github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/pkg/sync/runtime_unsafe.go (about)

     1  // Copyright 2020 The gVisor Authors.
     2  //
     3  // Use of this source code is governed by a BSD-style
     4  // license that can be found in the LICENSE file.
     5  
     6  // +build go1.13
     7  // +build !go1.18
     8  
     9  // Check go:linkname function signatures, type definitions, and constants when
    10  // updating Go version.
    11  
    12  package sync
    13  
    14  import (
    15  	"fmt"
    16  	"reflect"
    17  	"unsafe"
    18  )
    19  
    20  // Gopark is runtime.gopark. Gopark calls unlockf(pointer to runtime.g, lock);
    21  // if unlockf returns true, Gopark blocks until Goready(pointer to runtime.g)
    22  // is called. unlockf and its callees must be nosplit and norace, since stack
    23  // splitting and race context are not available where it is called.
    24  //
    25  //go:nosplit
    26  func Gopark(unlockf func(uintptr, unsafe.Pointer) bool, lock unsafe.Pointer, reason uint8, traceEv byte, traceskip int) {
    27  	gopark(unlockf, lock, reason, traceEv, traceskip)
    28  }
    29  
    30  //go:linkname gopark runtime.gopark
    31  func gopark(unlockf func(uintptr, unsafe.Pointer) bool, lock unsafe.Pointer, reason uint8, traceEv byte, traceskip int)
    32  
    33  // Goready is runtime.goready.
    34  //
    35  //go:nosplit
    36  func Goready(gp uintptr, traceskip int) {
    37  	goready(gp, traceskip)
    38  }
    39  
    40  //go:linkname goready runtime.goready
    41  func goready(gp uintptr, traceskip int)
    42  
    43  // Values for the reason argument to gopark, from Go's src/runtime/runtime2.go.
    44  const (
    45  	WaitReasonSelect      uint8 = 9
    46  	WaitReasonChanReceive uint8 = 14
    47  	WaitReasonSemacquire  uint8 = 18
    48  )
    49  
    50  // Values for the traceEv argument to gopark, from Go's src/runtime/trace.go.
    51  const (
    52  	TraceEvGoBlockRecv   byte = 23
    53  	TraceEvGoBlockSelect byte = 24
    54  	TraceEvGoBlockSync   byte = 25
    55  )
    56  
    57  // Rand32 returns a non-cryptographically-secure random uint32.
    58  func Rand32() uint32 {
    59  	return fastrand()
    60  }
    61  
    62  // Rand64 returns a non-cryptographically-secure random uint64.
    63  func Rand64() uint64 {
    64  	return uint64(fastrand())<<32 | uint64(fastrand())
    65  }
    66  
    67  //go:linkname fastrand runtime.fastrand
    68  func fastrand() uint32
    69  
    70  // RandUintptr returns a non-cryptographically-secure random uintptr.
    71  func RandUintptr() uintptr {
    72  	if unsafe.Sizeof(uintptr(0)) == 4 {
    73  		return uintptr(Rand32())
    74  	}
    75  	return uintptr(Rand64())
    76  }
    77  
    78  // MapKeyHasher returns a hash function for pointers of m's key type.
    79  //
    80  // Preconditions: m must be a map.
    81  func MapKeyHasher(m interface{}) func(unsafe.Pointer, uintptr) uintptr {
    82  	if rtyp := reflect.TypeOf(m); rtyp.Kind() != reflect.Map {
    83  		panic(fmt.Sprintf("sync.MapKeyHasher: m is %v, not map", rtyp))
    84  	}
    85  	mtyp := *(**maptype)(unsafe.Pointer(&m))
    86  	return mtyp.hasher
    87  }
    88  
    89  // maptype is equivalent to the beginning of runtime.maptype.
    90  type maptype struct {
    91  	size       uintptr
    92  	ptrdata    uintptr
    93  	hash       uint32
    94  	tflag      uint8
    95  	align      uint8
    96  	fieldAlign uint8
    97  	kind       uint8
    98  	equal      func(unsafe.Pointer, unsafe.Pointer) bool
    99  	gcdata     *byte
   100  	str        int32
   101  	ptrToThis  int32
   102  	key        unsafe.Pointer
   103  	elem       unsafe.Pointer
   104  	bucket     unsafe.Pointer
   105  	hasher     func(unsafe.Pointer, uintptr) uintptr
   106  	// more fields
   107  }
   108  
   109  // These functions are only used within the sync package.
   110  
   111  //go:linkname semacquire sync.runtime_Semacquire
   112  func semacquire(s *uint32)
   113  
   114  //go:linkname semrelease sync.runtime_Semrelease
   115  func semrelease(s *uint32, handoff bool, skipframes int)
   116  
   117  //go:linkname canSpin sync.runtime_canSpin
   118  func canSpin(i int) bool
   119  
   120  //go:linkname doSpin sync.runtime_doSpin
   121  func doSpin()