perf callchain: Fix stitch LBR memory leaks

The 'struct callchain_cursor_node' has a 'struct map_symbol' whose maps
and map members are reference counted. Ensure these values use a _get
routine to increment the reference counts and use map_symbol__exit() to
release the reference counts.

Do similar for 'struct thread's prev_lbr_cursor, but save the size of
the prev_lbr_cursor array so that it may be iterated.

Ensure that when stitch_nodes are placed on the free list the
map_symbols are exited.

Fix resolve_lbr_callchain_sample() by replacing list_replace_init() to
list_splice_init(), so the whole list is moved and nodes aren't leaked.

A reproduction of the memory leaks is possible with a leak sanitizer
build in the perf report command of:

  ```
  $ perf record -e cycles --call-graph lbr perf test -w thloop
  $ perf report --stitch-lbr
  ```

Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Fixes: ff165628d72644e3 ("perf callchain: Stitch LBR call stack")
Signed-off-by: Ian Rogers <irogers@google.com>
[ Basic tests after applying the patch, repeating the example above ]
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Anne Macedo <retpolanne@posteo.net>
Cc: Changbin Du <changbin.du@huawei.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240808054644.1286065-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index 87c59aa9fe38..0ffdd52d86d7 100644
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -476,6 +476,7 @@ void thread__free_stitch_list(struct thread *thread)
 		return;
 
 	list_for_each_entry_safe(pos, tmp, &lbr_stitch->lists, node) {
+		map_symbol__exit(&pos->cursor.ms);
 		list_del_init(&pos->node);
 		free(pos);
 	}
@@ -485,6 +486,9 @@ void thread__free_stitch_list(struct thread *thread)
 		free(pos);
 	}
 
+	for (unsigned int i = 0 ; i < lbr_stitch->prev_lbr_cursor_size; i++)
+		map_symbol__exit(&lbr_stitch->prev_lbr_cursor[i].ms);
+
 	zfree(&lbr_stitch->prev_lbr_cursor);
 	free(thread__lbr_stitch(thread));
 	thread__set_lbr_stitch(thread, NULL);