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

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Date:	Tue, 5 Jan 2010 16:50:53 +0100
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Roland McGrath <roland@...hat.com>, caiqian@...hat.com,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Jan Kratochvil <jkratoch@...hat.com>,
	linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
	utrace-devel@...hat.com
Subject: Re: s390 && user_enable_single_step() (Was: odd utrace testing
 results on s390x)

On Tue, 5 Jan 2010 16:47:25 +0100
Oleg Nesterov <oleg@...hat.com> wrote:

> On 01/05, Oleg Nesterov wrote:
> >
> > Anyway. I modified the debugging patch a bit:
> >
> > --- K/arch/s390/kernel/traps.c~	2009-12-22 10:41:52.909174198 -0500
> > +++ K/arch/s390/kernel/traps.c	2010-01-05 09:49:19.541792379 -0500
> > @@ -384,6 +384,8 @@ void __kprobes do_single_step(struct pt_
> >  	}
> >  	if (tracehook_consider_fatal_signal(current, SIGTRAP))
> >  		force_sig(SIGTRAP, current);
> > +	else
> > +		printk("XXX: %d %d\n", current->pid, test_thread_flag(TIF_SINGLE_STEP));
> >  }
> >
> >  static void default_trap_handler(struct pt_regs * regs, long interruption_code)
> > -------------------------------------------------------------------------------
> 
> Ah, please ignore. I guess TIF_SINGLE_STEP was already cleared by the caller
> in entry.S

Yes, TIF_SINGLE_STEP is checked in entry.S and cleared before do_signal
is called. That is the "ni" instruction at sysc_singlestep and
sysc_sigpending.

-- 
blue skies,
   Martin.

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

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