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

Summary

In this chapter, you learned – to a good level of detail – how both the page (or buddy system) as well as the slab allocators work. Recall that the actual "engine" of allocating (and freeing) RAM within the kernel is ultimately the page (or buddy system) allocator, the slab allocator being layered on top of it to provide optimization for typical less-than-a-page-in-size allocation requests and to efficiently allocate several well-known kernel data structures ('objects').

You learned how to efficiently use the APIs exposed by both the page and slab allocators, with several demo kernel modules to help show this in a hands-on manner. A good deal of focus was (quite rightly) given to the real issue of the developer issuing a memory request for a certain N number of bytes, but you learned that it can be very sub-optimal, with the kernel actually allocating much more (the wastage can climb to very close to 100%)! You now know how to check...