Compiling Linux with Buildroot

About

This tutorial is an adapted version of NiosII Linux User Manual.

Requirements

• Download Mentor's compiler;
• Download buildroot Embedded Linux Generator;
• Create a work directory, e.g. "mkdir my_first_linux";
• Extract bot files to my_first_linux directory as "sourcery" and "buildroot" respectively;

Nios II Configuration

• Export the need environment variables in order to continue:
  • export PATH=$PATH:/home/aluno/Documentos/sourceryg/bin (path to the binaries of your compiler)
  • export ARCH=nios2
  • export CROSS_COMPILE=nios2-linux-gnu-
• Go to the my_first_linux/buildroot/configs/ directory and run "wget https://rocketboards.org/foswiki/pub/Documentation/NiosIILinuxUserManual/nios2_defconfig";
• Now edit this file with any editor like "vim nios2_defconfig";
• At the third line, change the value of the variable 'BR2_TOOLCHAIN_EXTERNAL_PATH' to the path where you extracted the compiler, e.g: '/home/aluno/Documentos/sourceryg++-2016.05'.

Buildroot Options

• Now go to the directory my_first_linux/buildroot/ and run "make nios2_defconfig";
• After that open the config menu with "make menuconfig";
• [Optional] Enter your root password at System Configuration -> Enable root login with password;
• [Optional] Add OpenSSH at Target packages -> Networking applications -> openssh;
• Select an text editor such as nano at Target packages-> Text Editors and viewers -> nano;
• Exit & Save;
• Run "make".

Bootloader

• Go to the my_first_linux/buildroot/ directory and download the bootloader running "git clone https://github.com/altera-opensource/u-boot-socfpga.git";
• To generate to bootloader, go to my_first_linux/buildroot/u-boot-socfpga/ directory and run "make nios2-generic_config";
• For an unknown reason it might require you to run this command again "make nios2-generic_config";
• Finally, run "make".

Linux Kernel

• Go to my_first_linux/;
• Download the kernel with "wget https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-4.6.3.tar.xz";
• Extract the file as a directory named "linux";
• Go to my_first_linux/linux/ and run "make clean";
• Then, run "make 3c120_defconfig";
• Then, "make vmImage";
• And finally "make 3c120_devboard.dtb"

Joint All Generated Files

• Create a new directory called joint_binaries at my_first_linux/;
• Go to my_first_linux/;
• Start copying all binaries to this directory:
  • cp buildroot/output/images/rootfs.* joint_binaries/
  • cp u-boot-socfpga/u-boot joint_binaries/
  • cp linux/arch/nios2/boot/vmImage joint_binaries/
  • cp linux/arch/nios2/boot/vmlinux.bin joint_binaries/
  • cp linux/arch/nios2/boot/3c120_devboard.dtb joint_binaries/