From 062e69c83449e4f5f363bb3caf4ba411907636d5 Mon Sep 17 00:00:00 2001
From: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
Date: Thu, 22 Oct 2015 23:30:04 +0300
Subject: [PATCH] UPSTREAM: configfs: implement binary attributes

ConfigFS lacked binary attributes up until now. This patch
introduces support for binary attributes in a somewhat similar
manner of sysfs binary attributes albeit with changes that
fit the configfs usage model.

Problems that configfs binary attributes fix are everything that
requires a binary blob as part of the configuration of a resource,
such as bitstream loading for FPGAs, DTBs for dynamically created
devices etc.

Look at Documentation/filesystems/configfs/configfs.txt for internals
and howto use them.

This patch is against linux-next as of today that contains
Christoph's configfs rework.

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
[hch: folded a fix from Geert Uytterhoeven <geert+renesas@glider.be>]
[hch: a few tiny updates based on review feedback]
Signed-off-by: Christoph Hellwig <hch@lst.de>
(cherry picked from commit 03607ace807b414eab46323c794b6fb8fcc2d48c)
---
 Documentation/filesystems/configfs/configfs.txt |  57 +++++-
 fs/configfs/configfs_internal.h                 |  14 +-
 fs/configfs/dir.c                               |  18 +-
 fs/configfs/file.c                              | 255 +++++++++++++++++++++++-
 fs/configfs/inode.c                             |   2 +-
 include/linux/configfs.h                        |  50 +++++
 6 files changed, 374 insertions(+), 22 deletions(-)

diff --git a/Documentation/filesystems/configfs/configfs.txt b/Documentation/filesystems/configfs/configfs.txt
index af68efdbbfad..e5fe521eea1d 100644
--- a/Documentation/filesystems/configfs/configfs.txt
+++ b/Documentation/filesystems/configfs/configfs.txt
@@ -51,15 +51,27 @@ configfs tree is always there, whether mounted on /config or not.
 An item is created via mkdir(2).  The item's attributes will also
 appear at this time.  readdir(3) can determine what the attributes are,
 read(2) can query their default values, and write(2) can store new
-values.  Like sysfs, attributes should be ASCII text files, preferably
-with only one value per file.  The same efficiency caveats from sysfs
-apply.  Don't mix more than one attribute in one attribute file.
-
-Like sysfs, configfs expects write(2) to store the entire buffer at
-once.  When writing to configfs attributes, userspace processes should
-first read the entire file, modify the portions they wish to change, and
-then write the entire buffer back.  Attribute files have a maximum size
-of one page (PAGE_SIZE, 4096 on i386).
+values.  Don't mix more than one attribute in one attribute file.
+
+There are two types of configfs attributes:
+
+* Normal attributes, which similar to sysfs attributes, are small ASCII text
+files, with a maximum size of one page (PAGE_SIZE, 4096 on i386).  Preferably
+only one value per file should be used, and the same caveats from sysfs apply.
+Configfs expects write(2) to store the entire buffer at once.  When writing to
+normal configfs attributes, userspace processes should first read the entire
+file, modify the portions they wish to change, and then write the entire
+buffer back.
+
+* Binary attributes, which are somewhat similar to sysfs binary attributes,
+but with a few slight changes to semantics.  The PAGE_SIZE limitation does not
+apply, but the whole binary item must fit in single kernel vmalloc'ed buffer.
+The write(2) calls from user space are buffered, and the attributes'
+write_bin_attribute method will be invoked on the final close, therefore it is
+imperative for user-space to check the return code of close(2) in order to
+verify that the operation finished successfully.
+To avoid a malicious user OOMing the kernel, there's a per-binary attribute
+maximum buffer value.
 
 When an item needs to be destroyed, remove it with rmdir(2).  An
 item cannot be destroyed if any other item has a link to it (via
@@ -171,6 +183,7 @@ among other things.  For that, it needs a type.
 		struct configfs_item_operations         *ct_item_ops;
 		struct configfs_group_operations        *ct_group_ops;
 		struct configfs_attribute               **ct_attrs;
+		struct configfs_bin_attribute		**ct_bin_attrs;
 	};
 
 The most basic function of a config_item_type is to define what
@@ -201,6 +214,32 @@ be called whenever userspace asks for a read(2) on the attribute.  If an
 attribute is writable and provides a ->store  method, that method will be
 be called whenever userspace asks for a write(2) on the attribute.
 
+[struct configfs_bin_attribute]
+
+	struct configfs_attribute {
+		struct configfs_attribute	cb_attr;
+		void				*cb_private;
+		size_t				cb_max_size;
+	};
+
+The binary attribute is used when the one needs to use binary blob to
+appear as the contents of a file in the item's configfs directory.
+To do so add the binary attribute to the NULL-terminated array
+config_item_type->ct_bin_attrs, and the item appears in configfs, the
+attribute file will appear with the configfs_bin_attribute->cb_attr.ca_name
+filename.  configfs_bin_attribute->cb_attr.ca_mode specifies the file
+permissions.
+The cb_private member is provided for use by the driver, while the
+cb_max_size member specifies the maximum amount of vmalloc buffer
+to be used.
+
+If binary attribute is readable and the config_item provides a
+ct_item_ops->read_bin_attribute() method, that method will be called
+whenever userspace asks for a read(2) on the attribute.  The converse
+will happen for write(2). The reads/writes are bufferred so only a
+single read/write will occur; the attributes' need not concern itself
+with it.
+
 [struct config_group]
 
 A config_item cannot live in a vacuum.  The only way one can be created
diff --git a/fs/configfs/configfs_internal.h b/fs/configfs/configfs_internal.h
index b65d1ef532d5..ccc31fa6f1a7 100644
--- a/fs/configfs/configfs_internal.h
+++ b/fs/configfs/configfs_internal.h
@@ -53,13 +53,14 @@ struct configfs_dirent {
 #define CONFIGFS_ROOT		0x0001
 #define CONFIGFS_DIR		0x0002
 #define CONFIGFS_ITEM_ATTR	0x0004
+#define CONFIGFS_ITEM_BIN_ATTR	0x0008
 #define CONFIGFS_ITEM_LINK	0x0020
 #define CONFIGFS_USET_DIR	0x0040
 #define CONFIGFS_USET_DEFAULT	0x0080
 #define CONFIGFS_USET_DROPPING	0x0100
 #define CONFIGFS_USET_IN_MKDIR	0x0200
 #define CONFIGFS_USET_CREATING	0x0400
-#define CONFIGFS_NOT_PINNED	(CONFIGFS_ITEM_ATTR)
+#define CONFIGFS_NOT_PINNED	(CONFIGFS_ITEM_ATTR | CONFIGFS_ITEM_BIN_ATTR)
 
 extern struct mutex configfs_symlink_mutex;
 extern spinlock_t configfs_dirent_lock;
@@ -72,6 +73,8 @@ extern struct inode * configfs_new_inode(umode_t mode, struct configfs_dirent *,
 extern int configfs_create(struct dentry *, umode_t mode, void (*init)(struct inode *));
 
 extern int configfs_create_file(struct config_item *, const struct configfs_attribute *);
+extern int configfs_create_bin_file(struct config_item *,
+				    const struct configfs_bin_attribute *);
 extern int configfs_make_dirent(struct configfs_dirent *,
 				struct dentry *, void *, umode_t, int);
 extern int configfs_dirent_is_ready(struct configfs_dirent *);
@@ -88,7 +91,7 @@ extern void configfs_release_fs(void);
 extern struct rw_semaphore configfs_rename_sem;
 extern const struct file_operations configfs_dir_operations;
 extern const struct file_operations configfs_file_operations;
-extern const struct file_operations bin_fops;
+extern const struct file_operations configfs_bin_file_operations;
 extern const struct inode_operations configfs_dir_inode_operations;
 extern const struct inode_operations configfs_root_inode_operations;
 extern const struct inode_operations configfs_symlink_inode_operations;
@@ -119,6 +122,13 @@ static inline struct configfs_attribute * to_attr(struct dentry * dentry)
 	return ((struct configfs_attribute *) sd->s_element);
 }
 
+static inline struct configfs_bin_attribute *to_bin_attr(struct dentry *dentry)
+{
+	struct configfs_attribute *attr = to_attr(dentry);
+
+	return container_of(attr, struct configfs_bin_attribute, cb_attr);
+}
+
 static inline struct config_item *configfs_get_config_item(struct dentry *dentry)
 {
 	struct config_item * item = NULL;
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index a7a1b218f308..7ae97e83f121 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -255,6 +255,12 @@ static void configfs_init_file(struct inode * inode)
 	inode->i_fop = &configfs_file_operations;
 }
 
+static void configfs_init_bin_file(struct inode *inode)
+{
+	inode->i_size = 0;
+	inode->i_fop = &configfs_bin_file_operations;
+}
+
 static void init_symlink(struct inode * inode)
 {
 	inode->i_op = &configfs_symlink_inode_operations;
@@ -423,7 +429,9 @@ static int configfs_attach_attr(struct configfs_dirent * sd, struct dentry * den
 	spin_unlock(&configfs_dirent_lock);
 
 	error = configfs_create(dentry, (attr->ca_mode & S_IALLUGO) | S_IFREG,
-				configfs_init_file);
+				(sd->s_type & CONFIGFS_ITEM_BIN_ATTR) ?
+					configfs_init_bin_file :
+					configfs_init_file);
 	if (error) {
 		configfs_put(sd);
 		return error;
@@ -583,6 +591,7 @@ static int populate_attrs(struct config_item *item)
 {
 	struct config_item_type *t = item->ci_type;
 	struct configfs_attribute *attr;
+	struct configfs_bin_attribute *bin_attr;
 	int error = 0;
 	int i;
 
@@ -594,6 +603,13 @@ static int populate_attrs(struct config_item *item)
 				break;
 		}
 	}
+	if (t->ct_bin_attrs) {
+		for (i = 0; (bin_attr = t->ct_bin_attrs[i]) != NULL; i++) {
+			error = configfs_create_bin_file(item, bin_attr);
+			if (error)
+				break;
+		}
+	}
 
 	if (error)
 		detach_attrs(item);
diff --git a/fs/configfs/file.c b/fs/configfs/file.c
index d39099ea7df7..3687187c8ea5 100644
--- a/fs/configfs/file.c
+++ b/fs/configfs/file.c
@@ -28,6 +28,7 @@
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/mutex.h>
+#include <linux/vmalloc.h>
 #include <asm/uaccess.h>
 
 #include <linux/configfs.h>
@@ -48,6 +49,10 @@ struct configfs_buffer {
 	struct configfs_item_operations	* ops;
 	struct mutex		mutex;
 	int			needs_read_fill;
+	bool			read_in_progress;
+	bool			write_in_progress;
+	char			*bin_buffer;
+	int			bin_buffer_size;
 };
 
 
@@ -123,6 +128,87 @@ out:
 	return retval;
 }
 
+/**
+ *	configfs_read_bin_file - read a binary attribute.
+ *	@file:	file pointer.
+ *	@buf:	buffer to fill.
+ *	@count:	number of bytes to read.
+ *	@ppos:	starting offset in file.
+ *
+ *	Userspace wants to read a binary attribute file. The attribute
+ *	descriptor is in the file's ->d_fsdata. The target item is in the
+ *	directory's ->d_fsdata.
+ *
+ *	We check whether we need to refill the buffer. If so we will
+ *	call the attributes' attr->read() twice. The first time we
+ *	will pass a NULL as a buffer pointer, which the attributes' method
+ *	will use to return the size of the buffer required. If no error
+ *	occurs we will allocate the buffer using vmalloc and call
+ *	attr->read() again passing that buffer as an argument.
+ *	Then we just copy to user-space using simple_read_from_buffer.
+ */
+
+static ssize_t
+configfs_read_bin_file(struct file *file, char __user *buf,
+		       size_t count, loff_t *ppos)
+{
+	struct configfs_buffer *buffer = file->private_data;
+	struct dentry *dentry = file->f_path.dentry;
+	struct config_item *item = to_item(dentry->d_parent);
+	struct configfs_bin_attribute *bin_attr = to_bin_attr(dentry);
+	ssize_t retval = 0;
+	ssize_t len = min_t(size_t, count, PAGE_SIZE);
+
+	mutex_lock(&buffer->mutex);
+
+	/* we don't support switching read/write modes */
+	if (buffer->write_in_progress) {
+		retval = -ETXTBSY;
+		goto out;
+	}
+	buffer->read_in_progress = 1;
+
+	if (buffer->needs_read_fill) {
+		/* perform first read with buf == NULL to get extent */
+		len = bin_attr->read(item, NULL, 0);
+		if (len <= 0) {
+			retval = len;
+			goto out;
+		}
+
+		/* do not exceed the maximum value */
+		if (bin_attr->cb_max_size && len > bin_attr->cb_max_size) {
+			retval = -EFBIG;
+			goto out;
+		}
+
+		buffer->bin_buffer = vmalloc(len);
+		if (buffer->bin_buffer == NULL) {
+			retval = -ENOMEM;
+			goto out;
+		}
+		buffer->bin_buffer_size = len;
+
+		/* perform second read to fill buffer */
+		len = bin_attr->read(item, buffer->bin_buffer, len);
+		if (len < 0) {
+			retval = len;
+			vfree(buffer->bin_buffer);
+			buffer->bin_buffer_size = 0;
+			buffer->bin_buffer = NULL;
+			goto out;
+		}
+
+		buffer->needs_read_fill = 0;
+	}
+
+	retval = simple_read_from_buffer(buf, count, ppos, buffer->bin_buffer,
+					buffer->bin_buffer_size);
+out:
+	mutex_unlock(&buffer->mutex);
+	return retval;
+}
+
 
 /**
  *	fill_write_buffer - copy buffer from userspace.
@@ -209,10 +295,80 @@ configfs_write_file(struct file *file, const char __user *buf, size_t count, lof
 	return len;
 }
 
-static int check_perm(struct inode * inode, struct file * file)
+/**
+ *	configfs_write_bin_file - write a binary attribute.
+ *	@file:	file pointer
+ *	@buf:	data to write
+ *	@count:	number of bytes
+ *	@ppos:	starting offset
+ *
+ *	Writing to a binary attribute file is similar to a normal read.
+ *	We buffer the consecutive writes (binary attribute files do not
+ *	support lseek) in a continuously growing buffer, but we don't
+ *	commit until the close of the file.
+ */
+
+static ssize_t
+configfs_write_bin_file(struct file *file, const char __user *buf,
+			size_t count, loff_t *ppos)
+{
+	struct configfs_buffer *buffer = file->private_data;
+	struct dentry *dentry = file->f_path.dentry;
+	struct configfs_bin_attribute *bin_attr = to_bin_attr(dentry);
+	void *tbuf = NULL;
+	ssize_t len;
+
+	mutex_lock(&buffer->mutex);
+
+	/* we don't support switching read/write modes */
+	if (buffer->read_in_progress) {
+		len = -ETXTBSY;
+		goto out;
+	}
+	buffer->write_in_progress = 1;
+
+	/* buffer grows? */
+	if (*ppos + count > buffer->bin_buffer_size) {
+
+		if (bin_attr->cb_max_size &&
+			*ppos + count > bin_attr->cb_max_size) {
+			len = -EFBIG;
+		}
+
+		tbuf = vmalloc(*ppos + count);
+		if (tbuf == NULL) {
+			len = -ENOMEM;
+			goto out;
+		}
+
+		/* copy old contents */
+		if (buffer->bin_buffer) {
+			memcpy(tbuf, buffer->bin_buffer,
+				buffer->bin_buffer_size);
+			vfree(buffer->bin_buffer);
+		}
+
+		/* clear the new area */
+		memset(tbuf + buffer->bin_buffer_size, 0,
+			*ppos + count - buffer->bin_buffer_size);
+		buffer->bin_buffer = tbuf;
+		buffer->bin_buffer_size = *ppos + count;
+	}
+
+	len = simple_write_to_buffer(buffer->bin_buffer,
+			buffer->bin_buffer_size, ppos, buf, count);
+	if (len > 0)
+		*ppos += len;
+out:
+	mutex_unlock(&buffer->mutex);
+	return len;
+}
+
+static int check_perm(struct inode * inode, struct file * file, int type)
 {
 	struct config_item *item = configfs_get_config_item(file->f_path.dentry->d_parent);
 	struct configfs_attribute * attr = to_attr(file->f_path.dentry);
+	struct configfs_bin_attribute *bin_attr = NULL;
 	struct configfs_buffer * buffer;
 	struct configfs_item_operations * ops = NULL;
 	int error = 0;
@@ -220,6 +376,9 @@ static int check_perm(struct inode * inode, struct file * file)
 	if (!item || !attr)
 		goto Einval;
 
+	if (type & CONFIGFS_ITEM_BIN_ATTR)
+		bin_attr = to_bin_attr(file->f_path.dentry);
+
 	/* Grab the module reference for this attribute if we have one */
 	if (!try_module_get(attr->ca_owner)) {
 		error = -ENODEV;
@@ -236,9 +395,14 @@ static int check_perm(struct inode * inode, struct file * file)
 	 * and we must have a store method.
 	 */
 	if (file->f_mode & FMODE_WRITE) {
-		if (!(inode->i_mode & S_IWUGO) || !attr->store)
+		if (!(inode->i_mode & S_IWUGO))
+			goto Eaccess;
+
+		if ((type & CONFIGFS_ITEM_ATTR) && !attr->store)
 			goto Eaccess;
 
+		if ((type & CONFIGFS_ITEM_BIN_ATTR) && !bin_attr->write)
+			goto Eaccess;
 	}
 
 	/* File needs read support.
@@ -246,7 +410,13 @@ static int check_perm(struct inode * inode, struct file * file)
 	 * must be a show method for it.
 	 */
 	if (file->f_mode & FMODE_READ) {
-		if (!(inode->i_mode & S_IRUGO) || !attr->show)
+		if (!(inode->i_mode & S_IRUGO))
+			goto Eaccess;
+
+		if ((type & CONFIGFS_ITEM_ATTR) && !attr->show)
+			goto Eaccess;
+
+		if ((type & CONFIGFS_ITEM_BIN_ATTR) && !bin_attr->read)
 			goto Eaccess;
 	}
 
@@ -260,6 +430,8 @@ static int check_perm(struct inode * inode, struct file * file)
 	}
 	mutex_init(&buffer->mutex);
 	buffer->needs_read_fill = 1;
+	buffer->read_in_progress = 0;
+	buffer->write_in_progress = 0;
 	buffer->ops = ops;
 	file->private_data = buffer;
 	goto Done;
@@ -277,12 +449,7 @@ static int check_perm(struct inode * inode, struct file * file)
 	return error;
 }
 
-static int configfs_open_file(struct inode * inode, struct file * filp)
-{
-	return check_perm(inode,filp);
-}
-
-static int configfs_release(struct inode * inode, struct file * filp)
+static int configfs_release(struct inode *inode, struct file *filp)
 {
 	struct config_item * item = to_item(filp->f_path.dentry->d_parent);
 	struct configfs_attribute * attr = to_attr(filp->f_path.dentry);
@@ -303,6 +470,47 @@ static int configfs_release(struct inode * inode, struct file * filp)
 	return 0;
 }
 
+static int configfs_open_file(struct inode *inode, struct file *filp)
+{
+	return check_perm(inode, filp, CONFIGFS_ITEM_ATTR);
+}
+
+static int configfs_open_bin_file(struct inode *inode, struct file *filp)
+{
+	return check_perm(inode, filp, CONFIGFS_ITEM_BIN_ATTR);
+}
+
+static int configfs_release_bin_file(struct inode *inode, struct file *filp)
+{
+	struct configfs_buffer *buffer = filp->private_data;
+	struct dentry *dentry = filp->f_path.dentry;
+	struct config_item *item = to_item(dentry->d_parent);
+	struct configfs_bin_attribute *bin_attr = to_bin_attr(dentry);
+	ssize_t len = 0;
+	int ret;
+
+	buffer->read_in_progress = 0;
+
+	if (buffer->write_in_progress) {
+		buffer->write_in_progress = 0;
+
+		len = bin_attr->write(item, buffer->bin_buffer,
+				buffer->bin_buffer_size);
+
+		/* vfree on NULL is safe */
+		vfree(buffer->bin_buffer);
+		buffer->bin_buffer = NULL;
+		buffer->bin_buffer_size = 0;
+		buffer->needs_read_fill = 1;
+	}
+
+	ret = configfs_release(inode, filp);
+	if (len < 0)
+		return len;
+	return ret;
+}
+
+
 const struct file_operations configfs_file_operations = {
 	.read		= configfs_read_file,
 	.write		= configfs_write_file,
@@ -311,6 +519,14 @@ const struct file_operations configfs_file_operations = {
 	.release	= configfs_release,
 };
 
+const struct file_operations configfs_bin_file_operations = {
+	.read		= configfs_read_bin_file,
+	.write		= configfs_write_bin_file,
+	.llseek		= NULL,		/* bin file is not seekable */
+	.open		= configfs_open_bin_file,
+	.release	= configfs_release_bin_file,
+};
+
 /**
  *	configfs_create_file - create an attribute file for an item.
  *	@item:	item we're creating for.
@@ -332,3 +548,24 @@ int configfs_create_file(struct config_item * item, const struct configfs_attrib
 	return error;
 }
 
+/**
+ *	configfs_create_bin_file - create a binary attribute file for an item.
+ *	@item:	item we're creating for.
+ *	@attr:	atrribute descriptor.
+ */
+
+int configfs_create_bin_file(struct config_item *item,
+		const struct configfs_bin_attribute *bin_attr)
+{
+	struct dentry *dir = item->ci_dentry;
+	struct configfs_dirent *parent_sd = dir->d_fsdata;
+	umode_t mode = (bin_attr->cb_attr.ca_mode & S_IALLUGO) | S_IFREG;
+	int error = 0;
+
+	mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_NORMAL);
+	error = configfs_make_dirent(parent_sd, NULL, (void *) bin_attr, mode,
+				     CONFIGFS_ITEM_BIN_ATTR);
+	mutex_unlock(&dir->d_inode->i_mutex);
+
+	return error;
+}
diff --git a/fs/configfs/inode.c b/fs/configfs/inode.c
index eae87575e681..0cc810e9dccc 100644
--- a/fs/configfs/inode.c
+++ b/fs/configfs/inode.c
@@ -218,7 +218,7 @@ const unsigned char * configfs_get_name(struct configfs_dirent *sd)
 	if (sd->s_type & (CONFIGFS_DIR | CONFIGFS_ITEM_LINK))
 		return sd->s_dentry->d_name.name;
 
-	if (sd->s_type & CONFIGFS_ITEM_ATTR) {
+	if (sd->s_type & (CONFIGFS_ITEM_ATTR | CONFIGFS_ITEM_BIN_ATTR)) {
 		attr = sd->s_element;
 		return attr->ca_name;
 	}
diff --git a/include/linux/configfs.h b/include/linux/configfs.h
index 758a029011b1..f7300d023dbe 100644
--- a/include/linux/configfs.h
+++ b/include/linux/configfs.h
@@ -51,6 +51,7 @@ struct module;
 struct configfs_item_operations;
 struct configfs_group_operations;
 struct configfs_attribute;
+struct configfs_bin_attribute;
 struct configfs_subsystem;
 
 struct config_item {
@@ -84,6 +85,7 @@ struct config_item_type {
 	struct configfs_item_operations		*ct_item_ops;
 	struct configfs_group_operations	*ct_group_ops;
 	struct configfs_attribute		**ct_attrs;
+	struct configfs_bin_attribute		**ct_bin_attrs;
 };
 
 /**
@@ -154,6 +156,54 @@ static struct configfs_attribute _pfx##attr_##_name = {	\
 	.store		= _pfx##_name##_store,		\
 }
 
+struct file;
+struct vm_area_struct;
+
+struct configfs_bin_attribute {
+	struct configfs_attribute cb_attr;	/* std. attribute */
+	void *cb_private;			/* for user       */
+	size_t cb_max_size;			/* max core size  */
+	ssize_t (*read)(struct config_item *, void *, size_t);
+	ssize_t (*write)(struct config_item *, const void *, size_t);
+};
+
+#define CONFIGFS_BIN_ATTR(_pfx, _name, _priv, _maxsz)		\
+static struct configfs_bin_attribute _pfx##attr_##_name = {	\
+	.cb_attr = {						\
+		.ca_name	= __stringify(_name),		\
+		.ca_mode	= S_IRUGO | S_IWUSR,		\
+		.ca_owner	= THIS_MODULE,			\
+	},							\
+	.cb_private	= _priv,				\
+	.cb_max_size	= _maxsz,				\
+	.read		= _pfx##_name##_read,			\
+	.write		= _pfx##_name##_write,			\
+}
+
+#define CONFIGFS_BIN_ATTR_RO(_pfx, _name, _priv, _maxsz)	\
+static struct configfs_attribute _pfx##attr_##_name = {		\
+	.cb_attr = {						\
+		.ca_name	= __stringify(_name),		\
+		.ca_mode	= S_IRUGO,			\
+		.ca_owner	= THIS_MODULE,			\
+	},							\
+	.cb_private	= _priv,				\
+	.cb_max_size	= _maxsz,				\
+	.read		= _pfx##_name##_read,			\
+}
+
+#define CONFIGFS_BIN_ATTR_WO(_pfx, _name, _priv, _maxsz)	\
+static struct configfs_attribute _pfx##attr_##_name = {		\
+	.cb_attr = {						\
+		.ca_name	= __stringify(_name),		\
+		.ca_mode	= S_IWUSR,			\
+		.ca_owner	= THIS_MODULE,			\
+	},							\
+	.cb_private	= _priv,				\
+	.cb_max_size	= _maxsz,				\
+	.write		= _pfx##_name##_write,			\
+}
+
 /*
  * If allow_link() exists, the item can symlink(2) out to other
  * items.  If the item is a group, it may support mkdir(2).

From 2dc994339b24321895cff69fda659e47648871be Mon Sep 17 00:00:00 2001
From: Octavian Purdila <octavian.purdila@intel.com>
Date: Wed, 23 Mar 2016 14:14:48 +0200
Subject: [PATCH] UPSTREAM: configfs: fix CONFIGFS_BIN_ATTR_[RW]O definitions

The type should be struct configfs_bin_attribute and not struct
configfs_attribute.

Signed-off-by: Octavian Purdila <octavian.purdila@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
(cherry picked from commit 96c22a3293512ba684e73a981196430f524689da)
---
 include/linux/configfs.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/configfs.h b/include/linux/configfs.h
index f7300d023dbe..658066d63180 100644
--- a/include/linux/configfs.h
+++ b/include/linux/configfs.h
@@ -181,7 +181,7 @@ static struct configfs_bin_attribute _pfx##attr_##_name = {	\
 }
 
 #define CONFIGFS_BIN_ATTR_RO(_pfx, _name, _priv, _maxsz)	\
-static struct configfs_attribute _pfx##attr_##_name = {		\
+static struct configfs_bin_attribute _pfx##attr_##_name = {	\
 	.cb_attr = {						\
 		.ca_name	= __stringify(_name),		\
 		.ca_mode	= S_IRUGO,			\
@@ -193,7 +193,7 @@ static struct configfs_attribute _pfx##attr_##_name = {		\
 }
 
 #define CONFIGFS_BIN_ATTR_WO(_pfx, _name, _priv, _maxsz)	\
-static struct configfs_attribute _pfx##attr_##_name = {		\
+static struct configfs_bin_attribute _pfx##attr_##_name = {	\
 	.cb_attr = {						\
 		.ca_name	= __stringify(_name),		\
 		.ca_mode	= S_IWUSR,			\

From a2a707f138cf997e098a6d3aceac4b0944f7d76e Mon Sep 17 00:00:00 2001
From: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
Date: Wed, 4 Dec 2013 19:32:00 +0200
Subject: [PATCH] FROMLIST: OF: DT-Overlay configfs interface (v7)

Add a runtime interface to using configfs for generic device tree overlay
usage. With it its possible to use device tree overlays without having
to use a per-platform overlay manager.

Please see Documentation/devicetree/configfs-overlays.txt for more info.

Changes since v6:
- Default groups properties API changed.

Changes since v5:
- New style configfs.

Changes since v4:
- Loading fix for multiple overlays as found out by
  Geert Uytterhoeven <geert@linux-m68k.org>

Changes since v3:
- Fixed compilation on SPARC & Xtensa

Changes since v2:
- Removed ifdef CONFIG_OF_OVERLAY (since for now it's required)
- Created a documentation entry
- Slight rewording in Kconfig

Changes since v1:
- of_resolve() -> of_resolve_phandles().

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
[geert: Use %zu to format size_t]
[geert: Let OF_CONFIGFS select OF_FLATTREE to fix sparc all*config]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
 Documentation/devicetree/configfs-overlays.txt |  31 +++
 drivers/of/Kconfig                             |   8 +
 drivers/of/Makefile                            |   1 +
 drivers/of/configfs.c                          | 314 +++++++++++++++++++++++++
 4 files changed, 354 insertions(+)
 create mode 100644 Documentation/devicetree/configfs-overlays.txt
 create mode 100644 drivers/of/configfs.c

diff --git a/Documentation/devicetree/configfs-overlays.txt b/Documentation/devicetree/configfs-overlays.txt
new file mode 100644
index 000000000000..5fa43e064307
--- /dev/null
+++ b/Documentation/devicetree/configfs-overlays.txt
@@ -0,0 +1,31 @@
+Howto use the configfs overlay interface.
+
+A device-tree configfs entry is created in /config/device-tree/overlays
+and and it is manipulated using standard file system I/O.
+Note that this is a debug level interface, for use by developers and
+not necessarily something accessed by normal users due to the
+security implications of having direct access to the kernel's device tree.
+
+* To create an overlay you mkdir the directory:
+
+	# mkdir /config/device-tree/overlays/foo
+
+* Either you echo the overlay firmware file to the path property file.
+
+	# echo foo.dtbo >/config/device-tree/overlays/foo/path
+
+* Or you cat the contents of the overlay to the dtbo file
+
+	# cat foo.dtbo >/config/device-tree/overlays/foo/dtbo
+
+The overlay file will be applied, and devices will be created/destroyed
+as required.
+
+To remove it simply rmdir the directory.
+
+	# rmdir /config/device-tree/overlays/foo
+
+The rationalle of the dual interface (firmware & direct copy) is that each is
+better suited to different use patterns. The firmware interface is what's
+intended to be used by hardware managers in the kernel, while the copy interface
+make sense for developers (since it avoids problems with namespaces).
diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
index e2a48415d969..c112c9f2ca6b 100644
--- a/drivers/of/Kconfig
+++ b/drivers/of/Kconfig
@@ -112,4 +112,12 @@ config OF_OVERLAY
 	  While this option is selected automatically when needed, you can
 	  enable it manually to improve device tree unit test coverage.
 
+config OF_CONFIGFS
+	bool "Device Tree Overlay ConfigFS interface"
+	select CONFIGFS_FS
+	select OF_FLATTREE
+	depends on OF_OVERLAY
+	help
+	  Enable a simple user-space driven DT overlay interface.
+
 endif # OF
diff --git a/drivers/of/Makefile b/drivers/of/Makefile
index 478d4edcd763..732fa66b5263 100644
--- a/drivers/of/Makefile
+++ b/drivers/of/Makefile
@@ -1,4 +1,5 @@
 obj-y = base.o device.o platform.o property.o
+obj-$(CONFIG_OF_CONFIGFS) += configfs.o
 obj-$(CONFIG_OF_DYNAMIC) += dynamic.o
 obj-$(CONFIG_OF_FLATTREE) += fdt.o
 obj-$(CONFIG_OF_EARLY_FLATTREE) += fdt_address.o
diff --git a/drivers/of/configfs.c b/drivers/of/configfs.c
new file mode 100644
index 000000000000..908ce4960c30
--- /dev/null
+++ b/drivers/of/configfs.c
@@ -0,0 +1,314 @@
+/*
+ * Configfs entries for device-tree
+ *
+ * Copyright (C) 2013 - Pantelis Antoniou <panto@antoniou-consulting.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+#include <linux/ctype.h>
+#include <linux/cpu.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_fdt.h>
+#include <linux/spinlock.h>
+#include <linux/slab.h>
+#include <linux/proc_fs.h>
+#include <linux/configfs.h>
+#include <linux/types.h>
+#include <linux/stat.h>
+#include <linux/limits.h>
+#include <linux/file.h>
+#include <linux/vmalloc.h>
+#include <linux/firmware.h>
+
+#include "of_private.h"
+
+struct cfs_overlay_item {
+	struct config_item	item;
+
+	char			path[PATH_MAX];
+
+	const struct firmware	*fw;
+	struct device_node	*overlay;
+	int			ov_id;
+
+	void			*dtbo;
+	int			dtbo_size;
+};
+
+static int create_overlay(struct cfs_overlay_item *overlay, void *blob)
+{
+	int err;
+
+	/* unflatten the tree */
+	of_fdt_unflatten_tree(blob, &overlay->overlay);
+	if (overlay->overlay == NULL) {
+		pr_err("%s: failed to unflatten tree\n", __func__);
+		err = -EINVAL;
+		goto out_err;
+	}
+	pr_debug("%s: unflattened OK\n", __func__);
+
+	/* mark it as detached */
+	of_node_set_flag(overlay->overlay, OF_DETACHED);
+
+	/* perform resolution */
+	err = of_resolve_phandles(overlay->overlay);
+	if (err != 0) {
+		pr_err("%s: Failed to resolve tree\n", __func__);
+		goto out_err;
+	}
+	pr_debug("%s: resolved OK\n", __func__);
+
+	err = of_overlay_create(overlay->overlay);
+	if (err < 0) {
+		pr_err("%s: Failed to create overlay (err=%d)\n",
+				__func__, err);
+		goto out_err;
+	}
+	overlay->ov_id = err;
+
+out_err:
+	return err;
+}
+
+static inline struct cfs_overlay_item *to_cfs_overlay_item(
+		struct config_item *item)
+{
+	return item ? container_of(item, struct cfs_overlay_item, item) : NULL;
+}
+
+static ssize_t cfs_overlay_item_path_show(struct config_item *item,
+		char *page)
+{
+	struct cfs_overlay_item *overlay = to_cfs_overlay_item(item);
+	return sprintf(page, "%s\n", overlay->path);
+}
+
+static ssize_t cfs_overlay_item_path_store(struct config_item *item,
+		const char *page, size_t count)
+{
+	struct cfs_overlay_item *overlay = to_cfs_overlay_item(item);
+	const char *p = page;
+	char *s;
+	int err;
+
+	/* if it's set do not allow changes */
+	if (overlay->path[0] != '\0' || overlay->dtbo_size > 0)
+		return -EPERM;
+
+	/* copy to path buffer (and make sure it's always zero terminated */
+	count = snprintf(overlay->path, sizeof(overlay->path) - 1, "%s", p);
+	overlay->path[sizeof(overlay->path) - 1] = '\0';
+
+	/* strip trailing newlines */
+	s = overlay->path + strlen(overlay->path);
+	while (s > overlay->path && *--s == '\n')
+		*s = '\0';
+
+	pr_debug("%s: path is '%s'\n", __func__, overlay->path);
+
+	err = request_firmware(&overlay->fw, overlay->path, NULL);
+	if (err != 0)
+		goto out_err;
+
+	err = create_overlay(overlay, (void *)overlay->fw->data);
+	if (err < 0)
+		goto out_err;
+
+	return count;
+
+out_err:
+
+	release_firmware(overlay->fw);
+	overlay->fw = NULL;
+
+	overlay->path[0] = '\0';
+	return err;
+}
+
+static ssize_t cfs_overlay_item_status_show(struct config_item *item,
+		char *page)
+{
+	struct cfs_overlay_item *overlay = to_cfs_overlay_item(item);
+
+	return sprintf(page, "%s\n",
+			overlay->ov_id >= 0 ? "applied" : "unapplied");
+}
+
+CONFIGFS_ATTR(cfs_overlay_item_, path);
+CONFIGFS_ATTR_RO(cfs_overlay_item_, status);
+
+static struct configfs_attribute *cfs_overlay_attrs[] = {
+	&cfs_overlay_item_attr_path,
+	&cfs_overlay_item_attr_status,
+	NULL,
+};
+
+ssize_t cfs_overlay_item_dtbo_read(struct config_item *item,
+		void *buf, size_t max_count)
+{
+	struct cfs_overlay_item *overlay = to_cfs_overlay_item(item);
+
+	pr_debug("%s: buf=%p max_count=%zu\n", __func__,
+			buf, max_count);
+
+	if (overlay->dtbo == NULL)
+		return 0;
+
+	/* copy if buffer provided */
+	if (buf != NULL) {
+		/* the buffer must be large enough */
+		if (overlay->dtbo_size > max_count)
+			return -ENOSPC;
+
+		memcpy(buf, overlay->dtbo, overlay->dtbo_size);
+	}
+
+	return overlay->dtbo_size;
+}
+
+ssize_t cfs_overlay_item_dtbo_write(struct config_item *item,
+		const void *buf, size_t count)
+{
+	struct cfs_overlay_item *overlay = to_cfs_overlay_item(item);
+	int err;
+
+	/* if it's set do not allow changes */
+	if (overlay->path[0] != '\0' || overlay->dtbo_size > 0)
+		return -EPERM;
+
+	/* copy the contents */
+	overlay->dtbo = kmemdup(buf, count, GFP_KERNEL);
+	if (overlay->dtbo == NULL)
+		return -ENOMEM;
+
+	overlay->dtbo_size = count;
+
+	err = create_overlay(overlay, overlay->dtbo);
+	if (err < 0)
+		goto out_err;
+
+	return count;
+
+out_err:
+	kfree(overlay->dtbo);
+	overlay->dtbo = NULL;
+	overlay->dtbo_size = 0;
+
+	return err;
+}
+
+CONFIGFS_BIN_ATTR(cfs_overlay_item_, dtbo, NULL, SZ_1M);
+
+static struct configfs_bin_attribute *cfs_overlay_bin_attrs[] = {
+	&cfs_overlay_item_attr_dtbo,
+	NULL,
+};
+
+static void cfs_overlay_release(struct config_item *item)
+{
+	struct cfs_overlay_item *overlay = to_cfs_overlay_item(item);
+
+	if (overlay->ov_id >= 0)
+		of_overlay_destroy(overlay->ov_id);
+	if (overlay->fw)
+		release_firmware(overlay->fw);
+	/* kfree with NULL is safe */
+	kfree(overlay->dtbo);
+	kfree(overlay);
+}
+
+static struct configfs_item_operations cfs_overlay_item_ops = {
+	.release	= cfs_overlay_release,
+};
+
+static struct config_item_type cfs_overlay_type = {
+	.ct_item_ops	= &cfs_overlay_item_ops,
+	.ct_attrs	= cfs_overlay_attrs,
+	.ct_bin_attrs	= cfs_overlay_bin_attrs,
+	.ct_owner	= THIS_MODULE,
+};
+
+static struct config_item *cfs_overlay_group_make_item(
+		struct config_group *group, const char *name)
+{
+	struct cfs_overlay_item *overlay;
+
+	overlay = kzalloc(sizeof(*overlay), GFP_KERNEL);
+	if (!overlay)
+		return ERR_PTR(-ENOMEM);
+	overlay->ov_id = -1;
+
+	config_item_init_type_name(&overlay->item, name, &cfs_overlay_type);
+	return &overlay->item;
+}
+
+static void cfs_overlay_group_drop_item(struct config_group *group,
+		struct config_item *item)
+{
+	struct cfs_overlay_item *overlay = to_cfs_overlay_item(item);
+
+	config_item_put(&overlay->item);
+}
+
+static struct configfs_group_operations overlays_ops = {
+	.make_item	= cfs_overlay_group_make_item,
+	.drop_item	= cfs_overlay_group_drop_item,
+};
+
+static struct config_item_type overlays_type = {
+	.ct_group_ops   = &overlays_ops,
+	.ct_owner       = THIS_MODULE,
+};
+
+static struct configfs_group_operations of_cfs_ops = {
+	/* empty - we don't allow anything to be created */
+};
+
+static struct config_item_type of_cfs_type = {
+	.ct_group_ops   = &of_cfs_ops,
+	.ct_owner       = THIS_MODULE,
+};
+
+struct config_group of_cfs_overlay_group;
+
+struct config_group *of_cfs_def_groups[] = {
+	&of_cfs_overlay_group,
+	NULL
+};
+
+static struct configfs_subsystem of_cfs_subsys = {
+	.su_group = {
+		.cg_item = {
+			.ci_namebuf = "device-tree",
+			.ci_type = &of_cfs_type,
+		},
+		.default_groups = of_cfs_def_groups,
+	},
+	.su_mutex = __MUTEX_INITIALIZER(of_cfs_subsys.su_mutex),
+};
+
+static int __init of_cfs_init(void)
+{
+	int ret;
+
+	pr_info("%s\n", __func__);
+
+	config_group_init(&of_cfs_subsys.su_group);
+	config_group_init_type_name(&of_cfs_overlay_group, "overlays",
+			&overlays_type);
+
+	ret = configfs_register_subsystem(&of_cfs_subsys);
+	if (ret != 0) {
+		pr_err("%s: failed to register subsys\n", __func__);
+		goto out;
+	}
+	pr_info("%s: OK\n", __func__);
+out:
+	return ret;
+}
+late_initcall(of_cfs_init);
