matthewT53/mbr-project

In this project, as apart of a team I messed around with the master boot record in an attempt to do some interesting things.

COMP6845 MBR project:

Setting up the environment:

Install:

1. qemu - Emulator
2. nasm - Assembler

Getting a bootloader:

• dd if="drive" of=boot.bin bs=512 count=1

Running this stuff:

• Compile asm to mbr bin: nasm -f bin ???.asm -o ???.bin
• Disassemble bin to asm: ndisasm -b16 -o7C00h ???.bin > ???.asm (can omit flag -07c00h to display assembly from 0x0000 instead of 0x7c00)
• qemu-system-i386 -fda boot.bin -boot a -s -S
• -s and -S pauses qemu allowing you to attach a debugger and also starts a debugging server at localhost:1234.

Option 2:

• Use bochs on linux.
• Follow the link below to setup:
  • https://stechazine.blogspot.com/2013/03/how-to-setup-boch-32-emulator-in-ubuntu.html

Attaching a debugger:

• We chose to use GDB.
• In gdb type:

    target remote localhost:1234

Debugging reading sectors:

• Put a breakpoint after the interrupt call (0x13).
• Don't try to step through the interrupt using "ni".

Scripts:

• Use create_disk.py to extend boot.bin with more sectors so we can test reading and writing.

Some useful links:

• https://blog.ghaiklor.com/how-to-implement-your-own-hello-world-boot-loader-c0210ef5e74b
• https://stackoverflow.com/questions/14242958/debugging-bootloader-with-gdb-in-qemu