2 # General architecture dependent options
9 tristate "OProfile system profiling"
11 depends on HAVE_OPROFILE
13 select RING_BUFFER_ALLOW_SWAP
15 OProfile is a profiling system capable of profiling the
16 whole system, include the kernel, kernel modules, libraries,
21 config OPROFILE_EVENT_MULTIPLEX
22 bool "OProfile multiplexing support (EXPERIMENTAL)"
24 depends on OPROFILE && X86
26 The number of hardware counters is limited. The multiplexing
27 feature enables OProfile to gather more events than counters
28 are provided by the hardware. This is realized by switching
29 between events at an user specified time interval.
36 config OPROFILE_NMI_TIMER
38 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
43 depends on HAVE_KPROBES
46 Kprobes allows you to trap at almost any kernel address and
47 execute a callback function. register_kprobe() establishes
48 a probepoint and specifies the callback. Kprobes is useful
49 for kernel debugging, non-intrusive instrumentation and testing.
53 bool "Optimize very unlikely/likely branches"
54 depends on HAVE_ARCH_JUMP_LABEL
56 This option enables a transparent branch optimization that
57 makes certain almost-always-true or almost-always-false branch
58 conditions even cheaper to execute within the kernel.
60 Certain performance-sensitive kernel code, such as trace points,
61 scheduler functionality, networking code and KVM have such
62 branches and include support for this optimization technique.
64 If it is detected that the compiler has support for "asm goto",
65 the kernel will compile such branches with just a nop
66 instruction. When the condition flag is toggled to true, the
67 nop will be converted to a jump instruction to execute the
68 conditional block of instructions.
70 This technique lowers overhead and stress on the branch prediction
71 of the processor and generally makes the kernel faster. The update
72 of the condition is slower, but those are always very rare.
74 ( On 32-bit x86, the necessary options added to the compiler
75 flags may increase the size of the kernel slightly. )
77 config STATIC_KEYS_SELFTEST
78 bool "Static key selftest"
81 Boot time self-test of the branch patching code.
85 depends on KPROBES && HAVE_OPTPROBES
88 config KPROBES_ON_FTRACE
90 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
91 depends on DYNAMIC_FTRACE_WITH_REGS
93 If function tracer is enabled and the arch supports full
94 passing of pt_regs to function tracing, then kprobes can
95 optimize on top of function tracing.
100 Uprobes is the user-space counterpart to kprobes: they
101 enable instrumentation applications (such as 'perf probe')
102 to establish unintrusive probes in user-space binaries and
103 libraries, by executing handler functions when the probes
104 are hit by user-space applications.
106 ( These probes come in the form of single-byte breakpoints,
107 managed by the kernel and kept transparent to the probed
110 config HAVE_64BIT_ALIGNED_ACCESS
111 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
113 Some architectures require 64 bit accesses to be 64 bit
114 aligned, which also requires structs containing 64 bit values
115 to be 64 bit aligned too. This includes some 32 bit
116 architectures which can do 64 bit accesses, as well as 64 bit
117 architectures without unaligned access.
119 This symbol should be selected by an architecture if 64 bit
120 accesses are required to be 64 bit aligned in this way even
121 though it is not a 64 bit architecture.
123 See Documentation/unaligned-memory-access.txt for more
124 information on the topic of unaligned memory accesses.
126 config HAVE_EFFICIENT_UNALIGNED_ACCESS
129 Some architectures are unable to perform unaligned accesses
130 without the use of get_unaligned/put_unaligned. Others are
131 unable to perform such accesses efficiently (e.g. trap on
132 unaligned access and require fixing it up in the exception
135 This symbol should be selected by an architecture if it can
136 perform unaligned accesses efficiently to allow different
137 code paths to be selected for these cases. Some network
138 drivers, for example, could opt to not fix up alignment
139 problems with received packets if doing so would not help
142 See Documentation/unaligned-memory-access.txt for more
143 information on the topic of unaligned memory accesses.
145 config ARCH_USE_BUILTIN_BSWAP
148 Modern versions of GCC (since 4.4) have builtin functions
149 for handling byte-swapping. Using these, instead of the old
150 inline assembler that the architecture code provides in the
151 __arch_bswapXX() macros, allows the compiler to see what's
152 happening and offers more opportunity for optimisation. In
153 particular, the compiler will be able to combine the byteswap
154 with a nearby load or store and use load-and-swap or
155 store-and-swap instructions if the architecture has them. It
156 should almost *never* result in code which is worse than the
157 hand-coded assembler in <asm/swab.h>. But just in case it
158 does, the use of the builtins is optional.
160 Any architecture with load-and-swap or store-and-swap
161 instructions should set this. And it shouldn't hurt to set it
162 on architectures that don't have such instructions.
166 depends on KPROBES && HAVE_KRETPROBES
168 config USER_RETURN_NOTIFIER
170 depends on HAVE_USER_RETURN_NOTIFIER
172 Provide a kernel-internal notification when a cpu is about to
175 config HAVE_IOREMAP_PROT
181 config HAVE_KRETPROBES
184 config HAVE_OPTPROBES
187 config HAVE_KPROBES_ON_FTRACE
193 config HAVE_NMI_WATCHDOG
197 # An arch should select this if it provides all these things:
199 # task_pt_regs() in asm/processor.h or asm/ptrace.h
200 # arch_has_single_step() if there is hardware single-step support
201 # arch_has_block_step() if there is hardware block-step support
202 # asm/syscall.h supplying asm-generic/syscall.h interface
203 # linux/regset.h user_regset interfaces
204 # CORE_DUMP_USE_REGSET #define'd in linux/elf.h
205 # TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit}
206 # TIF_NOTIFY_RESUME calls tracehook_notify_resume()
207 # signal delivery calls tracehook_signal_handler()
209 config HAVE_ARCH_TRACEHOOK
212 config HAVE_DMA_CONTIGUOUS
215 config GENERIC_SMP_IDLE_THREAD
218 config GENERIC_IDLE_POLL_SETUP
221 # Select if arch init_task initializer is different to init/init_task.c
222 config ARCH_INIT_TASK
225 # Select if arch has its private alloc_task_struct() function
226 config ARCH_TASK_STRUCT_ALLOCATOR
229 # Select if arch has its private alloc_thread_stack() function
230 config ARCH_THREAD_STACK_ALLOCATOR
233 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
234 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
237 config HAVE_REGS_AND_STACK_ACCESS_API
240 This symbol should be selected by an architecure if it supports
241 the API needed to access registers and stack entries from pt_regs,
242 declared in asm/ptrace.h
243 For example the kprobes-based event tracer needs this API.
248 The <linux/clk.h> calls support software clock gating and
249 thus are a key power management tool on many systems.
251 config HAVE_DMA_API_DEBUG
254 config HAVE_HW_BREAKPOINT
256 depends on PERF_EVENTS
258 config HAVE_MIXED_BREAKPOINTS_REGS
260 depends on HAVE_HW_BREAKPOINT
262 Depending on the arch implementation of hardware breakpoints,
263 some of them have separate registers for data and instruction
264 breakpoints addresses, others have mixed registers to store
265 them but define the access type in a control register.
266 Select this option if your arch implements breakpoints under the
269 config HAVE_USER_RETURN_NOTIFIER
272 config HAVE_PERF_EVENTS_NMI
275 System hardware can generate an NMI using the perf event
276 subsystem. Also has support for calculating CPU cycle events
277 to determine how many clock cycles in a given period.
279 config HAVE_PERF_REGS
282 Support selective register dumps for perf events. This includes
283 bit-mapping of each registers and a unique architecture id.
285 config HAVE_PERF_USER_STACK_DUMP
288 Support user stack dumps for perf event samples. This needs
289 access to the user stack pointer which is not unified across
292 config HAVE_ARCH_JUMP_LABEL
295 config HAVE_RCU_TABLE_FREE
298 config ARCH_HAVE_NMI_SAFE_CMPXCHG
301 config HAVE_ALIGNED_STRUCT_PAGE
304 This makes sure that struct pages are double word aligned and that
305 e.g. the SLUB allocator can perform double word atomic operations
306 on a struct page for better performance. However selecting this
307 might increase the size of a struct page by a word.
309 config HAVE_CMPXCHG_LOCAL
312 config HAVE_CMPXCHG_DOUBLE
315 config ARCH_WANT_IPC_PARSE_VERSION
318 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
321 config ARCH_WANT_OLD_COMPAT_IPC
322 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
325 config HAVE_ARCH_SECCOMP_FILTER
328 An arch should select this symbol if it provides all of these things:
330 - syscall_get_arguments()
332 - syscall_set_return_value()
333 - SIGSYS siginfo_t support
334 - secure_computing is called from a ptrace_event()-safe context
335 - secure_computing return value is checked and a return value of -1
336 results in the system call being skipped immediately.
337 - seccomp syscall wired up
339 config SECCOMP_FILTER
341 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
343 Enable tasks to build secure computing environments defined
344 in terms of Berkeley Packet Filter programs which implement
345 task-defined system call filtering polices.
347 See Documentation/prctl/seccomp_filter.txt for details.
349 config HAVE_GCC_PLUGINS
352 An arch should select this symbol if it supports building with
355 menuconfig GCC_PLUGINS
357 depends on HAVE_GCC_PLUGINS
358 depends on !COMPILE_TEST
360 GCC plugins are loadable modules that provide extra features to the
361 compiler. They are useful for runtime instrumentation and static analysis.
363 See Documentation/gcc-plugins.txt for details.
365 config GCC_PLUGIN_CYC_COMPLEXITY
366 bool "Compute the cyclomatic complexity of a function"
367 depends on GCC_PLUGINS
369 The complexity M of a function's control flow graph is defined as:
373 E = the number of edges
374 N = the number of nodes
375 P = the number of connected components (exit nodes).
377 config GCC_PLUGIN_SANCOV
379 depends on GCC_PLUGINS
381 This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
382 basic blocks. It supports all gcc versions with plugin support (from
383 gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
384 by Dmitry Vyukov <dvyukov@google.com>.
386 config GCC_PLUGIN_LATENT_ENTROPY
387 bool "Generate some entropy during boot and runtime"
388 depends on GCC_PLUGINS
390 By saying Y here the kernel will instrument some kernel code to
391 extract some entropy from both original and artificially created
392 program state. This will help especially embedded systems where
393 there is little 'natural' source of entropy normally. The cost
394 is some slowdown of the boot process (about 0.5%) and fork and
397 Note that entropy extracted this way is not cryptographically
400 This plugin was ported from grsecurity/PaX. More information at:
401 * https://grsecurity.net/
402 * https://pax.grsecurity.net/
404 config HAVE_CC_STACKPROTECTOR
407 An arch should select this symbol if:
408 - its compiler supports the -fstack-protector option
409 - it has implemented a stack canary (e.g. __stack_chk_guard)
411 config CC_STACKPROTECTOR
414 Set when a stack-protector mode is enabled, so that the build
415 can enable kernel-side support for the GCC feature.
418 prompt "Stack Protector buffer overflow detection"
419 depends on HAVE_CC_STACKPROTECTOR
420 default CC_STACKPROTECTOR_NONE
422 This option turns on the "stack-protector" GCC feature. This
423 feature puts, at the beginning of functions, a canary value on
424 the stack just before the return address, and validates
425 the value just before actually returning. Stack based buffer
426 overflows (that need to overwrite this return address) now also
427 overwrite the canary, which gets detected and the attack is then
428 neutralized via a kernel panic.
430 config CC_STACKPROTECTOR_NONE
433 Disable "stack-protector" GCC feature.
435 config CC_STACKPROTECTOR_REGULAR
437 select CC_STACKPROTECTOR
439 Functions will have the stack-protector canary logic added if they
440 have an 8-byte or larger character array on the stack.
442 This feature requires gcc version 4.2 or above, or a distribution
443 gcc with the feature backported ("-fstack-protector").
445 On an x86 "defconfig" build, this feature adds canary checks to
446 about 3% of all kernel functions, which increases kernel code size
449 config CC_STACKPROTECTOR_STRONG
451 select CC_STACKPROTECTOR
453 Functions will have the stack-protector canary logic added in any
454 of the following conditions:
456 - local variable's address used as part of the right hand side of an
457 assignment or function argument
458 - local variable is an array (or union containing an array),
459 regardless of array type or length
460 - uses register local variables
462 This feature requires gcc version 4.9 or above, or a distribution
463 gcc with the feature backported ("-fstack-protector-strong").
465 On an x86 "defconfig" build, this feature adds canary checks to
466 about 20% of all kernel functions, which increases the kernel code
471 config HAVE_ARCH_WITHIN_STACK_FRAMES
474 An architecture should select this if it can walk the kernel stack
475 frames to determine if an object is part of either the arguments
476 or local variables (i.e. that it excludes saved return addresses,
477 and similar) by implementing an inline arch_within_stack_frames(),
478 which is used by CONFIG_HARDENED_USERCOPY.
483 Select this if the architecture wants to use thin archives
484 instead of ld -r to create the built-in.o files.
486 config LD_DEAD_CODE_DATA_ELIMINATION
489 Select this if the architecture wants to do dead code and
490 data elimination with the linker by compiling with
491 -ffunction-sections -fdata-sections and linking with
494 This requires that the arch annotates or otherwise protects
495 its external entry points from being discarded. Linker scripts
496 must also merge .text.*, .data.*, and .bss.* correctly into
499 config HAVE_CONTEXT_TRACKING
502 Provide kernel/user boundaries probes necessary for subsystems
503 that need it, such as userspace RCU extended quiescent state.
504 Syscalls need to be wrapped inside user_exit()-user_enter() through
505 the slow path using TIF_NOHZ flag. Exceptions handlers must be
506 wrapped as well. Irqs are already protected inside
507 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
508 irq exit still need to be protected.
510 config HAVE_VIRT_CPU_ACCOUNTING
513 config HAVE_VIRT_CPU_ACCOUNTING_GEN
517 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
518 Before enabling this option, arch code must be audited
519 to ensure there are no races in concurrent read/write of
520 cputime_t. For example, reading/writing 64-bit cputime_t on
521 some 32-bit arches may require multiple accesses, so proper
522 locking is needed to protect against concurrent accesses.
525 config HAVE_IRQ_TIME_ACCOUNTING
528 Archs need to ensure they use a high enough resolution clock to
529 support irq time accounting and then call enable_sched_clock_irqtime().
531 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
534 config HAVE_ARCH_HUGE_VMAP
537 config HAVE_ARCH_SOFT_DIRTY
540 config HAVE_MOD_ARCH_SPECIFIC
543 The arch uses struct mod_arch_specific to store data. Many arches
544 just need a simple module loader without arch specific data - those
545 should not enable this.
547 config MODULES_USE_ELF_RELA
550 Modules only use ELF RELA relocations. Modules with ELF REL
551 relocations will give an error.
553 config MODULES_USE_ELF_REL
556 Modules only use ELF REL relocations. Modules with ELF RELA
557 relocations will give an error.
559 config HAVE_UNDERSCORE_SYMBOL_PREFIX
562 Some architectures generate an _ in front of C symbols; things like
563 module loading and assembly files need to know about this.
565 config HAVE_IRQ_EXIT_ON_IRQ_STACK
568 Architecture doesn't only execute the irq handler on the irq stack
569 but also irq_exit(). This way we can process softirqs on this irq
570 stack instead of switching to a new one when we call __do_softirq()
571 in the end of an hardirq.
572 This spares a stack switch and improves cache usage on softirq
575 config PGTABLE_LEVELS
579 config ARCH_HAS_ELF_RANDOMIZE
582 An architecture supports choosing randomized locations for
583 stack, mmap, brk, and ET_DYN. Defined functions:
585 - arch_randomize_brk()
587 config HAVE_ARCH_MMAP_RND_BITS
590 An arch should select this symbol if it supports setting a variable
591 number of bits for use in establishing the base address for mmap
592 allocations, has MMU enabled and provides values for both:
593 - ARCH_MMAP_RND_BITS_MIN
594 - ARCH_MMAP_RND_BITS_MAX
596 config HAVE_EXIT_THREAD
599 An architecture implements exit_thread.
601 config ARCH_MMAP_RND_BITS_MIN
604 config ARCH_MMAP_RND_BITS_MAX
607 config ARCH_MMAP_RND_BITS_DEFAULT
610 config ARCH_MMAP_RND_BITS
611 int "Number of bits to use for ASLR of mmap base address" if EXPERT
612 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
613 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
614 default ARCH_MMAP_RND_BITS_MIN
615 depends on HAVE_ARCH_MMAP_RND_BITS
617 This value can be used to select the number of bits to use to
618 determine the random offset to the base address of vma regions
619 resulting from mmap allocations. This value will be bounded
620 by the architecture's minimum and maximum supported values.
622 This value can be changed after boot using the
623 /proc/sys/vm/mmap_rnd_bits tunable
625 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
628 An arch should select this symbol if it supports running applications
629 in compatibility mode, supports setting a variable number of bits for
630 use in establishing the base address for mmap allocations, has MMU
631 enabled and provides values for both:
632 - ARCH_MMAP_RND_COMPAT_BITS_MIN
633 - ARCH_MMAP_RND_COMPAT_BITS_MAX
635 config ARCH_MMAP_RND_COMPAT_BITS_MIN
638 config ARCH_MMAP_RND_COMPAT_BITS_MAX
641 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
644 config ARCH_MMAP_RND_COMPAT_BITS
645 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
646 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
647 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
648 default ARCH_MMAP_RND_COMPAT_BITS_MIN
649 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
651 This value can be used to select the number of bits to use to
652 determine the random offset to the base address of vma regions
653 resulting from mmap allocations for compatible applications This
654 value will be bounded by the architecture's minimum and maximum
657 This value can be changed after boot using the
658 /proc/sys/vm/mmap_rnd_compat_bits tunable
660 config HAVE_COPY_THREAD_TLS
663 Architecture provides copy_thread_tls to accept tls argument via
664 normal C parameter passing, rather than extracting the syscall
665 argument from pt_regs.
667 config HAVE_STACK_VALIDATION
670 Architecture supports the 'objtool check' host tool command, which
671 performs compile-time stack metadata validation.
673 config HAVE_ARCH_HASH
677 If this is set, the architecture provides an <asm/hash.h>
678 file which provides platform-specific implementations of some
679 functions in <linux/hash.h> or fs/namei.c.
687 config CLONE_BACKWARDS
690 Architecture has tls passed as the 4th argument of clone(2),
693 config CLONE_BACKWARDS2
696 Architecture has the first two arguments of clone(2) swapped.
698 config CLONE_BACKWARDS3
701 Architecture has tls passed as the 3rd argument of clone(2),
704 config ODD_RT_SIGACTION
707 Architecture has unusual rt_sigaction(2) arguments
709 config OLD_SIGSUSPEND
712 Architecture has old sigsuspend(2) syscall, of one-argument variety
714 config OLD_SIGSUSPEND3
717 Even weirder antique ABI - three-argument sigsuspend(2)
722 Architecture has old sigaction(2) syscall. Nope, not the same
723 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
724 but fairly different variant of sigaction(2), thanks to OSF/1
727 config COMPAT_OLD_SIGACTION
730 config ARCH_NO_COHERENT_DMA_MMAP
733 config CPU_NO_EFFICIENT_FFS
736 source "kernel/gcov/Kconfig"