/**
   * @file oprofilefs.c
   *
   * @remark Copyright 2002 OProfile authors
   * @remark Read the file COPYING
   *
   * @author John Levon
   *
   * A simple filesystem for configuration and
   * access of oprofile.
   */
  
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/oprofile.h>
  #include <linux/fs.h>
  #include <linux/pagemap.h>
  #include <asm/uaccess.h>
  
  #include "oprof.h"
  
  #define OPROFILEFS_MAGIC 0x6f70726f

  DEFINE_RAW_SPINLOCK(oprofilefs_lock);

  static struct inode *oprofilefs_get_inode(struct super_block *sb, int mode)

  {

  	struct inode *inode = new_inode(sb);

  
  	if (inode) {

  		inode->i_ino = get_next_ino();

  		inode->i_mode = mode;

  		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  	}
  	return inode;
  }

  static const struct super_operations s_ops = {

  	.statfs		= simple_statfs,
  	.drop_inode 	= generic_delete_inode,
  };

  ssize_t oprofilefs_str_to_user(char const *str, char __user *buf, size_t count, loff_t *offset)

  {
  	return simple_read_from_buffer(buf, count, offset, str, strlen(str));
  }
  
  
  #define TMPBUFSIZE 50

  ssize_t oprofilefs_ulong_to_user(unsigned long val, char __user *buf, size_t count, loff_t *offset)

  {
  	char tmpbuf[TMPBUFSIZE];
  	size_t maxlen = snprintf(tmpbuf, TMPBUFSIZE, "%lu
  ", val);
  	if (maxlen > TMPBUFSIZE)
  		maxlen = TMPBUFSIZE;
  	return simple_read_from_buffer(buf, count, offset, tmpbuf, maxlen);
  }

  /*
   * Note: If oprofilefs_ulong_from_user() returns 0, then *val remains
   * unchanged and might be uninitialized. This follows write syscall
   * implementation when count is zero: "If count is zero ... [and if]
   * no errors are detected, 0 will be returned without causing any
   * other effect." (man 2 write)
   */

  int oprofilefs_ulong_from_user(unsigned long *val, char const __user *buf, size_t count)

  {
  	char tmpbuf[TMPBUFSIZE];

  	unsigned long flags;

  
  	if (!count)
  		return 0;
  
  	if (count > TMPBUFSIZE - 1)
  		return -EINVAL;
  
  	memset(tmpbuf, 0x0, TMPBUFSIZE);
  
  	if (copy_from_user(tmpbuf, buf, count))
  		return -EFAULT;

  	raw_spin_lock_irqsave(&oprofilefs_lock, flags);

  	*val = simple_strtoul(tmpbuf, NULL, 0);

  	raw_spin_unlock_irqrestore(&oprofilefs_lock, flags);

  	return count;

  }

  static ssize_t ulong_read_file(struct file *file, char __user *buf, size_t count, loff_t *offset)

  {

  	unsigned long *val = file->private_data;

  	return oprofilefs_ulong_to_user(*val, buf, count, offset);
  }

  static ssize_t ulong_write_file(struct file *file, char const __user *buf, size_t count, loff_t *offset)

  {

  	unsigned long value;

  	int retval;
  
  	if (*offset)
  		return -EINVAL;

  	retval = oprofilefs_ulong_from_user(&value, buf, count);

  	if (retval <= 0)

  		return retval;

  	retval = oprofile_set_ulong(file->private_data, value);

  	if (retval)
  		return retval;

  	return count;
  }

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

  {

  	if (inode->i_private)
  		filp->private_data = inode->i_private;

  	return 0;
  }

  static const struct file_operations ulong_fops = {

  	.read		= ulong_read_file,
  	.write		= ulong_write_file,
  	.open		= default_open,

  	.llseek		= default_llseek,

  };

  static const struct file_operations ulong_ro_fops = {

  	.read		= ulong_read_file,
  	.open		= default_open,

  	.llseek		= default_llseek,

  };

  static int __oprofilefs_create_file(struct super_block *sb,

  	struct dentry *root, char const *name, const struct file_operations *fops,

  	int perm, void *priv)

  {

  	struct dentry *dentry;
  	struct inode *inode;

  
  	dentry = d_alloc_name(root, name);
  	if (!dentry)

  		return -ENOMEM;

  	inode = oprofilefs_get_inode(sb, S_IFREG | perm);
  	if (!inode) {
  		dput(dentry);

  		return -ENOMEM;

  	}
  	inode->i_fop = fops;
  	d_add(dentry, inode);

  	dentry->d_inode->i_private = priv;
  	return 0;

  }

  int oprofilefs_create_ulong(struct super_block *sb, struct dentry *root,
  	char const *name, unsigned long *val)

  {

  	return __oprofilefs_create_file(sb, root, name,
  					&ulong_fops, 0644, val);

  }

  int oprofilefs_create_ro_ulong(struct super_block *sb, struct dentry *root,
  	char const *name, unsigned long *val)

  {

  	return __oprofilefs_create_file(sb, root, name,
  					&ulong_ro_fops, 0444, val);

  }

  static ssize_t atomic_read_file(struct file *file, char __user *buf, size_t count, loff_t *offset)

  {

  	atomic_t *val = file->private_data;

  	return oprofilefs_ulong_to_user(atomic_read(val), buf, count, offset);
  }

  static const struct file_operations atomic_ro_fops = {

  	.read		= atomic_read_file,
  	.open		= default_open,

  	.llseek		= default_llseek,

  };

  int oprofilefs_create_ro_atomic(struct super_block *sb, struct dentry *root,
  	char const *name, atomic_t *val)

  {

  	return __oprofilefs_create_file(sb, root, name,
  					&atomic_ro_fops, 0444, val);

  }

  int oprofilefs_create_file(struct super_block *sb, struct dentry *root,
  	char const *name, const struct file_operations *fops)

  {

  	return __oprofilefs_create_file(sb, root, name, fops, 0644, NULL);

  }

  int oprofilefs_create_file_perm(struct super_block *sb, struct dentry *root,
  	char const *name, const struct file_operations *fops, int perm)

  {

  	return __oprofilefs_create_file(sb, root, name, fops, perm, NULL);

  }

  struct dentry *oprofilefs_mkdir(struct super_block *sb,
  	struct dentry *root, char const *name)

  {

  	struct dentry *dentry;
  	struct inode *inode;

  
  	dentry = d_alloc_name(root, name);
  	if (!dentry)
  		return NULL;
  	inode = oprofilefs_get_inode(sb, S_IFDIR | 0755);
  	if (!inode) {
  		dput(dentry);
  		return NULL;
  	}
  	inode->i_op = &simple_dir_inode_operations;
  	inode->i_fop = &simple_dir_operations;
  	d_add(dentry, inode);
  	return dentry;
  }

  static int oprofilefs_fill_super(struct super_block *sb, void *data, int silent)

  {

  	struct inode *root_inode;
  	struct dentry *root_dentry;

  
  	sb->s_blocksize = PAGE_CACHE_SIZE;
  	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
  	sb->s_magic = OPROFILEFS_MAGIC;
  	sb->s_op = &s_ops;
  	sb->s_time_gran = 1;
  
  	root_inode = oprofilefs_get_inode(sb, S_IFDIR | 0755);
  	if (!root_inode)
  		return -ENOMEM;
  	root_inode->i_op = &simple_dir_inode_operations;
  	root_inode->i_fop = &simple_dir_operations;
  	root_dentry = d_alloc_root(root_inode);
  	if (!root_dentry) {
  		iput(root_inode);
  		return -ENOMEM;
  	}
  
  	sb->s_root = root_dentry;
  
  	oprofile_create_files(sb, root_dentry);
  
  	// FIXME: verify kill_litter_super removes our dentries
  	return 0;
  }

  static struct dentry *oprofilefs_mount(struct file_system_type *fs_type,
  	int flags, const char *dev_name, void *data)

  {

  	return mount_single(fs_type, flags, data, oprofilefs_fill_super);

  }
  
  
  static struct file_system_type oprofilefs_type = {
  	.owner		= THIS_MODULE,
  	.name		= "oprofilefs",

  	.mount		= oprofilefs_mount,

  	.kill_sb	= kill_litter_super,
  };
  
  
  int __init oprofilefs_register(void)
  {
  	return register_filesystem(&oprofilefs_type);
  }
  
  
  void __exit oprofilefs_unregister(void)
  {
  	unregister_filesystem(&oprofilefs_type);
  }