X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=ltt-debugfs-abi.c;h=1314c663e77e321fc32bc638d0183bacc74f727a;hb=c24a0d710f6aac1484bd02bb6375e8de7429edd0;hp=fe70f9a9fd3b9c3ea1ce9f2f66138dee892b68df;hpb=ad1c05e136eba463795ba592e5f6c27542643e16;p=lttng-modules.git

diff --git a/ltt-debugfs-abi.c b/ltt-debugfs-abi.c
index fe70f9a9..1314c663 100644
--- a/ltt-debugfs-abi.c
+++ b/ltt-debugfs-abi.c
@@ -20,10 +20,21 @@
  *     - Takes an instrumentation source as parameter
  *       - e.g. tracepoints, dynamic_probes...
  *     - Takes instrumentation source specific arguments.
+ *
+ * Dual LGPL v2.1/GPL v2 license.
  */
 
+#include <linux/module.h>
 #include <linux/debugfs.h>
+#include <linux/anon_inodes.h>
+#include <linux/file.h>
+#include <linux/uaccess.h>
+#include <linux/slab.h>
+#include "wrapper/vmalloc.h"	/* for wrapper_vmalloc_sync_all() */
+#include "wrapper/ringbuffer/vfs.h"
+#include "ltt-debugfs-abi.h"
 #include "ltt-events.h"
+#include "ltt-tracer.h"
 
 /*
  * This is LTTng's own personal way to create a system call as an external
@@ -34,24 +45,12 @@ static struct dentry *lttng_dentry;
 static const struct file_operations lttng_fops;
 static const struct file_operations lttng_session_fops;
 static const struct file_operations lttng_channel_fops;
+static const struct file_operations lttng_metadata_fops;
+static const struct file_operations lttng_event_fops;
 
-/*
- * LTTng DebugFS ABI structures.
- */
-
-struct lttng_channel {
-	int session;			/* Session file descriptor */
-	int overwrite;			/* 1: overwrite, 0: discard */
-	u64 subbuf_size;
-	u64 num_subbuf;
-	unsigned int switch_timer_interval;
-	unsigned int read_timer_interval;
-};
-
-struct lttng_event {
-	int channel;			/* Channel file descriptor */
-	enum instrum_type itype;
-	char name[];
+enum channel_type {
+	PER_CPU_CHANNEL,
+	METADATA_CHANNEL,
 };
 
 static
@@ -59,12 +58,12 @@ int lttng_abi_create_session(void)
 {
 	struct ltt_session *session;
 	struct file *session_file;
-	int session_fd;
+	int session_fd, ret;
 
-	session = ltt_session_create()
+	session = ltt_session_create();
 	if (!session)
 		return -ENOMEM;
-	session_fd = get_unused_fd_flags(O_RDWR);
+	session_fd = get_unused_fd();
 	if (session_fd < 0) {
 		ret = session_fd;
 		goto fd_error;
@@ -76,6 +75,7 @@ int lttng_abi_create_session(void)
 		ret = PTR_ERR(session_file);
 		goto file_error;
 	}
+	session->file = session_file;
 	fd_install(session_fd, session_file);
 	return session_fd;
 
@@ -86,243 +86,587 @@ fd_error:
 	return ret;
 }
 
+static
+int lttng_abi_tracepoint_list(void)
+{
+	struct file *tracepoint_list_file;
+	int file_fd, ret;
+
+	file_fd = get_unused_fd();
+	if (file_fd < 0) {
+		ret = file_fd;
+		goto fd_error;
+	}
+
+	tracepoint_list_file = anon_inode_getfile("[lttng_session]",
+					  &lttng_tracepoint_list_fops,
+					  NULL, O_RDWR);
+	if (IS_ERR(tracepoint_list_file)) {
+		ret = PTR_ERR(tracepoint_list_file);
+		goto file_error;
+	}
+	ret = lttng_tracepoint_list_fops.open(NULL, tracepoint_list_file);
+	if (ret < 0)
+		goto open_error;
+	fd_install(file_fd, tracepoint_list_file);
+	if (file_fd < 0) {
+		ret = file_fd;
+		goto fd_error;
+	}
+	return file_fd;
+
+open_error:
+	fput(tracepoint_list_file);
+file_error:
+	put_unused_fd(file_fd);
+fd_error:
+	return ret;
+}
+
+static
+long lttng_abi_tracer_version(struct file *file, 
+	struct lttng_kernel_tracer_version __user *uversion_param)
+{
+	struct lttng_kernel_tracer_version v;
+
+	v.version = LTTNG_VERSION;
+	v.patchlevel = LTTNG_PATCHLEVEL;
+	v.sublevel = LTTNG_SUBLEVEL;
+
+	if (copy_to_user(uversion_param, &v, sizeof(v)))
+		return -EFAULT;
+	return 0;
+}
+
+static
+long lttng_abi_add_context(struct file *file,
+	struct lttng_kernel_context __user *ucontext_param,
+	struct lttng_ctx **ctx, struct ltt_session *session)
+{
+	struct lttng_kernel_context context_param;
+
+	if (session->been_active)
+		return -EPERM;
+
+	if (copy_from_user(&context_param, ucontext_param, sizeof(context_param)))
+		return -EFAULT;
+
+	switch (context_param.ctx) {
+	case LTTNG_KERNEL_CONTEXT_PID:
+		return lttng_add_pid_to_ctx(ctx);
+	case LTTNG_KERNEL_CONTEXT_PRIO:
+		return lttng_add_prio_to_ctx(ctx);
+	case LTTNG_KERNEL_CONTEXT_NICE:
+		return lttng_add_nice_to_ctx(ctx);
+	case LTTNG_KERNEL_CONTEXT_PERF_COUNTER:
+		context_param.u.perf_counter.name[LTTNG_SYM_NAME_LEN - 1] = '\0';
+		return lttng_add_perf_counter_to_ctx(context_param.u.perf_counter.type,
+				context_param.u.perf_counter.config,
+				context_param.u.perf_counter.name,
+				ctx);
+	case LTTNG_KERNEL_CONTEXT_COMM:
+		return lttng_add_comm_to_ctx(ctx);
+	default:
+		return -EINVAL;
+	}
+}
+
 /**
  *	lttng_ioctl - lttng syscall through ioctl
  *
- *	@filp: the file
+ *	@file: the file
  *	@cmd: the command
  *	@arg: command arg
  *
  *	This ioctl implements lttng commands:
- *	LTTNG_SESSION
+ *	LTTNG_KERNEL_SESSION
  *		Returns a LTTng trace session file descriptor
+ *	LTTNG_KERNEL_TRACER_VERSION
+ *		Returns the LTTng kernel tracer version
+ *	LTTNG_KERNEL_TRACEPOINT_LIST
+ *		Returns a file descriptor listing available tracepoints
  *
  * The returned session will be deleted when its file descriptor is closed.
  */
 static
-long lttng_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+long lttng_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
 	switch (cmd) {
-	case LTTNG_SESSION:
+	case LTTNG_KERNEL_SESSION:
 		return lttng_abi_create_session();
+	case LTTNG_KERNEL_TRACER_VERSION:
+		return lttng_abi_tracer_version(file,
+				(struct lttng_kernel_tracer_version __user *) arg);
+	case LTTNG_KERNEL_TRACEPOINT_LIST:
+		return lttng_abi_tracepoint_list();
 	default:
 		return -ENOIOCTLCMD;
 	}
 }
 
+static const struct file_operations lttng_fops = {
+	.unlocked_ioctl = lttng_ioctl,
 #ifdef CONFIG_COMPAT
+	.compat_ioctl = lttng_ioctl,
+#endif
+};
+
+/*
+ * We tolerate no failure in this function (if one happens, we print a dmesg
+ * error, but cannot return any error, because the channel information is
+ * invariant.
+ */
 static
-long lttng_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+void lttng_metadata_create_events(struct file *channel_file)
 {
-	switch (cmd) {
-	case LTTNG_SESSION:
-		return lttng_abi_create_session();
-	default:
-		return -ENOIOCTLCMD;
+	struct ltt_channel *channel = channel_file->private_data;
+	static struct lttng_kernel_event metadata_params = {
+		.instrumentation = LTTNG_KERNEL_TRACEPOINT,
+		.name = "lttng_metadata",
+	};
+	struct ltt_event *event;
+	int ret;
+
+	/*
+	 * We tolerate no failure path after event creation. It will stay
+	 * invariant for the rest of the session.
+	 */
+	event = ltt_event_create(channel, &metadata_params, NULL);
+	if (!event) {
+		ret = -EINVAL;
+		goto create_error;
 	}
-}
-#endif
+	return;
 
-static const struct file_operations lttng_fops = {
-	.unlocked_ioctl = lttng_ioctl,
-#ifdef CONFIG_COMPAT
-	.compat_ioctl = lttng_compat_ioctl,
-#endif
+create_error:
+	WARN_ON(1);
+	return;		/* not allowed to return error */
 }
 
-int lttng_abi_create_channel(struct file *session_filp,
-			     struct lttng_channel __user *uchan_param)
+static
+int lttng_abi_create_channel(struct file *session_file,
+			     struct lttng_kernel_channel __user *uchan_param,
+			     enum channel_type channel_type)
 {
-	struct ltt_session *session = session_filp->private_data;
+	struct ltt_session *session = session_file->private_data;
+	const struct file_operations *fops;
+	const char *transport_name;
 	struct ltt_channel *chan;
-	struct file *chan_filp;
-	struct lttng_channel chan_param;
+	struct file *chan_file;
+	struct lttng_kernel_channel chan_param;
 	int chan_fd;
 	int ret = 0;
 
-	if (copy_from_user(&chan_param, ucham_param, sizeof(chan_param)))
+	if (copy_from_user(&chan_param, uchan_param, sizeof(chan_param)))
 		return -EFAULT;
-	chan = ltt_channel_create(session, chan_param->overwrite, NULL,
-				  chan_param->subbuf_size,
-				  chan_param->num_subbuf,
-				  chan_param->switch_timer_interval,
-				  chan_param->read_timer_interval);
-	if (!chan) {
-		ret = -ENOMEM;
-		goto chan_error;
-	}
-	chan_fd = get_unused_fd_flags(O_RDWR);
+	chan_fd = get_unused_fd();
 	if (chan_fd < 0) {
 		ret = chan_fd;
 		goto fd_error;
 	}
-	chan_filp = anon_inode_getfile("[lttng_channel]",
+	chan_file = anon_inode_getfile("[lttng_channel]",
 				       &lttng_channel_fops,
-				       chan, O_RDWR);
-	if (IS_ERR(chan_filp)) {
-		ret = PTR_ERR(chan_filp);
+				       NULL, O_RDWR);
+	if (IS_ERR(chan_file)) {
+		ret = PTR_ERR(chan_file);
 		goto file_error;
 	}
+	switch (channel_type) {
+	case PER_CPU_CHANNEL:
+		transport_name = chan_param.overwrite ?
+			"relay-overwrite" : "relay-discard";
+		fops = &lttng_channel_fops;
+		break;
+	case METADATA_CHANNEL:
+		transport_name = "relay-metadata";
+		fops = &lttng_metadata_fops;
+		break;
+	default:
+		transport_name = "<unknown>";
+		break;
+	}
+	/*
+	 * We tolerate no failure path after channel creation. It will stay
+	 * invariant for the rest of the session.
+	 */
+	chan = ltt_channel_create(session, transport_name, NULL,
+				  chan_param.subbuf_size,
+				  chan_param.num_subbuf,
+				  chan_param.switch_timer_interval,
+				  chan_param.read_timer_interval);
+	if (!chan) {
+		ret = -EINVAL;
+		goto chan_error;
+	}
+	chan->file = chan_file;
+	chan_file->private_data = chan;
+	fd_install(chan_fd, chan_file);
+	if (channel_type == METADATA_CHANNEL) {
+		session->metadata = chan;
+		lttng_metadata_create_events(chan_file);
+	}
 
 	/* The channel created holds a reference on the session */
-	atomic_inc(&session_filp->f_count);
+	atomic_long_inc(&session_file->f_count);
 
 	return chan_fd;
 
+chan_error:
+	fput(chan_file);
 file_error:
 	put_unused_fd(chan_fd);
 fd_error:
-	ltt_channel_destroy(chan);
-chan_error:
 	return ret;
 }
 
 /**
  *	lttng_session_ioctl - lttng session fd ioctl
  *
- *	@filp: the file
+ *	@file: the file
  *	@cmd: the command
  *	@arg: command arg
  *
  *	This ioctl implements lttng commands:
- *	LTTNG_CHANNEL
+ *	LTTNG_KERNEL_CHANNEL
  *		Returns a LTTng channel file descriptor
+ *	LTTNG_KERNEL_SESSION_START
+ *		Starts tracing session
+ *	LTTNG_KERNEL_SESSION_STOP
+ *		Stops tracing session
+ *	LTTNG_KERNEL_METADATA
+ *		Returns a LTTng metadata file descriptor
  *
  * The returned channel will be deleted when its file descriptor is closed.
  */
 static
-long lttng_session_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+long lttng_session_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
+	struct ltt_session *session = file->private_data;
+
 	switch (cmd) {
-	case LTTNG_CHANNEL:
-		return lttng_abi_create_channel(filp, (struct lttng_channel __user *)arg);
+	case LTTNG_KERNEL_CHANNEL:
+		return lttng_abi_create_channel(file,
+				(struct lttng_kernel_channel __user *) arg,
+				PER_CPU_CHANNEL);
+	case LTTNG_KERNEL_SESSION_START:
+		return ltt_session_start(session);
+	case LTTNG_KERNEL_SESSION_STOP:
+		return ltt_session_stop(session);
+	case LTTNG_KERNEL_METADATA:
+		return lttng_abi_create_channel(file,
+				(struct lttng_kernel_channel __user *) arg,
+				METADATA_CHANNEL);
 	default:
 		return -ENOIOCTLCMD;
 	}
 }
 
-#ifdef CONFIG_COMPAT
+/*
+ * Called when the last file reference is dropped.
+ *
+ * Big fat note: channels and events are invariant for the whole session after
+ * their creation. So this session destruction also destroys all channel and
+ * event structures specific to this session (they are not destroyed when their
+ * individual file is released).
+ */
 static
-long lttng_session_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+int lttng_session_release(struct inode *inode, struct file *file)
 {
-	switch (cmd) {
-	case LTTNG_CHANNEL:
-		return lttng_abi_create_channel(filp, (struct lttng_channel __user *)arg);
-	default:
-		return -ENOIOCTLCMD;
-	}
+	struct ltt_session *session = file->private_data;
+
+	if (session)
+		ltt_session_destroy(session);
+	return 0;
 }
-#endif
 
 static const struct file_operations lttng_session_fops = {
+	.release = lttng_session_release,
 	.unlocked_ioctl = lttng_session_ioctl,
 #ifdef CONFIG_COMPAT
-	.compat_ioctl = lttng_session_compat_ioctl,
+	.compat_ioctl = lttng_session_ioctl,
 #endif
-}
+};
 
 static
-int lttng_abi_open_stream(struct file *channel_filp)
+int lttng_abi_open_stream(struct file *channel_file)
 {
-	struct ltt_channel *channel = channel_filp->private_data;
+	struct ltt_channel *channel = channel_file->private_data;
 	struct lib_ring_buffer *buf;
 	int stream_fd, ret;
+	struct file *stream_file;
 
-	buf = ltt_buffer_read_open(channel->chan);
+	buf = channel->ops->buffer_read_open(channel->chan);
 	if (!buf)
 		return -ENOENT;
 
-	stream_fd = get_unused_fd_flags(O_RDWR);
+	stream_fd = get_unused_fd();
 	if (stream_fd < 0) {
 		ret = stream_fd;
 		goto fd_error;
 	}
-	stream_filp = anon_inode_getfile("[lttng_stream]",
-					 &lttng_stream_fops,
+	stream_file = anon_inode_getfile("[lttng_stream]",
+					 &lib_ring_buffer_file_operations,
 					 buf, O_RDWR);
-	if (IS_ERR(stream_filp)) {
-		ret = PTR_ERR(stream_filp);
+	if (IS_ERR(stream_file)) {
+		ret = PTR_ERR(stream_file);
 		goto file_error;
 	}
-
-	/* The stream holds a reference on the channel */
-	atomic_inc(&channel_filp->f_count);
+	/*
+	 * OPEN_FMODE, called within anon_inode_getfile/alloc_file, don't honor
+	 * FMODE_LSEEK, FMODE_PREAD nor FMODE_PWRITE. We need to read from this
+	 * file descriptor, so we set FMODE_PREAD here.
+	 */
+	stream_file->f_mode |= FMODE_PREAD;
+	fd_install(stream_fd, stream_file);
+	/*
+	 * The stream holds a reference to the channel within the generic ring
+	 * buffer library, so no need to hold a refcount on the channel and
+	 * session files here.
+	 */
 	return stream_fd;
 
 file_error:
 	put_unused_fd(stream_fd);
 fd_error:
-	ltt_buffer_read_close(buf);
+	channel->ops->buffer_read_close(buf);
 	return ret;
 }
 
+static
+int lttng_abi_create_event(struct file *channel_file,
+			   struct lttng_kernel_event __user *uevent_param)
+{
+	struct ltt_channel *channel = channel_file->private_data;
+	struct ltt_event *event;
+	struct lttng_kernel_event event_param;
+	int event_fd, ret;
+	struct file *event_file;
+
+	if (copy_from_user(&event_param, uevent_param, sizeof(event_param)))
+		return -EFAULT;
+	event_param.name[LTTNG_SYM_NAME_LEN - 1] = '\0';
+	switch (event_param.instrumentation) {
+	case LTTNG_KERNEL_KPROBE:
+		event_param.u.kprobe.symbol_name[LTTNG_SYM_NAME_LEN - 1] = '\0';
+		break;
+	case LTTNG_KERNEL_FUNCTION:
+		event_param.u.ftrace.symbol_name[LTTNG_SYM_NAME_LEN - 1] = '\0';
+		break;
+	default:
+		break;
+	}
+	event_fd = get_unused_fd();
+	if (event_fd < 0) {
+		ret = event_fd;
+		goto fd_error;
+	}
+	event_file = anon_inode_getfile("[lttng_event]",
+					&lttng_event_fops,
+					NULL, O_RDWR);
+	if (IS_ERR(event_file)) {
+		ret = PTR_ERR(event_file);
+		goto file_error;
+	}
+	/*
+	 * We tolerate no failure path after event creation. It will stay
+	 * invariant for the rest of the session.
+	 */
+	event = ltt_event_create(channel, &event_param, NULL);
+	if (!event) {
+		ret = -EINVAL;
+		goto event_error;
+	}
+	event_file->private_data = event;
+	fd_install(event_fd, event_file);
+	/* The event holds a reference on the channel */
+	atomic_long_inc(&channel_file->f_count);
+	return event_fd;
+
+event_error:
+	fput(event_file);
+file_error:
+	put_unused_fd(event_fd);
+fd_error:
+	return ret;
+}
 
 /**
  *	lttng_channel_ioctl - lttng syscall through ioctl
  *
- *	@filp: the file
+ *	@file: the file
  *	@cmd: the command
  *	@arg: command arg
  *
  *	This ioctl implements lttng commands:
- *      LTTNG_STREAM
+ *      LTTNG_KERNEL_STREAM
  *              Returns an event stream file descriptor or failure.
  *              (typically, one event stream records events from one CPU)
- *      LTTNG_STREAM_NOTIFIER
- *              Returns a file descriptor that can be used to monitor
- *              addition/removal of streams to/from a channel. (e.g. notifier
- *              called on CPU hotplug).
- *	LTTNG_EVENT
+ *	LTTNG_KERNEL_EVENT
  *		Returns an event file descriptor or failure.
+ *	LTTNG_KERNEL_CONTEXT
+ *		Prepend a context field to each event in the channel
  *
- * The returned session will be deleted when its file descriptor is closed.
  * Channel and event file descriptors also hold a reference on the session.
  */
 static
-long lttng_channel_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+long lttng_channel_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
+	struct ltt_channel *channel = file->private_data;
+
 	switch (cmd) {
-	case LTTNG_STREAM:
-		return lttng_abi_open_stream(filp);
-	case LTTNG_STREAM_NOTIFIER:
-		return lttng_abi_open_stream_notifier(filp);
-	case LTTNG_EVENT:
-		return lttng_abi_create_event(filp, (struct lttng_event __user *)arg);
+	case LTTNG_KERNEL_STREAM:
+		return lttng_abi_open_stream(file);
+	case LTTNG_KERNEL_EVENT:
+		return lttng_abi_create_event(file, (struct lttng_kernel_event __user *) arg);
+	case LTTNG_KERNEL_CONTEXT:
+		return lttng_abi_add_context(file,
+				(struct lttng_kernel_context __user *) arg,
+				&channel->ctx, channel->session);
 	default:
 		return -ENOIOCTLCMD;
 	}
 }
 
-#ifdef CONFIG_COMPAT
+/**
+ *	lttng_metadata_ioctl - lttng syscall through ioctl
+ *
+ *	@file: the file
+ *	@cmd: the command
+ *	@arg: command arg
+ *
+ *	This ioctl implements lttng commands:
+ *      LTTNG_KERNEL_STREAM
+ *              Returns an event stream file descriptor or failure.
+ *
+ * Channel and event file descriptors also hold a reference on the session.
+ */
 static
-long lttng_channel_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+long lttng_metadata_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
 	switch (cmd) {
-	case LTTNG_STREAM:
-		return lttng_abi_get_stream(filp);
-	case LTTNG_STREAM_NOTIFIER:
-		return lttng_abi_get_stream_notifier(filp);
-	case LTTNG_EVENT:
-		return lttng_abi_create_event(filp, (struct lttng_event __user *)arg);
+	case LTTNG_KERNEL_STREAM:
+		return lttng_abi_open_stream(file);
 	default:
 		return -ENOIOCTLCMD;
 	}
 }
-#endif
+
+/* TODO: poll */
+#if 0
+/**
+ *	lttng_channel_poll - lttng stream addition/removal monitoring
+ *
+ *	@file: the file
+ *	@wait: poll table
+ */
+unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
+{
+	struct ltt_channel *channel = file->private_data;
+	unsigned int mask = 0;
+
+	if (file->f_mode & FMODE_READ) {
+		poll_wait_set_exclusive(wait);
+		poll_wait(file, &channel->notify_wait, wait);
+
+		/* TODO: identify when the channel is being finalized. */
+		if (finalized)
+			return POLLHUP;
+		else
+			return POLLIN | POLLRDNORM;
+	}
+	return mask;
+
+}
+#endif //0
+
+static
+int lttng_channel_release(struct inode *inode, struct file *file)
+{
+	struct ltt_channel *channel = file->private_data;
+
+	if (channel)
+		fput(channel->session->file);
+	return 0;
+}
 
 static const struct file_operations lttng_channel_fops = {
+	.release = lttng_channel_release,
+/* TODO */
+#if 0
+	.poll = lttng_channel_poll,
+#endif //0
 	.unlocked_ioctl = lttng_channel_ioctl,
 #ifdef CONFIG_COMPAT
-	.compat_ioctl = lttng_channel_compat_ioctl,
+	.compat_ioctl = lttng_channel_ioctl,
+#endif
+};
+
+static const struct file_operations lttng_metadata_fops = {
+	.release = lttng_channel_release,
+	.unlocked_ioctl = lttng_metadata_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl = lttng_metadata_ioctl,
 #endif
+};
+
+/**
+ *	lttng_event_ioctl - lttng syscall through ioctl
+ *
+ *	@file: the file
+ *	@cmd: the command
+ *	@arg: command arg
+ *
+ *	This ioctl implements lttng commands:
+ *      LTTNG_KERNEL_STREAM
+ *              Returns an event stream file descriptor or failure.
+ *              (typically, one event stream records events from one CPU)
+ *	LTTNG_KERNEL_EVENT
+ *		Returns an event file descriptor or failure.
+ *	LTTNG_KERNEL_CONTEXT
+ *		Prepend a context field to each record of this event
+ */
+static
+long lttng_event_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct ltt_event *event = file->private_data;
+
+	switch (cmd) {
+	case LTTNG_KERNEL_CONTEXT:
+		return lttng_abi_add_context(file,
+				(struct lttng_kernel_context __user *) arg,
+				&event->ctx, event->chan->session);
+	default:
+		return -ENOIOCTLCMD;
+	}
 }
 
-static int __init ltt_debugfs_abi_init(void)
+static
+int lttng_event_release(struct inode *inode, struct file *file)
+{
+	struct ltt_event *event = file->private_data;
+
+	if (event)
+		fput(event->chan->file);
+	return 0;
+}
+
+/* TODO: filter control ioctl */
+static const struct file_operations lttng_event_fops = {
+	.release = lttng_event_release,
+	.unlocked_ioctl = lttng_event_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl = lttng_event_ioctl,
+#endif
+};
+
+int __init ltt_debugfs_abi_init(void)
 {
 	int ret = 0;
 
-	lttng_dentry = debugfs_create_file("lttng", NULL);
-	if (IS_ERR(lttng_dentry) || !lttng_dentry)
+	wrapper_vmalloc_sync_all();
+	lttng_dentry = debugfs_create_file("lttng", S_IWUSR, NULL, NULL,
+					   &lttng_fops);
+	if (IS_ERR(lttng_dentry) || !lttng_dentry) {
 		printk(KERN_ERR "Error creating LTTng control file\n");
 		ret = -ENOMEM;
 		goto error;
@@ -331,7 +675,7 @@ error:
 	return ret;
 }
 
-static void __exit ltt_debugfs_abi_exit(void)
+void __exit ltt_debugfs_abi_exit(void)
 {
-	debugfs_remote(lttng_dentry);
+	debugfs_remove(lttng_dentry);
 }