Re: /dev/ksyms under Xen-4.7

[Roger Pau Monné <roger.pau%citrix.com@localhost>]

On Thu, Sep 29, 2016 at 01:22:48PM +0200, Manuel Bouyer wrote:
> On Thu, Sep 29, 2016 at 12:35:01AM -0400, Brian Marcotte wrote:
> > I upgraded some of my systems to Xen 4.7.0 and found that in NetBSD domUs,
> > /dev/ksyms no longer works:
> > 
> >     # hexdump -C /dev/ksyms
> >     hexdump: /dev/ksyms: Device not configured
> >     hexdump: /dev/ksyms: Bad file descriptor
> > 
> > This prevents some utilities like fstat or lsof from working.
> > 
> > The NetBSD domUs are 6.1.5, 7.0, or current (from NetBSD-daily).
> > The dom0s are Linux 4.1 or 4.7.
> > 
> > The kernel output, below, doesn't give me any indication why this is.
> 
> I fear this is a Xen problem. It looks like Xen 4.7 fails to load the
> right section from the kernel's ELF image.
> Earlier Xen version did get it right, so we'll have to find what
> changed in 4.7 sources ...

I've done some changes to strtab/symtab loading, and supposedly tested them 
with a NetBSD kernel and didn't see it complaining (IIRC NetBSD will 
complain during early boot if it doesn't find a symtab/strtab), but I guess 
I've missed something. In any case, just bisecting the changes to 
xen/common/libelf should give you the offending one, here's the history:

http://xenbits.xen.org/gitweb/?p=xen.git;a=history;f=xen/common/libelf

Roger.