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_WATCHDOG
 191         bool
 192 #
 193 # An arch should select this if it provides all these things:
 194 #
 195 #       task_pt_regs()          in asm/processor.h or asm/ptrace.h
 196 #       arch_has_single_step()  if there is hardware single-step support
 197 #       arch_has_block_step()   if there is hardware block-step support
 198 #       asm/syscall.h           supplying asm-generic/syscall.h interface
 199 #       linux/regset.h          user_regset interfaces
 200 #       CORE_DUMP_USE_REGSET    #define'd in linux/elf.h
 201 #       TIF_SYSCALL_TRACE       calls tracehook_report_syscall_{entry,exit}
 202 #       TIF_NOTIFY_RESUME       calls tracehook_notify_resume()
 203 #       signal delivery         calls tracehook_signal_handler()
 204 #
 205 config HAVE_ARCH_TRACEHOOK
 206         bool
 207
 208 config HAVE_DMA_ATTRS
 209         bool
 210
 211 config HAVE_DMA_CONTIGUOUS
 212         bool
 213
 214 config GENERIC_SMP_IDLE_THREAD
 215        bool
 216
 217 config GENERIC_IDLE_POLL_SETUP
 218        bool
 219
 220 # Select if arch init_task initializer is different to init/init_task.c
 221 config ARCH_INIT_TASK
 222        bool
 223
 224 # Select if arch has its private alloc_task_struct() function
 225 config ARCH_TASK_STRUCT_ALLOCATOR
 226         bool
 227
 228 # Select if arch has its private alloc_thread_stack() function
 229 config ARCH_THREAD_STACK_ALLOCATOR
 230         bool
 231
 232 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 233 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 234         bool
 235
 236 config HAVE_REGS_AND_STACK_ACCESS_API
 237         bool
 238         help
 239           This symbol should be selected by an architecure if it supports
 240           the API needed to access registers and stack entries from pt_regs,
 241           declared in asm/ptrace.h
 242           For example the kprobes-based event tracer needs this API.
 243
 244 config HAVE_CLK
 245         bool
 246         help
 247           The <linux/clk.h> calls support software clock gating and
 248           thus are a key power management tool on many systems.
 249
 250 config HAVE_DMA_API_DEBUG
 251         bool
 252
 253 config HAVE_HW_BREAKPOINT
 254         bool
 255         depends on PERF_EVENTS
 256
 257 config HAVE_MIXED_BREAKPOINTS_REGS
 258         bool
 259         depends on HAVE_HW_BREAKPOINT
 260         help
 261           Depending on the arch implementation of hardware breakpoints,
 262           some of them have separate registers for data and instruction
 263           breakpoints addresses, others have mixed registers to store
 264           them but define the access type in a control register.
 265           Select this option if your arch implements breakpoints under the
 266           latter fashion.
 267
 268 config HAVE_USER_RETURN_NOTIFIER
 269         bool
 270
 271 config HAVE_PERF_EVENTS_NMI
 272         bool
 273         help
 274           System hardware can generate an NMI using the perf event
 275           subsystem.  Also has support for calculating CPU cycle events
 276           to determine how many clock cycles in a given period.
 277
 278 config HAVE_PERF_REGS
 279         bool
 280         help
 281           Support selective register dumps for perf events. This includes
 282           bit-mapping of each registers and a unique architecture id.
 283
 284 config HAVE_PERF_USER_STACK_DUMP
 285         bool
 286         help
 287           Support user stack dumps for perf event samples. This needs
 288           access to the user stack pointer which is not unified across
 289           architectures.
 290
 291 config HAVE_ARCH_JUMP_LABEL
 292         bool
 293
 294 config HAVE_RCU_TABLE_FREE
 295         bool
 296
 297 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 298         bool
 299
 300 config HAVE_ALIGNED_STRUCT_PAGE
 301         bool
 302         help
 303           This makes sure that struct pages are double word aligned and that
 304           e.g. the SLUB allocator can perform double word atomic operations
 305           on a struct page for better performance. However selecting this
 306           might increase the size of a struct page by a word.
 307
 308 config HAVE_CMPXCHG_LOCAL
 309         bool
 310
 311 config HAVE_CMPXCHG_DOUBLE
 312         bool
 313
 314 config ARCH_WANT_IPC_PARSE_VERSION
 315         bool
 316
 317 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 318         bool
 319
 320 config ARCH_WANT_OLD_COMPAT_IPC
 321         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 322         bool
 323
 324 config HAVE_ARCH_SECCOMP_FILTER
 325         bool
 326         help
 327           An arch should select this symbol if it provides all of these things:
 328           - syscall_get_arch()
 329           - syscall_get_arguments()
 330           - syscall_rollback()
 331           - syscall_set_return_value()
 332           - SIGSYS siginfo_t support
 333           - secure_computing is called from a ptrace_event()-safe context
 334           - secure_computing return value is checked and a return value of -1
 335             results in the system call being skipped immediately.
 336           - seccomp syscall wired up
 337
 338           For best performance, an arch should use seccomp_phase1 and
 339           seccomp_phase2 directly.  It should call seccomp_phase1 for all
 340           syscalls if TIF_SECCOMP is set, but seccomp_phase1 does not
 341           need to be called from a ptrace-safe context.  It must then
 342           call seccomp_phase2 if seccomp_phase1 returns anything other
 343           than SECCOMP_PHASE1_OK or SECCOMP_PHASE1_SKIP.
 344
 345           As an additional optimization, an arch may provide seccomp_data
 346           directly to seccomp_phase1; this avoids multiple calls
 347           to the syscall_xyz helpers for every syscall.
 348
 349 config SECCOMP_FILTER
 350         def_bool y
 351         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 352         help
 353           Enable tasks to build secure computing environments defined
 354           in terms of Berkeley Packet Filter programs which implement
 355           task-defined system call filtering polices.
 356
 357           See Documentation/prctl/seccomp_filter.txt for details.
 358
 359 config HAVE_CC_STACKPROTECTOR
 360         bool
 361         help
 362           An arch should select this symbol if:
 363           - its compiler supports the -fstack-protector option
 364           - it has implemented a stack canary (e.g. __stack_chk_guard)
 365
 366 config CC_STACKPROTECTOR
 367         def_bool n
 368         help
 369           Set when a stack-protector mode is enabled, so that the build
 370           can enable kernel-side support for the GCC feature.
 371
 372 choice
 373         prompt "Stack Protector buffer overflow detection"
 374         depends on HAVE_CC_STACKPROTECTOR
 375         default CC_STACKPROTECTOR_NONE
 376         help
 377           This option turns on the "stack-protector" GCC feature. This
 378           feature puts, at the beginning of functions, a canary value on
 379           the stack just before the return address, and validates
 380           the value just before actually returning.  Stack based buffer
 381           overflows (that need to overwrite this return address) now also
 382           overwrite the canary, which gets detected and the attack is then
 383           neutralized via a kernel panic.
 384
 385 config CC_STACKPROTECTOR_NONE
 386         bool "None"
 387         help
 388           Disable "stack-protector" GCC feature.
 389
 390 config CC_STACKPROTECTOR_REGULAR
 391         bool "Regular"
 392         select CC_STACKPROTECTOR
 393         help
 394           Functions will have the stack-protector canary logic added if they
 395           have an 8-byte or larger character array on the stack.
 396
 397           This feature requires gcc version 4.2 or above, or a distribution
 398           gcc with the feature backported ("-fstack-protector").
 399
 400           On an x86 "defconfig" build, this feature adds canary checks to
 401           about 3% of all kernel functions, which increases kernel code size
 402           by about 0.3%.
 403
 404 config CC_STACKPROTECTOR_STRONG
 405         bool "Strong"
 406         select CC_STACKPROTECTOR
 407         help
 408           Functions will have the stack-protector canary logic added in any
 409           of the following conditions:
 410
 411           - local variable's address used as part of the right hand side of an
 412             assignment or function argument
 413           - local variable is an array (or union containing an array),
 414             regardless of array type or length
 415           - uses register local variables
 416
 417           This feature requires gcc version 4.9 or above, or a distribution
 418           gcc with the feature backported ("-fstack-protector-strong").
 419
 420           On an x86 "defconfig" build, this feature adds canary checks to
 421           about 20% of all kernel functions, which increases the kernel code
 422           size by about 2%.
 423
 424 endchoice
 425
 426 config HAVE_ARCH_WITHIN_STACK_FRAMES
 427         bool
 428         help
 429           An architecture should select this if it can walk the kernel stack
 430           frames to determine if an object is part of either the arguments
 431           or local variables (i.e. that it excludes saved return addresses,
 432           and similar) by implementing an inline arch_within_stack_frames(),
 433           which is used by CONFIG_HARDENED_USERCOPY.
 434
 435 config HAVE_CONTEXT_TRACKING
 436         bool
 437         help
 438           Provide kernel/user boundaries probes necessary for subsystems
 439           that need it, such as userspace RCU extended quiescent state.
 440           Syscalls need to be wrapped inside user_exit()-user_enter() through
 441           the slow path using TIF_NOHZ flag. Exceptions handlers must be
 442           wrapped as well. Irqs are already protected inside
 443           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
 444           irq exit still need to be protected.
 445
 446 config HAVE_VIRT_CPU_ACCOUNTING
 447         bool
 448
 449 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 450         bool
 451         default y if 64BIT
 452         help
 453           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 454           Before enabling this option, arch code must be audited
 455           to ensure there are no races in concurrent read/write of
 456           cputime_t. For example, reading/writing 64-bit cputime_t on
 457           some 32-bit arches may require multiple accesses, so proper
 458           locking is needed to protect against concurrent accesses.
 459
 460
 461 config HAVE_IRQ_TIME_ACCOUNTING
 462         bool
 463         help
 464           Archs need to ensure they use a high enough resolution clock to
 465           support irq time accounting and then call enable_sched_clock_irqtime().
 466
 467 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 468         bool
 469
 470 config HAVE_ARCH_HUGE_VMAP
 471         bool
 472
 473 config HAVE_ARCH_SOFT_DIRTY
 474         bool
 475
 476 config HAVE_MOD_ARCH_SPECIFIC
 477         bool
 478         help
 479           The arch uses struct mod_arch_specific to store data.  Many arches
 480           just need a simple module loader without arch specific data - those
 481           should not enable this.
 482
 483 config MODULES_USE_ELF_RELA
 484         bool
 485         help
 486           Modules only use ELF RELA relocations.  Modules with ELF REL
 487           relocations will give an error.
 488
 489 config MODULES_USE_ELF_REL
 490         bool
 491         help
 492           Modules only use ELF REL relocations.  Modules with ELF RELA
 493           relocations will give an error.
 494
 495 config HAVE_UNDERSCORE_SYMBOL_PREFIX
 496         bool
 497         help
 498           Some architectures generate an _ in front of C symbols; things like
 499           module loading and assembly files need to know about this.
 500
 501 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 502         bool
 503         help
 504           Architecture doesn't only execute the irq handler on the irq stack
 505           but also irq_exit(). This way we can process softirqs on this irq
 506           stack instead of switching to a new one when we call __do_softirq()
 507           in the end of an hardirq.
 508           This spares a stack switch and improves cache usage on softirq
 509           processing.
 510
 511 config PGTABLE_LEVELS
 512         int
 513         default 2
 514
 515 config ARCH_HAS_ELF_RANDOMIZE
 516         bool
 517         help
 518           An architecture supports choosing randomized locations for
 519           stack, mmap, brk, and ET_DYN. Defined functions:
 520           - arch_mmap_rnd()
 521           - arch_randomize_brk()
 522
 523 config HAVE_COPY_THREAD_TLS
 524         bool
 525         help
 526           Architecture provides copy_thread_tls to accept tls argument via
 527           normal C parameter passing, rather than extracting the syscall
 528           argument from pt_regs.
 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 ARCH_MMAP_RND_BITS_MIN
 540         int
 541
 542 config ARCH_MMAP_RND_BITS_MAX
 543         int
 544
 545 config ARCH_MMAP_RND_BITS_DEFAULT
 546         int
 547
 548 config ARCH_MMAP_RND_BITS
 549         int "Number of bits to use for ASLR of mmap base address" if EXPERT
 550         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
 551         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
 552         default ARCH_MMAP_RND_BITS_MIN
 553         depends on HAVE_ARCH_MMAP_RND_BITS
 554         help
 555           This value can be used to select the number of bits to use to
 556           determine the random offset to the base address of vma regions
 557           resulting from mmap allocations. This value will be bounded
 558           by the architecture's minimum and maximum supported values.
 559
 560           This value can be changed after boot using the
 561           /proc/sys/vm/mmap_rnd_bits tunable
 562
 563 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
 564         bool
 565         help
 566           An arch should select this symbol if it supports running applications
 567           in compatibility mode, supports setting a variable number of bits for
 568           use in establishing the base address for mmap allocations, has MMU
 569           enabled and provides values for both:
 570           - ARCH_MMAP_RND_COMPAT_BITS_MIN
 571           - ARCH_MMAP_RND_COMPAT_BITS_MAX
 572
 573 config ARCH_MMAP_RND_COMPAT_BITS_MIN
 574         int
 575
 576 config ARCH_MMAP_RND_COMPAT_BITS_MAX
 577         int
 578
 579 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 580         int
 581
 582 config ARCH_MMAP_RND_COMPAT_BITS
 583         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
 584         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
 585         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 586         default ARCH_MMAP_RND_COMPAT_BITS_MIN
 587         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
 588         help
 589           This value can be used to select the number of bits to use to
 590           determine the random offset to the base address of vma regions
 591           resulting from mmap allocations for compatible applications This
 592           value will be bounded by the architecture's minimum and maximum
 593           supported values.
 594
 595           This value can be changed after boot using the
 596           /proc/sys/vm/mmap_rnd_compat_bits tunable
 597
 598 #
 599 # ABI hall of shame
 600 #
 601 config CLONE_BACKWARDS
 602         bool
 603         help
 604           Architecture has tls passed as the 4th argument of clone(2),
 605           not the 5th one.
 606
 607 config CLONE_BACKWARDS2
 608         bool
 609         help
 610           Architecture has the first two arguments of clone(2) swapped.
 611
 612 config CLONE_BACKWARDS3
 613         bool
 614         help
 615           Architecture has tls passed as the 3rd argument of clone(2),
 616           not the 5th one.
 617
 618 config ODD_RT_SIGACTION
 619         bool
 620         help
 621           Architecture has unusual rt_sigaction(2) arguments
 622
 623 config OLD_SIGSUSPEND
 624         bool
 625         help
 626           Architecture has old sigsuspend(2) syscall, of one-argument variety
 627
 628 config OLD_SIGSUSPEND3
 629         bool
 630         help
 631           Even weirder antique ABI - three-argument sigsuspend(2)
 632
 633 config OLD_SIGACTION
 634         bool
 635         help
 636           Architecture has old sigaction(2) syscall.  Nope, not the same
 637           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
 638           but fairly different variant of sigaction(2), thanks to OSF/1
 639           compatibility...
 640
 641 config COMPAT_OLD_SIGACTION
 642         bool
 643
 644 source "kernel/gcov/Kconfig"