1 files changed, 14 insertions, 0 deletions
diff --git a/libgo/go/os/error.go b/libgo/go/os/error.go
index e26ce27970..7235bfb6d6 100644
--- a/libgo/go/os/error.go
+++ b/libgo/go/os/error.go
@@ -14,6 +14,7 @@ var (
 	ErrPermission = errors.New("permission denied")
 	ErrExist      = errors.New("file already exists")
 	ErrNotExist   = errors.New("file does not exist")
+	ErrClosed     = errors.New("file already closed")
 )
 
 // PathError records an error and the operation and file path that caused it.
@@ -63,3 +64,16 @@ func IsNotExist(err error) bool {
 func IsPermission(err error) bool {
 	return isPermission(err)
 }
+
+// underlyingError returns the underlying error for known os error types.
+func underlyingError(err error) error {
+	switch err := err.(type) {
+	case *PathError:
+		return err.Err
+	case *LinkError:
+		return err.Err
+	case *SyscallError:
+		return err.Err
+	}
+	return err
+}