/*

   * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)

   * Licensed under the GPL
   */

  #include <linux/ctype.h>
  #include <linux/dcache.h>

  #include <linux/file.h>

  #include <linux/fs.h>

  #include <linux/init.h>

  #include <linux/kernel.h>

  #include <linux/list.h>
  #include <linux/module.h>
  #include <linux/mount.h>
  #include <linux/slab.h>

  #include <linux/statfs.h>

  #include <linux/types.h>

  #include <linux/pid_namespace.h>

  #include <linux/namei.h>

  #include <asm/uaccess.h>

  #include "os.h"

  static struct inode *get_inode(struct super_block *, struct dentry *);

  
  struct hppfs_data {
  	struct list_head list;
  	char contents[PAGE_SIZE - sizeof(struct list_head)];
  };
  
  struct hppfs_private {
  	struct file *proc_file;
  	int host_fd;
  	loff_t len;
  	struct hppfs_data *contents;
  };
  
  struct hppfs_inode_info {

  	struct dentry *proc_dentry;

  	struct inode vfs_inode;
  };
  
  static inline struct hppfs_inode_info *HPPFS_I(struct inode *inode)
  {

  	return container_of(inode, struct hppfs_inode_info, vfs_inode);

  }
  
  #define HPPFS_SUPER_MAGIC 0xb00000ee

  static const struct super_operations hppfs_sbops;

  
  static int is_pid(struct dentry *dentry)
  {
  	struct super_block *sb;
  	int i;
  
  	sb = dentry->d_sb;

  	if (dentry->d_parent != sb->s_root)

  		return 0;

  	for (i = 0; i < dentry->d_name.len; i++) {
  		if (!isdigit(dentry->d_name.name[i]))
  			return 0;

  	}

  	return 1;

  }
  
  static char *dentry_name(struct dentry *dentry, int extra)
  {
  	struct dentry *parent;
  	char *root, *name;
  	const char *seg_name;
  	int len, seg_len;
  
  	len = 0;
  	parent = dentry;

  	while (parent->d_parent != parent) {
  		if (is_pid(parent))

  			len += strlen("pid") + 1;
  		else len += parent->d_name.len + 1;
  		parent = parent->d_parent;
  	}
  
  	root = "proc";
  	len += strlen(root);
  	name = kmalloc(len + extra + 1, GFP_KERNEL);

  	if (name == NULL)
  		return NULL;

  
  	name[len] = '\0';
  	parent = dentry;

  	while (parent->d_parent != parent) {
  		if (is_pid(parent)) {

  			seg_name = "pid";
  			seg_len = strlen("pid");
  		}
  		else {
  			seg_name = parent->d_name.name;
  			seg_len = parent->d_name.len;
  		}
  
  		len -= seg_len + 1;
  		name[len] = '/';
  		strncpy(&name[len + 1], seg_name, seg_len);
  		parent = parent->d_parent;
  	}
  	strncpy(name, root, strlen(root));

  	return name;

  }

  static int file_removed(struct dentry *dentry, const char *file)
  {
  	char *host_file;
  	int extra, fd;
  
  	extra = 0;

  	if (file != NULL)
  		extra += strlen(file) + 1;

  
  	host_file = dentry_name(dentry, extra + strlen("/remove"));

  	if (host_file == NULL) {
  		printk(KERN_ERR "file_removed : allocation failed
  ");
  		return -ENOMEM;

  	}

  	if (file != NULL) {

  		strcat(host_file, "/");
  		strcat(host_file, file);
  	}
  	strcat(host_file, "/remove");
  
  	fd = os_open_file(host_file, of_read(OPENFLAGS()), 0);
  	kfree(host_file);

  	if (fd > 0) {

  		os_close_file(fd);

  		return 1;

  	}

  	return 0;

  }

  static struct dentry *hppfs_lookup(struct inode *ino, struct dentry *dentry,

  				   struct nameidata *nd)

  {

  	struct dentry *proc_dentry, *parent;
  	struct qstr *name = &dentry->d_name;

  	struct inode *inode;
  	int err, deleted;
  
  	deleted = file_removed(dentry, NULL);

  	if (deleted < 0)
  		return ERR_PTR(deleted);
  	else if (deleted)
  		return ERR_PTR(-ENOENT);

  	parent = HPPFS_I(ino)->proc_dentry;

  	mutex_lock(&parent->d_inode->i_mutex);

  	proc_dentry = lookup_one_len(name->name, parent, name->len);

  	mutex_unlock(&parent->d_inode->i_mutex);

  	if (IS_ERR(proc_dentry))
  		return proc_dentry;

  	err = -ENOMEM;
  	inode = get_inode(ino->i_sb, proc_dentry);
  	if (!inode)

  		goto out;

  
   	d_add(dentry, inode);

  	return NULL;

   out:

  	return ERR_PTR(err);

  }

  static const struct inode_operations hppfs_file_iops = {

  };

  static ssize_t read_proc(struct file *file, char __user *buf, ssize_t count,

  			 loff_t *ppos, int is_user)
  {

  	ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);

  	ssize_t n;

  	read = file->f_path.dentry->d_inode->i_fop->read;

  	if (!is_user)

  		set_fs(KERNEL_DS);
  
  	n = (*read)(file, buf, count, &file->f_pos);

  	if (!is_user)

  		set_fs(USER_DS);

  	if (ppos)
  		*ppos = file->f_pos;

  	return n;

  }

  static ssize_t hppfs_read_file(int fd, char __user *buf, ssize_t count)

  {
  	ssize_t n;
  	int cur, err;
  	char *new_buf;
  
  	n = -ENOMEM;
  	new_buf = kmalloc(PAGE_SIZE, GFP_KERNEL);

  	if (new_buf == NULL) {
  		printk(KERN_ERR "hppfs_read_file : kmalloc failed
  ");

  		goto out;
  	}
  	n = 0;

  	while (count > 0) {

  		cur = min_t(ssize_t, count, PAGE_SIZE);
  		err = os_read_file(fd, new_buf, cur);

  		if (err < 0) {
  			printk(KERN_ERR "hppfs_read : read failed, "
  			       "errno = %d
  ", err);

  			n = err;
  			goto out_free;

  		} else if (err == 0)

  			break;

  		if (copy_to_user(buf, new_buf, err)) {

  			n = -EFAULT;
  			goto out_free;
  		}
  		n += err;
  		count -= err;
  	}
   out_free:
  	kfree(new_buf);
   out:

  	return n;

  }

  static ssize_t hppfs_read(struct file *file, char __user *buf, size_t count,

  			  loff_t *ppos)
  {
  	struct hppfs_private *hppfs = file->private_data;
  	struct hppfs_data *data;
  	loff_t off;
  	int err;

  	if (hppfs->contents != NULL) {

  		int rem;

  		if (*ppos >= hppfs->len)
  			return 0;

  
  		data = hppfs->contents;
  		off = *ppos;

  		while (off >= sizeof(data->contents)) {

  			data = list_entry(data->list.next, struct hppfs_data,
  					  list);
  			off -= sizeof(data->contents);
  		}

  		if (off + count > hppfs->len)

  			count = hppfs->len - off;

  		rem = copy_to_user(buf, &data->contents[off], count);
  		*ppos += count - rem;
  		if (rem > 0)
  			return -EFAULT;

  	} else if (hppfs->host_fd != -1) {

  		err = os_seek_file(hppfs->host_fd, *ppos);

  		if (err) {
  			printk(KERN_ERR "hppfs_read : seek failed, "
  			       "errno = %d
  ", err);
  			return err;

  		}

  		err = hppfs_read_file(hppfs->host_fd, buf, count);
  		if (err < 0) {
  			printk(KERN_ERR "hppfs_read: read failed: %d
  ", err);
  			return err;
  		}
  		count = err;

  		if (count > 0)

  			*ppos += count;
  	}
  	else count = read_proc(hppfs->proc_file, buf, count, ppos, 1);

  	return count;

  }

  static ssize_t hppfs_write(struct file *file, const char __user *buf,
  			   size_t len, loff_t *ppos)

  {
  	struct hppfs_private *data = file->private_data;
  	struct file *proc_file = data->proc_file;

  	ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);

  	write = proc_file->f_path.dentry->d_inode->i_fop->write;

  	return (*write)(proc_file, buf, len, ppos);

  }
  
  static int open_host_sock(char *host_file, int *filter_out)
  {
  	char *end;
  	int fd;
  
  	end = &host_file[strlen(host_file)];
  	strcpy(end, "/rw");
  	*filter_out = 1;
  	fd = os_connect_socket(host_file);

  	if (fd > 0)
  		return fd;

  
  	strcpy(end, "/r");
  	*filter_out = 0;
  	fd = os_connect_socket(host_file);

  	return fd;

  }
  
  static void free_contents(struct hppfs_data *head)
  {
  	struct hppfs_data *data;
  	struct list_head *ele, *next;

  	if (head == NULL)
  		return;

  	list_for_each_safe(ele, next, &head->list) {

  		data = list_entry(ele, struct hppfs_data, list);
  		kfree(data);
  	}
  	kfree(head);
  }
  
  static struct hppfs_data *hppfs_get_data(int fd, int filter,
  					 struct file *proc_file,
  					 struct file *hppfs_file,
  					 loff_t *size_out)
  {
  	struct hppfs_data *data, *new, *head;
  	int n, err;
  
  	err = -ENOMEM;
  	data = kmalloc(sizeof(*data), GFP_KERNEL);

  	if (data == NULL) {
  		printk(KERN_ERR "hppfs_get_data : head allocation failed
  ");

  		goto failed;
  	}
  
  	INIT_LIST_HEAD(&data->list);
  
  	head = data;
  	*size_out = 0;

  	if (filter) {
  		while ((n = read_proc(proc_file, data->contents,

  				      sizeof(data->contents), NULL, 0)) > 0)

  			os_write_file(fd, data->contents, n);
  		err = os_shutdown_socket(fd, 0, 1);

  		if (err) {
  			printk(KERN_ERR "hppfs_get_data : failed to shut down "

  			       "socket
  ");
  			goto failed_free;
  		}
  	}

  	while (1) {

  		n = os_read_file(fd, data->contents, sizeof(data->contents));

  		if (n < 0) {

  			err = n;

  			printk(KERN_ERR "hppfs_get_data : read failed, "
  			       "errno = %d
  ", err);

  			goto failed_free;

  		} else if (n == 0)

  			break;
  
  		*size_out += n;

  		if (n < sizeof(data->contents))

  			break;
  
  		new = kmalloc(sizeof(*data), GFP_KERNEL);

  		if (new == 0) {
  			printk(KERN_ERR "hppfs_get_data : data allocation "
  			       "failed
  ");

  			err = -ENOMEM;
  			goto failed_free;
  		}
  
  		INIT_LIST_HEAD(&new->list);
  		list_add(&new->list, &data->list);
  		data = new;
  	}

  	return head;

  
   failed_free:
  	free_contents(head);
   failed:

  	return ERR_PTR(err);

  }
  
  static struct hppfs_private *hppfs_data(void)
  {
  	struct hppfs_private *data;
  
  	data = kmalloc(sizeof(*data), GFP_KERNEL);

  	if (data == NULL)
  		return data;

  
  	*data = ((struct hppfs_private ) { .host_fd  		= -1,
  					   .len  		= -1,
  					   .contents 		= NULL } );

  	return data;

  }
  
  static int file_mode(int fmode)
  {

  	if (fmode == (FMODE_READ | FMODE_WRITE))
  		return O_RDWR;
  	if (fmode == FMODE_READ)
  		return O_RDONLY;
  	if (fmode == FMODE_WRITE)
  		return O_WRONLY;
  	return 0;

  }
  
  static int hppfs_open(struct inode *inode, struct file *file)
  {

  	const struct cred *cred = file->f_cred;

  	struct hppfs_private *data;

  	struct vfsmount *proc_mnt;

  	struct dentry *proc_dentry;

  	char *host_file;
  	int err, fd, type, filter;
  
  	err = -ENOMEM;
  	data = hppfs_data();

  	if (data == NULL)

  		goto out;

  	host_file = dentry_name(file->f_path.dentry, strlen("/rw"));

  	if (host_file == NULL)

  		goto out_free2;
  
  	proc_dentry = HPPFS_I(inode)->proc_dentry;

  	proc_mnt = inode->i_sb->s_fs_info;

  
  	/* XXX This isn't closed anywhere */

  	data->proc_file = dentry_open(dget(proc_dentry), mntget(proc_mnt),

  				      file_mode(file->f_mode), cred);

  	err = PTR_ERR(data->proc_file);

  	if (IS_ERR(data->proc_file))

  		goto out_free1;
  
  	type = os_file_type(host_file);

  	if (type == OS_TYPE_FILE) {

  		fd = os_open_file(host_file, of_read(OPENFLAGS()), 0);

  		if (fd >= 0)

  			data->host_fd = fd;

  		else
  			printk(KERN_ERR "hppfs_open : failed to open '%s', "
  			       "errno = %d
  ", host_file, -fd);

  
  		data->contents = NULL;

  	} else if (type == OS_TYPE_DIR) {

  		fd = open_host_sock(host_file, &filter);

  		if (fd > 0) {

  			data->contents = hppfs_get_data(fd, filter,

  							data->proc_file,

  							file, &data->len);

  			if (!IS_ERR(data->contents))

  				data->host_fd = fd;

  		} else
  			printk(KERN_ERR "hppfs_open : failed to open a socket "
  			       "in '%s', errno = %d
  ", host_file, -fd);

  	}
  	kfree(host_file);
  
  	file->private_data = data;

  	return 0;

  
   out_free1:
  	kfree(host_file);
   out_free2:
  	free_contents(data->contents);
  	kfree(data);
   out:

  	return err;

  }
  
  static int hppfs_dir_open(struct inode *inode, struct file *file)
  {

  	const struct cred *cred = file->f_cred;

  	struct hppfs_private *data;

  	struct vfsmount *proc_mnt;

  	struct dentry *proc_dentry;

  	int err;
  
  	err = -ENOMEM;
  	data = hppfs_data();

  	if (data == NULL)

  		goto out;
  
  	proc_dentry = HPPFS_I(inode)->proc_dentry;

  	proc_mnt = inode->i_sb->s_fs_info;

  	data->proc_file = dentry_open(dget(proc_dentry), mntget(proc_mnt),

  				      file_mode(file->f_mode), cred);

  	err = PTR_ERR(data->proc_file);

  	if (IS_ERR(data->proc_file))

  		goto out_free;
  
  	file->private_data = data;

  	return 0;

  
   out_free:
  	kfree(data);
   out:

  	return err;

  }
  
  static loff_t hppfs_llseek(struct file *file, loff_t off, int where)
  {
  	struct hppfs_private *data = file->private_data;

  	struct file *proc_file = data->proc_file;

  	loff_t (*llseek)(struct file *, loff_t, int);
  	loff_t ret;

  	llseek = proc_file->f_path.dentry->d_inode->i_fop->llseek;

  	if (llseek != NULL) {

  		ret = (*llseek)(proc_file, off, where);

  		if (ret < 0)
  			return ret;

  	}

  	return default_llseek(file, off, where);

  }

  static const struct file_operations hppfs_file_fops = {

  	.owner		= NULL,
  	.llseek		= hppfs_llseek,
  	.read		= hppfs_read,
  	.write		= hppfs_write,
  	.open		= hppfs_open,
  };
  
  struct hppfs_dirent {
  	void *vfs_dirent;
  	filldir_t filldir;
  	struct dentry *dentry;
  };
  
  static int hppfs_filldir(void *d, const char *name, int size,

  			 loff_t offset, u64 inode, unsigned int type)

  {
  	struct hppfs_dirent *dirent = d;

  	if (file_removed(dirent->dentry, name))
  		return 0;

  	return (*dirent->filldir)(dirent->vfs_dirent, name, size, offset,
  				  inode, type);

  }
  
  static int hppfs_readdir(struct file *file, void *ent, filldir_t filldir)
  {
  	struct hppfs_private *data = file->private_data;

  	struct file *proc_file = data->proc_file;

  	int (*readdir)(struct file *, void *, filldir_t);
  	struct hppfs_dirent dirent = ((struct hppfs_dirent)
  		                      { .vfs_dirent  	= ent,
  					.filldir 	= filldir,

  					.dentry  	= file->f_path.dentry
  				      });

  	int err;

  	readdir = proc_file->f_path.dentry->d_inode->i_fop->readdir;

  
  	proc_file->f_pos = file->f_pos;
  	err = (*readdir)(proc_file, &dirent, hppfs_filldir);
  	file->f_pos = proc_file->f_pos;

  	return err;

  }

  static int hppfs_fsync(struct file *file, loff_t start, loff_t end,
  		       int datasync)

  {

  	return filemap_write_and_wait_range(file->f_mapping, start, end);

  }

  static const struct file_operations hppfs_dir_fops = {

  	.owner		= NULL,
  	.readdir	= hppfs_readdir,
  	.open		= hppfs_dir_open,
  	.fsync		= hppfs_fsync,

  	.llseek		= default_llseek,

  };

  static int hppfs_statfs(struct dentry *dentry, struct kstatfs *sf)

  {
  	sf->f_blocks = 0;
  	sf->f_bfree = 0;
  	sf->f_bavail = 0;
  	sf->f_files = 0;
  	sf->f_ffree = 0;
  	sf->f_type = HPPFS_SUPER_MAGIC;

  	return 0;

  }
  
  static struct inode *hppfs_alloc_inode(struct super_block *sb)
  {
  	struct hppfs_inode_info *hi;
  
  	hi = kmalloc(sizeof(*hi), GFP_KERNEL);

  	if (!hi)
  		return NULL;

  	hi->proc_dentry = NULL;

  	inode_init_once(&hi->vfs_inode);

  	return &hi->vfs_inode;

  }

  void hppfs_evict_inode(struct inode *ino)

  {

  	end_writeback(ino);

  	dput(HPPFS_I(ino)->proc_dentry);
  	mntput(ino->i_sb->s_fs_info);

  }

  static void hppfs_i_callback(struct rcu_head *head)

  {

  	struct inode *inode = container_of(head, struct inode, i_rcu);

  	kfree(HPPFS_I(inode));
  }

  static void hppfs_destroy_inode(struct inode *inode)
  {
  	call_rcu(&inode->i_rcu, hppfs_i_callback);
  }

  static const struct super_operations hppfs_sbops = {

  	.alloc_inode	= hppfs_alloc_inode,
  	.destroy_inode	= hppfs_destroy_inode,

  	.evict_inode	= hppfs_evict_inode,

  	.statfs		= hppfs_statfs,
  };

  static int hppfs_readlink(struct dentry *dentry, char __user *buffer,
  			  int buflen)

  {

  	struct dentry *proc_dentry = HPPFS_I(dentry->d_inode)->proc_dentry;

  	return proc_dentry->d_inode->i_op->readlink(proc_dentry, buffer,
  						    buflen);

  }

  static void *hppfs_follow_link(struct dentry *dentry, struct nameidata *nd)

  {

  	struct dentry *proc_dentry = HPPFS_I(dentry->d_inode)->proc_dentry;

  	return proc_dentry->d_inode->i_op->follow_link(proc_dentry, nd);
  }

  static void hppfs_put_link(struct dentry *dentry, struct nameidata *nd,
  			   void *cookie)
  {
  	struct dentry *proc_dentry = HPPFS_I(dentry->d_inode)->proc_dentry;
  
  	if (proc_dentry->d_inode->i_op->put_link)
  		proc_dentry->d_inode->i_op->put_link(proc_dentry, nd, cookie);
  }

  static const struct inode_operations hppfs_dir_iops = {

  	.lookup		= hppfs_lookup,
  };

  static const struct inode_operations hppfs_link_iops = {

  	.readlink	= hppfs_readlink,
  	.follow_link	= hppfs_follow_link,

  	.put_link	= hppfs_put_link,

  };

  static struct inode *get_inode(struct super_block *sb, struct dentry *dentry)

  {

  	struct inode *proc_ino = dentry->d_inode;
  	struct inode *inode = new_inode(sb);

  	if (!inode) {
  		dput(dentry);

  		return ERR_PTR(-ENOMEM);

  	}

  	if (S_ISDIR(dentry->d_inode->i_mode)) {

  		inode->i_op = &hppfs_dir_iops;
  		inode->i_fop = &hppfs_dir_fops;

  	} else if (S_ISLNK(dentry->d_inode->i_mode)) {

  		inode->i_op = &hppfs_link_iops;
  		inode->i_fop = &hppfs_file_fops;

  	} else {

  		inode->i_op = &hppfs_file_iops;
  		inode->i_fop = &hppfs_file_fops;
  	}

  	HPPFS_I(inode)->proc_dentry = dentry;

  
  	inode->i_uid = proc_ino->i_uid;
  	inode->i_gid = proc_ino->i_gid;
  	inode->i_atime = proc_ino->i_atime;
  	inode->i_mtime = proc_ino->i_mtime;
  	inode->i_ctime = proc_ino->i_ctime;
  	inode->i_ino = proc_ino->i_ino;
  	inode->i_mode = proc_ino->i_mode;

  	set_nlink(inode, proc_ino->i_nlink);

  	inode->i_size = proc_ino->i_size;
  	inode->i_blocks = proc_ino->i_blocks;

  	return inode;

  }
  
  static int hppfs_fill_super(struct super_block *sb, void *d, int silent)
  {
  	struct inode *root_inode;

  	struct vfsmount *proc_mnt;

  	int err = -ENOENT;

  	proc_mnt = mntget(current->nsproxy->pid_ns->proc_mnt);

  	if (IS_ERR(proc_mnt))

  		goto out;

  	sb->s_blocksize = 1024;
  	sb->s_blocksize_bits = 10;
  	sb->s_magic = HPPFS_SUPER_MAGIC;
  	sb->s_op = &hppfs_sbops;

  	sb->s_fs_info = proc_mnt;

  
  	err = -ENOMEM;

  	root_inode = get_inode(sb, dget(proc_mnt->mnt_root));

  	if (!root_inode)
  		goto out_mntput;

  	sb->s_root = d_alloc_root(root_inode);

  	if (!sb->s_root)
  		goto out_iput;

  	return 0;

   out_iput:

  	iput(root_inode);

   out_mntput:
  	mntput(proc_mnt);

   out:
  	return(err);
  }

  static struct dentry *hppfs_read_super(struct file_system_type *type,

  			    int flags, const char *dev_name,

  			    void *data)

  {

  	return mount_nodev(type, flags, data, hppfs_fill_super);

  }
  
  static struct file_system_type hppfs_type = {
  	.owner 		= THIS_MODULE,
  	.name 		= "hppfs",

  	.mount 		= hppfs_read_super,

  	.kill_sb	= kill_anon_super,
  	.fs_flags 	= 0,
  };
  
  static int __init init_hppfs(void)
  {

  	return register_filesystem(&hppfs_type);

  }
  
  static void __exit exit_hppfs(void)
  {
  	unregister_filesystem(&hppfs_type);
  }
  
  module_init(init_hppfs)
  module_exit(exit_hppfs)
  MODULE_LICENSE("GPL");