On Thu, Oct 08, 2020 at 11:15:58AM +0100, Mark Rutland wrote:

> I reckon we should remove the special case entirely rather than trying
> to shore up the comment here -- the related comment in entry.S is stale
> and misleading, and this will be a mystery to unfamiliar readers anyhow.

That works too, so long as the check isn't really doing anything it can
just be deleted and the comment with it - it's certainly one less weird
special case.  So long as all the things relying on it are already gone.

> Does the below patch look ok to you? I suspect the explicit check for the
> terminal case may help with the reliable stacktrace stuff? e.g. we could
> make that return -ENOENT to distinguish a terminal case from a broken
> frame record.

That's almost exactly what I've got in my reliable stacktrace queue,
down to the choice of -ENOENT for reporting the end of an intact stack.
I'll pick this up for my changes if it doesn't get picked up separately.