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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 config SECCOMP_FILTER
340         def_bool y
341         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
342         help
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.
346 
347           See Documentation/prctl/seccomp_filter.txt for details.
348 
349 config HAVE_GCC_PLUGINS
350         bool
351         help
352           An arch should select this symbol if it supports building with
353           GCC plugins.
354 
355 menuconfig GCC_PLUGINS
356         bool "GCC plugins"
357         depends on HAVE_GCC_PLUGINS
358         depends on !COMPILE_TEST
359         help
360           GCC plugins are loadable modules that provide extra features to the
361           compiler. They are useful for runtime instrumentation and static analysis.
362 
363           See Documentation/gcc-plugins.txt for details.
364 
365 config GCC_PLUGIN_CYC_COMPLEXITY
366         bool "Compute the cyclomatic complexity of a function"
367         depends on GCC_PLUGINS
368         help
369           The complexity M of a function's control flow graph is defined as:
370            M = E - N + 2P
371           where
372 
373           E = the number of edges
374           N = the number of nodes
375           P = the number of connected components (exit nodes).
376 
377 config GCC_PLUGIN_SANCOV
378         bool
379         depends on GCC_PLUGINS
380         help
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>.
385 
386 config HAVE_CC_STACKPROTECTOR
387         bool
388         help
389           An arch should select this symbol if:
390           - its compiler supports the -fstack-protector option
391           - it has implemented a stack canary (e.g. __stack_chk_guard)
392 
393 config CC_STACKPROTECTOR
394         def_bool n
395         help
396           Set when a stack-protector mode is enabled, so that the build
397           can enable kernel-side support for the GCC feature.
398 
399 choice
400         prompt "Stack Protector buffer overflow detection"
401         depends on HAVE_CC_STACKPROTECTOR
402         default CC_STACKPROTECTOR_NONE
403         help
404           This option turns on the "stack-protector" GCC feature. This
405           feature puts, at the beginning of functions, a canary value on
406           the stack just before the return address, and validates
407           the value just before actually returning.  Stack based buffer
408           overflows (that need to overwrite this return address) now also
409           overwrite the canary, which gets detected and the attack is then
410           neutralized via a kernel panic.
411 
412 config CC_STACKPROTECTOR_NONE
413         bool "None"
414         help
415           Disable "stack-protector" GCC feature.
416 
417 config CC_STACKPROTECTOR_REGULAR
418         bool "Regular"
419         select CC_STACKPROTECTOR
420         help
421           Functions will have the stack-protector canary logic added if they
422           have an 8-byte or larger character array on the stack.
423 
424           This feature requires gcc version 4.2 or above, or a distribution
425           gcc with the feature backported ("-fstack-protector").
426 
427           On an x86 "defconfig" build, this feature adds canary checks to
428           about 3% of all kernel functions, which increases kernel code size
429           by about 0.3%.
430 
431 config CC_STACKPROTECTOR_STRONG
432         bool "Strong"
433         select CC_STACKPROTECTOR
434         help
435           Functions will have the stack-protector canary logic added in any
436           of the following conditions:
437 
438           - local variable's address used as part of the right hand side of an
439             assignment or function argument
440           - local variable is an array (or union containing an array),
441             regardless of array type or length
442           - uses register local variables
443 
444           This feature requires gcc version 4.9 or above, or a distribution
445           gcc with the feature backported ("-fstack-protector-strong").
446 
447           On an x86 "defconfig" build, this feature adds canary checks to
448           about 20% of all kernel functions, which increases the kernel code
449           size by about 2%.
450 
451 endchoice
452 
453 config HAVE_ARCH_WITHIN_STACK_FRAMES
454         bool
455         help
456           An architecture should select this if it can walk the kernel stack
457           frames to determine if an object is part of either the arguments
458           or local variables (i.e. that it excludes saved return addresses,
459           and similar) by implementing an inline arch_within_stack_frames(),
460           which is used by CONFIG_HARDENED_USERCOPY.
461 
462 config HAVE_CONTEXT_TRACKING
463         bool
464         help
465           Provide kernel/user boundaries probes necessary for subsystems
466           that need it, such as userspace RCU extended quiescent state.
467           Syscalls need to be wrapped inside user_exit()-user_enter() through
468           the slow path using TIF_NOHZ flag. Exceptions handlers must be
469           wrapped as well. Irqs are already protected inside
470           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
471           irq exit still need to be protected.
472 
473 config HAVE_VIRT_CPU_ACCOUNTING
474         bool
475 
476 config HAVE_VIRT_CPU_ACCOUNTING_GEN
477         bool
478         default y if 64BIT
479         help
480           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
481           Before enabling this option, arch code must be audited
482           to ensure there are no races in concurrent read/write of
483           cputime_t. For example, reading/writing 64-bit cputime_t on
484           some 32-bit arches may require multiple accesses, so proper
485           locking is needed to protect against concurrent accesses.
486 
487 
488 config HAVE_IRQ_TIME_ACCOUNTING
489         bool
490         help
491           Archs need to ensure they use a high enough resolution clock to
492           support irq time accounting and then call enable_sched_clock_irqtime().
493 
494 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
495         bool
496 
497 config HAVE_ARCH_HUGE_VMAP
498         bool
499 
500 config HAVE_ARCH_SOFT_DIRTY
501         bool
502 
503 config HAVE_MOD_ARCH_SPECIFIC
504         bool
505         help
506           The arch uses struct mod_arch_specific to store data.  Many arches
507           just need a simple module loader without arch specific data - those
508           should not enable this.
509 
510 config MODULES_USE_ELF_RELA
511         bool
512         help
513           Modules only use ELF RELA relocations.  Modules with ELF REL
514           relocations will give an error.
515 
516 config MODULES_USE_ELF_REL
517         bool
518         help
519           Modules only use ELF REL relocations.  Modules with ELF RELA
520           relocations will give an error.
521 
522 config HAVE_UNDERSCORE_SYMBOL_PREFIX
523         bool
524         help
525           Some architectures generate an _ in front of C symbols; things like
526           module loading and assembly files need to know about this.
527 
528 config HAVE_IRQ_EXIT_ON_IRQ_STACK
529         bool
530         help
531           Architecture doesn't only execute the irq handler on the irq stack
532           but also irq_exit(). This way we can process softirqs on this irq
533           stack instead of switching to a new one when we call __do_softirq()
534           in the end of an hardirq.
535           This spares a stack switch and improves cache usage on softirq
536           processing.
537 
538 config PGTABLE_LEVELS
539         int
540         default 2
541 
542 config ARCH_HAS_ELF_RANDOMIZE
543         bool
544         help
545           An architecture supports choosing randomized locations for
546           stack, mmap, brk, and ET_DYN. Defined functions:
547           - arch_mmap_rnd()
548           - arch_randomize_brk()
549 
550 config HAVE_ARCH_MMAP_RND_BITS
551         bool
552         help
553           An arch should select this symbol if it supports setting a variable
554           number of bits for use in establishing the base address for mmap
555           allocations, has MMU enabled and provides values for both:
556           - ARCH_MMAP_RND_BITS_MIN
557           - ARCH_MMAP_RND_BITS_MAX
558 
559 config HAVE_EXIT_THREAD
560         bool
561         help
562           An architecture implements exit_thread.
563 
564 config ARCH_MMAP_RND_BITS_MIN
565         int
566 
567 config ARCH_MMAP_RND_BITS_MAX
568         int
569 
570 config ARCH_MMAP_RND_BITS_DEFAULT
571         int
572 
573 config ARCH_MMAP_RND_BITS
574         int "Number of bits to use for ASLR of mmap base address" if EXPERT
575         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
576         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
577         default ARCH_MMAP_RND_BITS_MIN
578         depends on HAVE_ARCH_MMAP_RND_BITS
579         help
580           This value can be used to select the number of bits to use to
581           determine the random offset to the base address of vma regions
582           resulting from mmap allocations. This value will be bounded
583           by the architecture's minimum and maximum supported values.
584 
585           This value can be changed after boot using the
586           /proc/sys/vm/mmap_rnd_bits tunable
587 
588 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
589         bool
590         help
591           An arch should select this symbol if it supports running applications
592           in compatibility mode, supports setting a variable number of bits for
593           use in establishing the base address for mmap allocations, has MMU
594           enabled and provides values for both:
595           - ARCH_MMAP_RND_COMPAT_BITS_MIN
596           - ARCH_MMAP_RND_COMPAT_BITS_MAX
597 
598 config ARCH_MMAP_RND_COMPAT_BITS_MIN
599         int
600 
601 config ARCH_MMAP_RND_COMPAT_BITS_MAX
602         int
603 
604 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
605         int
606 
607 config ARCH_MMAP_RND_COMPAT_BITS
608         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
609         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
610         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
611         default ARCH_MMAP_RND_COMPAT_BITS_MIN
612         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
613         help
614           This value can be used to select the number of bits to use to
615           determine the random offset to the base address of vma regions
616           resulting from mmap allocations for compatible applications This
617           value will be bounded by the architecture's minimum and maximum
618           supported values.
619 
620           This value can be changed after boot using the
621           /proc/sys/vm/mmap_rnd_compat_bits tunable
622 
623 config HAVE_COPY_THREAD_TLS
624         bool
625         help
626           Architecture provides copy_thread_tls to accept tls argument via
627           normal C parameter passing, rather than extracting the syscall
628           argument from pt_regs.
629 
630 config HAVE_STACK_VALIDATION
631         bool
632         help
633           Architecture supports the 'objtool check' host tool command, which
634           performs compile-time stack metadata validation.
635 
636 config HAVE_ARCH_HASH
637         bool
638         default n
639         help
640           If this is set, the architecture provides an <asm/hash.h>
641           file which provides platform-specific implementations of some
642           functions in <linux/hash.h> or fs/namei.c.
643 
644 config ISA_BUS_API
645         def_bool ISA
646 
647 #
648 # ABI hall of shame
649 #
650 config CLONE_BACKWARDS
651         bool
652         help
653           Architecture has tls passed as the 4th argument of clone(2),
654           not the 5th one.
655 
656 config CLONE_BACKWARDS2
657         bool
658         help
659           Architecture has the first two arguments of clone(2) swapped.
660 
661 config CLONE_BACKWARDS3
662         bool
663         help
664           Architecture has tls passed as the 3rd argument of clone(2),
665           not the 5th one.
666 
667 config ODD_RT_SIGACTION
668         bool
669         help
670           Architecture has unusual rt_sigaction(2) arguments
671 
672 config OLD_SIGSUSPEND
673         bool
674         help
675           Architecture has old sigsuspend(2) syscall, of one-argument variety
676 
677 config OLD_SIGSUSPEND3
678         bool
679         help
680           Even weirder antique ABI - three-argument sigsuspend(2)
681 
682 config OLD_SIGACTION
683         bool
684         help
685           Architecture has old sigaction(2) syscall.  Nope, not the same
686           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
687           but fairly different variant of sigaction(2), thanks to OSF/1
688           compatibility...
689 
690 config COMPAT_OLD_SIGACTION
691         bool
692 
693 config ARCH_NO_COHERENT_DMA_MMAP
694         bool
695 
696 config CPU_NO_EFFICIENT_FFS
697         def_bool n
698 
699 source "kernel/gcov/Kconfig"

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