From: Philippe Proulx <eeppeliteloop@gmail.com>
Date: Thu, 13 Jul 2017 16:18:29 +0000 (-0400)
Subject: Fix: ctf: notif-iter: error on empty events (0 bits of data)
X-Git-Url: http://git.efficios.com/?p=babeltrace.git;a=commitdiff_plain;h=174e773b037534d485c72a5f558651f2857af243

Fix: ctf: notif-iter: error on empty events (0 bits of data)

Do not create an event which consumed 0 bits of data stream: log an
error and return without creating it. We keep the buffer position at the
beginning of the last decoded event header, and we compare to the
current buffer position: if they are the same, then we consumed 0 bits
of data. It is possible, when we compare, that notit->buf.last_eh_at is
-1ULL (reset when requesting bytes from medium): in this case, we know
we requested bytes anyway, which means we consumed something to get to
this starvation point, thus the event is not empty.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---

diff --git a/plugins/ctf/common/notif-iter/notif-iter.c b/plugins/ctf/common/notif-iter/notif-iter.c
index 7d570a63..4ac971a9 100644
--- a/plugins/ctf/common/notif-iter/notif-iter.c
+++ b/plugins/ctf/common/notif-iter/notif-iter.c
@@ -211,6 +211,9 @@ struct bt_ctf_notif_iter {
 
 		/* Current position from addr (bits) */
 		size_t at;
+
+		/* Position of the last event header from addr (bits) */
+		size_t last_eh_at;
 	} buf;
 
 	/* Binary type reader */
@@ -477,6 +480,7 @@ enum bt_ctf_notif_iter_status request_medium_bytes(
 
 		/* Restart at the beginning of the new medium buffer */
 		notit->buf.at = 0;
+		notit->buf.last_eh_at = -1ULL;
 
 		/* New medium buffer size */
 		notit->buf.sz = buffer_sz;
@@ -1252,6 +1256,9 @@ enum bt_ctf_notif_iter_status read_event_header_begin_state(
 	enum bt_ctf_notif_iter_status status = BT_CTF_NOTIF_ITER_STATUS_OK;
 	struct bt_ctf_field_type *event_header_type = NULL;
 
+	/* Reset the position of the last event header */
+	notit->buf.last_eh_at = notit->buf.at;
+
 	/* Check if we have some content left */
 	if (notit->cur_content_size >= 0) {
 		if (packet_at(notit) == notit->cur_content_size) {
@@ -1782,6 +1789,7 @@ void bt_ctf_notif_iter_reset(struct bt_ctf_notif_iter *notit)
 	notit->buf.addr = NULL;
 	notit->buf.sz = 0;
 	notit->buf.at = 0;
+	notit->buf.last_eh_at = -1ULL;
 	notit->buf.packet_offset = 0;
 	notit->state = STATE_INIT;
 	notit->cur_content_size = -1;
@@ -2962,9 +2970,17 @@ void notify_event(struct bt_ctf_notif_iter *notit,
 		struct bt_clock_class_priority_map *cc_prio_map,
 		struct bt_notification **notification)
 {
-	struct bt_ctf_event *event;
+	struct bt_ctf_event *event = NULL;
 	struct bt_notification *ret = NULL;
 
+	/* Make sure that the event contains at least one bit of data */
+	if (notit->buf.at == notit->buf.last_eh_at) {
+		BT_LOGE("Cannot create empty event with 0 bits of data: "
+			"notit-addr=%p, packet-cur=%zu",
+			notit, packet_at(notit));
+		goto end;
+	}
+
 	/* Create event */
 	event = create_event(notit);
 	if (!event) {