Referenece book: Designing BSD Rootkits An Introduction To Kernel Hacking.Apr.2007.ISBN.1593271425

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Warnings

We use FreeBSD-14.0-Release version, which may be different from the version of reference book.

The point is, when facing the bug, please go to check FreebBSD developer handbook or manual on web. Reading with patience, try to solve problem on your own!

Of course, you can ask problem in discord forum. Discussing with peers is one of the main purposes of this book club~

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Objective:

In this assignment, you will learn how to implement a new system call in FreeBSD by creating a Kernel Loadable Module (KLD). The system call will be dynamically loaded into the kernel, registered in the system call table, and later executed via user-space code.

Prerequisite

• Reading “Designing BSD Rootkits An Introduction To Kernel Hacking” Ch 1.1 - 1.4
• Installing VirtualBox
• Installing freebsd-14-release image
  • https://download.freebsd.org/ftp/releases/ISO-IMAGES/14.0/
• Create an freebsd vm on virtualbox
• F.Y.I, FreeBSD comes with a Base System concept.
  • This means that when you install FreeBSD you install a minimal system as a whole.
  • That means you should BUILD KERNEL FROM SOURCE

Resources may be useful

• https://docs.freebsd.org/en/books/developers-handbook/kernelbuild/
• https://docs.freebsd.org/en/books/handbook/cutting-edge/#makeworld

Hand in this Practice

• Please send system call finish screenshot to discord

Knowledge base

System Call Overview

• A system call is a mechanism that allows user-space programs to request services or resources from the operating system's kernel
• In FreeBSD, the system call table is an array of sysent structures, where each entry describes a system call.

KLD Overview