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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 HOTPLUG_SMT
28 bool
29
30config OPROFILE
31 tristate "OProfile system profiling"
32 depends on PROFILING
33 depends on HAVE_OPROFILE
34 select RING_BUFFER
35 select RING_BUFFER_ALLOW_SWAP
36 help
37 OProfile is a profiling system capable of profiling the
38 whole system, include the kernel, kernel modules, libraries,
39 and applications.
40
41 If unsure, say N.
42
43config OPROFILE_EVENT_MULTIPLEX
44 bool "OProfile multiplexing support (EXPERIMENTAL)"
45 default n
46 depends on OPROFILE && X86
47 help
48 The number of hardware counters is limited. The multiplexing
49 feature enables OProfile to gather more events than counters
50 are provided by the hardware. This is realized by switching
51 between events at a user specified time interval.
52
53 If unsure, say N.
54
55config HAVE_OPROFILE
56 bool
57
58config OPROFILE_NMI_TIMER
59 def_bool y
60 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
61
62config KPROBES
63 bool "Kprobes"
64 depends on MODULES
65 depends on HAVE_KPROBES
66 select KALLSYMS
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 depends on CC_HAS_ASM_GOTO
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 OPTPROBES
107 def_bool y
108 depends on KPROBES && HAVE_OPTPROBES
109 select TASKS_RCU if PREEMPTION
110
111config KPROBES_ON_FTRACE
112 def_bool y
113 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
114 depends on DYNAMIC_FTRACE_WITH_REGS
115 help
116 If function tracer is enabled and the arch supports full
117 passing of pt_regs to function tracing, then kprobes can
118 optimize on top of function tracing.
119
120config UPROBES
121 def_bool n
122 depends on ARCH_SUPPORTS_UPROBES
123 help
124 Uprobes is the user-space counterpart to kprobes: they
125 enable instrumentation applications (such as 'perf probe')
126 to establish unintrusive probes in user-space binaries and
127 libraries, by executing handler functions when the probes
128 are hit by user-space applications.
129
130 ( These probes come in the form of single-byte breakpoints,
131 managed by the kernel and kept transparent to the probed
132 application. )
133
134config HAVE_EFFICIENT_UNALIGNED_ACCESS
135 bool
136 help
137 Some architectures are unable to perform unaligned accesses
138 without the use of get_unaligned/put_unaligned. Others are
139 unable to perform such accesses efficiently (e.g. trap on
140 unaligned access and require fixing it up in the exception
141 handler.)
142
143 This symbol should be selected by an architecture if it can
144 perform unaligned accesses efficiently to allow different
145 code paths to be selected for these cases. Some network
146 drivers, for example, could opt to not fix up alignment
147 problems with received packets if doing so would not help
148 much.
149
150 See Documentation/unaligned-memory-access.txt for more
151 information on the topic of unaligned memory accesses.
152
153config ARCH_USE_BUILTIN_BSWAP
154 bool
155 help
156 Modern versions of GCC (since 4.4) have builtin functions
157 for handling byte-swapping. Using these, instead of the old
158 inline assembler that the architecture code provides in the
159 __arch_bswapXX() macros, allows the compiler to see what's
160 happening and offers more opportunity for optimisation. In
161 particular, the compiler will be able to combine the byteswap
162 with a nearby load or store and use load-and-swap or
163 store-and-swap instructions if the architecture has them. It
164 should almost *never* result in code which is worse than the
165 hand-coded assembler in <asm/swab.h>. But just in case it
166 does, the use of the builtins is optional.
167
168 Any architecture with load-and-swap or store-and-swap
169 instructions should set this. And it shouldn't hurt to set it
170 on architectures that don't have such instructions.
171
172config KRETPROBES
173 def_bool y
174 depends on KPROBES && HAVE_KRETPROBES
175
176config USER_RETURN_NOTIFIER
177 bool
178 depends on HAVE_USER_RETURN_NOTIFIER
179 help
180 Provide a kernel-internal notification when a cpu is about to
181 switch to user mode.
182
183config HAVE_IOREMAP_PROT
184 bool
185
186config HAVE_KPROBES
187 bool
188
189config HAVE_KRETPROBES
190 bool
191
192config HAVE_OPTPROBES
193 bool
194
195config HAVE_KPROBES_ON_FTRACE
196 bool
197
198config HAVE_FUNCTION_ERROR_INJECTION
199 bool
200
201config HAVE_NMI
202 bool
203
204#
205# An arch should select this if it provides all these things:
206#
207# task_pt_regs() in asm/processor.h or asm/ptrace.h
208# arch_has_single_step() if there is hardware single-step support
209# arch_has_block_step() if there is hardware block-step support
210# asm/syscall.h supplying asm-generic/syscall.h interface
211# linux/regset.h user_regset interfaces
212# CORE_DUMP_USE_REGSET #define'd in linux/elf.h
213# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit}
214# TIF_NOTIFY_RESUME calls tracehook_notify_resume()
215# signal delivery calls tracehook_signal_handler()
216#
217config HAVE_ARCH_TRACEHOOK
218 bool
219
220config HAVE_DMA_CONTIGUOUS
221 bool
222
223config GENERIC_SMP_IDLE_THREAD
224 bool
225
226config GENERIC_IDLE_POLL_SETUP
227 bool
228
229config ARCH_HAS_FORTIFY_SOURCE
230 bool
231 help
232 An architecture should select this when it can successfully
233 build and run with CONFIG_FORTIFY_SOURCE.
234
235#
236# Select if the arch provides a historic keepinit alias for the retain_initrd
237# command line option
238#
239config ARCH_HAS_KEEPINITRD
240 bool
241
242# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
243config ARCH_HAS_SET_MEMORY
244 bool
245
246# Select if arch has all set_direct_map_invalid/default() functions
247config ARCH_HAS_SET_DIRECT_MAP
248 bool
249
250#
251# Select if arch has an uncached kernel segment and provides the
252# uncached_kernel_address / cached_kernel_address symbols to use it
253#
254config ARCH_HAS_UNCACHED_SEGMENT
255 select ARCH_HAS_DMA_PREP_COHERENT
256 bool
257
258# Select if arch init_task must go in the __init_task_data section
259config ARCH_TASK_STRUCT_ON_STACK
260 bool
261
262# Select if arch has its private alloc_task_struct() function
263config ARCH_TASK_STRUCT_ALLOCATOR
264 bool
265
266config HAVE_ARCH_THREAD_STRUCT_WHITELIST
267 bool
268 depends on !ARCH_TASK_STRUCT_ALLOCATOR
269 help
270 An architecture should select this to provide hardened usercopy
271 knowledge about what region of the thread_struct should be
272 whitelisted for copying to userspace. Normally this is only the
273 FPU registers. Specifically, arch_thread_struct_whitelist()
274 should be implemented. Without this, the entire thread_struct
275 field in task_struct will be left whitelisted.
276
277# Select if arch has its private alloc_thread_stack() function
278config ARCH_THREAD_STACK_ALLOCATOR
279 bool
280
281# Select if arch wants to size task_struct dynamically via arch_task_struct_size:
282config ARCH_WANTS_DYNAMIC_TASK_STRUCT
283 bool
284
285config ARCH_32BIT_OFF_T
286 bool
287 depends on !64BIT
288 help
289 All new 32-bit architectures should have 64-bit off_t type on
290 userspace side which corresponds to the loff_t kernel type. This
291 is the requirement for modern ABIs. Some existing architectures
292 still support 32-bit off_t. This option is enabled for all such
293 architectures explicitly.
294
295config HAVE_ASM_MODVERSIONS
296 bool
297 help
298 This symbol should be selected by an architecure if it provides
299 <asm/asm-prototypes.h> to support the module versioning for symbols
300 exported from assembly code.
301
302config HAVE_REGS_AND_STACK_ACCESS_API
303 bool
304 help
305 This symbol should be selected by an architecure if it supports
306 the API needed to access registers and stack entries from pt_regs,
307 declared in asm/ptrace.h
308 For example the kprobes-based event tracer needs this API.
309
310config HAVE_RSEQ
311 bool
312 depends on HAVE_REGS_AND_STACK_ACCESS_API
313 help
314 This symbol should be selected by an architecture if it
315 supports an implementation of restartable sequences.
316
317config HAVE_FUNCTION_ARG_ACCESS_API
318 bool
319 help
320 This symbol should be selected by an architecure if it supports
321 the API needed to access function arguments from pt_regs,
322 declared in asm/ptrace.h
323
324config HAVE_CLK
325 bool
326 help
327 The <linux/clk.h> calls support software clock gating and
328 thus are a key power management tool on many systems.
329
330config HAVE_HW_BREAKPOINT
331 bool
332 depends on PERF_EVENTS
333
334config HAVE_MIXED_BREAKPOINTS_REGS
335 bool
336 depends on HAVE_HW_BREAKPOINT
337 help
338 Depending on the arch implementation of hardware breakpoints,
339 some of them have separate registers for data and instruction
340 breakpoints addresses, others have mixed registers to store
341 them but define the access type in a control register.
342 Select this option if your arch implements breakpoints under the
343 latter fashion.
344
345config HAVE_USER_RETURN_NOTIFIER
346 bool
347
348config HAVE_PERF_EVENTS_NMI
349 bool
350 help
351 System hardware can generate an NMI using the perf event
352 subsystem. Also has support for calculating CPU cycle events
353 to determine how many clock cycles in a given period.
354
355config HAVE_HARDLOCKUP_DETECTOR_PERF
356 bool
357 depends on HAVE_PERF_EVENTS_NMI
358 help
359 The arch chooses to use the generic perf-NMI-based hardlockup
360 detector. Must define HAVE_PERF_EVENTS_NMI.
361
362config HAVE_NMI_WATCHDOG
363 depends on HAVE_NMI
364 bool
365 help
366 The arch provides a low level NMI watchdog. It provides
367 asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
368
369config HAVE_HARDLOCKUP_DETECTOR_ARCH
370 bool
371 select HAVE_NMI_WATCHDOG
372 help
373 The arch chooses to provide its own hardlockup detector, which is
374 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
375 interfaces and parameters provided by hardlockup detector subsystem.
376
377config HAVE_PERF_REGS
378 bool
379 help
380 Support selective register dumps for perf events. This includes
381 bit-mapping of each registers and a unique architecture id.
382
383config HAVE_PERF_USER_STACK_DUMP
384 bool
385 help
386 Support user stack dumps for perf event samples. This needs
387 access to the user stack pointer which is not unified across
388 architectures.
389
390config HAVE_ARCH_JUMP_LABEL
391 bool
392
393config HAVE_ARCH_JUMP_LABEL_RELATIVE
394 bool
395
396config HAVE_RCU_TABLE_FREE
397 bool
398
399config HAVE_RCU_TABLE_NO_INVALIDATE
400 bool
401
402config HAVE_MMU_GATHER_PAGE_SIZE
403 bool
404
405config HAVE_MMU_GATHER_NO_GATHER
406 bool
407
408config ARCH_HAVE_NMI_SAFE_CMPXCHG
409 bool
410
411config HAVE_ALIGNED_STRUCT_PAGE
412 bool
413 help
414 This makes sure that struct pages are double word aligned and that
415 e.g. the SLUB allocator can perform double word atomic operations
416 on a struct page for better performance. However selecting this
417 might increase the size of a struct page by a word.
418
419config HAVE_CMPXCHG_LOCAL
420 bool
421
422config HAVE_CMPXCHG_DOUBLE
423 bool
424
425config ARCH_WEAK_RELEASE_ACQUIRE
426 bool
427
428config ARCH_WANT_IPC_PARSE_VERSION
429 bool
430
431config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
432 bool
433
434config ARCH_WANT_OLD_COMPAT_IPC
435 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
436 bool
437
438config HAVE_ARCH_SECCOMP_FILTER
439 bool
440 help
441 An arch should select this symbol if it provides all of these things:
442 - syscall_get_arch()
443 - syscall_get_arguments()
444 - syscall_rollback()
445 - syscall_set_return_value()
446 - SIGSYS siginfo_t support
447 - secure_computing is called from a ptrace_event()-safe context
448 - secure_computing return value is checked and a return value of -1
449 results in the system call being skipped immediately.
450 - seccomp syscall wired up
451
452config SECCOMP_FILTER
453 def_bool y
454 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
455 help
456 Enable tasks to build secure computing environments defined
457 in terms of Berkeley Packet Filter programs which implement
458 task-defined system call filtering polices.
459
460 See Documentation/userspace-api/seccomp_filter.rst for details.
461
462config HAVE_ARCH_STACKLEAK
463 bool
464 help
465 An architecture should select this if it has the code which
466 fills the used part of the kernel stack with the STACKLEAK_POISON
467 value before returning from system calls.
468
469config HAVE_STACKPROTECTOR
470 bool
471 help
472 An arch should select this symbol if:
473 - it has implemented a stack canary (e.g. __stack_chk_guard)
474
475config CC_HAS_STACKPROTECTOR_NONE
476 def_bool $(cc-option,-fno-stack-protector)
477
478config STACKPROTECTOR
479 bool "Stack Protector buffer overflow detection"
480 depends on HAVE_STACKPROTECTOR
481 depends on $(cc-option,-fstack-protector)
482 default y
483 help
484 This option turns on the "stack-protector" GCC feature. This
485 feature puts, at the beginning of functions, a canary value on
486 the stack just before the return address, and validates
487 the value just before actually returning. Stack based buffer
488 overflows (that need to overwrite this return address) now also
489 overwrite the canary, which gets detected and the attack is then
490 neutralized via a kernel panic.
491
492 Functions will have the stack-protector canary logic added if they
493 have an 8-byte or larger character array on the stack.
494
495 This feature requires gcc version 4.2 or above, or a distribution
496 gcc with the feature backported ("-fstack-protector").
497
498 On an x86 "defconfig" build, this feature adds canary checks to
499 about 3% of all kernel functions, which increases kernel code size
500 by about 0.3%.
501
502config STACKPROTECTOR_STRONG
503 bool "Strong Stack Protector"
504 depends on STACKPROTECTOR
505 depends on $(cc-option,-fstack-protector-strong)
506 default y
507 help
508 Functions will have the stack-protector canary logic added in any
509 of the following conditions:
510
511 - local variable's address used as part of the right hand side of an
512 assignment or function argument
513 - local variable is an array (or union containing an array),
514 regardless of array type or length
515 - uses register local variables
516
517 This feature requires gcc version 4.9 or above, or a distribution
518 gcc with the feature backported ("-fstack-protector-strong").
519
520 On an x86 "defconfig" build, this feature adds canary checks to
521 about 20% of all kernel functions, which increases the kernel code
522 size by about 2%.
523
524config HAVE_ARCH_WITHIN_STACK_FRAMES
525 bool
526 help
527 An architecture should select this if it can walk the kernel stack
528 frames to determine if an object is part of either the arguments
529 or local variables (i.e. that it excludes saved return addresses,
530 and similar) by implementing an inline arch_within_stack_frames(),
531 which is used by CONFIG_HARDENED_USERCOPY.
532
533config HAVE_CONTEXT_TRACKING
534 bool
535 help
536 Provide kernel/user boundaries probes necessary for subsystems
537 that need it, such as userspace RCU extended quiescent state.
538 Syscalls need to be wrapped inside user_exit()-user_enter() through
539 the slow path using TIF_NOHZ flag. Exceptions handlers must be
540 wrapped as well. Irqs are already protected inside
541 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
542 irq exit still need to be protected.
543
544config HAVE_VIRT_CPU_ACCOUNTING
545 bool
546
547config ARCH_HAS_SCALED_CPUTIME
548 bool
549
550config HAVE_VIRT_CPU_ACCOUNTING_GEN
551 bool
552 default y if 64BIT
553 help
554 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
555 Before enabling this option, arch code must be audited
556 to ensure there are no races in concurrent read/write of
557 cputime_t. For example, reading/writing 64-bit cputime_t on
558 some 32-bit arches may require multiple accesses, so proper
559 locking is needed to protect against concurrent accesses.
560
561
562config HAVE_IRQ_TIME_ACCOUNTING
563 bool
564 help
565 Archs need to ensure they use a high enough resolution clock to
566 support irq time accounting and then call enable_sched_clock_irqtime().
567
568config HAVE_MOVE_PMD
569 bool
570 help
571 Archs that select this are able to move page tables at the PMD level.
572
573config HAVE_ARCH_TRANSPARENT_HUGEPAGE
574 bool
575
576config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
577 bool
578
579config HAVE_ARCH_HUGE_VMAP
580 bool
581
582config ARCH_WANT_HUGE_PMD_SHARE
583 bool
584
585config HAVE_ARCH_SOFT_DIRTY
586 bool
587
588config HAVE_MOD_ARCH_SPECIFIC
589 bool
590 help
591 The arch uses struct mod_arch_specific to store data. Many arches
592 just need a simple module loader without arch specific data - those
593 should not enable this.
594
595config MODULES_USE_ELF_RELA
596 bool
597 help
598 Modules only use ELF RELA relocations. Modules with ELF REL
599 relocations will give an error.
600
601config MODULES_USE_ELF_REL
602 bool
603 help
604 Modules only use ELF REL relocations. Modules with ELF RELA
605 relocations will give an error.
606
607config HAVE_IRQ_EXIT_ON_IRQ_STACK
608 bool
609 help
610 Architecture doesn't only execute the irq handler on the irq stack
611 but also irq_exit(). This way we can process softirqs on this irq
612 stack instead of switching to a new one when we call __do_softirq()
613 in the end of an hardirq.
614 This spares a stack switch and improves cache usage on softirq
615 processing.
616
617config PGTABLE_LEVELS
618 int
619 default 2
620
621config ARCH_HAS_ELF_RANDOMIZE
622 bool
623 help
624 An architecture supports choosing randomized locations for
625 stack, mmap, brk, and ET_DYN. Defined functions:
626 - arch_mmap_rnd()
627 - arch_randomize_brk()
628
629config HAVE_ARCH_MMAP_RND_BITS
630 bool
631 help
632 An arch should select this symbol if it supports setting a variable
633 number of bits for use in establishing the base address for mmap
634 allocations, has MMU enabled and provides values for both:
635 - ARCH_MMAP_RND_BITS_MIN
636 - ARCH_MMAP_RND_BITS_MAX
637
638config HAVE_EXIT_THREAD
639 bool
640 help
641 An architecture implements exit_thread.
642
643config ARCH_MMAP_RND_BITS_MIN
644 int
645
646config ARCH_MMAP_RND_BITS_MAX
647 int
648
649config ARCH_MMAP_RND_BITS_DEFAULT
650 int
651
652config ARCH_MMAP_RND_BITS
653 int "Number of bits to use for ASLR of mmap base address" if EXPERT
654 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
655 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
656 default ARCH_MMAP_RND_BITS_MIN
657 depends on HAVE_ARCH_MMAP_RND_BITS
658 help
659 This value can be used to select the number of bits to use to
660 determine the random offset to the base address of vma regions
661 resulting from mmap allocations. This value will be bounded
662 by the architecture's minimum and maximum supported values.
663
664 This value can be changed after boot using the
665 /proc/sys/vm/mmap_rnd_bits tunable
666
667config HAVE_ARCH_MMAP_RND_COMPAT_BITS
668 bool
669 help
670 An arch should select this symbol if it supports running applications
671 in compatibility mode, supports setting a variable number of bits for
672 use in establishing the base address for mmap allocations, has MMU
673 enabled and provides values for both:
674 - ARCH_MMAP_RND_COMPAT_BITS_MIN
675 - ARCH_MMAP_RND_COMPAT_BITS_MAX
676
677config ARCH_MMAP_RND_COMPAT_BITS_MIN
678 int
679
680config ARCH_MMAP_RND_COMPAT_BITS_MAX
681 int
682
683config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
684 int
685
686config ARCH_MMAP_RND_COMPAT_BITS
687 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
688 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
689 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
690 default ARCH_MMAP_RND_COMPAT_BITS_MIN
691 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
692 help
693 This value can be used to select the number of bits to use to
694 determine the random offset to the base address of vma regions
695 resulting from mmap allocations for compatible applications This
696 value will be bounded by the architecture's minimum and maximum
697 supported values.
698
699 This value can be changed after boot using the
700 /proc/sys/vm/mmap_rnd_compat_bits tunable
701
702config HAVE_ARCH_COMPAT_MMAP_BASES
703 bool
704 help
705 This allows 64bit applications to invoke 32-bit mmap() syscall
706 and vice-versa 32-bit applications to call 64-bit mmap().
707 Required for applications doing different bitness syscalls.
708
709# This allows to use a set of generic functions to determine mmap base
710# address by giving priority to top-down scheme only if the process
711# is not in legacy mode (compat task, unlimited stack size or
712# sysctl_legacy_va_layout).
713# Architecture that selects this option can provide its own version of:
714# - STACK_RND_MASK
715config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
716 bool
717 depends on MMU
718 select ARCH_HAS_ELF_RANDOMIZE
719
720config HAVE_COPY_THREAD_TLS
721 bool
722 help
723 Architecture provides copy_thread_tls to accept tls argument via
724 normal C parameter passing, rather than extracting the syscall
725 argument from pt_regs.
726
727config HAVE_STACK_VALIDATION
728 bool
729 help
730 Architecture supports the 'objtool check' host tool command, which
731 performs compile-time stack metadata validation.
732
733config HAVE_RELIABLE_STACKTRACE
734 bool
735 help
736 Architecture has a save_stack_trace_tsk_reliable() function which
737 only returns a stack trace if it can guarantee the trace is reliable.
738
739config HAVE_ARCH_HASH
740 bool
741 default n
742 help
743 If this is set, the architecture provides an <asm/hash.h>
744 file which provides platform-specific implementations of some
745 functions in <linux/hash.h> or fs/namei.c.
746
747config HAVE_ARCH_NVRAM_OPS
748 bool
749
750config ISA_BUS_API
751 def_bool ISA
752
753#
754# ABI hall of shame
755#
756config CLONE_BACKWARDS
757 bool
758 help
759 Architecture has tls passed as the 4th argument of clone(2),
760 not the 5th one.
761
762config CLONE_BACKWARDS2
763 bool
764 help
765 Architecture has the first two arguments of clone(2) swapped.
766
767config CLONE_BACKWARDS3
768 bool
769 help
770 Architecture has tls passed as the 3rd argument of clone(2),
771 not the 5th one.
772
773config ODD_RT_SIGACTION
774 bool
775 help
776 Architecture has unusual rt_sigaction(2) arguments
777
778config OLD_SIGSUSPEND
779 bool
780 help
781 Architecture has old sigsuspend(2) syscall, of one-argument variety
782
783config OLD_SIGSUSPEND3
784 bool
785 help
786 Even weirder antique ABI - three-argument sigsuspend(2)
787
788config OLD_SIGACTION
789 bool
790 help
791 Architecture has old sigaction(2) syscall. Nope, not the same
792 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
793 but fairly different variant of sigaction(2), thanks to OSF/1
794 compatibility...
795
796config COMPAT_OLD_SIGACTION
797 bool
798
799config 64BIT_TIME
800 def_bool y
801 help
802 This should be selected by all architectures that need to support
803 new system calls with a 64-bit time_t. This is relevant on all 32-bit
804 architectures, and 64-bit architectures as part of compat syscall
805 handling.
806
807config COMPAT_32BIT_TIME
808 def_bool !64BIT || COMPAT
809 help
810 This enables 32 bit time_t support in addition to 64 bit time_t support.
811 This is relevant on all 32-bit architectures, and 64-bit architectures
812 as part of compat syscall handling.
813
814config ARCH_NO_PREEMPT
815 bool
816
817config ARCH_SUPPORTS_RT
818 bool
819
820config CPU_NO_EFFICIENT_FFS
821 def_bool n
822
823config HAVE_ARCH_VMAP_STACK
824 def_bool n
825 help
826 An arch should select this symbol if it can support kernel stacks
827 in vmalloc space. This means:
828
829 - vmalloc space must be large enough to hold many kernel stacks.
830 This may rule out many 32-bit architectures.
831
832 - Stacks in vmalloc space need to work reliably. For example, if
833 vmap page tables are created on demand, either this mechanism
834 needs to work while the stack points to a virtual address with
835 unpopulated page tables or arch code (switch_to() and switch_mm(),
836 most likely) needs to ensure that the stack's page table entries
837 are populated before running on a possibly unpopulated stack.
838
839 - If the stack overflows into a guard page, something reasonable
840 should happen. The definition of "reasonable" is flexible, but
841 instantly rebooting without logging anything would be unfriendly.
842
843config VMAP_STACK
844 default y
845 bool "Use a virtually-mapped stack"
846 depends on HAVE_ARCH_VMAP_STACK && !KASAN
847 ---help---
848 Enable this if you want the use virtually-mapped kernel stacks
849 with guard pages. This causes kernel stack overflows to be
850 caught immediately rather than causing difficult-to-diagnose
851 corruption.
852
853 This is presently incompatible with KASAN because KASAN expects
854 the stack to map directly to the KASAN shadow map using a formula
855 that is incorrect if the stack is in vmalloc space.
856
857config ARCH_OPTIONAL_KERNEL_RWX
858 def_bool n
859
860config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
861 def_bool n
862
863config ARCH_HAS_STRICT_KERNEL_RWX
864 def_bool n
865
866config STRICT_KERNEL_RWX
867 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
868 depends on ARCH_HAS_STRICT_KERNEL_RWX
869 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
870 help
871 If this is set, kernel text and rodata memory will be made read-only,
872 and non-text memory will be made non-executable. This provides
873 protection against certain security exploits (e.g. executing the heap
874 or modifying text)
875
876 These features are considered standard security practice these days.
877 You should say Y here in almost all cases.
878
879config ARCH_HAS_STRICT_MODULE_RWX
880 def_bool n
881
882config STRICT_MODULE_RWX
883 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
884 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
885 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
886 help
887 If this is set, module text and rodata memory will be made read-only,
888 and non-text memory will be made non-executable. This provides
889 protection against certain security exploits (e.g. writing to text)
890
891# select if the architecture provides an asm/dma-direct.h header
892config ARCH_HAS_PHYS_TO_DMA
893 bool
894
895config ARCH_HAS_REFCOUNT
896 bool
897 help
898 An architecture selects this when it has implemented refcount_t
899 using open coded assembly primitives that provide an optimized
900 refcount_t implementation, possibly at the expense of some full
901 refcount state checks of CONFIG_REFCOUNT_FULL=y.
902
903 The refcount overflow check behavior, however, must be retained.
904 Catching overflows is the primary security concern for protecting
905 against bugs in reference counts.
906
907config REFCOUNT_FULL
908 bool "Perform full reference count validation at the expense of speed"
909 help
910 Enabling this switches the refcounting infrastructure from a fast
911 unchecked atomic_t implementation to a fully state checked
912 implementation, which can be (slightly) slower but provides protections
913 against various use-after-free conditions that can be used in
914 security flaw exploits.
915
916config HAVE_ARCH_COMPILER_H
917 bool
918 help
919 An architecture can select this if it provides an
920 asm/compiler.h header that should be included after
921 linux/compiler-*.h in order to override macro definitions that those
922 headers generally provide.
923
924config HAVE_ARCH_PREL32_RELOCATIONS
925 bool
926 help
927 May be selected by an architecture if it supports place-relative
928 32-bit relocations, both in the toolchain and in the module loader,
929 in which case relative references can be used in special sections
930 for PCI fixup, initcalls etc which are only half the size on 64 bit
931 architectures, and don't require runtime relocation on relocatable
932 kernels.
933
934config ARCH_USE_MEMREMAP_PROT
935 bool
936
937config LOCK_EVENT_COUNTS
938 bool "Locking event counts collection"
939 depends on DEBUG_FS
940 ---help---
941 Enable light-weight counting of various locking related events
942 in the system with minimal performance impact. This reduces
943 the chance of application behavior change because of timing
944 differences. The counts are reported via debugfs.
945
946# Select if the architecture has support for applying RELR relocations.
947config ARCH_HAS_RELR
948 bool
949
950config RELR
951 bool "Use RELR relocation packing"
952 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
953 default y
954 help
955 Store the kernel's dynamic relocations in the RELR relocation packing
956 format. Requires a compatible linker (LLD supports this feature), as
957 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
958 are compatible).
959
960config ARCH_HAS_MEM_ENCRYPT
961 bool
962
963source "kernel/gcov/Kconfig"
964
965source "scripts/gcc-plugins/Kconfig"
966
967endmenu