Messages in this thread | | | Date | Fri, 09 Jan 2015 17:06:54 +0000 | From | Daniel Thompson <> | Subject | Re: [PATCH] arm: Remove early stack deallocation from restore_user_regs |
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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 <daniel.thompson@linaro.org> >> --- > > 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.
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.
Daniel.
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