2 # General architecture dependent options
12 tristate "OProfile system profiling"
14 depends on HAVE_OPROFILE
16 select RING_BUFFER_ALLOW_SWAP
18 OProfile is a profiling system capable of profiling the
19 whole system, include the kernel, kernel modules, libraries,
24 config OPROFILE_EVENT_MULTIPLEX
25 bool "OProfile multiplexing support (EXPERIMENTAL)"
27 depends on OPROFILE && X86
29 The number of hardware counters is limited. The multiplexing
30 feature enables OProfile to gather more events than counters
31 are provided by the hardware. This is realized by switching
32 between events at an user specified time interval.
39 config OPROFILE_NMI_TIMER
41 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
46 depends on HAVE_KPROBES
49 Kprobes allows you to trap at almost any kernel address and
50 execute a callback function. register_kprobe() establishes
51 a probepoint and specifies the callback. Kprobes is useful
52 for kernel debugging, non-intrusive instrumentation and testing.
56 bool "Optimize very unlikely/likely branches"
57 depends on HAVE_ARCH_JUMP_LABEL
59 This option enables a transparent branch optimization that
60 makes certain almost-always-true or almost-always-false branch
61 conditions even cheaper to execute within the kernel.
63 Certain performance-sensitive kernel code, such as trace points,
64 scheduler functionality, networking code and KVM have such
65 branches and include support for this optimization technique.
67 If it is detected that the compiler has support for "asm goto",
68 the kernel will compile such branches with just a nop
69 instruction. When the condition flag is toggled to true, the
70 nop will be converted to a jump instruction to execute the
71 conditional block of instructions.
73 This technique lowers overhead and stress on the branch prediction
74 of the processor and generally makes the kernel faster. The update
75 of the condition is slower, but those are always very rare.
77 ( On 32-bit x86, the necessary options added to the compiler
78 flags may increase the size of the kernel slightly. )
80 config STATIC_KEYS_SELFTEST
81 bool "Static key selftest"
84 Boot time self-test of the branch patching code.
88 depends on KPROBES && HAVE_OPTPROBES
91 config KPROBES_ON_FTRACE
93 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
94 depends on DYNAMIC_FTRACE_WITH_REGS
96 If function tracer is enabled and the arch supports full
97 passing of pt_regs to function tracing, then kprobes can
98 optimize on top of function tracing.
102 depends on ARCH_SUPPORTS_UPROBES
104 Uprobes is the user-space counterpart to kprobes: they
105 enable instrumentation applications (such as 'perf probe')
106 to establish unintrusive probes in user-space binaries and
107 libraries, by executing handler functions when the probes
108 are hit by user-space applications.
110 ( These probes come in the form of single-byte breakpoints,
111 managed by the kernel and kept transparent to the probed
114 config HAVE_64BIT_ALIGNED_ACCESS
115 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
117 Some architectures require 64 bit accesses to be 64 bit
118 aligned, which also requires structs containing 64 bit values
119 to be 64 bit aligned too. This includes some 32 bit
120 architectures which can do 64 bit accesses, as well as 64 bit
121 architectures without unaligned access.
123 This symbol should be selected by an architecture if 64 bit
124 accesses are required to be 64 bit aligned in this way even
125 though it is not a 64 bit architecture.
127 See Documentation/unaligned-memory-access.txt for more
128 information on the topic of unaligned memory accesses.
130 config HAVE_EFFICIENT_UNALIGNED_ACCESS
133 Some architectures are unable to perform unaligned accesses
134 without the use of get_unaligned/put_unaligned. Others are
135 unable to perform such accesses efficiently (e.g. trap on
136 unaligned access and require fixing it up in the exception
139 This symbol should be selected by an architecture if it can
140 perform unaligned accesses efficiently to allow different
141 code paths to be selected for these cases. Some network
142 drivers, for example, could opt to not fix up alignment
143 problems with received packets if doing so would not help
146 See Documentation/unaligned-memory-access.txt for more
147 information on the topic of unaligned memory accesses.
149 config ARCH_USE_BUILTIN_BSWAP
152 Modern versions of GCC (since 4.4) have builtin functions
153 for handling byte-swapping. Using these, instead of the old
154 inline assembler that the architecture code provides in the
155 __arch_bswapXX() macros, allows the compiler to see what's
156 happening and offers more opportunity for optimisation. In
157 particular, the compiler will be able to combine the byteswap
158 with a nearby load or store and use load-and-swap or
159 store-and-swap instructions if the architecture has them. It
160 should almost *never* result in code which is worse than the
161 hand-coded assembler in <asm/swab.h>. But just in case it
162 does, the use of the builtins is optional.
164 Any architecture with load-and-swap or store-and-swap
165 instructions should set this. And it shouldn't hurt to set it
166 on architectures that don't have such instructions.
170 depends on KPROBES && HAVE_KRETPROBES
172 config USER_RETURN_NOTIFIER
174 depends on HAVE_USER_RETURN_NOTIFIER
176 Provide a kernel-internal notification when a cpu is about to
179 config HAVE_IOREMAP_PROT
185 config HAVE_KRETPROBES
188 config HAVE_OPTPROBES
191 config HAVE_KPROBES_ON_FTRACE
197 config HAVE_NMI_WATCHDOG
201 # An arch should select this if it provides all these things:
203 # task_pt_regs() in asm/processor.h or asm/ptrace.h
204 # arch_has_single_step() if there is hardware single-step support
205 # arch_has_block_step() if there is hardware block-step support
206 # asm/syscall.h supplying asm-generic/syscall.h interface
207 # linux/regset.h user_regset interfaces
208 # CORE_DUMP_USE_REGSET #define'd in linux/elf.h
209 # TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit}
210 # TIF_NOTIFY_RESUME calls tracehook_notify_resume()
211 # signal delivery calls tracehook_signal_handler()
213 config HAVE_ARCH_TRACEHOOK
216 config HAVE_DMA_CONTIGUOUS
219 config GENERIC_SMP_IDLE_THREAD
222 config GENERIC_IDLE_POLL_SETUP
225 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
226 config ARCH_HAS_SET_MEMORY
229 # Select if arch init_task initializer is different to init/init_task.c
230 config ARCH_INIT_TASK
233 # Select if arch has its private alloc_task_struct() function
234 config ARCH_TASK_STRUCT_ALLOCATOR
237 # Select if arch has its private alloc_thread_stack() function
238 config ARCH_THREAD_STACK_ALLOCATOR
241 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
242 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
245 config HAVE_REGS_AND_STACK_ACCESS_API
248 This symbol should be selected by an architecure if it supports
249 the API needed to access registers and stack entries from pt_regs,
250 declared in asm/ptrace.h
251 For example the kprobes-based event tracer needs this API.
256 The <linux/clk.h> calls support software clock gating and
257 thus are a key power management tool on many systems.
259 config HAVE_DMA_API_DEBUG
262 config HAVE_HW_BREAKPOINT
264 depends on PERF_EVENTS
266 config HAVE_MIXED_BREAKPOINTS_REGS
268 depends on HAVE_HW_BREAKPOINT
270 Depending on the arch implementation of hardware breakpoints,
271 some of them have separate registers for data and instruction
272 breakpoints addresses, others have mixed registers to store
273 them but define the access type in a control register.
274 Select this option if your arch implements breakpoints under the
277 config HAVE_USER_RETURN_NOTIFIER
280 config HAVE_PERF_EVENTS_NMI
283 System hardware can generate an NMI using the perf event
284 subsystem. Also has support for calculating CPU cycle events
285 to determine how many clock cycles in a given period.
287 config HAVE_PERF_REGS
290 Support selective register dumps for perf events. This includes
291 bit-mapping of each registers and a unique architecture id.
293 config HAVE_PERF_USER_STACK_DUMP
296 Support user stack dumps for perf event samples. This needs
297 access to the user stack pointer which is not unified across
300 config HAVE_ARCH_JUMP_LABEL
303 config HAVE_RCU_TABLE_FREE
306 config ARCH_HAVE_NMI_SAFE_CMPXCHG
309 config HAVE_ALIGNED_STRUCT_PAGE
312 This makes sure that struct pages are double word aligned and that
313 e.g. the SLUB allocator can perform double word atomic operations
314 on a struct page for better performance. However selecting this
315 might increase the size of a struct page by a word.
317 config HAVE_CMPXCHG_LOCAL
320 config HAVE_CMPXCHG_DOUBLE
323 config ARCH_WANT_IPC_PARSE_VERSION
326 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
329 config ARCH_WANT_OLD_COMPAT_IPC
330 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
333 config HAVE_ARCH_SECCOMP_FILTER
336 An arch should select this symbol if it provides all of these things:
338 - syscall_get_arguments()
340 - syscall_set_return_value()
341 - SIGSYS siginfo_t support
342 - secure_computing is called from a ptrace_event()-safe context
343 - secure_computing return value is checked and a return value of -1
344 results in the system call being skipped immediately.
345 - seccomp syscall wired up
347 config SECCOMP_FILTER
349 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
351 Enable tasks to build secure computing environments defined
352 in terms of Berkeley Packet Filter programs which implement
353 task-defined system call filtering polices.
355 See Documentation/prctl/seccomp_filter.txt for details.
357 config HAVE_GCC_PLUGINS
360 An arch should select this symbol if it supports building with
363 menuconfig GCC_PLUGINS
365 depends on HAVE_GCC_PLUGINS
366 depends on !COMPILE_TEST
368 GCC plugins are loadable modules that provide extra features to the
369 compiler. They are useful for runtime instrumentation and static analysis.
371 See Documentation/gcc-plugins.txt for details.
373 config GCC_PLUGIN_CYC_COMPLEXITY
374 bool "Compute the cyclomatic complexity of a function" if EXPERT
375 depends on GCC_PLUGINS
376 depends on !COMPILE_TEST
378 The complexity M of a function's control flow graph is defined as:
382 E = the number of edges
383 N = the number of nodes
384 P = the number of connected components (exit nodes).
386 Enabling this plugin reports the complexity to stderr during the
387 build. It mainly serves as a simple example of how to create a
388 gcc plugin for the kernel.
390 config GCC_PLUGIN_SANCOV
392 depends on GCC_PLUGINS
394 This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
395 basic blocks. It supports all gcc versions with plugin support (from
396 gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
397 by Dmitry Vyukov <dvyukov@google.com>.
399 config GCC_PLUGIN_LATENT_ENTROPY
400 bool "Generate some entropy during boot and runtime"
401 depends on GCC_PLUGINS
403 By saying Y here the kernel will instrument some kernel code to
404 extract some entropy from both original and artificially created
405 program state. This will help especially embedded systems where
406 there is little 'natural' source of entropy normally. The cost
407 is some slowdown of the boot process (about 0.5%) and fork and
410 Note that entropy extracted this way is not cryptographically
413 This plugin was ported from grsecurity/PaX. More information at:
414 * https://grsecurity.net/
415 * https://pax.grsecurity.net/
417 config HAVE_CC_STACKPROTECTOR
420 An arch should select this symbol if:
421 - its compiler supports the -fstack-protector option
422 - it has implemented a stack canary (e.g. __stack_chk_guard)
424 config CC_STACKPROTECTOR
427 Set when a stack-protector mode is enabled, so that the build
428 can enable kernel-side support for the GCC feature.
431 prompt "Stack Protector buffer overflow detection"
432 depends on HAVE_CC_STACKPROTECTOR
433 default CC_STACKPROTECTOR_NONE
435 This option turns on the "stack-protector" GCC feature. This
436 feature puts, at the beginning of functions, a canary value on
437 the stack just before the return address, and validates
438 the value just before actually returning. Stack based buffer
439 overflows (that need to overwrite this return address) now also
440 overwrite the canary, which gets detected and the attack is then
441 neutralized via a kernel panic.
443 config CC_STACKPROTECTOR_NONE
446 Disable "stack-protector" GCC feature.
448 config CC_STACKPROTECTOR_REGULAR
450 select CC_STACKPROTECTOR
452 Functions will have the stack-protector canary logic added if they
453 have an 8-byte or larger character array on the stack.
455 This feature requires gcc version 4.2 or above, or a distribution
456 gcc with the feature backported ("-fstack-protector").
458 On an x86 "defconfig" build, this feature adds canary checks to
459 about 3% of all kernel functions, which increases kernel code size
462 config CC_STACKPROTECTOR_STRONG
464 select CC_STACKPROTECTOR
466 Functions will have the stack-protector canary logic added in any
467 of the following conditions:
469 - local variable's address used as part of the right hand side of an
470 assignment or function argument
471 - local variable is an array (or union containing an array),
472 regardless of array type or length
473 - uses register local variables
475 This feature requires gcc version 4.9 or above, or a distribution
476 gcc with the feature backported ("-fstack-protector-strong").
478 On an x86 "defconfig" build, this feature adds canary checks to
479 about 20% of all kernel functions, which increases the kernel code
487 Select this if the architecture wants to use thin archives
488 instead of ld -r to create the built-in.o files.
490 config LD_DEAD_CODE_DATA_ELIMINATION
493 Select this if the architecture wants to do dead code and
494 data elimination with the linker by compiling with
495 -ffunction-sections -fdata-sections and linking with
498 This requires that the arch annotates or otherwise protects
499 its external entry points from being discarded. Linker scripts
500 must also merge .text.*, .data.*, and .bss.* correctly into
501 output sections. Care must be taken not to pull in unrelated
502 sections (e.g., '.text.init'). Typically '.' in section names
503 is used to distinguish them from label names / C identifiers.
505 config HAVE_ARCH_WITHIN_STACK_FRAMES
508 An architecture should select this if it can walk the kernel stack
509 frames to determine if an object is part of either the arguments
510 or local variables (i.e. that it excludes saved return addresses,
511 and similar) by implementing an inline arch_within_stack_frames(),
512 which is used by CONFIG_HARDENED_USERCOPY.
514 config HAVE_CONTEXT_TRACKING
517 Provide kernel/user boundaries probes necessary for subsystems
518 that need it, such as userspace RCU extended quiescent state.
519 Syscalls need to be wrapped inside user_exit()-user_enter() through
520 the slow path using TIF_NOHZ flag. Exceptions handlers must be
521 wrapped as well. Irqs are already protected inside
522 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
523 irq exit still need to be protected.
525 config HAVE_VIRT_CPU_ACCOUNTING
528 config ARCH_HAS_SCALED_CPUTIME
531 config HAVE_VIRT_CPU_ACCOUNTING_GEN
535 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
536 Before enabling this option, arch code must be audited
537 to ensure there are no races in concurrent read/write of
538 cputime_t. For example, reading/writing 64-bit cputime_t on
539 some 32-bit arches may require multiple accesses, so proper
540 locking is needed to protect against concurrent accesses.
543 config HAVE_IRQ_TIME_ACCOUNTING
546 Archs need to ensure they use a high enough resolution clock to
547 support irq time accounting and then call enable_sched_clock_irqtime().
549 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
552 config HAVE_ARCH_HUGE_VMAP
555 config HAVE_ARCH_SOFT_DIRTY
558 config HAVE_MOD_ARCH_SPECIFIC
561 The arch uses struct mod_arch_specific to store data. Many arches
562 just need a simple module loader without arch specific data - those
563 should not enable this.
565 config MODULES_USE_ELF_RELA
568 Modules only use ELF RELA relocations. Modules with ELF REL
569 relocations will give an error.
571 config MODULES_USE_ELF_REL
574 Modules only use ELF REL relocations. Modules with ELF RELA
575 relocations will give an error.
577 config HAVE_UNDERSCORE_SYMBOL_PREFIX
580 Some architectures generate an _ in front of C symbols; things like
581 module loading and assembly files need to know about this.
583 config HAVE_IRQ_EXIT_ON_IRQ_STACK
586 Architecture doesn't only execute the irq handler on the irq stack
587 but also irq_exit(). This way we can process softirqs on this irq
588 stack instead of switching to a new one when we call __do_softirq()
589 in the end of an hardirq.
590 This spares a stack switch and improves cache usage on softirq
593 config PGTABLE_LEVELS
597 config ARCH_HAS_ELF_RANDOMIZE
600 An architecture supports choosing randomized locations for
601 stack, mmap, brk, and ET_DYN. Defined functions:
603 - arch_randomize_brk()
605 config HAVE_ARCH_MMAP_RND_BITS
608 An arch should select this symbol if it supports setting a variable
609 number of bits for use in establishing the base address for mmap
610 allocations, has MMU enabled and provides values for both:
611 - ARCH_MMAP_RND_BITS_MIN
612 - ARCH_MMAP_RND_BITS_MAX
614 config HAVE_EXIT_THREAD
617 An architecture implements exit_thread.
619 config ARCH_MMAP_RND_BITS_MIN
622 config ARCH_MMAP_RND_BITS_MAX
625 config ARCH_MMAP_RND_BITS_DEFAULT
628 config ARCH_MMAP_RND_BITS
629 int "Number of bits to use for ASLR of mmap base address" if EXPERT
630 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
631 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
632 default ARCH_MMAP_RND_BITS_MIN
633 depends on HAVE_ARCH_MMAP_RND_BITS
635 This value can be used to select the number of bits to use to
636 determine the random offset to the base address of vma regions
637 resulting from mmap allocations. This value will be bounded
638 by the architecture's minimum and maximum supported values.
640 This value can be changed after boot using the
641 /proc/sys/vm/mmap_rnd_bits tunable
643 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
646 An arch should select this symbol if it supports running applications
647 in compatibility mode, supports setting a variable number of bits for
648 use in establishing the base address for mmap allocations, has MMU
649 enabled and provides values for both:
650 - ARCH_MMAP_RND_COMPAT_BITS_MIN
651 - ARCH_MMAP_RND_COMPAT_BITS_MAX
653 config ARCH_MMAP_RND_COMPAT_BITS_MIN
656 config ARCH_MMAP_RND_COMPAT_BITS_MAX
659 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
662 config ARCH_MMAP_RND_COMPAT_BITS
663 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
664 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
665 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
666 default ARCH_MMAP_RND_COMPAT_BITS_MIN
667 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
669 This value can be used to select the number of bits to use to
670 determine the random offset to the base address of vma regions
671 resulting from mmap allocations for compatible applications This
672 value will be bounded by the architecture's minimum and maximum
675 This value can be changed after boot using the
676 /proc/sys/vm/mmap_rnd_compat_bits tunable
678 config HAVE_COPY_THREAD_TLS
681 Architecture provides copy_thread_tls to accept tls argument via
682 normal C parameter passing, rather than extracting the syscall
683 argument from pt_regs.
685 config HAVE_STACK_VALIDATION
688 Architecture supports the 'objtool check' host tool command, which
689 performs compile-time stack metadata validation.
691 config HAVE_ARCH_HASH
695 If this is set, the architecture provides an <asm/hash.h>
696 file which provides platform-specific implementations of some
697 functions in <linux/hash.h> or fs/namei.c.
705 config CLONE_BACKWARDS
708 Architecture has tls passed as the 4th argument of clone(2),
711 config CLONE_BACKWARDS2
714 Architecture has the first two arguments of clone(2) swapped.
716 config CLONE_BACKWARDS3
719 Architecture has tls passed as the 3rd argument of clone(2),
722 config ODD_RT_SIGACTION
725 Architecture has unusual rt_sigaction(2) arguments
727 config OLD_SIGSUSPEND
730 Architecture has old sigsuspend(2) syscall, of one-argument variety
732 config OLD_SIGSUSPEND3
735 Even weirder antique ABI - three-argument sigsuspend(2)
740 Architecture has old sigaction(2) syscall. Nope, not the same
741 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
742 but fairly different variant of sigaction(2), thanks to OSF/1
745 config COMPAT_OLD_SIGACTION
748 config ARCH_NO_COHERENT_DMA_MMAP
751 config CPU_NO_EFFICIENT_FFS
754 config HAVE_ARCH_VMAP_STACK
757 An arch should select this symbol if it can support kernel stacks
758 in vmalloc space. This means:
760 - vmalloc space must be large enough to hold many kernel stacks.
761 This may rule out many 32-bit architectures.
763 - Stacks in vmalloc space need to work reliably. For example, if
764 vmap page tables are created on demand, either this mechanism
765 needs to work while the stack points to a virtual address with
766 unpopulated page tables or arch code (switch_to() and switch_mm(),
767 most likely) needs to ensure that the stack's page table entries
768 are populated before running on a possibly unpopulated stack.
770 - If the stack overflows into a guard page, something reasonable
771 should happen. The definition of "reasonable" is flexible, but
772 instantly rebooting without logging anything would be unfriendly.
776 bool "Use a virtually-mapped stack"
777 depends on HAVE_ARCH_VMAP_STACK && !KASAN
779 Enable this if you want the use virtually-mapped kernel stacks
780 with guard pages. This causes kernel stack overflows to be
781 caught immediately rather than causing difficult-to-diagnose
784 This is presently incompatible with KASAN because KASAN expects
785 the stack to map directly to the KASAN shadow map using a formula
786 that is incorrect if the stack is in vmalloc space.
788 config ARCH_WANT_RELAX_ORDER
791 source "kernel/gcov/Kconfig"