Book Image

Mastering Embedded Linux Programming

By : Chris Simmonds
Book Image

Mastering Embedded Linux Programming

By: Chris Simmonds

Overview of this book

Mastering Embedded Linux Programming takes you through the product cycle and gives you an in-depth description of the components and options that are available at each stage. You will begin by learning about toolchains, bootloaders, the Linux kernel, and how to configure a root filesystem to create a basic working device. You will then learn how to use the two most commonly used build systems, Buildroot and Yocto, to speed up and simplify the development process. Building on this solid base, the next section considers how to make best use of raw NAND/NOR flash memory and managed flash eMMC chips, including mechanisms for increasing the lifetime of the devices and to perform reliable in-field updates. Next, you need to consider what techniques are best suited to writing applications for your device. We will then see how functions are split between processes and the usage of POSIX threads, which have a big impact on the responsiveness and performance of the final device The closing sections look at the techniques available to developers for profiling and tracing applications and kernel code using perf and ftrace.
Table of Contents (16 chapters)
15
Index

What should be in the root filesystem?

The kernel will get a root filesystem, either as a ramdisk, passed as a pointer from the bootloader, or by mounting the block device given on the kernel command line by the root= parameter. Once it has a root filesystem, the kernel will execute the first program, by default named init, as described in the section Early Userspace in Chapter 4, Porting and Configuring the Kernel. Then, as far as the kernel is concerned, its job is complete. It is up to the init program to begin processing scripts, start other programs, and so on, by calling system functions in the C library, which translate into kernel system calls.

To make a useful system, you need these components as a minimum:

  • init: The program that starts everything off, usually by running a series of scripts.
  • shell: Needed to give you a command prompt but, more importantly, to run the shell scripts called by init and other programs.
  • daemons: Various server programs, started by init.
  • libraries: Usually...