linux-packaging-mono/external/corert/Documentation/cross-building.md

Cross Compilation for ARM on Linux

Through cross compilation, on Linux it is possible to build CoreRT for arm or arm64.

Requirements

You need a Debian based host and the following packages needs to be installed:

$ sudo apt-get install qemu qemu-user-static binfmt-support debootstrap

In addition, to cross compile CoreCLR the binutils for the target are required. So for arm you need:

$ sudo apt-get install binutils-arm-linux-gnueabihf

and conversely for arm64:

$ sudo apt-get install binutils-aarch64-linux-gnu

Generating the rootfs

The cross\build-rootfs.sh script can be used to download the files needed for cross compilation. It will generate an Ubuntu 14.04 rootfs as this is what CoreRT targets.

Usage: build-rootfs.sh [BuildArch]
BuildArch can be: arm, arm64

The build-rootfs.sh script must be run as root as it has to make some symlinks to the system, it will by default generate the rootfs in cross\rootfs\<BuildArch> however this can be changed by setting the ROOTFS_DIR environment variable.

For example, to generate an arm rootfs:

$ sudo ./cross/build-rootfs.sh arm

and if you wanted to generate the rootfs elsewhere:

$ sudo ROOTFS_DIR=~/coreclr-cross/arm ./build-rootfs.sh arm

Cross compiling CoreCLR

Once the rootfs has been generated, it will be possible to cross compile CoreRT. If ROOTFS_DIR was set when generating the rootfs, then it must also be set when running build.sh.

So, without ROOTFS_DIR:

$ ./build.sh arm debug verbose clean cross

And with:

$ ROOTFS_DIR=~/coreclr-cross/arm ./build.sh arm debug verbose clean cross

As usual the resulting binaries will be found in bin/Product/BuildOS.BuildArch.BuildType/

Using CoreRT for cross compiling under arm on x86 host

It is possible to use CoreRT for compiling under arm/armel on x86 host (or on x64 machine using roots).

1. Build CoreCLR for x86 (checked version)

sudo ./cross/build-rootfs.sh x86 xenial
./build.sh clang3.9 x86 checked verbose cross skiptests

2. Build CoreFX (Debug version)
3. Build CoreRT for armel, x64, x86

sudo ./cross/build-rootfs.sh armel tizen cross
./build.sh clang3.9 armel debug verbose cross
./build.sh debug verbose skiptests
./build.sh clang3.9 x86 debug verbose cross skiptests

4. Copy necessary binaries to working directory (in x86 rootfs)

cp ${CORECLR}/bin/Product/Linux.x86.Checked ${WORKING_DIR}
cp ${CORERT}/bin/Linux.x86.Debug/tools/ilc.dll ${WORKING_DIR}
cp ${CORERT}/bin/Linux.x86.Debug/tools/ILCompiler.* ${WORKING_DIR}
cp ${CORERT}/bin/Linux.x86.Debug/tools/System.CommandLine.dll ${WORKING_DIR}
cp ${CORERT}/bin/Linux.x86.Debug/tools/Microsoft.DiaSymReader.dll ${WORKING_DIR}
cp ${CORERT}/bin/Linux.x86.Debug/tools/jitinterface.so ${WORKING_DIR}
cp -r ${CORERT}/bin/Linux.x86.Debug/framework ${WORKING_DIR}

# Copy CoreRT sdk binaries from target (armel) output folder
cp -r ${CORERT}/bin/Linux.armel.Debug/sdk ${WORKING_DIR}

5. Rename RyuJIT compiler library

# Use cross-compiler library as default for ILC
cp ${WORKING_DIR}/libarmelnonjit.so ${WORKING_DIR}/libclrjitilc.so

# ... or ARM version instead if it's needed
# cp ${WORKING_DIR}/libprotojit.so ${WORKING_DIR}/libclrjitilc.so

6. Build ObjectWriter library. You have to compile it on x86 chroot.

7. And to execute use:

./corerun ilc.dll --codegenopt "AltJitNgen=*" --verbose @Hello.ilc.rsp
# Any other options to RyuJIT could be passed via --codegenopt argument, e.g.:
#./corerun ilc.dll --codegenopt "AltJitNgen=*" --codegenopt "NgenDisasm=*" --verbose @Hello.ilc.rsp

# For linking
clang-3.9 -target arm-linux-gnueabi --sysroot=corert/cross/rootfs/armel -Bcorert/cross/rootfs/armel/usr/lib/gcc/armv7l-tizen-linux-gnueabi/6.2.1 -Lcorert/cross/rootfs/armel/usr/lib/gcc/armv7l-tizen-linux-gnueabi/6.2.1 Hello.o -o Hello corert/bin/Linux.armel.Debug/sdk/libbootstrapper.a corert/bin/Linux.armel.Debug/sdk/libRuntime.a corert/bin/Linux.armel.Debug/sdk/libSystem.Private.CoreLib.Native.a corert/bin/Linux.armel.Debug/framework/System.Native.a corert/bin/Linux.armel.Debug/framework/libSystem.Globalization.Native.a -g -Wl,-rpath,'$ORIGIN' -pthread -lstdc++ -ldl -lm -luuid -lrt -fPIC