On Fri, Jan 09, 2015 at 05:20:35PM +0000, Russell King - ARM Linux wrote: > On Fri, Jan 09, 2015 at 05:06:54PM +0000, Daniel Thompson wrote: > > On 09/01/15 16:46, Russell King - ARM Linux wrote: > > > On Mon, Jan 05, 2015 at 03:12:38PM +0000, Daniel Thompson wrote: > > >> Currently restore_user_regs deallocates the SVC stack early in > > >> its execution and relies on no exception being taken between > > >> the deallocation and the registers being restored. The introduction > > >> of a default FIQ handler that also uses the SVC stack breaks this > > >> assumption and can result in corrupted register state. > > >> > > >> This patch works around the problem by removing the early > > >> stack deallocation and using r2 as a temporary instead. I have > > >> not found a way to do this without introducing an extra mov > > >> instruction to the macro. > > >> > > >> Signed-off-by: Daniel Thompson <[email protected]> > > >> --- > > > > > > Please put it in the patch system, thanks. > > > > Will do. > > > > > > > I think we should queue > > > this one for stable too, as I think we need this for v3.18 > > > (as a result of c0e7f7ee717e2b4c5791e7422424c96b5008c39e, > > > ARM: 8150/3: fiq: Replace default FIQ handler)? > > > > It's a close call. > > I agree. > > > Before 8150/3 the system would probably crash if the default FIQ handler > > ran. After 8150/3 the system is also likely to crash since there's no > > code hooked into the handler in v3.18 that can clear the source of FIQ > > leaving us stuck re-entering the FIQ handler. > > > > Nevertheless, this is a nasty gremlin to leave for backporters (it > > wasn't easy to find) so I'd be very happy to Cc: stable and see what > > they think. > > Well, we could ask Greg now. It's not a regression (as nothing makes > use of the previously merged changes yet), but it is a nasty latent bug > which we could easily solve. > > Having thought about it some more, I'm tempted to say... leave the > stable tag off it, and we can make the decision later - after it's had > a chance to really prove itself to a much wider audience. That'd be > the lowest risk for the 3.18 stable tree.
That sounds like a good idea, you can always email stable@ to let us know of a patch we should add at a later time. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
