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 segement 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 architecure 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 architecure 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 architecure 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
489 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE,
490 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If
491 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too.
494 prompt "Enable seccomp to safely execute untrusted bytecode"
496 depends on HAVE_ARCH_SECCOMP
498 This kernel feature is useful for number crunching applications
499 that may need to handle untrusted bytecode during their
500 execution. By using pipes or other transports made available
501 to the process as file descriptors supporting the read/write
502 syscalls, it's possible to isolate those applications in their
503 own address space using seccomp. Once seccomp is enabled via
504 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
505 disabled and the task is only allowed to execute a few safe
506 syscalls defined by each seccomp mode.
510 config SECCOMP_FILTER
512 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
514 Enable tasks to build secure computing environments defined
515 in terms of Berkeley Packet Filter programs which implement
516 task-defined system call filtering polices.
518 See Documentation/userspace-api/seccomp_filter.rst for details.
520 config SECCOMP_CACHE_DEBUG
521 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache"
522 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR
525 This enables the /proc/pid/seccomp_cache interface to monitor
526 seccomp cache data. The file format is subject to change. Reading
527 the file requires CAP_SYS_ADMIN.
529 This option is for debugging only. Enabling presents the risk that
530 an adversary may be able to infer the seccomp filter logic.
534 config HAVE_ARCH_STACKLEAK
537 An architecture should select this if it has the code which
538 fills the used part of the kernel stack with the STACKLEAK_POISON
539 value before returning from system calls.
541 config HAVE_STACKPROTECTOR
544 An arch should select this symbol if:
545 - it has implemented a stack canary (e.g. __stack_chk_guard)
547 config STACKPROTECTOR
548 bool "Stack Protector buffer overflow detection"
549 depends on HAVE_STACKPROTECTOR
550 depends on $(cc-option,-fstack-protector)
553 This option turns on the "stack-protector" GCC feature. This
554 feature puts, at the beginning of functions, a canary value on
555 the stack just before the return address, and validates
556 the value just before actually returning. Stack based buffer
557 overflows (that need to overwrite this return address) now also
558 overwrite the canary, which gets detected and the attack is then
559 neutralized via a kernel panic.
561 Functions will have the stack-protector canary logic added if they
562 have an 8-byte or larger character array on the stack.
564 This feature requires gcc version 4.2 or above, or a distribution
565 gcc with the feature backported ("-fstack-protector").
567 On an x86 "defconfig" build, this feature adds canary checks to
568 about 3% of all kernel functions, which increases kernel code size
571 config STACKPROTECTOR_STRONG
572 bool "Strong Stack Protector"
573 depends on STACKPROTECTOR
574 depends on $(cc-option,-fstack-protector-strong)
577 Functions will have the stack-protector canary logic added in any
578 of the following conditions:
580 - local variable's address used as part of the right hand side of an
581 assignment or function argument
582 - local variable is an array (or union containing an array),
583 regardless of array type or length
584 - uses register local variables
586 This feature requires gcc version 4.9 or above, or a distribution
587 gcc with the feature backported ("-fstack-protector-strong").
589 On an x86 "defconfig" build, this feature adds canary checks to
590 about 20% of all kernel functions, which increases the kernel code
593 config ARCH_SUPPORTS_SHADOW_CALL_STACK
596 An architecture should select this if it supports Clang's Shadow
597 Call Stack and implements runtime support for shadow stack
600 config SHADOW_CALL_STACK
601 bool "Clang Shadow Call Stack"
602 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK
603 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
605 This option enables Clang's Shadow Call Stack, which uses a
606 shadow stack to protect function return addresses from being
607 overwritten by an attacker. More information can be found in
608 Clang's documentation:
610 https://clang.llvm.org/docs/ShadowCallStack.html
612 Note that security guarantees in the kernel differ from the
613 ones documented for user space. The kernel must store addresses
614 of shadow stacks in memory, which means an attacker capable of
615 reading and writing arbitrary memory may be able to locate them
616 and hijack control flow by modifying the stacks.
618 config HAVE_ARCH_WITHIN_STACK_FRAMES
621 An architecture should select this if it can walk the kernel stack
622 frames to determine if an object is part of either the arguments
623 or local variables (i.e. that it excludes saved return addresses,
624 and similar) by implementing an inline arch_within_stack_frames(),
625 which is used by CONFIG_HARDENED_USERCOPY.
627 config HAVE_CONTEXT_TRACKING
630 Provide kernel/user boundaries probes necessary for subsystems
631 that need it, such as userspace RCU extended quiescent state.
632 Syscalls need to be wrapped inside user_exit()-user_enter(), either
633 optimized behind static key or through the slow path using TIF_NOHZ
634 flag. Exceptions handlers must be wrapped as well. Irqs are already
635 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal
636 handling on irq exit still need to be protected.
641 Arch relies on TIF_NOHZ and syscall slow path to implement context
642 tracking calls to user_enter()/user_exit().
644 config HAVE_VIRT_CPU_ACCOUNTING
647 config ARCH_HAS_SCALED_CPUTIME
650 config HAVE_VIRT_CPU_ACCOUNTING_GEN
654 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
655 Before enabling this option, arch code must be audited
656 to ensure there are no races in concurrent read/write of
657 cputime_t. For example, reading/writing 64-bit cputime_t on
658 some 32-bit arches may require multiple accesses, so proper
659 locking is needed to protect against concurrent accesses.
662 config HAVE_IRQ_TIME_ACCOUNTING
665 Archs need to ensure they use a high enough resolution clock to
666 support irq time accounting and then call enable_sched_clock_irqtime().
671 Archs that select this are able to move page tables at the PMD level.
673 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
676 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
679 config HAVE_ARCH_HUGE_VMAP
682 config ARCH_WANT_HUGE_PMD_SHARE
685 config HAVE_ARCH_SOFT_DIRTY
688 config HAVE_MOD_ARCH_SPECIFIC
691 The arch uses struct mod_arch_specific to store data. Many arches
692 just need a simple module loader without arch specific data - those
693 should not enable this.
695 config MODULES_USE_ELF_RELA
698 Modules only use ELF RELA relocations. Modules with ELF REL
699 relocations will give an error.
701 config MODULES_USE_ELF_REL
704 Modules only use ELF REL relocations. Modules with ELF RELA
705 relocations will give an error.
707 config HAVE_IRQ_EXIT_ON_IRQ_STACK
710 Architecture doesn't only execute the irq handler on the irq stack
711 but also irq_exit(). This way we can process softirqs on this irq
712 stack instead of switching to a new one when we call __do_softirq()
713 in the end of an hardirq.
714 This spares a stack switch and improves cache usage on softirq
717 config PGTABLE_LEVELS
721 config ARCH_HAS_ELF_RANDOMIZE
724 An architecture supports choosing randomized locations for
725 stack, mmap, brk, and ET_DYN. Defined functions:
727 - arch_randomize_brk()
729 config HAVE_ARCH_MMAP_RND_BITS
732 An arch should select this symbol if it supports setting a variable
733 number of bits for use in establishing the base address for mmap
734 allocations, has MMU enabled and provides values for both:
735 - ARCH_MMAP_RND_BITS_MIN
736 - ARCH_MMAP_RND_BITS_MAX
738 config HAVE_EXIT_THREAD
741 An architecture implements exit_thread.
743 config ARCH_MMAP_RND_BITS_MIN
746 config ARCH_MMAP_RND_BITS_MAX
749 config ARCH_MMAP_RND_BITS_DEFAULT
752 config ARCH_MMAP_RND_BITS
753 int "Number of bits to use for ASLR of mmap base address" if EXPERT
754 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
755 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
756 default ARCH_MMAP_RND_BITS_MIN
757 depends on HAVE_ARCH_MMAP_RND_BITS
759 This value can be used to select the number of bits to use to
760 determine the random offset to the base address of vma regions
761 resulting from mmap allocations. This value will be bounded
762 by the architecture's minimum and maximum supported values.
764 This value can be changed after boot using the
765 /proc/sys/vm/mmap_rnd_bits tunable
767 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
770 An arch should select this symbol if it supports running applications
771 in compatibility mode, supports setting a variable number of bits for
772 use in establishing the base address for mmap allocations, has MMU
773 enabled and provides values for both:
774 - ARCH_MMAP_RND_COMPAT_BITS_MIN
775 - ARCH_MMAP_RND_COMPAT_BITS_MAX
777 config ARCH_MMAP_RND_COMPAT_BITS_MIN
780 config ARCH_MMAP_RND_COMPAT_BITS_MAX
783 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
786 config ARCH_MMAP_RND_COMPAT_BITS
787 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
788 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
789 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
790 default ARCH_MMAP_RND_COMPAT_BITS_MIN
791 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
793 This value can be used to select the number of bits to use to
794 determine the random offset to the base address of vma regions
795 resulting from mmap allocations for compatible applications This
796 value will be bounded by the architecture's minimum and maximum
799 This value can be changed after boot using the
800 /proc/sys/vm/mmap_rnd_compat_bits tunable
802 config HAVE_ARCH_COMPAT_MMAP_BASES
805 This allows 64bit applications to invoke 32-bit mmap() syscall
806 and vice-versa 32-bit applications to call 64-bit mmap().
807 Required for applications doing different bitness syscalls.
809 # This allows to use a set of generic functions to determine mmap base
810 # address by giving priority to top-down scheme only if the process
811 # is not in legacy mode (compat task, unlimited stack size or
812 # sysctl_legacy_va_layout).
813 # Architecture that selects this option can provide its own version of:
815 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
818 select ARCH_HAS_ELF_RANDOMIZE
820 config HAVE_STACK_VALIDATION
823 Architecture supports the 'objtool check' host tool command, which
824 performs compile-time stack metadata validation.
826 config HAVE_RELIABLE_STACKTRACE
829 Architecture has either save_stack_trace_tsk_reliable() or
830 arch_stack_walk_reliable() function which only returns a stack trace
831 if it can guarantee the trace is reliable.
833 config HAVE_ARCH_HASH
837 If this is set, the architecture provides an <asm/hash.h>
838 file which provides platform-specific implementations of some
839 functions in <linux/hash.h> or fs/namei.c.
841 config HAVE_ARCH_NVRAM_OPS
850 config CLONE_BACKWARDS
853 Architecture has tls passed as the 4th argument of clone(2),
856 config CLONE_BACKWARDS2
859 Architecture has the first two arguments of clone(2) swapped.
861 config CLONE_BACKWARDS3
864 Architecture has tls passed as the 3rd argument of clone(2),
867 config ODD_RT_SIGACTION
870 Architecture has unusual rt_sigaction(2) arguments
872 config OLD_SIGSUSPEND
875 Architecture has old sigsuspend(2) syscall, of one-argument variety
877 config OLD_SIGSUSPEND3
880 Even weirder antique ABI - three-argument sigsuspend(2)
885 Architecture has old sigaction(2) syscall. Nope, not the same
886 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
887 but fairly different variant of sigaction(2), thanks to OSF/1
890 config COMPAT_OLD_SIGACTION
893 config COMPAT_32BIT_TIME
894 bool "Provide system calls for 32-bit time_t"
895 default !64BIT || COMPAT
897 This enables 32 bit time_t support in addition to 64 bit time_t support.
898 This is relevant on all 32-bit architectures, and 64-bit architectures
899 as part of compat syscall handling.
901 config ARCH_NO_PREEMPT
904 config ARCH_SUPPORTS_RT
907 config CPU_NO_EFFICIENT_FFS
910 config HAVE_ARCH_VMAP_STACK
913 An arch should select this symbol if it can support kernel stacks
914 in vmalloc space. This means:
916 - vmalloc space must be large enough to hold many kernel stacks.
917 This may rule out many 32-bit architectures.
919 - Stacks in vmalloc space need to work reliably. For example, if
920 vmap page tables are created on demand, either this mechanism
921 needs to work while the stack points to a virtual address with
922 unpopulated page tables or arch code (switch_to() and switch_mm(),
923 most likely) needs to ensure that the stack's page table entries
924 are populated before running on a possibly unpopulated stack.
926 - If the stack overflows into a guard page, something reasonable
927 should happen. The definition of "reasonable" is flexible, but
928 instantly rebooting without logging anything would be unfriendly.
932 bool "Use a virtually-mapped stack"
933 depends on HAVE_ARCH_VMAP_STACK
934 depends on !KASAN || KASAN_VMALLOC
936 Enable this if you want the use virtually-mapped kernel stacks
937 with guard pages. This causes kernel stack overflows to be
938 caught immediately rather than causing difficult-to-diagnose
941 To use this with KASAN, the architecture must support backing
942 virtual mappings with real shadow memory, and KASAN_VMALLOC must
945 config ARCH_OPTIONAL_KERNEL_RWX
948 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
951 config ARCH_HAS_STRICT_KERNEL_RWX
954 config STRICT_KERNEL_RWX
955 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
956 depends on ARCH_HAS_STRICT_KERNEL_RWX
957 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
959 If this is set, kernel text and rodata memory will be made read-only,
960 and non-text memory will be made non-executable. This provides
961 protection against certain security exploits (e.g. executing the heap
964 These features are considered standard security practice these days.
965 You should say Y here in almost all cases.
967 config ARCH_HAS_STRICT_MODULE_RWX
970 config STRICT_MODULE_RWX
971 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
972 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
973 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
975 If this is set, module text and rodata memory will be made read-only,
976 and non-text memory will be made non-executable. This provides
977 protection against certain security exploits (e.g. writing to text)
979 # select if the architecture provides an asm/dma-direct.h header
980 config ARCH_HAS_PHYS_TO_DMA
983 config HAVE_ARCH_COMPILER_H
986 An architecture can select this if it provides an
987 asm/compiler.h header that should be included after
988 linux/compiler-*.h in order to override macro definitions that those
989 headers generally provide.
991 config HAVE_ARCH_PREL32_RELOCATIONS
994 May be selected by an architecture if it supports place-relative
995 32-bit relocations, both in the toolchain and in the module loader,
996 in which case relative references can be used in special sections
997 for PCI fixup, initcalls etc which are only half the size on 64 bit
998 architectures, and don't require runtime relocation on relocatable
1001 config ARCH_USE_MEMREMAP_PROT
1004 config LOCK_EVENT_COUNTS
1005 bool "Locking event counts collection"
1008 Enable light-weight counting of various locking related events
1009 in the system with minimal performance impact. This reduces
1010 the chance of application behavior change because of timing
1011 differences. The counts are reported via debugfs.
1013 # Select if the architecture has support for applying RELR relocations.
1014 config ARCH_HAS_RELR
1018 bool "Use RELR relocation packing"
1019 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1022 Store the kernel's dynamic relocations in the RELR relocation packing
1023 format. Requires a compatible linker (LLD supports this feature), as
1024 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1027 config ARCH_HAS_MEM_ENCRYPT
1030 config HAVE_SPARSE_SYSCALL_NR
1033 An architecture should select this if its syscall numbering is sparse
1034 to save space. For example, MIPS architecture has a syscall array with
1035 entries at 4000, 5000 and 6000 locations. This option turns on syscall
1036 related optimizations for a given architecture.
1038 config ARCH_HAS_VDSO_DATA
1041 config HAVE_STATIC_CALL
1044 config HAVE_STATIC_CALL_INLINE
1046 depends on HAVE_STATIC_CALL
1048 source "kernel/gcov/Kconfig"
1050 source "scripts/gcc-plugins/Kconfig"