS_DEPRECATED
  1022. bool "Enable deprecated sysfs features to support old userspace tools"
  1023. depends on SYSFS
  1024. default n
  1025. help
  1026. This option adds code that switches the layout of the "block" class
  1027. devices, to not show up in /sys/class/block/, but only in
  1028. /sys/block/.
  1029. This switch is only active when the sysfs.deprecated=1 boot option is
  1030. passed or the SYSFS_DEPRECATED_V2 option is set.
  1031. This option allows new kernels to run on old distributions and tools,
  1032. which might get confused by /sys/class/block/. Since 2007/2008 all
  1033. major distributions and tools handle this just fine.
  1034. Recent distributions and userspace tools after 2009/2010 depend on
  1035. the existence of /sys/class/block/, and will not work with this
  1036. option enabled.
  1037. Only if you are using a new kernel on an old distribution, you might
  1038. need to say Y here.
  1039. config SYSFS_DEPRECATED_V2
  1040. bool "Enable deprecated sysfs features by default"
  1041. default n
  1042. depends on SYSFS
  1043. depends on SYSFS_DEPRECATED
  1044. help
  1045. Enable deprecated sysfs by default.
  1046. See the CONFIG_SYSFS_DEPRECATED option for more details about this
  1047. option.
  1048. Only if you are using a new kernel on an old distribution, you might
  1049. need to say Y here. Even then, odds are you would not need it
  1050. enabled, you can always pass the boot option if absolutely necessary.
  1051. config RELAY
  1052. bool "Kernel->user space relay support (formerly relayfs)"
  1053. help
  1054. This option enables support for relay interface support in
  1055. certain file systems (such as debugfs).
  1056. It is designed to provide an efficient mechanism for tools and
  1057. facilities to relay large amounts of data from kernel space to
  1058. user space.
  1059. If unsure, say N.
  1060. config BLK_DEV_INITRD
  1061. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  1062. depends on BROKEN || !FRV
  1063. help
  1064. The initial RAM filesystem is a ramfs which is loaded by the
  1065. boot loader (loadlin or lilo) and that is mounted as root
  1066. before the normal boot procedure. It is typically used to
  1067. load modules needed to mount the "real" root file system,
  1068. etc. See <file:Documentation/initrd.txt> for details.
  1069. If RAM disk support (BLK_DEV_RAM) is also included, this
  1070. also enables initial RAM disk (initrd) support and adds
  1071. 15 Kbytes (more on some other architectures) to the kernel size.
  1072. If unsure say Y.
  1073. if BLK_DEV_INITRD
  1074. source "usr/Kconfig"
  1075. endif
  1076. config CC_OPTIMIZE_FOR_SIZE
  1077. bool "Optimize for size"
  1078. help
  1079. Enabling this option will pass "-Os" instead of "-O2" to
  1080. your compiler resulting in a smaller kernel.
  1081. If unsure, say N.
  1082. config SYSCTL
  1083. bool
  1084. config ANON_INODES
  1085. bool
  1086. config HAVE_UID16
  1087. bool
  1088. config SYSCTL_EXCEPTION_TRACE
  1089. bool
  1090. help
  1091. Enable support for /proc/sys/debug/exception-trace.
  1092. config SYSCTL_ARCH_UNALIGN_NO_WARN
  1093. bool
  1094. help
  1095. Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
  1096. Allows arch to define/use @no_unaligned_warning to possibly warn
  1097. about unaligned access emulation going on under the hood.
  1098. config SYSCTL_ARCH_UNALIGN_ALLOW
  1099. bool
  1100. help
  1101. Enable support for /proc/sys/kernel/unaligned-trap
  1102. Allows arches to define/use @unaligned_enabled to runtime toggle
  1103. the unaligned access emulation.
  1104. see arch/parisc/kernel/unaligned.c for reference
  1105. config HAVE_PCSPKR_PLATFORM
  1106. bool
  1107. # interpreter that classic socket filters depend on
  1108. config BPF
  1109. bool
  1110. menuconfig EXPERT
  1111. bool "Configure standard kernel features (expert users)"
  1112. # Unhide debug options, to make the on-by-default options visible
  1113. select DEBUG_KERNEL
  1114. help
  1115. This option allows certain base kernel options and settings
  1116. to be disabled or tweaked. This is for specialized
  1117. environments which can tolerate a "non-standard" kernel.
  1118. Only use this if you really know what you are doing.
  1119. config UID16
  1120. bool "Enable 16-bit UID system calls" if EXPERT
  1121. depends on HAVE_UID16 && MULTIUSER
  1122. default y
  1123. help
  1124. This enables the legacy 16-bit UID syscall wrappers.
  1125. config MULTIUSER
  1126. bool "Multiple users, groups and capabilities support" if EXPERT
  1127. default y
  1128. help
  1129. This option enables support for non-root users, groups and
  1130. capabilities.
  1131. If you say N here, all processes will run with UID 0, GID 0, and all
  1132. possible capabilities. Saying N here also compiles out support for
  1133. system calls related to UIDs, GIDs, and capabilities, such as setuid,
  1134. setgid, and capset.
  1135. If unsure, say Y here.
  1136. config SGETMASK_SYSCALL
  1137. bool "sgetmask/ssetmask syscalls support" if EXPERT
  1138. def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
  1139. ---help---
  1140. sys_sgetmask and sys_ssetmask are obsolete system calls
  1141. no longer supported in libc but still enabled by default in some
  1142. architectures.
  1143. If unsure, leave the default option here.
  1144. config SYSFS_SYSCALL
  1145. bool "Sysfs syscall support" if EXPERT
  1146. default y
  1147. ---help---
  1148. sys_sysfs is an obsolete system call no longer supported in libc.
  1149. Note that disabling this option is more secure but might break
  1150. compatibility with some systems.
  1151. If unsure say Y here.
  1152. config SYSCTL_SYSCALL
  1153. bool "Sysctl syscall support" if EXPERT
  1154. depends on PROC_SYSCTL
  1155. default n
  1156. select SYSCTL
  1157. ---help---
  1158. sys_sysctl uses binary paths that have been found challenging
  1159. to properly maintain and use. The interface in /proc/sys
  1160. using paths with ascii names is now the primary path to this
  1161. information.
  1162. Almost nothing using the binary sysctl interface so if you are
  1163. trying to save some space it is probably safe to disable this,
  1164. making your kernel marginally smaller.
  1165. If unsure say N here.
  1166. config KALLSYMS
  1167. bool "Load all symbols for debugging/ksymoops" if EXPERT
  1168. default y
  1169. help
  1170. Say Y here to let the kernel print out symbolic crash information and
  1171. symbolic stack backtraces. This increases the size of the kernel
  1172. somewhat, as all symbols have to be loaded into the kernel image.
  1173. config KALLSYMS_ALL
  1174. bool "Include all symbols in kallsyms"
  1175. depends on DEBUG_KERNEL && KALLSYMS
  1176. help
  1177. Normally kallsyms only contains the symbols of functions for nicer
  1178. OOPS messages and backtraces (i.e., symbols from the text and inittext
  1179. sections). This is sufficient for most cases. And only in very rare
  1180. cases (e.g., when a debugger is used) all symbols are required (e.g.,
  1181. names of variables from the data sections, etc).
  1182. This option makes sure that all symbols are loaded into the kernel
  1183. image (i.e., symbols from all sections) in cost of increased kernel
  1184. size (depending on the kernel configuration, it may be 300KiB or
  1185. something like this).
  1186. Say N unless you really need all symbols.
  1187. config KALLSYMS_ABSOLUTE_PERCPU
  1188. bool
  1189. default X86_64 && SMP
  1190. config PRINTK
  1191. default y
  1192. bool "Enable support for printk" if EXPERT
  1193. select IRQ_WORK
  1194. help
  1195. This option enables normal printk support. Removing it
  1196. eliminates most of the message strings from the kernel image
  1197. and makes the kernel more or less silent. As this makes it
  1198. very difficult to diagnose system problems, saying N here is
  1199. strongly discouraged.
  1200. config BUG
  1201. bool "BUG() support" if EXPERT
  1202. default y
  1203. help
  1204. Disabling this option eliminates support for BUG and WARN, reducing
  1205. the size of your kernel image and potentially quietly ignoring
  1206. numerous fatal conditions. You should only consider disabling this
  1207. option for embedded systems with no facilities for reporting errors.
  1208. Just say Y.
  1209. config ELF_CORE
  1210. depends on COREDUMP
  1211. default y
  1212. bool "Enable ELF core dumps" if EXPERT
  1213. help
  1214. Enable support for generating core dumps. Disabling saves about 4k.
  1215. config PCSPKR_PLATFORM
  1216. bool "Enable PC-Speaker support" if EXPERT
  1217. depends on HAVE_PCSPKR_PLATFORM
  1218. select I8253_LOCK
  1219. default y
  1220. help
  1221. This option allows to disable the internal PC-Speaker
  1222. support, saving some memory.
  1223. config BASE_FULL
  1224. default y
  1225. bool "Enable full-sized data structures for core" if EXPERT
  1226. help
  1227. Disabling this option reduces the size of miscellaneous core
  1228. kernel data structures. This saves memory on small machines,
  1229. but may reduce performance.
  1230. config FUTEX
  1231. bool "Enable futex support" if EXPERT
  1232. default y
  1233. select RT_MUTEXES
  1234. help
  1235. Disabling this option will cause the kernel to be built without
  1236. support for "fast userspace mutexes". The resulting kernel may not
  1237. run glibc-based applications correctly.
  1238. config HAVE_FUTEX_CMPXCHG
  1239. bool
  1240. depends on FUTEX
  1241. help
  1242. Architectures should select this if futex_atomic_cmpxchg_inatomic()
  1243. is implemented and always working. This removes a couple of runtime
  1244. checks.
  1245. config EPOLL
  1246. bool "Enable eventpoll support" if EXPERT
  1247. default y
  1248. select ANON_INODES
  1249. help
  1250. Disabling this option will cause the kernel to be built without
  1251. support for epoll family of system calls.
  1252. config SIGNALFD
  1253. bool "Enable signalfd() system call" if EXPERT
  1254. select ANON_INODES
  1255. default y
  1256. help
  1257. Enable the signalfd() system call that allows to receive signals
  1258. on a file descriptor.
  1259. If unsure, say Y.
  1260. config TIMERFD
  1261. bool "Enable timerfd() system call" if EXPERT
  1262. select ANON_INODES
  1263. default y
  1264. help
  1265. Enable the timerfd() system call that allows to receive timer
  1266. events on a file descriptor.
  1267. If unsure, say Y.
  1268. config EVENTFD
  1269. bool "Enable eventfd() system call" if EXPERT
  1270. select ANON_INODES
  1271. default y
  1272. help
  1273. Enable the eventfd() system call that allows to receive both
  1274. kernel notification (ie. KAIO) or userspace notifications.
  1275. If unsure, say Y.
  1276. # syscall, maps, verifier
  1277. config BPF_SYSCALL
  1278. bool "Enable bpf() system call"
  1279. select ANON_INODES
  1280. select BPF
  1281. default n
  1282. help
  1283. Enable the bpf() system call that allows to manipulate eBPF
  1284. programs and maps via file descriptors.
  1285. config SHMEM
  1286. bool "Use full shmem filesystem" if EXPERT
  1287. default y
  1288. depends on MMU
  1289. help
  1290. The shmem is an internal filesystem used to manage shared memory.
  1291. It is backed by swap and manages resource limits. It is also exported
  1292. to userspace as tmpfs if TMPFS is enabled. Disabling this
  1293. option replaces shmem and tmpfs with the much simpler ramfs code,
  1294. which may be appropriate on small systems without swap.
  1295. config AIO
  1296. bool "Enable AIO support" if EXPERT
  1297. default y
  1298. help
  1299. This option enables POSIX asynchronous I/O which may by used
  1300. by some high performance threaded applications. Disabling
  1301. this option saves about 7k.
  1302. config ADVISE_SYSCALLS
  1303. bool "Enable madvise/fadvise syscalls" if EXPERT
  1304. default y
  1305. help
  1306. This option enables the madvise and fadvise syscalls, used by
  1307. applications to advise the kernel about their future memory or file
  1308. usage, improving performance. If building an embedded system where no
  1309. applications use these syscalls, you can disable this option to save
  1310. space.
  1311. config USERFAULTFD
  1312. bool "Enable userfaultfd() system call"
  1313. select ANON_INODES
  1314. depends on MMU
  1315. help
  1316. Enable the userfaultfd() system call that allows to intercept and
  1317. handle page faults in userland.
  1318. config PCI_QUIRKS
  1319. default y
  1320. bool "Enable PCI quirk workarounds" if EXPERT
  1321. depends on PCI
  1322. help
  1323. This enables workarounds for various PCI chipset
  1324. bugs/quirks. Disable this only if your target machine is
  1325. unaffected by PCI quirks.
  1326. config MEMBARRIER
  1327. bool "Enable membarrier() system call" if EXPERT
  1328. default y
  1329. help
  1330. Enable the membarrier() system call that allows issuing memory
  1331. barriers across all running threads, which can be used to distribute
  1332. the cost of user-space memory barriers asymmetrically by transforming
  1333. pairs of memory barriers into pairs consisting of membarrier() and a
  1334. compiler barrier.
  1335. If unsure, say Y.
  1336. config EMBEDDED
  1337. bool "Embedded system"
  1338. option allnoconfig_y
  1339. select EXPERT
  1340. help
  1341. This option should be enabled if compiling the kernel for
  1342. an embedded system so certain expert options are available
  1343. for configuration.
  1344. config HAVE_PERF_EVENTS
  1345. bool
  1346. help
  1347. See tools/perf/design.txt for details.
  1348. config PERF_USE_VMALLOC
  1349. bool
  1350. help
  1351. See tools/perf/design.txt for details
  1352. menu "Kernel Performance Events And Counters"
  1353. config PERF_EVENTS
  1354. bool "Kernel performance events and counters"
  1355. default y if PROFILING
  1356. depends on HAVE_PERF_EVENTS
  1357. select ANON_INODES
  1358. select IRQ_WORK
  1359. select SRCU
  1360. help
  1361. Enable kernel support for various performance events provided
  1362. by software and hardware.
  1363. Software events are supported either built-in or via the
  1364. use of generic tracepoints.
  1365. Most modern CPUs support performance events via performance
  1366. counter registers. These registers count the number of certain
  1367. types of hw events: such as instructions executed, cachemisses
  1368. suffered, or branches mis-predicted - without slowing down the
  1369. kernel or applications. These registers can also trigger interrupts
  1370. when a threshold number of events have passed - and can thus be
  1371. used to profile the code that runs on that CPU.
  1372. The Linux Performance Event subsystem provides an abstraction of
  1373. these software and hardware event capabilities, available via a
  1374. system call and used by the "perf" utility in tools/perf/. It
  1375. provides per task and per CPU counters, and it provides event
  1376. capabilities on top of those.
  1377. Say Y if unsure.
  1378. config DEBUG_PERF_USE_VMALLOC
  1379. default n
  1380. bool "Debug: use vmalloc to back perf mmap() buffers"
  1381. depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
  1382. select PERF_USE_VMALLOC
  1383. help
  1384. Use vmalloc memory to back perf mmap() buffers.
  1385. Mostly useful for debugging the vmalloc code on platforms
  1386. that don't require it.
  1387. Say N if unsure.
  1388. endmenu
  1389. config VM_EVENT_COUNTERS
  1390. default y
  1391. bool "Enable VM event counters for /proc/vmstat" if EXPERT
  1392. help
  1393. VM event counters are needed for event counts to be shown.
  1394. This option allows the disabling of the VM event counters
  1395. on EXPERT systems. /proc/vmstat will only show page counts
  1396. if VM event counters are disabled.
  1397. config SLUB_DEBUG
  1398. default y
  1399. bool "Enable SLUB debugging support" if EXPERT
  1400. depends on SLUB && SYSFS
  1401. help
  1402. SLUB has extensive debug support features. Disabling these can
  1403. result in significant savings in code size. This also disables
  1404. SLUB sysfs support. /sys/slab will not exist and there will be
  1405. no support for cache validation etc.
  1406. config COMPAT_BRK
  1407. bool "Disable heap randomization"
  1408. default y
  1409. help
  1410. Randomizing heap placement makes heap exploits harder, but it
  1411. also breaks ancient binaries (including anything libc5 based).
  1412. This option changes the bootup default to heap randomization
  1413. disabled, and can be overridden at runtime by setting
  1414. /proc/sys/kernel/randomize_va_space to 2.
  1415. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  1416. choice
  1417. prompt "Choose SLAB allocator"
  1418. default SLUB
  1419. help
  1420. This option allows to select a slab allocator.
  1421. config SLAB
  1422. bool "SLAB"
  1423. help
  1424. The regular slab allocator that is established and known to work
  1425. well in all environments. It organizes cache hot objects in
  1426. per cpu and per node queues.
  1427. config SLUB
  1428. bool "SLUB (Unqueued Allocator)"
  1429. help
  1430. SLUB is a slab allocator that minimizes cache line usage
  1431. instead of managing queues of cached objects (SLAB approach).
  1432. Per cpu caching is realized using slabs of objects instead
  1433. of queues of objects. SLUB can use memory efficiently
  1434. and has enhanced diagnostics. SLUB is the default choice for
  1435. a slab allocator.
  1436. config SLOB
  1437. depends on EXPERT
  1438. bool "SLOB (Simple Allocator)"
  1439. help
  1440. SLOB replaces the stock allocator with a drastically simpler
  1441. allocator. SLOB is generally more space efficient but
  1442. does not perform as well on large systems.
  1443. endchoice
  1444. config SLUB_CPU_PARTIAL
  1445. default y
  1446. depends on SLUB && SMP
  1447. bool "SLUB per cpu partial cache"
  1448. help
  1449. Per cpu partial caches accellerate objects allocation and freeing
  1450. that is local to a processor at the price of more indeterminism
  1451. in the latency of the free. On overflow these caches will be cleared
  1452. which requires the taking of locks that may cause latency spikes.
  1453. Typically one would choose no for a realtime system.
  1454. config MMAP_ALLOW_UNINITIALIZED
  1455. bool "Allow mmapped anonymous memory to be uninitialized"
  1456. depends on EXPERT && !MMU
  1457. default n
  1458. help
  1459. Normally, and according to the Linux spec, anonymous memory obtained
  1460. from mmap() has it's contents cleared before it is passed to
  1461. userspace. Enabling this config option allows you to request that
  1462. mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
  1463. providing a huge performance boost. If this option is not enabled,
  1464. then the flag will be ignored.
  1465. This is taken advantage of by uClibc's malloc(), and also by
  1466. ELF-FDPIC binfmt's brk and stack allocator.
  1467. Because of the obvious security issues, this option should only be
  1468. enabled on embedded devices where you control what is run in
  1469. userspace. Since that isn't generally a problem on no-MMU systems,
  1470. it is normally safe to say Y here.
  1471. See Documentation/nommu-mmap.txt for more information.
  1472. config SYSTEM_DATA_VERIFICATION
  1473. def_bool n
  1474. select SYSTEM_TRUSTED_KEYRING
  1475. select KEYS
  1476. select CRYPTO
  1477. select ASYMMETRIC_KEY_TYPE
  1478. select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
  1479. select PUBLIC_KEY_ALGO_RSA
  1480. select ASN1
  1481. select OID_REGISTRY
  1482. select X509_CERTIFICATE_PARSER
  1483. select PKCS7_MESSAGE_PARSER
  1484. help
  1485. Provide PKCS#7 message verification using the contents of the system
  1486. trusted keyring to provide public keys. This then can be used for
  1487. module verification, kexec image verification and firmware blob
  1488. verification.
  1489. config PROFILING
  1490. bool "Profiling support"
  1491. help
  1492. Say Y here to enable the extended profiling support mechanisms used
  1493. by profilers such as OProfile.
  1494. #
  1495. # Place an empty function call at each tracepoint site. Can be
  1496. # dynamically changed for a probe function.
  1497. #
  1498. config TRACEPOINTS
  1499. bool
  1500. source "arch/Kconfig"
  1501. endmenu # General setup
  1502. config HAVE_GENERIC_DMA_COHERENT
  1503. bool
  1504. default n
  1505. config SLABINFO
  1506. bool
  1507. depends on PROC_FS
  1508. depends on SLAB || SLUB_DEBUG
  1509. default y
  1510. config RT_MUTEXES
  1511. bool
  1512. config BASE_SMALL
  1513. int
  1514. default 0 if BASE_FULL
  1515. default 1 if !BASE_FULL
  1516. menuconfig MODULES
  1517. bool "Enable loadable module support"
  1518. option modules
  1519. help
  1520. Kernel modules are small pieces of compiled code which can
  1521. be inserted in the running kernel, rather than being
  1522. permanently built into the kernel. You use the "modprobe"
  1523. tool to add (and sometimes remove) them. If you say Y here,
  1524. many parts of the kernel can be built as modules (by
  1525. answering M instead of Y where indicated): this is most
  1526. useful for infrequently used options which are not required
  1527. for booting. For more information, see the man pages for
  1528. modprobe, lsmod, modinfo, insmod and rmmod.
  1529. If you say Y here, you will need to run "make
  1530. modules_install" to put the modules under /lib/modules/
  1531. where modprobe can find them (you may need to be root to do
  1532. this).
  1533. If unsure, say Y.
  1534. if MODULES
  1535. config MODULE_FORCE_LOAD
  1536. bool "Forced module loading"
  1537. default n
  1538. help
  1539. Allow loading of modules without version information (ie. modprobe
  1540. --force). Forced module loading sets the 'F' (forced) taint flag and
  1541. is usually a really bad idea.
  1542. config MODULE_UNLOAD
  1543. bool "Module unloading"
  1544. help
  1545. Without this option you will not be able to unload any
  1546. modules (note that some modules may not be unloadable
  1547. anyway), which makes your kernel smaller, faster
  1548. and simpler. If unsure, say Y.
  1549. config MODULE_FORCE_UNLOAD
  1550. bool "Forced module unloading"
  1551. depends on MODULE_UNLOAD
  1552. help
  1553. This option allows you to force a module to unload, even if the
  1554. kernel believes it is unsafe: the kernel will remove the module
  1555. without waiting for anyone to stop using it (using the -f option to
  1556. rmmod). This is mainly for kernel developers and desperate users.
  1557. If unsure, say N.
  1558. config MODVERSIONS
  1559. bool "Module versioning support"
  1560. help
  1561. Usually, you have to use modules compiled with your kernel.
  1562. Saying Y here makes it sometimes possible to use modules
  1563. compiled for different kernels, by adding enough information
  1564. to the modules to (hopefully) spot any changes which would
  1565. make them incompatible with the kernel you are running. If
  1566. unsure, say N.
  1567. config MODULE_SRCVERSION_ALL
  1568. bool "Source checksum for all modules"
  1569. help
  1570. Modules which contain a MODULE_VERSION get an extra "srcversion"
  1571. field inserted into their modinfo section, which contains a
  1572. sum of the source files which made it. This helps maintainers
  1573. see exactly which source was used to build a module (since
  1574. others sometimes change the module source without updating
  1575. the version). With this option, such a "srcversion" field
  1576. will be created for all modules. If unsure, say N.
  1577. config MODULE_SIG
  1578. bool "Module signature verification"
  1579. depends on MODULES
  1580. select SYSTEM_DATA_VERIFICATION
  1581. help
  1582. Check modules for valid signatures upon load: the signature
  1583. is simply appended to the module. For more information see
  1584. Documentation/module-signing.txt.
  1585. Note that this option adds the OpenSSL development packages as a
  1586. kernel build dependency so that the signing tool can use its crypto
  1587. library.
  1588. !!!WARNING!!! If you enable this option, you MUST make sure that the
  1589. module DOES NOT get stripped after being signed. This includes the
  1590. debuginfo strip done by some packagers (such as rpmbuild) and
  1591. inclusion into an initramfs that wants the module size reduced.
  1592. config MODULE_SIG_FORCE
  1593. bool "Require modules to be validly signed"
  1594. depends on MODULE_SIG
  1595. help
  1596. Reject unsigned modules or signed modules for which we don't have a
  1597. key. Without this, such modules will simply taint the kernel.
  1598. config MODULE_SIG_ALL
  1599. bool "Automatically sign all modules"
  1600. default y
  1601. depends on MODULE_SIG
  1602. help
  1603. Sign all modules during make modules_install. Without this option,
  1604. modules must be signed manually, using the scripts/sign-file tool.
  1605. comment "Do not forget to sign required modules with scripts/sign-file"
  1606. depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
  1607. choice
  1608. prompt "Which hash algorithm should modules be signed with?"
  1609. depends on MODULE_SIG
  1610. help
  1611. This determines which sort of hashing algorithm will be used during
  1612. signature generation. This algorithm _must_ be built into the kernel
  1613. directly so that signature verification can take place. It is not
  1614. possible to load a signed module containing the algorithm to check
  1615. the signature on that module.
  1616. config MODULE_SIG_SHA1
  1617. bool "Sign modules with SHA-1"
  1618. select CRYPTO_SHA1
  1619. config MODULE_SIG_SHA224
  1620. bool "Sign modules with SHA-224"
  1621. select CRYPTO_SHA256
  1622. config MODULE_SIG_SHA256
  1623. bool "Sign modules with SHA-256"
  1624. select CRYPTO_SHA256
  1625. config MODULE_SIG_SHA384
  1626. bool "Sign modules with SHA-384"
  1627. select CRYPTO_SHA512
  1628. config MODULE_SIG_SHA512
  1629. bool "Sign modules with SHA-512"
  1630. select CRYPTO_SHA512
  1631. endchoice
  1632. config MODULE_SIG_HASH
  1633. string
  1634. depends on MODULE_SIG
  1635. default "sha1" if MODULE_SIG_SHA1
  1636. default "sha224" if MODULE_SIG_SHA224
  1637. default "sha256" if MODULE_SIG_SHA256
  1638. default "sha384" if MODULE_SIG_SHA384
  1639. default "sha512" if MODULE_SIG_SHA512
  1640. config MODULE_COMPRESS
  1641. bool "Compress modules on installation"
  1642. depends on MODULES
  1643. help
  1644. Compresses kernel modules when 'make modules_install' is run; gzip or
  1645. xz depending on "Compression algorithm" below.
  1646. module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
  1647. Out-of-tree kernel modules installed using Kbuild will also be
  1648. compressed upon installation.
  1649. Note: for modules inside an initrd or initramfs, it's more efficient
  1650. to compress the whole initrd or initramfs instead.
  1651. Note: This is fully compatible with signed modules.
  1652. If in doubt, say N.
  1653. choice
  1654. prompt "Compression algorithm"
  1655. depends on MODULE_COMPRESS
  1656. default MODULE_COMPRESS_GZIP
  1657. help
  1658. This determines which sort of compression will be used during
  1659. 'make modules_install'.
  1660. GZIP (default) and XZ are supported.
  1661. config MODULE_COMPRESS_GZIP
  1662. bool "GZIP"
  1663. config MODULE_COMPRESS_XZ
  1664. bool "XZ"
  1665. endchoice
  1666. endif # MODULES
  1667. config MODULES_TREE_LOOKUP
  1668. def_bool y
  1669. depends on PERF_EVENTS || TRACING
  1670. config INIT_ALL_POSSIBLE
  1671. bool
  1672. help
  1673. Back when each arch used to define their own cpu_online_mask and
  1674. cpu_possible_mask, some of them chose to initialize cpu_possible_mask
  1675. with all 1s, and others with all 0s. When they were centralised,
  1676. it was better to provide this option than to break all the archs
  1677. and have several arch maintainers pursuing me down dark alleys.
  1678. source "block/Kconfig"
  1679. config PREEMPT_NOTIFIERS
  1680. bool
  1681. config PADATA
  1682. depends on SMP
  1683. bool
  1684. # Can be selected by architectures with broken toolchains
  1685. # that get confused by correct const<->read_only section
  1686. # mappings
  1687. config BROKEN_RODATA
  1688. bool
  1689. config ASN1
  1690. tristate
  1691. help
  1692. Build a simple ASN.1 grammar compiler that produces a bytecode output
  1693. that can be interpreted by the ASN.1 stream decoder and used to
  1694. inform it as to what tags are to be expected in a stream and what
  1695. functions to call on what tags.
  1696. source "kernel/Kconfig.locks"