/fryy

A tiny operating system running on 8086

Primary LanguageC

OVERVIEW

  1. Get deep understanding of INTEL 8086 architecture
  2. Build a micro OS kernel including
    • FAT12 Filesystem support
    • Process Management (PM) with Multi-Task support
    • System call support

ROADMAP

  1. Understanding BOOT procedure of 8086 system (FLOPPY only!)
    • Creating DEV environment -- QEMU, an emulator that can provides virtual environments of 80386, x86_64, ARM, MIPS, SPARC, etc.
  2. Getting familar with INTEL 8086 ISA
  3. Understanding FAT12 specifications
    • Create a virtual floppy image (boot.img, source: boot.nasm)
  4. Build a bootloader of our future OS
    • Understanding the limit of floppy boot: code size limit of 512B
    • BootLoader construction process:
      • Search KERNEL.BIN in RootDirSectors
      • Read File Allocation Table (FAT) for details
      • Loading KERNEL.BIN using BIOS INT (0x13)
      • Transfer control to KERNEL.BIN
  5. Build KERNEL.BIN

    • Download Bruce's C Compiler (bcc)

        bcc -0 -ansi -c source.c   
      -0:     generating 8086 (16bit) code    
      -ansi:  support ANSI C    
      -c:     compile only    

  ld86 -d -M source.o -o source.bin   
      -d:     generate flat binary file    
      -M:     print organization    
      -o:     target file

      See manuals for details of bcc, as86, ld86.

    • Build a simple process management system

      • Task scheduling subsystem (supporting multiprocesses)
      • A basic IPC subsystem (PV operators && resources)

    • Write a simple SHELL process dealing with I/O
      TIPS: Library functions (e.g. strcmp) can be linked to target image

HOW TO RUN

  1. Install QEMU & BCC (including bcc, as86 and ld86)
  2. make
  3. Put os.bin to boot.img (e.g. under Linux).
    • mkdir /mnt/floppy/
    • mount -o loop boot.img /mnt/floppy/
    • cp os.bin /mnt/floppy/
    • umount /mnt/floppy/
  4. qemu -fda boot.img