linux-kernel - [PATCH] perf symbols: take in account symfs setting when reading file build ID

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Date:   Mon,  6 Feb 2017 15:48:28 -0800
From:   Victor Kamensky <kamensky@...co.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-kernel@...r.kernel.org
Cc:     xe-linux-external@...co.com, Dima Kogan <dima@...retsauce.net>,
        Kan Liang <kan.liang@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
        Wang Nan <wangnan0@...wei.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Chris Phlipot <cphlipot0@...il.com>,
        He Kuang <hekuang@...wei.com>,
        Adrian Hunter <adrian.hunter@...el.com>
Subject: [PATCH] perf symbols: take in account symfs setting when reading file build ID

After 5baecbc 'perf symbols: we can now read separate debug-info files based on
a build ID' and when --symfs option is used perf failed to pick up symbols for
file with the same name between host and sysroot specified by --symfs option.
One can see message like this:

bin/bash with build id 26f0062cb6950d4d1ab0fd9c43eae8b10ca42062 not found, continuing without symbols

It happens because code added by 5baecbc opens files directly by dso->long_name
without symbol_conf.symfs consideration, which as result picks one from the
host. It reads its build ID and later even code finds another proper file in
directory pointed by --symfs perf ignores it because build id mismatches.

Fix is to use __symbol__join_symfs to adjust file name according to --symfs
setting. If no --symfs passed the operation would noop and picks the same host
file as before.

Also note in latter tree after 5baecbc commit additional check for
'!dso->has_build_id' was added, so to observe error condition 'perf record'
should run with --no-buildid, so perf.data itself would not have build id for
target binary in buildid perf section and 'perf report' will pass
'!dso->has_build_id' condition. Or target binary should not have build id, but
the same binary on host has build id, again '!dso->has_build_id' will pass in
this case and incorrect build id could be read if --symfs is used.

Fixes: 5baecbcd9c9a ("perf symbols: we can now read separate debug-info files based on a build ID")
Signed-off-by: Victor Kamensky <kamensky@...co.com>
Cc: xe-linux-external@...co.com
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Dima Kogan <dima@...retsauce.net>
Cc: Kan Liang <kan.liang@...el.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: Wang Nan <wangnan0@...wei.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Chris Phlipot <cphlipot0@...il.com>
Cc: He Kuang <hekuang@...wei.com>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: linux-kernel@...r.kernel.org
---
 tools/perf/util/symbol.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index dc93940..70e389bc 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1460,9 +1460,11 @@ int dso__load(struct dso *dso, struct map *map)
 	 * DSO_BINARY_TYPE__BUILDID_DEBUGINFO to work
 	 */
 	if (!dso->has_build_id &&
-	    is_regular_file(dso->long_name) &&
-	    filename__read_build_id(dso->long_name, build_id, BUILD_ID_SIZE) > 0)
+	    is_regular_file(dso->long_name)) {
+	    __symbol__join_symfs(name, PATH_MAX, dso->long_name);
+	    if (filename__read_build_id(name, build_id, BUILD_ID_SIZE) > 0)
 		dso__set_build_id(dso, build_id);
+	}

 	/*
 	 * Iterate over candidate debug images.
-- 
2.7.4