BonfireOS

A minimal, modular x86_64 operating system from scratch: bootloader → kernel → drivers → filesystem → shell.

Features

• Boot: GRUB (Multiboot 1) loads the kernel; 32-bit boot stub switches to long mode and jumps to 64-bit kernel.
• Kernel: C + assembly, with IDT, PIC, and basic interrupt handling.
• Processes & scheduling: Round-robin scheduler, PIT timer (~100 Hz), context switch; idle process + shell process.
• Drivers: VGA text mode (80×25), PS/2 keyboard, PIT timer, ATA PIO (disk).
• FS: In-memory minimal filesystem (mkdir, create, read, write, list, chdir). FAT12/16 read from disk (mount at boot, fatcat FILE.TXT).
• POSIX layer: open/read/write/close, lseek, getcwd/chdir/mkdir, stat; fd 0/1/2 = stdin/stdout/stderr.
• Shell: Commands: help, clear, echo, ls, cd, mkdir, cat, edit, alias, fatcat, DOOM.
• DOOM host API: Video (mode 13h), input (keyboard scancodes + mouse), time, malloc/free, file I/O. Type DOOM to run a linked DOOM port; see docs/DOOM_PORT.md.

Quick start

1. Install toolchain (see docs/BUILD.md):

   • nasm
   • x86_64-elf-gcc and x86_64-elf-ld (cross-compiler)
   • For ISO: grub-mkrescue
   • For run: qemu-system-x86_64

2. Build and run

   make          # build kernel
   make run      # run in QEMU (direct kernel)
   make iso      # build bootable ISO
   make run-iso  # run ISO in QEMU

3. In the shell

   • help — list commands
   • ls / ls /path — list directory
   • cd /path — change directory
   • mkdir /path — create directory
   • cat file — print file
   • edit file — create or overwrite file (single line)
   • alias ll ls — alias ll to ls
   • fatcat FILE.TXT — read file from FAT root on disk (8.3 name)
   • echo hello — print text
   • clear — clear screen

Layout

BonfireOS/
├── Makefile           # Build: kernel, ISO, QEMU targets
├── linker.ld          # Kernel link layout (sections, stack)
├── scripts/grub.cfg   # GRUB menu for ISO
├── include/kernel/   # Headers (vga, port, idt, irq, keyboard, fs, fat, ata, process, timer, posix, shell, alias)
├── src/
│   ├── boot/boot.asm         # Multiboot, long mode switch, 64-bit entry
│   ├── kernel/kernel.c       # kernel_main: init, process, shell
│   ├── kernel/arch/          # idt.c, idt_asm.asm, context_switch.asm, irq.c
│   ├── kernel/drivers/      # vga.c, keyboard.c, timer.c, ata.c
│   ├── kernel/fs/            # fs.c (in-memory), fat.c (FAT12/16)
│   ├── kernel/mm/heap.c     # Bump allocator
│   ├── kernel/process/      # process.c (PCB, scheduler)
│   ├── kernel/posix/        # posix.c (open/read/write/close, etc.)
│   └── kernel/shell/        # shell.c, alias.c
└── docs/
    ├── BUILD.md
    └── ARCHITECTURE.md

Milestones

1. Bootloader — GRUB + multiboot; assembly stub and long mode.
2. Kernel init — GDT, IDT, PIC, VGA, keyboard.
3. Process/scheduling — PCB, context switch, PIT timer, round-robin (idle + shell).
4. Memory — Heap (bump allocator) for process stacks.
5. Drivers — VGA, keyboard, timer, ATA PIO (disk).
6. Filesystem — In-memory FS; FAT12/16 read from disk.
7. POSIX layer — open/read/write/close, getcwd/chdir/mkdir, stat.
8. Shell — Commands and alias, fatcat.

License

GNU Affero General Public License v3.0