Fun and Games with FreeBSD Kernel Modules – Kernel hacking using kernel modules and kmem patching. Contains information on how to intercept system calls and other calls in the kernel by altering the corresponding call table. Also shows how to alter these tables by writing to kernel memory and gives an example of patching the kernel directly without the use of modules. Furthermore an example is given on how the symbol table in the kernel can be altered.
You can download it from the following link: https://packetstormsecurity.com/files/download/25297/fbsdfun.htm
Source: https://packetstormsecurity.com/files/25297/fbsdfun.htm.html