perf symbols: Update kcore map before merging in remaining symbols

When loading kcore, the main vmlinux map is updated in the same loop
that merges the remaining maps. If a map that overlaps is merged in
before kcore, the list can become unsortable when the main map addresses
are updated. This will later trigger the check_invariants() assert:

  $ perf record
  $ perf report

  util/maps.c:96: check_invariants: Assertion `map__end(prev) <=
    map__start(map) || map__start(prev) == map__start(map)' failed.
  Aborted

Fix it by moving the main map update prior to the loop so that
maps__merge_in() can split it if necessary.

Fixes: 659ad3492b913c90 ("perf maps: Switch from rbtree to lazily sorted array for addresses")
Signed-off-by: James Clark <james.clark@arm.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Ian Rogers <irogers@google.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/20240507141210.195939-4-james.clark@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 0d4de786358d394f51e5db6d2eabab0f5ab91244..f21fe5772bd870f91cc06025cb3187bc5ed2982e 100644 (file)
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1290,7 +1290,7 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
 {
        struct maps *kmaps = map__kmaps(map);
        struct kcore_mapfn_data md;
-       struct map *replacement_map = NULL;
+       struct map *map_ref, *replacement_map = NULL;
        struct machine *machine;
        bool is_64_bit;
        int err, fd;
@@ -1368,6 +1368,24 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
        if (!replacement_map)
                replacement_map = list_entry(md.maps.next, struct map_list_node, node)->map;
 
+       /*
+        * Update addresses of vmlinux map. Re-insert it to ensure maps are
+        * correctly ordered. Do this before using maps__merge_in() for the
+        * remaining maps so vmlinux gets split if necessary.
+        */
+       map_ref = map__get(map);
+       maps__remove(kmaps, map_ref);
+
+       map__set_start(map_ref, map__start(replacement_map));
+       map__set_end(map_ref, map__end(replacement_map));
+       map__set_pgoff(map_ref, map__pgoff(replacement_map));
+       map__set_mapping_type(map_ref, map__mapping_type(replacement_map));
+
+       err = maps__insert(kmaps, map_ref);
+       map__put(map_ref);
+       if (err)
+               goto out_err;
+
        /* Add new maps */
        while (!list_empty(&md.maps)) {
                struct map_list_node *new_node = list_entry(md.maps.next, struct map_list_node, node);
@@ -1375,24 +1393,8 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
 
                list_del_init(&new_node->node);
 
-               if (RC_CHK_EQUAL(new_map, replacement_map)) {
-                       struct map *map_ref;
-
-                       /* Ensure maps are correctly ordered */
-                       map_ref = map__get(map);
-                       maps__remove(kmaps, map_ref);
-
-                       map__set_start(map_ref, map__start(new_map));
-                       map__set_end(map_ref, map__end(new_map));
-                       map__set_pgoff(map_ref, map__pgoff(new_map));
-                       map__set_mapping_type(map_ref, map__mapping_type(new_map));
-
-                       err = maps__insert(kmaps, map_ref);
-                       map__put(map_ref);
-                       map__put(new_map);
-                       if (err)
-                               goto out_err;
-               } else {
+               /* skip if replacement_map, already inserted above */
+               if (!RC_CHK_EQUAL(new_map, replacement_map)) {
                        /*
                         * Merge kcore map into existing maps,
                         * and ensure that current maps (eBPF)