linux-kernel - [PATCH 2/6] perf script python: Use PyBytes for attr in trace-event-python

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Date:   Wed, 23 Jan 2019 16:52:25 -0800
From:   Tony Jones <tonyj@...e.de>
To:     linux-kernel@...r.kernel.org
Cc:     Seeteena Thoufeek <s1seetee@...ux.vnet.ibm.com>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>, Jonathan Corbet <corbet@....net>,
        linux-perf-users@...r.kernel.org, Tony Jones <tonyj@...e.de>,
        Jaroslav Škarvada <jskarvad@...hat.com>
Subject: [PATCH 2/6] perf script python: Use PyBytes for attr in trace-event-python

With Python3.  PyUnicode_FromStringAndSize is unsafe to call on attr and will
return NULL.  Use _PyBytes_FromStringAndSize (as with raw_buf).

Below is the observed behavior without the fix.  Note it is first necessary
to apply the prior fix (Add trace_context extension module to sys,modules):

# ldd /usr/bin/perf | grep -i python
        libpython3.6m.so.1.0 => /usr/lib64/libpython3.6m.so.1.0 (0x00007f8e1dfb2000)

# perf record -e raw_syscalls:sys_enter /bin/false
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.018 MB perf.data (21 samples) ]

# perf script -g python | cat
generated Python script: perf-script.py

# perf script -s ./perf-script.py
in trace_begin
Segmentation fault (core dumped)

Signed-off-By: Tony Jones <tonyj@...e.de>
Cc: Jaroslav Škarvada <jskarvad@...hat.com>
Fixes: 66dfdff03d196e51322c6a85c0d8db8bb2bdd655
---
 tools/perf/util/scripting-engines/trace-event-python.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/tools/perf/util/scripting-engines/trace-event-python.c b/tools/perf/util/scripting-engines/trace-event-python.c
index 40300d8e80a7..777c97b13905 100644
--- a/tools/perf/util/scripting-engines/trace-event-python.c
+++ b/tools/perf/util/scripting-engines/trace-event-python.c
@@ -733,8 +733,7 @@ static PyObject *get_perf_sample_dict(struct perf_sample *sample,
 		Py_FatalError("couldn't create Python dictionary");
 
 	pydict_set_item_string_decref(dict, "ev_name", _PyUnicode_FromString(perf_evsel__name(evsel)));
-	pydict_set_item_string_decref(dict, "attr", _PyUnicode_FromStringAndSize(
-			(const char *)&evsel->attr, sizeof(evsel->attr)));
+	pydict_set_item_string_decref(dict, "attr", _PyBytes_FromStringAndSize((const char *)&evsel->attr, sizeof(evsel->attr)));
 
 	pydict_set_item_string_decref(dict_sample, "pid",
 			_PyLong_FromLong(sample->pid));
-- 
2.20.1