[PATCH v6 6/8] perf: build-id: extend build_id_cache__find_debug() to find local debugging vdso

[Changbin Du]

Just like vmlinux, try to search vdso in predefined paths when collecting
build-ids. The searched paths usually have debugging info.

For example, the vdso can be found in
/lib/modules/<version>/build/arch/x86/entry/vdso/vdso*.so.dbg for local
build on x86.

Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Signed-off-by: Changbin Du <changbin.du@xxxxxxxxxx>

---
v3:
  - continue to try build_id_cache__find_debug_normal() if
    build_id_cache__find_debug_vdso() failed.
v2:
  - Searching the vdso in record stage instead of report. So the debugging
    vdso will be in build-id cache. This is friendly for cross-machine
    analysis.
---
 tools/perf/util/build-id.c | 48 ++++++++++++++++++++++++++++++++++----
 tools/perf/util/symbol.c   | 17 ++++++++++++++
 tools/perf/util/symbol.h   |  1 +
 3 files changed, 62 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index 5bda47de5cf2..67f88b492279 100644
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -593,9 +593,8 @@ static int build_id_cache__add_sdt_cache(const char *sbuild_id,
 #define build_id_cache__add_sdt_cache(sbuild_id, realname, nsi) (0)
 #endif
 
-static char *build_id_cache__find_debug(const char *sbuild_id,
-					struct nsinfo *nsi,
-					const char *root_dir)
+static char *build_id_cache__find_debug_normal(const char *sbuild_id,
+				struct nsinfo *nsi, const char *root_dir)
 {
 	const char *dirname = "/usr/lib/debug/.build-id/";
 	char *realname = NULL;
@@ -646,6 +645,47 @@ static char *build_id_cache__find_debug(const char *sbuild_id,
 	return realname;
 }
 
+static char *build_id_cache__find_debug_vdso(const char *sbuild_id)
+{
+	char sbuild_id_tmp[SBUILD_ID_SIZE];
+	struct build_id bid;
+	int i, ret = 0;
+
+	if (!vdso_paths.paths)
+		return NULL;
+
+	pr_debug("Looking at the vdso_path (%d entries long)\n",
+		 vdso_paths.nr_entries + 1);
+
+	for (i = 0; i < vdso_paths.nr_entries; ++i) {
+		ret = filename__read_build_id(vdso_paths.paths[i], &bid);
+		if (ret < 0)
+			continue;
+
+		build_id__sprintf(&bid, sbuild_id_tmp);
+		if (!strcmp(sbuild_id, sbuild_id_tmp)) {
+			pr_debug("Found debugging vdso %s\n", vdso_paths.paths[i]);
+			return strdup(vdso_paths.paths[i]);
+		}
+	}
+
+	return NULL;
+}
+
+static char *build_id_cache__find_debug(const char *sbuild_id,
+					struct nsinfo *nsi,
+					bool is_vdso,
+					const char *root_dir)
+{
+	char *name = NULL;
+
+	if (is_vdso)
+		name = build_id_cache__find_debug_vdso(sbuild_id);
+	if (!name)
+		name = build_id_cache__find_debug_normal(sbuild_id, nsi, root_dir);
+	return name;
+}
+
 int
 build_id_cache__add(const char *sbuild_id, const char *name, const char *realname,
 		    struct nsinfo *nsi, bool is_kallsyms, bool is_vdso,
@@ -702,7 +742,7 @@ build_id_cache__add(const char *sbuild_id, const char *name, const char *realnam
 	 * symtab.
 	 */
 	if (!is_kallsyms && strncmp(".ko", name + strlen(name) - 3, 3)) {
-		debugfile = build_id_cache__find_debug(sbuild_id, nsi, root_dir);
+		debugfile = build_id_cache__find_debug(sbuild_id, nsi, is_vdso, root_dir);
 		if (debugfile) {
 			zfree(&filename);
 			if (asprintf(&filename, "%s/%s", dir_name,
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 6bf75c98e1f2..8e982e68b717 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -49,6 +49,7 @@ static int dso__load_vdso_sym(struct dso *dso, struct map *map);
 static bool symbol__is_idle(const char *name);
 
 struct dso_filename_paths vmlinux_paths;
+struct dso_filename_paths vdso_paths;
 
 struct symbol_conf symbol_conf = {
 	.nanosecs		= false,
@@ -2303,6 +2304,16 @@ struct dso_filename_pattern vmlinux_patterns[] = {
 	{"/usr/lib/debug/boot/vmlinux-%s.debug", 1},
 };
 
+struct dso_filename_pattern vdso_patterns[] = {
+	{"/lib/modules/%s/vdso/vdso.so", 1},
+	{"/lib/modules/%s/vdso/vdso64.so", 1},
+	{"/lib/modules/%s/vdso/vdso32.so", 1},
+	{"/lib/modules/%s/build/arch/%s/vdso/vdso.so.dbg", 2},
+	{"/lib/modules/%s/build/arch/%s/kernel/vdso/vdso.so.dbg", 2},
+	{"/lib/modules/%s/build/arch/%s/entry/vdso/vdso32.so.dbg", 2},
+	{"/lib/modules/%s/build/arch/%s/entry/vdso/vdso64.so.dbg", 2},
+};
+
 static int dso_filename_path__add(struct dso_filename_paths *paths, const char *new_entry)
 {
 	paths->paths[paths->nr_entries] = strdup(new_entry);
@@ -2565,6 +2576,11 @@ int symbol__init(struct perf_env *env)
 		return -1;
 	}
 
+	if (dso_filename_path__init(&vdso_paths, vdso_patterns,
+				    ARRAY_SIZE(vdso_patterns), env) < 0) {
+		return -1;
+	}
+
 	if (symbol_conf.field_sep && *symbol_conf.field_sep == '.') {
 		pr_err("'.' is the only non valid --field-separator argument\n");
 		return -1;
@@ -2641,6 +2657,7 @@ void symbol__exit(void)
 	intlist__delete(symbol_conf.pid_list);
 	intlist__delete(symbol_conf.addr_list);
 	dso_filename_path__exit(&vmlinux_paths);
+	dso_filename_path__exit(&vdso_paths);
 	symbol_conf.sym_list = symbol_conf.dso_list = symbol_conf.comm_list = NULL;
 	symbol_conf.bt_stop_list = NULL;
 	symbol_conf.initialized = false;
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index 30056884945b..08c339594d4e 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -107,6 +107,7 @@ struct dso_filename_paths {
 };
 
 extern struct dso_filename_paths vmlinux_paths;
+extern struct dso_filename_paths vdso_paths;
 
 static inline void *symbol__priv(struct symbol *sym)
 {
-- 
2.34.1