text: /*
   * 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,
  };
  