binder: Add stats, state and transactions files

The following binder stat files currently live in debugfs.

/sys/kernel/debug/binder/state
/sys/kernel/debug/binder/stats
/sys/kernel/debug/binder/transactions

This patch makes these files available in a binderfs instance
mounted with the mount option 'stats=global'. For example, if a binderfs
instance is mounted at path /dev/binderfs, the above files will be
available at the following locations:

/dev/binderfs/binder_logs/state
/dev/binderfs/binder_logs/stats
/dev/binderfs/binder_logs/transactions

This provides a way to access them even when debugfs is not mounted.

Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Hridya Valsaraju <hridya@google.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/20190903161655.107408-3-hridya@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/android/binder.c

@@ -5907,7 +5907,7 @@ static void print_binder_proc_stats(struct seq_file *m,
 }
 
 
-static int state_show(struct seq_file *m, void *unused)
+int binder_state_show(struct seq_file *m, void *unused)
 {
 	struct binder_proc *proc;
 	struct binder_node *node;
@@ -5946,7 +5946,7 @@ static int state_show(struct seq_file *m, void *unused)
 	return 0;
 }
 
-static int stats_show(struct seq_file *m, void *unused)
+int binder_stats_show(struct seq_file *m, void *unused)
 {
 	struct binder_proc *proc;
 
@@ -5962,7 +5962,7 @@ static int stats_show(struct seq_file *m, void *unused)
 	return 0;
 }
 
-static int transactions_show(struct seq_file *m, void *unused)
+int binder_transactions_show(struct seq_file *m, void *unused)
 {
 	struct binder_proc *proc;
 
@@ -6050,9 +6050,6 @@ const struct file_operations binder_fops = {
 	.release = binder_release,
 };
 
-DEFINE_SHOW_ATTRIBUTE(state);
-DEFINE_SHOW_ATTRIBUTE(stats);
-DEFINE_SHOW_ATTRIBUTE(transactions);
 DEFINE_SHOW_ATTRIBUTE(transaction_log);
 
 static int __init init_binder_device(const char *name)
@@ -6108,17 +6105,17 @@ static int __init binder_init(void)
 				    0444,
 				    binder_debugfs_dir_entry_root,
 				    NULL,
-				    &state_fops);
+				    &binder_state_fops);
 		debugfs_create_file("stats",
 				    0444,
 				    binder_debugfs_dir_entry_root,
 				    NULL,
-				    &stats_fops);
+				    &binder_stats_fops);
 		debugfs_create_file("transactions",
 				    0444,
 				    binder_debugfs_dir_entry_root,
 				    NULL,
-				    &transactions_fops);
+				    &binder_transactions_fops);
 		debugfs_create_file("transaction_log",
 				    0444,
 				    binder_debugfs_dir_entry_root,

drivers/android/binder_internal.h

@@ -57,4 +57,12 @@ static inline int __init init_binderfs(void)
 }
 #endif
 
+int binder_stats_show(struct seq_file *m, void *unused);
+DEFINE_SHOW_ATTRIBUTE(binder_stats);
+
+int binder_state_show(struct seq_file *m, void *unused);
+DEFINE_SHOW_ATTRIBUTE(binder_state);
+
+int binder_transactions_show(struct seq_file *m, void *unused);
+DEFINE_SHOW_ATTRIBUTE(binder_transactions);
 #endif /* _LINUX_BINDER_INTERNAL_H */

drivers/android/binderfs.c

@@ -280,7 +280,7 @@ static void binderfs_evict_inode(struct inode *inode)
 
 	clear_inode(inode);
 
-	if (!device)
+	if (!S_ISCHR(inode->i_mode) || !device)
 		return;
 
 	mutex_lock(&binderfs_minors_mutex);
@@ -502,6 +502,141 @@ static const struct inode_operations binderfs_dir_inode_operations = {
 	.unlink = binderfs_unlink,
 };
 
+static struct inode *binderfs_make_inode(struct super_block *sb, int mode)
+{
+	struct inode *ret;
+
+	ret = new_inode(sb);
+	if (ret) {
+		ret->i_ino = iunique(sb, BINDERFS_MAX_MINOR + INODE_OFFSET);
+		ret->i_mode = mode;
+		ret->i_atime = ret->i_mtime = ret->i_ctime = current_time(ret);
+	}
+	return ret;
+}
+
+static struct dentry *binderfs_create_dentry(struct dentry *parent,
+					     const char *name)
+{
+	struct dentry *dentry;
+
+	dentry = lookup_one_len(name, parent, strlen(name));
+	if (IS_ERR(dentry))
+		return dentry;
+
+	/* Return error if the file/dir already exists. */
+	if (d_really_is_positive(dentry)) {
+		dput(dentry);
+		return ERR_PTR(-EEXIST);
+	}
+
+	return dentry;
+}
+
+static struct dentry *binderfs_create_file(struct dentry *parent,
+					   const char *name,
+					   const struct file_operations *fops,
+					   void *data)
+{
+	struct dentry *dentry;
+	struct inode *new_inode, *parent_inode;
+	struct super_block *sb;
+
+	parent_inode = d_inode(parent);
+	inode_lock(parent_inode);
+
+	dentry = binderfs_create_dentry(parent, name);
+	if (IS_ERR(dentry))
+		goto out;
+
+	sb = parent_inode->i_sb;
+	new_inode = binderfs_make_inode(sb, S_IFREG | 0444);
+	if (!new_inode) {
+		dput(dentry);
+		dentry = ERR_PTR(-ENOMEM);
+		goto out;
+	}
+
+	new_inode->i_fop = fops;
+	new_inode->i_private = data;
+	d_instantiate(dentry, new_inode);
+	fsnotify_create(parent_inode, dentry);
+
+out:
+	inode_unlock(parent_inode);
+	return dentry;
+}
+
+static struct dentry *binderfs_create_dir(struct dentry *parent,
+					  const char *name)
+{
+	struct dentry *dentry;
+	struct inode *new_inode, *parent_inode;
+	struct super_block *sb;
+
+	parent_inode = d_inode(parent);
+	inode_lock(parent_inode);
+
+	dentry = binderfs_create_dentry(parent, name);
+	if (IS_ERR(dentry))
+		goto out;
+
+	sb = parent_inode->i_sb;
+	new_inode = binderfs_make_inode(sb, S_IFDIR | 0755);
+	if (!new_inode) {
+		dput(dentry);
+		dentry = ERR_PTR(-ENOMEM);
+		goto out;
+	}
+
+	new_inode->i_fop = &simple_dir_operations;
+	new_inode->i_op = &simple_dir_inode_operations;
+
+	set_nlink(new_inode, 2);
+	d_instantiate(dentry, new_inode);
+	inc_nlink(parent_inode);
+	fsnotify_mkdir(parent_inode, dentry);
+
+out:
+	inode_unlock(parent_inode);
+	return dentry;
+}
+
+static int init_binder_logs(struct super_block *sb)
+{
+	struct dentry *binder_logs_root_dir, *dentry;
+	int ret = 0;
+
+	binder_logs_root_dir = binderfs_create_dir(sb->s_root,
+						   "binder_logs");
+	if (IS_ERR(binder_logs_root_dir)) {
+		ret = PTR_ERR(binder_logs_root_dir);
+		goto out;
+	}
+
+	dentry = binderfs_create_file(binder_logs_root_dir, "stats",
+				      &binder_stats_fops, NULL);
+	if (IS_ERR(dentry)) {
+		ret = PTR_ERR(dentry);
+		goto out;
+	}
+
+	dentry = binderfs_create_file(binder_logs_root_dir, "state",
+				      &binder_state_fops, NULL);
+	if (IS_ERR(dentry)) {
+		ret = PTR_ERR(dentry);
+		goto out;
+	}
+
+	dentry = binderfs_create_file(binder_logs_root_dir, "transactions",
+				      &binder_transactions_fops, NULL);
+	if (IS_ERR(dentry))
+		ret = PTR_ERR(dentry);
+
+out:
+	return ret;
+}
+
 static int binderfs_fill_super(struct super_block *sb, void *data, int silent)
 {
 	int ret;
@@ -579,6 +714,9 @@ static int binderfs_fill_super(struct super_block *sb, void *data, int silent)
 			name++;
 	}
 
+	if (info->mount_opts.stats_mode == STATS_GLOBAL)
+		return init_binder_logs(sb);
+
 	return 0;
 }