OS Development Project

A custom x86 operating system developed from scratch in Assembly language. This educational project is to dive into low-level system programming concepts . For now the OS loads the GDT and then jumps to the kernel.THe CPU is completely stable in 32 bit protected mode. IDT and GDT are loaded, paging is enabled , IRWs rewired correctly and also syscalls configured.

Project Structure

arch/x86/          - x86 architecture-specific assembly code
  ├── boot.asm     - Bootloader entry point
  ├── kernel.asm   - Kernel core assembly routines
  ├── IDT.asm      - Interrupt Descriptor Table setup
  ├── pic.asm      - Programmable Interrupt Controller
  └── temp.asm     - Temporary/experimental code

kernel/            - Kernel implementation (C)
  ├── kernel.c     - Main kernel initialization
  ├── shell.c      - Simple shell/CLI interface
  ├── console/     - Console and terminal output
  ├── interrupt/   - Interrupt handling
  ├── mm/          - Memory management (paging, frame allocation)
  └── syscall/     - System call handling

drivers/           - Hardware drivers
  └── display/     - Display drivers (VGA, framebuffer)

include/           - Header files (.h)
esp/               - EFI boot partition (for debugging and development purposes)
EFI/               - UEFI bootloader files (for direct RAW use)

Prerequisites

• NASM - Netwide Assembler for compiling x86 assembly
• GCC - GNU C Compiler for compiling C code
• QEMU - For emulating and testing the OS

Building the OS

To build the OS, you'll need:

• NASM (Netwide Assembler)
• QEMU (for emulation)

Build Commands

./buildbin    # Builds all binaries (bootloader, kernel, drivers)

Other build scripts available:

• ./buildefi - Build EFI bootloader
• ./buildimg - Create bootable disk image
• ./buildrun - Build and run in QEMU (one command)

Running the OS

To run the compiled OS in QEMU emulator:

./run           # Runs the OS in QEMU
./buildrun      # Builds and runs in one step

Debugging

To debug the OS with QEMU and GDB:

./debug         # Launches QEMU with GDB support for debugging

This starts QEMU in debug mode, allowing you to set breakpoints and step through code with GDB.