Book Image

Mastering Embedded Linux Programming - Third Edition

By : Frank Vasquez, Chris Simmonds
5 (3)
Book Image

Mastering Embedded Linux Programming - Third Edition

5 (3)
By: Frank Vasquez, Chris Simmonds

Overview of this book

If you’re looking for a book that will demystify embedded Linux, then you’ve come to the right place. Mastering Embedded Linux Programming is a fully comprehensive guide that can serve both as means to learn new things or as a handy reference. The first few chapters of this book will break down the fundamental elements that underpin all embedded Linux projects: the toolchain, the bootloader, the kernel, and the root filesystem. After that, you will learn how to create each of these elements from scratch and automate the process using Buildroot and the Yocto Project. As you progress, the book will show you how to implement an effective storage strategy for flash memory chips and install updates to a device remotely once it’s deployed. You’ll also learn about the key aspects of writing code for embedded Linux, such as how to access hardware from apps, the implications of writing multi-threaded code, and techniques to manage memory in an efficient way. The final chapters demonstrate how to debug your code, whether it resides in apps or in the Linux kernel itself. You’ll also cover the different tracers and profilers that are available for Linux so that you can quickly pinpoint any performance bottlenecks in your system. By the end of this Linux book, you’ll be able to create efficient and secure embedded devices using Linux.
Table of Contents (27 chapters)
1
Section 1: Elements of Embedded Linux
10
Section 2: System Architecture and Design Decisions
18
Section 3: Writing Embedded Applications
22
Section 4: Debugging and Optimizing Performance

Avoiding page faults

A page fault occurs when an application reads or writes to memory that is not committed to physical memory. It is impossible (or very hard) to predict when a page fault will happen, so they are another source of non-determinism in computers.

Fortunately, there is a function that allows you to commit all the memory used by the process and lock it down so that it cannot cause a page fault. It is mlockall(2). These are its two flags:

  • MCL_CURRENT: This locks all pages currently mapped.
  • MCL_FUTURE: This locks pages that are mapped in later.

You usually call mlockall during the startup of the application with both flags set to lock all current and future memory mappings.

Tip

MCL_FUTURE is not magic, in that there will still be a non-deterministic delay when allocating or freeing heap memory using malloc()/free()
or mmap(). Such operations are best done at startup and not in the main control loops.

Memory allocated on the stack is trickier...