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"
34 tristate "OProfile system profiling"
36 depends on HAVE_OPROFILE
38 select RING_BUFFER_ALLOW_SWAP
40 OProfile is a profiling system capable of profiling the
41 whole system, include the kernel, kernel modules, libraries,
46 config OPROFILE_EVENT_MULTIPLEX
47 bool "OProfile multiplexing support (EXPERIMENTAL)"
49 depends on OPROFILE && X86
51 The number of hardware counters is limited. The multiplexing
52 feature enables OProfile to gather more events than counters
53 are provided by the hardware. This is realized by switching
54 between events at a user specified time interval.
61 config OPROFILE_NMI_TIMER
63 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
68 depends on HAVE_KPROBES
71 Kprobes allows you to trap at almost any kernel address and
72 execute a callback function. register_kprobe() establishes
73 a probepoint and specifies the callback. Kprobes is useful
74 for kernel debugging, non-intrusive instrumentation and testing.
78 bool "Optimize very unlikely/likely branches"
79 depends on HAVE_ARCH_JUMP_LABEL
80 depends on CC_HAS_ASM_GOTO
82 This option enables a transparent branch optimization that
83 makes certain almost-always-true or almost-always-false branch
84 conditions even cheaper to execute within the kernel.
86 Certain performance-sensitive kernel code, such as trace points,
87 scheduler functionality, networking code and KVM have such
88 branches and include support for this optimization technique.
90 If it is detected that the compiler has support for "asm goto",
91 the kernel will compile such branches with just a nop
92 instruction. When the condition flag is toggled to true, the
93 nop will be converted to a jump instruction to execute the
94 conditional block of instructions.
96 This technique lowers overhead and stress on the branch prediction
97 of the processor and generally makes the kernel faster. The update
98 of the condition is slower, but those are always very rare.
100 ( On 32-bit x86, the necessary options added to the compiler
101 flags may increase the size of the kernel slightly. )
103 config STATIC_KEYS_SELFTEST
104 bool "Static key selftest"
105 depends on JUMP_LABEL
107 Boot time self-test of the branch patching code.
109 config STATIC_CALL_SELFTEST
110 bool "Static call selftest"
111 depends on HAVE_STATIC_CALL
113 Boot time self-test of the call patching code.
117 depends on KPROBES && HAVE_OPTPROBES
118 select TASKS_RCU if PREEMPTION
120 config KPROBES_ON_FTRACE
122 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
123 depends on DYNAMIC_FTRACE_WITH_REGS
125 If function tracer is enabled and the arch supports full
126 passing of pt_regs to function tracing, then kprobes can
127 optimize on top of function tracing.
131 depends on ARCH_SUPPORTS_UPROBES
133 Uprobes is the user-space counterpart to kprobes: they
134 enable instrumentation applications (such as 'perf probe')
135 to establish unintrusive probes in user-space binaries and
136 libraries, by executing handler functions when the probes
137 are hit by user-space applications.
139 ( These probes come in the form of single-byte breakpoints,
140 managed by the kernel and kept transparent to the probed
143 config HAVE_EFFICIENT_UNALIGNED_ACCESS
146 Some architectures are unable to perform unaligned accesses
147 without the use of get_unaligned/put_unaligned. Others are
148 unable to perform such accesses efficiently (e.g. trap on
149 unaligned access and require fixing it up in the exception
152 This symbol should be selected by an architecture if it can
153 perform unaligned accesses efficiently to allow different
154 code paths to be selected for these cases. Some network
155 drivers, for example, could opt to not fix up alignment
156 problems with received packets if doing so would not help
159 See Documentation/core-api/unaligned-memory-access.rst for more
160 information on the topic of unaligned memory accesses.
162 config ARCH_USE_BUILTIN_BSWAP
165 Modern versions of GCC (since 4.4) have builtin functions
166 for handling byte-swapping. Using these, instead of the old
167 inline assembler that the architecture code provides in the
168 __arch_bswapXX() macros, allows the compiler to see what's
169 happening and offers more opportunity for optimisation. In
170 particular, the compiler will be able to combine the byteswap
171 with a nearby load or store and use load-and-swap or
172 store-and-swap instructions if the architecture has them. It
173 should almost *never* result in code which is worse than the
174 hand-coded assembler in <asm/swab.h>. But just in case it
175 does, the use of the builtins is optional.
177 Any architecture with load-and-swap or store-and-swap
178 instructions should set this. And it shouldn't hurt to set it
179 on architectures that don't have such instructions.
183 depends on KPROBES && HAVE_KRETPROBES
185 config USER_RETURN_NOTIFIER
187 depends on HAVE_USER_RETURN_NOTIFIER
189 Provide a kernel-internal notification when a cpu is about to
192 config HAVE_IOREMAP_PROT
198 config HAVE_KRETPROBES
201 config HAVE_OPTPROBES
204 config HAVE_KPROBES_ON_FTRACE
207 config HAVE_FUNCTION_ERROR_INJECTION
214 # An arch should select this if it provides all these things:
216 # task_pt_regs() in asm/processor.h or asm/ptrace.h
217 # arch_has_single_step() if there is hardware single-step support
218 # arch_has_block_step() if there is hardware block-step support
219 # asm/syscall.h supplying asm-generic/syscall.h interface
220 # linux/regset.h user_regset interfaces
221 # CORE_DUMP_USE_REGSET #define'd in linux/elf.h
222 # TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit}
223 # TIF_NOTIFY_RESUME calls tracehook_notify_resume()
224 # signal delivery calls tracehook_signal_handler()
226 config HAVE_ARCH_TRACEHOOK
229 config HAVE_DMA_CONTIGUOUS
232 config GENERIC_SMP_IDLE_THREAD
235 config GENERIC_IDLE_POLL_SETUP
238 config ARCH_HAS_FORTIFY_SOURCE
241 An architecture should select this when it can successfully
242 build and run with CONFIG_FORTIFY_SOURCE.
245 # Select if the arch provides a historic keepinit alias for the retain_initrd
246 # command line option
248 config ARCH_HAS_KEEPINITRD
251 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
252 config ARCH_HAS_SET_MEMORY
255 # Select if arch has all set_direct_map_invalid/default() functions
256 config ARCH_HAS_SET_DIRECT_MAP
260 # Select if the architecture provides the arch_dma_set_uncached symbol to
261 # either provide an uncached segement alias for a DMA allocation, or
262 # to remap the page tables in place.
264 config ARCH_HAS_DMA_SET_UNCACHED
268 # Select if the architectures provides the arch_dma_clear_uncached symbol
269 # to undo an in-place page table remap for uncached access.
271 config ARCH_HAS_DMA_CLEAR_UNCACHED
274 # Select if arch init_task must go in the __init_task_data section
275 config ARCH_TASK_STRUCT_ON_STACK
278 # Select if arch has its private alloc_task_struct() function
279 config ARCH_TASK_STRUCT_ALLOCATOR
282 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
284 depends on !ARCH_TASK_STRUCT_ALLOCATOR
286 An architecture should select this to provide hardened usercopy
287 knowledge about what region of the thread_struct should be
288 whitelisted for copying to userspace. Normally this is only the
289 FPU registers. Specifically, arch_thread_struct_whitelist()
290 should be implemented. Without this, the entire thread_struct
291 field in task_struct will be left whitelisted.
293 # Select if arch has its private alloc_thread_stack() function
294 config ARCH_THREAD_STACK_ALLOCATOR
297 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
298 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
301 config ARCH_32BIT_OFF_T
305 All new 32-bit architectures should have 64-bit off_t type on
306 userspace side which corresponds to the loff_t kernel type. This
307 is the requirement for modern ABIs. Some existing architectures
308 still support 32-bit off_t. This option is enabled for all such
309 architectures explicitly.
311 config HAVE_ASM_MODVERSIONS
314 This symbol should be selected by an architecure if it provides
315 <asm/asm-prototypes.h> to support the module versioning for symbols
316 exported from assembly code.
318 config HAVE_REGS_AND_STACK_ACCESS_API
321 This symbol should be selected by an architecure if it supports
322 the API needed to access registers and stack entries from pt_regs,
323 declared in asm/ptrace.h
324 For example the kprobes-based event tracer needs this API.
328 depends on HAVE_REGS_AND_STACK_ACCESS_API
330 This symbol should be selected by an architecture if it
331 supports an implementation of restartable sequences.
333 config HAVE_FUNCTION_ARG_ACCESS_API
336 This symbol should be selected by an architecure if it supports
337 the API needed to access function arguments from pt_regs,
338 declared in asm/ptrace.h
340 config HAVE_HW_BREAKPOINT
342 depends on PERF_EVENTS
344 config HAVE_MIXED_BREAKPOINTS_REGS
346 depends on HAVE_HW_BREAKPOINT
348 Depending on the arch implementation of hardware breakpoints,
349 some of them have separate registers for data and instruction
350 breakpoints addresses, others have mixed registers to store
351 them but define the access type in a control register.
352 Select this option if your arch implements breakpoints under the
355 config HAVE_USER_RETURN_NOTIFIER
358 config HAVE_PERF_EVENTS_NMI
361 System hardware can generate an NMI using the perf event
362 subsystem. Also has support for calculating CPU cycle events
363 to determine how many clock cycles in a given period.
365 config HAVE_HARDLOCKUP_DETECTOR_PERF
367 depends on HAVE_PERF_EVENTS_NMI
369 The arch chooses to use the generic perf-NMI-based hardlockup
370 detector. Must define HAVE_PERF_EVENTS_NMI.
372 config HAVE_NMI_WATCHDOG
376 The arch provides a low level NMI watchdog. It provides
377 asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
379 config HAVE_HARDLOCKUP_DETECTOR_ARCH
381 select HAVE_NMI_WATCHDOG
383 The arch chooses to provide its own hardlockup detector, which is
384 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
385 interfaces and parameters provided by hardlockup detector subsystem.
387 config HAVE_PERF_REGS
390 Support selective register dumps for perf events. This includes
391 bit-mapping of each registers and a unique architecture id.
393 config HAVE_PERF_USER_STACK_DUMP
396 Support user stack dumps for perf event samples. This needs
397 access to the user stack pointer which is not unified across
400 config HAVE_ARCH_JUMP_LABEL
403 config HAVE_ARCH_JUMP_LABEL_RELATIVE
406 config MMU_GATHER_TABLE_FREE
409 config MMU_GATHER_RCU_TABLE_FREE
411 select MMU_GATHER_TABLE_FREE
413 config MMU_GATHER_PAGE_SIZE
416 config MMU_GATHER_NO_RANGE
419 config MMU_GATHER_NO_GATHER
421 depends on MMU_GATHER_TABLE_FREE
423 config ARCH_HAVE_NMI_SAFE_CMPXCHG
426 config HAVE_ALIGNED_STRUCT_PAGE
429 This makes sure that struct pages are double word aligned and that
430 e.g. the SLUB allocator can perform double word atomic operations
431 on a struct page for better performance. However selecting this
432 might increase the size of a struct page by a word.
434 config HAVE_CMPXCHG_LOCAL
437 config HAVE_CMPXCHG_DOUBLE
440 config ARCH_WEAK_RELEASE_ACQUIRE
443 config ARCH_WANT_IPC_PARSE_VERSION
446 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
449 config ARCH_WANT_OLD_COMPAT_IPC
450 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
453 config HAVE_ARCH_SECCOMP
456 An arch should select this symbol to support seccomp mode 1 (the fixed
457 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
458 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
459 - __NR_seccomp_read_32
460 - __NR_seccomp_write_32
461 - __NR_seccomp_exit_32
462 - __NR_seccomp_sigreturn_32
464 config HAVE_ARCH_SECCOMP_FILTER
466 select HAVE_ARCH_SECCOMP
468 An arch should select this symbol if it provides all of these things:
469 - all the requirements for HAVE_ARCH_SECCOMP
471 - syscall_get_arguments()
473 - syscall_set_return_value()
474 - SIGSYS siginfo_t support
475 - secure_computing is called from a ptrace_event()-safe context
476 - secure_computing return value is checked and a return value of -1
477 results in the system call being skipped immediately.
478 - seccomp syscall wired up
481 prompt "Enable seccomp to safely execute untrusted bytecode"
483 depends on HAVE_ARCH_SECCOMP
485 This kernel feature is useful for number crunching applications
486 that may need to handle untrusted bytecode during their
487 execution. By using pipes or other transports made available
488 to the process as file descriptors supporting the read/write
489 syscalls, it's possible to isolate those applications in their
490 own address space using seccomp. Once seccomp is enabled via
491 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
492 disabled and the task is only allowed to execute a few safe
493 syscalls defined by each seccomp mode.
497 config SECCOMP_FILTER
499 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
501 Enable tasks to build secure computing environments defined
502 in terms of Berkeley Packet Filter programs which implement
503 task-defined system call filtering polices.
505 See Documentation/userspace-api/seccomp_filter.rst for details.
507 config HAVE_ARCH_STACKLEAK
510 An architecture should select this if it has the code which
511 fills the used part of the kernel stack with the STACKLEAK_POISON
512 value before returning from system calls.
514 config HAVE_STACKPROTECTOR
517 An arch should select this symbol if:
518 - it has implemented a stack canary (e.g. __stack_chk_guard)
520 config STACKPROTECTOR
521 bool "Stack Protector buffer overflow detection"
522 depends on HAVE_STACKPROTECTOR
523 depends on $(cc-option,-fstack-protector)
526 This option turns on the "stack-protector" GCC feature. This
527 feature puts, at the beginning of functions, a canary value on
528 the stack just before the return address, and validates
529 the value just before actually returning. Stack based buffer
530 overflows (that need to overwrite this return address) now also
531 overwrite the canary, which gets detected and the attack is then
532 neutralized via a kernel panic.
534 Functions will have the stack-protector canary logic added if they
535 have an 8-byte or larger character array on the stack.
537 This feature requires gcc version 4.2 or above, or a distribution
538 gcc with the feature backported ("-fstack-protector").
540 On an x86 "defconfig" build, this feature adds canary checks to
541 about 3% of all kernel functions, which increases kernel code size
544 config STACKPROTECTOR_STRONG
545 bool "Strong Stack Protector"
546 depends on STACKPROTECTOR
547 depends on $(cc-option,-fstack-protector-strong)
550 Functions will have the stack-protector canary logic added in any
551 of the following conditions:
553 - local variable's address used as part of the right hand side of an
554 assignment or function argument
555 - local variable is an array (or union containing an array),
556 regardless of array type or length
557 - uses register local variables
559 This feature requires gcc version 4.9 or above, or a distribution
560 gcc with the feature backported ("-fstack-protector-strong").
562 On an x86 "defconfig" build, this feature adds canary checks to
563 about 20% of all kernel functions, which increases the kernel code
566 config ARCH_SUPPORTS_SHADOW_CALL_STACK
569 An architecture should select this if it supports Clang's Shadow
570 Call Stack and implements runtime support for shadow stack
573 config SHADOW_CALL_STACK
574 bool "Clang Shadow Call Stack"
575 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK
576 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
578 This option enables Clang's Shadow Call Stack, which uses a
579 shadow stack to protect function return addresses from being
580 overwritten by an attacker. More information can be found in
581 Clang's documentation:
583 https://clang.llvm.org/docs/ShadowCallStack.html
585 Note that security guarantees in the kernel differ from the
586 ones documented for user space. The kernel must store addresses
587 of shadow stacks in memory, which means an attacker capable of
588 reading and writing arbitrary memory may be able to locate them
589 and hijack control flow by modifying the stacks.
591 config HAVE_ARCH_WITHIN_STACK_FRAMES
594 An architecture should select this if it can walk the kernel stack
595 frames to determine if an object is part of either the arguments
596 or local variables (i.e. that it excludes saved return addresses,
597 and similar) by implementing an inline arch_within_stack_frames(),
598 which is used by CONFIG_HARDENED_USERCOPY.
600 config HAVE_CONTEXT_TRACKING
603 Provide kernel/user boundaries probes necessary for subsystems
604 that need it, such as userspace RCU extended quiescent state.
605 Syscalls need to be wrapped inside user_exit()-user_enter(), either
606 optimized behind static key or through the slow path using TIF_NOHZ
607 flag. Exceptions handlers must be wrapped as well. Irqs are already
608 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal
609 handling on irq exit still need to be protected.
614 Arch relies on TIF_NOHZ and syscall slow path to implement context
615 tracking calls to user_enter()/user_exit().
617 config HAVE_VIRT_CPU_ACCOUNTING
620 config ARCH_HAS_SCALED_CPUTIME
623 config HAVE_VIRT_CPU_ACCOUNTING_GEN
627 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
628 Before enabling this option, arch code must be audited
629 to ensure there are no races in concurrent read/write of
630 cputime_t. For example, reading/writing 64-bit cputime_t on
631 some 32-bit arches may require multiple accesses, so proper
632 locking is needed to protect against concurrent accesses.
635 config HAVE_IRQ_TIME_ACCOUNTING
638 Archs need to ensure they use a high enough resolution clock to
639 support irq time accounting and then call enable_sched_clock_irqtime().
644 Archs that select this are able to move page tables at the PMD level.
646 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
649 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
652 config HAVE_ARCH_HUGE_VMAP
655 config ARCH_WANT_HUGE_PMD_SHARE
658 config HAVE_ARCH_SOFT_DIRTY
661 config HAVE_MOD_ARCH_SPECIFIC
664 The arch uses struct mod_arch_specific to store data. Many arches
665 just need a simple module loader without arch specific data - those
666 should not enable this.
668 config MODULES_USE_ELF_RELA
671 Modules only use ELF RELA relocations. Modules with ELF REL
672 relocations will give an error.
674 config MODULES_USE_ELF_REL
677 Modules only use ELF REL relocations. Modules with ELF RELA
678 relocations will give an error.
680 config HAVE_IRQ_EXIT_ON_IRQ_STACK
683 Architecture doesn't only execute the irq handler on the irq stack
684 but also irq_exit(). This way we can process softirqs on this irq
685 stack instead of switching to a new one when we call __do_softirq()
686 in the end of an hardirq.
687 This spares a stack switch and improves cache usage on softirq
690 config PGTABLE_LEVELS
694 config ARCH_HAS_ELF_RANDOMIZE
697 An architecture supports choosing randomized locations for
698 stack, mmap, brk, and ET_DYN. Defined functions:
700 - arch_randomize_brk()
702 config HAVE_ARCH_MMAP_RND_BITS
705 An arch should select this symbol if it supports setting a variable
706 number of bits for use in establishing the base address for mmap
707 allocations, has MMU enabled and provides values for both:
708 - ARCH_MMAP_RND_BITS_MIN
709 - ARCH_MMAP_RND_BITS_MAX
711 config HAVE_EXIT_THREAD
714 An architecture implements exit_thread.
716 config ARCH_MMAP_RND_BITS_MIN
719 config ARCH_MMAP_RND_BITS_MAX
722 config ARCH_MMAP_RND_BITS_DEFAULT
725 config ARCH_MMAP_RND_BITS
726 int "Number of bits to use for ASLR of mmap base address" if EXPERT
727 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
728 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
729 default ARCH_MMAP_RND_BITS_MIN
730 depends on HAVE_ARCH_MMAP_RND_BITS
732 This value can be used to select the number of bits to use to
733 determine the random offset to the base address of vma regions
734 resulting from mmap allocations. This value will be bounded
735 by the architecture's minimum and maximum supported values.
737 This value can be changed after boot using the
738 /proc/sys/vm/mmap_rnd_bits tunable
740 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
743 An arch should select this symbol if it supports running applications
744 in compatibility mode, supports setting a variable number of bits for
745 use in establishing the base address for mmap allocations, has MMU
746 enabled and provides values for both:
747 - ARCH_MMAP_RND_COMPAT_BITS_MIN
748 - ARCH_MMAP_RND_COMPAT_BITS_MAX
750 config ARCH_MMAP_RND_COMPAT_BITS_MIN
753 config ARCH_MMAP_RND_COMPAT_BITS_MAX
756 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
759 config ARCH_MMAP_RND_COMPAT_BITS
760 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
761 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
762 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
763 default ARCH_MMAP_RND_COMPAT_BITS_MIN
764 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
766 This value can be used to select the number of bits to use to
767 determine the random offset to the base address of vma regions
768 resulting from mmap allocations for compatible applications This
769 value will be bounded by the architecture's minimum and maximum
772 This value can be changed after boot using the
773 /proc/sys/vm/mmap_rnd_compat_bits tunable
775 config HAVE_ARCH_COMPAT_MMAP_BASES
778 This allows 64bit applications to invoke 32-bit mmap() syscall
779 and vice-versa 32-bit applications to call 64-bit mmap().
780 Required for applications doing different bitness syscalls.
782 # This allows to use a set of generic functions to determine mmap base
783 # address by giving priority to top-down scheme only if the process
784 # is not in legacy mode (compat task, unlimited stack size or
785 # sysctl_legacy_va_layout).
786 # Architecture that selects this option can provide its own version of:
788 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
791 select ARCH_HAS_ELF_RANDOMIZE
793 config HAVE_STACK_VALIDATION
796 Architecture supports the 'objtool check' host tool command, which
797 performs compile-time stack metadata validation.
799 config HAVE_RELIABLE_STACKTRACE
802 Architecture has either save_stack_trace_tsk_reliable() or
803 arch_stack_walk_reliable() function which only returns a stack trace
804 if it can guarantee the trace is reliable.
806 config HAVE_ARCH_HASH
810 If this is set, the architecture provides an <asm/hash.h>
811 file which provides platform-specific implementations of some
812 functions in <linux/hash.h> or fs/namei.c.
814 config HAVE_ARCH_NVRAM_OPS
823 config CLONE_BACKWARDS
826 Architecture has tls passed as the 4th argument of clone(2),
829 config CLONE_BACKWARDS2
832 Architecture has the first two arguments of clone(2) swapped.
834 config CLONE_BACKWARDS3
837 Architecture has tls passed as the 3rd argument of clone(2),
840 config ODD_RT_SIGACTION
843 Architecture has unusual rt_sigaction(2) arguments
845 config OLD_SIGSUSPEND
848 Architecture has old sigsuspend(2) syscall, of one-argument variety
850 config OLD_SIGSUSPEND3
853 Even weirder antique ABI - three-argument sigsuspend(2)
858 Architecture has old sigaction(2) syscall. Nope, not the same
859 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
860 but fairly different variant of sigaction(2), thanks to OSF/1
863 config COMPAT_OLD_SIGACTION
866 config COMPAT_32BIT_TIME
867 bool "Provide system calls for 32-bit time_t"
868 default !64BIT || COMPAT
870 This enables 32 bit time_t support in addition to 64 bit time_t support.
871 This is relevant on all 32-bit architectures, and 64-bit architectures
872 as part of compat syscall handling.
874 config ARCH_NO_PREEMPT
877 config ARCH_SUPPORTS_RT
880 config CPU_NO_EFFICIENT_FFS
883 config HAVE_ARCH_VMAP_STACK
886 An arch should select this symbol if it can support kernel stacks
887 in vmalloc space. This means:
889 - vmalloc space must be large enough to hold many kernel stacks.
890 This may rule out many 32-bit architectures.
892 - Stacks in vmalloc space need to work reliably. For example, if
893 vmap page tables are created on demand, either this mechanism
894 needs to work while the stack points to a virtual address with
895 unpopulated page tables or arch code (switch_to() and switch_mm(),
896 most likely) needs to ensure that the stack's page table entries
897 are populated before running on a possibly unpopulated stack.
899 - If the stack overflows into a guard page, something reasonable
900 should happen. The definition of "reasonable" is flexible, but
901 instantly rebooting without logging anything would be unfriendly.
905 bool "Use a virtually-mapped stack"
906 depends on HAVE_ARCH_VMAP_STACK
907 depends on !KASAN || KASAN_VMALLOC
909 Enable this if you want the use virtually-mapped kernel stacks
910 with guard pages. This causes kernel stack overflows to be
911 caught immediately rather than causing difficult-to-diagnose
914 To use this with KASAN, the architecture must support backing
915 virtual mappings with real shadow memory, and KASAN_VMALLOC must
918 config ARCH_OPTIONAL_KERNEL_RWX
921 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
924 config ARCH_HAS_STRICT_KERNEL_RWX
927 config STRICT_KERNEL_RWX
928 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
929 depends on ARCH_HAS_STRICT_KERNEL_RWX
930 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
932 If this is set, kernel text and rodata memory will be made read-only,
933 and non-text memory will be made non-executable. This provides
934 protection against certain security exploits (e.g. executing the heap
937 These features are considered standard security practice these days.
938 You should say Y here in almost all cases.
940 config ARCH_HAS_STRICT_MODULE_RWX
943 config STRICT_MODULE_RWX
944 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
945 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
946 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
948 If this is set, module text and rodata memory will be made read-only,
949 and non-text memory will be made non-executable. This provides
950 protection against certain security exploits (e.g. writing to text)
952 # select if the architecture provides an asm/dma-direct.h header
953 config ARCH_HAS_PHYS_TO_DMA
956 config HAVE_ARCH_COMPILER_H
959 An architecture can select this if it provides an
960 asm/compiler.h header that should be included after
961 linux/compiler-*.h in order to override macro definitions that those
962 headers generally provide.
964 config HAVE_ARCH_PREL32_RELOCATIONS
967 May be selected by an architecture if it supports place-relative
968 32-bit relocations, both in the toolchain and in the module loader,
969 in which case relative references can be used in special sections
970 for PCI fixup, initcalls etc which are only half the size on 64 bit
971 architectures, and don't require runtime relocation on relocatable
974 config ARCH_USE_MEMREMAP_PROT
977 config LOCK_EVENT_COUNTS
978 bool "Locking event counts collection"
981 Enable light-weight counting of various locking related events
982 in the system with minimal performance impact. This reduces
983 the chance of application behavior change because of timing
984 differences. The counts are reported via debugfs.
986 # Select if the architecture has support for applying RELR relocations.
991 bool "Use RELR relocation packing"
992 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
995 Store the kernel's dynamic relocations in the RELR relocation packing
996 format. Requires a compatible linker (LLD supports this feature), as
997 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1000 config ARCH_HAS_MEM_ENCRYPT
1003 config HAVE_SPARSE_SYSCALL_NR
1006 An architecture should select this if its syscall numbering is sparse
1007 to save space. For example, MIPS architecture has a syscall array with
1008 entries at 4000, 5000 and 6000 locations. This option turns on syscall
1009 related optimizations for a given architecture.
1011 config ARCH_HAS_VDSO_DATA
1014 config HAVE_STATIC_CALL
1017 config HAVE_STATIC_CALL_INLINE
1019 depends on HAVE_STATIC_CALL
1021 source "kernel/gcov/Kconfig"
1023 source "scripts/gcc-plugins/Kconfig"