RFR (trivial): 8250826: jhsdb does not work with coredump which comes from Substrate VM

[Chris Plummer]

Hi Yasumasa,

I'm reviewing this RFR, and I'd like to ask that it not be pushed as 
trivial. Although it is just a one line change, it takes an extensive 
knowledge to understand the impact. I'll read up on the filed graal 
issue and try to understand the ELF code a bit better.

thanks,

Chris

On 7/30/20 6:45 AM, Yasumasa Suenaga wrote:
> Hi all,
>
> Please review this trivial change:
>
>   JBS: https://bugs.openjdk.java.net/browse/JDK-8250826
>   webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8250826/webrev.00/
>
> I played Truffle NFI on GraalVM, but I cannot get Java stacks from 
> coredump via jhsdb.
>
> I've reported this issue to GraalVM community [1], and I 've found out 
> the cause of this issue is .svm_heap would be separated to RO and RW 
> areas by mprotect() calls in run time in spite of .svm_heap is RO 
> section in ELF (please see [1] for details).
>
> It is corner case, but we will see same problem on jhsdb when we 
> attempt to analyze coredump which comes from some applications / 
> libraries which would separate RO sections in ELF like Substrate VM.
>
> I sent PR to fix libsaproc.so in LabsJDK 11 for this issue [2], then 
> community members suggested me to discuss in serviceability-dev.
>
>
> Thanks,
>
> Yasumasa
>
>
> [1] https://github.com/oracle/graal/issues/2579
> [2] https://github.com/graalvm/labs-openjdk-11/pull/9