linux-kernel - Re: [PATCH 1/4] perf-probe: Avoid setting probes on same address on same event

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Message-Id: <20200710211447.da9a6e436f7b527c26849c4c@kernel.org>
Date:   Fri, 10 Jul 2020 21:14:47 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org,
        Andi Kleen <andi@...stfloor.org>,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 1/4] perf-probe: Avoid setting probes on same address on
 same event

On Fri, 10 Jul 2020 16:48:47 +0530
Srikar Dronamraju <srikar@...ux.vnet.ibm.com> wrote:

> * Masami Hiramatsu <mhiramat@...nel.org> [2020-07-09 17:07:01]:
> 
> > There is a case that the several same-name symbols points
> > same address. In that case, perf probe returns an error.
> > 
> > E.g.
> > 
> > With this patch;
> > 
> >   # perf probe -x /lib64/libc-2.30.so -a "memcpy arg1=%di"
> >   Failed to find the location of the '%di' variable at this address.
> >    Perhaps it has been optimized out.
> >    Use -V with the --range option to show '%di' location range.
> >   Added new events:
> >     probe_libc:memcpy    (on memcpy in /usr/lib64/libc-2.30.so with arg1=%di)
> >     probe_libc:memcpy    (on memcpy in /usr/lib64/libc-2.30.so with arg1=%di)
> > 
> >   You can now use it in all perf tools, such as:
> > 
> >   	perf record -e probe_libc:memcpy -aR sleep 1
> > 
> > 
> > Reported-by: Andi Kleen <andi@...stfloor.org>
> > Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> 
> One small nit:
> 
> > ---
> >  tools/perf/util/probe-event.c |    9 +++++++++
> >  1 file changed, 9 insertions(+)
> > 
> > diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> > index df713a5d1e26..1e95a336862c 100644
> > --- a/tools/perf/util/probe-event.c
> > +++ b/tools/perf/util/probe-event.c
> > @@ -2968,6 +2968,15 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev,
> >  	for (j = 0; j < num_matched_functions; j++) {
> >  		sym = syms[j];
> > 
> > +		/* There can be duplicated symbols in the map */
> > +		for (i = 0; i < j; i++)
> > +			if (sym->start == syms[i]->start) {
> > +				pr_debug("find duplicated symbol %s @ %lx\n", sym->name, sym->start);
> 	
> Would "Found" sound better than "find"?

OK.

> 
> > +				break;
> > +			}
> > +		if (i != j)
> > +			continue;
> > +
> 
> Reviewed-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>

Thank you!

> 
> 
> >  		tev = (*tevs) + ret;
> >  		tp = &tev->point;
> >  		if (ret == num_matched_functions) {
> > 
> 
> -- 
> Thanks and Regards
> Srikar Dronamraju


-- 
Masami Hiramatsu <mhiramat@...nel.org>