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)
• Ninja or GNU make
• (Optional) QEMU for RISC-V to run the OS without real hardware:

Example installation (MSYS2 / Arch ):

sudo pacman -S riscv64-elf-gcc riscv64-elf-newlib # or riscv64-unknown-elf-gcc
sudo pacman -S cmake ninja qemu-system-riscv

in Ubuntu

sudo apt install riscv64-unknown-elf-gcc #or gcc-riscv64-unknown-elf
sudo apt install cmake ninja-build qemu-system-riscv

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Build Steps

From the project root:

cmake -S . -B build-x86_64  -DCMAKE_BUILD_TYPE=Debug -DCMAKE_C_COMPILER=riscv64-elf-gcc -DCMAKE_CXX_COMPILER=riscv64-elf-g++ -G Ninja #[deprecate]
# You need to set the `-DCMAKE_C_COMPILER`(default `riscv64-elf-gcc`) parameter in the root directory `ExternalProject_Add` first
cmake -S . -B build-x86_64 -G Ninja
cmake --build build-x86_64 -v

This generates in builddir:

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

Run on QEMU

After building target run manual

qemu-system-riscv64 -nographic -smp 1 -machine virt -bios none -serial mon:stdio -kernel [target name]

or run cmake target:

cmake --build build-x86_64/build-RVOS -v -t run-[target]

Alternatively, target debug:

qemu-system-riscv64 -nographic -smp 1 -machine virt -bios none -serial mon:stdio -kernel [target name] -s -S&
gdb [target name] -ex "target remote :1234" -ex "b _start" -ex "c"

or run cmake target:

cmake --build build-x86_64/build-RVOS -v -t dbg-[target]

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