Re: s390 && user_enable_single_step() (Was: odd utrace testing results on s390x)

Martin Schwidefsky
2010-01-08T08:35:06Z

On Thu, 7 Jan 2010 19:16:32 +0100
Oleg Nesterov <oleg@redhat.com> wrote:

> On 01/07, Martin Schwidefsky wrote:
> >
> > On Wed, 6 Jan 2010 13:08:12 -0800 (PST)
> > Roland McGrath <roland@redhat.com> wrote:
> >
> > > That's what tracehook_signal_handler is for. You're both doing it yourself
> > > in the arch code (by setting TIF_SINGLE_STEP), and then telling the generic
> > > code to do it (by passing stepping=1 to tracehook_signal_handler).
> >
> > Ok, so with the full utrace the semantics of tracehook_signal_handler
> > is more than just causing a SIGTRAP. It is an indication for a signal
> > AND a SIGTRAP if single-stepping is active. To make both cases work we
> > should stop setting TIF_SINGLE_STEP in do_signal and pass
> > current->thread.per_info.single_step to tracehook_signal_handler
> > instead of test_thread_flag(TIF_SINGLE_STEP).
>
> Can't understand why do we need TIF_SINGLE_STEP at all.
>
> Just pass current->thread.per_info.single_step to
> tracehook_signal_handler() ?
>
> Oleg.
>
> --- a/arch/s390/kernel/signal.c
> +++ b/arch/s390/kernel/signal.c
> @@ -504,14 +504,8 @@ void do_signal(struct pt_regs *regs)
> * for a normal instruction, act like we took
> * one for the handler setup.
> */
> - if (current->thread.per_info.single_step)
> - set_thread_flag(TIF_SINGLE_STEP);
> -
> - /*
> - * Let tracing know that we've done the handler setup.
> - */
> tracehook_signal_handler(signr, &info, &ka, regs,
> - test_thread_flag(TIF_SINGLE_STEP));
> + current->thread.per_info.single_step);
> }
> return;
> }
>

That is what I meant in the other mail. The patch on my local disk
looks almost the same but it removes the comment prior to the
TIF_SINGLE_STEP if statement as well.

--
blue skies,
Martin.

"Reality continues to ruin my life." - Calvin.