The 7 dwarves: debugging information beyond gdb Arnaldo Carvalho de Melo Red Hat, Inc.
[email protected] [email protected] Abstract • To find out possibilities for reduction of such data structures; The DWARF debugging information format has been so • Use of information about function parameters and far used in debuggers such as gdb, and more recently in return types to generate Linux kernel modules for tools such as systemtap and frysk. obtaining data needed for generation of callgraphs In this paper the author will show additional scenarios and values set to fields at runtime; where such information can be useful, such as: • A tool that given two object files shows a binary diff to help understanding the effects of source • Showing the layout of data structures; code changes on size of functions and data struc- tures. • Reorganizing such data structures to remove align- ment holes; Some use cases will be presented, showing how the tools • Improving CPU cache utilization; can be used to solve real world problems. • Displaying statistics about inlining of functions; Ideas discussed with some fellow developers but not yet • Re-creating structs and functions from the debug- tried will also be presented, with the intent of hopefully ging information; having them finally tested in practice by interested read- ers. • Showing binary diffs to help understand the effects of any code change. 2 DWARF Debugging Format And much more. DWARF [3] is a debugging file format used by many compilers to store information about data structures, 1 Introduction variables, functions and other language aspects needed by high level debuggers.