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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 
325 config SECCOMP_FILTER
326         def_bool y
327         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
328         help
329           Enable tasks to build secure computing environments defined
330           in terms of Berkeley Packet Filter programs which implement
331           task-defined system call filtering polices.
332 
333           See Documentation/prctl/seccomp_filter.txt for details.
334 
335 config HAVE_CC_STACKPROTECTOR
336         bool
337         help
338           An arch should select this symbol if:
339           - its compiler supports the -fstack-protector option
340           - it has implemented a stack canary (e.g. __stack_chk_guard)
341 
342 config CC_STACKPROTECTOR
343         def_bool n
344         help
345           Set when a stack-protector mode is enabled, so that the build
346           can enable kernel-side support for the GCC feature.
347 
348 choice
349         prompt "Stack Protector buffer overflow detection"
350         depends on HAVE_CC_STACKPROTECTOR
351         default CC_STACKPROTECTOR_NONE
352         help
353           This option turns on the "stack-protector" GCC feature. This
354           feature puts, at the beginning of functions, a canary value on
355           the stack just before the return address, and validates
356           the value just before actually returning.  Stack based buffer
357           overflows (that need to overwrite this return address) now also
358           overwrite the canary, which gets detected and the attack is then
359           neutralized via a kernel panic.
360 
361 config CC_STACKPROTECTOR_NONE
362         bool "None"
363         help
364           Disable "stack-protector" GCC feature.
365 
366 config CC_STACKPROTECTOR_REGULAR
367         bool "Regular"
368         select CC_STACKPROTECTOR
369         help
370           Functions will have the stack-protector canary logic added if they
371           have an 8-byte or larger character array on the stack.
372 
373           This feature requires gcc version 4.2 or above, or a distribution
374           gcc with the feature backported ("-fstack-protector").
375 
376           On an x86 "defconfig" build, this feature adds canary checks to
377           about 3% of all kernel functions, which increases kernel code size
378           by about 0.3%.
379 
380 config CC_STACKPROTECTOR_STRONG
381         bool "Strong"
382         select CC_STACKPROTECTOR
383         help
384           Functions will have the stack-protector canary logic added in any
385           of the following conditions:
386 
387           - local variable's address used as part of the right hand side of an
388             assignment or function argument
389           - local variable is an array (or union containing an array),
390             regardless of array type or length
391           - uses register local variables
392 
393           This feature requires gcc version 4.9 or above, or a distribution
394           gcc with the feature backported ("-fstack-protector-strong").
395 
396           On an x86 "defconfig" build, this feature adds canary checks to
397           about 20% of all kernel functions, which increases the kernel code
398           size by about 2%.
399 
400 endchoice
401 
402 config HAVE_CONTEXT_TRACKING
403         bool
404         help
405           Provide kernel/user boundaries probes necessary for subsystems
406           that need it, such as userspace RCU extended quiescent state.
407           Syscalls need to be wrapped inside user_exit()-user_enter() through
408           the slow path using TIF_NOHZ flag. Exceptions handlers must be
409           wrapped as well. Irqs are already protected inside
410           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
411           irq exit still need to be protected.
412 
413 config HAVE_VIRT_CPU_ACCOUNTING
414         bool
415 
416 config HAVE_VIRT_CPU_ACCOUNTING_GEN
417         bool
418         default y if 64BIT
419         help
420           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
421           Before enabling this option, arch code must be audited
422           to ensure there are no races in concurrent read/write of
423           cputime_t. For example, reading/writing 64-bit cputime_t on
424           some 32-bit arches may require multiple accesses, so proper
425           locking is needed to protect against concurrent accesses.
426 
427 
428 config HAVE_IRQ_TIME_ACCOUNTING
429         bool
430         help
431           Archs need to ensure they use a high enough resolution clock to
432           support irq time accounting and then call enable_sched_clock_irqtime().
433 
434 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
435         bool
436 
437 config HAVE_ARCH_SOFT_DIRTY
438         bool
439 
440 config HAVE_MOD_ARCH_SPECIFIC
441         bool
442         help
443           The arch uses struct mod_arch_specific to store data.  Many arches
444           just need a simple module loader without arch specific data - those
445           should not enable this.
446 
447 config MODULES_USE_ELF_RELA
448         bool
449         help
450           Modules only use ELF RELA relocations.  Modules with ELF REL
451           relocations will give an error.
452 
453 config MODULES_USE_ELF_REL
454         bool
455         help
456           Modules only use ELF REL relocations.  Modules with ELF RELA
457           relocations will give an error.
458 
459 config HAVE_UNDERSCORE_SYMBOL_PREFIX
460         bool
461         help
462           Some architectures generate an _ in front of C symbols; things like
463           module loading and assembly files need to know about this.
464 
465 config HAVE_IRQ_EXIT_ON_IRQ_STACK
466         bool
467         help
468           Architecture doesn't only execute the irq handler on the irq stack
469           but also irq_exit(). This way we can process softirqs on this irq
470           stack instead of switching to a new one when we call __do_softirq()
471           in the end of an hardirq.
472           This spares a stack switch and improves cache usage on softirq
473           processing.
474 
475 #
476 # ABI hall of shame
477 #
478 config CLONE_BACKWARDS
479         bool
480         help
481           Architecture has tls passed as the 4th argument of clone(2),
482           not the 5th one.
483 
484 config CLONE_BACKWARDS2
485         bool
486         help
487           Architecture has the first two arguments of clone(2) swapped.
488 
489 config CLONE_BACKWARDS3
490         bool
491         help
492           Architecture has tls passed as the 3rd argument of clone(2),
493           not the 5th one.
494 
495 config ODD_RT_SIGACTION
496         bool
497         help
498           Architecture has unusual rt_sigaction(2) arguments
499 
500 config OLD_SIGSUSPEND
501         bool
502         help
503           Architecture has old sigsuspend(2) syscall, of one-argument variety
504 
505 config OLD_SIGSUSPEND3
506         bool
507         help
508           Even weirder antique ABI - three-argument sigsuspend(2)
509 
510 config OLD_SIGACTION
511         bool
512         help
513           Architecture has old sigaction(2) syscall.  Nope, not the same
514           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
515           but fairly different variant of sigaction(2), thanks to OSF/1
516           compatibility...
517 
518 config COMPAT_OLD_SIGACTION
519         bool
520 
521 source "kernel/gcov/Kconfig"

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