gdb: Writing JIT Debug Info Readers
29.4.2 Writing JIT Debug Info Readers
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As mentioned, a reader is essentially a shared object conforming to a
certain ABI. This ABI is described in 'jit-reader.h'.
'jit-reader.h' defines the structures, macros and functions required
to write a reader. It is installed (along with GDB), in
'INCLUDEDIR/gdb' where INCLUDEDIR is the system include directory.
Readers need to be released under a GPL compatible license. A reader
can be declared as released under such a license by placing the macro
'GDB_DECLARE_GPL_COMPATIBLE_READER' in a source file.
The entry point for readers is the symbol 'gdb_init_reader', which is
expected to be a function with the prototype
extern struct gdb_reader_funcs *gdb_init_reader (void);
'struct gdb_reader_funcs' contains a set of pointers to callback
functions. These functions are executed to read the debug info
generated by the JIT compiler ('read'), to unwind stack frames
('unwind') and to create canonical frame IDs ('get_Frame_id'). It also
has a callback that is called when the reader is being unloaded
('destroy'). The struct looks like this
struct gdb_reader_funcs
{
/* Must be set to GDB_READER_INTERFACE_VERSION. */
int reader_version;
/* For use by the reader. */
void *priv_data;
gdb_read_debug_info *read;
gdb_unwind_frame *unwind;
gdb_get_frame_id *get_frame_id;
gdb_destroy_reader *destroy;
};
The callbacks are provided with another set of callbacks by GDB to do
their job. For 'read', these callbacks are passed in a 'struct
gdb_symbol_callbacks' and for 'unwind' and 'get_frame_id', in a 'struct
gdb_unwind_callbacks'. 'struct gdb_symbol_callbacks' has callbacks to
create new object files and new symbol tables inside those object files.
'struct gdb_unwind_callbacks' has callbacks to read registers off the
current frame and to write out the values of the registers in the
previous frame. Both have a callback ('target_read') to read bytes off
the target's address space.
Info Catalog
gdb: Using JIT Debug Info Readers
gdb: Custom Debug Info