linux-kernel - Re: [PATCH 05/12] perf pmu: Fix pmu events parsing rule

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Date:   Thu, 3 May 2018 12:37:17 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Clark Williams <williams@...hat.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Jiri Olsa <jolsa@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        David Ahern <dsahern@...il.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH 05/12] perf pmu: Fix pmu events parsing rule

On Thu, May 03, 2018 at 11:25:16AM +0300, Adrian Hunter wrote:
> Hi
> 
> This breaks Intel PT i.e.
> 
> $ perf record -e intel_pt//u uname
> event syntax error: 'intel_pt//u'
>                              \___ parser error
> Run 'perf list' for a list of valid events
> 
>  Usage: perf record [<options>] [<command>]
>     or: perf record [<options>] -- <command> [<options>]
> 
>     -e, --event <event>   event selector. use 'perf list' to list available events
> 
> See below for cause.
> 
> On 25/04/18 19:00, Arnaldo Carvalho de Melo wrote:
> > From: Jiri Olsa <jolsa@...nel.org>
> > 
> > Currently all the event parsing fails end up in the event_pmu rule, and
> > display misleading help like:
> > 
> >   $ perf stat -e inst kill
> >   event syntax error: 'inst'
> >                        \___ Cannot find PMU `inst'. Missing kernel support?
> >   ...
> > 
> > The reason is that the event_pmu is too strong and match also single
> > string. Changing it to force the '/' separators to be part of the rule,
> > and getting the proper error now:
> > 
> >   $ perf stat -e inst kill
> >   event syntax error: 'inst'
> >                        \___ parser error
> >   Run 'perf list' for a list of valid events
> >   ...
> > 
> > Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> > Reported-by: Ingo Molnar <mingo@...nel.org>
> > Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> > Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> > Cc: David Ahern <dsahern@...il.com>
> > Cc: Namhyung Kim <namhyung@...nel.org>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Link: http://lkml.kernel.org/r/20180423090823.32309-5-jolsa@kernel.org
> > Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> > ---
> >  tools/perf/util/parse-events.y | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/tools/perf/util/parse-events.y b/tools/perf/util/parse-events.y
> > index 7afeb80cc39e..d14464c42714 100644
> > --- a/tools/perf/util/parse-events.y
> > +++ b/tools/perf/util/parse-events.y
> > @@ -224,15 +224,15 @@ event_def: event_pmu |
> >  	   event_bpf_file
> >  
> >  event_pmu:
> > -PE_NAME opt_event_config
> > +PE_NAME '/' event_config '/'
> 
> These are not equivalent because opt_event_config allows '//'
> but event_config cannot be an empty string.

yep, overlooked this one, how about patch below

jirka

---
diff --git a/tools/perf/util/parse-events.y b/tools/perf/util/parse-events.y
index d14464c42714..1ed2befeca8a 100644
--- a/tools/perf/util/parse-events.y
+++ b/tools/perf/util/parse-events.y
@@ -523,6 +523,10 @@ event_term
 	list_add_tail(&term->list, head);
 	$$ = head;
 }
+|
+{
+	$$ = NULL;
+}
 
 event_term:
 PE_NAME '=' PE_NAME