Introduction

Debugging is the process of analyzing the execution and state of a software program in order to remove defects. Traditional debugging tools provide facilities for execution control so that programmers can re-execute programs in a controlled environment and display the current state of program data or evaluate expressions in the source language used to develop the program. Unfortunately, these techniques are often inappropriate for debugging complex software systems such as:

• An operating system, where bugs might not be reproducible and program state is massive and distributed

• Programs that are highly optimized or have had their debug information removed

• Programs that are themselves low-level debugging tools

• Customer situations where the developer can only access post-mortem information

MDB is a tool that provides a completely customizable environment for debugging these programs and scenarios, including a dynamic module facility that programmers can use to implement their own debugging commands to perform program-specific analysis. Each MDB module can be used to examine the program in several different contexts, including live and post-mortem. The Solaris Operating Environment includes a set of MDB modules designed to aid programmers in debugging the Solaris kernel and related device drivers and kernel modules. Third-party developers might find it useful to develop and deliver their own debugging modules for supervisor or user software.