[PATCH 4/6] perf maps: Fixup maps_by_name when modifying maps_by_address

Arnaldo Carvalho de Melo
2025-02-28T21:17:57Z

From: Namhyung Kim <namhyung@kernel.org>

We can't just replacing the map in the maps_by_address and not touching
on the maps_by_name, that would leave the refcount as 1 and thus trip
another consistency check, this one:

perf: util/maps.c:110: check_invariants:
Assertion `refcount_read(map__refcnt(map)) > 1' failed.

106 /*
107 * Maps by name maps should be in maps_by_address, so
108 * the reference count should be higher.
109 */
110 assert(refcount_read(map__refcnt(map)) > 1);

Committer notice:

Initialize the newly added 'ni' variable, that really can't be
accessed unitialized trips some gcc versions, like:

12 20.00 archlinux:base : FAIL gcc version 13.2.1 20230801 (GCC)
util/maps.c: In function ‘__maps__fixup_overlap_and_insert’:
util/maps.c:896:54: error: ‘ni’ may be used uninitialized [-Werror=maybe-uninitialized]
896 | map__put(maps_by_name[ni]);
| ^
util/maps.c:816:25: note: ‘ni’ was declared here
816 | unsigned int i, ni;
| ^~
cc1: all warnings being treated as errors
make[3]: *** [/git/perf-6.14.0-rc1/tools/build/Makefile.build:138: util] Error 2

Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/lkml/Z79std66tPq-nqsD@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/maps.c | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/maps.c b/tools/perf/util/maps.c
index 8c5f5d79cd24a6bc..77df9701d5ad7de3 100644
--- a/tools/perf/util/maps.c
+++ b/tools/perf/util/maps.c
@@ -813,7 +813,7 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
{
int err = 0;
FILE *fp = debug_file();
- unsigned int i;
+ unsigned int i, ni = INT_MAX; // Some gcc complain, but depends on maps_by_name...

if (!maps__maps_by_address_sorted(maps))
__maps__sort_by_address(maps);
@@ -824,6 +824,7 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
*/
for (i = first_ending_after(maps, new); i < maps__nr_maps(maps); ) {
struct map **maps_by_address = maps__maps_by_address(maps);
+ struct map **maps_by_name = maps__maps_by_name(maps);
struct map *pos = maps_by_address[i];
struct map *before = NULL, *after = NULL;

@@ -843,6 +844,9 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
map__fprintf(pos, fp);
}

+ if (maps_by_name)
+ ni = maps__by_name_index(maps, pos);
+
/*
* Now check if we need to create new maps for areas not
* overlapped by the new map:
@@ -887,6 +891,12 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
if (before) {
map__put(maps_by_address[i]);
maps_by_address[i] = before;
+
+ if (maps_by_name) {
+ map__put(maps_by_name[ni]);
+ maps_by_name[ni] = map__get(before);
+ }
+
/* Maps are still ordered, go to next one. */
i++;
if (after) {
@@ -908,6 +918,12 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
*/
map__put(maps_by_address[i]);
maps_by_address[i] = map__get(new);
+
+ if (maps_by_name) {
+ map__put(maps_by_name[ni]);
+ maps_by_name[ni] = map__get(new);
+ }
+
err = __maps__insert_sorted(maps, i + 1, after, NULL);
map__put(after);
check_invariants(maps);
@@ -926,6 +942,12 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
*/
map__put(maps_by_address[i]);
maps_by_address[i] = map__get(new);
+
+ if (maps_by_name) {
+ map__put(maps_by_name[ni]);
+ maps_by_name[ni] = map__get(new);
+ }
+
check_invariants(maps);
return err;
}
--
2.48.1