linux-kernel - [PATCH 1/1] Fixes: cfc8874a485 ("perf script: Process cpu/threads maps")

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Date:	Tue,  8 Mar 2016 21:11:54 -0800
From:	Chris Phlipot <cphlipot0@...il.com>
To:	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Chris Phlipot <cphlipot0@...il.com>
Subject: [PATCH 1/1] Fixes: cfc8874a485 ("perf script: Process cpu/threads maps")

fix the perf script python database export crash.
Remove the union in evsel so that the database id and priv pointer can be
used simultainously without conflicting and crashing.

Detailed Description for the fixed bug follows:

perf script crashes with a segmentaiton fault on user space tool version
4.5.rc7.ge2857b when using the python database export API. It works
properly in 4.4 and prior versions.

the crash fist appeared in
cfc8874a485 ("perf script: Process cpu/threads maps")

How to reprodcue the bug:

remove any temporary files left over from a previous crash
(if you have already attemped to reproduce the bug):
$ rm -r test_db-perf-data
$ dropdb test_db

$ ./perf record timeout 1 yes >/dev/null
$ ./perf script -s scripts/python/export-to-postgresql.py test_db

Stack Trace:
Program received signal SIGSEGV, Segmentation fault.
__GI___libc_free (mem=0x1) at malloc.c:2929
2929	malloc.c: No such file or directory.
(gdb) bt
    at util/stat.c:122
    argv=<optimized out>, prefix=<optimized out>) at builtin-script.c:2231
    argc=argc@...ry=4, argv=argv@...ry=0x7fffffffdf70) at perf.c:390
    at perf.c:451

Signed-off-by: Chris Phlipot <cphlipot0@...il.com>
---
 tools/perf/util/evsel.h | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index 8e75434..4d8037a 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -93,10 +93,8 @@ struct perf_evsel {
 	const char		*unit;
 	struct event_format	*tp_format;
 	off_t			id_offset;
-	union {
-		void		*priv;
-		u64		db_id;
-	};
+	void			*priv;
+	u64			db_id;
 	struct cgroup_sel	*cgrp;
 	void			*handler;
 	struct cpu_map		*cpus;
-- 
1.9.1