RFC: Should x86-64 support arbitrary calling conventions?

[Florian Weimer]

* H. J. Lu:

> On Sun, Mar 26, 2017 at 10:36 PM, Richard Henderson <rth@twiddle.net> wrote:
>> Not quite true, at least as written.  The STATE_SAVE_MASK define selects
>> which components get saved.  This would have to be changed for additional
>> cpu bits that could be modified.
>>
>> One *could* set EAX:EDX = -1 and store everything, and then, yes, we'd be
>> done with changes to glibc for all cpu changes.
>>
>
> For relevant CPU features, they probably need kernel support.  It should
> be trivial to update STATE_SAVE_MASK when adding kernel support.

Then we should add a mechanism to get the value from the kernel.

I can assure you that it is *not* trivial to update the value once
glibc releases have shipped.