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

Viewing kernel documentation on the memory layout

Back to the kernel segment; obviously, with a 64-bit VAS, the kernel segment is much larger than on 32-bit. As we saw earlier, it's typically 128 TB on the x86_64. Study again the VM split table shown previously (Figure 7.4 in the section VM split on 64-bit Linux systems); there, the fourth column is the VM split for different architectures. You can see how on the 64-bit Intel/AMD and AArch64 (ARM64), the numbers are much larger than for their 32-bit counterparts. For arch-specific details, we refer you to the 'official' kernel documentation on the process virtual memory layout here:

Architecture Documentation location in kernel source tree
ARM-32 Documentation/arm/memory.txt.
AArch64 Documentation/arm64/memory.txt.
x86_64 Documentation/x86/x86_64/mm.txt
Note: this document's readability was vastly improved recently (as of the time of writing) with commit 32b8976 for Linux 4.20: https://github...