Kernel command using Linux system calls

A system call is an interface between a user-space application and a service that the kernel provides. Because the service is provided in the kernel, a direct call cannot be performed; instead, you must use a process of crossing the user-space/kernel boundary. The way you do this differs based on the particular architecture. For this reason, I'll stick to the most common architecture, i386.

In this article, I explore the Linux SCI, demonstrate adding a system call to the 2.6.20 kernel, and then use this function from user-space. I also investigate some of the functions that you'll find useful for system call development and alternatives to system calls. Finally, I look at some of the ancillary mechanisms related to system calls, such as tracing their usage from a given process.