1 # SPDX-License-Identifier: GPL-2.0
2 #
3 # General architecture dependent options
4 #
5
6 #
7 # Note: arch/$(SRCARCH)/Kconfig needs to be included first so that it can
8 # override the default values in this file.
9 #
10 source "arch/$(SRCARCH)/Kconfig"
11
12 config ARCH_CONFIGURES_CPU_MITIGATIONS
13 bool
14
15 if !ARCH_CONFIGURES_CPU_MITIGATIONS
16 config CPU_MITIGATIONS
17 def_bool y
18 endif
19
20 #
21 # Selected by architectures that need custom DMA operations for e.g. legacy
22 # IOMMUs not handled by dma-iommu. Drivers must never select this symbol.
23 #
24 config ARCH_HAS_DMA_OPS
25 depends on HAS_DMA
26 select DMA_OPS_HELPERS
27 bool
28
29 menu "General architecture-dependent options"
30
31 config ARCH_HAS_SUBPAGE_FAULTS
32 bool
33 help
34 Select if the architecture can check permissions at sub-page
35 granularity (e.g. arm64 MTE). The probe_user_*() functions
36 must be implemented.
37
38 config HOTPLUG_SMT
39 bool
40
41 config SMT_NUM_THREADS_DYNAMIC
42 bool
43
44 # Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL
45 config HOTPLUG_CORE_SYNC
46 bool
47
48 # Basic CPU dead synchronization selected by architecture
49 config HOTPLUG_CORE_SYNC_DEAD
50 bool
51 select HOTPLUG_CORE_SYNC
52
53 # Full CPU synchronization with alive state selected by architecture
54 config HOTPLUG_CORE_SYNC_FULL
55 bool
56 select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU
57 select HOTPLUG_CORE_SYNC
58
59 config HOTPLUG_SPLIT_STARTUP
60 bool
61 select HOTPLUG_CORE_SYNC_FULL
62
63 config HOTPLUG_PARALLEL
64 bool
65 select HOTPLUG_SPLIT_STARTUP
66
67 config GENERIC_ENTRY
68 bool
69
70 config KPROBES
71 bool "Kprobes"
72 depends on HAVE_KPROBES
73 select KALLSYMS
74 select EXECMEM
75 select NEED_TASKS_RCU
76 help
77 Kprobes allows you to trap at almost any kernel address and
78 execute a callback function. register_kprobe() establishes
79 a probepoint and specifies the callback. Kprobes is useful
80 for kernel debugging, non-intrusive instrumentation and testing.
81 If in doubt, say "N".
82
83 config JUMP_LABEL
84 bool "Optimize very unlikely/likely branches"
85 depends on HAVE_ARCH_JUMP_LABEL
86 select OBJTOOL if HAVE_JUMP_LABEL_HACK
87 help
88 This option enables a transparent branch optimization that
89 makes certain almost-always-true or almost-always-false branch
90 conditions even cheaper to execute within the kernel.
91
92 Certain performance-sensitive kernel code, such as trace points,
93 scheduler functionality, networking code and KVM have such
94 branches and include support for this optimization technique.
95
96 If it is detected that the compiler has support for "asm goto",
97 the kernel will compile such branches with just a nop
98 instruction. When the condition flag is toggled to true, the
99 nop will be converted to a jump instruction to execute the
100 conditional block of instructions.
101
102 This technique lowers overhead and stress on the branch prediction
103 of the processor and generally makes the kernel faster. The update
104 of the condition is slower, but those are always very rare.
105
106 ( On 32-bit x86, the necessary options added to the compiler
107 flags may increase the size of the kernel slightly. )
108
109 config STATIC_KEYS_SELFTEST
110 bool "Static key selftest"
111 depends on JUMP_LABEL
112 help
113 Boot time self-test of the branch patching code.
114
115 config STATIC_CALL_SELFTEST
116 bool "Static call selftest"
117 depends on HAVE_STATIC_CALL
118 help
119 Boot time self-test of the call patching code.
120
121 config OPTPROBES
122 def_bool y
123 depends on KPROBES && HAVE_OPTPROBES
124 select NEED_TASKS_RCU
125
126 config KPROBES_ON_FTRACE
127 def_bool y
128 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
129 depends on DYNAMIC_FTRACE_WITH_REGS
130 help
131 If function tracer is enabled and the arch supports full
132 passing of pt_regs to function tracing, then kprobes can
133 optimize on top of function tracing.
134
135 config UPROBES
136 def_bool n
137 depends on ARCH_SUPPORTS_UPROBES
138 help
139 Uprobes is the user-space counterpart to kprobes: they
140 enable instrumentation applications (such as 'perf probe')
141 to establish unintrusive probes in user-space binaries and
142 libraries, by executing handler functions when the probes
143 are hit by user-space applications.
144
145 ( These probes come in the form of single-byte breakpoints,
146 managed by the kernel and kept transparent to the probed
147 application. )
148
149 config HAVE_64BIT_ALIGNED_ACCESS
150 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
151 help
152 Some architectures require 64 bit accesses to be 64 bit
153 aligned, which also requires structs containing 64 bit values
154 to be 64 bit aligned too. This includes some 32 bit
155 architectures which can do 64 bit accesses, as well as 64 bit
156 architectures without unaligned access.
157
158 This symbol should be selected by an architecture if 64 bit
159 accesses are required to be 64 bit aligned in this way even
160 though it is not a 64 bit architecture.
161
162 See Documentation/core-api/unaligned-memory-access.rst for
163 more information on the topic of unaligned memory accesses.
164
165 config HAVE_EFFICIENT_UNALIGNED_ACCESS
166 bool
167 help
168 Some architectures are unable to perform unaligned accesses
169 without the use of get_unaligned/put_unaligned. Others are
170 unable to perform such accesses efficiently (e.g. trap on
171 unaligned access and require fixing it up in the exception
172 handler.)
173
174 This symbol should be selected by an architecture if it can
175 perform unaligned accesses efficiently to allow different
176 code paths to be selected for these cases. Some network
177 drivers, for example, could opt to not fix up alignment
178 problems with received packets if doing so would not help
179 much.
180
181 See Documentation/core-api/unaligned-memory-access.rst for more
182 information on the topic of unaligned memory accesses.
183
184 config ARCH_USE_BUILTIN_BSWAP
185 bool
186 help
187 Modern versions of GCC (since 4.4) have builtin functions
188 for handling byte-swapping. Using these, instead of the old
189 inline assembler that the architecture code provides in the
190 __arch_bswapXX() macros, allows the compiler to see what's
191 happening and offers more opportunity for optimisation. In
192 particular, the compiler will be able to combine the byteswap
193 with a nearby load or store and use load-and-swap or
194 store-and-swap instructions if the architecture has them. It
195 should almost *never* result in code which is worse than the
196 hand-coded assembler in <asm/swab.h>. But just in case it
197 does, the use of the builtins is optional.
198
199 Any architecture with load-and-swap or store-and-swap
200 instructions should set this. And it shouldn't hurt to set it
201 on architectures that don't have such instructions.
202
203 config KRETPROBES
204 def_bool y
205 depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK)
206
207 config KRETPROBE_ON_RETHOOK
208 def_bool y
209 depends on HAVE_RETHOOK
210 depends on KRETPROBES
211 select RETHOOK
212
213 config USER_RETURN_NOTIFIER
214 bool
215 depends on HAVE_USER_RETURN_NOTIFIER
216 help
217 Provide a kernel-internal notification when a cpu is about to
218 switch to user mode.
219
220 config HAVE_IOREMAP_PROT
221 bool
222
223 config HAVE_KPROBES
224 bool
225
226 config HAVE_KRETPROBES
227 bool
228
229 config HAVE_OPTPROBES
230 bool
231
232 config HAVE_KPROBES_ON_FTRACE
233 bool
234
235 config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
236 bool
237 help
238 Since kretprobes modifies return address on the stack, the
239 stacktrace may see the kretprobe trampoline address instead
240 of correct one. If the architecture stacktrace code and
241 unwinder can adjust such entries, select this configuration.
242
243 config HAVE_FUNCTION_ERROR_INJECTION
244 bool
245
246 config HAVE_NMI
247 bool
248
249 config HAVE_FUNCTION_DESCRIPTORS
250 bool
251
252 config TRACE_IRQFLAGS_SUPPORT
253 bool
254
255 config TRACE_IRQFLAGS_NMI_SUPPORT
256 bool
257
258 #
259 # An arch should select this if it provides all these things:
260 #
261 # task_pt_regs() in asm/processor.h or asm/ptrace.h
262 # arch_has_single_step() if there is hardware single-step support
263 # arch_has_block_step() if there is hardware block-step support
264 # asm/syscall.h supplying asm-generic/syscall.h interface
265 # linux/regset.h user_regset interfaces
266 # CORE_DUMP_USE_REGSET #define'd in linux/elf.h
267 # TIF_SYSCALL_TRACE calls ptrace_report_syscall_{entry,exit}
268 # TIF_NOTIFY_RESUME calls resume_user_mode_work()
269 #
270 config HAVE_ARCH_TRACEHOOK
271 bool
272
273 config HAVE_DMA_CONTIGUOUS
274 bool
275
276 config GENERIC_SMP_IDLE_THREAD
277 bool
278
279 config GENERIC_IDLE_POLL_SETUP
280 bool
281
282 config ARCH_HAS_FORTIFY_SOURCE
283 bool
284 help
285 An architecture should select this when it can successfully
286 build and run with CONFIG_FORTIFY_SOURCE.
287
288 #
289 # Select if the arch provides a historic keepinit alias for the retain_initrd
290 # command line option
291 #
292 config ARCH_HAS_KEEPINITRD
293 bool
294
295 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
296 config ARCH_HAS_SET_MEMORY
297 bool
298
299 # Select if arch has all set_direct_map_invalid/default() functions
300 config ARCH_HAS_SET_DIRECT_MAP
301 bool
302
303 #
304 # Select if the architecture provides the arch_dma_set_uncached symbol to
305 # either provide an uncached segment alias for a DMA allocation, or
306 # to remap the page tables in place.
307 #
308 config ARCH_HAS_DMA_SET_UNCACHED
309 bool
310
311 #
312 # Select if the architectures provides the arch_dma_clear_uncached symbol
313 # to undo an in-place page table remap for uncached access.
314 #
315 config ARCH_HAS_DMA_CLEAR_UNCACHED
316 bool
317
318 config ARCH_HAS_CPU_FINALIZE_INIT
319 bool
320
321 # The architecture has a per-task state that includes the mm's PASID
322 config ARCH_HAS_CPU_PASID
323 bool
324 select IOMMU_MM_DATA
325
326 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
327 bool
328 help
329 An architecture should select this to provide hardened usercopy
330 knowledge about what region of the thread_struct should be
331 whitelisted for copying to userspace. Normally this is only the
332 FPU registers. Specifically, arch_thread_struct_whitelist()
333 should be implemented. Without this, the entire thread_struct
334 field in task_struct will be left whitelisted.
335
336 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
337 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
338 bool
339
340 config ARCH_WANTS_NO_INSTR
341 bool
342 help
343 An architecture should select this if the noinstr macro is being used on
344 functions to denote that the toolchain should avoid instrumenting such
345 functions and is required for correctness.
346
347 config ARCH_32BIT_OFF_T
348 bool
349 depends on !64BIT
350 help
351 All new 32-bit architectures should have 64-bit off_t type on
352 userspace side which corresponds to the loff_t kernel type. This
353 is the requirement for modern ABIs. Some existing architectures
354 still support 32-bit off_t. This option is enabled for all such
355 architectures explicitly.
356
357 # Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat
358 config ARCH_32BIT_USTAT_F_TINODE
359 bool
360
361 config HAVE_ASM_MODVERSIONS
362 bool
363 help
364 This symbol should be selected by an architecture if it provides
365 <asm/asm-prototypes.h> to support the module versioning for symbols
366 exported from assembly code.
367
368 config HAVE_REGS_AND_STACK_ACCESS_API
369 bool
370 help
371 This symbol should be selected by an architecture if it supports
372 the API needed to access registers and stack entries from pt_regs,
373 declared in asm/ptrace.h
374 For example the kprobes-based event tracer needs this API.
375
376 config HAVE_RSEQ
377 bool
378 depends on HAVE_REGS_AND_STACK_ACCESS_API
379 help
380 This symbol should be selected by an architecture if it
381 supports an implementation of restartable sequences.
382
383 config HAVE_RUST
384 bool
385 help
386 This symbol should be selected by an architecture if it
387 supports Rust.
388
389 config HAVE_FUNCTION_ARG_ACCESS_API
390 bool
391 help
392 This symbol should be selected by an architecture if it supports
393 the API needed to access function arguments from pt_regs,
394 declared in asm/ptrace.h
395
396 config HAVE_HW_BREAKPOINT
397 bool
398 depends on PERF_EVENTS
399
400 config HAVE_MIXED_BREAKPOINTS_REGS
401 bool
402 depends on HAVE_HW_BREAKPOINT
403 help
404 Depending on the arch implementation of hardware breakpoints,
405 some of them have separate registers for data and instruction
406 breakpoints addresses, others have mixed registers to store
407 them but define the access type in a control register.
408 Select this option if your arch implements breakpoints under the
409 latter fashion.
410
411 config HAVE_USER_RETURN_NOTIFIER
412 bool
413
414 config HAVE_PERF_EVENTS_NMI
415 bool
416 help
417 System hardware can generate an NMI using the perf event
418 subsystem. Also has support for calculating CPU cycle events
419 to determine how many clock cycles in a given period.
420
421 config HAVE_HARDLOCKUP_DETECTOR_PERF
422 bool
423 depends on HAVE_PERF_EVENTS_NMI
424 help
425 The arch chooses to use the generic perf-NMI-based hardlockup
426 detector. Must define HAVE_PERF_EVENTS_NMI.
427
428 config HAVE_HARDLOCKUP_DETECTOR_ARCH
429 bool
430 help
431 The arch provides its own hardlockup detector implementation instead
432 of the generic ones.
433
434 It uses the same command line parameters, and sysctl interface,
435 as the generic hardlockup detectors.
436
437 config HAVE_PERF_REGS
438 bool
439 help
440 Support selective register dumps for perf events. This includes
441 bit-mapping of each registers and a unique architecture id.
442
443 config HAVE_PERF_USER_STACK_DUMP
444 bool
445 help
446 Support user stack dumps for perf event samples. This needs
447 access to the user stack pointer which is not unified across
448 architectures.
449
450 config HAVE_ARCH_JUMP_LABEL
451 bool
452
453 config HAVE_ARCH_JUMP_LABEL_RELATIVE
454 bool
455
456 config MMU_GATHER_TABLE_FREE
457 bool
458
459 config MMU_GATHER_RCU_TABLE_FREE
460 bool
461 select MMU_GATHER_TABLE_FREE
462
463 config MMU_GATHER_PAGE_SIZE
464 bool
465
466 config MMU_GATHER_NO_RANGE
467 bool
468 select MMU_GATHER_MERGE_VMAS
469
470 config MMU_GATHER_NO_FLUSH_CACHE
471 bool
472
473 config MMU_GATHER_MERGE_VMAS
474 bool
475
476 config MMU_GATHER_NO_GATHER
477 bool
478 depends on MMU_GATHER_TABLE_FREE
479
480 config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
481 bool
482 help
483 Temporary select until all architectures can be converted to have
484 irqs disabled over activate_mm. Architectures that do IPI based TLB
485 shootdowns should enable this.
486
487 # Use normal mm refcounting for MMU_LAZY_TLB kernel thread references.
488 # MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching
489 # to/from kernel threads when the same mm is running on a lot of CPUs (a large
490 # multi-threaded application), by reducing contention on the mm refcount.
491 #
492 # This can be disabled if the architecture ensures no CPUs are using an mm as a
493 # "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm
494 # or its kernel page tables). This could be arranged by arch_exit_mmap(), or
495 # final exit(2) TLB flush, for example.
496 #
497 # To implement this, an arch *must*:
498 # Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating
499 # the lazy tlb reference of a kthread's ->active_mm (non-arch code has been
500 # converted already).
501 config MMU_LAZY_TLB_REFCOUNT
502 def_bool y
503 depends on !MMU_LAZY_TLB_SHOOTDOWN
504
505 # This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an
506 # mm as a lazy tlb beyond its last reference count, by shooting down these
507 # users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may
508 # be using the mm as a lazy tlb, so that they may switch themselves to using
509 # init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs
510 # may be using mm as a lazy tlb mm.
511 #
512 # To implement this, an arch *must*:
513 # - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains
514 # at least all possible CPUs in which the mm is lazy.
515 # - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above).
516 config MMU_LAZY_TLB_SHOOTDOWN
517 bool
518
519 config ARCH_HAVE_NMI_SAFE_CMPXCHG
520 bool
521
522 config ARCH_HAVE_EXTRA_ELF_NOTES
523 bool
524 help
525 An architecture should select this in order to enable adding an
526 arch-specific ELF note section to core files. It must provide two
527 functions: elf_coredump_extra_notes_size() and
528 elf_coredump_extra_notes_write() which are invoked by the ELF core
529 dumper.
530
531 config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
532 bool
533
534 config HAVE_ALIGNED_STRUCT_PAGE
535 bool
536 help
537 This makes sure that struct pages are double word aligned and that
538 e.g. the SLUB allocator can perform double word atomic operations
539 on a struct page for better performance. However selecting this
540 might increase the size of a struct page by a word.
541
542 config HAVE_CMPXCHG_LOCAL
543 bool
544
545 config HAVE_CMPXCHG_DOUBLE
546 bool
547
548 config ARCH_WEAK_RELEASE_ACQUIRE
549 bool
550
551 config ARCH_WANT_IPC_PARSE_VERSION
552 bool
553
554 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
555 bool
556
557 config ARCH_WANT_OLD_COMPAT_IPC
558 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
559 bool
560
561 config HAVE_ARCH_SECCOMP
562 bool
563 help
564 An arch should select this symbol to support seccomp mode 1 (the fixed
565 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
566 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
567 - __NR_seccomp_read_32
568 - __NR_seccomp_write_32
569 - __NR_seccomp_exit_32
570 - __NR_seccomp_sigreturn_32
571
572 config HAVE_ARCH_SECCOMP_FILTER
573 bool
574 select HAVE_ARCH_SECCOMP
575 help
576 An arch should select this symbol if it provides all of these things:
577 - all the requirements for HAVE_ARCH_SECCOMP
578 - syscall_get_arch()
579 - syscall_get_arguments()
580 - syscall_rollback()
581 - syscall_set_return_value()
582 - SIGSYS siginfo_t support
583 - secure_computing is called from a ptrace_event()-safe context
584 - secure_computing return value is checked and a return value of -1
585 results in the system call being skipped immediately.
586 - seccomp syscall wired up
587 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE,
588 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If
589 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too.
590
591 config SECCOMP
592 prompt "Enable seccomp to safely execute untrusted bytecode"
593 def_bool y
594 depends on HAVE_ARCH_SECCOMP
595 help
596 This kernel feature is useful for number crunching applications
597 that may need to handle untrusted bytecode during their
598 execution. By using pipes or other transports made available
599 to the process as file descriptors supporting the read/write
600 syscalls, it's possible to isolate those applications in their
601 own address space using seccomp. Once seccomp is enabled via
602 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
603 disabled and the task is only allowed to execute a few safe
604 syscalls defined by each seccomp mode.
605
606 If unsure, say Y.
607
608 config SECCOMP_FILTER
609 def_bool y
610 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
611 help
612 Enable tasks to build secure computing environments defined
613 in terms of Berkeley Packet Filter programs which implement
614 task-defined system call filtering polices.
615
616 See Documentation/userspace-api/seccomp_filter.rst for details.
617
618 config SECCOMP_CACHE_DEBUG
619 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache"
620 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR
621 depends on PROC_FS
622 help
623 This enables the /proc/pid/seccomp_cache interface to monitor
624 seccomp cache data. The file format is subject to change. Reading
625 the file requires CAP_SYS_ADMIN.
626
627 This option is for debugging only. Enabling presents the risk that
628 an adversary may be able to infer the seccomp filter logic.
629
630 If unsure, say N.
631
632 config HAVE_ARCH_STACKLEAK
633 bool
634 help
635 An architecture should select this if it has the code which
636 fills the used part of the kernel stack with the STACKLEAK_POISON
637 value before returning from system calls.
638
639 config HAVE_STACKPROTECTOR
640 bool
641 help
642 An arch should select this symbol if:
643 - it has implemented a stack canary (e.g. __stack_chk_guard)
644
645 config STACKPROTECTOR
646 bool "Stack Protector buffer overflow detection"
647 depends on HAVE_STACKPROTECTOR
648 depends on $(cc-option,-fstack-protector)
649 default y
650 help
651 This option turns on the "stack-protector" GCC feature. This
652 feature puts, at the beginning of functions, a canary value on
653 the stack just before the return address, and validates
654 the value just before actually returning. Stack based buffer
655 overflows (that need to overwrite this return address) now also
656 overwrite the canary, which gets detected and the attack is then
657 neutralized via a kernel panic.
658
659 Functions will have the stack-protector canary logic added if they
660 have an 8-byte or larger character array on the stack.
661
662 This feature requires gcc version 4.2 or above, or a distribution
663 gcc with the feature backported ("-fstack-protector").
664
665 On an x86 "defconfig" build, this feature adds canary checks to
666 about 3% of all kernel functions, which increases kernel code size
667 by about 0.3%.
668
669 config STACKPROTECTOR_STRONG
670 bool "Strong Stack Protector"
671 depends on STACKPROTECTOR
672 depends on $(cc-option,-fstack-protector-strong)
673 default y
674 help
675 Functions will have the stack-protector canary logic added in any
676 of the following conditions:
677
678 - local variable's address used as part of the right hand side of an
679 assignment or function argument
680 - local variable is an array (or union containing an array),
681 regardless of array type or length
682 - uses register local variables
683
684 This feature requires gcc version 4.9 or above, or a distribution
685 gcc with the feature backported ("-fstack-protector-strong").
686
687 On an x86 "defconfig" build, this feature adds canary checks to
688 about 20% of all kernel functions, which increases the kernel code
689 size by about 2%.
690
691 config ARCH_SUPPORTS_SHADOW_CALL_STACK
692 bool
693 help
694 An architecture should select this if it supports the compiler's
695 Shadow Call Stack and implements runtime support for shadow stack
696 switching.
697
698 config SHADOW_CALL_STACK
699 bool "Shadow Call Stack"
700 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
701 depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
702 depends on MMU
703 help
704 This option enables the compiler's Shadow Call Stack, which
705 uses a shadow stack to protect function return addresses from
706 being overwritten by an attacker. More information can be found
707 in the compiler's documentation:
708
709 - Clang: https://clang.llvm.org/docs/ShadowCallStack.html
710 - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options
711
712 Note that security guarantees in the kernel differ from the
713 ones documented for user space. The kernel must store addresses
714 of shadow stacks in memory, which means an attacker capable of
715 reading and writing arbitrary memory may be able to locate them
716 and hijack control flow by modifying the stacks.
717
718 config DYNAMIC_SCS
719 bool
720 help
721 Set by the arch code if it relies on code patching to insert the
722 shadow call stack push and pop instructions rather than on the
723 compiler.
724
725 config LTO
726 bool
727 help
728 Selected if the kernel will be built using the compiler's LTO feature.
729
730 config LTO_CLANG
731 bool
732 select LTO
733 help
734 Selected if the kernel will be built using Clang's LTO feature.
735
736 config ARCH_SUPPORTS_LTO_CLANG
737 bool
738 help
739 An architecture should select this option if it supports:
740 - compiling with Clang,
741 - compiling inline assembly with Clang's integrated assembler,
742 - and linking with LLD.
743
744 config ARCH_SUPPORTS_LTO_CLANG_THIN
745 bool
746 help
747 An architecture should select this option if it can support Clang's
748 ThinLTO mode.
749
750 config HAS_LTO_CLANG
751 def_bool y
752 depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM
753 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
754 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
755 depends on ARCH_SUPPORTS_LTO_CLANG
756 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT
757 # https://github.com/ClangBuiltLinux/linux/issues/1721
758 depends on (!KASAN || KASAN_HW_TAGS || CLANG_VERSION >= 170000) || !DEBUG_INFO
759 depends on (!KCOV || CLANG_VERSION >= 170000) || !DEBUG_INFO
760 depends on !GCOV_KERNEL
761 help
762 The compiler and Kconfig options support building with Clang's
763 LTO.
764
765 choice
766 prompt "Link Time Optimization (LTO)"
767 default LTO_NONE
768 help
769 This option enables Link Time Optimization (LTO), which allows the
770 compiler to optimize binaries globally.
771
772 If unsure, select LTO_NONE. Note that LTO is very resource-intensive
773 so it's disabled by default.
774
775 config LTO_NONE
776 bool "None"
777 help
778 Build the kernel normally, without Link Time Optimization (LTO).
779
780 config LTO_CLANG_FULL
781 bool "Clang Full LTO (EXPERIMENTAL)"
782 depends on HAS_LTO_CLANG
783 depends on !COMPILE_TEST
784 select LTO_CLANG
785 help
786 This option enables Clang's full Link Time Optimization (LTO), which
787 allows the compiler to optimize the kernel globally. If you enable
788 this option, the compiler generates LLVM bitcode instead of ELF
789 object files, and the actual compilation from bitcode happens at
790 the LTO link step, which may take several minutes depending on the
791 kernel configuration. More information can be found from LLVM's
792 documentation:
793
794 https://llvm.org/docs/LinkTimeOptimization.html
795
796 During link time, this option can use a large amount of RAM, and
797 may take much longer than the ThinLTO option.
798
799 config LTO_CLANG_THIN
800 bool "Clang ThinLTO (EXPERIMENTAL)"
801 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN
802 select LTO_CLANG
803 help
804 This option enables Clang's ThinLTO, which allows for parallel
805 optimization and faster incremental compiles compared to the
806 CONFIG_LTO_CLANG_FULL option. More information can be found
807 from Clang's documentation:
808
809 https://clang.llvm.org/docs/ThinLTO.html
810
811 If unsure, say Y.
812 endchoice
813
814 config ARCH_SUPPORTS_CFI_CLANG
815 bool
816 help
817 An architecture should select this option if it can support Clang's
818 Control-Flow Integrity (CFI) checking.
819
820 config ARCH_USES_CFI_TRAPS
821 bool
822
823 config CFI_CLANG
824 bool "Use Clang's Control Flow Integrity (CFI)"
825 depends on ARCH_SUPPORTS_CFI_CLANG
826 depends on $(cc-option,-fsanitize=kcfi)
827 help
828 This option enables Clang's forward-edge Control Flow Integrity
829 (CFI) checking, where the compiler injects a runtime check to each
830 indirect function call to ensure the target is a valid function with
831 the correct static type. This restricts possible call targets and
832 makes it more difficult for an attacker to exploit bugs that allow
833 the modification of stored function pointers. More information can be
834 found from Clang's documentation:
835
836 https://clang.llvm.org/docs/ControlFlowIntegrity.html
837
838 config CFI_ICALL_NORMALIZE_INTEGERS
839 bool "Normalize CFI tags for integers"
840 depends on CFI_CLANG
841 depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG
842 help
843 This option normalizes the CFI tags for integer types so that all
844 integer types of the same size and signedness receive the same CFI
845 tag.
846
847 The option is separate from CONFIG_RUST because it affects the ABI.
848 When working with build systems that care about the ABI, it is
849 convenient to be able to turn on this flag first, before Rust is
850 turned on.
851
852 This option is necessary for using CFI with Rust. If unsure, say N.
853
854 config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG
855 def_bool y
856 depends on $(cc-option,-fsanitize=kcfi -fsanitize-cfi-icall-experimental-normalize-integers)
857 # With GCOV/KASAN we need this fix: https://github.com/llvm/llvm-project/pull/104826
858 depends on CLANG_VERSION >= 190103 || (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS)
859
860 config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC
861 def_bool y
862 depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG
863 depends on RUSTC_VERSION >= 107900
864 # With GCOV/KASAN we need this fix: https://github.com/rust-lang/rust/pull/129373
865 depends on (RUSTC_LLVM_VERSION >= 190103 && RUSTC_VERSION >= 108200) || \
866 (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS)
867
868 config CFI_PERMISSIVE
869 bool "Use CFI in permissive mode"
870 depends on CFI_CLANG
871 help
872 When selected, Control Flow Integrity (CFI) violations result in a
873 warning instead of a kernel panic. This option should only be used
874 for finding indirect call type mismatches during development.
875
876 If unsure, say N.
877
878 config HAVE_ARCH_WITHIN_STACK_FRAMES
879 bool
880 help
881 An architecture should select this if it can walk the kernel stack
882 frames to determine if an object is part of either the arguments
883 or local variables (i.e. that it excludes saved return addresses,
884 and similar) by implementing an inline arch_within_stack_frames(),
885 which is used by CONFIG_HARDENED_USERCOPY.
886
887 config HAVE_CONTEXT_TRACKING_USER
888 bool
889 help
890 Provide kernel/user boundaries probes necessary for subsystems
891 that need it, such as userspace RCU extended quiescent state.
892 Syscalls need to be wrapped inside user_exit()-user_enter(), either
893 optimized behind static key or through the slow path using TIF_NOHZ
894 flag. Exceptions handlers must be wrapped as well. Irqs are already
895 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal
896 handling on irq exit still need to be protected.
897
898 config HAVE_CONTEXT_TRACKING_USER_OFFSTACK
899 bool
900 help
901 Architecture neither relies on exception_enter()/exception_exit()
902 nor on schedule_user(). Also preempt_schedule_notrace() and
903 preempt_schedule_irq() can't be called in a preemptible section
904 while context tracking is CT_STATE_USER. This feature reflects a sane
905 entry implementation where the following requirements are met on
906 critical entry code, ie: before user_exit() or after user_enter():
907
908 - Critical entry code isn't preemptible (or better yet:
909 not interruptible).
910 - No use of RCU read side critical sections, unless ct_nmi_enter()
911 got called.
912 - No use of instrumentation, unless instrumentation_begin() got
913 called.
914
915 config HAVE_TIF_NOHZ
916 bool
917 help
918 Arch relies on TIF_NOHZ and syscall slow path to implement context
919 tracking calls to user_enter()/user_exit().
920
921 config HAVE_VIRT_CPU_ACCOUNTING
922 bool
923
924 config HAVE_VIRT_CPU_ACCOUNTING_IDLE
925 bool
926 help
927 Architecture has its own way to account idle CPU time and therefore
928 doesn't implement vtime_account_idle().
929
930 config ARCH_HAS_SCALED_CPUTIME
931 bool
932
933 config HAVE_VIRT_CPU_ACCOUNTING_GEN
934 bool
935 default y if 64BIT
936 help
937 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
938 Before enabling this option, arch code must be audited
939 to ensure there are no races in concurrent read/write of
940 cputime_t. For example, reading/writing 64-bit cputime_t on
941 some 32-bit arches may require multiple accesses, so proper
942 locking is needed to protect against concurrent accesses.
943
944 config HAVE_IRQ_TIME_ACCOUNTING
945 bool
946 help
947 Archs need to ensure they use a high enough resolution clock to
948 support irq time accounting and then call enable_sched_clock_irqtime().
949
950 config HAVE_MOVE_PUD
951 bool
952 help
953 Architectures that select this are able to move page tables at the
954 PUD level. If there are only 3 page table levels, the move effectively
955 happens at the PGD level.
956
957 config HAVE_MOVE_PMD
958 bool
959 help
960 Archs that select this are able to move page tables at the PMD level.
961
962 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
963 bool
964
965 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
966 bool
967
968 config HAVE_ARCH_HUGE_VMAP
969 bool
970
971 #
972 # Archs that select this would be capable of PMD-sized vmaps (i.e.,
973 # arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag
974 # must be used to enable allocations to use hugepages.
975 #
976 config HAVE_ARCH_HUGE_VMALLOC
977 depends on HAVE_ARCH_HUGE_VMAP
978 bool
979
980 config ARCH_WANT_HUGE_PMD_SHARE
981 bool
982
983 # Archs that want to use pmd_mkwrite on kernel memory need it defined even
984 # if there are no userspace memory management features that use it
985 config ARCH_WANT_KERNEL_PMD_MKWRITE
986 bool
987
988 config ARCH_WANT_PMD_MKWRITE
989 def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE
990
991 config HAVE_ARCH_SOFT_DIRTY
992 bool
993
994 config HAVE_MOD_ARCH_SPECIFIC
995 bool
996 help
997 The arch uses struct mod_arch_specific to store data. Many arches
998 just need a simple module loader without arch specific data - those
999 should not enable this.
1000
1001 config MODULES_USE_ELF_RELA
1002 bool
1003 help
1004 Modules only use ELF RELA relocations. Modules with ELF REL
1005 relocations will give an error.
1006
1007 config MODULES_USE_ELF_REL
1008 bool
1009 help
1010 Modules only use ELF REL relocations. Modules with ELF RELA
1011 relocations will give an error.
1012
1013 config ARCH_WANTS_MODULES_DATA_IN_VMALLOC
1014 bool
1015 help
1016 For architectures like powerpc/32 which have constraints on module
1017 allocation and need to allocate module data outside of module area.
1018
1019 config ARCH_WANTS_EXECMEM_LATE
1020 bool
1021 help
1022 For architectures that do not allocate executable memory early on
1023 boot, but rather require its initialization late when there is
1024 enough entropy for module space randomization, for instance
1025 arm64.
1026
1027 config HAVE_IRQ_EXIT_ON_IRQ_STACK
1028 bool
1029 help
1030 Architecture doesn't only execute the irq handler on the irq stack
1031 but also irq_exit(). This way we can process softirqs on this irq
1032 stack instead of switching to a new one when we call __do_softirq()
1033 in the end of an hardirq.
1034 This spares a stack switch and improves cache usage on softirq
1035 processing.
1036
1037 config HAVE_SOFTIRQ_ON_OWN_STACK
1038 bool
1039 help
1040 Architecture provides a function to run __do_softirq() on a
1041 separate stack.
1042
1043 config SOFTIRQ_ON_OWN_STACK
1044 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT
1045
1046 config ALTERNATE_USER_ADDRESS_SPACE
1047 bool
1048 help
1049 Architectures set this when the CPU uses separate address
1050 spaces for kernel and user space pointers. In this case, the
1051 access_ok() check on a __user pointer is skipped.
1052
1053 config PGTABLE_LEVELS
1054 int
1055 default 2
1056
1057 config ARCH_HAS_ELF_RANDOMIZE
1058 bool
1059 help
1060 An architecture supports choosing randomized locations for
1061 stack, mmap, brk, and ET_DYN. Defined functions:
1062 - arch_mmap_rnd()
1063 - arch_randomize_brk()
1064
1065 config HAVE_ARCH_MMAP_RND_BITS
1066 bool
1067 help
1068 An arch should select this symbol if it supports setting a variable
1069 number of bits for use in establishing the base address for mmap
1070 allocations, has MMU enabled and provides values for both:
1071 - ARCH_MMAP_RND_BITS_MIN
1072 - ARCH_MMAP_RND_BITS_MAX
1073
1074 config HAVE_EXIT_THREAD
1075 bool
1076 help
1077 An architecture implements exit_thread.
1078
1079 config ARCH_MMAP_RND_BITS_MIN
1080 int
1081
1082 config ARCH_MMAP_RND_BITS_MAX
1083 int
1084
1085 config ARCH_MMAP_RND_BITS_DEFAULT
1086 int
1087
1088 config ARCH_MMAP_RND_BITS
1089 int "Number of bits to use for ASLR of mmap base address" if EXPERT
1090 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
1091 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
1092 default ARCH_MMAP_RND_BITS_MIN
1093 depends on HAVE_ARCH_MMAP_RND_BITS
1094 help
1095 This value can be used to select the number of bits to use to
1096 determine the random offset to the base address of vma regions
1097 resulting from mmap allocations. This value will be bounded
1098 by the architecture's minimum and maximum supported values.
1099
1100 This value can be changed after boot using the
1101 /proc/sys/vm/mmap_rnd_bits tunable
1102
1103 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
1104 bool
1105 help
1106 An arch should select this symbol if it supports running applications
1107 in compatibility mode, supports setting a variable number of bits for
1108 use in establishing the base address for mmap allocations, has MMU
1109 enabled and provides values for both:
1110 - ARCH_MMAP_RND_COMPAT_BITS_MIN
1111 - ARCH_MMAP_RND_COMPAT_BITS_MAX
1112
1113 config ARCH_MMAP_RND_COMPAT_BITS_MIN
1114 int
1115
1116 config ARCH_MMAP_RND_COMPAT_BITS_MAX
1117 int
1118
1119 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
1120 int
1121
1122 config ARCH_MMAP_RND_COMPAT_BITS
1123 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
1124 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
1125 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
1126 default ARCH_MMAP_RND_COMPAT_BITS_MIN
1127 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
1128 help
1129 This value can be used to select the number of bits to use to
1130 determine the random offset to the base address of vma regions
1131 resulting from mmap allocations for compatible applications This
1132 value will be bounded by the architecture's minimum and maximum
1133 supported values.
1134
1135 This value can be changed after boot using the
1136 /proc/sys/vm/mmap_rnd_compat_bits tunable
1137
1138 config HAVE_ARCH_COMPAT_MMAP_BASES
1139 bool
1140 help
1141 This allows 64bit applications to invoke 32-bit mmap() syscall
1142 and vice-versa 32-bit applications to call 64-bit mmap().
1143 Required for applications doing different bitness syscalls.
1144
1145 config HAVE_PAGE_SIZE_4KB
1146 bool
1147
1148 config HAVE_PAGE_SIZE_8KB
1149 bool
1150
1151 config HAVE_PAGE_SIZE_16KB
1152 bool
1153
1154 config HAVE_PAGE_SIZE_32KB
1155 bool
1156
1157 config HAVE_PAGE_SIZE_64KB
1158 bool
1159
1160 config HAVE_PAGE_SIZE_256KB
1161 bool
1162
1163 choice
1164 prompt "MMU page size"
1165
1166 config PAGE_SIZE_4KB
1167 bool "4KiB pages"
1168 depends on HAVE_PAGE_SIZE_4KB
1169 help
1170 This option select the standard 4KiB Linux page size and the only
1171 available option on many architectures. Using 4KiB page size will
1172 minimize memory consumption and is therefore recommended for low
1173 memory systems.
1174 Some software that is written for x86 systems makes incorrect
1175 assumptions about the page size and only runs on 4KiB pages.
1176
1177 config PAGE_SIZE_8KB
1178 bool "8KiB pages"
1179 depends on HAVE_PAGE_SIZE_8KB
1180 help
1181 This option is the only supported page size on a few older
1182 processors, and can be slightly faster than 4KiB pages.
1183
1184 config PAGE_SIZE_16KB
1185 bool "16KiB pages"
1186 depends on HAVE_PAGE_SIZE_16KB
1187 help
1188 This option is usually a good compromise between memory
1189 consumption and performance for typical desktop and server
1190 workloads, often saving a level of page table lookups compared
1191 to 4KB pages as well as reducing TLB pressure and overhead of
1192 per-page operations in the kernel at the expense of a larger
1193 page cache.
1194
1195 config PAGE_SIZE_32KB
1196 bool "32KiB pages"
1197 depends on HAVE_PAGE_SIZE_32KB
1198 help
1199 Using 32KiB page size will result in slightly higher performance
1200 kernel at the price of higher memory consumption compared to
1201 16KiB pages. This option is available only on cnMIPS cores.
1202 Note that you will need a suitable Linux distribution to
1203 support this.
1204
1205 config PAGE_SIZE_64KB
1206 bool "64KiB pages"
1207 depends on HAVE_PAGE_SIZE_64KB
1208 help
1209 Using 64KiB page size will result in slightly higher performance
1210 kernel at the price of much higher memory consumption compared to
1211 4KiB or 16KiB pages.
1212 This is not suitable for general-purpose workloads but the
1213 better performance may be worth the cost for certain types of
1214 supercomputing or database applications that work mostly with
1215 large in-memory data rather than small files.
1216
1217 config PAGE_SIZE_256KB
1218 bool "256KiB pages"
1219 depends on HAVE_PAGE_SIZE_256KB
1220 help
1221 256KiB pages have little practical value due to their extreme
1222 memory usage. The kernel will only be able to run applications
1223 that have been compiled with '-zmax-page-size' set to 256KiB
1224 (the default is 64KiB or 4KiB on most architectures).
1225
1226 endchoice
1227
1228 config PAGE_SIZE_LESS_THAN_64KB
1229 def_bool y
1230 depends on !PAGE_SIZE_64KB
1231 depends on PAGE_SIZE_LESS_THAN_256KB
1232
1233 config PAGE_SIZE_LESS_THAN_256KB
1234 def_bool y
1235 depends on !PAGE_SIZE_256KB
1236
1237 config PAGE_SHIFT
1238 int
1239 default 12 if PAGE_SIZE_4KB
1240 default 13 if PAGE_SIZE_8KB
1241 default 14 if PAGE_SIZE_16KB
1242 default 15 if PAGE_SIZE_32KB
1243 default 16 if PAGE_SIZE_64KB
1244 default 18 if PAGE_SIZE_256KB
1245
1246 # This allows to use a set of generic functions to determine mmap base
1247 # address by giving priority to top-down scheme only if the process
1248 # is not in legacy mode (compat task, unlimited stack size or
1249 # sysctl_legacy_va_layout).
1250 # Architecture that selects this option can provide its own version of:
1251 # - STACK_RND_MASK
1252 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
1253 bool
1254 depends on MMU
1255 select ARCH_HAS_ELF_RANDOMIZE
1256
1257 config HAVE_OBJTOOL
1258 bool
1259
1260 config HAVE_JUMP_LABEL_HACK
1261 bool
1262
1263 config HAVE_NOINSTR_HACK
1264 bool
1265
1266 config HAVE_NOINSTR_VALIDATION
1267 bool
1268
1269 config HAVE_UACCESS_VALIDATION
1270 bool
1271 select OBJTOOL
1272
1273 config HAVE_STACK_VALIDATION
1274 bool
1275 help
1276 Architecture supports objtool compile-time frame pointer rule
1277 validation.
1278
1279 config HAVE_RELIABLE_STACKTRACE
1280 bool
1281 help
1282 Architecture has either save_stack_trace_tsk_reliable() or
1283 arch_stack_walk_reliable() function which only returns a stack trace
1284 if it can guarantee the trace is reliable.
1285
1286 config HAVE_ARCH_HASH
1287 bool
1288 default n
1289 help
1290 If this is set, the architecture provides an <asm/hash.h>
1291 file which provides platform-specific implementations of some
1292 functions in <linux/hash.h> or fs/namei.c.
1293
1294 config HAVE_ARCH_NVRAM_OPS
1295 bool
1296
1297 config ISA_BUS_API
1298 def_bool ISA
1299
1300 #
1301 # ABI hall of shame
1302 #
1303 config CLONE_BACKWARDS
1304 bool
1305 help
1306 Architecture has tls passed as the 4th argument of clone(2),
1307 not the 5th one.
1308
1309 config CLONE_BACKWARDS2
1310 bool
1311 help
1312 Architecture has the first two arguments of clone(2) swapped.
1313
1314 config CLONE_BACKWARDS3
1315 bool
1316 help
1317 Architecture has tls passed as the 3rd argument of clone(2),
1318 not the 5th one.
1319
1320 config ODD_RT_SIGACTION
1321 bool
1322 help
1323 Architecture has unusual rt_sigaction(2) arguments
1324
1325 config OLD_SIGSUSPEND
1326 bool
1327 help
1328 Architecture has old sigsuspend(2) syscall, of one-argument variety
1329
1330 config OLD_SIGSUSPEND3
1331 bool
1332 help
1333 Even weirder antique ABI - three-argument sigsuspend(2)
1334
1335 config OLD_SIGACTION
1336 bool
1337 help
1338 Architecture has old sigaction(2) syscall. Nope, not the same
1339 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
1340 but fairly different variant of sigaction(2), thanks to OSF/1
1341 compatibility...
1342
1343 config COMPAT_OLD_SIGACTION
1344 bool
1345
1346 config COMPAT_32BIT_TIME
1347 bool "Provide system calls for 32-bit time_t"
1348 default !64BIT || COMPAT
1349 help
1350 This enables 32 bit time_t support in addition to 64 bit time_t support.
1351 This is relevant on all 32-bit architectures, and 64-bit architectures
1352 as part of compat syscall handling.
1353
1354 config ARCH_NO_PREEMPT
1355 bool
1356
1357 config ARCH_SUPPORTS_RT
1358 bool
1359
1360 config CPU_NO_EFFICIENT_FFS
1361 def_bool n
1362
1363 config HAVE_ARCH_VMAP_STACK
1364 def_bool n
1365 help
1366 An arch should select this symbol if it can support kernel stacks
1367 in vmalloc space. This means:
1368
1369 - vmalloc space must be large enough to hold many kernel stacks.
1370 This may rule out many 32-bit architectures.
1371
1372 - Stacks in vmalloc space need to work reliably. For example, if
1373 vmap page tables are created on demand, either this mechanism
1374 needs to work while the stack points to a virtual address with
1375 unpopulated page tables or arch code (switch_to() and switch_mm(),
1376 most likely) needs to ensure that the stack's page table entries
1377 are populated before running on a possibly unpopulated stack.
1378
1379 - If the stack overflows into a guard page, something reasonable
1380 should happen. The definition of "reasonable" is flexible, but
1381 instantly rebooting without logging anything would be unfriendly.
1382
1383 config VMAP_STACK
1384 default y
1385 bool "Use a virtually-mapped stack"
1386 depends on HAVE_ARCH_VMAP_STACK
1387 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC
1388 help
1389 Enable this if you want the use virtually-mapped kernel stacks
1390 with guard pages. This causes kernel stack overflows to be
1391 caught immediately rather than causing difficult-to-diagnose
1392 corruption.
1393
1394 To use this with software KASAN modes, the architecture must support
1395 backing virtual mappings with real shadow memory, and KASAN_VMALLOC
1396 must be enabled.
1397
1398 config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1399 def_bool n
1400 help
1401 An arch should select this symbol if it can support kernel stack
1402 offset randomization with calls to add_random_kstack_offset()
1403 during syscall entry and choose_random_kstack_offset() during
1404 syscall exit. Careful removal of -fstack-protector-strong and
1405 -fstack-protector should also be applied to the entry code and
1406 closely examined, as the artificial stack bump looks like an array
1407 to the compiler, so it will attempt to add canary checks regardless
1408 of the static branch state.
1409
1410 config RANDOMIZE_KSTACK_OFFSET
1411 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT
1412 default y
1413 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1414 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000
1415 help
1416 The kernel stack offset can be randomized (after pt_regs) by
1417 roughly 5 bits of entropy, frustrating memory corruption
1418 attacks that depend on stack address determinism or
1419 cross-syscall address exposures.
1420
1421 The feature is controlled via the "randomize_kstack_offset=on/off"
1422 kernel boot param, and if turned off has zero overhead due to its use
1423 of static branches (see JUMP_LABEL).
1424
1425 If unsure, say Y.
1426
1427 config RANDOMIZE_KSTACK_OFFSET_DEFAULT
1428 bool "Default state of kernel stack offset randomization"
1429 depends on RANDOMIZE_KSTACK_OFFSET
1430 help
1431 Kernel stack offset randomization is controlled by kernel boot param
1432 "randomize_kstack_offset=on/off", and this config chooses the default
1433 boot state.
1434
1435 config ARCH_OPTIONAL_KERNEL_RWX
1436 def_bool n
1437
1438 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1439 def_bool n
1440
1441 config ARCH_HAS_STRICT_KERNEL_RWX
1442 def_bool n
1443
1444 config STRICT_KERNEL_RWX
1445 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
1446 depends on ARCH_HAS_STRICT_KERNEL_RWX
1447 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1448 help
1449 If this is set, kernel text and rodata memory will be made read-only,
1450 and non-text memory will be made non-executable. This provides
1451 protection against certain security exploits (e.g. executing the heap
1452 or modifying text)
1453
1454 These features are considered standard security practice these days.
1455 You should say Y here in almost all cases.
1456
1457 config ARCH_HAS_STRICT_MODULE_RWX
1458 def_bool n
1459
1460 config STRICT_MODULE_RWX
1461 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
1462 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
1463 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1464 help
1465 If this is set, module text and rodata memory will be made read-only,
1466 and non-text memory will be made non-executable. This provides
1467 protection against certain security exploits (e.g. writing to text)
1468
1469 # select if the architecture provides an asm/dma-direct.h header
1470 config ARCH_HAS_PHYS_TO_DMA
1471 bool
1472
1473 config HAVE_ARCH_COMPILER_H
1474 bool
1475 help
1476 An architecture can select this if it provides an
1477 asm/compiler.h header that should be included after
1478 linux/compiler-*.h in order to override macro definitions that those
1479 headers generally provide.
1480
1481 config HAVE_ARCH_PREL32_RELOCATIONS
1482 bool
1483 help
1484 May be selected by an architecture if it supports place-relative
1485 32-bit relocations, both in the toolchain and in the module loader,
1486 in which case relative references can be used in special sections
1487 for PCI fixup, initcalls etc which are only half the size on 64 bit
1488 architectures, and don't require runtime relocation on relocatable
1489 kernels.
1490
1491 config ARCH_USE_MEMREMAP_PROT
1492 bool
1493
1494 config LOCK_EVENT_COUNTS
1495 bool "Locking event counts collection"
1496 depends on DEBUG_FS
1497 help
1498 Enable light-weight counting of various locking related events
1499 in the system with minimal performance impact. This reduces
1500 the chance of application behavior change because of timing
1501 differences. The counts are reported via debugfs.
1502
1503 # Select if the architecture has support for applying RELR relocations.
1504 config ARCH_HAS_RELR
1505 bool
1506
1507 config RELR
1508 bool "Use RELR relocation packing"
1509 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1510 default y
1511 help
1512 Store the kernel's dynamic relocations in the RELR relocation packing
1513 format. Requires a compatible linker (LLD supports this feature), as
1514 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1515 are compatible).
1516
1517 config ARCH_HAS_MEM_ENCRYPT
1518 bool
1519
1520 config ARCH_HAS_CC_PLATFORM
1521 bool
1522
1523 config HAVE_SPARSE_SYSCALL_NR
1524 bool
1525 help
1526 An architecture should select this if its syscall numbering is sparse
1527 to save space. For example, MIPS architecture has a syscall array with
1528 entries at 4000, 5000 and 6000 locations. This option turns on syscall
1529 related optimizations for a given architecture.
1530
1531 config ARCH_HAS_VDSO_DATA
1532 bool
1533
1534 config HAVE_STATIC_CALL
1535 bool
1536
1537 config HAVE_STATIC_CALL_INLINE
1538 bool
1539 depends on HAVE_STATIC_CALL
1540 select OBJTOOL
1541
1542 config HAVE_PREEMPT_DYNAMIC
1543 bool
1544
1545 config HAVE_PREEMPT_DYNAMIC_CALL
1546 bool
1547 depends on HAVE_STATIC_CALL
1548 select HAVE_PREEMPT_DYNAMIC
1549 help
1550 An architecture should select this if it can handle the preemption
1551 model being selected at boot time using static calls.
1552
1553 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a
1554 preemption function will be patched directly.
1555
1556 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any
1557 call to a preemption function will go through a trampoline, and the
1558 trampoline will be patched.
1559
1560 It is strongly advised to support inline static call to avoid any
1561 overhead.
1562
1563 config HAVE_PREEMPT_DYNAMIC_KEY
1564 bool
1565 depends on HAVE_ARCH_JUMP_LABEL
1566 select HAVE_PREEMPT_DYNAMIC
1567 help
1568 An architecture should select this if it can handle the preemption
1569 model being selected at boot time using static keys.
1570
1571 Each preemption function will be given an early return based on a
1572 static key. This should have slightly lower overhead than non-inline
1573 static calls, as this effectively inlines each trampoline into the
1574 start of its callee. This may avoid redundant work, and may
1575 integrate better with CFI schemes.
1576
1577 This will have greater overhead than using inline static calls as
1578 the call to the preemption function cannot be entirely elided.
1579
1580 config ARCH_WANT_LD_ORPHAN_WARN
1581 bool
1582 help
1583 An arch should select this symbol once all linker sections are explicitly
1584 included, size-asserted, or discarded in the linker scripts. This is
1585 important because we never want expected sections to be placed heuristically
1586 by the linker, since the locations of such sections can change between linker
1587 versions.
1588
1589 config HAVE_ARCH_PFN_VALID
1590 bool
1591
1592 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
1593 bool
1594
1595 config ARCH_SUPPORTS_PAGE_TABLE_CHECK
1596 bool
1597
1598 config ARCH_SPLIT_ARG64
1599 bool
1600 help
1601 If a 32-bit architecture requires 64-bit arguments to be split into
1602 pairs of 32-bit arguments, select this option.
1603
1604 config ARCH_HAS_ELFCORE_COMPAT
1605 bool
1606
1607 config ARCH_HAS_PARANOID_L1D_FLUSH
1608 bool
1609
1610 config ARCH_HAVE_TRACE_MMIO_ACCESS
1611 bool
1612
1613 config DYNAMIC_SIGFRAME
1614 bool
1615
1616 # Select, if arch has a named attribute group bound to NUMA device nodes.
1617 config HAVE_ARCH_NODE_DEV_GROUP
1618 bool
1619
1620 config ARCH_HAS_HW_PTE_YOUNG
1621 bool
1622 help
1623 Architectures that select this option are capable of setting the
1624 accessed bit in PTE entries when using them as part of linear address
1625 translations. Architectures that require runtime check should select
1626 this option and override arch_has_hw_pte_young().
1627
1628 config ARCH_HAS_NONLEAF_PMD_YOUNG
1629 bool
1630 help
1631 Architectures that select this option are capable of setting the
1632 accessed bit in non-leaf PMD entries when using them as part of linear
1633 address translations. Page table walkers that clear the accessed bit
1634 may use this capability to reduce their search space.
1635
1636 config ARCH_HAS_KERNEL_FPU_SUPPORT
1637 bool
1638 help
1639 Architectures that select this option can run floating-point code in
1640 the kernel, as described in Documentation/core-api/floating-point.rst.
1641
1642 source "kernel/gcov/Kconfig"
1643
1644 source "scripts/gcc-plugins/Kconfig"
1645
1646 config FUNCTION_ALIGNMENT_4B
1647 bool
1648
1649 config FUNCTION_ALIGNMENT_8B
1650 bool
1651
1652 config FUNCTION_ALIGNMENT_16B
1653 bool
1654
1655 config FUNCTION_ALIGNMENT_32B
1656 bool
1657
1658 config FUNCTION_ALIGNMENT_64B
1659 bool
1660
1661 config FUNCTION_ALIGNMENT
1662 int
1663 default 64 if FUNCTION_ALIGNMENT_64B
1664 default 32 if FUNCTION_ALIGNMENT_32B
1665 default 16 if FUNCTION_ALIGNMENT_16B
1666 default 8 if FUNCTION_ALIGNMENT_8B
1667 default 4 if FUNCTION_ALIGNMENT_4B
1668 default 0
1669
1670 config CC_HAS_MIN_FUNCTION_ALIGNMENT
1671 # Detect availability of the GCC option -fmin-function-alignment which
1672 # guarantees minimal alignment for all functions, unlike
1673 # -falign-functions which the compiler ignores for cold functions.
1674 def_bool $(cc-option, -fmin-function-alignment=8)
1675
1676 config CC_HAS_SANE_FUNCTION_ALIGNMENT
1677 # Set if the guaranteed alignment with -fmin-function-alignment is
1678 # available or extra care is required in the kernel. Clang provides
1679 # strict alignment always, even with -falign-functions.
1680 def_bool CC_HAS_MIN_FUNCTION_ALIGNMENT || CC_IS_CLANG
1681
1682 config ARCH_NEED_CMPXCHG_1_EMU
1683 bool
1684
1685 endmenu
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