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Linux/arch/Kconfig

  1 #
  2 # General architecture dependent options
  3 #
  4 
  5 config KEXEC_CORE
  6         bool
  7 
  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 
 19           If unsure, say N.
 20 
 21 config OPROFILE_EVENT_MULTIPLEX
 22         bool "OProfile multiplexing support (EXPERIMENTAL)"
 23         default n
 24         depends on OPROFILE && X86
 25         help
 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.
 30 
 31           If unsure, say N.
 32 
 33 config HAVE_OPROFILE
 34         bool
 35 
 36 config OPROFILE_NMI_TIMER
 37         def_bool y
 38         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
 39 
 40 config KPROBES
 41         bool "Kprobes"
 42         depends on MODULES
 43         depends on HAVE_KPROBES
 44         select KALLSYMS
 45         help
 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.
 50           If in doubt, say "N".
 51 
 52 config JUMP_LABEL
 53        bool "Optimize very unlikely/likely branches"
 54        depends on HAVE_ARCH_JUMP_LABEL
 55        help
 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.
 59 
 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.
 63 
 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.
 69 
 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.
 73 
 74          ( On 32-bit x86, the necessary options added to the compiler
 75            flags may increase the size of the kernel slightly. )
 76 
 77 config STATIC_KEYS_SELFTEST
 78         bool "Static key selftest"
 79         depends on JUMP_LABEL
 80         help
 81           Boot time self-test of the branch patching code.
 82 
 83 config OPTPROBES
 84         def_bool y
 85         depends on KPROBES && HAVE_OPTPROBES
 86         depends on !PREEMPT
 87 
 88 config KPROBES_ON_FTRACE
 89         def_bool y
 90         depends on KPROBES && HAVE_KPROBES_ON_FTRACE
 91         depends on DYNAMIC_FTRACE_WITH_REGS
 92         help
 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.
 96 
 97 config UPROBES
 98         def_bool n
 99         help
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.
105 
106           ( These probes come in the form of single-byte breakpoints,
107             managed by the kernel and kept transparent to the probed
108             application. )
109 
110 config HAVE_64BIT_ALIGNED_ACCESS
111         def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
112         help
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.
118 
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.
122 
123           See Documentation/unaligned-memory-access.txt for more
124           information on the topic of unaligned memory accesses.
125 
126 config HAVE_EFFICIENT_UNALIGNED_ACCESS
127         bool
128         help
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
133           handler.)
134 
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
140           much.
141 
142           See Documentation/unaligned-memory-access.txt for more
143           information on the topic of unaligned memory accesses.
144 
145 config ARCH_USE_BUILTIN_BSWAP
146        bool
147        help
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.
159 
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.
163 
164 config KRETPROBES
165         def_bool y
166         depends on KPROBES && HAVE_KRETPROBES
167 
168 config USER_RETURN_NOTIFIER
169         bool
170         depends on HAVE_USER_RETURN_NOTIFIER
171         help
172           Provide a kernel-internal notification when a cpu is about to
173           switch to user mode.
174 
175 config HAVE_IOREMAP_PROT
176         bool
177 
178 config HAVE_KPROBES
179         bool
180 
181 config HAVE_KRETPROBES
182         bool
183 
184 config HAVE_OPTPROBES
185         bool
186 
187 config HAVE_KPROBES_ON_FTRACE
188         bool
189 
190 config HAVE_NMI
191         bool
192 
193 config HAVE_NMI_WATCHDOG
194         depends on HAVE_NMI
195         bool
196 #
197 # An arch should select this if it provides all these things:
198 #
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()
208 #
209 config HAVE_ARCH_TRACEHOOK
210         bool
211 
212 config HAVE_DMA_CONTIGUOUS
213         bool
214 
215 config GENERIC_SMP_IDLE_THREAD
216        bool
217 
218 config GENERIC_IDLE_POLL_SETUP
219        bool
220 
221 # Select if arch init_task initializer is different to init/init_task.c
222 config ARCH_INIT_TASK
223        bool
224 
225 # Select if arch has its private alloc_task_struct() function
226 config ARCH_TASK_STRUCT_ALLOCATOR
227         bool
228 
229 # Select if arch has its private alloc_thread_stack() function
230 config ARCH_THREAD_STACK_ALLOCATOR
231         bool
232 
233 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
234 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
235         bool
236 
237 config HAVE_REGS_AND_STACK_ACCESS_API
238         bool
239         help
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.
244 
245 config HAVE_CLK
246         bool
247         help
248           The <linux/clk.h> calls support software clock gating and
249           thus are a key power management tool on many systems.
250 
251 config HAVE_DMA_API_DEBUG
252         bool
253 
254 config HAVE_HW_BREAKPOINT
255         bool
256         depends on PERF_EVENTS
257 
258 config HAVE_MIXED_BREAKPOINTS_REGS
259         bool
260         depends on HAVE_HW_BREAKPOINT
261         help
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
267           latter fashion.
268 
269 config HAVE_USER_RETURN_NOTIFIER
270         bool
271 
272 config HAVE_PERF_EVENTS_NMI
273         bool
274         help
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.
278 
279 config HAVE_PERF_REGS
280         bool
281         help
282           Support selective register dumps for perf events. This includes
283           bit-mapping of each registers and a unique architecture id.
284 
285 config HAVE_PERF_USER_STACK_DUMP
286         bool
287         help
288           Support user stack dumps for perf event samples. This needs
289           access to the user stack pointer which is not unified across
290           architectures.
291 
292 config HAVE_ARCH_JUMP_LABEL
293         bool
294 
295 config HAVE_RCU_TABLE_FREE
296         bool
297 
298 config ARCH_HAVE_NMI_SAFE_CMPXCHG
299         bool
300 
301 config HAVE_ALIGNED_STRUCT_PAGE
302         bool
303         help
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.
308 
309 config HAVE_CMPXCHG_LOCAL
310         bool
311 
312 config HAVE_CMPXCHG_DOUBLE
313         bool
314 
315 config ARCH_WANT_IPC_PARSE_VERSION
316         bool
317 
318 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
319         bool
320 
321 config ARCH_WANT_OLD_COMPAT_IPC
322         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
323         bool
324 
325 config HAVE_ARCH_SECCOMP_FILTER
326         bool
327         help
328           An arch should select this symbol if it provides all of these things:
329           - syscall_get_arch()
330           - syscall_get_arguments()
331           - syscall_rollback()
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
338 
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.
345 
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.
349 
350 config SECCOMP_FILTER
351         def_bool y
352         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
353         help
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.
357 
358           See Documentation/prctl/seccomp_filter.txt for details.
359 
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 
367 config CC_STACKPROTECTOR
368         def_bool n
369         help
370           Set when a stack-protector mode is enabled, so that the build
371           can enable kernel-side support for the GCC feature.
372 
373 choice
374         prompt "Stack Protector buffer overflow detection"
375         depends on HAVE_CC_STACKPROTECTOR
376         default CC_STACKPROTECTOR_NONE
377         help
378           This option turns on the "stack-protector" GCC feature. This
379           feature puts, at the beginning of functions, a canary value on
380           the stack just before the return address, and validates
381           the value just before actually returning.  Stack based buffer
382           overflows (that need to overwrite this return address) now also
383           overwrite the canary, which gets detected and the attack is then
384           neutralized via a kernel panic.
385 
386 config CC_STACKPROTECTOR_NONE
387         bool "None"
388         help
389           Disable "stack-protector" GCC feature.
390 
391 config CC_STACKPROTECTOR_REGULAR
392         bool "Regular"
393         select CC_STACKPROTECTOR
394         help
395           Functions will have the stack-protector canary logic added if they
396           have an 8-byte or larger character array on the stack.
397 
398           This feature requires gcc version 4.2 or above, or a distribution
399           gcc with the feature backported ("-fstack-protector").
400 
401           On an x86 "defconfig" build, this feature adds canary checks to
402           about 3% of all kernel functions, which increases kernel code size
403           by about 0.3%.
404 
405 config CC_STACKPROTECTOR_STRONG
406         bool "Strong"
407         select CC_STACKPROTECTOR
408         help
409           Functions will have the stack-protector canary logic added in any
410           of the following conditions:
411 
412           - local variable's address used as part of the right hand side of an
413             assignment or function argument
414           - local variable is an array (or union containing an array),
415             regardless of array type or length
416           - uses register local variables
417 
418           This feature requires gcc version 4.9 or above, or a distribution
419           gcc with the feature backported ("-fstack-protector-strong").
420 
421           On an x86 "defconfig" build, this feature adds canary checks to
422           about 20% of all kernel functions, which increases the kernel code
423           size by about 2%.
424 
425 endchoice
426 
427 config HAVE_CONTEXT_TRACKING
428         bool
429         help
430           Provide kernel/user boundaries probes necessary for subsystems
431           that need it, such as userspace RCU extended quiescent state.
432           Syscalls need to be wrapped inside user_exit()-user_enter() through
433           the slow path using TIF_NOHZ flag. Exceptions handlers must be
434           wrapped as well. Irqs are already protected inside
435           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
436           irq exit still need to be protected.
437 
438 config HAVE_VIRT_CPU_ACCOUNTING
439         bool
440 
441 config HAVE_VIRT_CPU_ACCOUNTING_GEN
442         bool
443         default y if 64BIT
444         help
445           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
446           Before enabling this option, arch code must be audited
447           to ensure there are no races in concurrent read/write of
448           cputime_t. For example, reading/writing 64-bit cputime_t on
449           some 32-bit arches may require multiple accesses, so proper
450           locking is needed to protect against concurrent accesses.
451 
452 
453 config HAVE_IRQ_TIME_ACCOUNTING
454         bool
455         help
456           Archs need to ensure they use a high enough resolution clock to
457           support irq time accounting and then call enable_sched_clock_irqtime().
458 
459 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
460         bool
461 
462 config HAVE_ARCH_HUGE_VMAP
463         bool
464 
465 config HAVE_ARCH_SOFT_DIRTY
466         bool
467 
468 config HAVE_MOD_ARCH_SPECIFIC
469         bool
470         help
471           The arch uses struct mod_arch_specific to store data.  Many arches
472           just need a simple module loader without arch specific data - those
473           should not enable this.
474 
475 config MODULES_USE_ELF_RELA
476         bool
477         help
478           Modules only use ELF RELA relocations.  Modules with ELF REL
479           relocations will give an error.
480 
481 config MODULES_USE_ELF_REL
482         bool
483         help
484           Modules only use ELF REL relocations.  Modules with ELF RELA
485           relocations will give an error.
486 
487 config HAVE_UNDERSCORE_SYMBOL_PREFIX
488         bool
489         help
490           Some architectures generate an _ in front of C symbols; things like
491           module loading and assembly files need to know about this.
492 
493 config HAVE_IRQ_EXIT_ON_IRQ_STACK
494         bool
495         help
496           Architecture doesn't only execute the irq handler on the irq stack
497           but also irq_exit(). This way we can process softirqs on this irq
498           stack instead of switching to a new one when we call __do_softirq()
499           in the end of an hardirq.
500           This spares a stack switch and improves cache usage on softirq
501           processing.
502 
503 config PGTABLE_LEVELS
504         int
505         default 2
506 
507 config ARCH_HAS_ELF_RANDOMIZE
508         bool
509         help
510           An architecture supports choosing randomized locations for
511           stack, mmap, brk, and ET_DYN. Defined functions:
512           - arch_mmap_rnd()
513           - arch_randomize_brk()
514 
515 config HAVE_ARCH_MMAP_RND_BITS
516         bool
517         help
518           An arch should select this symbol if it supports setting a variable
519           number of bits for use in establishing the base address for mmap
520           allocations, has MMU enabled and provides values for both:
521           - ARCH_MMAP_RND_BITS_MIN
522           - ARCH_MMAP_RND_BITS_MAX
523 
524 config HAVE_EXIT_THREAD
525         bool
526         help
527           An architecture implements exit_thread.
528 
529 config ARCH_MMAP_RND_BITS_MIN
530         int
531 
532 config ARCH_MMAP_RND_BITS_MAX
533         int
534 
535 config ARCH_MMAP_RND_BITS_DEFAULT
536         int
537 
538 config ARCH_MMAP_RND_BITS
539         int "Number of bits to use for ASLR of mmap base address" if EXPERT
540         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
541         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
542         default ARCH_MMAP_RND_BITS_MIN
543         depends on HAVE_ARCH_MMAP_RND_BITS
544         help
545           This value can be used to select the number of bits to use to
546           determine the random offset to the base address of vma regions
547           resulting from mmap allocations. This value will be bounded
548           by the architecture's minimum and maximum supported values.
549 
550           This value can be changed after boot using the
551           /proc/sys/vm/mmap_rnd_bits tunable
552 
553 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
554         bool
555         help
556           An arch should select this symbol if it supports running applications
557           in compatibility mode, supports setting a variable number of bits for
558           use in establishing the base address for mmap allocations, has MMU
559           enabled and provides values for both:
560           - ARCH_MMAP_RND_COMPAT_BITS_MIN
561           - ARCH_MMAP_RND_COMPAT_BITS_MAX
562 
563 config ARCH_MMAP_RND_COMPAT_BITS_MIN
564         int
565 
566 config ARCH_MMAP_RND_COMPAT_BITS_MAX
567         int
568 
569 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
570         int
571 
572 config ARCH_MMAP_RND_COMPAT_BITS
573         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
574         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
575         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
576         default ARCH_MMAP_RND_COMPAT_BITS_MIN
577         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
578         help
579           This value can be used to select the number of bits to use to
580           determine the random offset to the base address of vma regions
581           resulting from mmap allocations for compatible applications This
582           value will be bounded by the architecture's minimum and maximum
583           supported values.
584 
585           This value can be changed after boot using the
586           /proc/sys/vm/mmap_rnd_compat_bits tunable
587 
588 config HAVE_COPY_THREAD_TLS
589         bool
590         help
591           Architecture provides copy_thread_tls to accept tls argument via
592           normal C parameter passing, rather than extracting the syscall
593           argument from pt_regs.
594 
595 config HAVE_STACK_VALIDATION
596         bool
597         help
598           Architecture supports the 'objtool check' host tool command, which
599           performs compile-time stack metadata validation.
600 
601 config HAVE_ARCH_HASH
602         bool
603         default n
604         help
605           If this is set, the architecture provides an <asm/hash.h>
606           file which provides platform-specific implementations of some
607           functions in <linux/hash.h> or fs/namei.c.
608 
609 config ISA_BUS_API
610         def_bool ISA
611 
612 #
613 # ABI hall of shame
614 #
615 config CLONE_BACKWARDS
616         bool
617         help
618           Architecture has tls passed as the 4th argument of clone(2),
619           not the 5th one.
620 
621 config CLONE_BACKWARDS2
622         bool
623         help
624           Architecture has the first two arguments of clone(2) swapped.
625 
626 config CLONE_BACKWARDS3
627         bool
628         help
629           Architecture has tls passed as the 3rd argument of clone(2),
630           not the 5th one.
631 
632 config ODD_RT_SIGACTION
633         bool
634         help
635           Architecture has unusual rt_sigaction(2) arguments
636 
637 config OLD_SIGSUSPEND
638         bool
639         help
640           Architecture has old sigsuspend(2) syscall, of one-argument variety
641 
642 config OLD_SIGSUSPEND3
643         bool
644         help
645           Even weirder antique ABI - three-argument sigsuspend(2)
646 
647 config OLD_SIGACTION
648         bool
649         help
650           Architecture has old sigaction(2) syscall.  Nope, not the same
651           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
652           but fairly different variant of sigaction(2), thanks to OSF/1
653           compatibility...
654 
655 config COMPAT_OLD_SIGACTION
656         bool
657 
658 config ARCH_NO_COHERENT_DMA_MMAP
659         bool
660 
661 config CPU_NO_EFFICIENT_FFS
662         def_bool n
663 
664 source "kernel/gcov/Kconfig"

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