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 CRASH_CORE
  15         bool
  16
  17 config KEXEC_CORE
  18         select CRASH_CORE
  19         bool
  20
  21 config KEXEC_ELF
  22         bool
  23
  24 config HAVE_IMA_KEXEC
  25         bool
  26
  27 config ARCH_HAS_SUBPAGE_FAULTS
  28         bool
  29         help
  30           Select if the architecture can check permissions at sub-page
  31           granularity (e.g. arm64 MTE). The probe_user_*() functions
  32           must be implemented.
  33
  34 config HOTPLUG_SMT
  35         bool
  36
  37 config SMT_NUM_THREADS_DYNAMIC
  38         bool
  39
  40 # Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL
  41 config HOTPLUG_CORE_SYNC
  42         bool
  43
  44 # Basic CPU dead synchronization selected by architecture
  45 config HOTPLUG_CORE_SYNC_DEAD
  46         bool
  47         select HOTPLUG_CORE_SYNC
  48
  49 # Full CPU synchronization with alive state selected by architecture
  50 config HOTPLUG_CORE_SYNC_FULL
  51         bool
  52         select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU
  53         select HOTPLUG_CORE_SYNC
  54
  55 config HOTPLUG_SPLIT_STARTUP
  56         bool
  57         select HOTPLUG_CORE_SYNC_FULL
  58
  59 config HOTPLUG_PARALLEL
  60         bool
  61         select HOTPLUG_SPLIT_STARTUP
  62
  63 config GENERIC_ENTRY
  64         bool
  65
  66 config KPROBES
  67         bool "Kprobes"
  68         depends on MODULES
  69         depends on HAVE_KPROBES
  70         select KALLSYMS
  71         select TASKS_RCU if PREEMPTION
  72         help
  73           Kprobes allows you to trap at almost any kernel address and
  74           execute a callback function.  register_kprobe() establishes
  75           a probepoint and specifies the callback.  Kprobes is useful
  76           for kernel debugging, non-intrusive instrumentation and testing.
  77           If in doubt, say "N".
  78
  79 config JUMP_LABEL
  80         bool "Optimize very unlikely/likely branches"
  81         depends on HAVE_ARCH_JUMP_LABEL
  82         select OBJTOOL if HAVE_JUMP_LABEL_HACK
  83         help
  84           This option enables a transparent branch optimization that
  85           makes certain almost-always-true or almost-always-false branch
  86           conditions even cheaper to execute within the kernel.
  87
  88           Certain performance-sensitive kernel code, such as trace points,
  89           scheduler functionality, networking code and KVM have such
  90           branches and include support for this optimization technique.
  91
  92           If it is detected that the compiler has support for "asm goto",
  93           the kernel will compile such branches with just a nop
  94           instruction. When the condition flag is toggled to true, the
  95           nop will be converted to a jump instruction to execute the
  96           conditional block of instructions.
  97
  98           This technique lowers overhead and stress on the branch prediction
  99           of the processor and generally makes the kernel faster. The update
 100           of the condition is slower, but those are always very rare.
 101
 102           ( On 32-bit x86, the necessary options added to the compiler
 103             flags may increase the size of the kernel slightly. )
 104
 105 config STATIC_KEYS_SELFTEST
 106         bool "Static key selftest"
 107         depends on JUMP_LABEL
 108         help
 109           Boot time self-test of the branch patching code.
 110
 111 config STATIC_CALL_SELFTEST
 112         bool "Static call selftest"
 113         depends on HAVE_STATIC_CALL
 114         help
 115           Boot time self-test of the call patching code.
 116
 117 config OPTPROBES
 118         def_bool y
 119         depends on KPROBES && HAVE_OPTPROBES
 120         select TASKS_RCU if PREEMPTION
 121
 122 config KPROBES_ON_FTRACE
 123         def_bool y
 124         depends on KPROBES && HAVE_KPROBES_ON_FTRACE
 125         depends on DYNAMIC_FTRACE_WITH_REGS
 126         help
 127           If function tracer is enabled and the arch supports full
 128           passing of pt_regs to function tracing, then kprobes can
 129           optimize on top of function tracing.
 130
 131 config UPROBES
 132         def_bool n
 133         depends on ARCH_SUPPORTS_UPROBES
 134         help
 135           Uprobes is the user-space counterpart to kprobes: they
 136           enable instrumentation applications (such as 'perf probe')
 137           to establish unintrusive probes in user-space binaries and
 138           libraries, by executing handler functions when the probes
 139           are hit by user-space applications.
 140
 141           ( These probes come in the form of single-byte breakpoints,
 142             managed by the kernel and kept transparent to the probed
 143             application. )
 144
 145 config HAVE_64BIT_ALIGNED_ACCESS
 146         def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
 147         help
 148           Some architectures require 64 bit accesses to be 64 bit
 149           aligned, which also requires structs containing 64 bit values
 150           to be 64 bit aligned too. This includes some 32 bit
 151           architectures which can do 64 bit accesses, as well as 64 bit
 152           architectures without unaligned access.
 153
 154           This symbol should be selected by an architecture if 64 bit
 155           accesses are required to be 64 bit aligned in this way even
 156           though it is not a 64 bit architecture.
 157
 158           See Documentation/core-api/unaligned-memory-access.rst for
 159           more information on the topic of unaligned memory accesses.
 160
 161 config HAVE_EFFICIENT_UNALIGNED_ACCESS
 162         bool
 163         help
 164           Some architectures are unable to perform unaligned accesses
 165           without the use of get_unaligned/put_unaligned. Others are
 166           unable to perform such accesses efficiently (e.g. trap on
 167           unaligned access and require fixing it up in the exception
 168           handler.)
 169
 170           This symbol should be selected by an architecture if it can
 171           perform unaligned accesses efficiently to allow different
 172           code paths to be selected for these cases. Some network
 173           drivers, for example, could opt to not fix up alignment
 174           problems with received packets if doing so would not help
 175           much.
 176
 177           See Documentation/core-api/unaligned-memory-access.rst for more
 178           information on the topic of unaligned memory accesses.
 179
 180 config ARCH_USE_BUILTIN_BSWAP
 181         bool
 182         help
 183           Modern versions of GCC (since 4.4) have builtin functions
 184           for handling byte-swapping. Using these, instead of the old
 185           inline assembler that the architecture code provides in the
 186           __arch_bswapXX() macros, allows the compiler to see what's
 187           happening and offers more opportunity for optimisation. In
 188           particular, the compiler will be able to combine the byteswap
 189           with a nearby load or store and use load-and-swap or
 190           store-and-swap instructions if the architecture has them. It
 191           should almost *never* result in code which is worse than the
 192           hand-coded assembler in <asm/swab.h>.  But just in case it
 193           does, the use of the builtins is optional.
 194
 195           Any architecture with load-and-swap or store-and-swap
 196           instructions should set this. And it shouldn't hurt to set it
 197           on architectures that don't have such instructions.
 198
 199 config KRETPROBES
 200         def_bool y
 201         depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK)
 202
 203 config KRETPROBE_ON_RETHOOK
 204         def_bool y
 205         depends on HAVE_RETHOOK
 206         depends on KRETPROBES
 207         select RETHOOK
 208
 209 config USER_RETURN_NOTIFIER
 210         bool
 211         depends on HAVE_USER_RETURN_NOTIFIER
 212         help
 213           Provide a kernel-internal notification when a cpu is about to
 214           switch to user mode.
 215
 216 config HAVE_IOREMAP_PROT
 217         bool
 218
 219 config HAVE_KPROBES
 220         bool
 221
 222 config HAVE_KRETPROBES
 223         bool
 224
 225 config HAVE_OPTPROBES
 226         bool
 227
 228 config HAVE_KPROBES_ON_FTRACE
 229         bool
 230
 231 config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
 232         bool
 233         help
 234           Since kretprobes modifies return address on the stack, the
 235           stacktrace may see the kretprobe trampoline address instead
 236           of correct one. If the architecture stacktrace code and
 237           unwinder can adjust such entries, select this configuration.
 238
 239 config HAVE_FUNCTION_ERROR_INJECTION
 240         bool
 241
 242 config HAVE_NMI
 243         bool
 244
 245 config HAVE_FUNCTION_DESCRIPTORS
 246         bool
 247
 248 config TRACE_IRQFLAGS_SUPPORT
 249         bool
 250
 251 config TRACE_IRQFLAGS_NMI_SUPPORT
 252         bool
 253
 254 #
 255 # An arch should select this if it provides all these things:
 256 #
 257 #       task_pt_regs()          in asm/processor.h or asm/ptrace.h
 258 #       arch_has_single_step()  if there is hardware single-step support
 259 #       arch_has_block_step()   if there is hardware block-step support
 260 #       asm/syscall.h           supplying asm-generic/syscall.h interface
 261 #       linux/regset.h          user_regset interfaces
 262 #       CORE_DUMP_USE_REGSET    #define'd in linux/elf.h
 263 #       TIF_SYSCALL_TRACE       calls ptrace_report_syscall_{entry,exit}
 264 #       TIF_NOTIFY_RESUME       calls resume_user_mode_work()
 265 #
 266 config HAVE_ARCH_TRACEHOOK
 267         bool
 268
 269 config HAVE_DMA_CONTIGUOUS
 270         bool
 271
 272 config GENERIC_SMP_IDLE_THREAD
 273         bool
 274
 275 config GENERIC_IDLE_POLL_SETUP
 276         bool
 277
 278 config ARCH_HAS_FORTIFY_SOURCE
 279         bool
 280         help
 281           An architecture should select this when it can successfully
 282           build and run with CONFIG_FORTIFY_SOURCE.
 283
 284 #
 285 # Select if the arch provides a historic keepinit alias for the retain_initrd
 286 # command line option
 287 #
 288 config ARCH_HAS_KEEPINITRD
 289         bool
 290
 291 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
 292 config ARCH_HAS_SET_MEMORY
 293         bool
 294
 295 # Select if arch has all set_direct_map_invalid/default() functions
 296 config ARCH_HAS_SET_DIRECT_MAP
 297         bool
 298
 299 #
 300 # Select if the architecture provides the arch_dma_set_uncached symbol to
 301 # either provide an uncached segment alias for a DMA allocation, or
 302 # to remap the page tables in place.
 303 #
 304 config ARCH_HAS_DMA_SET_UNCACHED
 305         bool
 306
 307 #
 308 # Select if the architectures provides the arch_dma_clear_uncached symbol
 309 # to undo an in-place page table remap for uncached access.
 310 #
 311 config ARCH_HAS_DMA_CLEAR_UNCACHED
 312         bool
 313
 314 config ARCH_HAS_CPU_FINALIZE_INIT
 315         bool
 316
 317 # Select if arch init_task must go in the __init_task_data section
 318 config ARCH_TASK_STRUCT_ON_STACK
 319         bool
 320
 321 # Select if arch has its private alloc_task_struct() function
 322 config ARCH_TASK_STRUCT_ALLOCATOR
 323         bool
 324
 325 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
 326         bool
 327         depends on !ARCH_TASK_STRUCT_ALLOCATOR
 328         help
 329           An architecture should select this to provide hardened usercopy
 330           knowledge about what region of the thread_struct should be
 331           whitelisted for copying to userspace. Normally this is only the
 332           FPU registers. Specifically, arch_thread_struct_whitelist()
 333           should be implemented. Without this, the entire thread_struct
 334           field in task_struct will be left whitelisted.
 335
 336 # Select if arch has its private alloc_thread_stack() function
 337 config ARCH_THREAD_STACK_ALLOCATOR
 338         bool
 339
 340 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 341 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 342         bool
 343
 344 config ARCH_WANTS_NO_INSTR
 345         bool
 346         help
 347           An architecture should select this if the noinstr macro is being used on
 348           functions to denote that the toolchain should avoid instrumenting such
 349           functions and is required for correctness.
 350
 351 config ARCH_32BIT_OFF_T
 352         bool
 353         depends on !64BIT
 354         help
 355           All new 32-bit architectures should have 64-bit off_t type on
 356           userspace side which corresponds to the loff_t kernel type. This
 357           is the requirement for modern ABIs. Some existing architectures
 358           still support 32-bit off_t. This option is enabled for all such
 359           architectures explicitly.
 360
 361 # Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat
 362 config ARCH_32BIT_USTAT_F_TINODE
 363         bool
 364
 365 config HAVE_ASM_MODVERSIONS
 366         bool
 367         help
 368           This symbol should be selected by an architecture if it provides
 369           <asm/asm-prototypes.h> to support the module versioning for symbols
 370           exported from assembly code.
 371
 372 config HAVE_REGS_AND_STACK_ACCESS_API
 373         bool
 374         help
 375           This symbol should be selected by an architecture if it supports
 376           the API needed to access registers and stack entries from pt_regs,
 377           declared in asm/ptrace.h
 378           For example the kprobes-based event tracer needs this API.
 379
 380 config HAVE_RSEQ
 381         bool
 382         depends on HAVE_REGS_AND_STACK_ACCESS_API
 383         help
 384           This symbol should be selected by an architecture if it
 385           supports an implementation of restartable sequences.
 386
 387 config HAVE_RUST
 388         bool
 389         help
 390           This symbol should be selected by an architecture if it
 391           supports Rust.
 392
 393 config HAVE_FUNCTION_ARG_ACCESS_API
 394         bool
 395         help
 396           This symbol should be selected by an architecture if it supports
 397           the API needed to access function arguments from pt_regs,
 398           declared in asm/ptrace.h
 399
 400 config HAVE_HW_BREAKPOINT
 401         bool
 402         depends on PERF_EVENTS
 403
 404 config HAVE_MIXED_BREAKPOINTS_REGS
 405         bool
 406         depends on HAVE_HW_BREAKPOINT
 407         help
 408           Depending on the arch implementation of hardware breakpoints,
 409           some of them have separate registers for data and instruction
 410           breakpoints addresses, others have mixed registers to store
 411           them but define the access type in a control register.
 412           Select this option if your arch implements breakpoints under the
 413           latter fashion.
 414
 415 config HAVE_USER_RETURN_NOTIFIER
 416         bool
 417
 418 config HAVE_PERF_EVENTS_NMI
 419         bool
 420         help
 421           System hardware can generate an NMI using the perf event
 422           subsystem.  Also has support for calculating CPU cycle events
 423           to determine how many clock cycles in a given period.
 424
 425 config HAVE_HARDLOCKUP_DETECTOR_PERF
 426         bool
 427         depends on HAVE_PERF_EVENTS_NMI
 428         help
 429           The arch chooses to use the generic perf-NMI-based hardlockup
 430           detector. Must define HAVE_PERF_EVENTS_NMI.
 431
 432 config HAVE_HARDLOCKUP_DETECTOR_ARCH
 433         bool
 434         help
 435           The arch provides its own hardlockup detector implementation instead
 436           of the generic ones.
 437
 438           It uses the same command line parameters, and sysctl interface,
 439           as the generic hardlockup detectors.
 440
 441 config HAVE_PERF_REGS
 442         bool
 443         help
 444           Support selective register dumps for perf events. This includes
 445           bit-mapping of each registers and a unique architecture id.
 446
 447 config HAVE_PERF_USER_STACK_DUMP
 448         bool
 449         help
 450           Support user stack dumps for perf event samples. This needs
 451           access to the user stack pointer which is not unified across
 452           architectures.
 453
 454 config HAVE_ARCH_JUMP_LABEL
 455         bool
 456
 457 config HAVE_ARCH_JUMP_LABEL_RELATIVE
 458         bool
 459
 460 config MMU_GATHER_TABLE_FREE
 461         bool
 462
 463 config MMU_GATHER_RCU_TABLE_FREE
 464         bool
 465         select MMU_GATHER_TABLE_FREE
 466
 467 config MMU_GATHER_PAGE_SIZE
 468         bool
 469
 470 config MMU_GATHER_NO_RANGE
 471         bool
 472         select MMU_GATHER_MERGE_VMAS
 473
 474 config MMU_GATHER_NO_FLUSH_CACHE
 475         bool
 476
 477 config MMU_GATHER_MERGE_VMAS
 478         bool
 479
 480 config MMU_GATHER_NO_GATHER
 481         bool
 482         depends on MMU_GATHER_TABLE_FREE
 483
 484 config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
 485         bool
 486         help
 487           Temporary select until all architectures can be converted to have
 488           irqs disabled over activate_mm. Architectures that do IPI based TLB
 489           shootdowns should enable this.
 490
 491 # Use normal mm refcounting for MMU_LAZY_TLB kernel thread references.
 492 # MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching
 493 # to/from kernel threads when the same mm is running on a lot of CPUs (a large
 494 # multi-threaded application), by reducing contention on the mm refcount.
 495 #
 496 # This can be disabled if the architecture ensures no CPUs are using an mm as a
 497 # "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm
 498 # or its kernel page tables). This could be arranged by arch_exit_mmap(), or
 499 # final exit(2) TLB flush, for example.
 500 #
 501 # To implement this, an arch *must*:
 502 # Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating
 503 # the lazy tlb reference of a kthread's ->active_mm (non-arch code has been
 504 # converted already).
 505 config MMU_LAZY_TLB_REFCOUNT
 506         def_bool y
 507         depends on !MMU_LAZY_TLB_SHOOTDOWN
 508
 509 # This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an
 510 # mm as a lazy tlb beyond its last reference count, by shooting down these
 511 # users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may
 512 # be using the mm as a lazy tlb, so that they may switch themselves to using
 513 # init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs
 514 # may be using mm as a lazy tlb mm.
 515 #
 516 # To implement this, an arch *must*:
 517 # - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains
 518 #   at least all possible CPUs in which the mm is lazy.
 519 # - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above).
 520 config MMU_LAZY_TLB_SHOOTDOWN
 521         bool
 522
 523 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 524         bool
 525
 526 config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
 527         bool
 528
 529 config HAVE_ALIGNED_STRUCT_PAGE
 530         bool
 531         help
 532           This makes sure that struct pages are double word aligned and that
 533           e.g. the SLUB allocator can perform double word atomic operations
 534           on a struct page for better performance. However selecting this
 535           might increase the size of a struct page by a word.
 536
 537 config HAVE_CMPXCHG_LOCAL
 538         bool
 539
 540 config HAVE_CMPXCHG_DOUBLE
 541         bool
 542
 543 config ARCH_WEAK_RELEASE_ACQUIRE
 544         bool
 545
 546 config ARCH_WANT_IPC_PARSE_VERSION
 547         bool
 548
 549 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 550         bool
 551
 552 config ARCH_WANT_OLD_COMPAT_IPC
 553         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 554         bool
 555
 556 config HAVE_ARCH_SECCOMP
 557         bool
 558         help
 559           An arch should select this symbol to support seccomp mode 1 (the fixed
 560           syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
 561           and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
 562           - __NR_seccomp_read_32
 563           - __NR_seccomp_write_32
 564           - __NR_seccomp_exit_32
 565           - __NR_seccomp_sigreturn_32
 566
 567 config HAVE_ARCH_SECCOMP_FILTER
 568         bool
 569         select HAVE_ARCH_SECCOMP
 570         help
 571           An arch should select this symbol if it provides all of these things:
 572           - all the requirements for HAVE_ARCH_SECCOMP
 573           - syscall_get_arch()
 574           - syscall_get_arguments()
 575           - syscall_rollback()
 576           - syscall_set_return_value()
 577           - SIGSYS siginfo_t support
 578           - secure_computing is called from a ptrace_event()-safe context
 579           - secure_computing return value is checked and a return value of -1
 580             results in the system call being skipped immediately.
 581           - seccomp syscall wired up
 582           - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE,
 583             SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If
 584             COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too.
 585
 586 config SECCOMP
 587         prompt "Enable seccomp to safely execute untrusted bytecode"
 588         def_bool y
 589         depends on HAVE_ARCH_SECCOMP
 590         help
 591           This kernel feature is useful for number crunching applications
 592           that may need to handle untrusted bytecode during their
 593           execution. By using pipes or other transports made available
 594           to the process as file descriptors supporting the read/write
 595           syscalls, it's possible to isolate those applications in their
 596           own address space using seccomp. Once seccomp is enabled via
 597           prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
 598           disabled and the task is only allowed to execute a few safe
 599           syscalls defined by each seccomp mode.
 600
 601           If unsure, say Y.
 602
 603 config SECCOMP_FILTER
 604         def_bool y
 605         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 606         help
 607           Enable tasks to build secure computing environments defined
 608           in terms of Berkeley Packet Filter programs which implement
 609           task-defined system call filtering polices.
 610
 611           See Documentation/userspace-api/seccomp_filter.rst for details.
 612
 613 config SECCOMP_CACHE_DEBUG
 614         bool "Show seccomp filter cache status in /proc/pid/seccomp_cache"
 615         depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR
 616         depends on PROC_FS
 617         help
 618           This enables the /proc/pid/seccomp_cache interface to monitor
 619           seccomp cache data. The file format is subject to change. Reading
 620           the file requires CAP_SYS_ADMIN.
 621
 622           This option is for debugging only. Enabling presents the risk that
 623           an adversary may be able to infer the seccomp filter logic.
 624
 625           If unsure, say N.
 626
 627 config HAVE_ARCH_STACKLEAK
 628         bool
 629         help
 630           An architecture should select this if it has the code which
 631           fills the used part of the kernel stack with the STACKLEAK_POISON
 632           value before returning from system calls.
 633
 634 config HAVE_STACKPROTECTOR
 635         bool
 636         help
 637           An arch should select this symbol if:
 638           - it has implemented a stack canary (e.g. __stack_chk_guard)
 639
 640 config STACKPROTECTOR
 641         bool "Stack Protector buffer overflow detection"
 642         depends on HAVE_STACKPROTECTOR
 643         depends on $(cc-option,-fstack-protector)
 644         default y
 645         help
 646           This option turns on the "stack-protector" GCC feature. This
 647           feature puts, at the beginning of functions, a canary value on
 648           the stack just before the return address, and validates
 649           the value just before actually returning.  Stack based buffer
 650           overflows (that need to overwrite this return address) now also
 651           overwrite the canary, which gets detected and the attack is then
 652           neutralized via a kernel panic.
 653
 654           Functions will have the stack-protector canary logic added if they
 655           have an 8-byte or larger character array on the stack.
 656
 657           This feature requires gcc version 4.2 or above, or a distribution
 658           gcc with the feature backported ("-fstack-protector").
 659
 660           On an x86 "defconfig" build, this feature adds canary checks to
 661           about 3% of all kernel functions, which increases kernel code size
 662           by about 0.3%.
 663
 664 config STACKPROTECTOR_STRONG
 665         bool "Strong Stack Protector"
 666         depends on STACKPROTECTOR
 667         depends on $(cc-option,-fstack-protector-strong)
 668         default y
 669         help
 670           Functions will have the stack-protector canary logic added in any
 671           of the following conditions:
 672
 673           - local variable's address used as part of the right hand side of an
 674             assignment or function argument
 675           - local variable is an array (or union containing an array),
 676             regardless of array type or length
 677           - uses register local variables
 678
 679           This feature requires gcc version 4.9 or above, or a distribution
 680           gcc with the feature backported ("-fstack-protector-strong").
 681
 682           On an x86 "defconfig" build, this feature adds canary checks to
 683           about 20% of all kernel functions, which increases the kernel code
 684           size by about 2%.
 685
 686 config ARCH_SUPPORTS_SHADOW_CALL_STACK
 687         bool
 688         help
 689           An architecture should select this if it supports the compiler's
 690           Shadow Call Stack and implements runtime support for shadow stack
 691           switching.
 692
 693 config SHADOW_CALL_STACK
 694         bool "Shadow Call Stack"
 695         depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
 696         depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
 697         help
 698           This option enables the compiler's Shadow Call Stack, which
 699           uses a shadow stack to protect function return addresses from
 700           being overwritten by an attacker. More information can be found
 701           in the compiler's documentation:
 702
 703           - Clang: https://clang.llvm.org/docs/ShadowCallStack.html
 704           - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options
 705
 706           Note that security guarantees in the kernel differ from the
 707           ones documented for user space. The kernel must store addresses
 708           of shadow stacks in memory, which means an attacker capable of
 709           reading and writing arbitrary memory may be able to locate them
 710           and hijack control flow by modifying the stacks.
 711
 712 config DYNAMIC_SCS
 713         bool
 714         help
 715           Set by the arch code if it relies on code patching to insert the
 716           shadow call stack push and pop instructions rather than on the
 717           compiler.
 718
 719 config LTO
 720         bool
 721         help
 722           Selected if the kernel will be built using the compiler's LTO feature.
 723
 724 config LTO_CLANG
 725         bool
 726         select LTO
 727         help
 728           Selected if the kernel will be built using Clang's LTO feature.
 729
 730 config ARCH_SUPPORTS_LTO_CLANG
 731         bool
 732         help
 733           An architecture should select this option if it supports:
 734           - compiling with Clang,
 735           - compiling inline assembly with Clang's integrated assembler,
 736           - and linking with LLD.
 737
 738 config ARCH_SUPPORTS_LTO_CLANG_THIN
 739         bool
 740         help
 741           An architecture should select this option if it can support Clang's
 742           ThinLTO mode.
 743
 744 config HAS_LTO_CLANG
 745         def_bool y
 746         depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM
 747         depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
 748         depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
 749         depends on ARCH_SUPPORTS_LTO_CLANG
 750         depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT
 751         depends on !KASAN || KASAN_HW_TAGS
 752         depends on !GCOV_KERNEL
 753         help
 754           The compiler and Kconfig options support building with Clang's
 755           LTO.
 756
 757 choice
 758         prompt "Link Time Optimization (LTO)"
 759         default LTO_NONE
 760         help
 761           This option enables Link Time Optimization (LTO), which allows the
 762           compiler to optimize binaries globally.
 763
 764           If unsure, select LTO_NONE. Note that LTO is very resource-intensive
 765           so it's disabled by default.
 766
 767 config LTO_NONE
 768         bool "None"
 769         help
 770           Build the kernel normally, without Link Time Optimization (LTO).
 771
 772 config LTO_CLANG_FULL
 773         bool "Clang Full LTO (EXPERIMENTAL)"
 774         depends on HAS_LTO_CLANG
 775         depends on !COMPILE_TEST
 776         select LTO_CLANG
 777         help
 778           This option enables Clang's full Link Time Optimization (LTO), which
 779           allows the compiler to optimize the kernel globally. If you enable
 780           this option, the compiler generates LLVM bitcode instead of ELF
 781           object files, and the actual compilation from bitcode happens at
 782           the LTO link step, which may take several minutes depending on the
 783           kernel configuration. More information can be found from LLVM's
 784           documentation:
 785
 786             https://llvm.org/docs/LinkTimeOptimization.html
 787
 788           During link time, this option can use a large amount of RAM, and
 789           may take much longer than the ThinLTO option.
 790
 791 config LTO_CLANG_THIN
 792         bool "Clang ThinLTO (EXPERIMENTAL)"
 793         depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN
 794         select LTO_CLANG
 795         help
 796           This option enables Clang's ThinLTO, which allows for parallel
 797           optimization and faster incremental compiles compared to the
 798           CONFIG_LTO_CLANG_FULL option. More information can be found
 799           from Clang's documentation:
 800
 801             https://clang.llvm.org/docs/ThinLTO.html
 802
 803           If unsure, say Y.
 804 endchoice
 805
 806 config ARCH_SUPPORTS_CFI_CLANG
 807         bool
 808         help
 809           An architecture should select this option if it can support Clang's
 810           Control-Flow Integrity (CFI) checking.
 811
 812 config ARCH_USES_CFI_TRAPS
 813         bool
 814
 815 config CFI_CLANG
 816         bool "Use Clang's Control Flow Integrity (CFI)"
 817         depends on ARCH_SUPPORTS_CFI_CLANG
 818         depends on $(cc-option,-fsanitize=kcfi)
 819         help
 820           This option enables Clang’s forward-edge Control Flow Integrity
 821           (CFI) checking, where the compiler injects a runtime check to each
 822           indirect function call to ensure the target is a valid function with
 823           the correct static type. This restricts possible call targets and
 824           makes it more difficult for an attacker to exploit bugs that allow
 825           the modification of stored function pointers. More information can be
 826           found from Clang's documentation:
 827
 828             https://clang.llvm.org/docs/ControlFlowIntegrity.html
 829
 830 config CFI_PERMISSIVE
 831         bool "Use CFI in permissive mode"
 832         depends on CFI_CLANG
 833         help
 834           When selected, Control Flow Integrity (CFI) violations result in a
 835           warning instead of a kernel panic. This option should only be used
 836           for finding indirect call type mismatches during development.
 837
 838           If unsure, say N.
 839
 840 config HAVE_ARCH_WITHIN_STACK_FRAMES
 841         bool
 842         help
 843           An architecture should select this if it can walk the kernel stack
 844           frames to determine if an object is part of either the arguments
 845           or local variables (i.e. that it excludes saved return addresses,
 846           and similar) by implementing an inline arch_within_stack_frames(),
 847           which is used by CONFIG_HARDENED_USERCOPY.
 848
 849 config HAVE_CONTEXT_TRACKING_USER
 850         bool
 851         help
 852           Provide kernel/user boundaries probes necessary for subsystems
 853           that need it, such as userspace RCU extended quiescent state.
 854           Syscalls need to be wrapped inside user_exit()-user_enter(), either
 855           optimized behind static key or through the slow path using TIF_NOHZ
 856           flag. Exceptions handlers must be wrapped as well. Irqs are already
 857           protected inside ct_irq_enter/ct_irq_exit() but preemption or signal
 858           handling on irq exit still need to be protected.
 859
 860 config HAVE_CONTEXT_TRACKING_USER_OFFSTACK
 861         bool
 862         help
 863           Architecture neither relies on exception_enter()/exception_exit()
 864           nor on schedule_user(). Also preempt_schedule_notrace() and
 865           preempt_schedule_irq() can't be called in a preemptible section
 866           while context tracking is CONTEXT_USER. This feature reflects a sane
 867           entry implementation where the following requirements are met on
 868           critical entry code, ie: before user_exit() or after user_enter():
 869
 870           - Critical entry code isn't preemptible (or better yet:
 871             not interruptible).
 872           - No use of RCU read side critical sections, unless ct_nmi_enter()
 873             got called.
 874           - No use of instrumentation, unless instrumentation_begin() got
 875             called.
 876
 877 config HAVE_TIF_NOHZ
 878         bool
 879         help
 880           Arch relies on TIF_NOHZ and syscall slow path to implement context
 881           tracking calls to user_enter()/user_exit().
 882
 883 config HAVE_VIRT_CPU_ACCOUNTING
 884         bool
 885
 886 config HAVE_VIRT_CPU_ACCOUNTING_IDLE
 887         bool
 888         help
 889           Architecture has its own way to account idle CPU time and therefore
 890           doesn't implement vtime_account_idle().
 891
 892 config ARCH_HAS_SCALED_CPUTIME
 893         bool
 894
 895 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 896         bool
 897         default y if 64BIT
 898         help
 899           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 900           Before enabling this option, arch code must be audited
 901           to ensure there are no races in concurrent read/write of
 902           cputime_t. For example, reading/writing 64-bit cputime_t on
 903           some 32-bit arches may require multiple accesses, so proper
 904           locking is needed to protect against concurrent accesses.
 905
 906 config HAVE_IRQ_TIME_ACCOUNTING
 907         bool
 908         help
 909           Archs need to ensure they use a high enough resolution clock to
 910           support irq time accounting and then call enable_sched_clock_irqtime().
 911
 912 config HAVE_MOVE_PUD
 913         bool
 914         help
 915           Architectures that select this are able to move page tables at the
 916           PUD level. If there are only 3 page table levels, the move effectively
 917           happens at the PGD level.
 918
 919 config HAVE_MOVE_PMD
 920         bool
 921         help
 922           Archs that select this are able to move page tables at the PMD level.
 923
 924 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 925         bool
 926
 927 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 928         bool
 929
 930 config HAVE_ARCH_HUGE_VMAP
 931         bool
 932
 933 #
 934 #  Archs that select this would be capable of PMD-sized vmaps (i.e.,
 935 #  arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag
 936 #  must be used to enable allocations to use hugepages.
 937 #
 938 config HAVE_ARCH_HUGE_VMALLOC
 939         depends on HAVE_ARCH_HUGE_VMAP
 940         bool
 941
 942 config ARCH_WANT_HUGE_PMD_SHARE
 943         bool
 944
 945 config HAVE_ARCH_SOFT_DIRTY
 946         bool
 947
 948 config HAVE_MOD_ARCH_SPECIFIC
 949         bool
 950         help
 951           The arch uses struct mod_arch_specific to store data.  Many arches
 952           just need a simple module loader without arch specific data - those
 953           should not enable this.
 954
 955 config MODULES_USE_ELF_RELA
 956         bool
 957         help
 958           Modules only use ELF RELA relocations.  Modules with ELF REL
 959           relocations will give an error.
 960
 961 config MODULES_USE_ELF_REL
 962         bool
 963         help
 964           Modules only use ELF REL relocations.  Modules with ELF RELA
 965           relocations will give an error.
 966
 967 config ARCH_WANTS_MODULES_DATA_IN_VMALLOC
 968         bool
 969         help
 970           For architectures like powerpc/32 which have constraints on module
 971           allocation and need to allocate module data outside of module area.
 972
 973 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 974         bool
 975         help
 976           Architecture doesn't only execute the irq handler on the irq stack
 977           but also irq_exit(). This way we can process softirqs on this irq
 978           stack instead of switching to a new one when we call __do_softirq()
 979           in the end of an hardirq.
 980           This spares a stack switch and improves cache usage on softirq
 981           processing.
 982
 983 config HAVE_SOFTIRQ_ON_OWN_STACK
 984         bool
 985         help
 986           Architecture provides a function to run __do_softirq() on a
 987           separate stack.
 988
 989 config SOFTIRQ_ON_OWN_STACK
 990         def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT
 991
 992 config ALTERNATE_USER_ADDRESS_SPACE
 993         bool
 994         help
 995           Architectures set this when the CPU uses separate address
 996           spaces for kernel and user space pointers. In this case, the
 997           access_ok() check on a __user pointer is skipped.
 998
 999 config PGTABLE_LEVELS
1000         int
1001         default 2
1002
1003 config ARCH_HAS_ELF_RANDOMIZE
1004         bool
1005         help
1006           An architecture supports choosing randomized locations for
1007           stack, mmap, brk, and ET_DYN. Defined functions:
1008           - arch_mmap_rnd()
1009           - arch_randomize_brk()
1010
1011 config HAVE_ARCH_MMAP_RND_BITS
1012         bool
1013         help
1014           An arch should select this symbol if it supports setting a variable
1015           number of bits for use in establishing the base address for mmap
1016           allocations, has MMU enabled and provides values for both:
1017           - ARCH_MMAP_RND_BITS_MIN
1018           - ARCH_MMAP_RND_BITS_MAX
1019
1020 config HAVE_EXIT_THREAD
1021         bool
1022         help
1023           An architecture implements exit_thread.
1024
1025 config ARCH_MMAP_RND_BITS_MIN
1026         int
1027
1028 config ARCH_MMAP_RND_BITS_MAX
1029         int
1030
1031 config ARCH_MMAP_RND_BITS_DEFAULT
1032         int
1033
1034 config ARCH_MMAP_RND_BITS
1035         int "Number of bits to use for ASLR of mmap base address" if EXPERT
1036         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
1037         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
1038         default ARCH_MMAP_RND_BITS_MIN
1039         depends on HAVE_ARCH_MMAP_RND_BITS
1040         help
1041           This value can be used to select the number of bits to use to
1042           determine the random offset to the base address of vma regions
1043           resulting from mmap allocations. This value will be bounded
1044           by the architecture's minimum and maximum supported values.
1045
1046           This value can be changed after boot using the
1047           /proc/sys/vm/mmap_rnd_bits tunable
1048
1049 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
1050         bool
1051         help
1052           An arch should select this symbol if it supports running applications
1053           in compatibility mode, supports setting a variable number of bits for
1054           use in establishing the base address for mmap allocations, has MMU
1055           enabled and provides values for both:
1056           - ARCH_MMAP_RND_COMPAT_BITS_MIN
1057           - ARCH_MMAP_RND_COMPAT_BITS_MAX
1058
1059 config ARCH_MMAP_RND_COMPAT_BITS_MIN
1060         int
1061
1062 config ARCH_MMAP_RND_COMPAT_BITS_MAX
1063         int
1064
1065 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
1066         int
1067
1068 config ARCH_MMAP_RND_COMPAT_BITS
1069         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
1070         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
1071         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
1072         default ARCH_MMAP_RND_COMPAT_BITS_MIN
1073         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
1074         help
1075           This value can be used to select the number of bits to use to
1076           determine the random offset to the base address of vma regions
1077           resulting from mmap allocations for compatible applications This
1078           value will be bounded by the architecture's minimum and maximum
1079           supported values.
1080
1081           This value can be changed after boot using the
1082           /proc/sys/vm/mmap_rnd_compat_bits tunable
1083
1084 config HAVE_ARCH_COMPAT_MMAP_BASES
1085         bool
1086         help
1087           This allows 64bit applications to invoke 32-bit mmap() syscall
1088           and vice-versa 32-bit applications to call 64-bit mmap().
1089           Required for applications doing different bitness syscalls.
1090
1091 config PAGE_SIZE_LESS_THAN_64KB
1092         def_bool y
1093         depends on !ARM64_64K_PAGES
1094         depends on !IA64_PAGE_SIZE_64KB
1095         depends on !PAGE_SIZE_64KB
1096         depends on !PARISC_PAGE_SIZE_64KB
1097         depends on PAGE_SIZE_LESS_THAN_256KB
1098
1099 config PAGE_SIZE_LESS_THAN_256KB
1100         def_bool y
1101         depends on !PAGE_SIZE_256KB
1102
1103 # This allows to use a set of generic functions to determine mmap base
1104 # address by giving priority to top-down scheme only if the process
1105 # is not in legacy mode (compat task, unlimited stack size or
1106 # sysctl_legacy_va_layout).
1107 # Architecture that selects this option can provide its own version of:
1108 # - STACK_RND_MASK
1109 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
1110         bool
1111         depends on MMU
1112         select ARCH_HAS_ELF_RANDOMIZE
1113
1114 config HAVE_OBJTOOL
1115         bool
1116
1117 config HAVE_JUMP_LABEL_HACK
1118         bool
1119
1120 config HAVE_NOINSTR_HACK
1121         bool
1122
1123 config HAVE_NOINSTR_VALIDATION
1124         bool
1125
1126 config HAVE_UACCESS_VALIDATION
1127         bool
1128         select OBJTOOL
1129
1130 config HAVE_STACK_VALIDATION
1131         bool
1132         help
1133           Architecture supports objtool compile-time frame pointer rule
1134           validation.
1135
1136 config HAVE_RELIABLE_STACKTRACE
1137         bool
1138         help
1139           Architecture has either save_stack_trace_tsk_reliable() or
1140           arch_stack_walk_reliable() function which only returns a stack trace
1141           if it can guarantee the trace is reliable.
1142
1143 config HAVE_ARCH_HASH
1144         bool
1145         default n
1146         help
1147           If this is set, the architecture provides an <asm/hash.h>
1148           file which provides platform-specific implementations of some
1149           functions in <linux/hash.h> or fs/namei.c.
1150
1151 config HAVE_ARCH_NVRAM_OPS
1152         bool
1153
1154 config ISA_BUS_API
1155         def_bool ISA
1156
1157 #
1158 # ABI hall of shame
1159 #
1160 config CLONE_BACKWARDS
1161         bool
1162         help
1163           Architecture has tls passed as the 4th argument of clone(2),
1164           not the 5th one.
1165
1166 config CLONE_BACKWARDS2
1167         bool
1168         help
1169           Architecture has the first two arguments of clone(2) swapped.
1170
1171 config CLONE_BACKWARDS3
1172         bool
1173         help
1174           Architecture has tls passed as the 3rd argument of clone(2),
1175           not the 5th one.
1176
1177 config ODD_RT_SIGACTION
1178         bool
1179         help
1180           Architecture has unusual rt_sigaction(2) arguments
1181
1182 config OLD_SIGSUSPEND
1183         bool
1184         help
1185           Architecture has old sigsuspend(2) syscall, of one-argument variety
1186
1187 config OLD_SIGSUSPEND3
1188         bool
1189         help
1190           Even weirder antique ABI - three-argument sigsuspend(2)
1191
1192 config OLD_SIGACTION
1193         bool
1194         help
1195           Architecture has old sigaction(2) syscall.  Nope, not the same
1196           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
1197           but fairly different variant of sigaction(2), thanks to OSF/1
1198           compatibility...
1199
1200 config COMPAT_OLD_SIGACTION
1201         bool
1202
1203 config COMPAT_32BIT_TIME
1204         bool "Provide system calls for 32-bit time_t"
1205         default !64BIT || COMPAT
1206         help
1207           This enables 32 bit time_t support in addition to 64 bit time_t support.
1208           This is relevant on all 32-bit architectures, and 64-bit architectures
1209           as part of compat syscall handling.
1210
1211 config ARCH_NO_PREEMPT
1212         bool
1213
1214 config ARCH_SUPPORTS_RT
1215         bool
1216
1217 config CPU_NO_EFFICIENT_FFS
1218         def_bool n
1219
1220 config HAVE_ARCH_VMAP_STACK
1221         def_bool n
1222         help
1223           An arch should select this symbol if it can support kernel stacks
1224           in vmalloc space.  This means:
1225
1226           - vmalloc space must be large enough to hold many kernel stacks.
1227             This may rule out many 32-bit architectures.
1228
1229           - Stacks in vmalloc space need to work reliably.  For example, if
1230             vmap page tables are created on demand, either this mechanism
1231             needs to work while the stack points to a virtual address with
1232             unpopulated page tables or arch code (switch_to() and switch_mm(),
1233             most likely) needs to ensure that the stack's page table entries
1234             are populated before running on a possibly unpopulated stack.
1235
1236           - If the stack overflows into a guard page, something reasonable
1237             should happen.  The definition of "reasonable" is flexible, but
1238             instantly rebooting without logging anything would be unfriendly.
1239
1240 config VMAP_STACK
1241         default y
1242         bool "Use a virtually-mapped stack"
1243         depends on HAVE_ARCH_VMAP_STACK
1244         depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC
1245         help
1246           Enable this if you want the use virtually-mapped kernel stacks
1247           with guard pages.  This causes kernel stack overflows to be
1248           caught immediately rather than causing difficult-to-diagnose
1249           corruption.
1250
1251           To use this with software KASAN modes, the architecture must support
1252           backing virtual mappings with real shadow memory, and KASAN_VMALLOC
1253           must be enabled.
1254
1255 config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1256         def_bool n
1257         help
1258           An arch should select this symbol if it can support kernel stack
1259           offset randomization with calls to add_random_kstack_offset()
1260           during syscall entry and choose_random_kstack_offset() during
1261           syscall exit. Careful removal of -fstack-protector-strong and
1262           -fstack-protector should also be applied to the entry code and
1263           closely examined, as the artificial stack bump looks like an array
1264           to the compiler, so it will attempt to add canary checks regardless
1265           of the static branch state.
1266
1267 config RANDOMIZE_KSTACK_OFFSET
1268         bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT
1269         default y
1270         depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1271         depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000
1272         help
1273           The kernel stack offset can be randomized (after pt_regs) by
1274           roughly 5 bits of entropy, frustrating memory corruption
1275           attacks that depend on stack address determinism or
1276           cross-syscall address exposures.
1277
1278           The feature is controlled via the "randomize_kstack_offset=on/off"
1279           kernel boot param, and if turned off has zero overhead due to its use
1280           of static branches (see JUMP_LABEL).
1281
1282           If unsure, say Y.
1283
1284 config RANDOMIZE_KSTACK_OFFSET_DEFAULT
1285         bool "Default state of kernel stack offset randomization"
1286         depends on RANDOMIZE_KSTACK_OFFSET
1287         help
1288           Kernel stack offset randomization is controlled by kernel boot param
1289           "randomize_kstack_offset=on/off", and this config chooses the default
1290           boot state.
1291
1292 config ARCH_OPTIONAL_KERNEL_RWX
1293         def_bool n
1294
1295 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1296         def_bool n
1297
1298 config ARCH_HAS_STRICT_KERNEL_RWX
1299         def_bool n
1300
1301 config STRICT_KERNEL_RWX
1302         bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
1303         depends on ARCH_HAS_STRICT_KERNEL_RWX
1304         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1305         help
1306           If this is set, kernel text and rodata memory will be made read-only,
1307           and non-text memory will be made non-executable. This provides
1308           protection against certain security exploits (e.g. executing the heap
1309           or modifying text)
1310
1311           These features are considered standard security practice these days.
1312           You should say Y here in almost all cases.
1313
1314 config ARCH_HAS_STRICT_MODULE_RWX
1315         def_bool n
1316
1317 config STRICT_MODULE_RWX
1318         bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
1319         depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
1320         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1321         help
1322           If this is set, module text and rodata memory will be made read-only,
1323           and non-text memory will be made non-executable. This provides
1324           protection against certain security exploits (e.g. writing to text)
1325
1326 # select if the architecture provides an asm/dma-direct.h header
1327 config ARCH_HAS_PHYS_TO_DMA
1328         bool
1329
1330 config HAVE_ARCH_COMPILER_H
1331         bool
1332         help
1333           An architecture can select this if it provides an
1334           asm/compiler.h header that should be included after
1335           linux/compiler-*.h in order to override macro definitions that those
1336           headers generally provide.
1337
1338 config HAVE_ARCH_PREL32_RELOCATIONS
1339         bool
1340         help
1341           May be selected by an architecture if it supports place-relative
1342           32-bit relocations, both in the toolchain and in the module loader,
1343           in which case relative references can be used in special sections
1344           for PCI fixup, initcalls etc which are only half the size on 64 bit
1345           architectures, and don't require runtime relocation on relocatable
1346           kernels.
1347
1348 config ARCH_USE_MEMREMAP_PROT
1349         bool
1350
1351 config LOCK_EVENT_COUNTS
1352         bool "Locking event counts collection"
1353         depends on DEBUG_FS
1354         help
1355           Enable light-weight counting of various locking related events
1356           in the system with minimal performance impact. This reduces
1357           the chance of application behavior change because of timing
1358           differences. The counts are reported via debugfs.
1359
1360 # Select if the architecture has support for applying RELR relocations.
1361 config ARCH_HAS_RELR
1362         bool
1363
1364 config RELR
1365         bool "Use RELR relocation packing"
1366         depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1367         default y
1368         help
1369           Store the kernel's dynamic relocations in the RELR relocation packing
1370           format. Requires a compatible linker (LLD supports this feature), as
1371           well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1372           are compatible).
1373
1374 config ARCH_HAS_MEM_ENCRYPT
1375         bool
1376
1377 config ARCH_HAS_CC_PLATFORM
1378         bool
1379
1380 config HAVE_SPARSE_SYSCALL_NR
1381         bool
1382         help
1383           An architecture should select this if its syscall numbering is sparse
1384           to save space. For example, MIPS architecture has a syscall array with
1385           entries at 4000, 5000 and 6000 locations. This option turns on syscall
1386           related optimizations for a given architecture.
1387
1388 config ARCH_HAS_VDSO_DATA
1389         bool
1390
1391 config HAVE_STATIC_CALL
1392         bool
1393
1394 config HAVE_STATIC_CALL_INLINE
1395         bool
1396         depends on HAVE_STATIC_CALL
1397         select OBJTOOL
1398
1399 config HAVE_PREEMPT_DYNAMIC
1400         bool
1401
1402 config HAVE_PREEMPT_DYNAMIC_CALL
1403         bool
1404         depends on HAVE_STATIC_CALL
1405         select HAVE_PREEMPT_DYNAMIC
1406         help
1407           An architecture should select this if it can handle the preemption
1408           model being selected at boot time using static calls.
1409
1410           Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a
1411           preemption function will be patched directly.
1412
1413           Where an architecture does not select HAVE_STATIC_CALL_INLINE, any
1414           call to a preemption function will go through a trampoline, and the
1415           trampoline will be patched.
1416
1417           It is strongly advised to support inline static call to avoid any
1418           overhead.
1419
1420 config HAVE_PREEMPT_DYNAMIC_KEY
1421         bool
1422         depends on HAVE_ARCH_JUMP_LABEL
1423         select HAVE_PREEMPT_DYNAMIC
1424         help
1425           An architecture should select this if it can handle the preemption
1426           model being selected at boot time using static keys.
1427
1428           Each preemption function will be given an early return based on a
1429           static key. This should have slightly lower overhead than non-inline
1430           static calls, as this effectively inlines each trampoline into the
1431           start of its callee. This may avoid redundant work, and may
1432           integrate better with CFI schemes.
1433
1434           This will have greater overhead than using inline static calls as
1435           the call to the preemption function cannot be entirely elided.
1436
1437 config ARCH_WANT_LD_ORPHAN_WARN
1438         bool
1439         help
1440           An arch should select this symbol once all linker sections are explicitly
1441           included, size-asserted, or discarded in the linker scripts. This is
1442           important because we never want expected sections to be placed heuristically
1443           by the linker, since the locations of such sections can change between linker
1444           versions.
1445
1446 config HAVE_ARCH_PFN_VALID
1447         bool
1448
1449 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
1450         bool
1451
1452 config ARCH_SUPPORTS_PAGE_TABLE_CHECK
1453         bool
1454
1455 config ARCH_SPLIT_ARG64
1456         bool
1457         help
1458           If a 32-bit architecture requires 64-bit arguments to be split into
1459           pairs of 32-bit arguments, select this option.
1460
1461 config ARCH_HAS_ELFCORE_COMPAT
1462         bool
1463
1464 config ARCH_HAS_PARANOID_L1D_FLUSH
1465         bool
1466
1467 config ARCH_HAVE_TRACE_MMIO_ACCESS
1468         bool
1469
1470 config DYNAMIC_SIGFRAME
1471         bool
1472
1473 # Select, if arch has a named attribute group bound to NUMA device nodes.
1474 config HAVE_ARCH_NODE_DEV_GROUP
1475         bool
1476
1477 config ARCH_HAS_NONLEAF_PMD_YOUNG
1478         bool
1479         help
1480           Architectures that select this option are capable of setting the
1481           accessed bit in non-leaf PMD entries when using them as part of linear
1482           address translations. Page table walkers that clear the accessed bit
1483           may use this capability to reduce their search space.
1484
1485 source "kernel/gcov/Kconfig"
1486
1487 source "scripts/gcc-plugins/Kconfig"
1488
1489 config FUNCTION_ALIGNMENT_4B
1490         bool
1491
1492 config FUNCTION_ALIGNMENT_8B
1493         bool
1494
1495 config FUNCTION_ALIGNMENT_16B
1496         bool
1497
1498 config FUNCTION_ALIGNMENT_32B
1499         bool
1500
1501 config FUNCTION_ALIGNMENT_64B
1502         bool
1503
1504 config FUNCTION_ALIGNMENT
1505         int
1506         default 64 if FUNCTION_ALIGNMENT_64B
1507         default 32 if FUNCTION_ALIGNMENT_32B
1508         default 16 if FUNCTION_ALIGNMENT_16B
1509         default 8 if FUNCTION_ALIGNMENT_8B
1510         default 4 if FUNCTION_ALIGNMENT_4B
1511         default 0
1512
1513 endmenu