1 # SPDX-License-Identifier: GPL-2.0
3 # General architecture dependent options
17 tristate "OProfile system profiling"
19 depends on HAVE_OPROFILE
21 select RING_BUFFER_ALLOW_SWAP
23 OProfile is a profiling system capable of profiling the
24 whole system, include the kernel, kernel modules, libraries,
29 config OPROFILE_EVENT_MULTIPLEX
30 bool "OProfile multiplexing support (EXPERIMENTAL)"
32 depends on OPROFILE && X86
34 The number of hardware counters is limited. The multiplexing
35 feature enables OProfile to gather more events than counters
36 are provided by the hardware. This is realized by switching
37 between events at a user specified time interval.
44 config OPROFILE_NMI_TIMER
46 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
51 depends on HAVE_KPROBES
54 Kprobes allows you to trap at almost any kernel address and
55 execute a callback function. register_kprobe() establishes
56 a probepoint and specifies the callback. Kprobes is useful
57 for kernel debugging, non-intrusive instrumentation and testing.
61 bool "Optimize very unlikely/likely branches"
62 depends on HAVE_ARCH_JUMP_LABEL
64 This option enables a transparent branch optimization that
65 makes certain almost-always-true or almost-always-false branch
66 conditions even cheaper to execute within the kernel.
68 Certain performance-sensitive kernel code, such as trace points,
69 scheduler functionality, networking code and KVM have such
70 branches and include support for this optimization technique.
72 If it is detected that the compiler has support for "asm goto",
73 the kernel will compile such branches with just a nop
74 instruction. When the condition flag is toggled to true, the
75 nop will be converted to a jump instruction to execute the
76 conditional block of instructions.
78 This technique lowers overhead and stress on the branch prediction
79 of the processor and generally makes the kernel faster. The update
80 of the condition is slower, but those are always very rare.
82 ( On 32-bit x86, the necessary options added to the compiler
83 flags may increase the size of the kernel slightly. )
85 config STATIC_KEYS_SELFTEST
86 bool "Static key selftest"
89 Boot time self-test of the branch patching code.
93 depends on KPROBES && HAVE_OPTPROBES
94 select TASKS_RCU if PREEMPT
96 config KPROBES_ON_FTRACE
98 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
99 depends on DYNAMIC_FTRACE_WITH_REGS
101 If function tracer is enabled and the arch supports full
102 passing of pt_regs to function tracing, then kprobes can
103 optimize on top of function tracing.
107 depends on ARCH_SUPPORTS_UPROBES
109 Uprobes is the user-space counterpart to kprobes: they
110 enable instrumentation applications (such as 'perf probe')
111 to establish unintrusive probes in user-space binaries and
112 libraries, by executing handler functions when the probes
113 are hit by user-space applications.
115 ( These probes come in the form of single-byte breakpoints,
116 managed by the kernel and kept transparent to the probed
119 config HAVE_64BIT_ALIGNED_ACCESS
120 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
122 Some architectures require 64 bit accesses to be 64 bit
123 aligned, which also requires structs containing 64 bit values
124 to be 64 bit aligned too. This includes some 32 bit
125 architectures which can do 64 bit accesses, as well as 64 bit
126 architectures without unaligned access.
128 This symbol should be selected by an architecture if 64 bit
129 accesses are required to be 64 bit aligned in this way even
130 though it is not a 64 bit architecture.
132 See Documentation/unaligned-memory-access.txt for more
133 information on the topic of unaligned memory accesses.
135 config HAVE_EFFICIENT_UNALIGNED_ACCESS
138 Some architectures are unable to perform unaligned accesses
139 without the use of get_unaligned/put_unaligned. Others are
140 unable to perform such accesses efficiently (e.g. trap on
141 unaligned access and require fixing it up in the exception
144 This symbol should be selected by an architecture if it can
145 perform unaligned accesses efficiently to allow different
146 code paths to be selected for these cases. Some network
147 drivers, for example, could opt to not fix up alignment
148 problems with received packets if doing so would not help
151 See Documentation/unaligned-memory-access.txt for more
152 information on the topic of unaligned memory accesses.
154 config ARCH_USE_BUILTIN_BSWAP
157 Modern versions of GCC (since 4.4) have builtin functions
158 for handling byte-swapping. Using these, instead of the old
159 inline assembler that the architecture code provides in the
160 __arch_bswapXX() macros, allows the compiler to see what's
161 happening and offers more opportunity for optimisation. In
162 particular, the compiler will be able to combine the byteswap
163 with a nearby load or store and use load-and-swap or
164 store-and-swap instructions if the architecture has them. It
165 should almost *never* result in code which is worse than the
166 hand-coded assembler in <asm/swab.h>. But just in case it
167 does, the use of the builtins is optional.
169 Any architecture with load-and-swap or store-and-swap
170 instructions should set this. And it shouldn't hurt to set it
171 on architectures that don't have such instructions.
175 depends on KPROBES && HAVE_KRETPROBES
177 config USER_RETURN_NOTIFIER
179 depends on HAVE_USER_RETURN_NOTIFIER
181 Provide a kernel-internal notification when a cpu is about to
184 config HAVE_IOREMAP_PROT
190 config HAVE_KRETPROBES
193 config HAVE_OPTPROBES
196 config HAVE_KPROBES_ON_FTRACE
199 config HAVE_FUNCTION_ERROR_INJECTION
206 # An arch should select this if it provides all these things:
208 # task_pt_regs() in asm/processor.h or asm/ptrace.h
209 # arch_has_single_step() if there is hardware single-step support
210 # arch_has_block_step() if there is hardware block-step support
211 # asm/syscall.h supplying asm-generic/syscall.h interface
212 # linux/regset.h user_regset interfaces
213 # CORE_DUMP_USE_REGSET #define'd in linux/elf.h
214 # TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit}
215 # TIF_NOTIFY_RESUME calls tracehook_notify_resume()
216 # signal delivery calls tracehook_signal_handler()
218 config HAVE_ARCH_TRACEHOOK
221 config HAVE_DMA_CONTIGUOUS
224 config GENERIC_SMP_IDLE_THREAD
227 config GENERIC_IDLE_POLL_SETUP
230 config ARCH_HAS_FORTIFY_SOURCE
233 An architecture should select this when it can successfully
234 build and run with CONFIG_FORTIFY_SOURCE.
236 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
237 config ARCH_HAS_SET_MEMORY
240 # Select if arch init_task must go in the __init_task_data section
241 config ARCH_TASK_STRUCT_ON_STACK
244 # Select if arch has its private alloc_task_struct() function
245 config ARCH_TASK_STRUCT_ALLOCATOR
248 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
250 depends on !ARCH_TASK_STRUCT_ALLOCATOR
252 An architecture should select this to provide hardened usercopy
253 knowledge about what region of the thread_struct should be
254 whitelisted for copying to userspace. Normally this is only the
255 FPU registers. Specifically, arch_thread_struct_whitelist()
256 should be implemented. Without this, the entire thread_struct
257 field in task_struct will be left whitelisted.
259 # Select if arch has its private alloc_thread_stack() function
260 config ARCH_THREAD_STACK_ALLOCATOR
263 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
264 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
267 config HAVE_REGS_AND_STACK_ACCESS_API
270 This symbol should be selected by an architecure if it supports
271 the API needed to access registers and stack entries from pt_regs,
272 declared in asm/ptrace.h
273 For example the kprobes-based event tracer needs this API.
278 The <linux/clk.h> calls support software clock gating and
279 thus are a key power management tool on many systems.
281 config HAVE_HW_BREAKPOINT
283 depends on PERF_EVENTS
285 config HAVE_MIXED_BREAKPOINTS_REGS
287 depends on HAVE_HW_BREAKPOINT
289 Depending on the arch implementation of hardware breakpoints,
290 some of them have separate registers for data and instruction
291 breakpoints addresses, others have mixed registers to store
292 them but define the access type in a control register.
293 Select this option if your arch implements breakpoints under the
296 config HAVE_USER_RETURN_NOTIFIER
299 config HAVE_PERF_EVENTS_NMI
302 System hardware can generate an NMI using the perf event
303 subsystem. Also has support for calculating CPU cycle events
304 to determine how many clock cycles in a given period.
306 config HAVE_HARDLOCKUP_DETECTOR_PERF
308 depends on HAVE_PERF_EVENTS_NMI
310 The arch chooses to use the generic perf-NMI-based hardlockup
311 detector. Must define HAVE_PERF_EVENTS_NMI.
313 config HAVE_NMI_WATCHDOG
317 The arch provides a low level NMI watchdog. It provides
318 asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
320 config HAVE_HARDLOCKUP_DETECTOR_ARCH
322 select HAVE_NMI_WATCHDOG
324 The arch chooses to provide its own hardlockup detector, which is
325 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
326 interfaces and parameters provided by hardlockup detector subsystem.
328 config HAVE_PERF_REGS
331 Support selective register dumps for perf events. This includes
332 bit-mapping of each registers and a unique architecture id.
334 config HAVE_PERF_USER_STACK_DUMP
337 Support user stack dumps for perf event samples. This needs
338 access to the user stack pointer which is not unified across
341 config HAVE_ARCH_JUMP_LABEL
344 config HAVE_RCU_TABLE_FREE
347 config ARCH_HAVE_NMI_SAFE_CMPXCHG
350 config HAVE_ALIGNED_STRUCT_PAGE
353 This makes sure that struct pages are double word aligned and that
354 e.g. the SLUB allocator can perform double word atomic operations
355 on a struct page for better performance. However selecting this
356 might increase the size of a struct page by a word.
358 config HAVE_CMPXCHG_LOCAL
361 config HAVE_CMPXCHG_DOUBLE
364 config ARCH_WEAK_RELEASE_ACQUIRE
367 config ARCH_WANT_IPC_PARSE_VERSION
370 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
373 config ARCH_WANT_OLD_COMPAT_IPC
374 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
377 config HAVE_ARCH_SECCOMP_FILTER
380 An arch should select this symbol if it provides all of these things:
382 - syscall_get_arguments()
384 - syscall_set_return_value()
385 - SIGSYS siginfo_t support
386 - secure_computing is called from a ptrace_event()-safe context
387 - secure_computing return value is checked and a return value of -1
388 results in the system call being skipped immediately.
389 - seccomp syscall wired up
391 config SECCOMP_FILTER
393 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
395 Enable tasks to build secure computing environments defined
396 in terms of Berkeley Packet Filter programs which implement
397 task-defined system call filtering polices.
399 See Documentation/prctl/seccomp_filter.txt for details.
401 config HAVE_GCC_PLUGINS
404 An arch should select this symbol if it supports building with
407 menuconfig GCC_PLUGINS
409 depends on HAVE_GCC_PLUGINS
410 depends on !COMPILE_TEST
412 GCC plugins are loadable modules that provide extra features to the
413 compiler. They are useful for runtime instrumentation and static analysis.
415 See Documentation/gcc-plugins.txt for details.
417 config GCC_PLUGIN_CYC_COMPLEXITY
418 bool "Compute the cyclomatic complexity of a function" if EXPERT
419 depends on GCC_PLUGINS
420 depends on !COMPILE_TEST
422 The complexity M of a function's control flow graph is defined as:
426 E = the number of edges
427 N = the number of nodes
428 P = the number of connected components (exit nodes).
430 Enabling this plugin reports the complexity to stderr during the
431 build. It mainly serves as a simple example of how to create a
432 gcc plugin for the kernel.
434 config GCC_PLUGIN_SANCOV
436 depends on GCC_PLUGINS
438 This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
439 basic blocks. It supports all gcc versions with plugin support (from
440 gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
441 by Dmitry Vyukov <dvyukov@google.com>.
443 config GCC_PLUGIN_LATENT_ENTROPY
444 bool "Generate some entropy during boot and runtime"
445 depends on GCC_PLUGINS
447 By saying Y here the kernel will instrument some kernel code to
448 extract some entropy from both original and artificially created
449 program state. This will help especially embedded systems where
450 there is little 'natural' source of entropy normally. The cost
451 is some slowdown of the boot process (about 0.5%) and fork and
454 Note that entropy extracted this way is not cryptographically
457 This plugin was ported from grsecurity/PaX. More information at:
458 * https://grsecurity.net/
459 * https://pax.grsecurity.net/
461 config GCC_PLUGIN_STRUCTLEAK
462 bool "Force initialization of variables containing userspace addresses"
463 depends on GCC_PLUGINS
464 # Currently STRUCTLEAK inserts initialization out of live scope of
465 # variables from KASAN point of view. This leads to KASAN false
466 # positive reports. Prohibit this combination for now.
467 depends on !KASAN_EXTRA
469 This plugin zero-initializes any structures containing a
470 __user attribute. This can prevent some classes of information
473 This plugin was ported from grsecurity/PaX. More information at:
474 * https://grsecurity.net/
475 * https://pax.grsecurity.net/
477 config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
478 bool "Force initialize all struct type variables passed by reference"
479 depends on GCC_PLUGIN_STRUCTLEAK
481 Zero initialize any struct type local variable that may be passed by
482 reference without having been initialized.
484 config GCC_PLUGIN_STRUCTLEAK_VERBOSE
485 bool "Report forcefully initialized variables"
486 depends on GCC_PLUGIN_STRUCTLEAK
487 depends on !COMPILE_TEST
489 This option will cause a warning to be printed each time the
490 structleak plugin finds a variable it thinks needs to be
491 initialized. Since not all existing initializers are detected
492 by the plugin, this can produce false positive warnings.
494 config GCC_PLUGIN_RANDSTRUCT
495 bool "Randomize layout of sensitive kernel structures"
496 depends on GCC_PLUGINS
497 select MODVERSIONS if MODULES
499 If you say Y here, the layouts of structures that are entirely
500 function pointers (and have not been manually annotated with
501 __no_randomize_layout), or structures that have been explicitly
502 marked with __randomize_layout, will be randomized at compile-time.
503 This can introduce the requirement of an additional information
504 exposure vulnerability for exploits targeting these structure
507 Enabling this feature will introduce some performance impact,
508 slightly increase memory usage, and prevent the use of forensic
509 tools like Volatility against the system (unless the kernel
510 source tree isn't cleaned after kernel installation).
512 The seed used for compilation is located at
513 scripts/gcc-plgins/randomize_layout_seed.h. It remains after
514 a make clean to allow for external modules to be compiled with
515 the existing seed and will be removed by a make mrproper or
518 Note that the implementation requires gcc 4.7 or newer.
520 This plugin was ported from grsecurity/PaX. More information at:
521 * https://grsecurity.net/
522 * https://pax.grsecurity.net/
524 config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE
525 bool "Use cacheline-aware structure randomization"
526 depends on GCC_PLUGIN_RANDSTRUCT
527 depends on !COMPILE_TEST
529 If you say Y here, the RANDSTRUCT randomization will make a
530 best effort at restricting randomization to cacheline-sized
531 groups of elements. It will further not randomize bitfields
532 in structures. This reduces the performance hit of RANDSTRUCT
533 at the cost of weakened randomization.
535 config HAVE_CC_STACKPROTECTOR
538 An arch should select this symbol if:
539 - its compiler supports the -fstack-protector option
540 - it has implemented a stack canary (e.g. __stack_chk_guard)
543 prompt "Stack Protector buffer overflow detection"
544 depends on HAVE_CC_STACKPROTECTOR
545 default CC_STACKPROTECTOR_AUTO
547 This option turns on the "stack-protector" GCC feature. This
548 feature puts, at the beginning of functions, a canary value on
549 the stack just before the return address, and validates
550 the value just before actually returning. Stack based buffer
551 overflows (that need to overwrite this return address) now also
552 overwrite the canary, which gets detected and the attack is then
553 neutralized via a kernel panic.
555 config CC_STACKPROTECTOR_NONE
558 Disable "stack-protector" GCC feature.
560 config CC_STACKPROTECTOR_REGULAR
563 Functions will have the stack-protector canary logic added if they
564 have an 8-byte or larger character array on the stack.
566 This feature requires gcc version 4.2 or above, or a distribution
567 gcc with the feature backported ("-fstack-protector").
569 On an x86 "defconfig" build, this feature adds canary checks to
570 about 3% of all kernel functions, which increases kernel code size
573 config CC_STACKPROTECTOR_STRONG
576 Functions will have the stack-protector canary logic added in any
577 of the following conditions:
579 - local variable's address used as part of the right hand side of an
580 assignment or function argument
581 - local variable is an array (or union containing an array),
582 regardless of array type or length
583 - uses register local variables
585 This feature requires gcc version 4.9 or above, or a distribution
586 gcc with the feature backported ("-fstack-protector-strong").
588 On an x86 "defconfig" build, this feature adds canary checks to
589 about 20% of all kernel functions, which increases the kernel code
592 config CC_STACKPROTECTOR_AUTO
595 If the compiler supports it, the best available stack-protector
596 option will be chosen.
600 config HAVE_ARCH_WITHIN_STACK_FRAMES
603 An architecture should select this if it can walk the kernel stack
604 frames to determine if an object is part of either the arguments
605 or local variables (i.e. that it excludes saved return addresses,
606 and similar) by implementing an inline arch_within_stack_frames(),
607 which is used by CONFIG_HARDENED_USERCOPY.
609 config HAVE_CONTEXT_TRACKING
612 Provide kernel/user boundaries probes necessary for subsystems
613 that need it, such as userspace RCU extended quiescent state.
614 Syscalls need to be wrapped inside user_exit()-user_enter() through
615 the slow path using TIF_NOHZ flag. Exceptions handlers must be
616 wrapped as well. Irqs are already protected inside
617 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
618 irq exit still need to be protected.
620 config HAVE_VIRT_CPU_ACCOUNTING
623 config ARCH_HAS_SCALED_CPUTIME
626 config HAVE_VIRT_CPU_ACCOUNTING_GEN
630 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
631 Before enabling this option, arch code must be audited
632 to ensure there are no races in concurrent read/write of
633 cputime_t. For example, reading/writing 64-bit cputime_t on
634 some 32-bit arches may require multiple accesses, so proper
635 locking is needed to protect against concurrent accesses.
638 config HAVE_IRQ_TIME_ACCOUNTING
641 Archs need to ensure they use a high enough resolution clock to
642 support irq time accounting and then call enable_sched_clock_irqtime().
644 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
647 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
650 config HAVE_ARCH_HUGE_VMAP
653 config HAVE_ARCH_SOFT_DIRTY
656 config HAVE_MOD_ARCH_SPECIFIC
659 The arch uses struct mod_arch_specific to store data. Many arches
660 just need a simple module loader without arch specific data - those
661 should not enable this.
663 config MODULES_USE_ELF_RELA
666 Modules only use ELF RELA relocations. Modules with ELF REL
667 relocations will give an error.
669 config MODULES_USE_ELF_REL
672 Modules only use ELF REL relocations. Modules with ELF RELA
673 relocations will give an error.
675 config HAVE_IRQ_EXIT_ON_IRQ_STACK
678 Architecture doesn't only execute the irq handler on the irq stack
679 but also irq_exit(). This way we can process softirqs on this irq
680 stack instead of switching to a new one when we call __do_softirq()
681 in the end of an hardirq.
682 This spares a stack switch and improves cache usage on softirq
685 config PGTABLE_LEVELS
689 config ARCH_HAS_ELF_RANDOMIZE
692 An architecture supports choosing randomized locations for
693 stack, mmap, brk, and ET_DYN. Defined functions:
695 - arch_randomize_brk()
697 config HAVE_ARCH_MMAP_RND_BITS
700 An arch should select this symbol if it supports setting a variable
701 number of bits for use in establishing the base address for mmap
702 allocations, has MMU enabled and provides values for both:
703 - ARCH_MMAP_RND_BITS_MIN
704 - ARCH_MMAP_RND_BITS_MAX
706 config HAVE_EXIT_THREAD
709 An architecture implements exit_thread.
711 config ARCH_MMAP_RND_BITS_MIN
714 config ARCH_MMAP_RND_BITS_MAX
717 config ARCH_MMAP_RND_BITS_DEFAULT
720 config ARCH_MMAP_RND_BITS
721 int "Number of bits to use for ASLR of mmap base address" if EXPERT
722 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
723 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
724 default ARCH_MMAP_RND_BITS_MIN
725 depends on HAVE_ARCH_MMAP_RND_BITS
727 This value can be used to select the number of bits to use to
728 determine the random offset to the base address of vma regions
729 resulting from mmap allocations. This value will be bounded
730 by the architecture's minimum and maximum supported values.
732 This value can be changed after boot using the
733 /proc/sys/vm/mmap_rnd_bits tunable
735 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
738 An arch should select this symbol if it supports running applications
739 in compatibility mode, supports setting a variable number of bits for
740 use in establishing the base address for mmap allocations, has MMU
741 enabled and provides values for both:
742 - ARCH_MMAP_RND_COMPAT_BITS_MIN
743 - ARCH_MMAP_RND_COMPAT_BITS_MAX
745 config ARCH_MMAP_RND_COMPAT_BITS_MIN
748 config ARCH_MMAP_RND_COMPAT_BITS_MAX
751 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
754 config ARCH_MMAP_RND_COMPAT_BITS
755 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
756 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
757 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
758 default ARCH_MMAP_RND_COMPAT_BITS_MIN
759 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
761 This value can be used to select the number of bits to use to
762 determine the random offset to the base address of vma regions
763 resulting from mmap allocations for compatible applications This
764 value will be bounded by the architecture's minimum and maximum
767 This value can be changed after boot using the
768 /proc/sys/vm/mmap_rnd_compat_bits tunable
770 config HAVE_ARCH_COMPAT_MMAP_BASES
773 This allows 64bit applications to invoke 32-bit mmap() syscall
774 and vice-versa 32-bit applications to call 64-bit mmap().
775 Required for applications doing different bitness syscalls.
777 config HAVE_COPY_THREAD_TLS
780 Architecture provides copy_thread_tls to accept tls argument via
781 normal C parameter passing, rather than extracting the syscall
782 argument from pt_regs.
784 config HAVE_STACK_VALIDATION
787 Architecture supports the 'objtool check' host tool command, which
788 performs compile-time stack metadata validation.
790 config HAVE_RELIABLE_STACKTRACE
793 Architecture has a save_stack_trace_tsk_reliable() function which
794 only returns a stack trace if it can guarantee the trace is reliable.
796 config HAVE_ARCH_HASH
800 If this is set, the architecture provides an <asm/hash.h>
801 file which provides platform-specific implementations of some
802 functions in <linux/hash.h> or fs/namei.c.
810 config CLONE_BACKWARDS
813 Architecture has tls passed as the 4th argument of clone(2),
816 config CLONE_BACKWARDS2
819 Architecture has the first two arguments of clone(2) swapped.
821 config CLONE_BACKWARDS3
824 Architecture has tls passed as the 3rd argument of clone(2),
827 config ODD_RT_SIGACTION
830 Architecture has unusual rt_sigaction(2) arguments
832 config OLD_SIGSUSPEND
835 Architecture has old sigsuspend(2) syscall, of one-argument variety
837 config OLD_SIGSUSPEND3
840 Even weirder antique ABI - three-argument sigsuspend(2)
845 Architecture has old sigaction(2) syscall. Nope, not the same
846 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
847 but fairly different variant of sigaction(2), thanks to OSF/1
850 config COMPAT_OLD_SIGACTION
854 def_bool ARCH_HAS_64BIT_TIME
856 This should be selected by all architectures that need to support
857 new system calls with a 64-bit time_t. This is relevant on all 32-bit
858 architectures, and 64-bit architectures as part of compat syscall
861 config COMPAT_32BIT_TIME
862 def_bool (!64BIT && 64BIT_TIME) || COMPAT
864 This enables 32 bit time_t support in addition to 64 bit time_t support.
865 This is relevant on all 32-bit architectures, and 64-bit architectures
866 as part of compat syscall handling.
868 config ARCH_NO_COHERENT_DMA_MMAP
871 config CPU_NO_EFFICIENT_FFS
874 config HAVE_ARCH_VMAP_STACK
877 An arch should select this symbol if it can support kernel stacks
878 in vmalloc space. This means:
880 - vmalloc space must be large enough to hold many kernel stacks.
881 This may rule out many 32-bit architectures.
883 - Stacks in vmalloc space need to work reliably. For example, if
884 vmap page tables are created on demand, either this mechanism
885 needs to work while the stack points to a virtual address with
886 unpopulated page tables or arch code (switch_to() and switch_mm(),
887 most likely) needs to ensure that the stack's page table entries
888 are populated before running on a possibly unpopulated stack.
890 - If the stack overflows into a guard page, something reasonable
891 should happen. The definition of "reasonable" is flexible, but
892 instantly rebooting without logging anything would be unfriendly.
896 bool "Use a virtually-mapped stack"
897 depends on HAVE_ARCH_VMAP_STACK && !KASAN
899 Enable this if you want the use virtually-mapped kernel stacks
900 with guard pages. This causes kernel stack overflows to be
901 caught immediately rather than causing difficult-to-diagnose
904 This is presently incompatible with KASAN because KASAN expects
905 the stack to map directly to the KASAN shadow map using a formula
906 that is incorrect if the stack is in vmalloc space.
908 config ARCH_OPTIONAL_KERNEL_RWX
911 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
914 config ARCH_HAS_STRICT_KERNEL_RWX
917 config STRICT_KERNEL_RWX
918 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
919 depends on ARCH_HAS_STRICT_KERNEL_RWX
920 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
922 If this is set, kernel text and rodata memory will be made read-only,
923 and non-text memory will be made non-executable. This provides
924 protection against certain security exploits (e.g. executing the heap
927 These features are considered standard security practice these days.
928 You should say Y here in almost all cases.
930 config ARCH_HAS_STRICT_MODULE_RWX
933 config STRICT_MODULE_RWX
934 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
935 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
936 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
938 If this is set, module text and rodata memory will be made read-only,
939 and non-text memory will be made non-executable. This provides
940 protection against certain security exploits (e.g. writing to text)
942 # select if the architecture provides an asm/dma-direct.h header
943 config ARCH_HAS_PHYS_TO_DMA
946 config ARCH_HAS_REFCOUNT
949 An architecture selects this when it has implemented refcount_t
950 using open coded assembly primitives that provide an optimized
951 refcount_t implementation, possibly at the expense of some full
952 refcount state checks of CONFIG_REFCOUNT_FULL=y.
954 The refcount overflow check behavior, however, must be retained.
955 Catching overflows is the primary security concern for protecting
956 against bugs in reference counts.
959 bool "Perform full reference count validation at the expense of speed"
961 Enabling this switches the refcounting infrastructure from a fast
962 unchecked atomic_t implementation to a fully state checked
963 implementation, which can be (slightly) slower but provides protections
964 against various use-after-free conditions that can be used in
965 security flaw exploits.
967 source "kernel/gcov/Kconfig"