README.md

Usage

Setup

Target architecture: i686

My setup, overall, is:

• 64 bit CPU
• 32 bit OS (compiled using i686 cross compiler)
• 32 bit applications will be able to be run

Building and running

I've been running this on a virtualized x86_64 processor.

$ make clean
$ make
$ qemu-system-x86_64 build/unnamed_os.bin 
# or for rhel:
$ qemu-kvm -cpu host -drive file=./build/unnamed_os.bin,format=raw -nographic
# View source 
$ objdump -D -b binary -mi386 -Maddr32,data32 build/disk.img

Notes:

• x86: (2.1.1) Refers to a processors in the 8086 family. (80186 80286 80386 80486...). Usually, it means compatability with the 80386 32 bit instruction set because 16 bit only is so old
• i686: (2.1.6) Intel686. P6 Family Microarchitecture on the Pentium Pro.
• One of the 6th generation of x86 processor.
• i386: (2.1.3) Intel386. AKA 80386. First 32 bit
• x86_64 The 64-bit instruction set (sometimes called amd64) brother of x86
  • backwards compatible to x86 (ie x86 instructions can run
  • on x86_64 processors)
• Here's a nice summary of intel cpu architecture (chapter 2.1).
• Here's another nice explanation of i related architectures
• 32 bit and 64 bit:
  • A 32-bit OS will run on a 32-bit or 64-bit processor without any problem.
  • A 32-bit application will run on a 32-bit or 64-bit OS without any problem.
  • But a 64-bit application will only run on a 64-bit OS and a 64-bit OS will only run on a 64-bit processor

References I've been using

• Intel Software Development Manual Volume 1A (Basic Architecture)
  • Not going to help you write code, but useful in learning about basics of computer stuff
• Intel Software Development Manual Volume 3A (System Programming Guide Part 1)
  • Good reference for GDT, protected mode, paging, etc. (The above also talks about paging, and segmentation)
• OS Dev Wiki
  • Eventually, I'll remove these as this grows, but this is the small subset of the wiki I've referenced so far:
  • Setting up a gcc cross compiler
  • GDT and GDT Tutorial
  • Protected mode
  • Segmentation
  • Rolling your own bootloader
  • Bootloader theory
• Assembly cheat sheet
• Daedalus Community - Making an OS
• NASM Reference
• NASM cheat sheet
• Assembly Programming Topics
• TODO - go through this tutorial
• Just a good website