PandOS - Operating System Project

I. Overview

PandOS is an educational operation system developed as part of the CS372 - Operating Systems course (taken in Spring '25), designed to illustrate fundamental concepts in operating system design and implementation. The operating system runs on the µMPS3 emulator, a MIPS-based architecture simulator specfically developed for educational purposes.

Project Goals

• Understand and implement key OS functionalities, including:

  • Process scheduling (Round-Robin algorithm)
  • Memory management (virtual memory and TLB handling)
  • Exception and interrupt handling
  • Device I/O operations
  • System call implementation (SYS1-SYS18)

• Gain hands-on experience with kernel-level programming and debugging.

II. Project Structure

The project is organized into five phases, corresponding to the coursework assignments. The repository is structured as follows:

CS372-Operating-System/
├── h/                       # Header files (constants, types, and function prototypes)
├── phase1/                  # Queue Manager: PCB allocation/deallocation, queue and semaphore management
│   ├── asl.c                # Active Semaphore List management
│   ├── pcb.c                # Process Control Block management
├── phase2/                  # Nucleus: Process scheduling, exception/interrupt handling, basic syscalls
│   ├── initial.c            # Kernel initialization
│   ├── scheduler.c          # Process scheduling
│   ├── exceptions.c         # Exception handling
│   ├── interrupts.c         # Interrupt handling
├── phase3/                  # Support Level: Virtual memory (paging), TLB refill, advanced syscall handling
│   ├── initProc.c           # Initialization for user-level processes
│   ├── sysSupport.c         # System call and exception handling for support level
├── phase4/                  # DMA Device Support: Disk and flash I/O operations, DMA buffer management
│   ├── deviceSupportDMA.c   # DMA device operations
├── phase5/                  # Delay Facility: Implements timed suspension for user processes
│   ├── delayDaemon.c        # Delay daemon and delay list management
├── testers/                 # Test programs for validating user-processes (from phase 3 and beyond)
├── README.md                # Project documentation
├── .gitignore               # Git ignore file

Each subsequent phase builds upon previous phases, with Phase 1-3 forming the PandOS core, while Phase 4-5 add advanced features.

III. Detailed Phase Description

Phase 1: Queue Manager

• Allocation/deallocation of process control blocks (PCBs)
• Maintenance of process queues and process trees
• Management of active semaphore lists (ASL)

Phase 2: Nucleus

• Kernel initialization and basic scheduling (Round-Robin with a 5ms quantum)
• Handling of device interrupts and exceptions
• Implementation of basic syscalls (SYS1-SYS8)

Phase 3: Support Level

• Virtual memory management (paging, TLB refill)
• Advanced syscall handling, including TLB exceptions and Program Traps
• Enhanced exception processing and address translation

Phase 4: DMA Device Support

• Implementation of DMA buffers
• Disk and flash device I/O operations
• Enhanced backing store management

Phase 5: Delay Facility

• Time suspension facility for user processes via the delay daemon
• Management of active delay list (ADL)

IV. Testing

Each phase includes dedicated testing program(s) to verify functionality and robustness. For Phase 1 and Phase 2, the test file is located within the respective phase directories. For Phase 3 and beyond, several testers are available in the testers/ directory, providing comprehensive diagnostics and validation. These testers can be utilized by loading them into the flash devices within the µMPS3 emulator.

V. Setup Instructions

1. Prerequisites

• µMPS3 Emulator: A MIPS-based emulator for OS development
• GCC cross-compiler for MIPS (mipsel-linux-gnu-gcc)
• Standard Linux environment (recommended Ubuntu or WSL)

2. Building and Running PandOS

1. Compile:

make

2. Run in µMPS3:

• Launch µMPS3 GUI.

umps3 &

• Create and configure a new machine with the following recommended settings:

  • TLB Floor Address: 0x8000.0000 or higher
  • RAM Size (Frames): at least 128 frames

• Device Setup:

  • Load and enable disk devices (disk0, disk1)
  • Load and enable flash devices corresponding to the desired UPROCMAX (defined in \h\constants.c)
  • Load and enable necessary printers and terminals

• Run the emulator.

V. Authors

Uyen Nguyen - Applied Math and Computer Science, Denison University (Class of 2026)

For questions, improvements, or issues, please contact via nguyen_u1@denison.edu or GitHub.