perf python: Add support to access tracepoint fields

Jirka reported that python code returns all arrays as strings. This makes impossible to get all items for byte array tracepoint field containing 0x00 value item.

Fixing this by scanning full length of the array and returning it as PyByteArray object in case non printable byte is found.

Link http://lkml.kernel.org/n/[email protected] open here

Signed-off-by Jiri Olsa <[email protected]>

---
.../util/scripting-engines/trace-event-python.c | 39 ++++++++++++++++++----

1 file changed, 33 insertions(+), 6 deletions(-)

tools/perf/util/scripting-engines/trace-event-python.c +33 -6

index 6ac6b7a33f42..7bd6da80533e 100644
@@ -386,6 +386,21 @@ exit:
 	return pylist;
 }
 
+static int is_printable_array(char *p, unsigned int len)
+{
+	unsigned int i;
+
+	if (!p || !len || p[len - 1] != 0)
+		return 0;
+
+	len--;
+
+	for (i = 0; i < len; i++) {
+		if (!isprint(p[i]) && !isspace(p[i]))
+			return 0;
+	}
+	return 1;
+}
 
 static void python_process_tracepoint(struct perf_sample *sample,
 				      struct perf_evsel *evsel,

@@ -457,14 +472,26 @@ static void python_process_tracepoint(struct perf_sample *sample,
 		pydict_set_item_string_decref(dict, "common_callchain", callchain);
 	}
 	for (field = event->format.fields; field; field = field->next) {
-		if (field->flags & FIELD_IS_STRING) {
-			int offset;
+		unsigned int offset, len;
+		unsigned long long val;
+
+		if (field->flags & FIELD_IS_ARRAY) {
+			offset = field->offset;
+			len    = field->size;
 			if (field->flags & FIELD_IS_DYNAMIC) {
-				offset = *(int *)(data + field->offset);
+				val     = pevent_read_number(scripting_context->pevent,
+							     data + offset, len);
+				offset  = val;
+				len     = offset >> 16;
 				offset &= 0xffff;
-			} else
-				offset = field->offset;
-			obj = PyString_FromString((char *)data + offset);
+			}
+			if (field->flags & FIELD_IS_STRING &&
+			    is_printable_array(data + offset, len)) {
+				obj = PyString_FromString((char *) data + offset);
+			} else {
+				obj = PyByteArray_FromStringAndSize((const char *) data + offset, len);
+				field->flags &= ~FIELD_IS_STRING;
+			}
 		} else { /* FIELD_IS_NUMERIC */
 			obj = get_field_numeric_entry(event, field, data);
 		}

Signature · 1 line

2.4.11

It's used from 2 objects in perf, so it's better
to keep just one copy.

Link http://lkml.kernel.org/n/[email protected] open here

Signed-off-by Jiri Olsa <[email protected]>

Add automated test for is_printable_array function.

Link http://lkml.kernel.org/n/[email protected] open here

Signed-off-by Jiri Olsa <[email protected]>

---

tools/perf/tests/Build                |  1 +
tools/perf/tests/builtin-test.c       |  4 ++++
tools/perf/tests/is_printable_array.c | 36 +++++++++++++++++++++++++++++++++++
tools/perf/tests/tests.h              |  1 +
4 files changed, 42 insertions(+)

create mode 100644 tools/perf/tests/is_printable_array.c

tools/perf/tests/Build +0 -0

index 4158422cc2a6..cb20ae1c0d35 100644
@@ -40,6 +40,7 @@ perf-y += event_update.o

perf-y += event-times.o
perf-y += backward-ring-buffer.o
perf-y += sdt.o
+perf-y += is_printable_array.o

$(OUTPUT)tests/llvm-src-base.c: tests/bpf-script-example.c tests/Build

	$(call rule_mkdir)

tools/perf/tests/builtin-test.c +4 -0

index 4dd2d050788a..10eb30686c9c 100644
@@ -222,6 +222,10 @@ static struct test generic_tests[] = {
 		.func = test__sdt_event,
 	},
 	{
+		.desc = "Test is_printable_array function",
+		.func = test__is_printable_array,
+	},
+	{
 		.func = NULL,
 	},
 };

tools/perf/tests/is_printable_array.c new file +6 -0

new file mode 100644
index 000000000000..42e13393e502
@@ -0,0 +1,36 @@
+#include <linux/compiler.h>
+#include "tests.h"
+#include "debug.h"
+#include "util.h"
+
+int test__is_printable_array(int subtest __maybe_unused)

Quoted 16 lines

tools/perf/tests/is_printable_array.c new file +10 -0

new file mode 100644
index 000000000000..42e13393e502
@@ -0,0 +1,36 @@
+#include <linux/compiler.h>
+#include "tests.h"
+#include "debug.h"
+#include "util.h"
+
+int test__is_printable_array(int subtest __maybe_unused)
+{
+	char buf1[] = { 'k', 'r', 4, 'v', 'a', 0 };
+	char buf2[] = { 'k', 'r', 'a', 'v', 4, 0 };
+	struct {

tools/perf/tests/is_printable_array.c line 16

Quoted 6 lines

tools/perf/tests/is_printable_array.c new file +6 -0

+		char		*buf;
+		unsigned int	 len;
+		int		 ret;
+	} t[] = {
+		{ (char *) "krava",	sizeof("krava"),	1 },
+		{ (char *) "krava",	sizeof("krava") - 1,	0 },

"a cow" ? Really? :))

SNIP

Quoted 16 lines

Quoted 16 lines

tools/perf/tests/is_printable_array.c new file +10 -0

new file mode 100644
index 000000000000..42e13393e502
@@ -0,0 +1,36 @@
+#include <linux/compiler.h>
+#include "tests.h"
+#include "debug.h"
+#include "util.h"
+
+int test__is_printable_array(int subtest __maybe_unused)
+{
+	char buf1[] = { 'k', 'r', 4, 'v', 'a', 0 };
+	char buf2[] = { 'k', 'r', 'a', 'v', 4, 0 };
+	struct {

Quoted 8 lines

tools/perf/tests/is_printable_array.c line 16

Quoted 6 lines

tools/perf/tests/is_printable_array.c new file +6 -0

+		char		*buf;
+		unsigned int	 len;
+		int		 ret;
+	} t[] = {
+		{ (char *) "krava",	sizeof("krava"),	1 },
+		{ (char *) "krava",	sizeof("krava") - 1,	0 },

"a cow" ? Really? :))

yea, trying to force it as 'perf animal' instead of that pony stuff ;-)

http://www.brendangregg.com/blog/2015-07-08/choosing-a-linux-tracer.html