[PATCH 0/1] perf script python: Garbled text in tracepoint fields

[PATCH 0/1] perf script python: Garbled text in tracepoint fields

[Arun Kalyanasundaram]

The string stored in some of the fields of tracepoint handlers has unused non-ascii characters beyond the first null ternimating character. As a result the call to is_printable_array fails and the python handlers receive the entire field as a byte array instead of just the subset of chars that represent the string.

This change calls is_printable_array with the correct length of the string instead of the entire field size.

Bug report: lkml/2017/7/18/228

Arun Kalyanasundaram (1):
  perf script python: Garbled text in tracepoint fields

 tools/perf/util/scripting-engines/trace-event-python.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

-- 
2.14.0.434.g98096fd7a8-goog

[PATCH 1/1] perf script python: Garbled text in tracepoint fields

[Arun Kalyanasundaram]

Pass the exact length of the string to is_printable_array instead of the
entire field size.

Signed-off-by: Arun Kalyanasundaram <arunkaly@google.com>
---
 tools/perf/util/scripting-engines/trace-event-python.c | 9 +++++++--
 1 file changed, 7 insertions(+), 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 c7187f067d31..45cc0c6635bb 100644
--- a/tools/perf/util/scripting-engines/trace-event-python.c
+++ b/tools/perf/util/scripting-engines/trace-event-python.c
@@ -601,6 +601,7 @@ static void python_process_tracepoint(struct perf_sample *sample,
 	for (field = event->format.fields; field; field = field->next) {
 		unsigned int offset, len;
 		unsigned long long val;
+		char *end_ptr = NULL;
 
 		if (field->flags & FIELD_IS_ARRAY) {
 			offset = field->offset;
@@ -612,8 +613,12 @@ static void python_process_tracepoint(struct perf_sample *sample,
 				len     = offset >> 16;
 				offset &= 0xffff;
 			}
-			if (field->flags & FIELD_IS_STRING &&
-			    is_printable_array(data + offset, len)) {
+			/* field may contain unused chars after the null char */
+			if (field->flags & FIELD_IS_STRING)
+				end_ptr = memchr(data + offset, '\0', len);
+			if (end_ptr &&
+			    is_printable_array(data + offset,
+				(int)(end_ptr - ((char *)data + offset)) + 1)) {
 				obj = PyString_FromString((char *) data + offset);
 			} else {
 				obj = PyByteArray_FromStringAndSize((const char *) data + offset, len);
-- 
2.14.0.434.g98096fd7a8-goog