Booting Riscv linux on Qemu

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The linux kernel on its own is not of any use, we need applications that leverage the power of the kernel. For this we must create a filesystem which contains these applications . Busybox is a software that provides minimalistic software utilities to create a file system.

Requirement

We need following softwares to successfully boot riscv linux on Qemu.

  • Qemu
  • Riscv compiler tool chain
  • Linux kernel
  • busybox

Qemu

cd workspace
git clone https://github.com/qemu/qemu.git
cd qemu
./configure --target-list=riscv64-softmmu
make -j $(nproc)
sudo make install

Linux

cd workspace
git clone https://github.com/torvalds/linux
cd linux
make ARCH=riscv CROSS_COMPILE=riscv64-unknown-linux-gnu- defconfig

Busybox file system

cd workspace
git clone https://git.busybox.net/busybox
dd if=/dev/zero of=rootfs.img bs=1M count=1024
mkfs.ext4 rootfs.img
mkdir rootfs
sudo mount rootfs.img mnt
cd busybox
sudo make CROSS_COMPILE=riscv64-linux-gnu- \
   CONFIG_PREFIX=../mnt \
   LDFLAGS=--static \
   install 
cd ..
sudo mkdir -p mnt/etc mnt/fstab mnt/etc/init.d

Run Qemu

qemu-system-riscv64 -nographic \
   -machine virt \
   -kernel ./kernel/arch/riscv/boot/Image \
   -append "root=/dev/vda ro console=ttyS0" \
   -drive file=rootfs.img,format=raw,id=hd0 \
   -device virtio-blk-device,drive=hd0

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