/*
   *  inode.c - securityfs
   *
   *  Copyright (C) 2005 Greg Kroah-Hartman <gregkh@suse.de>
   *
   *	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.
   *
   *  Based on fs/debugfs/inode.c which had the following copyright notice:
   *    Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
   *    Copyright (C) 2004 IBM Inc.
   */
  
  /* #define DEBUG */

  #include <linux/module.h>
  #include <linux/fs.h>
  #include <linux/mount.h>
  #include <linux/pagemap.h>
  #include <linux/init.h>
  #include <linux/namei.h>
  #include <linux/security.h>

  #include <linux/magic.h>

  
  static struct vfsmount *mount;
  static int mount_count;

  static inline int positive(struct dentry *dentry)
  {

  	return d_really_is_positive(dentry) && !d_unhashed(dentry);

  }
  
  static int fill_super(struct super_block *sb, void *data, int silent)
  {
  	static struct tree_descr files[] = {{""}};
  
  	return simple_fill_super(sb, SECURITYFS_MAGIC, files);
  }

  static struct dentry *get_sb(struct file_system_type *fs_type,

  		  int flags, const char *dev_name,

  		  void *data)

  {

  	return mount_single(fs_type, flags, data, fill_super);

  }
  
  static struct file_system_type fs_type = {
  	.owner =	THIS_MODULE,
  	.name =		"securityfs",

  	.mount =	get_sb,

  	.kill_sb =	kill_litter_super,
  };

  /**
   * securityfs_create_file - create a file in the securityfs filesystem
   *
   * @name: a pointer to a string containing the name of the file to create.
   * @mode: the permission that the file should have
   * @parent: a pointer to the parent dentry for this file.  This should be a

   *          directory dentry if set.  If this parameter is %NULL, then the

   *          file will be created in the root of the securityfs filesystem.
   * @data: a pointer to something that the caller will want to get to later

   *        on.  The inode.i_private pointer will point to this value on

   *        the open() call.
   * @fops: a pointer to a struct file_operations that should be used for
   *        this file.
   *
   * This is the basic "create a file" function for securityfs.  It allows for a

   * wide range of flexibility in creating a file, or a directory (if you

   * want to create a directory, the securityfs_create_dir() function is

   * recommended to be used instead).

   *

   * This function returns a pointer to a dentry if it succeeds.  This

   * pointer must be passed to the securityfs_remove() function when the file is
   * to be removed (no automatic cleanup happens if your module is unloaded,

   * you are responsible here).  If an error occurs, the function will return

   * the error value (via ERR_PTR).

   *

   * If securityfs is not enabled in the kernel, the value %-ENODEV is

   * returned.

   */

  struct dentry *securityfs_create_file(const char *name, umode_t mode,

  				   struct dentry *parent, void *data,

  				   const struct file_operations *fops)

  {

  	struct dentry *dentry;
  	int is_dir = S_ISDIR(mode);
  	struct inode *dir, *inode;

  	int error;

  	if (!is_dir) {
  		BUG_ON(!fops);
  		mode = (mode & S_IALLUGO) | S_IFREG;
  	}

  	pr_debug("securityfs: creating file '%s'
  ",name);

  	error = simple_pin_fs(&fs_type, &mount, &mount_count);

  	if (error)
  		return ERR_PTR(error);
  
  	if (!parent)
  		parent = mount->mnt_root;

  	dir = d_inode(parent);

  
  	mutex_lock(&dir->i_mutex);
  	dentry = lookup_one_len(name, parent, strlen(name));
  	if (IS_ERR(dentry))
  		goto out;

  	if (d_really_is_positive(dentry)) {

  		error = -EEXIST;
  		goto out1;

  	}

  	inode = new_inode(dir->i_sb);
  	if (!inode) {
  		error = -ENOMEM;
  		goto out1;

  	}

  	inode->i_ino = get_next_ino();
  	inode->i_mode = mode;
  	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  	inode->i_private = data;
  	if (is_dir) {
  		inode->i_op = &simple_dir_inode_operations;
  		inode->i_fop = &simple_dir_operations;
  		inc_nlink(inode);
  		inc_nlink(dir);
  	} else {
  		inode->i_fop = fops;

  	}

  	d_instantiate(dentry, inode);
  	dget(dentry);
  	mutex_unlock(&dir->i_mutex);
  	return dentry;
  
  out1:
  	dput(dentry);
  	dentry = ERR_PTR(error);
  out:
  	mutex_unlock(&dir->i_mutex);
  	simple_release_fs(&mount, &mount_count);

  	return dentry;
  }
  EXPORT_SYMBOL_GPL(securityfs_create_file);
  
  /**
   * securityfs_create_dir - create a directory in the securityfs filesystem
   *
   * @name: a pointer to a string containing the name of the directory to
   *        create.
   * @parent: a pointer to the parent dentry for this file.  This should be a

   *          directory dentry if set.  If this parameter is %NULL, then the

   *          directory will be created in the root of the securityfs filesystem.
   *

   * This function creates a directory in securityfs with the given @name.

   *

   * This function returns a pointer to a dentry if it succeeds.  This

   * pointer must be passed to the securityfs_remove() function when the file is
   * to be removed (no automatic cleanup happens if your module is unloaded,

   * you are responsible here).  If an error occurs, %NULL will be returned.

   *

   * If securityfs is not enabled in the kernel, the value %-ENODEV is

   * returned.  It is not wise to check for this value, but rather, check for

   * %NULL or !%NULL instead as to eliminate the need for #ifdef in the calling

   * code.
   */
  struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
  {
  	return securityfs_create_file(name,
  				      S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
  				      parent, NULL, NULL);
  }
  EXPORT_SYMBOL_GPL(securityfs_create_dir);
  
  /**
   * securityfs_remove - removes a file or directory from the securityfs filesystem
   *

   * @dentry: a pointer to a the dentry of the file or directory to be removed.

   *
   * This function removes a file or directory in securityfs that was previously
   * created with a call to another securityfs function (like
   * securityfs_create_file() or variants thereof.)
   *
   * This function is required to be called in order for the file to be

   * removed. No automatic cleanup of files will happen when a module is
   * removed; you are responsible here.

   */
  void securityfs_remove(struct dentry *dentry)
  {
  	struct dentry *parent;

  	if (!dentry || IS_ERR(dentry))

  		return;
  
  	parent = dentry->d_parent;

  	if (!parent || d_really_is_negative(parent))

  		return;

  	mutex_lock(&d_inode(parent)->i_mutex);

  	if (positive(dentry)) {

  		if (d_really_is_positive(dentry)) {

  			if (d_is_dir(dentry))

  				simple_rmdir(d_inode(parent), dentry);

  			else

  				simple_unlink(d_inode(parent), dentry);

  			dput(dentry);
  		}
  	}

  	mutex_unlock(&d_inode(parent)->i_mutex);

  	simple_release_fs(&mount, &mount_count);
  }
  EXPORT_SYMBOL_GPL(securityfs_remove);

  static int __init securityfs_init(void)
  {
  	int retval;

  	retval = sysfs_create_mount_point(kernel_kobj, "security");
  	if (retval)
  		return retval;

  
  	retval = register_filesystem(&fs_type);
  	if (retval)

  		sysfs_remove_mount_point(kernel_kobj, "security");

  	return retval;
  }

  core_initcall(securityfs_init);

  MODULE_LICENSE("GPL");