ftrace: Add helper find_direct_entry() to consolidate code

Both unregister_ftrace_direct() and modify_ftrace_direct() needs to
normalize the ip passed in to match the rec->ip, as it is acceptable to have
the ip on the ftrace call site but not the start. There are also common
validity checks with the record found by the ip, these should be done for
both unregister_ftrace_direct() and modify_ftrace_direct().
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/ftrace.c

@@ -5112,30 +5112,40 @@ int register_ftrace_direct(unsigned long ip, unsigned long addr)
 }
 EXPORT_SYMBOL_GPL(register_ftrace_direct);
 
-int unregister_ftrace_direct(unsigned long ip, unsigned long addr)
+static struct ftrace_func_entry *find_direct_entry(unsigned long *ip)
 {
 	struct ftrace_func_entry *entry;
-	struct ftrace_direct_func *direct;
 	struct dyn_ftrace *rec;
-	int ret = -ENODEV;
 
-	mutex_lock(&direct_mutex);
+	rec = lookup_rec(*ip, *ip);
+	if (!rec)
+		return NULL;
 
-	entry = __ftrace_lookup_ip(direct_functions, ip);
+	entry = __ftrace_lookup_ip(direct_functions, rec->ip);
 	if (!entry) {
-		/* OK if it is off by a little */
-		rec = lookup_rec(ip, ip);
-		if (!rec || rec->ip == ip)
-			goto out_unlock;
+		WARN_ON(rec->flags & FTRACE_FL_DIRECT);
+		return NULL;
+	}
 
-		entry = __ftrace_lookup_ip(direct_functions, rec->ip);
-		if (!entry) {
-			WARN_ON(rec->flags & FTRACE_FL_DIRECT);
-			goto out_unlock;
-		}
+	WARN_ON(!(rec->flags & FTRACE_FL_DIRECT));
 
-		WARN_ON(!(rec->flags & FTRACE_FL_DIRECT));
-	}
+	/* Passed in ip just needs to be on the call site */
+	*ip = rec->ip;
+
+	return entry;
+}
+
+int unregister_ftrace_direct(unsigned long ip, unsigned long addr)
+{
+	struct ftrace_direct_func *direct;
+	struct ftrace_func_entry *entry;
+	int ret = -ENODEV;
+
+	mutex_lock(&direct_mutex);
+
+	entry = find_direct_entry(&ip);
+	if (!entry)
+		goto out_unlock;
 
 	if (direct_functions->count == 1)
 		unregister_ftrace_function(&direct_ops);
@@ -5187,24 +5197,13 @@ int modify_ftrace_direct(unsigned long ip,
 			 unsigned long old_addr, unsigned long new_addr)
 {
 	struct ftrace_func_entry *entry;
-	struct dyn_ftrace *rec;
 	int ret = -ENODEV;
 
 	mutex_lock(&direct_mutex);
-	entry = __ftrace_lookup_ip(direct_functions, ip);
-	if (!entry) {
-		/* OK if it is off by a little */
-		rec = lookup_rec(ip, ip);
-		if (!rec || rec->ip == ip)
-			goto out_unlock;
-
-		entry = __ftrace_lookup_ip(direct_functions, rec->ip);
-		if (!entry)
-			goto out_unlock;
 
-		ip = rec->ip;
-		WARN_ON(!(rec->flags & FTRACE_FL_DIRECT));
-	}
+	entry = find_direct_entry(&ip);
+	if (!entry)
+		goto out_unlock;
 
 	ret = -EINVAL;
 	if (entry->direct != old_addr)