Fix umovestr of unmapped page for UnixWare
diff --git a/util.c b/util.c
index 595b847..c59d25a 100644
--- a/util.c
+++ b/util.c
@@ -711,7 +711,7 @@
 
 	while (left) {
 		if (move > left) move = left;
-		if ((move = read(fd, laddr, move)) == -1)
+		if ((move = read(fd, laddr, move)) <= 0)
 			return left != len ? 0 : -1;
 		if (memchr (laddr, 0, move)) break;
 		left -= move;