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 KPROBES
37	bool "Kprobes"
38	depends on MODULES
39	depends on HAVE_KPROBES
40	select KALLSYMS
41	help
42	  Kprobes allows you to trap at almost any kernel address and
43	  execute a callback function.  register_kprobe() establishes
44	  a probepoint and specifies the callback.  Kprobes is useful
45	  for kernel debugging, non-intrusive instrumentation and testing.
46	  If in doubt, say "N".
47
48config JUMP_LABEL
49	bool "Optimize very unlikely/likely branches"
50	depends on HAVE_ARCH_JUMP_LABEL
51	depends on CC_HAS_ASM_GOTO
52	help
53	 This option enables a transparent branch optimization that
54	 makes certain almost-always-true or almost-always-false branch
55	 conditions even cheaper to execute within the kernel.
56
57	 Certain performance-sensitive kernel code, such as trace points,
58	 scheduler functionality, networking code and KVM have such
59	 branches and include support for this optimization technique.
60
61	 If it is detected that the compiler has support for "asm goto",
62	 the kernel will compile such branches with just a nop
63	 instruction. When the condition flag is toggled to true, the
64	 nop will be converted to a jump instruction to execute the
65	 conditional block of instructions.
66
67	 This technique lowers overhead and stress on the branch prediction
68	 of the processor and generally makes the kernel faster. The update
69	 of the condition is slower, but those are always very rare.
70
71	 ( On 32-bit x86, the necessary options added to the compiler
72	   flags may increase the size of the kernel slightly. )
73
74config STATIC_KEYS_SELFTEST
75	bool "Static key selftest"
76	depends on JUMP_LABEL
77	help
78	  Boot time self-test of the branch patching code.
79
80config STATIC_CALL_SELFTEST
81	bool "Static call selftest"
82	depends on HAVE_STATIC_CALL
83	help
84	  Boot time self-test of the call patching code.
85
86config OPTPROBES
87	def_bool y
88	depends on KPROBES && HAVE_OPTPROBES
89	select TASKS_RCU if PREEMPTION
90
91config KPROBES_ON_FTRACE
92	def_bool y
93	depends on KPROBES && HAVE_KPROBES_ON_FTRACE
94	depends on DYNAMIC_FTRACE_WITH_REGS
95	help
96	 If function tracer is enabled and the arch supports full
97	 passing of pt_regs to function tracing, then kprobes can
98	 optimize on top of function tracing.
99
100config UPROBES
101	def_bool n
102	depends on ARCH_SUPPORTS_UPROBES
103	help
104	  Uprobes is the user-space counterpart to kprobes: they
105	  enable instrumentation applications (such as 'perf probe')
106	  to establish unintrusive probes in user-space binaries and
107	  libraries, by executing handler functions when the probes
108	  are hit by user-space applications.
109
110	  ( These probes come in the form of single-byte breakpoints,
111	    managed by the kernel and kept transparent to the probed
112	    application. )
113
114config HAVE_64BIT_ALIGNED_ACCESS
115	def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
116	help
117	  Some architectures require 64 bit accesses to be 64 bit
118	  aligned, which also requires structs containing 64 bit values
119	  to be 64 bit aligned too. This includes some 32 bit
120	  architectures which can do 64 bit accesses, as well as 64 bit
121	  architectures without unaligned access.
122
123	  This symbol should be selected by an architecture if 64 bit
124	  accesses are required to be 64 bit aligned in this way even
125	  though it is not a 64 bit architecture.
126
127	  See Documentation/core-api/unaligned-memory-access.rst for
128	  more information on the topic of unaligned memory accesses.
129
130config HAVE_EFFICIENT_UNALIGNED_ACCESS
131	bool
132	help
133	  Some architectures are unable to perform unaligned accesses
134	  without the use of get_unaligned/put_unaligned. Others are
135	  unable to perform such accesses efficiently (e.g. trap on
136	  unaligned access and require fixing it up in the exception
137	  handler.)
138
139	  This symbol should be selected by an architecture if it can
140	  perform unaligned accesses efficiently to allow different
141	  code paths to be selected for these cases. Some network
142	  drivers, for example, could opt to not fix up alignment
143	  problems with received packets if doing so would not help
144	  much.
145
146	  See Documentation/core-api/unaligned-memory-access.rst for more
147	  information on the topic of unaligned memory accesses.
148
149config ARCH_USE_BUILTIN_BSWAP
150	bool
151	help
152	 Modern versions of GCC (since 4.4) have builtin functions
153	 for handling byte-swapping. Using these, instead of the old
154	 inline assembler that the architecture code provides in the
155	 __arch_bswapXX() macros, allows the compiler to see what's
156	 happening and offers more opportunity for optimisation. In
157	 particular, the compiler will be able to combine the byteswap
158	 with a nearby load or store and use load-and-swap or
159	 store-and-swap instructions if the architecture has them. It
160	 should almost *never* result in code which is worse than the
161	 hand-coded assembler in <asm/swab.h>.  But just in case it
162	 does, the use of the builtins is optional.
163
164	 Any architecture with load-and-swap or store-and-swap
165	 instructions should set this. And it shouldn't hurt to set it
166	 on architectures that don't have such instructions.
167
168config KRETPROBES
169	def_bool y
170	depends on KPROBES && HAVE_KRETPROBES
171
172config USER_RETURN_NOTIFIER
173	bool
174	depends on HAVE_USER_RETURN_NOTIFIER
175	help
176	  Provide a kernel-internal notification when a cpu is about to
177	  switch to user mode.
178
179config HAVE_IOREMAP_PROT
180	bool
181
182config HAVE_KPROBES
183	bool
184
185config HAVE_KRETPROBES
186	bool
187
188config HAVE_OPTPROBES
189	bool
190
191config HAVE_KPROBES_ON_FTRACE
192	bool
193
194config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
195	bool
196	help
197	  Since kretprobes modifies return address on the stack, the
198	  stacktrace may see the kretprobe trampoline address instead
199	  of correct one. If the architecture stacktrace code and
200	  unwinder can adjust such entries, select this configuration.
201
202config HAVE_FUNCTION_ERROR_INJECTION
203	bool
204
205config HAVE_NMI
206	bool
207
208config TRACE_IRQFLAGS_SUPPORT
209	bool
210
211#
212# An arch should select this if it provides all these things:
213#
214#	task_pt_regs()		in asm/processor.h or asm/ptrace.h
215#	arch_has_single_step()	if there is hardware single-step support
216#	arch_has_block_step()	if there is hardware block-step support
217#	asm/syscall.h		supplying asm-generic/syscall.h interface
218#	linux/regset.h		user_regset interfaces
219#	CORE_DUMP_USE_REGSET	#define'd in linux/elf.h
220#	TIF_SYSCALL_TRACE	calls tracehook_report_syscall_{entry,exit}
221#	TIF_NOTIFY_RESUME	calls tracehook_notify_resume()
222#	signal delivery		calls tracehook_signal_handler()
223#
224config HAVE_ARCH_TRACEHOOK
225	bool
226
227config HAVE_DMA_CONTIGUOUS
228	bool
229
230config GENERIC_SMP_IDLE_THREAD
231	bool
232
233config GENERIC_IDLE_POLL_SETUP
234	bool
235
236config ARCH_HAS_FORTIFY_SOURCE
237	bool
238	help
239	  An architecture should select this when it can successfully
240	  build and run with CONFIG_FORTIFY_SOURCE.
241
242#
243# Select if the arch provides a historic keepinit alias for the retain_initrd
244# command line option
245#
246config ARCH_HAS_KEEPINITRD
247	bool
248
249# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
250config ARCH_HAS_SET_MEMORY
251	bool
252
253# Select if arch has all set_direct_map_invalid/default() functions
254config ARCH_HAS_SET_DIRECT_MAP
255	bool
256
257#
258# Select if the architecture provides the arch_dma_set_uncached symbol to
259# either provide an uncached segment alias for a DMA allocation, or
260# to remap the page tables in place.
261#
262config ARCH_HAS_DMA_SET_UNCACHED
263	bool
264
265#
266# Select if the architectures provides the arch_dma_clear_uncached symbol
267# to undo an in-place page table remap for uncached access.
268#
269config ARCH_HAS_DMA_CLEAR_UNCACHED
270	bool
271
272# Select if arch init_task must go in the __init_task_data section
273config ARCH_TASK_STRUCT_ON_STACK
274	bool
275
276# Select if arch has its private alloc_task_struct() function
277config ARCH_TASK_STRUCT_ALLOCATOR
278	bool
279
280config HAVE_ARCH_THREAD_STRUCT_WHITELIST
281	bool
282	depends on !ARCH_TASK_STRUCT_ALLOCATOR
283	help
284	  An architecture should select this to provide hardened usercopy
285	  knowledge about what region of the thread_struct should be
286	  whitelisted for copying to userspace. Normally this is only the
287	  FPU registers. Specifically, arch_thread_struct_whitelist()
288	  should be implemented. Without this, the entire thread_struct
289	  field in task_struct will be left whitelisted.
290
291# Select if arch has its private alloc_thread_stack() function
292config ARCH_THREAD_STACK_ALLOCATOR
293	bool
294
295# Select if arch wants to size task_struct dynamically via arch_task_struct_size:
296config ARCH_WANTS_DYNAMIC_TASK_STRUCT
297	bool
298
299config ARCH_WANTS_NO_INSTR
300	bool
301	help
302	  An architecture should select this if the noinstr macro is being used on
303	  functions to denote that the toolchain should avoid instrumenting such
304	  functions and is required for correctness.
305
306config ARCH_32BIT_OFF_T
307	bool
308	depends on !64BIT
309	help
310	  All new 32-bit architectures should have 64-bit off_t type on
311	  userspace side which corresponds to the loff_t kernel type. This
312	  is the requirement for modern ABIs. Some existing architectures
313	  still support 32-bit off_t. This option is enabled for all such
314	  architectures explicitly.
315
316# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat
317config ARCH_32BIT_USTAT_F_TINODE
318	bool
319
320config HAVE_ASM_MODVERSIONS
321	bool
322	help
323	  This symbol should be selected by an architecture if it provides
324	  <asm/asm-prototypes.h> to support the module versioning for symbols
325	  exported from assembly code.
326
327config HAVE_REGS_AND_STACK_ACCESS_API
328	bool
329	help
330	  This symbol should be selected by an architecture if it supports
331	  the API needed to access registers and stack entries from pt_regs,
332	  declared in asm/ptrace.h
333	  For example the kprobes-based event tracer needs this API.
334
335config HAVE_RSEQ
336	bool
337	depends on HAVE_REGS_AND_STACK_ACCESS_API
338	help
339	  This symbol should be selected by an architecture if it
340	  supports an implementation of restartable sequences.
341
342config HAVE_FUNCTION_ARG_ACCESS_API
343	bool
344	help
345	  This symbol should be selected by an architecture if it supports
346	  the API needed to access function arguments from pt_regs,
347	  declared in asm/ptrace.h
348
349config HAVE_HW_BREAKPOINT
350	bool
351	depends on PERF_EVENTS
352
353config HAVE_MIXED_BREAKPOINTS_REGS
354	bool
355	depends on HAVE_HW_BREAKPOINT
356	help
357	  Depending on the arch implementation of hardware breakpoints,
358	  some of them have separate registers for data and instruction
359	  breakpoints addresses, others have mixed registers to store
360	  them but define the access type in a control register.
361	  Select this option if your arch implements breakpoints under the
362	  latter fashion.
363
364config HAVE_USER_RETURN_NOTIFIER
365	bool
366
367config HAVE_PERF_EVENTS_NMI
368	bool
369	help
370	  System hardware can generate an NMI using the perf event
371	  subsystem.  Also has support for calculating CPU cycle events
372	  to determine how many clock cycles in a given period.
373
374config HAVE_HARDLOCKUP_DETECTOR_PERF
375	bool
376	depends on HAVE_PERF_EVENTS_NMI
377	help
378	  The arch chooses to use the generic perf-NMI-based hardlockup
379	  detector. Must define HAVE_PERF_EVENTS_NMI.
380
381config HAVE_NMI_WATCHDOG
382	depends on HAVE_NMI
383	bool
384	help
385	  The arch provides a low level NMI watchdog. It provides
386	  asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
387
388config HAVE_HARDLOCKUP_DETECTOR_ARCH
389	bool
390	select HAVE_NMI_WATCHDOG
391	help
392	  The arch chooses to provide its own hardlockup detector, which is
393	  a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
394	  interfaces and parameters provided by hardlockup detector subsystem.
395
396config HAVE_PERF_REGS
397	bool
398	help
399	  Support selective register dumps for perf events. This includes
400	  bit-mapping of each registers and a unique architecture id.
401
402config HAVE_PERF_USER_STACK_DUMP
403	bool
404	help
405	  Support user stack dumps for perf event samples. This needs
406	  access to the user stack pointer which is not unified across
407	  architectures.
408
409config HAVE_ARCH_JUMP_LABEL
410	bool
411
412config HAVE_ARCH_JUMP_LABEL_RELATIVE
413	bool
414
415config MMU_GATHER_TABLE_FREE
416	bool
417
418config MMU_GATHER_RCU_TABLE_FREE
419	bool
420	select MMU_GATHER_TABLE_FREE
421
422config MMU_GATHER_PAGE_SIZE
423	bool
424
425config MMU_GATHER_NO_RANGE
426	bool
427
428config MMU_GATHER_NO_GATHER
429	bool
430	depends on MMU_GATHER_TABLE_FREE
431
432config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
433	bool
434	help
435	  Temporary select until all architectures can be converted to have
436	  irqs disabled over activate_mm. Architectures that do IPI based TLB
437	  shootdowns should enable this.
438
439config ARCH_HAVE_NMI_SAFE_CMPXCHG
440	bool
441
442config HAVE_ALIGNED_STRUCT_PAGE
443	bool
444	help
445	  This makes sure that struct pages are double word aligned and that
446	  e.g. the SLUB allocator can perform double word atomic operations
447	  on a struct page for better performance. However selecting this
448	  might increase the size of a struct page by a word.
449
450config HAVE_CMPXCHG_LOCAL
451	bool
452
453config HAVE_CMPXCHG_DOUBLE
454	bool
455
456config ARCH_WEAK_RELEASE_ACQUIRE
457	bool
458
459config ARCH_WANT_IPC_PARSE_VERSION
460	bool
461
462config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
463	bool
464
465config ARCH_WANT_OLD_COMPAT_IPC
466	select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
467	bool
468
469config HAVE_ARCH_SECCOMP
470	bool
471	help
472	  An arch should select this symbol to support seccomp mode 1 (the fixed
473	  syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
474	  and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
475	  - __NR_seccomp_read_32
476	  - __NR_seccomp_write_32
477	  - __NR_seccomp_exit_32
478	  - __NR_seccomp_sigreturn_32
479
480config HAVE_ARCH_SECCOMP_FILTER
481	bool
482	select HAVE_ARCH_SECCOMP
483	help
484	  An arch should select this symbol if it provides all of these things:
485	  - all the requirements for HAVE_ARCH_SECCOMP
486	  - syscall_get_arch()
487	  - syscall_get_arguments()
488	  - syscall_rollback()
489	  - syscall_set_return_value()
490	  - SIGSYS siginfo_t support
491	  - secure_computing is called from a ptrace_event()-safe context
492	  - secure_computing return value is checked and a return value of -1
493	    results in the system call being skipped immediately.
494	  - seccomp syscall wired up
495	  - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE,
496	    SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If
497	    COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too.
498
499config SECCOMP
500	prompt "Enable seccomp to safely execute untrusted bytecode"
501	def_bool y
502	depends on HAVE_ARCH_SECCOMP
503	help
504	  This kernel feature is useful for number crunching applications
505	  that may need to handle untrusted bytecode during their
506	  execution. By using pipes or other transports made available
507	  to the process as file descriptors supporting the read/write
508	  syscalls, it's possible to isolate those applications in their
509	  own address space using seccomp. Once seccomp is enabled via
510	  prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
511	  disabled and the task is only allowed to execute a few safe
512	  syscalls defined by each seccomp mode.
513
514	  If unsure, say Y.
515
516config SECCOMP_FILTER
517	def_bool y
518	depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
519	help
520	  Enable tasks to build secure computing environments defined
521	  in terms of Berkeley Packet Filter programs which implement
522	  task-defined system call filtering polices.
523
524	  See Documentation/userspace-api/seccomp_filter.rst for details.
525
526config SECCOMP_CACHE_DEBUG
527	bool "Show seccomp filter cache status in /proc/pid/seccomp_cache"
528	depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR
529	depends on PROC_FS
530	help
531	  This enables the /proc/pid/seccomp_cache interface to monitor
532	  seccomp cache data. The file format is subject to change. Reading
533	  the file requires CAP_SYS_ADMIN.
534
535	  This option is for debugging only. Enabling presents the risk that
536	  an adversary may be able to infer the seccomp filter logic.
537
538	  If unsure, say N.
539
540config HAVE_ARCH_STACKLEAK
541	bool
542	help
543	  An architecture should select this if it has the code which
544	  fills the used part of the kernel stack with the STACKLEAK_POISON
545	  value before returning from system calls.
546
547config HAVE_STACKPROTECTOR
548	bool
549	help
550	  An arch should select this symbol if:
551	  - it has implemented a stack canary (e.g. __stack_chk_guard)
552
553config STACKPROTECTOR
554	bool "Stack Protector buffer overflow detection"
555	depends on HAVE_STACKPROTECTOR
556	depends on $(cc-option,-fstack-protector)
557	default y
558	help
559	  This option turns on the "stack-protector" GCC feature. This
560	  feature puts, at the beginning of functions, a canary value on
561	  the stack just before the return address, and validates
562	  the value just before actually returning.  Stack based buffer
563	  overflows (that need to overwrite this return address) now also
564	  overwrite the canary, which gets detected and the attack is then
565	  neutralized via a kernel panic.
566
567	  Functions will have the stack-protector canary logic added if they
568	  have an 8-byte or larger character array on the stack.
569
570	  This feature requires gcc version 4.2 or above, or a distribution
571	  gcc with the feature backported ("-fstack-protector").
572
573	  On an x86 "defconfig" build, this feature adds canary checks to
574	  about 3% of all kernel functions, which increases kernel code size
575	  by about 0.3%.
576
577config STACKPROTECTOR_STRONG
578	bool "Strong Stack Protector"
579	depends on STACKPROTECTOR
580	depends on $(cc-option,-fstack-protector-strong)
581	default y
582	help
583	  Functions will have the stack-protector canary logic added in any
584	  of the following conditions:
585
586	  - local variable's address used as part of the right hand side of an
587	    assignment or function argument
588	  - local variable is an array (or union containing an array),
589	    regardless of array type or length
590	  - uses register local variables
591
592	  This feature requires gcc version 4.9 or above, or a distribution
593	  gcc with the feature backported ("-fstack-protector-strong").
594
595	  On an x86 "defconfig" build, this feature adds canary checks to
596	  about 20% of all kernel functions, which increases the kernel code
597	  size by about 2%.
598
599config ARCH_SUPPORTS_SHADOW_CALL_STACK
600	bool
601	help
602	  An architecture should select this if it supports Clang's Shadow
603	  Call Stack and implements runtime support for shadow stack
604	  switching.
605
606config SHADOW_CALL_STACK
607	bool "Clang Shadow Call Stack"
608	depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK
609	depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
610	help
611	  This option enables Clang's Shadow Call Stack, which uses a
612	  shadow stack to protect function return addresses from being
613	  overwritten by an attacker. More information can be found in
614	  Clang's documentation:
615
616	    https://clang.llvm.org/docs/ShadowCallStack.html
617
618	  Note that security guarantees in the kernel differ from the
619	  ones documented for user space. The kernel must store addresses
620	  of shadow stacks in memory, which means an attacker capable of
621	  reading and writing arbitrary memory may be able to locate them
622	  and hijack control flow by modifying the stacks.
623
624config LTO
625	bool
626	help
627	  Selected if the kernel will be built using the compiler's LTO feature.
628
629config LTO_CLANG
630	bool
631	select LTO
632	help
633	  Selected if the kernel will be built using Clang's LTO feature.
634
635config ARCH_SUPPORTS_LTO_CLANG
636	bool
637	help
638	  An architecture should select this option if it supports:
639	  - compiling with Clang,
640	  - compiling inline assembly with Clang's integrated assembler,
641	  - and linking with LLD.
642
643config ARCH_SUPPORTS_LTO_CLANG_THIN
644	bool
645	help
646	  An architecture should select this option if it can support Clang's
647	  ThinLTO mode.
648
649config HAS_LTO_CLANG
650	def_bool y
651	# Clang >= 11: https://github.com/ClangBuiltLinux/linux/issues/510
652	depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD && AS_IS_LLVM
653	depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
654	depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
655	depends on ARCH_SUPPORTS_LTO_CLANG
656	depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT
657	depends on !KASAN || KASAN_HW_TAGS
658	depends on !GCOV_KERNEL
659	help
660	  The compiler and Kconfig options support building with Clang's
661	  LTO.
662
663choice
664	prompt "Link Time Optimization (LTO)"
665	default LTO_NONE
666	help
667	  This option enables Link Time Optimization (LTO), which allows the
668	  compiler to optimize binaries globally.
669
670	  If unsure, select LTO_NONE. Note that LTO is very resource-intensive
671	  so it's disabled by default.
672
673config LTO_NONE
674	bool "None"
675	help
676	  Build the kernel normally, without Link Time Optimization (LTO).
677
678config LTO_CLANG_FULL
679	bool "Clang Full LTO (EXPERIMENTAL)"
680	depends on HAS_LTO_CLANG
681	depends on !COMPILE_TEST
682	select LTO_CLANG
683	help
684          This option enables Clang's full Link Time Optimization (LTO), which
685          allows the compiler to optimize the kernel globally. If you enable
686          this option, the compiler generates LLVM bitcode instead of ELF
687          object files, and the actual compilation from bitcode happens at
688          the LTO link step, which may take several minutes depending on the
689          kernel configuration. More information can be found from LLVM's
690          documentation:
691
692	    https://llvm.org/docs/LinkTimeOptimization.html
693
694	  During link time, this option can use a large amount of RAM, and
695	  may take much longer than the ThinLTO option.
696
697config LTO_CLANG_THIN
698	bool "Clang ThinLTO (EXPERIMENTAL)"
699	depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN
700	select LTO_CLANG
701	help
702	  This option enables Clang's ThinLTO, which allows for parallel
703	  optimization and faster incremental compiles compared to the
704	  CONFIG_LTO_CLANG_FULL option. More information can be found
705	  from Clang's documentation:
706
707	    https://clang.llvm.org/docs/ThinLTO.html
708
709	  If unsure, say Y.
710endchoice
711
712config ARCH_SUPPORTS_CFI_CLANG
713	bool
714	help
715	  An architecture should select this option if it can support Clang's
716	  Control-Flow Integrity (CFI) checking.
717
718config CFI_CLANG
719	bool "Use Clang's Control Flow Integrity (CFI)"
720	depends on LTO_CLANG && ARCH_SUPPORTS_CFI_CLANG
721	# Clang >= 12:
722	# - https://bugs.llvm.org/show_bug.cgi?id=46258
723	# - https://bugs.llvm.org/show_bug.cgi?id=47479
724	depends on CLANG_VERSION >= 120000
725	select KALLSYMS
726	help
727	  This option enables Clang’s forward-edge Control Flow Integrity
728	  (CFI) checking, where the compiler injects a runtime check to each
729	  indirect function call to ensure the target is a valid function with
730	  the correct static type. This restricts possible call targets and
731	  makes it more difficult for an attacker to exploit bugs that allow
732	  the modification of stored function pointers. More information can be
733	  found from Clang's documentation:
734
735	    https://clang.llvm.org/docs/ControlFlowIntegrity.html
736
737config CFI_CLANG_SHADOW
738	bool "Use CFI shadow to speed up cross-module checks"
739	default y
740	depends on CFI_CLANG && MODULES
741	help
742	  If you select this option, the kernel builds a fast look-up table of
743	  CFI check functions in loaded modules to reduce performance overhead.
744
745	  If unsure, say Y.
746
747config CFI_PERMISSIVE
748	bool "Use CFI in permissive mode"
749	depends on CFI_CLANG
750	help
751	  When selected, Control Flow Integrity (CFI) violations result in a
752	  warning instead of a kernel panic. This option should only be used
753	  for finding indirect call type mismatches during development.
754
755	  If unsure, say N.
756
757config HAVE_ARCH_WITHIN_STACK_FRAMES
758	bool
759	help
760	  An architecture should select this if it can walk the kernel stack
761	  frames to determine if an object is part of either the arguments
762	  or local variables (i.e. that it excludes saved return addresses,
763	  and similar) by implementing an inline arch_within_stack_frames(),
764	  which is used by CONFIG_HARDENED_USERCOPY.
765
766config HAVE_CONTEXT_TRACKING
767	bool
768	help
769	  Provide kernel/user boundaries probes necessary for subsystems
770	  that need it, such as userspace RCU extended quiescent state.
771	  Syscalls need to be wrapped inside user_exit()-user_enter(), either
772	  optimized behind static key or through the slow path using TIF_NOHZ
773	  flag. Exceptions handlers must be wrapped as well. Irqs are already
774	  protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal
775	  handling on irq exit still need to be protected.
776
777config HAVE_CONTEXT_TRACKING_OFFSTACK
778	bool
779	help
780	  Architecture neither relies on exception_enter()/exception_exit()
781	  nor on schedule_user(). Also preempt_schedule_notrace() and
782	  preempt_schedule_irq() can't be called in a preemptible section
783	  while context tracking is CONTEXT_USER. This feature reflects a sane
784	  entry implementation where the following requirements are met on
785	  critical entry code, ie: before user_exit() or after user_enter():
786
787	  - Critical entry code isn't preemptible (or better yet:
788	    not interruptible).
789	  - No use of RCU read side critical sections, unless rcu_nmi_enter()
790	    got called.
791	  - No use of instrumentation, unless instrumentation_begin() got
792	    called.
793
794config HAVE_TIF_NOHZ
795	bool
796	help
797	  Arch relies on TIF_NOHZ and syscall slow path to implement context
798	  tracking calls to user_enter()/user_exit().
799
800config HAVE_VIRT_CPU_ACCOUNTING
801	bool
802
803config HAVE_VIRT_CPU_ACCOUNTING_IDLE
804	bool
805	help
806	  Architecture has its own way to account idle CPU time and therefore
807	  doesn't implement vtime_account_idle().
808
809config ARCH_HAS_SCALED_CPUTIME
810	bool
811
812config HAVE_VIRT_CPU_ACCOUNTING_GEN
813	bool
814	default y if 64BIT
815	help
816	  With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
817	  Before enabling this option, arch code must be audited
818	  to ensure there are no races in concurrent read/write of
819	  cputime_t. For example, reading/writing 64-bit cputime_t on
820	  some 32-bit arches may require multiple accesses, so proper
821	  locking is needed to protect against concurrent accesses.
822
823config HAVE_IRQ_TIME_ACCOUNTING
824	bool
825	help
826	  Archs need to ensure they use a high enough resolution clock to
827	  support irq time accounting and then call enable_sched_clock_irqtime().
828
829config HAVE_MOVE_PUD
830	bool
831	help
832	  Architectures that select this are able to move page tables at the
833	  PUD level. If there are only 3 page table levels, the move effectively
834	  happens at the PGD level.
835
836config HAVE_MOVE_PMD
837	bool
838	help
839	  Archs that select this are able to move page tables at the PMD level.
840
841config HAVE_ARCH_TRANSPARENT_HUGEPAGE
842	bool
843
844config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
845	bool
846
847config HAVE_ARCH_HUGE_VMAP
848	bool
849
850#
851#  Archs that select this would be capable of PMD-sized vmaps (i.e.,
852#  arch_vmap_pmd_supported() returns true), and they must make no assumptions
853#  that vmalloc memory is mapped with PAGE_SIZE ptes. The VM_NO_HUGE_VMAP flag
854#  can be used to prohibit arch-specific allocations from using hugepages to
855#  help with this (e.g., modules may require it).
856#
857config HAVE_ARCH_HUGE_VMALLOC
858	depends on HAVE_ARCH_HUGE_VMAP
859	bool
860
861config ARCH_WANT_HUGE_PMD_SHARE
862	bool
863
864config HAVE_ARCH_SOFT_DIRTY
865	bool
866
867config HAVE_MOD_ARCH_SPECIFIC
868	bool
869	help
870	  The arch uses struct mod_arch_specific to store data.  Many arches
871	  just need a simple module loader without arch specific data - those
872	  should not enable this.
873
874config MODULES_USE_ELF_RELA
875	bool
876	help
877	  Modules only use ELF RELA relocations.  Modules with ELF REL
878	  relocations will give an error.
879
880config MODULES_USE_ELF_REL
881	bool
882	help
883	  Modules only use ELF REL relocations.  Modules with ELF RELA
884	  relocations will give an error.
885
886config HAVE_IRQ_EXIT_ON_IRQ_STACK
887	bool
888	help
889	  Architecture doesn't only execute the irq handler on the irq stack
890	  but also irq_exit(). This way we can process softirqs on this irq
891	  stack instead of switching to a new one when we call __do_softirq()
892	  in the end of an hardirq.
893	  This spares a stack switch and improves cache usage on softirq
894	  processing.
895
896config HAVE_SOFTIRQ_ON_OWN_STACK
897	bool
898	help
899	  Architecture provides a function to run __do_softirq() on a
900	  separate stack.
901
902config PGTABLE_LEVELS
903	int
904	default 2
905
906config ARCH_HAS_ELF_RANDOMIZE
907	bool
908	help
909	  An architecture supports choosing randomized locations for
910	  stack, mmap, brk, and ET_DYN. Defined functions:
911	  - arch_mmap_rnd()
912	  - arch_randomize_brk()
913
914config HAVE_ARCH_MMAP_RND_BITS
915	bool
916	help
917	  An arch should select this symbol if it supports setting a variable
918	  number of bits for use in establishing the base address for mmap
919	  allocations, has MMU enabled and provides values for both:
920	  - ARCH_MMAP_RND_BITS_MIN
921	  - ARCH_MMAP_RND_BITS_MAX
922
923config HAVE_EXIT_THREAD
924	bool
925	help
926	  An architecture implements exit_thread.
927
928config ARCH_MMAP_RND_BITS_MIN
929	int
930
931config ARCH_MMAP_RND_BITS_MAX
932	int
933
934config ARCH_MMAP_RND_BITS_DEFAULT
935	int
936
937config ARCH_MMAP_RND_BITS
938	int "Number of bits to use for ASLR of mmap base address" if EXPERT
939	range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
940	default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
941	default ARCH_MMAP_RND_BITS_MIN
942	depends on HAVE_ARCH_MMAP_RND_BITS
943	help
944	  This value can be used to select the number of bits to use to
945	  determine the random offset to the base address of vma regions
946	  resulting from mmap allocations. This value will be bounded
947	  by the architecture's minimum and maximum supported values.
948
949	  This value can be changed after boot using the
950	  /proc/sys/vm/mmap_rnd_bits tunable
951
952config HAVE_ARCH_MMAP_RND_COMPAT_BITS
953	bool
954	help
955	  An arch should select this symbol if it supports running applications
956	  in compatibility mode, supports setting a variable number of bits for
957	  use in establishing the base address for mmap allocations, has MMU
958	  enabled and provides values for both:
959	  - ARCH_MMAP_RND_COMPAT_BITS_MIN
960	  - ARCH_MMAP_RND_COMPAT_BITS_MAX
961
962config ARCH_MMAP_RND_COMPAT_BITS_MIN
963	int
964
965config ARCH_MMAP_RND_COMPAT_BITS_MAX
966	int
967
968config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
969	int
970
971config ARCH_MMAP_RND_COMPAT_BITS
972	int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
973	range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
974	default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
975	default ARCH_MMAP_RND_COMPAT_BITS_MIN
976	depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
977	help
978	  This value can be used to select the number of bits to use to
979	  determine the random offset to the base address of vma regions
980	  resulting from mmap allocations for compatible applications This
981	  value will be bounded by the architecture's minimum and maximum
982	  supported values.
983
984	  This value can be changed after boot using the
985	  /proc/sys/vm/mmap_rnd_compat_bits tunable
986
987config HAVE_ARCH_COMPAT_MMAP_BASES
988	bool
989	help
990	  This allows 64bit applications to invoke 32-bit mmap() syscall
991	  and vice-versa 32-bit applications to call 64-bit mmap().
992	  Required for applications doing different bitness syscalls.
993
994config PAGE_SIZE_LESS_THAN_64KB
995	def_bool y
996	depends on !ARM64_64K_PAGES
997	depends on !IA64_PAGE_SIZE_64KB
998	depends on !PAGE_SIZE_64KB
999	depends on !PARISC_PAGE_SIZE_64KB
1000	depends on !PPC_64K_PAGES
1001	depends on !PPC_256K_PAGES
1002	depends on !PAGE_SIZE_256KB
1003
1004# This allows to use a set of generic functions to determine mmap base
1005# address by giving priority to top-down scheme only if the process
1006# is not in legacy mode (compat task, unlimited stack size or
1007# sysctl_legacy_va_layout).
1008# Architecture that selects this option can provide its own version of:
1009# - STACK_RND_MASK
1010config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
1011	bool
1012	depends on MMU
1013	select ARCH_HAS_ELF_RANDOMIZE
1014
1015config HAVE_STACK_VALIDATION
1016	bool
1017	help
1018	  Architecture supports the 'objtool check' host tool command, which
1019	  performs compile-time stack metadata validation.
1020
1021config HAVE_RELIABLE_STACKTRACE
1022	bool
1023	help
1024	  Architecture has either save_stack_trace_tsk_reliable() or
1025	  arch_stack_walk_reliable() function which only returns a stack trace
1026	  if it can guarantee the trace is reliable.
1027
1028config HAVE_ARCH_HASH
1029	bool
1030	default n
1031	help
1032	  If this is set, the architecture provides an <asm/hash.h>
1033	  file which provides platform-specific implementations of some
1034	  functions in <linux/hash.h> or fs/namei.c.
1035
1036config HAVE_ARCH_NVRAM_OPS
1037	bool
1038
1039config ISA_BUS_API
1040	def_bool ISA
1041
1042#
1043# ABI hall of shame
1044#
1045config CLONE_BACKWARDS
1046	bool
1047	help
1048	  Architecture has tls passed as the 4th argument of clone(2),
1049	  not the 5th one.
1050
1051config CLONE_BACKWARDS2
1052	bool
1053	help
1054	  Architecture has the first two arguments of clone(2) swapped.
1055
1056config CLONE_BACKWARDS3
1057	bool
1058	help
1059	  Architecture has tls passed as the 3rd argument of clone(2),
1060	  not the 5th one.
1061
1062config ODD_RT_SIGACTION
1063	bool
1064	help
1065	  Architecture has unusual rt_sigaction(2) arguments
1066
1067config OLD_SIGSUSPEND
1068	bool
1069	help
1070	  Architecture has old sigsuspend(2) syscall, of one-argument variety
1071
1072config OLD_SIGSUSPEND3
1073	bool
1074	help
1075	  Even weirder antique ABI - three-argument sigsuspend(2)
1076
1077config OLD_SIGACTION
1078	bool
1079	help
1080	  Architecture has old sigaction(2) syscall.  Nope, not the same
1081	  as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
1082	  but fairly different variant of sigaction(2), thanks to OSF/1
1083	  compatibility...
1084
1085config COMPAT_OLD_SIGACTION
1086	bool
1087
1088config COMPAT_32BIT_TIME
1089	bool "Provide system calls for 32-bit time_t"
1090	default !64BIT || COMPAT
1091	help
1092	  This enables 32 bit time_t support in addition to 64 bit time_t support.
1093	  This is relevant on all 32-bit architectures, and 64-bit architectures
1094	  as part of compat syscall handling.
1095
1096config ARCH_NO_PREEMPT
1097	bool
1098
1099config ARCH_EPHEMERAL_INODES
1100	def_bool n
1101	help
1102	  An arch should select this symbol if it doesn't keep track of inode
1103	  instances on its own, but instead relies on something else (e.g. the
1104	  host kernel for an UML kernel).
1105
1106config ARCH_SUPPORTS_RT
1107	bool
1108
1109config CPU_NO_EFFICIENT_FFS
1110	def_bool n
1111
1112config HAVE_ARCH_VMAP_STACK
1113	def_bool n
1114	help
1115	  An arch should select this symbol if it can support kernel stacks
1116	  in vmalloc space.  This means:
1117
1118	  - vmalloc space must be large enough to hold many kernel stacks.
1119	    This may rule out many 32-bit architectures.
1120
1121	  - Stacks in vmalloc space need to work reliably.  For example, if
1122	    vmap page tables are created on demand, either this mechanism
1123	    needs to work while the stack points to a virtual address with
1124	    unpopulated page tables or arch code (switch_to() and switch_mm(),
1125	    most likely) needs to ensure that the stack's page table entries
1126	    are populated before running on a possibly unpopulated stack.
1127
1128	  - If the stack overflows into a guard page, something reasonable
1129	    should happen.  The definition of "reasonable" is flexible, but
1130	    instantly rebooting without logging anything would be unfriendly.
1131
1132config VMAP_STACK
1133	default y
1134	bool "Use a virtually-mapped stack"
1135	depends on HAVE_ARCH_VMAP_STACK
1136	depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC
1137	help
1138	  Enable this if you want the use virtually-mapped kernel stacks
1139	  with guard pages.  This causes kernel stack overflows to be
1140	  caught immediately rather than causing difficult-to-diagnose
1141	  corruption.
1142
1143	  To use this with software KASAN modes, the architecture must support
1144	  backing virtual mappings with real shadow memory, and KASAN_VMALLOC
1145	  must be enabled.
1146
1147config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1148	def_bool n
1149	help
1150	  An arch should select this symbol if it can support kernel stack
1151	  offset randomization with calls to add_random_kstack_offset()
1152	  during syscall entry and choose_random_kstack_offset() during
1153	  syscall exit. Careful removal of -fstack-protector-strong and
1154	  -fstack-protector should also be applied to the entry code and
1155	  closely examined, as the artificial stack bump looks like an array
1156	  to the compiler, so it will attempt to add canary checks regardless
1157	  of the static branch state.
1158
1159config RANDOMIZE_KSTACK_OFFSET_DEFAULT
1160	bool "Randomize kernel stack offset on syscall entry"
1161	depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1162	help
1163	  The kernel stack offset can be randomized (after pt_regs) by
1164	  roughly 5 bits of entropy, frustrating memory corruption
1165	  attacks that depend on stack address determinism or
1166	  cross-syscall address exposures. This feature is controlled
1167	  by kernel boot param "randomize_kstack_offset=on/off", and this
1168	  config chooses the default boot state.
1169
1170config ARCH_OPTIONAL_KERNEL_RWX
1171	def_bool n
1172
1173config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1174	def_bool n
1175
1176config ARCH_HAS_STRICT_KERNEL_RWX
1177	def_bool n
1178
1179config STRICT_KERNEL_RWX
1180	bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
1181	depends on ARCH_HAS_STRICT_KERNEL_RWX
1182	default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1183	help
1184	  If this is set, kernel text and rodata memory will be made read-only,
1185	  and non-text memory will be made non-executable. This provides
1186	  protection against certain security exploits (e.g. executing the heap
1187	  or modifying text)
1188
1189	  These features are considered standard security practice these days.
1190	  You should say Y here in almost all cases.
1191
1192config ARCH_HAS_STRICT_MODULE_RWX
1193	def_bool n
1194
1195config STRICT_MODULE_RWX
1196	bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
1197	depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
1198	default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1199	help
1200	  If this is set, module text and rodata memory will be made read-only,
1201	  and non-text memory will be made non-executable. This provides
1202	  protection against certain security exploits (e.g. writing to text)
1203
1204# select if the architecture provides an asm/dma-direct.h header
1205config ARCH_HAS_PHYS_TO_DMA
1206	bool
1207
1208config HAVE_ARCH_COMPILER_H
1209	bool
1210	help
1211	  An architecture can select this if it provides an
1212	  asm/compiler.h header that should be included after
1213	  linux/compiler-*.h in order to override macro definitions that those
1214	  headers generally provide.
1215
1216config HAVE_ARCH_PREL32_RELOCATIONS
1217	bool
1218	help
1219	  May be selected by an architecture if it supports place-relative
1220	  32-bit relocations, both in the toolchain and in the module loader,
1221	  in which case relative references can be used in special sections
1222	  for PCI fixup, initcalls etc which are only half the size on 64 bit
1223	  architectures, and don't require runtime relocation on relocatable
1224	  kernels.
1225
1226config ARCH_USE_MEMREMAP_PROT
1227	bool
1228
1229config LOCK_EVENT_COUNTS
1230	bool "Locking event counts collection"
1231	depends on DEBUG_FS
1232	help
1233	  Enable light-weight counting of various locking related events
1234	  in the system with minimal performance impact. This reduces
1235	  the chance of application behavior change because of timing
1236	  differences. The counts are reported via debugfs.
1237
1238# Select if the architecture has support for applying RELR relocations.
1239config ARCH_HAS_RELR
1240	bool
1241
1242config RELR
1243	bool "Use RELR relocation packing"
1244	depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1245	default y
1246	help
1247	  Store the kernel's dynamic relocations in the RELR relocation packing
1248	  format. Requires a compatible linker (LLD supports this feature), as
1249	  well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1250	  are compatible).
1251
1252config ARCH_HAS_MEM_ENCRYPT
1253	bool
1254
1255config ARCH_HAS_CC_PLATFORM
1256	bool
1257
1258config HAVE_SPARSE_SYSCALL_NR
1259       bool
1260       help
1261          An architecture should select this if its syscall numbering is sparse
1262	  to save space. For example, MIPS architecture has a syscall array with
1263	  entries at 4000, 5000 and 6000 locations. This option turns on syscall
1264	  related optimizations for a given architecture.
1265
1266config ARCH_HAS_VDSO_DATA
1267	bool
1268
1269config HAVE_STATIC_CALL
1270	bool
1271
1272config HAVE_STATIC_CALL_INLINE
1273	bool
1274	depends on HAVE_STATIC_CALL
1275
1276config HAVE_PREEMPT_DYNAMIC
1277	bool
1278	depends on HAVE_STATIC_CALL
1279	depends on GENERIC_ENTRY
1280	help
1281	   Select this if the architecture support boot time preempt setting
1282	   on top of static calls. It is strongly advised to support inline
1283	   static call to avoid any overhead.
1284
1285config ARCH_WANT_LD_ORPHAN_WARN
1286	bool
1287	help
1288	  An arch should select this symbol once all linker sections are explicitly
1289	  included, size-asserted, or discarded in the linker scripts. This is
1290	  important because we never want expected sections to be placed heuristically
1291	  by the linker, since the locations of such sections can change between linker
1292	  versions.
1293
1294config HAVE_ARCH_PFN_VALID
1295	bool
1296
1297config ARCH_SUPPORTS_DEBUG_PAGEALLOC
1298	bool
1299
1300config ARCH_SPLIT_ARG64
1301	bool
1302	help
1303	   If a 32-bit architecture requires 64-bit arguments to be split into
1304	   pairs of 32-bit arguments, select this option.
1305
1306config ARCH_HAS_ELFCORE_COMPAT
1307	bool
1308
1309config ARCH_HAS_PARANOID_L1D_FLUSH
1310	bool
1311
1312config DYNAMIC_SIGFRAME
1313	bool
1314
1315source "kernel/gcov/Kconfig"
1316
1317source "scripts/gcc-plugins/Kconfig"
1318
1319endmenu
1320