X-Git-Url: http://git.lttng.org./?a=blobdiff_plain;f=src%2Flttng-event-notifier-notification.c;h=957883a801e6651e48b307ba3320e688f740b25b;hb=b9315ad80f02c7299cf499d8edf5f7b9dbbf5876;hp=b8f01395c57bf4e7fd3954f555aa26a286acbf7a;hpb=76db48089b6717136c4712db4e663011fcb4714b;p=lttng-modules.git

diff --git a/src/lttng-event-notifier-notification.c b/src/lttng-event-notifier-notification.c
index b8f01395..957883a8 100644
--- a/src/lttng-event-notifier-notification.c
+++ b/src/lttng-event-notifier-notification.c
@@ -25,6 +25,8 @@
  */
 #define CAPTURE_BUFFER_SIZE 512
 
+#define MSG_WRITE_NIL_LEN 1
+
 struct lttng_event_notifier_notification {
 	int notification_fd;
 	uint64_t event_notifier_token;
@@ -442,20 +444,34 @@ void notification_send(struct lttng_event_notifier_notification *notif,
 	irq_work_queue(&event_notifier_group->wakeup_pending);
 }
 
+/*
+ * Validate that the buffer has enough room to hold empty capture fields.
+ */
+static
+bool validate_buffer_len(struct lttng_event_notifier_notification *notif, size_t captures_left)
+{
+	if (notif->writer.end_write_pos - notif->writer.write_pos < MSG_WRITE_NIL_LEN * captures_left)
+		return false;
+	return true;
+}
+
 void lttng_event_notifier_notification_send(struct lttng_kernel_event_notifier *event_notifier,
 		const char *stack_data,
 		struct lttng_kernel_probe_ctx *probe_ctx,
 		struct lttng_kernel_notification_ctx *notif_ctx)
 {
 	struct lttng_event_notifier_notification notif = { 0 };
+	size_t captures_left;
 
 	if (unlikely(!READ_ONCE(event_notifier->parent.enabled)))
 		return;
 
-	if (notification_init(&notif, event_notifier)) {
-		record_error(event_notifier);
-		goto end;
-	}
+	if (notification_init(&notif, event_notifier))
+		goto error;
+
+	captures_left = event_notifier->priv->num_captures;
+	if (!validate_buffer_len(&notif, captures_left))
+		goto error;
 
 	if (unlikely(notif_ctx->eval_capture)) {
 		struct lttng_kernel_bytecode_runtime *capture_bc_runtime;
@@ -470,30 +486,40 @@ void lttng_event_notifier_notification_send(struct lttng_kernel_event_notifier *
 				&event_notifier->priv->capture_bytecode_runtime_head, node) {
 			struct lttng_interpreter_output output;
 			uint8_t *save_pos;
-			int ret;
+			int ret = -1;
 
 			lttng_msgpack_save_writer_pos(&notif.writer, &save_pos);
+			captures_left--;
 			if (capture_bc_runtime->interpreter_func(capture_bc_runtime,
 					stack_data, probe_ctx, &output) == LTTNG_KERNEL_BYTECODE_INTERPRETER_OK)
 				ret = notification_append_capture(&notif, &output);
-			else
-				ret = notification_append_empty_capture(&notif);
-			if (ret) {
+			if (ret || !validate_buffer_len(&notif, captures_left)) {
 				/*
-				 * On append capture error, skip the field
-				 * capture by restoring the msgpack writer
-				 * position.
+				 * On append capture error or if the generated
+				 * buffer data would not leave enough room to
+				 * write empty capture fields for the remaining
+				 * fields, skip the field capture by restoring
+				 * the msgpack writer position and writing an
+				 * empty capture field.
 				 */
 				lttng_msgpack_restore_writer_pos(&notif.writer, save_pos);
+				ret = notification_append_empty_capture(&notif);
+				WARN_ON_ONCE(ret);
 			}
 		}
 	}
 
+	if (notif.has_captures && lttng_msgpack_end_array(&notif.writer))
+		goto error;
+
 	/*
 	 * Send the notification (including the capture buffer) to the
 	 * sessiond.
 	 */
 	notification_send(&notif, event_notifier);
-end:
+	return;
+
+error:
+	record_error(event_notifier);
 	return;
 }