// SPDX-License-Identifier: GPL-2.0

  /*
   * linux/fs/seq_file.c
   *
   * helper functions for making synthetic files from sequences of records.
   * initial implementation -- AV, Oct 2001.
   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/cache.h>

  #include <linux/fs.h>

  #include <linux/export.h>

  #include <linux/seq_file.h>

  #include <linux/vmalloc.h>

  #include <linux/slab.h>

  #include <linux/cred.h>

  #include <linux/mm.h>

  #include <linux/printk.h>

  #include <linux/string_helpers.h>

  #include <linux/uio.h>

  #include <linux/uaccess.h>

  #include <asm/page.h>

  static struct kmem_cache *seq_file_cache __ro_after_init;

  static void seq_set_overflow(struct seq_file *m)
  {
  	m->count = m->size;
  }

  static void *seq_buf_alloc(unsigned long size)
  {

  	return kvmalloc(size, GFP_KERNEL_ACCOUNT);

  }

  /**
   *	seq_open -	initialize sequential file
   *	@file: file we initialize
   *	@op: method table describing the sequence
   *
   *	seq_open() sets @file, associating it with a sequence described
   *	by @op.  @op->start() sets the iterator up and returns the first
   *	element of sequence. @op->stop() shuts it down.  @op->next()
   *	returns the next element of sequence.  @op->show() prints element
   *	into the buffer.  In case of error ->start() and ->next() return
   *	ERR_PTR(error).  In the end of sequence they return %NULL. ->show()
   *	returns 0 in case of success and negative number in case of error.

   *	Returning SEQ_SKIP means "discard this element and move on".

   *	Note: seq_open() will allocate a struct seq_file and store its
   *	pointer in @file->private_data. This pointer should not be modified.

   */

  int seq_open(struct file *file, const struct seq_operations *op)

  {

  	struct seq_file *p;
  
  	WARN_ON(file->private_data);

  	p = kmem_cache_zalloc(seq_file_cache, GFP_KERNEL);

  	if (!p)
  		return -ENOMEM;
  
  	file->private_data = p;

  	mutex_init(&p->lock);

  	p->op = op;

  
  	// No refcounting: the lifetime of 'p' is constrained
  	// to the lifetime of the file.
  	p->file = file;

  
  	/*

  	 * seq_files support lseek() and pread().  They do not implement
  	 * write() at all, but we clear FMODE_PWRITE here for historical
  	 * reasons.
  	 *
  	 * If a client of seq_files a) implements file.write() and b) wishes to
  	 * support pwrite() then that client will need to implement its own
  	 * file.open() which calls seq_open() and then sets FMODE_PWRITE.
  	 */
  	file->f_mode &= ~FMODE_PWRITE;

  	return 0;
  }
  EXPORT_SYMBOL(seq_open);

  static int traverse(struct seq_file *m, loff_t offset)
  {

  	loff_t pos = 0;

  	int error = 0;
  	void *p;

  	m->index = 0;

  	m->count = m->from = 0;

  	if (!offset)

  		return 0;

  	if (!m->buf) {

  		m->buf = seq_buf_alloc(m->size = PAGE_SIZE);

  		if (!m->buf)
  			return -ENOMEM;
  	}

  	p = m->op->start(m, &m->index);

  	while (p) {
  		error = PTR_ERR(p);
  		if (IS_ERR(p))
  			break;
  		error = m->op->show(m, p);
  		if (error < 0)
  			break;
  		if (unlikely(error)) {
  			error = 0;
  			m->count = 0;
  		}

  		if (seq_has_overflowed(m))

  			goto Eoverflow;

  		p = m->op->next(m, p, &m->index);

  		if (pos + m->count > offset) {
  			m->from = offset - pos;
  			m->count -= m->from;

  			break;
  		}
  		pos += m->count;
  		m->count = 0;

  		if (pos == offset)

  			break;

  	}
  	m->op->stop(m, p);
  	return error;
  
  Eoverflow:
  	m->op->stop(m, p);

  	kvfree(m->buf);

  	m->count = 0;

  	m->buf = seq_buf_alloc(m->size <<= 1);

  	return !m->buf ? -ENOMEM : -EAGAIN;
  }

  /**
   *	seq_read -	->read() method for sequential files.

   *	@file: the file to read from
   *	@buf: the buffer to read to
   *	@size: the maximum number of bytes to read
   *	@ppos: the current position in the file

   *
   *	Ready-made ->f_op->read()
   */
  ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
  {

  	struct iovec iov = { .iov_base = buf, .iov_len = size};
  	struct kiocb kiocb;
  	struct iov_iter iter;
  	ssize_t ret;
  
  	init_sync_kiocb(&kiocb, file);
  	iov_iter_init(&iter, READ, &iov, 1, size);
  
  	kiocb.ki_pos = *ppos;
  	ret = seq_read_iter(&kiocb, &iter);
  	*ppos = kiocb.ki_pos;
  	return ret;
  }
  EXPORT_SYMBOL(seq_read);
  
  /*
   * Ready-made ->f_op->read_iter()
   */
  ssize_t seq_read_iter(struct kiocb *iocb, struct iov_iter *iter)
  {
  	struct seq_file *m = iocb->ki_filp->private_data;

  	size_t copied = 0;

  	size_t n;
  	void *p;
  	int err = 0;

  	if (!iov_iter_count(iter))
  		return 0;

  	mutex_lock(&m->lock);

  	/*

  	 * if request is to read from zero offset, reset iterator to first
  	 * record as it might have been already advanced by previous requests
  	 */

  	if (iocb->ki_pos == 0) {

  		m->index = 0;

  		m->count = 0;
  	}

  	/* Don't assume ki_pos is where we left it */
  	if (unlikely(iocb->ki_pos != m->read_pos)) {
  		while ((err = traverse(m, iocb->ki_pos)) == -EAGAIN)

  			;
  		if (err) {
  			/* With prejudice... */
  			m->read_pos = 0;

  			m->index = 0;
  			m->count = 0;
  			goto Done;

  		} else {

  			m->read_pos = iocb->ki_pos;

  		}
  	}

  	/* grab buffer if we didn't have one */
  	if (!m->buf) {

  		m->buf = seq_buf_alloc(m->size = PAGE_SIZE);

  		if (!m->buf)
  			goto Enomem;
  	}

  	// something left in the buffer - copy it out first

  	if (m->count) {

  		n = copy_to_iter(m->buf + m->from, m->count, iter);

  		m->count -= n;
  		m->from += n;

  		copied += n;

  		if (m->count)	// hadn't managed to copy everything

  			goto Done;
  	}

  	// get a non-empty record in the buffer

  	m->from = 0;
  	p = m->op->start(m, &m->index);

  	while (1) {

  		err = PTR_ERR(p);

  		if (!p || IS_ERR(p))	// EOF or an error

  			break;
  		err = m->op->show(m, p);

  		if (err < 0)		// hard error

  			break;

  		if (unlikely(err))	// ->show() says "skip it"

  			m->count = 0;

  		if (unlikely(!m->count)) { // empty record

  			p = m->op->next(m, p, &m->index);

  			continue;
  		}

  		if (!seq_has_overflowed(m)) // got it

  			goto Fill;

  		// need a bigger buffer

  		m->op->stop(m, p);

  		kvfree(m->buf);

  		m->count = 0;

  		m->buf = seq_buf_alloc(m->size <<= 1);

  		if (!m->buf)
  			goto Enomem;

  		p = m->op->start(m, &m->index);

  	}

  	// EOF or an error

  	m->op->stop(m, p);
  	m->count = 0;
  	goto Done;
  Fill:

  	// one non-empty record is in the buffer; if they want more,
  	// try to fit more in, but in any case we need to advance
  	// the iterator once for every record shown.

  	while (1) {

  		size_t offs = m->count;

  		loff_t pos = m->index;
  
  		p = m->op->next(m, p, &m->index);

  		if (pos == m->index) {

  			pr_info_ratelimited("buggy .next function %ps did not update position index
  ",
  					    m->op->next);

  			m->index++;

  		}

  		if (!p || IS_ERR(p))	// no next record for us

  			break;

  		if (m->count >= iov_iter_count(iter))

  			break;

  		err = m->op->show(m, p);

  		if (err > 0) {		// ->show() says "skip it"

  			m->count = offs;

  		} else if (err || seq_has_overflowed(m)) {
  			m->count = offs;
  			break;

  		}

  	}
  	m->op->stop(m, p);

  	n = copy_to_iter(m->buf, m->count, iter);

  	copied += n;
  	m->count -= n;

  	m->from = n;

  Done:

  	if (unlikely(!copied)) {
  		copied = m->count ? -EFAULT : err;
  	} else {

  		iocb->ki_pos += copied;

  		m->read_pos += copied;
  	}

  	mutex_unlock(&m->lock);

  	return copied;
  Enomem:
  	err = -ENOMEM;
  	goto Done;

  }

  EXPORT_SYMBOL(seq_read_iter);

  /**
   *	seq_lseek -	->llseek() method for sequential files.

   *	@file: the file in question
   *	@offset: new position

   *	@whence: 0 for absolute, 1 for relative position

   *
   *	Ready-made ->f_op->llseek()
   */

  loff_t seq_lseek(struct file *file, loff_t offset, int whence)

  {

  	struct seq_file *m = file->private_data;

  	loff_t retval = -EINVAL;

  	mutex_lock(&m->lock);

  	switch (whence) {

  	case SEEK_CUR:
  		offset += file->f_pos;

  		fallthrough;

  	case SEEK_SET:
  		if (offset < 0)
  			break;
  		retval = offset;
  		if (offset != m->read_pos) {
  			while ((retval = traverse(m, offset)) == -EAGAIN)
  				;
  			if (retval) {
  				/* with extreme prejudice... */
  				file->f_pos = 0;
  				m->read_pos = 0;

  				m->index = 0;
  				m->count = 0;
  			} else {
  				m->read_pos = offset;
  				retval = file->f_pos = offset;

  			}

  		} else {
  			file->f_pos = offset;

  		}

  	}

  	mutex_unlock(&m->lock);

  	return retval;
  }
  EXPORT_SYMBOL(seq_lseek);
  
  /**
   *	seq_release -	free the structures associated with sequential file.
   *	@file: file in question

   *	@inode: its inode

   *
   *	Frees the structures associated with sequential file; can be used
   *	as ->f_op->release() if you don't have private data to destroy.
   */
  int seq_release(struct inode *inode, struct file *file)
  {

  	struct seq_file *m = file->private_data;

  	kvfree(m->buf);

  	kmem_cache_free(seq_file_cache, m);

  	return 0;
  }
  EXPORT_SYMBOL(seq_release);
  
  /**
   *	seq_escape -	print string into buffer, escaping some characters
   *	@m:	target buffer
   *	@s:	string
   *	@esc:	set of characters that need escaping
   *
   *	Puts string into buffer, replacing each occurrence of character from

   *	@esc with usual octal escape.
   *	Use seq_has_overflowed() to check for errors.

   */

  void seq_escape(struct seq_file *m, const char *s, const char *esc)

  {

  	char *buf;
  	size_t size = seq_get_buf(m, &buf);
  	int ret;

  	ret = string_escape_str(s, buf, size, ESCAPE_OCTAL, esc);
  	seq_commit(m, ret < size ? ret : -1);

  }
  EXPORT_SYMBOL(seq_escape);

  void seq_escape_mem_ascii(struct seq_file *m, const char *src, size_t isz)
  {
  	char *buf;
  	size_t size = seq_get_buf(m, &buf);
  	int ret;
  
  	ret = string_escape_mem_ascii(src, isz, buf, size);
  	seq_commit(m, ret < size ? ret : -1);
  }
  EXPORT_SYMBOL(seq_escape_mem_ascii);

  void seq_vprintf(struct seq_file *m, const char *f, va_list args)

  {

  	int len;
  
  	if (m->count < m->size) {

  		len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);

  		if (m->count + len < m->size) {
  			m->count += len;

  			return;

  		}
  	}

  	seq_set_overflow(m);

  }

  EXPORT_SYMBOL(seq_vprintf);

  void seq_printf(struct seq_file *m, const char *f, ...)

  {

  	va_list args;
  
  	va_start(args, f);

  	seq_vprintf(m, f, args);

  	va_end(args);

  }

  EXPORT_SYMBOL(seq_printf);

  /**

   *	mangle_path -	mangle and copy path to buffer beginning
   *	@s: buffer start
   *	@p: beginning of path in above buffer
   *	@esc: set of characters that need escaping

   *
   *      Copy the path from @p to @s, replacing each occurrence of character from
   *      @esc with usual octal escape.
   *      Returns pointer past last written character in @s, or NULL in case of
   *      failure.
   */

  char *mangle_path(char *s, const char *p, const char *esc)

  {
  	while (s <= p) {
  		char c = *p++;
  		if (!c) {
  			return s;
  		} else if (!strchr(esc, c)) {
  			*s++ = c;
  		} else if (s + 4 > p) {
  			break;
  		} else {
  			*s++ = '\\';
  			*s++ = '0' + ((c & 0300) >> 6);
  			*s++ = '0' + ((c & 070) >> 3);
  			*s++ = '0' + (c & 07);
  		}
  	}
  	return NULL;
  }

  EXPORT_SYMBOL(mangle_path);

  /**
   * seq_path - seq_file interface to print a pathname
   * @m: the seq_file handle
   * @path: the struct path to print
   * @esc: set of characters to escape in the output
   *
   * return the absolute path of 'path', as represented by the
   * dentry / mnt pair in the path parameter.

   */

  int seq_path(struct seq_file *m, const struct path *path, const char *esc)

  {

  	char *buf;
  	size_t size = seq_get_buf(m, &buf);
  	int res = -1;
  
  	if (size) {
  		char *p = d_path(path, buf, size);

  		if (!IS_ERR(p)) {

  			char *end = mangle_path(buf, p, esc);
  			if (end)
  				res = end - buf;

  		}
  	}

  	seq_commit(m, res);
  
  	return res;

  }
  EXPORT_SYMBOL(seq_path);

  /**
   * seq_file_path - seq_file interface to print a pathname of a file
   * @m: the seq_file handle
   * @file: the struct file to print
   * @esc: set of characters to escape in the output
   *
   * return the absolute path to the file.
   */
  int seq_file_path(struct seq_file *m, struct file *file, const char *esc)
  {
  	return seq_path(m, &file->f_path, esc);
  }
  EXPORT_SYMBOL(seq_file_path);

  /*

   * Same as seq_path, but relative to supplied root.

   */

  int seq_path_root(struct seq_file *m, const struct path *path,
  		  const struct path *root, const char *esc)

  {

  	char *buf;
  	size_t size = seq_get_buf(m, &buf);
  	int res = -ENAMETOOLONG;
  
  	if (size) {

  		char *p;

  		p = __d_path(path, root, buf, size);

  		if (!p)
  			return SEQ_SKIP;

  		res = PTR_ERR(p);

  		if (!IS_ERR(p)) {

  			char *end = mangle_path(buf, p, esc);
  			if (end)
  				res = end - buf;
  			else
  				res = -ENAMETOOLONG;

  		}
  	}

  	seq_commit(m, res);

  	return res < 0 && res != -ENAMETOOLONG ? res : 0;

  }
  
  /*

   * returns the path of the 'dentry' from the root of its filesystem.
   */

  int seq_dentry(struct seq_file *m, struct dentry *dentry, const char *esc)

  {

  	char *buf;
  	size_t size = seq_get_buf(m, &buf);
  	int res = -1;
  
  	if (size) {
  		char *p = dentry_path(dentry, buf, size);

  		if (!IS_ERR(p)) {

  			char *end = mangle_path(buf, p, esc);
  			if (end)
  				res = end - buf;

  		}
  	}

  	seq_commit(m, res);
  
  	return res;

  }

  EXPORT_SYMBOL(seq_dentry);

  static void *single_start(struct seq_file *p, loff_t *pos)
  {
  	return NULL + (*pos == 0);
  }
  
  static void *single_next(struct seq_file *p, void *v, loff_t *pos)
  {
  	++*pos;
  	return NULL;
  }
  
  static void single_stop(struct seq_file *p, void *v)
  {
  }
  
  int single_open(struct file *file, int (*show)(struct seq_file *, void *),
  		void *data)
  {

  	struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL_ACCOUNT);

  	int res = -ENOMEM;
  
  	if (op) {
  		op->start = single_start;
  		op->next = single_next;
  		op->stop = single_stop;
  		op->show = show;
  		res = seq_open(file, op);
  		if (!res)
  			((struct seq_file *)file->private_data)->private = data;
  		else
  			kfree(op);
  	}
  	return res;
  }
  EXPORT_SYMBOL(single_open);

  int single_open_size(struct file *file, int (*show)(struct seq_file *, void *),
  		void *data, size_t size)
  {

  	char *buf = seq_buf_alloc(size);

  	int ret;
  	if (!buf)
  		return -ENOMEM;
  	ret = single_open(file, show, data);
  	if (ret) {

  		kvfree(buf);

  		return ret;
  	}
  	((struct seq_file *)file->private_data)->buf = buf;
  	((struct seq_file *)file->private_data)->size = size;
  	return 0;
  }
  EXPORT_SYMBOL(single_open_size);

  int single_release(struct inode *inode, struct file *file)
  {

  	const struct seq_operations *op = ((struct seq_file *)file->private_data)->op;

  	int res = seq_release(inode, file);
  	kfree(op);
  	return res;
  }
  EXPORT_SYMBOL(single_release);
  
  int seq_release_private(struct inode *inode, struct file *file)
  {
  	struct seq_file *seq = file->private_data;
  
  	kfree(seq->private);
  	seq->private = NULL;
  	return seq_release(inode, file);
  }
  EXPORT_SYMBOL(seq_release_private);

  void *__seq_open_private(struct file *f, const struct seq_operations *ops,
  		int psize)
  {
  	int rc;
  	void *private;
  	struct seq_file *seq;

  	private = kzalloc(psize, GFP_KERNEL_ACCOUNT);

  	if (private == NULL)
  		goto out;
  
  	rc = seq_open(f, ops);
  	if (rc < 0)
  		goto out_free;
  
  	seq = f->private_data;
  	seq->private = private;
  	return private;
  
  out_free:
  	kfree(private);
  out:
  	return NULL;
  }
  EXPORT_SYMBOL(__seq_open_private);
  
  int seq_open_private(struct file *filp, const struct seq_operations *ops,
  		int psize)
  {
  	return __seq_open_private(filp, ops, psize) ? 0 : -ENOMEM;
  }
  EXPORT_SYMBOL(seq_open_private);

  void seq_putc(struct seq_file *m, char c)

  {

  	if (m->count >= m->size)
  		return;
  
  	m->buf[m->count++] = c;

  }
  EXPORT_SYMBOL(seq_putc);

  void seq_puts(struct seq_file *m, const char *s)

  {
  	int len = strlen(s);

  
  	if (m->count + len >= m->size) {
  		seq_set_overflow(m);
  		return;

  	}

  	memcpy(m->buf + m->count, s, len);
  	m->count += len;

  }
  EXPORT_SYMBOL(seq_puts);

  /**

   * A helper routine for putting decimal numbers without rich format of printf().
   * only 'unsigned long long' is supported.

   * @m: seq_file identifying the buffer to which data should be written
   * @delimiter: a string which is printed before the number
   * @num: the number
   * @width: a minimum field width
   *
   * This routine will put strlen(delimiter) + number into seq_filed.

   * This routine is very quick when you show lots of numbers.
   * In usual cases, it will be better to use seq_printf(). It's easier to read.
   */

  void seq_put_decimal_ull_width(struct seq_file *m, const char *delimiter,
  			 unsigned long long num, unsigned int width)

  {
  	int len;
  
  	if (m->count + 2 >= m->size) /* we'll write 2 bytes at least */
  		goto overflow;

  	if (delimiter && delimiter[0]) {
  		if (delimiter[1] == 0)
  			seq_putc(m, delimiter[0]);
  		else
  			seq_puts(m, delimiter);
  	}

  	if (!width)
  		width = 1;
  
  	if (m->count + width >= m->size)

  		goto overflow;

  	len = num_to_str(m->buf + m->count, m->size - m->count, num, width);

  	if (!len)
  		goto overflow;

  	m->count += len;

  	return;

  overflow:

  	seq_set_overflow(m);

  }

  
  void seq_put_decimal_ull(struct seq_file *m, const char *delimiter,
  			 unsigned long long num)
  {
  	return seq_put_decimal_ull_width(m, delimiter, num, 0);
  }

  EXPORT_SYMBOL(seq_put_decimal_ull);

  /**
   * seq_put_hex_ll - put a number in hexadecimal notation
   * @m: seq_file identifying the buffer to which data should be written
   * @delimiter: a string which is printed before the number
   * @v: the number
   * @width: a minimum field width
   *
   * seq_put_hex_ll(m, "", v, 8) is equal to seq_printf(m, "%08llx", v)
   *
   * This routine is very quick when you show lots of numbers.
   * In usual cases, it will be better to use seq_printf(). It's easier to read.
   */
  void seq_put_hex_ll(struct seq_file *m, const char *delimiter,
  				unsigned long long v, unsigned int width)
  {
  	unsigned int len;
  	int i;
  
  	if (delimiter && delimiter[0]) {
  		if (delimiter[1] == 0)
  			seq_putc(m, delimiter[0]);
  		else
  			seq_puts(m, delimiter);
  	}
  
  	/* If x is 0, the result of __builtin_clzll is undefined */
  	if (v == 0)
  		len = 1;
  	else
  		len = (sizeof(v) * 8 - __builtin_clzll(v) + 3) / 4;
  
  	if (len < width)
  		len = width;
  
  	if (m->count + len > m->size) {
  		seq_set_overflow(m);
  		return;
  	}
  
  	for (i = len - 1; i >= 0; i--) {
  		m->buf[m->count + i] = hex_asc[0xf & v];
  		v = v >> 4;
  	}
  	m->count += len;
  }

  void seq_put_decimal_ll(struct seq_file *m, const char *delimiter, long long num)

  {

  	int len;
  
  	if (m->count + 3 >= m->size) /* we'll write 2 bytes at least */
  		goto overflow;

  	if (delimiter && delimiter[0]) {
  		if (delimiter[1] == 0)
  			seq_putc(m, delimiter[0]);
  		else
  			seq_puts(m, delimiter);
  	}

  
  	if (m->count + 2 >= m->size)
  		goto overflow;

  	if (num < 0) {

  		m->buf[m->count++] = '-';

  		num = -num;

  	}

  
  	if (num < 10) {
  		m->buf[m->count++] = num + '0';
  		return;
  	}

  	len = num_to_str(m->buf + m->count, m->size - m->count, num, 0);

  	if (!len)
  		goto overflow;
  
  	m->count += len;
  	return;
  
  overflow:
  	seq_set_overflow(m);

  }
  EXPORT_SYMBOL(seq_put_decimal_ll);

  /**
   * seq_write - write arbitrary data to buffer
   * @seq: seq_file identifying the buffer to which data should be written
   * @data: data address
   * @len: number of bytes
   *
   * Return 0 on success, non-zero otherwise.
   */
  int seq_write(struct seq_file *seq, const void *data, size_t len)
  {
  	if (seq->count + len < seq->size) {
  		memcpy(seq->buf + seq->count, data, len);
  		seq->count += len;
  		return 0;
  	}

  	seq_set_overflow(seq);

  	return -1;
  }
  EXPORT_SYMBOL(seq_write);

  /**
   * seq_pad - write padding spaces to buffer
   * @m: seq_file identifying the buffer to which data should be written
   * @c: the byte to append after padding if non-zero
   */
  void seq_pad(struct seq_file *m, char c)
  {
  	int size = m->pad_until - m->count;

  	if (size > 0) {
  		if (size + m->count > m->size) {
  			seq_set_overflow(m);
  			return;
  		}
  		memset(m->buf + m->count, ' ', size);
  		m->count += size;
  	}

  	if (c)
  		seq_putc(m, c);
  }
  EXPORT_SYMBOL(seq_pad);

  /* A complete analogue of print_hex_dump() */
  void seq_hex_dump(struct seq_file *m, const char *prefix_str, int prefix_type,
  		  int rowsize, int groupsize, const void *buf, size_t len,
  		  bool ascii)
  {
  	const u8 *ptr = buf;
  	int i, linelen, remaining = len;

  	char *buffer;
  	size_t size;

  	int ret;
  
  	if (rowsize != 16 && rowsize != 32)
  		rowsize = 16;
  
  	for (i = 0; i < len && !seq_has_overflowed(m); i += rowsize) {
  		linelen = min(remaining, rowsize);
  		remaining -= rowsize;
  
  		switch (prefix_type) {
  		case DUMP_PREFIX_ADDRESS:
  			seq_printf(m, "%s%p: ", prefix_str, ptr + i);
  			break;
  		case DUMP_PREFIX_OFFSET:
  			seq_printf(m, "%s%.8x: ", prefix_str, i);
  			break;
  		default:
  			seq_printf(m, "%s", prefix_str);
  			break;
  		}

  		size = seq_get_buf(m, &buffer);

  		ret = hex_dump_to_buffer(ptr + i, linelen, rowsize, groupsize,

  					 buffer, size, ascii);
  		seq_commit(m, ret < size ? ret : -1);
  
  		seq_putc(m, '
  ');

  	}
  }
  EXPORT_SYMBOL(seq_hex_dump);

  struct list_head *seq_list_start(struct list_head *head, loff_t pos)
  {
  	struct list_head *lh;
  
  	list_for_each(lh, head)
  		if (pos-- == 0)
  			return lh;
  
  	return NULL;
  }

  EXPORT_SYMBOL(seq_list_start);
  
  struct list_head *seq_list_start_head(struct list_head *head, loff_t pos)
  {
  	if (!pos)
  		return head;
  
  	return seq_list_start(head, pos - 1);
  }

  EXPORT_SYMBOL(seq_list_start_head);
  
  struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
  {
  	struct list_head *lh;
  
  	lh = ((struct list_head *)v)->next;
  	++*ppos;
  	return lh == head ? NULL : lh;
  }

  EXPORT_SYMBOL(seq_list_next);

  
  /**
   * seq_hlist_start - start an iteration of a hlist
   * @head: the head of the hlist
   * @pos:  the start position of the sequence
   *
   * Called at seq_file->op->start().
   */
  struct hlist_node *seq_hlist_start(struct hlist_head *head, loff_t pos)
  {
  	struct hlist_node *node;
  
  	hlist_for_each(node, head)
  		if (pos-- == 0)
  			return node;
  	return NULL;
  }
  EXPORT_SYMBOL(seq_hlist_start);
  
  /**
   * seq_hlist_start_head - start an iteration of a hlist
   * @head: the head of the hlist
   * @pos:  the start position of the sequence
   *
   * Called at seq_file->op->start(). Call this function if you want to
   * print a header at the top of the output.
   */
  struct hlist_node *seq_hlist_start_head(struct hlist_head *head, loff_t pos)
  {
  	if (!pos)
  		return SEQ_START_TOKEN;
  
  	return seq_hlist_start(head, pos - 1);
  }
  EXPORT_SYMBOL(seq_hlist_start_head);
  
  /**
   * seq_hlist_next - move to the next position of the hlist
   * @v:    the current iterator
   * @head: the head of the hlist

   * @ppos: the current position

   *
   * Called at seq_file->op->next().
   */
  struct hlist_node *seq_hlist_next(void *v, struct hlist_head *head,
  				  loff_t *ppos)
  {
  	struct hlist_node *node = v;
  
  	++*ppos;
  	if (v == SEQ_START_TOKEN)
  		return head->first;
  	else
  		return node->next;
  }
  EXPORT_SYMBOL(seq_hlist_next);

  
  /**
   * seq_hlist_start_rcu - start an iteration of a hlist protected by RCU
   * @head: the head of the hlist
   * @pos:  the start position of the sequence
   *
   * Called at seq_file->op->start().
   *
   * This list-traversal primitive may safely run concurrently with
   * the _rcu list-mutation primitives such as hlist_add_head_rcu()
   * as long as the traversal is guarded by rcu_read_lock().
   */
  struct hlist_node *seq_hlist_start_rcu(struct hlist_head *head,
  				       loff_t pos)
  {
  	struct hlist_node *node;
  
  	__hlist_for_each_rcu(node, head)
  		if (pos-- == 0)
  			return node;
  	return NULL;
  }
  EXPORT_SYMBOL(seq_hlist_start_rcu);
  
  /**
   * seq_hlist_start_head_rcu - start an iteration of a hlist protected by RCU
   * @head: the head of the hlist
   * @pos:  the start position of the sequence
   *
   * Called at seq_file->op->start(). Call this function if you want to
   * print a header at the top of the output.
   *
   * This list-traversal primitive may safely run concurrently with
   * the _rcu list-mutation primitives such as hlist_add_head_rcu()
   * as long as the traversal is guarded by rcu_read_lock().
   */
  struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head,
  					    loff_t pos)
  {
  	if (!pos)
  		return SEQ_START_TOKEN;
  
  	return seq_hlist_start_rcu(head, pos - 1);
  }
  EXPORT_SYMBOL(seq_hlist_start_head_rcu);
  
  /**
   * seq_hlist_next_rcu - move to the next position of the hlist protected by RCU
   * @v:    the current iterator
   * @head: the head of the hlist

   * @ppos: the current position

   *
   * Called at seq_file->op->next().
   *
   * This list-traversal primitive may safely run concurrently with
   * the _rcu list-mutation primitives such as hlist_add_head_rcu()
   * as long as the traversal is guarded by rcu_read_lock().
   */
  struct hlist_node *seq_hlist_next_rcu(void *v,
  				      struct hlist_head *head,
  				      loff_t *ppos)
  {
  	struct hlist_node *node = v;
  
  	++*ppos;
  	if (v == SEQ_START_TOKEN)
  		return rcu_dereference(head->first);
  	else
  		return rcu_dereference(node->next);
  }
  EXPORT_SYMBOL(seq_hlist_next_rcu);

  
  /**
   * seq_hlist_start_precpu - start an iteration of a percpu hlist array
   * @head: pointer to percpu array of struct hlist_heads
   * @cpu:  pointer to cpu "cursor"
   * @pos:  start position of sequence
   *
   * Called at seq_file->op->start().
   */
  struct hlist_node *
  seq_hlist_start_percpu(struct hlist_head __percpu *head, int *cpu, loff_t pos)
  {
  	struct hlist_node *node;
  
  	for_each_possible_cpu(*cpu) {
  		hlist_for_each(node, per_cpu_ptr(head, *cpu)) {
  			if (pos-- == 0)
  				return node;
  		}
  	}
  	return NULL;
  }
  EXPORT_SYMBOL(seq_hlist_start_percpu);
  
  /**
   * seq_hlist_next_percpu - move to the next position of the percpu hlist array
   * @v:    pointer to current hlist_node
   * @head: pointer to percpu array of struct hlist_heads
   * @cpu:  pointer to cpu "cursor"
   * @pos:  start position of sequence
   *
   * Called at seq_file->op->next().
   */
  struct hlist_node *
  seq_hlist_next_percpu(void *v, struct hlist_head __percpu *head,
  			int *cpu, loff_t *pos)
  {
  	struct hlist_node *node = v;
  
  	++*pos;
  
  	if (node->next)
  		return node->next;
  
  	for (*cpu = cpumask_next(*cpu, cpu_possible_mask); *cpu < nr_cpu_ids;
  	     *cpu = cpumask_next(*cpu, cpu_possible_mask)) {
  		struct hlist_head *bucket = per_cpu_ptr(head, *cpu);
  
  		if (!hlist_empty(bucket))
  			return bucket->first;
  	}
  	return NULL;
  }
  EXPORT_SYMBOL(seq_hlist_next_percpu);

  
  void __init seq_file_init(void)
  {

  	seq_file_cache = KMEM_CACHE(seq_file, SLAB_ACCOUNT|SLAB_PANIC);

  }