Chronos OS

A hobby x86_64 kernel written in Rust, demonstrating memory management, preemptive multitasking, interrupt handling, and async/await.

Features

• Memory: Virtual memory with paging, heap allocation (bump/linked-list/fixed-size block), physical frame allocator
• Interrupts: IDT, PIT-based preemptive scheduling, PS/2 keyboard, exception handling
• Multitasking: Kernel threads with EEVDF scheduler (round-robin alternative), context switching
• Async: Custom executor, waker-based task scheduling, async sleep, keyboard input stream
• Shell: VGA text mode (80x25), serial debug output, built-in commands: help, clear, echo, uptime, mem

Build

Requires Rust nightly, bootimage, and QEMU.

cargo build   # build
cargo run     # run in QEMU
cargo test    # run tests

Project Structure

src/
├── main.rs / lib.rs     # Entry point, initialization
├── gdt.rs               # Global Descriptor Table
├── interrupts.rs        # IDT, PIC, interrupt handlers
├── memory.rs            # Page tables, frame allocation
├── allocator.rs         # Heap allocator implementations
├── vga_buffer.rs        # VGA text mode driver
├── serial.rs            # Serial port output
├── task/                # Async executor, shell, keyboard, sleep
└── thread/              # Scheduler (EEVDF/RR), context switch, stacks

Memory Layout

• Heap: 100 KiB at 0x4444_4444_0000
• Stacks: 16 KiB per thread
• VGA buffer: 0xb8000 (identity-mapped)

Boot Sequence

GDT/TSS → IDT → PIC → heap → VGA map → spawn executor thread → scheduler loop