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

Creating a new menu item in the Kconfig file

As a trivial example, let's add our own Boolean dummy config option within the General Setup menu. We want the config name to be CONFIG_LLKD_OPTION1. As can be seen from the preceding table, the relevant Kconfig file to edit is the init/Kconfig one as this is the menu meta file that defines the General Setup menu.

Let's get to it:

  1. To be safe, always make a backup copy:
cp init/Kconfig init/Kconfig.orig
  1. Now, edit the init/Kconfig file:
vi init/Kconfig

Scroll down to an appropriate location within the file; here, we choose to insert our menu entry just after the CONFIG_LOCALVERSION_AUTO one. The following screenshot shows our new entry:

Figure 2.12 – Editing init/Kconfig and inserting our own menu entry
We have provided the preceding text as a patch to the original init/Kconfig file in our book's GitHub source tree. Find it under ch2/Kconfig.patch.

The new item starts with...