Re: [PATCH 07/30] bsd-user/arm/target_arch_cpu.h: Use force_sig_fault for EXCP_UDEF

[Richard Henderson]

On 1/14/22 4:19 AM, Peter Maydell wrote:
> On Sun, 9 Jan 2022 at 16:27, Warner Losh <imp@bsdimp.com> wrote:
> > Use force_sig_fault to implement unknown opcode. This just uninlines
> > that function, so simplify things by using it. Fold in EXCP_NOCP and
> > EXCP_INVSTATE, as is done in linux-user.
> >
> > Signed-off-by: Warner Losh <imp@bsdimp.com>
> > ---
> >   bsd-user/arm/target_arch_cpu.h | 18 ++++++------------
> >   1 file changed, 6 insertions(+), 12 deletions(-)
> >
> > diff --git a/bsd-user/arm/target_arch_cpu.h b/bsd-user/arm/target_arch_cpu.h
> > index 905f13aa1b9..996a361e3fe 100644
> > --- a/bsd-user/arm/target_arch_cpu.h
> > +++ b/bsd-user/arm/target_arch_cpu.h
> > @@ -51,18 +51,12 @@ static inline void target_cpu_loop(CPUARMState *env)
> >           process_queued_cpu_work(cs);
> >           switch (trapnr) {
> >           case EXCP_UDEF:
> > -            {
> > -                /* See arm/arm/undefined.c undefinedinstruction(); */
> > -                info.si_addr = env->regs[15];
> > -
> > -                /* illegal instruction */
> > -                info.si_signo = TARGET_SIGILL;
> > -                info.si_errno = 0;
> > -                info.si_code = TARGET_ILL_ILLOPC;
> > -                queue_signal(env, info.si_signo, &info);
> > -
> > -                /* TODO: What about instruction emulation? */
> > -            }
> > +        case EXCP_NOCP:
> > +        case EXCP_INVSTATE:
> > +            /*
> > +             * See arm/arm/undefined.c undefinedinstruction();
> > +             */
> > +            force_sig_fault(TARGET_SIGILL, TARGET_ILL_ILLOPC, env->regs[15]);
> >               break;
>
> Do you want to keep the TODO comment ?
>
> Either way,
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
>
> (Looks like FreeBSD sends SIGILL/ILL_ILLADR for UNDEF where the PC
> is misaligned and we're not in Thumb mode, but that's a pretty oddball
> corner case so not really worth emulating.)

For qemu, that case will never happen: we'll raise EXCP_PREFETCH_ABORT with fsr=1 
(Alignment).  The freebsd kernel might have this code because the behaviour with real hw 
is CONSTRAINED UNPREDICTABLE (iirc).

Anyway,
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~