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A minimal operating system for the Risc-V architecture written in Zig. It can handle simple processes multitasking, memory management with a 2 level page table and provides a simple shell which can spawn processes.

Modules

• kernel.zig is the main entrypoint for the kernel. It defines a panic handler, some assembly required for the bootloader, and definitions for processes. Processes can spawned after the proc.initialize call in the main function. Most importantly, it prints the welcome banner.
• riscv.zig contains the actual Risc-V instructions for syscalls and other architecture specific routines.
• memory.zig defines an alloc implementation and a 2 level page that that utilizes Risc-V's virtual memory facilities.
• proc.zig defines routines for creating processes and mapping memory to them, as well as multitasking.
• shell.zig and common.zig define various routines to input and output text from the operating system.

Running

You will need qemu with the risc-v plugins installed. The Zig build script should handle building the kernel, linking (including linker scripts) and lauching the VM:

zig build run