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

Experimenting with the GRUB prompt

You could experiment further; instead of merely pressing Enter while on the Ubuntu, with Linux 5.4.0-llkd01 kernel's menu entry, ensure that this line is highlighted and press the e ke(for edit). We shall now enter GRUB's edit screen, wherein we are free to change any value we like. Here's a screenshot after pressing the e key:

Figure 3.5 – The GRUB2 bootloader – detail on the custom 5.4.0-llkd01 kernel

The screenshot has been taken after scrolling down a few lines; look carefully, you can spot the cursor (an underscore-like one, "_") at the very beginning of the third line from the bottom of the edit box. This is the crucial line; it starts with the suitably indented keyword linux. It specifies the list of kernel parameters being passed via the GRUB bootloader to the Linux kernel.

Try experimenting a bit here. As a simple example, delete the words quiet and splash from this entry, then press...