Chapter 16. Modules

Despite being "monolithic," in the sense of the whole kernel running in a single protection domain, the Linux kernel is modular, allowing the dynamic insertion and removal of code from the kernel at run-time. Related subroutines, data, and entry and exit points are grouped together in a single binary image, a loadable kernel object, called a module. Support for modules allows systems to have only a minimal base kernel image, with optional features and drivers supplied via module. Modules also provide easy removal and reloading of kernel code, facilitate debugging, and allow for the loading of new drivers on demand in response to the hotplugging of new devices.

This chapter looks at the magic behind modules in the kernel and how you can write your very own module.