perf annotate: Fix symbolic link of build-id cache

The commit 6ebd2547dd24 ("perf annotate: Fix a bug following symbolic
link of a build-id file") changed to use dirname to follow the symlink.
But it only considers new-style build-id cache names so old names fail
on readlink() and force to use system path which might not available.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Taeung Song <treeze.taeung@gmail.com>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: kernel-team@lge.com
Fixes: 6ebd2547dd24 ("perf annotate: Fix a bug following symbolic link of a build-id file")
Link: http://lkml.kernel.org/r/20170608073109.30699-2-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
index 1367d7e35242..df4486c3a2fa 100644
--- a/tools/perf/util/annotate.c
+++ b/tools/perf/util/annotate.c
@@ -1321,6 +1321,7 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
         char linkname[PATH_MAX];
         char *build_id_filename;
         char *build_id_path = NULL;
+        char *pos;
 
         if (dso->symtab_type == DSO_BINARY_TYPE__KALLSYMS &&
             !dso__is_kcore(dso))
@@ -1340,7 +1341,14 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
         if (!build_id_path)
                 return -1;
 
-        dirname(build_id_path);
+        /*
+         * old style build-id cache has name of XX/XXXXXXX.. while
+         * new style has XX/XXXXXXX../{elf,kallsyms,vdso}.
+         * extract the build-id part of dirname in the new style only.
+         */
+        pos = strrchr(build_id_path, '/');
+        if (pos && strlen(pos) < SBUILD_ID_SIZE - 2)
+                dirname(build_id_path);
 
         if (dso__is_kcore(dso) ||
             readlink(build_id_path, linkname, sizeof(linkname)) < 0 ||