fs/efivarfs/super.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (C) 2012 Red Hat, Inc.
  * Copyright (C) 2012 Jeremy Kerr <jeremy.kerr@canonical.com>
  */

 #include <linux/ctype.h>
 #include <linux/efi.h>
 #include <linux/fs.h>
 #include <linux/fs_context.h>
 #include <linux/fs_parser.h>
 #include <linux/module.h>
 #include <linux/pagemap.h>
 #include <linux/ucs2_string.h>
 #include <linux/slab.h>
 #include <linux/suspend.h>
 #include <linux/magic.h>
 #include <linux/statfs.h>
 #include <linux/notifier.h>
 #include <linux/printk.h>

 #include "internal.h"

 static int efivarfs_ops_notifier(struct notifier_block *nb, unsigned long event,
 				 void *data)
 {
 	struct efivarfs_fs_info *sfi = container_of(nb, struct efivarfs_fs_info, nb);

 	switch (event) {
 	case EFIVAR_OPS_RDONLY:
 		sfi->sb->s_flags |= SB_RDONLY;
 		break;
 	case EFIVAR_OPS_RDWR:
 		sfi->sb->s_flags &= ~SB_RDONLY;
 		break;
 	default:
 		return NOTIFY_DONE;
 	}

 	return NOTIFY_OK;
 }

 static struct inode *efivarfs_alloc_inode(struct super_block *sb)
 {
 	struct efivar_entry *entry = kzalloc(sizeof(*entry), GFP_KERNEL);

 	if (!entry)
 		return NULL;

 	inode_init_once(&entry->vfs_inode);
 	entry->removed = false;

 	return &entry->vfs_inode;
 }

 static void efivarfs_free_inode(struct inode *inode)
 {
 	struct efivar_entry *entry = efivar_entry(inode);

 	kfree(entry);
 }

 static int efivarfs_show_options(struct seq_file *m, struct dentry *root)
 {
 	struct super_block *sb = root->d_sb;
 	struct efivarfs_fs_info *sbi = sb->s_fs_info;
 	struct efivarfs_mount_opts *opts = &sbi->mount_opts;

 	if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
 		seq_printf(m, ",uid=%u",
 				from_kuid_munged(&init_user_ns, opts->uid));
 	if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
 		seq_printf(m, ",gid=%u",
 				from_kgid_munged(&init_user_ns, opts->gid));
 	return 0;
 }

 static int efivarfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
 	const u32 attr = EFI_VARIABLE_NON_VOLATILE |
 			 EFI_VARIABLE_BOOTSERVICE_ACCESS |
 			 EFI_VARIABLE_RUNTIME_ACCESS;
 	u64 storage_space, remaining_space, max_variable_size;
 	u64 id = huge_encode_dev(dentry->d_sb->s_dev);
 	efi_status_t status;

 	/* Some UEFI firmware does not implement QueryVariableInfo() */
 	storage_space = remaining_space = 0;
 	if (efi_rt_services_supported(EFI_RT_SUPPORTED_QUERY_VARIABLE_INFO)) {
 		status = efivar_query_variable_info(attr, &storage_space,
 						    &remaining_space,
 						    &max_variable_size);
 		if (status != EFI_SUCCESS && status != EFI_UNSUPPORTED)
 			pr_warn_ratelimited("query_variable_info() failed: 0x%lx\n",
 					    status);
 	}

 	/*
 	 * This is not a normal filesystem, so no point in pretending it has a block
 	 * size; we declare f_bsize to 1, so that we can then report the exact value
 	 * sent by EFI QueryVariableInfo in f_blocks and f_bfree
 	 */
 	buf->f_bsize	= 1;
 	buf->f_namelen	= NAME_MAX;
 	buf->f_blocks	= storage_space;
 	buf->f_bfree	= remaining_space;
 	buf->f_type	= dentry->d_sb->s_magic;
 	buf->f_fsid	= u64_to_fsid(id);

 	/*
 	 * In f_bavail we declare the free space that the kernel will allow writing
 	 * when the storage_paranoia x86 quirk is active. To use more, users
 	 * should boot the kernel with efi_no_storage_paranoia.
 	 */
 	if (remaining_space > efivar_reserved_space())
 		buf->f_bavail = remaining_space - efivar_reserved_space();
 	else
 		buf->f_bavail = 0;

 	return 0;
 }
 static const struct super_operations efivarfs_ops = {
 	.statfs = efivarfs_statfs,
 	.drop_inode = generic_delete_inode,
 	.alloc_inode = efivarfs_alloc_inode,
 	.free_inode = efivarfs_free_inode,
 	.show_options = efivarfs_show_options,
 };

 /*
  * Compare two efivarfs file names.
  *
  * An efivarfs filename is composed of two parts,
  *
  *	1. A case-sensitive variable name
  *	2. A case-insensitive GUID
  *
  * So we need to perform a case-sensitive match on part 1 and a
  * case-insensitive match on part 2.
  */
 static int efivarfs_d_compare(const struct dentry *dentry,
 			      unsigned int len, const char *str,
 			      const struct qstr *name)
 {
 	int guid = len - EFI_VARIABLE_GUID_LEN;

 	if (name->len != len)
 		return 1;

 	/* Case-sensitive compare for the variable name */
 	if (memcmp(str, name->name, guid))
 		return 1;

 	/* Case-insensitive compare for the GUID */
 	return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN);
 }

 static int efivarfs_d_hash(const struct dentry *dentry, struct qstr *qstr)
 {
 	unsigned long hash = init_name_hash(dentry);
 	const unsigned char *s = qstr->name;
 	unsigned int len = qstr->len;

 	while (len-- > EFI_VARIABLE_GUID_LEN)
 		hash = partial_name_hash(*s++, hash);

 	/* GUID is case-insensitive. */
 	while (len--)
 		hash = partial_name_hash(tolower(*s++), hash);

 	qstr->hash = end_name_hash(hash);
 	return 0;
 }

 static const struct dentry_operations efivarfs_d_ops = {
 	.d_compare = efivarfs_d_compare,
 	.d_hash = efivarfs_d_hash,
 	.d_delete = always_delete_dentry,
 };

 static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
 {
 	struct dentry *d;
 	struct qstr q;
 	int err;

 	q.name = name;
 	q.len = strlen(name);

 	err = efivarfs_d_hash(parent, &q);
 	if (err)
 		return ERR_PTR(err);

 	d = d_alloc(parent, &q);
 	if (d)
 		return d;

 	return ERR_PTR(-ENOMEM);
 }

 bool efivarfs_variable_is_present(efi_char16_t *variable_name,
 				  efi_guid_t *vendor, void *data)
 {
 	char *name = efivar_get_utf8name(variable_name, vendor);
 	struct super_block *sb = data;
 	struct dentry *dentry;
 	struct qstr qstr;

 	if (!name)
 		/*
 		 * If the allocation failed there'll already be an
 		 * error in the log (and likely a huge and growing
 		 * number of them since they system will be under
 		 * extreme memory pressure), so simply assume
 		 * collision for safety but don't add to the log
 		 * flood.
 		 */
 		return true;

 	qstr.name = name;
 	qstr.len = strlen(name);
 	dentry = d_hash_and_lookup(sb->s_root, &qstr);
 	kfree(name);
 	if (!IS_ERR_OR_NULL(dentry))
 		dput(dentry);

 	return dentry != NULL;
 }

 static int efivarfs_create_dentry(struct super_block *sb, efi_char16_t *name16,
 				  unsigned long name_size, efi_guid_t vendor,
 				  char *name)
 {
 	struct efivar_entry *entry;
 	struct inode *inode;
 	struct dentry *dentry, *root = sb->s_root;
 	unsigned long size = 0;
 	int len;
 	int err = -ENOMEM;
 	bool is_removable = false;

 	/* length of the variable name itself: remove GUID and separator */
 	len = strlen(name) - EFI_VARIABLE_GUID_LEN - 1;

 	if (efivar_variable_is_removable(vendor, name, len))
 		is_removable = true;

 	inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0,
 				   is_removable);
 	if (!inode)
 		goto fail_name;

 	entry = efivar_entry(inode);

 	memcpy(entry->var.VariableName, name16, name_size);
 	memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));

 	dentry = efivarfs_alloc_dentry(root, name);
 	if (IS_ERR(dentry)) {
 		err = PTR_ERR(dentry);
 		goto fail_inode;
 	}

 	__efivar_entry_get(entry, NULL, &size, NULL);

 	/* copied by the above to local storage in the dentry. */
 	kfree(name);

 	inode_lock(inode);
 	inode->i_private = entry;
 	i_size_write(inode, size + sizeof(__u32)); /* attributes + data */
 	inode_unlock(inode);
 	d_add(dentry, inode);

 	return 0;

 fail_inode:
 	iput(inode);
 fail_name:
 	kfree(name);

 	return err;
 }

 static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
 			     unsigned long name_size, void *data)
 {
 	struct super_block *sb = (struct super_block *)data;
 	char *name;

 	if (guid_equal(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
 		return 0;

 	name = efivar_get_utf8name(name16, &vendor);
 	if (!name)
 		return -ENOMEM;

 	return efivarfs_create_dentry(sb, name16, name_size, vendor, name);
 }

 enum {
 	Opt_uid, Opt_gid,
 };

 static const struct fs_parameter_spec efivarfs_parameters[] = {
 	fsparam_uid("uid", Opt_uid),
 	fsparam_gid("gid", Opt_gid),
 	{},
 };

 static int efivarfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
 {
 	struct efivarfs_fs_info *sbi = fc->s_fs_info;
 	struct efivarfs_mount_opts *opts = &sbi->mount_opts;
 	struct fs_parse_result result;
 	int opt;

 	opt = fs_parse(fc, efivarfs_parameters, param, &result);
 	if (opt < 0)
 		return opt;

 	switch (opt) {
 	case Opt_uid:
 		opts->uid = result.uid;
 		break;
 	case Opt_gid:
 		opts->gid = result.gid;
 		break;
 	default:
 		return -EINVAL;
 	}

 	return 0;
 }

 static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
 {
 	struct efivarfs_fs_info *sfi = sb->s_fs_info;
 	struct inode *inode = NULL;
 	struct dentry *root;
 	int err;

 	sb->s_maxbytes          = MAX_LFS_FILESIZE;
 	sb->s_blocksize         = PAGE_SIZE;
 	sb->s_blocksize_bits    = PAGE_SHIFT;
 	sb->s_magic             = EFIVARFS_MAGIC;
 	sb->s_op                = &efivarfs_ops;
 	sb->s_d_op		= &efivarfs_d_ops;
 	sb->s_time_gran         = 1;

 	if (!efivar_supports_writes())
 		sb->s_flags |= SB_RDONLY;

 	inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0, true);
 	if (!inode)
 		return -ENOMEM;
 	inode->i_op = &efivarfs_dir_inode_operations;

 	root = d_make_root(inode);
 	sb->s_root = root;
 	if (!root)
 		return -ENOMEM;

 	sfi->sb = sb;
 	sfi->nb.notifier_call = efivarfs_ops_notifier;
 	err = blocking_notifier_chain_register(&efivar_ops_nh, &sfi->nb);
 	if (err)
 		return err;

 	return efivar_init(efivarfs_callback, sb, true);
 }

 static int efivarfs_get_tree(struct fs_context *fc)
 {
 	return get_tree_single(fc, efivarfs_fill_super);
 }

 static int efivarfs_reconfigure(struct fs_context *fc)
 {
 	if (!efivar_supports_writes() && !(fc->sb_flags & SB_RDONLY)) {
 		pr_err("Firmware does not support SetVariableRT. Can not remount with rw\n");
 		return -EINVAL;
 	}

 	return 0;
 }

 static const struct fs_context_operations efivarfs_context_ops = {
 	.get_tree	= efivarfs_get_tree,
 	.parse_param	= efivarfs_parse_param,
 	.reconfigure	= efivarfs_reconfigure,
 };

 struct efivarfs_ctx {
 	struct dir_context ctx;
 	struct super_block *sb;
 	struct dentry *dentry;
 };

 static bool efivarfs_actor(struct dir_context *ctx, const char *name, int len,
 			   loff_t offset, u64 ino, unsigned mode)
 {
 	unsigned long size;
 	struct efivarfs_ctx *ectx = container_of(ctx, struct efivarfs_ctx, ctx);
 	struct qstr qstr = { .name = name, .len = len };
 	struct dentry *dentry = d_hash_and_lookup(ectx->sb->s_root, &qstr);
 	struct inode *inode;
 	struct efivar_entry *entry;
 	int err;

 	if (IS_ERR_OR_NULL(dentry))
 		return true;

 	inode = d_inode(dentry);
 	entry = efivar_entry(inode);

 	err = efivar_entry_size(entry, &size);
 	size += sizeof(__u32);	/* attributes */
 	if (err)
 		size = 0;

 	inode_lock(inode);
 	i_size_write(inode, size);
 	inode_unlock(inode);

 	if (!size) {
 		ectx->dentry = dentry;
 		return false;
 	}

 	dput(dentry);

 	return true;
 }

 static int efivarfs_check_missing(efi_char16_t *name16, efi_guid_t vendor,
 				  unsigned long name_size, void *data)
 {
 	char *name;
 	struct super_block *sb = data;
 	struct dentry *dentry;
 	struct qstr qstr;
 	int err;

 	if (guid_equal(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
 		return 0;

 	name = efivar_get_utf8name(name16, &vendor);
 	if (!name)
 		return -ENOMEM;

 	qstr.name = name;
 	qstr.len = strlen(name);
 	dentry = d_hash_and_lookup(sb->s_root, &qstr);
 	if (IS_ERR(dentry)) {
 		err = PTR_ERR(dentry);
 		goto out;
 	}

 	if (!dentry) {
 		/* found missing entry */
 		pr_info("efivarfs: creating variable %s\n", name);
 		return efivarfs_create_dentry(sb, name16, name_size, vendor, name);
 	}

 	dput(dentry);
 	err = 0;

  out:
 	kfree(name);

 	return err;
 }

 static int efivarfs_pm_notify(struct notifier_block *nb, unsigned long action,
 			      void *ptr)
 {
 	struct efivarfs_fs_info *sfi = container_of(nb, struct efivarfs_fs_info,
 						    pm_nb);
 	struct path path = { .mnt = NULL, .dentry = sfi->sb->s_root, };
 	struct efivarfs_ctx ectx = {
 		.ctx = {
 			.actor	= efivarfs_actor,
 		},
 		.sb = sfi->sb,
 	};
 	struct file *file;
 	static bool rescan_done = true;

 	if (action == PM_HIBERNATION_PREPARE) {
 		rescan_done = false;
 		return NOTIFY_OK;
 	} else if (action != PM_POST_HIBERNATION) {
 		return NOTIFY_DONE;
 	}

 	if (rescan_done)
 		return NOTIFY_DONE;

 	pr_info("efivarfs: resyncing variable state\n");

 	/* O_NOATIME is required to prevent oops on NULL mnt */
 	file = kernel_file_open(&path, O_RDONLY | O_DIRECTORY | O_NOATIME,
 				current_cred());
 	if (IS_ERR(file))
 		return NOTIFY_DONE;

 	rescan_done = true;

 	/*
 	 * First loop over the directory and verify each entry exists,
 	 * removing it if it doesn't
 	 */
 	file->f_pos = 2;	/* skip . and .. */
 	do {
 		ectx.dentry = NULL;
 		iterate_dir(file, &ectx.ctx);
 		if (ectx.dentry) {
 			pr_info("efivarfs: removing variable %pd\n",
 				ectx.dentry);
 			simple_recursive_removal(ectx.dentry, NULL);
 			dput(ectx.dentry);
 		}
 	} while (ectx.dentry);
 	fput(file);

 	/*
 	 * then loop over variables, creating them if there's no matching
 	 * dentry
 	 */
 	efivar_init(efivarfs_check_missing, sfi->sb, false);

 	return NOTIFY_OK;
 }

 static int efivarfs_init_fs_context(struct fs_context *fc)
 {
 	struct efivarfs_fs_info *sfi;

 	if (!efivar_is_available())
 		return -EOPNOTSUPP;

 	sfi = kzalloc(sizeof(*sfi), GFP_KERNEL);
 	if (!sfi)
 		return -ENOMEM;

 	sfi->mount_opts.uid = GLOBAL_ROOT_UID;
 	sfi->mount_opts.gid = GLOBAL_ROOT_GID;

 	fc->s_fs_info = sfi;
 	fc->ops = &efivarfs_context_ops;

 	sfi->pm_nb.notifier_call = efivarfs_pm_notify;
 	sfi->pm_nb.priority = 0;
 	register_pm_notifier(&sfi->pm_nb);

 	return 0;
 }

 static void efivarfs_kill_sb(struct super_block *sb)
 {
 	struct efivarfs_fs_info *sfi = sb->s_fs_info;

 	blocking_notifier_chain_unregister(&efivar_ops_nh, &sfi->nb);
 	kill_litter_super(sb);
 	unregister_pm_notifier(&sfi->pm_nb);

 	kfree(sfi);
 }

 static struct file_system_type efivarfs_type = {
 	.owner   = THIS_MODULE,
 	.name    = "efivarfs",
 	.init_fs_context = efivarfs_init_fs_context,
 	.kill_sb = efivarfs_kill_sb,
 	.parameters = efivarfs_parameters,
 };

 static __init int efivarfs_init(void)
 {
 	return register_filesystem(&efivarfs_type);
 }

 static __exit void efivarfs_exit(void)
 {
 	unregister_filesystem(&efivarfs_type);
 }

 MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
 MODULE_DESCRIPTION("EFI Variable Filesystem");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS_FS("efivarfs");

 module_init(efivarfs_init);
 module_exit(efivarfs_exit);
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Copyright (C) 2012 Red Hat, Inc.
	* Copyright (C) 2012 Jeremy Kerr <jeremy.kerr@canonical.com>
	*/

	#include <linux/ctype.h>
	#include <linux/efi.h>
	#include <linux/fs.h>
	#include <linux/fs_context.h>
	#include <linux/fs_parser.h>
	#include <linux/module.h>
	#include <linux/pagemap.h>
	#include <linux/ucs2_string.h>
	#include <linux/slab.h>
	#include <linux/suspend.h>
	#include <linux/magic.h>
	#include <linux/statfs.h>
	#include <linux/notifier.h>
	#include <linux/printk.h>

	#include "internal.h"

	static int efivarfs_ops_notifier(struct notifier_block *nb, unsigned long event,
	void *data)
	{
	struct efivarfs_fs_info *sfi = container_of(nb, struct efivarfs_fs_info, nb);

	switch (event) {
	case EFIVAR_OPS_RDONLY:
	sfi->sb->s_flags \|= SB_RDONLY;
	break;
	case EFIVAR_OPS_RDWR:
	sfi->sb->s_flags &= ~SB_RDONLY;
	break;
	default:
	return NOTIFY_DONE;
	}

	return NOTIFY_OK;
	}

	static struct inode efivarfs_alloc_inode(struct super_block sb)
	{
	struct efivar_entry entry = kzalloc(sizeof(entry), GFP_KERNEL);

	if (!entry)
	return NULL;

	inode_init_once(&entry->vfs_inode);
	entry->removed = false;

	return &entry->vfs_inode;
	}

	static void efivarfs_free_inode(struct inode *inode)
	{
	struct efivar_entry *entry = efivar_entry(inode);

	kfree(entry);
	}

	static int efivarfs_show_options(struct seq_file m, struct dentry root)
	{
	struct super_block *sb = root->d_sb;
	struct efivarfs_fs_info *sbi = sb->s_fs_info;
	struct efivarfs_mount_opts *opts = &sbi->mount_opts;

	if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
	seq_printf(m, ",uid=%u",
	from_kuid_munged(&init_user_ns, opts->uid));
	if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
	seq_printf(m, ",gid=%u",
	from_kgid_munged(&init_user_ns, opts->gid));
	return 0;
	}

	static int efivarfs_statfs(struct dentry dentry, struct kstatfs buf)
	{
	const u32 attr = EFI_VARIABLE_NON_VOLATILE \|
	EFI_VARIABLE_BOOTSERVICE_ACCESS \|
	EFI_VARIABLE_RUNTIME_ACCESS;
	u64 storage_space, remaining_space, max_variable_size;
	u64 id = huge_encode_dev(dentry->d_sb->s_dev);
	efi_status_t status;

	/* Some UEFI firmware does not implement QueryVariableInfo() */
	storage_space = remaining_space = 0;
	if (efi_rt_services_supported(EFI_RT_SUPPORTED_QUERY_VARIABLE_INFO)) {
	status = efivar_query_variable_info(attr, &storage_space,
	&remaining_space,
	&max_variable_size);
	if (status != EFI_SUCCESS && status != EFI_UNSUPPORTED)
	pr_warn_ratelimited("query_variable_info() failed: 0x%lx\n",
	status);
	}

	/*
	* This is not a normal filesystem, so no point in pretending it has a block
	* size; we declare f_bsize to 1, so that we can then report the exact value
	* sent by EFI QueryVariableInfo in f_blocks and f_bfree
	*/
	buf->f_bsize = 1;
	buf->f_namelen = NAME_MAX;
	buf->f_blocks = storage_space;
	buf->f_bfree = remaining_space;
	buf->f_type = dentry->d_sb->s_magic;
	buf->f_fsid = u64_to_fsid(id);

	/*
	* In f_bavail we declare the free space that the kernel will allow writing
	* when the storage_paranoia x86 quirk is active. To use more, users
	* should boot the kernel with efi_no_storage_paranoia.
	*/
	if (remaining_space > efivar_reserved_space())
	buf->f_bavail = remaining_space - efivar_reserved_space();
	else
	buf->f_bavail = 0;

	return 0;
	}
	static const struct super_operations efivarfs_ops = {
	.statfs = efivarfs_statfs,
	.drop_inode = generic_delete_inode,
	.alloc_inode = efivarfs_alloc_inode,
	.free_inode = efivarfs_free_inode,
	.show_options = efivarfs_show_options,
	};

	/*
	* Compare two efivarfs file names.
	*
	* An efivarfs filename is composed of two parts,
	*
	* 1. A case-sensitive variable name
	* 2. A case-insensitive GUID
	*
	* So we need to perform a case-sensitive match on part 1 and a
	* case-insensitive match on part 2.
	*/
	static int efivarfs_d_compare(const struct dentry *dentry,
	unsigned int len, const char *str,
	const struct qstr *name)
	{
	int guid = len - EFI_VARIABLE_GUID_LEN;

	if (name->len != len)
	return 1;

	/* Case-sensitive compare for the variable name */
	if (memcmp(str, name->name, guid))
	return 1;

	/* Case-insensitive compare for the GUID */
	return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN);
	}

	static int efivarfs_d_hash(const struct dentry dentry, struct qstr qstr)
	{
	unsigned long hash = init_name_hash(dentry);
	const unsigned char *s = qstr->name;
	unsigned int len = qstr->len;

	while (len-- > EFI_VARIABLE_GUID_LEN)
	hash = partial_name_hash(*s++, hash);

	/* GUID is case-insensitive. */
	while (len--)
	hash = partial_name_hash(tolower(*s++), hash);

	qstr->hash = end_name_hash(hash);
	return 0;
	}

	static const struct dentry_operations efivarfs_d_ops = {
	.d_compare = efivarfs_d_compare,
	.d_hash = efivarfs_d_hash,
	.d_delete = always_delete_dentry,
	};

	static struct dentry efivarfs_alloc_dentry(struct dentry parent, char *name)
	{
	struct dentry *d;
	struct qstr q;
	int err;

	q.name = name;
	q.len = strlen(name);

	err = efivarfs_d_hash(parent, &q);
	if (err)
	return ERR_PTR(err);

	d = d_alloc(parent, &q);
	if (d)
	return d;

	return ERR_PTR(-ENOMEM);
	}

	bool efivarfs_variable_is_present(efi_char16_t *variable_name,
	efi_guid_t vendor, void data)
	{
	char *name = efivar_get_utf8name(variable_name, vendor);
	struct super_block *sb = data;
	struct dentry *dentry;
	struct qstr qstr;

	if (!name)
	/*
	* If the allocation failed there'll already be an
	* error in the log (and likely a huge and growing
	* number of them since they system will be under
	* extreme memory pressure), so simply assume
	* collision for safety but don't add to the log
	* flood.
	*/
	return true;

	qstr.name = name;
	qstr.len = strlen(name);
	dentry = d_hash_and_lookup(sb->s_root, &qstr);
	kfree(name);
	if (!IS_ERR_OR_NULL(dentry))
	dput(dentry);

	return dentry != NULL;
	}

	static int efivarfs_create_dentry(struct super_block sb, efi_char16_t name16,
	unsigned long name_size, efi_guid_t vendor,
	char *name)
	{
	struct efivar_entry *entry;
	struct inode *inode;
	struct dentry dentry, root = sb->s_root;
	unsigned long size = 0;
	int len;
	int err = -ENOMEM;
	bool is_removable = false;

	/* length of the variable name itself: remove GUID and separator */
	len = strlen(name) - EFI_VARIABLE_GUID_LEN - 1;

	if (efivar_variable_is_removable(vendor, name, len))
	is_removable = true;

	inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG \| 0644, 0,
	is_removable);
	if (!inode)
	goto fail_name;

	entry = efivar_entry(inode);

	memcpy(entry->var.VariableName, name16, name_size);
	memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));

	dentry = efivarfs_alloc_dentry(root, name);
	if (IS_ERR(dentry)) {
	err = PTR_ERR(dentry);
	goto fail_inode;
	}

	__efivar_entry_get(entry, NULL, &size, NULL);

	/* copied by the above to local storage in the dentry. */
	kfree(name);

	inode_lock(inode);
	inode->i_private = entry;
	i_size_write(inode, size + sizeof(__u32)); /* attributes + data */
	inode_unlock(inode);
	d_add(dentry, inode);

	return 0;

	fail_inode:
	iput(inode);
	fail_name:
	kfree(name);

	return err;
	}

	static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
	unsigned long name_size, void *data)
	{
	struct super_block sb = (struct super_block )data;
	char *name;

	if (guid_equal(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
	return 0;

	name = efivar_get_utf8name(name16, &vendor);
	if (!name)
	return -ENOMEM;

	return efivarfs_create_dentry(sb, name16, name_size, vendor, name);
	}

	enum {
	Opt_uid, Opt_gid,
	};

	static const struct fs_parameter_spec efivarfs_parameters[] = {
	fsparam_uid("uid", Opt_uid),
	fsparam_gid("gid", Opt_gid),
	{},
	};

	static int efivarfs_parse_param(struct fs_context fc, struct fs_parameter param)
	{
	struct efivarfs_fs_info *sbi = fc->s_fs_info;
	struct efivarfs_mount_opts *opts = &sbi->mount_opts;
	struct fs_parse_result result;
	int opt;

	opt = fs_parse(fc, efivarfs_parameters, param, &result);
	if (opt < 0)
	return opt;

	switch (opt) {
	case Opt_uid:
	opts->uid = result.uid;
	break;
	case Opt_gid:
	opts->gid = result.gid;
	break;
	default:
	return -EINVAL;
	}

	return 0;
	}

	static int efivarfs_fill_super(struct super_block sb, struct fs_context fc)
	{
	struct efivarfs_fs_info *sfi = sb->s_fs_info;
	struct inode *inode = NULL;
	struct dentry *root;
	int err;

	sb->s_maxbytes = MAX_LFS_FILESIZE;
	sb->s_blocksize = PAGE_SIZE;
	sb->s_blocksize_bits = PAGE_SHIFT;
	sb->s_magic = EFIVARFS_MAGIC;
	sb->s_op = &efivarfs_ops;
	sb->s_d_op = &efivarfs_d_ops;
	sb->s_time_gran = 1;

	if (!efivar_supports_writes())
	sb->s_flags \|= SB_RDONLY;

	inode = efivarfs_get_inode(sb, NULL, S_IFDIR \| 0755, 0, true);
	if (!inode)
	return -ENOMEM;
	inode->i_op = &efivarfs_dir_inode_operations;

	root = d_make_root(inode);
	sb->s_root = root;
	if (!root)
	return -ENOMEM;

	sfi->sb = sb;
	sfi->nb.notifier_call = efivarfs_ops_notifier;
	err = blocking_notifier_chain_register(&efivar_ops_nh, &sfi->nb);
	if (err)
	return err;

	return efivar_init(efivarfs_callback, sb, true);
	}

	static int efivarfs_get_tree(struct fs_context *fc)
	{
	return get_tree_single(fc, efivarfs_fill_super);
	}

	static int efivarfs_reconfigure(struct fs_context *fc)
	{
	if (!efivar_supports_writes() && !(fc->sb_flags & SB_RDONLY)) {
	pr_err("Firmware does not support SetVariableRT. Can not remount with rw\n");
	return -EINVAL;
	}

	return 0;
	}

	static const struct fs_context_operations efivarfs_context_ops = {
	.get_tree = efivarfs_get_tree,
	.parse_param = efivarfs_parse_param,
	.reconfigure = efivarfs_reconfigure,
	};

	struct efivarfs_ctx {
	struct dir_context ctx;
	struct super_block *sb;
	struct dentry *dentry;
	};

	static bool efivarfs_actor(struct dir_context ctx, const char name, int len,
	loff_t offset, u64 ino, unsigned mode)
	{
	unsigned long size;
	struct efivarfs_ctx *ectx = container_of(ctx, struct efivarfs_ctx, ctx);
	struct qstr qstr = { .name = name, .len = len };
	struct dentry *dentry = d_hash_and_lookup(ectx->sb->s_root, &qstr);
	struct inode *inode;
	struct efivar_entry *entry;
	int err;

	if (IS_ERR_OR_NULL(dentry))
	return true;

	inode = d_inode(dentry);
	entry = efivar_entry(inode);

	err = efivar_entry_size(entry, &size);
	size += sizeof(__u32); /* attributes */
	if (err)
	size = 0;

	inode_lock(inode);
	i_size_write(inode, size);
	inode_unlock(inode);

	if (!size) {
	ectx->dentry = dentry;
	return false;
	}

	dput(dentry);

	return true;
	}

	static int efivarfs_check_missing(efi_char16_t *name16, efi_guid_t vendor,
	unsigned long name_size, void *data)
	{
	char *name;
	struct super_block *sb = data;
	struct dentry *dentry;
	struct qstr qstr;
	int err;

	if (guid_equal(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
	return 0;

	name = efivar_get_utf8name(name16, &vendor);
	if (!name)
	return -ENOMEM;

	qstr.name = name;
	qstr.len = strlen(name);
	dentry = d_hash_and_lookup(sb->s_root, &qstr);
	if (IS_ERR(dentry)) {
	err = PTR_ERR(dentry);
	goto out;
	}

	if (!dentry) {
	/* found missing entry */
	pr_info("efivarfs: creating variable %s\n", name);
	return efivarfs_create_dentry(sb, name16, name_size, vendor, name);
	}

	dput(dentry);
	err = 0;

	out:
	kfree(name);

	return err;
	}

	static int efivarfs_pm_notify(struct notifier_block *nb, unsigned long action,
	void *ptr)
	{
	struct efivarfs_fs_info *sfi = container_of(nb, struct efivarfs_fs_info,
	pm_nb);
	struct path path = { .mnt = NULL, .dentry = sfi->sb->s_root, };
	struct efivarfs_ctx ectx = {
	.ctx = {
	.actor = efivarfs_actor,
	},
	.sb = sfi->sb,
	};
	struct file *file;
	static bool rescan_done = true;

	if (action == PM_HIBERNATION_PREPARE) {
	rescan_done = false;
	return NOTIFY_OK;
	} else if (action != PM_POST_HIBERNATION) {
	return NOTIFY_DONE;
	}

	if (rescan_done)
	return NOTIFY_DONE;

	pr_info("efivarfs: resyncing variable state\n");

	/* O_NOATIME is required to prevent oops on NULL mnt */
	file = kernel_file_open(&path, O_RDONLY \| O_DIRECTORY \| O_NOATIME,
	current_cred());
	if (IS_ERR(file))
	return NOTIFY_DONE;

	rescan_done = true;

	/*
	* First loop over the directory and verify each entry exists,
	* removing it if it doesn't
	*/
	file->f_pos = 2; /* skip . and .. */
	do {
	ectx.dentry = NULL;
	iterate_dir(file, &ectx.ctx);
	if (ectx.dentry) {
	pr_info("efivarfs: removing variable %pd\n",
	ectx.dentry);
	simple_recursive_removal(ectx.dentry, NULL);
	dput(ectx.dentry);
	}
	} while (ectx.dentry);
	fput(file);

	/*
	* then loop over variables, creating them if there's no matching
	* dentry
	*/
	efivar_init(efivarfs_check_missing, sfi->sb, false);

	return NOTIFY_OK;
	}

	static int efivarfs_init_fs_context(struct fs_context *fc)
	{
	struct efivarfs_fs_info *sfi;

	if (!efivar_is_available())
	return -EOPNOTSUPP;

	sfi = kzalloc(sizeof(*sfi), GFP_KERNEL);
	if (!sfi)
	return -ENOMEM;

	sfi->mount_opts.uid = GLOBAL_ROOT_UID;
	sfi->mount_opts.gid = GLOBAL_ROOT_GID;

	fc->s_fs_info = sfi;
	fc->ops = &efivarfs_context_ops;

	sfi->pm_nb.notifier_call = efivarfs_pm_notify;
	sfi->pm_nb.priority = 0;
	register_pm_notifier(&sfi->pm_nb);

	return 0;
	}

	static void efivarfs_kill_sb(struct super_block *sb)
	{
	struct efivarfs_fs_info *sfi = sb->s_fs_info;

	blocking_notifier_chain_unregister(&efivar_ops_nh, &sfi->nb);
	kill_litter_super(sb);
	unregister_pm_notifier(&sfi->pm_nb);

	kfree(sfi);
	}

	static struct file_system_type efivarfs_type = {
	.owner = THIS_MODULE,
	.name = "efivarfs",
	.init_fs_context = efivarfs_init_fs_context,
	.kill_sb = efivarfs_kill_sb,
	.parameters = efivarfs_parameters,
	};

	static __init int efivarfs_init(void)
	{
	return register_filesystem(&efivarfs_type);
	}

	static __exit void efivarfs_exit(void)
	{
	unregister_filesystem(&efivarfs_type);
	}

	MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
	MODULE_DESCRIPTION("EFI Variable Filesystem");
	MODULE_LICENSE("GPL");
	MODULE_ALIAS_FS("efivarfs");

	module_init(efivarfs_init);
	module_exit(efivarfs_exit);