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

Tools and techniques to help determine the location of the Oops

While analyzing a kernel Oops, we can certainly use all the help we can get, right?! There are several tools and helper scripts that can be leveraged. Among them, and part of the (cross) toolchain, are the objdump, the GNU DeBugger (GDB), and addr2line programs. Besides them, a few kernel helper scripts (found within the kernel source tree) can prove very useful as well.

In this section, we'll start learning how to exploit these tools to help interpret an Oops.

Tip – Getting the Unstripped vmlinux Kernel Image with Debug Symbols

Many, if not most, of the tools and techniques to help debug kernel issues do depend on your having an unstripped uncompressed vmlinux kernel image with debug symbols. Now, if you've built both a debug and production kernel, as we've recommended from literally the outset of this book, you'll of course have the debug vmlinux kernel image file (which fulfills this...