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 process VAS – the full view

Once again, refer to Figure 7.1; it shows the actual process VAS layout for a single 32-bit process. The reality, of course – and this is key – is that all processes alive on the system have their own unique user-mode VAS but share the same kernel segment. For some contrast from Figure 7.1, which showed a 2:2 (GB) VM split, the following figure shows the actual situation for a typical IA-32 system, with a 3:1 (GB) VM split:

Figure 7.5 – Processes have a unique user VAS but share the kernel segment (32-bit OS); IA-32 with a 3:1 VM split

Notice in the preceding figure how the address space reflects a 3:1 (GB) VM split. The user address space extends from 0 to 0xbfff ffff (0xc000 0000 is the 3 GB mark; this is what the PAGE_OFFSET macro is set to), and the kernel VAS extends from 0xc000 0000 (3 GB) to 0xffff ffff (4 GB).

Later in this chapter, we will cover the...