xref: /openbmc/linux/arch/Kconfig (revision 239480ab)
1#
2# General architecture dependent options
3#
4
5config CRASH_CORE
6	bool
7
8config KEXEC_CORE
9	select CRASH_CORE
10	bool
11
12config HAVE_IMA_KEXEC
13	bool
14
15config OPROFILE
16	tristate "OProfile system profiling"
17	depends on PROFILING
18	depends on HAVE_OPROFILE
19	select RING_BUFFER
20	select RING_BUFFER_ALLOW_SWAP
21	help
22	  OProfile is a profiling system capable of profiling the
23	  whole system, include the kernel, kernel modules, libraries,
24	  and applications.
25
26	  If unsure, say N.
27
28config OPROFILE_EVENT_MULTIPLEX
29	bool "OProfile multiplexing support (EXPERIMENTAL)"
30	default n
31	depends on OPROFILE && X86
32	help
33	  The number of hardware counters is limited. The multiplexing
34	  feature enables OProfile to gather more events than counters
35	  are provided by the hardware. This is realized by switching
36	  between events at a user specified time interval.
37
38	  If unsure, say N.
39
40config HAVE_OPROFILE
41	bool
42
43config OPROFILE_NMI_TIMER
44	def_bool y
45	depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
46
47config KPROBES
48	bool "Kprobes"
49	depends on MODULES
50	depends on HAVE_KPROBES
51	select KALLSYMS
52	help
53	  Kprobes allows you to trap at almost any kernel address and
54	  execute a callback function.  register_kprobe() establishes
55	  a probepoint and specifies the callback.  Kprobes is useful
56	  for kernel debugging, non-intrusive instrumentation and testing.
57	  If in doubt, say "N".
58
59config JUMP_LABEL
60       bool "Optimize very unlikely/likely branches"
61       depends on HAVE_ARCH_JUMP_LABEL
62       help
63         This option enables a transparent branch optimization that
64	 makes certain almost-always-true or almost-always-false branch
65	 conditions even cheaper to execute within the kernel.
66
67	 Certain performance-sensitive kernel code, such as trace points,
68	 scheduler functionality, networking code and KVM have such
69	 branches and include support for this optimization technique.
70
71         If it is detected that the compiler has support for "asm goto",
72	 the kernel will compile such branches with just a nop
73	 instruction. When the condition flag is toggled to true, the
74	 nop will be converted to a jump instruction to execute the
75	 conditional block of instructions.
76
77	 This technique lowers overhead and stress on the branch prediction
78	 of the processor and generally makes the kernel faster. The update
79	 of the condition is slower, but those are always very rare.
80
81	 ( On 32-bit x86, the necessary options added to the compiler
82	   flags may increase the size of the kernel slightly. )
83
84config STATIC_KEYS_SELFTEST
85	bool "Static key selftest"
86	depends on JUMP_LABEL
87	help
88	  Boot time self-test of the branch patching code.
89
90config OPTPROBES
91	def_bool y
92	depends on KPROBES && HAVE_OPTPROBES
93	depends on !PREEMPT
94
95config KPROBES_ON_FTRACE
96	def_bool y
97	depends on KPROBES && HAVE_KPROBES_ON_FTRACE
98	depends on DYNAMIC_FTRACE_WITH_REGS
99	help
100	 If function tracer is enabled and the arch supports full
101	 passing of pt_regs to function tracing, then kprobes can
102	 optimize on top of function tracing.
103
104config UPROBES
105	def_bool n
106	depends on ARCH_SUPPORTS_UPROBES
107	help
108	  Uprobes is the user-space counterpart to kprobes: they
109	  enable instrumentation applications (such as 'perf probe')
110	  to establish unintrusive probes in user-space binaries and
111	  libraries, by executing handler functions when the probes
112	  are hit by user-space applications.
113
114	  ( These probes come in the form of single-byte breakpoints,
115	    managed by the kernel and kept transparent to the probed
116	    application. )
117
118config HAVE_64BIT_ALIGNED_ACCESS
119	def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
120	help
121	  Some architectures require 64 bit accesses to be 64 bit
122	  aligned, which also requires structs containing 64 bit values
123	  to be 64 bit aligned too. This includes some 32 bit
124	  architectures which can do 64 bit accesses, as well as 64 bit
125	  architectures without unaligned access.
126
127	  This symbol should be selected by an architecture if 64 bit
128	  accesses are required to be 64 bit aligned in this way even
129	  though it is not a 64 bit architecture.
130
131	  See Documentation/unaligned-memory-access.txt for more
132	  information on the topic of unaligned memory accesses.
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_NMI
199	bool
200
201config HAVE_NMI_WATCHDOG
202	depends on HAVE_NMI
203	bool
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
229# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
230config ARCH_HAS_SET_MEMORY
231	bool
232
233# Select if arch init_task initializer is different to init/init_task.c
234config ARCH_INIT_TASK
235       bool
236
237# Select if arch has its private alloc_task_struct() function
238config ARCH_TASK_STRUCT_ALLOCATOR
239	bool
240
241# Select if arch has its private alloc_thread_stack() function
242config ARCH_THREAD_STACK_ALLOCATOR
243	bool
244
245# Select if arch wants to size task_struct dynamically via arch_task_struct_size:
246config ARCH_WANTS_DYNAMIC_TASK_STRUCT
247	bool
248
249config HAVE_REGS_AND_STACK_ACCESS_API
250	bool
251	help
252	  This symbol should be selected by an architecure if it supports
253	  the API needed to access registers and stack entries from pt_regs,
254	  declared in asm/ptrace.h
255	  For example the kprobes-based event tracer needs this API.
256
257config HAVE_CLK
258	bool
259	help
260	  The <linux/clk.h> calls support software clock gating and
261	  thus are a key power management tool on many systems.
262
263config HAVE_DMA_API_DEBUG
264	bool
265
266config HAVE_HW_BREAKPOINT
267	bool
268	depends on PERF_EVENTS
269
270config HAVE_MIXED_BREAKPOINTS_REGS
271	bool
272	depends on HAVE_HW_BREAKPOINT
273	help
274	  Depending on the arch implementation of hardware breakpoints,
275	  some of them have separate registers for data and instruction
276	  breakpoints addresses, others have mixed registers to store
277	  them but define the access type in a control register.
278	  Select this option if your arch implements breakpoints under the
279	  latter fashion.
280
281config HAVE_USER_RETURN_NOTIFIER
282	bool
283
284config HAVE_PERF_EVENTS_NMI
285	bool
286	help
287	  System hardware can generate an NMI using the perf event
288	  subsystem.  Also has support for calculating CPU cycle events
289	  to determine how many clock cycles in a given period.
290
291config HAVE_PERF_REGS
292	bool
293	help
294	  Support selective register dumps for perf events. This includes
295	  bit-mapping of each registers and a unique architecture id.
296
297config HAVE_PERF_USER_STACK_DUMP
298	bool
299	help
300	  Support user stack dumps for perf event samples. This needs
301	  access to the user stack pointer which is not unified across
302	  architectures.
303
304config HAVE_ARCH_JUMP_LABEL
305	bool
306
307config HAVE_RCU_TABLE_FREE
308	bool
309
310config ARCH_HAVE_NMI_SAFE_CMPXCHG
311	bool
312
313config HAVE_ALIGNED_STRUCT_PAGE
314	bool
315	help
316	  This makes sure that struct pages are double word aligned and that
317	  e.g. the SLUB allocator can perform double word atomic operations
318	  on a struct page for better performance. However selecting this
319	  might increase the size of a struct page by a word.
320
321config HAVE_CMPXCHG_LOCAL
322	bool
323
324config HAVE_CMPXCHG_DOUBLE
325	bool
326
327config ARCH_WEAK_RELEASE_ACQUIRE
328	bool
329
330config ARCH_WANT_IPC_PARSE_VERSION
331	bool
332
333config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
334	bool
335
336config ARCH_WANT_OLD_COMPAT_IPC
337	select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
338	bool
339
340config HAVE_ARCH_SECCOMP_FILTER
341	bool
342	help
343	  An arch should select this symbol if it provides all of these things:
344	  - syscall_get_arch()
345	  - syscall_get_arguments()
346	  - syscall_rollback()
347	  - syscall_set_return_value()
348	  - SIGSYS siginfo_t support
349	  - secure_computing is called from a ptrace_event()-safe context
350	  - secure_computing return value is checked and a return value of -1
351	    results in the system call being skipped immediately.
352	  - seccomp syscall wired up
353
354config SECCOMP_FILTER
355	def_bool y
356	depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
357	help
358	  Enable tasks to build secure computing environments defined
359	  in terms of Berkeley Packet Filter programs which implement
360	  task-defined system call filtering polices.
361
362	  See Documentation/prctl/seccomp_filter.txt for details.
363
364config HAVE_GCC_PLUGINS
365	bool
366	help
367	  An arch should select this symbol if it supports building with
368	  GCC plugins.
369
370menuconfig GCC_PLUGINS
371	bool "GCC plugins"
372	depends on HAVE_GCC_PLUGINS
373	depends on !COMPILE_TEST
374	help
375	  GCC plugins are loadable modules that provide extra features to the
376	  compiler. They are useful for runtime instrumentation and static analysis.
377
378	  See Documentation/gcc-plugins.txt for details.
379
380config GCC_PLUGIN_CYC_COMPLEXITY
381	bool "Compute the cyclomatic complexity of a function" if EXPERT
382	depends on GCC_PLUGINS
383	depends on !COMPILE_TEST
384	help
385	  The complexity M of a function's control flow graph is defined as:
386	   M = E - N + 2P
387	  where
388
389	  E = the number of edges
390	  N = the number of nodes
391	  P = the number of connected components (exit nodes).
392
393	  Enabling this plugin reports the complexity to stderr during the
394	  build. It mainly serves as a simple example of how to create a
395	  gcc plugin for the kernel.
396
397config GCC_PLUGIN_SANCOV
398	bool
399	depends on GCC_PLUGINS
400	help
401	  This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
402	  basic blocks. It supports all gcc versions with plugin support (from
403	  gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
404	  by Dmitry Vyukov <dvyukov@google.com>.
405
406config GCC_PLUGIN_LATENT_ENTROPY
407	bool "Generate some entropy during boot and runtime"
408	depends on GCC_PLUGINS
409	help
410	  By saying Y here the kernel will instrument some kernel code to
411	  extract some entropy from both original and artificially created
412	  program state.  This will help especially embedded systems where
413	  there is little 'natural' source of entropy normally.  The cost
414	  is some slowdown of the boot process (about 0.5%) and fork and
415	  irq processing.
416
417	  Note that entropy extracted this way is not cryptographically
418	  secure!
419
420	  This plugin was ported from grsecurity/PaX. More information at:
421	   * https://grsecurity.net/
422	   * https://pax.grsecurity.net/
423
424config GCC_PLUGIN_STRUCTLEAK
425	bool "Force initialization of variables containing userspace addresses"
426	depends on GCC_PLUGINS
427	help
428	  This plugin zero-initializes any structures that containing a
429	  __user attribute. This can prevent some classes of information
430	  exposures.
431
432	  This plugin was ported from grsecurity/PaX. More information at:
433	   * https://grsecurity.net/
434	   * https://pax.grsecurity.net/
435
436config GCC_PLUGIN_STRUCTLEAK_VERBOSE
437	bool "Report forcefully initialized variables"
438	depends on GCC_PLUGIN_STRUCTLEAK
439	depends on !COMPILE_TEST
440	help
441	  This option will cause a warning to be printed each time the
442	  structleak plugin finds a variable it thinks needs to be
443	  initialized. Since not all existing initializers are detected
444	  by the plugin, this can produce false positive warnings.
445
446config HAVE_CC_STACKPROTECTOR
447	bool
448	help
449	  An arch should select this symbol if:
450	  - its compiler supports the -fstack-protector option
451	  - it has implemented a stack canary (e.g. __stack_chk_guard)
452
453config CC_STACKPROTECTOR
454	def_bool n
455	help
456	  Set when a stack-protector mode is enabled, so that the build
457	  can enable kernel-side support for the GCC feature.
458
459choice
460	prompt "Stack Protector buffer overflow detection"
461	depends on HAVE_CC_STACKPROTECTOR
462	default CC_STACKPROTECTOR_NONE
463	help
464	  This option turns on the "stack-protector" GCC feature. This
465	  feature puts, at the beginning of functions, a canary value on
466	  the stack just before the return address, and validates
467	  the value just before actually returning.  Stack based buffer
468	  overflows (that need to overwrite this return address) now also
469	  overwrite the canary, which gets detected and the attack is then
470	  neutralized via a kernel panic.
471
472config CC_STACKPROTECTOR_NONE
473	bool "None"
474	help
475	  Disable "stack-protector" GCC feature.
476
477config CC_STACKPROTECTOR_REGULAR
478	bool "Regular"
479	select CC_STACKPROTECTOR
480	help
481	  Functions will have the stack-protector canary logic added if they
482	  have an 8-byte or larger character array on the stack.
483
484	  This feature requires gcc version 4.2 or above, or a distribution
485	  gcc with the feature backported ("-fstack-protector").
486
487	  On an x86 "defconfig" build, this feature adds canary checks to
488	  about 3% of all kernel functions, which increases kernel code size
489	  by about 0.3%.
490
491config CC_STACKPROTECTOR_STRONG
492	bool "Strong"
493	select CC_STACKPROTECTOR
494	help
495	  Functions will have the stack-protector canary logic added in any
496	  of the following conditions:
497
498	  - local variable's address used as part of the right hand side of an
499	    assignment or function argument
500	  - local variable is an array (or union containing an array),
501	    regardless of array type or length
502	  - uses register local variables
503
504	  This feature requires gcc version 4.9 or above, or a distribution
505	  gcc with the feature backported ("-fstack-protector-strong").
506
507	  On an x86 "defconfig" build, this feature adds canary checks to
508	  about 20% of all kernel functions, which increases the kernel code
509	  size by about 2%.
510
511endchoice
512
513config THIN_ARCHIVES
514	bool
515	help
516	  Select this if the architecture wants to use thin archives
517	  instead of ld -r to create the built-in.o files.
518
519config LD_DEAD_CODE_DATA_ELIMINATION
520	bool
521	help
522	  Select this if the architecture wants to do dead code and
523	  data elimination with the linker by compiling with
524	  -ffunction-sections -fdata-sections and linking with
525	  --gc-sections.
526
527	  This requires that the arch annotates or otherwise protects
528	  its external entry points from being discarded. Linker scripts
529	  must also merge .text.*, .data.*, and .bss.* correctly into
530	  output sections. Care must be taken not to pull in unrelated
531	  sections (e.g., '.text.init'). Typically '.' in section names
532	  is used to distinguish them from label names / C identifiers.
533
534config HAVE_ARCH_WITHIN_STACK_FRAMES
535	bool
536	help
537	  An architecture should select this if it can walk the kernel stack
538	  frames to determine if an object is part of either the arguments
539	  or local variables (i.e. that it excludes saved return addresses,
540	  and similar) by implementing an inline arch_within_stack_frames(),
541	  which is used by CONFIG_HARDENED_USERCOPY.
542
543config HAVE_CONTEXT_TRACKING
544	bool
545	help
546	  Provide kernel/user boundaries probes necessary for subsystems
547	  that need it, such as userspace RCU extended quiescent state.
548	  Syscalls need to be wrapped inside user_exit()-user_enter() through
549	  the slow path using TIF_NOHZ flag. Exceptions handlers must be
550	  wrapped as well. Irqs are already protected inside
551	  rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
552	  irq exit still need to be protected.
553
554config HAVE_VIRT_CPU_ACCOUNTING
555	bool
556
557config ARCH_HAS_SCALED_CPUTIME
558	bool
559
560config HAVE_VIRT_CPU_ACCOUNTING_GEN
561	bool
562	default y if 64BIT
563	help
564	  With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
565	  Before enabling this option, arch code must be audited
566	  to ensure there are no races in concurrent read/write of
567	  cputime_t. For example, reading/writing 64-bit cputime_t on
568	  some 32-bit arches may require multiple accesses, so proper
569	  locking is needed to protect against concurrent accesses.
570
571
572config HAVE_IRQ_TIME_ACCOUNTING
573	bool
574	help
575	  Archs need to ensure they use a high enough resolution clock to
576	  support irq time accounting and then call enable_sched_clock_irqtime().
577
578config HAVE_ARCH_TRANSPARENT_HUGEPAGE
579	bool
580
581config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
582	bool
583
584config HAVE_ARCH_HUGE_VMAP
585	bool
586
587config HAVE_ARCH_SOFT_DIRTY
588	bool
589
590config HAVE_MOD_ARCH_SPECIFIC
591	bool
592	help
593	  The arch uses struct mod_arch_specific to store data.  Many arches
594	  just need a simple module loader without arch specific data - those
595	  should not enable this.
596
597config MODULES_USE_ELF_RELA
598	bool
599	help
600	  Modules only use ELF RELA relocations.  Modules with ELF REL
601	  relocations will give an error.
602
603config MODULES_USE_ELF_REL
604	bool
605	help
606	  Modules only use ELF REL relocations.  Modules with ELF RELA
607	  relocations will give an error.
608
609config HAVE_UNDERSCORE_SYMBOL_PREFIX
610	bool
611	help
612	  Some architectures generate an _ in front of C symbols; things like
613	  module loading and assembly files need to know about this.
614
615config HAVE_IRQ_EXIT_ON_IRQ_STACK
616	bool
617	help
618	  Architecture doesn't only execute the irq handler on the irq stack
619	  but also irq_exit(). This way we can process softirqs on this irq
620	  stack instead of switching to a new one when we call __do_softirq()
621	  in the end of an hardirq.
622	  This spares a stack switch and improves cache usage on softirq
623	  processing.
624
625config PGTABLE_LEVELS
626	int
627	default 2
628
629config ARCH_HAS_ELF_RANDOMIZE
630	bool
631	help
632	  An architecture supports choosing randomized locations for
633	  stack, mmap, brk, and ET_DYN. Defined functions:
634	  - arch_mmap_rnd()
635	  - arch_randomize_brk()
636
637config HAVE_ARCH_MMAP_RND_BITS
638	bool
639	help
640	  An arch should select this symbol if it supports setting a variable
641	  number of bits for use in establishing the base address for mmap
642	  allocations, has MMU enabled and provides values for both:
643	  - ARCH_MMAP_RND_BITS_MIN
644	  - ARCH_MMAP_RND_BITS_MAX
645
646config HAVE_EXIT_THREAD
647	bool
648	help
649	  An architecture implements exit_thread.
650
651config ARCH_MMAP_RND_BITS_MIN
652	int
653
654config ARCH_MMAP_RND_BITS_MAX
655	int
656
657config ARCH_MMAP_RND_BITS_DEFAULT
658	int
659
660config ARCH_MMAP_RND_BITS
661	int "Number of bits to use for ASLR of mmap base address" if EXPERT
662	range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
663	default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
664	default ARCH_MMAP_RND_BITS_MIN
665	depends on HAVE_ARCH_MMAP_RND_BITS
666	help
667	  This value can be used to select the number of bits to use to
668	  determine the random offset to the base address of vma regions
669	  resulting from mmap allocations. This value will be bounded
670	  by the architecture's minimum and maximum supported values.
671
672	  This value can be changed after boot using the
673	  /proc/sys/vm/mmap_rnd_bits tunable
674
675config HAVE_ARCH_MMAP_RND_COMPAT_BITS
676	bool
677	help
678	  An arch should select this symbol if it supports running applications
679	  in compatibility mode, supports setting a variable number of bits for
680	  use in establishing the base address for mmap allocations, has MMU
681	  enabled and provides values for both:
682	  - ARCH_MMAP_RND_COMPAT_BITS_MIN
683	  - ARCH_MMAP_RND_COMPAT_BITS_MAX
684
685config ARCH_MMAP_RND_COMPAT_BITS_MIN
686	int
687
688config ARCH_MMAP_RND_COMPAT_BITS_MAX
689	int
690
691config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
692	int
693
694config ARCH_MMAP_RND_COMPAT_BITS
695	int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
696	range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
697	default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
698	default ARCH_MMAP_RND_COMPAT_BITS_MIN
699	depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
700	help
701	  This value can be used to select the number of bits to use to
702	  determine the random offset to the base address of vma regions
703	  resulting from mmap allocations for compatible applications This
704	  value will be bounded by the architecture's minimum and maximum
705	  supported values.
706
707	  This value can be changed after boot using the
708	  /proc/sys/vm/mmap_rnd_compat_bits tunable
709
710config HAVE_ARCH_COMPAT_MMAP_BASES
711	bool
712	help
713	  This allows 64bit applications to invoke 32-bit mmap() syscall
714	  and vice-versa 32-bit applications to call 64-bit mmap().
715	  Required for applications doing different bitness syscalls.
716
717config HAVE_COPY_THREAD_TLS
718	bool
719	help
720	  Architecture provides copy_thread_tls to accept tls argument via
721	  normal C parameter passing, rather than extracting the syscall
722	  argument from pt_regs.
723
724config HAVE_STACK_VALIDATION
725	bool
726	help
727	  Architecture supports the 'objtool check' host tool command, which
728	  performs compile-time stack metadata validation.
729
730config HAVE_RELIABLE_STACKTRACE
731	bool
732	help
733	  Architecture has a save_stack_trace_tsk_reliable() function which
734	  only returns a stack trace if it can guarantee the trace is reliable.
735
736config HAVE_ARCH_HASH
737	bool
738	default n
739	help
740	  If this is set, the architecture provides an <asm/hash.h>
741	  file which provides platform-specific implementations of some
742	  functions in <linux/hash.h> or fs/namei.c.
743
744config ISA_BUS_API
745	def_bool ISA
746
747#
748# ABI hall of shame
749#
750config CLONE_BACKWARDS
751	bool
752	help
753	  Architecture has tls passed as the 4th argument of clone(2),
754	  not the 5th one.
755
756config CLONE_BACKWARDS2
757	bool
758	help
759	  Architecture has the first two arguments of clone(2) swapped.
760
761config CLONE_BACKWARDS3
762	bool
763	help
764	  Architecture has tls passed as the 3rd argument of clone(2),
765	  not the 5th one.
766
767config ODD_RT_SIGACTION
768	bool
769	help
770	  Architecture has unusual rt_sigaction(2) arguments
771
772config OLD_SIGSUSPEND
773	bool
774	help
775	  Architecture has old sigsuspend(2) syscall, of one-argument variety
776
777config OLD_SIGSUSPEND3
778	bool
779	help
780	  Even weirder antique ABI - three-argument sigsuspend(2)
781
782config OLD_SIGACTION
783	bool
784	help
785	  Architecture has old sigaction(2) syscall.  Nope, not the same
786	  as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
787	  but fairly different variant of sigaction(2), thanks to OSF/1
788	  compatibility...
789
790config COMPAT_OLD_SIGACTION
791	bool
792
793config ARCH_NO_COHERENT_DMA_MMAP
794	bool
795
796config CPU_NO_EFFICIENT_FFS
797	def_bool n
798
799config HAVE_ARCH_VMAP_STACK
800	def_bool n
801	help
802	  An arch should select this symbol if it can support kernel stacks
803	  in vmalloc space.  This means:
804
805	  - vmalloc space must be large enough to hold many kernel stacks.
806	    This may rule out many 32-bit architectures.
807
808	  - Stacks in vmalloc space need to work reliably.  For example, if
809	    vmap page tables are created on demand, either this mechanism
810	    needs to work while the stack points to a virtual address with
811	    unpopulated page tables or arch code (switch_to() and switch_mm(),
812	    most likely) needs to ensure that the stack's page table entries
813	    are populated before running on a possibly unpopulated stack.
814
815	  - If the stack overflows into a guard page, something reasonable
816	    should happen.  The definition of "reasonable" is flexible, but
817	    instantly rebooting without logging anything would be unfriendly.
818
819config VMAP_STACK
820	default y
821	bool "Use a virtually-mapped stack"
822	depends on HAVE_ARCH_VMAP_STACK && !KASAN
823	---help---
824	  Enable this if you want the use virtually-mapped kernel stacks
825	  with guard pages.  This causes kernel stack overflows to be
826	  caught immediately rather than causing difficult-to-diagnose
827	  corruption.
828
829	  This is presently incompatible with KASAN because KASAN expects
830	  the stack to map directly to the KASAN shadow map using a formula
831	  that is incorrect if the stack is in vmalloc space.
832
833config ARCH_OPTIONAL_KERNEL_RWX
834	def_bool n
835
836config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
837	def_bool n
838
839config ARCH_HAS_STRICT_KERNEL_RWX
840	def_bool n
841
842config STRICT_KERNEL_RWX
843	bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
844	depends on ARCH_HAS_STRICT_KERNEL_RWX
845	default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
846	help
847	  If this is set, kernel text and rodata memory will be made read-only,
848	  and non-text memory will be made non-executable. This provides
849	  protection against certain security exploits (e.g. executing the heap
850	  or modifying text)
851
852	  These features are considered standard security practice these days.
853	  You should say Y here in almost all cases.
854
855config ARCH_HAS_STRICT_MODULE_RWX
856	def_bool n
857
858config STRICT_MODULE_RWX
859	bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
860	depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
861	default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
862	help
863	  If this is set, module text and rodata memory will be made read-only,
864	  and non-text memory will be made non-executable. This provides
865	  protection against certain security exploits (e.g. writing to text)
866
867config ARCH_WANT_RELAX_ORDER
868	bool
869
870source "kernel/gcov/Kconfig"
871