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| = How to use CMake to cross compile software for eCos =
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| == Install the eCos host tools ==
| | This page has moved [https://gitlab.kitware.com/cmake/community/wikis/doc/cmake/cross_compiling/Ecos here]. |
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| To build eCos software, you need the host tools for eCos, ecosconfig and optionally configtool. Make sure
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| both ecosconfig and configtool can be found via the PATH.
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| There are different way how to get them.
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| * For some Linux distributions there exist ready-to-use packages, which you can simply install. E.g. for Ubuntu this
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| is done using "apt-get install ecosconfig".
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| * Download and install a recent prebuilt version of the hosttools provided by eCosCtentric. You can find it at http://www.ecoscentric.com/devzone/configtool.shtml
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| * Download and install the binary ecos 2.0 releases you can find at ftp://ecos.sourceware.org/pub/ecos/releases/ecos-2.0 . Ignore the actual eCos sources in the package and use only configtool and ecosconfig which you can find in ecos-2.0/tools/bin/ in the package.
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| * Download the sources from cvs and build it yourself. You can find instructions [[http://ecos.sourceware.org/anoncvs.html || here]]
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| and [[http://www.ecoscentric.com/devzone/configtool.shtml || here]].
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| == Install a toolchain for building eCos applications ==
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| You need to install a suitable cross compiling toolchain to be able to build software for eCos. You can download them either from ftp://ecos.sourceware.org/pub/ecos/gnutools or build it yourself following the instructions you can find at http://ecos.sourceware.org/build-toolchain.html . Install the toolchain to any location you like,
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| e.g. $HOME/ecostoolchains/ . Make sure the compiler is available via PATH, e.g. EXPORT PATH=$HOME/ecostoolchains/arm-elf/bin:$PATH.
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| == Get the eCos sources and set ECOS_REPOSITORY ==
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| eCos release 2.0 is very old, it is recommended to use current anonymous cvs.
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| You can find instructions here:
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| http://ecos.sourceware.org/anoncvs.html
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| If you can't access cvs you can also download a weekly snapshot of cvs provided by eCosCentric: http://www.ecoscentric.com/devzone/snapshots.shtml
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| Once you have the eCos sources installed somewhere on your development machine, e.g. in $HOME/ecos, set the
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| ECOS_REPOSITORY environment variable. This is required for running ecosconfig and configtool. It has to point to the directory
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| where the file ecos.db is located, e.g. $HOME/ecos/packages/ .
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| == Build an eCos ==
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| eCos is a configurable operating system, so you have to configure the system you want to use.
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| Here's a simple example for the ARM integrator board:
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| <pre>
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| ~/ $ cd src/ecos-arm-integrator
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| ~/src/ecos-arm-integrator/ $ ecosconfig new integrator_arm9 default
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| ~/src/ecos-arm-integrator/ $ ecosconfig tree
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| ~/src/ecos-arm-integrator/ $ make
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| ~/src/ecos-arm-integrator/ $ ls install/
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| include lib
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| ~/src/ecos-arm-integrator/ $ ls install/lib
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| extras.o libextras.a libtarget.a target.ld vectors.o
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| </pre>
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| The first step will create an ecos.ecc file, which contains the configuration of the operating system. The second step
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| uses this information to generate makefiles, which you use to build in the final make step. Once make has finished, you will
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| find an include/ and a lib/ directory created in the install/ subdirectory. This is the target environment which will
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| be used for compiling your software for this eCos.
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| == Write a CMake toolchain file ==
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| For CMake to be able to crosscompile software, it requires you to write a toolchain file, which tells CMake
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| some information about the toolchain.
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| With the examples used above it will look like:
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| <pre>
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| INCLUDE(CMakeForceCompiler)
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| # the name of the target operating system
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| SET(CMAKE_SYSTEM_NAME eCos)
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| # which compiler to use
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| # since the compiler can't build a simple program by default without knowing
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| # where the eCos target library is, the FORCE macros have to be used
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| # use arm-elf-gcc for C, the compiler id is "GNU", the sizeof(void*) is 4
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| CMAKE_FORCE_C_COMPILER(/home/alex/src/ecostoolchains/arm-elf/bin/arm-elf-gcc GNU 4)
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| # use arm-elf-g++ for C++, the compiler id is "GNU", the sizeof(void*) is 4
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| CMAKE_FORCE_CXX_COMPILER(/home/alex/src/ecostoolchains/arm-elf/bin/arm-elf-g++ GNU)
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| # here is the target environment located
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| SET(CMAKE_FIND_ROOT_PATH /home/alex/src/ecos-arm-integrator/install )
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| # adjust the default behaviour of the FIND_XXX() commands:
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| # search headers and libraries in the target environment, search
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| # programs in the host environment
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| set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
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| set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
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| set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
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| </pre>
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| Save this file as Toolchain-eCos-arm-elf.cmake to some location where you will put
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| all your toolchain files, e.g. $HOME.
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| == Build the software for eCos ==
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| Let's say you have the classical hello world software with a CMake based buildsystem and want to build this for the eCos
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| you built above.
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| main.c:
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| <pre>
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| include <stdio.h>
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| int main()
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| {
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| printf("Hello world\n");
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| return 0;
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| }
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| </pre>
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| CMakeLists.txt:
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| <pre>
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| ADD_EXECUTABLE(hello main.c)
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| </pre>
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| Then run CMake on it to generate the buildfiles, the important point is that you tell it to use the toochain file you just wrote:
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| <pre>
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| ~/src/helloworld/ $ mkdir build
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| ~/src/helloworld/ $ cd build
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| ~/src/helloworld/build/ $ cmake -DCMAKE_TOOLCHAIN_FILE=~/Toolchain-eCos-arm-elf.cmake ..
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| -- Configuring done
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| -- Generating done
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| -- Build files have been written to: /home/alex/src/helloworld/build
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| ~/src/helloworld/build/ $ make
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| Scanning dependencies of target hello
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| [100%] Building C object CMakeFiles/hello.dir/main.o
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| Linking C executable hello.elf
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| [100%] Built target hello
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| </pre>
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| So that's all. It actually doesn't matter whether it's just a "hello world" or some complex piece of software,
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| the only difference is the usage of the toolchain file. If the software has all required configure checks, it should just
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| build also for eCos.
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