binder: Make transaction_log available in binderfs

Currently, the binder transaction log files 'transaction_log'
and 'failed_transaction_log' live in debugfs at the following locations:

/sys/kernel/debug/binder/failed_transaction_log
/sys/kernel/debug/binder/transaction_log

This patch makes these files also available in a binderfs instance
mounted with the mount option "stats=global".
It does not affect the presence of these files in debugfs.
If a binderfs instance is mounted at path /dev/binderfs, the location of
these files will be as follows:

/dev/binderfs/binder_logs/failed_transaction_log
/dev/binderfs/binder_logs/transaction_log

This change provides an alternate option to access these files when
debugfs is not mounted.
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Hridya Valsaraju <hridya@google.com>
Link: https://lore.kernel.org/r/20190903161655.107408-4-hridya@google.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/android/binder.c

@@ -196,30 +196,8 @@ static inline void binder_stats_created(enum binder_stat_types type)
 	atomic_inc(&binder_stats.obj_created[type]);
 }
 
-struct binder_transaction_log_entry {
-	int debug_id;
-	int debug_id_done;
-	int call_type;
-	int from_proc;
-	int from_thread;
-	int target_handle;
-	int to_proc;
-	int to_thread;
-	int to_node;
-	int data_size;
-	int offsets_size;
-	int return_error_line;
-	uint32_t return_error;
-	uint32_t return_error_param;
-	const char *context_name;
-};
-struct binder_transaction_log {
-	atomic_t cur;
-	bool full;
-	struct binder_transaction_log_entry entry[32];
-};
-static struct binder_transaction_log binder_transaction_log;
-static struct binder_transaction_log binder_transaction_log_failed;
+struct binder_transaction_log binder_transaction_log;
+struct binder_transaction_log binder_transaction_log_failed;
 
 static struct binder_transaction_log_entry *binder_transaction_log_add(
 	struct binder_transaction_log *log)
@@ -6018,7 +5996,7 @@ static void print_binder_transaction_log_entry(struct seq_file *m,
 			"\n" : " (incomplete)\n");
 }
 
-static int transaction_log_show(struct seq_file *m, void *unused)
+int binder_transaction_log_show(struct seq_file *m, void *unused)
 {
 	struct binder_transaction_log *log = m->private;
 	unsigned int log_cur = atomic_read(&log->cur);
@@ -6050,8 +6028,6 @@ const struct file_operations binder_fops = {
 	.release = binder_release,
 };
 
-DEFINE_SHOW_ATTRIBUTE(transaction_log);
-
 static int __init init_binder_device(const char *name)
 {
 	int ret;
@@ -6120,12 +6096,12 @@ static int __init binder_init(void)
 				    0444,
 				    binder_debugfs_dir_entry_root,
 				    &binder_transaction_log,
-				    &transaction_log_fops);
+				    &binder_transaction_log_fops);
 		debugfs_create_file("failed_transaction_log",
 				    0444,
 				    binder_debugfs_dir_entry_root,
 				    &binder_transaction_log_failed,
-				    &transaction_log_fops);
+				    &binder_transaction_log_fops);
 	}
 
 	if (!IS_ENABLED(CONFIG_ANDROID_BINDERFS) &&

drivers/android/binder_internal.h

@@ -65,4 +65,34 @@ DEFINE_SHOW_ATTRIBUTE(binder_state);
 
 int binder_transactions_show(struct seq_file *m, void *unused);
 DEFINE_SHOW_ATTRIBUTE(binder_transactions);
+
+int binder_transaction_log_show(struct seq_file *m, void *unused);
+DEFINE_SHOW_ATTRIBUTE(binder_transaction_log);
+
+struct binder_transaction_log_entry {
+	int debug_id;
+	int debug_id_done;
+	int call_type;
+	int from_proc;
+	int from_thread;
+	int target_handle;
+	int to_proc;
+	int to_thread;
+	int to_node;
+	int data_size;
+	int offsets_size;
+	int return_error_line;
+	uint32_t return_error;
+	uint32_t return_error_param;
+	const char *context_name;
+};
+
+struct binder_transaction_log {
+	atomic_t cur;
+	bool full;
+	struct binder_transaction_log_entry entry[32];
+};
+
+extern struct binder_transaction_log binder_transaction_log;
+extern struct binder_transaction_log binder_transaction_log_failed;
 #endif /* _LINUX_BINDER_INTERNAL_H */

drivers/android/binderfs.c

@@ -630,6 +630,24 @@ static int init_binder_logs(struct super_block *sb)
 
 	dentry = binderfs_create_file(binder_logs_root_dir, "transactions",
 				      &binder_transactions_fops, NULL);
+	if (IS_ERR(dentry)) {
+		ret = PTR_ERR(dentry);
+		goto out;
+	}
+
+	dentry = binderfs_create_file(binder_logs_root_dir,
+				      "transaction_log",
+				      &binder_transaction_log_fops,
+				      &binder_transaction_log);
+	if (IS_ERR(dentry)) {
+		ret = PTR_ERR(dentry);
+		goto out;
+	}
+
+	dentry = binderfs_create_file(binder_logs_root_dir,
+				      "failed_transaction_log",
+				      &binder_transaction_log_fops,
+				      &binder_transaction_log_failed);
 	if (IS_ERR(dentry))
 		ret = PTR_ERR(dentry);