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

Why the initramfs framework?

The initramfs framework is essentially a kind of middle-man between the early kernel boot and usermode. It allows us to run user space applications (or scripts) before the actual root filesystem has been mounted. This is useful in many circumstances, a couple of which are detailed in the following list. The key point is that initramfs allows us to run user mode apps that the kernel cannot normally run during boot time.

Practically speaking, among various uses, this framework allows us to do things including the following:

  • Set up a console font.
  • Customize keyboard layout settings.
  • Print a custom welcome message on the console device.
  • Accept a password (for encrypted disks).
  • Load up kernel modules as required.
  • Spawn a "rescue" shell if something fails.
  • And many more!

Imagine for a moment that you are in the business of building and maintaining a new Linux distribution. Now, at installation time, the end user of your distribution might decide...