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

Chapter 9: Tracing the Kernel Flow

Tracing is the ability to collect relevant details as code executes. Typically, data collected will include function names (and perhaps parameters and return values) of function calls made along the code path being followed, the context that issued the call, when the call was made (a timestamp), the duration of the function call, and so on. Tracing allows you to study and understand the detailed flow of a system or a component within it. It's akin to the black box in an aircraft – it simply collects data, allowing you to interpret and analyze it later. (You can also consider tracing to be loosely analogous to logging.)

Profiling is different from tracing in that it typically works by taking samples (of various interesting events/counters) at periodic points in time. It won't capture everything; it (usually) captures just enough to help with runtime performance analysis. A profile of code execution, a report, can usually be generated...