arch/Kconfig

   1 #
   2 # General architecture dependent options
   3 #
   4
   5 config KEXEC_CORE
   6         bool
   7
   8 config OPROFILE
   9         tristate "OProfile system profiling"
  10         depends on PROFILING
  11         depends on HAVE_OPROFILE
  12         select RING_BUFFER
  13         select RING_BUFFER_ALLOW_SWAP
  14         help
  15           OProfile is a profiling system capable of profiling the
  16           whole system, include the kernel, kernel modules, libraries,
  17           and applications.
  18
  19           If unsure, say N.
  20
  21 config OPROFILE_EVENT_MULTIPLEX
  22         bool "OProfile multiplexing support (EXPERIMENTAL)"
  23         default n
  24         depends on OPROFILE && X86
  25         help
  26           The number of hardware counters is limited. The multiplexing
  27           feature enables OProfile to gather more events than counters
  28           are provided by the hardware. This is realized by switching
  29           between events at an user specified time interval.
  30
  31           If unsure, say N.
  32
  33 config HAVE_OPROFILE
  34         bool
  35
  36 config OPROFILE_NMI_TIMER
  37         def_bool y
  38         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
  39
  40 config KPROBES
  41         bool "Kprobes"
  42         depends on MODULES
  43         depends on HAVE_KPROBES
  44         select KALLSYMS
  45         help
  46           Kprobes allows you to trap at almost any kernel address and
  47           execute a callback function.  register_kprobe() establishes
  48           a probepoint and specifies the callback.  Kprobes is useful
  49           for kernel debugging, non-intrusive instrumentation and testing.
  50           If in doubt, say "N".
  51
  52 config JUMP_LABEL
  53        bool "Optimize very unlikely/likely branches"
  54        depends on HAVE_ARCH_JUMP_LABEL
  55        help
  56          This option enables a transparent branch optimization that
  57          makes certain almost-always-true or almost-always-false branch
  58          conditions even cheaper to execute within the kernel.
  59
  60          Certain performance-sensitive kernel code, such as trace points,
  61          scheduler functionality, networking code and KVM have such
  62          branches and include support for this optimization technique.
  63
  64          If it is detected that the compiler has support for "asm goto",
  65          the kernel will compile such branches with just a nop
  66          instruction. When the condition flag is toggled to true, the
  67          nop will be converted to a jump instruction to execute the
  68          conditional block of instructions.
  69
  70          This technique lowers overhead and stress on the branch prediction
  71          of the processor and generally makes the kernel faster. The update
  72          of the condition is slower, but those are always very rare.
  73
  74          ( On 32-bit x86, the necessary options added to the compiler
  75            flags may increase the size of the kernel slightly. )
  76
  77 config STATIC_KEYS_SELFTEST
  78         bool "Static key selftest"
  79         depends on JUMP_LABEL
  80         help
  81           Boot time self-test of the branch patching code.
  82
  83 config OPTPROBES
  84         def_bool y
  85         depends on KPROBES && HAVE_OPTPROBES
  86         depends on !PREEMPT
  87
  88 config KPROBES_ON_FTRACE
  89         def_bool y
  90         depends on KPROBES && HAVE_KPROBES_ON_FTRACE
  91         depends on DYNAMIC_FTRACE_WITH_REGS
  92         help
  93          If function tracer is enabled and the arch supports full
  94          passing of pt_regs to function tracing, then kprobes can
  95          optimize on top of function tracing.
  96
  97 config UPROBES
  98         def_bool n
  99         help
 100           Uprobes is the user-space counterpart to kprobes: they
 101           enable instrumentation applications (such as 'perf probe')
 102           to establish unintrusive probes in user-space binaries and
 103           libraries, by executing handler functions when the probes
 104           are hit by user-space applications.
 105
 106           ( These probes come in the form of single-byte breakpoints,
 107             managed by the kernel and kept transparent to the probed
 108             application. )
 109
 110 config HAVE_64BIT_ALIGNED_ACCESS
 111         def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
 112         help
 113           Some architectures require 64 bit accesses to be 64 bit
 114           aligned, which also requires structs containing 64 bit values
 115           to be 64 bit aligned too. This includes some 32 bit
 116           architectures which can do 64 bit accesses, as well as 64 bit
 117           architectures without unaligned access.
 118
 119           This symbol should be selected by an architecture if 64 bit
 120           accesses are required to be 64 bit aligned in this way even
 121           though it is not a 64 bit architecture.
 122
 123           See Documentation/unaligned-memory-access.txt for more
 124           information on the topic of unaligned memory accesses.
 125
 126 config HAVE_EFFICIENT_UNALIGNED_ACCESS
 127         bool
 128         help
 129           Some architectures are unable to perform unaligned accesses
 130           without the use of get_unaligned/put_unaligned. Others are
 131           unable to perform such accesses efficiently (e.g. trap on
 132           unaligned access and require fixing it up in the exception
 133           handler.)
 134
 135           This symbol should be selected by an architecture if it can
 136           perform unaligned accesses efficiently to allow different
 137           code paths to be selected for these cases. Some network
 138           drivers, for example, could opt to not fix up alignment
 139           problems with received packets if doing so would not help
 140           much.
 141
 142           See Documentation/unaligned-memory-access.txt for more
 143           information on the topic of unaligned memory accesses.
 144
 145 config ARCH_USE_BUILTIN_BSWAP
 146        bool
 147        help
 148          Modern versions of GCC (since 4.4) have builtin functions
 149          for handling byte-swapping. Using these, instead of the old
 150          inline assembler that the architecture code provides in the
 151          __arch_bswapXX() macros, allows the compiler to see what's
 152          happening and offers more opportunity for optimisation. In
 153          particular, the compiler will be able to combine the byteswap
 154          with a nearby load or store and use load-and-swap or
 155          store-and-swap instructions if the architecture has them. It
 156          should almost *never* result in code which is worse than the
 157          hand-coded assembler in <asm/swab.h>.  But just in case it
 158          does, the use of the builtins is optional.
 159
 160          Any architecture with load-and-swap or store-and-swap
 161          instructions should set this. And it shouldn't hurt to set it
 162          on architectures that don't have such instructions.
 163
 164 config KRETPROBES
 165         def_bool y
 166         depends on KPROBES && HAVE_KRETPROBES
 167
 168 config USER_RETURN_NOTIFIER
 169         bool
 170         depends on HAVE_USER_RETURN_NOTIFIER
 171         help
 172           Provide a kernel-internal notification when a cpu is about to
 173           switch to user mode.
 174
 175 config HAVE_IOREMAP_PROT
 176         bool
 177
 178 config HAVE_KPROBES
 179         bool
 180
 181 config HAVE_KRETPROBES
 182         bool
 183
 184 config HAVE_OPTPROBES
 185         bool
 186
 187 config HAVE_KPROBES_ON_FTRACE
 188         bool
 189
 190 config HAVE_NMI
 191         bool
 192
 193 config HAVE_NMI_WATCHDOG
 194         depends on HAVE_NMI
 195         bool
 196 #
 197 # An arch should select this if it provides all these things:
 198 #
 199 #       task_pt_regs()          in asm/processor.h or asm/ptrace.h
 200 #       arch_has_single_step()  if there is hardware single-step support
 201 #       arch_has_block_step()   if there is hardware block-step support
 202 #       asm/syscall.h           supplying asm-generic/syscall.h interface
 203 #       linux/regset.h          user_regset interfaces
 204 #       CORE_DUMP_USE_REGSET    #define'd in linux/elf.h
 205 #       TIF_SYSCALL_TRACE       calls tracehook_report_syscall_{entry,exit}
 206 #       TIF_NOTIFY_RESUME       calls tracehook_notify_resume()
 207 #       signal delivery         calls tracehook_signal_handler()
 208 #
 209 config HAVE_ARCH_TRACEHOOK
 210         bool
 211
 212 config HAVE_DMA_CONTIGUOUS
 213         bool
 214
 215 config GENERIC_SMP_IDLE_THREAD
 216        bool
 217
 218 config GENERIC_IDLE_POLL_SETUP
 219        bool
 220
 221 # Select if arch init_task initializer is different to init/init_task.c
 222 config ARCH_INIT_TASK
 223        bool
 224
 225 # Select if arch has its private alloc_task_struct() function
 226 config ARCH_TASK_STRUCT_ALLOCATOR
 227         bool
 228
 229 # Select if arch has its private alloc_thread_stack() function
 230 config ARCH_THREAD_STACK_ALLOCATOR
 231         bool
 232
 233 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 234 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 235         bool
 236
 237 config HAVE_REGS_AND_STACK_ACCESS_API
 238         bool
 239         help
 240           This symbol should be selected by an architecure if it supports
 241           the API needed to access registers and stack entries from pt_regs,
 242           declared in asm/ptrace.h
 243           For example the kprobes-based event tracer needs this API.
 244
 245 config HAVE_CLK
 246         bool
 247         help
 248           The <linux/clk.h> calls support software clock gating and
 249           thus are a key power management tool on many systems.
 250
 251 config HAVE_DMA_API_DEBUG
 252         bool
 253
 254 config HAVE_HW_BREAKPOINT
 255         bool
 256         depends on PERF_EVENTS
 257
 258 config HAVE_MIXED_BREAKPOINTS_REGS
 259         bool
 260         depends on HAVE_HW_BREAKPOINT
 261         help
 262           Depending on the arch implementation of hardware breakpoints,
 263           some of them have separate registers for data and instruction
 264           breakpoints addresses, others have mixed registers to store
 265           them but define the access type in a control register.
 266           Select this option if your arch implements breakpoints under the
 267           latter fashion.
 268
 269 config HAVE_USER_RETURN_NOTIFIER
 270         bool
 271
 272 config HAVE_PERF_EVENTS_NMI
 273         bool
 274         help
 275           System hardware can generate an NMI using the perf event
 276           subsystem.  Also has support for calculating CPU cycle events
 277           to determine how many clock cycles in a given period.
 278
 279 config HAVE_PERF_REGS
 280         bool
 281         help
 282           Support selective register dumps for perf events. This includes
 283           bit-mapping of each registers and a unique architecture id.
 284
 285 config HAVE_PERF_USER_STACK_DUMP
 286         bool
 287         help
 288           Support user stack dumps for perf event samples. This needs
 289           access to the user stack pointer which is not unified across
 290           architectures.
 291
 292 config HAVE_ARCH_JUMP_LABEL
 293         bool
 294
 295 config HAVE_RCU_TABLE_FREE
 296         bool
 297
 298 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 299         bool
 300
 301 config HAVE_ALIGNED_STRUCT_PAGE
 302         bool
 303         help
 304           This makes sure that struct pages are double word aligned and that
 305           e.g. the SLUB allocator can perform double word atomic operations
 306           on a struct page for better performance. However selecting this
 307           might increase the size of a struct page by a word.
 308
 309 config HAVE_CMPXCHG_LOCAL
 310         bool
 311
 312 config HAVE_CMPXCHG_DOUBLE
 313         bool
 314
 315 config ARCH_WANT_IPC_PARSE_VERSION
 316         bool
 317
 318 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 319         bool
 320
 321 config ARCH_WANT_OLD_COMPAT_IPC
 322         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 323         bool
 324
 325 config HAVE_ARCH_SECCOMP_FILTER
 326         bool
 327         help
 328           An arch should select this symbol if it provides all of these things:
 329           - syscall_get_arch()
 330           - syscall_get_arguments()
 331           - syscall_rollback()
 332           - syscall_set_return_value()
 333           - SIGSYS siginfo_t support
 334           - secure_computing is called from a ptrace_event()-safe context
 335           - secure_computing return value is checked and a return value of -1
 336             results in the system call being skipped immediately.
 337           - seccomp syscall wired up
 338
 339 config SECCOMP_FILTER
 340         def_bool y
 341         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 342         help
 343           Enable tasks to build secure computing environments defined
 344           in terms of Berkeley Packet Filter programs which implement
 345           task-defined system call filtering polices.
 346
 347           See Documentation/prctl/seccomp_filter.txt for details.
 348
 349 config HAVE_GCC_PLUGINS
 350         bool
 351         help
 352           An arch should select this symbol if it supports building with
 353           GCC plugins.
 354
 355 menuconfig GCC_PLUGINS
 356         bool "GCC plugins"
 357         depends on HAVE_GCC_PLUGINS
 358         depends on !COMPILE_TEST
 359         help
 360           GCC plugins are loadable modules that provide extra features to the
 361           compiler. They are useful for runtime instrumentation and static analysis.
 362
 363           See Documentation/gcc-plugins.txt for details.
 364
 365 config GCC_PLUGIN_CYC_COMPLEXITY
 366         bool "Compute the cyclomatic complexity of a function"
 367         depends on GCC_PLUGINS
 368         help
 369           The complexity M of a function's control flow graph is defined as:
 370            M = E - N + 2P
 371           where
 372
 373           E = the number of edges
 374           N = the number of nodes
 375           P = the number of connected components (exit nodes).
 376
 377 config GCC_PLUGIN_SANCOV
 378         bool
 379         depends on GCC_PLUGINS
 380         help
 381           This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
 382           basic blocks. It supports all gcc versions with plugin support (from
 383           gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
 384           by Dmitry Vyukov <dvyukov@google.com>.
 385
 386 config GCC_PLUGIN_LATENT_ENTROPY
 387         bool "Generate some entropy during boot and runtime"
 388         depends on GCC_PLUGINS
 389         help
 390           By saying Y here the kernel will instrument some kernel code to
 391           extract some entropy from both original and artificially created
 392           program state.  This will help especially embedded systems where
 393           there is little 'natural' source of entropy normally.  The cost
 394           is some slowdown of the boot process (about 0.5%) and fork and
 395           irq processing.
 396
 397           Note that entropy extracted this way is not cryptographically
 398           secure!
 399
 400           This plugin was ported from grsecurity/PaX. More information at:
 401            * https://grsecurity.net/
 402            * https://pax.grsecurity.net/
 403
 404 config HAVE_CC_STACKPROTECTOR
 405         bool
 406         help
 407           An arch should select this symbol if:
 408           - its compiler supports the -fstack-protector option
 409           - it has implemented a stack canary (e.g. __stack_chk_guard)
 410
 411 config CC_STACKPROTECTOR
 412         def_bool n
 413         help
 414           Set when a stack-protector mode is enabled, so that the build
 415           can enable kernel-side support for the GCC feature.
 416
 417 choice
 418         prompt "Stack Protector buffer overflow detection"
 419         depends on HAVE_CC_STACKPROTECTOR
 420         default CC_STACKPROTECTOR_NONE
 421         help
 422           This option turns on the "stack-protector" GCC feature. This
 423           feature puts, at the beginning of functions, a canary value on
 424           the stack just before the return address, and validates
 425           the value just before actually returning.  Stack based buffer
 426           overflows (that need to overwrite this return address) now also
 427           overwrite the canary, which gets detected and the attack is then
 428           neutralized via a kernel panic.
 429
 430 config CC_STACKPROTECTOR_NONE
 431         bool "None"
 432         help
 433           Disable "stack-protector" GCC feature.
 434
 435 config CC_STACKPROTECTOR_REGULAR
 436         bool "Regular"
 437         select CC_STACKPROTECTOR
 438         help
 439           Functions will have the stack-protector canary logic added if they
 440           have an 8-byte or larger character array on the stack.
 441
 442           This feature requires gcc version 4.2 or above, or a distribution
 443           gcc with the feature backported ("-fstack-protector").
 444
 445           On an x86 "defconfig" build, this feature adds canary checks to
 446           about 3% of all kernel functions, which increases kernel code size
 447           by about 0.3%.
 448
 449 config CC_STACKPROTECTOR_STRONG
 450         bool "Strong"
 451         select CC_STACKPROTECTOR
 452         help
 453           Functions will have the stack-protector canary logic added in any
 454           of the following conditions:
 455
 456           - local variable's address used as part of the right hand side of an
 457             assignment or function argument
 458           - local variable is an array (or union containing an array),
 459             regardless of array type or length
 460           - uses register local variables
 461
 462           This feature requires gcc version 4.9 or above, or a distribution
 463           gcc with the feature backported ("-fstack-protector-strong").
 464
 465           On an x86 "defconfig" build, this feature adds canary checks to
 466           about 20% of all kernel functions, which increases the kernel code
 467           size by about 2%.
 468
 469 endchoice
 470
 471 config THIN_ARCHIVES
 472         bool
 473         help
 474           Select this if the architecture wants to use thin archives
 475           instead of ld -r to create the built-in.o files.
 476
 477 config LD_DEAD_CODE_DATA_ELIMINATION
 478         bool
 479         help
 480           Select this if the architecture wants to do dead code and
 481           data elimination with the linker by compiling with
 482           -ffunction-sections -fdata-sections and linking with
 483           --gc-sections.
 484
 485           This requires that the arch annotates or otherwise protects
 486           its external entry points from being discarded. Linker scripts
 487           must also merge .text.*, .data.*, and .bss.* correctly into
 488           output sections. Care must be taken not to pull in unrelated
 489           sections (e.g., '.text.init'). Typically '.' in section names
 490           is used to distinguish them from label names / C identifiers.
 491
 492 config HAVE_ARCH_WITHIN_STACK_FRAMES
 493         bool
 494         help
 495           An architecture should select this if it can walk the kernel stack
 496           frames to determine if an object is part of either the arguments
 497           or local variables (i.e. that it excludes saved return addresses,
 498           and similar) by implementing an inline arch_within_stack_frames(),
 499           which is used by CONFIG_HARDENED_USERCOPY.
 500
 501 config HAVE_CONTEXT_TRACKING
 502         bool
 503         help
 504           Provide kernel/user boundaries probes necessary for subsystems
 505           that need it, such as userspace RCU extended quiescent state.
 506           Syscalls need to be wrapped inside user_exit()-user_enter() through
 507           the slow path using TIF_NOHZ flag. Exceptions handlers must be
 508           wrapped as well. Irqs are already protected inside
 509           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
 510           irq exit still need to be protected.
 511
 512 config HAVE_VIRT_CPU_ACCOUNTING
 513         bool
 514
 515 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 516         bool
 517         default y if 64BIT
 518         help
 519           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 520           Before enabling this option, arch code must be audited
 521           to ensure there are no races in concurrent read/write of
 522           cputime_t. For example, reading/writing 64-bit cputime_t on
 523           some 32-bit arches may require multiple accesses, so proper
 524           locking is needed to protect against concurrent accesses.
 525
 526
 527 config HAVE_IRQ_TIME_ACCOUNTING
 528         bool
 529         help
 530           Archs need to ensure they use a high enough resolution clock to
 531           support irq time accounting and then call enable_sched_clock_irqtime().
 532
 533 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 534         bool
 535
 536 config HAVE_ARCH_HUGE_VMAP
 537         bool
 538
 539 config HAVE_ARCH_SOFT_DIRTY
 540         bool
 541
 542 config HAVE_MOD_ARCH_SPECIFIC
 543         bool
 544         help
 545           The arch uses struct mod_arch_specific to store data.  Many arches
 546           just need a simple module loader without arch specific data - those
 547           should not enable this.
 548
 549 config MODULES_USE_ELF_RELA
 550         bool
 551         help
 552           Modules only use ELF RELA relocations.  Modules with ELF REL
 553           relocations will give an error.
 554
 555 config MODULES_USE_ELF_REL
 556         bool
 557         help
 558           Modules only use ELF REL relocations.  Modules with ELF RELA
 559           relocations will give an error.
 560
 561 config HAVE_UNDERSCORE_SYMBOL_PREFIX
 562         bool
 563         help
 564           Some architectures generate an _ in front of C symbols; things like
 565           module loading and assembly files need to know about this.
 566
 567 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 568         bool
 569         help
 570           Architecture doesn't only execute the irq handler on the irq stack
 571           but also irq_exit(). This way we can process softirqs on this irq
 572           stack instead of switching to a new one when we call __do_softirq()
 573           in the end of an hardirq.
 574           This spares a stack switch and improves cache usage on softirq
 575           processing.
 576
 577 config PGTABLE_LEVELS
 578         int
 579         default 2
 580
 581 config ARCH_HAS_ELF_RANDOMIZE
 582         bool
 583         help
 584           An architecture supports choosing randomized locations for
 585           stack, mmap, brk, and ET_DYN. Defined functions:
 586           - arch_mmap_rnd()
 587           - arch_randomize_brk()
 588
 589 config HAVE_ARCH_MMAP_RND_BITS
 590         bool
 591         help
 592           An arch should select this symbol if it supports setting a variable
 593           number of bits for use in establishing the base address for mmap
 594           allocations, has MMU enabled and provides values for both:
 595           - ARCH_MMAP_RND_BITS_MIN
 596           - ARCH_MMAP_RND_BITS_MAX
 597
 598 config HAVE_EXIT_THREAD
 599         bool
 600         help
 601           An architecture implements exit_thread.
 602
 603 config ARCH_MMAP_RND_BITS_MIN
 604         int
 605
 606 config ARCH_MMAP_RND_BITS_MAX
 607         int
 608
 609 config ARCH_MMAP_RND_BITS_DEFAULT
 610         int
 611
 612 config ARCH_MMAP_RND_BITS
 613         int "Number of bits to use for ASLR of mmap base address" if EXPERT
 614         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
 615         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
 616         default ARCH_MMAP_RND_BITS_MIN
 617         depends on HAVE_ARCH_MMAP_RND_BITS
 618         help
 619           This value can be used to select the number of bits to use to
 620           determine the random offset to the base address of vma regions
 621           resulting from mmap allocations. This value will be bounded
 622           by the architecture's minimum and maximum supported values.
 623
 624           This value can be changed after boot using the
 625           /proc/sys/vm/mmap_rnd_bits tunable
 626
 627 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
 628         bool
 629         help
 630           An arch should select this symbol if it supports running applications
 631           in compatibility mode, supports setting a variable number of bits for
 632           use in establishing the base address for mmap allocations, has MMU
 633           enabled and provides values for both:
 634           - ARCH_MMAP_RND_COMPAT_BITS_MIN
 635           - ARCH_MMAP_RND_COMPAT_BITS_MAX
 636
 637 config ARCH_MMAP_RND_COMPAT_BITS_MIN
 638         int
 639
 640 config ARCH_MMAP_RND_COMPAT_BITS_MAX
 641         int
 642
 643 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 644         int
 645
 646 config ARCH_MMAP_RND_COMPAT_BITS
 647         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
 648         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
 649         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 650         default ARCH_MMAP_RND_COMPAT_BITS_MIN
 651         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
 652         help
 653           This value can be used to select the number of bits to use to
 654           determine the random offset to the base address of vma regions
 655           resulting from mmap allocations for compatible applications This
 656           value will be bounded by the architecture's minimum and maximum
 657           supported values.
 658
 659           This value can be changed after boot using the
 660           /proc/sys/vm/mmap_rnd_compat_bits tunable
 661
 662 config HAVE_COPY_THREAD_TLS
 663         bool
 664         help
 665           Architecture provides copy_thread_tls to accept tls argument via
 666           normal C parameter passing, rather than extracting the syscall
 667           argument from pt_regs.
 668
 669 config HAVE_STACK_VALIDATION
 670         bool
 671         help
 672           Architecture supports the 'objtool check' host tool command, which
 673           performs compile-time stack metadata validation.
 674
 675 config HAVE_ARCH_HASH
 676         bool
 677         default n
 678         help
 679           If this is set, the architecture provides an <asm/hash.h>
 680           file which provides platform-specific implementations of some
 681           functions in <linux/hash.h> or fs/namei.c.
 682
 683 config ISA_BUS_API
 684         def_bool ISA
 685
 686 #
 687 # ABI hall of shame
 688 #
 689 config CLONE_BACKWARDS
 690         bool
 691         help
 692           Architecture has tls passed as the 4th argument of clone(2),
 693           not the 5th one.
 694
 695 config CLONE_BACKWARDS2
 696         bool
 697         help
 698           Architecture has the first two arguments of clone(2) swapped.
 699
 700 config CLONE_BACKWARDS3
 701         bool
 702         help
 703           Architecture has tls passed as the 3rd argument of clone(2),
 704           not the 5th one.
 705
 706 config ODD_RT_SIGACTION
 707         bool
 708         help
 709           Architecture has unusual rt_sigaction(2) arguments
 710
 711 config OLD_SIGSUSPEND
 712         bool
 713         help
 714           Architecture has old sigsuspend(2) syscall, of one-argument variety
 715
 716 config OLD_SIGSUSPEND3
 717         bool
 718         help
 719           Even weirder antique ABI - three-argument sigsuspend(2)
 720
 721 config OLD_SIGACTION
 722         bool
 723         help
 724           Architecture has old sigaction(2) syscall.  Nope, not the same
 725           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
 726           but fairly different variant of sigaction(2), thanks to OSF/1
 727           compatibility...
 728
 729 config COMPAT_OLD_SIGACTION
 730         bool
 731
 732 config ARCH_NO_COHERENT_DMA_MMAP
 733         bool
 734
 735 config CPU_NO_EFFICIENT_FFS
 736         def_bool n
 737
 738 config HAVE_ARCH_VMAP_STACK
 739         def_bool n
 740         help
 741           An arch should select this symbol if it can support kernel stacks
 742           in vmalloc space.  This means:
 743
 744           - vmalloc space must be large enough to hold many kernel stacks.
 745             This may rule out many 32-bit architectures.
 746
 747           - Stacks in vmalloc space need to work reliably.  For example, if
 748             vmap page tables are created on demand, either this mechanism
 749             needs to work while the stack points to a virtual address with
 750             unpopulated page tables or arch code (switch_to() and switch_mm(),
 751             most likely) needs to ensure that the stack's page table entries
 752             are populated before running on a possibly unpopulated stack.
 753
 754           - If the stack overflows into a guard page, something reasonable
 755             should happen.  The definition of "reasonable" is flexible, but
 756             instantly rebooting without logging anything would be unfriendly.
 757
 758 config VMAP_STACK
 759         default y
 760         bool "Use a virtually-mapped stack"
 761         depends on HAVE_ARCH_VMAP_STACK && !KASAN
 762         ---help---
 763           Enable this if you want the use virtually-mapped kernel stacks
 764           with guard pages.  This causes kernel stack overflows to be
 765           caught immediately rather than causing difficult-to-diagnose
 766           corruption.
 767
 768           This is presently incompatible with KASAN because KASAN expects
 769           the stack to map directly to the KASAN shadow map using a formula
 770           that is incorrect if the stack is in vmalloc space.
 771
 772 source "kernel/gcov/Kconfig"