Cross Compiling: Difference between revisions

Latest revision as of 20:02, 29 November 2016

Issues:

need cross compile toolchain
- you need to find or build an entire toolchain environment; ubuntu has some, others have some, Crosstool-NG will build one from scratch
- for autotools, you typically need to define tools like ar, gcc, g++ in the build script
- for cmake, you typically need a toolchain file to specify details
need to cross compile any dependencies (static link what you can)
need to match the libraries on target machine for any dynamic linking requirements
need to match the build to the target kernel (or you might get "kernel too old")

libz example

   echo Getting source code for libraries...
   if [ ! -d zlib ]; then
       wget http://zlib.net/zlib-${zlib_version}.tar.gz
       untar zlib-${zlib_version}.tar.gz
       ln -s zlib-${zlib_version} zlib
   fi
   echo Building libraries...
   if [ "$rebuild_libs" = true ]; then
   
       export cross=arm-linux-gnueabi-
   
       # ZLIB
       cd zlib
       ./configure --prefix=${install_root}
       make CC="${cross}gcc" AR="${cross}ar r" RANLIB="${cross}ranlib"
       make install
       cd ..
   fi

openssl example

   echo Getting source code for libraries...
   if [ ! -d openssl ]; then
       wget https://www.openssl.org/source/openssl-${openssl_version}.tar.gz
       untar openssl-${openssl_version}.tar.gz
       ln -s openssl-${openssl_version} openssl
   fi
   
   echo Building libraries...
   
   if [ "$rebuild_libs" = true ]; then
   
       export cross=arm-linux-gnueabi-
   
       # OPENSSL
       cd openssl
       ./Configure dist --prefix=${install_root} --openssldir=${install_root}
       make CC="${cross}gcc" AR="${cross}ar r" RANLIB="${cross}ranlib"
       make install
       cd ..
   fi

multi-lib complete example

   # Cross compile env for armv4 chipset 
   # Conel cellular modem (Verizon/Pogens)
   # ARM 926EJ-S processor
   # Using toolchain on vpn.causam.com that was built a while ago by Bryan G. with Crosstool-NG 1.20.0
   
   # We will cross compile these libraries:
   # zlib for compression
   # openssl for encryption - NOTE that it is considered unsafe to bake zlib directly into openssl
   # libwebsockets for wss
   
   
   # LIB VERSIONS: No reason I know of not to use the latest
   # It's just that the versions are needed in the script
   zlib_version=1.2.8     # see http://www.zlib.net/
   openssl_version=1.1.0c # see https://www.openssl.org/source/
   lws_branch=v2.0-stable
   
   
   # Turn this on at least at the first run, again as needed.
   rebuild_libs=true
   
   
   # ==========================================
   # cross compile toolchain magic happens here
   # ==========================================
   
   nickname=armv4
   
   # We will use a cross-compile toolchain that was built a while ago by Bryan G. with Crosstool-NG 1.20.0
   # We will build on an older machine (vpn.causam.com) since this did not seem to help limit the kernel: --enable-kernel=${max_kernel}
   if [ ! -d /opt/crosstool-source-v4 ]; then
       echo "Cross-compile toolchain not found..."
       kill -SIGINT $$;
   fi
   
   export cross=arm-926ejs-linux-gnueabi-
   CC=${cross}gcc
   CMAKE_TOOLCHAIN_FILE=/home/m/development/causam/git/np/nop-bigress-client-c/${nickname}/toolchain.cmake
   export PATH=/opt/crosstool-source-v4/arm-926ejs-linux-gnueabi/bin:${PATH}
   
   export install_root=/home/m/development/${nickname}
   
   # ==========================================
   
   
   echo Getting source code for libraries...
   cd ${install_root}/source
   if [ ! -d zlib ]; then
       wget http://zlib.net/zlib-${zlib_version}.tar.gz
       tar -xzvf zlib-${zlib_version}.tar.gz
       ln -s zlib-${zlib_version} zlib
   fi
   if [ ! -d openssl ]; then
       wget https://www.openssl.org/source/openssl-${openssl_version}.tar.gz
       tar -xzvf openssl-${openssl_version}.tar.gz
       ln -s openssl-${openssl_version} openssl
   fi
   if [ ! -d libwebsockets ]; then
       git clone https://github.com/warmcat/libwebsockets.git
       cd libwebsockets
       git checkout ${lws_branch}
       cd ..
   fi
   
   echo Building libraries...
   
   if [ "$rebuild_libs" = true ]; then
   
       # Good help: http://stackoverflow.com/questions/11841919/cross-compile-openssh-for-arm
       # BUT full of landmines...    
       # Use [file ##.so.##] or [file executable] to find out the architecture of an asset.
   
       # ZLIB
       # THIS IS EXTREMELY BRITTLE, do not adjust
       # THIS DOES NOT USE 'ar r', IT USES 'ar', BUT OPENSSL WILL USE 'ar r'
       # Make sure we build static
       # NOTE the global CC define WILL NOT WORK HERE, use this CC define specifically or it WILL BREAK
       cd zlib
       CC="${cross}gcc" AR="${cross}ar" RANLIB="${cross}ranlib" ./configure --static --prefix=${install_root}
   
       make clean
       make
       make install
       cd ..
       
       # OPENSSL
       # THIS IS EXTREMELY BRITTLE, do not adjust
       cd openssl
       ./Configure dist --prefix=${install_root} --openssldir=${install_root}
       make clean
       make CC="${cross}gcc" AR="${cross}ar r" RANLIB="${cross}ranlib"
       make install
       cd ..
   
       # LIBWEBSOCKETS
       # NOTE: we basically need most lws features, with the exception of PLUGINS support.
       cd libwebsockets
       git pull
       mkdir -p cmake-${nickname}-release
       cd cmake-${nickname}-release
       rm -rf CMakeCache.txt CMakeFiles cmake_install.cmake *.cpb Makefile
       cmake -static \
           -DCMAKE_INSTALL_PREFIX:PATH=${install_root}         \
           -DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE}      \
           -DZLIB_LIBRARY=${install_root}/lib                  \
           -DZLIB_INCLUDE_DIR=${install_root}/include          \
           -DLWS_OPENSSL_LIBRARIES=${install_root}/lib         \
           -DLWS_OPENSSL_INCLUDE_DIRS=${install_root}/include  \
           -DLWS_WITH_SHARED=OFF           \
           -DLWS_WITHOUT_TESTAPPS=1        \
           -DLWS_WITH_SSL=1                \
           -DLWS_WITH_ZLIB=1               \
           -DLWS_WITHOUT_EXTENSIONS=0      \
           -DLWS_HAVE_SSL_CTX_set1_param=1 \
           -DLWS_WITHOUT_DAEMONIZE=0       \
           -DLWS_WITHOUT_SERVER=1          \
           -DLWS_MAX_SMP=4                 \
           ..
       make
       make install
       cd ../..
   fi
   
   echo =========================================================
   echo Cross-compiled libraries have been built here [${install_root}/lib]:
   echo =========================================================
   ls -la ${install_root}/lib
   echo =========================================================
   
   echo Copy nop-client source and toolchain CMakeLists.txt...
   mkdir -p nop-client
   cp -rp /home/m/development/causam/git/np/nop-bigress-client-c/* nop-client/
   cp -rp /home/m/development/causam/git/np/nop-bigress-client-c/${nickname}/CMakeLists.txt nop-client/
   cd nop-client
   mkdir -p cmake-${nickname}-release
   cd cmake-${nickname}-release
   
   echo Building nop-client...
   rm -rf CMakeCache.txt CMakeFiles cmake_install.cmake *.cpb Makefile
   cmake -static \
       -DCMAKE_INSTALL_PREFIX:PATH=${install_root}         \
       -DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE}      \
       ..
   make
   
   echo =========================================================
   echo Binary details of build...
   echo =========================================================
   file nop-client
   echo =========================================================
   
   echo Copying to remote device...
   ssh -p 2222 root@sp-c703.energynet.io "cat > nop-client-${nickname}" < nop-client
   ssh -p 2222 root@sp-c703.energynet.io "chmod a+x nop-client-${nickname}"
   
   # Here are some other remote commands
   #
   # rm the bin (had to do this when cp failed due to lack of space on device)
   # ssh -p 2222 root@sp-c703.energynet.io "rm nop-client-${nickname}"
   #
   # cp FROM the device back to host (again, to clean space on device)
   # ssh -p 2222 root@sp-c703.energynet.io "cat nop-client.0" > nop-client.0

cmake toolchain file example

   # https://github.com/zyga/cmake-toolchains/blob/master/Toolchain-Ubuntu-gnueabi.cmake
   # Sample toolchain file for building for ARM from an Ubuntu Linux system.
   #
   # Typical usage:
   #    *) install cross compiler: `sudo apt-get install gcc-arm-linux-gnueabi`
   #    *) cd build
   #    *) cmake -DCMAKE_TOOLCHAIN_FILE=~/Toolchain-Ubuntu-gnueabi.cmake ..
   
   set(CMAKE_SYSTEM_NAME Linux)
   set(TOOLCHAIN_PREFIX arm-926ejs-linux-gnueabi)
   
   # cross compilers to use for C and C++
   set(CMAKE_C_COMPILER ${TOOLCHAIN_PREFIX}-gcc)
   set(CMAKE_CXX_COMPILER ${TOOLCHAIN_PREFIX}-g++)
   
   # target environment on the build host system
   #   set 1st to dir with the cross compiler's C/C++ headers/libs
   set(CMAKE_FIND_ROOT_PATH /opt/crosstool-source-v4/arm-926ejs-linux-gnueabi)
   
   # modify default behavior of FIND_XXX() commands to
   # search for headers/libs in the target environment and
   # search for programs in the build host environment
   set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
   set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
   set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

CMakeLists.txt example

   cmake_minimum_required(VERSION 2.8)

   # MDM silently append relative paths to absolute paths without warnings
   cmake_policy(SET CMP0015 NEW)

   # MDM Set the executable name!
   # project(nop-bigress-client-c)
   project(nop-client)

   # -------------------------------
   # To ensure we get a static build.
   # For this to work, the linker needs to be able to find all libraries.
   # Make sure they are included next in [include|link]_directories.
   # Also make sure they are included in TARGET_LINK_LIBRARIES.
   # -------------------------------
   SET(CMAKE_FIND_LIBRARY_SUFFIXES ".a")
   SET(BUILD_SHARED_LIBRARIES OFF)
   SET(CMAKE_EXE_LINKER_FLAGS "-static")
   # -------------------------------

   # -------------------------------
   # MDM For cross compile, we must provide all lib paths.
   # We have ours: /home/m/development/armv4
   # And the toolchain is here: /opt/crosstool-source-v4/arm-926ejs-linux-gnueabi
   # -------------------------------
   include_directories(/home/m/development/armv4/include /opt/crosstool-source-v4/arm-926ejs-linux-gnueabi/include)
   link_directories(/home/m/development/armv4/lib /opt/crosstool-source-v4/arm-926ejs-linux-gnueabi/lib)
   # -------------------------------

   # -------------------------------
   # MDM Build *everything* in ./src
   # -------------------------------
   # WARNING: [make] won't pick up new files until you rerun [cmake].
   # Change this to be explicit if that becomes a problem.
   # Easy to change:
   #    set( NOP_SOURCES src/nop_client.c src/helpers.c )
   aux_source_directory(./src NOP_SOURCES)

   add_executable(
       ${PROJECT_NAME}
       ${NOP_SOURCES}
   )

   # The main linker line used to create the executable
   # MDM added [c] after ubuntu xenial started giving segfaults in dl -> openssl - didn't help!
   # see http://stackoverflow.com/questions/7526255/unknown-reference-to-dlopen-in-dlopen
   # TARGET_LINK_LIBRARIES(${PROJECT_NAME} websockets ssl crypto pthread dl z c)
   # MDM NO LINKING since we built websockets static!  no, this doesn't work...
   #TARGET_LINK_LIBRARIES(${PROJECT_NAME} websockets)
   # MDM cJSON requires floor + pow, in the C math lib, so we add "m"
   TARGET_LINK_LIBRARIES(${PROJECT_NAME} websockets ssl crypto pthread dl z c m)