[PATCH v2 0/4] libtracefs: Facilitate adding and removing kprobes

[PATCH v2 0/4] libtracefs: Facilitate adding and removing kprobes

[Steven Rostedt]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Add a tracefs_kprobe_raw() to facilitate adding kprobe events. It's
denoted as "raw" because it still requires knowing the complex format of
a kprobe, but at least it helps with other formats:

 p:[[system/]event] addr fmt

The user only needs to know the "fmt" part above, and not worry about
what file to open, or how to open it.

Also add a tracefs_kprobe_clear() to clear all kprobes and a
tracefs_kprobe_clear_probe() to clear an individual kprobe. Both have a
"force" parameter, that if set, will then try to disable the kprobe in
all instances (including the top) and then remove the kprobe(s).

(Man pages still coming after this).

Changes since v1:
 - Added a tracefs_instances() to get the names of all instances
 - Rewrote the tracefs_kprobe_clear*() to use the tracefs_instances,
   which simplified the code tremendously.
 - Do not fail on failed: allocating various memory, disabling
   events, finding instances, etc, in the tracefs_kprobe_clear*()
   because it may still succeed, if the failed part were not what
   was causing it to not succeed.

Steven Rostedt (VMware) (4):
  libtracefs: Implement tracefs_instances()
  libtracefs: Implement tracefs_kprobe_raw()
  libtracefs: Implement tracefs_kprobe_clear() to remove all kprobes
  libtracefs: Implement tracefs_kprobe_clear_probe()

 include/tracefs.h      |   6 ++
 src/Makefile           |   1 +
 src/tracefs-instance.c |  78 +++++++++++++++
 src/tracefs-kprobes.c  | 215 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 300 insertions(+)
 create mode 100644 src/tracefs-kprobes.c

-- 
2.30.2

[PATCH v2 1/4] libtracefs: Implement tracefs_instances()

[Steven Rostedt]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Implement tracefs_instances() that will take a regex (or NULL for all) and
return a list of instances in the system.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 include/tracefs.h      |  1 +
 src/tracefs-instance.c | 78 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 79 insertions(+)

diff --git a/include/tracefs.h b/include/tracefs.h
index da8ad4189d4d..a21d2d2f22a6 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -44,6 +44,7 @@ int tracefs_instance_file_read_number(struct tracefs_instance *instance,
 int tracefs_instance_file_open(struct tracefs_instance *instance,
 			       const char *file, int mode);
 int tracefs_instances_walk(int (*callback)(const char *, void *), void *context);
+char **tracefs_instances(const char *regex);
 
 bool tracefs_instance_exists(const char *name);
 bool tracefs_file_exists(struct tracefs_instance *instance, const char *name);
diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c
index 2aeb529903bd..d833fae0fb0c 100644
--- a/src/tracefs-instance.c
+++ b/src/tracefs-instance.c
@@ -14,6 +14,7 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <dirent.h>
+#include <regex.h>
 #include <limits.h>
 #include <pthread.h>
 #include "tracefs.h"
@@ -630,6 +631,83 @@ out:
 	return fret;
 }
 
+static inline bool match(const char *str, regex_t *re)
+{
+	if (!re)
+		return true;
+	return regexec(re, str, 0, NULL, 0) == 0;
+}
+
+struct instance_list {
+	regex_t		*re;
+	char		**list;
+	int		size;
+	int		failed;
+};
+
+static int build_list(const char *name, void *data)
+{
+	struct instance_list *list = data;
+	char **instances;
+	int ret = -1;
+
+	if (!match(name, list->re))
+		return 0;
+
+	instances = realloc(list->list, list->size + 2);
+	if (!instances)
+		goto out;
+
+	list->list = instances;
+	list->list[list->size] = strdup(name);
+	if (!list->list[list->size])
+		goto out;
+
+	list->size++;
+	ret = 0;
+
+ out:
+	list->failed = ret;
+	return ret;
+}
+
+/**
+ * tracefs_instances - return a list of instance names
+ * @regex: A regex of instances to filter on (NULL to match all)
+ *
+ * Returns a list of names of existing instances, that must be
+ * freed with tracefs_list_free(). Note, if there are no matches
+ * then an empty list will be returned (not NULL).
+ * NULL on error.
+ */
+char **tracefs_instances(const char *regex)
+{
+	struct instance_list list = { .re = NULL, .list = NULL };
+	regex_t re;
+	int ret;
+
+	if (regex) {
+		ret = regcomp(&re, regex, REG_ICASE|REG_NOSUB);
+		if (ret < 0)
+			return NULL;
+		list.re = &re;
+	}
+
+	ret = tracefs_instances_walk(build_list, &list);
+	if (ret < 0 || list.failed) {
+		tracefs_list_free(list.list);
+		list.list = NULL;
+	} else {
+		if (!list.list) {
+			/* No matches should produce an empty list */
+			list.list = malloc(sizeof(*list.list));
+			if (list.list)
+				list.list[0] = NULL;
+		}
+	}
+	return list.list;
+}
+
 /**
  * tracefs_get_clock - Get the current trace clock
  * @instance: ftrace instance, can be NULL for the top instance
-- 
2.30.2

[PATCH v2 2/4] libtracefs: Implement tracefs_kprobe_raw()

[Steven Rostedt]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Add a function to facilitate creating a kprobe event. It has the "raw" in
its name because it still requires knowing the format of the kprobe. But
does handle the kprobe naming better and writing to the kprobe_event file.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 include/tracefs.h     |  4 +++
 src/Makefile          |  1 +
 src/tracefs-kprobes.c | 70 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 75 insertions(+)
 create mode 100644 src/tracefs-kprobes.c

diff --git a/include/tracefs.h b/include/tracefs.h
index a21d2d2f22a6..bc504bcb0188 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -214,4 +214,8 @@ int tracefs_tracer_clear(struct tracefs_instance *instance);
 ssize_t tracefs_trace_pipe_stream(int fd, struct tracefs_instance *instance, int flags);
 ssize_t tracefs_trace_pipe_print(struct tracefs_instance *instance, int flags);
 void tracefs_trace_pipe_stop(struct tracefs_instance *instance);
+
+int tracefs_kprobe_raw(const char *system, const char *event,
+		       const char *addr, const char *format);
+
 #endif /* _TRACE_FS_H */
diff --git a/src/Makefile b/src/Makefile
index b4cff07efc50..0697a047f4bc 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -8,6 +8,7 @@ OBJS += tracefs-instance.o
 OBJS += tracefs-events.o
 OBJS += tracefs-tools.o
 OBJS += tracefs-marker.o
+OBJS += tracefs-kprobes.o
 
 OBJS := $(OBJS:%.o=$(bdir)/%.o)
 DEPS := $(OBJS:$(bdir)/%.o=$(bdir)/.%.d)
diff --git a/src/tracefs-kprobes.c b/src/tracefs-kprobes.c
new file mode 100644
index 000000000000..e4b28cff9f08
--- /dev/null
+++ b/src/tracefs-kprobes.c
@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: LGPL-2.1
+/*
+ * Copyright (C) 2021 VMware Inc, Steven Rostedt <rostedt@goodmis.org>
+ *
+ * Updates:
+ * Copyright (C) 2021, VMware, Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
+ *
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <dirent.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <limits.h>
+
+#include "tracefs.h"
+#include "tracefs-local.h"
+
+#define KPROBE_EVENTS "kprobe_events"
+
+/**
+ * tracefs_kprobe_raw - Create a kprobe using raw format
+ * @system: The system name (NULL for the default kprobes)
+ * @event: The event to create (NULL to use @addr for the event)
+ * @addr: The function and offset (or address) to insert the probe
+ * @format: The raw format string to define the probe.
+ *
+ * Create a kprobe that will be in the @system group (or kprobes if
+ * @system is NULL). Have the name of @event (or @addr if @event is
+ * NULL). Will be inserted to @addr (function name, with or without
+ * offset, or a address). And the @format will define the raw format
+ * of the kprobe. See the Linux documentation file under:
+ * Documentation/trace/kprobetrace.rst
+ *
+ * Return 0 on success, or -1 on error.
+ *   If the syntex of @format was incorrect, running
+ *   tracefs_error_last(NULL) may show what went wrong.
+ *
+ * errno will be set to EBADMSG if addr or format is NULL.
+ */
+int tracefs_kprobe_raw(const char *system, const char *event,
+		       const char *addr, const char *format)
+{
+	char *str;
+	int ret;
+
+	errno = EBADMSG;
+	if (!addr || !format)
+		return -1;
+
+	if (!event)
+		event = addr;
+
+	if (system)
+		ret = asprintf(&str, "p:%s/%s %s %s\n",
+			       system, event, addr, format);
+	else
+		ret = asprintf(&str, "p:%s %s %s\n",
+			       event, addr, format);
+
+	if (ret < 0)
+		return -1;
+
+	ret = tracefs_instance_file_append(NULL, KPROBE_EVENTS, str);
+	free(str);
+
+	return ret < 0 ? ret : 0;
+}
-- 
2.30.2

[PATCH v2 3/4] libtracefs: Implement tracefs_kprobe_clear() to remove all kprobes

[Steven Rostedt]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

A call to tracefs_kprobe_clear() will attempt to disable all kprobes. If
any kprobe is set, and the @force parameter is set, it will fail with
errno set to EBUSY. If @force is set, then it will attempt to disable all
the defined kprobe events and then clear it.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 include/tracefs.h     |   2 +-
 src/tracefs-kprobes.c | 116 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 117 insertions(+), 1 deletion(-)

diff --git a/include/tracefs.h b/include/tracefs.h
index bc504bcb0188..19b9b49d2dae 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -217,5 +217,5 @@ void tracefs_trace_pipe_stop(struct tracefs_instance *instance);
 
 int tracefs_kprobe_raw(const char *system, const char *event,
 		       const char *addr, const char *format);
-
+int tracefs_kprobe_clear(bool force);
 #endif /* _TRACE_FS_H */
diff --git a/src/tracefs-kprobes.c b/src/tracefs-kprobes.c
index e4b28cff9f08..a6faf69fc010 100644
--- a/src/tracefs-kprobes.c
+++ b/src/tracefs-kprobes.c
@@ -68,3 +68,119 @@ int tracefs_kprobe_raw(const char *system, const char *event,
 
 	return ret < 0 ? ret : 0;
 }
+
+struct instance_list {
+	struct instance_list	*next;
+	struct tracefs_instance	*instance;
+};
+
+static void disable_events(const char *system, const char *event,
+			   char **list)
+{
+	struct tracefs_instance *instance;
+	int i;
+
+	/*
+	 * Note, this will not fail even on error.
+	 * That is because even if something fails, it may still
+	 * work enough to clear the kprobes. If that's the case
+	 * the clearing after the loop will succeed and the function
+	 * is a success, even though other parts had failed. If
+	 * one of the kprobe events is enabled in one of the
+	 * instances that fail, then the clearing will fail too
+	 * and the function will return an error.
+	 */
+
+	tracefs_event_disable(NULL, system, event);
+	/* No need to test results */
+
+	if (!list)
+		return;
+
+	for (i = 0; list[i]; i++) {
+		instance = tracefs_instance_alloc(NULL, list[i]);
+		/* If this fails, try the next one */
+		if (!instance)
+			continue;
+		tracefs_event_disable(instance, system, event);
+		tracefs_instance_free(instance);
+	}
+	return;
+}
+
+/**
+ * tracefs_kprobe_clear - clear kprobe events
+ * @force: Will attempt to disable all kprobe events and clear them
+ *
+ * Will remove all defined kprobe events. If any of them are enabled,
+ * and @force is not set, then it will error with -1 and errno to be
+ * EBUSY. If @force is set, then it will attempt to disable all the kprobe
+ * events in all instances, and try again.
+ *
+ * Returns zero on success, -1 otherwise.
+ */
+int tracefs_kprobe_clear(bool force)
+{
+	char **instance_list;
+	char *content;
+	char *saveptr;
+	char *system;
+	char *event;
+	char *p;
+	int ret;
+
+	ret = tracefs_instance_file_clear(NULL, KPROBE_EVENTS);
+	if (!ret)
+		return 0;
+
+	if (!force)
+		return -1;
+
+	/* Attempt to disable all kprobe events */
+	content = tracefs_instance_file_read(NULL, KPROBE_EVENTS, NULL);
+	if (!content)
+		return -1;
+
+	instance_list = tracefs_instances(NULL);
+	/*
+	 * Even if the above failed and instance_list is NULL,
+	 * keep going, as the enabled event may simply be in the
+	 * top level.
+	 */
+
+	ret = -1;
+	p = strtok_r(content, ":", &saveptr);
+	if (!p)
+		goto out;
+
+	for (;;) {
+		p = strtok_r(NULL, "/", &saveptr);
+		if (!p)
+			goto out;
+
+		system = p;
+
+		p = strtok_r(NULL," ", &saveptr);
+		if (!p)
+			goto out;
+		event = p;
+
+		disable_events(system, event, instance_list);
+
+		ret = tracefs_instance_file_clear(NULL, KPROBE_EVENTS);
+		/* On success stop the loop */
+		if (!ret)
+			goto out;
+
+		ret = -1;
+		p = strtok_r(NULL, "\n", &saveptr);
+		if (!p)
+			goto out;
+
+		p = strtok_r(NULL, ":", &saveptr);
+	}
+ out:
+	tracefs_list_free(instance_list);
+	free(content);
+	return ret;
+}
-- 
2.30.2

[PATCH v2 4/4] libtracefs: Implement tracefs_kprobe_clear_probe()

[Steven Rostedt]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Add the function tracefs_kprobe_clear_probe() that will remove a single
kprobe. If the @force parameter is set, it will disable that probe in all
instances (including the top level instance) before removing it.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 include/tracefs.h     |  1 +
 src/tracefs-kprobes.c | 29 +++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/include/tracefs.h b/include/tracefs.h
index 19b9b49d2dae..d7980c773b3d 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -218,4 +218,5 @@ void tracefs_trace_pipe_stop(struct tracefs_instance *instance);
 int tracefs_kprobe_raw(const char *system, const char *event,
 		       const char *addr, const char *format);
 int tracefs_kprobe_clear(bool force);
+int tracefs_kprobe_clear_probe(const char *system, const char *event, bool force);
 #endif /* _TRACE_FS_H */
diff --git a/src/tracefs-kprobes.c b/src/tracefs-kprobes.c
index a6faf69fc010..6f3fbac35d76 100644
--- a/src/tracefs-kprobes.c
+++ b/src/tracefs-kprobes.c
@@ -184,3 +184,32 @@ int tracefs_kprobe_clear(bool force)
 	free(content);
 	return ret;
 }
+
+int tracefs_kprobe_clear_probe(const char *system, const char *event, bool force)
+{
+	char **instance_list;
+	char *content;
+	int ret;
+
+	if (!system)
+		system = "kprobes";
+
+	ret = asprintf(&content, "-:%s/%s", system, event);
+	if (ret < 0)
+		return -1;
+
+	/*
+	 * Since we know we are disabling a specific event, try
+	 * to disable it first before clearing it.
+	 */
+	if (force) {
+		instance_list = tracefs_instances(NULL);
+		disable_events(system, event, instance_list);
+		tracefs_list_free(instance_list);
+	}
+
+	ret = tracefs_instance_file_append(NULL, KPROBE_EVENTS, content);
+	free(content);
+
+	return ret < 0 ? -1 : 0;
+}
-- 
2.30.2

Re: [PATCH v2 2/4] libtracefs: Implement tracefs_kprobe_raw()

[Yordan Karadzhov (VMware)]

On 30.06.21 г. 18:47, Steven Rostedt wrote:
> From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
> 
> Add a function to facilitate creating a kprobe event. It has the "raw" in
> its name because it still requires knowing the format of the kprobe. But
> does handle the kprobe naming better and writing to the kprobe_event file.
> 
> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> ---
>   include/tracefs.h     |  4 +++
>   src/Makefile          |  1 +
>   src/tracefs-kprobes.c | 70 +++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 75 insertions(+)
>   create mode 100644 src/tracefs-kprobes.c
> 
> diff --git a/include/tracefs.h b/include/tracefs.h
> index a21d2d2f22a6..bc504bcb0188 100644
> --- a/include/tracefs.h
> +++ b/include/tracefs.h
> @@ -214,4 +214,8 @@ int tracefs_tracer_clear(struct tracefs_instance *instance);
>   ssize_t tracefs_trace_pipe_stream(int fd, struct tracefs_instance *instance, int flags);
>   ssize_t tracefs_trace_pipe_print(struct tracefs_instance *instance, int flags);
>   void tracefs_trace_pipe_stop(struct tracefs_instance *instance);
> +
> +int tracefs_kprobe_raw(const char *system, const char *event,
> +		       const char *addr, const char *format);
> +
>   #endif /* _TRACE_FS_H */
> diff --git a/src/Makefile b/src/Makefile
> index b4cff07efc50..0697a047f4bc 100644
> --- a/src/Makefile
> +++ b/src/Makefile
> @@ -8,6 +8,7 @@ OBJS += tracefs-instance.o
>   OBJS += tracefs-events.o
>   OBJS += tracefs-tools.o
>   OBJS += tracefs-marker.o
> +OBJS += tracefs-kprobes.o
>   
>   OBJS := $(OBJS:%.o=$(bdir)/%.o)
>   DEPS := $(OBJS:$(bdir)/%.o=$(bdir)/.%.d)
> diff --git a/src/tracefs-kprobes.c b/src/tracefs-kprobes.c
> new file mode 100644
> index 000000000000..e4b28cff9f08
> --- /dev/null
> +++ b/src/tracefs-kprobes.c
> @@ -0,0 +1,70 @@
> +// SPDX-License-Identifier: LGPL-2.1
> +/*
> + * Copyright (C) 2021 VMware Inc, Steven Rostedt <rostedt@goodmis.org>
> + *
> + * Updates:
> + * Copyright (C) 2021, VMware, Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
> + *
> + */
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <dirent.h>
> +#include <unistd.h>
> +#include <errno.h>
> +#include <sys/stat.h>
> +#include <fcntl.h>
> +#include <limits.h>
> +
> +#include "tracefs.h"
> +#include "tracefs-local.h"
> +
> +#define KPROBE_EVENTS "kprobe_events"
> +
> +/**
> + * tracefs_kprobe_raw - Create a kprobe using raw format
> + * @system: The system name (NULL for the default kprobes)
> + * @event: The event to create (NULL to use @addr for the event)
> + * @addr: The function and offset (or address) to insert the probe
> + * @format: The raw format string to define the probe.
> + *
> + * Create a kprobe that will be in the @system group (or kprobes if
> + * @system is NULL). Have the name of @event (or @addr if @event is
> + * NULL). Will be inserted to @addr (function name, with or without
> + * offset, or a address). And the @format will define the raw format
> + * of the kprobe. See the Linux documentation file under:
> + * Documentation/trace/kprobetrace.rst
> + *
> + * Return 0 on success, or -1 on error.
> + *   If the syntex of @format was incorrect, running
> + *   tracefs_error_last(NULL) may show what went wrong.
> + *
> + * errno will be set to EBADMSG if addr or format is NULL.
> + */
> +int tracefs_kprobe_raw(const char *system, const char *event,
> +		       const char *addr, const char *format)
> +{
> +	char *str;
> +	int ret;
> +
> +	errno = EBADMSG;
> +	if (!addr || !format)
> +		return -1;
> +
> +	if (!event)
> +		event = addr;
> +
> +	if (system)
> +		ret = asprintf(&str, "p:%s/%s %s %s\n",
> +			       system, event, addr, format);
> +	else
> +		ret = asprintf(&str, "p:%s %s %s\n",
> +			       event, addr, format);

I wonder what will be the way to register a "return value" ("r:") 
kprobe. Do you consider having a separate API for them?

Thanks!
Yordan

> +
> +	if (ret < 0)
> +		return -1;
> +
> +	ret = tracefs_instance_file_append(NULL, KPROBE_EVENTS, str);
> +	free(str);
> +
> +	return ret < 0 ? ret : 0;
> +}
> 

Re: [PATCH v2 2/4] libtracefs: Implement tracefs_kprobe_raw()

[Steven Rostedt]

On Wed, 30 Jun 2021 22:46:19 +0300
"Yordan Karadzhov (VMware)" <y.karadz@gmail.com> wrote:

> > +int tracefs_kprobe_raw(const char *system, const char *event,
> > +		       const char *addr, const char *format)
> > +{
> > +	char *str;
> > +	int ret;
> > +
> > +	errno = EBADMSG;
> > +	if (!addr || !format)
> > +		return -1;
> > +
> > +	if (!event)
> > +		event = addr;
> > +
> > +	if (system)
> > +		ret = asprintf(&str, "p:%s/%s %s %s\n",
> > +			       system, event, addr, format);
> > +	else
> > +		ret = asprintf(&str, "p:%s %s %s\n",
> > +			       event, addr, format);  
> 
> I wonder what will be the way to register a "return value" ("r:") 
> kprobe. Do you consider having a separate API for them?

Yes, I was thinking about having a "tracefs_kretprobe_raw()" as well.

I also thought of adding a flag in the parameter, but thought that a
separate function would be better instead.

I wanted to play with this interface before creating the retprobe one.
If you are happy with the current design, I can add that too.

-- Steve

Re: [PATCH v2 2/4] libtracefs: Implement tracefs_kprobe_raw()

[Yordan Karadzhov (VMware)]

On 30.06.21 г. 22:53, Steven Rostedt wrote:
> On Wed, 30 Jun 2021 22:46:19 +0300
> "Yordan Karadzhov (VMware)" <y.karadz@gmail.com> wrote:
> 
>>> +int tracefs_kprobe_raw(const char *system, const char *event,
>>> +		       const char *addr, const char *format)
>>> +{
>>> +	char *str;
>>> +	int ret;
>>> +
>>> +	errno = EBADMSG;
>>> +	if (!addr || !format)
>>> +		return -1;
>>> +
>>> +	if (!event)
>>> +		event = addr;
>>> +
>>> +	if (system)
>>> +		ret = asprintf(&str, "p:%s/%s %s %s\n",
>>> +			       system, event, addr, format);
>>> +	else
>>> +		ret = asprintf(&str, "p:%s %s %s\n",
>>> +			       event, addr, format);
>>
>> I wonder what will be the way to register a "return value" ("r:")
>> kprobe. Do you consider having a separate API for them?
> 
> Yes, I was thinking about having a "tracefs_kretprobe_raw()" as well.
> 
> I also thought of adding a flag in the parameter, but thought that a
> separate function would be better instead.
> 
> I wanted to play with this interface before creating the retprobe one.
> If you are happy with the current design, I can add that too.
> 

The design looks good to me.

Thanks!
Y.

> -- Steve
>