Embedded Linux on ARM – Porting Steps

Brief:

– This section helps you to get all the needed files. Here we have used the available version as of updating this page. You may download       the latest version by visiting the corresponding package website.

– Create a directory named, Sources and store all the required tar files into it.

– Change directory to Sources

– Download Buildroot

– Download U-Boot

– Download Linux kernel

Brief:

– The simplest method of building toolchain is using automated scripts provided by the build system.

– In our case we will be using Buildroot to build all the necessary stuffs (including toolchains) to bring up our board

– Create a directory named Buildroot under EOS and change directory to it

– Untar the provided buildroot file from the Sources directory

– Start buildroot configuration

– Just change the Target Architecture and its Variant and keep everything else default and just type

– If everything goes fine the build should be successful
– The toolchain output can be found in output/host/usr/bin

Brief:

– The embedded linux system can be emulated in the host system with the help of Qemu

– Follow the step to install qemu on your host

– To list the available system try

– Pick the closest board you try to emulate

– This document follows vexpress-a9 (ARM Versatile Express for Cortex-A9) board

Brief:

– Create a directory named UBoot under EOS and change directory to it

– Untar the provided u-boot file from the Sources directory

– Do u-boot configuration

– Build the package

– On successful compilation you should get spl/u-boot-spl.bin and u-boot.img files

Brief:

– It is assumed that you have created a network bridge with tap

– To run the bootloader image just run the following command

Brief:

– Create a directory named LinuxKernel under EOS and change directory to it

– Untar the provided linux tar file from the Sources directory

– Do kernel configuration

– On a successful build you should get the final outputs in arch/arm/boot/ directory

– Copy the required file to tftpboot folder

Brief:

– Assuming the tap is configured

– Check the ip address of the host and note it

– Assuming the target is running the u-boot.

– Set the IP addresses of client and server on target board

– You should get “Host is alive” message on target on successful connection
– Load the kernel image on target

– You should see ‘###’ printed on screen with transfer summary

– Load the dtb image on target

– You should see ‘###’ printed on screen with transfer summary

– Set kernel command line arguments

– Boot the loaded image

– The target board should boot up with a kernel panic

Brief:

Adding the RootFS directory path to Initramfs

– Create a directory named RootFS under EOS and change directory to it

– Untar the built rootfs tar file from the buildroot directory

– You should see the entire file system present in the current directory

– Link busybox as init

– Configure the kernel for initramfs

– A ncurses based configuration window will be opened, follow the below steps

– Save and exit the configuration window and build again

– Load the new image

– The board should boot fine. But this time it should complain about null

Brief:

– Change directory to your RootFS

– Change directory to init.d as

– Write a rc script like with folloing lines

– Save and exit

– Give the file executable permission

– Build the kernel

– Load the image

– The board should boot fine

– Login and type

– You should see edit the file system created by you

Well you target board up with Embedded Linux running on it. Now you may proceed further to explore your system as needed and take it further.