Hacking the OS

Phase I

Bootloader and Kernel Initialization

This repository demonstrates the sequence of bootloader and kernel setup for a basic operating system using BIOS:

1. Stage 1 Bootloader:

   • Loaded by the BIOS to 0x7C00.
   • Initializes the CPU in real mode, sets up a stack, and loads the Stage 2 bootloader or kernel from disk using BIOS interrupts.

2. Stage 2 Bootloader:

   • Handles advanced initialization, loads the kernel into memory, and switches to protected or long mode (for 64-bit systems).

3. Kernel Execution:

   • Starts at the kernel’s entry point, initializes system resources, and begins execution.

Tools

• Assembler: NASM or similar.
• Testing: QEMU or Bochs for emulation.
• Disk Imaging: Use dd to write bootloader to a disk image.

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Instructions

• Run the build.sh to create the bootimage
• Install QEMU in Ubuntu
• Head to the repo machine
• Execute the boot image via QEMU using qemu-system-x86_64 -drive format=raw,file=boot.img -cpu qemu64,pdpe1gb