RFR: 8277204: Implementation of JEP 8264130: PAC-RET protection for Linux/AArch64 [v8]

[Alan Hayward]

On Thu, 9 Dec 2021 17:12:45 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> Alan Hayward has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix up UseROPProtection flag
>
> make/autoconf/flags-cflags.m4 line 902:
> 
>> 900:   BRANCH_PROTECTION_CFLAGS=""
>> 901:   UTIL_ARG_ENABLE(NAME: branch-protection, DEFAULT: auto,
>> 902:       RESULT: USE_BRANCH_PROTECTION, AVAILABLE: $BRANCH_PROTECTION_AVAILABLE,
> 
> What exactly is going on here? Is it that if the host compiler has "branch protection" supported, we will build with it on by default? if so, no, we don't want to do that. For now, branch protection should be an explicit opt in.

The idea was that the same JDK could be used on PAC and non PAC systems. I agree that right now it's probably better being explicit opt in. Will update.

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