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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

Debugging the kernel with KGDB

By now, I'll assume that you've configured and built a Linux target system suitable for KGDB (as described in detail in the previous section). It could be for any machine, including a guest system... Here, we'll continue to use the SEALS-generated ARM32 VExpress platform that we just set up as the target.

The intention here is to demo debugging the kernel early in the boot process with KGDB. To do so, the GDB server component within the target kernel will have to make it wait early in the boot process. This is so that the remote GDB client can connect to it. Linux supplies a boot parameter to do precisely this – it's named kgdbwait. To use it, you need to have a KGDB I/O driver built into the kernel image and specify which one via the kgdboc boot parameter (for example, kgdboc=/dev/ttyS0). You can also set it up later (on the console) by echoing the device name into the pseudofile /sys/module/kgdboc/parameters/kgdboc.

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