A very simple, self-teaching, educational operating system. Developped and released under GPLv2+ license (see LICENSE file)
Copyright (C) Nicolas Sauzede 2009-2022.
Required tools: qemu-system-i386, nasm, gcc and make (and optionally gdb for debug) Note that "gcc-multilib" might also be needed to build 32-bit binaries. Note also that bcc is needed to build the C 16-bit kernel (experimental).
Run and debug the 64-bit kernel as a HDD boot sector:
$ make db64
You should see this after setting a breakpoint in the function cmd_help, finish its execution and enter the command help:
Run the 16-bit kernel as a HDD boot sector:
$ make check16
You should see this after typing 'abcd' (0x1e, 0x30, 0x2e, 0x20) on the keyboard:
Debug the 16-bit boot part nicely in real-mode:
$ make check16_dbg
...
real-mode-gdb$ tb *0x7c00
Temporary breakpoint 1 at 0x7c00
real-mode-gdb$ cYou should then see the first instructions of the 16-bit loader:
---------------------------[ CODE ]----
=> 0x7c00: cli
0x7c01: push cs
0x7c02: pop ds
- Add 16-bits support
- Add 32-bits support
- Add 64-bits support
- Fix static variables initialization
- Fix multiboot support (test in grub)
- Rewrite common video routines in C
- Fix 16-bits C support
Some parts inspired by SOS (another educational operating system)
Uses protothread from Contiki-NG OS project (see LICENSE_pt.md BSD-3-Clause license).
This project was started in 2009 to learn by myself how operating systems are written and work at their lowest level, and is only sporadically updated. It is focused mainly on intel x86 architecture.
KEYWORDS : os boot loaders, 16/32/64 bit assembly, real/protected/long mode, segmentation, paging, interrupts, multi-tasking, etc..
Basically composed of x86 code, comprising a bootloader and a kernel (well three in fact).
The main target is emulation via qemu, as a bios rom extension or a bootable floppy disk image. But it should also run as well on a real machine.
-the loader is a nasm x86 assembly code, bootstrapping 16/32 bit kernels. -the 16 bit kernel is pure nasm 16 bit real mode code. -the 32 bit kernel is plain ANSI C code, running in 32 bit protected mode, with few small gas/nasm assembly code. -the 64 bit kernel is plain ANSI C code, running in 64 bit long mode, with few small gas/nasm assembly code.
See doc/specs.txt for more technical details / general low level OS infos.
The code should normally be quite portable and build under both windows and linux, thanks to some trickery concerning some asm symbol names, as inspired by this post