How to cross compile OpenJDK for Arm32?

[ChenLong]

Thanks a lot for sharing these! It seems a lot of efforts needed to cross-compiling OpenJDK (I do hope it could be easier :). A couple of more quick questions:
1) Is it same as OpenJDK 8? (I prefer 8 as it is the latest release, right?)
2) Is there any place that I can download prebuilt sysroot/rootfs? That would be great helpful.
3) Can you give me more hints on "bytecode generator tool" compilation? I'm not familiar with this..

Chen Long

Xerxes Rånby <xerxes at zafena.se>编写：

>
>Den 2014-12-09 10:27, Severin Gehwolf skrev:
>> Hi,
>>
>> On Mon, 2014-12-08 at 21:46 +1000, David Holmes wrote:
>>> On 8/12/2014 7:10 PM, ChenLong wrote:
>>>> Hi
>>>>
>>>> Apologize if this is not the right place to ask.
>>>> I want to try OpenJDK8 on Armv7. Is there a guideline on how to cross compile OpenJDK8 for Armv7? And if not, could someone share some experiences? I went through the README-builds.html and did not find any clues for cross compiling.
>>> The only OpenJDK build for ARM would be a ZERO build. But I don't know
>>> how to do Zero builds - though I'm sure the Zero folk will chime in.
>> CC'ing zero-dev.
>
>when I cross-compile OpenJDK 9 for ARM32 I pass the following configure 
>options
>
>configure
># these options tell openjdk to do a cross compile build.
>--build=x86_64-unknown-linux-gnu
>--host=arm-buildroot-linux-gnueabi
>--target=arm-buildroot-linux-gnueabi
>
># these two options enable zero
>--with-jvm-interpreter=cpp
>--with-jvm-variants=zero
>
># specific options to make the build find the X and freetype headers and 
>librarys found on the ARM32 root filesystem.
>--disable-freetype-bundling
>--with-freetype-include=/home/xranby/rpi-buildroot/output/host/usr/arm-buildroot-linux-gnueabi/sysroot/usr/include/freetype2
>--with-freetype-lib=/home/xranby/rpi-buildroot/output/host/usr/arm-buildroot-linux-gnueabi/sysroot/usr/lib
>--with-freetype=/home/xranby/rpi-buildroot/output/host/usr/arm-buildroot-linux-gnueabi/sysroot/usr/
>--with-x=/home/xranby/rpi-buildroot/output/host/usr/arm-buildroot-linux-gnueabi/sysroot/usr/include
>
># the sysroot shall point to the ARM32 root file system, the build will 
>use librarys inside the sys root during linking native libraries.
>--with-sys-root=/home/xranby/rpi-buildroot/output/host/usr/arm-buildroot-linux-gnueabi/sysroot
># The tools dir contains binarys to run on the host x86 system, you may 
>point this to your system root dir /
># in my case the tools i use have been compiled by buildroot thus I use 
>the buildroot tools dir.
>--with-tools-dir=/home/xranby/rpi-buildroot/output/host
># OpenJDK 9 require OpenJDK 8, i point with boot jdk to an OpenJDK 8 
>image that can be run on the host x86 system.
>--with-boot-jdk=/home/xranby/images-jdk8/j2sdk-image/
>
># some parts of the openjdk build still expect that the cross compile 
>tools are found in the system PATH
># on my system i have to explicitly tell where the tools are located 
>because my cross compile toolchain is not found on the path.
># i use gcc to do the linking instead of ld because the openjdk build 
>passes -Xlinker -z
>OBJCOPY=/home/xranby/rpi-buildroot/output/host/usr/bin/arm-buildroot-linux-gnueabi-objcopy
>STRIP=/home/xranby/rpi-buildroot/output/host/usr/bin/arm-buildroot-linux-gnueabi-strip
>CPP=/home/xranby/rpi-buildroot/output/host/usr/bin/arm-buildroot-linux-gnueabi-cpp
>CXX=/home/xranby/rpi-buildroot/output/host/usr/bin/arm-buildroot-linux-gnueabi-g++
>CC=/home/xranby/rpi-buildroot/output/host/usr/bin/arm-buildroot-linux-gnueabi-gcc
>LD=/home/xranby/rpi-buildroot/output/host/usr/bin/arm-buildroot-linux-gnueabi-gcc
>CPP_FLAGS=-lstdc++
>CXX_FLAGS=-lstdc++
>
>
>when running make i pass the following options to make
># BUILD_CC and BUILD_LD shall point to host x86 executables.
>BUILD_CC=gcc
>BUILD_LD=gcc
>OBJCOPY=/home/xranby/rpi-buildroot/output/host/usr/bin/arm-buildroot-linux-gnueabi-objcopy
>STRIP=/home/xranby/rpi-buildroot/output/host/usr/bin/arm-buildroot-linux-gnueabi-strip
>CPP=/home/xranby/rpi-buildroot/output/host/usr/bin/arm-buildroot-linux-gnueabi-cpp
>CXX=/home/xranby/rpi-buildroot/output/host/usr/bin/arm-buildroot-linux-gnueabi-g++
>CC=/home/xranby/rpi-buildroot/output/host/usr/bin/arm-buildroot-linux-gnueabi-gcc
>LD=/home/xranby/rpi-buildroot/output/host/usr/bin/arm-buildroot-linux-gnueabi-gcc
>#and finally the target, this will build compact profiles, jre and jdk 
>images.
>all images profiles CONF=linux-arm-normal-zero-release
>
>
>I have automated these configure and make options for openjdk 9 into 
>buildroot build scripts
>https://github.com/xranby/rpi-buildroot/tree/openjdk
>
>>
>> I've done Zero builds before but have never used OpenJDK's cross-compile
>> feature to build it on ARMv7. There is an Arm32 bit JIT in IcedTea[1],
>> but I don't know if that can be cross-compiled.
>
>If you cross compile icedtea then you need to make sure that the 
>bytecode generator tool is compiled by the host x86 toolchain.
>openembedded meta-java contains buildscripts that can cross compile the 
>Arm32 JIT found in IcedTea.
>https://github.com/woglinde/meta-java
>
>Cheers
>Xerxes
>
>>
>> Cheers,
>> Severin
>>
>> [1]
>> http://blog.fuseyism.com/index.php/2014/03/28/icedtea-2-3-14-2-4-6-considered-armful-released/
>>
>>> David
>>>
>>>> Thanks
>>>> Chen Long
>>>>
>>
>>
>