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

[Andrew Haley]

On Mon, 7 Feb 2022 11:28:30 GMT, Alan Hayward <duke at openjdk.java.net> wrote:

>>> Let's see both pc and signed pc here, if they are different.
>
> Are you sure? At the moment with PAC we get:
> 
> patch_pc at address 0x0000fffff58edf98 [0x0068ffffed17b5fc -> 0x00abffffed17b7f8]
> 
> With both signed and unsigned you'd have:
> 
> patch_pc at address 0x0000fffff58edf98 [0x0068ffffed17b5fc (0x0000ffffed17b5fc) -> 0x00abffffed17b7f8 (0x0000ffffed17b7f8)]
> 
> I prefer the first - it's shorter and you can infer the address from the signed version. Happy to go with the longer version if you think the shorter version is confusing.

You've been looking at PAC-signed addresses for a long time. 
Let's see "at address [prev true dest -> new true dest] [signed prev signed dest -> new signed dest]", but only show the signed dests if they're different. So it appears as 
`patch_pc at address 0x0000fffff58edf98 [0x0068ffffed17b5fc -> 0x00abffffed17b7f8] [signed 0x0000ffffed17b5fc ->  0x0000ffffed17b7f8]` .

-------------

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