/**
   * @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/fs_context.h>

  #include <linux/pagemap.h>

  #include <linux/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(inode);

  	}
  	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 const struct file_operations ulong_fops = {

  	.read		= ulong_read_file,
  	.write		= ulong_write_file,

  	.open		= simple_open,

  	.llseek		= default_llseek,

  };

  static const struct file_operations ulong_ro_fops = {

  	.read		= ulong_read_file,

  	.open		= simple_open,

  	.llseek		= default_llseek,

  };

  static int __oprofilefs_create_file(struct dentry *root, char const *name,
  	const struct file_operations *fops, int perm, void *priv)

  {

  	struct dentry *dentry;
  	struct inode *inode;

  	if (!root)
  		return -ENOMEM;

  	inode_lock(d_inode(root));

  	dentry = d_alloc_name(root, name);

  	if (!dentry) {

  		inode_unlock(d_inode(root));

  		return -ENOMEM;

  	}

  	inode = oprofilefs_get_inode(root->d_sb, S_IFREG | perm);

  	if (!inode) {
  		dput(dentry);

  		inode_unlock(d_inode(root));

  		return -ENOMEM;

  	}
  	inode->i_fop = fops;

  	inode->i_private = priv;

  	d_add(dentry, inode);

  	inode_unlock(d_inode(root));

  	return 0;

  }

  int oprofilefs_create_ulong(struct dentry *root,

  	char const *name, unsigned long *val)

  {

  	return __oprofilefs_create_file(root, name,

  					&ulong_fops, 0644, val);

  }

  int oprofilefs_create_ro_ulong(struct dentry *root,

  	char const *name, unsigned long *val)

  {

  	return __oprofilefs_create_file(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		= simple_open,

  	.llseek		= default_llseek,

  };

  int oprofilefs_create_ro_atomic(struct dentry *root,

  	char const *name, atomic_t *val)

  {

  	return __oprofilefs_create_file(root, name,

  					&atomic_ro_fops, 0444, val);

  }

  int oprofilefs_create_file(struct dentry *root,

  	char const *name, const struct file_operations *fops)

  {

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

  }

  int oprofilefs_create_file_perm(struct dentry *root,

  	char const *name, const struct file_operations *fops, int perm)

  {

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

  }

  struct dentry *oprofilefs_mkdir(struct dentry *parent, char const *name)

  {

  	struct dentry *dentry;
  	struct inode *inode;

  	inode_lock(d_inode(parent));

  	dentry = d_alloc_name(parent, name);

  	if (!dentry) {

  		inode_unlock(d_inode(parent));

  		return NULL;

  	}

  	inode = oprofilefs_get_inode(parent->d_sb, S_IFDIR | 0755);

  	if (!inode) {
  		dput(dentry);

  		inode_unlock(d_inode(parent));

  		return NULL;
  	}
  	inode->i_op = &simple_dir_inode_operations;
  	inode->i_fop = &simple_dir_operations;
  	d_add(dentry, inode);

  	inode_unlock(d_inode(parent));

  	return dentry;
  }

  static int oprofilefs_fill_super(struct super_block *sb, struct fs_context *fc)

  {

  	struct inode *root_inode;

  	sb->s_blocksize = PAGE_SIZE;
  	sb->s_blocksize_bits = PAGE_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;

  	sb->s_root = d_make_root(root_inode);
  	if (!sb->s_root)

  		return -ENOMEM;

  	oprofile_create_files(sb->s_root);

  
  	// FIXME: verify kill_litter_super removes our dentries
  	return 0;
  }

  static int oprofilefs_get_tree(struct fs_context *fc)

  {

  	return get_tree_single(fc, oprofilefs_fill_super);

  }

  static const struct fs_context_operations oprofilefs_context_ops = {
  	.get_tree	= oprofilefs_get_tree,
  };
  
  static int oprofilefs_init_fs_context(struct fs_context *fc)
  {
  	fc->ops = &oprofilefs_context_ops;
  	return 0;
  }

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

  	.init_fs_context = oprofilefs_init_fs_context,

  	.kill_sb	= kill_litter_super,
  };

  MODULE_ALIAS_FS("oprofilefs");

  
  
  int __init oprofilefs_register(void)
  {
  	return register_filesystem(&oprofilefs_type);
  }
  
  
  void __exit oprofilefs_unregister(void)
  {
  	unregister_filesystem(&oprofilefs_type);
  }