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

Summary

Most dynamic memory allocation (and freeing) in the kernel is done via the kernel's powerful slab (internally, SLUB) interfaces. To debug them, the kernel provides a strong SLUB debug framework and several associated utilities (slabtop, slabratetop [-bpfcc], vmstat, and so on). Here, you learned how to catch SLUB bugs via the kernel's SLUB debug framework as well as how to leverage these utilities.

Among memory bugs, the very mention of the leakage defect raises dread and fear, even in very experienced developers! It's a deadly one indeed, as we (hopefully) showed you in the Can I see some real kernel memory leakage bugs? section! The kernel's powerful kmemleak framework can catch these dangerous leakage bugs. Be sure to test your product (for long durations) with it running!

As we covered these tools and frameworks, we tabulated the results, showing you the bugs a given tool can (or cannot) catch. To then summarize the whole thing, we built a larger...