Cross-compiling Berkelium for ARMv6 with Emdebian Toolchain

On 64-bit build machines (required for debug build) also install g++-multi and possibly some 32-bit libraries with xapt:

If you don’t, you’ll get the following error:

LINK(host) out/Release/mksnapshot
/usr/bin/ld: warning: skipping incompatible /usr/lib/gcc/x86_64-linux-gnu/4.6/libstdc++.so while searching for stdc++
/usr/bin/ld: error: cannot find -lstdc++

Then retrieve berkelium source code (I’ve done that in ~/edev/raspberry-pi directory):

git clone git://github.com/sirikata/berkelium.git
cd berkelium/externals
git clone git://github.com/sirikata/cxxtest.git

You’ll also need to install tools specific to Chromium (gclient):

cd  ~/edev/raspberry-pi/berkelium/build/
svn co http://src.chromium.org/svn/trunk/tools/depot_tools

In ~/edev/raspberry-pi/berkelium/, I’ve created arm.env with the environment variables required to build chromium and berkelium:

I also had to create ~/.gyp/include.gypi:

{
'variables': {
'target_arch': 'arm',
'disable_nacl': 1,  # NaCL does not build for ARM.
'linux_use_tcmalloc': 0, # tcmalloc does not build for ARM.
'armv7': 0, # Optional, for targeting ARMv7.
'armv6': 1, # Optional, for targeting ARMv7.
'arm_thumb': 0, # Optional, for targeting thumb.  Combine with armv7 to target thumb2.
'arm_neon': 0, # Optional, to disable NEON. 1 is the default, and most people want to keep it that way.
'arm_fpu': 'vfp', # Optional, to select which version of vfp to use if NEON is off. Default is vfpv3.
'verbose': 1
}
}

Once this is done,  source the environment variables, and start the script to checkout and build the code:

source arm.env
./util/build-chromium.sh

I would recommend that you also export V=1 in order to see the arm-linux-gnueabi-xxx command line used. This will greatly help if case the build fails.

After the checkout part is completed and compilation start (CXX messages appear), you can stop the build with Ctrl+C and modify 2 gyp files to be able to compile as Emdebian compiler defaults to armv4 architecture which is not supported by Chromium:

• 1 line at line 851 in build/chromium/src/skia/skia.gyp:
  ‘cflags’: [
  ‘-fomit-frame-pointer’,
                 ‘-march=armv6 -mfpu=vfp -mfloat-abi=softfp’,
  ],
• 5 lines at line 621 in build/chromium/src/v8/tools/gyp/v8.gyp:
  ‘conditions’: [
  # The ARM assembler assumes the host is 32 bits,
  # so force building 32-bit host tools.
  [‘host_arch==”x64″ and _toolset==”host”‘, {
  ‘cflags’: [‘-m32’],
  ‘ldflags’: [‘-m32’],
  }],
                  [‘_toolset==”target”‘, {
                    ‘cflags’: [‘-march=armv6’,
                               ‘-mfpu=vfp’,
                               ‘-mfloat-abi=softfp’],
                  }]
  ]

Start the build again and let it complete:

./util/build-chromium.sh

This step can take several hours depending, of course,  on your build machine.

At this point, Chromium should be built, and you just need to build berkelium library with cmake.

Since allocator, seccomp_sandbox and yuv_convert_sse2 are not compiled for ARM, you’ll have to remove references to those in FindChrome.cmake. You also need to disable all TEST code in CMakeList.txt.

Cross-compile berkelium and install it in a specific directory (e.g. ~/edev/raspberry-pi/libs):

cmake . -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=~/edev/raspberry-pi/libs/
make
make install

If you have problems at the link stage with missing libraries, you may need to modify CMakeFiles/libberkelium.dir/link.txt and add the paths (LDFLAGS) to the libraries.