29.2 Registering Code

To register code with GDB, the JIT should follow this protocol:

• Generate an object file in memory with symbols and other desired debug information. The file must include the virtual addresses of the sections.
• Create a code entry for the file, which gives the start and size of the symbol file.
• Add it to the linked list in the JIT descriptor.
• Point the relevant_entry field of the descriptor at the entry.
• Set action_flag to JIT_REGISTER and call __jit_debug_register_code.

When GDB is attached and the breakpoint fires, GDB uses the relevant_entry pointer so it doesn’t have to walk the list looking for new code. However, the linked list must still be maintained in order to allow GDB to attach to a running process and still find the symbol files.