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"
28 tristate "OProfile system profiling"
30 depends on HAVE_OPROFILE
32 select RING_BUFFER_ALLOW_SWAP
34 OProfile is a profiling system capable of profiling the
35 whole system, include the kernel, kernel modules, libraries,
40 config OPROFILE_EVENT_MULTIPLEX
41 bool "OProfile multiplexing support (EXPERIMENTAL)"
43 depends on OPROFILE && X86
45 The number of hardware counters is limited. The multiplexing
46 feature enables OProfile to gather more events than counters
47 are provided by the hardware. This is realized by switching
48 between events at a user specified time interval.
55 config OPROFILE_NMI_TIMER
57 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
62 depends on HAVE_KPROBES
65 Kprobes allows you to trap at almost any kernel address and
66 execute a callback function. register_kprobe() establishes
67 a probepoint and specifies the callback. Kprobes is useful
68 for kernel debugging, non-intrusive instrumentation and testing.
72 bool "Optimize very unlikely/likely branches"
73 depends on HAVE_ARCH_JUMP_LABEL
74 depends on CC_HAS_ASM_GOTO
76 This option enables a transparent branch optimization that
77 makes certain almost-always-true or almost-always-false branch
78 conditions even cheaper to execute within the kernel.
80 Certain performance-sensitive kernel code, such as trace points,
81 scheduler functionality, networking code and KVM have such
82 branches and include support for this optimization technique.
84 If it is detected that the compiler has support for "asm goto",
85 the kernel will compile such branches with just a nop
86 instruction. When the condition flag is toggled to true, the
87 nop will be converted to a jump instruction to execute the
88 conditional block of instructions.
90 This technique lowers overhead and stress on the branch prediction
91 of the processor and generally makes the kernel faster. The update
92 of the condition is slower, but those are always very rare.
94 ( On 32-bit x86, the necessary options added to the compiler
95 flags may increase the size of the kernel slightly. )
97 config STATIC_KEYS_SELFTEST
98 bool "Static key selftest"
101 Boot time self-test of the branch patching code.
105 depends on KPROBES && HAVE_OPTPROBES
106 select TASKS_RCU if PREEMPT
108 config KPROBES_ON_FTRACE
110 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
111 depends on DYNAMIC_FTRACE_WITH_REGS
113 If function tracer is enabled and the arch supports full
114 passing of pt_regs to function tracing, then kprobes can
115 optimize on top of function tracing.
119 depends on ARCH_SUPPORTS_UPROBES
121 Uprobes is the user-space counterpart to kprobes: they
122 enable instrumentation applications (such as 'perf probe')
123 to establish unintrusive probes in user-space binaries and
124 libraries, by executing handler functions when the probes
125 are hit by user-space applications.
127 ( These probes come in the form of single-byte breakpoints,
128 managed by the kernel and kept transparent to the probed
131 config HAVE_64BIT_ALIGNED_ACCESS
132 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
134 Some architectures require 64 bit accesses to be 64 bit
135 aligned, which also requires structs containing 64 bit values
136 to be 64 bit aligned too. This includes some 32 bit
137 architectures which can do 64 bit accesses, as well as 64 bit
138 architectures without unaligned access.
140 This symbol should be selected by an architecture if 64 bit
141 accesses are required to be 64 bit aligned in this way even
142 though it is not a 64 bit architecture.
144 See Documentation/unaligned-memory-access.txt for more
145 information on the topic of unaligned memory accesses.
147 config HAVE_EFFICIENT_UNALIGNED_ACCESS
150 Some architectures are unable to perform unaligned accesses
151 without the use of get_unaligned/put_unaligned. Others are
152 unable to perform such accesses efficiently (e.g. trap on
153 unaligned access and require fixing it up in the exception
156 This symbol should be selected by an architecture if it can
157 perform unaligned accesses efficiently to allow different
158 code paths to be selected for these cases. Some network
159 drivers, for example, could opt to not fix up alignment
160 problems with received packets if doing so would not help
163 See Documentation/unaligned-memory-access.txt for more
164 information on the topic of unaligned memory accesses.
166 config ARCH_USE_BUILTIN_BSWAP
169 Modern versions of GCC (since 4.4) have builtin functions
170 for handling byte-swapping. Using these, instead of the old
171 inline assembler that the architecture code provides in the
172 __arch_bswapXX() macros, allows the compiler to see what's
173 happening and offers more opportunity for optimisation. In
174 particular, the compiler will be able to combine the byteswap
175 with a nearby load or store and use load-and-swap or
176 store-and-swap instructions if the architecture has them. It
177 should almost *never* result in code which is worse than the
178 hand-coded assembler in <asm/swab.h>. But just in case it
179 does, the use of the builtins is optional.
181 Any architecture with load-and-swap or store-and-swap
182 instructions should set this. And it shouldn't hurt to set it
183 on architectures that don't have such instructions.
187 depends on KPROBES && HAVE_KRETPROBES
189 config USER_RETURN_NOTIFIER
191 depends on HAVE_USER_RETURN_NOTIFIER
193 Provide a kernel-internal notification when a cpu is about to
196 config HAVE_IOREMAP_PROT
202 config HAVE_KRETPROBES
205 config HAVE_OPTPROBES
208 config HAVE_KPROBES_ON_FTRACE
211 config HAVE_FUNCTION_ERROR_INJECTION
218 # An arch should select this if it provides all these things:
220 # task_pt_regs() in asm/processor.h or asm/ptrace.h
221 # arch_has_single_step() if there is hardware single-step support
222 # arch_has_block_step() if there is hardware block-step support
223 # asm/syscall.h supplying asm-generic/syscall.h interface
224 # linux/regset.h user_regset interfaces
225 # CORE_DUMP_USE_REGSET #define'd in linux/elf.h
226 # TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit}
227 # TIF_NOTIFY_RESUME calls tracehook_notify_resume()
228 # signal delivery calls tracehook_signal_handler()
230 config HAVE_ARCH_TRACEHOOK
233 config HAVE_DMA_CONTIGUOUS
236 config GENERIC_SMP_IDLE_THREAD
239 config GENERIC_IDLE_POLL_SETUP
242 config ARCH_HAS_FORTIFY_SOURCE
245 An architecture should select this when it can successfully
246 build and run with CONFIG_FORTIFY_SOURCE.
248 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
249 config ARCH_HAS_SET_MEMORY
252 config ARCH_HAS_CPU_FINALIZE_INIT
255 # Select if arch init_task must go in the __init_task_data section
256 config ARCH_TASK_STRUCT_ON_STACK
259 # Select if arch has its private alloc_task_struct() function
260 config ARCH_TASK_STRUCT_ALLOCATOR
263 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
265 depends on !ARCH_TASK_STRUCT_ALLOCATOR
267 An architecture should select this to provide hardened usercopy
268 knowledge about what region of the thread_struct should be
269 whitelisted for copying to userspace. Normally this is only the
270 FPU registers. Specifically, arch_thread_struct_whitelist()
271 should be implemented. Without this, the entire thread_struct
272 field in task_struct will be left whitelisted.
274 # Select if arch has its private alloc_thread_stack() function
275 config ARCH_THREAD_STACK_ALLOCATOR
278 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
279 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
282 config HAVE_REGS_AND_STACK_ACCESS_API
285 This symbol should be selected by an architecure if it supports
286 the API needed to access registers and stack entries from pt_regs,
287 declared in asm/ptrace.h
288 For example the kprobes-based event tracer needs this API.
292 depends on HAVE_REGS_AND_STACK_ACCESS_API
294 This symbol should be selected by an architecture if it
295 supports an implementation of restartable sequences.
300 The <linux/clk.h> calls support software clock gating and
301 thus are a key power management tool on many systems.
303 config HAVE_HW_BREAKPOINT
305 depends on PERF_EVENTS
307 config HAVE_MIXED_BREAKPOINTS_REGS
309 depends on HAVE_HW_BREAKPOINT
311 Depending on the arch implementation of hardware breakpoints,
312 some of them have separate registers for data and instruction
313 breakpoints addresses, others have mixed registers to store
314 them but define the access type in a control register.
315 Select this option if your arch implements breakpoints under the
318 config HAVE_USER_RETURN_NOTIFIER
321 config HAVE_PERF_EVENTS_NMI
324 System hardware can generate an NMI using the perf event
325 subsystem. Also has support for calculating CPU cycle events
326 to determine how many clock cycles in a given period.
328 config HAVE_HARDLOCKUP_DETECTOR_PERF
330 depends on HAVE_PERF_EVENTS_NMI
332 The arch chooses to use the generic perf-NMI-based hardlockup
333 detector. Must define HAVE_PERF_EVENTS_NMI.
335 config HAVE_NMI_WATCHDOG
339 The arch provides a low level NMI watchdog. It provides
340 asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
342 config HAVE_HARDLOCKUP_DETECTOR_ARCH
344 select HAVE_NMI_WATCHDOG
346 The arch chooses to provide its own hardlockup detector, which is
347 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
348 interfaces and parameters provided by hardlockup detector subsystem.
350 config HAVE_PERF_REGS
353 Support selective register dumps for perf events. This includes
354 bit-mapping of each registers and a unique architecture id.
356 config HAVE_PERF_USER_STACK_DUMP
359 Support user stack dumps for perf event samples. This needs
360 access to the user stack pointer which is not unified across
363 config HAVE_ARCH_JUMP_LABEL
366 config HAVE_RCU_TABLE_FREE
369 config HAVE_RCU_TABLE_INVALIDATE
372 config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
375 Temporary select until all architectures can be converted to have
376 irqs disabled over activate_mm. Architectures that do IPI based TLB
377 shootdowns should enable this.
379 config ARCH_HAVE_NMI_SAFE_CMPXCHG
382 config HAVE_ALIGNED_STRUCT_PAGE
385 This makes sure that struct pages are double word aligned and that
386 e.g. the SLUB allocator can perform double word atomic operations
387 on a struct page for better performance. However selecting this
388 might increase the size of a struct page by a word.
390 config HAVE_CMPXCHG_LOCAL
393 config HAVE_CMPXCHG_DOUBLE
396 config ARCH_WEAK_RELEASE_ACQUIRE
399 config ARCH_WANT_IPC_PARSE_VERSION
402 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
405 config ARCH_WANT_OLD_COMPAT_IPC
406 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
409 config HAVE_ARCH_SECCOMP_FILTER
412 An arch should select this symbol if it provides all of these things:
414 - syscall_get_arguments()
416 - syscall_set_return_value()
417 - SIGSYS siginfo_t support
418 - secure_computing is called from a ptrace_event()-safe context
419 - secure_computing return value is checked and a return value of -1
420 results in the system call being skipped immediately.
421 - seccomp syscall wired up
423 config SECCOMP_FILTER
425 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
427 Enable tasks to build secure computing environments defined
428 in terms of Berkeley Packet Filter programs which implement
429 task-defined system call filtering polices.
431 See Documentation/userspace-api/seccomp_filter.rst for details.
433 config HAVE_STACKPROTECTOR
436 An arch should select this symbol if:
437 - it has implemented a stack canary (e.g. __stack_chk_guard)
439 config CC_HAS_STACKPROTECTOR_NONE
440 def_bool $(cc-option,-fno-stack-protector)
442 config STACKPROTECTOR
443 bool "Stack Protector buffer overflow detection"
444 depends on HAVE_STACKPROTECTOR
445 depends on $(cc-option,-fstack-protector)
448 This option turns on the "stack-protector" GCC feature. This
449 feature puts, at the beginning of functions, a canary value on
450 the stack just before the return address, and validates
451 the value just before actually returning. Stack based buffer
452 overflows (that need to overwrite this return address) now also
453 overwrite the canary, which gets detected and the attack is then
454 neutralized via a kernel panic.
456 Functions will have the stack-protector canary logic added if they
457 have an 8-byte or larger character array on the stack.
459 This feature requires gcc version 4.2 or above, or a distribution
460 gcc with the feature backported ("-fstack-protector").
462 On an x86 "defconfig" build, this feature adds canary checks to
463 about 3% of all kernel functions, which increases kernel code size
466 config STACKPROTECTOR_STRONG
467 bool "Strong Stack Protector"
468 depends on STACKPROTECTOR
469 depends on $(cc-option,-fstack-protector-strong)
472 Functions will have the stack-protector canary logic added in any
473 of the following conditions:
475 - local variable's address used as part of the right hand side of an
476 assignment or function argument
477 - local variable is an array (or union containing an array),
478 regardless of array type or length
479 - uses register local variables
481 This feature requires gcc version 4.9 or above, or a distribution
482 gcc with the feature backported ("-fstack-protector-strong").
484 On an x86 "defconfig" build, this feature adds canary checks to
485 about 20% of all kernel functions, which increases the kernel code
488 config HAVE_ARCH_WITHIN_STACK_FRAMES
491 An architecture should select this if it can walk the kernel stack
492 frames to determine if an object is part of either the arguments
493 or local variables (i.e. that it excludes saved return addresses,
494 and similar) by implementing an inline arch_within_stack_frames(),
495 which is used by CONFIG_HARDENED_USERCOPY.
497 config HAVE_CONTEXT_TRACKING
500 Provide kernel/user boundaries probes necessary for subsystems
501 that need it, such as userspace RCU extended quiescent state.
502 Syscalls need to be wrapped inside user_exit()-user_enter() through
503 the slow path using TIF_NOHZ flag. Exceptions handlers must be
504 wrapped as well. Irqs are already protected inside
505 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
506 irq exit still need to be protected.
508 config HAVE_VIRT_CPU_ACCOUNTING
511 config ARCH_HAS_SCALED_CPUTIME
514 config HAVE_VIRT_CPU_ACCOUNTING_GEN
518 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
519 Before enabling this option, arch code must be audited
520 to ensure there are no races in concurrent read/write of
521 cputime_t. For example, reading/writing 64-bit cputime_t on
522 some 32-bit arches may require multiple accesses, so proper
523 locking is needed to protect against concurrent accesses.
526 config HAVE_IRQ_TIME_ACCOUNTING
529 Archs need to ensure they use a high enough resolution clock to
530 support irq time accounting and then call enable_sched_clock_irqtime().
532 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
535 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
538 config HAVE_ARCH_HUGE_VMAP
541 config HAVE_ARCH_SOFT_DIRTY
544 config HAVE_MOD_ARCH_SPECIFIC
547 The arch uses struct mod_arch_specific to store data. Many arches
548 just need a simple module loader without arch specific data - those
549 should not enable this.
551 config MODULES_USE_ELF_RELA
554 Modules only use ELF RELA relocations. Modules with ELF REL
555 relocations will give an error.
557 config MODULES_USE_ELF_REL
560 Modules only use ELF REL relocations. Modules with ELF RELA
561 relocations will give an error.
563 config HAVE_IRQ_EXIT_ON_IRQ_STACK
566 Architecture doesn't only execute the irq handler on the irq stack
567 but also irq_exit(). This way we can process softirqs on this irq
568 stack instead of switching to a new one when we call __do_softirq()
569 in the end of an hardirq.
570 This spares a stack switch and improves cache usage on softirq
573 config PGTABLE_LEVELS
577 config ARCH_HAS_ELF_RANDOMIZE
580 An architecture supports choosing randomized locations for
581 stack, mmap, brk, and ET_DYN. Defined functions:
583 - arch_randomize_brk()
585 config HAVE_ARCH_MMAP_RND_BITS
588 An arch should select this symbol if it supports setting a variable
589 number of bits for use in establishing the base address for mmap
590 allocations, has MMU enabled and provides values for both:
591 - ARCH_MMAP_RND_BITS_MIN
592 - ARCH_MMAP_RND_BITS_MAX
594 config HAVE_EXIT_THREAD
597 An architecture implements exit_thread.
599 config ARCH_MMAP_RND_BITS_MIN
602 config ARCH_MMAP_RND_BITS_MAX
605 config ARCH_MMAP_RND_BITS_DEFAULT
608 config ARCH_MMAP_RND_BITS
609 int "Number of bits to use for ASLR of mmap base address" if EXPERT
610 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
611 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
612 default ARCH_MMAP_RND_BITS_MIN
613 depends on HAVE_ARCH_MMAP_RND_BITS
615 This value can be used to select the number of bits to use to
616 determine the random offset to the base address of vma regions
617 resulting from mmap allocations. This value will be bounded
618 by the architecture's minimum and maximum supported values.
620 This value can be changed after boot using the
621 /proc/sys/vm/mmap_rnd_bits tunable
623 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
626 An arch should select this symbol if it supports running applications
627 in compatibility mode, supports setting a variable number of bits for
628 use in establishing the base address for mmap allocations, has MMU
629 enabled and provides values for both:
630 - ARCH_MMAP_RND_COMPAT_BITS_MIN
631 - ARCH_MMAP_RND_COMPAT_BITS_MAX
633 config ARCH_MMAP_RND_COMPAT_BITS_MIN
636 config ARCH_MMAP_RND_COMPAT_BITS_MAX
639 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
642 config ARCH_MMAP_RND_COMPAT_BITS
643 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
644 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
645 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
646 default ARCH_MMAP_RND_COMPAT_BITS_MIN
647 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
649 This value can be used to select the number of bits to use to
650 determine the random offset to the base address of vma regions
651 resulting from mmap allocations for compatible applications This
652 value will be bounded by the architecture's minimum and maximum
655 This value can be changed after boot using the
656 /proc/sys/vm/mmap_rnd_compat_bits tunable
658 config HAVE_ARCH_COMPAT_MMAP_BASES
661 This allows 64bit applications to invoke 32-bit mmap() syscall
662 and vice-versa 32-bit applications to call 64-bit mmap().
663 Required for applications doing different bitness syscalls.
665 config HAVE_COPY_THREAD_TLS
668 Architecture provides copy_thread_tls to accept tls argument via
669 normal C parameter passing, rather than extracting the syscall
670 argument from pt_regs.
672 config HAVE_STACK_VALIDATION
675 Architecture supports the 'objtool check' host tool command, which
676 performs compile-time stack metadata validation.
678 config HAVE_RELIABLE_STACKTRACE
681 Architecture has a save_stack_trace_tsk_reliable() function which
682 only returns a stack trace if it can guarantee the trace is reliable.
684 config HAVE_ARCH_HASH
688 If this is set, the architecture provides an <asm/hash.h>
689 file which provides platform-specific implementations of some
690 functions in <linux/hash.h> or fs/namei.c.
698 config CLONE_BACKWARDS
701 Architecture has tls passed as the 4th argument of clone(2),
704 config CLONE_BACKWARDS2
707 Architecture has the first two arguments of clone(2) swapped.
709 config CLONE_BACKWARDS3
712 Architecture has tls passed as the 3rd argument of clone(2),
715 config ODD_RT_SIGACTION
718 Architecture has unusual rt_sigaction(2) arguments
720 config OLD_SIGSUSPEND
723 Architecture has old sigsuspend(2) syscall, of one-argument variety
725 config OLD_SIGSUSPEND3
728 Even weirder antique ABI - three-argument sigsuspend(2)
733 Architecture has old sigaction(2) syscall. Nope, not the same
734 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
735 but fairly different variant of sigaction(2), thanks to OSF/1
738 config COMPAT_OLD_SIGACTION
742 def_bool ARCH_HAS_64BIT_TIME
744 This should be selected by all architectures that need to support
745 new system calls with a 64-bit time_t. This is relevant on all 32-bit
746 architectures, and 64-bit architectures as part of compat syscall
749 config COMPAT_32BIT_TIME
750 def_bool (!64BIT && 64BIT_TIME) || COMPAT
752 This enables 32 bit time_t support in addition to 64 bit time_t support.
753 This is relevant on all 32-bit architectures, and 64-bit architectures
754 as part of compat syscall handling.
756 config ARCH_NO_COHERENT_DMA_MMAP
759 config ARCH_NO_PREEMPT
762 config CPU_NO_EFFICIENT_FFS
765 config HAVE_ARCH_VMAP_STACK
768 An arch should select this symbol if it can support kernel stacks
769 in vmalloc space. This means:
771 - vmalloc space must be large enough to hold many kernel stacks.
772 This may rule out many 32-bit architectures.
774 - Stacks in vmalloc space need to work reliably. For example, if
775 vmap page tables are created on demand, either this mechanism
776 needs to work while the stack points to a virtual address with
777 unpopulated page tables or arch code (switch_to() and switch_mm(),
778 most likely) needs to ensure that the stack's page table entries
779 are populated before running on a possibly unpopulated stack.
781 - If the stack overflows into a guard page, something reasonable
782 should happen. The definition of "reasonable" is flexible, but
783 instantly rebooting without logging anything would be unfriendly.
787 bool "Use a virtually-mapped stack"
788 depends on HAVE_ARCH_VMAP_STACK && !KASAN
790 Enable this if you want the use virtually-mapped kernel stacks
791 with guard pages. This causes kernel stack overflows to be
792 caught immediately rather than causing difficult-to-diagnose
795 This is presently incompatible with KASAN because KASAN expects
796 the stack to map directly to the KASAN shadow map using a formula
797 that is incorrect if the stack is in vmalloc space.
799 config ARCH_OPTIONAL_KERNEL_RWX
802 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
805 config ARCH_HAS_STRICT_KERNEL_RWX
808 config STRICT_KERNEL_RWX
809 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
810 depends on ARCH_HAS_STRICT_KERNEL_RWX
811 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
813 If this is set, kernel text and rodata memory will be made read-only,
814 and non-text memory will be made non-executable. This provides
815 protection against certain security exploits (e.g. executing the heap
818 These features are considered standard security practice these days.
819 You should say Y here in almost all cases.
821 config ARCH_HAS_STRICT_MODULE_RWX
824 config STRICT_MODULE_RWX
825 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
826 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
827 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
829 If this is set, module text and rodata memory will be made read-only,
830 and non-text memory will be made non-executable. This provides
831 protection against certain security exploits (e.g. writing to text)
833 # select if the architecture provides an asm/dma-direct.h header
834 config ARCH_HAS_PHYS_TO_DMA
837 config ARCH_HAS_REFCOUNT
840 An architecture selects this when it has implemented refcount_t
841 using open coded assembly primitives that provide an optimized
842 refcount_t implementation, possibly at the expense of some full
843 refcount state checks of CONFIG_REFCOUNT_FULL=y.
845 The refcount overflow check behavior, however, must be retained.
846 Catching overflows is the primary security concern for protecting
847 against bugs in reference counts.
850 bool "Perform full reference count validation at the expense of speed"
852 Enabling this switches the refcounting infrastructure from a fast
853 unchecked atomic_t implementation to a fully state checked
854 implementation, which can be (slightly) slower but provides protections
855 against various use-after-free conditions that can be used in
856 security flaw exploits.
858 config HAVE_ARCH_COMPILER_H
861 An architecture can select this if it provides an
862 asm/compiler.h header that should be included after
863 linux/compiler-*.h in order to override macro definitions that those
864 headers generally provide.
866 config HAVE_ARCH_PREL32_RELOCATIONS
869 May be selected by an architecture if it supports place-relative
870 32-bit relocations, both in the toolchain and in the module loader,
871 in which case relative references can be used in special sections
872 for PCI fixup, initcalls etc which are only half the size on 64 bit
873 architectures, and don't require runtime relocation on relocatable
876 config ARCH_USE_MEMREMAP_PROT
879 source "kernel/gcov/Kconfig"
881 source "scripts/gcc-plugins/Kconfig"