linux-kernel - [PATCH AUTOSEL for 4.9 014/293] perf annotate: Fix symbolic link of build-id cache

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Date:   Mon, 9 Apr 2018 00:22:59 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        David Ahern <dsahern@...il.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Taeung Song <treeze.taeung@...il.com>,
        Wang Nan <wangnan0@...wei.com>,
        "kernel-team@....com" <kernel-team@....com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.9 014/293] perf annotate: Fix symbolic link of
 build-id cache

From: Namhyung Kim <namhyung@...nel.org>

[ Upstream commit 3619ef76b37d4803bc9daee9d03d82c8526db378 ]

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@...nel.org>
Acked-by: Jiri Olsa <jolsa@...nel.org>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: David Ahern <dsahern@...il.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Taeung Song <treeze.taeung@...il.com>
Cc: Wang Nan <wangnan0@...wei.com>
Cc: kernel-team@....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@...hat.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 tools/perf/util/annotate.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
index a38227eb5450..ffe9153480a8 100644
--- a/tools/perf/util/annotate.c
+++ b/tools/perf/util/annotate.c
@@ -1251,6 +1251,7 @@ 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))
@@ -1270,7 +1271,14 @@ 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 ||
-- 
2.15.1