RFR(S): 8166689: PPC64: Race condition between stack bang and non-entrant patching

[Doerr, Martin]

Hi,

I found a race condition between stack bang and non-entrant patching on linux PPC64.

The signal handler on linux PPC64 investigates the instruction when a stack bang has hit the protected zone. Another thread may patch the verified entry point preventing the signal handler from recognizing the stack overflow.
This problem can be prevented by rearranging C1's prolog code such that the stack bang instruction will never be at the verified entry point. C2's prolog code is already implemented accordingly.

My proposed fix is here:
http://cr.openjdk.java.net/~mdoerr/8166689_PPC64_C1_stackbang/webrev.00/

I have also fixed a missing RewriteControl check in the template interpreter on PPC64.

Please review.

Thanks and best regards,
Martin

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