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

Learning how to use the page allocator APIs

The Linux kernel provides (exposes to the core and modules) a set of APIs to allocate and deallocate memory (RAM) via the page allocator. These are often referred to as the low-level (de)allocator routines. The following table summarizes the page allocation APIs; you'll notice that all the APIs or macros that have two parameters, the first parameter is called the GFP flags or bitmask; we shall explain it in detail shortly, please ignore it for now. The second parameters is the order - the order of the freelist, that is, the amount of memory to allocate is 2order page frames. All prototypes can be found in include/linux/gfp.h:

API or macro name Comments API signature or macro
__get_free_page() Allocates exactly one page frame. The allocated memory will have random content; it's a wrapper around the __get_free_pages() API. The return value is a pointer to the just-allocated memory's kernel logical...