1 # SPDX-License-Identifier: GPL-2.0
3 # General architecture dependent options
20 tristate "OProfile system profiling"
22 depends on HAVE_OPROFILE
24 select RING_BUFFER_ALLOW_SWAP
26 OProfile is a profiling system capable of profiling the
27 whole system, include the kernel, kernel modules, libraries,
32 config OPROFILE_EVENT_MULTIPLEX
33 bool "OProfile multiplexing support (EXPERIMENTAL)"
35 depends on OPROFILE && X86
37 The number of hardware counters is limited. The multiplexing
38 feature enables OProfile to gather more events than counters
39 are provided by the hardware. This is realized by switching
40 between events at a user specified time interval.
47 config OPROFILE_NMI_TIMER
49 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
54 depends on HAVE_KPROBES
57 Kprobes allows you to trap at almost any kernel address and
58 execute a callback function. register_kprobe() establishes
59 a probepoint and specifies the callback. Kprobes is useful
60 for kernel debugging, non-intrusive instrumentation and testing.
64 bool "Optimize very unlikely/likely branches"
65 depends on HAVE_ARCH_JUMP_LABEL
67 This option enables a transparent branch optimization that
68 makes certain almost-always-true or almost-always-false branch
69 conditions even cheaper to execute within the kernel.
71 Certain performance-sensitive kernel code, such as trace points,
72 scheduler functionality, networking code and KVM have such
73 branches and include support for this optimization technique.
75 If it is detected that the compiler has support for "asm goto",
76 the kernel will compile such branches with just a nop
77 instruction. When the condition flag is toggled to true, the
78 nop will be converted to a jump instruction to execute the
79 conditional block of instructions.
81 This technique lowers overhead and stress on the branch prediction
82 of the processor and generally makes the kernel faster. The update
83 of the condition is slower, but those are always very rare.
85 ( On 32-bit x86, the necessary options added to the compiler
86 flags may increase the size of the kernel slightly. )
88 config STATIC_KEYS_SELFTEST
89 bool "Static key selftest"
92 Boot time self-test of the branch patching code.
96 depends on KPROBES && HAVE_OPTPROBES
97 select TASKS_RCU if PREEMPT
99 config KPROBES_ON_FTRACE
101 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
102 depends on DYNAMIC_FTRACE_WITH_REGS
104 If function tracer is enabled and the arch supports full
105 passing of pt_regs to function tracing, then kprobes can
106 optimize on top of function tracing.
110 depends on ARCH_SUPPORTS_UPROBES
112 Uprobes is the user-space counterpart to kprobes: they
113 enable instrumentation applications (such as 'perf probe')
114 to establish unintrusive probes in user-space binaries and
115 libraries, by executing handler functions when the probes
116 are hit by user-space applications.
118 ( These probes come in the form of single-byte breakpoints,
119 managed by the kernel and kept transparent to the probed
122 config HAVE_64BIT_ALIGNED_ACCESS
123 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
125 Some architectures require 64 bit accesses to be 64 bit
126 aligned, which also requires structs containing 64 bit values
127 to be 64 bit aligned too. This includes some 32 bit
128 architectures which can do 64 bit accesses, as well as 64 bit
129 architectures without unaligned access.
131 This symbol should be selected by an architecture if 64 bit
132 accesses are required to be 64 bit aligned in this way even
133 though it is not a 64 bit architecture.
135 See Documentation/unaligned-memory-access.txt for more
136 information on the topic of unaligned memory accesses.
138 config HAVE_EFFICIENT_UNALIGNED_ACCESS
141 Some architectures are unable to perform unaligned accesses
142 without the use of get_unaligned/put_unaligned. Others are
143 unable to perform such accesses efficiently (e.g. trap on
144 unaligned access and require fixing it up in the exception
147 This symbol should be selected by an architecture if it can
148 perform unaligned accesses efficiently to allow different
149 code paths to be selected for these cases. Some network
150 drivers, for example, could opt to not fix up alignment
151 problems with received packets if doing so would not help
154 See Documentation/unaligned-memory-access.txt for more
155 information on the topic of unaligned memory accesses.
157 config ARCH_USE_BUILTIN_BSWAP
160 Modern versions of GCC (since 4.4) have builtin functions
161 for handling byte-swapping. Using these, instead of the old
162 inline assembler that the architecture code provides in the
163 __arch_bswapXX() macros, allows the compiler to see what's
164 happening and offers more opportunity for optimisation. In
165 particular, the compiler will be able to combine the byteswap
166 with a nearby load or store and use load-and-swap or
167 store-and-swap instructions if the architecture has them. It
168 should almost *never* result in code which is worse than the
169 hand-coded assembler in <asm/swab.h>. But just in case it
170 does, the use of the builtins is optional.
172 Any architecture with load-and-swap or store-and-swap
173 instructions should set this. And it shouldn't hurt to set it
174 on architectures that don't have such instructions.
178 depends on KPROBES && HAVE_KRETPROBES
180 config USER_RETURN_NOTIFIER
182 depends on HAVE_USER_RETURN_NOTIFIER
184 Provide a kernel-internal notification when a cpu is about to
187 config HAVE_IOREMAP_PROT
193 config HAVE_KRETPROBES
196 config HAVE_OPTPROBES
199 config HAVE_KPROBES_ON_FTRACE
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 initializer is different to init/init_task.c
241 config ARCH_INIT_TASK
244 # Select if arch has its private alloc_task_struct() function
245 config ARCH_TASK_STRUCT_ALLOCATOR
248 # Select if arch has its private alloc_thread_stack() function
249 config ARCH_THREAD_STACK_ALLOCATOR
252 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
253 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
256 config HAVE_REGS_AND_STACK_ACCESS_API
259 This symbol should be selected by an architecure if it supports
260 the API needed to access registers and stack entries from pt_regs,
261 declared in asm/ptrace.h
262 For example the kprobes-based event tracer needs this API.
267 The <linux/clk.h> calls support software clock gating and
268 thus are a key power management tool on many systems.
270 config HAVE_DMA_API_DEBUG
273 config HAVE_HW_BREAKPOINT
275 depends on PERF_EVENTS
277 config HAVE_MIXED_BREAKPOINTS_REGS
279 depends on HAVE_HW_BREAKPOINT
281 Depending on the arch implementation of hardware breakpoints,
282 some of them have separate registers for data and instruction
283 breakpoints addresses, others have mixed registers to store
284 them but define the access type in a control register.
285 Select this option if your arch implements breakpoints under the
288 config HAVE_USER_RETURN_NOTIFIER
291 config HAVE_PERF_EVENTS_NMI
294 System hardware can generate an NMI using the perf event
295 subsystem. Also has support for calculating CPU cycle events
296 to determine how many clock cycles in a given period.
298 config HAVE_HARDLOCKUP_DETECTOR_PERF
300 depends on HAVE_PERF_EVENTS_NMI
302 The arch chooses to use the generic perf-NMI-based hardlockup
303 detector. Must define HAVE_PERF_EVENTS_NMI.
305 config HAVE_NMI_WATCHDOG
309 The arch provides a low level NMI watchdog. It provides
310 asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
312 config HAVE_HARDLOCKUP_DETECTOR_ARCH
314 select HAVE_NMI_WATCHDOG
316 The arch chooses to provide its own hardlockup detector, which is
317 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
318 interfaces and parameters provided by hardlockup detector subsystem.
320 config HAVE_PERF_REGS
323 Support selective register dumps for perf events. This includes
324 bit-mapping of each registers and a unique architecture id.
326 config HAVE_PERF_USER_STACK_DUMP
329 Support user stack dumps for perf event samples. This needs
330 access to the user stack pointer which is not unified across
333 config HAVE_ARCH_JUMP_LABEL
336 config HAVE_RCU_TABLE_FREE
339 config HAVE_RCU_TABLE_INVALIDATE
342 config ARCH_HAVE_NMI_SAFE_CMPXCHG
345 config HAVE_ALIGNED_STRUCT_PAGE
348 This makes sure that struct pages are double word aligned and that
349 e.g. the SLUB allocator can perform double word atomic operations
350 on a struct page for better performance. However selecting this
351 might increase the size of a struct page by a word.
353 config HAVE_CMPXCHG_LOCAL
356 config HAVE_CMPXCHG_DOUBLE
359 config ARCH_WEAK_RELEASE_ACQUIRE
362 config ARCH_WANT_IPC_PARSE_VERSION
365 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
368 config ARCH_WANT_OLD_COMPAT_IPC
369 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
372 config HAVE_ARCH_SECCOMP_FILTER
375 An arch should select this symbol if it provides all of these things:
377 - syscall_get_arguments()
379 - syscall_set_return_value()
380 - SIGSYS siginfo_t support
381 - secure_computing is called from a ptrace_event()-safe context
382 - secure_computing return value is checked and a return value of -1
383 results in the system call being skipped immediately.
384 - seccomp syscall wired up
386 config SECCOMP_FILTER
388 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
390 Enable tasks to build secure computing environments defined
391 in terms of Berkeley Packet Filter programs which implement
392 task-defined system call filtering polices.
394 See Documentation/prctl/seccomp_filter.txt for details.
396 config HAVE_GCC_PLUGINS
399 An arch should select this symbol if it supports building with
402 menuconfig GCC_PLUGINS
404 depends on HAVE_GCC_PLUGINS
405 depends on !COMPILE_TEST
407 GCC plugins are loadable modules that provide extra features to the
408 compiler. They are useful for runtime instrumentation and static analysis.
410 See Documentation/gcc-plugins.txt for details.
412 config GCC_PLUGIN_CYC_COMPLEXITY
413 bool "Compute the cyclomatic complexity of a function" if EXPERT
414 depends on GCC_PLUGINS
415 depends on !COMPILE_TEST
417 The complexity M of a function's control flow graph is defined as:
421 E = the number of edges
422 N = the number of nodes
423 P = the number of connected components (exit nodes).
425 Enabling this plugin reports the complexity to stderr during the
426 build. It mainly serves as a simple example of how to create a
427 gcc plugin for the kernel.
429 config GCC_PLUGIN_SANCOV
431 depends on GCC_PLUGINS
433 This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
434 basic blocks. It supports all gcc versions with plugin support (from
435 gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
436 by Dmitry Vyukov <dvyukov@google.com>.
438 config GCC_PLUGIN_LATENT_ENTROPY
439 bool "Generate some entropy during boot and runtime"
440 depends on GCC_PLUGINS
442 By saying Y here the kernel will instrument some kernel code to
443 extract some entropy from both original and artificially created
444 program state. This will help especially embedded systems where
445 there is little 'natural' source of entropy normally. The cost
446 is some slowdown of the boot process (about 0.5%) and fork and
449 Note that entropy extracted this way is not cryptographically
452 This plugin was ported from grsecurity/PaX. More information at:
453 * https://grsecurity.net/
454 * https://pax.grsecurity.net/
456 config GCC_PLUGIN_STRUCTLEAK
457 bool "Force initialization of variables containing userspace addresses"
458 depends on GCC_PLUGINS
460 This plugin zero-initializes any structures containing a
461 __user attribute. This can prevent some classes of information
464 This plugin was ported from grsecurity/PaX. More information at:
465 * https://grsecurity.net/
466 * https://pax.grsecurity.net/
468 config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
469 bool "Force initialize all struct type variables passed by reference"
470 depends on GCC_PLUGIN_STRUCTLEAK
472 Zero initialize any struct type local variable that may be passed by
473 reference without having been initialized.
475 config GCC_PLUGIN_STRUCTLEAK_VERBOSE
476 bool "Report forcefully initialized variables"
477 depends on GCC_PLUGIN_STRUCTLEAK
478 depends on !COMPILE_TEST
480 This option will cause a warning to be printed each time the
481 structleak plugin finds a variable it thinks needs to be
482 initialized. Since not all existing initializers are detected
483 by the plugin, this can produce false positive warnings.
485 config GCC_PLUGIN_RANDSTRUCT
486 bool "Randomize layout of sensitive kernel structures"
487 depends on GCC_PLUGINS
488 select MODVERSIONS if MODULES
490 If you say Y here, the layouts of structures that are entirely
491 function pointers (and have not been manually annotated with
492 __no_randomize_layout), or structures that have been explicitly
493 marked with __randomize_layout, will be randomized at compile-time.
494 This can introduce the requirement of an additional information
495 exposure vulnerability for exploits targeting these structure
498 Enabling this feature will introduce some performance impact,
499 slightly increase memory usage, and prevent the use of forensic
500 tools like Volatility against the system (unless the kernel
501 source tree isn't cleaned after kernel installation).
503 The seed used for compilation is located at
504 scripts/gcc-plgins/randomize_layout_seed.h. It remains after
505 a make clean to allow for external modules to be compiled with
506 the existing seed and will be removed by a make mrproper or
509 Note that the implementation requires gcc 4.7 or newer.
511 This plugin was ported from grsecurity/PaX. More information at:
512 * https://grsecurity.net/
513 * https://pax.grsecurity.net/
515 config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE
516 bool "Use cacheline-aware structure randomization"
517 depends on GCC_PLUGIN_RANDSTRUCT
518 depends on !COMPILE_TEST
520 If you say Y here, the RANDSTRUCT randomization will make a
521 best effort at restricting randomization to cacheline-sized
522 groups of elements. It will further not randomize bitfields
523 in structures. This reduces the performance hit of RANDSTRUCT
524 at the cost of weakened randomization.
526 config HAVE_CC_STACKPROTECTOR
529 An arch should select this symbol if:
530 - its compiler supports the -fstack-protector option
531 - it has implemented a stack canary (e.g. __stack_chk_guard)
533 config CC_STACKPROTECTOR
536 Set when a stack-protector mode is enabled, so that the build
537 can enable kernel-side support for the GCC feature.
540 prompt "Stack Protector buffer overflow detection"
541 depends on HAVE_CC_STACKPROTECTOR
542 default CC_STACKPROTECTOR_NONE
544 This option turns on the "stack-protector" GCC feature. This
545 feature puts, at the beginning of functions, a canary value on
546 the stack just before the return address, and validates
547 the value just before actually returning. Stack based buffer
548 overflows (that need to overwrite this return address) now also
549 overwrite the canary, which gets detected and the attack is then
550 neutralized via a kernel panic.
552 config CC_STACKPROTECTOR_NONE
555 Disable "stack-protector" GCC feature.
557 config CC_STACKPROTECTOR_REGULAR
559 select CC_STACKPROTECTOR
561 Functions will have the stack-protector canary logic added if they
562 have an 8-byte or larger character array on the stack.
564 This feature requires gcc version 4.2 or above, or a distribution
565 gcc with the feature backported ("-fstack-protector").
567 On an x86 "defconfig" build, this feature adds canary checks to
568 about 3% of all kernel functions, which increases kernel code size
571 config CC_STACKPROTECTOR_STRONG
573 select CC_STACKPROTECTOR
575 Functions will have the stack-protector canary logic added in any
576 of the following conditions:
578 - local variable's address used as part of the right hand side of an
579 assignment or function argument
580 - local variable is an array (or union containing an array),
581 regardless of array type or length
582 - uses register local variables
584 This feature requires gcc version 4.9 or above, or a distribution
585 gcc with the feature backported ("-fstack-protector-strong").
587 On an x86 "defconfig" build, this feature adds canary checks to
588 about 20% of all kernel functions, which increases the kernel code
596 Select this if the architecture wants to use thin archives
597 instead of ld -r to create the built-in.o files.
599 config LD_DEAD_CODE_DATA_ELIMINATION
602 Select this if the architecture wants to do dead code and
603 data elimination with the linker by compiling with
604 -ffunction-sections -fdata-sections and linking with
607 This requires that the arch annotates or otherwise protects
608 its external entry points from being discarded. Linker scripts
609 must also merge .text.*, .data.*, and .bss.* correctly into
610 output sections. Care must be taken not to pull in unrelated
611 sections (e.g., '.text.init'). Typically '.' in section names
612 is used to distinguish them from label names / C identifiers.
614 config HAVE_ARCH_WITHIN_STACK_FRAMES
617 An architecture should select this if it can walk the kernel stack
618 frames to determine if an object is part of either the arguments
619 or local variables (i.e. that it excludes saved return addresses,
620 and similar) by implementing an inline arch_within_stack_frames(),
621 which is used by CONFIG_HARDENED_USERCOPY.
623 config HAVE_CONTEXT_TRACKING
626 Provide kernel/user boundaries probes necessary for subsystems
627 that need it, such as userspace RCU extended quiescent state.
628 Syscalls need to be wrapped inside user_exit()-user_enter() through
629 the slow path using TIF_NOHZ flag. Exceptions handlers must be
630 wrapped as well. Irqs are already protected inside
631 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
632 irq exit still need to be protected.
634 config HAVE_VIRT_CPU_ACCOUNTING
637 config ARCH_HAS_SCALED_CPUTIME
640 config HAVE_VIRT_CPU_ACCOUNTING_GEN
644 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
645 Before enabling this option, arch code must be audited
646 to ensure there are no races in concurrent read/write of
647 cputime_t. For example, reading/writing 64-bit cputime_t on
648 some 32-bit arches may require multiple accesses, so proper
649 locking is needed to protect against concurrent accesses.
652 config HAVE_IRQ_TIME_ACCOUNTING
655 Archs need to ensure they use a high enough resolution clock to
656 support irq time accounting and then call enable_sched_clock_irqtime().
658 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
661 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
664 config HAVE_ARCH_HUGE_VMAP
667 config HAVE_ARCH_SOFT_DIRTY
670 config HAVE_MOD_ARCH_SPECIFIC
673 The arch uses struct mod_arch_specific to store data. Many arches
674 just need a simple module loader without arch specific data - those
675 should not enable this.
677 config MODULES_USE_ELF_RELA
680 Modules only use ELF RELA relocations. Modules with ELF REL
681 relocations will give an error.
683 config MODULES_USE_ELF_REL
686 Modules only use ELF REL relocations. Modules with ELF RELA
687 relocations will give an error.
689 config HAVE_UNDERSCORE_SYMBOL_PREFIX
692 Some architectures generate an _ in front of C symbols; things like
693 module loading and assembly files need to know about this.
695 config HAVE_IRQ_EXIT_ON_IRQ_STACK
698 Architecture doesn't only execute the irq handler on the irq stack
699 but also irq_exit(). This way we can process softirqs on this irq
700 stack instead of switching to a new one when we call __do_softirq()
701 in the end of an hardirq.
702 This spares a stack switch and improves cache usage on softirq
705 config PGTABLE_LEVELS
709 config ARCH_HAS_ELF_RANDOMIZE
712 An architecture supports choosing randomized locations for
713 stack, mmap, brk, and ET_DYN. Defined functions:
715 - arch_randomize_brk()
717 config HAVE_ARCH_MMAP_RND_BITS
720 An arch should select this symbol if it supports setting a variable
721 number of bits for use in establishing the base address for mmap
722 allocations, has MMU enabled and provides values for both:
723 - ARCH_MMAP_RND_BITS_MIN
724 - ARCH_MMAP_RND_BITS_MAX
726 config HAVE_EXIT_THREAD
729 An architecture implements exit_thread.
731 config ARCH_MMAP_RND_BITS_MIN
734 config ARCH_MMAP_RND_BITS_MAX
737 config ARCH_MMAP_RND_BITS_DEFAULT
740 config ARCH_MMAP_RND_BITS
741 int "Number of bits to use for ASLR of mmap base address" if EXPERT
742 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
743 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
744 default ARCH_MMAP_RND_BITS_MIN
745 depends on HAVE_ARCH_MMAP_RND_BITS
747 This value can be used to select the number of bits to use to
748 determine the random offset to the base address of vma regions
749 resulting from mmap allocations. This value will be bounded
750 by the architecture's minimum and maximum supported values.
752 This value can be changed after boot using the
753 /proc/sys/vm/mmap_rnd_bits tunable
755 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
758 An arch should select this symbol if it supports running applications
759 in compatibility mode, supports setting a variable number of bits for
760 use in establishing the base address for mmap allocations, has MMU
761 enabled and provides values for both:
762 - ARCH_MMAP_RND_COMPAT_BITS_MIN
763 - ARCH_MMAP_RND_COMPAT_BITS_MAX
765 config ARCH_MMAP_RND_COMPAT_BITS_MIN
768 config ARCH_MMAP_RND_COMPAT_BITS_MAX
771 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
774 config ARCH_MMAP_RND_COMPAT_BITS
775 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
776 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
777 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
778 default ARCH_MMAP_RND_COMPAT_BITS_MIN
779 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
781 This value can be used to select the number of bits to use to
782 determine the random offset to the base address of vma regions
783 resulting from mmap allocations for compatible applications This
784 value will be bounded by the architecture's minimum and maximum
787 This value can be changed after boot using the
788 /proc/sys/vm/mmap_rnd_compat_bits tunable
790 config HAVE_ARCH_COMPAT_MMAP_BASES
793 This allows 64bit applications to invoke 32-bit mmap() syscall
794 and vice-versa 32-bit applications to call 64-bit mmap().
795 Required for applications doing different bitness syscalls.
797 config HAVE_COPY_THREAD_TLS
800 Architecture provides copy_thread_tls to accept tls argument via
801 normal C parameter passing, rather than extracting the syscall
802 argument from pt_regs.
804 config HAVE_STACK_VALIDATION
807 Architecture supports the 'objtool check' host tool command, which
808 performs compile-time stack metadata validation.
810 config HAVE_RELIABLE_STACKTRACE
813 Architecture has a save_stack_trace_tsk_reliable() function which
814 only returns a stack trace if it can guarantee the trace is reliable.
816 config HAVE_ARCH_HASH
820 If this is set, the architecture provides an <asm/hash.h>
821 file which provides platform-specific implementations of some
822 functions in <linux/hash.h> or fs/namei.c.
830 config CLONE_BACKWARDS
833 Architecture has tls passed as the 4th argument of clone(2),
836 config CLONE_BACKWARDS2
839 Architecture has the first two arguments of clone(2) swapped.
841 config CLONE_BACKWARDS3
844 Architecture has tls passed as the 3rd argument of clone(2),
847 config ODD_RT_SIGACTION
850 Architecture has unusual rt_sigaction(2) arguments
852 config OLD_SIGSUSPEND
855 Architecture has old sigsuspend(2) syscall, of one-argument variety
857 config OLD_SIGSUSPEND3
860 Even weirder antique ABI - three-argument sigsuspend(2)
865 Architecture has old sigaction(2) syscall. Nope, not the same
866 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
867 but fairly different variant of sigaction(2), thanks to OSF/1
870 config COMPAT_OLD_SIGACTION
873 config ARCH_NO_COHERENT_DMA_MMAP
876 config CPU_NO_EFFICIENT_FFS
879 config HAVE_ARCH_VMAP_STACK
882 An arch should select this symbol if it can support kernel stacks
883 in vmalloc space. This means:
885 - vmalloc space must be large enough to hold many kernel stacks.
886 This may rule out many 32-bit architectures.
888 - Stacks in vmalloc space need to work reliably. For example, if
889 vmap page tables are created on demand, either this mechanism
890 needs to work while the stack points to a virtual address with
891 unpopulated page tables or arch code (switch_to() and switch_mm(),
892 most likely) needs to ensure that the stack's page table entries
893 are populated before running on a possibly unpopulated stack.
895 - If the stack overflows into a guard page, something reasonable
896 should happen. The definition of "reasonable" is flexible, but
897 instantly rebooting without logging anything would be unfriendly.
901 bool "Use a virtually-mapped stack"
902 depends on HAVE_ARCH_VMAP_STACK && !KASAN
904 Enable this if you want the use virtually-mapped kernel stacks
905 with guard pages. This causes kernel stack overflows to be
906 caught immediately rather than causing difficult-to-diagnose
909 This is presently incompatible with KASAN because KASAN expects
910 the stack to map directly to the KASAN shadow map using a formula
911 that is incorrect if the stack is in vmalloc space.
913 config ARCH_OPTIONAL_KERNEL_RWX
916 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
919 config ARCH_HAS_STRICT_KERNEL_RWX
922 config STRICT_KERNEL_RWX
923 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
924 depends on ARCH_HAS_STRICT_KERNEL_RWX
925 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
927 If this is set, kernel text and rodata memory will be made read-only,
928 and non-text memory will be made non-executable. This provides
929 protection against certain security exploits (e.g. executing the heap
932 These features are considered standard security practice these days.
933 You should say Y here in almost all cases.
935 config ARCH_HAS_STRICT_MODULE_RWX
938 config STRICT_MODULE_RWX
939 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
940 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
941 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
943 If this is set, module text and rodata memory will be made read-only,
944 and non-text memory will be made non-executable. This provides
945 protection against certain security exploits (e.g. writing to text)
947 config ARCH_HAS_REFCOUNT
950 An architecture selects this when it has implemented refcount_t
951 using open coded assembly primitives that provide an optimized
952 refcount_t implementation, possibly at the expense of some full
953 refcount state checks of CONFIG_REFCOUNT_FULL=y.
955 The refcount overflow check behavior, however, must be retained.
956 Catching overflows is the primary security concern for protecting
957 against bugs in reference counts.
960 bool "Perform full reference count validation at the expense of speed"
962 Enabling this switches the refcounting infrastructure from a fast
963 unchecked atomic_t implementation to a fully state checked
964 implementation, which can be (slightly) slower but provides protections
965 against various use-after-free conditions that can be used in
966 security flaw exploits.
968 source "kernel/gcov/Kconfig"