Re: [PATCH v2 2/5] perf pmu: Support more complex PMU event aliasing

[John Garry]

On 16/06/2019 10:58, Jiri Olsa wrote:
> On Fri, Jun 14, 2019 at 10:08:00PM +0800, John Garry wrote:
> > The jevent "Unit" field is used for uncore PMU alias definition.
> >
> > The form uncore_pmu_example_X is supported, where "X" is a wildcard,
> > to support multiple instances of the same PMU in a system.
> >
> > Unfortunately this format not suitable for all uncore PMUs; take the Hisi
> > DDRC uncore PMU for example, where the name is in the form
> > hisi_scclX_ddrcY.
> >
> > For the current jevent parsing, we would be required to hardcode an uncore
> > alias translation for each possible value of X. This is not scalable.
> >
> > Instead, add support for "Unit" field in the form "hisi_sccl,ddrc", where
> > we can match by hisi_scclX and ddrcY. Tokens in Unit field are
> > delimited by ','.
> >
> > Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
> > ---
> >  tools/perf/util/pmu.c | 39 ++++++++++++++++++++++++++++++++++-----
> >  1 file changed, 34 insertions(+), 5 deletions(-)
> >
> > diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> > index 7e7299fee550..bc71c60589b5 100644
> > --- a/tools/perf/util/pmu.c
> > +++ b/tools/perf/util/pmu.c
> > @@ -700,6 +700,39 @@ struct pmu_events_map *perf_pmu__find_map(struct perf_pmu *pmu)
> >  	return map;
> >  }
> >
> > +static bool pmu_uncore_alias_match(const char *pmu_name, const char *name)
> > +{
> > +	char *tmp, *tok, *str;
> > +	bool res;
> > +
> > +	str = strdup(pmu_name);
> > +	if (!str)
> > +		return false;
> > +
> > +	/*
> > +	 * uncore alias may be from different PMU with common
> > +	 * prefix or matching tokens.
> > +	 */
> > +	tok = strtok_r(str, ",", &tmp);
> > +	if (strncmp(pmu_name, tok, strlen(tok))) {

Hi Jirka,

> if tok is NULL in here we crash

As I see, tok could not be NULL. If str contains no delimiters, then we 
just return same as str in tok.

Can you see tok being NULL?

> > +		res = false;
> > +		goto out;
> > +	}
> > +
> > +	for (; tok; name += strlen(tok), tok = strtok_r(NULL, ",", &tmp)) {
>
> why is name shifted in here?

I want to ensure that we match the tokens in order and also guard 
against possible repeated token matches in 'name'.

Thanks,
John

> jirka
>
> > +		name = strstr(name, tok);
> > +		if (!name) {
> > +			res = false;
> > +			goto out;
> > +		}
> > +	}
> > +
> > +	res = true;
> > +out:
> > +	free(str);
> > +	return res;
> > +}
> > +
> >  /*
> >   * From the pmu_events_map, find the table of PMU events that corresponds
> >   * to the current running CPU. Then, add all PMU events from that table
> > @@ -730,12 +763,8 @@ static void pmu_add_cpu_aliases(struct list_head *head, struct perf_pmu *pmu)
> >  			break;
> >  		}
> >
> > -		/*
> > -		 * uncore alias may be from different PMU
> > -		 * with common prefix
> > -		 */
> >  		if (pmu_is_uncore(name) &&
> > -		    !strncmp(pname, name, strlen(pname)))
> > +		    pmu_uncore_alias_match(pname, name))
> >  			goto new_alias;
> >
> >  		if (strcmp(pname, name))
> > --
> > 2.17.1
>
> .