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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#
2# General architecture dependent options
3#
4
5config KEXEC_CORE
6 bool
7
8config HAVE_IMA_KEXEC
9 bool
10
11config OPROFILE
12 tristate "OProfile system profiling"
13 depends on PROFILING
14 depends on HAVE_OPROFILE
15 select RING_BUFFER
16 select RING_BUFFER_ALLOW_SWAP
17 help
18 OProfile is a profiling system capable of profiling the
19 whole system, include the kernel, kernel modules, libraries,
20 and applications.
21
22 If unsure, say N.
23
24config OPROFILE_EVENT_MULTIPLEX
25 bool "OProfile multiplexing support (EXPERIMENTAL)"
26 default n
27 depends on OPROFILE && X86
28 help
29 The number of hardware counters is limited. The multiplexing
30 feature enables OProfile to gather more events than counters
31 are provided by the hardware. This is realized by switching
32 between events at an user specified time interval.
33
34 If unsure, say N.
35
36config HAVE_OPROFILE
37 bool
38
39config OPROFILE_NMI_TIMER
40 def_bool y
41 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
42
43config KPROBES
44 bool "Kprobes"
45 depends on MODULES
46 depends on HAVE_KPROBES
47 select KALLSYMS
48 help
49 Kprobes allows you to trap at almost any kernel address and
50 execute a callback function. register_kprobe() establishes
51 a probepoint and specifies the callback. Kprobes is useful
52 for kernel debugging, non-intrusive instrumentation and testing.
53 If in doubt, say "N".
54
55config JUMP_LABEL
56 bool "Optimize very unlikely/likely branches"
57 depends on HAVE_ARCH_JUMP_LABEL
58 help
59 This option enables a transparent branch optimization that
60 makes certain almost-always-true or almost-always-false branch
61 conditions even cheaper to execute within the kernel.
62
63 Certain performance-sensitive kernel code, such as trace points,
64 scheduler functionality, networking code and KVM have such
65 branches and include support for this optimization technique.
66
67 If it is detected that the compiler has support for "asm goto",
68 the kernel will compile such branches with just a nop
69 instruction. When the condition flag is toggled to true, the
70 nop will be converted to a jump instruction to execute the
71 conditional block of instructions.
72
73 This technique lowers overhead and stress on the branch prediction
74 of the processor and generally makes the kernel faster. The update
75 of the condition is slower, but those are always very rare.
76
77 ( On 32-bit x86, the necessary options added to the compiler
78 flags may increase the size of the kernel slightly. )
79
80config STATIC_KEYS_SELFTEST
81 bool "Static key selftest"
82 depends on JUMP_LABEL
83 help
84 Boot time self-test of the branch patching code.
85
86config OPTPROBES
87 def_bool y
88 depends on KPROBES && HAVE_OPTPROBES
89 depends on !PREEMPT
90
91config KPROBES_ON_FTRACE
92 def_bool y
93 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
94 depends on DYNAMIC_FTRACE_WITH_REGS
95 help
96 If function tracer is enabled and the arch supports full
97 passing of pt_regs to function tracing, then kprobes can
98 optimize on top of function tracing.
99
100config UPROBES
101 def_bool n
102 depends on ARCH_SUPPORTS_UPROBES
103 help
104 Uprobes is the user-space counterpart to kprobes: they
105 enable instrumentation applications (such as 'perf probe')
106 to establish unintrusive probes in user-space binaries and
107 libraries, by executing handler functions when the probes
108 are hit by user-space applications.
109
110 ( These probes come in the form of single-byte breakpoints,
111 managed by the kernel and kept transparent to the probed
112 application. )
113
114config HAVE_64BIT_ALIGNED_ACCESS
115 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
116 help
117 Some architectures require 64 bit accesses to be 64 bit
118 aligned, which also requires structs containing 64 bit values
119 to be 64 bit aligned too. This includes some 32 bit
120 architectures which can do 64 bit accesses, as well as 64 bit
121 architectures without unaligned access.
122
123 This symbol should be selected by an architecture if 64 bit
124 accesses are required to be 64 bit aligned in this way even
125 though it is not a 64 bit architecture.
126
127 See Documentation/unaligned-memory-access.txt for more
128 information on the topic of unaligned memory accesses.
129
130config HAVE_EFFICIENT_UNALIGNED_ACCESS
131 bool
132 help
133 Some architectures are unable to perform unaligned accesses
134 without the use of get_unaligned/put_unaligned. Others are
135 unable to perform such accesses efficiently (e.g. trap on
136 unaligned access and require fixing it up in the exception
137 handler.)
138
139 This symbol should be selected by an architecture if it can
140 perform unaligned accesses efficiently to allow different
141 code paths to be selected for these cases. Some network
142 drivers, for example, could opt to not fix up alignment
143 problems with received packets if doing so would not help
144 much.
145
146 See Documentation/unaligned-memory-access.txt for more
147 information on the topic of unaligned memory accesses.
148
149config ARCH_USE_BUILTIN_BSWAP
150 bool
151 help
152 Modern versions of GCC (since 4.4) have builtin functions
153 for handling byte-swapping. Using these, instead of the old
154 inline assembler that the architecture code provides in the
155 __arch_bswapXX() macros, allows the compiler to see what's
156 happening and offers more opportunity for optimisation. In
157 particular, the compiler will be able to combine the byteswap
158 with a nearby load or store and use load-and-swap or
159 store-and-swap instructions if the architecture has them. It
160 should almost *never* result in code which is worse than the
161 hand-coded assembler in <asm/swab.h>. But just in case it
162 does, the use of the builtins is optional.
163
164 Any architecture with load-and-swap or store-and-swap
165 instructions should set this. And it shouldn't hurt to set it
166 on architectures that don't have such instructions.
167
168config KRETPROBES
169 def_bool y
170 depends on KPROBES && HAVE_KRETPROBES
171
172config USER_RETURN_NOTIFIER
173 bool
174 depends on HAVE_USER_RETURN_NOTIFIER
175 help
176 Provide a kernel-internal notification when a cpu is about to
177 switch to user mode.
178
179config HAVE_IOREMAP_PROT
180 bool
181
182config HAVE_KPROBES
183 bool
184
185config HAVE_KRETPROBES
186 bool
187
188config HAVE_OPTPROBES
189 bool
190
191config HAVE_KPROBES_ON_FTRACE
192 bool
193
194config HAVE_NMI
195 bool
196
197config HAVE_NMI_WATCHDOG
198 depends on HAVE_NMI
199 bool
200#
201# An arch should select this if it provides all these things:
202#
203# task_pt_regs() in asm/processor.h or asm/ptrace.h
204# arch_has_single_step() if there is hardware single-step support
205# arch_has_block_step() if there is hardware block-step support
206# asm/syscall.h supplying asm-generic/syscall.h interface
207# linux/regset.h user_regset interfaces
208# CORE_DUMP_USE_REGSET #define'd in linux/elf.h
209# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit}
210# TIF_NOTIFY_RESUME calls tracehook_notify_resume()
211# signal delivery calls tracehook_signal_handler()
212#
213config HAVE_ARCH_TRACEHOOK
214 bool
215
216config HAVE_DMA_CONTIGUOUS
217 bool
218
219config GENERIC_SMP_IDLE_THREAD
220 bool
221
222config GENERIC_IDLE_POLL_SETUP
223 bool
224
225# Select if arch init_task initializer is different to init/init_task.c
226config ARCH_INIT_TASK
227 bool
228
229# Select if arch has its private alloc_task_struct() function
230config ARCH_TASK_STRUCT_ALLOCATOR
231 bool
232
233# Select if arch has its private alloc_thread_stack() function
234config ARCH_THREAD_STACK_ALLOCATOR
235 bool
236
237# Select if arch wants to size task_struct dynamically via arch_task_struct_size:
238config ARCH_WANTS_DYNAMIC_TASK_STRUCT
239 bool
240
241config HAVE_REGS_AND_STACK_ACCESS_API
242 bool
243 help
244 This symbol should be selected by an architecure if it supports
245 the API needed to access registers and stack entries from pt_regs,
246 declared in asm/ptrace.h
247 For example the kprobes-based event tracer needs this API.
248
249config HAVE_CLK
250 bool
251 help
252 The <linux/clk.h> calls support software clock gating and
253 thus are a key power management tool on many systems.
254
255config HAVE_DMA_API_DEBUG
256 bool
257
258config HAVE_HW_BREAKPOINT
259 bool
260 depends on PERF_EVENTS
261
262config HAVE_MIXED_BREAKPOINTS_REGS
263 bool
264 depends on HAVE_HW_BREAKPOINT
265 help
266 Depending on the arch implementation of hardware breakpoints,
267 some of them have separate registers for data and instruction
268 breakpoints addresses, others have mixed registers to store
269 them but define the access type in a control register.
270 Select this option if your arch implements breakpoints under the
271 latter fashion.
272
273config HAVE_USER_RETURN_NOTIFIER
274 bool
275
276config HAVE_PERF_EVENTS_NMI
277 bool
278 help
279 System hardware can generate an NMI using the perf event
280 subsystem. Also has support for calculating CPU cycle events
281 to determine how many clock cycles in a given period.
282
283config HAVE_PERF_REGS
284 bool
285 help
286 Support selective register dumps for perf events. This includes
287 bit-mapping of each registers and a unique architecture id.
288
289config HAVE_PERF_USER_STACK_DUMP
290 bool
291 help
292 Support user stack dumps for perf event samples. This needs
293 access to the user stack pointer which is not unified across
294 architectures.
295
296config HAVE_ARCH_JUMP_LABEL
297 bool
298
299config HAVE_RCU_TABLE_FREE
300 bool
301
302config ARCH_HAVE_NMI_SAFE_CMPXCHG
303 bool
304
305config HAVE_ALIGNED_STRUCT_PAGE
306 bool
307 help
308 This makes sure that struct pages are double word aligned and that
309 e.g. the SLUB allocator can perform double word atomic operations
310 on a struct page for better performance. However selecting this
311 might increase the size of a struct page by a word.
312
313config HAVE_CMPXCHG_LOCAL
314 bool
315
316config HAVE_CMPXCHG_DOUBLE
317 bool
318
319config ARCH_WANT_IPC_PARSE_VERSION
320 bool
321
322config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
323 bool
324
325config ARCH_WANT_OLD_COMPAT_IPC
326 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
327 bool
328
329config HAVE_ARCH_SECCOMP_FILTER
330 bool
331 help
332 An arch should select this symbol if it provides all of these things:
333 - syscall_get_arch()
334 - syscall_get_arguments()
335 - syscall_rollback()
336 - syscall_set_return_value()
337 - SIGSYS siginfo_t support
338 - secure_computing is called from a ptrace_event()-safe context
339 - secure_computing return value is checked and a return value of -1
340 results in the system call being skipped immediately.
341 - seccomp syscall wired up
342
343config SECCOMP_FILTER
344 def_bool y
345 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
346 help
347 Enable tasks to build secure computing environments defined
348 in terms of Berkeley Packet Filter programs which implement
349 task-defined system call filtering polices.
350
351 See Documentation/prctl/seccomp_filter.txt for details.
352
353config HAVE_GCC_PLUGINS
354 bool
355 help
356 An arch should select this symbol if it supports building with
357 GCC plugins.
358
359menuconfig GCC_PLUGINS
360 bool "GCC plugins"
361 depends on HAVE_GCC_PLUGINS
362 depends on !COMPILE_TEST
363 help
364 GCC plugins are loadable modules that provide extra features to the
365 compiler. They are useful for runtime instrumentation and static analysis.
366
367 See Documentation/gcc-plugins.txt for details.
368
369config GCC_PLUGIN_CYC_COMPLEXITY
370 bool "Compute the cyclomatic complexity of a function" if EXPERT
371 depends on GCC_PLUGINS
372 depends on !COMPILE_TEST
373 help
374 The complexity M of a function's control flow graph is defined as:
375 M = E - N + 2P
376 where
377
378 E = the number of edges
379 N = the number of nodes
380 P = the number of connected components (exit nodes).
381
382 Enabling this plugin reports the complexity to stderr during the
383 build. It mainly serves as a simple example of how to create a
384 gcc plugin for the kernel.
385
386config GCC_PLUGIN_SANCOV
387 bool
388 depends on GCC_PLUGINS
389 help
390 This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
391 basic blocks. It supports all gcc versions with plugin support (from
392 gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
393 by Dmitry Vyukov <dvyukov@google.com>.
394
395config GCC_PLUGIN_LATENT_ENTROPY
396 bool "Generate some entropy during boot and runtime"
397 depends on GCC_PLUGINS
398 help
399 By saying Y here the kernel will instrument some kernel code to
400 extract some entropy from both original and artificially created
401 program state. This will help especially embedded systems where
402 there is little 'natural' source of entropy normally. The cost
403 is some slowdown of the boot process (about 0.5%) and fork and
404 irq processing.
405
406 Note that entropy extracted this way is not cryptographically
407 secure!
408
409 This plugin was ported from grsecurity/PaX. More information at:
410 * https://grsecurity.net/
411 * https://pax.grsecurity.net/
412
413config HAVE_CC_STACKPROTECTOR
414 bool
415 help
416 An arch should select this symbol if:
417 - its compiler supports the -fstack-protector option
418 - it has implemented a stack canary (e.g. __stack_chk_guard)
419
420config CC_STACKPROTECTOR
421 def_bool n
422 help
423 Set when a stack-protector mode is enabled, so that the build
424 can enable kernel-side support for the GCC feature.
425
426choice
427 prompt "Stack Protector buffer overflow detection"
428 depends on HAVE_CC_STACKPROTECTOR
429 default CC_STACKPROTECTOR_NONE
430 help
431 This option turns on the "stack-protector" GCC feature. This
432 feature puts, at the beginning of functions, a canary value on
433 the stack just before the return address, and validates
434 the value just before actually returning. Stack based buffer
435 overflows (that need to overwrite this return address) now also
436 overwrite the canary, which gets detected and the attack is then
437 neutralized via a kernel panic.
438
439config CC_STACKPROTECTOR_NONE
440 bool "None"
441 help
442 Disable "stack-protector" GCC feature.
443
444config CC_STACKPROTECTOR_REGULAR
445 bool "Regular"
446 select CC_STACKPROTECTOR
447 help
448 Functions will have the stack-protector canary logic added if they
449 have an 8-byte or larger character array on the stack.
450
451 This feature requires gcc version 4.2 or above, or a distribution
452 gcc with the feature backported ("-fstack-protector").
453
454 On an x86 "defconfig" build, this feature adds canary checks to
455 about 3% of all kernel functions, which increases kernel code size
456 by about 0.3%.
457
458config CC_STACKPROTECTOR_STRONG
459 bool "Strong"
460 select CC_STACKPROTECTOR
461 help
462 Functions will have the stack-protector canary logic added in any
463 of the following conditions:
464
465 - local variable's address used as part of the right hand side of an
466 assignment or function argument
467 - local variable is an array (or union containing an array),
468 regardless of array type or length
469 - uses register local variables
470
471 This feature requires gcc version 4.9 or above, or a distribution
472 gcc with the feature backported ("-fstack-protector-strong").
473
474 On an x86 "defconfig" build, this feature adds canary checks to
475 about 20% of all kernel functions, which increases the kernel code
476 size by about 2%.
477
478endchoice
479
480config THIN_ARCHIVES
481 bool
482 help
483 Select this if the architecture wants to use thin archives
484 instead of ld -r to create the built-in.o files.
485
486config LD_DEAD_CODE_DATA_ELIMINATION
487 bool
488 help
489 Select this if the architecture wants to do dead code and
490 data elimination with the linker by compiling with
491 -ffunction-sections -fdata-sections and linking with
492 --gc-sections.
493
494 This requires that the arch annotates or otherwise protects
495 its external entry points from being discarded. Linker scripts
496 must also merge .text.*, .data.*, and .bss.* correctly into
497 output sections. Care must be taken not to pull in unrelated
498 sections (e.g., '.text.init'). Typically '.' in section names
499 is used to distinguish them from label names / C identifiers.
500
501config HAVE_ARCH_WITHIN_STACK_FRAMES
502 bool
503 help
504 An architecture should select this if it can walk the kernel stack
505 frames to determine if an object is part of either the arguments
506 or local variables (i.e. that it excludes saved return addresses,
507 and similar) by implementing an inline arch_within_stack_frames(),
508 which is used by CONFIG_HARDENED_USERCOPY.
509
510config HAVE_CONTEXT_TRACKING
511 bool
512 help
513 Provide kernel/user boundaries probes necessary for subsystems
514 that need it, such as userspace RCU extended quiescent state.
515 Syscalls need to be wrapped inside user_exit()-user_enter() through
516 the slow path using TIF_NOHZ flag. Exceptions handlers must be
517 wrapped as well. Irqs are already protected inside
518 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
519 irq exit still need to be protected.
520
521config HAVE_VIRT_CPU_ACCOUNTING
522 bool
523
524config ARCH_HAS_SCALED_CPUTIME
525 bool
526
527config HAVE_VIRT_CPU_ACCOUNTING_GEN
528 bool
529 default y if 64BIT
530 help
531 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
532 Before enabling this option, arch code must be audited
533 to ensure there are no races in concurrent read/write of
534 cputime_t. For example, reading/writing 64-bit cputime_t on
535 some 32-bit arches may require multiple accesses, so proper
536 locking is needed to protect against concurrent accesses.
537
538
539config HAVE_IRQ_TIME_ACCOUNTING
540 bool
541 help
542 Archs need to ensure they use a high enough resolution clock to
543 support irq time accounting and then call enable_sched_clock_irqtime().
544
545config HAVE_ARCH_TRANSPARENT_HUGEPAGE
546 bool
547
548config HAVE_ARCH_HUGE_VMAP
549 bool
550
551config HAVE_ARCH_SOFT_DIRTY
552 bool
553
554config HAVE_MOD_ARCH_SPECIFIC
555 bool
556 help
557 The arch uses struct mod_arch_specific to store data. Many arches
558 just need a simple module loader without arch specific data - those
559 should not enable this.
560
561config MODULES_USE_ELF_RELA
562 bool
563 help
564 Modules only use ELF RELA relocations. Modules with ELF REL
565 relocations will give an error.
566
567config MODULES_USE_ELF_REL
568 bool
569 help
570 Modules only use ELF REL relocations. Modules with ELF RELA
571 relocations will give an error.
572
573config HAVE_UNDERSCORE_SYMBOL_PREFIX
574 bool
575 help
576 Some architectures generate an _ in front of C symbols; things like
577 module loading and assembly files need to know about this.
578
579config HAVE_IRQ_EXIT_ON_IRQ_STACK
580 bool
581 help
582 Architecture doesn't only execute the irq handler on the irq stack
583 but also irq_exit(). This way we can process softirqs on this irq
584 stack instead of switching to a new one when we call __do_softirq()
585 in the end of an hardirq.
586 This spares a stack switch and improves cache usage on softirq
587 processing.
588
589config PGTABLE_LEVELS
590 int
591 default 2
592
593config ARCH_HAS_ELF_RANDOMIZE
594 bool
595 help
596 An architecture supports choosing randomized locations for
597 stack, mmap, brk, and ET_DYN. Defined functions:
598 - arch_mmap_rnd()
599 - arch_randomize_brk()
600
601config HAVE_ARCH_MMAP_RND_BITS
602 bool
603 help
604 An arch should select this symbol if it supports setting a variable
605 number of bits for use in establishing the base address for mmap
606 allocations, has MMU enabled and provides values for both:
607 - ARCH_MMAP_RND_BITS_MIN
608 - ARCH_MMAP_RND_BITS_MAX
609
610config HAVE_EXIT_THREAD
611 bool
612 help
613 An architecture implements exit_thread.
614
615config ARCH_MMAP_RND_BITS_MIN
616 int
617
618config ARCH_MMAP_RND_BITS_MAX
619 int
620
621config ARCH_MMAP_RND_BITS_DEFAULT
622 int
623
624config ARCH_MMAP_RND_BITS
625 int "Number of bits to use for ASLR of mmap base address" if EXPERT
626 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
627 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
628 default ARCH_MMAP_RND_BITS_MIN
629 depends on HAVE_ARCH_MMAP_RND_BITS
630 help
631 This value can be used to select the number of bits to use to
632 determine the random offset to the base address of vma regions
633 resulting from mmap allocations. This value will be bounded
634 by the architecture's minimum and maximum supported values.
635
636 This value can be changed after boot using the
637 /proc/sys/vm/mmap_rnd_bits tunable
638
639config HAVE_ARCH_MMAP_RND_COMPAT_BITS
640 bool
641 help
642 An arch should select this symbol if it supports running applications
643 in compatibility mode, supports setting a variable number of bits for
644 use in establishing the base address for mmap allocations, has MMU
645 enabled and provides values for both:
646 - ARCH_MMAP_RND_COMPAT_BITS_MIN
647 - ARCH_MMAP_RND_COMPAT_BITS_MAX
648
649config ARCH_MMAP_RND_COMPAT_BITS_MIN
650 int
651
652config ARCH_MMAP_RND_COMPAT_BITS_MAX
653 int
654
655config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
656 int
657
658config ARCH_MMAP_RND_COMPAT_BITS
659 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
660 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
661 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
662 default ARCH_MMAP_RND_COMPAT_BITS_MIN
663 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
664 help
665 This value can be used to select the number of bits to use to
666 determine the random offset to the base address of vma regions
667 resulting from mmap allocations for compatible applications This
668 value will be bounded by the architecture's minimum and maximum
669 supported values.
670
671 This value can be changed after boot using the
672 /proc/sys/vm/mmap_rnd_compat_bits tunable
673
674config HAVE_COPY_THREAD_TLS
675 bool
676 help
677 Architecture provides copy_thread_tls to accept tls argument via
678 normal C parameter passing, rather than extracting the syscall
679 argument from pt_regs.
680
681config HAVE_STACK_VALIDATION
682 bool
683 help
684 Architecture supports the 'objtool check' host tool command, which
685 performs compile-time stack metadata validation.
686
687config HAVE_ARCH_HASH
688 bool
689 default n
690 help
691 If this is set, the architecture provides an <asm/hash.h>
692 file which provides platform-specific implementations of some
693 functions in <linux/hash.h> or fs/namei.c.
694
695config ISA_BUS_API
696 def_bool ISA
697
698#
699# ABI hall of shame
700#
701config CLONE_BACKWARDS
702 bool
703 help
704 Architecture has tls passed as the 4th argument of clone(2),
705 not the 5th one.
706
707config CLONE_BACKWARDS2
708 bool
709 help
710 Architecture has the first two arguments of clone(2) swapped.
711
712config CLONE_BACKWARDS3
713 bool
714 help
715 Architecture has tls passed as the 3rd argument of clone(2),
716 not the 5th one.
717
718config ODD_RT_SIGACTION
719 bool
720 help
721 Architecture has unusual rt_sigaction(2) arguments
722
723config OLD_SIGSUSPEND
724 bool
725 help
726 Architecture has old sigsuspend(2) syscall, of one-argument variety
727
728config OLD_SIGSUSPEND3
729 bool
730 help
731 Even weirder antique ABI - three-argument sigsuspend(2)
732
733config OLD_SIGACTION
734 bool
735 help
736 Architecture has old sigaction(2) syscall. Nope, not the same
737 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
738 but fairly different variant of sigaction(2), thanks to OSF/1
739 compatibility...
740
741config COMPAT_OLD_SIGACTION
742 bool
743
744config ARCH_NO_COHERENT_DMA_MMAP
745 bool
746
747config CPU_NO_EFFICIENT_FFS
748 def_bool n
749
750config HAVE_ARCH_VMAP_STACK
751 def_bool n
752 help
753 An arch should select this symbol if it can support kernel stacks
754 in vmalloc space. This means:
755
756 - vmalloc space must be large enough to hold many kernel stacks.
757 This may rule out many 32-bit architectures.
758
759 - Stacks in vmalloc space need to work reliably. For example, if
760 vmap page tables are created on demand, either this mechanism
761 needs to work while the stack points to a virtual address with
762 unpopulated page tables or arch code (switch_to() and switch_mm(),
763 most likely) needs to ensure that the stack's page table entries
764 are populated before running on a possibly unpopulated stack.
765
766 - If the stack overflows into a guard page, something reasonable
767 should happen. The definition of "reasonable" is flexible, but
768 instantly rebooting without logging anything would be unfriendly.
769
770config VMAP_STACK
771 default y
772 bool "Use a virtually-mapped stack"
773 depends on HAVE_ARCH_VMAP_STACK && !KASAN
774 ---help---
775 Enable this if you want the use virtually-mapped kernel stacks
776 with guard pages. This causes kernel stack overflows to be
777 caught immediately rather than causing difficult-to-diagnose
778 corruption.
779
780 This is presently incompatible with KASAN because KASAN expects
781 the stack to map directly to the KASAN shadow map using a formula
782 that is incorrect if the stack is in vmalloc space.
783
784source "kernel/gcov/Kconfig"