1 # SPDX-License-Identifier: GPL-2.0
3 # General architecture dependent options
7 # Note: arch/$(SRCARCH)/Kconfig needs to be included first so that it can
8 # override the default values in this file.
10 source "arch/$(SRCARCH)/Kconfig"
12 menu "General architecture-dependent options"
37 tristate "OProfile system profiling"
39 depends on HAVE_OPROFILE
41 select RING_BUFFER_ALLOW_SWAP
43 OProfile is a profiling system capable of profiling the
44 whole system, include the kernel, kernel modules, libraries,
49 config OPROFILE_EVENT_MULTIPLEX
50 bool "OProfile multiplexing support (EXPERIMENTAL)"
52 depends on OPROFILE && X86
54 The number of hardware counters is limited. The multiplexing
55 feature enables OProfile to gather more events than counters
56 are provided by the hardware. This is realized by switching
57 between events at a user specified time interval.
64 config OPROFILE_NMI_TIMER
66 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
71 depends on HAVE_KPROBES
74 Kprobes allows you to trap at almost any kernel address and
75 execute a callback function. register_kprobe() establishes
76 a probepoint and specifies the callback. Kprobes is useful
77 for kernel debugging, non-intrusive instrumentation and testing.
81 bool "Optimize very unlikely/likely branches"
82 depends on HAVE_ARCH_JUMP_LABEL
83 depends on CC_HAS_ASM_GOTO
85 This option enables a transparent branch optimization that
86 makes certain almost-always-true or almost-always-false branch
87 conditions even cheaper to execute within the kernel.
89 Certain performance-sensitive kernel code, such as trace points,
90 scheduler functionality, networking code and KVM have such
91 branches and include support for this optimization technique.
93 If it is detected that the compiler has support for "asm goto",
94 the kernel will compile such branches with just a nop
95 instruction. When the condition flag is toggled to true, the
96 nop will be converted to a jump instruction to execute the
97 conditional block of instructions.
99 This technique lowers overhead and stress on the branch prediction
100 of the processor and generally makes the kernel faster. The update
101 of the condition is slower, but those are always very rare.
103 ( On 32-bit x86, the necessary options added to the compiler
104 flags may increase the size of the kernel slightly. )
106 config STATIC_KEYS_SELFTEST
107 bool "Static key selftest"
108 depends on JUMP_LABEL
110 Boot time self-test of the branch patching code.
112 config STATIC_CALL_SELFTEST
113 bool "Static call selftest"
114 depends on HAVE_STATIC_CALL
116 Boot time self-test of the call patching code.
120 depends on KPROBES && HAVE_OPTPROBES
121 select TASKS_RCU if PREEMPTION
123 config KPROBES_ON_FTRACE
125 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
126 depends on DYNAMIC_FTRACE_WITH_REGS
128 If function tracer is enabled and the arch supports full
129 passing of pt_regs to function tracing, then kprobes can
130 optimize on top of function tracing.
134 depends on ARCH_SUPPORTS_UPROBES
136 Uprobes is the user-space counterpart to kprobes: they
137 enable instrumentation applications (such as 'perf probe')
138 to establish unintrusive probes in user-space binaries and
139 libraries, by executing handler functions when the probes
140 are hit by user-space applications.
142 ( These probes come in the form of single-byte breakpoints,
143 managed by the kernel and kept transparent to the probed
146 config HAVE_64BIT_ALIGNED_ACCESS
147 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
149 Some architectures require 64 bit accesses to be 64 bit
150 aligned, which also requires structs containing 64 bit values
151 to be 64 bit aligned too. This includes some 32 bit
152 architectures which can do 64 bit accesses, as well as 64 bit
153 architectures without unaligned access.
155 This symbol should be selected by an architecture if 64 bit
156 accesses are required to be 64 bit aligned in this way even
157 though it is not a 64 bit architecture.
159 See Documentation/unaligned-memory-access.txt for more
160 information on the topic of unaligned memory accesses.
162 config HAVE_EFFICIENT_UNALIGNED_ACCESS
165 Some architectures are unable to perform unaligned accesses
166 without the use of get_unaligned/put_unaligned. Others are
167 unable to perform such accesses efficiently (e.g. trap on
168 unaligned access and require fixing it up in the exception
171 This symbol should be selected by an architecture if it can
172 perform unaligned accesses efficiently to allow different
173 code paths to be selected for these cases. Some network
174 drivers, for example, could opt to not fix up alignment
175 problems with received packets if doing so would not help
178 See Documentation/core-api/unaligned-memory-access.rst for more
179 information on the topic of unaligned memory accesses.
181 config ARCH_USE_BUILTIN_BSWAP
184 Modern versions of GCC (since 4.4) have builtin functions
185 for handling byte-swapping. Using these, instead of the old
186 inline assembler that the architecture code provides in the
187 __arch_bswapXX() macros, allows the compiler to see what's
188 happening and offers more opportunity for optimisation. In
189 particular, the compiler will be able to combine the byteswap
190 with a nearby load or store and use load-and-swap or
191 store-and-swap instructions if the architecture has them. It
192 should almost *never* result in code which is worse than the
193 hand-coded assembler in <asm/swab.h>. But just in case it
194 does, the use of the builtins is optional.
196 Any architecture with load-and-swap or store-and-swap
197 instructions should set this. And it shouldn't hurt to set it
198 on architectures that don't have such instructions.
202 depends on KPROBES && HAVE_KRETPROBES
204 config USER_RETURN_NOTIFIER
206 depends on HAVE_USER_RETURN_NOTIFIER
208 Provide a kernel-internal notification when a cpu is about to
211 config HAVE_IOREMAP_PROT
217 config HAVE_KRETPROBES
220 config HAVE_OPTPROBES
223 config HAVE_KPROBES_ON_FTRACE
226 config HAVE_FUNCTION_ERROR_INJECTION
233 # An arch should select this if it provides all these things:
235 # task_pt_regs() in asm/processor.h or asm/ptrace.h
236 # arch_has_single_step() if there is hardware single-step support
237 # arch_has_block_step() if there is hardware block-step support
238 # asm/syscall.h supplying asm-generic/syscall.h interface
239 # linux/regset.h user_regset interfaces
240 # CORE_DUMP_USE_REGSET #define'd in linux/elf.h
241 # TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit}
242 # TIF_NOTIFY_RESUME calls tracehook_notify_resume()
243 # signal delivery calls tracehook_signal_handler()
245 config HAVE_ARCH_TRACEHOOK
248 config HAVE_DMA_CONTIGUOUS
251 config GENERIC_SMP_IDLE_THREAD
254 config GENERIC_IDLE_POLL_SETUP
257 config ARCH_HAS_FORTIFY_SOURCE
260 An architecture should select this when it can successfully
261 build and run with CONFIG_FORTIFY_SOURCE.
264 # Select if the arch provides a historic keepinit alias for the retain_initrd
265 # command line option
267 config ARCH_HAS_KEEPINITRD
270 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
271 config ARCH_HAS_SET_MEMORY
274 # Select if arch has all set_direct_map_invalid/default() functions
275 config ARCH_HAS_SET_DIRECT_MAP
279 # Select if the architecture provides the arch_dma_set_uncached symbol to
280 # either provide an uncached segement alias for a DMA allocation, or
281 # to remap the page tables in place.
283 config ARCH_HAS_DMA_SET_UNCACHED
287 # Select if the architectures provides the arch_dma_clear_uncached symbol
288 # to undo an in-place page table remap for uncached access.
290 config ARCH_HAS_DMA_CLEAR_UNCACHED
293 config ARCH_HAS_CPU_FINALIZE_INIT
296 # Select if arch init_task must go in the __init_task_data section
297 config ARCH_TASK_STRUCT_ON_STACK
300 # Select if arch has its private alloc_task_struct() function
301 config ARCH_TASK_STRUCT_ALLOCATOR
304 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
306 depends on !ARCH_TASK_STRUCT_ALLOCATOR
308 An architecture should select this to provide hardened usercopy
309 knowledge about what region of the thread_struct should be
310 whitelisted for copying to userspace. Normally this is only the
311 FPU registers. Specifically, arch_thread_struct_whitelist()
312 should be implemented. Without this, the entire thread_struct
313 field in task_struct will be left whitelisted.
315 # Select if arch has its private alloc_thread_stack() function
316 config ARCH_THREAD_STACK_ALLOCATOR
319 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
320 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
323 config ARCH_32BIT_OFF_T
327 All new 32-bit architectures should have 64-bit off_t type on
328 userspace side which corresponds to the loff_t kernel type. This
329 is the requirement for modern ABIs. Some existing architectures
330 still support 32-bit off_t. This option is enabled for all such
331 architectures explicitly.
333 config HAVE_ASM_MODVERSIONS
336 This symbol should be selected by an architecure if it provides
337 <asm/asm-prototypes.h> to support the module versioning for symbols
338 exported from assembly code.
340 config HAVE_REGS_AND_STACK_ACCESS_API
343 This symbol should be selected by an architecure if it supports
344 the API needed to access registers and stack entries from pt_regs,
345 declared in asm/ptrace.h
346 For example the kprobes-based event tracer needs this API.
350 depends on HAVE_REGS_AND_STACK_ACCESS_API
352 This symbol should be selected by an architecture if it
353 supports an implementation of restartable sequences.
355 config HAVE_FUNCTION_ARG_ACCESS_API
358 This symbol should be selected by an architecure if it supports
359 the API needed to access function arguments from pt_regs,
360 declared in asm/ptrace.h
362 config HAVE_HW_BREAKPOINT
364 depends on PERF_EVENTS
366 config HAVE_MIXED_BREAKPOINTS_REGS
368 depends on HAVE_HW_BREAKPOINT
370 Depending on the arch implementation of hardware breakpoints,
371 some of them have separate registers for data and instruction
372 breakpoints addresses, others have mixed registers to store
373 them but define the access type in a control register.
374 Select this option if your arch implements breakpoints under the
377 config HAVE_USER_RETURN_NOTIFIER
380 config HAVE_PERF_EVENTS_NMI
383 System hardware can generate an NMI using the perf event
384 subsystem. Also has support for calculating CPU cycle events
385 to determine how many clock cycles in a given period.
387 config HAVE_HARDLOCKUP_DETECTOR_PERF
389 depends on HAVE_PERF_EVENTS_NMI
391 The arch chooses to use the generic perf-NMI-based hardlockup
392 detector. Must define HAVE_PERF_EVENTS_NMI.
394 config HAVE_NMI_WATCHDOG
398 The arch provides a low level NMI watchdog. It provides
399 asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
401 config HAVE_HARDLOCKUP_DETECTOR_ARCH
403 select HAVE_NMI_WATCHDOG
405 The arch chooses to provide its own hardlockup detector, which is
406 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
407 interfaces and parameters provided by hardlockup detector subsystem.
409 config HAVE_PERF_REGS
412 Support selective register dumps for perf events. This includes
413 bit-mapping of each registers and a unique architecture id.
415 config HAVE_PERF_USER_STACK_DUMP
418 Support user stack dumps for perf event samples. This needs
419 access to the user stack pointer which is not unified across
422 config HAVE_ARCH_JUMP_LABEL
425 config HAVE_ARCH_JUMP_LABEL_RELATIVE
428 config MMU_GATHER_TABLE_FREE
431 config MMU_GATHER_RCU_TABLE_FREE
433 select MMU_GATHER_TABLE_FREE
435 config MMU_GATHER_PAGE_SIZE
438 config MMU_GATHER_NO_RANGE
441 config MMU_GATHER_NO_GATHER
443 depends on MMU_GATHER_TABLE_FREE
445 config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
448 Temporary select until all architectures can be converted to have
449 irqs disabled over activate_mm. Architectures that do IPI based TLB
450 shootdowns should enable this.
452 config ARCH_HAVE_NMI_SAFE_CMPXCHG
455 config HAVE_ALIGNED_STRUCT_PAGE
458 This makes sure that struct pages are double word aligned and that
459 e.g. the SLUB allocator can perform double word atomic operations
460 on a struct page for better performance. However selecting this
461 might increase the size of a struct page by a word.
463 config HAVE_CMPXCHG_LOCAL
466 config HAVE_CMPXCHG_DOUBLE
469 config ARCH_WEAK_RELEASE_ACQUIRE
472 config ARCH_WANT_IPC_PARSE_VERSION
475 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
478 config ARCH_WANT_OLD_COMPAT_IPC
479 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
482 config HAVE_ARCH_SECCOMP
485 An arch should select this symbol to support seccomp mode 1 (the fixed
486 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
487 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
488 - __NR_seccomp_read_32
489 - __NR_seccomp_write_32
490 - __NR_seccomp_exit_32
491 - __NR_seccomp_sigreturn_32
493 config HAVE_ARCH_SECCOMP_FILTER
495 select HAVE_ARCH_SECCOMP
497 An arch should select this symbol if it provides all of these things:
498 - all the requirements for HAVE_ARCH_SECCOMP
500 - syscall_get_arguments()
502 - syscall_set_return_value()
503 - SIGSYS siginfo_t support
504 - secure_computing is called from a ptrace_event()-safe context
505 - secure_computing return value is checked and a return value of -1
506 results in the system call being skipped immediately.
507 - seccomp syscall wired up
510 prompt "Enable seccomp to safely execute untrusted bytecode"
512 depends on HAVE_ARCH_SECCOMP
514 This kernel feature is useful for number crunching applications
515 that may need to handle untrusted bytecode during their
516 execution. By using pipes or other transports made available
517 to the process as file descriptors supporting the read/write
518 syscalls, it's possible to isolate those applications in their
519 own address space using seccomp. Once seccomp is enabled via
520 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
521 disabled and the task is only allowed to execute a few safe
522 syscalls defined by each seccomp mode.
526 config SECCOMP_FILTER
528 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
530 Enable tasks to build secure computing environments defined
531 in terms of Berkeley Packet Filter programs which implement
532 task-defined system call filtering polices.
534 See Documentation/userspace-api/seccomp_filter.rst for details.
536 config HAVE_ARCH_STACKLEAK
539 An architecture should select this if it has the code which
540 fills the used part of the kernel stack with the STACKLEAK_POISON
541 value before returning from system calls.
543 config HAVE_STACKPROTECTOR
546 An arch should select this symbol if:
547 - it has implemented a stack canary (e.g. __stack_chk_guard)
549 config STACKPROTECTOR
550 bool "Stack Protector buffer overflow detection"
551 depends on HAVE_STACKPROTECTOR
552 depends on $(cc-option,-fstack-protector)
555 This option turns on the "stack-protector" GCC feature. This
556 feature puts, at the beginning of functions, a canary value on
557 the stack just before the return address, and validates
558 the value just before actually returning. Stack based buffer
559 overflows (that need to overwrite this return address) now also
560 overwrite the canary, which gets detected and the attack is then
561 neutralized via a kernel panic.
563 Functions will have the stack-protector canary logic added if they
564 have an 8-byte or larger character array on the stack.
566 This feature requires gcc version 4.2 or above, or a distribution
567 gcc with the feature backported ("-fstack-protector").
569 On an x86 "defconfig" build, this feature adds canary checks to
570 about 3% of all kernel functions, which increases kernel code size
573 config STACKPROTECTOR_STRONG
574 bool "Strong Stack Protector"
575 depends on STACKPROTECTOR
576 depends on $(cc-option,-fstack-protector-strong)
579 Functions will have the stack-protector canary logic added in any
580 of the following conditions:
582 - local variable's address used as part of the right hand side of an
583 assignment or function argument
584 - local variable is an array (or union containing an array),
585 regardless of array type or length
586 - uses register local variables
588 This feature requires gcc version 4.9 or above, or a distribution
589 gcc with the feature backported ("-fstack-protector-strong").
591 On an x86 "defconfig" build, this feature adds canary checks to
592 about 20% of all kernel functions, which increases the kernel code
595 config ARCH_SUPPORTS_SHADOW_CALL_STACK
598 An architecture should select this if it supports Clang's Shadow
599 Call Stack and implements runtime support for shadow stack
602 config SHADOW_CALL_STACK
603 bool "Clang Shadow Call Stack"
604 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK
605 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
607 This option enables Clang's Shadow Call Stack, which uses a
608 shadow stack to protect function return addresses from being
609 overwritten by an attacker. More information can be found in
610 Clang's documentation:
612 https://clang.llvm.org/docs/ShadowCallStack.html
614 Note that security guarantees in the kernel differ from the
615 ones documented for user space. The kernel must store addresses
616 of shadow stacks in memory, which means an attacker capable of
617 reading and writing arbitrary memory may be able to locate them
618 and hijack control flow by modifying the stacks.
620 config HAVE_ARCH_WITHIN_STACK_FRAMES
623 An architecture should select this if it can walk the kernel stack
624 frames to determine if an object is part of either the arguments
625 or local variables (i.e. that it excludes saved return addresses,
626 and similar) by implementing an inline arch_within_stack_frames(),
627 which is used by CONFIG_HARDENED_USERCOPY.
629 config HAVE_CONTEXT_TRACKING
632 Provide kernel/user boundaries probes necessary for subsystems
633 that need it, such as userspace RCU extended quiescent state.
634 Syscalls need to be wrapped inside user_exit()-user_enter(), either
635 optimized behind static key or through the slow path using TIF_NOHZ
636 flag. Exceptions handlers must be wrapped as well. Irqs are already
637 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal
638 handling on irq exit still need to be protected.
643 Arch relies on TIF_NOHZ and syscall slow path to implement context
644 tracking calls to user_enter()/user_exit().
646 config HAVE_VIRT_CPU_ACCOUNTING
649 config ARCH_HAS_SCALED_CPUTIME
652 config HAVE_VIRT_CPU_ACCOUNTING_GEN
656 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
657 Before enabling this option, arch code must be audited
658 to ensure there are no races in concurrent read/write of
659 cputime_t. For example, reading/writing 64-bit cputime_t on
660 some 32-bit arches may require multiple accesses, so proper
661 locking is needed to protect against concurrent accesses.
664 config HAVE_IRQ_TIME_ACCOUNTING
667 Archs need to ensure they use a high enough resolution clock to
668 support irq time accounting and then call enable_sched_clock_irqtime().
673 Archs that select this are able to move page tables at the PMD level.
675 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
678 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
681 config HAVE_ARCH_HUGE_VMAP
684 config ARCH_WANT_HUGE_PMD_SHARE
687 config HAVE_ARCH_SOFT_DIRTY
690 config HAVE_MOD_ARCH_SPECIFIC
693 The arch uses struct mod_arch_specific to store data. Many arches
694 just need a simple module loader without arch specific data - those
695 should not enable this.
697 config MODULES_USE_ELF_RELA
700 Modules only use ELF RELA relocations. Modules with ELF REL
701 relocations will give an error.
703 config MODULES_USE_ELF_REL
706 Modules only use ELF REL relocations. Modules with ELF RELA
707 relocations will give an error.
709 config HAVE_IRQ_EXIT_ON_IRQ_STACK
712 Architecture doesn't only execute the irq handler on the irq stack
713 but also irq_exit(). This way we can process softirqs on this irq
714 stack instead of switching to a new one when we call __do_softirq()
715 in the end of an hardirq.
716 This spares a stack switch and improves cache usage on softirq
719 config PGTABLE_LEVELS
723 config ARCH_HAS_ELF_RANDOMIZE
726 An architecture supports choosing randomized locations for
727 stack, mmap, brk, and ET_DYN. Defined functions:
729 - arch_randomize_brk()
731 config HAVE_ARCH_MMAP_RND_BITS
734 An arch should select this symbol if it supports setting a variable
735 number of bits for use in establishing the base address for mmap
736 allocations, has MMU enabled and provides values for both:
737 - ARCH_MMAP_RND_BITS_MIN
738 - ARCH_MMAP_RND_BITS_MAX
740 config HAVE_EXIT_THREAD
743 An architecture implements exit_thread.
745 config ARCH_MMAP_RND_BITS_MIN
748 config ARCH_MMAP_RND_BITS_MAX
751 config ARCH_MMAP_RND_BITS_DEFAULT
754 config ARCH_MMAP_RND_BITS
755 int "Number of bits to use for ASLR of mmap base address" if EXPERT
756 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
757 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
758 default ARCH_MMAP_RND_BITS_MIN
759 depends on HAVE_ARCH_MMAP_RND_BITS
761 This value can be used to select the number of bits to use to
762 determine the random offset to the base address of vma regions
763 resulting from mmap allocations. This value will be bounded
764 by the architecture's minimum and maximum supported values.
766 This value can be changed after boot using the
767 /proc/sys/vm/mmap_rnd_bits tunable
769 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
772 An arch should select this symbol if it supports running applications
773 in compatibility mode, supports setting a variable number of bits for
774 use in establishing the base address for mmap allocations, has MMU
775 enabled and provides values for both:
776 - ARCH_MMAP_RND_COMPAT_BITS_MIN
777 - ARCH_MMAP_RND_COMPAT_BITS_MAX
779 config ARCH_MMAP_RND_COMPAT_BITS_MIN
782 config ARCH_MMAP_RND_COMPAT_BITS_MAX
785 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
788 config ARCH_MMAP_RND_COMPAT_BITS
789 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
790 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
791 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
792 default ARCH_MMAP_RND_COMPAT_BITS_MIN
793 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
795 This value can be used to select the number of bits to use to
796 determine the random offset to the base address of vma regions
797 resulting from mmap allocations for compatible applications This
798 value will be bounded by the architecture's minimum and maximum
801 This value can be changed after boot using the
802 /proc/sys/vm/mmap_rnd_compat_bits tunable
804 config HAVE_ARCH_COMPAT_MMAP_BASES
807 This allows 64bit applications to invoke 32-bit mmap() syscall
808 and vice-versa 32-bit applications to call 64-bit mmap().
809 Required for applications doing different bitness syscalls.
811 # This allows to use a set of generic functions to determine mmap base
812 # address by giving priority to top-down scheme only if the process
813 # is not in legacy mode (compat task, unlimited stack size or
814 # sysctl_legacy_va_layout).
815 # Architecture that selects this option can provide its own version of:
817 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
820 select ARCH_HAS_ELF_RANDOMIZE
822 config HAVE_STACK_VALIDATION
825 Architecture supports the 'objtool check' host tool command, which
826 performs compile-time stack metadata validation.
828 config HAVE_RELIABLE_STACKTRACE
831 Architecture has either save_stack_trace_tsk_reliable() or
832 arch_stack_walk_reliable() function which only returns a stack trace
833 if it can guarantee the trace is reliable.
835 config HAVE_ARCH_HASH
839 If this is set, the architecture provides an <asm/hash.h>
840 file which provides platform-specific implementations of some
841 functions in <linux/hash.h> or fs/namei.c.
843 config HAVE_ARCH_NVRAM_OPS
852 config CLONE_BACKWARDS
855 Architecture has tls passed as the 4th argument of clone(2),
858 config CLONE_BACKWARDS2
861 Architecture has the first two arguments of clone(2) swapped.
863 config CLONE_BACKWARDS3
866 Architecture has tls passed as the 3rd argument of clone(2),
869 config ODD_RT_SIGACTION
872 Architecture has unusual rt_sigaction(2) arguments
874 config OLD_SIGSUSPEND
877 Architecture has old sigsuspend(2) syscall, of one-argument variety
879 config OLD_SIGSUSPEND3
882 Even weirder antique ABI - three-argument sigsuspend(2)
887 Architecture has old sigaction(2) syscall. Nope, not the same
888 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
889 but fairly different variant of sigaction(2), thanks to OSF/1
892 config COMPAT_OLD_SIGACTION
895 config COMPAT_32BIT_TIME
896 bool "Provide system calls for 32-bit time_t"
897 default !64BIT || COMPAT
899 This enables 32 bit time_t support in addition to 64 bit time_t support.
900 This is relevant on all 32-bit architectures, and 64-bit architectures
901 as part of compat syscall handling.
903 config ARCH_NO_PREEMPT
906 config ARCH_SUPPORTS_RT
909 config CPU_NO_EFFICIENT_FFS
912 config HAVE_ARCH_VMAP_STACK
915 An arch should select this symbol if it can support kernel stacks
916 in vmalloc space. This means:
918 - vmalloc space must be large enough to hold many kernel stacks.
919 This may rule out many 32-bit architectures.
921 - Stacks in vmalloc space need to work reliably. For example, if
922 vmap page tables are created on demand, either this mechanism
923 needs to work while the stack points to a virtual address with
924 unpopulated page tables or arch code (switch_to() and switch_mm(),
925 most likely) needs to ensure that the stack's page table entries
926 are populated before running on a possibly unpopulated stack.
928 - If the stack overflows into a guard page, something reasonable
929 should happen. The definition of "reasonable" is flexible, but
930 instantly rebooting without logging anything would be unfriendly.
934 bool "Use a virtually-mapped stack"
935 depends on HAVE_ARCH_VMAP_STACK
936 depends on !KASAN || KASAN_VMALLOC
938 Enable this if you want the use virtually-mapped kernel stacks
939 with guard pages. This causes kernel stack overflows to be
940 caught immediately rather than causing difficult-to-diagnose
943 To use this with KASAN, the architecture must support backing
944 virtual mappings with real shadow memory, and KASAN_VMALLOC must
947 config ARCH_OPTIONAL_KERNEL_RWX
950 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
953 config ARCH_HAS_STRICT_KERNEL_RWX
956 config STRICT_KERNEL_RWX
957 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
958 depends on ARCH_HAS_STRICT_KERNEL_RWX
959 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
961 If this is set, kernel text and rodata memory will be made read-only,
962 and non-text memory will be made non-executable. This provides
963 protection against certain security exploits (e.g. executing the heap
966 These features are considered standard security practice these days.
967 You should say Y here in almost all cases.
969 config ARCH_HAS_STRICT_MODULE_RWX
972 config STRICT_MODULE_RWX
973 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
974 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
975 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
977 If this is set, module text and rodata memory will be made read-only,
978 and non-text memory will be made non-executable. This provides
979 protection against certain security exploits (e.g. writing to text)
981 # select if the architecture provides an asm/dma-direct.h header
982 config ARCH_HAS_PHYS_TO_DMA
985 config HAVE_ARCH_COMPILER_H
988 An architecture can select this if it provides an
989 asm/compiler.h header that should be included after
990 linux/compiler-*.h in order to override macro definitions that those
991 headers generally provide.
993 config HAVE_ARCH_PREL32_RELOCATIONS
996 May be selected by an architecture if it supports place-relative
997 32-bit relocations, both in the toolchain and in the module loader,
998 in which case relative references can be used in special sections
999 for PCI fixup, initcalls etc which are only half the size on 64 bit
1000 architectures, and don't require runtime relocation on relocatable
1003 config ARCH_USE_MEMREMAP_PROT
1006 config LOCK_EVENT_COUNTS
1007 bool "Locking event counts collection"
1010 Enable light-weight counting of various locking related events
1011 in the system with minimal performance impact. This reduces
1012 the chance of application behavior change because of timing
1013 differences. The counts are reported via debugfs.
1015 # Select if the architecture has support for applying RELR relocations.
1016 config ARCH_HAS_RELR
1020 bool "Use RELR relocation packing"
1021 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1024 Store the kernel's dynamic relocations in the RELR relocation packing
1025 format. Requires a compatible linker (LLD supports this feature), as
1026 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1029 config ARCH_HAS_MEM_ENCRYPT
1032 config ARCH_HAS_CC_PLATFORM
1035 config HAVE_SPARSE_SYSCALL_NR
1038 An architecture should select this if its syscall numbering is sparse
1039 to save space. For example, MIPS architecture has a syscall array with
1040 entries at 4000, 5000 and 6000 locations. This option turns on syscall
1041 related optimizations for a given architecture.
1043 config ARCH_HAS_VDSO_DATA
1046 config HAVE_STATIC_CALL
1049 config HAVE_STATIC_CALL_INLINE
1051 depends on HAVE_STATIC_CALL
1053 config ARCH_WANT_LD_ORPHAN_WARN
1056 An arch should select this symbol once all linker sections are explicitly
1057 included, size-asserted, or discarded in the linker scripts. This is
1058 important because we never want expected sections to be placed heuristically
1059 by the linker, since the locations of such sections can change between linker
1062 config ARCH_SPLIT_ARG64
1065 If a 32-bit architecture requires 64-bit arguments to be split into
1066 pairs of 32-bit arguments, select this option.
1068 source "kernel/gcov/Kconfig"
1070 source "scripts/gcc-plugins/Kconfig"