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

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