Re: [Qemu-arm] [Qemu-devel] [PATCH for-2.12] linux-user/signal.c: Put AArch64 frame record in the right place

[Richard Henderson]

On 04/12/2018 04:02 AM, Peter Maydell wrote:
> AArch64 stack frames include a 'frame record' which holds a pointer
> to the next frame record in the chain and the LR on entry to the
> function. The procedure calling standard doesn't mandate where
> exactly this frame record is in the stack frame, but for signal
> frames the kernel puts it right at the top. We used to put it
> there too, but in commit 7f0f4208b3a96f22 we accidentally put
> the "enlarge to the 4K reserved space minimum" check after the
> "allow for the frame record" code, rather than before it, with
> the effect that the frame record would be inside the reserved
> space and immediately after the last used part of it.
> 
> Move the frame record back out of the reserved space to where
> we used to put it.
> 
> This bug shouldn't break any sensible guest code, but test
> programs that deliberately look at the internal details
> of the signal frame layout will not find what they are
> expecting to see.
> 
> Fixes: 7f0f4208b3a96f22
> Signed-off-by: Peter Maydell <address@hidden>

Reviewed-by: Richard Henderson <address@hidden>

> I'm marking this as for-2.12 on the basis that it puts our frame
> layout back to exactly what 2.11 had, and so seems safest.
> No sensible guest code should really care, though, so this is
> in the "only if we're doing an rc4" bucket; but I think that the
> softfloat fixes deserve an rc4 anyway.

Granted.


r~