Index: btxld.c
===================================================================
--- btxld.c	(.../stable/7/usr.sbin/btxld)	(revision 192688)
+++ btxld.c	(.../head/usr.sbin/btxld)	(revision 192688)
@@ -336,6 +336,8 @@
     if (sb.st_size > MAXU32)
 	errx(1, "%s: Too big", fname);
     hdr->size = sb.st_size;
+    if (!hdr->size)
+	return;
     if ((p = mmap(NULL, hdr->size, PROT_READ, MAP_SHARED, fd,
 		  0)) == MAP_FAILED)
 	err(2, "%s", fname);