Re: [RFC PATCH] tests/tcg: add a multiarch signals test to stress test signal delivery

[Peter Maydell]

On Wed, 21 Apr 2021 at 20:51, Alex Bennée <alex.bennee@linaro.org> wrote:
>
>
> Alex Bennée <alex.bennee@linaro.org> writes:
> > To further document my confusion:
> >
> >   gdb --args $QEMU ./tests/tcg/$ARCH/signals
> >
> > will SEGV in generated code for every target I've run. This seems to be
> > some sort of change of behaviour by running inside a debug
> > environment.
>
> This bit at least seems to be triggered by the page protections for
> detecting SMC - I think. If you skip past them it triggers:
>
>     if (is_write && info->si_signo == SIGSEGV && info->si_code == SEGV_ACCERR 
> &&
>         h2g_valid(address)) {
>         switch (page_unprotect(h2g(address), pc)) {
>
> and runs.

Yeah, for linux-user code SEGV in generated code is expected and
handled -- it's how we catch things like SMC and other cases that
in softmmu we handle via the softmmu slowpath.

thanks
-- PMM