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Introduction to Debugging the FreeBSD Kernel

John H. Baldwin

Yahoo!, Inc.

Atlanta, GA 30327


Just like every other piece of software, the FreeBSD kernel has bugs. Debugging a kernel is a bit different from debugging a userland program as there is nothing underneath the kernel to provide debugging facilities such as ptrace() or procfs. This paper will give a brief overview of some of the tools available for investigating bugs in the FreeBSD kernel. It will cover the in-kernel debugger DDB and the external debugger kgdb which is used to perform post-mortem analysis on kernel crash dumps.