perf map: Move map list node into symbol

Using a perf map as a list node is only done in symbol. Move the
list_node struct into symbol as a single pointer to the map. This makes
reference count behavior more obvious and easy to check.

Committer notes:

Some changes to reduce the number of lines touched by keeping, for
instance, the 'new_map' variable and setting it to new_node->map, so
that we keep more of the project history in place and keep as much
as possible the value of the 'git blame' tool.

Also use map__zput() when putting a struct members, so that when we free
the container struct we can get use-after-free errors as NULL pointer
derefs sometimes.
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Bayduraev <alexey.v.bayduraev@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Darren Hart <dvhart@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: German Gomez <german.gomez@arm.com>
Cc: Hao Luo <haoluo@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Miaoqian Lin <linmq006@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Riccardo Mancini <rickyman7@gmail.com>
Cc: Shunsuke Nakamura <nakamura.shun@fujitsu.com>
Cc: Song Liu <song@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Brennan <stephen.s.brennan@oracle.com>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Yury Norov <yury.norov@gmail.com>
Link: https://lore.kernel.org/r/20230320212248.1175731-2-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/map.h

@@ -16,10 +16,7 @@ struct maps;
 struct machine;
 
 struct map {
-	union {
-		struct rb_node	rb_node;
-		struct list_head node;
-	};
+	struct rb_node		rb_node;
 	u64			start;
 	u64			end;
 	bool			erange_warned:1;

tools/perf/util/symbol.c

@@ -48,6 +48,11 @@ static bool symbol__is_idle(const char *name);
 int vmlinux_path__nr_entries;
 char **vmlinux_path;
 
+struct map_list_node {
+	struct list_head node;
+	struct map *map;
+};
+
 struct symbol_conf symbol_conf = {
 	.nanosecs		= false,
 	.use_modules		= true,
@@ -85,6 +90,11 @@ static enum dso_binary_type binary_type_symtab[] = {
 
 #define DSO_BINARY_TYPE__SYMTAB_CNT ARRAY_SIZE(binary_type_symtab)
 
+static struct map_list_node *map_list_node__new(void)
+{
+	return malloc(sizeof(struct map_list_node));
+}
+
 static bool symbol_type__filter(char symbol_type)
 {
 	symbol_type = toupper(symbol_type);
@@ -1219,16 +1229,21 @@ struct kcore_mapfn_data {
 static int kcore_mapfn(u64 start, u64 len, u64 pgoff, void *data)
 {
 	struct kcore_mapfn_data *md = data;
-	struct map *map;
+	struct map_list_node *list_node = map_list_node__new();
 
-	map = map__new2(start, md->dso);
-	if (map == NULL)
+	if (!list_node)
 		return -ENOMEM;
 
-	map->end = map->start + len;
-	map->pgoff = pgoff;
+	list_node->map = map__new2(start, md->dso);
+	if (!list_node->map) {
+		free(list_node);
+		return -ENOMEM;
+	}
 
-	list_add(&map->node, &md->maps);
+	list_node->map->end = list_node->map->start + len;
+	list_node->map->pgoff = pgoff;
+
+	list_add(&list_node->node, &md->maps);
 
 	return 0;
 }
@@ -1264,12 +1279,18 @@ int maps__merge_in(struct maps *kmaps, struct map *new_map)
 				 * |new.............| -> |new..|       |new..|
 				 *       |old....|    ->       |old....|
 				 */
-				struct map *m = map__clone(new_map);
+				struct map_list_node *m = map_list_node__new();
 
 				if (!m)
 					return -ENOMEM;
 
-				m->end = old_map->start;
+				m->map = map__clone(new_map);
+				if (!m->map) {
+					free(m);
+					return -ENOMEM;
+				}
+
+				m->map->end = old_map->start;
 				list_add_tail(&m->node, &merged);
 				new_map->pgoff += old_map->end - new_map->start;
 				new_map->start = old_map->end;
@@ -1299,10 +1320,13 @@ int maps__merge_in(struct maps *kmaps, struct map *new_map)
 	}
 
 	while (!list_empty(&merged)) {
-		old_map = list_entry(merged.next, struct map, node);
-		list_del_init(&old_map->node);
-		maps__insert(kmaps, old_map);
-		map__put(old_map);
+		struct map_list_node *old_node;
+
+		old_node = list_entry(merged.next, struct map_list_node, node);
+		list_del_init(&old_node->node);
+		maps__insert(kmaps, old_node->map);
+		map__put(old_node->map);
+		free(old_node);
 	}
 
 	if (new_map) {
@@ -1317,7 +1341,7 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
 {
 	struct maps *kmaps = map__kmaps(map);
 	struct kcore_mapfn_data md;
-	struct map *old_map, *new_map, *replacement_map = NULL, *next;
+	struct map *old_map, *replacement_map = NULL, *next;
 	struct machine *machine;
 	bool is_64_bit;
 	int err, fd;
@@ -1378,8 +1402,10 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
 	/* Find the kernel map using the '_stext' symbol */
 	if (!kallsyms__get_function_start(kallsyms_filename, "_stext", &stext)) {
 		u64 replacement_size = 0;
+		struct map_list_node *new_node;
 
-		list_for_each_entry(new_map, &md.maps, node) {
+		list_for_each_entry(new_node, &md.maps, node) {
+			struct map *new_map = new_node->map;
 			u64 new_size = new_map->end - new_map->start;
 
 			if (!(stext >= new_map->start && stext < new_map->end))
@@ -1399,12 +1425,15 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
 	}
 
 	if (!replacement_map)
-		replacement_map = list_entry(md.maps.next, struct map, node);
+		replacement_map = list_entry(md.maps.next, struct map_list_node, node)->map;
 
 	/* Add new maps */
 	while (!list_empty(&md.maps)) {
-		new_map = list_entry(md.maps.next, struct map, node);
-		list_del_init(&new_map->node);
+		struct map_list_node *new_node = list_entry(md.maps.next, struct map_list_node, node);
+		struct map *new_map = new_node->map;
+
+		list_del_init(&new_node->node);
+
 		if (new_map == replacement_map) {
 			map->start	= new_map->start;
 			map->end	= new_map->end;
@@ -1426,6 +1455,7 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
 			if (maps__merge_in(kmaps, new_map))
 				goto out_err;
 		}
+		free(new_node);
 	}
 
 	if (machine__is(machine, "x86_64")) {
@@ -1462,9 +1492,12 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
 
 out_err:
 	while (!list_empty(&md.maps)) {
-		map = list_entry(md.maps.next, struct map, node);
-		list_del_init(&map->node);
-		map__put(map);
+		struct map_list_node *list_node;
+
+		list_node = list_entry(md.maps.next, struct map_list_node, node);
+		list_del_init(&list_node->node);
+		map__zput(list_node->map);
+		free(list_node);
 	}
 	close(fd);
 	return -EINVAL;