Cross-compiling for the RaspberryPi

This page will guide you to setup a complete cross-compiling environment for the RaspberryPi board. This procedure is tailored for and tested on Ubuntu 12.10, but it can be easily adapted for the use on other distributions.

Prerequisites

• Install all the required software packages:

sudo apt-get install git rsync cmake

• If you are using a 64-bit version of Ubuntu, also install the 32-bit compatibility libraries:

sudo apt-get install ia32-libs

• If you are using a 64-bit version of Debian, the ia32-libs metapackage is no longer installable. Execute instead

 su -
 dpkg --add-architecture i386
 apt-get update && apt-get install libc6-i386 lib32stdc++6 zlib1g:i386

• The guide will take for granted that you are using the official Raspbian OS image, downloadable from the RaspberryPi website.
• Moreover, you will need a working SSH connection between the Raspberry and your computer (not covered by this guide).

Step One: installing the cross-compiler

• Select a directory in which you will install everything. For the purposes of this guide, I will consider a subdirectory of your home folder, ~/raspberrypi . Create it and then access it:

cd
mkdir raspberrypi
cd raspberrypi

• Download the "official" cross-compiler of the Raspberry Pi project through git:

git clone git://github.com/raspberrypi/tools.git

This will create, among other things, a tools/arm-bcm2708 subfolder containing three different compiler toolchains:

arm-bcm2708-linux-gnueabi

arm-bcm2708hardfp-linux-gnueabi

gcc-linaro-arm-linux-gnueabihf-raspbian

We are going to use the third of these toolchains, since it's the most optimized and supports the FPU that is available on the RaspberryPi board.

• Go back to your home directory, and open your .bashrc configuration file with any text editor, like nano, gedit or leafpad, and add this string at the bottom:

PATH=$PATH:$HOME/raspberrypi/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian/bin

• Now, either logout and login back again, or just close and reopen the terminal window, and type:

arm-linux-gnueabihf-gcc -v

If all goes well, you should see something like

tudhalyas@gondor:~$ arm-linux-gnueabihf-gcc -v
Using built-in specs.
COLLECT_GCC=arm-linux-gnueabihf-gcc
COLLECT_LTO_WRAPPER=/home/tudhalyas/raspberrypi/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian/bin/../libexec/gcc/arm-linux-gnueabihf/4.7.2/lto-wrapper
Target: arm-linux-gnueabihf
Configured with: /cbuild/slaves/oort61/crosstool-ng/builds/arm-linux-gnueabihf-raspbian-linux/.build/src/gcc-linaro-4.7-2012.08/configure --build=i686-build_pc-linux-gnu --host=i686-build_pc-linux-gnu --target=arm-linux-gnueabihf --prefix=/cbuild/slaves/oort61/crosstool-ng/builds/arm-linux-gnueabihf-raspbian-linux/install --with-sysroot=/cbuild/slaves/oort61/crosstool-ng/builds/arm-linux-gnueabihf-raspbian-linux/install/arm-linux-gnueabihf/libc --enable-languages=c,c++,fortran --disable-multilib --with-arch=armv6 --with-tune=arm1176jz-s --with-fpu=vfp --with-float=hard --with-pkgversion='crosstool-NG linaro-1.13.1+bzr2458 - Linaro GCC 2012.08' --with-bugurl=https://bugs.launchpad.net/gcc-linaro --enable-__cxa_atexit --enable-libmudflap --enable-libgomp --enable-libssp --with-gmp=/cbuild/slaves/oort61/crosstool-ng/builds/arm-linux-gnueabihf-raspbian-linux/.build/arm-linux-gnueabihf/build/static --with-mpfr=/cbuild/slaves/oort61/crosstool-ng/builds/arm-linux-gnueabihf-raspbian-linux/.build/arm-linux-gnueabihf/build/static --with-mpc=/cbuild/slaves/oort61/crosstool-ng/builds/arm-linux-gnueabihf-raspbian-linux/.build/arm-linux-gnueabihf/build/static --with-ppl=/cbuild/slaves/oort61/crosstool-ng/builds/arm-linux-gnueabihf-raspbian-linux/.build/arm-linux-gnueabihf/build/static --with-cloog=/cbuild/slaves/oort61/crosstool-ng/builds/arm-linux-gnueabihf-raspbian-linux/.build/arm-linux-gnueabihf/build/static --with-libelf=/cbuild/slaves/oort61/crosstool-ng/builds/arm-linux-gnueabihf-raspbian-linux/.build/arm-linux-gnueabihf/build/static --with-host-libstdcxx='-L/cbuild/slaves/oort61/crosstool-ng/builds/arm-linux-gnueabihf-raspbian-linux/.build/arm-linux-gnueabihf/build/static/lib -lpwl' --enable-threads=posix --disable-libstdcxx-pch --enable-linker-build-id --enable-plugin --enable-gold --with-local-prefix=/cbuild/slaves/oort61/crosstool-ng/builds/arm-linux-gnueabihf-raspbian-linux/install/arm-linux-gnueabihf/libc --enable-c99 --enable-long-long
Thread model: posix
gcc version 4.7.2 20120731 (prerelease) (crosstool-NG linaro-1.13.1+bzr2458 - Linaro GCC 2012.08)

Step Two: set-up your compiling environment

• Go back into the raspberrypi directory and create a subfolder named rootfs:

 cd
cd raspberrypi
mkdir rootfs

• Now tell rsync to copy the entirety of the /usr and /lib directories of your RaspberryPi filesystem into the newly created folder on your computer:

rsync -rl --delete-after --safe-links pi@$RASPI:/{lib,usr} $HOME/raspberrypi/rootfs

where $RASPI is the IP address of the Raspberry. You can put this line of code in a text file and save it as a shell script for your convenience.

• Create a text file called Toolchain-RaspberryPi.cmake and insert the following into it:

SET(CMAKE_SYSTEM_NAME Linux)
SET(CMAKE_SYSTEM_VERSION 1)
# specify the cross compiler
SET(CMAKE_C_COMPILER $ENV{HOME}/raspberrypi/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian/bin/arm-linux-gnueabihf-gcc)
SET(CMAKE_CXX_COMPILER $ENV{HOME}/raspberrypi/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian/bin/arm-linux-gnueabihf-g++)
# where is the target environment
SET(CMAKE_FIND_ROOT_PATH $ENV{HOME}/raspberrypi/rootfs)
# search for programs in the build host directories
SET(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
# for libraries and headers in the target directories
SET(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
SET(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

• Now you are able to compile your own projects using cmake, by passing the path of the Toolchain specification file to the program (supposing that the sources are located into a src directory which in turn is located into ${PROJECT_DIR}):

mkdir ${PROJECT_DIR}/build
cd ${PROJECT_DIR}/build
cmake -G"Eclipse CDT4 - Unix Makefiles" -D CMAKE_BUILD_TYPE=Debug -D CMAKE_TOOLCHAIN_FILE=$HOME/raspberrypi/Toolchain-RaspberryPi.cmake ../src

Step Three: Remote program execution through Eclipse

... to be continued ...

References

• http://wiki.debian.org/Multiarch/HOWTO
• http://hertaville.com/2012/09/28/development-environment-raspberry-pi-cross-compiler/
• http://www.kitware.com/blog/home/post/426
• http://www.cmake.org/Wiki/CMake_Cross_Compiling