RFR: 8277204: Implementation of JEP 8264130: PAC-RET protection for Linux/AArch64 [v14]

[Alan Hayward]

On Mon, 24 Jan 2022 16:36:18 GMT, Andrew Dinn <adinn at openjdk.org> wrote:

>> Alan Hayward has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix popframe failures
>
> src/hotspot/cpu/aarch64/templateInterpreterGenerator_aarch64.cpp line 835:
> 
>> 833:   __ stp(rlocals, rcpool, Address(sp, 2 * wordSize));
>> 834: 
>> 835:   __ protect_return_address();
> 
> Most of the changes to fix the tests look fairly self-explanatory but I don't really understand why you relocated call to protect_return-_address from its previous location at line 801. Can you explain why it has been moved?

I originally moved it as part of debugging (a GC load_at occurs during the load_mirror).
Once all the GC changes went in (all the enter_subframe calls), this change was no longer required.
Then, when I came to change it back, I realised it made more sense in the new place. The protect is now directly before the storing of lr to the stack. That's logically a better place and should make the assembler easier to read.

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PR: https://git.openjdk.java.net/jdk/pull/6334