1 files changed, 65 insertions, 0 deletions
diff --git a/src/pkg/syscall/syscall.go b/src/pkg/syscall/syscall.go
index 96975376f..2a9ffd4af 100644
--- a/src/pkg/syscall/syscall.go
+++ b/src/pkg/syscall/syscall.go
@@ -13,6 +13,11 @@
 // errno is an operating system error number describing the failure.
 package syscall
 
+import (
+	"sync"
+	"unsafe"
+)
+
 // StringByteSlice returns a NUL-terminated slice of bytes
 // containing the text of s.
 func StringByteSlice(s string) []byte {
@@ -28,3 +33,63 @@ func StringBytePtr(s string) *byte { return &StringByteSlice(s)[0] }
 // Single-word zero for use when we need a valid pointer to 0 bytes.
 // See mksyscall.sh.
 var _zero uintptr
+
+// Mmap manager, for use by operating system-specific implementations.
+
+type mmapper struct {
+	sync.Mutex
+	active map[*byte][]byte // active mappings; key is last byte in mapping
+	mmap   func(addr, length uintptr, prot, flags, fd int, offset int64) (uintptr, int)
+	munmap func(addr uintptr, length uintptr) int
+}
+
+func (m *mmapper) Mmap(fd int, offset int64, length int, prot int, flags int) (data []byte, errno int) {
+	if length <= 0 {
+		return nil, EINVAL
+	}
+
+	// Map the requested memory.
+	addr, errno := m.mmap(0, uintptr(length), prot, flags, fd, offset)
+	if errno != 0 {
+		return nil, errno
+	}
+
+	// Slice memory layout
+	var sl = struct {
+		addr uintptr
+		len  int
+		cap  int
+	}{addr, length, length}
+
+	// Use unsafe to turn sl into a []byte.
+	b := *(*[]byte)(unsafe.Pointer(&sl))
+
+	// Register mapping in m and return it.
+	p := &b[cap(b)-1]
+	m.Lock()
+	defer m.Unlock()
+	m.active[p] = b
+	return b, 0
+}
+
+func (m *mmapper) Munmap(data []byte) (errno int) {
+	if len(data) == 0 || len(data) != cap(data) {
+		return EINVAL
+	}
+
+	// Find the base of the mapping.
+	p := &data[cap(data)-1]
+	m.Lock()
+	defer m.Unlock()
+	b := m.active[p]
+	if b == nil || &b[0] != &data[0] {
+		return EINVAL
+	}
+
+	// Unmap the memory and update m.
+	if errno := m.munmap(uintptr(unsafe.Pointer(&b[0])), uintptr(len(b))); errno != 0 {
+		return errno
+	}
+	m.active[p] = nil, false
+	return 0
+}