[PATCH v1 0/5] perf: Default use of build IDs and improvements

[PATCH v1 0/5] perf: Default use of build IDs and improvements

[Ian Rogers]

Build ID mmap2 events have been available since Linux v5.12 and avoid
post-processing the perf.data file to inject build IDs for DSOs
referenced by samples. Enable these by default as discussed in:
https://lore.kernel.org/linux-perf-users/CAP-5=fXP7jN_QrGUcd55_QH5J-Y-FCaJ6=NaHVtyx0oyNh8_-Q@mail.gmail.com/

The dso_id is used to indentify a DSO that may change by being
overwritten. The inode generation isn't present in /proc/pid/maps and
so was already only optionally filled in. With build ID mmap events
the other major, minor and inode varialbes aren't filled in. Change
the dso_id implementation to make optional values explicit, rather
than injecting a dso_id we want to improve it during find operations,
add the buildid to the dso_id for sorting and so that matching fails
when build IDs vary between DSOs.

Other minor bits of build_id clean up.

Ian Rogers (5):
  perf build-id: Reduce size of "size" variable
  perf build-id: Truncate to avoid overflowing the build_id data
  perf build-id: Change sprintf functions to snprintf
  perf dso: Move build_id to dso_id
  perf record: Make --buildid-mmap the default

 tools/perf/builtin-buildid-cache.c            |  12 +-
 tools/perf/builtin-buildid-list.c             |   6 +-
 tools/perf/builtin-inject.c                   |  32 ++---
 tools/perf/builtin-record.c                   |  35 ++++--
 tools/perf/builtin-report.c                   |  11 +-
 tools/perf/include/perf/perf_dlfilter.h       |   2 +-
 tools/perf/tests/symbols.c                    |   4 +-
 tools/perf/util/build-id.c                    |  40 +++----
 tools/perf/util/build-id.h                    |   8 +-
 tools/perf/util/disasm.c                      |   2 +-
 tools/perf/util/dso.c                         | 111 ++++++++++--------
 tools/perf/util/dso.h                         |  75 ++++++------
 tools/perf/util/dsos.c                        |  20 ++--
 tools/perf/util/event.c                       |   2 +-
 tools/perf/util/header.c                      |   2 +-
 tools/perf/util/machine.c                     |  28 ++---
 tools/perf/util/map.c                         |  15 ++-
 tools/perf/util/map.h                         |   5 +-
 tools/perf/util/probe-file.c                  |   4 +-
 .../scripting-engines/trace-event-python.c    |   7 +-
 tools/perf/util/sort.c                        |  27 +++--
 tools/perf/util/symbol.c                      |   2 +-
 tools/perf/util/symbol_conf.h                 |   2 +-
 tools/perf/util/synthetic-events.c            |  42 ++++---
 24 files changed, 271 insertions(+), 223 deletions(-)

-- 
2.49.0.805.g082f7c87e0-goog

[PATCH v1 1/5] perf build-id: Reduce size of "size" variable

[Ian Rogers]

Later clean up of the dso_id to include a build_id will suffer from
alignment and size issues. The size can only hold up to a value of
BUILD_ID_SIZE (20) and the mmap2 event uses a byte for the value.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/build-id.h         | 2 +-
 tools/perf/util/synthetic-events.c | 8 ++++++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/build-id.h b/tools/perf/util/build-id.h
index a212497bfdb0..e3e0a446ff0c 100644
--- a/tools/perf/util/build-id.h
+++ b/tools/perf/util/build-id.h
@@ -13,7 +13,7 @@
 
 struct build_id {
 	u8	data[BUILD_ID_SIZE];
-	size_t	size;
+	u8	size;
 };
 
 struct dso;
diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
index 2fc4d0537840..68bb7c5fe1b1 100644
--- a/tools/perf/util/synthetic-events.c
+++ b/tools/perf/util/synthetic-events.c
@@ -2248,7 +2248,9 @@ int perf_event__synthesize_build_id(const struct perf_tool *tool,
 
 	memset(&ev, 0, len);
 
-	ev.build_id.size = min(bid->size, sizeof(ev.build_id.build_id));
+	ev.build_id.size = bid->size;
+	if (ev.build_id.size > sizeof(ev.build_id.build_id))
+		ev.build_id.size = sizeof(ev.build_id.build_id);
 	memcpy(ev.build_id.build_id, bid->data, ev.build_id.size);
 	ev.build_id.header.type = PERF_RECORD_HEADER_BUILD_ID;
 	ev.build_id.header.misc = misc | PERF_RECORD_MISC_BUILD_ID_SIZE;
@@ -2308,7 +2310,9 @@ int perf_event__synthesize_mmap2_build_id(const struct perf_tool *tool,
 	ev.mmap2.len = len;
 	ev.mmap2.pgoff = pgoff;
 
-	ev.mmap2.build_id_size = min(bid->size, sizeof(ev.mmap2.build_id));
+	ev.mmap2.build_id_size = bid->size;
+	if (ev.mmap2.build_id_size > sizeof(ev.mmap2.build_id))
+		ev.build_id.size = sizeof(ev.mmap2.build_id);
 	memcpy(ev.mmap2.build_id, bid->data, ev.mmap2.build_id_size);
 
 	ev.mmap2.prot = prot;
-- 
2.49.0.805.g082f7c87e0-goog

[PATCH v1 2/5] perf build-id: Truncate to avoid overflowing the build_id data

[Ian Rogers]

Warning when the build_id data would be overflowed would lead to
memory corruption, switch to truncation.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/build-id.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index e763e8d99a43..5bc2040bdd0d 100644
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -951,7 +951,10 @@ bool perf_session__read_build_ids(struct perf_session *session, bool with_hits)
 
 void build_id__init(struct build_id *bid, const u8 *data, size_t size)
 {
-	WARN_ON(size > BUILD_ID_SIZE);
+	if (size > BUILD_ID_SIZE) {
+		pr_debug("Truncating build_id size from %zd\n", size);
+		size = BUILD_ID_SIZE;
+	}
 	memcpy(bid->data, data, size);
 	bid->size = size;
 }
-- 
2.49.0.805.g082f7c87e0-goog

[PATCH v1 3/5] perf build-id: Change sprintf functions to snprintf

[Ian Rogers]

Pass in a size argument rather than implying all build id strings must
be SBUILD_ID_SIZE.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/builtin-buildid-cache.c            | 12 +++----
 tools/perf/builtin-buildid-list.c             |  6 ++--
 tools/perf/util/build-id.c                    | 33 ++++++++-----------
 tools/perf/util/build-id.h                    |  6 ++--
 tools/perf/util/disasm.c                      |  2 +-
 tools/perf/util/dso.c                         |  4 +--
 tools/perf/util/dsos.c                        |  2 +-
 tools/perf/util/event.c                       |  2 +-
 tools/perf/util/header.c                      |  2 +-
 tools/perf/util/map.c                         |  2 +-
 tools/perf/util/probe-file.c                  |  4 +--
 .../scripting-engines/trace-event-python.c    |  7 ++--
 tools/perf/util/symbol.c                      |  2 +-
 13 files changed, 38 insertions(+), 46 deletions(-)

diff --git a/tools/perf/builtin-buildid-cache.c b/tools/perf/builtin-buildid-cache.c
index b0511d16aeb6..3f7739b21148 100644
--- a/tools/perf/builtin-buildid-cache.c
+++ b/tools/perf/builtin-buildid-cache.c
@@ -31,7 +31,7 @@
 #include <linux/string.h>
 #include <linux/err.h>
 
-static int build_id_cache__kcore_buildid(const char *proc_dir, char *sbuildid)
+static int build_id_cache__kcore_buildid(const char *proc_dir, char *sbuildid, size_t sbuildid_size)
 {
 	char root_dir[PATH_MAX];
 	char *p;
@@ -42,7 +42,7 @@ static int build_id_cache__kcore_buildid(const char *proc_dir, char *sbuildid)
 	if (!p)
 		return -1;
 	*p = '\0';
-	return sysfs__sprintf_build_id(root_dir, sbuildid);
+	return sysfs__snprintf_build_id(root_dir, sbuildid, sbuildid_size);
 }
 
 static int build_id_cache__kcore_dir(char *dir, size_t sz)
@@ -128,7 +128,7 @@ static int build_id_cache__add_kcore(const char *filename, bool force)
 		return -1;
 	*p = '\0';
 
-	if (build_id_cache__kcore_buildid(from_dir, sbuildid) < 0)
+	if (build_id_cache__kcore_buildid(from_dir, sbuildid, sizeof(sbuildid)) < 0)
 		return -1;
 
 	scnprintf(to_dir, sizeof(to_dir), "%s/%s/%s",
@@ -187,7 +187,7 @@ static int build_id_cache__add_file(const char *filename, struct nsinfo *nsi)
 		return -1;
 	}
 
-	build_id__sprintf(&bid, sbuild_id);
+	build_id__snprintf(&bid, sbuild_id, sizeof(sbuild_id));
 	err = build_id_cache__add_s(sbuild_id, filename, nsi,
 				    false, false);
 	pr_debug("Adding %s %s: %s\n", sbuild_id, filename,
@@ -211,7 +211,7 @@ static int build_id_cache__remove_file(const char *filename, struct nsinfo *nsi)
 		return -1;
 	}
 
-	build_id__sprintf(&bid, sbuild_id);
+	build_id__snprintf(&bid, sbuild_id, sizeof(sbuild_id));
 	err = build_id_cache__remove_s(sbuild_id);
 	pr_debug("Removing %s %s: %s\n", sbuild_id, filename,
 		 err ? "FAIL" : "Ok");
@@ -317,7 +317,7 @@ static int build_id_cache__update_file(const char *filename, struct nsinfo *nsi)
 	}
 	err = 0;
 
-	build_id__sprintf(&bid, sbuild_id);
+	build_id__snprintf(&bid, sbuild_id, sizeof(sbuild_id));
 	if (build_id_cache__cached(sbuild_id))
 		err = build_id_cache__remove_s(sbuild_id);
 
diff --git a/tools/perf/builtin-buildid-list.c b/tools/perf/builtin-buildid-list.c
index 52dfacaff8e3..ba8ba0303920 100644
--- a/tools/perf/builtin-buildid-list.c
+++ b/tools/perf/builtin-buildid-list.c
@@ -31,7 +31,7 @@ static int buildid__map_cb(struct map *map, void *arg __maybe_unused)
 
 	memset(bid_buf, 0, sizeof(bid_buf));
 	if (dso__has_build_id(dso))
-		build_id__sprintf(dso__bid_const(dso), bid_buf);
+		build_id__snprintf(dso__bid_const(dso), bid_buf, sizeof(bid_buf));
 	printf("%s %16" PRIx64 " %16" PRIx64, bid_buf, map__start(map), map__end(map));
 	if (dso_long_name != NULL)
 		printf(" %s", dso_long_name);
@@ -57,7 +57,7 @@ static int sysfs__fprintf_build_id(FILE *fp)
 	char sbuild_id[SBUILD_ID_SIZE];
 	int ret;
 
-	ret = sysfs__sprintf_build_id("/", sbuild_id);
+	ret = sysfs__snprintf_build_id("/", sbuild_id, sizeof(sbuild_id));
 	if (ret != sizeof(sbuild_id))
 		return ret < 0 ? ret : -EINVAL;
 
@@ -69,7 +69,7 @@ static int filename__fprintf_build_id(const char *name, FILE *fp)
 	char sbuild_id[SBUILD_ID_SIZE];
 	int ret;
 
-	ret = filename__sprintf_build_id(name, sbuild_id);
+	ret = filename__snprintf_build_id(name, sbuild_id, sizeof(sbuild_id));
 	if (ret != sizeof(sbuild_id))
 		return ret < 0 ? ret : -EINVAL;
 
diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index 5bc2040bdd0d..aa35dceace90 100644
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -67,24 +67,17 @@ int build_id__mark_dso_hit(const struct perf_tool *tool __maybe_unused,
 	return 0;
 }
 
-int build_id__sprintf(const struct build_id *build_id, char *bf)
+int build_id__snprintf(const struct build_id *build_id, char *bf, size_t bf_size)
 {
-	char *bid = bf;
-	const u8 *raw = build_id->data;
-	size_t i;
-
-	bf[0] = 0x0;
+	size_t offs = 0;
 
-	for (i = 0; i < build_id->size; ++i) {
-		sprintf(bid, "%02x", *raw);
-		++raw;
-		bid += 2;
-	}
+	for (size_t i = 0; i < build_id->size && offs < bf_size; ++i)
+		offs += snprintf(bf + offs, bf_size - offs, "%02x", build_id->data[i]);
 
-	return (bid - bf) + 1;
+	return offs;
 }
 
-int sysfs__sprintf_build_id(const char *root_dir, char *sbuild_id)
+int sysfs__snprintf_build_id(const char *root_dir, char *sbuild_id, size_t sbuild_id_size)
 {
 	char notes[PATH_MAX];
 	struct build_id bid;
@@ -99,10 +92,10 @@ int sysfs__sprintf_build_id(const char *root_dir, char *sbuild_id)
 	if (ret < 0)
 		return ret;
 
-	return build_id__sprintf(&bid, sbuild_id);
+	return build_id__snprintf(&bid, sbuild_id, sbuild_id_size);
 }
 
-int filename__sprintf_build_id(const char *pathname, char *sbuild_id)
+int filename__snprintf_build_id(const char *pathname, char *sbuild_id, size_t sbuild_id_size)
 {
 	struct build_id bid;
 	int ret;
@@ -111,7 +104,7 @@ int filename__sprintf_build_id(const char *pathname, char *sbuild_id)
 	if (ret < 0)
 		return ret;
 
-	return build_id__sprintf(&bid, sbuild_id);
+	return build_id__snprintf(&bid, sbuild_id, sbuild_id_size);
 }
 
 /* asnprintf consolidates asprintf and snprintf */
@@ -212,9 +205,9 @@ static bool build_id_cache__valid_id(char *sbuild_id)
 		return false;
 
 	if (!strcmp(pathname, DSO__NAME_KALLSYMS))
-		ret = sysfs__sprintf_build_id("/", real_sbuild_id);
+		ret = sysfs__snprintf_build_id("/", real_sbuild_id, sizeof(real_sbuild_id));
 	else if (pathname[0] == '/')
-		ret = filename__sprintf_build_id(pathname, real_sbuild_id);
+		ret = filename__snprintf_build_id(pathname, real_sbuild_id, sizeof(real_sbuild_id));
 	else
 		ret = -EINVAL;	/* Should we support other special DSO cache? */
 	if (ret >= 0)
@@ -243,7 +236,7 @@ char *__dso__build_id_filename(const struct dso *dso, char *bf, size_t size,
 	if (!dso__has_build_id(dso))
 		return NULL;
 
-	build_id__sprintf(dso__bid_const(dso), sbuild_id);
+	build_id__snprintf(dso__bid_const(dso), sbuild_id, sizeof(sbuild_id));
 	linkname = build_id_cache__linkname(sbuild_id, NULL, 0);
 	if (!linkname)
 		return NULL;
@@ -769,7 +762,7 @@ static int build_id_cache__add_b(const struct build_id *bid,
 {
 	char sbuild_id[SBUILD_ID_SIZE];
 
-	build_id__sprintf(bid, sbuild_id);
+	build_id__snprintf(bid, sbuild_id, sizeof(sbuild_id));
 
 	return __build_id_cache__add_s(sbuild_id, name, nsi, is_kallsyms,
 				       is_vdso, proper_name, root_dir);
diff --git a/tools/perf/util/build-id.h b/tools/perf/util/build-id.h
index e3e0a446ff0c..47e621cebe1b 100644
--- a/tools/perf/util/build-id.h
+++ b/tools/perf/util/build-id.h
@@ -21,10 +21,10 @@ struct feat_fd;
 struct nsinfo;
 
 void build_id__init(struct build_id *bid, const u8 *data, size_t size);
-int build_id__sprintf(const struct build_id *build_id, char *bf);
+int build_id__snprintf(const struct build_id *build_id, char *bf, size_t bf_size);
 bool build_id__is_defined(const struct build_id *bid);
-int sysfs__sprintf_build_id(const char *root_dir, char *sbuild_id);
-int filename__sprintf_build_id(const char *pathname, char *sbuild_id);
+int sysfs__snprintf_build_id(const char *root_dir, char *sbuild_id, size_t sbuild_id_size);
+int filename__snprintf_build_id(const char *pathname, char *sbuild_id, size_t sbuild_id_size);
 char *build_id_cache__kallsyms_path(const char *sbuild_id, char *bf,
 				    size_t size);
 
diff --git a/tools/perf/util/disasm.c b/tools/perf/util/disasm.c
index 8f0eb56c6fc6..96e6a5d6eacc 100644
--- a/tools/perf/util/disasm.c
+++ b/tools/perf/util/disasm.c
@@ -1218,7 +1218,7 @@ int symbol__strerror_disassemble(struct map_symbol *ms, int errnum, char *buf, s
 		char *build_id_msg = NULL;
 
 		if (dso__has_build_id(dso)) {
-			build_id__sprintf(dso__bid(dso), bf + 15);
+			build_id__snprintf(dso__bid(dso), bf + 15, sizeof(bf) - 15);
 			build_id_msg = bf;
 		}
 		scnprintf(buf, buflen,
diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index 8619b6eea62d..776506b93b8b 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -217,7 +217,7 @@ int dso__read_binary_type_filename(const struct dso *dso,
 			break;
 		}
 
-		build_id__sprintf(dso__bid_const(dso), build_id_hex);
+		build_id__snprintf(dso__bid_const(dso), build_id_hex, sizeof(build_id_hex));
 		len = __symbol__join_symfs(filename, size, "/usr/lib/debug/.build-id/");
 		snprintf(filename + len, size - len, "%.2s/%s.debug",
 			 build_id_hex, build_id_hex + 2);
@@ -1697,7 +1697,7 @@ static size_t dso__fprintf_buildid(struct dso *dso, FILE *fp)
 {
 	char sbuild_id[SBUILD_ID_SIZE];
 
-	build_id__sprintf(dso__bid(dso), sbuild_id);
+	build_id__snprintf(dso__bid(dso), sbuild_id, sizeof(sbuild_id));
 	return fprintf(fp, "%s", sbuild_id);
 }
 
diff --git a/tools/perf/util/dsos.c b/tools/perf/util/dsos.c
index e0998e2a7c4e..b2172632b3cd 100644
--- a/tools/perf/util/dsos.c
+++ b/tools/perf/util/dsos.c
@@ -370,7 +370,7 @@ static int dsos__fprintf_buildid_cb(struct dso *dso, void *data)
 
 	if (args->skip && args->skip(dso, args->parm))
 		return 0;
-	build_id__sprintf(dso__bid(dso), sbuild_id);
+	build_id__snprintf(dso__bid(dso), sbuild_id, sizeof(sbuild_id));
 	args->ret += fprintf(args->fp, "%-40s %s\n", sbuild_id, dso__long_name(dso));
 	return 0;
 }
diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index c23b77f8f854..34176050ebac 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -329,7 +329,7 @@ size_t perf_event__fprintf_mmap2(union perf_event *event, FILE *fp)
 
 		build_id__init(&bid, event->mmap2.build_id,
 			       event->mmap2.build_id_size);
-		build_id__sprintf(&bid, sbuild_id);
+		build_id__snprintf(&bid, sbuild_id, sizeof(sbuild_id));
 
 		return fprintf(fp, " %d/%d: [%#" PRI_lx64 "(%#" PRI_lx64 ") @ %#" PRI_lx64
 				   " <%s>]: %c%c%c%c %s\n",
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index e3cdc3b7b4ab..38e903307e8e 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -2291,7 +2291,7 @@ static int __event_process_build_id(struct perf_record_header_build_id *bev,
 			free(m.name);
 		}
 
-		build_id__sprintf(dso__bid(dso), sbuild_id);
+		build_id__snprintf(dso__bid(dso), sbuild_id, sizeof(sbuild_id));
 		pr_debug("build id event received for %s: %s [%zu]\n",
 			 dso__long_name(dso), sbuild_id, size);
 		dso__put(dso);
diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index d729438b7d65..0f6b185f9589 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -354,7 +354,7 @@ int map__load(struct map *map)
 		if (dso__has_build_id(dso)) {
 			char sbuild_id[SBUILD_ID_SIZE];
 
-			build_id__sprintf(dso__bid(dso), sbuild_id);
+			build_id__snprintf(dso__bid(dso), sbuild_id, sizeof(sbuild_id));
 			pr_debug("%s with build id %s not found", name, sbuild_id);
 		} else
 			pr_debug("Failed to open %s", name);
diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
index ec8ac242fedb..5069fb61f48c 100644
--- a/tools/perf/util/probe-file.c
+++ b/tools/perf/util/probe-file.c
@@ -448,10 +448,10 @@ static int probe_cache__open(struct probe_cache *pcache, const char *target,
 	if (!target || !strcmp(target, DSO__NAME_KALLSYMS)) {
 		target = DSO__NAME_KALLSYMS;
 		is_kallsyms = true;
-		ret = sysfs__sprintf_build_id("/", sbuildid);
+		ret = sysfs__snprintf_build_id("/", sbuildid, sizeof(sbuildid));
 	} else {
 		nsinfo__mountns_enter(nsi, &nsc);
-		ret = filename__sprintf_build_id(target, sbuildid);
+		ret = filename__snprintf_build_id(target, sbuildid, sizeof(sbuildid));
 		nsinfo__mountns_exit(&nsc);
 	}
 
diff --git a/tools/perf/util/scripting-engines/trace-event-python.c b/tools/perf/util/scripting-engines/trace-event-python.c
index 520729e78965..68e92552d954 100644
--- a/tools/perf/util/scripting-engines/trace-event-python.c
+++ b/tools/perf/util/scripting-engines/trace-event-python.c
@@ -780,14 +780,13 @@ static void set_sym_in_dict(PyObject *dict, struct addr_location *al,
 			    const char *sym_field, const char *symoff_field,
 			    const char *map_pgoff)
 {
-	char sbuild_id[SBUILD_ID_SIZE];
-
 	if (al->map) {
+		char sbuild_id[SBUILD_ID_SIZE];
 		struct dso *dso = map__dso(al->map);
 
 		pydict_set_item_string_decref(dict, dso_field,
 					      _PyUnicode_FromString(dso__name(dso)));
-		build_id__sprintf(dso__bid(dso), sbuild_id);
+		build_id__snprintf(dso__bid(dso), sbuild_id, sizeof(sbuild_id));
 		pydict_set_item_string_decref(dict, dso_bid_field,
 			_PyUnicode_FromString(sbuild_id));
 		pydict_set_item_string_decref(dict, dso_map_start,
@@ -1238,7 +1237,7 @@ static int python_export_dso(struct db_export *dbe, struct dso *dso,
 	char sbuild_id[SBUILD_ID_SIZE];
 	PyObject *t;
 
-	build_id__sprintf(dso__bid(dso), sbuild_id);
+	build_id__snprintf(dso__bid(dso), sbuild_id, sizeof(sbuild_id));
 
 	t = tuple_new(5);
 
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 11540219481b..30750ed313ca 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -2143,7 +2143,7 @@ static char *dso__find_kallsyms(struct dso *dso, struct map *map)
 			goto proc_kallsyms;
 	}
 
-	build_id__sprintf(dso__bid(dso), sbuild_id);
+	build_id__snprintf(dso__bid(dso), sbuild_id, sizeof(sbuild_id));
 
 	/* Find kallsyms in build-id cache with kcore */
 	scnprintf(path, sizeof(path), "%s/%s/%s",
-- 
2.49.0.805.g082f7c87e0-goog

[PATCH v1 4/5] perf dso: Move build_id to dso_id

[Ian Rogers]

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>
---
 tools/perf/builtin-buildid-list.c       |   2 +-
 tools/perf/builtin-inject.c             |  32 ++++---
 tools/perf/builtin-report.c             |  11 ++-
 tools/perf/include/perf/perf_dlfilter.h |   2 +-
 tools/perf/tests/symbols.c              |   4 +-
 tools/perf/util/build-id.c              |   4 +-
 tools/perf/util/dso.c                   | 109 +++++++++++++-----------
 tools/perf/util/dso.h                   |  75 ++++++++--------
 tools/perf/util/dsos.c                  |  18 ++--
 tools/perf/util/machine.c               |  28 +++---
 tools/perf/util/map.c                   |  13 ++-
 tools/perf/util/map.h                   |   5 +-
 tools/perf/util/sort.c                  |  27 +++---
 tools/perf/util/synthetic-events.c      |  18 ++--
 14 files changed, 194 insertions(+), 154 deletions(-)

diff --git a/tools/perf/builtin-buildid-list.c b/tools/perf/builtin-buildid-list.c
index ba8ba0303920..151cd84b6dfe 100644
--- a/tools/perf/builtin-buildid-list.c
+++ b/tools/perf/builtin-buildid-list.c
@@ -31,7 +31,7 @@ static int buildid__map_cb(struct map *map, void *arg __maybe_unused)
 
 	memset(bid_buf, 0, sizeof(bid_buf));
 	if (dso__has_build_id(dso))
-		build_id__snprintf(dso__bid_const(dso), bid_buf, sizeof(bid_buf));
+		build_id__snprintf(dso__bid(dso), bid_buf, sizeof(bid_buf));
 	printf("%s %16" PRIx64 " %16" PRIx64, bid_buf, map__start(map), map__end(map));
 	if (dso_long_name != NULL)
 		printf(" %s", dso_long_name);
diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
index 11e49cafa3af..e74a3a70ff6f 100644
--- a/tools/perf/builtin-inject.c
+++ b/tools/perf/builtin-inject.c
@@ -587,15 +587,17 @@ static int perf_event__repipe_mmap2(const struct perf_tool *tool,
 				struct perf_sample *sample,
 				struct machine *machine)
 {
-	struct dso_id id;
-	struct dso_id *dso_id = NULL;
+	struct dso_id id = dso_id_empty;
 
-	if (!(event->header.misc & PERF_RECORD_MISC_MMAP_BUILD_ID)) {
+	if (event->header.misc & PERF_RECORD_MISC_MMAP_BUILD_ID) {
+		build_id__init(&id.build_id, event->mmap2.build_id, event->mmap2.build_id_size);
+	} else {
 		id.maj = event->mmap2.maj;
 		id.min = event->mmap2.min;
 		id.ino = event->mmap2.ino;
 		id.ino_generation = event->mmap2.ino_generation;
-		dso_id = &id;
+		id.mmap2_valid = true;
+		id.mmap2_ino_generation_valid = true;
 	}
 
 	return perf_event__repipe_common_mmap(
@@ -603,7 +605,7 @@ static int perf_event__repipe_mmap2(const struct perf_tool *tool,
 		event->mmap2.pid, event->mmap2.tid,
 		event->mmap2.start, event->mmap2.len, event->mmap2.pgoff,
 		event->mmap2.flags, event->mmap2.prot,
-		event->mmap2.filename, dso_id,
+		event->mmap2.filename, &id,
 		perf_event__process_mmap2);
 }
 
@@ -671,19 +673,20 @@ static int perf_event__repipe_tracing_data(struct perf_session *session,
 static int dso__read_build_id(struct dso *dso)
 {
 	struct nscookie nsc;
+	struct build_id bid;
 
 	if (dso__has_build_id(dso))
 		return 0;
 
 	mutex_lock(dso__lock(dso));
 	nsinfo__mountns_enter(dso__nsinfo(dso), &nsc);
-	if (filename__read_build_id(dso__long_name(dso), dso__bid(dso)) > 0)
-		dso__set_has_build_id(dso);
+	if (filename__read_build_id(dso__long_name(dso), &bid) > 0)
+		dso__set_build_id(dso, &bid);
 	else if (dso__nsinfo(dso)) {
 		char *new_name = dso__filename_with_chroot(dso, dso__long_name(dso));
 
-		if (new_name && filename__read_build_id(new_name, dso__bid(dso)) > 0)
-			dso__set_has_build_id(dso);
+		if (new_name && filename__read_build_id(new_name, &bid) > 0)
+			dso__set_build_id(dso, &bid);
 		free(new_name);
 	}
 	nsinfo__mountns_exit(&nsc);
@@ -732,10 +735,11 @@ static bool perf_inject__lookup_known_build_id(struct perf_inject *inject,
 					       struct dso *dso)
 {
 	struct str_node *pos;
-	int bid_len;
+	struct build_id bid;
 
 	strlist__for_each_entry(pos, inject->known_build_ids) {
 		const char *build_id, *dso_name;
+		int bid_len;
 
 		build_id = skip_spaces(pos->s);
 		dso_name = strchr(build_id, ' ');
@@ -744,11 +748,11 @@ static bool perf_inject__lookup_known_build_id(struct perf_inject *inject,
 		if (strcmp(dso__long_name(dso), dso_name))
 			continue;
 		for (int ix = 0; 2 * ix + 1 < bid_len; ++ix) {
-			dso__bid(dso)->data[ix] = (hex(build_id[2 * ix]) << 4 |
-						  hex(build_id[2 * ix + 1]));
+			bid.data[ix] = (hex(build_id[2 * ix]) << 4 |
+					hex(build_id[2 * ix + 1]));
 		}
-		dso__bid(dso)->size = bid_len / 2;
-		dso__set_has_build_id(dso);
+		bid.size = bid_len / 2;
+		dso__set_build_id(dso, &bid);
 		return true;
 	}
 	return false;
diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index b030ce72e13e..a92953c03781 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -858,17 +858,24 @@ static int maps__fprintf_task_cb(struct map *map, void *data)
 	struct maps__fprintf_task_args *args = data;
 	const struct dso *dso = map__dso(map);
 	u32 prot = map__prot(map);
+	const struct dso_id *dso_id = dso__id_const(dso);
 	int ret;
+	char buf[SBUILD_ID_SIZE];
+
+	if (dso_id->mmap2_valid)
+		snprintf(buf, sizeof(buf), "%" PRIu64, dso_id->ino);
+	else
+		build_id__snprintf(&dso_id->build_id, buf, sizeof(buf));
 
 	ret = fprintf(args->fp,
-		"%*s  %" PRIx64 "-%" PRIx64 " %c%c%c%c %08" PRIx64 " %" PRIu64 " %s\n",
+		"%*s  %" PRIx64 "-%" PRIx64 " %c%c%c%c %08" PRIx64 " %s %s\n",
 		args->indent, "", map__start(map), map__end(map),
 		prot & PROT_READ ? 'r' : '-',
 		prot & PROT_WRITE ? 'w' : '-',
 		prot & PROT_EXEC ? 'x' : '-',
 		map__flags(map) ? 's' : 'p',
 		map__pgoff(map),
-		dso__id_const(dso)->ino, dso__name(dso));
+		buf, dso__name(dso));
 
 	if (ret < 0)
 		return ret;
diff --git a/tools/perf/include/perf/perf_dlfilter.h b/tools/perf/include/perf/perf_dlfilter.h
index 16fc4568ac53..2d3540ed3c58 100644
--- a/tools/perf/include/perf/perf_dlfilter.h
+++ b/tools/perf/include/perf/perf_dlfilter.h
@@ -87,7 +87,7 @@ struct perf_dlfilter_al {
 	__u8  is_64_bit; /* Only valid if dso is not NULL */
 	__u8  is_kernel_ip; /* True if in kernel space */
 	__u32 buildid_size;
-	__u8 *buildid;
+	const __u8 *buildid;
 	/* Below members are only populated by resolve_ip() */
 	__u8 filtered; /* True if this sample event will be filtered out */
 	const char *comm;
diff --git a/tools/perf/tests/symbols.c b/tools/perf/tests/symbols.c
index ee20a366f32f..b07fdf831868 100644
--- a/tools/perf/tests/symbols.c
+++ b/tools/perf/tests/symbols.c
@@ -96,8 +96,8 @@ static int create_map(struct test_info *ti, char *filename, struct map **map_p)
 	dso__put(dso);
 
 	/* Create a dummy map at 0x100000 */
-	*map_p = map__new(ti->machine, 0x100000, 0xffffffff, 0, NULL,
-			  PROT_EXEC, 0, NULL, filename, ti->thread);
+	*map_p = map__new(ti->machine, 0x100000, 0xffffffff, 0, &dso_id_empty,
+			  PROT_EXEC, /*flags=*/0, filename, ti->thread);
 	if (!*map_p) {
 		pr_debug("Failed to create map!");
 		return TEST_FAIL;
diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index aa35dceace90..f64a1761d7ca 100644
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -236,7 +236,7 @@ char *__dso__build_id_filename(const struct dso *dso, char *bf, size_t size,
 	if (!dso__has_build_id(dso))
 		return NULL;
 
-	build_id__snprintf(dso__bid_const(dso), sbuild_id, sizeof(sbuild_id));
+	build_id__snprintf(dso__bid(dso), sbuild_id, sizeof(sbuild_id));
 	linkname = build_id_cache__linkname(sbuild_id, NULL, 0);
 	if (!linkname)
 		return NULL;
@@ -319,7 +319,7 @@ static int machine__write_buildid_table_cb(struct dso *dso, void *data)
 	}
 
 	in_kernel = dso__kernel(dso) || is_kernel_module(name, PERF_RECORD_MISC_CPUMODE_UNKNOWN);
-	return write_buildid(name, name_len, dso__bid(dso), args->machine->pid,
+	return write_buildid(name, name_len, &dso__id(dso)->build_id, args->machine->pid,
 			     in_kernel ? args->kmisc : args->umisc, args->fd);
 }
 
diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index 776506b93b8b..493750142de7 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -217,7 +217,7 @@ int dso__read_binary_type_filename(const struct dso *dso,
 			break;
 		}
 
-		build_id__snprintf(dso__bid_const(dso), build_id_hex, sizeof(build_id_hex));
+		build_id__snprintf(dso__bid(dso), build_id_hex, sizeof(build_id_hex));
 		len = __symbol__join_symfs(filename, size, "/usr/lib/debug/.build-id/");
 		snprintf(filename + len, size - len, "%.2s/%s.debug",
 			 build_id_hex, build_id_hex + 2);
@@ -1379,64 +1379,76 @@ static void dso__set_long_name_id(struct dso *dso, const char *name, bool name_a
 
 static int __dso_id__cmp(const struct dso_id *a, const struct dso_id *b)
 {
-	if (a->maj > b->maj) return -1;
-	if (a->maj < b->maj) return 1;
+	if (a->mmap2_valid && b->mmap2_valid) {
+		if (a->maj > b->maj) return -1;
+		if (a->maj < b->maj) return 1;
 
-	if (a->min > b->min) return -1;
-	if (a->min < b->min) return 1;
+		if (a->min > b->min) return -1;
+		if (a->min < b->min) return 1;
 
-	if (a->ino > b->ino) return -1;
-	if (a->ino < b->ino) return 1;
-
-	/*
-	 * Synthesized MMAP events have zero ino_generation, avoid comparing
-	 * them with MMAP events with actual ino_generation.
-	 *
-	 * I found it harmful because the mismatch resulted in a new
-	 * dso that did not have a build ID whereas the original dso did have a
-	 * build ID. The build ID was essential because the object was not found
-	 * otherwise. - Adrian
-	 */
-	if (a->ino_generation && b->ino_generation) {
+		if (a->ino > b->ino) return -1;
+		if (a->ino < b->ino) return 1;
+	}
+	if (a->mmap2_ino_generation_valid && b->mmap2_ino_generation_valid) {
 		if (a->ino_generation > b->ino_generation) return -1;
 		if (a->ino_generation < b->ino_generation) return 1;
 	}
-
+	if (build_id__is_defined(&a->build_id) && build_id__is_defined(&b->build_id)) {
+		if (a->build_id.size != b->build_id.size)
+			return a->build_id.size < b->build_id.size ? -1 : 1;
+		return memcmp(a->build_id.data, b->build_id.data, a->build_id.size);
+	}
 	return 0;
 }
 
-bool dso_id__empty(const struct dso_id *id)
-{
-	if (!id)
-		return true;
-
-	return !id->maj && !id->min && !id->ino && !id->ino_generation;
-}
+const struct dso_id dso_id_empty = {
+	{
+		.maj = 0,
+		.min = 0,
+		.ino = 0,
+		.ino_generation = 0,
+	},
+	.mmap2_valid = false,
+	.mmap2_ino_generation_valid = false,
+	{
+		.size = 0,
+	}
+};
 
-void __dso__inject_id(struct dso *dso, const struct dso_id *id)
+void __dso__improve_id(struct dso *dso, const struct dso_id *id)
 {
 	struct dsos *dsos = dso__dsos(dso);
 	struct dso_id *dso_id = dso__id(dso);
+	bool changed = false;
 
 	/* dsos write lock held by caller. */
 
-	dso_id->maj = id->maj;
-	dso_id->min = id->min;
-	dso_id->ino = id->ino;
-	dso_id->ino_generation = id->ino_generation;
-
-	if (dsos)
+	if (id->mmap2_valid && !dso_id->mmap2_valid) {
+		dso_id->maj = id->maj;
+		dso_id->min = id->min;
+		dso_id->ino = id->ino;
+		dso_id->mmap2_valid = true;
+		changed = true;
+	}
+	if (id->mmap2_ino_generation_valid && !dso_id->mmap2_ino_generation_valid) {
+		dso_id->ino_generation = id->ino_generation;
+		dso_id->mmap2_ino_generation_valid = true;
+		changed = true;
+	}
+	if (build_id__is_defined(&id->build_id) && !build_id__is_defined(&dso_id->build_id)) {
+		dso_id->build_id = id->build_id;
+		changed = true;
+	}
+	if (changed && dsos)
 		dsos->sorted = false;
 }
 
 int dso_id__cmp(const struct dso_id *a, const struct dso_id *b)
 {
-	/*
-	 * The second is always dso->id, so zeroes if not set, assume passing
-	 * NULL for a means a zeroed id
-	 */
-	if (dso_id__empty(a) || dso_id__empty(b))
+	if (a == &dso_id_empty || b == &dso_id_empty) {
+		/* There is no valid data to compare so the comparison always returns identical. */
 		return 0;
+	}
 
 	return __dso_id__cmp(a, b);
 }
@@ -1533,7 +1545,6 @@ struct dso *dso__new_id(const char *name, const struct dso_id *id)
 		dso->loaded = 0;
 		dso->rel = 0;
 		dso->sorted_by_name = 0;
-		dso->has_build_id = 0;
 		dso->has_srcline = 1;
 		dso->a2l_fails = 1;
 		dso->kernel = DSO_SPACE__USER;
@@ -1638,15 +1649,14 @@ int dso__swap_init(struct dso *dso, unsigned char eidata)
 	return 0;
 }
 
-void dso__set_build_id(struct dso *dso, struct build_id *bid)
+void dso__set_build_id(struct dso *dso, const struct build_id *bid)
 {
-	RC_CHK_ACCESS(dso)->bid = *bid;
-	RC_CHK_ACCESS(dso)->has_build_id = 1;
+	dso__id(dso)->build_id = *bid;
 }
 
-bool dso__build_id_equal(const struct dso *dso, struct build_id *bid)
+bool dso__build_id_equal(const struct dso *dso, const struct build_id *bid)
 {
-	const struct build_id *dso_bid = dso__bid_const(dso);
+	const struct build_id *dso_bid = dso__bid(dso);
 
 	if (dso_bid->size > bid->size && dso_bid->size == BUILD_ID_SIZE) {
 		/*
@@ -1665,18 +1675,20 @@ bool dso__build_id_equal(const struct dso *dso, struct build_id *bid)
 void dso__read_running_kernel_build_id(struct dso *dso, struct machine *machine)
 {
 	char path[PATH_MAX];
+	struct build_id bid;
 
 	if (machine__is_default_guest(machine))
 		return;
 	sprintf(path, "%s/sys/kernel/notes", machine->root_dir);
-	if (sysfs__read_build_id(path, dso__bid(dso)) == 0)
-		dso__set_has_build_id(dso);
+	sysfs__read_build_id(path, &bid);
+	dso__set_build_id(dso, &bid);
 }
 
 int dso__kernel_module_get_build_id(struct dso *dso,
 				    const char *root_dir)
 {
 	char filename[PATH_MAX];
+	struct build_id bid;
 	/*
 	 * kernel module short names are of the form "[module]" and
 	 * we need just "module" here.
@@ -1687,9 +1699,8 @@ int dso__kernel_module_get_build_id(struct dso *dso,
 		 "%s/sys/module/%.*s/notes/.note.gnu.build-id",
 		 root_dir, (int)strlen(name) - 1, name);
 
-	if (sysfs__read_build_id(filename, dso__bid(dso)) == 0)
-		dso__set_has_build_id(dso);
-
+	sysfs__read_build_id(filename, &bid);
+	dso__set_build_id(dso, &bid);
 	return 0;
 }
 
diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index c87564471f9b..3457d713d3c5 100644
--- a/tools/perf/util/dso.h
+++ b/tools/perf/util/dso.h
@@ -185,14 +185,33 @@ enum dso_load_errno {
 #define DSO__DATA_CACHE_SIZE 4096
 #define DSO__DATA_CACHE_MASK ~(DSO__DATA_CACHE_SIZE - 1)
 
-/*
- * Data about backing storage DSO, comes from PERF_RECORD_MMAP2 meta events
+/**
+ * struct dso_id
+ *
+ * Data about backing storage DSO, comes from PERF_RECORD_MMAP2 meta events,
+ * reading from /proc/pid/maps or synthesis of build_ids from DSOs. Possibly
+ * incomplete at any particular use.
  */
 struct dso_id {
-	u32	maj;
-	u32	min;
-	u64	ino;
-	u64	ino_generation;
+	/* Data related to the mmap2 event or read from /proc/pid/maps. */
+	struct {
+		u32	maj;
+		u32	min;
+		u64	ino;
+		u64	ino_generation;
+	};
+	/** @mmap2_valid: Are the maj, min and ino fields valid? */
+	bool	mmap2_valid;
+	/**
+	 * @mmap2_ino_generation_valid: Is the ino_generation valid? Generally
+	 * false for /proc/pid/maps mmap event.
+	 */
+	bool	mmap2_ino_generation_valid;
+	/**
+	 * @build_id: A possibly populated build_id. build_id__is_defined checks
+	 * whether it is populated.
+	 */
+	struct build_id build_id;
 };
 
 struct dso_cache {
@@ -243,7 +262,6 @@ DECLARE_RC_STRUCT(dso) {
 		u64		addr;
 		struct symbol	*symbol;
 	} last_find_result;
-	struct build_id	 bid;
 	u64		 text_offset;
 	u64		 text_end;
 	const char	 *short_name;
@@ -276,7 +294,6 @@ DECLARE_RC_STRUCT(dso) {
 	enum dso_swap_type	needs_swap:2;
 	bool			is_kmod:1;
 	u8		 adjust_symbols:1;
-	u8		 has_build_id:1;
 	u8		 header_build_id:1;
 	u8		 has_srcline:1;
 	u8		 hit:1;
@@ -292,6 +309,9 @@ DECLARE_RC_STRUCT(dso) {
 };
 
 extern struct mutex _dso__data_open_lock;
+extern const struct dso_id dso_id_empty;
+
+int dso_id__cmp(const struct dso_id *a, const struct dso_id *b);
 
 /* dso__for_each_symbol - iterate over the symbols of given type
  *
@@ -362,31 +382,11 @@ static inline void dso__set_auxtrace_cache(struct dso *dso, struct auxtrace_cach
 	RC_CHK_ACCESS(dso)->auxtrace_cache = cache;
 }
 
-static inline struct build_id *dso__bid(struct dso *dso)
-{
-	return &RC_CHK_ACCESS(dso)->bid;
-}
-
-static inline const struct build_id *dso__bid_const(const struct dso *dso)
-{
-	return &RC_CHK_ACCESS(dso)->bid;
-}
-
 static inline struct dso_bpf_prog *dso__bpf_prog(struct dso *dso)
 {
 	return &RC_CHK_ACCESS(dso)->bpf_prog;
 }
 
-static inline bool dso__has_build_id(const struct dso *dso)
-{
-	return RC_CHK_ACCESS(dso)->has_build_id;
-}
-
-static inline void dso__set_has_build_id(struct dso *dso)
-{
-	RC_CHK_ACCESS(dso)->has_build_id = true;
-}
-
 static inline bool dso__has_srcline(const struct dso *dso)
 {
 	return RC_CHK_ACCESS(dso)->has_srcline;
@@ -462,6 +462,16 @@ static inline const struct dso_id *dso__id_const(const struct dso *dso)
 	return &RC_CHK_ACCESS(dso)->id;
 }
 
+static inline const struct build_id *dso__bid(const struct dso *dso)
+{
+	return &dso__id_const(dso)->build_id;
+}
+
+static inline bool dso__has_build_id(const struct dso *dso)
+{
+	return build_id__is_defined(dso__bid(dso));
+}
+
 static inline struct rb_root_cached *dso__inlined_nodes(struct dso *dso)
 {
 	return &RC_CHK_ACCESS(dso)->inlined_nodes;
@@ -699,9 +709,6 @@ static inline void dso__set_text_offset(struct dso *dso, u64 val)
 	RC_CHK_ACCESS(dso)->text_offset = val;
 }
 
-int dso_id__cmp(const struct dso_id *a, const struct dso_id *b);
-bool dso_id__empty(const struct dso_id *id);
-
 struct dso *dso__new_id(const char *name, const struct dso_id *id);
 struct dso *dso__new(const char *name);
 void dso__delete(struct dso *dso);
@@ -709,7 +716,7 @@ void dso__delete(struct dso *dso);
 int dso__cmp_id(struct dso *a, struct dso *b);
 void dso__set_short_name(struct dso *dso, const char *name, bool name_allocated);
 void dso__set_long_name(struct dso *dso, const char *name, bool name_allocated);
-void __dso__inject_id(struct dso *dso, const struct dso_id *id);
+void __dso__improve_id(struct dso *dso, const struct dso_id *id);
 
 int dso__name_len(const struct dso *dso);
 
@@ -739,8 +746,8 @@ void dso__sort_by_name(struct dso *dso);
 
 int dso__swap_init(struct dso *dso, unsigned char eidata);
 
-void dso__set_build_id(struct dso *dso, struct build_id *bid);
-bool dso__build_id_equal(const struct dso *dso, struct build_id *bid);
+void dso__set_build_id(struct dso *dso, const struct build_id *bid);
+bool dso__build_id_equal(const struct dso *dso, const struct build_id *bid);
 void dso__read_running_kernel_build_id(struct dso *dso,
 				       struct machine *machine);
 int dso__kernel_module_get_build_id(struct dso *dso, const char *root_dir);
diff --git a/tools/perf/util/dsos.c b/tools/perf/util/dsos.c
index b2172632b3cd..ad919ed28ba4 100644
--- a/tools/perf/util/dsos.c
+++ b/tools/perf/util/dsos.c
@@ -72,6 +72,7 @@ static int dsos__read_build_ids_cb(struct dso *dso, void *data)
 {
 	struct dsos__read_build_ids_cb_args *args = data;
 	struct nscookie nsc;
+	struct build_id bid;
 
 	if (args->with_hits && !dso__hit(dso) && !dso__is_vdso(dso))
 		return 0;
@@ -80,15 +81,15 @@ static int dsos__read_build_ids_cb(struct dso *dso, void *data)
 		return 0;
 	}
 	nsinfo__mountns_enter(dso__nsinfo(dso), &nsc);
-	if (filename__read_build_id(dso__long_name(dso), dso__bid(dso)) > 0) {
+	if (filename__read_build_id(dso__long_name(dso), &bid) > 0) {
+		dso__set_build_id(dso, &bid);
 		args->have_build_id = true;
-		dso__set_has_build_id(dso);
 	} else if (errno == ENOENT && dso__nsinfo(dso)) {
 		char *new_name = dso__filename_with_chroot(dso, dso__long_name(dso));
 
-		if (new_name && filename__read_build_id(new_name, dso__bid(dso)) > 0) {
+		if (new_name && filename__read_build_id(new_name, &bid) > 0) {
+			dso__set_build_id(dso, &bid);
 			args->have_build_id = true;
-			dso__set_has_build_id(dso);
 		}
 		free(new_name);
 	}
@@ -284,7 +285,7 @@ struct dso *dsos__find(struct dsos *dsos, const char *name, bool cmp_short)
 	struct dso *res;
 
 	down_read(&dsos->lock);
-	res = __dsos__find_id(dsos, name, NULL, cmp_short, /*write_locked=*/false);
+	res = __dsos__find_id(dsos, name, &dso_id_empty, cmp_short, /*write_locked=*/false);
 	up_read(&dsos->lock);
 	return res;
 }
@@ -341,8 +342,8 @@ static struct dso *__dsos__findnew_id(struct dsos *dsos, const char *name, const
 {
 	struct dso *dso = __dsos__find_id(dsos, name, id, false, /*write_locked=*/true);
 
-	if (dso && dso_id__empty(dso__id(dso)) && !dso_id__empty(id))
-		__dso__inject_id(dso, id);
+	if (dso)
+		__dso__improve_id(dso, id);
 
 	return dso ? dso : __dsos__addnew_id(dsos, name, id);
 }
@@ -433,7 +434,8 @@ struct dso *dsos__findnew_module_dso(struct dsos *dsos,
 
 	down_write(&dsos->lock);
 
-	dso = __dsos__find_id(dsos, m->name, NULL, /*cmp_short=*/true, /*write_locked=*/true);
+	dso = __dsos__find_id(dsos, m->name, &dso_id_empty, /*cmp_short=*/true,
+			      /*write_locked=*/true);
 	if (dso) {
 		up_write(&dsos->lock);
 		return dso;
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 2531b373f2cf..3a840fe395eb 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1696,21 +1696,21 @@ int machine__process_mmap2_event(struct machine *machine,
 {
 	struct thread *thread;
 	struct map *map;
-	struct dso_id dso_id = {
-		.maj = event->mmap2.maj,
-		.min = event->mmap2.min,
-		.ino = event->mmap2.ino,
-		.ino_generation = event->mmap2.ino_generation,
-	};
-	struct build_id __bid, *bid = NULL;
+	struct dso_id dso_id;
 	int ret = 0;
 
 	if (dump_trace)
 		perf_event__fprintf_mmap2(event, stdout);
 
 	if (event->header.misc & PERF_RECORD_MISC_MMAP_BUILD_ID) {
-		bid = &__bid;
-		build_id__init(bid, event->mmap2.build_id, event->mmap2.build_id_size);
+		build_id__init(&dso_id.build_id, event->mmap2.build_id, event->mmap2.build_id_size);
+	} else {
+		dso_id.maj = event->mmap2.maj;
+		dso_id.min = event->mmap2.min;
+		dso_id.ino = event->mmap2.ino;
+		dso_id.ino_generation = event->mmap2.ino_generation;
+		dso_id.mmap2_valid = true;
+		dso_id.mmap2_ino_generation_valid = true;
 	}
 
 	if (sample->cpumode == PERF_RECORD_MISC_GUEST_KERNEL ||
@@ -1722,7 +1722,7 @@ int machine__process_mmap2_event(struct machine *machine,
 		};
 
 		strlcpy(xm.name, event->mmap2.filename, KMAP_NAME_LEN);
-		ret = machine__process_kernel_mmap_event(machine, &xm, bid);
+		ret = machine__process_kernel_mmap_event(machine, &xm, &dso_id.build_id);
 		if (ret < 0)
 			goto out_problem;
 		return 0;
@@ -1736,7 +1736,7 @@ int machine__process_mmap2_event(struct machine *machine,
 	map = map__new(machine, event->mmap2.start,
 			event->mmap2.len, event->mmap2.pgoff,
 			&dso_id, event->mmap2.prot,
-			event->mmap2.flags, bid,
+			event->mmap2.flags,
 			event->mmap2.filename, thread);
 
 	if (map == NULL)
@@ -1794,8 +1794,8 @@ int machine__process_mmap_event(struct machine *machine, union perf_event *event
 		prot = PROT_EXEC;
 
 	map = map__new(machine, event->mmap.start,
-			event->mmap.len, event->mmap.pgoff,
-			NULL, prot, 0, NULL, event->mmap.filename, thread);
+		       event->mmap.len, event->mmap.pgoff,
+		       &dso_id_empty, prot, /*flags=*/0, event->mmap.filename, thread);
 
 	if (map == NULL)
 		goto out_problem_map;
@@ -3155,7 +3155,7 @@ struct dso *machine__findnew_dso_id(struct machine *machine, const char *filenam
 
 struct dso *machine__findnew_dso(struct machine *machine, const char *filename)
 {
-	return machine__findnew_dso_id(machine, filename, NULL);
+	return machine__findnew_dso_id(machine, filename, &dso_id_empty);
 }
 
 char *machine__resolve_kernel_addr(void *vmachine, unsigned long long *addrp, char **modp)
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);
diff --git a/tools/perf/util/map.h b/tools/perf/util/map.h
index 4262f5a143be..9cadf533a561 100644
--- a/tools/perf/util/map.h
+++ b/tools/perf/util/map.h
@@ -173,11 +173,10 @@ struct thread;
 	__map__for_each_symbol_by_name(map, sym_name, (pos), idx)
 
 struct dso_id;
-struct build_id;
 
 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, char *filename, struct thread *thread);
+		     u64 pgoff, const struct dso_id *id, u32 prot, u32 flags,
+		     char *filename, struct thread *thread);
 struct map *map__new2(u64 start, struct dso *dso);
 void map__delete(struct map *map);
 struct map *map__clone(struct map *map);
diff --git a/tools/perf/util/sort.c b/tools/perf/util/sort.c
index c51049087e4e..eae8b74ab3f3 100644
--- a/tools/perf/util/sort.c
+++ b/tools/perf/util/sort.c
@@ -1709,22 +1709,27 @@ sort__dcacheline_cmp(struct hist_entry *left, struct hist_entry *right)
 	if (rc)
 		return rc;
 	/*
-	 * Addresses with no major/minor numbers are assumed to be
+	 * Addresses with no major/minor numbers or build ID are assumed to be
 	 * anonymous in userspace.  Sort those on pid then address.
 	 *
 	 * The kernel and non-zero major/minor mapped areas are
 	 * assumed to be unity mapped.  Sort those on address.
 	 */
+	if (left->cpumode != PERF_RECORD_MISC_KERNEL && (map__flags(l_map) & MAP_SHARED) == 0) {
+		const struct dso_id *dso_id = dso__id_const(l_dso);
 
-	if ((left->cpumode != PERF_RECORD_MISC_KERNEL) &&
-	    (!(map__flags(l_map) & MAP_SHARED)) && !dso__id(l_dso)->maj && !dso__id(l_dso)->min &&
-	     !dso__id(l_dso)->ino && !dso__id(l_dso)->ino_generation) {
-		/* userspace anonymous */
+		if (!dso_id->mmap2_valid)
+			dso_id = dso__id_const(r_dso);
 
-		if (thread__pid(left->thread) > thread__pid(right->thread))
-			return -1;
-		if (thread__pid(left->thread) < thread__pid(right->thread))
-			return 1;
+		if (!build_id__is_defined(&dso_id->build_id) &&
+		    (!dso_id->mmap2_valid || (dso_id->maj == 0 && dso_id->min == 0))) {
+			/* userspace anonymous */
+
+			if (thread__pid(left->thread) > thread__pid(right->thread))
+				return -1;
+			if (thread__pid(left->thread) < thread__pid(right->thread))
+				return 1;
+		}
 	}
 
 addr:
@@ -1749,6 +1754,7 @@ static int hist_entry__dcacheline_snprintf(struct hist_entry *he, char *bf,
 	if (he->mem_info) {
 		struct map *map = mem_info__daddr(he->mem_info)->ms.map;
 		struct dso *dso = map ? map__dso(map) : NULL;
+		const struct dso_id *dso_id = dso ? dso__id_const(dso) : &dso_id_empty;
 
 		addr = cl_address(mem_info__daddr(he->mem_info)->al_addr, chk_double_cl);
 		ms = &mem_info__daddr(he->mem_info)->ms;
@@ -1757,8 +1763,7 @@ static int hist_entry__dcacheline_snprintf(struct hist_entry *he, char *bf,
 		if ((he->cpumode != PERF_RECORD_MISC_KERNEL) &&
 		     map && !(map__prot(map) & PROT_EXEC) &&
 		     (map__flags(map) & MAP_SHARED) &&
-		     (dso__id(dso)->maj || dso__id(dso)->min || dso__id(dso)->ino ||
-		      dso__id(dso)->ino_generation))
+		     (!dso_id->mmap2_valid || (dso_id->maj == 0 && dso_id->min == 0)))
 			level = 's';
 		else if (!map)
 			level = 'X';
diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
index 68bb7c5fe1b1..8fb2ea544d3a 100644
--- a/tools/perf/util/synthetic-events.c
+++ b/tools/perf/util/synthetic-events.c
@@ -372,7 +372,7 @@ static void perf_record_mmap2__read_build_id(struct perf_record_mmap2 *event,
 	struct nsinfo *nsi;
 	struct nscookie nc;
 	struct dso *dso = NULL;
-	struct dso_id id;
+	struct dso_id dso_id = dso_id_empty;
 	int rc;
 
 	if (is_kernel) {
@@ -380,12 +380,18 @@ static void perf_record_mmap2__read_build_id(struct perf_record_mmap2 *event,
 		goto out;
 	}
 
-	id.maj = event->maj;
-	id.min = event->min;
-	id.ino = event->ino;
-	id.ino_generation = event->ino_generation;
+	if (event->header.misc & PERF_RECORD_MISC_MMAP_BUILD_ID) {
+		build_id__init(&dso_id.build_id, event->build_id, event->build_id_size);
+	} else {
+		dso_id.maj = event->maj;
+		dso_id.min = event->min;
+		dso_id.ino = event->ino;
+		dso_id.ino_generation = event->ino_generation;
+		dso_id.mmap2_valid = true;
+		dso_id.mmap2_ino_generation_valid = true;
+	};
 
-	dso = dsos__findnew_id(&machine->dsos, event->filename, &id);
+	dso = dsos__findnew_id(&machine->dsos, event->filename, &dso_id);
 	if (dso && dso__has_build_id(dso)) {
 		bid = *dso__bid(dso);
 		rc = 0;
-- 
2.49.0.805.g082f7c87e0-goog

[PATCH v1 5/5] perf record: Make --buildid-mmap the default

[Ian Rogers]

Support for build IDs in mmap2 perf events has been present since
Linux v5.12:
https://lore.kernel.org/lkml/20210219194619.1780437-1-acme@kernel.org/
Build ID mmap events avoid the need to inject build IDs for DSO
touched by samples when perf record completes and can avoid some cases
of symbol mis-resolution.

Unlike the --buildid-mmap option, this doesn't disable the build ID
cache but it does disable the processing of samples looking for DSOs
to inject build IDs for. To disable the build ID cache the -N
(--no-buildid-cache) option is necessary.

Making this option the default was raised on the list in:
https://lore.kernel.org/linux-perf-users/CAP-5=fXP7jN_QrGUcd55_QH5J-Y-FCaJ6=NaHVtyx0oyNh8_-Q@mail.gmail.com/

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/builtin-record.c        | 35 +++++++++++++++++++-----------
 tools/perf/util/symbol_conf.h      |  2 +-
 tools/perf/util/synthetic-events.c | 16 +++++++-------
 3 files changed, 31 insertions(+), 22 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index ba20bf7c011d..0fcb0f469488 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -169,6 +169,7 @@ struct record {
 	bool			no_buildid_cache_set;
 	bool			buildid_all;
 	bool			buildid_mmap;
+	bool			buildid_mmap_set;
 	bool			timestamp_filename;
 	bool			timestamp_boundary;
 	bool			off_cpu;
@@ -1795,7 +1796,8 @@ record__finish_output(struct record *rec)
 			data->dir.files[i].size = lseek(data->dir.files[i].fd, 0, SEEK_CUR);
 	}
 
-	if (!rec->no_buildid) {
+	/* Buildid scanning disabled or build ID in kernel and synthesized map events. */
+	if (!rec->no_buildid && !rec->buildid_mmap) {
 		process_buildids(rec);
 
 		if (rec->buildid_all)
@@ -2966,6 +2968,8 @@ static int perf_record_config(const char *var, const char *value, void *cb)
 			rec->no_buildid = true;
 		else if (!strcmp(value, "mmap"))
 			rec->buildid_mmap = true;
+		else if (!strcmp(value, "no-mmap"))
+			rec->buildid_mmap = false;
 		else
 			return -1;
 		return 0;
@@ -3349,6 +3353,7 @@ static struct record record = {
 		.ctl_fd_ack          = -1,
 		.synth               = PERF_SYNTH_ALL,
 	},
+	.buildid_mmap = true,
 };
 
 const char record_callchain_help[] = CALLCHAIN_RECORD_HELP
@@ -3514,8 +3519,8 @@ static struct option __record_options[] = {
 		   "file", "vmlinux pathname"),
 	OPT_BOOLEAN(0, "buildid-all", &record.buildid_all,
 		    "Record build-id of all DSOs regardless of hits"),
-	OPT_BOOLEAN(0, "buildid-mmap", &record.buildid_mmap,
-		    "Record build-id in map events"),
+	OPT_BOOLEAN_SET(0, "buildid-mmap", &record.buildid_mmap, &record.buildid_mmap_set,
+			"Legacy record build-id in map events option which is now the default. Behaves indentically to --no-buildid. Disable with --no-buildid-mmap"),
 	OPT_BOOLEAN(0, "timestamp-filename", &record.timestamp_filename,
 		    "append timestamp to output filename"),
 	OPT_BOOLEAN(0, "timestamp-boundary", &record.timestamp_boundary,
@@ -4042,19 +4047,23 @@ int cmd_record(int argc, const char **argv)
 		record.opts.record_switch_events = true;
 	}
 
+	if (!rec->buildid_mmap) {
+		pr_debug("Disabling build id in synthesized mmap2 events.\n");
+		symbol_conf.no_buildid_mmap2 = true;
+	} else if (rec->buildid_mmap_set) {
+		/*
+		 * Explicitly passing --buildid-mmap disables buildid processing
+		 * and cache generation.
+		 */
+		rec->no_buildid = true;
+	}
+	if (rec->buildid_mmap && !perf_can_record_build_id()) {
+		pr_warning("Missing support for build id in kernel mmap events. Disable this warning with --no-buildid-mmap\n");
+		rec->buildid_mmap = false;
+	}
 	if (rec->buildid_mmap) {
-		if (!perf_can_record_build_id()) {
-			pr_err("Failed: no support to record build id in mmap events, update your kernel.\n");
-			err = -EINVAL;
-			goto out_opts;
-		}
-		pr_debug("Enabling build id in mmap2 events.\n");
-		/* Enable mmap build id synthesizing. */
-		symbol_conf.buildid_mmap2 = true;
 		/* Enable perf_event_attr::build_id bit. */
 		rec->opts.build_id = true;
-		/* Disable build id cache. */
-		rec->no_buildid = true;
 	}
 
 	if (rec->opts.record_cgroup && !perf_can_record_cgroup()) {
diff --git a/tools/perf/util/symbol_conf.h b/tools/perf/util/symbol_conf.h
index cd9aa82c7d5a..7a80d2c14d9b 100644
--- a/tools/perf/util/symbol_conf.h
+++ b/tools/perf/util/symbol_conf.h
@@ -43,7 +43,7 @@ struct symbol_conf {
 			report_individual_block,
 			inline_name,
 			disable_add2line_warn,
-			buildid_mmap2,
+			no_buildid_mmap2,
 			guest_code,
 			lazy_load_kernel_maps,
 			keep_exited_threads,
diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
index 8fb2ea544d3a..f48109c14235 100644
--- a/tools/perf/util/synthetic-events.c
+++ b/tools/perf/util/synthetic-events.c
@@ -532,7 +532,7 @@ int perf_event__synthesize_mmap_events(const struct perf_tool *tool,
 		event->mmap2.pid = tgid;
 		event->mmap2.tid = pid;
 
-		if (symbol_conf.buildid_mmap2)
+		if (!symbol_conf.no_buildid_mmap2)
 			perf_record_mmap2__read_build_id(&event->mmap2, machine, false);
 
 		if (perf_tool__process_synth_event(tool, event, machine, process) != 0) {
@@ -690,7 +690,7 @@ static int perf_event__synthesize_modules_maps_cb(struct map *map, void *data)
 		return 0;
 
 	dso = map__dso(map);
-	if (symbol_conf.buildid_mmap2) {
+	if (!symbol_conf.no_buildid_mmap2) {
 		size = PERF_ALIGN(dso__long_name_len(dso) + 1, sizeof(u64));
 		event->mmap2.header.type = PERF_RECORD_MMAP2;
 		event->mmap2.header.size = (sizeof(event->mmap2) -
@@ -734,9 +734,9 @@ int perf_event__synthesize_modules(const struct perf_tool *tool, perf_event__han
 		.process = process,
 		.machine = machine,
 	};
-	size_t size = symbol_conf.buildid_mmap2
-		? sizeof(args.event->mmap2)
-		: sizeof(args.event->mmap);
+	size_t size = symbol_conf.no_buildid_mmap2
+		? sizeof(args.event->mmap)
+		: sizeof(args.event->mmap2);
 
 	args.event = zalloc(size + machine->id_hdr_size);
 	if (args.event == NULL) {
@@ -1124,8 +1124,8 @@ static int __perf_event__synthesize_kernel_mmap(const struct perf_tool *tool,
 						struct machine *machine)
 {
 	union perf_event *event;
-	size_t size = symbol_conf.buildid_mmap2 ?
-			sizeof(event->mmap2) : sizeof(event->mmap);
+	size_t size = symbol_conf.no_buildid_mmap2 ?
+			sizeof(event->mmap) : sizeof(event->mmap2);
 	struct map *map = machine__kernel_map(machine);
 	struct kmap *kmap;
 	int err;
@@ -1159,7 +1159,7 @@ static int __perf_event__synthesize_kernel_mmap(const struct perf_tool *tool,
 		event->header.misc = PERF_RECORD_MISC_GUEST_KERNEL;
 	}
 
-	if (symbol_conf.buildid_mmap2) {
+	if (!symbol_conf.no_buildid_mmap2) {
 		size = snprintf(event->mmap2.filename, sizeof(event->mmap2.filename),
 				"%s%s", machine->mmap_name, kmap->ref_reloc_sym->name) + 1;
 		size = PERF_ALIGN(size, sizeof(u64));
-- 
2.49.0.805.g082f7c87e0-goog

Re: [PATCH v1 5/5] perf record: Make --buildid-mmap the default

[Ian Rogers]

On Wed, Apr 23, 2025 at 11:19 PM Ian Rogers <irogers@google.com> wrote:
>
> Support for build IDs in mmap2 perf events has been present since
> Linux v5.12:
> https://lore.kernel.org/lkml/20210219194619.1780437-1-acme@kernel.org/
> Build ID mmap events avoid the need to inject build IDs for DSO
> touched by samples when perf record completes and can avoid some cases
> of symbol mis-resolution.
>
> Unlike the --buildid-mmap option, this doesn't disable the build ID
> cache but it does disable the processing of samples looking for DSOs
> to inject build IDs for. To disable the build ID cache the -N
> (--no-buildid-cache) option is necessary.
>
> Making this option the default was raised on the list in:
> https://lore.kernel.org/linux-perf-users/CAP-5=fXP7jN_QrGUcd55_QH5J-Y-FCaJ6=NaHVtyx0oyNh8_-Q@mail.gmail.com/
>
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  tools/perf/builtin-record.c        | 35 +++++++++++++++++++-----------
>  tools/perf/util/symbol_conf.h      |  2 +-
>  tools/perf/util/synthetic-events.c | 16 +++++++-------
>  3 files changed, 31 insertions(+), 22 deletions(-)
>
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index ba20bf7c011d..0fcb0f469488 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -169,6 +169,7 @@ struct record {
>         bool                    no_buildid_cache_set;
>         bool                    buildid_all;
>         bool                    buildid_mmap;
> +       bool                    buildid_mmap_set;
>         bool                    timestamp_filename;
>         bool                    timestamp_boundary;
>         bool                    off_cpu;
> @@ -1795,7 +1796,8 @@ record__finish_output(struct record *rec)
>                         data->dir.files[i].size = lseek(data->dir.files[i].fd, 0, SEEK_CUR);
>         }
>
> -       if (!rec->no_buildid) {
> +       /* Buildid scanning disabled or build ID in kernel and synthesized map events. */
> +       if (!rec->no_buildid && !rec->buildid_mmap) {

So I think this is wrong. It matches current behaviors, but it is
wrong. If we don't process the kernel's mmap events the DSOs won't be
loaded and the build ID cache won't contain the DSOs. There is also
the bug that the sample processing to find maps to find DSOs, doesn't
handle call chains. Given the broken nature of the build ID cache I'm
not sure it makes any sense for perf record to be by default
populating it. I think it probably makes sense to consider the default
population a legacy feature and make -N the default along with
--buildid-mmap.

Thanks,
Ian

>                 process_buildids(rec);
>
>                 if (rec->buildid_all)
> @@ -2966,6 +2968,8 @@ static int perf_record_config(const char *var, const char *value, void *cb)
>                         rec->no_buildid = true;
>                 else if (!strcmp(value, "mmap"))
>                         rec->buildid_mmap = true;
> +               else if (!strcmp(value, "no-mmap"))
> +                       rec->buildid_mmap = false;
>                 else
>                         return -1;
>                 return 0;
> @@ -3349,6 +3353,7 @@ static struct record record = {
>                 .ctl_fd_ack          = -1,
>                 .synth               = PERF_SYNTH_ALL,
>         },
> +       .buildid_mmap = true,
>  };
>
>  const char record_callchain_help[] = CALLCHAIN_RECORD_HELP
> @@ -3514,8 +3519,8 @@ static struct option __record_options[] = {
>                    "file", "vmlinux pathname"),
>         OPT_BOOLEAN(0, "buildid-all", &record.buildid_all,
>                     "Record build-id of all DSOs regardless of hits"),
> -       OPT_BOOLEAN(0, "buildid-mmap", &record.buildid_mmap,
> -                   "Record build-id in map events"),
> +       OPT_BOOLEAN_SET(0, "buildid-mmap", &record.buildid_mmap, &record.buildid_mmap_set,
> +                       "Legacy record build-id in map events option which is now the default. Behaves indentically to --no-buildid. Disable with --no-buildid-mmap"),
>         OPT_BOOLEAN(0, "timestamp-filename", &record.timestamp_filename,
>                     "append timestamp to output filename"),
>         OPT_BOOLEAN(0, "timestamp-boundary", &record.timestamp_boundary,
> @@ -4042,19 +4047,23 @@ int cmd_record(int argc, const char **argv)
>                 record.opts.record_switch_events = true;
>         }
>
> +       if (!rec->buildid_mmap) {
> +               pr_debug("Disabling build id in synthesized mmap2 events.\n");
> +               symbol_conf.no_buildid_mmap2 = true;
> +       } else if (rec->buildid_mmap_set) {
> +               /*
> +                * Explicitly passing --buildid-mmap disables buildid processing
> +                * and cache generation.
> +                */
> +               rec->no_buildid = true;
> +       }
> +       if (rec->buildid_mmap && !perf_can_record_build_id()) {
> +               pr_warning("Missing support for build id in kernel mmap events. Disable this warning with --no-buildid-mmap\n");
> +               rec->buildid_mmap = false;
> +       }
>         if (rec->buildid_mmap) {
> -               if (!perf_can_record_build_id()) {
> -                       pr_err("Failed: no support to record build id in mmap events, update your kernel.\n");
> -                       err = -EINVAL;
> -                       goto out_opts;
> -               }
> -               pr_debug("Enabling build id in mmap2 events.\n");
> -               /* Enable mmap build id synthesizing. */
> -               symbol_conf.buildid_mmap2 = true;
>                 /* Enable perf_event_attr::build_id bit. */
>                 rec->opts.build_id = true;
> -               /* Disable build id cache. */
> -               rec->no_buildid = true;
>         }
>
>         if (rec->opts.record_cgroup && !perf_can_record_cgroup()) {
> diff --git a/tools/perf/util/symbol_conf.h b/tools/perf/util/symbol_conf.h
> index cd9aa82c7d5a..7a80d2c14d9b 100644
> --- a/tools/perf/util/symbol_conf.h
> +++ b/tools/perf/util/symbol_conf.h
> @@ -43,7 +43,7 @@ struct symbol_conf {
>                         report_individual_block,
>                         inline_name,
>                         disable_add2line_warn,
> -                       buildid_mmap2,
> +                       no_buildid_mmap2,
>                         guest_code,
>                         lazy_load_kernel_maps,
>                         keep_exited_threads,
> diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
> index 8fb2ea544d3a..f48109c14235 100644
> --- a/tools/perf/util/synthetic-events.c
> +++ b/tools/perf/util/synthetic-events.c
> @@ -532,7 +532,7 @@ int perf_event__synthesize_mmap_events(const struct perf_tool *tool,
>                 event->mmap2.pid = tgid;
>                 event->mmap2.tid = pid;
>
> -               if (symbol_conf.buildid_mmap2)
> +               if (!symbol_conf.no_buildid_mmap2)
>                         perf_record_mmap2__read_build_id(&event->mmap2, machine, false);
>
>                 if (perf_tool__process_synth_event(tool, event, machine, process) != 0) {
> @@ -690,7 +690,7 @@ static int perf_event__synthesize_modules_maps_cb(struct map *map, void *data)
>                 return 0;
>
>         dso = map__dso(map);
> -       if (symbol_conf.buildid_mmap2) {
> +       if (!symbol_conf.no_buildid_mmap2) {
>                 size = PERF_ALIGN(dso__long_name_len(dso) + 1, sizeof(u64));
>                 event->mmap2.header.type = PERF_RECORD_MMAP2;
>                 event->mmap2.header.size = (sizeof(event->mmap2) -
> @@ -734,9 +734,9 @@ int perf_event__synthesize_modules(const struct perf_tool *tool, perf_event__han
>                 .process = process,
>                 .machine = machine,
>         };
> -       size_t size = symbol_conf.buildid_mmap2
> -               ? sizeof(args.event->mmap2)
> -               : sizeof(args.event->mmap);
> +       size_t size = symbol_conf.no_buildid_mmap2
> +               ? sizeof(args.event->mmap)
> +               : sizeof(args.event->mmap2);
>
>         args.event = zalloc(size + machine->id_hdr_size);
>         if (args.event == NULL) {
> @@ -1124,8 +1124,8 @@ static int __perf_event__synthesize_kernel_mmap(const struct perf_tool *tool,
>                                                 struct machine *machine)
>  {
>         union perf_event *event;
> -       size_t size = symbol_conf.buildid_mmap2 ?
> -                       sizeof(event->mmap2) : sizeof(event->mmap);
> +       size_t size = symbol_conf.no_buildid_mmap2 ?
> +                       sizeof(event->mmap) : sizeof(event->mmap2);
>         struct map *map = machine__kernel_map(machine);
>         struct kmap *kmap;
>         int err;
> @@ -1159,7 +1159,7 @@ static int __perf_event__synthesize_kernel_mmap(const struct perf_tool *tool,
>                 event->header.misc = PERF_RECORD_MISC_GUEST_KERNEL;
>         }
>
> -       if (symbol_conf.buildid_mmap2) {
> +       if (!symbol_conf.no_buildid_mmap2) {
>                 size = snprintf(event->mmap2.filename, sizeof(event->mmap2.filename),
>                                 "%s%s", machine->mmap_name, kmap->ref_reloc_sym->name) + 1;
>                 size = PERF_ALIGN(size, sizeof(u64));
> --
> 2.49.0.805.g082f7c87e0-goog
>

Re: [PATCH v1 5/5] perf record: Make --buildid-mmap the default

[Arnaldo Carvalho de Melo]

On Thu, Apr 24, 2025 at 12:20:44AM -0700, Ian Rogers wrote:
> On Wed, Apr 23, 2025 at 11:19 PM Ian Rogers <irogers@google.com> wrote:
> > @@ -1795,7 +1796,8 @@ record__finish_output(struct record *rec)
> >                         data->dir.files[i].size = lseek(data->dir.files[i].fd, 0, SEEK_CUR);
> >         }
> >
> > -       if (!rec->no_buildid) {
> > +       /* Buildid scanning disabled or build ID in kernel and synthesized map events. */
> > +       if (!rec->no_buildid && !rec->buildid_mmap) {
 
> So I think this is wrong. It matches current behaviors, but it is
> wrong. If we don't process the kernel's mmap events the DSOs won't be
> loaded and the build ID cache won't contain the DSOs. There is also
> the bug that the sample processing to find maps to find DSOs, doesn't
> handle call chains. Given the broken nature of the build ID cache I'm
> not sure it makes any sense for perf record to be by default
> populating it. I think it probably makes sense to consider the default
> population a legacy feature and make -N the default along with
> --buildid-mmap.

The first four patches are good fixes/cleanups, so I'm picking them, ok?

- Arnaldo

Re: [PATCH v1 5/5] perf record: Make --buildid-mmap the default

[Arnaldo Carvalho de Melo]

On Fri, Apr 25, 2025 at 11:45:28AM -0300, Arnaldo Carvalho de Melo wrote:
> On Thu, Apr 24, 2025 at 12:20:44AM -0700, Ian Rogers wrote:
> > On Wed, Apr 23, 2025 at 11:19 PM Ian Rogers <irogers@google.com> wrote:
> > > @@ -1795,7 +1796,8 @@ record__finish_output(struct record *rec)
> > >                         data->dir.files[i].size = lseek(data->dir.files[i].fd, 0, SEEK_CUR);
> > >         }
> > >
> > > -       if (!rec->no_buildid) {
> > > +       /* Buildid scanning disabled or build ID in kernel and synthesized map events. */
> > > +       if (!rec->no_buildid && !rec->buildid_mmap) {
>  
> > So I think this is wrong. It matches current behaviors, but it is
> > wrong. If we don't process the kernel's mmap events the DSOs won't be
> > loaded and the build ID cache won't contain the DSOs. There is also
> > the bug that the sample processing to find maps to find DSOs, doesn't
> > handle call chains. Given the broken nature of the build ID cache I'm
> > not sure it makes any sense for perf record to be by default
> > populating it. I think it probably makes sense to consider the default
> > population a legacy feature and make -N the default along with
> > --buildid-mmap.
> 
> The first four patches are good fixes/cleanups, so I'm picking them, ok?

I (and b4) missed v2, looking at it now.

- Arnaldo

Re: [PATCH v1 5/5] perf record: Make --buildid-mmap the default

[Ian Rogers]

On Fri, Apr 25, 2025 at 7:45 AM Arnaldo Carvalho de Melo
<acme@kernel.org> wrote:
>
> On Thu, Apr 24, 2025 at 12:20:44AM -0700, Ian Rogers wrote:
> > On Wed, Apr 23, 2025 at 11:19 PM Ian Rogers <irogers@google.com> wrote:
> > > @@ -1795,7 +1796,8 @@ record__finish_output(struct record *rec)
> > >                         data->dir.files[i].size = lseek(data->dir.files[i].fd, 0, SEEK_CUR);
> > >         }
> > >
> > > -       if (!rec->no_buildid) {
> > > +       /* Buildid scanning disabled or build ID in kernel and synthesized map events. */
> > > +       if (!rec->no_buildid && !rec->buildid_mmap) {
>
> > So I think this is wrong. It matches current behaviors, but it is
> > wrong. If we don't process the kernel's mmap events the DSOs won't be
> > loaded and the build ID cache won't contain the DSOs. There is also
> > the bug that the sample processing to find maps to find DSOs, doesn't
> > handle call chains. Given the broken nature of the build ID cache I'm
> > not sure it makes any sense for perf record to be by default
> > populating it. I think it probably makes sense to consider the default
> > population a legacy feature and make -N the default along with
> > --buildid-mmap.
>
> The first four patches are good fixes/cleanups, so I'm picking them, ok?

Thanks, happy for the clean ups to land. I'm keen to push the needle
on making build IDs the norm in the codebase so if we don't take the
switching on build ID mmap by default change, let me know what I can
do to make it so it can land.

Thanks,
Ian