RFR: 8277204: Implement PAC-RET branch protection on Linux/AArch64 [v25]

[David Holmes]

On Thu, 24 Feb 2022 10:52:00 GMT, Alan Hayward <duke at openjdk.java.net> wrote:

>> Alan Hayward has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 34 commits:
>> 
>>  - Merge master
>>  - Merge master
>>  - Merge master
>>  - Error on -XX:-PreserveFramePointer -XX:UseBranchProtection=pac-ret
>>  - Add comments to enter calls
>>  - Set PreserveFramePointer if use_rop_protection is set
>>  - Merge enter_subframe into enter
>>  - Review fixups
>>  - Documentation updates
>>  - Update copyrights to 2022
>>  - ... and 24 more: https://git.openjdk.java.net/jdk/compare/022d8070...c4e0ee31
>
> Any more comments? Otherwise I'll integrate later

@a74nh this seems to have broken the Zero build:

src/hotspot/share/gc/shared/barrierSetNMethod.cpp:58:33: error: 'pauth_strip_pointer' was not declared in this scope
 58 |   AARCH64_ONLY(return_address = pauth_strip_pointer(return_address));

I'm guessing a missing include file.

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