linux-kernel - [PATCH v2] perf unwind: Fix map reference counts

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Message-Id: <20230623043107.4077510-1-irogers@google.com>
Date:   Thu, 22 Jun 2023 21:31:07 -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>,
        Ivan Babrou <ivan@...udflare.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] perf unwind: Fix map reference counts

The result of thread__find_map is the map in the passed in
addr_location. Calling addr_location__exit puts that map and so copies
need to do a map__get. Add in the corresponding map__puts.

Signed-off-by: Ian Rogers <irogers@...gle.com>

v2. Add missing map__put when dso is missing.
---
 tools/perf/util/unwind-libunwind-local.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/tools/perf/util/unwind-libunwind-local.c b/tools/perf/util/unwind-libunwind-local.c
index 36bf5100bad2..ebfde537b99b 100644
--- a/tools/perf/util/unwind-libunwind-local.c
+++ b/tools/perf/util/unwind-libunwind-local.c
@@ -419,7 +419,8 @@ static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
 	struct map *ret;
 
 	addr_location__init(&al);
-	ret = thread__find_map(ui->thread, PERF_RECORD_MISC_USER, ip, &al);
+	thread__find_map(ui->thread, PERF_RECORD_MISC_USER, ip, &al);
+	ret = map__get(al.map);
 	addr_location__exit(&al);
 	return ret;
 }
@@ -440,8 +441,10 @@ find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
 		return -EINVAL;
 
 	dso = map__dso(map);
-	if (!dso)
+	if (!dso) {
+		map__put(map);
 		return -EINVAL;
+	}
 
 	pr_debug("unwind: find_proc_info dso %s\n", dso->name);
 
@@ -476,11 +479,11 @@ find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
 
 		memset(&di, 0, sizeof(di));
 		if (dwarf_find_debug_frame(0, &di, ip, base, symfile, start, map__end(map)))
-			return dwarf_search_unwind_table(as, ip, &di, pi,
-							 need_unwind_info, arg);
+			ret = dwarf_search_unwind_table(as, ip, &di, pi,
+							need_unwind_info, arg);
 	}
 #endif
-
+	map__put(map);
 	return ret;
 }
 
@@ -534,12 +537,14 @@ static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
 
 	dso = map__dso(map);
 
-	if (!dso)
+	if (!dso) {
+		map__put(map);
 		return -1;
+	}
 
 	size = dso__data_read_addr(dso, map, ui->machine,
 				   addr, (u8 *) data, sizeof(*data));
-
+	map__put(map);
 	return !(size == sizeof(*data));
 }
 
-- 
2.41.0.162.gfafddb0af9-goog