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

[Alan Hayward]

On Tue, 25 Jan 2022 13:41:38 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> 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.
>
> Was this ever resolved?

Sort of. That code has changed quite a bit - UseROPProtection now is a string field not a bool.
"none" or not set - pac disabled.
"pac-ret" - pac always enabled
"standard" - pac enabled if the cpu+os support it.

Also, the pac instructions used aren't all in the NOP space. So, it will crash on a non-pac machine.  It might be possible to change it so it does only use nop space instructions, but I don't think it'll be optimal (need to double check).

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