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

Setting up an ARM target system and kernel for KGDB

When a Linux kernel is built, a couple of arch-specific kernel image files are generated: the uncompressed kernel image file, vmlinux, along with the compressed kernel image, found within the arch/<your-arch>/boot directory and named bzImage or zImage, and so on. The latter is always the image with which the Linux OS is booted. Both these kernel image files are rendered in the usual Executable and Linker Format (ELF), thus they're amenable to being used with a variety of tooling on Linux, including GDB. So, if we use GDB to interpret the kernel's uncompressed vmlinux file, it should work. Practically speaking, though, without debug symbolic information embedded within this file, it's a lot less useful. What we really require for kernel debug purposes using KGDB is the target's uncompressed vmlinux kernel image along with debug symbolic information and the kernel symbols within it. This is achieved by enabling...