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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
12config ARCH_CONFIGURES_CPU_MITIGATIONS
13 bool
14
15if !ARCH_CONFIGURES_CPU_MITIGATIONS
16config CPU_MITIGATIONS
17 def_bool y
18endif
19
20menu "General architecture-dependent options"
21
22config ARCH_HAS_SUBPAGE_FAULTS
23 bool
24 help
25 Select if the architecture can check permissions at sub-page
26 granularity (e.g. arm64 MTE). The probe_user_*() functions
27 must be implemented.
28
29config HOTPLUG_SMT
30 bool
31
32config SMT_NUM_THREADS_DYNAMIC
33 bool
34
35# Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL
36config HOTPLUG_CORE_SYNC
37 bool
38
39# Basic CPU dead synchronization selected by architecture
40config HOTPLUG_CORE_SYNC_DEAD
41 bool
42 select HOTPLUG_CORE_SYNC
43
44# Full CPU synchronization with alive state selected by architecture
45config HOTPLUG_CORE_SYNC_FULL
46 bool
47 select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU
48 select HOTPLUG_CORE_SYNC
49
50config HOTPLUG_SPLIT_STARTUP
51 bool
52 select HOTPLUG_CORE_SYNC_FULL
53
54config HOTPLUG_PARALLEL
55 bool
56 select HOTPLUG_SPLIT_STARTUP
57
58config GENERIC_ENTRY
59 bool
60
61config KPROBES
62 bool "Kprobes"
63 depends on MODULES
64 depends on HAVE_KPROBES
65 select KALLSYMS
66 select TASKS_RCU if PREEMPTION
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 select OBJTOOL if HAVE_JUMP_LABEL_HACK
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 STATIC_CALL_SELFTEST
107 bool "Static call selftest"
108 depends on HAVE_STATIC_CALL
109 help
110 Boot time self-test of the call patching code.
111
112config OPTPROBES
113 def_bool y
114 depends on KPROBES && HAVE_OPTPROBES
115 select TASKS_RCU if PREEMPTION
116
117config KPROBES_ON_FTRACE
118 def_bool y
119 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
120 depends on DYNAMIC_FTRACE_WITH_REGS
121 help
122 If function tracer is enabled and the arch supports full
123 passing of pt_regs to function tracing, then kprobes can
124 optimize on top of function tracing.
125
126config UPROBES
127 def_bool n
128 depends on ARCH_SUPPORTS_UPROBES
129 help
130 Uprobes is the user-space counterpart to kprobes: they
131 enable instrumentation applications (such as 'perf probe')
132 to establish unintrusive probes in user-space binaries and
133 libraries, by executing handler functions when the probes
134 are hit by user-space applications.
135
136 ( These probes come in the form of single-byte breakpoints,
137 managed by the kernel and kept transparent to the probed
138 application. )
139
140config HAVE_64BIT_ALIGNED_ACCESS
141 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
142 help
143 Some architectures require 64 bit accesses to be 64 bit
144 aligned, which also requires structs containing 64 bit values
145 to be 64 bit aligned too. This includes some 32 bit
146 architectures which can do 64 bit accesses, as well as 64 bit
147 architectures without unaligned access.
148
149 This symbol should be selected by an architecture if 64 bit
150 accesses are required to be 64 bit aligned in this way even
151 though it is not a 64 bit architecture.
152
153 See Documentation/core-api/unaligned-memory-access.rst for
154 more information on the topic of unaligned memory accesses.
155
156config HAVE_EFFICIENT_UNALIGNED_ACCESS
157 bool
158 help
159 Some architectures are unable to perform unaligned accesses
160 without the use of get_unaligned/put_unaligned. Others are
161 unable to perform such accesses efficiently (e.g. trap on
162 unaligned access and require fixing it up in the exception
163 handler.)
164
165 This symbol should be selected by an architecture if it can
166 perform unaligned accesses efficiently to allow different
167 code paths to be selected for these cases. Some network
168 drivers, for example, could opt to not fix up alignment
169 problems with received packets if doing so would not help
170 much.
171
172 See Documentation/core-api/unaligned-memory-access.rst for more
173 information on the topic of unaligned memory accesses.
174
175config ARCH_USE_BUILTIN_BSWAP
176 bool
177 help
178 Modern versions of GCC (since 4.4) have builtin functions
179 for handling byte-swapping. Using these, instead of the old
180 inline assembler that the architecture code provides in the
181 __arch_bswapXX() macros, allows the compiler to see what's
182 happening and offers more opportunity for optimisation. In
183 particular, the compiler will be able to combine the byteswap
184 with a nearby load or store and use load-and-swap or
185 store-and-swap instructions if the architecture has them. It
186 should almost *never* result in code which is worse than the
187 hand-coded assembler in <asm/swab.h>. But just in case it
188 does, the use of the builtins is optional.
189
190 Any architecture with load-and-swap or store-and-swap
191 instructions should set this. And it shouldn't hurt to set it
192 on architectures that don't have such instructions.
193
194config KRETPROBES
195 def_bool y
196 depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK)
197
198config KRETPROBE_ON_RETHOOK
199 def_bool y
200 depends on HAVE_RETHOOK
201 depends on KRETPROBES
202 select RETHOOK
203
204config USER_RETURN_NOTIFIER
205 bool
206 depends on HAVE_USER_RETURN_NOTIFIER
207 help
208 Provide a kernel-internal notification when a cpu is about to
209 switch to user mode.
210
211config HAVE_IOREMAP_PROT
212 bool
213
214config HAVE_KPROBES
215 bool
216
217config HAVE_KRETPROBES
218 bool
219
220config HAVE_OPTPROBES
221 bool
222
223config HAVE_KPROBES_ON_FTRACE
224 bool
225
226config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
227 bool
228 help
229 Since kretprobes modifies return address on the stack, the
230 stacktrace may see the kretprobe trampoline address instead
231 of correct one. If the architecture stacktrace code and
232 unwinder can adjust such entries, select this configuration.
233
234config HAVE_FUNCTION_ERROR_INJECTION
235 bool
236
237config HAVE_NMI
238 bool
239
240config HAVE_FUNCTION_DESCRIPTORS
241 bool
242
243config TRACE_IRQFLAGS_SUPPORT
244 bool
245
246config TRACE_IRQFLAGS_NMI_SUPPORT
247 bool
248
249#
250# An arch should select this if it provides all these things:
251#
252# task_pt_regs() in asm/processor.h or asm/ptrace.h
253# arch_has_single_step() if there is hardware single-step support
254# arch_has_block_step() if there is hardware block-step support
255# asm/syscall.h supplying asm-generic/syscall.h interface
256# linux/regset.h user_regset interfaces
257# CORE_DUMP_USE_REGSET #define'd in linux/elf.h
258# TIF_SYSCALL_TRACE calls ptrace_report_syscall_{entry,exit}
259# TIF_NOTIFY_RESUME calls resume_user_mode_work()
260#
261config HAVE_ARCH_TRACEHOOK
262 bool
263
264config HAVE_DMA_CONTIGUOUS
265 bool
266
267config GENERIC_SMP_IDLE_THREAD
268 bool
269
270config GENERIC_IDLE_POLL_SETUP
271 bool
272
273config ARCH_HAS_FORTIFY_SOURCE
274 bool
275 help
276 An architecture should select this when it can successfully
277 build and run with CONFIG_FORTIFY_SOURCE.
278
279#
280# Select if the arch provides a historic keepinit alias for the retain_initrd
281# command line option
282#
283config ARCH_HAS_KEEPINITRD
284 bool
285
286# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
287config ARCH_HAS_SET_MEMORY
288 bool
289
290# Select if arch has all set_direct_map_invalid/default() functions
291config ARCH_HAS_SET_DIRECT_MAP
292 bool
293
294#
295# Select if the architecture provides the arch_dma_set_uncached symbol to
296# either provide an uncached segment alias for a DMA allocation, or
297# to remap the page tables in place.
298#
299config ARCH_HAS_DMA_SET_UNCACHED
300 bool
301
302#
303# Select if the architectures provides the arch_dma_clear_uncached symbol
304# to undo an in-place page table remap for uncached access.
305#
306config ARCH_HAS_DMA_CLEAR_UNCACHED
307 bool
308
309config ARCH_HAS_CPU_FINALIZE_INIT
310 bool
311
312# The architecture has a per-task state that includes the mm's PASID
313config ARCH_HAS_CPU_PASID
314 bool
315 select IOMMU_MM_DATA
316
317config HAVE_ARCH_THREAD_STRUCT_WHITELIST
318 bool
319 help
320 An architecture should select this to provide hardened usercopy
321 knowledge about what region of the thread_struct should be
322 whitelisted for copying to userspace. Normally this is only the
323 FPU registers. Specifically, arch_thread_struct_whitelist()
324 should be implemented. Without this, the entire thread_struct
325 field in task_struct will be left whitelisted.
326
327# Select if arch wants to size task_struct dynamically via arch_task_struct_size:
328config ARCH_WANTS_DYNAMIC_TASK_STRUCT
329 bool
330
331config ARCH_WANTS_NO_INSTR
332 bool
333 help
334 An architecture should select this if the noinstr macro is being used on
335 functions to denote that the toolchain should avoid instrumenting such
336 functions and is required for correctness.
337
338config ARCH_32BIT_OFF_T
339 bool
340 depends on !64BIT
341 help
342 All new 32-bit architectures should have 64-bit off_t type on
343 userspace side which corresponds to the loff_t kernel type. This
344 is the requirement for modern ABIs. Some existing architectures
345 still support 32-bit off_t. This option is enabled for all such
346 architectures explicitly.
347
348# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat
349config ARCH_32BIT_USTAT_F_TINODE
350 bool
351
352config HAVE_ASM_MODVERSIONS
353 bool
354 help
355 This symbol should be selected by an architecture if it provides
356 <asm/asm-prototypes.h> to support the module versioning for symbols
357 exported from assembly code.
358
359config HAVE_REGS_AND_STACK_ACCESS_API
360 bool
361 help
362 This symbol should be selected by an architecture if it supports
363 the API needed to access registers and stack entries from pt_regs,
364 declared in asm/ptrace.h
365 For example the kprobes-based event tracer needs this API.
366
367config HAVE_RSEQ
368 bool
369 depends on HAVE_REGS_AND_STACK_ACCESS_API
370 help
371 This symbol should be selected by an architecture if it
372 supports an implementation of restartable sequences.
373
374config HAVE_RUST
375 bool
376 help
377 This symbol should be selected by an architecture if it
378 supports Rust.
379
380config HAVE_FUNCTION_ARG_ACCESS_API
381 bool
382 help
383 This symbol should be selected by an architecture if it supports
384 the API needed to access function arguments from pt_regs,
385 declared in asm/ptrace.h
386
387config HAVE_HW_BREAKPOINT
388 bool
389 depends on PERF_EVENTS
390
391config HAVE_MIXED_BREAKPOINTS_REGS
392 bool
393 depends on HAVE_HW_BREAKPOINT
394 help
395 Depending on the arch implementation of hardware breakpoints,
396 some of them have separate registers for data and instruction
397 breakpoints addresses, others have mixed registers to store
398 them but define the access type in a control register.
399 Select this option if your arch implements breakpoints under the
400 latter fashion.
401
402config HAVE_USER_RETURN_NOTIFIER
403 bool
404
405config HAVE_PERF_EVENTS_NMI
406 bool
407 help
408 System hardware can generate an NMI using the perf event
409 subsystem. Also has support for calculating CPU cycle events
410 to determine how many clock cycles in a given period.
411
412config HAVE_HARDLOCKUP_DETECTOR_PERF
413 bool
414 depends on HAVE_PERF_EVENTS_NMI
415 help
416 The arch chooses to use the generic perf-NMI-based hardlockup
417 detector. Must define HAVE_PERF_EVENTS_NMI.
418
419config HAVE_HARDLOCKUP_DETECTOR_ARCH
420 bool
421 help
422 The arch provides its own hardlockup detector implementation instead
423 of the generic ones.
424
425 It uses the same command line parameters, and sysctl interface,
426 as the generic hardlockup detectors.
427
428config HAVE_PERF_REGS
429 bool
430 help
431 Support selective register dumps for perf events. This includes
432 bit-mapping of each registers and a unique architecture id.
433
434config HAVE_PERF_USER_STACK_DUMP
435 bool
436 help
437 Support user stack dumps for perf event samples. This needs
438 access to the user stack pointer which is not unified across
439 architectures.
440
441config HAVE_ARCH_JUMP_LABEL
442 bool
443
444config HAVE_ARCH_JUMP_LABEL_RELATIVE
445 bool
446
447config MMU_GATHER_TABLE_FREE
448 bool
449
450config MMU_GATHER_RCU_TABLE_FREE
451 bool
452 select MMU_GATHER_TABLE_FREE
453
454config MMU_GATHER_PAGE_SIZE
455 bool
456
457config MMU_GATHER_NO_RANGE
458 bool
459 select MMU_GATHER_MERGE_VMAS
460
461config MMU_GATHER_NO_FLUSH_CACHE
462 bool
463
464config MMU_GATHER_MERGE_VMAS
465 bool
466
467config MMU_GATHER_NO_GATHER
468 bool
469 depends on MMU_GATHER_TABLE_FREE
470
471config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
472 bool
473 help
474 Temporary select until all architectures can be converted to have
475 irqs disabled over activate_mm. Architectures that do IPI based TLB
476 shootdowns should enable this.
477
478# Use normal mm refcounting for MMU_LAZY_TLB kernel thread references.
479# MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching
480# to/from kernel threads when the same mm is running on a lot of CPUs (a large
481# multi-threaded application), by reducing contention on the mm refcount.
482#
483# This can be disabled if the architecture ensures no CPUs are using an mm as a
484# "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm
485# or its kernel page tables). This could be arranged by arch_exit_mmap(), or
486# final exit(2) TLB flush, for example.
487#
488# To implement this, an arch *must*:
489# Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating
490# the lazy tlb reference of a kthread's ->active_mm (non-arch code has been
491# converted already).
492config MMU_LAZY_TLB_REFCOUNT
493 def_bool y
494 depends on !MMU_LAZY_TLB_SHOOTDOWN
495
496# This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an
497# mm as a lazy tlb beyond its last reference count, by shooting down these
498# users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may
499# be using the mm as a lazy tlb, so that they may switch themselves to using
500# init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs
501# may be using mm as a lazy tlb mm.
502#
503# To implement this, an arch *must*:
504# - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains
505# at least all possible CPUs in which the mm is lazy.
506# - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above).
507config MMU_LAZY_TLB_SHOOTDOWN
508 bool
509
510config ARCH_HAVE_NMI_SAFE_CMPXCHG
511 bool
512
513config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
514 bool
515
516config HAVE_ALIGNED_STRUCT_PAGE
517 bool
518 help
519 This makes sure that struct pages are double word aligned and that
520 e.g. the SLUB allocator can perform double word atomic operations
521 on a struct page for better performance. However selecting this
522 might increase the size of a struct page by a word.
523
524config HAVE_CMPXCHG_LOCAL
525 bool
526
527config HAVE_CMPXCHG_DOUBLE
528 bool
529
530config ARCH_WEAK_RELEASE_ACQUIRE
531 bool
532
533config ARCH_WANT_IPC_PARSE_VERSION
534 bool
535
536config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
537 bool
538
539config ARCH_WANT_OLD_COMPAT_IPC
540 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
541 bool
542
543config HAVE_ARCH_SECCOMP
544 bool
545 help
546 An arch should select this symbol to support seccomp mode 1 (the fixed
547 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
548 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
549 - __NR_seccomp_read_32
550 - __NR_seccomp_write_32
551 - __NR_seccomp_exit_32
552 - __NR_seccomp_sigreturn_32
553
554config HAVE_ARCH_SECCOMP_FILTER
555 bool
556 select HAVE_ARCH_SECCOMP
557 help
558 An arch should select this symbol if it provides all of these things:
559 - all the requirements for HAVE_ARCH_SECCOMP
560 - syscall_get_arch()
561 - syscall_get_arguments()
562 - syscall_rollback()
563 - syscall_set_return_value()
564 - SIGSYS siginfo_t support
565 - secure_computing is called from a ptrace_event()-safe context
566 - secure_computing return value is checked and a return value of -1
567 results in the system call being skipped immediately.
568 - seccomp syscall wired up
569 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE,
570 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If
571 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too.
572
573config SECCOMP
574 prompt "Enable seccomp to safely execute untrusted bytecode"
575 def_bool y
576 depends on HAVE_ARCH_SECCOMP
577 help
578 This kernel feature is useful for number crunching applications
579 that may need to handle untrusted bytecode during their
580 execution. By using pipes or other transports made available
581 to the process as file descriptors supporting the read/write
582 syscalls, it's possible to isolate those applications in their
583 own address space using seccomp. Once seccomp is enabled via
584 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
585 disabled and the task is only allowed to execute a few safe
586 syscalls defined by each seccomp mode.
587
588 If unsure, say Y.
589
590config SECCOMP_FILTER
591 def_bool y
592 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
593 help
594 Enable tasks to build secure computing environments defined
595 in terms of Berkeley Packet Filter programs which implement
596 task-defined system call filtering polices.
597
598 See Documentation/userspace-api/seccomp_filter.rst for details.
599
600config SECCOMP_CACHE_DEBUG
601 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache"
602 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR
603 depends on PROC_FS
604 help
605 This enables the /proc/pid/seccomp_cache interface to monitor
606 seccomp cache data. The file format is subject to change. Reading
607 the file requires CAP_SYS_ADMIN.
608
609 This option is for debugging only. Enabling presents the risk that
610 an adversary may be able to infer the seccomp filter logic.
611
612 If unsure, say N.
613
614config HAVE_ARCH_STACKLEAK
615 bool
616 help
617 An architecture should select this if it has the code which
618 fills the used part of the kernel stack with the STACKLEAK_POISON
619 value before returning from system calls.
620
621config HAVE_STACKPROTECTOR
622 bool
623 help
624 An arch should select this symbol if:
625 - it has implemented a stack canary (e.g. __stack_chk_guard)
626
627config STACKPROTECTOR
628 bool "Stack Protector buffer overflow detection"
629 depends on HAVE_STACKPROTECTOR
630 depends on $(cc-option,-fstack-protector)
631 default y
632 help
633 This option turns on the "stack-protector" GCC feature. This
634 feature puts, at the beginning of functions, a canary value on
635 the stack just before the return address, and validates
636 the value just before actually returning. Stack based buffer
637 overflows (that need to overwrite this return address) now also
638 overwrite the canary, which gets detected and the attack is then
639 neutralized via a kernel panic.
640
641 Functions will have the stack-protector canary logic added if they
642 have an 8-byte or larger character array on the stack.
643
644 This feature requires gcc version 4.2 or above, or a distribution
645 gcc with the feature backported ("-fstack-protector").
646
647 On an x86 "defconfig" build, this feature adds canary checks to
648 about 3% of all kernel functions, which increases kernel code size
649 by about 0.3%.
650
651config STACKPROTECTOR_STRONG
652 bool "Strong Stack Protector"
653 depends on STACKPROTECTOR
654 depends on $(cc-option,-fstack-protector-strong)
655 default y
656 help
657 Functions will have the stack-protector canary logic added in any
658 of the following conditions:
659
660 - local variable's address used as part of the right hand side of an
661 assignment or function argument
662 - local variable is an array (or union containing an array),
663 regardless of array type or length
664 - uses register local variables
665
666 This feature requires gcc version 4.9 or above, or a distribution
667 gcc with the feature backported ("-fstack-protector-strong").
668
669 On an x86 "defconfig" build, this feature adds canary checks to
670 about 20% of all kernel functions, which increases the kernel code
671 size by about 2%.
672
673config ARCH_SUPPORTS_SHADOW_CALL_STACK
674 bool
675 help
676 An architecture should select this if it supports the compiler's
677 Shadow Call Stack and implements runtime support for shadow stack
678 switching.
679
680config SHADOW_CALL_STACK
681 bool "Shadow Call Stack"
682 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
683 depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
684 depends on MMU
685 help
686 This option enables the compiler's Shadow Call Stack, which
687 uses a shadow stack to protect function return addresses from
688 being overwritten by an attacker. More information can be found
689 in the compiler's documentation:
690
691 - Clang: https://clang.llvm.org/docs/ShadowCallStack.html
692 - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options
693
694 Note that security guarantees in the kernel differ from the
695 ones documented for user space. The kernel must store addresses
696 of shadow stacks in memory, which means an attacker capable of
697 reading and writing arbitrary memory may be able to locate them
698 and hijack control flow by modifying the stacks.
699
700config DYNAMIC_SCS
701 bool
702 help
703 Set by the arch code if it relies on code patching to insert the
704 shadow call stack push and pop instructions rather than on the
705 compiler.
706
707config LTO
708 bool
709 help
710 Selected if the kernel will be built using the compiler's LTO feature.
711
712config LTO_CLANG
713 bool
714 select LTO
715 help
716 Selected if the kernel will be built using Clang's LTO feature.
717
718config ARCH_SUPPORTS_LTO_CLANG
719 bool
720 help
721 An architecture should select this option if it supports:
722 - compiling with Clang,
723 - compiling inline assembly with Clang's integrated assembler,
724 - and linking with LLD.
725
726config ARCH_SUPPORTS_LTO_CLANG_THIN
727 bool
728 help
729 An architecture should select this option if it can support Clang's
730 ThinLTO mode.
731
732config HAS_LTO_CLANG
733 def_bool y
734 depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM
735 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
736 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
737 depends on ARCH_SUPPORTS_LTO_CLANG
738 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT
739 # https://github.com/ClangBuiltLinux/linux/issues/1721
740 depends on (!KASAN || KASAN_HW_TAGS || CLANG_VERSION >= 170000) || !DEBUG_INFO
741 depends on (!KCOV || CLANG_VERSION >= 170000) || !DEBUG_INFO
742 depends on !GCOV_KERNEL
743 help
744 The compiler and Kconfig options support building with Clang's
745 LTO.
746
747choice
748 prompt "Link Time Optimization (LTO)"
749 default LTO_NONE
750 help
751 This option enables Link Time Optimization (LTO), which allows the
752 compiler to optimize binaries globally.
753
754 If unsure, select LTO_NONE. Note that LTO is very resource-intensive
755 so it's disabled by default.
756
757config LTO_NONE
758 bool "None"
759 help
760 Build the kernel normally, without Link Time Optimization (LTO).
761
762config LTO_CLANG_FULL
763 bool "Clang Full LTO (EXPERIMENTAL)"
764 depends on HAS_LTO_CLANG
765 depends on !COMPILE_TEST
766 select LTO_CLANG
767 help
768 This option enables Clang's full Link Time Optimization (LTO), which
769 allows the compiler to optimize the kernel globally. If you enable
770 this option, the compiler generates LLVM bitcode instead of ELF
771 object files, and the actual compilation from bitcode happens at
772 the LTO link step, which may take several minutes depending on the
773 kernel configuration. More information can be found from LLVM's
774 documentation:
775
776 https://llvm.org/docs/LinkTimeOptimization.html
777
778 During link time, this option can use a large amount of RAM, and
779 may take much longer than the ThinLTO option.
780
781config LTO_CLANG_THIN
782 bool "Clang ThinLTO (EXPERIMENTAL)"
783 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN
784 select LTO_CLANG
785 help
786 This option enables Clang's ThinLTO, which allows for parallel
787 optimization and faster incremental compiles compared to the
788 CONFIG_LTO_CLANG_FULL option. More information can be found
789 from Clang's documentation:
790
791 https://clang.llvm.org/docs/ThinLTO.html
792
793 If unsure, say Y.
794endchoice
795
796config ARCH_SUPPORTS_CFI_CLANG
797 bool
798 help
799 An architecture should select this option if it can support Clang's
800 Control-Flow Integrity (CFI) checking.
801
802config ARCH_USES_CFI_TRAPS
803 bool
804
805config CFI_CLANG
806 bool "Use Clang's Control Flow Integrity (CFI)"
807 depends on ARCH_SUPPORTS_CFI_CLANG
808 depends on $(cc-option,-fsanitize=kcfi)
809 help
810 This option enables Clang's forward-edge Control Flow Integrity
811 (CFI) checking, where the compiler injects a runtime check to each
812 indirect function call to ensure the target is a valid function with
813 the correct static type. This restricts possible call targets and
814 makes it more difficult for an attacker to exploit bugs that allow
815 the modification of stored function pointers. More information can be
816 found from Clang's documentation:
817
818 https://clang.llvm.org/docs/ControlFlowIntegrity.html
819
820config CFI_PERMISSIVE
821 bool "Use CFI in permissive mode"
822 depends on CFI_CLANG
823 help
824 When selected, Control Flow Integrity (CFI) violations result in a
825 warning instead of a kernel panic. This option should only be used
826 for finding indirect call type mismatches during development.
827
828 If unsure, say N.
829
830config HAVE_ARCH_WITHIN_STACK_FRAMES
831 bool
832 help
833 An architecture should select this if it can walk the kernel stack
834 frames to determine if an object is part of either the arguments
835 or local variables (i.e. that it excludes saved return addresses,
836 and similar) by implementing an inline arch_within_stack_frames(),
837 which is used by CONFIG_HARDENED_USERCOPY.
838
839config HAVE_CONTEXT_TRACKING_USER
840 bool
841 help
842 Provide kernel/user boundaries probes necessary for subsystems
843 that need it, such as userspace RCU extended quiescent state.
844 Syscalls need to be wrapped inside user_exit()-user_enter(), either
845 optimized behind static key or through the slow path using TIF_NOHZ
846 flag. Exceptions handlers must be wrapped as well. Irqs are already
847 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal
848 handling on irq exit still need to be protected.
849
850config HAVE_CONTEXT_TRACKING_USER_OFFSTACK
851 bool
852 help
853 Architecture neither relies on exception_enter()/exception_exit()
854 nor on schedule_user(). Also preempt_schedule_notrace() and
855 preempt_schedule_irq() can't be called in a preemptible section
856 while context tracking is CONTEXT_USER. This feature reflects a sane
857 entry implementation where the following requirements are met on
858 critical entry code, ie: before user_exit() or after user_enter():
859
860 - Critical entry code isn't preemptible (or better yet:
861 not interruptible).
862 - No use of RCU read side critical sections, unless ct_nmi_enter()
863 got called.
864 - No use of instrumentation, unless instrumentation_begin() got
865 called.
866
867config HAVE_TIF_NOHZ
868 bool
869 help
870 Arch relies on TIF_NOHZ and syscall slow path to implement context
871 tracking calls to user_enter()/user_exit().
872
873config HAVE_VIRT_CPU_ACCOUNTING
874 bool
875
876config HAVE_VIRT_CPU_ACCOUNTING_IDLE
877 bool
878 help
879 Architecture has its own way to account idle CPU time and therefore
880 doesn't implement vtime_account_idle().
881
882config ARCH_HAS_SCALED_CPUTIME
883 bool
884
885config HAVE_VIRT_CPU_ACCOUNTING_GEN
886 bool
887 default y if 64BIT
888 help
889 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
890 Before enabling this option, arch code must be audited
891 to ensure there are no races in concurrent read/write of
892 cputime_t. For example, reading/writing 64-bit cputime_t on
893 some 32-bit arches may require multiple accesses, so proper
894 locking is needed to protect against concurrent accesses.
895
896config HAVE_IRQ_TIME_ACCOUNTING
897 bool
898 help
899 Archs need to ensure they use a high enough resolution clock to
900 support irq time accounting and then call enable_sched_clock_irqtime().
901
902config HAVE_MOVE_PUD
903 bool
904 help
905 Architectures that select this are able to move page tables at the
906 PUD level. If there are only 3 page table levels, the move effectively
907 happens at the PGD level.
908
909config HAVE_MOVE_PMD
910 bool
911 help
912 Archs that select this are able to move page tables at the PMD level.
913
914config HAVE_ARCH_TRANSPARENT_HUGEPAGE
915 bool
916
917config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
918 bool
919
920config HAVE_ARCH_HUGE_VMAP
921 bool
922
923#
924# Archs that select this would be capable of PMD-sized vmaps (i.e.,
925# arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag
926# must be used to enable allocations to use hugepages.
927#
928config HAVE_ARCH_HUGE_VMALLOC
929 depends on HAVE_ARCH_HUGE_VMAP
930 bool
931
932config ARCH_WANT_HUGE_PMD_SHARE
933 bool
934
935# Archs that want to use pmd_mkwrite on kernel memory need it defined even
936# if there are no userspace memory management features that use it
937config ARCH_WANT_KERNEL_PMD_MKWRITE
938 bool
939
940config ARCH_WANT_PMD_MKWRITE
941 def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE
942
943config HAVE_ARCH_SOFT_DIRTY
944 bool
945
946config HAVE_MOD_ARCH_SPECIFIC
947 bool
948 help
949 The arch uses struct mod_arch_specific to store data. Many arches
950 just need a simple module loader without arch specific data - those
951 should not enable this.
952
953config MODULES_USE_ELF_RELA
954 bool
955 help
956 Modules only use ELF RELA relocations. Modules with ELF REL
957 relocations will give an error.
958
959config MODULES_USE_ELF_REL
960 bool
961 help
962 Modules only use ELF REL relocations. Modules with ELF RELA
963 relocations will give an error.
964
965config ARCH_WANTS_MODULES_DATA_IN_VMALLOC
966 bool
967 help
968 For architectures like powerpc/32 which have constraints on module
969 allocation and need to allocate module data outside of module area.
970
971config HAVE_IRQ_EXIT_ON_IRQ_STACK
972 bool
973 help
974 Architecture doesn't only execute the irq handler on the irq stack
975 but also irq_exit(). This way we can process softirqs on this irq
976 stack instead of switching to a new one when we call __do_softirq()
977 in the end of an hardirq.
978 This spares a stack switch and improves cache usage on softirq
979 processing.
980
981config HAVE_SOFTIRQ_ON_OWN_STACK
982 bool
983 help
984 Architecture provides a function to run __do_softirq() on a
985 separate stack.
986
987config SOFTIRQ_ON_OWN_STACK
988 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT
989
990config ALTERNATE_USER_ADDRESS_SPACE
991 bool
992 help
993 Architectures set this when the CPU uses separate address
994 spaces for kernel and user space pointers. In this case, the
995 access_ok() check on a __user pointer is skipped.
996
997config PGTABLE_LEVELS
998 int
999 default 2
1000
1001config ARCH_HAS_ELF_RANDOMIZE
1002 bool
1003 help
1004 An architecture supports choosing randomized locations for
1005 stack, mmap, brk, and ET_DYN. Defined functions:
1006 - arch_mmap_rnd()
1007 - arch_randomize_brk()
1008
1009config HAVE_ARCH_MMAP_RND_BITS
1010 bool
1011 help
1012 An arch should select this symbol if it supports setting a variable
1013 number of bits for use in establishing the base address for mmap
1014 allocations, has MMU enabled and provides values for both:
1015 - ARCH_MMAP_RND_BITS_MIN
1016 - ARCH_MMAP_RND_BITS_MAX
1017
1018config HAVE_EXIT_THREAD
1019 bool
1020 help
1021 An architecture implements exit_thread.
1022
1023config ARCH_MMAP_RND_BITS_MIN
1024 int
1025
1026config ARCH_MMAP_RND_BITS_MAX
1027 int
1028
1029config ARCH_MMAP_RND_BITS_DEFAULT
1030 int
1031
1032config ARCH_MMAP_RND_BITS
1033 int "Number of bits to use for ASLR of mmap base address" if EXPERT
1034 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
1035 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
1036 default ARCH_MMAP_RND_BITS_MIN
1037 depends on HAVE_ARCH_MMAP_RND_BITS
1038 help
1039 This value can be used to select the number of bits to use to
1040 determine the random offset to the base address of vma regions
1041 resulting from mmap allocations. This value will be bounded
1042 by the architecture's minimum and maximum supported values.
1043
1044 This value can be changed after boot using the
1045 /proc/sys/vm/mmap_rnd_bits tunable
1046
1047config HAVE_ARCH_MMAP_RND_COMPAT_BITS
1048 bool
1049 help
1050 An arch should select this symbol if it supports running applications
1051 in compatibility mode, supports setting a variable number of bits for
1052 use in establishing the base address for mmap allocations, has MMU
1053 enabled and provides values for both:
1054 - ARCH_MMAP_RND_COMPAT_BITS_MIN
1055 - ARCH_MMAP_RND_COMPAT_BITS_MAX
1056
1057config ARCH_MMAP_RND_COMPAT_BITS_MIN
1058 int
1059
1060config ARCH_MMAP_RND_COMPAT_BITS_MAX
1061 int
1062
1063config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
1064 int
1065
1066config ARCH_MMAP_RND_COMPAT_BITS
1067 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
1068 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
1069 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
1070 default ARCH_MMAP_RND_COMPAT_BITS_MIN
1071 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
1072 help
1073 This value can be used to select the number of bits to use to
1074 determine the random offset to the base address of vma regions
1075 resulting from mmap allocations for compatible applications This
1076 value will be bounded by the architecture's minimum and maximum
1077 supported values.
1078
1079 This value can be changed after boot using the
1080 /proc/sys/vm/mmap_rnd_compat_bits tunable
1081
1082config HAVE_ARCH_COMPAT_MMAP_BASES
1083 bool
1084 help
1085 This allows 64bit applications to invoke 32-bit mmap() syscall
1086 and vice-versa 32-bit applications to call 64-bit mmap().
1087 Required for applications doing different bitness syscalls.
1088
1089config HAVE_PAGE_SIZE_4KB
1090 bool
1091
1092config HAVE_PAGE_SIZE_8KB
1093 bool
1094
1095config HAVE_PAGE_SIZE_16KB
1096 bool
1097
1098config HAVE_PAGE_SIZE_32KB
1099 bool
1100
1101config HAVE_PAGE_SIZE_64KB
1102 bool
1103
1104config HAVE_PAGE_SIZE_256KB
1105 bool
1106
1107choice
1108 prompt "MMU page size"
1109
1110config PAGE_SIZE_4KB
1111 bool "4KiB pages"
1112 depends on HAVE_PAGE_SIZE_4KB
1113 help
1114 This option select the standard 4KiB Linux page size and the only
1115 available option on many architectures. Using 4KiB page size will
1116 minimize memory consumption and is therefore recommended for low
1117 memory systems.
1118 Some software that is written for x86 systems makes incorrect
1119 assumptions about the page size and only runs on 4KiB pages.
1120
1121config PAGE_SIZE_8KB
1122 bool "8KiB pages"
1123 depends on HAVE_PAGE_SIZE_8KB
1124 help
1125 This option is the only supported page size on a few older
1126 processors, and can be slightly faster than 4KiB pages.
1127
1128config PAGE_SIZE_16KB
1129 bool "16KiB pages"
1130 depends on HAVE_PAGE_SIZE_16KB
1131 help
1132 This option is usually a good compromise between memory
1133 consumption and performance for typical desktop and server
1134 workloads, often saving a level of page table lookups compared
1135 to 4KB pages as well as reducing TLB pressure and overhead of
1136 per-page operations in the kernel at the expense of a larger
1137 page cache.
1138
1139config PAGE_SIZE_32KB
1140 bool "32KiB pages"
1141 depends on HAVE_PAGE_SIZE_32KB
1142 help
1143 Using 32KiB page size will result in slightly higher performance
1144 kernel at the price of higher memory consumption compared to
1145 16KiB pages. This option is available only on cnMIPS cores.
1146 Note that you will need a suitable Linux distribution to
1147 support this.
1148
1149config PAGE_SIZE_64KB
1150 bool "64KiB pages"
1151 depends on HAVE_PAGE_SIZE_64KB
1152 help
1153 Using 64KiB page size will result in slightly higher performance
1154 kernel at the price of much higher memory consumption compared to
1155 4KiB or 16KiB pages.
1156 This is not suitable for general-purpose workloads but the
1157 better performance may be worth the cost for certain types of
1158 supercomputing or database applications that work mostly with
1159 large in-memory data rather than small files.
1160
1161config PAGE_SIZE_256KB
1162 bool "256KiB pages"
1163 depends on HAVE_PAGE_SIZE_256KB
1164 help
1165 256KiB pages have little practical value due to their extreme
1166 memory usage. The kernel will only be able to run applications
1167 that have been compiled with '-zmax-page-size' set to 256KiB
1168 (the default is 64KiB or 4KiB on most architectures).
1169
1170endchoice
1171
1172config PAGE_SIZE_LESS_THAN_64KB
1173 def_bool y
1174 depends on !PAGE_SIZE_64KB
1175 depends on PAGE_SIZE_LESS_THAN_256KB
1176
1177config PAGE_SIZE_LESS_THAN_256KB
1178 def_bool y
1179 depends on !PAGE_SIZE_256KB
1180
1181config PAGE_SHIFT
1182 int
1183 default 12 if PAGE_SIZE_4KB
1184 default 13 if PAGE_SIZE_8KB
1185 default 14 if PAGE_SIZE_16KB
1186 default 15 if PAGE_SIZE_32KB
1187 default 16 if PAGE_SIZE_64KB
1188 default 18 if PAGE_SIZE_256KB
1189
1190# This allows to use a set of generic functions to determine mmap base
1191# address by giving priority to top-down scheme only if the process
1192# is not in legacy mode (compat task, unlimited stack size or
1193# sysctl_legacy_va_layout).
1194# Architecture that selects this option can provide its own version of:
1195# - STACK_RND_MASK
1196config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
1197 bool
1198 depends on MMU
1199 select ARCH_HAS_ELF_RANDOMIZE
1200
1201config HAVE_OBJTOOL
1202 bool
1203
1204config HAVE_JUMP_LABEL_HACK
1205 bool
1206
1207config HAVE_NOINSTR_HACK
1208 bool
1209
1210config HAVE_NOINSTR_VALIDATION
1211 bool
1212
1213config HAVE_UACCESS_VALIDATION
1214 bool
1215 select OBJTOOL
1216
1217config HAVE_STACK_VALIDATION
1218 bool
1219 help
1220 Architecture supports objtool compile-time frame pointer rule
1221 validation.
1222
1223config HAVE_RELIABLE_STACKTRACE
1224 bool
1225 help
1226 Architecture has either save_stack_trace_tsk_reliable() or
1227 arch_stack_walk_reliable() function which only returns a stack trace
1228 if it can guarantee the trace is reliable.
1229
1230config HAVE_ARCH_HASH
1231 bool
1232 default n
1233 help
1234 If this is set, the architecture provides an <asm/hash.h>
1235 file which provides platform-specific implementations of some
1236 functions in <linux/hash.h> or fs/namei.c.
1237
1238config HAVE_ARCH_NVRAM_OPS
1239 bool
1240
1241config ISA_BUS_API
1242 def_bool ISA
1243
1244#
1245# ABI hall of shame
1246#
1247config CLONE_BACKWARDS
1248 bool
1249 help
1250 Architecture has tls passed as the 4th argument of clone(2),
1251 not the 5th one.
1252
1253config CLONE_BACKWARDS2
1254 bool
1255 help
1256 Architecture has the first two arguments of clone(2) swapped.
1257
1258config CLONE_BACKWARDS3
1259 bool
1260 help
1261 Architecture has tls passed as the 3rd argument of clone(2),
1262 not the 5th one.
1263
1264config ODD_RT_SIGACTION
1265 bool
1266 help
1267 Architecture has unusual rt_sigaction(2) arguments
1268
1269config OLD_SIGSUSPEND
1270 bool
1271 help
1272 Architecture has old sigsuspend(2) syscall, of one-argument variety
1273
1274config OLD_SIGSUSPEND3
1275 bool
1276 help
1277 Even weirder antique ABI - three-argument sigsuspend(2)
1278
1279config OLD_SIGACTION
1280 bool
1281 help
1282 Architecture has old sigaction(2) syscall. Nope, not the same
1283 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
1284 but fairly different variant of sigaction(2), thanks to OSF/1
1285 compatibility...
1286
1287config COMPAT_OLD_SIGACTION
1288 bool
1289
1290config COMPAT_32BIT_TIME
1291 bool "Provide system calls for 32-bit time_t"
1292 default !64BIT || COMPAT
1293 help
1294 This enables 32 bit time_t support in addition to 64 bit time_t support.
1295 This is relevant on all 32-bit architectures, and 64-bit architectures
1296 as part of compat syscall handling.
1297
1298config ARCH_NO_PREEMPT
1299 bool
1300
1301config ARCH_SUPPORTS_RT
1302 bool
1303
1304config CPU_NO_EFFICIENT_FFS
1305 def_bool n
1306
1307config HAVE_ARCH_VMAP_STACK
1308 def_bool n
1309 help
1310 An arch should select this symbol if it can support kernel stacks
1311 in vmalloc space. This means:
1312
1313 - vmalloc space must be large enough to hold many kernel stacks.
1314 This may rule out many 32-bit architectures.
1315
1316 - Stacks in vmalloc space need to work reliably. For example, if
1317 vmap page tables are created on demand, either this mechanism
1318 needs to work while the stack points to a virtual address with
1319 unpopulated page tables or arch code (switch_to() and switch_mm(),
1320 most likely) needs to ensure that the stack's page table entries
1321 are populated before running on a possibly unpopulated stack.
1322
1323 - If the stack overflows into a guard page, something reasonable
1324 should happen. The definition of "reasonable" is flexible, but
1325 instantly rebooting without logging anything would be unfriendly.
1326
1327config VMAP_STACK
1328 default y
1329 bool "Use a virtually-mapped stack"
1330 depends on HAVE_ARCH_VMAP_STACK
1331 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC
1332 help
1333 Enable this if you want the use virtually-mapped kernel stacks
1334 with guard pages. This causes kernel stack overflows to be
1335 caught immediately rather than causing difficult-to-diagnose
1336 corruption.
1337
1338 To use this with software KASAN modes, the architecture must support
1339 backing virtual mappings with real shadow memory, and KASAN_VMALLOC
1340 must be enabled.
1341
1342config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1343 def_bool n
1344 help
1345 An arch should select this symbol if it can support kernel stack
1346 offset randomization with calls to add_random_kstack_offset()
1347 during syscall entry and choose_random_kstack_offset() during
1348 syscall exit. Careful removal of -fstack-protector-strong and
1349 -fstack-protector should also be applied to the entry code and
1350 closely examined, as the artificial stack bump looks like an array
1351 to the compiler, so it will attempt to add canary checks regardless
1352 of the static branch state.
1353
1354config RANDOMIZE_KSTACK_OFFSET
1355 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT
1356 default y
1357 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1358 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000
1359 help
1360 The kernel stack offset can be randomized (after pt_regs) by
1361 roughly 5 bits of entropy, frustrating memory corruption
1362 attacks that depend on stack address determinism or
1363 cross-syscall address exposures.
1364
1365 The feature is controlled via the "randomize_kstack_offset=on/off"
1366 kernel boot param, and if turned off has zero overhead due to its use
1367 of static branches (see JUMP_LABEL).
1368
1369 If unsure, say Y.
1370
1371config RANDOMIZE_KSTACK_OFFSET_DEFAULT
1372 bool "Default state of kernel stack offset randomization"
1373 depends on RANDOMIZE_KSTACK_OFFSET
1374 help
1375 Kernel stack offset randomization is controlled by kernel boot param
1376 "randomize_kstack_offset=on/off", and this config chooses the default
1377 boot state.
1378
1379config ARCH_OPTIONAL_KERNEL_RWX
1380 def_bool n
1381
1382config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1383 def_bool n
1384
1385config ARCH_HAS_STRICT_KERNEL_RWX
1386 def_bool n
1387
1388config STRICT_KERNEL_RWX
1389 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
1390 depends on ARCH_HAS_STRICT_KERNEL_RWX
1391 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1392 help
1393 If this is set, kernel text and rodata memory will be made read-only,
1394 and non-text memory will be made non-executable. This provides
1395 protection against certain security exploits (e.g. executing the heap
1396 or modifying text)
1397
1398 These features are considered standard security practice these days.
1399 You should say Y here in almost all cases.
1400
1401config ARCH_HAS_STRICT_MODULE_RWX
1402 def_bool n
1403
1404config STRICT_MODULE_RWX
1405 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
1406 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
1407 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1408 help
1409 If this is set, module text and rodata memory will be made read-only,
1410 and non-text memory will be made non-executable. This provides
1411 protection against certain security exploits (e.g. writing to text)
1412
1413# select if the architecture provides an asm/dma-direct.h header
1414config ARCH_HAS_PHYS_TO_DMA
1415 bool
1416
1417config HAVE_ARCH_COMPILER_H
1418 bool
1419 help
1420 An architecture can select this if it provides an
1421 asm/compiler.h header that should be included after
1422 linux/compiler-*.h in order to override macro definitions that those
1423 headers generally provide.
1424
1425config HAVE_ARCH_PREL32_RELOCATIONS
1426 bool
1427 help
1428 May be selected by an architecture if it supports place-relative
1429 32-bit relocations, both in the toolchain and in the module loader,
1430 in which case relative references can be used in special sections
1431 for PCI fixup, initcalls etc which are only half the size on 64 bit
1432 architectures, and don't require runtime relocation on relocatable
1433 kernels.
1434
1435config ARCH_USE_MEMREMAP_PROT
1436 bool
1437
1438config LOCK_EVENT_COUNTS
1439 bool "Locking event counts collection"
1440 depends on DEBUG_FS
1441 help
1442 Enable light-weight counting of various locking related events
1443 in the system with minimal performance impact. This reduces
1444 the chance of application behavior change because of timing
1445 differences. The counts are reported via debugfs.
1446
1447# Select if the architecture has support for applying RELR relocations.
1448config ARCH_HAS_RELR
1449 bool
1450
1451config RELR
1452 bool "Use RELR relocation packing"
1453 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1454 default y
1455 help
1456 Store the kernel's dynamic relocations in the RELR relocation packing
1457 format. Requires a compatible linker (LLD supports this feature), as
1458 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1459 are compatible).
1460
1461config ARCH_HAS_MEM_ENCRYPT
1462 bool
1463
1464config ARCH_HAS_CC_PLATFORM
1465 bool
1466
1467config HAVE_SPARSE_SYSCALL_NR
1468 bool
1469 help
1470 An architecture should select this if its syscall numbering is sparse
1471 to save space. For example, MIPS architecture has a syscall array with
1472 entries at 4000, 5000 and 6000 locations. This option turns on syscall
1473 related optimizations for a given architecture.
1474
1475config ARCH_HAS_VDSO_DATA
1476 bool
1477
1478config HAVE_STATIC_CALL
1479 bool
1480
1481config HAVE_STATIC_CALL_INLINE
1482 bool
1483 depends on HAVE_STATIC_CALL
1484 select OBJTOOL
1485
1486config HAVE_PREEMPT_DYNAMIC
1487 bool
1488
1489config HAVE_PREEMPT_DYNAMIC_CALL
1490 bool
1491 depends on HAVE_STATIC_CALL
1492 select HAVE_PREEMPT_DYNAMIC
1493 help
1494 An architecture should select this if it can handle the preemption
1495 model being selected at boot time using static calls.
1496
1497 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a
1498 preemption function will be patched directly.
1499
1500 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any
1501 call to a preemption function will go through a trampoline, and the
1502 trampoline will be patched.
1503
1504 It is strongly advised to support inline static call to avoid any
1505 overhead.
1506
1507config HAVE_PREEMPT_DYNAMIC_KEY
1508 bool
1509 depends on HAVE_ARCH_JUMP_LABEL
1510 select HAVE_PREEMPT_DYNAMIC
1511 help
1512 An architecture should select this if it can handle the preemption
1513 model being selected at boot time using static keys.
1514
1515 Each preemption function will be given an early return based on a
1516 static key. This should have slightly lower overhead than non-inline
1517 static calls, as this effectively inlines each trampoline into the
1518 start of its callee. This may avoid redundant work, and may
1519 integrate better with CFI schemes.
1520
1521 This will have greater overhead than using inline static calls as
1522 the call to the preemption function cannot be entirely elided.
1523
1524config ARCH_WANT_LD_ORPHAN_WARN
1525 bool
1526 help
1527 An arch should select this symbol once all linker sections are explicitly
1528 included, size-asserted, or discarded in the linker scripts. This is
1529 important because we never want expected sections to be placed heuristically
1530 by the linker, since the locations of such sections can change between linker
1531 versions.
1532
1533config HAVE_ARCH_PFN_VALID
1534 bool
1535
1536config ARCH_SUPPORTS_DEBUG_PAGEALLOC
1537 bool
1538
1539config ARCH_SUPPORTS_PAGE_TABLE_CHECK
1540 bool
1541
1542config ARCH_SPLIT_ARG64
1543 bool
1544 help
1545 If a 32-bit architecture requires 64-bit arguments to be split into
1546 pairs of 32-bit arguments, select this option.
1547
1548config ARCH_HAS_ELFCORE_COMPAT
1549 bool
1550
1551config ARCH_HAS_PARANOID_L1D_FLUSH
1552 bool
1553
1554config ARCH_HAVE_TRACE_MMIO_ACCESS
1555 bool
1556
1557config DYNAMIC_SIGFRAME
1558 bool
1559
1560# Select, if arch has a named attribute group bound to NUMA device nodes.
1561config HAVE_ARCH_NODE_DEV_GROUP
1562 bool
1563
1564config ARCH_HAS_HW_PTE_YOUNG
1565 bool
1566 help
1567 Architectures that select this option are capable of setting the
1568 accessed bit in PTE entries when using them as part of linear address
1569 translations. Architectures that require runtime check should select
1570 this option and override arch_has_hw_pte_young().
1571
1572config ARCH_HAS_NONLEAF_PMD_YOUNG
1573 bool
1574 help
1575 Architectures that select this option are capable of setting the
1576 accessed bit in non-leaf PMD entries when using them as part of linear
1577 address translations. Page table walkers that clear the accessed bit
1578 may use this capability to reduce their search space.
1579
1580source "kernel/gcov/Kconfig"
1581
1582source "scripts/gcc-plugins/Kconfig"
1583
1584config FUNCTION_ALIGNMENT_4B
1585 bool
1586
1587config FUNCTION_ALIGNMENT_8B
1588 bool
1589
1590config FUNCTION_ALIGNMENT_16B
1591 bool
1592
1593config FUNCTION_ALIGNMENT_32B
1594 bool
1595
1596config FUNCTION_ALIGNMENT_64B
1597 bool
1598
1599config FUNCTION_ALIGNMENT
1600 int
1601 default 64 if FUNCTION_ALIGNMENT_64B
1602 default 32 if FUNCTION_ALIGNMENT_32B
1603 default 16 if FUNCTION_ALIGNMENT_16B
1604 default 8 if FUNCTION_ALIGNMENT_8B
1605 default 4 if FUNCTION_ALIGNMENT_4B
1606 default 0
1607
1608config CC_HAS_MIN_FUNCTION_ALIGNMENT
1609 # Detect availability of the GCC option -fmin-function-alignment which
1610 # guarantees minimal alignment for all functions, unlike
1611 # -falign-functions which the compiler ignores for cold functions.
1612 def_bool $(cc-option, -fmin-function-alignment=8)
1613
1614config CC_HAS_SANE_FUNCTION_ALIGNMENT
1615 # Set if the guaranteed alignment with -fmin-function-alignment is
1616 # available or extra care is required in the kernel. Clang provides
1617 # strict alignment always, even with -falign-functions.
1618 def_bool CC_HAS_MIN_FUNCTION_ALIGNMENT || CC_IS_CLANG
1619
1620endmenu