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kernel/linux-imx6_3.14.28/fs/sysfs/mount.c 1.68 KB
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  /*
   * fs/sysfs/symlink.c - operations for initializing and mounting sysfs
   *
   * Copyright (c) 2001-3 Patrick Mochel
   * Copyright (c) 2007 SUSE Linux Products GmbH
   * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
   *
   * This file is released under the GPLv2.
   *
   * Please see Documentation/filesystems/sysfs.txt for more information.
   */
  
  #define DEBUG
  
  #include <linux/fs.h>
  #include <linux/mount.h>
  #include <linux/init.h>
  #include <linux/user_namespace.h>
  
  #include "sysfs.h"
  
  static struct kernfs_root *sysfs_root;
  struct kernfs_node *sysfs_root_kn;
  
  static struct dentry *sysfs_mount(struct file_system_type *fs_type,
  	int flags, const char *dev_name, void *data)
  {
  	struct dentry *root;
  	void *ns;
  	bool new_sb;
  
  	if (!(flags & MS_KERNMOUNT)) {
  		if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
  			return ERR_PTR(-EPERM);
  
  		if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
  			return ERR_PTR(-EPERM);
  	}
  
  	ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
  	root = kernfs_mount_ns(fs_type, flags, sysfs_root, &new_sb, ns);
  	if (IS_ERR(root) || !new_sb)
  		kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
  	return root;
  }
  
  static void sysfs_kill_sb(struct super_block *sb)
  {
  	void *ns = (void *)kernfs_super_ns(sb);
  
  	kernfs_kill_sb(sb);
  	kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
  }
  
  static struct file_system_type sysfs_fs_type = {
  	.name		= "sysfs",
  	.mount		= sysfs_mount,
  	.kill_sb	= sysfs_kill_sb,
  	.fs_flags	= FS_USERNS_MOUNT,
  };
  
  int __init sysfs_init(void)
  {
  	int err;
  
  	sysfs_root = kernfs_create_root(NULL, NULL);
  	if (IS_ERR(sysfs_root))
  		return PTR_ERR(sysfs_root);
  
  	sysfs_root_kn = sysfs_root->kn;
  
  	err = register_filesystem(&sysfs_fs_type);
  	if (err) {
  		kernfs_destroy_root(sysfs_root);
  		return err;
  	}
  
  	return 0;
  }