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_info() function
 230 config ARCH_THREAD_INFO_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           For best performance, an arch should use seccomp_phase1 and
 340           seccomp_phase2 directly.  It should call seccomp_phase1 for all
 341           syscalls if TIF_SECCOMP is set, but seccomp_phase1 does not
 342           need to be called from a ptrace-safe context.  It must then
 343           call seccomp_phase2 if seccomp_phase1 returns anything other
 344           than SECCOMP_PHASE1_OK or SECCOMP_PHASE1_SKIP.
 345
 346           As an additional optimization, an arch may provide seccomp_data
 347           directly to seccomp_phase1; this avoids multiple calls
 348           to the syscall_xyz helpers for every syscall.
 349
 350 config SECCOMP_FILTER
 351         def_bool y
 352         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 353         help
 354           Enable tasks to build secure computing environments defined
 355           in terms of Berkeley Packet Filter programs which implement
 356           task-defined system call filtering polices.
 357
 358           See Documentation/prctl/seccomp_filter.txt for details.
 359
 360 config HAVE_GCC_PLUGINS
 361         bool
 362         help
 363           An arch should select this symbol if it supports building with
 364           GCC plugins.
 365
 366 menuconfig GCC_PLUGINS
 367         bool "GCC plugins"
 368         depends on HAVE_GCC_PLUGINS
 369         help
 370           GCC plugins are loadable modules that provide extra features to the
 371           compiler. They are useful for runtime instrumentation and static analysis.
 372
 373           See Documentation/gcc-plugins.txt for details.
 374
 375 config HAVE_CC_STACKPROTECTOR
 376         bool
 377         help
 378           An arch should select this symbol if:
 379           - its compiler supports the -fstack-protector option
 380           - it has implemented a stack canary (e.g. __stack_chk_guard)
 381
 382 config CC_STACKPROTECTOR
 383         def_bool n
 384         help
 385           Set when a stack-protector mode is enabled, so that the build
 386           can enable kernel-side support for the GCC feature.
 387
 388 choice
 389         prompt "Stack Protector buffer overflow detection"
 390         depends on HAVE_CC_STACKPROTECTOR
 391         default CC_STACKPROTECTOR_NONE
 392         help
 393           This option turns on the "stack-protector" GCC feature. This
 394           feature puts, at the beginning of functions, a canary value on
 395           the stack just before the return address, and validates
 396           the value just before actually returning.  Stack based buffer
 397           overflows (that need to overwrite this return address) now also
 398           overwrite the canary, which gets detected and the attack is then
 399           neutralized via a kernel panic.
 400
 401 config CC_STACKPROTECTOR_NONE
 402         bool "None"
 403         help
 404           Disable "stack-protector" GCC feature.
 405
 406 config CC_STACKPROTECTOR_REGULAR
 407         bool "Regular"
 408         select CC_STACKPROTECTOR
 409         help
 410           Functions will have the stack-protector canary logic added if they
 411           have an 8-byte or larger character array on the stack.
 412
 413           This feature requires gcc version 4.2 or above, or a distribution
 414           gcc with the feature backported ("-fstack-protector").
 415
 416           On an x86 "defconfig" build, this feature adds canary checks to
 417           about 3% of all kernel functions, which increases kernel code size
 418           by about 0.3%.
 419
 420 config CC_STACKPROTECTOR_STRONG
 421         bool "Strong"
 422         select CC_STACKPROTECTOR
 423         help
 424           Functions will have the stack-protector canary logic added in any
 425           of the following conditions:
 426
 427           - local variable's address used as part of the right hand side of an
 428             assignment or function argument
 429           - local variable is an array (or union containing an array),
 430             regardless of array type or length
 431           - uses register local variables
 432
 433           This feature requires gcc version 4.9 or above, or a distribution
 434           gcc with the feature backported ("-fstack-protector-strong").
 435
 436           On an x86 "defconfig" build, this feature adds canary checks to
 437           about 20% of all kernel functions, which increases the kernel code
 438           size by about 2%.
 439
 440 endchoice
 441
 442 config HAVE_CONTEXT_TRACKING
 443         bool
 444         help
 445           Provide kernel/user boundaries probes necessary for subsystems
 446           that need it, such as userspace RCU extended quiescent state.
 447           Syscalls need to be wrapped inside user_exit()-user_enter() through
 448           the slow path using TIF_NOHZ flag. Exceptions handlers must be
 449           wrapped as well. Irqs are already protected inside
 450           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
 451           irq exit still need to be protected.
 452
 453 config HAVE_VIRT_CPU_ACCOUNTING
 454         bool
 455
 456 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 457         bool
 458         default y if 64BIT
 459         help
 460           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 461           Before enabling this option, arch code must be audited
 462           to ensure there are no races in concurrent read/write of
 463           cputime_t. For example, reading/writing 64-bit cputime_t on
 464           some 32-bit arches may require multiple accesses, so proper
 465           locking is needed to protect against concurrent accesses.
 466
 467
 468 config HAVE_IRQ_TIME_ACCOUNTING
 469         bool
 470         help
 471           Archs need to ensure they use a high enough resolution clock to
 472           support irq time accounting and then call enable_sched_clock_irqtime().
 473
 474 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 475         bool
 476
 477 config HAVE_ARCH_HUGE_VMAP
 478         bool
 479
 480 config HAVE_ARCH_SOFT_DIRTY
 481         bool
 482
 483 config HAVE_MOD_ARCH_SPECIFIC
 484         bool
 485         help
 486           The arch uses struct mod_arch_specific to store data.  Many arches
 487           just need a simple module loader without arch specific data - those
 488           should not enable this.
 489
 490 config MODULES_USE_ELF_RELA
 491         bool
 492         help
 493           Modules only use ELF RELA relocations.  Modules with ELF REL
 494           relocations will give an error.
 495
 496 config MODULES_USE_ELF_REL
 497         bool
 498         help
 499           Modules only use ELF REL relocations.  Modules with ELF RELA
 500           relocations will give an error.
 501
 502 config HAVE_UNDERSCORE_SYMBOL_PREFIX
 503         bool
 504         help
 505           Some architectures generate an _ in front of C symbols; things like
 506           module loading and assembly files need to know about this.
 507
 508 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 509         bool
 510         help
 511           Architecture doesn't only execute the irq handler on the irq stack
 512           but also irq_exit(). This way we can process softirqs on this irq
 513           stack instead of switching to a new one when we call __do_softirq()
 514           in the end of an hardirq.
 515           This spares a stack switch and improves cache usage on softirq
 516           processing.
 517
 518 config PGTABLE_LEVELS
 519         int
 520         default 2
 521
 522 config ARCH_HAS_ELF_RANDOMIZE
 523         bool
 524         help
 525           An architecture supports choosing randomized locations for
 526           stack, mmap, brk, and ET_DYN. Defined functions:
 527           - arch_mmap_rnd()
 528           - arch_randomize_brk()
 529
 530 config HAVE_ARCH_MMAP_RND_BITS
 531         bool
 532         help
 533           An arch should select this symbol if it supports setting a variable
 534           number of bits for use in establishing the base address for mmap
 535           allocations, has MMU enabled and provides values for both:
 536           - ARCH_MMAP_RND_BITS_MIN
 537           - ARCH_MMAP_RND_BITS_MAX
 538
 539 config HAVE_EXIT_THREAD
 540         bool
 541         help
 542           An architecture implements exit_thread.
 543
 544 config ARCH_MMAP_RND_BITS_MIN
 545         int
 546
 547 config ARCH_MMAP_RND_BITS_MAX
 548         int
 549
 550 config ARCH_MMAP_RND_BITS_DEFAULT
 551         int
 552
 553 config ARCH_MMAP_RND_BITS
 554         int "Number of bits to use for ASLR of mmap base address" if EXPERT
 555         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
 556         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
 557         default ARCH_MMAP_RND_BITS_MIN
 558         depends on HAVE_ARCH_MMAP_RND_BITS
 559         help
 560           This value can be used to select the number of bits to use to
 561           determine the random offset to the base address of vma regions
 562           resulting from mmap allocations. This value will be bounded
 563           by the architecture's minimum and maximum supported values.
 564
 565           This value can be changed after boot using the
 566           /proc/sys/vm/mmap_rnd_bits tunable
 567
 568 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
 569         bool
 570         help
 571           An arch should select this symbol if it supports running applications
 572           in compatibility mode, supports setting a variable number of bits for
 573           use in establishing the base address for mmap allocations, has MMU
 574           enabled and provides values for both:
 575           - ARCH_MMAP_RND_COMPAT_BITS_MIN
 576           - ARCH_MMAP_RND_COMPAT_BITS_MAX
 577
 578 config ARCH_MMAP_RND_COMPAT_BITS_MIN
 579         int
 580
 581 config ARCH_MMAP_RND_COMPAT_BITS_MAX
 582         int
 583
 584 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 585         int
 586
 587 config ARCH_MMAP_RND_COMPAT_BITS
 588         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
 589         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
 590         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 591         default ARCH_MMAP_RND_COMPAT_BITS_MIN
 592         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
 593         help
 594           This value can be used to select the number of bits to use to
 595           determine the random offset to the base address of vma regions
 596           resulting from mmap allocations for compatible applications This
 597           value will be bounded by the architecture's minimum and maximum
 598           supported values.
 599
 600           This value can be changed after boot using the
 601           /proc/sys/vm/mmap_rnd_compat_bits tunable
 602
 603 config HAVE_COPY_THREAD_TLS
 604         bool
 605         help
 606           Architecture provides copy_thread_tls to accept tls argument via
 607           normal C parameter passing, rather than extracting the syscall
 608           argument from pt_regs.
 609
 610 config HAVE_STACK_VALIDATION
 611         bool
 612         help
 613           Architecture supports the 'objtool check' host tool command, which
 614           performs compile-time stack metadata validation.
 615
 616 config HAVE_ARCH_HASH
 617         bool
 618         default n
 619         help
 620           If this is set, the architecture provides an <asm/hash.h>
 621           file which provides platform-specific implementations of some
 622           functions in <linux/hash.h> or fs/namei.c.
 623
 624 #
 625 # ABI hall of shame
 626 #
 627 config CLONE_BACKWARDS
 628         bool
 629         help
 630           Architecture has tls passed as the 4th argument of clone(2),
 631           not the 5th one.
 632
 633 config CLONE_BACKWARDS2
 634         bool
 635         help
 636           Architecture has the first two arguments of clone(2) swapped.
 637
 638 config CLONE_BACKWARDS3
 639         bool
 640         help
 641           Architecture has tls passed as the 3rd argument of clone(2),
 642           not the 5th one.
 643
 644 config ODD_RT_SIGACTION
 645         bool
 646         help
 647           Architecture has unusual rt_sigaction(2) arguments
 648
 649 config OLD_SIGSUSPEND
 650         bool
 651         help
 652           Architecture has old sigsuspend(2) syscall, of one-argument variety
 653
 654 config OLD_SIGSUSPEND3
 655         bool
 656         help
 657           Even weirder antique ABI - three-argument sigsuspend(2)
 658
 659 config OLD_SIGACTION
 660         bool
 661         help
 662           Architecture has old sigaction(2) syscall.  Nope, not the same
 663           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
 664           but fairly different variant of sigaction(2), thanks to OSF/1
 665           compatibility...
 666
 667 config COMPAT_OLD_SIGACTION
 668         bool
 669
 670 config ARCH_NO_COHERENT_DMA_MMAP
 671         bool
 672
 673 config CPU_NO_EFFICIENT_FFS
 674         def_bool n
 675
 676 source "kernel/gcov/Kconfig"