arch/Kconfig

   1 #
   2 # General architecture dependent options
   3 #
   4
   5 config OPROFILE
   6         tristate "OProfile system profiling"
   7         depends on PROFILING
   8         depends on HAVE_OPROFILE
   9         select RING_BUFFER
  10         select RING_BUFFER_ALLOW_SWAP
  11         help
  12           OProfile is a profiling system capable of profiling the
  13           whole system, include the kernel, kernel modules, libraries,
  14           and applications.
  15
  16           If unsure, say N.
  17
  18 config OPROFILE_EVENT_MULTIPLEX
  19         bool "OProfile multiplexing support (EXPERIMENTAL)"
  20         default n
  21         depends on OPROFILE && X86
  22         help
  23           The number of hardware counters is limited. The multiplexing
  24           feature enables OProfile to gather more events than counters
  25           are provided by the hardware. This is realized by switching
  26           between events at an user specified time interval.
  27
  28           If unsure, say N.
  29
  30 config HAVE_OPROFILE
  31         bool
  32
  33 config OPROFILE_NMI_TIMER
  34         def_bool y
  35         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
  36
  37 config KPROBES
  38         bool "Kprobes"
  39         depends on MODULES
  40         depends on HAVE_KPROBES
  41         select KALLSYMS
  42         help
  43           Kprobes allows you to trap at almost any kernel address and
  44           execute a callback function.  register_kprobe() establishes
  45           a probepoint and specifies the callback.  Kprobes is useful
  46           for kernel debugging, non-intrusive instrumentation and testing.
  47           If in doubt, say "N".
  48
  49 config JUMP_LABEL
  50        bool "Optimize very unlikely/likely branches"
  51        depends on HAVE_ARCH_JUMP_LABEL
  52        help
  53          This option enables a transparent branch optimization that
  54          makes certain almost-always-true or almost-always-false branch
  55          conditions even cheaper to execute within the kernel.
  56
  57          Certain performance-sensitive kernel code, such as trace points,
  58          scheduler functionality, networking code and KVM have such
  59          branches and include support for this optimization technique.
  60
  61          If it is detected that the compiler has support for "asm goto",
  62          the kernel will compile such branches with just a nop
  63          instruction. When the condition flag is toggled to true, the
  64          nop will be converted to a jump instruction to execute the
  65          conditional block of instructions.
  66
  67          This technique lowers overhead and stress on the branch prediction
  68          of the processor and generally makes the kernel faster. The update
  69          of the condition is slower, but those are always very rare.
  70
  71          ( On 32-bit x86, the necessary options added to the compiler
  72            flags may increase the size of the kernel slightly. )
  73
  74 config STATIC_KEYS_SELFTEST
  75         bool "Static key selftest"
  76         depends on JUMP_LABEL
  77         help
  78           Boot time self-test of the branch patching code.
  79
  80 config OPTPROBES
  81         def_bool y
  82         depends on KPROBES && HAVE_OPTPROBES
  83         depends on !PREEMPT
  84
  85 config KPROBES_ON_FTRACE
  86         def_bool y
  87         depends on KPROBES && HAVE_KPROBES_ON_FTRACE
  88         depends on DYNAMIC_FTRACE_WITH_REGS
  89         help
  90          If function tracer is enabled and the arch supports full
  91          passing of pt_regs to function tracing, then kprobes can
  92          optimize on top of function tracing.
  93
  94 config UPROBES
  95         def_bool n
  96         help
  97           Uprobes is the user-space counterpart to kprobes: they
  98           enable instrumentation applications (such as 'perf probe')
  99           to establish unintrusive probes in user-space binaries and
 100           libraries, by executing handler functions when the probes
 101           are hit by user-space applications.
 102
 103           ( These probes come in the form of single-byte breakpoints,
 104             managed by the kernel and kept transparent to the probed
 105             application. )
 106
 107 config HAVE_64BIT_ALIGNED_ACCESS
 108         def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
 109         help
 110           Some architectures require 64 bit accesses to be 64 bit
 111           aligned, which also requires structs containing 64 bit values
 112           to be 64 bit aligned too. This includes some 32 bit
 113           architectures which can do 64 bit accesses, as well as 64 bit
 114           architectures without unaligned access.
 115
 116           This symbol should be selected by an architecture if 64 bit
 117           accesses are required to be 64 bit aligned in this way even
 118           though it is not a 64 bit architecture.
 119
 120           See Documentation/unaligned-memory-access.txt for more
 121           information on the topic of unaligned memory accesses.
 122
 123 config HAVE_EFFICIENT_UNALIGNED_ACCESS
 124         bool
 125         help
 126           Some architectures are unable to perform unaligned accesses
 127           without the use of get_unaligned/put_unaligned. Others are
 128           unable to perform such accesses efficiently (e.g. trap on
 129           unaligned access and require fixing it up in the exception
 130           handler.)
 131
 132           This symbol should be selected by an architecture if it can
 133           perform unaligned accesses efficiently to allow different
 134           code paths to be selected for these cases. Some network
 135           drivers, for example, could opt to not fix up alignment
 136           problems with received packets if doing so would not help
 137           much.
 138
 139           See Documentation/unaligned-memory-access.txt for more
 140           information on the topic of unaligned memory accesses.
 141
 142 config ARCH_USE_BUILTIN_BSWAP
 143        bool
 144        help
 145          Modern versions of GCC (since 4.4) have builtin functions
 146          for handling byte-swapping. Using these, instead of the old
 147          inline assembler that the architecture code provides in the
 148          __arch_bswapXX() macros, allows the compiler to see what's
 149          happening and offers more opportunity for optimisation. In
 150          particular, the compiler will be able to combine the byteswap
 151          with a nearby load or store and use load-and-swap or
 152          store-and-swap instructions if the architecture has them. It
 153          should almost *never* result in code which is worse than the
 154          hand-coded assembler in <asm/swab.h>.  But just in case it
 155          does, the use of the builtins is optional.
 156
 157          Any architecture with load-and-swap or store-and-swap
 158          instructions should set this. And it shouldn't hurt to set it
 159          on architectures that don't have such instructions.
 160
 161 config KRETPROBES
 162         def_bool y
 163         depends on KPROBES && HAVE_KRETPROBES
 164
 165 config USER_RETURN_NOTIFIER
 166         bool
 167         depends on HAVE_USER_RETURN_NOTIFIER
 168         help
 169           Provide a kernel-internal notification when a cpu is about to
 170           switch to user mode.
 171
 172 config HAVE_IOREMAP_PROT
 173         bool
 174
 175 config HAVE_KPROBES
 176         bool
 177
 178 config HAVE_KRETPROBES
 179         bool
 180
 181 config HAVE_OPTPROBES
 182         bool
 183
 184 config HAVE_KPROBES_ON_FTRACE
 185         bool
 186
 187 config HAVE_NMI_WATCHDOG
 188         bool
 189 #
 190 # An arch should select this if it provides all these things:
 191 #
 192 #       task_pt_regs()          in asm/processor.h or asm/ptrace.h
 193 #       arch_has_single_step()  if there is hardware single-step support
 194 #       arch_has_block_step()   if there is hardware block-step support
 195 #       asm/syscall.h           supplying asm-generic/syscall.h interface
 196 #       linux/regset.h          user_regset interfaces
 197 #       CORE_DUMP_USE_REGSET    #define'd in linux/elf.h
 198 #       TIF_SYSCALL_TRACE       calls tracehook_report_syscall_{entry,exit}
 199 #       TIF_NOTIFY_RESUME       calls tracehook_notify_resume()
 200 #       signal delivery         calls tracehook_signal_handler()
 201 #
 202 config HAVE_ARCH_TRACEHOOK
 203         bool
 204
 205 config HAVE_DMA_ATTRS
 206         bool
 207
 208 config HAVE_DMA_CONTIGUOUS
 209         bool
 210
 211 config GENERIC_SMP_IDLE_THREAD
 212        bool
 213
 214 config GENERIC_IDLE_POLL_SETUP
 215        bool
 216
 217 # Select if arch init_task initializer is different to init/init_task.c
 218 config ARCH_INIT_TASK
 219        bool
 220
 221 # Select if arch has its private alloc_task_struct() function
 222 config ARCH_TASK_STRUCT_ALLOCATOR
 223         bool
 224
 225 # Select if arch has its private alloc_thread_info() function
 226 config ARCH_THREAD_INFO_ALLOCATOR
 227         bool
 228
 229 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 230 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 231         bool
 232
 233 config HAVE_REGS_AND_STACK_ACCESS_API
 234         bool
 235         help
 236           This symbol should be selected by an architecure if it supports
 237           the API needed to access registers and stack entries from pt_regs,
 238           declared in asm/ptrace.h
 239           For example the kprobes-based event tracer needs this API.
 240
 241 config HAVE_CLK
 242         bool
 243         help
 244           The <linux/clk.h> calls support software clock gating and
 245           thus are a key power management tool on many systems.
 246
 247 config HAVE_DMA_API_DEBUG
 248         bool
 249
 250 config HAVE_HW_BREAKPOINT
 251         bool
 252         depends on PERF_EVENTS
 253
 254 config HAVE_MIXED_BREAKPOINTS_REGS
 255         bool
 256         depends on HAVE_HW_BREAKPOINT
 257         help
 258           Depending on the arch implementation of hardware breakpoints,
 259           some of them have separate registers for data and instruction
 260           breakpoints addresses, others have mixed registers to store
 261           them but define the access type in a control register.
 262           Select this option if your arch implements breakpoints under the
 263           latter fashion.
 264
 265 config HAVE_USER_RETURN_NOTIFIER
 266         bool
 267
 268 config HAVE_PERF_EVENTS_NMI
 269         bool
 270         help
 271           System hardware can generate an NMI using the perf event
 272           subsystem.  Also has support for calculating CPU cycle events
 273           to determine how many clock cycles in a given period.
 274
 275 config HAVE_PERF_REGS
 276         bool
 277         help
 278           Support selective register dumps for perf events. This includes
 279           bit-mapping of each registers and a unique architecture id.
 280
 281 config HAVE_PERF_USER_STACK_DUMP
 282         bool
 283         help
 284           Support user stack dumps for perf event samples. This needs
 285           access to the user stack pointer which is not unified across
 286           architectures.
 287
 288 config HAVE_ARCH_JUMP_LABEL
 289         bool
 290
 291 config HAVE_RCU_TABLE_FREE
 292         bool
 293
 294 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 295         bool
 296
 297 config HAVE_ALIGNED_STRUCT_PAGE
 298         bool
 299         help
 300           This makes sure that struct pages are double word aligned and that
 301           e.g. the SLUB allocator can perform double word atomic operations
 302           on a struct page for better performance. However selecting this
 303           might increase the size of a struct page by a word.
 304
 305 config HAVE_CMPXCHG_LOCAL
 306         bool
 307
 308 config HAVE_CMPXCHG_DOUBLE
 309         bool
 310
 311 config ARCH_WANT_IPC_PARSE_VERSION
 312         bool
 313
 314 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 315         bool
 316
 317 config ARCH_WANT_OLD_COMPAT_IPC
 318         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 319         bool
 320
 321 config HAVE_ARCH_SECCOMP_FILTER
 322         bool
 323         help
 324           An arch should select this symbol if it provides all of these things:
 325           - syscall_get_arch()
 326           - syscall_get_arguments()
 327           - syscall_rollback()
 328           - syscall_set_return_value()
 329           - SIGSYS siginfo_t support
 330           - secure_computing is called from a ptrace_event()-safe context
 331           - secure_computing return value is checked and a return value of -1
 332             results in the system call being skipped immediately.
 333           - seccomp syscall wired up
 334
 335           For best performance, an arch should use seccomp_phase1 and
 336           seccomp_phase2 directly.  It should call seccomp_phase1 for all
 337           syscalls if TIF_SECCOMP is set, but seccomp_phase1 does not
 338           need to be called from a ptrace-safe context.  It must then
 339           call seccomp_phase2 if seccomp_phase1 returns anything other
 340           than SECCOMP_PHASE1_OK or SECCOMP_PHASE1_SKIP.
 341
 342           As an additional optimization, an arch may provide seccomp_data
 343           directly to seccomp_phase1; this avoids multiple calls
 344           to the syscall_xyz helpers for every syscall.
 345
 346 config SECCOMP_FILTER
 347         def_bool y
 348         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 349         help
 350           Enable tasks to build secure computing environments defined
 351           in terms of Berkeley Packet Filter programs which implement
 352           task-defined system call filtering polices.
 353
 354           See Documentation/prctl/seccomp_filter.txt for details.
 355
 356 config HAVE_CC_STACKPROTECTOR
 357         bool
 358         help
 359           An arch should select this symbol if:
 360           - its compiler supports the -fstack-protector option
 361           - it has implemented a stack canary (e.g. __stack_chk_guard)
 362
 363 config CC_STACKPROTECTOR
 364         def_bool n
 365         help
 366           Set when a stack-protector mode is enabled, so that the build
 367           can enable kernel-side support for the GCC feature.
 368
 369 choice
 370         prompt "Stack Protector buffer overflow detection"
 371         depends on HAVE_CC_STACKPROTECTOR
 372         default CC_STACKPROTECTOR_NONE
 373         help
 374           This option turns on the "stack-protector" GCC feature. This
 375           feature puts, at the beginning of functions, a canary value on
 376           the stack just before the return address, and validates
 377           the value just before actually returning.  Stack based buffer
 378           overflows (that need to overwrite this return address) now also
 379           overwrite the canary, which gets detected and the attack is then
 380           neutralized via a kernel panic.
 381
 382 config CC_STACKPROTECTOR_NONE
 383         bool "None"
 384         help
 385           Disable "stack-protector" GCC feature.
 386
 387 config CC_STACKPROTECTOR_REGULAR
 388         bool "Regular"
 389         select CC_STACKPROTECTOR
 390         help
 391           Functions will have the stack-protector canary logic added if they
 392           have an 8-byte or larger character array on the stack.
 393
 394           This feature requires gcc version 4.2 or above, or a distribution
 395           gcc with the feature backported ("-fstack-protector").
 396
 397           On an x86 "defconfig" build, this feature adds canary checks to
 398           about 3% of all kernel functions, which increases kernel code size
 399           by about 0.3%.
 400
 401 config CC_STACKPROTECTOR_STRONG
 402         bool "Strong"
 403         select CC_STACKPROTECTOR
 404         help
 405           Functions will have the stack-protector canary logic added in any
 406           of the following conditions:
 407
 408           - local variable's address used as part of the right hand side of an
 409             assignment or function argument
 410           - local variable is an array (or union containing an array),
 411             regardless of array type or length
 412           - uses register local variables
 413
 414           This feature requires gcc version 4.9 or above, or a distribution
 415           gcc with the feature backported ("-fstack-protector-strong").
 416
 417           On an x86 "defconfig" build, this feature adds canary checks to
 418           about 20% of all kernel functions, which increases the kernel code
 419           size by about 2%.
 420
 421 endchoice
 422
 423 config HAVE_CONTEXT_TRACKING
 424         bool
 425         help
 426           Provide kernel/user boundaries probes necessary for subsystems
 427           that need it, such as userspace RCU extended quiescent state.
 428           Syscalls need to be wrapped inside user_exit()-user_enter() through
 429           the slow path using TIF_NOHZ flag. Exceptions handlers must be
 430           wrapped as well. Irqs are already protected inside
 431           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
 432           irq exit still need to be protected.
 433
 434 config HAVE_VIRT_CPU_ACCOUNTING
 435         bool
 436
 437 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 438         bool
 439         default y if 64BIT
 440         help
 441           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 442           Before enabling this option, arch code must be audited
 443           to ensure there are no races in concurrent read/write of
 444           cputime_t. For example, reading/writing 64-bit cputime_t on
 445           some 32-bit arches may require multiple accesses, so proper
 446           locking is needed to protect against concurrent accesses.
 447
 448
 449 config HAVE_IRQ_TIME_ACCOUNTING
 450         bool
 451         help
 452           Archs need to ensure they use a high enough resolution clock to
 453           support irq time accounting and then call enable_sched_clock_irqtime().
 454
 455 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 456         bool
 457
 458 config HAVE_ARCH_HUGE_VMAP
 459         bool
 460
 461 config HAVE_ARCH_SOFT_DIRTY
 462         bool
 463
 464 config HAVE_MOD_ARCH_SPECIFIC
 465         bool
 466         help
 467           The arch uses struct mod_arch_specific to store data.  Many arches
 468           just need a simple module loader without arch specific data - those
 469           should not enable this.
 470
 471 config MODULES_USE_ELF_RELA
 472         bool
 473         help
 474           Modules only use ELF RELA relocations.  Modules with ELF REL
 475           relocations will give an error.
 476
 477 config MODULES_USE_ELF_REL
 478         bool
 479         help
 480           Modules only use ELF REL relocations.  Modules with ELF RELA
 481           relocations will give an error.
 482
 483 config HAVE_UNDERSCORE_SYMBOL_PREFIX
 484         bool
 485         help
 486           Some architectures generate an _ in front of C symbols; things like
 487           module loading and assembly files need to know about this.
 488
 489 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 490         bool
 491         help
 492           Architecture doesn't only execute the irq handler on the irq stack
 493           but also irq_exit(). This way we can process softirqs on this irq
 494           stack instead of switching to a new one when we call __do_softirq()
 495           in the end of an hardirq.
 496           This spares a stack switch and improves cache usage on softirq
 497           processing.
 498
 499 config PGTABLE_LEVELS
 500         int
 501         default 2
 502
 503 config ARCH_HAS_ELF_RANDOMIZE
 504         bool
 505         help
 506           An architecture supports choosing randomized locations for
 507           stack, mmap, brk, and ET_DYN. Defined functions:
 508           - arch_mmap_rnd()
 509           - arch_randomize_brk()
 510
 511 config HAVE_COPY_THREAD_TLS
 512         bool
 513         help
 514           Architecture provides copy_thread_tls to accept tls argument via
 515           normal C parameter passing, rather than extracting the syscall
 516           argument from pt_regs.
 517
 518 #
 519 # ABI hall of shame
 520 #
 521 config CLONE_BACKWARDS
 522         bool
 523         help
 524           Architecture has tls passed as the 4th argument of clone(2),
 525           not the 5th one.
 526
 527 config CLONE_BACKWARDS2
 528         bool
 529         help
 530           Architecture has the first two arguments of clone(2) swapped.
 531
 532 config CLONE_BACKWARDS3
 533         bool
 534         help
 535           Architecture has tls passed as the 3rd argument of clone(2),
 536           not the 5th one.
 537
 538 config ODD_RT_SIGACTION
 539         bool
 540         help
 541           Architecture has unusual rt_sigaction(2) arguments
 542
 543 config OLD_SIGSUSPEND
 544         bool
 545         help
 546           Architecture has old sigsuspend(2) syscall, of one-argument variety
 547
 548 config OLD_SIGSUSPEND3
 549         bool
 550         help
 551           Even weirder antique ABI - three-argument sigsuspend(2)
 552
 553 config OLD_SIGACTION
 554         bool
 555         help
 556           Architecture has old sigaction(2) syscall.  Nope, not the same
 557           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
 558           but fairly different variant of sigaction(2), thanks to OSF/1
 559           compatibility...
 560
 561 config COMPAT_OLD_SIGACTION
 562         bool
 563
 564 source "kernel/gcov/Kconfig"