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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
12config ARCH_CONFIGURES_CPU_MITIGATIONS
13 bool
14
15if !ARCH_CONFIGURES_CPU_MITIGATIONS
16config CPU_MITIGATIONS
17 def_bool y
18endif
19
20menu "General architecture-dependent options"
21
22config ARCH_HAS_SUBPAGE_FAULTS
23 bool
24 help
25 Select if the architecture can check permissions at sub-page
26 granularity (e.g. arm64 MTE). The probe_user_*() functions
27 must be implemented.
28
29config HOTPLUG_SMT
30 bool
31
32config SMT_NUM_THREADS_DYNAMIC
33 bool
34
35# Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL
36config HOTPLUG_CORE_SYNC
37 bool
38
39# Basic CPU dead synchronization selected by architecture
40config HOTPLUG_CORE_SYNC_DEAD
41 bool
42 select HOTPLUG_CORE_SYNC
43
44# Full CPU synchronization with alive state selected by architecture
45config HOTPLUG_CORE_SYNC_FULL
46 bool
47 select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU
48 select HOTPLUG_CORE_SYNC
49
50config HOTPLUG_SPLIT_STARTUP
51 bool
52 select HOTPLUG_CORE_SYNC_FULL
53
54config HOTPLUG_PARALLEL
55 bool
56 select HOTPLUG_SPLIT_STARTUP
57
58config GENERIC_ENTRY
59 bool
60
61config KPROBES
62 bool "Kprobes"
63 depends on MODULES
64 depends on HAVE_KPROBES
65 select KALLSYMS
66 select TASKS_RCU if PREEMPTION
67 help
68 Kprobes allows you to trap at almost any kernel address and
69 execute a callback function. register_kprobe() establishes
70 a probepoint and specifies the callback. Kprobes is useful
71 for kernel debugging, non-intrusive instrumentation and testing.
72 If in doubt, say "N".
73
74config JUMP_LABEL
75 bool "Optimize very unlikely/likely branches"
76 depends on HAVE_ARCH_JUMP_LABEL
77 select OBJTOOL if HAVE_JUMP_LABEL_HACK
78 help
79 This option enables a transparent branch optimization that
80 makes certain almost-always-true or almost-always-false branch
81 conditions even cheaper to execute within the kernel.
82
83 Certain performance-sensitive kernel code, such as trace points,
84 scheduler functionality, networking code and KVM have such
85 branches and include support for this optimization technique.
86
87 If it is detected that the compiler has support for "asm goto",
88 the kernel will compile such branches with just a nop
89 instruction. When the condition flag is toggled to true, the
90 nop will be converted to a jump instruction to execute the
91 conditional block of instructions.
92
93 This technique lowers overhead and stress on the branch prediction
94 of the processor and generally makes the kernel faster. The update
95 of the condition is slower, but those are always very rare.
96
97 ( On 32-bit x86, the necessary options added to the compiler
98 flags may increase the size of the kernel slightly. )
99
100config STATIC_KEYS_SELFTEST
101 bool "Static key selftest"
102 depends on JUMP_LABEL
103 help
104 Boot time self-test of the branch patching code.
105
106config STATIC_CALL_SELFTEST
107 bool "Static call selftest"
108 depends on HAVE_STATIC_CALL
109 help
110 Boot time self-test of the call patching code.
111
112config OPTPROBES
113 def_bool y
114 depends on KPROBES && HAVE_OPTPROBES
115 select TASKS_RCU if PREEMPTION
116
117config KPROBES_ON_FTRACE
118 def_bool y
119 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
120 depends on DYNAMIC_FTRACE_WITH_REGS
121 help
122 If function tracer is enabled and the arch supports full
123 passing of pt_regs to function tracing, then kprobes can
124 optimize on top of function tracing.
125
126config UPROBES
127 def_bool n
128 depends on ARCH_SUPPORTS_UPROBES
129 help
130 Uprobes is the user-space counterpart to kprobes: they
131 enable instrumentation applications (such as 'perf probe')
132 to establish unintrusive probes in user-space binaries and
133 libraries, by executing handler functions when the probes
134 are hit by user-space applications.
135
136 ( These probes come in the form of single-byte breakpoints,
137 managed by the kernel and kept transparent to the probed
138 application. )
139
140config HAVE_64BIT_ALIGNED_ACCESS
141 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
142 help
143 Some architectures require 64 bit accesses to be 64 bit
144 aligned, which also requires structs containing 64 bit values
145 to be 64 bit aligned too. This includes some 32 bit
146 architectures which can do 64 bit accesses, as well as 64 bit
147 architectures without unaligned access.
148
149 This symbol should be selected by an architecture if 64 bit
150 accesses are required to be 64 bit aligned in this way even
151 though it is not a 64 bit architecture.
152
153 See Documentation/core-api/unaligned-memory-access.rst for
154 more information on the topic of unaligned memory accesses.
155
156config HAVE_EFFICIENT_UNALIGNED_ACCESS
157 bool
158 help
159 Some architectures are unable to perform unaligned accesses
160 without the use of get_unaligned/put_unaligned. Others are
161 unable to perform such accesses efficiently (e.g. trap on
162 unaligned access and require fixing it up in the exception
163 handler.)
164
165 This symbol should be selected by an architecture if it can
166 perform unaligned accesses efficiently to allow different
167 code paths to be selected for these cases. Some network
168 drivers, for example, could opt to not fix up alignment
169 problems with received packets if doing so would not help
170 much.
171
172 See Documentation/core-api/unaligned-memory-access.rst for more
173 information on the topic of unaligned memory accesses.
174
175config ARCH_USE_BUILTIN_BSWAP
176 bool
177 help
178 Modern versions of GCC (since 4.4) have builtin functions
179 for handling byte-swapping. Using these, instead of the old
180 inline assembler that the architecture code provides in the
181 __arch_bswapXX() macros, allows the compiler to see what's
182 happening and offers more opportunity for optimisation. In
183 particular, the compiler will be able to combine the byteswap
184 with a nearby load or store and use load-and-swap or
185 store-and-swap instructions if the architecture has them. It
186 should almost *never* result in code which is worse than the
187 hand-coded assembler in <asm/swab.h>. But just in case it
188 does, the use of the builtins is optional.
189
190 Any architecture with load-and-swap or store-and-swap
191 instructions should set this. And it shouldn't hurt to set it
192 on architectures that don't have such instructions.
193
194config KRETPROBES
195 def_bool y
196 depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK)
197
198config KRETPROBE_ON_RETHOOK
199 def_bool y
200 depends on HAVE_RETHOOK
201 depends on KRETPROBES
202 select RETHOOK
203
204config USER_RETURN_NOTIFIER
205 bool
206 depends on HAVE_USER_RETURN_NOTIFIER
207 help
208 Provide a kernel-internal notification when a cpu is about to
209 switch to user mode.
210
211config HAVE_IOREMAP_PROT
212 bool
213
214config HAVE_KPROBES
215 bool
216
217config HAVE_KRETPROBES
218 bool
219
220config HAVE_OPTPROBES
221 bool
222
223config HAVE_KPROBES_ON_FTRACE
224 bool
225
226config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
227 bool
228 help
229 Since kretprobes modifies return address on the stack, the
230 stacktrace may see the kretprobe trampoline address instead
231 of correct one. If the architecture stacktrace code and
232 unwinder can adjust such entries, select this configuration.
233
234config HAVE_FUNCTION_ERROR_INJECTION
235 bool
236
237config HAVE_NMI
238 bool
239
240config HAVE_FUNCTION_DESCRIPTORS
241 bool
242
243config TRACE_IRQFLAGS_SUPPORT
244 bool
245
246config TRACE_IRQFLAGS_NMI_SUPPORT
247 bool
248
249#
250# An arch should select this if it provides all these things:
251#
252# task_pt_regs() in asm/processor.h or asm/ptrace.h
253# arch_has_single_step() if there is hardware single-step support
254# arch_has_block_step() if there is hardware block-step support
255# asm/syscall.h supplying asm-generic/syscall.h interface
256# linux/regset.h user_regset interfaces
257# CORE_DUMP_USE_REGSET #define'd in linux/elf.h
258# TIF_SYSCALL_TRACE calls ptrace_report_syscall_{entry,exit}
259# TIF_NOTIFY_RESUME calls resume_user_mode_work()
260#
261config HAVE_ARCH_TRACEHOOK
262 bool
263
264config HAVE_DMA_CONTIGUOUS
265 bool
266
267config GENERIC_SMP_IDLE_THREAD
268 bool
269
270config GENERIC_IDLE_POLL_SETUP
271 bool
272
273config ARCH_HAS_FORTIFY_SOURCE
274 bool
275 help
276 An architecture should select this when it can successfully
277 build and run with CONFIG_FORTIFY_SOURCE.
278
279#
280# Select if the arch provides a historic keepinit alias for the retain_initrd
281# command line option
282#
283config ARCH_HAS_KEEPINITRD
284 bool
285
286# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
287config ARCH_HAS_SET_MEMORY
288 bool
289
290# Select if arch has all set_direct_map_invalid/default() functions
291config ARCH_HAS_SET_DIRECT_MAP
292 bool
293
294#
295# Select if the architecture provides the arch_dma_set_uncached symbol to
296# either provide an uncached segment alias for a DMA allocation, or
297# to remap the page tables in place.
298#
299config ARCH_HAS_DMA_SET_UNCACHED
300 bool
301
302#
303# Select if the architectures provides the arch_dma_clear_uncached symbol
304# to undo an in-place page table remap for uncached access.
305#
306config ARCH_HAS_DMA_CLEAR_UNCACHED
307 bool
308
309config ARCH_HAS_CPU_FINALIZE_INIT
310 bool
311
312# The architecture has a per-task state that includes the mm's PASID
313config ARCH_HAS_CPU_PASID
314 bool
315 select IOMMU_MM_DATA
316
317config HAVE_ARCH_THREAD_STRUCT_WHITELIST
318 bool
319 help
320 An architecture should select this to provide hardened usercopy
321 knowledge about what region of the thread_struct should be
322 whitelisted for copying to userspace. Normally this is only the
323 FPU registers. Specifically, arch_thread_struct_whitelist()
324 should be implemented. Without this, the entire thread_struct
325 field in task_struct will be left whitelisted.
326
327# Select if arch wants to size task_struct dynamically via arch_task_struct_size:
328config ARCH_WANTS_DYNAMIC_TASK_STRUCT
329 bool
330
331config ARCH_WANTS_NO_INSTR
332 bool
333 help
334 An architecture should select this if the noinstr macro is being used on
335 functions to denote that the toolchain should avoid instrumenting such
336 functions and is required for correctness.
337
338config ARCH_32BIT_OFF_T
339 bool
340 depends on !64BIT
341 help
342 All new 32-bit architectures should have 64-bit off_t type on
343 userspace side which corresponds to the loff_t kernel type. This
344 is the requirement for modern ABIs. Some existing architectures
345 still support 32-bit off_t. This option is enabled for all such
346 architectures explicitly.
347
348# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat
349config ARCH_32BIT_USTAT_F_TINODE
350 bool
351
352config HAVE_ASM_MODVERSIONS
353 bool
354 help
355 This symbol should be selected by an architecture if it provides
356 <asm/asm-prototypes.h> to support the module versioning for symbols
357 exported from assembly code.
358
359config HAVE_REGS_AND_STACK_ACCESS_API
360 bool
361 help
362 This symbol should be selected by an architecture if it supports
363 the API needed to access registers and stack entries from pt_regs,
364 declared in asm/ptrace.h
365 For example the kprobes-based event tracer needs this API.
366
367config HAVE_RSEQ
368 bool
369 depends on HAVE_REGS_AND_STACK_ACCESS_API
370 help
371 This symbol should be selected by an architecture if it
372 supports an implementation of restartable sequences.
373
374config HAVE_RUST
375 bool
376 help
377 This symbol should be selected by an architecture if it
378 supports Rust.
379
380config HAVE_FUNCTION_ARG_ACCESS_API
381 bool
382 help
383 This symbol should be selected by an architecture if it supports
384 the API needed to access function arguments from pt_regs,
385 declared in asm/ptrace.h
386
387config HAVE_HW_BREAKPOINT
388 bool
389 depends on PERF_EVENTS
390
391config HAVE_MIXED_BREAKPOINTS_REGS
392 bool
393 depends on HAVE_HW_BREAKPOINT
394 help
395 Depending on the arch implementation of hardware breakpoints,
396 some of them have separate registers for data and instruction
397 breakpoints addresses, others have mixed registers to store
398 them but define the access type in a control register.
399 Select this option if your arch implements breakpoints under the
400 latter fashion.
401
402config HAVE_USER_RETURN_NOTIFIER
403 bool
404
405config HAVE_PERF_EVENTS_NMI
406 bool
407 help
408 System hardware can generate an NMI using the perf event
409 subsystem. Also has support for calculating CPU cycle events
410 to determine how many clock cycles in a given period.
411
412config HAVE_HARDLOCKUP_DETECTOR_PERF
413 bool
414 depends on HAVE_PERF_EVENTS_NMI
415 help
416 The arch chooses to use the generic perf-NMI-based hardlockup
417 detector. Must define HAVE_PERF_EVENTS_NMI.
418
419config HAVE_HARDLOCKUP_DETECTOR_ARCH
420 bool
421 help
422 The arch provides its own hardlockup detector implementation instead
423 of the generic ones.
424
425 It uses the same command line parameters, and sysctl interface,
426 as the generic hardlockup detectors.
427
428config HAVE_PERF_REGS
429 bool
430 help
431 Support selective register dumps for perf events. This includes
432 bit-mapping of each registers and a unique architecture id.
433
434config HAVE_PERF_USER_STACK_DUMP
435 bool
436 help
437 Support user stack dumps for perf event samples. This needs
438 access to the user stack pointer which is not unified across
439 architectures.
440
441config HAVE_ARCH_JUMP_LABEL
442 bool
443
444config HAVE_ARCH_JUMP_LABEL_RELATIVE
445 bool
446
447config MMU_GATHER_TABLE_FREE
448 bool
449
450config MMU_GATHER_RCU_TABLE_FREE
451 bool
452 select MMU_GATHER_TABLE_FREE
453
454config MMU_GATHER_PAGE_SIZE
455 bool
456
457config MMU_GATHER_NO_RANGE
458 bool
459 select MMU_GATHER_MERGE_VMAS
460
461config MMU_GATHER_NO_FLUSH_CACHE
462 bool
463
464config MMU_GATHER_MERGE_VMAS
465 bool
466
467config MMU_GATHER_NO_GATHER
468 bool
469 depends on MMU_GATHER_TABLE_FREE
470
471config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
472 bool
473 help
474 Temporary select until all architectures can be converted to have
475 irqs disabled over activate_mm. Architectures that do IPI based TLB
476 shootdowns should enable this.
477
478# Use normal mm refcounting for MMU_LAZY_TLB kernel thread references.
479# MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching
480# to/from kernel threads when the same mm is running on a lot of CPUs (a large
481# multi-threaded application), by reducing contention on the mm refcount.
482#
483# This can be disabled if the architecture ensures no CPUs are using an mm as a
484# "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm
485# or its kernel page tables). This could be arranged by arch_exit_mmap(), or
486# final exit(2) TLB flush, for example.
487#
488# To implement this, an arch *must*:
489# Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating
490# the lazy tlb reference of a kthread's ->active_mm (non-arch code has been
491# converted already).
492config MMU_LAZY_TLB_REFCOUNT
493 def_bool y
494 depends on !MMU_LAZY_TLB_SHOOTDOWN
495
496# This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an
497# mm as a lazy tlb beyond its last reference count, by shooting down these
498# users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may
499# be using the mm as a lazy tlb, so that they may switch themselves to using
500# init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs
501# may be using mm as a lazy tlb mm.
502#
503# To implement this, an arch *must*:
504# - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains
505# at least all possible CPUs in which the mm is lazy.
506# - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above).
507config MMU_LAZY_TLB_SHOOTDOWN
508 bool
509
510config ARCH_HAVE_NMI_SAFE_CMPXCHG
511 bool
512
513config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
514 bool
515
516config HAVE_ALIGNED_STRUCT_PAGE
517 bool
518 help
519 This makes sure that struct pages are double word aligned and that
520 e.g. the SLUB allocator can perform double word atomic operations
521 on a struct page for better performance. However selecting this
522 might increase the size of a struct page by a word.
523
524config HAVE_CMPXCHG_LOCAL
525 bool
526
527config HAVE_CMPXCHG_DOUBLE
528 bool
529
530config ARCH_WEAK_RELEASE_ACQUIRE
531 bool
532
533config ARCH_WANT_IPC_PARSE_VERSION
534 bool
535
536config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
537 bool
538
539config ARCH_WANT_OLD_COMPAT_IPC
540 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
541 bool
542
543config HAVE_ARCH_SECCOMP
544 bool
545 help
546 An arch should select this symbol to support seccomp mode 1 (the fixed
547 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
548 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
549 - __NR_seccomp_read_32
550 - __NR_seccomp_write_32
551 - __NR_seccomp_exit_32
552 - __NR_seccomp_sigreturn_32
553
554config HAVE_ARCH_SECCOMP_FILTER
555 bool
556 select HAVE_ARCH_SECCOMP
557 help
558 An arch should select this symbol if it provides all of these things:
559 - all the requirements for HAVE_ARCH_SECCOMP
560 - syscall_get_arch()
561 - syscall_get_arguments()
562 - syscall_rollback()
563 - syscall_set_return_value()
564 - SIGSYS siginfo_t support
565 - secure_computing is called from a ptrace_event()-safe context
566 - secure_computing return value is checked and a return value of -1
567 results in the system call being skipped immediately.
568 - seccomp syscall wired up
569 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE,
570 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If
571 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too.
572
573config SECCOMP
574 prompt "Enable seccomp to safely execute untrusted bytecode"
575 def_bool y
576 depends on HAVE_ARCH_SECCOMP
577 help
578 This kernel feature is useful for number crunching applications
579 that may need to handle untrusted bytecode during their
580 execution. By using pipes or other transports made available
581 to the process as file descriptors supporting the read/write
582 syscalls, it's possible to isolate those applications in their
583 own address space using seccomp. Once seccomp is enabled via
584 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
585 disabled and the task is only allowed to execute a few safe
586 syscalls defined by each seccomp mode.
587
588 If unsure, say Y.
589
590config SECCOMP_FILTER
591 def_bool y
592 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
593 help
594 Enable tasks to build secure computing environments defined
595 in terms of Berkeley Packet Filter programs which implement
596 task-defined system call filtering polices.
597
598 See Documentation/userspace-api/seccomp_filter.rst for details.
599
600config SECCOMP_CACHE_DEBUG
601 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache"
602 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR
603 depends on PROC_FS
604 help
605 This enables the /proc/pid/seccomp_cache interface to monitor
606 seccomp cache data. The file format is subject to change. Reading
607 the file requires CAP_SYS_ADMIN.
608
609 This option is for debugging only. Enabling presents the risk that
610 an adversary may be able to infer the seccomp filter logic.
611
612 If unsure, say N.
613
614config HAVE_ARCH_STACKLEAK
615 bool
616 help
617 An architecture should select this if it has the code which
618 fills the used part of the kernel stack with the STACKLEAK_POISON
619 value before returning from system calls.
620
621config HAVE_STACKPROTECTOR
622 bool
623 help
624 An arch should select this symbol if:
625 - it has implemented a stack canary (e.g. __stack_chk_guard)
626
627config STACKPROTECTOR
628 bool "Stack Protector buffer overflow detection"
629 depends on HAVE_STACKPROTECTOR
630 depends on $(cc-option,-fstack-protector)
631 default y
632 help
633 This option turns on the "stack-protector" GCC feature. This
634 feature puts, at the beginning of functions, a canary value on
635 the stack just before the return address, and validates
636 the value just before actually returning. Stack based buffer
637 overflows (that need to overwrite this return address) now also
638 overwrite the canary, which gets detected and the attack is then
639 neutralized via a kernel panic.
640
641 Functions will have the stack-protector canary logic added if they
642 have an 8-byte or larger character array on the stack.
643
644 This feature requires gcc version 4.2 or above, or a distribution
645 gcc with the feature backported ("-fstack-protector").
646
647 On an x86 "defconfig" build, this feature adds canary checks to
648 about 3% of all kernel functions, which increases kernel code size
649 by about 0.3%.
650
651config STACKPROTECTOR_STRONG
652 bool "Strong Stack Protector"
653 depends on STACKPROTECTOR
654 depends on $(cc-option,-fstack-protector-strong)
655 default y
656 help
657 Functions will have the stack-protector canary logic added in any
658 of the following conditions:
659
660 - local variable's address used as part of the right hand side of an
661 assignment or function argument
662 - local variable is an array (or union containing an array),
663 regardless of array type or length
664 - uses register local variables
665
666 This feature requires gcc version 4.9 or above, or a distribution
667 gcc with the feature backported ("-fstack-protector-strong").
668
669 On an x86 "defconfig" build, this feature adds canary checks to
670 about 20% of all kernel functions, which increases the kernel code
671 size by about 2%.
672
673config ARCH_SUPPORTS_SHADOW_CALL_STACK
674 bool
675 help
676 An architecture should select this if it supports the compiler's
677 Shadow Call Stack and implements runtime support for shadow stack
678 switching.
679
680config SHADOW_CALL_STACK
681 bool "Shadow Call Stack"
682 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
683 depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
684 depends on MMU
685 help
686 This option enables the compiler's Shadow Call Stack, which
687 uses a shadow stack to protect function return addresses from
688 being overwritten by an attacker. More information can be found
689 in the compiler's documentation:
690
691 - Clang: https://clang.llvm.org/docs/ShadowCallStack.html
692 - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options
693
694 Note that security guarantees in the kernel differ from the
695 ones documented for user space. The kernel must store addresses
696 of shadow stacks in memory, which means an attacker capable of
697 reading and writing arbitrary memory may be able to locate them
698 and hijack control flow by modifying the stacks.
699
700config DYNAMIC_SCS
701 bool
702 help
703 Set by the arch code if it relies on code patching to insert the
704 shadow call stack push and pop instructions rather than on the
705 compiler.
706
707config LTO
708 bool
709 help
710 Selected if the kernel will be built using the compiler's LTO feature.
711
712config LTO_CLANG
713 bool
714 select LTO
715 help
716 Selected if the kernel will be built using Clang's LTO feature.
717
718config ARCH_SUPPORTS_LTO_CLANG
719 bool
720 help
721 An architecture should select this option if it supports:
722 - compiling with Clang,
723 - compiling inline assembly with Clang's integrated assembler,
724 - and linking with LLD.
725
726config ARCH_SUPPORTS_LTO_CLANG_THIN
727 bool
728 help
729 An architecture should select this option if it can support Clang's
730 ThinLTO mode.
731
732config HAS_LTO_CLANG
733 def_bool y
734 depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM
735 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
736 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
737 depends on ARCH_SUPPORTS_LTO_CLANG
738 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT
739 # https://github.com/ClangBuiltLinux/linux/issues/1721
740 depends on (!KASAN || KASAN_HW_TAGS || CLANG_VERSION >= 170000) || !DEBUG_INFO
741 depends on (!KCOV || CLANG_VERSION >= 170000) || !DEBUG_INFO
742 depends on !GCOV_KERNEL
743 help
744 The compiler and Kconfig options support building with Clang's
745 LTO.
746
747choice
748 prompt "Link Time Optimization (LTO)"
749 default LTO_NONE
750 help
751 This option enables Link Time Optimization (LTO), which allows the
752 compiler to optimize binaries globally.
753
754 If unsure, select LTO_NONE. Note that LTO is very resource-intensive
755 so it's disabled by default.
756
757config LTO_NONE
758 bool "None"
759 help
760 Build the kernel normally, without Link Time Optimization (LTO).
761
762config LTO_CLANG_FULL
763 bool "Clang Full LTO (EXPERIMENTAL)"
764 depends on HAS_LTO_CLANG
765 depends on !COMPILE_TEST
766 select LTO_CLANG
767 help
768 This option enables Clang's full Link Time Optimization (LTO), which
769 allows the compiler to optimize the kernel globally. If you enable
770 this option, the compiler generates LLVM bitcode instead of ELF
771 object files, and the actual compilation from bitcode happens at
772 the LTO link step, which may take several minutes depending on the
773 kernel configuration. More information can be found from LLVM's
774 documentation:
775
776 https://llvm.org/docs/LinkTimeOptimization.html
777
778 During link time, this option can use a large amount of RAM, and
779 may take much longer than the ThinLTO option.
780
781config LTO_CLANG_THIN
782 bool "Clang ThinLTO (EXPERIMENTAL)"
783 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN
784 select LTO_CLANG
785 help
786 This option enables Clang's ThinLTO, which allows for parallel
787 optimization and faster incremental compiles compared to the
788 CONFIG_LTO_CLANG_FULL option. More information can be found
789 from Clang's documentation:
790
791 https://clang.llvm.org/docs/ThinLTO.html
792
793 If unsure, say Y.
794endchoice
795
796config ARCH_SUPPORTS_CFI_CLANG
797 bool
798 help
799 An architecture should select this option if it can support Clang's
800 Control-Flow Integrity (CFI) checking.
801
802config ARCH_USES_CFI_TRAPS
803 bool
804
805config CFI_CLANG
806 bool "Use Clang's Control Flow Integrity (CFI)"
807 depends on ARCH_SUPPORTS_CFI_CLANG
808 depends on $(cc-option,-fsanitize=kcfi)
809 help
810 This option enables Clang's forward-edge Control Flow Integrity
811 (CFI) checking, where the compiler injects a runtime check to each
812 indirect function call to ensure the target is a valid function with
813 the correct static type. This restricts possible call targets and
814 makes it more difficult for an attacker to exploit bugs that allow
815 the modification of stored function pointers. More information can be
816 found from Clang's documentation:
817
818 https://clang.llvm.org/docs/ControlFlowIntegrity.html
819
820config CFI_PERMISSIVE
821 bool "Use CFI in permissive mode"
822 depends on CFI_CLANG
823 help
824 When selected, Control Flow Integrity (CFI) violations result in a
825 warning instead of a kernel panic. This option should only be used
826 for finding indirect call type mismatches during development.
827
828 If unsure, say N.
829
830config HAVE_ARCH_WITHIN_STACK_FRAMES
831 bool
832 help
833 An architecture should select this if it can walk the kernel stack
834 frames to determine if an object is part of either the arguments
835 or local variables (i.e. that it excludes saved return addresses,
836 and similar) by implementing an inline arch_within_stack_frames(),
837 which is used by CONFIG_HARDENED_USERCOPY.
838
839config HAVE_CONTEXT_TRACKING_USER
840 bool
841 help
842 Provide kernel/user boundaries probes necessary for subsystems
843 that need it, such as userspace RCU extended quiescent state.
844 Syscalls need to be wrapped inside user_exit()-user_enter(), either
845 optimized behind static key or through the slow path using TIF_NOHZ
846 flag. Exceptions handlers must be wrapped as well. Irqs are already
847 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal
848 handling on irq exit still need to be protected.
849
850config HAVE_CONTEXT_TRACKING_USER_OFFSTACK
851 bool
852 help
853 Architecture neither relies on exception_enter()/exception_exit()
854 nor on schedule_user(). Also preempt_schedule_notrace() and
855 preempt_schedule_irq() can't be called in a preemptible section
856 while context tracking is CONTEXT_USER. This feature reflects a sane
857 entry implementation where the following requirements are met on
858 critical entry code, ie: before user_exit() or after user_enter():
859
860 - Critical entry code isn't preemptible (or better yet:
861 not interruptible).
862 - No use of RCU read side critical sections, unless ct_nmi_enter()
863 got called.
864 - No use of instrumentation, unless instrumentation_begin() got
865 called.
866
867config HAVE_TIF_NOHZ
868 bool
869 help
870 Arch relies on TIF_NOHZ and syscall slow path to implement context
871 tracking calls to user_enter()/user_exit().
872
873config HAVE_VIRT_CPU_ACCOUNTING
874 bool
875
876config HAVE_VIRT_CPU_ACCOUNTING_IDLE
877 bool
878 help
879 Architecture has its own way to account idle CPU time and therefore
880 doesn't implement vtime_account_idle().
881
882config ARCH_HAS_SCALED_CPUTIME
883 bool
884
885config HAVE_VIRT_CPU_ACCOUNTING_GEN
886 bool
887 default y if 64BIT
888 help
889 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
890 Before enabling this option, arch code must be audited
891 to ensure there are no races in concurrent read/write of
892 cputime_t. For example, reading/writing 64-bit cputime_t on
893 some 32-bit arches may require multiple accesses, so proper
894 locking is needed to protect against concurrent accesses.
895
896config HAVE_IRQ_TIME_ACCOUNTING
897 bool
898 help
899 Archs need to ensure they use a high enough resolution clock to
900 support irq time accounting and then call enable_sched_clock_irqtime().
901
902config HAVE_MOVE_PUD
903 bool
904 help
905 Architectures that select this are able to move page tables at the
906 PUD level. If there are only 3 page table levels, the move effectively
907 happens at the PGD level.
908
909config HAVE_MOVE_PMD
910 bool
911 help
912 Archs that select this are able to move page tables at the PMD level.
913
914config HAVE_ARCH_TRANSPARENT_HUGEPAGE
915 bool
916
917config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
918 bool
919
920config HAVE_ARCH_HUGE_VMAP
921 bool
922
923#
924# Archs that select this would be capable of PMD-sized vmaps (i.e.,
925# arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag
926# must be used to enable allocations to use hugepages.
927#
928config HAVE_ARCH_HUGE_VMALLOC
929 depends on HAVE_ARCH_HUGE_VMAP
930 bool
931
932config ARCH_WANT_HUGE_PMD_SHARE
933 bool
934
935# Archs that want to use pmd_mkwrite on kernel memory need it defined even
936# if there are no userspace memory management features that use it
937config ARCH_WANT_KERNEL_PMD_MKWRITE
938 bool
939
940config ARCH_WANT_PMD_MKWRITE
941 def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE
942
943config HAVE_ARCH_SOFT_DIRTY
944 bool
945
946config HAVE_MOD_ARCH_SPECIFIC
947 bool
948 help
949 The arch uses struct mod_arch_specific to store data. Many arches
950 just need a simple module loader without arch specific data - those
951 should not enable this.
952
953config MODULES_USE_ELF_RELA
954 bool
955 help
956 Modules only use ELF RELA relocations. Modules with ELF REL
957 relocations will give an error.
958
959config MODULES_USE_ELF_REL
960 bool
961 help
962 Modules only use ELF REL relocations. Modules with ELF RELA
963 relocations will give an error.
964
965config ARCH_WANTS_MODULES_DATA_IN_VMALLOC
966 bool
967 help
968 For architectures like powerpc/32 which have constraints on module
969 allocation and need to allocate module data outside of module area.
970
971config HAVE_IRQ_EXIT_ON_IRQ_STACK
972 bool
973 help
974 Architecture doesn't only execute the irq handler on the irq stack
975 but also irq_exit(). This way we can process softirqs on this irq
976 stack instead of switching to a new one when we call __do_softirq()
977 in the end of an hardirq.
978 This spares a stack switch and improves cache usage on softirq
979 processing.
980
981config HAVE_SOFTIRQ_ON_OWN_STACK
982 bool
983 help
984 Architecture provides a function to run __do_softirq() on a
985 separate stack.
986
987config SOFTIRQ_ON_OWN_STACK
988 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT
989
990config ALTERNATE_USER_ADDRESS_SPACE
991 bool
992 help
993 Architectures set this when the CPU uses separate address
994 spaces for kernel and user space pointers. In this case, the
995 access_ok() check on a __user pointer is skipped.
996
997config PGTABLE_LEVELS
998 int
999 default 2
1000
1001config ARCH_HAS_ELF_RANDOMIZE
1002 bool
1003 help
1004 An architecture supports choosing randomized locations for
1005 stack, mmap, brk, and ET_DYN. Defined functions:
1006 - arch_mmap_rnd()
1007 - arch_randomize_brk()
1008
1009config HAVE_ARCH_MMAP_RND_BITS
1010 bool
1011 help
1012 An arch should select this symbol if it supports setting a variable
1013 number of bits for use in establishing the base address for mmap
1014 allocations, has MMU enabled and provides values for both:
1015 - ARCH_MMAP_RND_BITS_MIN
1016 - ARCH_MMAP_RND_BITS_MAX
1017
1018config HAVE_EXIT_THREAD
1019 bool
1020 help
1021 An architecture implements exit_thread.
1022
1023config ARCH_MMAP_RND_BITS_MIN
1024 int
1025
1026config ARCH_MMAP_RND_BITS_MAX
1027 int
1028
1029config ARCH_MMAP_RND_BITS_DEFAULT
1030 int
1031
1032config ARCH_MMAP_RND_BITS
1033 int "Number of bits to use for ASLR of mmap base address" if EXPERT
1034 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
1035 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
1036 default ARCH_MMAP_RND_BITS_MIN
1037 depends on HAVE_ARCH_MMAP_RND_BITS
1038 help
1039 This value can be used to select the number of bits to use to
1040 determine the random offset to the base address of vma regions
1041 resulting from mmap allocations. This value will be bounded
1042 by the architecture's minimum and maximum supported values.
1043
1044 This value can be changed after boot using the
1045 /proc/sys/vm/mmap_rnd_bits tunable
1046
1047config HAVE_ARCH_MMAP_RND_COMPAT_BITS
1048 bool
1049 help
1050 An arch should select this symbol if it supports running applications
1051 in compatibility mode, supports setting a variable number of bits for
1052 use in establishing the base address for mmap allocations, has MMU
1053 enabled and provides values for both:
1054 - ARCH_MMAP_RND_COMPAT_BITS_MIN
1055 - ARCH_MMAP_RND_COMPAT_BITS_MAX
1056
1057config ARCH_MMAP_RND_COMPAT_BITS_MIN
1058 int
1059
1060config ARCH_MMAP_RND_COMPAT_BITS_MAX
1061 int
1062
1063config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
1064 int
1065
1066config ARCH_MMAP_RND_COMPAT_BITS
1067 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
1068 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
1069 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
1070 default ARCH_MMAP_RND_COMPAT_BITS_MIN
1071 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
1072 help
1073 This value can be used to select the number of bits to use to
1074 determine the random offset to the base address of vma regions
1075 resulting from mmap allocations for compatible applications This
1076 value will be bounded by the architecture's minimum and maximum
1077 supported values.
1078
1079 This value can be changed after boot using the
1080 /proc/sys/vm/mmap_rnd_compat_bits tunable
1081
1082config HAVE_ARCH_COMPAT_MMAP_BASES
1083 bool
1084 help
1085 This allows 64bit applications to invoke 32-bit mmap() syscall
1086 and vice-versa 32-bit applications to call 64-bit mmap().
1087 Required for applications doing different bitness syscalls.
1088
1089config HAVE_PAGE_SIZE_4KB
1090 bool
1091
1092config HAVE_PAGE_SIZE_8KB
1093 bool
1094
1095config HAVE_PAGE_SIZE_16KB
1096 bool
1097
1098config HAVE_PAGE_SIZE_32KB
1099 bool
1100
1101config HAVE_PAGE_SIZE_64KB
1102 bool
1103
1104config HAVE_PAGE_SIZE_256KB
1105 bool
1106
1107choice
1108 prompt "MMU page size"
1109
1110config PAGE_SIZE_4KB
1111 bool "4KiB pages"
1112 depends on HAVE_PAGE_SIZE_4KB
1113 help
1114 This option select the standard 4KiB Linux page size and the only
1115 available option on many architectures. Using 4KiB page size will
1116 minimize memory consumption and is therefore recommended for low
1117 memory systems.
1118 Some software that is written for x86 systems makes incorrect
1119 assumptions about the page size and only runs on 4KiB pages.
1120
1121config PAGE_SIZE_8KB
1122 bool "8KiB pages"
1123 depends on HAVE_PAGE_SIZE_8KB
1124 help
1125 This option is the only supported page size on a few older
1126 processors, and can be slightly faster than 4KiB pages.
1127
1128config PAGE_SIZE_16KB
1129 bool "16KiB pages"
1130 depends on HAVE_PAGE_SIZE_16KB
1131 help
1132 This option is usually a good compromise between memory
1133 consumption and performance for typical desktop and server
1134 workloads, often saving a level of page table lookups compared
1135 to 4KB pages as well as reducing TLB pressure and overhead of
1136 per-page operations in the kernel at the expense of a larger
1137 page cache.
1138
1139config PAGE_SIZE_32KB
1140 bool "32KiB pages"
1141 depends on HAVE_PAGE_SIZE_32KB
1142 help
1143 Using 32KiB page size will result in slightly higher performance
1144 kernel at the price of higher memory consumption compared to
1145 16KiB pages. This option is available only on cnMIPS cores.
1146 Note that you will need a suitable Linux distribution to
1147 support this.
1148
1149config PAGE_SIZE_64KB
1150 bool "64KiB pages"
1151 depends on HAVE_PAGE_SIZE_64KB
1152 help
1153 Using 64KiB page size will result in slightly higher performance
1154 kernel at the price of much higher memory consumption compared to
1155 4KiB or 16KiB pages.
1156 This is not suitable for general-purpose workloads but the
1157 better performance may be worth the cost for certain types of
1158 supercomputing or database applications that work mostly with
1159 large in-memory data rather than small files.
1160
1161config PAGE_SIZE_256KB
1162 bool "256KiB pages"
1163 depends on HAVE_PAGE_SIZE_256KB
1164 help
1165 256KiB pages have little practical value due to their extreme
1166 memory usage. The kernel will only be able to run applications
1167 that have been compiled with '-zmax-page-size' set to 256KiB
1168 (the default is 64KiB or 4KiB on most architectures).
1169
1170endchoice
1171
1172config PAGE_SIZE_LESS_THAN_64KB
1173 def_bool y
1174 depends on !PAGE_SIZE_64KB
1175 depends on PAGE_SIZE_LESS_THAN_256KB
1176
1177config PAGE_SIZE_LESS_THAN_256KB
1178 def_bool y
1179 depends on !PAGE_SIZE_256KB
1180
1181config PAGE_SHIFT
1182 int
1183 default 12 if PAGE_SIZE_4KB
1184 default 13 if PAGE_SIZE_8KB
1185 default 14 if PAGE_SIZE_16KB
1186 default 15 if PAGE_SIZE_32KB
1187 default 16 if PAGE_SIZE_64KB
1188 default 18 if PAGE_SIZE_256KB
1189
1190# This allows to use a set of generic functions to determine mmap base
1191# address by giving priority to top-down scheme only if the process
1192# is not in legacy mode (compat task, unlimited stack size or
1193# sysctl_legacy_va_layout).
1194# Architecture that selects this option can provide its own version of:
1195# - STACK_RND_MASK
1196config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
1197 bool
1198 depends on MMU
1199 select ARCH_HAS_ELF_RANDOMIZE
1200
1201config HAVE_OBJTOOL
1202 bool
1203
1204config HAVE_JUMP_LABEL_HACK
1205 bool
1206
1207config HAVE_NOINSTR_HACK
1208 bool
1209
1210config HAVE_NOINSTR_VALIDATION
1211 bool
1212
1213config HAVE_UACCESS_VALIDATION
1214 bool
1215 select OBJTOOL
1216
1217config HAVE_STACK_VALIDATION
1218 bool
1219 help
1220 Architecture supports objtool compile-time frame pointer rule
1221 validation.
1222
1223config HAVE_RELIABLE_STACKTRACE
1224 bool
1225 help
1226 Architecture has either save_stack_trace_tsk_reliable() or
1227 arch_stack_walk_reliable() function which only returns a stack trace
1228 if it can guarantee the trace is reliable.
1229
1230config HAVE_ARCH_HASH
1231 bool
1232 default n
1233 help
1234 If this is set, the architecture provides an <asm/hash.h>
1235 file which provides platform-specific implementations of some
1236 functions in <linux/hash.h> or fs/namei.c.
1237
1238config HAVE_ARCH_NVRAM_OPS
1239 bool
1240
1241config ISA_BUS_API
1242 def_bool ISA
1243
1244#
1245# ABI hall of shame
1246#
1247config CLONE_BACKWARDS
1248 bool
1249 help
1250 Architecture has tls passed as the 4th argument of clone(2),
1251 not the 5th one.
1252
1253config CLONE_BACKWARDS2
1254 bool
1255 help
1256 Architecture has the first two arguments of clone(2) swapped.
1257
1258config CLONE_BACKWARDS3
1259 bool
1260 help
1261 Architecture has tls passed as the 3rd argument of clone(2),
1262 not the 5th one.
1263
1264config ODD_RT_SIGACTION
1265 bool
1266 help
1267 Architecture has unusual rt_sigaction(2) arguments
1268
1269config OLD_SIGSUSPEND
1270 bool
1271 help
1272 Architecture has old sigsuspend(2) syscall, of one-argument variety
1273
1274config OLD_SIGSUSPEND3
1275 bool
1276 help
1277 Even weirder antique ABI - three-argument sigsuspend(2)
1278
1279config OLD_SIGACTION
1280 bool
1281 help
1282 Architecture has old sigaction(2) syscall. Nope, not the same
1283 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
1284 but fairly different variant of sigaction(2), thanks to OSF/1
1285 compatibility...
1286
1287config COMPAT_OLD_SIGACTION
1288 bool
1289
1290config COMPAT_32BIT_TIME
1291 bool "Provide system calls for 32-bit time_t"
1292 default !64BIT || COMPAT
1293 help
1294 This enables 32 bit time_t support in addition to 64 bit time_t support.
1295 This is relevant on all 32-bit architectures, and 64-bit architectures
1296 as part of compat syscall handling.
1297
1298config ARCH_NO_PREEMPT
1299 bool
1300
1301config ARCH_SUPPORTS_RT
1302 bool
1303
1304config CPU_NO_EFFICIENT_FFS
1305 def_bool n
1306
1307config HAVE_ARCH_VMAP_STACK
1308 def_bool n
1309 help
1310 An arch should select this symbol if it can support kernel stacks
1311 in vmalloc space. This means:
1312
1313 - vmalloc space must be large enough to hold many kernel stacks.
1314 This may rule out many 32-bit architectures.
1315
1316 - Stacks in vmalloc space need to work reliably. For example, if
1317 vmap page tables are created on demand, either this mechanism
1318 needs to work while the stack points to a virtual address with
1319 unpopulated page tables or arch code (switch_to() and switch_mm(),
1320 most likely) needs to ensure that the stack's page table entries
1321 are populated before running on a possibly unpopulated stack.
1322
1323 - If the stack overflows into a guard page, something reasonable
1324 should happen. The definition of "reasonable" is flexible, but
1325 instantly rebooting without logging anything would be unfriendly.
1326
1327config VMAP_STACK
1328 default y
1329 bool "Use a virtually-mapped stack"
1330 depends on HAVE_ARCH_VMAP_STACK
1331 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC
1332 help
1333 Enable this if you want the use virtually-mapped kernel stacks
1334 with guard pages. This causes kernel stack overflows to be
1335 caught immediately rather than causing difficult-to-diagnose
1336 corruption.
1337
1338 To use this with software KASAN modes, the architecture must support
1339 backing virtual mappings with real shadow memory, and KASAN_VMALLOC
1340 must be enabled.
1341
1342config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1343 def_bool n
1344 help
1345 An arch should select this symbol if it can support kernel stack
1346 offset randomization with calls to add_random_kstack_offset()
1347 during syscall entry and choose_random_kstack_offset() during
1348 syscall exit. Careful removal of -fstack-protector-strong and
1349 -fstack-protector should also be applied to the entry code and
1350 closely examined, as the artificial stack bump looks like an array
1351 to the compiler, so it will attempt to add canary checks regardless
1352 of the static branch state.
1353
1354config RANDOMIZE_KSTACK_OFFSET
1355 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT
1356 default y
1357 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1358 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000
1359 help
1360 The kernel stack offset can be randomized (after pt_regs) by
1361 roughly 5 bits of entropy, frustrating memory corruption
1362 attacks that depend on stack address determinism or
1363 cross-syscall address exposures.
1364
1365 The feature is controlled via the "randomize_kstack_offset=on/off"
1366 kernel boot param, and if turned off has zero overhead due to its use
1367 of static branches (see JUMP_LABEL).
1368
1369 If unsure, say Y.
1370
1371config RANDOMIZE_KSTACK_OFFSET_DEFAULT
1372 bool "Default state of kernel stack offset randomization"
1373 depends on RANDOMIZE_KSTACK_OFFSET
1374 help
1375 Kernel stack offset randomization is controlled by kernel boot param
1376 "randomize_kstack_offset=on/off", and this config chooses the default
1377 boot state.
1378
1379config ARCH_OPTIONAL_KERNEL_RWX
1380 def_bool n
1381
1382config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1383 def_bool n
1384
1385config ARCH_HAS_STRICT_KERNEL_RWX
1386 def_bool n
1387
1388config STRICT_KERNEL_RWX
1389 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
1390 depends on ARCH_HAS_STRICT_KERNEL_RWX
1391 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1392 help
1393 If this is set, kernel text and rodata memory will be made read-only,
1394 and non-text memory will be made non-executable. This provides
1395 protection against certain security exploits (e.g. executing the heap
1396 or modifying text)
1397
1398 These features are considered standard security practice these days.
1399 You should say Y here in almost all cases.
1400
1401config ARCH_HAS_STRICT_MODULE_RWX
1402 def_bool n
1403
1404config STRICT_MODULE_RWX
1405 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
1406 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
1407 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1408 help
1409 If this is set, module text and rodata memory will be made read-only,
1410 and non-text memory will be made non-executable. This provides
1411 protection against certain security exploits (e.g. writing to text)
1412
1413# select if the architecture provides an asm/dma-direct.h header
1414config ARCH_HAS_PHYS_TO_DMA
1415 bool
1416
1417config HAVE_ARCH_COMPILER_H
1418 bool
1419 help
1420 An architecture can select this if it provides an
1421 asm/compiler.h header that should be included after
1422 linux/compiler-*.h in order to override macro definitions that those
1423 headers generally provide.
1424
1425config HAVE_ARCH_PREL32_RELOCATIONS
1426 bool
1427 help
1428 May be selected by an architecture if it supports place-relative
1429 32-bit relocations, both in the toolchain and in the module loader,
1430 in which case relative references can be used in special sections
1431 for PCI fixup, initcalls etc which are only half the size on 64 bit
1432 architectures, and don't require runtime relocation on relocatable
1433 kernels.
1434
1435config ARCH_USE_MEMREMAP_PROT
1436 bool
1437
1438config LOCK_EVENT_COUNTS
1439 bool "Locking event counts collection"
1440 depends on DEBUG_FS
1441 help
1442 Enable light-weight counting of various locking related events
1443 in the system with minimal performance impact. This reduces
1444 the chance of application behavior change because of timing
1445 differences. The counts are reported via debugfs.
1446
1447# Select if the architecture has support for applying RELR relocations.
1448config ARCH_HAS_RELR
1449 bool
1450
1451config RELR
1452 bool "Use RELR relocation packing"
1453 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1454 default y
1455 help
1456 Store the kernel's dynamic relocations in the RELR relocation packing
1457 format. Requires a compatible linker (LLD supports this feature), as
1458 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1459 are compatible).
1460
1461config ARCH_HAS_MEM_ENCRYPT
1462 bool
1463
1464config ARCH_HAS_CC_PLATFORM
1465 bool
1466
1467config HAVE_SPARSE_SYSCALL_NR
1468 bool
1469 help
1470 An architecture should select this if its syscall numbering is sparse
1471 to save space. For example, MIPS architecture has a syscall array with
1472 entries at 4000, 5000 and 6000 locations. This option turns on syscall
1473 related optimizations for a given architecture.
1474
1475config ARCH_HAS_VDSO_DATA
1476 bool
1477
1478config HAVE_STATIC_CALL
1479 bool
1480
1481config HAVE_STATIC_CALL_INLINE
1482 bool
1483 depends on HAVE_STATIC_CALL
1484 select OBJTOOL
1485
1486config HAVE_PREEMPT_DYNAMIC
1487 bool
1488
1489config HAVE_PREEMPT_DYNAMIC_CALL
1490 bool
1491 depends on HAVE_STATIC_CALL
1492 select HAVE_PREEMPT_DYNAMIC
1493 help
1494 An architecture should select this if it can handle the preemption
1495 model being selected at boot time using static calls.
1496
1497 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a
1498 preemption function will be patched directly.
1499
1500 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any
1501 call to a preemption function will go through a trampoline, and the
1502 trampoline will be patched.
1503
1504 It is strongly advised to support inline static call to avoid any
1505 overhead.
1506
1507config HAVE_PREEMPT_DYNAMIC_KEY
1508 bool
1509 depends on HAVE_ARCH_JUMP_LABEL
1510 select HAVE_PREEMPT_DYNAMIC
1511 help
1512 An architecture should select this if it can handle the preemption
1513 model being selected at boot time using static keys.
1514
1515 Each preemption function will be given an early return based on a
1516 static key. This should have slightly lower overhead than non-inline
1517 static calls, as this effectively inlines each trampoline into the
1518 start of its callee. This may avoid redundant work, and may
1519 integrate better with CFI schemes.
1520
1521 This will have greater overhead than using inline static calls as
1522 the call to the preemption function cannot be entirely elided.
1523
1524config ARCH_WANT_LD_ORPHAN_WARN
1525 bool
1526 help
1527 An arch should select this symbol once all linker sections are explicitly
1528 included, size-asserted, or discarded in the linker scripts. This is
1529 important because we never want expected sections to be placed heuristically
1530 by the linker, since the locations of such sections can change between linker
1531 versions.
1532
1533config HAVE_ARCH_PFN_VALID
1534 bool
1535
1536config ARCH_SUPPORTS_DEBUG_PAGEALLOC
1537 bool
1538
1539config ARCH_SUPPORTS_PAGE_TABLE_CHECK
1540 bool
1541
1542config ARCH_SPLIT_ARG64
1543 bool
1544 help
1545 If a 32-bit architecture requires 64-bit arguments to be split into
1546 pairs of 32-bit arguments, select this option.
1547
1548config ARCH_HAS_ELFCORE_COMPAT
1549 bool
1550
1551config ARCH_HAS_PARANOID_L1D_FLUSH
1552 bool
1553
1554config ARCH_HAVE_TRACE_MMIO_ACCESS
1555 bool
1556
1557config DYNAMIC_SIGFRAME
1558 bool
1559
1560# Select, if arch has a named attribute group bound to NUMA device nodes.
1561config HAVE_ARCH_NODE_DEV_GROUP
1562 bool
1563
1564config ARCH_HAS_HW_PTE_YOUNG
1565 bool
1566 help
1567 Architectures that select this option are capable of setting the
1568 accessed bit in PTE entries when using them as part of linear address
1569 translations. Architectures that require runtime check should select
1570 this option and override arch_has_hw_pte_young().
1571
1572config ARCH_HAS_NONLEAF_PMD_YOUNG
1573 bool
1574 help
1575 Architectures that select this option are capable of setting the
1576 accessed bit in non-leaf PMD entries when using them as part of linear
1577 address translations. Page table walkers that clear the accessed bit
1578 may use this capability to reduce their search space.
1579
1580source "kernel/gcov/Kconfig"
1581
1582source "scripts/gcc-plugins/Kconfig"
1583
1584config FUNCTION_ALIGNMENT_4B
1585 bool
1586
1587config FUNCTION_ALIGNMENT_8B
1588 bool
1589
1590config FUNCTION_ALIGNMENT_16B
1591 bool
1592
1593config FUNCTION_ALIGNMENT_32B
1594 bool
1595
1596config FUNCTION_ALIGNMENT_64B
1597 bool
1598
1599config FUNCTION_ALIGNMENT
1600 int
1601 default 64 if FUNCTION_ALIGNMENT_64B
1602 default 32 if FUNCTION_ALIGNMENT_32B
1603 default 16 if FUNCTION_ALIGNMENT_16B
1604 default 8 if FUNCTION_ALIGNMENT_8B
1605 default 4 if FUNCTION_ALIGNMENT_4B
1606 default 0
1607
1608config CC_HAS_MIN_FUNCTION_ALIGNMENT
1609 # Detect availability of the GCC option -fmin-function-alignment which
1610 # guarantees minimal alignment for all functions, unlike
1611 # -falign-functions which the compiler ignores for cold functions.
1612 def_bool $(cc-option, -fmin-function-alignment=8)
1613
1614config CC_HAS_SANE_FUNCTION_ALIGNMENT
1615 # Set if the guaranteed alignment with -fmin-function-alignment is
1616 # available or extra care is required in the kernel. Clang provides
1617 # strict alignment always, even with -falign-functions.
1618 def_bool CC_HAS_MIN_FUNCTION_ALIGNMENT || CC_IS_CLANG
1619
1620endmenu