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 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         help
  91           Uprobes is the user-space counterpart to kprobes: they
  92           enable instrumentation applications (such as 'perf probe')
  93           to establish unintrusive probes in user-space binaries and
  94           libraries, by executing handler functions when the probes
  95           are hit by user-space applications.
  96
  97           ( These probes come in the form of single-byte breakpoints,
  98             managed by the kernel and kept transparent to the probed
  99             application. )
 100
 101 config HAVE_64BIT_ALIGNED_ACCESS
 102         def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
 103         help
 104           Some architectures require 64 bit accesses to be 64 bit
 105           aligned, which also requires structs containing 64 bit values
 106           to be 64 bit aligned too. This includes some 32 bit
 107           architectures which can do 64 bit accesses, as well as 64 bit
 108           architectures without unaligned access.
 109
 110           This symbol should be selected by an architecture if 64 bit
 111           accesses are required to be 64 bit aligned in this way even
 112           though it is not a 64 bit architecture.
 113
 114           See Documentation/unaligned-memory-access.txt for more
 115           information on the topic of unaligned memory accesses.
 116
 117 config HAVE_EFFICIENT_UNALIGNED_ACCESS
 118         bool
 119         help
 120           Some architectures are unable to perform unaligned accesses
 121           without the use of get_unaligned/put_unaligned. Others are
 122           unable to perform such accesses efficiently (e.g. trap on
 123           unaligned access and require fixing it up in the exception
 124           handler.)
 125
 126           This symbol should be selected by an architecture if it can
 127           perform unaligned accesses efficiently to allow different
 128           code paths to be selected for these cases. Some network
 129           drivers, for example, could opt to not fix up alignment
 130           problems with received packets if doing so would not help
 131           much.
 132
 133           See Documentation/unaligned-memory-access.txt for more
 134           information on the topic of unaligned memory accesses.
 135
 136 config ARCH_USE_BUILTIN_BSWAP
 137        bool
 138        help
 139          Modern versions of GCC (since 4.4) have builtin functions
 140          for handling byte-swapping. Using these, instead of the old
 141          inline assembler that the architecture code provides in the
 142          __arch_bswapXX() macros, allows the compiler to see what's
 143          happening and offers more opportunity for optimisation. In
 144          particular, the compiler will be able to combine the byteswap
 145          with a nearby load or store and use load-and-swap or
 146          store-and-swap instructions if the architecture has them. It
 147          should almost *never* result in code which is worse than the
 148          hand-coded assembler in <asm/swab.h>.  But just in case it
 149          does, the use of the builtins is optional.
 150
 151          Any architecture with load-and-swap or store-and-swap
 152          instructions should set this. And it shouldn't hurt to set it
 153          on architectures that don't have such instructions.
 154
 155 config KRETPROBES
 156         def_bool y
 157         depends on KPROBES && HAVE_KRETPROBES
 158
 159 config USER_RETURN_NOTIFIER
 160         bool
 161         depends on HAVE_USER_RETURN_NOTIFIER
 162         help
 163           Provide a kernel-internal notification when a cpu is about to
 164           switch to user mode.
 165
 166 config HAVE_IOREMAP_PROT
 167         bool
 168
 169 config HAVE_KPROBES
 170         bool
 171
 172 config HAVE_KRETPROBES
 173         bool
 174
 175 config HAVE_OPTPROBES
 176         bool
 177
 178 config HAVE_KPROBES_ON_FTRACE
 179         bool
 180
 181 config HAVE_NMI_WATCHDOG
 182         bool
 183 #
 184 # An arch should select this if it provides all these things:
 185 #
 186 #       task_pt_regs()          in asm/processor.h or asm/ptrace.h
 187 #       arch_has_single_step()  if there is hardware single-step support
 188 #       arch_has_block_step()   if there is hardware block-step support
 189 #       asm/syscall.h           supplying asm-generic/syscall.h interface
 190 #       linux/regset.h          user_regset interfaces
 191 #       CORE_DUMP_USE_REGSET    #define'd in linux/elf.h
 192 #       TIF_SYSCALL_TRACE       calls tracehook_report_syscall_{entry,exit}
 193 #       TIF_NOTIFY_RESUME       calls tracehook_notify_resume()
 194 #       signal delivery         calls tracehook_signal_handler()
 195 #
 196 config HAVE_ARCH_TRACEHOOK
 197         bool
 198
 199 config HAVE_DMA_ATTRS
 200         bool
 201
 202 config HAVE_DMA_CONTIGUOUS
 203         bool
 204
 205 config GENERIC_SMP_IDLE_THREAD
 206        bool
 207
 208 config GENERIC_IDLE_POLL_SETUP
 209        bool
 210
 211 # Select if arch init_task initializer is different to init/init_task.c
 212 config ARCH_INIT_TASK
 213        bool
 214
 215 # Select if arch has its private alloc_task_struct() function
 216 config ARCH_TASK_STRUCT_ALLOCATOR
 217         bool
 218
 219 # Select if arch has its private alloc_thread_info() function
 220 config ARCH_THREAD_INFO_ALLOCATOR
 221         bool
 222
 223 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 224 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 225         bool
 226
 227 config HAVE_REGS_AND_STACK_ACCESS_API
 228         bool
 229         help
 230           This symbol should be selected by an architecure if it supports
 231           the API needed to access registers and stack entries from pt_regs,
 232           declared in asm/ptrace.h
 233           For example the kprobes-based event tracer needs this API.
 234
 235 config HAVE_CLK
 236         bool
 237         help
 238           The <linux/clk.h> calls support software clock gating and
 239           thus are a key power management tool on many systems.
 240
 241 config HAVE_DMA_API_DEBUG
 242         bool
 243
 244 config HAVE_HW_BREAKPOINT
 245         bool
 246         depends on PERF_EVENTS
 247
 248 config HAVE_MIXED_BREAKPOINTS_REGS
 249         bool
 250         depends on HAVE_HW_BREAKPOINT
 251         help
 252           Depending on the arch implementation of hardware breakpoints,
 253           some of them have separate registers for data and instruction
 254           breakpoints addresses, others have mixed registers to store
 255           them but define the access type in a control register.
 256           Select this option if your arch implements breakpoints under the
 257           latter fashion.
 258
 259 config HAVE_USER_RETURN_NOTIFIER
 260         bool
 261
 262 config HAVE_PERF_EVENTS_NMI
 263         bool
 264         help
 265           System hardware can generate an NMI using the perf event
 266           subsystem.  Also has support for calculating CPU cycle events
 267           to determine how many clock cycles in a given period.
 268
 269 config HAVE_PERF_REGS
 270         bool
 271         help
 272           Support selective register dumps for perf events. This includes
 273           bit-mapping of each registers and a unique architecture id.
 274
 275 config HAVE_PERF_USER_STACK_DUMP
 276         bool
 277         help
 278           Support user stack dumps for perf event samples. This needs
 279           access to the user stack pointer which is not unified across
 280           architectures.
 281
 282 config HAVE_ARCH_JUMP_LABEL
 283         bool
 284
 285 config HAVE_RCU_TABLE_FREE
 286         bool
 287
 288 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 289         bool
 290
 291 config HAVE_ALIGNED_STRUCT_PAGE
 292         bool
 293         help
 294           This makes sure that struct pages are double word aligned and that
 295           e.g. the SLUB allocator can perform double word atomic operations
 296           on a struct page for better performance. However selecting this
 297           might increase the size of a struct page by a word.
 298
 299 config HAVE_CMPXCHG_LOCAL
 300         bool
 301
 302 config HAVE_CMPXCHG_DOUBLE
 303         bool
 304
 305 config ARCH_WANT_IPC_PARSE_VERSION
 306         bool
 307
 308 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 309         bool
 310
 311 config ARCH_WANT_OLD_COMPAT_IPC
 312         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 313         bool
 314
 315 config HAVE_ARCH_SECCOMP_FILTER
 316         bool
 317         help
 318           An arch should select this symbol if it provides all of these things:
 319           - syscall_get_arch()
 320           - syscall_get_arguments()
 321           - syscall_rollback()
 322           - syscall_set_return_value()
 323           - SIGSYS siginfo_t support
 324           - secure_computing is called from a ptrace_event()-safe context
 325           - secure_computing return value is checked and a return value of -1
 326             results in the system call being skipped immediately.
 327           - seccomp syscall wired up
 328
 329           For best performance, an arch should use seccomp_phase1 and
 330           seccomp_phase2 directly.  It should call seccomp_phase1 for all
 331           syscalls if TIF_SECCOMP is set, but seccomp_phase1 does not
 332           need to be called from a ptrace-safe context.  It must then
 333           call seccomp_phase2 if seccomp_phase1 returns anything other
 334           than SECCOMP_PHASE1_OK or SECCOMP_PHASE1_SKIP.
 335
 336           As an additional optimization, an arch may provide seccomp_data
 337           directly to seccomp_phase1; this avoids multiple calls
 338           to the syscall_xyz helpers for every syscall.
 339
 340 config SECCOMP_FILTER
 341         def_bool y
 342         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 343         help
 344           Enable tasks to build secure computing environments defined
 345           in terms of Berkeley Packet Filter programs which implement
 346           task-defined system call filtering polices.
 347
 348           See Documentation/prctl/seccomp_filter.txt for details.
 349
 350 config HAVE_CC_STACKPROTECTOR
 351         bool
 352         help
 353           An arch should select this symbol if:
 354           - its compiler supports the -fstack-protector option
 355           - it has implemented a stack canary (e.g. __stack_chk_guard)
 356
 357 config CC_STACKPROTECTOR
 358         def_bool n
 359         help
 360           Set when a stack-protector mode is enabled, so that the build
 361           can enable kernel-side support for the GCC feature.
 362
 363 choice
 364         prompt "Stack Protector buffer overflow detection"
 365         depends on HAVE_CC_STACKPROTECTOR
 366         default CC_STACKPROTECTOR_NONE
 367         help
 368           This option turns on the "stack-protector" GCC feature. This
 369           feature puts, at the beginning of functions, a canary value on
 370           the stack just before the return address, and validates
 371           the value just before actually returning.  Stack based buffer
 372           overflows (that need to overwrite this return address) now also
 373           overwrite the canary, which gets detected and the attack is then
 374           neutralized via a kernel panic.
 375
 376 config CC_STACKPROTECTOR_NONE
 377         bool "None"
 378         help
 379           Disable "stack-protector" GCC feature.
 380
 381 config CC_STACKPROTECTOR_REGULAR
 382         bool "Regular"
 383         select CC_STACKPROTECTOR
 384         help
 385           Functions will have the stack-protector canary logic added if they
 386           have an 8-byte or larger character array on the stack.
 387
 388           This feature requires gcc version 4.2 or above, or a distribution
 389           gcc with the feature backported ("-fstack-protector").
 390
 391           On an x86 "defconfig" build, this feature adds canary checks to
 392           about 3% of all kernel functions, which increases kernel code size
 393           by about 0.3%.
 394
 395 config CC_STACKPROTECTOR_STRONG
 396         bool "Strong"
 397         select CC_STACKPROTECTOR
 398         help
 399           Functions will have the stack-protector canary logic added in any
 400           of the following conditions:
 401
 402           - local variable's address used as part of the right hand side of an
 403             assignment or function argument
 404           - local variable is an array (or union containing an array),
 405             regardless of array type or length
 406           - uses register local variables
 407
 408           This feature requires gcc version 4.9 or above, or a distribution
 409           gcc with the feature backported ("-fstack-protector-strong").
 410
 411           On an x86 "defconfig" build, this feature adds canary checks to
 412           about 20% of all kernel functions, which increases the kernel code
 413           size by about 2%.
 414
 415 endchoice
 416
 417 config HAVE_CONTEXT_TRACKING
 418         bool
 419         help
 420           Provide kernel/user boundaries probes necessary for subsystems
 421           that need it, such as userspace RCU extended quiescent state.
 422           Syscalls need to be wrapped inside user_exit()-user_enter() through
 423           the slow path using TIF_NOHZ flag. Exceptions handlers must be
 424           wrapped as well. Irqs are already protected inside
 425           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
 426           irq exit still need to be protected.
 427
 428 config HAVE_VIRT_CPU_ACCOUNTING
 429         bool
 430
 431 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 432         bool
 433         default y if 64BIT
 434         help
 435           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 436           Before enabling this option, arch code must be audited
 437           to ensure there are no races in concurrent read/write of
 438           cputime_t. For example, reading/writing 64-bit cputime_t on
 439           some 32-bit arches may require multiple accesses, so proper
 440           locking is needed to protect against concurrent accesses.
 441
 442
 443 config HAVE_IRQ_TIME_ACCOUNTING
 444         bool
 445         help
 446           Archs need to ensure they use a high enough resolution clock to
 447           support irq time accounting and then call enable_sched_clock_irqtime().
 448
 449 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 450         bool
 451
 452 config HAVE_ARCH_HUGE_VMAP
 453         bool
 454
 455 config HAVE_ARCH_SOFT_DIRTY
 456         bool
 457
 458 config HAVE_MOD_ARCH_SPECIFIC
 459         bool
 460         help
 461           The arch uses struct mod_arch_specific to store data.  Many arches
 462           just need a simple module loader without arch specific data - those
 463           should not enable this.
 464
 465 config MODULES_USE_ELF_RELA
 466         bool
 467         help
 468           Modules only use ELF RELA relocations.  Modules with ELF REL
 469           relocations will give an error.
 470
 471 config MODULES_USE_ELF_REL
 472         bool
 473         help
 474           Modules only use ELF REL relocations.  Modules with ELF RELA
 475           relocations will give an error.
 476
 477 config HAVE_UNDERSCORE_SYMBOL_PREFIX
 478         bool
 479         help
 480           Some architectures generate an _ in front of C symbols; things like
 481           module loading and assembly files need to know about this.
 482
 483 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 484         bool
 485         help
 486           Architecture doesn't only execute the irq handler on the irq stack
 487           but also irq_exit(). This way we can process softirqs on this irq
 488           stack instead of switching to a new one when we call __do_softirq()
 489           in the end of an hardirq.
 490           This spares a stack switch and improves cache usage on softirq
 491           processing.
 492
 493 config PGTABLE_LEVELS
 494         int
 495         default 2
 496
 497 config ARCH_HAS_ELF_RANDOMIZE
 498         bool
 499         help
 500           An architecture supports choosing randomized locations for
 501           stack, mmap, brk, and ET_DYN. Defined functions:
 502           - arch_mmap_rnd()
 503           - arch_randomize_brk()
 504
 505 config HAVE_COPY_THREAD_TLS
 506         bool
 507         help
 508           Architecture provides copy_thread_tls to accept tls argument via
 509           normal C parameter passing, rather than extracting the syscall
 510           argument from pt_regs.
 511
 512 #
 513 # ABI hall of shame
 514 #
 515 config CLONE_BACKWARDS
 516         bool
 517         help
 518           Architecture has tls passed as the 4th argument of clone(2),
 519           not the 5th one.
 520
 521 config CLONE_BACKWARDS2
 522         bool
 523         help
 524           Architecture has the first two arguments of clone(2) swapped.
 525
 526 config CLONE_BACKWARDS3
 527         bool
 528         help
 529           Architecture has tls passed as the 3rd argument of clone(2),
 530           not the 5th one.
 531
 532 config ODD_RT_SIGACTION
 533         bool
 534         help
 535           Architecture has unusual rt_sigaction(2) arguments
 536
 537 config OLD_SIGSUSPEND
 538         bool
 539         help
 540           Architecture has old sigsuspend(2) syscall, of one-argument variety
 541
 542 config OLD_SIGSUSPEND3
 543         bool
 544         help
 545           Even weirder antique ABI - three-argument sigsuspend(2)
 546
 547 config OLD_SIGACTION
 548         bool
 549         help
 550           Architecture has old sigaction(2) syscall.  Nope, not the same
 551           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
 552           but fairly different variant of sigaction(2), thanks to OSF/1
 553           compatibility...
 554
 555 config COMPAT_OLD_SIGACTION
 556         bool
 557
 558 source "kernel/gcov/Kconfig"