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

[Andrew Haley]

On Mon, 7 Feb 2022 10:55:52 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> Alan Hayward has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Documentation updates
>
> src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp line 5293:
> 
>> 5291: // Create an additional frame for a function.
>> 5292: void MacroAssembler::enter_subframe() {
>> 5293:   // Addresses can only be signed once, so strip it first. PAC safe because the value is not
> 
> This needs a more descriptive name. `enter_and_sign()` ? No, that's not right either. How do we come up with a name that's more descriptive?

Because enter always enters a subframe. That's what it's for.

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