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"
31 tristate "OProfile system profiling"
33 depends on HAVE_OPROFILE
35 select RING_BUFFER_ALLOW_SWAP
37 OProfile is a profiling system capable of profiling the
38 whole system, include the kernel, kernel modules, libraries,
43 config OPROFILE_EVENT_MULTIPLEX
44 bool "OProfile multiplexing support (EXPERIMENTAL)"
46 depends on OPROFILE && X86
48 The number of hardware counters is limited. The multiplexing
49 feature enables OProfile to gather more events than counters
50 are provided by the hardware. This is realized by switching
51 between events at a user specified time interval.
58 config OPROFILE_NMI_TIMER
60 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
65 depends on HAVE_KPROBES
68 Kprobes allows you to trap at almost any kernel address and
69 execute a callback function. register_kprobe() establishes
70 a probepoint and specifies the callback. Kprobes is useful
71 for kernel debugging, non-intrusive instrumentation and testing.
75 bool "Optimize very unlikely/likely branches"
76 depends on HAVE_ARCH_JUMP_LABEL
77 depends on CC_HAS_ASM_GOTO
79 This option enables a transparent branch optimization that
80 makes certain almost-always-true or almost-always-false branch
81 conditions even cheaper to execute within the kernel.
83 Certain performance-sensitive kernel code, such as trace points,
84 scheduler functionality, networking code and KVM have such
85 branches and include support for this optimization technique.
87 If it is detected that the compiler has support for "asm goto",
88 the kernel will compile such branches with just a nop
89 instruction. When the condition flag is toggled to true, the
90 nop will be converted to a jump instruction to execute the
91 conditional block of instructions.
93 This technique lowers overhead and stress on the branch prediction
94 of the processor and generally makes the kernel faster. The update
95 of the condition is slower, but those are always very rare.
97 ( On 32-bit x86, the necessary options added to the compiler
98 flags may increase the size of the kernel slightly. )
100 config STATIC_KEYS_SELFTEST
101 bool "Static key selftest"
102 depends on JUMP_LABEL
104 Boot time self-test of the branch patching code.
108 depends on KPROBES && HAVE_OPTPROBES
109 select TASKS_RCU if PREEMPTION
111 config KPROBES_ON_FTRACE
113 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
114 depends on DYNAMIC_FTRACE_WITH_REGS
116 If function tracer is enabled and the arch supports full
117 passing of pt_regs to function tracing, then kprobes can
118 optimize on top of function tracing.
122 depends on ARCH_SUPPORTS_UPROBES
124 Uprobes is the user-space counterpart to kprobes: they
125 enable instrumentation applications (such as 'perf probe')
126 to establish unintrusive probes in user-space binaries and
127 libraries, by executing handler functions when the probes
128 are hit by user-space applications.
130 ( These probes come in the form of single-byte breakpoints,
131 managed by the kernel and kept transparent to the probed
134 config HAVE_64BIT_ALIGNED_ACCESS
135 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
137 Some architectures require 64 bit accesses to be 64 bit
138 aligned, which also requires structs containing 64 bit values
139 to be 64 bit aligned too. This includes some 32 bit
140 architectures which can do 64 bit accesses, as well as 64 bit
141 architectures without unaligned access.
143 This symbol should be selected by an architecture if 64 bit
144 accesses are required to be 64 bit aligned in this way even
145 though it is not a 64 bit architecture.
147 See Documentation/unaligned-memory-access.txt for more
148 information on the topic of unaligned memory accesses.
150 config HAVE_EFFICIENT_UNALIGNED_ACCESS
153 Some architectures are unable to perform unaligned accesses
154 without the use of get_unaligned/put_unaligned. Others are
155 unable to perform such accesses efficiently (e.g. trap on
156 unaligned access and require fixing it up in the exception
159 This symbol should be selected by an architecture if it can
160 perform unaligned accesses efficiently to allow different
161 code paths to be selected for these cases. Some network
162 drivers, for example, could opt to not fix up alignment
163 problems with received packets if doing so would not help
166 See Documentation/unaligned-memory-access.txt for more
167 information on the topic of unaligned memory accesses.
169 config ARCH_USE_BUILTIN_BSWAP
172 Modern versions of GCC (since 4.4) have builtin functions
173 for handling byte-swapping. Using these, instead of the old
174 inline assembler that the architecture code provides in the
175 __arch_bswapXX() macros, allows the compiler to see what's
176 happening and offers more opportunity for optimisation. In
177 particular, the compiler will be able to combine the byteswap
178 with a nearby load or store and use load-and-swap or
179 store-and-swap instructions if the architecture has them. It
180 should almost *never* result in code which is worse than the
181 hand-coded assembler in <asm/swab.h>. But just in case it
182 does, the use of the builtins is optional.
184 Any architecture with load-and-swap or store-and-swap
185 instructions should set this. And it shouldn't hurt to set it
186 on architectures that don't have such instructions.
190 depends on KPROBES && HAVE_KRETPROBES
192 config USER_RETURN_NOTIFIER
194 depends on HAVE_USER_RETURN_NOTIFIER
196 Provide a kernel-internal notification when a cpu is about to
199 config HAVE_IOREMAP_PROT
205 config HAVE_KRETPROBES
208 config HAVE_OPTPROBES
211 config HAVE_KPROBES_ON_FTRACE
214 config HAVE_FUNCTION_ERROR_INJECTION
221 # An arch should select this if it provides all these things:
223 # task_pt_regs() in asm/processor.h or asm/ptrace.h
224 # arch_has_single_step() if there is hardware single-step support
225 # arch_has_block_step() if there is hardware block-step support
226 # asm/syscall.h supplying asm-generic/syscall.h interface
227 # linux/regset.h user_regset interfaces
228 # CORE_DUMP_USE_REGSET #define'd in linux/elf.h
229 # TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit}
230 # TIF_NOTIFY_RESUME calls tracehook_notify_resume()
231 # signal delivery calls tracehook_signal_handler()
233 config HAVE_ARCH_TRACEHOOK
236 config HAVE_DMA_CONTIGUOUS
239 config GENERIC_SMP_IDLE_THREAD
242 config GENERIC_IDLE_POLL_SETUP
245 config ARCH_HAS_FORTIFY_SOURCE
248 An architecture should select this when it can successfully
249 build and run with CONFIG_FORTIFY_SOURCE.
252 # Select if the arch provides a historic keepinit alias for the retain_initrd
253 # command line option
255 config ARCH_HAS_KEEPINITRD
258 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
259 config ARCH_HAS_SET_MEMORY
262 # Select if arch has all set_direct_map_invalid/default() functions
263 config ARCH_HAS_SET_DIRECT_MAP
267 # Select if arch has an uncached kernel segment and provides the
268 # uncached_kernel_address / cached_kernel_address symbols to use it
270 config ARCH_HAS_UNCACHED_SEGMENT
271 select ARCH_HAS_DMA_PREP_COHERENT
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
343 The <linux/clk.h> calls support software clock gating and
344 thus are a key power management tool on many systems.
346 config HAVE_HW_BREAKPOINT
348 depends on PERF_EVENTS
350 config HAVE_MIXED_BREAKPOINTS_REGS
352 depends on HAVE_HW_BREAKPOINT
354 Depending on the arch implementation of hardware breakpoints,
355 some of them have separate registers for data and instruction
356 breakpoints addresses, others have mixed registers to store
357 them but define the access type in a control register.
358 Select this option if your arch implements breakpoints under the
361 config HAVE_USER_RETURN_NOTIFIER
364 config HAVE_PERF_EVENTS_NMI
367 System hardware can generate an NMI using the perf event
368 subsystem. Also has support for calculating CPU cycle events
369 to determine how many clock cycles in a given period.
371 config HAVE_HARDLOCKUP_DETECTOR_PERF
373 depends on HAVE_PERF_EVENTS_NMI
375 The arch chooses to use the generic perf-NMI-based hardlockup
376 detector. Must define HAVE_PERF_EVENTS_NMI.
378 config HAVE_NMI_WATCHDOG
382 The arch provides a low level NMI watchdog. It provides
383 asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
385 config HAVE_HARDLOCKUP_DETECTOR_ARCH
387 select HAVE_NMI_WATCHDOG
389 The arch chooses to provide its own hardlockup detector, which is
390 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
391 interfaces and parameters provided by hardlockup detector subsystem.
393 config HAVE_PERF_REGS
396 Support selective register dumps for perf events. This includes
397 bit-mapping of each registers and a unique architecture id.
399 config HAVE_PERF_USER_STACK_DUMP
402 Support user stack dumps for perf event samples. This needs
403 access to the user stack pointer which is not unified across
406 config HAVE_ARCH_JUMP_LABEL
409 config HAVE_ARCH_JUMP_LABEL_RELATIVE
412 config HAVE_RCU_TABLE_FREE
415 config HAVE_MMU_GATHER_PAGE_SIZE
418 config MMU_GATHER_NO_RANGE
421 config HAVE_MMU_GATHER_NO_GATHER
424 config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
427 Temporary select until all architectures can be converted to have
428 irqs disabled over activate_mm. Architectures that do IPI based TLB
429 shootdowns should enable this.
431 config ARCH_HAVE_NMI_SAFE_CMPXCHG
434 config HAVE_ALIGNED_STRUCT_PAGE
437 This makes sure that struct pages are double word aligned and that
438 e.g. the SLUB allocator can perform double word atomic operations
439 on a struct page for better performance. However selecting this
440 might increase the size of a struct page by a word.
442 config HAVE_CMPXCHG_LOCAL
445 config HAVE_CMPXCHG_DOUBLE
448 config ARCH_WEAK_RELEASE_ACQUIRE
451 config ARCH_WANT_IPC_PARSE_VERSION
454 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
457 config ARCH_WANT_OLD_COMPAT_IPC
458 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
461 config HAVE_ARCH_SECCOMP_FILTER
464 An arch should select this symbol if it provides all of these things:
466 - syscall_get_arguments()
468 - syscall_set_return_value()
469 - SIGSYS siginfo_t support
470 - secure_computing is called from a ptrace_event()-safe context
471 - secure_computing return value is checked and a return value of -1
472 results in the system call being skipped immediately.
473 - seccomp syscall wired up
475 config SECCOMP_FILTER
477 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
479 Enable tasks to build secure computing environments defined
480 in terms of Berkeley Packet Filter programs which implement
481 task-defined system call filtering polices.
483 See Documentation/userspace-api/seccomp_filter.rst for details.
485 config HAVE_ARCH_STACKLEAK
488 An architecture should select this if it has the code which
489 fills the used part of the kernel stack with the STACKLEAK_POISON
490 value before returning from system calls.
492 config HAVE_STACKPROTECTOR
495 An arch should select this symbol if:
496 - it has implemented a stack canary (e.g. __stack_chk_guard)
498 config CC_HAS_STACKPROTECTOR_NONE
499 def_bool $(cc-option,-fno-stack-protector)
501 config STACKPROTECTOR
502 bool "Stack Protector buffer overflow detection"
503 depends on HAVE_STACKPROTECTOR
504 depends on $(cc-option,-fstack-protector)
507 This option turns on the "stack-protector" GCC feature. This
508 feature puts, at the beginning of functions, a canary value on
509 the stack just before the return address, and validates
510 the value just before actually returning. Stack based buffer
511 overflows (that need to overwrite this return address) now also
512 overwrite the canary, which gets detected and the attack is then
513 neutralized via a kernel panic.
515 Functions will have the stack-protector canary logic added if they
516 have an 8-byte or larger character array on the stack.
518 This feature requires gcc version 4.2 or above, or a distribution
519 gcc with the feature backported ("-fstack-protector").
521 On an x86 "defconfig" build, this feature adds canary checks to
522 about 3% of all kernel functions, which increases kernel code size
525 config STACKPROTECTOR_STRONG
526 bool "Strong Stack Protector"
527 depends on STACKPROTECTOR
528 depends on $(cc-option,-fstack-protector-strong)
531 Functions will have the stack-protector canary logic added in any
532 of the following conditions:
534 - local variable's address used as part of the right hand side of an
535 assignment or function argument
536 - local variable is an array (or union containing an array),
537 regardless of array type or length
538 - uses register local variables
540 This feature requires gcc version 4.9 or above, or a distribution
541 gcc with the feature backported ("-fstack-protector-strong").
543 On an x86 "defconfig" build, this feature adds canary checks to
544 about 20% of all kernel functions, which increases the kernel code
547 config HAVE_ARCH_WITHIN_STACK_FRAMES
550 An architecture should select this if it can walk the kernel stack
551 frames to determine if an object is part of either the arguments
552 or local variables (i.e. that it excludes saved return addresses,
553 and similar) by implementing an inline arch_within_stack_frames(),
554 which is used by CONFIG_HARDENED_USERCOPY.
556 config HAVE_CONTEXT_TRACKING
559 Provide kernel/user boundaries probes necessary for subsystems
560 that need it, such as userspace RCU extended quiescent state.
561 Syscalls need to be wrapped inside user_exit()-user_enter() through
562 the slow path using TIF_NOHZ flag. Exceptions handlers must be
563 wrapped as well. Irqs are already protected inside
564 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
565 irq exit still need to be protected.
567 config HAVE_VIRT_CPU_ACCOUNTING
570 config ARCH_HAS_SCALED_CPUTIME
573 config HAVE_VIRT_CPU_ACCOUNTING_GEN
577 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
578 Before enabling this option, arch code must be audited
579 to ensure there are no races in concurrent read/write of
580 cputime_t. For example, reading/writing 64-bit cputime_t on
581 some 32-bit arches may require multiple accesses, so proper
582 locking is needed to protect against concurrent accesses.
585 config HAVE_IRQ_TIME_ACCOUNTING
588 Archs need to ensure they use a high enough resolution clock to
589 support irq time accounting and then call enable_sched_clock_irqtime().
594 Archs that select this are able to move page tables at the PMD level.
596 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
599 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
602 config HAVE_ARCH_HUGE_VMAP
605 config ARCH_WANT_HUGE_PMD_SHARE
608 config HAVE_ARCH_SOFT_DIRTY
611 config HAVE_MOD_ARCH_SPECIFIC
614 The arch uses struct mod_arch_specific to store data. Many arches
615 just need a simple module loader without arch specific data - those
616 should not enable this.
618 config MODULES_USE_ELF_RELA
621 Modules only use ELF RELA relocations. Modules with ELF REL
622 relocations will give an error.
624 config MODULES_USE_ELF_REL
627 Modules only use ELF REL relocations. Modules with ELF RELA
628 relocations will give an error.
630 config HAVE_IRQ_EXIT_ON_IRQ_STACK
633 Architecture doesn't only execute the irq handler on the irq stack
634 but also irq_exit(). This way we can process softirqs on this irq
635 stack instead of switching to a new one when we call __do_softirq()
636 in the end of an hardirq.
637 This spares a stack switch and improves cache usage on softirq
640 config PGTABLE_LEVELS
644 config ARCH_HAS_ELF_RANDOMIZE
647 An architecture supports choosing randomized locations for
648 stack, mmap, brk, and ET_DYN. Defined functions:
650 - arch_randomize_brk()
652 config HAVE_ARCH_MMAP_RND_BITS
655 An arch should select this symbol if it supports setting a variable
656 number of bits for use in establishing the base address for mmap
657 allocations, has MMU enabled and provides values for both:
658 - ARCH_MMAP_RND_BITS_MIN
659 - ARCH_MMAP_RND_BITS_MAX
661 config HAVE_EXIT_THREAD
664 An architecture implements exit_thread.
666 config ARCH_MMAP_RND_BITS_MIN
669 config ARCH_MMAP_RND_BITS_MAX
672 config ARCH_MMAP_RND_BITS_DEFAULT
675 config ARCH_MMAP_RND_BITS
676 int "Number of bits to use for ASLR of mmap base address" if EXPERT
677 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
678 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
679 default ARCH_MMAP_RND_BITS_MIN
680 depends on HAVE_ARCH_MMAP_RND_BITS
682 This value can be used to select the number of bits to use to
683 determine the random offset to the base address of vma regions
684 resulting from mmap allocations. This value will be bounded
685 by the architecture's minimum and maximum supported values.
687 This value can be changed after boot using the
688 /proc/sys/vm/mmap_rnd_bits tunable
690 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
693 An arch should select this symbol if it supports running applications
694 in compatibility mode, supports setting a variable number of bits for
695 use in establishing the base address for mmap allocations, has MMU
696 enabled and provides values for both:
697 - ARCH_MMAP_RND_COMPAT_BITS_MIN
698 - ARCH_MMAP_RND_COMPAT_BITS_MAX
700 config ARCH_MMAP_RND_COMPAT_BITS_MIN
703 config ARCH_MMAP_RND_COMPAT_BITS_MAX
706 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
709 config ARCH_MMAP_RND_COMPAT_BITS
710 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
711 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
712 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
713 default ARCH_MMAP_RND_COMPAT_BITS_MIN
714 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
716 This value can be used to select the number of bits to use to
717 determine the random offset to the base address of vma regions
718 resulting from mmap allocations for compatible applications This
719 value will be bounded by the architecture's minimum and maximum
722 This value can be changed after boot using the
723 /proc/sys/vm/mmap_rnd_compat_bits tunable
725 config HAVE_ARCH_COMPAT_MMAP_BASES
728 This allows 64bit applications to invoke 32-bit mmap() syscall
729 and vice-versa 32-bit applications to call 64-bit mmap().
730 Required for applications doing different bitness syscalls.
732 # This allows to use a set of generic functions to determine mmap base
733 # address by giving priority to top-down scheme only if the process
734 # is not in legacy mode (compat task, unlimited stack size or
735 # sysctl_legacy_va_layout).
736 # Architecture that selects this option can provide its own version of:
738 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
741 select ARCH_HAS_ELF_RANDOMIZE
743 config HAVE_COPY_THREAD_TLS
746 Architecture provides copy_thread_tls to accept tls argument via
747 normal C parameter passing, rather than extracting the syscall
748 argument from pt_regs.
750 config HAVE_STACK_VALIDATION
753 Architecture supports the 'objtool check' host tool command, which
754 performs compile-time stack metadata validation.
756 config HAVE_RELIABLE_STACKTRACE
759 Architecture has a save_stack_trace_tsk_reliable() function which
760 only returns a stack trace if it can guarantee the trace is reliable.
762 config HAVE_ARCH_HASH
766 If this is set, the architecture provides an <asm/hash.h>
767 file which provides platform-specific implementations of some
768 functions in <linux/hash.h> or fs/namei.c.
770 config HAVE_ARCH_NVRAM_OPS
779 config CLONE_BACKWARDS
782 Architecture has tls passed as the 4th argument of clone(2),
785 config CLONE_BACKWARDS2
788 Architecture has the first two arguments of clone(2) swapped.
790 config CLONE_BACKWARDS3
793 Architecture has tls passed as the 3rd argument of clone(2),
796 config ODD_RT_SIGACTION
799 Architecture has unusual rt_sigaction(2) arguments
801 config OLD_SIGSUSPEND
804 Architecture has old sigsuspend(2) syscall, of one-argument variety
806 config OLD_SIGSUSPEND3
809 Even weirder antique ABI - three-argument sigsuspend(2)
814 Architecture has old sigaction(2) syscall. Nope, not the same
815 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
816 but fairly different variant of sigaction(2), thanks to OSF/1
819 config COMPAT_OLD_SIGACTION
825 This should be selected by all architectures that need to support
826 new system calls with a 64-bit time_t. This is relevant on all 32-bit
827 architectures, and 64-bit architectures as part of compat syscall
830 config COMPAT_32BIT_TIME
831 def_bool !64BIT || COMPAT
833 This enables 32 bit time_t support in addition to 64 bit time_t support.
834 This is relevant on all 32-bit architectures, and 64-bit architectures
835 as part of compat syscall handling.
837 config ARCH_NO_PREEMPT
840 config ARCH_SUPPORTS_RT
843 config CPU_NO_EFFICIENT_FFS
846 config HAVE_ARCH_VMAP_STACK
849 An arch should select this symbol if it can support kernel stacks
850 in vmalloc space. This means:
852 - vmalloc space must be large enough to hold many kernel stacks.
853 This may rule out many 32-bit architectures.
855 - Stacks in vmalloc space need to work reliably. For example, if
856 vmap page tables are created on demand, either this mechanism
857 needs to work while the stack points to a virtual address with
858 unpopulated page tables or arch code (switch_to() and switch_mm(),
859 most likely) needs to ensure that the stack's page table entries
860 are populated before running on a possibly unpopulated stack.
862 - If the stack overflows into a guard page, something reasonable
863 should happen. The definition of "reasonable" is flexible, but
864 instantly rebooting without logging anything would be unfriendly.
868 bool "Use a virtually-mapped stack"
869 depends on HAVE_ARCH_VMAP_STACK && !KASAN
871 Enable this if you want the use virtually-mapped kernel stacks
872 with guard pages. This causes kernel stack overflows to be
873 caught immediately rather than causing difficult-to-diagnose
876 This is presently incompatible with KASAN because KASAN expects
877 the stack to map directly to the KASAN shadow map using a formula
878 that is incorrect if the stack is in vmalloc space.
880 config ARCH_OPTIONAL_KERNEL_RWX
883 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
886 config ARCH_HAS_STRICT_KERNEL_RWX
889 config STRICT_KERNEL_RWX
890 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
891 depends on ARCH_HAS_STRICT_KERNEL_RWX
892 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
894 If this is set, kernel text and rodata memory will be made read-only,
895 and non-text memory will be made non-executable. This provides
896 protection against certain security exploits (e.g. executing the heap
899 These features are considered standard security practice these days.
900 You should say Y here in almost all cases.
902 config ARCH_HAS_STRICT_MODULE_RWX
905 config STRICT_MODULE_RWX
906 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
907 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
908 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
910 If this is set, module text and rodata memory will be made read-only,
911 and non-text memory will be made non-executable. This provides
912 protection against certain security exploits (e.g. writing to text)
914 # select if the architecture provides an asm/dma-direct.h header
915 config ARCH_HAS_PHYS_TO_DMA
918 config ARCH_HAS_REFCOUNT
921 An architecture selects this when it has implemented refcount_t
922 using open coded assembly primitives that provide an optimized
923 refcount_t implementation, possibly at the expense of some full
924 refcount state checks of CONFIG_REFCOUNT_FULL=y.
926 The refcount overflow check behavior, however, must be retained.
927 Catching overflows is the primary security concern for protecting
928 against bugs in reference counts.
931 bool "Perform full reference count validation at the expense of speed"
933 Enabling this switches the refcounting infrastructure from a fast
934 unchecked atomic_t implementation to a fully state checked
935 implementation, which can be (slightly) slower but provides protections
936 against various use-after-free conditions that can be used in
937 security flaw exploits.
939 config HAVE_ARCH_COMPILER_H
942 An architecture can select this if it provides an
943 asm/compiler.h header that should be included after
944 linux/compiler-*.h in order to override macro definitions that those
945 headers generally provide.
947 config HAVE_ARCH_PREL32_RELOCATIONS
950 May be selected by an architecture if it supports place-relative
951 32-bit relocations, both in the toolchain and in the module loader,
952 in which case relative references can be used in special sections
953 for PCI fixup, initcalls etc which are only half the size on 64 bit
954 architectures, and don't require runtime relocation on relocatable
957 config ARCH_USE_MEMREMAP_PROT
960 config LOCK_EVENT_COUNTS
961 bool "Locking event counts collection"
964 Enable light-weight counting of various locking related events
965 in the system with minimal performance impact. This reduces
966 the chance of application behavior change because of timing
967 differences. The counts are reported via debugfs.
969 # Select if the architecture has support for applying RELR relocations.
974 bool "Use RELR relocation packing"
975 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
978 Store the kernel's dynamic relocations in the RELR relocation packing
979 format. Requires a compatible linker (LLD supports this feature), as
980 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
983 config ARCH_HAS_MEM_ENCRYPT
986 source "kernel/gcov/Kconfig"
988 source "scripts/gcc-plugins/Kconfig"