Kconfig 26 KB

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  1. #
  2. # General architecture dependent options
  3. #
  4. config KEXEC_CORE
  5. bool
  6. config HAVE_IMA_KEXEC
  7. bool
  8. config OPROFILE
  9. tristate "OProfile system profiling"
  10. depends on PROFILING
  11. depends on HAVE_OPROFILE
  12. select RING_BUFFER
  13. select RING_BUFFER_ALLOW_SWAP
  14. help
  15. OProfile is a profiling system capable of profiling the
  16. whole system, include the kernel, kernel modules, libraries,
  17. and applications.
  18. If unsure, say N.
  19. config OPROFILE_EVENT_MULTIPLEX
  20. bool "OProfile multiplexing support (EXPERIMENTAL)"
  21. default n
  22. depends on OPROFILE && X86
  23. help
  24. The number of hardware counters is limited. The multiplexing
  25. feature enables OProfile to gather more events than counters
  26. are provided by the hardware. This is realized by switching
  27. between events at a user specified time interval.
  28. If unsure, say N.
  29. config HAVE_OPROFILE
  30. bool
  31. config OPROFILE_NMI_TIMER
  32. def_bool y
  33. depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
  34. config KPROBES
  35. bool "Kprobes"
  36. depends on MODULES
  37. depends on HAVE_KPROBES
  38. select KALLSYMS
  39. help
  40. Kprobes allows you to trap at almost any kernel address and
  41. execute a callback function. register_kprobe() establishes
  42. a probepoint and specifies the callback. Kprobes is useful
  43. for kernel debugging, non-intrusive instrumentation and testing.
  44. If in doubt, say "N".
  45. config JUMP_LABEL
  46. bool "Optimize very unlikely/likely branches"
  47. depends on HAVE_ARCH_JUMP_LABEL
  48. help
  49. This option enables a transparent branch optimization that
  50. makes certain almost-always-true or almost-always-false branch
  51. conditions even cheaper to execute within the kernel.
  52. Certain performance-sensitive kernel code, such as trace points,
  53. scheduler functionality, networking code and KVM have such
  54. branches and include support for this optimization technique.
  55. If it is detected that the compiler has support for "asm goto",
  56. the kernel will compile such branches with just a nop
  57. instruction. When the condition flag is toggled to true, the
  58. nop will be converted to a jump instruction to execute the
  59. conditional block of instructions.
  60. This technique lowers overhead and stress on the branch prediction
  61. of the processor and generally makes the kernel faster. The update
  62. of the condition is slower, but those are always very rare.
  63. ( On 32-bit x86, the necessary options added to the compiler
  64. flags may increase the size of the kernel slightly. )
  65. config STATIC_KEYS_SELFTEST
  66. bool "Static key selftest"
  67. depends on JUMP_LABEL
  68. help
  69. Boot time self-test of the branch patching code.
  70. config OPTPROBES
  71. def_bool y
  72. depends on KPROBES && HAVE_OPTPROBES
  73. depends on !PREEMPT
  74. config KPROBES_ON_FTRACE
  75. def_bool y
  76. depends on KPROBES && HAVE_KPROBES_ON_FTRACE
  77. depends on DYNAMIC_FTRACE_WITH_REGS
  78. help
  79. If function tracer is enabled and the arch supports full
  80. passing of pt_regs to function tracing, then kprobes can
  81. optimize on top of function tracing.
  82. config UPROBES
  83. def_bool n
  84. depends on ARCH_SUPPORTS_UPROBES
  85. help
  86. Uprobes is the user-space counterpart to kprobes: they
  87. enable instrumentation applications (such as 'perf probe')
  88. to establish unintrusive probes in user-space binaries and
  89. libraries, by executing handler functions when the probes
  90. are hit by user-space applications.
  91. ( These probes come in the form of single-byte breakpoints,
  92. managed by the kernel and kept transparent to the probed
  93. application. )
  94. config HAVE_64BIT_ALIGNED_ACCESS
  95. def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
  96. help
  97. Some architectures require 64 bit accesses to be 64 bit
  98. aligned, which also requires structs containing 64 bit values
  99. to be 64 bit aligned too. This includes some 32 bit
  100. architectures which can do 64 bit accesses, as well as 64 bit
  101. architectures without unaligned access.
  102. This symbol should be selected by an architecture if 64 bit
  103. accesses are required to be 64 bit aligned in this way even
  104. though it is not a 64 bit architecture.
  105. See Documentation/unaligned-memory-access.txt for more
  106. information on the topic of unaligned memory accesses.
  107. config HAVE_EFFICIENT_UNALIGNED_ACCESS
  108. bool
  109. help
  110. Some architectures are unable to perform unaligned accesses
  111. without the use of get_unaligned/put_unaligned. Others are
  112. unable to perform such accesses efficiently (e.g. trap on
  113. unaligned access and require fixing it up in the exception
  114. handler.)
  115. This symbol should be selected by an architecture if it can
  116. perform unaligned accesses efficiently to allow different
  117. code paths to be selected for these cases. Some network
  118. drivers, for example, could opt to not fix up alignment
  119. problems with received packets if doing so would not help
  120. much.
  121. See Documentation/unaligned-memory-access.txt for more
  122. information on the topic of unaligned memory accesses.
  123. config ARCH_USE_BUILTIN_BSWAP
  124. bool
  125. help
  126. Modern versions of GCC (since 4.4) have builtin functions
  127. for handling byte-swapping. Using these, instead of the old
  128. inline assembler that the architecture code provides in the
  129. __arch_bswapXX() macros, allows the compiler to see what's
  130. happening and offers more opportunity for optimisation. In
  131. particular, the compiler will be able to combine the byteswap
  132. with a nearby load or store and use load-and-swap or
  133. store-and-swap instructions if the architecture has them. It
  134. should almost *never* result in code which is worse than the
  135. hand-coded assembler in <asm/swab.h>. But just in case it
  136. does, the use of the builtins is optional.
  137. Any architecture with load-and-swap or store-and-swap
  138. instructions should set this. And it shouldn't hurt to set it
  139. on architectures that don't have such instructions.
  140. config KRETPROBES
  141. def_bool y
  142. depends on KPROBES && HAVE_KRETPROBES
  143. config USER_RETURN_NOTIFIER
  144. bool
  145. depends on HAVE_USER_RETURN_NOTIFIER
  146. help
  147. Provide a kernel-internal notification when a cpu is about to
  148. switch to user mode.
  149. config HAVE_IOREMAP_PROT
  150. bool
  151. config HAVE_KPROBES
  152. bool
  153. config HAVE_KRETPROBES
  154. bool
  155. config HAVE_OPTPROBES
  156. bool
  157. config HAVE_KPROBES_ON_FTRACE
  158. bool
  159. config HAVE_NMI
  160. bool
  161. config HAVE_NMI_WATCHDOG
  162. depends on HAVE_NMI
  163. bool
  164. #
  165. # An arch should select this if it provides all these things:
  166. #
  167. # task_pt_regs() in asm/processor.h or asm/ptrace.h
  168. # arch_has_single_step() if there is hardware single-step support
  169. # arch_has_block_step() if there is hardware block-step support
  170. # asm/syscall.h supplying asm-generic/syscall.h interface
  171. # linux/regset.h user_regset interfaces
  172. # CORE_DUMP_USE_REGSET #define'd in linux/elf.h
  173. # TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit}
  174. # TIF_NOTIFY_RESUME calls tracehook_notify_resume()
  175. # signal delivery calls tracehook_signal_handler()
  176. #
  177. config HAVE_ARCH_TRACEHOOK
  178. bool
  179. config HAVE_DMA_CONTIGUOUS
  180. bool
  181. config GENERIC_SMP_IDLE_THREAD
  182. bool
  183. config GENERIC_IDLE_POLL_SETUP
  184. bool
  185. # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
  186. config ARCH_HAS_SET_MEMORY
  187. bool
  188. # Select if arch init_task initializer is different to init/init_task.c
  189. config ARCH_INIT_TASK
  190. bool
  191. # Select if arch has its private alloc_task_struct() function
  192. config ARCH_TASK_STRUCT_ALLOCATOR
  193. bool
  194. # Select if arch has its private alloc_thread_stack() function
  195. config ARCH_THREAD_STACK_ALLOCATOR
  196. bool
  197. # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
  198. config ARCH_WANTS_DYNAMIC_TASK_STRUCT
  199. bool
  200. config HAVE_REGS_AND_STACK_ACCESS_API
  201. bool
  202. help
  203. This symbol should be selected by an architecure if it supports
  204. the API needed to access registers and stack entries from pt_regs,
  205. declared in asm/ptrace.h
  206. For example the kprobes-based event tracer needs this API.
  207. config HAVE_CLK
  208. bool
  209. help
  210. The <linux/clk.h> calls support software clock gating and
  211. thus are a key power management tool on many systems.
  212. config HAVE_DMA_API_DEBUG
  213. bool
  214. config HAVE_HW_BREAKPOINT
  215. bool
  216. depends on PERF_EVENTS
  217. config HAVE_MIXED_BREAKPOINTS_REGS
  218. bool
  219. depends on HAVE_HW_BREAKPOINT
  220. help
  221. Depending on the arch implementation of hardware breakpoints,
  222. some of them have separate registers for data and instruction
  223. breakpoints addresses, others have mixed registers to store
  224. them but define the access type in a control register.
  225. Select this option if your arch implements breakpoints under the
  226. latter fashion.
  227. config HAVE_USER_RETURN_NOTIFIER
  228. bool
  229. config HAVE_PERF_EVENTS_NMI
  230. bool
  231. help
  232. System hardware can generate an NMI using the perf event
  233. subsystem. Also has support for calculating CPU cycle events
  234. to determine how many clock cycles in a given period.
  235. config HAVE_PERF_REGS
  236. bool
  237. help
  238. Support selective register dumps for perf events. This includes
  239. bit-mapping of each registers and a unique architecture id.
  240. config HAVE_PERF_USER_STACK_DUMP
  241. bool
  242. help
  243. Support user stack dumps for perf event samples. This needs
  244. access to the user stack pointer which is not unified across
  245. architectures.
  246. config HAVE_ARCH_JUMP_LABEL
  247. bool
  248. config HAVE_RCU_TABLE_FREE
  249. bool
  250. config ARCH_HAVE_NMI_SAFE_CMPXCHG
  251. bool
  252. config HAVE_ALIGNED_STRUCT_PAGE
  253. bool
  254. help
  255. This makes sure that struct pages are double word aligned and that
  256. e.g. the SLUB allocator can perform double word atomic operations
  257. on a struct page for better performance. However selecting this
  258. might increase the size of a struct page by a word.
  259. config HAVE_CMPXCHG_LOCAL
  260. bool
  261. config HAVE_CMPXCHG_DOUBLE
  262. bool
  263. config ARCH_WANT_IPC_PARSE_VERSION
  264. bool
  265. config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
  266. bool
  267. config ARCH_WANT_OLD_COMPAT_IPC
  268. select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
  269. bool
  270. config HAVE_ARCH_SECCOMP_FILTER
  271. bool
  272. help
  273. An arch should select this symbol if it provides all of these things:
  274. - syscall_get_arch()
  275. - syscall_get_arguments()
  276. - syscall_rollback()
  277. - syscall_set_return_value()
  278. - SIGSYS siginfo_t support
  279. - secure_computing is called from a ptrace_event()-safe context
  280. - secure_computing return value is checked and a return value of -1
  281. results in the system call being skipped immediately.
  282. - seccomp syscall wired up
  283. config SECCOMP_FILTER
  284. def_bool y
  285. depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
  286. help
  287. Enable tasks to build secure computing environments defined
  288. in terms of Berkeley Packet Filter programs which implement
  289. task-defined system call filtering polices.
  290. See Documentation/prctl/seccomp_filter.txt for details.
  291. config HAVE_GCC_PLUGINS
  292. bool
  293. help
  294. An arch should select this symbol if it supports building with
  295. GCC plugins.
  296. menuconfig GCC_PLUGINS
  297. bool "GCC plugins"
  298. depends on HAVE_GCC_PLUGINS
  299. depends on !COMPILE_TEST
  300. help
  301. GCC plugins are loadable modules that provide extra features to the
  302. compiler. They are useful for runtime instrumentation and static analysis.
  303. See Documentation/gcc-plugins.txt for details.
  304. config GCC_PLUGIN_CYC_COMPLEXITY
  305. bool "Compute the cyclomatic complexity of a function" if EXPERT
  306. depends on GCC_PLUGINS
  307. depends on !COMPILE_TEST
  308. help
  309. The complexity M of a function's control flow graph is defined as:
  310. M = E - N + 2P
  311. where
  312. E = the number of edges
  313. N = the number of nodes
  314. P = the number of connected components (exit nodes).
  315. Enabling this plugin reports the complexity to stderr during the
  316. build. It mainly serves as a simple example of how to create a
  317. gcc plugin for the kernel.
  318. config GCC_PLUGIN_SANCOV
  319. bool
  320. depends on GCC_PLUGINS
  321. help
  322. This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
  323. basic blocks. It supports all gcc versions with plugin support (from
  324. gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
  325. by Dmitry Vyukov <dvyukov@google.com>.
  326. config GCC_PLUGIN_LATENT_ENTROPY
  327. bool "Generate some entropy during boot and runtime"
  328. depends on GCC_PLUGINS
  329. help
  330. By saying Y here the kernel will instrument some kernel code to
  331. extract some entropy from both original and artificially created
  332. program state. This will help especially embedded systems where
  333. there is little 'natural' source of entropy normally. The cost
  334. is some slowdown of the boot process (about 0.5%) and fork and
  335. irq processing.
  336. Note that entropy extracted this way is not cryptographically
  337. secure!
  338. This plugin was ported from grsecurity/PaX. More information at:
  339. * https://grsecurity.net/
  340. * https://pax.grsecurity.net/
  341. config GCC_PLUGIN_STRUCTLEAK
  342. bool "Force initialization of variables containing userspace addresses"
  343. depends on GCC_PLUGINS
  344. help
  345. This plugin zero-initializes any structures that containing a
  346. __user attribute. This can prevent some classes of information
  347. exposures.
  348. This plugin was ported from grsecurity/PaX. More information at:
  349. * https://grsecurity.net/
  350. * https://pax.grsecurity.net/
  351. config GCC_PLUGIN_STRUCTLEAK_VERBOSE
  352. bool "Report forcefully initialized variables"
  353. depends on GCC_PLUGIN_STRUCTLEAK
  354. depends on !COMPILE_TEST
  355. help
  356. This option will cause a warning to be printed each time the
  357. structleak plugin finds a variable it thinks needs to be
  358. initialized. Since not all existing initializers are detected
  359. by the plugin, this can produce false positive warnings.
  360. config HAVE_CC_STACKPROTECTOR
  361. bool
  362. help
  363. An arch should select this symbol if:
  364. - its compiler supports the -fstack-protector option
  365. - it has implemented a stack canary (e.g. __stack_chk_guard)
  366. config CC_STACKPROTECTOR
  367. def_bool n
  368. help
  369. Set when a stack-protector mode is enabled, so that the build
  370. can enable kernel-side support for the GCC feature.
  371. choice
  372. prompt "Stack Protector buffer overflow detection"
  373. depends on HAVE_CC_STACKPROTECTOR
  374. default CC_STACKPROTECTOR_NONE
  375. help
  376. This option turns on the "stack-protector" GCC feature. This
  377. feature puts, at the beginning of functions, a canary value on
  378. the stack just before the return address, and validates
  379. the value just before actually returning. Stack based buffer
  380. overflows (that need to overwrite this return address) now also
  381. overwrite the canary, which gets detected and the attack is then
  382. neutralized via a kernel panic.
  383. config CC_STACKPROTECTOR_NONE
  384. bool "None"
  385. help
  386. Disable "stack-protector" GCC feature.
  387. config CC_STACKPROTECTOR_REGULAR
  388. bool "Regular"
  389. select CC_STACKPROTECTOR
  390. help
  391. Functions will have the stack-protector canary logic added if they
  392. have an 8-byte or larger character array on the stack.
  393. This feature requires gcc version 4.2 or above, or a distribution
  394. gcc with the feature backported ("-fstack-protector").
  395. On an x86 "defconfig" build, this feature adds canary checks to
  396. about 3% of all kernel functions, which increases kernel code size
  397. by about 0.3%.
  398. config CC_STACKPROTECTOR_STRONG
  399. bool "Strong"
  400. select CC_STACKPROTECTOR
  401. help
  402. Functions will have the stack-protector canary logic added in any
  403. of the following conditions:
  404. - local variable's address used as part of the right hand side of an
  405. assignment or function argument
  406. - local variable is an array (or union containing an array),
  407. regardless of array type or length
  408. - uses register local variables
  409. This feature requires gcc version 4.9 or above, or a distribution
  410. gcc with the feature backported ("-fstack-protector-strong").
  411. On an x86 "defconfig" build, this feature adds canary checks to
  412. about 20% of all kernel functions, which increases the kernel code
  413. size by about 2%.
  414. endchoice
  415. config THIN_ARCHIVES
  416. bool
  417. help
  418. Select this if the architecture wants to use thin archives
  419. instead of ld -r to create the built-in.o files.
  420. config LD_DEAD_CODE_DATA_ELIMINATION
  421. bool
  422. help
  423. Select this if the architecture wants to do dead code and
  424. data elimination with the linker by compiling with
  425. -ffunction-sections -fdata-sections and linking with
  426. --gc-sections.
  427. This requires that the arch annotates or otherwise protects
  428. its external entry points from being discarded. Linker scripts
  429. must also merge .text.*, .data.*, and .bss.* correctly into
  430. output sections. Care must be taken not to pull in unrelated
  431. sections (e.g., '.text.init'). Typically '.' in section names
  432. is used to distinguish them from label names / C identifiers.
  433. config HAVE_ARCH_WITHIN_STACK_FRAMES
  434. bool
  435. help
  436. An architecture should select this if it can walk the kernel stack
  437. frames to determine if an object is part of either the arguments
  438. or local variables (i.e. that it excludes saved return addresses,
  439. and similar) by implementing an inline arch_within_stack_frames(),
  440. which is used by CONFIG_HARDENED_USERCOPY.
  441. config HAVE_CONTEXT_TRACKING
  442. bool
  443. help
  444. Provide kernel/user boundaries probes necessary for subsystems
  445. that need it, such as userspace RCU extended quiescent state.
  446. Syscalls need to be wrapped inside user_exit()-user_enter() through
  447. the slow path using TIF_NOHZ flag. Exceptions handlers must be
  448. wrapped as well. Irqs are already protected inside
  449. rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
  450. irq exit still need to be protected.
  451. config HAVE_VIRT_CPU_ACCOUNTING
  452. bool
  453. config ARCH_HAS_SCALED_CPUTIME
  454. bool
  455. config HAVE_VIRT_CPU_ACCOUNTING_GEN
  456. bool
  457. default y if 64BIT
  458. help
  459. With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
  460. Before enabling this option, arch code must be audited
  461. to ensure there are no races in concurrent read/write of
  462. cputime_t. For example, reading/writing 64-bit cputime_t on
  463. some 32-bit arches may require multiple accesses, so proper
  464. locking is needed to protect against concurrent accesses.
  465. config HAVE_IRQ_TIME_ACCOUNTING
  466. bool
  467. help
  468. Archs need to ensure they use a high enough resolution clock to
  469. support irq time accounting and then call enable_sched_clock_irqtime().
  470. config HAVE_ARCH_TRANSPARENT_HUGEPAGE
  471. bool
  472. config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
  473. bool
  474. config HAVE_ARCH_HUGE_VMAP
  475. bool
  476. config HAVE_ARCH_SOFT_DIRTY
  477. bool
  478. config HAVE_MOD_ARCH_SPECIFIC
  479. bool
  480. help
  481. The arch uses struct mod_arch_specific to store data. Many arches
  482. just need a simple module loader without arch specific data - those
  483. should not enable this.
  484. config MODULES_USE_ELF_RELA
  485. bool
  486. help
  487. Modules only use ELF RELA relocations. Modules with ELF REL
  488. relocations will give an error.
  489. config MODULES_USE_ELF_REL
  490. bool
  491. help
  492. Modules only use ELF REL relocations. Modules with ELF RELA
  493. relocations will give an error.
  494. config HAVE_UNDERSCORE_SYMBOL_PREFIX
  495. bool
  496. help
  497. Some architectures generate an _ in front of C symbols; things like
  498. module loading and assembly files need to know about this.
  499. config HAVE_IRQ_EXIT_ON_IRQ_STACK
  500. bool
  501. help
  502. Architecture doesn't only execute the irq handler on the irq stack
  503. but also irq_exit(). This way we can process softirqs on this irq
  504. stack instead of switching to a new one when we call __do_softirq()
  505. in the end of an hardirq.
  506. This spares a stack switch and improves cache usage on softirq
  507. processing.
  508. config PGTABLE_LEVELS
  509. int
  510. default 2
  511. config ARCH_HAS_ELF_RANDOMIZE
  512. bool
  513. help
  514. An architecture supports choosing randomized locations for
  515. stack, mmap, brk, and ET_DYN. Defined functions:
  516. - arch_mmap_rnd()
  517. - arch_randomize_brk()
  518. config HAVE_ARCH_MMAP_RND_BITS
  519. bool
  520. help
  521. An arch should select this symbol if it supports setting a variable
  522. number of bits for use in establishing the base address for mmap
  523. allocations, has MMU enabled and provides values for both:
  524. - ARCH_MMAP_RND_BITS_MIN
  525. - ARCH_MMAP_RND_BITS_MAX
  526. config HAVE_EXIT_THREAD
  527. bool
  528. help
  529. An architecture implements exit_thread.
  530. config ARCH_MMAP_RND_BITS_MIN
  531. int
  532. config ARCH_MMAP_RND_BITS_MAX
  533. int
  534. config ARCH_MMAP_RND_BITS_DEFAULT
  535. int
  536. config ARCH_MMAP_RND_BITS
  537. int "Number of bits to use for ASLR of mmap base address" if EXPERT
  538. range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
  539. default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
  540. default ARCH_MMAP_RND_BITS_MIN
  541. depends on HAVE_ARCH_MMAP_RND_BITS
  542. help
  543. This value can be used to select the number of bits to use to
  544. determine the random offset to the base address of vma regions
  545. resulting from mmap allocations. This value will be bounded
  546. by the architecture's minimum and maximum supported values.
  547. This value can be changed after boot using the
  548. /proc/sys/vm/mmap_rnd_bits tunable
  549. config HAVE_ARCH_MMAP_RND_COMPAT_BITS
  550. bool
  551. help
  552. An arch should select this symbol if it supports running applications
  553. in compatibility mode, supports setting a variable number of bits for
  554. use in establishing the base address for mmap allocations, has MMU
  555. enabled and provides values for both:
  556. - ARCH_MMAP_RND_COMPAT_BITS_MIN
  557. - ARCH_MMAP_RND_COMPAT_BITS_MAX
  558. config ARCH_MMAP_RND_COMPAT_BITS_MIN
  559. int
  560. config ARCH_MMAP_RND_COMPAT_BITS_MAX
  561. int
  562. config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
  563. int
  564. config ARCH_MMAP_RND_COMPAT_BITS
  565. int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
  566. range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
  567. default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
  568. default ARCH_MMAP_RND_COMPAT_BITS_MIN
  569. depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
  570. help
  571. This value can be used to select the number of bits to use to
  572. determine the random offset to the base address of vma regions
  573. resulting from mmap allocations for compatible applications This
  574. value will be bounded by the architecture's minimum and maximum
  575. supported values.
  576. This value can be changed after boot using the
  577. /proc/sys/vm/mmap_rnd_compat_bits tunable
  578. config HAVE_COPY_THREAD_TLS
  579. bool
  580. help
  581. Architecture provides copy_thread_tls to accept tls argument via
  582. normal C parameter passing, rather than extracting the syscall
  583. argument from pt_regs.
  584. config HAVE_STACK_VALIDATION
  585. bool
  586. help
  587. Architecture supports the 'objtool check' host tool command, which
  588. performs compile-time stack metadata validation.
  589. config HAVE_RELIABLE_STACKTRACE
  590. bool
  591. help
  592. Architecture has a save_stack_trace_tsk_reliable() function which
  593. only returns a stack trace if it can guarantee the trace is reliable.
  594. config HAVE_ARCH_HASH
  595. bool
  596. default n
  597. help
  598. If this is set, the architecture provides an <asm/hash.h>
  599. file which provides platform-specific implementations of some
  600. functions in <linux/hash.h> or fs/namei.c.
  601. config ISA_BUS_API
  602. def_bool ISA
  603. #
  604. # ABI hall of shame
  605. #
  606. config CLONE_BACKWARDS
  607. bool
  608. help
  609. Architecture has tls passed as the 4th argument of clone(2),
  610. not the 5th one.
  611. config CLONE_BACKWARDS2
  612. bool
  613. help
  614. Architecture has the first two arguments of clone(2) swapped.
  615. config CLONE_BACKWARDS3
  616. bool
  617. help
  618. Architecture has tls passed as the 3rd argument of clone(2),
  619. not the 5th one.
  620. config ODD_RT_SIGACTION
  621. bool
  622. help
  623. Architecture has unusual rt_sigaction(2) arguments
  624. config OLD_SIGSUSPEND
  625. bool
  626. help
  627. Architecture has old sigsuspend(2) syscall, of one-argument variety
  628. config OLD_SIGSUSPEND3
  629. bool
  630. help
  631. Even weirder antique ABI - three-argument sigsuspend(2)
  632. config OLD_SIGACTION
  633. bool
  634. help
  635. Architecture has old sigaction(2) syscall. Nope, not the same
  636. as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
  637. but fairly different variant of sigaction(2), thanks to OSF/1
  638. compatibility...
  639. config COMPAT_OLD_SIGACTION
  640. bool
  641. config ARCH_NO_COHERENT_DMA_MMAP
  642. bool
  643. config CPU_NO_EFFICIENT_FFS
  644. def_bool n
  645. config HAVE_ARCH_VMAP_STACK
  646. def_bool n
  647. help
  648. An arch should select this symbol if it can support kernel stacks
  649. in vmalloc space. This means:
  650. - vmalloc space must be large enough to hold many kernel stacks.
  651. This may rule out many 32-bit architectures.
  652. - Stacks in vmalloc space need to work reliably. For example, if
  653. vmap page tables are created on demand, either this mechanism
  654. needs to work while the stack points to a virtual address with
  655. unpopulated page tables or arch code (switch_to() and switch_mm(),
  656. most likely) needs to ensure that the stack's page table entries
  657. are populated before running on a possibly unpopulated stack.
  658. - If the stack overflows into a guard page, something reasonable
  659. should happen. The definition of "reasonable" is flexible, but
  660. instantly rebooting without logging anything would be unfriendly.
  661. config VMAP_STACK
  662. default y
  663. bool "Use a virtually-mapped stack"
  664. depends on HAVE_ARCH_VMAP_STACK && !KASAN
  665. ---help---
  666. Enable this if you want the use virtually-mapped kernel stacks
  667. with guard pages. This causes kernel stack overflows to be
  668. caught immediately rather than causing difficult-to-diagnose
  669. corruption.
  670. This is presently incompatible with KASAN because KASAN expects
  671. the stack to map directly to the KASAN shadow map using a formula
  672. that is incorrect if the stack is in vmalloc space.
  673. config ARCH_OPTIONAL_KERNEL_RWX
  674. def_bool n
  675. config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
  676. def_bool n
  677. config ARCH_HAS_STRICT_KERNEL_RWX
  678. def_bool n
  679. config STRICT_KERNEL_RWX
  680. bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
  681. depends on ARCH_HAS_STRICT_KERNEL_RWX
  682. default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
  683. help
  684. If this is set, kernel text and rodata memory will be made read-only,
  685. and non-text memory will be made non-executable. This provides
  686. protection against certain security exploits (e.g. executing the heap
  687. or modifying text)
  688. These features are considered standard security practice these days.
  689. You should say Y here in almost all cases.
  690. config ARCH_HAS_STRICT_MODULE_RWX
  691. def_bool n
  692. config STRICT_MODULE_RWX
  693. bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
  694. depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
  695. default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
  696. help
  697. If this is set, module text and rodata memory will be made read-only,
  698. and non-text memory will be made non-executable. This provides
  699. protection against certain security exploits (e.g. writing to text)
  700. config ARCH_WANT_RELAX_ORDER
  701. bool
  702. source "kernel/gcov/Kconfig"