🚀 GT-OS

The Gaurav Thakur Operating System

"To understand the machine, one must become the machine's architect."

A 32-bit preemptive multitasking operating system kernel built from scratch

Features • Architecture • Quick Start • Documentation

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📖 About

GT-OS is a research-grade operating system kernel developed from first principles for the x86 architecture. This project explores the intricate world of protected mode execution, virtual memory management, and POSIX-compliant system interfaces.

This isn't just code—it's a journey into the heart of how computers work, bridging the gap between raw hardware and elegant software abstraction.

🎯 Purpose

• Educational: Designed for developers who want to understand OS internals from the boot sector up
• Research: A platform for exploring kernel design patterns and low-level systems programming
• Professional: Built with production-grade structure and engineering discipline

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✨ Features

🔄 Process Management Preemptive multitasking Round-robin scheduling Context switching Process state management 💾 Memory Management Paging-enabled VMM Dynamic kernel heap Slab allocator Protected mode execution

📁 File Systems ext2 read/write support Virtual File System (VFS) layer procfs for process info devfs for device nodes 🔧 Hardware Support PS/2 keyboard controller ATA/PIO disk driver PCI bus enumeration RTC & PIT timers

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🏛 System Architecture

GT-OS follows a modular monolithic kernel design, where core services run in kernel space for performance while maintaining strict separation of concerns.

┌─────────────────────────────────────────┐
│         User Space Applications         │
├─────────────────────────────────────────┤
│          System Call Interface          │
├─────────────────────────────────────────┤
│                                         │
│  ┌──────────┬──────────┬──────────┐   │
│  │Scheduler │   VFS    │   IPC    │   │
│  ├──────────┼──────────┼──────────┤   │
│  │   VMM    │  Heap    │  Slab    │   │
│  └──────────┴──────────┴──────────┘   │
│            Kernel Core                  │
├─────────────────────────────────────────┤
│     Hardware Abstraction Layer (HAL)    │
├─────────────────────────────────────────┤
│  PS/2  │  ATA  │  PCI  │  RTC  │  PIT  │
└─────────────────────────────────────────┘

Core Subsystems

Subsystem	Description
Scheduler	Preemptive multitasking with round-robin arbitration, process state tracking, and context switching
Memory Manager	Paging-enabled Virtual Memory Manager with dynamic kernel heap and slab allocator
VFS	Virtual File System abstraction decoupling userspace from physical storage
IPC	UNIX-style signals and system call interfaces for inter-process communication

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🚀 Quick Start

Prerequisites

Ensure you have the following tools installed:

# Required Tools
- i586-elf-gcc      # Cross-compiler
- i586-elf-as       # Assembler
- QEMU (i386)       # Emulator
- make              # Build system
- Linux/WSL/macOS   # Host environment

Building GT-OS

# Clone the repository
git clone https://github.com/yourusername/GT-OS.git
cd GT-OS/osdev-source

# Clean previous builds
make clean

# Compile the kernel
make all

Running in QEMU

# Boot the kernel
make start

Default Login:

• Username: root
• Password: toor

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💻 User Space Interface

Upon boot, GT-OS drops you into a user-mode shell that communicates with the kernel through a Linux-compatible syscall interface.

Available Commands

Command	Description
ps	Display running processes and PIDs
ls	List directory contents (VFS query)
cat <file>	Output file contents to stdout
time	Poll CMOS RTC for current time
mod <module>	Load/unload kernel modules dynamically

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📂 Project Structure

GT-OS/
├── osdev-source/
│   ├── arch/i386/          # x86 architecture-specific code
│   │   ├── boot.S          # Bootstrap assembly
│   │   └── interrupts.S    # Interrupt handlers
│   ├── kernel/             # Core kernel subsystems
│   │   ├── panic.c         # Kernel panic handler
│   │   ├── elf.c           # ELF binary loader
│   │   └── syscalls.c      # System call dispatcher
│   ├── mm/                 # Memory management
│   │   ├── pmm.c           # Physical memory manager
│   │   ├── vmm.c           # Virtual memory manager
│   │   └── heap.c          # Kernel heap allocator
│   ├── fs/                 # File system implementations
│   │   ├── vfs.c           # Virtual File System
│   │   └── ext2.c          # ext2 driver
│   ├── drivers/            # Hardware drivers
│   │   ├── screen.c        # VGA text mode
│   │   ├── keyboard.c      # PS/2 keyboard
│   │   └── ata.c           # ATA/PIO disk
│   └── include/            # System-wide headers
└── README.md

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🧠 Design Philosophy

GT-OS embodies three core principles of systems programming:

1. Concurrency Control

Managing race conditions and synchronization in a preemptive multitasking environment

2. Resource Abstraction

Transforming raw electrical signals into elegant abstractions like files, streams, and processes

3. Bare Metal Mastery

Direct hardware interfacing through port I/O and memory-mapped registers—no safety nets

This kernel is educational in nature but professional in structure, demonstrating that with curiosity and discipline, the computer's "black box" becomes a glass house.

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🛠 Technical Specifications

Architecture x86 (32-bit) Protected mode Ring 0/3 separation

Binary Format ELF loader Dynamic linking support Symbol resolution

Interrupts IDT management ISR handlers IRQ routing

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🤝 Contributing

Contributions are welcome! Areas of interest include:

• 🔌 Additional hardware drivers
• 📁 Filesystem optimization
• 🔧 POSIX compliance improvements
• 📚 Documentation enhancements

Code Style

Please adhere to K&R coding style for consistency.

Pull Request Process

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

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📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

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👨‍💻 Author

Gaurav Thakur

Concept, Architecture & Implementation

The name GT-OS reflects the personal nature of this architectural study. It stands as a testament to the fact that with enough curiosity and determination, the "black box" of the computer becomes transparent.

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🌟 Acknowledgments

• The OSDev community for their invaluable resources
• The GNU toolchain developers
• QEMU project for excellent emulation
• Everyone who believes in understanding technology from the ground up

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⭐ Star this repo if you find it interesting!

Built with passion for operating systems and low-level programming

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