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1# SPDX-License-Identifier: GPL-2.0
2#
3# General architecture dependent options
4#
5
6#
7# Note: arch/$(SRCARCH)/Kconfig needs to be included first so that it can
8# override the default values in this file.
9#
10source "arch/$(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 KEXEC_ELF
22 bool
23
24config HAVE_IMA_KEXEC
25 bool
26
27config HOTPLUG_SMT
28 bool
29
30config OPROFILE
31 tristate "OProfile system profiling"
32 depends on PROFILING
33 depends on HAVE_OPROFILE
34 select RING_BUFFER
35 select RING_BUFFER_ALLOW_SWAP
36 help
37 OProfile is a profiling system capable of profiling the
38 whole system, include the kernel, kernel modules, libraries,
39 and applications.
40
41 If unsure, say N.
42
43config OPROFILE_EVENT_MULTIPLEX
44 bool "OProfile multiplexing support (EXPERIMENTAL)"
45 default n
46 depends on OPROFILE && X86
47 help
48 The number of hardware counters is limited. The multiplexing
49 feature enables OProfile to gather more events than counters
50 are provided by the hardware. This is realized by switching
51 between events at a user specified time interval.
52
53 If unsure, say N.
54
55config HAVE_OPROFILE
56 bool
57
58config OPROFILE_NMI_TIMER
59 def_bool y
60 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
61
62config KPROBES
63 bool "Kprobes"
64 depends on MODULES
65 depends on HAVE_KPROBES
66 select KALLSYMS
67 help
68 Kprobes allows you to trap at almost any kernel address and
69 execute a callback function. register_kprobe() establishes
70 a probepoint and specifies the callback. Kprobes is useful
71 for kernel debugging, non-intrusive instrumentation and testing.
72 If in doubt, say "N".
73
74config JUMP_LABEL
75 bool "Optimize very unlikely/likely branches"
76 depends on HAVE_ARCH_JUMP_LABEL
77 depends on CC_HAS_ASM_GOTO
78 help
79 This option enables a transparent branch optimization that
80 makes certain almost-always-true or almost-always-false branch
81 conditions even cheaper to execute within the kernel.
82
83 Certain performance-sensitive kernel code, such as trace points,
84 scheduler functionality, networking code and KVM have such
85 branches and include support for this optimization technique.
86
87 If it is detected that the compiler has support for "asm goto",
88 the kernel will compile such branches with just a nop
89 instruction. When the condition flag is toggled to true, the
90 nop will be converted to a jump instruction to execute the
91 conditional block of instructions.
92
93 This technique lowers overhead and stress on the branch prediction
94 of the processor and generally makes the kernel faster. The update
95 of the condition is slower, but those are always very rare.
96
97 ( On 32-bit x86, the necessary options added to the compiler
98 flags may increase the size of the kernel slightly. )
99
100config STATIC_KEYS_SELFTEST
101 bool "Static key selftest"
102 depends on JUMP_LABEL
103 help
104 Boot time self-test of the branch patching code.
105
106config OPTPROBES
107 def_bool y
108 depends on KPROBES && HAVE_OPTPROBES
109 select TASKS_RCU if PREEMPTION
110
111config KPROBES_ON_FTRACE
112 def_bool y
113 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
114 depends on DYNAMIC_FTRACE_WITH_REGS
115 help
116 If function tracer is enabled and the arch supports full
117 passing of pt_regs to function tracing, then kprobes can
118 optimize on top of function tracing.
119
120config UPROBES
121 def_bool n
122 depends on ARCH_SUPPORTS_UPROBES
123 help
124 Uprobes is the user-space counterpart to kprobes: they
125 enable instrumentation applications (such as 'perf probe')
126 to establish unintrusive probes in user-space binaries and
127 libraries, by executing handler functions when the probes
128 are hit by user-space applications.
129
130 ( These probes come in the form of single-byte breakpoints,
131 managed by the kernel and kept transparent to the probed
132 application. )
133
134config HAVE_EFFICIENT_UNALIGNED_ACCESS
135 bool
136 help
137 Some architectures are unable to perform unaligned accesses
138 without the use of get_unaligned/put_unaligned. Others are
139 unable to perform such accesses efficiently (e.g. trap on
140 unaligned access and require fixing it up in the exception
141 handler.)
142
143 This symbol should be selected by an architecture if it can
144 perform unaligned accesses efficiently to allow different
145 code paths to be selected for these cases. Some network
146 drivers, for example, could opt to not fix up alignment
147 problems with received packets if doing so would not help
148 much.
149
150 See Documentation/unaligned-memory-access.txt for more
151 information on the topic of unaligned memory accesses.
152
153config ARCH_USE_BUILTIN_BSWAP
154 bool
155 help
156 Modern versions of GCC (since 4.4) have builtin functions
157 for handling byte-swapping. Using these, instead of the old
158 inline assembler that the architecture code provides in the
159 __arch_bswapXX() macros, allows the compiler to see what's
160 happening and offers more opportunity for optimisation. In
161 particular, the compiler will be able to combine the byteswap
162 with a nearby load or store and use load-and-swap or
163 store-and-swap instructions if the architecture has them. It
164 should almost *never* result in code which is worse than the
165 hand-coded assembler in <asm/swab.h>. But just in case it
166 does, the use of the builtins is optional.
167
168 Any architecture with load-and-swap or store-and-swap
169 instructions should set this. And it shouldn't hurt to set it
170 on architectures that don't have such instructions.
171
172config KRETPROBES
173 def_bool y
174 depends on KPROBES && HAVE_KRETPROBES
175
176config USER_RETURN_NOTIFIER
177 bool
178 depends on HAVE_USER_RETURN_NOTIFIER
179 help
180 Provide a kernel-internal notification when a cpu is about to
181 switch to user mode.
182
183config HAVE_IOREMAP_PROT
184 bool
185
186config HAVE_KPROBES
187 bool
188
189config HAVE_KRETPROBES
190 bool
191
192config HAVE_OPTPROBES
193 bool
194
195config HAVE_KPROBES_ON_FTRACE
196 bool
197
198config HAVE_FUNCTION_ERROR_INJECTION
199 bool
200
201config HAVE_NMI
202 bool
203
204#
205# An arch should select this if it provides all these things:
206#
207# task_pt_regs() in asm/processor.h or asm/ptrace.h
208# arch_has_single_step() if there is hardware single-step support
209# arch_has_block_step() if there is hardware block-step support
210# asm/syscall.h supplying asm-generic/syscall.h interface
211# linux/regset.h user_regset interfaces
212# CORE_DUMP_USE_REGSET #define'd in linux/elf.h
213# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit}
214# TIF_NOTIFY_RESUME calls tracehook_notify_resume()
215# signal delivery calls tracehook_signal_handler()
216#
217config HAVE_ARCH_TRACEHOOK
218 bool
219
220config HAVE_DMA_CONTIGUOUS
221 bool
222
223config GENERIC_SMP_IDLE_THREAD
224 bool
225
226config GENERIC_IDLE_POLL_SETUP
227 bool
228
229config ARCH_HAS_FORTIFY_SOURCE
230 bool
231 help
232 An architecture should select this when it can successfully
233 build and run with CONFIG_FORTIFY_SOURCE.
234
235#
236# Select if the arch provides a historic keepinit alias for the retain_initrd
237# command line option
238#
239config ARCH_HAS_KEEPINITRD
240 bool
241
242# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
243config ARCH_HAS_SET_MEMORY
244 bool
245
246# Select if arch has all set_direct_map_invalid/default() functions
247config ARCH_HAS_SET_DIRECT_MAP
248 bool
249
250#
251# Select if arch has an uncached kernel segment and provides the
252# uncached_kernel_address / cached_kernel_address symbols to use it
253#
254config ARCH_HAS_UNCACHED_SEGMENT
255 select ARCH_HAS_DMA_PREP_COHERENT
256 bool
257
258# Select if arch init_task must go in the __init_task_data section
259config ARCH_TASK_STRUCT_ON_STACK
260 bool
261
262# Select if arch has its private alloc_task_struct() function
263config ARCH_TASK_STRUCT_ALLOCATOR
264 bool
265
266config HAVE_ARCH_THREAD_STRUCT_WHITELIST
267 bool
268 depends on !ARCH_TASK_STRUCT_ALLOCATOR
269 help
270 An architecture should select this to provide hardened usercopy
271 knowledge about what region of the thread_struct should be
272 whitelisted for copying to userspace. Normally this is only the
273 FPU registers. Specifically, arch_thread_struct_whitelist()
274 should be implemented. Without this, the entire thread_struct
275 field in task_struct will be left whitelisted.
276
277# Select if arch has its private alloc_thread_stack() function
278config ARCH_THREAD_STACK_ALLOCATOR
279 bool
280
281# Select if arch wants to size task_struct dynamically via arch_task_struct_size:
282config ARCH_WANTS_DYNAMIC_TASK_STRUCT
283 bool
284
285config ARCH_32BIT_OFF_T
286 bool
287 depends on !64BIT
288 help
289 All new 32-bit architectures should have 64-bit off_t type on
290 userspace side which corresponds to the loff_t kernel type. This
291 is the requirement for modern ABIs. Some existing architectures
292 still support 32-bit off_t. This option is enabled for all such
293 architectures explicitly.
294
295config HAVE_ASM_MODVERSIONS
296 bool
297 help
298 This symbol should be selected by an architecure if it provides
299 <asm/asm-prototypes.h> to support the module versioning for symbols
300 exported from assembly code.
301
302config HAVE_REGS_AND_STACK_ACCESS_API
303 bool
304 help
305 This symbol should be selected by an architecure if it supports
306 the API needed to access registers and stack entries from pt_regs,
307 declared in asm/ptrace.h
308 For example the kprobes-based event tracer needs this API.
309
310config HAVE_RSEQ
311 bool
312 depends on HAVE_REGS_AND_STACK_ACCESS_API
313 help
314 This symbol should be selected by an architecture if it
315 supports an implementation of restartable sequences.
316
317config HAVE_FUNCTION_ARG_ACCESS_API
318 bool
319 help
320 This symbol should be selected by an architecure if it supports
321 the API needed to access function arguments from pt_regs,
322 declared in asm/ptrace.h
323
324config HAVE_CLK
325 bool
326 help
327 The <linux/clk.h> calls support software clock gating and
328 thus are a key power management tool on many systems.
329
330config HAVE_HW_BREAKPOINT
331 bool
332 depends on PERF_EVENTS
333
334config HAVE_MIXED_BREAKPOINTS_REGS
335 bool
336 depends on HAVE_HW_BREAKPOINT
337 help
338 Depending on the arch implementation of hardware breakpoints,
339 some of them have separate registers for data and instruction
340 breakpoints addresses, others have mixed registers to store
341 them but define the access type in a control register.
342 Select this option if your arch implements breakpoints under the
343 latter fashion.
344
345config HAVE_USER_RETURN_NOTIFIER
346 bool
347
348config HAVE_PERF_EVENTS_NMI
349 bool
350 help
351 System hardware can generate an NMI using the perf event
352 subsystem. Also has support for calculating CPU cycle events
353 to determine how many clock cycles in a given period.
354
355config HAVE_HARDLOCKUP_DETECTOR_PERF
356 bool
357 depends on HAVE_PERF_EVENTS_NMI
358 help
359 The arch chooses to use the generic perf-NMI-based hardlockup
360 detector. Must define HAVE_PERF_EVENTS_NMI.
361
362config HAVE_NMI_WATCHDOG
363 depends on HAVE_NMI
364 bool
365 help
366 The arch provides a low level NMI watchdog. It provides
367 asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
368
369config HAVE_HARDLOCKUP_DETECTOR_ARCH
370 bool
371 select HAVE_NMI_WATCHDOG
372 help
373 The arch chooses to provide its own hardlockup detector, which is
374 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
375 interfaces and parameters provided by hardlockup detector subsystem.
376
377config HAVE_PERF_REGS
378 bool
379 help
380 Support selective register dumps for perf events. This includes
381 bit-mapping of each registers and a unique architecture id.
382
383config HAVE_PERF_USER_STACK_DUMP
384 bool
385 help
386 Support user stack dumps for perf event samples. This needs
387 access to the user stack pointer which is not unified across
388 architectures.
389
390config HAVE_ARCH_JUMP_LABEL
391 bool
392
393config HAVE_ARCH_JUMP_LABEL_RELATIVE
394 bool
395
396config HAVE_RCU_TABLE_FREE
397 bool
398
399config HAVE_RCU_TABLE_NO_INVALIDATE
400 bool
401
402config HAVE_MMU_GATHER_PAGE_SIZE
403 bool
404
405config HAVE_MMU_GATHER_NO_GATHER
406 bool
407
408config ARCH_HAVE_NMI_SAFE_CMPXCHG
409 bool
410
411config HAVE_ALIGNED_STRUCT_PAGE
412 bool
413 help
414 This makes sure that struct pages are double word aligned and that
415 e.g. the SLUB allocator can perform double word atomic operations
416 on a struct page for better performance. However selecting this
417 might increase the size of a struct page by a word.
418
419config HAVE_CMPXCHG_LOCAL
420 bool
421
422config HAVE_CMPXCHG_DOUBLE
423 bool
424
425config ARCH_WEAK_RELEASE_ACQUIRE
426 bool
427
428config ARCH_WANT_IPC_PARSE_VERSION
429 bool
430
431config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
432 bool
433
434config ARCH_WANT_OLD_COMPAT_IPC
435 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
436 bool
437
438config HAVE_ARCH_SECCOMP_FILTER
439 bool
440 help
441 An arch should select this symbol if it provides all of these things:
442 - syscall_get_arch()
443 - syscall_get_arguments()
444 - syscall_rollback()
445 - syscall_set_return_value()
446 - SIGSYS siginfo_t support
447 - secure_computing is called from a ptrace_event()-safe context
448 - secure_computing return value is checked and a return value of -1
449 results in the system call being skipped immediately.
450 - seccomp syscall wired up
451
452config SECCOMP_FILTER
453 def_bool y
454 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
455 help
456 Enable tasks to build secure computing environments defined
457 in terms of Berkeley Packet Filter programs which implement
458 task-defined system call filtering polices.
459
460 See Documentation/userspace-api/seccomp_filter.rst for details.
461
462config HAVE_ARCH_STACKLEAK
463 bool
464 help
465 An architecture should select this if it has the code which
466 fills the used part of the kernel stack with the STACKLEAK_POISON
467 value before returning from system calls.
468
469config HAVE_STACKPROTECTOR
470 bool
471 help
472 An arch should select this symbol if:
473 - it has implemented a stack canary (e.g. __stack_chk_guard)
474
475config CC_HAS_STACKPROTECTOR_NONE
476 def_bool $(cc-option,-fno-stack-protector)
477
478config STACKPROTECTOR
479 bool "Stack Protector buffer overflow detection"
480 depends on HAVE_STACKPROTECTOR
481 depends on $(cc-option,-fstack-protector)
482 default y
483 help
484 This option turns on the "stack-protector" GCC feature. This
485 feature puts, at the beginning of functions, a canary value on
486 the stack just before the return address, and validates
487 the value just before actually returning. Stack based buffer
488 overflows (that need to overwrite this return address) now also
489 overwrite the canary, which gets detected and the attack is then
490 neutralized via a kernel panic.
491
492 Functions will have the stack-protector canary logic added if they
493 have an 8-byte or larger character array on the stack.
494
495 This feature requires gcc version 4.2 or above, or a distribution
496 gcc with the feature backported ("-fstack-protector").
497
498 On an x86 "defconfig" build, this feature adds canary checks to
499 about 3% of all kernel functions, which increases kernel code size
500 by about 0.3%.
501
502config STACKPROTECTOR_STRONG
503 bool "Strong Stack Protector"
504 depends on STACKPROTECTOR
505 depends on $(cc-option,-fstack-protector-strong)
506 default y
507 help
508 Functions will have the stack-protector canary logic added in any
509 of the following conditions:
510
511 - local variable's address used as part of the right hand side of an
512 assignment or function argument
513 - local variable is an array (or union containing an array),
514 regardless of array type or length
515 - uses register local variables
516
517 This feature requires gcc version 4.9 or above, or a distribution
518 gcc with the feature backported ("-fstack-protector-strong").
519
520 On an x86 "defconfig" build, this feature adds canary checks to
521 about 20% of all kernel functions, which increases the kernel code
522 size by about 2%.
523
524config HAVE_ARCH_WITHIN_STACK_FRAMES
525 bool
526 help
527 An architecture should select this if it can walk the kernel stack
528 frames to determine if an object is part of either the arguments
529 or local variables (i.e. that it excludes saved return addresses,
530 and similar) by implementing an inline arch_within_stack_frames(),
531 which is used by CONFIG_HARDENED_USERCOPY.
532
533config HAVE_CONTEXT_TRACKING
534 bool
535 help
536 Provide kernel/user boundaries probes necessary for subsystems
537 that need it, such as userspace RCU extended quiescent state.
538 Syscalls need to be wrapped inside user_exit()-user_enter() through
539 the slow path using TIF_NOHZ flag. Exceptions handlers must be
540 wrapped as well. Irqs are already protected inside
541 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
542 irq exit still need to be protected.
543
544config HAVE_VIRT_CPU_ACCOUNTING
545 bool
546
547config ARCH_HAS_SCALED_CPUTIME
548 bool
549
550config HAVE_VIRT_CPU_ACCOUNTING_GEN
551 bool
552 default y if 64BIT
553 help
554 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
555 Before enabling this option, arch code must be audited
556 to ensure there are no races in concurrent read/write of
557 cputime_t. For example, reading/writing 64-bit cputime_t on
558 some 32-bit arches may require multiple accesses, so proper
559 locking is needed to protect against concurrent accesses.
560
561
562config HAVE_IRQ_TIME_ACCOUNTING
563 bool
564 help
565 Archs need to ensure they use a high enough resolution clock to
566 support irq time accounting and then call enable_sched_clock_irqtime().
567
568config HAVE_MOVE_PMD
569 bool
570 help
571 Archs that select this are able to move page tables at the PMD level.
572
573config HAVE_ARCH_TRANSPARENT_HUGEPAGE
574 bool
575
576config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
577 bool
578
579config HAVE_ARCH_HUGE_VMAP
580 bool
581
582config ARCH_WANT_HUGE_PMD_SHARE
583 bool
584
585config HAVE_ARCH_SOFT_DIRTY
586 bool
587
588config HAVE_MOD_ARCH_SPECIFIC
589 bool
590 help
591 The arch uses struct mod_arch_specific to store data. Many arches
592 just need a simple module loader without arch specific data - those
593 should not enable this.
594
595config MODULES_USE_ELF_RELA
596 bool
597 help
598 Modules only use ELF RELA relocations. Modules with ELF REL
599 relocations will give an error.
600
601config MODULES_USE_ELF_REL
602 bool
603 help
604 Modules only use ELF REL relocations. Modules with ELF RELA
605 relocations will give an error.
606
607config HAVE_IRQ_EXIT_ON_IRQ_STACK
608 bool
609 help
610 Architecture doesn't only execute the irq handler on the irq stack
611 but also irq_exit(). This way we can process softirqs on this irq
612 stack instead of switching to a new one when we call __do_softirq()
613 in the end of an hardirq.
614 This spares a stack switch and improves cache usage on softirq
615 processing.
616
617config PGTABLE_LEVELS
618 int
619 default 2
620
621config ARCH_HAS_ELF_RANDOMIZE
622 bool
623 help
624 An architecture supports choosing randomized locations for
625 stack, mmap, brk, and ET_DYN. Defined functions:
626 - arch_mmap_rnd()
627 - arch_randomize_brk()
628
629config HAVE_ARCH_MMAP_RND_BITS
630 bool
631 help
632 An arch should select this symbol if it supports setting a variable
633 number of bits for use in establishing the base address for mmap
634 allocations, has MMU enabled and provides values for both:
635 - ARCH_MMAP_RND_BITS_MIN
636 - ARCH_MMAP_RND_BITS_MAX
637
638config HAVE_EXIT_THREAD
639 bool
640 help
641 An architecture implements exit_thread.
642
643config ARCH_MMAP_RND_BITS_MIN
644 int
645
646config ARCH_MMAP_RND_BITS_MAX
647 int
648
649config ARCH_MMAP_RND_BITS_DEFAULT
650 int
651
652config ARCH_MMAP_RND_BITS
653 int "Number of bits to use for ASLR of mmap base address" if EXPERT
654 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
655 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
656 default ARCH_MMAP_RND_BITS_MIN
657 depends on HAVE_ARCH_MMAP_RND_BITS
658 help
659 This value can be used to select the number of bits to use to
660 determine the random offset to the base address of vma regions
661 resulting from mmap allocations. This value will be bounded
662 by the architecture's minimum and maximum supported values.
663
664 This value can be changed after boot using the
665 /proc/sys/vm/mmap_rnd_bits tunable
666
667config HAVE_ARCH_MMAP_RND_COMPAT_BITS
668 bool
669 help
670 An arch should select this symbol if it supports running applications
671 in compatibility mode, supports setting a variable number of bits for
672 use in establishing the base address for mmap allocations, has MMU
673 enabled and provides values for both:
674 - ARCH_MMAP_RND_COMPAT_BITS_MIN
675 - ARCH_MMAP_RND_COMPAT_BITS_MAX
676
677config ARCH_MMAP_RND_COMPAT_BITS_MIN
678 int
679
680config ARCH_MMAP_RND_COMPAT_BITS_MAX
681 int
682
683config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
684 int
685
686config ARCH_MMAP_RND_COMPAT_BITS
687 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
688 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
689 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
690 default ARCH_MMAP_RND_COMPAT_BITS_MIN
691 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
692 help
693 This value can be used to select the number of bits to use to
694 determine the random offset to the base address of vma regions
695 resulting from mmap allocations for compatible applications This
696 value will be bounded by the architecture's minimum and maximum
697 supported values.
698
699 This value can be changed after boot using the
700 /proc/sys/vm/mmap_rnd_compat_bits tunable
701
702config HAVE_ARCH_COMPAT_MMAP_BASES
703 bool
704 help
705 This allows 64bit applications to invoke 32-bit mmap() syscall
706 and vice-versa 32-bit applications to call 64-bit mmap().
707 Required for applications doing different bitness syscalls.
708
709# This allows to use a set of generic functions to determine mmap base
710# address by giving priority to top-down scheme only if the process
711# is not in legacy mode (compat task, unlimited stack size or
712# sysctl_legacy_va_layout).
713# Architecture that selects this option can provide its own version of:
714# - STACK_RND_MASK
715config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
716 bool
717 depends on MMU
718 select ARCH_HAS_ELF_RANDOMIZE
719
720config HAVE_COPY_THREAD_TLS
721 bool
722 help
723 Architecture provides copy_thread_tls to accept tls argument via
724 normal C parameter passing, rather than extracting the syscall
725 argument from pt_regs.
726
727config HAVE_STACK_VALIDATION
728 bool
729 help
730 Architecture supports the 'objtool check' host tool command, which
731 performs compile-time stack metadata validation.
732
733config HAVE_RELIABLE_STACKTRACE
734 bool
735 help
736 Architecture has a save_stack_trace_tsk_reliable() function which
737 only returns a stack trace if it can guarantee the trace is reliable.
738
739config HAVE_ARCH_HASH
740 bool
741 default n
742 help
743 If this is set, the architecture provides an <asm/hash.h>
744 file which provides platform-specific implementations of some
745 functions in <linux/hash.h> or fs/namei.c.
746
747config HAVE_ARCH_NVRAM_OPS
748 bool
749
750config ISA_BUS_API
751 def_bool ISA
752
753#
754# ABI hall of shame
755#
756config CLONE_BACKWARDS
757 bool
758 help
759 Architecture has tls passed as the 4th argument of clone(2),
760 not the 5th one.
761
762config CLONE_BACKWARDS2
763 bool
764 help
765 Architecture has the first two arguments of clone(2) swapped.
766
767config CLONE_BACKWARDS3
768 bool
769 help
770 Architecture has tls passed as the 3rd argument of clone(2),
771 not the 5th one.
772
773config ODD_RT_SIGACTION
774 bool
775 help
776 Architecture has unusual rt_sigaction(2) arguments
777
778config OLD_SIGSUSPEND
779 bool
780 help
781 Architecture has old sigsuspend(2) syscall, of one-argument variety
782
783config OLD_SIGSUSPEND3
784 bool
785 help
786 Even weirder antique ABI - three-argument sigsuspend(2)
787
788config OLD_SIGACTION
789 bool
790 help
791 Architecture has old sigaction(2) syscall. Nope, not the same
792 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
793 but fairly different variant of sigaction(2), thanks to OSF/1
794 compatibility...
795
796config COMPAT_OLD_SIGACTION
797 bool
798
799config 64BIT_TIME
800 def_bool y
801 help
802 This should be selected by all architectures that need to support
803 new system calls with a 64-bit time_t. This is relevant on all 32-bit
804 architectures, and 64-bit architectures as part of compat syscall
805 handling.
806
807config COMPAT_32BIT_TIME
808 def_bool !64BIT || COMPAT
809 help
810 This enables 32 bit time_t support in addition to 64 bit time_t support.
811 This is relevant on all 32-bit architectures, and 64-bit architectures
812 as part of compat syscall handling.
813
814config ARCH_NO_PREEMPT
815 bool
816
817config ARCH_SUPPORTS_RT
818 bool
819
820config CPU_NO_EFFICIENT_FFS
821 def_bool n
822
823config HAVE_ARCH_VMAP_STACK
824 def_bool n
825 help
826 An arch should select this symbol if it can support kernel stacks
827 in vmalloc space. This means:
828
829 - vmalloc space must be large enough to hold many kernel stacks.
830 This may rule out many 32-bit architectures.
831
832 - Stacks in vmalloc space need to work reliably. For example, if
833 vmap page tables are created on demand, either this mechanism
834 needs to work while the stack points to a virtual address with
835 unpopulated page tables or arch code (switch_to() and switch_mm(),
836 most likely) needs to ensure that the stack's page table entries
837 are populated before running on a possibly unpopulated stack.
838
839 - If the stack overflows into a guard page, something reasonable
840 should happen. The definition of "reasonable" is flexible, but
841 instantly rebooting without logging anything would be unfriendly.
842
843config VMAP_STACK
844 default y
845 bool "Use a virtually-mapped stack"
846 depends on HAVE_ARCH_VMAP_STACK && !KASAN
847 ---help---
848 Enable this if you want the use virtually-mapped kernel stacks
849 with guard pages. This causes kernel stack overflows to be
850 caught immediately rather than causing difficult-to-diagnose
851 corruption.
852
853 This is presently incompatible with KASAN because KASAN expects
854 the stack to map directly to the KASAN shadow map using a formula
855 that is incorrect if the stack is in vmalloc space.
856
857config ARCH_OPTIONAL_KERNEL_RWX
858 def_bool n
859
860config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
861 def_bool n
862
863config ARCH_HAS_STRICT_KERNEL_RWX
864 def_bool n
865
866config STRICT_KERNEL_RWX
867 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
868 depends on ARCH_HAS_STRICT_KERNEL_RWX
869 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
870 help
871 If this is set, kernel text and rodata memory will be made read-only,
872 and non-text memory will be made non-executable. This provides
873 protection against certain security exploits (e.g. executing the heap
874 or modifying text)
875
876 These features are considered standard security practice these days.
877 You should say Y here in almost all cases.
878
879config ARCH_HAS_STRICT_MODULE_RWX
880 def_bool n
881
882config STRICT_MODULE_RWX
883 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
884 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
885 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
886 help
887 If this is set, module text and rodata memory will be made read-only,
888 and non-text memory will be made non-executable. This provides
889 protection against certain security exploits (e.g. writing to text)
890
891# select if the architecture provides an asm/dma-direct.h header
892config ARCH_HAS_PHYS_TO_DMA
893 bool
894
895config ARCH_HAS_REFCOUNT
896 bool
897 help
898 An architecture selects this when it has implemented refcount_t
899 using open coded assembly primitives that provide an optimized
900 refcount_t implementation, possibly at the expense of some full
901 refcount state checks of CONFIG_REFCOUNT_FULL=y.
902
903 The refcount overflow check behavior, however, must be retained.
904 Catching overflows is the primary security concern for protecting
905 against bugs in reference counts.
906
907config REFCOUNT_FULL
908 bool "Perform full reference count validation at the expense of speed"
909 help
910 Enabling this switches the refcounting infrastructure from a fast
911 unchecked atomic_t implementation to a fully state checked
912 implementation, which can be (slightly) slower but provides protections
913 against various use-after-free conditions that can be used in
914 security flaw exploits.
915
916config HAVE_ARCH_COMPILER_H
917 bool
918 help
919 An architecture can select this if it provides an
920 asm/compiler.h header that should be included after
921 linux/compiler-*.h in order to override macro definitions that those
922 headers generally provide.
923
924config HAVE_ARCH_PREL32_RELOCATIONS
925 bool
926 help
927 May be selected by an architecture if it supports place-relative
928 32-bit relocations, both in the toolchain and in the module loader,
929 in which case relative references can be used in special sections
930 for PCI fixup, initcalls etc which are only half the size on 64 bit
931 architectures, and don't require runtime relocation on relocatable
932 kernels.
933
934config ARCH_USE_MEMREMAP_PROT
935 bool
936
937config LOCK_EVENT_COUNTS
938 bool "Locking event counts collection"
939 depends on DEBUG_FS
940 ---help---
941 Enable light-weight counting of various locking related events
942 in the system with minimal performance impact. This reduces
943 the chance of application behavior change because of timing
944 differences. The counts are reported via debugfs.
945
946# Select if the architecture has support for applying RELR relocations.
947config ARCH_HAS_RELR
948 bool
949
950config RELR
951 bool "Use RELR relocation packing"
952 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
953 default y
954 help
955 Store the kernel's dynamic relocations in the RELR relocation packing
956 format. Requires a compatible linker (LLD supports this feature), as
957 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
958 are compatible).
959
960config ARCH_HAS_MEM_ENCRYPT
961 bool
962
963source "kernel/gcov/Kconfig"
964
965source "scripts/gcc-plugins/Kconfig"
966
967endmenu
1# SPDX-License-Identifier: GPL-2.0
2#
3# General architecture dependent options
4#
5
6#
7# Note: arch/$(SRCARCH)/Kconfig needs to be included first so that it can
8# override the default values in this file.
9#
10source "arch/$(SRCARCH)/Kconfig"
11
12menu "General architecture-dependent options"
13
14config ARCH_HAS_SUBPAGE_FAULTS
15 bool
16 help
17 Select if the architecture can check permissions at sub-page
18 granularity (e.g. arm64 MTE). The probe_user_*() functions
19 must be implemented.
20
21config HOTPLUG_SMT
22 bool
23
24config SMT_NUM_THREADS_DYNAMIC
25 bool
26
27# Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL
28config HOTPLUG_CORE_SYNC
29 bool
30
31# Basic CPU dead synchronization selected by architecture
32config HOTPLUG_CORE_SYNC_DEAD
33 bool
34 select HOTPLUG_CORE_SYNC
35
36# Full CPU synchronization with alive state selected by architecture
37config HOTPLUG_CORE_SYNC_FULL
38 bool
39 select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU
40 select HOTPLUG_CORE_SYNC
41
42config HOTPLUG_SPLIT_STARTUP
43 bool
44 select HOTPLUG_CORE_SYNC_FULL
45
46config HOTPLUG_PARALLEL
47 bool
48 select HOTPLUG_SPLIT_STARTUP
49
50config GENERIC_ENTRY
51 bool
52
53config KPROBES
54 bool "Kprobes"
55 depends on MODULES
56 depends on HAVE_KPROBES
57 select KALLSYMS
58 select TASKS_RCU if PREEMPTION
59 help
60 Kprobes allows you to trap at almost any kernel address and
61 execute a callback function. register_kprobe() establishes
62 a probepoint and specifies the callback. Kprobes is useful
63 for kernel debugging, non-intrusive instrumentation and testing.
64 If in doubt, say "N".
65
66config JUMP_LABEL
67 bool "Optimize very unlikely/likely branches"
68 depends on HAVE_ARCH_JUMP_LABEL
69 select OBJTOOL if HAVE_JUMP_LABEL_HACK
70 help
71 This option enables a transparent branch optimization that
72 makes certain almost-always-true or almost-always-false branch
73 conditions even cheaper to execute within the kernel.
74
75 Certain performance-sensitive kernel code, such as trace points,
76 scheduler functionality, networking code and KVM have such
77 branches and include support for this optimization technique.
78
79 If it is detected that the compiler has support for "asm goto",
80 the kernel will compile such branches with just a nop
81 instruction. When the condition flag is toggled to true, the
82 nop will be converted to a jump instruction to execute the
83 conditional block of instructions.
84
85 This technique lowers overhead and stress on the branch prediction
86 of the processor and generally makes the kernel faster. The update
87 of the condition is slower, but those are always very rare.
88
89 ( On 32-bit x86, the necessary options added to the compiler
90 flags may increase the size of the kernel slightly. )
91
92config STATIC_KEYS_SELFTEST
93 bool "Static key selftest"
94 depends on JUMP_LABEL
95 help
96 Boot time self-test of the branch patching code.
97
98config STATIC_CALL_SELFTEST
99 bool "Static call selftest"
100 depends on HAVE_STATIC_CALL
101 help
102 Boot time self-test of the call patching code.
103
104config OPTPROBES
105 def_bool y
106 depends on KPROBES && HAVE_OPTPROBES
107 select TASKS_RCU if PREEMPTION
108
109config KPROBES_ON_FTRACE
110 def_bool y
111 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
112 depends on DYNAMIC_FTRACE_WITH_REGS
113 help
114 If function tracer is enabled and the arch supports full
115 passing of pt_regs to function tracing, then kprobes can
116 optimize on top of function tracing.
117
118config UPROBES
119 def_bool n
120 depends on ARCH_SUPPORTS_UPROBES
121 help
122 Uprobes is the user-space counterpart to kprobes: they
123 enable instrumentation applications (such as 'perf probe')
124 to establish unintrusive probes in user-space binaries and
125 libraries, by executing handler functions when the probes
126 are hit by user-space applications.
127
128 ( These probes come in the form of single-byte breakpoints,
129 managed by the kernel and kept transparent to the probed
130 application. )
131
132config HAVE_64BIT_ALIGNED_ACCESS
133 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
134 help
135 Some architectures require 64 bit accesses to be 64 bit
136 aligned, which also requires structs containing 64 bit values
137 to be 64 bit aligned too. This includes some 32 bit
138 architectures which can do 64 bit accesses, as well as 64 bit
139 architectures without unaligned access.
140
141 This symbol should be selected by an architecture if 64 bit
142 accesses are required to be 64 bit aligned in this way even
143 though it is not a 64 bit architecture.
144
145 See Documentation/core-api/unaligned-memory-access.rst for
146 more information on the topic of unaligned memory accesses.
147
148config HAVE_EFFICIENT_UNALIGNED_ACCESS
149 bool
150 help
151 Some architectures are unable to perform unaligned accesses
152 without the use of get_unaligned/put_unaligned. Others are
153 unable to perform such accesses efficiently (e.g. trap on
154 unaligned access and require fixing it up in the exception
155 handler.)
156
157 This symbol should be selected by an architecture if it can
158 perform unaligned accesses efficiently to allow different
159 code paths to be selected for these cases. Some network
160 drivers, for example, could opt to not fix up alignment
161 problems with received packets if doing so would not help
162 much.
163
164 See Documentation/core-api/unaligned-memory-access.rst for more
165 information on the topic of unaligned memory accesses.
166
167config ARCH_USE_BUILTIN_BSWAP
168 bool
169 help
170 Modern versions of GCC (since 4.4) have builtin functions
171 for handling byte-swapping. Using these, instead of the old
172 inline assembler that the architecture code provides in the
173 __arch_bswapXX() macros, allows the compiler to see what's
174 happening and offers more opportunity for optimisation. In
175 particular, the compiler will be able to combine the byteswap
176 with a nearby load or store and use load-and-swap or
177 store-and-swap instructions if the architecture has them. It
178 should almost *never* result in code which is worse than the
179 hand-coded assembler in <asm/swab.h>. But just in case it
180 does, the use of the builtins is optional.
181
182 Any architecture with load-and-swap or store-and-swap
183 instructions should set this. And it shouldn't hurt to set it
184 on architectures that don't have such instructions.
185
186config KRETPROBES
187 def_bool y
188 depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK)
189
190config KRETPROBE_ON_RETHOOK
191 def_bool y
192 depends on HAVE_RETHOOK
193 depends on KRETPROBES
194 select RETHOOK
195
196config USER_RETURN_NOTIFIER
197 bool
198 depends on HAVE_USER_RETURN_NOTIFIER
199 help
200 Provide a kernel-internal notification when a cpu is about to
201 switch to user mode.
202
203config HAVE_IOREMAP_PROT
204 bool
205
206config HAVE_KPROBES
207 bool
208
209config HAVE_KRETPROBES
210 bool
211
212config HAVE_OPTPROBES
213 bool
214
215config HAVE_KPROBES_ON_FTRACE
216 bool
217
218config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
219 bool
220 help
221 Since kretprobes modifies return address on the stack, the
222 stacktrace may see the kretprobe trampoline address instead
223 of correct one. If the architecture stacktrace code and
224 unwinder can adjust such entries, select this configuration.
225
226config HAVE_FUNCTION_ERROR_INJECTION
227 bool
228
229config HAVE_NMI
230 bool
231
232config HAVE_FUNCTION_DESCRIPTORS
233 bool
234
235config TRACE_IRQFLAGS_SUPPORT
236 bool
237
238config TRACE_IRQFLAGS_NMI_SUPPORT
239 bool
240
241#
242# An arch should select this if it provides all these things:
243#
244# task_pt_regs() in asm/processor.h or asm/ptrace.h
245# arch_has_single_step() if there is hardware single-step support
246# arch_has_block_step() if there is hardware block-step support
247# asm/syscall.h supplying asm-generic/syscall.h interface
248# linux/regset.h user_regset interfaces
249# CORE_DUMP_USE_REGSET #define'd in linux/elf.h
250# TIF_SYSCALL_TRACE calls ptrace_report_syscall_{entry,exit}
251# TIF_NOTIFY_RESUME calls resume_user_mode_work()
252#
253config HAVE_ARCH_TRACEHOOK
254 bool
255
256config HAVE_DMA_CONTIGUOUS
257 bool
258
259config GENERIC_SMP_IDLE_THREAD
260 bool
261
262config GENERIC_IDLE_POLL_SETUP
263 bool
264
265config ARCH_HAS_FORTIFY_SOURCE
266 bool
267 help
268 An architecture should select this when it can successfully
269 build and run with CONFIG_FORTIFY_SOURCE.
270
271#
272# Select if the arch provides a historic keepinit alias for the retain_initrd
273# command line option
274#
275config ARCH_HAS_KEEPINITRD
276 bool
277
278# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
279config ARCH_HAS_SET_MEMORY
280 bool
281
282# Select if arch has all set_direct_map_invalid/default() functions
283config ARCH_HAS_SET_DIRECT_MAP
284 bool
285
286#
287# Select if the architecture provides the arch_dma_set_uncached symbol to
288# either provide an uncached segment alias for a DMA allocation, or
289# to remap the page tables in place.
290#
291config ARCH_HAS_DMA_SET_UNCACHED
292 bool
293
294#
295# Select if the architectures provides the arch_dma_clear_uncached symbol
296# to undo an in-place page table remap for uncached access.
297#
298config ARCH_HAS_DMA_CLEAR_UNCACHED
299 bool
300
301config ARCH_HAS_CPU_FINALIZE_INIT
302 bool
303
304# The architecture has a per-task state that includes the mm's PASID
305config ARCH_HAS_CPU_PASID
306 bool
307 select IOMMU_MM_DATA
308
309config HAVE_ARCH_THREAD_STRUCT_WHITELIST
310 bool
311 help
312 An architecture should select this to provide hardened usercopy
313 knowledge about what region of the thread_struct should be
314 whitelisted for copying to userspace. Normally this is only the
315 FPU registers. Specifically, arch_thread_struct_whitelist()
316 should be implemented. Without this, the entire thread_struct
317 field in task_struct will be left whitelisted.
318
319# Select if arch wants to size task_struct dynamically via arch_task_struct_size:
320config ARCH_WANTS_DYNAMIC_TASK_STRUCT
321 bool
322
323config ARCH_WANTS_NO_INSTR
324 bool
325 help
326 An architecture should select this if the noinstr macro is being used on
327 functions to denote that the toolchain should avoid instrumenting such
328 functions and is required for correctness.
329
330config ARCH_32BIT_OFF_T
331 bool
332 depends on !64BIT
333 help
334 All new 32-bit architectures should have 64-bit off_t type on
335 userspace side which corresponds to the loff_t kernel type. This
336 is the requirement for modern ABIs. Some existing architectures
337 still support 32-bit off_t. This option is enabled for all such
338 architectures explicitly.
339
340# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat
341config ARCH_32BIT_USTAT_F_TINODE
342 bool
343
344config HAVE_ASM_MODVERSIONS
345 bool
346 help
347 This symbol should be selected by an architecture if it provides
348 <asm/asm-prototypes.h> to support the module versioning for symbols
349 exported from assembly code.
350
351config HAVE_REGS_AND_STACK_ACCESS_API
352 bool
353 help
354 This symbol should be selected by an architecture if it supports
355 the API needed to access registers and stack entries from pt_regs,
356 declared in asm/ptrace.h
357 For example the kprobes-based event tracer needs this API.
358
359config HAVE_RSEQ
360 bool
361 depends on HAVE_REGS_AND_STACK_ACCESS_API
362 help
363 This symbol should be selected by an architecture if it
364 supports an implementation of restartable sequences.
365
366config HAVE_RUST
367 bool
368 help
369 This symbol should be selected by an architecture if it
370 supports Rust.
371
372config HAVE_FUNCTION_ARG_ACCESS_API
373 bool
374 help
375 This symbol should be selected by an architecture if it supports
376 the API needed to access function arguments from pt_regs,
377 declared in asm/ptrace.h
378
379config HAVE_HW_BREAKPOINT
380 bool
381 depends on PERF_EVENTS
382
383config HAVE_MIXED_BREAKPOINTS_REGS
384 bool
385 depends on HAVE_HW_BREAKPOINT
386 help
387 Depending on the arch implementation of hardware breakpoints,
388 some of them have separate registers for data and instruction
389 breakpoints addresses, others have mixed registers to store
390 them but define the access type in a control register.
391 Select this option if your arch implements breakpoints under the
392 latter fashion.
393
394config HAVE_USER_RETURN_NOTIFIER
395 bool
396
397config HAVE_PERF_EVENTS_NMI
398 bool
399 help
400 System hardware can generate an NMI using the perf event
401 subsystem. Also has support for calculating CPU cycle events
402 to determine how many clock cycles in a given period.
403
404config HAVE_HARDLOCKUP_DETECTOR_PERF
405 bool
406 depends on HAVE_PERF_EVENTS_NMI
407 help
408 The arch chooses to use the generic perf-NMI-based hardlockup
409 detector. Must define HAVE_PERF_EVENTS_NMI.
410
411config HAVE_HARDLOCKUP_DETECTOR_ARCH
412 bool
413 help
414 The arch provides its own hardlockup detector implementation instead
415 of the generic ones.
416
417 It uses the same command line parameters, and sysctl interface,
418 as the generic hardlockup detectors.
419
420config HAVE_PERF_REGS
421 bool
422 help
423 Support selective register dumps for perf events. This includes
424 bit-mapping of each registers and a unique architecture id.
425
426config HAVE_PERF_USER_STACK_DUMP
427 bool
428 help
429 Support user stack dumps for perf event samples. This needs
430 access to the user stack pointer which is not unified across
431 architectures.
432
433config HAVE_ARCH_JUMP_LABEL
434 bool
435
436config HAVE_ARCH_JUMP_LABEL_RELATIVE
437 bool
438
439config MMU_GATHER_TABLE_FREE
440 bool
441
442config MMU_GATHER_RCU_TABLE_FREE
443 bool
444 select MMU_GATHER_TABLE_FREE
445
446config MMU_GATHER_PAGE_SIZE
447 bool
448
449config MMU_GATHER_NO_RANGE
450 bool
451 select MMU_GATHER_MERGE_VMAS
452
453config MMU_GATHER_NO_FLUSH_CACHE
454 bool
455
456config MMU_GATHER_MERGE_VMAS
457 bool
458
459config MMU_GATHER_NO_GATHER
460 bool
461 depends on MMU_GATHER_TABLE_FREE
462
463config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
464 bool
465 help
466 Temporary select until all architectures can be converted to have
467 irqs disabled over activate_mm. Architectures that do IPI based TLB
468 shootdowns should enable this.
469
470# Use normal mm refcounting for MMU_LAZY_TLB kernel thread references.
471# MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching
472# to/from kernel threads when the same mm is running on a lot of CPUs (a large
473# multi-threaded application), by reducing contention on the mm refcount.
474#
475# This can be disabled if the architecture ensures no CPUs are using an mm as a
476# "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm
477# or its kernel page tables). This could be arranged by arch_exit_mmap(), or
478# final exit(2) TLB flush, for example.
479#
480# To implement this, an arch *must*:
481# Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating
482# the lazy tlb reference of a kthread's ->active_mm (non-arch code has been
483# converted already).
484config MMU_LAZY_TLB_REFCOUNT
485 def_bool y
486 depends on !MMU_LAZY_TLB_SHOOTDOWN
487
488# This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an
489# mm as a lazy tlb beyond its last reference count, by shooting down these
490# users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may
491# be using the mm as a lazy tlb, so that they may switch themselves to using
492# init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs
493# may be using mm as a lazy tlb mm.
494#
495# To implement this, an arch *must*:
496# - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains
497# at least all possible CPUs in which the mm is lazy.
498# - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above).
499config MMU_LAZY_TLB_SHOOTDOWN
500 bool
501
502config ARCH_HAVE_NMI_SAFE_CMPXCHG
503 bool
504
505config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
506 bool
507
508config HAVE_ALIGNED_STRUCT_PAGE
509 bool
510 help
511 This makes sure that struct pages are double word aligned and that
512 e.g. the SLUB allocator can perform double word atomic operations
513 on a struct page for better performance. However selecting this
514 might increase the size of a struct page by a word.
515
516config HAVE_CMPXCHG_LOCAL
517 bool
518
519config HAVE_CMPXCHG_DOUBLE
520 bool
521
522config ARCH_WEAK_RELEASE_ACQUIRE
523 bool
524
525config ARCH_WANT_IPC_PARSE_VERSION
526 bool
527
528config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
529 bool
530
531config ARCH_WANT_OLD_COMPAT_IPC
532 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
533 bool
534
535config HAVE_ARCH_SECCOMP
536 bool
537 help
538 An arch should select this symbol to support seccomp mode 1 (the fixed
539 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
540 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
541 - __NR_seccomp_read_32
542 - __NR_seccomp_write_32
543 - __NR_seccomp_exit_32
544 - __NR_seccomp_sigreturn_32
545
546config HAVE_ARCH_SECCOMP_FILTER
547 bool
548 select HAVE_ARCH_SECCOMP
549 help
550 An arch should select this symbol if it provides all of these things:
551 - all the requirements for HAVE_ARCH_SECCOMP
552 - syscall_get_arch()
553 - syscall_get_arguments()
554 - syscall_rollback()
555 - syscall_set_return_value()
556 - SIGSYS siginfo_t support
557 - secure_computing is called from a ptrace_event()-safe context
558 - secure_computing return value is checked and a return value of -1
559 results in the system call being skipped immediately.
560 - seccomp syscall wired up
561 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE,
562 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If
563 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too.
564
565config SECCOMP
566 prompt "Enable seccomp to safely execute untrusted bytecode"
567 def_bool y
568 depends on HAVE_ARCH_SECCOMP
569 help
570 This kernel feature is useful for number crunching applications
571 that may need to handle untrusted bytecode during their
572 execution. By using pipes or other transports made available
573 to the process as file descriptors supporting the read/write
574 syscalls, it's possible to isolate those applications in their
575 own address space using seccomp. Once seccomp is enabled via
576 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
577 disabled and the task is only allowed to execute a few safe
578 syscalls defined by each seccomp mode.
579
580 If unsure, say Y.
581
582config SECCOMP_FILTER
583 def_bool y
584 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
585 help
586 Enable tasks to build secure computing environments defined
587 in terms of Berkeley Packet Filter programs which implement
588 task-defined system call filtering polices.
589
590 See Documentation/userspace-api/seccomp_filter.rst for details.
591
592config SECCOMP_CACHE_DEBUG
593 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache"
594 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR
595 depends on PROC_FS
596 help
597 This enables the /proc/pid/seccomp_cache interface to monitor
598 seccomp cache data. The file format is subject to change. Reading
599 the file requires CAP_SYS_ADMIN.
600
601 This option is for debugging only. Enabling presents the risk that
602 an adversary may be able to infer the seccomp filter logic.
603
604 If unsure, say N.
605
606config HAVE_ARCH_STACKLEAK
607 bool
608 help
609 An architecture should select this if it has the code which
610 fills the used part of the kernel stack with the STACKLEAK_POISON
611 value before returning from system calls.
612
613config HAVE_STACKPROTECTOR
614 bool
615 help
616 An arch should select this symbol if:
617 - it has implemented a stack canary (e.g. __stack_chk_guard)
618
619config STACKPROTECTOR
620 bool "Stack Protector buffer overflow detection"
621 depends on HAVE_STACKPROTECTOR
622 depends on $(cc-option,-fstack-protector)
623 default y
624 help
625 This option turns on the "stack-protector" GCC feature. This
626 feature puts, at the beginning of functions, a canary value on
627 the stack just before the return address, and validates
628 the value just before actually returning. Stack based buffer
629 overflows (that need to overwrite this return address) now also
630 overwrite the canary, which gets detected and the attack is then
631 neutralized via a kernel panic.
632
633 Functions will have the stack-protector canary logic added if they
634 have an 8-byte or larger character array on the stack.
635
636 This feature requires gcc version 4.2 or above, or a distribution
637 gcc with the feature backported ("-fstack-protector").
638
639 On an x86 "defconfig" build, this feature adds canary checks to
640 about 3% of all kernel functions, which increases kernel code size
641 by about 0.3%.
642
643config STACKPROTECTOR_STRONG
644 bool "Strong Stack Protector"
645 depends on STACKPROTECTOR
646 depends on $(cc-option,-fstack-protector-strong)
647 default y
648 help
649 Functions will have the stack-protector canary logic added in any
650 of the following conditions:
651
652 - local variable's address used as part of the right hand side of an
653 assignment or function argument
654 - local variable is an array (or union containing an array),
655 regardless of array type or length
656 - uses register local variables
657
658 This feature requires gcc version 4.9 or above, or a distribution
659 gcc with the feature backported ("-fstack-protector-strong").
660
661 On an x86 "defconfig" build, this feature adds canary checks to
662 about 20% of all kernel functions, which increases the kernel code
663 size by about 2%.
664
665config ARCH_SUPPORTS_SHADOW_CALL_STACK
666 bool
667 help
668 An architecture should select this if it supports the compiler's
669 Shadow Call Stack and implements runtime support for shadow stack
670 switching.
671
672config SHADOW_CALL_STACK
673 bool "Shadow Call Stack"
674 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
675 depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
676 depends on MMU
677 help
678 This option enables the compiler's Shadow Call Stack, which
679 uses a shadow stack to protect function return addresses from
680 being overwritten by an attacker. More information can be found
681 in the compiler's documentation:
682
683 - Clang: https://clang.llvm.org/docs/ShadowCallStack.html
684 - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options
685
686 Note that security guarantees in the kernel differ from the
687 ones documented for user space. The kernel must store addresses
688 of shadow stacks in memory, which means an attacker capable of
689 reading and writing arbitrary memory may be able to locate them
690 and hijack control flow by modifying the stacks.
691
692config DYNAMIC_SCS
693 bool
694 help
695 Set by the arch code if it relies on code patching to insert the
696 shadow call stack push and pop instructions rather than on the
697 compiler.
698
699config LTO
700 bool
701 help
702 Selected if the kernel will be built using the compiler's LTO feature.
703
704config LTO_CLANG
705 bool
706 select LTO
707 help
708 Selected if the kernel will be built using Clang's LTO feature.
709
710config ARCH_SUPPORTS_LTO_CLANG
711 bool
712 help
713 An architecture should select this option if it supports:
714 - compiling with Clang,
715 - compiling inline assembly with Clang's integrated assembler,
716 - and linking with LLD.
717
718config ARCH_SUPPORTS_LTO_CLANG_THIN
719 bool
720 help
721 An architecture should select this option if it can support Clang's
722 ThinLTO mode.
723
724config HAS_LTO_CLANG
725 def_bool y
726 depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM
727 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
728 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
729 depends on ARCH_SUPPORTS_LTO_CLANG
730 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT
731 # https://github.com/ClangBuiltLinux/linux/issues/1721
732 depends on (!KASAN || KASAN_HW_TAGS || CLANG_VERSION >= 170000) || !DEBUG_INFO
733 depends on (!KCOV || CLANG_VERSION >= 170000) || !DEBUG_INFO
734 depends on !GCOV_KERNEL
735 help
736 The compiler and Kconfig options support building with Clang's
737 LTO.
738
739choice
740 prompt "Link Time Optimization (LTO)"
741 default LTO_NONE
742 help
743 This option enables Link Time Optimization (LTO), which allows the
744 compiler to optimize binaries globally.
745
746 If unsure, select LTO_NONE. Note that LTO is very resource-intensive
747 so it's disabled by default.
748
749config LTO_NONE
750 bool "None"
751 help
752 Build the kernel normally, without Link Time Optimization (LTO).
753
754config LTO_CLANG_FULL
755 bool "Clang Full LTO (EXPERIMENTAL)"
756 depends on HAS_LTO_CLANG
757 depends on !COMPILE_TEST
758 select LTO_CLANG
759 help
760 This option enables Clang's full Link Time Optimization (LTO), which
761 allows the compiler to optimize the kernel globally. If you enable
762 this option, the compiler generates LLVM bitcode instead of ELF
763 object files, and the actual compilation from bitcode happens at
764 the LTO link step, which may take several minutes depending on the
765 kernel configuration. More information can be found from LLVM's
766 documentation:
767
768 https://llvm.org/docs/LinkTimeOptimization.html
769
770 During link time, this option can use a large amount of RAM, and
771 may take much longer than the ThinLTO option.
772
773config LTO_CLANG_THIN
774 bool "Clang ThinLTO (EXPERIMENTAL)"
775 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN
776 select LTO_CLANG
777 help
778 This option enables Clang's ThinLTO, which allows for parallel
779 optimization and faster incremental compiles compared to the
780 CONFIG_LTO_CLANG_FULL option. More information can be found
781 from Clang's documentation:
782
783 https://clang.llvm.org/docs/ThinLTO.html
784
785 If unsure, say Y.
786endchoice
787
788config ARCH_SUPPORTS_CFI_CLANG
789 bool
790 help
791 An architecture should select this option if it can support Clang's
792 Control-Flow Integrity (CFI) checking.
793
794config ARCH_USES_CFI_TRAPS
795 bool
796
797config CFI_CLANG
798 bool "Use Clang's Control Flow Integrity (CFI)"
799 depends on ARCH_SUPPORTS_CFI_CLANG
800 depends on $(cc-option,-fsanitize=kcfi)
801 help
802 This option enables Clang’s forward-edge Control Flow Integrity
803 (CFI) checking, where the compiler injects a runtime check to each
804 indirect function call to ensure the target is a valid function with
805 the correct static type. This restricts possible call targets and
806 makes it more difficult for an attacker to exploit bugs that allow
807 the modification of stored function pointers. More information can be
808 found from Clang's documentation:
809
810 https://clang.llvm.org/docs/ControlFlowIntegrity.html
811
812config CFI_PERMISSIVE
813 bool "Use CFI in permissive mode"
814 depends on CFI_CLANG
815 help
816 When selected, Control Flow Integrity (CFI) violations result in a
817 warning instead of a kernel panic. This option should only be used
818 for finding indirect call type mismatches during development.
819
820 If unsure, say N.
821
822config HAVE_ARCH_WITHIN_STACK_FRAMES
823 bool
824 help
825 An architecture should select this if it can walk the kernel stack
826 frames to determine if an object is part of either the arguments
827 or local variables (i.e. that it excludes saved return addresses,
828 and similar) by implementing an inline arch_within_stack_frames(),
829 which is used by CONFIG_HARDENED_USERCOPY.
830
831config HAVE_CONTEXT_TRACKING_USER
832 bool
833 help
834 Provide kernel/user boundaries probes necessary for subsystems
835 that need it, such as userspace RCU extended quiescent state.
836 Syscalls need to be wrapped inside user_exit()-user_enter(), either
837 optimized behind static key or through the slow path using TIF_NOHZ
838 flag. Exceptions handlers must be wrapped as well. Irqs are already
839 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal
840 handling on irq exit still need to be protected.
841
842config HAVE_CONTEXT_TRACKING_USER_OFFSTACK
843 bool
844 help
845 Architecture neither relies on exception_enter()/exception_exit()
846 nor on schedule_user(). Also preempt_schedule_notrace() and
847 preempt_schedule_irq() can't be called in a preemptible section
848 while context tracking is CONTEXT_USER. This feature reflects a sane
849 entry implementation where the following requirements are met on
850 critical entry code, ie: before user_exit() or after user_enter():
851
852 - Critical entry code isn't preemptible (or better yet:
853 not interruptible).
854 - No use of RCU read side critical sections, unless ct_nmi_enter()
855 got called.
856 - No use of instrumentation, unless instrumentation_begin() got
857 called.
858
859config HAVE_TIF_NOHZ
860 bool
861 help
862 Arch relies on TIF_NOHZ and syscall slow path to implement context
863 tracking calls to user_enter()/user_exit().
864
865config HAVE_VIRT_CPU_ACCOUNTING
866 bool
867
868config HAVE_VIRT_CPU_ACCOUNTING_IDLE
869 bool
870 help
871 Architecture has its own way to account idle CPU time and therefore
872 doesn't implement vtime_account_idle().
873
874config ARCH_HAS_SCALED_CPUTIME
875 bool
876
877config HAVE_VIRT_CPU_ACCOUNTING_GEN
878 bool
879 default y if 64BIT
880 help
881 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
882 Before enabling this option, arch code must be audited
883 to ensure there are no races in concurrent read/write of
884 cputime_t. For example, reading/writing 64-bit cputime_t on
885 some 32-bit arches may require multiple accesses, so proper
886 locking is needed to protect against concurrent accesses.
887
888config HAVE_IRQ_TIME_ACCOUNTING
889 bool
890 help
891 Archs need to ensure they use a high enough resolution clock to
892 support irq time accounting and then call enable_sched_clock_irqtime().
893
894config HAVE_MOVE_PUD
895 bool
896 help
897 Architectures that select this are able to move page tables at the
898 PUD level. If there are only 3 page table levels, the move effectively
899 happens at the PGD level.
900
901config HAVE_MOVE_PMD
902 bool
903 help
904 Archs that select this are able to move page tables at the PMD level.
905
906config HAVE_ARCH_TRANSPARENT_HUGEPAGE
907 bool
908
909config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
910 bool
911
912config HAVE_ARCH_HUGE_VMAP
913 bool
914
915#
916# Archs that select this would be capable of PMD-sized vmaps (i.e.,
917# arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag
918# must be used to enable allocations to use hugepages.
919#
920config HAVE_ARCH_HUGE_VMALLOC
921 depends on HAVE_ARCH_HUGE_VMAP
922 bool
923
924config ARCH_WANT_HUGE_PMD_SHARE
925 bool
926
927# Archs that want to use pmd_mkwrite on kernel memory need it defined even
928# if there are no userspace memory management features that use it
929config ARCH_WANT_KERNEL_PMD_MKWRITE
930 bool
931
932config ARCH_WANT_PMD_MKWRITE
933 def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE
934
935config HAVE_ARCH_SOFT_DIRTY
936 bool
937
938config HAVE_MOD_ARCH_SPECIFIC
939 bool
940 help
941 The arch uses struct mod_arch_specific to store data. Many arches
942 just need a simple module loader without arch specific data - those
943 should not enable this.
944
945config MODULES_USE_ELF_RELA
946 bool
947 help
948 Modules only use ELF RELA relocations. Modules with ELF REL
949 relocations will give an error.
950
951config MODULES_USE_ELF_REL
952 bool
953 help
954 Modules only use ELF REL relocations. Modules with ELF RELA
955 relocations will give an error.
956
957config ARCH_WANTS_MODULES_DATA_IN_VMALLOC
958 bool
959 help
960 For architectures like powerpc/32 which have constraints on module
961 allocation and need to allocate module data outside of module area.
962
963config HAVE_IRQ_EXIT_ON_IRQ_STACK
964 bool
965 help
966 Architecture doesn't only execute the irq handler on the irq stack
967 but also irq_exit(). This way we can process softirqs on this irq
968 stack instead of switching to a new one when we call __do_softirq()
969 in the end of an hardirq.
970 This spares a stack switch and improves cache usage on softirq
971 processing.
972
973config HAVE_SOFTIRQ_ON_OWN_STACK
974 bool
975 help
976 Architecture provides a function to run __do_softirq() on a
977 separate stack.
978
979config SOFTIRQ_ON_OWN_STACK
980 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT
981
982config ALTERNATE_USER_ADDRESS_SPACE
983 bool
984 help
985 Architectures set this when the CPU uses separate address
986 spaces for kernel and user space pointers. In this case, the
987 access_ok() check on a __user pointer is skipped.
988
989config PGTABLE_LEVELS
990 int
991 default 2
992
993config ARCH_HAS_ELF_RANDOMIZE
994 bool
995 help
996 An architecture supports choosing randomized locations for
997 stack, mmap, brk, and ET_DYN. Defined functions:
998 - arch_mmap_rnd()
999 - arch_randomize_brk()
1000
1001config HAVE_ARCH_MMAP_RND_BITS
1002 bool
1003 help
1004 An arch should select this symbol if it supports setting a variable
1005 number of bits for use in establishing the base address for mmap
1006 allocations, has MMU enabled and provides values for both:
1007 - ARCH_MMAP_RND_BITS_MIN
1008 - ARCH_MMAP_RND_BITS_MAX
1009
1010config HAVE_EXIT_THREAD
1011 bool
1012 help
1013 An architecture implements exit_thread.
1014
1015config ARCH_MMAP_RND_BITS_MIN
1016 int
1017
1018config ARCH_MMAP_RND_BITS_MAX
1019 int
1020
1021config ARCH_MMAP_RND_BITS_DEFAULT
1022 int
1023
1024config ARCH_MMAP_RND_BITS
1025 int "Number of bits to use for ASLR of mmap base address" if EXPERT
1026 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
1027 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
1028 default ARCH_MMAP_RND_BITS_MIN
1029 depends on HAVE_ARCH_MMAP_RND_BITS
1030 help
1031 This value can be used to select the number of bits to use to
1032 determine the random offset to the base address of vma regions
1033 resulting from mmap allocations. This value will be bounded
1034 by the architecture's minimum and maximum supported values.
1035
1036 This value can be changed after boot using the
1037 /proc/sys/vm/mmap_rnd_bits tunable
1038
1039config HAVE_ARCH_MMAP_RND_COMPAT_BITS
1040 bool
1041 help
1042 An arch should select this symbol if it supports running applications
1043 in compatibility mode, supports setting a variable number of bits for
1044 use in establishing the base address for mmap allocations, has MMU
1045 enabled and provides values for both:
1046 - ARCH_MMAP_RND_COMPAT_BITS_MIN
1047 - ARCH_MMAP_RND_COMPAT_BITS_MAX
1048
1049config ARCH_MMAP_RND_COMPAT_BITS_MIN
1050 int
1051
1052config ARCH_MMAP_RND_COMPAT_BITS_MAX
1053 int
1054
1055config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
1056 int
1057
1058config ARCH_MMAP_RND_COMPAT_BITS
1059 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
1060 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
1061 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
1062 default ARCH_MMAP_RND_COMPAT_BITS_MIN
1063 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
1064 help
1065 This value can be used to select the number of bits to use to
1066 determine the random offset to the base address of vma regions
1067 resulting from mmap allocations for compatible applications This
1068 value will be bounded by the architecture's minimum and maximum
1069 supported values.
1070
1071 This value can be changed after boot using the
1072 /proc/sys/vm/mmap_rnd_compat_bits tunable
1073
1074config HAVE_ARCH_COMPAT_MMAP_BASES
1075 bool
1076 help
1077 This allows 64bit applications to invoke 32-bit mmap() syscall
1078 and vice-versa 32-bit applications to call 64-bit mmap().
1079 Required for applications doing different bitness syscalls.
1080
1081config PAGE_SIZE_LESS_THAN_64KB
1082 def_bool y
1083 depends on !ARM64_64K_PAGES
1084 depends on !PAGE_SIZE_64KB
1085 depends on !PARISC_PAGE_SIZE_64KB
1086 depends on PAGE_SIZE_LESS_THAN_256KB
1087
1088config PAGE_SIZE_LESS_THAN_256KB
1089 def_bool y
1090 depends on !PAGE_SIZE_256KB
1091
1092# This allows to use a set of generic functions to determine mmap base
1093# address by giving priority to top-down scheme only if the process
1094# is not in legacy mode (compat task, unlimited stack size or
1095# sysctl_legacy_va_layout).
1096# Architecture that selects this option can provide its own version of:
1097# - STACK_RND_MASK
1098config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
1099 bool
1100 depends on MMU
1101 select ARCH_HAS_ELF_RANDOMIZE
1102
1103config HAVE_OBJTOOL
1104 bool
1105
1106config HAVE_JUMP_LABEL_HACK
1107 bool
1108
1109config HAVE_NOINSTR_HACK
1110 bool
1111
1112config HAVE_NOINSTR_VALIDATION
1113 bool
1114
1115config HAVE_UACCESS_VALIDATION
1116 bool
1117 select OBJTOOL
1118
1119config HAVE_STACK_VALIDATION
1120 bool
1121 help
1122 Architecture supports objtool compile-time frame pointer rule
1123 validation.
1124
1125config HAVE_RELIABLE_STACKTRACE
1126 bool
1127 help
1128 Architecture has either save_stack_trace_tsk_reliable() or
1129 arch_stack_walk_reliable() function which only returns a stack trace
1130 if it can guarantee the trace is reliable.
1131
1132config HAVE_ARCH_HASH
1133 bool
1134 default n
1135 help
1136 If this is set, the architecture provides an <asm/hash.h>
1137 file which provides platform-specific implementations of some
1138 functions in <linux/hash.h> or fs/namei.c.
1139
1140config HAVE_ARCH_NVRAM_OPS
1141 bool
1142
1143config ISA_BUS_API
1144 def_bool ISA
1145
1146#
1147# ABI hall of shame
1148#
1149config CLONE_BACKWARDS
1150 bool
1151 help
1152 Architecture has tls passed as the 4th argument of clone(2),
1153 not the 5th one.
1154
1155config CLONE_BACKWARDS2
1156 bool
1157 help
1158 Architecture has the first two arguments of clone(2) swapped.
1159
1160config CLONE_BACKWARDS3
1161 bool
1162 help
1163 Architecture has tls passed as the 3rd argument of clone(2),
1164 not the 5th one.
1165
1166config ODD_RT_SIGACTION
1167 bool
1168 help
1169 Architecture has unusual rt_sigaction(2) arguments
1170
1171config OLD_SIGSUSPEND
1172 bool
1173 help
1174 Architecture has old sigsuspend(2) syscall, of one-argument variety
1175
1176config OLD_SIGSUSPEND3
1177 bool
1178 help
1179 Even weirder antique ABI - three-argument sigsuspend(2)
1180
1181config OLD_SIGACTION
1182 bool
1183 help
1184 Architecture has old sigaction(2) syscall. Nope, not the same
1185 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
1186 but fairly different variant of sigaction(2), thanks to OSF/1
1187 compatibility...
1188
1189config COMPAT_OLD_SIGACTION
1190 bool
1191
1192config COMPAT_32BIT_TIME
1193 bool "Provide system calls for 32-bit time_t"
1194 default !64BIT || COMPAT
1195 help
1196 This enables 32 bit time_t support in addition to 64 bit time_t support.
1197 This is relevant on all 32-bit architectures, and 64-bit architectures
1198 as part of compat syscall handling.
1199
1200config ARCH_NO_PREEMPT
1201 bool
1202
1203config ARCH_SUPPORTS_RT
1204 bool
1205
1206config CPU_NO_EFFICIENT_FFS
1207 def_bool n
1208
1209config HAVE_ARCH_VMAP_STACK
1210 def_bool n
1211 help
1212 An arch should select this symbol if it can support kernel stacks
1213 in vmalloc space. This means:
1214
1215 - vmalloc space must be large enough to hold many kernel stacks.
1216 This may rule out many 32-bit architectures.
1217
1218 - Stacks in vmalloc space need to work reliably. For example, if
1219 vmap page tables are created on demand, either this mechanism
1220 needs to work while the stack points to a virtual address with
1221 unpopulated page tables or arch code (switch_to() and switch_mm(),
1222 most likely) needs to ensure that the stack's page table entries
1223 are populated before running on a possibly unpopulated stack.
1224
1225 - If the stack overflows into a guard page, something reasonable
1226 should happen. The definition of "reasonable" is flexible, but
1227 instantly rebooting without logging anything would be unfriendly.
1228
1229config VMAP_STACK
1230 default y
1231 bool "Use a virtually-mapped stack"
1232 depends on HAVE_ARCH_VMAP_STACK
1233 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC
1234 help
1235 Enable this if you want the use virtually-mapped kernel stacks
1236 with guard pages. This causes kernel stack overflows to be
1237 caught immediately rather than causing difficult-to-diagnose
1238 corruption.
1239
1240 To use this with software KASAN modes, the architecture must support
1241 backing virtual mappings with real shadow memory, and KASAN_VMALLOC
1242 must be enabled.
1243
1244config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1245 def_bool n
1246 help
1247 An arch should select this symbol if it can support kernel stack
1248 offset randomization with calls to add_random_kstack_offset()
1249 during syscall entry and choose_random_kstack_offset() during
1250 syscall exit. Careful removal of -fstack-protector-strong and
1251 -fstack-protector should also be applied to the entry code and
1252 closely examined, as the artificial stack bump looks like an array
1253 to the compiler, so it will attempt to add canary checks regardless
1254 of the static branch state.
1255
1256config RANDOMIZE_KSTACK_OFFSET
1257 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT
1258 default y
1259 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1260 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000
1261 help
1262 The kernel stack offset can be randomized (after pt_regs) by
1263 roughly 5 bits of entropy, frustrating memory corruption
1264 attacks that depend on stack address determinism or
1265 cross-syscall address exposures.
1266
1267 The feature is controlled via the "randomize_kstack_offset=on/off"
1268 kernel boot param, and if turned off has zero overhead due to its use
1269 of static branches (see JUMP_LABEL).
1270
1271 If unsure, say Y.
1272
1273config RANDOMIZE_KSTACK_OFFSET_DEFAULT
1274 bool "Default state of kernel stack offset randomization"
1275 depends on RANDOMIZE_KSTACK_OFFSET
1276 help
1277 Kernel stack offset randomization is controlled by kernel boot param
1278 "randomize_kstack_offset=on/off", and this config chooses the default
1279 boot state.
1280
1281config ARCH_OPTIONAL_KERNEL_RWX
1282 def_bool n
1283
1284config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1285 def_bool n
1286
1287config ARCH_HAS_STRICT_KERNEL_RWX
1288 def_bool n
1289
1290config STRICT_KERNEL_RWX
1291 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
1292 depends on ARCH_HAS_STRICT_KERNEL_RWX
1293 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1294 help
1295 If this is set, kernel text and rodata memory will be made read-only,
1296 and non-text memory will be made non-executable. This provides
1297 protection against certain security exploits (e.g. executing the heap
1298 or modifying text)
1299
1300 These features are considered standard security practice these days.
1301 You should say Y here in almost all cases.
1302
1303config ARCH_HAS_STRICT_MODULE_RWX
1304 def_bool n
1305
1306config STRICT_MODULE_RWX
1307 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
1308 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
1309 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1310 help
1311 If this is set, module text and rodata memory will be made read-only,
1312 and non-text memory will be made non-executable. This provides
1313 protection against certain security exploits (e.g. writing to text)
1314
1315# select if the architecture provides an asm/dma-direct.h header
1316config ARCH_HAS_PHYS_TO_DMA
1317 bool
1318
1319config HAVE_ARCH_COMPILER_H
1320 bool
1321 help
1322 An architecture can select this if it provides an
1323 asm/compiler.h header that should be included after
1324 linux/compiler-*.h in order to override macro definitions that those
1325 headers generally provide.
1326
1327config HAVE_ARCH_PREL32_RELOCATIONS
1328 bool
1329 help
1330 May be selected by an architecture if it supports place-relative
1331 32-bit relocations, both in the toolchain and in the module loader,
1332 in which case relative references can be used in special sections
1333 for PCI fixup, initcalls etc which are only half the size on 64 bit
1334 architectures, and don't require runtime relocation on relocatable
1335 kernels.
1336
1337config ARCH_USE_MEMREMAP_PROT
1338 bool
1339
1340config LOCK_EVENT_COUNTS
1341 bool "Locking event counts collection"
1342 depends on DEBUG_FS
1343 help
1344 Enable light-weight counting of various locking related events
1345 in the system with minimal performance impact. This reduces
1346 the chance of application behavior change because of timing
1347 differences. The counts are reported via debugfs.
1348
1349# Select if the architecture has support for applying RELR relocations.
1350config ARCH_HAS_RELR
1351 bool
1352
1353config RELR
1354 bool "Use RELR relocation packing"
1355 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1356 default y
1357 help
1358 Store the kernel's dynamic relocations in the RELR relocation packing
1359 format. Requires a compatible linker (LLD supports this feature), as
1360 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1361 are compatible).
1362
1363config ARCH_HAS_MEM_ENCRYPT
1364 bool
1365
1366config ARCH_HAS_CC_PLATFORM
1367 bool
1368
1369config HAVE_SPARSE_SYSCALL_NR
1370 bool
1371 help
1372 An architecture should select this if its syscall numbering is sparse
1373 to save space. For example, MIPS architecture has a syscall array with
1374 entries at 4000, 5000 and 6000 locations. This option turns on syscall
1375 related optimizations for a given architecture.
1376
1377config ARCH_HAS_VDSO_DATA
1378 bool
1379
1380config HAVE_STATIC_CALL
1381 bool
1382
1383config HAVE_STATIC_CALL_INLINE
1384 bool
1385 depends on HAVE_STATIC_CALL
1386 select OBJTOOL
1387
1388config HAVE_PREEMPT_DYNAMIC
1389 bool
1390
1391config HAVE_PREEMPT_DYNAMIC_CALL
1392 bool
1393 depends on HAVE_STATIC_CALL
1394 select HAVE_PREEMPT_DYNAMIC
1395 help
1396 An architecture should select this if it can handle the preemption
1397 model being selected at boot time using static calls.
1398
1399 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a
1400 preemption function will be patched directly.
1401
1402 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any
1403 call to a preemption function will go through a trampoline, and the
1404 trampoline will be patched.
1405
1406 It is strongly advised to support inline static call to avoid any
1407 overhead.
1408
1409config HAVE_PREEMPT_DYNAMIC_KEY
1410 bool
1411 depends on HAVE_ARCH_JUMP_LABEL
1412 select HAVE_PREEMPT_DYNAMIC
1413 help
1414 An architecture should select this if it can handle the preemption
1415 model being selected at boot time using static keys.
1416
1417 Each preemption function will be given an early return based on a
1418 static key. This should have slightly lower overhead than non-inline
1419 static calls, as this effectively inlines each trampoline into the
1420 start of its callee. This may avoid redundant work, and may
1421 integrate better with CFI schemes.
1422
1423 This will have greater overhead than using inline static calls as
1424 the call to the preemption function cannot be entirely elided.
1425
1426config ARCH_WANT_LD_ORPHAN_WARN
1427 bool
1428 help
1429 An arch should select this symbol once all linker sections are explicitly
1430 included, size-asserted, or discarded in the linker scripts. This is
1431 important because we never want expected sections to be placed heuristically
1432 by the linker, since the locations of such sections can change between linker
1433 versions.
1434
1435config HAVE_ARCH_PFN_VALID
1436 bool
1437
1438config ARCH_SUPPORTS_DEBUG_PAGEALLOC
1439 bool
1440
1441config ARCH_SUPPORTS_PAGE_TABLE_CHECK
1442 bool
1443
1444config ARCH_SPLIT_ARG64
1445 bool
1446 help
1447 If a 32-bit architecture requires 64-bit arguments to be split into
1448 pairs of 32-bit arguments, select this option.
1449
1450config ARCH_HAS_ELFCORE_COMPAT
1451 bool
1452
1453config ARCH_HAS_PARANOID_L1D_FLUSH
1454 bool
1455
1456config ARCH_HAVE_TRACE_MMIO_ACCESS
1457 bool
1458
1459config DYNAMIC_SIGFRAME
1460 bool
1461
1462# Select, if arch has a named attribute group bound to NUMA device nodes.
1463config HAVE_ARCH_NODE_DEV_GROUP
1464 bool
1465
1466config ARCH_HAS_HW_PTE_YOUNG
1467 bool
1468 help
1469 Architectures that select this option are capable of setting the
1470 accessed bit in PTE entries when using them as part of linear address
1471 translations. Architectures that require runtime check should select
1472 this option and override arch_has_hw_pte_young().
1473
1474config ARCH_HAS_NONLEAF_PMD_YOUNG
1475 bool
1476 help
1477 Architectures that select this option are capable of setting the
1478 accessed bit in non-leaf PMD entries when using them as part of linear
1479 address translations. Page table walkers that clear the accessed bit
1480 may use this capability to reduce their search space.
1481
1482source "kernel/gcov/Kconfig"
1483
1484source "scripts/gcc-plugins/Kconfig"
1485
1486config FUNCTION_ALIGNMENT_4B
1487 bool
1488
1489config FUNCTION_ALIGNMENT_8B
1490 bool
1491
1492config FUNCTION_ALIGNMENT_16B
1493 bool
1494
1495config FUNCTION_ALIGNMENT_32B
1496 bool
1497
1498config FUNCTION_ALIGNMENT_64B
1499 bool
1500
1501config FUNCTION_ALIGNMENT
1502 int
1503 default 64 if FUNCTION_ALIGNMENT_64B
1504 default 32 if FUNCTION_ALIGNMENT_32B
1505 default 16 if FUNCTION_ALIGNMENT_16B
1506 default 8 if FUNCTION_ALIGNMENT_8B
1507 default 4 if FUNCTION_ALIGNMENT_4B
1508 default 0
1509
1510endmenu