[PATCH v7 04/10] libtracefs: Implement tracefs_get_kprobes()

[Steven Rostedt <rostedt@goodmis.org>]

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

Add the function tracefs_get_kprobes() that returns a list of kprobes that
are registered. The list contains strings that are of the format
"group/event" (i.e. "kprobes/open"). The last element in the list is a
NULL pointer. In the case that there are no kprobes, the list will return
a single entry of a NULL pointer.

tracefs_get_kprobes() takes a type parameter to determine which kprobes to
return:

  TRACEFS_ALL_KPROBES	- return all that are found
  TRACEFS_KPROBE	- return only normal kprobes ("p:")
  TRACEFS_KRETPROBE	- return only kretprobes ("r:")

NULL is returned in the case of error (mainly a memory issue, or bad
parsing).

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 include/tracefs.h     |  7 ++++
 src/tracefs-kprobes.c | 93 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 100 insertions(+)

diff --git a/include/tracefs.h b/include/tracefs.h
index 64164c8c2b20..e8a2008d9714 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -215,8 +215,15 @@ ssize_t tracefs_trace_pipe_stream(int fd, struct tracefs_instance *instance, int
 ssize_t tracefs_trace_pipe_print(struct tracefs_instance *instance, int flags);
 void tracefs_trace_pipe_stop(struct tracefs_instance *instance);
 
+enum tracefs_kprobe_type {
+	TRACEFS_ALL_KPROBES,
+	TRACEFS_KPROBE,
+	TRACEFS_KRETPROBE,
+};
+
 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);
+char **tracefs_get_kprobes(enum tracefs_kprobe_type type);
 #endif /* _TRACE_FS_H */
diff --git a/src/tracefs-kprobes.c b/src/tracefs-kprobes.c
index 4970620b28f2..3bba3683f29b 100644
--- a/src/tracefs-kprobes.c
+++ b/src/tracefs-kprobes.c
@@ -103,3 +103,96 @@ int tracefs_kretprobe_raw(const char *system, const char *event,
 {
 	return insert_kprobe("r", system, event, addr, format);
 }
+
+/**
+ * tracefs_get_kprobes - return a list kprobes (by group/event name)
+ * @type: The type of kprobes to return.
+ *
+ * If @type is TRACEFS_ALL_KPROBES all kprobes in the kprobe_events
+ * are returned. Otherwise if it is TRACEFS_KPROBE, then only
+ * normal kprobes (p:) are returned, or if type is TRACEFS_KRETPROBE
+ * then only kretprobes (r:) are returned.
+ *
+ * Returns a list of strings that contain the kprobes that exist
+ * in the kprobe_events files. The strings returned are in the
+ * "group/event" format.
+ * The list must be freed with tracefs_list_free().
+ * If there are no kprobes, a list is still returned, but it contains
+ * only a NULL pointer.
+ * On error, NULL is returned.
+ */
+char **tracefs_get_kprobes(enum tracefs_kprobe_type type)
+{
+	char **list = NULL;
+	char *content;
+	char *saveptr;
+	char *event;
+	char *p;
+	int cnt = 0;
+
+	errno = 0;
+	content = tracefs_instance_file_read(NULL, KPROBE_EVENTS, NULL);
+	if (!content) {
+		if (errno)
+			return NULL;
+		/* content is NULL on empty file, return an empty list */
+		list = calloc(1, sizeof(*list));
+		return list;
+	}
+
+	p = strtok_r(content, ":", &saveptr);
+
+	while (p) {
+		char **tmp;
+
+		if (type != TRACEFS_ALL_KPROBES) {
+			switch (*p) {
+			case 'p':
+				if (type != TRACEFS_KPROBE)
+					goto next;
+				break;
+			case 'r':
+				if (type != TRACEFS_KRETPROBE)
+					goto next;
+				break;
+			default:
+				goto next;
+			}
+		}
+
+		/* Failed parsing always return a failure */
+		p = strtok_r(NULL, " ", &saveptr);
+		if (!p)
+			break;
+
+		event = strdup(p);
+		if (!event)
+			goto fail;
+
+		tmp = realloc(list, sizeof(*list) * (cnt + 2));
+		if (!tmp)
+			goto fail;
+
+		list = tmp;
+		list[cnt++] = event;
+		list[cnt] = NULL;
+ next:
+		p = strtok_r(NULL, "\n", &saveptr);
+		/* Could be end of content */
+		if (!p)
+			break;
+
+		/* p is NULL on end of content */
+		p = strtok_r(NULL, ":", &saveptr);
+	}
+
+	if (!list)
+		list = calloc(1, sizeof(*list));
+ out:
+	free(content);
+	return list;
+ fail:
+	free(list);
+	list = NULL;
+	goto out;
+}
-- 
2.30.2