linux-kernel - [PATCH 4.9 068/241] perf annotate: Fix a bug following symbolic link of a build-id file

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Message-Id: <20180319180754.020953503@linuxfoundation.org>
Date:   Mon, 19 Mar 2018 19:05:33 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Taeung Song <treeze.taeung@...il.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Wang Nan <wangnan0@...wei.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.9 068/241] perf annotate: Fix a bug following symbolic link of a build-id file

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Taeung Song <treeze.taeung@...il.com>


[ Upstream commit 6ebd2547dd24daf95a21b2bc59931de8502afcc3 ]

It is wrong way to read link name from a build-id file.  Because a
build-id file is not anymore a symbolic link but build-id directory of
it is symbolic link, so fix it.

For example, if build-id file name gotten from
dso__build_id_filename() is as below,

  /root/.debug/.build-id/4f/75c7d197c951659d1c1b8b5fd49bcdf8f3f8b1/elf

To correctly read link name of build-id, use the build-id dir path that
is a symbolic link, instead of the above build-id file name like below.

  /root/.debug/.build-id/4f/75c7d197c951659d1c1b8b5fd49bcdf8f3f8b1

Signed-off-by: Taeung Song <treeze.taeung@...il.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Wang Nan <wangnan0@...wei.com>
Link: http://lkml.kernel.org/r/1490598638-13947-2-git-send-email-treeze.taeung@gmail.com
Fixes: 01412261d994 ("perf buildid-cache: Use path/to/bin/buildid/elf instead of path/to/bin/buildid")
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 tools/perf/util/annotate.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/tools/perf/util/annotate.c
+++ b/tools/perf/util/annotate.c
@@ -1250,6 +1250,7 @@ static int dso__disassemble_filename(str
 {
 	char linkname[PATH_MAX];
 	char *build_id_filename;
+	char *build_id_path = NULL;
 
 	if (dso->symtab_type == DSO_BINARY_TYPE__KALLSYMS &&
 	    !dso__is_kcore(dso))
@@ -1265,8 +1266,14 @@ static int dso__disassemble_filename(str
 		goto fallback;
 	}
 
+	build_id_path = strdup(filename);
+	if (!build_id_path)
+		return -1;
+
+	dirname(build_id_path);
+
 	if (dso__is_kcore(dso) ||
-	    readlink(filename, linkname, sizeof(linkname)) < 0 ||
+	    readlink(build_id_path, linkname, sizeof(linkname)) < 0 ||
 	    strstr(linkname, DSO__NAME_KALLSYMS) ||
 	    access(filename, R_OK)) {
 fallback:
@@ -1278,6 +1285,7 @@ fallback:
 		__symbol__join_symfs(filename, filename_size, dso->long_name);
 	}
 
+	free(build_id_path);
 	return 0;
 }