xref: /openbmc/linux/arch/Kconfig (revision 958ef1e3)
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 HAVE_IMA_KEXEC
22	bool
23
24config HOTPLUG_SMT
25	bool
26
27config OPROFILE
28	tristate "OProfile system profiling"
29	depends on PROFILING
30	depends on HAVE_OPROFILE
31	select RING_BUFFER
32	select RING_BUFFER_ALLOW_SWAP
33	help
34	  OProfile is a profiling system capable of profiling the
35	  whole system, include the kernel, kernel modules, libraries,
36	  and applications.
37
38	  If unsure, say N.
39
40config OPROFILE_EVENT_MULTIPLEX
41	bool "OProfile multiplexing support (EXPERIMENTAL)"
42	default n
43	depends on OPROFILE && X86
44	help
45	  The number of hardware counters is limited. The multiplexing
46	  feature enables OProfile to gather more events than counters
47	  are provided by the hardware. This is realized by switching
48	  between events at a user specified time interval.
49
50	  If unsure, say N.
51
52config HAVE_OPROFILE
53	bool
54
55config OPROFILE_NMI_TIMER
56	def_bool y
57	depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
58
59config KPROBES
60	bool "Kprobes"
61	depends on MODULES
62	depends on HAVE_KPROBES
63	select KALLSYMS
64	help
65	  Kprobes allows you to trap at almost any kernel address and
66	  execute a callback function.  register_kprobe() establishes
67	  a probepoint and specifies the callback.  Kprobes is useful
68	  for kernel debugging, non-intrusive instrumentation and testing.
69	  If in doubt, say "N".
70
71config JUMP_LABEL
72       bool "Optimize very unlikely/likely branches"
73       depends on HAVE_ARCH_JUMP_LABEL
74       help
75         This option enables a transparent branch optimization that
76	 makes certain almost-always-true or almost-always-false branch
77	 conditions even cheaper to execute within the kernel.
78
79	 Certain performance-sensitive kernel code, such as trace points,
80	 scheduler functionality, networking code and KVM have such
81	 branches and include support for this optimization technique.
82
83         If it is detected that the compiler has support for "asm goto",
84	 the kernel will compile such branches with just a nop
85	 instruction. When the condition flag is toggled to true, the
86	 nop will be converted to a jump instruction to execute the
87	 conditional block of instructions.
88
89	 This technique lowers overhead and stress on the branch prediction
90	 of the processor and generally makes the kernel faster. The update
91	 of the condition is slower, but those are always very rare.
92
93	 ( On 32-bit x86, the necessary options added to the compiler
94	   flags may increase the size of the kernel slightly. )
95
96config STATIC_KEYS_SELFTEST
97	bool "Static key selftest"
98	depends on JUMP_LABEL
99	help
100	  Boot time self-test of the branch patching code.
101
102config OPTPROBES
103	def_bool y
104	depends on KPROBES && HAVE_OPTPROBES
105	select TASKS_RCU if PREEMPT
106
107config KPROBES_ON_FTRACE
108	def_bool y
109	depends on KPROBES && HAVE_KPROBES_ON_FTRACE
110	depends on DYNAMIC_FTRACE_WITH_REGS
111	help
112	 If function tracer is enabled and the arch supports full
113	 passing of pt_regs to function tracing, then kprobes can
114	 optimize on top of function tracing.
115
116config UPROBES
117	def_bool n
118	depends on ARCH_SUPPORTS_UPROBES
119	help
120	  Uprobes is the user-space counterpart to kprobes: they
121	  enable instrumentation applications (such as 'perf probe')
122	  to establish unintrusive probes in user-space binaries and
123	  libraries, by executing handler functions when the probes
124	  are hit by user-space applications.
125
126	  ( These probes come in the form of single-byte breakpoints,
127	    managed by the kernel and kept transparent to the probed
128	    application. )
129
130config HAVE_64BIT_ALIGNED_ACCESS
131	def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
132	help
133	  Some architectures require 64 bit accesses to be 64 bit
134	  aligned, which also requires structs containing 64 bit values
135	  to be 64 bit aligned too. This includes some 32 bit
136	  architectures which can do 64 bit accesses, as well as 64 bit
137	  architectures without unaligned access.
138
139	  This symbol should be selected by an architecture if 64 bit
140	  accesses are required to be 64 bit aligned in this way even
141	  though it is not a 64 bit architecture.
142
143	  See Documentation/unaligned-memory-access.txt for more
144	  information on the topic of unaligned memory accesses.
145
146config HAVE_EFFICIENT_UNALIGNED_ACCESS
147	bool
148	help
149	  Some architectures are unable to perform unaligned accesses
150	  without the use of get_unaligned/put_unaligned. Others are
151	  unable to perform such accesses efficiently (e.g. trap on
152	  unaligned access and require fixing it up in the exception
153	  handler.)
154
155	  This symbol should be selected by an architecture if it can
156	  perform unaligned accesses efficiently to allow different
157	  code paths to be selected for these cases. Some network
158	  drivers, for example, could opt to not fix up alignment
159	  problems with received packets if doing so would not help
160	  much.
161
162	  See Documentation/unaligned-memory-access.txt for more
163	  information on the topic of unaligned memory accesses.
164
165config ARCH_USE_BUILTIN_BSWAP
166       bool
167       help
168	 Modern versions of GCC (since 4.4) have builtin functions
169	 for handling byte-swapping. Using these, instead of the old
170	 inline assembler that the architecture code provides in the
171	 __arch_bswapXX() macros, allows the compiler to see what's
172	 happening and offers more opportunity for optimisation. In
173	 particular, the compiler will be able to combine the byteswap
174	 with a nearby load or store and use load-and-swap or
175	 store-and-swap instructions if the architecture has them. It
176	 should almost *never* result in code which is worse than the
177	 hand-coded assembler in <asm/swab.h>.  But just in case it
178	 does, the use of the builtins is optional.
179
180	 Any architecture with load-and-swap or store-and-swap
181	 instructions should set this. And it shouldn't hurt to set it
182	 on architectures that don't have such instructions.
183
184config KRETPROBES
185	def_bool y
186	depends on KPROBES && HAVE_KRETPROBES
187
188config USER_RETURN_NOTIFIER
189	bool
190	depends on HAVE_USER_RETURN_NOTIFIER
191	help
192	  Provide a kernel-internal notification when a cpu is about to
193	  switch to user mode.
194
195config HAVE_IOREMAP_PROT
196	bool
197
198config HAVE_KPROBES
199	bool
200
201config HAVE_KRETPROBES
202	bool
203
204config HAVE_OPTPROBES
205	bool
206
207config HAVE_KPROBES_ON_FTRACE
208	bool
209
210config HAVE_FUNCTION_ERROR_INJECTION
211	bool
212
213config HAVE_NMI
214	bool
215
216#
217# An arch should select this if it provides all these things:
218#
219#	task_pt_regs()		in asm/processor.h or asm/ptrace.h
220#	arch_has_single_step()	if there is hardware single-step support
221#	arch_has_block_step()	if there is hardware block-step support
222#	asm/syscall.h		supplying asm-generic/syscall.h interface
223#	linux/regset.h		user_regset interfaces
224#	CORE_DUMP_USE_REGSET	#define'd in linux/elf.h
225#	TIF_SYSCALL_TRACE	calls tracehook_report_syscall_{entry,exit}
226#	TIF_NOTIFY_RESUME	calls tracehook_notify_resume()
227#	signal delivery		calls tracehook_signal_handler()
228#
229config HAVE_ARCH_TRACEHOOK
230	bool
231
232config HAVE_DMA_CONTIGUOUS
233	bool
234
235config GENERIC_SMP_IDLE_THREAD
236       bool
237
238config GENERIC_IDLE_POLL_SETUP
239       bool
240
241config ARCH_HAS_FORTIFY_SOURCE
242	bool
243	help
244	  An architecture should select this when it can successfully
245	  build and run with CONFIG_FORTIFY_SOURCE.
246
247# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
248config ARCH_HAS_SET_MEMORY
249	bool
250
251# Select if arch init_task must go in the __init_task_data section
252config ARCH_TASK_STRUCT_ON_STACK
253       bool
254
255# Select if arch has its private alloc_task_struct() function
256config ARCH_TASK_STRUCT_ALLOCATOR
257	bool
258
259config HAVE_ARCH_THREAD_STRUCT_WHITELIST
260	bool
261	depends on !ARCH_TASK_STRUCT_ALLOCATOR
262	help
263	  An architecture should select this to provide hardened usercopy
264	  knowledge about what region of the thread_struct should be
265	  whitelisted for copying to userspace. Normally this is only the
266	  FPU registers. Specifically, arch_thread_struct_whitelist()
267	  should be implemented. Without this, the entire thread_struct
268	  field in task_struct will be left whitelisted.
269
270# Select if arch has its private alloc_thread_stack() function
271config ARCH_THREAD_STACK_ALLOCATOR
272	bool
273
274# Select if arch wants to size task_struct dynamically via arch_task_struct_size:
275config ARCH_WANTS_DYNAMIC_TASK_STRUCT
276	bool
277
278config HAVE_REGS_AND_STACK_ACCESS_API
279	bool
280	help
281	  This symbol should be selected by an architecure if it supports
282	  the API needed to access registers and stack entries from pt_regs,
283	  declared in asm/ptrace.h
284	  For example the kprobes-based event tracer needs this API.
285
286config HAVE_RSEQ
287	bool
288	depends on HAVE_REGS_AND_STACK_ACCESS_API
289	help
290	  This symbol should be selected by an architecture if it
291	  supports an implementation of restartable sequences.
292
293config HAVE_FUNCTION_ARG_ACCESS_API
294	bool
295	help
296	  This symbol should be selected by an architecure if it supports
297	  the API needed to access function arguments from pt_regs,
298	  declared in asm/ptrace.h
299
300config HAVE_CLK
301	bool
302	help
303	  The <linux/clk.h> calls support software clock gating and
304	  thus are a key power management tool on many systems.
305
306config HAVE_HW_BREAKPOINT
307	bool
308	depends on PERF_EVENTS
309
310config HAVE_MIXED_BREAKPOINTS_REGS
311	bool
312	depends on HAVE_HW_BREAKPOINT
313	help
314	  Depending on the arch implementation of hardware breakpoints,
315	  some of them have separate registers for data and instruction
316	  breakpoints addresses, others have mixed registers to store
317	  them but define the access type in a control register.
318	  Select this option if your arch implements breakpoints under the
319	  latter fashion.
320
321config HAVE_USER_RETURN_NOTIFIER
322	bool
323
324config HAVE_PERF_EVENTS_NMI
325	bool
326	help
327	  System hardware can generate an NMI using the perf event
328	  subsystem.  Also has support for calculating CPU cycle events
329	  to determine how many clock cycles in a given period.
330
331config HAVE_HARDLOCKUP_DETECTOR_PERF
332	bool
333	depends on HAVE_PERF_EVENTS_NMI
334	help
335	  The arch chooses to use the generic perf-NMI-based hardlockup
336	  detector. Must define HAVE_PERF_EVENTS_NMI.
337
338config HAVE_NMI_WATCHDOG
339	depends on HAVE_NMI
340	bool
341	help
342	  The arch provides a low level NMI watchdog. It provides
343	  asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
344
345config HAVE_HARDLOCKUP_DETECTOR_ARCH
346	bool
347	select HAVE_NMI_WATCHDOG
348	help
349	  The arch chooses to provide its own hardlockup detector, which is
350	  a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
351	  interfaces and parameters provided by hardlockup detector subsystem.
352
353config HAVE_PERF_REGS
354	bool
355	help
356	  Support selective register dumps for perf events. This includes
357	  bit-mapping of each registers and a unique architecture id.
358
359config HAVE_PERF_USER_STACK_DUMP
360	bool
361	help
362	  Support user stack dumps for perf event samples. This needs
363	  access to the user stack pointer which is not unified across
364	  architectures.
365
366config HAVE_ARCH_JUMP_LABEL
367	bool
368
369config HAVE_ARCH_JUMP_LABEL_RELATIVE
370	bool
371
372config HAVE_RCU_TABLE_FREE
373	bool
374
375config HAVE_RCU_TABLE_INVALIDATE
376	bool
377
378config ARCH_HAVE_NMI_SAFE_CMPXCHG
379	bool
380
381config HAVE_ALIGNED_STRUCT_PAGE
382	bool
383	help
384	  This makes sure that struct pages are double word aligned and that
385	  e.g. the SLUB allocator can perform double word atomic operations
386	  on a struct page for better performance. However selecting this
387	  might increase the size of a struct page by a word.
388
389config HAVE_CMPXCHG_LOCAL
390	bool
391
392config HAVE_CMPXCHG_DOUBLE
393	bool
394
395config ARCH_WEAK_RELEASE_ACQUIRE
396	bool
397
398config ARCH_WANT_IPC_PARSE_VERSION
399	bool
400
401config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
402	bool
403
404config ARCH_WANT_OLD_COMPAT_IPC
405	select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
406	bool
407
408config HAVE_ARCH_SECCOMP_FILTER
409	bool
410	help
411	  An arch should select this symbol if it provides all of these things:
412	  - syscall_get_arch()
413	  - syscall_get_arguments()
414	  - syscall_rollback()
415	  - syscall_set_return_value()
416	  - SIGSYS siginfo_t support
417	  - secure_computing is called from a ptrace_event()-safe context
418	  - secure_computing return value is checked and a return value of -1
419	    results in the system call being skipped immediately.
420	  - seccomp syscall wired up
421
422config SECCOMP_FILTER
423	def_bool y
424	depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
425	help
426	  Enable tasks to build secure computing environments defined
427	  in terms of Berkeley Packet Filter programs which implement
428	  task-defined system call filtering polices.
429
430	  See Documentation/userspace-api/seccomp_filter.rst for details.
431
432config HAVE_ARCH_STACKLEAK
433	bool
434	help
435	  An architecture should select this if it has the code which
436	  fills the used part of the kernel stack with the STACKLEAK_POISON
437	  value before returning from system calls.
438
439config HAVE_STACKPROTECTOR
440	bool
441	help
442	  An arch should select this symbol if:
443	  - it has implemented a stack canary (e.g. __stack_chk_guard)
444
445config CC_HAS_STACKPROTECTOR_NONE
446	def_bool $(cc-option,-fno-stack-protector)
447
448config STACKPROTECTOR
449	bool "Stack Protector buffer overflow detection"
450	depends on HAVE_STACKPROTECTOR
451	depends on $(cc-option,-fstack-protector)
452	default y
453	help
454	  This option turns on the "stack-protector" GCC feature. This
455	  feature puts, at the beginning of functions, a canary value on
456	  the stack just before the return address, and validates
457	  the value just before actually returning.  Stack based buffer
458	  overflows (that need to overwrite this return address) now also
459	  overwrite the canary, which gets detected and the attack is then
460	  neutralized via a kernel panic.
461
462	  Functions will have the stack-protector canary logic added if they
463	  have an 8-byte or larger character array on the stack.
464
465	  This feature requires gcc version 4.2 or above, or a distribution
466	  gcc with the feature backported ("-fstack-protector").
467
468	  On an x86 "defconfig" build, this feature adds canary checks to
469	  about 3% of all kernel functions, which increases kernel code size
470	  by about 0.3%.
471
472config STACKPROTECTOR_STRONG
473	bool "Strong Stack Protector"
474	depends on STACKPROTECTOR
475	depends on $(cc-option,-fstack-protector-strong)
476	default y
477	help
478	  Functions will have the stack-protector canary logic added in any
479	  of the following conditions:
480
481	  - local variable's address used as part of the right hand side of an
482	    assignment or function argument
483	  - local variable is an array (or union containing an array),
484	    regardless of array type or length
485	  - uses register local variables
486
487	  This feature requires gcc version 4.9 or above, or a distribution
488	  gcc with the feature backported ("-fstack-protector-strong").
489
490	  On an x86 "defconfig" build, this feature adds canary checks to
491	  about 20% of all kernel functions, which increases the kernel code
492	  size by about 2%.
493
494config HAVE_ARCH_WITHIN_STACK_FRAMES
495	bool
496	help
497	  An architecture should select this if it can walk the kernel stack
498	  frames to determine if an object is part of either the arguments
499	  or local variables (i.e. that it excludes saved return addresses,
500	  and similar) by implementing an inline arch_within_stack_frames(),
501	  which is used by CONFIG_HARDENED_USERCOPY.
502
503config HAVE_CONTEXT_TRACKING
504	bool
505	help
506	  Provide kernel/user boundaries probes necessary for subsystems
507	  that need it, such as userspace RCU extended quiescent state.
508	  Syscalls need to be wrapped inside user_exit()-user_enter() through
509	  the slow path using TIF_NOHZ flag. Exceptions handlers must be
510	  wrapped as well. Irqs are already protected inside
511	  rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
512	  irq exit still need to be protected.
513
514config HAVE_VIRT_CPU_ACCOUNTING
515	bool
516
517config ARCH_HAS_SCALED_CPUTIME
518	bool
519
520config HAVE_VIRT_CPU_ACCOUNTING_GEN
521	bool
522	default y if 64BIT
523	help
524	  With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
525	  Before enabling this option, arch code must be audited
526	  to ensure there are no races in concurrent read/write of
527	  cputime_t. For example, reading/writing 64-bit cputime_t on
528	  some 32-bit arches may require multiple accesses, so proper
529	  locking is needed to protect against concurrent accesses.
530
531
532config HAVE_IRQ_TIME_ACCOUNTING
533	bool
534	help
535	  Archs need to ensure they use a high enough resolution clock to
536	  support irq time accounting and then call enable_sched_clock_irqtime().
537
538config HAVE_MOVE_PMD
539	bool
540	help
541	  Archs that select this are able to move page tables at the PMD level.
542
543config HAVE_ARCH_TRANSPARENT_HUGEPAGE
544	bool
545
546config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
547	bool
548
549config HAVE_ARCH_HUGE_VMAP
550	bool
551
552config HAVE_ARCH_SOFT_DIRTY
553	bool
554
555config HAVE_MOD_ARCH_SPECIFIC
556	bool
557	help
558	  The arch uses struct mod_arch_specific to store data.  Many arches
559	  just need a simple module loader without arch specific data - those
560	  should not enable this.
561
562config MODULES_USE_ELF_RELA
563	bool
564	help
565	  Modules only use ELF RELA relocations.  Modules with ELF REL
566	  relocations will give an error.
567
568config MODULES_USE_ELF_REL
569	bool
570	help
571	  Modules only use ELF REL relocations.  Modules with ELF RELA
572	  relocations will give an error.
573
574config HAVE_IRQ_EXIT_ON_IRQ_STACK
575	bool
576	help
577	  Architecture doesn't only execute the irq handler on the irq stack
578	  but also irq_exit(). This way we can process softirqs on this irq
579	  stack instead of switching to a new one when we call __do_softirq()
580	  in the end of an hardirq.
581	  This spares a stack switch and improves cache usage on softirq
582	  processing.
583
584config PGTABLE_LEVELS
585	int
586	default 2
587
588config ARCH_HAS_ELF_RANDOMIZE
589	bool
590	help
591	  An architecture supports choosing randomized locations for
592	  stack, mmap, brk, and ET_DYN. Defined functions:
593	  - arch_mmap_rnd()
594	  - arch_randomize_brk()
595
596config HAVE_ARCH_MMAP_RND_BITS
597	bool
598	help
599	  An arch should select this symbol if it supports setting a variable
600	  number of bits for use in establishing the base address for mmap
601	  allocations, has MMU enabled and provides values for both:
602	  - ARCH_MMAP_RND_BITS_MIN
603	  - ARCH_MMAP_RND_BITS_MAX
604
605config HAVE_EXIT_THREAD
606	bool
607	help
608	  An architecture implements exit_thread.
609
610config ARCH_MMAP_RND_BITS_MIN
611	int
612
613config ARCH_MMAP_RND_BITS_MAX
614	int
615
616config ARCH_MMAP_RND_BITS_DEFAULT
617	int
618
619config ARCH_MMAP_RND_BITS
620	int "Number of bits to use for ASLR of mmap base address" if EXPERT
621	range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
622	default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
623	default ARCH_MMAP_RND_BITS_MIN
624	depends on HAVE_ARCH_MMAP_RND_BITS
625	help
626	  This value can be used to select the number of bits to use to
627	  determine the random offset to the base address of vma regions
628	  resulting from mmap allocations. This value will be bounded
629	  by the architecture's minimum and maximum supported values.
630
631	  This value can be changed after boot using the
632	  /proc/sys/vm/mmap_rnd_bits tunable
633
634config HAVE_ARCH_MMAP_RND_COMPAT_BITS
635	bool
636	help
637	  An arch should select this symbol if it supports running applications
638	  in compatibility mode, supports setting a variable number of bits for
639	  use in establishing the base address for mmap allocations, has MMU
640	  enabled and provides values for both:
641	  - ARCH_MMAP_RND_COMPAT_BITS_MIN
642	  - ARCH_MMAP_RND_COMPAT_BITS_MAX
643
644config ARCH_MMAP_RND_COMPAT_BITS_MIN
645	int
646
647config ARCH_MMAP_RND_COMPAT_BITS_MAX
648	int
649
650config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
651	int
652
653config ARCH_MMAP_RND_COMPAT_BITS
654	int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
655	range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
656	default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
657	default ARCH_MMAP_RND_COMPAT_BITS_MIN
658	depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
659	help
660	  This value can be used to select the number of bits to use to
661	  determine the random offset to the base address of vma regions
662	  resulting from mmap allocations for compatible applications This
663	  value will be bounded by the architecture's minimum and maximum
664	  supported values.
665
666	  This value can be changed after boot using the
667	  /proc/sys/vm/mmap_rnd_compat_bits tunable
668
669config HAVE_ARCH_COMPAT_MMAP_BASES
670	bool
671	help
672	  This allows 64bit applications to invoke 32-bit mmap() syscall
673	  and vice-versa 32-bit applications to call 64-bit mmap().
674	  Required for applications doing different bitness syscalls.
675
676config HAVE_COPY_THREAD_TLS
677	bool
678	help
679	  Architecture provides copy_thread_tls to accept tls argument via
680	  normal C parameter passing, rather than extracting the syscall
681	  argument from pt_regs.
682
683config HAVE_STACK_VALIDATION
684	bool
685	help
686	  Architecture supports the 'objtool check' host tool command, which
687	  performs compile-time stack metadata validation.
688
689config HAVE_RELIABLE_STACKTRACE
690	bool
691	help
692	  Architecture has a save_stack_trace_tsk_reliable() function which
693	  only returns a stack trace if it can guarantee the trace is reliable.
694
695config HAVE_ARCH_HASH
696	bool
697	default n
698	help
699	  If this is set, the architecture provides an <asm/hash.h>
700	  file which provides platform-specific implementations of some
701	  functions in <linux/hash.h> or fs/namei.c.
702
703config ISA_BUS_API
704	def_bool ISA
705
706#
707# ABI hall of shame
708#
709config CLONE_BACKWARDS
710	bool
711	help
712	  Architecture has tls passed as the 4th argument of clone(2),
713	  not the 5th one.
714
715config CLONE_BACKWARDS2
716	bool
717	help
718	  Architecture has the first two arguments of clone(2) swapped.
719
720config CLONE_BACKWARDS3
721	bool
722	help
723	  Architecture has tls passed as the 3rd argument of clone(2),
724	  not the 5th one.
725
726config ODD_RT_SIGACTION
727	bool
728	help
729	  Architecture has unusual rt_sigaction(2) arguments
730
731config OLD_SIGSUSPEND
732	bool
733	help
734	  Architecture has old sigsuspend(2) syscall, of one-argument variety
735
736config OLD_SIGSUSPEND3
737	bool
738	help
739	  Even weirder antique ABI - three-argument sigsuspend(2)
740
741config OLD_SIGACTION
742	bool
743	help
744	  Architecture has old sigaction(2) syscall.  Nope, not the same
745	  as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
746	  but fairly different variant of sigaction(2), thanks to OSF/1
747	  compatibility...
748
749config COMPAT_OLD_SIGACTION
750	bool
751
752config 64BIT_TIME
753	def_bool ARCH_HAS_64BIT_TIME
754	help
755	  This should be selected by all architectures that need to support
756	  new system calls with a 64-bit time_t. This is relevant on all 32-bit
757	  architectures, and 64-bit architectures as part of compat syscall
758	  handling.
759
760config COMPAT_32BIT_TIME
761	def_bool (!64BIT && 64BIT_TIME) || COMPAT
762	help
763	  This enables 32 bit time_t support in addition to 64 bit time_t support.
764	  This is relevant on all 32-bit architectures, and 64-bit architectures
765	  as part of compat syscall handling.
766
767config ARCH_NO_COHERENT_DMA_MMAP
768	bool
769
770config ARCH_NO_PREEMPT
771	bool
772
773config CPU_NO_EFFICIENT_FFS
774	def_bool n
775
776config HAVE_ARCH_VMAP_STACK
777	def_bool n
778	help
779	  An arch should select this symbol if it can support kernel stacks
780	  in vmalloc space.  This means:
781
782	  - vmalloc space must be large enough to hold many kernel stacks.
783	    This may rule out many 32-bit architectures.
784
785	  - Stacks in vmalloc space need to work reliably.  For example, if
786	    vmap page tables are created on demand, either this mechanism
787	    needs to work while the stack points to a virtual address with
788	    unpopulated page tables or arch code (switch_to() and switch_mm(),
789	    most likely) needs to ensure that the stack's page table entries
790	    are populated before running on a possibly unpopulated stack.
791
792	  - If the stack overflows into a guard page, something reasonable
793	    should happen.  The definition of "reasonable" is flexible, but
794	    instantly rebooting without logging anything would be unfriendly.
795
796config VMAP_STACK
797	default y
798	bool "Use a virtually-mapped stack"
799	depends on HAVE_ARCH_VMAP_STACK && !KASAN
800	---help---
801	  Enable this if you want the use virtually-mapped kernel stacks
802	  with guard pages.  This causes kernel stack overflows to be
803	  caught immediately rather than causing difficult-to-diagnose
804	  corruption.
805
806	  This is presently incompatible with KASAN because KASAN expects
807	  the stack to map directly to the KASAN shadow map using a formula
808	  that is incorrect if the stack is in vmalloc space.
809
810config ARCH_OPTIONAL_KERNEL_RWX
811	def_bool n
812
813config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
814	def_bool n
815
816config ARCH_HAS_STRICT_KERNEL_RWX
817	def_bool n
818
819config STRICT_KERNEL_RWX
820	bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
821	depends on ARCH_HAS_STRICT_KERNEL_RWX
822	default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
823	help
824	  If this is set, kernel text and rodata memory will be made read-only,
825	  and non-text memory will be made non-executable. This provides
826	  protection against certain security exploits (e.g. executing the heap
827	  or modifying text)
828
829	  These features are considered standard security practice these days.
830	  You should say Y here in almost all cases.
831
832config ARCH_HAS_STRICT_MODULE_RWX
833	def_bool n
834
835config STRICT_MODULE_RWX
836	bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
837	depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
838	default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
839	help
840	  If this is set, module text and rodata memory will be made read-only,
841	  and non-text memory will be made non-executable. This provides
842	  protection against certain security exploits (e.g. writing to text)
843
844# select if the architecture provides an asm/dma-direct.h header
845config ARCH_HAS_PHYS_TO_DMA
846	bool
847
848config ARCH_HAS_REFCOUNT
849	bool
850	help
851	  An architecture selects this when it has implemented refcount_t
852	  using open coded assembly primitives that provide an optimized
853	  refcount_t implementation, possibly at the expense of some full
854	  refcount state checks of CONFIG_REFCOUNT_FULL=y.
855
856	  The refcount overflow check behavior, however, must be retained.
857	  Catching overflows is the primary security concern for protecting
858	  against bugs in reference counts.
859
860config REFCOUNT_FULL
861	bool "Perform full reference count validation at the expense of speed"
862	help
863	  Enabling this switches the refcounting infrastructure from a fast
864	  unchecked atomic_t implementation to a fully state checked
865	  implementation, which can be (slightly) slower but provides protections
866	  against various use-after-free conditions that can be used in
867	  security flaw exploits.
868
869config HAVE_ARCH_COMPILER_H
870	bool
871	help
872	  An architecture can select this if it provides an
873	  asm/compiler.h header that should be included after
874	  linux/compiler-*.h in order to override macro definitions that those
875	  headers generally provide.
876
877config HAVE_ARCH_PREL32_RELOCATIONS
878	bool
879	help
880	  May be selected by an architecture if it supports place-relative
881	  32-bit relocations, both in the toolchain and in the module loader,
882	  in which case relative references can be used in special sections
883	  for PCI fixup, initcalls etc which are only half the size on 64 bit
884	  architectures, and don't require runtime relocation on relocatable
885	  kernels.
886
887source "kernel/gcov/Kconfig"
888
889source "scripts/gcc-plugins/Kconfig"
890
891endmenu
892