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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_WATCHDOG
191         bool
192 #
193 # An arch should select this if it provides all these things:
194 #
195 #       task_pt_regs()          in asm/processor.h or asm/ptrace.h
196 #       arch_has_single_step()  if there is hardware single-step support
197 #       arch_has_block_step()   if there is hardware block-step support
198 #       asm/syscall.h           supplying asm-generic/syscall.h interface
199 #       linux/regset.h          user_regset interfaces
200 #       CORE_DUMP_USE_REGSET    #define'd in linux/elf.h
201 #       TIF_SYSCALL_TRACE       calls tracehook_report_syscall_{entry,exit}
202 #       TIF_NOTIFY_RESUME       calls tracehook_notify_resume()
203 #       signal delivery         calls tracehook_signal_handler()
204 #
205 config HAVE_ARCH_TRACEHOOK
206         bool
207 
208 config HAVE_DMA_ATTRS
209         bool
210 
211 config HAVE_DMA_CONTIGUOUS
212         bool
213 
214 config GENERIC_SMP_IDLE_THREAD
215        bool
216 
217 config GENERIC_IDLE_POLL_SETUP
218        bool
219 
220 # Select if arch init_task initializer is different to init/init_task.c
221 config ARCH_INIT_TASK
222        bool
223 
224 # Select if arch has its private alloc_task_struct() function
225 config ARCH_TASK_STRUCT_ALLOCATOR
226         bool
227 
228 # Select if arch has its private alloc_thread_info() function
229 config ARCH_THREAD_INFO_ALLOCATOR
230         bool
231 
232 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
233 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
234         bool
235 
236 config HAVE_REGS_AND_STACK_ACCESS_API
237         bool
238         help
239           This symbol should be selected by an architecure if it supports
240           the API needed to access registers and stack entries from pt_regs,
241           declared in asm/ptrace.h
242           For example the kprobes-based event tracer needs this API.
243 
244 config HAVE_CLK
245         bool
246         help
247           The <linux/clk.h> calls support software clock gating and
248           thus are a key power management tool on many systems.
249 
250 config HAVE_DMA_API_DEBUG
251         bool
252 
253 config HAVE_HW_BREAKPOINT
254         bool
255         depends on PERF_EVENTS
256 
257 config HAVE_MIXED_BREAKPOINTS_REGS
258         bool
259         depends on HAVE_HW_BREAKPOINT
260         help
261           Depending on the arch implementation of hardware breakpoints,
262           some of them have separate registers for data and instruction
263           breakpoints addresses, others have mixed registers to store
264           them but define the access type in a control register.
265           Select this option if your arch implements breakpoints under the
266           latter fashion.
267 
268 config HAVE_USER_RETURN_NOTIFIER
269         bool
270 
271 config HAVE_PERF_EVENTS_NMI
272         bool
273         help
274           System hardware can generate an NMI using the perf event
275           subsystem.  Also has support for calculating CPU cycle events
276           to determine how many clock cycles in a given period.
277 
278 config HAVE_PERF_REGS
279         bool
280         help
281           Support selective register dumps for perf events. This includes
282           bit-mapping of each registers and a unique architecture id.
283 
284 config HAVE_PERF_USER_STACK_DUMP
285         bool
286         help
287           Support user stack dumps for perf event samples. This needs
288           access to the user stack pointer which is not unified across
289           architectures.
290 
291 config HAVE_ARCH_JUMP_LABEL
292         bool
293 
294 config HAVE_RCU_TABLE_FREE
295         bool
296 
297 config ARCH_HAVE_NMI_SAFE_CMPXCHG
298         bool
299 
300 config HAVE_ALIGNED_STRUCT_PAGE
301         bool
302         help
303           This makes sure that struct pages are double word aligned and that
304           e.g. the SLUB allocator can perform double word atomic operations
305           on a struct page for better performance. However selecting this
306           might increase the size of a struct page by a word.
307 
308 config HAVE_CMPXCHG_LOCAL
309         bool
310 
311 config HAVE_CMPXCHG_DOUBLE
312         bool
313 
314 config ARCH_WANT_IPC_PARSE_VERSION
315         bool
316 
317 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
318         bool
319 
320 config ARCH_WANT_OLD_COMPAT_IPC
321         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
322         bool
323 
324 config HAVE_ARCH_SECCOMP_FILTER
325         bool
326         help
327           An arch should select this symbol if it provides all of these things:
328           - syscall_get_arch()
329           - syscall_get_arguments()
330           - syscall_rollback()
331           - syscall_set_return_value()
332           - SIGSYS siginfo_t support
333           - secure_computing is called from a ptrace_event()-safe context
334           - secure_computing return value is checked and a return value of -1
335             results in the system call being skipped immediately.
336           - seccomp syscall wired up
337 
338           For best performance, an arch should use seccomp_phase1 and
339           seccomp_phase2 directly.  It should call seccomp_phase1 for all
340           syscalls if TIF_SECCOMP is set, but seccomp_phase1 does not
341           need to be called from a ptrace-safe context.  It must then
342           call seccomp_phase2 if seccomp_phase1 returns anything other
343           than SECCOMP_PHASE1_OK or SECCOMP_PHASE1_SKIP.
344 
345           As an additional optimization, an arch may provide seccomp_data
346           directly to seccomp_phase1; this avoids multiple calls
347           to the syscall_xyz helpers for every syscall.
348 
349 config SECCOMP_FILTER
350         def_bool y
351         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
352         help
353           Enable tasks to build secure computing environments defined
354           in terms of Berkeley Packet Filter programs which implement
355           task-defined system call filtering polices.
356 
357           See Documentation/prctl/seccomp_filter.txt for details.
358 
359 config HAVE_CC_STACKPROTECTOR
360         bool
361         help
362           An arch should select this symbol if:
363           - its compiler supports the -fstack-protector option
364           - it has implemented a stack canary (e.g. __stack_chk_guard)
365 
366 config CC_STACKPROTECTOR
367         def_bool n
368         help
369           Set when a stack-protector mode is enabled, so that the build
370           can enable kernel-side support for the GCC feature.
371 
372 choice
373         prompt "Stack Protector buffer overflow detection"
374         depends on HAVE_CC_STACKPROTECTOR
375         default CC_STACKPROTECTOR_NONE
376         help
377           This option turns on the "stack-protector" GCC feature. This
378           feature puts, at the beginning of functions, a canary value on
379           the stack just before the return address, and validates
380           the value just before actually returning.  Stack based buffer
381           overflows (that need to overwrite this return address) now also
382           overwrite the canary, which gets detected and the attack is then
383           neutralized via a kernel panic.
384 
385 config CC_STACKPROTECTOR_NONE
386         bool "None"
387         help
388           Disable "stack-protector" GCC feature.
389 
390 config CC_STACKPROTECTOR_REGULAR
391         bool "Regular"
392         select CC_STACKPROTECTOR
393         help
394           Functions will have the stack-protector canary logic added if they
395           have an 8-byte or larger character array on the stack.
396 
397           This feature requires gcc version 4.2 or above, or a distribution
398           gcc with the feature backported ("-fstack-protector").
399 
400           On an x86 "defconfig" build, this feature adds canary checks to
401           about 3% of all kernel functions, which increases kernel code size
402           by about 0.3%.
403 
404 config CC_STACKPROTECTOR_STRONG
405         bool "Strong"
406         select CC_STACKPROTECTOR
407         help
408           Functions will have the stack-protector canary logic added in any
409           of the following conditions:
410 
411           - local variable's address used as part of the right hand side of an
412             assignment or function argument
413           - local variable is an array (or union containing an array),
414             regardless of array type or length
415           - uses register local variables
416 
417           This feature requires gcc version 4.9 or above, or a distribution
418           gcc with the feature backported ("-fstack-protector-strong").
419 
420           On an x86 "defconfig" build, this feature adds canary checks to
421           about 20% of all kernel functions, which increases the kernel code
422           size by about 2%.
423 
424 endchoice
425 
426 config HAVE_CONTEXT_TRACKING
427         bool
428         help
429           Provide kernel/user boundaries probes necessary for subsystems
430           that need it, such as userspace RCU extended quiescent state.
431           Syscalls need to be wrapped inside user_exit()-user_enter() through
432           the slow path using TIF_NOHZ flag. Exceptions handlers must be
433           wrapped as well. Irqs are already protected inside
434           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
435           irq exit still need to be protected.
436 
437 config HAVE_VIRT_CPU_ACCOUNTING
438         bool
439 
440 config HAVE_VIRT_CPU_ACCOUNTING_GEN
441         bool
442         default y if 64BIT
443         help
444           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
445           Before enabling this option, arch code must be audited
446           to ensure there are no races in concurrent read/write of
447           cputime_t. For example, reading/writing 64-bit cputime_t on
448           some 32-bit arches may require multiple accesses, so proper
449           locking is needed to protect against concurrent accesses.
450 
451 
452 config HAVE_IRQ_TIME_ACCOUNTING
453         bool
454         help
455           Archs need to ensure they use a high enough resolution clock to
456           support irq time accounting and then call enable_sched_clock_irqtime().
457 
458 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
459         bool
460 
461 config HAVE_ARCH_HUGE_VMAP
462         bool
463 
464 config HAVE_ARCH_SOFT_DIRTY
465         bool
466 
467 config HAVE_MOD_ARCH_SPECIFIC
468         bool
469         help
470           The arch uses struct mod_arch_specific to store data.  Many arches
471           just need a simple module loader without arch specific data - those
472           should not enable this.
473 
474 config MODULES_USE_ELF_RELA
475         bool
476         help
477           Modules only use ELF RELA relocations.  Modules with ELF REL
478           relocations will give an error.
479 
480 config MODULES_USE_ELF_REL
481         bool
482         help
483           Modules only use ELF REL relocations.  Modules with ELF RELA
484           relocations will give an error.
485 
486 config HAVE_UNDERSCORE_SYMBOL_PREFIX
487         bool
488         help
489           Some architectures generate an _ in front of C symbols; things like
490           module loading and assembly files need to know about this.
491 
492 config HAVE_IRQ_EXIT_ON_IRQ_STACK
493         bool
494         help
495           Architecture doesn't only execute the irq handler on the irq stack
496           but also irq_exit(). This way we can process softirqs on this irq
497           stack instead of switching to a new one when we call __do_softirq()
498           in the end of an hardirq.
499           This spares a stack switch and improves cache usage on softirq
500           processing.
501 
502 config PGTABLE_LEVELS
503         int
504         default 2
505 
506 config ARCH_HAS_ELF_RANDOMIZE
507         bool
508         help
509           An architecture supports choosing randomized locations for
510           stack, mmap, brk, and ET_DYN. Defined functions:
511           - arch_mmap_rnd()
512           - arch_randomize_brk()
513 
514 config HAVE_COPY_THREAD_TLS
515         bool
516         help
517           Architecture provides copy_thread_tls to accept tls argument via
518           normal C parameter passing, rather than extracting the syscall
519           argument from pt_regs.
520 
521 #
522 # ABI hall of shame
523 #
524 config CLONE_BACKWARDS
525         bool
526         help
527           Architecture has tls passed as the 4th argument of clone(2),
528           not the 5th one.
529 
530 config CLONE_BACKWARDS2
531         bool
532         help
533           Architecture has the first two arguments of clone(2) swapped.
534 
535 config CLONE_BACKWARDS3
536         bool
537         help
538           Architecture has tls passed as the 3rd argument of clone(2),
539           not the 5th one.
540 
541 config ODD_RT_SIGACTION
542         bool
543         help
544           Architecture has unusual rt_sigaction(2) arguments
545 
546 config OLD_SIGSUSPEND
547         bool
548         help
549           Architecture has old sigsuspend(2) syscall, of one-argument variety
550 
551 config OLD_SIGSUSPEND3
552         bool
553         help
554           Even weirder antique ABI - three-argument sigsuspend(2)
555 
556 config OLD_SIGACTION
557         bool
558         help
559           Architecture has old sigaction(2) syscall.  Nope, not the same
560           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
561           but fairly different variant of sigaction(2), thanks to OSF/1
562           compatibility...
563 
564 config COMPAT_OLD_SIGACTION
565         bool
566 
567 source "kernel/gcov/Kconfig"

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