Any decent operating system can be extended by loadable modules. This is required to support hardware that is not specifically supported by the organization that created the operating system, and so these loadable modules are often named device drivers.
However, this extensibility of operating systems can also be exploited for other purposes. For example, a specific filesystem or network protocol can be supported by the kernel itself through loadable modules without changing and recompiling the actual kernel.
In this chapter, we will look at how to build a kernel-loadable module, specifically for the Linux operating system and the x86_64 CPU architecture. The concepts and commands that are described here are ...
