Fixed MTP to work with TWRP

fs/efivarfs/file.c

@@ -0,0 +1,111 @@
+/*
+ * Copyright (C) 2012 Red Hat, Inc.
+ * Copyright (C) 2012 Jeremy Kerr <jeremy.kerr@canonical.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/efi.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+
+#include "internal.h"
+
+static ssize_t efivarfs_file_write(struct file *file,
+		const char __user *userbuf, size_t count, loff_t *ppos)
+{
+	struct efivar_entry *var = file->private_data;
+	void *data;
+	u32 attributes;
+	struct inode *inode = file->f_mapping->host;
+	unsigned long datasize = count - sizeof(attributes);
+	ssize_t bytes;
+	bool set = false;
+
+	if (count < sizeof(attributes))
+		return -EINVAL;
+
+	if (copy_from_user(&attributes, userbuf, sizeof(attributes)))
+		return -EFAULT;
+
+	if (attributes & ~(EFI_VARIABLE_MASK))
+		return -EINVAL;
+
+	data = memdup_user(userbuf + sizeof(attributes), datasize);
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	bytes = efivar_entry_set_get_size(var, attributes, &datasize,
+					  data, &set);
+	if (!set && bytes) {
+		if (bytes == -ENOENT)
+			bytes = -EIO;
+		goto out;
+	}
+
+	if (bytes == -ENOENT) {
+		drop_nlink(inode);
+		d_delete(file->f_dentry);
+		dput(file->f_dentry);
+	} else {
+		mutex_lock(&inode->i_mutex);
+		i_size_write(inode, datasize + sizeof(attributes));
+		mutex_unlock(&inode->i_mutex);
+	}
+
+	bytes = count;
+
+out:
+	kfree(data);
+
+	return bytes;
+}
+
+static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
+		size_t count, loff_t *ppos)
+{
+	struct efivar_entry *var = file->private_data;
+	unsigned long datasize = 0;
+	u32 attributes;
+	void *data;
+	ssize_t size = 0;
+	int err;
+
+	err = efivar_entry_size(var, &datasize);
+
+	/*
+	 * efivarfs represents uncommitted variables with
+	 * zero-length files. Reading them should return EOF.
+	 */
+	if (err == -ENOENT)
+		return 0;
+	else if (err)
+		return err;
+
+	data = kmalloc(datasize + sizeof(attributes), GFP_KERNEL);
+
+	if (!data)
+		return -ENOMEM;
+
+	size = efivar_entry_get(var, &attributes, &datasize,
+				data + sizeof(attributes));
+	if (size)
+		goto out_free;
+
+	memcpy(data, &attributes, sizeof(attributes));
+	size = simple_read_from_buffer(userbuf, count, ppos,
+				       data, datasize + sizeof(attributes));
+out_free:
+	kfree(data);
+
+	return size;
+}
+
+const struct file_operations efivarfs_file_operations = {
+	.open	= simple_open,
+	.read	= efivarfs_file_read,
+	.write	= efivarfs_file_write,
+	.llseek	= no_llseek,
+};