Kconfig 68 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 TOOLS_SUPPORT_RELR
  17. bool "Declare tool support for RELR"
  18. # Prevent this from being enabled by default in allyesconfig or
  19. # allmodconfig builds.
  20. depends on !COMPILE_TEST
  21. config CONSTRUCTORS
  22. bool
  23. depends on !UML
  24. config IRQ_WORK
  25. bool
  26. config BUILDTIME_EXTABLE_SORT
  27. bool
  28. config THREAD_INFO_IN_TASK
  29. bool
  30. help
  31. Select this to move thread_info off the stack into task_struct. To
  32. make this work, an arch will need to remove all thread_info fields
  33. except flags and fix any runtime bugs.
  34. One subtle change that will be needed is to use try_get_task_stack()
  35. and put_task_stack() in save_thread_stack_tsk() and get_wchan().
  36. menu "General setup"
  37. config BROKEN
  38. bool
  39. config BROKEN_ON_SMP
  40. bool
  41. depends on BROKEN || !SMP
  42. default y
  43. config INIT_ENV_ARG_LIMIT
  44. int
  45. default 32 if !UML
  46. default 128 if UML
  47. help
  48. Maximum of each of the number of arguments and environment
  49. variables passed to init from the kernel command line.
  50. config CROSS_COMPILE
  51. string "Cross-compiler tool prefix"
  52. help
  53. Same as running 'make CROSS_COMPILE=prefix-' but stored for
  54. default make runs in this kernel build directory. You don't
  55. need to set this unless you want the configured kernel build
  56. directory to select the cross-compiler automatically.
  57. config COMPILE_TEST
  58. bool "Compile also drivers which will not load"
  59. depends on HAS_IOMEM
  60. help
  61. Some drivers can be compiled on a different platform than they are
  62. intended to be run on. Despite they cannot be loaded there (or even
  63. when they load they cannot be used due to missing HW support),
  64. developers still, opposing to distributors, might want to build such
  65. drivers to compile-test them.
  66. If you are a developer and want to build everything available, say Y
  67. here. If you are a user/distributor, say N here to exclude useless
  68. drivers to be distributed.
  69. config LOCALVERSION
  70. string "Local version - append to kernel release"
  71. help
  72. Append an extra string to the end of your kernel version.
  73. This will show up when you type uname, for example.
  74. The string you set here will be appended after the contents of
  75. any files with a filename matching localversion* in your
  76. object and source tree, in that order. Your total string can
  77. be a maximum of 64 characters.
  78. config LOCALVERSION_AUTO
  79. bool "Automatically append version information to the version string"
  80. default y
  81. depends on !COMPILE_TEST
  82. help
  83. This will try to automatically determine if the current tree is a
  84. release tree by looking for git tags that belong to the current
  85. top of tree revision.
  86. A string of the format -gxxxxxxxx will be added to the localversion
  87. if a git-based tree is found. The string generated by this will be
  88. appended after any matching localversion* files, and after the value
  89. set in CONFIG_LOCALVERSION.
  90. (The actual string used here is the first eight characters produced
  91. by running the command:
  92. $ git rev-parse --verify HEAD
  93. which is done within the script "scripts/setlocalversion".)
  94. config HAVE_KERNEL_GZIP
  95. bool
  96. config HAVE_KERNEL_BZIP2
  97. bool
  98. config HAVE_KERNEL_LZMA
  99. bool
  100. config HAVE_KERNEL_XZ
  101. bool
  102. config HAVE_KERNEL_LZO
  103. bool
  104. config HAVE_KERNEL_LZ4
  105. bool
  106. choice
  107. prompt "Kernel compression mode"
  108. default KERNEL_GZIP
  109. depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
  110. help
  111. The linux kernel is a kind of self-extracting executable.
  112. Several compression algorithms are available, which differ
  113. in efficiency, compression and decompression speed.
  114. Compression speed is only relevant when building a kernel.
  115. Decompression speed is relevant at each boot.
  116. If you have any problems with bzip2 or lzma compressed
  117. kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
  118. version of this functionality (bzip2 only), for 2.4, was
  119. supplied by Christian Ludwig)
  120. High compression options are mostly useful for users, who
  121. are low on disk space (embedded systems), but for whom ram
  122. size matters less.
  123. If in doubt, select 'gzip'
  124. config KERNEL_GZIP
  125. bool "Gzip"
  126. depends on HAVE_KERNEL_GZIP
  127. help
  128. The old and tried gzip compression. It provides a good balance
  129. between compression ratio and decompression speed.
  130. config KERNEL_BZIP2
  131. bool "Bzip2"
  132. depends on HAVE_KERNEL_BZIP2
  133. help
  134. Its compression ratio and speed is intermediate.
  135. Decompression speed is slowest among the choices. The kernel
  136. size is about 10% smaller with bzip2, in comparison to gzip.
  137. Bzip2 uses a large amount of memory. For modern kernels you
  138. will need at least 8MB RAM or more for booting.
  139. config KERNEL_LZMA
  140. bool "LZMA"
  141. depends on HAVE_KERNEL_LZMA
  142. help
  143. This compression algorithm's ratio is best. Decompression speed
  144. is between gzip and bzip2. Compression is slowest.
  145. The kernel size is about 33% smaller with LZMA in comparison to gzip.
  146. config KERNEL_XZ
  147. bool "XZ"
  148. depends on HAVE_KERNEL_XZ
  149. help
  150. XZ uses the LZMA2 algorithm and instruction set specific
  151. BCJ filters which can improve compression ratio of executable
  152. code. The size of the kernel is about 30% smaller with XZ in
  153. comparison to gzip. On architectures for which there is a BCJ
  154. filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
  155. will create a few percent smaller kernel than plain LZMA.
  156. The speed is about the same as with LZMA: The decompression
  157. speed of XZ is better than that of bzip2 but worse than gzip
  158. and LZO. Compression is slow.
  159. config KERNEL_LZO
  160. bool "LZO"
  161. depends on HAVE_KERNEL_LZO
  162. help
  163. Its compression ratio is the poorest among the choices. The kernel
  164. size is about 10% bigger than gzip; however its speed
  165. (both compression and decompression) is the fastest.
  166. config KERNEL_LZ4
  167. bool "LZ4"
  168. depends on HAVE_KERNEL_LZ4
  169. help
  170. LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
  171. A preliminary version of LZ4 de/compression tool is available at
  172. <https://code.google.com/p/lz4/>.
  173. Its compression ratio is worse than LZO. The size of the kernel
  174. is about 8% bigger than LZO. But the decompression speed is
  175. faster than LZO.
  176. endchoice
  177. config DEFAULT_HOSTNAME
  178. string "Default hostname"
  179. default "(none)"
  180. help
  181. This option determines the default system hostname before userspace
  182. calls sethostname(2). The kernel traditionally uses "(none)" here,
  183. but you may wish to use a different default here to make a minimal
  184. system more usable with less configuration.
  185. config SWAP
  186. bool "Support for paging of anonymous memory (swap)"
  187. depends on MMU && BLOCK
  188. default y
  189. help
  190. This option allows you to choose whether you want to have support
  191. for so called swap devices or swap files in your kernel that are
  192. used to provide more virtual memory than the actual RAM present
  193. in your computer. If unsure say Y.
  194. config SYSVIPC
  195. bool "System V IPC"
  196. ---help---
  197. Inter Process Communication is a suite of library functions and
  198. system calls which let processes (running programs) synchronize and
  199. exchange information. It is generally considered to be a good thing,
  200. and some programs won't run unless you say Y here. In particular, if
  201. you want to run the DOS emulator dosemu under Linux (read the
  202. DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
  203. you'll need to say Y here.
  204. You can find documentation about IPC with "info ipc" and also in
  205. section 6.4 of the Linux Programmer's Guide, available from
  206. <http://www.tldp.org/guides.html>.
  207. config SYSVIPC_SYSCTL
  208. bool
  209. depends on SYSVIPC
  210. depends on SYSCTL
  211. default y
  212. config POSIX_MQUEUE
  213. bool "POSIX Message Queues"
  214. depends on NET
  215. ---help---
  216. POSIX variant of message queues is a part of IPC. In POSIX message
  217. queues every message has a priority which decides about succession
  218. of receiving it by a process. If you want to compile and run
  219. programs written e.g. for Solaris with use of its POSIX message
  220. queues (functions mq_*) say Y here.
  221. POSIX message queues are visible as a filesystem called 'mqueue'
  222. and can be mounted somewhere if you want to do filesystem
  223. operations on message queues.
  224. If unsure, say Y.
  225. config POSIX_MQUEUE_SYSCTL
  226. bool
  227. depends on POSIX_MQUEUE
  228. depends on SYSCTL
  229. default y
  230. config CROSS_MEMORY_ATTACH
  231. bool "Enable process_vm_readv/writev syscalls"
  232. depends on MMU
  233. default y
  234. help
  235. Enabling this option adds the system calls process_vm_readv and
  236. process_vm_writev which allow a process with the correct privileges
  237. to directly read from or write to another process' address space.
  238. See the man page for more details.
  239. config FHANDLE
  240. bool "open by fhandle syscalls" if EXPERT
  241. select EXPORTFS
  242. default y
  243. help
  244. If you say Y here, a user level program will be able to map
  245. file names to handle and then later use the handle for
  246. different file system operations. This is useful in implementing
  247. userspace file servers, which now track files using handles instead
  248. of names. The handle would remain the same even if file names
  249. get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
  250. syscalls.
  251. config USELIB
  252. bool "uselib syscall"
  253. def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
  254. help
  255. This option enables the uselib syscall, a system call used in the
  256. dynamic linker from libc5 and earlier. glibc does not use this
  257. system call. If you intend to run programs built on libc5 or
  258. earlier, you may need to enable this syscall. Current systems
  259. running glibc can safely disable this.
  260. config AUDIT
  261. bool "Auditing support"
  262. depends on NET
  263. help
  264. Enable auditing infrastructure that can be used with another
  265. kernel subsystem, such as SELinux (which requires this for
  266. logging of avc messages output). System call auditing is included
  267. on architectures which support it.
  268. config HAVE_ARCH_AUDITSYSCALL
  269. bool
  270. config AUDITSYSCALL
  271. def_bool y
  272. depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
  273. config AUDIT_WATCH
  274. def_bool y
  275. depends on AUDITSYSCALL
  276. select FSNOTIFY
  277. config AUDIT_TREE
  278. def_bool y
  279. depends on AUDITSYSCALL
  280. select FSNOTIFY
  281. source "kernel/irq/Kconfig"
  282. source "kernel/time/Kconfig"
  283. menu "CPU/Task time and stats accounting"
  284. config VIRT_CPU_ACCOUNTING
  285. bool
  286. choice
  287. prompt "Cputime accounting"
  288. default TICK_CPU_ACCOUNTING if !PPC64
  289. default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
  290. # Kind of a stub config for the pure tick based cputime accounting
  291. config TICK_CPU_ACCOUNTING
  292. bool "Simple tick based cputime accounting"
  293. depends on !S390 && !NO_HZ_FULL
  294. help
  295. This is the basic tick based cputime accounting that maintains
  296. statistics about user, system and idle time spent on per jiffies
  297. granularity.
  298. If unsure, say Y.
  299. config VIRT_CPU_ACCOUNTING_NATIVE
  300. bool "Deterministic task and CPU time accounting"
  301. depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
  302. select VIRT_CPU_ACCOUNTING
  303. help
  304. Select this option to enable more accurate task and CPU time
  305. accounting. This is done by reading a CPU counter on each
  306. kernel entry and exit and on transitions within the kernel
  307. between system, softirq and hardirq state, so there is a
  308. small performance impact. In the case of s390 or IBM POWER > 5,
  309. this also enables accounting of stolen time on logically-partitioned
  310. systems.
  311. config VIRT_CPU_ACCOUNTING_GEN
  312. bool "Full dynticks CPU time accounting"
  313. depends on HAVE_CONTEXT_TRACKING
  314. depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
  315. select VIRT_CPU_ACCOUNTING
  316. select CONTEXT_TRACKING
  317. help
  318. Select this option to enable task and CPU time accounting on full
  319. dynticks systems. This accounting is implemented by watching every
  320. kernel-user boundaries using the context tracking subsystem.
  321. The accounting is thus performed at the expense of some significant
  322. overhead.
  323. For now this is only useful if you are working on the full
  324. dynticks subsystem development.
  325. If unsure, say N.
  326. endchoice
  327. config IRQ_TIME_ACCOUNTING
  328. bool "Fine granularity task level IRQ time accounting"
  329. depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
  330. help
  331. Select this option to enable fine granularity task irq time
  332. accounting. This is done by reading a timestamp on each
  333. transitions between softirq and hardirq state, so there can be a
  334. small performance impact.
  335. If in doubt, say N here.
  336. config SCHED_WALT
  337. bool "Support window based load tracking"
  338. depends on SMP
  339. help
  340. This feature will allow the scheduler to maintain a tunable window
  341. based set of metrics for tasks and runqueues. These metrics can be
  342. used to guide task placement as well as task frequency requirements
  343. for cpufreq governors.
  344. config BSD_PROCESS_ACCT
  345. bool "BSD Process Accounting"
  346. depends on MULTIUSER
  347. help
  348. If you say Y here, a user level program will be able to instruct the
  349. kernel (via a special system call) to write process accounting
  350. information to a file: whenever a process exits, information about
  351. that process will be appended to the file by the kernel. The
  352. information includes things such as creation time, owning user,
  353. command name, memory usage, controlling terminal etc. (the complete
  354. list is in the struct acct in <file:include/linux/acct.h>). It is
  355. up to the user level program to do useful things with this
  356. information. This is generally a good idea, so say Y.
  357. config BSD_PROCESS_ACCT_V3
  358. bool "BSD Process Accounting version 3 file format"
  359. depends on BSD_PROCESS_ACCT
  360. default n
  361. help
  362. If you say Y here, the process accounting information is written
  363. in a new file format that also logs the process IDs of each
  364. process and it's parent. Note that this file format is incompatible
  365. with previous v0/v1/v2 file formats, so you will need updated tools
  366. for processing it. A preliminary version of these tools is available
  367. at <http://www.gnu.org/software/acct/>.
  368. config TASKSTATS
  369. bool "Export task/process statistics through netlink"
  370. depends on NET
  371. depends on MULTIUSER
  372. default n
  373. help
  374. Export selected statistics for tasks/processes through the
  375. generic netlink interface. Unlike BSD process accounting, the
  376. statistics are available during the lifetime of tasks/processes as
  377. responses to commands. Like BSD accounting, they are sent to user
  378. space on task exit.
  379. Say N if unsure.
  380. config TASK_DELAY_ACCT
  381. bool "Enable per-task delay accounting"
  382. depends on TASKSTATS
  383. select SCHED_INFO
  384. help
  385. Collect information on time spent by a task waiting for system
  386. resources like cpu, synchronous block I/O completion and swapping
  387. in pages. Such statistics can help in setting a task's priorities
  388. relative to other tasks for cpu, io, rss limits etc.
  389. Say N if unsure.
  390. config TASK_XACCT
  391. bool "Enable extended accounting over taskstats"
  392. depends on TASKSTATS
  393. help
  394. Collect extended task accounting data and send the data
  395. to userland for processing over the taskstats interface.
  396. Say N if unsure.
  397. config TASK_IO_ACCOUNTING
  398. bool "Enable per-task storage I/O accounting"
  399. depends on TASK_XACCT
  400. help
  401. Collect information on the number of bytes of storage I/O which this
  402. task has caused.
  403. Say N if unsure.
  404. config PSI
  405. bool "Pressure stall information tracking"
  406. help
  407. Collect metrics that indicate how overcommitted the CPU, memory,
  408. and IO capacity are in the system.
  409. If you say Y here, the kernel will create /proc/pressure/ with the
  410. pressure statistics files cpu, memory, and io. These will indicate
  411. the share of walltime in which some or all tasks in the system are
  412. delayed due to contention of the respective resource.
  413. In kernels with cgroup support, cgroups (cgroup2 only) will
  414. have cpu.pressure, memory.pressure, and io.pressure files,
  415. which aggregate pressure stalls for the grouped tasks only.
  416. For more details see Documentation/accounting/psi.txt.
  417. Say N if unsure.
  418. config PSI_DEFAULT_DISABLED
  419. bool "Require boot parameter to enable pressure stall information tracking"
  420. default n
  421. depends on PSI
  422. help
  423. If set, pressure stall information tracking will be disabled
  424. per default but can be enabled through passing psi=1 on the
  425. kernel commandline during boot.
  426. This feature adds some code to the task wakeup and sleep
  427. paths of the scheduler. The overhead is too low to affect
  428. common scheduling-intense workloads in practice (such as
  429. webservers, memcache), but it does show up in artificial
  430. scheduler stress tests, such as hackbench.
  431. If you are paranoid and not sure what the kernel will be
  432. used for, say Y.
  433. Say N if unsure.
  434. endmenu # "CPU/Task time and stats accounting"
  435. source "kernel/rcu/Kconfig"
  436. config BUILD_BIN2C
  437. bool
  438. default n
  439. config IKCONFIG
  440. tristate "Kernel .config support"
  441. select BUILD_BIN2C
  442. ---help---
  443. This option enables the complete Linux kernel ".config" file
  444. contents to be saved in the kernel. It provides documentation
  445. of which kernel options are used in a running kernel or in an
  446. on-disk kernel. This information can be extracted from the kernel
  447. image file with the script scripts/extract-ikconfig and used as
  448. input to rebuild the current kernel or to build another kernel.
  449. It can also be extracted from a running kernel by reading
  450. /proc/config.gz if enabled (below).
  451. config IKCONFIG_PROC
  452. bool "Enable access to .config through /proc/config.gz"
  453. depends on IKCONFIG && PROC_FS
  454. ---help---
  455. This option enables access to the kernel configuration file
  456. through /proc/config.gz.
  457. config IKHEADERS
  458. tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
  459. depends on SYSFS
  460. help
  461. This option enables access to the in-kernel headers that are generated during
  462. the build process. These can be used to build eBPF tracing programs,
  463. or similar programs. If you build the headers as a module, a module called
  464. kheaders.ko is built which can be loaded on-demand to get access to headers.
  465. config LOG_BUF_SHIFT
  466. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  467. range 12 25 if !H8300
  468. range 12 19 if H8300
  469. default 17
  470. depends on PRINTK
  471. help
  472. Select the minimal kernel log buffer size as a power of 2.
  473. The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
  474. parameter, see below. Any higher size also might be forced
  475. by "log_buf_len" boot parameter.
  476. Examples:
  477. 17 => 128 KB
  478. 16 => 64 KB
  479. 15 => 32 KB
  480. 14 => 16 KB
  481. 13 => 8 KB
  482. 12 => 4 KB
  483. config LOG_CPU_MAX_BUF_SHIFT
  484. int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
  485. depends on SMP
  486. range 0 21
  487. default 12 if !BASE_SMALL
  488. default 0 if BASE_SMALL
  489. depends on PRINTK
  490. help
  491. This option allows to increase the default ring buffer size
  492. according to the number of CPUs. The value defines the contribution
  493. of each CPU as a power of 2. The used space is typically only few
  494. lines however it might be much more when problems are reported,
  495. e.g. backtraces.
  496. The increased size means that a new buffer has to be allocated and
  497. the original static one is unused. It makes sense only on systems
  498. with more CPUs. Therefore this value is used only when the sum of
  499. contributions is greater than the half of the default kernel ring
  500. buffer as defined by LOG_BUF_SHIFT. The default values are set
  501. so that more than 64 CPUs are needed to trigger the allocation.
  502. Also this option is ignored when "log_buf_len" kernel parameter is
  503. used as it forces an exact (power of two) size of the ring buffer.
  504. The number of possible CPUs is used for this computation ignoring
  505. hotplugging making the computation optimal for the worst case
  506. scenario while allowing a simple algorithm to be used from bootup.
  507. Examples shift values and their meaning:
  508. 17 => 128 KB for each CPU
  509. 16 => 64 KB for each CPU
  510. 15 => 32 KB for each CPU
  511. 14 => 16 KB for each CPU
  512. 13 => 8 KB for each CPU
  513. 12 => 4 KB for each CPU
  514. config PRINTK_SAFE_LOG_BUF_SHIFT
  515. int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
  516. range 10 21
  517. default 13
  518. depends on PRINTK
  519. help
  520. Select the size of an alternate printk per-CPU buffer where messages
  521. printed from usafe contexts are temporary stored. One example would
  522. be NMI messages, another one - printk recursion. The messages are
  523. copied to the main log buffer in a safe context to avoid a deadlock.
  524. The value defines the size as a power of 2.
  525. Those messages are rare and limited. The largest one is when
  526. a backtrace is printed. It usually fits into 4KB. Select
  527. 8KB if you want to be on the safe side.
  528. Examples:
  529. 17 => 128 KB for each CPU
  530. 16 => 64 KB for each CPU
  531. 15 => 32 KB for each CPU
  532. 14 => 16 KB for each CPU
  533. 13 => 8 KB for each CPU
  534. 12 => 4 KB for each CPU
  535. #
  536. # Architectures with an unreliable sched_clock() should select this:
  537. #
  538. config HAVE_UNSTABLE_SCHED_CLOCK
  539. bool
  540. config GENERIC_SCHED_CLOCK
  541. bool
  542. menu "Scheduler features"
  543. config UCLAMP_TASK
  544. bool "Enable utilization clamping for RT/FAIR tasks"
  545. depends on CPU_FREQ_GOV_SCHEDUTIL
  546. default n
  547. help
  548. This feature enables the scheduler to track the clamped utilization
  549. of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
  550. When this option is enabled, the user can specify a min and max CPU
  551. bandwidth which is allowed for a task.
  552. The max bandwidth allows to clamp the maximum frequency a task can
  553. use, while the min bandwidth allows to define a minimum frequency a
  554. task will always use.
  555. If in doubt, say N.
  556. config UCLAMP_GROUPS_COUNT
  557. int "Number of different utilization clamp values supported"
  558. range 0 32
  559. default 5
  560. depends on UCLAMP_TASK
  561. help
  562. This defines the maximum number of different utilization clamp
  563. values which can be concurrently enforced for each utilization
  564. clamp index (i.e. minimum and maximum utilization).
  565. Only a limited number of clamp values are supported because:
  566. 1. there are usually only few classes of workloads for which it
  567. makes sense to boost/cap for different frequencies,
  568. e.g. background vs foreground, interactive vs low-priority.
  569. 2. it allows a simpler and more memory/time efficient tracking of
  570. the per-CPU clamp values.
  571. If in doubt, use the default value.
  572. config UCLAMP_MAP_OPP
  573. bool "Map utilization clamping to opp corresponding capacity"
  574. depends on UCLAMP_TASK
  575. depends on MTK_UNIFY_POWER
  576. default n
  577. help
  578. This feature map utilization clamping value to cpu opp capacity.
  579. If in doubt, say N.
  580. config NONLINEAR_FREQ_CTL
  581. bool "Non-linear frequency control"
  582. depends on MTK_CPU_FREQ
  583. depends on MTK_UNIFY_POWER
  584. default n
  585. help
  586. Use power table capacity to control DVFS, cpu capacity/
  587. loading tracking/opp calculation will be affected.
  588. If unsure, say N.
  589. endmenu
  590. menu "FAIR Scheuler tunables"
  591. choice
  592. prompt "Utilization's PELT half-Life"
  593. default PELT_UTIL_HALFLIFE_32
  594. help
  595. Allows choosing one of the possible values for the PELT half-life to
  596. be used for the update of the utilization of tasks and CPUs.
  597. The half-life is the amount of [ms] required by the PELT signal to
  598. build up to 50% utilization. The higher the half-life the longer it
  599. takes for a task to be represented as a big one.
  600. If not sure, use the default of 32 ms.
  601. config PELT_UTIL_HALFLIFE_32
  602. bool "32 ms, default for server"
  603. config PELT_UTIL_HALFLIFE_16
  604. bool "16 ms, suggested for interactive workloads"
  605. help
  606. Use 16ms as PELT half-life value. This will increase the ramp-up and
  607. decay of utlization and load twice as fast as for the default
  608. configuration using 32ms.
  609. config PELT_UTIL_HALFLIFE_8
  610. bool "8 ms, very fast"
  611. help
  612. Use 8ms as PELT half-life value. This will increase the ramp-up and
  613. decay of utlization and load four time as fast as for the default
  614. configuration using 32ms.
  615. endchoice
  616. endmenu # FAIR Scheduler tunables"
  617. #
  618. # For architectures that want to enable the support for NUMA-affine scheduler
  619. # balancing logic:
  620. #
  621. config ARCH_SUPPORTS_NUMA_BALANCING
  622. bool
  623. #
  624. # For architectures that prefer to flush all TLBs after a number of pages
  625. # are unmapped instead of sending one IPI per page to flush. The architecture
  626. # must provide guarantees on what happens if a clean TLB cache entry is
  627. # written after the unmap. Details are in mm/rmap.c near the check for
  628. # should_defer_flush. The architecture should also consider if the full flush
  629. # and the refill costs are offset by the savings of sending fewer IPIs.
  630. config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
  631. bool
  632. #
  633. # For architectures that know their GCC __int128 support is sound
  634. #
  635. config ARCH_SUPPORTS_INT128
  636. bool
  637. # For architectures that (ab)use NUMA to represent different memory regions
  638. # all cpu-local but of different latencies, such as SuperH.
  639. #
  640. config ARCH_WANT_NUMA_VARIABLE_LOCALITY
  641. bool
  642. config NUMA_BALANCING
  643. bool "Memory placement aware NUMA scheduler"
  644. depends on ARCH_SUPPORTS_NUMA_BALANCING
  645. depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
  646. depends on SMP && NUMA && MIGRATION
  647. help
  648. This option adds support for automatic NUMA aware memory/task placement.
  649. The mechanism is quite primitive and is based on migrating memory when
  650. it has references to the node the task is running on.
  651. This system will be inactive on UMA systems.
  652. config NUMA_BALANCING_DEFAULT_ENABLED
  653. bool "Automatically enable NUMA aware memory/task placement"
  654. default y
  655. depends on NUMA_BALANCING
  656. help
  657. If set, automatic NUMA balancing will be enabled if running on a NUMA
  658. machine.
  659. menuconfig CGROUPS
  660. bool "Control Group support"
  661. select KERNFS
  662. help
  663. This option adds support for grouping sets of processes together, for
  664. use with process control subsystems such as Cpusets, CFS, memory
  665. controls or device isolation.
  666. See
  667. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  668. - Documentation/cgroup-v1/ (features for grouping, isolation
  669. and resource control)
  670. Say N if unsure.
  671. if CGROUPS
  672. config PAGE_COUNTER
  673. bool
  674. config MEMCG
  675. bool "Memory controller"
  676. select PAGE_COUNTER
  677. select EVENTFD
  678. help
  679. Provides control over the memory footprint of tasks in a cgroup.
  680. config MEMCG_SWAP
  681. bool "Swap controller"
  682. depends on MEMCG && SWAP
  683. help
  684. Provides control over the swap space consumed by tasks in a cgroup.
  685. config MEMCG_SWAP_ENABLED
  686. bool "Swap controller enabled by default"
  687. depends on MEMCG_SWAP
  688. default y
  689. help
  690. Memory Resource Controller Swap Extension comes with its price in
  691. a bigger memory consumption. General purpose distribution kernels
  692. which want to enable the feature but keep it disabled by default
  693. and let the user enable it by swapaccount=1 boot command line
  694. parameter should have this option unselected.
  695. For those who want to have the feature enabled by default should
  696. select this option (if, for some reason, they need to disable it
  697. then swapaccount=0 does the trick).
  698. config BLK_CGROUP
  699. bool "IO controller"
  700. depends on BLOCK
  701. default n
  702. ---help---
  703. Generic block IO controller cgroup interface. This is the common
  704. cgroup interface which should be used by various IO controlling
  705. policies.
  706. Currently, CFQ IO scheduler uses it to recognize task groups and
  707. control disk bandwidth allocation (proportional time slice allocation)
  708. to such task groups. It is also used by bio throttling logic in
  709. block layer to implement upper limit in IO rates on a device.
  710. This option only enables generic Block IO controller infrastructure.
  711. One needs to also enable actual IO controlling logic/policy. For
  712. enabling proportional weight division of disk bandwidth in CFQ, set
  713. CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
  714. CONFIG_BLK_DEV_THROTTLING=y.
  715. See Documentation/cgroup-v1/blkio-controller.txt for more information.
  716. config DEBUG_BLK_CGROUP
  717. bool "IO controller debugging"
  718. depends on BLK_CGROUP
  719. default n
  720. ---help---
  721. Enable some debugging help. Currently it exports additional stat
  722. files in a cgroup which can be useful for debugging.
  723. config CGROUP_WRITEBACK
  724. bool
  725. depends on MEMCG && BLK_CGROUP
  726. default y
  727. menuconfig CGROUP_SCHED
  728. bool "CPU controller"
  729. default n
  730. help
  731. This feature lets CPU scheduler recognize task groups and control CPU
  732. bandwidth allocation to such task groups. It uses cgroups to group
  733. tasks.
  734. if CGROUP_SCHED
  735. config FAIR_GROUP_SCHED
  736. bool "Group scheduling for SCHED_OTHER"
  737. depends on CGROUP_SCHED
  738. default CGROUP_SCHED
  739. config CFS_BANDWIDTH
  740. bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
  741. depends on FAIR_GROUP_SCHED
  742. default n
  743. help
  744. This option allows users to define CPU bandwidth rates (limits) for
  745. tasks running within the fair group scheduler. Groups with no limit
  746. set are considered to be unconstrained and will run with no
  747. restriction.
  748. See tip/Documentation/scheduler/sched-bwc.txt for more information.
  749. config RT_GROUP_SCHED
  750. bool "Group scheduling for SCHED_RR/FIFO"
  751. depends on CGROUP_SCHED
  752. default n
  753. help
  754. This feature lets you explicitly allocate real CPU bandwidth
  755. to task groups. If enabled, it will also make it impossible to
  756. schedule realtime tasks for non-root users until you allocate
  757. realtime bandwidth for them.
  758. See Documentation/scheduler/sched-rt-group.txt for more information.
  759. endif #CGROUP_SCHED
  760. config UCLAMP_TASK_GROUP
  761. bool "Utilization clamping per group of tasks"
  762. depends on CGROUP_SCHED
  763. depends on UCLAMP_TASK
  764. default n
  765. help
  766. This feature enables the scheduler to track the clamped utilization
  767. of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
  768. When this option is enabled, the user can specify a min and max
  769. CPU bandwidth which is allowed for each single task in a group.
  770. The max bandwidth allows to clamp the maximum frequency a task
  771. can use, while the min bandwidth allows to define a minimum
  772. frequency a task will always use.
  773. When task group based utilization clamping is enabled, an eventually
  774. specified task-specific clamp value is constrained by the cgroup
  775. specified clamp value. Both minimum and maximum task clamping cannot
  776. be bigger than the corresponding clamping defined at task group level.
  777. If in doubt, say N.
  778. config CGROUP_PIDS
  779. bool "PIDs controller"
  780. help
  781. Provides enforcement of process number limits in the scope of a
  782. cgroup. Any attempt to fork more processes than is allowed in the
  783. cgroup will fail. PIDs are fundamentally a global resource because it
  784. is fairly trivial to reach PID exhaustion before you reach even a
  785. conservative kmemcg limit. As a result, it is possible to grind a
  786. system to halt without being limited by other cgroup policies. The
  787. PIDs controller is designed to stop this from happening.
  788. It should be noted that organisational operations (such as attaching
  789. to a cgroup hierarchy will *not* be blocked by the PIDs controller),
  790. since the PIDs limit only affects a process's ability to fork, not to
  791. attach to a cgroup.
  792. config CGROUP_RDMA
  793. bool "RDMA controller"
  794. help
  795. Provides enforcement of RDMA resources defined by IB stack.
  796. It is fairly easy for consumers to exhaust RDMA resources, which
  797. can result into resource unavailability to other consumers.
  798. RDMA controller is designed to stop this from happening.
  799. Attaching processes with active RDMA resources to the cgroup
  800. hierarchy is allowed even if can cross the hierarchy's limit.
  801. config CGROUP_FREEZER
  802. bool "Freezer controller"
  803. help
  804. Provides a way to freeze and unfreeze all tasks in a
  805. cgroup.
  806. This option affects the ORIGINAL cgroup interface. The cgroup2 memory
  807. controller includes important in-kernel memory consumers per default.
  808. If you're using cgroup2, say N.
  809. config CGROUP_HUGETLB
  810. bool "HugeTLB controller"
  811. depends on HUGETLB_PAGE
  812. select PAGE_COUNTER
  813. default n
  814. help
  815. Provides a cgroup controller for HugeTLB pages.
  816. When you enable this, you can put a per cgroup limit on HugeTLB usage.
  817. The limit is enforced during page fault. Since HugeTLB doesn't
  818. support page reclaim, enforcing the limit at page fault time implies
  819. that, the application will get SIGBUS signal if it tries to access
  820. HugeTLB pages beyond its limit. This requires the application to know
  821. beforehand how much HugeTLB pages it would require for its use. The
  822. control group is tracked in the third page lru pointer. This means
  823. that we cannot use the controller with huge page less than 3 pages.
  824. config CPUSETS
  825. bool "Cpuset controller"
  826. depends on SMP
  827. help
  828. This option will let you create and manage CPUSETs which
  829. allow dynamically partitioning a system into sets of CPUs and
  830. Memory Nodes and assigning tasks to run only within those sets.
  831. This is primarily useful on large SMP or NUMA systems.
  832. Say N if unsure.
  833. config PROC_PID_CPUSET
  834. bool "Include legacy /proc/<pid>/cpuset file"
  835. depends on CPUSETS
  836. default y
  837. config CGROUP_DEVICE
  838. bool "Device controller"
  839. help
  840. Provides a cgroup controller implementing whitelists for
  841. devices which a process in the cgroup can mknod or open.
  842. config CGROUP_CPUACCT
  843. bool "Simple CPU accounting controller"
  844. help
  845. Provides a simple controller for monitoring the
  846. total CPU consumed by the tasks in a cgroup.
  847. config CGROUP_PERF
  848. bool "Perf controller"
  849. depends on PERF_EVENTS
  850. help
  851. This option extends the perf per-cpu mode to restrict monitoring
  852. to threads which belong to the cgroup specified and run on the
  853. designated cpu.
  854. Say N if unsure.
  855. config CGROUP_BPF
  856. bool "Support for eBPF programs attached to cgroups"
  857. depends on BPF_SYSCALL
  858. select SOCK_CGROUP_DATA
  859. help
  860. Allow attaching eBPF programs to a cgroup using the bpf(2)
  861. syscall command BPF_PROG_ATTACH.
  862. In which context these programs are accessed depends on the type
  863. of attachment. For instance, programs that are attached using
  864. BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
  865. inet sockets.
  866. config CGROUP_DEBUG
  867. bool "Debug controller"
  868. default n
  869. depends on DEBUG_KERNEL
  870. help
  871. This option enables a simple controller that exports
  872. debugging information about the cgroups framework. This
  873. controller is for control cgroup debugging only. Its
  874. interfaces are not stable.
  875. Say N.
  876. config SOCK_CGROUP_DATA
  877. bool
  878. default n
  879. endif # CGROUPS
  880. config CHECKPOINT_RESTORE
  881. bool "Checkpoint/restore support" if EXPERT
  882. select PROC_CHILDREN
  883. default n
  884. help
  885. Enables additional kernel features in a sake of checkpoint/restore.
  886. In particular it adds auxiliary prctl codes to setup process text,
  887. data and heap segment sizes, and a few additional /proc filesystem
  888. entries.
  889. If unsure, say N here.
  890. menuconfig NAMESPACES
  891. bool "Namespaces support" if EXPERT
  892. depends on MULTIUSER
  893. default !EXPERT
  894. help
  895. Provides the way to make tasks work with different objects using
  896. the same id. For example same IPC id may refer to different objects
  897. or same user id or pid may refer to different tasks when used in
  898. different namespaces.
  899. if NAMESPACES
  900. config UTS_NS
  901. bool "UTS namespace"
  902. default y
  903. help
  904. In this namespace tasks see different info provided with the
  905. uname() system call
  906. config IPC_NS
  907. bool "IPC namespace"
  908. depends on (SYSVIPC || POSIX_MQUEUE)
  909. default y
  910. help
  911. In this namespace tasks work with IPC ids which correspond to
  912. different IPC objects in different namespaces.
  913. config USER_NS
  914. bool "User namespace"
  915. default n
  916. help
  917. This allows containers, i.e. vservers, to use user namespaces
  918. to provide different user info for different servers.
  919. When user namespaces are enabled in the kernel it is
  920. recommended that the MEMCG option also be enabled and that
  921. user-space use the memory control groups to limit the amount
  922. of memory a memory unprivileged users can use.
  923. If unsure, say N.
  924. config PID_NS
  925. bool "PID Namespaces"
  926. default y
  927. help
  928. Support process id namespaces. This allows having multiple
  929. processes with the same pid as long as they are in different
  930. pid namespaces. This is a building block of containers.
  931. config NET_NS
  932. bool "Network namespace"
  933. depends on NET
  934. default y
  935. help
  936. Allow user space to create what appear to be multiple instances
  937. of the network stack.
  938. endif # NAMESPACES
  939. config SCHED_AUTOGROUP
  940. bool "Automatic process group scheduling"
  941. select CGROUPS
  942. select CGROUP_SCHED
  943. select FAIR_GROUP_SCHED
  944. help
  945. This option optimizes the scheduler for common desktop workloads by
  946. automatically creating and populating task groups. This separation
  947. of workloads isolates aggressive CPU burners (like build jobs) from
  948. desktop applications. Task group autogeneration is currently based
  949. upon task session.
  950. config SCHED_TUNE
  951. bool "Boosting for CFS tasks (EXPERIMENTAL)"
  952. depends on SMP
  953. help
  954. This option enables support for task classification using a new
  955. cgroup controller, schedtune. Schedtune allows tasks to be given
  956. a boost value and marked as latency-sensitive or not. This option
  957. provides the "schedtune" controller.
  958. This new controller:
  959. 1. allows only a two layers hierarchy, where the root defines the
  960. system-wide boost value and its direct childrens define each one a
  961. different "class of tasks" to be boosted with a different value
  962. 2. supports up to 16 different task classes, each one which could be
  963. configured with a different boost value
  964. Latency-sensitive tasks are not subject to energy-aware wakeup
  965. task placement. The boost value assigned to tasks is used to
  966. influence task placement and CPU frequency selection (if
  967. utilization-driven frequency selection is in use).
  968. If unsure, say N.
  969. config DEFAULT_USE_ENERGY_AWARE
  970. bool "Default to enabling the Energy Aware Scheduler feature"
  971. default n
  972. help
  973. This option defaults the ENERGY_AWARE scheduling feature to true,
  974. as without SCHED_DEBUG set this feature can't be enabled or disabled
  975. via sysctl.
  976. Say N if unsure.
  977. config SYSFS_DEPRECATED
  978. bool "Enable deprecated sysfs features to support old userspace tools"
  979. depends on SYSFS
  980. default n
  981. help
  982. This option adds code that switches the layout of the "block" class
  983. devices, to not show up in /sys/class/block/, but only in
  984. /sys/block/.
  985. This switch is only active when the sysfs.deprecated=1 boot option is
  986. passed or the SYSFS_DEPRECATED_V2 option is set.
  987. This option allows new kernels to run on old distributions and tools,
  988. which might get confused by /sys/class/block/. Since 2007/2008 all
  989. major distributions and tools handle this just fine.
  990. Recent distributions and userspace tools after 2009/2010 depend on
  991. the existence of /sys/class/block/, and will not work with this
  992. option enabled.
  993. Only if you are using a new kernel on an old distribution, you might
  994. need to say Y here.
  995. config SYSFS_DEPRECATED_V2
  996. bool "Enable deprecated sysfs features by default"
  997. default n
  998. depends on SYSFS
  999. depends on SYSFS_DEPRECATED
  1000. help
  1001. Enable deprecated sysfs by default.
  1002. See the CONFIG_SYSFS_DEPRECATED option for more details about this
  1003. option.
  1004. Only if you are using a new kernel on an old distribution, you might
  1005. need to say Y here. Even then, odds are you would not need it
  1006. enabled, you can always pass the boot option if absolutely necessary.
  1007. config RELAY
  1008. bool "Kernel->user space relay support (formerly relayfs)"
  1009. select IRQ_WORK
  1010. help
  1011. This option enables support for relay interface support in
  1012. certain file systems (such as debugfs).
  1013. It is designed to provide an efficient mechanism for tools and
  1014. facilities to relay large amounts of data from kernel space to
  1015. user space.
  1016. If unsure, say N.
  1017. config BLK_DEV_INITRD
  1018. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  1019. depends on BROKEN || !FRV
  1020. help
  1021. The initial RAM filesystem is a ramfs which is loaded by the
  1022. boot loader (loadlin or lilo) and that is mounted as root
  1023. before the normal boot procedure. It is typically used to
  1024. load modules needed to mount the "real" root file system,
  1025. etc. See <file:Documentation/admin-guide/initrd.rst> for details.
  1026. If RAM disk support (BLK_DEV_RAM) is also included, this
  1027. also enables initial RAM disk (initrd) support and adds
  1028. 15 Kbytes (more on some other architectures) to the kernel size.
  1029. If unsure say Y.
  1030. if BLK_DEV_INITRD
  1031. source "usr/Kconfig"
  1032. endif
  1033. choice
  1034. prompt "Compiler optimization level"
  1035. default CC_OPTIMIZE_FOR_PERFORMANCE
  1036. config CC_OPTIMIZE_FOR_PERFORMANCE
  1037. bool "Optimize for performance"
  1038. help
  1039. This is the default optimization level for the kernel, building
  1040. with the "-O2" compiler flag for best performance and most
  1041. helpful compile-time warnings.
  1042. config CC_OPTIMIZE_FOR_SIZE
  1043. bool "Optimize for size"
  1044. help
  1045. Enabling this option will pass "-Os" instead of "-O2" to
  1046. your compiler resulting in a smaller kernel.
  1047. If unsure, say N.
  1048. endchoice
  1049. config LTO_GCC
  1050. bool "Enable Link Time Optimization for GCC"
  1051. config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
  1052. bool
  1053. help
  1054. This requires that the arch annotates or otherwise protects
  1055. its external entry points from being discarded. Linker scripts
  1056. must also merge .text.*, .data.*, and .bss.* correctly into
  1057. output sections. Care must be taken not to pull in unrelated
  1058. sections (e.g., '.text.init'). Typically '.' in section names
  1059. is used to distinguish them from label names / C identifiers.
  1060. config LD_DEAD_CODE_DATA_ELIMINATION
  1061. bool "Dead code and data elimination (EXPERIMENTAL)"
  1062. depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
  1063. depends on EXPERT
  1064. help
  1065. Select this if the architecture wants to do dead code and
  1066. data elimination with the linker by compiling with
  1067. -ffunction-sections -fdata-sections, and linking with
  1068. --gc-sections.
  1069. This can reduce on disk and in-memory size of the kernel
  1070. code and static data, particularly for small configs and
  1071. on small systems. This has the possibility of introducing
  1072. silently broken kernel if the required annotations are not
  1073. present. This option is not well tested yet, so use at your
  1074. own risk.
  1075. config SYSCTL
  1076. bool
  1077. config HAVE_UID16
  1078. bool
  1079. config SYSCTL_EXCEPTION_TRACE
  1080. bool
  1081. help
  1082. Enable support for /proc/sys/debug/exception-trace.
  1083. config SYSCTL_ARCH_UNALIGN_NO_WARN
  1084. bool
  1085. help
  1086. Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
  1087. Allows arch to define/use @no_unaligned_warning to possibly warn
  1088. about unaligned access emulation going on under the hood.
  1089. config SYSCTL_ARCH_UNALIGN_ALLOW
  1090. bool
  1091. help
  1092. Enable support for /proc/sys/kernel/unaligned-trap
  1093. Allows arches to define/use @unaligned_enabled to runtime toggle
  1094. the unaligned access emulation.
  1095. see arch/parisc/kernel/unaligned.c for reference
  1096. config HAVE_PCSPKR_PLATFORM
  1097. bool
  1098. # interpreter that classic socket filters depend on
  1099. config BPF
  1100. bool
  1101. menuconfig EXPERT
  1102. bool "Configure standard kernel features (expert users)"
  1103. # Unhide debug options, to make the on-by-default options visible
  1104. select DEBUG_KERNEL
  1105. help
  1106. This option allows certain base kernel options and settings
  1107. to be disabled or tweaked. This is for specialized
  1108. environments which can tolerate a "non-standard" kernel.
  1109. Only use this if you really know what you are doing.
  1110. config UID16
  1111. bool "Enable 16-bit UID system calls" if EXPERT
  1112. depends on HAVE_UID16 && MULTIUSER
  1113. default y
  1114. help
  1115. This enables the legacy 16-bit UID syscall wrappers.
  1116. config MULTIUSER
  1117. bool "Multiple users, groups and capabilities support" if EXPERT
  1118. default y
  1119. help
  1120. This option enables support for non-root users, groups and
  1121. capabilities.
  1122. If you say N here, all processes will run with UID 0, GID 0, and all
  1123. possible capabilities. Saying N here also compiles out support for
  1124. system calls related to UIDs, GIDs, and capabilities, such as setuid,
  1125. setgid, and capset.
  1126. If unsure, say Y here.
  1127. config SGETMASK_SYSCALL
  1128. bool "sgetmask/ssetmask syscalls support" if EXPERT
  1129. def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
  1130. ---help---
  1131. sys_sgetmask and sys_ssetmask are obsolete system calls
  1132. no longer supported in libc but still enabled by default in some
  1133. architectures.
  1134. If unsure, leave the default option here.
  1135. config SYSFS_SYSCALL
  1136. bool "Sysfs syscall support" if EXPERT
  1137. default y
  1138. ---help---
  1139. sys_sysfs is an obsolete system call no longer supported in libc.
  1140. Note that disabling this option is more secure but might break
  1141. compatibility with some systems.
  1142. If unsure say Y here.
  1143. config SYSCTL_SYSCALL
  1144. bool "Sysctl syscall support" if EXPERT
  1145. depends on PROC_SYSCTL
  1146. default n
  1147. select SYSCTL
  1148. ---help---
  1149. sys_sysctl uses binary paths that have been found challenging
  1150. to properly maintain and use. The interface in /proc/sys
  1151. using paths with ascii names is now the primary path to this
  1152. information.
  1153. Almost nothing using the binary sysctl interface so if you are
  1154. trying to save some space it is probably safe to disable this,
  1155. making your kernel marginally smaller.
  1156. If unsure say N here.
  1157. config POSIX_TIMERS
  1158. bool "Posix Clocks & timers" if EXPERT
  1159. default y
  1160. help
  1161. This includes native support for POSIX timers to the kernel.
  1162. Some embedded systems have no use for them and therefore they
  1163. can be configured out to reduce the size of the kernel image.
  1164. When this option is disabled, the following syscalls won't be
  1165. available: timer_create, timer_gettime: timer_getoverrun,
  1166. timer_settime, timer_delete, clock_adjtime, getitimer,
  1167. setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
  1168. clock_getres and clock_nanosleep syscalls will be limited to
  1169. CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
  1170. If unsure say y.
  1171. config KALLSYMS
  1172. bool "Load all symbols for debugging/ksymoops" if EXPERT
  1173. default y
  1174. help
  1175. Say Y here to let the kernel print out symbolic crash information and
  1176. symbolic stack backtraces. This increases the size of the kernel
  1177. somewhat, as all symbols have to be loaded into the kernel image.
  1178. config KALLSYMS_ALL
  1179. bool "Include all symbols in kallsyms"
  1180. depends on DEBUG_KERNEL && KALLSYMS
  1181. help
  1182. Normally kallsyms only contains the symbols of functions for nicer
  1183. OOPS messages and backtraces (i.e., symbols from the text and inittext
  1184. sections). This is sufficient for most cases. And only in very rare
  1185. cases (e.g., when a debugger is used) all symbols are required (e.g.,
  1186. names of variables from the data sections, etc).
  1187. This option makes sure that all symbols are loaded into the kernel
  1188. image (i.e., symbols from all sections) in cost of increased kernel
  1189. size (depending on the kernel configuration, it may be 300KiB or
  1190. something like this).
  1191. Say N unless you really need all symbols.
  1192. config KALLSYMS_ABSOLUTE_PERCPU
  1193. bool
  1194. depends on KALLSYMS
  1195. default X86_64 && SMP
  1196. config KALLSYMS_BASE_RELATIVE
  1197. bool "Enable KALLSYMS_BASE_RELATIVE or not"
  1198. depends on KALLSYMS
  1199. default !IA64 && !(TILE && 64BIT)
  1200. help
  1201. Instead of emitting them as absolute values in the native word size,
  1202. emit the symbol references in the kallsyms table as 32-bit entries,
  1203. each containing a relative value in the range [base, base + U32_MAX]
  1204. or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
  1205. an absolute value in the range [0, S32_MAX] or a relative value in the
  1206. range [base, base + S32_MAX], where base is the lowest relative symbol
  1207. address encountered in the image.
  1208. On 64-bit builds, this reduces the size of the address table by 50%,
  1209. but more importantly, it results in entries whose values are build
  1210. time constants, and no relocation pass is required at runtime to fix
  1211. up the entries based on the runtime load address of the kernel.
  1212. config PRINTK
  1213. default y
  1214. bool "Enable support for printk" if EXPERT
  1215. select IRQ_WORK
  1216. help
  1217. This option enables normal printk support. Removing it
  1218. eliminates most of the message strings from the kernel image
  1219. and makes the kernel more or less silent. As this makes it
  1220. very difficult to diagnose system problems, saying N here is
  1221. strongly discouraged.
  1222. config PRINTK_NMI
  1223. def_bool y
  1224. depends on PRINTK
  1225. depends on HAVE_NMI
  1226. config BUG
  1227. bool "BUG() support" if EXPERT
  1228. default y
  1229. help
  1230. Disabling this option eliminates support for BUG and WARN, reducing
  1231. the size of your kernel image and potentially quietly ignoring
  1232. numerous fatal conditions. You should only consider disabling this
  1233. option for embedded systems with no facilities for reporting errors.
  1234. Just say Y.
  1235. config ELF_CORE
  1236. depends on COREDUMP
  1237. default y
  1238. bool "Enable ELF core dumps" if EXPERT
  1239. help
  1240. Enable support for generating core dumps. Disabling saves about 4k.
  1241. config PCSPKR_PLATFORM
  1242. bool "Enable PC-Speaker support" if EXPERT
  1243. depends on HAVE_PCSPKR_PLATFORM
  1244. select I8253_LOCK
  1245. default y
  1246. help
  1247. This option allows to disable the internal PC-Speaker
  1248. support, saving some memory.
  1249. config BASE_FULL
  1250. default y
  1251. bool "Enable full-sized data structures for core" if EXPERT
  1252. help
  1253. Disabling this option reduces the size of miscellaneous core
  1254. kernel data structures. This saves memory on small machines,
  1255. but may reduce performance.
  1256. config FUTEX
  1257. bool "Enable futex support" if EXPERT
  1258. default y
  1259. imply RT_MUTEXES
  1260. help
  1261. Disabling this option will cause the kernel to be built without
  1262. support for "fast userspace mutexes". The resulting kernel may not
  1263. run glibc-based applications correctly.
  1264. config FUTEX_PI
  1265. bool
  1266. depends on FUTEX && RT_MUTEXES
  1267. default y
  1268. config HAVE_FUTEX_CMPXCHG
  1269. bool
  1270. depends on FUTEX
  1271. help
  1272. Architectures should select this if futex_atomic_cmpxchg_inatomic()
  1273. is implemented and always working. This removes a couple of runtime
  1274. checks.
  1275. config EPOLL
  1276. bool "Enable eventpoll support" if EXPERT
  1277. default y
  1278. help
  1279. Disabling this option will cause the kernel to be built without
  1280. support for epoll family of system calls.
  1281. config SIGNALFD
  1282. bool "Enable signalfd() system call" if EXPERT
  1283. default y
  1284. help
  1285. Enable the signalfd() system call that allows to receive signals
  1286. on a file descriptor.
  1287. If unsure, say Y.
  1288. config TIMERFD
  1289. bool "Enable timerfd() system call" if EXPERT
  1290. default y
  1291. help
  1292. Enable the timerfd() system call that allows to receive timer
  1293. events on a file descriptor.
  1294. If unsure, say Y.
  1295. config EVENTFD
  1296. bool "Enable eventfd() system call" if EXPERT
  1297. default y
  1298. help
  1299. Enable the eventfd() system call that allows to receive both
  1300. kernel notification (ie. KAIO) or userspace notifications.
  1301. If unsure, say Y.
  1302. # syscall, maps, verifier
  1303. config BPF_SYSCALL
  1304. bool "Enable bpf() system call"
  1305. select BPF
  1306. default n
  1307. help
  1308. Enable the bpf() system call that allows to manipulate eBPF
  1309. programs and maps via file descriptors.
  1310. config BPF_JIT_ALWAYS_ON
  1311. bool "Permanently enable BPF JIT and remove BPF interpreter"
  1312. depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
  1313. help
  1314. Enables BPF JIT and removes BPF interpreter to avoid
  1315. speculative execution of BPF instructions by the interpreter
  1316. config SHMEM
  1317. bool "Use full shmem filesystem" if EXPERT
  1318. default y
  1319. depends on MMU
  1320. help
  1321. The shmem is an internal filesystem used to manage shared memory.
  1322. It is backed by swap and manages resource limits. It is also exported
  1323. to userspace as tmpfs if TMPFS is enabled. Disabling this
  1324. option replaces shmem and tmpfs with the much simpler ramfs code,
  1325. which may be appropriate on small systems without swap.
  1326. config AIO
  1327. bool "Enable AIO support" if EXPERT
  1328. default y
  1329. help
  1330. This option enables POSIX asynchronous I/O which may by used
  1331. by some high performance threaded applications. Disabling
  1332. this option saves about 7k.
  1333. config ADVISE_SYSCALLS
  1334. bool "Enable madvise/fadvise syscalls" if EXPERT
  1335. default y
  1336. help
  1337. This option enables the madvise and fadvise syscalls, used by
  1338. applications to advise the kernel about their future memory or file
  1339. usage, improving performance. If building an embedded system where no
  1340. applications use these syscalls, you can disable this option to save
  1341. space.
  1342. config USERFAULTFD
  1343. bool "Enable userfaultfd() system call"
  1344. depends on MMU
  1345. help
  1346. Enable the userfaultfd() system call that allows to intercept and
  1347. handle page faults in userland.
  1348. config PCI_QUIRKS
  1349. default y
  1350. bool "Enable PCI quirk workarounds" if EXPERT
  1351. depends on PCI
  1352. help
  1353. This enables workarounds for various PCI chipset
  1354. bugs/quirks. Disable this only if your target machine is
  1355. unaffected by PCI quirks.
  1356. config MEMBARRIER
  1357. bool "Enable membarrier() system call" if EXPERT
  1358. default y
  1359. help
  1360. Enable the membarrier() system call that allows issuing memory
  1361. barriers across all running threads, which can be used to distribute
  1362. the cost of user-space memory barriers asymmetrically by transforming
  1363. pairs of memory barriers into pairs consisting of membarrier() and a
  1364. compiler barrier.
  1365. If unsure, say Y.
  1366. config EMBEDDED
  1367. bool "Embedded system"
  1368. option allnoconfig_y
  1369. select EXPERT
  1370. help
  1371. This option should be enabled if compiling the kernel for
  1372. an embedded system so certain expert options are available
  1373. for configuration.
  1374. config HAVE_PERF_EVENTS
  1375. bool
  1376. help
  1377. See tools/perf/design.txt for details.
  1378. config PERF_USE_VMALLOC
  1379. bool
  1380. help
  1381. See tools/perf/design.txt for details
  1382. config PC104
  1383. bool "PC/104 support"
  1384. help
  1385. Expose PC/104 form factor device drivers and options available for
  1386. selection and configuration. Enable this option if your target
  1387. machine has a PC/104 bus.
  1388. menu "Kernel Performance Events And Counters"
  1389. config PERF_EVENTS
  1390. bool "Kernel performance events and counters"
  1391. default y if PROFILING
  1392. depends on HAVE_PERF_EVENTS
  1393. select IRQ_WORK
  1394. select SRCU
  1395. help
  1396. Enable kernel support for various performance events provided
  1397. by software and hardware.
  1398. Software events are supported either built-in or via the
  1399. use of generic tracepoints.
  1400. Most modern CPUs support performance events via performance
  1401. counter registers. These registers count the number of certain
  1402. types of hw events: such as instructions executed, cachemisses
  1403. suffered, or branches mis-predicted - without slowing down the
  1404. kernel or applications. These registers can also trigger interrupts
  1405. when a threshold number of events have passed - and can thus be
  1406. used to profile the code that runs on that CPU.
  1407. The Linux Performance Event subsystem provides an abstraction of
  1408. these software and hardware event capabilities, available via a
  1409. system call and used by the "perf" utility in tools/perf/. It
  1410. provides per task and per CPU counters, and it provides event
  1411. capabilities on top of those.
  1412. Say Y if unsure.
  1413. config DEBUG_PERF_USE_VMALLOC
  1414. default n
  1415. bool "Debug: use vmalloc to back perf mmap() buffers"
  1416. depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
  1417. select PERF_USE_VMALLOC
  1418. help
  1419. Use vmalloc memory to back perf mmap() buffers.
  1420. Mostly useful for debugging the vmalloc code on platforms
  1421. that don't require it.
  1422. Say N if unsure.
  1423. endmenu
  1424. config VM_EVENT_COUNTERS
  1425. default y
  1426. bool "Enable VM event counters for /proc/vmstat" if EXPERT
  1427. help
  1428. VM event counters are needed for event counts to be shown.
  1429. This option allows the disabling of the VM event counters
  1430. on EXPERT systems. /proc/vmstat will only show page counts
  1431. if VM event counters are disabled.
  1432. config SLUB_DEBUG
  1433. default y
  1434. bool "Enable SLUB debugging support" if EXPERT
  1435. depends on SLUB && SYSFS
  1436. help
  1437. SLUB has extensive debug support features. Disabling these can
  1438. result in significant savings in code size. This also disables
  1439. SLUB sysfs support. /sys/slab will not exist and there will be
  1440. no support for cache validation etc.
  1441. config SLUB_MEMCG_SYSFS_ON
  1442. default n
  1443. bool "Enable memcg SLUB sysfs support by default" if EXPERT
  1444. depends on SLUB && SYSFS && MEMCG
  1445. help
  1446. SLUB creates a directory under /sys/kernel/slab for each
  1447. allocation cache to host info and debug files. If memory
  1448. cgroup is enabled, each cache can have per memory cgroup
  1449. caches. SLUB can create the same sysfs directories for these
  1450. caches under /sys/kernel/slab/CACHE/cgroup but it can lead
  1451. to a very high number of debug files being created. This is
  1452. controlled by slub_memcg_sysfs boot parameter and this
  1453. config option determines the parameter's default value.
  1454. config COMPAT_BRK
  1455. bool "Disable heap randomization"
  1456. default y
  1457. help
  1458. Randomizing heap placement makes heap exploits harder, but it
  1459. also breaks ancient binaries (including anything libc5 based).
  1460. This option changes the bootup default to heap randomization
  1461. disabled, and can be overridden at runtime by setting
  1462. /proc/sys/kernel/randomize_va_space to 2.
  1463. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  1464. choice
  1465. prompt "Choose SLAB allocator"
  1466. default SLUB
  1467. help
  1468. This option allows to select a slab allocator.
  1469. config SLAB
  1470. bool "SLAB"
  1471. select HAVE_HARDENED_USERCOPY_ALLOCATOR
  1472. help
  1473. The regular slab allocator that is established and known to work
  1474. well in all environments. It organizes cache hot objects in
  1475. per cpu and per node queues.
  1476. config SLUB
  1477. bool "SLUB (Unqueued Allocator)"
  1478. select HAVE_HARDENED_USERCOPY_ALLOCATOR
  1479. help
  1480. SLUB is a slab allocator that minimizes cache line usage
  1481. instead of managing queues of cached objects (SLAB approach).
  1482. Per cpu caching is realized using slabs of objects instead
  1483. of queues of objects. SLUB can use memory efficiently
  1484. and has enhanced diagnostics. SLUB is the default choice for
  1485. a slab allocator.
  1486. config SLOB
  1487. depends on EXPERT
  1488. bool "SLOB (Simple Allocator)"
  1489. help
  1490. SLOB replaces the stock allocator with a drastically simpler
  1491. allocator. SLOB is generally more space efficient but
  1492. does not perform as well on large systems.
  1493. endchoice
  1494. config SLAB_MERGE_DEFAULT
  1495. bool "Allow slab caches to be merged"
  1496. default y
  1497. help
  1498. For reduced kernel memory fragmentation, slab caches can be
  1499. merged when they share the same size and other characteristics.
  1500. This carries a risk of kernel heap overflows being able to
  1501. overwrite objects from merged caches (and more easily control
  1502. cache layout), which makes such heap attacks easier to exploit
  1503. by attackers. By keeping caches unmerged, these kinds of exploits
  1504. can usually only damage objects in the same cache. To disable
  1505. merging at runtime, "slab_nomerge" can be passed on the kernel
  1506. command line.
  1507. config SLAB_FREELIST_RANDOM
  1508. default n
  1509. depends on SLAB || SLUB
  1510. bool "SLAB freelist randomization"
  1511. help
  1512. Randomizes the freelist order used on creating new pages. This
  1513. security feature reduces the predictability of the kernel slab
  1514. allocator against heap overflows.
  1515. config SLAB_FREELIST_HARDENED
  1516. bool "Harden slab freelist metadata"
  1517. depends on SLUB
  1518. help
  1519. Many kernel heap attacks try to target slab cache metadata and
  1520. other infrastructure. This options makes minor performance
  1521. sacrifies to harden the kernel slab allocator against common
  1522. freelist exploit methods.
  1523. config SLUB_CPU_PARTIAL
  1524. default y
  1525. depends on SLUB && SMP
  1526. bool "SLUB per cpu partial cache"
  1527. help
  1528. Per cpu partial caches accellerate objects allocation and freeing
  1529. that is local to a processor at the price of more indeterminism
  1530. in the latency of the free. On overflow these caches will be cleared
  1531. which requires the taking of locks that may cause latency spikes.
  1532. Typically one would choose no for a realtime system.
  1533. config MMAP_ALLOW_UNINITIALIZED
  1534. bool "Allow mmapped anonymous memory to be uninitialized"
  1535. depends on EXPERT && !MMU
  1536. default n
  1537. help
  1538. Normally, and according to the Linux spec, anonymous memory obtained
  1539. from mmap() has it's contents cleared before it is passed to
  1540. userspace. Enabling this config option allows you to request that
  1541. mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
  1542. providing a huge performance boost. If this option is not enabled,
  1543. then the flag will be ignored.
  1544. This is taken advantage of by uClibc's malloc(), and also by
  1545. ELF-FDPIC binfmt's brk and stack allocator.
  1546. Because of the obvious security issues, this option should only be
  1547. enabled on embedded devices where you control what is run in
  1548. userspace. Since that isn't generally a problem on no-MMU systems,
  1549. it is normally safe to say Y here.
  1550. See Documentation/nommu-mmap.txt for more information.
  1551. config SYSTEM_DATA_VERIFICATION
  1552. def_bool n
  1553. select SYSTEM_TRUSTED_KEYRING
  1554. select KEYS
  1555. select CRYPTO
  1556. select CRYPTO_RSA
  1557. select ASYMMETRIC_KEY_TYPE
  1558. select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
  1559. select ASN1
  1560. select OID_REGISTRY
  1561. select X509_CERTIFICATE_PARSER
  1562. select PKCS7_MESSAGE_PARSER
  1563. help
  1564. Provide PKCS#7 message verification using the contents of the system
  1565. trusted keyring to provide public keys. This then can be used for
  1566. module verification, kexec image verification and firmware blob
  1567. verification.
  1568. config PROFILING
  1569. bool "Profiling support"
  1570. help
  1571. Say Y here to enable the extended profiling support mechanisms used
  1572. by profilers such as OProfile.
  1573. #
  1574. # Place an empty function call at each tracepoint site. Can be
  1575. # dynamically changed for a probe function.
  1576. #
  1577. config TRACEPOINTS
  1578. bool
  1579. source "arch/Kconfig"
  1580. endmenu # General setup
  1581. config HAVE_GENERIC_DMA_COHERENT
  1582. bool
  1583. default n
  1584. config SLABINFO
  1585. bool
  1586. depends on PROC_FS
  1587. depends on SLAB || SLUB_DEBUG
  1588. default y
  1589. config RT_MUTEXES
  1590. bool
  1591. config BASE_SMALL
  1592. int
  1593. default 0 if BASE_FULL
  1594. default 1 if !BASE_FULL
  1595. menuconfig MODULES
  1596. bool "Enable loadable module support"
  1597. option modules
  1598. help
  1599. Kernel modules are small pieces of compiled code which can
  1600. be inserted in the running kernel, rather than being
  1601. permanently built into the kernel. You use the "modprobe"
  1602. tool to add (and sometimes remove) them. If you say Y here,
  1603. many parts of the kernel can be built as modules (by
  1604. answering M instead of Y where indicated): this is most
  1605. useful for infrequently used options which are not required
  1606. for booting. For more information, see the man pages for
  1607. modprobe, lsmod, modinfo, insmod and rmmod.
  1608. If you say Y here, you will need to run "make
  1609. modules_install" to put the modules under /lib/modules/
  1610. where modprobe can find them (you may need to be root to do
  1611. this).
  1612. If unsure, say Y.
  1613. if MODULES
  1614. config MODULE_FORCE_LOAD
  1615. bool "Forced module loading"
  1616. default n
  1617. help
  1618. Allow loading of modules without version information (ie. modprobe
  1619. --force). Forced module loading sets the 'F' (forced) taint flag and
  1620. is usually a really bad idea.
  1621. config MODULE_UNLOAD
  1622. bool "Module unloading"
  1623. help
  1624. Without this option you will not be able to unload any
  1625. modules (note that some modules may not be unloadable
  1626. anyway), which makes your kernel smaller, faster
  1627. and simpler. If unsure, say Y.
  1628. config MODULE_FORCE_UNLOAD
  1629. bool "Forced module unloading"
  1630. depends on MODULE_UNLOAD
  1631. help
  1632. This option allows you to force a module to unload, even if the
  1633. kernel believes it is unsafe: the kernel will remove the module
  1634. without waiting for anyone to stop using it (using the -f option to
  1635. rmmod). This is mainly for kernel developers and desperate users.
  1636. If unsure, say N.
  1637. config MODVERSIONS
  1638. bool "Module versioning support"
  1639. help
  1640. Usually, you have to use modules compiled with your kernel.
  1641. Saying Y here makes it sometimes possible to use modules
  1642. compiled for different kernels, by adding enough information
  1643. to the modules to (hopefully) spot any changes which would
  1644. make them incompatible with the kernel you are running. If
  1645. unsure, say N.
  1646. config MODULE_REL_CRCS
  1647. bool
  1648. depends on MODVERSIONS
  1649. config MODULE_SRCVERSION_ALL
  1650. bool "Source checksum for all modules"
  1651. help
  1652. Modules which contain a MODULE_VERSION get an extra "srcversion"
  1653. field inserted into their modinfo section, which contains a
  1654. sum of the source files which made it. This helps maintainers
  1655. see exactly which source was used to build a module (since
  1656. others sometimes change the module source without updating
  1657. the version). With this option, such a "srcversion" field
  1658. will be created for all modules. If unsure, say N.
  1659. config MODULE_SIG
  1660. bool "Module signature verification"
  1661. depends on MODULES
  1662. select SYSTEM_DATA_VERIFICATION
  1663. help
  1664. Check modules for valid signatures upon load: the signature
  1665. is simply appended to the module. For more information see
  1666. Documentation/module-signing.txt.
  1667. Note that this option adds the OpenSSL development packages as a
  1668. kernel build dependency so that the signing tool can use its crypto
  1669. library.
  1670. !!!WARNING!!! If you enable this option, you MUST make sure that the
  1671. module DOES NOT get stripped after being signed. This includes the
  1672. debuginfo strip done by some packagers (such as rpmbuild) and
  1673. inclusion into an initramfs that wants the module size reduced.
  1674. config MODULE_SIG_FORCE
  1675. bool "Require modules to be validly signed"
  1676. depends on MODULE_SIG
  1677. help
  1678. Reject unsigned modules or signed modules for which we don't have a
  1679. key. Without this, such modules will simply taint the kernel.
  1680. config MODULE_SIG_ALL
  1681. bool "Automatically sign all modules"
  1682. default y
  1683. depends on MODULE_SIG
  1684. help
  1685. Sign all modules during make modules_install. Without this option,
  1686. modules must be signed manually, using the scripts/sign-file tool.
  1687. comment "Do not forget to sign required modules with scripts/sign-file"
  1688. depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
  1689. choice
  1690. prompt "Which hash algorithm should modules be signed with?"
  1691. depends on MODULE_SIG
  1692. help
  1693. This determines which sort of hashing algorithm will be used during
  1694. signature generation. This algorithm _must_ be built into the kernel
  1695. directly so that signature verification can take place. It is not
  1696. possible to load a signed module containing the algorithm to check
  1697. the signature on that module.
  1698. config MODULE_SIG_SHA1
  1699. bool "Sign modules with SHA-1"
  1700. select CRYPTO_SHA1
  1701. config MODULE_SIG_SHA224
  1702. bool "Sign modules with SHA-224"
  1703. select CRYPTO_SHA256
  1704. config MODULE_SIG_SHA256
  1705. bool "Sign modules with SHA-256"
  1706. select CRYPTO_SHA256
  1707. config MODULE_SIG_SHA384
  1708. bool "Sign modules with SHA-384"
  1709. select CRYPTO_SHA512
  1710. config MODULE_SIG_SHA512
  1711. bool "Sign modules with SHA-512"
  1712. select CRYPTO_SHA512
  1713. endchoice
  1714. config MODULE_SIG_HASH
  1715. string
  1716. depends on MODULE_SIG
  1717. default "sha1" if MODULE_SIG_SHA1
  1718. default "sha224" if MODULE_SIG_SHA224
  1719. default "sha256" if MODULE_SIG_SHA256
  1720. default "sha384" if MODULE_SIG_SHA384
  1721. default "sha512" if MODULE_SIG_SHA512
  1722. config MODULE_COMPRESS
  1723. bool "Compress modules on installation"
  1724. depends on MODULES
  1725. help
  1726. Compresses kernel modules when 'make modules_install' is run; gzip or
  1727. xz depending on "Compression algorithm" below.
  1728. module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
  1729. Out-of-tree kernel modules installed using Kbuild will also be
  1730. compressed upon installation.
  1731. Note: for modules inside an initrd or initramfs, it's more efficient
  1732. to compress the whole initrd or initramfs instead.
  1733. Note: This is fully compatible with signed modules.
  1734. If in doubt, say N.
  1735. choice
  1736. prompt "Compression algorithm"
  1737. depends on MODULE_COMPRESS
  1738. default MODULE_COMPRESS_GZIP
  1739. help
  1740. This determines which sort of compression will be used during
  1741. 'make modules_install'.
  1742. GZIP (default) and XZ are supported.
  1743. config MODULE_COMPRESS_GZIP
  1744. bool "GZIP"
  1745. config MODULE_COMPRESS_XZ
  1746. bool "XZ"
  1747. endchoice
  1748. config TRIM_UNUSED_KSYMS
  1749. bool "Trim unused exported kernel symbols"
  1750. depends on MODULES && !UNUSED_SYMBOLS
  1751. help
  1752. The kernel and some modules make many symbols available for
  1753. other modules to use via EXPORT_SYMBOL() and variants. Depending
  1754. on the set of modules being selected in your kernel configuration,
  1755. many of those exported symbols might never be used.
  1756. This option allows for unused exported symbols to be dropped from
  1757. the build. In turn, this provides the compiler more opportunities
  1758. (especially when using LTO) for optimizing the code and reducing
  1759. binary size. This might have some security advantages as well.
  1760. If unsure, or if you need to build out-of-tree modules, say N.
  1761. endif # MODULES
  1762. config MODULES_TREE_LOOKUP
  1763. def_bool y
  1764. depends on PERF_EVENTS || TRACING || CFI_CLANG
  1765. config INIT_ALL_POSSIBLE
  1766. bool
  1767. help
  1768. Back when each arch used to define their own cpu_online_mask and
  1769. cpu_possible_mask, some of them chose to initialize cpu_possible_mask
  1770. with all 1s, and others with all 0s. When they were centralised,
  1771. it was better to provide this option than to break all the archs
  1772. and have several arch maintainers pursuing me down dark alleys.
  1773. source "block/Kconfig"
  1774. config PREEMPT_NOTIFIERS
  1775. bool
  1776. config PADATA
  1777. depends on SMP
  1778. bool
  1779. config ASN1
  1780. tristate
  1781. help
  1782. Build a simple ASN.1 grammar compiler that produces a bytecode output
  1783. that can be interpreted by the ASN.1 stream decoder and used to
  1784. inform it as to what tags are to be expected in a stream and what
  1785. functions to call on what tags.
  1786. source "kernel/Kconfig.locks"