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
  12config ARCH_CONFIGURES_CPU_MITIGATIONS
  13	bool
  14
  15if !ARCH_CONFIGURES_CPU_MITIGATIONS
  16config CPU_MITIGATIONS
  17	def_bool y
  18endif
  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#
  24config ARCH_HAS_DMA_OPS
  25	depends on HAS_DMA
  26	select DMA_OPS_HELPERS
  27	bool
  28
  29menu "General architecture-dependent options"
  30
  31config 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
  38config HOTPLUG_SMT
  39	bool
  40
  41config SMT_NUM_THREADS_DYNAMIC
  42	bool
  43
  44# Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL
  45config HOTPLUG_CORE_SYNC
  46	bool
  47
  48# Basic CPU dead synchronization selected by architecture
  49config HOTPLUG_CORE_SYNC_DEAD
  50	bool
  51	select HOTPLUG_CORE_SYNC
  52
  53# Full CPU synchronization with alive state selected by architecture
  54config HOTPLUG_CORE_SYNC_FULL
  55	bool
  56	select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU
  57	select HOTPLUG_CORE_SYNC
  58
  59config HOTPLUG_SPLIT_STARTUP
  60	bool
  61	select HOTPLUG_CORE_SYNC_FULL
  62
  63config HOTPLUG_PARALLEL
  64	bool
  65	select HOTPLUG_SPLIT_STARTUP
  66
  67config GENERIC_ENTRY
  68	bool
  69
  70config 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
  83config 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
 109config 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
 115config 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
 121config OPTPROBES
 122	def_bool y
 123	depends on KPROBES && HAVE_OPTPROBES
 124	select NEED_TASKS_RCU
 125
 126config 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
 135config UPROBES
 136	def_bool n
 137	depends on ARCH_SUPPORTS_UPROBES
 138	select TASKS_TRACE_RCU
 139	help
 140	  Uprobes is the user-space counterpart to kprobes: they
 141	  enable instrumentation applications (such as 'perf probe')
 142	  to establish unintrusive probes in user-space binaries and
 143	  libraries, by executing handler functions when the probes
 144	  are hit by user-space applications.
 145
 146	  ( These probes come in the form of single-byte breakpoints,
 147	    managed by the kernel and kept transparent to the probed
 148	    application. )
 149
 150config HAVE_64BIT_ALIGNED_ACCESS
 151	def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
 152	help
 153	  Some architectures require 64 bit accesses to be 64 bit
 154	  aligned, which also requires structs containing 64 bit values
 155	  to be 64 bit aligned too. This includes some 32 bit
 156	  architectures which can do 64 bit accesses, as well as 64 bit
 157	  architectures without unaligned access.
 158
 159	  This symbol should be selected by an architecture if 64 bit
 160	  accesses are required to be 64 bit aligned in this way even
 161	  though it is not a 64 bit architecture.
 162
 163	  See Documentation/core-api/unaligned-memory-access.rst for
 164	  more information on the topic of unaligned memory accesses.
 165
 166config HAVE_EFFICIENT_UNALIGNED_ACCESS
 167	bool
 168	help
 169	  Some architectures are unable to perform unaligned accesses
 170	  without the use of get_unaligned/put_unaligned. Others are
 171	  unable to perform such accesses efficiently (e.g. trap on
 172	  unaligned access and require fixing it up in the exception
 173	  handler.)
 174
 175	  This symbol should be selected by an architecture if it can
 176	  perform unaligned accesses efficiently to allow different
 177	  code paths to be selected for these cases. Some network
 178	  drivers, for example, could opt to not fix up alignment
 179	  problems with received packets if doing so would not help
 180	  much.
 181
 182	  See Documentation/core-api/unaligned-memory-access.rst for more
 183	  information on the topic of unaligned memory accesses.
 184
 185config ARCH_USE_BUILTIN_BSWAP
 186	bool
 187	help
 188	  Modern versions of GCC (since 4.4) have builtin functions
 189	  for handling byte-swapping. Using these, instead of the old
 190	  inline assembler that the architecture code provides in the
 191	  __arch_bswapXX() macros, allows the compiler to see what's
 192	  happening and offers more opportunity for optimisation. In
 193	  particular, the compiler will be able to combine the byteswap
 194	  with a nearby load or store and use load-and-swap or
 195	  store-and-swap instructions if the architecture has them. It
 196	  should almost *never* result in code which is worse than the
 197	  hand-coded assembler in <asm/swab.h>.  But just in case it
 198	  does, the use of the builtins is optional.
 199
 200	  Any architecture with load-and-swap or store-and-swap
 201	  instructions should set this. And it shouldn't hurt to set it
 202	  on architectures that don't have such instructions.
 203
 204config KRETPROBES
 205	def_bool y
 206	depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK)
 207
 208config KRETPROBE_ON_RETHOOK
 209	def_bool y
 210	depends on HAVE_RETHOOK
 211	depends on KRETPROBES
 212	select RETHOOK
 213
 214config USER_RETURN_NOTIFIER
 215	bool
 216	depends on HAVE_USER_RETURN_NOTIFIER
 217	help
 218	  Provide a kernel-internal notification when a cpu is about to
 219	  switch to user mode.
 220
 221config HAVE_IOREMAP_PROT
 222	bool
 223
 224config HAVE_KPROBES
 225	bool
 226
 227config HAVE_KRETPROBES
 228	bool
 229
 230config HAVE_OPTPROBES
 231	bool
 232
 233config HAVE_KPROBES_ON_FTRACE
 234	bool
 235
 236config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
 237	bool
 238	help
 239	  Since kretprobes modifies return address on the stack, the
 240	  stacktrace may see the kretprobe trampoline address instead
 241	  of correct one. If the architecture stacktrace code and
 242	  unwinder can adjust such entries, select this configuration.
 243
 244config HAVE_FUNCTION_ERROR_INJECTION
 245	bool
 246
 247config HAVE_NMI
 248	bool
 249
 250config HAVE_FUNCTION_DESCRIPTORS
 251	bool
 252
 253config TRACE_IRQFLAGS_SUPPORT
 254	bool
 255
 256config TRACE_IRQFLAGS_NMI_SUPPORT
 257	bool
 258
 259#
 260# An arch should select this if it provides all these things:
 261#
 262#	task_pt_regs()		in asm/processor.h or asm/ptrace.h
 263#	arch_has_single_step()	if there is hardware single-step support
 264#	arch_has_block_step()	if there is hardware block-step support
 265#	asm/syscall.h		supplying asm-generic/syscall.h interface
 266#	linux/regset.h		user_regset interfaces
 267#	CORE_DUMP_USE_REGSET	#define'd in linux/elf.h
 268#	TIF_SYSCALL_TRACE	calls ptrace_report_syscall_{entry,exit}
 269#	TIF_NOTIFY_RESUME	calls resume_user_mode_work()
 270#
 271config HAVE_ARCH_TRACEHOOK
 272	bool
 273
 274config HAVE_DMA_CONTIGUOUS
 275	bool
 276
 277config GENERIC_SMP_IDLE_THREAD
 278	bool
 279
 280config GENERIC_IDLE_POLL_SETUP
 281	bool
 282
 283config ARCH_HAS_FORTIFY_SOURCE
 284	bool
 285	help
 286	  An architecture should select this when it can successfully
 287	  build and run with CONFIG_FORTIFY_SOURCE.
 288
 289#
 290# Select if the arch provides a historic keepinit alias for the retain_initrd
 291# command line option
 292#
 293config ARCH_HAS_KEEPINITRD
 294	bool
 295
 296# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
 297config ARCH_HAS_SET_MEMORY
 298	bool
 299
 300# Select if arch has all set_direct_map_invalid/default() functions
 301config ARCH_HAS_SET_DIRECT_MAP
 302	bool
 303
 304#
 305# Select if the architecture provides the arch_dma_set_uncached symbol to
 306# either provide an uncached segment alias for a DMA allocation, or
 307# to remap the page tables in place.
 308#
 309config ARCH_HAS_DMA_SET_UNCACHED
 310	bool
 311
 312#
 313# Select if the architectures provides the arch_dma_clear_uncached symbol
 314# to undo an in-place page table remap for uncached access.
 315#
 316config ARCH_HAS_DMA_CLEAR_UNCACHED
 317	bool
 318
 319config ARCH_HAS_CPU_FINALIZE_INIT
 320	bool
 321
 322# The architecture has a per-task state that includes the mm's PASID
 323config ARCH_HAS_CPU_PASID
 324	bool
 325	select IOMMU_MM_DATA
 326
 327config HAVE_ARCH_THREAD_STRUCT_WHITELIST
 328	bool
 329	help
 330	  An architecture should select this to provide hardened usercopy
 331	  knowledge about what region of the thread_struct should be
 332	  whitelisted for copying to userspace. Normally this is only the
 333	  FPU registers. Specifically, arch_thread_struct_whitelist()
 334	  should be implemented. Without this, the entire thread_struct
 335	  field in task_struct will be left whitelisted.
 336
 337# Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 338config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 339	bool
 340
 341config ARCH_WANTS_NO_INSTR
 342	bool
 343	help
 344	  An architecture should select this if the noinstr macro is being used on
 345	  functions to denote that the toolchain should avoid instrumenting such
 346	  functions and is required for correctness.
 347
 348config ARCH_32BIT_OFF_T
 349	bool
 350	depends on !64BIT
 351	help
 352	  All new 32-bit architectures should have 64-bit off_t type on
 353	  userspace side which corresponds to the loff_t kernel type. This
 354	  is the requirement for modern ABIs. Some existing architectures
 355	  still support 32-bit off_t. This option is enabled for all such
 356	  architectures explicitly.
 357
 358# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat
 359config ARCH_32BIT_USTAT_F_TINODE
 360	bool
 361
 362config HAVE_ASM_MODVERSIONS
 363	bool
 364	help
 365	  This symbol should be selected by an architecture if it provides
 366	  <asm/asm-prototypes.h> to support the module versioning for symbols
 367	  exported from assembly code.
 368
 369config HAVE_REGS_AND_STACK_ACCESS_API
 370	bool
 371	help
 372	  This symbol should be selected by an architecture if it supports
 373	  the API needed to access registers and stack entries from pt_regs,
 374	  declared in asm/ptrace.h
 375	  For example the kprobes-based event tracer needs this API.
 376
 377config HAVE_RSEQ
 378	bool
 379	depends on HAVE_REGS_AND_STACK_ACCESS_API
 380	help
 381	  This symbol should be selected by an architecture if it
 382	  supports an implementation of restartable sequences.
 383
 384config HAVE_RUST
 385	bool
 386	help
 387	  This symbol should be selected by an architecture if it
 388	  supports Rust.
 389
 390config HAVE_FUNCTION_ARG_ACCESS_API
 391	bool
 392	help
 393	  This symbol should be selected by an architecture if it supports
 394	  the API needed to access function arguments from pt_regs,
 395	  declared in asm/ptrace.h
 396
 397config HAVE_HW_BREAKPOINT
 398	bool
 399	depends on PERF_EVENTS
 400
 401config HAVE_MIXED_BREAKPOINTS_REGS
 402	bool
 403	depends on HAVE_HW_BREAKPOINT
 404	help
 405	  Depending on the arch implementation of hardware breakpoints,
 406	  some of them have separate registers for data and instruction
 407	  breakpoints addresses, others have mixed registers to store
 408	  them but define the access type in a control register.
 409	  Select this option if your arch implements breakpoints under the
 410	  latter fashion.
 411
 412config HAVE_USER_RETURN_NOTIFIER
 413	bool
 414
 415config HAVE_PERF_EVENTS_NMI
 416	bool
 417	help
 418	  System hardware can generate an NMI using the perf event
 419	  subsystem.  Also has support for calculating CPU cycle events
 420	  to determine how many clock cycles in a given period.
 421
 422config HAVE_HARDLOCKUP_DETECTOR_PERF
 423	bool
 424	depends on HAVE_PERF_EVENTS_NMI
 425	help
 426	  The arch chooses to use the generic perf-NMI-based hardlockup
 427	  detector. Must define HAVE_PERF_EVENTS_NMI.
 428
 429config HAVE_HARDLOCKUP_DETECTOR_ARCH
 430	bool
 431	help
 432	  The arch provides its own hardlockup detector implementation instead
 433	  of the generic ones.
 434
 435	  It uses the same command line parameters, and sysctl interface,
 436	  as the generic hardlockup detectors.
 437
 438config HAVE_PERF_REGS
 439	bool
 440	help
 441	  Support selective register dumps for perf events. This includes
 442	  bit-mapping of each registers and a unique architecture id.
 443
 444config HAVE_PERF_USER_STACK_DUMP
 445	bool
 446	help
 447	  Support user stack dumps for perf event samples. This needs
 448	  access to the user stack pointer which is not unified across
 449	  architectures.
 450
 451config HAVE_ARCH_JUMP_LABEL
 452	bool
 453
 454config HAVE_ARCH_JUMP_LABEL_RELATIVE
 455	bool
 456
 457config MMU_GATHER_TABLE_FREE
 458	bool
 459
 460config MMU_GATHER_RCU_TABLE_FREE
 461	bool
 462	select MMU_GATHER_TABLE_FREE
 463
 464config MMU_GATHER_PAGE_SIZE
 465	bool
 466
 467config MMU_GATHER_NO_RANGE
 468	bool
 469	select MMU_GATHER_MERGE_VMAS
 470
 471config MMU_GATHER_NO_FLUSH_CACHE
 472	bool
 473
 474config MMU_GATHER_MERGE_VMAS
 475	bool
 476
 477config MMU_GATHER_NO_GATHER
 478	bool
 479	depends on MMU_GATHER_TABLE_FREE
 480
 481config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
 482	bool
 483	help
 484	  Temporary select until all architectures can be converted to have
 485	  irqs disabled over activate_mm. Architectures that do IPI based TLB
 486	  shootdowns should enable this.
 487
 488# Use normal mm refcounting for MMU_LAZY_TLB kernel thread references.
 489# MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching
 490# to/from kernel threads when the same mm is running on a lot of CPUs (a large
 491# multi-threaded application), by reducing contention on the mm refcount.
 492#
 493# This can be disabled if the architecture ensures no CPUs are using an mm as a
 494# "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm
 495# or its kernel page tables). This could be arranged by arch_exit_mmap(), or
 496# final exit(2) TLB flush, for example.
 497#
 498# To implement this, an arch *must*:
 499# Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating
 500# the lazy tlb reference of a kthread's ->active_mm (non-arch code has been
 501# converted already).
 502config MMU_LAZY_TLB_REFCOUNT
 503	def_bool y
 504	depends on !MMU_LAZY_TLB_SHOOTDOWN
 505
 506# This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an
 507# mm as a lazy tlb beyond its last reference count, by shooting down these
 508# users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may
 509# be using the mm as a lazy tlb, so that they may switch themselves to using
 510# init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs
 511# may be using mm as a lazy tlb mm.
 512#
 513# To implement this, an arch *must*:
 514# - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains
 515#   at least all possible CPUs in which the mm is lazy.
 516# - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above).
 517config MMU_LAZY_TLB_SHOOTDOWN
 518	bool
 519
 520config ARCH_HAVE_NMI_SAFE_CMPXCHG
 521	bool
 522
 523config ARCH_HAVE_EXTRA_ELF_NOTES
 524	bool
 525	help
 526	  An architecture should select this in order to enable adding an
 527	  arch-specific ELF note section to core files. It must provide two
 528	  functions: elf_coredump_extra_notes_size() and
 529	  elf_coredump_extra_notes_write() which are invoked by the ELF core
 530	  dumper.
 531
 532config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
 533	bool
 534
 535config HAVE_ALIGNED_STRUCT_PAGE
 536	bool
 537	help
 538	  This makes sure that struct pages are double word aligned and that
 539	  e.g. the SLUB allocator can perform double word atomic operations
 540	  on a struct page for better performance. However selecting this
 541	  might increase the size of a struct page by a word.
 542
 543config HAVE_CMPXCHG_LOCAL
 544	bool
 545
 546config HAVE_CMPXCHG_DOUBLE
 547	bool
 548
 549config ARCH_WEAK_RELEASE_ACQUIRE
 550	bool
 551
 552config ARCH_WANT_IPC_PARSE_VERSION
 553	bool
 554
 555config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 556	bool
 557
 558config ARCH_WANT_OLD_COMPAT_IPC
 559	select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 560	bool
 561
 562config HAVE_ARCH_SECCOMP
 563	bool
 564	help
 565	  An arch should select this symbol to support seccomp mode 1 (the fixed
 566	  syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
 567	  and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
 568	  - __NR_seccomp_read_32
 569	  - __NR_seccomp_write_32
 570	  - __NR_seccomp_exit_32
 571	  - __NR_seccomp_sigreturn_32
 572
 573config HAVE_ARCH_SECCOMP_FILTER
 574	bool
 575	select HAVE_ARCH_SECCOMP
 576	help
 577	  An arch should select this symbol if it provides all of these things:
 578	  - all the requirements for HAVE_ARCH_SECCOMP
 579	  - syscall_get_arch()
 580	  - syscall_get_arguments()
 581	  - syscall_rollback()
 582	  - syscall_set_return_value()
 583	  - SIGSYS siginfo_t support
 584	  - secure_computing is called from a ptrace_event()-safe context
 585	  - secure_computing return value is checked and a return value of -1
 586	    results in the system call being skipped immediately.
 587	  - seccomp syscall wired up
 588	  - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE,
 589	    SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If
 590	    COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too.
 591
 592config SECCOMP
 593	prompt "Enable seccomp to safely execute untrusted bytecode"
 594	def_bool y
 595	depends on HAVE_ARCH_SECCOMP
 596	help
 597	  This kernel feature is useful for number crunching applications
 598	  that may need to handle untrusted bytecode during their
 599	  execution. By using pipes or other transports made available
 600	  to the process as file descriptors supporting the read/write
 601	  syscalls, it's possible to isolate those applications in their
 602	  own address space using seccomp. Once seccomp is enabled via
 603	  prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
 604	  disabled and the task is only allowed to execute a few safe
 605	  syscalls defined by each seccomp mode.
 606
 607	  If unsure, say Y.
 608
 609config SECCOMP_FILTER
 610	def_bool y
 611	depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 612	help
 613	  Enable tasks to build secure computing environments defined
 614	  in terms of Berkeley Packet Filter programs which implement
 615	  task-defined system call filtering polices.
 616
 617	  See Documentation/userspace-api/seccomp_filter.rst for details.
 618
 619config SECCOMP_CACHE_DEBUG
 620	bool "Show seccomp filter cache status in /proc/pid/seccomp_cache"
 621	depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR
 622	depends on PROC_FS
 623	help
 624	  This enables the /proc/pid/seccomp_cache interface to monitor
 625	  seccomp cache data. The file format is subject to change. Reading
 626	  the file requires CAP_SYS_ADMIN.
 627
 628	  This option is for debugging only. Enabling presents the risk that
 629	  an adversary may be able to infer the seccomp filter logic.
 630
 631	  If unsure, say N.
 632
 633config HAVE_ARCH_STACKLEAK
 634	bool
 635	help
 636	  An architecture should select this if it has the code which
 637	  fills the used part of the kernel stack with the STACKLEAK_POISON
 638	  value before returning from system calls.
 639
 640config HAVE_STACKPROTECTOR
 641	bool
 642	help
 643	  An arch should select this symbol if:
 644	  - it has implemented a stack canary (e.g. __stack_chk_guard)
 645
 646config STACKPROTECTOR
 647	bool "Stack Protector buffer overflow detection"
 648	depends on HAVE_STACKPROTECTOR
 649	depends on $(cc-option,-fstack-protector)
 650	default y
 651	help
 652	  This option turns on the "stack-protector" GCC feature. This
 653	  feature puts, at the beginning of functions, a canary value on
 654	  the stack just before the return address, and validates
 655	  the value just before actually returning.  Stack based buffer
 656	  overflows (that need to overwrite this return address) now also
 657	  overwrite the canary, which gets detected and the attack is then
 658	  neutralized via a kernel panic.
 659
 660	  Functions will have the stack-protector canary logic added if they
 661	  have an 8-byte or larger character array on the stack.
 662
 663	  This feature requires gcc version 4.2 or above, or a distribution
 664	  gcc with the feature backported ("-fstack-protector").
 665
 666	  On an x86 "defconfig" build, this feature adds canary checks to
 667	  about 3% of all kernel functions, which increases kernel code size
 668	  by about 0.3%.
 669
 670config STACKPROTECTOR_STRONG
 671	bool "Strong Stack Protector"
 672	depends on STACKPROTECTOR
 673	depends on $(cc-option,-fstack-protector-strong)
 674	default y
 675	help
 676	  Functions will have the stack-protector canary logic added in any
 677	  of the following conditions:
 678
 679	  - local variable's address used as part of the right hand side of an
 680	    assignment or function argument
 681	  - local variable is an array (or union containing an array),
 682	    regardless of array type or length
 683	  - uses register local variables
 684
 685	  This feature requires gcc version 4.9 or above, or a distribution
 686	  gcc with the feature backported ("-fstack-protector-strong").
 687
 688	  On an x86 "defconfig" build, this feature adds canary checks to
 689	  about 20% of all kernel functions, which increases the kernel code
 690	  size by about 2%.
 691
 692config ARCH_SUPPORTS_SHADOW_CALL_STACK
 693	bool
 694	help
 695	  An architecture should select this if it supports the compiler's
 696	  Shadow Call Stack and implements runtime support for shadow stack
 697	  switching.
 698
 699config SHADOW_CALL_STACK
 700	bool "Shadow Call Stack"
 701	depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
 702	depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
 703	depends on MMU
 704	help
 705	  This option enables the compiler's Shadow Call Stack, which
 706	  uses a shadow stack to protect function return addresses from
 707	  being overwritten by an attacker. More information can be found
 708	  in the compiler's documentation:
 709
 710	  - Clang: https://clang.llvm.org/docs/ShadowCallStack.html
 711	  - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options
 712
 713	  Note that security guarantees in the kernel differ from the
 714	  ones documented for user space. The kernel must store addresses
 715	  of shadow stacks in memory, which means an attacker capable of
 716	  reading and writing arbitrary memory may be able to locate them
 717	  and hijack control flow by modifying the stacks.
 718
 719config DYNAMIC_SCS
 720	bool
 721	help
 722	  Set by the arch code if it relies on code patching to insert the
 723	  shadow call stack push and pop instructions rather than on the
 724	  compiler.
 725
 726config LTO
 727	bool
 728	help
 729	  Selected if the kernel will be built using the compiler's LTO feature.
 730
 731config LTO_CLANG
 732	bool
 733	select LTO
 734	help
 735	  Selected if the kernel will be built using Clang's LTO feature.
 736
 737config ARCH_SUPPORTS_LTO_CLANG
 738	bool
 739	help
 740	  An architecture should select this option if it supports:
 741	  - compiling with Clang,
 742	  - compiling inline assembly with Clang's integrated assembler,
 743	  - and linking with LLD.
 744
 745config ARCH_SUPPORTS_LTO_CLANG_THIN
 746	bool
 747	help
 748	  An architecture should select this option if it can support Clang's
 749	  ThinLTO mode.
 750
 751config HAS_LTO_CLANG
 752	def_bool y
 753	depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM
 754	depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
 755	depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
 756	depends on ARCH_SUPPORTS_LTO_CLANG
 757	depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT
 758	# https://github.com/ClangBuiltLinux/linux/issues/1721
 759	depends on (!KASAN || KASAN_HW_TAGS || CLANG_VERSION >= 170000) || !DEBUG_INFO
 760	depends on (!KCOV || CLANG_VERSION >= 170000) || !DEBUG_INFO
 761	depends on !GCOV_KERNEL
 762	help
 763	  The compiler and Kconfig options support building with Clang's
 764	  LTO.
 765
 766choice
 767	prompt "Link Time Optimization (LTO)"
 768	default LTO_NONE
 769	help
 770	  This option enables Link Time Optimization (LTO), which allows the
 771	  compiler to optimize binaries globally.
 772
 773	  If unsure, select LTO_NONE. Note that LTO is very resource-intensive
 774	  so it's disabled by default.
 775
 776config LTO_NONE
 777	bool "None"
 778	help
 779	  Build the kernel normally, without Link Time Optimization (LTO).
 780
 781config LTO_CLANG_FULL
 782	bool "Clang Full LTO (EXPERIMENTAL)"
 783	depends on HAS_LTO_CLANG
 784	depends on !COMPILE_TEST
 785	select LTO_CLANG
 786	help
 787	  This option enables Clang's full Link Time Optimization (LTO), which
 788	  allows the compiler to optimize the kernel globally. If you enable
 789	  this option, the compiler generates LLVM bitcode instead of ELF
 790	  object files, and the actual compilation from bitcode happens at
 791	  the LTO link step, which may take several minutes depending on the
 792	  kernel configuration. More information can be found from LLVM's
 793	  documentation:
 794
 795	    https://llvm.org/docs/LinkTimeOptimization.html
 796
 797	  During link time, this option can use a large amount of RAM, and
 798	  may take much longer than the ThinLTO option.
 799
 800config LTO_CLANG_THIN
 801	bool "Clang ThinLTO (EXPERIMENTAL)"
 802	depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN
 803	select LTO_CLANG
 804	help
 805	  This option enables Clang's ThinLTO, which allows for parallel
 806	  optimization and faster incremental compiles compared to the
 807	  CONFIG_LTO_CLANG_FULL option. More information can be found
 808	  from Clang's documentation:
 809
 810	    https://clang.llvm.org/docs/ThinLTO.html
 811
 812	  If unsure, say Y.
 813endchoice
 814
 815config ARCH_SUPPORTS_AUTOFDO_CLANG
 816	bool
 817
 818config AUTOFDO_CLANG
 819	bool "Enable Clang's AutoFDO build (EXPERIMENTAL)"
 820	depends on ARCH_SUPPORTS_AUTOFDO_CLANG
 821	depends on CC_IS_CLANG && CLANG_VERSION >= 170000
 822	help
 823	  This option enables Clang’s AutoFDO build. When
 824	  an AutoFDO profile is specified in variable
 825	  CLANG_AUTOFDO_PROFILE during the build process,
 826	  Clang uses the profile to optimize the kernel.
 827
 828	  If no profile is specified, AutoFDO options are
 829	  still passed to Clang to facilitate the collection
 830	  of perf data for creating an AutoFDO profile in
 831	  subsequent builds.
 832
 833	  If unsure, say N.
 834
 835config ARCH_SUPPORTS_PROPELLER_CLANG
 836	bool
 837
 838config PROPELLER_CLANG
 839	bool "Enable Clang's Propeller build"
 840	depends on ARCH_SUPPORTS_PROPELLER_CLANG
 841	depends on CC_IS_CLANG && CLANG_VERSION >= 190000
 842	help
 843	  This option enables Clang’s Propeller build. When the Propeller
 844	  profiles is specified in variable CLANG_PROPELLER_PROFILE_PREFIX
 845	  during the build process, Clang uses the profiles to optimize
 846	  the kernel.
 847
 848	  If no profile is specified, Propeller options are still passed
 849	  to Clang to facilitate the collection of perf data for creating
 850	  the Propeller profiles in subsequent builds.
 851
 852	  If unsure, say N.
 853
 854config ARCH_SUPPORTS_CFI_CLANG
 855	bool
 856	help
 857	  An architecture should select this option if it can support Clang's
 858	  Control-Flow Integrity (CFI) checking.
 859
 860config ARCH_USES_CFI_TRAPS
 861	bool
 862
 863config CFI_CLANG
 864	bool "Use Clang's Control Flow Integrity (CFI)"
 865	depends on ARCH_SUPPORTS_CFI_CLANG
 866	depends on $(cc-option,-fsanitize=kcfi)
 867	help
 868	  This option enables Clang's forward-edge Control Flow Integrity
 869	  (CFI) checking, where the compiler injects a runtime check to each
 870	  indirect function call to ensure the target is a valid function with
 871	  the correct static type. This restricts possible call targets and
 872	  makes it more difficult for an attacker to exploit bugs that allow
 873	  the modification of stored function pointers. More information can be
 874	  found from Clang's documentation:
 875
 876	    https://clang.llvm.org/docs/ControlFlowIntegrity.html
 877
 878config CFI_ICALL_NORMALIZE_INTEGERS
 879	bool "Normalize CFI tags for integers"
 880	depends on CFI_CLANG
 881	depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG
 882	help
 883	  This option normalizes the CFI tags for integer types so that all
 884	  integer types of the same size and signedness receive the same CFI
 885	  tag.
 886
 887	  The option is separate from CONFIG_RUST because it affects the ABI.
 888	  When working with build systems that care about the ABI, it is
 889	  convenient to be able to turn on this flag first, before Rust is
 890	  turned on.
 891
 892	  This option is necessary for using CFI with Rust. If unsure, say N.
 893
 894config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG
 895	def_bool y
 896	depends on $(cc-option,-fsanitize=kcfi -fsanitize-cfi-icall-experimental-normalize-integers)
 897	# With GCOV/KASAN we need this fix: https://github.com/llvm/llvm-project/pull/104826
 898	depends on CLANG_VERSION >= 190103 || (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS)
 899
 900config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC
 901	def_bool y
 902	depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG
 903	depends on RUSTC_VERSION >= 107900
 904	# With GCOV/KASAN we need this fix: https://github.com/rust-lang/rust/pull/129373
 905	depends on (RUSTC_LLVM_VERSION >= 190103 && RUSTC_VERSION >= 108200) || \
 906		(!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS)
 907
 908config CFI_PERMISSIVE
 909	bool "Use CFI in permissive mode"
 910	depends on CFI_CLANG
 911	help
 912	  When selected, Control Flow Integrity (CFI) violations result in a
 913	  warning instead of a kernel panic. This option should only be used
 914	  for finding indirect call type mismatches during development.
 915
 916	  If unsure, say N.
 917
 918config HAVE_ARCH_WITHIN_STACK_FRAMES
 919	bool
 920	help
 921	  An architecture should select this if it can walk the kernel stack
 922	  frames to determine if an object is part of either the arguments
 923	  or local variables (i.e. that it excludes saved return addresses,
 924	  and similar) by implementing an inline arch_within_stack_frames(),
 925	  which is used by CONFIG_HARDENED_USERCOPY.
 926
 927config HAVE_CONTEXT_TRACKING_USER
 928	bool
 929	help
 930	  Provide kernel/user boundaries probes necessary for subsystems
 931	  that need it, such as userspace RCU extended quiescent state.
 932	  Syscalls need to be wrapped inside user_exit()-user_enter(), either
 933	  optimized behind static key or through the slow path using TIF_NOHZ
 934	  flag. Exceptions handlers must be wrapped as well. Irqs are already
 935	  protected inside ct_irq_enter/ct_irq_exit() but preemption or signal
 936	  handling on irq exit still need to be protected.
 937
 938config HAVE_CONTEXT_TRACKING_USER_OFFSTACK
 939	bool
 940	help
 941	  Architecture neither relies on exception_enter()/exception_exit()
 942	  nor on schedule_user(). Also preempt_schedule_notrace() and
 943	  preempt_schedule_irq() can't be called in a preemptible section
 944	  while context tracking is CT_STATE_USER. This feature reflects a sane
 945	  entry implementation where the following requirements are met on
 946	  critical entry code, ie: before user_exit() or after user_enter():
 947
 948	  - Critical entry code isn't preemptible (or better yet:
 949	    not interruptible).
 950	  - No use of RCU read side critical sections, unless ct_nmi_enter()
 951	    got called.
 952	  - No use of instrumentation, unless instrumentation_begin() got
 953	    called.
 954
 955config HAVE_TIF_NOHZ
 956	bool
 957	help
 958	  Arch relies on TIF_NOHZ and syscall slow path to implement context
 959	  tracking calls to user_enter()/user_exit().
 960
 961config HAVE_VIRT_CPU_ACCOUNTING
 962	bool
 963
 964config HAVE_VIRT_CPU_ACCOUNTING_IDLE
 965	bool
 966	help
 967	  Architecture has its own way to account idle CPU time and therefore
 968	  doesn't implement vtime_account_idle().
 969
 970config ARCH_HAS_SCALED_CPUTIME
 971	bool
 972
 973config HAVE_VIRT_CPU_ACCOUNTING_GEN
 974	bool
 975	default y if 64BIT
 976	help
 977	  With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 978	  Before enabling this option, arch code must be audited
 979	  to ensure there are no races in concurrent read/write of
 980	  cputime_t. For example, reading/writing 64-bit cputime_t on
 981	  some 32-bit arches may require multiple accesses, so proper
 982	  locking is needed to protect against concurrent accesses.
 983
 984config HAVE_IRQ_TIME_ACCOUNTING
 985	bool
 986	help
 987	  Archs need to ensure they use a high enough resolution clock to
 988	  support irq time accounting and then call enable_sched_clock_irqtime().
 989
 990config HAVE_MOVE_PUD
 991	bool
 992	help
 993	  Architectures that select this are able to move page tables at the
 994	  PUD level. If there are only 3 page table levels, the move effectively
 995	  happens at the PGD level.
 996
 997config HAVE_MOVE_PMD
 998	bool
 999	help
1000	  Archs that select this are able to move page tables at the PMD level.
1001
1002config HAVE_ARCH_TRANSPARENT_HUGEPAGE
1003	bool
1004
1005config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1006	bool
1007
1008config HAVE_ARCH_HUGE_VMAP
1009	bool
1010
1011#
1012#  Archs that select this would be capable of PMD-sized vmaps (i.e.,
1013#  arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag
1014#  must be used to enable allocations to use hugepages.
1015#
1016config HAVE_ARCH_HUGE_VMALLOC
1017	depends on HAVE_ARCH_HUGE_VMAP
1018	bool
1019
1020config ARCH_WANT_HUGE_PMD_SHARE
1021	bool
1022
1023# Archs that want to use pmd_mkwrite on kernel memory need it defined even
1024# if there are no userspace memory management features that use it
1025config ARCH_WANT_KERNEL_PMD_MKWRITE
1026	bool
1027
1028config ARCH_WANT_PMD_MKWRITE
1029	def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE
1030
1031config HAVE_ARCH_SOFT_DIRTY
1032	bool
1033
1034config HAVE_MOD_ARCH_SPECIFIC
1035	bool
1036	help
1037	  The arch uses struct mod_arch_specific to store data.  Many arches
1038	  just need a simple module loader without arch specific data - those
1039	  should not enable this.
1040
1041config MODULES_USE_ELF_RELA
1042	bool
1043	help
1044	  Modules only use ELF RELA relocations.  Modules with ELF REL
1045	  relocations will give an error.
1046
1047config MODULES_USE_ELF_REL
1048	bool
1049	help
1050	  Modules only use ELF REL relocations.  Modules with ELF RELA
1051	  relocations will give an error.
1052
1053config ARCH_WANTS_MODULES_DATA_IN_VMALLOC
1054	bool
1055	help
1056	  For architectures like powerpc/32 which have constraints on module
1057	  allocation and need to allocate module data outside of module area.
1058
1059config ARCH_WANTS_EXECMEM_LATE
1060	bool
1061	help
1062	  For architectures that do not allocate executable memory early on
1063	  boot, but rather require its initialization late when there is
1064	  enough entropy for module space randomization, for instance
1065	  arm64.
1066
1067config ARCH_HAS_EXECMEM_ROX
1068	bool
1069	depends on MMU && !HIGHMEM
1070	help
1071	  For architectures that support allocations of executable memory
1072	  with read-only execute permissions. Architecture must implement
1073	  execmem_fill_trapping_insns() callback to enable this.
1074
1075config HAVE_IRQ_EXIT_ON_IRQ_STACK
1076	bool
1077	help
1078	  Architecture doesn't only execute the irq handler on the irq stack
1079	  but also irq_exit(). This way we can process softirqs on this irq
1080	  stack instead of switching to a new one when we call __do_softirq()
1081	  in the end of an hardirq.
1082	  This spares a stack switch and improves cache usage on softirq
1083	  processing.
1084
1085config HAVE_SOFTIRQ_ON_OWN_STACK
1086	bool
1087	help
1088	  Architecture provides a function to run __do_softirq() on a
1089	  separate stack.
1090
1091config SOFTIRQ_ON_OWN_STACK
1092	def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT
1093
1094config ALTERNATE_USER_ADDRESS_SPACE
1095	bool
1096	help
1097	  Architectures set this when the CPU uses separate address
1098	  spaces for kernel and user space pointers. In this case, the
1099	  access_ok() check on a __user pointer is skipped.
1100
1101config PGTABLE_LEVELS
1102	int
1103	default 2
1104
1105config ARCH_HAS_ELF_RANDOMIZE
1106	bool
1107	help
1108	  An architecture supports choosing randomized locations for
1109	  stack, mmap, brk, and ET_DYN. Defined functions:
1110	  - arch_mmap_rnd()
1111	  - arch_randomize_brk()
1112
1113config HAVE_ARCH_MMAP_RND_BITS
1114	bool
1115	help
1116	  An arch should select this symbol if it supports setting a variable
1117	  number of bits for use in establishing the base address for mmap
1118	  allocations, has MMU enabled and provides values for both:
1119	  - ARCH_MMAP_RND_BITS_MIN
1120	  - ARCH_MMAP_RND_BITS_MAX
1121
1122config HAVE_EXIT_THREAD
1123	bool
1124	help
1125	  An architecture implements exit_thread.
1126
1127config ARCH_MMAP_RND_BITS_MIN
1128	int
1129
1130config ARCH_MMAP_RND_BITS_MAX
1131	int
1132
1133config ARCH_MMAP_RND_BITS_DEFAULT
1134	int
1135
1136config ARCH_MMAP_RND_BITS
1137	int "Number of bits to use for ASLR of mmap base address" if EXPERT
1138	range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
1139	default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
1140	default ARCH_MMAP_RND_BITS_MIN
1141	depends on HAVE_ARCH_MMAP_RND_BITS
1142	help
1143	  This value can be used to select the number of bits to use to
1144	  determine the random offset to the base address of vma regions
1145	  resulting from mmap allocations. This value will be bounded
1146	  by the architecture's minimum and maximum supported values.
1147
1148	  This value can be changed after boot using the
1149	  /proc/sys/vm/mmap_rnd_bits tunable
1150
1151config HAVE_ARCH_MMAP_RND_COMPAT_BITS
1152	bool
1153	help
1154	  An arch should select this symbol if it supports running applications
1155	  in compatibility mode, supports setting a variable number of bits for
1156	  use in establishing the base address for mmap allocations, has MMU
1157	  enabled and provides values for both:
1158	  - ARCH_MMAP_RND_COMPAT_BITS_MIN
1159	  - ARCH_MMAP_RND_COMPAT_BITS_MAX
1160
1161config ARCH_MMAP_RND_COMPAT_BITS_MIN
1162	int
1163
1164config ARCH_MMAP_RND_COMPAT_BITS_MAX
1165	int
1166
1167config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
1168	int
1169
1170config ARCH_MMAP_RND_COMPAT_BITS
1171	int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
1172	range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
1173	default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
1174	default ARCH_MMAP_RND_COMPAT_BITS_MIN
1175	depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
1176	help
1177	  This value can be used to select the number of bits to use to
1178	  determine the random offset to the base address of vma regions
1179	  resulting from mmap allocations for compatible applications This
1180	  value will be bounded by the architecture's minimum and maximum
1181	  supported values.
1182
1183	  This value can be changed after boot using the
1184	  /proc/sys/vm/mmap_rnd_compat_bits tunable
1185
1186config HAVE_ARCH_COMPAT_MMAP_BASES
1187	bool
1188	help
1189	  This allows 64bit applications to invoke 32-bit mmap() syscall
1190	  and vice-versa 32-bit applications to call 64-bit mmap().
1191	  Required for applications doing different bitness syscalls.
1192
1193config HAVE_PAGE_SIZE_4KB
1194	bool
1195
1196config HAVE_PAGE_SIZE_8KB
1197	bool
1198
1199config HAVE_PAGE_SIZE_16KB
1200	bool
1201
1202config HAVE_PAGE_SIZE_32KB
1203	bool
1204
1205config HAVE_PAGE_SIZE_64KB
1206	bool
1207
1208config HAVE_PAGE_SIZE_256KB
1209	bool
1210
1211choice
1212	prompt "MMU page size"
1213
1214config PAGE_SIZE_4KB
1215	bool "4KiB pages"
1216	depends on HAVE_PAGE_SIZE_4KB
1217	help
1218	  This option select the standard 4KiB Linux page size and the only
1219	  available option on many architectures. Using 4KiB page size will
1220	  minimize memory consumption and is therefore recommended for low
1221	  memory systems.
1222	  Some software that is written for x86 systems makes incorrect
1223	  assumptions about the page size and only runs on 4KiB pages.
1224
1225config PAGE_SIZE_8KB
1226	bool "8KiB pages"
1227	depends on HAVE_PAGE_SIZE_8KB
1228	help
1229	  This option is the only supported page size on a few older
1230	  processors, and can be slightly faster than 4KiB pages.
1231
1232config PAGE_SIZE_16KB
1233	bool "16KiB pages"
1234	depends on HAVE_PAGE_SIZE_16KB
1235	help
1236	  This option is usually a good compromise between memory
1237	  consumption and performance for typical desktop and server
1238	  workloads, often saving a level of page table lookups compared
1239	  to 4KB pages as well as reducing TLB pressure and overhead of
1240	  per-page operations in the kernel at the expense of a larger
1241	  page cache.
1242
1243config PAGE_SIZE_32KB
1244	bool "32KiB pages"
1245	depends on HAVE_PAGE_SIZE_32KB
1246	help
1247	  Using 32KiB page size will result in slightly higher performance
1248	  kernel at the price of higher memory consumption compared to
1249	  16KiB pages.	This option is available only on cnMIPS cores.
1250	  Note that you will need a suitable Linux distribution to
1251	  support this.
1252
1253config PAGE_SIZE_64KB
1254	bool "64KiB pages"
1255	depends on HAVE_PAGE_SIZE_64KB
1256	help
1257	  Using 64KiB page size will result in slightly higher performance
1258	  kernel at the price of much higher memory consumption compared to
1259	  4KiB or 16KiB pages.
1260	  This is not suitable for general-purpose workloads but the
1261	  better performance may be worth the cost for certain types of
1262	  supercomputing or database applications that work mostly with
1263	  large in-memory data rather than small files.
1264
1265config PAGE_SIZE_256KB
1266	bool "256KiB pages"
1267	depends on HAVE_PAGE_SIZE_256KB
1268	help
1269	  256KiB pages have little practical value due to their extreme
1270	  memory usage.  The kernel will only be able to run applications
1271	  that have been compiled with '-zmax-page-size' set to 256KiB
1272	  (the default is 64KiB or 4KiB on most architectures).
1273
1274endchoice
1275
1276config PAGE_SIZE_LESS_THAN_64KB
1277	def_bool y
1278	depends on !PAGE_SIZE_64KB
1279	depends on PAGE_SIZE_LESS_THAN_256KB
1280
1281config PAGE_SIZE_LESS_THAN_256KB
1282	def_bool y
1283	depends on !PAGE_SIZE_256KB
1284
1285config PAGE_SHIFT
1286	int
1287	default	12 if PAGE_SIZE_4KB
1288	default	13 if PAGE_SIZE_8KB
1289	default	14 if PAGE_SIZE_16KB
1290	default	15 if PAGE_SIZE_32KB
1291	default	16 if PAGE_SIZE_64KB
1292	default	18 if PAGE_SIZE_256KB
1293
1294# This allows to use a set of generic functions to determine mmap base
1295# address by giving priority to top-down scheme only if the process
1296# is not in legacy mode (compat task, unlimited stack size or
1297# sysctl_legacy_va_layout).
1298# Architecture that selects this option can provide its own version of:
1299# - STACK_RND_MASK
1300config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
1301	bool
1302	depends on MMU
1303	select ARCH_HAS_ELF_RANDOMIZE
1304
1305config HAVE_OBJTOOL
1306	bool
1307
1308config HAVE_JUMP_LABEL_HACK
1309	bool
1310
1311config HAVE_NOINSTR_HACK
1312	bool
1313
1314config HAVE_NOINSTR_VALIDATION
1315	bool
1316
1317config HAVE_UACCESS_VALIDATION
1318	bool
1319	select OBJTOOL
1320
1321config HAVE_STACK_VALIDATION
1322	bool
1323	help
1324	  Architecture supports objtool compile-time frame pointer rule
1325	  validation.
1326
1327config HAVE_RELIABLE_STACKTRACE
1328	bool
1329	help
1330	  Architecture has either save_stack_trace_tsk_reliable() or
1331	  arch_stack_walk_reliable() function which only returns a stack trace
1332	  if it can guarantee the trace is reliable.
1333
1334config HAVE_ARCH_HASH
1335	bool
1336	default n
1337	help
1338	  If this is set, the architecture provides an <asm/hash.h>
1339	  file which provides platform-specific implementations of some
1340	  functions in <linux/hash.h> or fs/namei.c.
1341
1342config HAVE_ARCH_NVRAM_OPS
1343	bool
1344
1345config ISA_BUS_API
1346	def_bool ISA
1347
1348#
1349# ABI hall of shame
1350#
1351config CLONE_BACKWARDS
1352	bool
1353	help
1354	  Architecture has tls passed as the 4th argument of clone(2),
1355	  not the 5th one.
1356
1357config CLONE_BACKWARDS2
1358	bool
1359	help
1360	  Architecture has the first two arguments of clone(2) swapped.
1361
1362config CLONE_BACKWARDS3
1363	bool
1364	help
1365	  Architecture has tls passed as the 3rd argument of clone(2),
1366	  not the 5th one.
1367
1368config ODD_RT_SIGACTION
1369	bool
1370	help
1371	  Architecture has unusual rt_sigaction(2) arguments
1372
1373config OLD_SIGSUSPEND
1374	bool
1375	help
1376	  Architecture has old sigsuspend(2) syscall, of one-argument variety
1377
1378config OLD_SIGSUSPEND3
1379	bool
1380	help
1381	  Even weirder antique ABI - three-argument sigsuspend(2)
1382
1383config OLD_SIGACTION
1384	bool
1385	help
1386	  Architecture has old sigaction(2) syscall.  Nope, not the same
1387	  as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
1388	  but fairly different variant of sigaction(2), thanks to OSF/1
1389	  compatibility...
1390
1391config COMPAT_OLD_SIGACTION
1392	bool
1393
1394config COMPAT_32BIT_TIME
1395	bool "Provide system calls for 32-bit time_t"
1396	default !64BIT || COMPAT
1397	help
1398	  This enables 32 bit time_t support in addition to 64 bit time_t support.
1399	  This is relevant on all 32-bit architectures, and 64-bit architectures
1400	  as part of compat syscall handling.
1401
1402config ARCH_NO_PREEMPT
1403	bool
1404
1405config ARCH_SUPPORTS_RT
1406	bool
1407
1408config CPU_NO_EFFICIENT_FFS
1409	def_bool n
1410
1411config HAVE_ARCH_VMAP_STACK
1412	def_bool n
1413	help
1414	  An arch should select this symbol if it can support kernel stacks
1415	  in vmalloc space.  This means:
1416
1417	  - vmalloc space must be large enough to hold many kernel stacks.
1418	    This may rule out many 32-bit architectures.
1419
1420	  - Stacks in vmalloc space need to work reliably.  For example, if
1421	    vmap page tables are created on demand, either this mechanism
1422	    needs to work while the stack points to a virtual address with
1423	    unpopulated page tables or arch code (switch_to() and switch_mm(),
1424	    most likely) needs to ensure that the stack's page table entries
1425	    are populated before running on a possibly unpopulated stack.
1426
1427	  - If the stack overflows into a guard page, something reasonable
1428	    should happen.  The definition of "reasonable" is flexible, but
1429	    instantly rebooting without logging anything would be unfriendly.
1430
1431config VMAP_STACK
1432	default y
1433	bool "Use a virtually-mapped stack"
1434	depends on HAVE_ARCH_VMAP_STACK
1435	depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC
1436	help
1437	  Enable this if you want the use virtually-mapped kernel stacks
1438	  with guard pages.  This causes kernel stack overflows to be
1439	  caught immediately rather than causing difficult-to-diagnose
1440	  corruption.
1441
1442	  To use this with software KASAN modes, the architecture must support
1443	  backing virtual mappings with real shadow memory, and KASAN_VMALLOC
1444	  must be enabled.
1445
1446config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1447	def_bool n
1448	help
1449	  An arch should select this symbol if it can support kernel stack
1450	  offset randomization with calls to add_random_kstack_offset()
1451	  during syscall entry and choose_random_kstack_offset() during
1452	  syscall exit. Careful removal of -fstack-protector-strong and
1453	  -fstack-protector should also be applied to the entry code and
1454	  closely examined, as the artificial stack bump looks like an array
1455	  to the compiler, so it will attempt to add canary checks regardless
1456	  of the static branch state.
1457
1458config RANDOMIZE_KSTACK_OFFSET
1459	bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT
1460	default y
1461	depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1462	depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000
1463	help
1464	  The kernel stack offset can be randomized (after pt_regs) by
1465	  roughly 5 bits of entropy, frustrating memory corruption
1466	  attacks that depend on stack address determinism or
1467	  cross-syscall address exposures.
1468
1469	  The feature is controlled via the "randomize_kstack_offset=on/off"
1470	  kernel boot param, and if turned off has zero overhead due to its use
1471	  of static branches (see JUMP_LABEL).
1472
1473	  If unsure, say Y.
1474
1475config RANDOMIZE_KSTACK_OFFSET_DEFAULT
1476	bool "Default state of kernel stack offset randomization"
1477	depends on RANDOMIZE_KSTACK_OFFSET
1478	help
1479	  Kernel stack offset randomization is controlled by kernel boot param
1480	  "randomize_kstack_offset=on/off", and this config chooses the default
1481	  boot state.
1482
1483config ARCH_OPTIONAL_KERNEL_RWX
1484	def_bool n
1485
1486config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1487	def_bool n
1488
1489config ARCH_HAS_STRICT_KERNEL_RWX
1490	def_bool n
1491
1492config STRICT_KERNEL_RWX
1493	bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
1494	depends on ARCH_HAS_STRICT_KERNEL_RWX
1495	default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1496	help
1497	  If this is set, kernel text and rodata memory will be made read-only,
1498	  and non-text memory will be made non-executable. This provides
1499	  protection against certain security exploits (e.g. executing the heap
1500	  or modifying text)
1501
1502	  These features are considered standard security practice these days.
1503	  You should say Y here in almost all cases.
1504
1505config ARCH_HAS_STRICT_MODULE_RWX
1506	def_bool n
1507
1508config STRICT_MODULE_RWX
1509	bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
1510	depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
1511	default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1512	help
1513	  If this is set, module text and rodata memory will be made read-only,
1514	  and non-text memory will be made non-executable. This provides
1515	  protection against certain security exploits (e.g. writing to text)
1516
1517# select if the architecture provides an asm/dma-direct.h header
1518config ARCH_HAS_PHYS_TO_DMA
1519	bool
1520
1521config HAVE_ARCH_COMPILER_H
1522	bool
1523	help
1524	  An architecture can select this if it provides an
1525	  asm/compiler.h header that should be included after
1526	  linux/compiler-*.h in order to override macro definitions that those
1527	  headers generally provide.
1528
1529config HAVE_ARCH_PREL32_RELOCATIONS
1530	bool
1531	help
1532	  May be selected by an architecture if it supports place-relative
1533	  32-bit relocations, both in the toolchain and in the module loader,
1534	  in which case relative references can be used in special sections
1535	  for PCI fixup, initcalls etc which are only half the size on 64 bit
1536	  architectures, and don't require runtime relocation on relocatable
1537	  kernels.
1538
1539config ARCH_USE_MEMREMAP_PROT
1540	bool
1541
1542config LOCK_EVENT_COUNTS
1543	bool "Locking event counts collection"
1544	depends on DEBUG_FS
1545	help
1546	  Enable light-weight counting of various locking related events
1547	  in the system with minimal performance impact. This reduces
1548	  the chance of application behavior change because of timing
1549	  differences. The counts are reported via debugfs.
1550
1551# Select if the architecture has support for applying RELR relocations.
1552config ARCH_HAS_RELR
1553	bool
1554
1555config RELR
1556	bool "Use RELR relocation packing"
1557	depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1558	default y
1559	help
1560	  Store the kernel's dynamic relocations in the RELR relocation packing
1561	  format. Requires a compatible linker (LLD supports this feature), as
1562	  well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1563	  are compatible).
1564
1565config ARCH_HAS_MEM_ENCRYPT
1566	bool
1567
1568config ARCH_HAS_CC_PLATFORM
1569	bool
1570
1571config HAVE_SPARSE_SYSCALL_NR
1572	bool
1573	help
1574	  An architecture should select this if its syscall numbering is sparse
1575	  to save space. For example, MIPS architecture has a syscall array with
1576	  entries at 4000, 5000 and 6000 locations. This option turns on syscall
1577	  related optimizations for a given architecture.
1578
1579config ARCH_HAS_VDSO_TIME_DATA
1580	bool
1581
1582config HAVE_STATIC_CALL
1583	bool
1584
1585config HAVE_STATIC_CALL_INLINE
1586	bool
1587	depends on HAVE_STATIC_CALL
1588	select OBJTOOL
1589
1590config HAVE_PREEMPT_DYNAMIC
1591	bool
1592
1593config HAVE_PREEMPT_DYNAMIC_CALL
1594	bool
1595	depends on HAVE_STATIC_CALL
1596	select HAVE_PREEMPT_DYNAMIC
1597	help
1598	  An architecture should select this if it can handle the preemption
1599	  model being selected at boot time using static calls.
1600
1601	  Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a
1602	  preemption function will be patched directly.
1603
1604	  Where an architecture does not select HAVE_STATIC_CALL_INLINE, any
1605	  call to a preemption function will go through a trampoline, and the
1606	  trampoline will be patched.
1607
1608	  It is strongly advised to support inline static call to avoid any
1609	  overhead.
1610
1611config HAVE_PREEMPT_DYNAMIC_KEY
1612	bool
1613	depends on HAVE_ARCH_JUMP_LABEL
1614	select HAVE_PREEMPT_DYNAMIC
1615	help
1616	  An architecture should select this if it can handle the preemption
1617	  model being selected at boot time using static keys.
1618
1619	  Each preemption function will be given an early return based on a
1620	  static key. This should have slightly lower overhead than non-inline
1621	  static calls, as this effectively inlines each trampoline into the
1622	  start of its callee. This may avoid redundant work, and may
1623	  integrate better with CFI schemes.
1624
1625	  This will have greater overhead than using inline static calls as
1626	  the call to the preemption function cannot be entirely elided.
1627
1628config ARCH_WANT_LD_ORPHAN_WARN
1629	bool
1630	help
1631	  An arch should select this symbol once all linker sections are explicitly
1632	  included, size-asserted, or discarded in the linker scripts. This is
1633	  important because we never want expected sections to be placed heuristically
1634	  by the linker, since the locations of such sections can change between linker
1635	  versions.
1636
1637config HAVE_ARCH_PFN_VALID
1638	bool
1639
1640config ARCH_SUPPORTS_DEBUG_PAGEALLOC
1641	bool
1642
1643config ARCH_SUPPORTS_PAGE_TABLE_CHECK
1644	bool
1645
1646config ARCH_SPLIT_ARG64
1647	bool
1648	help
1649	  If a 32-bit architecture requires 64-bit arguments to be split into
1650	  pairs of 32-bit arguments, select this option.
1651
1652config ARCH_HAS_ELFCORE_COMPAT
1653	bool
1654
1655config ARCH_HAS_PARANOID_L1D_FLUSH
1656	bool
1657
1658config ARCH_HAVE_TRACE_MMIO_ACCESS
1659	bool
1660
1661config DYNAMIC_SIGFRAME
1662	bool
1663
1664# Select, if arch has a named attribute group bound to NUMA device nodes.
1665config HAVE_ARCH_NODE_DEV_GROUP
1666	bool
1667
1668config ARCH_HAS_HW_PTE_YOUNG
1669	bool
1670	help
1671	  Architectures that select this option are capable of setting the
1672	  accessed bit in PTE entries when using them as part of linear address
1673	  translations. Architectures that require runtime check should select
1674	  this option and override arch_has_hw_pte_young().
1675
1676config ARCH_HAS_NONLEAF_PMD_YOUNG
1677	bool
1678	help
1679	  Architectures that select this option are capable of setting the
1680	  accessed bit in non-leaf PMD entries when using them as part of linear
1681	  address translations. Page table walkers that clear the accessed bit
1682	  may use this capability to reduce their search space.
1683
1684config ARCH_HAS_KERNEL_FPU_SUPPORT
1685	bool
1686	help
1687	  Architectures that select this option can run floating-point code in
1688	  the kernel, as described in Documentation/core-api/floating-point.rst.
1689
1690source "kernel/gcov/Kconfig"
1691
1692source "scripts/gcc-plugins/Kconfig"
1693
1694config FUNCTION_ALIGNMENT_4B
1695	bool
1696
1697config FUNCTION_ALIGNMENT_8B
1698	bool
1699
1700config FUNCTION_ALIGNMENT_16B
1701	bool
1702
1703config FUNCTION_ALIGNMENT_32B
1704	bool
1705
1706config FUNCTION_ALIGNMENT_64B
1707	bool
1708
1709config FUNCTION_ALIGNMENT
1710	int
1711	default 64 if FUNCTION_ALIGNMENT_64B
1712	default 32 if FUNCTION_ALIGNMENT_32B
1713	default 16 if FUNCTION_ALIGNMENT_16B
1714	default 8 if FUNCTION_ALIGNMENT_8B
1715	default 4 if FUNCTION_ALIGNMENT_4B
1716	default 0
1717
1718config CC_HAS_MIN_FUNCTION_ALIGNMENT
1719	# Detect availability of the GCC option -fmin-function-alignment which
1720	# guarantees minimal alignment for all functions, unlike
1721	# -falign-functions which the compiler ignores for cold functions.
1722	def_bool $(cc-option, -fmin-function-alignment=8)
1723
1724config CC_HAS_SANE_FUNCTION_ALIGNMENT
1725	# Set if the guaranteed alignment with -fmin-function-alignment is
1726	# available or extra care is required in the kernel. Clang provides
1727	# strict alignment always, even with -falign-functions.
1728	def_bool CC_HAS_MIN_FUNCTION_ALIGNMENT || CC_IS_CLANG
1729
1730config ARCH_NEED_CMPXCHG_1_EMU
1731	bool
1732
1733config ARCH_WANTS_PRE_LINK_VMLINUX
1734	bool
1735	help
1736	  An architecture can select this if it provides arch/<arch>/tools/Makefile
1737	  with .arch.vmlinux.o target to be linked into vmlinux.
1738
1739endmenu