Description

This project is a very-very commented and detailed explanation on writing your own small kernel for 32-bit RISC-V. It is built upon QEMU - an emulation software, using virt.

Build

1. Install Zig programming language:

• Linux: https://ziglang.org/download

1. Install QEMU system for RISC-V:

• Ubuntu: apt install qemu-system-misc
• Arch: pacman -S qemu-system-riscv

1. Install Just command runner:

• Ubuntu: apt install just
• Arch: pacman -S just

1. Install gdb debugger:

• Ubuntu: apt install gdb
• Arch: pacman -S gdb

1. Run or build in an appropriate way:

• just build: builds a whole project as a single binary
• just run: builds a whole project and runs built binary in a QEMU
• just dbg: builds a whole project and runs build binary in a QEMU with open debugging port
• just gdb: connects to the open QEMU debugging port (see just dbg) using gdb

There is also helper.gdb GDB script for printing relevant information while debugging. You may find it useful.

Code

Order of look-through:

1. src/linker.lds
2. src/boot.s
3. src/kernel.zig
4. src/uart.zig Just read comments from file in a provided order.

Clarifications

Kernel is built for 4-core RV32IM ISA compatible CPU with ILP32 ABI using GNU toolchain (see GCC). The source code does not implement BIOS, only the kernel itself!