Re: [RFC PATCH 2/5] unwind: Export unwind_user symbol to GPL modules

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Fri, 2025-07-11 at 13:38 +0200, Greg KH wrote:
> On Fri, Jul 11, 2025 at 06:57:42AM -0400, Steven Rostedt wrote:
> > 
> > [ Adding the TAB to this as well ]
> > 
> > On Fri, 11 Jul 2025 00:36:28 -0700
> > Christoph Hellwig <hch@infradead.org> wrote:
> > 
> > > On Wed, Jul 09, 2025 at 05:25:49PM -0400, Mathieu Desnoyers
> > > wrote:
> > > > Allow the unwind_user symbol to be used by GPL modules, for
> > > > instance LTTng.  
> > > 
> > > I don't see a LTTng submission or any other user in this series.
> > > So the usual prohibition against adding unused exports applies
> > > here as usual.
> > 
> > I want to bring up this discussion. I understand there's a policy
> > not to add EXPORT_SYMBOL_GPL() unless there's a current user of it
> > in the kernel proper. My question is, does this policy have to be
> > draconian?
> 
> It's not "draconian", it is "we do not add exports for stuff that is
> not in our kernel tree."  Simple, direct, and obvious.  We have no
> idea how, or if, external modules do anything with apis that we
> export and do not use internally, so we can't change them without
> breaking anything, so it's simpler and more obvious to not even
> attempt to care about
> them.

Since the argument is still going on, I've got to say I agree with
Greg: it's not draconian it's a simple technical rule which is easily
enforceable and gets us out of making political decisions like what's a
"good" use of a symbol and what isn't.  Once we start making political
decisions about kernel symbol exports we open ourselves up to
accusations of partisanship and favouritism ... since we have a clear
technical criterion, it's just way easier not to descend that slippery
slope.

Regards,

James