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

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:

  1. 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.

  1. 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.
  1. 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.