Re: New arm alignment issue with 6.2.0 - bisected to single revision

[Peter Maydell]

On Wed, 29 Dec 2021 at 20:15, Mark Watson <scrameta@googlemail.com> wrote:
> I'm seeing a repeatable alignment exception running m68k system mode on 
> armv7l (arm cortex a9) following this commit:
> "fa947a667fceab02f9f85fc99f54aebcc9ae6b51 is the first bad commit
> commit fa947a667fceab02f9f85fc99f54aebcc9ae6b51
> Author: Richard Henderson <richard.henderson@linaro.org>
> Date: Thu Jul 29 10:45:10 2021 -1000
>
> hw/core: Make do_unaligned_access noreturn


cc'ing Richard as this was his commit. Do you have a repro case
(QEMU command line, any necessary files/images, etc) ?

>
> While we may have had some thought of allowing system-mode
> to return from this hook, we have no guests that require this.
> "
> With this included I see this in the kernel dmesg log:
> [10621.993234] Alignment trap: not handling instruction f843b004 at 
> [<b677bb2e>]
> [10622.000479] 8<--- cut here ---
> [10622.003609] Unhandled fault: alignment exception (0x811) at 0xb13eed96
> [10622.010162] pgd = 45acdb93
> [10622.012941] [b13eed96] *pgd=0557a831, *pte=c01ee743, *ppte=c01eec33
>
> As well as bisecting I've verified it is this revision by checking out clean 
> HEAD then reverting just this revision (+ fixing conflicts).
>
> The patch itself just seems to be adding QEMU_NORETURN (aka '__attribute__ 
> ((__noreturn__))') which I'd expect to be benign, so I'm not really sure what 
> is going on.
>
> I cross-compiled it on Ubuntu using gcc/g++ (Ubuntu 9.3.0-17ubuntu1~20.04) 
> 9.3.0.
>


thanks
-- PMM