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

Locking – a quick summarization of key points

As mentioned just above, do refer to the Linux Kernel Programming – Part 2 book to brush up on the basics of locking within the Linux kernel (if you need to) – more importantly, on kernel-level debug techniques as well as guidelines on preventing and detecting dangerous locking bugs such as the deadly deadlock.

Nevertheless, I'd like to summarize some really key points with respect to locking here as well. Here they are:

  • A critical section is a code path that can execute in parallel and that works on (reads and/or writes) shared writeable data (also known as shared state).
  • Because it works on shared writable data, the critical section requires protection from the following:
    • Parallelism (that is, it must run alone, serialized, in a mutually exclusive fashion)
    • When running in an atomic (for example, interrupt) non-blocking context, it must run atomically: indivisibly, to completion, without interruption...