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Kernel Workspace Setup

Hello, and welcome to this book on learning Linux kernel development. To get the most out of this book, it is very important that you first set up the workspace environment that we will be using throughout the book. This chapter will teach you exactly how to do this and get started.

We will install a recent Linux distribution, preferably as a Virtual Machine (VM), and set it up to include all the required software packages. We will also clone this book's code repository on GitHub, and learn about a few useful projects that will help along this journey.

The best way to learn something is to do so empirically – not taking anyone's word on anything at all, but trying it out and experiencing it for yourself. Hence, this book gives you many hands-on experiments and kernel code examples that you can and indeed must try out yourself; this will greatly aid in your making real progress and deeply learning and understanding various aspects of Linux kernel and driver development. So, let's begin!

This chapter will take us through the following topics, which will help us set up our environment:

Running Linux as a guest VM
Setting up the software – distribution and packages
A few additional useful projects

Technical requirements

You will need a modern desktop PC or laptop. Ubuntu Desktop specifies the following as "recommended system requirements" for the installation and usage of the distribution:

A 2 GHz dual core processor or better.
RAM:
- Running on physical host: 2 GB or more system memory (more will certainly help).
- Running as a guest VM: The host system should have at least 4 GB RAM (the more the better and the smoother the experience).
25 GB of free hard drive space (I suggest more, at least double this).
Either a DVD drive or a USB port for the installer media (not required when setting up Ubuntu as a guest VM).
Internet access is definitely helpful and required at times.

As performing tasks such as building a Linux kernel from source is a very memory- and CPU-intensive process, I highly recommend that you try it out on a powerful Linux system with plenty of RAM and disk space to spare as well. It should be pretty obvious – the more RAM and CPU power the host system has, the better!

Like any seasoned kernel contributor, I would say that working on a native Linux system is best. However, for the purposes of this book, we cannot assume that you will always have a dedicated native Linux box available to you. So, we will assume that you are working on a Linux guest. Working within a guest VM also adds an additional layer of isolation and thus safety.

Cloning our code repository: The complete source code for this book is freely available on GitHub at https://github.com/PacktPublishing/Linux-Kernel-Programming. You can clone and work on it by cloning the git tree, like so:

git clone https://github.com/PacktPublishing/Linux-Kernel-Programming.git

The source code is organized chapter-wise. Each chapter is represented as a directory – for example, ch1/ has the source code for this chapter. The root of the source tree has some code that is common to all chapters, such as the source files convenient.h, klib_llkd.c, as well as others.

For efficient code browsing, I would strongly recommend that you always index the code base with ctags(1) and/or cscope(1). For example, to set up the ctags index, just cd to the root of the source tree and type ctags -R .

Unless noted otherwise, the code output we show in the book is the output as seen on an x86-64 Ubuntu 18.04.3 LTS guest VM (running under Oracle VirtualBox 6.1). You should realize that due to (usually minor) distribution – and even within the same distributions but differing versions – differences, the output shown here may not perfectly match what you see on your Linux system.

Turn on your x86 system's virtualization extension support

Installing a 64-bit Linux guest requires that CPU virtualization extension support (Intel VT-x or AMD-SV) be turned on within the host system's basic input/output system (BIOS) settings. Let's see how to do this:

Our first step is to ensure that our CPU supports virtualization:
1. There are two broad ways to check this while on a Windows host:
  - One, run the Task Manager app and switch to the Performance tab. Below the CPU graph, you will see, among several other things, Virtualization, with Enabled or Disabled following it.
  - A second way to check on Windows systems is to open a Command window (cmd). In Command Prompt, type systeminfo and press Enter. Among the output seen will be the Virtualization Enabled in firmware line. It will be followed by either Yes or No.
2. To check this while on a Linux host, from Terminal, issue the following commands (processor virtualization extension support: vmx is the check for Intel processors, smv is the check for AMD processors):

egrep --color "vmx|svm" /proc/cpuinfo

For Intel CPUs, the vmx flag will show up (in color) if virtualization is supported. In the case of AMD CPUs, svm will show up (in color). With this, we know that our CPU supports virtualization. But in order to use it, we need to enable it in the computer BIOS.

Enter the BIOS by pressing Del or F12 while booting (the precise key to press varies with the BIOS). Please refer to your system's manual to see which key to use. Search for terms such as Virtualization or Virtualization Technology (VT-x). Here is an example for Award BIOS:

Figure 1.1 – Setting the BIOS Virtualization option to the Enabled state

If you are using an Asus EFI-BIOS, you will have to set the entry to [Enabled] if it is not set by default. Visit https://superuser.com/questions/367290/how-to-enable-hardware-virtualization-on-asus-motherboard/375351#375351.

Now, choose to use hardware virtualization in VirtualBox's Settings menu for your VM. To do this, click on System and then Acceleration. After that, check the boxes, as shown in the following screenshot:

Figure 1.2 – Enabling hardware virtualization options within the VirtualBox VM settings

This is how we enable our host processor's hardware virtualization features for optimal performance.

Install the Oracle VirtualBox Guest Additions

For best performance, it's important to install the Oracle VirtualBox Guest Additions as well within the guest VM. These are essentially para-virtualization accelerator software, which greatly helps with optimal performance. Let's see how to do this on an Ubuntu guest session:

First, update your Ubuntu guest OS's software packages. You can do so using the following command:

sudo apt update

sudo apt upgrade

On completion, reboot your Ubuntu guest OS and then install the required packages using the following command:

sudo apt install build-essential dkms linux-headers-$(uname -r)

Now, from the VM menu bar, go to Devices | Insert Guest Additions CD image.... This will mount the Guest Additions ISO file inside your VM. The following screenshot shows what it looks like doing this:

Figure 1.3 – VirtualBox | Devices | Insert Guest Additions CD image

Now, a dialog window will pop up that will prompt you to run the installer in order to launch it. Select Run.
The Guest Additions installation will now take place in a Terminal window that shows up. Once complete, hit the Enter key to close the window. Then, power off your Ubuntu guest OS in order to change some settings from the VirtualBox manager, as explained next.

Now, to enable Shared Clipboard and Drag'n'Drop functionalities between the guest and host machines, go to General | Advanced and enable the two options (Shared Clipboard and Drag'n'Drop) as you wish with the dropdowns:

Figure 1.4 – VirtualBox: enabling functionality between the host and guest

Then, click OK to save the settings. Now boot into your guest system, log in, and test that everything is working fine.

As of the time of writing, Fedora 29 has an issue with the installation of the vboxsf kernel module required for the Shared Folders feature. I refer you to the following resource to attempt to rectify the situation: Bug 1576832 - virtualbox-guest-additions does not mount shared folder (https://bugzilla.redhat.com/show_bug.cgi?id=1576832).

If this refuses to work, you can simply transfer files between your host and guest VM over SSH (using scp(1)); to do so, install and start up the SSH daemon with the following commands:
sudo yum install openssh-server
sudo systemctl start sshd

Remember to update the guest VM regularly and when prompted. This is an essential security requirement. You can do so manually by using the following:

sudo /usr/bin/update-manager

Finally, to be safe, please do not keep any important data on the guest VM. We will be working on kernel development. Crashing the guest kernel is actually a commonplace occurrence. While this usually does not cause data loss, you can never tell! To be safe, always back up any important data. This applies to Fedora as well. To learn how to install Fedora as a VirtualBox guest, visit https://fedoramagazine.org/install-fedora-virtualbox-guest/.

Sometimes, especially when the overhead of the X Window System (or Wayland) GUI is too high, it's preferable to simply work in console mode. You can do so by appending 3 (the run level) to the kernel command line via the bootloader. However, working in console mode within VirtualBox may not be that pleasant an experience (for one, the clipboard is unavailable, and the screen size and fonts are less than desirable). Thus, simply doing a remote login (via ssh, putty, or equivalent) into the VM from the host system can be a great way to work.

Key benefits

Discover how to write kernel code using the Loadable Kernel Module framework

Explore industry-grade techniques to perform efficient memory allocation and data synchronization within the kernel

Understand the essentials of key internals topics such as kernel architecture, memory management, CPU scheduling, and kernel synchronization

Description

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.

Who is this book for?

This book is for Linux programmers beginning to find their way with Linux kernel development. If you’re a Linux kernel and driver developer looking to overcome frequent and common kernel development issues, or understand kernel intervals, you’ll find plenty of useful information. You’ll need a solid foundation of Linux CLI and C programming before you can jump in.

What you will learn

Write high-quality modular kernel code (LKM framework) for 5.x kernels

Configure and build a kernel from source

Explore the Linux kernel architecture

Get to grips with key internals regarding memory management within the kernel

Understand and work with various dynamic kernel memory alloc/dealloc APIs

Discover key internals aspects regarding CPU scheduling within the kernel

Gain an understanding of kernel concurrency issues

Find out how to work with key kernel synchronization primitives

What do you get with Print?

Instant access to your digital copy whilst your Print order is Shipped

Paperback book shipped to your preferred address

Redeem a companion digital copy on all Print orders

Access this title in our online reader with advanced features

DRM FREE - Read whenever, wherever and however you want

AI Assistant (beta) to help accelerate your learning

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Linux Kernel Programming Part 2 - Char Device Drivers and Kernel Synchronization

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Andreas Hecht May 31, 2021

This book covers the vast field that is Linux Kernel Programming with sufficient amount of detail needed for module/driver development. The book is a hands-on guide as each chapter features example code, designed to illustrate the presented topics, which you can try out for yourself. Along with the code come questions (with solutions), exercises and a very well composed 'Further Reading' list, all of which you can download from the books GitHub repository. The book starts with fundamentals such as 'Building the Linux Kernel from Source' and 'Writing Your First Kernel Module' and leads to advanced topics such as memory management, scheduling and synchronization/concurrency. Thanks to the easy to follow instructions, this book is for anyone with a minimal amount of experience with Linux, C and embedded-/low-level-programming. Aside from the sound technical expertise this book brings to the table, it is written in a style that is inspiring and motivational. This book is actually fun to read and I would recommend it to anyone who would like to learn the skills and knowledge needed to become a Linux Kernel developer.

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David Conteh May 19, 2022

Great book. Well written and easy to follow.

Swaran May 30, 2021

I was trying to find out a book with latest linux kernel development. Most of the available books are outdated. Finally found this book. This book provide the study material for which I was waiting since long. Book is written in clear and precise manner and guide the reader for "learning by doing" methodology.Complete book is divide into three sections1. First section explains about setting up the development environment, how to build linux kernel(of-course kernel 5.x) from source, how to write the kernel module2. Second section give in-depth understanding about kernel internals, processes, threads, memory management internals, kernel memory allocation, and deep understanding of CPU Schedulers.3. Third section goes even more deeper and explain about kernel synchronisation- critical sections, mutex and spinlock, debugging of locks in kernel.

Shashank Apr 06, 2021

I met this guy and he is the most genuine person who has knowledge on kernel in depth. Read his book and helps me to brush the concepts and gives more charity on various topics such as memory management, cpu scheduling, interrupts, task structure, driver related concepts and many things. you will find the latest information as compare to other LDD books.definetly recommend this book to all who wants to deep dive into coding level, kernel concepts.

Nayana Rao Mar 23, 2021

If you are looking for a comprehensive guide to Linux kernel and it’s configuration for a custom platform, I highly recommend this book. The book is very detailed and comes with the Github source base with a lot of sample codes to assist you.Disclaimer: I have helped with the technical review of this book.

Linux Kernel Programming: A comprehensive guide to kernel internals, writing kernel modules, and kernel synchronization

What do you get with Print?

Linux Kernel Programming

Technical requirements

Running Linux as a guest VM

Installing a 64-bit Linux guest

Turn on your x86 system's virtualization extension support

Allocate sufficient space to the disk

Install the Oracle VirtualBox Guest Additions

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