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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 && !PPC64
 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 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
225 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
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           - seccomp syscall wired up
329 
330           For best performance, an arch should use seccomp_phase1 and
331           seccomp_phase2 directly.  It should call seccomp_phase1 for all
332           syscalls if TIF_SECCOMP is set, but seccomp_phase1 does not
333           need to be called from a ptrace-safe context.  It must then
334           call seccomp_phase2 if seccomp_phase1 returns anything other
335           than SECCOMP_PHASE1_OK or SECCOMP_PHASE1_SKIP.
336 
337           As an additional optimization, an arch may provide seccomp_data
338           directly to seccomp_phase1; this avoids multiple calls
339           to the syscall_xyz helpers for every syscall.
340 
341 config SECCOMP_FILTER
342         def_bool y
343         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
344         help
345           Enable tasks to build secure computing environments defined
346           in terms of Berkeley Packet Filter programs which implement
347           task-defined system call filtering polices.
348 
349           See Documentation/prctl/seccomp_filter.txt for details.
350 
351 config HAVE_CC_STACKPROTECTOR
352         bool
353         help
354           An arch should select this symbol if:
355           - its compiler supports the -fstack-protector option
356           - it has implemented a stack canary (e.g. __stack_chk_guard)
357 
358 config CC_STACKPROTECTOR
359         def_bool n
360         help
361           Set when a stack-protector mode is enabled, so that the build
362           can enable kernel-side support for the GCC feature.
363 
364 choice
365         prompt "Stack Protector buffer overflow detection"
366         depends on HAVE_CC_STACKPROTECTOR
367         default CC_STACKPROTECTOR_NONE
368         help
369           This option turns on the "stack-protector" GCC feature. This
370           feature puts, at the beginning of functions, a canary value on
371           the stack just before the return address, and validates
372           the value just before actually returning.  Stack based buffer
373           overflows (that need to overwrite this return address) now also
374           overwrite the canary, which gets detected and the attack is then
375           neutralized via a kernel panic.
376 
377 config CC_STACKPROTECTOR_NONE
378         bool "None"
379         help
380           Disable "stack-protector" GCC feature.
381 
382 config CC_STACKPROTECTOR_REGULAR
383         bool "Regular"
384         select CC_STACKPROTECTOR
385         help
386           Functions will have the stack-protector canary logic added if they
387           have an 8-byte or larger character array on the stack.
388 
389           This feature requires gcc version 4.2 or above, or a distribution
390           gcc with the feature backported ("-fstack-protector").
391 
392           On an x86 "defconfig" build, this feature adds canary checks to
393           about 3% of all kernel functions, which increases kernel code size
394           by about 0.3%.
395 
396 config CC_STACKPROTECTOR_STRONG
397         bool "Strong"
398         select CC_STACKPROTECTOR
399         help
400           Functions will have the stack-protector canary logic added in any
401           of the following conditions:
402 
403           - local variable's address used as part of the right hand side of an
404             assignment or function argument
405           - local variable is an array (or union containing an array),
406             regardless of array type or length
407           - uses register local variables
408 
409           This feature requires gcc version 4.9 or above, or a distribution
410           gcc with the feature backported ("-fstack-protector-strong").
411 
412           On an x86 "defconfig" build, this feature adds canary checks to
413           about 20% of all kernel functions, which increases the kernel code
414           size by about 2%.
415 
416 endchoice
417 
418 config HAVE_CONTEXT_TRACKING
419         bool
420         help
421           Provide kernel/user boundaries probes necessary for subsystems
422           that need it, such as userspace RCU extended quiescent state.
423           Syscalls need to be wrapped inside user_exit()-user_enter() through
424           the slow path using TIF_NOHZ flag. Exceptions handlers must be
425           wrapped as well. Irqs are already protected inside
426           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
427           irq exit still need to be protected.
428 
429 config HAVE_VIRT_CPU_ACCOUNTING
430         bool
431 
432 config HAVE_VIRT_CPU_ACCOUNTING_GEN
433         bool
434         default y if 64BIT
435         help
436           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
437           Before enabling this option, arch code must be audited
438           to ensure there are no races in concurrent read/write of
439           cputime_t. For example, reading/writing 64-bit cputime_t on
440           some 32-bit arches may require multiple accesses, so proper
441           locking is needed to protect against concurrent accesses.
442 
443 
444 config HAVE_IRQ_TIME_ACCOUNTING
445         bool
446         help
447           Archs need to ensure they use a high enough resolution clock to
448           support irq time accounting and then call enable_sched_clock_irqtime().
449 
450 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
451         bool
452 
453 config HAVE_ARCH_HUGE_VMAP
454         bool
455 
456 config HAVE_ARCH_SOFT_DIRTY
457         bool
458 
459 config HAVE_MOD_ARCH_SPECIFIC
460         bool
461         help
462           The arch uses struct mod_arch_specific to store data.  Many arches
463           just need a simple module loader without arch specific data - those
464           should not enable this.
465 
466 config MODULES_USE_ELF_RELA
467         bool
468         help
469           Modules only use ELF RELA relocations.  Modules with ELF REL
470           relocations will give an error.
471 
472 config MODULES_USE_ELF_REL
473         bool
474         help
475           Modules only use ELF REL relocations.  Modules with ELF RELA
476           relocations will give an error.
477 
478 config HAVE_UNDERSCORE_SYMBOL_PREFIX
479         bool
480         help
481           Some architectures generate an _ in front of C symbols; things like
482           module loading and assembly files need to know about this.
483 
484 config HAVE_IRQ_EXIT_ON_IRQ_STACK
485         bool
486         help
487           Architecture doesn't only execute the irq handler on the irq stack
488           but also irq_exit(). This way we can process softirqs on this irq
489           stack instead of switching to a new one when we call __do_softirq()
490           in the end of an hardirq.
491           This spares a stack switch and improves cache usage on softirq
492           processing.
493 
494 config PGTABLE_LEVELS
495         int
496         default 2
497 
498 config ARCH_HAS_ELF_RANDOMIZE
499         bool
500         help
501           An architecture supports choosing randomized locations for
502           stack, mmap, brk, and ET_DYN. Defined functions:
503           - arch_mmap_rnd()
504           - arch_randomize_brk()
505 
506 config HAVE_COPY_THREAD_TLS
507         bool
508         help
509           Architecture provides copy_thread_tls to accept tls argument via
510           normal C parameter passing, rather than extracting the syscall
511           argument from pt_regs.
512 
513 #
514 # ABI hall of shame
515 #
516 config CLONE_BACKWARDS
517         bool
518         help
519           Architecture has tls passed as the 4th argument of clone(2),
520           not the 5th one.
521 
522 config CLONE_BACKWARDS2
523         bool
524         help
525           Architecture has the first two arguments of clone(2) swapped.
526 
527 config CLONE_BACKWARDS3
528         bool
529         help
530           Architecture has tls passed as the 3rd argument of clone(2),
531           not the 5th one.
532 
533 config ODD_RT_SIGACTION
534         bool
535         help
536           Architecture has unusual rt_sigaction(2) arguments
537 
538 config OLD_SIGSUSPEND
539         bool
540         help
541           Architecture has old sigsuspend(2) syscall, of one-argument variety
542 
543 config OLD_SIGSUSPEND3
544         bool
545         help
546           Even weirder antique ABI - three-argument sigsuspend(2)
547 
548 config OLD_SIGACTION
549         bool
550         help
551           Architecture has old sigaction(2) syscall.  Nope, not the same
552           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
553           but fairly different variant of sigaction(2), thanks to OSF/1
554           compatibility...
555 
556 config COMPAT_OLD_SIGACTION
557         bool
558 
559 source "kernel/gcov/Kconfig"

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