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

Selecting an appropriate API for kernel memory allocation

With all this choice of APIs, how do we choose? Though we have already talked about this very case in this chapter as well as the previous one, we'll again summarize it as it's very important. Broadly speaking, there are two ways to look at it – the API to use depends upon the following:

  • The amount of memory required
  • The type of memory required

We will illustrate both cases in this section.

First, to decide which API to use by the type, amount, and contiguity of the memory to be allocated, scan through the following flowchart (starting at the upper right from the label Start here):

Figure 9.7 – Decision flowchart for which kernel memory allocation API(s) to use for a module/driver

Of course, it's not trivial; not only that, I'd like to remind you to recall the detailed discussions we covered earlier in this chapter, including the GFP flags to use (and the do not sleep in atomic...