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)
Section 1: The Basics
Writing Your First Kernel Module - LKMs Part 2
Section 2: Understanding and Working with the Kernel
Kernel Memory Allocation for Module Authors - Part 1
Kernel Memory Allocation for Module Authors - Part 2
Section 3: Delving Deeper
About Packt

Background details and conclusions

So far, you have learned some key points:

  • The page (or buddy system) allocator allocates power-of-2 pages to the caller. The power to raise 2 to is called the order; it typically ranges from 0 to 10 (on both x86[_64] and ARM).
  • This is fine, except when it's not. When the amount of memory requested is very small, the wastage (or internal fragmentation) can be huge.
  • Requests for fragments of a page (less than 4,096 bytes) are very common. Thus, the slab allocator, layered upon the page allocator (see Figure 8.1) is designed with object caches, as well as small generic memory caches, to efficiently fulfill requests for small amounts of memory.
  • The page allocator guarantees physically contiguous page and cacheline-aligned memory.
  • The slab allocator guarantees physically contiguous and cacheline-aligned memory.

So, fantastic – this leads us to conclude that when the amount of memory required...