Re: CONFIG_MARKERS

Mathieu Desnoyers
2008-01-23T15:01:54Z

* Mathieu Desnoyers (mathieu.desnoyers@polymtl.ca) wrote:
> * Frank Ch. Eigler (fche@redhat.com) wrote:
> > Hi -
> >
> > On Tue, Jan 22, 2008 at 11:17:40PM -0500, Jon Masters wrote:
> > > On Tue, 2008-01-22 at 22:10 -0500, Mathieu Desnoyers wrote:
> > > > [...]
> > > > > > Is this an attempt to not set a marker for proprietary modules? [...]
> > > > >
> > > > > I can't seem to find any discussion about this aspect. If this is the
> > > > > intent, it seems misguided to me. There may instead be a relationship
> > > > > to TAINT_FORCED_{RMMOD,MODULE}. Mathieu?
> >
> > > > On my part, its mostly a matter of not crashing the kernel when someone
> > > > tries to force modprobe of a proprietary module (where the checksums
> > > > doesn't match) on a kernel that supports the markers. Not doing so
> > > > causes the markers to try to find the marker-specific information in
> > > > struct module which doesn't exist and OOPSes.
> >
> > But you have the wrong target: it is not proprietary modules that have
> > this risk but those built out-of-tree without checksums. Maybe
> > oopsing in this case is not so bad; or the check could just limit itself to
> > FORCED_MODULE.
> >
>
> I guess that for this one I could have a :
>
> if (!mod->taints & TAINT_FORCED_MODULE)
> ...
>

as one could notice: missing parenthesis
if (!(mod->taints & TAINT_FORCED_MODULE))

>
> >
> > > > Christoph's point of view is rather more drastic than mine : it's not
> > > > interesting for the kernel community to help proprietary modules writers,
> > > > so it's a good idea not to give them marker support. (I CC'ed him so he
> > > > can clarify his position).
> > > Right. I thought that was your collective opinion
> >
> > Another way of looking at this though is that by allowing/encouraging
> > proprietary module writers to include markers, we and their users get
> > new diagnostic capabilities. It constitutes a little bit of opening
> > up, which IMO we should reward rather than punish.
> >
> >
>
> This specific one is a kernel policy matter, and I personally don't
> have a strong opinion about it. I agree that you raise a good counter
> argument : it can be useful to proprietary modules users to be able to
> extract tracing information from those modules to argue with their
> vendors that their driver/hardware is broken (a tracer is _very_ useful
> in that kind of situation). However, it is also useful to proprieraty
> module writers who can benefit from the merged kernel/modules traces.
> Do we want to give them this ability ? It would surely help writing
> better proprieraty kernel modules. Do we want this, or rather prefer to
> put more pressure on them so they open their code ?
>
> I will let others fight in the mud on this one. :)
>
> for this one, we could add, instead :
>
> if (!mod->taints & (TAINT_FORCED_MODULE | TAINT_PROPRIETARY_MODULE))
>

here too
if (!(mod->taints & (TAINT_FORCED_MODULE | TAINT_PROPRIETARY_MODULE)))

Which remembers me to never write code before my first coffee in the
morning ;)

Mathieu

> Mathieu
>
> > - FChE
>
> --
> Mathieu Desnoyers
> Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
> OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68

--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68