Linux Build

This section explains how to build a Linux system for RVComp. Using Buildroot, we generate the Linux kernel and root filesystem. The following tools and software are required. Please refer to the Installation Guide.

  • riscv-gnu-toolchain

  • Buildroot

  • OpenSBI (modified for RVComp)

  • Device Tree Compiler

If you want to use the latest Linux kernel, download the latest Linux kernel.

Building with Buildroot

Buildroot is a tool that can easily build embedded Linux systems. Buildroot configuration files for RVComp are included in the RVComp repository.

Setting Environment Variables

If you do not set environment variables as follows before building, the build may fail.

$ unset CPATH
$ unset C_INCLUDE_PATH
$ unset CPLUS_INCLUDE_PATH

Replace <install dir> with the path to the directory where RVComp is installed (either relative or absolute path).

$ git clone https://github.com/buildroot/buildroot.git
$ cd buildroot
$ git checkout 2025.02
$ make BR2_EXTERNAL=<install dir>/rvcomp/buildroot/ uart_defconfig
$ make

Before executing make, you can select Linux kernel version and additional packages with make menuconfig. For details, refer to the Buildroot documentation.

If the build succeeds, the following files are generated in the output/images/ directory:

  • rootfs.cpio: Root filesystem

  • Image: Linux kernel image

  • fw_payload.elf: OpenSBI ELF file

  • fw_payload.bin: OpenSBI image fw_payload.bin is an image containing initramfs + Linux + OpenSBI. When booting Linux on RVComp, this file is sent.

By copying output/images/fw_payload.bin to rvcomp/images, it becomes possible to perform Linux boot simulation with make linux.

Also, when booting Linux on FPGA, the first bootloader needs to recognize the size of fw_payload.bin, so check the size with the following command:

$ stat fw_payload.bin

Set the Size: value in BIN_SIZE in config.mk.