Re: [PATCH v1] perf tools: Fix pattern matching for same substring used in different pmu type

[Jiri Olsa]

On Wed, Jun 23, 2021 at 10:02:01AM +0800, Jin, Yao wrote:
> Hi Arnaldo, Jiri,
> 
> Any comments for this bug fix patch?
> 
> The issue does impact some uncore events and even some metrics.

sry for delay

SNIP

> > > Some different pmu types may have same substring. For example,
> > > on Icelake server, we have pmu types "uncore_imc" and
> > > "uncore_imc_free_running". Both pmu types have substring "uncore_imc".
> > > But the parser would wrongly think they are the same pmu type.
> > > 
> > > We enable an imc event,
> > > perf stat -e uncore_imc/event=0xe3/ -a -- sleep 1
> > > 
> > > Perf actually expands the event to:
> > > uncore_imc_0/event=0xe3/
> > > uncore_imc_1/event=0xe3/
> > > uncore_imc_2/event=0xe3/
> > > uncore_imc_3/event=0xe3/
> > > uncore_imc_4/event=0xe3/
> > > uncore_imc_5/event=0xe3/
> > > uncore_imc_6/event=0xe3/
> > > uncore_imc_7/event=0xe3/
> > > uncore_imc_free_running_0/event=0xe3/
> > > uncore_imc_free_running_1/event=0xe3/
> > > uncore_imc_free_running_3/event=0xe3/
> > > uncore_imc_free_running_4/event=0xe3/
> > > 
> > > That's because the "uncore_imc_free_running" matches the
> > > pattern "uncore_imc*".
> > > 
> > > Now we check that the last characters of pmu name is
> > > '_<digit>'.
> > > 
> > > Fixes: b2b9d3a3f021 ("perf pmu: Support wildcards on pmu name in dynamic pmu events")
> > > Signed-off-by: Jin Yao <yao.jin@xxxxxxxxxxxxxxx>
> > > ---
> > >   tools/perf/util/parse-events.y |  2 ++
> > >   tools/perf/util/pmu.c          | 25 ++++++++++++++++++++++++-
> > >   tools/perf/util/pmu.h          |  1 +
> > >   3 files changed, 27 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/tools/perf/util/parse-events.y b/tools/perf/util/parse-events.y
> > > index aba12a4d488e..7a694c7f7f1a 100644
> > > --- a/tools/perf/util/parse-events.y
> > > +++ b/tools/perf/util/parse-events.y
> > > @@ -317,6 +317,8 @@ event_pmu_name opt_pmu_config
> > >                   strncmp($1, "uncore_", 7))
> > >                   name += 7;
> > >               if (!fnmatch(pattern, name, 0)) {
> > > +                if (!perf_pmu__valid_suffix($1, name))
> > > +                    continue;

could this be part of the fnmatch's pattern?

> > >                   if (parse_events_copy_term_list(orig_terms, &terms))
> > >                       CLEANUP_YYABORT;
> > >                   if (!parse_events_add_pmu(_parse_state, list, pmu->name, terms, true, false))
> > > diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> > > index 88c8ecdc60b0..78af01959830 100644
> > > --- a/tools/perf/util/pmu.c
> > > +++ b/tools/perf/util/pmu.c
> > > @@ -3,6 +3,7 @@
> > >   #include <linux/compiler.h>
> > >   #include <linux/string.h>
> > >   #include <linux/zalloc.h>
> > > +#include <linux/ctype.h>
> > >   #include <subcmd/pager.h>
> > >   #include <sys/types.h>
> > >   #include <errno.h>
> > > @@ -768,7 +769,7 @@ bool pmu_uncore_alias_match(const char *pmu_name, const char *name)
> > >        */
> > >       for (; tok; name += strlen(tok), tok = strtok_r(NULL, ",", &tmp)) {
> > >           name = strstr(name, tok);
> > > -        if (!name) {
> > > +        if (!name || !perf_pmu__valid_suffix(tok, (char *)name)) {
> > >               res = false;
> > >               goto out;
> > >           }
> > > @@ -1872,3 +1873,25 @@ bool perf_pmu__has_hybrid(void)
> > >       return !list_empty(&perf_pmu__hybrid_pmus);
> > >   }
> > > +
> > > +bool perf_pmu__valid_suffix(char *tok, char *pmu_name)
> > > +{
> > > +    char *p;
> > > +
> > > +    /*
> > > +     * The pmu_name has substring tok. If the format of
> > > +     * pmu_name is <tok> or <tok>_<digit>, return true.
> > > +     */
> > > +    p = pmu_name + strlen(tok);
> > > +    if (*p == 0)
> > > +        return true;
> > > +
> > > +    if (*p != '_')
> > > +        return false;
> > > +
> > > +    ++p;
> > > +    if (*p == 0 || !isdigit(*p))
> > > +        return false;
> > > +
> > > +    return true;
> > > +}

hum, so we have pattern serch and then another function checking
if that search was ok.. I understand that's convenient, because
it's on 2 different places, but could we have some generic solution,
line one function/search that returns/search for valid pmu name?

thanks,
jirka