linux-kernel - Re: [PATCH v2 13/13] perf parse-events: Remove ABORT

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Date:   Fri, 30 Jun 2023 08:14:21 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH v2 13/13] perf parse-events: Remove ABORT_ON

On Thu, Jun 29, 2023 at 2:49 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> On Tue, Jun 27, 2023 at 11:11 AM Ian Rogers <irogers@...gle.com> wrote:
> >
> > Prefer informative messages rather than none with ABORT_ON. Document
> > one failure mode and add an error message for another.
> >
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > ---
> >  tools/perf/util/parse-events.y | 22 ++++++++++++++--------
> >  1 file changed, 14 insertions(+), 8 deletions(-)
> >
> > diff --git a/tools/perf/util/parse-events.y b/tools/perf/util/parse-events.y
> > index 844646752462..454577f7aff6 100644
> > --- a/tools/perf/util/parse-events.y
> > +++ b/tools/perf/util/parse-events.y
> > @@ -22,12 +22,6 @@
> >
> >  void parse_events_error(YYLTYPE *loc, void *parse_state, void *scanner, char const *msg);
> >
> > -#define ABORT_ON(val) \
> > -do { \
> > -       if (val) \
> > -               YYABORT; \
> > -} while (0)
> > -
> >  #define PE_ABORT(val) \
> >  do { \
> >         if (val == -ENOMEM) \
> > @@ -618,7 +612,9 @@ PE_RAW opt_event_config
> >                 YYNOMEM;
> >         errno = 0;
> >         num = strtoull($1 + 1, NULL, 16);
> > -       ABORT_ON(errno);
> > +       /* Given the lexer will only give [a-fA-F0-9]+ a failure here should be impossible. */
> > +       if (errno)
> > +               YYABORT;
> >         free($1);
> >         err = parse_events_add_numeric(_parse_state, list, PERF_TYPE_RAW, num, $2,
> >                                        /*wildcard=*/false);
> > @@ -978,7 +974,17 @@ PE_VALUE PE_ARRAY_RANGE PE_VALUE
> >  {
> >         struct parse_events_array array;
> >
> > -       ABORT_ON($3 < $1);
> > +       if ($3 < $1) {
> > +               struct parse_events_state *parse_state = _parse_state;
> > +               struct parse_events_error *error = parse_state->error;
> > +               char *err_str;
> > +
> > +               if (asprintf(&err_str, "Expected '%ld' to be less-than '%ld'", $3, $1) < 0)
>
> Isn't it to be "greater-than or equal" ?

I think the order is right. From the man page:

       When  successful,  these  functions return the number of bytes printed,
       just like sprintf(3).  If memory allocation wasn't  possible,  or  some
       other error occurs, these functions will return -1, and the contents of
       strp are undefined.

So here we need to catch -1 and ensure strp (&err_str) is NULL before
passing it to parse_events_error__handle.

Thanks,
Ian

> Thanks,
> Namhyung
>
>
> > +                       err_str = NULL;
> > +
> > +               parse_events_error__handle(error, @1.first_column, err_str, NULL);
> > +               YYABORT;
> > +       }
> >         array.nr_ranges = 1;
> >         array.ranges = malloc(sizeof(array.ranges[0]));
> >         if (!array.ranges)
> > --
> > 2.41.0.162.gfafddb0af9-goog
> >