On Fri, Feb 28, 2014 at 11:29:46AM -0500, Steven Rostedt wrote: > On Fri, 28 Feb 2014 08:15:11 -0800 > "H. Peter Anvin" <h...@zytor.com> wrote: > > > Well, I was talking about the assumption spelled out in the comment > > above copy_from_user_nmi() which pretty much states "cr2 is safe because > > cr2 is saved/restored in the NMI wrappers." > > Yeah, it seems that the name "copy_from_user_nmi()" is a misnomer. As > it can be called outside of nmi context. Perhaps we should have a > copy_from_user_trace() that does the save and restore of the cr2. > > As that's the only place that faults, it may be the best answer. > > Arnaldo, > > Can you test this patch and see if it fixes the bug for you too. Vince > already said it fixes it for him. > > I'm attaching it below (it's from H. Peter). > > Peter Z., as both Jiri's and my patch fixed the callers of the problem > area, and as we have been discussing, there may be more problem areas, > I'm thinking the best solution is to just use H. Peter's patch instead. > And then we should rename it to copy_from_user_trace().
Like already said; _trace is an absolutely abysmal name. Also you _really_ don't want an unconditional CR2 write in there, that's just stupidly expensive. Also, this function is called a _LOT_ under certain workloads, I don't know how cheap a CR2 read is, but it had better be really cheap. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/