RFR: 8304006: jlink should create the jimage file in the native endian for the target platform [v12]

[Mandy Chung]

On Thu, 23 Mar 2023 01:46:47 GMT, Jaikiran Pai <jpai at openjdk.org> wrote:

>> Can I please get a review for this change which proposes to fix the issue reported in https://bugs.openjdk.org/browse/JDK-8206890?
>> 
>> The `jlink` command allows a `--endian` option to specify the byte order in the generated image. Before this change, when such a image was being launched, the code would assume the byte order in the image to be the native order of the host where the image is being launched. That would result in failure to launch java, as noted in the linked issue.
>> 
>> The commit in this PR, changes relevant places to not assume native order and instead determine the byte order by reading the magic bytes in the image file's header content.
>> 
>> A new jtreg test has been added which reproduces the issue and verifies the fix.
>
> Jaikiran Pai has updated the pull request incrementally with one additional commit since the last revision:
> 
>   ARM is 32 bit as per platform.m4 in OpenJDK build

src/jdk.jlink/share/classes/jdk/tools/jlink/internal/JlinkTask.java line 823:

> 821:             if (order != null) {
> 822:                 this.order = order;
> 823:                 String targetPlatformVal = readJavaBaseTargetPlatform(cf);

Thanks for the update.

This should also do the fast-path check `isJavaBaseFromCurrentPlatform(javaBasePath)` as in line 838-860.  I suggest to refactor line 838-860 to return the target platform (either runtime platform or from java.base in the given module path).   

I also suggest to include `endianness` in the `Platform` record class.

I sent you a patch offline with these suggestions.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/11943#discussion_r1146654036