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 # Select if arch init_task must go in the __init_task_data section
294 config ARCH_TASK_STRUCT_ON_STACK
297 # Select if arch has its private alloc_task_struct() function
298 config ARCH_TASK_STRUCT_ALLOCATOR
301 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
303 depends on !ARCH_TASK_STRUCT_ALLOCATOR
305 An architecture should select this to provide hardened usercopy
306 knowledge about what region of the thread_struct should be
307 whitelisted for copying to userspace. Normally this is only the
308 FPU registers. Specifically, arch_thread_struct_whitelist()
309 should be implemented. Without this, the entire thread_struct
310 field in task_struct will be left whitelisted.
312 # Select if arch has its private alloc_thread_stack() function
313 config ARCH_THREAD_STACK_ALLOCATOR
316 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
317 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
320 config ARCH_32BIT_OFF_T
324 All new 32-bit architectures should have 64-bit off_t type on
325 userspace side which corresponds to the loff_t kernel type. This
326 is the requirement for modern ABIs. Some existing architectures
327 still support 32-bit off_t. This option is enabled for all such
328 architectures explicitly.
330 config HAVE_ASM_MODVERSIONS
333 This symbol should be selected by an architecure if it provides
334 <asm/asm-prototypes.h> to support the module versioning for symbols
335 exported from assembly code.
337 config HAVE_REGS_AND_STACK_ACCESS_API
340 This symbol should be selected by an architecure if it supports
341 the API needed to access registers and stack entries from pt_regs,
342 declared in asm/ptrace.h
343 For example the kprobes-based event tracer needs this API.
347 depends on HAVE_REGS_AND_STACK_ACCESS_API
349 This symbol should be selected by an architecture if it
350 supports an implementation of restartable sequences.
352 config HAVE_FUNCTION_ARG_ACCESS_API
355 This symbol should be selected by an architecure if it supports
356 the API needed to access function arguments from pt_regs,
357 declared in asm/ptrace.h
359 config HAVE_HW_BREAKPOINT
361 depends on PERF_EVENTS
363 config HAVE_MIXED_BREAKPOINTS_REGS
365 depends on HAVE_HW_BREAKPOINT
367 Depending on the arch implementation of hardware breakpoints,
368 some of them have separate registers for data and instruction
369 breakpoints addresses, others have mixed registers to store
370 them but define the access type in a control register.
371 Select this option if your arch implements breakpoints under the
374 config HAVE_USER_RETURN_NOTIFIER
377 config HAVE_PERF_EVENTS_NMI
380 System hardware can generate an NMI using the perf event
381 subsystem. Also has support for calculating CPU cycle events
382 to determine how many clock cycles in a given period.
384 config HAVE_HARDLOCKUP_DETECTOR_PERF
386 depends on HAVE_PERF_EVENTS_NMI
388 The arch chooses to use the generic perf-NMI-based hardlockup
389 detector. Must define HAVE_PERF_EVENTS_NMI.
391 config HAVE_NMI_WATCHDOG
395 The arch provides a low level NMI watchdog. It provides
396 asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
398 config HAVE_HARDLOCKUP_DETECTOR_ARCH
400 select HAVE_NMI_WATCHDOG
402 The arch chooses to provide its own hardlockup detector, which is
403 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
404 interfaces and parameters provided by hardlockup detector subsystem.
406 config HAVE_PERF_REGS
409 Support selective register dumps for perf events. This includes
410 bit-mapping of each registers and a unique architecture id.
412 config HAVE_PERF_USER_STACK_DUMP
415 Support user stack dumps for perf event samples. This needs
416 access to the user stack pointer which is not unified across
419 config HAVE_ARCH_JUMP_LABEL
422 config HAVE_ARCH_JUMP_LABEL_RELATIVE
425 config MMU_GATHER_TABLE_FREE
428 config MMU_GATHER_RCU_TABLE_FREE
430 select MMU_GATHER_TABLE_FREE
432 config MMU_GATHER_PAGE_SIZE
435 config MMU_GATHER_NO_RANGE
438 config MMU_GATHER_NO_GATHER
440 depends on MMU_GATHER_TABLE_FREE
442 config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
445 Temporary select until all architectures can be converted to have
446 irqs disabled over activate_mm. Architectures that do IPI based TLB
447 shootdowns should enable this.
449 config ARCH_HAVE_NMI_SAFE_CMPXCHG
452 config HAVE_ALIGNED_STRUCT_PAGE
455 This makes sure that struct pages are double word aligned and that
456 e.g. the SLUB allocator can perform double word atomic operations
457 on a struct page for better performance. However selecting this
458 might increase the size of a struct page by a word.
460 config HAVE_CMPXCHG_LOCAL
463 config HAVE_CMPXCHG_DOUBLE
466 config ARCH_WEAK_RELEASE_ACQUIRE
469 config ARCH_WANT_IPC_PARSE_VERSION
472 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
475 config ARCH_WANT_OLD_COMPAT_IPC
476 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
479 config HAVE_ARCH_SECCOMP
482 An arch should select this symbol to support seccomp mode 1 (the fixed
483 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
484 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
485 - __NR_seccomp_read_32
486 - __NR_seccomp_write_32
487 - __NR_seccomp_exit_32
488 - __NR_seccomp_sigreturn_32
490 config HAVE_ARCH_SECCOMP_FILTER
492 select HAVE_ARCH_SECCOMP
494 An arch should select this symbol if it provides all of these things:
495 - all the requirements for HAVE_ARCH_SECCOMP
497 - syscall_get_arguments()
499 - syscall_set_return_value()
500 - SIGSYS siginfo_t support
501 - secure_computing is called from a ptrace_event()-safe context
502 - secure_computing return value is checked and a return value of -1
503 results in the system call being skipped immediately.
504 - seccomp syscall wired up
507 prompt "Enable seccomp to safely execute untrusted bytecode"
509 depends on HAVE_ARCH_SECCOMP
511 This kernel feature is useful for number crunching applications
512 that may need to handle untrusted bytecode during their
513 execution. By using pipes or other transports made available
514 to the process as file descriptors supporting the read/write
515 syscalls, it's possible to isolate those applications in their
516 own address space using seccomp. Once seccomp is enabled via
517 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
518 disabled and the task is only allowed to execute a few safe
519 syscalls defined by each seccomp mode.
523 config SECCOMP_FILTER
525 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
527 Enable tasks to build secure computing environments defined
528 in terms of Berkeley Packet Filter programs which implement
529 task-defined system call filtering polices.
531 See Documentation/userspace-api/seccomp_filter.rst for details.
533 config HAVE_ARCH_STACKLEAK
536 An architecture should select this if it has the code which
537 fills the used part of the kernel stack with the STACKLEAK_POISON
538 value before returning from system calls.
540 config HAVE_STACKPROTECTOR
543 An arch should select this symbol if:
544 - it has implemented a stack canary (e.g. __stack_chk_guard)
546 config STACKPROTECTOR
547 bool "Stack Protector buffer overflow detection"
548 depends on HAVE_STACKPROTECTOR
549 depends on $(cc-option,-fstack-protector)
552 This option turns on the "stack-protector" GCC feature. This
553 feature puts, at the beginning of functions, a canary value on
554 the stack just before the return address, and validates
555 the value just before actually returning. Stack based buffer
556 overflows (that need to overwrite this return address) now also
557 overwrite the canary, which gets detected and the attack is then
558 neutralized via a kernel panic.
560 Functions will have the stack-protector canary logic added if they
561 have an 8-byte or larger character array on the stack.
563 This feature requires gcc version 4.2 or above, or a distribution
564 gcc with the feature backported ("-fstack-protector").
566 On an x86 "defconfig" build, this feature adds canary checks to
567 about 3% of all kernel functions, which increases kernel code size
570 config STACKPROTECTOR_STRONG
571 bool "Strong Stack Protector"
572 depends on STACKPROTECTOR
573 depends on $(cc-option,-fstack-protector-strong)
576 Functions will have the stack-protector canary logic added in any
577 of the following conditions:
579 - local variable's address used as part of the right hand side of an
580 assignment or function argument
581 - local variable is an array (or union containing an array),
582 regardless of array type or length
583 - uses register local variables
585 This feature requires gcc version 4.9 or above, or a distribution
586 gcc with the feature backported ("-fstack-protector-strong").
588 On an x86 "defconfig" build, this feature adds canary checks to
589 about 20% of all kernel functions, which increases the kernel code
592 config ARCH_SUPPORTS_SHADOW_CALL_STACK
595 An architecture should select this if it supports Clang's Shadow
596 Call Stack and implements runtime support for shadow stack
599 config SHADOW_CALL_STACK
600 bool "Clang Shadow Call Stack"
601 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK
602 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
604 This option enables Clang's Shadow Call Stack, which uses a
605 shadow stack to protect function return addresses from being
606 overwritten by an attacker. More information can be found in
607 Clang's documentation:
609 https://clang.llvm.org/docs/ShadowCallStack.html
611 Note that security guarantees in the kernel differ from the
612 ones documented for user space. The kernel must store addresses
613 of shadow stacks in memory, which means an attacker capable of
614 reading and writing arbitrary memory may be able to locate them
615 and hijack control flow by modifying the stacks.
617 config HAVE_ARCH_WITHIN_STACK_FRAMES
620 An architecture should select this if it can walk the kernel stack
621 frames to determine if an object is part of either the arguments
622 or local variables (i.e. that it excludes saved return addresses,
623 and similar) by implementing an inline arch_within_stack_frames(),
624 which is used by CONFIG_HARDENED_USERCOPY.
626 config HAVE_CONTEXT_TRACKING
629 Provide kernel/user boundaries probes necessary for subsystems
630 that need it, such as userspace RCU extended quiescent state.
631 Syscalls need to be wrapped inside user_exit()-user_enter(), either
632 optimized behind static key or through the slow path using TIF_NOHZ
633 flag. Exceptions handlers must be wrapped as well. Irqs are already
634 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal
635 handling on irq exit still need to be protected.
640 Arch relies on TIF_NOHZ and syscall slow path to implement context
641 tracking calls to user_enter()/user_exit().
643 config HAVE_VIRT_CPU_ACCOUNTING
646 config ARCH_HAS_SCALED_CPUTIME
649 config HAVE_VIRT_CPU_ACCOUNTING_GEN
653 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
654 Before enabling this option, arch code must be audited
655 to ensure there are no races in concurrent read/write of
656 cputime_t. For example, reading/writing 64-bit cputime_t on
657 some 32-bit arches may require multiple accesses, so proper
658 locking is needed to protect against concurrent accesses.
661 config HAVE_IRQ_TIME_ACCOUNTING
664 Archs need to ensure they use a high enough resolution clock to
665 support irq time accounting and then call enable_sched_clock_irqtime().
670 Archs that select this are able to move page tables at the PMD level.
672 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
675 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
678 config HAVE_ARCH_HUGE_VMAP
681 config ARCH_WANT_HUGE_PMD_SHARE
684 config HAVE_ARCH_SOFT_DIRTY
687 config HAVE_MOD_ARCH_SPECIFIC
690 The arch uses struct mod_arch_specific to store data. Many arches
691 just need a simple module loader without arch specific data - those
692 should not enable this.
694 config MODULES_USE_ELF_RELA
697 Modules only use ELF RELA relocations. Modules with ELF REL
698 relocations will give an error.
700 config MODULES_USE_ELF_REL
703 Modules only use ELF REL relocations. Modules with ELF RELA
704 relocations will give an error.
706 config HAVE_IRQ_EXIT_ON_IRQ_STACK
709 Architecture doesn't only execute the irq handler on the irq stack
710 but also irq_exit(). This way we can process softirqs on this irq
711 stack instead of switching to a new one when we call __do_softirq()
712 in the end of an hardirq.
713 This spares a stack switch and improves cache usage on softirq
716 config PGTABLE_LEVELS
720 config ARCH_HAS_ELF_RANDOMIZE
723 An architecture supports choosing randomized locations for
724 stack, mmap, brk, and ET_DYN. Defined functions:
726 - arch_randomize_brk()
728 config HAVE_ARCH_MMAP_RND_BITS
731 An arch should select this symbol if it supports setting a variable
732 number of bits for use in establishing the base address for mmap
733 allocations, has MMU enabled and provides values for both:
734 - ARCH_MMAP_RND_BITS_MIN
735 - ARCH_MMAP_RND_BITS_MAX
737 config HAVE_EXIT_THREAD
740 An architecture implements exit_thread.
742 config ARCH_MMAP_RND_BITS_MIN
745 config ARCH_MMAP_RND_BITS_MAX
748 config ARCH_MMAP_RND_BITS_DEFAULT
751 config ARCH_MMAP_RND_BITS
752 int "Number of bits to use for ASLR of mmap base address" if EXPERT
753 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
754 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
755 default ARCH_MMAP_RND_BITS_MIN
756 depends on HAVE_ARCH_MMAP_RND_BITS
758 This value can be used to select the number of bits to use to
759 determine the random offset to the base address of vma regions
760 resulting from mmap allocations. This value will be bounded
761 by the architecture's minimum and maximum supported values.
763 This value can be changed after boot using the
764 /proc/sys/vm/mmap_rnd_bits tunable
766 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
769 An arch should select this symbol if it supports running applications
770 in compatibility mode, supports setting a variable number of bits for
771 use in establishing the base address for mmap allocations, has MMU
772 enabled and provides values for both:
773 - ARCH_MMAP_RND_COMPAT_BITS_MIN
774 - ARCH_MMAP_RND_COMPAT_BITS_MAX
776 config ARCH_MMAP_RND_COMPAT_BITS_MIN
779 config ARCH_MMAP_RND_COMPAT_BITS_MAX
782 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
785 config ARCH_MMAP_RND_COMPAT_BITS
786 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
787 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
788 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
789 default ARCH_MMAP_RND_COMPAT_BITS_MIN
790 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
792 This value can be used to select the number of bits to use to
793 determine the random offset to the base address of vma regions
794 resulting from mmap allocations for compatible applications This
795 value will be bounded by the architecture's minimum and maximum
798 This value can be changed after boot using the
799 /proc/sys/vm/mmap_rnd_compat_bits tunable
801 config HAVE_ARCH_COMPAT_MMAP_BASES
804 This allows 64bit applications to invoke 32-bit mmap() syscall
805 and vice-versa 32-bit applications to call 64-bit mmap().
806 Required for applications doing different bitness syscalls.
808 # This allows to use a set of generic functions to determine mmap base
809 # address by giving priority to top-down scheme only if the process
810 # is not in legacy mode (compat task, unlimited stack size or
811 # sysctl_legacy_va_layout).
812 # Architecture that selects this option can provide its own version of:
814 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
817 select ARCH_HAS_ELF_RANDOMIZE
819 config HAVE_STACK_VALIDATION
822 Architecture supports the 'objtool check' host tool command, which
823 performs compile-time stack metadata validation.
825 config HAVE_RELIABLE_STACKTRACE
828 Architecture has either save_stack_trace_tsk_reliable() or
829 arch_stack_walk_reliable() function which only returns a stack trace
830 if it can guarantee the trace is reliable.
832 config HAVE_ARCH_HASH
836 If this is set, the architecture provides an <asm/hash.h>
837 file which provides platform-specific implementations of some
838 functions in <linux/hash.h> or fs/namei.c.
840 config HAVE_ARCH_NVRAM_OPS
849 config CLONE_BACKWARDS
852 Architecture has tls passed as the 4th argument of clone(2),
855 config CLONE_BACKWARDS2
858 Architecture has the first two arguments of clone(2) swapped.
860 config CLONE_BACKWARDS3
863 Architecture has tls passed as the 3rd argument of clone(2),
866 config ODD_RT_SIGACTION
869 Architecture has unusual rt_sigaction(2) arguments
871 config OLD_SIGSUSPEND
874 Architecture has old sigsuspend(2) syscall, of one-argument variety
876 config OLD_SIGSUSPEND3
879 Even weirder antique ABI - three-argument sigsuspend(2)
884 Architecture has old sigaction(2) syscall. Nope, not the same
885 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
886 but fairly different variant of sigaction(2), thanks to OSF/1
889 config COMPAT_OLD_SIGACTION
892 config COMPAT_32BIT_TIME
893 bool "Provide system calls for 32-bit time_t"
894 default !64BIT || COMPAT
896 This enables 32 bit time_t support in addition to 64 bit time_t support.
897 This is relevant on all 32-bit architectures, and 64-bit architectures
898 as part of compat syscall handling.
900 config ARCH_NO_PREEMPT
903 config ARCH_SUPPORTS_RT
906 config CPU_NO_EFFICIENT_FFS
909 config HAVE_ARCH_VMAP_STACK
912 An arch should select this symbol if it can support kernel stacks
913 in vmalloc space. This means:
915 - vmalloc space must be large enough to hold many kernel stacks.
916 This may rule out many 32-bit architectures.
918 - Stacks in vmalloc space need to work reliably. For example, if
919 vmap page tables are created on demand, either this mechanism
920 needs to work while the stack points to a virtual address with
921 unpopulated page tables or arch code (switch_to() and switch_mm(),
922 most likely) needs to ensure that the stack's page table entries
923 are populated before running on a possibly unpopulated stack.
925 - If the stack overflows into a guard page, something reasonable
926 should happen. The definition of "reasonable" is flexible, but
927 instantly rebooting without logging anything would be unfriendly.
931 bool "Use a virtually-mapped stack"
932 depends on HAVE_ARCH_VMAP_STACK
933 depends on !KASAN || KASAN_VMALLOC
935 Enable this if you want the use virtually-mapped kernel stacks
936 with guard pages. This causes kernel stack overflows to be
937 caught immediately rather than causing difficult-to-diagnose
940 To use this with KASAN, the architecture must support backing
941 virtual mappings with real shadow memory, and KASAN_VMALLOC must
944 config ARCH_OPTIONAL_KERNEL_RWX
947 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
950 config ARCH_HAS_STRICT_KERNEL_RWX
953 config STRICT_KERNEL_RWX
954 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
955 depends on ARCH_HAS_STRICT_KERNEL_RWX
956 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
958 If this is set, kernel text and rodata memory will be made read-only,
959 and non-text memory will be made non-executable. This provides
960 protection against certain security exploits (e.g. executing the heap
963 These features are considered standard security practice these days.
964 You should say Y here in almost all cases.
966 config ARCH_HAS_STRICT_MODULE_RWX
969 config STRICT_MODULE_RWX
970 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
971 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
972 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
974 If this is set, module text and rodata memory will be made read-only,
975 and non-text memory will be made non-executable. This provides
976 protection against certain security exploits (e.g. writing to text)
978 # select if the architecture provides an asm/dma-direct.h header
979 config ARCH_HAS_PHYS_TO_DMA
982 config HAVE_ARCH_COMPILER_H
985 An architecture can select this if it provides an
986 asm/compiler.h header that should be included after
987 linux/compiler-*.h in order to override macro definitions that those
988 headers generally provide.
990 config HAVE_ARCH_PREL32_RELOCATIONS
993 May be selected by an architecture if it supports place-relative
994 32-bit relocations, both in the toolchain and in the module loader,
995 in which case relative references can be used in special sections
996 for PCI fixup, initcalls etc which are only half the size on 64 bit
997 architectures, and don't require runtime relocation on relocatable
1000 config ARCH_USE_MEMREMAP_PROT
1003 config LOCK_EVENT_COUNTS
1004 bool "Locking event counts collection"
1007 Enable light-weight counting of various locking related events
1008 in the system with minimal performance impact. This reduces
1009 the chance of application behavior change because of timing
1010 differences. The counts are reported via debugfs.
1012 # Select if the architecture has support for applying RELR relocations.
1013 config ARCH_HAS_RELR
1017 bool "Use RELR relocation packing"
1018 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1021 Store the kernel's dynamic relocations in the RELR relocation packing
1022 format. Requires a compatible linker (LLD supports this feature), as
1023 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1026 config ARCH_HAS_MEM_ENCRYPT
1029 config HAVE_SPARSE_SYSCALL_NR
1032 An architecture should select this if its syscall numbering is sparse
1033 to save space. For example, MIPS architecture has a syscall array with
1034 entries at 4000, 5000 and 6000 locations. This option turns on syscall
1035 related optimizations for a given architecture.
1037 config ARCH_HAS_VDSO_DATA
1040 config HAVE_STATIC_CALL
1043 config HAVE_STATIC_CALL_INLINE
1045 depends on HAVE_STATIC_CALL
1047 source "kernel/gcov/Kconfig"
1049 source "scripts/gcc-plugins/Kconfig"