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_info() function
230 config ARCH_THREAD_INFO_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 For best performance, an arch should use seccomp_phase1 and
340 seccomp_phase2 directly. It should call seccomp_phase1 for all
341 syscalls if TIF_SECCOMP is set, but seccomp_phase1 does not
342 need to be called from a ptrace-safe context. It must then
343 call seccomp_phase2 if seccomp_phase1 returns anything other
344 than SECCOMP_PHASE1_OK or SECCOMP_PHASE1_SKIP.
346 As an additional optimization, an arch may provide seccomp_data
347 directly to seccomp_phase1; this avoids multiple calls
348 to the syscall_xyz helpers for every syscall.
350 config SECCOMP_FILTER
352 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
354 Enable tasks to build secure computing environments defined
355 in terms of Berkeley Packet Filter programs which implement
356 task-defined system call filtering polices.
358 See Documentation/prctl/seccomp_filter.txt for details.
360 config HAVE_GCC_PLUGINS
363 An arch should select this symbol if it supports building with
366 menuconfig GCC_PLUGINS
368 depends on HAVE_GCC_PLUGINS
370 GCC plugins are loadable modules that provide extra features to the
371 compiler. They are useful for runtime instrumentation and static analysis.
373 See Documentation/gcc-plugins.txt for details.
375 config GCC_PLUGIN_CYC_COMPLEXITY
376 bool "Compute the cyclomatic complexity of a function"
377 depends on GCC_PLUGINS
379 The complexity M of a function's control flow graph is defined as:
383 E = the number of edges
384 N = the number of nodes
385 P = the number of connected components (exit nodes).
387 config HAVE_CC_STACKPROTECTOR
390 An arch should select this symbol if:
391 - its compiler supports the -fstack-protector option
392 - it has implemented a stack canary (e.g. __stack_chk_guard)
394 config CC_STACKPROTECTOR
397 Set when a stack-protector mode is enabled, so that the build
398 can enable kernel-side support for the GCC feature.
401 prompt "Stack Protector buffer overflow detection"
402 depends on HAVE_CC_STACKPROTECTOR
403 default CC_STACKPROTECTOR_NONE
405 This option turns on the "stack-protector" GCC feature. This
406 feature puts, at the beginning of functions, a canary value on
407 the stack just before the return address, and validates
408 the value just before actually returning. Stack based buffer
409 overflows (that need to overwrite this return address) now also
410 overwrite the canary, which gets detected and the attack is then
411 neutralized via a kernel panic.
413 config CC_STACKPROTECTOR_NONE
416 Disable "stack-protector" GCC feature.
418 config CC_STACKPROTECTOR_REGULAR
420 select CC_STACKPROTECTOR
422 Functions will have the stack-protector canary logic added if they
423 have an 8-byte or larger character array on the stack.
425 This feature requires gcc version 4.2 or above, or a distribution
426 gcc with the feature backported ("-fstack-protector").
428 On an x86 "defconfig" build, this feature adds canary checks to
429 about 3% of all kernel functions, which increases kernel code size
432 config CC_STACKPROTECTOR_STRONG
434 select CC_STACKPROTECTOR
436 Functions will have the stack-protector canary logic added in any
437 of the following conditions:
439 - local variable's address used as part of the right hand side of an
440 assignment or function argument
441 - local variable is an array (or union containing an array),
442 regardless of array type or length
443 - uses register local variables
445 This feature requires gcc version 4.9 or above, or a distribution
446 gcc with the feature backported ("-fstack-protector-strong").
448 On an x86 "defconfig" build, this feature adds canary checks to
449 about 20% of all kernel functions, which increases the kernel code
454 config HAVE_CONTEXT_TRACKING
457 Provide kernel/user boundaries probes necessary for subsystems
458 that need it, such as userspace RCU extended quiescent state.
459 Syscalls need to be wrapped inside user_exit()-user_enter() through
460 the slow path using TIF_NOHZ flag. Exceptions handlers must be
461 wrapped as well. Irqs are already protected inside
462 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
463 irq exit still need to be protected.
465 config HAVE_VIRT_CPU_ACCOUNTING
468 config HAVE_VIRT_CPU_ACCOUNTING_GEN
472 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
473 Before enabling this option, arch code must be audited
474 to ensure there are no races in concurrent read/write of
475 cputime_t. For example, reading/writing 64-bit cputime_t on
476 some 32-bit arches may require multiple accesses, so proper
477 locking is needed to protect against concurrent accesses.
480 config HAVE_IRQ_TIME_ACCOUNTING
483 Archs need to ensure they use a high enough resolution clock to
484 support irq time accounting and then call enable_sched_clock_irqtime().
486 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
489 config HAVE_ARCH_HUGE_VMAP
492 config HAVE_ARCH_SOFT_DIRTY
495 config HAVE_MOD_ARCH_SPECIFIC
498 The arch uses struct mod_arch_specific to store data. Many arches
499 just need a simple module loader without arch specific data - those
500 should not enable this.
502 config MODULES_USE_ELF_RELA
505 Modules only use ELF RELA relocations. Modules with ELF REL
506 relocations will give an error.
508 config MODULES_USE_ELF_REL
511 Modules only use ELF REL relocations. Modules with ELF RELA
512 relocations will give an error.
514 config HAVE_UNDERSCORE_SYMBOL_PREFIX
517 Some architectures generate an _ in front of C symbols; things like
518 module loading and assembly files need to know about this.
520 config HAVE_IRQ_EXIT_ON_IRQ_STACK
523 Architecture doesn't only execute the irq handler on the irq stack
524 but also irq_exit(). This way we can process softirqs on this irq
525 stack instead of switching to a new one when we call __do_softirq()
526 in the end of an hardirq.
527 This spares a stack switch and improves cache usage on softirq
530 config PGTABLE_LEVELS
534 config ARCH_HAS_ELF_RANDOMIZE
537 An architecture supports choosing randomized locations for
538 stack, mmap, brk, and ET_DYN. Defined functions:
540 - arch_randomize_brk()
542 config HAVE_ARCH_MMAP_RND_BITS
545 An arch should select this symbol if it supports setting a variable
546 number of bits for use in establishing the base address for mmap
547 allocations, has MMU enabled and provides values for both:
548 - ARCH_MMAP_RND_BITS_MIN
549 - ARCH_MMAP_RND_BITS_MAX
551 config HAVE_EXIT_THREAD
554 An architecture implements exit_thread.
556 config ARCH_MMAP_RND_BITS_MIN
559 config ARCH_MMAP_RND_BITS_MAX
562 config ARCH_MMAP_RND_BITS_DEFAULT
565 config ARCH_MMAP_RND_BITS
566 int "Number of bits to use for ASLR of mmap base address" if EXPERT
567 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
568 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
569 default ARCH_MMAP_RND_BITS_MIN
570 depends on HAVE_ARCH_MMAP_RND_BITS
572 This value can be used to select the number of bits to use to
573 determine the random offset to the base address of vma regions
574 resulting from mmap allocations. This value will be bounded
575 by the architecture's minimum and maximum supported values.
577 This value can be changed after boot using the
578 /proc/sys/vm/mmap_rnd_bits tunable
580 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
583 An arch should select this symbol if it supports running applications
584 in compatibility mode, supports setting a variable number of bits for
585 use in establishing the base address for mmap allocations, has MMU
586 enabled and provides values for both:
587 - ARCH_MMAP_RND_COMPAT_BITS_MIN
588 - ARCH_MMAP_RND_COMPAT_BITS_MAX
590 config ARCH_MMAP_RND_COMPAT_BITS_MIN
593 config ARCH_MMAP_RND_COMPAT_BITS_MAX
596 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
599 config ARCH_MMAP_RND_COMPAT_BITS
600 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
601 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
602 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
603 default ARCH_MMAP_RND_COMPAT_BITS_MIN
604 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
606 This value can be used to select the number of bits to use to
607 determine the random offset to the base address of vma regions
608 resulting from mmap allocations for compatible applications This
609 value will be bounded by the architecture's minimum and maximum
612 This value can be changed after boot using the
613 /proc/sys/vm/mmap_rnd_compat_bits tunable
615 config HAVE_COPY_THREAD_TLS
618 Architecture provides copy_thread_tls to accept tls argument via
619 normal C parameter passing, rather than extracting the syscall
620 argument from pt_regs.
622 config HAVE_STACK_VALIDATION
625 Architecture supports the 'objtool check' host tool command, which
626 performs compile-time stack metadata validation.
628 config HAVE_ARCH_HASH
632 If this is set, the architecture provides an <asm/hash.h>
633 file which provides platform-specific implementations of some
634 functions in <linux/hash.h> or fs/namei.c.
639 config CLONE_BACKWARDS
642 Architecture has tls passed as the 4th argument of clone(2),
645 config CLONE_BACKWARDS2
648 Architecture has the first two arguments of clone(2) swapped.
650 config CLONE_BACKWARDS3
653 Architecture has tls passed as the 3rd argument of clone(2),
656 config ODD_RT_SIGACTION
659 Architecture has unusual rt_sigaction(2) arguments
661 config OLD_SIGSUSPEND
664 Architecture has old sigsuspend(2) syscall, of one-argument variety
666 config OLD_SIGSUSPEND3
669 Even weirder antique ABI - three-argument sigsuspend(2)
674 Architecture has old sigaction(2) syscall. Nope, not the same
675 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
676 but fairly different variant of sigaction(2), thanks to OSF/1
679 config COMPAT_OLD_SIGACTION
682 config ARCH_NO_COHERENT_DMA_MMAP
685 config CPU_NO_EFFICIENT_FFS
688 source "kernel/gcov/Kconfig"