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 HAVE_IMA_KEXEC
  22         bool
  23
  24 config HOTPLUG_SMT
  25         bool
  26
  27 config OPROFILE
  28         tristate "OProfile system profiling"
  29         depends on PROFILING
  30         depends on HAVE_OPROFILE
  31         select RING_BUFFER
  32         select RING_BUFFER_ALLOW_SWAP
  33         help
  34           OProfile is a profiling system capable of profiling the
  35           whole system, include the kernel, kernel modules, libraries,
  36           and applications.
  37
  38           If unsure, say N.
  39
  40 config OPROFILE_EVENT_MULTIPLEX
  41         bool "OProfile multiplexing support (EXPERIMENTAL)"
  42         default n
  43         depends on OPROFILE && X86
  44         help
  45           The number of hardware counters is limited. The multiplexing
  46           feature enables OProfile to gather more events than counters
  47           are provided by the hardware. This is realized by switching
  48           between events at a user specified time interval.
  49
  50           If unsure, say N.
  51
  52 config HAVE_OPROFILE
  53         bool
  54
  55 config OPROFILE_NMI_TIMER
  56         def_bool y
  57         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
  58
  59 config KPROBES
  60         bool "Kprobes"
  61         depends on MODULES
  62         depends on HAVE_KPROBES
  63         select KALLSYMS
  64         help
  65           Kprobes allows you to trap at almost any kernel address and
  66           execute a callback function.  register_kprobe() establishes
  67           a probepoint and specifies the callback.  Kprobes is useful
  68           for kernel debugging, non-intrusive instrumentation and testing.
  69           If in doubt, say "N".
  70
  71 config JUMP_LABEL
  72        bool "Optimize very unlikely/likely branches"
  73        depends on HAVE_ARCH_JUMP_LABEL
  74        depends on CC_HAS_ASM_GOTO
  75        help
  76          This option enables a transparent branch optimization that
  77          makes certain almost-always-true or almost-always-false branch
  78          conditions even cheaper to execute within the kernel.
  79
  80          Certain performance-sensitive kernel code, such as trace points,
  81          scheduler functionality, networking code and KVM have such
  82          branches and include support for this optimization technique.
  83
  84          If it is detected that the compiler has support for "asm goto",
  85          the kernel will compile such branches with just a nop
  86          instruction. When the condition flag is toggled to true, the
  87          nop will be converted to a jump instruction to execute the
  88          conditional block of instructions.
  89
  90          This technique lowers overhead and stress on the branch prediction
  91          of the processor and generally makes the kernel faster. The update
  92          of the condition is slower, but those are always very rare.
  93
  94          ( On 32-bit x86, the necessary options added to the compiler
  95            flags may increase the size of the kernel slightly. )
  96
  97 config STATIC_KEYS_SELFTEST
  98         bool "Static key selftest"
  99         depends on JUMP_LABEL
 100         help
 101           Boot time self-test of the branch patching code.
 102
 103 config OPTPROBES
 104         def_bool y
 105         depends on KPROBES && HAVE_OPTPROBES
 106         select TASKS_RCU if PREEMPT
 107
 108 config KPROBES_ON_FTRACE
 109         def_bool y
 110         depends on KPROBES && HAVE_KPROBES_ON_FTRACE
 111         depends on DYNAMIC_FTRACE_WITH_REGS
 112         help
 113          If function tracer is enabled and the arch supports full
 114          passing of pt_regs to function tracing, then kprobes can
 115          optimize on top of function tracing.
 116
 117 config UPROBES
 118         def_bool n
 119         depends on ARCH_SUPPORTS_UPROBES
 120         help
 121           Uprobes is the user-space counterpart to kprobes: they
 122           enable instrumentation applications (such as 'perf probe')
 123           to establish unintrusive probes in user-space binaries and
 124           libraries, by executing handler functions when the probes
 125           are hit by user-space applications.
 126
 127           ( These probes come in the form of single-byte breakpoints,
 128             managed by the kernel and kept transparent to the probed
 129             application. )
 130
 131 config HAVE_EFFICIENT_UNALIGNED_ACCESS
 132         bool
 133         help
 134           Some architectures are unable to perform unaligned accesses
 135           without the use of get_unaligned/put_unaligned. Others are
 136           unable to perform such accesses efficiently (e.g. trap on
 137           unaligned access and require fixing it up in the exception
 138           handler.)
 139
 140           This symbol should be selected by an architecture if it can
 141           perform unaligned accesses efficiently to allow different
 142           code paths to be selected for these cases. Some network
 143           drivers, for example, could opt to not fix up alignment
 144           problems with received packets if doing so would not help
 145           much.
 146
 147           See Documentation/unaligned-memory-access.txt for more
 148           information on the topic of unaligned memory accesses.
 149
 150 config ARCH_USE_BUILTIN_BSWAP
 151        bool
 152        help
 153          Modern versions of GCC (since 4.4) have builtin functions
 154          for handling byte-swapping. Using these, instead of the old
 155          inline assembler that the architecture code provides in the
 156          __arch_bswapXX() macros, allows the compiler to see what's
 157          happening and offers more opportunity for optimisation. In
 158          particular, the compiler will be able to combine the byteswap
 159          with a nearby load or store and use load-and-swap or
 160          store-and-swap instructions if the architecture has them. It
 161          should almost *never* result in code which is worse than the
 162          hand-coded assembler in <asm/swab.h>.  But just in case it
 163          does, the use of the builtins is optional.
 164
 165          Any architecture with load-and-swap or store-and-swap
 166          instructions should set this. And it shouldn't hurt to set it
 167          on architectures that don't have such instructions.
 168
 169 config KRETPROBES
 170         def_bool y
 171         depends on KPROBES && HAVE_KRETPROBES
 172
 173 config USER_RETURN_NOTIFIER
 174         bool
 175         depends on HAVE_USER_RETURN_NOTIFIER
 176         help
 177           Provide a kernel-internal notification when a cpu is about to
 178           switch to user mode.
 179
 180 config HAVE_IOREMAP_PROT
 181         bool
 182
 183 config HAVE_KPROBES
 184         bool
 185
 186 config HAVE_KRETPROBES
 187         bool
 188
 189 config HAVE_OPTPROBES
 190         bool
 191
 192 config HAVE_KPROBES_ON_FTRACE
 193         bool
 194
 195 config HAVE_FUNCTION_ERROR_INJECTION
 196         bool
 197
 198 config HAVE_NMI
 199         bool
 200
 201 #
 202 # An arch should select this if it provides all these things:
 203 #
 204 #       task_pt_regs()          in asm/processor.h or asm/ptrace.h
 205 #       arch_has_single_step()  if there is hardware single-step support
 206 #       arch_has_block_step()   if there is hardware block-step support
 207 #       asm/syscall.h           supplying asm-generic/syscall.h interface
 208 #       linux/regset.h          user_regset interfaces
 209 #       CORE_DUMP_USE_REGSET    #define'd in linux/elf.h
 210 #       TIF_SYSCALL_TRACE       calls tracehook_report_syscall_{entry,exit}
 211 #       TIF_NOTIFY_RESUME       calls tracehook_notify_resume()
 212 #       signal delivery         calls tracehook_signal_handler()
 213 #
 214 config HAVE_ARCH_TRACEHOOK
 215         bool
 216
 217 config HAVE_DMA_CONTIGUOUS
 218         bool
 219
 220 config GENERIC_SMP_IDLE_THREAD
 221        bool
 222
 223 config GENERIC_IDLE_POLL_SETUP
 224        bool
 225
 226 config ARCH_HAS_FORTIFY_SOURCE
 227         bool
 228         help
 229           An architecture should select this when it can successfully
 230           build and run with CONFIG_FORTIFY_SOURCE.
 231
 232 #
 233 # Select if the arch provides a historic keepinit alias for the retain_initrd
 234 # command line option
 235 #
 236 config ARCH_HAS_KEEPINITRD
 237         bool
 238
 239 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
 240 config ARCH_HAS_SET_MEMORY
 241         bool
 242
 243 # Select if arch has all set_direct_map_invalid/default() functions
 244 config ARCH_HAS_SET_DIRECT_MAP
 245         bool
 246
 247 #
 248 # Select if arch has an uncached kernel segment and provides the
 249 # uncached_kernel_address / cached_kernel_address symbols to use it
 250 #
 251 config ARCH_HAS_UNCACHED_SEGMENT
 252         select ARCH_HAS_DMA_PREP_COHERENT
 253         bool
 254
 255 # Select if arch init_task must go in the __init_task_data section
 256 config ARCH_TASK_STRUCT_ON_STACK
 257        bool
 258
 259 # Select if arch has its private alloc_task_struct() function
 260 config ARCH_TASK_STRUCT_ALLOCATOR
 261         bool
 262
 263 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
 264         bool
 265         depends on !ARCH_TASK_STRUCT_ALLOCATOR
 266         help
 267           An architecture should select this to provide hardened usercopy
 268           knowledge about what region of the thread_struct should be
 269           whitelisted for copying to userspace. Normally this is only the
 270           FPU registers. Specifically, arch_thread_struct_whitelist()
 271           should be implemented. Without this, the entire thread_struct
 272           field in task_struct will be left whitelisted.
 273
 274 # Select if arch has its private alloc_thread_stack() function
 275 config ARCH_THREAD_STACK_ALLOCATOR
 276         bool
 277
 278 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 279 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 280         bool
 281
 282 config ARCH_32BIT_OFF_T
 283         bool
 284         depends on !64BIT
 285         help
 286           All new 32-bit architectures should have 64-bit off_t type on
 287           userspace side which corresponds to the loff_t kernel type. This
 288           is the requirement for modern ABIs. Some existing architectures
 289           still support 32-bit off_t. This option is enabled for all such
 290           architectures explicitly.
 291
 292 config HAVE_REGS_AND_STACK_ACCESS_API
 293         bool
 294         help
 295           This symbol should be selected by an architecure if it supports
 296           the API needed to access registers and stack entries from pt_regs,
 297           declared in asm/ptrace.h
 298           For example the kprobes-based event tracer needs this API.
 299
 300 config HAVE_RSEQ
 301         bool
 302         depends on HAVE_REGS_AND_STACK_ACCESS_API
 303         help
 304           This symbol should be selected by an architecture if it
 305           supports an implementation of restartable sequences.
 306
 307 config HAVE_FUNCTION_ARG_ACCESS_API
 308         bool
 309         help
 310           This symbol should be selected by an architecure if it supports
 311           the API needed to access function arguments from pt_regs,
 312           declared in asm/ptrace.h
 313
 314 config HAVE_CLK
 315         bool
 316         help
 317           The <linux/clk.h> calls support software clock gating and
 318           thus are a key power management tool on many systems.
 319
 320 config HAVE_HW_BREAKPOINT
 321         bool
 322         depends on PERF_EVENTS
 323
 324 config HAVE_MIXED_BREAKPOINTS_REGS
 325         bool
 326         depends on HAVE_HW_BREAKPOINT
 327         help
 328           Depending on the arch implementation of hardware breakpoints,
 329           some of them have separate registers for data and instruction
 330           breakpoints addresses, others have mixed registers to store
 331           them but define the access type in a control register.
 332           Select this option if your arch implements breakpoints under the
 333           latter fashion.
 334
 335 config HAVE_USER_RETURN_NOTIFIER
 336         bool
 337
 338 config HAVE_PERF_EVENTS_NMI
 339         bool
 340         help
 341           System hardware can generate an NMI using the perf event
 342           subsystem.  Also has support for calculating CPU cycle events
 343           to determine how many clock cycles in a given period.
 344
 345 config HAVE_HARDLOCKUP_DETECTOR_PERF
 346         bool
 347         depends on HAVE_PERF_EVENTS_NMI
 348         help
 349           The arch chooses to use the generic perf-NMI-based hardlockup
 350           detector. Must define HAVE_PERF_EVENTS_NMI.
 351
 352 config HAVE_NMI_WATCHDOG
 353         depends on HAVE_NMI
 354         bool
 355         help
 356           The arch provides a low level NMI watchdog. It provides
 357           asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
 358
 359 config HAVE_HARDLOCKUP_DETECTOR_ARCH
 360         bool
 361         select HAVE_NMI_WATCHDOG
 362         help
 363           The arch chooses to provide its own hardlockup detector, which is
 364           a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
 365           interfaces and parameters provided by hardlockup detector subsystem.
 366
 367 config HAVE_PERF_REGS
 368         bool
 369         help
 370           Support selective register dumps for perf events. This includes
 371           bit-mapping of each registers and a unique architecture id.
 372
 373 config HAVE_PERF_USER_STACK_DUMP
 374         bool
 375         help
 376           Support user stack dumps for perf event samples. This needs
 377           access to the user stack pointer which is not unified across
 378           architectures.
 379
 380 config HAVE_ARCH_JUMP_LABEL
 381         bool
 382
 383 config HAVE_ARCH_JUMP_LABEL_RELATIVE
 384         bool
 385
 386 config HAVE_RCU_TABLE_FREE
 387         bool
 388
 389 config HAVE_RCU_TABLE_NO_INVALIDATE
 390         bool
 391
 392 config HAVE_MMU_GATHER_PAGE_SIZE
 393         bool
 394
 395 config HAVE_MMU_GATHER_NO_GATHER
 396         bool
 397
 398 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 399         bool
 400
 401 config HAVE_ALIGNED_STRUCT_PAGE
 402         bool
 403         help
 404           This makes sure that struct pages are double word aligned and that
 405           e.g. the SLUB allocator can perform double word atomic operations
 406           on a struct page for better performance. However selecting this
 407           might increase the size of a struct page by a word.
 408
 409 config HAVE_CMPXCHG_LOCAL
 410         bool
 411
 412 config HAVE_CMPXCHG_DOUBLE
 413         bool
 414
 415 config ARCH_WEAK_RELEASE_ACQUIRE
 416         bool
 417
 418 config ARCH_WANT_IPC_PARSE_VERSION
 419         bool
 420
 421 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 422         bool
 423
 424 config ARCH_WANT_OLD_COMPAT_IPC
 425         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 426         bool
 427
 428 config HAVE_ARCH_SECCOMP_FILTER
 429         bool
 430         help
 431           An arch should select this symbol if it provides all of these things:
 432           - syscall_get_arch()
 433           - syscall_get_arguments()
 434           - syscall_rollback()
 435           - syscall_set_return_value()
 436           - SIGSYS siginfo_t support
 437           - secure_computing is called from a ptrace_event()-safe context
 438           - secure_computing return value is checked and a return value of -1
 439             results in the system call being skipped immediately.
 440           - seccomp syscall wired up
 441
 442 config SECCOMP_FILTER
 443         def_bool y
 444         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 445         help
 446           Enable tasks to build secure computing environments defined
 447           in terms of Berkeley Packet Filter programs which implement
 448           task-defined system call filtering polices.
 449
 450           See Documentation/userspace-api/seccomp_filter.rst for details.
 451
 452 config HAVE_ARCH_STACKLEAK
 453         bool
 454         help
 455           An architecture should select this if it has the code which
 456           fills the used part of the kernel stack with the STACKLEAK_POISON
 457           value before returning from system calls.
 458
 459 config HAVE_STACKPROTECTOR
 460         bool
 461         help
 462           An arch should select this symbol if:
 463           - it has implemented a stack canary (e.g. __stack_chk_guard)
 464
 465 config CC_HAS_STACKPROTECTOR_NONE
 466         def_bool $(cc-option,-fno-stack-protector)
 467
 468 config STACKPROTECTOR
 469         bool "Stack Protector buffer overflow detection"
 470         depends on HAVE_STACKPROTECTOR
 471         depends on $(cc-option,-fstack-protector)
 472         default y
 473         help
 474           This option turns on the "stack-protector" GCC feature. This
 475           feature puts, at the beginning of functions, a canary value on
 476           the stack just before the return address, and validates
 477           the value just before actually returning.  Stack based buffer
 478           overflows (that need to overwrite this return address) now also
 479           overwrite the canary, which gets detected and the attack is then
 480           neutralized via a kernel panic.
 481
 482           Functions will have the stack-protector canary logic added if they
 483           have an 8-byte or larger character array on the stack.
 484
 485           This feature requires gcc version 4.2 or above, or a distribution
 486           gcc with the feature backported ("-fstack-protector").
 487
 488           On an x86 "defconfig" build, this feature adds canary checks to
 489           about 3% of all kernel functions, which increases kernel code size
 490           by about 0.3%.
 491
 492 config STACKPROTECTOR_STRONG
 493         bool "Strong Stack Protector"
 494         depends on STACKPROTECTOR
 495         depends on $(cc-option,-fstack-protector-strong)
 496         default y
 497         help
 498           Functions will have the stack-protector canary logic added in any
 499           of the following conditions:
 500
 501           - local variable's address used as part of the right hand side of an
 502             assignment or function argument
 503           - local variable is an array (or union containing an array),
 504             regardless of array type or length
 505           - uses register local variables
 506
 507           This feature requires gcc version 4.9 or above, or a distribution
 508           gcc with the feature backported ("-fstack-protector-strong").
 509
 510           On an x86 "defconfig" build, this feature adds canary checks to
 511           about 20% of all kernel functions, which increases the kernel code
 512           size by about 2%.
 513
 514 config HAVE_ARCH_WITHIN_STACK_FRAMES
 515         bool
 516         help
 517           An architecture should select this if it can walk the kernel stack
 518           frames to determine if an object is part of either the arguments
 519           or local variables (i.e. that it excludes saved return addresses,
 520           and similar) by implementing an inline arch_within_stack_frames(),
 521           which is used by CONFIG_HARDENED_USERCOPY.
 522
 523 config HAVE_CONTEXT_TRACKING
 524         bool
 525         help
 526           Provide kernel/user boundaries probes necessary for subsystems
 527           that need it, such as userspace RCU extended quiescent state.
 528           Syscalls need to be wrapped inside user_exit()-user_enter() through
 529           the slow path using TIF_NOHZ flag. Exceptions handlers must be
 530           wrapped as well. Irqs are already protected inside
 531           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
 532           irq exit still need to be protected.
 533
 534 config HAVE_VIRT_CPU_ACCOUNTING
 535         bool
 536
 537 config ARCH_HAS_SCALED_CPUTIME
 538         bool
 539
 540 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 541         bool
 542         default y if 64BIT
 543         help
 544           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 545           Before enabling this option, arch code must be audited
 546           to ensure there are no races in concurrent read/write of
 547           cputime_t. For example, reading/writing 64-bit cputime_t on
 548           some 32-bit arches may require multiple accesses, so proper
 549           locking is needed to protect against concurrent accesses.
 550
 551
 552 config HAVE_IRQ_TIME_ACCOUNTING
 553         bool
 554         help
 555           Archs need to ensure they use a high enough resolution clock to
 556           support irq time accounting and then call enable_sched_clock_irqtime().
 557
 558 config HAVE_MOVE_PMD
 559         bool
 560         help
 561           Archs that select this are able to move page tables at the PMD level.
 562
 563 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 564         bool
 565
 566 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 567         bool
 568
 569 config HAVE_ARCH_HUGE_VMAP
 570         bool
 571
 572 config ARCH_WANT_HUGE_PMD_SHARE
 573         bool
 574
 575 config HAVE_ARCH_SOFT_DIRTY
 576         bool
 577
 578 config HAVE_MOD_ARCH_SPECIFIC
 579         bool
 580         help
 581           The arch uses struct mod_arch_specific to store data.  Many arches
 582           just need a simple module loader without arch specific data - those
 583           should not enable this.
 584
 585 config MODULES_USE_ELF_RELA
 586         bool
 587         help
 588           Modules only use ELF RELA relocations.  Modules with ELF REL
 589           relocations will give an error.
 590
 591 config MODULES_USE_ELF_REL
 592         bool
 593         help
 594           Modules only use ELF REL relocations.  Modules with ELF RELA
 595           relocations will give an error.
 596
 597 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 598         bool
 599         help
 600           Architecture doesn't only execute the irq handler on the irq stack
 601           but also irq_exit(). This way we can process softirqs on this irq
 602           stack instead of switching to a new one when we call __do_softirq()
 603           in the end of an hardirq.
 604           This spares a stack switch and improves cache usage on softirq
 605           processing.
 606
 607 config PGTABLE_LEVELS
 608         int
 609         default 2
 610
 611 config ARCH_HAS_ELF_RANDOMIZE
 612         bool
 613         help
 614           An architecture supports choosing randomized locations for
 615           stack, mmap, brk, and ET_DYN. Defined functions:
 616           - arch_mmap_rnd()
 617           - arch_randomize_brk()
 618
 619 config HAVE_ARCH_MMAP_RND_BITS
 620         bool
 621         help
 622           An arch should select this symbol if it supports setting a variable
 623           number of bits for use in establishing the base address for mmap
 624           allocations, has MMU enabled and provides values for both:
 625           - ARCH_MMAP_RND_BITS_MIN
 626           - ARCH_MMAP_RND_BITS_MAX
 627
 628 config HAVE_EXIT_THREAD
 629         bool
 630         help
 631           An architecture implements exit_thread.
 632
 633 config ARCH_MMAP_RND_BITS_MIN
 634         int
 635
 636 config ARCH_MMAP_RND_BITS_MAX
 637         int
 638
 639 config ARCH_MMAP_RND_BITS_DEFAULT
 640         int
 641
 642 config ARCH_MMAP_RND_BITS
 643         int "Number of bits to use for ASLR of mmap base address" if EXPERT
 644         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
 645         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
 646         default ARCH_MMAP_RND_BITS_MIN
 647         depends on HAVE_ARCH_MMAP_RND_BITS
 648         help
 649           This value can be used to select the number of bits to use to
 650           determine the random offset to the base address of vma regions
 651           resulting from mmap allocations. This value will be bounded
 652           by the architecture's minimum and maximum supported values.
 653
 654           This value can be changed after boot using the
 655           /proc/sys/vm/mmap_rnd_bits tunable
 656
 657 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
 658         bool
 659         help
 660           An arch should select this symbol if it supports running applications
 661           in compatibility mode, supports setting a variable number of bits for
 662           use in establishing the base address for mmap allocations, has MMU
 663           enabled and provides values for both:
 664           - ARCH_MMAP_RND_COMPAT_BITS_MIN
 665           - ARCH_MMAP_RND_COMPAT_BITS_MAX
 666
 667 config ARCH_MMAP_RND_COMPAT_BITS_MIN
 668         int
 669
 670 config ARCH_MMAP_RND_COMPAT_BITS_MAX
 671         int
 672
 673 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 674         int
 675
 676 config ARCH_MMAP_RND_COMPAT_BITS
 677         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
 678         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
 679         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 680         default ARCH_MMAP_RND_COMPAT_BITS_MIN
 681         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
 682         help
 683           This value can be used to select the number of bits to use to
 684           determine the random offset to the base address of vma regions
 685           resulting from mmap allocations for compatible applications This
 686           value will be bounded by the architecture's minimum and maximum
 687           supported values.
 688
 689           This value can be changed after boot using the
 690           /proc/sys/vm/mmap_rnd_compat_bits tunable
 691
 692 config HAVE_ARCH_COMPAT_MMAP_BASES
 693         bool
 694         help
 695           This allows 64bit applications to invoke 32-bit mmap() syscall
 696           and vice-versa 32-bit applications to call 64-bit mmap().
 697           Required for applications doing different bitness syscalls.
 698
 699 config HAVE_COPY_THREAD_TLS
 700         bool
 701         help
 702           Architecture provides copy_thread_tls to accept tls argument via
 703           normal C parameter passing, rather than extracting the syscall
 704           argument from pt_regs.
 705
 706 config HAVE_STACK_VALIDATION
 707         bool
 708         help
 709           Architecture supports the 'objtool check' host tool command, which
 710           performs compile-time stack metadata validation.
 711
 712 config HAVE_RELIABLE_STACKTRACE
 713         bool
 714         help
 715           Architecture has a save_stack_trace_tsk_reliable() function which
 716           only returns a stack trace if it can guarantee the trace is reliable.
 717
 718 config HAVE_ARCH_HASH
 719         bool
 720         default n
 721         help
 722           If this is set, the architecture provides an <asm/hash.h>
 723           file which provides platform-specific implementations of some
 724           functions in <linux/hash.h> or fs/namei.c.
 725
 726 config HAVE_ARCH_NVRAM_OPS
 727         bool
 728
 729 config ISA_BUS_API
 730         def_bool ISA
 731
 732 #
 733 # ABI hall of shame
 734 #
 735 config CLONE_BACKWARDS
 736         bool
 737         help
 738           Architecture has tls passed as the 4th argument of clone(2),
 739           not the 5th one.
 740
 741 config CLONE_BACKWARDS2
 742         bool
 743         help
 744           Architecture has the first two arguments of clone(2) swapped.
 745
 746 config CLONE_BACKWARDS3
 747         bool
 748         help
 749           Architecture has tls passed as the 3rd argument of clone(2),
 750           not the 5th one.
 751
 752 config ODD_RT_SIGACTION
 753         bool
 754         help
 755           Architecture has unusual rt_sigaction(2) arguments
 756
 757 config OLD_SIGSUSPEND
 758         bool
 759         help
 760           Architecture has old sigsuspend(2) syscall, of one-argument variety
 761
 762 config OLD_SIGSUSPEND3
 763         bool
 764         help
 765           Even weirder antique ABI - three-argument sigsuspend(2)
 766
 767 config OLD_SIGACTION
 768         bool
 769         help
 770           Architecture has old sigaction(2) syscall.  Nope, not the same
 771           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
 772           but fairly different variant of sigaction(2), thanks to OSF/1
 773           compatibility...
 774
 775 config COMPAT_OLD_SIGACTION
 776         bool
 777
 778 config 64BIT_TIME
 779         def_bool y
 780         help
 781           This should be selected by all architectures that need to support
 782           new system calls with a 64-bit time_t. This is relevant on all 32-bit
 783           architectures, and 64-bit architectures as part of compat syscall
 784           handling.
 785
 786 config COMPAT_32BIT_TIME
 787         def_bool !64BIT || COMPAT
 788         help
 789           This enables 32 bit time_t support in addition to 64 bit time_t support.
 790           This is relevant on all 32-bit architectures, and 64-bit architectures
 791           as part of compat syscall handling.
 792
 793 config ARCH_NO_COHERENT_DMA_MMAP
 794         bool
 795
 796 config ARCH_NO_PREEMPT
 797         bool
 798
 799 config ARCH_SUPPORTS_RT
 800         bool
 801
 802 config CPU_NO_EFFICIENT_FFS
 803         def_bool n
 804
 805 config HAVE_ARCH_VMAP_STACK
 806         def_bool n
 807         help
 808           An arch should select this symbol if it can support kernel stacks
 809           in vmalloc space.  This means:
 810
 811           - vmalloc space must be large enough to hold many kernel stacks.
 812             This may rule out many 32-bit architectures.
 813
 814           - Stacks in vmalloc space need to work reliably.  For example, if
 815             vmap page tables are created on demand, either this mechanism
 816             needs to work while the stack points to a virtual address with
 817             unpopulated page tables or arch code (switch_to() and switch_mm(),
 818             most likely) needs to ensure that the stack's page table entries
 819             are populated before running on a possibly unpopulated stack.
 820
 821           - If the stack overflows into a guard page, something reasonable
 822             should happen.  The definition of "reasonable" is flexible, but
 823             instantly rebooting without logging anything would be unfriendly.
 824
 825 config VMAP_STACK
 826         default y
 827         bool "Use a virtually-mapped stack"
 828         depends on HAVE_ARCH_VMAP_STACK && !KASAN
 829         ---help---
 830           Enable this if you want the use virtually-mapped kernel stacks
 831           with guard pages.  This causes kernel stack overflows to be
 832           caught immediately rather than causing difficult-to-diagnose
 833           corruption.
 834
 835           This is presently incompatible with KASAN because KASAN expects
 836           the stack to map directly to the KASAN shadow map using a formula
 837           that is incorrect if the stack is in vmalloc space.
 838
 839 config ARCH_OPTIONAL_KERNEL_RWX
 840         def_bool n
 841
 842 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 843         def_bool n
 844
 845 config ARCH_HAS_STRICT_KERNEL_RWX
 846         def_bool n
 847
 848 config STRICT_KERNEL_RWX
 849         bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
 850         depends on ARCH_HAS_STRICT_KERNEL_RWX
 851         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 852         help
 853           If this is set, kernel text and rodata memory will be made read-only,
 854           and non-text memory will be made non-executable. This provides
 855           protection against certain security exploits (e.g. executing the heap
 856           or modifying text)
 857
 858           These features are considered standard security practice these days.
 859           You should say Y here in almost all cases.
 860
 861 config ARCH_HAS_STRICT_MODULE_RWX
 862         def_bool n
 863
 864 config STRICT_MODULE_RWX
 865         bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
 866         depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
 867         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 868         help
 869           If this is set, module text and rodata memory will be made read-only,
 870           and non-text memory will be made non-executable. This provides
 871           protection against certain security exploits (e.g. writing to text)
 872
 873 # select if the architecture provides an asm/dma-direct.h header
 874 config ARCH_HAS_PHYS_TO_DMA
 875         bool
 876
 877 config ARCH_HAS_REFCOUNT
 878         bool
 879         help
 880           An architecture selects this when it has implemented refcount_t
 881           using open coded assembly primitives that provide an optimized
 882           refcount_t implementation, possibly at the expense of some full
 883           refcount state checks of CONFIG_REFCOUNT_FULL=y.
 884
 885           The refcount overflow check behavior, however, must be retained.
 886           Catching overflows is the primary security concern for protecting
 887           against bugs in reference counts.
 888
 889 config REFCOUNT_FULL
 890         bool "Perform full reference count validation at the expense of speed"
 891         help
 892           Enabling this switches the refcounting infrastructure from a fast
 893           unchecked atomic_t implementation to a fully state checked
 894           implementation, which can be (slightly) slower but provides protections
 895           against various use-after-free conditions that can be used in
 896           security flaw exploits.
 897
 898 config HAVE_ARCH_COMPILER_H
 899         bool
 900         help
 901           An architecture can select this if it provides an
 902           asm/compiler.h header that should be included after
 903           linux/compiler-*.h in order to override macro definitions that those
 904           headers generally provide.
 905
 906 config HAVE_ARCH_PREL32_RELOCATIONS
 907         bool
 908         help
 909           May be selected by an architecture if it supports place-relative
 910           32-bit relocations, both in the toolchain and in the module loader,
 911           in which case relative references can be used in special sections
 912           for PCI fixup, initcalls etc which are only half the size on 64 bit
 913           architectures, and don't require runtime relocation on relocatable
 914           kernels.
 915
 916 config ARCH_USE_MEMREMAP_PROT
 917         bool
 918
 919 config LOCK_EVENT_COUNTS
 920         bool "Locking event counts collection"
 921         depends on DEBUG_FS
 922         ---help---
 923           Enable light-weight counting of various locking related events
 924           in the system with minimal performance impact. This reduces
 925           the chance of application behavior change because of timing
 926           differences. The counts are reported via debugfs.
 927
 928 source "kernel/gcov/Kconfig"
 929
 930 source "scripts/gcc-plugins/Kconfig"
 931
 932 endmenu