This project involved the creation of custom system calls within a simplified operating system.
The xv6 Operating System has the benefit of being both simplified and open-source. This means
that the system is well-documented and useful for better understanding the structure and
functionality of operating systems in general. This project has the goal of implementing
customized system calls at the kernel level of an operating system, which adds additional
functions or system calls for a user to use at the user level.
The system calls added in this project include the following functions. Note that to implement
these system calls, multiple attributes of processes in the xv6 Operating System were added.
Notably, this includes a color attribute and tickets attribute:
int setColor(enum COLOR) –- This system call assigns a color to a process when passed a
valid enum color.
int setTickets(int) –- This system call assigns a number of tickets to a process, which can be
utilized in a lottery scheduler. Child processes inherit their parent’s number of tickets,
if a child process were created.
int getpinfo(struct pstat *) –- This system call returns information pertaining to a process’
attributes. This system call allows us to ensure that ticket values and colors were correctly assigned.
A user-space test program was also created to call each of these system calls from the user space
and verify their operation. As mentioned, the xv6 Operating System is altered to add these
additional system calls, and requires changing many of the files throughout the system’s entire
directory. This includes declaring and instantiating many values within the kernel space of the
operating system.
A full list of the changed files can be found below. For brevity’s sake, the files that implement and test
the added system calls are the only files included in the below download link. Further explanations of the
flies' relevance to the project can be found in the zipped folder’s README. This code can be found on my
GitHub page if desired.
David Denny Zipped System Call Project Folder
xv6 Operating System Files Altered to Implement Custom System Calls:
/Makefile
/kernel/defs.h
/kernel/proc.c
/kernel/proc.h
/kernel/pstat.h
/kernel/syscall.c
/kernel/syscall.h
/kernel/sysproc.c
/user/user.h
/user/usys.pl
Custom UNIX Shell:
This project involved the creation of my own, simple Unix shell. The shell is a fundamental
component of interfacing with the Unix environment, and this project has the goal of understanding
how modern shells function. This project allowed me to familiarize myself with the Linux programming
environment and understand the creation, destruction, and management of processes in operating
systems. All of these concepts enabled me to understand and create a fully functionally Unix shell.
Specifically, my shell, otherwise known as a Command line Interpreter, implements the standard Unix
commands you would expect out of a command line interface. This includes running test files, navigating
directories, and exiting when desired using fork(), execv(), and more. This project is foundational to
my understanding of Operating Systems.
All code for my custom shell is consolidated into one file in the download link below.
A copy of this code can also be found at my GitHub page: