1. How We Are Porting OpenJDK + Eclipse OpenJ9 to z/OS
Presenter: Jason Yong

2. Background IBM licensed Java source code
Add in the JVM implementation J9
Added other “Value add” features
Patches added to get it working
Jan 2017 – 900+ patches
…..
Patch
Patch
Patch
Patch
Patch
Patch
Patch
Patch

3. Open Sourcing General move to improve our Open Source activity
J9 becomes the Eclipse Foundation Project OpenJ9 in early 2017
Work begins in making OpenJDK and Eclipse OpenJ9 work together

4. OpenJDK with OpenJ9 - Mercurial to Git
Initially multiple Mercurial Repositories to a Single Git repository
Using hg-git to do the conversion
Getting the tagging correct
Removal of Hotspot straight forward
Long process
Mid way through Java 9 it became a Single Mercurial Repository
Removal of Hotspot has been made slightly more complicated
Quicker but not by much

5. OpenJDK with OpenJ9 - Patches
Contribute as much back to OpenJDK as possible
Analyzed then into several categories
Platform Specific
Codepages
Bring-up Patches, etc
Bring-up Patches became the basis for the extensions repositories

6. OpenJDK with OpenJ9 - The Result
Several Github repositories (e.g. openj9-openjdk-jdk11)
Build an Open source Java 8 to 11 with OpenJ9
Instructions here -
Binaries of OpenJDK with OpenJ9 as well as OpenJDK with Hotspot and are available from AdoptOpenJDK -

7. Porting to z/OS - Tooling
The building of Java has some hard dependencies on various tools and utilities
Lack of correct tooling on z/OS
Incorrect version
Missing functionality
RocketSoftware
Codepage tagging
Compile our own versions

8. Porting to z/OS - Ebcdic or Ascii?
Attempted to build in Ascii
Build does file substitutions by default in Ebcdic
Attempted to build in Ebcdic
Used .gitattributes to do a blanket convert
Binaries were converted
Certain files were expected to be in Ascii
Methods to read in data assumed Ascii

9. Porting to z/OS - Native Code
If a brand new port, largest area of work needed
Over 100+ files of Java and c/c++ added
Majority from earlier patches

10. What next? In its current form it will not open sourced
High maintenance due to complex merge
z/OS specific changes can not be contributed back to OpenJDK
Is there a demand for an Open Source Java for z/OS?
Missing some key components that will stop it being production ready
Ziip/Zaap
Native z/OS security