linux-kernel - RE: perf tools: interface for improved PEBS ABI can accept wrong parameter

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Date:	Wed, 19 Oct 2011 10:23:12 +0800
From:	"Xu, Anhua" <anhua.xu@...el.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>
CC:	Arnaldo Carvalho de Melo <acme@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: perf tools: interface for improved PEBS ABI can accept wrong
 parameter

Thanks Peter:). The key point for this is that the detailed information about "PRECISE_IP" may not be exposed to user space.
Error reporting may come from syscall. Anyway, expect acme's suggestions.


-----Original Message-----
From: Peter Zijlstra [mailto:a.p.zijlstra@...llo.nl] 
Sent: Wednesday, October 19, 2011 2:28 AM
To: Ingo Molnar
Cc: Xu, Anhua; Arnaldo Carvalho de Melo; linux-kernel@...r.kernel.org
Subject: Re: perf tools: interface for improved PEBS ABI can accept wrong parameter

On Tue, 2011-10-18 at 20:19 +0200, Ingo Molnar wrote:
> > +#define SAMPLE_IP_MAX        3 
> >                               precise_ip     :  2, /* skid constraint       */
> >                               mmap_data      :  1, /* non-exec mmap data    */
> >                               sample_id_all  :  1, /* sample_type all events */
> > diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> > index 928918b..a2068cc 100644
> > --- a/tools/perf/util/parse-events.c
> > +++ b/tools/perf/util/parse-events.c
> > @@ -775,7 +775,10 @@ parse_event_modifier(const char **strp, struct perf_event_attr *attr)
> >       attr->exclude_user   = eu;
> >       attr->exclude_kernel = ek;
> >       attr->exclude_hv     = eh;
> > -     attr->precise_ip     = precise;
> > +     if ( precise < SAMPLE_IP_MAX )
> > +             attr->precise_ip = precise;
> > +     else
> > +             return -1; 

That name is horrid, how about PRECISE_IP_MAX? Also, I suspect acme will
want a better error return than -1, but I'll leave that up to him.