ECS-150, Fall 2007, Programming Assignment #1
Due date: 11:59 p.m., October 15, 2007
Total 10% (2% penalty if turned in before the end of October 17, and then
1% penalty for each extra day after that)
Modifying the FreeBSD 5.4 kernel and Loading new kernel modules
In this homework assignment, you will learn how to modify and compile a new FreeBSD
kernel as well as how to utilize the “kld” (Kernel Loadable Module) interface to change
the behavior of the kernel such as adding new system calls. Information regarding how to
compile a FreeBSD kernel and how to program the KLD is available in the class website.
During the discussion hours, the TA will also talk about kernel compilation and
dynamically loadable kernel modules. The TA will provide a test program as well.
You must use the 5.4 kernel to do this and other kernel programming assignments, and
you need to submit all the kernel source code files you modify as well as the
Makefile. Please do NOT hand-in the whole source tree or any binary. You also need to
write a README file regarding which files you have changed, and a brief
description (less than two pages) about the steps for a system call to trap into the
FreeBSD kernel. In order to do this part, you need to identify the path of “system
call” implementation in the FreeBSD source tree.
In this programming assignment, you will add one new attribute “int tickets” into
“struct proc” defined in “/usr/src/sys/sys/proc.h”, and one global
variable “int lottery_mode” in “/usr/src/sys/kern/kern_switch.c”.
Then, you will add the following four system calls via the KLD interface:
int setProcessTickets(int pid, int tickets);
int getProcessTickets(int pid);
int setLotteryMode(int mode);
int getLotteryMode(void);
The first two system calls will return an error code (-1) if the PID doesn’t exist in the
kernel.
Please note that you need to re-compile the kernel in order to add the new attribute
(tickets in struct proc) and the new global variable (lottery_mode), but you don’t need to
re-build the kernel to add new system calls.
Finally, in the development of this programming assignment, you will likely use the
“printf” function call. Please also describe, in the README file, the difference
between calling printf in the user space and in kernel space (i.e., in the kernel
module).
If you encounter any difficulty, please feel free to ask the instructor or the TA.