System calls in the Linux kernel

“This post opens new chapter in linux-insides book and as you may understand from the title, this chapter will devoted to the System call concept in the Linux kernel. The choice of the topic for this chapter is not accidental. In the previouschapter we saw interrupts and interrupt handling. Concept of system calls is very similar to interrupts, because the most common way to implement system calls as software interrupts. We will see many different aspects that are related to the system call concept. For example, we will learn what’s happening when a system call occurs from userspace, we will see implementation of a couple system call handlers in the Linux kernel, VDSO and vsyscall concepts and many many more.

Before we will start to dive into the implementation of the system calls related stuff in the Linux kernel source code, it is good to know some theory about system calls. Let’s do it in the following paragraph…”