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)
Section 1: The Basics
Writing Your First Kernel Module - LKMs Part 2
Section 2: Understanding and Working with the Kernel
Kernel Memory Allocation for Module Authors - Part 1
Kernel Memory Allocation for Module Authors - Part 2
Section 3: Delving Deeper
About Packt

Generating the initramfs image – under the hood

Recall from the previous section what you will first see when the sudo make install command executes (reproduced as follows for your convenience):

$ sudo make install
sh ./arch/x86/boot/ 5.4.0-llkd01 arch/x86/boot/bzImage \ "/boot"

Clearly, it's ( a script being executed. Internally, as part of its work, it copies the following files into the /boot folder, with the name format typically being <filename>-$(uname -r):, initrd.img-5.4.0-llkd01, vmlinuz-5.4.0-llkd01, config-5.4.0-llkd01

The initramfs image is built as well. A shell script named update-initramfs performs this task (which is itself a convenience wrapper over another script called mkinitramfs(8) that performs the actual work). Once built, the initramfs image is also copied into the /boot directory, seen as initrd.img-5.4.0-llkd01 in the preceding output snippet.

If at all a file being copied...