diff --git a/include/gdb/ChangeLog b/include/gdb/ChangeLog
index 3a17b1d79..80a9e0650 100644
--- a/include/gdb/ChangeLog
+++ b/include/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2004-06-25  J"orn Rennecke <joern.rennecke@superh.com>
+
+	* callback.h (host_callback_struct): Replace members fdopen and
+	alwaysopen with fd_buddy.
+	[sim/common: * callback.c: Changed all users.  ]
+
 2003-10-31  Kevin Buettner  <kevin@redhat.com>
 
 	* sim-frv.h: New file.
diff --git a/include/gdb/callback.h b/include/gdb/callback.h
index 3fa419143..aa956d05f 100644
--- a/include/gdb/callback.h
+++ b/include/gdb/callback.h
@@ -123,8 +123,15 @@ struct host_callback_struct
   int last_errno;		/* host format */
 
   int fdmap[MAX_CALLBACK_FDS];
-  char fdopen[MAX_CALLBACK_FDS];
-  char alwaysopen[MAX_CALLBACK_FDS];
+  /* fd_buddy is used to contruct circular lists of target fds that point to
+     the same host fd.  A uniquely mapped fd points to itself; for a closed
+     one, fd_buddy has the value -1.  The host file descriptors for stdin /
+     stdout / stderr are never closed by the simulators, so they are put
+     in a special fd_buddy circular list which also has MAX_CALLBACK_FDS
+     as a member.  */
+  /* ??? We don't have a callback entry for dup, although it is trival to
+     implement now.  */
+  short fd_buddy[MAX_CALLBACK_FDS+1];
 
   /* System call numbers.  */
   CB_TARGET_DEFS_MAP *syscall_map;