RFR: 8353185: Introduce the concept of upgradeable files in context of JEP 493 [v2]

[Severin Gehwolf]

On Fri, 4 Apr 2025 15:22:10 GMT, Severin Gehwolf <sgehwolf at openjdk.org> wrote:

>> For JEP 493-enabled builds there are no JMODs. Certain files come from the installed JDK image when a user creates a custom run-time from it. This is problematic for example for files that often come from a different package (e.g. `cacerts` file for Linux distro builds of OpenJDK packaged as RPMs), or more generally when they get updated out-of-band of the JDK build itself like the tzupdater tool.
>> 
>> When that happens the hash sum recorded at JDK build time of those files no longer match, causing `jlink` to fail. I propose to allow for those files to get "upgraded" should this happen. The way this works is as follows:
>> 
>> 1. The list of upgradeable files is configured by a resource file in `jdk.jlink` on a per module basis. Right now, only two files from the `java.base` module will be allowed to be upgraded with a link from the current run-time image.
>> 2. For those files the hash sum checks are skipped.
>> 
>> **Testing**
>> 
>> - [x] GHA
>> - [x] `jdk/tools/jlink` jtreg tests
>> - [x] Some manual tests with updated `tzdb.dat` and `cacerts` files.
>> 
>> Thoughts?
>
> Severin Gehwolf has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:
> 
>  - Reboot upgradeable files approach
>  - Revert "8353185: Introduce the concept of upgradeable files in context of JEP 493"
>    
>    This reverts commit bfbfbcb8212ed0f9825549b02b4b52e930c379a7.
>  - Merge branch 'master' into jdk-8353185-upgradable-files-jep493
>  - 8353185: Introduce the concept of upgradeable files in context of JEP 493

It took me a while to find the magic trick to get the jlink resource file copied, so adding build-dev for their input too.

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PR Comment: https://git.openjdk.org/jdk/pull/24388#issuecomment-2779101393