BACKPORT: binderfs: add extended_error feature entry

Add extended_error to the binderfs feature list, to help userspace
determine whether the BINDER_GET_EXTENDED_ERROR ioctl is supported by
the binder driver.

Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Acked-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20220429235644.697372-4-cmllamas@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Change-Id: I68a686e9d7620d1901d139d367f736d5a0a7ad54

drivers/android/binderfs.c

@@ -61,6 +61,7 @@ enum binderfs_stats_mode {
 
 struct binder_features {
 	bool oneway_spam_detection;
+	bool extended_error;
 };
 
 static const match_table_t tokens = {
@@ -71,6 +72,7 @@ static const match_table_t tokens = {
 
 static struct binder_features binder_features = {
 	.oneway_spam_detection = true,
+	.extended_error = true,
 };
 
 static inline struct binderfs_info *BINDERFS_I(const struct inode *inode)
@@ -620,6 +622,12 @@ static int init_binder_features(struct super_block *sb)
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 
+	dentry = binderfs_create_file(dir, "extended_error",
+				      &binder_features_fops,
+				      &binder_features.extended_error);
+	if (IS_ERR(dentry))
+		return PTR_ERR(dentry);
+
 	return 0;
 }