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