Re: [PATCH] tcg/arm: Increase stack alignment for function generation

[Richard W.M. Jones]

On Wed, Sep 01, 2021 at 07:18:03PM +0100, Peter Maydell wrote:
> On Wed, 1 Sept 2021 at 18:01, Richard W.M. Jones <rjones@redhat.com> wrote:
> >
> > This avoids the following assertion when the kernel initializes X.509
> > certificates:
> >
> > [    7.315373] Loading compiled-in X.509 certificates
> > qemu-system-arm: ../tcg/tcg.c:3063: temp_allocate_frame: Assertion `align 
> > <= TCG_TARGET_STACK_ALIGN' failed.
> >
> > Fixes: commit c1c091948ae
> > Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1999878
> > Cc: qemu-stable@nongnu.org
> > Tested-by: Richard W.M. Jones <rjones@redhat.com>
> > Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
> > ---
> >  tcg/arm/tcg-target.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/tcg/arm/tcg-target.h b/tcg/arm/tcg-target.h
> > index d113b7f8db..09df3b39a1 100644
> > --- a/tcg/arm/tcg-target.h
> > +++ b/tcg/arm/tcg-target.h
> > @@ -115,7 +115,7 @@ extern bool use_neon_instructions;
> >  #endif
> >
> >  /* used for function call generation */
> > -#define TCG_TARGET_STACK_ALIGN         8
> > +#define TCG_TARGET_STACK_ALIGN          16
> >  #define TCG_TARGET_CALL_ALIGN_ARGS     1
> >  #define TCG_TARGET_CALL_STACK_OFFSET   0
> 
> The 32-bit Arm procedure call standard only guarantees 8-alignment
> of SP, not 16-alignment, so I suspect this is not the correct fix.

Wouldn't it be a good idea if asserts in TCG dumped out something
useful about the guest code?  Because I can only reproduce this bug in
a very awkward batch environment I need to collect as much information
from log messages as possible.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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