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Linux/arch/Kconfig

  1 #
  2 # General architecture dependent options
  3 #
  4 
  5 config OPROFILE
  6         tristate "OProfile system profiling"
  7         depends on PROFILING
  8         depends on HAVE_OPROFILE
  9         select RING_BUFFER
 10         select RING_BUFFER_ALLOW_SWAP
 11         help
 12           OProfile is a profiling system capable of profiling the
 13           whole system, include the kernel, kernel modules, libraries,
 14           and applications.
 15 
 16           If unsure, say N.
 17 
 18 config OPROFILE_EVENT_MULTIPLEX
 19         bool "OProfile multiplexing support (EXPERIMENTAL)"
 20         default n
 21         depends on OPROFILE && X86
 22         help
 23           The number of hardware counters is limited. The multiplexing
 24           feature enables OProfile to gather more events than counters
 25           are provided by the hardware. This is realized by switching
 26           between events at an user specified time interval.
 27 
 28           If unsure, say N.
 29 
 30 config HAVE_OPROFILE
 31         bool
 32 
 33 config OPROFILE_NMI_TIMER
 34         def_bool y
 35         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
 36 
 37 config KPROBES
 38         bool "Kprobes"
 39         depends on MODULES
 40         depends on HAVE_KPROBES
 41         select KALLSYMS
 42         help
 43           Kprobes allows you to trap at almost any kernel address and
 44           execute a callback function.  register_kprobe() establishes
 45           a probepoint and specifies the callback.  Kprobes is useful
 46           for kernel debugging, non-intrusive instrumentation and testing.
 47           If in doubt, say "N".
 48 
 49 config JUMP_LABEL
 50        bool "Optimize very unlikely/likely branches"
 51        depends on HAVE_ARCH_JUMP_LABEL
 52        help
 53          This option enables a transparent branch optimization that
 54          makes certain almost-always-true or almost-always-false branch
 55          conditions even cheaper to execute within the kernel.
 56 
 57          Certain performance-sensitive kernel code, such as trace points,
 58          scheduler functionality, networking code and KVM have such
 59          branches and include support for this optimization technique.
 60 
 61          If it is detected that the compiler has support for "asm goto",
 62          the kernel will compile such branches with just a nop
 63          instruction. When the condition flag is toggled to true, the
 64          nop will be converted to a jump instruction to execute the
 65          conditional block of instructions.
 66 
 67          This technique lowers overhead and stress on the branch prediction
 68          of the processor and generally makes the kernel faster. The update
 69          of the condition is slower, but those are always very rare.
 70 
 71          ( On 32-bit x86, the necessary options added to the compiler
 72            flags may increase the size of the kernel slightly. )
 73 
 74 config OPTPROBES
 75         def_bool y
 76         depends on KPROBES && HAVE_OPTPROBES
 77         depends on !PREEMPT
 78 
 79 config KPROBES_ON_FTRACE
 80         def_bool y
 81         depends on KPROBES && HAVE_KPROBES_ON_FTRACE
 82         depends on DYNAMIC_FTRACE_WITH_REGS
 83         help
 84          If function tracer is enabled and the arch supports full
 85          passing of pt_regs to function tracing, then kprobes can
 86          optimize on top of function tracing.
 87 
 88 config UPROBES
 89         def_bool n
 90         select PERCPU_RWSEM
 91         help
 92           Uprobes is the user-space counterpart to kprobes: they
 93           enable instrumentation applications (such as 'perf probe')
 94           to establish unintrusive probes in user-space binaries and
 95           libraries, by executing handler functions when the probes
 96           are hit by user-space applications.
 97 
 98           ( These probes come in the form of single-byte breakpoints,
 99             managed by the kernel and kept transparent to the probed
100             application. )
101 
102 config HAVE_64BIT_ALIGNED_ACCESS
103         def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
104         help
105           Some architectures require 64 bit accesses to be 64 bit
106           aligned, which also requires structs containing 64 bit values
107           to be 64 bit aligned too. This includes some 32 bit
108           architectures which can do 64 bit accesses, as well as 64 bit
109           architectures without unaligned access.
110 
111           This symbol should be selected by an architecture if 64 bit
112           accesses are required to be 64 bit aligned in this way even
113           though it is not a 64 bit architecture.
114 
115           See Documentation/unaligned-memory-access.txt for more
116           information on the topic of unaligned memory accesses.
117 
118 config HAVE_EFFICIENT_UNALIGNED_ACCESS
119         bool
120         help
121           Some architectures are unable to perform unaligned accesses
122           without the use of get_unaligned/put_unaligned. Others are
123           unable to perform such accesses efficiently (e.g. trap on
124           unaligned access and require fixing it up in the exception
125           handler.)
126 
127           This symbol should be selected by an architecture if it can
128           perform unaligned accesses efficiently to allow different
129           code paths to be selected for these cases. Some network
130           drivers, for example, could opt to not fix up alignment
131           problems with received packets if doing so would not help
132           much.
133 
134           See Documentation/unaligned-memory-access.txt for more
135           information on the topic of unaligned memory accesses.
136 
137 config ARCH_USE_BUILTIN_BSWAP
138        bool
139        help
140          Modern versions of GCC (since 4.4) have builtin functions
141          for handling byte-swapping. Using these, instead of the old
142          inline assembler that the architecture code provides in the
143          __arch_bswapXX() macros, allows the compiler to see what's
144          happening and offers more opportunity for optimisation. In
145          particular, the compiler will be able to combine the byteswap
146          with a nearby load or store and use load-and-swap or
147          store-and-swap instructions if the architecture has them. It
148          should almost *never* result in code which is worse than the
149          hand-coded assembler in <asm/swab.h>.  But just in case it
150          does, the use of the builtins is optional.
151 
152          Any architecture with load-and-swap or store-and-swap
153          instructions should set this. And it shouldn't hurt to set it
154          on architectures that don't have such instructions.
155 
156 config KRETPROBES
157         def_bool y
158         depends on KPROBES && HAVE_KRETPROBES
159 
160 config USER_RETURN_NOTIFIER
161         bool
162         depends on HAVE_USER_RETURN_NOTIFIER
163         help
164           Provide a kernel-internal notification when a cpu is about to
165           switch to user mode.
166 
167 config HAVE_IOREMAP_PROT
168         bool
169 
170 config HAVE_KPROBES
171         bool
172 
173 config HAVE_KRETPROBES
174         bool
175 
176 config HAVE_OPTPROBES
177         bool
178 
179 config HAVE_KPROBES_ON_FTRACE
180         bool
181 
182 config HAVE_NMI_WATCHDOG
183         bool
184 #
185 # An arch should select this if it provides all these things:
186 #
187 #       task_pt_regs()          in asm/processor.h or asm/ptrace.h
188 #       arch_has_single_step()  if there is hardware single-step support
189 #       arch_has_block_step()   if there is hardware block-step support
190 #       asm/syscall.h           supplying asm-generic/syscall.h interface
191 #       linux/regset.h          user_regset interfaces
192 #       CORE_DUMP_USE_REGSET    #define'd in linux/elf.h
193 #       TIF_SYSCALL_TRACE       calls tracehook_report_syscall_{entry,exit}
194 #       TIF_NOTIFY_RESUME       calls tracehook_notify_resume()
195 #       signal delivery         calls tracehook_signal_handler()
196 #
197 config HAVE_ARCH_TRACEHOOK
198         bool
199 
200 config HAVE_DMA_ATTRS
201         bool
202 
203 config HAVE_DMA_CONTIGUOUS
204         bool
205 
206 config GENERIC_SMP_IDLE_THREAD
207        bool
208 
209 config GENERIC_IDLE_POLL_SETUP
210        bool
211 
212 # Select if arch init_task initializer is different to init/init_task.c
213 config ARCH_INIT_TASK
214        bool
215 
216 # Select if arch has its private alloc_task_struct() function
217 config ARCH_TASK_STRUCT_ALLOCATOR
218         bool
219 
220 # Select if arch has its private alloc_thread_info() function
221 config ARCH_THREAD_INFO_ALLOCATOR
222         bool
223 
224 config HAVE_REGS_AND_STACK_ACCESS_API
225         bool
226         help
227           This symbol should be selected by an architecure if it supports
228           the API needed to access registers and stack entries from pt_regs,
229           declared in asm/ptrace.h
230           For example the kprobes-based event tracer needs this API.
231 
232 config HAVE_CLK
233         bool
234         help
235           The <linux/clk.h> calls support software clock gating and
236           thus are a key power management tool on many systems.
237 
238 config HAVE_DMA_API_DEBUG
239         bool
240 
241 config HAVE_HW_BREAKPOINT
242         bool
243         depends on PERF_EVENTS
244 
245 config HAVE_MIXED_BREAKPOINTS_REGS
246         bool
247         depends on HAVE_HW_BREAKPOINT
248         help
249           Depending on the arch implementation of hardware breakpoints,
250           some of them have separate registers for data and instruction
251           breakpoints addresses, others have mixed registers to store
252           them but define the access type in a control register.
253           Select this option if your arch implements breakpoints under the
254           latter fashion.
255 
256 config HAVE_USER_RETURN_NOTIFIER
257         bool
258 
259 config HAVE_PERF_EVENTS_NMI
260         bool
261         help
262           System hardware can generate an NMI using the perf event
263           subsystem.  Also has support for calculating CPU cycle events
264           to determine how many clock cycles in a given period.
265 
266 config HAVE_PERF_REGS
267         bool
268         help
269           Support selective register dumps for perf events. This includes
270           bit-mapping of each registers and a unique architecture id.
271 
272 config HAVE_PERF_USER_STACK_DUMP
273         bool
274         help
275           Support user stack dumps for perf event samples. This needs
276           access to the user stack pointer which is not unified across
277           architectures.
278 
279 config HAVE_ARCH_JUMP_LABEL
280         bool
281 
282 config HAVE_RCU_TABLE_FREE
283         bool
284 
285 config ARCH_HAVE_NMI_SAFE_CMPXCHG
286         bool
287 
288 config HAVE_ALIGNED_STRUCT_PAGE
289         bool
290         help
291           This makes sure that struct pages are double word aligned and that
292           e.g. the SLUB allocator can perform double word atomic operations
293           on a struct page for better performance. However selecting this
294           might increase the size of a struct page by a word.
295 
296 config HAVE_CMPXCHG_LOCAL
297         bool
298 
299 config HAVE_CMPXCHG_DOUBLE
300         bool
301 
302 config ARCH_WANT_IPC_PARSE_VERSION
303         bool
304 
305 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
306         bool
307 
308 config ARCH_WANT_OLD_COMPAT_IPC
309         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
310         bool
311 
312 config HAVE_ARCH_SECCOMP_FILTER
313         bool
314         help
315           An arch should select this symbol if it provides all of these things:
316           - syscall_get_arch()
317           - syscall_get_arguments()
318           - syscall_rollback()
319           - syscall_set_return_value()
320           - SIGSYS siginfo_t support
321           - secure_computing is called from a ptrace_event()-safe context
322           - secure_computing return value is checked and a return value of -1
323             results in the system call being skipped immediately.
324           - seccomp syscall wired up
325 
326           For best performance, an arch should use seccomp_phase1 and
327           seccomp_phase2 directly.  It should call seccomp_phase1 for all
328           syscalls if TIF_SECCOMP is set, but seccomp_phase1 does not
329           need to be called from a ptrace-safe context.  It must then
330           call seccomp_phase2 if seccomp_phase1 returns anything other
331           than SECCOMP_PHASE1_OK or SECCOMP_PHASE1_SKIP.
332 
333           As an additional optimization, an arch may provide seccomp_data
334           directly to seccomp_phase1; this avoids multiple calls
335           to the syscall_xyz helpers for every syscall.
336 
337 config SECCOMP_FILTER
338         def_bool y
339         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
340         help
341           Enable tasks to build secure computing environments defined
342           in terms of Berkeley Packet Filter programs which implement
343           task-defined system call filtering polices.
344 
345           See Documentation/prctl/seccomp_filter.txt for details.
346 
347 config HAVE_CC_STACKPROTECTOR
348         bool
349         help
350           An arch should select this symbol if:
351           - its compiler supports the -fstack-protector option
352           - it has implemented a stack canary (e.g. __stack_chk_guard)
353 
354 config CC_STACKPROTECTOR
355         def_bool n
356         help
357           Set when a stack-protector mode is enabled, so that the build
358           can enable kernel-side support for the GCC feature.
359 
360 choice
361         prompt "Stack Protector buffer overflow detection"
362         depends on HAVE_CC_STACKPROTECTOR
363         default CC_STACKPROTECTOR_NONE
364         help
365           This option turns on the "stack-protector" GCC feature. This
366           feature puts, at the beginning of functions, a canary value on
367           the stack just before the return address, and validates
368           the value just before actually returning.  Stack based buffer
369           overflows (that need to overwrite this return address) now also
370           overwrite the canary, which gets detected and the attack is then
371           neutralized via a kernel panic.
372 
373 config CC_STACKPROTECTOR_NONE
374         bool "None"
375         help
376           Disable "stack-protector" GCC feature.
377 
378 config CC_STACKPROTECTOR_REGULAR
379         bool "Regular"
380         select CC_STACKPROTECTOR
381         help
382           Functions will have the stack-protector canary logic added if they
383           have an 8-byte or larger character array on the stack.
384 
385           This feature requires gcc version 4.2 or above, or a distribution
386           gcc with the feature backported ("-fstack-protector").
387 
388           On an x86 "defconfig" build, this feature adds canary checks to
389           about 3% of all kernel functions, which increases kernel code size
390           by about 0.3%.
391 
392 config CC_STACKPROTECTOR_STRONG
393         bool "Strong"
394         select CC_STACKPROTECTOR
395         help
396           Functions will have the stack-protector canary logic added in any
397           of the following conditions:
398 
399           - local variable's address used as part of the right hand side of an
400             assignment or function argument
401           - local variable is an array (or union containing an array),
402             regardless of array type or length
403           - uses register local variables
404 
405           This feature requires gcc version 4.9 or above, or a distribution
406           gcc with the feature backported ("-fstack-protector-strong").
407 
408           On an x86 "defconfig" build, this feature adds canary checks to
409           about 20% of all kernel functions, which increases the kernel code
410           size by about 2%.
411 
412 endchoice
413 
414 config HAVE_CONTEXT_TRACKING
415         bool
416         help
417           Provide kernel/user boundaries probes necessary for subsystems
418           that need it, such as userspace RCU extended quiescent state.
419           Syscalls need to be wrapped inside user_exit()-user_enter() through
420           the slow path using TIF_NOHZ flag. Exceptions handlers must be
421           wrapped as well. Irqs are already protected inside
422           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
423           irq exit still need to be protected.
424 
425 config HAVE_VIRT_CPU_ACCOUNTING
426         bool
427 
428 config HAVE_VIRT_CPU_ACCOUNTING_GEN
429         bool
430         default y if 64BIT
431         help
432           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
433           Before enabling this option, arch code must be audited
434           to ensure there are no races in concurrent read/write of
435           cputime_t. For example, reading/writing 64-bit cputime_t on
436           some 32-bit arches may require multiple accesses, so proper
437           locking is needed to protect against concurrent accesses.
438 
439 
440 config HAVE_IRQ_TIME_ACCOUNTING
441         bool
442         help
443           Archs need to ensure they use a high enough resolution clock to
444           support irq time accounting and then call enable_sched_clock_irqtime().
445 
446 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
447         bool
448 
449 config HAVE_ARCH_SOFT_DIRTY
450         bool
451 
452 config HAVE_MOD_ARCH_SPECIFIC
453         bool
454         help
455           The arch uses struct mod_arch_specific to store data.  Many arches
456           just need a simple module loader without arch specific data - those
457           should not enable this.
458 
459 config MODULES_USE_ELF_RELA
460         bool
461         help
462           Modules only use ELF RELA relocations.  Modules with ELF REL
463           relocations will give an error.
464 
465 config MODULES_USE_ELF_REL
466         bool
467         help
468           Modules only use ELF REL relocations.  Modules with ELF RELA
469           relocations will give an error.
470 
471 config HAVE_UNDERSCORE_SYMBOL_PREFIX
472         bool
473         help
474           Some architectures generate an _ in front of C symbols; things like
475           module loading and assembly files need to know about this.
476 
477 config HAVE_IRQ_EXIT_ON_IRQ_STACK
478         bool
479         help
480           Architecture doesn't only execute the irq handler on the irq stack
481           but also irq_exit(). This way we can process softirqs on this irq
482           stack instead of switching to a new one when we call __do_softirq()
483           in the end of an hardirq.
484           This spares a stack switch and improves cache usage on softirq
485           processing.
486 
487 #
488 # ABI hall of shame
489 #
490 config CLONE_BACKWARDS
491         bool
492         help
493           Architecture has tls passed as the 4th argument of clone(2),
494           not the 5th one.
495 
496 config CLONE_BACKWARDS2
497         bool
498         help
499           Architecture has the first two arguments of clone(2) swapped.
500 
501 config CLONE_BACKWARDS3
502         bool
503         help
504           Architecture has tls passed as the 3rd argument of clone(2),
505           not the 5th one.
506 
507 config ODD_RT_SIGACTION
508         bool
509         help
510           Architecture has unusual rt_sigaction(2) arguments
511 
512 config OLD_SIGSUSPEND
513         bool
514         help
515           Architecture has old sigsuspend(2) syscall, of one-argument variety
516 
517 config OLD_SIGSUSPEND3
518         bool
519         help
520           Even weirder antique ABI - three-argument sigsuspend(2)
521 
522 config OLD_SIGACTION
523         bool
524         help
525           Architecture has old sigaction(2) syscall.  Nope, not the same
526           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
527           but fairly different variant of sigaction(2), thanks to OSF/1
528           compatibility...
529 
530 config COMPAT_OLD_SIGACTION
531         bool
532 
533 source "kernel/gcov/Kconfig"

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