// SPDX-License-Identifier: GPL-2.0-or-later

  /* -*- mode: c; c-basic-offset: 8; -*-
   * vim: noexpandtab sw=8 ts=8 sts=0:
   *
   * file.c - operations for regular (text) files.
   *

   * Based on sysfs:
   * 	sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
   *
   * configfs Copyright (C) 2005 Oracle.  All rights reserved.
   */
  
  #include <linux/fs.h>
  #include <linux/module.h>

  #include <linux/slab.h>

  #include <linux/mutex.h>

  #include <linux/vmalloc.h>

  #include <linux/uaccess.h>

  
  #include <linux/configfs.h>
  #include "configfs_internal.h"

  /*
   * A simple attribute can only be 4096 characters.  Why 4k?  Because the
   * original code limited it to PAGE_SIZE.  That's a bad idea, though,
   * because an attribute of 16k on ia64 won't work on x86.  So we limit to
   * 4k, our minimum common page size.
   */
  #define SIMPLE_ATTR_SIZE 4096

  
  struct configfs_buffer {
  	size_t			count;
  	loff_t			pos;
  	char			* page;
  	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;

  	int			cb_max_size;
  	struct config_item	*item;
  	struct module		*owner;
  	union {
  		struct configfs_attribute	*attr;
  		struct configfs_bin_attribute	*bin_attr;
  	};

  };

  static inline struct configfs_fragment *to_frag(struct file *file)
  {
  	struct configfs_dirent *sd = file->f_path.dentry->d_fsdata;
  
  	return sd->s_frag;
  }

  static int fill_read_buffer(struct file *file, struct configfs_buffer *buffer)

  {

  	struct configfs_fragment *frag = to_frag(file);
  	ssize_t count = -ENOENT;

  
  	if (!buffer->page)
  		buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
  	if (!buffer->page)
  		return -ENOMEM;

  	down_read(&frag->frag_sem);
  	if (!frag->frag_dead)
  		count = buffer->attr->show(buffer->item, buffer->page);
  	up_read(&frag->frag_sem);

  	if (count < 0)
  		return count;
  	if (WARN_ON_ONCE(count > (ssize_t)SIMPLE_ATTR_SIZE))
  		return -EIO;

  	buffer->needs_read_fill = 0;
  	buffer->count = count;
  	return 0;

  }

  /**
   *	configfs_read_file - read an attribute.
   *	@file:	file pointer.
   *	@buf:	buffer to fill.
   *	@count:	number of bytes to read.
   *	@ppos:	starting offset in file.
   *
   *	Userspace wants to read an attribute file. The attribute descriptor
   *	is in the file's ->d_fsdata. The target item is in the directory's
   *	->d_fsdata.
   *
   *	We call fill_read_buffer() to allocate and fill the buffer from the
   *	item's show() method exactly once (if the read is happening from
   *	the beginning of the file). That should fill the entire buffer with
   *	all the data the item has to offer for that attribute.
   *	We then call flush_read_buffer() to copy the buffer to userspace
   *	in the increments specified.
   */
  
  static ssize_t
  configfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
  {

  	struct configfs_buffer *buffer = file->private_data;

  	ssize_t retval = 0;

  	mutex_lock(&buffer->mutex);

  	if (buffer->needs_read_fill) {

  		retval = fill_read_buffer(file, buffer);

  		if (retval)

  			goto out;
  	}

  	pr_debug("%s: count = %zd, ppos = %lld, buf = %s
  ",

  		 __func__, count, *ppos, buffer->page);

  	retval = simple_read_from_buffer(buf, count, ppos, buffer->page,
  					 buffer->count);

  out:

  	mutex_unlock(&buffer->mutex);

  	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_fragment *frag = to_frag(file);

  	struct configfs_buffer *buffer = file->private_data;

  	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 = true;

  
  	if (buffer->needs_read_fill) {
  		/* perform first read with buf == NULL to get extent */

  		down_read(&frag->frag_sem);
  		if (!frag->frag_dead)
  			len = buffer->bin_attr->read(buffer->item, NULL, 0);
  		else
  			len = -ENOENT;
  		up_read(&frag->frag_sem);

  		if (len <= 0) {
  			retval = len;
  			goto out;
  		}
  
  		/* do not exceed the maximum value */

  		if (buffer->cb_max_size && len > buffer->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 */

  		down_read(&frag->frag_sem);
  		if (!frag->frag_dead)
  			len = buffer->bin_attr->read(buffer->item,
  						     buffer->bin_buffer, len);
  		else
  			len = -ENOENT;
  		up_read(&frag->frag_sem);

  		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.
   *	@buffer:	data buffer for file.

   *	@buf:		data from user.

   *	@count:		number of bytes in @userbuf.
   *
   *	Allocate @buffer->page if it hasn't been already, then
   *	copy the user-supplied buffer into it.
   */
  
  static int
  fill_write_buffer(struct configfs_buffer * buffer, const char __user * buf, size_t count)
  {
  	int error;
  
  	if (!buffer->page)

  		buffer->page = (char *)__get_free_pages(GFP_KERNEL, 0);

  	if (!buffer->page)
  		return -ENOMEM;

  	if (count >= SIMPLE_ATTR_SIZE)
  		count = SIMPLE_ATTR_SIZE - 1;

  	error = copy_from_user(buffer->page,buf,count);
  	buffer->needs_read_fill = 1;

  	/* if buf is assumed to contain a string, terminate it by \0,
  	 * so e.g. sscanf() can scan the string easily */
  	buffer->page[count] = 0;

  	return error ? -EFAULT : count;
  }

  static int

  flush_write_buffer(struct file *file, struct configfs_buffer *buffer, size_t count)

  {

  	struct configfs_fragment *frag = to_frag(file);
  	int res = -ENOENT;
  
  	down_read(&frag->frag_sem);
  	if (!frag->frag_dead)
  		res = buffer->attr->store(buffer->item, buffer->page, count);
  	up_read(&frag->frag_sem);
  	return res;

  }
  
  
  /**
   *	configfs_write_file - write an attribute.
   *	@file:	file pointer
   *	@buf:	data to write
   *	@count:	number of bytes
   *	@ppos:	starting offset
   *
   *	Similar to configfs_read_file(), though working in the opposite direction.
   *	We allocate and fill the data from the user in fill_write_buffer(),
   *	then push it to the config_item in flush_write_buffer().
   *	There is no easy way for us to know if userspace is only doing a partial
   *	write, so we don't support them. We expect the entire buffer to come
   *	on the first write.

   *	Hint: if you're writing a value, first read the file, modify only

   *	the value you're changing, then write entire buffer back.
   */
  
  static ssize_t
  configfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
  {

  	struct configfs_buffer *buffer = file->private_data;

  	ssize_t len;

  	mutex_lock(&buffer->mutex);

  	len = fill_write_buffer(buffer, buf, count);
  	if (len > 0)

  		len = flush_write_buffer(file, buffer, len);

  	if (len > 0)
  		*ppos += len;

  	mutex_unlock(&buffer->mutex);

  	return len;

  }

  /**
   *	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;

  	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 = true;

  
  	/* buffer grows? */
  	if (*ppos + count > buffer->bin_buffer_size) {

  		if (buffer->cb_max_size &&
  			*ppos + count > buffer->cb_max_size) {

  			len = -EFBIG;

  			goto out;

  		}
  
  		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);

  out:
  	mutex_unlock(&buffer->mutex);
  	return len;
  }

  static int __configfs_open_file(struct inode *inode, struct file *file, int type)

  {

  	struct dentry *dentry = file->f_path.dentry;

  	struct configfs_fragment *frag = to_frag(file);

  	struct configfs_attribute *attr;
  	struct configfs_buffer *buffer;
  	int error;

  	error = -ENOMEM;
  	buffer = kzalloc(sizeof(struct configfs_buffer), GFP_KERNEL);
  	if (!buffer)
  		goto out;

  	error = -ENOENT;
  	down_read(&frag->frag_sem);
  	if (unlikely(frag->frag_dead))
  		goto out_free_buffer;

  	error = -EINVAL;

  	buffer->item = to_item(dentry->d_parent);

  	if (!buffer->item)
  		goto out_free_buffer;
  
  	attr = to_attr(dentry);
  	if (!attr)
  		goto out_put_item;
  
  	if (type & CONFIGFS_ITEM_BIN_ATTR) {
  		buffer->bin_attr = to_bin_attr(dentry);
  		buffer->cb_max_size = buffer->bin_attr->cb_max_size;
  	} else {
  		buffer->attr = attr;
  	}

  	buffer->owner = attr->ca_owner;

  	/* Grab the module reference for this attribute if we have one */

  	error = -ENODEV;
  	if (!try_module_get(buffer->owner))
  		goto out_put_item;

  	error = -EACCES;
  	if (!buffer->item->ci_type)
  		goto out_put_module;
  
  	buffer->ops = buffer->item->ci_type->ct_item_ops;

  
  	/* File needs write support.
  	 * The inode's perms must say it's ok,
  	 * and we must have a store method.
  	 */
  	if (file->f_mode & FMODE_WRITE) {

  		if (!(inode->i_mode & S_IWUGO))

  			goto out_put_module;

  		if ((type & CONFIGFS_ITEM_ATTR) && !attr->store)

  			goto out_put_module;
  		if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->write)
  			goto out_put_module;

  	}
  
  	/* File needs read support.
  	 * The inode's perms must say it's ok, and we there
  	 * must be a show method for it.
  	 */
  	if (file->f_mode & FMODE_READ) {

  		if (!(inode->i_mode & S_IRUGO))

  			goto out_put_module;

  		if ((type & CONFIGFS_ITEM_ATTR) && !attr->show)

  			goto out_put_module;
  		if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->read)
  			goto out_put_module;

  	}

  	mutex_init(&buffer->mutex);

  	buffer->needs_read_fill = 1;

  	buffer->read_in_progress = false;
  	buffer->write_in_progress = false;

  	file->private_data = buffer;

  	up_read(&frag->frag_sem);

  	return 0;

  out_put_module:
  	module_put(buffer->owner);
  out_put_item:
  	config_item_put(buffer->item);
  out_free_buffer:

  	up_read(&frag->frag_sem);

  	kfree(buffer);
  out:

  	return error;
  }

  static int configfs_release(struct inode *inode, struct file *filp)

  {

  	struct configfs_buffer *buffer = filp->private_data;

  	module_put(buffer->owner);
  	if (buffer->page)
  		free_page((unsigned long)buffer->page);
  	mutex_destroy(&buffer->mutex);
  	kfree(buffer);

  	return 0;
  }

  static int configfs_open_file(struct inode *inode, struct file *filp)
  {

  	return __configfs_open_file(inode, filp, CONFIGFS_ITEM_ATTR);

  }
  
  static int configfs_open_bin_file(struct inode *inode, struct file *filp)
  {

  	return __configfs_open_file(inode, filp, CONFIGFS_ITEM_BIN_ATTR);

  }

  static int configfs_release_bin_file(struct inode *inode, struct file *file)

  {

  	struct configfs_buffer *buffer = file->private_data;

  	buffer->read_in_progress = false;

  
  	if (buffer->write_in_progress) {

  		struct configfs_fragment *frag = to_frag(file);

  		buffer->write_in_progress = false;

  		down_read(&frag->frag_sem);
  		if (!frag->frag_dead) {
  			/* result of ->release() is ignored */
  			buffer->bin_attr->write(buffer->item,
  					buffer->bin_buffer,
  					buffer->bin_buffer_size);
  		}
  		up_read(&frag->frag_sem);

  		/* vfree on NULL is safe */
  		vfree(buffer->bin_buffer);
  		buffer->bin_buffer = NULL;
  		buffer->bin_buffer_size = 0;
  		buffer->needs_read_fill = 1;
  	}

  	configfs_release(inode, file);
  	return 0;

  }

  const struct file_operations configfs_file_operations = {

  	.read		= configfs_read_file,
  	.write		= configfs_write_file,
  	.llseek		= generic_file_llseek,
  	.open		= configfs_open_file,
  	.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.
   *	@attr:	atrribute descriptor.
   */
  
  int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr)
  {

  	struct dentry *dir = item->ci_dentry;
  	struct configfs_dirent *parent_sd = dir->d_fsdata;
  	umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
  	int error = 0;

  	inode_lock_nested(d_inode(dir), I_MUTEX_NORMAL);

  	error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode,

  				     CONFIGFS_ITEM_ATTR, parent_sd->s_frag);

  	inode_unlock(d_inode(dir));

  
  	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;

  	inode_lock_nested(dir->d_inode, I_MUTEX_NORMAL);

  	error = configfs_make_dirent(parent_sd, NULL, (void *) bin_attr, mode,

  				     CONFIGFS_ITEM_BIN_ATTR, parent_sd->s_frag);

  	inode_unlock(dir->d_inode);

  
  	return error;
  }