eXpOS – Experimental Operating System

An educational operating system built from scratch as part of the eXpOS (Experimental Operating System) project developed by National Institute of Technology Calicut.

The repository contains implementations of:

• eXpOS running on the XSM (Experimental String Machine) architecture simulator
• neXpOS, a dual-core extension of eXpOS running on the NEXSM architecture simulator

Official references:

• Documentation
• Roadmap

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Overview

This project was completed as part of an Operating Systems laboratory course and involved implementing core operating system components from scratch, including:

• Process management
• Memory management
• File systems
• Interrupt and exception handling
• System calls
• CPU scheduling
• Synchronization primitives
• Multi-user support
• Disk management
• Shell and user programs
• Dual-core execution support

The operating system is developed using:

• SPL (System Programming Language) for kernel modules
• ExpL (Experimental Language) for user programs

Both systems run on the XSM/NEXSM architecture simulators provided by the eXpOS project.

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Project Architecture

+--------------------------------------------------+
|                User Programs (ExpL)              |
+--------------------------------------------------+
|                eXpOS Library                     |
+--------------------------------------------------+
|                  eXpOS Kernel                    |
|  - Scheduler                                     |
|  - Memory Manager                                |
|  - File System                                   |
|  - Process Manager                               |
|  - Device Handlers                               |
+--------------------------------------------------+
|             XSM Machine Simulator                |
+--------------------------------------------------+

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Features Implemented

• Process Management
  • Process creation and termination
  • Context switching
  • Round-robin scheduling
  • Multi-process execution
  • Process table management
• Memory Management
  • Paging-based memory management
  • Page table handling
  • Heap and stack management
  • Shared library loading
• File System
  • File creation and deletion
  • File read/write operations
  • Inode management
  • Disk block allocation
  • Root file system support
• Interrupts & Exceptions
  • Timer interrupt handling
  • Console interrupt handling
  • Exception handling routines
  • System call interface
• Synchronization
  • Process synchronization using semaphores
  • Resource sharing management
  • Concurrency control mechanisms
• Dual Core Architecture Support
  • Dual-core execution support on NEXSM
  • Parallel process scheduling
  • Shared memory coordination between cores
  • Inter-processor synchronization
  • Kernel support for concurrent execution
• User Programs
  • Shell implementation
  • Basic command execution
  • User-level applications in ExpL

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Key Concepts Explored

• Operating system internals
• Process scheduling and context switching
• Paging and memory management
• Synchronization and concurrency control
• Dual-core kernel execution
• Interrupt-driven execution
• File system implementation
• Low-level system programming
• Assembly-level debugging

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Installation and Setup

• To clone the repo and open it:

git clone https://github.com/HattoriMan/OS_Lab.git
cd OS_Lab

• For setup of the ExpL and SPL compilers as well as the libraries and other installations required for it to work follow from Stage 1 listed in the roadmap. There is a setup.sh file in Stage_01 folder which also does the installation.
• The project can be reproduced by following the official eXpOS roadmap from Stage 1 onward.

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Important Notes

• All files required to build the OS up to a particular stage are included in the corresponding stage directory of my implementation.
• Only files modified or newly added have been pushed till Stage_24 (including it).
• All stages from Stage_25 onward contain the complete set of SPL and ExpL source files, not just the modified or newly added ones.
• For easier compilation a compile bash script has been written for Stage_25 and above which compiles all the files in the stage. You can change the directory location constants in it according to your setup.
• Stages_25 to Stage_28 contains run_comms file which contains the command to be executed in the xfs-interface to load the files but it might depend on your setup.
• Stage_28 contains the implementation of neXpOS, a dual-core operating system running on the NEXSM architecture.