rust-riscv64-qemu-starter

A starter repo for writing an OS in Rust. The OS is intended to be run on a RISC-V 64-bit (RV64) computer. The starter repo sets you up to emulate the RV64 computer with QEMU.

The OS code is based off chapter 1 in The Adventures of OS: Making a RISC-V Operating System using Rust (osblog) by Stephen Marz. I created this repo because I was very excited to work through osblog but had a difficult time setting up my development environment. I hope this repo makes it easier for others to follow along with Stephen's amazing work.

Assumptions

• setup.sh uses apt to install QEMU. In other words, your development host is assumed to be Debian-based.
• setup.sh downloads the prebuilt GNU Compiler Toolchain that is intended for Ubuntu 22.04.

Get started

$ source setup.sh

This script:

• Installs QEMU through apt
• Downloads and extracts the prebuilt RISC-V GNU Compiler Toolchain to //tools
• Creates a disk for QEMU

Build the OS

$ make all

Troubleshooting: can't link double-float modules with soft-float modules

See my answer on Stack Overflow.

Run the OS on QEMU

$ make qemu

You should see something like this followed by a blinking cursor:

$ make qemu
qemu-system-riscv64 -machine virt -cpu rv64 -smp 4 -m 128M  -nographic
    -serial mon:stdio -bios none -kernel os.elf -drive if=none,format=raw,file=qemu.dsk,id=foo
    -device virtio-blk-device,scsi=off,drive=foo

Try pressing Ctrl+A and then press C. If you see (qemu) before the blinking cursor then you have successfully accessed QEMU Monitor.

Try running info registers in QEMU Monitor. You should see something like this:

(qemu) info registers

CPU#0
 V      =   0
 pc       000000008000006c
 mhartid  0000000000000000
 mstatus  0000000a00000088
 hstatus  0000000200000000
 vsstatus 0000000a00000000
 mip      0000000000000080
...

To exit, press Ctrl+A again and then press X.

Next steps

Check out chapter 1 in The Adventures of OS: Making a RISC-V Operating System using Rust by Stephen Marz for an explanation of this code.