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1# SPDX-License-Identifier: GPL-2.0
2#
3# General architecture dependent options
4#
5
6config CRASH_CORE
7 bool
8
9config KEXEC_CORE
10 select CRASH_CORE
11 bool
12
13config HAVE_IMA_KEXEC
14 bool
15
16config OPROFILE
17 tristate "OProfile system profiling"
18 depends on PROFILING
19 depends on HAVE_OPROFILE
20 select RING_BUFFER
21 select RING_BUFFER_ALLOW_SWAP
22 help
23 OProfile is a profiling system capable of profiling the
24 whole system, include the kernel, kernel modules, libraries,
25 and applications.
26
27 If unsure, say N.
28
29config OPROFILE_EVENT_MULTIPLEX
30 bool "OProfile multiplexing support (EXPERIMENTAL)"
31 default n
32 depends on OPROFILE && X86
33 help
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.
38
39 If unsure, say N.
40
41config HAVE_OPROFILE
42 bool
43
44config OPROFILE_NMI_TIMER
45 def_bool y
46 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
47
48config KPROBES
49 bool "Kprobes"
50 depends on MODULES
51 depends on HAVE_KPROBES
52 select KALLSYMS
53 help
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.
58 If in doubt, say "N".
59
60config JUMP_LABEL
61 bool "Optimize very unlikely/likely branches"
62 depends on HAVE_ARCH_JUMP_LABEL
63 help
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.
67
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.
71
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.
77
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.
81
82 ( On 32-bit x86, the necessary options added to the compiler
83 flags may increase the size of the kernel slightly. )
84
85config STATIC_KEYS_SELFTEST
86 bool "Static key selftest"
87 depends on JUMP_LABEL
88 help
89 Boot time self-test of the branch patching code.
90
91config OPTPROBES
92 def_bool y
93 depends on KPROBES && HAVE_OPTPROBES
94 select TASKS_RCU if PREEMPT
95
96config KPROBES_ON_FTRACE
97 def_bool y
98 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
99 depends on DYNAMIC_FTRACE_WITH_REGS
100 help
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.
104
105config UPROBES
106 def_bool n
107 depends on ARCH_SUPPORTS_UPROBES
108 help
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.
114
115 ( These probes come in the form of single-byte breakpoints,
116 managed by the kernel and kept transparent to the probed
117 application. )
118
119config HAVE_64BIT_ALIGNED_ACCESS
120 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
121 help
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.
127
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.
131
132 See Documentation/unaligned-memory-access.txt for more
133 information on the topic of unaligned memory accesses.
134
135config HAVE_EFFICIENT_UNALIGNED_ACCESS
136 bool
137 help
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
142 handler.)
143
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
149 much.
150
151 See Documentation/unaligned-memory-access.txt for more
152 information on the topic of unaligned memory accesses.
153
154config ARCH_USE_BUILTIN_BSWAP
155 bool
156 help
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.
168
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.
172
173config KRETPROBES
174 def_bool y
175 depends on KPROBES && HAVE_KRETPROBES
176
177config USER_RETURN_NOTIFIER
178 bool
179 depends on HAVE_USER_RETURN_NOTIFIER
180 help
181 Provide a kernel-internal notification when a cpu is about to
182 switch to user mode.
183
184config HAVE_IOREMAP_PROT
185 bool
186
187config HAVE_KPROBES
188 bool
189
190config HAVE_KRETPROBES
191 bool
192
193config HAVE_OPTPROBES
194 bool
195
196config HAVE_KPROBES_ON_FTRACE
197 bool
198
199config HAVE_FUNCTION_ERROR_INJECTION
200 bool
201
202config HAVE_NMI
203 bool
204
205#
206# An arch should select this if it provides all these things:
207#
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()
217#
218config HAVE_ARCH_TRACEHOOK
219 bool
220
221config HAVE_DMA_CONTIGUOUS
222 bool
223
224config GENERIC_SMP_IDLE_THREAD
225 bool
226
227config GENERIC_IDLE_POLL_SETUP
228 bool
229
230config ARCH_HAS_FORTIFY_SOURCE
231 bool
232 help
233 An architecture should select this when it can successfully
234 build and run with CONFIG_FORTIFY_SOURCE.
235
236# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
237config ARCH_HAS_SET_MEMORY
238 bool
239
240# Select if arch init_task must go in the __init_task_data section
241config ARCH_TASK_STRUCT_ON_STACK
242 bool
243
244# Select if arch has its private alloc_task_struct() function
245config ARCH_TASK_STRUCT_ALLOCATOR
246 bool
247
248config HAVE_ARCH_THREAD_STRUCT_WHITELIST
249 bool
250 depends on !ARCH_TASK_STRUCT_ALLOCATOR
251 help
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.
258
259# Select if arch has its private alloc_thread_stack() function
260config ARCH_THREAD_STACK_ALLOCATOR
261 bool
262
263# Select if arch wants to size task_struct dynamically via arch_task_struct_size:
264config ARCH_WANTS_DYNAMIC_TASK_STRUCT
265 bool
266
267config HAVE_REGS_AND_STACK_ACCESS_API
268 bool
269 help
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.
274
275config HAVE_CLK
276 bool
277 help
278 The <linux/clk.h> calls support software clock gating and
279 thus are a key power management tool on many systems.
280
281config HAVE_DMA_API_DEBUG
282 bool
283
284config HAVE_HW_BREAKPOINT
285 bool
286 depends on PERF_EVENTS
287
288config HAVE_MIXED_BREAKPOINTS_REGS
289 bool
290 depends on HAVE_HW_BREAKPOINT
291 help
292 Depending on the arch implementation of hardware breakpoints,
293 some of them have separate registers for data and instruction
294 breakpoints addresses, others have mixed registers to store
295 them but define the access type in a control register.
296 Select this option if your arch implements breakpoints under the
297 latter fashion.
298
299config HAVE_USER_RETURN_NOTIFIER
300 bool
301
302config HAVE_PERF_EVENTS_NMI
303 bool
304 help
305 System hardware can generate an NMI using the perf event
306 subsystem. Also has support for calculating CPU cycle events
307 to determine how many clock cycles in a given period.
308
309config HAVE_HARDLOCKUP_DETECTOR_PERF
310 bool
311 depends on HAVE_PERF_EVENTS_NMI
312 help
313 The arch chooses to use the generic perf-NMI-based hardlockup
314 detector. Must define HAVE_PERF_EVENTS_NMI.
315
316config HAVE_NMI_WATCHDOG
317 depends on HAVE_NMI
318 bool
319 help
320 The arch provides a low level NMI watchdog. It provides
321 asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
322
323config HAVE_HARDLOCKUP_DETECTOR_ARCH
324 bool
325 select HAVE_NMI_WATCHDOG
326 help
327 The arch chooses to provide its own hardlockup detector, which is
328 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
329 interfaces and parameters provided by hardlockup detector subsystem.
330
331config HAVE_PERF_REGS
332 bool
333 help
334 Support selective register dumps for perf events. This includes
335 bit-mapping of each registers and a unique architecture id.
336
337config HAVE_PERF_USER_STACK_DUMP
338 bool
339 help
340 Support user stack dumps for perf event samples. This needs
341 access to the user stack pointer which is not unified across
342 architectures.
343
344config HAVE_ARCH_JUMP_LABEL
345 bool
346
347config HAVE_RCU_TABLE_FREE
348 bool
349
350config ARCH_HAVE_NMI_SAFE_CMPXCHG
351 bool
352
353config HAVE_ALIGNED_STRUCT_PAGE
354 bool
355 help
356 This makes sure that struct pages are double word aligned and that
357 e.g. the SLUB allocator can perform double word atomic operations
358 on a struct page for better performance. However selecting this
359 might increase the size of a struct page by a word.
360
361config HAVE_CMPXCHG_LOCAL
362 bool
363
364config HAVE_CMPXCHG_DOUBLE
365 bool
366
367config ARCH_WEAK_RELEASE_ACQUIRE
368 bool
369
370config ARCH_WANT_IPC_PARSE_VERSION
371 bool
372
373config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
374 bool
375
376config ARCH_WANT_OLD_COMPAT_IPC
377 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
378 bool
379
380config HAVE_ARCH_SECCOMP_FILTER
381 bool
382 help
383 An arch should select this symbol if it provides all of these things:
384 - syscall_get_arch()
385 - syscall_get_arguments()
386 - syscall_rollback()
387 - syscall_set_return_value()
388 - SIGSYS siginfo_t support
389 - secure_computing is called from a ptrace_event()-safe context
390 - secure_computing return value is checked and a return value of -1
391 results in the system call being skipped immediately.
392 - seccomp syscall wired up
393
394config SECCOMP_FILTER
395 def_bool y
396 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
397 help
398 Enable tasks to build secure computing environments defined
399 in terms of Berkeley Packet Filter programs which implement
400 task-defined system call filtering polices.
401
402 See Documentation/prctl/seccomp_filter.txt for details.
403
404config HAVE_GCC_PLUGINS
405 bool
406 help
407 An arch should select this symbol if it supports building with
408 GCC plugins.
409
410menuconfig GCC_PLUGINS
411 bool "GCC plugins"
412 depends on HAVE_GCC_PLUGINS
413 depends on !COMPILE_TEST
414 help
415 GCC plugins are loadable modules that provide extra features to the
416 compiler. They are useful for runtime instrumentation and static analysis.
417
418 See Documentation/gcc-plugins.txt for details.
419
420config GCC_PLUGIN_CYC_COMPLEXITY
421 bool "Compute the cyclomatic complexity of a function" if EXPERT
422 depends on GCC_PLUGINS
423 depends on !COMPILE_TEST
424 help
425 The complexity M of a function's control flow graph is defined as:
426 M = E - N + 2P
427 where
428
429 E = the number of edges
430 N = the number of nodes
431 P = the number of connected components (exit nodes).
432
433 Enabling this plugin reports the complexity to stderr during the
434 build. It mainly serves as a simple example of how to create a
435 gcc plugin for the kernel.
436
437config GCC_PLUGIN_SANCOV
438 bool
439 depends on GCC_PLUGINS
440 help
441 This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
442 basic blocks. It supports all gcc versions with plugin support (from
443 gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
444 by Dmitry Vyukov <dvyukov@google.com>.
445
446config GCC_PLUGIN_LATENT_ENTROPY
447 bool "Generate some entropy during boot and runtime"
448 depends on GCC_PLUGINS
449 help
450 By saying Y here the kernel will instrument some kernel code to
451 extract some entropy from both original and artificially created
452 program state. This will help especially embedded systems where
453 there is little 'natural' source of entropy normally. The cost
454 is some slowdown of the boot process (about 0.5%) and fork and
455 irq processing.
456
457 Note that entropy extracted this way is not cryptographically
458 secure!
459
460 This plugin was ported from grsecurity/PaX. More information at:
461 * https://grsecurity.net/
462 * https://pax.grsecurity.net/
463
464config GCC_PLUGIN_STRUCTLEAK
465 bool "Force initialization of variables containing userspace addresses"
466 depends on GCC_PLUGINS
467 # Currently STRUCTLEAK inserts initialization out of live scope of
468 # variables from KASAN point of view. This leads to KASAN false
469 # positive reports. Prohibit this combination for now.
470 depends on !KASAN_EXTRA
471 help
472 This plugin zero-initializes any structures containing a
473 __user attribute. This can prevent some classes of information
474 exposures.
475
476 This plugin was ported from grsecurity/PaX. More information at:
477 * https://grsecurity.net/
478 * https://pax.grsecurity.net/
479
480config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
481 bool "Force initialize all struct type variables passed by reference"
482 depends on GCC_PLUGIN_STRUCTLEAK
483 help
484 Zero initialize any struct type local variable that may be passed by
485 reference without having been initialized.
486
487config GCC_PLUGIN_STRUCTLEAK_VERBOSE
488 bool "Report forcefully initialized variables"
489 depends on GCC_PLUGIN_STRUCTLEAK
490 depends on !COMPILE_TEST
491 help
492 This option will cause a warning to be printed each time the
493 structleak plugin finds a variable it thinks needs to be
494 initialized. Since not all existing initializers are detected
495 by the plugin, this can produce false positive warnings.
496
497config GCC_PLUGIN_RANDSTRUCT
498 bool "Randomize layout of sensitive kernel structures"
499 depends on GCC_PLUGINS
500 select MODVERSIONS if MODULES
501 help
502 If you say Y here, the layouts of structures that are entirely
503 function pointers (and have not been manually annotated with
504 __no_randomize_layout), or structures that have been explicitly
505 marked with __randomize_layout, will be randomized at compile-time.
506 This can introduce the requirement of an additional information
507 exposure vulnerability for exploits targeting these structure
508 types.
509
510 Enabling this feature will introduce some performance impact,
511 slightly increase memory usage, and prevent the use of forensic
512 tools like Volatility against the system (unless the kernel
513 source tree isn't cleaned after kernel installation).
514
515 The seed used for compilation is located at
516 scripts/gcc-plgins/randomize_layout_seed.h. It remains after
517 a make clean to allow for external modules to be compiled with
518 the existing seed and will be removed by a make mrproper or
519 make distclean.
520
521 Note that the implementation requires gcc 4.7 or newer.
522
523 This plugin was ported from grsecurity/PaX. More information at:
524 * https://grsecurity.net/
525 * https://pax.grsecurity.net/
526
527config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE
528 bool "Use cacheline-aware structure randomization"
529 depends on GCC_PLUGIN_RANDSTRUCT
530 depends on !COMPILE_TEST
531 help
532 If you say Y here, the RANDSTRUCT randomization will make a
533 best effort at restricting randomization to cacheline-sized
534 groups of elements. It will further not randomize bitfields
535 in structures. This reduces the performance hit of RANDSTRUCT
536 at the cost of weakened randomization.
537
538config HAVE_CC_STACKPROTECTOR
539 bool
540 help
541 An arch should select this symbol if:
542 - its compiler supports the -fstack-protector option
543 - it has implemented a stack canary (e.g. __stack_chk_guard)
544
545choice
546 prompt "Stack Protector buffer overflow detection"
547 depends on HAVE_CC_STACKPROTECTOR
548 default CC_STACKPROTECTOR_AUTO
549 help
550 This option turns on the "stack-protector" GCC feature. This
551 feature puts, at the beginning of functions, a canary value on
552 the stack just before the return address, and validates
553 the value just before actually returning. Stack based buffer
554 overflows (that need to overwrite this return address) now also
555 overwrite the canary, which gets detected and the attack is then
556 neutralized via a kernel panic.
557
558config CC_STACKPROTECTOR_NONE
559 bool "None"
560 help
561 Disable "stack-protector" GCC feature.
562
563config CC_STACKPROTECTOR_REGULAR
564 bool "Regular"
565 help
566 Functions will have the stack-protector canary logic added if they
567 have an 8-byte or larger character array on the stack.
568
569 This feature requires gcc version 4.2 or above, or a distribution
570 gcc with the feature backported ("-fstack-protector").
571
572 On an x86 "defconfig" build, this feature adds canary checks to
573 about 3% of all kernel functions, which increases kernel code size
574 by about 0.3%.
575
576config CC_STACKPROTECTOR_STRONG
577 bool "Strong"
578 help
579 Functions will have the stack-protector canary logic added in any
580 of the following conditions:
581
582 - local variable's address used as part of the right hand side of an
583 assignment or function argument
584 - local variable is an array (or union containing an array),
585 regardless of array type or length
586 - uses register local variables
587
588 This feature requires gcc version 4.9 or above, or a distribution
589 gcc with the feature backported ("-fstack-protector-strong").
590
591 On an x86 "defconfig" build, this feature adds canary checks to
592 about 20% of all kernel functions, which increases the kernel code
593 size by about 2%.
594
595config CC_STACKPROTECTOR_AUTO
596 bool "Automatic"
597 help
598 If the compiler supports it, the best available stack-protector
599 option will be chosen.
600
601endchoice
602
603config LD_DEAD_CODE_DATA_ELIMINATION
604 bool
605 help
606 Select this if the architecture wants to do dead code and
607 data elimination with the linker by compiling with
608 -ffunction-sections -fdata-sections and linking with
609 --gc-sections.
610
611 This requires that the arch annotates or otherwise protects
612 its external entry points from being discarded. Linker scripts
613 must also merge .text.*, .data.*, and .bss.* correctly into
614 output sections. Care must be taken not to pull in unrelated
615 sections (e.g., '.text.init'). Typically '.' in section names
616 is used to distinguish them from label names / C identifiers.
617
618config HAVE_ARCH_WITHIN_STACK_FRAMES
619 bool
620 help
621 An architecture should select this if it can walk the kernel stack
622 frames to determine if an object is part of either the arguments
623 or local variables (i.e. that it excludes saved return addresses,
624 and similar) by implementing an inline arch_within_stack_frames(),
625 which is used by CONFIG_HARDENED_USERCOPY.
626
627config HAVE_CONTEXT_TRACKING
628 bool
629 help
630 Provide kernel/user boundaries probes necessary for subsystems
631 that need it, such as userspace RCU extended quiescent state.
632 Syscalls need to be wrapped inside user_exit()-user_enter() through
633 the slow path using TIF_NOHZ flag. Exceptions handlers must be
634 wrapped as well. Irqs are already protected inside
635 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
636 irq exit still need to be protected.
637
638config HAVE_VIRT_CPU_ACCOUNTING
639 bool
640
641config ARCH_HAS_SCALED_CPUTIME
642 bool
643
644config HAVE_VIRT_CPU_ACCOUNTING_GEN
645 bool
646 default y if 64BIT
647 help
648 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
649 Before enabling this option, arch code must be audited
650 to ensure there are no races in concurrent read/write of
651 cputime_t. For example, reading/writing 64-bit cputime_t on
652 some 32-bit arches may require multiple accesses, so proper
653 locking is needed to protect against concurrent accesses.
654
655
656config HAVE_IRQ_TIME_ACCOUNTING
657 bool
658 help
659 Archs need to ensure they use a high enough resolution clock to
660 support irq time accounting and then call enable_sched_clock_irqtime().
661
662config HAVE_ARCH_TRANSPARENT_HUGEPAGE
663 bool
664
665config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
666 bool
667
668config HAVE_ARCH_HUGE_VMAP
669 bool
670
671config HAVE_ARCH_SOFT_DIRTY
672 bool
673
674config HAVE_MOD_ARCH_SPECIFIC
675 bool
676 help
677 The arch uses struct mod_arch_specific to store data. Many arches
678 just need a simple module loader without arch specific data - those
679 should not enable this.
680
681config MODULES_USE_ELF_RELA
682 bool
683 help
684 Modules only use ELF RELA relocations. Modules with ELF REL
685 relocations will give an error.
686
687config MODULES_USE_ELF_REL
688 bool
689 help
690 Modules only use ELF REL relocations. Modules with ELF RELA
691 relocations will give an error.
692
693config HAVE_UNDERSCORE_SYMBOL_PREFIX
694 bool
695 help
696 Some architectures generate an _ in front of C symbols; things like
697 module loading and assembly files need to know about this.
698
699config HAVE_IRQ_EXIT_ON_IRQ_STACK
700 bool
701 help
702 Architecture doesn't only execute the irq handler on the irq stack
703 but also irq_exit(). This way we can process softirqs on this irq
704 stack instead of switching to a new one when we call __do_softirq()
705 in the end of an hardirq.
706 This spares a stack switch and improves cache usage on softirq
707 processing.
708
709config PGTABLE_LEVELS
710 int
711 default 2
712
713config ARCH_HAS_ELF_RANDOMIZE
714 bool
715 help
716 An architecture supports choosing randomized locations for
717 stack, mmap, brk, and ET_DYN. Defined functions:
718 - arch_mmap_rnd()
719 - arch_randomize_brk()
720
721config HAVE_ARCH_MMAP_RND_BITS
722 bool
723 help
724 An arch should select this symbol if it supports setting a variable
725 number of bits for use in establishing the base address for mmap
726 allocations, has MMU enabled and provides values for both:
727 - ARCH_MMAP_RND_BITS_MIN
728 - ARCH_MMAP_RND_BITS_MAX
729
730config HAVE_EXIT_THREAD
731 bool
732 help
733 An architecture implements exit_thread.
734
735config ARCH_MMAP_RND_BITS_MIN
736 int
737
738config ARCH_MMAP_RND_BITS_MAX
739 int
740
741config ARCH_MMAP_RND_BITS_DEFAULT
742 int
743
744config ARCH_MMAP_RND_BITS
745 int "Number of bits to use for ASLR of mmap base address" if EXPERT
746 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
747 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
748 default ARCH_MMAP_RND_BITS_MIN
749 depends on HAVE_ARCH_MMAP_RND_BITS
750 help
751 This value can be used to select the number of bits to use to
752 determine the random offset to the base address of vma regions
753 resulting from mmap allocations. This value will be bounded
754 by the architecture's minimum and maximum supported values.
755
756 This value can be changed after boot using the
757 /proc/sys/vm/mmap_rnd_bits tunable
758
759config HAVE_ARCH_MMAP_RND_COMPAT_BITS
760 bool
761 help
762 An arch should select this symbol if it supports running applications
763 in compatibility mode, supports setting a variable number of bits for
764 use in establishing the base address for mmap allocations, has MMU
765 enabled and provides values for both:
766 - ARCH_MMAP_RND_COMPAT_BITS_MIN
767 - ARCH_MMAP_RND_COMPAT_BITS_MAX
768
769config ARCH_MMAP_RND_COMPAT_BITS_MIN
770 int
771
772config ARCH_MMAP_RND_COMPAT_BITS_MAX
773 int
774
775config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
776 int
777
778config ARCH_MMAP_RND_COMPAT_BITS
779 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
780 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
781 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
782 default ARCH_MMAP_RND_COMPAT_BITS_MIN
783 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
784 help
785 This value can be used to select the number of bits to use to
786 determine the random offset to the base address of vma regions
787 resulting from mmap allocations for compatible applications This
788 value will be bounded by the architecture's minimum and maximum
789 supported values.
790
791 This value can be changed after boot using the
792 /proc/sys/vm/mmap_rnd_compat_bits tunable
793
794config HAVE_ARCH_COMPAT_MMAP_BASES
795 bool
796 help
797 This allows 64bit applications to invoke 32-bit mmap() syscall
798 and vice-versa 32-bit applications to call 64-bit mmap().
799 Required for applications doing different bitness syscalls.
800
801config HAVE_COPY_THREAD_TLS
802 bool
803 help
804 Architecture provides copy_thread_tls to accept tls argument via
805 normal C parameter passing, rather than extracting the syscall
806 argument from pt_regs.
807
808config HAVE_STACK_VALIDATION
809 bool
810 help
811 Architecture supports the 'objtool check' host tool command, which
812 performs compile-time stack metadata validation.
813
814config HAVE_RELIABLE_STACKTRACE
815 bool
816 help
817 Architecture has a save_stack_trace_tsk_reliable() function which
818 only returns a stack trace if it can guarantee the trace is reliable.
819
820config HAVE_ARCH_HASH
821 bool
822 default n
823 help
824 If this is set, the architecture provides an <asm/hash.h>
825 file which provides platform-specific implementations of some
826 functions in <linux/hash.h> or fs/namei.c.
827
828config ISA_BUS_API
829 def_bool ISA
830
831#
832# ABI hall of shame
833#
834config CLONE_BACKWARDS
835 bool
836 help
837 Architecture has tls passed as the 4th argument of clone(2),
838 not the 5th one.
839
840config CLONE_BACKWARDS2
841 bool
842 help
843 Architecture has the first two arguments of clone(2) swapped.
844
845config CLONE_BACKWARDS3
846 bool
847 help
848 Architecture has tls passed as the 3rd argument of clone(2),
849 not the 5th one.
850
851config ODD_RT_SIGACTION
852 bool
853 help
854 Architecture has unusual rt_sigaction(2) arguments
855
856config OLD_SIGSUSPEND
857 bool
858 help
859 Architecture has old sigsuspend(2) syscall, of one-argument variety
860
861config OLD_SIGSUSPEND3
862 bool
863 help
864 Even weirder antique ABI - three-argument sigsuspend(2)
865
866config OLD_SIGACTION
867 bool
868 help
869 Architecture has old sigaction(2) syscall. Nope, not the same
870 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
871 but fairly different variant of sigaction(2), thanks to OSF/1
872 compatibility...
873
874config COMPAT_OLD_SIGACTION
875 bool
876
877config ARCH_NO_COHERENT_DMA_MMAP
878 bool
879
880config CPU_NO_EFFICIENT_FFS
881 def_bool n
882
883config HAVE_ARCH_VMAP_STACK
884 def_bool n
885 help
886 An arch should select this symbol if it can support kernel stacks
887 in vmalloc space. This means:
888
889 - vmalloc space must be large enough to hold many kernel stacks.
890 This may rule out many 32-bit architectures.
891
892 - Stacks in vmalloc space need to work reliably. For example, if
893 vmap page tables are created on demand, either this mechanism
894 needs to work while the stack points to a virtual address with
895 unpopulated page tables or arch code (switch_to() and switch_mm(),
896 most likely) needs to ensure that the stack's page table entries
897 are populated before running on a possibly unpopulated stack.
898
899 - If the stack overflows into a guard page, something reasonable
900 should happen. The definition of "reasonable" is flexible, but
901 instantly rebooting without logging anything would be unfriendly.
902
903config VMAP_STACK
904 default y
905 bool "Use a virtually-mapped stack"
906 depends on HAVE_ARCH_VMAP_STACK && !KASAN
907 ---help---
908 Enable this if you want the use virtually-mapped kernel stacks
909 with guard pages. This causes kernel stack overflows to be
910 caught immediately rather than causing difficult-to-diagnose
911 corruption.
912
913 This is presently incompatible with KASAN because KASAN expects
914 the stack to map directly to the KASAN shadow map using a formula
915 that is incorrect if the stack is in vmalloc space.
916
917config ARCH_OPTIONAL_KERNEL_RWX
918 def_bool n
919
920config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
921 def_bool n
922
923config ARCH_HAS_STRICT_KERNEL_RWX
924 def_bool n
925
926config STRICT_KERNEL_RWX
927 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
928 depends on ARCH_HAS_STRICT_KERNEL_RWX
929 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
930 help
931 If this is set, kernel text and rodata memory will be made read-only,
932 and non-text memory will be made non-executable. This provides
933 protection against certain security exploits (e.g. executing the heap
934 or modifying text)
935
936 These features are considered standard security practice these days.
937 You should say Y here in almost all cases.
938
939config ARCH_HAS_STRICT_MODULE_RWX
940 def_bool n
941
942config STRICT_MODULE_RWX
943 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
944 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
945 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
946 help
947 If this is set, module text and rodata memory will be made read-only,
948 and non-text memory will be made non-executable. This provides
949 protection against certain security exploits (e.g. writing to text)
950
951# select if the architecture provides an asm/dma-direct.h header
952config ARCH_HAS_PHYS_TO_DMA
953 bool
954
955config ARCH_HAS_REFCOUNT
956 bool
957 help
958 An architecture selects this when it has implemented refcount_t
959 using open coded assembly primitives that provide an optimized
960 refcount_t implementation, possibly at the expense of some full
961 refcount state checks of CONFIG_REFCOUNT_FULL=y.
962
963 The refcount overflow check behavior, however, must be retained.
964 Catching overflows is the primary security concern for protecting
965 against bugs in reference counts.
966
967config REFCOUNT_FULL
968 bool "Perform full reference count validation at the expense of speed"
969 help
970 Enabling this switches the refcounting infrastructure from a fast
971 unchecked atomic_t implementation to a fully state checked
972 implementation, which can be (slightly) slower but provides protections
973 against various use-after-free conditions that can be used in
974 security flaw exploits.
975
976source "kernel/gcov/Kconfig"
1# SPDX-License-Identifier: GPL-2.0
2#
3# General architecture dependent options
4#
5
6#
7# Note: arch/$(SRCARCH)/Kconfig needs to be included first so that it can
8# override the default values in this file.
9#
10source "arch/$(SRCARCH)/Kconfig"
11
12menu "General architecture-dependent options"
13
14config CRASH_CORE
15 bool
16
17config KEXEC_CORE
18 select CRASH_CORE
19 bool
20
21config KEXEC_ELF
22 bool
23
24config HAVE_IMA_KEXEC
25 bool
26
27config SET_FS
28 bool
29
30config HOTPLUG_SMT
31 bool
32
33config GENERIC_ENTRY
34 bool
35
36config KPROBES
37 bool "Kprobes"
38 depends on MODULES
39 depends on HAVE_KPROBES
40 select KALLSYMS
41 help
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.
46 If in doubt, say "N".
47
48config JUMP_LABEL
49 bool "Optimize very unlikely/likely branches"
50 depends on HAVE_ARCH_JUMP_LABEL
51 depends on CC_HAS_ASM_GOTO
52 help
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.
56
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.
60
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.
66
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.
70
71 ( On 32-bit x86, the necessary options added to the compiler
72 flags may increase the size of the kernel slightly. )
73
74config STATIC_KEYS_SELFTEST
75 bool "Static key selftest"
76 depends on JUMP_LABEL
77 help
78 Boot time self-test of the branch patching code.
79
80config STATIC_CALL_SELFTEST
81 bool "Static call selftest"
82 depends on HAVE_STATIC_CALL
83 help
84 Boot time self-test of the call patching code.
85
86config OPTPROBES
87 def_bool y
88 depends on KPROBES && HAVE_OPTPROBES
89 select TASKS_RCU if PREEMPTION
90
91config KPROBES_ON_FTRACE
92 def_bool y
93 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
94 depends on DYNAMIC_FTRACE_WITH_REGS
95 help
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.
99
100config UPROBES
101 def_bool n
102 depends on ARCH_SUPPORTS_UPROBES
103 help
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.
109
110 ( These probes come in the form of single-byte breakpoints,
111 managed by the kernel and kept transparent to the probed
112 application. )
113
114config HAVE_64BIT_ALIGNED_ACCESS
115 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
116 help
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.
122
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.
126
127 See Documentation/core-api/unaligned-memory-access.rst for
128 more information on the topic of unaligned memory accesses.
129
130config HAVE_EFFICIENT_UNALIGNED_ACCESS
131 bool
132 help
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
137 handler.)
138
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
144 much.
145
146 See Documentation/core-api/unaligned-memory-access.rst for more
147 information on the topic of unaligned memory accesses.
148
149config ARCH_USE_BUILTIN_BSWAP
150 bool
151 help
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.
163
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.
167
168config KRETPROBES
169 def_bool y
170 depends on KPROBES && HAVE_KRETPROBES
171
172config USER_RETURN_NOTIFIER
173 bool
174 depends on HAVE_USER_RETURN_NOTIFIER
175 help
176 Provide a kernel-internal notification when a cpu is about to
177 switch to user mode.
178
179config HAVE_IOREMAP_PROT
180 bool
181
182config HAVE_KPROBES
183 bool
184
185config HAVE_KRETPROBES
186 bool
187
188config HAVE_OPTPROBES
189 bool
190
191config HAVE_KPROBES_ON_FTRACE
192 bool
193
194config HAVE_FUNCTION_ERROR_INJECTION
195 bool
196
197config HAVE_NMI
198 bool
199
200#
201# An arch should select this if it provides all these things:
202#
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()
212#
213config HAVE_ARCH_TRACEHOOK
214 bool
215
216config HAVE_DMA_CONTIGUOUS
217 bool
218
219config GENERIC_SMP_IDLE_THREAD
220 bool
221
222config GENERIC_IDLE_POLL_SETUP
223 bool
224
225config ARCH_HAS_FORTIFY_SOURCE
226 bool
227 help
228 An architecture should select this when it can successfully
229 build and run with CONFIG_FORTIFY_SOURCE.
230
231#
232# Select if the arch provides a historic keepinit alias for the retain_initrd
233# command line option
234#
235config ARCH_HAS_KEEPINITRD
236 bool
237
238# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
239config ARCH_HAS_SET_MEMORY
240 bool
241
242# Select if arch has all set_direct_map_invalid/default() functions
243config ARCH_HAS_SET_DIRECT_MAP
244 bool
245
246#
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.
250#
251config ARCH_HAS_DMA_SET_UNCACHED
252 bool
253
254#
255# Select if the architectures provides the arch_dma_clear_uncached symbol
256# to undo an in-place page table remap for uncached access.
257#
258config ARCH_HAS_DMA_CLEAR_UNCACHED
259 bool
260
261# Select if arch init_task must go in the __init_task_data section
262config ARCH_TASK_STRUCT_ON_STACK
263 bool
264
265# Select if arch has its private alloc_task_struct() function
266config ARCH_TASK_STRUCT_ALLOCATOR
267 bool
268
269config HAVE_ARCH_THREAD_STRUCT_WHITELIST
270 bool
271 depends on !ARCH_TASK_STRUCT_ALLOCATOR
272 help
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.
279
280# Select if arch has its private alloc_thread_stack() function
281config ARCH_THREAD_STACK_ALLOCATOR
282 bool
283
284# Select if arch wants to size task_struct dynamically via arch_task_struct_size:
285config ARCH_WANTS_DYNAMIC_TASK_STRUCT
286 bool
287
288config ARCH_WANTS_NO_INSTR
289 bool
290 help
291 An architecture should select this if the noinstr macro is being used on
292 functions to denote that the toolchain should avoid instrumenting such
293 functions and is required for correctness.
294
295config ARCH_32BIT_OFF_T
296 bool
297 depends on !64BIT
298 help
299 All new 32-bit architectures should have 64-bit off_t type on
300 userspace side which corresponds to the loff_t kernel type. This
301 is the requirement for modern ABIs. Some existing architectures
302 still support 32-bit off_t. This option is enabled for all such
303 architectures explicitly.
304
305# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat
306config ARCH_32BIT_USTAT_F_TINODE
307 bool
308
309config HAVE_ASM_MODVERSIONS
310 bool
311 help
312 This symbol should be selected by an architecture if it provides
313 <asm/asm-prototypes.h> to support the module versioning for symbols
314 exported from assembly code.
315
316config HAVE_REGS_AND_STACK_ACCESS_API
317 bool
318 help
319 This symbol should be selected by an architecture if it supports
320 the API needed to access registers and stack entries from pt_regs,
321 declared in asm/ptrace.h
322 For example the kprobes-based event tracer needs this API.
323
324config HAVE_RSEQ
325 bool
326 depends on HAVE_REGS_AND_STACK_ACCESS_API
327 help
328 This symbol should be selected by an architecture if it
329 supports an implementation of restartable sequences.
330
331config HAVE_FUNCTION_ARG_ACCESS_API
332 bool
333 help
334 This symbol should be selected by an architecture if it supports
335 the API needed to access function arguments from pt_regs,
336 declared in asm/ptrace.h
337
338config HAVE_HW_BREAKPOINT
339 bool
340 depends on PERF_EVENTS
341
342config HAVE_MIXED_BREAKPOINTS_REGS
343 bool
344 depends on HAVE_HW_BREAKPOINT
345 help
346 Depending on the arch implementation of hardware breakpoints,
347 some of them have separate registers for data and instruction
348 breakpoints addresses, others have mixed registers to store
349 them but define the access type in a control register.
350 Select this option if your arch implements breakpoints under the
351 latter fashion.
352
353config HAVE_USER_RETURN_NOTIFIER
354 bool
355
356config HAVE_PERF_EVENTS_NMI
357 bool
358 help
359 System hardware can generate an NMI using the perf event
360 subsystem. Also has support for calculating CPU cycle events
361 to determine how many clock cycles in a given period.
362
363config HAVE_HARDLOCKUP_DETECTOR_PERF
364 bool
365 depends on HAVE_PERF_EVENTS_NMI
366 help
367 The arch chooses to use the generic perf-NMI-based hardlockup
368 detector. Must define HAVE_PERF_EVENTS_NMI.
369
370config HAVE_NMI_WATCHDOG
371 depends on HAVE_NMI
372 bool
373 help
374 The arch provides a low level NMI watchdog. It provides
375 asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
376
377config HAVE_HARDLOCKUP_DETECTOR_ARCH
378 bool
379 select HAVE_NMI_WATCHDOG
380 help
381 The arch chooses to provide its own hardlockup detector, which is
382 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
383 interfaces and parameters provided by hardlockup detector subsystem.
384
385config HAVE_PERF_REGS
386 bool
387 help
388 Support selective register dumps for perf events. This includes
389 bit-mapping of each registers and a unique architecture id.
390
391config HAVE_PERF_USER_STACK_DUMP
392 bool
393 help
394 Support user stack dumps for perf event samples. This needs
395 access to the user stack pointer which is not unified across
396 architectures.
397
398config HAVE_ARCH_JUMP_LABEL
399 bool
400
401config HAVE_ARCH_JUMP_LABEL_RELATIVE
402 bool
403
404config MMU_GATHER_TABLE_FREE
405 bool
406
407config MMU_GATHER_RCU_TABLE_FREE
408 bool
409 select MMU_GATHER_TABLE_FREE
410
411config MMU_GATHER_PAGE_SIZE
412 bool
413
414config MMU_GATHER_NO_RANGE
415 bool
416
417config MMU_GATHER_NO_GATHER
418 bool
419 depends on MMU_GATHER_TABLE_FREE
420
421config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
422 bool
423 help
424 Temporary select until all architectures can be converted to have
425 irqs disabled over activate_mm. Architectures that do IPI based TLB
426 shootdowns should enable this.
427
428config ARCH_HAVE_NMI_SAFE_CMPXCHG
429 bool
430
431config HAVE_ALIGNED_STRUCT_PAGE
432 bool
433 help
434 This makes sure that struct pages are double word aligned and that
435 e.g. the SLUB allocator can perform double word atomic operations
436 on a struct page for better performance. However selecting this
437 might increase the size of a struct page by a word.
438
439config HAVE_CMPXCHG_LOCAL
440 bool
441
442config HAVE_CMPXCHG_DOUBLE
443 bool
444
445config ARCH_WEAK_RELEASE_ACQUIRE
446 bool
447
448config ARCH_WANT_IPC_PARSE_VERSION
449 bool
450
451config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
452 bool
453
454config ARCH_WANT_OLD_COMPAT_IPC
455 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
456 bool
457
458config HAVE_ARCH_SECCOMP
459 bool
460 help
461 An arch should select this symbol to support seccomp mode 1 (the fixed
462 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
463 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
464 - __NR_seccomp_read_32
465 - __NR_seccomp_write_32
466 - __NR_seccomp_exit_32
467 - __NR_seccomp_sigreturn_32
468
469config HAVE_ARCH_SECCOMP_FILTER
470 bool
471 select HAVE_ARCH_SECCOMP
472 help
473 An arch should select this symbol if it provides all of these things:
474 - all the requirements for HAVE_ARCH_SECCOMP
475 - syscall_get_arch()
476 - syscall_get_arguments()
477 - syscall_rollback()
478 - syscall_set_return_value()
479 - SIGSYS siginfo_t support
480 - secure_computing is called from a ptrace_event()-safe context
481 - secure_computing return value is checked and a return value of -1
482 results in the system call being skipped immediately.
483 - seccomp syscall wired up
484 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE,
485 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If
486 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too.
487
488config SECCOMP
489 prompt "Enable seccomp to safely execute untrusted bytecode"
490 def_bool y
491 depends on HAVE_ARCH_SECCOMP
492 help
493 This kernel feature is useful for number crunching applications
494 that may need to handle untrusted bytecode during their
495 execution. By using pipes or other transports made available
496 to the process as file descriptors supporting the read/write
497 syscalls, it's possible to isolate those applications in their
498 own address space using seccomp. Once seccomp is enabled via
499 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
500 disabled and the task is only allowed to execute a few safe
501 syscalls defined by each seccomp mode.
502
503 If unsure, say Y.
504
505config SECCOMP_FILTER
506 def_bool y
507 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
508 help
509 Enable tasks to build secure computing environments defined
510 in terms of Berkeley Packet Filter programs which implement
511 task-defined system call filtering polices.
512
513 See Documentation/userspace-api/seccomp_filter.rst for details.
514
515config SECCOMP_CACHE_DEBUG
516 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache"
517 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR
518 depends on PROC_FS
519 help
520 This enables the /proc/pid/seccomp_cache interface to monitor
521 seccomp cache data. The file format is subject to change. Reading
522 the file requires CAP_SYS_ADMIN.
523
524 This option is for debugging only. Enabling presents the risk that
525 an adversary may be able to infer the seccomp filter logic.
526
527 If unsure, say N.
528
529config HAVE_ARCH_STACKLEAK
530 bool
531 help
532 An architecture should select this if it has the code which
533 fills the used part of the kernel stack with the STACKLEAK_POISON
534 value before returning from system calls.
535
536config HAVE_STACKPROTECTOR
537 bool
538 help
539 An arch should select this symbol if:
540 - it has implemented a stack canary (e.g. __stack_chk_guard)
541
542config STACKPROTECTOR
543 bool "Stack Protector buffer overflow detection"
544 depends on HAVE_STACKPROTECTOR
545 depends on $(cc-option,-fstack-protector)
546 default y
547 help
548 This option turns on the "stack-protector" GCC feature. This
549 feature puts, at the beginning of functions, a canary value on
550 the stack just before the return address, and validates
551 the value just before actually returning. Stack based buffer
552 overflows (that need to overwrite this return address) now also
553 overwrite the canary, which gets detected and the attack is then
554 neutralized via a kernel panic.
555
556 Functions will have the stack-protector canary logic added if they
557 have an 8-byte or larger character array on the stack.
558
559 This feature requires gcc version 4.2 or above, or a distribution
560 gcc with the feature backported ("-fstack-protector").
561
562 On an x86 "defconfig" build, this feature adds canary checks to
563 about 3% of all kernel functions, which increases kernel code size
564 by about 0.3%.
565
566config STACKPROTECTOR_STRONG
567 bool "Strong Stack Protector"
568 depends on STACKPROTECTOR
569 depends on $(cc-option,-fstack-protector-strong)
570 default y
571 help
572 Functions will have the stack-protector canary logic added in any
573 of the following conditions:
574
575 - local variable's address used as part of the right hand side of an
576 assignment or function argument
577 - local variable is an array (or union containing an array),
578 regardless of array type or length
579 - uses register local variables
580
581 This feature requires gcc version 4.9 or above, or a distribution
582 gcc with the feature backported ("-fstack-protector-strong").
583
584 On an x86 "defconfig" build, this feature adds canary checks to
585 about 20% of all kernel functions, which increases the kernel code
586 size by about 2%.
587
588config ARCH_SUPPORTS_SHADOW_CALL_STACK
589 bool
590 help
591 An architecture should select this if it supports Clang's Shadow
592 Call Stack and implements runtime support for shadow stack
593 switching.
594
595config SHADOW_CALL_STACK
596 bool "Clang Shadow Call Stack"
597 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK
598 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
599 help
600 This option enables Clang's Shadow Call Stack, which uses a
601 shadow stack to protect function return addresses from being
602 overwritten by an attacker. More information can be found in
603 Clang's documentation:
604
605 https://clang.llvm.org/docs/ShadowCallStack.html
606
607 Note that security guarantees in the kernel differ from the
608 ones documented for user space. The kernel must store addresses
609 of shadow stacks in memory, which means an attacker capable of
610 reading and writing arbitrary memory may be able to locate them
611 and hijack control flow by modifying the stacks.
612
613config LTO
614 bool
615 help
616 Selected if the kernel will be built using the compiler's LTO feature.
617
618config LTO_CLANG
619 bool
620 select LTO
621 help
622 Selected if the kernel will be built using Clang's LTO feature.
623
624config ARCH_SUPPORTS_LTO_CLANG
625 bool
626 help
627 An architecture should select this option if it supports:
628 - compiling with Clang,
629 - compiling inline assembly with Clang's integrated assembler,
630 - and linking with LLD.
631
632config ARCH_SUPPORTS_LTO_CLANG_THIN
633 bool
634 help
635 An architecture should select this option if it can support Clang's
636 ThinLTO mode.
637
638config HAS_LTO_CLANG
639 def_bool y
640 # Clang >= 11: https://github.com/ClangBuiltLinux/linux/issues/510
641 depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD && AS_IS_LLVM
642 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
643 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
644 depends on ARCH_SUPPORTS_LTO_CLANG
645 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT
646 depends on !KASAN || KASAN_HW_TAGS
647 depends on !GCOV_KERNEL
648 help
649 The compiler and Kconfig options support building with Clang's
650 LTO.
651
652choice
653 prompt "Link Time Optimization (LTO)"
654 default LTO_NONE
655 help
656 This option enables Link Time Optimization (LTO), which allows the
657 compiler to optimize binaries globally.
658
659 If unsure, select LTO_NONE. Note that LTO is very resource-intensive
660 so it's disabled by default.
661
662config LTO_NONE
663 bool "None"
664 help
665 Build the kernel normally, without Link Time Optimization (LTO).
666
667config LTO_CLANG_FULL
668 bool "Clang Full LTO (EXPERIMENTAL)"
669 depends on HAS_LTO_CLANG
670 depends on !COMPILE_TEST
671 select LTO_CLANG
672 help
673 This option enables Clang's full Link Time Optimization (LTO), which
674 allows the compiler to optimize the kernel globally. If you enable
675 this option, the compiler generates LLVM bitcode instead of ELF
676 object files, and the actual compilation from bitcode happens at
677 the LTO link step, which may take several minutes depending on the
678 kernel configuration. More information can be found from LLVM's
679 documentation:
680
681 https://llvm.org/docs/LinkTimeOptimization.html
682
683 During link time, this option can use a large amount of RAM, and
684 may take much longer than the ThinLTO option.
685
686config LTO_CLANG_THIN
687 bool "Clang ThinLTO (EXPERIMENTAL)"
688 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN
689 select LTO_CLANG
690 help
691 This option enables Clang's ThinLTO, which allows for parallel
692 optimization and faster incremental compiles compared to the
693 CONFIG_LTO_CLANG_FULL option. More information can be found
694 from Clang's documentation:
695
696 https://clang.llvm.org/docs/ThinLTO.html
697
698 If unsure, say Y.
699endchoice
700
701config ARCH_SUPPORTS_CFI_CLANG
702 bool
703 help
704 An architecture should select this option if it can support Clang's
705 Control-Flow Integrity (CFI) checking.
706
707config CFI_CLANG
708 bool "Use Clang's Control Flow Integrity (CFI)"
709 depends on LTO_CLANG && ARCH_SUPPORTS_CFI_CLANG
710 # Clang >= 12:
711 # - https://bugs.llvm.org/show_bug.cgi?id=46258
712 # - https://bugs.llvm.org/show_bug.cgi?id=47479
713 depends on CLANG_VERSION >= 120000
714 select KALLSYMS
715 help
716 This option enables Clang’s forward-edge Control Flow Integrity
717 (CFI) checking, where the compiler injects a runtime check to each
718 indirect function call to ensure the target is a valid function with
719 the correct static type. This restricts possible call targets and
720 makes it more difficult for an attacker to exploit bugs that allow
721 the modification of stored function pointers. More information can be
722 found from Clang's documentation:
723
724 https://clang.llvm.org/docs/ControlFlowIntegrity.html
725
726config CFI_CLANG_SHADOW
727 bool "Use CFI shadow to speed up cross-module checks"
728 default y
729 depends on CFI_CLANG && MODULES
730 help
731 If you select this option, the kernel builds a fast look-up table of
732 CFI check functions in loaded modules to reduce performance overhead.
733
734 If unsure, say Y.
735
736config CFI_PERMISSIVE
737 bool "Use CFI in permissive mode"
738 depends on CFI_CLANG
739 help
740 When selected, Control Flow Integrity (CFI) violations result in a
741 warning instead of a kernel panic. This option should only be used
742 for finding indirect call type mismatches during development.
743
744 If unsure, say N.
745
746config HAVE_ARCH_WITHIN_STACK_FRAMES
747 bool
748 help
749 An architecture should select this if it can walk the kernel stack
750 frames to determine if an object is part of either the arguments
751 or local variables (i.e. that it excludes saved return addresses,
752 and similar) by implementing an inline arch_within_stack_frames(),
753 which is used by CONFIG_HARDENED_USERCOPY.
754
755config HAVE_CONTEXT_TRACKING
756 bool
757 help
758 Provide kernel/user boundaries probes necessary for subsystems
759 that need it, such as userspace RCU extended quiescent state.
760 Syscalls need to be wrapped inside user_exit()-user_enter(), either
761 optimized behind static key or through the slow path using TIF_NOHZ
762 flag. Exceptions handlers must be wrapped as well. Irqs are already
763 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal
764 handling on irq exit still need to be protected.
765
766config HAVE_CONTEXT_TRACKING_OFFSTACK
767 bool
768 help
769 Architecture neither relies on exception_enter()/exception_exit()
770 nor on schedule_user(). Also preempt_schedule_notrace() and
771 preempt_schedule_irq() can't be called in a preemptible section
772 while context tracking is CONTEXT_USER. This feature reflects a sane
773 entry implementation where the following requirements are met on
774 critical entry code, ie: before user_exit() or after user_enter():
775
776 - Critical entry code isn't preemptible (or better yet:
777 not interruptible).
778 - No use of RCU read side critical sections, unless rcu_nmi_enter()
779 got called.
780 - No use of instrumentation, unless instrumentation_begin() got
781 called.
782
783config HAVE_TIF_NOHZ
784 bool
785 help
786 Arch relies on TIF_NOHZ and syscall slow path to implement context
787 tracking calls to user_enter()/user_exit().
788
789config HAVE_VIRT_CPU_ACCOUNTING
790 bool
791
792config HAVE_VIRT_CPU_ACCOUNTING_IDLE
793 bool
794 help
795 Architecture has its own way to account idle CPU time and therefore
796 doesn't implement vtime_account_idle().
797
798config ARCH_HAS_SCALED_CPUTIME
799 bool
800
801config HAVE_VIRT_CPU_ACCOUNTING_GEN
802 bool
803 default y if 64BIT
804 help
805 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
806 Before enabling this option, arch code must be audited
807 to ensure there are no races in concurrent read/write of
808 cputime_t. For example, reading/writing 64-bit cputime_t on
809 some 32-bit arches may require multiple accesses, so proper
810 locking is needed to protect against concurrent accesses.
811
812config HAVE_IRQ_TIME_ACCOUNTING
813 bool
814 help
815 Archs need to ensure they use a high enough resolution clock to
816 support irq time accounting and then call enable_sched_clock_irqtime().
817
818config HAVE_MOVE_PUD
819 bool
820 help
821 Architectures that select this are able to move page tables at the
822 PUD level. If there are only 3 page table levels, the move effectively
823 happens at the PGD level.
824
825config HAVE_MOVE_PMD
826 bool
827 help
828 Archs that select this are able to move page tables at the PMD level.
829
830config HAVE_ARCH_TRANSPARENT_HUGEPAGE
831 bool
832
833config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
834 bool
835
836config HAVE_ARCH_HUGE_VMAP
837 bool
838
839#
840# Archs that select this would be capable of PMD-sized vmaps (i.e.,
841# arch_vmap_pmd_supported() returns true), and they must make no assumptions
842# that vmalloc memory is mapped with PAGE_SIZE ptes. The VM_NO_HUGE_VMAP flag
843# can be used to prohibit arch-specific allocations from using hugepages to
844# help with this (e.g., modules may require it).
845#
846config HAVE_ARCH_HUGE_VMALLOC
847 depends on HAVE_ARCH_HUGE_VMAP
848 bool
849
850config ARCH_WANT_HUGE_PMD_SHARE
851 bool
852
853config HAVE_ARCH_SOFT_DIRTY
854 bool
855
856config HAVE_MOD_ARCH_SPECIFIC
857 bool
858 help
859 The arch uses struct mod_arch_specific to store data. Many arches
860 just need a simple module loader without arch specific data - those
861 should not enable this.
862
863config MODULES_USE_ELF_RELA
864 bool
865 help
866 Modules only use ELF RELA relocations. Modules with ELF REL
867 relocations will give an error.
868
869config MODULES_USE_ELF_REL
870 bool
871 help
872 Modules only use ELF REL relocations. Modules with ELF RELA
873 relocations will give an error.
874
875config HAVE_IRQ_EXIT_ON_IRQ_STACK
876 bool
877 help
878 Architecture doesn't only execute the irq handler on the irq stack
879 but also irq_exit(). This way we can process softirqs on this irq
880 stack instead of switching to a new one when we call __do_softirq()
881 in the end of an hardirq.
882 This spares a stack switch and improves cache usage on softirq
883 processing.
884
885config HAVE_SOFTIRQ_ON_OWN_STACK
886 bool
887 help
888 Architecture provides a function to run __do_softirq() on a
889 seperate stack.
890
891config PGTABLE_LEVELS
892 int
893 default 2
894
895config ARCH_HAS_ELF_RANDOMIZE
896 bool
897 help
898 An architecture supports choosing randomized locations for
899 stack, mmap, brk, and ET_DYN. Defined functions:
900 - arch_mmap_rnd()
901 - arch_randomize_brk()
902
903config HAVE_ARCH_MMAP_RND_BITS
904 bool
905 help
906 An arch should select this symbol if it supports setting a variable
907 number of bits for use in establishing the base address for mmap
908 allocations, has MMU enabled and provides values for both:
909 - ARCH_MMAP_RND_BITS_MIN
910 - ARCH_MMAP_RND_BITS_MAX
911
912config HAVE_EXIT_THREAD
913 bool
914 help
915 An architecture implements exit_thread.
916
917config ARCH_MMAP_RND_BITS_MIN
918 int
919
920config ARCH_MMAP_RND_BITS_MAX
921 int
922
923config ARCH_MMAP_RND_BITS_DEFAULT
924 int
925
926config ARCH_MMAP_RND_BITS
927 int "Number of bits to use for ASLR of mmap base address" if EXPERT
928 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
929 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
930 default ARCH_MMAP_RND_BITS_MIN
931 depends on HAVE_ARCH_MMAP_RND_BITS
932 help
933 This value can be used to select the number of bits to use to
934 determine the random offset to the base address of vma regions
935 resulting from mmap allocations. This value will be bounded
936 by the architecture's minimum and maximum supported values.
937
938 This value can be changed after boot using the
939 /proc/sys/vm/mmap_rnd_bits tunable
940
941config HAVE_ARCH_MMAP_RND_COMPAT_BITS
942 bool
943 help
944 An arch should select this symbol if it supports running applications
945 in compatibility mode, supports setting a variable number of bits for
946 use in establishing the base address for mmap allocations, has MMU
947 enabled and provides values for both:
948 - ARCH_MMAP_RND_COMPAT_BITS_MIN
949 - ARCH_MMAP_RND_COMPAT_BITS_MAX
950
951config ARCH_MMAP_RND_COMPAT_BITS_MIN
952 int
953
954config ARCH_MMAP_RND_COMPAT_BITS_MAX
955 int
956
957config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
958 int
959
960config ARCH_MMAP_RND_COMPAT_BITS
961 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
962 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
963 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
964 default ARCH_MMAP_RND_COMPAT_BITS_MIN
965 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
966 help
967 This value can be used to select the number of bits to use to
968 determine the random offset to the base address of vma regions
969 resulting from mmap allocations for compatible applications This
970 value will be bounded by the architecture's minimum and maximum
971 supported values.
972
973 This value can be changed after boot using the
974 /proc/sys/vm/mmap_rnd_compat_bits tunable
975
976config HAVE_ARCH_COMPAT_MMAP_BASES
977 bool
978 help
979 This allows 64bit applications to invoke 32-bit mmap() syscall
980 and vice-versa 32-bit applications to call 64-bit mmap().
981 Required for applications doing different bitness syscalls.
982
983# This allows to use a set of generic functions to determine mmap base
984# address by giving priority to top-down scheme only if the process
985# is not in legacy mode (compat task, unlimited stack size or
986# sysctl_legacy_va_layout).
987# Architecture that selects this option can provide its own version of:
988# - STACK_RND_MASK
989config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
990 bool
991 depends on MMU
992 select ARCH_HAS_ELF_RANDOMIZE
993
994config HAVE_STACK_VALIDATION
995 bool
996 help
997 Architecture supports the 'objtool check' host tool command, which
998 performs compile-time stack metadata validation.
999
1000config HAVE_RELIABLE_STACKTRACE
1001 bool
1002 help
1003 Architecture has either save_stack_trace_tsk_reliable() or
1004 arch_stack_walk_reliable() function which only returns a stack trace
1005 if it can guarantee the trace is reliable.
1006
1007config HAVE_ARCH_HASH
1008 bool
1009 default n
1010 help
1011 If this is set, the architecture provides an <asm/hash.h>
1012 file which provides platform-specific implementations of some
1013 functions in <linux/hash.h> or fs/namei.c.
1014
1015config HAVE_ARCH_NVRAM_OPS
1016 bool
1017
1018config ISA_BUS_API
1019 def_bool ISA
1020
1021#
1022# ABI hall of shame
1023#
1024config CLONE_BACKWARDS
1025 bool
1026 help
1027 Architecture has tls passed as the 4th argument of clone(2),
1028 not the 5th one.
1029
1030config CLONE_BACKWARDS2
1031 bool
1032 help
1033 Architecture has the first two arguments of clone(2) swapped.
1034
1035config CLONE_BACKWARDS3
1036 bool
1037 help
1038 Architecture has tls passed as the 3rd argument of clone(2),
1039 not the 5th one.
1040
1041config ODD_RT_SIGACTION
1042 bool
1043 help
1044 Architecture has unusual rt_sigaction(2) arguments
1045
1046config OLD_SIGSUSPEND
1047 bool
1048 help
1049 Architecture has old sigsuspend(2) syscall, of one-argument variety
1050
1051config OLD_SIGSUSPEND3
1052 bool
1053 help
1054 Even weirder antique ABI - three-argument sigsuspend(2)
1055
1056config OLD_SIGACTION
1057 bool
1058 help
1059 Architecture has old sigaction(2) syscall. Nope, not the same
1060 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
1061 but fairly different variant of sigaction(2), thanks to OSF/1
1062 compatibility...
1063
1064config COMPAT_OLD_SIGACTION
1065 bool
1066
1067config COMPAT_32BIT_TIME
1068 bool "Provide system calls for 32-bit time_t"
1069 default !64BIT || COMPAT
1070 help
1071 This enables 32 bit time_t support in addition to 64 bit time_t support.
1072 This is relevant on all 32-bit architectures, and 64-bit architectures
1073 as part of compat syscall handling.
1074
1075config ARCH_NO_PREEMPT
1076 bool
1077
1078config ARCH_EPHEMERAL_INODES
1079 def_bool n
1080 help
1081 An arch should select this symbol if it doesn't keep track of inode
1082 instances on its own, but instead relies on something else (e.g. the
1083 host kernel for an UML kernel).
1084
1085config ARCH_SUPPORTS_RT
1086 bool
1087
1088config CPU_NO_EFFICIENT_FFS
1089 def_bool n
1090
1091config HAVE_ARCH_VMAP_STACK
1092 def_bool n
1093 help
1094 An arch should select this symbol if it can support kernel stacks
1095 in vmalloc space. This means:
1096
1097 - vmalloc space must be large enough to hold many kernel stacks.
1098 This may rule out many 32-bit architectures.
1099
1100 - Stacks in vmalloc space need to work reliably. For example, if
1101 vmap page tables are created on demand, either this mechanism
1102 needs to work while the stack points to a virtual address with
1103 unpopulated page tables or arch code (switch_to() and switch_mm(),
1104 most likely) needs to ensure that the stack's page table entries
1105 are populated before running on a possibly unpopulated stack.
1106
1107 - If the stack overflows into a guard page, something reasonable
1108 should happen. The definition of "reasonable" is flexible, but
1109 instantly rebooting without logging anything would be unfriendly.
1110
1111config VMAP_STACK
1112 default y
1113 bool "Use a virtually-mapped stack"
1114 depends on HAVE_ARCH_VMAP_STACK
1115 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC
1116 help
1117 Enable this if you want the use virtually-mapped kernel stacks
1118 with guard pages. This causes kernel stack overflows to be
1119 caught immediately rather than causing difficult-to-diagnose
1120 corruption.
1121
1122 To use this with software KASAN modes, the architecture must support
1123 backing virtual mappings with real shadow memory, and KASAN_VMALLOC
1124 must be enabled.
1125
1126config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1127 def_bool n
1128 help
1129 An arch should select this symbol if it can support kernel stack
1130 offset randomization with calls to add_random_kstack_offset()
1131 during syscall entry and choose_random_kstack_offset() during
1132 syscall exit. Careful removal of -fstack-protector-strong and
1133 -fstack-protector should also be applied to the entry code and
1134 closely examined, as the artificial stack bump looks like an array
1135 to the compiler, so it will attempt to add canary checks regardless
1136 of the static branch state.
1137
1138config RANDOMIZE_KSTACK_OFFSET_DEFAULT
1139 bool "Randomize kernel stack offset on syscall entry"
1140 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1141 help
1142 The kernel stack offset can be randomized (after pt_regs) by
1143 roughly 5 bits of entropy, frustrating memory corruption
1144 attacks that depend on stack address determinism or
1145 cross-syscall address exposures. This feature is controlled
1146 by kernel boot param "randomize_kstack_offset=on/off", and this
1147 config chooses the default boot state.
1148
1149config ARCH_OPTIONAL_KERNEL_RWX
1150 def_bool n
1151
1152config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1153 def_bool n
1154
1155config ARCH_HAS_STRICT_KERNEL_RWX
1156 def_bool n
1157
1158config STRICT_KERNEL_RWX
1159 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
1160 depends on ARCH_HAS_STRICT_KERNEL_RWX
1161 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1162 help
1163 If this is set, kernel text and rodata memory will be made read-only,
1164 and non-text memory will be made non-executable. This provides
1165 protection against certain security exploits (e.g. executing the heap
1166 or modifying text)
1167
1168 These features are considered standard security practice these days.
1169 You should say Y here in almost all cases.
1170
1171config ARCH_HAS_STRICT_MODULE_RWX
1172 def_bool n
1173
1174config STRICT_MODULE_RWX
1175 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
1176 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
1177 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1178 help
1179 If this is set, module text and rodata memory will be made read-only,
1180 and non-text memory will be made non-executable. This provides
1181 protection against certain security exploits (e.g. writing to text)
1182
1183# select if the architecture provides an asm/dma-direct.h header
1184config ARCH_HAS_PHYS_TO_DMA
1185 bool
1186
1187config HAVE_ARCH_COMPILER_H
1188 bool
1189 help
1190 An architecture can select this if it provides an
1191 asm/compiler.h header that should be included after
1192 linux/compiler-*.h in order to override macro definitions that those
1193 headers generally provide.
1194
1195config HAVE_ARCH_PREL32_RELOCATIONS
1196 bool
1197 help
1198 May be selected by an architecture if it supports place-relative
1199 32-bit relocations, both in the toolchain and in the module loader,
1200 in which case relative references can be used in special sections
1201 for PCI fixup, initcalls etc which are only half the size on 64 bit
1202 architectures, and don't require runtime relocation on relocatable
1203 kernels.
1204
1205config ARCH_USE_MEMREMAP_PROT
1206 bool
1207
1208config LOCK_EVENT_COUNTS
1209 bool "Locking event counts collection"
1210 depends on DEBUG_FS
1211 help
1212 Enable light-weight counting of various locking related events
1213 in the system with minimal performance impact. This reduces
1214 the chance of application behavior change because of timing
1215 differences. The counts are reported via debugfs.
1216
1217# Select if the architecture has support for applying RELR relocations.
1218config ARCH_HAS_RELR
1219 bool
1220
1221config RELR
1222 bool "Use RELR relocation packing"
1223 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1224 default y
1225 help
1226 Store the kernel's dynamic relocations in the RELR relocation packing
1227 format. Requires a compatible linker (LLD supports this feature), as
1228 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1229 are compatible).
1230
1231config ARCH_HAS_MEM_ENCRYPT
1232 bool
1233
1234config HAVE_SPARSE_SYSCALL_NR
1235 bool
1236 help
1237 An architecture should select this if its syscall numbering is sparse
1238 to save space. For example, MIPS architecture has a syscall array with
1239 entries at 4000, 5000 and 6000 locations. This option turns on syscall
1240 related optimizations for a given architecture.
1241
1242config ARCH_HAS_VDSO_DATA
1243 bool
1244
1245config HAVE_STATIC_CALL
1246 bool
1247
1248config HAVE_STATIC_CALL_INLINE
1249 bool
1250 depends on HAVE_STATIC_CALL
1251
1252config HAVE_PREEMPT_DYNAMIC
1253 bool
1254 depends on HAVE_STATIC_CALL
1255 depends on GENERIC_ENTRY
1256 help
1257 Select this if the architecture support boot time preempt setting
1258 on top of static calls. It is strongly advised to support inline
1259 static call to avoid any overhead.
1260
1261config ARCH_WANT_LD_ORPHAN_WARN
1262 bool
1263 help
1264 An arch should select this symbol once all linker sections are explicitly
1265 included, size-asserted, or discarded in the linker scripts. This is
1266 important because we never want expected sections to be placed heuristically
1267 by the linker, since the locations of such sections can change between linker
1268 versions.
1269
1270config HAVE_ARCH_PFN_VALID
1271 bool
1272
1273config ARCH_SUPPORTS_DEBUG_PAGEALLOC
1274 bool
1275
1276config ARCH_SPLIT_ARG64
1277 bool
1278 help
1279 If a 32-bit architecture requires 64-bit arguments to be split into
1280 pairs of 32-bit arguments, select this option.
1281
1282config ARCH_HAS_ELFCORE_COMPAT
1283 bool
1284
1285source "kernel/gcov/Kconfig"
1286
1287source "scripts/gcc-plugins/Kconfig"
1288
1289endmenu