From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Wed, 18 May 2016 01:16:22 +0000 (-0400)
Subject: Fix: compat ioctl for flush/get metadata version
X-Git-Tag: v2.7.4~6
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=b96080a0f89ea706365d685ad136d1572813451f;p=lttng-modules.git

Fix: compat ioctl for flush/get metadata version

Unlike the non-compat version, the compat ioctl lttng ABI code for the
ring buffer flush operation does not invoke
lttng_metadata_output_channel before calling the ring buffer operation.
This could lead to incomplete metadata on 64-bit kernels running with
32-bit lttng userland.

There is also a discrepancy between the non-compat and compat code: the
GET_METADATA_VERSION operation is performed before calling the ring
buffer code. Ensure both non-compat and compat code are alike.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/lttng-abi.c b/lttng-abi.c
index 9845930d..cc3d4b5b 100644
--- a/lttng-abi.c
+++ b/lttng-abi.c
@@ -739,6 +739,21 @@ long lttng_metadata_ring_buffer_compat_ioctl(struct file *filp,
 		 */
 		return -ENOSYS;
 	}
+	case RING_BUFFER_FLUSH:
+	{
+		struct lttng_metadata_stream *stream = filp->private_data;
+		struct lib_ring_buffer *buf = stream->priv;
+		struct channel *chan = buf->backend.chan;
+
+		/*
+		 * Before doing the actual ring buffer flush, write up to one
+		 * packet of metadata in the ring buffer.
+		 */
+		ret = lttng_metadata_output_channel(stream, chan);
+		if (ret < 0)
+			goto err;
+		break;
+	}
 	default:
 		break;
 	}