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_RSEQ
 246         bool
 247         depends on HAVE_REGS_AND_STACK_ACCESS_API
 248         help
 249           This symbol should be selected by an architecture if it
 250           supports an implementation of restartable sequences.
 251
 252 config HAVE_CLK
 253         bool
 254         help
 255           The <linux/clk.h> calls support software clock gating and
 256           thus are a key power management tool on many systems.
 257
 258 config HAVE_DMA_API_DEBUG
 259         bool
 260
 261 config HAVE_HW_BREAKPOINT
 262         bool
 263         depends on PERF_EVENTS
 264
 265 config HAVE_MIXED_BREAKPOINTS_REGS
 266         bool
 267         depends on HAVE_HW_BREAKPOINT
 268         help
 269           Depending on the arch implementation of hardware breakpoints,
 270           some of them have separate registers for data and instruction
 271           breakpoints addresses, others have mixed registers to store
 272           them but define the access type in a control register.
 273           Select this option if your arch implements breakpoints under the
 274           latter fashion.
 275
 276 config HAVE_USER_RETURN_NOTIFIER
 277         bool
 278
 279 config HAVE_PERF_EVENTS_NMI
 280         bool
 281         help
 282           System hardware can generate an NMI using the perf event
 283           subsystem.  Also has support for calculating CPU cycle events
 284           to determine how many clock cycles in a given period.
 285
 286 config HAVE_PERF_REGS
 287         bool
 288         help
 289           Support selective register dumps for perf events. This includes
 290           bit-mapping of each registers and a unique architecture id.
 291
 292 config HAVE_PERF_USER_STACK_DUMP
 293         bool
 294         help
 295           Support user stack dumps for perf event samples. This needs
 296           access to the user stack pointer which is not unified across
 297           architectures.
 298
 299 config HAVE_ARCH_JUMP_LABEL
 300         bool
 301
 302 config HAVE_RCU_TABLE_FREE
 303         bool
 304
 305 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 306         bool
 307
 308 config HAVE_ALIGNED_STRUCT_PAGE
 309         bool
 310         help
 311           This makes sure that struct pages are double word aligned and that
 312           e.g. the SLUB allocator can perform double word atomic operations
 313           on a struct page for better performance. However selecting this
 314           might increase the size of a struct page by a word.
 315
 316 config HAVE_CMPXCHG_LOCAL
 317         bool
 318
 319 config HAVE_CMPXCHG_DOUBLE
 320         bool
 321
 322 config ARCH_WANT_IPC_PARSE_VERSION
 323         bool
 324
 325 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 326         bool
 327
 328 config ARCH_WANT_OLD_COMPAT_IPC
 329         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 330         bool
 331
 332 config HAVE_ARCH_SECCOMP_FILTER
 333         bool
 334         help
 335           An arch should select this symbol if it provides all of these things:
 336           - syscall_get_arch()
 337           - syscall_get_arguments()
 338           - syscall_rollback()
 339           - syscall_set_return_value()
 340           - SIGSYS siginfo_t support
 341           - secure_computing is called from a ptrace_event()-safe context
 342           - secure_computing return value is checked and a return value of -1
 343             results in the system call being skipped immediately.
 344           - seccomp syscall wired up
 345
 346           For best performance, an arch should use seccomp_phase1 and
 347           seccomp_phase2 directly.  It should call seccomp_phase1 for all
 348           syscalls if TIF_SECCOMP is set, but seccomp_phase1 does not
 349           need to be called from a ptrace-safe context.  It must then
 350           call seccomp_phase2 if seccomp_phase1 returns anything other
 351           than SECCOMP_PHASE1_OK or SECCOMP_PHASE1_SKIP.
 352
 353           As an additional optimization, an arch may provide seccomp_data
 354           directly to seccomp_phase1; this avoids multiple calls
 355           to the syscall_xyz helpers for every syscall.
 356
 357 config SECCOMP_FILTER
 358         def_bool y
 359         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 360         help
 361           Enable tasks to build secure computing environments defined
 362           in terms of Berkeley Packet Filter programs which implement
 363           task-defined system call filtering polices.
 364
 365           See Documentation/prctl/seccomp_filter.txt for details.
 366
 367 config HAVE_GCC_PLUGINS
 368         bool
 369         help
 370           An arch should select this symbol if it supports building with
 371           GCC plugins.
 372
 373 menuconfig GCC_PLUGINS
 374         bool "GCC plugins"
 375         depends on HAVE_GCC_PLUGINS
 376         depends on !COMPILE_TEST
 377         help
 378           GCC plugins are loadable modules that provide extra features to the
 379           compiler. They are useful for runtime instrumentation and static analysis.
 380
 381           See Documentation/gcc-plugins.txt for details.
 382
 383 config GCC_PLUGIN_CYC_COMPLEXITY
 384         bool "Compute the cyclomatic complexity of a function"
 385         depends on GCC_PLUGINS
 386         help
 387           The complexity M of a function's control flow graph is defined as:
 388            M = E - N + 2P
 389           where
 390
 391           E = the number of edges
 392           N = the number of nodes
 393           P = the number of connected components (exit nodes).
 394
 395 config GCC_PLUGIN_SANCOV
 396         bool
 397         depends on GCC_PLUGINS
 398         help
 399           This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
 400           basic blocks. It supports all gcc versions with plugin support (from
 401           gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
 402           by Dmitry Vyukov <dvyukov@google.com>.
 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 HAVE_CONTEXT_TRACKING
 481         bool
 482         help
 483           Provide kernel/user boundaries probes necessary for subsystems
 484           that need it, such as userspace RCU extended quiescent state.
 485           Syscalls need to be wrapped inside user_exit()-user_enter() through
 486           the slow path using TIF_NOHZ flag. Exceptions handlers must be
 487           wrapped as well. Irqs are already protected inside
 488           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
 489           irq exit still need to be protected.
 490
 491 config HAVE_VIRT_CPU_ACCOUNTING
 492         bool
 493
 494 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 495         bool
 496         default y if 64BIT
 497         help
 498           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 499           Before enabling this option, arch code must be audited
 500           to ensure there are no races in concurrent read/write of
 501           cputime_t. For example, reading/writing 64-bit cputime_t on
 502           some 32-bit arches may require multiple accesses, so proper
 503           locking is needed to protect against concurrent accesses.
 504
 505
 506 config HAVE_IRQ_TIME_ACCOUNTING
 507         bool
 508         help
 509           Archs need to ensure they use a high enough resolution clock to
 510           support irq time accounting and then call enable_sched_clock_irqtime().
 511
 512 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 513         bool
 514
 515 config HAVE_ARCH_HUGE_VMAP
 516         bool
 517
 518 config HAVE_ARCH_SOFT_DIRTY
 519         bool
 520
 521 config HAVE_MOD_ARCH_SPECIFIC
 522         bool
 523         help
 524           The arch uses struct mod_arch_specific to store data.  Many arches
 525           just need a simple module loader without arch specific data - those
 526           should not enable this.
 527
 528 config MODULES_USE_ELF_RELA
 529         bool
 530         help
 531           Modules only use ELF RELA relocations.  Modules with ELF REL
 532           relocations will give an error.
 533
 534 config MODULES_USE_ELF_REL
 535         bool
 536         help
 537           Modules only use ELF REL relocations.  Modules with ELF RELA
 538           relocations will give an error.
 539
 540 config HAVE_UNDERSCORE_SYMBOL_PREFIX
 541         bool
 542         help
 543           Some architectures generate an _ in front of C symbols; things like
 544           module loading and assembly files need to know about this.
 545
 546 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 547         bool
 548         help
 549           Architecture doesn't only execute the irq handler on the irq stack
 550           but also irq_exit(). This way we can process softirqs on this irq
 551           stack instead of switching to a new one when we call __do_softirq()
 552           in the end of an hardirq.
 553           This spares a stack switch and improves cache usage on softirq
 554           processing.
 555
 556 config PGTABLE_LEVELS
 557         int
 558         default 2
 559
 560 config ARCH_HAS_ELF_RANDOMIZE
 561         bool
 562         help
 563           An architecture supports choosing randomized locations for
 564           stack, mmap, brk, and ET_DYN. Defined functions:
 565           - arch_mmap_rnd()
 566           - arch_randomize_brk()
 567
 568 config HAVE_ARCH_MMAP_RND_BITS
 569         bool
 570         help
 571           An arch should select this symbol if it supports setting a variable
 572           number of bits for use in establishing the base address for mmap
 573           allocations, has MMU enabled and provides values for both:
 574           - ARCH_MMAP_RND_BITS_MIN
 575           - ARCH_MMAP_RND_BITS_MAX
 576
 577 config HAVE_EXIT_THREAD
 578         bool
 579         help
 580           An architecture implements exit_thread.
 581
 582 config ARCH_MMAP_RND_BITS_MIN
 583         int
 584
 585 config ARCH_MMAP_RND_BITS_MAX
 586         int
 587
 588 config ARCH_MMAP_RND_BITS_DEFAULT
 589         int
 590
 591 config ARCH_MMAP_RND_BITS
 592         int "Number of bits to use for ASLR of mmap base address" if EXPERT
 593         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
 594         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
 595         default ARCH_MMAP_RND_BITS_MIN
 596         depends on HAVE_ARCH_MMAP_RND_BITS
 597         help
 598           This value can be used to select the number of bits to use to
 599           determine the random offset to the base address of vma regions
 600           resulting from mmap allocations. This value will be bounded
 601           by the architecture's minimum and maximum supported values.
 602
 603           This value can be changed after boot using the
 604           /proc/sys/vm/mmap_rnd_bits tunable
 605
 606 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
 607         bool
 608         help
 609           An arch should select this symbol if it supports running applications
 610           in compatibility mode, supports setting a variable number of bits for
 611           use in establishing the base address for mmap allocations, has MMU
 612           enabled and provides values for both:
 613           - ARCH_MMAP_RND_COMPAT_BITS_MIN
 614           - ARCH_MMAP_RND_COMPAT_BITS_MAX
 615
 616 config ARCH_MMAP_RND_COMPAT_BITS_MIN
 617         int
 618
 619 config ARCH_MMAP_RND_COMPAT_BITS_MAX
 620         int
 621
 622 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 623         int
 624
 625 config ARCH_MMAP_RND_COMPAT_BITS
 626         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
 627         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
 628         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 629         default ARCH_MMAP_RND_COMPAT_BITS_MIN
 630         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
 631         help
 632           This value can be used to select the number of bits to use to
 633           determine the random offset to the base address of vma regions
 634           resulting from mmap allocations for compatible applications This
 635           value will be bounded by the architecture's minimum and maximum
 636           supported values.
 637
 638           This value can be changed after boot using the
 639           /proc/sys/vm/mmap_rnd_compat_bits tunable
 640
 641 config HAVE_COPY_THREAD_TLS
 642         bool
 643         help
 644           Architecture provides copy_thread_tls to accept tls argument via
 645           normal C parameter passing, rather than extracting the syscall
 646           argument from pt_regs.
 647
 648 config HAVE_STACK_VALIDATION
 649         bool
 650         help
 651           Architecture supports the 'objtool check' host tool command, which
 652           performs compile-time stack metadata validation.
 653
 654 config HAVE_ARCH_HASH
 655         bool
 656         default n
 657         help
 658           If this is set, the architecture provides an <asm/hash.h>
 659           file which provides platform-specific implementations of some
 660           functions in <linux/hash.h> or fs/namei.c.
 661
 662 config ISA_BUS_API
 663         def_bool ISA
 664
 665 #
 666 # ABI hall of shame
 667 #
 668 config CLONE_BACKWARDS
 669         bool
 670         help
 671           Architecture has tls passed as the 4th argument of clone(2),
 672           not the 5th one.
 673
 674 config CLONE_BACKWARDS2
 675         bool
 676         help
 677           Architecture has the first two arguments of clone(2) swapped.
 678
 679 config CLONE_BACKWARDS3
 680         bool
 681         help
 682           Architecture has tls passed as the 3rd argument of clone(2),
 683           not the 5th one.
 684
 685 config ODD_RT_SIGACTION
 686         bool
 687         help
 688           Architecture has unusual rt_sigaction(2) arguments
 689
 690 config OLD_SIGSUSPEND
 691         bool
 692         help
 693           Architecture has old sigsuspend(2) syscall, of one-argument variety
 694
 695 config OLD_SIGSUSPEND3
 696         bool
 697         help
 698           Even weirder antique ABI - three-argument sigsuspend(2)
 699
 700 config OLD_SIGACTION
 701         bool
 702         help
 703           Architecture has old sigaction(2) syscall.  Nope, not the same
 704           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
 705           but fairly different variant of sigaction(2), thanks to OSF/1
 706           compatibility...
 707
 708 config COMPAT_OLD_SIGACTION
 709         bool
 710
 711 config ARCH_NO_COHERENT_DMA_MMAP
 712         bool
 713
 714 config CPU_NO_EFFICIENT_FFS
 715         def_bool n
 716
 717 source "kernel/gcov/Kconfig"