A 32-bit x86 teaching operating system: its own BIOS bootloader and GRUB support, higher-half paging, preemptive multitasking, ring-3 programs with system calls, a VFS, VGA text and graphics, and drivers for the usual PC hardware, in small readable C and NASM.
| Area | What DrakeOS does |
|---|---|
| Boot | Its own two-stage BIOS bootloader (A20, E820 memory map, LBA/CHS disk loading, protected-mode switch, Multiboot hand-off) and GRUB 2 via Multiboot. QEMU's -kernel also works. |
| CPU | GDT with ring-0/ring-3 segments and a TSS, IDT with all exceptions, 8259 PIC remapped to 32–47, PIT at 100 Hz. |
| Memory | Bitmap page-frame allocator from the BIOS map, higher-half kernel at 0xC0000000, per-process page directories, first-fit kernel heap. |
| Processes | Preemptive round-robin scheduler, kernel threads, ring-3 user processes loaded from ELF, exec/wait/exit, sleeping, blocking I/O, kill. |
| System calls | int 0x80: exit, write, read, yield, getpid, sleep, open, close, exec, wait. User pointers are validated. |
| Files | VFS with a read-only initrd built into the kernel (/), DrakeFS on a data disk (/disk), and /dev/console. |
| Drivers | VGA text console with scrolling and a hardware cursor, serial logging (COM1), PS/2 keyboard and mouse, ATA PIO, PC speaker, VGA mode 13h graphics set through the registers, with the font and palette saved and restored. |
| Shell | History, Ctrl+C/Ctrl+L, and 27 commands: files, processes, gfx, logo, paint (mouse), beep/play, hi, vid, reboot, shutdown. |
| User space | crt0 + a small libc (printf, strings, syscall wrappers) and 7 programs: hello, ticker, spin, fault, ucat, greet, spawn. |
sudo pacman -S qemu-system-x86 nasm grub xorriso mtools gdb base-devel python
yay -S i686-elf-gcc i686-elf-binutils # optional: the cross compilerWithout i686-elf-gcc the Makefile uses the host gcc in 32-bit freestanding mode
(-m32 -ffreestanding -nostdinc); it only needs the 32-bit libgcc, which Arch's gcc ships.
Regenerating the logo asset (tools/mklogo.py) needs Pillow; the generated
assets/drakelogo.bin is committed, so normal builds do not.
make # build/drakeos.img (own bootloader), build/drakeos.iso (GRUB), build/data.img
make run # boot the disk image with the DrakeOS bootloader
make run-grub # boot the ISO through GRUB
make run-direct # QEMU's built-in Multiboot loader
make debug # QEMU stopped at reset + gdb with kernel symbols (breaks at kmain)
make test # headless end-to-end tests on both boot paths
make help # all targets and variablesThe serial log appears in the terminal. AUDIO=pa|pipewire|alsa|none selects the PC-speaker
backend (default pa). The data disk build/data.img survives make clean; run format
once in the shell to create DrakeFS on it.
Everything runs inside QEMU; the images are never booted on the host.
drake> ls initrd files, plus the dev/ and disk/ mount points
drake> run hello a b ring-3 program printing its argv
drake> run ticker 20 & background process; it keeps printing while you type
drake> ps process table
drake> run spin 2 busy loop without yield: the ticker still runs (preemption)
drake> run fault writes kernel memory -> page fault -> only the process dies
drake> run fault cli privileged instruction in ring 3 -> general protection fault
drake> format create DrakeFS on the data disk
drake> write note hello disk then: cat disk/note, ls disk, rm disk/note
drake> run greet read() from the keyboard
drake> logo / gfx / paint mode 13h; paint uses the PS/2 mouse (Esc to quit)
drake> beep 440 300 / play PC speaker
boot/ stage1.asm (boot sector), stage2.asm (A20, E820, loader, PM switch), grub.cfg
kernel/
arch/i386/ boot.asm (Multiboot entry, higher-half jump), GDT/TSS, IDT, stubs, PIC, PIT, context switch
mm/ pmm.c (frames), vmm.c (paging), heap.c (kmalloc)
proc/ process.c (scheduler, threads, processes), elf.c, syscall.c
drivers/ vga, serial, keyboard, mouse, speaker, gfx (mode 13h), ata
fs/ vfs.c, initrd.c, drakefs.c
shell/ shell.c (line editing), commands.c
lib/ string, printf, console (kprintf/klog/panic)
user/ crt0, libc, syscall wrappers, programs/
rootfs/ text files packed into the initrd
tools/ mkinitrd.c, mklogo.py, gdbinit
tests/ boot_test.py
docs/ architecture.md
See docs/architecture.md for the boot flow, memory map and design.
GPL-3.0, see LICENSE.