linux-kernel - [PATCH v1] perf parse: Avoid false uncore matches

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Message-Id: <20200416162119.619956-1-andi@firstfloor.org>
Date:   Thu, 16 Apr 2020 09:21:19 -0700
From:   Andi Kleen <andi@...stfloor.org>
To:     acme@...nel.org
Cc:     jolsa@...nel.org, linux-kernel@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH v1] perf parse: Avoid false uncore matches

From: Andi Kleen <ak@...ux.intel.com>

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 <ak@...ux.intel.com>
---
 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