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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

The devil is in the details – decoding the Oops

We'll use the third scenario (or use/test case), covered in the section, Case 3 – Oops by writing to a structure member when the structure pointer's NULL. To quickly recap, this is what we did to trigger this particular kernel Oops (case #3):

cd ch7/oops_tryv2
make
sudo insmod ./oops_tryv2.ko bug_in_workq=yes

As seen earlier, it triggers an Oops. Now we get to the interesting part – deciphering the Oops, step by step, line by line.

Before starting, it's important to realize that the detailed discussion below is necessarily arch-specific, here and now pertaining to the x86_64 platform (as portions of the Oops output are, of course, very arch-specific). We shall also show how a typical Oops appears on the ARM platform in a later section.

Line-by-line interpretation of an Oops

The initial, and really key, portion of the Oops we get is seen in Figure 7.5. Now, to help refer to it line by...

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