RFR: 8277204: Implement PAC-RET branch protection on Linux/AArch64 [v18]

[Alan Hayward]

On Mon, 7 Feb 2022 12:25:44 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> PreserveFramePointer is doing some additional stuff. I'll give it a test to make sure everything still works with PreserveFramePointer fully set. It would make things easier just to force it set with rop protection on.
>
>> PreserveFramePointer is doing some additional stuff. I'll give it a test to make sure everything still works with PreserveFramePointer fully set. It would make things easier just to force it set with rop protection on.
> 
> Using PreserveFramePointer greatly simplifies the testing matrix, and has little adverse performance impact beyond disallowing C2 from allocating FP as a scratch register. It also simplifies this patch, which would be a very Good Thing. Let's do it.

Doing this caused 7 failures across a full jtreg run, namely:

serviceability/sa/ClhsdbFindPC.java#xcomp-core
vmTestbase/jit/misctests/fpustack/GraphApplet.java
vmTestbase/nsk/jdi/MonitorWaitRequest/MonitorWaitRequest001/TestDescription.java
vmTestbase/nsk/jdi/MonitorWaitedRequest/MonitorWaitedRequest001/TestDescription.java
vmTestbase/nsk/jdwp/ThreadReference/ForceEarlyReturn/forceEarlyReturn002/forceEarlyReturn002.java
vmTestbase/nsk/jdwp/ThreadReference/OwnedMonitorsStackDepthInfo/ownedMonitorsStackDepthInfo002/ownedMonitorsStackDepthInfo002.java
vmTestbase/nsk/jvmti/RedefineClasses/StressRedefine/TestDescription.java

....I'll investigate.

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