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binderfs: add support for feature files

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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: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20210715031805.1725878-1-cmllamas@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Carlos Llamas 2021-07-15 03:18:03 +00:00 committed by Greg Kroah-Hartman
parent ec7b5eda8a
commit fc470abf54
1 changed files with 39 additions and 0 deletions
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39
drivers/android/binderfs.c
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@ -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 @@ out:
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);