Re: [RFC PATCH 1/2] x86: Fix rbp saving in pt_regs on irq entry

Ingo Molnar
2011-01-07T16:59:04Z

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> On Fri, Jan 07, 2011 at 04:13:58PM +0000, Jan Beulich wrote:
> > >>> On 07.01.11 at 17:05, Frederic Weisbecker <fweisbec@gmail.com> wrote:
> > > Once I'll have perf callchain based on CFI ready, we'll perhaps find some
> > > issues
> > > there. Although I guess there are already tools that can make use of that.
> >
> > Is this to read that you're planning to do a re-spin of the CFI
> > unwinding code (which I'm not allowed to submit another time,
> > but which we've been using for years in SuSE distros) then?
>
> An in-kernel CFI unwinder?
>
> No the intended CFI unwinding that I'm working on for perf is made
> on post-processing, on top of partial stack and regs snapshots.
>
> The true unwinding is computed in userspace.

I think that design will be fundamentally more robust and more flexible than an
in-kernel unwinder.

Thanks,

Ingo