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

The proc and sysfs filesystems


proc and sysfs are two pseudo filesystems that give a window onto the inner workings of the kernel. They both represent kernel data as files in a hierarchy of directories: when you read one of the files, the contents you see do not come from disk storage, it has been formatted on-the-fly by a function in the kernel. Some files are also writable, meaning that a kernel function is called with the new data you have written and, if it is of the correct format and you have sufficient permissions, it will modify the value stored in the kernel's memory. In other works, proc and sysfs provide another way to interact with device drivers and other kernel code.

proc and sysfs should be mounted on the directories /proc and /sys:

mount -t proc proc /proc
mount -t sysfs sysfs /sys

Although they are very similar in concept, they perform different functions. proc has been part of Linux since the early days. Its original purpose was to expose information about processes to user...