This first patch of the reverse debugging sequence affects
only the target_ops interface (adding several target methods
and some enums and such).  

Adding this patch alone does not affect gdb's behavior, and 
I have run testsuites under RHEL with no change in results.


2008-09-30  Michael Snyder  <msnyder@vmware.com>
	Target interface for reverse debugging.
	* target.h (enum target_waitkind): 
	Add new wait event, TARGET_WAITKIND_NO_HISTORY.
	(enum exec_direction_kind): New enum.
	(struct target_ops): New methods to_set_execdir, to_get_execdir.
	* target.c (target_get_execdir): New generic method.
	(target_set_execdir): Ditto.

Index: target.c
===================================================================
RCS file: /cvs/src/src/gdb/target.c,v
retrieving revision 1.184
diff -u -p -r1.184 target.c
--- target.c	22 Sep 2008 15:21:30 -0000	1.184
+++ target.c	30 Sep 2008 18:19:00 -0000
@@ -455,6 +455,8 @@ update_current_target (void)
       INHERIT (to_find_memory_regions, t);
       INHERIT (to_make_corefile_notes, t);
       INHERIT (to_get_thread_local_address, t);
+      INHERIT (to_get_execdir, t);
+      INHERIT (to_set_execdir, t);
       /* Do not inherit to_read_description.  */
       /* Do not inherit to_search_memory.  */
       INHERIT (to_magic, t);
Index: target.h
===================================================================
RCS file: /cvs/src/src/gdb/target.h,v
retrieving revision 1.130
diff -u -p -r1.130 target.h
--- target.h	19 Aug 2008 13:22:14 -0000	1.130
+++ target.h	30 Sep 2008 18:19:00 -0000
@@ -128,7 +128,11 @@ enum target_waitkind
        inferior, rather than being stuck in the remote_async_wait()
        function. This way the event loop is responsive to other events,
        like for instance the user typing.  */
-    TARGET_WAITKIND_IGNORE
+    TARGET_WAITKIND_IGNORE,
+
+    /* The target has run out of history information,
+       and cannot run backward any further.  */
+    TARGET_WAITKIND_NO_HISTORY
   };
 
 struct target_waitstatus
@@ -147,6 +151,14 @@ struct target_waitstatus
     value;
   };
 
+/* Reverse execution.  */
+enum exec_direction_kind
+  {
+    EXEC_FORWARD,
+    EXEC_REVERSE,
+    EXEC_ERROR
+  };
+
 /* Possible types of events that the inferior handler will have to
    deal with.  */
 enum inferior_event_type
@@ -523,6 +535,11 @@ struct target_ops
 			     const gdb_byte *pattern, ULONGEST pattern_len,
 			     CORE_ADDR *found_addrp);
 
+    /* Set execution direction (forward/reverse).  */
+    int (*to_set_execdir) (enum exec_direction_kind);
+    /* Get execution direction (forward/reverse).  */
+    enum exec_direction_kind (*to_get_execdir) (void);
+
     int to_magic;
     /* Need sub-structure for target machine related rather than comm related?
      */
@@ -1127,6 +1144,18 @@ extern int target_stopped_data_address_p
 #define target_watchpoint_addr_within_range(target, addr, start, length) \
   (*target.to_watchpoint_addr_within_range) (target, addr, start, length)
 
+/* Forward/reverse execution direction.
+   These will only be implemented by a target that supports reverse execution.
+*/
+#define target_get_execution_direction() \
+    (current_target.to_get_execdir ? \
+     (*current_target.to_get_execdir) () : EXEC_ERROR)
+
+#define target_set_execution_direction(DIR) \
+    (current_target.to_set_execdir ? \
+     (*current_target.to_set_execdir) (DIR) : EXEC_ERROR)
+
+
 extern const struct target_desc *target_read_description (struct target_ops *);
 
 /* Utility implementation of searching memory.  */