arch/Kconfig

   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 menu "General architecture-dependent options"
  13
  14 config ARCH_HAS_SUBPAGE_FAULTS
  15         bool
  16         help
  17           Select if the architecture can check permissions at sub-page
  18           granularity (e.g. arm64 MTE). The probe_user_*() functions
  19           must be implemented.
  20
  21 config HOTPLUG_SMT
  22         bool
  23
  24 config SMT_NUM_THREADS_DYNAMIC
  25         bool
  26
  27 # Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL
  28 config HOTPLUG_CORE_SYNC
  29         bool
  30
  31 # Basic CPU dead synchronization selected by architecture
  32 config HOTPLUG_CORE_SYNC_DEAD
  33         bool
  34         select HOTPLUG_CORE_SYNC
  35
  36 # Full CPU synchronization with alive state selected by architecture
  37 config HOTPLUG_CORE_SYNC_FULL
  38         bool
  39         select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU
  40         select HOTPLUG_CORE_SYNC
  41
  42 config HOTPLUG_SPLIT_STARTUP
  43         bool
  44         select HOTPLUG_CORE_SYNC_FULL
  45
  46 config HOTPLUG_PARALLEL
  47         bool
  48         select HOTPLUG_SPLIT_STARTUP
  49
  50 config GENERIC_ENTRY
  51         bool
  52
  53 config KPROBES
  54         bool "Kprobes"
  55         depends on MODULES
  56         depends on HAVE_KPROBES
  57         select KALLSYMS
  58         select TASKS_RCU if PREEMPTION
  59         help
  60           Kprobes allows you to trap at almost any kernel address and
  61           execute a callback function.  register_kprobe() establishes
  62           a probepoint and specifies the callback.  Kprobes is useful
  63           for kernel debugging, non-intrusive instrumentation and testing.
  64           If in doubt, say "N".
  65
  66 config JUMP_LABEL
  67         bool "Optimize very unlikely/likely branches"
  68         depends on HAVE_ARCH_JUMP_LABEL
  69         select OBJTOOL if HAVE_JUMP_LABEL_HACK
  70         help
  71           This option enables a transparent branch optimization that
  72           makes certain almost-always-true or almost-always-false branch
  73           conditions even cheaper to execute within the kernel.
  74
  75           Certain performance-sensitive kernel code, such as trace points,
  76           scheduler functionality, networking code and KVM have such
  77           branches and include support for this optimization technique.
  78
  79           If it is detected that the compiler has support for "asm goto",
  80           the kernel will compile such branches with just a nop
  81           instruction. When the condition flag is toggled to true, the
  82           nop will be converted to a jump instruction to execute the
  83           conditional block of instructions.
  84
  85           This technique lowers overhead and stress on the branch prediction
  86           of the processor and generally makes the kernel faster. The update
  87           of the condition is slower, but those are always very rare.
  88
  89           ( On 32-bit x86, the necessary options added to the compiler
  90             flags may increase the size of the kernel slightly. )
  91
  92 config STATIC_KEYS_SELFTEST
  93         bool "Static key selftest"
  94         depends on JUMP_LABEL
  95         help
  96           Boot time self-test of the branch patching code.
  97
  98 config STATIC_CALL_SELFTEST
  99         bool "Static call selftest"
 100         depends on HAVE_STATIC_CALL
 101         help
 102           Boot time self-test of the call patching code.
 103
 104 config OPTPROBES
 105         def_bool y
 106         depends on KPROBES && HAVE_OPTPROBES
 107         select TASKS_RCU if PREEMPTION
 108
 109 config KPROBES_ON_FTRACE
 110         def_bool y
 111         depends on KPROBES && HAVE_KPROBES_ON_FTRACE
 112         depends on DYNAMIC_FTRACE_WITH_REGS
 113         help
 114           If function tracer is enabled and the arch supports full
 115           passing of pt_regs to function tracing, then kprobes can
 116           optimize on top of function tracing.
 117
 118 config UPROBES
 119         def_bool n
 120         depends on ARCH_SUPPORTS_UPROBES
 121         help
 122           Uprobes is the user-space counterpart to kprobes: they
 123           enable instrumentation applications (such as 'perf probe')
 124           to establish unintrusive probes in user-space binaries and
 125           libraries, by executing handler functions when the probes
 126           are hit by user-space applications.
 127
 128           ( These probes come in the form of single-byte breakpoints,
 129             managed by the kernel and kept transparent to the probed
 130             application. )
 131
 132 config HAVE_64BIT_ALIGNED_ACCESS
 133         def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
 134         help
 135           Some architectures require 64 bit accesses to be 64 bit
 136           aligned, which also requires structs containing 64 bit values
 137           to be 64 bit aligned too. This includes some 32 bit
 138           architectures which can do 64 bit accesses, as well as 64 bit
 139           architectures without unaligned access.
 140
 141           This symbol should be selected by an architecture if 64 bit
 142           accesses are required to be 64 bit aligned in this way even
 143           though it is not a 64 bit architecture.
 144
 145           See Documentation/core-api/unaligned-memory-access.rst for
 146           more information on the topic of unaligned memory accesses.
 147
 148 config HAVE_EFFICIENT_UNALIGNED_ACCESS
 149         bool
 150         help
 151           Some architectures are unable to perform unaligned accesses
 152           without the use of get_unaligned/put_unaligned. Others are
 153           unable to perform such accesses efficiently (e.g. trap on
 154           unaligned access and require fixing it up in the exception
 155           handler.)
 156
 157           This symbol should be selected by an architecture if it can
 158           perform unaligned accesses efficiently to allow different
 159           code paths to be selected for these cases. Some network
 160           drivers, for example, could opt to not fix up alignment
 161           problems with received packets if doing so would not help
 162           much.
 163
 164           See Documentation/core-api/unaligned-memory-access.rst for more
 165           information on the topic of unaligned memory accesses.
 166
 167 config ARCH_USE_BUILTIN_BSWAP
 168         bool
 169         help
 170           Modern versions of GCC (since 4.4) have builtin functions
 171           for handling byte-swapping. Using these, instead of the old
 172           inline assembler that the architecture code provides in the
 173           __arch_bswapXX() macros, allows the compiler to see what's
 174           happening and offers more opportunity for optimisation. In
 175           particular, the compiler will be able to combine the byteswap
 176           with a nearby load or store and use load-and-swap or
 177           store-and-swap instructions if the architecture has them. It
 178           should almost *never* result in code which is worse than the
 179           hand-coded assembler in <asm/swab.h>.  But just in case it
 180           does, the use of the builtins is optional.
 181
 182           Any architecture with load-and-swap or store-and-swap
 183           instructions should set this. And it shouldn't hurt to set it
 184           on architectures that don't have such instructions.
 185
 186 config KRETPROBES
 187         def_bool y
 188         depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK)
 189
 190 config KRETPROBE_ON_RETHOOK
 191         def_bool y
 192         depends on HAVE_RETHOOK
 193         depends on KRETPROBES
 194         select RETHOOK
 195
 196 config USER_RETURN_NOTIFIER
 197         bool
 198         depends on HAVE_USER_RETURN_NOTIFIER
 199         help
 200           Provide a kernel-internal notification when a cpu is about to
 201           switch to user mode.
 202
 203 config HAVE_IOREMAP_PROT
 204         bool
 205
 206 config HAVE_KPROBES
 207         bool
 208
 209 config HAVE_KRETPROBES
 210         bool
 211
 212 config HAVE_OPTPROBES
 213         bool
 214
 215 config HAVE_KPROBES_ON_FTRACE
 216         bool
 217
 218 config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
 219         bool
 220         help
 221           Since kretprobes modifies return address on the stack, the
 222           stacktrace may see the kretprobe trampoline address instead
 223           of correct one. If the architecture stacktrace code and
 224           unwinder can adjust such entries, select this configuration.
 225
 226 config HAVE_FUNCTION_ERROR_INJECTION
 227         bool
 228
 229 config HAVE_NMI
 230         bool
 231
 232 config HAVE_FUNCTION_DESCRIPTORS
 233         bool
 234
 235 config TRACE_IRQFLAGS_SUPPORT
 236         bool
 237
 238 config TRACE_IRQFLAGS_NMI_SUPPORT
 239         bool
 240
 241 #
 242 # An arch should select this if it provides all these things:
 243 #
 244 #       task_pt_regs()          in asm/processor.h or asm/ptrace.h
 245 #       arch_has_single_step()  if there is hardware single-step support
 246 #       arch_has_block_step()   if there is hardware block-step support
 247 #       asm/syscall.h           supplying asm-generic/syscall.h interface
 248 #       linux/regset.h          user_regset interfaces
 249 #       CORE_DUMP_USE_REGSET    #define'd in linux/elf.h
 250 #       TIF_SYSCALL_TRACE       calls ptrace_report_syscall_{entry,exit}
 251 #       TIF_NOTIFY_RESUME       calls resume_user_mode_work()
 252 #
 253 config HAVE_ARCH_TRACEHOOK
 254         bool
 255
 256 config HAVE_DMA_CONTIGUOUS
 257         bool
 258
 259 config GENERIC_SMP_IDLE_THREAD
 260         bool
 261
 262 config GENERIC_IDLE_POLL_SETUP
 263         bool
 264
 265 config ARCH_HAS_FORTIFY_SOURCE
 266         bool
 267         help
 268           An architecture should select this when it can successfully
 269           build and run with CONFIG_FORTIFY_SOURCE.
 270
 271 #
 272 # Select if the arch provides a historic keepinit alias for the retain_initrd
 273 # command line option
 274 #
 275 config ARCH_HAS_KEEPINITRD
 276         bool
 277
 278 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
 279 config ARCH_HAS_SET_MEMORY
 280         bool
 281
 282 # Select if arch has all set_direct_map_invalid/default() functions
 283 config ARCH_HAS_SET_DIRECT_MAP
 284         bool
 285
 286 #
 287 # Select if the architecture provides the arch_dma_set_uncached symbol to
 288 # either provide an uncached segment alias for a DMA allocation, or
 289 # to remap the page tables in place.
 290 #
 291 config ARCH_HAS_DMA_SET_UNCACHED
 292         bool
 293
 294 #
 295 # Select if the architectures provides the arch_dma_clear_uncached symbol
 296 # to undo an in-place page table remap for uncached access.
 297 #
 298 config ARCH_HAS_DMA_CLEAR_UNCACHED
 299         bool
 300
 301 config ARCH_HAS_CPU_FINALIZE_INIT
 302         bool
 303
 304 # The architecture has a per-task state that includes the mm's PASID
 305 config ARCH_HAS_CPU_PASID
 306         bool
 307         select IOMMU_MM_DATA
 308
 309 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
 310         bool
 311         help
 312           An architecture should select this to provide hardened usercopy
 313           knowledge about what region of the thread_struct should be
 314           whitelisted for copying to userspace. Normally this is only the
 315           FPU registers. Specifically, arch_thread_struct_whitelist()
 316           should be implemented. Without this, the entire thread_struct
 317           field in task_struct will be left whitelisted.
 318
 319 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 320 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 321         bool
 322
 323 config ARCH_WANTS_NO_INSTR
 324         bool
 325         help
 326           An architecture should select this if the noinstr macro is being used on
 327           functions to denote that the toolchain should avoid instrumenting such
 328           functions and is required for correctness.
 329
 330 config ARCH_32BIT_OFF_T
 331         bool
 332         depends on !64BIT
 333         help
 334           All new 32-bit architectures should have 64-bit off_t type on
 335           userspace side which corresponds to the loff_t kernel type. This
 336           is the requirement for modern ABIs. Some existing architectures
 337           still support 32-bit off_t. This option is enabled for all such
 338           architectures explicitly.
 339
 340 # Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat
 341 config ARCH_32BIT_USTAT_F_TINODE
 342         bool
 343
 344 config HAVE_ASM_MODVERSIONS
 345         bool
 346         help
 347           This symbol should be selected by an architecture if it provides
 348           <asm/asm-prototypes.h> to support the module versioning for symbols
 349           exported from assembly code.
 350
 351 config HAVE_REGS_AND_STACK_ACCESS_API
 352         bool
 353         help
 354           This symbol should be selected by an architecture if it supports
 355           the API needed to access registers and stack entries from pt_regs,
 356           declared in asm/ptrace.h
 357           For example the kprobes-based event tracer needs this API.
 358
 359 config HAVE_RSEQ
 360         bool
 361         depends on HAVE_REGS_AND_STACK_ACCESS_API
 362         help
 363           This symbol should be selected by an architecture if it
 364           supports an implementation of restartable sequences.
 365
 366 config HAVE_RUST
 367         bool
 368         help
 369           This symbol should be selected by an architecture if it
 370           supports Rust.
 371
 372 config HAVE_FUNCTION_ARG_ACCESS_API
 373         bool
 374         help
 375           This symbol should be selected by an architecture if it supports
 376           the API needed to access function arguments from pt_regs,
 377           declared in asm/ptrace.h
 378
 379 config HAVE_HW_BREAKPOINT
 380         bool
 381         depends on PERF_EVENTS
 382
 383 config HAVE_MIXED_BREAKPOINTS_REGS
 384         bool
 385         depends on HAVE_HW_BREAKPOINT
 386         help
 387           Depending on the arch implementation of hardware breakpoints,
 388           some of them have separate registers for data and instruction
 389           breakpoints addresses, others have mixed registers to store
 390           them but define the access type in a control register.
 391           Select this option if your arch implements breakpoints under the
 392           latter fashion.
 393
 394 config HAVE_USER_RETURN_NOTIFIER
 395         bool
 396
 397 config HAVE_PERF_EVENTS_NMI
 398         bool
 399         help
 400           System hardware can generate an NMI using the perf event
 401           subsystem.  Also has support for calculating CPU cycle events
 402           to determine how many clock cycles in a given period.
 403
 404 config HAVE_HARDLOCKUP_DETECTOR_PERF
 405         bool
 406         depends on HAVE_PERF_EVENTS_NMI
 407         help
 408           The arch chooses to use the generic perf-NMI-based hardlockup
 409           detector. Must define HAVE_PERF_EVENTS_NMI.
 410
 411 config HAVE_HARDLOCKUP_DETECTOR_ARCH
 412         bool
 413         help
 414           The arch provides its own hardlockup detector implementation instead
 415           of the generic ones.
 416
 417           It uses the same command line parameters, and sysctl interface,
 418           as the generic hardlockup detectors.
 419
 420 config HAVE_PERF_REGS
 421         bool
 422         help
 423           Support selective register dumps for perf events. This includes
 424           bit-mapping of each registers and a unique architecture id.
 425
 426 config HAVE_PERF_USER_STACK_DUMP
 427         bool
 428         help
 429           Support user stack dumps for perf event samples. This needs
 430           access to the user stack pointer which is not unified across
 431           architectures.
 432
 433 config HAVE_ARCH_JUMP_LABEL
 434         bool
 435
 436 config HAVE_ARCH_JUMP_LABEL_RELATIVE
 437         bool
 438
 439 config MMU_GATHER_TABLE_FREE
 440         bool
 441
 442 config MMU_GATHER_RCU_TABLE_FREE
 443         bool
 444         select MMU_GATHER_TABLE_FREE
 445
 446 config MMU_GATHER_PAGE_SIZE
 447         bool
 448
 449 config MMU_GATHER_NO_RANGE
 450         bool
 451         select MMU_GATHER_MERGE_VMAS
 452
 453 config MMU_GATHER_NO_FLUSH_CACHE
 454         bool
 455
 456 config MMU_GATHER_MERGE_VMAS
 457         bool
 458
 459 config MMU_GATHER_NO_GATHER
 460         bool
 461         depends on MMU_GATHER_TABLE_FREE
 462
 463 config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
 464         bool
 465         help
 466           Temporary select until all architectures can be converted to have
 467           irqs disabled over activate_mm. Architectures that do IPI based TLB
 468           shootdowns should enable this.
 469
 470 # Use normal mm refcounting for MMU_LAZY_TLB kernel thread references.
 471 # MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching
 472 # to/from kernel threads when the same mm is running on a lot of CPUs (a large
 473 # multi-threaded application), by reducing contention on the mm refcount.
 474 #
 475 # This can be disabled if the architecture ensures no CPUs are using an mm as a
 476 # "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm
 477 # or its kernel page tables). This could be arranged by arch_exit_mmap(), or
 478 # final exit(2) TLB flush, for example.
 479 #
 480 # To implement this, an arch *must*:
 481 # Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating
 482 # the lazy tlb reference of a kthread's ->active_mm (non-arch code has been
 483 # converted already).
 484 config MMU_LAZY_TLB_REFCOUNT
 485         def_bool y
 486         depends on !MMU_LAZY_TLB_SHOOTDOWN
 487
 488 # This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an
 489 # mm as a lazy tlb beyond its last reference count, by shooting down these
 490 # users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may
 491 # be using the mm as a lazy tlb, so that they may switch themselves to using
 492 # init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs
 493 # may be using mm as a lazy tlb mm.
 494 #
 495 # To implement this, an arch *must*:
 496 # - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains
 497 #   at least all possible CPUs in which the mm is lazy.
 498 # - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above).
 499 config MMU_LAZY_TLB_SHOOTDOWN
 500         bool
 501
 502 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 503         bool
 504
 505 config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
 506         bool
 507
 508 config HAVE_ALIGNED_STRUCT_PAGE
 509         bool
 510         help
 511           This makes sure that struct pages are double word aligned and that
 512           e.g. the SLUB allocator can perform double word atomic operations
 513           on a struct page for better performance. However selecting this
 514           might increase the size of a struct page by a word.
 515
 516 config HAVE_CMPXCHG_LOCAL
 517         bool
 518
 519 config HAVE_CMPXCHG_DOUBLE
 520         bool
 521
 522 config ARCH_WEAK_RELEASE_ACQUIRE
 523         bool
 524
 525 config ARCH_WANT_IPC_PARSE_VERSION
 526         bool
 527
 528 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 529         bool
 530
 531 config ARCH_WANT_OLD_COMPAT_IPC
 532         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 533         bool
 534
 535 config HAVE_ARCH_SECCOMP
 536         bool
 537         help
 538           An arch should select this symbol to support seccomp mode 1 (the fixed
 539           syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
 540           and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
 541           - __NR_seccomp_read_32
 542           - __NR_seccomp_write_32
 543           - __NR_seccomp_exit_32
 544           - __NR_seccomp_sigreturn_32
 545
 546 config HAVE_ARCH_SECCOMP_FILTER
 547         bool
 548         select HAVE_ARCH_SECCOMP
 549         help
 550           An arch should select this symbol if it provides all of these things:
 551           - all the requirements for HAVE_ARCH_SECCOMP
 552           - syscall_get_arch()
 553           - syscall_get_arguments()
 554           - syscall_rollback()
 555           - syscall_set_return_value()
 556           - SIGSYS siginfo_t support
 557           - secure_computing is called from a ptrace_event()-safe context
 558           - secure_computing return value is checked and a return value of -1
 559             results in the system call being skipped immediately.
 560           - seccomp syscall wired up
 561           - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE,
 562             SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If
 563             COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too.
 564
 565 config SECCOMP
 566         prompt "Enable seccomp to safely execute untrusted bytecode"
 567         def_bool y
 568         depends on HAVE_ARCH_SECCOMP
 569         help
 570           This kernel feature is useful for number crunching applications
 571           that may need to handle untrusted bytecode during their
 572           execution. By using pipes or other transports made available
 573           to the process as file descriptors supporting the read/write
 574           syscalls, it's possible to isolate those applications in their
 575           own address space using seccomp. Once seccomp is enabled via
 576           prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
 577           disabled and the task is only allowed to execute a few safe
 578           syscalls defined by each seccomp mode.
 579
 580           If unsure, say Y.
 581
 582 config SECCOMP_FILTER
 583         def_bool y
 584         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 585         help
 586           Enable tasks to build secure computing environments defined
 587           in terms of Berkeley Packet Filter programs which implement
 588           task-defined system call filtering polices.
 589
 590           See Documentation/userspace-api/seccomp_filter.rst for details.
 591
 592 config SECCOMP_CACHE_DEBUG
 593         bool "Show seccomp filter cache status in /proc/pid/seccomp_cache"
 594         depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR
 595         depends on PROC_FS
 596         help
 597           This enables the /proc/pid/seccomp_cache interface to monitor
 598           seccomp cache data. The file format is subject to change. Reading
 599           the file requires CAP_SYS_ADMIN.
 600
 601           This option is for debugging only. Enabling presents the risk that
 602           an adversary may be able to infer the seccomp filter logic.
 603
 604           If unsure, say N.
 605
 606 config HAVE_ARCH_STACKLEAK
 607         bool
 608         help
 609           An architecture should select this if it has the code which
 610           fills the used part of the kernel stack with the STACKLEAK_POISON
 611           value before returning from system calls.
 612
 613 config HAVE_STACKPROTECTOR
 614         bool
 615         help
 616           An arch should select this symbol if:
 617           - it has implemented a stack canary (e.g. __stack_chk_guard)
 618
 619 config STACKPROTECTOR
 620         bool "Stack Protector buffer overflow detection"
 621         depends on HAVE_STACKPROTECTOR
 622         depends on $(cc-option,-fstack-protector)
 623         default y
 624         help
 625           This option turns on the "stack-protector" GCC feature. This
 626           feature puts, at the beginning of functions, a canary value on
 627           the stack just before the return address, and validates
 628           the value just before actually returning.  Stack based buffer
 629           overflows (that need to overwrite this return address) now also
 630           overwrite the canary, which gets detected and the attack is then
 631           neutralized via a kernel panic.
 632
 633           Functions will have the stack-protector canary logic added if they
 634           have an 8-byte or larger character array on the stack.
 635
 636           This feature requires gcc version 4.2 or above, or a distribution
 637           gcc with the feature backported ("-fstack-protector").
 638
 639           On an x86 "defconfig" build, this feature adds canary checks to
 640           about 3% of all kernel functions, which increases kernel code size
 641           by about 0.3%.
 642
 643 config STACKPROTECTOR_STRONG
 644         bool "Strong Stack Protector"
 645         depends on STACKPROTECTOR
 646         depends on $(cc-option,-fstack-protector-strong)
 647         default y
 648         help
 649           Functions will have the stack-protector canary logic added in any
 650           of the following conditions:
 651
 652           - local variable's address used as part of the right hand side of an
 653             assignment or function argument
 654           - local variable is an array (or union containing an array),
 655             regardless of array type or length
 656           - uses register local variables
 657
 658           This feature requires gcc version 4.9 or above, or a distribution
 659           gcc with the feature backported ("-fstack-protector-strong").
 660
 661           On an x86 "defconfig" build, this feature adds canary checks to
 662           about 20% of all kernel functions, which increases the kernel code
 663           size by about 2%.
 664
 665 config ARCH_SUPPORTS_SHADOW_CALL_STACK
 666         bool
 667         help
 668           An architecture should select this if it supports the compiler's
 669           Shadow Call Stack and implements runtime support for shadow stack
 670           switching.
 671
 672 config SHADOW_CALL_STACK
 673         bool "Shadow Call Stack"
 674         depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
 675         depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
 676         depends on MMU
 677         help
 678           This option enables the compiler's Shadow Call Stack, which
 679           uses a shadow stack to protect function return addresses from
 680           being overwritten by an attacker. More information can be found
 681           in the compiler's documentation:
 682
 683           - Clang: https://clang.llvm.org/docs/ShadowCallStack.html
 684           - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options
 685
 686           Note that security guarantees in the kernel differ from the
 687           ones documented for user space. The kernel must store addresses
 688           of shadow stacks in memory, which means an attacker capable of
 689           reading and writing arbitrary memory may be able to locate them
 690           and hijack control flow by modifying the stacks.
 691
 692 config DYNAMIC_SCS
 693         bool
 694         help
 695           Set by the arch code if it relies on code patching to insert the
 696           shadow call stack push and pop instructions rather than on the
 697           compiler.
 698
 699 config LTO
 700         bool
 701         help
 702           Selected if the kernel will be built using the compiler's LTO feature.
 703
 704 config LTO_CLANG
 705         bool
 706         select LTO
 707         help
 708           Selected if the kernel will be built using Clang's LTO feature.
 709
 710 config ARCH_SUPPORTS_LTO_CLANG
 711         bool
 712         help
 713           An architecture should select this option if it supports:
 714           - compiling with Clang,
 715           - compiling inline assembly with Clang's integrated assembler,
 716           - and linking with LLD.
 717
 718 config ARCH_SUPPORTS_LTO_CLANG_THIN
 719         bool
 720         help
 721           An architecture should select this option if it can support Clang's
 722           ThinLTO mode.
 723
 724 config HAS_LTO_CLANG
 725         def_bool y
 726         depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM
 727         depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
 728         depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
 729         depends on ARCH_SUPPORTS_LTO_CLANG
 730         depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT
 731         # https://github.com/ClangBuiltLinux/linux/issues/1721
 732         depends on (!KASAN || KASAN_HW_TAGS || CLANG_VERSION >= 170000) || !DEBUG_INFO
 733         depends on (!KCOV || CLANG_VERSION >= 170000) || !DEBUG_INFO
 734         depends on !GCOV_KERNEL
 735         help
 736           The compiler and Kconfig options support building with Clang's
 737           LTO.
 738
 739 choice
 740         prompt "Link Time Optimization (LTO)"
 741         default LTO_NONE
 742         help
 743           This option enables Link Time Optimization (LTO), which allows the
 744           compiler to optimize binaries globally.
 745
 746           If unsure, select LTO_NONE. Note that LTO is very resource-intensive
 747           so it's disabled by default.
 748
 749 config LTO_NONE
 750         bool "None"
 751         help
 752           Build the kernel normally, without Link Time Optimization (LTO).
 753
 754 config LTO_CLANG_FULL
 755         bool "Clang Full LTO (EXPERIMENTAL)"
 756         depends on HAS_LTO_CLANG
 757         depends on !COMPILE_TEST
 758         select LTO_CLANG
 759         help
 760           This option enables Clang's full Link Time Optimization (LTO), which
 761           allows the compiler to optimize the kernel globally. If you enable
 762           this option, the compiler generates LLVM bitcode instead of ELF
 763           object files, and the actual compilation from bitcode happens at
 764           the LTO link step, which may take several minutes depending on the
 765           kernel configuration. More information can be found from LLVM's
 766           documentation:
 767
 768             https://llvm.org/docs/LinkTimeOptimization.html
 769
 770           During link time, this option can use a large amount of RAM, and
 771           may take much longer than the ThinLTO option.
 772
 773 config LTO_CLANG_THIN
 774         bool "Clang ThinLTO (EXPERIMENTAL)"
 775         depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN
 776         select LTO_CLANG
 777         help
 778           This option enables Clang's ThinLTO, which allows for parallel
 779           optimization and faster incremental compiles compared to the
 780           CONFIG_LTO_CLANG_FULL option. More information can be found
 781           from Clang's documentation:
 782
 783             https://clang.llvm.org/docs/ThinLTO.html
 784
 785           If unsure, say Y.
 786 endchoice
 787
 788 config ARCH_SUPPORTS_CFI_CLANG
 789         bool
 790         help
 791           An architecture should select this option if it can support Clang's
 792           Control-Flow Integrity (CFI) checking.
 793
 794 config ARCH_USES_CFI_TRAPS
 795         bool
 796
 797 config CFI_CLANG
 798         bool "Use Clang's Control Flow Integrity (CFI)"
 799         depends on ARCH_SUPPORTS_CFI_CLANG
 800         depends on $(cc-option,-fsanitize=kcfi)
 801         help
 802           This option enables Clang’s forward-edge Control Flow Integrity
 803           (CFI) checking, where the compiler injects a runtime check to each
 804           indirect function call to ensure the target is a valid function with
 805           the correct static type. This restricts possible call targets and
 806           makes it more difficult for an attacker to exploit bugs that allow
 807           the modification of stored function pointers. More information can be
 808           found from Clang's documentation:
 809
 810             https://clang.llvm.org/docs/ControlFlowIntegrity.html
 811
 812 config CFI_PERMISSIVE
 813         bool "Use CFI in permissive mode"
 814         depends on CFI_CLANG
 815         help
 816           When selected, Control Flow Integrity (CFI) violations result in a
 817           warning instead of a kernel panic. This option should only be used
 818           for finding indirect call type mismatches during development.
 819
 820           If unsure, say N.
 821
 822 config HAVE_ARCH_WITHIN_STACK_FRAMES
 823         bool
 824         help
 825           An architecture should select this if it can walk the kernel stack
 826           frames to determine if an object is part of either the arguments
 827           or local variables (i.e. that it excludes saved return addresses,
 828           and similar) by implementing an inline arch_within_stack_frames(),
 829           which is used by CONFIG_HARDENED_USERCOPY.
 830
 831 config HAVE_CONTEXT_TRACKING_USER
 832         bool
 833         help
 834           Provide kernel/user boundaries probes necessary for subsystems
 835           that need it, such as userspace RCU extended quiescent state.
 836           Syscalls need to be wrapped inside user_exit()-user_enter(), either
 837           optimized behind static key or through the slow path using TIF_NOHZ
 838           flag. Exceptions handlers must be wrapped as well. Irqs are already
 839           protected inside ct_irq_enter/ct_irq_exit() but preemption or signal
 840           handling on irq exit still need to be protected.
 841
 842 config HAVE_CONTEXT_TRACKING_USER_OFFSTACK
 843         bool
 844         help
 845           Architecture neither relies on exception_enter()/exception_exit()
 846           nor on schedule_user(). Also preempt_schedule_notrace() and
 847           preempt_schedule_irq() can't be called in a preemptible section
 848           while context tracking is CONTEXT_USER. This feature reflects a sane
 849           entry implementation where the following requirements are met on
 850           critical entry code, ie: before user_exit() or after user_enter():
 851
 852           - Critical entry code isn't preemptible (or better yet:
 853             not interruptible).
 854           - No use of RCU read side critical sections, unless ct_nmi_enter()
 855             got called.
 856           - No use of instrumentation, unless instrumentation_begin() got
 857             called.
 858
 859 config HAVE_TIF_NOHZ
 860         bool
 861         help
 862           Arch relies on TIF_NOHZ and syscall slow path to implement context
 863           tracking calls to user_enter()/user_exit().
 864
 865 config HAVE_VIRT_CPU_ACCOUNTING
 866         bool
 867
 868 config HAVE_VIRT_CPU_ACCOUNTING_IDLE
 869         bool
 870         help
 871           Architecture has its own way to account idle CPU time and therefore
 872           doesn't implement vtime_account_idle().
 873
 874 config ARCH_HAS_SCALED_CPUTIME
 875         bool
 876
 877 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 878         bool
 879         default y if 64BIT
 880         help
 881           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 882           Before enabling this option, arch code must be audited
 883           to ensure there are no races in concurrent read/write of
 884           cputime_t. For example, reading/writing 64-bit cputime_t on
 885           some 32-bit arches may require multiple accesses, so proper
 886           locking is needed to protect against concurrent accesses.
 887
 888 config HAVE_IRQ_TIME_ACCOUNTING
 889         bool
 890         help
 891           Archs need to ensure they use a high enough resolution clock to
 892           support irq time accounting and then call enable_sched_clock_irqtime().
 893
 894 config HAVE_MOVE_PUD
 895         bool
 896         help
 897           Architectures that select this are able to move page tables at the
 898           PUD level. If there are only 3 page table levels, the move effectively
 899           happens at the PGD level.
 900
 901 config HAVE_MOVE_PMD
 902         bool
 903         help
 904           Archs that select this are able to move page tables at the PMD level.
 905
 906 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 907         bool
 908
 909 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 910         bool
 911
 912 config HAVE_ARCH_HUGE_VMAP
 913         bool
 914
 915 #
 916 #  Archs that select this would be capable of PMD-sized vmaps (i.e.,
 917 #  arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag
 918 #  must be used to enable allocations to use hugepages.
 919 #
 920 config HAVE_ARCH_HUGE_VMALLOC
 921         depends on HAVE_ARCH_HUGE_VMAP
 922         bool
 923
 924 config ARCH_WANT_HUGE_PMD_SHARE
 925         bool
 926
 927 # Archs that want to use pmd_mkwrite on kernel memory need it defined even
 928 # if there are no userspace memory management features that use it
 929 config ARCH_WANT_KERNEL_PMD_MKWRITE
 930         bool
 931
 932 config ARCH_WANT_PMD_MKWRITE
 933         def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE
 934
 935 config HAVE_ARCH_SOFT_DIRTY
 936         bool
 937
 938 config HAVE_MOD_ARCH_SPECIFIC
 939         bool
 940         help
 941           The arch uses struct mod_arch_specific to store data.  Many arches
 942           just need a simple module loader without arch specific data - those
 943           should not enable this.
 944
 945 config MODULES_USE_ELF_RELA
 946         bool
 947         help
 948           Modules only use ELF RELA relocations.  Modules with ELF REL
 949           relocations will give an error.
 950
 951 config MODULES_USE_ELF_REL
 952         bool
 953         help
 954           Modules only use ELF REL relocations.  Modules with ELF RELA
 955           relocations will give an error.
 956
 957 config ARCH_WANTS_MODULES_DATA_IN_VMALLOC
 958         bool
 959         help
 960           For architectures like powerpc/32 which have constraints on module
 961           allocation and need to allocate module data outside of module area.
 962
 963 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 964         bool
 965         help
 966           Architecture doesn't only execute the irq handler on the irq stack
 967           but also irq_exit(). This way we can process softirqs on this irq
 968           stack instead of switching to a new one when we call __do_softirq()
 969           in the end of an hardirq.
 970           This spares a stack switch and improves cache usage on softirq
 971           processing.
 972
 973 config HAVE_SOFTIRQ_ON_OWN_STACK
 974         bool
 975         help
 976           Architecture provides a function to run __do_softirq() on a
 977           separate stack.
 978
 979 config SOFTIRQ_ON_OWN_STACK
 980         def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT
 981
 982 config ALTERNATE_USER_ADDRESS_SPACE
 983         bool
 984         help
 985           Architectures set this when the CPU uses separate address
 986           spaces for kernel and user space pointers. In this case, the
 987           access_ok() check on a __user pointer is skipped.
 988
 989 config PGTABLE_LEVELS
 990         int
 991         default 2
 992
 993 config ARCH_HAS_ELF_RANDOMIZE
 994         bool
 995         help
 996           An architecture supports choosing randomized locations for
 997           stack, mmap, brk, and ET_DYN. Defined functions:
 998           - arch_mmap_rnd()
 999           - arch_randomize_brk()
1000
1001 config HAVE_ARCH_MMAP_RND_BITS
1002         bool
1003         help
1004           An arch should select this symbol if it supports setting a variable
1005           number of bits for use in establishing the base address for mmap
1006           allocations, has MMU enabled and provides values for both:
1007           - ARCH_MMAP_RND_BITS_MIN
1008           - ARCH_MMAP_RND_BITS_MAX
1009
1010 config HAVE_EXIT_THREAD
1011         bool
1012         help
1013           An architecture implements exit_thread.
1014
1015 config ARCH_MMAP_RND_BITS_MIN
1016         int
1017
1018 config ARCH_MMAP_RND_BITS_MAX
1019         int
1020
1021 config ARCH_MMAP_RND_BITS_DEFAULT
1022         int
1023
1024 config ARCH_MMAP_RND_BITS
1025         int "Number of bits to use for ASLR of mmap base address" if EXPERT
1026         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
1027         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
1028         default ARCH_MMAP_RND_BITS_MIN
1029         depends on HAVE_ARCH_MMAP_RND_BITS
1030         help
1031           This value can be used to select the number of bits to use to
1032           determine the random offset to the base address of vma regions
1033           resulting from mmap allocations. This value will be bounded
1034           by the architecture's minimum and maximum supported values.
1035
1036           This value can be changed after boot using the
1037           /proc/sys/vm/mmap_rnd_bits tunable
1038
1039 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
1040         bool
1041         help
1042           An arch should select this symbol if it supports running applications
1043           in compatibility mode, supports setting a variable number of bits for
1044           use in establishing the base address for mmap allocations, has MMU
1045           enabled and provides values for both:
1046           - ARCH_MMAP_RND_COMPAT_BITS_MIN
1047           - ARCH_MMAP_RND_COMPAT_BITS_MAX
1048
1049 config ARCH_MMAP_RND_COMPAT_BITS_MIN
1050         int
1051
1052 config ARCH_MMAP_RND_COMPAT_BITS_MAX
1053         int
1054
1055 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
1056         int
1057
1058 config ARCH_MMAP_RND_COMPAT_BITS
1059         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
1060         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
1061         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
1062         default ARCH_MMAP_RND_COMPAT_BITS_MIN
1063         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
1064         help
1065           This value can be used to select the number of bits to use to
1066           determine the random offset to the base address of vma regions
1067           resulting from mmap allocations for compatible applications This
1068           value will be bounded by the architecture's minimum and maximum
1069           supported values.
1070
1071           This value can be changed after boot using the
1072           /proc/sys/vm/mmap_rnd_compat_bits tunable
1073
1074 config HAVE_ARCH_COMPAT_MMAP_BASES
1075         bool
1076         help
1077           This allows 64bit applications to invoke 32-bit mmap() syscall
1078           and vice-versa 32-bit applications to call 64-bit mmap().
1079           Required for applications doing different bitness syscalls.
1080
1081 config PAGE_SIZE_LESS_THAN_64KB
1082         def_bool y
1083         depends on !ARM64_64K_PAGES
1084         depends on !PAGE_SIZE_64KB
1085         depends on !PARISC_PAGE_SIZE_64KB
1086         depends on PAGE_SIZE_LESS_THAN_256KB
1087
1088 config PAGE_SIZE_LESS_THAN_256KB
1089         def_bool y
1090         depends on !PAGE_SIZE_256KB
1091
1092 # This allows to use a set of generic functions to determine mmap base
1093 # address by giving priority to top-down scheme only if the process
1094 # is not in legacy mode (compat task, unlimited stack size or
1095 # sysctl_legacy_va_layout).
1096 # Architecture that selects this option can provide its own version of:
1097 # - STACK_RND_MASK
1098 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
1099         bool
1100         depends on MMU
1101         select ARCH_HAS_ELF_RANDOMIZE
1102
1103 config HAVE_OBJTOOL
1104         bool
1105
1106 config HAVE_JUMP_LABEL_HACK
1107         bool
1108
1109 config HAVE_NOINSTR_HACK
1110         bool
1111
1112 config HAVE_NOINSTR_VALIDATION
1113         bool
1114
1115 config HAVE_UACCESS_VALIDATION
1116         bool
1117         select OBJTOOL
1118
1119 config HAVE_STACK_VALIDATION
1120         bool
1121         help
1122           Architecture supports objtool compile-time frame pointer rule
1123           validation.
1124
1125 config HAVE_RELIABLE_STACKTRACE
1126         bool
1127         help
1128           Architecture has either save_stack_trace_tsk_reliable() or
1129           arch_stack_walk_reliable() function which only returns a stack trace
1130           if it can guarantee the trace is reliable.
1131
1132 config HAVE_ARCH_HASH
1133         bool
1134         default n
1135         help
1136           If this is set, the architecture provides an <asm/hash.h>
1137           file which provides platform-specific implementations of some
1138           functions in <linux/hash.h> or fs/namei.c.
1139
1140 config HAVE_ARCH_NVRAM_OPS
1141         bool
1142
1143 config ISA_BUS_API
1144         def_bool ISA
1145
1146 #
1147 # ABI hall of shame
1148 #
1149 config CLONE_BACKWARDS
1150         bool
1151         help
1152           Architecture has tls passed as the 4th argument of clone(2),
1153           not the 5th one.
1154
1155 config CLONE_BACKWARDS2
1156         bool
1157         help
1158           Architecture has the first two arguments of clone(2) swapped.
1159
1160 config CLONE_BACKWARDS3
1161         bool
1162         help
1163           Architecture has tls passed as the 3rd argument of clone(2),
1164           not the 5th one.
1165
1166 config ODD_RT_SIGACTION
1167         bool
1168         help
1169           Architecture has unusual rt_sigaction(2) arguments
1170
1171 config OLD_SIGSUSPEND
1172         bool
1173         help
1174           Architecture has old sigsuspend(2) syscall, of one-argument variety
1175
1176 config OLD_SIGSUSPEND3
1177         bool
1178         help
1179           Even weirder antique ABI - three-argument sigsuspend(2)
1180
1181 config OLD_SIGACTION
1182         bool
1183         help
1184           Architecture has old sigaction(2) syscall.  Nope, not the same
1185           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
1186           but fairly different variant of sigaction(2), thanks to OSF/1
1187           compatibility...
1188
1189 config COMPAT_OLD_SIGACTION
1190         bool
1191
1192 config COMPAT_32BIT_TIME
1193         bool "Provide system calls for 32-bit time_t"
1194         default !64BIT || COMPAT
1195         help
1196           This enables 32 bit time_t support in addition to 64 bit time_t support.
1197           This is relevant on all 32-bit architectures, and 64-bit architectures
1198           as part of compat syscall handling.
1199
1200 config ARCH_NO_PREEMPT
1201         bool
1202
1203 config ARCH_SUPPORTS_RT
1204         bool
1205
1206 config CPU_NO_EFFICIENT_FFS
1207         def_bool n
1208
1209 config HAVE_ARCH_VMAP_STACK
1210         def_bool n
1211         help
1212           An arch should select this symbol if it can support kernel stacks
1213           in vmalloc space.  This means:
1214
1215           - vmalloc space must be large enough to hold many kernel stacks.
1216             This may rule out many 32-bit architectures.
1217
1218           - Stacks in vmalloc space need to work reliably.  For example, if
1219             vmap page tables are created on demand, either this mechanism
1220             needs to work while the stack points to a virtual address with
1221             unpopulated page tables or arch code (switch_to() and switch_mm(),
1222             most likely) needs to ensure that the stack's page table entries
1223             are populated before running on a possibly unpopulated stack.
1224
1225           - If the stack overflows into a guard page, something reasonable
1226             should happen.  The definition of "reasonable" is flexible, but
1227             instantly rebooting without logging anything would be unfriendly.
1228
1229 config VMAP_STACK
1230         default y
1231         bool "Use a virtually-mapped stack"
1232         depends on HAVE_ARCH_VMAP_STACK
1233         depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC
1234         help
1235           Enable this if you want the use virtually-mapped kernel stacks
1236           with guard pages.  This causes kernel stack overflows to be
1237           caught immediately rather than causing difficult-to-diagnose
1238           corruption.
1239
1240           To use this with software KASAN modes, the architecture must support
1241           backing virtual mappings with real shadow memory, and KASAN_VMALLOC
1242           must be enabled.
1243
1244 config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1245         def_bool n
1246         help
1247           An arch should select this symbol if it can support kernel stack
1248           offset randomization with calls to add_random_kstack_offset()
1249           during syscall entry and choose_random_kstack_offset() during
1250           syscall exit. Careful removal of -fstack-protector-strong and
1251           -fstack-protector should also be applied to the entry code and
1252           closely examined, as the artificial stack bump looks like an array
1253           to the compiler, so it will attempt to add canary checks regardless
1254           of the static branch state.
1255
1256 config RANDOMIZE_KSTACK_OFFSET
1257         bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT
1258         default y
1259         depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1260         depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000
1261         help
1262           The kernel stack offset can be randomized (after pt_regs) by
1263           roughly 5 bits of entropy, frustrating memory corruption
1264           attacks that depend on stack address determinism or
1265           cross-syscall address exposures.
1266
1267           The feature is controlled via the "randomize_kstack_offset=on/off"
1268           kernel boot param, and if turned off has zero overhead due to its use
1269           of static branches (see JUMP_LABEL).
1270
1271           If unsure, say Y.
1272
1273 config RANDOMIZE_KSTACK_OFFSET_DEFAULT
1274         bool "Default state of kernel stack offset randomization"
1275         depends on RANDOMIZE_KSTACK_OFFSET
1276         help
1277           Kernel stack offset randomization is controlled by kernel boot param
1278           "randomize_kstack_offset=on/off", and this config chooses the default
1279           boot state.
1280
1281 config ARCH_OPTIONAL_KERNEL_RWX
1282         def_bool n
1283
1284 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1285         def_bool n
1286
1287 config ARCH_HAS_STRICT_KERNEL_RWX
1288         def_bool n
1289
1290 config STRICT_KERNEL_RWX
1291         bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
1292         depends on ARCH_HAS_STRICT_KERNEL_RWX
1293         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1294         help
1295           If this is set, kernel text and rodata memory will be made read-only,
1296           and non-text memory will be made non-executable. This provides
1297           protection against certain security exploits (e.g. executing the heap
1298           or modifying text)
1299
1300           These features are considered standard security practice these days.
1301           You should say Y here in almost all cases.
1302
1303 config ARCH_HAS_STRICT_MODULE_RWX
1304         def_bool n
1305
1306 config STRICT_MODULE_RWX
1307         bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
1308         depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
1309         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1310         help
1311           If this is set, module text and rodata memory will be made read-only,
1312           and non-text memory will be made non-executable. This provides
1313           protection against certain security exploits (e.g. writing to text)
1314
1315 # select if the architecture provides an asm/dma-direct.h header
1316 config ARCH_HAS_PHYS_TO_DMA
1317         bool
1318
1319 config HAVE_ARCH_COMPILER_H
1320         bool
1321         help
1322           An architecture can select this if it provides an
1323           asm/compiler.h header that should be included after
1324           linux/compiler-*.h in order to override macro definitions that those
1325           headers generally provide.
1326
1327 config HAVE_ARCH_PREL32_RELOCATIONS
1328         bool
1329         help
1330           May be selected by an architecture if it supports place-relative
1331           32-bit relocations, both in the toolchain and in the module loader,
1332           in which case relative references can be used in special sections
1333           for PCI fixup, initcalls etc which are only half the size on 64 bit
1334           architectures, and don't require runtime relocation on relocatable
1335           kernels.
1336
1337 config ARCH_USE_MEMREMAP_PROT
1338         bool
1339
1340 config LOCK_EVENT_COUNTS
1341         bool "Locking event counts collection"
1342         depends on DEBUG_FS
1343         help
1344           Enable light-weight counting of various locking related events
1345           in the system with minimal performance impact. This reduces
1346           the chance of application behavior change because of timing
1347           differences. The counts are reported via debugfs.
1348
1349 # Select if the architecture has support for applying RELR relocations.
1350 config ARCH_HAS_RELR
1351         bool
1352
1353 config RELR
1354         bool "Use RELR relocation packing"
1355         depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1356         default y
1357         help
1358           Store the kernel's dynamic relocations in the RELR relocation packing
1359           format. Requires a compatible linker (LLD supports this feature), as
1360           well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1361           are compatible).
1362
1363 config ARCH_HAS_MEM_ENCRYPT
1364         bool
1365
1366 config ARCH_HAS_CC_PLATFORM
1367         bool
1368
1369 config HAVE_SPARSE_SYSCALL_NR
1370         bool
1371         help
1372           An architecture should select this if its syscall numbering is sparse
1373           to save space. For example, MIPS architecture has a syscall array with
1374           entries at 4000, 5000 and 6000 locations. This option turns on syscall
1375           related optimizations for a given architecture.
1376
1377 config ARCH_HAS_VDSO_DATA
1378         bool
1379
1380 config HAVE_STATIC_CALL
1381         bool
1382
1383 config HAVE_STATIC_CALL_INLINE
1384         bool
1385         depends on HAVE_STATIC_CALL
1386         select OBJTOOL
1387
1388 config HAVE_PREEMPT_DYNAMIC
1389         bool
1390
1391 config HAVE_PREEMPT_DYNAMIC_CALL
1392         bool
1393         depends on HAVE_STATIC_CALL
1394         select HAVE_PREEMPT_DYNAMIC
1395         help
1396           An architecture should select this if it can handle the preemption
1397           model being selected at boot time using static calls.
1398
1399           Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a
1400           preemption function will be patched directly.
1401
1402           Where an architecture does not select HAVE_STATIC_CALL_INLINE, any
1403           call to a preemption function will go through a trampoline, and the
1404           trampoline will be patched.
1405
1406           It is strongly advised to support inline static call to avoid any
1407           overhead.
1408
1409 config HAVE_PREEMPT_DYNAMIC_KEY
1410         bool
1411         depends on HAVE_ARCH_JUMP_LABEL
1412         select HAVE_PREEMPT_DYNAMIC
1413         help
1414           An architecture should select this if it can handle the preemption
1415           model being selected at boot time using static keys.
1416
1417           Each preemption function will be given an early return based on a
1418           static key. This should have slightly lower overhead than non-inline
1419           static calls, as this effectively inlines each trampoline into the
1420           start of its callee. This may avoid redundant work, and may
1421           integrate better with CFI schemes.
1422
1423           This will have greater overhead than using inline static calls as
1424           the call to the preemption function cannot be entirely elided.
1425
1426 config ARCH_WANT_LD_ORPHAN_WARN
1427         bool
1428         help
1429           An arch should select this symbol once all linker sections are explicitly
1430           included, size-asserted, or discarded in the linker scripts. This is
1431           important because we never want expected sections to be placed heuristically
1432           by the linker, since the locations of such sections can change between linker
1433           versions.
1434
1435 config HAVE_ARCH_PFN_VALID
1436         bool
1437
1438 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
1439         bool
1440
1441 config ARCH_SUPPORTS_PAGE_TABLE_CHECK
1442         bool
1443
1444 config ARCH_SPLIT_ARG64
1445         bool
1446         help
1447           If a 32-bit architecture requires 64-bit arguments to be split into
1448           pairs of 32-bit arguments, select this option.
1449
1450 config ARCH_HAS_ELFCORE_COMPAT
1451         bool
1452
1453 config ARCH_HAS_PARANOID_L1D_FLUSH
1454         bool
1455
1456 config ARCH_HAVE_TRACE_MMIO_ACCESS
1457         bool
1458
1459 config DYNAMIC_SIGFRAME
1460         bool
1461
1462 # Select, if arch has a named attribute group bound to NUMA device nodes.
1463 config HAVE_ARCH_NODE_DEV_GROUP
1464         bool
1465
1466 config ARCH_HAS_HW_PTE_YOUNG
1467         bool
1468         help
1469           Architectures that select this option are capable of setting the
1470           accessed bit in PTE entries when using them as part of linear address
1471           translations. Architectures that require runtime check should select
1472           this option and override arch_has_hw_pte_young().
1473
1474 config ARCH_HAS_NONLEAF_PMD_YOUNG
1475         bool
1476         help
1477           Architectures that select this option are capable of setting the
1478           accessed bit in non-leaf PMD entries when using them as part of linear
1479           address translations. Page table walkers that clear the accessed bit
1480           may use this capability to reduce their search space.
1481
1482 source "kernel/gcov/Kconfig"
1483
1484 source "scripts/gcc-plugins/Kconfig"
1485
1486 config FUNCTION_ALIGNMENT_4B
1487         bool
1488
1489 config FUNCTION_ALIGNMENT_8B
1490         bool
1491
1492 config FUNCTION_ALIGNMENT_16B
1493         bool
1494
1495 config FUNCTION_ALIGNMENT_32B
1496         bool
1497
1498 config FUNCTION_ALIGNMENT_64B
1499         bool
1500
1501 config FUNCTION_ALIGNMENT
1502         int
1503         default 64 if FUNCTION_ALIGNMENT_64B
1504         default 32 if FUNCTION_ALIGNMENT_32B
1505         default 16 if FUNCTION_ALIGNMENT_16B
1506         default 8 if FUNCTION_ALIGNMENT_8B
1507         default 4 if FUNCTION_ALIGNMENT_4B
1508         default 0
1509
1510 endmenu