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 5: Debugging Kernel Memory Issues – Part 1

There's no doubt about it, C (and C++) is a really powerful programming language, one that allows the developer to straddle both high-level layered abstractions (after all, object-oriented languages such as Java and Python are written in C) as well as to work upon the bare metal, as it were. This is fantastic. Of course, there's a price to pay: the compiler will do only so much. You want to overflow a memory buffer? Go ahead, it doesn't care. Want to peek at or poke an unmapped memory region? No problem.

Well, no problem for the compiler, but big problems for us! This is nothing new really. We mentioned just this in Chapter 2, Approaches to Kernel Debugging. C being a procedural and non-managed programming language (in memory terms), it's ultimately the programmer's responsibility to ensure that runtime memory usage is correct and well behaved.

The Linux kernel is almost entirely written in C ...