Re: [Xen-devel] [PATCH LIVEPATCH-BUILD-TOOLS] Fix patch creation with GCC 6.1+

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

On 11/25/2016 05:05 PM, Andrew Cooper wrote:
> On 25/11/16 16:59, M A Young wrote:
> > On Thu, 24 Nov 2016, Ross Lagerwall wrote:
> >
> > > GCC 6.1+ fixed https://gcc.gnu.org/bugzilla/show_bug.cgi?id=192 which
> > > means that .rodata.str* sections are now split by function.  We could
> > > probably be smarter about including just the sections we need, but for
> > > now, include all .rodata.str* sections as is done for previous versions
> > > of GCC.
> > >
> > > This manifests itself as symbol error. E.g.:
> > > (XEN)  Unknown symbol: .LC0
> > There may be a problem with this patch. I built livepatch-build-tools
> > (from the xenbits git repo) with this and the other patch posted yesterday
> > and successfully built and applied xsa191 to xsa193 (cumulatively) to
> > xen-4.8.0-rc6, but the computer freezes if I try to apply xsa194
> > (cumulatively or on its own). This was the only patch I tried which got
> > the Unknown symbol: .LC3 message ie.
> > (XEN) livepatch_elf.c:295: livepatch: xsa194: Unknown symbol: .LC3
> > so this may be related to the crash.
> XSA-194 is a toolstack patch.  It isn't applicable to livepatch.
>
> There is one copy of the vulnerable code in Xen, but it is only used to
> construct dom0 and discarded along with all the other __init code.
>
> Such a livepatch should be rejected by Xen...
elf_init() is not marked __init, so it is included in the live patch.

--
Ross Lagerwall

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