perf buildid-cache: Add new buildid cache if update target is not cached

Add new buildid cache if the update target file is not cached.

This can happen when an old binary is replaced by new one after caching
the old one. In this case, user sees his operation just failed.

But it does not look straight, since user just pass the binary "path",
not "build-id".

  ----
  # ./perf buildid-cache --add ./perf
  (update ./perf to new binary)
  # ./perf buildid-cache --update ./perf
  ./perf wasn't in the cache
  #
  ----

This patch adds given new binary to cache if the new binary is
not cached. So we'll not see the above error.

  ----
  # ./perf buildid-cache --add ./perf
  (update ./perf to new binary)
  # ./perf buildid-cache --update ./perf
  #
  ----

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Hemant Kumar <hemant@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20150226065440.23912.1494.stgit@localhost.localdomain
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-buildid-cache.txt

@@ -41,9 +41,14 @@ OPTIONS
 --missing=::
 	List missing build ids in the cache for the specified file.
 -u::
---update::
-	Update specified file of the cache. It can be used to update kallsyms
-	kernel dso to vmlinux in order to support annotation.
+--update=::
+	Update specified file of the cache. Note that this doesn't remove
+	older entires since those may be still needed for annotating old
+	(or remote) perf.data. Only if there is already a cache which has
+	exactly same build-id, that is replaced by new one. It can be used
+	to update kallsyms and kernel dso to vmlinux in order to support
+	annotation.
+
 -v::
 --verbose::
 	Be more verbose.

tools/perf/builtin-buildid-cache.c

@@ -255,7 +255,7 @@ static int build_id_cache__update_file(const char *filename)
 	u8 build_id[BUILD_ID_SIZE];
 	char sbuild_id[BUILD_ID_SIZE * 2 + 1];
 
-	int err;
+	int err = 0;
 
 	if (filename__read_build_id(filename, &build_id, sizeof(build_id)) < 0) {
 		pr_debug("Couldn't read a build-id in %s\n", filename);
@@ -263,7 +263,9 @@ static int build_id_cache__update_file(const char *filename)
 	}
 
 	build_id__sprintf(build_id, sizeof(build_id), sbuild_id);
-	err = build_id_cache__remove_s(sbuild_id);
+	if (build_id_cache__cached(sbuild_id))
+		err = build_id_cache__remove_s(sbuild_id);
+
 	if (!err)
 		err = build_id_cache__add_s(sbuild_id, filename, false, false);
 

tools/perf/util/build-id.c

@@ -352,6 +352,18 @@ static int build_id_cache__add_b(const u8 *build_id, size_t build_id_size,
 	return build_id_cache__add_s(sbuild_id, name, is_kallsyms, is_vdso);
 }
 
+bool build_id_cache__cached(const char *sbuild_id)
+{
+	bool ret = false;
+	char *filename = build_id__filename(sbuild_id, NULL, 0);
+
+	if (filename && !access(filename, F_OK))
+		ret = true;
+	free(filename);
+
+	return ret;
+}
+
 int build_id_cache__remove_s(const char *sbuild_id)
 {
 	const size_t size = PATH_MAX;

tools/perf/util/build-id.h

@@ -22,6 +22,7 @@ bool perf_session__read_build_ids(struct perf_session *session, bool with_hits);
 int perf_session__write_buildid_table(struct perf_session *session, int fd);
 int perf_session__cache_build_ids(struct perf_session *session);
 
+bool build_id_cache__cached(const char *sbuild_id);
 int build_id_cache__add_s(const char *sbuild_id,
 			  const char *name, bool is_kallsyms, bool is_vdso);
 int build_id_cache__remove_s(const char *sbuild_id);