Re: [PATCH 1/3] perf script python: Fix string vs byte array resolving

From: Jiri Pirko <jiri@mellanox.com>
To: Jiri Olsa <jolsa@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
	"Steven Rostedt (Red Hat)" <rostedt@goodmis.org>,
	lkml <linux-kernel@vger.kernel.org>,
	David Ahern <dsahern@gmail.com>, Ingo Molnar <mingo@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCH 1/3] perf script python: Fix string vs byte array resolving
Date: Fri, 15 Jul 2016 17:51:10 +0200	[thread overview]
Message-ID: <20160715155110.GF1983@nanopsycho.orion> (raw)
In-Reply-To: <1468567797-27564-2-git-send-email-jolsa@kernel.org>

Fri, Jul 15, 2016 at 09:29:55AM CEST, jolsa@kernel.org wrote:
>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.
>
>Cc: Steven Rostedt (Red Hat) <rostedt@goodmis.org>
>Cc: Jiri Pirko <jiri@mellanox.com>
>Link: http://lkml.kernel.org/n/tip-22f4vhhz5uytegkggy1on8u3@git.kernel.org
>Signed-off-by: Jiri Olsa <jolsa@kernel.org>
>---
> .../util/scripting-engines/trace-event-python.c    | 37 ++++++++++++++++++----
> 1 file changed, 31 insertions(+), 6 deletions(-)
>
>diff --git a/tools/perf/util/scripting-engines/trace-event-python.c b/tools/perf/util/scripting-engines/trace-event-python.c
>index 6ac6b7a33f42..1bc995de5a6d 100644
>--- a/tools/perf/util/scripting-engines/trace-event-python.c
>+++ b/tools/perf/util/scripting-engines/trace-event-python.c
>@@ -386,6 +386,19 @@ exit:
> 	return pylist;
> }
> 
>+static int is_printable_array(char *p, unsigned int len)
>+{
>+	unsigned int i;
>+
>+	if (p[len - 1] == 0)
>+		len--;
>+
>+	for (i = 0; i < len - 1; i++)
>+		if (!isprint(p[i]) && !isspace(p[i]))
>+			return 0;

for "AA\1\0" this returns "1" although that should return "0".

orig len 4
decremented len 3
for:
0 1

index 2 would not be inspected. Or am I missing something?

I think that the for check should be "i < len"

Thanks.

>+
>+	return 1;
>+}
> 
> static void python_process_tracepoint(struct perf_sample *sample,
> 				      struct perf_evsel *evsel,
>@@ -457,14 +470,26 @@ 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);
> 		}
>-- 
>2.4.11
>