Compiling code for the RISC-V

(Updated 2026-01)

Tested on Ubuntu 24.04.1 (WSL2)

Kernel 6.6.87.2-microsoft-standard-WSL2

Requirements

• RISC-V Toolchain (32 or 64 bits, in this example I will use the 32 version)
  • This is the repository I used to install the toolchain, precisely tag 2026.01.01.
  • Basically clone the repo, checkout the tag and install the Prerequisites for Ubuntu.
  • Then configure the installation for baremetal Risc-V, 32 bits RV32I

    sudo mkdir /opt/riscv
    sudo chown -R <your_ubuntu_username> /opt/riscv/
    sudo chgrp -R <your_ubuntu_username> /opt/riscv/
    
    ./configure --prefix=/opt/riscv --with-arch=rv32i --with-abi=ilp32
    make

  • The installation might take up around 1 hour. Verify it went successful by:

    cd /opt/riscv/bin
    ./riscv32-unknown-elf-gcc --version

  • Add the riscv toolchain to PATH by adding this to the .bashrc:

    export PATH=$PATH:/opt/riscv/bin

Assembler example

riscv32-unknown-elf-as exampleAsm.S -o exampleAsm.o
riscv32-unknown-elf-ld -o exampleAsm.elf -T asm.ld -m elf32lriscv -nostdlib --no-relax

C example (compiling and linking)

riscv32-unknown-elf-gcc -c example.c -o example.o
riscv32-unknown-elf-gcc example.o -o example.elf -nostdlib -lgcc -T loader.ld

Trying to use multiplication or other advanced math operations with the rv32I arch? No problem, by linking with the flag -lgcc the compiler will use software multiplication by using libgcc.

(Optional) Generating .HEX dump (for FPGA)

Alternative 1: use standard tools

riscv32-unknown-elf-objcopy -O binary exampleProg.elf exampleProg.bin
hexdump -e '"%08x\n"' exampleProg.bin > exampleProg.hex

Alternative 2: use elf2hex

• A guide to install the elf2hex tool

riscv32-unknown-elf-elf2hex --bit-width 32 --input exampleProg.elf --output exampleProg.hex