/*
   *  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>
  
  #define SECURITYFS_MAGIC	0x73636673
  
  static struct vfsmount *mount;
  static int mount_count;
  
  /*
   * TODO:
   *   I think I can get rid of these default_file_ops, but not quite sure...
   */
  static ssize_t default_read_file(struct file *file, char __user *buf,
  				 size_t count, loff_t *ppos)
  {
  	return 0;
  }
  
  static ssize_t default_write_file(struct file *file, const char __user *buf,
  				   size_t count, loff_t *ppos)
  {
  	return count;
  }
  
  static int default_open(struct inode *inode, struct file *file)
  {

  	if (inode->i_private)
  		file->private_data = inode->i_private;

  
  	return 0;
  }

  static const struct file_operations default_file_ops = {

  	.read =		default_read_file,
  	.write =	default_write_file,
  	.open =		default_open,
  };
  
  static struct inode *get_inode(struct super_block *sb, int mode, dev_t dev)
  {
  	struct inode *inode = new_inode(sb);
  
  	if (inode) {
  		inode->i_mode = mode;
  		inode->i_uid = 0;
  		inode->i_gid = 0;

  		inode->i_blocks = 0;
  		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  		switch (mode & S_IFMT) {
  		default:
  			init_special_inode(inode, mode, dev);
  			break;
  		case S_IFREG:
  			inode->i_fop = &default_file_ops;
  			break;
  		case S_IFDIR:
  			inode->i_op = &simple_dir_inode_operations;
  			inode->i_fop = &simple_dir_operations;
  
  			/* directory inodes start off with i_nlink == 2 (for "." entry) */

  			inc_nlink(inode);

  			break;
  		}
  	}
  	return inode;
  }
  
  /* SMP-safe */
  static int mknod(struct inode *dir, struct dentry *dentry,
  			 int mode, dev_t dev)
  {
  	struct inode *inode;
  	int error = -EPERM;
  
  	if (dentry->d_inode)
  		return -EEXIST;
  
  	inode = get_inode(dir->i_sb, mode, dev);
  	if (inode) {
  		d_instantiate(dentry, inode);
  		dget(dentry);
  		error = 0;
  	}
  	return error;
  }
  
  static int mkdir(struct inode *dir, struct dentry *dentry, int mode)
  {
  	int res;
  
  	mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
  	res = mknod(dir, dentry, mode, 0);
  	if (!res)

  		inc_nlink(dir);

  	return res;
  }
  
  static int create(struct inode *dir, struct dentry *dentry, int mode)
  {
  	mode = (mode & S_IALLUGO) | S_IFREG;
  	return mknod(dir, dentry, mode, 0);
  }
  
  static inline int positive(struct dentry *dentry)
  {
  	return dentry->d_inode && !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 int get_sb(struct file_system_type *fs_type,
  		  int flags, const char *dev_name,
  		  void *data, struct vfsmount *mnt)

  {

  	return get_sb_single(fs_type, flags, data, fill_super, mnt);

  }
  
  static struct file_system_type fs_type = {
  	.owner =	THIS_MODULE,
  	.name =		"securityfs",
  	.get_sb =	get_sb,
  	.kill_sb =	kill_litter_super,
  };
  
  static int create_by_name(const char *name, mode_t mode,
  			  struct dentry *parent,
  			  struct dentry **dentry)
  {
  	int error = 0;
  
  	*dentry = NULL;
  
  	/* If the parent is not specified, we create it in the root.
  	 * We need the root dentry to do this, which is in the super
  	 * block. A pointer to that is in the struct vfsmount that we
  	 * have around.
  	 */
  	if (!parent ) {
  		if (mount && mount->mnt_sb) {
  			parent = mount->mnt_sb->s_root;
  		}
  	}
  	if (!parent) {
  		pr_debug("securityfs: Ah! can not find a parent!
  ");
  		return -EFAULT;
  	}

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

  	*dentry = lookup_one_len(name, parent, strlen(name));
  	if (!IS_ERR(dentry)) {
  		if ((mode & S_IFMT) == S_IFDIR)
  			error = mkdir(parent->d_inode, *dentry, mode);
  		else
  			error = create(parent->d_inode, *dentry, mode);
  	} else
  		error = PTR_ERR(dentry);

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

  
  	return error;
  }
  
  /**
   * 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 paramater 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 createing 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 will return 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 will be
   * 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_file(const char *name, mode_t mode,
  				   struct dentry *parent, void *data,

  				   const struct file_operations *fops)

  {
  	struct dentry *dentry = NULL;
  	int error;
  
  	pr_debug("securityfs: creating file '%s'
  ",name);

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

  	if (error) {
  		dentry = ERR_PTR(error);
  		goto exit;
  	}
  
  	error = create_by_name(name, mode, parent, &dentry);
  	if (error) {
  		dentry = ERR_PTR(error);
  		simple_release_fs(&mount, &mount_count);
  		goto exit;
  	}
  
  	if (dentry->d_inode) {
  		if (fops)
  			dentry->d_inode->i_fop = fops;
  		if (data)

  			dentry->d_inode->i_private = data;

  	}
  exit:
  	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 paramater 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 will return 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 will be
   * 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)
  		return;
  
  	parent = dentry->d_parent;
  	if (!parent || !parent->d_inode)
  		return;

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

  	if (positive(dentry)) {
  		if (dentry->d_inode) {
  			if (S_ISDIR(dentry->d_inode->i_mode))
  				simple_rmdir(parent->d_inode, dentry);
  			else
  				simple_unlink(parent->d_inode, dentry);
  			dput(dentry);
  		}
  	}

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

  	simple_release_fs(&mount, &mount_count);
  }
  EXPORT_SYMBOL_GPL(securityfs_remove);
  
  static decl_subsys(security, NULL, NULL);
  
  static int __init securityfs_init(void)
  {
  	int retval;

  	kobj_set_kset_s(&security_subsys, kernel_subsys);

  	retval = subsystem_register(&security_subsys);
  	if (retval)
  		return retval;
  
  	retval = register_filesystem(&fs_type);
  	if (retval)
  		subsystem_unregister(&security_subsys);
  	return retval;
  }
  
  static void __exit securityfs_exit(void)
  {
  	simple_release_fs(&mount, &mount_count);
  	unregister_filesystem(&fs_type);
  	subsystem_unregister(&security_subsys);
  }
  
  core_initcall(securityfs_init);
  module_exit(securityfs_exit);
  MODULE_LICENSE("GPL");