Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 919 insertions, 0 deletions

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
new file mode 100644
index 000000000..08ef68516
--- /dev/null
+++ b/fs/debugfs/inode.c
@@ -0,0 +1,919 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  inode.c - part of debugfs, a tiny little debug file system
+ *
+ *  Copyright (C) 2004,2019 Greg Kroah-Hartman <greg@kroah.com>
+ *  Copyright (C) 2004 IBM Inc.
+ *  Copyright (C) 2019 Linux Foundation <gregkh@linuxfoundation.org>
+ *
+ *  debugfs is for people to use instead of /proc or /sys.
+ *  See ./Documentation/core-api/kernel-api.rst for more details.
+ */
+
+#define pr_fmt(fmt)	"debugfs: " fmt
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/pagemap.h>
+#include <linux/init.h>
+#include <linux/kobject.h>
+#include <linux/namei.h>
+#include <linux/debugfs.h>
+#include <linux/fsnotify.h>
+#include <linux/string.h>
+#include <linux/seq_file.h>
+#include <linux/parser.h>
+#include <linux/magic.h>
+#include <linux/slab.h>
+#include <linux/security.h>
+
+#include "internal.h"
+
+#define DEBUGFS_DEFAULT_MODE	0700
+
+static struct vfsmount *debugfs_mount;
+static int debugfs_mount_count;
+static bool debugfs_registered;
+static unsigned int debugfs_allow __ro_after_init = DEFAULT_DEBUGFS_ALLOW_BITS;
+
+/*
+ * Don't allow access attributes to be changed whilst the kernel is locked down
+ * so that we can use the file mode as part of a heuristic to determine whether
+ * to lock down individual files.
+ */
+static int debugfs_setattr(struct user_namespace *mnt_userns,
+			   struct dentry *dentry, struct iattr *ia)
+{
+	int ret;
+
+	if (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) {
+		ret = security_locked_down(LOCKDOWN_DEBUGFS);
+		if (ret)
+			return ret;
+	}
+	return simple_setattr(&init_user_ns, dentry, ia);
+}
+
+static const struct inode_operations debugfs_file_inode_operations = {
+	.setattr	= debugfs_setattr,
+};
+static const struct inode_operations debugfs_dir_inode_operations = {
+	.lookup		= simple_lookup,
+	.setattr	= debugfs_setattr,
+};
+static const struct inode_operations debugfs_symlink_inode_operations = {
+	.get_link	= simple_get_link,
+	.setattr	= debugfs_setattr,
+};
+
+static struct inode *debugfs_get_inode(struct super_block *sb)
+{
+	struct inode *inode = new_inode(sb);
+	if (inode) {
+		inode->i_ino = get_next_ino();
+		inode->i_atime = inode->i_mtime =
+			inode->i_ctime = current_time(inode);
+	}
+	return inode;
+}
+
+struct debugfs_mount_opts {
+	kuid_t uid;
+	kgid_t gid;
+	umode_t mode;
+	/* Opt_* bitfield. */
+	unsigned int opts;
+};
+
+enum {
+	Opt_uid,
+	Opt_gid,
+	Opt_mode,
+	Opt_err
+};
+
+static const match_table_t tokens = {
+	{Opt_uid, "uid=%u"},
+	{Opt_gid, "gid=%u"},
+	{Opt_mode, "mode=%o"},
+	{Opt_err, NULL}
+};
+
+struct debugfs_fs_info {
+	struct debugfs_mount_opts mount_opts;
+};
+
+static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
+{
+	substring_t args[MAX_OPT_ARGS];
+	int option;
+	int token;
+	kuid_t uid;
+	kgid_t gid;
+	char *p;
+
+	opts->opts = 0;
+	opts->mode = DEBUGFS_DEFAULT_MODE;
+
+	while ((p = strsep(&data, ",")) != NULL) {
+		if (!*p)
+			continue;
+
+		token = match_token(p, tokens, args);
+		switch (token) {
+		case Opt_uid:
+			if (match_int(&args[0], &option))
+				return -EINVAL;
+			uid = make_kuid(current_user_ns(), option);
+			if (!uid_valid(uid))
+				return -EINVAL;
+			opts->uid = uid;
+			break;
+		case Opt_gid:
+			if (match_int(&args[0], &option))
+				return -EINVAL;
+			gid = make_kgid(current_user_ns(), option);
+			if (!gid_valid(gid))
+				return -EINVAL;
+			opts->gid = gid;
+			break;
+		case Opt_mode:
+			if (match_octal(&args[0], &option))
+				return -EINVAL;
+			opts->mode = option & S_IALLUGO;
+			break;
+		/*
+		 * We might like to report bad mount options here;
+		 * but traditionally debugfs has ignored all mount options
+		 */
+		}
+
+		opts->opts |= BIT(token);
+	}
+
+	return 0;
+}
+
+static void _debugfs_apply_options(struct super_block *sb, bool remount)
+{
+	struct debugfs_fs_info *fsi = sb->s_fs_info;
+	struct inode *inode = d_inode(sb->s_root);
+	struct debugfs_mount_opts *opts = &fsi->mount_opts;
+
+	/*
+	 * On remount, only reset mode/uid/gid if they were provided as mount
+	 * options.
+	 */
+
+	if (!remount || opts->opts & BIT(Opt_mode)) {
+		inode->i_mode &= ~S_IALLUGO;
+		inode->i_mode |= opts->mode;
+	}
+
+	if (!remount || opts->opts & BIT(Opt_uid))
+		inode->i_uid = opts->uid;
+
+	if (!remount || opts->opts & BIT(Opt_gid))
+		inode->i_gid = opts->gid;
+}
+
+static void debugfs_apply_options(struct super_block *sb)
+{
+	_debugfs_apply_options(sb, false);
+}
+
+static void debugfs_apply_options_remount(struct super_block *sb)
+{
+	_debugfs_apply_options(sb, true);
+}
+
+static int debugfs_remount(struct super_block *sb, int *flags, char *data)
+{
+	int err;
+	struct debugfs_fs_info *fsi = sb->s_fs_info;
+
+	sync_filesystem(sb);
+	err = debugfs_parse_options(data, &fsi->mount_opts);
+	if (err)
+		goto fail;
+
+	debugfs_apply_options_remount(sb);
+
+fail:
+	return err;
+}
+
+static int debugfs_show_options(struct seq_file *m, struct dentry *root)
+{
+	struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
+	struct debugfs_mount_opts *opts = &fsi->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));
+	if (opts->mode != DEBUGFS_DEFAULT_MODE)
+		seq_printf(m, ",mode=%o", opts->mode);
+
+	return 0;
+}
+
+static void debugfs_free_inode(struct inode *inode)
+{
+	if (S_ISLNK(inode->i_mode))
+		kfree(inode->i_link);
+	free_inode_nonrcu(inode);
+}
+
+static const struct super_operations debugfs_super_operations = {
+	.statfs		= simple_statfs,
+	.remount_fs	= debugfs_remount,
+	.show_options	= debugfs_show_options,
+	.free_inode	= debugfs_free_inode,
+};
+
+static void debugfs_release_dentry(struct dentry *dentry)
+{
+	struct debugfs_fsdata *fsd = dentry->d_fsdata;
+
+	if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
+		return;
+
+	kfree(fsd);
+}
+
+static struct vfsmount *debugfs_automount(struct path *path)
+{
+	struct debugfs_fsdata *fsd = path->dentry->d_fsdata;
+
+	return fsd->automount(path->dentry, d_inode(path->dentry)->i_private);
+}
+
+static const struct dentry_operations debugfs_dops = {
+	.d_delete = always_delete_dentry,
+	.d_release = debugfs_release_dentry,
+	.d_automount = debugfs_automount,
+};
+
+static int debug_fill_super(struct super_block *sb, void *data, int silent)
+{
+	static const struct tree_descr debug_files[] = {{""}};
+	struct debugfs_fs_info *fsi;
+	int err;
+
+	fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
+	sb->s_fs_info = fsi;
+	if (!fsi) {
+		err = -ENOMEM;
+		goto fail;
+	}
+
+	err = debugfs_parse_options(data, &fsi->mount_opts);
+	if (err)
+		goto fail;
+
+	err  =  simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
+	if (err)
+		goto fail;
+
+	sb->s_op = &debugfs_super_operations;
+	sb->s_d_op = &debugfs_dops;
+
+	debugfs_apply_options(sb);
+
+	return 0;
+
+fail:
+	kfree(fsi);
+	sb->s_fs_info = NULL;
+	return err;
+}
+
+static struct dentry *debug_mount(struct file_system_type *fs_type,
+			int flags, const char *dev_name,
+			void *data)
+{
+	if (!(debugfs_allow & DEBUGFS_ALLOW_API))
+		return ERR_PTR(-EPERM);
+
+	return mount_single(fs_type, flags, data, debug_fill_super);
+}
+
+static struct file_system_type debug_fs_type = {
+	.owner =	THIS_MODULE,
+	.name =		"debugfs",
+	.mount =	debug_mount,
+	.kill_sb =	kill_litter_super,
+};
+MODULE_ALIAS_FS("debugfs");
+
+/**
+ * debugfs_lookup() - look up an existing debugfs file
+ * @name: a pointer to a string containing the name of the file to look up.
+ * @parent: a pointer to the parent dentry of the file.
+ *
+ * This function will return a pointer to a dentry if it succeeds.  If the file
+ * doesn't exist or an error occurs, %NULL will be returned.  The returned
+ * dentry must be passed to dput() when it is no longer needed.
+ *
+ * If debugfs is not enabled in the kernel, the value -%ENODEV will be
+ * returned.
+ */
+struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
+{
+	struct dentry *dentry;
+
+	if (!debugfs_initialized() || IS_ERR_OR_NULL(name) || IS_ERR(parent))
+		return NULL;
+
+	if (!parent)
+		parent = debugfs_mount->mnt_root;
+
+	dentry = lookup_positive_unlocked(name, parent, strlen(name));
+	if (IS_ERR(dentry))
+		return NULL;
+	return dentry;
+}
+EXPORT_SYMBOL_GPL(debugfs_lookup);
+
+static struct dentry *start_creating(const char *name, struct dentry *parent)
+{
+	struct dentry *dentry;
+	int error;
+
+	if (!(debugfs_allow & DEBUGFS_ALLOW_API))
+		return ERR_PTR(-EPERM);
+
+	if (!debugfs_initialized())
+		return ERR_PTR(-ENOENT);
+
+	pr_debug("creating file '%s'\n", name);
+
+	if (IS_ERR(parent))
+		return parent;
+
+	error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
+			      &debugfs_mount_count);
+	if (error) {
+		pr_err("Unable to pin filesystem for file '%s'\n", name);
+		return ERR_PTR(error);
+	}
+
+	/* 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)
+		parent = debugfs_mount->mnt_root;
+
+	inode_lock(d_inode(parent));
+	if (unlikely(IS_DEADDIR(d_inode(parent))))
+		dentry = ERR_PTR(-ENOENT);
+	else
+		dentry = lookup_one_len(name, parent, strlen(name));
+	if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
+		if (d_is_dir(dentry))
+			pr_err("Directory '%s' with parent '%s' already present!\n",
+			       name, parent->d_name.name);
+		else
+			pr_err("File '%s' in directory '%s' already present!\n",
+			       name, parent->d_name.name);
+		dput(dentry);
+		dentry = ERR_PTR(-EEXIST);
+	}
+
+	if (IS_ERR(dentry)) {
+		inode_unlock(d_inode(parent));
+		simple_release_fs(&debugfs_mount, &debugfs_mount_count);
+	}
+
+	return dentry;
+}
+
+static struct dentry *failed_creating(struct dentry *dentry)
+{
+	inode_unlock(d_inode(dentry->d_parent));
+	dput(dentry);
+	simple_release_fs(&debugfs_mount, &debugfs_mount_count);
+	return ERR_PTR(-ENOMEM);
+}
+
+static struct dentry *end_creating(struct dentry *dentry)
+{
+	inode_unlock(d_inode(dentry->d_parent));
+	return dentry;
+}
+
+static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
+				struct dentry *parent, void *data,
+				const struct file_operations *proxy_fops,
+				const struct file_operations *real_fops)
+{
+	struct dentry *dentry;
+	struct inode *inode;
+
+	if (!(mode & S_IFMT))
+		mode |= S_IFREG;
+	BUG_ON(!S_ISREG(mode));
+	dentry = start_creating(name, parent);
+
+	if (IS_ERR(dentry))
+		return dentry;
+
+	if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
+		failed_creating(dentry);
+		return ERR_PTR(-EPERM);
+	}
+
+	inode = debugfs_get_inode(dentry->d_sb);
+	if (unlikely(!inode)) {
+		pr_err("out of free dentries, can not create file '%s'\n",
+		       name);
+		return failed_creating(dentry);
+	}
+
+	inode->i_mode = mode;
+	inode->i_private = data;
+
+	inode->i_op = &debugfs_file_inode_operations;
+	inode->i_fop = proxy_fops;
+	dentry->d_fsdata = (void *)((unsigned long)real_fops |
+				DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
+
+	d_instantiate(dentry, inode);
+	fsnotify_create(d_inode(dentry->d_parent), dentry);
+	return end_creating(dentry);
+}
+
+/**
+ * debugfs_create_file - create a file in the debugfs 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 debugfs 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 debugfs.  It allows for a
+ * wide range of flexibility in creating a file, or a directory (if you want
+ * to create a directory, the debugfs_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 debugfs_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, ERR_PTR(-ERROR) will be
+ * returned.
+ *
+ * If debugfs is not enabled in the kernel, the value -%ENODEV will be
+ * returned.
+ *
+ * NOTE: it's expected that most callers should _ignore_ the errors returned
+ * by this function. Other debugfs functions handle the fact that the "dentry"
+ * passed to them could be an error and they don't crash in that case.
+ * Drivers should generally work fine even if debugfs fails to init anyway.
+ */
+struct dentry *debugfs_create_file(const char *name, umode_t mode,
+				   struct dentry *parent, void *data,
+				   const struct file_operations *fops)
+{
+
+	return __debugfs_create_file(name, mode, parent, data,
+				fops ? &debugfs_full_proxy_file_operations :
+					&debugfs_noop_file_operations,
+				fops);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_file);
+
+/**
+ * debugfs_create_file_unsafe - create a file in the debugfs 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 debugfs 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.
+ *
+ * debugfs_create_file_unsafe() is completely analogous to
+ * debugfs_create_file(), the only difference being that the fops
+ * handed it will not get protected against file removals by the
+ * debugfs core.
+ *
+ * It is your responsibility to protect your struct file_operation
+ * methods against file removals by means of debugfs_file_get()
+ * and debugfs_file_put(). ->open() is still protected by
+ * debugfs though.
+ *
+ * Any struct file_operations defined by means of
+ * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
+ * thus, may be used here.
+ */
+struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
+				   struct dentry *parent, void *data,
+				   const struct file_operations *fops)
+{
+
+	return __debugfs_create_file(name, mode, parent, data,
+				fops ? &debugfs_open_proxy_file_operations :
+					&debugfs_noop_file_operations,
+				fops);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
+
+/**
+ * debugfs_create_file_size - create a file in the debugfs 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 debugfs 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.
+ * @file_size: initial file size
+ *
+ * This is the basic "create a file" function for debugfs.  It allows for a
+ * wide range of flexibility in creating a file, or a directory (if you want
+ * to create a directory, the debugfs_create_dir() function is
+ * recommended to be used instead.)
+ */
+void debugfs_create_file_size(const char *name, umode_t mode,
+			      struct dentry *parent, void *data,
+			      const struct file_operations *fops,
+			      loff_t file_size)
+{
+	struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
+
+	if (!IS_ERR(de))
+		d_inode(de)->i_size = file_size;
+}
+EXPORT_SYMBOL_GPL(debugfs_create_file_size);
+
+/**
+ * debugfs_create_dir - create a directory in the debugfs 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 debugfs filesystem.
+ *
+ * This function creates a directory in debugfs with the given name.
+ *
+ * This function will return a pointer to a dentry if it succeeds.  This
+ * pointer must be passed to the debugfs_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, ERR_PTR(-ERROR) will be
+ * returned.
+ *
+ * If debugfs is not enabled in the kernel, the value -%ENODEV will be
+ * returned.
+ *
+ * NOTE: it's expected that most callers should _ignore_ the errors returned
+ * by this function. Other debugfs functions handle the fact that the "dentry"
+ * passed to them could be an error and they don't crash in that case.
+ * Drivers should generally work fine even if debugfs fails to init anyway.
+ */
+struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
+{
+	struct dentry *dentry = start_creating(name, parent);
+	struct inode *inode;
+
+	if (IS_ERR(dentry))
+		return dentry;
+
+	if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
+		failed_creating(dentry);
+		return ERR_PTR(-EPERM);
+	}
+
+	inode = debugfs_get_inode(dentry->d_sb);
+	if (unlikely(!inode)) {
+		pr_err("out of free dentries, can not create directory '%s'\n",
+		       name);
+		return failed_creating(dentry);
+	}
+
+	inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
+	inode->i_op = &debugfs_dir_inode_operations;
+	inode->i_fop = &simple_dir_operations;
+
+	/* directory inodes start off with i_nlink == 2 (for "." entry) */
+	inc_nlink(inode);
+	d_instantiate(dentry, inode);
+	inc_nlink(d_inode(dentry->d_parent));
+	fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
+	return end_creating(dentry);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_dir);
+
+/**
+ * debugfs_create_automount - create automount point in the debugfs filesystem
+ * @name: a pointer to a string containing the name of the file 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
+ *          file will be created in the root of the debugfs filesystem.
+ * @f: function to be called when pathname resolution steps on that one.
+ * @data: opaque argument to pass to f().
+ *
+ * @f should return what ->d_automount() would.
+ */
+struct dentry *debugfs_create_automount(const char *name,
+					struct dentry *parent,
+					debugfs_automount_t f,
+					void *data)
+{
+	struct dentry *dentry = start_creating(name, parent);
+	struct debugfs_fsdata *fsd;
+	struct inode *inode;
+
+	if (IS_ERR(dentry))
+		return dentry;
+
+	fsd = kzalloc(sizeof(*fsd), GFP_KERNEL);
+	if (!fsd) {
+		failed_creating(dentry);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	fsd->automount = f;
+
+	if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
+		failed_creating(dentry);
+		kfree(fsd);
+		return ERR_PTR(-EPERM);
+	}
+
+	inode = debugfs_get_inode(dentry->d_sb);
+	if (unlikely(!inode)) {
+		pr_err("out of free dentries, can not create automount '%s'\n",
+		       name);
+		kfree(fsd);
+		return failed_creating(dentry);
+	}
+
+	make_empty_dir_inode(inode);
+	inode->i_flags |= S_AUTOMOUNT;
+	inode->i_private = data;
+	dentry->d_fsdata = fsd;
+	/* directory inodes start off with i_nlink == 2 (for "." entry) */
+	inc_nlink(inode);
+	d_instantiate(dentry, inode);
+	inc_nlink(d_inode(dentry->d_parent));
+	fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
+	return end_creating(dentry);
+}
+EXPORT_SYMBOL(debugfs_create_automount);
+
+/**
+ * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
+ * @name: a pointer to a string containing the name of the symbolic link to
+ *        create.
+ * @parent: a pointer to the parent dentry for this symbolic link.  This
+ *          should be a directory dentry if set.  If this parameter is NULL,
+ *          then the symbolic link will be created in the root of the debugfs
+ *          filesystem.
+ * @target: a pointer to a string containing the path to the target of the
+ *          symbolic link.
+ *
+ * This function creates a symbolic link with the given name in debugfs that
+ * links to the given target path.
+ *
+ * This function will return a pointer to a dentry if it succeeds.  This
+ * pointer must be passed to the debugfs_remove() function when the symbolic
+ * link is to be removed (no automatic cleanup happens if your module is
+ * unloaded, you are responsible here.)  If an error occurs, ERR_PTR(-ERROR)
+ * will be returned.
+ *
+ * If debugfs is not enabled in the kernel, the value -%ENODEV will be
+ * returned.
+ */
+struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
+				      const char *target)
+{
+	struct dentry *dentry;
+	struct inode *inode;
+	char *link = kstrdup(target, GFP_KERNEL);
+	if (!link)
+		return ERR_PTR(-ENOMEM);
+
+	dentry = start_creating(name, parent);
+	if (IS_ERR(dentry)) {
+		kfree(link);
+		return dentry;
+	}
+
+	inode = debugfs_get_inode(dentry->d_sb);
+	if (unlikely(!inode)) {
+		pr_err("out of free dentries, can not create symlink '%s'\n",
+		       name);
+		kfree(link);
+		return failed_creating(dentry);
+	}
+	inode->i_mode = S_IFLNK | S_IRWXUGO;
+	inode->i_op = &debugfs_symlink_inode_operations;
+	inode->i_link = link;
+	d_instantiate(dentry, inode);
+	return end_creating(dentry);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_symlink);
+
+static void __debugfs_file_removed(struct dentry *dentry)
+{
+	struct debugfs_fsdata *fsd;
+
+	/*
+	 * Paired with the closing smp_mb() implied by a successful
+	 * cmpxchg() in debugfs_file_get(): either
+	 * debugfs_file_get() must see a dead dentry or we must see a
+	 * debugfs_fsdata instance at ->d_fsdata here (or both).
+	 */
+	smp_mb();
+	fsd = READ_ONCE(dentry->d_fsdata);
+	if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
+		return;
+	if (!refcount_dec_and_test(&fsd->active_users))
+		wait_for_completion(&fsd->active_users_drained);
+}
+
+static void remove_one(struct dentry *victim)
+{
+        if (d_is_reg(victim))
+		__debugfs_file_removed(victim);
+	simple_release_fs(&debugfs_mount, &debugfs_mount_count);
+}
+
+/**
+ * debugfs_remove - recursively removes a directory
+ * @dentry: a pointer to a the dentry of the directory to be removed.  If this
+ *          parameter is NULL or an error value, nothing will be done.
+ *
+ * This function recursively removes a directory tree in debugfs that
+ * was previously created with a call to another debugfs function
+ * (like debugfs_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 debugfs_remove(struct dentry *dentry)
+{
+	if (IS_ERR_OR_NULL(dentry))
+		return;
+
+	simple_pin_fs(&debug_fs_type, &debugfs_mount, &debugfs_mount_count);
+	simple_recursive_removal(dentry, remove_one);
+	simple_release_fs(&debugfs_mount, &debugfs_mount_count);
+}
+EXPORT_SYMBOL_GPL(debugfs_remove);
+
+/**
+ * debugfs_lookup_and_remove - lookup a directory or file and recursively remove it
+ * @name: a pointer to a string containing the name of the item to look up.
+ * @parent: a pointer to the parent dentry of the item.
+ *
+ * This is the equlivant of doing something like
+ * debugfs_remove(debugfs_lookup(..)) but with the proper reference counting
+ * handled for the directory being looked up.
+ */
+void debugfs_lookup_and_remove(const char *name, struct dentry *parent)
+{
+	struct dentry *dentry;
+
+	dentry = debugfs_lookup(name, parent);
+	if (!dentry)
+		return;
+
+	debugfs_remove(dentry);
+	dput(dentry);
+}
+EXPORT_SYMBOL_GPL(debugfs_lookup_and_remove);
+
+/**
+ * debugfs_rename - rename a file/directory in the debugfs filesystem
+ * @old_dir: a pointer to the parent dentry for the renamed object. This
+ *          should be a directory dentry.
+ * @old_dentry: dentry of an object to be renamed.
+ * @new_dir: a pointer to the parent dentry where the object should be
+ *          moved. This should be a directory dentry.
+ * @new_name: a pointer to a string containing the target name.
+ *
+ * This function renames a file/directory in debugfs.  The target must not
+ * exist for rename to succeed.
+ *
+ * This function will return a pointer to old_dentry (which is updated to
+ * reflect renaming) if it succeeds. If an error occurs, %NULL will be
+ * returned.
+ *
+ * If debugfs is not enabled in the kernel, the value -%ENODEV will be
+ * returned.
+ */
+struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
+		struct dentry *new_dir, const char *new_name)
+{
+	int error;
+	struct dentry *dentry = NULL, *trap;
+	struct name_snapshot old_name;
+
+	if (IS_ERR(old_dir))
+		return old_dir;
+	if (IS_ERR(new_dir))
+		return new_dir;
+	if (IS_ERR_OR_NULL(old_dentry))
+		return old_dentry;
+
+	trap = lock_rename(new_dir, old_dir);
+	/* Source or destination directories don't exist? */
+	if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
+		goto exit;
+	/* Source does not exist, cyclic rename, or mountpoint? */
+	if (d_really_is_negative(old_dentry) || old_dentry == trap ||
+	    d_mountpoint(old_dentry))
+		goto exit;
+	dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
+	/* Lookup failed, cyclic rename or target exists? */
+	if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
+		goto exit;
+
+	take_dentry_name_snapshot(&old_name, old_dentry);
+
+	error = simple_rename(&init_user_ns, d_inode(old_dir), old_dentry,
+			      d_inode(new_dir), dentry, 0);
+	if (error) {
+		release_dentry_name_snapshot(&old_name);
+		goto exit;
+	}
+	d_move(old_dentry, dentry);
+	fsnotify_move(d_inode(old_dir), d_inode(new_dir), &old_name.name,
+		d_is_dir(old_dentry),
+		NULL, old_dentry);
+	release_dentry_name_snapshot(&old_name);
+	unlock_rename(new_dir, old_dir);
+	dput(dentry);
+	return old_dentry;
+exit:
+	if (dentry && !IS_ERR(dentry))
+		dput(dentry);
+	unlock_rename(new_dir, old_dir);
+	if (IS_ERR(dentry))
+		return dentry;
+	return ERR_PTR(-EINVAL);
+}
+EXPORT_SYMBOL_GPL(debugfs_rename);
+
+/**
+ * debugfs_initialized - Tells whether debugfs has been registered
+ */
+bool debugfs_initialized(void)
+{
+	return debugfs_registered;
+}
+EXPORT_SYMBOL_GPL(debugfs_initialized);
+
+static int __init debugfs_kernel(char *str)
+{
+	if (str) {
+		if (!strcmp(str, "on"))
+			debugfs_allow = DEBUGFS_ALLOW_API | DEBUGFS_ALLOW_MOUNT;
+		else if (!strcmp(str, "no-mount"))
+			debugfs_allow = DEBUGFS_ALLOW_API;
+		else if (!strcmp(str, "off"))
+			debugfs_allow = 0;
+	}
+
+	return 0;
+}
+early_param("debugfs", debugfs_kernel);
+static int __init debugfs_init(void)
+{
+	int retval;
+
+	if (!(debugfs_allow & DEBUGFS_ALLOW_MOUNT))
+		return -EPERM;
+
+	retval = sysfs_create_mount_point(kernel_kobj, "debug");
+	if (retval)
+		return retval;
+
+	retval = register_filesystem(&debug_fs_type);
+	if (retval)
+		sysfs_remove_mount_point(kernel_kobj, "debug");
+	else
+		debugfs_registered = true;
+
+	return retval;
+}
+core_initcall(debugfs_init);