perf python: Add support to resolve tracepoint fields

Adding tp_getattro callback for sample event. It resolves tracepoint
fields in runtime.

It's now possible to access tracepoint fields in normal fashion like
hardcoded ones (see the example in the next patch).

Reported-and-Tested-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1468148882-10362-9-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/python.c

@@ -290,6 +290,97 @@ static PyObject *pyrf_sample_event__repr(struct pyrf_event *pevent)
 	return ret;
 }
 
+static bool is_tracepoint(struct pyrf_event *pevent)
+{
+	return pevent->evsel->attr.type == PERF_TYPE_TRACEPOINT;
+}
+
+static int is_printable_array(char *p, unsigned int len)
+{
+	unsigned int i;
+
+	for (i = 0; i < len; i++) {
+		if (!isprint(p[i]) && !isspace(p[i]))
+			return 0;
+	}
+
+	return 1;
+}
+
+static PyObject*
+tracepoint_field(struct pyrf_event *pe, struct format_field *field)
+{
+	struct pevent *pevent = field->event->pevent;
+	void *data = pe->sample.raw_data;
+	PyObject *ret = NULL;
+	unsigned long long val;
+	unsigned int offset, len;
+
+	if (field->flags & FIELD_IS_ARRAY) {
+		offset = field->offset;
+		len    = field->size;
+		if (field->flags & FIELD_IS_DYNAMIC) {
+			val     = pevent_read_number(pevent, data + offset, len);
+			offset  = val;
+			len     = offset >> 16;
+			offset &= 0xffff;
+		}
+		if (field->flags & FIELD_IS_STRING &&
+		    is_printable_array(data + offset, len)) {
+			ret = PyString_FromString((char *)data + offset);
+		} else {
+			ret = PyByteArray_FromStringAndSize((const char *) data + offset, len);
+			field->flags &= ~FIELD_IS_STRING;
+		}
+	} else {
+		val = pevent_read_number(pevent, data + field->offset,
+					 field->size);
+		if (field->flags & FIELD_IS_POINTER)
+			ret = PyLong_FromUnsignedLong((unsigned long) val);
+		else if (field->flags & FIELD_IS_SIGNED)
+			ret = PyLong_FromLong((long) val);
+		else
+			ret = PyLong_FromUnsignedLong((unsigned long) val);
+	}
+
+	return ret;
+}
+
+static PyObject*
+get_tracepoint_field(struct pyrf_event *pevent, PyObject *attr_name)
+{
+	const char *str = PyString_AsString(PyObject_Str(attr_name));
+	struct perf_evsel *evsel = pevent->evsel;
+	struct format_field *field;
+
+	if (!evsel->tp_format) {
+		struct event_format *tp_format;
+
+		tp_format = trace_event__tp_format_id(evsel->attr.config);
+		if (!tp_format)
+			return NULL;
+
+		evsel->tp_format = tp_format;
+	}
+
+	field = pevent_find_any_field(evsel->tp_format, str);
+	if (!field)
+		return NULL;
+
+	return tracepoint_field(pevent, field);
+}
+
+static PyObject*
+pyrf_sample_event__getattro(struct pyrf_event *pevent, PyObject *attr_name)
+{
+	PyObject *obj = NULL;
+
+	if (is_tracepoint(pevent))
+		obj = get_tracepoint_field(pevent, attr_name);
+
+	return obj ?: PyObject_GenericGetAttr((PyObject *) pevent, attr_name);
+}
+
 static PyTypeObject pyrf_sample_event__type = {
 	PyVarObject_HEAD_INIT(NULL, 0)
 	.tp_name	= "perf.sample_event",
@@ -298,6 +389,7 @@ static PyTypeObject pyrf_sample_event__type = {
 	.tp_doc		= pyrf_sample_event__doc,
 	.tp_members	= pyrf_sample_event__members,
 	.tp_repr	= (reprfunc)pyrf_sample_event__repr,
+	.tp_getattro	= (getattrofunc) pyrf_sample_event__getattro,
 };
 
 static char pyrf_context_switch_event__doc[] = PyDoc_STR("perf context_switch event object.");