Compiling Rust for the Omega2

After receiving my Onion Omega2 from Indiegogo perk, I really wanted to see what was possible with it. So this would be a great opportunity for me to learn Rust and see what it takes to get it running on the Omega2.

I found a good blog from Shane Logsdon explaining how to get it to work with MacOS. I thought I create a simple guide how to compile Rust for the Omega2 on Linux (or windows WSL)

The Onion OS on the Omega2 is a modified version of the LEDE project and the microcontroller used in the Omega2 is the MediaTek Ralink MIPS MT7688. So our goal is to cross-compile rust for the MIPS platform.

This guide continues from on a previous guide where I explain how to compile LEDE (on windows).

Installing Rust

To install and configure rust we need to tell it how to install it and what targets it should support.

The IDE

For the IDE I use visual studio code, which is freely available from here, the following blog shows you how to configure the IDE to run and debug rust. But instead of the RustyCode extension I use the Rust extension which is more actively maintained and installs the dependencies needed automatically.

Tip: If you are unable to debug after following every instruction make sure you have configured rust to use GCC instead of MSVC (MSVC is default). There is a stackoverflow answer here.

We are now going to configure in visual studio code a task that enables us to compile a Rust application, the task is going to use the WSL to compile in Linux with the GCC compiler from the LEDE project we created in the previous guide.

Use CTRL + SHIFT + P and type task, select Configure TaskRunner and then select Other. Replace the existing content with the configuration below, be sure to replace the path with your location.

From now on its possible to execute CTRL + P and type the following to create a build ready for upload to the Omega2.

Now you are able to compile from within windows through the Linux Subsystem for the Omega2.

Creating a rust project and compile

We are almost ready to compile our program to run on the Omega2, first we need to create a rust project. Execute the following command to create a hello_world project in rust.

Next up is to create a config file for rust so that rust knows which linker to use for out target. Creating a directory .cargo and placing a file named config

The configuration will contain the following, replace <user> with your user of course.

Make sure you are in the directory of the project and execute the following to compile the application.

Copy and run it on the Omega2

I use scp to copy it to the /root/ directory on the Omega2, of course replace <ipadres> with the one of your Omega2.

Then use SSH to connect to the omega and give our hello_world executable rights by using the following command

And this will print “Hello, world from rust!”

 

Compiling LEDE on Windows 10

After receiving my Onion Omega2 from my Indiegogo perk, I really wanted to see what was possible with it. I thought this would be a great opportunity for me to try to compile something and see what it takes to get it running on the Omega2. I always develop on windows and that is a challenge when trying to work with IOT.

Before we can compile anything for the Omega2 we need an environment where we can cross compile our sources. The Onion OS on the Omega2 is a modified version of the LEDE project and the microcontroller used in the Omega2 is the MediaTek Ralink MIPS MT7688. So our goal is to compile LEDE, that gives us as result a GCC compiler capable of compiling source to MIPS that we can run on the Omega2.

Windows On Linux (Beta)

In windows 10 pro version 1607 there is a feature called Windows Subsystem for Linux. The Linux subsystem enables native ELF binaries to run under windows and thus enabling us to compile using GCC without the need to have a virtual machine running. There is a good video from one of the architects giving a presentation at blackhat if you want to know more about the system.

As of writing I’m using Windows Insider Build of the Creators Update Build 15031. You can get this build by enabling the Windows Insider Program under Settings –> Update & security –> Windows Insider Program (can take a couple of hours before you are able to see the updates) or you can download the ISO and run it as an update, if you are not willing to wait a few hours.

Setting up the WSL environment

Before this feature is available you need to enable developer mode on windows 10. Which is found in Settings –> Update & security –> For developers. After enabling you are able to turn the feature on.

After you have restarted, we are going to execute the following command, this will be our gateway to the Linux Subsystem.

Windows asks a few question for you to answer, after you have answered those,  you see the bash environment we will be working in. We are almost ready to install the needed dependencies. Before we continue we first update our environment so we have the latest version of our environment.

Next up is editing the file ~/.bashrc and append a line to it so at start the ~/.profile is also loaded, the WSL doesn’t do that.

We also need to edit the ~/.profile file when left as it is will load the ~/.bashrc file and cause an infinite loop. To prevent that from happening we need to remove the following lines from the file ~/.profile.

Downloading source code of LEDE

We need the LEDE sources so we can build a compiler that emits MIPS code that will run on the Omega2. We will start with the download of the sources to your home directory, thanks to WereCatf for the source. Do not work on the windows drives in /mnt/[c-d]. Every mount under /mnt points to the windows mounts, these mounts work with the DriveFs System and has some deadlock issues for now. If that happens then the only way to get WSL working again is to restart windows.

Installing dependencies

Before we continue with compiling LEDE, we first need to install some dependencies. Use the following command to install the dependencies.

Configuring and compiling LEDE

We need to configure the LEDE project before we compile the toolchain. Set the following options.

  • Target System: MediaTek Ralink MIPS
  • Subtarget: MT7688 based boards
  • Target Profile: Onion Omega2 or Onion Omega2+

Use the following command to configure the options for LEDE.

Tip: If navigating with arrows don’t seem to work try using +- and use <TAB> for navigating the bottom menu.

After you have configured LEDE you are ready to compile, use the following command. Compiling LEDE can take more than an hour to complete.

Tip: If the compilation fails try to remove the j4 argument, this argument tell how many hardware threads to use for the compilation.

After the compilation completes, we have the following directory containing the tools needed to compile our sources for the Omega2.

That is all to it, now we can use the mipsel-openwrt-linux-gcc to compile c code or we can use mipsel-openwrt-linux-g++ to compile our c++ code.

Adjust our environment

Now if we edit our ~/.profile again and add some extra paths, then we can compile without having to reference the complete path to our compiler.

We now have a working environment where we can compile c and c++ code.