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