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

The procmap utility

Visualizing the complete memory map of the kernel Virtual Address Space (VAS) as well as any given process's user VAS is what the procmap utility is designed to do.

The description on its GitHub page sums it up:

It outputs a simple visualization of the complete memory map of a given process in a vertically-tiled format ordered by descending virtual address. The script has the intelligence to show kernel and userspace mappings as well as calculate and show the sparse memory regions that will be present. Also, each segment or mapping is scaled by relative size (and color-coded for readability). On 64-bit systems, it also shows the so-called non-canonical sparse region or 'hole' (typically close to 16,384 PB on the x86_64).

The utility includes options to see only kernel space or userspace, verbose and debug modes, the ability to export its output in convenient CSV format to a specified file, as well as other options. It has a kernel component as well and currently works (and auto-detects) on x86_64, AArch32, and Aarch64 CPUs.

Do note, though, that I am still working on this utility; it's currently under development... there are several caveats. Feedback and contributions are most appreciated!

Download/clone it from https://github.com/kaiwan/procmap:

Figure 1.10 – A partial screenshot of the procmap utility's output, showing only the top portion of kernel VAS on x86_64

We make good use of this utility in Chapter 7, Memory Management Internals - Essentials.