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