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