[Xen-bugs] [Bug 682] New: xen_features exported incorrectly

http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=682

           Summary: xen_features exported incorrectly
           Product: Xen
           Version: 3.0.2
          Platform: Other
        OS/Version: Linux-2.6
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Unspecified
        AssignedTo: xen-bugs@xxxxxxxxxxxxxxxxxxx
        ReportedBy: fozzy@xxxxxxxxxx
                CC: fozzy@xxxxxxxxxx


Running Xen 3.0.2 on Ubuntu Dapper.  Also wanted to install/use VMware Server
on the same machine.  I installed Xen then installed VMware Server 2.  The
modload of VMware failed due to the xen_features symbol not being found.

After much searching on the net I found this tweak to
drivers/xen/core/features.c that someone had posted that will enable the
modload to work:

diff features.c.orig features.c
15c15,18
< EXPORT_SYMBOL_GPL(xen_features);
---
> /*
>  * was EXPORT_SYMBOL_GPL(xen_features);
>  */
> EXPORT_SYMBOL(xen_features);


I realise this is not a valid solution.  I also subsequently found that VMware
wouldn't work on a Xen kernel and that Xen and VMware can't co-exist.  However,
I found others had similar problems with loading NVidia drivers.

In my research I found a post where the Xen developers passed the Xen kernel
patches upstream and someone (can't rememeber for sure who but I think it was
Chris Wright) fed back that this should be exported GPL instead of normally and
this change was subsequently made.

Whilst I now realise I'm doing something that won't work (Xen and VMware
co-existance), I think the bug is still valid.

My suspicion is that VMware has indirectly pulled in a header that's wanting to
use xen_features.  When the request was made to change the export from
EXPORT_SYMBOL to EXPORT_SYMBOL_GPL, it was simply done without properly
auditing what would be the ramificiations of that in terms of header files
being implicitly used elsewhere and wanting this symbol.

As the NVidia, post I found suggests.  This is not really an issue with VMware,
but with the Xen interaction generally with non-GPL modules.

I realise this is likely to re-ignite the "non-GPL modules in the kernel"
debate.  That however, is not my reason for reporting this.


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