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 HAVE_ARCH_WITHIN_STACK_FRAMES
 472         bool
 473         help
 474           An architecture should select this if it can walk the kernel stack
 475           frames to determine if an object is part of either the arguments
 476           or local variables (i.e. that it excludes saved return addresses,
 477           and similar) by implementing an inline arch_within_stack_frames(),
 478           which is used by CONFIG_HARDENED_USERCOPY.
 479
 480 config THIN_ARCHIVES
 481         bool
 482         help
 483           Select this if the architecture wants to use thin archives
 484           instead of ld -r to create the built-in.o files.
 485
 486 config LD_DEAD_CODE_DATA_ELIMINATION
 487         bool
 488         help
 489           Select this if the architecture wants to do dead code and
 490           data elimination with the linker by compiling with
 491           -ffunction-sections -fdata-sections and linking with
 492           --gc-sections.
 493
 494           This requires that the arch annotates or otherwise protects
 495           its external entry points from being discarded. Linker scripts
 496           must also merge .text.*, .data.*, and .bss.* correctly into
 497           output sections.
 498
 499 config HAVE_CONTEXT_TRACKING
 500         bool
 501         help
 502           Provide kernel/user boundaries probes necessary for subsystems
 503           that need it, such as userspace RCU extended quiescent state.
 504           Syscalls need to be wrapped inside user_exit()-user_enter() through
 505           the slow path using TIF_NOHZ flag. Exceptions handlers must be
 506           wrapped as well. Irqs are already protected inside
 507           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
 508           irq exit still need to be protected.
 509
 510 config HAVE_VIRT_CPU_ACCOUNTING
 511         bool
 512
 513 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 514         bool
 515         default y if 64BIT
 516         help
 517           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 518           Before enabling this option, arch code must be audited
 519           to ensure there are no races in concurrent read/write of
 520           cputime_t. For example, reading/writing 64-bit cputime_t on
 521           some 32-bit arches may require multiple accesses, so proper
 522           locking is needed to protect against concurrent accesses.
 523
 524
 525 config HAVE_IRQ_TIME_ACCOUNTING
 526         bool
 527         help
 528           Archs need to ensure they use a high enough resolution clock to
 529           support irq time accounting and then call enable_sched_clock_irqtime().
 530
 531 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 532         bool
 533
 534 config HAVE_ARCH_HUGE_VMAP
 535         bool
 536
 537 config HAVE_ARCH_SOFT_DIRTY
 538         bool
 539
 540 config HAVE_MOD_ARCH_SPECIFIC
 541         bool
 542         help
 543           The arch uses struct mod_arch_specific to store data.  Many arches
 544           just need a simple module loader without arch specific data - those
 545           should not enable this.
 546
 547 config MODULES_USE_ELF_RELA
 548         bool
 549         help
 550           Modules only use ELF RELA relocations.  Modules with ELF REL
 551           relocations will give an error.
 552
 553 config MODULES_USE_ELF_REL
 554         bool
 555         help
 556           Modules only use ELF REL relocations.  Modules with ELF RELA
 557           relocations will give an error.
 558
 559 config HAVE_UNDERSCORE_SYMBOL_PREFIX
 560         bool
 561         help
 562           Some architectures generate an _ in front of C symbols; things like
 563           module loading and assembly files need to know about this.
 564
 565 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 566         bool
 567         help
 568           Architecture doesn't only execute the irq handler on the irq stack
 569           but also irq_exit(). This way we can process softirqs on this irq
 570           stack instead of switching to a new one when we call __do_softirq()
 571           in the end of an hardirq.
 572           This spares a stack switch and improves cache usage on softirq
 573           processing.
 574
 575 config PGTABLE_LEVELS
 576         int
 577         default 2
 578
 579 config ARCH_HAS_ELF_RANDOMIZE
 580         bool
 581         help
 582           An architecture supports choosing randomized locations for
 583           stack, mmap, brk, and ET_DYN. Defined functions:
 584           - arch_mmap_rnd()
 585           - arch_randomize_brk()
 586
 587 config HAVE_ARCH_MMAP_RND_BITS
 588         bool
 589         help
 590           An arch should select this symbol if it supports setting a variable
 591           number of bits for use in establishing the base address for mmap
 592           allocations, has MMU enabled and provides values for both:
 593           - ARCH_MMAP_RND_BITS_MIN
 594           - ARCH_MMAP_RND_BITS_MAX
 595
 596 config HAVE_EXIT_THREAD
 597         bool
 598         help
 599           An architecture implements exit_thread.
 600
 601 config ARCH_MMAP_RND_BITS_MIN
 602         int
 603
 604 config ARCH_MMAP_RND_BITS_MAX
 605         int
 606
 607 config ARCH_MMAP_RND_BITS_DEFAULT
 608         int
 609
 610 config ARCH_MMAP_RND_BITS
 611         int "Number of bits to use for ASLR of mmap base address" if EXPERT
 612         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
 613         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
 614         default ARCH_MMAP_RND_BITS_MIN
 615         depends on HAVE_ARCH_MMAP_RND_BITS
 616         help
 617           This value can be used to select the number of bits to use to
 618           determine the random offset to the base address of vma regions
 619           resulting from mmap allocations. This value will be bounded
 620           by the architecture's minimum and maximum supported values.
 621
 622           This value can be changed after boot using the
 623           /proc/sys/vm/mmap_rnd_bits tunable
 624
 625 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
 626         bool
 627         help
 628           An arch should select this symbol if it supports running applications
 629           in compatibility mode, supports setting a variable number of bits for
 630           use in establishing the base address for mmap allocations, has MMU
 631           enabled and provides values for both:
 632           - ARCH_MMAP_RND_COMPAT_BITS_MIN
 633           - ARCH_MMAP_RND_COMPAT_BITS_MAX
 634
 635 config ARCH_MMAP_RND_COMPAT_BITS_MIN
 636         int
 637
 638 config ARCH_MMAP_RND_COMPAT_BITS_MAX
 639         int
 640
 641 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 642         int
 643
 644 config ARCH_MMAP_RND_COMPAT_BITS
 645         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
 646         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
 647         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 648         default ARCH_MMAP_RND_COMPAT_BITS_MIN
 649         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
 650         help
 651           This value can be used to select the number of bits to use to
 652           determine the random offset to the base address of vma regions
 653           resulting from mmap allocations for compatible applications This
 654           value will be bounded by the architecture's minimum and maximum
 655           supported values.
 656
 657           This value can be changed after boot using the
 658           /proc/sys/vm/mmap_rnd_compat_bits tunable
 659
 660 config HAVE_COPY_THREAD_TLS
 661         bool
 662         help
 663           Architecture provides copy_thread_tls to accept tls argument via
 664           normal C parameter passing, rather than extracting the syscall
 665           argument from pt_regs.
 666
 667 config HAVE_STACK_VALIDATION
 668         bool
 669         help
 670           Architecture supports the 'objtool check' host tool command, which
 671           performs compile-time stack metadata validation.
 672
 673 config HAVE_ARCH_HASH
 674         bool
 675         default n
 676         help
 677           If this is set, the architecture provides an <asm/hash.h>
 678           file which provides platform-specific implementations of some
 679           functions in <linux/hash.h> or fs/namei.c.
 680
 681 config ISA_BUS_API
 682         def_bool ISA
 683
 684 #
 685 # ABI hall of shame
 686 #
 687 config CLONE_BACKWARDS
 688         bool
 689         help
 690           Architecture has tls passed as the 4th argument of clone(2),
 691           not the 5th one.
 692
 693 config CLONE_BACKWARDS2
 694         bool
 695         help
 696           Architecture has the first two arguments of clone(2) swapped.
 697
 698 config CLONE_BACKWARDS3
 699         bool
 700         help
 701           Architecture has tls passed as the 3rd argument of clone(2),
 702           not the 5th one.
 703
 704 config ODD_RT_SIGACTION
 705         bool
 706         help
 707           Architecture has unusual rt_sigaction(2) arguments
 708
 709 config OLD_SIGSUSPEND
 710         bool
 711         help
 712           Architecture has old sigsuspend(2) syscall, of one-argument variety
 713
 714 config OLD_SIGSUSPEND3
 715         bool
 716         help
 717           Even weirder antique ABI - three-argument sigsuspend(2)
 718
 719 config OLD_SIGACTION
 720         bool
 721         help
 722           Architecture has old sigaction(2) syscall.  Nope, not the same
 723           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
 724           but fairly different variant of sigaction(2), thanks to OSF/1
 725           compatibility...
 726
 727 config COMPAT_OLD_SIGACTION
 728         bool
 729
 730 config ARCH_NO_COHERENT_DMA_MMAP
 731         bool
 732
 733 config CPU_NO_EFFICIENT_FFS
 734         def_bool n
 735
 736 config HAVE_ARCH_VMAP_STACK
 737         def_bool n
 738         help
 739           An arch should select this symbol if it can support kernel stacks
 740           in vmalloc space.  This means:
 741
 742           - vmalloc space must be large enough to hold many kernel stacks.
 743             This may rule out many 32-bit architectures.
 744
 745           - Stacks in vmalloc space need to work reliably.  For example, if
 746             vmap page tables are created on demand, either this mechanism
 747             needs to work while the stack points to a virtual address with
 748             unpopulated page tables or arch code (switch_to() and switch_mm(),
 749             most likely) needs to ensure that the stack's page table entries
 750             are populated before running on a possibly unpopulated stack.
 751
 752           - If the stack overflows into a guard page, something reasonable
 753             should happen.  The definition of "reasonable" is flexible, but
 754             instantly rebooting without logging anything would be unfriendly.
 755
 756 config VMAP_STACK
 757         default y
 758         bool "Use a virtually-mapped stack"
 759         depends on HAVE_ARCH_VMAP_STACK && !KASAN
 760         ---help---
 761           Enable this if you want the use virtually-mapped kernel stacks
 762           with guard pages.  This causes kernel stack overflows to be
 763           caught immediately rather than causing difficult-to-diagnose
 764           corruption.
 765
 766           This is presently incompatible with KASAN because KASAN expects
 767           the stack to map directly to the KASAN shadow map using a formula
 768           that is incorrect if the stack is in vmalloc space.
 769
 770 source "kernel/gcov/Kconfig"