linux-kernel - [PATCH] perf: intel-pt: Fix seg fault tracing transactions

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Date:	Mon, 18 Apr 2016 13:57:48 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org,
	Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH] perf: intel-pt: Fix seg fault tracing transactions

Tracing a workload that uses transactions gave a
seg fault as follows:

perf record -e intel_pt// workload
perf report
Program received signal SIGSEGV, Segmentation fault.
0x000000000054b58c in intel_pt_reset_last_branch_rb (ptq=0x1a36110)
	at util/intel-pt.c:929
929 ptq->last_branch_rb->nr = 0;
(gdb) p ptq->last_branch_rb
$1 = (struct branch_stack *) 0x0
(gdb) up
1148 intel_pt_reset_last_branch_rb(ptq);
(gdb) l
1143 if (ret)
1144 pr_err("Intel Processor Trace: failed to deliver transaction event
1145 ret);
1146
1147 if (pt->synth_opts.callchain)
1148 intel_pt_reset_last_branch_rb(ptq);
1149
1150 return ret;
1151 }
1152
(gdb) p pt->synth_opts.callchain
$2 = true
(gdb)
(gdb) bt
 #0 0x000000000054b58c in intel_pt_reset_last_branch_rb (ptq=0x1a36110)
 #1 0x000000000054c1e0 in intel_pt_synth_transaction_sample (ptq=0x1a36110)
 #2 0x000000000054c5b2 in intel_pt_sample (ptq=0x1a36110)

Caused by checking the 'callchain' flag when it should
have been the 'last_branch' flag.  Fix that.

Reported-by: Andi Kleen <ak@...ux.intel.com>
Fixes: f14445ee72c5 ("perf intel-pt: Support generating branch stack")
Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
Cc: stable@...r.kernel.org # v4.4+
---
 tools/perf/util/intel-pt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
index ddec87f6e616..137196990012 100644
--- a/tools/perf/util/intel-pt.c
+++ b/tools/perf/util/intel-pt.c
@@ -1144,7 +1144,7 @@ static int intel_pt_synth_transaction_sample(struct intel_pt_queue *ptq)
 		pr_err("Intel Processor Trace: failed to deliver transaction event, error %d\n",
 		       ret);
 
-	if (pt->synth_opts.callchain)
+	if (pt->synth_opts.last_branch)
 		intel_pt_reset_last_branch_rb(ptq);
 
 	return ret;
-- 
1.9.1