Comment 17 for bug 429241

No, those 2 traces were clean of wrapped instructions in the ringbuffer. Eric spotted an issue inside ... one of the layers, I think it was drm, where he adjusted the presumed_offset by the real address and not a delta, resulting in the GPU making out-of-bounds reads.

You can try testing the patch available from:
http://lists.freedesktop.org/archives/intel-gfx/2009-September/004090.html
to see if detects this error.