RVOS — A Minimal, Modern RISC-V Operating System written in Contemporary C++

RVOS is a minimal, educational-oriented operating system designed for the RISC-V architecture. The project is fully implemented using modern C++ (C++20/23) with clean abstractions, a focus on clarity, and an emphasis on understanding low-level system behavior.

RVOS aims to provide a compact and comprehensible codebase for exploring:

• Bare-metal RISC-V execution flow
• Low-level hardware initialization
• Memory layout & privilege levels
• Interrupt handling
• Simple kernel infrastructure
• Hardware–software interaction from power-on to running C++ code

It is designed as a personal research project to deepen understanding of operating systems and kernel

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Build

RVOS uses a minimal and portable build setup based on CMake and a RISC-V bare-metal toolchain. Only standard tools are required, allowing the project to be built on Linux, macOS, or MSYS2 (Windows).

Prerequisites

You will need:

• CMake ≥ 3.20
• RISC-V GCC bare-metal toolchain >= 12.0 (e.g., riscv64-unknown-elf-gcc riscv64-unknown-elf-toolchain)
  • note:Your compilation toolchain must be -mcmodel=medany model, otherwise you will encounter relocation truncated to fit: R_RISCV_HI20 against .LC0'
  • read this SiFive blog article.
• Ninja or GNU make
• (Optional) QEMU for RISC-V to run the OS without real hardware
• If you want to compile sub projects, you also need gtkmm-4.0

git clone https://github.com/BaiLei27/RVOS --recurse-submodules #Clone sub projects are necessary because they have some dependencies between them

Build Steps

From the project root:

cd path/RVOS
Arch=$(uname -m)
cmake -B build-${Arch} -G Ninja -DCMAKE_BUILD_TYPE=Release
cmake --build build-${Arch} -v

This generates in builddir root:

RVOS   # Bare-metal RISC-V kernel image
RVOS.map   # Linker map

Run on QEMU

After building target run manual

qemu-system-riscv64 -M virt -m 1G -nographic -smp 1 -bios none -kernel [target] # [target] such as `RVOS`

or run cmake target:

cmake --build build-${Arch}/build-RVOS -v -t run-[target]
#or
sh ./scripts/shell/qemu_run_tst.sh [target]

Alternatively, target debug:

qemu-system-riscv64 -M virt -m 1G -nographic -smp 1 -bios none -kernel-kernel [target] -s -S &
gdb [target] -ex "target remote :1234" -ex "b _start" -ex "c"

or run cmake target:

cmake --build build-${Arch}/build-RVOS -v -t dbg-[target]
#or
sh ./scripts/shell/qemu_debug.sh [target]

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