[Bug gdb/28947] GDB does not remove AArch64 pointer signatures before doing memory accesses

["luis.machado at arm dot com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=28947

--- Comment #3 from Luis Machado <luis.machado at arm dot com> ---
Thinking a bit more about this, I'm not sure if GDB/debuggers should go out of
their way to remove signature bits from the pointers.

Accessing memory using a signed pointer is invalid anyway, and will result in a
fault. Having debuggers remove that information may cause confusion for a
developer that is trying to debug a PAC-related crash of some kind, as it will
not show the signature part of the pointer.

I can imagine a scenario where a pointer wasn't signed properly, but GDB will
strip the signature of that pointer and will show things as if they were
correct, when in fact they are not. Does that make sense?

Accessing memory using a tagged pointer is valid though, but debuggers need to
be cautious not to pass tagged pointers down to syscalls. GDB does this.

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