[v3,3/7] libtracefs: Implement tracefs_kretprobe_raw()

Commit Message

Steven Rostedt July 2, 2021, 3:10 a.m. UTC

From: "Steven Rostedt (VMware)" <[e-mail]>

Add an interface that is similar to tracefs_kprobe_raw() but creates a
"kretprobe". The difference between a kprobe and a kretprobe is that a
kretprobe comes at the end of a function.

See Documentation/trace/kprobetrace.rst in the Linux kernel source code
for more information. Note, kprobes are started with "p" and kretprobe
lines start with an "r".

Signed-off-by: Steven Rostedt (VMware) <[e-mail]>
---
 include/tracefs.h     |  3 +-
 src/tracefs-kprobes.c | 85 ++++++++++++++++++++++++++++++-------------
 2 files changed, 61 insertions(+), 27 deletions(-)

Patch

diff --git a/include/tracefs.h b/include/tracefs.h
index bc504bcb0188..64164c8c2b20 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -217,5 +217,6 @@  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_kretprobe_raw(const char *system, const char *event,
+			  const char *addr, const char *format);
 #endif /* _TRACE_FS_H */
diff --git a/src/tracefs-kprobes.c b/src/tracefs-kprobes.c
index 78548030e5bb..9bd9b2df9287 100644
--- a/src/tracefs-kprobes.c
+++ b/src/tracefs-kprobes.c
@@ -20,28 +20,9 @@ 
 
 #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)
+static int insert_kprobe(const char *type, const char *system,
+			 const char *event, const char *addr,
+			 const char *format)
 {
 	struct stat st;
 	char *str;
@@ -58,11 +39,11 @@  int tracefs_kprobe_raw(const char *system, const char *event,
 		event = addr;
 
 	if (system)
-		ret = asprintf(&str, "p:%s/%s %s %s\n",
-			       system, event, addr, format);
+		ret = asprintf(&str, "%s:%s/%s %s %s\n",
+			       type, system, event, addr, format);
 	else
-		ret = asprintf(&str, "p:%s %s %s\n",
-			       event, addr, format);
+		ret = asprintf(&str, "%s:%s %s %s\n",
+			       type, event, addr, format);
 
 	if (ret < 0)
 		return -1;
@@ -72,3 +53,55 @@  int tracefs_kprobe_raw(const char *system, const char *event,
 
 	return ret < 0 ? ret : 0;
 }
+
+/**
+ * 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)
+{
+	return insert_kprobe("p", system, event, addr, format);
+}
+
+/**
+ * tracefs_kretprobe_raw - Create a kretprobe 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 retprobe
+ * @format: The raw format string to define the retprobe.
+ *
+ * Create a kretprobe 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_kretprobe_raw(const char *system, const char *event,
+			  const char *addr, const char *format)
+{
+	return insert_kprobe("r", system, event, addr, format);
+}