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Fixes #113

Signed-off-by: Marcos Lilljedahl <marcosnils@gmail.com>

vendor/github.com/opencontainers/runc/libcontainer/system/xattrs_linux.go

@@ -0,0 +1,99 @@
+package system
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+var _zero uintptr
+
+// Returns the size of xattrs and nil error
+// Requires path, takes allocated []byte or nil as last argument
+func Llistxattr(path string, dest []byte) (size int, err error) {
+	pathBytes, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return -1, err
+	}
+	var newpathBytes unsafe.Pointer
+	if len(dest) > 0 {
+		newpathBytes = unsafe.Pointer(&dest[0])
+	} else {
+		newpathBytes = unsafe.Pointer(&_zero)
+	}
+
+	_size, _, errno := syscall.Syscall6(syscall.SYS_LLISTXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(newpathBytes), uintptr(len(dest)), 0, 0, 0)
+	size = int(_size)
+	if errno != 0 {
+		return -1, errno
+	}
+
+	return size, nil
+}
+
+// Returns a []byte slice if the xattr is set and nil otherwise
+// Requires path and its attribute as arguments
+func Lgetxattr(path string, attr string) ([]byte, error) {
+	var sz int
+	pathBytes, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return nil, err
+	}
+	attrBytes, err := syscall.BytePtrFromString(attr)
+	if err != nil {
+		return nil, err
+	}
+
+	// Start with a 128 length byte array
+	sz = 128
+	dest := make([]byte, sz)
+	destBytes := unsafe.Pointer(&dest[0])
+	_sz, _, errno := syscall.Syscall6(syscall.SYS_LGETXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(unsafe.Pointer(attrBytes)), uintptr(destBytes), uintptr(len(dest)), 0, 0)
+
+	switch {
+	case errno == syscall.ENODATA:
+		return nil, errno
+	case errno == syscall.ENOTSUP:
+		return nil, errno
+	case errno == syscall.ERANGE:
+		// 128 byte array might just not be good enough,
+		// A dummy buffer is used ``uintptr(0)`` to get real size
+		// of the xattrs on disk
+		_sz, _, errno = syscall.Syscall6(syscall.SYS_LGETXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(unsafe.Pointer(attrBytes)), uintptr(unsafe.Pointer(nil)), uintptr(0), 0, 0)
+		sz = int(_sz)
+		if sz < 0 {
+			return nil, errno
+		}
+		dest = make([]byte, sz)
+		destBytes := unsafe.Pointer(&dest[0])
+		_sz, _, errno = syscall.Syscall6(syscall.SYS_LGETXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(unsafe.Pointer(attrBytes)), uintptr(destBytes), uintptr(len(dest)), 0, 0)
+		if errno != 0 {
+			return nil, errno
+		}
+	case errno != 0:
+		return nil, errno
+	}
+	sz = int(_sz)
+	return dest[:sz], nil
+}
+
+func Lsetxattr(path string, attr string, data []byte, flags int) error {
+	pathBytes, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return err
+	}
+	attrBytes, err := syscall.BytePtrFromString(attr)
+	if err != nil {
+		return err
+	}
+	var dataBytes unsafe.Pointer
+	if len(data) > 0 {
+		dataBytes = unsafe.Pointer(&data[0])
+	} else {
+		dataBytes = unsafe.Pointer(&_zero)
+	}
+	_, _, errno := syscall.Syscall6(syscall.SYS_LSETXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(unsafe.Pointer(attrBytes)), uintptr(dataBytes), uintptr(len(data)), uintptr(flags), 0)
+	if errno != 0 {
+		return errno
+	}
+	return nil
+}