Tiny RISC-V OS (CSCE Project)

Overview

this is a tiny educational operating system for the RISC-V architecture, designed to run on QEMU's virt machine. It was generated and then extended by using ChatGPT, and serves as a starting point for exploring:

• Bare-metal boot on RISC-V
• Memory-mapped I/O via UART
• A simple cooperative scheduler
• Simulated "processes" (programs)
• Basic synchronization via a spinlock
• A toy in-memory file system
• A minimal command-line shell

Features (mapping to assignment)

• Loading separate programs
  • "Programs" are registered as tasks (tasks_register_demo_programs) and can be extended by adding new functions and registering them via tasks_add.
• Running multiple programs simultaneously
  • The scheduler calls each active task's step function round-robin.
• Synchronization
  • Shared shared_counter guarded by a spinlock (lock() / unlock()).
• Protection
  • Logical separation: each task has an ID and only cooperatively accesses shared state. (Physical protection/MMU is not implemented but could be a future extension.)
• File system
  • In-memory "files" in fs.c with ls and cat commands in the shell.
• Create/load new programs
  • New programs can be added by:
    1. Writing a new void myprog_step(void) function
    2. Adding it via tasks_add("myprog", myprog_step)
    3. Calling tick / run N in the shell to schedule them.

Building on a lab machine

The exact commands may vary depending on how RISC-V tools are installed in the lab. Replace the toolchain prefix if needed (e.g., riscv64-linux-gnu-).

1. Clone or copy this directory to your home:

   cd ~/riscv-os
   
   

To boot using QEMU MSYS2

Run these lines: "/c/Program Files/qemu/qemu-system-riscv64.exe"
-machine virt -nographic
-bios none
-kernel kernel.elf
-serial mon:stdio

Go to DOCUMENTATION.md for the documentation process.