Module registry

[ifakhrutdinov]

Proposed changes

To address potential LPA shortages when multiple ZIS instances are running on the same LPAR, a new feature--the module registry--has been introduced.

The module registry is a set of data structures in common storage in which eligible modules are traced. An eligible module is a module marked with a special macro; the mark and the module names are then used to uniquely identify the module. Once ZIS and its plug-in modules are marked, they can be added to the registry and shared: if another ZIS instance needs to load an identical module to the LPA, it will reuse a previously registered (and loaded to the LPA) module instead. Sharing identical modules should dramatically decrease the LPA footprint.

This feature must not be used when an application wants to remove its modules from the LPA (e.g., ZIS does that in dev mode) because it will affect any other applications using the same modules.

This PR addresses Issue: #405

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

PR Checklist

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• If the changes in this PR are meant for the next release / mainline, this PR targets the "staging" branch.
• My code follows the style guidelines of this project (see: Contributing guideline)
• I have commented my code, particularly in hard-to-understand areas
• New and existing unit tests pass locally with my changes
• Relevant update to CHANGELOG.md
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works, or describe a test method below

Testing

• Clone this repo and check out the source branch for this change;
• Go to ./tests and run build_modreg.sh;
• Make sure that the load library with the test module is APF-authorized;
• Make sure a ZIS instance has been run since the latest IPL;
• Use the JCL from ./tests/modregtest.c to run the test program;
• The job must end with RC 0.

Further comments