To get the most out of this book

To get the most out of this book, we expect the following:

• You need to know your way around a Linux system, on the command line (the shell).
• You need to know the C programming language.
• It’s not mandatory, but experience with Linux system programming concepts and technologies will greatly help.

The details on hardware and software requirements, as well as their installation, are covered completely and in depth in Online Chapter, Kernel Workspace Setup. It’s critical that you read it in detail and follow the instructions therein.

Also, we have tested all the code in this book (it has its own GitHub repository) on these platforms:

• x86_64 Ubuntu 22.04 LTS and guest OS (running on Oracle VirtualBox 7.0)
• x86_64 Ubuntu 23.04 LTS guest OS (running on Oracle VirtualBox 7.0)
• x86_64 Fedora 38 (and 39) on a native (laptop) system
• ARM Raspberry Pi 4 Model B (64-bit, running both its “distro” kernel as well as our custom 6.1 kernel); lightly tested

We assume that, when running Linux as a guest (VM), the host system is either Windows 10 or later (of course, even Windows 7 will work), a recent Linux distribution (for example, Ubuntu or Fedora), or even macOS.

If you are using the digital version of this book, we advise you to type the code yourself or, much better, access the code via the GitHub repository (link available in the next section). Doing so will help you avoid any potential errors related to the copying and pasting of code.

I strongly recommend that you follow the empirical approach: 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 must try out yourself; this will greatly aid you in making real progress, deepening your understanding of the various aspects of Linux kernel development.

Download the example code files

You can download the example code files for this book from GitHub at https://github.com/PacktPublishing/Linux-Kernel-Programming_2E. If there’s an update to the code, it will be updated on the existing GitHub repository. (So be sure to regularly do a “git pull” as well to stay up to date.)

We also have other code bundles from our rich catalog of books and videos available at https://github.com/PacktPublishing/. Check them out!

Download the color images

We also provide a PDF file that has color images of the screenshots/diagrams used in this book. You can download it here: https://packt.link/gbp/9781803232225.

Conventions used

There are a number of text conventions used throughout this book.

CodeInText: Indicates code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles. Here is an example: “The ioremap() API returns a KVA of the void * type (since it’s an address location).”

A block of code is set as follows:

static int __init miscdrv_init(void)
{
    int ret;
    struct device *dev;

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

#if LINUX_VERSION_CODE < KERNEL_VERSION(5, 8, 0)
    vrx = __vmalloc(42 * PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL_RO);
    if (!vrx) {
        pr_warn("__vmalloc failed\n");
        goto err_out5;
    }
[ … ]

Any command-line input or output is written as follows:

pi@raspberrypi:~ $ sudo cat /proc/iomem

Bold: Indicates a new term, an important word, or words that you see onscreen. For instance, words in menus or dialog boxes appear in the text like this. Here is an example: “Select System info from the Administration panel.”