Info Catalog gdb: Overlay Commands gdb: Overlays gdb: Overlay Sample Program

gdb: Automatic Overlay Debugging

 
 14.3 Automatic Overlay Debugging
 ================================
 
 GDB can automatically track which overlays are mapped and which are not,
 given some simple co-operation from the overlay manager in the inferior.
 If you enable automatic overlay debugging with the 'overlay auto'
 command (Overlay Commands), GDB looks in the inferior's memory
 for certain variables describing the current state of the overlays.
 
    Here are the variables your overlay manager must define to support
 GDB's automatic overlay debugging:
 
 '_ovly_table':
      This variable must be an array of the following structures:
 
           struct
           {
             /* The overlay's mapped address.  */
             unsigned long vma;
 
             /* The size of the overlay, in bytes.  */
             unsigned long size;
 
             /* The overlay's load address.  */
             unsigned long lma;
 
             /* Non-zero if the overlay is currently mapped;
                zero otherwise.  */
             unsigned long mapped;
           }
 
 '_novlys':
      This variable must be a four-byte signed integer, holding the total
      number of elements in '_ovly_table'.
 
    To decide whether a particular overlay is mapped or not, GDB looks
 for an entry in '_ovly_table' whose 'vma' and 'lma' members equal the
 VMA and LMA of the overlay's section in the executable file.  When GDB
 finds a matching entry, it consults the entry's 'mapped' member to
 determine whether the overlay is currently mapped.
 
    In addition, your overlay manager may define a function called
 '_ovly_debug_event'.  If this function is defined, GDB will silently set
 a breakpoint there.  If the overlay manager then calls this function
 whenever it has changed the overlay table, this will enable GDB to
 accurately keep track of which overlays are in program memory, and
 update any breakpoints that may be set in overlays.  This will allow
 breakpoints to work even if the overlays are kept in ROM or other
 non-writable memory while they are not being executed.
 

Info Catalog gdb: Overlay Commands gdb: Overlays gdb: Overlay Sample Program