perf dso: Move build_id to dso_id

The dso_id previously contained the major, minor, inode and inode
generation information from a mmap2 event - the inode generation would
be zero when reading from /proc/pid/maps. The build_id was in the
dso. With build ID mmap2 events these fields wouldn't be initialized
which would largely mean the special empty case where any dso would
match for equality. This isn't desirable as if a dso is replaced we
want the comparison to yield a difference.

To support detecting the difference between DSOs based on build_id,
move the build_id out of the DSO and into the dso_id. The dso_id is
also stored in the DSO so nothing is lost. Capture in the dso_id what
parts have been initialized and rename dso_id__inject to
dso_id__improve_id so that it is clear the dso_id is being improved
upon with additional information. With the build_id in the dso_id, use
memcmp to compare for equality.

Signed-off-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250724163302.596743-7-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

1 files changed, 6 insertions, 7 deletions

diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index 0f6b185f9589..b46c68c24d1c 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -120,8 +120,8 @@ static void map__init(struct map *map, u64 start, u64 end, u64 pgoff,
 }
 
 struct map *map__new(struct machine *machine, u64 start, u64 len,
-		     u64 pgoff, struct dso_id *id,
-		     u32 prot, u32 flags, struct build_id *bid,
+		     u64 pgoff, const struct dso_id *id,
+		     u32 prot, u32 flags,
 		     char *filename, struct thread *thread)
 {
 	struct map *result;
@@ -132,7 +132,7 @@ struct map *map__new(struct machine *machine, u64 start, u64 len,
 	map = zalloc(sizeof(*map));
 	if (ADD_RC_CHK(result, map)) {
 		char newfilename[PATH_MAX];
-		struct dso *dso, *header_bid_dso;
+		struct dso *dso;
 		int anon, no_dso, vdso, android;
 
 		android = is_android_lib(filename);
@@ -189,16 +189,15 @@ struct map *map__new(struct machine *machine, u64 start, u64 len,
 		dso__set_nsinfo(dso, nsi);
 		mutex_unlock(dso__lock(dso));
 
-		if (build_id__is_defined(bid)) {
-			dso__set_build_id(dso, bid);
-		} else {
+		if (!build_id__is_defined(&id->build_id)) {
 			/*
 			 * If the mmap event had no build ID, search for an existing dso from the
 			 * build ID header by name. Otherwise only the dso loaded at the time of
 			 * reading the header will have the build ID set and all future mmaps will
 			 * have it missing.
 			 */
-			header_bid_dso = dsos__find(&machine->dsos, filename, false);
+			struct dso *header_bid_dso = dsos__find(&machine->dsos, filename, false);
+
 			if (header_bid_dso && dso__header_build_id(header_bid_dso)) {
 				dso__set_build_id(dso, dso__bid(header_bid_dso));
 				dso__set_header_build_id(dso, 1);