Re: [PATCH v4] Documentation: livepatch: document reliable stacktrace

From: Mark Rutland
Date: Mon Jan 18 2021 - 12:52:57 EST

Hi Petr,

On Mon, Jan 18, 2021 at 03:02:31PM +0100, Petr Mladek wrote:
> On Fri 2021-01-15 17:16:17, Mark Brown wrote:
> > I've made a few assumptions about preferred behaviour, notably:
> >
> > * If you can reliably unwind through exceptions, you should (as x86_64
> > does).

IIRC this was confirmed as desireable, and the text already reflects

> > * It's fine to omit ftrace_return_to_handler and other return
> > trampolines so long as these are not subject to patching and the
> > original return address is reported. Most architectures do this for
> > ftrace_return_handler, but not other return trampolines.

Likewise I think we agreed this was fine, given these were not
themselves subkect to patching.

> > * For cases where link register unreliability could result in duplicate
> > entries in the trace or an inverted trace, I've assumed this should be
> > treated as unreliable. This specific case shouldn't matter to
> > livepatching, but I assume that that we want a reliable trace to have
> > the correct order.

I don't think we had any comments either way on this, but I think it's
sane to say this for now and later relax it if we need to.

... so I reckon we can just delete all this as Josh suggests. Any acks
for the patch itself tacitly agrees with these points. :)