Commit fc470abf authored by Carlos Llamas's avatar Carlos Llamas Committed by Greg Kroah-Hartman
Browse files

binderfs: add support for feature files 



Provide userspace with a mechanism to discover features supported by
the binder driver to refrain from using any unsupported ones in the
first place. Starting with "oneway_spam_detection" only new features
are to be listed under binderfs and all previous ones are assumed to
be supported.

Assuming an instance of binderfs has been mounted at /dev/binderfs,
binder feature files can be found under /dev/binderfs/features/.
Usage example:

  $ mkdir /dev/binderfs
  $ mount -t binder binder /dev/binderfs
  $ cat /dev/binderfs/features/oneway_spam_detection
  1

Acked-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: default avatarCarlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20210715031805.1725878-1-cmllamas@google.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent ec7b5eda

drivers/android/binderfs.c

+39 −0
Original line number Diff line number Diff line
@@ -58,6 +58,10 @@ enum binderfs_stats_mode { 
	binderfs_stats_mode_global,

};



struct binder_features {

	bool oneway_spam_detection;

};



static const struct constant_table binderfs_param_stats[] = {

	{ "global", binderfs_stats_mode_global },

	{}
@@ -69,6 +73,10 @@ static const struct fs_parameter_spec binderfs_fs_parameters[] = { 
	{}

};



static struct binder_features binder_features = {

	.oneway_spam_detection = true,

};



static inline struct binderfs_info *BINDERFS_SB(const struct super_block *sb)

{

	return sb->s_fs_info;
@@ -583,6 +591,33 @@ static struct dentry *binderfs_create_dir(struct dentry *parent, 
	return dentry;

}



static int binder_features_show(struct seq_file *m, void *unused)

{

	bool *feature = m->private;



	seq_printf(m, "%d\n", *feature);



	return 0;

}

DEFINE_SHOW_ATTRIBUTE(binder_features);



static int init_binder_features(struct super_block *sb)

{

	struct dentry *dentry, *dir;



	dir = binderfs_create_dir(sb->s_root, "features");

	if (IS_ERR(dir))

		return PTR_ERR(dir);



	dentry = binderfs_create_file(dir, "oneway_spam_detection",

				      &binder_features_fops,

				      &binder_features.oneway_spam_detection);

	if (IS_ERR(dentry))

		return PTR_ERR(dentry);



	return 0;

}



static int init_binder_logs(struct super_block *sb)

{

	struct dentry *binder_logs_root_dir, *dentry, *proc_log_dir;
@@ -723,6 +758,10 @@ static int binderfs_fill_super(struct super_block *sb, struct fs_context *fc) 
			name++;

	}



	ret = init_binder_features(sb);

	if (ret)

		return ret;



	if (info->mount_opts.stats_mode == binderfs_stats_mode_global)

		return init_binder_logs(sb);