Writing an Operating System in 1,000 Lines

My implementation of https://operating-system-in-1000-lines.vercel.app/en A small operating system written from scratch for RISC-V CPU architecture

This project will have basic context switching, paging, user mode, a command-line shell, a disk device driver, and file read/write operations in C. And also I'll try to add some more functionality to it

Getting Started

You have to be on UNIS-like OS to run this OS. If you're on Windows you need to install WSL2 (Windows Subsystem for Linux) and follow Ubuntu instructions

Install tools

macOS

Install Homebrew and run this command to get all tools you need:

brew install llvm lld qemu

Also, you need to add LLVM binutils to your PATH:

$ export PATH="$PATH:$(brew --prefix)/opt/llvm/bin"
$ which llvm-objcopy
/opt/homebrew/opt/llvm/bin/llvm-objcopy

Ubuntu

Install packages with apt:

sudo apt update && sudo apt install -y clang llvm lld qemu-system-riscv32 curl

Also, download OpenSBI (think of it as BIOS/UEFI for PCs):

curl -LO https://github.com/qemu/qemu/raw/v8.0.4/pc-bios/opensbi-riscv32-generic-fw_dynamic.bin

Warning

When you run QEMU, make sure opensbi-riscv32-generic-fw_dynamic.bin is in your current directory. If it's not, you'll see this error:

qemu-system-riscv32: Unable to load the RISC-V firmware "opensbi-riscv32-generic-fw_dynamic.bin"

Other OS users

If you are using other OSes, get the following tools:

• bash: The command-line shell. Usually it's pre-installed.
• tar: Usually it's pre-installed. Prefer GNU version, not BSD.
• clang: C compiler. Make sure it supports 32-bit RISC-V CPU (see below).
• lld: LLVM linker, which bundles complied object files into an executable.
• llvm-objcopy: Object file editor. It comes with the LLVM package (typically llvm package).
• llvm-objdump: A disassembler. Same as llvm-objcopy.
• llvm-readelf: An ELF file reader. Same as llvm-objcopy.
• qemu-system-riscv32: 32-bit RISC-V CPU emulator. It's part of the QEMU package (typically qemu package).

Tip

To check if your clang supports 32-bit RISC-V CPU, run this command:

$ clang -print-targets | grep riscv32
    riscv32     - 32-bit RISC-V

You should see riscv32. Note pre-installed clang on macOS won't show this. That's why you need to install another clang in Homebrew's llvm package.