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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
191 bool
192
193 config HAVE_NMI_WATCHDOG
194 depends on HAVE_NMI
195 bool
196 #
197 # An arch should select this if it provides all these things:
198 #
199 # task_pt_regs() in asm/processor.h or asm/ptrace.h
200 # arch_has_single_step() if there is hardware single-step support
201 # arch_has_block_step() if there is hardware block-step support
202 # asm/syscall.h supplying asm-generic/syscall.h interface
203 # linux/regset.h user_regset interfaces
204 # CORE_DUMP_USE_REGSET #define'd in linux/elf.h
205 # TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit}
206 # TIF_NOTIFY_RESUME calls tracehook_notify_resume()
207 # signal delivery calls tracehook_signal_handler()
208 #
209 config HAVE_ARCH_TRACEHOOK
210 bool
211
212 config HAVE_DMA_CONTIGUOUS
213 bool
214
215 config GENERIC_SMP_IDLE_THREAD
216 bool
217
218 config GENERIC_IDLE_POLL_SETUP
219 bool
220
221 # Select if arch init_task initializer is different to init/init_task.c
222 config ARCH_INIT_TASK
223 bool
224
225 # Select if arch has its private alloc_task_struct() function
226 config ARCH_TASK_STRUCT_ALLOCATOR
227 bool
228
229 # Select if arch has its private alloc_thread_stack() function
230 config ARCH_THREAD_STACK_ALLOCATOR
231 bool
232
233 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
234 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
235 bool
236
237 config HAVE_REGS_AND_STACK_ACCESS_API
238 bool
239 help
240 This symbol should be selected by an architecure if it supports
241 the API needed to access registers and stack entries from pt_regs,
242 declared in asm/ptrace.h
243 For example the kprobes-based event tracer needs this API.
244
245 config HAVE_CLK
246 bool
247 help
248 The <linux/clk.h> calls support software clock gating and
249 thus are a key power management tool on many systems.
250
251 config HAVE_DMA_API_DEBUG
252 bool
253
254 config HAVE_HW_BREAKPOINT
255 bool
256 depends on PERF_EVENTS
257
258 config HAVE_MIXED_BREAKPOINTS_REGS
259 bool
260 depends on HAVE_HW_BREAKPOINT
261 help
262 Depending on the arch implementation of hardware breakpoints,
263 some of them have separate registers for data and instruction
264 breakpoints addresses, others have mixed registers to store
265 them but define the access type in a control register.
266 Select this option if your arch implements breakpoints under the
267 latter fashion.
268
269 config HAVE_USER_RETURN_NOTIFIER
270 bool
271
272 config HAVE_PERF_EVENTS_NMI
273 bool
274 help
275 System hardware can generate an NMI using the perf event
276 subsystem. Also has support for calculating CPU cycle events
277 to determine how many clock cycles in a given period.
278
279 config HAVE_PERF_REGS
280 bool
281 help
282 Support selective register dumps for perf events. This includes
283 bit-mapping of each registers and a unique architecture id.
284
285 config HAVE_PERF_USER_STACK_DUMP
286 bool
287 help
288 Support user stack dumps for perf event samples. This needs
289 access to the user stack pointer which is not unified across
290 architectures.
291
292 config HAVE_ARCH_JUMP_LABEL
293 bool
294
295 config HAVE_RCU_TABLE_FREE
296 bool
297
298 config ARCH_HAVE_NMI_SAFE_CMPXCHG
299 bool
300
301 config HAVE_ALIGNED_STRUCT_PAGE
302 bool
303 help
304 This makes sure that struct pages are double word aligned and that
305 e.g. the SLUB allocator can perform double word atomic operations
306 on a struct page for better performance. However selecting this
307 might increase the size of a struct page by a word.
308
309 config HAVE_CMPXCHG_LOCAL
310 bool
311
312 config HAVE_CMPXCHG_DOUBLE
313 bool
314
315 config ARCH_WANT_IPC_PARSE_VERSION
316 bool
317
318 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
319 bool
320
321 config ARCH_WANT_OLD_COMPAT_IPC
322 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
323 bool
324
325 config HAVE_ARCH_SECCOMP_FILTER
326 bool
327 help
328 An arch should select this symbol if it provides all of these things:
329 - syscall_get_arch()
330 - syscall_get_arguments()
331 - syscall_rollback()
332 - syscall_set_return_value()
333 - SIGSYS siginfo_t support
334 - secure_computing is called from a ptrace_event()-safe context
335 - secure_computing return value is checked and a return value of -1
336 results in the system call being skipped immediately.
337 - seccomp syscall wired up
338
339 For best performance, an arch should use seccomp_phase1 and
340 seccomp_phase2 directly. It should call seccomp_phase1 for all
341 syscalls if TIF_SECCOMP is set, but seccomp_phase1 does not
342 need to be called from a ptrace-safe context. It must then
343 call seccomp_phase2 if seccomp_phase1 returns anything other
344 than SECCOMP_PHASE1_OK or SECCOMP_PHASE1_SKIP.
345
346 As an additional optimization, an arch may provide seccomp_data
347 directly to seccomp_phase1; this avoids multiple calls
348 to the syscall_xyz helpers for every syscall.
349
350 config SECCOMP_FILTER
351 def_bool y
352 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
353 help
354 Enable tasks to build secure computing environments defined
355 in terms of Berkeley Packet Filter programs which implement
356 task-defined system call filtering polices.
357
358 See Documentation/prctl/seccomp_filter.txt for details.
359
360 config HAVE_GCC_PLUGINS
361 bool
362 help
363 An arch should select this symbol if it supports building with
364 GCC plugins.
365
366 menuconfig GCC_PLUGINS
367 bool "GCC plugins"
368 depends on HAVE_GCC_PLUGINS
369 depends on !COMPILE_TEST
370 help
371 GCC plugins are loadable modules that provide extra features to the
372 compiler. They are useful for runtime instrumentation and static analysis.
373
374 See Documentation/gcc-plugins.txt for details.
375
376 config GCC_PLUGIN_CYC_COMPLEXITY
377 bool "Compute the cyclomatic complexity of a function"
378 depends on GCC_PLUGINS
379 help
380 The complexity M of a function's control flow graph is defined as:
381 M = E - N + 2P
382 where
383
384 E = the number of edges
385 N = the number of nodes
386 P = the number of connected components (exit nodes).
387
388 config GCC_PLUGIN_SANCOV
389 bool
390 depends on GCC_PLUGINS
391 help
392 This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
393 basic blocks. It supports all gcc versions with plugin support (from
394 gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
395 by Dmitry Vyukov <dvyukov@google.com>.
396
397 config HAVE_CC_STACKPROTECTOR
398 bool
399 help
400 An arch should select this symbol if:
401 - its compiler supports the -fstack-protector option
402 - it has implemented a stack canary (e.g. __stack_chk_guard)
403
404 config CC_STACKPROTECTOR
405 def_bool n
406 help
407 Set when a stack-protector mode is enabled, so that the build
408 can enable kernel-side support for the GCC feature.
409
410 choice
411 prompt "Stack Protector buffer overflow detection"
412 depends on HAVE_CC_STACKPROTECTOR
413 default CC_STACKPROTECTOR_NONE
414 help
415 This option turns on the "stack-protector" GCC feature. This
416 feature puts, at the beginning of functions, a canary value on
417 the stack just before the return address, and validates
418 the value just before actually returning. Stack based buffer
419 overflows (that need to overwrite this return address) now also
420 overwrite the canary, which gets detected and the attack is then
421 neutralized via a kernel panic.
422
423 config CC_STACKPROTECTOR_NONE
424 bool "None"
425 help
426 Disable "stack-protector" GCC feature.
427
428 config CC_STACKPROTECTOR_REGULAR
429 bool "Regular"
430 select CC_STACKPROTECTOR
431 help
432 Functions will have the stack-protector canary logic added if they
433 have an 8-byte or larger character array on the stack.
434
435 This feature requires gcc version 4.2 or above, or a distribution
436 gcc with the feature backported ("-fstack-protector").
437
438 On an x86 "defconfig" build, this feature adds canary checks to
439 about 3% of all kernel functions, which increases kernel code size
440 by about 0.3%.
441
442 config CC_STACKPROTECTOR_STRONG
443 bool "Strong"
444 select CC_STACKPROTECTOR
445 help
446 Functions will have the stack-protector canary logic added in any
447 of the following conditions:
448
449 - local variable's address used as part of the right hand side of an
450 assignment or function argument
451 - local variable is an array (or union containing an array),
452 regardless of array type or length
453 - uses register local variables
454
455 This feature requires gcc version 4.9 or above, or a distribution
456 gcc with the feature backported ("-fstack-protector-strong").
457
458 On an x86 "defconfig" build, this feature adds canary checks to
459 about 20% of all kernel functions, which increases the kernel code
460 size by about 2%.
461
462 endchoice
463
464 config HAVE_ARCH_WITHIN_STACK_FRAMES
465 bool
466 help
467 An architecture should select this if it can walk the kernel stack
468 frames to determine if an object is part of either the arguments
469 or local variables (i.e. that it excludes saved return addresses,
470 and similar) by implementing an inline arch_within_stack_frames(),
471 which is used by CONFIG_HARDENED_USERCOPY.
472
473 config HAVE_CONTEXT_TRACKING
474 bool
475 help
476 Provide kernel/user boundaries probes necessary for subsystems
477 that need it, such as userspace RCU extended quiescent state.
478 Syscalls need to be wrapped inside user_exit()-user_enter() through
479 the slow path using TIF_NOHZ flag. Exceptions handlers must be
480 wrapped as well. Irqs are already protected inside
481 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
482 irq exit still need to be protected.
483
484 config HAVE_VIRT_CPU_ACCOUNTING
485 bool
486
487 config HAVE_VIRT_CPU_ACCOUNTING_GEN
488 bool
489 default y if 64BIT
490 help
491 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
492 Before enabling this option, arch code must be audited
493 to ensure there are no races in concurrent read/write of
494 cputime_t. For example, reading/writing 64-bit cputime_t on
495 some 32-bit arches may require multiple accesses, so proper
496 locking is needed to protect against concurrent accesses.
497
498
499 config HAVE_IRQ_TIME_ACCOUNTING
500 bool
501 help
502 Archs need to ensure they use a high enough resolution clock to
503 support irq time accounting and then call enable_sched_clock_irqtime().
504
505 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
506 bool
507
508 config HAVE_ARCH_HUGE_VMAP
509 bool
510
511 config HAVE_ARCH_SOFT_DIRTY
512 bool
513
514 config HAVE_MOD_ARCH_SPECIFIC
515 bool
516 help
517 The arch uses struct mod_arch_specific to store data. Many arches
518 just need a simple module loader without arch specific data - those
519 should not enable this.
520
521 config MODULES_USE_ELF_RELA
522 bool
523 help
524 Modules only use ELF RELA relocations. Modules with ELF REL
525 relocations will give an error.
526
527 config MODULES_USE_ELF_REL
528 bool
529 help
530 Modules only use ELF REL relocations. Modules with ELF RELA
531 relocations will give an error.
532
533 config HAVE_UNDERSCORE_SYMBOL_PREFIX
534 bool
535 help
536 Some architectures generate an _ in front of C symbols; things like
537 module loading and assembly files need to know about this.
538
539 config HAVE_IRQ_EXIT_ON_IRQ_STACK
540 bool
541 help
542 Architecture doesn't only execute the irq handler on the irq stack
543 but also irq_exit(). This way we can process softirqs on this irq
544 stack instead of switching to a new one when we call __do_softirq()
545 in the end of an hardirq.
546 This spares a stack switch and improves cache usage on softirq
547 processing.
548
549 config PGTABLE_LEVELS
550 int
551 default 2
552
553 config ARCH_HAS_ELF_RANDOMIZE
554 bool
555 help
556 An architecture supports choosing randomized locations for
557 stack, mmap, brk, and ET_DYN. Defined functions:
558 - arch_mmap_rnd()
559 - arch_randomize_brk()
560
561 config HAVE_ARCH_MMAP_RND_BITS
562 bool
563 help
564 An arch should select this symbol if it supports setting a variable
565 number of bits for use in establishing the base address for mmap
566 allocations, has MMU enabled and provides values for both:
567 - ARCH_MMAP_RND_BITS_MIN
568 - ARCH_MMAP_RND_BITS_MAX
569
570 config HAVE_EXIT_THREAD
571 bool
572 help
573 An architecture implements exit_thread.
574
575 config ARCH_MMAP_RND_BITS_MIN
576 int
577
578 config ARCH_MMAP_RND_BITS_MAX
579 int
580
581 config ARCH_MMAP_RND_BITS_DEFAULT
582 int
583
584 config ARCH_MMAP_RND_BITS
585 int "Number of bits to use for ASLR of mmap base address" if EXPERT
586 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
587 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
588 default ARCH_MMAP_RND_BITS_MIN
589 depends on HAVE_ARCH_MMAP_RND_BITS
590 help
591 This value can be used to select the number of bits to use to
592 determine the random offset to the base address of vma regions
593 resulting from mmap allocations. This value will be bounded
594 by the architecture's minimum and maximum supported values.
595
596 This value can be changed after boot using the
597 /proc/sys/vm/mmap_rnd_bits tunable
598
599 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
600 bool
601 help
602 An arch should select this symbol if it supports running applications
603 in compatibility mode, supports setting a variable number of bits for
604 use in establishing the base address for mmap allocations, has MMU
605 enabled and provides values for both:
606 - ARCH_MMAP_RND_COMPAT_BITS_MIN
607 - ARCH_MMAP_RND_COMPAT_BITS_MAX
608
609 config ARCH_MMAP_RND_COMPAT_BITS_MIN
610 int
611
612 config ARCH_MMAP_RND_COMPAT_BITS_MAX
613 int
614
615 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
616 int
617
618 config ARCH_MMAP_RND_COMPAT_BITS
619 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
620 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
621 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
622 default ARCH_MMAP_RND_COMPAT_BITS_MIN
623 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
624 help
625 This value can be used to select the number of bits to use to
626 determine the random offset to the base address of vma regions
627 resulting from mmap allocations for compatible applications This
628 value will be bounded by the architecture's minimum and maximum
629 supported values.
630
631 This value can be changed after boot using the
632 /proc/sys/vm/mmap_rnd_compat_bits tunable
633
634 config HAVE_COPY_THREAD_TLS
635 bool
636 help
637 Architecture provides copy_thread_tls to accept tls argument via
638 normal C parameter passing, rather than extracting the syscall
639 argument from pt_regs.
640
641 config HAVE_STACK_VALIDATION
642 bool
643 help
644 Architecture supports the 'objtool check' host tool command, which
645 performs compile-time stack metadata validation.
646
647 config HAVE_ARCH_HASH
648 bool
649 default n
650 help
651 If this is set, the architecture provides an <asm/hash.h>
652 file which provides platform-specific implementations of some
653 functions in <linux/hash.h> or fs/namei.c.
654
655 config ISA_BUS_API
656 def_bool ISA
657
658 #
659 # ABI hall of shame
660 #
661 config CLONE_BACKWARDS
662 bool
663 help
664 Architecture has tls passed as the 4th argument of clone(2),
665 not the 5th one.
666
667 config CLONE_BACKWARDS2
668 bool
669 help
670 Architecture has the first two arguments of clone(2) swapped.
671
672 config CLONE_BACKWARDS3
673 bool
674 help
675 Architecture has tls passed as the 3rd argument of clone(2),
676 not the 5th one.
677
678 config ODD_RT_SIGACTION
679 bool
680 help
681 Architecture has unusual rt_sigaction(2) arguments
682
683 config OLD_SIGSUSPEND
684 bool
685 help
686 Architecture has old sigsuspend(2) syscall, of one-argument variety
687
688 config OLD_SIGSUSPEND3
689 bool
690 help
691 Even weirder antique ABI - three-argument sigsuspend(2)
692
693 config OLD_SIGACTION
694 bool
695 help
696 Architecture has old sigaction(2) syscall. Nope, not the same
697 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
698 but fairly different variant of sigaction(2), thanks to OSF/1
699 compatibility...
700
701 config COMPAT_OLD_SIGACTION
702 bool
703
704 config ARCH_NO_COHERENT_DMA_MMAP
705 bool
706
707 config CPU_NO_EFFICIENT_FFS
708 def_bool n
709
710 source "kernel/gcov/Kconfig"