linux-kernel - [PATCH v1] perf parse-events: Avoid string for PE_BP_COLON, PE_BP

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Date:   Tue, 13 Jun 2023 11:26:29 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     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>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Rob Herring <robh@...nel.org>,
        Kan Liang <kan.liang@...ux.intel.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1] perf parse-events: Avoid string for PE_BP_COLON, PE_BP_SLASH

There's no need to read the string ':' or '/' for PE_BP_COLON or
PE_BP_SLASH and doing so causes parse-events.y to leak memory.

The original patch has a committer note about not using these tokens
presumably as yacc spotted they were a memory leak because no
%destructor could be run. Remove the unused token workaround as there
is now no value associated with these tokens.

Fixes: f0617f526cb0 ("perf parse: Allow config terms with breakpoints")
Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/parse-events.h | 4 ----
 tools/perf/util/parse-events.l | 4 ++--
 tools/perf/util/parse-events.y | 9 ---------
 3 files changed, 2 insertions(+), 15 deletions(-)

diff --git a/tools/perf/util/parse-events.h b/tools/perf/util/parse-events.h
index 5fdc1f33f57e..b0eb95f93e9c 100644
--- a/tools/perf/util/parse-events.h
+++ b/tools/perf/util/parse-events.h
@@ -228,10 +228,6 @@ void parse_events_error__handle(struct parse_events_error *err, int idx,
 void parse_events_error__print(struct parse_events_error *err,
 			       const char *event);
 
-static inline void parse_events_unused_value(const void *x __maybe_unused)
-{
-}
-
 #ifdef HAVE_LIBELF_SUPPORT
 /*
  * If the probe point starts with '%',
diff --git a/tools/perf/util/parse-events.l b/tools/perf/util/parse-events.l
index 7629af3d5c7c..99335ec586ae 100644
--- a/tools/perf/util/parse-events.l
+++ b/tools/perf/util/parse-events.l
@@ -315,13 +315,13 @@ r0x{num_raw_hex}	{ return str(yyscanner, PE_RAW); }
 	 * are the same, so trailing context can be used disambiguate the two
 	 * cases.
 	 */
-":"/{modifier_bp}	{ return str(yyscanner, PE_BP_COLON); }
+":"/{modifier_bp}	{ return PE_BP_COLON; }
 	/*
 	 * The slash before memory length can get mixed up with the slash before
 	 * config terms. Fortunately config terms do not start with a numeric
 	 * digit, so trailing context can be used disambiguate the two cases.
 	 */
-"/"/{digit}		{ return str(yyscanner, PE_BP_SLASH); }
+"/"/{digit}		{ return PE_BP_SLASH; }
 "/"/{non_digit}		{ BEGIN(config); return '/'; }
 {num_dec}		{ return value(yyscanner, 10); }
 {num_hex}		{ return value(yyscanner, 16); }
diff --git a/tools/perf/util/parse-events.y b/tools/perf/util/parse-events.y
index 0c3d086cc22a..9f28d4b5502f 100644
--- a/tools/perf/util/parse-events.y
+++ b/tools/perf/util/parse-events.y
@@ -80,8 +80,6 @@ static void free_list_evsel(struct list_head* list_evsel)
 %type <str> PE_LEGACY_CACHE
 %type <str> PE_MODIFIER_EVENT
 %type <str> PE_MODIFIER_BP
-%type <str> PE_BP_COLON
-%type <str> PE_BP_SLASH
 %type <str> PE_EVENT_NAME
 %type <str> PE_KERNEL_PMU_EVENT PE_PMU_EVENT_FAKE
 %type <str> PE_DRV_CFG_TERM
@@ -510,9 +508,6 @@ PE_PREFIX_MEM PE_VALUE PE_BP_SLASH PE_VALUE PE_BP_COLON PE_MODIFIER_BP opt_event
 	struct list_head *list;
 	int err;
 
-	parse_events_unused_value(&$3);
-	parse_events_unused_value(&$5);
-
 	list = alloc_list();
 	ABORT_ON(!list);
 	err = parse_events_add_breakpoint(_parse_state, list,
@@ -531,8 +526,6 @@ PE_PREFIX_MEM PE_VALUE PE_BP_SLASH PE_VALUE opt_event_config
 	struct list_head *list;
 	int err;
 
-	parse_events_unused_value(&$3);
-
 	list = alloc_list();
 	ABORT_ON(!list);
 	err = parse_events_add_breakpoint(_parse_state, list,
@@ -550,8 +543,6 @@ PE_PREFIX_MEM PE_VALUE PE_BP_COLON PE_MODIFIER_BP opt_event_config
 	struct list_head *list;
 	int err;
 
-	parse_events_unused_value(&$3);
-
 	list = alloc_list();
 	ABORT_ON(!list);
 	err = parse_events_add_breakpoint(_parse_state, list,
-- 
2.41.0.162.gfafddb0af9-goog