linux-kernel - Re: [PATCH v5 3/5] tracing/probes: Fix to update dynamic data counter if fetcharg uses it

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Date:   Thu, 13 Jul 2023 23:34:13 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Dan Carpenter <dan.carpenter@...aro.org>,
        linux-trace-kernel@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 3/5] tracing/probes: Fix to update dynamic data
 counter if fetcharg uses it

On Thu, 13 Jul 2023 09:34:36 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Tue, 11 Jul 2023 23:15:48 +0900
> "Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:
> 
> > From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > 
> > Fix to update dynamic data counter ('dyndata') and max length ('maxlen')
> > only if the fetcharg uses the dynamic data. Also get out arg->dynamic
> > from unlikely(). This makes dynamic data address wrong if
> > process_fetch_insn() returns error on !arg->dynamic case.
> > 
> > Suggested-by: Steven Rostedt <rostedt@...dmis.org>
> > Link: https://lore.kernel.org/all/20230710233400.5aaf024e@gandalf.local.home/
> > Fixes: 9178412ddf5a ("tracing: probeevent: Return consumed bytes of dynamic area")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> 
> Reviewed-by: Steven Rostedt (Google) <rostedt@...dmis.org>

Thank you! I'll pull this series. 

> 
> -- Steve
> 
> > ---
> >  kernel/trace/trace_probe_tmpl.h |   12 +++++++-----
> >  1 file changed, 7 insertions(+), 5 deletions(-)
> > 
> > diff --git a/kernel/trace/trace_probe_tmpl.h b/kernel/trace/trace_probe_tmpl.h
> > index ed9d57c6b041..185da001f4c3 100644
> > --- a/kernel/trace/trace_probe_tmpl.h
> > +++ b/kernel/trace/trace_probe_tmpl.h
> > @@ -267,11 +267,13 @@ store_trace_args(void *data, struct trace_probe *tp, void *rec,
> >  		if (unlikely(arg->dynamic))
> >  			*dl = make_data_loc(maxlen, dyndata - base);
> >  		ret = process_fetch_insn(arg->code, rec, dl, base);
> > -		if (unlikely(ret < 0 && arg->dynamic)) {
> > -			*dl = make_data_loc(0, dyndata - base);
> > -		} else {
> > -			dyndata += ret;
> > -			maxlen -= ret;
> > +		if (arg->dynamic) {
> > +			if (unlikely(ret < 0)) {
> > +				*dl = make_data_loc(0, dyndata - base);
> > +			} else {
> > +				dyndata += ret;
> > +				maxlen -= ret;
> > +			}
> >  		}
> >  	}
> >  }
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>