Fixed MTP to work with TWRP

fs/sysfs/Kconfig

@@ -0,0 +1,24 @@
+config SYSFS
+	bool "sysfs file system support" if EXPERT
+	default y
+	select KERNFS
+	help
+	The sysfs filesystem is a virtual filesystem that the kernel uses to
+	export internal kernel objects, their attributes, and their
+	relationships to one another.
+
+	Users can use sysfs to ascertain useful information about the running
+	kernel, such as the devices the kernel has discovered on each bus and
+	which driver each is bound to. sysfs can also be used to tune devices
+	and other kernel subsystems.
+
+	Some system agents rely on the information in sysfs to operate.
+	/sbin/hotplug uses device and object attributes in sysfs to assist in
+	delegating policy decisions, like persistently naming devices.
+
+	sysfs is currently used by the block subsystem to mount the root
+	partition.  If sysfs is disabled you must specify the boot device on
+	the kernel boot command line via its major and minor numbers.  For
+	example, "root=03:01" for /dev/hda1.
+
+	Designers of embedded systems may wish to say N here to conserve space.

fs/sysfs/Makefile

@@ -0,0 +1,5 @@
+#
+# Makefile for the sysfs virtual filesystem
+#
+
+obj-y		:= file.o dir.o symlink.o mount.o group.o

fs/sysfs/dir.c

@@ -0,0 +1,123 @@
+/*
+ * fs/sysfs/dir.c - sysfs core and dir operation implementation
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
+ *
+ * This file is released under the GPLv2.
+ *
+ * Please see Documentation/filesystems/sysfs.txt for more information.
+ */
+
+#undef DEBUG
+
+#include <linux/fs.h>
+#include <linux/kobject.h>
+#include <linux/slab.h>
+#include "sysfs.h"
+
+DEFINE_SPINLOCK(sysfs_symlink_target_lock);
+
+void sysfs_warn_dup(struct kernfs_node *parent, const char *name)
+{
+	char *buf, *path = NULL;
+
+	buf = kzalloc(PATH_MAX, GFP_KERNEL);
+	if (buf)
+		path = kernfs_path(parent, buf, PATH_MAX);
+
+	WARN(1, KERN_WARNING "sysfs: cannot create duplicate filename '%s/%s'\n",
+	     path, name);
+
+	kfree(buf);
+}
+
+/**
+ * sysfs_create_dir_ns - create a directory for an object with a namespace tag
+ * @kobj: object we're creating directory for
+ * @ns: the namespace tag to use
+ */
+int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
+{
+	struct kernfs_node *parent, *kn;
+
+	BUG_ON(!kobj);
+
+	if (kobj->parent)
+		parent = kobj->parent->sd;
+	else
+		parent = sysfs_root_kn;
+
+	if (!parent)
+		return -ENOENT;
+
+	kn = kernfs_create_dir_ns(parent, kobject_name(kobj),
+				  S_IRWXU | S_IRUGO | S_IXUGO, kobj, ns);
+	if (IS_ERR(kn)) {
+		if (PTR_ERR(kn) == -EEXIST)
+			sysfs_warn_dup(parent, kobject_name(kobj));
+		return PTR_ERR(kn);
+	}
+
+	kobj->sd = kn;
+	return 0;
+}
+
+/**
+ *	sysfs_remove_dir - remove an object's directory.
+ *	@kobj:	object.
+ *
+ *	The only thing special about this is that we remove any files in
+ *	the directory before we remove the directory, and we've inlined
+ *	what used to be sysfs_rmdir() below, instead of calling separately.
+ */
+void sysfs_remove_dir(struct kobject *kobj)
+{
+	struct kernfs_node *kn = kobj->sd;
+
+	/*
+	 * In general, kboject owner is responsible for ensuring removal
+	 * doesn't race with other operations and sysfs doesn't provide any
+	 * protection; however, when @kobj is used as a symlink target, the
+	 * symlinking entity usually doesn't own @kobj and thus has no
+	 * control over removal.  @kobj->sd may be removed anytime
+	 * and symlink code may end up dereferencing an already freed node.
+	 *
+	 * sysfs_symlink_target_lock synchronizes @kobj->sd
+	 * disassociation against symlink operations so that symlink code
+	 * can safely dereference @kobj->sd.
+	 */
+	spin_lock(&sysfs_symlink_target_lock);
+	kobj->sd = NULL;
+	spin_unlock(&sysfs_symlink_target_lock);
+
+	if (kn) {
+		WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
+		kernfs_remove(kn);
+	}
+}
+
+int sysfs_rename_dir_ns(struct kobject *kobj, const char *new_name,
+			const void *new_ns)
+{
+	struct kernfs_node *parent;
+	int ret;
+
+	parent = kernfs_get_parent(kobj->sd);
+	ret = kernfs_rename_ns(kobj->sd, parent, new_name, new_ns);
+	kernfs_put(parent);
+	return ret;
+}
+
+int sysfs_move_dir_ns(struct kobject *kobj, struct kobject *new_parent_kobj,
+		      const void *new_ns)
+{
+	struct kernfs_node *kn = kobj->sd;
+	struct kernfs_node *new_parent;
+
+	new_parent = new_parent_kobj && new_parent_kobj->sd ?
+		new_parent_kobj->sd : sysfs_root_kn;
+
+	return kernfs_rename_ns(kn, new_parent, kn->name, new_ns);
+}

fs/sysfs/file.c

@@ -0,0 +1,456 @@
+/*
+ * fs/sysfs/file.c - sysfs regular (text) file implementation
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
+ *
+ * This file is released under the GPLv2.
+ *
+ * Please see Documentation/filesystems/sysfs.txt for more information.
+ */
+
+#include <linux/module.h>
+#include <linux/kobject.h>
+#include <linux/kallsyms.h>
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/seq_file.h>
+
+#include "sysfs.h"
+#include "../kernfs/kernfs-internal.h"
+
+/*
+ * Determine ktype->sysfs_ops for the given kernfs_node.  This function
+ * must be called while holding an active reference.
+ */
+static const struct sysfs_ops *sysfs_file_ops(struct kernfs_node *kn)
+{
+	struct kobject *kobj = kn->parent->priv;
+
+	if (kn->flags & KERNFS_LOCKDEP)
+		lockdep_assert_held(kn);
+	return kobj->ktype ? kobj->ktype->sysfs_ops : NULL;
+}
+
+/*
+ * Reads on sysfs are handled through seq_file, which takes care of hairy
+ * details like buffering and seeking.  The following function pipes
+ * sysfs_ops->show() result through seq_file.
+ */
+static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
+{
+	struct kernfs_open_file *of = sf->private;
+	struct kobject *kobj = of->kn->parent->priv;
+	const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
+	ssize_t count;
+	char *buf;
+
+	/* acquire buffer and ensure that it's >= PAGE_SIZE and clear */
+	count = seq_get_buf(sf, &buf);
+	if (count < PAGE_SIZE) {
+		seq_commit(sf, -1);
+		return 0;
+	}
+	memset(buf, 0, PAGE_SIZE);
+
+	/*
+	 * Invoke show().  Control may reach here via seq file lseek even
+	 * if @ops->show() isn't implemented.
+	 */
+	if (ops->show) {
+		count = ops->show(kobj, of->kn->priv, buf);
+		if (count < 0)
+			return count;
+	}
+
+	/*
+	 * The code works fine with PAGE_SIZE return but it's likely to
+	 * indicate truncated result or overflow in normal use cases.
+	 */
+	if (count >= (ssize_t)PAGE_SIZE) {
+		print_symbol("fill_read_buffer: %s returned bad count\n",
+			(unsigned long)ops->show);
+		/* Try to struggle along */
+		count = PAGE_SIZE - 1;
+	}
+	seq_commit(sf, count);
+	return 0;
+}
+
+static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf,
+				 size_t count, loff_t pos)
+{
+	struct bin_attribute *battr = of->kn->priv;
+	struct kobject *kobj = of->kn->parent->priv;
+	loff_t size = file_inode(of->file)->i_size;
+
+	if (!count)
+		return 0;
+
+	if (size) {
+		if (pos > size)
+			return 0;
+		if (pos + count > size)
+			count = size - pos;
+	}
+
+	if (!battr->read)
+		return -EIO;
+
+	return battr->read(of->file, kobj, battr, buf, pos, count);
+}
+
+/* kernfs write callback for regular sysfs files */
+static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
+			      size_t count, loff_t pos)
+{
+	const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
+	struct kobject *kobj = of->kn->parent->priv;
+
+	if (!count)
+		return 0;
+
+	return ops->store(kobj, of->kn->priv, buf, count);
+}
+
+/* kernfs write callback for bin sysfs files */
+static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
+				  size_t count, loff_t pos)
+{
+	struct bin_attribute *battr = of->kn->priv;
+	struct kobject *kobj = of->kn->parent->priv;
+	loff_t size = file_inode(of->file)->i_size;
+
+	if (size) {
+		if (size <= pos)
+			return 0;
+		count = min_t(ssize_t, count, size - pos);
+	}
+	if (!count)
+		return 0;
+
+	if (!battr->write)
+		return -EIO;
+
+	return battr->write(of->file, kobj, battr, buf, pos, count);
+}
+
+static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
+			     struct vm_area_struct *vma)
+{
+	struct bin_attribute *battr = of->kn->priv;
+	struct kobject *kobj = of->kn->parent->priv;
+
+	return battr->mmap(of->file, kobj, battr, vma);
+}
+
+void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
+{
+	struct kernfs_node *kn = kobj->sd, *tmp;
+
+	if (kn && dir)
+		kn = kernfs_find_and_get(kn, dir);
+	else
+		kernfs_get(kn);
+
+	if (kn && attr) {
+		tmp = kernfs_find_and_get(kn, attr);
+		kernfs_put(kn);
+		kn = tmp;
+	}
+
+	if (kn) {
+		kernfs_notify(kn);
+		kernfs_put(kn);
+	}
+}
+EXPORT_SYMBOL_GPL(sysfs_notify);
+
+static const struct kernfs_ops sysfs_file_kfops_empty = {
+};
+
+static const struct kernfs_ops sysfs_file_kfops_ro = {
+	.seq_show	= sysfs_kf_seq_show,
+};
+
+static const struct kernfs_ops sysfs_file_kfops_wo = {
+	.write		= sysfs_kf_write,
+};
+
+static const struct kernfs_ops sysfs_file_kfops_rw = {
+	.seq_show	= sysfs_kf_seq_show,
+	.write		= sysfs_kf_write,
+};
+
+static const struct kernfs_ops sysfs_bin_kfops_ro = {
+	.read		= sysfs_kf_bin_read,
+};
+
+static const struct kernfs_ops sysfs_bin_kfops_wo = {
+	.write		= sysfs_kf_bin_write,
+};
+
+static const struct kernfs_ops sysfs_bin_kfops_rw = {
+	.read		= sysfs_kf_bin_read,
+	.write		= sysfs_kf_bin_write,
+};
+
+static const struct kernfs_ops sysfs_bin_kfops_mmap = {
+	.read		= sysfs_kf_bin_read,
+	.write		= sysfs_kf_bin_write,
+	.mmap		= sysfs_kf_bin_mmap,
+};
+
+int sysfs_add_file_mode_ns(struct kernfs_node *parent,
+			   const struct attribute *attr, bool is_bin,
+			   umode_t mode, const void *ns)
+{
+	struct lock_class_key *key = NULL;
+	const struct kernfs_ops *ops;
+	struct kernfs_node *kn;
+	loff_t size;
+
+	if (!is_bin) {
+		struct kobject *kobj = parent->priv;
+		const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
+
+		/* every kobject with an attribute needs a ktype assigned */
+		if (WARN(!sysfs_ops, KERN_ERR
+			 "missing sysfs attribute operations for kobject: %s\n",
+			 kobject_name(kobj)))
+			return -EINVAL;
+
+		if (sysfs_ops->show && sysfs_ops->store)
+			ops = &sysfs_file_kfops_rw;
+		else if (sysfs_ops->show)
+			ops = &sysfs_file_kfops_ro;
+		else if (sysfs_ops->store)
+			ops = &sysfs_file_kfops_wo;
+		else
+			ops = &sysfs_file_kfops_empty;
+
+		size = PAGE_SIZE;
+	} else {
+		struct bin_attribute *battr = (void *)attr;
+
+		if (battr->mmap)
+			ops = &sysfs_bin_kfops_mmap;
+		else if (battr->read && battr->write)
+			ops = &sysfs_bin_kfops_rw;
+		else if (battr->read)
+			ops = &sysfs_bin_kfops_ro;
+		else if (battr->write)
+			ops = &sysfs_bin_kfops_wo;
+		else
+			ops = &sysfs_file_kfops_empty;
+
+		size = battr->size;
+	}
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	if (!attr->ignore_lockdep)
+		key = attr->key ?: (struct lock_class_key *)&attr->skey;
+#endif
+	kn = __kernfs_create_file(parent, attr->name, mode, size, ops,
+				  (void *)attr, ns, true, key);
+	if (IS_ERR(kn)) {
+		if (PTR_ERR(kn) == -EEXIST)
+			sysfs_warn_dup(parent, attr->name);
+		return PTR_ERR(kn);
+	}
+	return 0;
+}
+
+int sysfs_add_file(struct kernfs_node *parent, const struct attribute *attr,
+		   bool is_bin)
+{
+	return sysfs_add_file_mode_ns(parent, attr, is_bin, attr->mode, NULL);
+}
+
+/**
+ * sysfs_create_file_ns - create an attribute file for an object with custom ns
+ * @kobj: object we're creating for
+ * @attr: attribute descriptor
+ * @ns: namespace the new file should belong to
+ */
+int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
+			 const void *ns)
+{
+	BUG_ON(!kobj || !kobj->sd || !attr);
+
+	return sysfs_add_file_mode_ns(kobj->sd, attr, false, attr->mode, ns);
+
+}
+EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
+
+int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
+{
+	int err = 0;
+	int i;
+
+	for (i = 0; ptr[i] && !err; i++)
+		err = sysfs_create_file(kobj, ptr[i]);
+	if (err)
+		while (--i >= 0)
+			sysfs_remove_file(kobj, ptr[i]);
+	return err;
+}
+EXPORT_SYMBOL_GPL(sysfs_create_files);
+
+/**
+ * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
+ * @kobj: object we're acting for.
+ * @attr: attribute descriptor.
+ * @group: group name.
+ */
+int sysfs_add_file_to_group(struct kobject *kobj,
+		const struct attribute *attr, const char *group)
+{
+	struct kernfs_node *parent;
+	int error;
+
+	if (group) {
+		parent = kernfs_find_and_get(kobj->sd, group);
+	} else {
+		parent = kobj->sd;
+		kernfs_get(parent);
+	}
+
+	if (!parent)
+		return -ENOENT;
+
+	error = sysfs_add_file(parent, attr, false);
+	kernfs_put(parent);
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
+
+/**
+ * sysfs_chmod_file - update the modified mode value on an object attribute.
+ * @kobj: object we're acting for.
+ * @attr: attribute descriptor.
+ * @mode: file permissions.
+ *
+ */
+int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
+		     umode_t mode)
+{
+	struct kernfs_node *kn;
+	struct iattr newattrs;
+	int rc;
+
+	kn = kernfs_find_and_get(kobj->sd, attr->name);
+	if (!kn)
+		return -ENOENT;
+
+	newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
+	newattrs.ia_valid = ATTR_MODE;
+
+	rc = kernfs_setattr(kn, &newattrs);
+
+	kernfs_put(kn);
+	return rc;
+}
+EXPORT_SYMBOL_GPL(sysfs_chmod_file);
+
+/**
+ * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
+ * @kobj: object we're acting for
+ * @attr: attribute descriptor
+ * @ns: namespace tag of the file to remove
+ *
+ * Hash the attribute name and namespace tag and kill the victim.
+ */
+void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
+			  const void *ns)
+{
+	struct kernfs_node *parent = kobj->sd;
+
+	kernfs_remove_by_name_ns(parent, attr->name, ns);
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
+
+/**
+ * sysfs_remove_file_self - remove an object attribute from its own method
+ * @kobj: object we're acting for
+ * @attr: attribute descriptor
+ *
+ * See kernfs_remove_self() for details.
+ */
+bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
+{
+	struct kernfs_node *parent = kobj->sd;
+	struct kernfs_node *kn;
+	bool ret;
+
+	kn = kernfs_find_and_get(parent, attr->name);
+	if (WARN_ON_ONCE(!kn))
+		return false;
+
+	ret = kernfs_remove_self(kn);
+
+	kernfs_put(kn);
+	return ret;
+}
+
+void sysfs_remove_files(struct kobject *kobj, const struct attribute **ptr)
+{
+	int i;
+	for (i = 0; ptr[i]; i++)
+		sysfs_remove_file(kobj, ptr[i]);
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_files);
+
+/**
+ * sysfs_remove_file_from_group - remove an attribute file from a group.
+ * @kobj: object we're acting for.
+ * @attr: attribute descriptor.
+ * @group: group name.
+ */
+void sysfs_remove_file_from_group(struct kobject *kobj,
+		const struct attribute *attr, const char *group)
+{
+	struct kernfs_node *parent;
+
+	if (group) {
+		parent = kernfs_find_and_get(kobj->sd, group);
+	} else {
+		parent = kobj->sd;
+		kernfs_get(parent);
+	}
+
+	if (parent) {
+		kernfs_remove_by_name(parent, attr->name);
+		kernfs_put(parent);
+	}
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
+
+/**
+ *	sysfs_create_bin_file - create binary file for object.
+ *	@kobj:	object.
+ *	@attr:	attribute descriptor.
+ */
+int sysfs_create_bin_file(struct kobject *kobj,
+			  const struct bin_attribute *attr)
+{
+	BUG_ON(!kobj || !kobj->sd || !attr);
+
+	return sysfs_add_file(kobj->sd, &attr->attr, true);
+}
+EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
+
+/**
+ *	sysfs_remove_bin_file - remove binary file for object.
+ *	@kobj:	object.
+ *	@attr:	attribute descriptor.
+ */
+void sysfs_remove_bin_file(struct kobject *kobj,
+			   const struct bin_attribute *attr)
+{
+	kernfs_remove_by_name(kobj->sd, attr->attr.name);
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);

fs/sysfs/group.c

@@ -0,0 +1,349 @@
+/*
+ * fs/sysfs/group.c - Operations for adding/removing multiple files at once.
+ *
+ * Copyright (c) 2003 Patrick Mochel
+ * Copyright (c) 2003 Open Source Development Lab
+ * Copyright (c) 2013 Greg Kroah-Hartman
+ * Copyright (c) 2013 The Linux Foundation
+ *
+ * This file is released undert the GPL v2.
+ *
+ */
+
+#include <linux/kobject.h>
+#include <linux/module.h>
+#include <linux/dcache.h>
+#include <linux/namei.h>
+#include <linux/err.h>
+#include "sysfs.h"
+
+
+static void remove_files(struct kernfs_node *parent,
+			 const struct attribute_group *grp)
+{
+	struct attribute *const *attr;
+	struct bin_attribute *const *bin_attr;
+
+	if (grp->attrs)
+		for (attr = grp->attrs; *attr; attr++)
+			kernfs_remove_by_name(parent, (*attr)->name);
+	if (grp->bin_attrs)
+		for (bin_attr = grp->bin_attrs; *bin_attr; bin_attr++)
+			kernfs_remove_by_name(parent, (*bin_attr)->attr.name);
+}
+
+static int create_files(struct kernfs_node *parent, struct kobject *kobj,
+			const struct attribute_group *grp, int update)
+{
+	struct attribute *const *attr;
+	struct bin_attribute *const *bin_attr;
+	int error = 0, i;
+
+	if (grp->attrs) {
+		for (i = 0, attr = grp->attrs; *attr && !error; i++, attr++) {
+			umode_t mode = 0;
+
+			/*
+			 * In update mode, we're changing the permissions or
+			 * visibility.  Do this by first removing then
+			 * re-adding (if required) the file.
+			 */
+			if (update)
+				kernfs_remove_by_name(parent, (*attr)->name);
+			if (grp->is_visible) {
+				mode = grp->is_visible(kobj, *attr, i);
+				if (!mode)
+					continue;
+			}
+			error = sysfs_add_file_mode_ns(parent, *attr, false,
+						       (*attr)->mode | mode,
+						       NULL);
+			if (unlikely(error))
+				break;
+		}
+		if (error) {
+			remove_files(parent, grp);
+			goto exit;
+		}
+	}
+
+	if (grp->bin_attrs) {
+		for (bin_attr = grp->bin_attrs; *bin_attr; bin_attr++) {
+			if (update)
+				kernfs_remove_by_name(parent,
+						(*bin_attr)->attr.name);
+			error = sysfs_add_file_mode_ns(parent,
+					&(*bin_attr)->attr, true,
+					(*bin_attr)->attr.mode, NULL);
+			if (error)
+				break;
+		}
+		if (error)
+			remove_files(parent, grp);
+	}
+exit:
+	return error;
+}
+
+
+static int internal_create_group(struct kobject *kobj, int update,
+				 const struct attribute_group *grp)
+{
+	struct kernfs_node *kn;
+	int error;
+
+	BUG_ON(!kobj || (!update && !kobj->sd));
+
+	/* Updates may happen before the object has been instantiated */
+	if (unlikely(update && !kobj->sd))
+		return -EINVAL;
+	if (!grp->attrs && !grp->bin_attrs) {
+		WARN(1, "sysfs: (bin_)attrs not set by subsystem for group: %s/%s\n",
+			kobj->name, grp->name ? "" : grp->name);
+		return -EINVAL;
+	}
+	if (grp->name) {
+		kn = kernfs_create_dir(kobj->sd, grp->name,
+				       S_IRWXU | S_IRUGO | S_IXUGO, kobj);
+		if (IS_ERR(kn)) {
+			if (PTR_ERR(kn) == -EEXIST)
+				sysfs_warn_dup(kobj->sd, grp->name);
+			return PTR_ERR(kn);
+		}
+	} else
+		kn = kobj->sd;
+	kernfs_get(kn);
+	error = create_files(kn, kobj, grp, update);
+	if (error) {
+		if (grp->name)
+			kernfs_remove(kn);
+	}
+	kernfs_put(kn);
+	return error;
+}
+
+/**
+ * sysfs_create_group - given a directory kobject, create an attribute group
+ * @kobj:	The kobject to create the group on
+ * @grp:	The attribute group to create
+ *
+ * This function creates a group for the first time.  It will explicitly
+ * warn and error if any of the attribute files being created already exist.
+ *
+ * Returns 0 on success or error.
+ */
+int sysfs_create_group(struct kobject *kobj,
+		       const struct attribute_group *grp)
+{
+	return internal_create_group(kobj, 0, grp);
+}
+EXPORT_SYMBOL_GPL(sysfs_create_group);
+
+/**
+ * sysfs_create_groups - given a directory kobject, create a bunch of attribute groups
+ * @kobj:	The kobject to create the group on
+ * @groups:	The attribute groups to create, NULL terminated
+ *
+ * This function creates a bunch of attribute groups.  If an error occurs when
+ * creating a group, all previously created groups will be removed, unwinding
+ * everything back to the original state when this function was called.
+ * It will explicitly warn and error if any of the attribute files being
+ * created already exist.
+ *
+ * Returns 0 on success or error code from sysfs_create_group on error.
+ */
+int sysfs_create_groups(struct kobject *kobj,
+			const struct attribute_group **groups)
+{
+	int error = 0;
+	int i;
+
+	if (!groups)
+		return 0;
+
+	for (i = 0; groups[i]; i++) {
+		error = sysfs_create_group(kobj, groups[i]);
+		if (error) {
+			while (--i >= 0)
+				sysfs_remove_group(kobj, groups[i]);
+			break;
+		}
+	}
+	return error;
+}
+EXPORT_SYMBOL_GPL(sysfs_create_groups);
+
+/**
+ * sysfs_update_group - given a directory kobject, update an attribute group
+ * @kobj:	The kobject to update the group on
+ * @grp:	The attribute group to update
+ *
+ * This function updates an attribute group.  Unlike
+ * sysfs_create_group(), it will explicitly not warn or error if any
+ * of the attribute files being created already exist.  Furthermore,
+ * if the visibility of the files has changed through the is_visible()
+ * callback, it will update the permissions and add or remove the
+ * relevant files.
+ *
+ * The primary use for this function is to call it after making a change
+ * that affects group visibility.
+ *
+ * Returns 0 on success or error.
+ */
+int sysfs_update_group(struct kobject *kobj,
+		       const struct attribute_group *grp)
+{
+	return internal_create_group(kobj, 1, grp);
+}
+EXPORT_SYMBOL_GPL(sysfs_update_group);
+
+/**
+ * sysfs_remove_group: remove a group from a kobject
+ * @kobj:	kobject to remove the group from
+ * @grp:	group to remove
+ *
+ * This function removes a group of attributes from a kobject.  The attributes
+ * previously have to have been created for this group, otherwise it will fail.
+ */
+void sysfs_remove_group(struct kobject *kobj,
+			const struct attribute_group *grp)
+{
+	struct kernfs_node *parent = kobj->sd;
+	struct kernfs_node *kn;
+
+	if (grp->name) {
+		kn = kernfs_find_and_get(parent, grp->name);
+		if (!kn) {
+			WARN(!kn, KERN_WARNING
+			     "sysfs group %p not found for kobject '%s'\n",
+			     grp, kobject_name(kobj));
+			return;
+		}
+	} else {
+		kn = parent;
+		kernfs_get(kn);
+	}
+
+	remove_files(kn, grp);
+	if (grp->name)
+		kernfs_remove(kn);
+
+	kernfs_put(kn);
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_group);
+
+/**
+ * sysfs_remove_groups - remove a list of groups
+ *
+ * @kobj:	The kobject for the groups to be removed from
+ * @groups:	NULL terminated list of groups to be removed
+ *
+ * If groups is not NULL, remove the specified groups from the kobject.
+ */
+void sysfs_remove_groups(struct kobject *kobj,
+			 const struct attribute_group **groups)
+{
+	int i;
+
+	if (!groups)
+		return;
+	for (i = 0; groups[i]; i++)
+		sysfs_remove_group(kobj, groups[i]);
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_groups);
+
+/**
+ * sysfs_merge_group - merge files into a pre-existing attribute group.
+ * @kobj:	The kobject containing the group.
+ * @grp:	The files to create and the attribute group they belong to.
+ *
+ * This function returns an error if the group doesn't exist or any of the
+ * files already exist in that group, in which case none of the new files
+ * are created.
+ */
+int sysfs_merge_group(struct kobject *kobj,
+		       const struct attribute_group *grp)
+{
+	struct kernfs_node *parent;
+	int error = 0;
+	struct attribute *const *attr;
+	int i;
+
+	parent = kernfs_find_and_get(kobj->sd, grp->name);
+	if (!parent)
+		return -ENOENT;
+
+	for ((i = 0, attr = grp->attrs); *attr && !error; (++i, ++attr))
+		error = sysfs_add_file(parent, *attr, false);
+	if (error) {
+		while (--i >= 0)
+			kernfs_remove_by_name(parent, (*--attr)->name);
+	}
+	kernfs_put(parent);
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(sysfs_merge_group);
+
+/**
+ * sysfs_unmerge_group - remove files from a pre-existing attribute group.
+ * @kobj:	The kobject containing the group.
+ * @grp:	The files to remove and the attribute group they belong to.
+ */
+void sysfs_unmerge_group(struct kobject *kobj,
+		       const struct attribute_group *grp)
+{
+	struct kernfs_node *parent;
+	struct attribute *const *attr;
+
+	parent = kernfs_find_and_get(kobj->sd, grp->name);
+	if (parent) {
+		for (attr = grp->attrs; *attr; ++attr)
+			kernfs_remove_by_name(parent, (*attr)->name);
+		kernfs_put(parent);
+	}
+}
+EXPORT_SYMBOL_GPL(sysfs_unmerge_group);
+
+/**
+ * sysfs_add_link_to_group - add a symlink to an attribute group.
+ * @kobj:	The kobject containing the group.
+ * @group_name:	The name of the group.
+ * @target:	The target kobject of the symlink to create.
+ * @link_name:	The name of the symlink to create.
+ */
+int sysfs_add_link_to_group(struct kobject *kobj, const char *group_name,
+			    struct kobject *target, const char *link_name)
+{
+	struct kernfs_node *parent;
+	int error = 0;
+
+	parent = kernfs_find_and_get(kobj->sd, group_name);
+	if (!parent)
+		return -ENOENT;
+
+	error = sysfs_create_link_sd(parent, target, link_name);
+	kernfs_put(parent);
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(sysfs_add_link_to_group);
+
+/**
+ * sysfs_remove_link_from_group - remove a symlink from an attribute group.
+ * @kobj:	The kobject containing the group.
+ * @group_name:	The name of the group.
+ * @link_name:	The name of the symlink to remove.
+ */
+void sysfs_remove_link_from_group(struct kobject *kobj, const char *group_name,
+				  const char *link_name)
+{
+	struct kernfs_node *parent;
+
+	parent = kernfs_find_and_get(kobj->sd, group_name);
+	if (parent) {
+		kernfs_remove_by_name(parent, link_name);
+		kernfs_put(parent);
+	}
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_link_from_group);

fs/sysfs/mount.c

@@ -0,0 +1,82 @@
+/*
+ * fs/sysfs/symlink.c - operations for initializing and mounting sysfs
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
+ *
+ * This file is released under the GPLv2.
+ *
+ * Please see Documentation/filesystems/sysfs.txt for more information.
+ */
+
+#define DEBUG
+
+#include <linux/fs.h>
+#include <linux/magic.h>
+#include <linux/mount.h>
+#include <linux/init.h>
+#include <linux/user_namespace.h>
+
+#include "sysfs.h"
+
+static struct kernfs_root *sysfs_root;
+struct kernfs_node *sysfs_root_kn;
+
+static struct dentry *sysfs_mount(struct file_system_type *fs_type,
+	int flags, const char *dev_name, void *data)
+{
+	struct dentry *root;
+	void *ns;
+	bool new_sb;
+
+	if (!(flags & MS_KERNMOUNT)) {
+		if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
+			return ERR_PTR(-EPERM);
+
+		if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
+			return ERR_PTR(-EPERM);
+	}
+
+	ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
+	root = kernfs_mount_ns(fs_type, flags, sysfs_root,
+				SYSFS_MAGIC, &new_sb, ns);
+	if (IS_ERR(root) || !new_sb)
+		kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
+	return root;
+}
+
+static void sysfs_kill_sb(struct super_block *sb)
+{
+	void *ns = (void *)kernfs_super_ns(sb);
+
+	kernfs_kill_sb(sb);
+	kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
+}
+
+static struct file_system_type sysfs_fs_type = {
+	.name		= "sysfs",
+	.mount		= sysfs_mount,
+	.kill_sb	= sysfs_kill_sb,
+	.fs_flags	= FS_USERNS_MOUNT,
+};
+
+int __init sysfs_init(void)
+{
+	int err;
+
+	sysfs_root = kernfs_create_root(NULL, KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK,
+					NULL);
+	if (IS_ERR(sysfs_root))
+		return PTR_ERR(sysfs_root);
+
+	sysfs_root_kn = sysfs_root->kn;
+
+	err = register_filesystem(&sysfs_fs_type);
+	if (err) {
+		kernfs_destroy_root(sysfs_root);
+		return err;
+	}
+
+	return 0;
+}

fs/sysfs/symlink.c

@@ -0,0 +1,197 @@
+/*
+ * fs/sysfs/symlink.c - sysfs symlink implementation
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
+ *
+ * This file is released under the GPLv2.
+ *
+ * Please see Documentation/filesystems/sysfs.txt for more information.
+ */
+
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/kobject.h>
+#include <linux/mutex.h>
+#include <linux/security.h>
+
+#include "sysfs.h"
+
+static int sysfs_do_create_link_sd(struct kernfs_node *parent,
+				   struct kobject *target_kobj,
+				   const char *name, int warn)
+{
+	struct kernfs_node *kn, *target = NULL;
+
+	BUG_ON(!name || !parent);
+
+	/*
+	 * We don't own @target_kobj and it may be removed at any time.
+	 * Synchronize using sysfs_symlink_target_lock.  See
+	 * sysfs_remove_dir() for details.
+	 */
+	spin_lock(&sysfs_symlink_target_lock);
+	if (target_kobj->sd) {
+		target = target_kobj->sd;
+		kernfs_get(target);
+	}
+	spin_unlock(&sysfs_symlink_target_lock);
+
+	if (!target)
+		return -ENOENT;
+
+	kn = kernfs_create_link(parent, name, target);
+	kernfs_put(target);
+
+	if (!IS_ERR(kn))
+		return 0;
+
+	if (warn && PTR_ERR(kn) == -EEXIST)
+		sysfs_warn_dup(parent, name);
+	return PTR_ERR(kn);
+}
+
+/**
+ *	sysfs_create_link_sd - create symlink to a given object.
+ *	@kn:		directory we're creating the link in.
+ *	@target:	object we're pointing to.
+ *	@name:		name of the symlink.
+ */
+int sysfs_create_link_sd(struct kernfs_node *kn, struct kobject *target,
+			 const char *name)
+{
+	return sysfs_do_create_link_sd(kn, target, name, 1);
+}
+
+static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
+				const char *name, int warn)
+{
+	struct kernfs_node *parent = NULL;
+
+	if (!kobj)
+		parent = sysfs_root_kn;
+	else
+		parent = kobj->sd;
+
+	if (!parent)
+		return -EFAULT;
+
+	return sysfs_do_create_link_sd(parent, target, name, warn);
+}
+
+/**
+ *	sysfs_create_link - create symlink between two objects.
+ *	@kobj:	object whose directory we're creating the link in.
+ *	@target:	object we're pointing to.
+ *	@name:		name of the symlink.
+ */
+int sysfs_create_link(struct kobject *kobj, struct kobject *target,
+		      const char *name)
+{
+	return sysfs_do_create_link(kobj, target, name, 1);
+}
+EXPORT_SYMBOL_GPL(sysfs_create_link);
+
+/**
+ *	sysfs_create_link_nowarn - create symlink between two objects.
+ *	@kobj:	object whose directory we're creating the link in.
+ *	@target:	object we're pointing to.
+ *	@name:		name of the symlink.
+ *
+ *	This function does the same as sysfs_create_link(), but it
+ *	doesn't warn if the link already exists.
+ */
+int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target,
+			     const char *name)
+{
+	return sysfs_do_create_link(kobj, target, name, 0);
+}
+
+/**
+ *	sysfs_delete_link - remove symlink in object's directory.
+ *	@kobj:	object we're acting for.
+ *	@targ:	object we're pointing to.
+ *	@name:	name of the symlink to remove.
+ *
+ *	Unlike sysfs_remove_link sysfs_delete_link has enough information
+ *	to successfully delete symlinks in tagged directories.
+ */
+void sysfs_delete_link(struct kobject *kobj, struct kobject *targ,
+			const char *name)
+{
+	const void *ns = NULL;
+
+	/*
+	 * We don't own @target and it may be removed at any time.
+	 * Synchronize using sysfs_symlink_target_lock.  See
+	 * sysfs_remove_dir() for details.
+	 */
+	spin_lock(&sysfs_symlink_target_lock);
+	if (targ->sd && kernfs_ns_enabled(kobj->sd))
+		ns = targ->sd->ns;
+	spin_unlock(&sysfs_symlink_target_lock);
+	kernfs_remove_by_name_ns(kobj->sd, name, ns);
+}
+
+/**
+ *	sysfs_remove_link - remove symlink in object's directory.
+ *	@kobj:	object we're acting for.
+ *	@name:	name of the symlink to remove.
+ */
+void sysfs_remove_link(struct kobject *kobj, const char *name)
+{
+	struct kernfs_node *parent = NULL;
+
+	if (!kobj)
+		parent = sysfs_root_kn;
+	else
+		parent = kobj->sd;
+
+	kernfs_remove_by_name(parent, name);
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_link);
+
+/**
+ *	sysfs_rename_link_ns - rename symlink in object's directory.
+ *	@kobj:	object we're acting for.
+ *	@targ:	object we're pointing to.
+ *	@old:	previous name of the symlink.
+ *	@new:	new name of the symlink.
+ *	@new_ns: new namespace of the symlink.
+ *
+ *	A helper function for the common rename symlink idiom.
+ */
+int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *targ,
+			 const char *old, const char *new, const void *new_ns)
+{
+	struct kernfs_node *parent, *kn = NULL;
+	const void *old_ns = NULL;
+	int result;
+
+	if (!kobj)
+		parent = sysfs_root_kn;
+	else
+		parent = kobj->sd;
+
+	if (targ->sd)
+		old_ns = targ->sd->ns;
+
+	result = -ENOENT;
+	kn = kernfs_find_and_get_ns(parent, old, old_ns);
+	if (!kn)
+		goto out;
+
+	result = -EINVAL;
+	if (kernfs_type(kn) != KERNFS_LINK)
+		goto out;
+	if (kn->symlink.target_kn->priv != targ)
+		goto out;
+
+	result = kernfs_rename_ns(kn, parent, new, new_ns);
+
+out:
+	kernfs_put(kn);
+	return result;
+}
+EXPORT_SYMBOL_GPL(sysfs_rename_link_ns);

fs/sysfs/sysfs.h

@@ -0,0 +1,43 @@
+/*
+ * fs/sysfs/sysfs.h - sysfs internal header file
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
+ *
+ * This file is released under the GPLv2.
+ */
+
+#ifndef __SYSFS_INTERNAL_H
+#define __SYSFS_INTERNAL_H
+
+#include <linux/sysfs.h>
+
+/*
+ * mount.c
+ */
+extern struct kernfs_node *sysfs_root_kn;
+
+/*
+ * dir.c
+ */
+extern spinlock_t sysfs_symlink_target_lock;
+
+void sysfs_warn_dup(struct kernfs_node *parent, const char *name);
+
+/*
+ * file.c
+ */
+int sysfs_add_file(struct kernfs_node *parent,
+		   const struct attribute *attr, bool is_bin);
+int sysfs_add_file_mode_ns(struct kernfs_node *parent,
+			   const struct attribute *attr, bool is_bin,
+			   umode_t amode, const void *ns);
+
+/*
+ * symlink.c
+ */
+int sysfs_create_link_sd(struct kernfs_node *kn, struct kobject *target,
+			 const char *name);
+
+#endif	/* __SYSFS_INTERNAL_H */