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 USE_GENERIC_SMP_HELPERS
 211         bool
 212
 213 config GENERIC_SMP_IDLE_THREAD
 214        bool
 215
 216 config GENERIC_IDLE_POLL_SETUP
 217        bool
 218
 219 # Select if arch init_task initializer is different to init/init_task.c
 220 config ARCH_INIT_TASK
 221        bool
 222
 223 # Select if arch has its private alloc_task_struct() function
 224 config ARCH_TASK_STRUCT_ALLOCATOR
 225         bool
 226
 227 # Select if arch has its private alloc_thread_info() function
 228 config ARCH_THREAD_INFO_ALLOCATOR
 229         bool
 230
 231 config HAVE_REGS_AND_STACK_ACCESS_API
 232         bool
 233         help
 234           This symbol should be selected by an architecure if it supports
 235           the API needed to access registers and stack entries from pt_regs,
 236           declared in asm/ptrace.h
 237           For example the kprobes-based event tracer needs this API.
 238
 239 config HAVE_CLK
 240         bool
 241         help
 242           The <linux/clk.h> calls support software clock gating and
 243           thus are a key power management tool on many systems.
 244
 245 config HAVE_DMA_API_DEBUG
 246         bool
 247
 248 config HAVE_HW_BREAKPOINT
 249         bool
 250         depends on PERF_EVENTS
 251
 252 config HAVE_MIXED_BREAKPOINTS_REGS
 253         bool
 254         depends on HAVE_HW_BREAKPOINT
 255         help
 256           Depending on the arch implementation of hardware breakpoints,
 257           some of them have separate registers for data and instruction
 258           breakpoints addresses, others have mixed registers to store
 259           them but define the access type in a control register.
 260           Select this option if your arch implements breakpoints under the
 261           latter fashion.
 262
 263 config HAVE_USER_RETURN_NOTIFIER
 264         bool
 265
 266 config HAVE_PERF_EVENTS_NMI
 267         bool
 268         help
 269           System hardware can generate an NMI using the perf event
 270           subsystem.  Also has support for calculating CPU cycle events
 271           to determine how many clock cycles in a given period.
 272
 273 config HAVE_PERF_REGS
 274         bool
 275         help
 276           Support selective register dumps for perf events. This includes
 277           bit-mapping of each registers and a unique architecture id.
 278
 279 config HAVE_PERF_USER_STACK_DUMP
 280         bool
 281         help
 282           Support user stack dumps for perf event samples. This needs
 283           access to the user stack pointer which is not unified across
 284           architectures.
 285
 286 config HAVE_ARCH_JUMP_LABEL
 287         bool
 288
 289 config HAVE_ARCH_MUTEX_CPU_RELAX
 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 config SECCOMP_FILTER
 337         def_bool y
 338         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 339         help
 340           Enable tasks to build secure computing environments defined
 341           in terms of Berkeley Packet Filter programs which implement
 342           task-defined system call filtering polices.
 343
 344           See Documentation/prctl/seccomp_filter.txt for details.
 345
 346 config HAVE_CONTEXT_TRACKING
 347         bool
 348         help
 349           Provide kernel/user boundaries probes necessary for subsystems
 350           that need it, such as userspace RCU extended quiescent state.
 351           Syscalls need to be wrapped inside user_exit()-user_enter() through
 352           the slow path using TIF_NOHZ flag. Exceptions handlers must be
 353           wrapped as well. Irqs are already protected inside
 354           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
 355           irq exit still need to be protected.
 356
 357 config HAVE_VIRT_CPU_ACCOUNTING
 358         bool
 359
 360 config HAVE_IRQ_TIME_ACCOUNTING
 361         bool
 362         help
 363           Archs need to ensure they use a high enough resolution clock to
 364           support irq time accounting and then call enable_sched_clock_irqtime().
 365
 366 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 367         bool
 368
 369 config HAVE_MOD_ARCH_SPECIFIC
 370         bool
 371         help
 372           The arch uses struct mod_arch_specific to store data.  Many arches
 373           just need a simple module loader without arch specific data - those
 374           should not enable this.
 375
 376 config MODULES_USE_ELF_RELA
 377         bool
 378         help
 379           Modules only use ELF RELA relocations.  Modules with ELF REL
 380           relocations will give an error.
 381
 382 config MODULES_USE_ELF_REL
 383         bool
 384         help
 385           Modules only use ELF REL relocations.  Modules with ELF RELA
 386           relocations will give an error.
 387
 388 config HAVE_UNDERSCORE_SYMBOL_PREFIX
 389         bool
 390         help
 391           Some architectures generate an _ in front of C symbols; things like
 392           module loading and assembly files need to know about this.
 393
 394 #
 395 # ABI hall of shame
 396 #
 397 config CLONE_BACKWARDS
 398         bool
 399         help
 400           Architecture has tls passed as the 4th argument of clone(2),
 401           not the 5th one.
 402
 403 config CLONE_BACKWARDS2
 404         bool
 405         help
 406           Architecture has the first two arguments of clone(2) swapped.
 407
 408 config CLONE_BACKWARDS3
 409         bool
 410         help
 411           Architecture has tls passed as the 3rd argument of clone(2),
 412           not the 5th one.
 413
 414 config ODD_RT_SIGACTION
 415         bool
 416         help
 417           Architecture has unusual rt_sigaction(2) arguments
 418
 419 config OLD_SIGSUSPEND
 420         bool
 421         help
 422           Architecture has old sigsuspend(2) syscall, of one-argument variety
 423
 424 config OLD_SIGSUSPEND3
 425         bool
 426         help
 427           Even weirder antique ABI - three-argument sigsuspend(2)
 428
 429 config OLD_SIGACTION
 430         bool
 431         help
 432           Architecture has old sigaction(2) syscall.  Nope, not the same
 433           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
 434           but fairly different variant of sigaction(2), thanks to OSF/1
 435           compatibility...
 436
 437 config COMPAT_OLD_SIGACTION
 438         bool
 439
 440 source "kernel/gcov/Kconfig"