[aarch64-port-dev ] RFR: 8209413: AArch64: NPE in clhsdb jstack command

[Andrew Haley]

On 2/7/19 2:36 PM, Nick Gasson (Arm Technology China) wrote:
> 
> Yeah I tried this method too (see the end of my first email). It
> works fine except the PC is off by a few instructions. That can be
> fixed quite easily though if required, and it always points into the
> right method.

We should fix those few cases.

> I ended up doing the stack scanning thing because as far as I can
> tell that constructor is only used when we need to find the return
> PC from a native frame

I don't think that ever happens. In the code I modified we know that
we have a good PC in the frame anchor. In the cases where we have a
native frame on the stack and nothing in the frame anchor we give
up. At least, I can see no counter-cases.

> (I might have been wrong about this), so I couldn't see how it would
> ever get the right value. If we check vm.isJavaPCDbg() before we use
> the SP[-1] value that will make the remaining callers a bit safer
> (and set this.pc to null otherwise).

That would be safe, for sure.

-- 
Andrew Haley
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
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