Re: [PATCH] Expose kernel tracer to user-space (version 5)

Re: [PATCH] Expose kernel tracer to user-space (version 5)

[Mathieu Desnoyers]

* Francis Giraldeau (francis.giraldeau@gmail.com) wrote:
> By writing to the file /proc/lttng, a user-space application creates a
> kernel event. The event's payload is by default UTF-8 text, but any data
> can be written, up to 1024 bytes. Null-character is optional and is not
> enforced. The event uses sequence for space efficiency and to store any
> data as payload.

Why limit to 1024 bytes ? We could use a string_from_user, and write it
into a null-terminated string instead.

> 
> The feature is enabled when both lttng-uevent and lttng-probe-uevent are
> loaded.

Why not combine those two into a single module ?

> The lttng-abi module exports a register function and includes a wrapper
> for lttng_fops write. This is required since struct file_operations must be
> const.
> 
> Module unload must be prevented while lttng-uevent is being used.
> rcu_synchronized() is call on module unload, and thus rcu_read_lock() can be

is call -> is called, or is invoked

Thanks,

Mathieu

> used to force waiting until the critical section is over.
> 
> Signed-off-by: Francis Giraldeau <francis.giraldeau@gmail.com>
> ---
>  instrumentation/events/lttng-module/uevent.h |   33 +++++++++++++++
>  lttng-abi.c                                  |   42 +++++++++++++++++++
>  lttng-abi.h                                  |    4 ++
>  probes/Makefile                              |    2 +
>  probes/lttng-probe-uevent.c                  |   36 ++++++++++++++++
>  probes/lttng-uevent.c                        |   58 ++++++++++++++++++++++++++
>  6 files changed, 175 insertions(+)
>  create mode 100644 instrumentation/events/lttng-module/uevent.h
>  create mode 100644 probes/lttng-probe-uevent.c
>  create mode 100644 probes/lttng-uevent.c
> 
> diff --git a/instrumentation/events/lttng-module/uevent.h b/instrumentation/events/lttng-module/uevent.h
> new file mode 100644
> index 0000000..f67d901
> --- /dev/null
> +++ b/instrumentation/events/lttng-module/uevent.h
> @@ -0,0 +1,33 @@
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM uevent
> +
> +#if !defined(UEVENT_H_) || defined(TRACE_HEADER_MULTI_READ)
> +#define UEVENT_H_
> +
> +#include <linux/tracepoint.h>
> +
> +TRACE_EVENT(lttng_uevent,
> +
> +	TP_PROTO(const char *str, size_t len),
> +
> +	TP_ARGS(str, len),
> +
> +	/*
> +	 * Uses sequence to hold variable size data, by default considered
> +	 * as text. Null-terminal character is optional and is not enforced.
> +	 */
> +	TP_STRUCT__entry(
> +		__dynamic_array_text(char, text, len)
> +	),
> +
> +	TP_fast_assign(
> +		tp_memcpy_dyn_from_user(text, str)
> +	),
> +
> +	TP_printk("")
> +)
> +
> +#endif /* UEVENT_H_ */
> +
> +/* This part must be outside protection */
> +#include "../../../probes/define_trace.h"
> diff --git a/lttng-abi.c b/lttng-abi.c
> index 26a02ed..0de79ab 100644
> --- a/lttng-abi.c
> +++ b/lttng-abi.c
> @@ -51,6 +51,11 @@
>  #include "lttng-tracer.h"
>  
>  /*
> + * Required data structure to support lttng-probe-uevent
> + */
> +static write_ops_t lttng_uevent_handler;
> +
> +/*
>   * This is LTTng's own personal way to create a system call as an external
>   * module. We use ioctl() on /proc/lttng.
>   */
> @@ -252,9 +257,46 @@ long lttng_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>  	}
>  }
>  
> +/*
> + * lttng_uevent_set_handler - set handler functions for uevent
> + */
> +
> +void lttng_uevent_set_handler(write_ops_t handler)
> +{
> +	lttng_uevent_handler = handler;
> +}
> +EXPORT_SYMBOL_GPL(lttng_uevent_set_handler);
> +
> +/*
> + * lttng_write_uevent - expose kernel tracer to user-space
> + *
> + * The handler function is protected with rcu_read_lock() to prevent the
> + * module to be unloaded while the tracepoint is being used. It assumes that
> + * rcu_synchronize() is called on module unload.
> + */
> +
> +static
> +ssize_t lttng_write_uevent(struct file *file, const char __user *ubuf,
> +		size_t count, loff_t *fpos)
> +{
> +	int ret;
> +	write_ops_t handler;
> +
> +	rcu_read_lock();
> +	handler = rcu_dereference(lttng_uevent_handler);
> +	if (unlikely(handler == NULL)) {
> +		rcu_read_unlock();
> +		return -ENOSYS;
> +	}
> +	ret = handler(file, ubuf, count, fpos);
> +	rcu_read_unlock();
> +	return ret;
> +}
> +
>  static const struct file_operations lttng_fops = {
>  	.owner = THIS_MODULE,
>  	.unlocked_ioctl = lttng_ioctl,
> +	.write = lttng_write_uevent,
>  #ifdef CONFIG_COMPAT
>  	.compat_ioctl = lttng_ioctl,
>  #endif
> diff --git a/lttng-abi.h b/lttng-abi.h
> index dc230d8..1f3847c 100644
> --- a/lttng-abi.h
> +++ b/lttng-abi.h
> @@ -27,6 +27,10 @@
>  
>  #define LTTNG_KERNEL_SYM_NAME_LEN	256
>  
> +typedef ssize_t (*write_ops_t) (struct file *, const char __user *, size_t,
> +		loff_t *);
> +void lttng_uevent_set_handler(write_ops_t handler);
> +
>  enum lttng_kernel_instrumentation {
>  	LTTNG_KERNEL_TRACEPOINT	= 0,
>  	LTTNG_KERNEL_KPROBE	= 1,
> diff --git a/probes/Makefile b/probes/Makefile
> index 698a9c9..a895e60 100644
> --- a/probes/Makefile
> +++ b/probes/Makefile
> @@ -14,6 +14,8 @@ obj-m += lttng-probe-sched.o
>  obj-m += lttng-probe-irq.o
>  obj-m += lttng-probe-signal.o
>  obj-m += lttng-probe-timer.o
> +obj-m += lttng-probe-uevent.o
> +obj-m += lttng-uevent.o
>  
>  obj-m += lttng-probe-statedump.o
>  
> diff --git a/probes/lttng-probe-uevent.c b/probes/lttng-probe-uevent.c
> new file mode 100644
> index 0000000..90abb5e
> --- /dev/null
> +++ b/probes/lttng-probe-uevent.c
> @@ -0,0 +1,36 @@
> +/*
> + * probes/lttng-probe-uevent.c
> + *
> + * Expose kernel tracer to user-space through /proc/lttng
> + *
> + * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; only
> + * version 2.1 of the License.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +#include <linux/module.h>
> +
> +/*
> + * Create lttng_uevent tracepoint probes.
> + */
> +#define LTTNG_PACKAGE_BUILD
> +#define CREATE_TRACE_POINTS
> +#define TRACE_INCLUDE_PATH ../instrumentation/events/lttng-module
> +
> +#include "../instrumentation/events/lttng-module/uevent.h"
> +
> +MODULE_LICENSE("GPL and additional rights");
> +MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
> +MODULE_DESCRIPTION("LTTng uevent probes");
> diff --git a/probes/lttng-uevent.c b/probes/lttng-uevent.c
> new file mode 100644
> index 0000000..7b4bffc
> --- /dev/null
> +++ b/probes/lttng-uevent.c
> @@ -0,0 +1,58 @@
> +/*
> + * probes/lttng-uevent.c
> + *
> + * Expose kernel tracer to user-space through /proc/lttng
> + *
> + * Copyright (C) 2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; only
> + * version 2.1 of the License.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +#include <linux/module.h>
> +#include "../lttng-abi.h"
> +
> +/* include our own uevent tracepoint */
> +#include "../instrumentation/events/lttng-module/uevent.h"
> +DEFINE_TRACE(lttng_uevent);
> +
> +#define LTTNG_UEVENT_SIZE 1024
> +
> +ssize_t uevent_write_handler(struct file *file, const char __user *ubuf,
> +		size_t count, loff_t *fpos)
> +{
> +	if (count > LTTNG_UEVENT_SIZE)
> +		count = LTTNG_UEVENT_SIZE;
> +
> +	trace_lttng_uevent(ubuf, count);
> +	return count;
> +}
> +
> +static int __init lttng_probe_uevent_init(void)
> +{
> +	lttng_uevent_set_handler(uevent_write_handler);
> +	return 0;
> +}
> +
> +static void __exit lttng_probe_uevent_exit(void)
> +{
> +	lttng_uevent_set_handler(NULL);
> +}
> +
> +module_init(lttng_probe_uevent_init);
> +module_exit(lttng_probe_uevent_exit);
> +
> +MODULE_LICENSE("GPL and additional rights");
> +MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
> +MODULE_DESCRIPTION("LTTng kernel event from user-space");
> -- 
> 1.7.9.5
> 
> 
> _______________________________________________
> lttng-dev mailing list
> lttng-dev@lists.lttng.org
> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com

Re: [PATCH] Expose kernel tracer to user-space (version 5)

[Francis Giraldeau]

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Le 2012-07-02 16:13, Mathieu Desnoyers a écrit :
> * Francis Giraldeau (francis.giraldeau@gmail.com) wrote:
>> By writing to the file /proc/lttng, a user-space application creates a
>> kernel event. The event's payload is by default UTF-8 text, but any data
>> can be written, up to 1024 bytes. Null-character is optional and is not
>> enforced. The event uses sequence for space efficiency and to store any
>> data as payload.
> 
> Why limit to 1024 bytes ? We could use a string_from_user, and write it
> into a null-terminated string instead.

This is the same limit as printk:

  #define LOG_LINE_MAX 1024

We can't use string_from_user because it's not possible to assume that
the string from user-space is null terminated and we can't changed it in
order to avoid double copy. Thus, I think the current mechanism is
appropriate.

Anyway, if the application really wants all the data to be written, then
it can create another event with the remaining data, since the number of
bytes written is returned.

>> The feature is enabled when both lttng-uevent and lttng-probe-uevent are
>> loaded.
> 
> Why not combine those two into a single module ?

The problem is that the probe code creates it's own module_init and
module_exit functions, and I didn't found a way to override properly and
still call the probe registration. The easy way was to create two
modules, but yes I would prefer it to be combined. What can be done for
that?

>> Module unload must be prevented while lttng-uevent is being used.
>> rcu_synchronized() is call on module unload, and thus rcu_read_lock() can be
> 
> is call -> is called, or is invoked

fixed.

Thanks!

Francis


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Re: [PATCH] Expose kernel tracer to user-space (version 5)

[Mathieu Desnoyers]

* Francis Giraldeau (francis.giraldeau@gmail.com) wrote:
> Le 2012-07-02 16:13, Mathieu Desnoyers a écrit :
> > * Francis Giraldeau (francis.giraldeau@gmail.com) wrote:
> >> By writing to the file /proc/lttng, a user-space application creates a
> >> kernel event. The event's payload is by default UTF-8 text, but any data
> >> can be written, up to 1024 bytes. Null-character is optional and is not
> >> enforced. The event uses sequence for space efficiency and to store any
> >> data as payload.
> > 
> > Why limit to 1024 bytes ? We could use a string_from_user, and write it
> > into a null-terminated string instead.
> 
> This is the same limit as printk:
> 
>   #define LOG_LINE_MAX 1024
> 
> We can't use string_from_user because it's not possible to assume that
> the string from user-space is null terminated and we can't changed it in
> order to avoid double copy. Thus, I think the current mechanism is
> appropriate.

Agreed that the sequence is appropriate in that case. However, why the
1024 byte limit ? What is the technical reason for having this limit ?
By understanding why we have it, we can find a way to remove it...

> 
> Anyway, if the application really wants all the data to be written, then
> it can create another event with the remaining data, since the number of
> bytes written is returned.

I'd like to avoid that. Ideally, I'd let the maximum event size be
limited by the packet size, which is configurable by the user.

> 
> >> The feature is enabled when both lttng-uevent and lttng-probe-uevent are
> >> loaded.
> > 
> > Why not combine those two into a single module ?
> 
> The problem is that the probe code creates it's own module_init and
> module_exit functions, and I didn't found a way to override properly and
> still call the probe registration. The easy way was to create two
> modules, but yes I would prefer it to be combined. What can be done for
> that?

#define TP_MODULE_OVERRIDE

before including the trace header.

see probes/lttng-events.h.

Thanks,

Mathieu

> 
> >> Module unload must be prevented while lttng-uevent is being used.
> >> rcu_synchronized() is call on module unload, and thus rcu_read_lock() can be
> > 
> > is call -> is called, or is invoked
> 
> fixed.
> 
> Thanks!
> 
> Francis
> 



> _______________________________________________
> lttng-dev mailing list
> lttng-dev@lists.lttng.org
> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev


-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com

[PATCH] Expose kernel tracer to user-space (version 5)

[Francis Giraldeau]

By writing to the file /proc/lttng, a user-space application creates a
kernel event. The event's payload is by default UTF-8 text, but any data
can be written, up to 1024 bytes. Null-character is optional and is not
enforced. The event uses sequence for space efficiency and to store any
data as payload.

The feature is enabled when both lttng-uevent and lttng-probe-uevent are
loaded. The lttng-abi module exports a register function and includes a wrapper
for lttng_fops write. This is required since struct file_operations must be
const.

Module unload must be prevented while lttng-uevent is being used.
rcu_synchronized() is call on module unload, and thus rcu_read_lock() can be
used to force waiting until the critical section is over.

Signed-off-by: Francis Giraldeau <francis.giraldeau@gmail.com>
---
 instrumentation/events/lttng-module/uevent.h |   33 +++++++++++++++
 lttng-abi.c                                  |   42 +++++++++++++++++++
 lttng-abi.h                                  |    4 ++
 probes/Makefile                              |    2 +
 probes/lttng-probe-uevent.c                  |   36 ++++++++++++++++
 probes/lttng-uevent.c                        |   58 ++++++++++++++++++++++++++
 6 files changed, 175 insertions(+)
 create mode 100644 instrumentation/events/lttng-module/uevent.h
 create mode 100644 probes/lttng-probe-uevent.c
 create mode 100644 probes/lttng-uevent.c

diff --git a/instrumentation/events/lttng-module/uevent.h b/instrumentation/events/lttng-module/uevent.h
new file mode 100644
index 0000000..f67d901
--- /dev/null
+++ b/instrumentation/events/lttng-module/uevent.h
@@ -0,0 +1,33 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM uevent
+
+#if !defined(UEVENT_H_) || defined(TRACE_HEADER_MULTI_READ)
+#define UEVENT_H_
+
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(lttng_uevent,
+
+	TP_PROTO(const char *str, size_t len),
+
+	TP_ARGS(str, len),
+
+	/*
+	 * Uses sequence to hold variable size data, by default considered
+	 * as text. Null-terminal character is optional and is not enforced.
+	 */
+	TP_STRUCT__entry(
+		__dynamic_array_text(char, text, len)
+	),
+
+	TP_fast_assign(
+		tp_memcpy_dyn_from_user(text, str)
+	),
+
+	TP_printk("")
+)
+
+#endif /* UEVENT_H_ */
+
+/* This part must be outside protection */
+#include "../../../probes/define_trace.h"
diff --git a/lttng-abi.c b/lttng-abi.c
index 26a02ed..0de79ab 100644
--- a/lttng-abi.c
+++ b/lttng-abi.c
@@ -51,6 +51,11 @@
 #include "lttng-tracer.h"
 
 /*
+ * Required data structure to support lttng-probe-uevent
+ */
+static write_ops_t lttng_uevent_handler;
+
+/*
  * This is LTTng's own personal way to create a system call as an external
  * module. We use ioctl() on /proc/lttng.
  */
@@ -252,9 +257,46 @@ long lttng_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	}
 }
 
+/*
+ * lttng_uevent_set_handler - set handler functions for uevent
+ */
+
+void lttng_uevent_set_handler(write_ops_t handler)
+{
+	lttng_uevent_handler = handler;
+}
+EXPORT_SYMBOL_GPL(lttng_uevent_set_handler);
+
+/*
+ * lttng_write_uevent - expose kernel tracer to user-space
+ *
+ * The handler function is protected with rcu_read_lock() to prevent the
+ * module to be unloaded while the tracepoint is being used. It assumes that
+ * rcu_synchronize() is called on module unload.
+ */
+
+static
+ssize_t lttng_write_uevent(struct file *file, const char __user *ubuf,
+		size_t count, loff_t *fpos)
+{
+	int ret;
+	write_ops_t handler;
+
+	rcu_read_lock();
+	handler = rcu_dereference(lttng_uevent_handler);
+	if (unlikely(handler == NULL)) {
+		rcu_read_unlock();
+		return -ENOSYS;
+	}
+	ret = handler(file, ubuf, count, fpos);
+	rcu_read_unlock();
+	return ret;
+}
+
 static const struct file_operations lttng_fops = {
 	.owner = THIS_MODULE,
 	.unlocked_ioctl = lttng_ioctl,
+	.write = lttng_write_uevent,
 #ifdef CONFIG_COMPAT
 	.compat_ioctl = lttng_ioctl,
 #endif
diff --git a/lttng-abi.h b/lttng-abi.h
index dc230d8..1f3847c 100644
--- a/lttng-abi.h
+++ b/lttng-abi.h
@@ -27,6 +27,10 @@
 
 #define LTTNG_KERNEL_SYM_NAME_LEN	256
 
+typedef ssize_t (*write_ops_t) (struct file *, const char __user *, size_t,
+		loff_t *);
+void lttng_uevent_set_handler(write_ops_t handler);
+
 enum lttng_kernel_instrumentation {
 	LTTNG_KERNEL_TRACEPOINT	= 0,
 	LTTNG_KERNEL_KPROBE	= 1,
diff --git a/probes/Makefile b/probes/Makefile
index 698a9c9..a895e60 100644
--- a/probes/Makefile
+++ b/probes/Makefile
@@ -14,6 +14,8 @@ obj-m += lttng-probe-sched.o
 obj-m += lttng-probe-irq.o
 obj-m += lttng-probe-signal.o
 obj-m += lttng-probe-timer.o
+obj-m += lttng-probe-uevent.o
+obj-m += lttng-uevent.o
 
 obj-m += lttng-probe-statedump.o
 
diff --git a/probes/lttng-probe-uevent.c b/probes/lttng-probe-uevent.c
new file mode 100644
index 0000000..90abb5e
--- /dev/null
+++ b/probes/lttng-probe-uevent.c
@@ -0,0 +1,36 @@
+/*
+ * probes/lttng-probe-uevent.c
+ *
+ * Expose kernel tracer to user-space through /proc/lttng
+ *
+ * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; only
+ * version 2.1 of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <linux/module.h>
+
+/*
+ * Create lttng_uevent tracepoint probes.
+ */
+#define LTTNG_PACKAGE_BUILD
+#define CREATE_TRACE_POINTS
+#define TRACE_INCLUDE_PATH ../instrumentation/events/lttng-module
+
+#include "../instrumentation/events/lttng-module/uevent.h"
+
+MODULE_LICENSE("GPL and additional rights");
+MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
+MODULE_DESCRIPTION("LTTng uevent probes");
diff --git a/probes/lttng-uevent.c b/probes/lttng-uevent.c
new file mode 100644
index 0000000..7b4bffc
--- /dev/null
+++ b/probes/lttng-uevent.c
@@ -0,0 +1,58 @@
+/*
+ * probes/lttng-uevent.c
+ *
+ * Expose kernel tracer to user-space through /proc/lttng
+ *
+ * Copyright (C) 2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; only
+ * version 2.1 of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <linux/module.h>
+#include "../lttng-abi.h"
+
+/* include our own uevent tracepoint */
+#include "../instrumentation/events/lttng-module/uevent.h"
+DEFINE_TRACE(lttng_uevent);
+
+#define LTTNG_UEVENT_SIZE 1024
+
+ssize_t uevent_write_handler(struct file *file, const char __user *ubuf,
+		size_t count, loff_t *fpos)
+{
+	if (count > LTTNG_UEVENT_SIZE)
+		count = LTTNG_UEVENT_SIZE;
+
+	trace_lttng_uevent(ubuf, count);
+	return count;
+}
+
+static int __init lttng_probe_uevent_init(void)
+{
+	lttng_uevent_set_handler(uevent_write_handler);
+	return 0;
+}
+
+static void __exit lttng_probe_uevent_exit(void)
+{
+	lttng_uevent_set_handler(NULL);
+}
+
+module_init(lttng_probe_uevent_init);
+module_exit(lttng_probe_uevent_exit);
+
+MODULE_LICENSE("GPL and additional rights");
+MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
+MODULE_DESCRIPTION("LTTng kernel event from user-space");
-- 
1.7.9.5