RFR: 8277204: Implementation of JEP 8264130: PAC-RET protection for Linux/AArch64 [v9]

[Andrew Haley]

On Fri, 10 Dec 2021 15:16:19 GMT, Alan Hayward <duke at openjdk.java.net> wrote:

>> src/hotspot/cpu/aarch64/vm_version_aarch64.cpp line 419:
>> 
>>> 417:     if (UseROPProtection) {
>>> 418:       warning("UseROPProtection specified, but not supported on this CPU.");
>>> 419:       FLAG_SET_DEFAULT(UseROPProtection, false);
>> 
>> Suggestion:
>> 
>>       FLAG_SET_DEFAULT(UseROPProtection, true);
>> 
>> Given that the instructions used are in NOP space, this won't do any harm, and it will allow developers without PAC-enabled systems to see what code PAC would generate.
>
> Ok, I think that's fine. How about on a non pac system allowing it for development only ?

Maybe. Mind you, a lot of the time I'm looking at the output from production systems.
>From a rather philosophical point of view, I assume that if the user of a computer asks for something that isn't going to break anything or confuse anyone, we should honour their request.

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