Fail to cross compiling jdk12 for mips64el-linux-gnu target
Leslie Zhai
zhaixiang at loongson.cn
Thu Jan 24 12:22:18 UTC 2019
Hi Magnus,
Thanks for your kind response!
在 2019/1/24 下午8:05, Magnus Ihse Bursie 写道:
>
>
> On 2019-01-24 05:45, David Holmes wrote:
>> On 24/01/2019 1:51 pm, Ao Qi wrote:
>>> Hi David,
>>>
>>> On Thu, Jan 24, 2019 at 10:47 AM David Holmes
>>> <david.holmes at oracle.com> wrote:
>>>>
>>>> Hi Leslie,
>>>>
>>>> I'm not Erik :) however ....
>>>>
>>>> On 24/01/2019 12:28 pm, Leslie Zhai wrote:
>>>>> Hi Erik,
>>>>>
>>>>> Because the flags' macro of MIPS is different from other
>>>>> targets[1], it
>>>>> will effect the `UnixConstants` of
>>>>> src/java.base/unix/classes/sun/nio/fs/UnixConstants.java.template,
>>>>> for
>>>>> example, PREFIX_O_APPEND, so the `Flags` in `FileChannel` is
>>>>> different
>>>>> from other targets. Then failed[2] to cross compiling jdk12 for
>>>>> mips64el-linux-gnu target by following the document[3].
>>>>
>>>> It's been quite a while since we built for a platform where the flags
>>>> had different values, but it is supposed to work. I suspect that
>>>> the way
>>>> we build now with the module system may not be quite correct in this
>>>> regard - but that is just supposition on my part. Because compile-time
>>>> constants are stored directly into class files that use them, we
>>>> have to
>>>> generate UnixConstants.java before compiling any class that needs
>>>> to use
>>>> it, then we must compile all classes that do use it. Those classes
>>>> must
>>>> only be executed in conjunction with a tool executing on the target
>>>> platform (javac, jmod etc). My suspicion is that we may be executing a
>>>> tool on the build platform using the newly compiled classes for the
>>>> target platform - and that would be wrong.
>>>>
>>>
>>> Yes. Some variables in UnixConstants.java is defined according to the
>>> target (fcntl.h of mips in this case), but would be executed on host
>>> (x86 in this case) during "make images". These variables of ppc64le,
>>> aarch64 and s390x are the same as x86, but the ones of mips are not.
>>> However, mips is not an official supported target and I did not find
>>> other targets have similar issue, I am not sure if this is a bug or if
>>> this is the right mailing list :)
>>
>> This is the right mailing list to discuss. :)
>>
>> So I went back to find when this happened in the past and I
>> mis-remembered how we solved it. We previously had a problem with the
>> Oracle Java SE Embedded PPC port where some Linux PPC-e500v2
>> platforms defined a different value for the O_NOFOLLOW and O_DIRECT
>> flags. The solution then was to commit a platform specific version of
>> UnixConstants.java and change the build system to only use the
>> template file if there was not a pre-existing .java file. But that
>> platform and the SE Embedded support was all removed.
>> (SocketOptions.java had a similar problem.) Further that build logic
>> is completely different to what we had back then (JDK 6/7).
>>
>> This is definitely a bug in our build logic IMHO as we specifically
>> use the build platform c-pre-processor to process the template file
>> based on the target header files, but then use the resulting class
>> when running tools on the build platform.
> I agree with David. This is a bug in the build system; arguably even a
> regression.
>
>> This was not something that happened in 6/7 or even 8 and I think the
>> module system tools are where the issue now lies.
>>
>> I think Erik and/or Magnus will have to give advice on how this may
>> be properly fixed. I can't see any simple solution.
> Unfortunately, I also agree that there is no simple solution. :-(
>
> The proper way to handle this is to generate two versions of
> UnixConstants and friends, one for the build platform, and one for the
> target platform. But as far as I know, there is no simple way to
> handle such complications in our current structure. Erik knows more
> about this, he was the one who designed the current solution for
> handling cross-compilation in the modularized world.
>
> However, I can at least help you with a relatively simple workaround.
> First some background: When we cross-compile, we need not only a Boot
> JDK (of version current N-1) running on the build host platform, but
> we also need a Build JDK, based on the current source code, running on
> the build host. (This is for running jmod/jlink; it needs to be up to
> date). If we have no Build JDK present, we start by creating one
> ourselves. This is more or less the same output as running a normal,
> non-cross compiled, build on the build host. (But Erik found some ways
> to cut a few corners to save time.) Your problem is that the Build JDK
> is broken, since UnixConstants has the wrong values.
> -
> But you can supply your own working Build JDK to configure!
>
> So, your workflow for cross-compiling to MIPS should be:
> 1) create a Build JDK, e.g. like this: "bash configure
> --with-conf-name=buildjdk && make jdk CONF=buildjdk"
> 2) create your cross-compilation JDK like this: "bash configure
> --openjdk-target=mipsel-unknown-linux-gnu
> --with-build-jdk=build/buildjdk/jdk"
> ... or something like that.
> Then you can build your cross-compiled jdk with "make images CONF=mips".
I will try that, thanks a lot for your teaching!
Regards,
Leslie Zhai
>
>
> In theory, you should rebuild your buildjdk for each and every change
> ("make jdk CONF=buildjdk && make images CONF=mips"); but in reality, I
> don't believe there is really any need to rebuild the buildjdk (unless
> major changes in jlink/jmod happens).
>
> /Magnus
>>
>> David
>> -----
>>
>>> For example:
>>>
>>> jdk/build$ find . -name UnixConstants.java | xargs grep -A2 O_APPEND
>>> ./linux-ppc64le-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java:
>>>
>>> static final int O_APPEND =
>>> ./linux-ppc64le-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>>>
>>> ./linux-ppc64le-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>>>
>>> 02000
>>> --
>>> ./linux-x86_64-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java:
>>>
>>> static final int O_APPEND =
>>> ./linux-x86_64-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>>>
>>> ./linux-x86_64-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>>>
>>> 02000
>>> --
>>> ./linux-s390x-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java:
>>>
>>> static final int O_APPEND =
>>> ./linux-s390x-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>>>
>>> ./linux-s390x-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>>>
>>> 02000
>>> --
>>> ./linux-aarch64-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java:
>>>
>>> static final int O_APPEND =
>>> ./linux-aarch64-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>>>
>>> ./linux-aarch64-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>>>
>>> 02000
>>> --
>>> ./linux-x86_64-zero-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java:
>>>
>>> static final int O_APPEND =
>>> ./linux-x86_64-zero-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>>>
>>> ./linux-x86_64-zero-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>>>
>>> 02000
>>> --
>>> ./linux-mips64el-zero-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java:
>>>
>>> static final int O_APPEND =
>>> ./linux-mips64el-zero-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>>>
>>> ./linux-mips64el-zero-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>>>
>>> 0x0008
>>> --
>>> ./linux-ppc64le-zero-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java:
>>>
>>> static final int O_APPEND =
>>> ./linux-ppc64le-zero-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>>>
>>> ./linux-ppc64le-zero-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>>>
>>> 02000
>>>
>>> log.mips:2of path:
>>> /home/loongson/aoqi/jdk-mips/build/linux-mips64el-normal-server-release/support/interim-jmods/temp/.java.base.jmod.tmp
>>>
>>> oflags: 769 O_TRUNC:512 O_APPEND:8 O_CREAT:256 O_EXCL:1024
>>> log.ppc:2of path:
>>> /home/loongson/aoqi/jdk-mips/build/linux-ppc64le-normal-server-release/support/interim-jmods/temp/.java.base.jmod.tmp
>>>
>>> oflags: 577 O_TRUNC:512 O_APPEND:1024 O_CREAT:64 O_EXCL:128
>>>
>>> Cheers,
>>> Ao Qi
>>>
>
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