RFR: 8219414: SA: jhsdb jsnap throws UnmappedAddressException with core generated by gcore

[Yasumasa Suenaga]

Hi all,

Please review this webrev:

  JBS: https://bugs.openjdk.java.net/browse/JDK-8219414
  webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8219414/webrev.00/

I tried to get PerfCounter values via `jhsdb jsnap` from core image
which is generated by `gcore` (provided by GDB), but I encountered
UnmappedAddressException.

It is caused by `generate-core-file` on GDB regards `coredump_filter` on procfs.

  https://sourceware.org/gdb/onlinedocs/gdb/Core-File-Generation.html

JDK-8200613 introduced `DumpPrivateMappingsInCore` for CDS. I want to
introduce `DumpSharedMappingsInCore` for shared memory mapping.

Currently `DumpPrivateMappingsInCore` affects when `UseSharedSpaces` is enabled.
I want `DumpPrivateMappingsInCore` to affect independently in this
change because file-backed private memory which is not CDS might be
useful in the future.


Thanks,

Yasumasa