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

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

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...

~Andrew

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