This repository represents the work I did for my Operating Systems class (CSE421) at UB. We were given a very basic implementation of an operating system that ran on an included simulator (simulating a MIPS r3000 processor). The entire semester was spent developing standard operating system features in a series of assignments. For a more detailed reference, please refer to: ops-class.org/asst/overview/
All header files reside in /kern/include
Given a spinlock implementation (implemented on a "hardware" level), we were required to build other synchronization primitives from it. They included: locks, condition variables, and read/write locks.
See files:
- /kern/thread/synch.c
This repository does not have a working Read/Write lock.
Given the framework for system calls (trapping has alreay been implemented), implement various system calls found in Unix-like systems. [Note: I chose to develop OS/161 by myself, rather than work in a group. Therefore, I was not required to implement the file syscalls detailed in the ASST2 description. I was required to implement the process-based syscalls (fork, execv, getpid, waitpid, exit)].
In addition to the system call interface, we were required to implement the process subsystem to keep track of processes and their lifecycles. Similarly, the subsystem needed to support inter-process communication.
See files:
- /kern/proc
- /kern/thread/thread.c
- /kern/syscall/proc_syscalls.c
If I recall correctly, my execv implementation leaks memory (or runs out of it when system < 768kB).
The last assignment, we were required to implement virtual memory. This meant designing and implementing paging as well as configuring TLB fault handling. In addition, we were required to design the address space abstraction from scratch, with tight bounds on memory leakage.
With virtual memory implemented, we were required to write the sbrk() syscall and it's implementation, malloc().
See files:
- /kern/vm.c
- /kern/addrspace.c
My virtual memory implementation doesn't pass all tests with 100%. I plan on redesigning my process subsystem entirely in Spring 2017 along with making my virtual memory system more robust, and implementing swapping to disk.