Add !walkj9hashtable DDR interactive command

[tomal-majumder]

Add !walkj9hashtable DDR command

Adds a new DDR extension command that walks all entries of a
J9HashTable and prints each entry as a runnable DDR command.

The command accepts a single hex address and an optional type
argument:

!walkj9hashtable <address> [type]

Issue: #23452

[tajila]

Look at https://github.com/eclipse-openj9/openj9/blob/master/CONTRIBUTING.md for how to format commit messages. The PR description should match the commit message. You can add comments to the PR for other things like questions, concerns, etc.

[tajila]

One thing to make this more usable is to add an optional type parameter.

!walkj9hashtable <address> [<type>]

I assume you are just printing out something like:

!j9x 0x1
!j9x 0x2
!j9x 0x3
...

But it would be better if the type was included, for example:

!j9class 0x1
!j9class 0x2
!j9class 0x3
...

[tajila]

Another thing is to test that the data outputted is actually correct. So writing a test that dumps the classes in a classloader (classLoader->classHashTable) for example is a good test since we can verify if the classes are valid.

[tajila]

!walkj9hashtable <address> [<type>]

!walkj9hashtable 0x1 j9class* //j9class pointers are stored

or

!walkj9hashtable 0x1 j9class //j9class structs inline are stored

[tomal-majumder]

Addressed the following in the latest commit:

1. Optional [<type>] parameter — the command now supports:

!walkj9hashtable <address> [<type>]

When <type> ends with * the slot is treated as a pointer to the entry (inline=false); otherwise the entry is stored inline.

Sample output - 1: Inline structs (e.g. classHashTable stores KeyHashTableClassEntry inline):

> !walkj9hashtable 0x000000001a2b3c00 KeyHashTableClassEntry

J9HashTable at 0x1a2b3c00
{
    !keyhashtableclassentry 0x00007f3a10042d80
    !keyhashtableclassentry 0x00007f3a10043100
    !keyhashtableclassentry 0x00007f3a10043480
    ...
}

Sample output - 2: Pointer entries (e.g. moduleHashTable stores J9Module* pointers):

 > !walkj9hashtable 0x000000001a2b4400 J9Module*

J9HashTable at 0x1a2b4400
{
    !j9module 0x00007f3a10051200
    !j9module 0x00007f3a10051600
    !j9module 0x00007f3a10051a00
    ...
}

Sample output - 3: No type argument specified:

 > !walkj9hashtable 0x000000001a2b4400

J9HashTable at 0x1a2b4400
{
    !j9x 0x00007f3a10051200
    !j9x 0x00007f3a10051600
    !j9x 0x00007f3a10051a00
    ...
}

2. Test coverage — testWalkJ9HashTable
   walks classHashTable and ModuleHashTable from the classLoaders; finding the expected classes and modules confirms the command is correctly iterating and reporting all entries.

[keithc-ca]

Sorry, I just noticed that my comments were still pending.

[tomal-majumder]

Grinder Tests: Set TARGET: testDDRExt_General

JDK 8: https://hyc-runtimes-jenkins.swg-devops.com/job/Grinder/59348/
JDK. 25: https://hyc-runtimes-jenkins.swg-devops.com/job/Grinder/59349/

[tajila]

@keithc-ca do you have any further comments

[keithc-ca]

I don't see the necessary fixes to HashTable_V1 to properly handle non-inline entries.

[keithc-ca]

Jenkins test extended.functional amac jdk25