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"
39 depends on HAVE_KPROBES
42 Kprobes allows you to trap at almost any kernel address and
43 execute a callback function. register_kprobe() establishes
44 a probepoint and specifies the callback. Kprobes is useful
45 for kernel debugging, non-intrusive instrumentation and testing.
49 bool "Optimize very unlikely/likely branches"
50 depends on HAVE_ARCH_JUMP_LABEL
51 depends on CC_HAS_ASM_GOTO
53 This option enables a transparent branch optimization that
54 makes certain almost-always-true or almost-always-false branch
55 conditions even cheaper to execute within the kernel.
57 Certain performance-sensitive kernel code, such as trace points,
58 scheduler functionality, networking code and KVM have such
59 branches and include support for this optimization technique.
61 If it is detected that the compiler has support for "asm goto",
62 the kernel will compile such branches with just a nop
63 instruction. When the condition flag is toggled to true, the
64 nop will be converted to a jump instruction to execute the
65 conditional block of instructions.
67 This technique lowers overhead and stress on the branch prediction
68 of the processor and generally makes the kernel faster. The update
69 of the condition is slower, but those are always very rare.
71 ( On 32-bit x86, the necessary options added to the compiler
72 flags may increase the size of the kernel slightly. )
74 config STATIC_KEYS_SELFTEST
75 bool "Static key selftest"
78 Boot time self-test of the branch patching code.
80 config STATIC_CALL_SELFTEST
81 bool "Static call selftest"
82 depends on HAVE_STATIC_CALL
84 Boot time self-test of the call patching code.
88 depends on KPROBES && HAVE_OPTPROBES
89 select TASKS_RCU if PREEMPTION
91 config KPROBES_ON_FTRACE
93 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
94 depends on DYNAMIC_FTRACE_WITH_REGS
96 If function tracer is enabled and the arch supports full
97 passing of pt_regs to function tracing, then kprobes can
98 optimize on top of function tracing.
102 depends on ARCH_SUPPORTS_UPROBES
104 Uprobes is the user-space counterpart to kprobes: they
105 enable instrumentation applications (such as 'perf probe')
106 to establish unintrusive probes in user-space binaries and
107 libraries, by executing handler functions when the probes
108 are hit by user-space applications.
110 ( These probes come in the form of single-byte breakpoints,
111 managed by the kernel and kept transparent to the probed
114 config HAVE_64BIT_ALIGNED_ACCESS
115 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
117 Some architectures require 64 bit accesses to be 64 bit
118 aligned, which also requires structs containing 64 bit values
119 to be 64 bit aligned too. This includes some 32 bit
120 architectures which can do 64 bit accesses, as well as 64 bit
121 architectures without unaligned access.
123 This symbol should be selected by an architecture if 64 bit
124 accesses are required to be 64 bit aligned in this way even
125 though it is not a 64 bit architecture.
127 See Documentation/unaligned-memory-access.txt for more
128 information on the topic of unaligned memory accesses.
130 config HAVE_EFFICIENT_UNALIGNED_ACCESS
133 Some architectures are unable to perform unaligned accesses
134 without the use of get_unaligned/put_unaligned. Others are
135 unable to perform such accesses efficiently (e.g. trap on
136 unaligned access and require fixing it up in the exception
139 This symbol should be selected by an architecture if it can
140 perform unaligned accesses efficiently to allow different
141 code paths to be selected for these cases. Some network
142 drivers, for example, could opt to not fix up alignment
143 problems with received packets if doing so would not help
146 See Documentation/core-api/unaligned-memory-access.rst for more
147 information on the topic of unaligned memory accesses.
149 config ARCH_USE_BUILTIN_BSWAP
152 Modern versions of GCC (since 4.4) have builtin functions
153 for handling byte-swapping. Using these, instead of the old
154 inline assembler that the architecture code provides in the
155 __arch_bswapXX() macros, allows the compiler to see what's
156 happening and offers more opportunity for optimisation. In
157 particular, the compiler will be able to combine the byteswap
158 with a nearby load or store and use load-and-swap or
159 store-and-swap instructions if the architecture has them. It
160 should almost *never* result in code which is worse than the
161 hand-coded assembler in <asm/swab.h>. But just in case it
162 does, the use of the builtins is optional.
164 Any architecture with load-and-swap or store-and-swap
165 instructions should set this. And it shouldn't hurt to set it
166 on architectures that don't have such instructions.
170 depends on KPROBES && HAVE_KRETPROBES
172 config USER_RETURN_NOTIFIER
174 depends on HAVE_USER_RETURN_NOTIFIER
176 Provide a kernel-internal notification when a cpu is about to
179 config HAVE_IOREMAP_PROT
185 config HAVE_KRETPROBES
188 config HAVE_OPTPROBES
191 config HAVE_KPROBES_ON_FTRACE
194 config HAVE_FUNCTION_ERROR_INJECTION
201 # An arch should select this if it provides all these things:
203 # task_pt_regs() in asm/processor.h or asm/ptrace.h
204 # arch_has_single_step() if there is hardware single-step support
205 # arch_has_block_step() if there is hardware block-step support
206 # asm/syscall.h supplying asm-generic/syscall.h interface
207 # linux/regset.h user_regset interfaces
208 # CORE_DUMP_USE_REGSET #define'd in linux/elf.h
209 # TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit}
210 # TIF_NOTIFY_RESUME calls tracehook_notify_resume()
211 # signal delivery calls tracehook_signal_handler()
213 config HAVE_ARCH_TRACEHOOK
216 config HAVE_DMA_CONTIGUOUS
219 config GENERIC_SMP_IDLE_THREAD
222 config GENERIC_IDLE_POLL_SETUP
225 config ARCH_HAS_FORTIFY_SOURCE
228 An architecture should select this when it can successfully
229 build and run with CONFIG_FORTIFY_SOURCE.
232 # Select if the arch provides a historic keepinit alias for the retain_initrd
233 # command line option
235 config ARCH_HAS_KEEPINITRD
238 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
239 config ARCH_HAS_SET_MEMORY
242 # Select if arch has all set_direct_map_invalid/default() functions
243 config ARCH_HAS_SET_DIRECT_MAP
247 # Select if the architecture provides the arch_dma_set_uncached symbol to
248 # either provide an uncached segment alias for a DMA allocation, or
249 # to remap the page tables in place.
251 config ARCH_HAS_DMA_SET_UNCACHED
255 # Select if the architectures provides the arch_dma_clear_uncached symbol
256 # to undo an in-place page table remap for uncached access.
258 config ARCH_HAS_DMA_CLEAR_UNCACHED
261 # Select if arch init_task must go in the __init_task_data section
262 config ARCH_TASK_STRUCT_ON_STACK
265 # Select if arch has its private alloc_task_struct() function
266 config ARCH_TASK_STRUCT_ALLOCATOR
269 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
271 depends on !ARCH_TASK_STRUCT_ALLOCATOR
273 An architecture should select this to provide hardened usercopy
274 knowledge about what region of the thread_struct should be
275 whitelisted for copying to userspace. Normally this is only the
276 FPU registers. Specifically, arch_thread_struct_whitelist()
277 should be implemented. Without this, the entire thread_struct
278 field in task_struct will be left whitelisted.
280 # Select if arch has its private alloc_thread_stack() function
281 config ARCH_THREAD_STACK_ALLOCATOR
284 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
285 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
288 config ARCH_32BIT_OFF_T
292 All new 32-bit architectures should have 64-bit off_t type on
293 userspace side which corresponds to the loff_t kernel type. This
294 is the requirement for modern ABIs. Some existing architectures
295 still support 32-bit off_t. This option is enabled for all such
296 architectures explicitly.
298 config HAVE_ASM_MODVERSIONS
301 This symbol should be selected by an architecture if it provides
302 <asm/asm-prototypes.h> to support the module versioning for symbols
303 exported from assembly code.
305 config HAVE_REGS_AND_STACK_ACCESS_API
308 This symbol should be selected by an architecture if it supports
309 the API needed to access registers and stack entries from pt_regs,
310 declared in asm/ptrace.h
311 For example the kprobes-based event tracer needs this API.
315 depends on HAVE_REGS_AND_STACK_ACCESS_API
317 This symbol should be selected by an architecture if it
318 supports an implementation of restartable sequences.
320 config HAVE_FUNCTION_ARG_ACCESS_API
323 This symbol should be selected by an architecture if it supports
324 the API needed to access function arguments from pt_regs,
325 declared in asm/ptrace.h
327 config HAVE_HW_BREAKPOINT
329 depends on PERF_EVENTS
331 config HAVE_MIXED_BREAKPOINTS_REGS
333 depends on HAVE_HW_BREAKPOINT
335 Depending on the arch implementation of hardware breakpoints,
336 some of them have separate registers for data and instruction
337 breakpoints addresses, others have mixed registers to store
338 them but define the access type in a control register.
339 Select this option if your arch implements breakpoints under the
342 config HAVE_USER_RETURN_NOTIFIER
345 config HAVE_PERF_EVENTS_NMI
348 System hardware can generate an NMI using the perf event
349 subsystem. Also has support for calculating CPU cycle events
350 to determine how many clock cycles in a given period.
352 config HAVE_HARDLOCKUP_DETECTOR_PERF
354 depends on HAVE_PERF_EVENTS_NMI
356 The arch chooses to use the generic perf-NMI-based hardlockup
357 detector. Must define HAVE_PERF_EVENTS_NMI.
359 config HAVE_NMI_WATCHDOG
363 The arch provides a low level NMI watchdog. It provides
364 asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
366 config HAVE_HARDLOCKUP_DETECTOR_ARCH
368 select HAVE_NMI_WATCHDOG
370 The arch chooses to provide its own hardlockup detector, which is
371 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
372 interfaces and parameters provided by hardlockup detector subsystem.
374 config HAVE_PERF_REGS
377 Support selective register dumps for perf events. This includes
378 bit-mapping of each registers and a unique architecture id.
380 config HAVE_PERF_USER_STACK_DUMP
383 Support user stack dumps for perf event samples. This needs
384 access to the user stack pointer which is not unified across
387 config HAVE_ARCH_JUMP_LABEL
390 config HAVE_ARCH_JUMP_LABEL_RELATIVE
393 config MMU_GATHER_TABLE_FREE
396 config MMU_GATHER_RCU_TABLE_FREE
398 select MMU_GATHER_TABLE_FREE
400 config MMU_GATHER_PAGE_SIZE
403 config MMU_GATHER_NO_RANGE
406 config MMU_GATHER_NO_GATHER
408 depends on MMU_GATHER_TABLE_FREE
410 config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
413 Temporary select until all architectures can be converted to have
414 irqs disabled over activate_mm. Architectures that do IPI based TLB
415 shootdowns should enable this.
417 config ARCH_HAVE_NMI_SAFE_CMPXCHG
420 config HAVE_ALIGNED_STRUCT_PAGE
423 This makes sure that struct pages are double word aligned and that
424 e.g. the SLUB allocator can perform double word atomic operations
425 on a struct page for better performance. However selecting this
426 might increase the size of a struct page by a word.
428 config HAVE_CMPXCHG_LOCAL
431 config HAVE_CMPXCHG_DOUBLE
434 config ARCH_WEAK_RELEASE_ACQUIRE
437 config ARCH_WANT_IPC_PARSE_VERSION
440 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
443 config ARCH_WANT_OLD_COMPAT_IPC
444 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
447 config HAVE_ARCH_SECCOMP
450 An arch should select this symbol to support seccomp mode 1 (the fixed
451 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
452 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
453 - __NR_seccomp_read_32
454 - __NR_seccomp_write_32
455 - __NR_seccomp_exit_32
456 - __NR_seccomp_sigreturn_32
458 config HAVE_ARCH_SECCOMP_FILTER
460 select HAVE_ARCH_SECCOMP
462 An arch should select this symbol if it provides all of these things:
463 - all the requirements for HAVE_ARCH_SECCOMP
465 - syscall_get_arguments()
467 - syscall_set_return_value()
468 - SIGSYS siginfo_t support
469 - secure_computing is called from a ptrace_event()-safe context
470 - secure_computing return value is checked and a return value of -1
471 results in the system call being skipped immediately.
472 - seccomp syscall wired up
473 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE,
474 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If
475 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too.
478 prompt "Enable seccomp to safely execute untrusted bytecode"
480 depends on HAVE_ARCH_SECCOMP
482 This kernel feature is useful for number crunching applications
483 that may need to handle untrusted bytecode during their
484 execution. By using pipes or other transports made available
485 to the process as file descriptors supporting the read/write
486 syscalls, it's possible to isolate those applications in their
487 own address space using seccomp. Once seccomp is enabled via
488 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
489 disabled and the task is only allowed to execute a few safe
490 syscalls defined by each seccomp mode.
494 config SECCOMP_FILTER
496 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
498 Enable tasks to build secure computing environments defined
499 in terms of Berkeley Packet Filter programs which implement
500 task-defined system call filtering polices.
502 See Documentation/userspace-api/seccomp_filter.rst for details.
504 config SECCOMP_CACHE_DEBUG
505 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache"
506 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR
509 This enables the /proc/pid/seccomp_cache interface to monitor
510 seccomp cache data. The file format is subject to change. Reading
511 the file requires CAP_SYS_ADMIN.
513 This option is for debugging only. Enabling presents the risk that
514 an adversary may be able to infer the seccomp filter logic.
518 config HAVE_ARCH_STACKLEAK
521 An architecture should select this if it has the code which
522 fills the used part of the kernel stack with the STACKLEAK_POISON
523 value before returning from system calls.
525 config HAVE_STACKPROTECTOR
528 An arch should select this symbol if:
529 - it has implemented a stack canary (e.g. __stack_chk_guard)
531 config STACKPROTECTOR
532 bool "Stack Protector buffer overflow detection"
533 depends on HAVE_STACKPROTECTOR
534 depends on $(cc-option,-fstack-protector)
537 This option turns on the "stack-protector" GCC feature. This
538 feature puts, at the beginning of functions, a canary value on
539 the stack just before the return address, and validates
540 the value just before actually returning. Stack based buffer
541 overflows (that need to overwrite this return address) now also
542 overwrite the canary, which gets detected and the attack is then
543 neutralized via a kernel panic.
545 Functions will have the stack-protector canary logic added if they
546 have an 8-byte or larger character array on the stack.
548 This feature requires gcc version 4.2 or above, or a distribution
549 gcc with the feature backported ("-fstack-protector").
551 On an x86 "defconfig" build, this feature adds canary checks to
552 about 3% of all kernel functions, which increases kernel code size
555 config STACKPROTECTOR_STRONG
556 bool "Strong Stack Protector"
557 depends on STACKPROTECTOR
558 depends on $(cc-option,-fstack-protector-strong)
561 Functions will have the stack-protector canary logic added in any
562 of the following conditions:
564 - local variable's address used as part of the right hand side of an
565 assignment or function argument
566 - local variable is an array (or union containing an array),
567 regardless of array type or length
568 - uses register local variables
570 This feature requires gcc version 4.9 or above, or a distribution
571 gcc with the feature backported ("-fstack-protector-strong").
573 On an x86 "defconfig" build, this feature adds canary checks to
574 about 20% of all kernel functions, which increases the kernel code
577 config ARCH_SUPPORTS_SHADOW_CALL_STACK
580 An architecture should select this if it supports Clang's Shadow
581 Call Stack and implements runtime support for shadow stack
584 config SHADOW_CALL_STACK
585 bool "Clang Shadow Call Stack"
586 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK
587 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
589 This option enables Clang's Shadow Call Stack, which uses a
590 shadow stack to protect function return addresses from being
591 overwritten by an attacker. More information can be found in
592 Clang's documentation:
594 https://clang.llvm.org/docs/ShadowCallStack.html
596 Note that security guarantees in the kernel differ from the
597 ones documented for user space. The kernel must store addresses
598 of shadow stacks in memory, which means an attacker capable of
599 reading and writing arbitrary memory may be able to locate them
600 and hijack control flow by modifying the stacks.
602 config HAVE_ARCH_WITHIN_STACK_FRAMES
605 An architecture should select this if it can walk the kernel stack
606 frames to determine if an object is part of either the arguments
607 or local variables (i.e. that it excludes saved return addresses,
608 and similar) by implementing an inline arch_within_stack_frames(),
609 which is used by CONFIG_HARDENED_USERCOPY.
611 config HAVE_CONTEXT_TRACKING
614 Provide kernel/user boundaries probes necessary for subsystems
615 that need it, such as userspace RCU extended quiescent state.
616 Syscalls need to be wrapped inside user_exit()-user_enter(), either
617 optimized behind static key or through the slow path using TIF_NOHZ
618 flag. Exceptions handlers must be wrapped as well. Irqs are already
619 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal
620 handling on irq exit still need to be protected.
622 config HAVE_CONTEXT_TRACKING_OFFSTACK
625 Architecture neither relies on exception_enter()/exception_exit()
626 nor on schedule_user(). Also preempt_schedule_notrace() and
627 preempt_schedule_irq() can't be called in a preemptible section
628 while context tracking is CONTEXT_USER. This feature reflects a sane
629 entry implementation where the following requirements are met on
630 critical entry code, ie: before user_exit() or after user_enter():
632 - Critical entry code isn't preemptible (or better yet:
634 - No use of RCU read side critical sections, unless rcu_nmi_enter()
636 - No use of instrumentation, unless instrumentation_begin() got
642 Arch relies on TIF_NOHZ and syscall slow path to implement context
643 tracking calls to user_enter()/user_exit().
645 config HAVE_VIRT_CPU_ACCOUNTING
648 config HAVE_VIRT_CPU_ACCOUNTING_IDLE
651 Architecture has its own way to account idle CPU time and therefore
652 doesn't implement vtime_account_idle().
654 config ARCH_HAS_SCALED_CPUTIME
657 config HAVE_VIRT_CPU_ACCOUNTING_GEN
661 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
662 Before enabling this option, arch code must be audited
663 to ensure there are no races in concurrent read/write of
664 cputime_t. For example, reading/writing 64-bit cputime_t on
665 some 32-bit arches may require multiple accesses, so proper
666 locking is needed to protect against concurrent accesses.
668 config HAVE_IRQ_TIME_ACCOUNTING
671 Archs need to ensure they use a high enough resolution clock to
672 support irq time accounting and then call enable_sched_clock_irqtime().
677 Architectures that select this are able to move page tables at the
678 PUD level. If there are only 3 page table levels, the move effectively
679 happens at the PGD level.
684 Archs that select this are able to move page tables at the PMD level.
686 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
689 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
692 config HAVE_ARCH_HUGE_VMAP
695 config ARCH_WANT_HUGE_PMD_SHARE
698 config HAVE_ARCH_SOFT_DIRTY
701 config HAVE_MOD_ARCH_SPECIFIC
704 The arch uses struct mod_arch_specific to store data. Many arches
705 just need a simple module loader without arch specific data - those
706 should not enable this.
708 config MODULES_USE_ELF_RELA
711 Modules only use ELF RELA relocations. Modules with ELF REL
712 relocations will give an error.
714 config MODULES_USE_ELF_REL
717 Modules only use ELF REL relocations. Modules with ELF RELA
718 relocations will give an error.
720 config HAVE_IRQ_EXIT_ON_IRQ_STACK
723 Architecture doesn't only execute the irq handler on the irq stack
724 but also irq_exit(). This way we can process softirqs on this irq
725 stack instead of switching to a new one when we call __do_softirq()
726 in the end of an hardirq.
727 This spares a stack switch and improves cache usage on softirq
730 config PGTABLE_LEVELS
734 config ARCH_HAS_ELF_RANDOMIZE
737 An architecture supports choosing randomized locations for
738 stack, mmap, brk, and ET_DYN. Defined functions:
740 - arch_randomize_brk()
742 config HAVE_ARCH_MMAP_RND_BITS
745 An arch should select this symbol if it supports setting a variable
746 number of bits for use in establishing the base address for mmap
747 allocations, has MMU enabled and provides values for both:
748 - ARCH_MMAP_RND_BITS_MIN
749 - ARCH_MMAP_RND_BITS_MAX
751 config HAVE_EXIT_THREAD
754 An architecture implements exit_thread.
756 config ARCH_MMAP_RND_BITS_MIN
759 config ARCH_MMAP_RND_BITS_MAX
762 config ARCH_MMAP_RND_BITS_DEFAULT
765 config ARCH_MMAP_RND_BITS
766 int "Number of bits to use for ASLR of mmap base address" if EXPERT
767 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
768 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
769 default ARCH_MMAP_RND_BITS_MIN
770 depends on HAVE_ARCH_MMAP_RND_BITS
772 This value can be used to select the number of bits to use to
773 determine the random offset to the base address of vma regions
774 resulting from mmap allocations. This value will be bounded
775 by the architecture's minimum and maximum supported values.
777 This value can be changed after boot using the
778 /proc/sys/vm/mmap_rnd_bits tunable
780 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
783 An arch should select this symbol if it supports running applications
784 in compatibility mode, supports setting a variable number of bits for
785 use in establishing the base address for mmap allocations, has MMU
786 enabled and provides values for both:
787 - ARCH_MMAP_RND_COMPAT_BITS_MIN
788 - ARCH_MMAP_RND_COMPAT_BITS_MAX
790 config ARCH_MMAP_RND_COMPAT_BITS_MIN
793 config ARCH_MMAP_RND_COMPAT_BITS_MAX
796 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
799 config ARCH_MMAP_RND_COMPAT_BITS
800 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
801 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
802 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
803 default ARCH_MMAP_RND_COMPAT_BITS_MIN
804 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
806 This value can be used to select the number of bits to use to
807 determine the random offset to the base address of vma regions
808 resulting from mmap allocations for compatible applications This
809 value will be bounded by the architecture's minimum and maximum
812 This value can be changed after boot using the
813 /proc/sys/vm/mmap_rnd_compat_bits tunable
815 config HAVE_ARCH_COMPAT_MMAP_BASES
818 This allows 64bit applications to invoke 32-bit mmap() syscall
819 and vice-versa 32-bit applications to call 64-bit mmap().
820 Required for applications doing different bitness syscalls.
822 # This allows to use a set of generic functions to determine mmap base
823 # address by giving priority to top-down scheme only if the process
824 # is not in legacy mode (compat task, unlimited stack size or
825 # sysctl_legacy_va_layout).
826 # Architecture that selects this option can provide its own version of:
828 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
831 select ARCH_HAS_ELF_RANDOMIZE
833 config HAVE_STACK_VALIDATION
836 Architecture supports the 'objtool check' host tool command, which
837 performs compile-time stack metadata validation.
839 config HAVE_RELIABLE_STACKTRACE
842 Architecture has either save_stack_trace_tsk_reliable() or
843 arch_stack_walk_reliable() function which only returns a stack trace
844 if it can guarantee the trace is reliable.
846 config HAVE_ARCH_HASH
850 If this is set, the architecture provides an <asm/hash.h>
851 file which provides platform-specific implementations of some
852 functions in <linux/hash.h> or fs/namei.c.
854 config HAVE_ARCH_NVRAM_OPS
863 config CLONE_BACKWARDS
866 Architecture has tls passed as the 4th argument of clone(2),
869 config CLONE_BACKWARDS2
872 Architecture has the first two arguments of clone(2) swapped.
874 config CLONE_BACKWARDS3
877 Architecture has tls passed as the 3rd argument of clone(2),
880 config ODD_RT_SIGACTION
883 Architecture has unusual rt_sigaction(2) arguments
885 config OLD_SIGSUSPEND
888 Architecture has old sigsuspend(2) syscall, of one-argument variety
890 config OLD_SIGSUSPEND3
893 Even weirder antique ABI - three-argument sigsuspend(2)
898 Architecture has old sigaction(2) syscall. Nope, not the same
899 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
900 but fairly different variant of sigaction(2), thanks to OSF/1
903 config COMPAT_OLD_SIGACTION
906 config COMPAT_32BIT_TIME
907 bool "Provide system calls for 32-bit time_t"
908 default !64BIT || COMPAT
910 This enables 32 bit time_t support in addition to 64 bit time_t support.
911 This is relevant on all 32-bit architectures, and 64-bit architectures
912 as part of compat syscall handling.
914 config ARCH_NO_PREEMPT
917 config ARCH_SUPPORTS_RT
920 config CPU_NO_EFFICIENT_FFS
923 config HAVE_ARCH_VMAP_STACK
926 An arch should select this symbol if it can support kernel stacks
927 in vmalloc space. This means:
929 - vmalloc space must be large enough to hold many kernel stacks.
930 This may rule out many 32-bit architectures.
932 - Stacks in vmalloc space need to work reliably. For example, if
933 vmap page tables are created on demand, either this mechanism
934 needs to work while the stack points to a virtual address with
935 unpopulated page tables or arch code (switch_to() and switch_mm(),
936 most likely) needs to ensure that the stack's page table entries
937 are populated before running on a possibly unpopulated stack.
939 - If the stack overflows into a guard page, something reasonable
940 should happen. The definition of "reasonable" is flexible, but
941 instantly rebooting without logging anything would be unfriendly.
945 bool "Use a virtually-mapped stack"
946 depends on HAVE_ARCH_VMAP_STACK
947 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC
949 Enable this if you want the use virtually-mapped kernel stacks
950 with guard pages. This causes kernel stack overflows to be
951 caught immediately rather than causing difficult-to-diagnose
954 To use this with software KASAN modes, the architecture must support
955 backing virtual mappings with real shadow memory, and KASAN_VMALLOC
958 config ARCH_OPTIONAL_KERNEL_RWX
961 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
964 config ARCH_HAS_STRICT_KERNEL_RWX
967 config STRICT_KERNEL_RWX
968 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
969 depends on ARCH_HAS_STRICT_KERNEL_RWX
970 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
972 If this is set, kernel text and rodata memory will be made read-only,
973 and non-text memory will be made non-executable. This provides
974 protection against certain security exploits (e.g. executing the heap
977 These features are considered standard security practice these days.
978 You should say Y here in almost all cases.
980 config ARCH_HAS_STRICT_MODULE_RWX
983 config STRICT_MODULE_RWX
984 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
985 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
986 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
988 If this is set, module text and rodata memory will be made read-only,
989 and non-text memory will be made non-executable. This provides
990 protection against certain security exploits (e.g. writing to text)
992 # select if the architecture provides an asm/dma-direct.h header
993 config ARCH_HAS_PHYS_TO_DMA
996 config HAVE_ARCH_COMPILER_H
999 An architecture can select this if it provides an
1000 asm/compiler.h header that should be included after
1001 linux/compiler-*.h in order to override macro definitions that those
1002 headers generally provide.
1004 config HAVE_ARCH_PREL32_RELOCATIONS
1007 May be selected by an architecture if it supports place-relative
1008 32-bit relocations, both in the toolchain and in the module loader,
1009 in which case relative references can be used in special sections
1010 for PCI fixup, initcalls etc which are only half the size on 64 bit
1011 architectures, and don't require runtime relocation on relocatable
1014 config ARCH_USE_MEMREMAP_PROT
1017 config LOCK_EVENT_COUNTS
1018 bool "Locking event counts collection"
1021 Enable light-weight counting of various locking related events
1022 in the system with minimal performance impact. This reduces
1023 the chance of application behavior change because of timing
1024 differences. The counts are reported via debugfs.
1026 # Select if the architecture has support for applying RELR relocations.
1027 config ARCH_HAS_RELR
1031 bool "Use RELR relocation packing"
1032 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1035 Store the kernel's dynamic relocations in the RELR relocation packing
1036 format. Requires a compatible linker (LLD supports this feature), as
1037 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1040 config ARCH_HAS_MEM_ENCRYPT
1043 config HAVE_SPARSE_SYSCALL_NR
1046 An architecture should select this if its syscall numbering is sparse
1047 to save space. For example, MIPS architecture has a syscall array with
1048 entries at 4000, 5000 and 6000 locations. This option turns on syscall
1049 related optimizations for a given architecture.
1051 config ARCH_HAS_VDSO_DATA
1054 config HAVE_STATIC_CALL
1057 config HAVE_STATIC_CALL_INLINE
1059 depends on HAVE_STATIC_CALL
1061 config ARCH_WANT_LD_ORPHAN_WARN
1064 An arch should select this symbol once all linker sections are explicitly
1065 included, size-asserted, or discarded in the linker scripts. This is
1066 important because we never want expected sections to be placed heuristically
1067 by the linker, since the locations of such sections can change between linker
1070 config HAVE_ARCH_PFN_VALID
1073 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
1076 config ARCH_SPLIT_ARG64
1079 If a 32-bit architecture requires 64-bit arguments to be split into
1080 pairs of 32-bit arguments, select this option.
1082 source "kernel/gcov/Kconfig"
1084 source "scripts/gcc-plugins/Kconfig"
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