Adding upstream version 4.19.249.upstream/4.19.249

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

4 files changed, 2074 insertions, 0 deletions

diff --git a/fs/debugfs/Makefile b/fs/debugfs/Makefile
new file mode 100644
index 000000000..840c45696
--- /dev/null
+++ b/fs/debugfs/Makefile
@@ -0,0 +1,4 @@
+debugfs-objs	:= inode.o file.o
+
+obj-$(CONFIG_DEBUG_FS)	+= debugfs.o
+
diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
new file mode 100644
index 000000000..4fce1da7d
--- /dev/null
+++ b/fs/debugfs/file.c
@@ -0,0 +1,1173 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  file.c - part of debugfs, a tiny little debug file system
+ *
+ *  Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
+ *  Copyright (C) 2004 IBM Inc.
+ *
+ *  debugfs is for people to use instead of /proc or /sys.
+ *  See Documentation/filesystems/ for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/seq_file.h>
+#include <linux/pagemap.h>
+#include <linux/debugfs.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+#include <linux/atomic.h>
+#include <linux/device.h>
+#include <linux/poll.h>
+
+#include "internal.h"
+
+struct poll_table_struct;
+
+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;
+}
+
+const struct file_operations debugfs_noop_file_operations = {
+	.read =		default_read_file,
+	.write =	default_write_file,
+	.open =		simple_open,
+	.llseek =	noop_llseek,
+};
+
+#define F_DENTRY(filp) ((filp)->f_path.dentry)
+
+const struct file_operations *debugfs_real_fops(const struct file *filp)
+{
+	struct debugfs_fsdata *fsd = F_DENTRY(filp)->d_fsdata;
+
+	if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT) {
+		/*
+		 * Urgh, we've been called w/o a protecting
+		 * debugfs_file_get().
+		 */
+		WARN_ON(1);
+		return NULL;
+	}
+
+	return fsd->real_fops;
+}
+EXPORT_SYMBOL_GPL(debugfs_real_fops);
+
+/**
+ * debugfs_file_get - mark the beginning of file data access
+ * @dentry: the dentry object whose data is being accessed.
+ *
+ * Up to a matching call to debugfs_file_put(), any successive call
+ * into the file removing functions debugfs_remove() and
+ * debugfs_remove_recursive() will block. Since associated private
+ * file data may only get freed after a successful return of any of
+ * the removal functions, you may safely access it after a successful
+ * call to debugfs_file_get() without worrying about lifetime issues.
+ *
+ * If -%EIO is returned, the file has already been removed and thus,
+ * it is not safe to access any of its data. If, on the other hand,
+ * it is allowed to access the file data, zero is returned.
+ */
+int debugfs_file_get(struct dentry *dentry)
+{
+	struct debugfs_fsdata *fsd;
+	void *d_fsd;
+
+	d_fsd = READ_ONCE(dentry->d_fsdata);
+	if (!((unsigned long)d_fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)) {
+		fsd = d_fsd;
+	} else {
+		fsd = kmalloc(sizeof(*fsd), GFP_KERNEL);
+		if (!fsd)
+			return -ENOMEM;
+
+		fsd->real_fops = (void *)((unsigned long)d_fsd &
+					~DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
+		refcount_set(&fsd->active_users, 1);
+		init_completion(&fsd->active_users_drained);
+		if (cmpxchg(&dentry->d_fsdata, d_fsd, fsd) != d_fsd) {
+			kfree(fsd);
+			fsd = READ_ONCE(dentry->d_fsdata);
+		}
+	}
+
+	/*
+	 * In case of a successful cmpxchg() above, this check is
+	 * strictly necessary and must follow it, see the comment in
+	 * __debugfs_remove_file().
+	 * OTOH, if the cmpxchg() hasn't been executed or wasn't
+	 * successful, this serves the purpose of not starving
+	 * removers.
+	 */
+	if (d_unlinked(dentry))
+		return -EIO;
+
+	if (!refcount_inc_not_zero(&fsd->active_users))
+		return -EIO;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(debugfs_file_get);
+
+/**
+ * debugfs_file_put - mark the end of file data access
+ * @dentry: the dentry object formerly passed to
+ *          debugfs_file_get().
+ *
+ * Allow any ongoing concurrent call into debugfs_remove() or
+ * debugfs_remove_recursive() blocked by a former call to
+ * debugfs_file_get() to proceed and return to its caller.
+ */
+void debugfs_file_put(struct dentry *dentry)
+{
+	struct debugfs_fsdata *fsd = READ_ONCE(dentry->d_fsdata);
+
+	if (refcount_dec_and_test(&fsd->active_users))
+		complete(&fsd->active_users_drained);
+}
+EXPORT_SYMBOL_GPL(debugfs_file_put);
+
+static int open_proxy_open(struct inode *inode, struct file *filp)
+{
+	struct dentry *dentry = F_DENTRY(filp);
+	const struct file_operations *real_fops = NULL;
+	int r;
+
+	r = debugfs_file_get(dentry);
+	if (r)
+		return r == -EIO ? -ENOENT : r;
+
+	real_fops = debugfs_real_fops(filp);
+	real_fops = fops_get(real_fops);
+	if (!real_fops) {
+		/* Huh? Module did not clean up after itself at exit? */
+		WARN(1, "debugfs file owner did not clean up at exit: %pd",
+			dentry);
+		r = -ENXIO;
+		goto out;
+	}
+	replace_fops(filp, real_fops);
+
+	if (real_fops->open)
+		r = real_fops->open(inode, filp);
+
+out:
+	debugfs_file_put(dentry);
+	return r;
+}
+
+const struct file_operations debugfs_open_proxy_file_operations = {
+	.open = open_proxy_open,
+};
+
+#define PROTO(args...) args
+#define ARGS(args...) args
+
+#define FULL_PROXY_FUNC(name, ret_type, filp, proto, args)		\
+static ret_type full_proxy_ ## name(proto)				\
+{									\
+	struct dentry *dentry = F_DENTRY(filp);			\
+	const struct file_operations *real_fops;			\
+	ret_type r;							\
+									\
+	r = debugfs_file_get(dentry);					\
+	if (unlikely(r))						\
+		return r;						\
+	real_fops = debugfs_real_fops(filp);				\
+	r = real_fops->name(args);					\
+	debugfs_file_put(dentry);					\
+	return r;							\
+}
+
+FULL_PROXY_FUNC(llseek, loff_t, filp,
+		PROTO(struct file *filp, loff_t offset, int whence),
+		ARGS(filp, offset, whence));
+
+FULL_PROXY_FUNC(read, ssize_t, filp,
+		PROTO(struct file *filp, char __user *buf, size_t size,
+			loff_t *ppos),
+		ARGS(filp, buf, size, ppos));
+
+FULL_PROXY_FUNC(write, ssize_t, filp,
+		PROTO(struct file *filp, const char __user *buf, size_t size,
+			loff_t *ppos),
+		ARGS(filp, buf, size, ppos));
+
+FULL_PROXY_FUNC(unlocked_ioctl, long, filp,
+		PROTO(struct file *filp, unsigned int cmd, unsigned long arg),
+		ARGS(filp, cmd, arg));
+
+static __poll_t full_proxy_poll(struct file *filp,
+				struct poll_table_struct *wait)
+{
+	struct dentry *dentry = F_DENTRY(filp);
+	__poll_t r = 0;
+	const struct file_operations *real_fops;
+
+	if (debugfs_file_get(dentry))
+		return EPOLLHUP;
+
+	real_fops = debugfs_real_fops(filp);
+	r = real_fops->poll(filp, wait);
+	debugfs_file_put(dentry);
+	return r;
+}
+
+static int full_proxy_release(struct inode *inode, struct file *filp)
+{
+	const struct dentry *dentry = F_DENTRY(filp);
+	const struct file_operations *real_fops = debugfs_real_fops(filp);
+	const struct file_operations *proxy_fops = filp->f_op;
+	int r = 0;
+
+	/*
+	 * We must not protect this against removal races here: the
+	 * original releaser should be called unconditionally in order
+	 * not to leak any resources. Releasers must not assume that
+	 * ->i_private is still being meaningful here.
+	 */
+	if (real_fops->release)
+		r = real_fops->release(inode, filp);
+
+	replace_fops(filp, d_inode(dentry)->i_fop);
+	kfree((void *)proxy_fops);
+	fops_put(real_fops);
+	return r;
+}
+
+static void __full_proxy_fops_init(struct file_operations *proxy_fops,
+				const struct file_operations *real_fops)
+{
+	proxy_fops->release = full_proxy_release;
+	if (real_fops->llseek)
+		proxy_fops->llseek = full_proxy_llseek;
+	if (real_fops->read)
+		proxy_fops->read = full_proxy_read;
+	if (real_fops->write)
+		proxy_fops->write = full_proxy_write;
+	if (real_fops->poll)
+		proxy_fops->poll = full_proxy_poll;
+	if (real_fops->unlocked_ioctl)
+		proxy_fops->unlocked_ioctl = full_proxy_unlocked_ioctl;
+}
+
+static int full_proxy_open(struct inode *inode, struct file *filp)
+{
+	struct dentry *dentry = F_DENTRY(filp);
+	const struct file_operations *real_fops = NULL;
+	struct file_operations *proxy_fops = NULL;
+	int r;
+
+	r = debugfs_file_get(dentry);
+	if (r)
+		return r == -EIO ? -ENOENT : r;
+
+	real_fops = debugfs_real_fops(filp);
+	real_fops = fops_get(real_fops);
+	if (!real_fops) {
+		/* Huh? Module did not cleanup after itself at exit? */
+		WARN(1, "debugfs file owner did not clean up at exit: %pd",
+			dentry);
+		r = -ENXIO;
+		goto out;
+	}
+
+	proxy_fops = kzalloc(sizeof(*proxy_fops), GFP_KERNEL);
+	if (!proxy_fops) {
+		r = -ENOMEM;
+		goto free_proxy;
+	}
+	__full_proxy_fops_init(proxy_fops, real_fops);
+	replace_fops(filp, proxy_fops);
+
+	if (real_fops->open) {
+		r = real_fops->open(inode, filp);
+		if (r) {
+			replace_fops(filp, d_inode(dentry)->i_fop);
+			goto free_proxy;
+		} else if (filp->f_op != proxy_fops) {
+			/* No protection against file removal anymore. */
+			WARN(1, "debugfs file owner replaced proxy fops: %pd",
+				dentry);
+			goto free_proxy;
+		}
+	}
+
+	goto out;
+free_proxy:
+	kfree(proxy_fops);
+	fops_put(real_fops);
+out:
+	debugfs_file_put(dentry);
+	return r;
+}
+
+const struct file_operations debugfs_full_proxy_file_operations = {
+	.open = full_proxy_open,
+};
+
+ssize_t debugfs_attr_read(struct file *file, char __user *buf,
+			size_t len, loff_t *ppos)
+{
+	struct dentry *dentry = F_DENTRY(file);
+	ssize_t ret;
+
+	ret = debugfs_file_get(dentry);
+	if (unlikely(ret))
+		return ret;
+	ret = simple_attr_read(file, buf, len, ppos);
+	debugfs_file_put(dentry);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(debugfs_attr_read);
+
+ssize_t debugfs_attr_write(struct file *file, const char __user *buf,
+			 size_t len, loff_t *ppos)
+{
+	struct dentry *dentry = F_DENTRY(file);
+	ssize_t ret;
+
+	ret = debugfs_file_get(dentry);
+	if (unlikely(ret))
+		return ret;
+	ret = simple_attr_write(file, buf, len, ppos);
+	debugfs_file_put(dentry);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(debugfs_attr_write);
+
+static struct dentry *debugfs_create_mode_unsafe(const char *name, umode_t mode,
+					struct dentry *parent, void *value,
+					const struct file_operations *fops,
+					const struct file_operations *fops_ro,
+					const struct file_operations *fops_wo)
+{
+	/* if there are no write bits set, make read only */
+	if (!(mode & S_IWUGO))
+		return debugfs_create_file_unsafe(name, mode, parent, value,
+						fops_ro);
+	/* if there are no read bits set, make write only */
+	if (!(mode & S_IRUGO))
+		return debugfs_create_file_unsafe(name, mode, parent, value,
+						fops_wo);
+
+	return debugfs_create_file_unsafe(name, mode, parent, value, fops);
+}
+
+static int debugfs_u8_set(void *data, u64 val)
+{
+	*(u8 *)data = val;
+	return 0;
+}
+static int debugfs_u8_get(void *data, u64 *val)
+{
+	*val = *(u8 *)data;
+	return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(fops_u8, debugfs_u8_get, debugfs_u8_set, "%llu\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_u8_ro, debugfs_u8_get, NULL, "%llu\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_u8_wo, NULL, debugfs_u8_set, "%llu\n");
+
+/**
+ * debugfs_create_u8 - create a debugfs file that is used to read and write an unsigned 8-bit value
+ * @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.
+ * @value: a pointer to the variable that the file should read to and write
+ *         from.
+ *
+ * This function creates a file in debugfs with the given name that
+ * contains the value of the variable @value.  If the @mode variable is so
+ * set, it can be read from, and written to.
+ *
+ * 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, %NULL will be returned.
+ *
+ * If debugfs 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 *debugfs_create_u8(const char *name, umode_t mode,
+				 struct dentry *parent, u8 *value)
+{
+	return debugfs_create_mode_unsafe(name, mode, parent, value, &fops_u8,
+				   &fops_u8_ro, &fops_u8_wo);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_u8);
+
+static int debugfs_u16_set(void *data, u64 val)
+{
+	*(u16 *)data = val;
+	return 0;
+}
+static int debugfs_u16_get(void *data, u64 *val)
+{
+	*val = *(u16 *)data;
+	return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(fops_u16, debugfs_u16_get, debugfs_u16_set, "%llu\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_u16_ro, debugfs_u16_get, NULL, "%llu\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_u16_wo, NULL, debugfs_u16_set, "%llu\n");
+
+/**
+ * debugfs_create_u16 - create a debugfs file that is used to read and write an unsigned 16-bit value
+ * @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.
+ * @value: a pointer to the variable that the file should read to and write
+ *         from.
+ *
+ * This function creates a file in debugfs with the given name that
+ * contains the value of the variable @value.  If the @mode variable is so
+ * set, it can be read from, and written to.
+ *
+ * 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, %NULL will be returned.
+ *
+ * If debugfs 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 *debugfs_create_u16(const char *name, umode_t mode,
+				  struct dentry *parent, u16 *value)
+{
+	return debugfs_create_mode_unsafe(name, mode, parent, value, &fops_u16,
+				   &fops_u16_ro, &fops_u16_wo);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_u16);
+
+static int debugfs_u32_set(void *data, u64 val)
+{
+	*(u32 *)data = val;
+	return 0;
+}
+static int debugfs_u32_get(void *data, u64 *val)
+{
+	*val = *(u32 *)data;
+	return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(fops_u32, debugfs_u32_get, debugfs_u32_set, "%llu\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_u32_ro, debugfs_u32_get, NULL, "%llu\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_u32_wo, NULL, debugfs_u32_set, "%llu\n");
+
+/**
+ * debugfs_create_u32 - create a debugfs file that is used to read and write an unsigned 32-bit value
+ * @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.
+ * @value: a pointer to the variable that the file should read to and write
+ *         from.
+ *
+ * This function creates a file in debugfs with the given name that
+ * contains the value of the variable @value.  If the @mode variable is so
+ * set, it can be read from, and written to.
+ *
+ * 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, %NULL will be returned.
+ *
+ * If debugfs 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 *debugfs_create_u32(const char *name, umode_t mode,
+				 struct dentry *parent, u32 *value)
+{
+	return debugfs_create_mode_unsafe(name, mode, parent, value, &fops_u32,
+				   &fops_u32_ro, &fops_u32_wo);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_u32);
+
+static int debugfs_u64_set(void *data, u64 val)
+{
+	*(u64 *)data = val;
+	return 0;
+}
+
+static int debugfs_u64_get(void *data, u64 *val)
+{
+	*val = *(u64 *)data;
+	return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(fops_u64, debugfs_u64_get, debugfs_u64_set, "%llu\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_u64_ro, debugfs_u64_get, NULL, "%llu\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_u64_wo, NULL, debugfs_u64_set, "%llu\n");
+
+/**
+ * debugfs_create_u64 - create a debugfs file that is used to read and write an unsigned 64-bit value
+ * @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.
+ * @value: a pointer to the variable that the file should read to and write
+ *         from.
+ *
+ * This function creates a file in debugfs with the given name that
+ * contains the value of the variable @value.  If the @mode variable is so
+ * set, it can be read from, and written to.
+ *
+ * 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, %NULL will be returned.
+ *
+ * If debugfs 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 *debugfs_create_u64(const char *name, umode_t mode,
+				 struct dentry *parent, u64 *value)
+{
+	return debugfs_create_mode_unsafe(name, mode, parent, value, &fops_u64,
+				   &fops_u64_ro, &fops_u64_wo);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_u64);
+
+static int debugfs_ulong_set(void *data, u64 val)
+{
+	*(unsigned long *)data = val;
+	return 0;
+}
+
+static int debugfs_ulong_get(void *data, u64 *val)
+{
+	*val = *(unsigned long *)data;
+	return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(fops_ulong, debugfs_ulong_get, debugfs_ulong_set,
+			"%llu\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_ulong_ro, debugfs_ulong_get, NULL, "%llu\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_ulong_wo, NULL, debugfs_ulong_set, "%llu\n");
+
+/**
+ * debugfs_create_ulong - create a debugfs file that is used to read and write
+ * an unsigned long value.
+ * @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.
+ * @value: a pointer to the variable that the file should read to and write
+ *         from.
+ *
+ * This function creates a file in debugfs with the given name that
+ * contains the value of the variable @value.  If the @mode variable is so
+ * set, it can be read from, and written to.
+ *
+ * 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, %NULL will be returned.
+ *
+ * If debugfs 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 *debugfs_create_ulong(const char *name, umode_t mode,
+				    struct dentry *parent, unsigned long *value)
+{
+	return debugfs_create_mode_unsafe(name, mode, parent, value,
+					&fops_ulong, &fops_ulong_ro,
+					&fops_ulong_wo);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_ulong);
+
+DEFINE_DEBUGFS_ATTRIBUTE(fops_x8, debugfs_u8_get, debugfs_u8_set, "0x%02llx\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_x8_ro, debugfs_u8_get, NULL, "0x%02llx\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_x8_wo, NULL, debugfs_u8_set, "0x%02llx\n");
+
+DEFINE_DEBUGFS_ATTRIBUTE(fops_x16, debugfs_u16_get, debugfs_u16_set,
+			"0x%04llx\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_x16_ro, debugfs_u16_get, NULL, "0x%04llx\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_x16_wo, NULL, debugfs_u16_set, "0x%04llx\n");
+
+DEFINE_DEBUGFS_ATTRIBUTE(fops_x32, debugfs_u32_get, debugfs_u32_set,
+			"0x%08llx\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_x32_ro, debugfs_u32_get, NULL, "0x%08llx\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_x32_wo, NULL, debugfs_u32_set, "0x%08llx\n");
+
+DEFINE_DEBUGFS_ATTRIBUTE(fops_x64, debugfs_u64_get, debugfs_u64_set,
+			"0x%016llx\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_x64_ro, debugfs_u64_get, NULL, "0x%016llx\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_x64_wo, NULL, debugfs_u64_set, "0x%016llx\n");
+
+/*
+ * debugfs_create_x{8,16,32,64} - create a debugfs file that is used to read and write an unsigned {8,16,32,64}-bit value
+ *
+ * These functions are exactly the same as the above functions (but use a hex
+ * output for the decimal challenged). For details look at the above unsigned
+ * decimal functions.
+ */
+
+/**
+ * debugfs_create_x8 - create a debugfs file that is used to read and write an unsigned 8-bit value
+ * @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.
+ * @value: a pointer to the variable that the file should read to and write
+ *         from.
+ */
+struct dentry *debugfs_create_x8(const char *name, umode_t mode,
+				 struct dentry *parent, u8 *value)
+{
+	return debugfs_create_mode_unsafe(name, mode, parent, value, &fops_x8,
+				   &fops_x8_ro, &fops_x8_wo);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_x8);
+
+/**
+ * debugfs_create_x16 - create a debugfs file that is used to read and write an unsigned 16-bit value
+ * @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.
+ * @value: a pointer to the variable that the file should read to and write
+ *         from.
+ */
+struct dentry *debugfs_create_x16(const char *name, umode_t mode,
+				 struct dentry *parent, u16 *value)
+{
+	return debugfs_create_mode_unsafe(name, mode, parent, value, &fops_x16,
+				   &fops_x16_ro, &fops_x16_wo);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_x16);
+
+/**
+ * debugfs_create_x32 - create a debugfs file that is used to read and write an unsigned 32-bit value
+ * @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.
+ * @value: a pointer to the variable that the file should read to and write
+ *         from.
+ */
+struct dentry *debugfs_create_x32(const char *name, umode_t mode,
+				 struct dentry *parent, u32 *value)
+{
+	return debugfs_create_mode_unsafe(name, mode, parent, value, &fops_x32,
+				   &fops_x32_ro, &fops_x32_wo);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_x32);
+
+/**
+ * debugfs_create_x64 - create a debugfs file that is used to read and write an unsigned 64-bit value
+ * @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.
+ * @value: a pointer to the variable that the file should read to and write
+ *         from.
+ */
+struct dentry *debugfs_create_x64(const char *name, umode_t mode,
+				 struct dentry *parent, u64 *value)
+{
+	return debugfs_create_mode_unsafe(name, mode, parent, value, &fops_x64,
+				   &fops_x64_ro, &fops_x64_wo);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_x64);
+
+
+static int debugfs_size_t_set(void *data, u64 val)
+{
+	*(size_t *)data = val;
+	return 0;
+}
+static int debugfs_size_t_get(void *data, u64 *val)
+{
+	*val = *(size_t *)data;
+	return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(fops_size_t, debugfs_size_t_get, debugfs_size_t_set,
+			"%llu\n"); /* %llu and %zu are more or less the same */
+DEFINE_DEBUGFS_ATTRIBUTE(fops_size_t_ro, debugfs_size_t_get, NULL, "%llu\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_size_t_wo, NULL, debugfs_size_t_set, "%llu\n");
+
+/**
+ * debugfs_create_size_t - create a debugfs file that is used to read and write an size_t value
+ * @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.
+ * @value: a pointer to the variable that the file should read to and write
+ *         from.
+ */
+struct dentry *debugfs_create_size_t(const char *name, umode_t mode,
+				     struct dentry *parent, size_t *value)
+{
+	return debugfs_create_mode_unsafe(name, mode, parent, value,
+					&fops_size_t, &fops_size_t_ro,
+					&fops_size_t_wo);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_size_t);
+
+static int debugfs_atomic_t_set(void *data, u64 val)
+{
+	atomic_set((atomic_t *)data, val);
+	return 0;
+}
+static int debugfs_atomic_t_get(void *data, u64 *val)
+{
+	*val = atomic_read((atomic_t *)data);
+	return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(fops_atomic_t, debugfs_atomic_t_get,
+			debugfs_atomic_t_set, "%lld\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_atomic_t_ro, debugfs_atomic_t_get, NULL,
+			"%lld\n");
+DEFINE_DEBUGFS_ATTRIBUTE(fops_atomic_t_wo, NULL, debugfs_atomic_t_set,
+			"%lld\n");
+
+/**
+ * debugfs_create_atomic_t - create a debugfs file that is used to read and
+ * write an atomic_t value
+ * @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.
+ * @value: a pointer to the variable that the file should read to and write
+ *         from.
+ */
+struct dentry *debugfs_create_atomic_t(const char *name, umode_t mode,
+				 struct dentry *parent, atomic_t *value)
+{
+	return debugfs_create_mode_unsafe(name, mode, parent, value,
+					&fops_atomic_t, &fops_atomic_t_ro,
+					&fops_atomic_t_wo);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_atomic_t);
+
+ssize_t debugfs_read_file_bool(struct file *file, char __user *user_buf,
+			       size_t count, loff_t *ppos)
+{
+	char buf[3];
+	bool val;
+	int r;
+	struct dentry *dentry = F_DENTRY(file);
+
+	r = debugfs_file_get(dentry);
+	if (unlikely(r))
+		return r;
+	val = *(bool *)file->private_data;
+	debugfs_file_put(dentry);
+
+	if (val)
+		buf[0] = 'Y';
+	else
+		buf[0] = 'N';
+	buf[1] = '\n';
+	buf[2] = 0x00;
+	return simple_read_from_buffer(user_buf, count, ppos, buf, 2);
+}
+EXPORT_SYMBOL_GPL(debugfs_read_file_bool);
+
+ssize_t debugfs_write_file_bool(struct file *file, const char __user *user_buf,
+				size_t count, loff_t *ppos)
+{
+	bool bv;
+	int r;
+	bool *val = file->private_data;
+	struct dentry *dentry = F_DENTRY(file);
+
+	r = kstrtobool_from_user(user_buf, count, &bv);
+	if (!r) {
+		r = debugfs_file_get(dentry);
+		if (unlikely(r))
+			return r;
+		*val = bv;
+		debugfs_file_put(dentry);
+	}
+
+	return count;
+}
+EXPORT_SYMBOL_GPL(debugfs_write_file_bool);
+
+static const struct file_operations fops_bool = {
+	.read =		debugfs_read_file_bool,
+	.write =	debugfs_write_file_bool,
+	.open =		simple_open,
+	.llseek =	default_llseek,
+};
+
+static const struct file_operations fops_bool_ro = {
+	.read =		debugfs_read_file_bool,
+	.open =		simple_open,
+	.llseek =	default_llseek,
+};
+
+static const struct file_operations fops_bool_wo = {
+	.write =	debugfs_write_file_bool,
+	.open =		simple_open,
+	.llseek =	default_llseek,
+};
+
+/**
+ * debugfs_create_bool - create a debugfs file that is used to read and write a boolean value
+ * @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.
+ * @value: a pointer to the variable that the file should read to and write
+ *         from.
+ *
+ * This function creates a file in debugfs with the given name that
+ * contains the value of the variable @value.  If the @mode variable is so
+ * set, it can be read from, and written to.
+ *
+ * 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, %NULL will be returned.
+ *
+ * If debugfs 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 *debugfs_create_bool(const char *name, umode_t mode,
+				   struct dentry *parent, bool *value)
+{
+	return debugfs_create_mode_unsafe(name, mode, parent, value, &fops_bool,
+				   &fops_bool_ro, &fops_bool_wo);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_bool);
+
+static ssize_t read_file_blob(struct file *file, char __user *user_buf,
+			      size_t count, loff_t *ppos)
+{
+	struct debugfs_blob_wrapper *blob = file->private_data;
+	struct dentry *dentry = F_DENTRY(file);
+	ssize_t r;
+
+	r = debugfs_file_get(dentry);
+	if (unlikely(r))
+		return r;
+	r = simple_read_from_buffer(user_buf, count, ppos, blob->data,
+				blob->size);
+	debugfs_file_put(dentry);
+	return r;
+}
+
+static const struct file_operations fops_blob = {
+	.read =		read_file_blob,
+	.open =		simple_open,
+	.llseek =	default_llseek,
+};
+
+/**
+ * debugfs_create_blob - create a debugfs file that is used to read a binary blob
+ * @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.
+ * @blob: a pointer to a struct debugfs_blob_wrapper which contains a pointer
+ *        to the blob data and the size of the data.
+ *
+ * This function creates a file in debugfs with the given name that exports
+ * @blob->data as a binary blob. If the @mode variable is so set it can be
+ * read from. Writing is not supported.
+ *
+ * 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, %NULL will be returned.
+ *
+ * If debugfs 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 *debugfs_create_blob(const char *name, umode_t mode,
+				   struct dentry *parent,
+				   struct debugfs_blob_wrapper *blob)
+{
+	return debugfs_create_file_unsafe(name, mode, parent, blob, &fops_blob);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_blob);
+
+struct array_data {
+	void *array;
+	u32 elements;
+};
+
+static size_t u32_format_array(char *buf, size_t bufsize,
+			       u32 *array, int array_size)
+{
+	size_t ret = 0;
+
+	while (--array_size >= 0) {
+		size_t len;
+		char term = array_size ? ' ' : '\n';
+
+		len = snprintf(buf, bufsize, "%u%c", *array++, term);
+		ret += len;
+
+		buf += len;
+		bufsize -= len;
+	}
+	return ret;
+}
+
+static int u32_array_open(struct inode *inode, struct file *file)
+{
+	struct array_data *data = inode->i_private;
+	int size, elements = data->elements;
+	char *buf;
+
+	/*
+	 * Max size:
+	 *  - 10 digits + ' '/'\n' = 11 bytes per number
+	 *  - terminating NUL character
+	 */
+	size = elements*11;
+	buf = kmalloc(size+1, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+	buf[size] = 0;
+
+	file->private_data = buf;
+	u32_format_array(buf, size, data->array, data->elements);
+
+	return nonseekable_open(inode, file);
+}
+
+static ssize_t u32_array_read(struct file *file, char __user *buf, size_t len,
+			      loff_t *ppos)
+{
+	size_t size = strlen(file->private_data);
+
+	return simple_read_from_buffer(buf, len, ppos,
+					file->private_data, size);
+}
+
+static int u32_array_release(struct inode *inode, struct file *file)
+{
+	kfree(file->private_data);
+
+	return 0;
+}
+
+static const struct file_operations u32_array_fops = {
+	.owner	 = THIS_MODULE,
+	.open	 = u32_array_open,
+	.release = u32_array_release,
+	.read	 = u32_array_read,
+	.llseek  = no_llseek,
+};
+
+/**
+ * debugfs_create_u32_array - create a debugfs file that is used to read u32
+ * array.
+ * @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.
+ * @array: u32 array that provides data.
+ * @elements: total number of elements in the array.
+ *
+ * This function creates a file in debugfs with the given name that exports
+ * @array as data. If the @mode variable is so set it can be read from.
+ * Writing is not supported. Seek within the file is also not supported.
+ * Once array is created its size can not be changed.
+ *
+ * The function returns a pointer to dentry on success. If debugfs is not
+ * enabled in the kernel, the value -%ENODEV will be returned.
+ */
+struct dentry *debugfs_create_u32_array(const char *name, umode_t mode,
+					    struct dentry *parent,
+					    u32 *array, u32 elements)
+{
+	struct array_data *data = kmalloc(sizeof(*data), GFP_KERNEL);
+
+	if (data == NULL)
+		return NULL;
+
+	data->array = array;
+	data->elements = elements;
+
+	return debugfs_create_file_unsafe(name, mode, parent, data,
+					&u32_array_fops);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_u32_array);
+
+#ifdef CONFIG_HAS_IOMEM
+
+/*
+ * The regset32 stuff is used to print 32-bit registers using the
+ * seq_file utilities. We offer printing a register set in an already-opened
+ * sequential file or create a debugfs file that only prints a regset32.
+ */
+
+/**
+ * debugfs_print_regs32 - use seq_print to describe a set of registers
+ * @s: the seq_file structure being used to generate output
+ * @regs: an array if struct debugfs_reg32 structures
+ * @nregs: the length of the above array
+ * @base: the base address to be used in reading the registers
+ * @prefix: a string to be prefixed to every output line
+ *
+ * This function outputs a text block describing the current values of
+ * some 32-bit hardware registers. It is meant to be used within debugfs
+ * files based on seq_file that need to show registers, intermixed with other
+ * information. The prefix argument may be used to specify a leading string,
+ * because some peripherals have several blocks of identical registers,
+ * for example configuration of dma channels
+ */
+void debugfs_print_regs32(struct seq_file *s, const struct debugfs_reg32 *regs,
+			  int nregs, void __iomem *base, char *prefix)
+{
+	int i;
+
+	for (i = 0; i < nregs; i++, regs++) {
+		if (prefix)
+			seq_printf(s, "%s", prefix);
+		seq_printf(s, "%s = 0x%08x\n", regs->name,
+			   readl(base + regs->offset));
+		if (seq_has_overflowed(s))
+			break;
+	}
+}
+EXPORT_SYMBOL_GPL(debugfs_print_regs32);
+
+static int debugfs_show_regset32(struct seq_file *s, void *data)
+{
+	struct debugfs_regset32 *regset = s->private;
+
+	debugfs_print_regs32(s, regset->regs, regset->nregs, regset->base, "");
+	return 0;
+}
+
+static int debugfs_open_regset32(struct inode *inode, struct file *file)
+{
+	return single_open(file, debugfs_show_regset32, inode->i_private);
+}
+
+static const struct file_operations fops_regset32 = {
+	.open =		debugfs_open_regset32,
+	.read =		seq_read,
+	.llseek =	seq_lseek,
+	.release =	single_release,
+};
+
+/**
+ * debugfs_create_regset32 - create a debugfs file that returns register values
+ * @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.
+ * @regset: a pointer to a struct debugfs_regset32, which contains a pointer
+ *          to an array of register definitions, the array size and the base
+ *          address where the register bank is to be found.
+ *
+ * This function creates a file in debugfs with the given name that reports
+ * the names and values of a set of 32-bit registers. If the @mode variable
+ * is so set it can be read from. Writing is not supported.
+ *
+ * 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, %NULL will be returned.
+ *
+ * If debugfs 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 *debugfs_create_regset32(const char *name, umode_t mode,
+				       struct dentry *parent,
+				       struct debugfs_regset32 *regset)
+{
+	return debugfs_create_file(name, mode, parent, regset, &fops_regset32);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_regset32);
+
+#endif /* CONFIG_HAS_IOMEM */
+
+struct debugfs_devm_entry {
+	int (*read)(struct seq_file *seq, void *data);
+	struct device *dev;
+};
+
+static int debugfs_devm_entry_open(struct inode *inode, struct file *f)
+{
+	struct debugfs_devm_entry *entry = inode->i_private;
+
+	return single_open(f, entry->read, entry->dev);
+}
+
+static const struct file_operations debugfs_devm_entry_ops = {
+	.owner = THIS_MODULE,
+	.open = debugfs_devm_entry_open,
+	.release = single_release,
+	.read = seq_read,
+	.llseek = seq_lseek
+};
+
+/**
+ * debugfs_create_devm_seqfile - create a debugfs file that is bound to device.
+ *
+ * @dev: device related to this debugfs file.
+ * @name: name of the debugfs file.
+ * @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.
+ * @read_fn: function pointer called to print the seq_file content.
+ */
+struct dentry *debugfs_create_devm_seqfile(struct device *dev, const char *name,
+					   struct dentry *parent,
+					   int (*read_fn)(struct seq_file *s,
+							  void *data))
+{
+	struct debugfs_devm_entry *entry;
+
+	if (IS_ERR(parent))
+		return ERR_PTR(-ENOENT);
+
+	entry = devm_kzalloc(dev, sizeof(*entry), GFP_KERNEL);
+	if (!entry)
+		return ERR_PTR(-ENOMEM);
+
+	entry->read = read_fn;
+	entry->dev = dev;
+
+	return debugfs_create_file(name, S_IRUGO, parent, entry,
+				   &debugfs_devm_entry_ops);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_devm_seqfile);
+
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
new file mode 100644
index 000000000..e5126fad5
--- /dev/null
+++ b/fs/debugfs/inode.c
@@ -0,0 +1,865 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  inode.c - part of debugfs, a tiny little debug file system
+ *
+ *  Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
+ *  Copyright (C) 2004 IBM Inc.
+ *
+ *  debugfs is for people to use instead of /proc or /sys.
+ *  See ./Documentation/core-api/kernel-api.rst for more details.
+ */
+
+#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 "internal.h"
+
+#define DEBUGFS_DEFAULT_MODE	0700
+
+static struct vfsmount *debugfs_mount;
+static int debugfs_mount_count;
+static bool debugfs_registered;
+
+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;
+};
+
+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->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
+		 */
+		}
+	}
+
+	return 0;
+}
+
+static int debugfs_apply_options(struct super_block *sb)
+{
+	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;
+
+	inode->i_mode &= ~S_IALLUGO;
+	inode->i_mode |= opts->mode;
+
+	inode->i_uid = opts->uid;
+	inode->i_gid = opts->gid;
+
+	return 0;
+}
+
+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(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_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	if (S_ISLNK(inode->i_mode))
+		kfree(inode->i_link);
+	free_inode_nonrcu(inode);
+}
+
+static void debugfs_destroy_inode(struct inode *inode)
+{
+	call_rcu(&inode->i_rcu, debugfs_i_callback);
+}
+
+static const struct super_operations debugfs_super_operations = {
+	.statfs		= simple_statfs,
+	.remount_fs	= debugfs_remount,
+	.show_options	= debugfs_show_options,
+	.destroy_inode	= debugfs_destroy_inode,
+};
+
+static void debugfs_release_dentry(struct dentry *dentry)
+{
+	void *fsd = dentry->d_fsdata;
+
+	if (!((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT))
+		kfree(dentry->d_fsdata);
+}
+
+static struct vfsmount *debugfs_automount(struct path *path)
+{
+	debugfs_automount_t f;
+	f = (debugfs_automount_t)path->dentry->d_fsdata;
+	return f(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)
+{
+	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 (IS_ERR(parent))
+		return NULL;
+
+	if (!parent)
+		parent = debugfs_mount->mnt_root;
+
+	dentry = lookup_one_len_unlocked(name, parent, strlen(name));
+	if (IS_ERR(dentry))
+		return NULL;
+	if (!d_really_is_positive(dentry)) {
+		dput(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;
+
+	pr_debug("debugfs: 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)
+		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));
+	dentry = lookup_one_len(name, parent, strlen(name));
+	if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
+		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 NULL;
+}
+
+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 NULL;
+
+	inode = debugfs_get_inode(dentry->d_sb);
+	if (unlikely(!inode))
+		return failed_creating(dentry);
+
+	inode->i_mode = mode;
+	inode->i_private = data;
+
+	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, %NULL will be returned.
+ *
+ * If debugfs is not enabled in the kernel, the value -%ENODEV will be
+ * returned.
+ */
+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_use_file_start()
+ * and debugfs_use_file_finish(). ->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.)
+ *
+ * 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, %NULL will be returned.
+ *
+ * If debugfs is not enabled in the kernel, the value -%ENODEV will be
+ * returned.
+ */
+struct dentry *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 (de)
+		d_inode(de)->i_size = file_size;
+	return de;
+}
+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, %NULL will be returned.
+ *
+ * If debugfs is not enabled in the kernel, the value -%ENODEV will be
+ * returned.
+ */
+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 NULL;
+
+	inode = debugfs_get_inode(dentry->d_sb);
+	if (unlikely(!inode))
+		return failed_creating(dentry);
+
+	inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
+	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);
+	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 inode *inode;
+
+	if (IS_ERR(dentry))
+		return NULL;
+
+	inode = debugfs_get_inode(dentry->d_sb);
+	if (unlikely(!inode))
+		return failed_creating(dentry);
+
+	make_empty_dir_inode(inode);
+	inode->i_flags |= S_AUTOMOUNT;
+	inode->i_private = data;
+	dentry->d_fsdata = (void *)f;
+	/* 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, %NULL 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 NULL;
+
+	dentry = start_creating(name, parent);
+	if (IS_ERR(dentry)) {
+		kfree(link);
+		return NULL;
+	}
+
+	inode = debugfs_get_inode(dentry->d_sb);
+	if (unlikely(!inode)) {
+		kfree(link);
+		return failed_creating(dentry);
+	}
+	inode->i_mode = S_IFLNK | S_IRWXUGO;
+	inode->i_op = &simple_symlink_inode_operations;
+	inode->i_link = link;
+	d_instantiate(dentry, inode);
+	return end_creating(dentry);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_symlink);
+
+static void __debugfs_remove_file(struct dentry *dentry, struct dentry *parent)
+{
+	struct debugfs_fsdata *fsd;
+
+	simple_unlink(d_inode(parent), dentry);
+	d_delete(dentry);
+
+	/*
+	 * 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 int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
+{
+	int ret = 0;
+
+	if (simple_positive(dentry)) {
+		dget(dentry);
+		if (!d_is_reg(dentry)) {
+			if (d_is_dir(dentry))
+				ret = simple_rmdir(d_inode(parent), dentry);
+			else
+				simple_unlink(d_inode(parent), dentry);
+			if (!ret)
+				d_delete(dentry);
+		} else {
+			__debugfs_remove_file(dentry, parent);
+		}
+		dput(dentry);
+	}
+	return ret;
+}
+
+/**
+ * debugfs_remove - removes a file or directory from the debugfs filesystem
+ * @dentry: a pointer to a the dentry of the file or directory to be
+ *          removed.  If this parameter is NULL or an error value, nothing
+ *          will be done.
+ *
+ * This function removes a file or directory 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)
+{
+	struct dentry *parent;
+	int ret;
+
+	if (IS_ERR_OR_NULL(dentry))
+		return;
+
+	parent = dentry->d_parent;
+	inode_lock(d_inode(parent));
+	ret = __debugfs_remove(dentry, parent);
+	inode_unlock(d_inode(parent));
+	if (!ret)
+		simple_release_fs(&debugfs_mount, &debugfs_mount_count);
+}
+EXPORT_SYMBOL_GPL(debugfs_remove);
+
+/**
+ * debugfs_remove_recursive - 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_recursive(struct dentry *dentry)
+{
+	struct dentry *child, *parent;
+
+	if (IS_ERR_OR_NULL(dentry))
+		return;
+
+	parent = dentry;
+ down:
+	inode_lock(d_inode(parent));
+ loop:
+	/*
+	 * The parent->d_subdirs is protected by the d_lock. Outside that
+	 * lock, the child can be unlinked and set to be freed which can
+	 * use the d_u.d_child as the rcu head and corrupt this list.
+	 */
+	spin_lock(&parent->d_lock);
+	list_for_each_entry(child, &parent->d_subdirs, d_child) {
+		if (!simple_positive(child))
+			continue;
+
+		/* perhaps simple_empty(child) makes more sense */
+		if (!list_empty(&child->d_subdirs)) {
+			spin_unlock(&parent->d_lock);
+			inode_unlock(d_inode(parent));
+			parent = child;
+			goto down;
+		}
+
+		spin_unlock(&parent->d_lock);
+
+		if (!__debugfs_remove(child, parent))
+			simple_release_fs(&debugfs_mount, &debugfs_mount_count);
+
+		/*
+		 * The parent->d_lock protects agaist child from unlinking
+		 * from d_subdirs. When releasing the parent->d_lock we can
+		 * no longer trust that the next pointer is valid.
+		 * Restart the loop. We'll skip this one with the
+		 * simple_positive() check.
+		 */
+		goto loop;
+	}
+	spin_unlock(&parent->d_lock);
+
+	inode_unlock(d_inode(parent));
+	child = parent;
+	parent = parent->d_parent;
+	inode_lock(d_inode(parent));
+
+	if (child != dentry)
+		/* go up */
+		goto loop;
+
+	if (!__debugfs_remove(child, parent))
+		simple_release_fs(&debugfs_mount, &debugfs_mount_count);
+	inode_unlock(d_inode(parent));
+}
+EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
+
+/**
+ * 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(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);
+	return NULL;
+}
+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_init(void)
+{
+	int retval;
+
+	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);
+
diff --git a/fs/debugfs/internal.h b/fs/debugfs/internal.h
new file mode 100644
index 000000000..f0d73d86c
--- /dev/null
+++ b/fs/debugfs/internal.h
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  internal.h - declarations internal to debugfs
+ *
+ *  Copyright (C) 2016 Nicolai Stange <nicstange@gmail.com>
+ */
+
+#ifndef _DEBUGFS_INTERNAL_H_
+#define _DEBUGFS_INTERNAL_H_
+
+struct file_operations;
+
+/* declared over in file.c */
+extern const struct file_operations debugfs_noop_file_operations;
+extern const struct file_operations debugfs_open_proxy_file_operations;
+extern const struct file_operations debugfs_full_proxy_file_operations;
+
+struct debugfs_fsdata {
+	const struct file_operations *real_fops;
+	refcount_t active_users;
+	struct completion active_users_drained;
+};
+
+/*
+ * A dentry's ->d_fsdata either points to the real fops or to a
+ * dynamically allocated debugfs_fsdata instance.
+ * In order to distinguish between these two cases, a real fops
+ * pointer gets its lowest bit set.
+ */
+#define DEBUGFS_FSDATA_IS_REAL_FOPS_BIT BIT(0)
+
+#endif /* _DEBUGFS_INTERNAL_H_ */