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Linux Kernel Debugging

Linux Kernel Debugging

By : Kaiwan N. Billimoria
4.8 (6)
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Linux Kernel Debugging

Linux Kernel Debugging

4.8 (6)
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)
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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

Generating a simple kernel bug and Oops

You've heard the quote It takes a thief to catch a thief. So, let's first learn how to generate a kernel bug (it shouldn't be too much of a challenge).

As you'll know, the classic pedagogical bug is the (in)famous NULL pointer dereference (the upcoming section, What's this NULL trap page anyway? elaborates on it). So, here's the plan:

  • We'll first write a very simple kernel module that performs the cardinal sin of dereferencing the NULL pointer (the address 0x0). We'll call it our version 1 oops_tryv1 module.
  • Once you try it out, we'll move on to a slightly more sophisticated version 2 oops_tryv2 module. Within it, we'll provide three distinct ways to generate an Oops!

Before embarking on our generate-an-Oops quest, let's better understand what the procmap utility does and what the NULL trap page is. First, let's go with the utility.

The procmap utility

Being...

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