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 UPROBES
  80         bool "Transparent user-space probes (EXPERIMENTAL)"
  81         depends on UPROBE_EVENT && PERF_EVENTS
  82         default n
  83         select PERCPU_RWSEM
  84         help
  85           Uprobes is the user-space counterpart to kprobes: they
  86           enable instrumentation applications (such as 'perf probe')
  87           to establish unintrusive probes in user-space binaries and
  88           libraries, by executing handler functions when the probes
  89           are hit by user-space applications.
  90
  91           ( These probes come in the form of single-byte breakpoints,
  92             managed by the kernel and kept transparent to the probed
  93             application. )
  94
  95           If in doubt, say "N".
  96
  97 config HAVE_EFFICIENT_UNALIGNED_ACCESS
  98         bool
  99         help
 100           Some architectures are unable to perform unaligned accesses
 101           without the use of get_unaligned/put_unaligned. Others are
 102           unable to perform such accesses efficiently (e.g. trap on
 103           unaligned access and require fixing it up in the exception
 104           handler.)
 105
 106           This symbol should be selected by an architecture if it can
 107           perform unaligned accesses efficiently to allow different
 108           code paths to be selected for these cases. Some network
 109           drivers, for example, could opt to not fix up alignment
 110           problems with received packets if doing so would not help
 111           much.
 112
 113           See Documentation/unaligned-memory-access.txt for more
 114           information on the topic of unaligned memory accesses.
 115
 116 config ARCH_USE_BUILTIN_BSWAP
 117        bool
 118        help
 119          Modern versions of GCC (since 4.4) have builtin functions
 120          for handling byte-swapping. Using these, instead of the old
 121          inline assembler that the architecture code provides in the
 122          __arch_bswapXX() macros, allows the compiler to see what's
 123          happening and offers more opportunity for optimisation. In
 124          particular, the compiler will be able to combine the byteswap
 125          with a nearby load or store and use load-and-swap or
 126          store-and-swap instructions if the architecture has them. It
 127          should almost *never* result in code which is worse than the
 128          hand-coded assembler in <asm/swab.h>.  But just in case it
 129          does, the use of the builtins is optional.
 130
 131          Any architecture with load-and-swap or store-and-swap
 132          instructions should set this. And it shouldn't hurt to set it
 133          on architectures that don't have such instructions.
 134
 135 config HAVE_SYSCALL_WRAPPERS
 136         bool
 137
 138 config KRETPROBES
 139         def_bool y
 140         depends on KPROBES && HAVE_KRETPROBES
 141
 142 config USER_RETURN_NOTIFIER
 143         bool
 144         depends on HAVE_USER_RETURN_NOTIFIER
 145         help
 146           Provide a kernel-internal notification when a cpu is about to
 147           switch to user mode.
 148
 149 config HAVE_IOREMAP_PROT
 150         bool
 151
 152 config HAVE_KPROBES
 153         bool
 154
 155 config HAVE_KRETPROBES
 156         bool
 157
 158 config HAVE_OPTPROBES
 159         bool
 160
 161 config HAVE_NMI_WATCHDOG
 162         bool
 163 #
 164 # An arch should select this if it provides all these things:
 165 #
 166 #       task_pt_regs()          in asm/processor.h or asm/ptrace.h
 167 #       arch_has_single_step()  if there is hardware single-step support
 168 #       arch_has_block_step()   if there is hardware block-step support
 169 #       asm/syscall.h           supplying asm-generic/syscall.h interface
 170 #       linux/regset.h          user_regset interfaces
 171 #       CORE_DUMP_USE_REGSET    #define'd in linux/elf.h
 172 #       TIF_SYSCALL_TRACE       calls tracehook_report_syscall_{entry,exit}
 173 #       TIF_NOTIFY_RESUME       calls tracehook_notify_resume()
 174 #       signal delivery         calls tracehook_signal_handler()
 175 #
 176 config HAVE_ARCH_TRACEHOOK
 177         bool
 178
 179 config HAVE_DMA_ATTRS
 180         bool
 181
 182 config HAVE_DMA_CONTIGUOUS
 183         bool
 184
 185 config USE_GENERIC_SMP_HELPERS
 186         bool
 187
 188 config GENERIC_SMP_IDLE_THREAD
 189        bool
 190
 191 # Select if arch init_task initializer is different to init/init_task.c
 192 config ARCH_INIT_TASK
 193        bool
 194
 195 # Select if arch has its private alloc_task_struct() function
 196 config ARCH_TASK_STRUCT_ALLOCATOR
 197         bool
 198
 199 # Select if arch has its private alloc_thread_info() function
 200 config ARCH_THREAD_INFO_ALLOCATOR
 201         bool
 202
 203 config HAVE_REGS_AND_STACK_ACCESS_API
 204         bool
 205         help
 206           This symbol should be selected by an architecure if it supports
 207           the API needed to access registers and stack entries from pt_regs,
 208           declared in asm/ptrace.h
 209           For example the kprobes-based event tracer needs this API.
 210
 211 config HAVE_CLK
 212         bool
 213         help
 214           The <linux/clk.h> calls support software clock gating and
 215           thus are a key power management tool on many systems.
 216
 217 config HAVE_DMA_API_DEBUG
 218         bool
 219
 220 config HAVE_HW_BREAKPOINT
 221         bool
 222         depends on PERF_EVENTS
 223
 224 config HAVE_MIXED_BREAKPOINTS_REGS
 225         bool
 226         depends on HAVE_HW_BREAKPOINT
 227         help
 228           Depending on the arch implementation of hardware breakpoints,
 229           some of them have separate registers for data and instruction
 230           breakpoints addresses, others have mixed registers to store
 231           them but define the access type in a control register.
 232           Select this option if your arch implements breakpoints under the
 233           latter fashion.
 234
 235 config HAVE_USER_RETURN_NOTIFIER
 236         bool
 237
 238 config HAVE_PERF_EVENTS_NMI
 239         bool
 240         help
 241           System hardware can generate an NMI using the perf event
 242           subsystem.  Also has support for calculating CPU cycle events
 243           to determine how many clock cycles in a given period.
 244
 245 config HAVE_PERF_REGS
 246         bool
 247         help
 248           Support selective register dumps for perf events. This includes
 249           bit-mapping of each registers and a unique architecture id.
 250
 251 config HAVE_PERF_USER_STACK_DUMP
 252         bool
 253         help
 254           Support user stack dumps for perf event samples. This needs
 255           access to the user stack pointer which is not unified across
 256           architectures.
 257
 258 config HAVE_ARCH_JUMP_LABEL
 259         bool
 260
 261 config HAVE_ARCH_MUTEX_CPU_RELAX
 262         bool
 263
 264 config HAVE_RCU_TABLE_FREE
 265         bool
 266
 267 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 268         bool
 269
 270 config HAVE_ALIGNED_STRUCT_PAGE
 271         bool
 272         help
 273           This makes sure that struct pages are double word aligned and that
 274           e.g. the SLUB allocator can perform double word atomic operations
 275           on a struct page for better performance. However selecting this
 276           might increase the size of a struct page by a word.
 277
 278 config HAVE_CMPXCHG_LOCAL
 279         bool
 280
 281 config HAVE_CMPXCHG_DOUBLE
 282         bool
 283
 284 config ARCH_WANT_IPC_PARSE_VERSION
 285         bool
 286
 287 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 288         bool
 289
 290 config ARCH_WANT_OLD_COMPAT_IPC
 291         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 292         bool
 293
 294 config GENERIC_KERNEL_THREAD
 295         bool
 296
 297 config GENERIC_KERNEL_EXECVE
 298         bool
 299
 300 config HAVE_ARCH_SECCOMP_FILTER
 301         bool
 302         help
 303           An arch should select this symbol if it provides all of these things:
 304           - syscall_get_arch()
 305           - syscall_get_arguments()
 306           - syscall_rollback()
 307           - syscall_set_return_value()
 308           - SIGSYS siginfo_t support
 309           - secure_computing is called from a ptrace_event()-safe context
 310           - secure_computing return value is checked and a return value of -1
 311             results in the system call being skipped immediately.
 312
 313 config SECCOMP_FILTER
 314         def_bool y
 315         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 316         help
 317           Enable tasks to build secure computing environments defined
 318           in terms of Berkeley Packet Filter programs which implement
 319           task-defined system call filtering polices.
 320
 321           See Documentation/prctl/seccomp_filter.txt for details.
 322
 323 config HAVE_CONTEXT_TRACKING
 324         bool
 325         help
 326           Provide kernel/user boundaries probes necessary for subsystems
 327           that need it, such as userspace RCU extended quiescent state.
 328           Syscalls need to be wrapped inside user_exit()-user_enter() through
 329           the slow path using TIF_NOHZ flag. Exceptions handlers must be
 330           wrapped as well. Irqs are already protected inside
 331           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
 332           irq exit still need to be protected.
 333
 334 config HAVE_VIRT_CPU_ACCOUNTING
 335         bool
 336
 337 config HAVE_IRQ_TIME_ACCOUNTING
 338         bool
 339         help
 340           Archs need to ensure they use a high enough resolution clock to
 341           support irq time accounting and then call enable_sched_clock_irqtime().
 342
 343 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 344         bool
 345
 346 config HAVE_MOD_ARCH_SPECIFIC
 347         bool
 348         help
 349           The arch uses struct mod_arch_specific to store data.  Many arches
 350           just need a simple module loader without arch specific data - those
 351           should not enable this.
 352
 353 config MODULES_USE_ELF_RELA
 354         bool
 355         help
 356           Modules only use ELF RELA relocations.  Modules with ELF REL
 357           relocations will give an error.
 358
 359 config MODULES_USE_ELF_REL
 360         bool
 361         help
 362           Modules only use ELF REL relocations.  Modules with ELF RELA
 363           relocations will give an error.
 364
 365 #
 366 # ABI hall of shame
 367 #
 368 config CLONE_BACKWARDS
 369         bool
 370         help
 371           Architecture has tls passed as the 4th argument of clone(2),
 372           not the 5th one.
 373
 374 config CLONE_BACKWARDS2
 375         bool
 376         help
 377           Architecture has the first two arguments of clone(2) swapped.
 378
 379 source "kernel/gcov/Kconfig"