Kconfig 72 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. config THREAD_INFO_IN_TASK
  24. bool
  25. help
  26. Select this to move thread_info off the stack into task_struct. To
  27. make this work, an arch will need to remove all thread_info fields
  28. except flags and fix any runtime bugs.
  29. One subtle change that will be needed is to use try_get_task_stack()
  30. and put_task_stack() in save_thread_stack_tsk() and get_wchan().
  31. menu "General setup"
  32. config BROKEN
  33. bool
  34. config BROKEN_ON_SMP
  35. bool
  36. depends on BROKEN || !SMP
  37. default y
  38. config INIT_ENV_ARG_LIMIT
  39. int
  40. default 32 if !UML
  41. default 128 if UML
  42. help
  43. Maximum of each of the number of arguments and environment
  44. variables passed to init from the kernel command line.
  45. config CROSS_COMPILE
  46. string "Cross-compiler tool prefix"
  47. help
  48. Same as running 'make CROSS_COMPILE=prefix-' but stored for
  49. default make runs in this kernel build directory. You don't
  50. need to set this unless you want the configured kernel build
  51. directory to select the cross-compiler automatically.
  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 HAVE_KERNEL_GZIP
  91. bool
  92. config HAVE_KERNEL_BZIP2
  93. bool
  94. config HAVE_KERNEL_LZMA
  95. bool
  96. config HAVE_KERNEL_XZ
  97. bool
  98. config HAVE_KERNEL_LZO
  99. bool
  100. config HAVE_KERNEL_LZ4
  101. bool
  102. choice
  103. prompt "Kernel compression mode"
  104. default KERNEL_GZIP
  105. depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
  106. help
  107. The linux kernel is a kind of self-extracting executable.
  108. Several compression algorithms are available, which differ
  109. in efficiency, compression and decompression speed.
  110. Compression speed is only relevant when building a kernel.
  111. Decompression speed is relevant at each boot.
  112. If you have any problems with bzip2 or lzma compressed
  113. kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
  114. version of this functionality (bzip2 only), for 2.4, was
  115. supplied by Christian Ludwig)
  116. High compression options are mostly useful for users, who
  117. are low on disk space (embedded systems), but for whom ram
  118. size matters less.
  119. If in doubt, select 'gzip'
  120. config KERNEL_GZIP
  121. bool "Gzip"
  122. depends on HAVE_KERNEL_GZIP
  123. help
  124. The old and tried gzip compression. It provides a good balance
  125. between compression ratio and decompression speed.
  126. config KERNEL_BZIP2
  127. bool "Bzip2"
  128. depends on HAVE_KERNEL_BZIP2
  129. help
  130. Its compression ratio and speed is intermediate.
  131. Decompression speed is slowest among the choices. The kernel
  132. size is about 10% smaller with bzip2, in comparison to gzip.
  133. Bzip2 uses a large amount of memory. For modern kernels you
  134. will need at least 8MB RAM or more for booting.
  135. config KERNEL_LZMA
  136. bool "LZMA"
  137. depends on HAVE_KERNEL_LZMA
  138. help
  139. This compression algorithm's ratio is best. Decompression speed
  140. is between gzip and bzip2. Compression is slowest.
  141. The kernel size is about 33% smaller with LZMA in comparison to gzip.
  142. config KERNEL_XZ
  143. bool "XZ"
  144. depends on HAVE_KERNEL_XZ
  145. help
  146. XZ uses the LZMA2 algorithm and instruction set specific
  147. BCJ filters which can improve compression ratio of executable
  148. code. The size of the kernel is about 30% smaller with XZ in
  149. comparison to gzip. On architectures for which there is a BCJ
  150. filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
  151. will create a few percent smaller kernel than plain LZMA.
  152. The speed is about the same as with LZMA: The decompression
  153. speed of XZ is better than that of bzip2 but worse than gzip
  154. and LZO. Compression is slow.
  155. config KERNEL_LZO
  156. bool "LZO"
  157. depends on HAVE_KERNEL_LZO
  158. help
  159. Its compression ratio is the poorest among the choices. The kernel
  160. size is about 10% bigger than gzip; however its speed
  161. (both compression and decompression) is the fastest.
  162. config KERNEL_LZ4
  163. bool "LZ4"
  164. depends on HAVE_KERNEL_LZ4
  165. help
  166. LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
  167. A preliminary version of LZ4 de/compression tool is available at
  168. <https://code.google.com/p/lz4/>.
  169. Its compression ratio is worse than LZO. The size of the kernel
  170. is about 8% bigger than LZO. But the decompression speed is
  171. faster than LZO.
  172. endchoice
  173. config DEFAULT_HOSTNAME
  174. string "Default hostname"
  175. default "(none)"
  176. help
  177. This option determines the default system hostname before userspace
  178. calls sethostname(2). The kernel traditionally uses "(none)" here,
  179. but you may wish to use a different default here to make a minimal
  180. system more usable with less configuration.
  181. config SWAP
  182. bool "Support for paging of anonymous memory (swap)"
  183. depends on MMU && BLOCK
  184. default y
  185. help
  186. This option allows you to choose whether you want to have support
  187. for so called swap devices or swap files in your kernel that are
  188. used to provide more virtual memory than the actual RAM present
  189. in your computer. If unsure say Y.
  190. config SYSVIPC
  191. bool "System V IPC"
  192. ---help---
  193. Inter Process Communication is a suite of library functions and
  194. system calls which let processes (running programs) synchronize and
  195. exchange information. It is generally considered to be a good thing,
  196. and some programs won't run unless you say Y here. In particular, if
  197. you want to run the DOS emulator dosemu under Linux (read the
  198. DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
  199. you'll need to say Y here.
  200. You can find documentation about IPC with "info ipc" and also in
  201. section 6.4 of the Linux Programmer's Guide, available from
  202. <http://www.tldp.org/guides.html>.
  203. config SYSVIPC_SYSCTL
  204. bool
  205. depends on SYSVIPC
  206. depends on SYSCTL
  207. default y
  208. config POSIX_MQUEUE
  209. bool "POSIX Message Queues"
  210. depends on NET
  211. ---help---
  212. POSIX variant of message queues is a part of IPC. In POSIX message
  213. queues every message has a priority which decides about succession
  214. of receiving it by a process. If you want to compile and run
  215. programs written e.g. for Solaris with use of its POSIX message
  216. queues (functions mq_*) say Y here.
  217. POSIX message queues are visible as a filesystem called 'mqueue'
  218. and can be mounted somewhere if you want to do filesystem
  219. operations on message queues.
  220. If unsure, say Y.
  221. config POSIX_MQUEUE_SYSCTL
  222. bool
  223. depends on POSIX_MQUEUE
  224. depends on SYSCTL
  225. default y
  226. config CROSS_MEMORY_ATTACH
  227. bool "Enable process_vm_readv/writev syscalls"
  228. depends on MMU
  229. default y
  230. help
  231. Enabling this option adds the system calls process_vm_readv and
  232. process_vm_writev which allow a process with the correct privileges
  233. to directly read from or write to another process' address space.
  234. See the man page for more details.
  235. config FHANDLE
  236. bool "open by fhandle syscalls" if EXPERT
  237. select EXPORTFS
  238. default y
  239. help
  240. If you say Y here, a user level program will be able to map
  241. file names to handle and then later use the handle for
  242. different file system operations. This is useful in implementing
  243. userspace file servers, which now track files using handles instead
  244. of names. The handle would remain the same even if file names
  245. get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
  246. syscalls.
  247. config USELIB
  248. bool "uselib syscall"
  249. def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
  250. help
  251. This option enables the uselib syscall, a system call used in the
  252. dynamic linker from libc5 and earlier. glibc does not use this
  253. system call. If you intend to run programs built on libc5 or
  254. earlier, you may need to enable this syscall. Current systems
  255. running glibc can safely disable this.
  256. config AUDIT
  257. bool "Auditing support"
  258. depends on NET
  259. help
  260. Enable auditing infrastructure that can be used with another
  261. kernel subsystem, such as SELinux (which requires this for
  262. logging of avc messages output). System call auditing is included
  263. on architectures which support it.
  264. config HAVE_ARCH_AUDITSYSCALL
  265. bool
  266. config AUDITSYSCALL
  267. def_bool y
  268. depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
  269. config AUDIT_WATCH
  270. def_bool y
  271. depends on AUDITSYSCALL
  272. select FSNOTIFY
  273. config AUDIT_TREE
  274. def_bool y
  275. depends on AUDITSYSCALL
  276. select FSNOTIFY
  277. source "kernel/irq/Kconfig"
  278. source "kernel/time/Kconfig"
  279. menu "CPU/Task time and stats accounting"
  280. config VIRT_CPU_ACCOUNTING
  281. bool
  282. choice
  283. prompt "Cputime accounting"
  284. default TICK_CPU_ACCOUNTING if !PPC64
  285. default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
  286. # Kind of a stub config for the pure tick based cputime accounting
  287. config TICK_CPU_ACCOUNTING
  288. bool "Simple tick based cputime accounting"
  289. depends on !S390 && !NO_HZ_FULL
  290. help
  291. This is the basic tick based cputime accounting that maintains
  292. statistics about user, system and idle time spent on per jiffies
  293. granularity.
  294. If unsure, say Y.
  295. config VIRT_CPU_ACCOUNTING_NATIVE
  296. bool "Deterministic task and CPU time accounting"
  297. depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
  298. select VIRT_CPU_ACCOUNTING
  299. help
  300. Select this option to enable more accurate task and CPU time
  301. accounting. This is done by reading a CPU counter on each
  302. kernel entry and exit and on transitions within the kernel
  303. between system, softirq and hardirq state, so there is a
  304. small performance impact. In the case of s390 or IBM POWER > 5,
  305. this also enables accounting of stolen time on logically-partitioned
  306. systems.
  307. config VIRT_CPU_ACCOUNTING_GEN
  308. bool "Full dynticks CPU time accounting"
  309. depends on HAVE_CONTEXT_TRACKING
  310. depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
  311. select VIRT_CPU_ACCOUNTING
  312. select CONTEXT_TRACKING
  313. help
  314. Select this option to enable task and CPU time accounting on full
  315. dynticks systems. This accounting is implemented by watching every
  316. kernel-user boundaries using the context tracking subsystem.
  317. The accounting is thus performed at the expense of some significant
  318. overhead.
  319. For now this is only useful if you are working on the full
  320. dynticks subsystem development.
  321. If unsure, say N.
  322. endchoice
  323. config IRQ_TIME_ACCOUNTING
  324. bool "Fine granularity task level IRQ time accounting"
  325. depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
  326. help
  327. Select this option to enable fine granularity task irq time
  328. accounting. This is done by reading a timestamp on each
  329. transitions between softirq and hardirq state, so there can be a
  330. small performance impact.
  331. If in doubt, say N here.
  332. config SCHED_WALT
  333. bool "Support window based load tracking"
  334. depends on SMP
  335. help
  336. This feature will allow the scheduler to maintain a tunable window
  337. based set of metrics for tasks and runqueues. These metrics can be
  338. used to guide task placement as well as task frequency requirements
  339. for cpufreq governors.
  340. config BSD_PROCESS_ACCT
  341. bool "BSD Process Accounting"
  342. depends on MULTIUSER
  343. help
  344. If you say Y here, a user level program will be able to instruct the
  345. kernel (via a special system call) to write process accounting
  346. information to a file: whenever a process exits, information about
  347. that process will be appended to the file by the kernel. The
  348. information includes things such as creation time, owning user,
  349. command name, memory usage, controlling terminal etc. (the complete
  350. list is in the struct acct in <file:include/linux/acct.h>). It is
  351. up to the user level program to do useful things with this
  352. information. This is generally a good idea, so say Y.
  353. config BSD_PROCESS_ACCT_V3
  354. bool "BSD Process Accounting version 3 file format"
  355. depends on BSD_PROCESS_ACCT
  356. default n
  357. help
  358. If you say Y here, the process accounting information is written
  359. in a new file format that also logs the process IDs of each
  360. process and it's parent. Note that this file format is incompatible
  361. with previous v0/v1/v2 file formats, so you will need updated tools
  362. for processing it. A preliminary version of these tools is available
  363. at <http://www.gnu.org/software/acct/>.
  364. config TASKSTATS
  365. bool "Export task/process statistics through netlink"
  366. depends on NET
  367. depends on MULTIUSER
  368. default n
  369. help
  370. Export selected statistics for tasks/processes through the
  371. generic netlink interface. Unlike BSD process accounting, the
  372. statistics are available during the lifetime of tasks/processes as
  373. responses to commands. Like BSD accounting, they are sent to user
  374. space on task exit.
  375. Say N if unsure.
  376. config TASK_DELAY_ACCT
  377. bool "Enable per-task delay accounting"
  378. depends on TASKSTATS
  379. select SCHED_INFO
  380. help
  381. Collect information on time spent by a task waiting for system
  382. resources like cpu, synchronous block I/O completion and swapping
  383. in pages. Such statistics can help in setting a task's priorities
  384. relative to other tasks for cpu, io, rss limits etc.
  385. Say N if unsure.
  386. config TASK_XACCT
  387. bool "Enable extended accounting over taskstats"
  388. depends on TASKSTATS
  389. help
  390. Collect extended task accounting data and send the data
  391. to userland for processing over the taskstats interface.
  392. Say N if unsure.
  393. config TASK_IO_ACCOUNTING
  394. bool "Enable per-task storage I/O accounting"
  395. depends on TASK_XACCT
  396. help
  397. Collect information on the number of bytes of storage I/O which this
  398. task has caused.
  399. Say N if unsure.
  400. endmenu # "CPU/Task time and stats accounting"
  401. menu "RCU Subsystem"
  402. config TREE_RCU
  403. bool
  404. default y if !PREEMPT && SMP
  405. help
  406. This option selects the RCU implementation that is
  407. designed for very large SMP system with hundreds or
  408. thousands of CPUs. It also scales down nicely to
  409. smaller systems.
  410. config PREEMPT_RCU
  411. bool
  412. default y if PREEMPT
  413. help
  414. This option selects the RCU implementation that is
  415. designed for very large SMP systems with hundreds or
  416. thousands of CPUs, but for which real-time response
  417. is also required. It also scales down nicely to
  418. smaller systems.
  419. Select this option if you are unsure.
  420. config TINY_RCU
  421. bool
  422. default y if !PREEMPT && !SMP
  423. help
  424. This option selects the RCU implementation that is
  425. designed for UP systems from which real-time response
  426. is not required. This option greatly reduces the
  427. memory footprint of RCU.
  428. config RCU_EXPERT
  429. bool "Make expert-level adjustments to RCU configuration"
  430. default n
  431. help
  432. This option needs to be enabled if you wish to make
  433. expert-level adjustments to RCU configuration. By default,
  434. no such adjustments can be made, which has the often-beneficial
  435. side-effect of preventing "make oldconfig" from asking you all
  436. sorts of detailed questions about how you would like numerous
  437. obscure RCU options to be set up.
  438. Say Y if you need to make expert-level adjustments to RCU.
  439. Say N if you are unsure.
  440. config SRCU
  441. bool
  442. help
  443. This option selects the sleepable version of RCU. This version
  444. permits arbitrary sleeping or blocking within RCU read-side critical
  445. sections.
  446. config TASKS_RCU
  447. bool
  448. default n
  449. depends on !UML
  450. select SRCU
  451. help
  452. This option enables a task-based RCU implementation that uses
  453. only voluntary context switch (not preemption!), idle, and
  454. user-mode execution as quiescent states.
  455. config RCU_STALL_COMMON
  456. def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
  457. help
  458. This option enables RCU CPU stall code that is common between
  459. the TINY and TREE variants of RCU. The purpose is to allow
  460. the tiny variants to disable RCU CPU stall warnings, while
  461. making these warnings mandatory for the tree variants.
  462. config CONTEXT_TRACKING
  463. bool
  464. config CONTEXT_TRACKING_FORCE
  465. bool "Force context tracking"
  466. depends on CONTEXT_TRACKING
  467. default y if !NO_HZ_FULL
  468. help
  469. The major pre-requirement for full dynticks to work is to
  470. support the context tracking subsystem. But there are also
  471. other dependencies to provide in order to make the full
  472. dynticks working.
  473. This option stands for testing when an arch implements the
  474. context tracking backend but doesn't yet fullfill all the
  475. requirements to make the full dynticks feature working.
  476. Without the full dynticks, there is no way to test the support
  477. for context tracking and the subsystems that rely on it: RCU
  478. userspace extended quiescent state and tickless cputime
  479. accounting. This option copes with the absence of the full
  480. dynticks subsystem by forcing the context tracking on all
  481. CPUs in the system.
  482. Say Y only if you're working on the development of an
  483. architecture backend for the context tracking.
  484. Say N otherwise, this option brings an overhead that you
  485. don't want in production.
  486. config RCU_FANOUT
  487. int "Tree-based hierarchical RCU fanout value"
  488. range 2 64 if 64BIT
  489. range 2 32 if !64BIT
  490. depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
  491. default 64 if 64BIT
  492. default 32 if !64BIT
  493. help
  494. This option controls the fanout of hierarchical implementations
  495. of RCU, allowing RCU to work efficiently on machines with
  496. large numbers of CPUs. This value must be at least the fourth
  497. root of NR_CPUS, which allows NR_CPUS to be insanely large.
  498. The default value of RCU_FANOUT should be used for production
  499. systems, but if you are stress-testing the RCU implementation
  500. itself, small RCU_FANOUT values allow you to test large-system
  501. code paths on small(er) systems.
  502. Select a specific number if testing RCU itself.
  503. Take the default if unsure.
  504. config RCU_FANOUT_LEAF
  505. int "Tree-based hierarchical RCU leaf-level fanout value"
  506. range 2 64 if 64BIT
  507. range 2 32 if !64BIT
  508. depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
  509. default 16
  510. help
  511. This option controls the leaf-level fanout of hierarchical
  512. implementations of RCU, and allows trading off cache misses
  513. against lock contention. Systems that synchronize their
  514. scheduling-clock interrupts for energy-efficiency reasons will
  515. want the default because the smaller leaf-level fanout keeps
  516. lock contention levels acceptably low. Very large systems
  517. (hundreds or thousands of CPUs) will instead want to set this
  518. value to the maximum value possible in order to reduce the
  519. number of cache misses incurred during RCU's grace-period
  520. initialization. These systems tend to run CPU-bound, and thus
  521. are not helped by synchronized interrupts, and thus tend to
  522. skew them, which reduces lock contention enough that large
  523. leaf-level fanouts work well.
  524. Select a specific number if testing RCU itself.
  525. Select the maximum permissible value for large systems.
  526. Take the default if unsure.
  527. config RCU_FAST_NO_HZ
  528. bool "Accelerate last non-dyntick-idle CPU's grace periods"
  529. depends on NO_HZ_COMMON && SMP && RCU_EXPERT
  530. default n
  531. help
  532. This option permits CPUs to enter dynticks-idle state even if
  533. they have RCU callbacks queued, and prevents RCU from waking
  534. these CPUs up more than roughly once every four jiffies (by
  535. default, you can adjust this using the rcutree.rcu_idle_gp_delay
  536. parameter), thus improving energy efficiency. On the other
  537. hand, this option increases the duration of RCU grace periods,
  538. for example, slowing down synchronize_rcu().
  539. Say Y if energy efficiency is critically important, and you
  540. don't care about increased grace-period durations.
  541. Say N if you are unsure.
  542. config TREE_RCU_TRACE
  543. def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
  544. select DEBUG_FS
  545. help
  546. This option provides tracing for the TREE_RCU and
  547. PREEMPT_RCU implementations, permitting Makefile to
  548. trivially select kernel/rcutree_trace.c.
  549. config RCU_BOOST
  550. bool "Enable RCU priority boosting"
  551. depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT
  552. default n
  553. help
  554. This option boosts the priority of preempted RCU readers that
  555. block the current preemptible RCU grace period for too long.
  556. This option also prevents heavy loads from blocking RCU
  557. callback invocation for all flavors of RCU.
  558. Say Y here if you are working with real-time apps or heavy loads
  559. Say N here if you are unsure.
  560. config RCU_KTHREAD_PRIO
  561. int "Real-time priority to use for RCU worker threads"
  562. range 1 99 if RCU_BOOST
  563. range 0 99 if !RCU_BOOST
  564. default 1 if RCU_BOOST
  565. default 0 if !RCU_BOOST
  566. depends on RCU_EXPERT
  567. help
  568. This option specifies the SCHED_FIFO priority value that will be
  569. assigned to the rcuc/n and rcub/n threads and is also the value
  570. used for RCU_BOOST (if enabled). If you are working with a
  571. real-time application that has one or more CPU-bound threads
  572. running at a real-time priority level, you should set
  573. RCU_KTHREAD_PRIO to a priority higher than the highest-priority
  574. real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO
  575. value of 1 is appropriate in the common case, which is real-time
  576. applications that do not have any CPU-bound threads.
  577. Some real-time applications might not have a single real-time
  578. thread that saturates a given CPU, but instead might have
  579. multiple real-time threads that, taken together, fully utilize
  580. that CPU. In this case, you should set RCU_KTHREAD_PRIO to
  581. a priority higher than the lowest-priority thread that is
  582. conspiring to prevent the CPU from running any non-real-time
  583. tasks. For example, if one thread at priority 10 and another
  584. thread at priority 5 are between themselves fully consuming
  585. the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
  586. set to priority 6 or higher.
  587. Specify the real-time priority, or take the default if unsure.
  588. config RCU_BOOST_DELAY
  589. int "Milliseconds to delay boosting after RCU grace-period start"
  590. range 0 3000
  591. depends on RCU_BOOST
  592. default 500
  593. help
  594. This option specifies the time to wait after the beginning of
  595. a given grace period before priority-boosting preempted RCU
  596. readers blocking that grace period. Note that any RCU reader
  597. blocking an expedited RCU grace period is boosted immediately.
  598. Accept the default if unsure.
  599. config RCU_NOCB_CPU
  600. bool "Offload RCU callback processing from boot-selected CPUs"
  601. depends on TREE_RCU || PREEMPT_RCU
  602. depends on RCU_EXPERT || NO_HZ_FULL
  603. default n
  604. help
  605. Use this option to reduce OS jitter for aggressive HPC or
  606. real-time workloads. It can also be used to offload RCU
  607. callback invocation to energy-efficient CPUs in battery-powered
  608. asymmetric multiprocessors.
  609. This option offloads callback invocation from the set of
  610. CPUs specified at boot time by the rcu_nocbs parameter.
  611. For each such CPU, a kthread ("rcuox/N") will be created to
  612. invoke callbacks, where the "N" is the CPU being offloaded,
  613. and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
  614. "s" for RCU-sched. Nothing prevents this kthread from running
  615. on the specified CPUs, but (1) the kthreads may be preempted
  616. between each callback, and (2) affinity or cgroups can be used
  617. to force the kthreads to run on whatever set of CPUs is desired.
  618. Say Y here if you want to help to debug reduced OS jitter.
  619. Say N here if you are unsure.
  620. choice
  621. prompt "Build-forced no-CBs CPUs"
  622. default RCU_NOCB_CPU_NONE
  623. depends on RCU_NOCB_CPU
  624. help
  625. This option allows no-CBs CPUs (whose RCU callbacks are invoked
  626. from kthreads rather than from softirq context) to be specified
  627. at build time. Additional no-CBs CPUs may be specified by
  628. the rcu_nocbs= boot parameter.
  629. config RCU_NOCB_CPU_NONE
  630. bool "No build_forced no-CBs CPUs"
  631. help
  632. This option does not force any of the CPUs to be no-CBs CPUs.
  633. Only CPUs designated by the rcu_nocbs= boot parameter will be
  634. no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
  635. kthreads whose names begin with "rcuo". All other CPUs will
  636. invoke their own RCU callbacks in softirq context.
  637. Select this option if you want to choose no-CBs CPUs at
  638. boot time, for example, to allow testing of different no-CBs
  639. configurations without having to rebuild the kernel each time.
  640. config RCU_NOCB_CPU_ZERO
  641. bool "CPU 0 is a build_forced no-CBs CPU"
  642. help
  643. This option forces CPU 0 to be a no-CBs CPU, so that its RCU
  644. callbacks are invoked by a per-CPU kthread whose name begins
  645. with "rcuo". Additional CPUs may be designated as no-CBs
  646. CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
  647. All other CPUs will invoke their own RCU callbacks in softirq
  648. context.
  649. Select this if CPU 0 needs to be a no-CBs CPU for real-time
  650. or energy-efficiency reasons, but the real reason it exists
  651. is to ensure that randconfig testing covers mixed systems.
  652. config RCU_NOCB_CPU_ALL
  653. bool "All CPUs are build_forced no-CBs CPUs"
  654. help
  655. This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
  656. boot parameter will be ignored. All CPUs' RCU callbacks will
  657. be executed in the context of per-CPU rcuo kthreads created for
  658. this purpose. Assuming that the kthreads whose names start with
  659. "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
  660. on the remaining CPUs, but might decrease memory locality during
  661. RCU-callback invocation, thus potentially degrading throughput.
  662. Select this if all CPUs need to be no-CBs CPUs for real-time
  663. or energy-efficiency reasons.
  664. endchoice
  665. config RCU_EXPEDITE_BOOT
  666. bool
  667. default n
  668. help
  669. This option enables expedited grace periods at boot time,
  670. as if rcu_expedite_gp() had been invoked early in boot.
  671. The corresponding rcu_unexpedite_gp() is invoked from
  672. rcu_end_inkernel_boot(), which is intended to be invoked
  673. at the end of the kernel-only boot sequence, just before
  674. init is exec'ed.
  675. Accept the default if unsure.
  676. endmenu # "RCU Subsystem"
  677. config BUILD_BIN2C
  678. bool
  679. default n
  680. config IKCONFIG
  681. tristate "Kernel .config support"
  682. select BUILD_BIN2C
  683. ---help---
  684. This option enables the complete Linux kernel ".config" file
  685. contents to be saved in the kernel. It provides documentation
  686. of which kernel options are used in a running kernel or in an
  687. on-disk kernel. This information can be extracted from the kernel
  688. image file with the script scripts/extract-ikconfig and used as
  689. input to rebuild the current kernel or to build another kernel.
  690. It can also be extracted from a running kernel by reading
  691. /proc/config.gz if enabled (below).
  692. config IKCONFIG_PROC
  693. bool "Enable access to .config through /proc/config.gz"
  694. depends on IKCONFIG && PROC_FS
  695. ---help---
  696. This option enables access to the kernel configuration file
  697. through /proc/config.gz.
  698. config LOG_BUF_SHIFT
  699. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  700. range 12 25
  701. default 17
  702. depends on PRINTK
  703. help
  704. Select the minimal kernel log buffer size as a power of 2.
  705. The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
  706. parameter, see below. Any higher size also might be forced
  707. by "log_buf_len" boot parameter.
  708. Examples:
  709. 17 => 128 KB
  710. 16 => 64 KB
  711. 15 => 32 KB
  712. 14 => 16 KB
  713. 13 => 8 KB
  714. 12 => 4 KB
  715. config LOG_CPU_MAX_BUF_SHIFT
  716. int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
  717. depends on SMP
  718. range 0 21
  719. default 12 if !BASE_SMALL
  720. default 0 if BASE_SMALL
  721. depends on PRINTK
  722. help
  723. This option allows to increase the default ring buffer size
  724. according to the number of CPUs. The value defines the contribution
  725. of each CPU as a power of 2. The used space is typically only few
  726. lines however it might be much more when problems are reported,
  727. e.g. backtraces.
  728. The increased size means that a new buffer has to be allocated and
  729. the original static one is unused. It makes sense only on systems
  730. with more CPUs. Therefore this value is used only when the sum of
  731. contributions is greater than the half of the default kernel ring
  732. buffer as defined by LOG_BUF_SHIFT. The default values are set
  733. so that more than 64 CPUs are needed to trigger the allocation.
  734. Also this option is ignored when "log_buf_len" kernel parameter is
  735. used as it forces an exact (power of two) size of the ring buffer.
  736. The number of possible CPUs is used for this computation ignoring
  737. hotplugging making the computation optimal for the worst case
  738. scenario while allowing a simple algorithm to be used from bootup.
  739. Examples shift values and their meaning:
  740. 17 => 128 KB for each CPU
  741. 16 => 64 KB for each CPU
  742. 15 => 32 KB for each CPU
  743. 14 => 16 KB for each CPU
  744. 13 => 8 KB for each CPU
  745. 12 => 4 KB for each CPU
  746. config NMI_LOG_BUF_SHIFT
  747. int "Temporary per-CPU NMI log buffer size (12 => 4KB, 13 => 8KB)"
  748. range 10 21
  749. default 13
  750. depends on PRINTK_NMI
  751. help
  752. Select the size of a per-CPU buffer where NMI messages are temporary
  753. stored. They are copied to the main log buffer in a safe context
  754. to avoid a deadlock. The value defines the size as a power of 2.
  755. NMI messages are rare and limited. The largest one is when
  756. a backtrace is printed. It usually fits into 4KB. Select
  757. 8KB if you want to be on the safe side.
  758. Examples:
  759. 17 => 128 KB for each CPU
  760. 16 => 64 KB for each CPU
  761. 15 => 32 KB for each CPU
  762. 14 => 16 KB for each CPU
  763. 13 => 8 KB for each CPU
  764. 12 => 4 KB for each CPU
  765. #
  766. # Architectures with an unreliable sched_clock() should select this:
  767. #
  768. config HAVE_UNSTABLE_SCHED_CLOCK
  769. bool
  770. config GENERIC_SCHED_CLOCK
  771. bool
  772. #
  773. # For architectures that want to enable the support for NUMA-affine scheduler
  774. # balancing logic:
  775. #
  776. config ARCH_SUPPORTS_NUMA_BALANCING
  777. bool
  778. #
  779. # For architectures that prefer to flush all TLBs after a number of pages
  780. # are unmapped instead of sending one IPI per page to flush. The architecture
  781. # must provide guarantees on what happens if a clean TLB cache entry is
  782. # written after the unmap. Details are in mm/rmap.c near the check for
  783. # should_defer_flush. The architecture should also consider if the full flush
  784. # and the refill costs are offset by the savings of sending fewer IPIs.
  785. config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
  786. bool
  787. #
  788. # For architectures that know their GCC __int128 support is sound
  789. #
  790. config ARCH_SUPPORTS_INT128
  791. bool
  792. # For architectures that (ab)use NUMA to represent different memory regions
  793. # all cpu-local but of different latencies, such as SuperH.
  794. #
  795. config ARCH_WANT_NUMA_VARIABLE_LOCALITY
  796. bool
  797. config NUMA_BALANCING
  798. bool "Memory placement aware NUMA scheduler"
  799. depends on ARCH_SUPPORTS_NUMA_BALANCING
  800. depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
  801. depends on SMP && NUMA && MIGRATION
  802. help
  803. This option adds support for automatic NUMA aware memory/task placement.
  804. The mechanism is quite primitive and is based on migrating memory when
  805. it has references to the node the task is running on.
  806. This system will be inactive on UMA systems.
  807. config NUMA_BALANCING_DEFAULT_ENABLED
  808. bool "Automatically enable NUMA aware memory/task placement"
  809. default y
  810. depends on NUMA_BALANCING
  811. help
  812. If set, automatic NUMA balancing will be enabled if running on a NUMA
  813. machine.
  814. menuconfig CGROUPS
  815. bool "Control Group support"
  816. select KERNFS
  817. help
  818. This option adds support for grouping sets of processes together, for
  819. use with process control subsystems such as Cpusets, CFS, memory
  820. controls or device isolation.
  821. See
  822. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  823. - Documentation/cgroup-v1/ (features for grouping, isolation
  824. and resource control)
  825. Say N if unsure.
  826. if CGROUPS
  827. config CGROUP_DEBUG
  828. bool "Example debug cgroup subsystem"
  829. default n
  830. help
  831. This option enables a simple cgroup subsystem that
  832. exports useful debugging information about the cgroups
  833. framework.
  834. Say N if unsure.
  835. config CGROUP_FREEZER
  836. bool "Freezer cgroup subsystem"
  837. help
  838. Provides a way to freeze and unfreeze all tasks in a
  839. cgroup.
  840. config CGROUP_PIDS
  841. bool "PIDs cgroup subsystem"
  842. help
  843. Provides enforcement of process number limits in the scope of a
  844. cgroup. Any attempt to fork more processes than is allowed in the
  845. cgroup will fail. PIDs are fundamentally a global resource because it
  846. is fairly trivial to reach PID exhaustion before you reach even a
  847. conservative kmemcg limit. As a result, it is possible to grind a
  848. system to halt without being limited by other cgroup policies. The
  849. PIDs cgroup subsystem is designed to stop this from happening.
  850. It should be noted that organisational operations (such as attaching
  851. to a cgroup hierarchy will *not* be blocked by the PIDs subsystem),
  852. since the PIDs limit only affects a process's ability to fork, not to
  853. attach to a cgroup.
  854. config CGROUP_DEVICE
  855. bool "Device controller for cgroups"
  856. help
  857. Provides a cgroup implementing whitelists for devices which
  858. a process in the cgroup can mknod or open.
  859. config CPUSETS
  860. bool "Cpuset support"
  861. help
  862. This option will let you create and manage CPUSETs which
  863. allow dynamically partitioning a system into sets of CPUs and
  864. Memory Nodes and assigning tasks to run only within those sets.
  865. This is primarily useful on large SMP or NUMA systems.
  866. Say N if unsure.
  867. config PROC_PID_CPUSET
  868. bool "Include legacy /proc/<pid>/cpuset file"
  869. depends on CPUSETS
  870. default y
  871. config CGROUP_CPUACCT
  872. bool "Simple CPU accounting cgroup subsystem"
  873. help
  874. Provides a simple Resource Controller for monitoring the
  875. total CPU consumed by the tasks in a cgroup.
  876. config CGROUP_SCHEDTUNE
  877. bool "CFS tasks boosting cgroup subsystem (EXPERIMENTAL)"
  878. depends on SCHED_TUNE
  879. help
  880. This option provides the "schedtune" controller which improves the
  881. flexibility of the task boosting mechanism by introducing the support
  882. to define "per task" boost values.
  883. This new controller:
  884. 1. allows only a two layers hierarchy, where the root defines the
  885. system-wide boost value and its direct childrens define each one a
  886. different "class of tasks" to be boosted with a different value
  887. 2. supports up to 16 different task classes, each one which could be
  888. configured with a different boost value
  889. Say N if unsure.
  890. config PAGE_COUNTER
  891. bool
  892. config MEMCG
  893. bool "Memory controller"
  894. select PAGE_COUNTER
  895. select EVENTFD
  896. help
  897. Provides control over the memory footprint of tasks in a cgroup.
  898. config MEMCG_SWAP
  899. bool "Swap controller"
  900. depends on MEMCG && SWAP
  901. help
  902. Provides control over the swap space consumed by tasks in a cgroup.
  903. config MEMCG_SWAP_ENABLED
  904. bool "Swap controller enabled by default"
  905. depends on MEMCG_SWAP
  906. default y
  907. help
  908. Memory Resource Controller Swap Extension comes with its price in
  909. a bigger memory consumption. General purpose distribution kernels
  910. which want to enable the feature but keep it disabled by default
  911. and let the user enable it by swapaccount=1 boot command line
  912. parameter should have this option unselected.
  913. For those who want to have the feature enabled by default should
  914. select this option (if, for some reason, they need to disable it
  915. then swapaccount=0 does the trick).
  916. config BLK_CGROUP
  917. bool "IO controller"
  918. depends on BLOCK
  919. default n
  920. ---help---
  921. Generic block IO controller cgroup interface. This is the common
  922. cgroup interface which should be used by various IO controlling
  923. policies.
  924. Currently, CFQ IO scheduler uses it to recognize task groups and
  925. control disk bandwidth allocation (proportional time slice allocation)
  926. to such task groups. It is also used by bio throttling logic in
  927. block layer to implement upper limit in IO rates on a device.
  928. This option only enables generic Block IO controller infrastructure.
  929. One needs to also enable actual IO controlling logic/policy. For
  930. enabling proportional weight division of disk bandwidth in CFQ, set
  931. CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
  932. CONFIG_BLK_DEV_THROTTLING=y.
  933. See Documentation/cgroup-v1/blkio-controller.txt for more information.
  934. config DEBUG_BLK_CGROUP
  935. bool "IO controller debugging"
  936. depends on BLK_CGROUP
  937. default n
  938. ---help---
  939. Enable some debugging help. Currently it exports additional stat
  940. files in a cgroup which can be useful for debugging.
  941. config CGROUP_WRITEBACK
  942. bool
  943. depends on MEMCG && BLK_CGROUP
  944. default y
  945. menuconfig CGROUP_SCHED
  946. bool "CPU controller"
  947. default n
  948. help
  949. This feature lets CPU scheduler recognize task groups and control CPU
  950. bandwidth allocation to such task groups. It uses cgroups to group
  951. tasks.
  952. if CGROUP_SCHED
  953. config FAIR_GROUP_SCHED
  954. bool "Group scheduling for SCHED_OTHER"
  955. depends on CGROUP_SCHED
  956. default CGROUP_SCHED
  957. config CFS_BANDWIDTH
  958. bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
  959. depends on FAIR_GROUP_SCHED
  960. default n
  961. help
  962. This option allows users to define CPU bandwidth rates (limits) for
  963. tasks running within the fair group scheduler. Groups with no limit
  964. set are considered to be unconstrained and will run with no
  965. restriction.
  966. See tip/Documentation/scheduler/sched-bwc.txt for more information.
  967. config RT_GROUP_SCHED
  968. bool "Group scheduling for SCHED_RR/FIFO"
  969. depends on CGROUP_SCHED
  970. default n
  971. help
  972. This feature lets you explicitly allocate real CPU bandwidth
  973. to task groups. If enabled, it will also make it impossible to
  974. schedule realtime tasks for non-root users until you allocate
  975. realtime bandwidth for them.
  976. See Documentation/scheduler/sched-rt-group.txt for more information.
  977. endif #CGROUP_SCHED
  978. config CGROUP_PIDS
  979. bool "PIDs controller"
  980. help
  981. Provides enforcement of process number limits in the scope of a
  982. cgroup. Any attempt to fork more processes than is allowed in the
  983. cgroup will fail. PIDs are fundamentally a global resource because it
  984. is fairly trivial to reach PID exhaustion before you reach even a
  985. conservative kmemcg limit. As a result, it is possible to grind a
  986. system to halt without being limited by other cgroup policies. The
  987. PIDs controller is designed to stop this from happening.
  988. It should be noted that organisational operations (such as attaching
  989. to a cgroup hierarchy will *not* be blocked by the PIDs controller),
  990. since the PIDs limit only affects a process's ability to fork, not to
  991. attach to a cgroup.
  992. config CGROUP_FREEZER
  993. bool "Freezer controller"
  994. help
  995. Provides a way to freeze and unfreeze all tasks in a
  996. cgroup.
  997. This option affects the ORIGINAL cgroup interface. The cgroup2 memory
  998. controller includes important in-kernel memory consumers per default.
  999. If you're using cgroup2, say N.
  1000. config CGROUP_HUGETLB
  1001. bool "HugeTLB controller"
  1002. depends on HUGETLB_PAGE
  1003. select PAGE_COUNTER
  1004. default n
  1005. help
  1006. Provides a cgroup controller for HugeTLB pages.
  1007. When you enable this, you can put a per cgroup limit on HugeTLB usage.
  1008. The limit is enforced during page fault. Since HugeTLB doesn't
  1009. support page reclaim, enforcing the limit at page fault time implies
  1010. that, the application will get SIGBUS signal if it tries to access
  1011. HugeTLB pages beyond its limit. This requires the application to know
  1012. beforehand how much HugeTLB pages it would require for its use. The
  1013. control group is tracked in the third page lru pointer. This means
  1014. that we cannot use the controller with huge page less than 3 pages.
  1015. config CPUSETS
  1016. bool "Cpuset controller"
  1017. help
  1018. This option will let you create and manage CPUSETs which
  1019. allow dynamically partitioning a system into sets of CPUs and
  1020. Memory Nodes and assigning tasks to run only within those sets.
  1021. This is primarily useful on large SMP or NUMA systems.
  1022. Say N if unsure.
  1023. config PROC_PID_CPUSET
  1024. bool "Include legacy /proc/<pid>/cpuset file"
  1025. depends on CPUSETS
  1026. default y
  1027. config CGROUP_DEVICE
  1028. bool "Device controller"
  1029. help
  1030. Provides a cgroup controller implementing whitelists for
  1031. devices which a process in the cgroup can mknod or open.
  1032. config CGROUP_CPUACCT
  1033. bool "Simple CPU accounting controller"
  1034. help
  1035. Provides a simple controller for monitoring the
  1036. total CPU consumed by the tasks in a cgroup.
  1037. config CGROUP_PERF
  1038. bool "Perf controller"
  1039. depends on PERF_EVENTS
  1040. help
  1041. This option extends the perf per-cpu mode to restrict monitoring
  1042. to threads which belong to the cgroup specified and run on the
  1043. designated cpu.
  1044. Say N if unsure.
  1045. config CGROUP_BPF
  1046. bool "Support for eBPF programs attached to cgroups"
  1047. depends on BPF_SYSCALL
  1048. select SOCK_CGROUP_DATA
  1049. help
  1050. Allow attaching eBPF programs to a cgroup using the bpf(2)
  1051. syscall command BPF_PROG_ATTACH.
  1052. In which context these programs are accessed depends on the type
  1053. of attachment. For instance, programs that are attached using
  1054. BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
  1055. inet sockets.
  1056. config CGROUP_DEBUG
  1057. bool "Example controller"
  1058. default n
  1059. help
  1060. This option enables a simple controller that exports
  1061. debugging information about the cgroups framework.
  1062. Say N.
  1063. config SOCK_CGROUP_DATA
  1064. bool
  1065. default n
  1066. endif # CGROUPS
  1067. config CHECKPOINT_RESTORE
  1068. bool "Checkpoint/restore support" if EXPERT
  1069. select PROC_CHILDREN
  1070. default n
  1071. help
  1072. Enables additional kernel features in a sake of checkpoint/restore.
  1073. In particular it adds auxiliary prctl codes to setup process text,
  1074. data and heap segment sizes, and a few additional /proc filesystem
  1075. entries.
  1076. If unsure, say N here.
  1077. menuconfig NAMESPACES
  1078. bool "Namespaces support" if EXPERT
  1079. depends on MULTIUSER
  1080. default !EXPERT
  1081. help
  1082. Provides the way to make tasks work with different objects using
  1083. the same id. For example same IPC id may refer to different objects
  1084. or same user id or pid may refer to different tasks when used in
  1085. different namespaces.
  1086. if NAMESPACES
  1087. config UTS_NS
  1088. bool "UTS namespace"
  1089. default y
  1090. help
  1091. In this namespace tasks see different info provided with the
  1092. uname() system call
  1093. config IPC_NS
  1094. bool "IPC namespace"
  1095. depends on (SYSVIPC || POSIX_MQUEUE)
  1096. default y
  1097. help
  1098. In this namespace tasks work with IPC ids which correspond to
  1099. different IPC objects in different namespaces.
  1100. config USER_NS
  1101. bool "User namespace"
  1102. default n
  1103. help
  1104. This allows containers, i.e. vservers, to use user namespaces
  1105. to provide different user info for different servers.
  1106. When user namespaces are enabled in the kernel it is
  1107. recommended that the MEMCG option also be enabled and that
  1108. user-space use the memory control groups to limit the amount
  1109. of memory a memory unprivileged users can use.
  1110. If unsure, say N.
  1111. config PID_NS
  1112. bool "PID Namespaces"
  1113. default y
  1114. help
  1115. Support process id namespaces. This allows having multiple
  1116. processes with the same pid as long as they are in different
  1117. pid namespaces. This is a building block of containers.
  1118. config NET_NS
  1119. bool "Network namespace"
  1120. depends on NET
  1121. default y
  1122. help
  1123. Allow user space to create what appear to be multiple instances
  1124. of the network stack.
  1125. endif # NAMESPACES
  1126. config SCHED_AUTOGROUP
  1127. bool "Automatic process group scheduling"
  1128. select CGROUPS
  1129. select CGROUP_SCHED
  1130. select FAIR_GROUP_SCHED
  1131. help
  1132. This option optimizes the scheduler for common desktop workloads by
  1133. automatically creating and populating task groups. This separation
  1134. of workloads isolates aggressive CPU burners (like build jobs) from
  1135. desktop applications. Task group autogeneration is currently based
  1136. upon task session.
  1137. config SCHED_TUNE
  1138. bool "Boosting for CFS tasks (EXPERIMENTAL)"
  1139. depends on SMP
  1140. help
  1141. This option enables the system-wide support for task boosting.
  1142. When this support is enabled a new sysctl interface is exposed to
  1143. userspace via:
  1144. /proc/sys/kernel/sched_cfs_boost
  1145. which allows to set a system-wide boost value in range [0..100].
  1146. The currently boosting strategy is implemented in such a way that:
  1147. - a 0% boost value requires to operate in "standard" mode by
  1148. scheduling all tasks at the minimum capacities required by their
  1149. workload demand
  1150. - a 100% boost value requires to push at maximum the task
  1151. performances, "regardless" of the incurred energy consumption
  1152. A boost value in between these two boundaries is used to bias the
  1153. power/performance trade-off, the higher the boost value the more the
  1154. scheduler is biased toward performance boosting instead of energy
  1155. efficiency.
  1156. Since this support exposes a single system-wide knob, the specified
  1157. boost value is applied to all (CFS) tasks in the system.
  1158. If unsure, say N.
  1159. config DEFAULT_USE_ENERGY_AWARE
  1160. bool "Default to enabling the Energy Aware Scheduler feature"
  1161. default n
  1162. help
  1163. This option defaults the ENERGY_AWARE scheduling feature to true,
  1164. as without SCHED_DEBUG set this feature can't be enabled or disabled
  1165. via sysctl.
  1166. Say N if unsure.
  1167. config SYSFS_DEPRECATED
  1168. bool "Enable deprecated sysfs features to support old userspace tools"
  1169. depends on SYSFS
  1170. default n
  1171. help
  1172. This option adds code that switches the layout of the "block" class
  1173. devices, to not show up in /sys/class/block/, but only in
  1174. /sys/block/.
  1175. This switch is only active when the sysfs.deprecated=1 boot option is
  1176. passed or the SYSFS_DEPRECATED_V2 option is set.
  1177. This option allows new kernels to run on old distributions and tools,
  1178. which might get confused by /sys/class/block/. Since 2007/2008 all
  1179. major distributions and tools handle this just fine.
  1180. Recent distributions and userspace tools after 2009/2010 depend on
  1181. the existence of /sys/class/block/, and will not work with this
  1182. option enabled.
  1183. Only if you are using a new kernel on an old distribution, you might
  1184. need to say Y here.
  1185. config SYSFS_DEPRECATED_V2
  1186. bool "Enable deprecated sysfs features by default"
  1187. default n
  1188. depends on SYSFS
  1189. depends on SYSFS_DEPRECATED
  1190. help
  1191. Enable deprecated sysfs by default.
  1192. See the CONFIG_SYSFS_DEPRECATED option for more details about this
  1193. option.
  1194. Only if you are using a new kernel on an old distribution, you might
  1195. need to say Y here. Even then, odds are you would not need it
  1196. enabled, you can always pass the boot option if absolutely necessary.
  1197. config RELAY
  1198. bool "Kernel->user space relay support (formerly relayfs)"
  1199. select IRQ_WORK
  1200. help
  1201. This option enables support for relay interface support in
  1202. certain file systems (such as debugfs).
  1203. It is designed to provide an efficient mechanism for tools and
  1204. facilities to relay large amounts of data from kernel space to
  1205. user space.
  1206. If unsure, say N.
  1207. config BLK_DEV_INITRD
  1208. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  1209. depends on BROKEN || !FRV
  1210. help
  1211. The initial RAM filesystem is a ramfs which is loaded by the
  1212. boot loader (loadlin or lilo) and that is mounted as root
  1213. before the normal boot procedure. It is typically used to
  1214. load modules needed to mount the "real" root file system,
  1215. etc. See <file:Documentation/initrd.txt> for details.
  1216. If RAM disk support (BLK_DEV_RAM) is also included, this
  1217. also enables initial RAM disk (initrd) support and adds
  1218. 15 Kbytes (more on some other architectures) to the kernel size.
  1219. If unsure say Y.
  1220. if BLK_DEV_INITRD
  1221. source "usr/Kconfig"
  1222. endif
  1223. choice
  1224. prompt "Compiler optimization level"
  1225. default CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE
  1226. config CC_OPTIMIZE_FOR_PERFORMANCE
  1227. bool "Optimize for performance"
  1228. help
  1229. This is the default optimization level for the kernel, building
  1230. with the "-O2" compiler flag for best performance and most
  1231. helpful compile-time warnings.
  1232. config CC_OPTIMIZE_FOR_SIZE
  1233. bool "Optimize for size"
  1234. help
  1235. Enabling this option will pass "-Os" instead of "-O2" to
  1236. your compiler resulting in a smaller kernel.
  1237. If unsure, say N.
  1238. endchoice
  1239. config SYSCTL
  1240. bool
  1241. config ANON_INODES
  1242. bool
  1243. config HAVE_UID16
  1244. bool
  1245. config SYSCTL_EXCEPTION_TRACE
  1246. bool
  1247. help
  1248. Enable support for /proc/sys/debug/exception-trace.
  1249. config SYSCTL_ARCH_UNALIGN_NO_WARN
  1250. bool
  1251. help
  1252. Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
  1253. Allows arch to define/use @no_unaligned_warning to possibly warn
  1254. about unaligned access emulation going on under the hood.
  1255. config SYSCTL_ARCH_UNALIGN_ALLOW
  1256. bool
  1257. help
  1258. Enable support for /proc/sys/kernel/unaligned-trap
  1259. Allows arches to define/use @unaligned_enabled to runtime toggle
  1260. the unaligned access emulation.
  1261. see arch/parisc/kernel/unaligned.c for reference
  1262. config HAVE_PCSPKR_PLATFORM
  1263. bool
  1264. # interpreter that classic socket filters depend on
  1265. config BPF
  1266. bool
  1267. menuconfig EXPERT
  1268. bool "Configure standard kernel features (expert users)"
  1269. # Unhide debug options, to make the on-by-default options visible
  1270. select DEBUG_KERNEL
  1271. help
  1272. This option allows certain base kernel options and settings
  1273. to be disabled or tweaked. This is for specialized
  1274. environments which can tolerate a "non-standard" kernel.
  1275. Only use this if you really know what you are doing.
  1276. config UID16
  1277. bool "Enable 16-bit UID system calls" if EXPERT
  1278. depends on HAVE_UID16 && MULTIUSER
  1279. default y
  1280. help
  1281. This enables the legacy 16-bit UID syscall wrappers.
  1282. config MULTIUSER
  1283. bool "Multiple users, groups and capabilities support" if EXPERT
  1284. default y
  1285. help
  1286. This option enables support for non-root users, groups and
  1287. capabilities.
  1288. If you say N here, all processes will run with UID 0, GID 0, and all
  1289. possible capabilities. Saying N here also compiles out support for
  1290. system calls related to UIDs, GIDs, and capabilities, such as setuid,
  1291. setgid, and capset.
  1292. If unsure, say Y here.
  1293. config SGETMASK_SYSCALL
  1294. bool "sgetmask/ssetmask syscalls support" if EXPERT
  1295. def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
  1296. ---help---
  1297. sys_sgetmask and sys_ssetmask are obsolete system calls
  1298. no longer supported in libc but still enabled by default in some
  1299. architectures.
  1300. If unsure, leave the default option here.
  1301. config SYSFS_SYSCALL
  1302. bool "Sysfs syscall support" if EXPERT
  1303. default y
  1304. ---help---
  1305. sys_sysfs is an obsolete system call no longer supported in libc.
  1306. Note that disabling this option is more secure but might break
  1307. compatibility with some systems.
  1308. If unsure say Y here.
  1309. config SYSCTL_SYSCALL
  1310. bool "Sysctl syscall support" if EXPERT
  1311. depends on PROC_SYSCTL
  1312. default n
  1313. select SYSCTL
  1314. ---help---
  1315. sys_sysctl uses binary paths that have been found challenging
  1316. to properly maintain and use. The interface in /proc/sys
  1317. using paths with ascii names is now the primary path to this
  1318. information.
  1319. Almost nothing using the binary sysctl interface so if you are
  1320. trying to save some space it is probably safe to disable this,
  1321. making your kernel marginally smaller.
  1322. If unsure say N here.
  1323. config KALLSYMS
  1324. bool "Load all symbols for debugging/ksymoops" if EXPERT
  1325. default y
  1326. help
  1327. Say Y here to let the kernel print out symbolic crash information and
  1328. symbolic stack backtraces. This increases the size of the kernel
  1329. somewhat, as all symbols have to be loaded into the kernel image.
  1330. config KALLSYMS_ALL
  1331. bool "Include all symbols in kallsyms"
  1332. depends on DEBUG_KERNEL && KALLSYMS
  1333. help
  1334. Normally kallsyms only contains the symbols of functions for nicer
  1335. OOPS messages and backtraces (i.e., symbols from the text and inittext
  1336. sections). This is sufficient for most cases. And only in very rare
  1337. cases (e.g., when a debugger is used) all symbols are required (e.g.,
  1338. names of variables from the data sections, etc).
  1339. This option makes sure that all symbols are loaded into the kernel
  1340. image (i.e., symbols from all sections) in cost of increased kernel
  1341. size (depending on the kernel configuration, it may be 300KiB or
  1342. something like this).
  1343. Say N unless you really need all symbols.
  1344. config KALLSYMS_ABSOLUTE_PERCPU
  1345. bool
  1346. depends on KALLSYMS
  1347. default X86_64 && SMP
  1348. config KALLSYMS_BASE_RELATIVE
  1349. bool "Enable KALLSYMS_BASE_RELATIVE or not"
  1350. depends on KALLSYMS
  1351. default !IA64 && !(TILE && 64BIT)
  1352. help
  1353. Instead of emitting them as absolute values in the native word size,
  1354. emit the symbol references in the kallsyms table as 32-bit entries,
  1355. each containing a relative value in the range [base, base + U32_MAX]
  1356. or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
  1357. an absolute value in the range [0, S32_MAX] or a relative value in the
  1358. range [base, base + S32_MAX], where base is the lowest relative symbol
  1359. address encountered in the image.
  1360. On 64-bit builds, this reduces the size of the address table by 50%,
  1361. but more importantly, it results in entries whose values are build
  1362. time constants, and no relocation pass is required at runtime to fix
  1363. up the entries based on the runtime load address of the kernel.
  1364. config PRINTK
  1365. default y
  1366. bool "Enable support for printk" if EXPERT
  1367. select IRQ_WORK
  1368. help
  1369. This option enables normal printk support. Removing it
  1370. eliminates most of the message strings from the kernel image
  1371. and makes the kernel more or less silent. As this makes it
  1372. very difficult to diagnose system problems, saying N here is
  1373. strongly discouraged.
  1374. config PRINTK_NMI
  1375. def_bool y
  1376. depends on PRINTK
  1377. depends on HAVE_NMI
  1378. config BUG
  1379. bool "BUG() support" if EXPERT
  1380. default y
  1381. help
  1382. Disabling this option eliminates support for BUG and WARN, reducing
  1383. the size of your kernel image and potentially quietly ignoring
  1384. numerous fatal conditions. You should only consider disabling this
  1385. option for embedded systems with no facilities for reporting errors.
  1386. Just say Y.
  1387. config ELF_CORE
  1388. depends on COREDUMP
  1389. default y
  1390. bool "Enable ELF core dumps" if EXPERT
  1391. help
  1392. Enable support for generating core dumps. Disabling saves about 4k.
  1393. config PCSPKR_PLATFORM
  1394. bool "Enable PC-Speaker support" if EXPERT
  1395. depends on HAVE_PCSPKR_PLATFORM
  1396. select I8253_LOCK
  1397. default y
  1398. help
  1399. This option allows to disable the internal PC-Speaker
  1400. support, saving some memory.
  1401. config BASE_FULL
  1402. default y
  1403. bool "Enable full-sized data structures for core" if EXPERT
  1404. help
  1405. Disabling this option reduces the size of miscellaneous core
  1406. kernel data structures. This saves memory on small machines,
  1407. but may reduce performance.
  1408. config FUTEX
  1409. bool "Enable futex support" if EXPERT
  1410. default y
  1411. select RT_MUTEXES
  1412. help
  1413. Disabling this option will cause the kernel to be built without
  1414. support for "fast userspace mutexes". The resulting kernel may not
  1415. run glibc-based applications correctly.
  1416. config HAVE_FUTEX_CMPXCHG
  1417. bool
  1418. depends on FUTEX
  1419. help
  1420. Architectures should select this if futex_atomic_cmpxchg_inatomic()
  1421. is implemented and always working. This removes a couple of runtime
  1422. checks.
  1423. config EPOLL
  1424. bool "Enable eventpoll support" if EXPERT
  1425. default y
  1426. select ANON_INODES
  1427. help
  1428. Disabling this option will cause the kernel to be built without
  1429. support for epoll family of system calls.
  1430. config SIGNALFD
  1431. bool "Enable signalfd() system call" if EXPERT
  1432. select ANON_INODES
  1433. default y
  1434. help
  1435. Enable the signalfd() system call that allows to receive signals
  1436. on a file descriptor.
  1437. If unsure, say Y.
  1438. config TIMERFD
  1439. bool "Enable timerfd() system call" if EXPERT
  1440. select ANON_INODES
  1441. default y
  1442. help
  1443. Enable the timerfd() system call that allows to receive timer
  1444. events on a file descriptor.
  1445. If unsure, say Y.
  1446. config EVENTFD
  1447. bool "Enable eventfd() system call" if EXPERT
  1448. select ANON_INODES
  1449. default y
  1450. help
  1451. Enable the eventfd() system call that allows to receive both
  1452. kernel notification (ie. KAIO) or userspace notifications.
  1453. If unsure, say Y.
  1454. # syscall, maps, verifier
  1455. config BPF_SYSCALL
  1456. bool "Enable bpf() system call"
  1457. select ANON_INODES
  1458. select BPF
  1459. default n
  1460. help
  1461. Enable the bpf() system call that allows to manipulate eBPF
  1462. programs and maps via file descriptors.
  1463. config BPF_JIT_ALWAYS_ON
  1464. bool "Permanently enable BPF JIT and remove BPF interpreter"
  1465. depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
  1466. help
  1467. Enables BPF JIT and removes BPF interpreter to avoid
  1468. speculative execution of BPF instructions by the interpreter
  1469. config SHMEM
  1470. bool "Use full shmem filesystem" if EXPERT
  1471. default y
  1472. depends on MMU
  1473. help
  1474. The shmem is an internal filesystem used to manage shared memory.
  1475. It is backed by swap and manages resource limits. It is also exported
  1476. to userspace as tmpfs if TMPFS is enabled. Disabling this
  1477. option replaces shmem and tmpfs with the much simpler ramfs code,
  1478. which may be appropriate on small systems without swap.
  1479. config AIO
  1480. bool "Enable AIO support" if EXPERT
  1481. default y
  1482. help
  1483. This option enables POSIX asynchronous I/O which may by used
  1484. by some high performance threaded applications. Disabling
  1485. this option saves about 7k.
  1486. config ADVISE_SYSCALLS
  1487. bool "Enable madvise/fadvise syscalls" if EXPERT
  1488. default y
  1489. help
  1490. This option enables the madvise and fadvise syscalls, used by
  1491. applications to advise the kernel about their future memory or file
  1492. usage, improving performance. If building an embedded system where no
  1493. applications use these syscalls, you can disable this option to save
  1494. space.
  1495. config USERFAULTFD
  1496. bool "Enable userfaultfd() system call"
  1497. select ANON_INODES
  1498. depends on MMU
  1499. help
  1500. Enable the userfaultfd() system call that allows to intercept and
  1501. handle page faults in userland.
  1502. config PCI_QUIRKS
  1503. default y
  1504. bool "Enable PCI quirk workarounds" if EXPERT
  1505. depends on PCI
  1506. help
  1507. This enables workarounds for various PCI chipset
  1508. bugs/quirks. Disable this only if your target machine is
  1509. unaffected by PCI quirks.
  1510. config MEMBARRIER
  1511. bool "Enable membarrier() system call" if EXPERT
  1512. default y
  1513. help
  1514. Enable the membarrier() system call that allows issuing memory
  1515. barriers across all running threads, which can be used to distribute
  1516. the cost of user-space memory barriers asymmetrically by transforming
  1517. pairs of memory barriers into pairs consisting of membarrier() and a
  1518. compiler barrier.
  1519. If unsure, say Y.
  1520. config EMBEDDED
  1521. bool "Embedded system"
  1522. option allnoconfig_y
  1523. select EXPERT
  1524. help
  1525. This option should be enabled if compiling the kernel for
  1526. an embedded system so certain expert options are available
  1527. for configuration.
  1528. config HAVE_PERF_EVENTS
  1529. bool
  1530. help
  1531. See tools/perf/design.txt for details.
  1532. config PERF_USE_VMALLOC
  1533. bool
  1534. help
  1535. See tools/perf/design.txt for details
  1536. menu "Kernel Performance Events And Counters"
  1537. config PERF_EVENTS
  1538. bool "Kernel performance events and counters"
  1539. default y if PROFILING
  1540. depends on HAVE_PERF_EVENTS
  1541. select ANON_INODES
  1542. select IRQ_WORK
  1543. select SRCU
  1544. help
  1545. Enable kernel support for various performance events provided
  1546. by software and hardware.
  1547. Software events are supported either built-in or via the
  1548. use of generic tracepoints.
  1549. Most modern CPUs support performance events via performance
  1550. counter registers. These registers count the number of certain
  1551. types of hw events: such as instructions executed, cachemisses
  1552. suffered, or branches mis-predicted - without slowing down the
  1553. kernel or applications. These registers can also trigger interrupts
  1554. when a threshold number of events have passed - and can thus be
  1555. used to profile the code that runs on that CPU.
  1556. The Linux Performance Event subsystem provides an abstraction of
  1557. these software and hardware event capabilities, available via a
  1558. system call and used by the "perf" utility in tools/perf/. It
  1559. provides per task and per CPU counters, and it provides event
  1560. capabilities on top of those.
  1561. Say Y if unsure.
  1562. config DEBUG_PERF_USE_VMALLOC
  1563. default n
  1564. bool "Debug: use vmalloc to back perf mmap() buffers"
  1565. depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
  1566. select PERF_USE_VMALLOC
  1567. help
  1568. Use vmalloc memory to back perf mmap() buffers.
  1569. Mostly useful for debugging the vmalloc code on platforms
  1570. that don't require it.
  1571. Say N if unsure.
  1572. endmenu
  1573. config VM_EVENT_COUNTERS
  1574. default y
  1575. bool "Enable VM event counters for /proc/vmstat" if EXPERT
  1576. help
  1577. VM event counters are needed for event counts to be shown.
  1578. This option allows the disabling of the VM event counters
  1579. on EXPERT systems. /proc/vmstat will only show page counts
  1580. if VM event counters are disabled.
  1581. config SLUB_DEBUG
  1582. default y
  1583. bool "Enable SLUB debugging support" if EXPERT
  1584. depends on SLUB && SYSFS
  1585. depends on !MTK_ENABLE_AGO
  1586. help
  1587. SLUB has extensive debug support features. Disabling these can
  1588. result in significant savings in code size. This also disables
  1589. SLUB sysfs support. /sys/slab will not exist and there will be
  1590. no support for cache validation etc.
  1591. config COMPAT_BRK
  1592. bool "Disable heap randomization"
  1593. default y
  1594. help
  1595. Randomizing heap placement makes heap exploits harder, but it
  1596. also breaks ancient binaries (including anything libc5 based).
  1597. This option changes the bootup default to heap randomization
  1598. disabled, and can be overridden at runtime by setting
  1599. /proc/sys/kernel/randomize_va_space to 2.
  1600. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  1601. choice
  1602. prompt "Choose SLAB allocator"
  1603. default SLUB
  1604. help
  1605. This option allows to select a slab allocator.
  1606. config SLAB
  1607. bool "SLAB"
  1608. select HAVE_HARDENED_USERCOPY_ALLOCATOR
  1609. help
  1610. The regular slab allocator that is established and known to work
  1611. well in all environments. It organizes cache hot objects in
  1612. per cpu and per node queues.
  1613. config SLUB
  1614. bool "SLUB (Unqueued Allocator)"
  1615. select HAVE_HARDENED_USERCOPY_ALLOCATOR
  1616. help
  1617. SLUB is a slab allocator that minimizes cache line usage
  1618. instead of managing queues of cached objects (SLAB approach).
  1619. Per cpu caching is realized using slabs of objects instead
  1620. of queues of objects. SLUB can use memory efficiently
  1621. and has enhanced diagnostics. SLUB is the default choice for
  1622. a slab allocator.
  1623. config SLOB
  1624. depends on EXPERT
  1625. bool "SLOB (Simple Allocator)"
  1626. help
  1627. SLOB replaces the stock allocator with a drastically simpler
  1628. allocator. SLOB is generally more space efficient but
  1629. does not perform as well on large systems.
  1630. endchoice
  1631. config SLAB_FREELIST_RANDOM
  1632. default n
  1633. depends on SLAB || SLUB
  1634. bool "SLAB freelist randomization"
  1635. help
  1636. Randomizes the freelist order used on creating new pages. This
  1637. security feature reduces the predictability of the kernel slab
  1638. allocator against heap overflows.
  1639. config SLUB_CPU_PARTIAL
  1640. default y
  1641. depends on SLUB && SMP
  1642. bool "SLUB per cpu partial cache"
  1643. help
  1644. Per cpu partial caches accellerate objects allocation and freeing
  1645. that is local to a processor at the price of more indeterminism
  1646. in the latency of the free. On overflow these caches will be cleared
  1647. which requires the taking of locks that may cause latency spikes.
  1648. Typically one would choose no for a realtime system.
  1649. config MMAP_ALLOW_UNINITIALIZED
  1650. bool "Allow mmapped anonymous memory to be uninitialized"
  1651. depends on EXPERT && !MMU
  1652. default n
  1653. help
  1654. Normally, and according to the Linux spec, anonymous memory obtained
  1655. from mmap() has it's contents cleared before it is passed to
  1656. userspace. Enabling this config option allows you to request that
  1657. mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
  1658. providing a huge performance boost. If this option is not enabled,
  1659. then the flag will be ignored.
  1660. This is taken advantage of by uClibc's malloc(), and also by
  1661. ELF-FDPIC binfmt's brk and stack allocator.
  1662. Because of the obvious security issues, this option should only be
  1663. enabled on embedded devices where you control what is run in
  1664. userspace. Since that isn't generally a problem on no-MMU systems,
  1665. it is normally safe to say Y here.
  1666. See Documentation/nommu-mmap.txt for more information.
  1667. config SYSTEM_DATA_VERIFICATION
  1668. def_bool n
  1669. select SYSTEM_TRUSTED_KEYRING
  1670. select KEYS
  1671. select CRYPTO
  1672. select CRYPTO_RSA
  1673. select ASYMMETRIC_KEY_TYPE
  1674. select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
  1675. select ASN1
  1676. select OID_REGISTRY
  1677. select X509_CERTIFICATE_PARSER
  1678. select PKCS7_MESSAGE_PARSER
  1679. help
  1680. Provide PKCS#7 message verification using the contents of the system
  1681. trusted keyring to provide public keys. This then can be used for
  1682. module verification, kexec image verification and firmware blob
  1683. verification.
  1684. config PROFILING
  1685. bool "Profiling support"
  1686. help
  1687. Say Y here to enable the extended profiling support mechanisms used
  1688. by profilers such as OProfile.
  1689. #
  1690. # Place an empty function call at each tracepoint site. Can be
  1691. # dynamically changed for a probe function.
  1692. #
  1693. config TRACEPOINTS
  1694. bool
  1695. source "arch/Kconfig"
  1696. endmenu # General setup
  1697. config HAVE_GENERIC_DMA_COHERENT
  1698. bool
  1699. default n
  1700. config SLABINFO
  1701. bool
  1702. depends on PROC_FS
  1703. depends on !MTK_ENABLE_GMO
  1704. depends on SLAB || SLUB_DEBUG
  1705. default y
  1706. config RT_MUTEXES
  1707. bool
  1708. config BASE_SMALL
  1709. int
  1710. default 0 if BASE_FULL
  1711. default 1 if !BASE_FULL
  1712. menuconfig MODULES
  1713. bool "Enable loadable module support"
  1714. option modules
  1715. help
  1716. Kernel modules are small pieces of compiled code which can
  1717. be inserted in the running kernel, rather than being
  1718. permanently built into the kernel. You use the "modprobe"
  1719. tool to add (and sometimes remove) them. If you say Y here,
  1720. many parts of the kernel can be built as modules (by
  1721. answering M instead of Y where indicated): this is most
  1722. useful for infrequently used options which are not required
  1723. for booting. For more information, see the man pages for
  1724. modprobe, lsmod, modinfo, insmod and rmmod.
  1725. If you say Y here, you will need to run "make
  1726. modules_install" to put the modules under /lib/modules/
  1727. where modprobe can find them (you may need to be root to do
  1728. this).
  1729. If unsure, say Y.
  1730. if MODULES
  1731. config MODULE_FORCE_LOAD
  1732. bool "Forced module loading"
  1733. default n
  1734. help
  1735. Allow loading of modules without version information (ie. modprobe
  1736. --force). Forced module loading sets the 'F' (forced) taint flag and
  1737. is usually a really bad idea.
  1738. config MODULE_UNLOAD
  1739. bool "Module unloading"
  1740. help
  1741. Without this option you will not be able to unload any
  1742. modules (note that some modules may not be unloadable
  1743. anyway), which makes your kernel smaller, faster
  1744. and simpler. If unsure, say Y.
  1745. config MODULE_FORCE_UNLOAD
  1746. bool "Forced module unloading"
  1747. depends on MODULE_UNLOAD
  1748. help
  1749. This option allows you to force a module to unload, even if the
  1750. kernel believes it is unsafe: the kernel will remove the module
  1751. without waiting for anyone to stop using it (using the -f option to
  1752. rmmod). This is mainly for kernel developers and desperate users.
  1753. If unsure, say N.
  1754. config MODVERSIONS
  1755. bool "Module versioning support"
  1756. help
  1757. Usually, you have to use modules compiled with your kernel.
  1758. Saying Y here makes it sometimes possible to use modules
  1759. compiled for different kernels, by adding enough information
  1760. to the modules to (hopefully) spot any changes which would
  1761. make them incompatible with the kernel you are running. If
  1762. unsure, say N.
  1763. config MODULE_SRCVERSION_ALL
  1764. bool "Source checksum for all modules"
  1765. help
  1766. Modules which contain a MODULE_VERSION get an extra "srcversion"
  1767. field inserted into their modinfo section, which contains a
  1768. sum of the source files which made it. This helps maintainers
  1769. see exactly which source was used to build a module (since
  1770. others sometimes change the module source without updating
  1771. the version). With this option, such a "srcversion" field
  1772. will be created for all modules. If unsure, say N.
  1773. config MODULE_SIG
  1774. bool "Module signature verification"
  1775. depends on MODULES
  1776. select SYSTEM_DATA_VERIFICATION
  1777. help
  1778. Check modules for valid signatures upon load: the signature
  1779. is simply appended to the module. For more information see
  1780. Documentation/module-signing.txt.
  1781. Note that this option adds the OpenSSL development packages as a
  1782. kernel build dependency so that the signing tool can use its crypto
  1783. library.
  1784. !!!WARNING!!! If you enable this option, you MUST make sure that the
  1785. module DOES NOT get stripped after being signed. This includes the
  1786. debuginfo strip done by some packagers (such as rpmbuild) and
  1787. inclusion into an initramfs that wants the module size reduced.
  1788. config MODULE_SIG_FORCE
  1789. bool "Require modules to be validly signed"
  1790. depends on MODULE_SIG
  1791. help
  1792. Reject unsigned modules or signed modules for which we don't have a
  1793. key. Without this, such modules will simply taint the kernel.
  1794. config MODULE_SIG_ALL
  1795. bool "Automatically sign all modules"
  1796. default y
  1797. depends on MODULE_SIG
  1798. help
  1799. Sign all modules during make modules_install. Without this option,
  1800. modules must be signed manually, using the scripts/sign-file tool.
  1801. comment "Do not forget to sign required modules with scripts/sign-file"
  1802. depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
  1803. choice
  1804. prompt "Which hash algorithm should modules be signed with?"
  1805. depends on MODULE_SIG
  1806. help
  1807. This determines which sort of hashing algorithm will be used during
  1808. signature generation. This algorithm _must_ be built into the kernel
  1809. directly so that signature verification can take place. It is not
  1810. possible to load a signed module containing the algorithm to check
  1811. the signature on that module.
  1812. config MODULE_SIG_SHA1
  1813. bool "Sign modules with SHA-1"
  1814. select CRYPTO_SHA1
  1815. config MODULE_SIG_SHA224
  1816. bool "Sign modules with SHA-224"
  1817. select CRYPTO_SHA256
  1818. config MODULE_SIG_SHA256
  1819. bool "Sign modules with SHA-256"
  1820. select CRYPTO_SHA256
  1821. config MODULE_SIG_SHA384
  1822. bool "Sign modules with SHA-384"
  1823. select CRYPTO_SHA512
  1824. config MODULE_SIG_SHA512
  1825. bool "Sign modules with SHA-512"
  1826. select CRYPTO_SHA512
  1827. endchoice
  1828. config MODULE_SIG_HASH
  1829. string
  1830. depends on MODULE_SIG
  1831. default "sha1" if MODULE_SIG_SHA1
  1832. default "sha224" if MODULE_SIG_SHA224
  1833. default "sha256" if MODULE_SIG_SHA256
  1834. default "sha384" if MODULE_SIG_SHA384
  1835. default "sha512" if MODULE_SIG_SHA512
  1836. config MODULE_COMPRESS
  1837. bool "Compress modules on installation"
  1838. depends on MODULES
  1839. help
  1840. Compresses kernel modules when 'make modules_install' is run; gzip or
  1841. xz depending on "Compression algorithm" below.
  1842. module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
  1843. Out-of-tree kernel modules installed using Kbuild will also be
  1844. compressed upon installation.
  1845. Note: for modules inside an initrd or initramfs, it's more efficient
  1846. to compress the whole initrd or initramfs instead.
  1847. Note: This is fully compatible with signed modules.
  1848. If in doubt, say N.
  1849. choice
  1850. prompt "Compression algorithm"
  1851. depends on MODULE_COMPRESS
  1852. default MODULE_COMPRESS_GZIP
  1853. help
  1854. This determines which sort of compression will be used during
  1855. 'make modules_install'.
  1856. GZIP (default) and XZ are supported.
  1857. config MODULE_COMPRESS_GZIP
  1858. bool "GZIP"
  1859. config MODULE_COMPRESS_XZ
  1860. bool "XZ"
  1861. endchoice
  1862. config TRIM_UNUSED_KSYMS
  1863. bool "Trim unused exported kernel symbols"
  1864. depends on MODULES && !UNUSED_SYMBOLS
  1865. help
  1866. The kernel and some modules make many symbols available for
  1867. other modules to use via EXPORT_SYMBOL() and variants. Depending
  1868. on the set of modules being selected in your kernel configuration,
  1869. many of those exported symbols might never be used.
  1870. This option allows for unused exported symbols to be dropped from
  1871. the build. In turn, this provides the compiler more opportunities
  1872. (especially when using LTO) for optimizing the code and reducing
  1873. binary size. This might have some security advantages as well.
  1874. If unsure, or if you need to build out-of-tree modules, say N.
  1875. endif # MODULES
  1876. config MODULES_TREE_LOOKUP
  1877. def_bool y
  1878. depends on PERF_EVENTS || TRACING || CFI_CLANG
  1879. config INIT_ALL_POSSIBLE
  1880. bool
  1881. help
  1882. Back when each arch used to define their own cpu_online_mask and
  1883. cpu_possible_mask, some of them chose to initialize cpu_possible_mask
  1884. with all 1s, and others with all 0s. When they were centralised,
  1885. it was better to provide this option than to break all the archs
  1886. and have several arch maintainers pursuing me down dark alleys.
  1887. source "block/Kconfig"
  1888. config PREEMPT_NOTIFIERS
  1889. bool
  1890. config PADATA
  1891. depends on SMP
  1892. bool
  1893. config ASN1
  1894. tristate
  1895. help
  1896. Build a simple ASN.1 grammar compiler that produces a bytecode output
  1897. that can be interpreted by the ASN.1 stream decoder and used to
  1898. inform it as to what tags are to be expected in a stream and what
  1899. functions to call on what tags.
  1900. source "kernel/Kconfig.locks"