Book Image

Linux Kernel Programming

By : Kaiwan N. Billimoria
Book Image

Linux Kernel Programming

By: Kaiwan N. Billimoria

Overview of this book

Linux Kernel Programming is a comprehensive introduction for those new to Linux kernel and module development. This easy-to-follow guide will have you up and running with writing kernel code in next-to-no time. This book uses the latest 5.4 Long-Term Support (LTS) Linux kernel, which will be maintained from November 2019 through to December 2025. By working with the 5.4 LTS kernel throughout the book, you can be confident that your knowledge will continue to be valid for years to come. You’ll start the journey by learning how to build the kernel from the source. Next, you’ll write your first kernel module using the powerful Loadable Kernel Module (LKM) framework. The following chapters will cover key kernel internals topics including Linux kernel architecture, memory management, and CPU scheduling. During the course of this book, you’ll delve into the fairly complex topic of concurrency within the kernel, understand the issues it can cause, and learn how they can be addressed with various locking technologies (mutexes, spinlocks, atomic, and refcount operators). You’ll also benefit from more advanced material on cache effects, a primer on lock-free techniques within the kernel, deadlock avoidance (with lockdep), and kernel lock debugging techniques. By the end of this kernel book, you’ll have a detailed understanding of the fundamentals of writing Linux kernel module code for real-world projects and products.
Table of Contents (19 chapters)
1
Section 1: The Basics
6
Writing Your First Kernel Module - LKMs Part 2
7
Section 2: Understanding and Working with the Kernel
10
Kernel Memory Allocation for Module Authors - Part 1
11
Kernel Memory Allocation for Module Authors - Part 2
14
Section 3: Delving Deeper
17
About Packt

Understanding the basics of a kernel module Makefile

You will have noticed that we tend to follow a one-kernel-module-per-directory rule of sorts. Yes, that definitely helps keep things organized. So, let's take our second kernel module, the ch4/printk_loglvl one. To build it, we just cd to its folder, type makeand (fingers crossed!) voilà, it's done. We have the printk_loglevel.ko kernel module object freshly generated (which we can then insmod(8)/rmmod(8)). But how exactly did it get built when we typed make? Ah, explaining this is the purpose of this section.

As this is our very first chapter that deals with the LKM framework and its corresponding Makefile, we will keep things nice and simple, especially with regard to the Makefile here. However, early in the following chapter, we shall introduce a more sophisticated, simply better Makefile (that is still quite simple to understand). We shall then use this better Makefile in...