kr0nos

kr0nos is a minimal operating system written entirely in x86 assembly. Its goal is to provide a small, understandable, and easily extendable OS kernel.

Version History

See CHANGELOG for full version history.

Features

• Minimal x86 Assembly-based kernel (32-bit protected mode)
• Simple command-line shell
  • help – Show available commands
  • clr – Clear the screen
  • exit – Shut down the OS (ACPI / HLT)
  • about – Show OS information
  • uname – Show system name
  • version – Show kernel version
  • reboot – Reboot the system
  • read – Read and hex-dump a disk sector (experimental, ATA PIO LBA28)
  • sysinfo – Show CPU info (CPUID) and RAM size (E820 via bootloader)
  • uptime – Show system uptime in ticks
  • sleep – Sleep for N ticks (sleep <n>)
  • free – Show physical memory usage (pages)
  • testalloc – Run heap allocator tests (malloc/free)
• IDT with exception handlers (kernel panic on crash instead of reboot)
• PIT timer (IRQ0, 100Hz) with tick counter
• Serial I/O (COM1, 115200 baud) for text-mode terminal support
• Interrupt-driven keyboard (IRQ1, scancode → ASCII)
• Physical page allocator (bitmap, 4KB pages)
• Heap allocator (malloc/free, free-list, coalescing)
• Modular driver system (drivers/)
• Structured build system (Makefile)
• Testable using QEMU

Build & Run

# Build
make

# Run in QEMU (graphical)
make run

# Run in terminal (text mode)
make run-text

# Debug mode (serial output)
make debug

# Syntax check
make check

# Clean build artifacts
make clean

Project Structure

kr0n/
├── boot/boot.asm           # Bootloader (real mode → PM)
├── kernel/
│   ├── kernel.asm          # Main kernel (screen, keyboard, serial I/O, shell)
│   ├── pit.asm             # PIT driver (IRQ0, 100Hz tick)
│   ├── idt.asm             # IDT, exception handlers, PIC, IRQ subsystem
│   ├── mm.asm              # Physical page allocator (bitmap, 4KB)
│   ├── heap.asm            # Heap allocator (malloc/free)
│   ├── commands.asm        # Command table and dispatcher
│   └── sc/                 # Shell commands
│       ├── help.asm
│       ├── clear.asm
│       ├── about.asm
│       ├── exit.asm
│       ├── uname.asm
│       ├── version.asm
│       ├── reboot.asm
│       ├── read.asm
│       ├── sysinfo.asm
│       ├── uptime.asm
│       ├── sleep.asm
│       ├── free.asm
│       └── testalloc.asm
├── drivers/
│   ├── cpuid.asm           # CPU vendor/brand detection
│   ├── memdetect.asm       # Memory size detection
│   └── ata.asm             # ATA PIO LBA28 disk driver
├── build/                  # Build outputs (auto-generated)
├── Makefile
├── CHANGELOG.md
└── README.md

License

GNU General Public License v3.0. See LICENSE.