2020-04-16 16:23:19

by Andi Kleen

Subject: [PATCH v1] perf parse: Avoid false uncore matches

From: Andi Kleen <[email protected]>

The PMU matching adds an implicit '*' to match multiple instances of PMUs.
But this causes problems when the user specified an explicit number,
in this case longer numbers with the same prefix could be matched too,
which is not intended.

Check for the number case and avoid the extra wildcard.

Also this fixes a memory leak with the pattern match. We would not
free the allocated pattern.

Before:

$ perf stat --no-merge -e cha_1// -a sleep 1

Performance counter stats for 'system wide':

698,393,431 uncore_cha_1//
698,395,491 uncore_cha_14//
698,393,873 uncore_cha_12//
698,392,975 uncore_cha_10//
698,391,167 uncore_cha_17//
698,390,371 uncore_cha_15//
698,389,007 uncore_cha_13//
698,388,069 uncore_cha_11//
698,386,991 uncore_cha_16//

1.001343184 seconds time elapsed

After

$ ./perf stat --no-merge -e cha_1// -a sleep 1

Performance counter stats for 'system wide':

741,490,611 uncore_cha_1//

1.000847326 seconds time elapsed

$

Signed-off-by: Andi Kleen <[email protected]>
---
tools/perf/util/parse-events.y | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/parse-events.y b/tools/perf/util/parse-events.y
index 94f8bcd83582..f38c90756476 100644
--- a/tools/perf/util/parse-events.y
+++ b/tools/perf/util/parse-events.y
@@ -286,7 +286,8 @@ PE_NAME opt_pmu_config
parse_events_terms__delete(orig_terms); \
free(list); \
free($1); \
- free(pattern); \
+ if ($1 != pattern) \
+ free(pattern); \
YYABORT; \
} while(0)

@@ -303,7 +304,9 @@ PE_NAME opt_pmu_config
struct perf_pmu *pmu = NULL;
int ok = 0;

- if (asprintf(&pattern, "%s*", $1) < 0)
+ if ($1[0] && isdigit($1[strlen($1) - 1]))
+ pattern = $1;
+ else if (asprintf(&pattern, "%s*", $1) < 0)
CLEANUP_YYABORT;

while ((pmu = perf_pmu__scan(pmu)) != NULL) {
@@ -320,6 +323,8 @@ PE_NAME opt_pmu_config
parse_events_terms__delete(terms);
}
}
+ if ($1 != pattern)
+ free(pattern);

if (!ok)
CLEANUP_YYABORT;
--
2.24.1

2020-04-16 22:25:24

by Jiri Olsa

Subject: Re: [PATCH v1] perf parse: Avoid false uncore matches

On Thu, Apr 16, 2020 at 09:21:19AM -0700, Andi Kleen wrote:

SNIP

> ---
> tools/perf/util/parse-events.y | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/parse-events.y b/tools/perf/util/parse-events.y
> index 94f8bcd83582..f38c90756476 100644
> --- a/tools/perf/util/parse-events.y
> +++ b/tools/perf/util/parse-events.y
> @@ -286,7 +286,8 @@ PE_NAME opt_pmu_config
> parse_events_terms__delete(orig_terms); \
> free(list); \
> free($1); \
> - free(pattern); \
> + if ($1 != pattern) \
> + free(pattern); \
> YYABORT; \
> } while(0)
>
> @@ -303,7 +304,9 @@ PE_NAME opt_pmu_config
> struct perf_pmu *pmu = NULL;
> int ok = 0;
>
> - if (asprintf(&pattern, "%s*", $1) < 0)
> + if ($1[0] && isdigit($1[strlen($1) - 1]))
> + pattern = $1;
> + else if (asprintf(&pattern, "%s*", $1) < 0)
> CLEANUP_YYABORT;
>
> while ((pmu = perf_pmu__scan(pmu)) != NULL) {
> @@ -320,6 +323,8 @@ PE_NAME opt_pmu_config
> parse_events_terms__delete(terms);
> }
> }
> + if ($1 != pattern)
> + free(pattern);

good catch

Acked-by: Jiri Olsa <[email protected]>

thanks,
jirka