linux-user/signal.c: Put AArch64 frame record in the right place
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 7f0f4208 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: 7f0f4208Signed-off-by: NPeter Maydell <peter.maydell@linaro.org> Reviewed-by: NRichard Henderson <richard.henderson@linaro.org> Reviewed-by: NLaurent Vivier <laurent@vivier.eu> Message-id: 20180412140222.2096-1-peter.maydell@linaro.org
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