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

An introduction to kernel code coverage tools and testing frameworks

Code coverage is tooling that can identify which lines of code get executed during a run and which lines of code don't. Tools such as GNU coverage (gcov), and kcov and frontend tools such as lcov can be very valuable in gleaning this key information.

Why is code coverage important?

Here are a few typical reasons why you should (I'd go so far as to say must) perform code coverage:

  • Debugging: To help identify code paths that are never executed (error paths are pretty typical), thereby making it clear that you need test cases for them (to then catch bugs that lurk in such regions).
  • Testing/QA: Identify test cases that work and, more to the point, ones that need to be written in order to cover lines of code that never get executed, as, after all, 100% code coverage is the objective!
  • They can help with (minimal) kernel configuration. Seeing that certain code paths are never taken perhaps...