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8
9
10source "arch/$(SRCARCH)/Kconfig"
11
12menu "General architecture-dependent options"
13
14config CRASH_CORE
15 bool
16
17config KEXEC_CORE
18 select CRASH_CORE
19 bool
20
21config HAVE_IMA_KEXEC
22 bool
23
24config HOTPLUG_SMT
25 bool
26
27config OPROFILE
28 tristate "OProfile system profiling"
29 depends on PROFILING
30 depends on HAVE_OPROFILE
31 select RING_BUFFER
32 select RING_BUFFER_ALLOW_SWAP
33 help
34 OProfile is a profiling system capable of profiling the
35 whole system, include the kernel, kernel modules, libraries,
36 and applications.
37
38 If unsure, say N.
39
40config OPROFILE_EVENT_MULTIPLEX
41 bool "OProfile multiplexing support (EXPERIMENTAL)"
42 default n
43 depends on OPROFILE && X86
44 help
45 The number of hardware counters is limited. The multiplexing
46 feature enables OProfile to gather more events than counters
47 are provided by the hardware. This is realized by switching
48 between events at a user specified time interval.
49
50 If unsure, say N.
51
52config HAVE_OPROFILE
53 bool
54
55config OPROFILE_NMI_TIMER
56 def_bool y
57 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
58
59config KPROBES
60 bool "Kprobes"
61 depends on MODULES
62 depends on HAVE_KPROBES
63 select KALLSYMS
64 help
65 Kprobes allows you to trap at almost any kernel address and
66 execute a callback function. register_kprobe() establishes
67 a probepoint and specifies the callback. Kprobes is useful
68 for kernel debugging, non-intrusive instrumentation and testing.
69 If in doubt, say "N".
70
71config JUMP_LABEL
72 bool "Optimize very unlikely/likely branches"
73 depends on HAVE_ARCH_JUMP_LABEL
74 help
75 This option enables a transparent branch optimization that
76 makes certain almost-always-true or almost-always-false branch
77 conditions even cheaper to execute within the kernel.
78
79 Certain performance-sensitive kernel code, such as trace points,
80 scheduler functionality, networking code and KVM have such
81 branches and include support for this optimization technique.
82
83 If it is detected that the compiler has support for "asm goto",
84 the kernel will compile such branches with just a nop
85 instruction. When the condition flag is toggled to true, the
86 nop will be converted to a jump instruction to execute the
87 conditional block of instructions.
88
89 This technique lowers overhead and stress on the branch prediction
90 of the processor and generally makes the kernel faster. The update
91 of the condition is slower, but those are always very rare.
92
93 ( On 32-bit x86, the necessary options added to the compiler
94 flags may increase the size of the kernel slightly. )
95
96config STATIC_KEYS_SELFTEST
97 bool "Static key selftest"
98 depends on JUMP_LABEL
99 help
100 Boot time self-test of the branch patching code.
101
102config OPTPROBES
103 def_bool y
104 depends on KPROBES && HAVE_OPTPROBES
105 select TASKS_RCU if PREEMPT
106
107config KPROBES_ON_FTRACE
108 def_bool y
109 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
110 depends on DYNAMIC_FTRACE_WITH_REGS
111 help
112 If function tracer is enabled and the arch supports full
113 passing of pt_regs to function tracing, then kprobes can
114 optimize on top of function tracing.
115
116config UPROBES
117 def_bool n
118 depends on ARCH_SUPPORTS_UPROBES
119 help
120 Uprobes is the user-space counterpart to kprobes: they
121 enable instrumentation applications (such as 'perf probe')
122 to establish unintrusive probes in user-space binaries and
123 libraries, by executing handler functions when the probes
124 are hit by user-space applications.
125
126 ( These probes come in the form of single-byte breakpoints,
127 managed by the kernel and kept transparent to the probed
128 application. )
129
130config HAVE_64BIT_ALIGNED_ACCESS
131 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
132 help
133 Some architectures require 64 bit accesses to be 64 bit
134 aligned, which also requires structs containing 64 bit values
135 to be 64 bit aligned too. This includes some 32 bit
136 architectures which can do 64 bit accesses, as well as 64 bit
137 architectures without unaligned access.
138
139 This symbol should be selected by an architecture if 64 bit
140 accesses are required to be 64 bit aligned in this way even
141 though it is not a 64 bit architecture.
142
143 See Documentation/unaligned-memory-access.txt for more
144 information on the topic of unaligned memory accesses.
145
146config HAVE_EFFICIENT_UNALIGNED_ACCESS
147 bool
148 help
149 Some architectures are unable to perform unaligned accesses
150 without the use of get_unaligned/put_unaligned. Others are
151 unable to perform such accesses efficiently (e.g. trap on
152 unaligned access and require fixing it up in the exception
153 handler.)
154
155 This symbol should be selected by an architecture if it can
156 perform unaligned accesses efficiently to allow different
157 code paths to be selected for these cases. Some network
158 drivers, for example, could opt to not fix up alignment
159 problems with received packets if doing so would not help
160 much.
161
162 See Documentation/unaligned-memory-access.txt for more
163 information on the topic of unaligned memory accesses.
164
165config ARCH_USE_BUILTIN_BSWAP
166 bool
167 help
168 Modern versions of GCC (since 4.4) have builtin functions
169 for handling byte-swapping. Using these, instead of the old
170 inline assembler that the architecture code provides in the
171 __arch_bswapXX() macros, allows the compiler to see what's
172 happening and offers more opportunity for optimisation. In
173 particular, the compiler will be able to combine the byteswap
174 with a nearby load or store and use load-and-swap or
175 store-and-swap instructions if the architecture has them. It
176 should almost *never* result in code which is worse than the
177 hand-coded assembler in <asm/swab.h>. But just in case it
178 does, the use of the builtins is optional.
179
180 Any architecture with load-and-swap or store-and-swap
181 instructions should set this. And it shouldn't hurt to set it
182 on architectures that don't have such instructions.
183
184config KRETPROBES
185 def_bool y
186 depends on KPROBES && HAVE_KRETPROBES
187
188config USER_RETURN_NOTIFIER
189 bool
190 depends on HAVE_USER_RETURN_NOTIFIER
191 help
192 Provide a kernel-internal notification when a cpu is about to
193 switch to user mode.
194
195config HAVE_IOREMAP_PROT
196 bool
197
198config HAVE_KPROBES
199 bool
200
201config HAVE_KRETPROBES
202 bool
203
204config HAVE_OPTPROBES
205 bool
206
207config HAVE_KPROBES_ON_FTRACE
208 bool
209
210config HAVE_FUNCTION_ERROR_INJECTION
211 bool
212
213config HAVE_NMI
214 bool
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229config HAVE_ARCH_TRACEHOOK
230 bool
231
232config HAVE_DMA_CONTIGUOUS
233 bool
234
235config GENERIC_SMP_IDLE_THREAD
236 bool
237
238config GENERIC_IDLE_POLL_SETUP
239 bool
240
241config ARCH_HAS_FORTIFY_SOURCE
242 bool
243 help
244 An architecture should select this when it can successfully
245 build and run with CONFIG_FORTIFY_SOURCE.
246
247
248config ARCH_HAS_SET_MEMORY
249 bool
250
251
252config ARCH_TASK_STRUCT_ON_STACK
253 bool
254
255
256config ARCH_TASK_STRUCT_ALLOCATOR
257 bool
258
259config HAVE_ARCH_THREAD_STRUCT_WHITELIST
260 bool
261 depends on !ARCH_TASK_STRUCT_ALLOCATOR
262 help
263 An architecture should select this to provide hardened usercopy
264 knowledge about what region of the thread_struct should be
265 whitelisted for copying to userspace. Normally this is only the
266 FPU registers. Specifically, arch_thread_struct_whitelist()
267 should be implemented. Without this, the entire thread_struct
268 field in task_struct will be left whitelisted.
269
270
271config ARCH_THREAD_STACK_ALLOCATOR
272 bool
273
274
275config ARCH_WANTS_DYNAMIC_TASK_STRUCT
276 bool
277
278config HAVE_REGS_AND_STACK_ACCESS_API
279 bool
280 help
281 This symbol should be selected by an architecure if it supports
282 the API needed to access registers and stack entries from pt_regs,
283 declared in asm/ptrace.h
284 For example the kprobes-based event tracer needs this API.
285
286config HAVE_RSEQ
287 bool
288 depends on HAVE_REGS_AND_STACK_ACCESS_API
289 help
290 This symbol should be selected by an architecture if it
291 supports an implementation of restartable sequences.
292
293config HAVE_CLK
294 bool
295 help
296 The <linux/clk.h> calls support software clock gating and
297 thus are a key power management tool on many systems.
298
299config HAVE_HW_BREAKPOINT
300 bool
301 depends on PERF_EVENTS
302
303config HAVE_MIXED_BREAKPOINTS_REGS
304 bool
305 depends on HAVE_HW_BREAKPOINT
306 help
307 Depending on the arch implementation of hardware breakpoints,
308 some of them have separate registers for data and instruction
309 breakpoints addresses, others have mixed registers to store
310 them but define the access type in a control register.
311 Select this option if your arch implements breakpoints under the
312 latter fashion.
313
314config HAVE_USER_RETURN_NOTIFIER
315 bool
316
317config HAVE_PERF_EVENTS_NMI
318 bool
319 help
320 System hardware can generate an NMI using the perf event
321 subsystem. Also has support for calculating CPU cycle events
322 to determine how many clock cycles in a given period.
323
324config HAVE_HARDLOCKUP_DETECTOR_PERF
325 bool
326 depends on HAVE_PERF_EVENTS_NMI
327 help
328 The arch chooses to use the generic perf-NMI-based hardlockup
329 detector. Must define HAVE_PERF_EVENTS_NMI.
330
331config HAVE_NMI_WATCHDOG
332 depends on HAVE_NMI
333 bool
334 help
335 The arch provides a low level NMI watchdog. It provides
336 asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
337
338config HAVE_HARDLOCKUP_DETECTOR_ARCH
339 bool
340 select HAVE_NMI_WATCHDOG
341 help
342 The arch chooses to provide its own hardlockup detector, which is
343 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
344 interfaces and parameters provided by hardlockup detector subsystem.
345
346config HAVE_PERF_REGS
347 bool
348 help
349 Support selective register dumps for perf events. This includes
350 bit-mapping of each registers and a unique architecture id.
351
352config HAVE_PERF_USER_STACK_DUMP
353 bool
354 help
355 Support user stack dumps for perf event samples. This needs
356 access to the user stack pointer which is not unified across
357 architectures.
358
359config HAVE_ARCH_JUMP_LABEL
360 bool
361
362config HAVE_RCU_TABLE_FREE
363 bool
364
365config HAVE_RCU_TABLE_INVALIDATE
366 bool
367
368config ARCH_HAVE_NMI_SAFE_CMPXCHG
369 bool
370
371config HAVE_ALIGNED_STRUCT_PAGE
372 bool
373 help
374 This makes sure that struct pages are double word aligned and that
375 e.g. the SLUB allocator can perform double word atomic operations
376 on a struct page for better performance. However selecting this
377 might increase the size of a struct page by a word.
378
379config HAVE_CMPXCHG_LOCAL
380 bool
381
382config HAVE_CMPXCHG_DOUBLE
383 bool
384
385config ARCH_WEAK_RELEASE_ACQUIRE
386 bool
387
388config ARCH_WANT_IPC_PARSE_VERSION
389 bool
390
391config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
392 bool
393
394config ARCH_WANT_OLD_COMPAT_IPC
395 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
396 bool
397
398config HAVE_ARCH_SECCOMP_FILTER
399 bool
400 help
401 An arch should select this symbol if it provides all of these things:
402 - syscall_get_arch()
403 - syscall_get_arguments()
404 - syscall_rollback()
405 - syscall_set_return_value()
406 - SIGSYS siginfo_t support
407 - secure_computing is called from a ptrace_event()-safe context
408 - secure_computing return value is checked and a return value of -1
409 results in the system call being skipped immediately.
410 - seccomp syscall wired up
411
412config SECCOMP_FILTER
413 def_bool y
414 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
415 help
416 Enable tasks to build secure computing environments defined
417 in terms of Berkeley Packet Filter programs which implement
418 task-defined system call filtering polices.
419
420 See Documentation/userspace-api/seccomp_filter.rst for details.
421
422config HAVE_STACKPROTECTOR
423 bool
424 help
425 An arch should select this symbol if:
426 - it has implemented a stack canary (e.g. __stack_chk_guard)
427
428config CC_HAS_STACKPROTECTOR_NONE
429 def_bool $(cc-option,-fno-stack-protector)
430
431config STACKPROTECTOR
432 bool "Stack Protector buffer overflow detection"
433 depends on HAVE_STACKPROTECTOR
434 depends on $(cc-option,-fstack-protector)
435 default y
436 help
437 This option turns on the "stack-protector" GCC feature. This
438 feature puts, at the beginning of functions, a canary value on
439 the stack just before the return address, and validates
440 the value just before actually returning. Stack based buffer
441 overflows (that need to overwrite this return address) now also
442 overwrite the canary, which gets detected and the attack is then
443 neutralized via a kernel panic.
444
445 Functions will have the stack-protector canary logic added if they
446 have an 8-byte or larger character array on the stack.
447
448 This feature requires gcc version 4.2 or above, or a distribution
449 gcc with the feature backported ("-fstack-protector").
450
451 On an x86 "defconfig" build, this feature adds canary checks to
452 about 3% of all kernel functions, which increases kernel code size
453 by about 0.3%.
454
455config STACKPROTECTOR_STRONG
456 bool "Strong Stack Protector"
457 depends on STACKPROTECTOR
458 depends on $(cc-option,-fstack-protector-strong)
459 default y
460 help
461 Functions will have the stack-protector canary logic added in any
462 of the following conditions:
463
464 - local variable's address used as part of the right hand side of an
465 assignment or function argument
466 - local variable is an array (or union containing an array),
467 regardless of array type or length
468 - uses register local variables
469
470 This feature requires gcc version 4.9 or above, or a distribution
471 gcc with the feature backported ("-fstack-protector-strong").
472
473 On an x86 "defconfig" build, this feature adds canary checks to
474 about 20% of all kernel functions, which increases the kernel code
475 size by about 2%.
476
477config HAVE_ARCH_WITHIN_STACK_FRAMES
478 bool
479 help
480 An architecture should select this if it can walk the kernel stack
481 frames to determine if an object is part of either the arguments
482 or local variables (i.e. that it excludes saved return addresses,
483 and similar) by implementing an inline arch_within_stack_frames(),
484 which is used by CONFIG_HARDENED_USERCOPY.
485
486config HAVE_CONTEXT_TRACKING
487 bool
488 help
489 Provide kernel/user boundaries probes necessary for subsystems
490 that need it, such as userspace RCU extended quiescent state.
491 Syscalls need to be wrapped inside user_exit()-user_enter() through
492 the slow path using TIF_NOHZ flag. Exceptions handlers must be
493 wrapped as well. Irqs are already protected inside
494 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
495 irq exit still need to be protected.
496
497config HAVE_VIRT_CPU_ACCOUNTING
498 bool
499
500config ARCH_HAS_SCALED_CPUTIME
501 bool
502
503config HAVE_VIRT_CPU_ACCOUNTING_GEN
504 bool
505 default y if 64BIT
506 help
507 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
508 Before enabling this option, arch code must be audited
509 to ensure there are no races in concurrent read/write of
510 cputime_t. For example, reading/writing 64-bit cputime_t on
511 some 32-bit arches may require multiple accesses, so proper
512 locking is needed to protect against concurrent accesses.
513
514
515config HAVE_IRQ_TIME_ACCOUNTING
516 bool
517 help
518 Archs need to ensure they use a high enough resolution clock to
519 support irq time accounting and then call enable_sched_clock_irqtime().
520
521config HAVE_ARCH_TRANSPARENT_HUGEPAGE
522 bool
523
524config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
525 bool
526
527config HAVE_ARCH_HUGE_VMAP
528 bool
529
530config HAVE_ARCH_SOFT_DIRTY
531 bool
532
533config HAVE_MOD_ARCH_SPECIFIC
534 bool
535 help
536 The arch uses struct mod_arch_specific to store data. Many arches
537 just need a simple module loader without arch specific data - those
538 should not enable this.
539
540config MODULES_USE_ELF_RELA
541 bool
542 help
543 Modules only use ELF RELA relocations. Modules with ELF REL
544 relocations will give an error.
545
546config MODULES_USE_ELF_REL
547 bool
548 help
549 Modules only use ELF REL relocations. Modules with ELF RELA
550 relocations will give an error.
551
552config HAVE_IRQ_EXIT_ON_IRQ_STACK
553 bool
554 help
555 Architecture doesn't only execute the irq handler on the irq stack
556 but also irq_exit(). This way we can process softirqs on this irq
557 stack instead of switching to a new one when we call __do_softirq()
558 in the end of an hardirq.
559 This spares a stack switch and improves cache usage on softirq
560 processing.
561
562config PGTABLE_LEVELS
563 int
564 default 2
565
566config ARCH_HAS_ELF_RANDOMIZE
567 bool
568 help
569 An architecture supports choosing randomized locations for
570 stack, mmap, brk, and ET_DYN. Defined functions:
571 - arch_mmap_rnd()
572 - arch_randomize_brk()
573
574config HAVE_ARCH_MMAP_RND_BITS
575 bool
576 help
577 An arch should select this symbol if it supports setting a variable
578 number of bits for use in establishing the base address for mmap
579 allocations, has MMU enabled and provides values for both:
580 - ARCH_MMAP_RND_BITS_MIN
581 - ARCH_MMAP_RND_BITS_MAX
582
583config HAVE_EXIT_THREAD
584 bool
585 help
586 An architecture implements exit_thread.
587
588config ARCH_MMAP_RND_BITS_MIN
589 int
590
591config ARCH_MMAP_RND_BITS_MAX
592 int
593
594config ARCH_MMAP_RND_BITS_DEFAULT
595 int
596
597config ARCH_MMAP_RND_BITS
598 int "Number of bits to use for ASLR of mmap base address" if EXPERT
599 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
600 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
601 default ARCH_MMAP_RND_BITS_MIN
602 depends on HAVE_ARCH_MMAP_RND_BITS
603 help
604 This value can be used to select the number of bits to use to
605 determine the random offset to the base address of vma regions
606 resulting from mmap allocations. This value will be bounded
607 by the architecture's minimum and maximum supported values.
608
609 This value can be changed after boot using the
610 /proc/sys/vm/mmap_rnd_bits tunable
611
612config HAVE_ARCH_MMAP_RND_COMPAT_BITS
613 bool
614 help
615 An arch should select this symbol if it supports running applications
616 in compatibility mode, supports setting a variable number of bits for
617 use in establishing the base address for mmap allocations, has MMU
618 enabled and provides values for both:
619 - ARCH_MMAP_RND_COMPAT_BITS_MIN
620 - ARCH_MMAP_RND_COMPAT_BITS_MAX
621
622config ARCH_MMAP_RND_COMPAT_BITS_MIN
623 int
624
625config ARCH_MMAP_RND_COMPAT_BITS_MAX
626 int
627
628config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
629 int
630
631config ARCH_MMAP_RND_COMPAT_BITS
632 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
633 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
634 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
635 default ARCH_MMAP_RND_COMPAT_BITS_MIN
636 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
637 help
638 This value can be used to select the number of bits to use to
639 determine the random offset to the base address of vma regions
640 resulting from mmap allocations for compatible applications This
641 value will be bounded by the architecture's minimum and maximum
642 supported values.
643
644 This value can be changed after boot using the
645 /proc/sys/vm/mmap_rnd_compat_bits tunable
646
647config HAVE_ARCH_COMPAT_MMAP_BASES
648 bool
649 help
650 This allows 64bit applications to invoke 32-bit mmap() syscall
651 and vice-versa 32-bit applications to call 64-bit mmap().
652 Required for applications doing different bitness syscalls.
653
654config HAVE_COPY_THREAD_TLS
655 bool
656 help
657 Architecture provides copy_thread_tls to accept tls argument via
658 normal C parameter passing, rather than extracting the syscall
659 argument from pt_regs.
660
661config HAVE_STACK_VALIDATION
662 bool
663 help
664 Architecture supports the 'objtool check' host tool command, which
665 performs compile-time stack metadata validation.
666
667config HAVE_RELIABLE_STACKTRACE
668 bool
669 help
670 Architecture has a save_stack_trace_tsk_reliable() function which
671 only returns a stack trace if it can guarantee the trace is reliable.
672
673config HAVE_ARCH_HASH
674 bool
675 default n
676 help
677 If this is set, the architecture provides an <asm/hash.h>
678 file which provides platform-specific implementations of some
679 functions in <linux/hash.h> or fs/namei.c.
680
681config ISA_BUS_API
682 def_bool ISA
683
684
685
686
687config CLONE_BACKWARDS
688 bool
689 help
690 Architecture has tls passed as the 4th argument of clone(2),
691 not the 5th one.
692
693config CLONE_BACKWARDS2
694 bool
695 help
696 Architecture has the first two arguments of clone(2) swapped.
697
698config CLONE_BACKWARDS3
699 bool
700 help
701 Architecture has tls passed as the 3rd argument of clone(2),
702 not the 5th one.
703
704config ODD_RT_SIGACTION
705 bool
706 help
707 Architecture has unusual rt_sigaction(2) arguments
708
709config OLD_SIGSUSPEND
710 bool
711 help
712 Architecture has old sigsuspend(2) syscall, of one-argument variety
713
714config OLD_SIGSUSPEND3
715 bool
716 help
717 Even weirder antique ABI - three-argument sigsuspend(2)
718
719config OLD_SIGACTION
720 bool
721 help
722 Architecture has old sigaction(2) syscall. Nope, not the same
723 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
724 but fairly different variant of sigaction(2), thanks to OSF/1
725 compatibility...
726
727config COMPAT_OLD_SIGACTION
728 bool
729
730config 64BIT_TIME
731 def_bool ARCH_HAS_64BIT_TIME
732 help
733 This should be selected by all architectures that need to support
734 new system calls with a 64-bit time_t. This is relevant on all 32-bit
735 architectures, and 64-bit architectures as part of compat syscall
736 handling.
737
738config COMPAT_32BIT_TIME
739 def_bool (!64BIT && 64BIT_TIME) || COMPAT
740 help
741 This enables 32 bit time_t support in addition to 64 bit time_t support.
742 This is relevant on all 32-bit architectures, and 64-bit architectures
743 as part of compat syscall handling.
744
745config ARCH_NO_COHERENT_DMA_MMAP
746 bool
747
748config ARCH_NO_PREEMPT
749 bool
750
751config CPU_NO_EFFICIENT_FFS
752 def_bool n
753
754config HAVE_ARCH_VMAP_STACK
755 def_bool n
756 help
757 An arch should select this symbol if it can support kernel stacks
758 in vmalloc space. This means:
759
760 - vmalloc space must be large enough to hold many kernel stacks.
761 This may rule out many 32-bit architectures.
762
763 - Stacks in vmalloc space need to work reliably. For example, if
764 vmap page tables are created on demand, either this mechanism
765 needs to work while the stack points to a virtual address with
766 unpopulated page tables or arch code (switch_to() and switch_mm(),
767 most likely) needs to ensure that the stack's page table entries
768 are populated before running on a possibly unpopulated stack.
769
770 - If the stack overflows into a guard page, something reasonable
771 should happen. The definition of "reasonable" is flexible, but
772 instantly rebooting without logging anything would be unfriendly.
773
774config VMAP_STACK
775 default y
776 bool "Use a virtually-mapped stack"
777 depends on HAVE_ARCH_VMAP_STACK && !KASAN
778 ---help---
779 Enable this if you want the use virtually-mapped kernel stacks
780 with guard pages. This causes kernel stack overflows to be
781 caught immediately rather than causing difficult-to-diagnose
782 corruption.
783
784 This is presently incompatible with KASAN because KASAN expects
785 the stack to map directly to the KASAN shadow map using a formula
786 that is incorrect if the stack is in vmalloc space.
787
788config ARCH_OPTIONAL_KERNEL_RWX
789 def_bool n
790
791config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
792 def_bool n
793
794config ARCH_HAS_STRICT_KERNEL_RWX
795 def_bool n
796
797config STRICT_KERNEL_RWX
798 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
799 depends on ARCH_HAS_STRICT_KERNEL_RWX
800 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
801 help
802 If this is set, kernel text and rodata memory will be made read-only,
803 and non-text memory will be made non-executable. This provides
804 protection against certain security exploits (e.g. executing the heap
805 or modifying text)
806
807 These features are considered standard security practice these days.
808 You should say Y here in almost all cases.
809
810config ARCH_HAS_STRICT_MODULE_RWX
811 def_bool n
812
813config STRICT_MODULE_RWX
814 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
815 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
816 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
817 help
818 If this is set, module text and rodata memory will be made read-only,
819 and non-text memory will be made non-executable. This provides
820 protection against certain security exploits (e.g. writing to text)
821
822
823config ARCH_HAS_PHYS_TO_DMA
824 bool
825
826config ARCH_HAS_REFCOUNT
827 bool
828 help
829 An architecture selects this when it has implemented refcount_t
830 using open coded assembly primitives that provide an optimized
831 refcount_t implementation, possibly at the expense of some full
832 refcount state checks of CONFIG_REFCOUNT_FULL=y.
833
834 The refcount overflow check behavior, however, must be retained.
835 Catching overflows is the primary security concern for protecting
836 against bugs in reference counts.
837
838config REFCOUNT_FULL
839 bool "Perform full reference count validation at the expense of speed"
840 help
841 Enabling this switches the refcounting infrastructure from a fast
842 unchecked atomic_t implementation to a fully state checked
843 implementation, which can be (slightly) slower but provides protections
844 against various use-after-free conditions that can be used in
845 security flaw exploits.
846
847config HAVE_ARCH_COMPILER_H
848 bool
849 help
850 An architecture can select this if it provides an
851 asm/compiler.h header that should be included after
852 linux/compiler-*.h in order to override macro definitions that those
853 headers generally provide.
854
855config HAVE_ARCH_PREL32_RELOCATIONS
856 bool
857 help
858 May be selected by an architecture if it supports place-relative
859 32-bit relocations, both in the toolchain and in the module loader,
860 in which case relative references can be used in special sections
861 for PCI fixup, initcalls etc which are only half the size on 64 bit
862 architectures, and don't require runtime relocation on relocatable
863 kernels.
864
865source "kernel/gcov/Kconfig"
866
867source "scripts/gcc-plugins/Kconfig"
868
869endmenu
870