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_EFFICIENT_UNALIGNED_ACCESS
149 Some architectures are unable to perform unaligned accesses
150 without the use of get_unaligned/put_unaligned. Others are
151 unable to perform such accesses efficiently (e.g. trap on
152 unaligned access and require fixing it up in the exception
155 This symbol should be selected by an architecture if it can
156 perform unaligned accesses efficiently to allow different
157 code paths to be selected for these cases. Some network
158 drivers, for example, could opt to not fix up alignment
159 problems with received packets if doing so would not help
162 See Documentation/core-api/unaligned-memory-access.rst for more
163 information on the topic of unaligned memory accesses.
165 config ARCH_USE_BUILTIN_BSWAP
168 Modern versions of GCC (since 4.4) have builtin functions
169 for handling byte-swapping. Using these, instead of the old
170 inline assembler that the architecture code provides in the
171 __arch_bswapXX() macros, allows the compiler to see what's
172 happening and offers more opportunity for optimisation. In
173 particular, the compiler will be able to combine the byteswap
174 with a nearby load or store and use load-and-swap or
175 store-and-swap instructions if the architecture has them. It
176 should almost *never* result in code which is worse than the
177 hand-coded assembler in <asm/swab.h>. But just in case it
178 does, the use of the builtins is optional.
180 Any architecture with load-and-swap or store-and-swap
181 instructions should set this. And it shouldn't hurt to set it
182 on architectures that don't have such instructions.
186 depends on KPROBES && HAVE_KRETPROBES
188 config USER_RETURN_NOTIFIER
190 depends on HAVE_USER_RETURN_NOTIFIER
192 Provide a kernel-internal notification when a cpu is about to
195 config HAVE_IOREMAP_PROT
201 config HAVE_KRETPROBES
204 config HAVE_OPTPROBES
207 config HAVE_KPROBES_ON_FTRACE
210 config HAVE_FUNCTION_ERROR_INJECTION
217 # An arch should select this if it provides all these things:
219 # task_pt_regs() in asm/processor.h or asm/ptrace.h
220 # arch_has_single_step() if there is hardware single-step support
221 # arch_has_block_step() if there is hardware block-step support
222 # asm/syscall.h supplying asm-generic/syscall.h interface
223 # linux/regset.h user_regset interfaces
224 # CORE_DUMP_USE_REGSET #define'd in linux/elf.h
225 # TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit}
226 # TIF_NOTIFY_RESUME calls tracehook_notify_resume()
227 # signal delivery calls tracehook_signal_handler()
229 config HAVE_ARCH_TRACEHOOK
232 config HAVE_DMA_CONTIGUOUS
235 config GENERIC_SMP_IDLE_THREAD
238 config GENERIC_IDLE_POLL_SETUP
241 config ARCH_HAS_FORTIFY_SOURCE
244 An architecture should select this when it can successfully
245 build and run with CONFIG_FORTIFY_SOURCE.
248 # Select if the arch provides a historic keepinit alias for the retain_initrd
249 # command line option
251 config ARCH_HAS_KEEPINITRD
254 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
255 config ARCH_HAS_SET_MEMORY
258 # Select if arch has all set_direct_map_invalid/default() functions
259 config ARCH_HAS_SET_DIRECT_MAP
263 # Select if the architecture provides the arch_dma_set_uncached symbol to
264 # either provide an uncached segment alias for a DMA allocation, or
265 # to remap the page tables in place.
267 config ARCH_HAS_DMA_SET_UNCACHED
271 # Select if the architectures provides the arch_dma_clear_uncached symbol
272 # to undo an in-place page table remap for uncached access.
274 config ARCH_HAS_DMA_CLEAR_UNCACHED
277 # Select if arch init_task must go in the __init_task_data section
278 config ARCH_TASK_STRUCT_ON_STACK
281 # Select if arch has its private alloc_task_struct() function
282 config ARCH_TASK_STRUCT_ALLOCATOR
285 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
287 depends on !ARCH_TASK_STRUCT_ALLOCATOR
289 An architecture should select this to provide hardened usercopy
290 knowledge about what region of the thread_struct should be
291 whitelisted for copying to userspace. Normally this is only the
292 FPU registers. Specifically, arch_thread_struct_whitelist()
293 should be implemented. Without this, the entire thread_struct
294 field in task_struct will be left whitelisted.
296 # Select if arch has its private alloc_thread_stack() function
297 config ARCH_THREAD_STACK_ALLOCATOR
300 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
301 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
304 config ARCH_32BIT_OFF_T
308 All new 32-bit architectures should have 64-bit off_t type on
309 userspace side which corresponds to the loff_t kernel type. This
310 is the requirement for modern ABIs. Some existing architectures
311 still support 32-bit off_t. This option is enabled for all such
312 architectures explicitly.
314 config HAVE_ASM_MODVERSIONS
317 This symbol should be selected by an architecture if it provides
318 <asm/asm-prototypes.h> to support the module versioning for symbols
319 exported from assembly code.
321 config HAVE_REGS_AND_STACK_ACCESS_API
324 This symbol should be selected by an architecture if it supports
325 the API needed to access registers and stack entries from pt_regs,
326 declared in asm/ptrace.h
327 For example the kprobes-based event tracer needs this API.
331 depends on HAVE_REGS_AND_STACK_ACCESS_API
333 This symbol should be selected by an architecture if it
334 supports an implementation of restartable sequences.
336 config HAVE_FUNCTION_ARG_ACCESS_API
339 This symbol should be selected by an architecture if it supports
340 the API needed to access function arguments from pt_regs,
341 declared in asm/ptrace.h
343 config HAVE_HW_BREAKPOINT
345 depends on PERF_EVENTS
347 config HAVE_MIXED_BREAKPOINTS_REGS
349 depends on HAVE_HW_BREAKPOINT
351 Depending on the arch implementation of hardware breakpoints,
352 some of them have separate registers for data and instruction
353 breakpoints addresses, others have mixed registers to store
354 them but define the access type in a control register.
355 Select this option if your arch implements breakpoints under the
358 config HAVE_USER_RETURN_NOTIFIER
361 config HAVE_PERF_EVENTS_NMI
364 System hardware can generate an NMI using the perf event
365 subsystem. Also has support for calculating CPU cycle events
366 to determine how many clock cycles in a given period.
368 config HAVE_HARDLOCKUP_DETECTOR_PERF
370 depends on HAVE_PERF_EVENTS_NMI
372 The arch chooses to use the generic perf-NMI-based hardlockup
373 detector. Must define HAVE_PERF_EVENTS_NMI.
375 config HAVE_NMI_WATCHDOG
379 The arch provides a low level NMI watchdog. It provides
380 asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
382 config HAVE_HARDLOCKUP_DETECTOR_ARCH
384 select HAVE_NMI_WATCHDOG
386 The arch chooses to provide its own hardlockup detector, which is
387 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
388 interfaces and parameters provided by hardlockup detector subsystem.
390 config HAVE_PERF_REGS
393 Support selective register dumps for perf events. This includes
394 bit-mapping of each registers and a unique architecture id.
396 config HAVE_PERF_USER_STACK_DUMP
399 Support user stack dumps for perf event samples. This needs
400 access to the user stack pointer which is not unified across
403 config HAVE_ARCH_JUMP_LABEL
406 config HAVE_ARCH_JUMP_LABEL_RELATIVE
409 config MMU_GATHER_TABLE_FREE
412 config MMU_GATHER_RCU_TABLE_FREE
414 select MMU_GATHER_TABLE_FREE
416 config MMU_GATHER_PAGE_SIZE
419 config MMU_GATHER_NO_RANGE
422 config MMU_GATHER_NO_GATHER
424 depends on MMU_GATHER_TABLE_FREE
426 config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
429 Temporary select until all architectures can be converted to have
430 irqs disabled over activate_mm. Architectures that do IPI based TLB
431 shootdowns should enable this.
433 config ARCH_HAVE_NMI_SAFE_CMPXCHG
436 config HAVE_ALIGNED_STRUCT_PAGE
439 This makes sure that struct pages are double word aligned and that
440 e.g. the SLUB allocator can perform double word atomic operations
441 on a struct page for better performance. However selecting this
442 might increase the size of a struct page by a word.
444 config HAVE_CMPXCHG_LOCAL
447 config HAVE_CMPXCHG_DOUBLE
450 config ARCH_WEAK_RELEASE_ACQUIRE
453 config ARCH_WANT_IPC_PARSE_VERSION
456 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
459 config ARCH_WANT_OLD_COMPAT_IPC
460 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
463 config HAVE_ARCH_SECCOMP
466 An arch should select this symbol to support seccomp mode 1 (the fixed
467 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
468 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
469 - __NR_seccomp_read_32
470 - __NR_seccomp_write_32
471 - __NR_seccomp_exit_32
472 - __NR_seccomp_sigreturn_32
474 config HAVE_ARCH_SECCOMP_FILTER
476 select HAVE_ARCH_SECCOMP
478 An arch should select this symbol if it provides all of these things:
479 - all the requirements for HAVE_ARCH_SECCOMP
481 - syscall_get_arguments()
483 - syscall_set_return_value()
484 - SIGSYS siginfo_t support
485 - secure_computing is called from a ptrace_event()-safe context
486 - secure_computing return value is checked and a return value of -1
487 results in the system call being skipped immediately.
488 - seccomp syscall wired up
491 prompt "Enable seccomp to safely execute untrusted bytecode"
493 depends on HAVE_ARCH_SECCOMP
495 This kernel feature is useful for number crunching applications
496 that may need to handle untrusted bytecode during their
497 execution. By using pipes or other transports made available
498 to the process as file descriptors supporting the read/write
499 syscalls, it's possible to isolate those applications in their
500 own address space using seccomp. Once seccomp is enabled via
501 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
502 disabled and the task is only allowed to execute a few safe
503 syscalls defined by each seccomp mode.
507 config SECCOMP_FILTER
509 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
511 Enable tasks to build secure computing environments defined
512 in terms of Berkeley Packet Filter programs which implement
513 task-defined system call filtering polices.
515 See Documentation/userspace-api/seccomp_filter.rst for details.
517 config HAVE_ARCH_STACKLEAK
520 An architecture should select this if it has the code which
521 fills the used part of the kernel stack with the STACKLEAK_POISON
522 value before returning from system calls.
524 config HAVE_STACKPROTECTOR
527 An arch should select this symbol if:
528 - it has implemented a stack canary (e.g. __stack_chk_guard)
530 config STACKPROTECTOR
531 bool "Stack Protector buffer overflow detection"
532 depends on HAVE_STACKPROTECTOR
533 depends on $(cc-option,-fstack-protector)
536 This option turns on the "stack-protector" GCC feature. This
537 feature puts, at the beginning of functions, a canary value on
538 the stack just before the return address, and validates
539 the value just before actually returning. Stack based buffer
540 overflows (that need to overwrite this return address) now also
541 overwrite the canary, which gets detected and the attack is then
542 neutralized via a kernel panic.
544 Functions will have the stack-protector canary logic added if they
545 have an 8-byte or larger character array on the stack.
547 This feature requires gcc version 4.2 or above, or a distribution
548 gcc with the feature backported ("-fstack-protector").
550 On an x86 "defconfig" build, this feature adds canary checks to
551 about 3% of all kernel functions, which increases kernel code size
554 config STACKPROTECTOR_STRONG
555 bool "Strong Stack Protector"
556 depends on STACKPROTECTOR
557 depends on $(cc-option,-fstack-protector-strong)
560 Functions will have the stack-protector canary logic added in any
561 of the following conditions:
563 - local variable's address used as part of the right hand side of an
564 assignment or function argument
565 - local variable is an array (or union containing an array),
566 regardless of array type or length
567 - uses register local variables
569 This feature requires gcc version 4.9 or above, or a distribution
570 gcc with the feature backported ("-fstack-protector-strong").
572 On an x86 "defconfig" build, this feature adds canary checks to
573 about 20% of all kernel functions, which increases the kernel code
576 config ARCH_SUPPORTS_SHADOW_CALL_STACK
579 An architecture should select this if it supports Clang's Shadow
580 Call Stack and implements runtime support for shadow stack
583 config SHADOW_CALL_STACK
584 bool "Clang Shadow Call Stack"
585 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK
586 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
588 This option enables Clang's Shadow Call Stack, which uses a
589 shadow stack to protect function return addresses from being
590 overwritten by an attacker. More information can be found in
591 Clang's documentation:
593 https://clang.llvm.org/docs/ShadowCallStack.html
595 Note that security guarantees in the kernel differ from the
596 ones documented for user space. The kernel must store addresses
597 of shadow stacks in memory, which means an attacker capable of
598 reading and writing arbitrary memory may be able to locate them
599 and hijack control flow by modifying the stacks.
601 config HAVE_ARCH_WITHIN_STACK_FRAMES
604 An architecture should select this if it can walk the kernel stack
605 frames to determine if an object is part of either the arguments
606 or local variables (i.e. that it excludes saved return addresses,
607 and similar) by implementing an inline arch_within_stack_frames(),
608 which is used by CONFIG_HARDENED_USERCOPY.
610 config HAVE_CONTEXT_TRACKING
613 Provide kernel/user boundaries probes necessary for subsystems
614 that need it, such as userspace RCU extended quiescent state.
615 Syscalls need to be wrapped inside user_exit()-user_enter(), either
616 optimized behind static key or through the slow path using TIF_NOHZ
617 flag. Exceptions handlers must be wrapped as well. Irqs are already
618 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal
619 handling on irq exit still need to be protected.
624 Arch relies on TIF_NOHZ and syscall slow path to implement context
625 tracking calls to user_enter()/user_exit().
627 config HAVE_VIRT_CPU_ACCOUNTING
630 config ARCH_HAS_SCALED_CPUTIME
633 config HAVE_VIRT_CPU_ACCOUNTING_GEN
637 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
638 Before enabling this option, arch code must be audited
639 to ensure there are no races in concurrent read/write of
640 cputime_t. For example, reading/writing 64-bit cputime_t on
641 some 32-bit arches may require multiple accesses, so proper
642 locking is needed to protect against concurrent accesses.
645 config HAVE_IRQ_TIME_ACCOUNTING
648 Archs need to ensure they use a high enough resolution clock to
649 support irq time accounting and then call enable_sched_clock_irqtime().
654 Architectures that select this are able to move page tables at the
655 PUD level. If there are only 3 page table levels, the move effectively
656 happens at the PGD level.
661 Archs that select this are able to move page tables at the PMD level.
663 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
666 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
669 config HAVE_ARCH_HUGE_VMAP
672 config ARCH_WANT_HUGE_PMD_SHARE
675 config HAVE_ARCH_SOFT_DIRTY
678 config HAVE_MOD_ARCH_SPECIFIC
681 The arch uses struct mod_arch_specific to store data. Many arches
682 just need a simple module loader without arch specific data - those
683 should not enable this.
685 config MODULES_USE_ELF_RELA
688 Modules only use ELF RELA relocations. Modules with ELF REL
689 relocations will give an error.
691 config MODULES_USE_ELF_REL
694 Modules only use ELF REL relocations. Modules with ELF RELA
695 relocations will give an error.
697 config HAVE_IRQ_EXIT_ON_IRQ_STACK
700 Architecture doesn't only execute the irq handler on the irq stack
701 but also irq_exit(). This way we can process softirqs on this irq
702 stack instead of switching to a new one when we call __do_softirq()
703 in the end of an hardirq.
704 This spares a stack switch and improves cache usage on softirq
707 config PGTABLE_LEVELS
711 config ARCH_HAS_ELF_RANDOMIZE
714 An architecture supports choosing randomized locations for
715 stack, mmap, brk, and ET_DYN. Defined functions:
717 - arch_randomize_brk()
719 config HAVE_ARCH_MMAP_RND_BITS
722 An arch should select this symbol if it supports setting a variable
723 number of bits for use in establishing the base address for mmap
724 allocations, has MMU enabled and provides values for both:
725 - ARCH_MMAP_RND_BITS_MIN
726 - ARCH_MMAP_RND_BITS_MAX
728 config HAVE_EXIT_THREAD
731 An architecture implements exit_thread.
733 config ARCH_MMAP_RND_BITS_MIN
736 config ARCH_MMAP_RND_BITS_MAX
739 config ARCH_MMAP_RND_BITS_DEFAULT
742 config ARCH_MMAP_RND_BITS
743 int "Number of bits to use for ASLR of mmap base address" if EXPERT
744 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
745 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
746 default ARCH_MMAP_RND_BITS_MIN
747 depends on HAVE_ARCH_MMAP_RND_BITS
749 This value can be used to select the number of bits to use to
750 determine the random offset to the base address of vma regions
751 resulting from mmap allocations. This value will be bounded
752 by the architecture's minimum and maximum supported values.
754 This value can be changed after boot using the
755 /proc/sys/vm/mmap_rnd_bits tunable
757 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
760 An arch should select this symbol if it supports running applications
761 in compatibility mode, supports setting a variable number of bits for
762 use in establishing the base address for mmap allocations, has MMU
763 enabled and provides values for both:
764 - ARCH_MMAP_RND_COMPAT_BITS_MIN
765 - ARCH_MMAP_RND_COMPAT_BITS_MAX
767 config ARCH_MMAP_RND_COMPAT_BITS_MIN
770 config ARCH_MMAP_RND_COMPAT_BITS_MAX
773 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
776 config ARCH_MMAP_RND_COMPAT_BITS
777 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
778 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
779 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
780 default ARCH_MMAP_RND_COMPAT_BITS_MIN
781 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
783 This value can be used to select the number of bits to use to
784 determine the random offset to the base address of vma regions
785 resulting from mmap allocations for compatible applications This
786 value will be bounded by the architecture's minimum and maximum
789 This value can be changed after boot using the
790 /proc/sys/vm/mmap_rnd_compat_bits tunable
792 config HAVE_ARCH_COMPAT_MMAP_BASES
795 This allows 64bit applications to invoke 32-bit mmap() syscall
796 and vice-versa 32-bit applications to call 64-bit mmap().
797 Required for applications doing different bitness syscalls.
799 # This allows to use a set of generic functions to determine mmap base
800 # address by giving priority to top-down scheme only if the process
801 # is not in legacy mode (compat task, unlimited stack size or
802 # sysctl_legacy_va_layout).
803 # Architecture that selects this option can provide its own version of:
805 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
808 select ARCH_HAS_ELF_RANDOMIZE
810 config HAVE_STACK_VALIDATION
813 Architecture supports the 'objtool check' host tool command, which
814 performs compile-time stack metadata validation.
816 config HAVE_RELIABLE_STACKTRACE
819 Architecture has either save_stack_trace_tsk_reliable() or
820 arch_stack_walk_reliable() function which only returns a stack trace
821 if it can guarantee the trace is reliable.
823 config HAVE_ARCH_HASH
827 If this is set, the architecture provides an <asm/hash.h>
828 file which provides platform-specific implementations of some
829 functions in <linux/hash.h> or fs/namei.c.
831 config HAVE_ARCH_NVRAM_OPS
840 config CLONE_BACKWARDS
843 Architecture has tls passed as the 4th argument of clone(2),
846 config CLONE_BACKWARDS2
849 Architecture has the first two arguments of clone(2) swapped.
851 config CLONE_BACKWARDS3
854 Architecture has tls passed as the 3rd argument of clone(2),
857 config ODD_RT_SIGACTION
860 Architecture has unusual rt_sigaction(2) arguments
862 config OLD_SIGSUSPEND
865 Architecture has old sigsuspend(2) syscall, of one-argument variety
867 config OLD_SIGSUSPEND3
870 Even weirder antique ABI - three-argument sigsuspend(2)
875 Architecture has old sigaction(2) syscall. Nope, not the same
876 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
877 but fairly different variant of sigaction(2), thanks to OSF/1
880 config COMPAT_OLD_SIGACTION
883 config COMPAT_32BIT_TIME
884 bool "Provide system calls for 32-bit time_t"
885 default !64BIT || COMPAT
887 This enables 32 bit time_t support in addition to 64 bit time_t support.
888 This is relevant on all 32-bit architectures, and 64-bit architectures
889 as part of compat syscall handling.
891 config ARCH_NO_PREEMPT
894 config ARCH_SUPPORTS_RT
897 config CPU_NO_EFFICIENT_FFS
900 config HAVE_ARCH_VMAP_STACK
903 An arch should select this symbol if it can support kernel stacks
904 in vmalloc space. This means:
906 - vmalloc space must be large enough to hold many kernel stacks.
907 This may rule out many 32-bit architectures.
909 - Stacks in vmalloc space need to work reliably. For example, if
910 vmap page tables are created on demand, either this mechanism
911 needs to work while the stack points to a virtual address with
912 unpopulated page tables or arch code (switch_to() and switch_mm(),
913 most likely) needs to ensure that the stack's page table entries
914 are populated before running on a possibly unpopulated stack.
916 - If the stack overflows into a guard page, something reasonable
917 should happen. The definition of "reasonable" is flexible, but
918 instantly rebooting without logging anything would be unfriendly.
922 bool "Use a virtually-mapped stack"
923 depends on HAVE_ARCH_VMAP_STACK
924 depends on !KASAN || KASAN_VMALLOC
926 Enable this if you want the use virtually-mapped kernel stacks
927 with guard pages. This causes kernel stack overflows to be
928 caught immediately rather than causing difficult-to-diagnose
931 To use this with KASAN, the architecture must support backing
932 virtual mappings with real shadow memory, and KASAN_VMALLOC must
935 config ARCH_OPTIONAL_KERNEL_RWX
938 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
941 config ARCH_HAS_STRICT_KERNEL_RWX
944 config STRICT_KERNEL_RWX
945 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
946 depends on ARCH_HAS_STRICT_KERNEL_RWX
947 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
949 If this is set, kernel text and rodata memory will be made read-only,
950 and non-text memory will be made non-executable. This provides
951 protection against certain security exploits (e.g. executing the heap
954 These features are considered standard security practice these days.
955 You should say Y here in almost all cases.
957 config ARCH_HAS_STRICT_MODULE_RWX
960 config STRICT_MODULE_RWX
961 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
962 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
963 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
965 If this is set, module text and rodata memory will be made read-only,
966 and non-text memory will be made non-executable. This provides
967 protection against certain security exploits (e.g. writing to text)
969 # select if the architecture provides an asm/dma-direct.h header
970 config ARCH_HAS_PHYS_TO_DMA
973 config HAVE_ARCH_COMPILER_H
976 An architecture can select this if it provides an
977 asm/compiler.h header that should be included after
978 linux/compiler-*.h in order to override macro definitions that those
979 headers generally provide.
981 config HAVE_ARCH_PREL32_RELOCATIONS
984 May be selected by an architecture if it supports place-relative
985 32-bit relocations, both in the toolchain and in the module loader,
986 in which case relative references can be used in special sections
987 for PCI fixup, initcalls etc which are only half the size on 64 bit
988 architectures, and don't require runtime relocation on relocatable
991 config ARCH_USE_MEMREMAP_PROT
994 config LOCK_EVENT_COUNTS
995 bool "Locking event counts collection"
998 Enable light-weight counting of various locking related events
999 in the system with minimal performance impact. This reduces
1000 the chance of application behavior change because of timing
1001 differences. The counts are reported via debugfs.
1003 # Select if the architecture has support for applying RELR relocations.
1004 config ARCH_HAS_RELR
1008 bool "Use RELR relocation packing"
1009 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1012 Store the kernel's dynamic relocations in the RELR relocation packing
1013 format. Requires a compatible linker (LLD supports this feature), as
1014 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1017 config ARCH_HAS_MEM_ENCRYPT
1020 config HAVE_SPARSE_SYSCALL_NR
1023 An architecture should select this if its syscall numbering is sparse
1024 to save space. For example, MIPS architecture has a syscall array with
1025 entries at 4000, 5000 and 6000 locations. This option turns on syscall
1026 related optimizations for a given architecture.
1028 config ARCH_HAS_VDSO_DATA
1031 config HAVE_STATIC_CALL
1034 config HAVE_STATIC_CALL_INLINE
1036 depends on HAVE_STATIC_CALL
1038 config ARCH_WANT_LD_ORPHAN_WARN
1041 An arch should select this symbol once all linker sections are explicitly
1042 included, size-asserted, or discarded in the linker scripts. This is
1043 important because we never want expected sections to be placed heuristically
1044 by the linker, since the locations of such sections can change between linker
1047 config HAVE_ARCH_PFN_VALID
1050 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
1053 source "kernel/gcov/Kconfig"
1055 source "scripts/gcc-plugins/Kconfig"