Book Image

Linux Kernel Debugging

By : Kaiwan N. Billimoria
Book Image

Linux Kernel Debugging

By: Kaiwan N. Billimoria

Overview of this book

The Linux kernel is at the very core of arguably the world’s best production-quality OS. Debugging it, though, can be a complex endeavor. Linux Kernel Debugging is a comprehensive guide to learning all about advanced kernel debugging. This book covers many areas in-depth, such as instrumentation-based debugging techniques (printk and the dynamic debug framework), and shows you how to use Kprobes. Memory-related bugs tend to be a nightmare – two chapters are packed with tools and techniques devoted to debugging them. When the kernel gifts you an Oops, how exactly do you interpret it to be able to debug the underlying issue? We’ve got you covered. Concurrency tends to be an inherently complex topic, so a chapter on lock debugging will help you to learn precisely what data races are, including using KCSAN to detect them. Some thorny issues, both debug- and performance-wise, require detailed kernel-level tracing; you’ll learn to wield the impressive power of Ftrace and its frontends. You’ll also discover how to handle kernel lockups, hangs, and the dreaded kernel panic, as well as leverage the venerable GDB tool within the kernel (KGDB), along with much more. By the end of this book, you will have at your disposal a wide range of powerful kernel debugging tools and techniques, along with a keen sense of when to use which.
Table of Contents (17 chapters)
1
Part 1: A General Introduction and Approaches to Kernel Debugging
4
Part 2: Kernel and Driver Debugging Tools and Techniques
11
Part 3: Additional Kernel Debugging Tools and Techniques

Chapter 10: Kernel Panic, Lockups, and Hangs

It's unpleasant – that queasy feeling deep in the pit of your stomach, the cold sweat forming on your brow – when you get that dreaded kernel panic message on the console, and those absolute, unforgiving pixels, with the hard cold eye of a god, tell you that the system is effectively dead:

Kernel panic - not syncing: [...]

Why, oh why? – your lamentations are futile. Unless, unless... you don't panic (pun intended), read this chapter, figure out what's going on (by writing your own custom panic handler to help with that), and get on with your life, dude!

In addition to understanding and dealing with kernel panics, we also delve into the causes of kernel lockups, hung tasks, stalls, and how to configure a kernel to detect them. In this chapter, we're going to cover the following main topics:

  • Panic! – what happens when a kernel panics
  • Writing a custom kernel panic handler...