Academic Operating System

We are developing an operating system for my personal research and practical education. For the academic purpose, this motivation is similar to MINIX, but we do not focus on theories. Our main objective is to provide knowledges on hardware-related programming. This is one of the most difficult and complex parts when we start the development of operating system from scratch.

The source code is available at the public github repository.

• Implementation Essentials
• Boot (BIOS, UEFI, PXE)
• 32-bit Protected Mode and 64-bit Long Mode in x86-64 processors
• Protection (ring, page)
• Multi-Processor System
• Design & Practices
• Scheduler (in multi-task operating system)
  • Batch system
    • First-Come First-Serve
    • Shortest Job First
    • Shortest Remaining Time Next
  • Interactive system
    • Round-Robin Scheduling
    • Priority Scheduling
    • Priority Scheduling w/ Multiple Queue (different quantum)
    • Shortest Process Next
    • Guaranteed Scheduling
    • Lottery Scheduling
    • Fair-Share Scheduling
  • Real-time system
• Memory management
  • Buddy system (page allocation)
  • Slab/Slub allocator
• Filesystem
• Network stack

I provide a text book to implement a fundamental operating system step by step. The following checkpoints are the implementation steps. Note well that I sometimes quote specifications and manuals with necessary references (e.g., hyper links) from other documents to provide a self-complete textbook. You may need to refer to official documents to completely understand how your computer and peripheral devices work.

• Checkpoints
  • Checkpoint 0: Display boot message
  • Checkpoint 1: Load and execute another program
  • Checkpoint 2: Load and execute another program in multiple sectors
  • Checkpoint 3: Power off the machine using APM
  • Checkpoint 4: Use programmable interrupt controller and read keyboard input
  • Checkpoint 5: Use programmable interval timer
  • Checkpoint 6: Execute a boot monitor and enter 32/64-bit mode
  • Checkpoint 7: Load the kernel file from FAT12/16 file system
  • Checkpoint 8: Load the memory map
  • Checkpoint 9: Setup global descriptor table and interrupt descriptor table
  • Checkpoint a: Initialize application processors from the bootstrap processor
  • Checkpoint b: Initialize APIC timer
  • Checkpoint c: Allocate memory (buddy system and slab allocator)
• Tips
  • Power off (APM / ACPI)

Memo

The development environment is definitely important. Some web sites or books on operating system development use Windows-based environment but I don't prefer that. In this site, we use open source software on a Unix-like system such as BSD, Linux, and Mac OS X.

• GCC (GNU C compiler): Assembler, compiler, and linker
• VirtualBox: Virtual machine monitor for the developed operating system
• make: Build tool (as you know...)
• dd: Convert your compiled program to a disk image (FD or HDD). N.B., we may also use mkisofs to build ISO file in the future.

You may be bothered by the GUI of VirtualBox to launch your virtual machine for testing. In that case, the following command will help you much! As for the other commands, you can find the manual at VBoxManage Manual.

$ VBoxManage startvm <your-os-name>

The following describes the floopy disk geometry.

For floppy disks

| LBA | Sector # | Head # | Cylinder # |
| --- | -------- | ------ | ---------- |
|   0 |        1 |      0 |          0 |
|   1 |        2 |      0 |          0 |
|   . |        . |      . |          . |
|  17 |       18 |      0 |          0 |
|  18 |        1 |      1 |          0 |
|   . |        . |      . |          . |
|  31 |       18 |      1 |          0 |
|  32 |        1 |      0 |          1 |
|   . |        . |      . |          . |

We partition the floppy disk image in this document although floppy disks are basically unpartitioned devices. I think everybody no longer uses floppy disks, so it is more generic for typical block devices such as hard disks and USB flash storages. In FAT12/16, the number of the reserved sectors is recommended to be one because some driver implementations do not check the value. However, the IPL in the first sector is not enough to parse the FAT filesystem, so we cannot place the other program outside of the filesystem. When we use the partition table, we can place this program below (before) the starting sector of the first partition entry.

If you DO prefer Japanese, please let me know... I'll try to translate it.