Re: [PATCH 1/4] linux-user/ppc: Fix XER access in save/restore_user_regs

[Matheus K. Ferst]

On 14/10/2021 20:43, Richard Henderson wrote:
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> On 10/14/21 3:32 PM, matheus.ferst@eldorado.org.br wrote:
> > From: Matheus Ferst <matheus.ferst@eldorado.org.br>
> >
> > We should use cpu_read_xer/cpu_write_xer to save/restore the complete
> > register since some of its bits are in other fields of CPUPPCState. A
> > test is added to prevent future regressions.
> >
> > Fixes: da91a00f191f ("target-ppc: Split out SO, OV, CA fields from XER")
> > Signed-off-by: Matheus Ferst <matheus.ferst@eldorado.org.br>
> > ---
> >   linux-user/ppc/signal.c                     |  9 +++--
> >   tests/tcg/ppc64/Makefile.target             |  2 +
> >   tests/tcg/ppc64le/Makefile.target           |  2 +
> >   tests/tcg/ppc64le/signal_save_restore_xer.c | 42 +++++++++++++++++++++
> >   4 files changed, 52 insertions(+), 3 deletions(-)
> >   create mode 100644 tests/tcg/ppc64le/signal_save_restore_xer.c
>
> The code is good so,
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
>
> > +    sigaction(SIGILL, &sa, NULL);
> > +
> > +    asm("mtspr 1, %1\n\t"
> > +        ".long 0x0\n\t"
>
> While Appendix B does guarantee that "0" is and always will be an 
> invalid instruction, I
> wonder if the test itself would be clearer (i.e. self-documenting the 
> intent) using
> SIGTRAP and "trap".
>
>
> r~

It would be better, but cpu_loop is currently calling cpu_abort for 
POWERPC_EXCP_TRAP, so the test would fail. I'll see if I can fix that in 
another patch, and then we can change the test to use trap.

--
Matheus K. Ferst
Instituto de Pesquisas ELDORADO <http://www.eldorado.org.br/>
Analista de Software Júnior
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