xref: /openbmc/linux/arch/Kconfig (revision faf7f3fd)
1# SPDX-License-Identifier: GPL-2.0
2#
3# General architecture dependent options
4#
5
6#
7# Note: arch/$(SRCARCH)/Kconfig needs to be included first so that it can
8# override the default values in this file.
9#
10source "arch/$(SRCARCH)/Kconfig"
11
12menu "General architecture-dependent options"
13
14config CRASH_CORE
15	bool
16
17config KEXEC_CORE
18	select CRASH_CORE
19	bool
20
21config KEXEC_ELF
22	bool
23
24config HAVE_IMA_KEXEC
25	bool
26
27config SET_FS
28	bool
29
30config HOTPLUG_SMT
31	bool
32
33config GENERIC_ENTRY
34       bool
35
36config OPROFILE
37	tristate "OProfile system profiling"
38	depends on PROFILING
39	depends on HAVE_OPROFILE
40	select RING_BUFFER
41	select RING_BUFFER_ALLOW_SWAP
42	help
43	  OProfile is a profiling system capable of profiling the
44	  whole system, include the kernel, kernel modules, libraries,
45	  and applications.
46
47	  If unsure, say N.
48
49config OPROFILE_EVENT_MULTIPLEX
50	bool "OProfile multiplexing support (EXPERIMENTAL)"
51	default n
52	depends on OPROFILE && X86
53	help
54	  The number of hardware counters is limited. The multiplexing
55	  feature enables OProfile to gather more events than counters
56	  are provided by the hardware. This is realized by switching
57	  between events at a user specified time interval.
58
59	  If unsure, say N.
60
61config HAVE_OPROFILE
62	bool
63
64config OPROFILE_NMI_TIMER
65	def_bool y
66	depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
67
68config KPROBES
69	bool "Kprobes"
70	depends on MODULES
71	depends on HAVE_KPROBES
72	select KALLSYMS
73	help
74	  Kprobes allows you to trap at almost any kernel address and
75	  execute a callback function.  register_kprobe() establishes
76	  a probepoint and specifies the callback.  Kprobes is useful
77	  for kernel debugging, non-intrusive instrumentation and testing.
78	  If in doubt, say "N".
79
80config JUMP_LABEL
81	bool "Optimize very unlikely/likely branches"
82	depends on HAVE_ARCH_JUMP_LABEL
83	depends on CC_HAS_ASM_GOTO
84	help
85	 This option enables a transparent branch optimization that
86	 makes certain almost-always-true or almost-always-false branch
87	 conditions even cheaper to execute within the kernel.
88
89	 Certain performance-sensitive kernel code, such as trace points,
90	 scheduler functionality, networking code and KVM have such
91	 branches and include support for this optimization technique.
92
93	 If it is detected that the compiler has support for "asm goto",
94	 the kernel will compile such branches with just a nop
95	 instruction. When the condition flag is toggled to true, the
96	 nop will be converted to a jump instruction to execute the
97	 conditional block of instructions.
98
99	 This technique lowers overhead and stress on the branch prediction
100	 of the processor and generally makes the kernel faster. The update
101	 of the condition is slower, but those are always very rare.
102
103	 ( On 32-bit x86, the necessary options added to the compiler
104	   flags may increase the size of the kernel slightly. )
105
106config STATIC_KEYS_SELFTEST
107	bool "Static key selftest"
108	depends on JUMP_LABEL
109	help
110	  Boot time self-test of the branch patching code.
111
112config STATIC_CALL_SELFTEST
113	bool "Static call selftest"
114	depends on HAVE_STATIC_CALL
115	help
116	  Boot time self-test of the call patching code.
117
118config OPTPROBES
119	def_bool y
120	depends on KPROBES && HAVE_OPTPROBES
121	select TASKS_RCU if PREEMPTION
122
123config KPROBES_ON_FTRACE
124	def_bool y
125	depends on KPROBES && HAVE_KPROBES_ON_FTRACE
126	depends on DYNAMIC_FTRACE_WITH_REGS
127	help
128	 If function tracer is enabled and the arch supports full
129	 passing of pt_regs to function tracing, then kprobes can
130	 optimize on top of function tracing.
131
132config UPROBES
133	def_bool n
134	depends on ARCH_SUPPORTS_UPROBES
135	help
136	  Uprobes is the user-space counterpart to kprobes: they
137	  enable instrumentation applications (such as 'perf probe')
138	  to establish unintrusive probes in user-space binaries and
139	  libraries, by executing handler functions when the probes
140	  are hit by user-space applications.
141
142	  ( These probes come in the form of single-byte breakpoints,
143	    managed by the kernel and kept transparent to the probed
144	    application. )
145
146config HAVE_64BIT_ALIGNED_ACCESS
147	def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
148	help
149	  Some architectures require 64 bit accesses to be 64 bit
150	  aligned, which also requires structs containing 64 bit values
151	  to be 64 bit aligned too. This includes some 32 bit
152	  architectures which can do 64 bit accesses, as well as 64 bit
153	  architectures without unaligned access.
154
155	  This symbol should be selected by an architecture if 64 bit
156	  accesses are required to be 64 bit aligned in this way even
157	  though it is not a 64 bit architecture.
158
159	  See Documentation/unaligned-memory-access.txt for more
160	  information on the topic of unaligned memory accesses.
161
162config HAVE_EFFICIENT_UNALIGNED_ACCESS
163	bool
164	help
165	  Some architectures are unable to perform unaligned accesses
166	  without the use of get_unaligned/put_unaligned. Others are
167	  unable to perform such accesses efficiently (e.g. trap on
168	  unaligned access and require fixing it up in the exception
169	  handler.)
170
171	  This symbol should be selected by an architecture if it can
172	  perform unaligned accesses efficiently to allow different
173	  code paths to be selected for these cases. Some network
174	  drivers, for example, could opt to not fix up alignment
175	  problems with received packets if doing so would not help
176	  much.
177
178	  See Documentation/core-api/unaligned-memory-access.rst for more
179	  information on the topic of unaligned memory accesses.
180
181config ARCH_USE_BUILTIN_BSWAP
182	bool
183	help
184	 Modern versions of GCC (since 4.4) have builtin functions
185	 for handling byte-swapping. Using these, instead of the old
186	 inline assembler that the architecture code provides in the
187	 __arch_bswapXX() macros, allows the compiler to see what's
188	 happening and offers more opportunity for optimisation. In
189	 particular, the compiler will be able to combine the byteswap
190	 with a nearby load or store and use load-and-swap or
191	 store-and-swap instructions if the architecture has them. It
192	 should almost *never* result in code which is worse than the
193	 hand-coded assembler in <asm/swab.h>.  But just in case it
194	 does, the use of the builtins is optional.
195
196	 Any architecture with load-and-swap or store-and-swap
197	 instructions should set this. And it shouldn't hurt to set it
198	 on architectures that don't have such instructions.
199
200config KRETPROBES
201	def_bool y
202	depends on KPROBES && HAVE_KRETPROBES
203
204config USER_RETURN_NOTIFIER
205	bool
206	depends on HAVE_USER_RETURN_NOTIFIER
207	help
208	  Provide a kernel-internal notification when a cpu is about to
209	  switch to user mode.
210
211config HAVE_IOREMAP_PROT
212	bool
213
214config HAVE_KPROBES
215	bool
216
217config HAVE_KRETPROBES
218	bool
219
220config HAVE_OPTPROBES
221	bool
222
223config HAVE_KPROBES_ON_FTRACE
224	bool
225
226config HAVE_FUNCTION_ERROR_INJECTION
227	bool
228
229config HAVE_NMI
230	bool
231
232#
233# An arch should select this if it provides all these things:
234#
235#	task_pt_regs()		in asm/processor.h or asm/ptrace.h
236#	arch_has_single_step()	if there is hardware single-step support
237#	arch_has_block_step()	if there is hardware block-step support
238#	asm/syscall.h		supplying asm-generic/syscall.h interface
239#	linux/regset.h		user_regset interfaces
240#	CORE_DUMP_USE_REGSET	#define'd in linux/elf.h
241#	TIF_SYSCALL_TRACE	calls tracehook_report_syscall_{entry,exit}
242#	TIF_NOTIFY_RESUME	calls tracehook_notify_resume()
243#	signal delivery		calls tracehook_signal_handler()
244#
245config HAVE_ARCH_TRACEHOOK
246	bool
247
248config HAVE_DMA_CONTIGUOUS
249	bool
250
251config GENERIC_SMP_IDLE_THREAD
252	bool
253
254config GENERIC_IDLE_POLL_SETUP
255	bool
256
257config ARCH_HAS_FORTIFY_SOURCE
258	bool
259	help
260	  An architecture should select this when it can successfully
261	  build and run with CONFIG_FORTIFY_SOURCE.
262
263#
264# Select if the arch provides a historic keepinit alias for the retain_initrd
265# command line option
266#
267config ARCH_HAS_KEEPINITRD
268	bool
269
270# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
271config ARCH_HAS_SET_MEMORY
272	bool
273
274# Select if arch has all set_direct_map_invalid/default() functions
275config ARCH_HAS_SET_DIRECT_MAP
276	bool
277
278#
279# Select if the architecture provides the arch_dma_set_uncached symbol to
280# either provide an uncached segment alias for a DMA allocation, or
281# to remap the page tables in place.
282#
283config ARCH_HAS_DMA_SET_UNCACHED
284	bool
285
286#
287# Select if the architectures provides the arch_dma_clear_uncached symbol
288# to undo an in-place page table remap for uncached access.
289#
290config ARCH_HAS_DMA_CLEAR_UNCACHED
291	bool
292
293# Select if arch init_task must go in the __init_task_data section
294config ARCH_TASK_STRUCT_ON_STACK
295	bool
296
297# Select if arch has its private alloc_task_struct() function
298config ARCH_TASK_STRUCT_ALLOCATOR
299	bool
300
301config HAVE_ARCH_THREAD_STRUCT_WHITELIST
302	bool
303	depends on !ARCH_TASK_STRUCT_ALLOCATOR
304	help
305	  An architecture should select this to provide hardened usercopy
306	  knowledge about what region of the thread_struct should be
307	  whitelisted for copying to userspace. Normally this is only the
308	  FPU registers. Specifically, arch_thread_struct_whitelist()
309	  should be implemented. Without this, the entire thread_struct
310	  field in task_struct will be left whitelisted.
311
312# Select if arch has its private alloc_thread_stack() function
313config ARCH_THREAD_STACK_ALLOCATOR
314	bool
315
316# Select if arch wants to size task_struct dynamically via arch_task_struct_size:
317config ARCH_WANTS_DYNAMIC_TASK_STRUCT
318	bool
319
320config ARCH_32BIT_OFF_T
321	bool
322	depends on !64BIT
323	help
324	  All new 32-bit architectures should have 64-bit off_t type on
325	  userspace side which corresponds to the loff_t kernel type. This
326	  is the requirement for modern ABIs. Some existing architectures
327	  still support 32-bit off_t. This option is enabled for all such
328	  architectures explicitly.
329
330config HAVE_ASM_MODVERSIONS
331	bool
332	help
333	  This symbol should be selected by an architecture if it provides
334	  <asm/asm-prototypes.h> to support the module versioning for symbols
335	  exported from assembly code.
336
337config HAVE_REGS_AND_STACK_ACCESS_API
338	bool
339	help
340	  This symbol should be selected by an architecture if it supports
341	  the API needed to access registers and stack entries from pt_regs,
342	  declared in asm/ptrace.h
343	  For example the kprobes-based event tracer needs this API.
344
345config HAVE_RSEQ
346	bool
347	depends on HAVE_REGS_AND_STACK_ACCESS_API
348	help
349	  This symbol should be selected by an architecture if it
350	  supports an implementation of restartable sequences.
351
352config HAVE_FUNCTION_ARG_ACCESS_API
353	bool
354	help
355	  This symbol should be selected by an architecture if it supports
356	  the API needed to access function arguments from pt_regs,
357	  declared in asm/ptrace.h
358
359config HAVE_HW_BREAKPOINT
360	bool
361	depends on PERF_EVENTS
362
363config HAVE_MIXED_BREAKPOINTS_REGS
364	bool
365	depends on HAVE_HW_BREAKPOINT
366	help
367	  Depending on the arch implementation of hardware breakpoints,
368	  some of them have separate registers for data and instruction
369	  breakpoints addresses, others have mixed registers to store
370	  them but define the access type in a control register.
371	  Select this option if your arch implements breakpoints under the
372	  latter fashion.
373
374config HAVE_USER_RETURN_NOTIFIER
375	bool
376
377config HAVE_PERF_EVENTS_NMI
378	bool
379	help
380	  System hardware can generate an NMI using the perf event
381	  subsystem.  Also has support for calculating CPU cycle events
382	  to determine how many clock cycles in a given period.
383
384config HAVE_HARDLOCKUP_DETECTOR_PERF
385	bool
386	depends on HAVE_PERF_EVENTS_NMI
387	help
388	  The arch chooses to use the generic perf-NMI-based hardlockup
389	  detector. Must define HAVE_PERF_EVENTS_NMI.
390
391config HAVE_NMI_WATCHDOG
392	depends on HAVE_NMI
393	bool
394	help
395	  The arch provides a low level NMI watchdog. It provides
396	  asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
397
398config HAVE_HARDLOCKUP_DETECTOR_ARCH
399	bool
400	select HAVE_NMI_WATCHDOG
401	help
402	  The arch chooses to provide its own hardlockup detector, which is
403	  a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
404	  interfaces and parameters provided by hardlockup detector subsystem.
405
406config HAVE_PERF_REGS
407	bool
408	help
409	  Support selective register dumps for perf events. This includes
410	  bit-mapping of each registers and a unique architecture id.
411
412config HAVE_PERF_USER_STACK_DUMP
413	bool
414	help
415	  Support user stack dumps for perf event samples. This needs
416	  access to the user stack pointer which is not unified across
417	  architectures.
418
419config HAVE_ARCH_JUMP_LABEL
420	bool
421
422config HAVE_ARCH_JUMP_LABEL_RELATIVE
423	bool
424
425config MMU_GATHER_TABLE_FREE
426	bool
427
428config MMU_GATHER_RCU_TABLE_FREE
429	bool
430	select MMU_GATHER_TABLE_FREE
431
432config MMU_GATHER_PAGE_SIZE
433	bool
434
435config MMU_GATHER_NO_RANGE
436	bool
437
438config MMU_GATHER_NO_GATHER
439	bool
440	depends on MMU_GATHER_TABLE_FREE
441
442config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
443	bool
444	help
445	  Temporary select until all architectures can be converted to have
446	  irqs disabled over activate_mm. Architectures that do IPI based TLB
447	  shootdowns should enable this.
448
449config ARCH_HAVE_NMI_SAFE_CMPXCHG
450	bool
451
452config HAVE_ALIGNED_STRUCT_PAGE
453	bool
454	help
455	  This makes sure that struct pages are double word aligned and that
456	  e.g. the SLUB allocator can perform double word atomic operations
457	  on a struct page for better performance. However selecting this
458	  might increase the size of a struct page by a word.
459
460config HAVE_CMPXCHG_LOCAL
461	bool
462
463config HAVE_CMPXCHG_DOUBLE
464	bool
465
466config ARCH_WEAK_RELEASE_ACQUIRE
467	bool
468
469config ARCH_WANT_IPC_PARSE_VERSION
470	bool
471
472config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
473	bool
474
475config ARCH_WANT_OLD_COMPAT_IPC
476	select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
477	bool
478
479config HAVE_ARCH_SECCOMP
480	bool
481	help
482	  An arch should select this symbol to support seccomp mode 1 (the fixed
483	  syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
484	  and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
485	  - __NR_seccomp_read_32
486	  - __NR_seccomp_write_32
487	  - __NR_seccomp_exit_32
488	  - __NR_seccomp_sigreturn_32
489
490config HAVE_ARCH_SECCOMP_FILTER
491	bool
492	select HAVE_ARCH_SECCOMP
493	help
494	  An arch should select this symbol if it provides all of these things:
495	  - all the requirements for HAVE_ARCH_SECCOMP
496	  - syscall_get_arch()
497	  - syscall_get_arguments()
498	  - syscall_rollback()
499	  - syscall_set_return_value()
500	  - SIGSYS siginfo_t support
501	  - secure_computing is called from a ptrace_event()-safe context
502	  - secure_computing return value is checked and a return value of -1
503	    results in the system call being skipped immediately.
504	  - seccomp syscall wired up
505	  - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE,
506	    SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If
507	    COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too.
508
509config SECCOMP
510	prompt "Enable seccomp to safely execute untrusted bytecode"
511	def_bool y
512	depends on HAVE_ARCH_SECCOMP
513	help
514	  This kernel feature is useful for number crunching applications
515	  that may need to handle untrusted bytecode during their
516	  execution. By using pipes or other transports made available
517	  to the process as file descriptors supporting the read/write
518	  syscalls, it's possible to isolate those applications in their
519	  own address space using seccomp. Once seccomp is enabled via
520	  prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
521	  disabled and the task is only allowed to execute a few safe
522	  syscalls defined by each seccomp mode.
523
524	  If unsure, say Y.
525
526config SECCOMP_FILTER
527	def_bool y
528	depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
529	help
530	  Enable tasks to build secure computing environments defined
531	  in terms of Berkeley Packet Filter programs which implement
532	  task-defined system call filtering polices.
533
534	  See Documentation/userspace-api/seccomp_filter.rst for details.
535
536config SECCOMP_CACHE_DEBUG
537	bool "Show seccomp filter cache status in /proc/pid/seccomp_cache"
538	depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR
539	depends on PROC_FS
540	help
541	  This enables the /proc/pid/seccomp_cache interface to monitor
542	  seccomp cache data. The file format is subject to change. Reading
543	  the file requires CAP_SYS_ADMIN.
544
545	  This option is for debugging only. Enabling presents the risk that
546	  an adversary may be able to infer the seccomp filter logic.
547
548	  If unsure, say N.
549
550config HAVE_ARCH_STACKLEAK
551	bool
552	help
553	  An architecture should select this if it has the code which
554	  fills the used part of the kernel stack with the STACKLEAK_POISON
555	  value before returning from system calls.
556
557config HAVE_STACKPROTECTOR
558	bool
559	help
560	  An arch should select this symbol if:
561	  - it has implemented a stack canary (e.g. __stack_chk_guard)
562
563config STACKPROTECTOR
564	bool "Stack Protector buffer overflow detection"
565	depends on HAVE_STACKPROTECTOR
566	depends on $(cc-option,-fstack-protector)
567	default y
568	help
569	  This option turns on the "stack-protector" GCC feature. This
570	  feature puts, at the beginning of functions, a canary value on
571	  the stack just before the return address, and validates
572	  the value just before actually returning.  Stack based buffer
573	  overflows (that need to overwrite this return address) now also
574	  overwrite the canary, which gets detected and the attack is then
575	  neutralized via a kernel panic.
576
577	  Functions will have the stack-protector canary logic added if they
578	  have an 8-byte or larger character array on the stack.
579
580	  This feature requires gcc version 4.2 or above, or a distribution
581	  gcc with the feature backported ("-fstack-protector").
582
583	  On an x86 "defconfig" build, this feature adds canary checks to
584	  about 3% of all kernel functions, which increases kernel code size
585	  by about 0.3%.
586
587config STACKPROTECTOR_STRONG
588	bool "Strong Stack Protector"
589	depends on STACKPROTECTOR
590	depends on $(cc-option,-fstack-protector-strong)
591	default y
592	help
593	  Functions will have the stack-protector canary logic added in any
594	  of the following conditions:
595
596	  - local variable's address used as part of the right hand side of an
597	    assignment or function argument
598	  - local variable is an array (or union containing an array),
599	    regardless of array type or length
600	  - uses register local variables
601
602	  This feature requires gcc version 4.9 or above, or a distribution
603	  gcc with the feature backported ("-fstack-protector-strong").
604
605	  On an x86 "defconfig" build, this feature adds canary checks to
606	  about 20% of all kernel functions, which increases the kernel code
607	  size by about 2%.
608
609config ARCH_SUPPORTS_SHADOW_CALL_STACK
610	bool
611	help
612	  An architecture should select this if it supports Clang's Shadow
613	  Call Stack and implements runtime support for shadow stack
614	  switching.
615
616config SHADOW_CALL_STACK
617	bool "Clang Shadow Call Stack"
618	depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK
619	depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
620	help
621	  This option enables Clang's Shadow Call Stack, which uses a
622	  shadow stack to protect function return addresses from being
623	  overwritten by an attacker. More information can be found in
624	  Clang's documentation:
625
626	    https://clang.llvm.org/docs/ShadowCallStack.html
627
628	  Note that security guarantees in the kernel differ from the
629	  ones documented for user space. The kernel must store addresses
630	  of shadow stacks in memory, which means an attacker capable of
631	  reading and writing arbitrary memory may be able to locate them
632	  and hijack control flow by modifying the stacks.
633
634config HAVE_ARCH_WITHIN_STACK_FRAMES
635	bool
636	help
637	  An architecture should select this if it can walk the kernel stack
638	  frames to determine if an object is part of either the arguments
639	  or local variables (i.e. that it excludes saved return addresses,
640	  and similar) by implementing an inline arch_within_stack_frames(),
641	  which is used by CONFIG_HARDENED_USERCOPY.
642
643config HAVE_CONTEXT_TRACKING
644	bool
645	help
646	  Provide kernel/user boundaries probes necessary for subsystems
647	  that need it, such as userspace RCU extended quiescent state.
648	  Syscalls need to be wrapped inside user_exit()-user_enter(), either
649	  optimized behind static key or through the slow path using TIF_NOHZ
650	  flag. Exceptions handlers must be wrapped as well. Irqs are already
651	  protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal
652	  handling on irq exit still need to be protected.
653
654config HAVE_CONTEXT_TRACKING_OFFSTACK
655	bool
656	help
657	  Architecture neither relies on exception_enter()/exception_exit()
658	  nor on schedule_user(). Also preempt_schedule_notrace() and
659	  preempt_schedule_irq() can't be called in a preemptible section
660	  while context tracking is CONTEXT_USER. This feature reflects a sane
661	  entry implementation where the following requirements are met on
662	  critical entry code, ie: before user_exit() or after user_enter():
663
664	  - Critical entry code isn't preemptible (or better yet:
665	    not interruptible).
666	  - No use of RCU read side critical sections, unless rcu_nmi_enter()
667	    got called.
668	  - No use of instrumentation, unless instrumentation_begin() got
669	    called.
670
671config HAVE_TIF_NOHZ
672	bool
673	help
674	  Arch relies on TIF_NOHZ and syscall slow path to implement context
675	  tracking calls to user_enter()/user_exit().
676
677config HAVE_VIRT_CPU_ACCOUNTING
678	bool
679
680config HAVE_VIRT_CPU_ACCOUNTING_IDLE
681	bool
682	help
683	  Architecture has its own way to account idle CPU time and therefore
684	  doesn't implement vtime_account_idle().
685
686config ARCH_HAS_SCALED_CPUTIME
687	bool
688
689config HAVE_VIRT_CPU_ACCOUNTING_GEN
690	bool
691	default y if 64BIT
692	help
693	  With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
694	  Before enabling this option, arch code must be audited
695	  to ensure there are no races in concurrent read/write of
696	  cputime_t. For example, reading/writing 64-bit cputime_t on
697	  some 32-bit arches may require multiple accesses, so proper
698	  locking is needed to protect against concurrent accesses.
699
700config HAVE_IRQ_TIME_ACCOUNTING
701	bool
702	help
703	  Archs need to ensure they use a high enough resolution clock to
704	  support irq time accounting and then call enable_sched_clock_irqtime().
705
706config HAVE_MOVE_PUD
707	bool
708	help
709	  Architectures that select this are able to move page tables at the
710	  PUD level. If there are only 3 page table levels, the move effectively
711	  happens at the PGD level.
712
713config HAVE_MOVE_PMD
714	bool
715	help
716	  Archs that select this are able to move page tables at the PMD level.
717
718config HAVE_ARCH_TRANSPARENT_HUGEPAGE
719	bool
720
721config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
722	bool
723
724config HAVE_ARCH_HUGE_VMAP
725	bool
726
727config ARCH_WANT_HUGE_PMD_SHARE
728	bool
729
730config HAVE_ARCH_SOFT_DIRTY
731	bool
732
733config HAVE_MOD_ARCH_SPECIFIC
734	bool
735	help
736	  The arch uses struct mod_arch_specific to store data.  Many arches
737	  just need a simple module loader without arch specific data - those
738	  should not enable this.
739
740config MODULES_USE_ELF_RELA
741	bool
742	help
743	  Modules only use ELF RELA relocations.  Modules with ELF REL
744	  relocations will give an error.
745
746config MODULES_USE_ELF_REL
747	bool
748	help
749	  Modules only use ELF REL relocations.  Modules with ELF RELA
750	  relocations will give an error.
751
752config HAVE_IRQ_EXIT_ON_IRQ_STACK
753	bool
754	help
755	  Architecture doesn't only execute the irq handler on the irq stack
756	  but also irq_exit(). This way we can process softirqs on this irq
757	  stack instead of switching to a new one when we call __do_softirq()
758	  in the end of an hardirq.
759	  This spares a stack switch and improves cache usage on softirq
760	  processing.
761
762config PGTABLE_LEVELS
763	int
764	default 2
765
766config ARCH_HAS_ELF_RANDOMIZE
767	bool
768	help
769	  An architecture supports choosing randomized locations for
770	  stack, mmap, brk, and ET_DYN. Defined functions:
771	  - arch_mmap_rnd()
772	  - arch_randomize_brk()
773
774config HAVE_ARCH_MMAP_RND_BITS
775	bool
776	help
777	  An arch should select this symbol if it supports setting a variable
778	  number of bits for use in establishing the base address for mmap
779	  allocations, has MMU enabled and provides values for both:
780	  - ARCH_MMAP_RND_BITS_MIN
781	  - ARCH_MMAP_RND_BITS_MAX
782
783config HAVE_EXIT_THREAD
784	bool
785	help
786	  An architecture implements exit_thread.
787
788config ARCH_MMAP_RND_BITS_MIN
789	int
790
791config ARCH_MMAP_RND_BITS_MAX
792	int
793
794config ARCH_MMAP_RND_BITS_DEFAULT
795	int
796
797config ARCH_MMAP_RND_BITS
798	int "Number of bits to use for ASLR of mmap base address" if EXPERT
799	range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
800	default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
801	default ARCH_MMAP_RND_BITS_MIN
802	depends on HAVE_ARCH_MMAP_RND_BITS
803	help
804	  This value can be used to select the number of bits to use to
805	  determine the random offset to the base address of vma regions
806	  resulting from mmap allocations. This value will be bounded
807	  by the architecture's minimum and maximum supported values.
808
809	  This value can be changed after boot using the
810	  /proc/sys/vm/mmap_rnd_bits tunable
811
812config HAVE_ARCH_MMAP_RND_COMPAT_BITS
813	bool
814	help
815	  An arch should select this symbol if it supports running applications
816	  in compatibility mode, supports setting a variable number of bits for
817	  use in establishing the base address for mmap allocations, has MMU
818	  enabled and provides values for both:
819	  - ARCH_MMAP_RND_COMPAT_BITS_MIN
820	  - ARCH_MMAP_RND_COMPAT_BITS_MAX
821
822config ARCH_MMAP_RND_COMPAT_BITS_MIN
823	int
824
825config ARCH_MMAP_RND_COMPAT_BITS_MAX
826	int
827
828config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
829	int
830
831config ARCH_MMAP_RND_COMPAT_BITS
832	int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
833	range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
834	default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
835	default ARCH_MMAP_RND_COMPAT_BITS_MIN
836	depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
837	help
838	  This value can be used to select the number of bits to use to
839	  determine the random offset to the base address of vma regions
840	  resulting from mmap allocations for compatible applications This
841	  value will be bounded by the architecture's minimum and maximum
842	  supported values.
843
844	  This value can be changed after boot using the
845	  /proc/sys/vm/mmap_rnd_compat_bits tunable
846
847config HAVE_ARCH_COMPAT_MMAP_BASES
848	bool
849	help
850	  This allows 64bit applications to invoke 32-bit mmap() syscall
851	  and vice-versa 32-bit applications to call 64-bit mmap().
852	  Required for applications doing different bitness syscalls.
853
854# This allows to use a set of generic functions to determine mmap base
855# address by giving priority to top-down scheme only if the process
856# is not in legacy mode (compat task, unlimited stack size or
857# sysctl_legacy_va_layout).
858# Architecture that selects this option can provide its own version of:
859# - STACK_RND_MASK
860config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
861	bool
862	depends on MMU
863	select ARCH_HAS_ELF_RANDOMIZE
864
865config HAVE_STACK_VALIDATION
866	bool
867	help
868	  Architecture supports the 'objtool check' host tool command, which
869	  performs compile-time stack metadata validation.
870
871config HAVE_RELIABLE_STACKTRACE
872	bool
873	help
874	  Architecture has either save_stack_trace_tsk_reliable() or
875	  arch_stack_walk_reliable() function which only returns a stack trace
876	  if it can guarantee the trace is reliable.
877
878config HAVE_ARCH_HASH
879	bool
880	default n
881	help
882	  If this is set, the architecture provides an <asm/hash.h>
883	  file which provides platform-specific implementations of some
884	  functions in <linux/hash.h> or fs/namei.c.
885
886config HAVE_ARCH_NVRAM_OPS
887	bool
888
889config ISA_BUS_API
890	def_bool ISA
891
892#
893# ABI hall of shame
894#
895config CLONE_BACKWARDS
896	bool
897	help
898	  Architecture has tls passed as the 4th argument of clone(2),
899	  not the 5th one.
900
901config CLONE_BACKWARDS2
902	bool
903	help
904	  Architecture has the first two arguments of clone(2) swapped.
905
906config CLONE_BACKWARDS3
907	bool
908	help
909	  Architecture has tls passed as the 3rd argument of clone(2),
910	  not the 5th one.
911
912config ODD_RT_SIGACTION
913	bool
914	help
915	  Architecture has unusual rt_sigaction(2) arguments
916
917config OLD_SIGSUSPEND
918	bool
919	help
920	  Architecture has old sigsuspend(2) syscall, of one-argument variety
921
922config OLD_SIGSUSPEND3
923	bool
924	help
925	  Even weirder antique ABI - three-argument sigsuspend(2)
926
927config OLD_SIGACTION
928	bool
929	help
930	  Architecture has old sigaction(2) syscall.  Nope, not the same
931	  as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
932	  but fairly different variant of sigaction(2), thanks to OSF/1
933	  compatibility...
934
935config COMPAT_OLD_SIGACTION
936	bool
937
938config COMPAT_32BIT_TIME
939	bool "Provide system calls for 32-bit time_t"
940	default !64BIT || COMPAT
941	help
942	  This enables 32 bit time_t support in addition to 64 bit time_t support.
943	  This is relevant on all 32-bit architectures, and 64-bit architectures
944	  as part of compat syscall handling.
945
946config ARCH_NO_PREEMPT
947	bool
948
949config ARCH_SUPPORTS_RT
950	bool
951
952config CPU_NO_EFFICIENT_FFS
953	def_bool n
954
955config HAVE_ARCH_VMAP_STACK
956	def_bool n
957	help
958	  An arch should select this symbol if it can support kernel stacks
959	  in vmalloc space.  This means:
960
961	  - vmalloc space must be large enough to hold many kernel stacks.
962	    This may rule out many 32-bit architectures.
963
964	  - Stacks in vmalloc space need to work reliably.  For example, if
965	    vmap page tables are created on demand, either this mechanism
966	    needs to work while the stack points to a virtual address with
967	    unpopulated page tables or arch code (switch_to() and switch_mm(),
968	    most likely) needs to ensure that the stack's page table entries
969	    are populated before running on a possibly unpopulated stack.
970
971	  - If the stack overflows into a guard page, something reasonable
972	    should happen.  The definition of "reasonable" is flexible, but
973	    instantly rebooting without logging anything would be unfriendly.
974
975config VMAP_STACK
976	default y
977	bool "Use a virtually-mapped stack"
978	depends on HAVE_ARCH_VMAP_STACK
979	depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC
980	help
981	  Enable this if you want the use virtually-mapped kernel stacks
982	  with guard pages.  This causes kernel stack overflows to be
983	  caught immediately rather than causing difficult-to-diagnose
984	  corruption.
985
986	  To use this with software KASAN modes, the architecture must support
987	  backing virtual mappings with real shadow memory, and KASAN_VMALLOC
988	  must be enabled.
989
990config ARCH_OPTIONAL_KERNEL_RWX
991	def_bool n
992
993config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
994	def_bool n
995
996config ARCH_HAS_STRICT_KERNEL_RWX
997	def_bool n
998
999config STRICT_KERNEL_RWX
1000	bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
1001	depends on ARCH_HAS_STRICT_KERNEL_RWX
1002	default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1003	help
1004	  If this is set, kernel text and rodata memory will be made read-only,
1005	  and non-text memory will be made non-executable. This provides
1006	  protection against certain security exploits (e.g. executing the heap
1007	  or modifying text)
1008
1009	  These features are considered standard security practice these days.
1010	  You should say Y here in almost all cases.
1011
1012config ARCH_HAS_STRICT_MODULE_RWX
1013	def_bool n
1014
1015config STRICT_MODULE_RWX
1016	bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
1017	depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
1018	default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1019	help
1020	  If this is set, module text and rodata memory will be made read-only,
1021	  and non-text memory will be made non-executable. This provides
1022	  protection against certain security exploits (e.g. writing to text)
1023
1024# select if the architecture provides an asm/dma-direct.h header
1025config ARCH_HAS_PHYS_TO_DMA
1026	bool
1027
1028config HAVE_ARCH_COMPILER_H
1029	bool
1030	help
1031	  An architecture can select this if it provides an
1032	  asm/compiler.h header that should be included after
1033	  linux/compiler-*.h in order to override macro definitions that those
1034	  headers generally provide.
1035
1036config HAVE_ARCH_PREL32_RELOCATIONS
1037	bool
1038	help
1039	  May be selected by an architecture if it supports place-relative
1040	  32-bit relocations, both in the toolchain and in the module loader,
1041	  in which case relative references can be used in special sections
1042	  for PCI fixup, initcalls etc which are only half the size on 64 bit
1043	  architectures, and don't require runtime relocation on relocatable
1044	  kernels.
1045
1046config ARCH_USE_MEMREMAP_PROT
1047	bool
1048
1049config LOCK_EVENT_COUNTS
1050	bool "Locking event counts collection"
1051	depends on DEBUG_FS
1052	help
1053	  Enable light-weight counting of various locking related events
1054	  in the system with minimal performance impact. This reduces
1055	  the chance of application behavior change because of timing
1056	  differences. The counts are reported via debugfs.
1057
1058# Select if the architecture has support for applying RELR relocations.
1059config ARCH_HAS_RELR
1060	bool
1061
1062config RELR
1063	bool "Use RELR relocation packing"
1064	depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1065	default y
1066	help
1067	  Store the kernel's dynamic relocations in the RELR relocation packing
1068	  format. Requires a compatible linker (LLD supports this feature), as
1069	  well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1070	  are compatible).
1071
1072config ARCH_HAS_MEM_ENCRYPT
1073	bool
1074
1075config HAVE_SPARSE_SYSCALL_NR
1076       bool
1077       help
1078          An architecture should select this if its syscall numbering is sparse
1079	  to save space. For example, MIPS architecture has a syscall array with
1080	  entries at 4000, 5000 and 6000 locations. This option turns on syscall
1081	  related optimizations for a given architecture.
1082
1083config ARCH_HAS_VDSO_DATA
1084	bool
1085
1086config HAVE_STATIC_CALL
1087	bool
1088
1089config HAVE_STATIC_CALL_INLINE
1090	bool
1091	depends on HAVE_STATIC_CALL
1092
1093config ARCH_WANT_LD_ORPHAN_WARN
1094	bool
1095	help
1096	  An arch should select this symbol once all linker sections are explicitly
1097	  included, size-asserted, or discarded in the linker scripts. This is
1098	  important because we never want expected sections to be placed heuristically
1099	  by the linker, since the locations of such sections can change between linker
1100	  versions.
1101
1102config HAVE_ARCH_PFN_VALID
1103	bool
1104
1105config ARCH_SUPPORTS_DEBUG_PAGEALLOC
1106	bool
1107
1108config ARCH_SPLIT_ARG64
1109	bool
1110	help
1111	   If a 32-bit architecture requires 64-bit arguments to be split into
1112	   pairs of 32-bit arguments, select this option.
1113
1114source "kernel/gcov/Kconfig"
1115
1116source "scripts/gcc-plugins/Kconfig"
1117
1118endmenu
1119