Saving to 32 bits of GPRs in signal context

[Segher Boessenkool]

>> I think actually it would be useful to have the saving/restoring of
>> the high 32 bits controlled by a prctl, so that programs have to ask
>> explicitly for the new behaviour (and programs that don't want to use
>> the high 32 bits don't incur the extra overhead).
>
> I like this, it means we can error if HW doesn't support it and
> requires applications to do something specific to enable the feature.

It also means every such application has to make sure
it calls the prctl() before running any 64-bit insns.
No one will get this right unless support for this
is put into the ELF loader.


Segher